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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>Andrew McMillan</item>
233 <item>Manoj Srivastava</item>
234 <item>Colin Watson</item>
239 While the authors of this document have tried hard to avoid
240 typos and other errors, these do still occur. If you discover
241 an error in this manual or if you want to give any
242 comments, suggestions, or criticisms please send an email to
243 the Debian Policy List,
244 <email>debian-policy@lists.debian.org</email>, or submit a
245 bug report against the <tt>debian-policy</tt> package.
249 Please do not try to reach the individual authors or maintainers
250 of the Policy Manual regarding changes to the Policy.
255 <heading>Related documents</heading>
258 There are several other documents other than this Policy Manual
259 that are necessary to fully understand some Debian policies and
264 The external "sub-policy" documents are referred to in:
265 <list compact="compact">
266 <item><ref id="fhs"></item>
267 <item><ref id="virtual_pkg"></item>
268 <item><ref id="menus"></item>
269 <item><ref id="perl"></item>
270 <item><ref id="maintscriptprompt"></item>
271 <item><ref id="emacs"></item>
276 In addition to those, which carry the weight of policy, there
277 is the Debian Developer's Reference. This document describes
278 procedures and resources for Debian developers, but it is
279 <em>not</em> normative; rather, it includes things that don't
280 belong in the Policy, such as best practices for developers.
284 The Developer's Reference is available in the
285 <package>developers-reference</package> package.
286 It's also available from the Debian web mirrors at
287 <tt><url name="/doc/developers-reference/"
288 id="http://www.debian.org/doc/developers-reference/"></tt>.
292 Finally, a <qref id="copyrightformat">specification for
293 machine-readable copyright files</qref> is maintained as part of
294 the <package>debian-policy</package> package using the same
295 procedure as the other policy documents. Use of this format is
300 <sect id="definitions">
301 <heading>Definitions</heading>
304 The following terms are used in this Policy Manual:
308 The character encoding specified by ANSI X3.4-1986 and its
309 predecessor standards, referred to in MIME as US-ASCII, and
310 corresponding to an encoding in eight bits per character of
311 the first 128 <url id="http://www.unicode.org/"
312 name="Unicode"> characters, with the eighth bit always zero.
316 The transformation format (sometimes called encoding) of
317 <url id="http://www.unicode.org/" name="Unicode"> defined by
318 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
319 name="RFC 3629">. UTF-8 has the useful property of having
320 ASCII as a subset, so any text encoded in ASCII is trivially
330 <heading>The Debian Archive</heading>
333 The Debian system is maintained and distributed as a
334 collection of <em>packages</em>. Since there are so many of
335 them (currently well over 15000), they are split into
336 <em>sections</em> and given <em>priorities</em> to simplify
337 the handling of them.
341 The effort of the Debian project is to build a free operating
342 system, but not every package we want to make accessible is
343 <em>free</em> in our sense (see the Debian Free Software
344 Guidelines, below), or may be imported/exported without
345 restrictions. Thus, the archive is split into areas<footnote>
346 The Debian archive software uses the term "component" internally
347 and in the Release file format to refer to the division of an
348 archive. The Debian Social Contract simply refers to "areas."
349 This document uses terminology similar to the Social Contract.
350 </footnote> based on their licenses and other restrictions.
354 The aims of this are:
356 <list compact="compact">
357 <item>to allow us to make as much software available as we can</item>
358 <item>to allow us to encourage everyone to write free software,
360 <item>to allow us to make it easy for people to produce
361 CD-ROMs of our system without violating any licenses,
362 import/export restrictions, or any other laws.</item>
367 The <em>main</em> archive area forms the <em>Debian distribution</em>.
371 Packages in the other archive areas (<tt>contrib</tt>,
372 <tt>non-free</tt>) are not considered to be part of the Debian
373 distribution, although we support their use and provide
374 infrastructure for them (such as our bug-tracking system and
375 mailing lists). This Debian Policy Manual applies to these
380 <heading>The Debian Free Software Guidelines</heading>
382 The Debian Free Software Guidelines (DFSG) form our
383 definition of "free software". These are:
385 <tag>1. Free Redistribution
388 The license of a Debian component may not restrict any
389 party from selling or giving away the software as a
390 component of an aggregate software distribution
391 containing programs from several different
392 sources. The license may not require a royalty or
393 other fee for such sale.
398 The program must include source code, and must allow
399 distribution in source code as well as compiled form.
401 <tag>3. Derived Works
404 The license must allow modifications and derived
405 works, and must allow them to be distributed under the
406 same terms as the license of the original software.
408 <tag>4. Integrity of The Author's Source Code
411 The license may restrict source-code from being
412 distributed in modified form <em>only</em> if the
413 license allows the distribution of "patch files"
414 with the source code for the purpose of modifying the
415 program at build time. The license must explicitly
416 permit distribution of software built from modified
417 source code. The license may require derived works to
418 carry a different name or version number from the
419 original software. (This is a compromise. The Debian
420 Project encourages all authors to not restrict any
421 files, source or binary, from being modified.)
423 <tag>5. No Discrimination Against Persons or Groups
426 The license must not discriminate against any person
429 <tag>6. No Discrimination Against Fields of Endeavor
432 The license must not restrict anyone from making use
433 of the program in a specific field of endeavor. For
434 example, it may not restrict the program from being
435 used in a business, or from being used for genetic
438 <tag>7. Distribution of License
441 The rights attached to the program must apply to all
442 to whom the program is redistributed without the need
443 for execution of an additional license by those
446 <tag>8. License Must Not Be Specific to Debian
449 The rights attached to the program must not depend on
450 the program's being part of a Debian system. If the
451 program is extracted from Debian and used or
452 distributed without Debian but otherwise within the
453 terms of the program's license, all parties to whom
454 the program is redistributed must have the same
455 rights as those that are granted in conjunction with
458 <tag>9. License Must Not Contaminate Other Software
461 The license must not place restrictions on other
462 software that is distributed along with the licensed
463 software. For example, the license must not insist
464 that all other programs distributed on the same medium
465 must be free software.
467 <tag>10. Example Licenses
470 The "GPL," "BSD," and "Artistic" licenses are examples of
471 licenses that we consider <em>free</em>.
478 <heading>Archive areas</heading>
481 <heading>The main archive area</heading>
484 The <em>main</em> archive area comprises the Debian
485 distribution. Only the packages in this area are considered
486 part of the distribution. None of the packages in
487 the <em>main</em> archive area require software outside of
488 that area to function. Anyone may use, share, modify and
489 redistribute the packages in this archive area
491 See <url id="http://www.debian.org/intro/free"
492 name="What Does Free Mean?"> for
493 more about what we mean by free software.
498 Every package in <em>main</em> must comply with the DFSG
499 (Debian Free Software Guidelines).
503 In addition, the packages in <em>main</em>
504 <list compact="compact">
506 must not require or recommend a package outside
507 of <em>main</em> for compilation or execution (thus, the
508 package must not declare a "Pre-Depends", "Depends",
509 "Recommends", "Build-Depends", or "Build-Depends-Indep"
510 relationship on a non-<em>main</em> package),
513 must not be so buggy that we refuse to support them,
517 must meet all policy requirements presented in this
526 <heading>The contrib archive area</heading>
529 The <em>contrib</em> archive area contains supplemental
530 packages intended to work with the Debian distribution, but
531 which require software outside of the distribution to either
536 Every package in <em>contrib</em> must comply with the DFSG.
540 In addition, the packages in <em>contrib</em>
541 <list compact="compact">
543 must not be so buggy that we refuse to support them,
547 must meet all policy requirements presented in this
554 Examples of packages which would be included in
555 <em>contrib</em> are:
556 <list compact="compact">
558 free packages which require <em>contrib</em>,
559 <em>non-free</em> packages or packages which are not
560 in our archive at all for compilation or execution,
564 wrapper packages or other sorts of free accessories for
571 <sect1 id="non-free">
572 <heading>The non-free archive area</heading>
575 The <em>non-free</em> archive area contains supplemental
576 packages intended to work with the Debian distribution that do
577 not comply with the DFSG or have other problems that make
578 their distribution problematic. They may not comply with all
579 of the policy requirements in this manual due to restrictions
580 on modifications or other limitations.
584 Packages must be placed in <em>non-free</em> if they are
585 not compliant with the DFSG or are encumbered by patents
586 or other legal issues that make their distribution
591 In addition, the packages in <em>non-free</em>
592 <list compact="compact">
594 must not be so buggy that we refuse to support them,
598 must meet all policy requirements presented in this
599 manual that it is possible for them to meet.
601 It is possible that there are policy
602 requirements which the package is unable to
603 meet, for example, if the source is
604 unavailable. These situations will need to be
605 handled on a case-by-case basis.
614 <sect id="pkgcopyright">
615 <heading>Copyright considerations</heading>
618 Every package must be accompanied by a verbatim copy of its
619 copyright information and distribution license in the file
620 <file>/usr/share/doc/<var>package</var>/copyright</file>
621 (see <ref id="copyrightfile"> for further details).
625 We reserve the right to restrict files from being included
626 anywhere in our archives if
627 <list compact="compact">
629 their use or distribution would break a law,
632 there is an ethical conflict in their distribution or
636 we would have to sign a license for them, or
639 their distribution would conflict with other project
646 Programs whose authors encourage the user to make
647 donations are fine for the main distribution, provided
648 that the authors do not claim that not donating is
649 immoral, unethical, illegal or something similar; in such
650 a case they must go in <em>non-free</em>.
654 Packages whose copyright permission notices (or patent
655 problems) do not even allow redistribution of binaries
656 only, and where no special permission has been obtained,
657 must not be placed on the Debian FTP site and its mirrors
662 Note that under international copyright law (this applies
663 in the United States, too), <em>no</em> distribution or
664 modification of a work is allowed without an explicit
665 notice saying so. Therefore a program without a copyright
666 notice <em>is</em> copyrighted and you may not do anything
667 to it without risking being sued! Likewise if a program
668 has a copyright notice but no statement saying what is
669 permitted then nothing is permitted.
673 Many authors are unaware of the problems that restrictive
674 copyrights (or lack of copyright notices) can cause for
675 the users of their supposedly-free software. It is often
676 worthwhile contacting such authors diplomatically to ask
677 them to modify their license terms. However, this can be a
678 politically difficult thing to do and you should ask for
679 advice on the <tt>debian-legal</tt> mailing list first, as
684 When in doubt about a copyright, send mail to
685 <email>debian-legal@lists.debian.org</email>. Be prepared
686 to provide us with the copyright statement. Software
687 covered by the GPL, public domain software and BSD-like
688 copyrights are safe; be wary of the phrases "commercial
689 use prohibited" and "distribution restricted".
693 <sect id="subsections">
694 <heading>Sections</heading>
697 The packages in the archive areas <em>main</em>,
698 <em>contrib</em> and <em>non-free</em> are grouped further into
699 <em>sections</em> to simplify handling.
703 The archive area and section for each package should be
704 specified in the package's <tt>Section</tt> control record (see
705 <ref id="f-Section">). However, the maintainer of the Debian
706 archive may override this selection to ensure the consistency of
707 the Debian distribution. The <tt>Section</tt> field should be
709 <list compact="compact">
711 <em>section</em> if the package is in the
712 <em>main</em> archive area,
715 <em>area/section</em> if the package is in
716 the <em>contrib</em> or <em>non-free</em>
723 The Debian archive maintainers provide the authoritative
724 list of sections. At present, they are:
780 The additional section <em>debian-installer</em>
781 contains special packages used by the installer and is not used
782 for normal Debian packages.
786 For more information about the sections and their definitions,
787 see the <url id="http://packages.debian.org/unstable/"
788 name="list of sections in unstable">.
792 <sect id="priorities">
793 <heading>Priorities</heading>
796 Each package should have a <em>priority</em> value, which is
797 included in the package's <em>control record</em>
798 (see <ref id="f-Priority">).
799 This information is used by the Debian package management tools to
800 separate high-priority packages from less-important packages.
804 The following <em>priority levels</em> are recognized by the
805 Debian package management tools.
807 <tag><tt>required</tt></tag>
809 Packages which are necessary for the proper
810 functioning of the system (usually, this means that
811 dpkg functionality depends on these packages).
812 Removing a <tt>required</tt> package may cause your
813 system to become totally broken and you may not even
814 be able to use <prgn>dpkg</prgn> to put things back,
815 so only do so if you know what you are doing. Systems
816 with only the <tt>required</tt> packages are probably
817 unusable, but they do have enough functionality to
818 allow the sysadmin to boot and install more software.
820 <tag><tt>important</tt></tag>
822 Important programs, including those which one would
823 expect to find on any Unix-like system. If the
824 expectation is that an experienced Unix person who
825 found it missing would say "What on earth is going on,
826 where is <prgn>foo</prgn>?", it must be an
827 <tt>important</tt> package.<footnote>
828 This is an important criterion because we are
829 trying to produce, amongst other things, a free
832 Other packages without which the system will not run
833 well or be usable must also have priority
834 <tt>important</tt>. This does
835 <em>not</em> include Emacs, the X Window System, TeX
836 or any other large applications. The
837 <tt>important</tt> packages are just a bare minimum of
838 commonly-expected and necessary tools.
840 <tag><tt>standard</tt></tag>
842 These packages provide a reasonably small but not too
843 limited character-mode system. This is what will be
844 installed by default if the user doesn't select anything
845 else. It doesn't include many large applications.
847 <tag><tt>optional</tt></tag>
849 (In a sense everything that isn't required is
850 optional, but that's not what is meant here.) This is
851 all the software that you might reasonably want to
852 install if you didn't know what it was and don't have
853 specialized requirements. This is a much larger system
854 and includes the X Window System, a full TeX
855 distribution, and many applications. Note that
856 optional packages should not conflict with each other.
858 <tag><tt>extra</tt></tag>
860 This contains all packages that conflict with others
861 with required, important, standard or optional
862 priorities, or are only likely to be useful if you
863 already know what they are or have specialized
864 requirements (such as packages containing only detached
871 Packages must not depend on packages with lower priority
872 values (excluding build-time dependencies). In order to
873 ensure this, the priorities of one or more packages may need
882 <heading>Binary packages</heading>
885 The Debian distribution is based on the Debian
886 package management system, called <prgn>dpkg</prgn>. Thus,
887 all packages in the Debian distribution must be provided
888 in the <tt>.deb</tt> file format.
892 A <tt>.deb</tt> package contains two sets of files: a set of files
893 to install on the system when the package is installed, and a set
894 of files that provide additional metadata about the package or
895 which are executed when the package is installed or removed. This
896 second set of files is called <em>control information files</em>.
897 Among those files are the package maintainer scripts
898 and <file>control</file>, the <qref id="binarycontrolfiles">binary
899 package control file</qref> that contains the control fields for
900 the package. Other control information files include
901 the <qref id="sharedlibs-symbols"><file>symbols</file> file</qref>
902 or <qref id="sharedlibs-shlibdeps"><file>shlibs</file> file</qref>
903 used to store shared library dependency information and
904 the <file>conffiles</file> file that lists the package's
905 configuration files (described in <ref id="config-files">).
909 There is unfortunately a collision of terminology here between
910 control information files and files in the Debian control file
911 format. Throughout this document, a <em>control file</em> refers
912 to a file in the Debian control file format. These files are
913 documented in <ref id="controlfields">. Only files referred to
914 specifically as <em>control information files</em> are the files
915 included in the control information file member of
916 the <file>.deb</file> file format used by binary packages. Most
917 control information files are not in the Debian control file
922 <heading>The package name</heading>
925 Every package must have a name that's unique within the Debian
930 The package name is included in the control field
931 <tt>Package</tt>, the format of which is described
932 in <ref id="f-Package">.
933 The package name is also included as a part of the file name
934 of the <tt>.deb</tt> file.
939 <heading>The version of a package</heading>
942 Every package has a version number recorded in its
943 <tt>Version</tt> control file field, described in
944 <ref id="f-Version">.
948 The package management system imposes an ordering on version
949 numbers, so that it can tell whether packages are being up- or
950 downgraded and so that package system front end applications
951 can tell whether a package it finds available is newer than
952 the one installed on the system. The version number format
953 has the most significant parts (as far as comparison is
954 concerned) at the beginning.
958 If an upstream package has problematic version numbers they
959 should be converted to a sane form for use in the
960 <tt>Version</tt> field.
964 <heading>Version numbers based on dates</heading>
967 In general, Debian packages should use the same version
968 numbers as the upstream sources. However, upstream version
969 numbers based on some date formats (sometimes used for
970 development or "snapshot" releases) will not be ordered
971 correctly by the package management software. For
972 example, <prgn>dpkg</prgn> will consider "96May01" to be
973 greater than "96Dec24".
977 To prevent having to use epochs for every new upstream
978 version, the date-based portion of any upstream version number
979 should be given in a way that sorts correctly: four-digit year
980 first, followed by a two-digit numeric month, followed by a
981 two-digit numeric date, possibly with punctuation between the
986 Native Debian packages (i.e., packages which have been written
987 especially for Debian) whose version numbers include dates
988 should also follow these rules. If punctuation is desired
989 between the date components, remember that hyphen (<tt>-</tt>)
990 cannot be used in native package versions. Period
991 (<tt>.</tt>) is normally a good choice.
997 <sect id="maintainer">
998 <heading>The maintainer of a package</heading>
1001 Every package must have a maintainer, except for orphaned
1002 packages as described below. The maintainer may be one person
1003 or a group of people reachable from a common email address, such
1004 as a mailing list. The maintainer is responsible for
1005 maintaining the Debian packaging files, evaluating and
1006 responding appropriately to reported bugs, uploading new
1007 versions of the package (either directly or through a sponsor),
1008 ensuring that the package is placed in the appropriate archive
1009 area and included in Debian releases as appropriate for the
1010 stability and utility of the package, and requesting removal of
1011 the package from the Debian distribution if it is no longer
1012 useful or maintainable.
1016 The maintainer must be specified in the <tt>Maintainer</tt>
1017 control field with their correct name and a working email
1018 address. The email address given in the <tt>Maintainer</tt>
1019 control field must accept mail from those role accounts in
1020 Debian used to send automated mails regarding the package. This
1021 includes non-spam mail from the bug-tracking system, all mail
1022 from the Debian archive maintenance software, and other role
1023 accounts or automated processes that are commonly agreed on by
1024 the project.<footnote>
1025 A sample implementation of such a whitelist written for the
1026 Mailman mailing list management software is used for mailing
1027 lists hosted by alioth.debian.org.
1029 If one person or team maintains several packages, they should
1030 use the same form of their name and email address in
1031 the <tt>Maintainer</tt> fields of those packages.
1035 The format of the <tt>Maintainer</tt> control field is
1036 described in <ref id="f-Maintainer">.
1040 If the maintainer of the package is a team of people with a
1041 shared email address, the <tt>Uploaders</tt> control field must
1042 be present and must contain at least one human with their
1043 personal email address. See <ref id="f-Uploaders"> for the
1044 syntax of that field.
1048 An orphaned package is one with no current maintainer. Orphaned
1049 packages should have their <tt>Maintainer</tt> control field set
1050 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1051 These packages are considered maintained by the Debian project
1052 as a whole until someone else volunteers to take over
1053 maintenance.<footnote>
1054 The detailed procedure for gracefully orphaning a package can
1055 be found in the Debian Developer's Reference
1056 (see <ref id="related">).
1061 <sect id="descriptions">
1062 <heading>The description of a package</heading>
1065 Every Debian package must have a <tt>Description</tt> control
1066 field which contains a synopsis and extended description of the
1067 package. Technical information about the format of the
1068 <tt>Description</tt> field is in <ref id="f-Description">.
1072 The description should describe the package (the program) to a
1073 user (system administrator) who has never met it before so that
1074 they have enough information to decide whether they want to
1075 install it. This description should not just be copied verbatim
1076 from the program's documentation.
1080 Put important information first, both in the synopsis and
1081 extended description. Sometimes only the first part of the
1082 synopsis or of the description will be displayed. You can
1083 assume that there will usually be a way to see the whole
1084 extended description.
1088 The description should also give information about the
1089 significant dependencies and conflicts between this package
1090 and others, so that the user knows why these dependencies and
1091 conflicts have been declared.
1095 Instructions for configuring or using the package should
1096 not be included (that is what installation scripts,
1097 manual pages, info files, etc., are for). Copyright
1098 statements and other administrivia should not be included
1099 either (that is what the copyright file is for).
1102 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1105 The single line synopsis should be kept brief - certainly
1106 under 80 characters.
1110 Do not include the package name in the synopsis line. The
1111 display software knows how to display this already, and you
1112 do not need to state it. Remember that in many situations
1113 the user may only see the synopsis line - make it as
1114 informative as you can.
1119 <sect1 id="extendeddesc"><heading>The extended description</heading>
1122 Do not try to continue the single line synopsis into the
1123 extended description. This will not work correctly when
1124 the full description is displayed, and makes no sense
1125 where only the summary (the single line synopsis) is
1130 The extended description should describe what the package
1131 does and how it relates to the rest of the system (in terms
1132 of, for example, which subsystem it is which part of).
1136 The description field needs to make sense to anyone, even
1137 people who have no idea about any of the things the
1138 package deals with.<footnote>
1139 The blurb that comes with a program in its
1140 announcements and/or <prgn>README</prgn> files is
1141 rarely suitable for use in a description. It is
1142 usually aimed at people who are already in the
1143 community where the package is used.
1151 <sect id="dependencies">
1152 <heading>Dependencies</heading>
1155 Every package must specify the dependency information
1156 about other packages that are required for the first to
1161 For example, a dependency entry must be provided for any
1162 shared libraries required by a dynamically-linked executable
1163 binary in a package.
1167 Packages are not required to declare any dependencies they
1168 have on other packages which are marked <tt>Essential</tt>
1169 (see below), and should not do so unless they depend on a
1170 particular version of that package.<footnote>
1172 Essential is needed in part to avoid unresolvable dependency
1173 loops on upgrade. If packages add unnecessary dependencies
1174 on packages in this set, the chances that there
1175 <strong>will</strong> be an unresolvable dependency loop
1176 caused by forcing these Essential packages to be configured
1177 first before they need to be is greatly increased. It also
1178 increases the chances that frontends will be unable to
1179 <strong>calculate</strong> an upgrade path, even if one
1183 Also, functionality is rarely ever removed from the
1184 Essential set, but <em>packages</em> have been removed from
1185 the Essential set when the functionality moved to a
1186 different package. So depending on these packages <em>just
1187 in case</em> they stop being essential does way more harm
1194 Sometimes, unpacking one package requires that another package
1195 be first unpacked <em>and</em> configured. In this case, the
1196 depending package must specify this dependency in
1197 the <tt>Pre-Depends</tt> control field.
1201 You should not specify a <tt>Pre-Depends</tt> entry for a
1202 package before this has been discussed on the
1203 <tt>debian-devel</tt> mailing list and a consensus about
1204 doing that has been reached.
1208 The format of the package interrelationship control fields is
1209 described in <ref id="relationships">.
1213 <sect id="virtual_pkg">
1214 <heading>Virtual packages</heading>
1217 Sometimes, there are several packages which offer
1218 more-or-less the same functionality. In this case, it's
1219 useful to define a <em>virtual package</em> whose name
1220 describes that common functionality. (The virtual
1221 packages only exist logically, not physically; that's why
1222 they are called <em>virtual</em>.) The packages with this
1223 particular function will then <em>provide</em> the virtual
1224 package. Thus, any other package requiring that function
1225 can simply depend on the virtual package without having to
1226 specify all possible packages individually.
1230 All packages should use virtual package names where
1231 appropriate, and arrange to create new ones if necessary.
1232 They should not use virtual package names (except privately,
1233 amongst a cooperating group of packages) unless they have
1234 been agreed upon and appear in the list of virtual package
1235 names. (See also <ref id="virtual">)
1239 The latest version of the authoritative list of virtual
1240 package names can be found in the <tt>debian-policy</tt> package.
1241 It is also available from the Debian web mirrors at
1242 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1243 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1247 The procedure for updating the list is described in the preface
1254 <heading>Base system</heading>
1257 The <tt>base system</tt> is a minimum subset of the Debian
1258 system that is installed before everything else
1259 on a new system. Only very few packages are allowed to form
1260 part of the base system, in order to keep the required disk
1265 The base system consists of all those packages with priority
1266 <tt>required</tt> or <tt>important</tt>. Many of them will
1267 be tagged <tt>essential</tt> (see below).
1272 <heading>Essential packages</heading>
1275 Essential is defined as the minimal set of functionality that
1276 must be available and usable on the system at all times, even
1277 when packages are in the "Unpacked" state.
1278 Packages are tagged <tt>essential</tt> for a system using the
1279 <tt>Essential</tt> control field. The format of the
1280 <tt>Essential</tt> control field is described in <ref
1285 Since these packages cannot be easily removed (one has to
1286 specify an extra <em>force option</em> to
1287 <prgn>dpkg</prgn> to do so), this flag must not be used
1288 unless absolutely necessary. A shared library package
1289 must not be tagged <tt>essential</tt>; dependencies will
1290 prevent its premature removal, and we need to be able to
1291 remove it when it has been superseded.
1295 Since dpkg will not prevent upgrading of other packages
1296 while an <tt>essential</tt> package is in an unconfigured
1297 state, all <tt>essential</tt> packages must supply all of
1298 their core functionality even when unconfigured. If the
1299 package cannot satisfy this requirement it must not be
1300 tagged as essential, and any packages depending on this
1301 package must instead have explicit dependency fields as
1306 Maintainers should take great care in adding any programs,
1307 interfaces, or functionality to <tt>essential</tt> packages.
1308 Packages may assume that functionality provided by
1309 <tt>essential</tt> packages is always available without
1310 declaring explicit dependencies, which means that removing
1311 functionality from the Essential set is very difficult and is
1312 almost never done. Any capability added to an
1313 <tt>essential</tt> package therefore creates an obligation to
1314 support that capability as part of the Essential set in
1319 You must not tag any packages <tt>essential</tt> before
1320 this has been discussed on the <tt>debian-devel</tt>
1321 mailing list and a consensus about doing that has been
1326 <sect id="maintscripts">
1327 <heading>Maintainer Scripts</heading>
1330 The package installation scripts should avoid producing
1331 output which is unnecessary for the user to see and
1332 should rely on <prgn>dpkg</prgn> to stave off boredom on
1333 the part of a user installing many packages. This means,
1334 amongst other things, not passing the <tt>--verbose</tt>
1335 option to <prgn>update-alternatives</prgn>.
1339 Errors which occur during the execution of an installation
1340 script must be checked and the installation must not
1341 continue after an error.
1345 Note that in general <ref id="scripts"> applies to package
1346 maintainer scripts, too.
1350 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1351 to another package without consulting the maintainer of that
1352 package first. When adding or removing diversions, package
1353 maintainer scripts must provide the <tt>--package</tt> flag
1354 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1358 All packages which supply an instance of a common command
1359 name (or, in general, filename) should generally use
1360 <prgn>update-alternatives</prgn>, so that they may be
1361 installed together. If <prgn>update-alternatives</prgn>
1362 is not used, then each package must use
1363 <tt>Conflicts</tt> to ensure that other packages are
1364 removed. (In this case, it may be appropriate to
1365 specify a conflict against earlier versions of something
1366 that previously did not use
1367 <prgn>update-alternatives</prgn>; this is an exception to
1368 the usual rule that versioned conflicts should be
1372 <sect1 id="maintscriptprompt">
1373 <heading>Prompting in maintainer scripts</heading>
1375 Package maintainer scripts may prompt the user if
1376 necessary. Prompting must be done by communicating
1377 through a program, such as <prgn>debconf</prgn>, which
1378 conforms to the Debian Configuration Management
1379 Specification, version 2 or higher.
1383 Packages which are essential, or which are dependencies of
1384 essential packages, may fall back on another prompting method
1385 if no such interface is available when they are executed.
1389 The Debian Configuration Management Specification is included
1390 in the <file>debconf_specification</file> files in the
1391 <package>debian-policy</package> package.
1392 It is also available from the Debian web mirrors at
1393 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1394 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1398 Packages which use the Debian Configuration Management
1399 Specification may contain the additional control information
1400 files <file>config</file>
1401 and <file>templates</file>. <file>config</file> is an
1402 additional maintainer script used for package configuration,
1403 and <file>templates</file> contains templates used for user
1404 prompting. The <prgn>config</prgn> script might be run before
1405 the <prgn>preinst</prgn> script and before the package is
1406 unpacked or any of its dependencies or pre-dependencies are
1407 satisfied. Therefore it must work using only the tools
1408 present in <em>essential</em> packages.<footnote>
1409 <package>Debconf</package> or another tool that
1410 implements the Debian Configuration Management
1411 Specification will also be installed, and any
1412 versioned dependencies on it will be satisfied
1413 before preconfiguration begins.
1418 Packages which use the Debian Configuration Management
1419 Specification must allow for translation of their user-visible
1420 messages by using a gettext-based system such as the one
1421 provided by the <package>po-debconf</package> package.
1425 Packages should try to minimize the amount of prompting
1426 they need to do, and they should ensure that the user
1427 will only ever be asked each question once. This means
1428 that packages should try to use appropriate shared
1429 configuration files (such as <file>/etc/papersize</file> and
1430 <file>/etc/news/server</file>), and shared
1431 <package>debconf</package> variables rather than each
1432 prompting for their own list of required pieces of
1437 It also means that an upgrade should not ask the same
1438 questions again, unless the user has used
1439 <tt>dpkg --purge</tt> to remove the package's configuration.
1440 The answers to configuration questions should be stored in an
1441 appropriate place in <file>/etc</file> so that the user can
1442 modify them, and how this has been done should be
1447 If a package has a vitally important piece of
1448 information to pass to the user (such as "don't run me
1449 as I am, you must edit the following configuration files
1450 first or you risk your system emitting badly-formatted
1451 messages"), it should display this in the
1452 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1453 prompt the user to hit return to acknowledge the
1454 message. Copyright messages do not count as vitally
1455 important (they belong in
1456 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1457 neither do instructions on how to use a program (these
1458 should be in on-line documentation, where all the users
1463 Any necessary prompting should almost always be confined
1464 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1465 script. If it is done in the <prgn>postinst</prgn>, it
1466 should be protected with a conditional so that
1467 unnecessary prompting doesn't happen if a package's
1468 installation fails and the <prgn>postinst</prgn> is
1469 called with <tt>abort-upgrade</tt>,
1470 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1480 <heading>Source packages</heading>
1482 <sect id="standardsversion">
1483 <heading>Standards conformance</heading>
1486 Source packages should specify the most recent version number
1487 of this policy document with which your package complied
1488 when it was last updated.
1492 This information may be used to file bug reports
1493 automatically if your package becomes too much out of date.
1497 The version is specified in the <tt>Standards-Version</tt>
1499 The format of the <tt>Standards-Version</tt> field is
1500 described in <ref id="f-Standards-Version">.
1504 You should regularly, and especially if your package has
1505 become out of date, check for the newest Policy Manual
1506 available and update your package, if necessary. When your
1507 package complies with the new standards you should update the
1508 <tt>Standards-Version</tt> source package field and
1509 release it.<footnote>
1510 See the file <file>upgrading-checklist</file> for
1511 information about policy which has changed between
1512 different versions of this document.
1518 <sect id="pkg-relations">
1519 <heading>Package relationships</heading>
1522 Source packages should specify which binary packages they
1523 require to be installed or not to be installed in order to
1524 build correctly. For example, if building a package
1525 requires a certain compiler, then the compiler should be
1526 specified as a build-time dependency.
1530 It is not necessary to explicitly specify build-time
1531 relationships on a minimal set of packages that are always
1532 needed to compile, link and put in a Debian package a
1533 standard "Hello World!" program written in C or C++. The
1534 required packages are called <em>build-essential</em>, and
1535 an informational list can be found in
1536 <file>/usr/share/doc/build-essential/list</file> (which is
1537 contained in the <tt>build-essential</tt>
1540 <list compact="compact">
1542 This allows maintaining the list separately
1543 from the policy documents (the list does not
1544 need the kind of control that the policy
1548 Having a separate package allows one to install
1549 the build-essential packages on a machine, as
1550 well as allowing other packages such as tasks to
1551 require installation of the build-essential
1552 packages using the depends relation.
1555 The separate package allows bug reports against
1556 the list to be categorized separately from
1557 the policy management process in the BTS.
1564 When specifying the set of build-time dependencies, one
1565 should list only those packages explicitly required by the
1566 build. It is not necessary to list packages which are
1567 required merely because some other package in the list of
1568 build-time dependencies depends on them.<footnote>
1569 The reason for this is that dependencies change, and
1570 you should list all those packages, and <em>only</em>
1571 those packages that <em>you</em> need directly. What
1572 others need is their business. For example, if you
1573 only link against <file>libimlib</file>, you will need to
1574 build-depend on <package>libimlib2-dev</package> but
1575 not against any <tt>libjpeg*</tt> packages, even
1576 though <tt>libimlib2-dev</tt> currently depends on
1577 them: installation of <package>libimlib2-dev</package>
1578 will automatically ensure that all of its run-time
1579 dependencies are satisfied.
1584 If build-time dependencies are specified, it must be
1585 possible to build the package and produce working binaries
1586 on a system with only essential and build-essential
1587 packages installed and also those required to satisfy the
1588 build-time relationships (including any implied
1589 relationships). In particular, this means that version
1590 clauses should be used rigorously in build-time
1591 relationships so that one cannot produce bad or
1592 inconsistently configured packages when the relationships
1593 are properly satisfied.
1597 <ref id="relationships"> explains the technical details.
1602 <heading>Changes to the upstream sources</heading>
1605 If changes to the source code are made that are not
1606 specific to the needs of the Debian system, they should be
1607 sent to the upstream authors in whatever form they prefer
1608 so as to be included in the upstream version of the
1613 If you need to configure the package differently for
1614 Debian or for Linux, and the upstream source doesn't
1615 provide a way to do so, you should add such configuration
1616 facilities (for example, a new <prgn>autoconf</prgn> test
1617 or <tt>#define</tt>) and send the patch to the upstream
1618 authors, with the default set to the way they originally
1619 had it. You can then easily override the default in your
1620 <file>debian/rules</file> or wherever is appropriate.
1624 You should make sure that the <prgn>configure</prgn> utility
1625 detects the correct architecture specification string
1626 (refer to <ref id="arch-spec"> for details).
1630 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1631 <prgn>configure</prgn> scripts are used, you should edit the
1632 <file>.in</file> files rather than editing the
1633 <prgn>Makefile</prgn> directly. This allows the user to
1634 reconfigure the package if necessary. You should
1635 <em>not</em> configure the package and edit the generated
1636 <prgn>Makefile</prgn>! This makes it impossible for someone
1637 else to later reconfigure the package without losing the
1643 <sect id="dpkgchangelog">
1644 <heading>Debian changelog: <file>debian/changelog</file></heading>
1647 Changes in the Debian version of the package should be
1648 briefly explained in the Debian changelog file
1649 <file>debian/changelog</file>.<footnote>
1651 Mistakes in changelogs are usually best rectified by
1652 making a new changelog entry rather than "rewriting
1653 history" by editing old changelog entries.
1656 This includes modifications
1657 made in the Debian package compared to the upstream one
1658 as well as other changes and updates to the package.
1660 Although there is nothing stopping an author who is also
1661 the Debian maintainer from using this changelog for all
1662 their changes, it will have to be renamed if the Debian
1663 and upstream maintainers become different people. In such
1664 a case, however, it might be better to maintain the package
1665 as a non-native package.
1670 The format of the <file>debian/changelog</file> allows the
1671 package building tools to discover which version of the package
1672 is being built and find out other release-specific information.
1676 That format is a series of entries like this:
1678 <example compact="compact">
1679 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1681 [optional blank line(s), stripped]
1683 * <var>change details</var>
1684 <var>more change details</var>
1686 [blank line(s), included in output of dpkg-parsechangelog]
1688 * <var>even more change details</var>
1690 [optional blank line(s), stripped]
1692 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1697 <var>package</var> and <var>version</var> are the source
1698 package name and version number.
1702 <var>distribution(s)</var> lists the distributions where
1703 this version should be installed when it is uploaded - it
1704 is copied to the <tt>Distribution</tt> field in the
1705 <file>.changes</file> file. See <ref id="f-Distribution">.
1709 <var>urgency</var> is the value for the <tt>Urgency</tt>
1710 field in the <file>.changes</file> file for the upload
1711 (see <ref id="f-Urgency">). It is not possible to specify
1712 an urgency containing commas; commas are used to separate
1713 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1714 <prgn>dpkg</prgn> changelog format (though there is
1715 currently only one useful <var>keyword</var>,
1720 The change details may in fact be any series of lines
1721 starting with at least two spaces, but conventionally each
1722 change starts with an asterisk and a separating space and
1723 continuation lines are indented so as to bring them in
1724 line with the start of the text above. Blank lines may be
1725 used here to separate groups of changes, if desired.
1729 If this upload resolves bugs recorded in the Bug Tracking
1730 System (BTS), they may be automatically closed on the
1731 inclusion of this package into the Debian archive by
1732 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1733 in the change details.<footnote>
1734 To be precise, the string should match the following
1735 Perl regular expression:
1737 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1739 Then all of the bug numbers listed will be closed by the
1740 archive maintenance software (<prgn>dak</prgn>) using the
1741 <var>version</var> of the changelog entry.
1743 This information is conveyed via the <tt>Closes</tt> field
1744 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1748 The maintainer name and email address used in the changelog
1749 should be the details of the person who prepared this release of
1750 the package. They are <em>not</em> necessarily those of the
1751 uploader or usual package maintainer.<footnote>
1752 In the case of a sponsored upload, the uploader signs the
1753 files, but the changelog maintainer name and address are those
1754 of the person who prepared this release. If the preparer of
1755 the release is not one of the usual maintainers of the package
1757 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1758 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1759 fields of the package), the first line of the changelog is
1760 conventionally used to explain why a non-maintainer is
1761 uploading the package. The Debian Developer's Reference
1762 (see <ref id="related">) documents the conventions
1764 The information here will be copied to the <tt>Changed-By</tt>
1765 field in the <tt>.changes</tt> file
1766 (see <ref id="f-Changed-By">), and then later used to send an
1767 acknowledgement when the upload has been installed.
1771 The <var>date</var> has the following format<footnote>
1772 This is the same as the format generated by <tt>date
1774 </footnote> (compatible and with the same semantics of
1775 RFC 2822 and RFC 5322):
1776 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1778 <list compact="compact">
1780 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1783 dd is a one- or two-digit day of the month (01-31)
1786 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1789 <item>yyyy is the four-digit year (e.g. 2010)</item>
1790 <item>hh is the two-digit hour (00-23)</item>
1791 <item>mm is the two-digit minutes (00-59)</item>
1792 <item>ss is the two-digit seconds (00-60)</item>
1794 +zzzz or -zzzz is the the time zone offset from Coordinated
1795 Universal Time (UTC). "+" indicates that the time is ahead
1796 of (i.e., east of) UTC and "-" indicates that the time is
1797 behind (i.e., west of) UTC. The first two digits indicate
1798 the hour difference from UTC and the last two digits
1799 indicate the number of additional minutes difference from
1800 UTC. The last two digits must be in the range 00-59.
1806 The first "title" line with the package name must start
1807 at the left hand margin. The "trailer" line with the
1808 maintainer and date details must be preceded by exactly
1809 one space. The maintainer details and the date must be
1810 separated by exactly two spaces.
1814 The entire changelog must be encoded in UTF-8.
1818 For more information on placement of the changelog files
1819 within binary packages, please see <ref id="changelogs">.
1823 <sect id="dpkgcopyright">
1824 <heading>Copyright: <file>debian/copyright</file></heading>
1826 Every package must be accompanied by a verbatim copy of its
1827 copyright information and distribution license in the file
1828 <file>/usr/share/doc/<var>package</var>/copyright</file>
1829 (see <ref id="copyrightfile"> for further details). Also see
1830 <ref id="pkgcopyright"> for further considerations related
1831 to copyrights for packages.
1835 <heading>Error trapping in makefiles</heading>
1838 When <prgn>make</prgn> invokes a command in a makefile
1839 (including your package's upstream makefiles and
1840 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1841 means that <prgn>sh</prgn>'s usual bad error handling
1842 properties apply: if you include a miniature script as one
1843 of the commands in your makefile you'll find that if you
1844 don't do anything about it then errors are not detected
1845 and <prgn>make</prgn> will blithely continue after
1850 Every time you put more than one shell command (this
1851 includes using a loop) in a makefile command you
1852 must make sure that errors are trapped. For
1853 simple compound commands, such as changing directory and
1854 then running a program, using <tt>&&</tt> rather
1855 than semicolon as a command separator is sufficient. For
1856 more complex commands including most loops and
1857 conditionals you should include a separate <tt>set -e</tt>
1858 command at the start of every makefile command that's
1859 actually one of these miniature shell scripts.
