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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
276 <sect id="definitions">
277 <heading>Definitions</heading>
280 The following terms are used in this Policy Manual:
284 The character encoding specified by ANSI X3.4-1986 and its
285 predecessor standards, referred to in MIME as US-ASCII, and
286 corresponding to an encoding in eight bits per character of
287 the first 128 <url id="http://www.unicode.org/"
288 name="Unicode"> characters, with the eighth bit always zero.
292 The transformation format (sometimes called encoding) of
293 <url id="http://www.unicode.org/" name="Unicode"> defined by
294 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
295 name="RFC 3629">. UTF-8 has the useful property of having
296 ASCII as a subset, so any text encoded in ASCII is trivially
306 <heading>The Debian Archive</heading>
309 The Debian GNU/Linux system is maintained and distributed as a
310 collection of <em>packages</em>. Since there are so many of
311 them (currently well over 15000), they are split into
312 <em>sections</em> and given <em>priorities</em> to simplify
313 the handling of them.
317 The effort of the Debian project is to build a free operating
318 system, but not every package we want to make accessible is
319 <em>free</em> in our sense (see the Debian Free Software
320 Guidelines, below), or may be imported/exported without
321 restrictions. Thus, the archive is split into areas<footnote>
322 The Debian archive software uses the term "component" internally
323 and in the Release file format to refer to the division of an
324 archive. The Debian Social Contract simply refers to "areas."
325 This document uses terminology similar to the Social Contract.
326 </footnote> based on their licenses and other restrictions.
330 The aims of this are:
332 <list compact="compact">
333 <item>to allow us to make as much software available as we can</item>
334 <item>to allow us to encourage everyone to write free software,
336 <item>to allow us to make it easy for people to produce
337 CD-ROMs of our system without violating any licenses,
338 import/export restrictions, or any other laws.</item>
343 The <em>main</em> archive area forms the <em>Debian GNU/Linux
348 Packages in the other archive areas (<tt>contrib</tt>,
349 <tt>non-free</tt>) are not considered to be part of the Debian
350 distribution, although we support their use and provide
351 infrastructure for them (such as our bug-tracking system and
352 mailing lists). This Debian Policy Manual applies to these
357 <heading>The Debian Free Software Guidelines</heading>
359 The Debian Free Software Guidelines (DFSG) form our
360 definition of "free software". These are:
362 <tag>Free Redistribution
365 The license of a Debian component may not restrict any
366 party from selling or giving away the software as a
367 component of an aggregate software distribution
368 containing programs from several different
369 sources. The license may not require a royalty or
370 other fee for such sale.
375 The program must include source code, and must allow
376 distribution in source code as well as compiled form.
381 The license must allow modifications and derived
382 works, and must allow them to be distributed under the
383 same terms as the license of the original software.
385 <tag>Integrity of The Author's Source Code
388 The license may restrict source-code from being
389 distributed in modified form <em>only</em> if the
390 license allows the distribution of "patch files"
391 with the source code for the purpose of modifying the
392 program at build time. The license must explicitly
393 permit distribution of software built from modified
394 source code. The license may require derived works to
395 carry a different name or version number from the
396 original software. (This is a compromise. The Debian
397 Project encourages all authors to not restrict any
398 files, source or binary, from being modified.)
400 <tag>No Discrimination Against Persons or Groups
403 The license must not discriminate against any person
406 <tag>No Discrimination Against Fields of Endeavor
409 The license must not restrict anyone from making use
410 of the program in a specific field of endeavor. For
411 example, it may not restrict the program from being
412 used in a business, or from being used for genetic
415 <tag>Distribution of License
418 The rights attached to the program must apply to all
419 to whom the program is redistributed without the need
420 for execution of an additional license by those
423 <tag>License Must Not Be Specific to Debian
426 The rights attached to the program must not depend on
427 the program's being part of a Debian system. If the
428 program is extracted from Debian and used or
429 distributed without Debian but otherwise within the
430 terms of the program's license, all parties to whom
431 the program is redistributed must have the same
432 rights as those that are granted in conjunction with
435 <tag>License Must Not Contaminate Other Software
438 The license must not place restrictions on other
439 software that is distributed along with the licensed
440 software. For example, the license must not insist
441 that all other programs distributed on the same medium
442 must be free software.
444 <tag>Example Licenses
447 The "GPL," "BSD," and "Artistic" licenses are examples of
448 licenses that we consider <em>free</em>.
455 <heading>Archive areas</heading>
458 <heading>The main archive area</heading>
461 Every package in <em>main</em> must comply with the DFSG
462 (Debian Free Software Guidelines).
466 In addition, the packages in <em>main</em>
467 <list compact="compact">
469 must not require a package outside of <em>main</em>
470 for compilation or execution (thus, the package must
471 not declare a "Depends", "Recommends", or
472 "Build-Depends" relationship on a non-<em>main</em>
476 must not be so buggy that we refuse to support them,
480 must meet all policy requirements presented in this
489 <heading>The contrib archive area</heading>
492 Every package in <em>contrib</em> must comply with the DFSG.
496 In addition, the packages in <em>contrib</em>
497 <list compact="compact">
499 must not be so buggy that we refuse to support them,
503 must meet all policy requirements presented in this
511 Examples of packages which would be included in
512 <em>contrib</em> are:
513 <list compact="compact">
515 free packages which require <em>contrib</em>,
516 <em>non-free</em> packages or packages which are not
517 in our archive at all for compilation or execution,
521 wrapper packages or other sorts of free accessories for
528 <sect1 id="non-free">
529 <heading>The non-free archive area</heading>
532 Packages must be placed in <em>non-free</em> if they are
533 not compliant with the DFSG or are encumbered by patents
534 or other legal issues that make their distribution
539 In addition, the packages in <em>non-free</em>
540 <list compact="compact">
542 must not be so buggy that we refuse to support them,
546 must meet all policy requirements presented in this
547 manual that it is possible for them to meet.
549 It is possible that there are policy
550 requirements which the package is unable to
551 meet, for example, if the source is
552 unavailable. These situations will need to be
553 handled on a case-by-case basis.
562 <sect id="pkgcopyright">
563 <heading>Copyright considerations</heading>
566 Every package must be accompanied by a verbatim copy of
567 its copyright and distribution license in the file
568 <file>/usr/share/doc/<var>package</var>/copyright</file>
569 (see <ref id="copyrightfile"> for further details).
573 We reserve the right to restrict files from being included
574 anywhere in our archives if
575 <list compact="compact">
577 their use or distribution would break a law,
580 there is an ethical conflict in their distribution or
584 we would have to sign a license for them, or
587 their distribution would conflict with other project
594 Programs whose authors encourage the user to make
595 donations are fine for the main distribution, provided
596 that the authors do not claim that not donating is
597 immoral, unethical, illegal or something similar; in such
598 a case they must go in <em>non-free</em>.
602 Packages whose copyright permission notices (or patent
603 problems) do not even allow redistribution of binaries
604 only, and where no special permission has been obtained,
605 must not be placed on the Debian FTP site and its mirrors
610 Note that under international copyright law (this applies
611 in the United States, too), <em>no</em> distribution or
612 modification of a work is allowed without an explicit
613 notice saying so. Therefore a program without a copyright
614 notice <em>is</em> copyrighted and you may not do anything
615 to it without risking being sued! Likewise if a program
616 has a copyright notice but no statement saying what is
617 permitted then nothing is permitted.
621 Many authors are unaware of the problems that restrictive
622 copyrights (or lack of copyright notices) can cause for
623 the users of their supposedly-free software. It is often
624 worthwhile contacting such authors diplomatically to ask
625 them to modify their license terms. However, this can be a
626 politically difficult thing to do and you should ask for
627 advice on the <tt>debian-legal</tt> mailing list first, as
632 When in doubt about a copyright, send mail to
633 <email>debian-legal@lists.debian.org</email>. Be prepared
634 to provide us with the copyright statement. Software
635 covered by the GPL, public domain software and BSD-like
636 copyrights are safe; be wary of the phrases "commercial
637 use prohibited" and "distribution restricted".
641 <sect id="subsections">
642 <heading>Sections</heading>
645 The packages in the archive areas <em>main</em>,
646 <em>contrib</em> and <em>non-free</em> are grouped further into
647 <em>sections</em> to simplify handling.
651 The archive area and section for each package should be
652 specified in the package's <tt>Section</tt> control record (see
653 <ref id="f-Section">). However, the maintainer of the Debian
654 archive may override this selection to ensure the consistency of
655 the Debian distribution. The <tt>Section</tt> field should be
657 <list compact="compact">
659 <em>section</em> if the package is in the
660 <em>main</em> archive area,
663 <em>area/section</em> if the package is in
664 the <em>contrib</em> or <em>non-free</em>
671 The Debian archive maintainers provide the authoritative
672 list of sections. At present, they are:
673 <em>admin</em>, <em>comm</em>,
674 <em>devel</em>, <em>doc</em>,
675 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
676 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
677 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
678 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
679 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
681 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
682 <em>science</em>, <em>shells</em>,
683 <em>sound</em>, <em>tex</em>, <em>text</em>,
684 <em>utils</em>, <em>web</em>, <em>x11</em>.
688 <sect id="priorities">
689 <heading>Priorities</heading>
692 Each package should have a <em>priority</em> value, which is
693 included in the package's <em>control record</em>
694 (see <ref id="f-Priority">).
695 This information is used by the Debian package management tools to
696 separate high-priority packages from less-important packages.
700 The following <em>priority levels</em> are recognized by the
701 Debian package management tools.
703 <tag><tt>required</tt></tag>
705 Packages which are necessary for the proper
706 functioning of the system (usually, this means that
707 dpkg functionality depends on these packages).
708 Removing a <tt>required</tt> package may cause your
709 system to become totally broken and you may not even
710 be able to use <prgn>dpkg</prgn> to put things back,
711 so only do so if you know what you are doing. Systems
712 with only the <tt>required</tt> packages are probably
713 unusable, but they do have enough functionality to
714 allow the sysadmin to boot and install more software.
716 <tag><tt>important</tt></tag>
718 Important programs, including those which one would
719 expect to find on any Unix-like system. If the
720 expectation is that an experienced Unix person who
721 found it missing would say "What on earth is going on,
722 where is <prgn>foo</prgn>?", it must be an
723 <tt>important</tt> package.<footnote>
724 This is an important criterion because we are
725 trying to produce, amongst other things, a free
728 Other packages without which the system will not run
729 well or be usable must also have priority
730 <tt>important</tt>. This does
731 <em>not</em> include Emacs, the X Window System, TeX
732 or any other large applications. The
733 <tt>important</tt> packages are just a bare minimum of
734 commonly-expected and necessary tools.
736 <tag><tt>standard</tt></tag>
738 These packages provide a reasonably small but not too
739 limited character-mode system. This is what will be
740 installed by default if the user doesn't select anything
741 else. It doesn't include many large applications.
743 <tag><tt>optional</tt></tag>
745 (In a sense everything that isn't required is
746 optional, but that's not what is meant here.) This is
747 all the software that you might reasonably want to
748 install if you didn't know what it was and don't have
749 specialized requirements. This is a much larger system
750 and includes the X Window System, a full TeX
751 distribution, and many applications. Note that
752 optional packages should not conflict with each other.
754 <tag><tt>extra</tt></tag>
756 This contains all packages that conflict with others
757 with required, important, standard or optional
758 priorities, or are only likely to be useful if you
759 already know what they are or have specialized
760 requirements (such as packages containing only detached
767 Packages must not depend on packages with lower priority
768 values (excluding build-time dependencies). In order to
769 ensure this, the priorities of one or more packages may need
778 <heading>Binary packages</heading>
781 The Debian GNU/Linux distribution is based on the Debian
782 package management system, called <prgn>dpkg</prgn>. Thus,
783 all packages in the Debian distribution must be provided
784 in the <tt>.deb</tt> file format.
788 <heading>The package name</heading>
791 Every package must have a name that's unique within the Debian
796 The package name is included in the control field
797 <tt>Package</tt>, the format of which is described
798 in <ref id="f-Package">.
799 The package name is also included as a part of the file name
800 of the <tt>.deb</tt> file.
805 <heading>The version of a package</heading>
808 Every package has a version number recorded in its
809 <tt>Version</tt> control file field, described in
810 <ref id="f-Version">.
814 The package management system imposes an ordering on version
815 numbers, so that it can tell whether packages are being up- or
816 downgraded and so that package system front end applications
817 can tell whether a package it finds available is newer than
818 the one installed on the system. The version number format
819 has the most significant parts (as far as comparison is
820 concerned) at the beginning.
824 If an upstream package has problematic version numbers they
825 should be converted to a sane form for use in the
826 <tt>Version</tt> field.
830 <heading>Version numbers based on dates</heading>
833 In general, Debian packages should use the same version
834 numbers as the upstream sources.
838 However, in some cases where the upstream version number is
839 based on a date (e.g., a development "snapshot" release) the
840 package management system cannot handle these version
841 numbers without epochs. For example, dpkg will consider
842 "96May01" to be greater than "96Dec24".
846 To prevent having to use epochs for every new upstream
847 version, the date based portion of the version number
848 should be changed to the following format in such cases:
849 "19960501", "19961224". It is up to the maintainer whether
850 they want to bother the upstream maintainer to change
851 the version numbers upstream, too.
855 Note that other version formats based on dates which are
856 parsed correctly by the package management system should
857 <em>not</em> be changed.
861 Native Debian packages (i.e., packages which have been
862 written especially for Debian) whose version numbers include
863 dates should always use the "YYYYMMDD" format.
870 <heading>The maintainer of a package</heading>
873 Every package must have a Debian maintainer (the
874 maintainer may be one person or a group of people
875 reachable from a common email address, such as a mailing
876 list). The maintainer is responsible for ensuring that
877 the package is placed in the appropriate distributions.
881 The maintainer must be specified in the
882 <tt>Maintainer</tt> control field with their correct name
883 and a working email address. If one person maintains
884 several packages, they should try to avoid having
885 different forms of their name and email address in
886 the <tt>Maintainer</tt> fields of those packages.
890 The format of the <tt>Maintainer</tt> control field is
891 described in <ref id="f-Maintainer">.
895 If the maintainer of a package quits from the Debian
896 project, "Debian QA Group"
897 <email>packages@qa.debian.org</email> takes over the
898 maintainer-ship of the package until someone else
899 volunteers for that task. These packages are called
900 <em>orphaned packages</em>.<footnote>
901 The detailed procedure for doing this gracefully can
902 be found in the Debian Developer's Reference,
903 see <ref id="related">.
908 <sect id="descriptions">
909 <heading>The description of a package</heading>
912 Every Debian package must have an extended description
913 stored in the appropriate field of the control record.
914 The technical information about the format of the
915 <tt>Description</tt> field is in <ref id="f-Description">.
919 The description should describe the package (the program) to a
920 user (system administrator) who has never met it before so that
921 they have enough information to decide whether they want to
922 install it. This description should not just be copied verbatim
923 from the program's documentation.
927 Put important information first, both in the synopsis and
928 extended description. Sometimes only the first part of the
929 synopsis or of the description will be displayed. You can
930 assume that there will usually be a way to see the whole
931 extended description.
935 The description should also give information about the
936 significant dependencies and conflicts between this package
937 and others, so that the user knows why these dependencies and
938 conflicts have been declared.
942 Instructions for configuring or using the package should
943 not be included (that is what installation scripts,
944 manual pages, info files, etc., are for). Copyright
945 statements and other administrivia should not be included
946 either (that is what the copyright file is for).
949 <sect1 id="synopsis"><heading>The single line synopsis</heading>
952 The single line synopsis should be kept brief - certainly
957 Do not include the package name in the synopsis line. The
958 display software knows how to display this already, and you
959 do not need to state it. Remember that in many situations
960 the user may only see the synopsis line - make it as
961 informative as you can.
966 <sect1 id="extendeddesc"><heading>The extended description</heading>
969 Do not try to continue the single line synopsis into the
970 extended description. This will not work correctly when
971 the full description is displayed, and makes no sense
972 where only the summary (the single line synopsis) is
977 The extended description should describe what the package
978 does and how it relates to the rest of the system (in terms
979 of, for example, which subsystem it is which part of).
983 The description field needs to make sense to anyone, even
984 people who have no idea about any of the things the
985 package deals with.<footnote>
986 The blurb that comes with a program in its
987 announcements and/or <prgn>README</prgn> files is
988 rarely suitable for use in a description. It is
989 usually aimed at people who are already in the
990 community where the package is used.
999 <heading>Dependencies</heading>
1002 Every package must specify the dependency information
1003 about other packages that are required for the first to
1008 For example, a dependency entry must be provided for any
1009 shared libraries required by a dynamically-linked executable
1010 binary in a package.
1014 Packages are not required to declare any dependencies they
1015 have on other packages which are marked <tt>Essential</tt>
1016 (see below), and should not do so unless they depend on a
1017 particular version of that package.<footnote>
1019 Essential is needed in part to avoid unresolvable dependency
1020 loops on upgrade. If packages add unnecessary dependencies
1021 on packages in this set, the chances that there
1022 <strong>will</strong> be an unresolvable dependency loop
1023 caused by forcing these Essential packages to be configured
1024 first before they need to be is greatly increased. It also
1025 increases the chances that frontends will be unable to
1026 <strong>calculate</strong> an upgrade path, even if one
1030 Also, functionality is rarely ever removed from the
1031 Essential set, but <em>packages</em> have been removed from
1032 the Essential set when the functionality moved to a
1033 different package. So depending on these packages <em>just
1034 in case</em> they stop being essential does way more harm
1041 Sometimes, a package requires another package to be installed
1042 <em>and</em> configured before it can be installed. In this
1043 case, you must specify a <tt>Pre-Depends</tt> entry for
1048 You should not specify a <tt>Pre-Depends</tt> entry for a
1049 package before this has been discussed on the
1050 <tt>debian-devel</tt> mailing list and a consensus about
1051 doing that has been reached.
1055 The format of the package interrelationship control fields is
1056 described in <ref id="relationships">.
1060 <sect id="virtual_pkg">
1061 <heading>Virtual packages</heading>
1064 Sometimes, there are several packages which offer
1065 more-or-less the same functionality. In this case, it's
1066 useful to define a <em>virtual package</em> whose name
1067 describes that common functionality. (The virtual
1068 packages only exist logically, not physically; that's why
1069 they are called <em>virtual</em>.) The packages with this
1070 particular function will then <em>provide</em> the virtual
1071 package. Thus, any other package requiring that function
1072 can simply depend on the virtual package without having to
1073 specify all possible packages individually.
1077 All packages should use virtual package names where
1078 appropriate, and arrange to create new ones if necessary.
1079 They should not use virtual package names (except privately,
1080 amongst a cooperating group of packages) unless they have
1081 been agreed upon and appear in the list of virtual package
1082 names. (See also <ref id="virtual">)
1086 The latest version of the authoritative list of virtual
1087 package names can be found in the <tt>debian-policy</tt> package.
1088 It is also available from the Debian web mirrors at
1089 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1090 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1094 The procedure for updating the list is described in the preface
1101 <heading>Base system</heading>
1104 The <tt>base system</tt> is a minimum subset of the Debian
1105 GNU/Linux system that is installed before everything else
1106 on a new system. Only very few packages are allowed to form
1107 part of the base system, in order to keep the required disk
1112 The base system consists of all those packages with priority
1113 <tt>required</tt> or <tt>important</tt>. Many of them will
1114 be tagged <tt>essential</tt> (see below).
1119 <heading>Essential packages</heading>
1122 Essential is defined as the minimal set of functionality that
1123 must be available and usable on the system at all times, even
1124 when packages are in an unconfigured (but unpacked) state.
1125 Packages are tagged <tt>essential</tt> for a system using the
1126 <tt>Essential</tt> control file field. The format of the
1127 <tt>Essential</tt> control field is described in <ref
1132 Since these packages cannot be easily removed (one has to
1133 specify an extra <em>force option</em> to
1134 <prgn>dpkg</prgn> to do so), this flag must not be used
1135 unless absolutely necessary. A shared library package
1136 must not be tagged <tt>essential</tt>; dependencies will
1137 prevent its premature removal, and we need to be able to
1138 remove it when it has been superseded.
1142 Since dpkg will not prevent upgrading of other packages
1143 while an <tt>essential</tt> package is in an unconfigured
1144 state, all <tt>essential</tt> packages must supply all of
1145 their core functionality even when unconfigured. If the
1146 package cannot satisfy this requirement it must not be
1147 tagged as essential, and any packages depending on this
1148 package must instead have explicit dependency fields as
1153 Maintainers should take great care in adding any programs,
1154 interfaces, or functionality to <tt>essential</tt> packages.
1155 Packages may assume that functionality provided by
1156 <tt>essential</tt> packages is always available without
1157 declaring explicit dependencies, which means that removing
1158 functionality from the Essential set is very difficult and is
1159 almost never done. Any capability added to an
1160 <tt>essential</tt> package therefore creates an obligation to
1161 support that capability as part of the Essential set in
1166 You must not tag any packages <tt>essential</tt> before
1167 this has been discussed on the <tt>debian-devel</tt>
1168 mailing list and a consensus about doing that has been
1173 <sect id="maintscripts">
1174 <heading>Maintainer Scripts</heading>
1177 The package installation scripts should avoid producing
1178 output which is unnecessary for the user to see and
1179 should rely on <prgn>dpkg</prgn> to stave off boredom on
1180 the part of a user installing many packages. This means,
1181 amongst other things, using the <tt>--quiet</tt> option on
1182 <prgn>install-info</prgn>.
1186 Errors which occur during the execution of an installation
1187 script must be checked and the installation must not
1188 continue after an error.
1192 Note that in general <ref id="scripts"> applies to package
1193 maintainer scripts, too.
1197 You should not use <prgn>dpkg-divert</prgn> on a file
1198 belonging to another package without consulting the
1199 maintainer of that package first.
1203 All packages which supply an instance of a common command
1204 name (or, in general, filename) should generally use
1205 <prgn>update-alternatives</prgn>, so that they may be
1206 installed together. If <prgn>update-alternatives</prgn>
1207 is not used, then each package must use
1208 <tt>Conflicts</tt> to ensure that other packages are
1209 de-installed. (In this case, it may be appropriate to
1210 specify a conflict against earlier versions of something
1211 that previously did not use
1212 <prgn>update-alternatives</prgn>; this is an exception to
1213 the usual rule that versioned conflicts should be
1217 <sect1 id="maintscriptprompt">
1218 <heading>Prompting in maintainer scripts</heading>
1220 Package maintainer scripts may prompt the user if
1221 necessary. Prompting should be done by communicating
1222 through a program, such as <prgn>debconf</prgn>, which
1223 conforms to the Debian Configuration Management
1224 Specification, version 2 or higher. Prompting the user by
1225 other means, such as by hand<footnote>
1226 From the Jargon file: by hand 2. By extension,
1227 writing code which does something in an explicit or
1228 low-level way for which a presupplied library
1229 (<em>debconf, in this instance</em>) routine ought
1230 to have been available.
1231 </footnote>, is now deprecated.
1235 The Debian Configuration Management Specification is included
1236 in the <file>debconf_specification</file> files in the
1237 <package>debian-policy</package> package.
