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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
163 udebs (stripped-down binary packages used by the Debian Installer) do
164 not comply with all of the requirements discussed here. See the
165 <url name="Debian Installer internals manual"
166 id="http://d-i.alioth.debian.org/doc/internals/ch03.html"> for more
167 information about them.
172 <heading>New versions of this document</heading>
175 This manual is distributed via the Debian package
176 <package><url name="debian-policy"
177 id="http://packages.debian.org/debian-policy"></package>
178 (<httpsite>packages.debian.org</httpsite>
179 <httppath>/debian-policy</httppath>).
183 The current version of this document is also available from
184 the Debian web mirrors at
185 <tt><url name="/doc/debian-policy/"
186 id="http://www.debian.org/doc/debian-policy/"></tt>.
188 <httpsite>www.debian.org</httpsite>
189 <httppath>/doc/debian-policy/</httppath>)
190 Also available from the same directory are several other
191 formats: <file>policy.html.tar.gz</file>
192 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
193 <file>policy.pdf.gz</file>
194 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
195 and <file>policy.ps.gz</file>
196 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
200 The <package>debian-policy</package> package also includes the file
201 <file>upgrading-checklist.txt.gz</file> which indicates policy
202 changes between versions of this document.
207 <heading>Authors and Maintainers</heading>
210 Originally called "Debian GNU/Linux Policy Manual", this
211 manual was initially written in 1996 by Ian Jackson.
212 It was revised on November 27th, 1996 by David A. Morris.
213 Christian Schwarz added new sections on March 15th, 1997,
214 and reworked/restructured it in April-July 1997.
215 Christoph Lameter contributed the "Web Standard".
216 Julian Gilbey largely restructured it in 2001.
220 Since September 1998, the responsibility for the contents of
221 this document lies on the <url name="debian-policy mailing list"
222 id="mailto:debian-policy@lists.debian.org">. Proposals
223 are discussed there and inserted into policy after a certain
224 consensus is established.
225 <!-- insert shameless policy-process plug here eventually -->
226 The actual editing is done by a group of maintainers that have
227 no editorial powers. These are the current maintainers:
230 <item>Russ Allbery</item>
231 <item>Bill Allombert</item>
232 <item>Andreas Barth</item>
233 <item>Jonathan Nieder</item>
238 While the authors of this document have tried hard to avoid
239 typos and other errors, these do still occur. If you discover
240 an error in this manual or if you want to give any
241 comments, suggestions, or criticisms please send an email to
242 the Debian Policy List,
243 <email>debian-policy@lists.debian.org</email>, or submit a
244 bug report against the <tt>debian-policy</tt> package.
248 Please do not try to reach the individual authors or maintainers
249 of the Policy Manual regarding changes to the Policy.
254 <heading>Related documents</heading>
257 There are several other documents other than this Policy Manual
258 that are necessary to fully understand some Debian policies and
263 The external "sub-policy" documents are referred to in:
264 <list compact="compact">
265 <item><ref id="fhs"></item>
266 <item><ref id="virtual_pkg"></item>
267 <item><ref id="menus"></item>
268 <item><ref id="perl"></item>
269 <item><ref id="maintscriptprompt"></item>
270 <item><ref id="emacs"></item>
275 In addition to those, which carry the weight of policy, there
276 is the Debian Developer's Reference. This document describes
277 procedures and resources for Debian developers, but it is
278 <em>not</em> normative; rather, it includes things that don't
279 belong in the Policy, such as best practices for developers.
283 The Developer's Reference is available in the
284 <package>developers-reference</package> package.
285 It's also available from the Debian web mirrors at
286 <tt><url name="/doc/developers-reference/"
287 id="http://www.debian.org/doc/developers-reference/"></tt>.
291 Finally, a <qref id="copyrightformat">specification for
292 machine-readable copyright files</qref> is maintained as part of
293 the <package>debian-policy</package> package using the same
294 procedure as the other policy documents. Use of this format is
299 <sect id="definitions">
300 <heading>Definitions</heading>
303 The following terms are used in this Policy Manual:
307 The character encoding specified by ANSI X3.4-1986 and its
308 predecessor standards, referred to in MIME as US-ASCII, and
309 corresponding to an encoding in eight bits per character of
310 the first 128 <url id="http://www.unicode.org/"
311 name="Unicode"> characters, with the eighth bit always zero.
315 The transformation format (sometimes called encoding) of
316 <url id="http://www.unicode.org/" name="Unicode"> defined by
317 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
318 name="RFC 3629">. UTF-8 has the useful property of having
319 ASCII as a subset, so any text encoded in ASCII is trivially
329 <heading>The Debian Archive</heading>
332 The Debian system is maintained and distributed as a
333 collection of <em>packages</em>. Since there are so many of
334 them (currently well over 15000), they are split into
335 <em>sections</em> and given <em>priorities</em> to simplify
336 the handling of them.
340 The effort of the Debian project is to build a free operating
341 system, but not every package we want to make accessible is
342 <em>free</em> in our sense (see the Debian Free Software
343 Guidelines, below), or may be imported/exported without
344 restrictions. Thus, the archive is split into areas<footnote>
345 The Debian archive software uses the term "component" internally
346 and in the Release file format to refer to the division of an
347 archive. The Debian Social Contract simply refers to "areas."
348 This document uses terminology similar to the Social Contract.
349 </footnote> based on their licenses and other restrictions.
353 The aims of this are:
355 <list compact="compact">
356 <item>to allow us to make as much software available as we can</item>
357 <item>to allow us to encourage everyone to write free software,
359 <item>to allow us to make it easy for people to produce
360 CD-ROMs of our system without violating any licenses,
361 import/export restrictions, or any other laws.</item>
366 The <em>main</em> archive area forms the <em>Debian distribution</em>.
370 Packages in the other archive areas (<tt>contrib</tt>,
371 <tt>non-free</tt>) are not considered to be part of the Debian
372 distribution, although we support their use and provide
373 infrastructure for them (such as our bug-tracking system and
374 mailing lists). This Debian Policy Manual applies to these
379 <heading>The Debian Free Software Guidelines</heading>
381 The Debian Free Software Guidelines (DFSG) form our
382 definition of "free software". These are:
384 <tag>1. Free Redistribution
387 The license of a Debian component may not restrict any
388 party from selling or giving away the software as a
389 component of an aggregate software distribution
390 containing programs from several different
391 sources. The license may not require a royalty or
392 other fee for such sale.
397 The program must include source code, and must allow
398 distribution in source code as well as compiled form.
400 <tag>3. Derived Works
403 The license must allow modifications and derived
404 works, and must allow them to be distributed under the
405 same terms as the license of the original software.
407 <tag>4. Integrity of The Author's Source Code
410 The license may restrict source-code from being
411 distributed in modified form <em>only</em> if the
412 license allows the distribution of "patch files"
413 with the source code for the purpose of modifying the
414 program at build time. The license must explicitly
415 permit distribution of software built from modified
416 source code. The license may require derived works to
417 carry a different name or version number from the
418 original software. (This is a compromise. The Debian
419 Project encourages all authors to not restrict any
420 files, source or binary, from being modified.)
422 <tag>5. No Discrimination Against Persons or Groups
425 The license must not discriminate against any person
428 <tag>6. No Discrimination Against Fields of Endeavor
431 The license must not restrict anyone from making use
432 of the program in a specific field of endeavor. For
433 example, it may not restrict the program from being
434 used in a business, or from being used for genetic
437 <tag>7. Distribution of License
440 The rights attached to the program must apply to all
441 to whom the program is redistributed without the need
442 for execution of an additional license by those
445 <tag>8. License Must Not Be Specific to Debian
448 The rights attached to the program must not depend on
449 the program's being part of a Debian system. If the
450 program is extracted from Debian and used or
451 distributed without Debian but otherwise within the
452 terms of the program's license, all parties to whom
453 the program is redistributed must have the same
454 rights as those that are granted in conjunction with
457 <tag>9. License Must Not Contaminate Other Software
460 The license must not place restrictions on other
461 software that is distributed along with the licensed
462 software. For example, the license must not insist
463 that all other programs distributed on the same medium
464 must be free software.
466 <tag>10. Example Licenses
469 The "GPL," "BSD," and "Artistic" licenses are examples of
470 licenses that we consider <em>free</em>.
477 <heading>Archive areas</heading>
480 <heading>The main archive area</heading>
483 The <em>main</em> archive area comprises the Debian
484 distribution. Only the packages in this area are considered
485 part of the distribution. None of the packages in
486 the <em>main</em> archive area require software outside of
487 that area to function. Anyone may use, share, modify and
488 redistribute the packages in this archive area
490 See <url id="http://www.debian.org/intro/free"
491 name="What Does Free Mean?"> for
492 more about what we mean by free software.
497 Every package in <em>main</em> must comply with the DFSG
498 (Debian Free Software Guidelines).
502 In addition, the packages in <em>main</em>
503 <list compact="compact">
505 must not require or recommend a package outside
506 of <em>main</em> for compilation or execution (thus, the
507 package must not declare a "Pre-Depends", "Depends",
508 "Recommends", "Build-Depends", or "Build-Depends-Indep"
509 relationship on a non-<em>main</em> package),
512 must not be so buggy that we refuse to support them,
516 must meet all policy requirements presented in this
525 <heading>The contrib archive area</heading>
528 The <em>contrib</em> archive area contains supplemental
529 packages intended to work with the Debian distribution, but
530 which require software outside of the distribution to either
535 Every package in <em>contrib</em> must comply with the DFSG.
539 In addition, the packages in <em>contrib</em>
540 <list compact="compact">
542 must not be so buggy that we refuse to support them,
546 must meet all policy requirements presented in this
553 Examples of packages which would be included in
554 <em>contrib</em> are:
555 <list compact="compact">
557 free packages which require <em>contrib</em>,
558 <em>non-free</em> packages or packages which are not
559 in our archive at all for compilation or execution,
563 wrapper packages or other sorts of free accessories for
570 <sect1 id="non-free">
571 <heading>The non-free archive area</heading>
574 The <em>non-free</em> archive area contains supplemental
575 packages intended to work with the Debian distribution that do
576 not comply with the DFSG or have other problems that make
577 their distribution problematic. They may not comply with all
578 of the policy requirements in this manual due to restrictions
579 on modifications or other limitations.
583 Packages must be placed in <em>non-free</em> if they are
584 not compliant with the DFSG or are encumbered by patents
585 or other legal issues that make their distribution
590 In addition, the packages in <em>non-free</em>
591 <list compact="compact">
593 must not be so buggy that we refuse to support them,
597 must meet all policy requirements presented in this
598 manual that it is possible for them to meet.
600 It is possible that there are policy
601 requirements which the package is unable to
602 meet, for example, if the source is
603 unavailable. These situations will need to be
604 handled on a case-by-case basis.
613 <sect id="pkgcopyright">
614 <heading>Copyright considerations</heading>
617 Every package must be accompanied by a verbatim copy of its
618 copyright information and distribution license in the file
619 <file>/usr/share/doc/<var>package</var>/copyright</file>
620 (see <ref id="copyrightfile"> for further details).
624 We reserve the right to restrict files from being included
625 anywhere in our archives if
626 <list compact="compact">
628 their use or distribution would break a law,
631 there is an ethical conflict in their distribution or
635 we would have to sign a license for them, or
638 their distribution would conflict with other project
645 Programs whose authors encourage the user to make
646 donations are fine for the main distribution, provided
647 that the authors do not claim that not donating is
648 immoral, unethical, illegal or something similar; in such
649 a case they must go in <em>non-free</em>.
653 Packages whose copyright permission notices (or patent
654 problems) do not even allow redistribution of binaries
655 only, and where no special permission has been obtained,
656 must not be placed on the Debian FTP site and its mirrors
661 Note that under international copyright law (this applies
662 in the United States, too), <em>no</em> distribution or
663 modification of a work is allowed without an explicit
664 notice saying so. Therefore a program without a copyright
665 notice <em>is</em> copyrighted and you may not do anything
666 to it without risking being sued! Likewise if a program
667 has a copyright notice but no statement saying what is
668 permitted then nothing is permitted.
672 Many authors are unaware of the problems that restrictive
673 copyrights (or lack of copyright notices) can cause for
674 the users of their supposedly-free software. It is often
675 worthwhile contacting such authors diplomatically to ask
676 them to modify their license terms. However, this can be a
677 politically difficult thing to do and you should ask for
678 advice on the <tt>debian-legal</tt> mailing list first, as
683 When in doubt about a copyright, send mail to
684 <email>debian-legal@lists.debian.org</email>. Be prepared
685 to provide us with the copyright statement. Software
686 covered by the GPL, public domain software and BSD-like
687 copyrights are safe; be wary of the phrases "commercial
688 use prohibited" and "distribution restricted".
692 <sect id="subsections">
693 <heading>Sections</heading>
696 The packages in the archive areas <em>main</em>,
697 <em>contrib</em> and <em>non-free</em> are grouped further into
698 <em>sections</em> to simplify handling.
702 The archive area and section for each package should be
703 specified in the package's <tt>Section</tt> control record (see
704 <ref id="f-Section">). However, the maintainer of the Debian
705 archive may override this selection to ensure the consistency of
706 the Debian distribution. The <tt>Section</tt> field should be
708 <list compact="compact">
710 <em>section</em> if the package is in the
711 <em>main</em> archive area,
714 <em>area/section</em> if the package is in
715 the <em>contrib</em> or <em>non-free</em>
722 The Debian archive maintainers provide the authoritative
723 list of sections. At present, they are:
779 The additional section <em>debian-installer</em>
780 contains special packages used by the installer and is not used
781 for normal Debian packages.
785 For more information about the sections and their definitions,
786 see the <url id="http://packages.debian.org/unstable/"
787 name="list of sections in unstable">.
791 <sect id="priorities">
792 <heading>Priorities</heading>
795 Each package should have a <em>priority</em> value, which is
796 included in the package's <em>control record</em>
797 (see <ref id="f-Priority">).
798 This information is used by the Debian package management tools to
799 separate high-priority packages from less-important packages.
803 The following <em>priority levels</em> are recognized by the
804 Debian package management tools.
806 <tag><tt>required</tt></tag>
808 Packages which are necessary for the proper
809 functioning of the system (usually, this means that
810 dpkg functionality depends on these packages).
811 Removing a <tt>required</tt> package may cause your
812 system to become totally broken and you may not even
813 be able to use <prgn>dpkg</prgn> to put things back,
814 so only do so if you know what you are doing. Systems
815 with only the <tt>required</tt> packages are probably
816 unusable, but they do have enough functionality to
817 allow the sysadmin to boot and install more software.
819 <tag><tt>important</tt></tag>
821 Important programs, including those which one would
822 expect to find on any Unix-like system. If the
823 expectation is that an experienced Unix person who
824 found it missing would say "What on earth is going on,
825 where is <prgn>foo</prgn>?", it must be an
826 <tt>important</tt> package.<footnote>
827 This is an important criterion because we are
828 trying to produce, amongst other things, a free
831 Other packages without which the system will not run
832 well or be usable must also have priority
833 <tt>important</tt>. This does
834 <em>not</em> include Emacs, the X Window System, TeX
835 or any other large applications. The
836 <tt>important</tt> packages are just a bare minimum of
837 commonly-expected and necessary tools.
839 <tag><tt>standard</tt></tag>
841 These packages provide a reasonably small but not too
842 limited character-mode system. This is what will be
843 installed by default if the user doesn't select anything
844 else. It doesn't include many large applications.
846 <tag><tt>optional</tt></tag>
848 (In a sense everything that isn't required is
849 optional, but that's not what is meant here.) This is
850 all the software that you might reasonably want to
851 install if you didn't know what it was and don't have
852 specialized requirements. This is a much larger system
853 and includes the X Window System, a full TeX
854 distribution, and many applications. Note that
855 optional packages should not conflict with each other.
857 <tag><tt>extra</tt></tag>
859 This contains all packages that conflict with others
860 with required, important, standard or optional
861 priorities, or are only likely to be useful if you
862 already know what they are or have specialized
863 requirements (such as packages containing only detached
870 Packages must not depend on packages with lower priority
871 values (excluding build-time dependencies). In order to
872 ensure this, the priorities of one or more packages may need
881 <heading>Binary packages</heading>
884 The Debian distribution is based on the Debian
885 package management system, called <prgn>dpkg</prgn>. Thus,
886 all packages in the Debian distribution must be provided
887 in the <tt>.deb</tt> file format.
891 A <tt>.deb</tt> package contains two sets of files: a set of files
892 to install on the system when the package is installed, and a set
893 of files that provide additional metadata about the package or
894 which are executed when the package is installed or removed. This
895 second set of files is called <em>control information files</em>.
896 Among those files are the package maintainer scripts
897 and <file>control</file>, the <qref id="binarycontrolfiles">binary
898 package control file</qref> that contains the control fields for
899 the package. Other control information files include
900 the <qref id="sharedlibs-symbols"><file>symbols</file> file</qref>
901 or <qref id="sharedlibs-shlibdeps"><file>shlibs</file> file</qref>
902 used to store shared library dependency information and
903 the <file>conffiles</file> file that lists the package's
904 configuration files (described in <ref id="config-files">).
908 There is unfortunately a collision of terminology here between
909 control information files and files in the Debian control file
910 format. Throughout this document, a <em>control file</em> refers
911 to a file in the Debian control file format. These files are
912 documented in <ref id="controlfields">. Only files referred to
913 specifically as <em>control information files</em> are the files
914 included in the control information file member of
915 the <file>.deb</file> file format used by binary packages. Most
916 control information files are not in the Debian control file
921 <heading>The package name</heading>
924 Every package must have a name that's unique within the Debian
929 The package name is included in the control field
930 <tt>Package</tt>, the format of which is described
931 in <ref id="f-Package">.
932 The package name is also included as a part of the file name
933 of the <tt>.deb</tt> file.
938 <heading>The version of a package</heading>
941 Every package has a version number recorded in its
942 <tt>Version</tt> control file field, described in
943 <ref id="f-Version">.
947 The package management system imposes an ordering on version
948 numbers, so that it can tell whether packages are being up- or
949 downgraded and so that package system front end applications
950 can tell whether a package it finds available is newer than
951 the one installed on the system. The version number format
952 has the most significant parts (as far as comparison is
953 concerned) at the beginning.
957 If an upstream package has problematic version numbers they
958 should be converted to a sane form for use in the
959 <tt>Version</tt> field.
963 <heading>Version numbers based on dates</heading>
966 In general, Debian packages should use the same version
967 numbers as the upstream sources. However, upstream version
968 numbers based on some date formats (sometimes used for
969 development or "snapshot" releases) will not be ordered
970 correctly by the package management software. For
971 example, <prgn>dpkg</prgn> will consider "96May01" to be
972 greater than "96Dec24".
976 To prevent having to use epochs for every new upstream
977 version, the date-based portion of any upstream version number
978 should be given in a way that sorts correctly: four-digit year
979 first, followed by a two-digit numeric month, followed by a
980 two-digit numeric date, possibly with punctuation between the
985 Native Debian packages (i.e., packages which have been written
986 especially for Debian) whose version numbers include dates
987 should also follow these rules. If punctuation is desired
988 between the date components, remember that hyphen (<tt>-</tt>)
989 cannot be used in native package versions. Period
990 (<tt>.</tt>) is normally a good choice.
996 <sect id="maintainer">
997 <heading>The maintainer of a package</heading>
1000 Every package must have a maintainer, except for orphaned
1001 packages as described below. The maintainer may be one person
1002 or a group of people reachable from a common email address, such
1003 as a mailing list. The maintainer is responsible for
1004 maintaining the Debian packaging files, evaluating and
1005 responding appropriately to reported bugs, uploading new
1006 versions of the package (either directly or through a sponsor),
1007 ensuring that the package is placed in the appropriate archive
1008 area and included in Debian releases as appropriate for the
1009 stability and utility of the package, and requesting removal of
1010 the package from the Debian distribution if it is no longer
1011 useful or maintainable.
1015 The maintainer must be specified in the <tt>Maintainer</tt>
1016 control field with their correct name and a working email
1017 address. The email address given in the <tt>Maintainer</tt>
1018 control field must accept mail from those role accounts in
1019 Debian used to send automated mails regarding the package. This
1020 includes non-spam mail from the bug-tracking system, all mail
1021 from the Debian archive maintenance software, and other role
1022 accounts or automated processes that are commonly agreed on by
1023 the project.<footnote>
1024 A sample implementation of such a whitelist written for the
1025 Mailman mailing list management software is used for mailing
1026 lists hosted by alioth.debian.org.
1028 If one person or team maintains several packages, they should
1029 use the same form of their name and email address in
1030 the <tt>Maintainer</tt> fields of those packages.
1034 The format of the <tt>Maintainer</tt> control field is
1035 described in <ref id="f-Maintainer">.
1039 If the maintainer of the package is a team of people with a
1040 shared email address, the <tt>Uploaders</tt> control field must
1041 be present and must contain at least one human with their
1042 personal email address. See <ref id="f-Uploaders"> for the
1043 syntax of that field.
1047 An orphaned package is one with no current maintainer. Orphaned
1048 packages should have their <tt>Maintainer</tt> control field set
1049 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1050 These packages are considered maintained by the Debian project
1051 as a whole until someone else volunteers to take over
1052 maintenance.<footnote>
1053 The detailed procedure for gracefully orphaning a package can
1054 be found in the Debian Developer's Reference
1055 (see <ref id="related">).
1060 <sect id="descriptions">
1061 <heading>The description of a package</heading>
1064 Every Debian package must have a <tt>Description</tt> control
1065 field which contains a synopsis and extended description of the
1066 package. Technical information about the format of the
1067 <tt>Description</tt> field is in <ref id="f-Description">.
1071 The description should describe the package (the program) to a
1072 user (system administrator) who has never met it before so that
1073 they have enough information to decide whether they want to
1074 install it. This description should not just be copied verbatim
1075 from the program's documentation.
1079 Put important information first, both in the synopsis and
1080 extended description. Sometimes only the first part of the
1081 synopsis or of the description will be displayed. You can
1082 assume that there will usually be a way to see the whole
1083 extended description.
1087 The description should also give information about the
1088 significant dependencies and conflicts between this package
1089 and others, so that the user knows why these dependencies and
1090 conflicts have been declared.
1094 Instructions for configuring or using the package should
1095 not be included (that is what installation scripts,
1096 manual pages, info files, etc., are for). Copyright
1097 statements and other administrivia should not be included
1098 either (that is what the copyright file is for).
1101 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1104 The single line synopsis should be kept brief - certainly
1105 under 80 characters.
1109 Do not include the package name in the synopsis line. The
1110 display software knows how to display this already, and you
1111 do not need to state it. Remember that in many situations
1112 the user may only see the synopsis line - make it as
1113 informative as you can.
1118 <sect1 id="extendeddesc"><heading>The extended description</heading>
1121 Do not try to continue the single line synopsis into the
1122 extended description. This will not work correctly when
1123 the full description is displayed, and makes no sense
1124 where only the summary (the single line synopsis) is
1129 The extended description should describe what the package
1130 does and how it relates to the rest of the system (in terms
1131 of, for example, which subsystem it is which part of).
1135 The description field needs to make sense to anyone, even
1136 people who have no idea about any of the things the
1137 package deals with.<footnote>
1138 The blurb that comes with a program in its
1139 announcements and/or <prgn>README</prgn> files is
1140 rarely suitable for use in a description. It is
1141 usually aimed at people who are already in the
1142 community where the package is used.
1150 <sect id="dependencies">
1151 <heading>Dependencies</heading>
1154 Every package must specify the dependency information
1155 about other packages that are required for the first to
1160 For example, a dependency entry must be provided for any
1161 shared libraries required by a dynamically-linked executable
1162 binary in a package.
1166 Packages are not required to declare any dependencies they
1167 have on other packages which are marked <tt>Essential</tt>
1168 (see below), and should not do so unless they depend on a
1169 particular version of that package.<footnote>
1171 Essential is needed in part to avoid unresolvable dependency
1172 loops on upgrade. If packages add unnecessary dependencies
1173 on packages in this set, the chances that there
1174 <strong>will</strong> be an unresolvable dependency loop
1175 caused by forcing these Essential packages to be configured
1176 first before they need to be is greatly increased. It also
1177 increases the chances that frontends will be unable to
1178 <strong>calculate</strong> an upgrade path, even if one
1182 Also, functionality is rarely ever removed from the
1183 Essential set, but <em>packages</em> have been removed from
1184 the Essential set when the functionality moved to a
1185 different package. So depending on these packages <em>just
1186 in case</em> they stop being essential does way more harm
1193 Sometimes, unpacking one package requires that another package
1194 be first unpacked <em>and</em> configured. In this case, the
1195 depending package must specify this dependency in
1196 the <tt>Pre-Depends</tt> control field.
1200 You should not specify a <tt>Pre-Depends</tt> entry for a
1201 package before this has been discussed on the
1202 <tt>debian-devel</tt> mailing list and a consensus about
1203 doing that has been reached.
1207 The format of the package interrelationship control fields is
1208 described in <ref id="relationships">.
1212 <sect id="virtual_pkg">
1213 <heading>Virtual packages</heading>
1216 Sometimes, there are several packages which offer
1217 more-or-less the same functionality. In this case, it's
1218 useful to define a <em>virtual package</em> whose name
1219 describes that common functionality. (The virtual
1220 packages only exist logically, not physically; that's why
1221 they are called <em>virtual</em>.) The packages with this
1222 particular function will then <em>provide</em> the virtual
1223 package. Thus, any other package requiring that function
1224 can simply depend on the virtual package without having to
1225 specify all possible packages individually.
1229 All packages should use virtual package names where
1230 appropriate, and arrange to create new ones if necessary.
1231 They should not use virtual package names (except privately,
1232 amongst a cooperating group of packages) unless they have
1233 been agreed upon and appear in the list of virtual package
1234 names. (See also <ref id="virtual">)
1238 The latest version of the authoritative list of virtual
1239 package names can be found in the <tt>debian-policy</tt> package.
1240 It is also available from the Debian web mirrors at
1241 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1242 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1246 The procedure for updating the list is described in the preface
1253 <heading>Base system</heading>
1256 The <tt>base system</tt> is a minimum subset of the Debian
1257 system that is installed before everything else
1258 on a new system. Only very few packages are allowed to form
1259 part of the base system, in order to keep the required disk
1264 The base system consists of all those packages with priority
1265 <tt>required</tt> or <tt>important</tt>. Many of them will
1266 be tagged <tt>essential</tt> (see below).
1271 <heading>Essential packages</heading>
1274 Essential is defined as the minimal set of functionality that
1275 must be available and usable on the system at all times, even
1276 when packages are in the "Unpacked" state.
1277 Packages are tagged <tt>essential</tt> for a system using the
1278 <tt>Essential</tt> control field. The format of the
1279 <tt>Essential</tt> control field is described in <ref
1284 Since these packages cannot be easily removed (one has to
1285 specify an extra <em>force option</em> to
1286 <prgn>dpkg</prgn> to do so), this flag must not be used
1287 unless absolutely necessary. A shared library package
1288 must not be tagged <tt>essential</tt>; dependencies will
1289 prevent its premature removal, and we need to be able to
1290 remove it when it has been superseded.
1294 Since dpkg will not prevent upgrading of other packages
1295 while an <tt>essential</tt> package is in an unconfigured
1296 state, all <tt>essential</tt> packages must supply all of
1297 their core functionality even when unconfigured. If the
1298 package cannot satisfy this requirement it must not be
1299 tagged as essential, and any packages depending on this
1300 package must instead have explicit dependency fields as
1305 Maintainers should take great care in adding any programs,
1306 interfaces, or functionality to <tt>essential</tt> packages.
1307 Packages may assume that functionality provided by
1308 <tt>essential</tt> packages is always available without
1309 declaring explicit dependencies, which means that removing
1310 functionality from the Essential set is very difficult and is
1311 almost never done. Any capability added to an
1312 <tt>essential</tt> package therefore creates an obligation to
1313 support that capability as part of the Essential set in
1318 You must not tag any packages <tt>essential</tt> before
1319 this has been discussed on the <tt>debian-devel</tt>
1320 mailing list and a consensus about doing that has been
1325 <sect id="maintscripts">
1326 <heading>Maintainer Scripts</heading>
1329 The package installation scripts should avoid producing
1330 output which is unnecessary for the user to see and
1331 should rely on <prgn>dpkg</prgn> to stave off boredom on
1332 the part of a user installing many packages. This means,
1333 amongst other things, not passing the <tt>--verbose</tt>
1334 option to <prgn>update-alternatives</prgn>.
1338 Errors which occur during the execution of an installation
1339 script must be checked and the installation must not
1340 continue after an error.
1344 Note that in general <ref id="scripts"> applies to package
1345 maintainer scripts, too.
1349 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1350 to another package without consulting the maintainer of that
1351 package first. When adding or removing diversions, package
1352 maintainer scripts must provide the <tt>--package</tt> flag
1353 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1357 All packages which supply an instance of a common command
1358 name (or, in general, filename) should generally use
1359 <prgn>update-alternatives</prgn>, so that they may be
1360 installed together. If <prgn>update-alternatives</prgn>
1361 is not used, then each package must use
1362 <tt>Conflicts</tt> to ensure that other packages are
1363 removed. (In this case, it may be appropriate to
1364 specify a conflict against earlier versions of something
1365 that previously did not use
1366 <prgn>update-alternatives</prgn>; this is an exception to
1367 the usual rule that versioned conflicts should be
1371 <sect1 id="maintscriptprompt">
1372 <heading>Prompting in maintainer scripts</heading>
1374 Package maintainer scripts may prompt the user if
1375 necessary. Prompting must be done by communicating
1376 through a program, such as <prgn>debconf</prgn>, which
1377 conforms to the Debian Configuration Management
1378 Specification, version 2 or higher.
1382 Packages which are essential, or which are dependencies of
1383 essential packages, may fall back on another prompting method
1384 if no such interface is available when they are executed.
1388 The Debian Configuration Management Specification is included
1389 in the <file>debconf_specification</file> files in the
1390 <package>debian-policy</package> package.
1391 It is also available from the Debian web mirrors at
1392 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1393 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1397 Packages which use the Debian Configuration Management
1398 Specification may contain the additional control information
1399 files <file>config</file>
1400 and <file>templates</file>. <file>config</file> is an
1401 additional maintainer script used for package configuration,
1402 and <file>templates</file> contains templates used for user
1403 prompting. The <prgn>config</prgn> script might be run before
1404 the <prgn>preinst</prgn> script and before the package is
1405 unpacked or any of its dependencies or pre-dependencies are
1406 satisfied. Therefore it must work using only the tools
1407 present in <em>essential</em> packages.<footnote>
1408 <package>Debconf</package> or another tool that
1409 implements the Debian Configuration Management
1410 Specification will also be installed, and any
1411 versioned dependencies on it will be satisfied
1412 before preconfiguration begins.
1417 Packages which use the Debian Configuration Management
1418 Specification must allow for translation of their user-visible
1419 messages by using a gettext-based system such as the one
1420 provided by the <package>po-debconf</package> package.
1424 Packages should try to minimize the amount of prompting
1425 they need to do, and they should ensure that the user
1426 will only ever be asked each question once. This means
1427 that packages should try to use appropriate shared
1428 configuration files (such as <file>/etc/papersize</file> and
1429 <file>/etc/news/server</file>), and shared
1430 <package>debconf</package> variables rather than each
1431 prompting for their own list of required pieces of
1436 It also means that an upgrade should not ask the same
1437 questions again, unless the user has used
1438 <tt>dpkg --purge</tt> to remove the package's configuration.
1439 The answers to configuration questions should be stored in an
1440 appropriate place in <file>/etc</file> so that the user can
1441 modify them, and how this has been done should be
1446 If a package has a vitally important piece of
1447 information to pass to the user (such as "don't run me
1448 as I am, you must edit the following configuration files
1449 first or you risk your system emitting badly-formatted
1450 messages"), it should display this in the
1451 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1452 prompt the user to hit return to acknowledge the
1453 message. Copyright messages do not count as vitally
1454 important (they belong in
1455 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1456 neither do instructions on how to use a program (these
1457 should be in on-line documentation, where all the users
1462 Any necessary prompting should almost always be confined
1463 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1464 script. If it is done in the <prgn>postinst</prgn>, it
1465 should be protected with a conditional so that
1466 unnecessary prompting doesn't happen if a package's
1467 installation fails and the <prgn>postinst</prgn> is
1468 called with <tt>abort-upgrade</tt>,
1469 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1479 <heading>Source packages</heading>
1481 <sect id="standardsversion">
1482 <heading>Standards conformance</heading>
1485 Source packages should specify the most recent version number
1486 of this policy document with which your package complied
1487 when it was last updated.
1491 This information may be used to file bug reports
1492 automatically if your package becomes too much out of date.
1496 The version is specified in the <tt>Standards-Version</tt>
1498 The format of the <tt>Standards-Version</tt> field is
1499 described in <ref id="f-Standards-Version">.
1503 You should regularly, and especially if your package has
1504 become out of date, check for the newest Policy Manual
1505 available and update your package, if necessary. When your
1506 package complies with the new standards you should update the
1507 <tt>Standards-Version</tt> source package field and
1508 release it.<footnote>
1509 See the file <file>upgrading-checklist</file> for
1510 information about policy which has changed between
1511 different versions of this document.
1517 <sect id="pkg-relations">
1518 <heading>Package relationships</heading>
1521 Source packages should specify which binary packages they
1522 require to be installed or not to be installed in order to
1523 build correctly. For example, if building a package
1524 requires a certain compiler, then the compiler should be
1525 specified as a build-time dependency.
1529 It is not necessary to explicitly specify build-time
1530 relationships on a minimal set of packages that are always
1531 needed to compile, link and put in a Debian package a
1532 standard "Hello World!" program written in C or C++. The
1533 required packages are called <em>build-essential</em>, and
1534 an informational list can be found in
1535 <file>/usr/share/doc/build-essential/list</file> (which is
1536 contained in the <tt>build-essential</tt>
1539 <list compact="compact">
1541 This allows maintaining the list separately
1542 from the policy documents (the list does not
1543 need the kind of control that the policy
1547 Having a separate package allows one to install
1548 the build-essential packages on a machine, as
1549 well as allowing other packages such as tasks to
1550 require installation of the build-essential
1551 packages using the depends relation.
1554 The separate package allows bug reports against
1555 the list to be categorized separately from
1556 the policy management process in the BTS.
1563 When specifying the set of build-time dependencies, one
1564 should list only those packages explicitly required by the
1565 build. It is not necessary to list packages which are
1566 required merely because some other package in the list of
1567 build-time dependencies depends on them.<footnote>
1568 The reason for this is that dependencies change, and
1569 you should list all those packages, and <em>only</em>
1570 those packages that <em>you</em> need directly. What
1571 others need is their business. For example, if you
1572 only link against <file>libimlib</file>, you will need to
1573 build-depend on <package>libimlib2-dev</package> but
1574 not against any <tt>libjpeg*</tt> packages, even
1575 though <tt>libimlib2-dev</tt> currently depends on
1576 them: installation of <package>libimlib2-dev</package>
1577 will automatically ensure that all of its run-time
1578 dependencies are satisfied.
1583 If build-time dependencies are specified, it must be
1584 possible to build the package and produce working binaries
1585 on a system with only essential and build-essential
1586 packages installed and also those required to satisfy the
1587 build-time relationships (including any implied
1588 relationships). In particular, this means that version
1589 clauses should be used rigorously in build-time
1590 relationships so that one cannot produce bad or
1591 inconsistently configured packages when the relationships
1592 are properly satisfied.
1596 <ref id="relationships"> explains the technical details.
1601 <heading>Changes to the upstream sources</heading>
1604 If changes to the source code are made that are not
1605 specific to the needs of the Debian system, they should be
1606 sent to the upstream authors in whatever form they prefer
1607 so as to be included in the upstream version of the
1612 If you need to configure the package differently for
1613 Debian or for Linux, and the upstream source doesn't
1614 provide a way to do so, you should add such configuration
1615 facilities (for example, a new <prgn>autoconf</prgn> test
1616 or <tt>#define</tt>) and send the patch to the upstream
1617 authors, with the default set to the way they originally
1618 had it. You can then easily override the default in your
1619 <file>debian/rules</file> or wherever is appropriate.
1623 You should make sure that the <prgn>configure</prgn> utility
1624 detects the correct architecture specification string
1625 (refer to <ref id="arch-spec"> for details).
1629 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1630 <prgn>configure</prgn> scripts are used, you should edit the
1631 <file>.in</file> files rather than editing the
1632 <prgn>Makefile</prgn> directly. This allows the user to
1633 reconfigure the package if necessary. You should
1634 <em>not</em> configure the package and edit the generated
1635 <prgn>Makefile</prgn>! This makes it impossible for someone
1636 else to later reconfigure the package without losing the
1642 <sect id="dpkgchangelog">
1643 <heading>Debian changelog: <file>debian/changelog</file></heading>
1646 Changes in the Debian version of the package should be
1647 briefly explained in the Debian changelog file
1648 <file>debian/changelog</file>.<footnote>
1650 Mistakes in changelogs are usually best rectified by
1651 making a new changelog entry rather than "rewriting
1652 history" by editing old changelog entries.
1655 This includes modifications
1656 made in the Debian package compared to the upstream one
1657 as well as other changes and updates to the package.
1659 Although there is nothing stopping an author who is also
1660 the Debian maintainer from using this changelog for all
1661 their changes, it will have to be renamed if the Debian
1662 and upstream maintainers become different people. In such
1663 a case, however, it might be better to maintain the package
1664 as a non-native package.
1669 The format of the <file>debian/changelog</file> allows the
1670 package building tools to discover which version of the package
1671 is being built and find out other release-specific information.
1675 That format is a series of entries like this:
1677 <example compact="compact">
1678 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1680 [optional blank line(s), stripped]
1682 * <var>change details</var>
1683 <var>more change details</var>
1685 [blank line(s), included in output of dpkg-parsechangelog]
1687 * <var>even more change details</var>
1689 [optional blank line(s), stripped]
1691 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1696 <var>package</var> and <var>version</var> are the source
1697 package name and version number.
1701 <var>distribution(s)</var> lists the distributions where
1702 this version should be installed when it is uploaded - it
1703 is copied to the <tt>Distribution</tt> field in the
1704 <file>.changes</file> file. See <ref id="f-Distribution">.
1708 <var>urgency</var> is the value for the <tt>Urgency</tt>
1709 field in the <file>.changes</file> file for the upload
1710 (see <ref id="f-Urgency">). It is not possible to specify
1711 an urgency containing commas; commas are used to separate
1712 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1713 <prgn>dpkg</prgn> changelog format (though there is
1714 currently only one useful <var>keyword</var>,
1719 The change details may in fact be any series of lines
1720 starting with at least two spaces, but conventionally each
1721 change starts with an asterisk and a separating space and
1722 continuation lines are indented so as to bring them in
1723 line with the start of the text above. Blank lines may be
1724 used here to separate groups of changes, if desired.
1728 If this upload resolves bugs recorded in the Bug Tracking
1729 System (BTS), they may be automatically closed on the
1730 inclusion of this package into the Debian archive by
1731 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1732 in the change details.<footnote>
1733 To be precise, the string should match the following
1734 Perl regular expression:
1736 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1738 Then all of the bug numbers listed will be closed by the
1739 archive maintenance software (<prgn>dak</prgn>) using the
1740 <var>version</var> of the changelog entry.
1742 This information is conveyed via the <tt>Closes</tt> field
1743 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1747 The maintainer name and email address used in the changelog
1748 should be the details of the person who prepared this release of
1749 the package. They are <em>not</em> necessarily those of the
1750 uploader or usual package maintainer.<footnote>
1751 In the case of a sponsored upload, the uploader signs the
1752 files, but the changelog maintainer name and address are those
1753 of the person who prepared this release. If the preparer of
1754 the release is not one of the usual maintainers of the package
1756 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1757 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1758 fields of the package), the first line of the changelog is
1759 conventionally used to explain why a non-maintainer is
1760 uploading the package. The Debian Developer's Reference
1761 (see <ref id="related">) documents the conventions
1763 The information here will be copied to the <tt>Changed-By</tt>
1764 field in the <tt>.changes</tt> file
1765 (see <ref id="f-Changed-By">), and then later used to send an
1766 acknowledgement when the upload has been installed.