1863 <sect id="timestamps">
1864 <heading>Time Stamps</heading>
1866 Maintainers should preserve the modification times of the
1867 upstream source files in a package, as far as is reasonably
1869 The rationale is that there is some information conveyed
1870 by knowing the age of the file, for example, you could
1871 recognize that some documentation is very old by looking
1872 at the modification time, so it would be nice if the
1873 modification time of the upstream source would be
1879 <sect id="restrictions">
1880 <heading>Restrictions on objects in source packages</heading>
1883 The source package may not contain any hard links<footnote>
1885 This is not currently detected when building source
1886 packages, but only when extracting
1890 Hard links may be permitted at some point in the
1891 future, but would require a fair amount of
1894 </footnote>, device special files, sockets or setuid or
1895 setgid files.<footnote>
1896 Setgid directories are allowed.
1901 <sect id="debianrules">
1902 <heading>Main building script: <file>debian/rules</file></heading>
1905 This file must be an executable makefile, and contains the
1906 package-specific recipes for compiling the package and
1907 building binary package(s) from the source.
1911 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1912 so that it can be invoked by saying its name rather than
1913 invoking <prgn>make</prgn> explicitly. That is, invoking
1914 either of <tt>make -f debian/rules <em>args...</em></tt>
1915 or <tt>./debian/rules <em>args...</em></tt> must result in
1920 The following targets are required and must be implemented
1921 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1922 <tt>binary-arch</tt>, <tt>binary-indep</tt>, <tt>build</tt>,
1923 <tt>build-arch</tt> and <tt>build-indep</tt>.
1924 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1928 Since an interactive <file>debian/rules</file> script makes it
1929 impossible to auto-compile that package and also makes it hard
1930 for other people to reproduce the same binary package, all
1931 required targets must be non-interactive. It also follows that
1932 any target that these targets depend on must also be
1937 The targets are as follows:
1939 <tag><tt>build</tt> (required)</tag>
1942 The <tt>build</tt> target should perform all the
1943 configuration and compilation of the package.
1944 If a package has an interactive pre-build
1945 configuration routine, the Debian source package
1946 must either be built after this has taken place (so
1947 that the binary package can be built without rerunning
1948 the configuration) or the configuration routine
1949 modified to become non-interactive. (The latter is
1950 preferable if there are architecture-specific features
1951 detected by the configuration routine.)
1955 For some packages, notably ones where the same
1956 source tree is compiled in different ways to produce
1957 two binary packages, the <tt>build</tt> target
1958 does not make much sense. For these packages it is
1959 good enough to provide two (or more) targets
1960 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1961 for each of the ways of building the package, and a
1962 <tt>build</tt> target that does nothing. The
1963 <tt>binary</tt> target will have to build the
1964 package in each of the possible ways and make the
1965 binary package out of each.
1969 The <tt>build</tt> target must not do anything
1970 that might require root privilege.
1974 The <tt>build</tt> target may need to run the
1975 <tt>clean</tt> target first - see below.
1979 When a package has a configuration and build routine
1980 which takes a long time, or when the makefiles are
1981 poorly designed, or when <tt>build</tt> needs to
1982 run <tt>clean</tt> first, it is a good idea to
1983 <tt>touch build</tt> when the build process is
1984 complete. This will ensure that if <tt>debian/rules
1985 build</tt> is run again it will not rebuild the whole
1987 Another common way to do this is for <tt>build</tt>
1988 to depend on <prgn>build-stamp</prgn> and to do
1989 nothing else, and for the <prgn>build-stamp</prgn>
1990 target to do the building and to <tt>touch
1991 build-stamp</tt> on completion. This is
1992 especially useful if the build routine creates a
1993 file or directory called <tt>build</tt>; in such a
1994 case, <tt>build</tt> will need to be listed as
1995 a phony target (i.e., as a dependency of the
1996 <tt>.PHONY</tt> target). See the documentation of
1997 <prgn>make</prgn> for more information on phony
2003 <tag><tt>build-arch</tt> (required),
2004 <tt>build-indep</tt> (required)
2008 The <tt>build-arch</tt> target must
2009 perform all the configuration and compilation required for
2010 producing all architecture-dependant binary packages
2011 (those packages for which the body of the
2012 <tt>Architecture</tt> field in <tt>debian/control</tt> is
2013 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
2014 target must perform all the configuration
2015 and compilation required for producing all
2016 architecture-independent binary packages (those packages
2017 for which the body of the <tt>Architecture</tt> field
2018 in <tt>debian/control</tt> is <tt>all</tt>).
2019 The <tt>build</tt> target
2020 should either depend on those targets or take the same
2021 actions as invoking those targets would perform.<footnote>
2022 This split allows binary-only builds to not install the
2023 dependencies required for the <tt>build-indep</tt>
2024 target and skip any resource-intensive build tasks that
2025 are only required when building architecture-independent
2031 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
2032 must not do anything that might require root privilege.
2036 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2037 (required), <tt>binary-indep</tt> (required)
2041 The <tt>binary</tt> target must be all that is
2042 necessary for the user to build the binary package(s)
2043 produced from this source package. It is
2044 split into two parts: <prgn>binary-arch</prgn> builds
2045 the binary packages which are specific to a particular
2046 architecture, and <tt>binary-indep</tt> builds
2047 those which are not.
2050 <tt>binary</tt> may be (and commonly is) a target with
2051 no commands which simply depends on
2052 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2055 Both <tt>binary-*</tt> targets should depend on the
2056 <tt>build</tt> target, or on the appropriate
2057 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2058 provided, so that the package is built if it has not
2059 been already. It should then create the relevant
2060 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2061 make their control files and <prgn>dpkg-deb</prgn> to
2062 build them and place them in the parent of the top
2067 Both the <tt>binary-arch</tt> and
2068 <tt>binary-indep</tt> targets <em>must</em> exist.
2069 If one of them has nothing to do (which will always be
2070 the case if the source generates only a single binary
2071 package, whether architecture-dependent or not), it
2072 must still exist and must always succeed.
2076 The <tt>binary</tt> targets must be invoked as
2078 The <prgn>fakeroot</prgn> package often allows one
2079 to build a package correctly even without being
2085 <tag><tt>clean</tt> (required)</tag>
2088 This must undo any effects that the <tt>build</tt>
2089 and <tt>binary</tt> targets may have had, except
2090 that it should leave alone any output files created in
2091 the parent directory by a run of a <tt>binary</tt>
2096 If a <tt>build</tt> file is touched at the end of
2097 the <tt>build</tt> target, as suggested above, it
2098 should be removed as the first action that
2099 <tt>clean</tt> performs, so that running
2100 <tt>build</tt> again after an interrupted
2101 <tt>clean</tt> doesn't think that everything is
2106 The <tt>clean</tt> target may need to be
2107 invoked as root if <tt>binary</tt> has been
2108 invoked since the last <tt>clean</tt>, or if
2109 <tt>build</tt> has been invoked as root (since
2110 <tt>build</tt> may create directories, for
2115 <tag><tt>get-orig-source</tt> (optional)</tag>
2118 This target fetches the most recent version of the
2119 original source package from a canonical archive site
2120 (via FTP or WWW, for example), does any necessary
2121 rearrangement to turn it into the original source
2122 tar file format described below, and leaves it in the
2127 This target may be invoked in any directory, and
2128 should take care to clean up any temporary files it
2133 This target is optional, but providing it if
2134 possible is a good idea.
2138 <tag><tt>patch</tt> (optional)</tag>
2141 This target performs whatever additional actions are
2142 required to make the source ready for editing (unpacking
2143 additional upstream archives, applying patches, etc.).
2144 It is recommended to be implemented for any package where
2145 <tt>dpkg-source -x</tt> does not result in source ready
2146 for additional modification. See
2147 <ref id="readmesource">.
2153 The <tt>build</tt>, <tt>binary</tt> and
2154 <tt>clean</tt> targets must be invoked with the current
2155 directory being the package's top-level directory.
2160 Additional targets may exist in <file>debian/rules</file>,
2161 either as published or undocumented interfaces or for the
2162 package's internal use.
2166 The architectures we build on and build for are determined
2167 by <prgn>make</prgn> variables using the
2168 utility <prgn>dpkg-architecture</prgn>.
2169 You can determine the Debian architecture and the GNU style
2170 architecture specification string for the build architecture as
2171 well as for the host architecture. The build architecture is
2172 the architecture on which <file>debian/rules</file> is run and
2173 the package build is performed. The host architecture is the
2174 architecture on which the resulting package will be installed
2175 and run. These are normally the same, but may be different in
2176 the case of cross-compilation (building packages for one
2177 architecture on machines of a different architecture).
2181 Here is a list of supported <prgn>make</prgn> variables:
2182 <list compact="compact">
2184 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2187 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2190 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2193 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2194 specification string)
2197 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2198 <tt>DEB_*_GNU_TYPE</tt>)
2201 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2202 <tt>DEB_*_GNU_TYPE</tt>)
2204 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2205 the build architecture or <tt>HOST</tt> for specification of the
2210 Backward compatibility can be provided in the rules file
2211 by setting the needed variables to suitable default
2212 values; please refer to the documentation of
2213 <prgn>dpkg-architecture</prgn> for details.
2217 It is important to understand that the <tt>DEB_*_ARCH</tt>
2218 string only determines which Debian architecture we are
2219 building on or for. It should not be used to get the CPU
2220 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2221 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2222 GNU style variables should generally only be used with upstream
2226 <sect1 id="debianrules-options">
2227 <heading><file>debian/rules</file> and
2228 <tt>DEB_BUILD_OPTIONS</tt></heading>
2231 Supporting the standardized environment variable
2232 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2233 contain several flags to change how a package is compiled and
2234 built. Each flag must be in the form <var>flag</var> or
2235 <var>flag</var>=<var>options</var>. If multiple flags are
2236 given, they must be separated by whitespace.<footnote>
2237 Some packages support any delimiter, but whitespace is the
2238 easiest to parse inside a makefile and avoids ambiguity with
2239 flag values that contain commas.
2241 <var>flag</var> must start with a lowercase letter
2242 (<tt>a-z</tt>) and consist only of lowercase letters,
2243 numbers (<tt>0-9</tt>), and the characters
2244 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2245 <var>options</var> must not contain whitespace. The same
2246 tag should not be given multiple times with conflicting
2247 values. Package maintainers may assume that
2248 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2252 The meaning of the following tags has been standardized:
2256 This tag says to not run any build-time test suite
2257 provided by the package.
2261 The presence of this tag means that the package should
2262 be compiled with a minimum of optimization. For C
2263 programs, it is best to add <tt>-O0</tt> to
2264 <tt>CFLAGS</tt> (although this is usually the default).
2265 Some programs might fail to build or run at this level
2266 of optimization; it may be necessary to use
2267 <tt>-O1</tt>, for example.
2271 This tag means that the debugging symbols should not be
2272 stripped from the binary during installation, so that
2273 debugging information may be included in the package.
2275 <tag>parallel=n</tag>
2277 This tag means that the package should be built using up
2278 to <tt>n</tt> parallel processes if the package build
2279 system supports this.<footnote>
2280 Packages built with <tt>make</tt> can often implement
2281 this by passing the <tt>-j</tt><var>n</var> option to
2284 If the package build system does not support parallel
2285 builds, this string must be ignored. If the package
2286 build system only supports a lower level of concurrency
2287 than <var>n</var>, the package should be built using as
2288 many parallel processes as the package build system
2289 supports. It is up to the package maintainer to decide
2290 whether the package build times are long enough and the
2291 package build system is robust enough to make supporting
2292 parallel builds worthwhile.
2298 Unknown flags must be ignored by <file>debian/rules</file>.
2302 The following makefile snippet is an example of how one may
2303 implement the build options; you will probably have to
2304 massage this example in order to make it work for your
2306 <example compact="compact">
2309 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2310 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2311 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2312 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2314 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2319 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2320 INSTALL_PROGRAM += -s
2322 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2323 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2324 MAKEFLAGS += -j$(NUMJOBS)
2329 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2330 # Code to run the package test suite.
2337 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2338 <sect id="substvars">
2339 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2342 When <prgn>dpkg-gencontrol</prgn>
2343 generates <qref id="binarycontrolfiles">binary package control
2344 files</qref> (<file>DEBIAN/control</file>), it performs variable
2345 substitutions on its output just before writing it. Variable
2346 substitutions have the form <tt>${<var>variable</var>}</tt>.
2347 The optional file <file>debian/substvars</file> contains
2348 variable substitutions to be used; variables can also be set
2349 directly from <file>debian/rules</file> using the <tt>-V</tt>
2350 option to the source packaging commands, and certain predefined
2351 variables are also available.
2355 The <file>debian/substvars</file> file is usually generated and
2356 modified dynamically by <file>debian/rules</file> targets, in
2357 which case it must be removed by the <tt>clean</tt> target.
2361 See <manref name="deb-substvars" section="5"> for full
2362 details about source variable substitutions, including the
2363 format of <file>debian/substvars</file>.</p>
2366 <sect id="debianwatch">
2367 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2370 This is an optional, recommended configuration file for the
2371 <tt>uscan</tt> utility which defines how to automatically scan
2372 ftp or http sites for newly available updates of the
2373 package. This is used Debian QA
2374 tools to help with quality control and maintenance of the
2375 distribution as a whole.
2380 <sect id="debianfiles">
2381 <heading>Generated files list: <file>debian/files</file></heading>
2384 This file is not a permanent part of the source tree; it
2385 is used while building packages to record which files are
2386 being generated. <prgn>dpkg-genchanges</prgn> uses it
2387 when it generates a <file>.changes</file> file.
2391 It should not exist in a shipped source package, and so it
2392 (and any backup files or temporary files such as
2393 <file>files.new</file><footnote>
2394 <file>files.new</file> is used as a temporary file by
2395 <prgn>dpkg-gencontrol</prgn> and
2396 <prgn>dpkg-distaddfile</prgn> - they write a new
2397 version of <tt>files</tt> here before renaming it,
2398 to avoid leaving a corrupted copy if an error
2400 </footnote>) should be removed by the
2401 <tt>clean</tt> target. It may also be wise to
2402 ensure a fresh start by emptying or removing it at the
2403 start of the <tt>binary</tt> target.
2407 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2408 package, it adds an entry to <file>debian/files</file> for the
2409 <file>.deb</file> file that will be created when <tt>dpkg-deb
2410 --build</tt> is run for that binary package. So for most
2411 packages all that needs to be done with this file is to
2412 delete it in the <tt>clean</tt> target.
2416 If a package upload includes files besides the source
2417 package and any binary packages whose control files were
2418 made with <prgn>dpkg-gencontrol</prgn> then they should be
2419 placed in the parent of the package's top-level directory
2420 and <prgn>dpkg-distaddfile</prgn> should be called to add
2421 the file to the list in <file>debian/files</file>.</p>
2424 <sect id="embeddedfiles">
2425 <heading>Convenience copies of code</heading>
2428 Some software packages include in their distribution convenience
2429 copies of code from other software packages, generally so that
2430 users compiling from source don't have to download multiple
2431 packages. Debian packages should not make use of these
2432 convenience copies unless the included package is explicitly
2433 intended to be used in this way.<footnote>
2434 For example, parts of the GNU build system work like this.
2436 If the included code is already in the Debian archive in the
2437 form of a library, the Debian packaging should ensure that
2438 binary packages reference the libraries already in Debian and
2439 the convenience copy is not used. If the included code is not
2440 already in Debian, it should be packaged separately as a
2441 prerequisite if possible.
2443 Having multiple copies of the same code in Debian is
2444 inefficient, often creates either static linking or shared
2445 library conflicts, and, most importantly, increases the
2446 difficulty of handling security vulnerabilities in the
2452 <sect id="readmesource">
2453 <heading>Source package handling:
2454 <file>debian/README.source</file></heading>
2457 If running <prgn>dpkg-source -x</prgn> on a source package
2458 doesn't produce the source of the package, ready for editing,
2459 and allow one to make changes and run
2460 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2461 without taking any additional steps, creating a
2462 <file>debian/README.source</file> documentation file is
2463 recommended. This file should explain how to do all of the
2466 <item>Generate the fully patched source, in a form ready for
2467 editing, that would be built to create Debian
2468 packages. Doing this with a <tt>patch</tt> target in
2469 <file>debian/rules</file> is recommended; see
2470 <ref id="debianrules">.</item>
2471 <item>Modify the source and save those modifications so that
2472 they will be applied when building the package.</item>
2473 <item>Remove source modifications that are currently being
2474 applied when building the package.</item>
2475 <item>Optionally, document what steps are necessary to
2476 upgrade the Debian source package to a new upstream version,
2477 if applicable.</item>
2479 This explanation should include specific commands and mention
2480 any additional required Debian packages. It should not assume
2481 familiarity with any specific Debian packaging system or patch
2486 This explanation may refer to a documentation file installed by
2487 one of the package's build dependencies provided that the
2488 referenced documentation clearly explains these tasks and is not
2489 a general reference manual.
2493 <file>debian/README.source</file> may also include any other
2494 information that would be helpful to someone modifying the
2495 source package. Even if the package doesn't fit the above
2496 description, maintainers are encouraged to document in a
2497 <file>debian/README.source</file> file any source package with a
2498 particularly complex or unintuitive source layout or build
2499 system (for example, a package that builds the same source
2500 multiple times to generate different binary packages).
2506 <chapt id="controlfields">
2507 <heading>Control files and their fields</heading>
2510 The package management system manipulates data represented in
2511 a common format, known as <em>control data</em>, stored in
2512 <em>control files</em>.
2513 Control files are used for source packages, binary packages and
2514 the <file>.changes</file> files which control the installation
2515 of uploaded files<footnote>
2516 <prgn>dpkg</prgn>'s internal databases are in a similar
2521 <sect id="controlsyntax">
2522 <heading>Syntax of control files</heading>
2525 A control file consists of one or more paragraphs of
2527 The paragraphs are also sometimes referred to as stanzas.
2529 The paragraphs are separated by empty lines. Parsers may accept
2530 lines consisting solely of spaces and tabs as paragraph
2531 separators, but control files should use empty lines. Some control
2532 files allow only one paragraph; others allow several, in
2533 which case each paragraph usually refers to a different
2534 package. (For example, in source packages, the first
2535 paragraph refers to the source package, and later paragraphs
2536 refer to binary packages generated from the source.) The
2537 ordering of the paragraphs in control files is significant.
2541 Each paragraph consists of a series of data fields. Each field
2542 consists of the field name followed by a colon and then the
2543 data/value associated with that field. The field name is
2544 composed of US-ASCII characters excluding control characters,
2545 space, and colon (i.e., characters in the ranges 33-57 and
2546 59-126, inclusive). Field names must not begin with the comment
2547 character, <tt>#</tt>, nor with the hyphen character, <tt>-</tt>.
2551 The field ends at the end of the line or at the end of the last
2552 continuation line (see below). Horizontal whitespace (spaces
2553 and tabs) may occur immediately before or after the value and is
2554 ignored there; it is conventional to put a single space after
2555 the colon. For example, a field might be:
2556 <example compact="compact">
2559 the field name is <tt>Package</tt> and the field value
2564 A paragraph must not contain more than one instance of a
2565 particular field name.
2569 There are three types of fields:
2573 The field, including its value, must be a single line. Folding
2574 of the field is not permitted. This is the default field type
2575 if the definition of the field does not specify a different
2580 The value of a folded field is a logical line that may span
2581 several lines. The lines after the first are called
2582 continuation lines and must start with a space or a tab.
2583 Whitespace, including any newlines, is not significant in the
2584 field values of folded fields.<footnote>
2585 This folding method is similar to RFC 5322, allowing control
2586 files that contain only one paragraph and no multiline fields
2587 to be read by parsers written for RFC 5322.
2590 <tag>multiline</tag>
2592 The value of a multiline field may comprise multiple continuation
2593 lines. The first line of the value, the part on the same line as
2594 the field name, often has special significance or may have to be
2595 empty. Other lines are added following the same syntax as the
2596 continuation lines of the folded fields. Whitespace, including newlines,
2597 is significant in the values of multiline fields.
2603 Whitespace must not appear
2604 inside names (of packages, architectures, files or anything
2605 else) or version numbers, or between the characters of
2606 multi-character version relationships.
2610 The presence and purpose of a field, and the syntax of its
2611 value may differ between types of control files.
2615 Field names are not case-sensitive, but it is usual to
2616 capitalize the field names using mixed case as shown below.
2617 Field values are case-sensitive unless the description of the
2618 field says otherwise.
2622 Paragraph separators (empty lines) and lines consisting only of
2623 spaces and tabs are not allowed within field values or between
2624 fields. Empty lines in field values are usually escaped by
2625 representing them by a space followed by a dot.
2629 Lines starting with # without any preceding whitespace are comments
2630 lines that are only permitted in source package control files
2631 (<file>debian/control</file>). These comment lines are ignored, even
2632 between two continuation lines. They do not end logical lines.
2636 All control files must be encoded in UTF-8.
2640 <sect id="sourcecontrolfiles">
2641 <heading>Source package control files -- <file>debian/control</file></heading>
2644 The <file>debian/control</file> file contains the most vital
2645 (and version-independent) information about the source package
2646 and about the binary packages it creates.
2650 The first paragraph of the control file contains information about
2651 the source package in general. The subsequent sets each describe a
2652 binary package that the source tree builds.
2656 The fields in the general paragraph (the first one, for the source
2659 <list compact="compact">
2660 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2661 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2662 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2663 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2664 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2665 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2666 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2667 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2668 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2673 The fields in the binary package paragraphs are:
2675 <list compact="compact">
2676 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2677 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2678 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2679 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2680 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2681 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2682 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2683 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2684 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2685 <item><qref id="f-Package-Type"><tt>Package-Type</tt></qref></item>
2690 The syntax and semantics of the fields are described below.
2694 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2695 generate control files for binary packages (see below), by
2696 <prgn>dpkg-genchanges</prgn> to generate the
2697 <file>.changes</file> file to accompany the upload, and by
2698 <prgn>dpkg-source</prgn> when it creates the
2699 <file>.dsc</file> source control file as part of a source
2700 archive. Some fields are folded in <file>debian/control</file>,
2701 but not in any other control
2702 file. These tools are responsible for removing the line
2703 breaks from such fields when using fields from
2704 <file>debian/control</file> to generate other control files.
2708 The fields here may contain variable references - their
2709 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2710 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2711 when they generate output control files.
2712 See <ref id="substvars"> for details.
2716 <sect id="binarycontrolfiles">
2717 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2720 The <file>DEBIAN/control</file> file contains the most vital
2721 (and version-dependent) information about a binary package. It
2722 consists of a single paragraph.
2726 The fields in this file are:
2728 <list compact="compact">
2729 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2730 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2731 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2732 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2733 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2734 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2735 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2736 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2737 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2738 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2739 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2740 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2741 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2746 <sect id="debiansourcecontrolfiles">
2747 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2750 This file consists of a single paragraph, possibly surrounded by
2751 a PGP signature. The fields of that paragraph are listed below.
2752 Their syntax is described above, in <ref id="controlsyntax">.
2754 <list compact="compact">
2755 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2756 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2757 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2758 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2759 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2760 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2761 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2762 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2763 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2764 <item><qref id="f-Dgit"><tt>Dgit</tt></qref></item>
2765 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2766 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2767 <item><qref id="f-Package-List"><tt>Package-List</tt></qref> (recommended)</item>
2768 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2769 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2770 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2775 The Debian source control file is generated by
2776 <prgn>dpkg-source</prgn> when it builds the source
2777 archive, from other files in the source package,
2778 described above. When unpacking, it is checked against
2779 the files and directories in the other parts of the
2785 <sect id="debianchangesfiles">
2786 <heading>Debian changes files -- <file>.changes</file></heading>
2789 The <file>.changes</file> files are used by the Debian archive
2790 maintenance software to process updates to packages. They
2791 consist of a single paragraph, possibly surrounded by a PGP
2792 signature. That paragraph contains information from the
2793 <file>debian/control</file> file and other data about the
2794 source package gathered via <file>debian/changelog</file>
2795 and <file>debian/rules</file>.
2799 <file>.changes</file> files have a format version that is
2800 incremented whenever the documented fields or their meaning
2801 change. This document describes format &changesversion;.
2805 The fields in this file are:
2807 <list compact="compact">
2808 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2809 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2810 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2811 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2812 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2813 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2814 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2815 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2816 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2817 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2818 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2819 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2820 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2821 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2822 and <tt>Checksums-Sha256</tt></qref> (mandatory)</item>
2823 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2828 <sect id="controlfieldslist">
2829 <heading>List of fields</heading>
2831 <sect1 id="f-Source">
2832 <heading><tt>Source</tt></heading>
2835 This field identifies the source package name.
2839 In <file>debian/control</file> or a <file>.dsc</file> file,
2840 this field must contain only the name of the source package.
2844 In a binary package control file or a <file>.changes</file>
2845 file, the source package name may be followed by a version
2846 number in parentheses<footnote>
2847 It is customary to leave a space after the package name
2848 if a version number is specified.
2850 This version number may be omitted (and is, by
2851 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2852 the <tt>Version</tt> field of the binary package in
2853 question. The field itself may be omitted from a binary
2854 package control file when the source package has the same
2855 name and version as the binary package.
2859 Package names (both source and binary,
2860 see <ref id="f-Package">) must consist only of lower case
2861 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2862 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2863 (<tt>.</tt>). They must be at least two characters long and
2864 must start with an alphanumeric character.
2868 <sect1 id="f-Maintainer">
2869 <heading><tt>Maintainer</tt></heading>
2872 The package maintainer's name and email address. The name
2873 must come first, then the email address inside angle
2874 brackets <tt><></tt> (in RFC822 format).
2878 If the maintainer's name contains a full stop then the
2879 whole field will not work directly as an email address due
2880 to a misfeature in the syntax specified in RFC822; a
2881 program using this field as an address must check for this
2882 and correct the problem if necessary (for example by
2883 putting the name in round brackets and moving it to the
2884 end, and bringing the email address forward).
2888 See <ref id="maintainer"> for additional requirements and
2889 information about package maintainers.
2893 <sect1 id="f-Uploaders">
2894 <heading><tt>Uploaders</tt></heading>
2897 List of the names and email addresses of co-maintainers of the
2898 package, if any. If the package has other maintainers besides
2899 the one named in the <qref id="f-Maintainer">Maintainer
2900 field</qref>, their names and email addresses should be listed
2901 here. The format of each entry is the same as that of the
2902 Maintainer field, and multiple entries must be comma
2907 This is normally an optional field, but if
2908 the <tt>Maintainer</tt> control field names a group of people
2909 and a shared email address, the <tt>Uploaders</tt> field must
2910 be present and must contain at least one human with their
2911 personal email address.
2915 The Uploaders field in <file>debian/control</file> can be folded.
2919 <sect1 id="f-Changed-By">
2920 <heading><tt>Changed-By</tt></heading>
2923 The name and email address of the person who prepared this
2924 version of the package, usually a maintainer. The syntax is
2925 the same as for the <qref id="f-Maintainer">Maintainer
2930 <sect1 id="f-Section">
2931 <heading><tt>Section</tt></heading>
2934 This field specifies an application area into which the package
2935 has been classified. See <ref id="subsections">.
2939 When it appears in the <file>debian/control</file> file,
2940 it gives the value for the subfield of the same name in
2941 the <tt>Files</tt> field of the <file>.changes</file> file.
2942 It also gives the default for the same field in the binary
2947 <sect1 id="f-Priority">
2948 <heading><tt>Priority</tt></heading>
2951 This field represents how important it is that the user
2952 have the package installed. See <ref id="priorities">.
2956 When it appears in the <file>debian/control</file> file,
2957 it gives the value for the subfield of the same name in
2958 the <tt>Files</tt> field of the <file>.changes</file> file.
2959 It also gives the default for the same field in the binary
2964 <sect1 id="f-Package">
2965 <heading><tt>Package</tt></heading>
2968 The name of the binary package.
2972 Binary package names must follow the same syntax and
2973 restrictions as source package names. See <ref id="f-Source">
2978 <sect1 id="f-Architecture">
2979 <heading><tt>Architecture</tt></heading>
2982 Depending on context and the control file used, the
2983 <tt>Architecture</tt> field can include the following sets of
2987 A unique single word identifying a Debian machine
2988 architecture as described in <ref id="arch-spec">.
2991 An architecture wildcard identifying a set of Debian
2992 machine architectures, see <ref id="arch-wildcard-spec">.
2993 <tt>any</tt> matches all Debian machine architectures
2994 and is the most frequently used.
2997 <tt>all</tt>, which indicates an
2998 architecture-independent package.
3001 <tt>source</tt>, which indicates a source package.
3007 In the main <file>debian/control</file> file in the source
3008 package, this field may contain the special
3009 value <tt>all</tt>, the special architecture
3010 wildcard <tt>any</tt>, or a list of specific and wildcard
3011 architectures separated by spaces. If <tt>all</tt>
3012 or <tt>any</tt> appears, that value must be the entire
3013 contents of the field. Most packages will use
3014 either <tt>all</tt> or <tt>any</tt>.
3018 Specifying a specific list of architectures indicates that the
3019 source will build an architecture-dependent package only on
3020 architectures included in the list. Specifying a list of
3021 architecture wildcards indicates that the source will build an
3022 architecture-dependent package on only those architectures
3023 that match any of the specified architecture wildcards.
3024 Specifying a list of architectures or architecture wildcards
3025 other than <tt>any</tt> is for the minority of cases where a
3026 program is not portable or is not useful on some
3027 architectures. Where possible, the program should be made
3032 In the Debian source control file <file>.dsc</file>, this
3033 field contains a list of architectures and architecture
3034 wildcards separated by spaces. When the list contains the
3035 architecture wildcard <tt>any</tt>, the only other value
3036 allowed in the list is <tt>all</tt>.
3040 The list may include (or consist solely of) the special
3041 value <tt>all</tt>. In other words, in <file>.dsc</file>
3042 files unlike the <file>debian/control</file>, <tt>all</tt> may
3043 occur in combination with specific architectures.
3044 The <tt>Architecture</tt> field in the Debian source control
3045 file <file>.dsc</file> is generally constructed from
3046 the <tt>Architecture</tt> fields in
3047 the <file>debian/control</file> in the source package.
3051 Specifying only <tt>any</tt> indicates that the source package
3052 isn't dependent on any particular architecture and should
3053 compile fine on any one. The produced binary package(s)
3054 will be specific to whatever the current build architecture is.
3058 Specifying only <tt>all</tt> indicates that the source package
3059 will only build architecture-independent packages.
3063 Specifying <tt>any all</tt> indicates that the source package
3064 isn't dependent on any particular architecture. The set of
3065 produced binary packages will include at least one
3066 architecture-dependant package and one architecture-independent
3071 Specifying a list of architectures or architecture wildcards
3072 indicates that the source will build an architecture-dependent
3073 package, and will only work correctly on the listed or
3074 matching architectures. If the source package also builds at
3075 least one architecture-independent package, <tt>all</tt> will
3076 also be included in the list.
3080 In a <file>.changes</file> file, the <tt>Architecture</tt>
3081 field lists the architecture(s) of the package(s) currently
3082 being uploaded. This will be a list; if the source for the
3083 package is also being uploaded, the special
3084 entry <tt>source</tt> is also present. <tt>all</tt> will be
3085 present if any architecture-independent packages are being
3086 uploaded. Architecture wildcards such as <tt>any</tt> must
3087 never occur in the <tt>Architecture</tt> field in
3088 the <file>.changes</file> file.
3092 See <ref id="debianrules"> for information on how to get
3093 the architecture for the build process.
3097 <sect1 id="f-Essential">
3098 <heading><tt>Essential</tt></heading>
3101 This is a boolean field which may occur only in the
3102 control file of a binary package or in a per-package fields
3103 paragraph of a source package control file.
3107 If set to <tt>yes</tt> then the package management system
3108 will refuse to remove the package (upgrading and replacing
3109 it is still possible). The other possible value is <tt>no</tt>,
3110 which is the same as not having the field at all.
3115 <heading>Package interrelationship fields:
3116 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3117 <tt>Recommends</tt>, <tt>Suggests</tt>,
3118 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3119 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3123 These fields describe the package's relationships with
3124 other packages. Their syntax and semantics are described
3125 in <ref id="relationships">.</p>
3128 <sect1 id="f-Standards-Version">
3129 <heading><tt>Standards-Version</tt></heading>
3132 The most recent version of the standards (the policy
3133 manual and associated texts) with which the package
3138 The version number has four components: major and minor
3139 version number and major and minor patch level. When the
3140 standards change in a way that requires every package to
3141 change the major number will be changed. Significant
3142 changes that will require work in many packages will be
3143 signaled by a change to the minor number. The major patch
3144 level will be changed for any change to the meaning of the
3145 standards, however small; the minor patch level will be
3146 changed when only cosmetic, typographical or other edits
3147 are made which neither change the meaning of the document
3148 nor affect the contents of packages.
3152 Thus only the first three components of the policy version
3153 are significant in the <em>Standards-Version</em> control
3154 field, and so either these three components or all four
3155 components may be specified.<footnote>
3156 In the past, people specified the full version number
3157 in the Standards-Version field, for example "2.3.0.0".
3158 Since minor patch-level changes don't introduce new
3159 policy, it was thought it would be better to relax
3160 policy and only require the first 3 components to be
3161 specified, in this example "2.3.0". All four
3162 components may still be used if someone wishes to do so.
3168 <sect1 id="f-Version">
3169 <heading><tt>Version</tt></heading>
3172 The version number of a package. The format is:
3173 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3177 The three components here are:
3179 <tag><var>epoch</var></tag>
3182 This is a single (generally small) unsigned integer. It
3183 may be omitted, in which case zero is assumed. If it is
3184 omitted then the <var>upstream_version</var> may not
3189 It is provided to allow mistakes in the version numbers
3190 of older versions of a package, and also a package's
3191 previous version numbering schemes, to be left behind.
3195 <tag><var>upstream_version</var></tag>
3198 This is the main part of the version number. It is
3199 usually the version number of the original ("upstream")
3200 package from which the <file>.deb</file> file has been made,
3201 if this is applicable. Usually this will be in the same
3202 format as that specified by the upstream author(s);
3203 however, it may need to be reformatted to fit into the
3204 package management system's format and comparison
3209 The comparison behavior of the package management system
3210 with respect to the <var>upstream_version</var> is
3211 described below. The <var>upstream_version</var>
3212 portion of the version number is mandatory.
3216 The <var>upstream_version</var> may contain only
3217 alphanumerics<footnote>
3218 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3220 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3221 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3222 tilde) and should start with a digit. If there is no
3223 <var>debian_revision</var> then hyphens are not allowed;
3224 if there is no <var>epoch</var> then colons are not
3229 <tag><var>debian_revision</var></tag>
3232 This part of the version number specifies the version of
3233 the Debian package based on the upstream version. It
3234 may contain only alphanumerics and the characters
3235 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3236 tilde) and is compared in the same way as the
3237 <var>upstream_version</var> is.
3241 It is optional; if it isn't present then the
3242 <var>upstream_version</var> may not contain a hyphen.
3243 This format represents the case where a piece of
3244 software was written specifically to be a Debian
3245 package, where the Debian package source must always
3246 be identical to the pristine source and therefore no
3247 revision indication is required.
3251 It is conventional to restart the
3252 <var>debian_revision</var> at <tt>1</tt> each time the
3253 <var>upstream_version</var> is increased.
3257 The package management system will break the version
3258 number apart at the last hyphen in the string (if there
3259 is one) to determine the <var>upstream_version</var> and
3260 <var>debian_revision</var>. The absence of a
3261 <var>debian_revision</var> is equivalent to a
3262 <var>debian_revision</var> of <tt>0</tt>.
3269 When comparing two version numbers, first the <var>epoch</var>
3270 of each are compared, then the <var>upstream_version</var> if
3271 <var>epoch</var> is equal, and then <var>debian_revision</var>
3272 if <var>upstream_version</var> is also equal.
3273 <var>epoch</var> is compared numerically. The
3274 <var>upstream_version</var> and <var>debian_revision</var>
3275 parts are compared by the package management system using the
3276 following algorithm:
3280 The strings are compared from left to right.
3284 First the initial part of each string consisting entirely of
3285 non-digit characters is determined. These two parts (one of
3286 which may be empty) are compared lexically. If a difference
3287 is found it is returned. The lexical comparison is a
3288 comparison of ASCII values modified so that all the letters
3289 sort earlier than all the non-letters and so that a tilde
3290 sorts before anything, even the end of a part. For example,
3291 the following parts are in sorted order from earliest to
3292 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3293 <tt>a</tt>.<footnote>
3294 One common use of <tt>~</tt> is for upstream pre-releases.
3295 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3296 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3301 Then the initial part of the remainder of each string which
3302 consists entirely of digit characters is determined. The
3303 numerical values of these two parts are compared, and any
3304 difference found is returned as the result of the comparison.
3305 For these purposes an empty string (which can only occur at
3306 the end of one or both version strings being compared) counts
3311 These two steps (comparing and removing initial non-digit
3312 strings and initial digit strings) are repeated until a
3313 difference is found or both strings are exhausted.
3317 Note that the purpose of epochs is to allow us to leave behind
3318 mistakes in version numbering, and to cope with situations
3319 where the version numbering scheme changes. It is
3320 <em>not</em> intended to cope with version numbers containing
3321 strings of letters which the package management system cannot
3322 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3323 silly orderings.<footnote>
3324 The author of this manual has heard of a package whose
3325 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3326 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3332 <sect1 id="f-Description">
3333 <heading><tt>Description</tt></heading>
3336 In a source or binary control file, the <tt>Description</tt>
3337 field contains a description of the binary package, consisting
3338 of two parts, the synopsis or the short description, and the
3339 long description. It is a multiline field with the following
3345 Description: <single line synopsis>
3346 <extended description over several lines>
3351 The lines in the extended description can have these formats:
3357 Those starting with a single space are part of a paragraph.
3358 Successive lines of this form will be word-wrapped when
3359 displayed. The leading space will usually be stripped off.
3360 The line must contain at least one non-whitespace character.
3364 Those starting with two or more spaces. These will be
3365 displayed verbatim. If the display cannot be panned
3366 horizontally, the displaying program will line wrap them "hard"
3367 (i.e., without taking account of word breaks). If it can they
3368 will be allowed to trail off to the right. None, one or two
3369 initial spaces may be deleted, but the number of spaces
3370 deleted from each line will be the same (so that you can have
3371 indenting work correctly, for example). The line must
3372 contain at least one non-whitespace character.
3376 Those containing a single space followed by a single full stop
3377 character. These are rendered as blank lines. This is the
3378 <em>only</em> way to get a blank line<footnote>
3379 Completely empty lines will not be rendered as blank lines.
3380 Instead, they will cause the parser to think you're starting
3381 a whole new record in the control file, and will therefore
3382 likely abort with an error.
3387 Those containing a space, a full stop and some more characters.
3388 These are for future expansion. Do not use them.
3394 Do not use tab characters. Their effect is not predictable.
3398 See <ref id="descriptions"> for further information on this.
3402 In a <file>.changes</file> file, the <tt>Description</tt>
3403 field contains a summary of the descriptions for the packages
3404 being uploaded. For this case, the first line of the field
3405 value (the part on the same line as <tt>Description:</tt>) is
3406 always empty. It is a multiline field, with one
3407 line per package. Each line is
3408 indented by one space and contains the name of a binary
3409 package, a space, a hyphen (<tt>-</tt>), a space, and the
3410 short description line from that package.
3414 <sect1 id="f-Distribution">
3415 <heading><tt>Distribution</tt></heading>
3418 In a <file>.changes</file> file or parsed changelog output
3419 this contains the (space-separated) name(s) of the
3420 distribution(s) where this version of the package should
3421 be installed. Valid distributions are determined by the
3422 archive maintainers.<footnote>
3423 Example distribution names in the Debian archive used in
3424 <file>.changes</file> files are:
3425 <taglist compact="compact">
3426 <tag><em>unstable</em></tag>
3428 This distribution value refers to the
3429 <em>developmental</em> part of the Debian distribution
3430 tree. Most new packages, new upstream versions of
3431 packages and bug fixes go into the <em>unstable</em>
3435 <tag><em>experimental</em></tag>
3437 The packages with this distribution value are deemed
3438 by their maintainers to be high risk. Oftentimes they
3439 represent early beta or developmental packages from
3440 various sources that the maintainers want people to
3441 try, but are not ready to be a part of the other parts
3442 of the Debian distribution tree.
3447 Others are used for updating stable releases or for
3448 security uploads. More information is available in the
3449 Debian Developer's Reference, section "The Debian
3453 The Debian archive software only supports listing a single
3454 distribution. Migration of packages to other distributions is
3455 handled outside of the upload process.
3460 <heading><tt>Date</tt></heading>
3463 This field includes the date the package was built or last
3464 edited. It must be in the same format as the <var>date</var>
3465 in a <file>debian/changelog</file> entry.
3469 The value of this field is usually extracted from the
3470 <file>debian/changelog</file> file - see
3471 <ref id="dpkgchangelog">).
3475 <sect1 id="f-Format">
3476 <heading><tt>Format</tt></heading>
3479 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3480 files, this field declares the format version of that file.