1238 It is also available from the Debian web mirrors at
1239 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1240 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1244 Packages which use the Debian Configuration Management
1245 Specification may contain an additional
1246 <prgn>config</prgn> script and a <tt>templates</tt>
1247 file in their control archive<footnote>
1248 The control.tar.gz inside the .deb.
1249 See <manref name="deb" section="5">.
1251 The <prgn>config</prgn> script might be run before the
1252 <prgn>preinst</prgn> script, and before the package is unpacked
1253 or any of its dependencies or pre-dependencies are satisfied.
1254 Therefore it must work using only the tools present in
1255 <em>essential</em> packages.<footnote>
1256 <package>Debconf</package> or another tool that
1257 implements the Debian Configuration Management
1258 Specification will also be installed, and any
1259 versioned dependencies on it will be satisfied
1260 before preconfiguration begins.
1265 Packages which use the Debian Configuration Management
1266 Specification must allow for translation of their user-visible
1267 messages by using a gettext-based system such as the one
1268 provided by the <package>po-debconf</package> package.
1272 Packages should try to minimize the amount of prompting
1273 they need to do, and they should ensure that the user
1274 will only ever be asked each question once. This means
1275 that packages should try to use appropriate shared
1276 configuration files (such as <file>/etc/papersize</file> and
1277 <file>/etc/news/server</file>), and shared
1278 <package>debconf</package> variables rather than each
1279 prompting for their own list of required pieces of
1284 It also means that an upgrade should not ask the same
1285 questions again, unless the user has used
1286 <tt>dpkg --purge</tt> to remove the package's configuration.
1287 The answers to configuration questions should be stored in an
1288 appropriate place in <file>/etc</file> so that the user can
1289 modify them, and how this has been done should be
1294 If a package has a vitally important piece of
1295 information to pass to the user (such as "don't run me
1296 as I am, you must edit the following configuration files
1297 first or you risk your system emitting badly-formatted
1298 messages"), it should display this in the
1299 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1300 prompt the user to hit return to acknowledge the
1301 message. Copyright messages do not count as vitally
1302 important (they belong in
1303 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1304 neither do instructions on how to use a program (these
1305 should be in on-line documentation, where all the users
1310 Any necessary prompting should almost always be confined
1311 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1312 script. If it is done in the <prgn>postinst</prgn>, it
1313 should be protected with a conditional so that
1314 unnecessary prompting doesn't happen if a package's
1315 installation fails and the <prgn>postinst</prgn> is
1316 called with <tt>abort-upgrade</tt>,
1317 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1327 <heading>Source packages</heading>
1329 <sect id="standardsversion">
1330 <heading>Standards conformance</heading>
1333 Source packages should specify the most recent version number
1334 of this policy document with which your package complied
1335 when it was last updated.
1339 This information may be used to file bug reports
1340 automatically if your package becomes too much out of date.
1344 The version is specified in the <tt>Standards-Version</tt>
1346 The format of the <tt>Standards-Version</tt> field is
1347 described in <ref id="f-Standards-Version">.
1351 You should regularly, and especially if your package has
1352 become out of date, check for the newest Policy Manual
1353 available and update your package, if necessary. When your
1354 package complies with the new standards you should update the
1355 <tt>Standards-Version</tt> source package field and
1356 release it.<footnote>
1357 See the file <file>upgrading-checklist</file> for
1358 information about policy which has changed between
1359 different versions of this document.
1365 <sect id="pkg-relations">
1366 <heading>Package relationships</heading>
1369 Source packages should specify which binary packages they
1370 require to be installed or not to be installed in order to
1371 build correctly. For example, if building a package
1372 requires a certain compiler, then the compiler should be
1373 specified as a build-time dependency.
1377 It is not necessary to explicitly specify build-time
1378 relationships on a minimal set of packages that are always
1379 needed to compile, link and put in a Debian package a
1380 standard "Hello World!" program written in C or C++. The
1381 required packages are called <em>build-essential</em>, and
1382 an informational list can be found in
1383 <file>/usr/share/doc/build-essential/list</file> (which is
1384 contained in the <tt>build-essential</tt>
1387 <list compact="compact">
1389 This allows maintaining the list separately
1390 from the policy documents (the list does not
1391 need the kind of control that the policy
1395 Having a separate package allows one to install
1396 the build-essential packages on a machine, as
1397 well as allowing other packages such as tasks to
1398 require installation of the build-essential
1399 packages using the depends relation.
1402 The separate package allows bug reports against
1403 the list to be categorized separately from
1404 the policy management process in the BTS.
1411 When specifying the set of build-time dependencies, one
1412 should list only those packages explicitly required by the
1413 build. It is not necessary to list packages which are
1414 required merely because some other package in the list of
1415 build-time dependencies depends on them.<footnote>
1416 The reason for this is that dependencies change, and
1417 you should list all those packages, and <em>only</em>
1418 those packages that <em>you</em> need directly. What
1419 others need is their business. For example, if you
1420 only link against <file>libimlib</file>, you will need to
1421 build-depend on <package>libimlib2-dev</package> but
1422 not against any <tt>libjpeg*</tt> packages, even
1423 though <tt>libimlib2-dev</tt> currently depends on
1424 them: installation of <package>libimlib2-dev</package>
1425 will automatically ensure that all of its run-time
1426 dependencies are satisfied.
1431 If build-time dependencies are specified, it must be
1432 possible to build the package and produce working binaries
1433 on a system with only essential and build-essential
1434 packages installed and also those required to satisfy the
1435 build-time relationships (including any implied
1436 relationships). In particular, this means that version
1437 clauses should be used rigorously in build-time
1438 relationships so that one cannot produce bad or
1439 inconsistently configured packages when the relationships
1440 are properly satisfied.
1444 <ref id="relationships"> explains the technical details.
1449 <heading>Changes to the upstream sources</heading>
1452 If changes to the source code are made that are not
1453 specific to the needs of the Debian system, they should be
1454 sent to the upstream authors in whatever form they prefer
1455 so as to be included in the upstream version of the
1460 If you need to configure the package differently for
1461 Debian or for Linux, and the upstream source doesn't
1462 provide a way to do so, you should add such configuration
1463 facilities (for example, a new <prgn>autoconf</prgn> test
1464 or <tt>#define</tt>) and send the patch to the upstream
1465 authors, with the default set to the way they originally
1466 had it. You can then easily override the default in your
1467 <file>debian/rules</file> or wherever is appropriate.
1471 You should make sure that the <prgn>configure</prgn> utility
1472 detects the correct architecture specification string
1473 (refer to <ref id="arch-spec"> for details).
1477 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1478 <prgn>configure</prgn> scripts are used, you should edit the
1479 <file>.in</file> files rather than editing the
1480 <prgn>Makefile</prgn> directly. This allows the user to
1481 reconfigure the package if necessary. You should
1482 <em>not</em> configure the package and edit the generated
1483 <prgn>Makefile</prgn>! This makes it impossible for someone
1484 else to later reconfigure the package without losing the
1490 <sect id="dpkgchangelog">
1491 <heading>Debian changelog: <file>debian/changelog</file></heading>
1494 Changes in the Debian version of the package should be
1495 briefly explained in the Debian changelog file
1496 <file>debian/changelog</file>.<footnote>
1498 Mistakes in changelogs are usually best rectified by
1499 making a new changelog entry rather than "rewriting
1500 history" by editing old changelog entries.
1503 This includes modifications
1504 made in the Debian package compared to the upstream one
1505 as well as other changes and updates to the package.
1507 Although there is nothing stopping an author who is also
1508 the Debian maintainer from using this changelog for all
1509 their changes, it will have to be renamed if the Debian
1510 and upstream maintainers become different people. In such
1511 a case, however, it might be better to maintain the package
1512 as a non-native package.
1517 The format of the <file>debian/changelog</file> allows the
1518 package building tools to discover which version of the package
1519 is being built and find out other release-specific information.
1523 That format is a series of entries like this:
1525 <example compact="compact">
1526 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1528 [optional blank line(s), stripped]
1530 * <var>change details</var>
1531 <var>more change details</var>
1533 [blank line(s), included in output of dpkg-parsechangelog]
1535 * <var>even more change details</var>
1537 [optional blank line(s), stripped]
1539 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1544 <var>package</var> and <var>version</var> are the source
1545 package name and version number.
1549 <var>distribution(s)</var> lists the distributions where
1550 this version should be installed when it is uploaded - it
1551 is copied to the <tt>Distribution</tt> field in the
1552 <file>.changes</file> file. See <ref id="f-Distribution">.
1556 <var>urgency</var> is the value for the <tt>Urgency</tt>
1557 field in the <file>.changes</file> file for the upload
1558 (see <ref id="f-Urgency">). It is not possible to specify
1559 an urgency containing commas; commas are used to separate
1560 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1561 <prgn>dpkg</prgn> changelog format (though there is
1562 currently only one useful <var>keyword</var>,
1567 The change details may in fact be any series of lines
1568 starting with at least two spaces, but conventionally each
1569 change starts with an asterisk and a separating space and
1570 continuation lines are indented so as to bring them in
1571 line with the start of the text above. Blank lines may be
1572 used here to separate groups of changes, if desired.
1576 If this upload resolves bugs recorded in the Bug Tracking
1577 System (BTS), they may be automatically closed on the
1578 inclusion of this package into the Debian archive by
1579 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1580 in the change details.<footnote>
1581 To be precise, the string should match the following
1582 Perl regular expression:
1584 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1586 Then all of the bug numbers listed will be closed by the
1587 archive maintenance script (<prgn>katie</prgn>) using the
1588 <var>version</var> of the changelog entry.
1590 This information is conveyed via the <tt>Closes</tt> field
1591 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1595 The maintainer name and email address used in the changelog
1596 should be the details of the person uploading <em>this</em>
1597 version. They are <em>not</em> necessarily those of the
1598 usual package maintainer. The information here will be
1599 copied to the <tt>Changed-By</tt> field in the
1600 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1601 and then later used to send an acknowledgement when the
1602 upload has been installed.
1606 The <var>date</var> must be in RFC822 format<footnote>
1607 This is generated by <tt>date -R</tt>.
1608 </footnote>; it must include the time zone specified
1609 numerically, with the time zone name or abbreviation
1610 optionally present as a comment in parentheses.
1614 The first "title" line with the package name must start
1615 at the left hand margin. The "trailer" line with the
1616 maintainer and date details must be preceded by exactly
1617 one space. The maintainer details and the date must be
1618 separated by exactly two spaces.
1622 The entire changelog must be encoded in UTF-8.
1626 For more information on placement of the changelog files
1627 within binary packages, please see <ref id="changelogs">.
1631 <sect id="dpkgcopyright">
1632 <heading>Copyright: <file>debian/copyright</file></heading>
1634 Every package must be accompanied by a verbatim copy of
1635 its copyright and distribution license in the file
1636 <file>/usr/share/doc/<var>package</var>/copyright</file>
1637 (see <ref id="copyrightfile"> for further details). Also see
1638 <ref id="pkgcopyright"> for further considerations relayed
1639 to copyrights for packages.
1643 <heading>Error trapping in makefiles</heading>
1646 When <prgn>make</prgn> invokes a command in a makefile
1647 (including your package's upstream makefiles and
1648 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1649 means that <prgn>sh</prgn>'s usual bad error handling
1650 properties apply: if you include a miniature script as one
1651 of the commands in your makefile you'll find that if you
1652 don't do anything about it then errors are not detected
1653 and <prgn>make</prgn> will blithely continue after
1658 Every time you put more than one shell command (this
1659 includes using a loop) in a makefile command you
1660 must make sure that errors are trapped. For
1661 simple compound commands, such as changing directory and
1662 then running a program, using <tt>&&</tt> rather
1663 than semicolon as a command separator is sufficient. For
1664 more complex commands including most loops and
1665 conditionals you should include a separate <tt>set -e</tt>
1666 command at the start of every makefile command that's
1667 actually one of these miniature shell scripts.
1671 <sect id="timestamps">
1672 <heading>Time Stamps</heading>
1674 Maintainers should preserve the modification times of the
1675 upstream source files in a package, as far as is reasonably
1677 The rationale is that there is some information conveyed
1678 by knowing the age of the file, for example, you could
1679 recognize that some documentation is very old by looking
1680 at the modification time, so it would be nice if the
1681 modification time of the upstream source would be
1687 <sect id="restrictions">
1688 <heading>Restrictions on objects in source packages</heading>
1691 The source package may not contain any hard links<footnote>
1693 This is not currently detected when building source
1694 packages, but only when extracting
1698 Hard links may be permitted at some point in the
1699 future, but would require a fair amount of
1702 </footnote>, device special files, sockets or setuid or
1703 setgid files.<footnote>
1704 Setgid directories are allowed.
1709 <sect id="debianrules">
1710 <heading>Main building script: <file>debian/rules</file></heading>
1713 This file must be an executable makefile, and contains the
1714 package-specific recipes for compiling the package and
1715 building binary package(s) from the source.
1719 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1720 so that it can be invoked by saying its name rather than
1721 invoking <prgn>make</prgn> explicitly.
1725 Since an interactive <file>debian/rules</file> script makes it
1726 impossible to auto-compile that package and also makes it
1727 hard for other people to reproduce the same binary
1728 package, all <em>required targets</em> MUST be
1729 non-interactive. At a minimum, required targets are the
1730 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1731 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1732 <em>binary-indep</em>, and <em>build</em>. It also follows
1733 that any target that these targets depend on must also be
1738 The targets are as follows (required unless stated otherwise):
1740 <tag><tt>build</tt></tag>
1743 The <tt>build</tt> target should perform all the
1744 configuration and compilation of the package.
1745 If a package has an interactive pre-build
1746 configuration routine, the Debianized source package
1747 must either be built after this has taken place (so
1748 that the binary package can be built without rerunning
1749 the configuration) or the configuration routine
1750 modified to become non-interactive. (The latter is
1751 preferable if there are architecture-specific features
1752 detected by the configuration routine.)
1756 For some packages, notably ones where the same
1757 source tree is compiled in different ways to produce
1758 two binary packages, the <tt>build</tt> target
1759 does not make much sense. For these packages it is
1760 good enough to provide two (or more) targets
1761 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1762 for each of the ways of building the package, and a
1763 <tt>build</tt> target that does nothing. The
1764 <tt>binary</tt> target will have to build the
1765 package in each of the possible ways and make the
1766 binary package out of each.
1770 The <tt>build</tt> target must not do anything
1771 that might require root privilege.
1775 The <tt>build</tt> target may need to run the
1776 <tt>clean</tt> target first - see below.
1780 When a package has a configuration and build routine
1781 which takes a long time, or when the makefiles are
1782 poorly designed, or when <tt>build</tt> needs to
1783 run <tt>clean</tt> first, it is a good idea to
1784 <tt>touch build</tt> when the build process is
1785 complete. This will ensure that if <tt>debian/rules
1786 build</tt> is run again it will not rebuild the whole
1788 Another common way to do this is for <tt>build</tt>
1789 to depend on <prgn>build-stamp</prgn> and to do
1790 nothing else, and for the <prgn>build-stamp</prgn>
1791 target to do the building and to <tt>touch
1792 build-stamp</tt> on completion. This is
1793 especially useful if the build routine creates a
1794 file or directory called <tt>build</tt>; in such a
1795 case, <tt>build</tt> will need to be listed as
1796 a phony target (i.e., as a dependency of the
1797 <tt>.PHONY</tt> target). See the documentation of
1798 <prgn>make</prgn> for more information on phony
1804 <tag><tt>build-arch</tt> (optional),
1805 <tt>build-indep</tt> (optional)
1809 A package may also provide both of the targets
1810 <tt>build-arch</tt> and <tt>build-indep</tt>.
1811 The <tt>build-arch</tt> target, if provided, should
1812 perform all the configuration and compilation required
1813 for producing all architecture-dependant binary packages
1814 (those packages for which the body of the
1815 <tt>Architecture</tt> field in <tt>debian/control</tt>
1816 is not <tt>all</tt>).
1817 Similarly, the <tt>build-indep</tt> target, if
1818 provided, should perform all the configuration and
1819 compilation required for producing all
1820 architecture-independent binary packages
1821 (those packages for which the body of the
1822 <tt>Architecture</tt> field in <tt>debian/control</tt>
1824 The <tt>build</tt> target should depend on those of the
1825 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1826 are provided in the rules file.
1830 If one or both of the targets <tt>build-arch</tt> and
1831 <tt>build-indep</tt> are not provided, then invoking
1832 <file>debian/rules</file> with one of the not-provided
1833 targets as arguments should produce a exit status code
1834 of 2. Usually this is provided automatically by make
1835 if the target is missing.
1839 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1840 must not do anything that might require root privilege.
1844 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1845 <tt>binary-indep</tt>
1849 The <tt>binary</tt> target must be all that is
1850 necessary for the user to build the binary package(s)
1851 produced from this source package. It is
1852 split into two parts: <prgn>binary-arch</prgn> builds
1853 the binary packages which are specific to a particular
1854 architecture, and <tt>binary-indep</tt> builds
1855 those which are not.
1858 <tt>binary</tt> may be (and commonly is) a target with
1859 no commands which simply depends on
1860 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1863 Both <tt>binary-*</tt> targets should depend on the
1864 <tt>build</tt> target, or on the appropriate
1865 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1866 provided, so that the package is built if it has not
1867 been already. It should then create the relevant
1868 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1869 make their control files and <prgn>dpkg-deb</prgn> to
1870 build them and place them in the parent of the top
1875 Both the <tt>binary-arch</tt> and
1876 <tt>binary-indep</tt> targets <em>must</em> exist.
1877 If one of them has nothing to do (which will always be
1878 the case if the source generates only a single binary
1879 package, whether architecture-dependent or not), it
1880 must still exist and must always succeed.
1884 The <tt>binary</tt> targets must be invoked as
1886 The <prgn>fakeroot</prgn> package often allows one
1887 to build a package correctly even without being
1893 <tag><tt>clean</tt></tag>
1896 This must undo any effects that the <tt>build</tt>
1897 and <tt>binary</tt> targets may have had, except
1898 that it should leave alone any output files created in
1899 the parent directory by a run of a <tt>binary</tt>
1904 If a <tt>build</tt> file is touched at the end of
1905 the <tt>build</tt> target, as suggested above, it
1906 should be removed as the first action that
1907 <tt>clean</tt> performs, so that running
1908 <tt>build</tt> again after an interrupted
1909 <tt>clean</tt> doesn't think that everything is
1914 The <tt>clean</tt> target may need to be
1915 invoked as root if <tt>binary</tt> has been
1916 invoked since the last <tt>clean</tt>, or if
1917 <tt>build</tt> has been invoked as root (since
1918 <tt>build</tt> may create directories, for
1923 <tag><tt>get-orig-source</tt> (optional)</tag>
1926 This target fetches the most recent version of the
1927 original source package from a canonical archive site
1928 (via FTP or WWW, for example), does any necessary
1929 rearrangement to turn it into the original source
1930 tar file format described below, and leaves it in the
1935 This target may be invoked in any directory, and
1936 should take care to clean up any temporary files it
1941 This target is optional, but providing it if
1942 possible is a good idea.
1946 <tag><tt>patch</tt> (optional)</tag>
1949 This target performs whatever additional actions are
1950 required to make the source ready for editing (unpacking
1951 additional upstream archives, applying patches, etc.).
1952 It is recommended to be implemented for any package where
1953 <tt>dpkg-source -x</tt> does not result in source ready
1954 for additional modification. See
1955 <ref id="readmesource">.
1961 The <tt>build</tt>, <tt>binary</tt> and
1962 <tt>clean</tt> targets must be invoked with the current
1963 directory being the package's top-level directory.
1968 Additional targets may exist in <file>debian/rules</file>,
1969 either as published or undocumented interfaces or for the
1970 package's internal use.
1974 The architectures we build on and build for are determined
1975 by <prgn>make</prgn> variables using the utility
1976 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1977 You can determine the
1978 Debian architecture and the GNU style architecture
1979 specification string for the build machine (the machine type
1980 we are building on) as well as for the host machine (the
1981 machine type we are building for). Here is a list of
1982 supported <prgn>make</prgn> variables:
1983 <list compact="compact">
1985 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1988 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1989 specification string)
1992 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1993 <tt>DEB_*_GNU_TYPE</tt>)
1996 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1997 <tt>DEB_*_GNU_TYPE</tt>)
1999 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2000 the build machine or <tt>HOST</tt> for specification of the
2005 Backward compatibility can be provided in the rules file
2006 by setting the needed variables to suitable default
2007 values; please refer to the documentation of
2008 <prgn>dpkg-architecture</prgn> for details.
2012 It is important to understand that the <tt>DEB_*_ARCH</tt>
2013 string only determines which Debian architecture we are
2014 building on or for. It should not be used to get the CPU
2015 or system information; the GNU style variables should be
2019 <sect1 id="debianrules-options">
2020 <heading><file>debian/rules</file> and
2021 <tt>DEB_BUILD_OPTIONS</tt></heading>
2024 Supporting the standardized environment variable
2025 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2026 contain several flags to change how a package is compiled and
2027 built. Each flag must be in the form <var>flag</var> or
2028 <var>flag</var>=<var>options</var>. If multiple flags are
2029 given, they must be separated by whitespace.<footnote>
2030 Some packages support any delimiter, but whitespace is the
2031 easiest to parse inside a makefile and avoids ambiguity with
2032 flag values that contain commas.
2034 <var>flag</var> must start with a lowercase letter
2035 (<tt>a-z</tt>) and consist only of lowercase letters,
2036 numbers (<tt>0-9</tt>), and the characters
2037 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2038 <var>options</var> must not contain whitespace. The same
2039 tag should not be given multiple times with conflicting
2040 values. Package maintainers may assume that
2041 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2045 The meaning of the following tags has been standardized:
2049 This tag says to not run any build-time test suite
2050 provided by the package.
2054 The presence of this tag means that the package should
2055 be compiled with a minimum of optimization. For C
2056 programs, it is best to add <tt>-O0</tt> to
2057 <tt>CFLAGS</tt> (although this is usually the default).
2058 Some programs might fail to build or run at this level
2059 of optimization; it may be necessary to use
2060 <tt>-O1</tt>, for example.
2064 This tag means that the debugging symbols should not be
2065 stripped from the binary during installation, so that
2066 debugging information may be included in the package.
2068 <tag>parallel=n</tag>
2070 This tag means that the package should be built using up
2071 to <tt>n</tt> parallel processes if the package build
2072 system supports this.<footnote>
2073 Packages built with <tt>make</tt> can often implement
2074 this by passing the <tt>-j</tt><var>n</var> option to
2077 If the package build system does not support parallel
2078 builds, this string must be ignored. If the package
2079 build system only supports a lower level of concurrency
2080 than <var>n</var>, the package should be built using as
2081 many parallel processes as the package build system
2082 supports. It is up to the package maintainer to decide
2083 whether the package build times are long enough and the
2084 package build system is robust enough to make supporting
2085 parallel builds worthwhile.