1770 The <var>date</var> has the following format<footnote>
1771 This is the same as the format generated by <tt>date
1773 </footnote> (compatible and with the same semantics of
1774 RFC 2822 and RFC 5322):
1775 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1777 <list compact="compact">
1779 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1782 dd is a one- or two-digit day of the month (01-31)
1785 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1788 <item>yyyy is the four-digit year (e.g. 2010)</item>
1789 <item>hh is the two-digit hour (00-23)</item>
1790 <item>mm is the two-digit minutes (00-59)</item>
1791 <item>ss is the two-digit seconds (00-60)</item>
1793 +zzzz or -zzzz is the the time zone offset from Coordinated
1794 Universal Time (UTC). "+" indicates that the time is ahead
1795 of (i.e., east of) UTC and "-" indicates that the time is
1796 behind (i.e., west of) UTC. The first two digits indicate
1797 the hour difference from UTC and the last two digits
1798 indicate the number of additional minutes difference from
1799 UTC. The last two digits must be in the range 00-59.
1805 The first "title" line with the package name must start
1806 at the left hand margin. The "trailer" line with the
1807 maintainer and date details must be preceded by exactly
1808 one space. The maintainer details and the date must be
1809 separated by exactly two spaces.
1813 The entire changelog must be encoded in UTF-8.
1817 For more information on placement of the changelog files
1818 within binary packages, please see <ref id="changelogs">.
1822 <sect id="dpkgcopyright">
1823 <heading>Copyright: <file>debian/copyright</file></heading>
1825 Every package must be accompanied by a verbatim copy of its
1826 copyright information and distribution license in the file
1827 <file>/usr/share/doc/<var>package</var>/copyright</file>
1828 (see <ref id="copyrightfile"> for further details). Also see
1829 <ref id="pkgcopyright"> for further considerations related
1830 to copyrights for packages.
1834 <heading>Error trapping in makefiles</heading>
1837 When <prgn>make</prgn> invokes a command in a makefile
1838 (including your package's upstream makefiles and
1839 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1840 means that <prgn>sh</prgn>'s usual bad error handling
1841 properties apply: if you include a miniature script as one
1842 of the commands in your makefile you'll find that if you
1843 don't do anything about it then errors are not detected
1844 and <prgn>make</prgn> will blithely continue after
1849 Every time you put more than one shell command (this
1850 includes using a loop) in a makefile command you
1851 must make sure that errors are trapped. For
1852 simple compound commands, such as changing directory and
1853 then running a program, using <tt>&&</tt> rather
1854 than semicolon as a command separator is sufficient. For
1855 more complex commands including most loops and
1856 conditionals you should include a separate <tt>set -e</tt>
1857 command at the start of every makefile command that's
1858 actually one of these miniature shell scripts.
1862 <sect id="timestamps">
1863 <heading>Time Stamps</heading>
1865 Maintainers should preserve the modification times of the
1866 upstream source files in a package, as far as is reasonably
1868 The rationale is that there is some information conveyed
1869 by knowing the age of the file, for example, you could
1870 recognize that some documentation is very old by looking
1871 at the modification time, so it would be nice if the
1872 modification time of the upstream source would be
1878 <sect id="restrictions">
1879 <heading>Restrictions on objects in source packages</heading>
1882 The source package may not contain any hard links<footnote>
1884 This is not currently detected when building source
1885 packages, but only when extracting
1889 Hard links may be permitted at some point in the
1890 future, but would require a fair amount of
1893 </footnote>, device special files, sockets or setuid or
1894 setgid files.<footnote>
1895 Setgid directories are allowed.
1900 <sect id="debianrules">
1901 <heading>Main building script: <file>debian/rules</file></heading>
1904 This file must be an executable makefile, and contains the
1905 package-specific recipes for compiling the package and
1906 building binary package(s) from the source.
1910 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1911 so that it can be invoked by saying its name rather than
1912 invoking <prgn>make</prgn> explicitly. That is, invoking
1913 either of <tt>make -f debian/rules <em>args...</em></tt>
1914 or <tt>./debian/rules <em>args...</em></tt> must result in
1919 The following targets are required and must be implemented
1920 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1921 <tt>binary-arch</tt>, <tt>binary-indep</tt>, <tt>build</tt>,
1922 <tt>build-arch</tt> and <tt>build-indep</tt>.
1923 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1927 Since an interactive <file>debian/rules</file> script makes it
1928 impossible to auto-compile that package and also makes it hard
1929 for other people to reproduce the same binary package, all
1930 required targets must be non-interactive. It also follows that
1931 any target that these targets depend on must also be
1936 The targets are as follows:
1938 <tag><tt>build</tt> (required)</tag>
1941 The <tt>build</tt> target should perform all the
1942 configuration and compilation of the package.
1943 If a package has an interactive pre-build
1944 configuration routine, the Debian source package
1945 must either be built after this has taken place (so
1946 that the binary package can be built without rerunning
1947 the configuration) or the configuration routine
1948 modified to become non-interactive. (The latter is
1949 preferable if there are architecture-specific features
1950 detected by the configuration routine.)
1954 For some packages, notably ones where the same
1955 source tree is compiled in different ways to produce
1956 two binary packages, the <tt>build</tt> target
1957 does not make much sense. For these packages it is
1958 good enough to provide two (or more) targets
1959 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1960 for each of the ways of building the package, and a
1961 <tt>build</tt> target that does nothing. The
1962 <tt>binary</tt> target will have to build the
1963 package in each of the possible ways and make the
1964 binary package out of each.
1968 The <tt>build</tt> target must not do anything
1969 that might require root privilege.
1973 The <tt>build</tt> target may need to run the
1974 <tt>clean</tt> target first - see below.
1978 When a package has a configuration and build routine
1979 which takes a long time, or when the makefiles are
1980 poorly designed, or when <tt>build</tt> needs to
1981 run <tt>clean</tt> first, it is a good idea to
1982 <tt>touch build</tt> when the build process is
1983 complete. This will ensure that if <tt>debian/rules
1984 build</tt> is run again it will not rebuild the whole
1986 Another common way to do this is for <tt>build</tt>
1987 to depend on <prgn>build-stamp</prgn> and to do
1988 nothing else, and for the <prgn>build-stamp</prgn>
1989 target to do the building and to <tt>touch
1990 build-stamp</tt> on completion. This is
1991 especially useful if the build routine creates a
1992 file or directory called <tt>build</tt>; in such a
1993 case, <tt>build</tt> will need to be listed as
1994 a phony target (i.e., as a dependency of the
1995 <tt>.PHONY</tt> target). See the documentation of
1996 <prgn>make</prgn> for more information on phony
2002 <tag><tt>build-arch</tt> (required),
2003 <tt>build-indep</tt> (required)
2007 The <tt>build-arch</tt> target must
2008 perform all the configuration and compilation required for
2009 producing all architecture-dependant binary packages
2010 (those packages for which the body of the
2011 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2012 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2013 target must perform all the configuration
2014 and compilation required for producing all
2015 architecture-independent binary packages (those packages
2016 for which the body of the <tt>Architecture</tt> field
2017 in <tt>debian/control</tt> is <tt>all</tt>).
2018 The <tt>build</tt> target
2019 should either depend on those targets or take the same
2020 actions as invoking those targets would perform.<footnote>
2021 This split allows binary-only builds to not install the
2022 dependencies required for the <tt>build-indep</tt>
2023 target and skip any resource-intensive build tasks that
2024 are only required when building architecture-independent
2030 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2031 must not do anything that might require root privilege.
2035 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2036 (required), <tt>binary-indep</tt> (required)
2040 The <tt>binary</tt> target must be all that is
2041 necessary for the user to build the binary package(s)
2042 produced from this source package. It is
2043 split into two parts: <prgn>binary-arch</prgn> builds
2044 the binary packages which are specific to a particular
2045 architecture, and <tt>binary-indep</tt> builds
2046 those which are not.
2049 <tt>binary</tt> may be (and commonly is) a target with
2050 no commands which simply depends on
2051 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2054 Both <tt>binary-*</tt> targets should depend on the
2055 <tt>build</tt> target, or on the appropriate
2056 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2057 provided, so that the package is built if it has not
2058 been already. It should then create the relevant
2059 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2060 make their control files and <prgn>dpkg-deb</prgn> to
2061 build them and place them in the parent of the top
2066 Both the <tt>binary-arch</tt> and
2067 <tt>binary-indep</tt> targets <em>must</em> exist.
2068 If one of them has nothing to do (which will always be
2069 the case if the source generates only a single binary
2070 package, whether architecture-dependent or not), it
2071 must still exist and must always succeed.
2075 The <tt>binary</tt> targets must be invoked as
2077 The <prgn>fakeroot</prgn> package often allows one
2078 to build a package correctly even without being
2084 <tag><tt>clean</tt> (required)</tag>
2087 This must undo any effects that the <tt>build</tt>
2088 and <tt>binary</tt> targets may have had, except
2089 that it should leave alone any output files created in
2090 the parent directory by a run of a <tt>binary</tt>
2095 If a <tt>build</tt> file is touched at the end of
2096 the <tt>build</tt> target, as suggested above, it
2097 should be removed as the first action that
2098 <tt>clean</tt> performs, so that running
2099 <tt>build</tt> again after an interrupted
2100 <tt>clean</tt> doesn't think that everything is
2105 The <tt>clean</tt> target may need to be
2106 invoked as root if <tt>binary</tt> has been
2107 invoked since the last <tt>clean</tt>, or if
2108 <tt>build</tt> has been invoked as root (since
2109 <tt>build</tt> may create directories, for
2114 <tag><tt>get-orig-source</tt> (optional)</tag>
2117 This target fetches the most recent version of the
2118 original source package from a canonical archive site
2119 (via FTP or WWW, for example), does any necessary
2120 rearrangement to turn it into the original source
2121 tar file format described below, and leaves it in the
2126 This target may be invoked in any directory, and
2127 should take care to clean up any temporary files it
2132 This target is optional, but providing it if
2133 possible is a good idea.
2137 <tag><tt>patch</tt> (optional)</tag>
2140 This target performs whatever additional actions are
2141 required to make the source ready for editing (unpacking
2142 additional upstream archives, applying patches, etc.).
2143 It is recommended to be implemented for any package where
2144 <tt>dpkg-source -x</tt> does not result in source ready
2145 for additional modification. See
2146 <ref id="readmesource">.
2152 The <tt>build</tt>, <tt>binary</tt> and
2153 <tt>clean</tt> targets must be invoked with the current
2154 directory being the package's top-level directory.
2159 Additional targets may exist in <file>debian/rules</file>,
2160 either as published or undocumented interfaces or for the
2161 package's internal use.
2165 The architectures we build on and build for are determined
2166 by <prgn>make</prgn> variables using the
2167 utility <prgn>dpkg-architecture</prgn>.
2168 You can determine the Debian architecture and the GNU style
2169 architecture specification string for the build architecture as
2170 well as for the host architecture. The build architecture is
2171 the architecture on which <file>debian/rules</file> is run and
2172 the package build is performed. The host architecture is the
2173 architecture on which the resulting package will be installed
2174 and run. These are normally the same, but may be different in
2175 the case of cross-compilation (building packages for one
2176 architecture on machines of a different architecture).
2180 Here is a list of supported <prgn>make</prgn> variables:
2181 <list compact="compact">
2183 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2186 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2189 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2192 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2193 specification string)
2196 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2197 <tt>DEB_*_GNU_TYPE</tt>)
2200 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2201 <tt>DEB_*_GNU_TYPE</tt>)
2203 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2204 the build architecture or <tt>HOST</tt> for specification of the
2209 Backward compatibility can be provided in the rules file
2210 by setting the needed variables to suitable default
2211 values; please refer to the documentation of
2212 <prgn>dpkg-architecture</prgn> for details.
2216 It is important to understand that the <tt>DEB_*_ARCH</tt>
2217 string only determines which Debian architecture we are
2218 building on or for. It should not be used to get the CPU
2219 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2220 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2221 GNU style variables should generally only be used with upstream
2225 <sect1 id="debianrules-options">
2226 <heading><file>debian/rules</file> and
2227 <tt>DEB_BUILD_OPTIONS</tt></heading>
2230 Supporting the standardized environment variable
2231 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2232 contain several flags to change how a package is compiled and
2233 built. Each flag must be in the form <var>flag</var> or
2234 <var>flag</var>=<var>options</var>. If multiple flags are
2235 given, they must be separated by whitespace.<footnote>
2236 Some packages support any delimiter, but whitespace is the
2237 easiest to parse inside a makefile and avoids ambiguity with
2238 flag values that contain commas.
2240 <var>flag</var> must start with a lowercase letter
2241 (<tt>a-z</tt>) and consist only of lowercase letters,
2242 numbers (<tt>0-9</tt>), and the characters
2243 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2244 <var>options</var> must not contain whitespace. The same
2245 tag should not be given multiple times with conflicting
2246 values. Package maintainers may assume that
2247 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2251 The meaning of the following tags has been standardized:
2255 This tag says to not run any build-time test suite
2256 provided by the package.
2260 The presence of this tag means that the package should
2261 be compiled with a minimum of optimization. For C
2262 programs, it is best to add <tt>-O0</tt> to
2263 <tt>CFLAGS</tt> (although this is usually the default).
2264 Some programs might fail to build or run at this level
2265 of optimization; it may be necessary to use
2266 <tt>-O1</tt>, for example.
2270 This tag means that the debugging symbols should not be
2271 stripped from the binary during installation, so that
2272 debugging information may be included in the package.
2274 <tag>parallel=n</tag>
2276 This tag means that the package should be built using up
2277 to <tt>n</tt> parallel processes if the package build
2278 system supports this.<footnote>
2279 Packages built with <tt>make</tt> can often implement
2280 this by passing the <tt>-j</tt><var>n</var> option to
2283 If the package build system does not support parallel
2284 builds, this string must be ignored. If the package
2285 build system only supports a lower level of concurrency
2286 than <var>n</var>, the package should be built using as
2287 many parallel processes as the package build system
2288 supports. It is up to the package maintainer to decide
2289 whether the package build times are long enough and the
2290 package build system is robust enough to make supporting
2291 parallel builds worthwhile.
2297 Unknown flags must be ignored by <file>debian/rules</file>.
2301 The following makefile snippet is an example of how one may
2302 implement the build options; you will probably have to
2303 massage this example in order to make it work for your
2305 <example compact="compact">
2308 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2309 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2310 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2311 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2313 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2318 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2319 INSTALL_PROGRAM += -s
2321 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2322 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2323 MAKEFLAGS += -j$(NUMJOBS)
2328 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2329 # Code to run the package test suite.
2336 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2337 <sect id="substvars">
2338 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2341 When <prgn>dpkg-gencontrol</prgn>
2342 generates <qref id="binarycontrolfiles">binary package control
2343 files</qref> (<file>DEBIAN/control</file>), it performs variable
2344 substitutions on its output just before writing it. Variable
2345 substitutions have the form <tt>${<var>variable</var>}</tt>.
2346 The optional file <file>debian/substvars</file> contains
2347 variable substitutions to be used; variables can also be set
2348 directly from <file>debian/rules</file> using the <tt>-V</tt>
2349 option to the source packaging commands, and certain predefined
2350 variables are also available.
2354 The <file>debian/substvars</file> file is usually generated and
2355 modified dynamically by <file>debian/rules</file> targets, in
2356 which case it must be removed by the <tt>clean</tt> target.
2360 See <manref name="deb-substvars" section="5"> for full
2361 details about source variable substitutions, including the
2362 format of <file>debian/substvars</file>.</p>
2365 <sect id="debianwatch">
2366 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2369 This is an optional, recommended configuration file for the
2370 <tt>uscan</tt> utility which defines how to automatically scan
2371 ftp or http sites for newly available updates of the
2372 package. This is used Debian QA
2373 tools to help with quality control and maintenance of the
2374 distribution as a whole.
2379 <sect id="debianfiles">
2380 <heading>Generated files list: <file>debian/files</file></heading>
2383 This file is not a permanent part of the source tree; it
2384 is used while building packages to record which files are
2385 being generated. <prgn>dpkg-genchanges</prgn> uses it
2386 when it generates a <file>.changes</file> file.
2390 It should not exist in a shipped source package, and so it
2391 (and any backup files or temporary files such as
2392 <file>files.new</file><footnote>
2393 <file>files.new</file> is used as a temporary file by
2394 <prgn>dpkg-gencontrol</prgn> and
2395 <prgn>dpkg-distaddfile</prgn> - they write a new
2396 version of <tt>files</tt> here before renaming it,
2397 to avoid leaving a corrupted copy if an error
2399 </footnote>) should be removed by the
2400 <tt>clean</tt> target. It may also be wise to
2401 ensure a fresh start by emptying or removing it at the
2402 start of the <tt>binary</tt> target.
2406 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2407 package, it adds an entry to <file>debian/files</file> for the
2408 <file>.deb</file> file that will be created when <tt>dpkg-deb
2409 --build</tt> is run for that binary package. So for most
2410 packages all that needs to be done with this file is to
2411 delete it in the <tt>clean</tt> target.
2415 If a package upload includes files besides the source
2416 package and any binary packages whose control files were
2417 made with <prgn>dpkg-gencontrol</prgn> then they should be
2418 placed in the parent of the package's top-level directory
2419 and <prgn>dpkg-distaddfile</prgn> should be called to add
2420 the file to the list in <file>debian/files</file>.</p>
2423 <sect id="embeddedfiles">
2424 <heading>Convenience copies of code</heading>
2427 Some software packages include in their distribution convenience
2428 copies of code from other software packages, generally so that
2429 users compiling from source don't have to download multiple
2430 packages. Debian packages should not make use of these
2431 convenience copies unless the included package is explicitly
2432 intended to be used in this way.<footnote>
2433 For example, parts of the GNU build system work like this.
2435 If the included code is already in the Debian archive in the
2436 form of a library, the Debian packaging should ensure that
2437 binary packages reference the libraries already in Debian and
2438 the convenience copy is not used. If the included code is not
2439 already in Debian, it should be packaged separately as a
2440 prerequisite if possible.
2442 Having multiple copies of the same code in Debian is
2443 inefficient, often creates either static linking or shared
2444 library conflicts, and, most importantly, increases the
2445 difficulty of handling security vulnerabilities in the
2451 <sect id="readmesource">
2452 <heading>Source package handling:
2453 <file>debian/README.source</file></heading>
2456 If running <prgn>dpkg-source -x</prgn> on a source package
2457 doesn't produce the source of the package, ready for editing,
2458 and allow one to make changes and run
2459 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2460 without taking any additional steps, creating a
2461 <file>debian/README.source</file> documentation file is
2462 recommended. This file should explain how to do all of the
2465 <item>Generate the fully patched source, in a form ready for
2466 editing, that would be built to create Debian
2467 packages. Doing this with a <tt>patch</tt> target in
2468 <file>debian/rules</file> is recommended; see
2469 <ref id="debianrules">.</item>
2470 <item>Modify the source and save those modifications so that
2471 they will be applied when building the package.</item>
2472 <item>Remove source modifications that are currently being
2473 applied when building the package.</item>
2474 <item>Optionally, document what steps are necessary to
2475 upgrade the Debian source package to a new upstream version,
2476 if applicable.</item>
2478 This explanation should include specific commands and mention
2479 any additional required Debian packages. It should not assume
2480 familiarity with any specific Debian packaging system or patch
2485 This explanation may refer to a documentation file installed by
2486 one of the package's build dependencies provided that the
2487 referenced documentation clearly explains these tasks and is not
2488 a general reference manual.
2492 <file>debian/README.source</file> may also include any other
2493 information that would be helpful to someone modifying the
2494 source package. Even if the package doesn't fit the above
2495 description, maintainers are encouraged to document in a
2496 <file>debian/README.source</file> file any source package with a
2497 particularly complex or unintuitive source layout or build
2498 system (for example, a package that builds the same source
2499 multiple times to generate different binary packages).
2505 <chapt id="controlfields">
2506 <heading>Control files and their fields</heading>
2509 The package management system manipulates data represented in
2510 a common format, known as <em>control data</em>, stored in
2511 <em>control files</em>.
2512 Control files are used for source packages, binary packages and
2513 the <file>.changes</file> files which control the installation
2514 of uploaded files<footnote>
2515 <prgn>dpkg</prgn>'s internal databases are in a similar
2520 <sect id="controlsyntax">
2521 <heading>Syntax of control files</heading>
2524 A control file consists of one or more paragraphs of
2526 The paragraphs are also sometimes referred to as stanzas.
2528 The paragraphs are separated by empty lines. Parsers may accept
2529 lines consisting solely of spaces and tabs as paragraph
2530 separators, but control files should use empty lines. Some control
2531 files allow only one paragraph; others allow several, in
2532 which case each paragraph usually refers to a different
2533 package. (For example, in source packages, the first
2534 paragraph refers to the source package, and later paragraphs
2535 refer to binary packages generated from the source.) The
2536 ordering of the paragraphs in control files is significant.
2540 Each paragraph consists of a series of data fields. Each field
2541 consists of the field name followed by a colon and then the
2542 data/value associated with that field. The field name is
2543 composed of US-ASCII characters excluding control characters,
2544 space, and colon (i.e., characters in the ranges 33-57 and
2545 59-126, inclusive). Field names must not begin with the comment
2546 character, <tt>#</tt>, nor with the hyphen character, <tt>-</tt>.
2550 The field ends at the end of the line or at the end of the last
2551 continuation line (see below). Horizontal whitespace (spaces
2552 and tabs) may occur immediately before or after the value and is
2553 ignored there; it is conventional to put a single space after
2554 the colon. For example, a field might be:
2555 <example compact="compact">
2558 the field name is <tt>Package</tt> and the field value
2561 <p> Empty field values are only permitted in source package control files
2562 (<file>debian/control</file>). Such fields are ignored.
2565 A paragraph must not contain more than one instance of a
2566 particular field name.
2570 There are three types of fields:
2574 The field, including its value, must be a single line. Folding
2575 of the field is not permitted. This is the default field type
2576 if the definition of the field does not specify a different
2581 The value of a folded field is a logical line that may span
2582 several lines. The lines after the first are called
2583 continuation lines and must start with a space or a tab.
2584 Whitespace, including any newlines, is not significant in the
2585 field values of folded fields.<footnote>
2586 This folding method is similar to RFC 5322, allowing control
2587 files that contain only one paragraph and no multiline fields
2588 to be read by parsers written for RFC 5322.
2591 <tag>multiline</tag>
2593 The value of a multiline field may comprise multiple continuation
2594 lines. The first line of the value, the part on the same line as
2595 the field name, often has special significance or may have to be
2596 empty. Other lines are added following the same syntax as the
2597 continuation lines of the folded fields. Whitespace, including newlines,
2598 is significant in the values of multiline fields.
2604 Whitespace must not appear
2605 inside names (of packages, architectures, files or anything
2606 else) or version numbers, or between the characters of
2607 multi-character version relationships.
2611 The presence and purpose of a field, and the syntax of its
2612 value may differ between types of control files.
2616 Field names are not case-sensitive, but it is usual to
2617 capitalize the field names using mixed case as shown below.
2618 Field values are case-sensitive unless the description of the
2619 field says otherwise.
2623 Paragraph separators (empty lines) and lines consisting only of
2624 spaces and tabs are not allowed within field values or between
2625 fields. Empty lines in field values are usually escaped by
2626 representing them by a space followed by a dot.
2630 Lines starting with # without any preceding whitespace are comments
2631 lines that are only permitted in source package control files
2632 (<file>debian/control</file>). These comment lines are ignored, even
2633 between two continuation lines. They do not end logical lines.
2637 All control files must be encoded in UTF-8.
2641 <sect id="sourcecontrolfiles">
2642 <heading>Source package control files -- <file>debian/control</file></heading>
2645 The <file>debian/control</file> file contains the most vital
2646 (and version-independent) information about the source package
2647 and about the binary packages it creates.
2651 The first paragraph of the control file contains information about
2652 the source package in general. The subsequent sets each describe a
2653 binary package that the source tree builds.
2657 The fields in the general paragraph (the first one, for the source
2660 <list compact="compact">
2661 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2662 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2663 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2664 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2665 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2666 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2667 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2668 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2669 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2674 The fields in the binary package paragraphs are:
2676 <list compact="compact">
2677 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2678 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2679 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2680 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2681 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2682 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2683 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2684 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2685 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2686 <item><qref id="f-Package-Type"><tt>Package-Type</tt></qref></item>
2691 The syntax and semantics of the fields are described below.
2695 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2696 generate control files for binary packages (see below), by
2697 <prgn>dpkg-genchanges</prgn> to generate the
2698 <file>.changes</file> file to accompany the upload, and by
2699 <prgn>dpkg-source</prgn> when it creates the
2700 <file>.dsc</file> source control file as part of a source
2701 archive. Some fields are folded in <file>debian/control</file>,
2702 but not in any other control
2703 file. These tools are responsible for removing the line
2704 breaks from such fields when using fields from
2705 <file>debian/control</file> to generate other control files.
2706 They are also responsible for discarding empty fields.
2710 The fields here may contain variable references - their
2711 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2712 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2713 when they generate output control files.
2714 See <ref id="substvars"> for details.
2718 <sect id="binarycontrolfiles">
2719 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2722 The <file>DEBIAN/control</file> file contains the most vital
2723 (and version-dependent) information about a binary package. It
2724 consists of a single paragraph.
2728 The fields in this file are:
2730 <list compact="compact">
2731 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2732 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2733 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2734 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2735 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2736 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2737 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2738 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2739 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2740 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2741 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2742 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2743 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2748 <sect id="debiansourcecontrolfiles">
2749 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2752 This file consists of a single paragraph, possibly surrounded by
2753 a PGP signature. The fields of that paragraph are listed below.
2754 Their syntax is described above, in <ref id="controlsyntax">.
2756 <list compact="compact">
2757 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2758 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2759 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2760 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2761 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2762 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2763 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2764 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2765 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2766 <item><qref id="f-Dgit"><tt>Dgit</tt></qref></item>
2767 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2768 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2769 <item><qref id="f-Package-List"><tt>Package-List</tt></qref> (recommended)</item>
2770 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2771 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2772 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2777 The Debian source control file is generated by
2778 <prgn>dpkg-source</prgn> when it builds the source
2779 archive, from other files in the source package,
2780 described above. When unpacking, it is checked against
2781 the files and directories in the other parts of the
2787 <sect id="debianchangesfiles">
2788 <heading>Debian changes files -- <file>.changes</file></heading>
2791 The <file>.changes</file> files are used by the Debian archive
2792 maintenance software to process updates to packages. They
2793 consist of a single paragraph, possibly surrounded by a PGP
2794 signature. That paragraph contains information from the
2795 <file>debian/control</file> file and other data about the
2796 source package gathered via <file>debian/changelog</file>
2797 and <file>debian/rules</file>.
2801 <file>.changes</file> files have a format version that is
2802 incremented whenever the documented fields or their meaning
2803 change. This document describes format &changesversion;.
2807 The fields in this file are:
2809 <list compact="compact">
2810 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2811 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2812 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2813 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2814 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2815 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2816 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2817 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2818 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2819 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2820 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2821 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2822 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2823 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2824 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2825 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2830 <sect id="controlfieldslist">
2831 <heading>List of fields</heading>
2833 <sect1 id="f-Source">
2834 <heading><tt>Source</tt></heading>
2837 This field identifies the source package name.
2841 In <file>debian/control</file> or a <file>.dsc</file> file,
2842 this field must contain only the name of the source package.
2846 In a binary package control file or a <file>.changes</file>
2847 file, the source package name may be followed by a version
2848 number in parentheses<footnote>
2849 It is customary to leave a space after the package name
2850 if a version number is specified.
2852 This version number may be omitted (and is, by
2853 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2854 the <tt>Version</tt> field of the binary package in
2855 question. The field itself may be omitted from a binary
2856 package control file when the source package has the same
2857 name and version as the binary package.
2861 Package names (both source and binary,
2862 see <ref id="f-Package">) must consist only of lower case
2863 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2864 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2865 (<tt>.</tt>). They must be at least two characters long and
2866 must start with an alphanumeric character.
2870 <sect1 id="f-Maintainer">
2871 <heading><tt>Maintainer</tt></heading>
2874 The package maintainer's name and email address. The name
2875 must come first, then the email address inside angle
2876 brackets <tt><></tt> (in RFC822 format).
2880 If the maintainer's name contains a full stop then the
2881 whole field will not work directly as an email address due
2882 to a misfeature in the syntax specified in RFC822; a
2883 program using this field as an address must check for this
2884 and correct the problem if necessary (for example by
2885 putting the name in round brackets and moving it to the
2886 end, and bringing the email address forward).
2890 See <ref id="maintainer"> for additional requirements and
2891 information about package maintainers.
2895 <sect1 id="f-Uploaders">
2896 <heading><tt>Uploaders</tt></heading>
2899 List of the names and email addresses of co-maintainers of the
2900 package, if any. If the package has other maintainers besides
2901 the one named in the <qref id="f-Maintainer">Maintainer
2902 field</qref>, their names and email addresses should be listed
2903 here. The format of each entry is the same as that of the
2904 Maintainer field, and multiple entries must be comma
2909 This is normally an optional field, but if
2910 the <tt>Maintainer</tt> control field names a group of people
2911 and a shared email address, the <tt>Uploaders</tt> field must
2912 be present and must contain at least one human with their
2913 personal email address.
2917 The Uploaders field in <file>debian/control</file> can be folded.
2921 <sect1 id="f-Changed-By">
2922 <heading><tt>Changed-By</tt></heading>
2925 The name and email address of the person who prepared this
2926 version of the package, usually a maintainer. The syntax is
2927 the same as for the <qref id="f-Maintainer">Maintainer
2932 <sect1 id="f-Section">
2933 <heading><tt>Section</tt></heading>
2936 This field specifies an application area into which the package
2937 has been classified. See <ref id="subsections">.
2941 When it appears in the <file>debian/control</file> file,
2942 it gives the value for the subfield of the same name in
2943 the <tt>Files</tt> field of the <file>.changes</file> file.
2944 It also gives the default for the same field in the binary
2949 <sect1 id="f-Priority">
2950 <heading><tt>Priority</tt></heading>
2953 This field represents how important it is that the user
2954 have the package installed. See <ref id="priorities">.
2958 When it appears in the <file>debian/control</file> file,
2959 it gives the value for the subfield of the same name in
2960 the <tt>Files</tt> field of the <file>.changes</file> file.
2961 It also gives the default for the same field in the binary
2966 <sect1 id="f-Package">
2967 <heading><tt>Package</tt></heading>
2970 The name of the binary package.
2974 Binary package names must follow the same syntax and
2975 restrictions as source package names. See <ref id="f-Source">
2980 <sect1 id="f-Architecture">
2981 <heading><tt>Architecture</tt></heading>
2984 Depending on context and the control file used, the
2985 <tt>Architecture</tt> field can include the following sets of
2989 A unique single word identifying a Debian machine
2990 architecture as described in <ref id="arch-spec">.
2993 An architecture wildcard identifying a set of Debian
2994 machine architectures, see <ref id="arch-wildcard-spec">.
2995 <tt>any</tt> matches all Debian machine architectures
2996 and is the most frequently used.
2999 <tt>all</tt>, which indicates an
3000 architecture-independent package.
3003 <tt>source</tt>, which indicates a source package.
3009 In the main <file>debian/control</file> file in the source
3010 package, this field may contain the special
3011 value <tt>all</tt>, the special architecture
3012 wildcard <tt>any</tt>, or a list of specific and wildcard
3013 architectures separated by spaces. If <tt>all</tt>
3014 or <tt>any</tt> appears, that value must be the entire
3015 contents of the field. Most packages will use
3016 either <tt>all</tt> or <tt>any</tt>.
3020 Specifying a specific list of architectures indicates that the
3021 source will build an architecture-dependent package only on
3022 architectures included in the list. Specifying a list of
3023 architecture wildcards indicates that the source will build an
3024 architecture-dependent package on only those architectures
3025 that match any of the specified architecture wildcards.
3026 Specifying a list of architectures or architecture wildcards
3027 other than <tt>any</tt> is for the minority of cases where a
3028 program is not portable or is not useful on some
3029 architectures. Where possible, the program should be made
3034 In the Debian source control file <file>.dsc</file>, this
3035 field contains a list of architectures and architecture
3036 wildcards separated by spaces. When the list contains the
3037 architecture wildcard <tt>any</tt>, the only other value
3038 allowed in the list is <tt>all</tt>.
3042 The list may include (or consist solely of) the special
3043 value <tt>all</tt>. In other words, in <file>.dsc</file>
3044 files unlike the <file>debian/control</file>, <tt>all</tt> may
3045 occur in combination with specific architectures.
3046 The <tt>Architecture</tt> field in the Debian source control
3047 file <file>.dsc</file> is generally constructed from
3048 the <tt>Architecture</tt> fields in
3049 the <file>debian/control</file> in the source package.
3053 Specifying only <tt>any</tt> indicates that the source package
3054 isn't dependent on any particular architecture and should
3055 compile fine on any one. The produced binary package(s)
3056 will be specific to whatever the current build architecture is.
3060 Specifying only <tt>all</tt> indicates that the source package
3061 will only build architecture-independent packages.
3065 Specifying <tt>any all</tt> indicates that the source package
3066 isn't dependent on any particular architecture. The set of
3067 produced binary packages will include at least one
3068 architecture-dependant package and one architecture-independent
3073 Specifying a list of architectures or architecture wildcards
3074 indicates that the source will build an architecture-dependent
3075 package, and will only work correctly on the listed or
3076 matching architectures. If the source package also builds at
3077 least one architecture-independent package, <tt>all</tt> will
3078 also be included in the list.
3082 In a <file>.changes</file> file, the <tt>Architecture</tt>
3083 field lists the architecture(s) of the package(s) currently
3084 being uploaded. This will be a list; if the source for the
3085 package is also being uploaded, the special
3086 entry <tt>source</tt> is also present. <tt>all</tt> will be
3087 present if any architecture-independent packages are being
3088 uploaded. Architecture wildcards such as <tt>any</tt> must
3089 never occur in the <tt>Architecture</tt> field in
3090 the <file>.changes</file> file.
3094 See <ref id="debianrules"> for information on how to get
3095 the architecture for the build process.
3099 <sect1 id="f-Essential">
3100 <heading><tt>Essential</tt></heading>
3103 This is a boolean field which may occur only in the
3104 control file of a binary package or in a per-package fields
3105 paragraph of a source package control file.
3109 If set to <tt>yes</tt> then the package management system
3110 will refuse to remove the package (upgrading and replacing
3111 it is still possible). The other possible value is <tt>no</tt>,
3112 which is the same as not having the field at all.
3117 <heading>Package interrelationship fields:
3118 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3119 <tt>Recommends</tt>, <tt>Suggests</tt>,
3120 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3121 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3125 These fields describe the package's relationships with
3126 other packages. Their syntax and semantics are described
3127 in <ref id="relationships">.</p>
3130 <sect1 id="f-Standards-Version">
3131 <heading><tt>Standards-Version</tt></heading>
3134 The most recent version of the standards (the policy
3135 manual and associated texts) with which the package
3140 The version number has four components: major and minor
3141 version number and major and minor patch level. When the
3142 standards change in a way that requires every package to
3143 change the major number will be changed. Significant
3144 changes that will require work in many packages will be
3145 signaled by a change to the minor number. The major patch
3146 level will be changed for any change to the meaning of the
3147 standards, however small; the minor patch level will be
3148 changed when only cosmetic, typographical or other edits
3149 are made which neither change the meaning of the document
3150 nor affect the contents of packages.
3154 Thus only the first three components of the policy version
3155 are significant in the <em>Standards-Version</em> control
3156 field, and so either these three components or all four
3157 components may be specified.<footnote>
3158 In the past, people specified the full version number
3159 in the Standards-Version field, for example "2.3.0.0".
3160 Since minor patch-level changes don't introduce new
3161 policy, it was thought it would be better to relax
3162 policy and only require the first 3 components to be
3163 specified, in this example "2.3.0". All four
3164 components may still be used if someone wishes to do so.
3170 <sect1 id="f-Version">
3171 <heading><tt>Version</tt></heading>
3174 The version number of a package. The format is:
3175 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3179 The three components here are:
3181 <tag><var>epoch</var></tag>
3184 This is a single (generally small) unsigned integer. It
3185 may be omitted, in which case zero is assumed. If it is
3186 omitted then the <var>upstream_version</var> may not
3191 It is provided to allow mistakes in the version numbers
3192 of older versions of a package, and also a package's
3193 previous version numbering schemes, to be left behind.
3197 <tag><var>upstream_version</var></tag>
3200 This is the main part of the version number. It is
3201 usually the version number of the original ("upstream")
3202 package from which the <file>.deb</file> file has been made,
3203 if this is applicable. Usually this will be in the same
3204 format as that specified by the upstream author(s);
3205 however, it may need to be reformatted to fit into the
3206 package management system's format and comparison
3211 The comparison behavior of the package management system
3212 with respect to the <var>upstream_version</var> is
3213 described below. The <var>upstream_version</var>
3214 portion of the version number is mandatory.
3218 The <var>upstream_version</var> may contain only
3219 alphanumerics<footnote>
3220 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3222 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3223 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3224 tilde) and should start with a digit. If there is no
3225 <var>debian_revision</var> then hyphens are not allowed;
3226 if there is no <var>epoch</var> then colons are not
3231 <tag><var>debian_revision</var></tag>
3234 This part of the version number specifies the version of
3235 the Debian package based on the upstream version. It
3236 may contain only alphanumerics and the characters
3237 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3238 tilde) and is compared in the same way as the
3239 <var>upstream_version</var> is.
3243 It is optional; if it isn't present then the
3244 <var>upstream_version</var> may not contain a hyphen.
3245 This format represents the case where a piece of
3246 software was written specifically to be a Debian
3247 package, where the Debian package source must always
3248 be identical to the pristine source and therefore no
3249 revision indication is required.
3253 It is conventional to restart the
3254 <var>debian_revision</var> at <tt>1</tt> each time the
3255 <var>upstream_version</var> is increased.
3259 The package management system will break the version
3260 number apart at the last hyphen in the string (if there
3261 is one) to determine the <var>upstream_version</var> and
3262 <var>debian_revision</var>. The absence of a
3263 <var>debian_revision</var> is equivalent to a
3264 <var>debian_revision</var> of <tt>0</tt>.
3271 When comparing two version numbers, first the <var>epoch</var>
3272 of each are compared, then the <var>upstream_version</var> if
3273 <var>epoch</var> is equal, and then <var>debian_revision</var>
3274 if <var>upstream_version</var> is also equal.
3275 <var>epoch</var> is compared numerically. The
3276 <var>upstream_version</var> and <var>debian_revision</var>
3277 parts are compared by the package management system using the
3278 following algorithm:
3282 The strings are compared from left to right.
3286 First the initial part of each string consisting entirely of
3287 non-digit characters is determined. These two parts (one of
3288 which may be empty) are compared lexically. If a difference
3289 is found it is returned. The lexical comparison is a
3290 comparison of ASCII values modified so that all the letters
3291 sort earlier than all the non-letters and so that a tilde
3292 sorts before anything, even the end of a part. For example,
3293 the following parts are in sorted order from earliest to
3294 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3295 <tt>a</tt>.<footnote>
3296 One common use of <tt>~</tt> is for upstream pre-releases.
3297 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3298 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3303 Then the initial part of the remainder of each string which
3304 consists entirely of digit characters is determined. The
3305 numerical values of these two parts are compared, and any
3306 difference found is returned as the result of the comparison.
3307 For these purposes an empty string (which can only occur at
3308 the end of one or both version strings being compared) counts
3313 These two steps (comparing and removing initial non-digit
3314 strings and initial digit strings) are repeated until a
3315 difference is found or both strings are exhausted.
3319 Note that the purpose of epochs is to allow us to leave behind
3320 mistakes in version numbering, and to cope with situations
3321 where the version numbering scheme changes. It is
3322 <em>not</em> intended to cope with version numbers containing
3323 strings of letters which the package management system cannot
3324 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3325 silly orderings.<footnote>
3326 The author of this manual has heard of a package whose
3327 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3328 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3334 <sect1 id="f-Description">
3335 <heading><tt>Description</tt></heading>
3338 In a source or binary control file, the <tt>Description</tt>
3339 field contains a description of the binary package, consisting
3340 of two parts, the synopsis or the short description, and the
3341 long description. It is a multiline field with the following
3347 Description: <single line synopsis>
3348 <extended description over several lines>
3353 The lines in the extended description can have these formats:
3359 Those starting with a single space are part of a paragraph.
3360 Successive lines of this form will be word-wrapped when
3361 displayed. The leading space will usually be stripped off.