3481 The syntax of the field value is the same as that of
3482 a <qref id="f-Version">package version number</qref> except
3483 that no epoch or Debian revision is allowed. The format
3484 described in this document is <tt>&changesversion;</tt>.
3488 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3489 Debian source control</qref> files, this field declares the
3490 format of the source package. The field value is used by
3491 programs acting on a source package to interpret the list of
3492 files in the source package and determine how to unpack it.
3493 The syntax of the field value is a numeric major revision, a
3494 period, a numeric minor revision, and then an optional subtype
3495 after whitespace, which if specified is an alphanumeric word
3496 in parentheses. The subtype is optional in the syntax but may
3497 be mandatory for particular source format revisions.
3499 The source formats currently supported by the Debian archive
3500 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3501 and <tt>3.0 (quilt)</tt>.
3506 <sect1 id="f-Urgency">
3507 <heading><tt>Urgency</tt></heading>
3510 This is a description of how important it is to upgrade to
3511 this version from previous ones. It consists of a single
3512 keyword taking one of the values <tt>low</tt>,
3513 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3514 <tt>critical</tt><footnote>
3515 Other urgency values are supported with configuration
3516 changes in the archive software but are not used in Debian.
3517 The urgency affects how quickly a package will be considered
3518 for inclusion into the <tt>testing</tt> distribution and
3519 gives an indication of the importance of any fixes included
3520 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3521 treated as synonymous.
3522 </footnote> (not case-sensitive) followed by an optional
3523 commentary (separated by a space) which is usually in
3524 parentheses. For example:
3527 Urgency: low (HIGH for users of diversions)
3533 The value of this field is usually extracted from the
3534 <file>debian/changelog</file> file - see
3535 <ref id="dpkgchangelog">.
3539 <sect1 id="f-Changes">
3540 <heading><tt>Changes</tt></heading>
3543 This multiline field contains the human-readable changes data, describing
3544 the differences between the last version and the current one.
3548 The first line of the field value (the part on the same line
3549 as <tt>Changes:</tt>) is always empty. The content of the
3550 field is expressed as continuation lines, with each line
3551 indented by at least one space. Blank lines must be
3552 represented by a line consisting only of a space and a full
3557 The value of this field is usually extracted from the
3558 <file>debian/changelog</file> file - see
3559 <ref id="dpkgchangelog">).
3563 Each version's change information should be preceded by a
3564 "title" line giving at least the version, distribution(s)
3565 and urgency, in a human-readable way.
3569 If data from several versions is being returned the entry
3570 for the most recent version should be returned first, and
3571 entries should be separated by the representation of a
3572 blank line (the "title" line may also be followed by the
3573 representation of a blank line).
3577 <sect1 id="f-Binary">
3578 <heading><tt>Binary</tt></heading>
3581 This folded field is a list of binary packages. Its syntax and
3582 meaning varies depending on the control file in which it
3587 When it appears in the <file>.dsc</file> file, it lists binary
3588 packages which a source package can produce, separated by
3590 A space after each comma is conventional.
3591 </footnote>. The source package
3592 does not necessarily produce all of these binary packages for
3593 every architecture. The source control file doesn't contain
3594 details of which architectures are appropriate for which of
3595 the binary packages.
3599 When it appears in a <file>.changes</file> file, it lists the
3600 names of the binary packages being uploaded, separated by
3601 whitespace (not commas).
3605 <sect1 id="f-Installed-Size">
3606 <heading><tt>Installed-Size</tt></heading>
3609 This field appears in the control files of binary packages,
3610 and in the <file>Packages</file> files. It gives an estimate
3611 of the total amount of disk space required to install the
3612 named package. Actual installed size may vary based on block
3613 size, file system properties, or actions taken by package
3618 The disk space is given as the integer value of the estimated
3619 installed size in bytes, divided by 1024 and rounded up.
3623 <sect1 id="f-Files">
3624 <heading><tt>Files</tt></heading>
3627 This field contains a list of files with information about
3628 each one. The exact information and syntax varies with
3633 In all cases, Files is a multiline field. The first line of
3634 the field value (the part on the same line as <tt>Files:</tt>)
3635 is always empty. The content of the field is expressed as
3636 continuation lines, one line per file. Each line must be
3637 indented by one space and contain a number of sub-fields,
3638 separated by spaces, as described below.
3642 In the <file>.dsc</file> file, each line contains the MD5
3643 checksum, size and filename of the tar file and (if
3644 applicable) diff file which make up the remainder of the
3645 source package<footnote>
3646 That is, the parts which are not the <tt>.dsc</tt>.
3647 </footnote>. For example:
3650 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3651 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3653 The exact forms of the filenames are described
3654 in <ref id="pkg-sourcearchives">.
3658 In the <file>.changes</file> file this contains one line per
3659 file being uploaded. Each line contains the MD5 checksum,
3660 size, section and priority and the filename. For example:
3663 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3664 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3665 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3666 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3668 The <qref id="f-Section">section</qref>
3669 and <qref id="f-Priority">priority</qref> are the values of
3670 the corresponding fields in the main source control file. If
3671 no section or priority is specified then <tt>-</tt> should be
3672 used, though section and priority values must be specified for
3673 new packages to be installed properly.
3677 The special value <tt>byhand</tt> for the section in a
3678 <tt>.changes</tt> file indicates that the file in question
3679 is not an ordinary package file and must be installed by
3680 hand by the distribution maintainers. If the section is
3681 <tt>byhand</tt> the priority should be <tt>-</tt>.
3685 If a new Debian revision of a package is being shipped and
3686 no new original source archive is being distributed the
3687 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3688 entry for the original source archive
3689 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3690 but the <file>.changes</file> file should leave it out. In
3691 this case the original source archive on the distribution
3692 site must match exactly, byte-for-byte, the original
3693 source archive which was used to generate the
3694 <file>.dsc</file> file and diff which are being uploaded.</p>
3697 <sect1 id="f-Closes">
3698 <heading><tt>Closes</tt></heading>
3701 A space-separated list of bug report numbers that the upload
3702 governed by the .changes file closes.
3706 <sect1 id="f-Homepage">
3707 <heading><tt>Homepage</tt></heading>
3710 The URL of the web site for this package, preferably (when
3711 applicable) the site from which the original source can be
3712 obtained and any additional upstream documentation or
3713 information may be found. The content of this field is a
3714 simple URL without any surrounding characters such as
3719 <sect1 id="f-Checksums">
3720 <heading><tt>Checksums-Sha1</tt>
3721 and <tt>Checksums-Sha256</tt></heading>
3724 These multiline fields contain a list of files with a checksum and size
3725 for each one. Both <tt>Checksums-Sha1</tt>
3726 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3727 only in the checksum algorithm used: SHA-1
3728 for <tt>Checksums-Sha1</tt> and SHA-256
3729 for <tt>Checksums-Sha256</tt>.
3733 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3734 multiline fields. The first line of the field value (the part
3735 on the same line as <tt>Checksums-Sha1:</tt>
3736 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3737 of the field is expressed as continuation lines, one line per
3738 file. Each line consists of the checksum, a space, the file
3739 size, a space, and the file name. For example (from
3740 a <file>.changes</file> file):
3743 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3744 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3745 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3746 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3748 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3749 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3750 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3751 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3756 In the <file>.dsc</file> file, these fields list all
3757 files that make up the source package. In
3758 the <file>.changes</file> file, these fields list all
3759 files being uploaded. The list of files in these fields
3760 must match the list of files in the <tt>Files</tt> field.
3765 <heading><tt>DM-Upload-Allowed</tt></heading>
3768 Obsolete, see <qref id="f-DM-Upload-Allowed">below</qref>.
3772 <sect1 id="f-VCS-fields">
3773 <heading>Version Control System (VCS) fields</heading>
3776 Debian source packages are increasingly developed using VCSs. The
3777 purpose of the following fields is to indicate a publicly accessible
3778 repository where the Debian source package is developed.
3781 <tag><tt>Vcs-Browser</tt></tag>
3784 URL of a web interface for browsing the repository.
3789 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3790 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3791 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3796 The field name identifies the VCS. The field's value uses the
3797 version control system's conventional syntax for describing
3798 repository locations and should be sufficient to locate the
3799 repository used for packaging. Ideally, it also locates the
3800 branch used for development of new versions of the Debian
3804 In the case of Git, the value consists of a URL, optionally
3805 followed by the word <tt>-b</tt> and the name of a branch in
3806 the indicated repository, following the syntax of the
3807 <tt>git clone</tt> command. If no branch is specified, the
3808 packaging should be on the default branch.
3811 More than one different VCS may be specified for the same
3819 <sect1 id="f-Package-List">
3820 <heading><tt>Package-List</tt></heading>
3823 Multiline field listing all the packages that can be built from
3824 the source package, considering every architecture. The first line
3825 of the field value is empty. Each one of the next lines describes
3826 one binary package, by listing its name, type, section and priority
3827 separated by spaces. Fifth and subsequent space-separated items
3828 may be present and parsers must allow them. See the
3829 <qref id="f-Package-Type">Package-Type</qref> field for a list of
3834 <sect1 id="f-Package-Type">
3835 <heading><tt>Package-Type</tt></heading>
3838 Simple field containing a word indicating the type of package:
3839 <tt>deb</tt> for binary packages and <tt>udeb</tt> for micro binary
3840 packages. Other types not defined here may be indicated. In
3841 source package control files, the <tt>Package-Type</tt> field
3842 should be omitted instead of giving it a value of <tt>deb</tt>, as
3843 this value is assumed for paragraphs lacking this field.
3848 <heading><tt>Dgit</tt></heading>
3851 Folded field containing a single git commit hash, presented in
3852 full, followed optionally by whitespace and other data to be
3853 defined in future extensions.
3857 Declares that the source package corresponds exactly to a
3858 referenced commit in a Git repository available at the canonical
3859 location called <em>dgit-repos</em>, used by <prgn>dgit</prgn>, a
3860 bidirectional gateway between the Debian archive and Git. The
3861 commit is reachable from at least one reference whose name matches
3862 <tt>refs/dgit/*</tt>. See the manual page of <prgn>dgit</prgn> for
3869 <heading>User-defined fields</heading>
3872 Additional user-defined fields may be added to the
3873 source package control file. Such fields will be
3874 ignored, and not copied to (for example) binary or
3875 Debian source control files or upload control files.
3879 If you wish to add additional unsupported fields to
3880 these output files you should use the mechanism
3885 Fields in the main source control information file with
3886 names starting <tt>X</tt>, followed by one or more of
3887 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3888 be copied to the output files. Only the part of the
3889 field name after the hyphen will be used in the output
3890 file. Where the letter <tt>B</tt> is used the field
3891 will appear in binary package control files, where the
3892 letter <tt>S</tt> is used in Debian source control
3893 files and where <tt>C</tt> is used in upload control
3894 (<tt>.changes</tt>) files.
3898 For example, if the main source information control file
3901 XBS-Comment: I stand between the candle and the star.
3903 then the binary and Debian source control files will contain the
3906 Comment: I stand between the candle and the star.
3912 <sect id="obsolete-control-data-fields">
3913 <heading>Obsolete fields</heading>
3916 The following fields have been obsoleted and may be found in packages
3917 conforming with previous versions of the Policy.
3920 <sect1 id="f-DM-Upload-Allowed">
3921 <heading><tt>DM-Upload-Allowed</tt></heading>
3924 Indicates that Debian Maintainers may upload this package to
3925 the Debian archive. The only valid value is <tt>yes</tt>. This
3926 field was used to regulate uploads by Debian Maintainers, See the
3927 General Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3928 name="Endorse the concept of Debian Maintainers"> for more details.
3937 <chapt id="maintainerscripts">
3938 <heading>Package maintainer scripts and installation procedure</heading>
3941 <heading>Introduction to package maintainer scripts</heading>
3944 It is possible to supply scripts as part of a package which
3945 the package management system will run for you when your
3946 package is installed, upgraded or removed.
3950 These scripts are the control information
3951 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3952 and <prgn>postrm</prgn>. They must be proper executable files;
3953 if they are scripts (which is recommended), they must start with
3954 the usual <tt>#!</tt> convention. They should be readable and
3955 executable by anyone, and must not be world-writable.
3959 The package management system looks at the exit status from
3960 these scripts. It is important that they exit with a
3961 non-zero status if there is an error, so that the package
3962 management system can stop its processing. For shell
3963 scripts this means that you <em>almost always</em> need to
3964 use <tt>set -e</tt> (this is usually true when writing shell
3965 scripts, in fact). It is also important, of course, that
3966 they exit with a zero status if everything went well.
3970 Additionally, packages interacting with users
3971 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3972 should install a <prgn>config</prgn> script as a control
3973 information file. See <ref id="maintscriptprompt"> for details.
3977 When a package is upgraded a combination of the scripts from
3978 the old and new packages is called during the upgrade
3979 procedure. If your scripts are going to be at all
3980 complicated you need to be aware of this, and may need to
3981 check the arguments to your scripts.
3985 Broadly speaking the <prgn>preinst</prgn> is called before
3986 (a particular version of) a package is unpacked, and the
3987 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3988 before (a version of) a package is removed and the
3989 <prgn>postrm</prgn> afterwards.
3993 Programs called from maintainer scripts should not normally
3994 have a path prepended to them. Before installation is
3995 started, the package management system checks to see if the
3996 programs <prgn>ldconfig</prgn>, <prgn>start-stop-daemon</prgn>,
3997 and <prgn>update-rc.d</prgn> can be found via the
3998 <tt>PATH</tt> environment variable. Those programs, and any
3999 other program that one would expect to be in the
4000 <tt>PATH</tt>, should thus be invoked without an absolute
4001 pathname. Maintainer scripts should also not reset the
4002 <tt>PATH</tt>, though they might choose to modify it by
4003 prepending or appending package-specific directories. These
4004 considerations really apply to all shell scripts.</p>
4007 <sect id="idempotency">
4008 <heading>Maintainer scripts idempotency</heading>
4011 It is necessary for the error recovery procedures that the
4012 scripts be idempotent. This means that if it is run
4013 successfully, and then it is called again, it doesn't bomb
4014 out or cause any harm, but just ensures that everything is
4015 the way it ought to be. If the first call failed, or
4016 aborted half way through for some reason, the second call
4017 should merely do the things that were left undone the first
4018 time, if any, and exit with a success status if everything
4020 This is so that if an error occurs, the user interrupts
4021 <prgn>dpkg</prgn> or some other unforeseen circumstance
4022 happens you don't leave the user with a badly-broken
4023 package when <prgn>dpkg</prgn> attempts to repeat the
4029 <sect id="controllingterminal">
4030 <heading>Controlling terminal for maintainer scripts</heading>
4033 Maintainer scripts are not guaranteed to run with a controlling
4034 terminal and may not be able to interact with the user. They
4035 must be able to fall back to noninteractive behavior if no
4036 controlling terminal is available. Maintainer scripts that
4037 prompt via a program conforming to the Debian Configuration
4038 Management Specification (see <ref id="maintscriptprompt">) may
4039 assume that program will handle falling back to noninteractive
4044 For high-priority prompts without a reasonable default answer,
4045 maintainer scripts may abort if there is no controlling
4046 terminal. However, this situation should be avoided if at all
4047 possible, since it prevents automated or unattended installs.
4048 In most cases, users will consider this to be a bug in the
4053 <sect id="exitstatus">
4054 <heading>Exit status</heading>
4057 Each script must return a zero exit status for
4058 success, or a nonzero one for failure, since the package
4059 management system looks for the exit status of these scripts
4060 and determines what action to take next based on that datum.
4064 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
4069 What follows is a summary of all the ways in which maintainer
4070 scripts may be called along with what facilities those scripts
4071 may rely on being available at that time. Script names preceded
4072 by <var>new-</var> are the scripts from the new version of a
4073 package being installed, upgraded to, or downgraded to. Script
4074 names preceded by <var>old-</var> are the scripts from the old
4075 version of a package that is being upgraded from or downgraded
4080 The <prgn>preinst</prgn> script may be called in the following
4083 <tag><var>new-preinst</var> <tt>install</tt></tag>
4084 <tag><var>new-preinst</var> <tt>install</tt>
4085 <var>old-version</var></tag>
4086 <tag><var>new-preinst</var> <tt>upgrade</tt>
4087 <var>old-version</var></tag>
4089 The package will not yet be unpacked, so
4090 the <prgn>preinst</prgn> script cannot rely on any files
4091 included in its package. Only essential packages and
4092 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
4093 available. Pre-dependencies will have been configured at
4094 least once, but at the time the <prgn>preinst</prgn> is
4095 called they may only be in an "Unpacked" or "Half-Configured"
4096 state if a previous version of the pre-dependency was
4097 completely configured and has not been removed since then.
4100 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4101 <var>new-version</var></tag>
4103 Called during error handling of an upgrade that failed after
4104 unpacking the new package because the <tt>postrm
4105 upgrade</tt> action failed. The unpacked files may be
4106 partly from the new version or partly missing, so the script
4107 cannot rely on files included in the package. Package
4108 dependencies may not be available. Pre-dependencies will be
4109 at least "Unpacked" following the same rules as above, except
4110 they may be only "Half-Installed" if an upgrade of the
4111 pre-dependency failed.<footnote>
4112 This can happen if the new version of the package no
4113 longer pre-depends on a package that had been partially
4121 The <prgn>postinst</prgn> script may be called in the following
4124 <tag><var>postinst</var> <tt>configure</tt>
4125 <var>most-recently-configured-version</var></tag>
4127 The files contained in the package will be unpacked. All
4128 package dependencies will at least be "Unpacked". If there
4129 are no circular dependencies involved, all package
4130 dependencies will be configured. For behavior in the case
4131 of circular dependencies, see the discussion
4132 in <ref id="binarydeps">.
4135 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4136 <var>new-version</var></tag>
4137 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4138 <tt>in-favour</tt> <var>package</var>
4139 <var>new-version</var></tag>
4140 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4141 <tag><var>deconfigured's-postinst</var>
4142 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4143 <var>failed-install-package</var> <var>version</var>
4144 [<tt>removing</tt> <var>conflicting-package</var>
4145 <var>version</var>]</tag>
4147 The files contained in the package will be unpacked. All
4148 package dependencies will at least be "Half-Installed" and
4149 will have previously been configured and not removed.
4150 However, dependencies may not be configured or even fully
4151 unpacked in some error situations.<footnote>
4152 For example, suppose packages foo and bar are "Installed"
4153 with foo depending on bar. If an upgrade of bar were
4154 started and then aborted, and then an attempt to remove
4155 foo failed because its <prgn>prerm</prgn> script failed,
4156 foo's <tt>postinst abort-remove</tt> would be called with
4157 bar only "Half-Installed".
4159 The <prgn>postinst</prgn> should still attempt any actions
4160 for which its dependencies are required, since they will
4161 normally be available, but consider the correct error
4162 handling approach if those actions fail. Aborting
4163 the <prgn>postinst</prgn> action if commands or facilities
4164 from the package dependencies are not available is often the
4171 The <prgn>prerm</prgn> script may be called in the following
4174 <tag><var>prerm</var> <tt>remove</tt></tag>
4175 <tag><var>old-prerm</var>
4176 <tt>upgrade</tt><var>new-version</var></tag>
4177 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4178 <tt>in-favour</tt> <var>package</var>
4179 <var>new-version</var></tag>
4180 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4181 <tt>in-favour</tt> <var>package-being-installed</var>
4182 <var>version</var> [<tt>removing</tt>
4183 <var>conflicting-package</var> <var>version</var>]</tag>
4185 The package whose <prgn>prerm</prgn> is being called will be
4186 at least "Half-Installed". All package dependencies will at
4187 least be "Half-Installed" and will have previously been
4188 configured and not removed. If there was no error, all
4189 dependencies will at least be "Unpacked", but these actions
4190 may be called in various error states where dependencies are
4191 only "Half-Installed" due to a partial upgrade.
4194 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4195 <var>old-version</var></tag>
4197 Called during error handling when <tt>prerm upgrade</tt>
4198 fails. The new package will not yet be unpacked, and all
4199 the same constraints as for <tt>preinst upgrade</tt> apply.
4205 The <prgn>postrm</prgn> script may be called in the following
4208 <tag><var>postrm</var> <tt>remove</tt></tag>
4209 <tag><var>postrm</var> <tt>purge</tt></tag>
4210 <tag><var>old-postrm</var> <tt>upgrade</tt>
4211 <var>new-version</var></tag>
4212 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4213 <var>overwriter</var> <var>overwriter-version</var></tag>
4215 The <prgn>postrm</prgn> script is called after the package's
4216 files have been removed or replaced. The package
4217 whose <prgn>postrm</prgn> is being called may have
4218 previously been deconfigured and only be "Unpacked", at which
4219 point subsequent package changes do not consider its
4220 dependencies. Therefore, all <prgn>postrm</prgn> actions
4221 may only rely on essential packages and must gracefully skip
4222 any actions that require the package's dependencies if those
4223 dependencies are unavailable.<footnote>
4224 This is often done by checking whether the command or
4225 facility the <prgn>postrm</prgn> intends to call is
4226 available before calling it. For example:
4228 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4229 . /usr/share/debconf/confmodule
4233 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4234 configuration for the package
4235 if <package>debconf</package> is installed.
4239 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4240 <var>old-version</var></tag>
4242 Called when the old <tt>postrm upgrade</tt> action fails.
4243 The new package will be unpacked, but only essential
4244 packages and pre-dependencies can be relied on.
4245 Pre-dependencies will either be configured or will be
4246 "Unpacked" or "Half-Configured" but previously had been
4247 configured and was never removed.
4250 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4251 <tag><var>new-postrm</var> <tt>abort-install</tt>
4252 <var>old-version</var></tag>
4253 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4254 <var>old-version</var></tag>
4256 Called before unpacking the new package as part of the
4257 error handling of <prgn>preinst</prgn> failures. May assume
4258 the same state as <prgn>preinst</prgn> can assume.
4264 <sect id="unpackphase">
4265 <heading>Details of unpack phase of installation or upgrade</heading>
4268 The procedure on installation/upgrade/overwrite/disappear
4269 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4270 stage of <tt>dpkg --install</tt>) is as follows. In each
4271 case, if a major error occurs (unless listed below) the
4272 actions are, in general, run backwards - this means that the
4273 maintainer scripts are run with different arguments in
4274 reverse order. These are the "error unwind" calls listed
4281 If a version of the package is already "Installed", call
4282 <example compact="compact">
4283 <var>old-prerm</var> upgrade <var>new-version</var>
4287 If the script runs but exits with a non-zero
4288 exit status, <prgn>dpkg</prgn> will attempt:
4289 <example compact="compact">
4290 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4292 If this works, the upgrade continues. If this
4293 does not work, the error unwind:
4294 <example compact="compact">
4295 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4297 If this works, then the old-version is
4298 "Installed", if not, the old version is in a
4299 "Half-Configured" state.
4305 If a "conflicting" package is being removed at the same time,
4306 or if any package will be broken (due to <tt>Breaks</tt>):
4309 If <tt>--auto-deconfigure</tt> is
4310 specified, call, for each package to be deconfigured
4311 due to <tt>Breaks</tt>:
4312 <example compact="compact">
4313 <var>deconfigured's-prerm</var> deconfigure \
4314 in-favour <var>package-being-installed</var> <var>version</var>
4317 <example compact="compact">
4318 <var>deconfigured's-postinst</var> abort-deconfigure \
4319 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4321 The deconfigured packages are marked as
4322 requiring configuration, so that if
4323 <tt>--install</tt> is used they will be
4324 configured again if possible.
4327 If any packages depended on a conflicting
4328 package being removed and <tt>--auto-deconfigure</tt> is
4329 specified, call, for each such package:
4330 <example compact="compact">
4331 <var>deconfigured's-prerm</var> deconfigure \
4332 in-favour <var>package-being-installed</var> <var>version</var> \
4333 removing <var>conflicting-package</var> <var>version</var>
4336 <example compact="compact">
4337 <var>deconfigured's-postinst</var> abort-deconfigure \
4338 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4339 removing <var>conflicting-package</var> <var>version</var>
4341 The deconfigured packages are marked as
4342 requiring configuration, so that if
4343 <tt>--install</tt> is used they will be
4344 configured again if possible.
4347 To prepare for removal of each conflicting package, call:
4348 <example compact="compact">
4349 <var>conflictor's-prerm</var> remove \
4350 in-favour <var>package</var> <var>new-version</var>
4353 <example compact="compact">
4354 <var>conflictor's-postinst</var> abort-remove \
4355 in-favour <var>package</var> <var>new-version</var>
4364 If the package is being upgraded, call:
4365 <example compact="compact">
4366 <var>new-preinst</var> upgrade <var>old-version</var>
4368 If this fails, we call:
4370 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4377 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4379 is called. If this works, then the old version
4380 is in an "Installed" state, or else it is left
4381 in an "Unpacked" state.
4386 If it fails, then the old version is left
4387 in an "Half-Installed" state.
4394 Otherwise, if the package had some configuration
4395 files from a previous version installed (i.e., it
4396 is in the "Config-Files" state):
4397 <example compact="compact">
4398 <var>new-preinst</var> install <var>old-version</var>
4402 <var>new-postrm</var> abort-install <var>old-version</var>
4404 If this fails, the package is left in a
4405 "Half-Installed" state, which requires a
4406 reinstall. If it works, the packages is left in
4407 a "Config-Files" state.
4410 Otherwise (i.e., the package was completely purged):
4411 <example compact="compact">
4412 <var>new-preinst</var> install
4415 <example compact="compact">
4416 <var>new-postrm</var> abort-install
4418 If the error-unwind fails, the package is in a
4419 "Half-Installed" phase, and requires a
4420 reinstall. If the error unwind works, the
4421 package is in the "Not-Installed" state.
4428 The new package's files are unpacked, overwriting any
4429 that may be on the system already, for example any
4430 from the old version of the same package or from
4431 another package. Backups of the old files are kept
4432 temporarily, and if anything goes wrong the package
4433 management system will attempt to put them back as
4434 part of the error unwind.
4438 It is an error for a package to contain files which
4439 are on the system in another package, unless
4440 <tt>Replaces</tt> is used (see <ref id="replaces">).
4442 The following paragraph is not currently the case:
4443 Currently the <tt>- - force-overwrite</tt> flag is
4444 enabled, downgrading it to a warning, but this may not
4450 It is a more serious error for a package to contain a
4451 plain file or other kind of non-directory where another
4452 package has a directory (again, unless
4453 <tt>Replaces</tt> is used). This error can be
4454 overridden if desired using
4455 <tt>--force-overwrite-dir</tt>, but this is not
4460 Packages which overwrite each other's files produce
4461 behavior which, though deterministic, is hard for the
4462 system administrator to understand. It can easily
4463 lead to "missing" programs if, for example, a package
4464 is unpacked which overwrites a file from another
4465 package, and is then removed again.<footnote>
4466 Part of the problem is due to what is arguably a
4467 bug in <prgn>dpkg</prgn>.
4472 A directory will never be replaced by a symbolic link
4473 to a directory or vice versa; instead, the existing
4474 state (symlink or not) will be left alone and
4475 <prgn>dpkg</prgn> will follow the symlink if there is
4484 If the package is being upgraded, call
4485 <example compact="compact">
4486 <var>old-postrm</var> upgrade <var>new-version</var>
4490 If this fails, <prgn>dpkg</prgn> will attempt:
4491 <example compact="compact">
4492 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4494 If this works, installation continues. If not,
4496 <example compact="compact">
4497 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4499 If this fails, the old version is left in a
4500 "Half-Installed" state. If it works, dpkg now
4502 <example compact="compact">
4503 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4505 If this fails, the old version is left in a
4506 "Half-Installed" state. If it works, dpkg now
4508 <example compact="compact">
4509 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4511 If this fails, the old version is in an
4518 This is the point of no return - if
4519 <prgn>dpkg</prgn> gets this far, it won't back off
4520 past this point if an error occurs. This will
4521 leave the package in a fairly bad state, which
4522 will require a successful re-installation to clear
4523 up, but it's when <prgn>dpkg</prgn> starts doing
4524 things that are irreversible.
4529 Any files which were in the old version of the package
4530 but not in the new are removed.
4534 The new file list replaces the old.
4538 The new maintainer scripts replace the old.
4542 Any packages all of whose files have been overwritten
4543 during the installation, and which aren't required for
4544 dependencies, are considered to have been removed.
4545 For each such package
4548 <prgn>dpkg</prgn> calls:
4549 <example compact="compact">
4550 <var>disappearer's-postrm</var> disappear \
4551 <var>overwriter</var> <var>overwriter-version</var>
4555 The package's maintainer scripts are removed.
4558 It is noted in the status database as being in a
4559 sane state, namely "Not-Installed" (any conffiles
4560 it may have are ignored, rather than being
4561 removed by <prgn>dpkg</prgn>). Note that
4562 disappearing packages do not have their prerm
4563 called, because <prgn>dpkg</prgn> doesn't know
4564 in advance that the package is going to
4571 Any files in the package we're unpacking that are also
4572 listed in the file lists of other packages are removed
4573 from those lists. (This will lobotomize the file list
4574 of the "conflicting" package if there is one.)
4578 The backup files made during installation, above, are
4584 The new package's status is now sane, and recorded as
4589 Here is another point of no return - if the
4590 conflicting package's removal fails we do not unwind
4591 the rest of the installation; the conflicting package
4592 is left in a half-removed limbo.
4597 If there was a conflicting package we go and do the
4598 removal actions (described below), starting with the
4599 removal of the conflicting package's files (any that
4600 are also in the package being unpacked have already
4601 been removed from the conflicting package's file list,
4602 and so do not get removed now).
4608 <sect id="configdetails"><heading>Details of configuration</heading>
4611 When we configure a package (this happens with <tt>dpkg
4612 --install</tt> and <tt>dpkg --configure</tt>), we first
4613 update any <tt>conffile</tt>s and then call:
4614 <example compact="compact">
4615 <var>postinst</var> configure <var>most-recently-configured-version</var>
4620 No attempt is made to unwind after errors during
4621 configuration. If the configuration fails, the package is in
4622 a "Half-Configured" state, and an error message is generated.
4626 If there is no most recently configured version
4627 <prgn>dpkg</prgn> will pass a null argument.
4630 Historical note: Truly ancient (pre-1997) versions of
4631 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4632 (including the angle brackets) in this case. Even older
4633 ones did not pass a second argument at all, under any
4634 circumstance. Note that upgrades using such an old dpkg
4635 version are unlikely to work for other reasons, even if
4636 this old argument behavior is handled by your postinst script.
4642 <sect id="removedetails"><heading>Details of removal and/or
4643 configuration purging</heading>
4649 <example compact="compact">
4650 <var>prerm</var> remove
4654 If prerm fails during replacement due to conflict
4656 <var>conflictor's-postinst</var> abort-remove \
4657 in-favour <var>package</var> <var>new-version</var>
4661 <var>postinst</var> abort-remove
4665 If this fails, the package is in a "Half-Configured"
4666 state, or else it remains "Installed".
4670 The package's files are removed (except <tt>conffile</tt>s).
4673 <example compact="compact">
4674 <var>postrm</var> remove
4678 If it fails, there's no error unwind, and the package is in
4679 an "Half-Installed" state.
4684 All the maintainer scripts except the <prgn>postrm</prgn>
4689 If we aren't purging the package we stop here. Note
4690 that packages which have no <prgn>postrm</prgn> and no
4691 <tt>conffile</tt>s are automatically purged when
4692 removed, as there is no difference except for the
4693 <prgn>dpkg</prgn> status.
4697 The <tt>conffile</tt>s and any backup files
4698 (<tt>~</tt>-files, <tt>#*#</tt> files,
4699 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4704 <example compact="compact">
4705 <var>postrm</var> purge
4709 If this fails, the package remains in a "Config-Files"
4714 The package's file list is removed.
4723 <chapt id="relationships">
4724 <heading>Declaring relationships between packages</heading>
4726 <sect id="depsyntax">
4727 <heading>Syntax of relationship fields</heading>
4730 These fields all have a uniform syntax. They are a list of
4731 package names separated by commas.
4735 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4736 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4737 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4738 control fields of the package, which declare
4739 dependencies on other packages, the package names listed may
4740 also include lists of alternative package names, separated
4741 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4742 that part of the dependency can be satisfied by any one of
4743 the alternative packages.
4747 All of the fields except for <tt>Provides</tt> may restrict
4748 their applicability to particular versions of each named
4749 package. This is done in parentheses after each individual
4750 package name; the parentheses should contain a relation from
4751 the list below followed by a version number, in the format
4752 described in <ref id="f-Version">.
4756 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4757 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4758 earlier, earlier or equal, exactly equal, later or equal and
4759 strictly later, respectively. The deprecated
4760 forms <tt><</tt> and <tt>></tt> were confusingly used to
4761 mean earlier/later or equal, rather than strictly earlier/later,
4762 and must not appear in new packages (though <prgn>dpkg</prgn>
4763 still supports them with a warning).
4767 Whitespace may appear at any point in the version
4768 specification subject to the rules in <ref
4769 id="controlsyntax">, and must appear where it's necessary to
4770 disambiguate; it is not otherwise significant. All of the
4771 relationship fields can only be folded in source package control files. For
4772 consistency and in case of future changes to
4773 <prgn>dpkg</prgn> it is recommended that a single space be
4774 used after a version relationship and before a version
4775 number; it is also conventional to put a single space after
4776 each comma, on either side of each vertical bar, and before
4777 each open parenthesis. When opening a continuation line in a relationship field, it
4778 is conventional to do so after a comma and before the space
4779 following that comma.
4783 For example, a list of dependencies might appear as:
4784 <example compact="compact">
4787 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4792 Relationships may be restricted to a certain set of
4793 architectures. This is indicated in brackets after each
4794 individual package name and the optional version specification.
4795 The brackets enclose a non-empty list of Debian architecture names
4796 in the format described in <ref id="arch-spec">,
4797 separated by whitespace. Exclamation marks may be prepended to
4798 each of the names. (It is not permitted for some names to be
4799 prepended with exclamation marks while others aren't.)
4803 For build relationship fields
4804 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4805 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4806 the current Debian host architecture is not in this list and
4807 there are no exclamation marks in the list, or it is in the list
4808 with a prepended exclamation mark, the package name and the
4809 associated version specification are ignored completely for the
4810 purposes of defining the relationships.
4815 <example compact="compact">
4817 Build-Depends-Indep: texinfo
4818 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4819 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4821 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4822 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4823 <tt>gnumach-dev</tt> only on hurd-i386.
4827 For binary relationship fields and the <tt>Built-Using</tt>
4828 field, the architecture restriction
4829 syntax is only supported in the source package control
4830 file <file>debian/control</file>. When the corresponding binary
4831 package control file is generated, the relationship will either
4832 be omitted or included without the architecture restriction
4833 based on the architecture of the binary package. This means
4834 that architecture restrictions must not be used in binary
4835 relationship fields for architecture-independent packages
4836 (<tt>Architecture: all</tt>).
4841 <example compact="compact">
4842 Depends: foo [i386], bar [amd64]
4844 becomes <tt>Depends: foo</tt> when the package is built on
4845 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4846 package is built on the <tt>amd64</tt> architecture, and omitted
4847 entirely in binary packages built on all other architectures.
4851 If the architecture-restricted dependency is part of a set of
4852 alternatives using <tt>|</tt>, that alternative is ignored
4853 completely on architectures that do not match the restriction.
4855 <example compact="compact">
4856 Build-Depends: foo [!i386] | bar [!amd64]
4858 is equivalent to <tt>bar</tt> on the i386 architecture, to
4859 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4860 bar</tt> on all other architectures.
4864 Relationships may also be restricted to a certain set of
4865 architectures using architecture wildcards in the format
4866 described in <ref id="arch-wildcard-spec">. The syntax for
4867 declaring such restrictions is the same as declaring
4868 restrictions using a certain set of architectures without
4869 architecture wildcards. For example:
4870 <example compact="compact">
4871 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4873 is equivalent to <tt>foo</tt> on architectures using the Linux
4874 kernel and any cpu, <tt>bar</tt> on architectures using any
4875 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4876 using a kernel other than Linux.
4880 Note that the binary package relationship fields such as
4881 <tt>Depends</tt> appear in one of the binary package
4882 sections of the control file, whereas the build-time
4883 relationships such as <tt>Build-Depends</tt> appear in the
4884 source package section of the control file (which is the
4889 <sect id="binarydeps">
4890 <heading>Binary Dependencies - <tt>Depends</tt>,
4891 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4892 <tt>Pre-Depends</tt>
4896 Packages can declare in their control file that they have
4897 certain relationships to other packages - for example, that
4898 they may not be installed at the same time as certain other
4899 packages, and/or that they depend on the presence of others.
4903 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4904 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4905 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4906 <tt>Breaks</tt> is described in <ref id="breaks">, and
4907 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4908 rest are described below.
4912 These seven fields are used to declare a dependency
4913 relationship by one package on another. Except for
4914 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4915 depending (binary) package's control file.
4916 (<tt>Enhances</tt> appears in the recommending package's
4917 control file, and <tt>Breaks</tt> appears in the version of
4918 depended-on package which causes the named package to
4923 A <tt>Depends</tt> field takes effect <em>only</em> when a
4924 package is to be configured. It does not prevent a package
4925 being on the system in an unconfigured state while its
4926 dependencies are unsatisfied, and it is possible to replace
4927 a package whose dependencies are satisfied and which is
4928 properly installed with a different version whose
4929 dependencies are not and cannot be satisfied; when this is
4930 done the depending package will be left unconfigured (since
4931 attempts to configure it will give errors) and will not
4932 function properly. If it is necessary, a
4933 <tt>Pre-Depends</tt> field can be used, which has a partial
4934 effect even when a package is being unpacked, as explained
4935 in detail below. (The other three dependency fields,
4936 <tt>Recommends</tt>, <tt>Suggests</tt> and
4937 <tt>Enhances</tt>, are only used by the various front-ends
4938 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4939 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4943 Since <tt>Depends</tt> only places requirements on the order in
4944 which packages are configured, packages in an installation run
4945 are usually all unpacked first and all configured later.
4947 This approach makes dependency resolution easier. If two
4948 packages A and B are being upgraded, the installed package A
4949 depends on exactly the installed package B, and the new
4950 package A depends on exactly the new package B (a common
4951 situation when upgrading shared libraries and their
4952 corresponding development packages), satisfying the
4953 dependencies at every stage of the upgrade would be
4954 impossible. This relaxed restriction means that both new
4955 packages can be unpacked together and then configured in their
4961 If there is a circular dependency among packages being installed
4962 or removed, installation or removal order honoring the
4963 dependency order is impossible, requiring the dependency loop be
4964 broken at some point and the dependency requirements violated
4965 for at least one package. Packages involved in circular
4966 dependencies may not be able to rely on their dependencies being
4967 configured before they themselves are configured, depending on
4968 which side of the break of the circular dependency loop they
4969 happen to be on. If one of the packages in the loop has
4970 no <prgn>postinst</prgn> script, then the cycle will be broken
4971 at that package; this ensures that all <prgn>postinst</prgn>
4972 scripts are run with their dependencies properly configured if
4973 this is possible. Otherwise the breaking point is arbitrary.
4974 Packages should therefore avoid circular dependencies where
4975 possible, particularly if they have <prgn>postinst</prgn>
4980 The meaning of the five dependency fields is as follows:
4982 <tag><tt>Depends</tt></tag>
4985 This declares an absolute dependency. A package will
4986 not be configured unless all of the packages listed in
4987 its <tt>Depends</tt> field have been correctly
4988 configured (unless there is a circular dependency as
4993 The <tt>Depends</tt> field should be used if the
4994 depended-on package is required for the depending
4995 package to provide a significant amount of
5000 The <tt>Depends</tt> field should also be used if the
5001 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
5002 require the depended-on package to be unpacked or
5003 configured in order to run. In the case of <tt>postinst
5004 configure</tt>, the depended-on packages will be unpacked
5005 and configured first. (If both packages are involved in a
5006 dependency loop, this might not work as expected; see the
5007 explanation a few paragraphs back.) In the case
5008 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
5009 actions, the package dependencies will normally be at
5010 least unpacked, but they may be only "Half-Installed" if a
5011 previous upgrade of the dependency failed.
5015 Finally, the <tt>Depends</tt> field should be used if the
5016 depended-on package is needed by the <prgn>postrm</prgn>
5017 script to fully clean up after the package removal. There
5018 is no guarantee that package dependencies will be
5019 available when <prgn>postrm</prgn> is run, but the
5020 depended-on package is more likely to be available if the
5021 package declares a dependency (particularly in the case
5022 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
5023 script must gracefully skip actions that require a
5024 dependency if that dependency isn't available.
5028 <tag><tt>Recommends</tt></tag>
5031 This declares a strong, but not absolute, dependency.
5035 The <tt>Recommends</tt> field should list packages
5036 that would be found together with this one in all but
5037 unusual installations.
5041 <tag><tt>Suggests</tt></tag>
5043 This is used to declare that one package may be more
5044 useful with one or more others. Using this field
5045 tells the packaging system and the user that the
5046 listed packages are related to this one and can
5047 perhaps enhance its usefulness, but that installing
5048 this one without them is perfectly reasonable.
