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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
2563 A paragraph must not contain more than one instance of a
2564 particular field name.
2568 There are three types of fields:
2572 The field, including its value, must be a single line. Folding
2573 of the field is not permitted. This is the default field type
2574 if the definition of the field does not specify a different
2579 The value of a folded field is a logical line that may span
2580 several lines. The lines after the first are called
2581 continuation lines and must start with a space or a tab.
2582 Whitespace, including any newlines, is not significant in the
2583 field values of folded fields.<footnote>
2584 This folding method is similar to RFC 5322, allowing control
2585 files that contain only one paragraph and no multiline fields
2586 to be read by parsers written for RFC 5322.
2589 <tag>multiline</tag>
2591 The value of a multiline field may comprise multiple continuation
2592 lines. The first line of the value, the part on the same line as
2593 the field name, often has special significance or may have to be
2594 empty. Other lines are added following the same syntax as the
2595 continuation lines of the folded fields. Whitespace, including newlines,
2596 is significant in the values of multiline fields.
2602 Whitespace must not appear
2603 inside names (of packages, architectures, files or anything
2604 else) or version numbers, or between the characters of
2605 multi-character version relationships.
2609 The presence and purpose of a field, and the syntax of its
2610 value may differ between types of control files.
2614 Field names are not case-sensitive, but it is usual to
2615 capitalize the field names using mixed case as shown below.
2616 Field values are case-sensitive unless the description of the
2617 field says otherwise.
2621 Paragraph separators (empty lines) and lines consisting only of
2622 spaces and tabs are not allowed within field values or between
2623 fields. Empty lines in field values are usually escaped by
2624 representing them by a space followed by a dot.
2628 Lines starting with # without any preceding whitespace are comments
2629 lines that are only permitted in source package control files
2630 (<file>debian/control</file>). These comment lines are ignored, even
2631 between two continuation lines. They do not end logical lines.
2635 All control files must be encoded in UTF-8.
2639 <sect id="sourcecontrolfiles">
2640 <heading>Source package control files -- <file>debian/control</file></heading>
2643 The <file>debian/control</file> file contains the most vital
2644 (and version-independent) information about the source package
2645 and about the binary packages it creates.
2649 The first paragraph of the control file contains information about
2650 the source package in general. The subsequent sets each describe a
2651 binary package that the source tree builds.
2655 The fields in the general paragraph (the first one, for the source
2658 <list compact="compact">
2659 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2660 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2661 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2662 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2663 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2664 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2665 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2666 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2667 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2672 The fields in the binary package paragraphs are:
2674 <list compact="compact">
2675 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2676 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2677 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2678 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2679 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2680 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2681 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2682 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2683 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2684 <item><qref id="f-Package-Type"><tt>Package-Type</tt></qref></item>
2689 The syntax and semantics of the fields are described below.
2693 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2694 generate control files for binary packages (see below), by
2695 <prgn>dpkg-genchanges</prgn> to generate the
2696 <file>.changes</file> file to accompany the upload, and by
2697 <prgn>dpkg-source</prgn> when it creates the
2698 <file>.dsc</file> source control file as part of a source
2699 archive. Some fields are folded in <file>debian/control</file>,
2700 but not in any other control
2701 file. These tools are responsible for removing the line
2702 breaks from such fields when using fields from
2703 <file>debian/control</file> to generate other control files.
2707 The fields here may contain variable references - their
2708 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2709 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2710 when they generate output control files.
2711 See <ref id="substvars"> for details.
2715 <sect id="binarycontrolfiles">
2716 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2719 The <file>DEBIAN/control</file> file contains the most vital
2720 (and version-dependent) information about a binary package. It
2721 consists of a single paragraph.
2725 The fields in this file are:
2727 <list compact="compact">
2728 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2729 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2730 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2731 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2732 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2733 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2734 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2735 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2736 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2737 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2738 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2739 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2740 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2745 <sect id="debiansourcecontrolfiles">
2746 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2749 This file consists of a single paragraph, possibly surrounded by
2750 a PGP signature. The fields of that paragraph are listed below.
2751 Their syntax is described above, in <ref id="controlsyntax">.
2753 <list compact="compact">
2754 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2755 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2756 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2757 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2758 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2759 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2760 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2761 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2762 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2763 <item><qref id="f-Dgit"><tt>Dgit</tt></qref></item>
2764 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2765 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2766 <item><qref id="f-Package-List"><tt>Package-List</tt></qref> (recommended)</item>
2767 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2768 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2769 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2774 The Debian source control file is generated by
2775 <prgn>dpkg-source</prgn> when it builds the source
2776 archive, from other files in the source package,
2777 described above. When unpacking, it is checked against
2778 the files and directories in the other parts of the
2784 <sect id="debianchangesfiles">
2785 <heading>Debian changes files -- <file>.changes</file></heading>
2788 The <file>.changes</file> files are used by the Debian archive
2789 maintenance software to process updates to packages. They
2790 consist of a single paragraph, possibly surrounded by a PGP
2791 signature. That paragraph contains information from the
2792 <file>debian/control</file> file and other data about the
2793 source package gathered via <file>debian/changelog</file>
2794 and <file>debian/rules</file>.
2798 <file>.changes</file> files have a format version that is
2799 incremented whenever the documented fields or their meaning
2800 change. This document describes format &changesversion;.
2804 The fields in this file are:
2806 <list compact="compact">
2807 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2808 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2809 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2810 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2811 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2812 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2813 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2814 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2815 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2816 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2817 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2818 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2819 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2820 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2821 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2822 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2827 <sect id="controlfieldslist">
2828 <heading>List of fields</heading>
2830 <sect1 id="f-Source">
2831 <heading><tt>Source</tt></heading>
2834 This field identifies the source package name.
2838 In <file>debian/control</file> or a <file>.dsc</file> file,
2839 this field must contain only the name of the source package.
2843 In a binary package control file or a <file>.changes</file>
2844 file, the source package name may be followed by a version
2845 number in parentheses<footnote>
2846 It is customary to leave a space after the package name
2847 if a version number is specified.
2849 This version number may be omitted (and is, by
2850 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2851 the <tt>Version</tt> field of the binary package in
2852 question. The field itself may be omitted from a binary
2853 package control file when the source package has the same
2854 name and version as the binary package.
2858 Package names (both source and binary,
2859 see <ref id="f-Package">) must consist only of lower case
2860 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2861 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2862 (<tt>.</tt>). They must be at least two characters long and
2863 must start with an alphanumeric character.
2867 <sect1 id="f-Maintainer">
2868 <heading><tt>Maintainer</tt></heading>
2871 The package maintainer's name and email address. The name
2872 must come first, then the email address inside angle
2873 brackets <tt><></tt> (in RFC822 format).
2877 If the maintainer's name contains a full stop then the
2878 whole field will not work directly as an email address due
2879 to a misfeature in the syntax specified in RFC822; a
2880 program using this field as an address must check for this
2881 and correct the problem if necessary (for example by
2882 putting the name in round brackets and moving it to the
2883 end, and bringing the email address forward).
2887 See <ref id="maintainer"> for additional requirements and
2888 information about package maintainers.
2892 <sect1 id="f-Uploaders">
2893 <heading><tt>Uploaders</tt></heading>
2896 List of the names and email addresses of co-maintainers of the
2897 package, if any. If the package has other maintainers besides
2898 the one named in the <qref id="f-Maintainer">Maintainer
2899 field</qref>, their names and email addresses should be listed
2900 here. The format of each entry is the same as that of the
2901 Maintainer field, and multiple entries must be comma
2906 This is normally an optional field, but if
2907 the <tt>Maintainer</tt> control field names a group of people
2908 and a shared email address, the <tt>Uploaders</tt> field must
2909 be present and must contain at least one human with their
2910 personal email address.
2914 The Uploaders field in <file>debian/control</file> can be folded.
2918 <sect1 id="f-Changed-By">
2919 <heading><tt>Changed-By</tt></heading>
2922 The name and email address of the person who prepared this
2923 version of the package, usually a maintainer. The syntax is
2924 the same as for the <qref id="f-Maintainer">Maintainer
2929 <sect1 id="f-Section">
2930 <heading><tt>Section</tt></heading>
2933 This field specifies an application area into which the package
2934 has been classified. See <ref id="subsections">.
2938 When it appears in the <file>debian/control</file> file,
2939 it gives the value for the subfield of the same name in
2940 the <tt>Files</tt> field of the <file>.changes</file> file.
2941 It also gives the default for the same field in the binary
2946 <sect1 id="f-Priority">
2947 <heading><tt>Priority</tt></heading>
2950 This field represents how important it is that the user
2951 have the package installed. See <ref id="priorities">.
2955 When it appears in the <file>debian/control</file> file,
2956 it gives the value for the subfield of the same name in
2957 the <tt>Files</tt> field of the <file>.changes</file> file.
2958 It also gives the default for the same field in the binary
2963 <sect1 id="f-Package">
2964 <heading><tt>Package</tt></heading>
2967 The name of the binary package.
2971 Binary package names must follow the same syntax and
2972 restrictions as source package names. See <ref id="f-Source">
2977 <sect1 id="f-Architecture">
2978 <heading><tt>Architecture</tt></heading>
2981 Depending on context and the control file used, the
2982 <tt>Architecture</tt> field can include the following sets of
2986 A unique single word identifying a Debian machine
2987 architecture as described in <ref id="arch-spec">.
2990 An architecture wildcard identifying a set of Debian
2991 machine architectures, see <ref id="arch-wildcard-spec">.
2992 <tt>any</tt> matches all Debian machine architectures
2993 and is the most frequently used.
2996 <tt>all</tt>, which indicates an
2997 architecture-independent package.
3000 <tt>source</tt>, which indicates a source package.
3006 In the main <file>debian/control</file> file in the source
3007 package, this field may contain the special
3008 value <tt>all</tt>, the special architecture
3009 wildcard <tt>any</tt>, or a list of specific and wildcard
3010 architectures separated by spaces. If <tt>all</tt>
3011 or <tt>any</tt> appears, that value must be the entire
3012 contents of the field. Most packages will use
3013 either <tt>all</tt> or <tt>any</tt>.
3017 Specifying a specific list of architectures indicates that the
3018 source will build an architecture-dependent package only on
3019 architectures included in the list. Specifying a list of
3020 architecture wildcards indicates that the source will build an
3021 architecture-dependent package on only those architectures
3022 that match any of the specified architecture wildcards.
3023 Specifying a list of architectures or architecture wildcards
3024 other than <tt>any</tt> is for the minority of cases where a
3025 program is not portable or is not useful on some
3026 architectures. Where possible, the program should be made
3031 In the Debian source control file <file>.dsc</file>, this
3032 field contains a list of architectures and architecture
3033 wildcards separated by spaces. When the list contains the
3034 architecture wildcard <tt>any</tt>, the only other value
3035 allowed in the list is <tt>all</tt>.
3039 The list may include (or consist solely of) the special
3040 value <tt>all</tt>. In other words, in <file>.dsc</file>
3041 files unlike the <file>debian/control</file>, <tt>all</tt> may
3042 occur in combination with specific architectures.
3043 The <tt>Architecture</tt> field in the Debian source control
3044 file <file>.dsc</file> is generally constructed from
3045 the <tt>Architecture</tt> fields in
3046 the <file>debian/control</file> in the source package.
3050 Specifying only <tt>any</tt> indicates that the source package
3051 isn't dependent on any particular architecture and should
3052 compile fine on any one. The produced binary package(s)
3053 will be specific to whatever the current build architecture is.
3057 Specifying only <tt>all</tt> indicates that the source package
3058 will only build architecture-independent packages.
3062 Specifying <tt>any all</tt> indicates that the source package
3063 isn't dependent on any particular architecture. The set of
3064 produced binary packages will include at least one
3065 architecture-dependant package and one architecture-independent
3070 Specifying a list of architectures or architecture wildcards
3071 indicates that the source will build an architecture-dependent
3072 package, and will only work correctly on the listed or
3073 matching architectures. If the source package also builds at
3074 least one architecture-independent package, <tt>all</tt> will
3075 also be included in the list.
3079 In a <file>.changes</file> file, the <tt>Architecture</tt>
3080 field lists the architecture(s) of the package(s) currently
3081 being uploaded. This will be a list; if the source for the
3082 package is also being uploaded, the special
3083 entry <tt>source</tt> is also present. <tt>all</tt> will be
3084 present if any architecture-independent packages are being
3085 uploaded. Architecture wildcards such as <tt>any</tt> must
3086 never occur in the <tt>Architecture</tt> field in
3087 the <file>.changes</file> file.
3091 See <ref id="debianrules"> for information on how to get
3092 the architecture for the build process.
3096 <sect1 id="f-Essential">
3097 <heading><tt>Essential</tt></heading>
3100 This is a boolean field which may occur only in the
3101 control file of a binary package or in a per-package fields
3102 paragraph of a source package control file.
3106 If set to <tt>yes</tt> then the package management system
3107 will refuse to remove the package (upgrading and replacing
3108 it is still possible). The other possible value is <tt>no</tt>,
3109 which is the same as not having the field at all.
3114 <heading>Package interrelationship fields:
3115 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3116 <tt>Recommends</tt>, <tt>Suggests</tt>,
3117 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3118 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3122 These fields describe the package's relationships with
3123 other packages. Their syntax and semantics are described
3124 in <ref id="relationships">.</p>
3127 <sect1 id="f-Standards-Version">
3128 <heading><tt>Standards-Version</tt></heading>
3131 The most recent version of the standards (the policy
3132 manual and associated texts) with which the package
3137 The version number has four components: major and minor
3138 version number and major and minor patch level. When the
3139 standards change in a way that requires every package to
3140 change the major number will be changed. Significant
3141 changes that will require work in many packages will be
3142 signaled by a change to the minor number. The major patch
3143 level will be changed for any change to the meaning of the
3144 standards, however small; the minor patch level will be
3145 changed when only cosmetic, typographical or other edits
3146 are made which neither change the meaning of the document
3147 nor affect the contents of packages.
3151 Thus only the first three components of the policy version
3152 are significant in the <em>Standards-Version</em> control
3153 field, and so either these three components or all four
3154 components may be specified.<footnote>
3155 In the past, people specified the full version number
3156 in the Standards-Version field, for example "2.3.0.0".
3157 Since minor patch-level changes don't introduce new
3158 policy, it was thought it would be better to relax
3159 policy and only require the first 3 components to be
3160 specified, in this example "2.3.0". All four
3161 components may still be used if someone wishes to do so.
3167 <sect1 id="f-Version">
3168 <heading><tt>Version</tt></heading>
3171 The version number of a package. The format is:
3172 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3176 The three components here are:
3178 <tag><var>epoch</var></tag>
3181 This is a single (generally small) unsigned integer. It
3182 may be omitted, in which case zero is assumed. If it is
3183 omitted then the <var>upstream_version</var> may not
3188 It is provided to allow mistakes in the version numbers
3189 of older versions of a package, and also a package's
3190 previous version numbering schemes, to be left behind.
3194 <tag><var>upstream_version</var></tag>
3197 This is the main part of the version number. It is
3198 usually the version number of the original ("upstream")
3199 package from which the <file>.deb</file> file has been made,
3200 if this is applicable. Usually this will be in the same
3201 format as that specified by the upstream author(s);
3202 however, it may need to be reformatted to fit into the
3203 package management system's format and comparison
3208 The comparison behavior of the package management system
3209 with respect to the <var>upstream_version</var> is
3210 described below. The <var>upstream_version</var>
3211 portion of the version number is mandatory.
3215 The <var>upstream_version</var> may contain only
3216 alphanumerics<footnote>
3217 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3219 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3220 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3221 tilde) and should start with a digit. If there is no
3222 <var>debian_revision</var> then hyphens are not allowed;
3223 if there is no <var>epoch</var> then colons are not
3228 <tag><var>debian_revision</var></tag>
3231 This part of the version number specifies the version of
3232 the Debian package based on the upstream version. It
3233 may contain only alphanumerics and the characters
3234 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3235 tilde) and is compared in the same way as the
3236 <var>upstream_version</var> is.
3240 It is optional; if it isn't present then the
3241 <var>upstream_version</var> may not contain a hyphen.
3242 This format represents the case where a piece of
3243 software was written specifically to be a Debian
3244 package, where the Debian package source must always
3245 be identical to the pristine source and therefore no
3246 revision indication is required.
3250 It is conventional to restart the
3251 <var>debian_revision</var> at <tt>1</tt> each time the
3252 <var>upstream_version</var> is increased.
3256 The package management system will break the version
3257 number apart at the last hyphen in the string (if there
3258 is one) to determine the <var>upstream_version</var> and
3259 <var>debian_revision</var>. The absence of a
3260 <var>debian_revision</var> is equivalent to a
3261 <var>debian_revision</var> of <tt>0</tt>.
3268 When comparing two version numbers, first the <var>epoch</var>
3269 of each are compared, then the <var>upstream_version</var> if
3270 <var>epoch</var> is equal, and then <var>debian_revision</var>
3271 if <var>upstream_version</var> is also equal.
3272 <var>epoch</var> is compared numerically. The
3273 <var>upstream_version</var> and <var>debian_revision</var>
3274 parts are compared by the package management system using the
3275 following algorithm:
3279 The strings are compared from left to right.
3283 First the initial part of each string consisting entirely of
3284 non-digit characters is determined. These two parts (one of
3285 which may be empty) are compared lexically. If a difference
3286 is found it is returned. The lexical comparison is a
3287 comparison of ASCII values modified so that all the letters
3288 sort earlier than all the non-letters and so that a tilde
3289 sorts before anything, even the end of a part. For example,
3290 the following parts are in sorted order from earliest to
3291 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3292 <tt>a</tt>.<footnote>
3293 One common use of <tt>~</tt> is for upstream pre-releases.
3294 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3295 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3300 Then the initial part of the remainder of each string which
3301 consists entirely of digit characters is determined. The
3302 numerical values of these two parts are compared, and any
3303 difference found is returned as the result of the comparison.
3304 For these purposes an empty string (which can only occur at
3305 the end of one or both version strings being compared) counts
3310 These two steps (comparing and removing initial non-digit
3311 strings and initial digit strings) are repeated until a
3312 difference is found or both strings are exhausted.
3316 Note that the purpose of epochs is to allow us to leave behind
3317 mistakes in version numbering, and to cope with situations
3318 where the version numbering scheme changes. It is
3319 <em>not</em> intended to cope with version numbers containing
3320 strings of letters which the package management system cannot
3321 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3322 silly orderings.<footnote>
3323 The author of this manual has heard of a package whose
3324 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3325 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3331 <sect1 id="f-Description">
3332 <heading><tt>Description</tt></heading>
3335 In a source or binary control file, the <tt>Description</tt>
3336 field contains a description of the binary package, consisting
3337 of two parts, the synopsis or the short description, and the
3338 long description. It is a multiline field with the following
3344 Description: <single line synopsis>
3345 <extended description over several lines>
3350 The lines in the extended description can have these formats:
3356 Those starting with a single space are part of a paragraph.
3357 Successive lines of this form will be word-wrapped when
3358 displayed. The leading space will usually be stripped off.
3359 The line must contain at least one non-whitespace character.
3363 Those starting with two or more spaces. These will be
3364 displayed verbatim. If the display cannot be panned
3365 horizontally, the displaying program will line wrap them "hard"
3366 (i.e., without taking account of word breaks). If it can they
3367 will be allowed to trail off to the right. None, one or two
3368 initial spaces may be deleted, but the number of spaces
3369 deleted from each line will be the same (so that you can have
3370 indenting work correctly, for example). The line must
3371 contain at least one non-whitespace character.
3375 Those containing a single space followed by a single full stop
3376 character. These are rendered as blank lines. This is the
3377 <em>only</em> way to get a blank line<footnote>
3378 Completely empty lines will not be rendered as blank lines.
3379 Instead, they will cause the parser to think you're starting
3380 a whole new record in the control file, and will therefore
3381 likely abort with an error.
3386 Those containing a space, a full stop and some more characters.
3387 These are for future expansion. Do not use them.
3393 Do not use tab characters. Their effect is not predictable.
3397 See <ref id="descriptions"> for further information on this.
3401 In a <file>.changes</file> file, the <tt>Description</tt>
3402 field contains a summary of the descriptions for the packages
3403 being uploaded. For this case, the first line of the field
3404 value (the part on the same line as <tt>Description:</tt>) is
3405 always empty. It is a multiline field, with one
3406 line per package. Each line is
3407 indented by one space and contains the name of a binary
3408 package, a space, a hyphen (<tt>-</tt>), a space, and the
3409 short description line from that package.
3413 <sect1 id="f-Distribution">
3414 <heading><tt>Distribution</tt></heading>
3417 In a <file>.changes</file> file or parsed changelog output
3418 this contains the (space-separated) name(s) of the
3419 distribution(s) where this version of the package should
3420 be installed. Valid distributions are determined by the
3421 archive maintainers.<footnote>
3422 Example distribution names in the Debian archive used in
3423 <file>.changes</file> files are:
3424 <taglist compact="compact">
3425 <tag><em>unstable</em></tag>
3427 This distribution value refers to the
3428 <em>developmental</em> part of the Debian distribution
3429 tree. Most new packages, new upstream versions of
3430 packages and bug fixes go into the <em>unstable</em>
3434 <tag><em>experimental</em></tag>
3436 The packages with this distribution value are deemed
3437 by their maintainers to be high risk. Oftentimes they
3438 represent early beta or developmental packages from
3439 various sources that the maintainers want people to
3440 try, but are not ready to be a part of the other parts
3441 of the Debian distribution tree.
3446 Others are used for updating stable releases or for
3447 security uploads. More information is available in the
3448 Debian Developer's Reference, section "The Debian
3452 The Debian archive software only supports listing a single
3453 distribution. Migration of packages to other distributions is
3454 handled outside of the upload process.
3459 <heading><tt>Date</tt></heading>
3462 This field includes the date the package was built or last
3463 edited. It must be in the same format as the <var>date</var>
3464 in a <file>debian/changelog</file> entry.
3468 The value of this field is usually extracted from the
3469 <file>debian/changelog</file> file - see
3470 <ref id="dpkgchangelog">).
3474 <sect1 id="f-Format">
3475 <heading><tt>Format</tt></heading>
3478 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3479 files, this field declares the format version of that file.
3480 The syntax of the field value is the same as that of
3481 a <qref id="f-Version">package version number</qref> except
3482 that no epoch or Debian revision is allowed. The format
3483 described in this document is <tt>&changesversion;</tt>.
3487 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3488 Debian source control</qref> files, this field declares the
3489 format of the source package. The field value is used by
3490 programs acting on a source package to interpret the list of
3491 files in the source package and determine how to unpack it.
3492 The syntax of the field value is a numeric major revision, a
3493 period, a numeric minor revision, and then an optional subtype
3494 after whitespace, which if specified is an alphanumeric word
3495 in parentheses. The subtype is optional in the syntax but may
3496 be mandatory for particular source format revisions.
3498 The source formats currently supported by the Debian archive
3499 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3500 and <tt>3.0 (quilt)</tt>.
3505 <sect1 id="f-Urgency">
3506 <heading><tt>Urgency</tt></heading>
3509 This is a description of how important it is to upgrade to
3510 this version from previous ones. It consists of a single
3511 keyword taking one of the values <tt>low</tt>,
3512 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3513 <tt>critical</tt><footnote>
3514 Other urgency values are supported with configuration
3515 changes in the archive software but are not used in Debian.
3516 The urgency affects how quickly a package will be considered
3517 for inclusion into the <tt>testing</tt> distribution and
3518 gives an indication of the importance of any fixes included
3519 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3520 treated as synonymous.
3521 </footnote> (not case-sensitive) followed by an optional
3522 commentary (separated by a space) which is usually in
3523 parentheses. For example:
3526 Urgency: low (HIGH for users of diversions)
3532 The value of this field is usually extracted from the
3533 <file>debian/changelog</file> file - see
3534 <ref id="dpkgchangelog">.
3538 <sect1 id="f-Changes">
3539 <heading><tt>Changes</tt></heading>
3542 This multiline field contains the human-readable changes data, describing
3543 the differences between the last version and the current one.
3547 The first line of the field value (the part on the same line
3548 as <tt>Changes:</tt>) is always empty. The content of the
3549 field is expressed as continuation lines, with each line
3550 indented by at least one space. Blank lines must be
3551 represented by a line consisting only of a space and a full
3556 The value of this field is usually extracted from the
3557 <file>debian/changelog</file> file - see
3558 <ref id="dpkgchangelog">).
3562 Each version's change information should be preceded by a
3563 "title" line giving at least the version, distribution(s)
3564 and urgency, in a human-readable way.
3568 If data from several versions is being returned the entry
3569 for the most recent version should be returned first, and
3570 entries should be separated by the representation of a
3571 blank line (the "title" line may also be followed by the
3572 representation of a blank line).
3576 <sect1 id="f-Binary">
3577 <heading><tt>Binary</tt></heading>
3580 This folded field is a list of binary packages. Its syntax and
3581 meaning varies depending on the control file in which it
3586 When it appears in the <file>.dsc</file> file, it lists binary
3587 packages which a source package can produce, separated by
3589 A space after each comma is conventional.
3590 </footnote>. The source package
3591 does not necessarily produce all of these binary packages for
3592 every architecture. The source control file doesn't contain
3593 details of which architectures are appropriate for which of
3594 the binary packages.
3598 When it appears in a <file>.changes</file> file, it lists the
3599 names of the binary packages being uploaded, separated by
3600 whitespace (not commas).
3604 <sect1 id="f-Installed-Size">
3605 <heading><tt>Installed-Size</tt></heading>
3608 This field appears in the control files of binary packages,
3609 and in the <file>Packages</file> files. It gives an estimate
3610 of the total amount of disk space required to install the
3611 named package. Actual installed size may vary based on block
3612 size, file system properties, or actions taken by package
3617 The disk space is given as the integer value of the estimated
3618 installed size in bytes, divided by 1024 and rounded up.
3622 <sect1 id="f-Files">
3623 <heading><tt>Files</tt></heading>
3626 This field contains a list of files with information about
3627 each one. The exact information and syntax varies with
3632 In all cases, Files is a multiline field. The first line of
3633 the field value (the part on the same line as <tt>Files:</tt>)
3634 is always empty. The content of the field is expressed as
3635 continuation lines, one line per file. Each line must be
3636 indented by one space and contain a number of sub-fields,
3637 separated by spaces, as described below.
3641 In the <file>.dsc</file> file, each line contains the MD5
3642 checksum, size and filename of the tar file and (if
3643 applicable) diff file which make up the remainder of the
3644 source package<footnote>
3645 That is, the parts which are not the <tt>.dsc</tt>.
3646 </footnote>. For example:
3649 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3650 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3652 The exact forms of the filenames are described
3653 in <ref id="pkg-sourcearchives">.
3657 In the <file>.changes</file> file this contains one line per
3658 file being uploaded. Each line contains the MD5 checksum,
3659 size, section and priority and the filename. For example:
3662 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3663 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3664 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3665 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3667 The <qref id="f-Section">section</qref>
3668 and <qref id="f-Priority">priority</qref> are the values of
3669 the corresponding fields in the main source control file. If
3670 no section or priority is specified then <tt>-</tt> should be
3671 used, though section and priority values must be specified for
3672 new packages to be installed properly.
3676 The special value <tt>byhand</tt> for the section in a
3677 <tt>.changes</tt> file indicates that the file in question
3678 is not an ordinary package file and must be installed by
3679 hand by the distribution maintainers. If the section is
3680 <tt>byhand</tt> the priority should be <tt>-</tt>.
3684 If a new Debian revision of a package is being shipped and
3685 no new original source archive is being distributed the
3686 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3687 entry for the original source archive
3688 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3689 but the <file>.changes</file> file should leave it out. In
3690 this case the original source archive on the distribution
3691 site must match exactly, byte-for-byte, the original
3692 source archive which was used to generate the
3693 <file>.dsc</file> file and diff which are being uploaded.</p>
3696 <sect1 id="f-Closes">
3697 <heading><tt>Closes</tt></heading>
3700 A space-separated list of bug report numbers that the upload
3701 governed by the .changes file closes.
3705 <sect1 id="f-Homepage">
3706 <heading><tt>Homepage</tt></heading>
3709 The URL of the web site for this package, preferably (when
3710 applicable) the site from which the original source can be
3711 obtained and any additional upstream documentation or
3712 information may be found. The content of this field is a
3713 simple URL without any surrounding characters such as
3718 <sect1 id="f-Checksums">
3719 <heading><tt>Checksums-Sha1</tt>
3720 and <tt>Checksums-Sha256</tt></heading>
3723 These multiline fields contain a list of files with a checksum and size
3724 for each one. Both <tt>Checksums-Sha1</tt>
3725 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3726 only in the checksum algorithm used: SHA-1
3727 for <tt>Checksums-Sha1</tt> and SHA-256
3728 for <tt>Checksums-Sha256</tt>.
3732 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3733 multiline fields. The first line of the field value (the part
3734 on the same line as <tt>Checksums-Sha1:</tt>
3735 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3736 of the field is expressed as continuation lines, one line per
3737 file. Each line consists of the checksum, a space, the file
3738 size, a space, and the file name. For example (from
3739 a <file>.changes</file> file):
3742 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3743 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3744 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3745 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3747 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3748 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3749 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3750 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3755 In the <file>.dsc</file> file, these fields list all
3756 files that make up the source package. In
3757 the <file>.changes</file> file, these fields list all
3758 files being uploaded. The list of files in these fields
3759 must match the list of files in the <tt>Files</tt> field.
3764 <heading><tt>DM-Upload-Allowed</tt></heading>
3767 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3771 <sect1 id="f-VCS-fields">
3772 <heading>Version Control System (VCS) fields</heading>
3775 Debian source packages are increasingly developed using VCSs. The
3776 purpose of the following fields is to indicate a publicly accessible
3777 repository where the Debian source package is developed.
3780 <tag><tt>Vcs-Browser</tt></tag>
3783 URL of a web interface for browsing the repository.
3788 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3789 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3790 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3795 The field name identifies the VCS. The field's value uses the
3796 version control system's conventional syntax for describing
3797 repository locations and should be sufficient to locate the
3798 repository used for packaging. Ideally, it also locates the
3799 branch used for development of new versions of the Debian
3803 In the case of Git, the value consists of a URL, optionally
3804 followed by the word <tt>-b</tt> and the name of a branch in
3805 the indicated repository, following the syntax of the
3806 <tt>git clone</tt> command. If no branch is specified, the
3807 packaging should be on the default branch.
3810 More than one different VCS may be specified for the same
3818 <sect1 id="f-Package-List">
3819 <heading><tt>Package-List</tt></heading>
3822 Multiline field listing all the packages that can be built from
3823 the source package, considering every architecture. The first line
3824 of the field value is empty. Each one of the next lines describes
3825 one binary package, by listing its name, type, section and priority
3826 separated by spaces. Fifth and subsequent space-separated items
3827 may be present and parsers must allow them. See the
3828 <qref id="f-Package-Type">Package-Type</qref> field for a list of
3833 <sect1 id="f-Package-Type">
3834 <heading><tt>Package-Type</tt></heading>
3837 Simple field containing a word indicating the type of package:
3838 <tt>deb</tt> for binary packages and <tt>udeb</tt> for micro binary
3839 packages. Other types not defined here may be indicated. In
3840 source package control files, the <tt>Package-Type</tt> field
3841 should be omitted instead of giving it a value of <tt>deb</tt>, as
3842 this value is assumed for paragraphs lacking this field.
3847 <heading><tt>Dgit</tt></heading>
3850 Folded field containing a single git commit hash, presented in
3851 full, followed optionally by whitespace and other data to be
3852 defined in future extensions.
3856 Declares that the source package corresponds exactly to a
3857 referenced commit in a Git repository available at the canonical
3858 location called <em>dgit-repos</em>, used by <prgn>dgit</prgn>, a
3859 bidirectional gateway between the Debian archive and Git. The
3860 commit is reachable from at least one reference whose name matches
3861 <tt>refs/dgit/*</tt>. See the manual page of <prgn>dgit</prgn> for
3868 <heading>User-defined fields</heading>
3871 Additional user-defined fields may be added to the
3872 source package control file. Such fields will be
3873 ignored, and not copied to (for example) binary or
3874 Debian source control files or upload control files.
3878 If you wish to add additional unsupported fields to
3879 these output files you should use the mechanism
3884 Fields in the main source control information file with
3885 names starting <tt>X</tt>, followed by one or more of
3886 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3887 be copied to the output files. Only the part of the
3888 field name after the hyphen will be used in the output
3889 file. Where the letter <tt>B</tt> is used the field
3890 will appear in binary package control files, where the
3891 letter <tt>S</tt> is used in Debian source control
3892 files and where <tt>C</tt> is used in upload control
3893 (<tt>.changes</tt>) files.