3362 The line must contain at least one non-whitespace character.
3366 Those starting with two or more spaces. These will be
3367 displayed verbatim. If the display cannot be panned
3368 horizontally, the displaying program will line wrap them "hard"
3369 (i.e., without taking account of word breaks). If it can they
3370 will be allowed to trail off to the right. None, one or two
3371 initial spaces may be deleted, but the number of spaces
3372 deleted from each line will be the same (so that you can have
3373 indenting work correctly, for example). The line must
3374 contain at least one non-whitespace character.
3378 Those containing a single space followed by a single full stop
3379 character. These are rendered as blank lines. This is the
3380 <em>only</em> way to get a blank line<footnote>
3381 Completely empty lines will not be rendered as blank lines.
3382 Instead, they will cause the parser to think you're starting
3383 a whole new record in the control file, and will therefore
3384 likely abort with an error.
3389 Those containing a space, a full stop and some more characters.
3390 These are for future expansion. Do not use them.
3396 Do not use tab characters. Their effect is not predictable.
3400 See <ref id="descriptions"> for further information on this.
3404 In a <file>.changes</file> file, the <tt>Description</tt>
3405 field contains a summary of the descriptions for the packages
3406 being uploaded. For this case, the first line of the field
3407 value (the part on the same line as <tt>Description:</tt>) is
3408 always empty. It is a multiline field, with one
3409 line per package. Each line is
3410 indented by one space and contains the name of a binary
3411 package, a space, a hyphen (<tt>-</tt>), a space, and the
3412 short description line from that package.
3416 <sect1 id="f-Distribution">
3417 <heading><tt>Distribution</tt></heading>
3420 In a <file>.changes</file> file or parsed changelog output
3421 this contains the (space-separated) name(s) of the
3422 distribution(s) where this version of the package should
3423 be installed. Valid distributions are determined by the
3424 archive maintainers.<footnote>
3425 Example distribution names in the Debian archive used in
3426 <file>.changes</file> files are:
3427 <taglist compact="compact">
3428 <tag><em>unstable</em></tag>
3430 This distribution value refers to the
3431 <em>developmental</em> part of the Debian distribution
3432 tree. Most new packages, new upstream versions of
3433 packages and bug fixes go into the <em>unstable</em>
3437 <tag><em>experimental</em></tag>
3439 The packages with this distribution value are deemed
3440 by their maintainers to be high risk. Oftentimes they
3441 represent early beta or developmental packages from
3442 various sources that the maintainers want people to
3443 try, but are not ready to be a part of the other parts
3444 of the Debian distribution tree.
3449 Others are used for updating stable releases or for
3450 security uploads. More information is available in the
3451 Debian Developer's Reference, section "The Debian
3455 The Debian archive software only supports listing a single
3456 distribution. Migration of packages to other distributions is
3457 handled outside of the upload process.
3462 <heading><tt>Date</tt></heading>
3465 This field includes the date the package was built or last
3466 edited. It must be in the same format as the <var>date</var>
3467 in a <file>debian/changelog</file> entry.
3471 The value of this field is usually extracted from the
3472 <file>debian/changelog</file> file - see
3473 <ref id="dpkgchangelog">).
3477 <sect1 id="f-Format">
3478 <heading><tt>Format</tt></heading>
3481 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3482 files, this field declares the format version of that file.
3483 The syntax of the field value is the same as that of
3484 a <qref id="f-Version">package version number</qref> except
3485 that no epoch or Debian revision is allowed. The format
3486 described in this document is <tt>&changesversion;</tt>.
3490 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3491 Debian source control</qref> files, this field declares the
3492 format of the source package. The field value is used by
3493 programs acting on a source package to interpret the list of
3494 files in the source package and determine how to unpack it.
3495 The syntax of the field value is a numeric major revision, a
3496 period, a numeric minor revision, and then an optional subtype
3497 after whitespace, which if specified is an alphanumeric word
3498 in parentheses. The subtype is optional in the syntax but may
3499 be mandatory for particular source format revisions.
3501 The source formats currently supported by the Debian archive
3502 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3503 and <tt>3.0 (quilt)</tt>.
3508 <sect1 id="f-Urgency">
3509 <heading><tt>Urgency</tt></heading>
3512 This is a description of how important it is to upgrade to
3513 this version from previous ones. It consists of a single
3514 keyword taking one of the values <tt>low</tt>,
3515 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3516 <tt>critical</tt><footnote>
3517 Other urgency values are supported with configuration
3518 changes in the archive software but are not used in Debian.
3519 The urgency affects how quickly a package will be considered
3520 for inclusion into the <tt>testing</tt> distribution and
3521 gives an indication of the importance of any fixes included
3522 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3523 treated as synonymous.
3524 </footnote> (not case-sensitive) followed by an optional
3525 commentary (separated by a space) which is usually in
3526 parentheses. For example:
3529 Urgency: low (HIGH for users of diversions)
3535 The value of this field is usually extracted from the
3536 <file>debian/changelog</file> file - see
3537 <ref id="dpkgchangelog">.
3541 <sect1 id="f-Changes">
3542 <heading><tt>Changes</tt></heading>
3545 This multiline field contains the human-readable changes data, describing
3546 the differences between the last version and the current one.
3550 The first line of the field value (the part on the same line
3551 as <tt>Changes:</tt>) is always empty. The content of the
3552 field is expressed as continuation lines, with each line
3553 indented by at least one space. Blank lines must be
3554 represented by a line consisting only of a space and a full
3559 The value of this field is usually extracted from the
3560 <file>debian/changelog</file> file - see
3561 <ref id="dpkgchangelog">).
3565 Each version's change information should be preceded by a
3566 "title" line giving at least the version, distribution(s)
3567 and urgency, in a human-readable way.
3571 If data from several versions is being returned the entry
3572 for the most recent version should be returned first, and
3573 entries should be separated by the representation of a
3574 blank line (the "title" line may also be followed by the
3575 representation of a blank line).
3579 <sect1 id="f-Binary">
3580 <heading><tt>Binary</tt></heading>
3583 This folded field is a list of binary packages. Its syntax and
3584 meaning varies depending on the control file in which it
3589 When it appears in the <file>.dsc</file> file, it lists binary
3590 packages which a source package can produce, separated by
3592 A space after each comma is conventional.
3593 </footnote>. The source package
3594 does not necessarily produce all of these binary packages for
3595 every architecture. The source control file doesn't contain
3596 details of which architectures are appropriate for which of
3597 the binary packages.
3601 When it appears in a <file>.changes</file> file, it lists the
3602 names of the binary packages being uploaded, separated by
3603 whitespace (not commas).
3607 <sect1 id="f-Installed-Size">
3608 <heading><tt>Installed-Size</tt></heading>
3611 This field appears in the control files of binary packages,
3612 and in the <file>Packages</file> files. It gives an estimate
3613 of the total amount of disk space required to install the
3614 named package. Actual installed size may vary based on block
3615 size, file system properties, or actions taken by package
3620 The disk space is given as the integer value of the estimated
3621 installed size in bytes, divided by 1024 and rounded up.
3625 <sect1 id="f-Files">
3626 <heading><tt>Files</tt></heading>
3629 This field contains a list of files with information about
3630 each one. The exact information and syntax varies with
3635 In all cases, Files is a multiline field. The first line of
3636 the field value (the part on the same line as <tt>Files:</tt>)
3637 is always empty. The content of the field is expressed as
3638 continuation lines, one line per file. Each line must be
3639 indented by one space and contain a number of sub-fields,
3640 separated by spaces, as described below.
3644 In the <file>.dsc</file> file, each line contains the MD5
3645 checksum, size and filename of the tar file and (if
3646 applicable) diff file which make up the remainder of the
3647 source package<footnote>
3648 That is, the parts which are not the <tt>.dsc</tt>.
3649 </footnote>. For example:
3652 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3653 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3655 The exact forms of the filenames are described
3656 in <ref id="pkg-sourcearchives">.
3660 In the <file>.changes</file> file this contains one line per
3661 file being uploaded. Each line contains the MD5 checksum,
3662 size, section and priority and the filename. For example:
3665 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3666 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3667 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3668 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3670 The <qref id="f-Section">section</qref>
3671 and <qref id="f-Priority">priority</qref> are the values of
3672 the corresponding fields in the main source control file. If
3673 no section or priority is specified then <tt>-</tt> should be
3674 used, though section and priority values must be specified for
3675 new packages to be installed properly.
3679 The special value <tt>byhand</tt> for the section in a
3680 <tt>.changes</tt> file indicates that the file in question
3681 is not an ordinary package file and must be installed by
3682 hand by the distribution maintainers. If the section is
3683 <tt>byhand</tt> the priority should be <tt>-</tt>.
3687 If a new Debian revision of a package is being shipped and
3688 no new original source archive is being distributed the
3689 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3690 entry for the original source archive
3691 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3692 but the <file>.changes</file> file should leave it out. In
3693 this case the original source archive on the distribution
3694 site must match exactly, byte-for-byte, the original
3695 source archive which was used to generate the
3696 <file>.dsc</file> file and diff which are being uploaded.</p>
3699 <sect1 id="f-Closes">
3700 <heading><tt>Closes</tt></heading>
3703 A space-separated list of bug report numbers that the upload
3704 governed by the .changes file closes.
3708 <sect1 id="f-Homepage">
3709 <heading><tt>Homepage</tt></heading>
3712 The URL of the web site for this package, preferably (when
3713 applicable) the site from which the original source can be
3714 obtained and any additional upstream documentation or
3715 information may be found. The content of this field is a
3716 simple URL without any surrounding characters such as
3721 <sect1 id="f-Checksums">
3722 <heading><tt>Checksums-Sha1</tt>
3723 and <tt>Checksums-Sha256</tt></heading>
3726 These multiline fields contain a list of files with a checksum and size
3727 for each one. Both <tt>Checksums-Sha1</tt>
3728 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3729 only in the checksum algorithm used: SHA-1
3730 for <tt>Checksums-Sha1</tt> and SHA-256
3731 for <tt>Checksums-Sha256</tt>.
3735 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3736 multiline fields. The first line of the field value (the part
3737 on the same line as <tt>Checksums-Sha1:</tt>
3738 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3739 of the field is expressed as continuation lines, one line per
3740 file. Each line consists of the checksum, a space, the file
3741 size, a space, and the file name. For example (from
3742 a <file>.changes</file> file):
3745 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3746 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3747 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3748 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3750 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3751 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3752 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3753 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3758 In the <file>.dsc</file> file, these fields list all
3759 files that make up the source package. In
3760 the <file>.changes</file> file, these fields list all
3761 files being uploaded. The list of files in these fields
3762 must match the list of files in the <tt>Files</tt> field.
3767 <heading><tt>DM-Upload-Allowed</tt></heading>
3770 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3774 <sect1 id="f-VCS-fields">
3775 <heading>Version Control System (VCS) fields</heading>
3778 Debian source packages are increasingly developed using VCSs. The
3779 purpose of the following fields is to indicate a publicly accessible
3780 repository where the Debian source package is developed.
3783 <tag><tt>Vcs-Browser</tt></tag>
3786 URL of a web interface for browsing the repository.
3791 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3792 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3793 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3798 The field name identifies the VCS. The field's value uses the
3799 version control system's conventional syntax for describing
3800 repository locations and should be sufficient to locate the
3801 repository used for packaging. Ideally, it also locates the
3802 branch used for development of new versions of the Debian
3806 In the case of Git, the value consists of a URL, optionally
3807 followed by the word <tt>-b</tt> and the name of a branch in
3808 the indicated repository, following the syntax of the
3809 <tt>git clone</tt> command. If no branch is specified, the
3810 packaging should be on the default branch.
3813 More than one different VCS may be specified for the same
3821 <sect1 id="f-Package-List">
3822 <heading><tt>Package-List</tt></heading>
3825 Multiline field listing all the packages that can be built from
3826 the source package, considering every architecture. The first line
3827 of the field value is empty. Each one of the next lines describes
3828 one binary package, by listing its name, type, section and priority
3829 separated by spaces. Fifth and subsequent space-separated items
3830 may be present and parsers must allow them. See the
3831 <qref id="f-Package-Type">Package-Type</qref> field for a list of
3836 <sect1 id="f-Package-Type">
3837 <heading><tt>Package-Type</tt></heading>
3840 Simple field containing a word indicating the type of package:
3841 <tt>deb</tt> for binary packages and <tt>udeb</tt> for micro binary
3842 packages. Other types not defined here may be indicated. In
3843 source package control files, the <tt>Package-Type</tt> field
3844 should be omitted instead of giving it a value of <tt>deb</tt>, as
3845 this value is assumed for paragraphs lacking this field.
3850 <heading><tt>Dgit</tt></heading>
3853 Folded field containing a single git commit hash, presented in
3854 full, followed optionally by whitespace and other data to be
3855 defined in future extensions.
3859 Declares that the source package corresponds exactly to a
3860 referenced commit in a Git repository available at the canonical
3861 location called <em>dgit-repos</em>, used by <prgn>dgit</prgn>, a
3862 bidirectional gateway between the Debian archive and Git. The
3863 commit is reachable from at least one reference whose name matches
3864 <tt>refs/dgit/*</tt>. See the manual page of <prgn>dgit</prgn> for
3871 <heading>User-defined fields</heading>
3874 Additional user-defined fields may be added to the
3875 source package control file. Such fields will be
3876 ignored, and not copied to (for example) binary or
3877 Debian source control files or upload control files.
3881 If you wish to add additional unsupported fields to
3882 these output files you should use the mechanism
3887 Fields in the main source control information file with
3888 names starting <tt>X</tt>, followed by one or more of
3889 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3890 be copied to the output files. Only the part of the
3891 field name after the hyphen will be used in the output
3892 file. Where the letter <tt>B</tt> is used the field
3893 will appear in binary package control files, where the
3894 letter <tt>S</tt> is used in Debian source control
3895 files and where <tt>C</tt> is used in upload control
3896 (<tt>.changes</tt>) files.
3900 For example, if the main source information control file
3903 XBS-Comment: I stand between the candle and the star.
3905 then the binary and Debian source control files will contain the
3908 Comment: I stand between the candle and the star.
3914 <sect id="obsolete-control-data-fields">
3915 <heading>Obsolete fields</heading>
3918 The following fields have been obsoleted and may be found in packages
3919 conforming with previous versions of the Policy.
3922 <sect1 id="f-DM-Upload-Allowed">
3923 <heading><tt>DM-Upload-Allowed</tt></heading>
3926 Indicates that Debian Maintainers may upload this package to
3927 the Debian archive. The only valid value is <tt>yes</tt>. This
3928 field was used to regulate uploads by Debian Maintainers, See the
3929 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3930 name="Endorse the concept of Debian Maintainers"> for more details.
3939 <chapt id="maintainerscripts">
3940 <heading>Package maintainer scripts and installation procedure</heading>
3943 <heading>Introduction to package maintainer scripts</heading>
3946 It is possible to supply scripts as part of a package which
3947 the package management system will run for you when your
3948 package is installed, upgraded or removed.
3952 These scripts are the control information
3953 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3954 and <prgn>postrm</prgn>. They must be proper executable files;
3955 if they are scripts (which is recommended), they must start with
3956 the usual <tt>#!</tt> convention. They should be readable and
3957 executable by anyone, and must not be world-writable.
3961 The package management system looks at the exit status from
3962 these scripts. It is important that they exit with a
3963 non-zero status if there is an error, so that the package
3964 management system can stop its processing. For shell
3965 scripts this means that you <em>almost always</em> need to
3966 use <tt>set -e</tt> (this is usually true when writing shell
3967 scripts, in fact). It is also important, of course, that
3968 they exit with a zero status if everything went well.
3972 Additionally, packages interacting with users
3973 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3974 should install a <prgn>config</prgn> script as a control
3975 information file. See <ref id="maintscriptprompt"> for details.
3979 When a package is upgraded a combination of the scripts from
3980 the old and new packages is called during the upgrade
3981 procedure. If your scripts are going to be at all
3982 complicated you need to be aware of this, and may need to
3983 check the arguments to your scripts.
3987 Broadly speaking the <prgn>preinst</prgn> is called before
3988 (a particular version of) a package is unpacked, and the
3989 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3990 before (a version of) a package is removed and the
3991 <prgn>postrm</prgn> afterwards.
3995 Programs called from maintainer scripts should not normally
3996 have a path prepended to them. Before installation is
3997 started, the package management system checks to see if the
3998 programs <prgn>ldconfig</prgn>, <prgn>start-stop-daemon</prgn>,
3999 and <prgn>update-rc.d</prgn> can be found via the
4000 <tt>PATH</tt> environment variable. Those programs, and any
4001 other program that one would expect to be in the
4002 <tt>PATH</tt>, should thus be invoked without an absolute
4003 pathname. Maintainer scripts should also not reset the
4004 <tt>PATH</tt>, though they might choose to modify it by
4005 prepending or appending package-specific directories. These
4006 considerations really apply to all shell scripts.</p>
4009 <sect id="idempotency">
4010 <heading>Maintainer scripts idempotency</heading>
4013 It is necessary for the error recovery procedures that the
4014 scripts be idempotent. This means that if it is run
4015 successfully, and then it is called again, it doesn't bomb
4016 out or cause any harm, but just ensures that everything is
4017 the way it ought to be. If the first call failed, or
4018 aborted half way through for some reason, the second call
4019 should merely do the things that were left undone the first
4020 time, if any, and exit with a success status if everything
4022 This is so that if an error occurs, the user interrupts
4023 <prgn>dpkg</prgn> or some other unforeseen circumstance
4024 happens you don't leave the user with a badly-broken
4025 package when <prgn>dpkg</prgn> attempts to repeat the
4031 <sect id="controllingterminal">
4032 <heading>Controlling terminal for maintainer scripts</heading>
4035 Maintainer scripts are not guaranteed to run with a controlling
4036 terminal and may not be able to interact with the user. They
4037 must be able to fall back to noninteractive behavior if no
4038 controlling terminal is available. Maintainer scripts that
4039 prompt via a program conforming to the Debian Configuration
4040 Management Specification (see <ref id="maintscriptprompt">) may
4041 assume that program will handle falling back to noninteractive
4046 For high-priority prompts without a reasonable default answer,
4047 maintainer scripts may abort if there is no controlling
4048 terminal. However, this situation should be avoided if at all
4049 possible, since it prevents automated or unattended installs.
4050 In most cases, users will consider this to be a bug in the
4055 <sect id="exitstatus">
4056 <heading>Exit status</heading>
4059 Each script must return a zero exit status for
4060 success, or a nonzero one for failure, since the package
4061 management system looks for the exit status of these scripts
4062 and determines what action to take next based on that datum.
4066 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4071 What follows is a summary of all the ways in which maintainer
4072 scripts may be called along with what facilities those scripts
4073 may rely on being available at that time. Script names preceded
4074 by <var>new-</var> are the scripts from the new version of a
4075 package being installed, upgraded to, or downgraded to. Script
4076 names preceded by <var>old-</var> are the scripts from the old
4077 version of a package that is being upgraded from or downgraded
4082 The <prgn>preinst</prgn> script may be called in the following
4085 <tag><var>new-preinst</var> <tt>install</tt></tag>
4086 <tag><var>new-preinst</var> <tt>install</tt>
4087 <var>old-version</var></tag>
4088 <tag><var>new-preinst</var> <tt>upgrade</tt>
4089 <var>old-version</var></tag>
4091 The package will not yet be unpacked, so
4092 the <prgn>preinst</prgn> script cannot rely on any files
4093 included in its package. Only essential packages and
4094 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4095 available. Pre-dependencies will have been configured at
4096 least once, but at the time the <prgn>preinst</prgn> is
4097 called they may only be in an "Unpacked" or "Half-Configured"
4098 state if a previous version of the pre-dependency was
4099 completely configured and has not been removed since then.
4102 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4103 <var>new-version</var></tag>
4105 Called during error handling of an upgrade that failed after
4106 unpacking the new package because the <tt>postrm
4107 upgrade</tt> action failed. The unpacked files may be
4108 partly from the new version or partly missing, so the script
4109 cannot rely on files included in the package. Package
4110 dependencies may not be available. Pre-dependencies will be
4111 at least "Unpacked" following the same rules as above, except
4112 they may be only "Half-Installed" if an upgrade of the
4113 pre-dependency failed.<footnote>
4114 This can happen if the new version of the package no
4115 longer pre-depends on a package that had been partially
4123 The <prgn>postinst</prgn> script may be called in the following
4126 <tag><var>postinst</var> <tt>configure</tt>
4127 <var>most-recently-configured-version</var></tag>
4129 The files contained in the package will be unpacked. All
4130 package dependencies will at least be "Unpacked". If there
4131 are no circular dependencies involved, all package
4132 dependencies will be configured. For behavior in the case
4133 of circular dependencies, see the discussion
4134 in <ref id="binarydeps">.
4137 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4138 <var>new-version</var></tag>
4139 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4140 <tt>in-favour</tt> <var>package</var>
4141 <var>new-version</var></tag>
4142 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4143 <tag><var>deconfigured's-postinst</var>
4144 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4145 <var>failed-install-package</var> <var>version</var>
4146 [<tt>removing</tt> <var>conflicting-package</var>
4147 <var>version</var>]</tag>
4149 The files contained in the package will be unpacked. All
4150 package dependencies will at least be "Half-Installed" and
4151 will have previously been configured and not removed.
4152 However, dependencies may not be configured or even fully
4153 unpacked in some error situations.<footnote>
4154 For example, suppose packages foo and bar are "Installed"
4155 with foo depending on bar. If an upgrade of bar were
4156 started and then aborted, and then an attempt to remove
4157 foo failed because its <prgn>prerm</prgn> script failed,
4158 foo's <tt>postinst abort-remove</tt> would be called with
4159 bar only "Half-Installed".
4161 The <prgn>postinst</prgn> should still attempt any actions
4162 for which its dependencies are required, since they will
4163 normally be available, but consider the correct error
4164 handling approach if those actions fail. Aborting
4165 the <prgn>postinst</prgn> action if commands or facilities
4166 from the package dependencies are not available is often the
4173 The <prgn>prerm</prgn> script may be called in the following
4176 <tag><var>prerm</var> <tt>remove</tt></tag>
4177 <tag><var>old-prerm</var>
4178 <tt>upgrade</tt><var>new-version</var></tag>
4179 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4180 <tt>in-favour</tt> <var>package</var>
4181 <var>new-version</var></tag>
4182 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4183 <tt>in-favour</tt> <var>package-being-installed</var>
4184 <var>version</var> [<tt>removing</tt>
4185 <var>conflicting-package</var> <var>version</var>]</tag>
4187 The package whose <prgn>prerm</prgn> is being called will be
4188 at least "Half-Installed". All package dependencies will at
4189 least be "Half-Installed" and will have previously been
4190 configured and not removed. If there was no error, all
4191 dependencies will at least be "Unpacked", but these actions
4192 may be called in various error states where dependencies are
4193 only "Half-Installed" due to a partial upgrade.
4196 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4197 <var>old-version</var></tag>
4199 Called during error handling when <tt>prerm upgrade</tt>
4200 fails. The new package will not yet be unpacked, and all
4201 the same constraints as for <tt>preinst upgrade</tt> apply.
4207 The <prgn>postrm</prgn> script may be called in the following
4210 <tag><var>postrm</var> <tt>remove</tt></tag>
4211 <tag><var>postrm</var> <tt>purge</tt></tag>
4212 <tag><var>old-postrm</var> <tt>upgrade</tt>
4213 <var>new-version</var></tag>
4214 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4215 <var>overwriter</var> <var>overwriter-version</var></tag>
4217 The <prgn>postrm</prgn> script is called after the package's
4218 files have been removed or replaced. The package
4219 whose <prgn>postrm</prgn> is being called may have
4220 previously been deconfigured and only be "Unpacked", at which
4221 point subsequent package changes do not consider its
4222 dependencies. Therefore, all <prgn>postrm</prgn> actions
4223 may only rely on essential packages and must gracefully skip
4224 any actions that require the package's dependencies if those
4225 dependencies are unavailable.<footnote>
4226 This is often done by checking whether the command or
4227 facility the <prgn>postrm</prgn> intends to call is
4228 available before calling it. For example:
4230 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4231 . /usr/share/debconf/confmodule
4235 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4236 configuration for the package
4237 if <package>debconf</package> is installed.
4241 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4242 <var>old-version</var></tag>
4244 Called when the old <tt>postrm upgrade</tt> action fails.
4245 The new package will be unpacked, but only essential
4246 packages and pre-dependencies can be relied on.
4247 Pre-dependencies will either be configured or will be
4248 "Unpacked" or "Half-Configured" but previously had been
4249 configured and was never removed.
4252 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4253 <tag><var>new-postrm</var> <tt>abort-install</tt>
4254 <var>old-version</var></tag>
4255 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4256 <var>old-version</var></tag>
4258 Called before unpacking the new package as part of the
4259 error handling of <prgn>preinst</prgn> failures. May assume
4260 the same state as <prgn>preinst</prgn> can assume.
4266 <sect id="unpackphase">
4267 <heading>Details of unpack phase of installation or upgrade</heading>
4270 The procedure on installation/upgrade/overwrite/disappear
4271 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4272 stage of <tt>dpkg --install</tt>) is as follows. In each
4273 case, if a major error occurs (unless listed below) the
4274 actions are, in general, run backwards - this means that the
4275 maintainer scripts are run with different arguments in
4276 reverse order. These are the "error unwind" calls listed
4283 If a version of the package is already "Installed", call
4284 <example compact="compact">
4285 <var>old-prerm</var> upgrade <var>new-version</var>
4289 If the script runs but exits with a non-zero
4290 exit status, <prgn>dpkg</prgn> will attempt:
4291 <example compact="compact">
4292 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4294 If this works, the upgrade continues. If this
4295 does not work, the error unwind:
4296 <example compact="compact">
4297 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4299 If this works, then the old-version is
4300 "Installed", if not, the old version is in a
4301 "Half-Configured" state.
4307 If a "conflicting" package is being removed at the same time,
4308 or if any package will be broken (due to <tt>Breaks</tt>):
4311 If <tt>--auto-deconfigure</tt> is
4312 specified, call, for each package to be deconfigured
4313 due to <tt>Breaks</tt>:
4314 <example compact="compact">
4315 <var>deconfigured's-prerm</var> deconfigure \
4316 in-favour <var>package-being-installed</var> <var>version</var>
4319 <example compact="compact">
4320 <var>deconfigured's-postinst</var> abort-deconfigure \
4321 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4323 The deconfigured packages are marked as
4324 requiring configuration, so that if
4325 <tt>--install</tt> is used they will be
4326 configured again if possible.
4329 If any packages depended on a conflicting
4330 package being removed and <tt>--auto-deconfigure</tt> is
4331 specified, call, for each such package:
4332 <example compact="compact">
4333 <var>deconfigured's-prerm</var> deconfigure \
4334 in-favour <var>package-being-installed</var> <var>version</var> \
4335 removing <var>conflicting-package</var> <var>version</var>
4338 <example compact="compact">
4339 <var>deconfigured's-postinst</var> abort-deconfigure \
4340 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4341 removing <var>conflicting-package</var> <var>version</var>
4343 The deconfigured packages are marked as
4344 requiring configuration, so that if
4345 <tt>--install</tt> is used they will be
4346 configured again if possible.
4349 To prepare for removal of each conflicting package, call:
4350 <example compact="compact">
4351 <var>conflictor's-prerm</var> remove \
4352 in-favour <var>package</var> <var>new-version</var>
4355 <example compact="compact">
4356 <var>conflictor's-postinst</var> abort-remove \
4357 in-favour <var>package</var> <var>new-version</var>
4366 If the package is being upgraded, call:
4367 <example compact="compact">
4368 <var>new-preinst</var> upgrade <var>old-version</var>
4370 If this fails, we call:
4372 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4379 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4381 is called. If this works, then the old version
4382 is in an "Installed" state, or else it is left
4383 in an "Unpacked" state.
4388 If it fails, then the old version is left
4389 in an "Half-Installed" state.
4396 Otherwise, if the package had some configuration
4397 files from a previous version installed (i.e., it
4398 is in the "Config-Files" state):
4399 <example compact="compact">
4400 <var>new-preinst</var> install <var>old-version</var>
4404 <var>new-postrm</var> abort-install <var>old-version</var>
4406 If this fails, the package is left in a
4407 "Half-Installed" state, which requires a
4408 reinstall. If it works, the packages is left in
4409 a "Config-Files" state.
4412 Otherwise (i.e., the package was completely purged):
4413 <example compact="compact">
4414 <var>new-preinst</var> install
4417 <example compact="compact">
4418 <var>new-postrm</var> abort-install
4420 If the error-unwind fails, the package is in a
4421 "Half-Installed" phase, and requires a
4422 reinstall. If the error unwind works, the
4423 package is in the "Not-Installed" state.
4430 The new package's files are unpacked, overwriting any
4431 that may be on the system already, for example any
4432 from the old version of the same package or from
4433 another package. Backups of the old files are kept
4434 temporarily, and if anything goes wrong the package
4435 management system will attempt to put them back as
4436 part of the error unwind.
4440 It is an error for a package to contain files which
4441 are on the system in another package, unless
4442 <tt>Replaces</tt> is used (see <ref id="replaces">).
4444 The following paragraph is not currently the case:
4445 Currently the <tt>- - force-overwrite</tt> flag is
4446 enabled, downgrading it to a warning, but this may not
4452 It is a more serious error for a package to contain a
4453 plain file or other kind of non-directory where another
4454 package has a directory (again, unless
4455 <tt>Replaces</tt> is used). This error can be
4456 overridden if desired using
4457 <tt>--force-overwrite-dir</tt>, but this is not
4462 Packages which overwrite each other's files produce
4463 behavior which, though deterministic, is hard for the
4464 system administrator to understand. It can easily
4465 lead to "missing" programs if, for example, a package
4466 is unpacked which overwrites a file from another
4467 package, and is then removed again.<footnote>
4468 Part of the problem is due to what is arguably a
4469 bug in <prgn>dpkg</prgn>.
4474 A directory will never be replaced by a symbolic link
4475 to a directory or vice versa; instead, the existing
4476 state (symlink or not) will be left alone and
4477 <prgn>dpkg</prgn> will follow the symlink if there is
4486 If the package is being upgraded, call
4487 <example compact="compact">
4488 <var>old-postrm</var> upgrade <var>new-version</var>
4492 If this fails, <prgn>dpkg</prgn> will attempt:
4493 <example compact="compact">
4494 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4496 If this works, installation continues. If not,
4498 <example compact="compact">
4499 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4501 If this fails, the old version is left in a
4502 "Half-Installed" state. If it works, dpkg now
4504 <example compact="compact">
4505 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4507 If this fails, the old version is left in a
4508 "Half-Installed" state. If it works, dpkg now
4510 <example compact="compact">
4511 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4513 If this fails, the old version is in an
4520 This is the point of no return - if
4521 <prgn>dpkg</prgn> gets this far, it won't back off
4522 past this point if an error occurs. This will
4523 leave the package in a fairly bad state, which
4524 will require a successful re-installation to clear
4525 up, but it's when <prgn>dpkg</prgn> starts doing
4526 things that are irreversible.
4531 Any files which were in the old version of the package
4532 but not in the new are removed.
4536 The new file list replaces the old.
4540 The new maintainer scripts replace the old.
4544 Any packages all of whose files have been overwritten
4545 during the installation, and which aren't required for
4546 dependencies, are considered to have been removed.
4547 For each such package
4550 <prgn>dpkg</prgn> calls:
4551 <example compact="compact">
4552 <var>disappearer's-postrm</var> disappear \
4553 <var>overwriter</var> <var>overwriter-version</var>
4557 The package's maintainer scripts are removed.
4560 It is noted in the status database as being in a
4561 sane state, namely "Not-Installed" (any conffiles
4562 it may have are ignored, rather than being
4563 removed by <prgn>dpkg</prgn>). Note that
4564 disappearing packages do not have their prerm
4565 called, because <prgn>dpkg</prgn> doesn't know
4566 in advance that the package is going to
4573 Any files in the package we're unpacking that are also
4574 listed in the file lists of other packages are removed
4575 from those lists. (This will lobotomize the file list
4576 of the "conflicting" package if there is one.)
4580 The backup files made during installation, above, are
4586 The new package's status is now sane, and recorded as
4591 Here is another point of no return - if the
4592 conflicting package's removal fails we do not unwind
4593 the rest of the installation; the conflicting package
4594 is left in a half-removed limbo.
4599 If there was a conflicting package we go and do the
4600 removal actions (described below), starting with the
4601 removal of the conflicting package's files (any that
4602 are also in the package being unpacked have already
4603 been removed from the conflicting package's file list,
4604 and so do not get removed now).
4610 <sect id="configdetails"><heading>Details of configuration</heading>
4613 When we configure a package (this happens with <tt>dpkg
4614 --install</tt> and <tt>dpkg --configure</tt>), we first
4615 update any <tt>conffile</tt>s and then call:
4616 <example compact="compact">
4617 <var>postinst</var> configure <var>most-recently-configured-version</var>
4622 No attempt is made to unwind after errors during
4623 configuration. If the configuration fails, the package is in
4624 a "Half-Configured" state, and an error message is generated.
4628 If there is no most recently configured version
4629 <prgn>dpkg</prgn> will pass a null argument.
4632 Historical note: Truly ancient (pre-1997) versions of
4633 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4634 (including the angle brackets) in this case. Even older
4635 ones did not pass a second argument at all, under any
4636 circumstance. Note that upgrades using such an old dpkg
4637 version are unlikely to work for other reasons, even if
4638 this old argument behavior is handled by your postinst script.
4644 <sect id="removedetails"><heading>Details of removal and/or
4645 configuration purging</heading>
4651 <example compact="compact">
4652 <var>prerm</var> remove
4656 If prerm fails during replacement due to conflict
4658 <var>conflictor's-postinst</var> abort-remove \
4659 in-favour <var>package</var> <var>new-version</var>
4663 <var>postinst</var> abort-remove
4667 If this fails, the package is in a "Half-Configured"
4668 state, or else it remains "Installed".
4672 The package's files are removed (except <tt>conffile</tt>s).
4675 <example compact="compact">
4676 <var>postrm</var> remove
4680 If it fails, there's no error unwind, and the package is in
4681 an "Half-Installed" state.
4686 All the maintainer scripts except the <prgn>postrm</prgn>
4691 If we aren't purging the package we stop here. Note
4692 that packages which have no <prgn>postrm</prgn> and no
4693 <tt>conffile</tt>s are automatically purged when
4694 removed, as there is no difference except for the
4695 <prgn>dpkg</prgn> status.
4699 The <tt>conffile</tt>s and any backup files
4700 (<tt>~</tt>-files, <tt>#*#</tt> files,
4701 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4706 <example compact="compact">
4707 <var>postrm</var> purge
4711 If this fails, the package remains in a "Config-Files"
4716 The package's file list is removed.
4725 <chapt id="relationships">
4726 <heading>Declaring relationships between packages</heading>
4728 <sect id="depsyntax">
4729 <heading>Syntax of relationship fields</heading>
4732 These fields all have a uniform syntax. They are a list of
4733 package names separated by commas.
4737 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4738 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4739 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4740 control fields of the package, which declare
4741 dependencies on other packages, the package names listed may
4742 also include lists of alternative package names, separated
4743 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4744 that part of the dependency can be satisfied by any one of
4745 the alternative packages.
4749 All of the fields except for <tt>Provides</tt> may restrict
4750 their applicability to particular versions of each named
4751 package. This is done in parentheses after each individual
4752 package name; the parentheses should contain a relation from
4753 the list below followed by a version number, in the format
4754 described in <ref id="f-Version">.
4758 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4759 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4760 earlier, earlier or equal, exactly equal, later or equal and
4761 strictly later, respectively. The deprecated
4762 forms <tt><</tt> and <tt>></tt> were confusingly used to
4763 mean earlier/later or equal, rather than strictly earlier/later,
4764 and must not appear in new packages (though <prgn>dpkg</prgn>
4765 still supports them with a warning).
4769 Whitespace may appear at any point in the version
4770 specification subject to the rules in <ref
4771 id="controlsyntax">, and must appear where it's necessary to
4772 disambiguate; it is not otherwise significant. All of the
4773 relationship fields can only be folded in source package control files. For
4774 consistency and in case of future changes to
4775 <prgn>dpkg</prgn> it is recommended that a single space be
4776 used after a version relationship and before a version
4777 number; it is also conventional to put a single space after
4778 each comma, on either side of each vertical bar, and before
4779 each open parenthesis. When opening a continuation line in a relationship field, it
4780 is conventional to do so after a comma and before the space
4781 following that comma.
4785 For example, a list of dependencies might appear as:
4786 <example compact="compact">
4789 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4794 Relationships may be restricted to a certain set of
4795 architectures. This is indicated in brackets after each
4796 individual package name and the optional version specification.
4797 The brackets enclose a non-empty list of Debian architecture names
4798 in the format described in <ref id="arch-spec">,
4799 separated by whitespace. Exclamation marks may be prepended to
4800 each of the names. (It is not permitted for some names to be
4801 prepended with exclamation marks while others aren't.)
4805 For build relationship fields
4806 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4807 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4808 the current Debian host architecture is not in this list and
4809 there are no exclamation marks in the list, or it is in the list
4810 with a prepended exclamation mark, the package name and the
4811 associated version specification are ignored completely for the
4812 purposes of defining the relationships.
4817 <example compact="compact">
4819 Build-Depends-Indep: texinfo
4820 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4821 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4823 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4824 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4825 <tt>gnumach-dev</tt> only on hurd-i386.
4829 For binary relationship fields and the <tt>Built-Using</tt>
4830 field, the architecture restriction
4831 syntax is only supported in the source package control
4832 file <file>debian/control</file>. When the corresponding binary
4833 package control file is generated, the relationship will either
4834 be omitted or included without the architecture restriction
4835 based on the architecture of the binary package. This means
4836 that architecture restrictions must not be used in binary
4837 relationship fields for architecture-independent packages
4838 (<tt>Architecture: all</tt>).
4843 <example compact="compact">
4844 Depends: foo [i386], bar [amd64]
4846 becomes <tt>Depends: foo</tt> when the package is built on
4847 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4848 package is built on the <tt>amd64</tt> architecture, and omitted
4849 entirely in binary packages built on all other architectures.
4853 If the architecture-restricted dependency is part of a set of
4854 alternatives using <tt>|</tt>, that alternative is ignored
4855 completely on architectures that do not match the restriction.
4857 <example compact="compact">
4858 Build-Depends: foo [!i386] | bar [!amd64]
4860 is equivalent to <tt>bar</tt> on the i386 architecture, to
4861 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4862 bar</tt> on all other architectures.
4866 Relationships may also be restricted to a certain set of
4867 architectures using architecture wildcards in the format
4868 described in <ref id="arch-wildcard-spec">. The syntax for
4869 declaring such restrictions is the same as declaring
4870 restrictions using a certain set of architectures without
4871 architecture wildcards. For example:
4872 <example compact="compact">
4873 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4875 is equivalent to <tt>foo</tt> on architectures using the Linux
4876 kernel and any cpu, <tt>bar</tt> on architectures using any
4877 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4878 using a kernel other than Linux.
4882 Note that the binary package relationship fields such as
4883 <tt>Depends</tt> appear in one of the binary package
4884 sections of the control file, whereas the build-time
4885 relationships such as <tt>Build-Depends</tt> appear in the
4886 source package section of the control file (which is the
4891 <sect id="binarydeps">
4892 <heading>Binary Dependencies - <tt>Depends</tt>,
4893 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4894 <tt>Pre-Depends</tt>
4898 Packages can declare in their control file that they have
4899 certain relationships to other packages - for example, that
4900 they may not be installed at the same time as certain other
4901 packages, and/or that they depend on the presence of others.
4905 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4906 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4907 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4908 <tt>Breaks</tt> is described in <ref id="breaks">, and
4909 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4910 rest are described below.
4914 These seven fields are used to declare a dependency
4915 relationship by one package on another. Except for
4916 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4917 depending (binary) package's control file.
4918 (<tt>Enhances</tt> appears in the recommending package's
4919 control file, and <tt>Breaks</tt> appears in the version of
4920 depended-on package which causes the named package to
4925 A <tt>Depends</tt> field takes effect <em>only</em> when a
4926 package is to be configured. It does not prevent a package
4927 being on the system in an unconfigured state while its
4928 dependencies are unsatisfied, and it is possible to replace
4929 a package whose dependencies are satisfied and which is
4930 properly installed with a different version whose
4931 dependencies are not and cannot be satisfied; when this is
4932 done the depending package will be left unconfigured (since
4933 attempts to configure it will give errors) and will not
4934 function properly. If it is necessary, a
4935 <tt>Pre-Depends</tt> field can be used, which has a partial
4936 effect even when a package is being unpacked, as explained
4937 in detail below. (The other three dependency fields,
4938 <tt>Recommends</tt>, <tt>Suggests</tt> and
4939 <tt>Enhances</tt>, are only used by the various front-ends
4940 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4941 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4945 Since <tt>Depends</tt> only places requirements on the order in
4946 which packages are configured, packages in an installation run
4947 are usually all unpacked first and all configured later.