2091 Unknown flags must be ignored by <file>debian/rules</file>.
2095 The following makefile snippet is an example of how one may
2096 implement the build options; you will probably have to
2097 massage this example in order to make it work for your
2099 <example compact="compact">
2102 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2103 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2104 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2105 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2107 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2112 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2113 INSTALL_PROGRAM += -s
2115 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2116 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2117 MAKEFLAGS += -j$(NUMJOBS)
2122 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2123 # Code to run the package test suite.
2130 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2131 <sect id="substvars">
2132 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2135 When <prgn>dpkg-gencontrol</prgn>,
2136 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2137 generate control files they perform variable substitutions
2138 on their output just before writing it. Variable
2139 substitutions have the form <tt>${<var>variable</var>}</tt>.
2140 The optional file <file>debian/substvars</file> contains
2141 variable substitutions to be used; variables can also be set
2142 directly from <file>debian/rules</file> using the <tt>-V</tt>
2143 option to the source packaging commands, and certain
2144 predefined variables are also available.
2148 The <file>debian/substvars</file> file is usually generated and
2149 modified dynamically by <file>debian/rules</file> targets, in
2150 which case it must be removed by the <tt>clean</tt> target.
2154 See <manref name="deb-substvars" section="5"> for full
2155 details about source variable substitutions, including the
2156 format of <file>debian/substvars</file>.</p>
2159 <sect id="debianwatch">
2160 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2163 This is an optional, recommended control file for the
2164 <tt>uscan</tt> utility which defines how to automatically
2165 scan ftp or http sites for newly available updates of the
2166 package. This is used by <url id="
2167 http://dehs.alioth.debian.org/"> and other Debian QA tools
2168 to help with quality control and maintenance of the
2169 distribution as a whole.
2174 <sect id="debianfiles">
2175 <heading>Generated files list: <file>debian/files</file></heading>
2178 This file is not a permanent part of the source tree; it
2179 is used while building packages to record which files are
2180 being generated. <prgn>dpkg-genchanges</prgn> uses it
2181 when it generates a <file>.changes</file> file.
2185 It should not exist in a shipped source package, and so it
2186 (and any backup files or temporary files such as
2187 <file>files.new</file><footnote>
2188 <file>files.new</file> is used as a temporary file by
2189 <prgn>dpkg-gencontrol</prgn> and
2190 <prgn>dpkg-distaddfile</prgn> - they write a new
2191 version of <tt>files</tt> here before renaming it,
2192 to avoid leaving a corrupted copy if an error
2194 </footnote>) should be removed by the
2195 <tt>clean</tt> target. It may also be wise to
2196 ensure a fresh start by emptying or removing it at the
2197 start of the <tt>binary</tt> target.
2201 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2202 package, it adds an entry to <file>debian/files</file> for the
2203 <file>.deb</file> file that will be created when <tt>dpkg-deb
2204 --build</tt> is run for that binary package. So for most
2205 packages all that needs to be done with this file is to
2206 delete it in the <tt>clean</tt> target.
2210 If a package upload includes files besides the source
2211 package and any binary packages whose control files were
2212 made with <prgn>dpkg-gencontrol</prgn> then they should be
2213 placed in the parent of the package's top-level directory
2214 and <prgn>dpkg-distaddfile</prgn> should be called to add
2215 the file to the list in <file>debian/files</file>.</p>
2218 <sect id="embeddedfiles">
2219 <heading>Convenience copies of code</heading>
2222 Some software packages include in their distribution convenience
2223 copies of code from other software packages, generally so that
2224 users compiling from source don't have to download multiple
2225 packages. Debian packages should not make use of these
2226 convenience copies unless the included package is explicitly
2227 intended to be used in this way.<footnote>
2228 For example, parts of the GNU build system work like this.
2230 If the included code is already in the Debian archive in the
2231 form of a library, the Debian packaging should ensure that
2232 binary packages reference the libraries already in Debian and
2233 the convenience copy is not used. If the included code is not
2234 already in Debian, it should be packaged separately as a
2235 prerequisite if possible.
2237 Having multiple copies of the same code in Debian is
2238 inefficient, often creates either static linking or shared
2239 library conflicts, and, most importantly, increases the
2240 difficulty of handling security vulnerabilities in the
2246 <sect id="readmesource">
2247 <heading>Source package handling:
2248 <file>debian/README.source</file></heading>
2251 If running <prgn>dpkg-source -x</prgn> on a source package
2252 doesn't produce the source of the package, ready for editing,
2253 and allow one to make changes and run
2254 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2255 without taking any additional steps, creating a
2256 <file>debian/README.source</file> documentation file is
2257 recommended. This file should explain how to do all of the
2260 <item>Generate the fully patched source, in a form ready for
2261 editing, that would be built to create Debian
2262 packages. Doing this with a <tt>patch</tt> target in
2263 <file>debian/rules</file> is recommended; see
2264 <ref id="debianrules">.</item>
2265 <item>Modify the source and save those modifications so that
2266 they will be applied when building the package.</item>
2267 <item>Remove source modifications that are currently being
2268 applied when building the package.</item>
2269 <item>Optionally, document what steps are necessary to
2270 upgrade the Debian source package to a new upstream version,
2271 if applicable.</item>
2273 This explanation should include specific commands and mention
2274 any additional required Debian packages. It should not assume
2275 familiarity with any specific Debian packaging system or patch
2280 This explanation may refer to a documentation file installed by
2281 one of the package's build dependencies provided that the
2282 referenced documentation clearly explains these tasks and is not
2283 a general reference manual.
2287 <file>debian/README.source</file> may also include any other
2288 information that would be helpful to someone modifying the
2289 source package. Even if the package doesn't fit the above
2290 description, maintainers are encouraged to document in a
2291 <file>debian/README.source</file> file any source package with a
2292 particularly complex or unintuitive source layout or build
2293 system (for example, a package that builds the same source
2294 multiple times to generate different binary packages).
2300 <chapt id="controlfields">
2301 <heading>Control files and their fields</heading>
2304 The package management system manipulates data represented in
2305 a common format, known as <em>control data</em>, stored in
2306 <em>control files</em>.
2307 Control files are used for source packages, binary packages and
2308 the <file>.changes</file> files which control the installation
2309 of uploaded files<footnote>
2310 <prgn>dpkg</prgn>'s internal databases are in a similar
2315 <sect id="controlsyntax">
2316 <heading>Syntax of control files</heading>
2319 A control file consists of one or more paragraphs of
2321 The paragraphs are also sometimes referred to as stanzas.
2323 The paragraphs are separated by blank lines. Some control
2324 files allow only one paragraph; others allow several, in
2325 which case each paragraph usually refers to a different
2326 package. (For example, in source packages, the first
2327 paragraph refers to the source package, and later paragraphs
2328 refer to binary packages generated from the source.)
2332 Each paragraph consists of a series of data fields; each
2333 field consists of the field name, followed by a colon and
2334 then the data/value associated with that field. It ends at
2335 the end of the (logical) line. Horizontal whitespace
2336 (spaces and tabs) may occur immediately before or after the
2337 value and is ignored there; it is conventional to put a
2338 single space after the colon. For example, a field might
2340 <example compact="compact">
2343 the field name is <tt>Package</tt> and the field value
2348 Many fields' values may span several lines; in this case
2349 each continuation line must start with a space or a tab.
2350 Any trailing spaces or tabs at the end of individual
2351 lines of a field value are ignored.
2355 In fields where it is specified that lines may not wrap,
2356 only a single line of data is allowed and whitespace is not
2357 significant in a field body. Whitespace must not appear
2358 inside names (of packages, architectures, files or anything
2359 else) or version numbers, or between the characters of
2360 multi-character version relationships.
2364 Field names are not case-sensitive, but it is usual to
2365 capitalize the field names using mixed case as shown below.
2369 Blank lines, or lines consisting only of spaces and tabs,
2370 are not allowed within field values or between fields - that
2371 would mean a new paragraph.
2375 All control files must be encoded in UTF-8.
2379 <sect id="sourcecontrolfiles">
2380 <heading>Source package control files -- <file>debian/control</file></heading>
2383 The <file>debian/control</file> file contains the most vital
2384 (and version-independent) information about the source package
2385 and about the binary packages it creates.
2389 The first paragraph of the control file contains information about
2390 the source package in general. The subsequent sets each describe a
2391 binary package that the source tree builds.
2395 The fields in the general paragraph (the first one, for the source
2398 <list compact="compact">
2399 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2400 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2401 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2402 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2403 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2404 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2405 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2406 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2411 The fields in the binary package paragraphs are:
2413 <list compact="compact">
2414 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2415 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2416 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2417 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2418 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2419 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2420 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2421 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2426 The syntax and semantics of the fields are described below.
2432 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2433 generate control files for binary packages (see below), by
2434 <prgn>dpkg-genchanges</prgn> to generate the
2435 <tt>.changes</tt> file to accompany the upload, and by
2436 <prgn>dpkg-source</prgn> when it creates the
2437 <file>.dsc</file> source control file as part of a source
2438 archive. Many fields are permitted to span multiple lines in
2439 <file>debian/control</file> but not in any other control
2440 file. These tools are responsible for removing the line
2441 breaks from such fields when using fields from
2442 <file>debian/control</file> to generate other control files.
2446 The fields here may contain variable references - their
2447 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2448 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2449 when they generate output control files.
2450 See <ref id="substvars"> for details.
2454 In addition to the control file syntax described <qref
2455 id="controlsyntax">above</qref>, this file may also contain
2456 comment lines starting with <tt>#</tt> without any preceding
2457 whitespace. All such lines are ignored, even in the middle of
2458 continuation lines for a multiline field, and do not end a
2464 <sect id="binarycontrolfiles">
2465 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2468 The <file>DEBIAN/control</file> file contains the most vital
2469 (and version-dependent) information about a binary package.
2473 The fields in this file are:
2475 <list compact="compact">
2476 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2477 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2478 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2479 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2480 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2481 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2482 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2483 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2484 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2485 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2486 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2487 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2492 <sect id="debiansourcecontrolfiles">
2493 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2496 This file contains a series of fields, identified and
2497 separated just like the fields in the control file of
2498 a binary package. The fields are listed below; their
2499 syntax is described above, in <ref id="pkg-controlfields">.
2501 <list compact="compact">
2502 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2503 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2504 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2505 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2506 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2507 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2508 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2509 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2510 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2511 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2512 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2517 The source package control file is generated by
2518 <prgn>dpkg-source</prgn> when it builds the source
2519 archive, from other files in the source package,
2520 described above. When unpacking, it is checked against
2521 the files and directories in the other parts of the
2527 <sect id="debianchangesfiles">
2528 <heading>Debian changes files -- <file>.changes</file></heading>
2531 The .changes files are used by the Debian archive maintenance
2532 software to process updates to packages. They contain one
2533 paragraph which contains information from the
2534 <tt>debian/control</tt> file and other data about the
2535 source package gathered via <tt>debian/changelog</tt>
2536 and <tt>debian/rules</tt>.
2540 The fields in this file are:
2542 <list compact="compact">
2543 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2544 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2545 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2546 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2548 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2550 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2551 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2553 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2554 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2555 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2556 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2561 <sect id="controlfieldslist">
2562 <heading>List of fields</heading>
2564 <sect1 id="f-Source">
2565 <heading><tt>Source</tt></heading>
2568 This field identifies the source package name.
2572 In <file>debian/control</file> or a <file>.dsc</file> file,
2573 this field must contain only the name of the source package.
2577 In a binary package control file or a <file>.changes</file>
2578 file, the source package name may be followed by a version
2579 number in parentheses<footnote>
2580 It is customary to leave a space after the package name
2581 if a version number is specified.
2583 This version number may be omitted (and is, by
2584 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2585 the <tt>Version</tt> field of the binary package in
2586 question. The field itself may be omitted from a binary
2587 package control file when the source package has the same
2588 name and version as the binary package.
2592 <sect1 id="f-Maintainer">
2593 <heading><tt>Maintainer</tt></heading>
2596 The package maintainer's name and email address. The name
2597 should come first, then the email address inside angle
2598 brackets <tt><></tt> (in RFC822 format).
2602 If the maintainer's name contains a full stop then the
2603 whole field will not work directly as an email address due
2604 to a misfeature in the syntax specified in RFC822; a
2605 program using this field as an address must check for this
2606 and correct the problem if necessary (for example by
2607 putting the name in round brackets and moving it to the
2608 end, and bringing the email address forward).
2612 <sect1 id="f-Uploaders">
2613 <heading><tt>Uploaders</tt></heading>
2616 List of the names and email addresses of co-maintainers of
2617 the package, if any. If the package has other maintainers
2618 beside the one named in the
2619 <qref id="f-Maintainer">Maintainer field</qref>, their
2620 names and email addresses should be listed here. The
2621 format is the same as that of the Maintainer tag, and
2622 multiple entries should be comma separated. Currently,
2623 this field is restricted to a single line of data. This
2624 is an optional field.
2627 Any parser that interprets the Uploaders field in
2628 <file>debian/control</file> must permit it to span multiple
2629 lines. Line breaks in an Uploaders field that spans multiple
2630 lines are not significant and the semantics of the field are
2631 the same as if the line breaks had not been present.
2635 <sect1 id="f-Changed-By">
2636 <heading><tt>Changed-By</tt></heading>
2639 The name and email address of the person who changed the
2640 said package. Usually the name of the maintainer.
2641 All the rules for the Maintainer field apply here, too.
2645 <sect1 id="f-Section">
2646 <heading><tt>Section</tt></heading>
2649 This field specifies an application area into which the package
2650 has been classified. See <ref id="subsections">.
2654 When it appears in the <file>debian/control</file> file,
2655 it gives the value for the subfield of the same name in
2656 the <tt>Files</tt> field of the <file>.changes</file> file.
2657 It also gives the default for the same field in the binary
2662 <sect1 id="f-Priority">
2663 <heading><tt>Priority</tt></heading>
2666 This field represents how important that it is that the user
2667 have the package installed. See <ref id="priorities">.
2671 When it appears in the <file>debian/control</file> file,
2672 it gives the value for the subfield of the same name in
2673 the <tt>Files</tt> field of the <file>.changes</file> file.
2674 It also gives the default for the same field in the binary
2679 <sect1 id="f-Package">
2680 <heading><tt>Package</tt></heading>
2683 The name of the binary package.
2687 Package names must consist only of lower case letters
2688 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2689 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2690 They must be at least two characters long and must start
2691 with an alphanumeric character.
2695 <sect1 id="f-Architecture">
2696 <heading><tt>Architecture</tt></heading>
2699 Depending on context and the control file used, the
2700 <tt>Architecture</tt> field can include the following sets of
2703 <item>A unique single word identifying a Debian machine
2704 architecture, see <ref id="arch-spec">.
2705 <item><tt>all</tt>, which indicates an
2706 architecture-independent package.
2707 <item><tt>any</tt>, which indicates a package available
2708 for building on any architecture.
2709 <item><tt>source</tt>, which indicates a source package.
2714 In the main <file>debian/control</file> file in the source
2715 package, or in the source package control file
2716 <file>.dsc</file>, one may specify a list of architectures
2717 separated by spaces, or the special values <tt>any</tt> or
2722 Specifying <tt>any</tt> indicates that the source package
2723 isn't dependent on any particular architecture and should
2724 compile fine on any one. The produced binary package(s)
2725 will be specific to whatever the current build architecture
2727 This is the most often used setting, and is recommended
2728 for new packages that aren't <tt>Architecture: all</tt>.
2733 Specifying a list of architectures indicates that the source
2734 will build an architecture-dependent package, and will only
2735 work correctly on the listed architectures.<footnote>
2736 This is a setting used for a minority of cases where the
2737 program is not portable. Generally, it should not be used
2743 In a <file>.changes</file> file, the <tt>Architecture</tt>
2744 field lists the architecture(s) of the package(s)
2745 currently being uploaded. This will be a list; if the
2746 source for the package is also being uploaded, the special
2747 entry <tt>source</tt> is also present.
2751 See <ref id="debianrules"> for information how to get the
2752 architecture for the build process.
2756 <sect1 id="f-Essential">
2757 <heading><tt>Essential</tt></heading>
2760 This is a boolean field which may occur only in the
2761 control file of a binary package or in a per-package fields
2762 paragraph of a main source control data file.
2766 If set to <tt>yes</tt> then the package management system
2767 will refuse to remove the package (upgrading and replacing
2768 it is still possible). The other possible value is <tt>no</tt>,
2769 which is the same as not having the field at all.
2774 <heading>Package interrelationship fields:
2775 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2776 <tt>Recommends</tt>, <tt>Suggests</tt>,
2777 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2778 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2782 These fields describe the package's relationships with
2783 other packages. Their syntax and semantics are described
2784 in <ref id="relationships">.</p>
2787 <sect1 id="f-Standards-Version">
2788 <heading><tt>Standards-Version</tt></heading>
2791 The most recent version of the standards (the policy
2792 manual and associated texts) with which the package
2797 The version number has four components: major and minor
2798 version number and major and minor patch level. When the
2799 standards change in a way that requires every package to
2800 change the major number will be changed. Significant
2801 changes that will require work in many packages will be
2802 signaled by a change to the minor number. The major patch
2803 level will be changed for any change to the meaning of the
2804 standards, however small; the minor patch level will be
2805 changed when only cosmetic, typographical or other edits
2806 are made which neither change the meaning of the document
2807 nor affect the contents of packages.
2811 Thus only the first three components of the policy version
2812 are significant in the <em>Standards-Version</em> control
2813 field, and so either these three components or the all
2814 four components may be specified.<footnote>
2815 In the past, people specified the full version number
2816 in the Standards-Version field, for example "2.3.0.0".
2817 Since minor patch-level changes don't introduce new
2818 policy, it was thought it would be better to relax
2819 policy and only require the first 3 components to be
2820 specified, in this example "2.3.0". All four
2821 components may still be used if someone wishes to do so.
2827 <sect1 id="f-Version">
2828 <heading><tt>Version</tt></heading>
2831 The version number of a package. The format is:
2832 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2836 The three components here are:
2838 <tag><var>epoch</var></tag>
2841 This is a single (generally small) unsigned integer. It
2842 may be omitted, in which case zero is assumed. If it is
2843 omitted then the <var>upstream_version</var> may not
2848 It is provided to allow mistakes in the version numbers
2849 of older versions of a package, and also a package's
2850 previous version numbering schemes, to be left behind.
2854 <tag><var>upstream_version</var></tag>
2857 This is the main part of the version number. It is
2858 usually the version number of the original ("upstream")
2859 package from which the <file>.deb</file> file has been made,
2860 if this is applicable. Usually this will be in the same
2861 format as that specified by the upstream author(s);
2862 however, it may need to be reformatted to fit into the
2863 package management system's format and comparison
2868 The comparison behavior of the package management system
2869 with respect to the <var>upstream_version</var> is
2870 described below. The <var>upstream_version</var>
2871 portion of the version number is mandatory.
2875 The <var>upstream_version</var> may contain only
2876 alphanumerics<footnote>
2877 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2879 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2880 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2881 tilde) and should start with a digit. If there is no
2882 <var>debian_revision</var> then hyphens are not allowed;
2883 if there is no <var>epoch</var> then colons are not
2888 <tag><var>debian_revision</var></tag>
2891 This part of the version number specifies the version of
2892 the Debian package based on the upstream version. It
2893 may contain only alphanumerics and the characters
2894 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2895 tilde) and is compared in the same way as the
2896 <var>upstream_version</var> is.
2900 It is optional; if it isn't present then the
2901 <var>upstream_version</var> may not contain a hyphen.
2902 This format represents the case where a piece of
2903 software was written specifically to be turned into a
2904 Debian package, and so there is only one "debianisation"
2905 of it and therefore no revision indication is required.
2909 It is conventional to restart the
2910 <var>debian_revision</var> at <tt>1</tt> each time the
2911 <var>upstream_version</var> is increased.
2915 The package management system will break the version
2916 number apart at the last hyphen in the string (if there
2917 is one) to determine the <var>upstream_version</var> and
2918 <var>debian_revision</var>. The absence of a
2919 <var>debian_revision</var> is equivalent to a
2920 <var>debian_revision</var> of <tt>0</tt>.
2927 When comparing two version numbers, first the <var>epoch</var>
2928 of each are compared, then the <var>upstream_version</var> if
2929 <var>epoch</var> is equal, and then <var>debian_revision</var>
2930 if <var>upstream_version</var> is also equal.
2931 <var>epoch</var> is compared numerically. The
2932 <var>upstream_version</var> and <var>debian_revision</var>
2933 parts are compared by the package management system using the
2934 following algorithm:
2938 The strings are compared from left to right.
2942 First the initial part of each string consisting entirely of
2943 non-digit characters is determined. These two parts (one of
2944 which may be empty) are compared lexically. If a difference
2945 is found it is returned. The lexical comparison is a
2946 comparison of ASCII values modified so that all the letters
2947 sort earlier than all the non-letters and so that a tilde
2948 sorts before anything, even the end of a part. For example,
2949 the following parts are in sorted order from earliest to
2950 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2951 <tt>a</tt>.<footnote>
2952 One common use of <tt>~</tt> is for upstream pre-releases.
2953 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2954 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2959 Then the initial part of the remainder of each string which
2960 consists entirely of digit characters is determined. The
2961 numerical values of these two parts are compared, and any
2962 difference found is returned as the result of the comparison.
2963 For these purposes an empty string (which can only occur at
2964 the end of one or both version strings being compared) counts
2969 These two steps (comparing and removing initial non-digit
2970 strings and initial digit strings) are repeated until a
2971 difference is found or both strings are exhausted.
2975 Note that the purpose of epochs is to allow us to leave behind
2976 mistakes in version numbering, and to cope with situations
2977 where the version numbering scheme changes. It is
2978 <em>not</em> intended to cope with version numbers containing
2979 strings of letters which the package management system cannot
2980 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2981 silly orderings (the author of this manual has heard of a
2982 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2983 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2984 <tt>2</tt> and so forth).
2988 <sect1 id="f-Description">
2989 <heading><tt>Description</tt></heading>
2992 In a source or binary control file, the <tt>Description</tt>
2993 field contains a description of the binary package, consisting
2994 of two parts, the synopsis or the short description, and the
2995 long description. The field's format is as follows:
3000 Description: <single line synopsis>
3001 <extended description over several lines>
3006 The lines in the extended description can have these formats:
3012 Those starting with a single space are part of a paragraph.
3013 Successive lines of this form will be word-wrapped when
3014 displayed. The leading space will usually be stripped off.
3018 Those starting with two or more spaces. These will be
3019 displayed verbatim. If the display cannot be panned
3020 horizontally, the displaying program will line wrap them "hard"
3021 (i.e., without taking account of word breaks). If it can they
3022 will be allowed to trail off to the right. None, one or two
3023 initial spaces may be deleted, but the number of spaces
3024 deleted from each line will be the same (so that you can have
3025 indenting work correctly, for example).
3029 Those containing a single space followed by a single full stop
3030 character. These are rendered as blank lines. This is the
3031 <em>only</em> way to get a blank line<footnote>
3032 Completely empty lines will not be rendered as blank lines.
3033 Instead, they will cause the parser to think you're starting
3034 a whole new record in the control file, and will therefore
3035 likely abort with an error.