3897 For example, if the main source information control file
3900 XBS-Comment: I stand between the candle and the star.
3902 then the binary and Debian source control files will contain the
3905 Comment: I stand between the candle and the star.
3911 <sect id="obsolete-control-data-fields">
3912 <heading>Obsolete fields</heading>
3915 The following fields have been obsoleted and may be found in packages
3916 conforming with previous versions of the Policy.
3919 <sect1 id="f-DM-Upload-Allowed">
3920 <heading><tt>DM-Upload-Allowed</tt></heading>
3923 Indicates that Debian Maintainers may upload this package to
3924 the Debian archive. The only valid value is <tt>yes</tt>. This
3925 field was used to regulate uploads by Debian Maintainers, See the
3926 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3927 name="Endorse the concept of Debian Maintainers"> for more details.
3936 <chapt id="maintainerscripts">
3937 <heading>Package maintainer scripts and installation procedure</heading>
3940 <heading>Introduction to package maintainer scripts</heading>
3943 It is possible to supply scripts as part of a package which
3944 the package management system will run for you when your
3945 package is installed, upgraded or removed.
3949 These scripts are the control information
3950 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3951 and <prgn>postrm</prgn>. They must be proper executable files;
3952 if they are scripts (which is recommended), they must start with
3953 the usual <tt>#!</tt> convention. They should be readable and
3954 executable by anyone, and must not be world-writable.
3958 The package management system looks at the exit status from
3959 these scripts. It is important that they exit with a
3960 non-zero status if there is an error, so that the package
3961 management system can stop its processing. For shell
3962 scripts this means that you <em>almost always</em> need to
3963 use <tt>set -e</tt> (this is usually true when writing shell
3964 scripts, in fact). It is also important, of course, that
3965 they exit with a zero status if everything went well.
3969 Additionally, packages interacting with users
3970 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3971 should install a <prgn>config</prgn> script as a control
3972 information file. See <ref id="maintscriptprompt"> for details.
3976 When a package is upgraded a combination of the scripts from
3977 the old and new packages is called during the upgrade
3978 procedure. If your scripts are going to be at all
3979 complicated you need to be aware of this, and may need to
3980 check the arguments to your scripts.
3984 Broadly speaking the <prgn>preinst</prgn> is called before
3985 (a particular version of) a package is unpacked, and the
3986 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3987 before (a version of) a package is removed and the
3988 <prgn>postrm</prgn> afterwards.
3992 Programs called from maintainer scripts should not normally
3993 have a path prepended to them. Before installation is
3994 started, the package management system checks to see if the
3995 programs <prgn>ldconfig</prgn>, <prgn>start-stop-daemon</prgn>,
3996 and <prgn>update-rc.d</prgn> can be found via the
3997 <tt>PATH</tt> environment variable. Those programs, and any
3998 other program that one would expect to be in the
3999 <tt>PATH</tt>, should thus be invoked without an absolute
4000 pathname. Maintainer scripts should also not reset the
4001 <tt>PATH</tt>, though they might choose to modify it by
4002 prepending or appending package-specific directories. These
4003 considerations really apply to all shell scripts.</p>
4006 <sect id="idempotency">
4007 <heading>Maintainer scripts idempotency</heading>
4010 It is necessary for the error recovery procedures that the
4011 scripts be idempotent. This means that if it is run
4012 successfully, and then it is called again, it doesn't bomb
4013 out or cause any harm, but just ensures that everything is
4014 the way it ought to be. If the first call failed, or
4015 aborted half way through for some reason, the second call
4016 should merely do the things that were left undone the first
4017 time, if any, and exit with a success status if everything
4019 This is so that if an error occurs, the user interrupts
4020 <prgn>dpkg</prgn> or some other unforeseen circumstance
4021 happens you don't leave the user with a badly-broken
4022 package when <prgn>dpkg</prgn> attempts to repeat the
4028 <sect id="controllingterminal">
4029 <heading>Controlling terminal for maintainer scripts</heading>
4032 Maintainer scripts are not guaranteed to run with a controlling
4033 terminal and may not be able to interact with the user. They
4034 must be able to fall back to noninteractive behavior if no
4035 controlling terminal is available. Maintainer scripts that
4036 prompt via a program conforming to the Debian Configuration
4037 Management Specification (see <ref id="maintscriptprompt">) may
4038 assume that program will handle falling back to noninteractive
4043 For high-priority prompts without a reasonable default answer,
4044 maintainer scripts may abort if there is no controlling
4045 terminal. However, this situation should be avoided if at all
4046 possible, since it prevents automated or unattended installs.
4047 In most cases, users will consider this to be a bug in the
4052 <sect id="exitstatus">
4053 <heading>Exit status</heading>
4056 Each script must return a zero exit status for
4057 success, or a nonzero one for failure, since the package
4058 management system looks for the exit status of these scripts
4059 and determines what action to take next based on that datum.
4063 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4068 What follows is a summary of all the ways in which maintainer
4069 scripts may be called along with what facilities those scripts
4070 may rely on being available at that time. Script names preceded
4071 by <var>new-</var> are the scripts from the new version of a
4072 package being installed, upgraded to, or downgraded to. Script
4073 names preceded by <var>old-</var> are the scripts from the old
4074 version of a package that is being upgraded from or downgraded
4079 The <prgn>preinst</prgn> script may be called in the following
4082 <tag><var>new-preinst</var> <tt>install</tt></tag>
4083 <tag><var>new-preinst</var> <tt>install</tt>
4084 <var>old-version</var></tag>
4085 <tag><var>new-preinst</var> <tt>upgrade</tt>
4086 <var>old-version</var></tag>
4088 The package will not yet be unpacked, so
4089 the <prgn>preinst</prgn> script cannot rely on any files
4090 included in its package. Only essential packages and
4091 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4092 available. Pre-dependencies will have been configured at
4093 least once, but at the time the <prgn>preinst</prgn> is
4094 called they may only be in an "Unpacked" or "Half-Configured"
4095 state if a previous version of the pre-dependency was
4096 completely configured and has not been removed since then.
4099 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4100 <var>new-version</var></tag>
4102 Called during error handling of an upgrade that failed after
4103 unpacking the new package because the <tt>postrm
4104 upgrade</tt> action failed. The unpacked files may be
4105 partly from the new version or partly missing, so the script
4106 cannot rely on files included in the package. Package
4107 dependencies may not be available. Pre-dependencies will be
4108 at least "Unpacked" following the same rules as above, except
4109 they may be only "Half-Installed" if an upgrade of the
4110 pre-dependency failed.<footnote>
4111 This can happen if the new version of the package no
4112 longer pre-depends on a package that had been partially
4120 The <prgn>postinst</prgn> script may be called in the following
4123 <tag><var>postinst</var> <tt>configure</tt>
4124 <var>most-recently-configured-version</var></tag>
4126 The files contained in the package will be unpacked. All
4127 package dependencies will at least be "Unpacked". If there
4128 are no circular dependencies involved, all package
4129 dependencies will be configured. For behavior in the case
4130 of circular dependencies, see the discussion
4131 in <ref id="binarydeps">.
4134 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4135 <var>new-version</var></tag>
4136 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4137 <tt>in-favour</tt> <var>package</var>
4138 <var>new-version</var></tag>
4139 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4140 <tag><var>deconfigured's-postinst</var>
4141 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4142 <var>failed-install-package</var> <var>version</var>
4143 [<tt>removing</tt> <var>conflicting-package</var>
4144 <var>version</var>]</tag>
4146 The files contained in the package will be unpacked. All
4147 package dependencies will at least be "Half-Installed" and
4148 will have previously been configured and not removed.
4149 However, dependencies may not be configured or even fully
4150 unpacked in some error situations.<footnote>
4151 For example, suppose packages foo and bar are "Installed"
4152 with foo depending on bar. If an upgrade of bar were
4153 started and then aborted, and then an attempt to remove
4154 foo failed because its <prgn>prerm</prgn> script failed,
4155 foo's <tt>postinst abort-remove</tt> would be called with
4156 bar only "Half-Installed".
4158 The <prgn>postinst</prgn> should still attempt any actions
4159 for which its dependencies are required, since they will
4160 normally be available, but consider the correct error
4161 handling approach if those actions fail. Aborting
4162 the <prgn>postinst</prgn> action if commands or facilities
4163 from the package dependencies are not available is often the
4170 The <prgn>prerm</prgn> script may be called in the following
4173 <tag><var>prerm</var> <tt>remove</tt></tag>
4174 <tag><var>old-prerm</var>
4175 <tt>upgrade</tt><var>new-version</var></tag>
4176 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4177 <tt>in-favour</tt> <var>package</var>
4178 <var>new-version</var></tag>
4179 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4180 <tt>in-favour</tt> <var>package-being-installed</var>
4181 <var>version</var> [<tt>removing</tt>
4182 <var>conflicting-package</var> <var>version</var>]</tag>
4184 The package whose <prgn>prerm</prgn> is being called will be
4185 at least "Half-Installed". All package dependencies will at
4186 least be "Half-Installed" and will have previously been
4187 configured and not removed. If there was no error, all
4188 dependencies will at least be "Unpacked", but these actions
4189 may be called in various error states where dependencies are
4190 only "Half-Installed" due to a partial upgrade.
4193 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4194 <var>old-version</var></tag>
4196 Called during error handling when <tt>prerm upgrade</tt>
4197 fails. The new package will not yet be unpacked, and all
4198 the same constraints as for <tt>preinst upgrade</tt> apply.
4204 The <prgn>postrm</prgn> script may be called in the following
4207 <tag><var>postrm</var> <tt>remove</tt></tag>
4208 <tag><var>postrm</var> <tt>purge</tt></tag>
4209 <tag><var>old-postrm</var> <tt>upgrade</tt>
4210 <var>new-version</var></tag>
4211 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4212 <var>overwriter</var> <var>overwriter-version</var></tag>
4214 The <prgn>postrm</prgn> script is called after the package's
4215 files have been removed or replaced. The package
4216 whose <prgn>postrm</prgn> is being called may have
4217 previously been deconfigured and only be "Unpacked", at which
4218 point subsequent package changes do not consider its
4219 dependencies. Therefore, all <prgn>postrm</prgn> actions
4220 may only rely on essential packages and must gracefully skip
4221 any actions that require the package's dependencies if those
4222 dependencies are unavailable.<footnote>
4223 This is often done by checking whether the command or
4224 facility the <prgn>postrm</prgn> intends to call is
4225 available before calling it. For example:
4227 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4228 . /usr/share/debconf/confmodule
4232 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4233 configuration for the package
4234 if <package>debconf</package> is installed.
4238 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4239 <var>old-version</var></tag>
4241 Called when the old <tt>postrm upgrade</tt> action fails.
4242 The new package will be unpacked, but only essential
4243 packages and pre-dependencies can be relied on.
4244 Pre-dependencies will either be configured or will be
4245 "Unpacked" or "Half-Configured" but previously had been
4246 configured and was never removed.
4249 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4250 <tag><var>new-postrm</var> <tt>abort-install</tt>
4251 <var>old-version</var></tag>
4252 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4253 <var>old-version</var></tag>
4255 Called before unpacking the new package as part of the
4256 error handling of <prgn>preinst</prgn> failures. May assume
4257 the same state as <prgn>preinst</prgn> can assume.
4263 <sect id="unpackphase">
4264 <heading>Details of unpack phase of installation or upgrade</heading>
4267 The procedure on installation/upgrade/overwrite/disappear
4268 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4269 stage of <tt>dpkg --install</tt>) is as follows. In each
4270 case, if a major error occurs (unless listed below) the
4271 actions are, in general, run backwards - this means that the
4272 maintainer scripts are run with different arguments in
4273 reverse order. These are the "error unwind" calls listed
4280 If a version of the package is already "Installed", call
4281 <example compact="compact">
4282 <var>old-prerm</var> upgrade <var>new-version</var>
4286 If the script runs but exits with a non-zero
4287 exit status, <prgn>dpkg</prgn> will attempt:
4288 <example compact="compact">
4289 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4291 If this works, the upgrade continues. If this
4292 does not work, the error unwind:
4293 <example compact="compact">
4294 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4296 If this works, then the old-version is
4297 "Installed", if not, the old version is in a
4298 "Half-Configured" state.
4304 If a "conflicting" package is being removed at the same time,
4305 or if any package will be broken (due to <tt>Breaks</tt>):
4308 If <tt>--auto-deconfigure</tt> is
4309 specified, call, for each package to be deconfigured
4310 due to <tt>Breaks</tt>:
4311 <example compact="compact">
4312 <var>deconfigured's-prerm</var> deconfigure \
4313 in-favour <var>package-being-installed</var> <var>version</var>
4316 <example compact="compact">
4317 <var>deconfigured's-postinst</var> abort-deconfigure \
4318 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4320 The deconfigured packages are marked as
4321 requiring configuration, so that if
4322 <tt>--install</tt> is used they will be
4323 configured again if possible.
4326 If any packages depended on a conflicting
4327 package being removed and <tt>--auto-deconfigure</tt> is
4328 specified, call, for each such package:
4329 <example compact="compact">
4330 <var>deconfigured's-prerm</var> deconfigure \
4331 in-favour <var>package-being-installed</var> <var>version</var> \
4332 removing <var>conflicting-package</var> <var>version</var>
4335 <example compact="compact">
4336 <var>deconfigured's-postinst</var> abort-deconfigure \
4337 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4338 removing <var>conflicting-package</var> <var>version</var>
4340 The deconfigured packages are marked as
4341 requiring configuration, so that if
4342 <tt>--install</tt> is used they will be
4343 configured again if possible.
4346 To prepare for removal of each conflicting package, call:
4347 <example compact="compact">
4348 <var>conflictor's-prerm</var> remove \
4349 in-favour <var>package</var> <var>new-version</var>
4352 <example compact="compact">
4353 <var>conflictor's-postinst</var> abort-remove \
4354 in-favour <var>package</var> <var>new-version</var>
4363 If the package is being upgraded, call:
4364 <example compact="compact">
4365 <var>new-preinst</var> upgrade <var>old-version</var>
4367 If this fails, we call:
4369 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4376 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4378 is called. If this works, then the old version
4379 is in an "Installed" state, or else it is left
4380 in an "Unpacked" state.
4385 If it fails, then the old version is left
4386 in an "Half-Installed" state.
4393 Otherwise, if the package had some configuration
4394 files from a previous version installed (i.e., it
4395 is in the "Config-Files" state):
4396 <example compact="compact">
4397 <var>new-preinst</var> install <var>old-version</var>
4401 <var>new-postrm</var> abort-install <var>old-version</var>
4403 If this fails, the package is left in a
4404 "Half-Installed" state, which requires a
4405 reinstall. If it works, the packages is left in
4406 a "Config-Files" state.
4409 Otherwise (i.e., the package was completely purged):
4410 <example compact="compact">
4411 <var>new-preinst</var> install
4414 <example compact="compact">
4415 <var>new-postrm</var> abort-install
4417 If the error-unwind fails, the package is in a
4418 "Half-Installed" phase, and requires a
4419 reinstall. If the error unwind works, the
4420 package is in the "Not-Installed" state.
4427 The new package's files are unpacked, overwriting any
4428 that may be on the system already, for example any
4429 from the old version of the same package or from
4430 another package. Backups of the old files are kept
4431 temporarily, and if anything goes wrong the package
4432 management system will attempt to put them back as
4433 part of the error unwind.
4437 It is an error for a package to contain files which
4438 are on the system in another package, unless
4439 <tt>Replaces</tt> is used (see <ref id="replaces">).
4441 The following paragraph is not currently the case:
4442 Currently the <tt>- - force-overwrite</tt> flag is
4443 enabled, downgrading it to a warning, but this may not
4449 It is a more serious error for a package to contain a
4450 plain file or other kind of non-directory where another
4451 package has a directory (again, unless
4452 <tt>Replaces</tt> is used). This error can be
4453 overridden if desired using
4454 <tt>--force-overwrite-dir</tt>, but this is not
4459 Packages which overwrite each other's files produce
4460 behavior which, though deterministic, is hard for the
4461 system administrator to understand. It can easily
4462 lead to "missing" programs if, for example, a package
4463 is unpacked which overwrites a file from another
4464 package, and is then removed again.<footnote>
4465 Part of the problem is due to what is arguably a
4466 bug in <prgn>dpkg</prgn>.
4471 A directory will never be replaced by a symbolic link
4472 to a directory or vice versa; instead, the existing
4473 state (symlink or not) will be left alone and
4474 <prgn>dpkg</prgn> will follow the symlink if there is
4483 If the package is being upgraded, call
4484 <example compact="compact">
4485 <var>old-postrm</var> upgrade <var>new-version</var>
4489 If this fails, <prgn>dpkg</prgn> will attempt:
4490 <example compact="compact">
4491 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4493 If this works, installation continues. If not,
4495 <example compact="compact">
4496 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4498 If this fails, the old version is left in a
4499 "Half-Installed" state. If it works, dpkg now
4501 <example compact="compact">
4502 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4504 If this fails, the old version is left in a
4505 "Half-Installed" state. If it works, dpkg now
4507 <example compact="compact">
4508 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4510 If this fails, the old version is in an
4517 This is the point of no return - if
4518 <prgn>dpkg</prgn> gets this far, it won't back off
4519 past this point if an error occurs. This will
4520 leave the package in a fairly bad state, which
4521 will require a successful re-installation to clear
4522 up, but it's when <prgn>dpkg</prgn> starts doing
4523 things that are irreversible.
4528 Any files which were in the old version of the package
4529 but not in the new are removed.
4533 The new file list replaces the old.
4537 The new maintainer scripts replace the old.
4541 Any packages all of whose files have been overwritten
4542 during the installation, and which aren't required for
4543 dependencies, are considered to have been removed.
4544 For each such package
4547 <prgn>dpkg</prgn> calls:
4548 <example compact="compact">
4549 <var>disappearer's-postrm</var> disappear \
4550 <var>overwriter</var> <var>overwriter-version</var>
4554 The package's maintainer scripts are removed.
4557 It is noted in the status database as being in a
4558 sane state, namely "Not-Installed" (any conffiles
4559 it may have are ignored, rather than being
4560 removed by <prgn>dpkg</prgn>). Note that
4561 disappearing packages do not have their prerm
4562 called, because <prgn>dpkg</prgn> doesn't know
4563 in advance that the package is going to
4570 Any files in the package we're unpacking that are also
4571 listed in the file lists of other packages are removed
4572 from those lists. (This will lobotomize the file list
4573 of the "conflicting" package if there is one.)
4577 The backup files made during installation, above, are
4583 The new package's status is now sane, and recorded as
4588 Here is another point of no return - if the
4589 conflicting package's removal fails we do not unwind
4590 the rest of the installation; the conflicting package
4591 is left in a half-removed limbo.
4596 If there was a conflicting package we go and do the
4597 removal actions (described below), starting with the
4598 removal of the conflicting package's files (any that
4599 are also in the package being unpacked have already
4600 been removed from the conflicting package's file list,
4601 and so do not get removed now).
4607 <sect id="configdetails"><heading>Details of configuration</heading>
4610 When we configure a package (this happens with <tt>dpkg
4611 --install</tt> and <tt>dpkg --configure</tt>), we first
4612 update any <tt>conffile</tt>s and then call:
4613 <example compact="compact">
4614 <var>postinst</var> configure <var>most-recently-configured-version</var>
4619 No attempt is made to unwind after errors during
4620 configuration. If the configuration fails, the package is in
4621 a "Half-Configured" state, and an error message is generated.
4625 If there is no most recently configured version
4626 <prgn>dpkg</prgn> will pass a null argument.
4629 Historical note: Truly ancient (pre-1997) versions of
4630 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4631 (including the angle brackets) in this case. Even older
4632 ones did not pass a second argument at all, under any
4633 circumstance. Note that upgrades using such an old dpkg
4634 version are unlikely to work for other reasons, even if
4635 this old argument behavior is handled by your postinst script.
4641 <sect id="removedetails"><heading>Details of removal and/or
4642 configuration purging</heading>
4648 <example compact="compact">
4649 <var>prerm</var> remove
4653 If prerm fails during replacement due to conflict
4655 <var>conflictor's-postinst</var> abort-remove \
4656 in-favour <var>package</var> <var>new-version</var>
4660 <var>postinst</var> abort-remove
4664 If this fails, the package is in a "Half-Configured"
4665 state, or else it remains "Installed".
4669 The package's files are removed (except <tt>conffile</tt>s).
4672 <example compact="compact">
4673 <var>postrm</var> remove
4677 If it fails, there's no error unwind, and the package is in
4678 an "Half-Installed" state.
4683 All the maintainer scripts except the <prgn>postrm</prgn>
4688 If we aren't purging the package we stop here. Note
4689 that packages which have no <prgn>postrm</prgn> and no
4690 <tt>conffile</tt>s are automatically purged when
4691 removed, as there is no difference except for the
4692 <prgn>dpkg</prgn> status.
4696 The <tt>conffile</tt>s and any backup files
4697 (<tt>~</tt>-files, <tt>#*#</tt> files,
4698 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4703 <example compact="compact">
4704 <var>postrm</var> purge
4708 If this fails, the package remains in a "Config-Files"
4713 The package's file list is removed.
4722 <chapt id="relationships">
4723 <heading>Declaring relationships between packages</heading>
4725 <sect id="depsyntax">
4726 <heading>Syntax of relationship fields</heading>
4729 These fields all have a uniform syntax. They are a list of
4730 package names separated by commas.
4734 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4735 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4736 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4737 control fields of the package, which declare
4738 dependencies on other packages, the package names listed may
4739 also include lists of alternative package names, separated
4740 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4741 that part of the dependency can be satisfied by any one of
4742 the alternative packages.
4746 All of the fields except for <tt>Provides</tt> may restrict
4747 their applicability to particular versions of each named
4748 package. This is done in parentheses after each individual
4749 package name; the parentheses should contain a relation from
4750 the list below followed by a version number, in the format
4751 described in <ref id="f-Version">.
4755 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4756 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4757 earlier, earlier or equal, exactly equal, later or equal and
4758 strictly later, respectively. The deprecated
4759 forms <tt><</tt> and <tt>></tt> were confusingly used to
4760 mean earlier/later or equal, rather than strictly earlier/later,
4761 and must not appear in new packages (though <prgn>dpkg</prgn>
4762 still supports them with a warning).
4766 Whitespace may appear at any point in the version
4767 specification subject to the rules in <ref
4768 id="controlsyntax">, and must appear where it's necessary to
4769 disambiguate; it is not otherwise significant. All of the
4770 relationship fields can only be folded in source package control files. For
4771 consistency and in case of future changes to
4772 <prgn>dpkg</prgn> it is recommended that a single space be
4773 used after a version relationship and before a version
4774 number; it is also conventional to put a single space after
4775 each comma, on either side of each vertical bar, and before
4776 each open parenthesis. When opening a continuation line in a relationship field, it
4777 is conventional to do so after a comma and before the space
4778 following that comma.
4782 For example, a list of dependencies might appear as:
4783 <example compact="compact">
4786 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4791 Relationships may be restricted to a certain set of
4792 architectures. This is indicated in brackets after each
4793 individual package name and the optional version specification.
4794 The brackets enclose a non-empty list of Debian architecture names
4795 in the format described in <ref id="arch-spec">,
4796 separated by whitespace. Exclamation marks may be prepended to
4797 each of the names. (It is not permitted for some names to be
4798 prepended with exclamation marks while others aren't.)
4802 For build relationship fields
4803 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4804 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4805 the current Debian host architecture is not in this list and
4806 there are no exclamation marks in the list, or it is in the list
4807 with a prepended exclamation mark, the package name and the
4808 associated version specification are ignored completely for the
4809 purposes of defining the relationships.
4814 <example compact="compact">
4816 Build-Depends-Indep: texinfo
4817 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4818 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4820 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4821 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4822 <tt>gnumach-dev</tt> only on hurd-i386.
4826 For binary relationship fields and the <tt>Built-Using</tt>
4827 field, the architecture restriction
4828 syntax is only supported in the source package control
4829 file <file>debian/control</file>. When the corresponding binary
4830 package control file is generated, the relationship will either
4831 be omitted or included without the architecture restriction
4832 based on the architecture of the binary package. This means
4833 that architecture restrictions must not be used in binary
4834 relationship fields for architecture-independent packages
4835 (<tt>Architecture: all</tt>).
4840 <example compact="compact">
4841 Depends: foo [i386], bar [amd64]
4843 becomes <tt>Depends: foo</tt> when the package is built on
4844 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4845 package is built on the <tt>amd64</tt> architecture, and omitted
4846 entirely in binary packages built on all other architectures.
4850 If the architecture-restricted dependency is part of a set of
4851 alternatives using <tt>|</tt>, that alternative is ignored
4852 completely on architectures that do not match the restriction.
4854 <example compact="compact">
4855 Build-Depends: foo [!i386] | bar [!amd64]
4857 is equivalent to <tt>bar</tt> on the i386 architecture, to
4858 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4859 bar</tt> on all other architectures.
4863 Relationships may also be restricted to a certain set of
4864 architectures using architecture wildcards in the format
4865 described in <ref id="arch-wildcard-spec">. The syntax for
4866 declaring such restrictions is the same as declaring
4867 restrictions using a certain set of architectures without
4868 architecture wildcards. For example:
4869 <example compact="compact">
4870 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4872 is equivalent to <tt>foo</tt> on architectures using the Linux
4873 kernel and any cpu, <tt>bar</tt> on architectures using any
4874 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4875 using a kernel other than Linux.
4879 Note that the binary package relationship fields such as
4880 <tt>Depends</tt> appear in one of the binary package
4881 sections of the control file, whereas the build-time
4882 relationships such as <tt>Build-Depends</tt> appear in the
4883 source package section of the control file (which is the
4888 <sect id="binarydeps">
4889 <heading>Binary Dependencies - <tt>Depends</tt>,
4890 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4891 <tt>Pre-Depends</tt>
4895 Packages can declare in their control file that they have
4896 certain relationships to other packages - for example, that
4897 they may not be installed at the same time as certain other
4898 packages, and/or that they depend on the presence of others.
4902 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4903 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4904 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4905 <tt>Breaks</tt> is described in <ref id="breaks">, and
4906 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4907 rest are described below.
4911 These seven fields are used to declare a dependency
4912 relationship by one package on another. Except for
4913 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4914 depending (binary) package's control file.
4915 (<tt>Enhances</tt> appears in the recommending package's
4916 control file, and <tt>Breaks</tt> appears in the version of
4917 depended-on package which causes the named package to
4922 A <tt>Depends</tt> field takes effect <em>only</em> when a
4923 package is to be configured. It does not prevent a package
4924 being on the system in an unconfigured state while its
4925 dependencies are unsatisfied, and it is possible to replace
4926 a package whose dependencies are satisfied and which is
4927 properly installed with a different version whose
4928 dependencies are not and cannot be satisfied; when this is
4929 done the depending package will be left unconfigured (since
4930 attempts to configure it will give errors) and will not
4931 function properly. If it is necessary, a
4932 <tt>Pre-Depends</tt> field can be used, which has a partial
4933 effect even when a package is being unpacked, as explained
4934 in detail below. (The other three dependency fields,
4935 <tt>Recommends</tt>, <tt>Suggests</tt> and
4936 <tt>Enhances</tt>, are only used by the various front-ends
4937 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4938 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4942 Since <tt>Depends</tt> only places requirements on the order in
4943 which packages are configured, packages in an installation run
4944 are usually all unpacked first and all configured later.
4946 This approach makes dependency resolution easier. If two
4947 packages A and B are being upgraded, the installed package A
4948 depends on exactly the installed package B, and the new
4949 package A depends on exactly the new package B (a common
4950 situation when upgrading shared libraries and their
4951 corresponding development packages), satisfying the
4952 dependencies at every stage of the upgrade would be
4953 impossible. This relaxed restriction means that both new
4954 packages can be unpacked together and then configured in their
4960 If there is a circular dependency among packages being installed
4961 or removed, installation or removal order honoring the
4962 dependency order is impossible, requiring the dependency loop be
4963 broken at some point and the dependency requirements violated
4964 for at least one package. Packages involved in circular
4965 dependencies may not be able to rely on their dependencies being
4966 configured before they themselves are configured, depending on
4967 which side of the break of the circular dependency loop they
4968 happen to be on. If one of the packages in the loop has
4969 no <prgn>postinst</prgn> script, then the cycle will be broken
4970 at that package; this ensures that all <prgn>postinst</prgn>
4971 scripts are run with their dependencies properly configured if
4972 this is possible. Otherwise the breaking point is arbitrary.
4973 Packages should therefore avoid circular dependencies where
4974 possible, particularly if they have <prgn>postinst</prgn>
4979 The meaning of the five dependency fields is as follows:
4981 <tag><tt>Depends</tt></tag>
4984 This declares an absolute dependency. A package will
4985 not be configured unless all of the packages listed in
4986 its <tt>Depends</tt> field have been correctly
4987 configured (unless there is a circular dependency as
4992 The <tt>Depends</tt> field should be used if the
4993 depended-on package is required for the depending
4994 package to provide a significant amount of
4999 The <tt>Depends</tt> field should also be used if the
5000 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
5001 require the depended-on package to be unpacked or
5002 configured in order to run. In the case of <tt>postinst
5003 configure</tt>, the depended-on packages will be unpacked
5004 and configured first. (If both packages are involved in a
5005 dependency loop, this might not work as expected; see the
5006 explanation a few paragraphs back.) In the case
5007 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
5008 actions, the package dependencies will normally be at
5009 least unpacked, but they may be only "Half-Installed" if a
5010 previous upgrade of the dependency failed.
5014 Finally, the <tt>Depends</tt> field should be used if the
5015 depended-on package is needed by the <prgn>postrm</prgn>
5016 script to fully clean up after the package removal. There
5017 is no guarantee that package dependencies will be
5018 available when <prgn>postrm</prgn> is run, but the
5019 depended-on package is more likely to be available if the
5020 package declares a dependency (particularly in the case
5021 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
5022 script must gracefully skip actions that require a
5023 dependency if that dependency isn't available.
5027 <tag><tt>Recommends</tt></tag>
5030 This declares a strong, but not absolute, dependency.
5034 The <tt>Recommends</tt> field should list packages
5035 that would be found together with this one in all but
5036 unusual installations.
5040 <tag><tt>Suggests</tt></tag>
5042 This is used to declare that one package may be more
5043 useful with one or more others. Using this field
5044 tells the packaging system and the user that the
5045 listed packages are related to this one and can
5046 perhaps enhance its usefulness, but that installing
5047 this one without them is perfectly reasonable.
5050 <tag><tt>Enhances</tt></tag>
5052 This field is similar to Suggests but works in the
5053 opposite direction. It is used to declare that a
5054 package can enhance the functionality of another
5058 <tag><tt>Pre-Depends</tt></tag>
5061 This field is like <tt>Depends</tt>, except that it
5062 also forces <prgn>dpkg</prgn> to complete installation
5063 of the packages named before even starting the
5064 installation of the package which declares the
5065 pre-dependency, as follows:
5069 When a package declaring a pre-dependency is about to
5070 be <em>unpacked</em> the pre-dependency can be
5071 satisfied if the depended-on package is either fully
5072 configured, <em>or even if</em> the depended-on
5073 package(s) are only in the "Unpacked" or the "Half-Configured"
5074 state, provided that they have been configured
5075 correctly at some point in the past (and not removed
5076 or partially removed since). In this case, both the
5077 previously-configured and currently "Unpacked" or
5078 "Half-Configured" versions must satisfy any version
5079 clause in the <tt>Pre-Depends</tt> field.
5083 When the package declaring a pre-dependency is about to
5084 be <em>configured</em>, the pre-dependency will be treated
5085 as a normal <tt>Depends</tt>. It will be considered
5086 satisfied only if the depended-on package has been
5087 correctly configured. However, unlike
5088 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5089 permit circular dependencies to be broken. If a circular
5090 dependency is encountered while attempting to honor
5091 <tt>Pre-Depends</tt>, the installation will be aborted.
5095 <tt>Pre-Depends</tt> are also required if the
5096 <prgn>preinst</prgn> script depends on the named package.
5097 It is best to avoid this situation if possible.
5101 <tt>Pre-Depends</tt> should be used sparingly,
5102 preferably only by packages whose premature upgrade or
5103 installation would hamper the ability of the system to
5104 continue with any upgrade that might be in progress.
5108 You should not specify a <tt>Pre-Depends</tt> entry for a
5109 package before this has been discussed on the
5110 <tt>debian-devel</tt> mailing list and a consensus about
5111 doing that has been reached. See <ref id="dependencies">.