4949 This approach makes dependency resolution easier. If two
4950 packages A and B are being upgraded, the installed package A
4951 depends on exactly the installed package B, and the new
4952 package A depends on exactly the new package B (a common
4953 situation when upgrading shared libraries and their
4954 corresponding development packages), satisfying the
4955 dependencies at every stage of the upgrade would be
4956 impossible. This relaxed restriction means that both new
4957 packages can be unpacked together and then configured in their
4963 If there is a circular dependency among packages being installed
4964 or removed, installation or removal order honoring the
4965 dependency order is impossible, requiring the dependency loop be
4966 broken at some point and the dependency requirements violated
4967 for at least one package. Packages involved in circular
4968 dependencies may not be able to rely on their dependencies being
4969 configured before they themselves are configured, depending on
4970 which side of the break of the circular dependency loop they
4971 happen to be on. If one of the packages in the loop has
4972 no <prgn>postinst</prgn> script, then the cycle will be broken
4973 at that package; this ensures that all <prgn>postinst</prgn>
4974 scripts are run with their dependencies properly configured if
4975 this is possible. Otherwise the breaking point is arbitrary.
4976 Packages should therefore avoid circular dependencies where
4977 possible, particularly if they have <prgn>postinst</prgn>
4982 The meaning of the five dependency fields is as follows:
4984 <tag><tt>Depends</tt></tag>
4987 This declares an absolute dependency. A package will
4988 not be configured unless all of the packages listed in
4989 its <tt>Depends</tt> field have been correctly
4990 configured (unless there is a circular dependency as
4995 The <tt>Depends</tt> field should be used if the
4996 depended-on package is required for the depending
4997 package to provide a significant amount of
5002 The <tt>Depends</tt> field should also be used if the
5003 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
5004 require the depended-on package to be unpacked or
5005 configured in order to run. In the case of <tt>postinst
5006 configure</tt>, the depended-on packages will be unpacked
5007 and configured first. (If both packages are involved in a
5008 dependency loop, this might not work as expected; see the
5009 explanation a few paragraphs back.) In the case
5010 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
5011 actions, the package dependencies will normally be at
5012 least unpacked, but they may be only "Half-Installed" if a
5013 previous upgrade of the dependency failed.
5017 Finally, the <tt>Depends</tt> field should be used if the
5018 depended-on package is needed by the <prgn>postrm</prgn>
5019 script to fully clean up after the package removal. There
5020 is no guarantee that package dependencies will be
5021 available when <prgn>postrm</prgn> is run, but the
5022 depended-on package is more likely to be available if the
5023 package declares a dependency (particularly in the case
5024 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
5025 script must gracefully skip actions that require a
5026 dependency if that dependency isn't available.
5030 <tag><tt>Recommends</tt></tag>
5033 This declares a strong, but not absolute, dependency.
5037 The <tt>Recommends</tt> field should list packages
5038 that would be found together with this one in all but
5039 unusual installations.
5043 <tag><tt>Suggests</tt></tag>
5045 This is used to declare that one package may be more
5046 useful with one or more others. Using this field
5047 tells the packaging system and the user that the
5048 listed packages are related to this one and can
5049 perhaps enhance its usefulness, but that installing
5050 this one without them is perfectly reasonable.
5053 <tag><tt>Enhances</tt></tag>
5055 This field is similar to Suggests but works in the
5056 opposite direction. It is used to declare that a
5057 package can enhance the functionality of another
5061 <tag><tt>Pre-Depends</tt></tag>
5064 This field is like <tt>Depends</tt>, except that it
5065 also forces <prgn>dpkg</prgn> to complete installation
5066 of the packages named before even starting the
5067 installation of the package which declares the
5068 pre-dependency, as follows:
5072 When a package declaring a pre-dependency is about to
5073 be <em>unpacked</em> the pre-dependency can be
5074 satisfied if the depended-on package is either fully
5075 configured, <em>or even if</em> the depended-on
5076 package(s) are only in the "Unpacked" or the "Half-Configured"
5077 state, provided that they have been configured
5078 correctly at some point in the past (and not removed
5079 or partially removed since). In this case, both the
5080 previously-configured and currently "Unpacked" or
5081 "Half-Configured" versions must satisfy any version
5082 clause in the <tt>Pre-Depends</tt> field.
5086 When the package declaring a pre-dependency is about to
5087 be <em>configured</em>, the pre-dependency will be treated
5088 as a normal <tt>Depends</tt>. It will be considered
5089 satisfied only if the depended-on package has been
5090 correctly configured. However, unlike
5091 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5092 permit circular dependencies to be broken. If a circular
5093 dependency is encountered while attempting to honor
5094 <tt>Pre-Depends</tt>, the installation will be aborted.
5098 <tt>Pre-Depends</tt> are also required if the
5099 <prgn>preinst</prgn> script depends on the named package.
5100 It is best to avoid this situation if possible.
5104 <tt>Pre-Depends</tt> should be used sparingly,
5105 preferably only by packages whose premature upgrade or
5106 installation would hamper the ability of the system to
5107 continue with any upgrade that might be in progress.
5111 You should not specify a <tt>Pre-Depends</tt> entry for a
5112 package before this has been discussed on the
5113 <tt>debian-devel</tt> mailing list and a consensus about
5114 doing that has been reached. See <ref id="dependencies">.
5121 When selecting which level of dependency to use you should
5122 consider how important the depended-on package is to the
5123 functionality of the one declaring the dependency. Some
5124 packages are composed of components of varying degrees of
5125 importance. Such a package should list using
5126 <tt>Depends</tt> the package(s) which are required by the
5127 more important components. The other components'
5128 requirements may be mentioned as Suggestions or
5129 Recommendations, as appropriate to the components' relative
5135 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5138 When one binary package declares that it breaks another,
5139 <prgn>dpkg</prgn> will refuse to allow the package which
5140 declares <tt>Breaks</tt> to be unpacked unless the broken
5141 package is deconfigured first, and it will refuse to
5142 allow the broken package to be reconfigured.
5146 A package will not be regarded as causing breakage merely
5147 because its configuration files are still installed; it must
5148 be at least "Half-Installed".
5152 A special exception is made for packages which declare that
5153 they break their own package name or a virtual package which
5154 they provide (see below): this does not count as a real
5159 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5160 version clause; such a <tt>Breaks</tt> is introduced in the
5161 version of an (implicit or explicit) dependency which violates
5162 an assumption or reveals a bug in earlier versions of the broken
5163 package, or which takes over a file from earlier versions of the
5164 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5165 will inform higher-level package management tools that the
5166 broken package must be upgraded before the new one.
5170 If the breaking package also overwrites some files from the
5171 older package, it should use <tt>Replaces</tt> to ensure this
5172 goes smoothly. See <ref id="replaces"> for a full discussion
5173 of taking over files from other packages, including how to
5174 use <tt>Breaks</tt> in those cases.
5178 Many of the cases where <tt>Breaks</tt> should be used were
5179 previously handled with <tt>Conflicts</tt>
5180 because <tt>Breaks</tt> did not yet exist.
5181 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5182 See <ref id="conflicts"> for more information about the
5187 <sect id="conflicts">
5188 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5191 When one binary package declares a conflict with another using
5192 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5193 allow them to be unpacked on the system at the same time. This
5194 is a stronger restriction than <tt>Breaks</tt>, which prevents
5195 the broken package from being configured while the breaking
5196 package is in the "Unpacked" state but allows both packages to
5197 be unpacked at the same time.
5201 If one package is to be unpacked, the other must be removed
5202 first. If the package being unpacked is marked as replacing
5203 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5204 normally be used in this case) the one on the system, or the one
5205 on the system is marked as deselected, or both packages are
5206 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5207 automatically remove the package which is causing the conflict.
5208 Otherwise, it will halt the installation of the new package with
5209 an error. This mechanism is specifically designed to produce an
5210 error when the installed package is <tt>Essential</tt>, but the
5215 A package will not cause a conflict merely because its
5216 configuration files are still installed; it must be at least
5221 A special exception is made for packages which declare a
5222 conflict with their own package name, or with a virtual
5223 package which they provide (see below): this does not
5224 prevent their installation, and allows a package to conflict
5225 with others providing a replacement for it. You use this
5226 feature when you want the package in question to be the only
5227 package providing some feature.
5231 Normally, <tt>Breaks</tt> should be used instead
5232 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5233 stronger restriction on the ordering of package installation or
5234 upgrade and can make it more difficult for the package manager
5235 to find a correct solution to an upgrade or installation
5236 problem. <tt>Breaks</tt> should be used
5238 <item>when moving a file from one package to another (see
5239 <ref id="replaces">),</item>
5240 <item>when splitting a package (a special case of the previous
5242 <item>when the breaking package exposes a bug in or interacts
5243 badly with particular versions of the broken
5246 <tt>Conflicts</tt> should be used
5248 <item>when two packages provide the same file and will
5249 continue to do so,</item>
5250 <item>in conjunction with <tt>Provides</tt> when only one
5251 package providing a given virtual facility may be unpacked
5252 at a time (see <ref id="virtual">),</item>
5253 <item>in other cases where one must prevent simultaneous
5254 installation of two packages for reasons that are ongoing
5255 (not fixed in a later version of one of the packages) or
5256 that must prevent both packages from being unpacked at the
5257 same time, not just configured.</item>
5259 Be aware that adding <tt>Conflicts</tt> is normally not the best
5260 solution when two packages provide the same files. Depending on
5261 the reason for that conflict, using alternatives or renaming the
5262 files is often a better approach. See, for
5263 example, <ref id="binaries">.
5267 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5268 unless two packages cannot be installed at the same time or
5269 installing them both causes one of them to be broken or
5270 unusable. Having similar functionality or performing the same
5271 tasks as another package is not sufficient reason to
5272 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5276 A <tt>Conflicts</tt> entry may have an "earlier than" version
5277 clause if the reason for the conflict is corrected in a later
5278 version of one of the packages. However, normally the presence
5279 of an "earlier than" version clause is a sign
5280 that <tt>Breaks</tt> should have been used instead. An "earlier
5281 than" version clause in <tt>Conflicts</tt>
5282 prevents <prgn>dpkg</prgn> from upgrading or installing the
5283 package which declares such a conflict until the upgrade or
5284 removal of the conflicted-with package has been completed, which
5285 is a strong restriction.
5289 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5293 As well as the names of actual ("concrete") packages, the
5294 package relationship fields <tt>Depends</tt>,
5295 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5296 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5297 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5298 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5299 may mention "virtual packages".
5303 A <em>virtual package</em> is one which appears in the
5304 <tt>Provides</tt> control field of another package. The effect
5305 is as if the package(s) which provide a particular virtual
5306 package name had been listed by name everywhere the virtual
5307 package name appears. (See also <ref id="virtual_pkg">)
5311 If there are both concrete and virtual packages of the same
5312 name, then the dependency may be satisfied (or the conflict
5313 caused) by either the concrete package with the name in
5314 question or any other concrete package which provides the
5315 virtual package with the name in question. This is so that,
5316 for example, supposing we have
5317 <example compact="compact">
5320 </example> and someone else releases an enhanced version of
5321 the <tt>bar</tt> package they can say:
5322 <example compact="compact">
5326 and the <tt>bar-plus</tt> package will now also satisfy the
5327 dependency for the <tt>foo</tt> package.
5331 If a relationship field has a version number attached, only real
5332 packages will be considered to see whether the relationship is
5333 satisfied (or the prohibition violated, for a conflict or
5334 breakage). In other words, if a version number is specified,
5335 this is a request to ignore all <tt>Provides</tt> for that
5336 package name and consider only real packages. The package
5337 manager will assume that a package providing that virtual
5338 package is not of the "right" version. A <tt>Provides</tt>
5339 field may not contain version numbers, and the version number of
5340 the concrete package which provides a particular virtual package
5341 will not be considered when considering a dependency on or
5342 conflict with the virtual package name.<footnote>
5343 It is possible that a future release of <prgn>dpkg</prgn> may
5344 add the ability to specify a version number for each virtual
5345 package it provides. This feature is not yet present,
5346 however, and is expected to be used only infrequently.
5351 To specify which of a set of real packages should be the default
5352 to satisfy a particular dependency on a virtual package, list
5353 the real package as an alternative before the virtual one.
5357 If the virtual package represents a facility that can only be
5358 provided by one real package at a time, such as
5359 the <package>mail-transport-agent</package> virtual package that
5360 requires installation of a binary that would conflict with all
5361 other providers of that virtual package (see
5362 <ref id="mail-transport-agents">), all packages providing that
5363 virtual package should also declare a conflict with it
5364 using <tt>Conflicts</tt>. This will ensure that at most one
5365 provider of that virtual package is unpacked or installed at a
5370 <sect id="replaces"><heading>Overwriting files and replacing
5371 packages - <tt>Replaces</tt></heading>
5374 Packages can declare in their control file that they should
5375 overwrite files in certain other packages, or completely replace
5376 other packages. The <tt>Replaces</tt> control field has these
5377 two distinct purposes.
5380 <sect1><heading>Overwriting files in other packages</heading>
5383 It is usually an error for a package to contain files which
5384 are on the system in another package. However, if the
5385 overwriting package declares that it <tt>Replaces</tt> the one
5386 containing the file being overwritten, then <prgn>dpkg</prgn>
5387 will replace the file from the old package with that from the
5388 new. The file will no longer be listed as "owned" by the old
5389 package and will be taken over by the new package.
5390 Normally, <tt>Breaks</tt> should be used in conjunction
5391 with <tt>Replaces</tt>.<footnote>
5392 To see why <tt>Breaks</tt> is normally needed in addition
5393 to <tt>Replaces</tt>, consider the case of a file in the
5394 package <package>foo</package> being taken over by the
5395 package <package>foo-data</package>.
5396 <tt>Replaces</tt> will allow <package>foo-data</package> to
5397 be installed and take over that file. However,
5398 without <tt>Breaks</tt>, nothing
5399 requires <package>foo</package> to be upgraded to a newer
5400 version that knows it does not include that file and instead
5401 depends on <package>foo-data</package>. Nothing would
5402 prevent the new <package>foo-data</package> package from
5403 being installed and then removed, removing the file that it
5404 took over from <package>foo</package>. After that
5405 operation, the package manager would think the system was in
5406 a consistent state, but the <package>foo</package> package
5407 would be missing one of its files.
5412 For example, if a package <package>foo</package> is split
5413 into <package>foo</package> and <package>foo-data</package>
5414 starting at version 1.2-3, <package>foo-data</package> would
5416 <example compact="compact">
5417 Replaces: foo (<< 1.2-3)
5418 Breaks: foo (<< 1.2-3)
5420 in its control file. The new version of the
5421 package <package>foo</package> would normally have the field
5422 <example compact="compact">
5423 Depends: foo-data (>= 1.2-3)
5425 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5426 the files moved into <package>foo-data</package> are not
5427 required for normal operation).
5431 If a package is completely replaced in this way, so that
5432 <prgn>dpkg</prgn> does not know of any files it still
5433 contains, it is considered to have "disappeared". It will
5434 be marked as not wanted on the system (selected for
5435 removal) and "Not-Installed". Any <tt>conffile</tt>s
5436 details noted for the package will be ignored, as they
5437 will have been taken over by the overwriting package. The
5438 package's <prgn>postrm</prgn> script will be run with a
5439 special argument to allow the package to do any final
5440 cleanup required. See <ref id="mscriptsinstact">.
5442 Replaces is a one way relationship. You have to install
5443 the replacing package after the replaced package.
5448 For this usage of <tt>Replaces</tt>, virtual packages (see
5449 <ref id="virtual">) are not considered when looking at a
5450 <tt>Replaces</tt> field. The packages declared as being
5451 replaced must be mentioned by their real names.
5455 This usage of <tt>Replaces</tt> only takes effect when both
5456 packages are at least partially on the system at once. It is
5457 not relevant if the packages conflict unless the conflict has
5462 <sect1><heading>Replacing whole packages, forcing their
5466 Second, <tt>Replaces</tt> allows the packaging system to
5467 resolve which package should be removed when there is a
5468 conflict (see <ref id="conflicts">). This usage only takes
5469 effect when the two packages <em>do</em> conflict, so that the
5470 two usages of this field do not interfere with each other.
5474 In this situation, the package declared as being replaced
5475 can be a virtual package, so for example, all mail
5476 transport agents (MTAs) would have the following fields in
5477 their control files:
5478 <example compact="compact">
5479 Provides: mail-transport-agent
5480 Conflicts: mail-transport-agent
5481 Replaces: mail-transport-agent
5483 ensuring that only one MTA can be unpacked at any one
5484 time. See <ref id="virtual"> for more information about this
5489 <sect id="sourcebinarydeps">
5490 <heading>Relationships between source and binary packages -
5491 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5492 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5496 Source packages that require certain binary packages to be
5497 installed or absent at the time of building the package
5498 can declare relationships to those binary packages.
5502 This is done using the <tt>Build-Depends</tt>,
5503 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5504 <tt>Build-Conflicts-Indep</tt> control fields.
5508 Build-dependencies on "build-essential" binary packages can be
5509 omitted. Please see <ref id="pkg-relations"> for more information.
5513 The dependencies and conflicts they define must be satisfied
5514 (as defined earlier for binary packages) in order to invoke
5515 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5517 There is no Build-Depends-Arch; this role is essentially
5518 met with Build-Depends. Anyone building the
5519 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5520 assumed to be building the whole package, and therefore
5521 installation of all build dependencies is required.
5524 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5525 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5526 not yet know how to check for its existence, and
5527 <tt>binary-arch</tt>. The purpose of the original split
5528 between <tt>Build-Depends</tt> and
5529 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5530 wouldn't need to install extra packages needed only for the
5531 binary-indep targets. But without a build-arch/build-indep
5532 split, this didn't work, since most of the work is done in
5533 the build target, not in the binary target.
5537 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5538 <tt>binary-arch</tt></tag>
5540 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5541 fields must be satisfied when these targets are invoked.
5543 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5544 and <tt>binary-indep</tt></tag>
5546 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5547 <tt>Build-Depends-Indep</tt>, and
5548 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5549 these targets are invoked.
5555 <sect id="built-using">
5556 <heading>Additional source packages used to build the binary
5557 - <tt>Built-Using</tt>
5561 Some binary packages incorporate parts of other packages when built
5562 but do not have to depend on those packages. Examples include
5563 linking with static libraries or incorporating source code from
5564 another package during the build. In this case, the source packages
5565 of those other packages are a required part of the complete source
5566 (the binary package is not reproducible without them).
5570 A <tt>Built-Using</tt> field must list the corresponding source
5571 package for any such binary package incorporated during the build
5573 <tt>Build-Depends</tt> in the source package is not adequate since
5574 it (rightfully) does not document the exact version used in the
5577 including an "exactly equal" ("=") version relation on the version
5578 that was used to build that binary package<footnote>
5579 The archive software might reject packages that refer to
5580 non-existent sources.
5585 A package using the source code from the gcc-4.6-source
5586 binary package built from the gcc-4.6 source package would
5587 have this field in its control file:
5588 <example compact="compact">
5589 Built-Using: gcc-4.6 (= 4.6.0-11)
5594 A package including binaries from grub2 and loadlin would
5595 have this field in its control file:
5596 <example compact="compact">
5597 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5604 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5607 Packages containing shared libraries must be constructed with
5608 a little care to make sure that the shared library is always
5609 available. This is especially important for packages whose
5610 shared libraries are vitally important, such as the C library
5611 (currently <tt>libc6</tt>).
5615 This section deals only with public shared libraries: shared
5616 libraries that are placed in directories searched by the dynamic
5617 linker by default or which are intended to be linked against
5618 normally and possibly used by other, independent packages. Shared
5619 libraries that are internal to a particular package or that are
5620 only loaded as dynamic modules are not covered by this section and
5621 are not subject to its requirements.
5625 A shared library is identified by the <tt>SONAME</tt> attribute
5626 stored in its dynamic section. When a binary is linked against a
5627 shared library, the <tt>SONAME</tt> of the shared library is
5628 recorded in the binary's <tt>NEEDED</tt> section so that the
5629 dynamic linker knows that library must be loaded at runtime. The
5630 shared library file's full name (which usually contains additional
5631 version information not needed in the <tt>SONAME</tt>) is
5632 therefore normally not referenced directly. Instead, the shared
5633 library is loaded by its <tt>SONAME</tt>, which exists on the file
5634 system as a symlink pointing to the full name of the shared
5635 library. This symlink must be provided by the
5636 package. <ref id="sharedlibs-runtime"> describes how to do this.
5638 This is a convention of shared library versioning, but not a
5639 requirement. Some libraries use the <tt>SONAME</tt> as the full
5640 library file name instead and therefore do not need a symlink.
5641 Most, however, encode additional information about
5642 backwards-compatible revisions as a minor version number in the
5643 file name. The <tt>SONAME</tt> itself only changes when
5644 binaries linked with the earlier version of the shared library
5645 may no longer work, but the filename may change with each
5646 release of the library. See <ref id="sharedlibs-runtime"> for
5652 When linking a binary or another shared library against a shared
5653 library, the <tt>SONAME</tt> for that shared library is not yet
5654 known. Instead, the shared library is found by looking for a file
5655 matching the library name with <tt>.so</tt> appended. This file
5656 exists on the file system as a symlink pointing to the shared
5661 Shared libraries are normally split into several binary packages.
5662 The <tt>SONAME</tt> symlink is installed by the runtime shared
5663 library package, and the bare <tt>.so</tt> symlink is installed in
5664 the development package since it's only used when linking binaries
5665 or shared libraries. However, there are some exceptions for
5666 unusual shared libraries or for shared libraries that are also
5667 loaded as dynamic modules by other programs.
5671 This section is primarily concerned with how the separation of
5672 shared libraries into multiple packages should be done and how
5673 dependencies on and between shared library binary packages are
5674 managed in Debian. <ref id="libraries"> should be read in
5675 conjunction with this section and contains additional rules for
5676 the files contained in the shared library packages.
5679 <sect id="sharedlibs-runtime">
5680 <heading>Run-time shared libraries</heading>
5683 The run-time shared library must be placed in a package
5684 whose name changes whenever the <tt>SONAME</tt> of the shared
5685 library changes. This allows several versions of the shared
5686 library to be installed at the same time, allowing installation
5687 of the new version of the shared library without immediately
5688 breaking binaries that depend on the old version. Normally, the
5689 run-time shared library and its <tt>SONAME</tt> symlink should
5690 be placed in a package named
5691 <package><var>libraryname</var><var>soversion</var></package>,
5692 where <var>soversion</var> is the version number in
5693 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5694 would be confusing to directly append <var>soversion</var>
5695 to <var>libraryname</var> (if, for
5696 example, <var>libraryname</var> itself ends in a number), you
5698 <package><var>libraryname</var>-<var>soversion</var></package>
5703 To determine the <var>soversion</var>, look at
5704 the <tt>SONAME</tt> of the library, stored in the
5705 ELF <tt>SONAME</tt> attribute. It is usually of the
5706 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5707 example, <tt>libz.so.1</tt>). The version part is the part
5708 which comes after <tt>.so.</tt>, so in that example it
5709 is <tt>1</tt>. The soname may instead be of the
5710 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5711 as <tt>libdb-5.1.so</tt>, in which case the name would
5712 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5716 If you have several shared libraries built from the same source
5717 tree, you may lump them all together into a single shared
5718 library package provided that all of their <tt>SONAME</tt>s will
5719 always change together. Be aware that this is not normally the
5720 case, and if the <tt>SONAME</tt>s do not change together,
5721 upgrading such a merged shared library package will be
5722 unnecessarily difficult because of file conflicts with the old
5723 version of the package. When in doubt, always split shared
5724 library packages so that each binary package installs a single
5729 Every time the shared library ABI changes in a way that may
5730 break binaries linked against older versions of the shared
5731 library, the <tt>SONAME</tt> of the library and the
5732 corresponding name for the binary package containing the runtime
5733 shared library should change. Normally, this means
5734 the <tt>SONAME</tt> should change any time an interface is
5735 removed from the shared library or the signature of an interface
5736 (the number of parameters or the types of parameters that it
5737 takes, for example) is changed. This practice is vital to
5738 allowing clean upgrades from older versions of the package and
5739 clean transitions between the old ABI and new ABI without having
5740 to upgrade every affected package simultaneously.
5744 The <tt>SONAME</tt> and binary package name need not, and indeed
5745 normally should not, change if new interfaces are added but none
5746 are removed or changed, since this will not break binaries
5747 linked against the old shared library. Correct versioning of
5748 dependencies on the newer shared library by binaries that use
5749 the new interfaces is handled via
5750 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5751 or <tt>shlibs</tt> system</qref>.
5755 The package should install the shared libraries under
5756 their normal names. For example, the <package>libgdbm3</package>
5757 package should install <file>libgdbm.so.3.0.0</file> as
5758 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5759 renamed or re-linked by any <prgn>prerm</prgn> or
5760 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5761 of renaming things safely without affecting running programs,
5762 and attempts to interfere with this are likely to lead to
5767 Shared libraries should not be installed executable, since
5768 the dynamic linker does not require this and trying to
5769 execute a shared library usually results in a core dump.
5773 The run-time library package should include the symbolic link for
5774 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5775 the shared libraries. For example,
5776 the <package>libgdbm3</package> package should include a symbolic
5777 link from <file>/usr/lib/libgdbm.so.3</file> to
5778 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5779 linker (for example <prgn>ld.so</prgn> or
5780 <prgn>ld-linux.so.*</prgn>) can find the library between the
5781 time that <prgn>dpkg</prgn> installs it and the time that
5782 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5784 The package management system requires the library to be
5785 placed before the symbolic link pointing to it in the
5786 <file>.deb</file> file. This is so that when
5787 <prgn>dpkg</prgn> comes to install the symlink
5788 (overwriting the previous symlink pointing at an older
5789 version of the library), the new shared library is already
5790 in place. In the past, this was achieved by creating the
5791 library in the temporary packaging directory before
5792 creating the symlink. Unfortunately, this was not always
5793 effective, since the building of the tar file in the
5794 <file>.deb</file> depended on the behavior of the underlying
5795 file system. Some file systems (such as reiserfs) reorder
5796 the files so that the order of creation is forgotten.
5797 Since version 1.7.0, <prgn>dpkg</prgn>
5798 reorders the files itself as necessary when building a
5799 package. Thus it is no longer important to concern
5800 oneself with the order of file creation.
5804 <sect1 id="ldconfig">
5805 <heading><tt>ldconfig</tt></heading>
5808 Any package installing shared libraries in one of the default
5809 library directories of the dynamic linker (which are currently
5810 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5811 listed in <file>/etc/ld.so.conf</file><footnote>
5812 These are currently <file>/usr/local/lib</file> plus
5813 directories under <file>/lib</file> and <file>/usr/lib</file>
5814 matching the multiarch triplet for the system architecture.
5816 must use <prgn>ldconfig</prgn> to update the shared library
5821 The package maintainer scripts must only call
5822 <prgn>ldconfig</prgn> under these circumstances:
5823 <list compact="compact">
5824 <item>When the <prgn>postinst</prgn> script is run with a
5825 first argument of <tt>configure</tt>, the script must call
5826 <prgn>ldconfig</prgn>, and may optionally invoke
5827 <prgn>ldconfig</prgn> at other times.
5829 <item>When the <prgn>postrm</prgn> script is run with a
5830 first argument of <tt>remove</tt>, the script should call
5831 <prgn>ldconfig</prgn>.
5836 During install or upgrade, the preinst is called before
5837 the new files are unpacked, so calling "ldconfig" is
5838 pointless. The preinst of an existing package can also be
5839 called if an upgrade fails. However, this happens during
5840 the critical time when a shared libs may exist on-disk
5841 under a temporary name. Thus, it is dangerous and
5842 forbidden by current policy to call "ldconfig" at this
5847 When a package is installed or upgraded, "postinst
5848 configure" runs after the new files are safely on-disk.
5849 Since it is perfectly safe to invoke ldconfig
5850 unconditionally in a postinst, it is OK for a package to
5851 simply put ldconfig in its postinst without checking the
5852 argument. The postinst can also be called to recover from
5853 a failed upgrade. This happens before any new files are
5854 unpacked, so there is no reason to call "ldconfig" at this
5859 For a package that is being removed, prerm is
5860 called with all the files intact, so calling ldconfig is
5861 useless. The other calls to "prerm" happen in the case of
5862 upgrade at a time when all the files of the old package
5863 are on-disk, so again calling "ldconfig" is pointless.
5867 postrm, on the other hand, is called with the "remove"
5868 argument just after the files are removed, so this is
5869 the proper time to call "ldconfig" to notify the system
5870 of the fact that the shared libraries from the package
5871 are removed. The postrm can be called at several other
5872 times. At the time of "postrm purge", "postrm
5873 abort-install", or "postrm abort-upgrade", calling
5874 "ldconfig" is useless because the shared lib files are
5875 not on-disk. However, when "postrm" is invoked with
5876 arguments "upgrade", "failed-upgrade", or "disappear", a
5877 shared lib may exist on-disk under a temporary filename.
5885 <sect id="sharedlibs-support-files">
5886 <heading>Shared library support files</heading>
5889 If your package contains files whose names do not change with
5890 each change in the library shared object version, you must not
5891 put them in the shared library package. Otherwise, several
5892 versions of the shared library cannot be installed at the same
5893 time without filename clashes, making upgrades and transitions
5894 unnecessarily difficult.
5898 It is recommended that supporting files and run-time support
5899 programs that do not need to be invoked manually by users, but
5900 are nevertheless required for the package to function, be placed
5901 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5902 preferably under <file>/usr/lib/</file><var>package-name</var>.
5903 If the program or file is architecture independent, the
5904 recommendation is for it to be placed in a subdirectory of
5905 <file>/usr/share</file> instead, preferably under
5906 <file>/usr/share/</file><var>package-name</var>. Following the
5907 <var>package-name</var> naming convention ensures that the file
5908 names change when the shared object version changes.
5912 Run-time support programs that use the shared library but are
5913 not required for the library to function or files used by the
5914 shared library that can be used by any version of the shared
5915 library package should instead be put in a separate package.
5916 This package might typically be named
5917 <package><var>libraryname</var>-tools</package>; note the
5918 absence of the <var>soversion</var> in the package name.
5922 Files and support programs only useful when compiling software
5923 against the library should be included in the development
5924 package for the library.<footnote>
5925 For example, a <file><var>package-name</var>-config</file>
5926 script or <package>pkg-config</package> configuration files.
5931 <sect id="sharedlibs-static">
5932 <heading>Static libraries</heading>
5935 The static library (<file><var>libraryname.a</var></file>)
5936 is usually provided in addition to the shared version.
5937 It is placed into the development package (see below).
5941 In some cases, it is acceptable for a library to be
5942 available in static form only; these cases include:
5944 <item>libraries for languages whose shared library support
5945 is immature or unstable</item>
5946 <item>libraries whose interfaces are in flux or under
5947 development (commonly the case when the library's
5948 major version number is zero, or where the ABI breaks
5949 across patchlevels)</item>
5950 <item>libraries which are explicitly intended to be
5951 available only in static form by their upstream
5956 <sect id="sharedlibs-dev">
5957 <heading>Development files</heading>
5960 If there are development files associated with a shared library,
5961 the source package needs to generate a binary development package
5962 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5963 or if you prefer only to support one development version at a
5964 time, <package><var>libraryname</var>-dev</package>. Installing
5965 the development package must result in installation of all the
5966 development files necessary for compiling programs against that
5967 shared library.<footnote>
5968 This wording allows the development files to be split into
5969 several packages, such as a separate architecture-independent
5970 <package><var>libraryname</var>-headers</package>, provided that
5971 the development package depends on all the required additional
5977 In case several development versions of a library exist, you may
5978 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5979 <ref id="conflicts">) to ensure that the user only installs one
5980 development version at a time (as different development versions are
5981 likely to have the same header files in them, which would cause a
5982 filename clash if both were unpacked).
5986 The development package should contain a symlink for the associated
5987 shared library without a version number. For example, the
5988 <package>libgdbm-dev</package> package should include a symlink
5989 from <file>/usr/lib/libgdbm.so</file> to
5990 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5991 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5992 <file>libgdbm.so</file> when compiling dynamically.
5996 If the package provides Ada Library Information
5997 (<file>*.ali</file>) files for use with GNAT, these files must be
5998 installed read-only (mode 0444) so that GNAT will not attempt to
5999 recompile them. This overrides the normal file mode requirements
6000 given in <ref id="permissions-owners">.
6004 <sect id="sharedlibs-intradeps">
6005 <heading>Dependencies between the packages of the same library</heading>
6008 Typically the development version should have an exact
6009 version dependency on the runtime library, to make sure that
6010 compilation and linking happens correctly. The
6011 <tt>${binary:Version}</tt> substitution variable can be
6012 useful for this purpose.
6014 Previously, <tt>${Source-Version}</tt> was used, but its name
6015 was confusing and it has been deprecated since dpkg 1.13.19.
6020 <sect id="sharedlibs-depends">
6021 <heading>Dependencies between the library and other
6025 If a package contains a binary or library which links to a
6026 shared library, we must ensure that, when the package is
6027 installed on the system, all of the libraries needed are also
6028 installed. These dependencies must be added to the binary
6029 package when it is built, since they may change based on which
6030 version of a shared library the binary or library was linked
6031 with even if there are no changes to the source of the binary
6032 (for example, symbol versions change, macros become functions or
6033 vice versa, or the binary package may determine at compile-time
6034 whether new library interfaces are available and can be called).
6035 To allow these dependencies to be constructed, shared libraries
6036 must provide either a <file>symbols</file> file or
6037 a <file>shlibs</file> file. These provide information on the
6038 package dependencies required to ensure the presence of
6039 interfaces provided by this library. Any package with binaries
6040 or libraries linking to a shared library must use these files to
6041 determine the required dependencies when it is built. Other
6042 packages which use a shared library (for example using
6043 <tt>dlopen()</tt>) should compute appropriate dependencies
6044 using these files at build time as well.
6048 The two mechanisms differ in the degree of detail that they
6049 provide. A <file>symbols</file> file documents, for each symbol
6050 exported by a library, the minimal version of the package any
6051 binary using this symbol will need. This is typically the
6052 version of the package in which the symbol was introduced. This
6053 information permits detailed analysis of the symbols used by a
6054 particular package and construction of an accurate dependency,
6055 but it requires the package maintainer to track more information
6056 about the shared library.
6060 A <file>shlibs</file> file, in contrast, only documents the last
6061 time the library ABI changed in any way. It only provides
6062 information about the library as a whole, not individual
6063 symbols. When a package is built using a shared library with
6064 only a <file>shlibs</file> file, the generated dependency will
6065 require a version of the shared library equal to or newer than
6066 the version of the last ABI change. This generates
6067 unnecessarily restrictive dependencies compared
6068 to <file>symbols</file> files if none of the symbols used by the
6069 package have changed. This, in turn, may make upgrades
6070 needlessly complex and unnecessarily restrict use of the package
6071 on systems with older versions of the shared libraries.
6075 <file>shlibs</file> files also only support a limited range of
6076 library SONAMEs, making it difficult to use <file>shlibs</file>
6077 files in some unusual corner cases.<footnote>
6078 A <file>shlibs</file> file represents an SONAME as a library
6079 name and version number, such as <tt>libfoo VERSION</tt>,
6080 instead of recording the actual SONAME. If the SONAME doesn't
6081 match one of the two expected formats
6082 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6083 cannot be represented.
6088 <file>symbols</file> files are therefore recommended for most
6089 shared library packages since they provide more accurate
6090 dependencies. For most C libraries, the additional detail
6091 required by <file>symbols</file> files is not too difficult to
6092 maintain. However, maintaining exhaustive symbols information
6093 for a C++ library can be quite onerous, so <file>shlibs</file>
6094 files may be more appropriate for most C++ libraries. Libraries
6095 with a corresponding udeb must also provide
6096 a <file>shlibs</file> file, since the udeb infrastructure does
6097 not use <file>symbols</file> files.
6100 <sect1 id="dpkg-shlibdeps">
6101 <heading>Generating dependencies on shared libraries</heading>
6104 When a package that contains any shared libraries or compiled
6105 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6106 each shared library and compiled binary to determine the
6107 libraries used and hence the dependencies needed by the
6109 <prgn>dpkg-shlibdeps</prgn> will use a program
6110 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6111 the libraries and the symbols in those libraries directly
6112 needed by the binaries or shared libraries in the package.
6114 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6115 your <file>debian/rules</file> file in the source package.
6116 List all of the compiled binaries, libraries, or loadable
6117 modules in your package.<footnote>
6118 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6119 correctly is to use a package helper framework such
6120 as <package>debhelper</package>. If you are
6121 using <package>debhelper</package>,
6122 the <prgn>dh_shlibdeps</prgn> program will do this work for
6123 you. It will also correctly handle multi-binary packages.
6125 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6126 or <file>shlibs</file> files installed by the shared libraries
6127 to generate dependency information. The package must then
6128 provide a substitution variable into which the discovered
6129 dependency information can be placed.
6133 If you are creating a udeb for use in the Debian Installer,
6134 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6135 should use the dependency line of type <tt>udeb</tt> by adding
6136 the <tt>-tudeb</tt> option<footnote>
6137 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6138 will automatically add this option if it knows it is
6140 </footnote>. If there is no dependency line of
6141 type <tt>udeb</tt> in the <file>shlibs</file>
6142 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6143 regular dependency line.
6147 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6148 into the <file>debian/substvars</file> file by default, which
6149 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6150 to place a <tt>${shlibs:Depends}</tt> variable in
6151 the <tt>Depends</tt> field in the control file of every binary
6152 package built by this source package that contains compiled
6153 binaries, libraries, or loadable modules. If you have
6154 multiple binary packages, you will need to
6155 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6156 compiled libraries or binaries. For example, you could use
6157 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6158 specify a different <file>substvars</file> file for each
6159 binary package.<footnote>
6160 Again, <prgn>dh_shlibdeps</prgn>
6161 and <prgn>dh_gencontrol</prgn> will handle everything except
6162 the addition of the variable to the control file for you if
6163 you're using <package>debhelper</package>, including
6164 generating separate <file>substvars</file> files for each
6165 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6166 the appropriate flags.
6171 For more details on <prgn>dpkg-shlibdeps</prgn>,
6172 see <manref name="dpkg-shlibdeps" section="1">.
6176 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6177 library <tt>libbar</tt> if it is explicitly linked with that
6178 library (that is, the library is listed in the
6179 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6180 to the link line when the binary is created). Other libraries
6181 that are needed by <tt>libbar</tt> are
6182 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6183 linker will load them automatically when it
6184 loads <tt>libbar</tt>. A package should depend on the
6185 libraries it directly uses, but not the libraries it only uses
6186 indirectly. The dependencies for the libraries used
6187 directly will automatically pull in the indirectly-used
6188 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6189 automatically, but package maintainers need to be aware of
6190 this distinction between directly and indirectly using a
6191 library if they have to override its results for some reason.
6193 A good example of where this helps is the following. We
6194 could update <tt>libimlib</tt> with a new version that
6195 supports a new revision of a graphics format called dgf (but
6196 retaining the same major version number) and depends on a
6197 new library package <package>libdgf4</package> instead of
6198 the older <package>libdgf3</package>. If we
6199 used <prgn>ldd</prgn> to add dependencies for every library
6200 directly or indirectly linked with a binary, every package
6201 that uses <tt>libimlib</tt> would need to be recompiled so
6202 it would also depend on <package>libdgf4</package> in order
6203 to retire the older <package>libdgf3</package> package.
6204 Since dependencies are only added based on
6205 ELF <tt>NEEDED</tt> attribute, packages
6206 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6207 having the dependency on an appropriate version
6208 of <tt>libdgf</tt> and do not need rebuilding.
6213 <sect1 id="sharedlibs-updates">
6214 <heading>Shared library ABI changes</heading>
6217 Maintaining a shared library package using
6218 either <file>symbols</file> or <file>shlibs</file> files
6219 requires being aware of the exposed ABI of the shared library
6220 and any changes to it. Both <file>symbols</file>
6221 and <file>shlibs</file> files record every change to the ABI
6222 of the shared library; <file>symbols</file> files do so per
6223 public symbol, whereas <file>shlibs</file> files record only
6224 the last change for the entire library.