3040 Those containing a space, a full stop and some more characters.
3041 These are for future expansion. Do not use them.
3047 Do not use tab characters. Their effect is not predictable.
3051 See <ref id="descriptions"> for further information on this.
3055 In a <file>.changes</file> file, the <tt>Description</tt> field
3056 contains a summary of the descriptions for the packages being
3061 The part of the field before the first newline is empty;
3062 thereafter each line has the name of a binary package and
3063 the summary description line from that binary package.
3064 Each line is indented by one space.
3069 <sect1 id="f-Distribution">
3070 <heading><tt>Distribution</tt></heading>
3073 In a <file>.changes</file> file or parsed changelog output
3074 this contains the (space-separated) name(s) of the
3075 distribution(s) where this version of the package should
3076 be installed. Valid distributions are determined by the
3077 archive maintainers.<footnote>
3078 Current distribution names are:
3079 <taglist compact="compact">
3080 <tag><em>stable</em></tag>
3082 This is the current "released" version of Debian
3083 GNU/Linux. Once the distribution is
3084 <em>stable</em> only security fixes and other
3085 major bug fixes are allowed. When changes are
3086 made to this distribution, the release number is
3087 increased (for example: 2.2r1 becomes 2.2r2 then
3091 <tag><em>unstable</em></tag>
3093 This distribution value refers to the
3094 <em>developmental</em> part of the Debian
3095 distribution tree. New packages, new upstream
3096 versions of packages and bug fixes go into the
3097 <em>unstable</em> directory tree. Download from
3098 this distribution at your own risk.
3101 <tag><em>testing</em></tag>
3103 This distribution value refers to the
3104 <em>testing</em> part of the Debian distribution
3105 tree. It receives its packages from the
3106 unstable distribution after a short time lag to
3107 ensure that there are no major issues with the
3108 unstable packages. It is less prone to breakage
3109 than unstable, but still risky. It is not
3110 possible to upload packages directly to
3114 <tag><em>frozen</em></tag>
3116 From time to time, the <em>testing</em>
3117 distribution enters a state of "code-freeze" in
3118 anticipation of release as a <em>stable</em>
3119 version. During this period of testing only
3120 fixes for existing or newly-discovered bugs will
3121 be allowed. The exact details of this stage are
3122 determined by the Release Manager.
3125 <tag><em>experimental</em></tag>
3127 The packages with this distribution value are
3128 deemed by their maintainers to be high
3129 risk. Oftentimes they represent early beta or
3130 developmental packages from various sources that
3131 the maintainers want people to try, but are not
3132 ready to be a part of the other parts of the
3133 Debian distribution tree. Download at your own
3139 You should list <em>all</em> distributions that the
3140 package should be installed into.
3144 More information is available in the Debian Developer's
3145 Reference, section "The Debian archive".
3152 <heading><tt>Date</tt></heading>
3155 This field includes the date the package was built or last edited.
3159 The value of this field is usually extracted from the
3160 <file>debian/changelog</file> file - see
3161 <ref id="dpkgchangelog">).
3165 <sect1 id="f-Format">
3166 <heading><tt>Format</tt></heading>
3169 This field specifies a format revision for the file.
3170 The most current format described in the Policy Manual
3171 is version <strong>1.5</strong>. The syntax of the
3172 format value is the same as that of a package version
3173 number except that no epoch or Debian revision is allowed
3174 - see <ref id="f-Version">.
3178 <sect1 id="f-Urgency">
3179 <heading><tt>Urgency</tt></heading>
3182 This is a description of how important it is to upgrade to
3183 this version from previous ones. It consists of a single
3184 keyword taking one of the values <tt>low</tt>,
3185 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3186 <tt>critical</tt><footnote>
3187 Other urgency values are supported with configuration
3188 changes in the archive software but are not used in Debian.
3189 The urgency affects how quickly a package will be considered
3190 for inclusion into the <tt>testing</tt> distribution and
3191 gives an indication of the importance of any fixes included
3192 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3193 treated as synonymous.
3194 </footnote> (not case-sensitive) followed by an optional
3195 commentary (separated by a space) which is usually in
3196 parentheses. For example:
3199 Urgency: low (HIGH for users of diversions)
3205 The value of this field is usually extracted from the
3206 <file>debian/changelog</file> file - see
3207 <ref id="dpkgchangelog">.
3211 <sect1 id="f-Changes">
3212 <heading><tt>Changes</tt></heading>
3215 This field contains the human-readable changes data, describing
3216 the differences between the last version and the current one.
3220 There should be nothing in this field before the first
3221 newline; all the subsequent lines must be indented by at
3222 least one space; blank lines must be represented by a line
3223 consisting only of a space and a full stop.
3227 The value of this field is usually extracted from the
3228 <file>debian/changelog</file> file - see
3229 <ref id="dpkgchangelog">).
3233 Each version's change information should be preceded by a
3234 "title" line giving at least the version, distribution(s)
3235 and urgency, in a human-readable way.
3239 If data from several versions is being returned the entry
3240 for the most recent version should be returned first, and
3241 entries should be separated by the representation of a
3242 blank line (the "title" line may also be followed by the
3243 representation of blank line).
3247 <sect1 id="f-Binary">
3248 <heading><tt>Binary</tt></heading>
3251 This field is a list of binary packages.
3255 When it appears in the <file>.dsc</file> file it is the list
3256 of binary packages which a source package can produce. It
3257 does not necessarily produce all of these binary packages
3258 for every architecture. The source control file doesn't
3259 contain details of which architectures are appropriate for
3260 which of the binary packages.
3264 When it appears in a <file>.changes</file> file it lists the
3265 names of the binary packages actually being uploaded.
3269 The syntax is a list of binary packages separated by
3271 A space after each comma is conventional.
3272 </footnote>. Currently the packages must be separated using
3273 only spaces in the <file>.changes</file> file.
3277 <sect1 id="f-Installed-Size">
3278 <heading><tt>Installed-Size</tt></heading>
3281 This field appears in the control files of binary
3282 packages, and in the <file>Packages</file> files. It gives
3283 the total amount of disk space required to install the
3288 The disk space is represented in kilobytes as a simple
3293 <sect1 id="f-Files">
3294 <heading><tt>Files</tt></heading>
3297 This field contains a list of files with information about
3298 each one. The exact information and syntax varies with
3299 the context. In all cases the part of the field
3300 contents on the same line as the field name is empty. The
3301 remainder of the field is one line per file, each line
3302 being indented by one space and containing a number of
3303 sub-fields separated by spaces.
3307 In the <file>.dsc</file> file, each line contains the MD5
3308 checksum, size and filename of the tar file and (if applicable)
3309 diff file which make up the remainder of the source
3311 That is, the parts which are not the <tt>.dsc</tt>.
3313 The exact forms of the filenames are described
3314 in <ref id="pkg-sourcearchives">.
3318 In the <file>.changes</file> file this contains one line per
3319 file being uploaded. Each line contains the MD5 checksum,
3320 size, section and priority and the filename.
3321 The <qref id="f-Section">section</qref>
3322 and <qref id="f-Priority">priority</qref>
3323 are the values of the corresponding fields in
3324 the main source control file. If no section or priority is
3325 specified then <tt>-</tt> should be used, though section
3326 and priority values must be specified for new packages to
3327 be installed properly.
3331 The special value <tt>byhand</tt> for the section in a
3332 <tt>.changes</tt> file indicates that the file in question
3333 is not an ordinary package file and must by installed by
3334 hand by the distribution maintainers. If the section is
3335 <tt>byhand</tt> the priority should be <tt>-</tt>.
3339 If a new Debian revision of a package is being shipped and
3340 no new original source archive is being distributed the
3341 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3342 entry for the original source archive
3343 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3344 but the <file>.changes</file> file should leave it out. In
3345 this case the original source archive on the distribution
3346 site must match exactly, byte-for-byte, the original
3347 source archive which was used to generate the
3348 <file>.dsc</file> file and diff which are being uploaded.</p>
3351 <sect1 id="f-Closes">
3352 <heading><tt>Closes</tt></heading>
3355 A space-separated list of bug report numbers that the upload
3356 governed by the .changes file closes.
3360 <sect1 id="f-Homepage">
3361 <heading><tt>Homepage</tt></heading>
3364 The URL of the web site for this package, preferably (when
3365 applicable) the site from which the original source can be
3366 obtained and any additional upstream documentation or
3367 information may be found. The content of this field is a
3368 simple URL without any surrounding characters such as
3376 <heading>User-defined fields</heading>
3379 Additional user-defined fields may be added to the
3380 source package control file. Such fields will be
3381 ignored, and not copied to (for example) binary or
3382 source package control files or upload control files.
3386 If you wish to add additional unsupported fields to
3387 these output files you should use the mechanism
3392 Fields in the main source control information file with
3393 names starting <tt>X</tt>, followed by one or more of
3394 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3395 be copied to the output files. Only the part of the
3396 field name after the hyphen will be used in the output
3397 file. Where the letter <tt>B</tt> is used the field
3398 will appear in binary package control files, where the
3399 letter <tt>S</tt> is used in source package control
3400 files and where <tt>C</tt> is used in upload control
3401 (<tt>.changes</tt>) files.
3405 For example, if the main source information control file
3408 XBS-Comment: I stand between the candle and the star.
3410 then the binary and source package control files will contain the
3413 Comment: I stand between the candle and the star.
3422 <chapt id="maintainerscripts">
3423 <heading>Package maintainer scripts and installation procedure</heading>
3426 <heading>Introduction to package maintainer scripts</heading>
3429 It is possible to supply scripts as part of a package which
3430 the package management system will run for you when your
3431 package is installed, upgraded or removed.
3435 These scripts are the files <prgn>preinst</prgn>,
3436 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3437 <prgn>postrm</prgn> in the control area of the package.
3438 They must be proper executable files; if they are scripts
3439 (which is recommended), they must start with the usual
3440 <tt>#!</tt> convention. They should be readable and
3441 executable by anyone, and must not be world-writable.
3445 The package management system looks at the exit status from
3446 these scripts. It is important that they exit with a
3447 non-zero status if there is an error, so that the package
3448 management system can stop its processing. For shell
3449 scripts this means that you <em>almost always</em> need to
3450 use <tt>set -e</tt> (this is usually true when writing shell
3451 scripts, in fact). It is also important, of course, that
3452 they exit with a zero status if everything went well.
3456 Additionally, packages interacting with users using
3457 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3458 install a <prgn>config</prgn> script in the control area,
3459 see <ref id="maintscriptprompt"> for details.
3463 When a package is upgraded a combination of the scripts from
3464 the old and new packages is called during the upgrade
3465 procedure. If your scripts are going to be at all
3466 complicated you need to be aware of this, and may need to
3467 check the arguments to your scripts.
3471 Broadly speaking the <prgn>preinst</prgn> is called before
3472 (a particular version of) a package is installed, and the
3473 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3474 before (a version of) a package is removed and the
3475 <prgn>postrm</prgn> afterwards.
3479 Programs called from maintainer scripts should not normally
3480 have a path prepended to them. Before installation is
3481 started, the package management system checks to see if the
3482 programs <prgn>ldconfig</prgn>,
3483 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3484 and <prgn>update-rc.d</prgn> can be found via the
3485 <tt>PATH</tt> environment variable. Those programs, and any
3486 other program that one would expect to be in the
3487 <tt>PATH</tt>, should thus be invoked without an absolute
3488 pathname. Maintainer scripts should also not reset the
3489 <tt>PATH</tt>, though they might choose to modify it by
3490 prepending or appending package-specific directories. These
3491 considerations really apply to all shell scripts.</p>
3494 <sect id="idempotency">
3495 <heading>Maintainer scripts idempotency</heading>
3498 It is necessary for the error recovery procedures that the
3499 scripts be idempotent. This means that if it is run
3500 successfully, and then it is called again, it doesn't bomb
3501 out or cause any harm, but just ensures that everything is
3502 the way it ought to be. If the first call failed, or
3503 aborted half way through for some reason, the second call
3504 should merely do the things that were left undone the first
3505 time, if any, and exit with a success status if everything
3507 This is so that if an error occurs, the user interrupts
3508 <prgn>dpkg</prgn> or some other unforeseen circumstance
3509 happens you don't leave the user with a badly-broken
3510 package when <prgn>dpkg</prgn> attempts to repeat the
3516 <sect id="controllingterminal">
3517 <heading>Controlling terminal for maintainer scripts</heading>
3520 The maintainer scripts are guaranteed to run with a
3521 controlling terminal and can interact with the user.
3522 Because these scripts may be executed with standard output
3523 redirected into a pipe for logging purposes, Perl scripts
3524 should set unbuffered output by setting <tt>$|=1</tt> so
3525 that the output is printed immediately rather than being
3529 <sect id="exitstatus">
3530 <heading>Exit status</heading>
3533 Each script must return a zero exit status for
3534 success, or a nonzero one for failure, since the package
3535 management system looks for the exit status of these scripts
3536 and determines what action to take next based on that datum.
3540 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3545 <list compact="compact">
3547 <var>new-preinst</var> <tt>install</tt>
3550 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3553 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3556 <var>old-preinst</var> <tt>abort-upgrade</tt>
3557 <var>new-version</var>
3562 <list compact="compact">
3564 <var>postinst</var> <tt>configure</tt>
3565 <var>most-recently-configured-version</var>
3568 <var>old-postinst</var> <tt>abort-upgrade</tt>
3569 <var>new-version</var>
3572 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3573 <tt>in-favour</tt> <var>package</var>
3574 <var>new-version</var>
3577 <var>postinst</var> <tt>abort-remove</tt>
3580 <var>deconfigured's-postinst</var>
3581 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3582 <var>failed-install-package</var> <var>version</var>
3583 [<tt>removing</tt> <var>conflicting-package</var>
3589 <list compact="compact">
3591 <var>prerm</var> <tt>remove</tt>
3594 <var>old-prerm</var> <tt>upgrade</tt>
3595 <var>new-version</var>
3598 <var>new-prerm</var> <tt>failed-upgrade</tt>
3599 <var>old-version</var>
3602 <var>conflictor's-prerm</var> <tt>remove</tt>
3603 <tt>in-favour</tt> <var>package</var>
3604 <var>new-version</var>
3607 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3608 <tt>in-favour</tt> <var>package-being-installed</var>
3609 <var>version</var> [<tt>removing</tt>
3610 <var>conflicting-package</var>
3616 <list compact="compact">
3618 <var>postrm</var> <tt>remove</tt>
3621 <var>postrm</var> <tt>purge</tt>
3624 <var>old-postrm</var> <tt>upgrade</tt>
3625 <var>new-version</var>
3628 <var>new-postrm</var> <tt>failed-upgrade</tt>
3629 <var>old-version</var>
3632 <var>new-postrm</var> <tt>abort-install</tt>
3635 <var>new-postrm</var> <tt>abort-install</tt>
3636 <var>old-version</var>
3639 <var>new-postrm</var> <tt>abort-upgrade</tt>
3640 <var>old-version</var>
3643 <var>disappearer's-postrm</var> <tt>disappear</tt>
3644 <var>overwriter</var>
3645 <var>overwriter-version</var>
3651 <sect id="unpackphase">
3652 <heading>Details of unpack phase of installation or upgrade</heading>
3655 The procedure on installation/upgrade/overwrite/disappear
3656 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3657 stage of <tt>dpkg --install</tt>) is as follows. In each
3658 case, if a major error occurs (unless listed below) the
3659 actions are, in general, run backwards - this means that the
3660 maintainer scripts are run with different arguments in
3661 reverse order. These are the "error unwind" calls listed
3668 If a version of the package is already installed, call
3669 <example compact="compact">
3670 <var>old-prerm</var> upgrade <var>new-version</var>
3674 If the script runs but exits with a non-zero
3675 exit status, <prgn>dpkg</prgn> will attempt:
3676 <example compact="compact">
3677 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3679 If this works, the upgrade continues. If this
3680 does not work, the error unwind:
3681 <example compact="compact">
3682 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3684 If this works, then the old-version is
3685 "Installed", if not, the old version is in a
3686 "Failed-Config" state.
3692 If a "conflicting" package is being removed at the same time,
3693 or if any package will be broken (due to <tt>Breaks</tt>):
3696 If <tt>--auto-deconfigure</tt> is
3697 specified, call, for each package to be deconfigured
3698 due to <tt>Breaks</tt>:
3699 <example compact="compact">
3700 <var>deconfigured's-prerm</var> deconfigure \
3701 in-favour <var>package-being-installed</var> <var>version</var>
3704 <example compact="compact">
3705 <var>deconfigured's-postinst</var> abort-deconfigure \
3706 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3708 The deconfigured packages are marked as
3709 requiring configuration, so that if
3710 <tt>--install</tt> is used they will be
3711 configured again if possible.
3714 If any packages depended on a conflicting
3715 package being removed and <tt>--auto-deconfigure</tt> is
3716 specified, call, for each such package:
3717 <example compact="compact">
3718 <var>deconfigured's-prerm</var> deconfigure \
3719 in-favour <var>package-being-installed</var> <var>version</var> \
3720 removing <var>conflicting-package</var> <var>version</var>
3723 <example compact="compact">
3724 <var>deconfigured's-postinst</var> abort-deconfigure \
3725 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3726 removing <var>conflicting-package</var> <var>version</var>
3728 The deconfigured packages are marked as
3729 requiring configuration, so that if
3730 <tt>--install</tt> is used they will be
3731 configured again if possible.
3734 To prepare for removal of each conflicting package, call:
3735 <example compact="compact">
3736 <var>conflictor's-prerm</var> remove \
3737 in-favour <var>package</var> <var>new-version</var>
3740 <example compact="compact">
3741 <var>conflictor's-postinst</var> abort-remove \
3742 in-favour <var>package</var> <var>new-version</var>
3751 If the package is being upgraded, call:
3752 <example compact="compact">
3753 <var>new-preinst</var> upgrade <var>old-version</var>
3755 If this fails, we call:
3757 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3764 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3766 is called. If this works, then the old version
3767 is in an "Installed" state, or else it is left
3768 in an "Unpacked" state.
3773 If it fails, then the old version is left
3774 in an "Half-Installed" state.
3781 Otherwise, if the package had some configuration
3782 files from a previous version installed (i.e., it
3783 is in the "configuration files only" state):
3784 <example compact="compact">
3785 <var>new-preinst</var> install <var>old-version</var>
3789 <var>new-postrm</var> abort-install <var>old-version</var>
3791 If this fails, the package is left in a
3792 "Half-Installed" state, which requires a
3793 reinstall. If it works, the packages is left in
3794 a "Config Files" state.
3797 Otherwise (i.e., the package was completely purged):
3798 <example compact="compact">
3799 <var>new-preinst</var> install
3802 <example compact="compact">
3803 <var>new-postrm</var> abort-install
3805 If the error-unwind fails, the package is in a
3806 "Half Installed" phase, and requires a
3807 reinstall. If the error unwind works, the
3808 package is in a not installed state.
3815 The new package's files are unpacked, overwriting any
3816 that may be on the system already, for example any
3817 from the old version of the same package or from
3818 another package. Backups of the old files are kept
3819 temporarily, and if anything goes wrong the package
3820 management system will attempt to put them back as
3821 part of the error unwind.
3825 It is an error for a package to contain files which
3826 are on the system in another package, unless
3827 <tt>Replaces</tt> is used (see <ref id="replaces">).
3829 The following paragraph is not currently the case:
3830 Currently the <tt>- - force-overwrite</tt> flag is
3831 enabled, downgrading it to a warning, but this may not
3837 It is a more serious error for a package to contain a
3838 plain file or other kind of non-directory where another
3839 package has a directory (again, unless
3840 <tt>Replaces</tt> is used). This error can be
3841 overridden if desired using
3842 <tt>--force-overwrite-dir</tt>, but this is not
3847 Packages which overwrite each other's files produce
3848 behavior which, though deterministic, is hard for the
3849 system administrator to understand. It can easily
3850 lead to "missing" programs if, for example, a package
3851 is installed which overwrites a file from another
3852 package, and is then removed again.<footnote>
3853 Part of the problem is due to what is arguably a
3854 bug in <prgn>dpkg</prgn>.
3859 A directory will never be replaced by a symbolic link
3860 to a directory or vice versa; instead, the existing
3861 state (symlink or not) will be left alone and
3862 <prgn>dpkg</prgn> will follow the symlink if there is
3871 If the package is being upgraded, call
3872 <example compact="compact">
3873 <var>old-postrm</var> upgrade <var>new-version</var>
3877 If this fails, <prgn>dpkg</prgn> will attempt:
3878 <example compact="compact">
3879 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3881 If this works, installation continues. If not,
3883 <example compact="compact">
3884 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3886 If this fails, the old version is left in an
3887 "Half Installed" state. If it works, dpkg now
3889 <example compact="compact">
3890 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3892 If this fails, the old version is left in an
3893 "Half Installed" state. If it works, dpkg now
3895 <example compact="compact">
3896 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3898 If this fails, the old version is in an
3905 This is the point of no return - if
3906 <prgn>dpkg</prgn> gets this far, it won't back off
3907 past this point if an error occurs. This will
3908 leave the package in a fairly bad state, which
3909 will require a successful re-installation to clear
3910 up, but it's when <prgn>dpkg</prgn> starts doing
3911 things that are irreversible.
3916 Any files which were in the old version of the package
3917 but not in the new are removed.
3921 The new file list replaces the old.
3925 The new maintainer scripts replace the old.
3929 Any packages all of whose files have been overwritten
3930 during the installation, and which aren't required for
3931 dependencies, are considered to have been removed.
3932 For each such package
3935 <prgn>dpkg</prgn> calls:
3936 <example compact="compact">
3937 <var>disappearer's-postrm</var> disappear \
3938 <var>overwriter</var> <var>overwriter-version</var>
3942 The package's maintainer scripts are removed.
3945 It is noted in the status database as being in a
3946 sane state, namely not installed (any conffiles
3947 it may have are ignored, rather than being
3948 removed by <prgn>dpkg</prgn>). Note that
3949 disappearing packages do not have their prerm
3950 called, because <prgn>dpkg</prgn> doesn't know
3951 in advance that the package is going to
3958 Any files in the package we're unpacking that are also
3959 listed in the file lists of other packages are removed
3960 from those lists. (This will lobotomize the file list
3961 of the "conflicting" package if there is one.)
3965 The backup files made during installation, above, are
3971 The new package's status is now sane, and recorded as
3976 Here is another point of no return - if the
3977 conflicting package's removal fails we do not unwind
3978 the rest of the installation; the conflicting package
3979 is left in a half-removed limbo.
3984 If there was a conflicting package we go and do the
3985 removal actions (described below), starting with the
3986 removal of the conflicting package's files (any that
3987 are also in the package being installed have already
3988 been removed from the conflicting package's file list,
3989 and so do not get removed now).
3995 <sect id="configdetails"><heading>Details of configuration</heading>
3998 When we configure a package (this happens with <tt>dpkg
3999 --install</tt> and <tt>dpkg --configure</tt>), we first
4000 update any <tt>conffile</tt>s and then call:
4001 <example compact="compact">
4002 <var>postinst</var> configure <var>most-recently-configured-version</var>
4007 No attempt is made to unwind after errors during
4008 configuration. If the configuration fails, the package is in
4009 a "Failed Config" state, and an error message is generated.