5118 When selecting which level of dependency to use you should
5119 consider how important the depended-on package is to the
5120 functionality of the one declaring the dependency. Some
5121 packages are composed of components of varying degrees of
5122 importance. Such a package should list using
5123 <tt>Depends</tt> the package(s) which are required by the
5124 more important components. The other components'
5125 requirements may be mentioned as Suggestions or
5126 Recommendations, as appropriate to the components' relative
5132 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5135 When one binary package declares that it breaks another,
5136 <prgn>dpkg</prgn> will refuse to allow the package which
5137 declares <tt>Breaks</tt> to be unpacked unless the broken
5138 package is deconfigured first, and it will refuse to
5139 allow the broken package to be reconfigured.
5143 A package will not be regarded as causing breakage merely
5144 because its configuration files are still installed; it must
5145 be at least "Half-Installed".
5149 A special exception is made for packages which declare that
5150 they break their own package name or a virtual package which
5151 they provide (see below): this does not count as a real
5156 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5157 version clause; such a <tt>Breaks</tt> is introduced in the
5158 version of an (implicit or explicit) dependency which violates
5159 an assumption or reveals a bug in earlier versions of the broken
5160 package, or which takes over a file from earlier versions of the
5161 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5162 will inform higher-level package management tools that the
5163 broken package must be upgraded before the new one.
5167 If the breaking package also overwrites some files from the
5168 older package, it should use <tt>Replaces</tt> to ensure this
5169 goes smoothly. See <ref id="replaces"> for a full discussion
5170 of taking over files from other packages, including how to
5171 use <tt>Breaks</tt> in those cases.
5175 Many of the cases where <tt>Breaks</tt> should be used were
5176 previously handled with <tt>Conflicts</tt>
5177 because <tt>Breaks</tt> did not yet exist.
5178 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5179 See <ref id="conflicts"> for more information about the
5184 <sect id="conflicts">
5185 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5188 When one binary package declares a conflict with another using
5189 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5190 allow them to be unpacked on the system at the same time. This
5191 is a stronger restriction than <tt>Breaks</tt>, which prevents
5192 the broken package from being configured while the breaking
5193 package is in the "Unpacked" state but allows both packages to
5194 be unpacked at the same time.
5198 If one package is to be unpacked, the other must be removed
5199 first. If the package being unpacked is marked as replacing
5200 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5201 normally be used in this case) the one on the system, or the one
5202 on the system is marked as deselected, or both packages are
5203 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5204 automatically remove the package which is causing the conflict.
5205 Otherwise, it will halt the installation of the new package with
5206 an error. This mechanism is specifically designed to produce an
5207 error when the installed package is <tt>Essential</tt>, but the
5212 A package will not cause a conflict merely because its
5213 configuration files are still installed; it must be at least
5218 A special exception is made for packages which declare a
5219 conflict with their own package name, or with a virtual
5220 package which they provide (see below): this does not
5221 prevent their installation, and allows a package to conflict
5222 with others providing a replacement for it. You use this
5223 feature when you want the package in question to be the only
5224 package providing some feature.
5228 Normally, <tt>Breaks</tt> should be used instead
5229 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5230 stronger restriction on the ordering of package installation or
5231 upgrade and can make it more difficult for the package manager
5232 to find a correct solution to an upgrade or installation
5233 problem. <tt>Breaks</tt> should be used
5235 <item>when moving a file from one package to another (see
5236 <ref id="replaces">),</item>
5237 <item>when splitting a package (a special case of the previous
5239 <item>when the breaking package exposes a bug in or interacts
5240 badly with particular versions of the broken
5243 <tt>Conflicts</tt> should be used
5245 <item>when two packages provide the same file and will
5246 continue to do so,</item>
5247 <item>in conjunction with <tt>Provides</tt> when only one
5248 package providing a given virtual facility may be unpacked
5249 at a time (see <ref id="virtual">),</item>
5250 <item>in other cases where one must prevent simultaneous
5251 installation of two packages for reasons that are ongoing
5252 (not fixed in a later version of one of the packages) or
5253 that must prevent both packages from being unpacked at the
5254 same time, not just configured.</item>
5256 Be aware that adding <tt>Conflicts</tt> is normally not the best
5257 solution when two packages provide the same files. Depending on
5258 the reason for that conflict, using alternatives or renaming the
5259 files is often a better approach. See, for
5260 example, <ref id="binaries">.
5264 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5265 unless two packages cannot be installed at the same time or
5266 installing them both causes one of them to be broken or
5267 unusable. Having similar functionality or performing the same
5268 tasks as another package is not sufficient reason to
5269 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5273 A <tt>Conflicts</tt> entry may have an "earlier than" version
5274 clause if the reason for the conflict is corrected in a later
5275 version of one of the packages. However, normally the presence
5276 of an "earlier than" version clause is a sign
5277 that <tt>Breaks</tt> should have been used instead. An "earlier
5278 than" version clause in <tt>Conflicts</tt>
5279 prevents <prgn>dpkg</prgn> from upgrading or installing the
5280 package which declares such a conflict until the upgrade or
5281 removal of the conflicted-with package has been completed, which
5282 is a strong restriction.
5286 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5290 As well as the names of actual ("concrete") packages, the
5291 package relationship fields <tt>Depends</tt>,
5292 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5293 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5294 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5295 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5296 may mention "virtual packages".
5300 A <em>virtual package</em> is one which appears in the
5301 <tt>Provides</tt> control field of another package. The effect
5302 is as if the package(s) which provide a particular virtual
5303 package name had been listed by name everywhere the virtual
5304 package name appears. (See also <ref id="virtual_pkg">)
5308 If there are both concrete and virtual packages of the same
5309 name, then the dependency may be satisfied (or the conflict
5310 caused) by either the concrete package with the name in
5311 question or any other concrete package which provides the
5312 virtual package with the name in question. This is so that,
5313 for example, supposing we have
5314 <example compact="compact">
5317 </example> and someone else releases an enhanced version of
5318 the <tt>bar</tt> package they can say:
5319 <example compact="compact">
5323 and the <tt>bar-plus</tt> package will now also satisfy the
5324 dependency for the <tt>foo</tt> package.
5328 If a relationship field has a version number attached, only real
5329 packages will be considered to see whether the relationship is
5330 satisfied (or the prohibition violated, for a conflict or
5331 breakage). In other words, if a version number is specified,
5332 this is a request to ignore all <tt>Provides</tt> for that
5333 package name and consider only real packages. The package
5334 manager will assume that a package providing that virtual
5335 package is not of the "right" version. A <tt>Provides</tt>
5336 field may not contain version numbers, and the version number of
5337 the concrete package which provides a particular virtual package
5338 will not be considered when considering a dependency on or
5339 conflict with the virtual package name.<footnote>
5340 It is possible that a future release of <prgn>dpkg</prgn> may
5341 add the ability to specify a version number for each virtual
5342 package it provides. This feature is not yet present,
5343 however, and is expected to be used only infrequently.
5348 To specify which of a set of real packages should be the default
5349 to satisfy a particular dependency on a virtual package, list
5350 the real package as an alternative before the virtual one.
5354 If the virtual package represents a facility that can only be
5355 provided by one real package at a time, such as
5356 the <package>mail-transport-agent</package> virtual package that
5357 requires installation of a binary that would conflict with all
5358 other providers of that virtual package (see
5359 <ref id="mail-transport-agents">), all packages providing that
5360 virtual package should also declare a conflict with it
5361 using <tt>Conflicts</tt>. This will ensure that at most one
5362 provider of that virtual package is unpacked or installed at a
5367 <sect id="replaces"><heading>Overwriting files and replacing
5368 packages - <tt>Replaces</tt></heading>
5371 Packages can declare in their control file that they should
5372 overwrite files in certain other packages, or completely replace
5373 other packages. The <tt>Replaces</tt> control field has these
5374 two distinct purposes.
5377 <sect1><heading>Overwriting files in other packages</heading>
5380 It is usually an error for a package to contain files which
5381 are on the system in another package. However, if the
5382 overwriting package declares that it <tt>Replaces</tt> the one
5383 containing the file being overwritten, then <prgn>dpkg</prgn>
5384 will replace the file from the old package with that from the
5385 new. The file will no longer be listed as "owned" by the old
5386 package and will be taken over by the new package.
5387 Normally, <tt>Breaks</tt> should be used in conjunction
5388 with <tt>Replaces</tt>.<footnote>
5389 To see why <tt>Breaks</tt> is normally needed in addition
5390 to <tt>Replaces</tt>, consider the case of a file in the
5391 package <package>foo</package> being taken over by the
5392 package <package>foo-data</package>.
5393 <tt>Replaces</tt> will allow <package>foo-data</package> to
5394 be installed and take over that file. However,
5395 without <tt>Breaks</tt>, nothing
5396 requires <package>foo</package> to be upgraded to a newer
5397 version that knows it does not include that file and instead
5398 depends on <package>foo-data</package>. Nothing would
5399 prevent the new <package>foo-data</package> package from
5400 being installed and then removed, removing the file that it
5401 took over from <package>foo</package>. After that
5402 operation, the package manager would think the system was in
5403 a consistent state, but the <package>foo</package> package
5404 would be missing one of its files.
5409 For example, if a package <package>foo</package> is split
5410 into <package>foo</package> and <package>foo-data</package>
5411 starting at version 1.2-3, <package>foo-data</package> would
5413 <example compact="compact">
5414 Replaces: foo (<< 1.2-3)
5415 Breaks: foo (<< 1.2-3)
5417 in its control file. The new version of the
5418 package <package>foo</package> would normally have the field
5419 <example compact="compact">
5420 Depends: foo-data (>= 1.2-3)
5422 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5423 the files moved into <package>foo-data</package> are not
5424 required for normal operation).
5428 If a package is completely replaced in this way, so that
5429 <prgn>dpkg</prgn> does not know of any files it still
5430 contains, it is considered to have "disappeared". It will
5431 be marked as not wanted on the system (selected for
5432 removal) and "Not-Installed". Any <tt>conffile</tt>s
5433 details noted for the package will be ignored, as they
5434 will have been taken over by the overwriting package. The
5435 package's <prgn>postrm</prgn> script will be run with a
5436 special argument to allow the package to do any final
5437 cleanup required. See <ref id="mscriptsinstact">.
5439 Replaces is a one way relationship. You have to install
5440 the replacing package after the replaced package.
5445 For this usage of <tt>Replaces</tt>, virtual packages (see
5446 <ref id="virtual">) are not considered when looking at a
5447 <tt>Replaces</tt> field. The packages declared as being
5448 replaced must be mentioned by their real names.
5452 This usage of <tt>Replaces</tt> only takes effect when both
5453 packages are at least partially on the system at once. It is
5454 not relevant if the packages conflict unless the conflict has
5459 <sect1><heading>Replacing whole packages, forcing their
5463 Second, <tt>Replaces</tt> allows the packaging system to
5464 resolve which package should be removed when there is a
5465 conflict (see <ref id="conflicts">). This usage only takes
5466 effect when the two packages <em>do</em> conflict, so that the
5467 two usages of this field do not interfere with each other.
5471 In this situation, the package declared as being replaced
5472 can be a virtual package, so for example, all mail
5473 transport agents (MTAs) would have the following fields in
5474 their control files:
5475 <example compact="compact">
5476 Provides: mail-transport-agent
5477 Conflicts: mail-transport-agent
5478 Replaces: mail-transport-agent
5480 ensuring that only one MTA can be unpacked at any one
5481 time. See <ref id="virtual"> for more information about this
5486 <sect id="sourcebinarydeps">
5487 <heading>Relationships between source and binary packages -
5488 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5489 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5493 Source packages that require certain binary packages to be
5494 installed or absent at the time of building the package
5495 can declare relationships to those binary packages.
5499 This is done using the <tt>Build-Depends</tt>,
5500 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5501 <tt>Build-Conflicts-Indep</tt> control fields.
5505 Build-dependencies on "build-essential" binary packages can be
5506 omitted. Please see <ref id="pkg-relations"> for more information.
5510 The dependencies and conflicts they define must be satisfied
5511 (as defined earlier for binary packages) in order to invoke
5512 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5514 There is no Build-Depends-Arch; this role is essentially
5515 met with Build-Depends. Anyone building the
5516 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5517 assumed to be building the whole package, and therefore
5518 installation of all build dependencies is required.
5521 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5522 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5523 not yet know how to check for its existence, and
5524 <tt>binary-arch</tt>. The purpose of the original split
5525 between <tt>Build-Depends</tt> and
5526 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5527 wouldn't need to install extra packages needed only for the
5528 binary-indep targets. But without a build-arch/build-indep
5529 split, this didn't work, since most of the work is done in
5530 the build target, not in the binary target.
5534 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5535 <tt>binary-arch</tt></tag>
5537 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5538 fields must be satisfied when these targets are invoked.
5540 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5541 and <tt>binary-indep</tt></tag>
5543 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5544 <tt>Build-Depends-Indep</tt>, and
5545 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5546 these targets are invoked.
5552 <sect id="built-using">
5553 <heading>Additional source packages used to build the binary
5554 - <tt>Built-Using</tt>
5558 Some binary packages incorporate parts of other packages when built
5559 but do not have to depend on those packages. Examples include
5560 linking with static libraries or incorporating source code from
5561 another package during the build. In this case, the source packages
5562 of those other packages are a required part of the complete source
5563 (the binary package is not reproducible without them).
5567 A <tt>Built-Using</tt> field must list the corresponding source
5568 package for any such binary package incorporated during the build
5570 <tt>Build-Depends</tt> in the source package is not adequate since
5571 it (rightfully) does not document the exact version used in the
5574 including an "exactly equal" ("=") version relation on the version
5575 that was used to build that binary package<footnote>
5576 The archive software might reject packages that refer to
5577 non-existent sources.
5582 A package using the source code from the gcc-4.6-source
5583 binary package built from the gcc-4.6 source package would
5584 have this field in its control file:
5585 <example compact="compact">
5586 Built-Using: gcc-4.6 (= 4.6.0-11)
5591 A package including binaries from grub2 and loadlin would
5592 have this field in its control file:
5593 <example compact="compact">
5594 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5601 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5604 Packages containing shared libraries must be constructed with
5605 a little care to make sure that the shared library is always
5606 available. This is especially important for packages whose
5607 shared libraries are vitally important, such as the C library
5608 (currently <tt>libc6</tt>).
5612 This section deals only with public shared libraries: shared
5613 libraries that are placed in directories searched by the dynamic
5614 linker by default or which are intended to be linked against
5615 normally and possibly used by other, independent packages. Shared
5616 libraries that are internal to a particular package or that are
5617 only loaded as dynamic modules are not covered by this section and
5618 are not subject to its requirements.
5622 A shared library is identified by the <tt>SONAME</tt> attribute
5623 stored in its dynamic section. When a binary is linked against a
5624 shared library, the <tt>SONAME</tt> of the shared library is
5625 recorded in the binary's <tt>NEEDED</tt> section so that the
5626 dynamic linker knows that library must be loaded at runtime. The
5627 shared library file's full name (which usually contains additional
5628 version information not needed in the <tt>SONAME</tt>) is
5629 therefore normally not referenced directly. Instead, the shared
5630 library is loaded by its <tt>SONAME</tt>, which exists on the file
5631 system as a symlink pointing to the full name of the shared
5632 library. This symlink must be provided by the
5633 package. <ref id="sharedlibs-runtime"> describes how to do this.
5635 This is a convention of shared library versioning, but not a
5636 requirement. Some libraries use the <tt>SONAME</tt> as the full
5637 library file name instead and therefore do not need a symlink.
5638 Most, however, encode additional information about
5639 backwards-compatible revisions as a minor version number in the
5640 file name. The <tt>SONAME</tt> itself only changes when
5641 binaries linked with the earlier version of the shared library
5642 may no longer work, but the filename may change with each
5643 release of the library. See <ref id="sharedlibs-runtime"> for
5649 When linking a binary or another shared library against a shared
5650 library, the <tt>SONAME</tt> for that shared library is not yet
5651 known. Instead, the shared library is found by looking for a file
5652 matching the library name with <tt>.so</tt> appended. This file
5653 exists on the file system as a symlink pointing to the shared
5658 Shared libraries are normally split into several binary packages.
5659 The <tt>SONAME</tt> symlink is installed by the runtime shared
5660 library package, and the bare <tt>.so</tt> symlink is installed in
5661 the development package since it's only used when linking binaries
5662 or shared libraries. However, there are some exceptions for
5663 unusual shared libraries or for shared libraries that are also
5664 loaded as dynamic modules by other programs.
5668 This section is primarily concerned with how the separation of
5669 shared libraries into multiple packages should be done and how
5670 dependencies on and between shared library binary packages are
5671 managed in Debian. <ref id="libraries"> should be read in
5672 conjunction with this section and contains additional rules for
5673 the files contained in the shared library packages.
5676 <sect id="sharedlibs-runtime">
5677 <heading>Run-time shared libraries</heading>
5680 The run-time shared library must be placed in a package
5681 whose name changes whenever the <tt>SONAME</tt> of the shared
5682 library changes. This allows several versions of the shared
5683 library to be installed at the same time, allowing installation
5684 of the new version of the shared library without immediately
5685 breaking binaries that depend on the old version. Normally, the
5686 run-time shared library and its <tt>SONAME</tt> symlink should
5687 be placed in a package named
5688 <package><var>libraryname</var><var>soversion</var></package>,
5689 where <var>soversion</var> is the version number in
5690 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5691 would be confusing to directly append <var>soversion</var>
5692 to <var>libraryname</var> (if, for
5693 example, <var>libraryname</var> itself ends in a number), you
5695 <package><var>libraryname</var>-<var>soversion</var></package>
5700 To determine the <var>soversion</var>, look at
5701 the <tt>SONAME</tt> of the library, stored in the
5702 ELF <tt>SONAME</tt> attribute. It is usually of the
5703 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5704 example, <tt>libz.so.1</tt>). The version part is the part
5705 which comes after <tt>.so.</tt>, so in that example it
5706 is <tt>1</tt>. The soname may instead be of the
5707 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5708 as <tt>libdb-5.1.so</tt>, in which case the name would
5709 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5713 If you have several shared libraries built from the same source
5714 tree, you may lump them all together into a single shared
5715 library package provided that all of their <tt>SONAME</tt>s will
5716 always change together. Be aware that this is not normally the
5717 case, and if the <tt>SONAME</tt>s do not change together,
5718 upgrading such a merged shared library package will be
5719 unnecessarily difficult because of file conflicts with the old
5720 version of the package. When in doubt, always split shared
5721 library packages so that each binary package installs a single
5726 Every time the shared library ABI changes in a way that may
5727 break binaries linked against older versions of the shared
5728 library, the <tt>SONAME</tt> of the library and the
5729 corresponding name for the binary package containing the runtime
5730 shared library should change. Normally, this means
5731 the <tt>SONAME</tt> should change any time an interface is
5732 removed from the shared library or the signature of an interface
5733 (the number of parameters or the types of parameters that it
5734 takes, for example) is changed. This practice is vital to
5735 allowing clean upgrades from older versions of the package and
5736 clean transitions between the old ABI and new ABI without having
5737 to upgrade every affected package simultaneously.
5741 The <tt>SONAME</tt> and binary package name need not, and indeed
5742 normally should not, change if new interfaces are added but none
5743 are removed or changed, since this will not break binaries
5744 linked against the old shared library. Correct versioning of
5745 dependencies on the newer shared library by binaries that use
5746 the new interfaces is handled via
5747 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5748 or <tt>shlibs</tt> system</qref>.
5752 The package should install the shared libraries under
5753 their normal names. For example, the <package>libgdbm3</package>
5754 package should install <file>libgdbm.so.3.0.0</file> as
5755 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5756 renamed or re-linked by any <prgn>prerm</prgn> or
5757 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5758 of renaming things safely without affecting running programs,
5759 and attempts to interfere with this are likely to lead to
5764 Shared libraries should not be installed executable, since
5765 the dynamic linker does not require this and trying to
5766 execute a shared library usually results in a core dump.
5770 The run-time library package should include the symbolic link for
5771 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5772 the shared libraries. For example,
5773 the <package>libgdbm3</package> package should include a symbolic
5774 link from <file>/usr/lib/libgdbm.so.3</file> to
5775 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5776 linker (for example <prgn>ld.so</prgn> or
5777 <prgn>ld-linux.so.*</prgn>) can find the library between the
5778 time that <prgn>dpkg</prgn> installs it and the time that
5779 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5781 The package management system requires the library to be
5782 placed before the symbolic link pointing to it in the
5783 <file>.deb</file> file. This is so that when
5784 <prgn>dpkg</prgn> comes to install the symlink
5785 (overwriting the previous symlink pointing at an older
5786 version of the library), the new shared library is already
5787 in place. In the past, this was achieved by creating the
5788 library in the temporary packaging directory before
5789 creating the symlink. Unfortunately, this was not always
5790 effective, since the building of the tar file in the
5791 <file>.deb</file> depended on the behavior of the underlying
5792 file system. Some file systems (such as reiserfs) reorder
5793 the files so that the order of creation is forgotten.
5794 Since version 1.7.0, <prgn>dpkg</prgn>
5795 reorders the files itself as necessary when building a
5796 package. Thus it is no longer important to concern
5797 oneself with the order of file creation.
5801 <sect1 id="ldconfig">
5802 <heading><tt>ldconfig</tt></heading>
5805 Any package installing shared libraries in one of the default
5806 library directories of the dynamic linker (which are currently
5807 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5808 listed in <file>/etc/ld.so.conf</file><footnote>
5809 These are currently <file>/usr/local/lib</file> plus
5810 directories under <file>/lib</file> and <file>/usr/lib</file>
5811 matching the multiarch triplet for the system architecture.
5813 must use <prgn>ldconfig</prgn> to update the shared library
5818 The package maintainer scripts must only call
5819 <prgn>ldconfig</prgn> under these circumstances:
5820 <list compact="compact">
5821 <item>When the <prgn>postinst</prgn> script is run with a
5822 first argument of <tt>configure</tt>, the script must call
5823 <prgn>ldconfig</prgn>, and may optionally invoke
5824 <prgn>ldconfig</prgn> at other times.
5826 <item>When the <prgn>postrm</prgn> script is run with a
5827 first argument of <tt>remove</tt>, the script should call
5828 <prgn>ldconfig</prgn>.
5833 During install or upgrade, the preinst is called before
5834 the new files are unpacked, so calling "ldconfig" is
5835 pointless. The preinst of an existing package can also be
5836 called if an upgrade fails. However, this happens during
5837 the critical time when a shared libs may exist on-disk
5838 under a temporary name. Thus, it is dangerous and
5839 forbidden by current policy to call "ldconfig" at this
5844 When a package is installed or upgraded, "postinst
5845 configure" runs after the new files are safely on-disk.
5846 Since it is perfectly safe to invoke ldconfig
5847 unconditionally in a postinst, it is OK for a package to
5848 simply put ldconfig in its postinst without checking the
5849 argument. The postinst can also be called to recover from
5850 a failed upgrade. This happens before any new files are
5851 unpacked, so there is no reason to call "ldconfig" at this
5856 For a package that is being removed, prerm is
5857 called with all the files intact, so calling ldconfig is
5858 useless. The other calls to "prerm" happen in the case of
5859 upgrade at a time when all the files of the old package
5860 are on-disk, so again calling "ldconfig" is pointless.
5864 postrm, on the other hand, is called with the "remove"
5865 argument just after the files are removed, so this is
5866 the proper time to call "ldconfig" to notify the system
5867 of the fact that the shared libraries from the package
5868 are removed. The postrm can be called at several other
5869 times. At the time of "postrm purge", "postrm
5870 abort-install", or "postrm abort-upgrade", calling
5871 "ldconfig" is useless because the shared lib files are
5872 not on-disk. However, when "postrm" is invoked with
5873 arguments "upgrade", "failed-upgrade", or "disappear", a
5874 shared lib may exist on-disk under a temporary filename.
5882 <sect id="sharedlibs-support-files">
5883 <heading>Shared library support files</heading>
5886 If your package contains files whose names do not change with
5887 each change in the library shared object version, you must not
5888 put them in the shared library package. Otherwise, several
5889 versions of the shared library cannot be installed at the same
5890 time without filename clashes, making upgrades and transitions
5891 unnecessarily difficult.
5895 It is recommended that supporting files and run-time support
5896 programs that do not need to be invoked manually by users, but
5897 are nevertheless required for the package to function, be placed
5898 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5899 preferably under <file>/usr/lib/</file><var>package-name</var>.
5900 If the program or file is architecture independent, the
5901 recommendation is for it to be placed in a subdirectory of
5902 <file>/usr/share</file> instead, preferably under
5903 <file>/usr/share/</file><var>package-name</var>. Following the
5904 <var>package-name</var> naming convention ensures that the file
5905 names change when the shared object version changes.
5909 Run-time support programs that use the shared library but are
5910 not required for the library to function or files used by the
5911 shared library that can be used by any version of the shared
5912 library package should instead be put in a separate package.
5913 This package might typically be named
5914 <package><var>libraryname</var>-tools</package>; note the
5915 absence of the <var>soversion</var> in the package name.
5919 Files and support programs only useful when compiling software
5920 against the library should be included in the development
5921 package for the library.<footnote>
5922 For example, a <file><var>package-name</var>-config</file>
5923 script or <package>pkg-config</package> configuration files.
5928 <sect id="sharedlibs-static">
5929 <heading>Static libraries</heading>
5932 The static library (<file><var>libraryname.a</var></file>)
5933 is usually provided in addition to the shared version.
5934 It is placed into the development package (see below).
5938 In some cases, it is acceptable for a library to be
5939 available in static form only; these cases include:
5941 <item>libraries for languages whose shared library support
5942 is immature or unstable</item>
5943 <item>libraries whose interfaces are in flux or under
5944 development (commonly the case when the library's
5945 major version number is zero, or where the ABI breaks
5946 across patchlevels)</item>
5947 <item>libraries which are explicitly intended to be
5948 available only in static form by their upstream
5953 <sect id="sharedlibs-dev">
5954 <heading>Development files</heading>
5957 If there are development files associated with a shared library,
5958 the source package needs to generate a binary development package
5959 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5960 or if you prefer only to support one development version at a
5961 time, <package><var>libraryname</var>-dev</package>. Installing
5962 the development package must result in installation of all the
5963 development files necessary for compiling programs against that
5964 shared library.<footnote>
5965 This wording allows the development files to be split into
5966 several packages, such as a separate architecture-independent
5967 <package><var>libraryname</var>-headers</package>, provided that
5968 the development package depends on all the required additional
5974 In case several development versions of a library exist, you may
5975 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5976 <ref id="conflicts">) to ensure that the user only installs one
5977 development version at a time (as different development versions are
5978 likely to have the same header files in them, which would cause a
5979 filename clash if both were unpacked).
5983 The development package should contain a symlink for the associated
5984 shared library without a version number. For example, the
5985 <package>libgdbm-dev</package> package should include a symlink
5986 from <file>/usr/lib/libgdbm.so</file> to
5987 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5988 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5989 <file>libgdbm.so</file> when compiling dynamically.
5993 If the package provides Ada Library Information
5994 (<file>*.ali</file>) files for use with GNAT, these files must be
5995 installed read-only (mode 0444) so that GNAT will not attempt to
5996 recompile them. This overrides the normal file mode requirements
5997 given in <ref id="permissions-owners">.
6001 <sect id="sharedlibs-intradeps">
6002 <heading>Dependencies between the packages of the same library</heading>
6005 Typically the development version should have an exact
6006 version dependency on the runtime library, to make sure that
6007 compilation and linking happens correctly. The
6008 <tt>${binary:Version}</tt> substitution variable can be
6009 useful for this purpose.
6011 Previously, <tt>${Source-Version}</tt> was used, but its name
6012 was confusing and it has been deprecated since dpkg 1.13.19.
6017 <sect id="sharedlibs-depends">
6018 <heading>Dependencies between the library and other
6022 If a package contains a binary or library which links to a
6023 shared library, we must ensure that, when the package is
6024 installed on the system, all of the libraries needed are also
6025 installed. These dependencies must be added to the binary
6026 package when it is built, since they may change based on which
6027 version of a shared library the binary or library was linked
6028 with even if there are no changes to the source of the binary
6029 (for example, symbol versions change, macros become functions or
6030 vice versa, or the binary package may determine at compile-time
6031 whether new library interfaces are available and can be called).
6032 To allow these dependencies to be constructed, shared libraries
6033 must provide either a <file>symbols</file> file or
6034 a <file>shlibs</file> file. These provide information on the
6035 package dependencies required to ensure the presence of
6036 interfaces provided by this library. Any package with binaries
6037 or libraries linking to a shared library must use these files to
6038 determine the required dependencies when it is built. Other
6039 packages which use a shared library (for example using
6040 <tt>dlopen()</tt>) should compute appropriate dependencies
6041 using these files at build time as well.
6045 The two mechanisms differ in the degree of detail that they
6046 provide. A <file>symbols</file> file documents, for each symbol
6047 exported by a library, the minimal version of the package any
6048 binary using this symbol will need. This is typically the
6049 version of the package in which the symbol was introduced. This
6050 information permits detailed analysis of the symbols used by a
6051 particular package and construction of an accurate dependency,
6052 but it requires the package maintainer to track more information
6053 about the shared library.
6057 A <file>shlibs</file> file, in contrast, only documents the last
6058 time the library ABI changed in any way. It only provides
6059 information about the library as a whole, not individual
6060 symbols. When a package is built using a shared library with
6061 only a <file>shlibs</file> file, the generated dependency will
6062 require a version of the shared library equal to or newer than
6063 the version of the last ABI change. This generates
6064 unnecessarily restrictive dependencies compared
6065 to <file>symbols</file> files if none of the symbols used by the
6066 package have changed. This, in turn, may make upgrades
6067 needlessly complex and unnecessarily restrict use of the package
6068 on systems with older versions of the shared libraries.
6072 <file>shlibs</file> files also only support a limited range of
6073 library SONAMEs, making it difficult to use <file>shlibs</file>
6074 files in some unusual corner cases.<footnote>
6075 A <file>shlibs</file> file represents an SONAME as a library
6076 name and version number, such as <tt>libfoo VERSION</tt>,
6077 instead of recording the actual SONAME. If the SONAME doesn't
6078 match one of the two expected formats
6079 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6080 cannot be represented.
6085 <file>symbols</file> files are therefore recommended for most
6086 shared library packages since they provide more accurate
6087 dependencies. For most C libraries, the additional detail
6088 required by <file>symbols</file> files is not too difficult to
6089 maintain. However, maintaining exhaustive symbols information
6090 for a C++ library can be quite onerous, so <file>shlibs</file>
6091 files may be more appropriate for most C++ libraries. Libraries
6092 with a corresponding udeb must also provide
6093 a <file>shlibs</file> file, since the udeb infrastructure does
6094 not use <file>symbols</file> files.
6097 <sect1 id="dpkg-shlibdeps">
6098 <heading>Generating dependencies on shared libraries</heading>
6101 When a package that contains any shared libraries or compiled
6102 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6103 each shared library and compiled binary to determine the
6104 libraries used and hence the dependencies needed by the
6106 <prgn>dpkg-shlibdeps</prgn> will use a program
6107 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6108 the libraries and the symbols in those libraries directly
6109 needed by the binaries or shared libraries in the package.
6111 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6112 your <file>debian/rules</file> file in the source package.
6113 List all of the compiled binaries, libraries, or loadable
6114 modules in your package.<footnote>
6115 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6116 correctly is to use a package helper framework such
6117 as <package>debhelper</package>. If you are
6118 using <package>debhelper</package>,
6119 the <prgn>dh_shlibdeps</prgn> program will do this work for
6120 you. It will also correctly handle multi-binary packages.
6122 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6123 or <file>shlibs</file> files installed by the shared libraries
6124 to generate dependency information. The package must then
6125 provide a substitution variable into which the discovered
6126 dependency information can be placed.
6130 If you are creating a udeb for use in the Debian Installer,
6131 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6132 should use the dependency line of type <tt>udeb</tt> by adding
6133 the <tt>-tudeb</tt> option<footnote>
6134 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6135 will automatically add this option if it knows it is
6137 </footnote>. If there is no dependency line of
6138 type <tt>udeb</tt> in the <file>shlibs</file>
6139 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6140 regular dependency line.
6144 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6145 into the <file>debian/substvars</file> file by default, which
6146 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6147 to place a <tt>${shlibs:Depends}</tt> variable in
6148 the <tt>Depends</tt> field in the control file of every binary
6149 package built by this source package that contains compiled
6150 binaries, libraries, or loadable modules. If you have
6151 multiple binary packages, you will need to
6152 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6153 compiled libraries or binaries. For example, you could use
6154 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6155 specify a different <file>substvars</file> file for each
6156 binary package.<footnote>
6157 Again, <prgn>dh_shlibdeps</prgn>
6158 and <prgn>dh_gencontrol</prgn> will handle everything except
6159 the addition of the variable to the control file for you if
6160 you're using <package>debhelper</package>, including
6161 generating separate <file>substvars</file> files for each
6162 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6163 the appropriate flags.