6228 There are two types of ABI changes: ones that are
6229 backward-compatible and ones that are not. An ABI change is
6230 backward-compatible if any reasonable program or library that
6231 was linked with the previous version of the shared library
6232 will still work correctly with the new version of the shared
6234 An example of an "unreasonable" program is one that uses
6235 library interfaces that are documented as internal and
6236 unsupported. If the only programs or libraries affected by
6237 a change are "unreasonable" ones, other techniques, such as
6238 declaring <tt>Breaks</tt> relationships with affected
6239 packages or treating their usage of the library as bugs in
6240 those packages, may be appropriate instead of changing the
6241 SONAME. However, the default approach is to change the
6242 SONAME for any change to the ABI that could break a program.
6244 Adding new symbols to the shared library is a
6245 backward-compatible change. Removing symbols from the shared
6246 library is not. Changing the behavior of a symbol may or may
6247 not be backward-compatible depending on the change; for
6248 example, changing a function to accept a new enum constant not
6249 previously used by the library is generally
6250 backward-compatible, but changing the members of a struct that
6251 is passed into library functions is generally not unless the
6252 library takes special precautions to accept old versions of
6257 ABI changes that are not backward-compatible normally require
6258 changing the <tt>SONAME</tt> of the library and therefore the
6259 shared library package name, which forces rebuilding all
6260 packages using that shared library to update their
6261 dependencies and allow them to use the new version of the
6262 shared library. For more information,
6263 see <ref id="sharedlibs-runtime">. The remainder of this
6264 section will deal with backward-compatible changes.
6268 Backward-compatible changes require either updating or
6269 recording the <var>minimal-version</var> for that symbol
6270 in <file>symbols</file> files or updating the version in
6271 the <var>dependencies</var> in <file>shlibs</file> files. For
6272 more information on how to do this in the two formats, see
6273 <ref id="symbols"> and <ref id="shlibs">. Below are general
6274 rules that apply to both files.
6278 The easy case is when a public symbol is added. Simply add
6279 the version at which the symbol was introduced
6280 (for <file>symbols</file> files) or update the dependency
6281 version (for <file>shlibs</file>) files. But special care
6282 should be taken to update dependency versions when the
6283 behavior of a public symbol changes. This is easy to neglect,
6284 since there is no automated method of determining such
6285 changes, but failing to update versions in this case may
6286 result in binary packages with too-weak dependencies that will
6287 fail at runtime, possibly in ways that can cause security
6288 vulnerabilities. If the package maintainer believes that a
6289 symbol behavior change may have occurred but isn't sure, it's
6290 safer to update the version rather than leave it unmodified.
6291 This may result in unnecessarily strict dependencies, but it
6292 ensures that packages whose dependencies are satisfied will
6297 A common example of when a change to the dependency version
6298 is required is a function that takes an enum or struct
6299 argument that controls what the function does. For example:
6301 enum library_op { OP_FOO, OP_BAR };
6302 int library_do_operation(enum library_op);
6304 If a new operation, <tt>OP_BAZ</tt>, is added,
6305 the <var>minimal-version</var>
6306 of <tt>library_do_operation</tt> (for <file>symbols</file>
6307 files) or the version in the dependency for the shared library
6308 (for <file>shlibs</file> files) must be increased to the
6309 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6310 binary built against the new version of the library (having
6311 detected at compile-time that the library
6312 supports <tt>OP_BAZ</tt>) may be installed with a shared
6313 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6314 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6319 Dependency versions in either <file>symbols</file>
6320 or <file>shlibs</file> files normally should not contain the
6321 Debian revision of the package, since the library behavior is
6322 normally fixed for a particular upstream version and any
6323 Debian packaging of that upstream version will have the same
6324 behavior. In the rare case that the library behavior was
6325 changed in a particular Debian revision, appending <tt>~</tt>
6326 to the end of the version that includes the Debian revision is
6327 recommended, since this allows backports of the shared library
6328 package using the normal backport versioning convention to
6329 satisfy the dependency.
6333 <sect1 id="sharedlibs-symbols">
6334 <heading>The <tt>symbols</tt> system</heading>
6337 In the following sections, we will first describe where the
6338 various <file>symbols</file> files are to be found, then
6339 the <file>symbols</file> file format, and finally how to
6340 create <file>symbols</file> files if your package contains a
6344 <sect2 id="symbols-paths">
6345 <heading>The <file>symbols</file> files present on the
6349 <file>symbols</file> files for a shared library are normally
6350 provided by the shared library package as a control file,
6351 but there are several override paths that are checked first
6352 in case that information is wrong or missing. The following
6353 list gives them in the order in which they are read
6354 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6355 the required information is used.
6358 <p><file>debian/*/DEBIAN/symbols</file></p>
6361 During the package build, if the package itself
6362 contains shared libraries with <file>symbols</file>
6363 files, they will be generated in these staging
6364 directories by <prgn>dpkg-gensymbols</prgn>
6365 (see <ref id="providing-symbols">). <file>symbols</file>
6366 files found in the build tree take precedence
6367 over <file>symbols</file> files from other binary
6372 These files must exist
6373 before <prgn>dpkg-shlibdeps</prgn> is run or the
6374 dependencies of binaries and libraries from a source
6375 package on other libraries from that same source
6376 package will not be correct. In practice, this means
6377 that <prgn>dpkg-gensymbols</prgn> must be run
6378 before <prgn>dpkg-shlibdeps</prgn> during the package
6380 An example may clarify. Suppose the source
6381 package <tt>foo</tt> generates two binary
6382 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6383 When building the binary packages, the contents of
6384 the packages are staged in the
6385 directories <file>debian/libfoo2</file>
6386 and <file>debian/foo-runtime</file> respectively.
6387 (<file>debian/tmp</file> could be used instead of
6388 one of these.) Since <tt>libfoo2</tt> provides
6389 the <tt>libfoo</tt> shared library, it will contain
6390 a <tt>symbols</tt> file, which will be installed
6391 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6392 eventually to be included as a control file in that
6393 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6395 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6397 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6398 to determine whether <tt>foo-prog</tt>'s library
6399 dependencies are satisfied by any of the libraries
6400 provided by <tt>libfoo2</tt>. Since those binaries
6401 were linked against the just-built shared library as
6402 part of the build process, the <file>symbols</file>
6403 file for the newly-built <tt>libfoo2</tt> must take
6404 precedence over a <file>symbols</file> file for any
6405 other <tt>libfoo2</tt> package already installed on
6413 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6414 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6418 Per-system overrides of shared library dependencies.
6419 These files normally do not exist. They are
6420 maintained by the local system administrator and must
6421 not be created by any Debian package.
6426 <p><file>symbols</file> control files for packages
6427 installed on the system</p>
6430 The <file>symbols</file> control files for all the
6431 packages currently installed on the system are
6432 searched last. This will be the most common source of
6433 shared library dependency information. These are
6435 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6436 packages should not rely on this and instead should
6437 use <tt>dpkg-query --control-path <var>package</var>
6438 symbols</tt> if for some reason these files need to be
6446 Be aware that if a <file>debian/shlibs.local</file> exists
6447 in the source package, it will override
6448 any <file>symbols</file> files. This is the only case where
6449 a <file>shlibs</file> is used despite <file>symbols</file>
6450 files being present. See <ref id="shlibs-paths">
6451 and <ref id="sharedlibs-shlibdeps"> for more information.
6455 <sect2 id="symbols">
6456 <heading>The <file>symbols</file> File Format</heading>
6459 The following documents the format of
6460 the <file>symbols</file> control file as included in binary
6461 packages. These files are built from
6462 template <file>symbols</file> files in the source package
6463 by <prgn>dpkg-gensymbols</prgn>. The template files support
6464 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6465 do some of the tedious work involved in
6466 maintaining <file>symbols</file> files, such as handling C++
6467 symbols or optional symbols that may not exist on particular
6468 architectures. When writing <file>symbols</file> files for
6469 a shared library package, refer
6470 to <manref name="dpkg-gensymbols" section="1"> for the
6475 A <file>symbols</file> may contain one or more entries, one
6476 for each shared library contained in the package
6477 corresponding to that <file>symbols</file>. Each entry has
6478 the following format:
6483 <var>library-soname</var> <var>main-dependency-template</var>
6484 [| <var>alternative-dependency-template</var>]
6486 [* <var>field-name</var>: <var>field-value</var>]
6488 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6493 To explain this format, we'll use the the <tt>zlib1g</tt>
6494 package as an example, which (at the time of writing)
6496 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6497 lines will be described first, followed by optional lines.
6501 <var>library-soname</var> must contain exactly the value of
6502 the ELF <tt>SONAME</tt> attribute of the shared library. In
6503 our example, this is <tt>libz.so.1</tt>.<footnote>
6504 This can be determined by using the command
6505 <example compact="compact">
6506 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6512 <var>main-dependency-template</var> has the same syntax as a
6513 dependency field in a binary package control file, except
6514 that the string <tt>#MINVER#</tt> is replaced by a version
6515 restriction like <tt>(>= <var>version</var>)</tt> or by
6516 nothing if an unversioned dependency is deemed sufficient.
6517 The version restriction will be based on which symbols from
6518 the shared library are referenced and the version at which
6519 they were introduced (see below). In nearly all
6520 cases, <var>main-dependency-template</var> will
6521 be <tt><var>package</var> #MINVER#</tt>,
6522 where <var>package</var> is the name of the binary package
6523 containing the shared library. This adds a simple,
6524 possibly-versioned dependency on the shared library package.
6525 In some rare cases, such as when multiple packages provide
6526 the same shared library ABI, the dependency template may
6527 need to be more complex.
6531 In our example, the first line of
6532 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6533 <example compact="compact">
6534 libz.so.1 zlib1g #MINVER#
6539 Each public symbol exported by the shared library must have
6540 a corresponding symbol line, indented by one
6541 space. <var>symbol</var> is the exported symbol (which, for
6542 C++, means the mangled symbol) followed by <tt>@</tt> and
6543 the symbol version, or the string <tt>Base</tt> if there is
6544 no symbol version. <var>minimal-version</var> is the most
6545 recent version of the shared library that changed the
6546 behavior of that symbol, whether by adding it, changing its
6547 function signature (the parameters, their types, or the
6548 return type), or changing its behavior in a way that is
6549 visible to a caller.
6550 <var>id-of-dependency-template</var> is an optional
6551 field that references
6552 an <var>alternative-dependency-template</var>; see below for
6557 For example, <tt>libz.so.1</tt> contains the
6558 symbols <tt>compress</tt>
6559 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6560 version and last changed its behavior in upstream
6561 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6562 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6563 upstream version <tt>1:1.2.0</tt>, and has not changed its
6564 behavior. Its <file>symbols</file> file therefore contains
6566 <example compact="compact">
6567 compress@Base 1:1.1.4
6568 compressBound@ZLIB_1.2.0 1:1.2.0
6570 Packages using only <tt>compress</tt> would then get a
6571 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6572 using <tt>compressBound</tt> would get a dependency
6573 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6577 One or more <var>alternative-dependency-template</var> lines
6578 may be provided. These are used in cases where some symbols
6579 in the shared library should use one dependency template
6580 while others should use a different template. The
6581 alternative dependency templates are used only if a symbol
6582 line contains the <var>id-of-dependency-template</var>
6583 field. The first alternative dependency template is
6584 numbered 1, the second 2, and so forth.<footnote>
6585 An example of where this may be needed is with a library
6586 that implements the libGL interface. All GL
6587 implementations provide the same set of base interfaces,
6588 and then may provide some additional interfaces only used
6589 by programs that require that specific GL implementation.
6590 So, for example, libgl1-mesa-glx may use the
6591 following <file>symbols</file> file:
6594 | libgl1-mesa-glx #MINVER#
6595 publicGlSymbol@Base 6.3-1
6597 implementationSpecificSymbol@Base 6.5.2-7 1
6600 Binaries or shared libraries using
6601 only <tt>publicGlSymbol</tt> would depend only
6602 on <tt>libgl1</tt> (which may be provided by multiple
6604 using <tt>implementationSpecificSymbol</tt> would get a
6605 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6610 Finally, the entry for the library may contain one or more
6611 metadata fields. Currently, the only
6612 supported <var>field-name</var>
6613 is <tt>Build-Depends-Package</tt>, whose value lists
6614 the <qref id="sharedlibs-dev">library development
6615 package</qref> on which packages using this shared library
6616 declare a build dependency. If this field is
6617 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6618 the resulting binary package dependency on the shared
6619 library is at least as strict as the source package
6620 dependency on the shared library development
6622 This field should normally not be necessary, since if the
6623 behavior of any symbol has changed, the corresponding
6624 symbol <var>minimal-version</var> should have been
6625 increased. But including it makes the <tt>symbols</tt>
6626 system more robust by tightening the dependency in cases
6627 where the package using the shared library specifically
6628 requires at least a particular version of the shared
6629 library development package for some reason.
6631 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6633 <example compact="compact">
6634 * Build-Depends-Package: zlib1g-dev
6639 Also see <manref name="deb-symbols" section="5">.
6643 <sect2 id="providing-symbols">
6644 <heading>Providing a <file>symbols</file> file</heading>
6647 If your package provides a shared library, you should
6648 arrange to include a <file>symbols</file> control file
6649 following the format described above in that package. You
6650 must include either a <file>symbols</file> control file or
6651 a <file>shlibs</file> control file.
6655 Normally, this is done by creating a <file>symbols</file> in
6657 named <file>debian/<var>package</var>.symbols</file>
6658 or <file>debian/symbols</file>, possibly
6659 with <file>.<var>arch</var></file> appended if the symbols
6660 information varies by architecture. This file may use the
6661 extended syntax documented in <manref name="dpkg-gensymbols"
6662 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6663 part of the package build process. It will
6664 create <file>symbols</file> files in the package staging
6665 area based on the binaries and libraries in the package
6666 staging area and the <file>symbols</file> files in the
6667 source package.<footnote>
6669 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6670 take care of calling either <prgn>dpkg-gensymbols</prgn>
6671 or generating a <file>shlibs</file> file as appropriate.
6676 Packages that provide <file>symbols</file> files must keep
6677 them up-to-date to ensure correct dependencies in packages
6678 that use the shared libraries. This means updating
6679 the <file>symbols</file> file whenever a new public symbol
6680 is added, changing the <var>minimal-version</var> field
6681 whenever a symbol changes behavior or signature in a
6682 backward-compatible way (see <ref id="sharedlibs-updates">),
6683 and changing the <var>library-soname</var>
6684 and <var>main-dependency-template</var>, and probably all of
6685 the <var>minimal-version</var> fields, when the library
6686 changes <tt>SONAME</tt>. Removing a public symbol from
6687 the <file>symbols</file> file because it's no longer
6688 provided by the library normally requires changing
6689 the <tt>SONAME</tt> of the library.
6690 See <ref id="sharedlibs-runtime"> for more information
6691 on <tt>SONAME</tt>s.
6696 <sect1 id="sharedlibs-shlibdeps">
6697 <heading>The <tt>shlibs</tt> system</heading>
6700 The <tt>shlibs</tt> system is a simpler alternative to
6701 the <tt>symbols</tt> system for declaring dependencies for
6702 shared libraries. It may be more appropriate for C++
6703 libraries and other cases where tracking individual symbols is
6704 too difficult. It predated the <tt>symbols</tt> system and is
6705 therefore frequently seen in older packages. It is also
6706 required for udebs, which do not support <tt>symbols</tt>.
6710 In the following sections, we will first describe where the
6711 various <file>shlibs</file> files are to be found, then how to
6712 use <prgn>dpkg-shlibdeps</prgn>, and finally
6713 the <file>shlibs</file> file format and how to create them.
6716 <sect2 id="shlibs-paths">
6717 <heading>The <file>shlibs</file> files present on the
6721 There are several places where <tt>shlibs</tt> files are
6722 found. The following list gives them in the order in which
6723 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6724 one which gives the required information is used.)
6727 <p><file>debian/shlibs.local</file></p>
6730 This lists overrides for this package. This file
6731 should normally not be used, but may be needed
6732 temporarily in unusual situations to work around bugs
6733 in other packages, or in unusual cases where the
6734 normally declared dependency information in the
6735 installed <file>shlibs</file> file for a library
6736 cannot be used. This file overrides information
6737 obtained from any other source.
6742 <p><file>/etc/dpkg/shlibs.override</file></p>
6745 This lists global overrides. This list is normally
6746 empty. It is maintained by the local system
6752 <p><file>DEBIAN/shlibs</file> files in the "build
6756 These files are generated as part of the package build
6757 process and staged for inclusion as control files in
6758 the binary packages being built. They provide details
6759 of any shared libraries included in the same package.
6764 <p><file>shlibs</file> control files for packages
6765 installed on the system</p>
6768 The <file>shlibs</file> control files for all the
6769 packages currently installed on the system. These are
6771 in <file>/var/lib/dpkg/info/*.shlibs</file>, but
6772 packages should not rely on this and instead should
6773 use <tt>dpkg-query --control-path <var>package</var>
6774 shlibs</tt> if for some reason these files need to be
6780 <p><file>/etc/dpkg/shlibs.default</file></p>
6783 This file lists any shared libraries whose packages
6784 have failed to provide correct <file>shlibs</file>
6785 files. It was used when the <file>shlibs</file> setup
6786 was first introduced, but it is now normally empty.
6787 It is maintained by the <tt>dpkg</tt> maintainer.
6794 If a <file>symbols</file> file for a shared library package
6795 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6796 in preference to a <file>shlibs</file>, with the exception
6797 of <file>debian/shlibs.local</file>. The latter overrides
6798 any other <file>shlibs</file> or <file>symbols</file> files.
6803 <heading>The <file>shlibs</file> File Format</heading>
6806 Each <file>shlibs</file> file has the same format. Lines
6807 beginning with <tt>#</tt> are considered to be comments and
6808 are ignored. Each line is of the form:
6809 <example compact="compact">
6810 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6815 We will explain this by reference to the example of the
6816 <tt>zlib1g</tt> package, which (at the time of writing)
6818 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6822 <var>type</var> is an optional element that indicates the
6823 type of package for which the line is valid. The only type
6824 currently in use is <tt>udeb</tt>. The colon and space
6825 after the type are required.
6829 <var>library-name</var> is the name of the shared library,
6830 in this case <tt>libz</tt>. (This must match the name part
6831 of the soname, see below.)
6835 <var>soname-version</var> is the version part of the
6836 ELF <tt>SONAME</tt> attribute of the library, determined the
6837 same way that the <var>soversion</var> component of the
6838 recommended shared library package name is determined.
6839 See <ref id="sharedlibs-runtime"> for the details.
6843 <var>dependencies</var> has the same syntax as a dependency
6844 field in a binary package control file. It should give
6845 details of which packages are required to satisfy a binary
6846 built against the version of the library contained in the
6847 package. See <ref id="depsyntax"> for details on the
6848 syntax, and <ref id="sharedlibs-updates"> for details on how
6849 to maintain the dependency version constraint.
6853 In our example, if the last change to the <tt>zlib1g</tt>
6854 package that could change behavior for a client of that
6855 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6856 the <tt>shlibs</tt> entry for this library could say:
6857 <example compact="compact">
6858 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6860 This version restriction must be new enough that any binary
6861 built against the current version of the library will work
6862 with any version of the shared library that satisfies that
6867 As zlib1g also provides a udeb containing the shared
6868 library, there would also be a second line:
6869 <example compact="compact">
6870 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6876 <heading>Providing a <file>shlibs</file> file</heading>
6879 To provide a <file>shlibs</file> file for a shared library
6880 binary package, create a <file>shlibs</file> file following
6881 the format described above and place it in
6882 the <file>DEBIAN</file> directory for that package during
6883 the build. It will then be included as a control file for
6884 that package<footnote>
6885 This is what <prgn>dh_makeshlibs</prgn> in
6886 the <package>debhelper</package> suite does. If your
6887 package also has a udeb that provides a shared
6888 library, <prgn>dh_makeshlibs</prgn> can automatically
6889 generate the <tt>udeb:</tt> lines if you specify the name
6890 of the udeb with the <tt>--add-udeb</tt> option.
6895 Since <prgn>dpkg-shlibdeps</prgn> reads
6896 the <file>DEBIAN/shlibs</file> files in all of the binary
6897 packages being built from this source package, all of
6898 the <file>DEBIAN/shlibs</file> files should be installed
6899 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6908 <chapt id="opersys"><heading>The Operating System</heading>
6911 <heading>File system hierarchy</heading>
6915 <heading>File System Structure</heading>
6918 The location of all files and directories must comply with the
6919 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6920 exceptions noted below, and except where doing so would
6921 violate other terms of Debian Policy. The following
6922 exceptions to the FHS apply:
6927 The FHS requirement that architecture-independent
6928 application-specific static files be located in
6929 <file>/usr/share</file> is relaxed to a suggestion.
6931 In particular, a subdirectory of <file>/usr/lib</file> may
6932 be used by a package (or a collection of packages) to hold a
6933 mixture of architecture-independent and
6934 architecture-dependent files. However, when a directory is
6935 entirely composed of architecture-independent files, it
6936 should be located in <file>/usr/share</file>.
6941 The optional rules related to user specific
6942 configuration files for applications are stored in
6943 the user's home directory are relaxed. It is
6944 recommended that such files start with the
6945 '<tt>.</tt>' character (a "dot file"), and if an
6946 application needs to create more than one dot file
6947 then the preferred placement is in a subdirectory
6948 with a name starting with a '.' character, (a "dot
6949 directory"). In this case it is recommended the
6950 configuration files not start with the '.'
6956 The requirement for amd64 to use <file>/lib64</file>
6957 for 64 bit binaries is removed.
6962 The requirement for object files, internal binaries, and
6963 libraries, including <file>libc.so.*</file>, to be located
6964 directly under <file>/lib{,32}</file> and
6965 <file>/usr/lib{,32}</file> is amended, permitting files
6966 to instead be installed to
6967 <file>/lib/<var>triplet</var></file> and
6968 <file>/usr/lib/<var>triplet</var></file>, where
6969 <tt><var>triplet</var></tt> is the value returned by
6970 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6971 architecture of the package. Packages may <em>not</em>
6972 install files to any <var>triplet</var> path other
6973 than the one matching the architecture of that package;
6974 for instance, an <tt>Architecture: amd64</tt> package
6975 containing 32-bit x86 libraries may not install these
6976 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6978 This is necessary in order to reserve the directories for
6979 use in cross-installation of library packages from other
6980 architectures, as part of <tt>multiarch</tt>.
6984 The requirement for C and C++ headers files to be
6985 accessible through the search path
6986 <file>/usr/include/</file> is amended, permitting files to
6987 be accessible through the search path
6988 <file>/usr/include/<var>triplet</var></file> where
6989 <tt><var>triplet</var></tt> is as above. <footnote>
6990 This is necessary for architecture-dependant headers
6991 file to coexist in a <tt>multiarch</tt> setup.
6995 Applications may also use a single subdirectory under
6996 <file>/usr/lib/<var>triplet</var></file>.
6999 The execution time linker/loader, ld*, must still be made
7000 available in the existing location under /lib or /lib64
7001 since this is part of the ELF ABI for the architecture.
7006 The requirement that
7007 <file>/usr/local/share/man</file> be "synonymous"
7008 with <file>/usr/local/man</file> is relaxed to a
7013 The requirement that windowmanagers with a single
7014 configuration file call it <file>system.*wmrc</file>
7015 is removed, as is the restriction that the window
7016 manager subdirectory be named identically to the
7017 window manager name itself.
7022 The requirement that boot manager configuration
7023 files live in <file>/etc</file>, or at least are
7024 symlinked there, is relaxed to a recommendation.
7029 The additional directory <file>/run</file> in the root
7030 file system is allowed. <file>/run</file>
7031 replaces <file>/var/run</file>, and the
7032 subdirectory <file>/run/lock</file>
7033 replaces <file>/var/lock</file>, with
7034 the <file>/var</file> directories replaced by symlinks
7035 for backwards compatibility. <file>/run</file>
7036 and <file>/run/lock</file> must follow all of the
7037 requirements in the FHS for <file>/var/run</file>
7038 and <file>/var/lock</file>, respectively, such as file
7039 naming conventions, file format requirements, or the
7040 requirement that files be cleared during the boot
7041 process. Files and directories residing
7042 in <file>/run</file> should be stored on a temporary
7046 Packages must not assume the <file>/run</file>
7047 directory exists or is usable without a dependency
7048 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
7049 stable release of Debian supports <file>/run</file>.
7054 The <file>/sys</file> directory in the root filesystem is
7055 additionally allowed. <footnote>This directory is used as
7056 mount point to mount virtual filesystems to get access to
7057 kernel information.</footnote>
7062 The <file>/var/www</file> directory is additionally allowed.
7067 The requirement for <file>/usr/local/lib<qual></file>
7068 to exist if <file>/lib<qual></file> or
7069 <file>/usr/lib<qual></file> exists (where
7070 <file>lib<qual></file> is a variant of
7071 <file>lib</file> such as <file>lib32</file> or
7072 <file>lib64</file>) is removed.
7077 On GNU/Hurd systems, the following additional
7078 directories are allowed in the root
7079 filesystem: <file>/hurd</file>
7080 and <file>/servers</file>.<footnote>
7081 These directories are used to store translators and as
7082 a set of standard names for mount points,
7091 The version of this document referred here can be
7092 found in the <tt>debian-policy</tt> package or on <url
7093 id="http://www.debian.org/doc/packaging-manuals/fhs/"
7094 name="FHS (Debian copy)"> alongside this manual (or, if
7095 you have the <package>debian-policy</package> installed,
7097 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
7098 (local copy)">). The
7099 latest version, which may be a more recent version, may
7101 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7102 Specific questions about following the standard may be
7103 asked on the <tt>debian-devel</tt> mailing list, or
7104 referred to the FHS mailing list (see the
7105 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7111 <heading>Site-specific programs</heading>
7114 As mandated by the FHS, packages must not place any
7115 files in <file>/usr/local</file>, either by putting them in
7116 the file system archive to be unpacked by <prgn>dpkg</prgn>
7117 or by manipulating them in their maintainer scripts.
7121 However, the package may create empty directories below
7122 <file>/usr/local</file> so that the system administrator knows
7123 where to place site-specific files. These are not
7124 directories <em>in</em> <file>/usr/local</file>, but are
7125 children of directories in <file>/usr/local</file>. These
7126 directories (<file>/usr/local/*/dir/</file>)
7127 should be removed on package removal if they are
7132 Note that this applies only to
7133 directories <em>below</em> <file>/usr/local</file>,
7134 not <em>in</em> <file>/usr/local</file>. Packages must
7135 not create sub-directories in the
7136 directory <file>/usr/local</file> itself, except those
7137 listed in FHS, section 4.5. However, you may create
7138 directories below them as you wish. You must not remove
7139 any of the directories listed in 4.5, even if you created
7144 Since <file>/usr/local</file> can be mounted read-only from a
7145 remote server, these directories must be created and
7146 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7147 maintainer scripts and not be included in the
7148 <file>.deb</file> archive. These scripts must not fail if
7149 either of these operations fail.
7153 For example, the <tt>emacsen-common</tt> package could
7154 contain something like
7155 <example compact="compact">
7156 if [ ! -e /usr/local/share/emacs ]; then
7157 if mkdir /usr/local/share/emacs 2>/dev/null; then
7158 if chown root:staff /usr/local/share/emacs; then
7159 chmod 2775 /usr/local/share/emacs || true
7164 in its <prgn>postinst</prgn> script, and
7165 <example compact="compact">
7166 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7167 rmdir /usr/local/share/emacs 2>/dev/null || true
7169 in the <prgn>prerm</prgn> script. (Note that this form is
7170 used to ensure that if the script is interrupted, the
7171 directory <file>/usr/local/share/emacs</file> will still be
7176 If you do create a directory in <file>/usr/local</file> for
7177 local additions to a package, you should ensure that
7178 settings in <file>/usr/local</file> take precedence over the
7179 equivalents in <file>/usr</file>.
7183 However, because <file>/usr/local</file> and its contents are
7184 for exclusive use of the local administrator, a package
7185 must not rely on the presence or absence of files or
7186 directories in <file>/usr/local</file> for normal operation.
7190 The <file>/usr/local</file> directory itself and all the
7191 subdirectories created by the package should (by default) have
7192 permissions 2775 (group-writable and set-group-id) and be
7193 owned by <tt>root:staff</tt>.
7198 <heading>The system-wide mail directory</heading>
7200 The system-wide mail directory
7201 is <file>/var/mail</file>. This directory is part of the
7202 base system and should not be owned by any particular mail
7203 agents. The use of the old
7204 location <file>/var/spool/mail</file> is deprecated, even
7205 though the spool may still be physically located there.
7209 <sect1 id="fhs-run">
7210 <heading><file>/run</file> and <file>/run/lock</file></heading>
7213 The directory <file>/run</file> is cleared at boot, normally
7214 by being a mount point for a temporary file system. Packages
7215 therefore must not assume that any files or directories
7216 under <file>/run</file> other than <file>/run/lock</file>
7217 exist unless the package has arranged to create those files or
7218 directories since the last reboot. Normally, this is done by
7219 the package via an init script. See <ref id="writing-init">
7220 for more information.
7224 Packages must not include files or directories
7225 under <file>/run</file>, or under the
7226 older <file>/var/run</file> and <file>/var/lock</file> paths.
7227 The latter paths will normally be symlinks or other
7228 redirections to <file>/run</file> for backwards compatibility.
7234 <heading>Users and groups</heading>
7237 <heading>Introduction</heading>
7239 The Debian system can be configured to use either plain or
7244 Some user ids (UIDs) and group ids (GIDs) are reserved
7245 globally for use by certain packages. Because some
7246 packages need to include files which are owned by these
7247 users or groups, or need the ids compiled into binaries,
7248 these ids must be used on any Debian system only for the
7249 purpose for which they are allocated. This is a serious
7250 restriction, and we should avoid getting in the way of
7251 local administration policies. In particular, many sites
7252 allocate users and/or local system groups starting at 100.
7256 Apart from this we should have dynamically allocated ids,
7257 which should by default be arranged in some sensible
7258 order, but the behavior should be configurable.
7262 Packages other than <tt>base-passwd</tt> must not modify
7263 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7264 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7269 <heading>UID and GID classes</heading>
7271 The UID and GID numbers are divided into classes as
7277 Globally allocated by the Debian project, the same
7278 on every Debian system. These ids will appear in
7279 the <file>passwd</file> and <file>group</file> files of all
7280 Debian systems, new ids in this range being added
7281 automatically as the <tt>base-passwd</tt> package is
7286 Packages which need a single statically allocated
7287 uid or gid should use one of these; their
7288 maintainers should ask the <tt>base-passwd</tt>
7296 Dynamically allocated system users and groups.
7297 Packages which need a user or group, but can have
7298 this user or group allocated dynamically and
7299 differently on each system, should use <tt>adduser
7300 --system</tt> to create the group and/or user.
7301 <prgn>adduser</prgn> will check for the existence of
7302 the user or group, and if necessary choose an unused
7303 id based on the ranges specified in
7304 <file>adduser.conf</file>.
7308 <tag>1000-59999:</tag>
7311 Dynamically allocated user accounts. By default
7312 <prgn>adduser</prgn> will choose UIDs and GIDs for
7313 user accounts in this range, though
7314 <file>adduser.conf</file> may be used to modify this
7319 <tag>60000-64999:</tag>
7322 Globally allocated by the Debian project, but only
7323 created on demand. The ids are allocated centrally
7324 and statically, but the actual accounts are only
7325 created on users' systems on demand.
7329 These ids are for packages which are obscure or
7330 which require many statically-allocated ids. These
7331 packages should check for and create the accounts in
7332 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7333 <prgn>adduser</prgn> if it has this facility) if
7334 necessary. Packages which are likely to require
7335 further allocations should have a "hole" left after
7336 them in the allocation, to give them room to
7341 <tag>65000-65533:</tag>
7349 User <tt>nobody</tt>. The corresponding gid refers
7350 to the group <tt>nogroup</tt>.
7357 This value <em>must not</em> be used, because it was
7358 the error return sentinel value when <tt>uid_t</tt>
7363 <tag>65536-4294967293:</tag>
7366 Dynamically allocated user accounts. By
7367 default <prgn>adduser</prgn> will not allocate UIDs
7368 and GIDs in this range, to ease compatibility with
7369 legacy systems where <tt>uid_t</tt> is still 16
7374 <tag>4294967294:</tag>
7377 <tt>(uid_t)(-2) == (gid_t)(-2)</tt> <em>must not</em> be
7378 used, because it is used as the anonymous, unauthenticated
7379 user by some NFS implementations.
7383 <tag>4294967295:</tag>
7386 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7387 not</em> be used, because it is the error return
7396 <sect id="sysvinit">
7397 <heading>System run levels and <file>init.d</file> scripts</heading>
7399 <sect1 id="/etc/init.d">
7400 <heading>Introduction</heading>
7403 The <file>/etc/init.d</file> directory contains the scripts
7404 executed by <prgn>init</prgn> at boot time and when the
7405 init state (or "runlevel") is changed (see <manref
7406 name="init" section="8">).
7410 There are at least two different, yet functionally
7411 equivalent, ways of handling these scripts. For the sake
7412 of simplicity, this document describes only the symbolic
7413 link method. However, it must not be assumed by maintainer
7414 scripts that this method is being used, and any automated
7415 manipulation of the various runlevel behaviors by
7416 maintainer scripts must be performed using
7417 <prgn>update-rc.d</prgn> as described below and not by
7418 manually installing or removing symlinks. For information
7419 on the implementation details of the other method,
7420 implemented in the <tt>file-rc</tt> package, please refer
7421 to the documentation of that package.
7425 These scripts are referenced by symbolic links in the
7426 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7427 runlevels, <prgn>init</prgn> looks in the directory
7428 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7429 execute, where <tt><var>n</var></tt> is the runlevel that
7430 is being changed to, or <tt>S</tt> for the boot-up
7435 The names of the links all have the form
7436 <file>S<var>mm</var><var>script</var></file> or
7437 <file>K<var>mm</var><var>script</var></file> where
7438 <var>mm</var> is a two-digit number and <var>script</var>
7439 is the name of the script (this should be the same as the
7440 name of the actual script in <file>/etc/init.d</file>).
7444 When <prgn>init</prgn> changes runlevel first the targets
7445 of the links whose names start with a <tt>K</tt> are
7446 executed, each with the single argument <tt>stop</tt>,
7447 followed by the scripts prefixed with an <tt>S</tt>, each
7448 with the single argument <tt>start</tt>. (The links are
7449 those in the <file>/etc/rc<var>n</var>.d</file> directory
7450 corresponding to the new runlevel.) The <tt>K</tt> links
7451 are responsible for killing services and the <tt>S</tt>
7452 link for starting services upon entering the runlevel.
7456 For example, if we are changing from runlevel 2 to
7457 runlevel 3, init will first execute all of the <tt>K</tt>
7458 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7459 all of the <tt>S</tt> prefixed scripts in that directory.
7460 The links starting with <tt>K</tt> will cause the
7461 referred-to file to be executed with an argument of
7462 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7467 The two-digit number <var>mm</var> is used to determine
7468 the order in which to run the scripts: low-numbered links
7469 have their scripts run first. For example, the
7470 <tt>K20</tt> scripts will be executed before the
7471 <tt>K30</tt> scripts. This is used when a certain service
7472 must be started before another. For example, the name
7473 server <prgn>bind</prgn> might need to be started before
7474 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7475 can set up its access lists. In this case, the script
7476 that starts <prgn>bind</prgn> would have a lower number
7477 than the script that starts <prgn>inn</prgn> so that it
7479 <example compact="compact">
7486 The two runlevels 0 (halt) and 6 (reboot) are slightly
7487 different. In these runlevels, the links with an
7488 <tt>S</tt> prefix are still called after those with a
7489 <tt>K</tt> prefix, but they too are called with the single
7490 argument <tt>stop</tt>.
7494 <sect1 id="writing-init">
7495 <heading>Writing the scripts</heading>
7498 Packages that include daemons for system services should
7499 place scripts in <file>/etc/init.d</file> to start or stop
7500 services at boot time or during a change of runlevel.
7501 These scripts should be named
7502 <file>/etc/init.d/<var>package</var></file>, and they should
7503 accept one argument, saying what to do:
7506 <tag><tt>start</tt></tag>
7507 <item>start the service,</item>
7509 <tag><tt>stop</tt></tag>
7510 <item>stop the service,</item>
7512 <tag><tt>restart</tt></tag>
7513 <item>stop and restart the service if it's already running,
7514 otherwise start the service</item>
7516 <tag><tt>reload</tt></tag>
7517 <item><p>cause the configuration of the service to be
7518 reloaded without actually stopping and restarting
7521 <tag><tt>force-reload</tt></tag>
7522 <item>cause the configuration to be reloaded if the
7523 service supports this, otherwise restart the
7527 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7528 <tt>force-reload</tt> options should be supported by all
7529 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7534 The <file>init.d</file> scripts must ensure that they will
7535 behave sensibly (i.e., returning success and not starting
7536 multiple copies of a service) if invoked with <tt>start</tt>
7537 when the service is already running, or with <tt>stop</tt>
7538 when it isn't, and that they don't kill unfortunately-named
7539 user processes. The best way to achieve this is usually to
7540 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7545 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7546 scripts. Writing correct <file>init.d</file> scripts requires
7547 accepting various error exit statuses when daemons are already
7548 running or already stopped without aborting
7549 the <file>init.d</file> script, and common <file>init.d</file>
7550 function libraries are not safe to call with <tt>set -e</tt>
7552 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7553 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7554 in effect and echoing status messages to the console fails,
7556 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7557 to not use <tt>set -e</tt> and instead check the result of
7558 each command separately.
7562 If a service reloads its configuration automatically (as
7563 in the case of <prgn>cron</prgn>, for example), the
7564 <tt>reload</tt> option of the <file>init.d</file> script
7565 should behave as if the configuration has been reloaded
7570 The <file>/etc/init.d</file> scripts must be treated as
7571 configuration files, either (if they are present in the
7572 package, that is, in the .deb file) by marking them as
7573 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7574 by managing them correctly in the maintainer scripts (see
7575 <ref id="config-files">). This is important since we want
7576 to give the local system administrator the chance to adapt
7577 the scripts to the local system, e.g., to disable a
7578 service without de-installing the package, or to specify
7579 some special command line options when starting a service,
7580 while making sure their changes aren't lost during the next
7585 These scripts should not fail obscurely when the
7586 configuration files remain but the package has been
7587 removed, as configuration files remain on the system after
7588 the package has been removed. Only when <prgn>dpkg</prgn>
7589 is executed with the <tt>--purge</tt> option will
7590 configuration files be removed. In particular, as the
7591 <file>/etc/init.d/<var>package</var></file> script itself is
7592 usually a <tt>conffile</tt>, it will remain on the system
7593 if the package is removed but not purged. Therefore, you
7594 should include a <tt>test</tt> statement at the top of the
7596 <example compact="compact">
7597 test -f <var>program-executed-later-in-script</var> || exit 0
7602 Often there are some variables in the <file>init.d</file>
7603 scripts whose values control the behavior of the scripts,
7604 and which a system administrator is likely to want to
7605 change. As the scripts themselves are frequently
7606 <tt>conffile</tt>s, modifying them requires that the
7607 administrator merge in their changes each time the package
7608 is upgraded and the <tt>conffile</tt> changes. To ease
7609 the burden on the system administrator, such configurable
7610 values should not be placed directly in the script.
7611 Instead, they should be placed in a file in
7612 <file>/etc/default</file>, which typically will have the same
7613 base name as the <file>init.d</file> script. This extra file
7614 should be sourced by the script when the script runs. It
7615 must contain only variable settings and comments in SUSv3
7616 <prgn>sh</prgn> format. It may either be a
7617 <tt>conffile</tt> or a configuration file maintained by
7618 the package maintainer scripts. See <ref id="config-files">
7623 To ensure that vital configurable values are always
7624 available, the <file>init.d</file> script should set default
7625 values for each of the shell variables it uses, either
7626 before sourcing the <file>/etc/default/</file> file or
7627 afterwards using something like the <tt>:
7628 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7629 script must behave sensibly and not fail if the
7630 <file>/etc/default</file> file is deleted.
7634 Files and directories under <file>/run</file>, including ones
7635 referred to via the compatibility paths <file>/var/run</file>
7636 and <file>/var/lock</file>, are normally stored on a temporary
7637 filesystem and are normally not persistent across a reboot.