4013 If there is no most recently configured version
4014 <prgn>dpkg</prgn> will pass a null argument.
4017 Historical note: Truly ancient (pre-1997) versions of
4018 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4019 (including the angle brackets) in this case. Even older
4020 ones did not pass a second argument at all, under any
4021 circumstance. Note that upgrades using such an old dpkg
4022 version are unlikely to work for other reasons, even if
4023 this old argument behavior is handled by your postinst script.
4029 <sect id="removedetails"><heading>Details of removal and/or
4030 configuration purging</heading>
4036 <example compact="compact">
4037 <var>prerm</var> remove
4041 If prerm fails during replacement due to conflict
4043 <var>conflictor's-postinst</var> abort-remove \
4044 in-favour <var>package</var> <var>new-version</var>
4048 <var>postinst</var> abort-remove
4052 If this fails, the package is in a "Failed-Config"
4053 state, or else it remains "Installed".
4057 The package's files are removed (except <tt>conffile</tt>s).
4060 <example compact="compact">
4061 <var>postrm</var> remove
4065 If it fails, there's no error unwind, and the package is in
4066 an "Half-Installed" state.
4071 All the maintainer scripts except the <prgn>postrm</prgn>
4076 If we aren't purging the package we stop here. Note
4077 that packages which have no <prgn>postrm</prgn> and no
4078 <tt>conffile</tt>s are automatically purged when
4079 removed, as there is no difference except for the
4080 <prgn>dpkg</prgn> status.
4084 The <tt>conffile</tt>s and any backup files
4085 (<tt>~</tt>-files, <tt>#*#</tt> files,
4086 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4091 <example compact="compact">
4092 <var>postrm</var> purge
4096 If this fails, the package remains in a "Config-Files"
4101 The package's file list is removed.
4110 <chapt id="relationships">
4111 <heading>Declaring relationships between packages</heading>
4113 <sect id="depsyntax">
4114 <heading>Syntax of relationship fields</heading>
4117 These fields all have a uniform syntax. They are a list of
4118 package names separated by commas.
4122 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4123 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4124 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4125 control file fields of the package, which declare
4126 dependencies on other packages, the package names listed may
4127 also include lists of alternative package names, separated
4128 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4129 if any one of the alternative packages is installed, that
4130 part of the dependency is considered to be satisfied.
4134 All of the fields except for <tt>Provides</tt> may restrict
4135 their applicability to particular versions of each named
4136 package. This is done in parentheses after each individual
4137 package name; the parentheses should contain a relation from
4138 the list below followed by a version number, in the format
4139 described in <ref id="f-Version">.
4143 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4144 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4145 strictly earlier, earlier or equal, exactly equal, later or
4146 equal and strictly later, respectively. The deprecated
4147 forms <tt><</tt> and <tt>></tt> were used to mean
4148 earlier/later or equal, rather than strictly earlier/later,
4149 so they should not appear in new packages (though
4150 <prgn>dpkg</prgn> still supports them).
4154 Whitespace may appear at any point in the version
4155 specification subject to the rules in <ref
4156 id="controlsyntax">, and must appear where it's necessary to
4157 disambiguate; it is not otherwise significant. All of the
4158 relationship fields may span multiple lines. For
4159 consistency and in case of future changes to
4160 <prgn>dpkg</prgn> it is recommended that a single space be
4161 used after a version relationship and before a version
4162 number; it is also conventional to put a single space after
4163 each comma, on either side of each vertical bar, and before
4164 each open parenthesis. When wrapping a relationship field, it
4165 is conventional to do so after a comma and before the space
4166 following that comma.
4170 For example, a list of dependencies might appear as:
4171 <example compact="compact">
4174 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4179 All fields that specify build-time relationships
4180 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4181 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4182 may be restricted to a certain set of architectures. This
4183 is indicated in brackets after each individual package name and
4184 the optional version specification. The brackets enclose a
4185 list of Debian architecture names separated by whitespace.
4186 Exclamation marks may be prepended to each of the names.
4187 (It is not permitted for some names to be prepended with
4188 exclamation marks while others aren't.) If the current Debian
4189 host architecture is not in this list and there are no
4190 exclamation marks in the list, or it is in the list with a
4191 prepended exclamation mark, the package name and the
4192 associated version specification are ignored completely for
4193 the purposes of defining the relationships.
4198 <example compact="compact">
4200 Build-Depends-Indep: texinfo
4201 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4202 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4204 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4205 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4206 <tt>gnumach-dev</tt> only on hurd-i386.
4210 If the architecture-restricted dependency is part of a set of
4211 alternatives using <tt>|</tt>, that alternative is ignored
4212 completely on architectures that do not match the restriction.
4214 <example compact="compact">
4215 Build-Depends: foo [!i386] | bar [!amd64]
4217 is equivalent to <tt>bar</tt> on the i386 architecture, to
4218 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4219 bar</tt> on all other architectures.
4223 Note that the binary package relationship fields such as
4224 <tt>Depends</tt> appear in one of the binary package
4225 sections of the control file, whereas the build-time
4226 relationships such as <tt>Build-Depends</tt> appear in the
4227 source package section of the control file (which is the
4232 <sect id="binarydeps">
4233 <heading>Binary Dependencies - <tt>Depends</tt>,
4234 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4235 <tt>Pre-Depends</tt>
4239 Packages can declare in their control file that they have
4240 certain relationships to other packages - for example, that
4241 they may not be installed at the same time as certain other
4242 packages, and/or that they depend on the presence of others.
4246 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4247 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4248 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4252 These seven fields are used to declare a dependency
4253 relationship by one package on another. Except for
4254 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4255 depending (binary) package's control file.
4256 (<tt>Enhances</tt> appears in the recommending package's
4257 control file, and <tt>Breaks</tt> appears in the version of
4258 depended-on package which causes the named package to
4263 A <tt>Depends</tt> field takes effect <em>only</em> when a
4264 package is to be configured. It does not prevent a package
4265 being on the system in an unconfigured state while its
4266 dependencies are unsatisfied, and it is possible to replace
4267 a package whose dependencies are satisfied and which is
4268 properly installed with a different version whose
4269 dependencies are not and cannot be satisfied; when this is
4270 done the depending package will be left unconfigured (since
4271 attempts to configure it will give errors) and will not
4272 function properly. If it is necessary, a
4273 <tt>Pre-Depends</tt> field can be used, which has a partial
4274 effect even when a package is being unpacked, as explained
4275 in detail below. (The other three dependency fields,
4276 <tt>Recommends</tt>, <tt>Suggests</tt> and
4277 <tt>Enhances</tt>, are only used by the various front-ends
4278 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4279 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4283 For this reason packages in an installation run are usually
4284 all unpacked first and all configured later; this gives
4285 later versions of packages with dependencies on later
4286 versions of other packages the opportunity to have their
4287 dependencies satisfied.
4291 In case of circular dependencies, since installation or
4292 removal order honoring the dependency order can't be
4293 established, dependency loops are broken at some point
4294 (based on rules below), and some packages may not be able to
4295 rely on their dependencies being present when being
4296 installed or removed, depending on which side of the break
4297 of the circular dependency loop they happen to be on. If one
4298 of the packages in the loop has no postinst script, then the
4299 cycle will be broken at that package, so as to ensure that
4300 all postinst scripts run with the dependencies properly
4301 configured if this is possible. Otherwise the breaking point
4306 The <tt>Depends</tt> field thus allows package maintainers
4307 to impose an order in which packages should be configured.
4311 The meaning of the five dependency fields is as follows:
4313 <tag><tt>Depends</tt></tag>
4316 This declares an absolute dependency. A package will
4317 not be configured unless all of the packages listed in
4318 its <tt>Depends</tt> field have been correctly
4323 The <tt>Depends</tt> field should be used if the
4324 depended-on package is required for the depending
4325 package to provide a significant amount of
4330 The <tt>Depends</tt> field should also be used if the
4331 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4332 <prgn>postrm</prgn> scripts require the package to be
4333 present in order to run. Note, however, that the
4334 <prgn>postrm</prgn> cannot rely on any non-essential
4335 packages to be present during the <tt>purge</tt>
4339 <tag><tt>Recommends</tt></tag>
4342 This declares a strong, but not absolute, dependency.
4346 The <tt>Recommends</tt> field should list packages
4347 that would be found together with this one in all but
4348 unusual installations.
4352 <tag><tt>Suggests</tt></tag>
4354 This is used to declare that one package may be more
4355 useful with one or more others. Using this field
4356 tells the packaging system and the user that the
4357 listed packages are related to this one and can
4358 perhaps enhance its usefulness, but that installing
4359 this one without them is perfectly reasonable.
4362 <tag><tt>Enhances</tt></tag>
4364 This field is similar to Suggests but works in the
4365 opposite direction. It is used to declare that a
4366 package can enhance the functionality of another
4370 <tag><tt>Pre-Depends</tt></tag>
4373 This field is like <tt>Depends</tt>, except that it
4374 also forces <prgn>dpkg</prgn> to complete installation
4375 of the packages named before even starting the
4376 installation of the package which declares the
4377 pre-dependency, as follows:
4381 When a package declaring a pre-dependency is about to
4382 be <em>unpacked</em> the pre-dependency can be
4383 satisfied if the depended-on package is either fully
4384 configured, <em>or even if</em> the depended-on
4385 package(s) are only unpacked or half-configured,
4386 provided that they have been configured correctly at
4387 some point in the past (and not removed or partially
4388 removed since). In this case, both the
4389 previously-configured and currently unpacked or
4390 half-configured versions must satisfy any version
4391 clause in the <tt>Pre-Depends</tt> field.
4395 When the package declaring a pre-dependency is about
4396 to be <em>configured</em>, the pre-dependency will be
4397 treated as a normal <tt>Depends</tt>, that is, it will
4398 be considered satisfied only if the depended-on
4399 package has been correctly configured.
4403 <tt>Pre-Depends</tt> should be used sparingly,
4404 preferably only by packages whose premature upgrade or
4405 installation would hamper the ability of the system to
4406 continue with any upgrade that might be in progress.
4410 <tt>Pre-Depends</tt> are also required if the
4411 <prgn>preinst</prgn> script depends on the named
4412 package. It is best to avoid this situation if
4420 When selecting which level of dependency to use you should
4421 consider how important the depended-on package is to the
4422 functionality of the one declaring the dependency. Some
4423 packages are composed of components of varying degrees of
4424 importance. Such a package should list using
4425 <tt>Depends</tt> the package(s) which are required by the
4426 more important components. The other components'
4427 requirements may be mentioned as Suggestions or
4428 Recommendations, as appropriate to the components' relative
4434 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4437 Using <tt>Breaks</tt> may cause problems for upgrades from older
4438 versions of Debian and should not be used until the stable
4439 release of Debian supports <tt>Breaks</tt>.
4443 When one binary package declares that it breaks another,
4444 <prgn>dpkg</prgn> will refuse to allow the package which
4445 declares <tt>Breaks</tt> be installed unless the broken
4446 package is deconfigured first, and it will refuse to
4447 allow the broken package to be reconfigured.
4451 A package will not be regarded as causing breakage merely
4452 because its configuration files are still installed; it must
4453 be at least half-installed.
4457 A special exception is made for packages which declare that
4458 they break their own package name or a virtual package which
4459 they provide (see below): this does not count as a real
4464 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4465 version clause; such a <tt>Breaks</tt> is introduced in the
4466 version of an (implicit or explicit) dependency which
4467 violates an assumption or reveals a bug in earlier versions
4468 of the broken package. This use of <tt>Breaks</tt> will
4469 inform higher-level package management tools that broken
4470 package must be upgraded before the new one.
4474 If the breaking package also overwrites some files from the
4475 older package, it should use <tt>Replaces</tt> (not
4476 <tt>Conflicts</tt>) to ensure this goes smoothly.
4480 <sect id="conflicts">
4481 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4484 When one binary package declares a conflict with another
4485 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4486 refuse to allow them to be installed on the system at the
4491 If one package is to be installed, the other must be removed
4492 first - if the package being installed is marked as
4493 replacing (see <ref id="replaces">) the one on the system,
4494 or the one on the system is marked as deselected, or both
4495 packages are marked <tt>Essential</tt>, then
4496 <prgn>dpkg</prgn> will automatically remove the package
4497 which is causing the conflict, otherwise it will halt the
4498 installation of the new package with an error. This
4499 mechanism is specifically designed to produce an error when
4500 the installed package is <tt>Essential</tt>, but the new
4505 A package will not cause a conflict merely because its
4506 configuration files are still installed; it must be at least
4511 A special exception is made for packages which declare a
4512 conflict with their own package name, or with a virtual
4513 package which they provide (see below): this does not
4514 prevent their installation, and allows a package to conflict
4515 with others providing a replacement for it. You use this
4516 feature when you want the package in question to be the only
4517 package providing some feature.
4521 A <tt>Conflicts</tt> entry should almost never have an
4522 "earlier than" version clause. This would prevent
4523 <prgn>dpkg</prgn> from upgrading or installing the package
4524 which declared such a conflict until the upgrade or removal
4525 of the conflicted-with package had been completed. Instead,
4526 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4527 by the stable release of Debian).
4531 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4535 As well as the names of actual ("concrete") packages, the
4536 package relationship fields <tt>Depends</tt>,
4537 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4538 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4539 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4540 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4541 may mention "virtual packages".
4545 A <em>virtual package</em> is one which appears in the
4546 <tt>Provides</tt> control file field of another package.
4547 The effect is as if the package(s) which provide a
4548 particular virtual package name had been listed by name
4549 everywhere the virtual package name appears. (See also <ref
4554 If there are both concrete and virtual packages of the same
4555 name, then the dependency may be satisfied (or the conflict
4556 caused) by either the concrete package with the name in
4557 question or any other concrete package which provides the
4558 virtual package with the name in question. This is so that,
4559 for example, supposing we have
4560 <example compact="compact">
4563 </example> and someone else releases an enhanced version of
4564 the <tt>bar</tt> package they can say:
4565 <example compact="compact">
4569 and the <tt>bar-plus</tt> package will now also satisfy the
4570 dependency for the <tt>foo</tt> package.
4574 If a relationship field has a version number attached
4575 then only real packages will be considered to see whether
4576 the relationship is satisfied (or the prohibition violated,
4577 for a conflict or breakage) - it is assumed that a real
4578 package which provides the virtual package is not of the
4579 "right" version. So, a <tt>Provides</tt> field may not
4580 contain version numbers, and the version number of the
4581 concrete package which provides a particular virtual package
4582 will not be looked at when considering a dependency on or
4583 conflict with the virtual package name.
4587 It is likely that the ability will be added in a future
4588 release of <prgn>dpkg</prgn> to specify a version number for
4589 each virtual package it provides. This feature is not yet
4590 present, however, and is expected to be used only
4595 If you want to specify which of a set of real packages
4596 should be the default to satisfy a particular dependency on
4597 a virtual package, you should list the real package as an
4598 alternative before the virtual one.
4603 <sect id="replaces"><heading>Overwriting files and replacing
4604 packages - <tt>Replaces</tt></heading>
4607 Packages can declare in their control file that they should
4608 overwrite files in certain other packages, or completely
4609 replace other packages. The <tt>Replaces</tt> control file
4610 field has these two distinct purposes.
4613 <sect1><heading>Overwriting files in other packages</heading>
4616 Firstly, as mentioned before, it is usually an error for a
4617 package to contain files which are on the system in
4622 However, if the overwriting package declares that it
4623 <tt>Replaces</tt> the one containing the file being
4624 overwritten, then <prgn>dpkg</prgn> will replace the file
4625 from the old package with that from the new. The file
4626 will no longer be listed as "owned" by the old package.
4630 If a package is completely replaced in this way, so that
4631 <prgn>dpkg</prgn> does not know of any files it still
4632 contains, it is considered to have "disappeared". It will
4633 be marked as not wanted on the system (selected for
4634 removal) and not installed. Any <tt>conffile</tt>s
4635 details noted for the package will be ignored, as they
4636 will have been taken over by the overwriting package. The
4637 package's <prgn>postrm</prgn> script will be run with a
4638 special argument to allow the package to do any final
4639 cleanup required. See <ref id="mscriptsinstact">.
4642 Replaces is a one way relationship -- you have to
4643 install the replacing package after the replaced
4650 For this usage of <tt>Replaces</tt>, virtual packages (see
4651 <ref id="virtual">) are not considered when looking at a
4652 <tt>Replaces</tt> field - the packages declared as being
4653 replaced must be mentioned by their real names.
4657 Furthermore, this usage of <tt>Replaces</tt> only takes
4658 effect when both packages are at least partially on the
4659 system at once, so that it can only happen if they do not
4660 conflict or if the conflict has been overridden.
4665 <sect1><heading>Replacing whole packages, forcing their
4669 Secondly, <tt>Replaces</tt> allows the packaging system to
4670 resolve which package should be removed when there is a
4671 conflict - see <ref id="conflicts">. This usage only
4672 takes effect when the two packages <em>do</em> conflict,
4673 so that the two usages of this field do not interfere with
4678 In this situation, the package declared as being replaced
4679 can be a virtual package, so for example, all mail
4680 transport agents (MTAs) would have the following fields in
4681 their control files:
4682 <example compact="compact">
4683 Provides: mail-transport-agent
4684 Conflicts: mail-transport-agent
4685 Replaces: mail-transport-agent
4687 ensuring that only one MTA can be installed at any one
4692 <sect id="sourcebinarydeps">
4693 <heading>Relationships between source and binary packages -
4694 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4695 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4699 Source packages that require certain binary packages to be
4700 installed or absent at the time of building the package
4701 can declare relationships to those binary packages.
4705 This is done using the <tt>Build-Depends</tt>,
4706 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4707 <tt>Build-Conflicts-Indep</tt> control file fields.
4711 Build-dependencies on "build-essential" binary packages can be
4712 omitted. Please see <ref id="pkg-relations"> for more information.
4716 The dependencies and conflicts they define must be satisfied
4717 (as defined earlier for binary packages) in order to invoke
4718 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4720 If you make "build-arch" or "binary-arch", you need
4721 Build-Depends. If you make "build-indep" or
4722 "binary-indep", you need Build-Depends and
4723 Build-Depends-Indep. If you make "build" or "binary",
4727 There is no Build-Depends-Arch; this role is essentially
4728 met with Build-Depends. Anyone building the
4729 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4730 is basically assumed to be building the whole package
4731 anyway and so installs all build dependencies. The
4732 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4733 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4734 does not yet know how to check for its existence) and
4735 <tt>binary-arch</tt>.
4738 The purpose of the original split, I recall, was so that
4739 the autobuilders wouldn't need to install extra packages
4740 needed only for the binary-indep targets. But without a
4741 build-arch/build-indep split, this didn't work, since
4742 most of the work is done in the build target, not in the
4748 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4750 The <tt>Build-Depends</tt> and
4751 <tt>Build-Conflicts</tt> fields must be satisfied when
4752 any of the following targets is invoked:
4753 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4754 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4755 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4757 <tag><tt>Build-Depends-Indep</tt>,
4758 <tt>Build-Conflicts-Indep</tt></tag>
4760 The <tt>Build-Depends-Indep</tt> and
4761 <tt>Build-Conflicts-Indep</tt> fields must be
4762 satisfied when any of the following targets is
4763 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4764 <tt>binary</tt> and <tt>binary-indep</tt>.
4774 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4777 Packages containing shared libraries must be constructed with
4778 a little care to make sure that the shared library is always
4779 available. This is especially important for packages whose
4780 shared libraries are vitally important, such as the C library
4781 (currently <tt>libc6</tt>).
4785 Packages involving shared libraries should be split up into
4786 several binary packages. This section mostly deals with how
4787 this separation is to be accomplished; rules for files within
4788 the shared library packages are in <ref id="libraries"> instead.
4791 <sect id="sharedlibs-runtime">
4792 <heading>Run-time shared libraries</heading>
4795 The run-time shared library needs to be placed in a package
4796 whose name changes whenever the shared object version
4799 Since it is common place to install several versions of a
4800 package that just provides shared libraries, it is a
4801 good idea that the library package should not
4802 contain any extraneous non-versioned files, unless they
4803 happen to be in versioned directories.</p>
4805 The most common mechanism is to place it in a package
4807 <package><var>libraryname</var><var>soversion</var></package>,
4808 where <file><var>soversion</var></file> is the version number
4809 in the soname of the shared library<footnote>
4810 The soname is the shared object name: it's the thing
4811 that has to match exactly between building an executable
4812 and running it for the dynamic linker to be able run the
4813 program. For example, if the soname of the library is
4814 <file>libfoo.so.6</file>, the library package would be
4815 called <file>libfoo6</file>.
4817 Alternatively, if it would be confusing to directly append
4818 <var>soversion</var> to <var>libraryname</var> (e.g. because
4819 <var>libraryname</var> itself ends in a number), you may use
4820 <package><var>libraryname</var>-<var>soversion</var></package> and
4821 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4826 If you have several shared libraries built from the same
4827 source tree you may lump them all together into a single
4828 shared library package, provided that you change all of
4829 their sonames at once (so that you don't get filename
4830 clashes if you try to install different versions of the
4831 combined shared libraries package).
4835 The package should install the shared libraries under
4836 their normal names. For example, the <package>libgdbm3</package>
4837 package should install <file>libgdbm.so.3.0.0</file> as
4838 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4839 renamed or re-linked by any <prgn>prerm</prgn> or
4840 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4841 of renaming things safely without affecting running programs,
4842 and attempts to interfere with this are likely to lead to
4847 Shared libraries should not be installed executable, since
4848 the dynamic linker does not require this and trying to
4849 execute a shared library usually results in a core dump.
4853 The run-time library package should include the symbolic link that
4854 <prgn>ldconfig</prgn> would create for the shared libraries.
4855 For example, the <package>libgdbm3</package> package should include
4856 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4857 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4858 linker (for example <prgn>ld.so</prgn> or
4859 <prgn>ld-linux.so.*</prgn>) can find the library between the
4860 time that <prgn>dpkg</prgn> installs it and the time that
4861 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4863 The package management system requires the library to be
4864 placed before the symbolic link pointing to it in the
4865 <file>.deb</file> file. This is so that when
4866 <prgn>dpkg</prgn> comes to install the symlink
4867 (overwriting the previous symlink pointing at an older
4868 version of the library), the new shared library is already
4869 in place. In the past, this was achieved by creating the
4870 library in the temporary packaging directory before
4871 creating the symlink. Unfortunately, this was not always
4872 effective, since the building of the tar file in the
4873 <file>.deb</file> depended on the behavior of the underlying
4874 file system. Some file systems (such as reiserfs) reorder
4875 the files so that the order of creation is forgotten.
4876 Since version 1.7.0, <prgn>dpkg</prgn>
4877 reorders the files itself as necessary when building a
4878 package. Thus it is no longer important to concern
4879 oneself with the order of file creation.