5051 <tag><tt>Enhances</tt></tag>
5053 This field is similar to Suggests but works in the
5054 opposite direction. It is used to declare that a
5055 package can enhance the functionality of another
5059 <tag><tt>Pre-Depends</tt></tag>
5062 This field is like <tt>Depends</tt>, except that it
5063 also forces <prgn>dpkg</prgn> to complete installation
5064 of the packages named before even starting the
5065 installation of the package which declares the
5066 pre-dependency, as follows:
5070 When a package declaring a pre-dependency is about to
5071 be <em>unpacked</em> the pre-dependency can be
5072 satisfied if the depended-on package is either fully
5073 configured, <em>or even if</em> the depended-on
5074 package(s) are only in the "Unpacked" or the "Half-Configured"
5075 state, provided that they have been configured
5076 correctly at some point in the past (and not removed
5077 or partially removed since). In this case, both the
5078 previously-configured and currently "Unpacked" or
5079 "Half-Configured" versions must satisfy any version
5080 clause in the <tt>Pre-Depends</tt> field.
5084 When the package declaring a pre-dependency is about to
5085 be <em>configured</em>, the pre-dependency will be treated
5086 as a normal <tt>Depends</tt>. It will be considered
5087 satisfied only if the depended-on package has been
5088 correctly configured. However, unlike
5089 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
5090 permit circular dependencies to be broken. If a circular
5091 dependency is encountered while attempting to honor
5092 <tt>Pre-Depends</tt>, the installation will be aborted.
5096 <tt>Pre-Depends</tt> are also required if the
5097 <prgn>preinst</prgn> script depends on the named package.
5098 It is best to avoid this situation if possible.
5102 <tt>Pre-Depends</tt> should be used sparingly,
5103 preferably only by packages whose premature upgrade or
5104 installation would hamper the ability of the system to
5105 continue with any upgrade that might be in progress.
5109 You should not specify a <tt>Pre-Depends</tt> entry for a
5110 package before this has been discussed on the
5111 <tt>debian-devel</tt> mailing list and a consensus about
5112 doing that has been reached. See <ref id="dependencies">.
5119 When selecting which level of dependency to use you should
5120 consider how important the depended-on package is to the
5121 functionality of the one declaring the dependency. Some
5122 packages are composed of components of varying degrees of
5123 importance. Such a package should list using
5124 <tt>Depends</tt> the package(s) which are required by the
5125 more important components. The other components'
5126 requirements may be mentioned as Suggestions or
5127 Recommendations, as appropriate to the components' relative
5133 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5136 When one binary package declares that it breaks another,
5137 <prgn>dpkg</prgn> will refuse to allow the package which
5138 declares <tt>Breaks</tt> to be unpacked unless the broken
5139 package is deconfigured first, and it will refuse to
5140 allow the broken package to be reconfigured.
5144 A package will not be regarded as causing breakage merely
5145 because its configuration files are still installed; it must
5146 be at least "Half-Installed".
5150 A special exception is made for packages which declare that
5151 they break their own package name or a virtual package which
5152 they provide (see below): this does not count as a real
5157 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5158 version clause; such a <tt>Breaks</tt> is introduced in the
5159 version of an (implicit or explicit) dependency which violates
5160 an assumption or reveals a bug in earlier versions of the broken
5161 package, or which takes over a file from earlier versions of the
5162 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5163 will inform higher-level package management tools that the
5164 broken package must be upgraded before the new one.
5168 If the breaking package also overwrites some files from the
5169 older package, it should use <tt>Replaces</tt> to ensure this
5170 goes smoothly. See <ref id="replaces"> for a full discussion
5171 of taking over files from other packages, including how to
5172 use <tt>Breaks</tt> in those cases.
5176 Many of the cases where <tt>Breaks</tt> should be used were
5177 previously handled with <tt>Conflicts</tt>
5178 because <tt>Breaks</tt> did not yet exist.
5179 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5180 See <ref id="conflicts"> for more information about the
5185 <sect id="conflicts">
5186 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5189 When one binary package declares a conflict with another using
5190 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5191 allow them to be unpacked on the system at the same time. This
5192 is a stronger restriction than <tt>Breaks</tt>, which prevents
5193 the broken package from being configured while the breaking
5194 package is in the "Unpacked" state but allows both packages to
5195 be unpacked at the same time.
5199 If one package is to be unpacked, the other must be removed
5200 first. If the package being unpacked is marked as replacing
5201 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5202 normally be used in this case) the one on the system, or the one
5203 on the system is marked as deselected, or both packages are
5204 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5205 automatically remove the package which is causing the conflict.
5206 Otherwise, it will halt the installation of the new package with
5207 an error. This mechanism is specifically designed to produce an
5208 error when the installed package is <tt>Essential</tt>, but the
5213 A package will not cause a conflict merely because its
5214 configuration files are still installed; it must be at least
5219 A special exception is made for packages which declare a
5220 conflict with their own package name, or with a virtual
5221 package which they provide (see below): this does not
5222 prevent their installation, and allows a package to conflict
5223 with others providing a replacement for it. You use this
5224 feature when you want the package in question to be the only
5225 package providing some feature.
5229 Normally, <tt>Breaks</tt> should be used instead
5230 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5231 stronger restriction on the ordering of package installation or
5232 upgrade and can make it more difficult for the package manager
5233 to find a correct solution to an upgrade or installation
5234 problem. <tt>Breaks</tt> should be used
5236 <item>when moving a file from one package to another (see
5237 <ref id="replaces">),</item>
5238 <item>when splitting a package (a special case of the previous
5240 <item>when the breaking package exposes a bug in or interacts
5241 badly with particular versions of the broken
5244 <tt>Conflicts</tt> should be used
5246 <item>when two packages provide the same file and will
5247 continue to do so,</item>
5248 <item>in conjunction with <tt>Provides</tt> when only one
5249 package providing a given virtual facility may be unpacked
5250 at a time (see <ref id="virtual">),</item>
5251 <item>in other cases where one must prevent simultaneous
5252 installation of two packages for reasons that are ongoing
5253 (not fixed in a later version of one of the packages) or
5254 that must prevent both packages from being unpacked at the
5255 same time, not just configured.</item>
5257 Be aware that adding <tt>Conflicts</tt> is normally not the best
5258 solution when two packages provide the same files. Depending on
5259 the reason for that conflict, using alternatives or renaming the
5260 files is often a better approach. See, for
5261 example, <ref id="binaries">.
5265 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5266 unless two packages cannot be installed at the same time or
5267 installing them both causes one of them to be broken or
5268 unusable. Having similar functionality or performing the same
5269 tasks as another package is not sufficient reason to
5270 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5274 A <tt>Conflicts</tt> entry may have an "earlier than" version
5275 clause if the reason for the conflict is corrected in a later
5276 version of one of the packages. However, normally the presence
5277 of an "earlier than" version clause is a sign
5278 that <tt>Breaks</tt> should have been used instead. An "earlier
5279 than" version clause in <tt>Conflicts</tt>
5280 prevents <prgn>dpkg</prgn> from upgrading or installing the
5281 package which declares such a conflict until the upgrade or
5282 removal of the conflicted-with package has been completed, which
5283 is a strong restriction.
5287 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5291 As well as the names of actual ("concrete") packages, the
5292 package relationship fields <tt>Depends</tt>,
5293 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5294 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5295 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5296 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5297 may mention "virtual packages".
5301 A <em>virtual package</em> is one which appears in the
5302 <tt>Provides</tt> control field of another package. The effect
5303 is as if the package(s) which provide a particular virtual
5304 package name had been listed by name everywhere the virtual
5305 package name appears. (See also <ref id="virtual_pkg">)
5309 If there are both concrete and virtual packages of the same
5310 name, then the dependency may be satisfied (or the conflict
5311 caused) by either the concrete package with the name in
5312 question or any other concrete package which provides the
5313 virtual package with the name in question. This is so that,
5314 for example, supposing we have
5315 <example compact="compact">
5318 </example> and someone else releases an enhanced version of
5319 the <tt>bar</tt> package they can say:
5320 <example compact="compact">
5324 and the <tt>bar-plus</tt> package will now also satisfy the
5325 dependency for the <tt>foo</tt> package.
5329 If a relationship field has a version number attached, only real
5330 packages will be considered to see whether the relationship is
5331 satisfied (or the prohibition violated, for a conflict or
5332 breakage). In other words, if a version number is specified,
5333 this is a request to ignore all <tt>Provides</tt> for that
5334 package name and consider only real packages. The package
5335 manager will assume that a package providing that virtual
5336 package is not of the "right" version. A <tt>Provides</tt>
5337 field may not contain version numbers, and the version number of
5338 the concrete package which provides a particular virtual package
5339 will not be considered when considering a dependency on or
5340 conflict with the virtual package name.<footnote>
5341 It is possible that a future release of <prgn>dpkg</prgn> may
5342 add the ability to specify a version number for each virtual
5343 package it provides. This feature is not yet present,
5344 however, and is expected to be used only infrequently.
5349 To specify which of a set of real packages should be the default
5350 to satisfy a particular dependency on a virtual package, list
5351 the real package as an alternative before the virtual one.
5355 If the virtual package represents a facility that can only be
5356 provided by one real package at a time, such as
5357 the <package>mail-transport-agent</package> virtual package that
5358 requires installation of a binary that would conflict with all
5359 other providers of that virtual package (see
5360 <ref id="mail-transport-agents">), all packages providing that
5361 virtual package should also declare a conflict with it
5362 using <tt>Conflicts</tt>. This will ensure that at most one
5363 provider of that virtual package is unpacked or installed at a
5368 <sect id="replaces"><heading>Overwriting files and replacing
5369 packages - <tt>Replaces</tt></heading>
5372 Packages can declare in their control file that they should
5373 overwrite files in certain other packages, or completely replace
5374 other packages. The <tt>Replaces</tt> control field has these
5375 two distinct purposes.
5378 <sect1><heading>Overwriting files in other packages</heading>
5381 It is usually an error for a package to contain files which
5382 are on the system in another package. However, if the
5383 overwriting package declares that it <tt>Replaces</tt> the one
5384 containing the file being overwritten, then <prgn>dpkg</prgn>
5385 will replace the file from the old package with that from the
5386 new. The file will no longer be listed as "owned" by the old
5387 package and will be taken over by the new package.
5388 Normally, <tt>Breaks</tt> should be used in conjunction
5389 with <tt>Replaces</tt>.<footnote>
5390 To see why <tt>Breaks</tt> is normally needed in addition
5391 to <tt>Replaces</tt>, consider the case of a file in the
5392 package <package>foo</package> being taken over by the
5393 package <package>foo-data</package>.
5394 <tt>Replaces</tt> will allow <package>foo-data</package> to
5395 be installed and take over that file. However,
5396 without <tt>Breaks</tt>, nothing
5397 requires <package>foo</package> to be upgraded to a newer
5398 version that knows it does not include that file and instead
5399 depends on <package>foo-data</package>. Nothing would
5400 prevent the new <package>foo-data</package> package from
5401 being installed and then removed, removing the file that it
5402 took over from <package>foo</package>. After that
5403 operation, the package manager would think the system was in
5404 a consistent state, but the <package>foo</package> package
5405 would be missing one of its files.
5410 For example, if a package <package>foo</package> is split
5411 into <package>foo</package> and <package>foo-data</package>
5412 starting at version 1.2-3, <package>foo-data</package> would
5414 <example compact="compact">
5415 Replaces: foo (<< 1.2-3)
5416 Breaks: foo (<< 1.2-3)
5418 in its control file. The new version of the
5419 package <package>foo</package> would normally have the field
5420 <example compact="compact">
5421 Depends: foo-data (>= 1.2-3)
5423 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5424 the files moved into <package>foo-data</package> are not
5425 required for normal operation).
5429 If a package is completely replaced in this way, so that
5430 <prgn>dpkg</prgn> does not know of any files it still
5431 contains, it is considered to have "disappeared". It will
5432 be marked as not wanted on the system (selected for
5433 removal) and "Not-Installed". Any <tt>conffile</tt>s
5434 details noted for the package will be ignored, as they
5435 will have been taken over by the overwriting package. The
5436 package's <prgn>postrm</prgn> script will be run with a
5437 special argument to allow the package to do any final
5438 cleanup required. See <ref id="mscriptsinstact">.
5440 Replaces is a one way relationship. You have to install
5441 the replacing package after the replaced package.
5446 For this usage of <tt>Replaces</tt>, virtual packages (see
5447 <ref id="virtual">) are not considered when looking at a
5448 <tt>Replaces</tt> field. The packages declared as being
5449 replaced must be mentioned by their real names.
5453 This usage of <tt>Replaces</tt> only takes effect when both
5454 packages are at least partially on the system at once. It is
5455 not relevant if the packages conflict unless the conflict has
5460 <sect1><heading>Replacing whole packages, forcing their
5464 Second, <tt>Replaces</tt> allows the packaging system to
5465 resolve which package should be removed when there is a
5466 conflict (see <ref id="conflicts">). This usage only takes
5467 effect when the two packages <em>do</em> conflict, so that the
5468 two usages of this field do not interfere with each other.
5472 In this situation, the package declared as being replaced
5473 can be a virtual package, so for example, all mail
5474 transport agents (MTAs) would have the following fields in
5475 their control files:
5476 <example compact="compact">
5477 Provides: mail-transport-agent
5478 Conflicts: mail-transport-agent
5479 Replaces: mail-transport-agent
5481 ensuring that only one MTA can be unpacked at any one
5482 time. See <ref id="virtual"> for more information about this
5487 <sect id="sourcebinarydeps">
5488 <heading>Relationships between source and binary packages -
5489 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5490 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5494 Source packages that require certain binary packages to be
5495 installed or absent at the time of building the package
5496 can declare relationships to those binary packages.
5500 This is done using the <tt>Build-Depends</tt>,
5501 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5502 <tt>Build-Conflicts-Indep</tt> control fields.
5506 Build-dependencies on "build-essential" binary packages can be
5507 omitted. Please see <ref id="pkg-relations"> for more information.
5511 The dependencies and conflicts they define must be satisfied
5512 (as defined earlier for binary packages) in order to invoke
5513 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5515 There is no Build-Depends-Arch; this role is essentially
5516 met with Build-Depends. Anyone building the
5517 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5518 assumed to be building the whole package, and therefore
5519 installation of all build dependencies is required.
5522 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5523 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5524 not yet know how to check for its existence, and
5525 <tt>binary-arch</tt>. The purpose of the original split
5526 between <tt>Build-Depends</tt> and
5527 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5528 wouldn't need to install extra packages needed only for the
5529 binary-indep targets. But without a build-arch/build-indep
5530 split, this didn't work, since most of the work is done in
5531 the build target, not in the binary target.
5535 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5536 <tt>binary-arch</tt></tag>
5538 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5539 fields must be satisfied when these targets are invoked.
5541 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5542 and <tt>binary-indep</tt></tag>
5544 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5545 <tt>Build-Depends-Indep</tt>, and
5546 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5547 these targets are invoked.
5553 <sect id="built-using">
5554 <heading>Additional source packages used to build the binary
5555 - <tt>Built-Using</tt>
5559 Some binary packages incorporate parts of other packages when built
5560 but do not have to depend on those packages. Examples include
5561 linking with static libraries or incorporating source code from
5562 another package during the build. In this case, the source packages
5563 of those other packages are a required part of the complete source
5564 (the binary package is not reproducible without them).
5568 A <tt>Built-Using</tt> field must list the corresponding source
5569 package for any such binary package incorporated during the build
5571 <tt>Build-Depends</tt> in the source package is not adequate since
5572 it (rightfully) does not document the exact version used in the
5575 including an "exactly equal" ("=") version relation on the version
5576 that was used to build that binary package<footnote>
5577 The archive software might reject packages that refer to
5578 non-existent sources.
5583 A package using the source code from the gcc-4.6-source
5584 binary package built from the gcc-4.6 source package would
5585 have this field in its control file:
5586 <example compact="compact">
5587 Built-Using: gcc-4.6 (= 4.6.0-11)
5592 A package including binaries from grub2 and loadlin would
5593 have this field in its control file:
5594 <example compact="compact">
5595 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5602 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5605 Packages containing shared libraries must be constructed with
5606 a little care to make sure that the shared library is always
5607 available. This is especially important for packages whose
5608 shared libraries are vitally important, such as the C library
5609 (currently <tt>libc6</tt>).
5613 This section deals only with public shared libraries: shared
5614 libraries that are placed in directories searched by the dynamic
5615 linker by default or which are intended to be linked against
5616 normally and possibly used by other, independent packages. Shared
5617 libraries that are internal to a particular package or that are
5618 only loaded as dynamic modules are not covered by this section and
5619 are not subject to its requirements.
5623 A shared library is identified by the <tt>SONAME</tt> attribute
5624 stored in its dynamic section. When a binary is linked against a
5625 shared library, the <tt>SONAME</tt> of the shared library is
5626 recorded in the binary's <tt>NEEDED</tt> section so that the
5627 dynamic linker knows that library must be loaded at runtime. The
5628 shared library file's full name (which usually contains additional
5629 version information not needed in the <tt>SONAME</tt>) is
5630 therefore normally not referenced directly. Instead, the shared
5631 library is loaded by its <tt>SONAME</tt>, which exists on the file
5632 system as a symlink pointing to the full name of the shared
5633 library. This symlink must be provided by the
5634 package. <ref id="sharedlibs-runtime"> describes how to do this.
5636 This is a convention of shared library versioning, but not a
5637 requirement. Some libraries use the <tt>SONAME</tt> as the full
5638 library file name instead and therefore do not need a symlink.
5639 Most, however, encode additional information about
5640 backwards-compatible revisions as a minor version number in the
5641 file name. The <tt>SONAME</tt> itself only changes when
5642 binaries linked with the earlier version of the shared library
5643 may no longer work, but the filename may change with each
5644 release of the library. See <ref id="sharedlibs-runtime"> for
5650 When linking a binary or another shared library against a shared
5651 library, the <tt>SONAME</tt> for that shared library is not yet
5652 known. Instead, the shared library is found by looking for a file
5653 matching the library name with <tt>.so</tt> appended. This file
5654 exists on the file system as a symlink pointing to the shared
5659 Shared libraries are normally split into several binary packages.
5660 The <tt>SONAME</tt> symlink is installed by the runtime shared
5661 library package, and the bare <tt>.so</tt> symlink is installed in
5662 the development package since it's only used when linking binaries
5663 or shared libraries. However, there are some exceptions for
5664 unusual shared libraries or for shared libraries that are also
5665 loaded as dynamic modules by other programs.
5669 This section is primarily concerned with how the separation of
5670 shared libraries into multiple packages should be done and how
5671 dependencies on and between shared library binary packages are
5672 managed in Debian. <ref id="libraries"> should be read in
5673 conjunction with this section and contains additional rules for
5674 the files contained in the shared library packages.
5677 <sect id="sharedlibs-runtime">
5678 <heading>Run-time shared libraries</heading>
5681 The run-time shared library must be placed in a package
5682 whose name changes whenever the <tt>SONAME</tt> of the shared
5683 library changes. This allows several versions of the shared
5684 library to be installed at the same time, allowing installation
5685 of the new version of the shared library without immediately
5686 breaking binaries that depend on the old version. Normally, the
5687 run-time shared library and its <tt>SONAME</tt> symlink should
5688 be placed in a package named
5689 <package><var>libraryname</var><var>soversion</var></package>,
5690 where <var>soversion</var> is the version number in
5691 the <tt>SONAME</tt> of the shared library. Alternatively, if it
5692 would be confusing to directly append <var>soversion</var>
5693 to <var>libraryname</var> (if, for
5694 example, <var>libraryname</var> itself ends in a number), you
5696 <package><var>libraryname</var>-<var>soversion</var></package>
5701 To determine the <var>soversion</var>, look at
5702 the <tt>SONAME</tt> of the library, stored in the
5703 ELF <tt>SONAME</tt> attribute. It is usually of the
5704 form <tt><var>name</var>.so.<var>major-version</var></tt> (for
5705 example, <tt>libz.so.1</tt>). The version part is the part
5706 which comes after <tt>.so.</tt>, so in that example it
5707 is <tt>1</tt>. The soname may instead be of the
5708 form <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5709 as <tt>libdb-5.1.so</tt>, in which case the name would
5710 be <tt>libdb</tt> and the version would be <tt>5.1</tt>.
5714 If you have several shared libraries built from the same source
5715 tree, you may lump them all together into a single shared
5716 library package provided that all of their <tt>SONAME</tt>s will
5717 always change together. Be aware that this is not normally the
5718 case, and if the <tt>SONAME</tt>s do not change together,
5719 upgrading such a merged shared library package will be
5720 unnecessarily difficult because of file conflicts with the old
5721 version of the package. When in doubt, always split shared
5722 library packages so that each binary package installs a single
5727 Every time the shared library ABI changes in a way that may
5728 break binaries linked against older versions of the shared
5729 library, the <tt>SONAME</tt> of the library and the
5730 corresponding name for the binary package containing the runtime
5731 shared library should change. Normally, this means
5732 the <tt>SONAME</tt> should change any time an interface is
5733 removed from the shared library or the signature of an interface
5734 (the number of parameters or the types of parameters that it
5735 takes, for example) is changed. This practice is vital to
5736 allowing clean upgrades from older versions of the package and
5737 clean transitions between the old ABI and new ABI without having
5738 to upgrade every affected package simultaneously.
5742 The <tt>SONAME</tt> and binary package name need not, and indeed
5743 normally should not, change if new interfaces are added but none
5744 are removed or changed, since this will not break binaries
5745 linked against the old shared library. Correct versioning of
5746 dependencies on the newer shared library by binaries that use
5747 the new interfaces is handled via
5748 the <qref id="sharedlibs-depends"><tt>symbols</tt>
5749 or <tt>shlibs</tt> system</qref>.
5753 The package should install the shared libraries under
5754 their normal names. For example, the <package>libgdbm3</package>
5755 package should install <file>libgdbm.so.3.0.0</file> as
5756 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5757 renamed or re-linked by any <prgn>prerm</prgn> or
5758 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5759 of renaming things safely without affecting running programs,
5760 and attempts to interfere with this are likely to lead to
5765 Shared libraries should not be installed executable, since
5766 the dynamic linker does not require this and trying to
5767 execute a shared library usually results in a core dump.
5771 The run-time library package should include the symbolic link for
5772 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5773 the shared libraries. For example,
5774 the <package>libgdbm3</package> package should include a symbolic
5775 link from <file>/usr/lib/libgdbm.so.3</file> to
5776 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5777 linker (for example <prgn>ld.so</prgn> or
5778 <prgn>ld-linux.so.*</prgn>) can find the library between the
5779 time that <prgn>dpkg</prgn> installs it and the time that
5780 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5782 The package management system requires the library to be
5783 placed before the symbolic link pointing to it in the
5784 <file>.deb</file> file. This is so that when
5785 <prgn>dpkg</prgn> comes to install the symlink
5786 (overwriting the previous symlink pointing at an older
5787 version of the library), the new shared library is already
5788 in place. In the past, this was achieved by creating the
5789 library in the temporary packaging directory before
5790 creating the symlink. Unfortunately, this was not always
5791 effective, since the building of the tar file in the
5792 <file>.deb</file> depended on the behavior of the underlying
5793 file system. Some file systems (such as reiserfs) reorder
5794 the files so that the order of creation is forgotten.
5795 Since version 1.7.0, <prgn>dpkg</prgn>
5796 reorders the files itself as necessary when building a
5797 package. Thus it is no longer important to concern
5798 oneself with the order of file creation.
5802 <sect1 id="ldconfig">
5803 <heading><tt>ldconfig</tt></heading>
5806 Any package installing shared libraries in one of the default
5807 library directories of the dynamic linker (which are currently
5808 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5809 listed in <file>/etc/ld.so.conf</file><footnote>
5810 These are currently <file>/usr/local/lib</file> plus
5811 directories under <file>/lib</file> and <file>/usr/lib</file>
5812 matching the multiarch triplet for the system architecture.
5814 must use <prgn>ldconfig</prgn> to update the shared library
5819 The package maintainer scripts must only call
5820 <prgn>ldconfig</prgn> under these circumstances:
5821 <list compact="compact">
5822 <item>When the <prgn>postinst</prgn> script is run with a
5823 first argument of <tt>configure</tt>, the script must call
5824 <prgn>ldconfig</prgn>, and may optionally invoke
5825 <prgn>ldconfig</prgn> at other times.
5827 <item>When the <prgn>postrm</prgn> script is run with a
5828 first argument of <tt>remove</tt>, the script should call
5829 <prgn>ldconfig</prgn>.
5834 During install or upgrade, the preinst is called before
5835 the new files are unpacked, so calling "ldconfig" is
5836 pointless. The preinst of an existing package can also be
5837 called if an upgrade fails. However, this happens during
5838 the critical time when a shared libs may exist on-disk
5839 under a temporary name. Thus, it is dangerous and
5840 forbidden by current policy to call "ldconfig" at this
5845 When a package is installed or upgraded, "postinst
5846 configure" runs after the new files are safely on-disk.
5847 Since it is perfectly safe to invoke ldconfig
5848 unconditionally in a postinst, it is OK for a package to
5849 simply put ldconfig in its postinst without checking the
5850 argument. The postinst can also be called to recover from
5851 a failed upgrade. This happens before any new files are
5852 unpacked, so there is no reason to call "ldconfig" at this
5857 For a package that is being removed, prerm is
5858 called with all the files intact, so calling ldconfig is
5859 useless. The other calls to "prerm" happen in the case of
5860 upgrade at a time when all the files of the old package
5861 are on-disk, so again calling "ldconfig" is pointless.
5865 postrm, on the other hand, is called with the "remove"
5866 argument just after the files are removed, so this is
5867 the proper time to call "ldconfig" to notify the system
5868 of the fact that the shared libraries from the package
5869 are removed. The postrm can be called at several other
5870 times. At the time of "postrm purge", "postrm
5871 abort-install", or "postrm abort-upgrade", calling
5872 "ldconfig" is useless because the shared lib files are
5873 not on-disk. However, when "postrm" is invoked with
5874 arguments "upgrade", "failed-upgrade", or "disappear", a
5875 shared lib may exist on-disk under a temporary filename.
5883 <sect id="sharedlibs-support-files">
5884 <heading>Shared library support files</heading>
5887 If your package contains files whose names do not change with
5888 each change in the library shared object version, you must not
5889 put them in the shared library package. Otherwise, several
5890 versions of the shared library cannot be installed at the same
5891 time without filename clashes, making upgrades and transitions
5892 unnecessarily difficult.
5896 It is recommended that supporting files and run-time support
5897 programs that do not need to be invoked manually by users, but
5898 are nevertheless required for the package to function, be placed
5899 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5900 preferably under <file>/usr/lib/</file><var>package-name</var>.
5901 If the program or file is architecture independent, the
5902 recommendation is for it to be placed in a subdirectory of
5903 <file>/usr/share</file> instead, preferably under
5904 <file>/usr/share/</file><var>package-name</var>. Following the
5905 <var>package-name</var> naming convention ensures that the file
5906 names change when the shared object version changes.
5910 Run-time support programs that use the shared library but are
5911 not required for the library to function or files used by the
5912 shared library that can be used by any version of the shared
5913 library package should instead be put in a separate package.
5914 This package might typically be named
5915 <package><var>libraryname</var>-tools</package>; note the
5916 absence of the <var>soversion</var> in the package name.
5920 Files and support programs only useful when compiling software
5921 against the library should be included in the development
5922 package for the library.<footnote>
5923 For example, a <file><var>package-name</var>-config</file>
5924 script or <package>pkg-config</package> configuration files.
5929 <sect id="sharedlibs-static">
5930 <heading>Static libraries</heading>
5933 The static library (<file><var>libraryname.a</var></file>)
5934 is usually provided in addition to the shared version.
5935 It is placed into the development package (see below).
5939 In some cases, it is acceptable for a library to be
5940 available in static form only; these cases include:
5942 <item>libraries for languages whose shared library support
5943 is immature or unstable</item>
5944 <item>libraries whose interfaces are in flux or under
5945 development (commonly the case when the library's
5946 major version number is zero, or where the ABI breaks
5947 across patchlevels)</item>
5948 <item>libraries which are explicitly intended to be
5949 available only in static form by their upstream
5954 <sect id="sharedlibs-dev">
5955 <heading>Development files</heading>
5958 If there are development files associated with a shared library,
5959 the source package needs to generate a binary development package
5960 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5961 or if you prefer only to support one development version at a
5962 time, <package><var>libraryname</var>-dev</package>. Installing
5963 the development package must result in installation of all the
5964 development files necessary for compiling programs against that
5965 shared library.<footnote>
5966 This wording allows the development files to be split into
5967 several packages, such as a separate architecture-independent
5968 <package><var>libraryname</var>-headers</package>, provided that
5969 the development package depends on all the required additional
5975 In case several development versions of a library exist, you may
5976 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5977 <ref id="conflicts">) to ensure that the user only installs one
5978 development version at a time (as different development versions are
5979 likely to have the same header files in them, which would cause a
5980 filename clash if both were unpacked).
5984 The development package should contain a symlink for the associated
5985 shared library without a version number. For example, the
5986 <package>libgdbm-dev</package> package should include a symlink
5987 from <file>/usr/lib/libgdbm.so</file> to
5988 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5989 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5990 <file>libgdbm.so</file> when compiling dynamically.
5994 If the package provides Ada Library Information
5995 (<file>*.ali</file>) files for use with GNAT, these files must be
5996 installed read-only (mode 0444) so that GNAT will not attempt to
5997 recompile them. This overrides the normal file mode requirements
5998 given in <ref id="permissions-owners">.
6002 <sect id="sharedlibs-intradeps">
6003 <heading>Dependencies between the packages of the same library</heading>
6006 Typically the development version should have an exact
6007 version dependency on the runtime library, to make sure that
6008 compilation and linking happens correctly. The
6009 <tt>${binary:Version}</tt> substitution variable can be
6010 useful for this purpose.
6012 Previously, <tt>${Source-Version}</tt> was used, but its name
6013 was confusing and it has been deprecated since dpkg 1.13.19.
6018 <sect id="sharedlibs-depends">
6019 <heading>Dependencies between the library and other
6023 If a package contains a binary or library which links to a
6024 shared library, we must ensure that, when the package is
6025 installed on the system, all of the libraries needed are also
6026 installed. These dependencies must be added to the binary
6027 package when it is built, since they may change based on which
6028 version of a shared library the binary or library was linked
6029 with even if there are no changes to the source of the binary
6030 (for example, symbol versions change, macros become functions or
6031 vice versa, or the binary package may determine at compile-time
6032 whether new library interfaces are available and can be called).
6033 To allow these dependencies to be constructed, shared libraries
6034 must provide either a <file>symbols</file> file or
6035 a <file>shlibs</file> file. These provide information on the
6036 package dependencies required to ensure the presence of
6037 interfaces provided by this library. Any package with binaries
6038 or libraries linking to a shared library must use these files to
6039 determine the required dependencies when it is built. Other
6040 packages which use a shared library (for example using
6041 <tt>dlopen()</tt>) should compute appropriate dependencies
6042 using these files at build time as well.
6046 The two mechanisms differ in the degree of detail that they
6047 provide. A <file>symbols</file> file documents, for each symbol
6048 exported by a library, the minimal version of the package any
6049 binary using this symbol will need. This is typically the
6050 version of the package in which the symbol was introduced. This
6051 information permits detailed analysis of the symbols used by a
6052 particular package and construction of an accurate dependency,
6053 but it requires the package maintainer to track more information
6054 about the shared library.
6058 A <file>shlibs</file> file, in contrast, only documents the last
6059 time the library ABI changed in any way. It only provides
6060 information about the library as a whole, not individual
6061 symbols. When a package is built using a shared library with
6062 only a <file>shlibs</file> file, the generated dependency will
6063 require a version of the shared library equal to or newer than
6064 the version of the last ABI change. This generates
6065 unnecessarily restrictive dependencies compared
6066 to <file>symbols</file> files if none of the symbols used by the
6067 package have changed. This, in turn, may make upgrades
6068 needlessly complex and unnecessarily restrict use of the package
6069 on systems with older versions of the shared libraries.
6073 <file>shlibs</file> files also only support a limited range of
6074 library SONAMEs, making it difficult to use <file>shlibs</file>
6075 files in some unusual corner cases.<footnote>
6076 A <file>shlibs</file> file represents an SONAME as a library
6077 name and version number, such as <tt>libfoo VERSION</tt>,
6078 instead of recording the actual SONAME. If the SONAME doesn't
6079 match one of the two expected formats
6080 (<tt>libfoo-VERSION.so</tt> or <tt>libfoo.so.VERSION</tt>), it
6081 cannot be represented.
6086 <file>symbols</file> files are therefore recommended for most
6087 shared library packages since they provide more accurate
6088 dependencies. For most C libraries, the additional detail
6089 required by <file>symbols</file> files is not too difficult to
6090 maintain. However, maintaining exhaustive symbols information
6091 for a C++ library can be quite onerous, so <file>shlibs</file>
6092 files may be more appropriate for most C++ libraries. Libraries
6093 with a corresponding udeb must also provide
6094 a <file>shlibs</file> file, since the udeb infrastructure does
6095 not use <file>symbols</file> files.
6098 <sect1 id="dpkg-shlibdeps">
6099 <heading>Generating dependencies on shared libraries</heading>
6102 When a package that contains any shared libraries or compiled
6103 binaries is built, it must run <prgn>dpkg-shlibdeps</prgn> on
6104 each shared library and compiled binary to determine the
6105 libraries used and hence the dependencies needed by the
6107 <prgn>dpkg-shlibdeps</prgn> will use a program
6108 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
6109 the libraries and the symbols in those libraries directly
6110 needed by the binaries or shared libraries in the package.
6112 To do this, put a call to <prgn>dpkg-shlibdeps</prgn> into
6113 your <file>debian/rules</file> file in the source package.
6114 List all of the compiled binaries, libraries, or loadable
6115 modules in your package.<footnote>
6116 The easiest way to call <prgn>dpkg-shlibdeps</prgn>
6117 correctly is to use a package helper framework such
6118 as <package>debhelper</package>. If you are
6119 using <package>debhelper</package>,
6120 the <prgn>dh_shlibdeps</prgn> program will do this work for
6121 you. It will also correctly handle multi-binary packages.
6123 <prgn>dpkg-shlibdeps</prgn> will use the <file>symbols</file>
6124 or <file>shlibs</file> files installed by the shared libraries
6125 to generate dependency information. The package must then
6126 provide a substitution variable into which the discovered
6127 dependency information can be placed.
6131 If you are creating a udeb for use in the Debian Installer,
6132 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6133 should use the dependency line of type <tt>udeb</tt> by adding
6134 the <tt>-tudeb</tt> option<footnote>
6135 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6136 will automatically add this option if it knows it is
6138 </footnote>. If there is no dependency line of
6139 type <tt>udeb</tt> in the <file>shlibs</file>
6140 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the
6141 regular dependency line.
6145 <prgn>dpkg-shlibdeps</prgn> puts the dependency information
6146 into the <file>debian/substvars</file> file by default, which
6147 is then used by <prgn>dpkg-gencontrol</prgn>. You will need
6148 to place a <tt>${shlibs:Depends}</tt> variable in
6149 the <tt>Depends</tt> field in the control file of every binary
6150 package built by this source package that contains compiled
6151 binaries, libraries, or loadable modules. If you have
6152 multiple binary packages, you will need to
6153 call <prgn>dpkg-shlibdeps</prgn> on each one which contains
6154 compiled libraries or binaries. For example, you could use
6155 the <tt>-T</tt> option to the <tt>dpkg</tt> utilities to
6156 specify a different <file>substvars</file> file for each
6157 binary package.<footnote>
6158 Again, <prgn>dh_shlibdeps</prgn>
6159 and <prgn>dh_gencontrol</prgn> will handle everything except
6160 the addition of the variable to the control file for you if
6161 you're using <package>debhelper</package>, including
6162 generating separate <file>substvars</file> files for each
6163 binary package and calling <prgn>dpkg-gencontrol</prgn> with
6164 the appropriate flags.
6169 For more details on <prgn>dpkg-shlibdeps</prgn>,
6170 see <manref name="dpkg-shlibdeps" section="1">.
6174 We say that a binary <tt>foo</tt> <em>directly</em> uses a
6175 library <tt>libbar</tt> if it is explicitly linked with that
6176 library (that is, the library is listed in the
6177 ELF <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
6178 to the link line when the binary is created). Other libraries
6179 that are needed by <tt>libbar</tt> are
6180 linked <em>indirectly</em> to <tt>foo</tt>, and the dynamic
6181 linker will load them automatically when it
6182 loads <tt>libbar</tt>. A package should depend on the
6183 libraries it directly uses, but not the libraries it only uses
6184 indirectly. The dependencies for the libraries used
6185 directly will automatically pull in the indirectly-used
6186 libraries. <prgn>dpkg-shlibdeps</prgn> will handle this logic
6187 automatically, but package maintainers need to be aware of
6188 this distinction between directly and indirectly using a
6189 library if they have to override its results for some reason.
6191 A good example of where this helps is the following. We
6192 could update <tt>libimlib</tt> with a new version that
6193 supports a new revision of a graphics format called dgf (but
6194 retaining the same major version number) and depends on a
6195 new library package <package>libdgf4</package> instead of
6196 the older <package>libdgf3</package>. If we
6197 used <prgn>ldd</prgn> to add dependencies for every library
6198 directly or indirectly linked with a binary, every package
6199 that uses <tt>libimlib</tt> would need to be recompiled so
6200 it would also depend on <package>libdgf4</package> in order
6201 to retire the older <package>libdgf3</package> package.
6202 Since dependencies are only added based on
6203 ELF <tt>NEEDED</tt> attribute, packages
6204 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
6205 having the dependency on an appropriate version
6206 of <tt>libdgf</tt> and do not need rebuilding.
6211 <sect1 id="sharedlibs-updates">
6212 <heading>Shared library ABI changes</heading>
6215 Maintaining a shared library package using
6216 either <file>symbols</file> or <file>shlibs</file> files
6217 requires being aware of the exposed ABI of the shared library
6218 and any changes to it. Both <file>symbols</file>
6219 and <file>shlibs</file> files record every change to the ABI
6220 of the shared library; <file>symbols</file> files do so per
6221 public symbol, whereas <file>shlibs</file> files record only
6222 the last change for the entire library.
6226 There are two types of ABI changes: ones that are
6227 backward-compatible and ones that are not. An ABI change is
6228 backward-compatible if any reasonable program or library that
6229 was linked with the previous version of the shared library
6230 will still work correctly with the new version of the shared
6232 An example of an "unreasonable" program is one that uses
6233 library interfaces that are documented as internal and
6234 unsupported. If the only programs or libraries affected by
6235 a change are "unreasonable" ones, other techniques, such as
6236 declaring <tt>Breaks</tt> relationships with affected
6237 packages or treating their usage of the library as bugs in
6238 those packages, may be appropriate instead of changing the
6239 SONAME. However, the default approach is to change the
6240 SONAME for any change to the ABI that could break a program.
6242 Adding new symbols to the shared library is a
6243 backward-compatible change. Removing symbols from the shared
6244 library is not. Changing the behavior of a symbol may or may
6245 not be backward-compatible depending on the change; for
6246 example, changing a function to accept a new enum constant not
6247 previously used by the library is generally
6248 backward-compatible, but changing the members of a struct that
6249 is passed into library functions is generally not unless the
6250 library takes special precautions to accept old versions of
6255 ABI changes that are not backward-compatible normally require
6256 changing the <tt>SONAME</tt> of the library and therefore the
6257 shared library package name, which forces rebuilding all
6258 packages using that shared library to update their
6259 dependencies and allow them to use the new version of the
6260 shared library. For more information,
6261 see <ref id="sharedlibs-runtime">. The remainder of this
6262 section will deal with backward-compatible changes.
6266 Backward-compatible changes require either updating or
6267 recording the <var>minimal-version</var> for that symbol
6268 in <file>symbols</file> files or updating the version in
6269 the <var>dependencies</var> in <file>shlibs</file> files. For
6270 more information on how to do this in the two formats, see
6271 <ref id="symbols"> and <ref id="shlibs">. Below are general
6272 rules that apply to both files.
6276 The easy case is when a public symbol is added. Simply add
6277 the version at which the symbol was introduced
6278 (for <file>symbols</file> files) or update the dependency
6279 version (for <file>shlibs</file>) files. But special care
6280 should be taken to update dependency versions when the
6281 behavior of a public symbol changes. This is easy to neglect,
6282 since there is no automated method of determining such
6283 changes, but failing to update versions in this case may
6284 result in binary packages with too-weak dependencies that will
6285 fail at runtime, possibly in ways that can cause security
6286 vulnerabilities. If the package maintainer believes that a
6287 symbol behavior change may have occurred but isn't sure, it's
6288 safer to update the version rather than leave it unmodified.