7638 The <file>init.d</file> scripts must handle this correctly.
7639 This will typically mean creating any required subdirectories
7640 dynamically when the <file>init.d</file> script is run.
7641 See <ref id="fhs-run"> for more information.
7646 <heading>Interfacing with the initscript system</heading>
7649 Maintainers should use the abstraction layer provided by
7650 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7651 programs to deal with initscripts in their packages'
7652 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7653 and <prgn>postrm</prgn>.
7657 Directly managing the /etc/rc?.d links and directly
7658 invoking the <file>/etc/init.d/</file> initscripts should
7659 be done only by packages providing the initscript
7660 subsystem (such as <prgn>sysv-rc</prgn> and
7661 <prgn>file-rc</prgn>).
7665 <heading>Managing the links</heading>
7668 The program <prgn>update-rc.d</prgn> is provided for
7669 package maintainers to arrange for the proper creation and
7670 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7671 or their functional equivalent if another method is being
7672 used. This may be used by maintainers in their packages'
7673 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7677 You must not include any <file>/etc/rc<var>n</var>.d</file>
7678 symbolic links in the actual archive or manually create or
7679 remove the symbolic links in maintainer scripts; you must
7680 use the <prgn>update-rc.d</prgn> program instead. (The
7681 former will fail if an alternative method of maintaining
7682 runlevel information is being used.) You must not include
7683 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7684 in the archive either. (Only the <tt>sysvinit</tt>
7689 By default <prgn>update-rc.d</prgn> will start services in
7690 each of the multi-user state runlevels (2, 3, 4, and 5)
7691 and stop them in the halt runlevel (0), the single-user
7692 runlevel (1) and the reboot runlevel (6). The system
7693 administrator will have the opportunity to customize
7694 runlevels by simply adding, moving, or removing the
7695 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7696 symbolic links are being used, or by modifying
7697 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7702 To get the default behavior for your package, put in your
7703 <prgn>postinst</prgn> script
7704 <example compact="compact">
7705 update-rc.d <var>package</var> defaults
7707 and in your <prgn>postrm</prgn>
7708 <example compact="compact">
7709 if [ "$1" = purge ]; then
7710 update-rc.d <var>package</var> remove
7712 </example>. Note that if your package changes runlevels
7713 or priority, you may have to remove and recreate the links,
7714 since otherwise the old links may persist. Refer to the
7715 documentation of <prgn>update-rc.d</prgn>.
7719 This will use a default sequence number of 20. If it does
7720 not matter when or in which order the <file>init.d</file>
7721 script is run, use this default. If it does, then you
7722 should talk to the maintainer of the <prgn>sysvinit</prgn>
7723 package or post to <tt>debian-devel</tt>, and they will
7724 help you choose a number.
7728 For more information about using <tt>update-rc.d</tt>,
7729 please consult its man page <manref name="update-rc.d"
7735 <heading>Running initscripts</heading>
7737 The program <prgn>invoke-rc.d</prgn> is provided to make
7738 it easier for package maintainers to properly invoke an
7739 initscript, obeying runlevel and other locally-defined
7740 constraints that might limit a package's right to start,
7741 stop and otherwise manage services. This program may be
7742 used by maintainers in their packages' scripts.
7746 The package maintainer scripts must use
7747 <prgn>invoke-rc.d</prgn> to invoke the
7748 <file>/etc/init.d/*</file> initscripts, instead of
7749 calling them directly.
7753 By default, <prgn>invoke-rc.d</prgn> will pass any
7754 action requests (start, stop, reload, restart...) to the
7755 <file>/etc/init.d</file> script, filtering out requests
7756 to start or restart a service out of its intended
7761 Most packages will simply need to change:
7762 <example compact="compact">/etc/init.d/<package>
7763 <action></example> in their <prgn>postinst</prgn>
7764 and <prgn>prerm</prgn> scripts to:
7765 <example compact="compact">
7766 if which invoke-rc.d >/dev/null 2>&1; then
7767 invoke-rc.d <var>package</var> <action>
7769 /etc/init.d/<var>package</var> <action>
7775 A package should register its initscript services using
7776 <prgn>update-rc.d</prgn> before it tries to invoke them
7777 using <prgn>invoke-rc.d</prgn>. Invocation of
7778 unregistered services may fail.
7782 For more information about using
7783 <prgn>invoke-rc.d</prgn>, please consult its man page
7784 <manref name="invoke-rc.d" section="8">.
7790 <heading>Boot-time initialization</heading>
7793 There used to be another directory, <file>/etc/rc.boot</file>,
7794 which contained scripts which were run once per machine
7795 boot. This has been deprecated in favour of links from
7796 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7797 described in <ref id="/etc/init.d">. Packages must not
7798 place files in <file>/etc/rc.boot</file>.
7803 <heading>Example</heading>
7806 An example on which you can base your
7807 <file>/etc/init.d</file> scripts is found in
7808 <file>/etc/init.d/skeleton</file>.
7815 <heading>Console messages from <file>init.d</file> scripts</heading>
7818 This section describes the formats to be used for messages
7819 written to standard output by the <file>/etc/init.d</file>
7820 scripts. The intent is to improve the consistency of
7821 Debian's startup and shutdown look and feel. For this
7822 reason, please look very carefully at the details. We want
7823 the messages to have the same format in terms of wording,
7824 spaces, punctuation and case of letters.
7828 Here is a list of overall rules that should be used for
7829 messages generated by <file>/etc/init.d</file> scripts.
7835 The message should fit in one line (fewer than 80
7836 characters), start with a capital letter and end with
7837 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7841 If the script is performing some time consuming task in
7842 the background (not merely starting or stopping a
7843 program, for instance), an ellipsis (three dots:
7844 <tt>...</tt>) should be output to the screen, with no
7845 leading or tailing whitespace or line feeds.
7849 The messages should appear as if the computer is telling
7850 the user what it is doing (politely :-), but should not
7851 mention "it" directly. For example, instead of:
7852 <example compact="compact">
7853 I'm starting network daemons: nfsd mountd.
7855 the message should say
7856 <example compact="compact">
7857 Starting network daemons: nfsd mountd.
7864 <tt>init.d</tt> script should use the following standard
7865 message formats for the situations enumerated below.
7871 <p>When daemons are started</p>
7874 If the script starts one or more daemons, the output
7875 should look like this (a single line, no leading
7877 <example compact="compact">
7878 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7880 The <var>description</var> should describe the
7881 subsystem the daemon or set of daemons are part of,
7882 while <var>daemon-1</var> up to <var>daemon-n</var>
7883 denote each daemon's name (typically the file name of
7888 For example, the output of <file>/etc/init.d/lpd</file>
7890 <example compact="compact">
7891 Starting printer spooler: lpd.
7896 This can be achieved by saying
7897 <example compact="compact">
7898 echo -n "Starting printer spooler: lpd"
7899 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7902 in the script. If there are more than one daemon to
7903 start, the output should look like this:
7904 <example compact="compact">
7905 echo -n "Starting remote file system services:"
7906 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7907 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7908 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7911 This makes it possible for the user to see what is
7912 happening and when the final daemon has been started.
7913 Care should be taken in the placement of white spaces:
7914 in the example above the system administrators can
7915 easily comment out a line if they don't want to start
7916 a specific daemon, while the displayed message still
7922 <p>When a system parameter is being set</p>
7925 If you have to set up different system parameters
7926 during the system boot, you should use this format:
7927 <example compact="compact">
7928 Setting <var>parameter</var> to "<var>value</var>".
7933 You can use a statement such as the following to get
7935 <example compact="compact">
7936 echo "Setting DNS domainname to \"$domainname\"."
7941 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7942 for the left and right quotation marks. A grave accent
7943 (<tt>`</tt>) is not a quote character; neither is an
7944 apostrophe (<tt>'</tt>).
7949 <p>When a daemon is stopped or restarted</p>
7952 When you stop or restart a daemon, you should issue a
7953 message identical to the startup message, except that
7954 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7955 or <tt>Restarting</tt> respectively.
7959 For example, stopping the printer daemon will look like
7961 <example compact="compact">
7962 Stopping printer spooler: lpd.
7968 <p>When something is executed</p>
7971 There are several examples where you have to run a
7972 program at system startup or shutdown to perform a
7973 specific task, for example, setting the system's clock
7974 using <prgn>netdate</prgn> or killing all processes
7975 when the system shuts down. Your message should look
7977 <example compact="compact">
7978 Doing something very useful...done.
7980 You should print the <tt>done.</tt> immediately after
7981 the job has been completed, so that the user is
7982 informed why they have to wait. You can get this
7984 <example compact="compact">
7985 echo -n "Doing something very useful..."
7994 <p>When the configuration is reloaded</p>
7997 When a daemon is forced to reload its configuration
7998 files you should use the following format:
7999 <example compact="compact">
8000 Reloading <var>description</var> configuration...done.
8002 where <var>description</var> is the same as in the
8003 daemon starting message.
8010 <sect id="cron-jobs">
8011 <heading>Cron jobs</heading>
8014 Packages must not modify the configuration file
8015 <file>/etc/crontab</file>, and they must not modify the files in
8016 <file>/var/spool/cron/crontabs</file>.
8020 If a package wants to install a job that has to be executed via
8021 cron, it should place a file named as specified
8022 in <ref id="cron-files"> into one or more of the following
8024 <example compact="compact">
8030 As these directory names imply, the files within them are
8031 executed on an hourly, daily, weekly, or monthly basis,
8032 respectively. The exact times are listed in
8033 <file>/etc/crontab</file>.
8037 All files installed in any of these directories must be
8038 scripts (e.g., shell scripts or Perl scripts) so that they
8039 can easily be modified by the local system administrator.
8040 In addition, they must be treated as configuration files.
8044 If a certain job has to be executed at some other frequency or
8045 at a specific time, the package should install a file in
8046 <file>/etc/cron.d</file> with a name as specified
8047 in <ref id="cron-files">. This file uses the same syntax
8048 as <file>/etc/crontab</file> and is processed
8049 by <prgn>cron</prgn> automatically. The file must also be
8050 treated as a configuration file. (Note that entries in the
8051 <file>/etc/cron.d</file> directory are not handled by
8052 <prgn>anacron</prgn>. Thus, you should only use this
8053 directory for jobs which may be skipped if the system is not
8058 Unlike <file>crontab</file> files described in the IEEE Std
8059 1003.1-2008 (POSIX.1) available from
8060 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
8061 name="The Open Group">, the files in
8062 <file>/etc/cron.d</file> and the file
8063 <file>/etc/crontab</file> have seven fields; namely:
8065 <item>Minute [0,59]</item>
8066 <item>Hour [0,23]</item>
8067 <item>Day of the month [1,31]</item>
8068 <item>Month of the year [1,12]</item>
8069 <item>Day of the week ([0,6] with 0=Sunday)</item>
8070 <item>Username</item>
8071 <item>Command to be run</item>
8073 Ranges of numbers are allowed. Ranges are two numbers
8074 separated with a hyphen. The specified range is inclusive.
8075 Lists are allowed. A list is a set of numbers (or ranges)
8076 separated by commas. Step values can be used in conjunction
8081 The scripts or <tt>crontab</tt> entries in these directories should
8082 check if all necessary programs are installed before they
8083 try to execute them. Otherwise, problems will arise when a
8084 package was removed but not purged since configuration files
8085 are kept on the system in this situation.
8089 Any <tt>cron</tt> daemon must provide
8090 <file>/usr/bin/crontab</file> and support normal
8091 <tt>crontab</tt> entries as specified in POSIX. The daemon
8092 must also support names for days and months, ranges, and
8093 step values. It has to support <file>/etc/crontab</file>,
8094 and correctly execute the scripts in
8095 <file>/etc/cron.d</file>. The daemon must also correctly
8097 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
8100 <sect1 id="cron-files">
8101 <heading>Cron job file names</heading>
8104 The file name of a cron job file should normally match the
8105 name of the package from which it comes.
8109 If a package supplies multiple cron job files files in the
8110 same directory, the file names should all start with the name
8111 of the package (possibly modified as described below) followed
8112 by a hyphen (<tt>-</tt>) and a suitable suffix.
8116 A cron job file name must not include any period or plus
8117 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
8118 cause cron to ignore the file. Underscores (<tt>_</tt>)
8119 should be used instead of <tt>.</tt> and <tt>+</tt>
8126 <heading>Menus</heading>
8129 The Debian <tt>menu</tt> package provides a standard
8130 interface between packages providing applications and
8131 <em>menu programs</em> (either X window managers or
8132 text-based menu programs such as <prgn>pdmenu</prgn>).
8136 All packages that provide applications that need not be
8137 passed any special command line arguments for normal
8138 operation should register a menu entry for those
8139 applications, so that users of the <tt>menu</tt> package
8140 will automatically get menu entries in their window
8141 managers, as well in shells like <tt>pdmenu</tt>.
8145 Menu entries should follow the current menu policy.
8149 The menu policy can be found in the <tt>menu-policy</tt>
8150 files in the <tt>debian-policy</tt> package.
8151 It is also available from the Debian web mirrors at
8152 <tt><url name="/doc/packaging-manuals/menu-policy/"
8153 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8157 Please also refer to the <em>Debian Menu System</em>
8158 documentation that comes with the <package>menu</package>
8159 package for information about how to register your
8165 <heading>Multimedia handlers</heading>
8168 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8169 is a mechanism for encoding files and data streams and
8170 providing meta-information about them, in particular their
8171 type (e.g. audio or video) and format (e.g. PNG, HTML,
8176 Registration of MIME type handlers allows programs like mail
8177 user agents and web browsers to invoke these handlers to
8178 view, edit or display MIME types they don't support directly.
8182 Packages which provide programs to view/show/play, compose, edit or
8183 print MIME types should register them as such by placing a file in
8184 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8185 <file>/usr/lib/mime/packages/</file>. The file name should be the
8186 binary package's name.
8190 The <package>mime-support</package> package provides the
8191 <prgn>update-mime</prgn> program, which integrates these
8192 registrations in the <file>/etc/mailcap</file> file, using dpkg
8194 Creating, modifying or removing a file in
8195 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8196 not activate the trigger. In that case, it can be done by calling
8197 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8198 the maintainer script after creating, modifying, or removing
8201 Packages using this facility <em>should not</em> depend on,
8202 recommend, or suggest <prgn>mime-support</prgn>.
8207 <heading>Keyboard configuration</heading>
8210 To achieve a consistent keyboard configuration so that all
8211 applications interpret a keyboard event the same way, all
8212 programs in the Debian distribution must be configured to
8213 comply with the following guidelines.
8217 The following keys must have the specified interpretations:
8220 <tag><tt><--</tt></tag>
8221 <item>delete the character to the left of the cursor</item>
8223 <tag><tt>Delete</tt></tag>
8224 <item>delete the character to the right of the cursor</item>
8226 <tag><tt>Control+H</tt></tag>
8227 <item>emacs: the help prefix</item>
8230 The interpretation of any keyboard events should be
8231 independent of the terminal that is used, be it a virtual
8232 console, an X terminal emulator, an rlogin/telnet session,
8237 The following list explains how the different programs
8238 should be set up to achieve this:
8244 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8248 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8252 X translations are set up to make
8253 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8254 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8255 is the vt220 escape code for the "delete character"
8256 key). This must be done by loading the X resources
8257 using <prgn>xrdb</prgn> on all local X displays, not
8258 using the application defaults, so that the
8259 translation resources used correspond to the
8260 <prgn>xmodmap</prgn> settings.
8264 The Linux console is configured to make
8265 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8266 generate <tt>ESC [ 3 ~</tt>.
8270 X applications are configured so that <tt><</tt>
8271 deletes left, and <tt>Delete</tt> deletes right. Motif
8272 applications already work like this.
8276 Terminals should have <tt>stty erase ^?</tt> .
8280 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8281 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8282 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8286 Emacs is programmed to map <tt>KB_Backspace</tt> or
8287 the <tt>stty erase</tt> character to
8288 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8289 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8290 <tt>^H</tt> to <tt>help</tt> as always.
8294 Other applications use the <tt>stty erase</tt>
8295 character and <tt>kdch1</tt> for the two delete keys,
8296 with ASCII DEL being "delete previous character" and
8297 <tt>kdch1</tt> being "delete character under
8305 This will solve the problem except for the following
8312 Some terminals have a <tt><--</tt> key that cannot
8313 be made to produce anything except <tt>^H</tt>. On
8314 these terminals Emacs help will be unavailable on
8315 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8316 character takes precedence in Emacs, and has been set
8317 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8318 available) can be used instead.
8322 Some operating systems use <tt>^H</tt> for <tt>stty
8323 erase</tt>. However, modern telnet versions and all
8324 rlogin versions propagate <tt>stty</tt> settings, and
8325 almost all UNIX versions honour <tt>stty erase</tt>.
8326 Where the <tt>stty</tt> settings are not propagated
8327 correctly, things can be made to work by using
8328 <tt>stty</tt> manually.
8332 Some systems (including previous Debian versions) use
8333 <prgn>xmodmap</prgn> to arrange for both
8334 <tt><--</tt> and <tt>Delete</tt> to generate
8335 <tt>KB_Delete</tt>. We can change the behavior of
8336 their X clients using the same X resources that we use
8337 to do it for our own clients, or configure our clients
8338 using their resources when things are the other way
8339 around. On displays configured like this
8340 <tt>Delete</tt> will not work, but <tt><--</tt>
8345 Some operating systems have different <tt>kdch1</tt>
8346 settings in their <tt>terminfo</tt> database for
8347 <tt>xterm</tt> and others. On these systems the
8348 <tt>Delete</tt> key will not work correctly when you
8349 log in from a system conforming to our policy, but
8350 <tt><--</tt> will.
8357 <heading>Environment variables</heading>
8360 A program must not depend on environment variables to get
8361 reasonable defaults. (That's because these environment
8362 variables would have to be set in a system-wide
8363 configuration file like <file>/etc/profile</file>, which is not
8364 supported by all shells.)
8368 If a program usually depends on environment variables for its
8369 configuration, the program should be changed to fall back to
8370 a reasonable default configuration if these environment
8371 variables are not present. If this cannot be done easily
8372 (e.g., if the source code of a non-free program is not
8373 available), the program must be replaced by a small
8374 "wrapper" shell script which sets the environment variables
8375 if they are not already defined, and calls the original program.
8379 Here is an example of a wrapper script for this purpose:
8381 <example compact="compact">
8383 BAR=${BAR:-/var/lib/fubar}
8385 exec /usr/lib/foo/foo "$@"
8390 Furthermore, as <file>/etc/profile</file> is a configuration
8391 file of the <prgn>base-files</prgn> package, other packages must
8392 not put any environment variables or other commands into that
8397 <sect id="doc-base">
8398 <heading>Registering Documents using doc-base</heading>
8401 The <package>doc-base</package> package implements a
8402 flexible mechanism for handling and presenting
8403 documentation. The recommended practice is for every Debian
8404 package that provides online documentation (other than just
8405 manual pages) to register these documents with
8406 <package>doc-base</package> by installing a
8407 <package>doc-base</package> control file in
8408 <file>/usr/share/doc-base/</file>.
8411 Please refer to the documentation that comes with the
8412 <package>doc-base</package> package for information and
8417 <sect id="alternateinit">
8418 <heading>Alternate init systems</heading>
8420 A number of other init systems are available now in Debian that
8421 can be used in place of <package>sysvinit</package>. Alternative
8422 init implementations must support running SysV init scripts as
8423 described at <ref id="sysvinit"> for compatibility.
8426 Packages may integrate with these replacement init systems by
8427 providing implementation-specific configuration information about
8428 how and when to start a service or in what order to run certain
8429 tasks at boot time. However, any package integrating with other
8430 init systems must also be backwards-compatible with
8431 <package>sysvinit</package> by providing a SysV-style init script
8432 with the same name as and equivalent functionality to any
8433 init-specific job, as this is the only start-up configuration
8434 method guaranteed to be supported by all init implementations. An
8435 exception to this rule is scripts or jobs provided by the init
8436 implementation itself; such jobs may be required for an
8437 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8438 scripts and may not have a one-to-one correspondence with the init
8441 <sect1 id="upstart">
8442 <heading>Event-based boot with upstart</heading>
8445 Packages may integrate with the <prgn>upstart</prgn> event-based
8446 boot system by installing job files in the
8447 <file>/etc/init</file> directory. SysV init scripts for which
8448 an equivalent upstart job is available must query the output of
8449 the command <prgn>initctl version</prgn> for the string
8450 <tt>upstart</tt> and avoid running in favor of the native
8451 upstart job, using a test such as this:
8452 <example compact="compact">
8453 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8460 Because packages shipping upstart jobs may be installed on
8461 systems that are not using upstart, maintainer scripts must
8462 still use the common <prgn>update-rc.d</prgn> and
8463 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8464 and for starting and stopping services. These maintainer
8465 scripts must not call the upstart <prgn>start</prgn>,
8466 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8467 interfaces directly. Instead, implementations of
8468 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8469 when an upstart job with the same name as an init script is
8470 present, and perform the requested action using the upstart job
8471 instead of the init script.
8474 Dependency-based boot managers for SysV init scripts, such as
8475 <prgn>startpar</prgn>, may avoid running a given init script
8476 entirely when an equivalent upstart job is present, to avoid
8477 unnecessary forking of no-op init scripts. In this case, the
8478 boot manager should integrate with upstart to detect when the
8479 upstart job in question is started or stopped to know when the
8480 dependency has been satisfied.
8489 <heading>Files</heading>
8491 <sect id="binaries">
8492 <heading>Binaries</heading>
8495 Two different packages must not install programs with
8496 different functionality but with the same filenames. (The
8497 case of two programs having the same functionality but
8498 different implementations is handled via "alternatives" or
8499 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8500 <ref id="conflicts"> respectively.) If this case happens,
8501 one of the programs must be renamed. The maintainers should
8502 report this to the <tt>debian-devel</tt> mailing list and
8503 try to find a consensus about which program will have to be
8504 renamed. If a consensus cannot be reached, <em>both</em>
8505 programs must be renamed.
8508 Binary executables must not be statically linked with the GNU C
8509 library, since this prevents the binary from benefiting from
8510 fixes and improvements to the C library without being rebuilt
8511 and complicates security updates. This requirement may be
8512 relaxed for binary executables whose intended purpose is to
8513 diagnose and fix the system in situations where the GNU C
8514 library may not be usable (such as system recovery shells or
8515 utilities like ldconfig) or for binary executables where the
8516 security benefits of static linking outweigh the drawbacks.
8519 By default, when a package is being built, any binaries
8520 created should include debugging information, as well as
8521 being compiled with optimization. You should also turn on
8522 as many reasonable compilation warnings as possible; this
8523 makes life easier for porters, who can then look at build
8524 logs for possible problems. For the C programming language,
8525 this means the following compilation parameters should be
8527 <example compact="compact">
8529 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8531 INSTALL = install -s # (or use strip on the files in debian/tmp)
8536 Note that by default all installed binaries should be stripped,
8537 either by using the <tt>-s</tt> flag to
8538 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8539 the binaries after they have been copied into
8540 <file>debian/tmp</file> but before the tree is made into a
8545 Although binaries in the build tree should be compiled with
8546 debugging information by default, it can often be difficult to
8547 debug programs if they are also subjected to compiler
8548 optimization. For this reason, it is recommended to support the
8549 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8550 (see <ref id="debianrules-options">). This variable can contain
8551 several flags to change how a package is compiled and built.
8555 It is up to the package maintainer to decide what
8556 compilation options are best for the package. Certain
8557 binaries (such as computationally-intensive programs) will
8558 function better with certain flags (<tt>-O3</tt>, for
8559 example); feel free to use them. Please use good judgment
8560 here. Don't use flags for the sake of it; only use them
8561 if there is good reason to do so. Feel free to override
8562 the upstream author's ideas about which compilation
8563 options are best: they are often inappropriate for our
8569 <sect id="libraries">
8570 <heading>Libraries</heading>
8573 If the package is <strong>architecture: any</strong>, then
8574 the shared library compilation and linking flags must have
8575 <tt>-fPIC</tt>, or the package shall not build on some of
8576 the supported architectures<footnote>
8578 If you are using GCC, <tt>-fPIC</tt> produces code with
8579 relocatable position independent code, which is required for
8580 most architectures to create a shared library, with i386 and
8581 perhaps some others where non position independent code is
8582 permitted in a shared library.
8585 Position independent code may have a performance penalty,
8586 especially on <tt>i386</tt>. However, in most cases the
8587 speed penalty must be measured against the memory wasted on
8588 the few architectures where non position independent code is
8591 </footnote>. Any exception to this rule must be discussed on
8592 the mailing list <em>debian-devel@lists.debian.org</em>, and
8593 a rough consensus obtained. The reasons for not compiling
8594 with <tt>-fPIC</tt> flag must be recorded in the file
8595 <tt>README.Debian</tt>, and care must be taken to either
8596 restrict the architecture or arrange for <tt>-fPIC</tt> to
8597 be used on architectures where it is required.<footnote>
8599 Some of the reasons why this might be required is if the
8600 library contains hand crafted assembly code that is not
8601 relocatable, the speed penalty is excessive for compute
8602 intensive libs, and similar reasons.
8607 As to the static libraries, the common case is not to have
8608 relocatable code, since there is no benefit, unless in specific
8609 cases; therefore the static version must not be compiled
8610 with the <tt>-fPIC</tt> flag. Any exception to this rule
8611 should be discussed on the mailing list
8612 <em>debian-devel@lists.debian.org</em>, and the reasons for
8613 compiling with the <tt>-fPIC</tt> flag must be recorded in
8614 the file <tt>README.Debian</tt>. <footnote>
8616 Some of the reasons for linking static libraries with
8617 the <tt>-fPIC</tt> flag are if, for example, one needs a
8618 Perl API for a library that is under rapid development,
8619 and has an unstable API, so shared libraries are
8620 pointless at this phase of the library's development. In
8621 that case, since Perl needs a library with relocatable
8622 code, it may make sense to create a static library with
8623 relocatable code. Another reason cited is if you are
8624 distilling various libraries into a common shared
8625 library, like <tt>mklibs</tt> does in the Debian
8631 In other words, if both a shared and a static library is
8632 being built, each source unit (<tt>*.c</tt>, for example,
8633 for C files) will need to be compiled twice, for the normal
8638 Libraries should be built with threading support and to be
8639 thread-safe if the library supports this.
8643 Although not enforced by the build tools, shared libraries
8644 must be linked against all libraries that they use symbols from
8645 in the same way that binaries are. This ensures the correct
8646 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8647 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8648 systems and guarantees that all libraries can be safely opened
8649 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8650 option <tt>-Wl,-z,defs</tt> when building a shared library.
8651 Since this option enforces symbol resolution at build time,
8652 a missing library reference will be caught early as a fatal
8657 All installed shared libraries should be stripped with
8658 <example compact="compact">
8659 strip --strip-unneeded <var>your-lib</var>
8661 (The option <tt>--strip-unneeded</tt> makes
8662 <prgn>strip</prgn> remove only the symbols which aren't
8663 needed for relocation processing.) Shared libraries can
8664 function perfectly well when stripped, since the symbols for
8665 dynamic linking are in a separate part of the ELF object
8667 You might also want to use the options
8668 <tt>--remove-section=.comment</tt> and
8669 <tt>--remove-section=.note</tt> on both shared libraries
8670 and executables, and <tt>--strip-debug</tt> on static
8676 Note that under some circumstances it may be useful to
8677 install a shared library unstripped, for example when
8678 building a separate package to support debugging.
8682 Shared object files (often <file>.so</file> files) that are not
8683 public libraries, that is, they are not meant to be linked
8684 to by third party executables (binaries of other packages),
8685 should be installed in subdirectories of the
8686 <file>/usr/lib</file> directory. Such files are exempt from the
8687 rules that govern ordinary shared libraries, except that
8688 they must not be installed executable and should be
8690 A common example are the so-called "plug-ins",
8691 internal shared objects that are dynamically loaded by
8692 programs using <manref name="dlopen" section="3">.
8697 Packages that use <prgn>libtool</prgn> to create and install
8698 their shared libraries install a file containing additional
8699 metadata (ending in <file>.la</file>) alongside the library.
8700 For public libraries intended for use by other packages, these
8701 files normally should not be included in the Debian package,
8702 since the information they include is not necessary to link with
8703 the shared library on Debian and can add unnecessary additional
8704 dependencies to other programs or libraries.<footnote>
8705 These files store, among other things, all libraries on which
8706 that shared library depends. Unfortunately, if
8707 the <file>.la</file> file is present and contains that
8708 dependency information, using <prgn>libtool</prgn> when
8709 linking against that library will cause the resulting program
8710 or library to be linked against those dependencies as well,
8711 even if this is unnecessary. This can create unneeded
8712 dependencies on shared library packages that would otherwise
8713 be hidden behind the library ABI, and can make library
8714 transitions to new SONAMEs unnecessarily complicated and
8715 difficult to manage.
8717 If the <file>.la</file> file is required for that library (if,
8718 for instance, it's loaded via <tt>libltdl</tt> in a way that
8719 requires that meta-information), the <tt>dependency_libs</tt>
8720 setting in the <file>.la</file> file should normally be set to
8721 the empty string. If the shared library development package has
8722 historically included the <file>.la</file>, it must be retained
8723 in the development package (with <tt>dependency_libs</tt>
8724 emptied) until all libraries that depend on it have removed or
8725 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8726 files to prevent linking with those other libraries
8727 using <prgn>libtool</prgn> from failing.
8731 If the <file>.la</file> must be included, it should be included
8732 in the development (<tt>-dev</tt>) package, unless the library
8733 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8734 library. If it is intended for use with <tt>libltdl</tt>,
8735 the <file>.la</file> files must go in the run-time library
8740 These requirements for handling of <file>.la</file> files do not
8741 apply to loadable modules or libraries not installed in
8742 directories searched by default by the dynamic linker. Packages
8743 installing loadable modules will frequently need to install
8744 the <file>.la</file> files alongside the modules so that they
8745 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8746 does not need to be modified for libraries or modules that are
8747 not installed in directories searched by the dynamic linker by
8748 default and not intended for use by other packages.
8752 You must make sure that you use only released versions of
8753 shared libraries to build your packages; otherwise other
8754 users will not be able to run your binaries
8755 properly. Producing source packages that depend on
8756 unreleased compilers is also usually a bad
8763 <heading>Shared libraries</heading>
8765 This section has moved to <ref id="sharedlibs">.
8771 <heading>Scripts</heading>
8774 All command scripts, including the package maintainer
8775 scripts inside the package and used by <prgn>dpkg</prgn>,
8776 should have a <tt>#!</tt> line naming the shell to be used
8781 In the case of Perl scripts this should be
8782 <tt>#!/usr/bin/perl</tt>.
8786 When scripts are installed into a directory in the system
8787 PATH, the script name should not include an extension such
8788 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8789 language currently used to implement it.
8792 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8793 <file>init.d</file> scripts should almost certainly start
8794 with <tt>set -e</tt> so that errors are detected.
8795 <file>init.d</file> scripts are something of a special case, due
8796 to how frequently they need to call commands that are allowed to
8797 fail, and it may instead be easier to check the exit status of
8798 commands directly. See <ref id="writing-init"> for more
8799 information about writing <file>init.d</file> scripts.
8802 Every script should use <tt>set -e</tt> or check the exit status
8803 of <em>every</em> command.
8806 Scripts may assume that <file>/bin/sh</file> implements the
8807 SUSv3 Shell Command Language<footnote>
8808 Single UNIX Specification, version 3, which is also IEEE
8809 1003.1-2004 (POSIX), and is available on the World Wide Web
8810 from <url id="http://www.unix.org/version3/online.html"
8811 name="The Open Group"> after free
8812 registration.</footnote>
8813 plus the following additional features not mandated by
8815 These features are in widespread use in the Linux community
8816 and are implemented in all of bash, dash, and ksh, the most
8817 common shells users may wish to use as <file>/bin/sh</file>.
8820 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8821 must not generate a newline.</item>
8822 <item><tt>test</tt>, if implemented as a shell built-in, must
8823 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8825 <item><tt>local</tt> to create a scoped variable must be
8826 supported, including listing multiple variables in a single
8827 local command and assigning a value to a variable at the
8828 same time as localizing it. <tt>local</tt> may or
8829 may not preserve the variable value from an outer scope if
8830 no assignment is present. Uses such as:
8834 # ... use a, b, c, d ...
8837 must be supported and must set the value of <tt>c</tt> to
8840 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8841 -<var>signal</var></tt>, where <var>signal</var> is either
8842 the name of a signal or one of the numeric signals listed in
8843 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8844 supported if <prgn>kill</prgn> is implemented as a shell
8847 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8848 signals must be supported. In addition to the signal
8849 numbers listed in the extension, which are the same as for
8850 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8853 If a shell script requires non-SUSv3 features from the shell
8854 interpreter other than those listed above, the appropriate shell
8855 must be specified in the first line of the script (e.g.,
8856 <tt>#!/bin/bash</tt>) and the package must depend on the package
8857 providing the shell (unless the shell package is marked
8858 "Essential", as in the case of <prgn>bash</prgn>).
8862 You may wish to restrict your script to SUSv3 features plus the
8863 above set when possible so that it may use <file>/bin/sh</file>
8864 as its interpreter. Checking your script
8865 with <prgn>checkbashisms</prgn> from
8866 the <package>devscripts</package> package or running your script
8867 with an alternate shell such as <prgn>posh</prgn> may help
8868 uncover violations of the above requirements. If in doubt
8869 whether a script complies with these requirements,
8870 use <file>/bin/bash</file>.
8874 Perl scripts should check for errors when making any
8875 system calls, including <tt>open</tt>, <tt>print</tt>,
8876 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8880 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8881 scripting languages. See <em>Csh Programming Considered
8882 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8883 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8884 If an upstream package comes with <prgn>csh</prgn> scripts
8885 then you must make sure that they start with
8886 <tt>#!/bin/csh</tt> and make your package depend on the
8887 <prgn>c-shell</prgn> virtual package.
8891 Any scripts which create files in world-writeable
8892 directories (e.g., in <file>/tmp</file>) must use a
8893 mechanism which will fail atomically if a file with the same
8894 name already exists.
8898 The Debian base system provides the <prgn>tempfile</prgn>
8899 and <prgn>mktemp</prgn> utilities for use by scripts for
8906 <heading>Symbolic links</heading>
8909 In general, symbolic links within a top-level directory should
8910 be relative, and symbolic links pointing from one top-level
8911 directory to or into another should be absolute. (A top-level
8912 directory is a sub-directory of the root
8913 directory <file>/</file>.) For example, a symbolic link
8914 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8915 should be relative (<file>../share/bar</file>), but a symbolic
8916 link from <file>/var/run</file> to <file>/run</file> should be
8918 This is necessary to allow top-level directories to be
8919 symlinks. If linking <file>/var/run</file>
8920 to <file>/run</file> were done with the relative symbolic
8921 link <file>../run</file>, but <file>/var</file> were a
8922 symbolic link to <file>/srv/disk1</file>, the symbolic link
8923 would point to <file>/srv/run</file> rather than the intended
8926 Symbolic links must not traverse above the root directory.
8930 In addition, symbolic links should be specified as short as
8931 possible, i.e., link targets like <file>foo/../bar</file> are
8936 Note that when creating a relative link using
8937 <prgn>ln</prgn> it is not necessary for the target of the
8938 link to exist relative to the working directory you're
8939 running <prgn>ln</prgn> from, nor is it necessary to change
8940 directory to the directory where the link is to be made.
8941 Simply include the string that should appear as the target
8942 of the link (this will be a pathname relative to the
8943 directory in which the link resides) as the first argument
8948 For example, in your <prgn>Makefile</prgn> or
8949 <file>debian/rules</file>, you can do things like:
8950 <example compact="compact">
8951 ln -fs gcc $(prefix)/bin/cc
8952 ln -fs gcc debian/tmp/usr/bin/cc
8953 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8954 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8959 A symbolic link pointing to a compressed file (in the sense
8960 that it is meant to be uncompressed with <prgn>unzip</prgn>
8961 or <prgn>zless</prgn> etc.) should always
8962 have the same file extension as the referenced file. (For
8963 example, if a file <file>foo.gz</file> is referenced by a
8964 symbolic link, the filename of the link has to end with
8965 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8970 <heading>Device files</heading>
8973 Packages must not include device files or named pipes in the
8978 If a package needs any special device files that are not
8979 included in the base system, it must call
8980 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8981 after notifying the user<footnote>
8982 This notification could be done via a (low-priority)
8983 debconf message, or an echo (printf) statement.
8988 Packages must not remove any device files in the
8989 <prgn>postrm</prgn> or any other script. This is left to the
8990 system administrator.
8994 Debian uses the serial devices
8995 <file>/dev/ttyS*</file>. Programs using the old
8996 <file>/dev/cu*</file> devices should be changed to use
8997 <file>/dev/ttyS*</file>.
9001 Named pipes needed by the package must be created in
9002 the <prgn>postinst</prgn> script<footnote>
9003 It's better to use <prgn>mkfifo</prgn> rather
9004 than <prgn>mknod</prgn> to create named pipes so that
9005 automated checks for packages incorrectly creating device
9006 files with <prgn>mknod</prgn> won't have false positives.
9007 </footnote> and removed in
9008 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
9013 <sect id="config-files">
9014 <heading>Configuration files</heading>
9017 <heading>Definitions</heading>
9021 <tag>configuration file</tag>
9023 A file that affects the operation of a program, or
9024 provides site- or host-specific information, or
9025 otherwise customizes the behavior of a program.
9026 Typically, configuration files are intended to be
9027 modified by the system administrator (if needed or
9028 desired) to conform to local policy or to provide
9029 more useful site-specific behavior.
9032 <tag><tt>conffile</tt></tag>
9034 A file listed in a package's <tt>conffiles</tt>
9035 file, and is treated specially by <prgn>dpkg</prgn>
9036 (see <ref id="configdetails">).
9042 The distinction between these two is important; they are
9043 not interchangeable concepts. Almost all
9044 <tt>conffile</tt>s are configuration files, but many
9045 configuration files are not <tt>conffiles</tt>.
9049 As noted elsewhere, <file>/etc/init.d</file> scripts,
9050 <file>/etc/default</file> files, scripts installed in
9051 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
9052 configuration installed in <file>/etc/cron.d</file> must be
9053 treated as configuration files. In general, any script that
9054 embeds configuration information is de-facto a configuration
9055 file and should be treated as such.
9060 <heading>Location</heading>
9063 Any configuration files created or used by your package
9064 must reside in <file>/etc</file>. If there are several,
9065 consider creating a subdirectory of <file>/etc</file>
9066 named after your package.
9070 If your package creates or uses configuration files
9071 outside of <file>/etc</file>, and it is not feasible to modify
9072 the package to use <file>/etc</file> directly, put the files
9073 in <file>/etc</file> and create symbolic links to those files
9074 from the location that the package requires.
9079 <heading>Behavior</heading>
9082 Configuration file handling must conform to the following
9084 <list compact="compact">
9086 local changes must be preserved during a package
9090 configuration files must be preserved when the
9091 package is removed, and only deleted when the
9095 Obsolete configuration files without local changes should be
9096 removed by the package during upgrade.<footnote>
9097 The <prgn>dpkg-maintscript-helper</prgn> tool, available from the
9098 <package>dpkg</package> package, can help for this task.</footnote>
9102 The easy way to achieve this behavior is to make the
9103 configuration file a <tt>conffile</tt>. This is
9104 appropriate only if it is possible to distribute a default
9105 version that will work for most installations, although
9106 some system administrators may choose to modify it. This
9107 implies that the default version will be part of the
9108 package distribution, and must not be modified by the
9109 maintainer scripts during installation (or at any other
9114 In order to ensure that local changes are preserved
9115 correctly, no package may contain or make hard links to
9116 conffiles.<footnote>
9117 Rationale: There are two problems with hard links.
9118 The first is that some editors break the link while
9119 editing one of the files, so that the two files may
9120 unwittingly become unlinked and different. The second
9121 is that <prgn>dpkg</prgn> might break the hard link
9122 while upgrading <tt>conffile</tt>s.