6168 For more details on <prgn>dpkg-shlibdeps</prgn>,
6169 see <manref name="dpkg-shlibdeps" section="1">.
6173 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6174 library <tt>libbar</tt> if it is explicitly linked with that
6175 library (that is, the library is listed in the
6176 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6177 to the link line when the binary is created). Other libraries
6178 that are needed by <tt>libbar</tt> are
6179 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6180 linker will load them automatically when it
6181 loads <tt>libbar</tt>. A package should depend on the
6182 libraries it directly uses, but not the libraries it only uses
6183 indirectly. The dependencies for the libraries used
6184 directly will automatically pull in the indirectly-used
6185 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6186 automatically, but package maintainers need to be aware of
6187 this distinction between directly and indirectly using a
6188 library if they have to override its results for some reason.
6190 A good example of where this helps is the following. We
6191 could update <tt>libimlib</tt> with a new version that
6192 supports a new revision of a graphics format called dgf (but
6193 retaining the same major version number) and depends on a
6194 new library package <package>libdgf4</package> instead of
6195 the older <package>libdgf3</package>. If we
6196 used <prgn>ldd</prgn> to add dependencies for every library
6197 directly or indirectly linked with a binary, every package
6198 that uses <tt>libimlib</tt> would need to be recompiled so
6199 it would also depend on <package>libdgf4</package> in order
6200 to retire the older <package>libdgf3</package> package.
6201 Since dependencies are only added based on
6202 ELF <tt>NEEDED</tt> attribute, packages
6203 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6204 having the dependency on an appropriate version
6205 of <tt>libdgf</tt> and do not need rebuilding.
6210 <sect1 id="sharedlibs-updates">
6211 <heading>Shared library ABI changes</heading>
6214 Maintaining a shared library package using
6215 either <file>symbols</file> or <file>shlibs</file> files
6216 requires being aware of the exposed ABI of the shared library
6217 and any changes to it. Both <file>symbols</file>
6218 and <file>shlibs</file> files record every change to the ABI
6219 of the shared library; <file>symbols</file> files do so per
6220 public symbol, whereas <file>shlibs</file> files record only
6221 the last change for the entire library.
6225 There are two types of ABI changes: ones that are
6226 backward-compatible and ones that are not. An ABI change is
6227 backward-compatible if any reasonable program or library that
6228 was linked with the previous version of the shared library
6229 will still work correctly with the new version of the shared
6231 An example of an "unreasonable" program is one that uses
6232 library interfaces that are documented as internal and
6233 unsupported. If the only programs or libraries affected by
6234 a change are "unreasonable" ones, other techniques, such as
6235 declaring <tt>Breaks</tt> relationships with affected
6236 packages or treating their usage of the library as bugs in
6237 those packages, may be appropriate instead of changing the
6238 SONAME. However, the default approach is to change the
6239 SONAME for any change to the ABI that could break a program.
6241 Adding new symbols to the shared library is a
6242 backward-compatible change. Removing symbols from the shared
6243 library is not. Changing the behavior of a symbol may or may
6244 not be backward-compatible depending on the change; for
6245 example, changing a function to accept a new enum constant not
6246 previously used by the library is generally
6247 backward-compatible, but changing the members of a struct that
6248 is passed into library functions is generally not unless the
6249 library takes special precautions to accept old versions of
6254 ABI changes that are not backward-compatible normally require
6255 changing the <tt>SONAME</tt> of the library and therefore the
6256 shared library package name, which forces rebuilding all
6257 packages using that shared library to update their
6258 dependencies and allow them to use the new version of the
6259 shared library. For more information,
6260 see <ref id="sharedlibs-runtime">. The remainder of this
6261 section will deal with backward-compatible changes.
6265 Backward-compatible changes require either updating or
6266 recording the <var>minimal-version</var> for that symbol
6267 in <file>symbols</file> files or updating the version in
6268 the <var>dependencies</var> in <file>shlibs</file> files. For
6269 more information on how to do this in the two formats, see
6270 <ref id="symbols"> and <ref id="shlibs">. Below are general
6271 rules that apply to both files.
6275 The easy case is when a public symbol is added. Simply add
6276 the version at which the symbol was introduced
6277 (for <file>symbols</file> files) or update the dependency
6278 version (for <file>shlibs</file>) files. But special care
6279 should be taken to update dependency versions when the
6280 behavior of a public symbol changes. This is easy to neglect,
6281 since there is no automated method of determining such
6282 changes, but failing to update versions in this case may
6283 result in binary packages with too-weak dependencies that will
6284 fail at runtime, possibly in ways that can cause security
6285 vulnerabilities. If the package maintainer believes that a
6286 symbol behavior change may have occurred but isn't sure, it's
6287 safer to update the version rather than leave it unmodified.
6288 This may result in unnecessarily strict dependencies, but it
6289 ensures that packages whose dependencies are satisfied will
6294 A common example of when a change to the dependency version
6295 is required is a function that takes an enum or struct
6296 argument that controls what the function does. For example:
6298 enum library_op { OP_FOO, OP_BAR };
6299 int library_do_operation(enum library_op);
6301 If a new operation, <tt>OP_BAZ</tt>, is added,
6302 the <var>minimal-version</var>
6303 of <tt>library_do_operation</tt> (for <file>symbols</file>
6304 files) or the version in the dependency for the shared library
6305 (for <file>shlibs</file> files) must be increased to the
6306 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6307 binary built against the new version of the library (having
6308 detected at compile-time that the library
6309 supports <tt>OP_BAZ</tt>) may be installed with a shared
6310 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6311 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6316 Dependency versions in either <file>symbols</file>
6317 or <file>shlibs</file> files normally should not contain the
6318 Debian revision of the package, since the library behavior is
6319 normally fixed for a particular upstream version and any
6320 Debian packaging of that upstream version will have the same
6321 behavior. In the rare case that the library behavior was
6322 changed in a particular Debian revision, appending <tt>~</tt>
6323 to the end of the version that includes the Debian revision is
6324 recommended, since this allows backports of the shared library
6325 package using the normal backport versioning convention to
6326 satisfy the dependency.
6330 <sect1 id="sharedlibs-symbols">
6331 <heading>The <tt>symbols</tt> system</heading>
6334 In the following sections, we will first describe where the
6335 various <file>symbols</file> files are to be found, then
6336 the <file>symbols</file> file format, and finally how to
6337 create <file>symbols</file> files if your package contains a
6341 <sect2 id="symbols-paths">
6342 <heading>The <file>symbols</file> files present on the
6346 <file>symbols</file> files for a shared library are normally
6347 provided by the shared library package as a control file,
6348 but there are several override paths that are checked first
6349 in case that information is wrong or missing. The following
6350 list gives them in the order in which they are read
6351 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6352 the required information is used.
6355 <p><file>debian/*/DEBIAN/symbols</file></p>
6358 During the package build, if the package itself
6359 contains shared libraries with <file>symbols</file>
6360 files, they will be generated in these staging
6361 directories by <prgn>dpkg-gensymbols</prgn>
6362 (see <ref id="providing-symbols">). <file>symbols</file>
6363 files found in the build tree take precedence
6364 over <file>symbols</file> files from other binary
6369 These files must exist
6370 before <prgn>dpkg-shlibdeps</prgn> is run or the
6371 dependencies of binaries and libraries from a source
6372 package on other libraries from that same source
6373 package will not be correct. In practice, this means
6374 that <prgn>dpkg-gensymbols</prgn> must be run
6375 before <prgn>dpkg-shlibdeps</prgn> during the package
6377 An example may clarify. Suppose the source
6378 package <tt>foo</tt> generates two binary
6379 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6380 When building the binary packages, the contents of
6381 the packages are staged in the
6382 directories <file>debian/libfoo2</file>
6383 and <file>debian/foo-runtime</file> respectively.
6384 (<file>debian/tmp</file> could be used instead of
6385 one of these.) Since <tt>libfoo2</tt> provides
6386 the <tt>libfoo</tt> shared library, it will contain
6387 a <tt>symbols</tt> file, which will be installed
6388 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6389 eventually to be included as a control file in that
6390 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6392 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6394 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6395 to determine whether <tt>foo-prog</tt>'s library
6396 dependencies are satisfied by any of the libraries
6397 provided by <tt>libfoo2</tt>. Since those binaries
6398 were linked against the just-built shared library as
6399 part of the build process, the <file>symbols</file>
6400 file for the newly-built <tt>libfoo2</tt> must take
6401 precedence over a <file>symbols</file> file for any
6402 other <tt>libfoo2</tt> package already installed on
6410 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6411 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6415 Per-system overrides of shared library dependencies.
6416 These files normally do not exist. They are
6417 maintained by the local system administrator and must
6418 not be created by any Debian package.
6423 <p><file>symbols</file> control files for packages
6424 installed on the system</p>
6427 The <file>symbols</file> control files for all the
6428 packages currently installed on the system are
6429 searched last. This will be the most common source of
6430 shared library dependency information. These are
6432 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6433 packages should not rely on this and instead should
6434 use <tt>dpkg-query --control-path <var>package</var>
6435 symbols</tt> if for some reason these files need to be
6443 Be aware that if a <file>debian/shlibs.local</file> exists
6444 in the source package, it will override
6445 any <file>symbols</file> files. This is the only case where
6446 a <file>shlibs</file> is used despite <file>symbols</file>
6447 files being present. See <ref id="shlibs-paths">
6448 and <ref id="sharedlibs-shlibdeps"> for more information.
6452 <sect2 id="symbols">
6453 <heading>The <file>symbols</file> File Format</heading>
6456 The following documents the format of
6457 the <file>symbols</file> control file as included in binary
6458 packages. These files are built from
6459 template <file>symbols</file> files in the source package
6460 by <prgn>dpkg-gensymbols</prgn>. The template files support
6461 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6462 do some of the tedious work involved in
6463 maintaining <file>symbols</file> files, such as handling C++
6464 symbols or optional symbols that may not exist on particular
6465 architectures. When writing <file>symbols</file> files for
6466 a shared library package, refer
6467 to <manref name="dpkg-gensymbols" section="1"> for the
6472 A <file>symbols</file> may contain one or more entries, one
6473 for each shared library contained in the package
6474 corresponding to that <file>symbols</file>. Each entry has
6475 the following format:
6480 <var>library-soname</var> <var>main-dependency-template</var>
6481 [| <var>alternative-dependency-template</var>]
6483 [* <var>field-name</var>: <var>field-value</var>]
6485 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6490 To explain this format, we'll use the the <tt>zlib1g</tt>
6491 package as an example, which (at the time of writing)
6493 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6494 lines will be described first, followed by optional lines.
6498 <var>library-soname</var> must contain exactly the value of
6499 the ELF <tt>SONAME</tt> attribute of the shared library. In
6500 our example, this is <tt>libz.so.1</tt>.<footnote>
6501 This can be determined by using the command
6502 <example compact="compact">
6503 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6509 <var>main-dependency-template</var> has the same syntax as a
6510 dependency field in a binary package control file, except
6511 that the string <tt>#MINVER#</tt> is replaced by a version
6512 restriction like <tt>(>= <var>version</var>)</tt> or by
6513 nothing if an unversioned dependency is deemed sufficient.
6514 The version restriction will be based on which symbols from
6515 the shared library are referenced and the version at which
6516 they were introduced (see below). In nearly all
6517 cases, <var>main-dependency-template</var> will
6518 be <tt><var>package</var> #MINVER#</tt>,
6519 where <var>package</var> is the name of the binary package
6520 containing the shared library. This adds a simple,
6521 possibly-versioned dependency on the shared library package.
6522 In some rare cases, such as when multiple packages provide
6523 the same shared library ABI, the dependency template may
6524 need to be more complex.
6528 In our example, the first line of
6529 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6530 <example compact="compact">
6531 libz.so.1 zlib1g #MINVER#
6536 Each public symbol exported by the shared library must have
6537 a corresponding symbol line, indented by one
6538 space. <var>symbol</var> is the exported symbol (which, for
6539 C++, means the mangled symbol) followed by <tt>@</tt> and
6540 the symbol version, or the string <tt>Base</tt> if there is
6541 no symbol version. <var>minimal-version</var> is the most
6542 recent version of the shared library that changed the
6543 behavior of that symbol, whether by adding it, changing its
6544 function signature (the parameters, their types, or the
6545 return type), or changing its behavior in a way that is
6546 visible to a caller.
6547 <var>id-of-dependency-template</var> is an optional
6548 field that references
6549 an <var>alternative-dependency-template</var>; see below for
6554 For example, <tt>libz.so.1</tt> contains the
6555 symbols <tt>compress</tt>
6556 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6557 version and last changed its behavior in upstream
6558 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6559 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6560 upstream version <tt>1:1.2.0</tt>, and has not changed its
6561 behavior. Its <file>symbols</file> file therefore contains
6563 <example compact="compact">
6564 compress@Base 1:1.1.4
6565 compressBound@ZLIB_1.2.0 1:1.2.0
6567 Packages using only <tt>compress</tt> would then get a
6568 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6569 using <tt>compressBound</tt> would get a dependency
6570 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6574 One or more <var>alternative-dependency-template</var> lines
6575 may be provided. These are used in cases where some symbols
6576 in the shared library should use one dependency template
6577 while others should use a different template. The
6578 alternative dependency templates are used only if a symbol
6579 line contains the <var>id-of-dependency-template</var>
6580 field. The first alternative dependency template is
6581 numbered 1, the second 2, and so forth.<footnote>
6582 An example of where this may be needed is with a library
6583 that implements the libGL interface. All GL
6584 implementations provide the same set of base interfaces,
6585 and then may provide some additional interfaces only used
6586 by programs that require that specific GL implementation.
6587 So, for example, libgl1-mesa-glx may use the
6588 following <file>symbols</file> file:
6591 | libgl1-mesa-glx #MINVER#
6592 publicGlSymbol@Base 6.3-1
6594 implementationSpecificSymbol@Base 6.5.2-7 1
6597 Binaries or shared libraries using
6598 only <tt>publicGlSymbol</tt> would depend only
6599 on <tt>libgl1</tt> (which may be provided by multiple
6601 using <tt>implementationSpecificSymbol</tt> would get a
6602 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6607 Finally, the entry for the library may contain one or more
6608 metadata fields. Currently, the only
6609 supported <var>field-name</var>
6610 is <tt>Build-Depends-Package</tt>, whose value lists
6611 the <qref id="sharedlibs-dev">library development
6612 package</qref> on which packages using this shared library
6613 declare a build dependency. If this field is
6614 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6615 the resulting binary package dependency on the shared
6616 library is at least as strict as the source package
6617 dependency on the shared library development
6619 This field should normally not be necessary, since if the
6620 behavior of any symbol has changed, the corresponding
6621 symbol <var>minimal-version</var> should have been
6622 increased. But including it makes the <tt>symbols</tt>
6623 system more robust by tightening the dependency in cases
6624 where the package using the shared library specifically
6625 requires at least a particular version of the shared
6626 library development package for some reason.
6628 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6630 <example compact="compact">
6631 * Build-Depends-Package: zlib1g-dev
6636 Also see <manref name="deb-symbols" section="5">.
6640 <sect2 id="providing-symbols">
6641 <heading>Providing a <file>symbols</file> file</heading>
6644 If your package provides a shared library, you should
6645 arrange to include a <file>symbols</file> control file
6646 following the format described above in that package. You
6647 must include either a <file>symbols</file> control file or
6648 a <file>shlibs</file> control file.
6652 Normally, this is done by creating a <file>symbols</file> in
6654 named <file>debian/<var>package</var>.symbols</file>
6655 or <file>debian/symbols</file>, possibly
6656 with <file>.<var>arch</var></file> appended if the symbols
6657 information varies by architecture. This file may use the
6658 extended syntax documented in <manref name="dpkg-gensymbols"
6659 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6660 part of the package build process. It will
6661 create <file>symbols</file> files in the package staging
6662 area based on the binaries and libraries in the package
6663 staging area and the <file>symbols</file> files in the
6664 source package.<footnote>
6666 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6667 take care of calling either <prgn>dpkg-gensymbols</prgn>
6668 or generating a <file>shlibs</file> file as appropriate.
6673 Packages that provide <file>symbols</file> files must keep
6674 them up-to-date to ensure correct dependencies in packages
6675 that use the shared libraries. This means updating
6676 the <file>symbols</file> file whenever a new public symbol
6677 is added, changing the <var>minimal-version</var> field
6678 whenever a symbol changes behavior or signature in a
6679 backward-compatible way (see <ref id="sharedlibs-updates">),
6680 and changing the <var>library-soname</var>
6681 and <var>main-dependency-template</var>, and probably all of
6682 the <var>minimal-version</var> fields, when the library
6683 changes <tt>SONAME</tt>. Removing a public symbol from
6684 the <file>symbols</file> file because it's no longer
6685 provided by the library normally requires changing
6686 the <tt>SONAME</tt> of the library.
6687 See <ref id="sharedlibs-runtime"> for more information
6688 on <tt>SONAME</tt>s.
6693 <sect1 id="sharedlibs-shlibdeps">
6694 <heading>The <tt>shlibs</tt> system</heading>
6697 The <tt>shlibs</tt> system is a simpler alternative to
6698 the <tt>symbols</tt> system for declaring dependencies for
6699 shared libraries. It may be more appropriate for C++
6700 libraries and other cases where tracking individual symbols is
6701 too difficult. It predated the <tt>symbols</tt> system and is
6702 therefore frequently seen in older packages. It is also
6703 required for udebs, which do not support <tt>symbols</tt>.
6707 In the following sections, we will first describe where the
6708 various <file>shlibs</file> files are to be found, then how to
6709 use <prgn>dpkg-shlibdeps</prgn>, and finally
6710 the <file>shlibs</file> file format and how to create them.
6713 <sect2 id="shlibs-paths">
6714 <heading>The <file>shlibs</file> files present on the
6718 There are several places where <tt>shlibs</tt> files are
6719 found. The following list gives them in the order in which
6720 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6721 one which gives the required information is used.)
6724 <p><file>debian/shlibs.local</file></p>
6727 This lists overrides for this package. This file
6728 should normally not be used, but may be needed
6729 temporarily in unusual situations to work around bugs
6730 in other packages, or in unusual cases where the
6731 normally declared dependency information in the
6732 installed <file>shlibs</file> file for a library
6733 cannot be used. This file overrides information
6734 obtained from any other source.
6739 <p><file>/etc/dpkg/shlibs.override</file></p>
6742 This lists global overrides. This list is normally
6743 empty. It is maintained by the local system
6749 <p><file>DEBIAN/shlibs</file> files in the "build
6753 These files are generated as part of the package build
6754 process and staged for inclusion as control files in
6755 the binary packages being built. They provide details
6756 of any shared libraries included in the same package.
6761 <p><file>shlibs</file> control files for packages
6762 installed on the system</p>
6765 The <file>shlibs</file> control files for all the
6766 packages currently installed on the system. These are
6768 in <file>/var/lib/dpkg/info/*.shlibs</file>, but
6769 packages should not rely on this and instead should
6770 use <tt>dpkg-query --control-path <var>package</var>
6771 shlibs</tt> if for some reason these files need to be
6777 <p><file>/etc/dpkg/shlibs.default</file></p>
6780 This file lists any shared libraries whose packages
6781 have failed to provide correct <file>shlibs</file>
6782 files. It was used when the <file>shlibs</file> setup
6783 was first introduced, but it is now normally empty.
6784 It is maintained by the <tt>dpkg</tt> maintainer.
6791 If a <file>symbols</file> file for a shared library package
6792 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6793 in preference to a <file>shlibs</file>, with the exception
6794 of <file>debian/shlibs.local</file>. The latter overrides
6795 any other <file>shlibs</file> or <file>symbols</file> files.
6800 <heading>The <file>shlibs</file> File Format</heading>
6803 Each <file>shlibs</file> file has the same format. Lines
6804 beginning with <tt>#</tt> are considered to be comments and
6805 are ignored. Each line is of the form:
6806 <example compact="compact">
6807 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6812 We will explain this by reference to the example of the
6813 <tt>zlib1g</tt> package, which (at the time of writing)
6815 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6819 <var>type</var> is an optional element that indicates the
6820 type of package for which the line is valid. The only type
6821 currently in use is <tt>udeb</tt>. The colon and space
6822 after the type are required.
6826 <var>library-name</var> is the name of the shared library,
6827 in this case <tt>libz</tt>. (This must match the name part
6828 of the soname, see below.)
6832 <var>soname-version</var> is the version part of the
6833 ELF <tt>SONAME</tt> attribute of the library, determined the
6834 same way that the <var>soversion</var> component of the
6835 recommended shared library package name is determined.
6836 See <ref id="sharedlibs-runtime"> for the details.
6840 <var>dependencies</var> has the same syntax as a dependency
6841 field in a binary package control file. It should give
6842 details of which packages are required to satisfy a binary
6843 built against the version of the library contained in the
6844 package. See <ref id="depsyntax"> for details on the
6845 syntax, and <ref id="sharedlibs-updates"> for details on how
6846 to maintain the dependency version constraint.
6850 In our example, if the last change to the <tt>zlib1g</tt>
6851 package that could change behavior for a client of that
6852 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6853 the <tt>shlibs</tt> entry for this library could say:
6854 <example compact="compact">
6855 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6857 This version restriction must be new enough that any binary
6858 built against the current version of the library will work
6859 with any version of the shared library that satisfies that
6864 As zlib1g also provides a udeb containing the shared
6865 library, there would also be a second line:
6866 <example compact="compact">
6867 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6873 <heading>Providing a <file>shlibs</file> file</heading>
6876 To provide a <file>shlibs</file> file for a shared library
6877 binary package, create a <file>shlibs</file> file following
6878 the format described above and place it in
6879 the <file>DEBIAN</file> directory for that package during
6880 the build. It will then be included as a control file for
6881 that package<footnote>
6882 This is what <prgn>dh_makeshlibs</prgn> in
6883 the <package>debhelper</package> suite does. If your
6884 package also has a udeb that provides a shared
6885 library, <prgn>dh_makeshlibs</prgn> can automatically
6886 generate the <tt>udeb:</tt> lines if you specify the name
6887 of the udeb with the <tt>--add-udeb</tt> option.
6892 Since <prgn>dpkg-shlibdeps</prgn> reads
6893 the <file>DEBIAN/shlibs</file> files in all of the binary
6894 packages being built from this source package, all of
6895 the <file>DEBIAN/shlibs</file> files should be installed
6896 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6905 <chapt id="opersys"><heading>The Operating System</heading>
6908 <heading>File system hierarchy</heading>
6912 <heading>File System Structure</heading>
6915 The location of all files and directories must comply with the
6916 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6917 exceptions noted below, and except where doing so would
6918 violate other terms of Debian Policy. The following
6919 exceptions to the FHS apply:
6924 The FHS requirement that architecture-independent
6925 application-specific static files be located in
6926 <file>/usr/share</file> is relaxed to a suggestion.
6928 In particular, a subdirectory of <file>/usr/lib</file> may
6929 be used by a package (or a collection of packages) to hold a
6930 mixture of architecture-independent and
6931 architecture-dependent files. However, when a directory is
6932 entirely composed of architecture-independent files, it
6933 should be located in <file>/usr/share</file>.
6938 The optional rules related to user specific
6939 configuration files for applications are stored in
6940 the user's home directory are relaxed. It is
6941 recommended that such files start with the
6942 '<tt>.</tt>' character (a "dot file"), and if an
6943 application needs to create more than one dot file
6944 then the preferred placement is in a subdirectory
6945 with a name starting with a '.' character, (a "dot
6946 directory"). In this case it is recommended the
6947 configuration files not start with the '.'
6953 The requirement for amd64 to use <file>/lib64</file>
6954 for 64 bit binaries is removed.
6959 The requirement for object files, internal binaries, and
6960 libraries, including <file>libc.so.*</file>, to be located
6961 directly under <file>/lib{,32}</file> and
6962 <file>/usr/lib{,32}</file> is amended, permitting files
6963 to instead be installed to
6964 <file>/lib/<var>triplet</var></file> and
6965 <file>/usr/lib/<var>triplet</var></file>, where
6966 <tt><var>triplet</var></tt> is the value returned by
6967 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6968 architecture of the package. Packages may <em>not</em>
6969 install files to any <var>triplet</var> path other
6970 than the one matching the architecture of that package;
6971 for instance, an <tt>Architecture: amd64</tt> package
6972 containing 32-bit x86 libraries may not install these
6973 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6975 This is necessary in order to reserve the directories for
6976 use in cross-installation of library packages from other
6977 architectures, as part of <tt>multiarch</tt>.
6981 The requirement for C and C++ headers files to be
6982 accessible through the search path
6983 <file>/usr/include/</file> is amended, permitting files to
6984 be accessible through the search path
6985 <file>/usr/include/<var>triplet</var></file> where
6986 <tt><var>triplet</var></tt> is as above. <footnote>
6987 This is necessary for architecture-dependant headers
6988 file to coexist in a <tt>multiarch</tt> setup.
6992 Applications may also use a single subdirectory under
6993 <file>/usr/lib/<var>triplet</var></file>.
6996 The execution time linker/loader, ld*, must still be made
6997 available in the existing location under /lib or /lib64
6998 since this is part of the ELF ABI for the architecture.
7003 The requirement that
7004 <file>/usr/local/share/man</file> be "synonymous"
7005 with <file>/usr/local/man</file> is relaxed to a
7010 The requirement that windowmanagers with a single
7011 configuration file call it <file>system.*wmrc</file>
7012 is removed, as is the restriction that the window
7013 manager subdirectory be named identically to the
7014 window manager name itself.
7019 The requirement that boot manager configuration
7020 files live in <file>/etc</file>, or at least are
7021 symlinked there, is relaxed to a recommendation.
7026 The additional directory <file>/run</file> in the root
7027 file system is allowed. <file>/run</file>
7028 replaces <file>/var/run</file>, and the
7029 subdirectory <file>/run/lock</file>
7030 replaces <file>/var/lock</file>, with
7031 the <file>/var</file> directories replaced by symlinks
7032 for backwards compatibility. <file>/run</file>
7033 and <file>/run/lock</file> must follow all of the
7034 requirements in the FHS for <file>/var/run</file>
7035 and <file>/var/lock</file>, respectively, such as file
7036 naming conventions, file format requirements, or the
7037 requirement that files be cleared during the boot
7038 process. Files and directories residing
7039 in <file>/run</file> should be stored on a temporary
7043 Packages must not assume the <file>/run</file>
7044 directory exists or is usable without a dependency
7045 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
7046 stable release of Debian supports <file>/run</file>.
7051 The <file>/sys</file> directory in the root filesystem is
7052 additionally allowed. <footnote>This directory is used as
7053 mount point to mount virtual filesystems to get access to
7054 kernel information.</footnote>
7059 The <file>/var/www</file> directory is additionally allowed.
7064 The requirement for <file>/usr/local/lib<qual></file>
7065 to exist if <file>/lib<qual></file> or
7066 <file>/usr/lib<qual></file> exists (where
7067 <file>lib<qual></file> is a variant of
7068 <file>lib</file> such as <file>lib32</file> or
7069 <file>lib64</file>) is removed.
7074 On GNU/Hurd systems, the following additional
7075 directories are allowed in the root
7076 filesystem: <file>/hurd</file>
7077 and <file>/servers</file>.<footnote>
7078 These directories are used to store translators and as
7079 a set of standard names for mount points,
7088 The version of this document referred here can be
7089 found in the <tt>debian-policy</tt> package or on <url
7090 id="http://www.debian.org/doc/packaging-manuals/fhs/"
7091 name="FHS (Debian copy)"> alongside this manual (or, if
7092 you have the <package>debian-policy</package> installed,
7094 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
7095 (local copy)">). The
7096 latest version, which may be a more recent version, may
7098 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7099 Specific questions about following the standard may be
7100 asked on the <tt>debian-devel</tt> mailing list, or
7101 referred to the FHS mailing list (see the
7102 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7108 <heading>Site-specific programs</heading>
7111 As mandated by the FHS, packages must not place any
7112 files in <file>/usr/local</file>, either by putting them in
7113 the file system archive to be unpacked by <prgn>dpkg</prgn>
7114 or by manipulating them in their maintainer scripts.
7118 However, the package may create empty directories below
7119 <file>/usr/local</file> so that the system administrator knows
7120 where to place site-specific files. These are not
7121 directories <em>in</em> <file>/usr/local</file>, but are
7122 children of directories in <file>/usr/local</file>. These
7123 directories (<file>/usr/local/*/dir/</file>)
7124 should be removed on package removal if they are
7129 Note that this applies only to
7130 directories <em>below</em> <file>/usr/local</file>,
7131 not <em>in</em> <file>/usr/local</file>. Packages must
7132 not create sub-directories in the
7133 directory <file>/usr/local</file> itself, except those
7134 listed in FHS, section 4.5. However, you may create
7135 directories below them as you wish. You must not remove
7136 any of the directories listed in 4.5, even if you created
7141 Since <file>/usr/local</file> can be mounted read-only from a
7142 remote server, these directories must be created and
7143 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7144 maintainer scripts and not be included in the
7145 <file>.deb</file> archive. These scripts must not fail if
7146 either of these operations fail.
7150 For example, the <tt>emacsen-common</tt> package could
7151 contain something like
7152 <example compact="compact">
7153 if [ ! -e /usr/local/share/emacs ]; then
7154 if mkdir /usr/local/share/emacs 2>/dev/null; then
7155 if chown root:staff /usr/local/share/emacs; then
7156 chmod 2775 /usr/local/share/emacs || true
7161 in its <prgn>postinst</prgn> script, and
7162 <example compact="compact">
7163 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7164 rmdir /usr/local/share/emacs 2>/dev/null || true
7166 in the <prgn>prerm</prgn> script. (Note that this form is
7167 used to ensure that if the script is interrupted, the
7168 directory <file>/usr/local/share/emacs</file> will still be
7173 If you do create a directory in <file>/usr/local</file> for
7174 local additions to a package, you should ensure that
7175 settings in <file>/usr/local</file> take precedence over the
7176 equivalents in <file>/usr</file>.
7180 However, because <file>/usr/local</file> and its contents are
7181 for exclusive use of the local administrator, a package
7182 must not rely on the presence or absence of files or
7183 directories in <file>/usr/local</file> for normal operation.
7187 The <file>/usr/local</file> directory itself and all the
7188 subdirectories created by the package should (by default) have
7189 permissions 2775 (group-writable and set-group-id) and be
7190 owned by <tt>root:staff</tt>.
7195 <heading>The system-wide mail directory</heading>
7197 The system-wide mail directory
7198 is <file>/var/mail</file>. This directory is part of the
7199 base system and should not be owned by any particular mail
7200 agents. The use of the old
7201 location <file>/var/spool/mail</file> is deprecated, even
7202 though the spool may still be physically located there.
7206 <sect1 id="fhs-run">
7207 <heading><file>/run</file> and <file>/run/lock</file></heading>
7210 The directory <file>/run</file> is cleared at boot, normally
7211 by being a mount point for a temporary file system. Packages
7212 therefore must not assume that any files or directories
7213 under <file>/run</file> other than <file>/run/lock</file>
7214 exist unless the package has arranged to create those files or
7215 directories since the last reboot. Normally, this is done by
7216 the package via an init script. See <ref id="writing-init">
7217 for more information.
7221 Packages must not include files or directories
7222 under <file>/run</file>, or under the
7223 older <file>/var/run</file> and <file>/var/lock</file> paths.
7224 The latter paths will normally be symlinks or other
7225 redirections to <file>/run</file> for backwards compatibility.
7231 <heading>Users and groups</heading>
7234 <heading>Introduction</heading>
7236 The Debian system can be configured to use either plain or
7241 Some user ids (UIDs) and group ids (GIDs) are reserved
7242 globally for use by certain packages. Because some
7243 packages need to include files which are owned by these
7244 users or groups, or need the ids compiled into binaries,
7245 these ids must be used on any Debian system only for the
7246 purpose for which they are allocated. This is a serious
7247 restriction, and we should avoid getting in the way of
7248 local administration policies. In particular, many sites
7249 allocate users and/or local system groups starting at 100.
7253 Apart from this we should have dynamically allocated ids,
7254 which should by default be arranged in some sensible
7255 order, but the behavior should be configurable.
7259 Packages other than <tt>base-passwd</tt> must not modify
7260 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7261 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7266 <heading>UID and GID classes</heading>
7268 The UID and GID numbers are divided into classes as
7274 Globally allocated by the Debian project, the same
7275 on every Debian system. These ids will appear in
7276 the <file>passwd</file> and <file>group</file> files of all
7277 Debian systems, new ids in this range being added
7278 automatically as the <tt>base-passwd</tt> package is
7283 Packages which need a single statically allocated
7284 uid or gid should use one of these; their
7285 maintainers should ask the <tt>base-passwd</tt>
7293 Dynamically allocated system users and groups.
7294 Packages which need a user or group, but can have
7295 this user or group allocated dynamically and
7296 differently on each system, should use <tt>adduser
7297 --system</tt> to create the group and/or user.