6289 This may result in unnecessarily strict dependencies, but it
6290 ensures that packages whose dependencies are satisfied will
6295 A common example of when a change to the dependency version
6296 is required is a function that takes an enum or struct
6297 argument that controls what the function does. For example:
6299 enum library_op { OP_FOO, OP_BAR };
6300 int library_do_operation(enum library_op);
6302 If a new operation, <tt>OP_BAZ</tt>, is added,
6303 the <var>minimal-version</var>
6304 of <tt>library_do_operation</tt> (for <file>symbols</file>
6305 files) or the version in the dependency for the shared library
6306 (for <file>shlibs</file> files) must be increased to the
6307 version at which <tt>OP_BAZ</tt> was introduced. Otherwise, a
6308 binary built against the new version of the library (having
6309 detected at compile-time that the library
6310 supports <tt>OP_BAZ</tt>) may be installed with a shared
6311 library that doesn't support <tt>OP_BAZ</tt> and will fail at
6312 runtime when it tries to pass <tt>OP_BAZ</tt> into this
6317 Dependency versions in either <file>symbols</file>
6318 or <file>shlibs</file> files normally should not contain the
6319 Debian revision of the package, since the library behavior is
6320 normally fixed for a particular upstream version and any
6321 Debian packaging of that upstream version will have the same
6322 behavior. In the rare case that the library behavior was
6323 changed in a particular Debian revision, appending <tt>~</tt>
6324 to the end of the version that includes the Debian revision is
6325 recommended, since this allows backports of the shared library
6326 package using the normal backport versioning convention to
6327 satisfy the dependency.
6331 <sect1 id="sharedlibs-symbols">
6332 <heading>The <tt>symbols</tt> system</heading>
6335 In the following sections, we will first describe where the
6336 various <file>symbols</file> files are to be found, then
6337 the <file>symbols</file> file format, and finally how to
6338 create <file>symbols</file> files if your package contains a
6342 <sect2 id="symbols-paths">
6343 <heading>The <file>symbols</file> files present on the
6347 <file>symbols</file> files for a shared library are normally
6348 provided by the shared library package as a control file,
6349 but there are several override paths that are checked first
6350 in case that information is wrong or missing. The following
6351 list gives them in the order in which they are read
6352 by <prgn>dpkg-shlibdeps</prgn> The first one that contains
6353 the required information is used.
6356 <p><file>debian/*/DEBIAN/symbols</file></p>
6359 During the package build, if the package itself
6360 contains shared libraries with <file>symbols</file>
6361 files, they will be generated in these staging
6362 directories by <prgn>dpkg-gensymbols</prgn>
6363 (see <ref id="providing-symbols">). <file>symbols</file>
6364 files found in the build tree take precedence
6365 over <file>symbols</file> files from other binary
6370 These files must exist
6371 before <prgn>dpkg-shlibdeps</prgn> is run or the
6372 dependencies of binaries and libraries from a source
6373 package on other libraries from that same source
6374 package will not be correct. In practice, this means
6375 that <prgn>dpkg-gensymbols</prgn> must be run
6376 before <prgn>dpkg-shlibdeps</prgn> during the package
6378 An example may clarify. Suppose the source
6379 package <tt>foo</tt> generates two binary
6380 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6381 When building the binary packages, the contents of
6382 the packages are staged in the
6383 directories <file>debian/libfoo2</file>
6384 and <file>debian/foo-runtime</file> respectively.
6385 (<file>debian/tmp</file> could be used instead of
6386 one of these.) Since <tt>libfoo2</tt> provides
6387 the <tt>libfoo</tt> shared library, it will contain
6388 a <tt>symbols</tt> file, which will be installed
6389 in <file>debian/libfoo2/DEBIAN/symbols</file>,
6390 eventually to be included as a control file in that
6391 package. When <prgn>dpkg-shlibdeps</prgn> is run on
6393 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6395 the <file>debian/libfoo2/DEBIAN/symbols</file> file
6396 to determine whether <tt>foo-prog</tt>'s library
6397 dependencies are satisfied by any of the libraries
6398 provided by <tt>libfoo2</tt>. Since those binaries
6399 were linked against the just-built shared library as
6400 part of the build process, the <file>symbols</file>
6401 file for the newly-built <tt>libfoo2</tt> must take
6402 precedence over a <file>symbols</file> file for any
6403 other <tt>libfoo2</tt> package already installed on
6411 <file>/etc/dpkg/symbols/<var>package</var>.symbols.<var>arch</var></file>
6412 and <file>/etc/dpkg/symbols/<var>package</var>.symbols</file>
6416 Per-system overrides of shared library dependencies.
6417 These files normally do not exist. They are
6418 maintained by the local system administrator and must
6419 not be created by any Debian package.
6424 <p><file>symbols</file> control files for packages
6425 installed on the system</p>
6428 The <file>symbols</file> control files for all the
6429 packages currently installed on the system are
6430 searched last. This will be the most common source of
6431 shared library dependency information. These are
6433 in <file>/var/lib/dpkg/info/*.symbols</file>, but
6434 packages should not rely on this and instead should
6435 use <tt>dpkg-query --control-path <var>package</var>
6436 symbols</tt> if for some reason these files need to be
6444 Be aware that if a <file>debian/shlibs.local</file> exists
6445 in the source package, it will override
6446 any <file>symbols</file> files. This is the only case where
6447 a <file>shlibs</file> is used despite <file>symbols</file>
6448 files being present. See <ref id="shlibs-paths">
6449 and <ref id="sharedlibs-shlibdeps"> for more information.
6453 <sect2 id="symbols">
6454 <heading>The <file>symbols</file> File Format</heading>
6457 The following documents the format of
6458 the <file>symbols</file> control file as included in binary
6459 packages. These files are built from
6460 template <file>symbols</file> files in the source package
6461 by <prgn>dpkg-gensymbols</prgn>. The template files support
6462 a richer syntax that allows <prgn>dpkg-gensymbols</prgn> to
6463 do some of the tedious work involved in
6464 maintaining <file>symbols</file> files, such as handling C++
6465 symbols or optional symbols that may not exist on particular
6466 architectures. When writing <file>symbols</file> files for
6467 a shared library package, refer
6468 to <manref name="dpkg-gensymbols" section="1"> for the
6473 A <file>symbols</file> may contain one or more entries, one
6474 for each shared library contained in the package
6475 corresponding to that <file>symbols</file>. Each entry has
6476 the following format:
6481 <var>library-soname</var> <var>main-dependency-template</var>
6482 [| <var>alternative-dependency-template</var>]
6484 [* <var>field-name</var>: <var>field-value</var>]
6486 <var>symbol</var> <var>minimal-version</var>[ <var>id-of-dependency-template</var> ]
6491 To explain this format, we'll use the the <tt>zlib1g</tt>
6492 package as an example, which (at the time of writing)
6494 library <file>/usr/lib/libz.so.1.2.3.4</file>. Mandatory
6495 lines will be described first, followed by optional lines.
6499 <var>library-soname</var> must contain exactly the value of
6500 the ELF <tt>SONAME</tt> attribute of the shared library. In
6501 our example, this is <tt>libz.so.1</tt>.<footnote>
6502 This can be determined by using the command
6503 <example compact="compact">
6504 readelf -d /usr/lib/libz.so.1.2.3.4 | grep SONAME
6510 <var>main-dependency-template</var> has the same syntax as a
6511 dependency field in a binary package control file, except
6512 that the string <tt>#MINVER#</tt> is replaced by a version
6513 restriction like <tt>(>= <var>version</var>)</tt> or by
6514 nothing if an unversioned dependency is deemed sufficient.
6515 The version restriction will be based on which symbols from
6516 the shared library are referenced and the version at which
6517 they were introduced (see below). In nearly all
6518 cases, <var>main-dependency-template</var> will
6519 be <tt><var>package</var> #MINVER#</tt>,
6520 where <var>package</var> is the name of the binary package
6521 containing the shared library. This adds a simple,
6522 possibly-versioned dependency on the shared library package.
6523 In some rare cases, such as when multiple packages provide
6524 the same shared library ABI, the dependency template may
6525 need to be more complex.
6529 In our example, the first line of
6530 the <tt>zlib1g</tt> <file>symbols</file> file would be:
6531 <example compact="compact">
6532 libz.so.1 zlib1g #MINVER#
6537 Each public symbol exported by the shared library must have
6538 a corresponding symbol line, indented by one
6539 space. <var>symbol</var> is the exported symbol (which, for
6540 C++, means the mangled symbol) followed by <tt>@</tt> and
6541 the symbol version, or the string <tt>Base</tt> if there is
6542 no symbol version. <var>minimal-version</var> is the most
6543 recent version of the shared library that changed the
6544 behavior of that symbol, whether by adding it, changing its
6545 function signature (the parameters, their types, or the
6546 return type), or changing its behavior in a way that is
6547 visible to a caller.
6548 <var>id-of-dependency-template</var> is an optional
6549 field that references
6550 an <var>alternative-dependency-template</var>; see below for
6555 For example, <tt>libz.so.1</tt> contains the
6556 symbols <tt>compress</tt>
6557 and <tt>compressBound</tt>. <tt>compress</tt> has no symbol
6558 version and last changed its behavior in upstream
6559 version <tt>1:1.1.4</tt>. <tt>compressBound</tt> has the
6560 symbol version <tt>ZLIB_1.2.0</tt>, was introduced in
6561 upstream version <tt>1:1.2.0</tt>, and has not changed its
6562 behavior. Its <file>symbols</file> file therefore contains
6564 <example compact="compact">
6565 compress@Base 1:1.1.4
6566 compressBound@ZLIB_1.2.0 1:1.2.0
6568 Packages using only <tt>compress</tt> would then get a
6569 dependency on <tt>zlib1g (>= 1:1.1.4)</tt>, but packages
6570 using <tt>compressBound</tt> would get a dependency
6571 on <tt>zlib1g (>= 1:1.2.0)</tt>.
6575 One or more <var>alternative-dependency-template</var> lines
6576 may be provided. These are used in cases where some symbols
6577 in the shared library should use one dependency template
6578 while others should use a different template. The
6579 alternative dependency templates are used only if a symbol
6580 line contains the <var>id-of-dependency-template</var>
6581 field. The first alternative dependency template is
6582 numbered 1, the second 2, and so forth.<footnote>
6583 An example of where this may be needed is with a library
6584 that implements the libGL interface. All GL
6585 implementations provide the same set of base interfaces,
6586 and then may provide some additional interfaces only used
6587 by programs that require that specific GL implementation.
6588 So, for example, libgl1-mesa-glx may use the
6589 following <file>symbols</file> file:
6592 | libgl1-mesa-glx #MINVER#
6593 publicGlSymbol@Base 6.3-1
6595 implementationSpecificSymbol@Base 6.5.2-7 1
6598 Binaries or shared libraries using
6599 only <tt>publicGlSymbol</tt> would depend only
6600 on <tt>libgl1</tt> (which may be provided by multiple
6602 using <tt>implementationSpecificSymbol</tt> would get a
6603 dependency on <tt>libgl1-mesa-glx (>= 6.5.2-7)</tt>
6608 Finally, the entry for the library may contain one or more
6609 metadata fields. Currently, the only
6610 supported <var>field-name</var>
6611 is <tt>Build-Depends-Package</tt>, whose value lists
6612 the <qref id="sharedlibs-dev">library development
6613 package</qref> on which packages using this shared library
6614 declare a build dependency. If this field is
6615 present, <prgn>dpkg-shlibdeps</prgn> uses it to ensure that
6616 the resulting binary package dependency on the shared
6617 library is at least as strict as the source package
6618 dependency on the shared library development
6620 This field should normally not be necessary, since if the
6621 behavior of any symbol has changed, the corresponding
6622 symbol <var>minimal-version</var> should have been
6623 increased. But including it makes the <tt>symbols</tt>
6624 system more robust by tightening the dependency in cases
6625 where the package using the shared library specifically
6626 requires at least a particular version of the shared
6627 library development package for some reason.
6629 For our example, the <tt>zlib1g</tt> <file>symbols</file>
6631 <example compact="compact">
6632 * Build-Depends-Package: zlib1g-dev
6637 Also see <manref name="deb-symbols" section="5">.
6641 <sect2 id="providing-symbols">
6642 <heading>Providing a <file>symbols</file> file</heading>
6645 If your package provides a shared library, you should
6646 arrange to include a <file>symbols</file> control file
6647 following the format described above in that package. You
6648 must include either a <file>symbols</file> control file or
6649 a <file>shlibs</file> control file.
6653 Normally, this is done by creating a <file>symbols</file> in
6655 named <file>debian/<var>package</var>.symbols</file>
6656 or <file>debian/symbols</file>, possibly
6657 with <file>.<var>arch</var></file> appended if the symbols
6658 information varies by architecture. This file may use the
6659 extended syntax documented in <manref name="dpkg-gensymbols"
6660 section="1">. Then, call <prgn>dpkg-gensymbols</prgn> as
6661 part of the package build process. It will
6662 create <file>symbols</file> files in the package staging
6663 area based on the binaries and libraries in the package
6664 staging area and the <file>symbols</file> files in the
6665 source package.<footnote>
6667 using <tt>debhelper</tt>, <prgn>dh_makeshlibs</prgn> will
6668 take care of calling either <prgn>dpkg-gensymbols</prgn>
6669 or generating a <file>shlibs</file> file as appropriate.
6674 Packages that provide <file>symbols</file> files must keep
6675 them up-to-date to ensure correct dependencies in packages
6676 that use the shared libraries. This means updating
6677 the <file>symbols</file> file whenever a new public symbol
6678 is added, changing the <var>minimal-version</var> field
6679 whenever a symbol changes behavior or signature in a
6680 backward-compatible way (see <ref id="sharedlibs-updates">),
6681 and changing the <var>library-soname</var>
6682 and <var>main-dependency-template</var>, and probably all of
6683 the <var>minimal-version</var> fields, when the library
6684 changes <tt>SONAME</tt>. Removing a public symbol from
6685 the <file>symbols</file> file because it's no longer
6686 provided by the library normally requires changing
6687 the <tt>SONAME</tt> of the library.
6688 See <ref id="sharedlibs-runtime"> for more information
6689 on <tt>SONAME</tt>s.
6694 <sect1 id="sharedlibs-shlibdeps">
6695 <heading>The <tt>shlibs</tt> system</heading>
6698 The <tt>shlibs</tt> system is a simpler alternative to
6699 the <tt>symbols</tt> system for declaring dependencies for
6700 shared libraries. It may be more appropriate for C++
6701 libraries and other cases where tracking individual symbols is
6702 too difficult. It predated the <tt>symbols</tt> system and is
6703 therefore frequently seen in older packages. It is also
6704 required for udebs, which do not support <tt>symbols</tt>.
6708 In the following sections, we will first describe where the
6709 various <file>shlibs</file> files are to be found, then how to
6710 use <prgn>dpkg-shlibdeps</prgn>, and finally
6711 the <file>shlibs</file> file format and how to create them.
6714 <sect2 id="shlibs-paths">
6715 <heading>The <file>shlibs</file> files present on the
6719 There are several places where <tt>shlibs</tt> files are
6720 found. The following list gives them in the order in which
6721 they are read by <prgn>dpkg-shlibdeps</prgn>. (The first
6722 one which gives the required information is used.)
6725 <p><file>debian/shlibs.local</file></p>
6728 This lists overrides for this package. This file
6729 should normally not be used, but may be needed
6730 temporarily in unusual situations to work around bugs
6731 in other packages, or in unusual cases where the
6732 normally declared dependency information in the
6733 installed <file>shlibs</file> file for a library
6734 cannot be used. This file overrides information
6735 obtained from any other source.
6740 <p><file>/etc/dpkg/shlibs.override</file></p>
6743 This lists global overrides. This list is normally
6744 empty. It is maintained by the local system
6750 <p><file>DEBIAN/shlibs</file> files in the "build
6754 These files are generated as part of the package build
6755 process and staged for inclusion as control files in
6756 the binary packages being built. They provide details
6757 of any shared libraries included in the same package.
6762 <p><file>shlibs</file> control files for packages
6763 installed on the system</p>
6766 The <file>shlibs</file> control files for all the
6767 packages currently installed on the system. These are
6769 in <file>/var/lib/dpkg/info/*.shlibs</file>, but
6770 packages should not rely on this and instead should
6771 use <tt>dpkg-query --control-path <var>package</var>
6772 shlibs</tt> if for some reason these files need to be
6778 <p><file>/etc/dpkg/shlibs.default</file></p>
6781 This file lists any shared libraries whose packages
6782 have failed to provide correct <file>shlibs</file>
6783 files. It was used when the <file>shlibs</file> setup
6784 was first introduced, but it is now normally empty.
6785 It is maintained by the <tt>dpkg</tt> maintainer.
6792 If a <file>symbols</file> file for a shared library package
6793 is available, <prgn>dpkg-shlibdeps</prgn> will always use it
6794 in preference to a <file>shlibs</file>, with the exception
6795 of <file>debian/shlibs.local</file>. The latter overrides
6796 any other <file>shlibs</file> or <file>symbols</file> files.
6801 <heading>The <file>shlibs</file> File Format</heading>
6804 Each <file>shlibs</file> file has the same format. Lines
6805 beginning with <tt>#</tt> are considered to be comments and
6806 are ignored. Each line is of the form:
6807 <example compact="compact">
6808 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6813 We will explain this by reference to the example of the
6814 <tt>zlib1g</tt> package, which (at the time of writing)
6816 library <file>/usr/lib/libz.so.1.2.3.4</file>.
6820 <var>type</var> is an optional element that indicates the
6821 type of package for which the line is valid. The only type
6822 currently in use is <tt>udeb</tt>. The colon and space
6823 after the type are required.
6827 <var>library-name</var> is the name of the shared library,
6828 in this case <tt>libz</tt>. (This must match the name part
6829 of the soname, see below.)
6833 <var>soname-version</var> is the version part of the
6834 ELF <tt>SONAME</tt> attribute of the library, determined the
6835 same way that the <var>soversion</var> component of the
6836 recommended shared library package name is determined.
6837 See <ref id="sharedlibs-runtime"> for the details.
6841 <var>dependencies</var> has the same syntax as a dependency
6842 field in a binary package control file. It should give
6843 details of which packages are required to satisfy a binary
6844 built against the version of the library contained in the
6845 package. See <ref id="depsyntax"> for details on the
6846 syntax, and <ref id="sharedlibs-updates"> for details on how
6847 to maintain the dependency version constraint.
6851 In our example, if the last change to the <tt>zlib1g</tt>
6852 package that could change behavior for a client of that
6853 library was in version <tt>1:1.2.3.3.dfsg-1</tt>, then
6854 the <tt>shlibs</tt> entry for this library could say:
6855 <example compact="compact">
6856 libz 1 zlib1g (>= 1:1.2.3.3.dfsg)
6858 This version restriction must be new enough that any binary
6859 built against the current version of the library will work
6860 with any version of the shared library that satisfies that
6865 As zlib1g also provides a udeb containing the shared
6866 library, there would also be a second line:
6867 <example compact="compact">
6868 udeb: libz 1 zlib1g-udeb (>= 1:1.2.3.3.dfsg)
6874 <heading>Providing a <file>shlibs</file> file</heading>
6877 To provide a <file>shlibs</file> file for a shared library
6878 binary package, create a <file>shlibs</file> file following
6879 the format described above and place it in
6880 the <file>DEBIAN</file> directory for that package during
6881 the build. It will then be included as a control file for
6882 that package<footnote>
6883 This is what <prgn>dh_makeshlibs</prgn> in
6884 the <package>debhelper</package> suite does. If your
6885 package also has a udeb that provides a shared
6886 library, <prgn>dh_makeshlibs</prgn> can automatically
6887 generate the <tt>udeb:</tt> lines if you specify the name
6888 of the udeb with the <tt>--add-udeb</tt> option.
6893 Since <prgn>dpkg-shlibdeps</prgn> reads
6894 the <file>DEBIAN/shlibs</file> files in all of the binary
6895 packages being built from this source package, all of
6896 the <file>DEBIAN/shlibs</file> files should be installed
6897 before <prgn>dpkg-shlibdeps</prgn> is called on any of the
6906 <chapt id="opersys"><heading>The Operating System</heading>
6909 <heading>File system hierarchy</heading>
6913 <heading>File System Structure</heading>
6916 The location of all files and directories must comply with the
6917 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6918 exceptions noted below, and except where doing so would
6919 violate other terms of Debian Policy. The following
6920 exceptions to the FHS apply:
6925 The FHS requirement that architecture-independent
6926 application-specific static files be located in
6927 <file>/usr/share</file> is relaxed to a suggestion.
6929 In particular, a subdirectory of <file>/usr/lib</file> may
6930 be used by a package (or a collection of packages) to hold a
6931 mixture of architecture-independent and
6932 architecture-dependent files. However, when a directory is
6933 entirely composed of architecture-independent files, it
6934 should be located in <file>/usr/share</file>.
6939 The optional rules related to user specific
6940 configuration files for applications are stored in
6941 the user's home directory are relaxed. It is
6942 recommended that such files start with the
6943 '<tt>.</tt>' character (a "dot file"), and if an
6944 application needs to create more than one dot file
6945 then the preferred placement is in a subdirectory
6946 with a name starting with a '.' character, (a "dot
6947 directory"). In this case it is recommended the
6948 configuration files not start with the '.'
6954 The requirement for amd64 to use <file>/lib64</file>
6955 for 64 bit binaries is removed.
6960 The requirement for object files, internal binaries, and
6961 libraries, including <file>libc.so.*</file>, to be located
6962 directly under <file>/lib{,32}</file> and
6963 <file>/usr/lib{,32}</file> is amended, permitting files
6964 to instead be installed to
6965 <file>/lib/<var>triplet</var></file> and
6966 <file>/usr/lib/<var>triplet</var></file>, where
6967 <tt><var>triplet</var></tt> is the value returned by
6968 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6969 architecture of the package. Packages may <em>not</em>
6970 install files to any <var>triplet</var> path other
6971 than the one matching the architecture of that package;
6972 for instance, an <tt>Architecture: amd64</tt> package
6973 containing 32-bit x86 libraries may not install these
6974 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6976 This is necessary in order to reserve the directories for
6977 use in cross-installation of library packages from other
6978 architectures, as part of <tt>multiarch</tt>.
6982 The requirement for C and C++ headers files to be
6983 accessible through the search path
6984 <file>/usr/include/</file> is amended, permitting files to
6985 be accessible through the search path
6986 <file>/usr/include/<var>triplet</var></file> where
6987 <tt><var>triplet</var></tt> is as above. <footnote>
6988 This is necessary for architecture-dependant headers
6989 file to coexist in a <tt>multiarch</tt> setup.
6993 Applications may also use a single subdirectory under
6994 <file>/usr/lib/<var>triplet</var></file>.
6997 The execution time linker/loader, ld*, must still be made
6998 available in the existing location under /lib or /lib64
6999 since this is part of the ELF ABI for the architecture.
7004 The requirement that
7005 <file>/usr/local/share/man</file> be "synonymous"
7006 with <file>/usr/local/man</file> is relaxed to a
7011 The requirement that windowmanagers with a single
7012 configuration file call it <file>system.*wmrc</file>
7013 is removed, as is the restriction that the window
7014 manager subdirectory be named identically to the
7015 window manager name itself.
7020 The requirement that boot manager configuration
7021 files live in <file>/etc</file>, or at least are
7022 symlinked there, is relaxed to a recommendation.
7027 The additional directory <file>/run</file> in the root
7028 file system is allowed. <file>/run</file>
7029 replaces <file>/var/run</file>, and the
7030 subdirectory <file>/run/lock</file>
7031 replaces <file>/var/lock</file>, with
7032 the <file>/var</file> directories replaced by symlinks
7033 for backwards compatibility. <file>/run</file>
7034 and <file>/run/lock</file> must follow all of the
7035 requirements in the FHS for <file>/var/run</file>
7036 and <file>/var/lock</file>, respectively, such as file
7037 naming conventions, file format requirements, or the
7038 requirement that files be cleared during the boot
7039 process. Files and directories residing
7040 in <file>/run</file> should be stored on a temporary
7044 Packages must not assume the <file>/run</file>
7045 directory exists or is usable without a dependency
7046 on <tt>initscripts (>= 2.88dsf-13.3)</tt> until the
7047 stable release of Debian supports <file>/run</file>.
7052 The <file>/sys</file> directory in the root filesystem is
7053 additionally allowed. <footnote>This directory is used as
7054 mount point to mount virtual filesystems to get access to
7055 kernel information.</footnote>
7060 The <file>/var/www</file> directory is additionally allowed.
7065 The requirement for <file>/usr/local/lib<qual></file>
7066 to exist if <file>/lib<qual></file> or
7067 <file>/usr/lib<qual></file> exists (where
7068 <file>lib<qual></file> is a variant of
7069 <file>lib</file> such as <file>lib32</file> or
7070 <file>lib64</file>) is removed.
7075 On GNU/Hurd systems, the following additional
7076 directories are allowed in the root
7077 filesystem: <file>/hurd</file>
7078 and <file>/servers</file>.<footnote>
7079 These directories are used to store translators and as
7080 a set of standard names for mount points,
7089 The version of this document referred here can be
7090 found in the <tt>debian-policy</tt> package or on <url
7091 id="http://www.debian.org/doc/packaging-manuals/fhs/"
7092 name="FHS (Debian copy)"> alongside this manual (or, if
7093 you have the <package>debian-policy</package> installed,
7095 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
7096 (local copy)">). The
7097 latest version, which may be a more recent version, may
7099 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
7100 Specific questions about following the standard may be
7101 asked on the <tt>debian-devel</tt> mailing list, or
7102 referred to the FHS mailing list (see the
7103 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
7109 <heading>Site-specific programs</heading>
7112 As mandated by the FHS, packages must not place any
7113 files in <file>/usr/local</file>, either by putting them in
7114 the file system archive to be unpacked by <prgn>dpkg</prgn>
7115 or by manipulating them in their maintainer scripts.
7119 However, the package may create empty directories below
7120 <file>/usr/local</file> so that the system administrator knows
7121 where to place site-specific files. These are not
7122 directories <em>in</em> <file>/usr/local</file>, but are
7123 children of directories in <file>/usr/local</file>. These
7124 directories (<file>/usr/local/*/dir/</file>)
7125 should be removed on package removal if they are
7130 Note that this applies only to
7131 directories <em>below</em> <file>/usr/local</file>,
7132 not <em>in</em> <file>/usr/local</file>. Packages must
7133 not create sub-directories in the
7134 directory <file>/usr/local</file> itself, except those
7135 listed in FHS, section 4.5. However, you may create
7136 directories below them as you wish. You must not remove
7137 any of the directories listed in 4.5, even if you created
7142 Since <file>/usr/local</file> can be mounted read-only from a
7143 remote server, these directories must be created and
7144 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
7145 maintainer scripts and not be included in the
7146 <file>.deb</file> archive. These scripts must not fail if
7147 either of these operations fail.
7151 For example, the <tt>emacsen-common</tt> package could
7152 contain something like
7153 <example compact="compact">
7154 if [ ! -e /usr/local/share/emacs ]; then
7155 if mkdir /usr/local/share/emacs 2>/dev/null; then
7156 if chown root:staff /usr/local/share/emacs; then
7157 chmod 2775 /usr/local/share/emacs || true
7162 in its <prgn>postinst</prgn> script, and
7163 <example compact="compact">
7164 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
7165 rmdir /usr/local/share/emacs 2>/dev/null || true
7167 in the <prgn>prerm</prgn> script. (Note that this form is
7168 used to ensure that if the script is interrupted, the
7169 directory <file>/usr/local/share/emacs</file> will still be
7174 If you do create a directory in <file>/usr/local</file> for
7175 local additions to a package, you should ensure that
7176 settings in <file>/usr/local</file> take precedence over the
7177 equivalents in <file>/usr</file>.
7181 However, because <file>/usr/local</file> and its contents are
7182 for exclusive use of the local administrator, a package
7183 must not rely on the presence or absence of files or
7184 directories in <file>/usr/local</file> for normal operation.
7188 The <file>/usr/local</file> directory itself and all the
7189 subdirectories created by the package should (by default) have
7190 permissions 2775 (group-writable and set-group-id) and be
7191 owned by <tt>root:staff</tt>.
7196 <heading>The system-wide mail directory</heading>
7198 The system-wide mail directory
7199 is <file>/var/mail</file>. This directory is part of the
7200 base system and should not be owned by any particular mail
7201 agents. The use of the old
7202 location <file>/var/spool/mail</file> is deprecated, even
7203 though the spool may still be physically located there.
7207 <sect1 id="fhs-run">
7208 <heading><file>/run</file> and <file>/run/lock</file></heading>
7211 The directory <file>/run</file> is cleared at boot, normally
7212 by being a mount point for a temporary file system. Packages
7213 therefore must not assume that any files or directories
7214 under <file>/run</file> other than <file>/run/lock</file>
7215 exist unless the package has arranged to create those files or
7216 directories since the last reboot. Normally, this is done by
7217 the package via an init script. See <ref id="writing-init">
7218 for more information.
7222 Packages must not include files or directories
7223 under <file>/run</file>, or under the
7224 older <file>/var/run</file> and <file>/var/lock</file> paths.
7225 The latter paths will normally be symlinks or other
7226 redirections to <file>/run</file> for backwards compatibility.
7232 <heading>Users and groups</heading>
7235 <heading>Introduction</heading>
7237 The Debian system can be configured to use either plain or
7242 Some user ids (UIDs) and group ids (GIDs) are reserved
7243 globally for use by certain packages. Because some
7244 packages need to include files which are owned by these
7245 users or groups, or need the ids compiled into binaries,
7246 these ids must be used on any Debian system only for the
7247 purpose for which they are allocated. This is a serious
7248 restriction, and we should avoid getting in the way of
7249 local administration policies. In particular, many sites
7250 allocate users and/or local system groups starting at 100.
7254 Apart from this we should have dynamically allocated ids,
7255 which should by default be arranged in some sensible
7256 order, but the behavior should be configurable.
7260 Packages other than <tt>base-passwd</tt> must not modify
7261 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
7262 <file>/etc/group</file> or <file>/etc/gshadow</file>.
7267 <heading>UID and GID classes</heading>
7269 The UID and GID numbers are divided into classes as
7275 Globally allocated by the Debian project, the same
7276 on every Debian system. These ids will appear in
7277 the <file>passwd</file> and <file>group</file> files of all
7278 Debian systems, new ids in this range being added
7279 automatically as the <tt>base-passwd</tt> package is
7284 Packages which need a single statically allocated
7285 uid or gid should use one of these; their
7286 maintainers should ask the <tt>base-passwd</tt>
7294 Dynamically allocated system users and groups.
7295 Packages which need a user or group, but can have
7296 this user or group allocated dynamically and
7297 differently on each system, should use <tt>adduser
7298 --system</tt> to create the group and/or user.
7299 <prgn>adduser</prgn> will check for the existence of
7300 the user or group, and if necessary choose an unused
7301 id based on the ranges specified in
7302 <file>adduser.conf</file>.
7306 <tag>1000-59999:</tag>
7309 Dynamically allocated user accounts. By default
7310 <prgn>adduser</prgn> will choose UIDs and GIDs for
7311 user accounts in this range, though
7312 <file>adduser.conf</file> may be used to modify this
7317 <tag>60000-64999:</tag>
7320 Globally allocated by the Debian project, but only
7321 created on demand. The ids are allocated centrally
7322 and statically, but the actual accounts are only
7323 created on users' systems on demand.
7327 These ids are for packages which are obscure or
7328 which require many statically-allocated ids. These
7329 packages should check for and create the accounts in
7330 <file>/etc/passwd</file> or <file>/etc/group</file> (using
7331 <prgn>adduser</prgn> if it has this facility) if
7332 necessary. Packages which are likely to require
7333 further allocations should have a "hole" left after
7334 them in the allocation, to give them room to
7339 <tag>65000-65533:</tag>
7347 User <tt>nobody</tt>. The corresponding gid refers
7348 to the group <tt>nogroup</tt>.
7355 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
7356 not</em> be used, because it is the error return
7365 <sect id="sysvinit">
7366 <heading>System run levels and <file>init.d</file> scripts</heading>
7368 <sect1 id="/etc/init.d">
7369 <heading>Introduction</heading>
7372 The <file>/etc/init.d</file> directory contains the scripts
7373 executed by <prgn>init</prgn> at boot time and when the
7374 init state (or "runlevel") is changed (see <manref
7375 name="init" section="8">).
7379 There are at least two different, yet functionally
7380 equivalent, ways of handling these scripts. For the sake
7381 of simplicity, this document describes only the symbolic
7382 link method. However, it must not be assumed by maintainer
7383 scripts that this method is being used, and any automated
7384 manipulation of the various runlevel behaviors by
7385 maintainer scripts must be performed using
7386 <prgn>update-rc.d</prgn> as described below and not by
7387 manually installing or removing symlinks. For information
7388 on the implementation details of the other method,
7389 implemented in the <tt>file-rc</tt> package, please refer
7390 to the documentation of that package.
7394 These scripts are referenced by symbolic links in the
7395 <file>/etc/rc<var>n</var>.d</file> directories. When changing
7396 runlevels, <prgn>init</prgn> looks in the directory
7397 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
7398 execute, where <tt><var>n</var></tt> is the runlevel that
7399 is being changed to, or <tt>S</tt> for the boot-up
7404 The names of the links all have the form
7405 <file>S<var>mm</var><var>script</var></file> or
7406 <file>K<var>mm</var><var>script</var></file> where
7407 <var>mm</var> is a two-digit number and <var>script</var>
7408 is the name of the script (this should be the same as the
7409 name of the actual script in <file>/etc/init.d</file>).
7413 When <prgn>init</prgn> changes runlevel first the targets
7414 of the links whose names start with a <tt>K</tt> are
7415 executed, each with the single argument <tt>stop</tt>,
7416 followed by the scripts prefixed with an <tt>S</tt>, each
7417 with the single argument <tt>start</tt>. (The links are
7418 those in the <file>/etc/rc<var>n</var>.d</file> directory
7419 corresponding to the new runlevel.) The <tt>K</tt> links
7420 are responsible for killing services and the <tt>S</tt>
7421 link for starting services upon entering the runlevel.
7425 For example, if we are changing from runlevel 2 to
7426 runlevel 3, init will first execute all of the <tt>K</tt>
7427 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
7428 all of the <tt>S</tt> prefixed scripts in that directory.
7429 The links starting with <tt>K</tt> will cause the
7430 referred-to file to be executed with an argument of
7431 <tt>stop</tt>, and the <tt>S</tt> links with an argument
7436 The two-digit number <var>mm</var> is used to determine
7437 the order in which to run the scripts: low-numbered links
7438 have their scripts run first. For example, the
7439 <tt>K20</tt> scripts will be executed before the
7440 <tt>K30</tt> scripts. This is used when a certain service
7441 must be started before another. For example, the name
7442 server <prgn>bind</prgn> might need to be started before
7443 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
7444 can set up its access lists. In this case, the script
7445 that starts <prgn>bind</prgn> would have a lower number
7446 than the script that starts <prgn>inn</prgn> so that it
7448 <example compact="compact">
7455 The two runlevels 0 (halt) and 6 (reboot) are slightly
7456 different. In these runlevels, the links with an
7457 <tt>S</tt> prefix are still called after those with a
7458 <tt>K</tt> prefix, but they too are called with the single
7459 argument <tt>stop</tt>.
7463 <sect1 id="writing-init">
7464 <heading>Writing the scripts</heading>
7467 Packages that include daemons for system services should
7468 place scripts in <file>/etc/init.d</file> to start or stop
7469 services at boot time or during a change of runlevel.
7470 These scripts should be named
7471 <file>/etc/init.d/<var>package</var></file>, and they should
7472 accept one argument, saying what to do:
7475 <tag><tt>start</tt></tag>
7476 <item>start the service,</item>
7478 <tag><tt>stop</tt></tag>
7479 <item>stop the service,</item>
7481 <tag><tt>restart</tt></tag>
7482 <item>stop and restart the service if it's already running,
7483 otherwise start the service</item>
7485 <tag><tt>reload</tt></tag>
7486 <item><p>cause the configuration of the service to be
7487 reloaded without actually stopping and restarting
7490 <tag><tt>force-reload</tt></tag>
7491 <item>cause the configuration to be reloaded if the
7492 service supports this, otherwise restart the
7496 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
7497 <tt>force-reload</tt> options should be supported by all
7498 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
7503 The <file>init.d</file> scripts must ensure that they will
7504 behave sensibly (i.e., returning success and not starting
7505 multiple copies of a service) if invoked with <tt>start</tt>
7506 when the service is already running, or with <tt>stop</tt>
7507 when it isn't, and that they don't kill unfortunately-named
7508 user processes. The best way to achieve this is usually to
7509 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
7514 Be careful of using <tt>set -e</tt> in <file>init.d</file>
7515 scripts. Writing correct <file>init.d</file> scripts requires
7516 accepting various error exit statuses when daemons are already
7517 running or already stopped without aborting
7518 the <file>init.d</file> script, and common <file>init.d</file>
7519 function libraries are not safe to call with <tt>set -e</tt>
7521 <tt>/lib/lsb/init-functions</tt>, which assists in writing
7522 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
7523 in effect and echoing status messages to the console fails,
7525 </footnote>. For <tt>init.d</tt> scripts, it's often easier
7526 to not use <tt>set -e</tt> and instead check the result of
7527 each command separately.
7531 If a service reloads its configuration automatically (as
7532 in the case of <prgn>cron</prgn>, for example), the
7533 <tt>reload</tt> option of the <file>init.d</file> script
7534 should behave as if the configuration has been reloaded
7539 The <file>/etc/init.d</file> scripts must be treated as
7540 configuration files, either (if they are present in the
7541 package, that is, in the .deb file) by marking them as
7542 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
7543 by managing them correctly in the maintainer scripts (see
7544 <ref id="config-files">). This is important since we want
7545 to give the local system administrator the chance to adapt
7546 the scripts to the local system, e.g., to disable a
7547 service without de-installing the package, or to specify
7548 some special command line options when starting a service,
7549 while making sure their changes aren't lost during the next
7554 These scripts should not fail obscurely when the
7555 configuration files remain but the package has been
7556 removed, as configuration files remain on the system after
7557 the package has been removed. Only when <prgn>dpkg</prgn>
7558 is executed with the <tt>--purge</tt> option will
7559 configuration files be removed. In particular, as the
7560 <file>/etc/init.d/<var>package</var></file> script itself is
7561 usually a <tt>conffile</tt>, it will remain on the system
7562 if the package is removed but not purged. Therefore, you
7563 should include a <tt>test</tt> statement at the top of the
7565 <example compact="compact">
7566 test -f <var>program-executed-later-in-script</var> || exit 0
7571 Often there are some variables in the <file>init.d</file>
7572 scripts whose values control the behavior of the scripts,
7573 and which a system administrator is likely to want to
7574 change. As the scripts themselves are frequently
7575 <tt>conffile</tt>s, modifying them requires that the
7576 administrator merge in their changes each time the package
7577 is upgraded and the <tt>conffile</tt> changes. To ease
7578 the burden on the system administrator, such configurable
7579 values should not be placed directly in the script.
7580 Instead, they should be placed in a file in
7581 <file>/etc/default</file>, which typically will have the same
7582 base name as the <file>init.d</file> script. This extra file
7583 should be sourced by the script when the script runs. It
7584 must contain only variable settings and comments in SUSv3
7585 <prgn>sh</prgn> format. It may either be a
7586 <tt>conffile</tt> or a configuration file maintained by
7587 the package maintainer scripts. See <ref id="config-files">
7592 To ensure that vital configurable values are always
7593 available, the <file>init.d</file> script should set default
7594 values for each of the shell variables it uses, either
7595 before sourcing the <file>/etc/default/</file> file or
7596 afterwards using something like the <tt>:
7597 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
7598 script must behave sensibly and not fail if the
7599 <file>/etc/default</file> file is deleted.
7603 Files and directories under <file>/run</file>, including ones
7604 referred to via the compatibility paths <file>/var/run</file>
7605 and <file>/var/lock</file>, are normally stored on a temporary
7606 filesystem and are normally not persistent across a reboot.
7607 The <file>init.d</file> scripts must handle this correctly.
7608 This will typically mean creating any required subdirectories
7609 dynamically when the <file>init.d</file> script is run.
7610 See <ref id="fhs-run"> for more information.
7615 <heading>Interfacing with the initscript system</heading>
7618 Maintainers should use the abstraction layer provided by
7619 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
7620 programs to deal with initscripts in their packages'
7621 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
7622 and <prgn>postrm</prgn>.
7626 Directly managing the /etc/rc?.d links and directly
7627 invoking the <file>/etc/init.d/</file> initscripts should
7628 be done only by packages providing the initscript
7629 subsystem (such as <prgn>sysv-rc</prgn> and
7630 <prgn>file-rc</prgn>).