9127 The other way to do it is via the maintainer scripts. In
9128 this case, the configuration file must not be listed as a
9129 <tt>conffile</tt> and must not be part of the package
9130 distribution. If the existence of a file is required for
9131 the package to be sensibly configured it is the
9132 responsibility of the package maintainer to provide
9133 maintainer scripts which correctly create, update and
9134 maintain the file and remove it on purge. (See <ref
9135 id="maintainerscripts"> for more information.) These
9136 scripts must be idempotent (i.e., must work correctly if
9137 <prgn>dpkg</prgn> needs to re-run them due to errors
9138 during installation or removal), must cope with all the
9139 variety of ways <prgn>dpkg</prgn> can call maintainer
9140 scripts, must not overwrite or otherwise mangle the user's
9141 configuration without asking, must not ask unnecessary
9142 questions (particularly during upgrades), and must
9143 otherwise be good citizens.
9147 The scripts are not required to configure every possible
9148 option for the package, but only those necessary to get
9149 the package running on a given system. Ideally the
9150 sysadmin should not have to do any configuration other
9151 than that done (semi-)automatically by the
9152 <prgn>postinst</prgn> script.
9156 A common practice is to create a script called
9157 <file><var>package</var>-configure</file> and have the
9158 package's <prgn>postinst</prgn> call it if and only if the
9159 configuration file does not already exist. In certain
9160 cases it is useful for there to be an example or template
9161 file which the maintainer scripts use. Such files should
9162 be in <file>/usr/share/<var>package</var></file> or
9163 <file>/usr/lib/<var>package</var></file> (depending on whether
9164 they are architecture-independent or not). There should
9165 be symbolic links to them from
9166 <file>/usr/share/doc/<var>package</var>/examples</file> if
9167 they are examples, and should be perfectly ordinary
9168 <prgn>dpkg</prgn>-handled files (<em>not</em>
9169 configuration files).
9173 These two styles of configuration file handling must
9174 not be mixed, for that way lies madness:
9175 <prgn>dpkg</prgn> will ask about overwriting the file
9176 every time the package is upgraded.
9181 <heading>Sharing configuration files</heading>
9184 If two or more packages use the same configuration file
9185 and it is reasonable for both to be installed at the same
9186 time, one of these packages must be defined as
9187 <em>owner</em> of the configuration file, i.e., it will be
9188 the package which handles that file as a configuration
9189 file. Other packages that use the configuration file must
9190 depend on the owning package if they require the
9191 configuration file to operate. If the other package will
9192 use the configuration file if present, but is capable of
9193 operating without it, no dependency need be declared.
9197 If it is desirable for two or more related packages to
9198 share a configuration file <em>and</em> for all of the
9199 related packages to be able to modify that configuration
9200 file, then the following should be done:
9201 <enumlist compact="compact">
9203 One of the related packages (the "owning" package)
9204 will manage the configuration file with maintainer
9205 scripts as described in the previous section.
9208 The owning package should also provide a program
9209 that the other packages may use to modify the
9213 The related packages must use the provided program
9214 to make any desired modifications to the
9215 configuration file. They should either depend on
9216 the core package to guarantee that the configuration
9217 modifier program is available or accept gracefully
9218 that they cannot modify the configuration file if it
9219 is not. (This is in addition to the fact that the
9220 configuration file may not even be present in the
9227 Sometimes it's appropriate to create a new package which
9228 provides the basic infrastructure for the other packages
9229 and which manages the shared configuration files. (The
9230 <tt>sgml-base</tt> package is a good example.)
9234 If the configuration file cannot be shared as described above,
9235 the packages must be marked as conflicting with each other.
9236 Two packages that specify the same file as
9237 a <tt>conffile</tt> must conflict. This is an instance of the
9238 general rule about not sharing files. Neither alternatives
9239 nor diversions are likely to be appropriate in this case; in
9240 particular, <prgn>dpkg</prgn> does not handle diverted
9241 <tt>conffile</tt>s well.
9245 When two packages both declare the same <tt>conffile</tt>, they
9246 may see left-over configuration files from each other even
9247 though they conflict with each other. If a user removes
9248 (without purging) one of the packages and installs the other,
9249 the new package will take over the <tt>conffile</tt> from the
9250 old package. If the file was modified by the user, it will be
9251 treated the same as any other locally
9252 modified <tt>conffile</tt> during an upgrade.
9256 The maintainer scripts must not alter a <tt>conffile</tt>
9257 of <em>any</em> package, including the one the scripts
9263 <heading>User configuration files ("dotfiles")</heading>
9266 The files in <file>/etc/skel</file> will automatically be
9267 copied into new user accounts by <prgn>adduser</prgn>.
9268 No other program should reference the files in
9269 <file>/etc/skel</file>.
9273 Therefore, if a program needs a dotfile to exist in
9274 advance in <file>$HOME</file> to work sensibly, that dotfile
9275 should be installed in <file>/etc/skel</file> and treated as a
9280 However, programs that require dotfiles in order to
9281 operate sensibly are a bad thing, unless they do create
9282 the dotfiles themselves automatically.
9286 Furthermore, programs should be configured by the Debian
9287 default installation to behave as closely to the upstream
9288 default behavior as possible.
9292 Therefore, if a program in a Debian package needs to be
9293 configured in some way in order to operate sensibly, that
9294 should be done using a site-wide configuration file placed
9295 in <file>/etc</file>. Only if the program doesn't support a
9296 site-wide default configuration and the package maintainer
9297 doesn't have time to add it may a default per-user file be
9298 placed in <file>/etc/skel</file>.
9302 <file>/etc/skel</file> should be as empty as we can make it.
9303 This is particularly true because there is no easy (or
9304 necessarily desirable) mechanism for ensuring that the
9305 appropriate dotfiles are copied into the accounts of
9306 existing users when a package is installed.
9312 <heading>Log files</heading>
9314 Log files should usually be named
9315 <file>/var/log/<var>package</var>.log</file>. If you have many
9316 log files, or need a separate directory for permission
9317 reasons (<file>/var/log</file> is writable only by
9318 <file>root</file>), you should usually create a directory named
9319 <file>/var/log/<var>package</var></file> and place your log
9324 Log files must be rotated occasionally so that they don't grow
9325 indefinitely. The best way to do this is to install a log
9326 rotation configuration file in the
9327 directory <file>/etc/logrotate.d</file>, normally
9328 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9329 the facilities provided by <prgn>logrotate</prgn>.
9332 The traditional approach to log files has been to set up
9333 <em>ad hoc</em> log rotation schemes using simple shell
9334 scripts and cron. While this approach is highly
9335 customizable, it requires quite a lot of sysadmin work.
9336 Even though the original Debian system helped a little
9337 by automatically installing a system which can be used
9338 as a template, this was deemed not enough.
9342 The use of <prgn>logrotate</prgn>, a program developed
9343 by Red Hat, is better, as it centralizes log management.
9344 It has both a configuration file
9345 (<file>/etc/logrotate.conf</file>) and a directory where
9346 packages can drop their individual log rotation
9347 configurations (<file>/etc/logrotate.d</file>).
9350 Here is a good example for a logrotate config
9351 file (for more information see <manref name="logrotate"
9353 <example compact="compact">
9354 /var/log/foo/*.log {
9360 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9364 This rotates all files under <file>/var/log/foo</file>, saves 12
9365 compressed generations, and tells the daemon to reopen its log
9366 files after the log rotation. It skips this log rotation
9367 (via <tt>missingok</tt>) if no such log file is present, which
9368 avoids errors if the package is removed but not purged.
9372 Log files should be removed when the package is
9373 purged (but not when it is only removed). This should be
9374 done by the <prgn>postrm</prgn> script when it is called
9375 with the argument <tt>purge</tt> (see <ref
9376 id="removedetails">).
9380 <sect id="permissions-owners">
9381 <heading>Permissions and owners</heading>
9384 The rules in this section are guidelines for general use.
9385 If necessary you may deviate from the details below.
9386 However, if you do so you must make sure that what is done
9387 is secure and you should try to be as consistent as possible
9388 with the rest of the system. You should probably also
9389 discuss it on <prgn>debian-devel</prgn> first.
9393 Files should be owned by <tt>root:root</tt>, and made
9394 writable only by the owner and universally readable (and
9395 executable, if appropriate), that is mode 644 or 755.
9399 Directories should be mode 755 or (for group-writability)
9400 mode 2775. The ownership of the directory should be
9401 consistent with its mode: if a directory is mode 2775, it
9402 should be owned by the group that needs write access to
9405 When a package is upgraded, and the owner or permissions
9406 of a file included in the package has changed, dpkg
9407 arranges for the ownership and permissions to be
9408 correctly set upon installation. However, this does not
9409 extend to directories; the permissions and ownership of
9410 directories already on the system does not change on
9411 install or upgrade of packages. This makes sense, since
9412 otherwise common directories like <tt>/usr</tt> would
9413 always be in flux. To correctly change permissions of a
9414 directory the package owns, explicit action is required,
9415 usually in the <tt>postinst</tt> script. Care must be
9416 taken to handle downgrades as well, in that case.
9422 Control information files should be owned by <tt>root:root</tt>
9423 and either mode 644 (for most files) or mode 755 (for
9424 executables such as <qref id="maintscripts">maintainer
9429 Setuid and setgid executables should be mode 4755 or 2755
9430 respectively, and owned by the appropriate user or group.
9431 They should not be made unreadable (modes like 4711 or
9432 2711 or even 4111); doing so achieves no extra security,
9433 because anyone can find the binary in the freely available
9434 Debian package; it is merely inconvenient. For the same
9435 reason you should not restrict read or execute permissions
9436 on non-set-id executables.
9440 Some setuid programs need to be restricted to particular
9441 sets of users, using file permissions. In this case they
9442 should be owned by the uid to which they are set-id, and by
9443 the group which should be allowed to execute them. They
9444 should have mode 4754; again there is no point in making
9445 them unreadable to those users who must not be allowed to
9450 It is possible to arrange that the system administrator can
9451 reconfigure the package to correspond to their local
9452 security policy by changing the permissions on a binary:
9453 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9454 described below.<footnote>
9455 Ordinary files installed by <prgn>dpkg</prgn> (as
9456 opposed to <tt>conffile</tt>s and other similar objects)
9457 normally have their permissions reset to the distributed
9458 permissions when the package is reinstalled. However,
9459 the use of <prgn>dpkg-statoverride</prgn> overrides this
9462 Another method you should consider is to create a group for
9463 people allowed to use the program(s) and make any setuid
9464 executables executable only by that group.
9468 If you need to create a new user or group for your package
9469 there are two possibilities. Firstly, you may need to
9470 make some files in the binary package be owned by this
9471 user or group, or you may need to compile the user or
9472 group id (rather than just the name) into the binary
9473 (though this latter should be avoided if possible, as in
9474 this case you need a statically allocated id).</p>
9477 If you need a statically allocated id, you must ask for a
9478 user or group id from the <tt>base-passwd</tt> maintainer,
9479 and must not release the package until you have been
9480 allocated one. Once you have been allocated one you must
9481 either make the package depend on a version of the
9482 <tt>base-passwd</tt> package with the id present in
9483 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9484 your package to create the user or group itself with the
9485 correct id (using <tt>adduser</tt>) in its
9486 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9487 the <prgn>postinst</prgn> is to be preferred if it is
9488 possible, otherwise a pre-dependency will be needed on the
9489 <tt>adduser</tt> package.)
9493 On the other hand, the program might be able to determine
9494 the uid or gid from the user or group name at runtime, so
9495 that a dynamically allocated id can be used. In this case
9496 you should choose an appropriate user or group name,
9497 discussing this on <prgn>debian-devel</prgn> and checking
9498 with the <package/base-passwd/ maintainer that it is unique and that
9499 they do not wish you to use a statically allocated id
9500 instead. When this has been checked you must arrange for
9501 your package to create the user or group if necessary using
9502 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9503 <prgn>postinst</prgn> script (again, the latter is to be
9504 preferred if it is possible).
9508 Note that changing the numeric value of an id associated
9509 with a name is very difficult, and involves searching the
9510 file system for all appropriate files. You need to think
9511 carefully whether a static or dynamic id is required, since
9512 changing your mind later will cause problems.
9515 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9517 This section is not intended as policy, but as a
9518 description of the use of <prgn>dpkg-statoverride</prgn>.
9522 If a system administrator wishes to have a file (or
9523 directory or other such thing) installed with owner and
9524 permissions different from those in the distributed Debian
9525 package, they can use the <prgn>dpkg-statoverride</prgn>
9526 program to instruct <prgn>dpkg</prgn> to use the different
9527 settings every time the file is installed. Thus the
9528 package maintainer should distribute the files with their
9529 normal permissions, and leave it for the system
9530 administrator to make any desired changes. For example, a
9531 daemon which is normally required to be setuid root, but
9532 in certain situations could be used without being setuid,
9533 should be installed setuid in the <tt>.deb</tt>. Then the
9534 local system administrator can change this if they wish.
9535 If there are two standard ways of doing it, the package
9536 maintainer can use <tt>debconf</tt> to find out the
9537 preference, and call <prgn>dpkg-statoverride</prgn> in the
9538 maintainer script if necessary to accommodate the system
9539 administrator's choice. Care must be taken during
9540 upgrades to not override an existing setting.
9544 Given the above, <prgn>dpkg-statoverride</prgn> is
9545 essentially a tool for system administrators and would not
9546 normally be needed in the maintainer scripts. There is
9547 one type of situation, though, where calls to
9548 <prgn>dpkg-statoverride</prgn> would be needed in the
9549 maintainer scripts, and that involves packages which use
9550 dynamically allocated user or group ids. In such a
9551 situation, something like the following idiom can be very
9552 helpful in the package's <prgn>postinst</prgn>, where
9553 <tt>sysuser</tt> is a dynamically allocated id:
9555 for i in /usr/bin/foo /usr/sbin/bar
9557 # only do something when no setting exists
9558 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9560 #include: debconf processing, question about foo and bar
9561 if [ "$RET" = "true" ] ; then
9562 dpkg-statoverride --update --add sysuser root 4755 $i
9567 The corresponding code to remove the override when the package
9570 for i in /usr/bin/foo /usr/sbin/bar
9572 if dpkg-statoverride --list $i >/dev/null 2>&1
9574 dpkg-statoverride --remove $i
9582 <sect id="filenames">
9583 <heading>File names</heading>
9586 The name of the files installed by binary packages in the system PATH
9587 (namely <tt>/bin</tt>, <tt>/sbin</tt>, <tt>/usr/bin</tt>,
9588 <tt>/usr/sbin</tt> and <tt>/usr/games</tt>) must be encoded in
9593 The name of the files and directories installed by binary packages
9594 outside the system PATH must be encoded in UTF-8 and should be
9595 restricted to ASCII when it is possible to do so.
9601 <chapt id="customized-programs">
9602 <heading>Customized programs</heading>
9604 <sect id="arch-spec">
9605 <heading>Architecture specification strings</heading>
9608 If a program needs to specify an <em>architecture specification
9609 string</em> in some place, it should select one of the strings
9610 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9611 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9612 part is sometimes elided, as when the OS is Linux.
9616 Note that we don't want to use
9617 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9618 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9619 since this would make our programs incompatible with other
9620 Linux distributions. We also don't use something like
9621 <tt><var>arch</var>-unknown-linux</tt>, since the
9622 <tt>unknown</tt> does not look very good.
9625 <sect1 id="arch-wildcard-spec">
9626 <heading>Architecture wildcards</heading>
9629 A package may specify an architecture wildcard. Architecture
9630 wildcards are in the format <tt>any</tt> (which matches every
9631 architecture), <tt><var>os</var></tt>-any, or
9632 any-<tt><var>cpu</var></tt>. <footnote>
9633 Internally, the package system normalizes the GNU triplets
9634 and the Debian arches into Debian arch triplets (which are
9635 kind of inverted GNU triplets), with the first component of
9636 the triplet representing the libc and ABI in use, and then
9637 does matching against those triplets. However, such
9638 triplets are an internal implementation detail that should
9639 not be used by packages directly. The libc and ABI portion
9640 is handled internally by the package system based on
9641 the <var>os</var> and <var>cpu</var>.
9648 <heading>Daemons</heading>
9651 The configuration files <file>/etc/services</file>,
9652 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9653 by the <prgn>netbase</prgn> package and must not be modified
9658 If a package requires a new entry in one of these files, the
9659 maintainer should get in contact with the
9660 <prgn>netbase</prgn> maintainer, who will add the entries
9661 and release a new version of the <prgn>netbase</prgn>
9666 The configuration file <file>/etc/inetd.conf</file> must not be
9667 modified by the package's scripts except via the
9668 <prgn>update-inetd</prgn> script or the
9669 <file>DebianNet.pm</file> Perl module. See their documentation
9670 for details on how to add entries.
9674 If a package wants to install an example entry into
9675 <file>/etc/inetd.conf</file>, the entry must be preceded with
9676 exactly one hash character (<tt>#</tt>). Such lines are
9677 treated as "commented out by user" by the
9678 <prgn>update-inetd</prgn> script and are not changed or
9679 activated during package updates.
9684 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9688 Some programs need to create pseudo-ttys. This should be done
9689 using Unix98 ptys if the C library supports it. The resulting
9690 program must not be installed setuid root, unless that
9691 is required for other functionality.
9695 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9696 <file>/var/log/lastlog</file> must be installed writable by
9697 group <tt>utmp</tt>. Programs which need to modify those
9698 files must be installed setgid <tt>utmp</tt>.
9703 <heading>Editors and pagers</heading>
9706 Some programs have the ability to launch an editor or pager
9707 program to edit or display a text document. Since there are
9708 lots of different editors and pagers available in the Debian
9709 distribution, the system administrator and each user should
9710 have the possibility to choose their preferred editor and
9715 In addition, every program should choose a good default
9716 editor/pager if none is selected by the user or system
9721 Thus, every program that launches an editor or pager must
9722 use the EDITOR or PAGER environment variable to determine
9723 the editor or pager the user wishes to use. If these
9724 variables are not set, the programs <file>/usr/bin/editor</file>
9725 and <file>/usr/bin/pager</file> should be used, respectively.
9729 These two files are managed through the <prgn>dpkg</prgn>
9730 "alternatives" mechanism. Every package providing an editor or
9731 pager must call the <prgn>update-alternatives</prgn> script to
9732 register as an alternative for <file>/usr/bin/editor</file>
9733 or <file>/usr/bin/pager</file> as appropriate. The alternative
9734 should have a slave alternative
9735 for <file>/usr/share/man/man1/editor.1.gz</file>
9736 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9737 corresponding manual page.
9741 If it is very hard to adapt a program to make use of the
9742 EDITOR or PAGER variables, that program may be configured to
9743 use <file>/usr/bin/sensible-editor</file> and
9744 <file>/usr/bin/sensible-pager</file> as the editor or pager
9745 program respectively. These are two scripts provided in the
9746 <package>sensible-utils</package> package that check the EDITOR
9747 and PAGER variables and launch the appropriate program, and fall
9748 back to <file>/usr/bin/editor</file>
9749 and <file>/usr/bin/pager</file> if the variable is not set.
9753 A program may also use the VISUAL environment variable to
9754 determine the user's choice of editor. If it exists, it
9755 should take precedence over EDITOR. This is in fact what
9756 <file>/usr/bin/sensible-editor</file> does.
9760 It is not required for a package to depend on
9761 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9762 package to provide such virtual packages.<footnote>
9763 The Debian base system already provides an editor and a
9769 <sect id="web-appl">
9770 <heading>Web servers and applications</heading>
9773 This section describes the locations and URLs that should
9774 be used by all web servers and web applications in the
9781 Cgi-bin executable files are installed in the
9783 <example compact="compact">
9786 or a subdirectory of that directory, and the script
9787 <example compact="compact">
9788 /usr/lib/cgi-bin/.../<var>cgi-bin-name</var>
9790 should be referred to as
9791 <example compact="compact">
9792 http://localhost/cgi-bin/.../<var>cgi-bin-name</var>
9801 <p>Access to images</p>
9803 It is recommended that images for a package be stored
9804 in <tt>/usr/share/images/<var>package</var></tt> and
9805 may be referred to through an alias <tt>/images/</tt>
9808 http://localhost/images/<package>/<filename>
9815 <p>Web Document Root</p>
9818 Web Applications should try to avoid storing files in
9819 the Web Document Root. Instead they should use the
9820 /usr/share/doc/<var>package</var> directory for
9821 documents and register the Web Application via the
9822 <package>doc-base</package> package. If access to the
9823 web document root is unavoidable then use
9824 <example compact="compact">
9827 as the Document Root. This might be just a symbolic
9828 link to the location where the system administrator
9829 has put the real document root.
9832 <item><p>Providing httpd and/or httpd-cgi</p>
9834 All web servers should provide the virtual package
9835 <tt>httpd</tt>. If a web server has CGI support it should
9836 provide <tt>httpd-cgi</tt> additionally.
9839 All web applications which do not contain CGI scripts should
9840 depend on <tt>httpd</tt>, all those web applications which
9841 <tt>do</tt> contain CGI scripts, should depend on
9849 <sect id="mail-transport-agents">
9850 <heading>Mail transport, delivery and user agents</heading>
9853 Debian packages which process electronic mail, whether mail
9854 user agents (MUAs) or mail transport agents (MTAs), must
9855 ensure that they are compatible with the configuration
9856 decisions below. Failure to do this may result in lost
9857 mail, broken <tt>From:</tt> lines, and other serious brain
9862 The mail spool is <file>/var/mail</file> and the interface to
9863 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9864 the FHS). On older systems, the mail spool may be
9865 physically located in <file>/var/spool/mail</file>, but all
9866 access to the mail spool should be via the
9867 <file>/var/mail</file> symlink. The mail spool is part of the
9868 base system and not part of the MTA package.
9872 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9873 programs (such as IMAP daemons) must lock the mailbox in an
9874 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9875 be combined with dot locking. To avoid deadlocks, a program
9876 should use <tt>fcntl()</tt> first and dot locking after
9877 this, or alternatively implement the two locking methods in
9878 a non blocking way<footnote>
9879 If it is not possible to establish both locks, the
9880 system shouldn't wait for the second lock to be
9881 established, but remove the first lock, wait a (random)
9882 time, and start over locking again.
9883 </footnote>. Using the functions <tt>maillock</tt> and
9884 <tt>mailunlock</tt> provided by the
9885 <tt>liblockfile*</tt><footnote>
9886 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9887 to use these functions.
9888 </footnote> packages is the recommended way to realize this.
9892 Mailboxes are generally either mode 600 and owned by
9893 <var>user</var> or mode 660 and owned by
9894 <tt><var>user</var>:mail</tt><footnote>
9895 There are two traditional permission schemes for mail spools:
9896 mode 600 with all mail delivery done by processes running as
9897 the destination user, or mode 660 and owned by group mail with
9898 mail delivery done by a process running as a system user in
9899 group mail. Historically, Debian required mode 660 mail
9900 spools to enable the latter model, but that model has become
9901 increasingly uncommon and the principle of least privilege
9902 indicates that mail systems that use the first model should
9903 use permissions of 600. If delivery to programs is permitted,
9904 it's easier to keep the mail system secure if the delivery
9905 agent runs as the destination user. Debian Policy therefore
9906 permits either scheme.
9907 </footnote>. The local system administrator may choose a
9908 different permission scheme; packages should not make
9909 assumptions about the permission and ownership of mailboxes
9910 unless required (such as when creating a new mailbox). A MUA
9911 may remove a mailbox (unless it has nonstandard permissions) in
9912 which case the MTA or another MUA must recreate it if needed.
9916 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9917 be setgid mail to do the locking mentioned above (and
9918 must obviously avoid accessing other users' mailboxes
9919 using this privilege).</p>
9922 <file>/etc/aliases</file> is the source file for the system mail
9923 aliases (e.g., postmaster, usenet, etc.), it is the one
9924 which the sysadmin and <prgn>postinst</prgn> scripts may
9925 edit. After <file>/etc/aliases</file> is edited the program or
9926 human editing it must call <prgn>newaliases</prgn>. All MTA
9927 packages must come with a <prgn>newaliases</prgn> program,
9928 even if it does nothing, but older MTA packages did not do
9929 this so programs should not fail if <prgn>newaliases</prgn>
9930 cannot be found. Note that because of this, all MTA
9931 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9932 <tt>Replaces: mail-transport-agent</tt> control fields.
9936 The convention of writing <tt>forward to
9937 <var>address</var></tt> in the mailbox itself is not
9938 supported. Use a <tt>.forward</tt> file instead.</p>
9941 The <prgn>rmail</prgn> program used by UUCP
9942 for incoming mail should be <file>/usr/sbin/rmail</file>.
9943 Likewise, <prgn>rsmtp</prgn>, for receiving
9944 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9948 If your package needs to know what hostname to use on (for
9949 example) outgoing news and mail messages which are generated
9950 locally, you should use the file <file>/etc/mailname</file>. It
9951 will contain the portion after the username and <tt>@</tt>
9952 (at) sign for email addresses of users on the machine
9953 (followed by a newline).
9957 Such a package should check for the existence of this file
9958 when it is being configured. If it exists, it should be
9959 used without comment, although an MTA's configuration script
9960 may wish to prompt the user even if it finds that this file
9961 exists. If the file does not exist, the package should
9962 prompt the user for the value (preferably using
9963 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9964 as well as using it in the package's configuration. The
9965 prompt should make it clear that the name will not just be
9966 used by that package. For example, in this situation the
9967 <tt>inn</tt> package could say something like:
9968 <example compact="compact">
9969 Please enter the "mail name" of your system. This is the
9970 hostname portion of the address to be shown on outgoing
9971 news and mail messages. The default is
9972 <var>syshostname</var>, your system's host name. Mail
9973 name ["<var>syshostname</var>"]:
9975 where <var>syshostname</var> is the output of <tt>hostname
9981 <heading>News system configuration</heading>
9984 All the configuration files related to the NNTP (news)
9985 servers and clients should be located under
9986 <file>/etc/news</file>.</p>
9989 There are some configuration issues that apply to a number
9990 of news clients and server packages on the machine. These
9994 <tag><file>/etc/news/organization</file></tag>
9996 A string which should appear as the
9997 organization header for all messages posted
9998 by NNTP clients on the machine
10001 <tag><file>/etc/news/server</file></tag>
10003 Contains the FQDN of the upstream NNTP
10004 server, or localhost if the local machine is
10009 Other global files may be added as required for cross-package news
10016 <heading>Programs for the X Window System</heading>
10019 <heading>Providing X support and package priorities</heading>
10022 Programs that can be configured with support for the X
10023 Window System must be configured to do so and must declare
10024 any package dependencies necessary to satisfy their
10025 runtime requirements when using the X Window System. If
10026 such a package is of higher priority than the X packages
10027 on which it depends, it is required that either the
10028 X-specific components be split into a separate package, or
10029 that an alternative version of the package, which includes
10030 X support, be provided, or that the package's priority be
10036 <heading>Packages providing an X server</heading>
10039 Packages that provide an X server that, directly or
10040 indirectly, communicates with real input and display
10041 hardware should declare in their <tt>Provides</tt> control
10042 field that they provide the virtual
10043 package <tt>xserver</tt>.<footnote>
10044 This implements current practice, and provides an
10045 actual policy for usage of the <tt>xserver</tt>
10046 virtual package which appears in the virtual packages
10047 list. In a nutshell, X servers that interface
10048 directly with the display and input hardware or via
10049 another subsystem (e.g., GGI) should provide
10050 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
10051 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
10057 <heading>Packages providing a terminal emulator</heading>
10060 Packages that provide a terminal emulator for the X Window
10061 System which meet the criteria listed below should declare in
10062 their <tt>Provides</tt> control field that they provide the
10063 virtual package <tt>x-terminal-emulator</tt>. They should
10064 also register themselves as an alternative for
10065 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
10066 20. That alternative should have a slave alternative
10067 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
10068 pointing to the corresponding manual page.
10072 To be an <tt>x-terminal-emulator</tt>, a program must:
10073 <list compact="compact">
10075 Be able to emulate a DEC VT100 terminal, or a
10076 compatible terminal.
10080 Support the command-line option <tt>-e
10081 <var>command</var></tt>, which creates a new
10082 terminal window<footnote>
10083 "New terminal window" does not necessarily mean
10084 a new top-level X window directly parented by
10085 the window manager; it could, if the terminal
10086 emulator application were so coded, be a new
10087 "view" in a multiple-document interface (MDI).
10089 and runs the specified <var>command</var>,
10090 interpreting the entirety of the rest of the command
10091 line as a command to pass straight to exec, in the
10092 manner that <tt>xterm</tt> does.
10096 Support the command-line option <tt>-T
10097 <var>title</var></tt>, which creates a new terminal
10098 window with the window title <var>title</var>.
10105 <heading>Packages providing a window manager</heading>
10108 Packages that provide a window manager should declare in
10109 their <tt>Provides</tt> control field that they provide the
10110 virtual package <tt>x-window-manager</tt>. They should also
10111 register themselves as an alternative for
10112 <file>/usr/bin/x-window-manager</file>, with a priority
10113 calculated as follows:
10114 <list compact="compact">
10116 Start with a priority of 20.
10120 If the window manager supports the Debian menu
10121 system, add 20 points if this support is available
10122 in the package's default configuration (i.e., no
10123 configuration files belonging to the system or user
10124 have to be edited to activate the feature); if
10125 configuration files must be modified, add only 10
10131 If the window manager complies with <url
10132 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
10133 name="The Window Manager Specification Project">,
10134 written by the <url id="http://www.freedesktop.org/wiki/"
10135 name="Free Desktop Group">, add 40 points.
10139 If the window manager permits the X session to be
10140 restarted using a <em>different</em> window manager
10141 (without killing the X server) in its default
10142 configuration, add 10 points; otherwise add none.
10145 That alternative should have a slave alternative
10146 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10147 pointing to the corresponding manual page.
10152 <heading>Packages providing fonts</heading>
10155 Packages that provide fonts for the X Window
10157 For the purposes of Debian Policy, a "font for the X
10158 Window System" is one which is accessed via X protocol
10159 requests. Fonts for the Linux console, for PostScript
10160 renderer, or any other purpose, do not fit this
10161 definition. Any tool which makes such fonts available
10162 to the X Window System, however, must abide by this
10165 must do a number of things to ensure that they are both
10166 available without modification of the X or font server
10167 configuration, and that they do not corrupt files used by
10168 other font packages to register information about
10172 Fonts of any type supported by the X Window System
10173 must be in a separate binary package from any
10174 executables, libraries, or documentation (except
10175 that specific to the fonts shipped, such as their
10176 license information). If one or more of the fonts
10177 so packaged are necessary for proper operation of
10178 the package with which they are associated the font
10179 package may be Recommended; if the fonts merely
10180 provide an enhancement, a Suggests relationship may
10181 be used. Packages must not Depend on font
10182 packages.<footnote>
10183 This is because the X server may retrieve fonts
10184 from the local file system or over the network
10185 from an X font server; the Debian package system
10186 is empowered to deal only with the local
10192 BDF fonts must be converted to PCF fonts with the
10193 <prgn>bdftopcf</prgn> utility (available in the
10194 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10195 placed in a directory that corresponds to their
10197 <list compact="compact">
10199 100 dpi fonts must be placed in
10200 <file>/usr/share/fonts/X11/100dpi/</file>.
10204 75 dpi fonts must be placed in
10205 <file>/usr/share/fonts/X11/75dpi/</file>.
10209 Character-cell fonts, cursor fonts, and other
10210 low-resolution fonts must be placed in
10211 <file>/usr/share/fonts/X11/misc/</file>.
10217 Type 1 fonts must be placed in
10218 <file>/usr/share/fonts/X11/Type1/</file>. If font
10219 metric files are available, they must be placed here
10224 Subdirectories of <file>/usr/share/fonts/X11/</file>
10225 other than those listed above must be neither
10226 created nor used. (The <file>PEX</file>, <file>CID</file>,
10227 <file>Speedo</file>, and <file>cyrillic</file> directories
10228 are excepted for historical reasons, but installation of
10229 files into these directories remains discouraged.)
10233 Font packages may, instead of placing files directly
10234 in the X font directories listed above, provide
10235 symbolic links in that font directory pointing to
10236 the files' actual location in the filesystem. Such
10237 a location must comply with the FHS.
10241 Font packages should not contain both 75dpi and
10242 100dpi versions of a font. If both are available,
10243 they should be provided in separate binary packages
10244 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10245 the names of the packages containing the
10246 corresponding fonts.
10250 Fonts destined for the <file>misc</file> subdirectory
10251 should not be included in the same package as 75dpi
10252 or 100dpi fonts; instead, they should be provided in
10253 a separate package with <tt>-misc</tt> appended to
10258 Font packages must not provide the files
10259 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10260 <file>fonts.scale</file> in a font directory:
10263 <file>fonts.dir</file> files must not be provided at all.
10267 <file>fonts.alias</file> and <file>fonts.scale</file>
10268 files, if needed, should be provided in the
10270 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10271 where <var>fontdir</var> is the name of the
10273 <file>/usr/share/fonts/X11/</file> where the
10274 package's corresponding fonts are stored
10275 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10276 <var>package</var> is the name of the package
10277 that provides these fonts, and
10278 <var>extension</var> is either <tt>scale</tt>
10279 or <tt>alias</tt>, whichever corresponds to
10286 Font packages must declare a dependency on
10287 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10288 or <tt>Pre-Depends</tt> control field.
10292 Font packages that provide one or more
10293 <file>fonts.scale</file> files as described above must
10294 invoke <prgn>update-fonts-scale</prgn> on each
10295 directory into which they installed fonts
10296 <em>before</em> invoking
10297 <prgn>update-fonts-dir</prgn> on that directory.
10298 This invocation must occur in both the
10299 <prgn>postinst</prgn> (for all arguments) and
10300 <prgn>postrm</prgn> (for all arguments except
10301 <tt>upgrade</tt>) scripts.
10305 Font packages that provide one or more
10306 <file>fonts.alias</file> files as described above must
10307 invoke <prgn>update-fonts-alias</prgn> on each
10308 directory into which they installed fonts. This
10309 invocation must occur in both the
10310 <prgn>postinst</prgn> (for all arguments) and
10311 <prgn>postrm</prgn> (for all arguments except
10312 <tt>upgrade</tt>) scripts.
10316 Font packages must invoke
10317 <prgn>update-fonts-dir</prgn> on each directory into
10318 which they installed fonts. This invocation must
10319 occur in both the <prgn>postinst</prgn> (for all
10320 arguments) and <prgn>postrm</prgn> (for all
10321 arguments except <tt>upgrade</tt>) scripts.
10325 Font packages must not provide alias names for the
10326 fonts they include which collide with alias names
10327 already in use by fonts already packaged.
10331 Font packages must not provide fonts with the same
10332 XLFD registry name as another font already packaged.
10338 <sect1 id="appdefaults">
10339 <heading>Application defaults files</heading>
10342 Application defaults files must be installed in the
10343 directory <file>/etc/X11/app-defaults/</file> (use of a
10344 localized subdirectory of <file>/etc/X11/</file> as described
10345 in the <em>X Toolkit Intrinsics - C Language
10346 Interface</em> manual is also permitted). They must be
10347 registered as <tt>conffile</tt>s or handled as
10348 configuration files.
10352 Customization of programs' X resources may also be
10353 supported with the provision of a file with the same name
10354 as that of the package placed in
10355 the <file>/etc/X11/Xresources/</file> directory, which
10356 must be registered as a <tt>conffile</tt> or handled as a
10357 configuration file.<footnote>
10358 Note that this mechanism is not the same as using
10359 app-defaults; app-defaults are tied to the client
10360 binary on the local file system, whereas X resources
10361 are stored in the X server and affect all connecting
10368 <heading>Installation directory issues</heading>
10371 Historically, packages using the X Window System used a
10372 separate set of installation directories from other packages.
10373 This practice has been discontinued and packages using the X
10374 Window System should now generally be installed in the same
10375 directories as any other package. Specifically, packages must
10376 not install files under the <file>/usr/X11R6/</file> directory
10377 and the <file>/usr/X11R6/</file> directory hierarchy should be
10378 regarded as obsolete.
10382 Include files previously installed under
10383 <file>/usr/X11R6/include/X11/</file> should be installed into
10384 <file>/usr/include/X11/</file>. For files previously
10385 installed into subdirectories of
10386 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10387 determine if subdirectories of <file>/usr/lib/</file> and
10388 <file>/usr/share/</file> can be used. If not, a subdirectory
10389 of <file>/usr/lib/X11/</file> should be used.
10393 Configuration files for window, display, or session managers
10394 or other applications that are tightly integrated with the X
10395 Window System may be placed in a subdirectory
10396 of <file>/etc/X11/</file> corresponding to the package name.
10397 Other X Window System applications should use
10398 the <file>/etc/</file> directory unless otherwise mandated by
10399 policy (such as for <ref id="appdefaults">).
10405 <heading>Perl programs and modules</heading>
10408 Perl programs and modules should follow the current Perl policy.
10412 The Perl policy can be found in the <tt>perl-policy</tt>
10413 files in the <tt>debian-policy</tt> package.
10414 It is also available from the Debian web mirrors at
10415 <tt><url name="/doc/packaging-manuals/perl-policy/"
10416 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10421 <heading>Emacs lisp programs</heading>
10424 Please refer to the "Debian Emacs Policy" for details of how to
10425 package emacs lisp programs.
10429 The Emacs policy is available in
10430 <file>debian-emacs-policy.gz</file> of the
10431 <package>emacsen-common</package> package.
10432 It is also available from the Debian web mirrors at
10433 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10434 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10439 <heading>Games</heading>
10442 The permissions on <file>/var/games</file> are mode 755, owner
10443 <tt>root</tt> and group <tt>root</tt>.
10447 Each game decides on its own security policy.</p>
10450 Games which require protected, privileged access to
10451 high-score files, saved games, etc., may be made
10452 set-<em>group</em>-id (mode 2755) and owned by
10453 <tt>root:games</tt>, and use files and directories with
10454 appropriate permissions (770 <tt>root:games</tt>, for
10455 example). They must not be made
10456 set-<em>user</em>-id, as this causes security problems. (If
10457 an attacker can subvert any set-user-id game they can
10458 overwrite the executable of any other, causing other players
10459 of these games to run a Trojan horse program. With a
10460 set-group-id game the attacker only gets access to less
10461 important game data, and if they can get at the other
10462 players' accounts at all it will take considerably more
10466 Some packages, for example some fortune cookie programs, are
10467 configured by the upstream authors to install with their
10468 data files or other static information made unreadable so
10469 that they can only be accessed through set-id programs
10470 provided. You should not do this in a Debian package: anyone can
10471 download the <file>.deb</file> file and read the data from it,
10472 so there is no point making the files unreadable. Not
10473 making the files unreadable also means that you don't have
10474 to make so many programs set-id, which reduces the risk of a
10478 As described in the FHS, binaries of games should be
10479 installed in the directory <file>/usr/games</file>. This also
10480 applies to games that use the X Window System. Manual pages
10481 for games (X and non-X games) should be installed in
10482 <file>/usr/share/man/man6</file>.</p>
10488 <heading>Documentation</heading>
10491 <heading>Manual pages</heading>
10494 You should install manual pages in <prgn>nroff</prgn> source
10495 form, in appropriate places under <file>/usr/share/man</file>.
10496 You should only use sections 1 to 9 (see the FHS for more
10497 details). You must not install a pre-formatted "cat page".
10501 Each program, utility, and function should have an
10502 associated manual page included in the same package. It is
10503 suggested that all configuration files also have a manual
10504 page included as well. Manual pages for protocols and other
10505 auxiliary things are optional.
10509 If no manual page is available, this is considered as a bug
10510 and should be reported to the Debian Bug Tracking System (the
10511 maintainer of the package is allowed to write this bug report
10512 themselves, if they so desire). Do not close the bug report
10513 until a proper man page is available.<footnote>
10514 It is not very hard to write a man page. See the
10515 <url id="http://www.schweikhardt.net/man_page_howto.html"
10516 name="Man-Page-HOWTO">,
10517 <manref name="man" section="7">, the examples created
10518 by <prgn>dh_make</prgn>, the helper
10519 program <prgn>help2man</prgn>, or the
10520 directory <file>/usr/share/doc/man-db/examples</file>.
10525 You may forward a complaint about a missing man page to the
10526 upstream authors, and mark the bug as forwarded in the
10527 Debian bug tracking system. Even though the GNU Project do
10528 not in general consider the lack of a man page to be a bug,
10529 we do; if they tell you that they don't consider it a bug
10530 you should leave the bug in our bug tracking system open
10535 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10539 If one man page needs to be accessible via several names it
10540 is better to use a symbolic link than the <file>.so</file>
10541 feature, but there is no need to fiddle with the relevant
10542 parts of the upstream source to change from <file>.so</file> to
10543 symlinks: don't do it unless it's easy. You should not
10544 create hard links in the manual page directories, nor put
10545 absolute filenames in <file>.so</file> directives. The filename
10546 in a <file>.so</file> in a man page should be relative to the
10547 base of the man page tree (usually
10548 <file>/usr/share/man</file>). If you do not create any links
10549 (whether symlinks, hard links, or <tt>.so</tt> directives)
10550 in the file system to the alternate names of the man page,
10551 then you should not rely on <prgn>man</prgn> finding your
10552 man page under those names based solely on the information in
10553 the man page's header.<footnote>
10554 Supporting this in <prgn>man</prgn> often requires
10555 unreasonable processing time to find a manual page or to
10556 report that none exists, and moves knowledge into man's
10557 database that would be better left in the file system.