7298 <prgn>adduser</prgn> will check for the existence of
7299 the user or group, and if necessary choose an unused
7300 id based on the ranges specified in
7301 <file>adduser.conf</file>.
7305 <tag>1000-59999:</tag>
7308 Dynamically allocated user accounts. By default
7309 <prgn>adduser</prgn> will choose UIDs and GIDs for
7310 user accounts in this range, though
7311 <file>adduser.conf</file> may be used to modify this
7316 <tag>60000-64999:</tag>
7319 Globally allocated by the Debian project, but only
7320 created on demand. The ids are allocated centrally
7321 and statically, but the actual accounts are only
7322 created on users' systems on demand.
7326 These ids are for packages which are obscure or
7327 which require many statically-allocated ids. These
7328 packages should check for and create the accounts in
7329 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7330 <prgn>adduser</prgn> if it has this facility) if
7331 necessary. Packages which are likely to require
7332 further allocations should have a "hole" left after
7333 them in the allocation, to give them room to
7338 <tag>65000-65533:</tag>
7346 User <tt>nobody</tt>. The corresponding gid refers
7347 to the group <tt>nogroup</tt>.
7354 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7355 not</em> be used, because it is the error return
7364 <sect id="sysvinit">
7365 <heading>System run levels and <file>init.d</file> scripts</heading>
7367 <sect1 id="/etc/init.d">
7368 <heading>Introduction</heading>
7371 The <file>/etc/init.d</file> directory contains the scripts
7372 executed by <prgn>init</prgn> at boot time and when the
7373 init state (or "runlevel") is changed (see <manref
7374 name="init" section="8">).
7378 There are at least two different, yet functionally
7379 equivalent, ways of handling these scripts. For the sake
7380 of simplicity, this document describes only the symbolic
7381 link method. However, it must not be assumed by maintainer
7382 scripts that this method is being used, and any automated
7383 manipulation of the various runlevel behaviors by
7384 maintainer scripts must be performed using
7385 <prgn>update-rc.d</prgn> as described below and not by
7386 manually installing or removing symlinks. For information
7387 on the implementation details of the other method,
7388 implemented in the <tt>file-rc</tt> package, please refer
7389 to the documentation of that package.
7393 These scripts are referenced by symbolic links in the
7394 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7395 runlevels, <prgn>init</prgn> looks in the directory
7396 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7397 execute, where <tt><var>n</var></tt> is the runlevel that
7398 is being changed to, or <tt>S</tt> for the boot-up
7403 The names of the links all have the form
7404 <file>S<var>mm</var><var>script</var></file> or
7405 <file>K<var>mm</var><var>script</var></file> where
7406 <var>mm</var> is a two-digit number and <var>script</var>
7407 is the name of the script (this should be the same as the
7408 name of the actual script in <file>/etc/init.d</file>).
7412 When <prgn>init</prgn> changes runlevel first the targets
7413 of the links whose names start with a <tt>K</tt> are
7414 executed, each with the single argument <tt>stop</tt>,
7415 followed by the scripts prefixed with an <tt>S</tt>, each
7416 with the single argument <tt>start</tt>. (The links are
7417 those in the <file>/etc/rc<var>n</var>.d</file> directory
7418 corresponding to the new runlevel.) The <tt>K</tt> links
7419 are responsible for killing services and the <tt>S</tt>
7420 link for starting services upon entering the runlevel.
7424 For example, if we are changing from runlevel 2 to
7425 runlevel 3, init will first execute all of the <tt>K</tt>
7426 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7427 all of the <tt>S</tt> prefixed scripts in that directory.
7428 The links starting with <tt>K</tt> will cause the
7429 referred-to file to be executed with an argument of
7430 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7435 The two-digit number <var>mm</var> is used to determine
7436 the order in which to run the scripts: low-numbered links
7437 have their scripts run first. For example, the
7438 <tt>K20</tt> scripts will be executed before the
7439 <tt>K30</tt> scripts. This is used when a certain service
7440 must be started before another. For example, the name
7441 server <prgn>bind</prgn> might need to be started before
7442 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7443 can set up its access lists. In this case, the script
7444 that starts <prgn>bind</prgn> would have a lower number
7445 than the script that starts <prgn>inn</prgn> so that it
7447 <example compact="compact">
7454 The two runlevels 0 (halt) and 6 (reboot) are slightly
7455 different. In these runlevels, the links with an
7456 <tt>S</tt> prefix are still called after those with a
7457 <tt>K</tt> prefix, but they too are called with the single
7458 argument <tt>stop</tt>.
7462 <sect1 id="writing-init">
7463 <heading>Writing the scripts</heading>
7466 Packages that include daemons for system services should
7467 place scripts in <file>/etc/init.d</file> to start or stop
7468 services at boot time or during a change of runlevel.
7469 These scripts should be named
7470 <file>/etc/init.d/<var>package</var></file>, and they should
7471 accept one argument, saying what to do:
7474 <tag><tt>start</tt></tag>
7475 <item>start the service,</item>
7477 <tag><tt>stop</tt></tag>
7478 <item>stop the service,</item>
7480 <tag><tt>restart</tt></tag>
7481 <item>stop and restart the service if it's already running,
7482 otherwise start the service</item>
7484 <tag><tt>reload</tt></tag>
7485 <item><p>cause the configuration of the service to be
7486 reloaded without actually stopping and restarting
7489 <tag><tt>force-reload</tt></tag>
7490 <item>cause the configuration to be reloaded if the
7491 service supports this, otherwise restart the
7495 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7496 <tt>force-reload</tt> options should be supported by all
7497 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7502 The <file>init.d</file> scripts must ensure that they will
7503 behave sensibly (i.e., returning success and not starting
7504 multiple copies of a service) if invoked with <tt>start</tt>
7505 when the service is already running, or with <tt>stop</tt>
7506 when it isn't, and that they don't kill unfortunately-named
7507 user processes. The best way to achieve this is usually to
7508 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7513 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7514 scripts. Writing correct <file>init.d</file> scripts requires
7515 accepting various error exit statuses when daemons are already
7516 running or already stopped without aborting
7517 the <file>init.d</file> script, and common <file>init.d</file>
7518 function libraries are not safe to call with <tt>set -e</tt>
7520 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7521 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7522 in effect and echoing status messages to the console fails,
7524 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7525 to not use <tt>set -e</tt> and instead check the result of
7526 each command separately.
7530 If a service reloads its configuration automatically (as
7531 in the case of <prgn>cron</prgn>, for example), the
7532 <tt>reload</tt> option of the <file>init.d</file> script
7533 should behave as if the configuration has been reloaded
7538 The <file>/etc/init.d</file> scripts must be treated as
7539 configuration files, either (if they are present in the
7540 package, that is, in the .deb file) by marking them as
7541 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7542 by managing them correctly in the maintainer scripts (see
7543 <ref id="config-files">). This is important since we want
7544 to give the local system administrator the chance to adapt
7545 the scripts to the local system, e.g., to disable a
7546 service without de-installing the package, or to specify
7547 some special command line options when starting a service,
7548 while making sure their changes aren't lost during the next
7553 These scripts should not fail obscurely when the
7554 configuration files remain but the package has been
7555 removed, as configuration files remain on the system after
7556 the package has been removed. Only when <prgn>dpkg</prgn>
7557 is executed with the <tt>--purge</tt> option will
7558 configuration files be removed. In particular, as the
7559 <file>/etc/init.d/<var>package</var></file> script itself is
7560 usually a <tt>conffile</tt>, it will remain on the system
7561 if the package is removed but not purged. Therefore, you
7562 should include a <tt>test</tt> statement at the top of the
7564 <example compact="compact">
7565 test -f <var>program-executed-later-in-script</var> || exit 0
7570 Often there are some variables in the <file>init.d</file>
7571 scripts whose values control the behavior of the scripts,
7572 and which a system administrator is likely to want to
7573 change. As the scripts themselves are frequently
7574 <tt>conffile</tt>s, modifying them requires that the
7575 administrator merge in their changes each time the package
7576 is upgraded and the <tt>conffile</tt> changes. To ease
7577 the burden on the system administrator, such configurable
7578 values should not be placed directly in the script.
7579 Instead, they should be placed in a file in
7580 <file>/etc/default</file>, which typically will have the same
7581 base name as the <file>init.d</file> script. This extra file
7582 should be sourced by the script when the script runs. It
7583 must contain only variable settings and comments in SUSv3
7584 <prgn>sh</prgn> format. It may either be a
7585 <tt>conffile</tt> or a configuration file maintained by
7586 the package maintainer scripts. See <ref id="config-files">
7591 To ensure that vital configurable values are always
7592 available, the <file>init.d</file> script should set default
7593 values for each of the shell variables it uses, either
7594 before sourcing the <file>/etc/default/</file> file or
7595 afterwards using something like the <tt>:
7596 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7597 script must behave sensibly and not fail if the
7598 <file>/etc/default</file> file is deleted.
7602 Files and directories under <file>/run</file>, including ones
7603 referred to via the compatibility paths <file>/var/run</file>
7604 and <file>/var/lock</file>, are normally stored on a temporary
7605 filesystem and are normally not persistent across a reboot.
7606 The <file>init.d</file> scripts must handle this correctly.
7607 This will typically mean creating any required subdirectories
7608 dynamically when the <file>init.d</file> script is run.
7609 See <ref id="fhs-run"> for more information.
7614 <heading>Interfacing with the initscript system</heading>
7617 Maintainers should use the abstraction layer provided by
7618 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7619 programs to deal with initscripts in their packages'
7620 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7621 and <prgn>postrm</prgn>.
7625 Directly managing the /etc/rc?.d links and directly
7626 invoking the <file>/etc/init.d/</file> initscripts should
7627 be done only by packages providing the initscript
7628 subsystem (such as <prgn>sysv-rc</prgn> and
7629 <prgn>file-rc</prgn>).
7633 <heading>Managing the links</heading>
7636 The program <prgn>update-rc.d</prgn> is provided for
7637 package maintainers to arrange for the proper creation and
7638 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7639 or their functional equivalent if another method is being
7640 used. This may be used by maintainers in their packages'
7641 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7645 You must not include any <file>/etc/rc<var>n</var>.d</file>
7646 symbolic links in the actual archive or manually create or
7647 remove the symbolic links in maintainer scripts; you must
7648 use the <prgn>update-rc.d</prgn> program instead. (The
7649 former will fail if an alternative method of maintaining
7650 runlevel information is being used.) You must not include
7651 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7652 in the archive either. (Only the <tt>sysvinit</tt>
7657 By default <prgn>update-rc.d</prgn> will start services in
7658 each of the multi-user state runlevels (2, 3, 4, and 5)
7659 and stop them in the halt runlevel (0), the single-user
7660 runlevel (1) and the reboot runlevel (6). The system
7661 administrator will have the opportunity to customize
7662 runlevels by simply adding, moving, or removing the
7663 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7664 symbolic links are being used, or by modifying
7665 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7670 To get the default behavior for your package, put in your
7671 <prgn>postinst</prgn> script
7672 <example compact="compact">
7673 update-rc.d <var>package</var> defaults
7675 and in your <prgn>postrm</prgn>
7676 <example compact="compact">
7677 if [ "$1" = purge ]; then
7678 update-rc.d <var>package</var> remove
7680 </example>. Note that if your package changes runlevels
7681 or priority, you may have to remove and recreate the links,
7682 since otherwise the old links may persist. Refer to the
7683 documentation of <prgn>update-rc.d</prgn>.
7687 This will use a default sequence number of 20. If it does
7688 not matter when or in which order the <file>init.d</file>
7689 script is run, use this default. If it does, then you
7690 should talk to the maintainer of the <prgn>sysvinit</prgn>
7691 package or post to <tt>debian-devel</tt>, and they will
7692 help you choose a number.
7696 For more information about using <tt>update-rc.d</tt>,
7697 please consult its man page <manref name="update-rc.d"
7703 <heading>Running initscripts</heading>
7705 The program <prgn>invoke-rc.d</prgn> is provided to make
7706 it easier for package maintainers to properly invoke an
7707 initscript, obeying runlevel and other locally-defined
7708 constraints that might limit a package's right to start,
7709 stop and otherwise manage services. This program may be
7710 used by maintainers in their packages' scripts.
7714 The package maintainer scripts must use
7715 <prgn>invoke-rc.d</prgn> to invoke the
7716 <file>/etc/init.d/*</file> initscripts, instead of
7717 calling them directly.
7721 By default, <prgn>invoke-rc.d</prgn> will pass any
7722 action requests (start, stop, reload, restart...) to the
7723 <file>/etc/init.d</file> script, filtering out requests
7724 to start or restart a service out of its intended
7729 Most packages will simply need to change:
7730 <example compact="compact">/etc/init.d/<package>
7731 <action></example> in their <prgn>postinst</prgn>
7732 and <prgn>prerm</prgn> scripts to:
7733 <example compact="compact">
7734 if which invoke-rc.d >/dev/null 2>&1; then
7735 invoke-rc.d <var>package</var> <action>
7737 /etc/init.d/<var>package</var> <action>
7743 A package should register its initscript services using
7744 <prgn>update-rc.d</prgn> before it tries to invoke them
7745 using <prgn>invoke-rc.d</prgn>. Invocation of
7746 unregistered services may fail.
7750 For more information about using
7751 <prgn>invoke-rc.d</prgn>, please consult its man page
7752 <manref name="invoke-rc.d" section="8">.
7758 <heading>Boot-time initialization</heading>
7761 There used to be another directory, <file>/etc/rc.boot</file>,
7762 which contained scripts which were run once per machine
7763 boot. This has been deprecated in favour of links from
7764 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7765 described in <ref id="/etc/init.d">. Packages must not
7766 place files in <file>/etc/rc.boot</file>.
7771 <heading>Example</heading>
7774 An example on which you can base your
7775 <file>/etc/init.d</file> scripts is found in
7776 <file>/etc/init.d/skeleton</file>.
7783 <heading>Console messages from <file>init.d</file> scripts</heading>
7786 This section describes the formats to be used for messages
7787 written to standard output by the <file>/etc/init.d</file>
7788 scripts. The intent is to improve the consistency of
7789 Debian's startup and shutdown look and feel. For this
7790 reason, please look very carefully at the details. We want
7791 the messages to have the same format in terms of wording,
7792 spaces, punctuation and case of letters.
7796 Here is a list of overall rules that should be used for
7797 messages generated by <file>/etc/init.d</file> scripts.
7803 The message should fit in one line (fewer than 80
7804 characters), start with a capital letter and end with
7805 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7809 If the script is performing some time consuming task in
7810 the background (not merely starting or stopping a
7811 program, for instance), an ellipsis (three dots:
7812 <tt>...</tt>) should be output to the screen, with no
7813 leading or tailing whitespace or line feeds.
7817 The messages should appear as if the computer is telling
7818 the user what it is doing (politely :-), but should not
7819 mention "it" directly. For example, instead of:
7820 <example compact="compact">
7821 I'm starting network daemons: nfsd mountd.
7823 the message should say
7824 <example compact="compact">
7825 Starting network daemons: nfsd mountd.
7832 <tt>init.d</tt> script should use the following standard
7833 message formats for the situations enumerated below.
7839 <p>When daemons are started</p>
7842 If the script starts one or more daemons, the output
7843 should look like this (a single line, no leading
7845 <example compact="compact">
7846 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7848 The <var>description</var> should describe the
7849 subsystem the daemon or set of daemons are part of,
7850 while <var>daemon-1</var> up to <var>daemon-n</var>
7851 denote each daemon's name (typically the file name of
7856 For example, the output of <file>/etc/init.d/lpd</file>
7858 <example compact="compact">
7859 Starting printer spooler: lpd.
7864 This can be achieved by saying
7865 <example compact="compact">
7866 echo -n "Starting printer spooler: lpd"
7867 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7870 in the script. If there are more than one daemon to
7871 start, the output should look like this:
7872 <example compact="compact">
7873 echo -n "Starting remote file system services:"
7874 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7875 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7876 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7879 This makes it possible for the user to see what is
7880 happening and when the final daemon has been started.
7881 Care should be taken in the placement of white spaces:
7882 in the example above the system administrators can
7883 easily comment out a line if they don't want to start
7884 a specific daemon, while the displayed message still
7890 <p>When a system parameter is being set</p>
7893 If you have to set up different system parameters
7894 during the system boot, you should use this format:
7895 <example compact="compact">
7896 Setting <var>parameter</var> to "<var>value</var>".
7901 You can use a statement such as the following to get
7903 <example compact="compact">
7904 echo "Setting DNS domainname to \"$domainname\"."
7909 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7910 for the left and right quotation marks. A grave accent
7911 (<tt>`</tt>) is not a quote character; neither is an
7912 apostrophe (<tt>'</tt>).
7917 <p>When a daemon is stopped or restarted</p>
7920 When you stop or restart a daemon, you should issue a
7921 message identical to the startup message, except that
7922 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7923 or <tt>Restarting</tt> respectively.
7927 For example, stopping the printer daemon will look like
7929 <example compact="compact">
7930 Stopping printer spooler: lpd.
7936 <p>When something is executed</p>
7939 There are several examples where you have to run a
7940 program at system startup or shutdown to perform a
7941 specific task, for example, setting the system's clock
7942 using <prgn>netdate</prgn> or killing all processes
7943 when the system shuts down. Your message should look
7945 <example compact="compact">
7946 Doing something very useful...done.
7948 You should print the <tt>done.</tt> immediately after
7949 the job has been completed, so that the user is
7950 informed why they have to wait. You can get this
7952 <example compact="compact">
7953 echo -n "Doing something very useful..."
7962 <p>When the configuration is reloaded</p>
7965 When a daemon is forced to reload its configuration
7966 files you should use the following format:
7967 <example compact="compact">
7968 Reloading <var>description</var> configuration...done.
7970 where <var>description</var> is the same as in the
7971 daemon starting message.
7978 <sect id="cron-jobs">
7979 <heading>Cron jobs</heading>
7982 Packages must not modify the configuration file
7983 <file>/etc/crontab</file>, and they must not modify the files in
7984 <file>/var/spool/cron/crontabs</file>.
7988 If a package wants to install a job that has to be executed via
7989 cron, it should place a file named as specified
7990 in <ref id="cron-files"> into one or more of the following
7992 <example compact="compact">
7998 As these directory names imply, the files within them are
7999 executed on an hourly, daily, weekly, or monthly basis,
8000 respectively. The exact times are listed in
8001 <file>/etc/crontab</file>.
8005 All files installed in any of these directories must be
8006 scripts (e.g., shell scripts or Perl scripts) so that they
8007 can easily be modified by the local system administrator.
8008 In addition, they must be treated as configuration files.
8012 If a certain job has to be executed at some other frequency or
8013 at a specific time, the package should install a file in
8014 <file>/etc/cron.d</file> with a name as specified
8015 in <ref id="cron-files">. This file uses the same syntax
8016 as <file>/etc/crontab</file> and is processed
8017 by <prgn>cron</prgn> automatically. The file must also be
8018 treated as a configuration file. (Note that entries in the
8019 <file>/etc/cron.d</file> directory are not handled by
8020 <prgn>anacron</prgn>. Thus, you should only use this
8021 directory for jobs which may be skipped if the system is not
8026 Unlike <file>crontab</file> files described in the IEEE Std
8027 1003.1-2008 (POSIX.1) available from
8028 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
8029 name="The Open Group">, the files in
8030 <file>/etc/cron.d</file> and the file
8031 <file>/etc/crontab</file> have seven fields; namely:
8033 <item>Minute [0,59]</item>
8034 <item>Hour [0,23]</item>
8035 <item>Day of the month [1,31]</item>
8036 <item>Month of the year [1,12]</item>
8037 <item>Day of the week ([0,6] with 0=Sunday)</item>
8038 <item>Username</item>
8039 <item>Command to be run</item>
8041 Ranges of numbers are allowed. Ranges are two numbers
8042 separated with a hyphen. The specified range is inclusive.
8043 Lists are allowed. A list is a set of numbers (or ranges)
8044 separated by commas. Step values can be used in conjunction
8049 The scripts or <tt>crontab</tt> entries in these directories should
8050 check if all necessary programs are installed before they
8051 try to execute them. Otherwise, problems will arise when a
8052 package was removed but not purged since configuration files
8053 are kept on the system in this situation.
8057 Any <tt>cron</tt> daemon must provide
8058 <file>/usr/bin/crontab</file> and support normal
8059 <tt>crontab</tt> entries as specified in POSIX. The daemon
8060 must also support names for days and months, ranges, and
8061 step values. It has to support <file>/etc/crontab</file>,
8062 and correctly execute the scripts in
8063 <file>/etc/cron.d</file>. The daemon must also correctly
8065 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
8068 <sect1 id="cron-files">
8069 <heading>Cron job file names</heading>
8072 The file name of a cron job file should normally match the
8073 name of the package from which it comes.
8077 If a package supplies multiple cron job files files in the
8078 same directory, the file names should all start with the name
8079 of the package (possibly modified as described below) followed
8080 by a hyphen (<tt>-</tt>) and a suitable suffix.
8084 A cron job file name must not include any period or plus
8085 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
8086 cause cron to ignore the file. Underscores (<tt>_</tt>)
8087 should be used instead of <tt>.</tt> and <tt>+</tt>
8094 <heading>Menus</heading>
8097 The Debian <tt>menu</tt> package provides a standard
8098 interface between packages providing applications and
8099 <em>menu programs</em> (either X window managers or
8100 text-based menu programs such as <prgn>pdmenu</prgn>).
8104 All packages that provide applications that need not be
8105 passed any special command line arguments for normal
8106 operation should register a menu entry for those
8107 applications, so that users of the <tt>menu</tt> package
8108 will automatically get menu entries in their window
8109 managers, as well in shells like <tt>pdmenu</tt>.
8113 Menu entries should follow the current menu policy.
8117 The menu policy can be found in the <tt>menu-policy</tt>
8118 files in the <tt>debian-policy</tt> package.
8119 It is also available from the Debian web mirrors at
8120 <tt><url name="/doc/packaging-manuals/menu-policy/"
8121 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8125 Please also refer to the <em>Debian Menu System</em>
8126 documentation that comes with the <package>menu</package>
8127 package for information about how to register your
8133 <heading>Multimedia handlers</heading>
8136 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8137 is a mechanism for encoding files and data streams and
8138 providing meta-information about them, in particular their
8139 type (e.g. audio or video) and format (e.g. PNG, HTML,
8144 Registration of MIME type handlers allows programs like mail
8145 user agents and web browsers to invoke these handlers to
8146 view, edit or display MIME types they don't support directly.
8150 Packages which provide programs to view/show/play, compose, edit or
8151 print MIME types should register them as such by placing a file in
8152 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8153 <file>/usr/lib/mime/packages/</file>. The file name should be the
8154 binary package's name.
8158 The <package>mime-support</package> package provides the
8159 <prgn>update-mime</prgn> program, which integrates these
8160 registrations in the <file>/etc/mailcap</file> file, using dpkg
8162 Creating, modifying or removing a file in
8163 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8164 not activate the trigger. In that case, it can be done by calling
8165 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8166 the maintainer script after creating, modifying, or removing
8169 Packages using this facility <em>should not</em> depend on,
8170 recommend, or suggest <prgn>mime-support</prgn>.
8175 <heading>Keyboard configuration</heading>
8178 To achieve a consistent keyboard configuration so that all
8179 applications interpret a keyboard event the same way, all
8180 programs in the Debian distribution must be configured to
8181 comply with the following guidelines.
8185 The following keys must have the specified interpretations:
8188 <tag><tt><--</tt></tag>
8189 <item>delete the character to the left of the cursor</item>
8191 <tag><tt>Delete</tt></tag>
8192 <item>delete the character to the right of the cursor</item>
8194 <tag><tt>Control+H</tt></tag>
8195 <item>emacs: the help prefix</item>
8198 The interpretation of any keyboard events should be
8199 independent of the terminal that is used, be it a virtual
8200 console, an X terminal emulator, an rlogin/telnet session,
8205 The following list explains how the different programs
8206 should be set up to achieve this:
8212 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8216 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8220 X translations are set up to make
8221 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8222 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8223 is the vt220 escape code for the "delete character"
8224 key). This must be done by loading the X resources
8225 using <prgn>xrdb</prgn> on all local X displays, not
8226 using the application defaults, so that the
8227 translation resources used correspond to the
8228 <prgn>xmodmap</prgn> settings.
8232 The Linux console is configured to make
8233 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8234 generate <tt>ESC [ 3 ~</tt>.
8238 X applications are configured so that <tt><</tt>
8239 deletes left, and <tt>Delete</tt> deletes right. Motif
8240 applications already work like this.
8244 Terminals should have <tt>stty erase ^?</tt> .
8248 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8249 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8250 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8254 Emacs is programmed to map <tt>KB_Backspace</tt> or
8255 the <tt>stty erase</tt> character to
8256 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8257 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8258 <tt>^H</tt> to <tt>help</tt> as always.
8262 Other applications use the <tt>stty erase</tt>
8263 character and <tt>kdch1</tt> for the two delete keys,
8264 with ASCII DEL being "delete previous character" and
8265 <tt>kdch1</tt> being "delete character under
8273 This will solve the problem except for the following
8280 Some terminals have a <tt><--</tt> key that cannot
8281 be made to produce anything except <tt>^H</tt>. On
8282 these terminals Emacs help will be unavailable on
8283 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8284 character takes precedence in Emacs, and has been set
8285 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8286 available) can be used instead.
8290 Some operating systems use <tt>^H</tt> for <tt>stty
8291 erase</tt>. However, modern telnet versions and all
8292 rlogin versions propagate <tt>stty</tt> settings, and
8293 almost all UNIX versions honour <tt>stty erase</tt>.
8294 Where the <tt>stty</tt> settings are not propagated
8295 correctly, things can be made to work by using
8296 <tt>stty</tt> manually.
8300 Some systems (including previous Debian versions) use
8301 <prgn>xmodmap</prgn> to arrange for both
8302 <tt><--</tt> and <tt>Delete</tt> to generate
8303 <tt>KB_Delete</tt>. We can change the behavior of
8304 their X clients using the same X resources that we use
8305 to do it for our own clients, or configure our clients
8306 using their resources when things are the other way
8307 around. On displays configured like this
8308 <tt>Delete</tt> will not work, but <tt><--</tt>
8313 Some operating systems have different <tt>kdch1</tt>
8314 settings in their <tt>terminfo</tt> database for
8315 <tt>xterm</tt> and others. On these systems the
8316 <tt>Delete</tt> key will not work correctly when you
8317 log in from a system conforming to our policy, but
8318 <tt><--</tt> will.
8325 <heading>Environment variables</heading>
8328 A program must not depend on environment variables to get
8329 reasonable defaults. (That's because these environment
8330 variables would have to be set in a system-wide
8331 configuration file like <file>/etc/profile</file>, which is not
8332 supported by all shells.)
8336 If a program usually depends on environment variables for its
8337 configuration, the program should be changed to fall back to
8338 a reasonable default configuration if these environment
8339 variables are not present. If this cannot be done easily
8340 (e.g., if the source code of a non-free program is not
8341 available), the program must be replaced by a small
8342 "wrapper" shell script which sets the environment variables
8343 if they are not already defined, and calls the original program.
8347 Here is an example of a wrapper script for this purpose:
8349 <example compact="compact">
8351 BAR=${BAR:-/var/lib/fubar}
8353 exec /usr/lib/foo/foo "$@"
8358 Furthermore, as <file>/etc/profile</file> is a configuration
8359 file of the <prgn>base-files</prgn> package, other packages must
8360 not put any environment variables or other commands into that
8365 <sect id="doc-base">
8366 <heading>Registering Documents using doc-base</heading>
8369 The <package>doc-base</package> package implements a
8370 flexible mechanism for handling and presenting
8371 documentation. The recommended practice is for every Debian
8372 package that provides online documentation (other than just
8373 manual pages) to register these documents with
8374 <package>doc-base</package> by installing a
8375 <package>doc-base</package> control file in
8376 <file>/usr/share/doc-base/</file>.
8379 Please refer to the documentation that comes with the
8380 <package>doc-base</package> package for information and
8385 <sect id="alternateinit">
8386 <heading>Alternate init systems</heading>
8388 A number of other init systems are available now in Debian that
8389 can be used in place of <package>sysvinit</package>. Alternative
8390 init implementations must support running SysV init scripts as
8391 described at <ref id="sysvinit"> for compatibility.
8394 Packages may integrate with these replacement init systems by
8395 providing implementation-specific configuration information about
8396 how and when to start a service or in what order to run certain
8397 tasks at boot time. However, any package integrating with other
8398 init systems must also be backwards-compatible with
8399 <package>sysvinit</package> by providing a SysV-style init script
8400 with the same name as and equivalent functionality to any
8401 init-specific job, as this is the only start-up configuration
8402 method guaranteed to be supported by all init implementations. An
8403 exception to this rule is scripts or jobs provided by the init
8404 implementation itself; such jobs may be required for an
8405 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8406 scripts and may not have a one-to-one correspondence with the init
8409 <sect1 id="upstart">
8410 <heading>Event-based boot with upstart</heading>
8413 Packages may integrate with the <prgn>upstart</prgn> event-based
8414 boot system by installing job files in the
8415 <file>/etc/init</file> directory. SysV init scripts for which
8416 an equivalent upstart job is available must query the output of
8417 the command <prgn>initctl version</prgn> for the string
8418 <tt>upstart</tt> and avoid running in favor of the native
8419 upstart job, using a test such as this:
8420 <example compact="compact">
8421 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8428 Because packages shipping upstart jobs may be installed on
8429 systems that are not using upstart, maintainer scripts must
8430 still use the common <prgn>update-rc.d</prgn> and
8431 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8432 and for starting and stopping services. These maintainer
8433 scripts must not call the upstart <prgn>start</prgn>,
8434 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8435 interfaces directly. Instead, implementations of
8436 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8437 when an upstart job with the same name as an init script is
8438 present, and perform the requested action using the upstart job
8439 instead of the init script.
8442 Dependency-based boot managers for SysV init scripts, such as
8443 <prgn>startpar</prgn>, may avoid running a given init script
8444 entirely when an equivalent upstart job is present, to avoid
8445 unnecessary forking of no-op init scripts. In this case, the
8446 boot manager should integrate with upstart to detect when the
8447 upstart job in question is started or stopped to know when the
8448 dependency has been satisfied.
8457 <heading>Files</heading>
8459 <sect id="binaries">
8460 <heading>Binaries</heading>
8463 Two different packages must not install programs with
8464 different functionality but with the same filenames. (The
8465 case of two programs having the same functionality but
8466 different implementations is handled via "alternatives" or
8467 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8468 <ref id="conflicts"> respectively.) If this case happens,
8469 one of the programs must be renamed. The maintainers should
8470 report this to the <tt>debian-devel</tt> mailing list and
8471 try to find a consensus about which program will have to be
8472 renamed. If a consensus cannot be reached, <em>both</em>
8473 programs must be renamed.
8476 Binary executables must not be statically linked with the GNU C
8477 library, since this prevents the binary from benefiting from
8478 fixes and improvements to the C library without being rebuilt
8479 and complicates security updates. This requirement may be
8480 relaxed for binary executables whose intended purpose is to
8481 diagnose and fix the system in situations where the GNU C
8482 library may not be usable (such as system recovery shells or
8483 utilities like ldconfig) or for binary executables where the
8484 security benefits of static linking outweigh the drawbacks.
8487 By default, when a package is being built, any binaries
8488 created should include debugging information, as well as
8489 being compiled with optimization. You should also turn on
8490 as many reasonable compilation warnings as possible; this
8491 makes life easier for porters, who can then look at build
8492 logs for possible problems. For the C programming language,
8493 this means the following compilation parameters should be
8495 <example compact="compact">
8497 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8499 INSTALL = install -s # (or use strip on the files in debian/tmp)
8504 Note that by default all installed binaries should be stripped,
8505 either by using the <tt>-s</tt> flag to
8506 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8507 the binaries after they have been copied into
8508 <file>debian/tmp</file> but before the tree is made into a
8513 Although binaries in the build tree should be compiled with
8514 debugging information by default, it can often be difficult to
8515 debug programs if they are also subjected to compiler
8516 optimization. For this reason, it is recommended to support the
8517 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8518 (see <ref id="debianrules-options">). This variable can contain
8519 several flags to change how a package is compiled and built.