7634 <heading>Managing the links</heading>
7637 The program <prgn>update-rc.d</prgn> is provided for
7638 package maintainers to arrange for the proper creation and
7639 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
7640 or their functional equivalent if another method is being
7641 used. This may be used by maintainers in their packages'
7642 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
7646 You must not include any <file>/etc/rc<var>n</var>.d</file>
7647 symbolic links in the actual archive or manually create or
7648 remove the symbolic links in maintainer scripts; you must
7649 use the <prgn>update-rc.d</prgn> program instead. (The
7650 former will fail if an alternative method of maintaining
7651 runlevel information is being used.) You must not include
7652 the <file>/etc/rc<var>n</var>.d</file> directories themselves
7653 in the archive either. (Only the <tt>sysvinit</tt>
7658 By default <prgn>update-rc.d</prgn> will start services in
7659 each of the multi-user state runlevels (2, 3, 4, and 5)
7660 and stop them in the halt runlevel (0), the single-user
7661 runlevel (1) and the reboot runlevel (6). The system
7662 administrator will have the opportunity to customize
7663 runlevels by simply adding, moving, or removing the
7664 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
7665 symbolic links are being used, or by modifying
7666 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
7671 To get the default behavior for your package, put in your
7672 <prgn>postinst</prgn> script
7673 <example compact="compact">
7674 update-rc.d <var>package</var> defaults
7676 and in your <prgn>postrm</prgn>
7677 <example compact="compact">
7678 if [ "$1" = purge ]; then
7679 update-rc.d <var>package</var> remove
7681 </example>. Note that if your package changes runlevels
7682 or priority, you may have to remove and recreate the links,
7683 since otherwise the old links may persist. Refer to the
7684 documentation of <prgn>update-rc.d</prgn>.
7688 This will use a default sequence number of 20. If it does
7689 not matter when or in which order the <file>init.d</file>
7690 script is run, use this default. If it does, then you
7691 should talk to the maintainer of the <prgn>sysvinit</prgn>
7692 package or post to <tt>debian-devel</tt>, and they will
7693 help you choose a number.
7697 For more information about using <tt>update-rc.d</tt>,
7698 please consult its man page <manref name="update-rc.d"
7704 <heading>Running initscripts</heading>
7706 The program <prgn>invoke-rc.d</prgn> is provided to make
7707 it easier for package maintainers to properly invoke an
7708 initscript, obeying runlevel and other locally-defined
7709 constraints that might limit a package's right to start,
7710 stop and otherwise manage services. This program may be
7711 used by maintainers in their packages' scripts.
7715 The package maintainer scripts must use
7716 <prgn>invoke-rc.d</prgn> to invoke the
7717 <file>/etc/init.d/*</file> initscripts, instead of
7718 calling them directly.
7722 By default, <prgn>invoke-rc.d</prgn> will pass any
7723 action requests (start, stop, reload, restart...) to the
7724 <file>/etc/init.d</file> script, filtering out requests
7725 to start or restart a service out of its intended
7730 Most packages will simply need to change:
7731 <example compact="compact">/etc/init.d/<package>
7732 <action></example> in their <prgn>postinst</prgn>
7733 and <prgn>prerm</prgn> scripts to:
7734 <example compact="compact">
7735 if which invoke-rc.d >/dev/null 2>&1; then
7736 invoke-rc.d <var>package</var> <action>
7738 /etc/init.d/<var>package</var> <action>
7744 A package should register its initscript services using
7745 <prgn>update-rc.d</prgn> before it tries to invoke them
7746 using <prgn>invoke-rc.d</prgn>. Invocation of
7747 unregistered services may fail.
7751 For more information about using
7752 <prgn>invoke-rc.d</prgn>, please consult its man page
7753 <manref name="invoke-rc.d" section="8">.
7759 <heading>Boot-time initialization</heading>
7762 There used to be another directory, <file>/etc/rc.boot</file>,
7763 which contained scripts which were run once per machine
7764 boot. This has been deprecated in favour of links from
7765 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7766 described in <ref id="/etc/init.d">. Packages must not
7767 place files in <file>/etc/rc.boot</file>.
7772 <heading>Example</heading>
7775 An example on which you can base your
7776 <file>/etc/init.d</file> scripts is found in
7777 <file>/etc/init.d/skeleton</file>.
7784 <heading>Console messages from <file>init.d</file> scripts</heading>
7787 This section describes the formats to be used for messages
7788 written to standard output by the <file>/etc/init.d</file>
7789 scripts. The intent is to improve the consistency of
7790 Debian's startup and shutdown look and feel. For this
7791 reason, please look very carefully at the details. We want
7792 the messages to have the same format in terms of wording,
7793 spaces, punctuation and case of letters.
7797 Here is a list of overall rules that should be used for
7798 messages generated by <file>/etc/init.d</file> scripts.
7804 The message should fit in one line (fewer than 80
7805 characters), start with a capital letter and end with
7806 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7810 If the script is performing some time consuming task in
7811 the background (not merely starting or stopping a
7812 program, for instance), an ellipsis (three dots:
7813 <tt>...</tt>) should be output to the screen, with no
7814 leading or tailing whitespace or line feeds.
7818 The messages should appear as if the computer is telling
7819 the user what it is doing (politely :-), but should not
7820 mention "it" directly. For example, instead of:
7821 <example compact="compact">
7822 I'm starting network daemons: nfsd mountd.
7824 the message should say
7825 <example compact="compact">
7826 Starting network daemons: nfsd mountd.
7833 <tt>init.d</tt> script should use the following standard
7834 message formats for the situations enumerated below.
7840 <p>When daemons are started</p>
7843 If the script starts one or more daemons, the output
7844 should look like this (a single line, no leading
7846 <example compact="compact">
7847 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7849 The <var>description</var> should describe the
7850 subsystem the daemon or set of daemons are part of,
7851 while <var>daemon-1</var> up to <var>daemon-n</var>
7852 denote each daemon's name (typically the file name of
7857 For example, the output of <file>/etc/init.d/lpd</file>
7859 <example compact="compact">
7860 Starting printer spooler: lpd.
7865 This can be achieved by saying
7866 <example compact="compact">
7867 echo -n "Starting printer spooler: lpd"
7868 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7871 in the script. If there are more than one daemon to
7872 start, the output should look like this:
7873 <example compact="compact">
7874 echo -n "Starting remote file system services:"
7875 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7876 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7877 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7880 This makes it possible for the user to see what is
7881 happening and when the final daemon has been started.
7882 Care should be taken in the placement of white spaces:
7883 in the example above the system administrators can
7884 easily comment out a line if they don't want to start
7885 a specific daemon, while the displayed message still
7891 <p>When a system parameter is being set</p>
7894 If you have to set up different system parameters
7895 during the system boot, you should use this format:
7896 <example compact="compact">
7897 Setting <var>parameter</var> to "<var>value</var>".
7902 You can use a statement such as the following to get
7904 <example compact="compact">
7905 echo "Setting DNS domainname to \"$domainname\"."
7910 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7911 for the left and right quotation marks. A grave accent
7912 (<tt>`</tt>) is not a quote character; neither is an
7913 apostrophe (<tt>'</tt>).
7918 <p>When a daemon is stopped or restarted</p>
7921 When you stop or restart a daemon, you should issue a
7922 message identical to the startup message, except that
7923 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7924 or <tt>Restarting</tt> respectively.
7928 For example, stopping the printer daemon will look like
7930 <example compact="compact">
7931 Stopping printer spooler: lpd.
7937 <p>When something is executed</p>
7940 There are several examples where you have to run a
7941 program at system startup or shutdown to perform a
7942 specific task, for example, setting the system's clock
7943 using <prgn>netdate</prgn> or killing all processes
7944 when the system shuts down. Your message should look
7946 <example compact="compact">
7947 Doing something very useful...done.
7949 You should print the <tt>done.</tt> immediately after
7950 the job has been completed, so that the user is
7951 informed why they have to wait. You can get this
7953 <example compact="compact">
7954 echo -n "Doing something very useful..."
7963 <p>When the configuration is reloaded</p>
7966 When a daemon is forced to reload its configuration
7967 files you should use the following format:
7968 <example compact="compact">
7969 Reloading <var>description</var> configuration...done.
7971 where <var>description</var> is the same as in the
7972 daemon starting message.
7979 <sect id="cron-jobs">
7980 <heading>Cron jobs</heading>
7983 Packages must not modify the configuration file
7984 <file>/etc/crontab</file>, and they must not modify the files in
7985 <file>/var/spool/cron/crontabs</file>.
7989 If a package wants to install a job that has to be executed via
7990 cron, it should place a file named as specified
7991 in <ref id="cron-files"> into one or more of the following
7993 <example compact="compact">
7999 As these directory names imply, the files within them are
8000 executed on an hourly, daily, weekly, or monthly basis,
8001 respectively. The exact times are listed in
8002 <file>/etc/crontab</file>.
8006 All files installed in any of these directories must be
8007 scripts (e.g., shell scripts or Perl scripts) so that they
8008 can easily be modified by the local system administrator.
8009 In addition, they must be treated as configuration files.
8013 If a certain job has to be executed at some other frequency or
8014 at a specific time, the package should install a file in
8015 <file>/etc/cron.d</file> with a name as specified
8016 in <ref id="cron-files">. This file uses the same syntax
8017 as <file>/etc/crontab</file> and is processed
8018 by <prgn>cron</prgn> automatically. The file must also be
8019 treated as a configuration file. (Note that entries in the
8020 <file>/etc/cron.d</file> directory are not handled by
8021 <prgn>anacron</prgn>. Thus, you should only use this
8022 directory for jobs which may be skipped if the system is not
8027 Unlike <file>crontab</file> files described in the IEEE Std
8028 1003.1-2008 (POSIX.1) available from
8029 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
8030 name="The Open Group">, the files in
8031 <file>/etc/cron.d</file> and the file
8032 <file>/etc/crontab</file> have seven fields; namely:
8034 <item>Minute [0,59]</item>
8035 <item>Hour [0,23]</item>
8036 <item>Day of the month [1,31]</item>
8037 <item>Month of the year [1,12]</item>
8038 <item>Day of the week ([0,6] with 0=Sunday)</item>
8039 <item>Username</item>
8040 <item>Command to be run</item>
8042 Ranges of numbers are allowed. Ranges are two numbers
8043 separated with a hyphen. The specified range is inclusive.
8044 Lists are allowed. A list is a set of numbers (or ranges)
8045 separated by commas. Step values can be used in conjunction
8050 The scripts or <tt>crontab</tt> entries in these directories should
8051 check if all necessary programs are installed before they
8052 try to execute them. Otherwise, problems will arise when a
8053 package was removed but not purged since configuration files
8054 are kept on the system in this situation.
8058 Any <tt>cron</tt> daemon must provide
8059 <file>/usr/bin/crontab</file> and support normal
8060 <tt>crontab</tt> entries as specified in POSIX. The daemon
8061 must also support names for days and months, ranges, and
8062 step values. It has to support <file>/etc/crontab</file>,
8063 and correctly execute the scripts in
8064 <file>/etc/cron.d</file>. The daemon must also correctly
8066 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
8069 <sect1 id="cron-files">
8070 <heading>Cron job file names</heading>
8073 The file name of a cron job file should normally match the
8074 name of the package from which it comes.
8078 If a package supplies multiple cron job files files in the
8079 same directory, the file names should all start with the name
8080 of the package (possibly modified as described below) followed
8081 by a hyphen (<tt>-</tt>) and a suitable suffix.
8085 A cron job file name must not include any period or plus
8086 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
8087 cause cron to ignore the file. Underscores (<tt>_</tt>)
8088 should be used instead of <tt>.</tt> and <tt>+</tt>
8095 <heading>Menus</heading>
8098 The Debian <tt>menu</tt> package provides a standard
8099 interface between packages providing applications and
8100 <em>menu programs</em> (either X window managers or
8101 text-based menu programs such as <prgn>pdmenu</prgn>).
8105 All packages that provide applications that need not be
8106 passed any special command line arguments for normal
8107 operation should register a menu entry for those
8108 applications, so that users of the <tt>menu</tt> package
8109 will automatically get menu entries in their window
8110 managers, as well in shells like <tt>pdmenu</tt>.
8114 Menu entries should follow the current menu policy.
8118 The menu policy can be found in the <tt>menu-policy</tt>
8119 files in the <tt>debian-policy</tt> package.
8120 It is also available from the Debian web mirrors at
8121 <tt><url name="/doc/packaging-manuals/menu-policy/"
8122 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
8126 Please also refer to the <em>Debian Menu System</em>
8127 documentation that comes with the <package>menu</package>
8128 package for information about how to register your
8134 <heading>Multimedia handlers</heading>
8137 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
8138 is a mechanism for encoding files and data streams and
8139 providing meta-information about them, in particular their
8140 type (e.g. audio or video) and format (e.g. PNG, HTML,
8145 Registration of MIME type handlers allows programs like mail
8146 user agents and web browsers to invoke these handlers to
8147 view, edit or display MIME types they don't support directly.
8151 Packages which provide programs to view/show/play, compose, edit or
8152 print MIME types should register them as such by placing a file in
8153 <manref name="mailcap" section="5"> format (RFC 1524) in the directory
8154 <file>/usr/lib/mime/packages/</file>. The file name should be the
8155 binary package's name.
8159 The <package>mime-support</package> package provides the
8160 <prgn>update-mime</prgn> program, which integrates these
8161 registrations in the <file>/etc/mailcap</file> file, using dpkg
8163 Creating, modifying or removing a file in
8164 <file>/usr/lib/mime/packages/</file> using maintainer scripts will
8165 not activate the trigger. In that case, it can be done by calling
8166 <tt>dpkg-trigger --no-await /usr/lib/mime/packages</tt> from
8167 the maintainer script after creating, modifying, or removing
8170 Packages using this facility <em>should not</em> depend on,
8171 recommend, or suggest <prgn>mime-support</prgn>.
8176 <heading>Keyboard configuration</heading>
8179 To achieve a consistent keyboard configuration so that all
8180 applications interpret a keyboard event the same way, all
8181 programs in the Debian distribution must be configured to
8182 comply with the following guidelines.
8186 The following keys must have the specified interpretations:
8189 <tag><tt><--</tt></tag>
8190 <item>delete the character to the left of the cursor</item>
8192 <tag><tt>Delete</tt></tag>
8193 <item>delete the character to the right of the cursor</item>
8195 <tag><tt>Control+H</tt></tag>
8196 <item>emacs: the help prefix</item>
8199 The interpretation of any keyboard events should be
8200 independent of the terminal that is used, be it a virtual
8201 console, an X terminal emulator, an rlogin/telnet session,
8206 The following list explains how the different programs
8207 should be set up to achieve this:
8213 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
8217 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
8221 X translations are set up to make
8222 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
8223 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
8224 is the vt220 escape code for the "delete character"
8225 key). This must be done by loading the X resources
8226 using <prgn>xrdb</prgn> on all local X displays, not
8227 using the application defaults, so that the
8228 translation resources used correspond to the
8229 <prgn>xmodmap</prgn> settings.
8233 The Linux console is configured to make
8234 <tt><--</tt> generate DEL, and <tt>Delete</tt>
8235 generate <tt>ESC [ 3 ~</tt>.
8239 X applications are configured so that <tt><</tt>
8240 deletes left, and <tt>Delete</tt> deletes right. Motif
8241 applications already work like this.
8245 Terminals should have <tt>stty erase ^?</tt> .
8249 The <tt>xterm</tt> terminfo entry should have <tt>ESC
8250 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
8251 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
8255 Emacs is programmed to map <tt>KB_Backspace</tt> or
8256 the <tt>stty erase</tt> character to
8257 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
8258 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
8259 <tt>^H</tt> to <tt>help</tt> as always.
8263 Other applications use the <tt>stty erase</tt>
8264 character and <tt>kdch1</tt> for the two delete keys,
8265 with ASCII DEL being "delete previous character" and
8266 <tt>kdch1</tt> being "delete character under
8274 This will solve the problem except for the following
8281 Some terminals have a <tt><--</tt> key that cannot
8282 be made to produce anything except <tt>^H</tt>. On
8283 these terminals Emacs help will be unavailable on
8284 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
8285 character takes precedence in Emacs, and has been set
8286 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
8287 available) can be used instead.
8291 Some operating systems use <tt>^H</tt> for <tt>stty
8292 erase</tt>. However, modern telnet versions and all
8293 rlogin versions propagate <tt>stty</tt> settings, and
8294 almost all UNIX versions honour <tt>stty erase</tt>.
8295 Where the <tt>stty</tt> settings are not propagated
8296 correctly, things can be made to work by using
8297 <tt>stty</tt> manually.
8301 Some systems (including previous Debian versions) use
8302 <prgn>xmodmap</prgn> to arrange for both
8303 <tt><--</tt> and <tt>Delete</tt> to generate
8304 <tt>KB_Delete</tt>. We can change the behavior of
8305 their X clients using the same X resources that we use
8306 to do it for our own clients, or configure our clients
8307 using their resources when things are the other way
8308 around. On displays configured like this
8309 <tt>Delete</tt> will not work, but <tt><--</tt>
8314 Some operating systems have different <tt>kdch1</tt>
8315 settings in their <tt>terminfo</tt> database for
8316 <tt>xterm</tt> and others. On these systems the
8317 <tt>Delete</tt> key will not work correctly when you
8318 log in from a system conforming to our policy, but
8319 <tt><--</tt> will.
8326 <heading>Environment variables</heading>
8329 A program must not depend on environment variables to get
8330 reasonable defaults. (That's because these environment
8331 variables would have to be set in a system-wide
8332 configuration file like <file>/etc/profile</file>, which is not
8333 supported by all shells.)
8337 If a program usually depends on environment variables for its
8338 configuration, the program should be changed to fall back to
8339 a reasonable default configuration if these environment
8340 variables are not present. If this cannot be done easily
8341 (e.g., if the source code of a non-free program is not
8342 available), the program must be replaced by a small
8343 "wrapper" shell script which sets the environment variables
8344 if they are not already defined, and calls the original program.
8348 Here is an example of a wrapper script for this purpose:
8350 <example compact="compact">
8352 BAR=${BAR:-/var/lib/fubar}
8354 exec /usr/lib/foo/foo "$@"
8359 Furthermore, as <file>/etc/profile</file> is a configuration
8360 file of the <prgn>base-files</prgn> package, other packages must
8361 not put any environment variables or other commands into that
8366 <sect id="doc-base">
8367 <heading>Registering Documents using doc-base</heading>
8370 The <package>doc-base</package> package implements a
8371 flexible mechanism for handling and presenting
8372 documentation. The recommended practice is for every Debian
8373 package that provides online documentation (other than just
8374 manual pages) to register these documents with
8375 <package>doc-base</package> by installing a
8376 <package>doc-base</package> control file in
8377 <file>/usr/share/doc-base/</file>.
8380 Please refer to the documentation that comes with the
8381 <package>doc-base</package> package for information and
8386 <sect id="alternateinit">
8387 <heading>Alternate init systems</heading>
8389 A number of other init systems are available now in Debian that
8390 can be used in place of <package>sysvinit</package>. Alternative
8391 init implementations must support running SysV init scripts as
8392 described at <ref id="sysvinit"> for compatibility.
8395 Packages may integrate with these replacement init systems by
8396 providing implementation-specific configuration information about
8397 how and when to start a service or in what order to run certain
8398 tasks at boot time. However, any package integrating with other
8399 init systems must also be backwards-compatible with
8400 <package>sysvinit</package> by providing a SysV-style init script
8401 with the same name as and equivalent functionality to any
8402 init-specific job, as this is the only start-up configuration
8403 method guaranteed to be supported by all init implementations. An
8404 exception to this rule is scripts or jobs provided by the init
8405 implementation itself; such jobs may be required for an
8406 implementation-specific equivalent of the <file>/etc/rcS.d/</file>
8407 scripts and may not have a one-to-one correspondence with the init
8410 <sect1 id="upstart">
8411 <heading>Event-based boot with upstart</heading>
8414 Packages may integrate with the <prgn>upstart</prgn> event-based
8415 boot system by installing job files in the
8416 <file>/etc/init</file> directory. SysV init scripts for which
8417 an equivalent upstart job is available must query the output of
8418 the command <prgn>initctl version</prgn> for the string
8419 <tt>upstart</tt> and avoid running in favor of the native
8420 upstart job, using a test such as this:
8421 <example compact="compact">
8422 if [ "$1" = start ] && which initctl >/dev/null && initctl version | grep -q upstart
8429 Because packages shipping upstart jobs may be installed on
8430 systems that are not using upstart, maintainer scripts must
8431 still use the common <prgn>update-rc.d</prgn> and
8432 <prgn>invoke-rc.d</prgn> interfaces for configuring runlevels
8433 and for starting and stopping services. These maintainer
8434 scripts must not call the upstart <prgn>start</prgn>,
8435 <prgn>restart</prgn>, <prgn>reload</prgn>, or <prgn>stop</prgn>
8436 interfaces directly. Instead, implementations of
8437 <prgn>invoke-rc.d</prgn> must detect when upstart is running and
8438 when an upstart job with the same name as an init script is
8439 present, and perform the requested action using the upstart job
8440 instead of the init script.
8443 Dependency-based boot managers for SysV init scripts, such as
8444 <prgn>startpar</prgn>, may avoid running a given init script
8445 entirely when an equivalent upstart job is present, to avoid
8446 unnecessary forking of no-op init scripts. In this case, the
8447 boot manager should integrate with upstart to detect when the
8448 upstart job in question is started or stopped to know when the
8449 dependency has been satisfied.
8458 <heading>Files</heading>
8460 <sect id="binaries">
8461 <heading>Binaries</heading>
8464 Two different packages must not install programs with
8465 different functionality but with the same filenames. (The
8466 case of two programs having the same functionality but
8467 different implementations is handled via "alternatives" or
8468 the "Conflicts" mechanism. See <ref id="maintscripts"> and
8469 <ref id="conflicts"> respectively.) If this case happens,
8470 one of the programs must be renamed. The maintainers should
8471 report this to the <tt>debian-devel</tt> mailing list and
8472 try to find a consensus about which program will have to be
8473 renamed. If a consensus cannot be reached, <em>both</em>
8474 programs must be renamed.
8477 Binary executables must not be statically linked with the GNU C
8478 library, since this prevents the binary from benefiting from
8479 fixes and improvements to the C library without being rebuilt
8480 and complicates security updates. This requirement may be
8481 relaxed for binary executables whose intended purpose is to
8482 diagnose and fix the system in situations where the GNU C
8483 library may not be usable (such as system recovery shells or
8484 utilities like ldconfig) or for binary executables where the
8485 security benefits of static linking outweigh the drawbacks.
8488 By default, when a package is being built, any binaries
8489 created should include debugging information, as well as
8490 being compiled with optimization. You should also turn on
8491 as many reasonable compilation warnings as possible; this
8492 makes life easier for porters, who can then look at build
8493 logs for possible problems. For the C programming language,
8494 this means the following compilation parameters should be
8496 <example compact="compact">
8498 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
8500 INSTALL = install -s # (or use strip on the files in debian/tmp)
8505 Note that by default all installed binaries should be stripped,
8506 either by using the <tt>-s</tt> flag to
8507 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
8508 the binaries after they have been copied into
8509 <file>debian/tmp</file> but before the tree is made into a
8514 Although binaries in the build tree should be compiled with
8515 debugging information by default, it can often be difficult to
8516 debug programs if they are also subjected to compiler
8517 optimization. For this reason, it is recommended to support the
8518 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
8519 (see <ref id="debianrules-options">). This variable can contain
8520 several flags to change how a package is compiled and built.
8524 It is up to the package maintainer to decide what
8525 compilation options are best for the package. Certain
8526 binaries (such as computationally-intensive programs) will
8527 function better with certain flags (<tt>-O3</tt>, for
8528 example); feel free to use them. Please use good judgment
8529 here. Don't use flags for the sake of it; only use them
8530 if there is good reason to do so. Feel free to override
8531 the upstream author's ideas about which compilation
8532 options are best: they are often inappropriate for our
8538 <sect id="libraries">
8539 <heading>Libraries</heading>
8542 If the package is <strong>architecture: any</strong>, then
8543 the shared library compilation and linking flags must have
8544 <tt>-fPIC</tt>, or the package shall not build on some of
8545 the supported architectures<footnote>
8547 If you are using GCC, <tt>-fPIC</tt> produces code with
8548 relocatable position independent code, which is required for
8549 most architectures to create a shared library, with i386 and
8550 perhaps some others where non position independent code is
8551 permitted in a shared library.
8554 Position independent code may have a performance penalty,
8555 especially on <tt>i386</tt>. However, in most cases the
8556 speed penalty must be measured against the memory wasted on
8557 the few architectures where non position independent code is
8560 </footnote>. Any exception to this rule must be discussed on
8561 the mailing list <em>debian-devel@lists.debian.org</em>, and
8562 a rough consensus obtained. The reasons for not compiling
8563 with <tt>-fPIC</tt> flag must be recorded in the file
8564 <tt>README.Debian</tt>, and care must be taken to either
8565 restrict the architecture or arrange for <tt>-fPIC</tt> to
8566 be used on architectures where it is required.<footnote>
8568 Some of the reasons why this might be required is if the
8569 library contains hand crafted assembly code that is not
8570 relocatable, the speed penalty is excessive for compute
8571 intensive libs, and similar reasons.
8576 As to the static libraries, the common case is not to have
8577 relocatable code, since there is no benefit, unless in specific
8578 cases; therefore the static version must not be compiled
8579 with the <tt>-fPIC</tt> flag. Any exception to this rule
8580 should be discussed on the mailing list
8581 <em>debian-devel@lists.debian.org</em>, and the reasons for
8582 compiling with the <tt>-fPIC</tt> flag must be recorded in
8583 the file <tt>README.Debian</tt>. <footnote>
8585 Some of the reasons for linking static libraries with
8586 the <tt>-fPIC</tt> flag are if, for example, one needs a
8587 Perl API for a library that is under rapid development,
8588 and has an unstable API, so shared libraries are
8589 pointless at this phase of the library's development. In
8590 that case, since Perl needs a library with relocatable
8591 code, it may make sense to create a static library with
8592 relocatable code. Another reason cited is if you are
8593 distilling various libraries into a common shared
8594 library, like <tt>mklibs</tt> does in the Debian
8600 In other words, if both a shared and a static library is
8601 being built, each source unit (<tt>*.c</tt>, for example,
8602 for C files) will need to be compiled twice, for the normal
8607 Libraries should be built with threading support and to be
8608 thread-safe if the library supports this.
8612 Although not enforced by the build tools, shared libraries
8613 must be linked against all libraries that they use symbols from
8614 in the same way that binaries are. This ensures the correct
8615 functioning of the <qref id="sharedlibs-symbols">symbols</qref>
8616 and <qref id="sharedlibs-shlibdeps">shlibs</qref>
8617 systems and guarantees that all libraries can be safely opened
8618 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
8619 option <tt>-Wl,-z,defs</tt> when building a shared library.
8620 Since this option enforces symbol resolution at build time,
8621 a missing library reference will be caught early as a fatal
8626 All installed shared libraries should be stripped with
8627 <example compact="compact">
8628 strip --strip-unneeded <var>your-lib</var>
8630 (The option <tt>--strip-unneeded</tt> makes
8631 <prgn>strip</prgn> remove only the symbols which aren't
8632 needed for relocation processing.) Shared libraries can
8633 function perfectly well when stripped, since the symbols for
8634 dynamic linking are in a separate part of the ELF object
8636 You might also want to use the options
8637 <tt>--remove-section=.comment</tt> and
8638 <tt>--remove-section=.note</tt> on both shared libraries
8639 and executables, and <tt>--strip-debug</tt> on static
8645 Note that under some circumstances it may be useful to
8646 install a shared library unstripped, for example when
8647 building a separate package to support debugging.
8651 Shared object files (often <file>.so</file> files) that are not
8652 public libraries, that is, they are not meant to be linked
8653 to by third party executables (binaries of other packages),
8654 should be installed in subdirectories of the
8655 <file>/usr/lib</file> directory. Such files are exempt from the
8656 rules that govern ordinary shared libraries, except that
8657 they must not be installed executable and should be
8659 A common example are the so-called "plug-ins",
8660 internal shared objects that are dynamically loaded by
8661 programs using <manref name="dlopen" section="3">.
8666 Packages that use <prgn>libtool</prgn> to create and install
8667 their shared libraries install a file containing additional
8668 metadata (ending in <file>.la</file>) alongside the library.
8669 For public libraries intended for use by other packages, these
8670 files normally should not be included in the Debian package,
8671 since the information they include is not necessary to link with
8672 the shared library on Debian and can add unnecessary additional
8673 dependencies to other programs or libraries.<footnote>
8674 These files store, among other things, all libraries on which
8675 that shared library depends. Unfortunately, if
8676 the <file>.la</file> file is present and contains that
8677 dependency information, using <prgn>libtool</prgn> when
8678 linking against that library will cause the resulting program
8679 or library to be linked against those dependencies as well,
8680 even if this is unnecessary. This can create unneeded
8681 dependencies on shared library packages that would otherwise
8682 be hidden behind the library ABI, and can make library
8683 transitions to new SONAMEs unnecessarily complicated and
8684 difficult to manage.
8686 If the <file>.la</file> file is required for that library (if,
8687 for instance, it's loaded via <tt>libltdl</tt> in a way that
8688 requires that meta-information), the <tt>dependency_libs</tt>
8689 setting in the <file>.la</file> file should normally be set to
8690 the empty string. If the shared library development package has
8691 historically included the <file>.la</file>, it must be retained
8692 in the development package (with <tt>dependency_libs</tt>
8693 emptied) until all libraries that depend on it have removed or
8694 emptied <tt>dependency_libs</tt> in their <file>.la</file>
8695 files to prevent linking with those other libraries
8696 using <prgn>libtool</prgn> from failing.
8700 If the <file>.la</file> must be included, it should be included
8701 in the development (<tt>-dev</tt>) package, unless the library
8702 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
8703 library. If it is intended for use with <tt>libltdl</tt>,
8704 the <file>.la</file> files must go in the run-time library
8709 These requirements for handling of <file>.la</file> files do not
8710 apply to loadable modules or libraries not installed in
8711 directories searched by default by the dynamic linker. Packages
8712 installing loadable modules will frequently need to install
8713 the <file>.la</file> files alongside the modules so that they
8714 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
8715 does not need to be modified for libraries or modules that are
8716 not installed in directories searched by the dynamic linker by
8717 default and not intended for use by other packages.
8721 You must make sure that you use only released versions of
8722 shared libraries to build your packages; otherwise other
8723 users will not be able to run your binaries
8724 properly. Producing source packages that depend on
8725 unreleased compilers is also usually a bad
8732 <heading>Shared libraries</heading>
8734 This section has moved to <ref id="sharedlibs">.
8740 <heading>Scripts</heading>
8743 All command scripts, including the package maintainer
8744 scripts inside the package and used by <prgn>dpkg</prgn>,
8745 should have a <tt>#!</tt> line naming the shell to be used
8750 In the case of Perl scripts this should be
8751 <tt>#!/usr/bin/perl</tt>.
8755 When scripts are installed into a directory in the system
8756 PATH, the script name should not include an extension such
8757 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8758 language currently used to implement it.
8761 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8762 <file>init.d</file> scripts should almost certainly start
8763 with <tt>set -e</tt> so that errors are detected.
8764 <file>init.d</file> scripts are something of a special case, due
8765 to how frequently they need to call commands that are allowed to
8766 fail, and it may instead be easier to check the exit status of
8767 commands directly. See <ref id="writing-init"> for more
8768 information about writing <file>init.d</file> scripts.
8771 Every script should use <tt>set -e</tt> or check the exit status
8772 of <em>every</em> command.
8775 Scripts may assume that <file>/bin/sh</file> implements the
8776 SUSv3 Shell Command Language<footnote>
8777 Single UNIX Specification, version 3, which is also IEEE
8778 1003.1-2004 (POSIX), and is available on the World Wide Web
8779 from <url id="http://www.unix.org/version3/online.html"
8780 name="The Open Group"> after free
8781 registration.</footnote>
8782 plus the following additional features not mandated by
8784 These features are in widespread use in the Linux community
8785 and are implemented in all of bash, dash, and ksh, the most
8786 common shells users may wish to use as <file>/bin/sh</file>.
8789 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8790 must not generate a newline.</item>
8791 <item><tt>test</tt>, if implemented as a shell built-in, must
8792 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8794 <item><tt>local</tt> to create a scoped variable must be
8795 supported, including listing multiple variables in a single
8796 local command and assigning a value to a variable at the
8797 same time as localizing it. <tt>local</tt> may or
8798 may not preserve the variable value from an outer scope if
8799 no assignment is present. Uses such as:
8803 # ... use a, b, c, d ...
8806 must be supported and must set the value of <tt>c</tt> to
8809 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8810 -<var>signal</var></tt>, where <var>signal</var> is either
8811 the name of a signal or one of the numeric signals listed in
8812 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8813 supported if <prgn>kill</prgn> is implemented as a shell
8816 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8817 signals must be supported. In addition to the signal
8818 numbers listed in the extension, which are the same as for
8819 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8822 If a shell script requires non-SUSv3 features from the shell
8823 interpreter other than those listed above, the appropriate shell
8824 must be specified in the first line of the script (e.g.,
8825 <tt>#!/bin/bash</tt>) and the package must depend on the package
8826 providing the shell (unless the shell package is marked
8827 "Essential", as in the case of <prgn>bash</prgn>).
8831 You may wish to restrict your script to SUSv3 features plus the
8832 above set when possible so that it may use <file>/bin/sh</file>
8833 as its interpreter. Checking your script
8834 with <prgn>checkbashisms</prgn> from
8835 the <package>devscripts</package> package or running your script
8836 with an alternate shell such as <prgn>posh</prgn> may help
8837 uncover violations of the above requirements. If in doubt
8838 whether a script complies with these requirements,
8839 use <file>/bin/bash</file>.
8843 Perl scripts should check for errors when making any
8844 system calls, including <tt>open</tt>, <tt>print</tt>,
8845 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8849 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8850 scripting languages. See <em>Csh Programming Considered
8851 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8852 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8853 If an upstream package comes with <prgn>csh</prgn> scripts
8854 then you must make sure that they start with
8855 <tt>#!/bin/csh</tt> and make your package depend on the
8856 <prgn>c-shell</prgn> virtual package.
8860 Any scripts which create files in world-writeable
8861 directories (e.g., in <file>/tmp</file>) must use a
8862 mechanism which will fail atomically if a file with the same
8863 name already exists.
8867 The Debian base system provides the <prgn>tempfile</prgn>
8868 and <prgn>mktemp</prgn> utilities for use by scripts for
8875 <heading>Symbolic links</heading>
8878 In general, symbolic links within a top-level directory should
8879 be relative, and symbolic links pointing from one top-level
8880 directory to or into another should be absolute. (A top-level
8881 directory is a sub-directory of the root
8882 directory <file>/</file>.) For example, a symbolic link
8883 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8884 should be relative (<file>../share/bar</file>), but a symbolic
8885 link from <file>/var/run</file> to <file>/run</file> should be
8887 This is necessary to allow top-level directories to be
8888 symlinks. If linking <file>/var/run</file>
8889 to <file>/run</file> were done with the relative symbolic
8890 link <file>../run</file>, but <file>/var</file> were a
8891 symbolic link to <file>/srv/disk1</file>, the symbolic link
8892 would point to <file>/srv/run</file> rather than the intended
8898 In addition, symbolic links should be specified as short as
8899 possible, i.e., link targets like <file>foo/../bar</file> are
8904 Note that when creating a relative link using
8905 <prgn>ln</prgn> it is not necessary for the target of the
8906 link to exist relative to the working directory you're
8907 running <prgn>ln</prgn> from, nor is it necessary to change
8908 directory to the directory where the link is to be made.
8909 Simply include the string that should appear as the target
8910 of the link (this will be a pathname relative to the
8911 directory in which the link resides) as the first argument
8916 For example, in your <prgn>Makefile</prgn> or
8917 <file>debian/rules</file>, you can do things like:
8918 <example compact="compact">
8919 ln -fs gcc $(prefix)/bin/cc
8920 ln -fs gcc debian/tmp/usr/bin/cc
8921 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8922 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8927 A symbolic link pointing to a compressed file (in the sense
8928 that it is meant to be uncompressed with <prgn>unzip</prgn>
8929 or <prgn>zless</prgn> etc.) should always
8930 have the same file extension as the referenced file. (For
8931 example, if a file <file>foo.gz</file> is referenced by a
8932 symbolic link, the filename of the link has to end with
8933 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8938 <heading>Device files</heading>
8941 Packages must not include device files or named pipes in the
8946 If a package needs any special device files that are not
8947 included in the base system, it must call
8948 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8949 after notifying the user<footnote>
8950 This notification could be done via a (low-priority)
8951 debconf message, or an echo (printf) statement.
8956 Packages must not remove any device files in the
8957 <prgn>postrm</prgn> or any other script. This is left to the
8958 system administrator.
8962 Debian uses the serial devices
8963 <file>/dev/ttyS*</file>. Programs using the old
8964 <file>/dev/cu*</file> devices should be changed to use
8965 <file>/dev/ttyS*</file>.
8969 Named pipes needed by the package must be created in
8970 the <prgn>postinst</prgn> script<footnote>
8971 It's better to use <prgn>mkfifo</prgn> rather
8972 than <prgn>mknod</prgn> to create named pipes so that
8973 automated checks for packages incorrectly creating device
8974 files with <prgn>mknod</prgn> won't have false positives.
8975 </footnote> and removed in
8976 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8981 <sect id="config-files">
8982 <heading>Configuration files</heading>
8985 <heading>Definitions</heading>
8989 <tag>configuration file</tag>
8991 A file that affects the operation of a program, or
8992 provides site- or host-specific information, or
8993 otherwise customizes the behavior of a program.
8994 Typically, configuration files are intended to be
8995 modified by the system administrator (if needed or
8996 desired) to conform to local policy or to provide
8997 more useful site-specific behavior.
9000 <tag><tt>conffile</tt></tag>
9002 A file listed in a package's <tt>conffiles</tt>
9003 file, and is treated specially by <prgn>dpkg</prgn>
9004 (see <ref id="configdetails">).
9010 The distinction between these two is important; they are
9011 not interchangeable concepts. Almost all
9012 <tt>conffile</tt>s are configuration files, but many
9013 configuration files are not <tt>conffiles</tt>.
9017 As noted elsewhere, <file>/etc/init.d</file> scripts,
9018 <file>/etc/default</file> files, scripts installed in
9019 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
9020 configuration installed in <file>/etc/cron.d</file> must be
9021 treated as configuration files. In general, any script that
9022 embeds configuration information is de-facto a configuration
9023 file and should be treated as such.
9028 <heading>Location</heading>
9031 Any configuration files created or used by your package
9032 must reside in <file>/etc</file>. If there are several,
9033 consider creating a subdirectory of <file>/etc</file>
9034 named after your package.
9038 If your package creates or uses configuration files
9039 outside of <file>/etc</file>, and it is not feasible to modify
9040 the package to use <file>/etc</file> directly, put the files
9041 in <file>/etc</file> and create symbolic links to those files
9042 from the location that the package requires.
9047 <heading>Behavior</heading>
9050 Configuration file handling must conform to the following
9052 <list compact="compact">
9054 local changes must be preserved during a package
9058 configuration files must be preserved when the
9059 package is removed, and only deleted when the
9063 Obsolete configuration files without local changes should be
9064 removed by the package during upgrade.<footnote>
9065 The <prgn>dpkg-maintscript-helper</prgn> tool, available from the
9066 <package>dpkg</package> package, can help for this task.</footnote>
9070 The easy way to achieve this behavior is to make the
9071 configuration file a <tt>conffile</tt>. This is
9072 appropriate only if it is possible to distribute a default
9073 version that will work for most installations, although
9074 some system administrators may choose to modify it. This
9075 implies that the default version will be part of the
9076 package distribution, and must not be modified by the
9077 maintainer scripts during installation (or at any other
9082 In order to ensure that local changes are preserved
9083 correctly, no package may contain or make hard links to
9084 conffiles.<footnote>
9085 Rationale: There are two problems with hard links.
9086 The first is that some editors break the link while
9087 editing one of the files, so that the two files may
9088 unwittingly become unlinked and different. The second
9089 is that <prgn>dpkg</prgn> might break the hard link
9090 while upgrading <tt>conffile</tt>s.
9095 The other way to do it is via the maintainer scripts. In
9096 this case, the configuration file must not be listed as a
9097 <tt>conffile</tt> and must not be part of the package
9098 distribution. If the existence of a file is required for
9099 the package to be sensibly configured it is the
9100 responsibility of the package maintainer to provide
9101 maintainer scripts which correctly create, update and
9102 maintain the file and remove it on purge. (See <ref
9103 id="maintainerscripts"> for more information.) These
9104 scripts must be idempotent (i.e., must work correctly if
9105 <prgn>dpkg</prgn> needs to re-run them due to errors
9106 during installation or removal), must cope with all the
9107 variety of ways <prgn>dpkg</prgn> can call maintainer
9108 scripts, must not overwrite or otherwise mangle the user's
9109 configuration without asking, must not ask unnecessary
9110 questions (particularly during upgrades), and must
9111 otherwise be good citizens.