10558 This support is therefore deprecated and will cease to
10559 be present in the future.
10564 Manual pages in locale-specific subdirectories of
10565 <file>/usr/share/man</file> should use either UTF-8 or the usual
10566 legacy encoding for that language (normally the one corresponding
10567 to the shortest relevant locale name in
10568 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10569 <file>/usr/share/man/fr</file> should use either UTF-8 or
10570 ISO-8859-1.<footnote>
10571 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10572 use. In future, all manual pages will be required to use
10578 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10579 included in the subdirectory name unless it indicates a
10580 significant difference in the language, as this excludes
10581 speakers of the language in other countries.<footnote>
10582 At the time of writing, Chinese and Portuguese are the main
10583 languages with such differences, so <file>pt_BR</file>,
10584 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10589 If a localized version of a manual page is provided, it should
10590 either be up-to-date or it should be obvious to the reader that
10591 it is outdated and the original manual page should be used
10592 instead. This can be done either by a note at the beginning of
10593 the manual page or by showing the missing or changed portions in
10594 the original language instead of the target language.
10599 <heading>Info documents</heading>
10602 Info documents should be installed in <file>/usr/share/info</file>.
10603 They should be compressed with <tt>gzip -9</tt>.
10607 The <prgn>install-info</prgn> program maintains a directory of
10608 installed info documents in <file>/usr/share/info/dir</file> for the
10609 use of info readers. This file must not be included in packages
10610 other than <package>install-info</package>.
10614 <prgn>install-info</prgn> is automatically invoked when
10615 appropriate using dpkg triggers. Packages other than
10616 <package>install-info</package> <em>should not</em> invoke
10617 <prgn>install-info</prgn> directly and <em>should not</em>
10618 depend on, recommend, or suggest <package>install-info</package>
10623 Info readers requiring the <file>/usr/share/info/dir</file> file
10624 should depend on <package>install-info</package>.
10628 Info documents should contain section and directory entry
10629 information in the document for the use
10630 of <prgn>install-info</prgn>. The section should be specified
10631 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10632 space and the section of this info page. The directory entry or
10633 entries should be included between
10634 a <tt>START-INFO-DIR-ENTRY</tt> line and
10635 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10637 INFO-DIR-SECTION Individual utilities
10638 START-INFO-DIR-ENTRY
10639 * example: (example). An example info directory entry.
10642 To determine which section to use, you should look
10643 at <file>/usr/share/info/dir</file> on your system and choose
10644 the most relevant (or create a new section if none of the
10645 current sections are relevant).<footnote>
10646 Normally, info documents are generated from Texinfo source.
10647 To include this information in the generated info document, if
10648 it is absent, add commands like:
10650 @dircategory Individual utilities
10652 * example: (example). An example info directory entry.
10655 to the Texinfo source of the document and ensure that the info
10656 documents are rebuilt from source during the package build.
10662 <heading>Additional documentation</heading>
10665 Any additional documentation that comes with the package may
10666 be installed at the discretion of the package maintainer.
10667 Plain text documentation should be installed in the directory
10668 <file>/usr/share/doc/<var>package</var></file>, where
10669 <var>package</var> is the name of the package, and
10670 compressed with <tt>gzip -9</tt> unless it is small.
10674 If a package comes with large amounts of documentation which
10675 many users of the package will not require you should create
10676 a separate binary package to contain it, so that it does not
10677 take up disk space on the machines of users who do not need
10678 or want it installed.</p>
10681 It is often a good idea to put text information files
10682 (<file>README</file>s, changelogs, and so forth) that come with
10683 the source package in <file>/usr/share/doc/<var>package</var></file>
10684 in the binary package. However, you don't need to install
10685 the instructions for building and installing the package, of
10689 Packages must not require the existence of any files in
10690 <file>/usr/share/doc/</file> in order to function
10692 The system administrator should be able to
10693 delete files in <file>/usr/share/doc/</file> without causing
10694 any programs to break.
10696 Any files that are referenced by programs but are also
10697 useful as stand alone documentation should be installed under
10698 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10699 <file>/usr/share/doc/<var>package</var></file>.
10703 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10704 link to another directory in <file>/usr/share/doc</file> only if
10705 the two packages both come from the same source and the
10706 first package Depends on the second.<footnote>
10708 Please note that this does not override the section on
10709 changelog files below, so the file
10710 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10711 must refer to the changelog for the current version of
10712 <var>package</var> in question. In practice, this means
10713 that the sources of the target and the destination of the
10714 symlink must be the same (same source package and
10721 Former Debian releases placed all additional documentation
10722 in <file>/usr/doc/<var>package</var></file>. This has been
10723 changed to <file>/usr/share/doc/<var>package</var></file>,
10724 and packages must not put documentation in the directory
10725 <file>/usr/doc/<var>package</var></file>. <footnote>
10726 At this phase of the transition, we no longer require a
10727 symbolic link in <file>/usr/doc/</file>. At a later point,
10728 policy shall change to make the symbolic links a bug.
10734 <heading>Preferred documentation formats</heading>
10737 The unification of Debian documentation is being carried out
10741 If your package comes with extensive documentation in a
10742 markup format that can be converted to various other formats
10743 you should if possible ship HTML versions in a binary
10744 package, in the directory
10745 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10746 its subdirectories.<footnote>
10747 The rationale: The important thing here is that HTML
10748 docs should be available in <em>some</em> package, not
10749 necessarily in the main binary package.
10754 Other formats such as PostScript may be provided at the
10755 package maintainer's discretion.
10759 <sect id="copyrightfile">
10760 <heading>Copyright information</heading>
10763 Every package must be accompanied by a verbatim copy of its
10764 copyright information and distribution license in the file
10765 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10766 file must neither be compressed nor be a symbolic link.
10770 In addition, the copyright file must say where the upstream
10771 sources (if any) were obtained, and should name the original
10776 Packages in the <em>contrib</em> or <em>non-free</em> archive
10777 areas should state in the copyright file that the package is not
10778 part of the Debian distribution and briefly explain why.
10782 A copy of the file which will be installed in
10783 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10784 be in <file>debian/copyright</file> in the source package.
10788 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10789 link to another directory in <file>/usr/share/doc</file> only if
10790 the two packages both come from the same source and the
10791 first package Depends on the second. These rules are important
10792 because <file>copyright</file> files must be extractable by
10797 Packages distributed under the Apache license (version 2.0), the
10798 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10799 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10800 1.3) should refer to the corresponding files
10801 under <file>/usr/share/common-licenses</file>,<footnote>
10804 <file>/usr/share/common-licenses/Apache-2.0</file>,
10805 <file>/usr/share/common-licenses/Artistic</file>,
10806 <file>/usr/share/common-licenses/GPL-1</file>,
10807 <file>/usr/share/common-licenses/GPL-2</file>,
10808 <file>/usr/share/common-licenses/GPL-3</file>,
10809 <file>/usr/share/common-licenses/LGPL-2</file>,
10810 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10811 <file>/usr/share/common-licenses/LGPL-3</file>,
10812 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10813 <file>/usr/share/common-licenses/GFDL-1.3</file>
10814 respectively. The University of California BSD license is
10815 also included in <package>base-files</package> as
10816 <file>/usr/share/common-licenses/BSD</file>, but given the
10817 brevity of this license, its specificity to code whose
10818 copyright is held by the Regents of the University of
10819 California, and the frequency of minor wording changes, its
10820 text should be included in the copyright file rather than
10821 referencing this file.
10823 </footnote> rather than quoting them in the copyright
10828 You should not use the copyright file as a general <file>README</file>
10829 file. If your package has such a file it should be
10830 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10831 <file>README.Debian</file> or some other appropriate place.
10835 All copyright files must be encoded in UTF-8.
10838 <sect1 id="copyrightformat">
10839 <heading>Machine-readable copyright information</heading>
10842 A specification for a standard, machine-readable format
10843 for <file>debian/copyright</file> files is maintained as part
10844 of the <package>debian-policy</package> package. This
10845 document may be found in the <file>copyright-format</file>
10846 files in the <package>debian-policy</package> package. It is
10847 also available from the Debian web mirrors at
10848 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10849 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10853 Use of this format is optional.
10859 <heading>Examples</heading>
10862 Any examples (configurations, source files, whatever),
10863 should be installed in a directory
10864 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10865 files should not be referenced by any program: they're there
10866 for the benefit of the system administrator and users as
10867 documentation only. Architecture-specific example files
10868 should be installed in a directory
10869 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10871 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10872 latter directory itself may be a symbolic link to the
10877 If the purpose of a package is to provide examples, then the
10878 example files may be installed into
10879 <file>/usr/share/doc/<var>package</var></file>.
10883 <sect id="changelogs">
10884 <heading>Changelog files</heading>
10887 Packages that are not Debian-native must contain a
10888 compressed copy of the <file>debian/changelog</file> file from
10889 the Debian source tree in
10890 <file>/usr/share/doc/<var>package</var></file> with the name
10891 <file>changelog.Debian.gz</file>.
10895 If an upstream changelog is available, it should be accessible as
10896 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10897 plain text. If the upstream changelog is distributed in
10898 HTML, it should be made available in that form as
10899 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10900 and a plain text <file>changelog.gz</file> should be generated
10901 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10902 the upstream changelog files do not already conform to this
10903 naming convention, then this may be achieved either by
10904 renaming the files, or by adding a symbolic link, at the
10905 maintainer's discretion.<footnote>
10906 Rationale: People should not have to look in places for
10907 upstream changelogs merely because they are given
10908 different names or are distributed in HTML format.
10913 All of these files should be installed compressed using
10914 <tt>gzip -9</tt>, as they will become large with time even
10915 if they start out small.
10919 If the package has only one changelog which is used both as
10920 the Debian changelog and the upstream one because there is
10921 no separate upstream maintainer then that changelog should
10922 usually be installed as
10923 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10924 there is a separate upstream maintainer, but no upstream
10925 changelog, then the Debian changelog should still be called
10926 <file>changelog.Debian.gz</file>.
10930 For details about the format and contents of the Debian
10931 changelog file, please see <ref id="dpkgchangelog">.
10936 <appendix id="pkg-scope">
10937 <heading>Introduction and scope of these appendices</heading>
10940 These appendices are taken essentially verbatim from the
10941 now-deprecated Packaging Manual, version 3.2.1.0. They are
10942 the chapters which are likely to be of use to package
10943 maintainers and which have not already been included in the
10944 policy document itself. Most of these sections are very likely
10945 not relevant to policy; they should be treated as
10946 documentation for the packaging system. Please note that these
10947 appendices are included for convenience, and for historical
10948 reasons: they used to be part of policy package, and they have
10949 not yet been incorporated into dpkg documentation. However,
10950 they still have value, and hence they are presented here.
10954 They have not yet been checked to ensure that they are
10955 compatible with the contents of policy, and if there are any
10956 contradictions, the version in the main policy document takes
10957 precedence. The remaining chapters of the old Packaging
10958 Manual have also not been read in detail to ensure that there
10959 are not parts which have been left out. Both of these will be
10960 done in due course.
10964 Certain parts of the Packaging manual were integrated into the
10965 Policy Manual proper, and removed from the appendices. Links
10966 have been placed from the old locations to the new ones.
10970 <prgn>dpkg</prgn> is a suite of programs for creating binary
10971 package files and installing and removing them on Unix
10973 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10974 work on or be ported to other systems.
10979 The binary packages are designed for the management of
10980 installed executable programs (usually compiled binaries) and
10981 their associated data, though source code examples and
10982 documentation are provided as part of some packages.</p>
10985 This manual describes the technical aspects of creating Debian
10986 binary packages (<file>.deb</file> files). It documents the
10987 behavior of the package management programs
10988 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10989 they interact with packages.</p>
10992 This manual does not go into detail about the options and
10993 usage of the package building and installation tools. It
10994 should therefore be read in conjunction with those programs'
10999 The utility programs which are provided with <prgn>dpkg</prgn>
11000 not described in detail here, are documented in their man pages.
11004 It is assumed that the reader is reasonably familiar with the
11005 <prgn>dpkg</prgn> System Administrators' manual.
11006 Unfortunately this manual does not yet exist.
11010 The Debian version of the FSF's GNU hello program is provided as
11011 an example for people wishing to create Debian packages. However,
11012 while the examples are helpful, they do not replace the need to
11013 read and follow the Policy and Programmer's Manual.</p>
11016 <appendix id="pkg-binarypkg">
11017 <heading>Binary packages (from old Packaging Manual)</heading>
11020 See <manref name="deb" section="5"> and <ref id="pkg-controlarea">.
11023 <sect id="pkg-bincreating"><heading>Creating package files -
11024 <prgn>dpkg-deb</prgn>
11028 All manipulation of binary package files is done by
11029 <prgn>dpkg-deb</prgn>; it's the only program that has
11030 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
11031 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
11032 will spot that the options requested are appropriate to
11033 <prgn>dpkg-deb</prgn> and invoke that instead with the same
11038 In order to create a binary package you must make a
11039 directory tree which contains all the files and directories
11040 you want to have in the file system data part of the package.
11041 In Debian-format source packages this directory is usually
11042 <file>debian/tmp</file>, relative to the top of the package's
11047 They should have the locations (relative to the root of the
11048 directory tree you're constructing) ownerships and
11049 permissions which you want them to have on the system when
11050 they are installed.
11054 With current versions of <prgn>dpkg</prgn> the uid/username
11055 and gid/groupname mappings for the users and groups being
11056 used should be the same on the system where the package is
11057 built and the one where it is installed.
11061 You need to add one special directory to the root of the
11062 miniature file system tree you're creating:
11063 <prgn>DEBIAN</prgn>. It should contain the control
11064 information files, notably the binary package control file
11065 (see <ref id="pkg-controlfile">).
11069 The <prgn>DEBIAN</prgn> directory will not appear in the
11070 file system archive of the package, and so won't be installed
11071 by <prgn>dpkg</prgn> when the package is unpacked.
11075 When you've prepared the package, you should invoke:
11077 dpkg --build <var>directory</var>
11082 This will build the package in
11083 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
11084 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
11085 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
11086 build the package.)
11090 See the man page <manref name="dpkg-deb" section="8"> for details of how
11091 to examine the contents of this newly-created file. You may find the
11092 output of following commands enlightening:
11094 dpkg-deb --info <var>filename</var>.deb
11095 dpkg-deb --contents <var>filename</var>.deb
11096 dpkg --contents <var>filename</var>.deb
11098 To view the copyright file for a package you could use this command:
11100 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
11105 <sect id="pkg-controlarea">
11106 <heading>Package control information files</heading>
11109 The control information portion of a binary package is a
11110 collection of files with names known to <prgn>dpkg</prgn>.
11111 It will treat the contents of these files specially - some
11112 of them contain information used by <prgn>dpkg</prgn> when
11113 installing or removing the package; others are scripts which
11114 the package maintainer wants <prgn>dpkg</prgn> to run.
11118 It is possible to put other files in the package control
11119 information file area, but this is not generally a good idea
11120 (though they will largely be ignored).
11124 Here is a brief list of the control information files supported
11125 by <prgn>dpkg</prgn> and a summary of what they're used for.
11130 <tag><tt>control</tt>
11133 This is the key description file used by
11134 <prgn>dpkg</prgn>. It specifies the package's name
11135 and version, gives its description for the user,
11136 states its relationships with other packages, and so
11137 forth. See <ref id="sourcecontrolfiles"> and
11138 <ref id="binarycontrolfiles">.
11142 It is usually generated automatically from information
11143 in the source package by the
11144 <prgn>dpkg-gencontrol</prgn> program, and with
11145 assistance from <prgn>dpkg-shlibdeps</prgn>.
11146 See <ref id="pkg-sourcetools">.
11150 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11155 These are executable files (usually scripts) which
11156 <prgn>dpkg</prgn> runs during installation, upgrade
11157 and removal of packages. They allow the package to
11158 deal with matters which are particular to that package
11159 or require more complicated processing than that
11160 provided by <prgn>dpkg</prgn>. Details of when and
11161 how they are called are in <ref id="maintainerscripts">.
11165 It is very important to make these scripts idempotent.
11166 See <ref id="idempotency">.
11170 The maintainer scripts are not guaranteed to run with a
11171 controlling terminal and may not be able to interact with
11172 the user. See <ref id="controllingterminal">.
11176 <tag><tt>conffiles</tt>
11179 This file contains a list of configuration files which
11180 are to be handled automatically by <prgn>dpkg</prgn>
11181 (see <ref id="pkg-conffiles">). Note that not necessarily
11182 every configuration file should be listed here.
11185 <tag><tt>shlibs</tt>
11188 This file contains a list of the shared libraries
11189 supplied by the package, with dependency details for
11190 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11191 when it determines what dependencies are required in a
11192 package control file. The <tt>shlibs</tt> file format
11193 is described on <ref id="shlibs">.
11198 <sect id="pkg-controlfile">
11199 <heading>The main control information file: <tt>control</tt></heading>
11202 The most important control information file used by
11203 <prgn>dpkg</prgn> when it installs a package is
11204 <tt>control</tt>. It contains all the package's "vital
11209 The binary package control files of packages built from
11210 Debian sources are made by a special tool,
11211 <prgn>dpkg-gencontrol</prgn>, which reads
11212 <file>debian/control</file> and <file>debian/changelog</file> to
11213 find the information it needs. See <ref id="pkg-sourcepkg"> for
11218 The fields in binary package control files are listed in
11219 <ref id="binarycontrolfiles">.
11223 A description of the syntax of control files and the purpose
11224 of the fields is available in <ref id="controlfields">.
11229 <heading>Time Stamps</heading>
11232 See <ref id="timestamps">.
11237 <appendix id="pkg-sourcepkg">
11238 <heading>Source packages (from old Packaging Manual) </heading>
11241 The Debian binary packages in the distribution are generated
11242 from Debian sources, which are in a special format to assist
11243 the easy and automatic building of binaries.
11246 <sect id="pkg-sourcetools">
11247 <heading>Tools for processing source packages</heading>
11250 Various tools are provided for manipulating source packages;
11251 they pack and unpack sources and help build of binary
11252 packages and help manage the distribution of new versions.
11256 They are introduced and typical uses described here; see
11257 <manref name="dpkg-source" section="1"> for full
11258 documentation about their arguments and operation.
11262 For examples of how to construct a Debian source package,
11263 and how to use those utilities that are used by Debian
11264 source packages, please see the <prgn>hello</prgn> example
11268 <sect1 id="pkg-dpkg-source">
11270 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11275 This program is frequently used by hand, and is also
11276 called from package-independent automated building scripts
11277 such as <prgn>dpkg-buildpackage</prgn>.
11281 To unpack a package it is typically invoked with
11283 dpkg-source -x <var>.../path/to/filename</var>.dsc
11288 with the <file><var>filename</var>.tar.gz</file> and
11289 <file><var>filename</var>.diff.gz</file> (if applicable) in
11290 the same directory. It unpacks into
11291 <file><var>package</var>-<var>version</var></file>, and if
11293 <file><var>package</var>-<var>version</var>.orig</file>, in
11294 the current directory.
11298 To create a packed source archive it is typically invoked:
11300 dpkg-source -b <var>package</var>-<var>version</var>
11305 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11306 <file>.diff.gz</file> (if appropriate) in the current
11307 directory. <prgn>dpkg-source</prgn> does not clean the
11308 source tree first - this must be done separately if it is
11313 See also <ref id="pkg-sourcearchives">.</p>
11317 <sect1 id="pkg-dpkg-buildpackage">
11319 <prgn>dpkg-buildpackage</prgn> - overall package-building
11324 See <manref name="dpkg-buildpackage" section="1">.
11328 <sect1 id="pkg-dpkg-gencontrol">
11330 <prgn>dpkg-gencontrol</prgn> - generates binary package
11335 This program is usually called from <file>debian/rules</file>
11336 (see <ref id="pkg-sourcetree">) in the top level of the source
11341 This is usually done just before the files and directories in the
11342 temporary directory tree where the package is being built have their
11343 permissions and ownerships set and the package is constructed using
11344 <prgn>dpkg-deb/</prgn>
11346 This is so that the control file which is produced has
11347 the right permissions
11352 <prgn>dpkg-gencontrol</prgn> must be called after all the
11353 files which are to go into the package have been placed in
11354 the temporary build directory, so that its calculation of
11355 the installed size of a package is correct.
11359 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11360 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11361 variable substitutions created by
11362 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11367 For a package which generates only one binary package, and
11368 which builds it in <file>debian/tmp</file> relative to the top
11369 of the source package, it is usually sufficient to call
11370 <prgn>dpkg-gencontrol</prgn>.
11374 Sources which build several binaries will typically need
11377 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11378 </example> The <tt>-P</tt> tells
11379 <prgn>dpkg-gencontrol</prgn> that the package is being
11380 built in a non-default directory, and the <tt>-p</tt>
11381 tells it which package's control file should be generated.
11385 <prgn>dpkg-gencontrol</prgn> also adds information to the
11386 list of files in <file>debian/files</file>, for the benefit of
11387 (for example) a future invocation of
11388 <prgn>dpkg-genchanges</prgn>.</p>
11391 <sect1 id="pkg-dpkg-shlibdeps">
11393 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11398 See <manref name="dpkg-shlibdeps" section="1">.
11402 <sect1 id="pkg-dpkg-distaddfile">
11404 <prgn>dpkg-distaddfile</prgn> - adds a file to
11405 <file>debian/files</file>
11409 Some packages' uploads need to include files other than
11410 the source and binary package files.
11414 <prgn>dpkg-distaddfile</prgn> adds a file to the
11415 <file>debian/files</file> file so that it will be included in
11416 the <file>.changes</file> file when
11417 <prgn>dpkg-genchanges</prgn> is run.
11421 It is usually invoked from the <tt>binary</tt> target of
11422 <file>debian/rules</file>:
11424 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11426 The <var>filename</var> is relative to the directory where
11427 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11428 is usually the directory above the top level of the source
11429 tree. The <file>debian/rules</file> target should put the
11430 file there just before or just after calling
11431 <prgn>dpkg-distaddfile</prgn>.
11435 The <var>section</var> and <var>priority</var> are passed
11436 unchanged into the resulting <file>.changes</file> file.
11441 <sect1 id="pkg-dpkg-genchanges">
11443 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11444 upload control file
11448 See <manref name="dpkg-genchanges" section="1">.
11452 <sect1 id="pkg-dpkg-parsechangelog">
11454 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11455 representation of a changelog
11459 See <manref name="dpkg-parsechangelog" section="1">.
11463 <sect1 id="pkg-dpkg-architecture">
11465 <prgn>dpkg-architecture</prgn> - information about the build and
11470 See <manref name="dpkg-architecture" section="1">.
11475 <sect id="pkg-sourcetree">
11476 <heading>The Debian package source tree</heading>
11479 The source archive scheme described later is intended to
11480 allow a Debian package source tree with some associated
11481 control information to be reproduced and transported easily.
11482 The Debian package source tree is a version of the original
11483 program with certain files added for the benefit of the
11484 packaging process, and with any other changes required
11485 made to the rest of the source code and installation
11490 The extra files created for Debian are in the subdirectory
11491 <file>debian</file> of the top level of the Debian package
11492 source tree. They are described below.
11495 <sect1 id="pkg-debianrules">
11496 <heading><file>debian/rules</file> - the main building script</heading>
11499 See <ref id="debianrules">.
11503 <sect1 id="pkg-srcsubstvars">
11504 <heading><file>debian/substvars</file> and variable substitutions</heading>
11507 See <ref id="substvars">.
11513 <heading><file>debian/files</file></heading>
11516 See <ref id="debianfiles">.
11520 <sect1><heading><file>debian/tmp</file>
11524 This is the canonical temporary location for the
11525 construction of binary packages by the <tt>binary</tt>
11526 target. The directory <file>tmp</file> serves as the root of
11527 the file system tree as it is being constructed (for
11528 example, by using the package's upstream makefiles install
11529 targets and redirecting the output there), and it also
11530 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11531 id="pkg-bincreating">.
11535 If several binary packages are generated from the same
11536 source tree it is usual to use several
11537 <file>debian/tmp<var>something</var></file> directories, for
11538 example <file>tmp-a</file> or <file>tmp-doc</file>.
11542 Whatever <file>tmp</file> directories are created and used by
11543 <tt>binary</tt> must of course be removed by the
11544 <tt>clean</tt> target.</p></sect1>
11548 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11552 As it exists on the FTP site, a Debian source package
11553 consists of three related files. You must have the right
11554 versions of all three to be able to use them.
11559 <tag>Debian source control file - <tt>.dsc</tt></tag>
11561 This file is a control file used by <prgn>dpkg-source</prgn>
11562 to extract a source package.
11563 See <ref id="debiansourcecontrolfiles">.
11567 Original source archive -
11569 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11575 This is a compressed (with <tt>gzip -9</tt>)
11576 <prgn>tar</prgn> file containing the source code from
11577 the upstream authors of the program.
11582 Debian package diff -
11584 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11590 This is a unified context diff (<tt>diff -u</tt>)
11591 giving the changes which are required to turn the
11592 original source into the Debian source. These changes
11593 may only include editing and creating plain files.
11594 The permissions of files, the targets of symbolic
11595 links and the characteristics of special files or
11596 pipes may not be changed and no files may be removed
11601 All the directories in the diff must exist, except the
11602 <file>debian</file> subdirectory of the top of the source
11603 tree, which will be created by
11604 <prgn>dpkg-source</prgn> if necessary when unpacking.
11608 The <prgn>dpkg-source</prgn> program will
11609 automatically make the <file>debian/rules</file> file
11610 executable (see below).</p></item>
11615 If there is no original source code - for example, if the
11616 package is specially prepared for Debian or the Debian
11617 maintainer is the same as the upstream maintainer - the
11618 format is slightly different: then there is no diff, and the
11620 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11621 and preferably contains a directory named
11622 <file><var>package</var>-<var>version</var></file>.
11627 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11630 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11631 Debian source package. However, if it is not available it
11632 is possible to unpack a Debian source archive as follows:
11633 <enumlist compact="compact">
11636 Untar the tarfile, which will create a <file>.orig</file>
11640 <p>Rename the <file>.orig</file> directory to
11641 <file><var>package</var>-<var>version</var></file>.</p>
11645 Create the subdirectory <file>debian</file> at the top of
11646 the source tree.</p>
11648 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11650 <item><p>Untar the tarfile again if you want a copy of the original
11651 source code alongside the Debian version.</p>
11656 It is not possible to generate a valid Debian source archive
11657 without using <prgn>dpkg-source</prgn>. In particular,
11658 attempting to use <prgn>diff</prgn> directly to generate the
11659 <file>.diff.gz</file> file will not work.
11663 <heading>Restrictions on objects in source packages</heading>
11666 The source package may not contain any hard links
11668 This is not currently detected when building source
11669 packages, but only when extracting
11673 Hard links may be permitted at some point in the
11674 future, but would require a fair amount of
11676 </footnote>, device special files, sockets or setuid or
11679 Setgid directories are allowed.
11684 The source packaging tools manage the changes between the
11685 original and Debian source using <prgn>diff</prgn> and
11686 <prgn>patch</prgn>. Turning the original source tree as
11687 included in the <file>.orig.tar.gz</file> into the Debian
11688 package source must not involve any changes which cannot be
11689 handled by these tools. Problematic changes which cause
11690 <prgn>dpkg-source</prgn> to halt with an error when
11691 building the source package are:
11692 <list compact="compact">
11693 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11695 <item><p>Changing the targets of symbolic links.</p>
11697 <item><p>Creating directories, other than <file>debian</file>.</p>
11699 <item><p>Changes to the contents of binary files.</p></item>
11700 </list> Changes which cause <prgn>dpkg-source</prgn> to
11701 print a warning but continue anyway are:
11702 <list compact="compact">
11705 Removing files, directories or symlinks.
11707 Renaming a file is not treated specially - it is
11708 seen as the removal of the old file (which
11709 generates a warning, but is otherwise ignored),
11710 and the creation of the new one.
11716 Changed text files which are missing the usual final
11717 newline (either in the original or the modified
11722 Changes which are not represented, but which are not detected by
11723 <prgn>dpkg-source</prgn>, are:
11724 <list compact="compact">
11725 <item><p>Changing the permissions of files (other than
11726 <file>debian/rules</file>) and directories.</p></item>
11731 The <file>debian</file> directory and <file>debian/rules</file>
11732 are handled specially by <prgn>dpkg-source</prgn> - before
11733 applying the changes it will create the <file>debian</file>
11734 directory, and afterwards it will make
11735 <file>debian/rules</file> world-executable.
11741 <appendix id="pkg-controlfields">
11742 <heading>Control files and their fields (from old Packaging Manual)</heading>
11745 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11746 data in a common format, known as control files. Binary and
11747 source packages have control data as do the <file>.changes</file>
11748 files which control the installation of uploaded files, and
11749 <prgn>dpkg</prgn>'s internal databases are in a similar
11754 <heading>Syntax of control files</heading>
11757 See <ref id="controlsyntax">.
11761 It is important to note that there are several fields which
11762 are optional as far as <prgn>dpkg</prgn> and the related
11763 tools are concerned, but which must appear in every Debian
11764 package, or whose omission may cause problems.
11769 <heading>List of fields</heading>
11772 See <ref id="controlfieldslist">.
11776 This section now contains only the fields that didn't belong
11777 to the Policy manual.
11780 <sect1 id="pkg-f-Filename">
11781 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11784 These fields in <tt>Packages</tt> files give the
11785 filename(s) of (the parts of) a package in the
11786 distribution directories, relative to the root of the
11787 Debian hierarchy. If the package has been split into
11788 several parts the parts are all listed in order, separated
11793 <sect1 id="pkg-f-Size">
11794 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11797 These fields in <file>Packages</file> files give the size (in
11798 bytes, expressed in decimal) and MD5 checksum of the
11799 file(s) which make(s) up a binary package in the
11800 distribution. If the package is split into several parts
11801 the values for the parts are listed in order, separated by
11806 <sect1 id="pkg-f-Status">
11807 <heading><tt>Status</tt></heading>
11810 This field in <prgn>dpkg</prgn>'s status file records
11811 whether the user wants a package installed, removed or
11812 left alone, whether it is broken (requiring
11813 re-installation) or not and what its current state on the
11814 system is. Each of these pieces of information is a
11819 <sect1 id="pkg-f-Config-Version">
11820 <heading><tt>Config-Version</tt></heading>
11823 If a package is not installed or not configured, this
11824 field in <prgn>dpkg</prgn>'s status file records the last
11825 version of the package which was successfully
11830 <sect1 id="pkg-f-Conffiles">
11831 <heading><tt>Conffiles</tt></heading>
11834 This field in <prgn>dpkg</prgn>'s status file contains
11835 information about the automatically-managed configuration
11836 files held by a package. This field should <em>not</em>
11837 appear anywhere in a package!
11842 <heading>Obsolete fields</heading>
11845 These are still recognized by <prgn>dpkg</prgn> but should
11846 not appear anywhere any more.
11848 <taglist compact="compact">
11850 <tag><tt>Revision</tt></tag>
11851 <tag><tt>Package-Revision</tt></tag>
11852 <tag><tt>Package_Revision</tt></tag>
11854 The Debian revision part of the package version was
11855 at one point in a separate control field. This
11856 field went through several names.
11859 <tag><tt>Recommended</tt></tag>
11860 <item>Old name for <tt>Recommends</tt>.</item>
11862 <tag><tt>Optional</tt></tag>
11863 <item>Old name for <tt>Suggests</tt>.</item>
11865 <tag><tt>Class</tt></tag>
11866 <item>Old name for <tt>Priority</tt>.</item>
11875 <appendix id="pkg-conffiles">
11876 <heading>Configuration file handling (from old Packaging Manual)</heading>
11879 <prgn>dpkg</prgn> can do a certain amount of automatic
11880 handling of package configuration files.
11884 Whether this mechanism is appropriate depends on a number of
11885 factors, but basically there are two approaches to any
11886 particular configuration file.
11890 The easy method is to ship a best-effort configuration in the
11891 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11892 handle updates. If the user is unlikely to want to edit the
11893 file, but you need them to be able to without losing their
11894 changes, and a new package with a changed version of the file
11895 is only released infrequently, this is a good approach.
11899 The hard method is to build the configuration file from
11900 scratch in the <prgn>postinst</prgn> script, and to take the
11901 responsibility for fixing any mistakes made in earlier
11902 versions of the package automatically. This will be
11903 appropriate if the file is likely to need to be different on
11907 <sect><heading>Automatic handling of configuration files by
11912 A package may contain a control information file called
11913 <tt>conffiles</tt>. This file should be a list of filenames
11914 of configuration files needing automatic handling, separated
11915 by newlines. The filenames should be absolute pathnames,
11916 and the files referred to should actually exist in the
11921 When a package is upgraded <prgn>dpkg</prgn> will process
11922 the configuration files during the configuration stage,
11923 shortly before it runs the package's <prgn>postinst</prgn>
11928 For each file it checks to see whether the version of the
11929 file included in the package is the same as the one that was
11930 included in the last version of the package (the one that is
11931 being upgraded from); it also compares the version currently
11932 installed on the system with the one shipped with the last
11937 If neither the user nor the package maintainer has changed
11938 the file, it is left alone. If one or the other has changed
11939 their version, then the changed version is preferred - i.e.,
11940 if the user edits their file, but the package maintainer
11941 doesn't ship a different version, the user's changes will
11942 stay, silently, but if the maintainer ships a new version
11943 and the user hasn't edited it the new version will be
11944 installed (with an informative message). If both have
11945 changed their version the user is prompted about the problem
11946 and must resolve the differences themselves.
11950 The comparisons are done by calculating the MD5 message
11951 digests of the files, and storing the MD5 of the file as it
11952 was included in the most recent version of the package.
11956 When a package is installed for the first time
11957 <prgn>dpkg</prgn> will install the file that comes with it,
11958 unless that would mean overwriting a file already on the
11963 However, note that <prgn>dpkg</prgn> will <em>not</em>
11964 replace a conffile that was removed by the user (or by a
11965 script). This is necessary because with some programs a
11966 missing file produces an effect hard or impossible to
11967 achieve in another way, so that a missing file needs to be
11968 kept that way if the user did it.
11972 Note that a package should <em>not</em> modify a
11973 <prgn>dpkg</prgn>-handled conffile in its maintainer
11974 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11975 the user confusing and possibly dangerous options for
11976 conffile update when the package is upgraded.</p>
11979 <sect><heading>Fully-featured maintainer script configuration
11984 For files which contain site-specific information such as
11985 the hostname and networking details and so forth, it is
11986 better to create the file in the package's
11987 <prgn>postinst</prgn> script.
11991 This will typically involve examining the state of the rest
11992 of the system to determine values and other information, and
11993 may involve prompting the user for some information which
11994 can't be obtained some other way.
11998 When using this method there are a couple of important
11999 issues which should be considered:
12003 If you discover a bug in the program which generates the
12004 configuration file, or if the format of the file changes
12005 from one version to the next, you will have to arrange for
12006 the postinst script to do something sensible - usually this
12007 will mean editing the installed configuration file to remove
12008 the problem or change the syntax. You will have to do this
12009 very carefully, since the user may have changed the file,
12010 perhaps to fix the very problem that your script is trying
12011 to deal with - you will have to detect these situations and
12012 deal with them correctly.
12016 If you do go down this route it's probably a good idea to
12017 make the program that generates the configuration file(s) a
12018 separate program in <file>/usr/sbin</file>, by convention called
12019 <file><var>package</var>config</file> and then run that if
12020 appropriate from the post-installation script. The
12021 <tt><var>package</var>config</tt> program should not
12022 unquestioningly overwrite an existing configuration - if its
12023 mode of operation is geared towards setting up a package for
12024 the first time (rather than any arbitrary reconfiguration
12025 later) you should have it check whether the configuration
12026 already exists, and require a <tt>--force</tt> flag to
12027 overwrite it.</p></sect>
12030 <appendix id="pkg-alternatives"><heading>Alternative versions of
12031 an interface - <prgn>update-alternatives</prgn> (from old
12036 When several packages all provide different versions of the
12037 same program or file it is useful to have the system select a
12038 default, but to allow the system administrator to change it
12039 and have their decisions respected.
12043 For example, there are several versions of the <prgn>vi</prgn>
12044 editor, and there is no reason to prevent all of them from
12045 being installed at once, each under their own name
12046 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
12047 Nevertheless it is desirable to have the name <tt>vi</tt>
12048 refer to something, at least by default.
12052 If all the packages involved cooperate, this can be done with
12053 <prgn>update-alternatives</prgn>.
12057 Each package provides its own version under its own name, and
12058 calls <prgn>update-alternatives</prgn> in its postinst to
12059 register its version (and again in its prerm to deregister
12064 See the man page <manref name="update-alternatives"
12065 section="8"> for details.
12069 If <prgn>update-alternatives</prgn> does not seem appropriate
12070 you may wish to consider using diversions instead.</p>
12073 <appendix id="pkg-diversions"><heading>Diversions - overriding a
12074 package's version of a file (from old Packaging Manual)
12078 It is possible to have <prgn>dpkg</prgn> not overwrite a file
12079 when it reinstalls the package it belongs to, and to have it
12080 put the file from the package somewhere else instead.
12084 This can be used locally to override a package's version of a
12085 file, or by one package to override another's version (or
12086 provide a wrapper for it).
12090 Before deciding to use a diversion, read <ref
12091 id="pkg-alternatives"> to see if you really want a diversion
12092 rather than several alternative versions of a program.
12096 There is a diversion list, which is read by <prgn>dpkg</prgn>,
12097 and updated by a special program <prgn>dpkg-divert</prgn>.
12098 Please see <manref name="dpkg-divert" section="8"> for full
12099 details of its operation.
12103 When a package wishes to divert a file from another, it should
12104 call <prgn>dpkg-divert</prgn> in its preinst to add the
12105 diversion and rename the existing file. For example,
12106 supposing that a <prgn>smailwrapper</prgn> package wishes to
12107 install a wrapper around <file>/usr/sbin/smail</file>:
12109 dpkg-divert --package smailwrapper --add --rename \
12110 --divert /usr/sbin/smail.real /usr/sbin/smail
12111 </example> The <tt>--package smailwrapper</tt> ensures that
12112 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
12113 can bypass the diversion and get installed as the true version.
12114 It's safe to add the diversion unconditionally on upgrades since
12115 it will be left unchanged if it already exists, but
12116 <prgn>dpkg-divert</prgn> will display a message. To suppress that
12117 message, make the command conditional on the version from which
12118 the package is being upgraded:
12120 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12121 dpkg-divert --package smailwrapper --add --rename \
12122 --divert /usr/sbin/smail.real /usr/sbin/smail
12124 </example> where <tt>1.0-2</tt> is the version at which the
12125 diversion was first added to the package. Running the command
12126 during abort-upgrade is pointless but harmless.
12130 The postrm has to do the reverse:
12132 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12133 dpkg-divert --package smailwrapper --remove --rename \
12134 --divert /usr/sbin/smail.real /usr/sbin/smail
12136 </example> If the diversion was added at a particular version, the
12137 postrm should also handle the failure case of upgrading from an
12138 older version (unless the older version is so old that direct
12139 upgrades are no longer supported):
12141 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12142 dpkg-divert --package smailwrapper --remove --rename \
12143 --divert /usr/sbin/smail.real /usr/sbin/smail
12145 </example> where <tt>1.0-2</tt> is the version at which the
12146 diversion was first added to the package. The postrm should not
12147 remove the diversion on upgrades both because there's no reason to
12148 remove the diversion only to immediately re-add it and since the
12149 postrm of the old package is run after unpacking so the removal of
12150 the diversion will fail.
12154 Do not attempt to divert a file which is vitally important for
12155 the system's operation - when using <prgn>dpkg-divert</prgn>
12156 there is a time, after it has been diverted but before
12157 <prgn>dpkg</prgn> has installed the new version, when the file
12158 does not exist.</p>
12161 Do not attempt to divert a conffile, as <prgn>dpkg</prgn> does not
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