4883 <sect1 id="ldconfig">
4884 <heading><tt>ldconfig</tt></heading>
4887 Any package installing shared libraries in one of the default
4888 library directories of the dynamic linker (which are currently
4889 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4890 listed in <file>/etc/ld.so.conf</file><footnote>
4892 <list compact="compact">
4893 <item>/usr/local/lib</item>
4894 <item>/usr/lib/libc5-compat</item>
4895 <item>/lib/libc5-compat</item>
4898 must use <prgn>ldconfig</prgn> to update the shared library
4903 The package maintainer scripts must only call
4904 <prgn>ldconfig</prgn> under these circumstances:
4905 <list compact="compact">
4906 <item>When the <prgn>postinst</prgn> script is run with a
4907 first argument of <tt>configure</tt>, the script must call
4908 <prgn>ldconfig</prgn>, and may optionally invoke
4909 <prgn>ldconfig</prgn> at other times.
4911 <item>When the <prgn>postrm</prgn> script is run with a
4912 first argument of <tt>remove</tt>, the script should call
4913 <prgn>ldconfig</prgn>.
4918 During install or upgrade, the preinst is called before
4919 the new files are installed, so calling "ldconfig" is
4920 pointless. The preinst of an existing package can also be
4921 called if an upgrade fails. However, this happens during
4922 the critical time when a shared libs may exist on-disk
4923 under a temporary name. Thus, it is dangerous and
4924 forbidden by current policy to call "ldconfig" at this
4929 When a package is installed or upgraded, "postinst
4930 configure" runs after the new files are safely on-disk.
4931 Since it is perfectly safe to invoke ldconfig
4932 unconditionally in a postinst, it is OK for a package to
4933 simply put ldconfig in its postinst without checking the
4934 argument. The postinst can also be called to recover from
4935 a failed upgrade. This happens before any new files are
4936 unpacked, so there is no reason to call "ldconfig" at this
4941 For a package that is being removed, prerm is
4942 called with all the files intact, so calling ldconfig is
4943 useless. The other calls to "prerm" happen in the case of
4944 upgrade at a time when all the files of the old package
4945 are on-disk, so again calling "ldconfig" is pointless.
4949 postrm, on the other hand, is called with the "remove"
4950 argument just after the files are removed, so this is
4951 the proper time to call "ldconfig" to notify the system
4952 of the fact that the shared libraries from the package
4953 are removed. The postrm can be called at several other
4954 times. At the time of "postrm purge", "postrm
4955 abort-install", or "postrm abort-upgrade", calling
4956 "ldconfig" is useless because the shared lib files are
4957 not on-disk. However, when "postrm" is invoked with
4958 arguments "upgrade", "failed-upgrade", or "disappear", a
4959 shared lib may exist on-disk under a temporary filename.
4967 <sect id="sharedlibs-support-files">
4968 <heading>Shared library support files</heading>
4971 If your package contains files whose names do not change with
4972 each change in the library shared object version, you must not
4973 put them in the shared library package. Otherwise, several
4974 versions of the shared library cannot be installed at the same
4975 time without filename clashes, making upgrades and transitions
4976 unnecessarily difficult.
4980 It is recommended that supporting files and run-time support
4981 programs that do not need to be invoked manually by users, but
4982 are nevertheless required for the package to function, be placed
4983 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4984 preferably under <file>/usr/lib/</file><var>package-name</var>.
4985 If the program or file is architecture independent, the
4986 recommendation is for it to be placed in a subdirectory of
4987 <file>/usr/share</file> instead, preferably under
4988 <file>/usr/share/</file><var>package-name</var>. Following the
4989 <var>package-name</var> naming convention ensures that the file
4990 names change when the shared object version changes.
4994 Run-time support programs that use the shared library but are
4995 not required for the library to function or files used by the
4996 shared library that can be used by any version of the shared
4997 library package should instead be put in a separate package.
4998 This package might typically be named
4999 <package><var>libraryname</var>-tools</package>; note the
5000 absence of the <var>soversion</var> in the package name.
5004 Files and support programs only useful when compiling software
5005 against the library should be included in the development
5006 package for the library.<footnote>
5007 For example, a <file><var>package-name</var>-config</file>
5008 script or <package>pkg-config</package> configuration files.
5013 <sect id="sharedlibs-static">
5014 <heading>Static libraries</heading>
5017 The static library (<file><var>libraryname.a</var></file>)
5018 is usually provided in addition to the shared version.
5019 It is placed into the development package (see below).
5023 In some cases, it is acceptable for a library to be
5024 available in static form only; these cases include:
5026 <item>libraries for languages whose shared library support
5027 is immature or unstable</item>
5028 <item>libraries whose interfaces are in flux or under
5029 development (commonly the case when the library's
5030 major version number is zero, or where the ABI breaks
5031 across patchlevels)</item>
5032 <item>libraries which are explicitly intended to be
5033 available only in static form by their upstream
5038 <sect id="sharedlibs-dev">
5039 <heading>Development files</heading>
5042 The development files associated to a shared library need to be
5043 placed in a package called
5044 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5045 or if you prefer only to support one development version at a
5046 time, <package><var>libraryname</var>-dev</package>.
5050 In case several development versions of a library exist, you may
5051 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5052 <ref id="conflicts">) to ensure that the user only installs one
5053 development version at a time (as different development versions are
5054 likely to have the same header files in them, which would cause a
5055 filename clash if both were installed).
5059 The development package should contain a symlink for the associated
5060 shared library without a version number. For example, the
5061 <package>libgdbm-dev</package> package should include a symlink
5062 from <file>/usr/lib/libgdbm.so</file> to
5063 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5064 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5065 <file>libgdbm.so</file> when compiling dynamically.
5069 <sect id="sharedlibs-intradeps">
5070 <heading>Dependencies between the packages of the same library</heading>
5073 Typically the development version should have an exact
5074 version dependency on the runtime library, to make sure that
5075 compilation and linking happens correctly. The
5076 <tt>${binary:Version}</tt> substitution variable can be
5077 useful for this purpose.
5079 Previously, <tt>${Source-Version}</tt> was used, but its name
5080 was confusing and it has been deprecated since dpkg 1.13.19.
5085 <sect id="sharedlibs-shlibdeps">
5086 <heading>Dependencies between the library and other packages -
5087 the <tt>shlibs</tt> system</heading>
5090 If a package contains a binary or library which links to a
5091 shared library, we must ensure that when the package is
5092 installed on the system, all of the libraries needed are
5093 also installed. This requirement led to the creation of the
5094 <tt>shlibs</tt> system, which is very simple in its design:
5095 any package which <em>provides</em> a shared library also
5096 provides information on the package dependencies required to
5097 ensure the presence of this library, and any package which
5098 <em>uses</em> a shared library uses this information to
5099 determine the dependencies it requires. The files which
5100 contain the mapping from shared libraries to the necessary
5101 dependency information are called <file>shlibs</file> files.
5105 Thus, when a package is built which contains any shared
5106 libraries, it must provide a <file>shlibs</file> file for other
5107 packages to use, and when a package is built which contains
5108 any shared libraries or compiled binaries, it must run
5109 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5110 on these to determine the libraries used and hence the
5111 dependencies needed by this package.<footnote>
5113 In the past, the shared libraries linked to were
5114 determined by calling <prgn>ldd</prgn>, but now
5115 <prgn>objdump</prgn> is used to do this. The only
5116 change this makes to package building is that
5117 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5118 libraries, whereas in the past this was unnecessary.
5119 The rest of this footnote explains the advantage that
5124 We say that a binary <tt>foo</tt> <em>directly</em> uses
5125 a library <tt>libbar</tt> if it is explicitly linked
5126 with that library (that is, it uses the flag
5127 <tt>-lbar</tt> during the linking stage). Other
5128 libraries that are needed by <tt>libbar</tt> are linked
5129 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5130 linker will load them automatically when it loads
5131 <tt>libbar</tt>. A package should depend on
5132 the libraries it directly uses, and the dependencies for
5133 those libraries should automatically pull in the other
5138 Unfortunately, the <prgn>ldd</prgn> program shows both
5139 the directly and indirectly used libraries, meaning that
5140 the dependencies determined included both direct and
5141 indirect dependencies. The use of <prgn>objdump</prgn>
5142 avoids this problem by determining only the directly
5147 A good example of where this helps is the following. We
5148 could update <tt>libimlib</tt> with a new version that
5149 supports a new graphics format called dgf (but retaining
5150 the same major version number). If we used the old
5151 <prgn>ldd</prgn> method, every package that uses
5152 <tt>libimlib</tt> would need to be recompiled so it
5153 would also depend on <tt>libdgf</tt> or it wouldn't run
5154 due to missing symbols. However with the new system,
5155 packages using <tt>libimlib</tt> can rely on
5156 <tt>libimlib</tt> itself having the dependency on
5157 <tt>libdgf</tt> and so they would not need rebuilding.
5163 In the following sections, we will first describe where the
5164 various <tt>shlibs</tt> files are to be found, then how to
5165 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5166 file format and how to create them if your package contains a
5171 <heading>The <tt>shlibs</tt> files present on the system</heading>
5174 There are several places where <tt>shlibs</tt> files are
5175 found. The following list gives them in the order in which
5177 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5178 (The first one which gives the required information is used.)
5184 <p><file>debian/shlibs.local</file></p>
5187 This lists overrides for this package. Its use is
5188 described below (see <ref id="shlibslocal">).
5193 <p><file>/etc/dpkg/shlibs.override</file></p>
5196 This lists global overrides. This list is normally
5197 empty. It is maintained by the local system
5203 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5206 When packages are being built, any
5207 <file>debian/shlibs</file> files are copied into the
5208 control file area of the temporary build directory and
5209 given the name <file>shlibs</file>. These files give
5210 details of any shared libraries included in the
5212 An example may help here. Let us say that the
5213 source package <tt>foo</tt> generates two binary
5214 packages, <tt>libfoo2</tt> and
5215 <tt>foo-runtime</tt>. When building the binary
5216 packages, the two packages are created in the
5217 directories <file>debian/libfoo2</file> and
5218 <file>debian/foo-runtime</file> respectively.
5219 (<file>debian/tmp</file> could be used instead of one
5220 of these.) Since <tt>libfoo2</tt> provides the
5221 <tt>libfoo</tt> shared library, it will require a
5222 <tt>shlibs</tt> file, which will be installed in
5223 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5225 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5226 when <prgn>dpkg-shlibdeps</prgn> is run on the
5228 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5230 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5231 determine whether <tt>foo-prog</tt>'s library
5232 dependencies are satisfied by any of the libraries
5233 provided by <tt>libfoo2</tt>. For this reason,
5234 <prgn>dpkg-shlibdeps</prgn> must only be run once
5235 all of the individual binary packages'
5236 <tt>shlibs</tt> files have been installed into the
5243 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5246 These are the <file>shlibs</file> files corresponding to
5247 all of the packages installed on the system, and are
5248 maintained by the relevant package maintainers.
5253 <p><file>/etc/dpkg/shlibs.default</file></p>
5256 This file lists any shared libraries whose packages
5257 have failed to provide correct <file>shlibs</file> files.
5258 It was used when the <file>shlibs</file> setup was first
5259 introduced, but it is now normally empty. It is
5260 maintained by the <tt>dpkg</tt> maintainer.
5268 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5269 <file>shlibs</file> files</heading>
5273 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5274 into your <file>debian/rules</file> file. If your package
5275 contains only compiled binaries and libraries (but no scripts),
5276 you can use a command such as:
5277 <example compact="compact">
5278 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5279 debian/tmp/usr/lib/*
5281 Otherwise, you will need to explicitly list the compiled
5282 binaries and libraries.<footnote>
5283 If you are using <tt>debhelper</tt>, the
5284 <prgn>dh_shlibdeps</prgn> program will do this work for
5285 you. It will also correctly handle multi-binary
5291 This command puts the dependency information into the
5292 <file>debian/substvars</file> file, which is then used by
5293 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5294 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5295 field in the control file for this to work.
5299 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5300 done. If it does complain you might need to create your own
5301 <file>debian/shlibs.local</file> file, as explained below (see
5302 <ref id="shlibslocal">).
5306 If you have multiple binary packages, you will need to call
5307 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5308 compiled libraries or binaries. In such a case, you will
5309 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5310 utilities to specify a different <file>substvars</file> file.
5314 If you are creating a udeb for use in the Debian Installer, you
5315 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5316 the dependency line of type <tt>udeb</tt> by adding
5317 <tt>-tudeb</tt> as option<footnote>
5318 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5319 will automatically add this option if it knows it is
5321 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5322 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5323 fall back to the regular dependency line.
5327 For more details on dpkg-shlibdeps, please see
5328 <ref id="pkg-dpkg-shlibdeps"> and
5329 <manref name="dpkg-shlibdeps" section="1">.
5334 <heading>The <file>shlibs</file> File Format</heading>
5337 Each <file>shlibs</file> file has the same format. Lines
5338 beginning with <tt>#</tt> are considered to be comments and
5339 are ignored. Each line is of the form:
5340 <example compact="compact">
5341 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5346 We will explain this by reference to the example of the
5347 <tt>zlib1g</tt> package, which (at the time of writing)
5348 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5352 <var>type</var> is an optional element that indicates the type
5353 of package for which the line is valid. The only type currently
5354 in use is <tt>udeb</tt>. The colon and space after the type are
5359 <var>library-name</var> is the name of the shared library,
5360 in this case <tt>libz</tt>. (This must match the name part
5361 of the soname, see below.)
5365 <var>soname-version</var> is the version part of the soname of
5366 the library. The soname is the thing that must exactly match
5367 for the library to be recognized by the dynamic linker, and is
5369 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5370 example, <tt>libz.so.1</tt>.<footnote>
5371 This can be determined using the command
5372 <example compact="compact">
5373 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5376 The version part is the part which comes after
5377 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5381 <var>dependencies</var> has the same syntax as a dependency
5382 field in a binary package control file. It should give
5383 details of which packages are required to satisfy a binary
5384 built against the version of the library contained in the
5385 package. See <ref id="depsyntax"> for details.
5389 In our example, if the first version of the <tt>zlib1g</tt>
5390 package which contained a minor number of at least
5391 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5392 <tt>shlibs</tt> entry for this library could say:
5393 <example compact="compact">
5394 libz 1 zlib1g (>= 1:1.1.3)
5396 The version-specific dependency is to avoid warnings from
5397 the dynamic linker about using older shared libraries with
5402 As zlib1g also provides a udeb containing the shared library,
5403 there would also be a second line:
5404 <example compact="compact">
5405 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5411 <heading>Providing a <file>shlibs</file> file</heading>
5414 If your package provides a shared library, you need to create
5415 a <file>shlibs</file> file following the format described above.
5416 It is usual to call this file <file>debian/shlibs</file> (but if
5417 you have multiple binary packages, you might want to call it
5418 <file>debian/shlibs.<var>package</var></file> instead). Then
5419 let <file>debian/rules</file> install it in the control area:
5420 <example compact="compact">
5421 install -m644 debian/shlibs debian/tmp/DEBIAN
5423 or, in the case of a multi-binary package:
5424 <example compact="compact">
5425 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5427 An alternative way of doing this is to create the
5428 <file>shlibs</file> file in the control area directly from
5429 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5430 file at all,<footnote>
5431 This is what <prgn>dh_makeshlibs</prgn> in the
5432 <tt>debhelper</tt> suite does. If your package also has a udeb
5433 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5434 automatically generate the <tt>udeb:</tt> lines if you specify
5435 the name of the udeb with the <tt>--add-udeb</tt> option.
5437 since the <file>debian/shlibs</file> file itself is ignored by
5438 <prgn>dpkg-shlibdeps</prgn>.
5442 As <prgn>dpkg-shlibdeps</prgn> reads the
5443 <file>DEBIAN/shlibs</file> files in all of the binary packages
5444 being built from this source package, all of the
5445 <file>DEBIAN/shlibs</file> files should be installed before
5446 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5451 <sect1 id="shlibslocal">
5452 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5455 This file is intended only as a <em>temporary</em> fix if
5456 your binaries or libraries depend on a library whose package
5457 does not yet provide a correct <file>shlibs</file> file.
5461 We will assume that you are trying to package a binary
5462 <tt>foo</tt>. When you try running
5463 <prgn>dpkg-shlibdeps</prgn> you get the following error
5464 message (<tt>-O</tt> displays the dependency information on
5465 <tt>stdout</tt> instead of writing it to
5466 <tt>debian/substvars</tt>, and the lines have been wrapped
5467 for ease of reading):
5468 <example compact="compact">
5469 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5470 dpkg-shlibdeps: warning: unable to find dependency
5471 information for shared library libbar (soname 1,
5472 path /usr/lib/libbar.so.1, dependency field Depends)
5473 shlibs:Depends=libc6 (>= 2.2.2-2)
5475 You can then run <prgn>ldd</prgn> on the binary to find the
5476 full location of the library concerned:
5477 <example compact="compact">
5479 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5480 libc.so.6 => /lib/libc.so.6 (0x40032000)
5481 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5483 So the <prgn>foo</prgn> binary depends on the
5484 <prgn>libbar</prgn> shared library, but no package seems to
5485 provide a <file>*.shlibs</file> file handling
5486 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5487 determine the package responsible:
5488 <example compact="compact">
5489 $ dpkg -S /usr/lib/libbar.so.1
5490 bar1: /usr/lib/libbar.so.1
5491 $ dpkg -s bar1 | grep Version
5494 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5495 is the one we are using. Now we can file a bug against the
5496 <tt>bar1</tt> package and create our own
5497 <file>debian/shlibs.local</file> to locally fix the problem.
5498 Including the following line into your
5499 <file>debian/shlibs.local</file> file:
5500 <example compact="compact">
5501 libbar 1 bar1 (>= 1.0-1)
5503 should allow the package build to work.
5507 As soon as the maintainer of <tt>bar1</tt> provides a
5508 correct <file>shlibs</file> file, you should remove this line
5509 from your <file>debian/shlibs.local</file> file. (You should
5510 probably also then have a versioned <tt>Build-Depends</tt>
5511 on <tt>bar1</tt> to help ensure that others do not have the
5512 same problem building your package.)
5521 <chapt id="opersys"><heading>The Operating System</heading>
5524 <heading>File system hierarchy</heading>
5528 <heading>File system Structure</heading>
5531 The location of all installed files and directories must
5532 comply with the File system Hierarchy Standard (FHS),
5533 version 2.3, with the exceptions noted below, and except
5534 where doing so would violate other terms of Debian
5535 Policy. The following exceptions to the FHS apply:
5540 Legacy XFree86 servers are permitted to retain the
5541 configuration file location
5542 <file>/etc/X11/XF86Config-4</file>.
5547 The optional rules related to user specific
5548 configuration files for applications are stored in
5549 the user's home directory are relaxed. It is
5550 recommended that such files start with the
5551 '<tt>.</tt>' character (a "dot file"), and if an
5552 application needs to create more than one dot file
5553 then the preferred placement is in a subdirectory
5554 with a name starting with a '.' character, (a "dot
5555 directory"). In this case it is recommended the
5556 configuration files not start with the '.'
5562 The requirement for amd64 to use <file>/lib64</file>
5563 for 64 bit binaries is removed.
5568 The requirement that
5569 <file>/usr/local/share/man</file> be "synonymous"
5570 with <file>/usr/local/man</file> is relaxed to a
5575 The requirement that windowmanagers with a single
5576 configuration file call it <file>system.*wmrc</file>
5577 is removed, as is the restriction that the window
5578 manager subdirectory be named identically to the
5579 window manager name itself.
5584 The requirement that boot manager configuration
5585 files live in <file>/etc</file>, or at least are
5586 symlinked there, is relaxed to a recommendation.
5593 The version of this document referred here can be
5594 found in the <tt>debian-policy</tt> package or on <url
5595 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5596 name="FHS (Debian copy)"> alongside this manual (or, if
5597 you have the <package>debian-policy</package> installed,
5599 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5600 (local copy)">). The
5601 latest version, which may be a more recent version, may
5603 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5604 Specific questions about following the standard may be
5605 asked on the <tt>debian-devel</tt> mailing list, or
5606 referred to the FHS mailing list (see the
5607 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5613 <heading>Site-specific programs</heading>
5616 As mandated by the FHS, packages must not place any
5617 files in <file>/usr/local</file>, either by putting them in
5618 the file system archive to be unpacked by <prgn>dpkg</prgn>
5619 or by manipulating them in their maintainer scripts.
5623 However, the package may create empty directories below
5624 <file>/usr/local</file> so that the system administrator knows
5625 where to place site-specific files. These are not
5626 directories <em>in</em> <file>/usr/local</file>, but are
5627 children of directories in <file>/usr/local</file>. These
5628 directories (<file>/usr/local/*/dir/</file>)
5629 should be removed on package removal if they are
5634 Note, that this applies only to directories <em>below</em>
5635 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5636 Packages must not create sub-directories in the directory
5637 <file>/usr/local</file> itself, except those listed in FHS,
5638 section 4.5. However, you may create directories below
5639 them as you wish. You must not remove any of the
5640 directories listed in 4.5, even if you created them.
5644 Since <file>/usr/local</file> can be mounted read-only from a
5645 remote server, these directories must be created and
5646 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5647 maintainer scripts and not be included in the
5648 <file>.deb</file> archive. These scripts must not fail if
5649 either of these operations fail.
5653 For example, the <tt>emacsen-common</tt> package could
5654 contain something like
5655 <example compact="compact">
5656 if [ ! -e /usr/local/share/emacs ]
5658 if mkdir /usr/local/share/emacs 2>/dev/null
5660 chown root:staff /usr/local/share/emacs
5661 chmod 2775 /usr/local/share/emacs
5665 in its <prgn>postinst</prgn> script, and
5666 <example compact="compact">
5667 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5668 rmdir /usr/local/share/emacs 2>/dev/null || true
5670 in the <prgn>prerm</prgn> script. (Note that this form is
5671 used to ensure that if the script is interrupted, the
5672 directory <file>/usr/local/share/emacs</file> will still be
5677 If you do create a directory in <file>/usr/local</file> for
5678 local additions to a package, you should ensure that
5679 settings in <file>/usr/local</file> take precedence over the
5680 equivalents in <file>/usr</file>.
5684 However, because <file>/usr/local</file> and its contents are
5685 for exclusive use of the local administrator, a package
5686 must not rely on the presence or absence of files or
5687 directories in <file>/usr/local</file> for normal operation.
5691 The <file>/usr/local</file> directory itself and all the
5692 subdirectories created by the package should (by default) have
5693 permissions 2775 (group-writable and set-group-id) and be
5694 owned by <tt>root:staff</tt>.
5699 <heading>The system-wide mail directory</heading>
5701 The system-wide mail directory is <file>/var/mail</file>. This
5702 directory is part of the base system and should not owned
5703 by any particular mail agents. The use of the old
5704 location <file>/var/spool/mail</file> is deprecated, even
5705 though the spool may still be physically located there.
5706 To maintain partial upgrade compatibility for systems
5707 which have <file>/var/spool/mail</file> as their physical mail
5708 spool, packages using <file>/var/mail</file> must depend on
5709 either <package>libc6</package> (>= 2.1.3-13), or on
5710 <package>base-files</package> (>= 2.2.0), or on later
5711 versions of either one of these packages.