8523 It is up to the package maintainer to decide what
8524 compilation options are best for the package. Certain
8525 binaries (such as computationally-intensive programs) will
8526 function better with certain flags (<tt>-O3</tt>, for
8527 example); feel free to use them. Please use good judgment
8528 here. Don't use flags for the sake of it; only use them
8529 if there is good reason to do so. Feel free to override
8530 the upstream author's ideas about which compilation
8531 options are best: they are often inappropriate for our
8537 <sect id="libraries">
8538 <heading>Libraries</heading>
8541 If the package is <strong>architecture: any</strong>, then
8542 the shared library compilation and linking flags must have
8543 <tt>-fPIC</tt>, or the package shall not build on some of
8544 the supported architectures<footnote>
8546 If you are using GCC, <tt>-fPIC</tt> produces code with
8547 relocatable position independent code, which is required for
8548 most architectures to create a shared library, with i386 and
8549 perhaps some others where non position independent code is
8550 permitted in a shared library.
8553 Position independent code may have a performance penalty,
8554 especially on <tt>i386</tt>. However, in most cases the
8555 speed penalty must be measured against the memory wasted on
8556 the few architectures where non position independent code is
8559 </footnote>. Any exception to this rule must be discussed on
8560 the mailing list <em>debian-devel@lists.debian.org</em>, and
8561 a rough consensus obtained. The reasons for not compiling
8562 with <tt>-fPIC</tt> flag must be recorded in the file
8563 <tt>README.Debian</tt>, and care must be taken to either
8564 restrict the architecture or arrange for <tt>-fPIC</tt> to
8565 be used on architectures where it is required.<footnote>
8567 Some of the reasons why this might be required is if the
8568 library contains hand crafted assembly code that is not
8569 relocatable, the speed penalty is excessive for compute
8570 intensive libs, and similar reasons.
8575 As to the static libraries, the common case is not to have
8576 relocatable code, since there is no benefit, unless in specific
8577 cases; therefore the static version must not be compiled
8578 with the <tt>-fPIC</tt> flag. Any exception to this rule
8579 should be discussed on the mailing list
8580 <em>debian-devel@lists.debian.org</em>, and the reasons for
8581 compiling with the <tt>-fPIC</tt> flag must be recorded in
8582 the file <tt>README.Debian</tt>. <footnote>
8584 Some of the reasons for linking static libraries with
8585 the <tt>-fPIC</tt> flag are if, for example, one needs a
8586 Perl API for a library that is under rapid development,
8587 and has an unstable API, so shared libraries are
8588 pointless at this phase of the library's development. In
8589 that case, since Perl needs a library with relocatable
8590 code, it may make sense to create a static library with
8591 relocatable code. Another reason cited is if you are
8592 distilling various libraries into a common shared
8593 library, like <tt>mklibs</tt> does in the Debian
8599 In other words, if both a shared and a static library is
8600 being built, each source unit (<tt>*.c</tt>, for example,
8601 for C files) will need to be compiled twice, for the normal
8606 Libraries should be built with threading support and to be
8607 thread-safe if the library supports this.
8611 Although not enforced by the build tools, shared libraries
8612 must be linked against all libraries that they use symbols from
8613 in the same way that binaries are. This ensures the correct
8614 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8615 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8616 systems and guarantees that all libraries can be safely opened
8617 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8618 option <tt>-Wl,-z,defs</tt> when building a shared library.
8619 Since this option enforces symbol resolution at build time,
8620 a missing library reference will be caught early as a fatal
8625 All installed shared libraries should be stripped with
8626 <example compact="compact">
8627 strip --strip-unneeded <var>your-lib</var>
8629 (The option <tt>--strip-unneeded</tt> makes
8630 <prgn>strip</prgn> remove only the symbols which aren't
8631 needed for relocation processing.) Shared libraries can
8632 function perfectly well when stripped, since the symbols for
8633 dynamic linking are in a separate part of the ELF object
8635 You might also want to use the options
8636 <tt>--remove-section=.comment</tt> and
8637 <tt>--remove-section=.note</tt> on both shared libraries
8638 and executables, and <tt>--strip-debug</tt> on static
8644 Note that under some circumstances it may be useful to
8645 install a shared library unstripped, for example when
8646 building a separate package to support debugging.
8650 Shared object files (often <file>.so</file> files) that are not
8651 public libraries, that is, they are not meant to be linked
8652 to by third party executables (binaries of other packages),
8653 should be installed in subdirectories of the
8654 <file>/usr/lib</file> directory. Such files are exempt from the
8655 rules that govern ordinary shared libraries, except that
8656 they must not be installed executable and should be
8658 A common example are the so-called "plug-ins",
8659 internal shared objects that are dynamically loaded by
8660 programs using <manref name="dlopen" section="3">.
8665 Packages that use <prgn>libtool</prgn> to create and install
8666 their shared libraries install a file containing additional
8667 metadata (ending in <file>.la</file>) alongside the library.
8668 For public libraries intended for use by other packages, these
8669 files normally should not be included in the Debian package,
8670 since the information they include is not necessary to link with
8671 the shared library on Debian and can add unnecessary additional
8672 dependencies to other programs or libraries.<footnote>
8673 These files store, among other things, all libraries on which
8674 that shared library depends. Unfortunately, if
8675 the <file>.la</file> file is present and contains that
8676 dependency information, using <prgn>libtool</prgn> when
8677 linking against that library will cause the resulting program
8678 or library to be linked against those dependencies as well,
8679 even if this is unnecessary. This can create unneeded
8680 dependencies on shared library packages that would otherwise
8681 be hidden behind the library ABI, and can make library
8682 transitions to new SONAMEs unnecessarily complicated and
8683 difficult to manage.
8685 If the <file>.la</file> file is required for that library (if,
8686 for instance, it's loaded via <tt>libltdl</tt> in a way that
8687 requires that meta-information), the <tt>dependency_libs</tt>
8688 setting in the <file>.la</file> file should normally be set to
8689 the empty string. If the shared library development package has
8690 historically included the <file>.la</file>, it must be retained
8691 in the development package (with <tt>dependency_libs</tt>
8692 emptied) until all libraries that depend on it have removed or
8693 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8694 files to prevent linking with those other libraries
8695 using <prgn>libtool</prgn> from failing.
8699 If the <file>.la</file> must be included, it should be included
8700 in the development (<tt>-dev</tt>) package, unless the library
8701 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8702 library. If it is intended for use with <tt>libltdl</tt>,
8703 the <file>.la</file> files must go in the run-time library
8708 These requirements for handling of <file>.la</file> files do not
8709 apply to loadable modules or libraries not installed in
8710 directories searched by default by the dynamic linker. Packages
8711 installing loadable modules will frequently need to install
8712 the <file>.la</file> files alongside the modules so that they
8713 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8714 does not need to be modified for libraries or modules that are
8715 not installed in directories searched by the dynamic linker by
8716 default and not intended for use by other packages.
8720 You must make sure that you use only released versions of
8721 shared libraries to build your packages; otherwise other
8722 users will not be able to run your binaries
8723 properly. Producing source packages that depend on
8724 unreleased compilers is also usually a bad
8731 <heading>Shared libraries</heading>
8733 This section has moved to <ref id="sharedlibs">.
8739 <heading>Scripts</heading>
8742 All command scripts, including the package maintainer
8743 scripts inside the package and used by <prgn>dpkg</prgn>,
8744 should have a <tt>#!</tt> line naming the shell to be used
8749 In the case of Perl scripts this should be
8750 <tt>#!/usr/bin/perl</tt>.
8754 When scripts are installed into a directory in the system
8755 PATH, the script name should not include an extension such
8756 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8757 language currently used to implement it.
8760 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8761 <file>init.d</file> scripts should almost certainly start
8762 with <tt>set -e</tt> so that errors are detected.
8763 <file>init.d</file> scripts are something of a special case, due
8764 to how frequently they need to call commands that are allowed to
8765 fail, and it may instead be easier to check the exit status of
8766 commands directly. See <ref id="writing-init"> for more
8767 information about writing <file>init.d</file> scripts.
8770 Every script should use <tt>set -e</tt> or check the exit status
8771 of <em>every</em> command.
8774 Scripts may assume that <file>/bin/sh</file> implements the
8775 SUSv3 Shell Command Language<footnote>
8776 Single UNIX Specification, version 3, which is also IEEE
8777 1003.1-2004 (POSIX), and is available on the World Wide Web
8778 from <url id="http://www.unix.org/version3/online.html"
8779 name="The Open Group"> after free
8780 registration.</footnote>
8781 plus the following additional features not mandated by
8783 These features are in widespread use in the Linux community
8784 and are implemented in all of bash, dash, and ksh, the most
8785 common shells users may wish to use as <file>/bin/sh</file>.
8788 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8789 must not generate a newline.</item>
8790 <item><tt>test</tt>, if implemented as a shell built-in, must
8791 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8793 <item><tt>local</tt> to create a scoped variable must be
8794 supported, including listing multiple variables in a single
8795 local command and assigning a value to a variable at the
8796 same time as localizing it. <tt>local</tt> may or
8797 may not preserve the variable value from an outer scope if
8798 no assignment is present. Uses such as:
8802 # ... use a, b, c, d ...
8805 must be supported and must set the value of <tt>c</tt> to
8808 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8809 -<var>signal</var></tt>, where <var>signal</var> is either
8810 the name of a signal or one of the numeric signals listed in
8811 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8812 supported if <prgn>kill</prgn> is implemented as a shell
8815 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8816 signals must be supported. In addition to the signal
8817 numbers listed in the extension, which are the same as for
8818 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8821 If a shell script requires non-SUSv3 features from the shell
8822 interpreter other than those listed above, the appropriate shell
8823 must be specified in the first line of the script (e.g.,
8824 <tt>#!/bin/bash</tt>) and the package must depend on the package
8825 providing the shell (unless the shell package is marked
8826 "Essential", as in the case of <prgn>bash</prgn>).
8830 You may wish to restrict your script to SUSv3 features plus the
8831 above set when possible so that it may use <file>/bin/sh</file>
8832 as its interpreter. Checking your script
8833 with <prgn>checkbashisms</prgn> from
8834 the <package>devscripts</package> package or running your script
8835 with an alternate shell such as <prgn>posh</prgn> may help
8836 uncover violations of the above requirements. If in doubt
8837 whether a script complies with these requirements,
8838 use <file>/bin/bash</file>.
8842 Perl scripts should check for errors when making any
8843 system calls, including <tt>open</tt>, <tt>print</tt>,
8844 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8848 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8849 scripting languages. See <em>Csh Programming Considered
8850 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8851 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8852 If an upstream package comes with <prgn>csh</prgn> scripts
8853 then you must make sure that they start with
8854 <tt>#!/bin/csh</tt> and make your package depend on the
8855 <prgn>c-shell</prgn> virtual package.
8859 Any scripts which create files in world-writeable
8860 directories (e.g., in <file>/tmp</file>) must use a
8861 mechanism which will fail atomically if a file with the same
8862 name already exists.
8866 The Debian base system provides the <prgn>tempfile</prgn>
8867 and <prgn>mktemp</prgn> utilities for use by scripts for
8874 <heading>Symbolic links</heading>
8877 In general, symbolic links within a top-level directory should
8878 be relative, and symbolic links pointing from one top-level
8879 directory to or into another should be absolute. (A top-level
8880 directory is a sub-directory of the root
8881 directory <file>/</file>.) For example, a symbolic link
8882 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8883 should be relative (<file>../share/bar</file>), but a symbolic
8884 link from <file>/var/run</file> to <file>/run</file> should be
8886 This is necessary to allow top-level directories to be
8887 symlinks. If linking <file>/var/run</file>
8888 to <file>/run</file> were done with the relative symbolic
8889 link <file>../run</file>, but <file>/var</file> were a
8890 symbolic link to <file>/srv/disk1</file>, the symbolic link
8891 would point to <file>/srv/run</file> rather than the intended
8897 In addition, symbolic links should be specified as short as
8898 possible, i.e., link targets like <file>foo/../bar</file> are
8903 Note that when creating a relative link using
8904 <prgn>ln</prgn> it is not necessary for the target of the
8905 link to exist relative to the working directory you're
8906 running <prgn>ln</prgn> from, nor is it necessary to change
8907 directory to the directory where the link is to be made.
8908 Simply include the string that should appear as the target
8909 of the link (this will be a pathname relative to the
8910 directory in which the link resides) as the first argument
8915 For example, in your <prgn>Makefile</prgn> or
8916 <file>debian/rules</file>, you can do things like:
8917 <example compact="compact">
8918 ln -fs gcc $(prefix)/bin/cc
8919 ln -fs gcc debian/tmp/usr/bin/cc
8920 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8921 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8926 A symbolic link pointing to a compressed file (in the sense
8927 that it is meant to be uncompressed with <prgn>unzip</prgn>
8928 or <prgn>zless</prgn> etc.) should always
8929 have the same file extension as the referenced file. (For
8930 example, if a file <file>foo.gz</file> is referenced by a
8931 symbolic link, the filename of the link has to end with
8932 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8937 <heading>Device files</heading>
8940 Packages must not include device files or named pipes in the
8945 If a package needs any special device files that are not
8946 included in the base system, it must call
8947 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8948 after notifying the user<footnote>
8949 This notification could be done via a (low-priority)
8950 debconf message, or an echo (printf) statement.
8955 Packages must not remove any device files in the
8956 <prgn>postrm</prgn> or any other script. This is left to the
8957 system administrator.
8961 Debian uses the serial devices
8962 <file>/dev/ttyS*</file>. Programs using the old
8963 <file>/dev/cu*</file> devices should be changed to use
8964 <file>/dev/ttyS*</file>.
8968 Named pipes needed by the package must be created in
8969 the <prgn>postinst</prgn> script<footnote>
8970 It's better to use <prgn>mkfifo</prgn> rather
8971 than <prgn>mknod</prgn> to create named pipes so that
8972 automated checks for packages incorrectly creating device
8973 files with <prgn>mknod</prgn> won't have false positives.
8974 </footnote> and removed in
8975 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8980 <sect id="config-files">
8981 <heading>Configuration files</heading>
8984 <heading>Definitions</heading>
8988 <tag>configuration file</tag>
8990 A file that affects the operation of a program, or
8991 provides site- or host-specific information, or
8992 otherwise customizes the behavior of a program.
8993 Typically, configuration files are intended to be
8994 modified by the system administrator (if needed or
8995 desired) to conform to local policy or to provide
8996 more useful site-specific behavior.
8999 <tag><tt>conffile</tt></tag>
9001 A file listed in a package's <tt>conffiles</tt>
9002 file, and is treated specially by <prgn>dpkg</prgn>
9003 (see <ref id="configdetails">).
9009 The distinction between these two is important; they are
9010 not interchangeable concepts. Almost all
9011 <tt>conffile</tt>s are configuration files, but many
9012 configuration files are not <tt>conffiles</tt>.
9016 As noted elsewhere, <file>/etc/init.d</file> scripts,
9017 <file>/etc/default</file> files, scripts installed in
9018 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
9019 configuration installed in <file>/etc/cron.d</file> must be
9020 treated as configuration files. In general, any script that
9021 embeds configuration information is de-facto a configuration
9022 file and should be treated as such.
9027 <heading>Location</heading>
9030 Any configuration files created or used by your package
9031 must reside in <file>/etc</file>. If there are several,
9032 consider creating a subdirectory of <file>/etc</file>
9033 named after your package.
9037 If your package creates or uses configuration files
9038 outside of <file>/etc</file>, and it is not feasible to modify
9039 the package to use <file>/etc</file> directly, put the files
9040 in <file>/etc</file> and create symbolic links to those files
9041 from the location that the package requires.
9046 <heading>Behavior</heading>
9049 Configuration file handling must conform to the following
9051 <list compact="compact">
9053 local changes must be preserved during a package
9057 configuration files must be preserved when the
9058 package is removed, and only deleted when the
9062 Obsolete configuration files without local changes should be
9063 removed by the package during upgrade.<footnote>
9064 The <prgn>dpkg-maintscript-helper</prgn> tool, available from the
9065 <package>dpkg</package> package, can help for this task.</footnote>
9069 The easy way to achieve this behavior is to make the
9070 configuration file a <tt>conffile</tt>. This is
9071 appropriate only if it is possible to distribute a default
9072 version that will work for most installations, although
9073 some system administrators may choose to modify it. This
9074 implies that the default version will be part of the
9075 package distribution, and must not be modified by the
9076 maintainer scripts during installation (or at any other
9081 In order to ensure that local changes are preserved
9082 correctly, no package may contain or make hard links to
9083 conffiles.<footnote>
9084 Rationale: There are two problems with hard links.
9085 The first is that some editors break the link while
9086 editing one of the files, so that the two files may
9087 unwittingly become unlinked and different. The second
9088 is that <prgn>dpkg</prgn> might break the hard link
9089 while upgrading <tt>conffile</tt>s.
9094 The other way to do it is via the maintainer scripts. In
9095 this case, the configuration file must not be listed as a
9096 <tt>conffile</tt> and must not be part of the package
9097 distribution. If the existence of a file is required for
9098 the package to be sensibly configured it is the
9099 responsibility of the package maintainer to provide
9100 maintainer scripts which correctly create, update and
9101 maintain the file and remove it on purge. (See <ref
9102 id="maintainerscripts"> for more information.) These
9103 scripts must be idempotent (i.e., must work correctly if
9104 <prgn>dpkg</prgn> needs to re-run them due to errors
9105 during installation or removal), must cope with all the
9106 variety of ways <prgn>dpkg</prgn> can call maintainer
9107 scripts, must not overwrite or otherwise mangle the user's
9108 configuration without asking, must not ask unnecessary
9109 questions (particularly during upgrades), and must
9110 otherwise be good citizens.
9114 The scripts are not required to configure every possible
9115 option for the package, but only those necessary to get
9116 the package running on a given system. Ideally the
9117 sysadmin should not have to do any configuration other
9118 than that done (semi-)automatically by the
9119 <prgn>postinst</prgn> script.
9123 A common practice is to create a script called
9124 <file><var>package</var>-configure</file> and have the
9125 package's <prgn>postinst</prgn> call it if and only if the
9126 configuration file does not already exist. In certain
9127 cases it is useful for there to be an example or template
9128 file which the maintainer scripts use. Such files should
9129 be in <file>/usr/share/<var>package</var></file> or
9130 <file>/usr/lib/<var>package</var></file> (depending on whether
9131 they are architecture-independent or not). There should
9132 be symbolic links to them from
9133 <file>/usr/share/doc/<var>package</var>/examples</file> if
9134 they are examples, and should be perfectly ordinary
9135 <prgn>dpkg</prgn>-handled files (<em>not</em>
9136 configuration files).
9140 These two styles of configuration file handling must
9141 not be mixed, for that way lies madness:
9142 <prgn>dpkg</prgn> will ask about overwriting the file
9143 every time the package is upgraded.
9148 <heading>Sharing configuration files</heading>
9151 If two or more packages use the same configuration file
9152 and it is reasonable for both to be installed at the same
9153 time, one of these packages must be defined as
9154 <em>owner</em> of the configuration file, i.e., it will be
9155 the package which handles that file as a configuration
9156 file. Other packages that use the configuration file must
9157 depend on the owning package if they require the
9158 configuration file to operate. If the other package will
9159 use the configuration file if present, but is capable of
9160 operating without it, no dependency need be declared.
9164 If it is desirable for two or more related packages to
9165 share a configuration file <em>and</em> for all of the
9166 related packages to be able to modify that configuration
9167 file, then the following should be done:
9168 <enumlist compact="compact">
9170 One of the related packages (the "owning" package)
9171 will manage the configuration file with maintainer
9172 scripts as described in the previous section.
9175 The owning package should also provide a program
9176 that the other packages may use to modify the
9180 The related packages must use the provided program
9181 to make any desired modifications to the
9182 configuration file. They should either depend on
9183 the core package to guarantee that the configuration
9184 modifier program is available or accept gracefully
9185 that they cannot modify the configuration file if it
9186 is not. (This is in addition to the fact that the
9187 configuration file may not even be present in the
9194 Sometimes it's appropriate to create a new package which
9195 provides the basic infrastructure for the other packages
9196 and which manages the shared configuration files. (The
9197 <tt>sgml-base</tt> package is a good example.)
9201 If the configuration file cannot be shared as described above,
9202 the packages must be marked as conflicting with each other.
9203 Two packages that specify the same file as
9204 a <tt>conffile</tt> must conflict. This is an instance of the
9205 general rule about not sharing files. Neither alternatives
9206 nor diversions are likely to be appropriate in this case; in
9207 particular, <prgn>dpkg</prgn> does not handle diverted
9208 <tt>conffile</tt>s well.
9212 When two packages both declare the same <tt>conffile</tt>, they
9213 may see left-over configuration files from each other even
9214 though they conflict with each other. If a user removes
9215 (without purging) one of the packages and installs the other,
9216 the new package will take over the <tt>conffile</tt> from the
9217 old package. If the file was modified by the user, it will be
9218 treated the same as any other locally
9219 modified <tt>conffile</tt> during an upgrade.
9223 The maintainer scripts must not alter a <tt>conffile</tt>
9224 of <em>any</em> package, including the one the scripts
9230 <heading>User configuration files ("dotfiles")</heading>
9233 The files in <file>/etc/skel</file> will automatically be
9234 copied into new user accounts by <prgn>adduser</prgn>.
9235 No other program should reference the files in
9236 <file>/etc/skel</file>.
9240 Therefore, if a program needs a dotfile to exist in
9241 advance in <file>$HOME</file> to work sensibly, that dotfile
9242 should be installed in <file>/etc/skel</file> and treated as a
9247 However, programs that require dotfiles in order to
9248 operate sensibly are a bad thing, unless they do create
9249 the dotfiles themselves automatically.
9253 Furthermore, programs should be configured by the Debian
9254 default installation to behave as closely to the upstream
9255 default behavior as possible.
9259 Therefore, if a program in a Debian package needs to be
9260 configured in some way in order to operate sensibly, that
9261 should be done using a site-wide configuration file placed
9262 in <file>/etc</file>. Only if the program doesn't support a
9263 site-wide default configuration and the package maintainer
9264 doesn't have time to add it may a default per-user file be
9265 placed in <file>/etc/skel</file>.
9269 <file>/etc/skel</file> should be as empty as we can make it.
9270 This is particularly true because there is no easy (or
9271 necessarily desirable) mechanism for ensuring that the
9272 appropriate dotfiles are copied into the accounts of
9273 existing users when a package is installed.
9279 <heading>Log files</heading>
9281 Log files should usually be named
9282 <file>/var/log/<var>package</var>.log</file>. If you have many
9283 log files, or need a separate directory for permission
9284 reasons (<file>/var/log</file> is writable only by
9285 <file>root</file>), you should usually create a directory named
9286 <file>/var/log/<var>package</var></file> and place your log
9291 Log files must be rotated occasionally so that they don't grow
9292 indefinitely. The best way to do this is to install a log
9293 rotation configuration file in the
9294 directory <file>/etc/logrotate.d</file>, normally
9295 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9296 the facilities provided by <prgn>logrotate</prgn>.
9299 The traditional approach to log files has been to set up
9300 <em>ad hoc</em> log rotation schemes using simple shell
9301 scripts and cron. While this approach is highly
9302 customizable, it requires quite a lot of sysadmin work.
9303 Even though the original Debian system helped a little
9304 by automatically installing a system which can be used
9305 as a template, this was deemed not enough.
9309 The use of <prgn>logrotate</prgn>, a program developed
9310 by Red Hat, is better, as it centralizes log management.
9311 It has both a configuration file
9312 (<file>/etc/logrotate.conf</file>) and a directory where
9313 packages can drop their individual log rotation
9314 configurations (<file>/etc/logrotate.d</file>).
9317 Here is a good example for a logrotate config
9318 file (for more information see <manref name="logrotate"
9320 <example compact="compact">
9321 /var/log/foo/*.log {
9327 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9331 This rotates all files under <file>/var/log/foo</file>, saves 12
9332 compressed generations, and tells the daemon to reopen its log
9333 files after the log rotation. It skips this log rotation
9334 (via <tt>missingok</tt>) if no such log file is present, which
9335 avoids errors if the package is removed but not purged.
9339 Log files should be removed when the package is
9340 purged (but not when it is only removed). This should be
9341 done by the <prgn>postrm</prgn> script when it is called
9342 with the argument <tt>purge</tt> (see <ref
9343 id="removedetails">).
9347 <sect id="permissions-owners">
9348 <heading>Permissions and owners</heading>
9351 The rules in this section are guidelines for general use.
9352 If necessary you may deviate from the details below.
9353 However, if you do so you must make sure that what is done
9354 is secure and you should try to be as consistent as possible
9355 with the rest of the system. You should probably also
9356 discuss it on <prgn>debian-devel</prgn> first.
9360 Files should be owned by <tt>root:root</tt>, and made
9361 writable only by the owner and universally readable (and
9362 executable, if appropriate), that is mode 644 or 755.
9366 Directories should be mode 755 or (for group-writability)
9367 mode 2775. The ownership of the directory should be
9368 consistent with its mode: if a directory is mode 2775, it
9369 should be owned by the group that needs write access to
9372 When a package is upgraded, and the owner or permissions
9373 of a file included in the package has changed, dpkg
9374 arranges for the ownership and permissions to be
9375 correctly set upon installation. However, this does not
9376 extend to directories; the permissions and ownership of
9377 directories already on the system does not change on
9378 install or upgrade of packages. This makes sense, since
9379 otherwise common directories like <tt>/usr</tt> would
9380 always be in flux. To correctly change permissions of a
9381 directory the package owns, explicit action is required,
9382 usually in the <tt>postinst</tt> script. Care must be
9383 taken to handle downgrades as well, in that case.
9389 Control information files should be owned by <tt>root:root</tt>
9390 and either mode 644 (for most files) or mode 755 (for
9391 executables such as <qref id="maintscripts">maintainer
9396 Setuid and setgid executables should be mode 4755 or 2755
9397 respectively, and owned by the appropriate user or group.
9398 They should not be made unreadable (modes like 4711 or
9399 2711 or even 4111); doing so achieves no extra security,
9400 because anyone can find the binary in the freely available
9401 Debian package; it is merely inconvenient. For the same
9402 reason you should not restrict read or execute permissions
9403 on non-set-id executables.
9407 Some setuid programs need to be restricted to particular
9408 sets of users, using file permissions. In this case they
9409 should be owned by the uid to which they are set-id, and by
9410 the group which should be allowed to execute them. They
9411 should have mode 4754; again there is no point in making
9412 them unreadable to those users who must not be allowed to
9417 It is possible to arrange that the system administrator can
9418 reconfigure the package to correspond to their local
9419 security policy by changing the permissions on a binary:
9420 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9421 described below.<footnote>
9422 Ordinary files installed by <prgn>dpkg</prgn> (as
9423 opposed to <tt>conffile</tt>s and other similar objects)
9424 normally have their permissions reset to the distributed
9425 permissions when the package is reinstalled. However,
9426 the use of <prgn>dpkg-statoverride</prgn> overrides this
9429 Another method you should consider is to create a group for
9430 people allowed to use the program(s) and make any setuid
9431 executables executable only by that group.
9435 If you need to create a new user or group for your package
9436 there are two possibilities. Firstly, you may need to
9437 make some files in the binary package be owned by this
9438 user or group, or you may need to compile the user or
9439 group id (rather than just the name) into the binary
9440 (though this latter should be avoided if possible, as in
9441 this case you need a statically allocated id).</p>
9444 If you need a statically allocated id, you must ask for a
9445 user or group id from the <tt>base-passwd</tt> maintainer,
9446 and must not release the package until you have been
9447 allocated one. Once you have been allocated one you must
9448 either make the package depend on a version of the
9449 <tt>base-passwd</tt> package with the id present in
9450 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9451 your package to create the user or group itself with the
9452 correct id (using <tt>adduser</tt>) in its
9453 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9454 the <prgn>postinst</prgn> is to be preferred if it is
9455 possible, otherwise a pre-dependency will be needed on the
9456 <tt>adduser</tt> package.)
9460 On the other hand, the program might be able to determine
9461 the uid or gid from the user or group name at runtime, so
9462 that a dynamically allocated id can be used. In this case
9463 you should choose an appropriate user or group name,
9464 discussing this on <prgn>debian-devel</prgn> and checking
9465 with the <package/base-passwd/ maintainer that it is unique and that
9466 they do not wish you to use a statically allocated id
9467 instead. When this has been checked you must arrange for
9468 your package to create the user or group if necessary using
9469 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9470 <prgn>postinst</prgn> script (again, the latter is to be
9471 preferred if it is possible).
9475 Note that changing the numeric value of an id associated
9476 with a name is very difficult, and involves searching the
9477 file system for all appropriate files. You need to think
9478 carefully whether a static or dynamic id is required, since
9479 changing your mind later will cause problems.
9482 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9484 This section is not intended as policy, but as a
9485 description of the use of <prgn>dpkg-statoverride</prgn>.
9489 If a system administrator wishes to have a file (or
9490 directory or other such thing) installed with owner and
9491 permissions different from those in the distributed Debian
9492 package, they can use the <prgn>dpkg-statoverride</prgn>
9493 program to instruct <prgn>dpkg</prgn> to use the different
9494 settings every time the file is installed. Thus the
9495 package maintainer should distribute the files with their
9496 normal permissions, and leave it for the system
9497 administrator to make any desired changes. For example, a
9498 daemon which is normally required to be setuid root, but
9499 in certain situations could be used without being setuid,
9500 should be installed setuid in the <tt>.deb</tt>. Then the
9501 local system administrator can change this if they wish.
9502 If there are two standard ways of doing it, the package
9503 maintainer can use <tt>debconf</tt> to find out the
9504 preference, and call <prgn>dpkg-statoverride</prgn> in the
9505 maintainer script if necessary to accommodate the system
9506 administrator's choice. Care must be taken during
9507 upgrades to not override an existing setting.
9511 Given the above, <prgn>dpkg-statoverride</prgn> is
9512 essentially a tool for system administrators and would not
9513 normally be needed in the maintainer scripts. There is
9514 one type of situation, though, where calls to
9515 <prgn>dpkg-statoverride</prgn> would be needed in the
9516 maintainer scripts, and that involves packages which use
9517 dynamically allocated user or group ids. In such a
9518 situation, something like the following idiom can be very
9519 helpful in the package's <prgn>postinst</prgn>, where
9520 <tt>sysuser</tt> is a dynamically allocated id:
9522 for i in /usr/bin/foo /usr/sbin/bar
9524 # only do something when no setting exists
9525 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9527 #include: debconf processing, question about foo and bar
9528 if [ "$RET" = "true" ] ; then
9529 dpkg-statoverride --update --add sysuser root 4755 $i
9534 The corresponding code to remove the override when the package
9537 for i in /usr/bin/foo /usr/sbin/bar
9539 if dpkg-statoverride --list $i >/dev/null 2>&1
9541 dpkg-statoverride --remove $i
9549 <sect id="filenames">
9550 <heading>File names</heading>
9553 The name of the files installed by binary packages in the system PATH
9554 (namely <tt>/bin</tt>, <tt>/sbin</tt>, <tt>/usr/bin</tt>,
9555 <tt>/usr/sbin</tt> and <tt>/usr/games</tt>) must be encoded in
9560 The name of the files and directories installed by binary packages
9561 outside the system PATH must be encoded in UTF-8 and should be
9562 restricted to ASCII when it is possible to do so.
9568 <chapt id="customized-programs">
9569 <heading>Customized programs</heading>
9571 <sect id="arch-spec">
9572 <heading>Architecture specification strings</heading>
9575 If a program needs to specify an <em>architecture specification
9576 string</em> in some place, it should select one of the strings
9577 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9578 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9579 part is sometimes elided, as when the OS is Linux.
9583 Note that we don't want to use
9584 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9585 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9586 since this would make our programs incompatible with other
9587 Linux distributions. We also don't use something like
9588 <tt><var>arch</var>-unknown-linux</tt>, since the
9589 <tt>unknown</tt> does not look very good.
9592 <sect1 id="arch-wildcard-spec">
9593 <heading>Architecture wildcards</heading>
9596 A package may specify an architecture wildcard. Architecture
9597 wildcards are in the format <tt>any</tt> (which matches every
9598 architecture), <tt><var>os</var></tt>-any, or
9599 any-<tt><var>cpu</var></tt>. <footnote>
9600 Internally, the package system normalizes the GNU triplets
9601 and the Debian arches into Debian arch triplets (which are
9602 kind of inverted GNU triplets), with the first component of
9603 the triplet representing the libc and ABI in use, and then
9604 does matching against those triplets. However, such
9605 triplets are an internal implementation detail that should
9606 not be used by packages directly. The libc and ABI portion
9607 is handled internally by the package system based on
9608 the <var>os</var> and <var>cpu</var>.