9115 The scripts are not required to configure every possible
9116 option for the package, but only those necessary to get
9117 the package running on a given system. Ideally the
9118 sysadmin should not have to do any configuration other
9119 than that done (semi-)automatically by the
9120 <prgn>postinst</prgn> script.
9124 A common practice is to create a script called
9125 <file><var>package</var>-configure</file> and have the
9126 package's <prgn>postinst</prgn> call it if and only if the
9127 configuration file does not already exist. In certain
9128 cases it is useful for there to be an example or template
9129 file which the maintainer scripts use. Such files should
9130 be in <file>/usr/share/<var>package</var></file> or
9131 <file>/usr/lib/<var>package</var></file> (depending on whether
9132 they are architecture-independent or not). There should
9133 be symbolic links to them from
9134 <file>/usr/share/doc/<var>package</var>/examples</file> if
9135 they are examples, and should be perfectly ordinary
9136 <prgn>dpkg</prgn>-handled files (<em>not</em>
9137 configuration files).
9141 These two styles of configuration file handling must
9142 not be mixed, for that way lies madness:
9143 <prgn>dpkg</prgn> will ask about overwriting the file
9144 every time the package is upgraded.
9149 <heading>Sharing configuration files</heading>
9152 If two or more packages use the same configuration file
9153 and it is reasonable for both to be installed at the same
9154 time, one of these packages must be defined as
9155 <em>owner</em> of the configuration file, i.e., it will be
9156 the package which handles that file as a configuration
9157 file. Other packages that use the configuration file must
9158 depend on the owning package if they require the
9159 configuration file to operate. If the other package will
9160 use the configuration file if present, but is capable of
9161 operating without it, no dependency need be declared.
9165 If it is desirable for two or more related packages to
9166 share a configuration file <em>and</em> for all of the
9167 related packages to be able to modify that configuration
9168 file, then the following should be done:
9169 <enumlist compact="compact">
9171 One of the related packages (the "owning" package)
9172 will manage the configuration file with maintainer
9173 scripts as described in the previous section.
9176 The owning package should also provide a program
9177 that the other packages may use to modify the
9181 The related packages must use the provided program
9182 to make any desired modifications to the
9183 configuration file. They should either depend on
9184 the core package to guarantee that the configuration
9185 modifier program is available or accept gracefully
9186 that they cannot modify the configuration file if it
9187 is not. (This is in addition to the fact that the
9188 configuration file may not even be present in the
9195 Sometimes it's appropriate to create a new package which
9196 provides the basic infrastructure for the other packages
9197 and which manages the shared configuration files. (The
9198 <tt>sgml-base</tt> package is a good example.)
9202 If the configuration file cannot be shared as described above,
9203 the packages must be marked as conflicting with each other.
9204 Two packages that specify the same file as
9205 a <tt>conffile</tt> must conflict. This is an instance of the
9206 general rule about not sharing files. Neither alternatives
9207 nor diversions are likely to be appropriate in this case; in
9208 particular, <prgn>dpkg</prgn> does not handle diverted
9209 <tt>conffile</tt>s well.
9213 When two packages both declare the same <tt>conffile</tt>, they
9214 may see left-over configuration files from each other even
9215 though they conflict with each other. If a user removes
9216 (without purging) one of the packages and installs the other,
9217 the new package will take over the <tt>conffile</tt> from the
9218 old package. If the file was modified by the user, it will be
9219 treated the same as any other locally
9220 modified <tt>conffile</tt> during an upgrade.
9224 The maintainer scripts must not alter a <tt>conffile</tt>
9225 of <em>any</em> package, including the one the scripts
9231 <heading>User configuration files ("dotfiles")</heading>
9234 The files in <file>/etc/skel</file> will automatically be
9235 copied into new user accounts by <prgn>adduser</prgn>.
9236 No other program should reference the files in
9237 <file>/etc/skel</file>.
9241 Therefore, if a program needs a dotfile to exist in
9242 advance in <file>$HOME</file> to work sensibly, that dotfile
9243 should be installed in <file>/etc/skel</file> and treated as a
9248 However, programs that require dotfiles in order to
9249 operate sensibly are a bad thing, unless they do create
9250 the dotfiles themselves automatically.
9254 Furthermore, programs should be configured by the Debian
9255 default installation to behave as closely to the upstream
9256 default behavior as possible.
9260 Therefore, if a program in a Debian package needs to be
9261 configured in some way in order to operate sensibly, that
9262 should be done using a site-wide configuration file placed
9263 in <file>/etc</file>. Only if the program doesn't support a
9264 site-wide default configuration and the package maintainer
9265 doesn't have time to add it may a default per-user file be
9266 placed in <file>/etc/skel</file>.
9270 <file>/etc/skel</file> should be as empty as we can make it.
9271 This is particularly true because there is no easy (or
9272 necessarily desirable) mechanism for ensuring that the
9273 appropriate dotfiles are copied into the accounts of
9274 existing users when a package is installed.
9280 <heading>Log files</heading>
9282 Log files should usually be named
9283 <file>/var/log/<var>package</var>.log</file>. If you have many
9284 log files, or need a separate directory for permission
9285 reasons (<file>/var/log</file> is writable only by
9286 <file>root</file>), you should usually create a directory named
9287 <file>/var/log/<var>package</var></file> and place your log
9292 Log files must be rotated occasionally so that they don't grow
9293 indefinitely. The best way to do this is to install a log
9294 rotation configuration file in the
9295 directory <file>/etc/logrotate.d</file>, normally
9296 named <file>/etc/logrotate.d/<var>package</var></file>, and use
9297 the facilities provided by <prgn>logrotate</prgn>.
9300 The traditional approach to log files has been to set up
9301 <em>ad hoc</em> log rotation schemes using simple shell
9302 scripts and cron. While this approach is highly
9303 customizable, it requires quite a lot of sysadmin work.
9304 Even though the original Debian system helped a little
9305 by automatically installing a system which can be used
9306 as a template, this was deemed not enough.
9310 The use of <prgn>logrotate</prgn>, a program developed
9311 by Red Hat, is better, as it centralizes log management.
9312 It has both a configuration file
9313 (<file>/etc/logrotate.conf</file>) and a directory where
9314 packages can drop their individual log rotation
9315 configurations (<file>/etc/logrotate.d</file>).
9318 Here is a good example for a logrotate config
9319 file (for more information see <manref name="logrotate"
9321 <example compact="compact">
9322 /var/log/foo/*.log {
9328 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
9332 This rotates all files under <file>/var/log/foo</file>, saves 12
9333 compressed generations, and tells the daemon to reopen its log
9334 files after the log rotation. It skips this log rotation
9335 (via <tt>missingok</tt>) if no such log file is present, which
9336 avoids errors if the package is removed but not purged.
9340 Log files should be removed when the package is
9341 purged (but not when it is only removed). This should be
9342 done by the <prgn>postrm</prgn> script when it is called
9343 with the argument <tt>purge</tt> (see <ref
9344 id="removedetails">).
9348 <sect id="permissions-owners">
9349 <heading>Permissions and owners</heading>
9352 The rules in this section are guidelines for general use.
9353 If necessary you may deviate from the details below.
9354 However, if you do so you must make sure that what is done
9355 is secure and you should try to be as consistent as possible
9356 with the rest of the system. You should probably also
9357 discuss it on <prgn>debian-devel</prgn> first.
9361 Files should be owned by <tt>root:root</tt>, and made
9362 writable only by the owner and universally readable (and
9363 executable, if appropriate), that is mode 644 or 755.
9367 Directories should be mode 755 or (for group-writability)
9368 mode 2775. The ownership of the directory should be
9369 consistent with its mode: if a directory is mode 2775, it
9370 should be owned by the group that needs write access to
9373 When a package is upgraded, and the owner or permissions
9374 of a file included in the package has changed, dpkg
9375 arranges for the ownership and permissions to be
9376 correctly set upon installation. However, this does not
9377 extend to directories; the permissions and ownership of
9378 directories already on the system does not change on
9379 install or upgrade of packages. This makes sense, since
9380 otherwise common directories like <tt>/usr</tt> would
9381 always be in flux. To correctly change permissions of a
9382 directory the package owns, explicit action is required,
9383 usually in the <tt>postinst</tt> script. Care must be
9384 taken to handle downgrades as well, in that case.
9390 Control information files should be owned by <tt>root:root</tt>
9391 and either mode 644 (for most files) or mode 755 (for
9392 executables such as <qref id="maintscripts">maintainer
9397 Setuid and setgid executables should be mode 4755 or 2755
9398 respectively, and owned by the appropriate user or group.
9399 They should not be made unreadable (modes like 4711 or
9400 2711 or even 4111); doing so achieves no extra security,
9401 because anyone can find the binary in the freely available
9402 Debian package; it is merely inconvenient. For the same
9403 reason you should not restrict read or execute permissions
9404 on non-set-id executables.
9408 Some setuid programs need to be restricted to particular
9409 sets of users, using file permissions. In this case they
9410 should be owned by the uid to which they are set-id, and by
9411 the group which should be allowed to execute them. They
9412 should have mode 4754; again there is no point in making
9413 them unreadable to those users who must not be allowed to
9418 It is possible to arrange that the system administrator can
9419 reconfigure the package to correspond to their local
9420 security policy by changing the permissions on a binary:
9421 they can do this by using <prgn>dpkg-statoverride</prgn>, as
9422 described below.<footnote>
9423 Ordinary files installed by <prgn>dpkg</prgn> (as
9424 opposed to <tt>conffile</tt>s and other similar objects)
9425 normally have their permissions reset to the distributed
9426 permissions when the package is reinstalled. However,
9427 the use of <prgn>dpkg-statoverride</prgn> overrides this
9430 Another method you should consider is to create a group for
9431 people allowed to use the program(s) and make any setuid
9432 executables executable only by that group.
9436 If you need to create a new user or group for your package
9437 there are two possibilities. Firstly, you may need to
9438 make some files in the binary package be owned by this
9439 user or group, or you may need to compile the user or
9440 group id (rather than just the name) into the binary
9441 (though this latter should be avoided if possible, as in
9442 this case you need a statically allocated id).</p>
9445 If you need a statically allocated id, you must ask for a
9446 user or group id from the <tt>base-passwd</tt> maintainer,
9447 and must not release the package until you have been
9448 allocated one. Once you have been allocated one you must
9449 either make the package depend on a version of the
9450 <tt>base-passwd</tt> package with the id present in
9451 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
9452 your package to create the user or group itself with the
9453 correct id (using <tt>adduser</tt>) in its
9454 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
9455 the <prgn>postinst</prgn> is to be preferred if it is
9456 possible, otherwise a pre-dependency will be needed on the
9457 <tt>adduser</tt> package.)
9461 On the other hand, the program might be able to determine
9462 the uid or gid from the user or group name at runtime, so
9463 that a dynamically allocated id can be used. In this case
9464 you should choose an appropriate user or group name,
9465 discussing this on <prgn>debian-devel</prgn> and checking
9466 with the <package/base-passwd/ maintainer that it is unique and that
9467 they do not wish you to use a statically allocated id
9468 instead. When this has been checked you must arrange for
9469 your package to create the user or group if necessary using
9470 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
9471 <prgn>postinst</prgn> script (again, the latter is to be
9472 preferred if it is possible).
9476 Note that changing the numeric value of an id associated
9477 with a name is very difficult, and involves searching the
9478 file system for all appropriate files. You need to think
9479 carefully whether a static or dynamic id is required, since
9480 changing your mind later will cause problems.
9483 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
9485 This section is not intended as policy, but as a
9486 description of the use of <prgn>dpkg-statoverride</prgn>.
9490 If a system administrator wishes to have a file (or
9491 directory or other such thing) installed with owner and
9492 permissions different from those in the distributed Debian
9493 package, they can use the <prgn>dpkg-statoverride</prgn>
9494 program to instruct <prgn>dpkg</prgn> to use the different
9495 settings every time the file is installed. Thus the
9496 package maintainer should distribute the files with their
9497 normal permissions, and leave it for the system
9498 administrator to make any desired changes. For example, a
9499 daemon which is normally required to be setuid root, but
9500 in certain situations could be used without being setuid,
9501 should be installed setuid in the <tt>.deb</tt>. Then the
9502 local system administrator can change this if they wish.
9503 If there are two standard ways of doing it, the package
9504 maintainer can use <tt>debconf</tt> to find out the
9505 preference, and call <prgn>dpkg-statoverride</prgn> in the
9506 maintainer script if necessary to accommodate the system
9507 administrator's choice. Care must be taken during
9508 upgrades to not override an existing setting.
9512 Given the above, <prgn>dpkg-statoverride</prgn> is
9513 essentially a tool for system administrators and would not
9514 normally be needed in the maintainer scripts. There is
9515 one type of situation, though, where calls to
9516 <prgn>dpkg-statoverride</prgn> would be needed in the
9517 maintainer scripts, and that involves packages which use
9518 dynamically allocated user or group ids. In such a
9519 situation, something like the following idiom can be very
9520 helpful in the package's <prgn>postinst</prgn>, where
9521 <tt>sysuser</tt> is a dynamically allocated id:
9523 for i in /usr/bin/foo /usr/sbin/bar
9525 # only do something when no setting exists
9526 if ! dpkg-statoverride --list $i >/dev/null 2>&1
9528 #include: debconf processing, question about foo and bar
9529 if [ "$RET" = "true" ] ; then
9530 dpkg-statoverride --update --add sysuser root 4755 $i
9535 The corresponding code to remove the override when the package
9538 for i in /usr/bin/foo /usr/sbin/bar
9540 if dpkg-statoverride --list $i >/dev/null 2>&1
9542 dpkg-statoverride --remove $i
9550 <sect id="filenames">
9551 <heading>File names</heading>
9554 The name of the files installed by binary packages in the system PATH
9555 (namely <tt>/bin</tt>, <tt>/sbin</tt>, <tt>/usr/bin</tt>,
9556 <tt>/usr/sbin</tt> and <tt>/usr/games</tt>) must be encoded in
9561 The name of the files and directories installed by binary packages
9562 outside the system PATH must be encoded in UTF-8 and should be
9563 restricted to ASCII when it is possible to do so.
9569 <chapt id="customized-programs">
9570 <heading>Customized programs</heading>
9572 <sect id="arch-spec">
9573 <heading>Architecture specification strings</heading>
9576 If a program needs to specify an <em>architecture specification
9577 string</em> in some place, it should select one of the strings
9578 provided by <tt>dpkg-architecture -L</tt>. The strings are in
9579 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
9580 part is sometimes elided, as when the OS is Linux.
9584 Note that we don't want to use
9585 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
9586 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
9587 since this would make our programs incompatible with other
9588 Linux distributions. We also don't use something like
9589 <tt><var>arch</var>-unknown-linux</tt>, since the
9590 <tt>unknown</tt> does not look very good.
9593 <sect1 id="arch-wildcard-spec">
9594 <heading>Architecture wildcards</heading>
9597 A package may specify an architecture wildcard. Architecture
9598 wildcards are in the format <tt>any</tt> (which matches every
9599 architecture), <tt><var>os</var></tt>-any, or
9600 any-<tt><var>cpu</var></tt>. <footnote>
9601 Internally, the package system normalizes the GNU triplets
9602 and the Debian arches into Debian arch triplets (which are
9603 kind of inverted GNU triplets), with the first component of
9604 the triplet representing the libc and ABI in use, and then
9605 does matching against those triplets. However, such
9606 triplets are an internal implementation detail that should
9607 not be used by packages directly. The libc and ABI portion
9608 is handled internally by the package system based on
9609 the <var>os</var> and <var>cpu</var>.
9616 <heading>Daemons</heading>
9619 The configuration files <file>/etc/services</file>,
9620 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
9621 by the <prgn>netbase</prgn> package and must not be modified
9626 If a package requires a new entry in one of these files, the
9627 maintainer should get in contact with the
9628 <prgn>netbase</prgn> maintainer, who will add the entries
9629 and release a new version of the <prgn>netbase</prgn>
9634 The configuration file <file>/etc/inetd.conf</file> must not be
9635 modified by the package's scripts except via the
9636 <prgn>update-inetd</prgn> script or the
9637 <file>DebianNet.pm</file> Perl module. See their documentation
9638 for details on how to add entries.
9642 If a package wants to install an example entry into
9643 <file>/etc/inetd.conf</file>, the entry must be preceded with
9644 exactly one hash character (<tt>#</tt>). Such lines are
9645 treated as "commented out by user" by the
9646 <prgn>update-inetd</prgn> script and are not changed or
9647 activated during package updates.
9652 <heading>Using pseudo-ttys and modifying wtmp, utmp and
9656 Some programs need to create pseudo-ttys. This should be done
9657 using Unix98 ptys if the C library supports it. The resulting
9658 program must not be installed setuid root, unless that
9659 is required for other functionality.
9663 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
9664 <file>/var/log/lastlog</file> must be installed writable by
9665 group <tt>utmp</tt>. Programs which need to modify those
9666 files must be installed setgid <tt>utmp</tt>.
9671 <heading>Editors and pagers</heading>
9674 Some programs have the ability to launch an editor or pager
9675 program to edit or display a text document. Since there are
9676 lots of different editors and pagers available in the Debian
9677 distribution, the system administrator and each user should
9678 have the possibility to choose their preferred editor and
9683 In addition, every program should choose a good default
9684 editor/pager if none is selected by the user or system
9689 Thus, every program that launches an editor or pager must
9690 use the EDITOR or PAGER environment variable to determine
9691 the editor or pager the user wishes to use. If these
9692 variables are not set, the programs <file>/usr/bin/editor</file>
9693 and <file>/usr/bin/pager</file> should be used, respectively.
9697 These two files are managed through the <prgn>dpkg</prgn>
9698 "alternatives" mechanism. Every package providing an editor or
9699 pager must call the <prgn>update-alternatives</prgn> script to
9700 register as an alternative for <file>/usr/bin/editor</file>
9701 or <file>/usr/bin/pager</file> as appropriate. The alternative
9702 should have a slave alternative
9703 for <file>/usr/share/man/man1/editor.1.gz</file>
9704 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
9705 corresponding manual page.
9709 If it is very hard to adapt a program to make use of the
9710 EDITOR or PAGER variables, that program may be configured to
9711 use <file>/usr/bin/sensible-editor</file> and
9712 <file>/usr/bin/sensible-pager</file> as the editor or pager
9713 program respectively. These are two scripts provided in the
9714 <package>sensible-utils</package> package that check the EDITOR
9715 and PAGER variables and launch the appropriate program, and fall
9716 back to <file>/usr/bin/editor</file>
9717 and <file>/usr/bin/pager</file> if the variable is not set.
9721 A program may also use the VISUAL environment variable to
9722 determine the user's choice of editor. If it exists, it
9723 should take precedence over EDITOR. This is in fact what
9724 <file>/usr/bin/sensible-editor</file> does.
9728 It is not required for a package to depend on
9729 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
9730 package to provide such virtual packages.<footnote>
9731 The Debian base system already provides an editor and a
9737 <sect id="web-appl">
9738 <heading>Web servers and applications</heading>
9741 This section describes the locations and URLs that should
9742 be used by all web servers and web applications in the
9749 Cgi-bin executable files are installed in the
9751 <example compact="compact">
9754 or a subdirectory of that directory, and the script
9755 <example compact="compact">
9756 /usr/lib/cgi-bin/.../<var>cgi-bin-name</var>
9758 should be referred to as
9759 <example compact="compact">
9760 http://localhost/cgi-bin/.../<var>cgi-bin-name</var>
9769 <p>Access to images</p>
9771 It is recommended that images for a package be stored
9772 in <tt>/usr/share/images/<var>package</var></tt> and
9773 may be referred to through an alias <tt>/images/</tt>
9776 http://localhost/images/<package>/<filename>
9783 <p>Web Document Root</p>
9786 Web Applications should try to avoid storing files in
9787 the Web Document Root. Instead they should use the
9788 /usr/share/doc/<var>package</var> directory for
9789 documents and register the Web Application via the
9790 <package>doc-base</package> package. If access to the
9791 web document root is unavoidable then use
9792 <example compact="compact">
9795 as the Document Root. This might be just a symbolic
9796 link to the location where the system administrator
9797 has put the real document root.
9800 <item><p>Providing httpd and/or httpd-cgi</p>
9802 All web servers should provide the virtual package
9803 <tt>httpd</tt>. If a web server has CGI support it should
9804 provide <tt>httpd-cgi</tt> additionally.
9807 All web applications which do not contain CGI scripts should
9808 depend on <tt>httpd</tt>, all those web applications which
9809 <tt>do</tt> contain CGI scripts, should depend on
9817 <sect id="mail-transport-agents">
9818 <heading>Mail transport, delivery and user agents</heading>
9821 Debian packages which process electronic mail, whether mail
9822 user agents (MUAs) or mail transport agents (MTAs), must
9823 ensure that they are compatible with the configuration
9824 decisions below. Failure to do this may result in lost
9825 mail, broken <tt>From:</tt> lines, and other serious brain
9830 The mail spool is <file>/var/mail</file> and the interface to
9831 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9832 the FHS). On older systems, the mail spool may be
9833 physically located in <file>/var/spool/mail</file>, but all
9834 access to the mail spool should be via the
9835 <file>/var/mail</file> symlink. The mail spool is part of the
9836 base system and not part of the MTA package.
9840 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9841 programs (such as IMAP daemons) must lock the mailbox in an
9842 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9843 be combined with dot locking. To avoid deadlocks, a program
9844 should use <tt>fcntl()</tt> first and dot locking after
9845 this, or alternatively implement the two locking methods in
9846 a non blocking way<footnote>
9847 If it is not possible to establish both locks, the
9848 system shouldn't wait for the second lock to be
9849 established, but remove the first lock, wait a (random)
9850 time, and start over locking again.
9851 </footnote>. Using the functions <tt>maillock</tt> and
9852 <tt>mailunlock</tt> provided by the
9853 <tt>liblockfile*</tt><footnote>
9854 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9855 to use these functions.
9856 </footnote> packages is the recommended way to realize this.
9860 Mailboxes are generally either mode 600 and owned by
9861 <var>user</var> or mode 660 and owned by
9862 <tt><var>user</var>:mail</tt><footnote>
9863 There are two traditional permission schemes for mail spools:
9864 mode 600 with all mail delivery done by processes running as
9865 the destination user, or mode 660 and owned by group mail with
9866 mail delivery done by a process running as a system user in
9867 group mail. Historically, Debian required mode 660 mail
9868 spools to enable the latter model, but that model has become
9869 increasingly uncommon and the principle of least privilege
9870 indicates that mail systems that use the first model should
9871 use permissions of 600. If delivery to programs is permitted,
9872 it's easier to keep the mail system secure if the delivery
9873 agent runs as the destination user. Debian Policy therefore
9874 permits either scheme.
9875 </footnote>. The local system administrator may choose a
9876 different permission scheme; packages should not make
9877 assumptions about the permission and ownership of mailboxes
9878 unless required (such as when creating a new mailbox). A MUA
9879 may remove a mailbox (unless it has nonstandard permissions) in
9880 which case the MTA or another MUA must recreate it if needed.
9884 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9885 be setgid mail to do the locking mentioned above (and
9886 must obviously avoid accessing other users' mailboxes
9887 using this privilege).</p>
9890 <file>/etc/aliases</file> is the source file for the system mail
9891 aliases (e.g., postmaster, usenet, etc.), it is the one
9892 which the sysadmin and <prgn>postinst</prgn> scripts may
9893 edit. After <file>/etc/aliases</file> is edited the program or
9894 human editing it must call <prgn>newaliases</prgn>. All MTA
9895 packages must come with a <prgn>newaliases</prgn> program,
9896 even if it does nothing, but older MTA packages did not do
9897 this so programs should not fail if <prgn>newaliases</prgn>
9898 cannot be found. Note that because of this, all MTA
9899 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9900 <tt>Replaces: mail-transport-agent</tt> control fields.
9904 The convention of writing <tt>forward to
9905 <var>address</var></tt> in the mailbox itself is not
9906 supported. Use a <tt>.forward</tt> file instead.</p>
9909 The <prgn>rmail</prgn> program used by UUCP
9910 for incoming mail should be <file>/usr/sbin/rmail</file>.
9911 Likewise, <prgn>rsmtp</prgn>, for receiving
9912 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9916 If your package needs to know what hostname to use on (for
9917 example) outgoing news and mail messages which are generated
9918 locally, you should use the file <file>/etc/mailname</file>. It
9919 will contain the portion after the username and <tt>@</tt>
9920 (at) sign for email addresses of users on the machine
9921 (followed by a newline).
9925 Such a package should check for the existence of this file
9926 when it is being configured. If it exists, it should be
9927 used without comment, although an MTA's configuration script
9928 may wish to prompt the user even if it finds that this file
9929 exists. If the file does not exist, the package should
9930 prompt the user for the value (preferably using
9931 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9932 as well as using it in the package's configuration. The
9933 prompt should make it clear that the name will not just be
9934 used by that package. For example, in this situation the
9935 <tt>inn</tt> package could say something like:
9936 <example compact="compact">
9937 Please enter the "mail name" of your system. This is the
9938 hostname portion of the address to be shown on outgoing
9939 news and mail messages. The default is
9940 <var>syshostname</var>, your system's host name. Mail
9941 name ["<var>syshostname</var>"]:
9943 where <var>syshostname</var> is the output of <tt>hostname
9949 <heading>News system configuration</heading>
9952 All the configuration files related to the NNTP (news)
9953 servers and clients should be located under
9954 <file>/etc/news</file>.</p>
9957 There are some configuration issues that apply to a number
9958 of news clients and server packages on the machine. These
9962 <tag><file>/etc/news/organization</file></tag>
9964 A string which should appear as the
9965 organization header for all messages posted
9966 by NNTP clients on the machine
9969 <tag><file>/etc/news/server</file></tag>
9971 Contains the FQDN of the upstream NNTP
9972 server, or localhost if the local machine is
9977 Other global files may be added as required for cross-package news
9984 <heading>Programs for the X Window System</heading>
9987 <heading>Providing X support and package priorities</heading>
9990 Programs that can be configured with support for the X
9991 Window System must be configured to do so and must declare
9992 any package dependencies necessary to satisfy their
9993 runtime requirements when using the X Window System. If
9994 such a package is of higher priority than the X packages
9995 on which it depends, it is required that either the
9996 X-specific components be split into a separate package, or
9997 that an alternative version of the package, which includes
9998 X support, be provided, or that the package's priority be
10004 <heading>Packages providing an X server</heading>
10007 Packages that provide an X server that, directly or
10008 indirectly, communicates with real input and display
10009 hardware should declare in their <tt>Provides</tt> control
10010 field that they provide the virtual
10011 package <tt>xserver</tt>.<footnote>
10012 This implements current practice, and provides an
10013 actual policy for usage of the <tt>xserver</tt>
10014 virtual package which appears in the virtual packages
10015 list. In a nutshell, X servers that interface
10016 directly with the display and input hardware or via
10017 another subsystem (e.g., GGI) should provide
10018 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
10019 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
10025 <heading>Packages providing a terminal emulator</heading>
10028 Packages that provide a terminal emulator for the X Window
10029 System which meet the criteria listed below should declare in
10030 their <tt>Provides</tt> control field that they provide the
10031 virtual package <tt>x-terminal-emulator</tt>. They should
10032 also register themselves as an alternative for
10033 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
10034 20. That alternative should have a slave alternative
10035 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
10036 pointing to the corresponding manual page.
10040 To be an <tt>x-terminal-emulator</tt>, a program must:
10041 <list compact="compact">
10043 Be able to emulate a DEC VT100 terminal, or a
10044 compatible terminal.
10048 Support the command-line option <tt>-e
10049 <var>command</var></tt>, which creates a new
10050 terminal window<footnote>
10051 "New terminal window" does not necessarily mean
10052 a new top-level X window directly parented by
10053 the window manager; it could, if the terminal
10054 emulator application were so coded, be a new
10055 "view" in a multiple-document interface (MDI).
10057 and runs the specified <var>command</var>,
10058 interpreting the entirety of the rest of the command
10059 line as a command to pass straight to exec, in the
10060 manner that <tt>xterm</tt> does.
10064 Support the command-line option <tt>-T
10065 <var>title</var></tt>, which creates a new terminal
10066 window with the window title <var>title</var>.
10073 <heading>Packages providing a window manager</heading>
10076 Packages that provide a window manager should declare in
10077 their <tt>Provides</tt> control field that they provide the
10078 virtual package <tt>x-window-manager</tt>. They should also
10079 register themselves as an alternative for
10080 <file>/usr/bin/x-window-manager</file>, with a priority
10081 calculated as follows:
10082 <list compact="compact">
10084 Start with a priority of 20.
10088 If the window manager supports the Debian menu
10089 system, add 20 points if this support is available
10090 in the package's default configuration (i.e., no
10091 configuration files belonging to the system or user
10092 have to be edited to activate the feature); if
10093 configuration files must be modified, add only 10
10099 If the window manager complies with <url
10100 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
10101 name="The Window Manager Specification Project">,
10102 written by the <url id="http://www.freedesktop.org/wiki/"
10103 name="Free Desktop Group">, add 40 points.
10107 If the window manager permits the X session to be
10108 restarted using a <em>different</em> window manager
10109 (without killing the X server) in its default
10110 configuration, add 10 points; otherwise add none.
10113 That alternative should have a slave alternative
10114 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
10115 pointing to the corresponding manual page.
10120 <heading>Packages providing fonts</heading>
10123 Packages that provide fonts for the X Window
10125 For the purposes of Debian Policy, a "font for the X
10126 Window System" is one which is accessed via X protocol
10127 requests. Fonts for the Linux console, for PostScript
10128 renderer, or any other purpose, do not fit this
10129 definition. Any tool which makes such fonts available
10130 to the X Window System, however, must abide by this
10133 must do a number of things to ensure that they are both
10134 available without modification of the X or font server
10135 configuration, and that they do not corrupt files used by
10136 other font packages to register information about
10140 Fonts of any type supported by the X Window System
10141 must be in a separate binary package from any
10142 executables, libraries, or documentation (except
10143 that specific to the fonts shipped, such as their
10144 license information). If one or more of the fonts
10145 so packaged are necessary for proper operation of
10146 the package with which they are associated the font
10147 package may be Recommended; if the fonts merely
10148 provide an enhancement, a Suggests relationship may
10149 be used. Packages must not Depend on font
10150 packages.<footnote>
10151 This is because the X server may retrieve fonts
10152 from the local file system or over the network
10153 from an X font server; the Debian package system
10154 is empowered to deal only with the local
10160 BDF fonts must be converted to PCF fonts with the
10161 <prgn>bdftopcf</prgn> utility (available in the
10162 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
10163 placed in a directory that corresponds to their
10165 <list compact="compact">
10167 100 dpi fonts must be placed in
10168 <file>/usr/share/fonts/X11/100dpi/</file>.
10172 75 dpi fonts must be placed in
10173 <file>/usr/share/fonts/X11/75dpi/</file>.
10177 Character-cell fonts, cursor fonts, and other
10178 low-resolution fonts must be placed in
10179 <file>/usr/share/fonts/X11/misc/</file>.
10185 Type 1 fonts must be placed in
10186 <file>/usr/share/fonts/X11/Type1/</file>. If font
10187 metric files are available, they must be placed here
10192 Subdirectories of <file>/usr/share/fonts/X11/</file>
10193 other than those listed above must be neither
10194 created nor used. (The <file>PEX</file>, <file>CID</file>,
10195 <file>Speedo</file>, and <file>cyrillic</file> directories
10196 are excepted for historical reasons, but installation of
10197 files into these directories remains discouraged.)
10201 Font packages may, instead of placing files directly
10202 in the X font directories listed above, provide
10203 symbolic links in that font directory pointing to
10204 the files' actual location in the filesystem. Such
10205 a location must comply with the FHS.
10209 Font packages should not contain both 75dpi and
10210 100dpi versions of a font. If both are available,
10211 they should be provided in separate binary packages
10212 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
10213 the names of the packages containing the
10214 corresponding fonts.
10218 Fonts destined for the <file>misc</file> subdirectory
10219 should not be included in the same package as 75dpi
10220 or 100dpi fonts; instead, they should be provided in
10221 a separate package with <tt>-misc</tt> appended to
10226 Font packages must not provide the files
10227 <file>fonts.dir</file>, <file>fonts.alias</file>, or
10228 <file>fonts.scale</file> in a font directory:
10231 <file>fonts.dir</file> files must not be provided at all.
10235 <file>fonts.alias</file> and <file>fonts.scale</file>
10236 files, if needed, should be provided in the
10238 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
10239 where <var>fontdir</var> is the name of the
10241 <file>/usr/share/fonts/X11/</file> where the
10242 package's corresponding fonts are stored
10243 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
10244 <var>package</var> is the name of the package
10245 that provides these fonts, and
10246 <var>extension</var> is either <tt>scale</tt>
10247 or <tt>alias</tt>, whichever corresponds to
10254 Font packages must declare a dependency on
10255 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
10256 or <tt>Pre-Depends</tt> control field.
10260 Font packages that provide one or more
10261 <file>fonts.scale</file> files as described above must
10262 invoke <prgn>update-fonts-scale</prgn> on each
10263 directory into which they installed fonts
10264 <em>before</em> invoking
10265 <prgn>update-fonts-dir</prgn> on that directory.
10266 This invocation must occur in both the
10267 <prgn>postinst</prgn> (for all arguments) and
10268 <prgn>postrm</prgn> (for all arguments except
10269 <tt>upgrade</tt>) scripts.
10273 Font packages that provide one or more
10274 <file>fonts.alias</file> files as described above must
10275 invoke <prgn>update-fonts-alias</prgn> on each
10276 directory into which they installed fonts. This
10277 invocation must occur in both the
10278 <prgn>postinst</prgn> (for all arguments) and
10279 <prgn>postrm</prgn> (for all arguments except
10280 <tt>upgrade</tt>) scripts.
10284 Font packages must invoke
10285 <prgn>update-fonts-dir</prgn> on each directory into
10286 which they installed fonts. This invocation must
10287 occur in both the <prgn>postinst</prgn> (for all
10288 arguments) and <prgn>postrm</prgn> (for all
10289 arguments except <tt>upgrade</tt>) scripts.
10293 Font packages must not provide alias names for the
10294 fonts they include which collide with alias names
10295 already in use by fonts already packaged.
10299 Font packages must not provide fonts with the same
10300 XLFD registry name as another font already packaged.
10306 <sect1 id="appdefaults">
10307 <heading>Application defaults files</heading>
10310 Application defaults files must be installed in the
10311 directory <file>/etc/X11/app-defaults/</file> (use of a
10312 localized subdirectory of <file>/etc/X11/</file> as described
10313 in the <em>X Toolkit Intrinsics - C Language
10314 Interface</em> manual is also permitted). They must be
10315 registered as <tt>conffile</tt>s or handled as
10316 configuration files.
10320 Customization of programs' X resources may also be
10321 supported with the provision of a file with the same name
10322 as that of the package placed in
10323 the <file>/etc/X11/Xresources/</file> directory, which
10324 must be registered as a <tt>conffile</tt> or handled as a
10325 configuration file.<footnote>
10326 Note that this mechanism is not the same as using
10327 app-defaults; app-defaults are tied to the client
10328 binary on the local file system, whereas X resources
10329 are stored in the X server and affect all connecting
10336 <heading>Installation directory issues</heading>
10339 Historically, packages using the X Window System used a
10340 separate set of installation directories from other packages.
10341 This practice has been discontinued and packages using the X
10342 Window System should now generally be installed in the same
10343 directories as any other package. Specifically, packages must
10344 not install files under the <file>/usr/X11R6/</file> directory
10345 and the <file>/usr/X11R6/</file> directory hierarchy should be
10346 regarded as obsolete.
10350 Include files previously installed under
10351 <file>/usr/X11R6/include/X11/</file> should be installed into
10352 <file>/usr/include/X11/</file>. For files previously
10353 installed into subdirectories of
10354 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
10355 determine if subdirectories of <file>/usr/lib/</file> and
10356 <file>/usr/share/</file> can be used. If not, a subdirectory
10357 of <file>/usr/lib/X11/</file> should be used.
10361 Configuration files for window, display, or session managers
10362 or other applications that are tightly integrated with the X
10363 Window System may be placed in a subdirectory
10364 of <file>/etc/X11/</file> corresponding to the package name.
10365 Other X Window System applications should use
10366 the <file>/etc/</file> directory unless otherwise mandated by
10367 policy (such as for <ref id="appdefaults">).
10373 <heading>Perl programs and modules</heading>
10376 Perl programs and modules should follow the current Perl policy.
10380 The Perl policy can be found in the <tt>perl-policy</tt>
10381 files in the <tt>debian-policy</tt> package.
10382 It is also available from the Debian web mirrors at
10383 <tt><url name="/doc/packaging-manuals/perl-policy/"
10384 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
10389 <heading>Emacs lisp programs</heading>
10392 Please refer to the "Debian Emacs Policy" for details of how to
10393 package emacs lisp programs.
10397 The Emacs policy is available in
10398 <file>debian-emacs-policy.gz</file> of the
10399 <package>emacsen-common</package> package.
10400 It is also available from the Debian web mirrors at
10401 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
10402 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
10407 <heading>Games</heading>
10410 The permissions on <file>/var/games</file> are mode 755, owner
10411 <tt>root</tt> and group <tt>root</tt>.
10415 Each game decides on its own security policy.</p>
10418 Games which require protected, privileged access to
10419 high-score files, saved games, etc., may be made
10420 set-<em>group</em>-id (mode 2755) and owned by
10421 <tt>root:games</tt>, and use files and directories with
10422 appropriate permissions (770 <tt>root:games</tt>, for
10423 example). They must not be made
10424 set-<em>user</em>-id, as this causes security problems. (If
10425 an attacker can subvert any set-user-id game they can
10426 overwrite the executable of any other, causing other players
10427 of these games to run a Trojan horse program. With a
10428 set-group-id game the attacker only gets access to less
10429 important game data, and if they can get at the other
10430 players' accounts at all it will take considerably more
10434 Some packages, for example some fortune cookie programs, are
10435 configured by the upstream authors to install with their
10436 data files or other static information made unreadable so
10437 that they can only be accessed through set-id programs
10438 provided. You should not do this in a Debian package: anyone can
10439 download the <file>.deb</file> file and read the data from it,
10440 so there is no point making the files unreadable. Not
10441 making the files unreadable also means that you don't have
10442 to make so many programs set-id, which reduces the risk of a
10446 As described in the FHS, binaries of games should be
10447 installed in the directory <file>/usr/games</file>. This also
10448 applies to games that use the X Window System. Manual pages
10449 for games (X and non-X games) should be installed in
10450 <file>/usr/share/man/man6</file>.</p>
10456 <heading>Documentation</heading>
10459 <heading>Manual pages</heading>
10462 You should install manual pages in <prgn>nroff</prgn> source
10463 form, in appropriate places under <file>/usr/share/man</file>.
10464 You should only use sections 1 to 9 (see the FHS for more
10465 details). You must not install a pre-formatted "cat page".
10469 Each program, utility, and function should have an
10470 associated manual page included in the same package. It is
10471 suggested that all configuration files also have a manual
10472 page included as well. Manual pages for protocols and other
10473 auxiliary things are optional.
10477 If no manual page is available, this is considered as a bug
10478 and should be reported to the Debian Bug Tracking System (the
10479 maintainer of the package is allowed to write this bug report
10480 themselves, if they so desire). Do not close the bug report
10481 until a proper man page is available.<footnote>
10482 It is not very hard to write a man page. See the
10483 <url id="http://www.schweikhardt.net/man_page_howto.html"
10484 name="Man-Page-HOWTO">,
10485 <manref name="man" section="7">, the examples created
10486 by <prgn>dh_make</prgn>, the helper
10487 program <prgn>help2man</prgn>, or the
10488 directory <file>/usr/share/doc/man-db/examples</file>.
10493 You may forward a complaint about a missing man page to the
10494 upstream authors, and mark the bug as forwarded in the
10495 Debian bug tracking system. Even though the GNU Project do
10496 not in general consider the lack of a man page to be a bug,
10497 we do; if they tell you that they don't consider it a bug
10498 you should leave the bug in our bug tracking system open
10503 Manual pages should be installed compressed using <tt>gzip -9</tt>.
10507 If one man page needs to be accessible via several names it
10508 is better to use a symbolic link than the <file>.so</file>
10509 feature, but there is no need to fiddle with the relevant
10510 parts of the upstream source to change from <file>.so</file> to
10511 symlinks: don't do it unless it's easy. You should not
10512 create hard links in the manual page directories, nor put
10513 absolute filenames in <file>.so</file> directives. The filename
10514 in a <file>.so</file> in a man page should be relative to the
10515 base of the man page tree (usually
10516 <file>/usr/share/man</file>). If you do not create any links
10517 (whether symlinks, hard links, or <tt>.so</tt> directives)
10518 in the file system to the alternate names of the man page,
10519 then you should not rely on <prgn>man</prgn> finding your
10520 man page under those names based solely on the information in
10521 the man page's header.<footnote>
10522 Supporting this in <prgn>man</prgn> often requires
10523 unreasonable processing time to find a manual page or to
10524 report that none exists, and moves knowledge into man's
10525 database that would be better left in the file system.