5717 <heading>Users and groups</heading>
5720 <heading>Introduction</heading>
5722 The Debian system can be configured to use either plain or
5727 Some user ids (UIDs) and group ids (GIDs) are reserved
5728 globally for use by certain packages. Because some
5729 packages need to include files which are owned by these
5730 users or groups, or need the ids compiled into binaries,
5731 these ids must be used on any Debian system only for the
5732 purpose for which they are allocated. This is a serious
5733 restriction, and we should avoid getting in the way of
5734 local administration policies. In particular, many sites
5735 allocate users and/or local system groups starting at 100.
5739 Apart from this we should have dynamically allocated ids,
5740 which should by default be arranged in some sensible
5741 order, but the behavior should be configurable.
5745 Packages other than <tt>base-passwd</tt> must not modify
5746 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5747 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5752 <heading>UID and GID classes</heading>
5754 The UID and GID numbers are divided into classes as
5760 Globally allocated by the Debian project, the same
5761 on every Debian system. These ids will appear in
5762 the <file>passwd</file> and <file>group</file> files of all
5763 Debian systems, new ids in this range being added
5764 automatically as the <tt>base-passwd</tt> package is
5769 Packages which need a single statically allocated
5770 uid or gid should use one of these; their
5771 maintainers should ask the <tt>base-passwd</tt>
5779 Dynamically allocated system users and groups.
5780 Packages which need a user or group, but can have
5781 this user or group allocated dynamically and
5782 differently on each system, should use <tt>adduser
5783 --system</tt> to create the group and/or user.
5784 <prgn>adduser</prgn> will check for the existence of
5785 the user or group, and if necessary choose an unused
5786 id based on the ranges specified in
5787 <file>adduser.conf</file>.
5791 <tag>1000-29999:</tag>
5794 Dynamically allocated user accounts. By default
5795 <prgn>adduser</prgn> will choose UIDs and GIDs for
5796 user accounts in this range, though
5797 <file>adduser.conf</file> may be used to modify this
5802 <tag>30000-59999:</tag>
5807 <tag>60000-64999:</tag>
5810 Globally allocated by the Debian project, but only
5811 created on demand. The ids are allocated centrally
5812 and statically, but the actual accounts are only
5813 created on users' systems on demand.
5817 These ids are for packages which are obscure or
5818 which require many statically-allocated ids. These
5819 packages should check for and create the accounts in
5820 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5821 <prgn>adduser</prgn> if it has this facility) if
5822 necessary. Packages which are likely to require
5823 further allocations should have a "hole" left after
5824 them in the allocation, to give them room to
5829 <tag>65000-65533:</tag>
5837 User <tt>nobody</tt>. The corresponding gid refers
5838 to the group <tt>nogroup</tt>.
5845 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5846 not</em> be used, because it is the error return
5855 <sect id="sysvinit">
5856 <heading>System run levels and <file>init.d</file> scripts</heading>
5858 <sect1 id="/etc/init.d">
5859 <heading>Introduction</heading>
5862 The <file>/etc/init.d</file> directory contains the scripts
5863 executed by <prgn>init</prgn> at boot time and when the
5864 init state (or "runlevel") is changed (see <manref
5865 name="init" section="8">).
5869 There are at least two different, yet functionally
5870 equivalent, ways of handling these scripts. For the sake
5871 of simplicity, this document describes only the symbolic
5872 link method. However, it must not be assumed by maintainer
5873 scripts that this method is being used, and any automated
5874 manipulation of the various runlevel behaviors by
5875 maintainer scripts must be performed using
5876 <prgn>update-rc.d</prgn> as described below and not by
5877 manually installing or removing symlinks. For information
5878 on the implementation details of the other method,
5879 implemented in the <tt>file-rc</tt> package, please refer
5880 to the documentation of that package.
5884 These scripts are referenced by symbolic links in the
5885 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5886 runlevels, <prgn>init</prgn> looks in the directory
5887 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5888 execute, where <tt><var>n</var></tt> is the runlevel that
5889 is being changed to, or <tt>S</tt> for the boot-up
5894 The names of the links all have the form
5895 <file>S<var>mm</var><var>script</var></file> or
5896 <file>K<var>mm</var><var>script</var></file> where
5897 <var>mm</var> is a two-digit number and <var>script</var>
5898 is the name of the script (this should be the same as the
5899 name of the actual script in <file>/etc/init.d</file>).
5903 When <prgn>init</prgn> changes runlevel first the targets
5904 of the links whose names start with a <tt>K</tt> are
5905 executed, each with the single argument <tt>stop</tt>,
5906 followed by the scripts prefixed with an <tt>S</tt>, each
5907 with the single argument <tt>start</tt>. (The links are
5908 those in the <file>/etc/rc<var>n</var>.d</file> directory
5909 corresponding to the new runlevel.) The <tt>K</tt> links
5910 are responsible for killing services and the <tt>S</tt>
5911 link for starting services upon entering the runlevel.
5915 For example, if we are changing from runlevel 2 to
5916 runlevel 3, init will first execute all of the <tt>K</tt>
5917 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5918 all of the <tt>S</tt> prefixed scripts in that directory.
5919 The links starting with <tt>K</tt> will cause the
5920 referred-to file to be executed with an argument of
5921 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5926 The two-digit number <var>mm</var> is used to determine
5927 the order in which to run the scripts: low-numbered links
5928 have their scripts run first. For example, the
5929 <tt>K20</tt> scripts will be executed before the
5930 <tt>K30</tt> scripts. This is used when a certain service
5931 must be started before another. For example, the name
5932 server <prgn>bind</prgn> might need to be started before
5933 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5934 can set up its access lists. In this case, the script
5935 that starts <prgn>bind</prgn> would have a lower number
5936 than the script that starts <prgn>inn</prgn> so that it
5938 <example compact="compact">
5945 The two runlevels 0 (halt) and 6 (reboot) are slightly
5946 different. In these runlevels, the links with an
5947 <tt>S</tt> prefix are still called after those with a
5948 <tt>K</tt> prefix, but they too are called with the single
5949 argument <tt>stop</tt>.
5954 <heading>Writing the scripts</heading>
5957 Packages that include daemons for system services should
5958 place scripts in <file>/etc/init.d</file> to start or stop
5959 services at boot time or during a change of runlevel.
5960 These scripts should be named
5961 <file>/etc/init.d/<var>package</var></file>, and they should
5962 accept one argument, saying what to do:
5965 <tag><tt>start</tt></tag>
5966 <item>start the service,</item>
5968 <tag><tt>stop</tt></tag>
5969 <item>stop the service,</item>
5971 <tag><tt>restart</tt></tag>
5972 <item>stop and restart the service if it's already running,
5973 otherwise start the service</item>
5975 <tag><tt>reload</tt></tag>
5976 <item><p>cause the configuration of the service to be
5977 reloaded without actually stopping and restarting
5980 <tag><tt>force-reload</tt></tag>
5981 <item>cause the configuration to be reloaded if the
5982 service supports this, otherwise restart the
5986 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5987 <tt>force-reload</tt> options should be supported by all
5988 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5993 The <file>init.d</file> scripts must ensure that they will
5994 behave sensibly (i.e., returning success and not starting
5995 multiple copies of a service) if invoked with <tt>start</tt>
5996 when the service is already running, or with <tt>stop</tt>
5997 when it isn't, and that they don't kill unfortunately-named
5998 user processes. The best way to achieve this is usually to
5999 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6004 If a service reloads its configuration automatically (as
6005 in the case of <prgn>cron</prgn>, for example), the
6006 <tt>reload</tt> option of the <file>init.d</file> script
6007 should behave as if the configuration has been reloaded
6012 The <file>/etc/init.d</file> scripts must be treated as
6013 configuration files, either (if they are present in the
6014 package, that is, in the .deb file) by marking them as
6015 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6016 by managing them correctly in the maintainer scripts (see
6017 <ref id="config-files">). This is important since we want
6018 to give the local system administrator the chance to adapt
6019 the scripts to the local system, e.g., to disable a
6020 service without de-installing the package, or to specify
6021 some special command line options when starting a service,
6022 while making sure their changes aren't lost during the next
6027 These scripts should not fail obscurely when the
6028 configuration files remain but the package has been
6029 removed, as configuration files remain on the system after
6030 the package has been removed. Only when <prgn>dpkg</prgn>
6031 is executed with the <tt>--purge</tt> option will
6032 configuration files be removed. In particular, as the
6033 <file>/etc/init.d/<var>package</var></file> script itself is
6034 usually a <tt>conffile</tt>, it will remain on the system
6035 if the package is removed but not purged. Therefore, you
6036 should include a <tt>test</tt> statement at the top of the
6038 <example compact="compact">
6039 test -f <var>program-executed-later-in-script</var> || exit 0
6044 Often there are some variables in the <file>init.d</file>
6045 scripts whose values control the behavior of the scripts,
6046 and which a system administrator is likely to want to
6047 change. As the scripts themselves are frequently
6048 <tt>conffile</tt>s, modifying them requires that the
6049 administrator merge in their changes each time the package
6050 is upgraded and the <tt>conffile</tt> changes. To ease
6051 the burden on the system administrator, such configurable
6052 values should not be placed directly in the script.
6053 Instead, they should be placed in a file in
6054 <file>/etc/default</file>, which typically will have the same
6055 base name as the <file>init.d</file> script. This extra file
6056 should be sourced by the script when the script runs. It
6057 must contain only variable settings and comments in SUSv3
6058 <prgn>sh</prgn> format. It may either be a
6059 <tt>conffile</tt> or a configuration file maintained by
6060 the package maintainer scripts. See <ref id="config-files">
6065 To ensure that vital configurable values are always
6066 available, the <file>init.d</file> script should set default
6067 values for each of the shell variables it uses, either
6068 before sourcing the <file>/etc/default/</file> file or
6069 afterwards using something like the <tt>:
6070 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6071 script must behave sensibly and not fail if the
6072 <file>/etc/default</file> file is deleted.
6076 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6077 as temporary filesystems<footnote>
6078 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6079 options in <file>/etc/default/rcS</file>.
6080 </footnote>, so the <file>init.d</file> scripts must handle this
6081 correctly. This will typically amount to creating any required
6082 subdirectories dynamically when the <file>init.d</file> script
6083 is run, rather than including them in the package and relying on
6084 <prgn>dpkg</prgn> to create them.
6089 <heading>Interfacing with the initscript system</heading>
6092 Maintainers should use the abstraction layer provided by
6093 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6094 programs to deal with initscripts in their packages'
6095 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6096 and <prgn>postrm</prgn>.
6100 Directly managing the /etc/rc?.d links and directly
6101 invoking the <file>/etc/init.d/</file> initscripts should
6102 be done only by packages providing the initscript
6103 subsystem (such as <prgn>sysv-rc</prgn> and
6104 <prgn>file-rc</prgn>).
6108 <heading>Managing the links</heading>
6111 The program <prgn>update-rc.d</prgn> is provided for
6112 package maintainers to arrange for the proper creation and
6113 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6114 or their functional equivalent if another method is being
6115 used. This may be used by maintainers in their packages'
6116 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6120 You must not include any <file>/etc/rc<var>n</var>.d</file>
6121 symbolic links in the actual archive or manually create or
6122 remove the symbolic links in maintainer scripts; you must
6123 use the <prgn>update-rc.d</prgn> program instead. (The
6124 former will fail if an alternative method of maintaining
6125 runlevel information is being used.) You must not include
6126 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6127 in the archive either. (Only the <tt>sysvinit</tt>
6132 By default <prgn>update-rc.d</prgn> will start services in
6133 each of the multi-user state runlevels (2, 3, 4, and 5)
6134 and stop them in the halt runlevel (0), the single-user
6135 runlevel (1) and the reboot runlevel (6). The system
6136 administrator will have the opportunity to customize
6137 runlevels by simply adding, moving, or removing the
6138 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6139 symbolic links are being used, or by modifying
6140 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6145 To get the default behavior for your package, put in your
6146 <prgn>postinst</prgn> script
6147 <example compact="compact">
6148 update-rc.d <var>package</var> defaults
6150 and in your <prgn>postrm</prgn>
6151 <example compact="compact">
6152 if [ "$1" = purge ]; then
6153 update-rc.d <var>package</var> remove
6155 </example>. Note that if your package changes runlevels
6156 or priority, you may have to remove and recreate the links,
6157 since otherwise the old links may persist. Refer to the
6158 documentation of <prgn>update-rc.d</prgn>.
6162 This will use a default sequence number of 20. If it does
6163 not matter when or in which order the <file>init.d</file>
6164 script is run, use this default. If it does, then you
6165 should talk to the maintainer of the <prgn>sysvinit</prgn>
6166 package or post to <tt>debian-devel</tt>, and they will
6167 help you choose a number.
6171 For more information about using <tt>update-rc.d</tt>,
6172 please consult its man page <manref name="update-rc.d"
6178 <heading>Running initscripts</heading>
6180 The program <prgn>invoke-rc.d</prgn> is provided to make
6181 it easier for package maintainers to properly invoke an
6182 initscript, obeying runlevel and other locally-defined
6183 constraints that might limit a package's right to start,
6184 stop and otherwise manage services. This program may be
6185 used by maintainers in their packages' scripts.
6189 The package maintainer scripts must use
6190 <prgn>invoke-rc.d</prgn> to invoke the
6191 <file>/etc/init.d/*</file> initscripts, instead of
6192 calling them directly.
6196 By default, <prgn>invoke-rc.d</prgn> will pass any
6197 action requests (start, stop, reload, restart...) to the
6198 <file>/etc/init.d</file> script, filtering out requests
6199 to start or restart a service out of its intended
6204 Most packages will simply need to change:
6205 <example compact="compact">/etc/init.d/<package>
6206 <action></example> in their <prgn>postinst</prgn>
6207 and <prgn>prerm</prgn> scripts to:
6208 <example compact="compact">
6209 if which invoke-rc.d >/dev/null 2>&1; then
6210 invoke-rc.d <var>package</var> <action>
6212 /etc/init.d/<var>package</var> <action>
6218 A package should register its initscript services using
6219 <prgn>update-rc.d</prgn> before it tries to invoke them
6220 using <prgn>invoke-rc.d</prgn>. Invocation of
6221 unregistered services may fail.
6225 For more information about using
6226 <prgn>invoke-rc.d</prgn>, please consult its man page
6227 <manref name="invoke-rc.d" section="8">.
6233 <heading>Boot-time initialization</heading>
6236 There used to be another directory, <file>/etc/rc.boot</file>,
6237 which contained scripts which were run once per machine
6238 boot. This has been deprecated in favour of links from
6239 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6240 described in <ref id="/etc/init.d">. Packages must not
6241 place files in <file>/etc/rc.boot</file>.
6246 <heading>Example</heading>
6249 An example on which you can base your
6250 <file>/etc/init.d</file> scripts is found in
6251 <file>/etc/init.d/skeleton</file>.
6258 <heading>Console messages from <file>init.d</file> scripts</heading>
6261 This section describes the formats to be used for messages
6262 written to standard output by the <file>/etc/init.d</file>
6263 scripts. The intent is to improve the consistency of
6264 Debian's startup and shutdown look and feel. For this
6265 reason, please look very carefully at the details. We want
6266 the messages to have the same format in terms of wording,
6267 spaces, punctuation and case of letters.
6271 Here is a list of overall rules that should be used for
6272 messages generated by <file>/etc/init.d</file> scripts.
6278 The message should fit in one line (fewer than 80
6279 characters), start with a capital letter and end with
6280 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6284 If the script is performing some time consuming task in
6285 the background (not merely starting or stopping a
6286 program, for instance), an ellipsis (three dots:
6287 <tt>...</tt>) should be output to the screen, with no
6288 leading or tailing whitespace or line feeds.
6292 The messages should appear as if the computer is telling
6293 the user what it is doing (politely :-), but should not
6294 mention "it" directly. For example, instead of:
6295 <example compact="compact">
6296 I'm starting network daemons: nfsd mountd.
6298 the message should say
6299 <example compact="compact">
6300 Starting network daemons: nfsd mountd.
6307 <tt>init.d</tt> script should use the following standard
6308 message formats for the situations enumerated below.
6314 <p>When daemons are started</p>
6317 If the script starts one or more daemons, the output
6318 should look like this (a single line, no leading
6320 <example compact="compact">
6321 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6323 The <var>description</var> should describe the
6324 subsystem the daemon or set of daemons are part of,
6325 while <var>daemon-1</var> up to <var>daemon-n</var>
6326 denote each daemon's name (typically the file name of
6331 For example, the output of <file>/etc/init.d/lpd</file>
6333 <example compact="compact">
6334 Starting printer spooler: lpd.
6339 This can be achieved by saying
6340 <example compact="compact">
6341 echo -n "Starting printer spooler: lpd"
6342 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6345 in the script. If there are more than one daemon to
6346 start, the output should look like this:
6347 <example compact="compact">
6348 echo -n "Starting remote file system services:"
6349 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6350 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6351 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6354 This makes it possible for the user to see what is
6355 happening and when the final daemon has been started.
6356 Care should be taken in the placement of white spaces:
6357 in the example above the system administrators can
6358 easily comment out a line if they don't want to start
6359 a specific daemon, while the displayed message still
6365 <p>When a system parameter is being set</p>
6368 If you have to set up different system parameters
6369 during the system boot, you should use this format:
6370 <example compact="compact">
6371 Setting <var>parameter</var> to "<var>value</var>".
6376 You can use a statement such as the following to get
6378 <example compact="compact">
6379 echo "Setting DNS domainname to \"$domainname\"."
6384 Note that the same symbol (<tt>"</tt>) is used for the left
6385 and right quotation marks. A grave accent (<tt>`</tt>) is
6386 not a quote character; neither is an apostrophe
6392 <p>When a daemon is stopped or restarted</p>
6395 When you stop or restart a daemon, you should issue a
6396 message identical to the startup message, except that
6397 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6398 or <tt>Restarting</tt> respectively.
6402 For example, stopping the printer daemon will look like
6404 <example compact="compact">
6405 Stopping printer spooler: lpd.
6411 <p>When something is executed</p>
6414 There are several examples where you have to run a
6415 program at system startup or shutdown to perform a
6416 specific task, for example, setting the system's clock
6417 using <prgn>netdate</prgn> or killing all processes
6418 when the system shuts down. Your message should look
6420 <example compact="compact">
6421 Doing something very useful...done.
6423 You should print the <tt>done.</tt> immediately after
6424 the job has been completed, so that the user is
6425 informed why they have to wait. You can get this
6427 <example compact="compact">
6428 echo -n "Doing something very useful..."
6437 <p>When the configuration is reloaded</p>
6440 When a daemon is forced to reload its configuration
6441 files you should use the following format:
6442 <example compact="compact">
6443 Reloading <var>description</var> configuration...done.
6445 where <var>description</var> is the same as in the
6446 daemon starting message.
6454 <heading>Cron jobs</heading>
6457 Packages must not modify the configuration file
6458 <file>/etc/crontab</file>, and they must not modify the files in
6459 <file>/var/spool/cron/crontabs</file>.</p>
6462 If a package wants to install a job that has to be executed
6463 via cron, it should place a file with the name of the
6464 package in one or more of the following directories:
6465 <example compact="compact">
6471 As these directory names imply, the files within them are
6472 executed on an hourly, daily, weekly, or monthly basis,
6473 respectively. The exact times are listed in
6474 <file>/etc/crontab</file>.</p>
6477 All files installed in any of these directories must be
6478 scripts (e.g., shell scripts or Perl scripts) so that they
6479 can easily be modified by the local system administrator.
6480 In addition, they must be treated as configuration files.
6484 If a certain job has to be executed at some other frequency or
6485 at a specific time, the package should install a file
6486 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6487 same syntax as <file>/etc/crontab</file> and is processed by
6488 <prgn>cron</prgn> automatically. The file must also be
6489 treated as a configuration file. (Note that entries in the
6490 <file>/etc/cron.d</file> directory are not handled by
6491 <prgn>anacron</prgn>. Thus, you should only use this
6492 directory for jobs which may be skipped if the system is not
6496 The scripts or crontab entries in these directories should
6497 check if all necessary programs are installed before they
6498 try to execute them. Otherwise, problems will arise when a
6499 package was removed but not purged since configuration files
6500 are kept on the system in this situation.</p>
6504 <heading>Menus</heading>
6507 The Debian <tt>menu</tt> package provides a standard
6508 interface between packages providing applications and
6509 <em>menu programs</em> (either X window managers or
6510 text-based menu programs such as <prgn>pdmenu</prgn>).
6514 All packages that provide applications that need not be
6515 passed any special command line arguments for normal
6516 operation should register a menu entry for those
6517 applications, so that users of the <tt>menu</tt> package
6518 will automatically get menu entries in their window
6519 managers, as well in shells like <tt>pdmenu</tt>.
6523 Menu entries should follow the current menu policy.
6527 The menu policy can be found in the <tt>menu-policy</tt>
6528 files in the <tt>debian-policy</tt> package.
6529 It is also available from the Debian web mirrors at
6530 <tt><url name="/doc/packaging-manuals/menu-policy/"
6531 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6535 Please also refer to the <em>Debian Menu System</em>
6536 documentation that comes with the <package>menu</package>
6537 package for information about how to register your
6543 <heading>Multimedia handlers</heading>
6546 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6547 is a mechanism for encoding files and data streams and
6548 providing meta-information about them, in particular their
6549 type (e.g. audio or video) and format (e.g. PNG, HTML,
6554 Registration of MIME type handlers allows programs like mail
6555 user agents and web browsers to invoke these handlers to
6556 view, edit or display MIME types they don't support directly.
6560 Packages which provide the ability to view/show/play,
6561 compose, edit or print MIME types should register themselves
6562 as such following the current MIME support policy.
6566 The MIME support policy can be found in the <tt>mime-policy</tt>
6567 files in the <tt>debian-policy</tt> package.
6568 It is also available from the Debian web mirrors at
6569 <tt><url name="/doc/packaging-manuals/mime-policy/"
6570 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6576 <heading>Keyboard configuration</heading>
6579 To achieve a consistent keyboard configuration so that all
6580 applications interpret a keyboard event the same way, all
6581 programs in the Debian distribution must be configured to
6582 comply with the following guidelines.
6586 The following keys must have the specified interpretations:
6589 <tag><tt><--</tt></tag>
6590 <item>delete the character to the left of the cursor</item>
6592 <tag><tt>Delete</tt></tag>
6593 <item>delete the character to the right of the cursor</item>
6595 <tag><tt>Control+H</tt></tag>
6596 <item>emacs: the help prefix</item>
6599 The interpretation of any keyboard events should be
6600 independent of the terminal that is used, be it a virtual
6601 console, an X terminal emulator, an rlogin/telnet session,
6606 The following list explains how the different programs
6607 should be set up to achieve this:
6613 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6617 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6621 X translations are set up to make
6622 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6623 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6624 is the vt220 escape code for the "delete character"
6625 key). This must be done by loading the X resources
6626 using <prgn>xrdb</prgn> on all local X displays, not
6627 using the application defaults, so that the
6628 translation resources used correspond to the
6629 <prgn>xmodmap</prgn> settings.
6633 The Linux console is configured to make
6634 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6635 generate <tt>ESC [ 3 ~</tt>.
6639 X applications are configured so that <tt><</tt>
6640 deletes left, and <tt>Delete</tt> deletes right. Motif
6641 applications already work like this.