9615 <heading>Daemons</heading>
9618 The configuration files <file>/etc/services</file>,
9619 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9620 by the <prgn>netbase</prgn> package and must not be modified
9625 If a package requires a new entry in one of these files, the
9626 maintainer should get in contact with the
9627 <prgn>netbase</prgn> maintainer, who will add the entries
9628 and release a new version of the <prgn>netbase</prgn>
9633 The configuration file <file>/etc/inetd.conf</file> must not be
9634 modified by the package's scripts except via the
9635 <prgn>update-inetd</prgn> script or the
9636 <file>DebianNet.pm</file> Perl module. See their documentation
9637 for details on how to add entries.
9641 If a package wants to install an example entry into
9642 <file>/etc/inetd.conf</file>, the entry must be preceded with
9643 exactly one hash character (<tt>#</tt>). Such lines are
9644 treated as "commented out by user" by the
9645 <prgn>update-inetd</prgn> script and are not changed or
9646 activated during package updates.
9651 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9655 Some programs need to create pseudo-ttys. This should be done
9656 using Unix98 ptys if the C library supports it. The resulting
9657 program must not be installed setuid root, unless that
9658 is required for other functionality.
9662 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9663 <file>/var/log/lastlog</file> must be installed writable by
9664 group <tt>utmp</tt>. Programs which need to modify those
9665 files must be installed setgid <tt>utmp</tt>.
9670 <heading>Editors and pagers</heading>
9673 Some programs have the ability to launch an editor or pager
9674 program to edit or display a text document. Since there are
9675 lots of different editors and pagers available in the Debian
9676 distribution, the system administrator and each user should
9677 have the possibility to choose their preferred editor and
9682 In addition, every program should choose a good default
9683 editor/pager if none is selected by the user or system
9688 Thus, every program that launches an editor or pager must
9689 use the EDITOR or PAGER environment variable to determine
9690 the editor or pager the user wishes to use. If these
9691 variables are not set, the programs <file>/usr/bin/editor</file>
9692 and <file>/usr/bin/pager</file> should be used, respectively.
9696 These two files are managed through the <prgn>dpkg</prgn>
9697 "alternatives" mechanism. Every package providing an editor or
9698 pager must call the <prgn>update-alternatives</prgn> script to
9699 register as an alternative for <file>/usr/bin/editor</file>
9700 or <file>/usr/bin/pager</file> as appropriate. The alternative
9701 should have a slave alternative
9702 for <file>/usr/share/man/man1/editor.1.gz</file>
9703 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9704 corresponding manual page.
9708 If it is very hard to adapt a program to make use of the
9709 EDITOR or PAGER variables, that program may be configured to
9710 use <file>/usr/bin/sensible-editor</file> and
9711 <file>/usr/bin/sensible-pager</file> as the editor or pager
9712 program respectively. These are two scripts provided in the
9713 <package>sensible-utils</package> package that check the EDITOR
9714 and PAGER variables and launch the appropriate program, and fall
9715 back to <file>/usr/bin/editor</file>
9716 and <file>/usr/bin/pager</file> if the variable is not set.
9720 A program may also use the VISUAL environment variable to
9721 determine the user's choice of editor. If it exists, it
9722 should take precedence over EDITOR. This is in fact what
9723 <file>/usr/bin/sensible-editor</file> does.
9727 It is not required for a package to depend on
9728 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9729 package to provide such virtual packages.<footnote>
9730 The Debian base system already provides an editor and a
9736 <sect id="web-appl">
9737 <heading>Web servers and applications</heading>
9740 This section describes the locations and URLs that should
9741 be used by all web servers and web applications in the
9748 Cgi-bin executable files are installed in the
9750 <example compact="compact">
9753 or a subdirectory of that directory, and the script
9754 <example compact="compact">
9755 /usr/lib/cgi-bin/.../<var>cgi-bin-name</var>
9757 should be referred to as
9758 <example compact="compact">
9759 http://localhost/cgi-bin/.../<var>cgi-bin-name</var>
9768 <p>Access to images</p>
9770 It is recommended that images for a package be stored
9771 in <tt>/usr/share/images/<var>package</var></tt> and
9772 may be referred to through an alias <tt>/images/</tt>
9775 http://localhost/images/<package>/<filename>
9782 <p>Web Document Root</p>
9785 Web Applications should try to avoid storing files in
9786 the Web Document Root. Instead they should use the
9787 /usr/share/doc/<var>package</var> directory for
9788 documents and register the Web Application via the
9789 <package>doc-base</package> package. If access to the
9790 web document root is unavoidable then use
9791 <example compact="compact">
9794 as the Document Root. This might be just a symbolic
9795 link to the location where the system administrator
9796 has put the real document root.
9799 <item><p>Providing httpd and/or httpd-cgi</p>
9801 All web servers should provide the virtual package
9802 <tt>httpd</tt>. If a web server has CGI support it should
9803 provide <tt>httpd-cgi</tt> additionally.
9806 All web applications which do not contain CGI scripts should
9807 depend on <tt>httpd</tt>, all those web applications which
9808 <tt>do</tt> contain CGI scripts, should depend on
9816 <sect id="mail-transport-agents">
9817 <heading>Mail transport, delivery and user agents</heading>
9820 Debian packages which process electronic mail, whether mail
9821 user agents (MUAs) or mail transport agents (MTAs), must
9822 ensure that they are compatible with the configuration
9823 decisions below. Failure to do this may result in lost
9824 mail, broken <tt>From:</tt> lines, and other serious brain
9829 The mail spool is <file>/var/mail</file> and the interface to
9830 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9831 the FHS). On older systems, the mail spool may be
9832 physically located in <file>/var/spool/mail</file>, but all
9833 access to the mail spool should be via the
9834 <file>/var/mail</file> symlink. The mail spool is part of the
9835 base system and not part of the MTA package.
9839 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9840 programs (such as IMAP daemons) must lock the mailbox in an
9841 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9842 be combined with dot locking. To avoid deadlocks, a program
9843 should use <tt>fcntl()</tt> first and dot locking after
9844 this, or alternatively implement the two locking methods in
9845 a non blocking way<footnote>
9846 If it is not possible to establish both locks, the
9847 system shouldn't wait for the second lock to be
9848 established, but remove the first lock, wait a (random)
9849 time, and start over locking again.
9850 </footnote>. Using the functions <tt>maillock</tt> and
9851 <tt>mailunlock</tt> provided by the
9852 <tt>liblockfile*</tt><footnote>
9853 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9854 to use these functions.
9855 </footnote> packages is the recommended way to realize this.
9859 Mailboxes are generally either mode 600 and owned by
9860 <var>user</var> or mode 660 and owned by
9861 <tt><var>user</var>:mail</tt><footnote>
9862 There are two traditional permission schemes for mail spools:
9863 mode 600 with all mail delivery done by processes running as
9864 the destination user, or mode 660 and owned by group mail with
9865 mail delivery done by a process running as a system user in
9866 group mail. Historically, Debian required mode 660 mail
9867 spools to enable the latter model, but that model has become
9868 increasingly uncommon and the principle of least privilege
9869 indicates that mail systems that use the first model should
9870 use permissions of 600. If delivery to programs is permitted,
9871 it's easier to keep the mail system secure if the delivery
9872 agent runs as the destination user. Debian Policy therefore
9873 permits either scheme.
9874 </footnote>. The local system administrator may choose a
9875 different permission scheme; packages should not make
9876 assumptions about the permission and ownership of mailboxes
9877 unless required (such as when creating a new mailbox). A MUA
9878 may remove a mailbox (unless it has nonstandard permissions) in
9879 which case the MTA or another MUA must recreate it if needed.
9883 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9884 be setgid mail to do the locking mentioned above (and
9885 must obviously avoid accessing other users' mailboxes
9886 using this privilege).</p>
9889 <file>/etc/aliases</file> is the source file for the system mail
9890 aliases (e.g., postmaster, usenet, etc.), it is the one
9891 which the sysadmin and <prgn>postinst</prgn> scripts may
9892 edit. After <file>/etc/aliases</file> is edited the program or
9893 human editing it must call <prgn>newaliases</prgn>. All MTA
9894 packages must come with a <prgn>newaliases</prgn> program,
9895 even if it does nothing, but older MTA packages did not do
9896 this so programs should not fail if <prgn>newaliases</prgn>
9897 cannot be found. Note that because of this, all MTA
9898 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9899 <tt>Replaces: mail-transport-agent</tt> control fields.
9903 The convention of writing <tt>forward to
9904 <var>address</var></tt> in the mailbox itself is not
9905 supported. Use a <tt>.forward</tt> file instead.</p>
9908 The <prgn>rmail</prgn> program used by UUCP
9909 for incoming mail should be <file>/usr/sbin/rmail</file>.
9910 Likewise, <prgn>rsmtp</prgn>, for receiving
9911 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9915 If your package needs to know what hostname to use on (for
9916 example) outgoing news and mail messages which are generated
9917 locally, you should use the file <file>/etc/mailname</file>. It
9918 will contain the portion after the username and <tt>@</tt>
9919 (at) sign for email addresses of users on the machine
9920 (followed by a newline).
9924 Such a package should check for the existence of this file
9925 when it is being configured. If it exists, it should be
9926 used without comment, although an MTA's configuration script
9927 may wish to prompt the user even if it finds that this file
9928 exists. If the file does not exist, the package should
9929 prompt the user for the value (preferably using
9930 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9931 as well as using it in the package's configuration. The
9932 prompt should make it clear that the name will not just be
9933 used by that package. For example, in this situation the
9934 <tt>inn</tt> package could say something like:
9935 <example compact="compact">
9936 Please enter the "mail name" of your system. This is the
9937 hostname portion of the address to be shown on outgoing
9938 news and mail messages. The default is
9939 <var>syshostname</var>, your system's host name. Mail
9940 name ["<var>syshostname</var>"]:
9942 where <var>syshostname</var> is the output of <tt>hostname
9948 <heading>News system configuration</heading>
9951 All the configuration files related to the NNTP (news)
9952 servers and clients should be located under
9953 <file>/etc/news</file>.</p>
9956 There are some configuration issues that apply to a number
9957 of news clients and server packages on the machine. These
9961 <tag><file>/etc/news/organization</file></tag>
9963 A string which should appear as the
9964 organization header for all messages posted
9965 by NNTP clients on the machine
9968 <tag><file>/etc/news/server</file></tag>
9970 Contains the FQDN of the upstream NNTP
9971 server, or localhost if the local machine is
9976 Other global files may be added as required for cross-package news
9983 <heading>Programs for the X Window System</heading>
9986 <heading>Providing X support and package priorities</heading>
9989 Programs that can be configured with support for the X
9990 Window System must be configured to do so and must declare
9991 any package dependencies necessary to satisfy their
9992 runtime requirements when using the X Window System. If
9993 such a package is of higher priority than the X packages
9994 on which it depends, it is required that either the
9995 X-specific components be split into a separate package, or
9996 that an alternative version of the package, which includes
9997 X support, be provided, or that the package's priority be
10003 <heading>Packages providing an X server</heading>
10006 Packages that provide an X server that, directly or
10007 indirectly, communicates with real input and display
10008 hardware should declare in their <tt>Provides</tt> control
10009 field that they provide the virtual
10010 package <tt>xserver</tt>.<footnote>
10011 This implements current practice, and provides an
10012 actual policy for usage of the <tt>xserver</tt>
10013 virtual package which appears in the virtual packages
10014 list. In a nutshell, X servers that interface
10015 directly with the display and input hardware or via
10016 another subsystem (e.g., GGI) should provide
10017 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
10018 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
10024 <heading>Packages providing a terminal emulator</heading>
10027 Packages that provide a terminal emulator for the X Window
10028 System which meet the criteria listed below should declare in
10029 their <tt>Provides</tt> control field that they provide the
10030 virtual package <tt>x-terminal-emulator</tt>. They should
10031 also register themselves as an alternative for
10032 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
10033 20. That alternative should have a slave alternative
10034 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
10035 pointing to the corresponding manual page.
10039 To be an <tt>x-terminal-emulator</tt>, a program must:
10040 <list compact="compact">
10042 Be able to emulate a DEC VT100 terminal, or a
10043 compatible terminal.
10047 Support the command-line option <tt>-e
10048 <var>command</var></tt>, which creates a new
10049 terminal window<footnote>
10050 "New terminal window" does not necessarily mean
10051 a new top-level X window directly parented by
10052 the window manager; it could, if the terminal
10053 emulator application were so coded, be a new
10054 "view" in a multiple-document interface (MDI).
10056 and runs the specified <var>command</var>,
10057 interpreting the entirety of the rest of the command
10058 line as a command to pass straight to exec, in the
10059 manner that <tt>xterm</tt> does.
10063 Support the command-line option <tt>-T
10064 <var>title</var></tt>, which creates a new terminal
10065 window with the window title <var>title</var>.
10072 <heading>Packages providing a window manager</heading>
10075 Packages that provide a window manager should declare in
10076 their <tt>Provides</tt> control field that they provide the
10077 virtual package <tt>x-window-manager</tt>. They should also
10078 register themselves as an alternative for
10079 <file>/usr/bin/x-window-manager</file>, with a priority
10080 calculated as follows:
10081 <list compact="compact">
10083 Start with a priority of 20.
10087 If the window manager supports the Debian menu
10088 system, add 20 points if this support is available
10089 in the package's default configuration (i.e., no
10090 configuration files belonging to the system or user
10091 have to be edited to activate the feature); if
10092 configuration files must be modified, add only 10
10098 If the window manager complies with <url
10099 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
10100 name="The Window Manager Specification Project">,
10101 written by the <url id="http://www.freedesktop.org/wiki/"
10102 name="Free Desktop Group">, add 40 points.
10106 If the window manager permits the X session to be
10107 restarted using a <em>different</em> window manager
10108 (without killing the X server) in its default
10109 configuration, add 10 points; otherwise add none.
10112 That alternative should have a slave alternative
10113 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10114 pointing to the corresponding manual page.
10119 <heading>Packages providing fonts</heading>
10122 Packages that provide fonts for the X Window
10124 For the purposes of Debian Policy, a "font for the X
10125 Window System" is one which is accessed via X protocol
10126 requests. Fonts for the Linux console, for PostScript
10127 renderer, or any other purpose, do not fit this
10128 definition. Any tool which makes such fonts available
10129 to the X Window System, however, must abide by this
10132 must do a number of things to ensure that they are both
10133 available without modification of the X or font server
10134 configuration, and that they do not corrupt files used by
10135 other font packages to register information about
10139 Fonts of any type supported by the X Window System
10140 must be in a separate binary package from any
10141 executables, libraries, or documentation (except
10142 that specific to the fonts shipped, such as their
10143 license information). If one or more of the fonts
10144 so packaged are necessary for proper operation of
10145 the package with which they are associated the font
10146 package may be Recommended; if the fonts merely
10147 provide an enhancement, a Suggests relationship may
10148 be used. Packages must not Depend on font
10149 packages.<footnote>
10150 This is because the X server may retrieve fonts
10151 from the local file system or over the network
10152 from an X font server; the Debian package system
10153 is empowered to deal only with the local
10159 BDF fonts must be converted to PCF fonts with the
10160 <prgn>bdftopcf</prgn> utility (available in the
10161 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10162 placed in a directory that corresponds to their
10164 <list compact="compact">
10166 100 dpi fonts must be placed in
10167 <file>/usr/share/fonts/X11/100dpi/</file>.
10171 75 dpi fonts must be placed in
10172 <file>/usr/share/fonts/X11/75dpi/</file>.
10176 Character-cell fonts, cursor fonts, and other
10177 low-resolution fonts must be placed in
10178 <file>/usr/share/fonts/X11/misc/</file>.
10184 Type 1 fonts must be placed in
10185 <file>/usr/share/fonts/X11/Type1/</file>. If font
10186 metric files are available, they must be placed here
10191 Subdirectories of <file>/usr/share/fonts/X11/</file>
10192 other than those listed above must be neither
10193 created nor used. (The <file>PEX</file>, <file>CID</file>,
10194 <file>Speedo</file>, and <file>cyrillic</file> directories
10195 are excepted for historical reasons, but installation of
10196 files into these directories remains discouraged.)
10200 Font packages may, instead of placing files directly
10201 in the X font directories listed above, provide
10202 symbolic links in that font directory pointing to
10203 the files' actual location in the filesystem. Such
10204 a location must comply with the FHS.
10208 Font packages should not contain both 75dpi and
10209 100dpi versions of a font. If both are available,
10210 they should be provided in separate binary packages
10211 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10212 the names of the packages containing the
10213 corresponding fonts.
10217 Fonts destined for the <file>misc</file> subdirectory
10218 should not be included in the same package as 75dpi
10219 or 100dpi fonts; instead, they should be provided in
10220 a separate package with <tt>-misc</tt> appended to
10225 Font packages must not provide the files
10226 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10227 <file>fonts.scale</file> in a font directory:
10230 <file>fonts.dir</file> files must not be provided at all.
10234 <file>fonts.alias</file> and <file>fonts.scale</file>
10235 files, if needed, should be provided in the
10237 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10238 where <var>fontdir</var> is the name of the
10240 <file>/usr/share/fonts/X11/</file> where the
10241 package's corresponding fonts are stored
10242 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10243 <var>package</var> is the name of the package
10244 that provides these fonts, and
10245 <var>extension</var> is either <tt>scale</tt>
10246 or <tt>alias</tt>, whichever corresponds to
10253 Font packages must declare a dependency on
10254 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10255 or <tt>Pre-Depends</tt> control field.
10259 Font packages that provide one or more
10260 <file>fonts.scale</file> files as described above must
10261 invoke <prgn>update-fonts-scale</prgn> on each
10262 directory into which they installed fonts
10263 <em>before</em> invoking
10264 <prgn>update-fonts-dir</prgn> on that directory.
10265 This invocation must occur in both the
10266 <prgn>postinst</prgn> (for all arguments) and
10267 <prgn>postrm</prgn> (for all arguments except
10268 <tt>upgrade</tt>) scripts.
10272 Font packages that provide one or more
10273 <file>fonts.alias</file> files as described above must
10274 invoke <prgn>update-fonts-alias</prgn> on each
10275 directory into which they installed fonts. This
10276 invocation must occur in both the
10277 <prgn>postinst</prgn> (for all arguments) and
10278 <prgn>postrm</prgn> (for all arguments except
10279 <tt>upgrade</tt>) scripts.
10283 Font packages must invoke
10284 <prgn>update-fonts-dir</prgn> on each directory into
10285 which they installed fonts. This invocation must
10286 occur in both the <prgn>postinst</prgn> (for all
10287 arguments) and <prgn>postrm</prgn> (for all
10288 arguments except <tt>upgrade</tt>) scripts.
10292 Font packages must not provide alias names for the
10293 fonts they include which collide with alias names
10294 already in use by fonts already packaged.
10298 Font packages must not provide fonts with the same
10299 XLFD registry name as another font already packaged.
10305 <sect1 id="appdefaults">
10306 <heading>Application defaults files</heading>
10309 Application defaults files must be installed in the
10310 directory <file>/etc/X11/app-defaults/</file> (use of a
10311 localized subdirectory of <file>/etc/X11/</file> as described
10312 in the <em>X Toolkit Intrinsics - C Language
10313 Interface</em> manual is also permitted). They must be
10314 registered as <tt>conffile</tt>s or handled as
10315 configuration files.
10319 Customization of programs' X resources may also be
10320 supported with the provision of a file with the same name
10321 as that of the package placed in
10322 the <file>/etc/X11/Xresources/</file> directory, which
10323 must be registered as a <tt>conffile</tt> or handled as a
10324 configuration file.<footnote>
10325 Note that this mechanism is not the same as using
10326 app-defaults; app-defaults are tied to the client
10327 binary on the local file system, whereas X resources
10328 are stored in the X server and affect all connecting
10335 <heading>Installation directory issues</heading>
10338 Historically, packages using the X Window System used a
10339 separate set of installation directories from other packages.
10340 This practice has been discontinued and packages using the X
10341 Window System should now generally be installed in the same
10342 directories as any other package. Specifically, packages must
10343 not install files under the <file>/usr/X11R6/</file> directory
10344 and the <file>/usr/X11R6/</file> directory hierarchy should be
10345 regarded as obsolete.
10349 Include files previously installed under
10350 <file>/usr/X11R6/include/X11/</file> should be installed into
10351 <file>/usr/include/X11/</file>. For files previously
10352 installed into subdirectories of
10353 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10354 determine if subdirectories of <file>/usr/lib/</file> and
10355 <file>/usr/share/</file> can be used. If not, a subdirectory
10356 of <file>/usr/lib/X11/</file> should be used.
10360 Configuration files for window, display, or session managers
10361 or other applications that are tightly integrated with the X
10362 Window System may be placed in a subdirectory
10363 of <file>/etc/X11/</file> corresponding to the package name.
10364 Other X Window System applications should use
10365 the <file>/etc/</file> directory unless otherwise mandated by
10366 policy (such as for <ref id="appdefaults">).
10372 <heading>Perl programs and modules</heading>
10375 Perl programs and modules should follow the current Perl policy.
10379 The Perl policy can be found in the <tt>perl-policy</tt>
10380 files in the <tt>debian-policy</tt> package.
10381 It is also available from the Debian web mirrors at
10382 <tt><url name="/doc/packaging-manuals/perl-policy/"
10383 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10388 <heading>Emacs lisp programs</heading>
10391 Please refer to the "Debian Emacs Policy" for details of how to
10392 package emacs lisp programs.
10396 The Emacs policy is available in
10397 <file>debian-emacs-policy.gz</file> of the
10398 <package>emacsen-common</package> package.
10399 It is also available from the Debian web mirrors at
10400 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10401 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10406 <heading>Games</heading>
10409 The permissions on <file>/var/games</file> are mode 755, owner
10410 <tt>root</tt> and group <tt>root</tt>.
10414 Each game decides on its own security policy.</p>
10417 Games which require protected, privileged access to
10418 high-score files, saved games, etc., may be made
10419 set-<em>group</em>-id (mode 2755) and owned by
10420 <tt>root:games</tt>, and use files and directories with
10421 appropriate permissions (770 <tt>root:games</tt>, for
10422 example). They must not be made
10423 set-<em>user</em>-id, as this causes security problems. (If
10424 an attacker can subvert any set-user-id game they can
10425 overwrite the executable of any other, causing other players
10426 of these games to run a Trojan horse program. With a
10427 set-group-id game the attacker only gets access to less
10428 important game data, and if they can get at the other
10429 players' accounts at all it will take considerably more
10433 Some packages, for example some fortune cookie programs, are
10434 configured by the upstream authors to install with their
10435 data files or other static information made unreadable so
10436 that they can only be accessed through set-id programs
10437 provided. You should not do this in a Debian package: anyone can
10438 download the <file>.deb</file> file and read the data from it,
10439 so there is no point making the files unreadable. Not
10440 making the files unreadable also means that you don't have
10441 to make so many programs set-id, which reduces the risk of a
10445 As described in the FHS, binaries of games should be
10446 installed in the directory <file>/usr/games</file>. This also
10447 applies to games that use the X Window System. Manual pages
10448 for games (X and non-X games) should be installed in
10449 <file>/usr/share/man/man6</file>.</p>
10455 <heading>Documentation</heading>
10458 <heading>Manual pages</heading>
10461 You should install manual pages in <prgn>nroff</prgn> source
10462 form, in appropriate places under <file>/usr/share/man</file>.
10463 You should only use sections 1 to 9 (see the FHS for more
10464 details). You must not install a pre-formatted "cat page".
10468 Each program, utility, and function should have an
10469 associated manual page included in the same package. It is
10470 suggested that all configuration files also have a manual
10471 page included as well. Manual pages for protocols and other
10472 auxiliary things are optional.
10476 If no manual page is available, this is considered as a bug
10477 and should be reported to the Debian Bug Tracking System (the
10478 maintainer of the package is allowed to write this bug report
10479 themselves, if they so desire). Do not close the bug report
10480 until a proper man page is available.<footnote>
10481 It is not very hard to write a man page. See the
10482 <url id="http://www.schweikhardt.net/man_page_howto.html"
10483 name="Man-Page-HOWTO">,
10484 <manref name="man" section="7">, the examples created
10485 by <prgn>dh_make</prgn>, the helper
10486 program <prgn>help2man</prgn>, or the
10487 directory <file>/usr/share/doc/man-db/examples</file>.
10492 You may forward a complaint about a missing man page to the
10493 upstream authors, and mark the bug as forwarded in the
10494 Debian bug tracking system. Even though the GNU Project do
10495 not in general consider the lack of a man page to be a bug,
10496 we do; if they tell you that they don't consider it a bug
10497 you should leave the bug in our bug tracking system open
10502 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10506 If one man page needs to be accessible via several names it
10507 is better to use a symbolic link than the <file>.so</file>
10508 feature, but there is no need to fiddle with the relevant
10509 parts of the upstream source to change from <file>.so</file> to
10510 symlinks: don't do it unless it's easy. You should not
10511 create hard links in the manual page directories, nor put
10512 absolute filenames in <file>.so</file> directives. The filename
10513 in a <file>.so</file> in a man page should be relative to the
10514 base of the man page tree (usually
10515 <file>/usr/share/man</file>). If you do not create any links
10516 (whether symlinks, hard links, or <tt>.so</tt> directives)
10517 in the file system to the alternate names of the man page,
10518 then you should not rely on <prgn>man</prgn> finding your
10519 man page under those names based solely on the information in
10520 the man page's header.<footnote>
10521 Supporting this in <prgn>man</prgn> often requires
10522 unreasonable processing time to find a manual page or to
10523 report that none exists, and moves knowledge into man's
10524 database that would be better left in the file system.
10525 This support is therefore deprecated and will cease to
10526 be present in the future.
10531 Manual pages in locale-specific subdirectories of
10532 <file>/usr/share/man</file> should use either UTF-8 or the usual
10533 legacy encoding for that language (normally the one corresponding
10534 to the shortest relevant locale name in
10535 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10536 <file>/usr/share/man/fr</file> should use either UTF-8 or
10537 ISO-8859-1.<footnote>
10538 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10539 use. In future, all manual pages will be required to use
10545 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10546 included in the subdirectory name unless it indicates a
10547 significant difference in the language, as this excludes
10548 speakers of the language in other countries.<footnote>
10549 At the time of writing, Chinese and Portuguese are the main
10550 languages with such differences, so <file>pt_BR</file>,
10551 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10556 If a localized version of a manual page is provided, it should
10557 either be up-to-date or it should be obvious to the reader that
10558 it is outdated and the original manual page should be used
10559 instead. This can be done either by a note at the beginning of
10560 the manual page or by showing the missing or changed portions in
10561 the original language instead of the target language.
10566 <heading>Info documents</heading>
10569 Info documents should be installed in <file>/usr/share/info</file>.
10570 They should be compressed with <tt>gzip -9</tt>.
10574 The <prgn>install-info</prgn> program maintains a directory of
10575 installed info documents in <file>/usr/share/info/dir</file> for the
10576 use of info readers. This file must not be included in packages
10577 other than <package>install-info</package>.
10581 <prgn>install-info</prgn> is automatically invoked when
10582 appropriate using dpkg triggers. Packages other than
10583 <package>install-info</package> <em>should not</em> invoke
10584 <prgn>install-info</prgn> directly and <em>should not</em>
10585 depend on, recommend, or suggest <package>install-info</package>
10590 Info readers requiring the <file>/usr/share/info/dir</file> file
10591 should depend on <package>install-info</package>.
10595 Info documents should contain section and directory entry
10596 information in the document for the use
10597 of <prgn>install-info</prgn>. The section should be specified
10598 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10599 space and the section of this info page. The directory entry or
10600 entries should be included between
10601 a <tt>START-INFO-DIR-ENTRY</tt> line and
10602 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10604 INFO-DIR-SECTION Individual utilities
10605 START-INFO-DIR-ENTRY
10606 * example: (example). An example info directory entry.
10609 To determine which section to use, you should look
10610 at <file>/usr/share/info/dir</file> on your system and choose
10611 the most relevant (or create a new section if none of the
10612 current sections are relevant).<footnote>
10613 Normally, info documents are generated from Texinfo source.
10614 To include this information in the generated info document, if
10615 it is absent, add commands like:
10617 @dircategory Individual utilities
10619 * example: (example). An example info directory entry.
10622 to the Texinfo source of the document and ensure that the info
10623 documents are rebuilt from source during the package build.
10629 <heading>Additional documentation</heading>
10632 Any additional documentation that comes with the package may
10633 be installed at the discretion of the package maintainer.
10634 Plain text documentation should be installed in the directory
10635 <file>/usr/share/doc/<var>package</var></file>, where
10636 <var>package</var> is the name of the package, and
10637 compressed with <tt>gzip -9</tt> unless it is small.
10641 If a package comes with large amounts of documentation which
10642 many users of the package will not require you should create
10643 a separate binary package to contain it, so that it does not
10644 take up disk space on the machines of users who do not need
10645 or want it installed.</p>
10648 It is often a good idea to put text information files
10649 (<file>README</file>s, changelogs, and so forth) that come with
10650 the source package in <file>/usr/share/doc/<var>package</var></file>
10651 in the binary package. However, you don't need to install
10652 the instructions for building and installing the package, of
10656 Packages must not require the existence of any files in
10657 <file>/usr/share/doc/</file> in order to function
10659 The system administrator should be able to
10660 delete files in <file>/usr/share/doc/</file> without causing
10661 any programs to break.
10663 Any files that are referenced by programs but are also
10664 useful as stand alone documentation should be installed under
10665 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10666 <file>/usr/share/doc/<var>package</var></file>.
10670 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10671 link to another directory in <file>/usr/share/doc</file> only if
10672 the two packages both come from the same source and the
10673 first package Depends on the second.<footnote>
10675 Please note that this does not override the section on
10676 changelog files below, so the file
10677 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10678 must refer to the changelog for the current version of
10679 <var>package</var> in question. In practice, this means
10680 that the sources of the target and the destination of the
10681 symlink must be the same (same source package and
10688 Former Debian releases placed all additional documentation
10689 in <file>/usr/doc/<var>package</var></file>. This has been
10690 changed to <file>/usr/share/doc/<var>package</var></file>,
10691 and packages must not put documentation in the directory
10692 <file>/usr/doc/<var>package</var></file>. <footnote>
10693 At this phase of the transition, we no longer require a
10694 symbolic link in <file>/usr/doc/</file>. At a later point,
10695 policy shall change to make the symbolic links a bug.
10701 <heading>Preferred documentation formats</heading>
10704 The unification of Debian documentation is being carried out
10708 If your package comes with extensive documentation in a
10709 markup format that can be converted to various other formats
10710 you should if possible ship HTML versions in a binary
10711 package, in the directory
10712 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10713 its subdirectories.<footnote>
10714 The rationale: The important thing here is that HTML
10715 docs should be available in <em>some</em> package, not
10716 necessarily in the main binary package.
10721 Other formats such as PostScript may be provided at the
10722 package maintainer's discretion.
10726 <sect id="copyrightfile">
10727 <heading>Copyright information</heading>
10730 Every package must be accompanied by a verbatim copy of its
10731 copyright information and distribution license in the file
10732 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10733 file must neither be compressed nor be a symbolic link.
10737 In addition, the copyright file must say where the upstream
10738 sources (if any) were obtained, and should name the original
10743 Packages in the <em>contrib</em> or <em>non-free</em> archive
10744 areas should state in the copyright file that the package is not
10745 part of the Debian distribution and briefly explain why.
10749 A copy of the file which will be installed in
10750 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10751 be in <file>debian/copyright</file> in the source package.
10755 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10756 link to another directory in <file>/usr/share/doc</file> only if
10757 the two packages both come from the same source and the
10758 first package Depends on the second. These rules are important
10759 because <file>copyright</file> files must be extractable by
10764 Packages distributed under the Apache license (version 2.0), the
10765 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10766 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10767 1.3) should refer to the corresponding files
10768 under <file>/usr/share/common-licenses</file>,<footnote>
10771 <file>/usr/share/common-licenses/Apache-2.0</file>,
10772 <file>/usr/share/common-licenses/Artistic</file>,
10773 <file>/usr/share/common-licenses/GPL-1</file>,
10774 <file>/usr/share/common-licenses/GPL-2</file>,
10775 <file>/usr/share/common-licenses/GPL-3</file>,
10776 <file>/usr/share/common-licenses/LGPL-2</file>,
10777 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10778 <file>/usr/share/common-licenses/LGPL-3</file>,
10779 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10780 <file>/usr/share/common-licenses/GFDL-1.3</file>
10781 respectively. The University of California BSD license is
10782 also included in <package>base-files</package> as
10783 <file>/usr/share/common-licenses/BSD</file>, but given the
10784 brevity of this license, its specificity to code whose
10785 copyright is held by the Regents of the University of
10786 California, and the frequency of minor wording changes, its
10787 text should be included in the copyright file rather than
10788 referencing this file.