10526 This support is therefore deprecated and will cease to
10527 be present in the future.
10532 Manual pages in locale-specific subdirectories of
10533 <file>/usr/share/man</file> should use either UTF-8 or the usual
10534 legacy encoding for that language (normally the one corresponding
10535 to the shortest relevant locale name in
10536 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
10537 <file>/usr/share/man/fr</file> should use either UTF-8 or
10538 ISO-8859-1.<footnote>
10539 <prgn>man</prgn> will automatically detect whether UTF-8 is in
10540 use. In future, all manual pages will be required to use
10546 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
10547 included in the subdirectory name unless it indicates a
10548 significant difference in the language, as this excludes
10549 speakers of the language in other countries.<footnote>
10550 At the time of writing, Chinese and Portuguese are the main
10551 languages with such differences, so <file>pt_BR</file>,
10552 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
10557 If a localized version of a manual page is provided, it should
10558 either be up-to-date or it should be obvious to the reader that
10559 it is outdated and the original manual page should be used
10560 instead. This can be done either by a note at the beginning of
10561 the manual page or by showing the missing or changed portions in
10562 the original language instead of the target language.
10567 <heading>Info documents</heading>
10570 Info documents should be installed in <file>/usr/share/info</file>.
10571 They should be compressed with <tt>gzip -9</tt>.
10575 The <prgn>install-info</prgn> program maintains a directory of
10576 installed info documents in <file>/usr/share/info/dir</file> for the
10577 use of info readers. This file must not be included in packages
10578 other than <package>install-info</package>.
10582 <prgn>install-info</prgn> is automatically invoked when
10583 appropriate using dpkg triggers. Packages other than
10584 <package>install-info</package> <em>should not</em> invoke
10585 <prgn>install-info</prgn> directly and <em>should not</em>
10586 depend on, recommend, or suggest <package>install-info</package>
10591 Info readers requiring the <file>/usr/share/info/dir</file> file
10592 should depend on <package>install-info</package>.
10596 Info documents should contain section and directory entry
10597 information in the document for the use
10598 of <prgn>install-info</prgn>. The section should be specified
10599 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
10600 space and the section of this info page. The directory entry or
10601 entries should be included between
10602 a <tt>START-INFO-DIR-ENTRY</tt> line and
10603 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
10605 INFO-DIR-SECTION Individual utilities
10606 START-INFO-DIR-ENTRY
10607 * example: (example). An example info directory entry.
10610 To determine which section to use, you should look
10611 at <file>/usr/share/info/dir</file> on your system and choose
10612 the most relevant (or create a new section if none of the
10613 current sections are relevant).<footnote>
10614 Normally, info documents are generated from Texinfo source.
10615 To include this information in the generated info document, if
10616 it is absent, add commands like:
10618 @dircategory Individual utilities
10620 * example: (example). An example info directory entry.
10623 to the Texinfo source of the document and ensure that the info
10624 documents are rebuilt from source during the package build.
10630 <heading>Additional documentation</heading>
10633 Any additional documentation that comes with the package may
10634 be installed at the discretion of the package maintainer.
10635 Plain text documentation should be installed in the directory
10636 <file>/usr/share/doc/<var>package</var></file>, where
10637 <var>package</var> is the name of the package, and
10638 compressed with <tt>gzip -9</tt> unless it is small.
10642 If a package comes with large amounts of documentation which
10643 many users of the package will not require you should create
10644 a separate binary package to contain it, so that it does not
10645 take up disk space on the machines of users who do not need
10646 or want it installed.</p>
10649 It is often a good idea to put text information files
10650 (<file>README</file>s, changelogs, and so forth) that come with
10651 the source package in <file>/usr/share/doc/<var>package</var></file>
10652 in the binary package. However, you don't need to install
10653 the instructions for building and installing the package, of
10657 Packages must not require the existence of any files in
10658 <file>/usr/share/doc/</file> in order to function
10660 The system administrator should be able to
10661 delete files in <file>/usr/share/doc/</file> without causing
10662 any programs to break.
10664 Any files that are referenced by programs but are also
10665 useful as stand alone documentation should be installed under
10666 <file>/usr/share/<var>package</var>/</file> with symbolic links from
10667 <file>/usr/share/doc/<var>package</var></file>.
10671 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10672 link to another directory in <file>/usr/share/doc</file> only if
10673 the two packages both come from the same source and the
10674 first package Depends on the second.<footnote>
10676 Please note that this does not override the section on
10677 changelog files below, so the file
10678 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
10679 must refer to the changelog for the current version of
10680 <var>package</var> in question. In practice, this means
10681 that the sources of the target and the destination of the
10682 symlink must be the same (same source package and
10689 Former Debian releases placed all additional documentation
10690 in <file>/usr/doc/<var>package</var></file>. This has been
10691 changed to <file>/usr/share/doc/<var>package</var></file>,
10692 and packages must not put documentation in the directory
10693 <file>/usr/doc/<var>package</var></file>. <footnote>
10694 At this phase of the transition, we no longer require a
10695 symbolic link in <file>/usr/doc/</file>. At a later point,
10696 policy shall change to make the symbolic links a bug.
10702 <heading>Preferred documentation formats</heading>
10705 The unification of Debian documentation is being carried out
10709 If your package comes with extensive documentation in a
10710 markup format that can be converted to various other formats
10711 you should if possible ship HTML versions in a binary
10712 package, in the directory
10713 <file>/usr/share/doc/<var>appropriate-package</var></file> or
10714 its subdirectories.<footnote>
10715 The rationale: The important thing here is that HTML
10716 docs should be available in <em>some</em> package, not
10717 necessarily in the main binary package.
10722 Other formats such as PostScript may be provided at the
10723 package maintainer's discretion.
10727 <sect id="copyrightfile">
10728 <heading>Copyright information</heading>
10731 Every package must be accompanied by a verbatim copy of its
10732 copyright information and distribution license in the file
10733 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
10734 file must neither be compressed nor be a symbolic link.
10738 In addition, the copyright file must say where the upstream
10739 sources (if any) were obtained, and should name the original
10744 Packages in the <em>contrib</em> or <em>non-free</em> archive
10745 areas should state in the copyright file that the package is not
10746 part of the Debian distribution and briefly explain why.
10750 A copy of the file which will be installed in
10751 <file>/usr/share/doc/<var>package</var>/copyright</file> should
10752 be in <file>debian/copyright</file> in the source package.
10756 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
10757 link to another directory in <file>/usr/share/doc</file> only if
10758 the two packages both come from the same source and the
10759 first package Depends on the second. These rules are important
10760 because <file>copyright</file> files must be extractable by
10765 Packages distributed under the Apache license (version 2.0), the
10766 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10767 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10768 1.3) should refer to the corresponding files
10769 under <file>/usr/share/common-licenses</file>,<footnote>
10772 <file>/usr/share/common-licenses/Apache-2.0</file>,
10773 <file>/usr/share/common-licenses/Artistic</file>,
10774 <file>/usr/share/common-licenses/GPL-1</file>,
10775 <file>/usr/share/common-licenses/GPL-2</file>,
10776 <file>/usr/share/common-licenses/GPL-3</file>,
10777 <file>/usr/share/common-licenses/LGPL-2</file>,
10778 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10779 <file>/usr/share/common-licenses/LGPL-3</file>,
10780 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10781 <file>/usr/share/common-licenses/GFDL-1.3</file>
10782 respectively. The University of California BSD license is
10783 also included in <package>base-files</package> as
10784 <file>/usr/share/common-licenses/BSD</file>, but given the
10785 brevity of this license, its specificity to code whose
10786 copyright is held by the Regents of the University of
10787 California, and the frequency of minor wording changes, its
10788 text should be included in the copyright file rather than
10789 referencing this file.
10791 </footnote> rather than quoting them in the copyright
10796 You should not use the copyright file as a general <file>README</file>
10797 file. If your package has such a file it should be
10798 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10799 <file>README.Debian</file> or some other appropriate place.
10803 All copyright files must be encoded in UTF-8.
10806 <sect1 id="copyrightformat">
10807 <heading>Machine-readable copyright information</heading>
10810 A specification for a standard, machine-readable format
10811 for <file>debian/copyright</file> files is maintained as part
10812 of the <package>debian-policy</package> package. This
10813 document may be found in the <file>copyright-format</file>
10814 files in the <package>debian-policy</package> package. It is
10815 also available from the Debian web mirrors at
10816 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10817 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10821 Use of this format is optional.
10827 <heading>Examples</heading>
10830 Any examples (configurations, source files, whatever),
10831 should be installed in a directory
10832 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10833 files should not be referenced by any program: they're there
10834 for the benefit of the system administrator and users as
10835 documentation only. Architecture-specific example files
10836 should be installed in a directory
10837 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10839 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10840 latter directory itself may be a symbolic link to the
10845 If the purpose of a package is to provide examples, then the
10846 example files may be installed into
10847 <file>/usr/share/doc/<var>package</var></file>.
10851 <sect id="changelogs">
10852 <heading>Changelog files</heading>
10855 Packages that are not Debian-native must contain a
10856 compressed copy of the <file>debian/changelog</file> file from
10857 the Debian source tree in
10858 <file>/usr/share/doc/<var>package</var></file> with the name
10859 <file>changelog.Debian.gz</file>.
10863 If an upstream changelog is available, it should be accessible as
10864 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10865 plain text. If the upstream changelog is distributed in
10866 HTML, it should be made available in that form as
10867 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10868 and a plain text <file>changelog.gz</file> should be generated
10869 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10870 the upstream changelog files do not already conform to this
10871 naming convention, then this may be achieved either by
10872 renaming the files, or by adding a symbolic link, at the
10873 maintainer's discretion.<footnote>
10874 Rationale: People should not have to look in places for
10875 upstream changelogs merely because they are given
10876 different names or are distributed in HTML format.
10881 All of these files should be installed compressed using
10882 <tt>gzip -9</tt>, as they will become large with time even
10883 if they start out small.
10887 If the package has only one changelog which is used both as
10888 the Debian changelog and the upstream one because there is
10889 no separate upstream maintainer then that changelog should
10890 usually be installed as
10891 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10892 there is a separate upstream maintainer, but no upstream
10893 changelog, then the Debian changelog should still be called
10894 <file>changelog.Debian.gz</file>.
10898 For details about the format and contents of the Debian
10899 changelog file, please see <ref id="dpkgchangelog">.
10904 <appendix id="pkg-scope">
10905 <heading>Introduction and scope of these appendices</heading>
10908 These appendices are taken essentially verbatim from the
10909 now-deprecated Packaging Manual, version 3.2.1.0. They are
10910 the chapters which are likely to be of use to package
10911 maintainers and which have not already been included in the
10912 policy document itself. Most of these sections are very likely
10913 not relevant to policy; they should be treated as
10914 documentation for the packaging system. Please note that these
10915 appendices are included for convenience, and for historical
10916 reasons: they used to be part of policy package, and they have
10917 not yet been incorporated into dpkg documentation. However,
10918 they still have value, and hence they are presented here.
10922 They have not yet been checked to ensure that they are
10923 compatible with the contents of policy, and if there are any
10924 contradictions, the version in the main policy document takes
10925 precedence. The remaining chapters of the old Packaging
10926 Manual have also not been read in detail to ensure that there
10927 are not parts which have been left out. Both of these will be
10928 done in due course.
10932 Certain parts of the Packaging manual were integrated into the
10933 Policy Manual proper, and removed from the appendices. Links
10934 have been placed from the old locations to the new ones.
10938 <prgn>dpkg</prgn> is a suite of programs for creating binary
10939 package files and installing and removing them on Unix
10941 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10942 work on or be ported to other systems.
10947 The binary packages are designed for the management of
10948 installed executable programs (usually compiled binaries) and
10949 their associated data, though source code examples and
10950 documentation are provided as part of some packages.</p>
10953 This manual describes the technical aspects of creating Debian
10954 binary packages (<file>.deb</file> files). It documents the
10955 behavior of the package management programs
10956 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10957 they interact with packages.</p>
10960 This manual does not go into detail about the options and
10961 usage of the package building and installation tools. It
10962 should therefore be read in conjunction with those programs'
10967 The utility programs which are provided with <prgn>dpkg</prgn>
10968 not described in detail here, are documented in their man pages.
10972 It is assumed that the reader is reasonably familiar with the
10973 <prgn>dpkg</prgn> System Administrators' manual.
10974 Unfortunately this manual does not yet exist.
10978 The Debian version of the FSF's GNU hello program is provided as
10979 an example for people wishing to create Debian packages. However,
10980 while the examples are helpful, they do not replace the need to
10981 read and follow the Policy and Programmer's Manual.</p>
10984 <appendix id="pkg-binarypkg">
10985 <heading>Binary packages (from old Packaging Manual)</heading>
10988 See <manref name="deb" section="5"> and <ref id="pkg-controlarea">.
10991 <sect id="pkg-bincreating"><heading>Creating package files -
10992 <prgn>dpkg-deb</prgn>
10996 All manipulation of binary package files is done by
10997 <prgn>dpkg-deb</prgn>; it's the only program that has
10998 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10999 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
11000 will spot that the options requested are appropriate to
11001 <prgn>dpkg-deb</prgn> and invoke that instead with the same
11006 In order to create a binary package you must make a
11007 directory tree which contains all the files and directories
11008 you want to have in the file system data part of the package.
11009 In Debian-format source packages this directory is usually
11010 <file>debian/tmp</file>, relative to the top of the package's
11015 They should have the locations (relative to the root of the
11016 directory tree you're constructing) ownerships and
11017 permissions which you want them to have on the system when
11018 they are installed.
11022 With current versions of <prgn>dpkg</prgn> the uid/username
11023 and gid/groupname mappings for the users and groups being
11024 used should be the same on the system where the package is
11025 built and the one where it is installed.
11029 You need to add one special directory to the root of the
11030 miniature file system tree you're creating:
11031 <prgn>DEBIAN</prgn>. It should contain the control
11032 information files, notably the binary package control file
11033 (see <ref id="pkg-controlfile">).
11037 The <prgn>DEBIAN</prgn> directory will not appear in the
11038 file system archive of the package, and so won't be installed
11039 by <prgn>dpkg</prgn> when the package is unpacked.
11043 When you've prepared the package, you should invoke:
11045 dpkg --build <var>directory</var>
11050 This will build the package in
11051 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
11052 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
11053 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
11054 build the package.)
11058 See the man page <manref name="dpkg-deb" section="8"> for details of how
11059 to examine the contents of this newly-created file. You may find the
11060 output of following commands enlightening:
11062 dpkg-deb --info <var>filename</var>.deb
11063 dpkg-deb --contents <var>filename</var>.deb
11064 dpkg --contents <var>filename</var>.deb
11066 To view the copyright file for a package you could use this command:
11068 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
11073 <sect id="pkg-controlarea">
11074 <heading>Package control information files</heading>
11077 The control information portion of a binary package is a
11078 collection of files with names known to <prgn>dpkg</prgn>.
11079 It will treat the contents of these files specially - some
11080 of them contain information used by <prgn>dpkg</prgn> when
11081 installing or removing the package; others are scripts which
11082 the package maintainer wants <prgn>dpkg</prgn> to run.
11086 It is possible to put other files in the package control
11087 information file area, but this is not generally a good idea
11088 (though they will largely be ignored).
11092 Here is a brief list of the control information files supported
11093 by <prgn>dpkg</prgn> and a summary of what they're used for.
11098 <tag><tt>control</tt>
11101 This is the key description file used by
11102 <prgn>dpkg</prgn>. It specifies the package's name
11103 and version, gives its description for the user,
11104 states its relationships with other packages, and so
11105 forth. See <ref id="sourcecontrolfiles"> and
11106 <ref id="binarycontrolfiles">.
11110 It is usually generated automatically from information
11111 in the source package by the
11112 <prgn>dpkg-gencontrol</prgn> program, and with
11113 assistance from <prgn>dpkg-shlibdeps</prgn>.
11114 See <ref id="pkg-sourcetools">.
11118 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
11123 These are executable files (usually scripts) which
11124 <prgn>dpkg</prgn> runs during installation, upgrade
11125 and removal of packages. They allow the package to
11126 deal with matters which are particular to that package
11127 or require more complicated processing than that
11128 provided by <prgn>dpkg</prgn>. Details of when and
11129 how they are called are in <ref id="maintainerscripts">.
11133 It is very important to make these scripts idempotent.
11134 See <ref id="idempotency">.
11138 The maintainer scripts are not guaranteed to run with a
11139 controlling terminal and may not be able to interact with
11140 the user. See <ref id="controllingterminal">.
11144 <tag><tt>conffiles</tt>
11147 This file contains a list of configuration files which
11148 are to be handled automatically by <prgn>dpkg</prgn>
11149 (see <ref id="pkg-conffiles">). Note that not necessarily
11150 every configuration file should be listed here.
11153 <tag><tt>shlibs</tt>
11156 This file contains a list of the shared libraries
11157 supplied by the package, with dependency details for
11158 each. This is used by <prgn>dpkg-shlibdeps</prgn>
11159 when it determines what dependencies are required in a
11160 package control file. The <tt>shlibs</tt> file format
11161 is described on <ref id="shlibs">.
11166 <sect id="pkg-controlfile">
11167 <heading>The main control information file: <tt>control</tt></heading>
11170 The most important control information file used by
11171 <prgn>dpkg</prgn> when it installs a package is
11172 <tt>control</tt>. It contains all the package's "vital
11177 The binary package control files of packages built from
11178 Debian sources are made by a special tool,
11179 <prgn>dpkg-gencontrol</prgn>, which reads
11180 <file>debian/control</file> and <file>debian/changelog</file> to
11181 find the information it needs. See <ref id="pkg-sourcepkg"> for
11186 The fields in binary package control files are listed in
11187 <ref id="binarycontrolfiles">.
11191 A description of the syntax of control files and the purpose
11192 of the fields is available in <ref id="controlfields">.
11197 <heading>Time Stamps</heading>
11200 See <ref id="timestamps">.
11205 <appendix id="pkg-sourcepkg">
11206 <heading>Source packages (from old Packaging Manual) </heading>
11209 The Debian binary packages in the distribution are generated
11210 from Debian sources, which are in a special format to assist
11211 the easy and automatic building of binaries.
11214 <sect id="pkg-sourcetools">
11215 <heading>Tools for processing source packages</heading>
11218 Various tools are provided for manipulating source packages;
11219 they pack and unpack sources and help build of binary
11220 packages and help manage the distribution of new versions.
11224 They are introduced and typical uses described here; see
11225 <manref name="dpkg-source" section="1"> for full
11226 documentation about their arguments and operation.
11230 For examples of how to construct a Debian source package,
11231 and how to use those utilities that are used by Debian
11232 source packages, please see the <prgn>hello</prgn> example
11236 <sect1 id="pkg-dpkg-source">
11238 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
11243 This program is frequently used by hand, and is also
11244 called from package-independent automated building scripts
11245 such as <prgn>dpkg-buildpackage</prgn>.
11249 To unpack a package it is typically invoked with
11251 dpkg-source -x <var>.../path/to/filename</var>.dsc
11256 with the <file><var>filename</var>.tar.gz</file> and
11257 <file><var>filename</var>.diff.gz</file> (if applicable) in
11258 the same directory. It unpacks into
11259 <file><var>package</var>-<var>version</var></file>, and if
11261 <file><var>package</var>-<var>version</var>.orig</file>, in
11262 the current directory.
11266 To create a packed source archive it is typically invoked:
11268 dpkg-source -b <var>package</var>-<var>version</var>
11273 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
11274 <file>.diff.gz</file> (if appropriate) in the current
11275 directory. <prgn>dpkg-source</prgn> does not clean the
11276 source tree first - this must be done separately if it is
11281 See also <ref id="pkg-sourcearchives">.</p>
11285 <sect1 id="pkg-dpkg-buildpackage">
11287 <prgn>dpkg-buildpackage</prgn> - overall package-building
11292 See <manref name="dpkg-buildpackage" section="1">.
11296 <sect1 id="pkg-dpkg-gencontrol">
11298 <prgn>dpkg-gencontrol</prgn> - generates binary package
11303 This program is usually called from <file>debian/rules</file>
11304 (see <ref id="pkg-sourcetree">) in the top level of the source
11309 This is usually done just before the files and directories in the
11310 temporary directory tree where the package is being built have their
11311 permissions and ownerships set and the package is constructed using
11312 <prgn>dpkg-deb/</prgn>
11314 This is so that the control file which is produced has
11315 the right permissions
11320 <prgn>dpkg-gencontrol</prgn> must be called after all the
11321 files which are to go into the package have been placed in
11322 the temporary build directory, so that its calculation of
11323 the installed size of a package is correct.
11327 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
11328 be run after <prgn>dpkg-shlibdeps</prgn> so that the
11329 variable substitutions created by
11330 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
11335 For a package which generates only one binary package, and
11336 which builds it in <file>debian/tmp</file> relative to the top
11337 of the source package, it is usually sufficient to call
11338 <prgn>dpkg-gencontrol</prgn>.
11342 Sources which build several binaries will typically need
11345 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
11346 </example> The <tt>-P</tt> tells
11347 <prgn>dpkg-gencontrol</prgn> that the package is being
11348 built in a non-default directory, and the <tt>-p</tt>
11349 tells it which package's control file should be generated.
11353 <prgn>dpkg-gencontrol</prgn> also adds information to the
11354 list of files in <file>debian/files</file>, for the benefit of
11355 (for example) a future invocation of
11356 <prgn>dpkg-genchanges</prgn>.</p>
11359 <sect1 id="pkg-dpkg-shlibdeps">
11361 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
11366 See <manref name="dpkg-shlibdeps" section="1">.
11370 <sect1 id="pkg-dpkg-distaddfile">
11372 <prgn>dpkg-distaddfile</prgn> - adds a file to
11373 <file>debian/files</file>
11377 Some packages' uploads need to include files other than
11378 the source and binary package files.
11382 <prgn>dpkg-distaddfile</prgn> adds a file to the
11383 <file>debian/files</file> file so that it will be included in
11384 the <file>.changes</file> file when
11385 <prgn>dpkg-genchanges</prgn> is run.
11389 It is usually invoked from the <tt>binary</tt> target of
11390 <file>debian/rules</file>:
11392 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
11394 The <var>filename</var> is relative to the directory where
11395 <prgn>dpkg-genchanges</prgn> will expect to find it - this
11396 is usually the directory above the top level of the source
11397 tree. The <file>debian/rules</file> target should put the
11398 file there just before or just after calling
11399 <prgn>dpkg-distaddfile</prgn>.
11403 The <var>section</var> and <var>priority</var> are passed
11404 unchanged into the resulting <file>.changes</file> file.
11409 <sect1 id="pkg-dpkg-genchanges">
11411 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
11412 upload control file
11416 See <manref name="dpkg-genchanges" section="1">.
11420 <sect1 id="pkg-dpkg-parsechangelog">
11422 <prgn>dpkg-parsechangelog</prgn> - produces parsed
11423 representation of a changelog
11427 See <manref name="dpkg-parsechangelog" section="1">.
11431 <sect1 id="pkg-dpkg-architecture">
11433 <prgn>dpkg-architecture</prgn> - information about the build and
11438 See <manref name="dpkg-architecture" section="1">.
11443 <sect id="pkg-sourcetree">
11444 <heading>The Debian package source tree</heading>
11447 The source archive scheme described later is intended to
11448 allow a Debian package source tree with some associated
11449 control information to be reproduced and transported easily.
11450 The Debian package source tree is a version of the original
11451 program with certain files added for the benefit of the
11452 packaging process, and with any other changes required
11453 made to the rest of the source code and installation
11458 The extra files created for Debian are in the subdirectory
11459 <file>debian</file> of the top level of the Debian package
11460 source tree. They are described below.
11463 <sect1 id="pkg-debianrules">
11464 <heading><file>debian/rules</file> - the main building script</heading>
11467 See <ref id="debianrules">.
11471 <sect1 id="pkg-srcsubstvars">
11472 <heading><file>debian/substvars</file> and variable substitutions</heading>
11475 See <ref id="substvars">.
11481 <heading><file>debian/files</file></heading>
11484 See <ref id="debianfiles">.
11488 <sect1><heading><file>debian/tmp</file>
11492 This is the canonical temporary location for the
11493 construction of binary packages by the <tt>binary</tt>
11494 target. The directory <file>tmp</file> serves as the root of
11495 the file system tree as it is being constructed (for
11496 example, by using the package's upstream makefiles install
11497 targets and redirecting the output there), and it also
11498 contains the <tt>DEBIAN</tt> subdirectory. See <ref
11499 id="pkg-bincreating">.
11503 If several binary packages are generated from the same
11504 source tree it is usual to use several
11505 <file>debian/tmp<var>something</var></file> directories, for
11506 example <file>tmp-a</file> or <file>tmp-doc</file>.
11510 Whatever <file>tmp</file> directories are created and used by
11511 <tt>binary</tt> must of course be removed by the
11512 <tt>clean</tt> target.</p></sect1>
11516 <sect id="pkg-sourcearchives"><heading>Source packages as archives
11520 As it exists on the FTP site, a Debian source package
11521 consists of three related files. You must have the right
11522 versions of all three to be able to use them.
11527 <tag>Debian source control file - <tt>.dsc</tt></tag>
11529 This file is a control file used by <prgn>dpkg-source</prgn>
11530 to extract a source package.
11531 See <ref id="debiansourcecontrolfiles">.
11535 Original source archive -
11537 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
11543 This is a compressed (with <tt>gzip -9</tt>)
11544 <prgn>tar</prgn> file containing the source code from
11545 the upstream authors of the program.
11550 Debian package diff -
11552 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
11558 This is a unified context diff (<tt>diff -u</tt>)
11559 giving the changes which are required to turn the
11560 original source into the Debian source. These changes
11561 may only include editing and creating plain files.
11562 The permissions of files, the targets of symbolic
11563 links and the characteristics of special files or
11564 pipes may not be changed and no files may be removed
11569 All the directories in the diff must exist, except the
11570 <file>debian</file> subdirectory of the top of the source
11571 tree, which will be created by
11572 <prgn>dpkg-source</prgn> if necessary when unpacking.
11576 The <prgn>dpkg-source</prgn> program will
11577 automatically make the <file>debian/rules</file> file
11578 executable (see below).</p></item>
11583 If there is no original source code - for example, if the
11584 package is specially prepared for Debian or the Debian
11585 maintainer is the same as the upstream maintainer - the
11586 format is slightly different: then there is no diff, and the
11588 <file><var>package</var>_<var>version</var>.tar.gz</file>,
11589 and preferably contains a directory named
11590 <file><var>package</var>-<var>version</var></file>.
11595 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11598 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11599 Debian source package. However, if it is not available it
11600 is possible to unpack a Debian source archive as follows:
11601 <enumlist compact="compact">
11604 Untar the tarfile, which will create a <file>.orig</file>
11608 <p>Rename the <file>.orig</file> directory to
11609 <file><var>package</var>-<var>version</var></file>.</p>
11613 Create the subdirectory <file>debian</file> at the top of
11614 the source tree.</p>
11616 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11618 <item><p>Untar the tarfile again if you want a copy of the original
11619 source code alongside the Debian version.</p>
11624 It is not possible to generate a valid Debian source archive
11625 without using <prgn>dpkg-source</prgn>. In particular,
11626 attempting to use <prgn>diff</prgn> directly to generate the
11627 <file>.diff.gz</file> file will not work.
11631 <heading>Restrictions on objects in source packages</heading>
11634 The source package may not contain any hard links
11636 This is not currently detected when building source
11637 packages, but only when extracting
11641 Hard links may be permitted at some point in the
11642 future, but would require a fair amount of
11644 </footnote>, device special files, sockets or setuid or
11647 Setgid directories are allowed.
11652 The source packaging tools manage the changes between the
11653 original and Debian source using <prgn>diff</prgn> and
11654 <prgn>patch</prgn>. Turning the original source tree as
11655 included in the <file>.orig.tar.gz</file> into the Debian
11656 package source must not involve any changes which cannot be
11657 handled by these tools. Problematic changes which cause
11658 <prgn>dpkg-source</prgn> to halt with an error when
11659 building the source package are:
11660 <list compact="compact">
11661 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11663 <item><p>Changing the targets of symbolic links.</p>
11665 <item><p>Creating directories, other than <file>debian</file>.</p>
11667 <item><p>Changes to the contents of binary files.</p></item>
11668 </list> Changes which cause <prgn>dpkg-source</prgn> to
11669 print a warning but continue anyway are:
11670 <list compact="compact">
11673 Removing files, directories or symlinks.
11675 Renaming a file is not treated specially - it is
11676 seen as the removal of the old file (which
11677 generates a warning, but is otherwise ignored),
11678 and the creation of the new one.
11684 Changed text files which are missing the usual final
11685 newline (either in the original or the modified
11690 Changes which are not represented, but which are not detected by
11691 <prgn>dpkg-source</prgn>, are:
11692 <list compact="compact">
11693 <item><p>Changing the permissions of files (other than
11694 <file>debian/rules</file>) and directories.</p></item>
11699 The <file>debian</file> directory and <file>debian/rules</file>
11700 are handled specially by <prgn>dpkg-source</prgn> - before
11701 applying the changes it will create the <file>debian</file>
11702 directory, and afterwards it will make
11703 <file>debian/rules</file> world-executable.
11709 <appendix id="pkg-controlfields">
11710 <heading>Control files and their fields (from old Packaging Manual)</heading>
11713 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11714 data in a common format, known as control files. Binary and
11715 source packages have control data as do the <file>.changes</file>
11716 files which control the installation of uploaded files, and
11717 <prgn>dpkg</prgn>'s internal databases are in a similar
11722 <heading>Syntax of control files</heading>
11725 See <ref id="controlsyntax">.
11729 It is important to note that there are several fields which
11730 are optional as far as <prgn>dpkg</prgn> and the related
11731 tools are concerned, but which must appear in every Debian
11732 package, or whose omission may cause problems.
11737 <heading>List of fields</heading>
11740 See <ref id="controlfieldslist">.
11744 This section now contains only the fields that didn't belong
11745 to the Policy manual.
11748 <sect1 id="pkg-f-Filename">
11749 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11752 These fields in <tt>Packages</tt> files give the
11753 filename(s) of (the parts of) a package in the
11754 distribution directories, relative to the root of the
11755 Debian hierarchy. If the package has been split into
11756 several parts the parts are all listed in order, separated
11761 <sect1 id="pkg-f-Size">
11762 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11765 These fields in <file>Packages</file> files give the size (in
11766 bytes, expressed in decimal) and MD5 checksum of the
11767 file(s) which make(s) up a binary package in the
11768 distribution. If the package is split into several parts
11769 the values for the parts are listed in order, separated by
11774 <sect1 id="pkg-f-Status">
11775 <heading><tt>Status</tt></heading>
11778 This field in <prgn>dpkg</prgn>'s status file records
11779 whether the user wants a package installed, removed or
11780 left alone, whether it is broken (requiring
11781 re-installation) or not and what its current state on the
11782 system is. Each of these pieces of information is a
11787 <sect1 id="pkg-f-Config-Version">
11788 <heading><tt>Config-Version</tt></heading>
11791 If a package is not installed or not configured, this
11792 field in <prgn>dpkg</prgn>'s status file records the last
11793 version of the package which was successfully
11798 <sect1 id="pkg-f-Conffiles">
11799 <heading><tt>Conffiles</tt></heading>
11802 This field in <prgn>dpkg</prgn>'s status file contains
11803 information about the automatically-managed configuration
11804 files held by a package. This field should <em>not</em>
11805 appear anywhere in a package!
11810 <heading>Obsolete fields</heading>
11813 These are still recognized by <prgn>dpkg</prgn> but should
11814 not appear anywhere any more.
11816 <taglist compact="compact">
11818 <tag><tt>Revision</tt></tag>
11819 <tag><tt>Package-Revision</tt></tag>
11820 <tag><tt>Package_Revision</tt></tag>
11822 The Debian revision part of the package version was
11823 at one point in a separate control field. This
11824 field went through several names.
11827 <tag><tt>Recommended</tt></tag>
11828 <item>Old name for <tt>Recommends</tt>.</item>
11830 <tag><tt>Optional</tt></tag>
11831 <item>Old name for <tt>Suggests</tt>.</item>
11833 <tag><tt>Class</tt></tag>
11834 <item>Old name for <tt>Priority</tt>.</item>
11843 <appendix id="pkg-conffiles">
11844 <heading>Configuration file handling (from old Packaging Manual)</heading>
11847 <prgn>dpkg</prgn> can do a certain amount of automatic
11848 handling of package configuration files.
11852 Whether this mechanism is appropriate depends on a number of
11853 factors, but basically there are two approaches to any
11854 particular configuration file.
11858 The easy method is to ship a best-effort configuration in the
11859 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11860 handle updates. If the user is unlikely to want to edit the
11861 file, but you need them to be able to without losing their
11862 changes, and a new package with a changed version of the file
11863 is only released infrequently, this is a good approach.
11867 The hard method is to build the configuration file from
11868 scratch in the <prgn>postinst</prgn> script, and to take the
11869 responsibility for fixing any mistakes made in earlier
11870 versions of the package automatically. This will be
11871 appropriate if the file is likely to need to be different on
11875 <sect><heading>Automatic handling of configuration files by
11880 A package may contain a control information file called
11881 <tt>conffiles</tt>. This file should be a list of filenames
11882 of configuration files needing automatic handling, separated
11883 by newlines. The filenames should be absolute pathnames,
11884 and the files referred to should actually exist in the
11889 When a package is upgraded <prgn>dpkg</prgn> will process
11890 the configuration files during the configuration stage,
11891 shortly before it runs the package's <prgn>postinst</prgn>
11896 For each file it checks to see whether the version of the
11897 file included in the package is the same as the one that was
11898 included in the last version of the package (the one that is
11899 being upgraded from); it also compares the version currently
11900 installed on the system with the one shipped with the last
11905 If neither the user nor the package maintainer has changed
11906 the file, it is left alone. If one or the other has changed
11907 their version, then the changed version is preferred - i.e.,
11908 if the user edits their file, but the package maintainer
11909 doesn't ship a different version, the user's changes will
11910 stay, silently, but if the maintainer ships a new version
11911 and the user hasn't edited it the new version will be
11912 installed (with an informative message). If both have
11913 changed their version the user is prompted about the problem
11914 and must resolve the differences themselves.
11918 The comparisons are done by calculating the MD5 message
11919 digests of the files, and storing the MD5 of the file as it
11920 was included in the most recent version of the package.
11924 When a package is installed for the first time
11925 <prgn>dpkg</prgn> will install the file that comes with it,
11926 unless that would mean overwriting a file already on the
11931 However, note that <prgn>dpkg</prgn> will <em>not</em>
11932 replace a conffile that was removed by the user (or by a
11933 script). This is necessary because with some programs a
11934 missing file produces an effect hard or impossible to
11935 achieve in another way, so that a missing file needs to be
11936 kept that way if the user did it.
11940 Note that a package should <em>not</em> modify a
11941 <prgn>dpkg</prgn>-handled conffile in its maintainer
11942 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11943 the user confusing and possibly dangerous options for
11944 conffile update when the package is upgraded.</p>
11947 <sect><heading>Fully-featured maintainer script configuration
11952 For files which contain site-specific information such as
11953 the hostname and networking details and so forth, it is
11954 better to create the file in the package's
11955 <prgn>postinst</prgn> script.
11959 This will typically involve examining the state of the rest
11960 of the system to determine values and other information, and
11961 may involve prompting the user for some information which
11962 can't be obtained some other way.
11966 When using this method there are a couple of important
11967 issues which should be considered:
11971 If you discover a bug in the program which generates the
11972 configuration file, or if the format of the file changes
11973 from one version to the next, you will have to arrange for
11974 the postinst script to do something sensible - usually this
11975 will mean editing the installed configuration file to remove
11976 the problem or change the syntax. You will have to do this
11977 very carefully, since the user may have changed the file,
11978 perhaps to fix the very problem that your script is trying
11979 to deal with - you will have to detect these situations and
11980 deal with them correctly.
11984 If you do go down this route it's probably a good idea to
11985 make the program that generates the configuration file(s) a
11986 separate program in <file>/usr/sbin</file>, by convention called
11987 <file><var>package</var>config</file> and then run that if
11988 appropriate from the post-installation script. The
11989 <tt><var>package</var>config</tt> program should not
11990 unquestioningly overwrite an existing configuration - if its
11991 mode of operation is geared towards setting up a package for
11992 the first time (rather than any arbitrary reconfiguration
11993 later) you should have it check whether the configuration
11994 already exists, and require a <tt>--force</tt> flag to
11995 overwrite it.</p></sect>
11998 <appendix id="pkg-alternatives"><heading>Alternative versions of
11999 an interface - <prgn>update-alternatives</prgn> (from old
12004 When several packages all provide different versions of the
12005 same program or file it is useful to have the system select a
12006 default, but to allow the system administrator to change it
12007 and have their decisions respected.
12011 For example, there are several versions of the <prgn>vi</prgn>
12012 editor, and there is no reason to prevent all of them from
12013 being installed at once, each under their own name
12014 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
12015 Nevertheless it is desirable to have the name <tt>vi</tt>
12016 refer to something, at least by default.
12020 If all the packages involved cooperate, this can be done with
12021 <prgn>update-alternatives</prgn>.
12025 Each package provides its own version under its own name, and
12026 calls <prgn>update-alternatives</prgn> in its postinst to
12027 register its version (and again in its prerm to deregister
12032 See the man page <manref name="update-alternatives"
12033 section="8"> for details.
12037 If <prgn>update-alternatives</prgn> does not seem appropriate
12038 you may wish to consider using diversions instead.</p>
12041 <appendix id="pkg-diversions"><heading>Diversions - overriding a
12042 package's version of a file (from old Packaging Manual)
12046 It is possible to have <prgn>dpkg</prgn> not overwrite a file
12047 when it reinstalls the package it belongs to, and to have it
12048 put the file from the package somewhere else instead.
12052 This can be used locally to override a package's version of a
12053 file, or by one package to override another's version (or
12054 provide a wrapper for it).
12058 Before deciding to use a diversion, read <ref
12059 id="pkg-alternatives"> to see if you really want a diversion
12060 rather than several alternative versions of a program.
12064 There is a diversion list, which is read by <prgn>dpkg</prgn>,
12065 and updated by a special program <prgn>dpkg-divert</prgn>.
12066 Please see <manref name="dpkg-divert" section="8"> for full
12067 details of its operation.
12071 When a package wishes to divert a file from another, it should
12072 call <prgn>dpkg-divert</prgn> in its preinst to add the
12073 diversion and rename the existing file. For example,
12074 supposing that a <prgn>smailwrapper</prgn> package wishes to
12075 install a wrapper around <file>/usr/sbin/smail</file>:
12077 dpkg-divert --package smailwrapper --add --rename \
12078 --divert /usr/sbin/smail.real /usr/sbin/smail
12079 </example> The <tt>--package smailwrapper</tt> ensures that
12080 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
12081 can bypass the diversion and get installed as the true version.
12082 It's safe to add the diversion unconditionally on upgrades since
12083 it will be left unchanged if it already exists, but
12084 <prgn>dpkg-divert</prgn> will display a message. To suppress that
12085 message, make the command conditional on the version from which
12086 the package is being upgraded:
12088 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
12089 dpkg-divert --package smailwrapper --add --rename \
12090 --divert /usr/sbin/smail.real /usr/sbin/smail
12092 </example> where <tt>1.0-2</tt> is the version at which the
12093 diversion was first added to the package. Running the command
12094 during abort-upgrade is pointless but harmless.
12098 The postrm has to do the reverse:
12100 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
12101 dpkg-divert --package smailwrapper --remove --rename \
12102 --divert /usr/sbin/smail.real /usr/sbin/smail
12104 </example> If the diversion was added at a particular version, the
12105 postrm should also handle the failure case of upgrading from an
12106 older version (unless the older version is so old that direct
12107 upgrades are no longer supported):
12109 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
12110 dpkg-divert --package smailwrapper --remove --rename \
12111 --divert /usr/sbin/smail.real /usr/sbin/smail
12113 </example> where <tt>1.0-2</tt> is the version at which the
12114 diversion was first added to the package. The postrm should not
12115 remove the diversion on upgrades both because there's no reason to
12116 remove the diversion only to immediately re-add it and since the
12117 postrm of the old package is run after unpacking so the removal of
12118 the diversion will fail.
12122 Do not attempt to divert a file which is vitally important for
12123 the system's operation - when using <prgn>dpkg-divert</prgn>
12124 there is a time, after it has been diverted but before
12125 <prgn>dpkg</prgn> has installed the new version, when the file
12126 does not exist.</p>
12129 Do not attempt to divert a conffile, as <prgn>dpkg</prgn> does not
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