10790 </footnote> rather than quoting them in the copyright
10795 You should not use the copyright file as a general <file>README</file>
10796 file. If your package has such a file it should be
10797 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10798 <file>README.Debian</file> or some other appropriate place.
10802 All copyright files must be encoded in UTF-8.
10805 <sect1 id="copyrightformat">
10806 <heading>Machine-readable copyright information</heading>
10809 A specification for a standard, machine-readable format
10810 for <file>debian/copyright</file> files is maintained as part
10811 of the <package>debian-policy</package> package. This
10812 document may be found in the <file>copyright-format</file>
10813 files in the <package>debian-policy</package> package. It is
10814 also available from the Debian web mirrors at
10815 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10816 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10820 Use of this format is optional.
10826 <heading>Examples</heading>
10829 Any examples (configurations, source files, whatever),
10830 should be installed in a directory
10831 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10832 files should not be referenced by any program: they're there
10833 for the benefit of the system administrator and users as
10834 documentation only. Architecture-specific example files
10835 should be installed in a directory
10836 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10838 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10839 latter directory itself may be a symbolic link to the
10844 If the purpose of a package is to provide examples, then the
10845 example files may be installed into
10846 <file>/usr/share/doc/<var>package</var></file>.
10850 <sect id="changelogs">
10851 <heading>Changelog files</heading>
10854 Packages that are not Debian-native must contain a
10855 compressed copy of the <file>debian/changelog</file> file from
10856 the Debian source tree in
10857 <file>/usr/share/doc/<var>package</var></file> with the name
10858 <file>changelog.Debian.gz</file>.
10862 If an upstream changelog is available, it should be accessible as
10863 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10864 plain text. If the upstream changelog is distributed in
10865 HTML, it should be made available in that form as
10866 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10867 and a plain text <file>changelog.gz</file> should be generated
10868 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10869 the upstream changelog files do not already conform to this
10870 naming convention, then this may be achieved either by
10871 renaming the files, or by adding a symbolic link, at the
10872 maintainer's discretion.<footnote>
10873 Rationale: People should not have to look in places for
10874 upstream changelogs merely because they are given
10875 different names or are distributed in HTML format.
10880 All of these files should be installed compressed using
10881 <tt>gzip -9</tt>, as they will become large with time even
10882 if they start out small.
10886 If the package has only one changelog which is used both as
10887 the Debian changelog and the upstream one because there is
10888 no separate upstream maintainer then that changelog should
10889 usually be installed as
10890 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10891 there is a separate upstream maintainer, but no upstream
10892 changelog, then the Debian changelog should still be called
10893 <file>changelog.Debian.gz</file>.
10897 For details about the format and contents of the Debian
10898 changelog file, please see <ref id="dpkgchangelog">.
10903 <appendix id="pkg-scope">
10904 <heading>Introduction and scope of these appendices</heading>
10907 These appendices are taken essentially verbatim from the
10908 now-deprecated Packaging Manual, version 3.2.1.0. They are
10909 the chapters which are likely to be of use to package
10910 maintainers and which have not already been included in the
10911 policy document itself. Most of these sections are very likely
10912 not relevant to policy; they should be treated as
10913 documentation for the packaging system. Please note that these
10914 appendices are included for convenience, and for historical
10915 reasons: they used to be part of policy package, and they have
10916 not yet been incorporated into dpkg documentation. However,
10917 they still have value, and hence they are presented here.
10921 They have not yet been checked to ensure that they are
10922 compatible with the contents of policy, and if there are any
10923 contradictions, the version in the main policy document takes
10924 precedence. The remaining chapters of the old Packaging
10925 Manual have also not been read in detail to ensure that there
10926 are not parts which have been left out. Both of these will be
10927 done in due course.
10931 Certain parts of the Packaging manual were integrated into the
10932 Policy Manual proper, and removed from the appendices. Links
10933 have been placed from the old locations to the new ones.
10937 <prgn>dpkg</prgn> is a suite of programs for creating binary
10938 package files and installing and removing them on Unix
10940 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10941 work on or be ported to other systems.
10946 The binary packages are designed for the management of
10947 installed executable programs (usually compiled binaries) and
10948 their associated data, though source code examples and
10949 documentation are provided as part of some packages.</p>
10952 This manual describes the technical aspects of creating Debian
10953 binary packages (<file>.deb</file> files). It documents the
10954 behavior of the package management programs
10955 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10956 they interact with packages.</p>
10959 This manual does not go into detail about the options and
10960 usage of the package building and installation tools. It
10961 should therefore be read in conjunction with those programs'
10966 The utility programs which are provided with <prgn>dpkg</prgn>
10967 not described in detail here, are documented in their man pages.
10971 It is assumed that the reader is reasonably familiar with the
10972 <prgn>dpkg</prgn> System Administrators' manual.
10973 Unfortunately this manual does not yet exist.
10977 The Debian version of the FSF's GNU hello program is provided as
10978 an example for people wishing to create Debian packages. However,
10979 while the examples are helpful, they do not replace the need to
10980 read and follow the Policy and Programmer's Manual.</p>
10983 <appendix id="pkg-binarypkg">
10984 <heading>Binary packages (from old Packaging Manual)</heading>
10987 See <manref name="deb" section="5"> and <ref id="pkg-controlarea">.
10990 <sect id="pkg-bincreating"><heading>Creating package files -
10991 <prgn>dpkg-deb</prgn>
10995 All manipulation of binary package files is done by
10996 <prgn>dpkg-deb</prgn>; it's the only program that has
10997 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10998 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10999 will spot that the options requested are appropriate to
11000 <prgn>dpkg-deb</prgn> and invoke that instead with the same
11005 In order to create a binary package you must make a
11006 directory tree which contains all the files and directories
11007 you want to have in the file system data part of the package.
11008 In Debian-format source packages this directory is usually
11009 <file>debian/tmp</file>, relative to the top of the package's
11014 They should have the locations (relative to the root of the
11015 directory tree you're constructing) ownerships and
11016 permissions which you want them to have on the system when
11017 they are installed.
11021 With current versions of <prgn>dpkg</prgn> the uid/username
11022 and gid/groupname mappings for the users and groups being
11023 used should be the same on the system where the package is
11024 built and the one where it is installed.
11028 You need to add one special directory to the root of the
11029 miniature file system tree you're creating:
11030 <prgn>DEBIAN</prgn>. It should contain the control
11031 information files, notably the binary package control file
11032 (see <ref id="pkg-controlfile">).
11036 The <prgn>DEBIAN</prgn> directory will not appear in the
11037 file system archive of the package, and so won't be installed
11038 by <prgn>dpkg</prgn> when the package is unpacked.
11042 When you've prepared the package, you should invoke:
11044 dpkg --build <var>directory</var>
11049 This will build the package in
11050 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
11051 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
11052 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
11053 build the package.)
11057 See the man page <manref name="dpkg-deb" section="8"> for details of how
11058 to examine the contents of this newly-created file. You may find the
11059 output of following commands enlightening:
11061 dpkg-deb --info <var>filename</var>.deb
11062 dpkg-deb --contents <var>filename</var>.deb
11063 dpkg --contents <var>filename</var>.deb
11065 To view the copyright file for a package you could use this command:
11067 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
11072 <sect id="pkg-controlarea">
11073 <heading>Package control information files</heading>
11076 The control information portion of a binary package is a
11077 collection of files with names known to <prgn>dpkg</prgn>.
11078 It will treat the contents of these files specially - some
11079 of them contain information used by <prgn>dpkg</prgn> when
11080 installing or removing the package; others are scripts which
11081 the package maintainer wants <prgn>dpkg</prgn> to run.
11085 It is possible to put other files in the package control
11086 information file area, but this is not generally a good idea
11087 (though they will largely be ignored).
11091 Here is a brief list of the control information files supported
11092 by <prgn>dpkg</prgn> and a summary of what they're used for.
11097 <tag><tt>control</tt>
11100 This is the key description file used by
11101 <prgn>dpkg</prgn>. It specifies the package's name
11102 and version, gives its description for the user,
11103 states its relationships with other packages, and so
11104 forth. See <ref id="sourcecontrolfiles"> and
11105 <ref id="binarycontrolfiles">.
11109 It is usually generated automatically from information
11110 in the source package by the
11111 <prgn>dpkg-gencontrol</prgn> program, and with
11112 assistance from <prgn>dpkg-shlibdeps</prgn>.
11113 See <ref id="pkg-sourcetools">.
11117 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11122 These are executable files (usually scripts) which
11123 <prgn>dpkg</prgn> runs during installation, upgrade
11124 and removal of packages. They allow the package to
11125 deal with matters which are particular to that package
11126 or require more complicated processing than that
11127 provided by <prgn>dpkg</prgn>. Details of when and
11128 how they are called are in <ref id="maintainerscripts">.
11132 It is very important to make these scripts idempotent.
11133 See <ref id="idempotency">.
11137 The maintainer scripts are not guaranteed to run with a
11138 controlling terminal and may not be able to interact with
11139 the user. See <ref id="controllingterminal">.
11143 <tag><tt>conffiles</tt>
11146 This file contains a list of configuration files which
11147 are to be handled automatically by <prgn>dpkg</prgn>
11148 (see <ref id="pkg-conffiles">). Note that not necessarily
11149 every configuration file should be listed here.
11152 <tag><tt>shlibs</tt>
11155 This file contains a list of the shared libraries
11156 supplied by the package, with dependency details for
11157 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11158 when it determines what dependencies are required in a
11159 package control file. The <tt>shlibs</tt> file format
11160 is described on <ref id="shlibs">.
11165 <sect id="pkg-controlfile">
11166 <heading>The main control information file: <tt>control</tt></heading>
11169 The most important control information file used by
11170 <prgn>dpkg</prgn> when it installs a package is
11171 <tt>control</tt>. It contains all the package's "vital
11176 The binary package control files of packages built from
11177 Debian sources are made by a special tool,
11178 <prgn>dpkg-gencontrol</prgn>, which reads
11179 <file>debian/control</file> and <file>debian/changelog</file> to
11180 find the information it needs. See <ref id="pkg-sourcepkg"> for
11185 The fields in binary package control files are listed in
11186 <ref id="binarycontrolfiles">.
11190 A description of the syntax of control files and the purpose
11191 of the fields is available in <ref id="controlfields">.
11196 <heading>Time Stamps</heading>
11199 See <ref id="timestamps">.
11204 <appendix id="pkg-sourcepkg">
11205 <heading>Source packages (from old Packaging Manual) </heading>
11208 The Debian binary packages in the distribution are generated
11209 from Debian sources, which are in a special format to assist
11210 the easy and automatic building of binaries.
11213 <sect id="pkg-sourcetools">
11214 <heading>Tools for processing source packages</heading>
11217 Various tools are provided for manipulating source packages;
11218 they pack and unpack sources and help build of binary
11219 packages and help manage the distribution of new versions.
11223 They are introduced and typical uses described here; see
11224 <manref name="dpkg-source" section="1"> for full
11225 documentation about their arguments and operation.
11229 For examples of how to construct a Debian source package,
11230 and how to use those utilities that are used by Debian
11231 source packages, please see the <prgn>hello</prgn> example
11235 <sect1 id="pkg-dpkg-source">
11237 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11242 This program is frequently used by hand, and is also
11243 called from package-independent automated building scripts
11244 such as <prgn>dpkg-buildpackage</prgn>.
11248 To unpack a package it is typically invoked with
11250 dpkg-source -x <var>.../path/to/filename</var>.dsc
11255 with the <file><var>filename</var>.tar.gz</file> and
11256 <file><var>filename</var>.diff.gz</file> (if applicable) in
11257 the same directory. It unpacks into
11258 <file><var>package</var>-<var>version</var></file>, and if
11260 <file><var>package</var>-<var>version</var>.orig</file>, in
11261 the current directory.
11265 To create a packed source archive it is typically invoked:
11267 dpkg-source -b <var>package</var>-<var>version</var>
11272 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11273 <file>.diff.gz</file> (if appropriate) in the current
11274 directory. <prgn>dpkg-source</prgn> does not clean the
11275 source tree first - this must be done separately if it is
11280 See also <ref id="pkg-sourcearchives">.</p>
11284 <sect1 id="pkg-dpkg-buildpackage">
11286 <prgn>dpkg-buildpackage</prgn> - overall package-building
11291 See <manref name="dpkg-buildpackage" section="1">.
11295 <sect1 id="pkg-dpkg-gencontrol">
11297 <prgn>dpkg-gencontrol</prgn> - generates binary package
11302 This program is usually called from <file>debian/rules</file>
11303 (see <ref id="pkg-sourcetree">) in the top level of the source
11308 This is usually done just before the files and directories in the
11309 temporary directory tree where the package is being built have their
11310 permissions and ownerships set and the package is constructed using
11311 <prgn>dpkg-deb/</prgn>
11313 This is so that the control file which is produced has
11314 the right permissions
11319 <prgn>dpkg-gencontrol</prgn> must be called after all the
11320 files which are to go into the package have been placed in
11321 the temporary build directory, so that its calculation of
11322 the installed size of a package is correct.
11326 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11327 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11328 variable substitutions created by
11329 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11334 For a package which generates only one binary package, and
11335 which builds it in <file>debian/tmp</file> relative to the top
11336 of the source package, it is usually sufficient to call
11337 <prgn>dpkg-gencontrol</prgn>.
11341 Sources which build several binaries will typically need
11344 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11345 </example> The <tt>-P</tt> tells
11346 <prgn>dpkg-gencontrol</prgn> that the package is being
11347 built in a non-default directory, and the <tt>-p</tt>
11348 tells it which package's control file should be generated.
11352 <prgn>dpkg-gencontrol</prgn> also adds information to the
11353 list of files in <file>debian/files</file>, for the benefit of
11354 (for example) a future invocation of
11355 <prgn>dpkg-genchanges</prgn>.</p>
11358 <sect1 id="pkg-dpkg-shlibdeps">
11360 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11365 See <manref name="dpkg-shlibdeps" section="1">.
11369 <sect1 id="pkg-dpkg-distaddfile">
11371 <prgn>dpkg-distaddfile</prgn> - adds a file to
11372 <file>debian/files</file>
11376 Some packages' uploads need to include files other than
11377 the source and binary package files.
11381 <prgn>dpkg-distaddfile</prgn> adds a file to the
11382 <file>debian/files</file> file so that it will be included in
11383 the <file>.changes</file> file when
11384 <prgn>dpkg-genchanges</prgn> is run.
11388 It is usually invoked from the <tt>binary</tt> target of
11389 <file>debian/rules</file>:
11391 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11393 The <var>filename</var> is relative to the directory where
11394 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11395 is usually the directory above the top level of the source
11396 tree. The <file>debian/rules</file> target should put the
11397 file there just before or just after calling
11398 <prgn>dpkg-distaddfile</prgn>.
11402 The <var>section</var> and <var>priority</var> are passed
11403 unchanged into the resulting <file>.changes</file> file.
11408 <sect1 id="pkg-dpkg-genchanges">
11410 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11411 upload control file
11415 See <manref name="dpkg-genchanges" section="1">.
11419 <sect1 id="pkg-dpkg-parsechangelog">
11421 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11422 representation of a changelog
11426 See <manref name="dpkg-parsechangelog" section="1">.
11430 <sect1 id="pkg-dpkg-architecture">
11432 <prgn>dpkg-architecture</prgn> - information about the build and
11437 See <manref name="dpkg-architecture" section="1">.
11442 <sect id="pkg-sourcetree">
11443 <heading>The Debian package source tree</heading>
11446 The source archive scheme described later is intended to
11447 allow a Debian package source tree with some associated
11448 control information to be reproduced and transported easily.
11449 The Debian package source tree is a version of the original
11450 program with certain files added for the benefit of the
11451 packaging process, and with any other changes required
11452 made to the rest of the source code and installation
11457 The extra files created for Debian are in the subdirectory
11458 <file>debian</file> of the top level of the Debian package
11459 source tree. They are described below.
11462 <sect1 id="pkg-debianrules">
11463 <heading><file>debian/rules</file> - the main building script</heading>
11466 See <ref id="debianrules">.
11470 <sect1 id="pkg-srcsubstvars">
11471 <heading><file>debian/substvars</file> and variable substitutions</heading>
11474 See <ref id="substvars">.
11480 <heading><file>debian/files</file></heading>
11483 See <ref id="debianfiles">.
11487 <sect1><heading><file>debian/tmp</file>
11491 This is the canonical temporary location for the
11492 construction of binary packages by the <tt>binary</tt>
11493 target. The directory <file>tmp</file> serves as the root of
11494 the file system tree as it is being constructed (for
11495 example, by using the package's upstream makefiles install
11496 targets and redirecting the output there), and it also
11497 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11498 id="pkg-bincreating">.
11502 If several binary packages are generated from the same
11503 source tree it is usual to use several
11504 <file>debian/tmp<var>something</var></file> directories, for
11505 example <file>tmp-a</file> or <file>tmp-doc</file>.
11509 Whatever <file>tmp</file> directories are created and used by
11510 <tt>binary</tt> must of course be removed by the
11511 <tt>clean</tt> target.</p></sect1>
11515 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11519 As it exists on the FTP site, a Debian source package
11520 consists of three related files. You must have the right
11521 versions of all three to be able to use them.
11526 <tag>Debian source control file - <tt>.dsc</tt></tag>
11528 This file is a control file used by <prgn>dpkg-source</prgn>
11529 to extract a source package.
11530 See <ref id="debiansourcecontrolfiles">.
11534 Original source archive -
11536 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11542 This is a compressed (with <tt>gzip -9</tt>)
11543 <prgn>tar</prgn> file containing the source code from
11544 the upstream authors of the program.
11549 Debian package diff -
11551 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11557 This is a unified context diff (<tt>diff -u</tt>)
11558 giving the changes which are required to turn the
11559 original source into the Debian source. These changes
11560 may only include editing and creating plain files.
11561 The permissions of files, the targets of symbolic
11562 links and the characteristics of special files or
11563 pipes may not be changed and no files may be removed
11568 All the directories in the diff must exist, except the
11569 <file>debian</file> subdirectory of the top of the source
11570 tree, which will be created by
11571 <prgn>dpkg-source</prgn> if necessary when unpacking.
11575 The <prgn>dpkg-source</prgn> program will
11576 automatically make the <file>debian/rules</file> file
11577 executable (see below).</p></item>
11582 If there is no original source code - for example, if the
11583 package is specially prepared for Debian or the Debian
11584 maintainer is the same as the upstream maintainer - the
11585 format is slightly different: then there is no diff, and the
11587 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11588 and preferably contains a directory named
11589 <file><var>package</var>-<var>version</var></file>.
11594 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11597 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11598 Debian source package. However, if it is not available it
11599 is possible to unpack a Debian source archive as follows:
11600 <enumlist compact="compact">
11603 Untar the tarfile, which will create a <file>.orig</file>
11607 <p>Rename the <file>.orig</file> directory to
11608 <file><var>package</var>-<var>version</var></file>.</p>
11612 Create the subdirectory <file>debian</file> at the top of
11613 the source tree.</p>
11615 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11617 <item><p>Untar the tarfile again if you want a copy of the original
11618 source code alongside the Debian version.</p>
11623 It is not possible to generate a valid Debian source archive
11624 without using <prgn>dpkg-source</prgn>. In particular,
11625 attempting to use <prgn>diff</prgn> directly to generate the
11626 <file>.diff.gz</file> file will not work.
11630 <heading>Restrictions on objects in source packages</heading>
11633 The source package may not contain any hard links
11635 This is not currently detected when building source
11636 packages, but only when extracting
11640 Hard links may be permitted at some point in the
11641 future, but would require a fair amount of
11643 </footnote>, device special files, sockets or setuid or
11646 Setgid directories are allowed.
11651 The source packaging tools manage the changes between the
11652 original and Debian source using <prgn>diff</prgn> and
11653 <prgn>patch</prgn>. Turning the original source tree as
11654 included in the <file>.orig.tar.gz</file> into the Debian
11655 package source must not involve any changes which cannot be
11656 handled by these tools. Problematic changes which cause
11657 <prgn>dpkg-source</prgn> to halt with an error when
11658 building the source package are:
11659 <list compact="compact">
11660 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11662 <item><p>Changing the targets of symbolic links.</p>
11664 <item><p>Creating directories, other than <file>debian</file>.</p>
11666 <item><p>Changes to the contents of binary files.</p></item>
11667 </list> Changes which cause <prgn>dpkg-source</prgn> to
11668 print a warning but continue anyway are:
11669 <list compact="compact">
11672 Removing files, directories or symlinks.
11674 Renaming a file is not treated specially - it is
11675 seen as the removal of the old file (which
11676 generates a warning, but is otherwise ignored),
11677 and the creation of the new one.
11683 Changed text files which are missing the usual final
11684 newline (either in the original or the modified
11689 Changes which are not represented, but which are not detected by
11690 <prgn>dpkg-source</prgn>, are:
11691 <list compact="compact">
11692 <item><p>Changing the permissions of files (other than
11693 <file>debian/rules</file>) and directories.</p></item>
11698 The <file>debian</file> directory and <file>debian/rules</file>
11699 are handled specially by <prgn>dpkg-source</prgn> - before
11700 applying the changes it will create the <file>debian</file>
11701 directory, and afterwards it will make
11702 <file>debian/rules</file> world-executable.
11708 <appendix id="pkg-controlfields">
11709 <heading>Control files and their fields (from old Packaging Manual)</heading>
11712 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11713 data in a common format, known as control files. Binary and
11714 source packages have control data as do the <file>.changes</file>
11715 files which control the installation of uploaded files, and
11716 <prgn>dpkg</prgn>'s internal databases are in a similar
11721 <heading>Syntax of control files</heading>
11724 See <ref id="controlsyntax">.
11728 It is important to note that there are several fields which
11729 are optional as far as <prgn>dpkg</prgn> and the related
11730 tools are concerned, but which must appear in every Debian
11731 package, or whose omission may cause problems.
11736 <heading>List of fields</heading>
11739 See <ref id="controlfieldslist">.
11743 This section now contains only the fields that didn't belong
11744 to the Policy manual.
11747 <sect1 id="pkg-f-Filename">
11748 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11751 These fields in <tt>Packages</tt> files give the
11752 filename(s) of (the parts of) a package in the
11753 distribution directories, relative to the root of the
11754 Debian hierarchy. If the package has been split into
11755 several parts the parts are all listed in order, separated
11760 <sect1 id="pkg-f-Size">
11761 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11764 These fields in <file>Packages</file> files give the size (in
11765 bytes, expressed in decimal) and MD5 checksum of the
11766 file(s) which make(s) up a binary package in the
11767 distribution. If the package is split into several parts
11768 the values for the parts are listed in order, separated by
11773 <sect1 id="pkg-f-Status">
11774 <heading><tt>Status</tt></heading>
11777 This field in <prgn>dpkg</prgn>'s status file records
11778 whether the user wants a package installed, removed or
11779 left alone, whether it is broken (requiring
11780 re-installation) or not and what its current state on the
11781 system is. Each of these pieces of information is a
11786 <sect1 id="pkg-f-Config-Version">
11787 <heading><tt>Config-Version</tt></heading>
11790 If a package is not installed or not configured, this
11791 field in <prgn>dpkg</prgn>'s status file records the last
11792 version of the package which was successfully
11797 <sect1 id="pkg-f-Conffiles">
11798 <heading><tt>Conffiles</tt></heading>
11801 This field in <prgn>dpkg</prgn>'s status file contains
11802 information about the automatically-managed configuration
11803 files held by a package. This field should <em>not</em>
11804 appear anywhere in a package!
11809 <heading>Obsolete fields</heading>
11812 These are still recognized by <prgn>dpkg</prgn> but should
11813 not appear anywhere any more.
11815 <taglist compact="compact">
11817 <tag><tt>Revision</tt></tag>
11818 <tag><tt>Package-Revision</tt></tag>
11819 <tag><tt>Package_Revision</tt></tag>
11821 The Debian revision part of the package version was
11822 at one point in a separate control field. This
11823 field went through several names.
11826 <tag><tt>Recommended</tt></tag>
11827 <item>Old name for <tt>Recommends</tt>.</item>
11829 <tag><tt>Optional</tt></tag>
11830 <item>Old name for <tt>Suggests</tt>.</item>
11832 <tag><tt>Class</tt></tag>
11833 <item>Old name for <tt>Priority</tt>.</item>
11842 <appendix id="pkg-conffiles">
11843 <heading>Configuration file handling (from old Packaging Manual)</heading>
11846 <prgn>dpkg</prgn> can do a certain amount of automatic
11847 handling of package configuration files.
11851 Whether this mechanism is appropriate depends on a number of
11852 factors, but basically there are two approaches to any
11853 particular configuration file.
11857 The easy method is to ship a best-effort configuration in the
11858 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11859 handle updates. If the user is unlikely to want to edit the
11860 file, but you need them to be able to without losing their
11861 changes, and a new package with a changed version of the file
11862 is only released infrequently, this is a good approach.
11866 The hard method is to build the configuration file from
11867 scratch in the <prgn>postinst</prgn> script, and to take the
11868 responsibility for fixing any mistakes made in earlier
11869 versions of the package automatically. This will be
11870 appropriate if the file is likely to need to be different on
11874 <sect><heading>Automatic handling of configuration files by
11879 A package may contain a control information file called
11880 <tt>conffiles</tt>. This file should be a list of filenames
11881 of configuration files needing automatic handling, separated
11882 by newlines. The filenames should be absolute pathnames,
11883 and the files referred to should actually exist in the
11888 When a package is upgraded <prgn>dpkg</prgn> will process
11889 the configuration files during the configuration stage,
11890 shortly before it runs the package's <prgn>postinst</prgn>
11895 For each file it checks to see whether the version of the
11896 file included in the package is the same as the one that was
11897 included in the last version of the package (the one that is
11898 being upgraded from); it also compares the version currently
11899 installed on the system with the one shipped with the last
11904 If neither the user nor the package maintainer has changed
11905 the file, it is left alone. If one or the other has changed
11906 their version, then the changed version is preferred - i.e.,
11907 if the user edits their file, but the package maintainer
11908 doesn't ship a different version, the user's changes will
11909 stay, silently, but if the maintainer ships a new version
11910 and the user hasn't edited it the new version will be
11911 installed (with an informative message). If both have
11912 changed their version the user is prompted about the problem
11913 and must resolve the differences themselves.
11917 The comparisons are done by calculating the MD5 message
11918 digests of the files, and storing the MD5 of the file as it
11919 was included in the most recent version of the package.
11923 When a package is installed for the first time
11924 <prgn>dpkg</prgn> will install the file that comes with it,
11925 unless that would mean overwriting a file already on the
11930 However, note that <prgn>dpkg</prgn> will <em>not</em>
11931 replace a conffile that was removed by the user (or by a
11932 script). This is necessary because with some programs a
11933 missing file produces an effect hard or impossible to
11934 achieve in another way, so that a missing file needs to be
11935 kept that way if the user did it.
11939 Note that a package should <em>not</em> modify a
11940 <prgn>dpkg</prgn>-handled conffile in its maintainer
11941 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11942 the user confusing and possibly dangerous options for
11943 conffile update when the package is upgraded.</p>
11946 <sect><heading>Fully-featured maintainer script configuration
11951 For files which contain site-specific information such as
11952 the hostname and networking details and so forth, it is
11953 better to create the file in the package's
11954 <prgn>postinst</prgn> script.
11958 This will typically involve examining the state of the rest
11959 of the system to determine values and other information, and
11960 may involve prompting the user for some information which
11961 can't be obtained some other way.
11965 When using this method there are a couple of important
11966 issues which should be considered:
11970 If you discover a bug in the program which generates the
11971 configuration file, or if the format of the file changes
11972 from one version to the next, you will have to arrange for
11973 the postinst script to do something sensible - usually this
11974 will mean editing the installed configuration file to remove
11975 the problem or change the syntax. You will have to do this
11976 very carefully, since the user may have changed the file,
11977 perhaps to fix the very problem that your script is trying
11978 to deal with - you will have to detect these situations and
11979 deal with them correctly.
11983 If you do go down this route it's probably a good idea to
11984 make the program that generates the configuration file(s) a
11985 separate program in <file>/usr/sbin</file>, by convention called
11986 <file><var>package</var>config</file> and then run that if
11987 appropriate from the post-installation script. The
11988 <tt><var>package</var>config</tt> program should not
11989 unquestioningly overwrite an existing configuration - if its
11990 mode of operation is geared towards setting up a package for
11991 the first time (rather than any arbitrary reconfiguration
11992 later) you should have it check whether the configuration
11993 already exists, and require a <tt>--force</tt> flag to
11994 overwrite it.</p></sect>
11997 <appendix id="pkg-alternatives"><heading>Alternative versions of
11998 an interface - <prgn>update-alternatives</prgn> (from old
12003 When several packages all provide different versions of the
12004 same program or file it is useful to have the system select a
12005 default, but to allow the system administrator to change it
12006 and have their decisions respected.
12010 For example, there are several versions of the <prgn>vi</prgn>
12011 editor, and there is no reason to prevent all of them from
12012 being installed at once, each under their own name
12013 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
12014 Nevertheless it is desirable to have the name <tt>vi</tt>
12015 refer to something, at least by default.
12019 If all the packages involved cooperate, this can be done with
12020 <prgn>update-alternatives</prgn>.
12024 Each package provides its own version under its own name, and
12025 calls <prgn>update-alternatives</prgn> in its postinst to
12026 register its version (and again in its prerm to deregister
12031 See the man page <manref name="update-alternatives"
12032 section="8"> for details.
12036 If <prgn>update-alternatives</prgn> does not seem appropriate
12037 you may wish to consider using diversions instead.</p>
12040 <appendix id="pkg-diversions"><heading>Diversions - overriding a
12041 package's version of a file (from old Packaging Manual)
12045 It is possible to have <prgn>dpkg</prgn> not overwrite a file
12046 when it reinstalls the package it belongs to, and to have it
12047 put the file from the package somewhere else instead.
12051 This can be used locally to override a package's version of a
12052 file, or by one package to override another's version (or
12053 provide a wrapper for it).
12057 Before deciding to use a diversion, read <ref
12058 id="pkg-alternatives"> to see if you really want a diversion
12059 rather than several alternative versions of a program.
12063 There is a diversion list, which is read by <prgn>dpkg</prgn>,
12064 and updated by a special program <prgn>dpkg-divert</prgn>.
12065 Please see <manref name="dpkg-divert" section="8"> for full
12066 details of its operation.
12070 When a package wishes to divert a file from another, it should
12071 call <prgn>dpkg-divert</prgn> in its preinst to add the
12072 diversion and rename the existing file. For example,
12073 supposing that a <prgn>smailwrapper</prgn> package wishes to
12074 install a wrapper around <file>/usr/sbin/smail</file>:
12076 dpkg-divert --package smailwrapper --add --rename \
12077 --divert /usr/sbin/smail.real /usr/sbin/smail
12078 </example> The <tt>--package smailwrapper</tt> ensures that
12079 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
12080 can bypass the diversion and get installed as the true version.
12081 It's safe to add the diversion unconditionally on upgrades since
12082 it will be left unchanged if it already exists, but
12083 <prgn>dpkg-divert</prgn> will display a message. To suppress that
12084 message, make the command conditional on the version from which
12085 the package is being upgraded:
12087 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12088 dpkg-divert --package smailwrapper --add --rename \
12089 --divert /usr/sbin/smail.real /usr/sbin/smail
12091 </example> where <tt>1.0-2</tt> is the version at which the
12092 diversion was first added to the package. Running the command
12093 during abort-upgrade is pointless but harmless.
12097 The postrm has to do the reverse:
12099 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12100 dpkg-divert --package smailwrapper --remove --rename \
12101 --divert /usr/sbin/smail.real /usr/sbin/smail
12103 </example> If the diversion was added at a particular version, the
12104 postrm should also handle the failure case of upgrading from an
12105 older version (unless the older version is so old that direct
12106 upgrades are no longer supported):
12108 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12109 dpkg-divert --package smailwrapper --remove --rename \
12110 --divert /usr/sbin/smail.real /usr/sbin/smail
12112 </example> where <tt>1.0-2</tt> is the version at which the
12113 diversion was first added to the package. The postrm should not
12114 remove the diversion on upgrades both because there's no reason to
12115 remove the diversion only to immediately re-add it and since the
12116 postrm of the old package is run after unpacking so the removal of
12117 the diversion will fail.
12121 Do not attempt to divert a file which is vitally important for
12122 the system's operation - when using <prgn>dpkg-divert</prgn>
12123 there is a time, after it has been diverted but before
12124 <prgn>dpkg</prgn> has installed the new version, when the file
12125 does not exist.</p>
12128 Do not attempt to divert a conffile, as <prgn>dpkg</prgn> does not
12135 <!-- Local variables: -->
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