6645 Terminals should have <tt>stty erase ^?</tt> .
6649 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6650 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6651 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6655 Emacs is programmed to map <tt>KB_Backspace</tt> or
6656 the <tt>stty erase</tt> character to
6657 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6658 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6659 <tt>^H</tt> to <tt>help</tt> as always.
6663 Other applications use the <tt>stty erase</tt>
6664 character and <tt>kdch1</tt> for the two delete keys,
6665 with ASCII DEL being "delete previous character" and
6666 <tt>kdch1</tt> being "delete character under
6674 This will solve the problem except for the following
6681 Some terminals have a <tt><--</tt> key that cannot
6682 be made to produce anything except <tt>^H</tt>. On
6683 these terminals Emacs help will be unavailable on
6684 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6685 character takes precedence in Emacs, and has been set
6686 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6687 available) can be used instead.
6691 Some operating systems use <tt>^H</tt> for <tt>stty
6692 erase</tt>. However, modern telnet versions and all
6693 rlogin versions propagate <tt>stty</tt> settings, and
6694 almost all UNIX versions honour <tt>stty erase</tt>.
6695 Where the <tt>stty</tt> settings are not propagated
6696 correctly, things can be made to work by using
6697 <tt>stty</tt> manually.
6701 Some systems (including previous Debian versions) use
6702 <prgn>xmodmap</prgn> to arrange for both
6703 <tt><--</tt> and <tt>Delete</tt> to generate
6704 <tt>KB_Delete</tt>. We can change the behavior of
6705 their X clients using the same X resources that we use
6706 to do it for our own clients, or configure our clients
6707 using their resources when things are the other way
6708 around. On displays configured like this
6709 <tt>Delete</tt> will not work, but <tt><--</tt>
6714 Some operating systems have different <tt>kdch1</tt>
6715 settings in their <tt>terminfo</tt> database for
6716 <tt>xterm</tt> and others. On these systems the
6717 <tt>Delete</tt> key will not work correctly when you
6718 log in from a system conforming to our policy, but
6719 <tt><--</tt> will.
6726 <heading>Environment variables</heading>
6729 A program must not depend on environment variables to get
6730 reasonable defaults. (That's because these environment
6731 variables would have to be set in a system-wide
6732 configuration file like <file>/etc/profile</file>, which is not
6733 supported by all shells.)
6737 If a program usually depends on environment variables for its
6738 configuration, the program should be changed to fall back to
6739 a reasonable default configuration if these environment
6740 variables are not present. If this cannot be done easily
6741 (e.g., if the source code of a non-free program is not
6742 available), the program must be replaced by a small
6743 "wrapper" shell script which sets the environment variables
6744 if they are not already defined, and calls the original program.
6748 Here is an example of a wrapper script for this purpose:
6750 <example compact="compact">
6752 BAR=${BAR:-/var/lib/fubar}
6754 exec /usr/lib/foo/foo "$@"
6759 Furthermore, as <file>/etc/profile</file> is a configuration
6760 file of the <prgn>base-files</prgn> package, other packages must
6761 not put any environment variables or other commands into that
6766 <sect id="doc-base">
6767 <heading>Registering Documents using doc-base</heading>
6770 The <package>doc-base</package> package implements a
6771 flexible mechanism for handling and presenting
6772 documentation. The recommended practice is for every Debian
6773 package that provides online documentation (other than just
6774 manual pages) to register these documents with
6775 <package>doc-base</package> by installing a
6776 <package>doc-base</package> control file via the
6777 <prgn/install-docs/ script at installation time and
6778 de-register the manuals again when the package is removed.
6781 Please refer to the documentation that comes with the
6782 <package>doc-base</package> package for information and
6791 <heading>Files</heading>
6794 <heading>Binaries</heading>
6797 Two different packages must not install programs with
6798 different functionality but with the same filenames. (The
6799 case of two programs having the same functionality but
6800 different implementations is handled via "alternatives" or
6801 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6802 <ref id="conflicts"> respectively.) If this case happens,
6803 one of the programs must be renamed. The maintainers should
6804 report this to the <tt>debian-devel</tt> mailing list and
6805 try to find a consensus about which program will have to be
6806 renamed. If a consensus cannot be reached, <em>both</em>
6807 programs must be renamed.
6811 By default, when a package is being built, any binaries
6812 created should include debugging information, as well as
6813 being compiled with optimization. You should also turn on
6814 as many reasonable compilation warnings as possible; this
6815 makes life easier for porters, who can then look at build
6816 logs for possible problems. For the C programming language,
6817 this means the following compilation parameters should be
6819 <example compact="compact">
6821 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6823 INSTALL = install -s # (or use strip on the files in debian/tmp)
6828 Note that by default all installed binaries should be stripped,
6829 either by using the <tt>-s</tt> flag to
6830 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6831 the binaries after they have been copied into
6832 <file>debian/tmp</file> but before the tree is made into a
6837 Although binaries in the build tree should be compiled with
6838 debugging information by default, it can often be difficult to
6839 debug programs if they are also subjected to compiler
6840 optimization. For this reason, it is recommended to support the
6841 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6842 (see <ref id="debianrules-options">). This variable can contain
6843 several flags to change how a package is compiled and built.
6847 It is up to the package maintainer to decide what
6848 compilation options are best for the package. Certain
6849 binaries (such as computationally-intensive programs) will
6850 function better with certain flags (<tt>-O3</tt>, for
6851 example); feel free to use them. Please use good judgment
6852 here. Don't use flags for the sake of it; only use them
6853 if there is good reason to do so. Feel free to override
6854 the upstream author's ideas about which compilation
6855 options are best: they are often inappropriate for our
6861 <sect id="libraries">
6862 <heading>Libraries</heading>
6865 If the package is <strong>architecture: any</strong>, then
6866 the shared library compilation and linking flags must have
6867 <tt>-fPIC</tt>, or the package shall not build on some of
6868 the supported architectures<footnote>
6870 If you are using GCC, <tt>-fPIC</tt> produces code with
6871 relocatable position independent code, which is required for
6872 most architectures to create a shared library, with i386 and
6873 perhaps some others where non position independent code is
6874 permitted in a shared library.
6877 Position independent code may have a performance penalty,
6878 especially on <tt>i386</tt>. However, in most cases the
6879 speed penalty must be measured against the memory wasted on
6880 the few architectures where non position independent code is
6883 </footnote>. Any exception to this rule must be discussed on
6884 the mailing list <em>debian-devel@lists.debian.org</em>, and
6885 a rough consensus obtained. The reasons for not compiling
6886 with <tt>-fPIC</tt> flag must be recorded in the file
6887 <tt>README.Debian</tt>, and care must be taken to either
6888 restrict the architecture or arrange for <tt>-fPIC</tt> to
6889 be used on architectures where it is required.<footnote>
6891 Some of the reasons why this might be required is if the
6892 library contains hand crafted assembly code that is not
6893 relocatable, the speed penalty is excessive for compute
6894 intensive libs, and similar reasons.
6899 As to the static libraries, the common case is not to have
6900 relocatable code, since there is no benefit, unless in specific
6901 cases; therefore the static version must not be compiled
6902 with the <tt>-fPIC</tt> flag. Any exception to this rule
6903 should be discussed on the mailing list
6904 <em>debian-devel@lists.debian.org</em>, and the reasons for
6905 compiling with the <tt>-fPIC</tt> flag must be recorded in
6906 the file <tt>README.Debian</tt>. <footnote>
6908 Some of the reasons for linking static libraries with
6909 the <tt>-fPIC</tt> flag are if, for example, one needs a
6910 Perl API for a library that is under rapid development,
6911 and has an unstable API, so shared libraries are
6912 pointless at this phase of the library's development. In
6913 that case, since Perl needs a library with relocatable
6914 code, it may make sense to create a static library with
6915 relocatable code. Another reason cited is if you are
6916 distilling various libraries into a common shared
6917 library, like <tt>mklibs</tt> does in the Debian
6923 In other words, if both a shared and a static library is
6924 being built, each source unit (<tt>*.c</tt>, for example,
6925 for C files) will need to be compiled twice, for the normal
6929 You must specify the gcc option <tt>-D_REENTRANT</tt>
6930 when building a library (either static or shared) to make
6931 the library compatible with LinuxThreads.
6935 Although not enforced by the build tools, shared libraries
6936 must be linked against all libraries that they use symbols from
6937 in the same way that binaries are. This ensures the correct
6938 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6939 system and guarantees that all libraries can be safely opened
6940 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6941 option <tt>-Wl,-z,defs</tt> when building a shared library.
6942 Since this option enforces symbol resolution at build time,
6943 a missing library reference will be caught early as a fatal
6948 All installed shared libraries should be stripped with
6949 <example compact="compact">
6950 strip --strip-unneeded <var>your-lib</var>
6952 (The option <tt>--strip-unneeded</tt> makes
6953 <prgn>strip</prgn> remove only the symbols which aren't
6954 needed for relocation processing.) Shared libraries can
6955 function perfectly well when stripped, since the symbols for
6956 dynamic linking are in a separate part of the ELF object
6958 You might also want to use the options
6959 <tt>--remove-section=.comment</tt> and
6960 <tt>--remove-section=.note</tt> on both shared libraries
6961 and executables, and <tt>--strip-debug</tt> on static
6967 Note that under some circumstances it may be useful to
6968 install a shared library unstripped, for example when
6969 building a separate package to support debugging.
6973 Shared object files (often <file>.so</file> files) that are not
6974 public libraries, that is, they are not meant to be linked
6975 to by third party executables (binaries of other packages),
6976 should be installed in subdirectories of the
6977 <file>/usr/lib</file> directory. Such files are exempt from the
6978 rules that govern ordinary shared libraries, except that
6979 they must not be installed executable and should be
6981 A common example are the so-called "plug-ins",
6982 internal shared objects that are dynamically loaded by
6983 programs using <manref name="dlopen" section="3">.
6988 Packages containing shared libraries that may be linked to
6989 by other packages' binaries, but which for some
6990 <em>compelling</em> reason can not be installed in
6991 <file>/usr/lib</file> directory, may install the shared library
6992 files in subdirectories of the <file>/usr/lib</file> directory,
6993 in which case they should arrange to add that directory in
6994 <file>/etc/ld.so.conf</file> in the package's post-installation
6995 script, and remove it in the package's post-removal script.
6999 An ever increasing number of packages are using
7000 <prgn>libtool</prgn> to do their linking. The latest GNU
7001 libtools (>= 1.3a) can take advantage of the metadata in the
7002 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7003 files). The main advantage of <prgn>libtool</prgn>'s
7004 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7005 store and subsequently access metadata with respect to the
7006 libraries it builds. <prgn>libtool</prgn> will search for
7007 those files, which contain a lot of useful information about
7008 a library (such as library dependency information for static
7009 linking). Also, they're <em>essential</em> for programs
7010 using <tt>libltdl</tt>.<footnote>
7011 Although <prgn>libtool</prgn> is fully capable of
7012 linking against shared libraries which don't have
7013 <tt>.la</tt> files, as it is a mere shell script it can
7014 add considerably to the build time of a
7015 <prgn>libtool</prgn>-using package if that shell script
7016 has to derive all this information from first principles
7017 for each library every time it is linked. With the
7018 advent of <prgn>libtool</prgn> version 1.4 (and to a
7019 lesser extent <prgn>libtool</prgn> version 1.3), the
7020 <file>.la</file> files also store information about
7021 inter-library dependencies which cannot necessarily be
7022 derived after the <file>.la</file> file is deleted.
7027 Packages that use <prgn>libtool</prgn> to create shared
7028 libraries should include the <file>.la</file> files in the
7029 <tt>-dev</tt> package, unless the package relies on
7030 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7031 the <tt>.la</tt> files must go in the run-time library
7036 You must make sure that you use only released versions of
7037 shared libraries to build your packages; otherwise other
7038 users will not be able to run your binaries
7039 properly. Producing source packages that depend on
7040 unreleased compilers is also usually a bad
7047 <heading>Shared libraries</heading>
7049 This section has moved to <ref id="sharedlibs">.
7055 <heading>Scripts</heading>
7058 All command scripts, including the package maintainer
7059 scripts inside the package and used by <prgn>dpkg</prgn>,
7060 should have a <tt>#!</tt> line naming the shell to be used
7065 In the case of Perl scripts this should be
7066 <tt>#!/usr/bin/perl</tt>.
7070 When scripts are installed into a directory in the system
7071 PATH, the script name should not include an extension such
7072 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7073 language currently used to implement it.
7076 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7077 should almost certainly start with <tt>set -e</tt> so that
7078 errors are detected. Every script should use
7079 <tt>set -e</tt> or check the exit status of <em>every</em>
7084 Scripts may assume that <file>/bin/sh</file> implements the
7085 SUSv3 Shell Command Language<footnote>
7086 Single UNIX Specification, version 3, which is also IEEE
7087 1003.1-2004 (POSIX), and is available on the World Wide Web
7088 from <url id="http://www.unix.org/version3/online.html"
7089 name="The Open Group"> after free
7090 registration.</footnote>
7091 plus the following additional features not mandated by
7093 These features are in widespread use in the Linux community
7094 and are implemented in all of bash, dash, and ksh, the most
7095 common shells users may wish to use as <file>/bin/sh</file>.
7098 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7099 must not generate a newline.</item>
7100 <item><tt>test</tt>, if implemented as a shell built-in, must
7101 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7103 <item><tt>local</tt> to create a scoped variable must be
7104 supported, including listing multiple variables in a single
7105 local command and assigning a value to a variable at the
7106 same time as localizing it. <tt>local</tt> may or
7107 may not preserve the variable value from an outer scope if
7108 no assignment is present. Uses such as:
7112 # ... use a, b, c, d ...
7115 must be supported and must set the value of <tt>c</tt> to
7119 If a shell script requires non-SUSv3 features from the shell
7120 interpreter other than those listed above, the appropriate shell
7121 must be specified in the first line of the script (e.g.,
7122 <tt>#!/bin/bash</tt>) and the package must depend on the package
7123 providing the shell (unless the shell package is marked
7124 "Essential", as in the case of <prgn>bash</prgn>).
7128 You may wish to restrict your script to SUSv3 features plus the
7129 above set when possible so that it may use <file>/bin/sh</file>
7130 as its interpreter. If your script works with <prgn>dash</prgn>
7131 (originally called <prgn>ash</prgn>), it probably complies with
7132 the above requirements, but if you are in doubt, use
7133 <file>/bin/bash</file>.
7137 Perl scripts should check for errors when making any
7138 system calls, including <tt>open</tt>, <tt>print</tt>,
7139 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7143 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7144 scripting languages. See <em>Csh Programming Considered
7145 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7146 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7147 If an upstream package comes with <prgn>csh</prgn> scripts
7148 then you must make sure that they start with
7149 <tt>#!/bin/csh</tt> and make your package depend on the
7150 <prgn>c-shell</prgn> virtual package.
7154 Any scripts which create files in world-writeable
7155 directories (e.g., in <file>/tmp</file>) must use a
7156 mechanism which will fail atomically if a file with the same
7157 name already exists.
7161 The Debian base system provides the <prgn>tempfile</prgn>
7162 and <prgn>mktemp</prgn> utilities for use by scripts for
7169 <heading>Symbolic links</heading>
7172 In general, symbolic links within a top-level directory
7173 should be relative, and symbolic links pointing from one
7174 top-level directory into another should be absolute. (A
7175 top-level directory is a sub-directory of the root
7176 directory <file>/</file>.)
7180 In addition, symbolic links should be specified as short as
7181 possible, i.e., link targets like <file>foo/../bar</file> are
7186 Note that when creating a relative link using
7187 <prgn>ln</prgn> it is not necessary for the target of the
7188 link to exist relative to the working directory you're
7189 running <prgn>ln</prgn> from, nor is it necessary to change
7190 directory to the directory where the link is to be made.
7191 Simply include the string that should appear as the target
7192 of the link (this will be a pathname relative to the
7193 directory in which the link resides) as the first argument
7198 For example, in your <prgn>Makefile</prgn> or
7199 <file>debian/rules</file>, you can do things like:
7200 <example compact="compact">
7201 ln -fs gcc $(prefix)/bin/cc
7202 ln -fs gcc debian/tmp/usr/bin/cc
7203 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7204 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7209 A symbolic link pointing to a compressed file should always
7210 have the same file extension as the referenced file. (For
7211 example, if a file <file>foo.gz</file> is referenced by a
7212 symbolic link, the filename of the link has to end with
7213 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7218 <heading>Device files</heading>
7221 Packages must not include device files in the package file
7226 If a package needs any special device files that are not
7227 included in the base system, it must call
7228 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7229 after notifying the user<footnote>
7230 This notification could be done via a (low-priority)
7231 debconf message, or an echo (printf) statement.
7236 Packages must not remove any device files in the
7237 <prgn>postrm</prgn> or any other script. This is left to the
7238 system administrator.
7242 Debian uses the serial devices
7243 <file>/dev/ttyS*</file>. Programs using the old
7244 <file>/dev/cu*</file> devices should be changed to use
7245 <file>/dev/ttyS*</file>.
7249 <sect id="config-files">
7250 <heading>Configuration files</heading>
7253 <heading>Definitions</heading>
7257 <tag>configuration file</tag>
7259 A file that affects the operation of a program, or
7260 provides site- or host-specific information, or
7261 otherwise customizes the behavior of a program.
7262 Typically, configuration files are intended to be
7263 modified by the system administrator (if needed or
7264 desired) to conform to local policy or to provide
7265 more useful site-specific behavior.
7268 <tag><tt>conffile</tt></tag>
7270 A file listed in a package's <tt>conffiles</tt>
7271 file, and is treated specially by <prgn>dpkg</prgn>
7272 (see <ref id="configdetails">).
7278 The distinction between these two is important; they are
7279 not interchangeable concepts. Almost all
7280 <tt>conffile</tt>s are configuration files, but many
7281 configuration files are not <tt>conffiles</tt>.
7285 As noted elsewhere, <file>/etc/init.d</file> scripts,
7286 <file>/etc/default</file> files, scripts installed in
7287 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7288 configuration installed in <file>/etc/cron.d</file> must be
7289 treated as configuration files. In general, any script that
7290 embeds configuration information is de-facto a configuration
7291 file and should be treated as such.
7296 <heading>Location</heading>
7299 Any configuration files created or used by your package
7300 must reside in <file>/etc</file>. If there are several,
7301 consider creating a subdirectory of <file>/etc</file>
7302 named after your package.
7306 If your package creates or uses configuration files
7307 outside of <file>/etc</file>, and it is not feasible to modify
7308 the package to use <file>/etc</file> directly, put the files
7309 in <file>/etc</file> and create symbolic links to those files
7310 from the location that the package requires.
7315 <heading>Behavior</heading>
7318 Configuration file handling must conform to the following
7320 <list compact="compact">
7322 local changes must be preserved during a package
7326 configuration files must be preserved when the
7327 package is removed, and only deleted when the
7334 The easy way to achieve this behavior is to make the
7335 configuration file a <tt>conffile</tt>. This is
7336 appropriate only if it is possible to distribute a default
7337 version that will work for most installations, although
7338 some system administrators may choose to modify it. This
7339 implies that the default version will be part of the
7340 package distribution, and must not be modified by the
7341 maintainer scripts during installation (or at any other
7346 In order to ensure that local changes are preserved
7347 correctly, no package may contain or make hard links to
7348 conffiles.<footnote>
7349 Rationale: There are two problems with hard links.
7350 The first is that some editors break the link while
7351 editing one of the files, so that the two files may
7352 unwittingly become unlinked and different. The second
7353 is that <prgn>dpkg</prgn> might break the hard link
7354 while upgrading <tt>conffile</tt>s.
7359 The other way to do it is via the maintainer scripts. In
7360 this case, the configuration file must not be listed as a
7361 <tt>conffile</tt> and must not be part of the package
7362 distribution. If the existence of a file is required for
7363 the package to be sensibly configured it is the
7364 responsibility of the package maintainer to provide
7365 maintainer scripts which correctly create, update and
7366 maintain the file and remove it on purge. (See <ref
7367 id="maintainerscripts"> for more information.) These
7368 scripts must be idempotent (i.e., must work correctly if
7369 <prgn>dpkg</prgn> needs to re-run them due to errors
7370 during installation or removal), must cope with all the
7371 variety of ways <prgn>dpkg</prgn> can call maintainer
7372 scripts, must not overwrite or otherwise mangle the user's
7373 configuration without asking, must not ask unnecessary
7374 questions (particularly during upgrades), and must
7375 otherwise be good citizens.
7379 The scripts are not required to configure every possible
7380 option for the package, but only those necessary to get
7381 the package running on a given system. Ideally the
7382 sysadmin should not have to do any configuration other
7383 than that done (semi-)automatically by the
7384 <prgn>postinst</prgn> script.
7388 A common practice is to create a script called
7389 <file><var>package</var>-configure</file> and have the
7390 package's <prgn>postinst</prgn> call it if and only if the
7391 configuration file does not already exist. In certain
7392 cases it is useful for there to be an example or template
7393 file which the maintainer scripts use. Such files should
7394 be in <file>/usr/share/<var>package</var></file> or
7395 <file>/usr/lib/<var>package</var></file> (depending on whether
7396 they are architecture-independent or not). There should
7397 be symbolic links to them from
7398 <file>/usr/share/doc/<var>package</var>/examples</file> if
7399 they are examples, and should be perfectly ordinary
7400 <prgn>dpkg</prgn>-handled files (<em>not</em>
7401 configuration files).
7405 These two styles of configuration file handling must
7406 not be mixed, for that way lies madness:
7407 <prgn>dpkg</prgn> will ask about overwriting the file
7408 every time the package is upgraded.
7413 <heading>Sharing configuration files</heading>
7416 Packages which specify the same file as a
7417 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7418 with each other. (This is an instance of the general rule
7419 about not sharing files. Note that neither alternatives
7420 nor diversions are likely to be appropriate in this case;
7421 in particular, <prgn>dpkg</prgn> does not handle diverted
7422 <tt>conffile</tt>s well.)
7426 The maintainer scripts must not alter a <tt>conffile</tt>
7427 of <em>any</em> package, including the one the scripts
7432 If two or more packages use the same configuration file
7433 and it is reasonable for both to be installed at the same
7434 time, one of these packages must be defined as
7435 <em>owner</em> of the configuration file, i.e., it will be
7436 the package which handles that file as a configuration
7437 file. Other packages that use the configuration file must
7438 depend on the owning package if they require the
7439 configuration file to operate. If the other package will
7440 use the configuration file if present, but is capable of
7441 operating without it, no dependency need be declared.
7445 If it is desirable for two or more related packages to
7446 share a configuration file <em>and</em> for all of the
7447 related packages to be able to modify that configuration
7448 file, then the following should be done:
7449 <enumlist compact="compact">
7451 One of the related packages (the "owning" package)
7452 will manage the configuration file with maintainer
7453 scripts as described in the previous section.
7456 The owning package should also provide a program
7457 that the other packages may use to modify the
7461 The related packages must use the provided program
7462 to make any desired modifications to the
7463 configuration file. They should either depend on
7464 the core package to guarantee that the configuration
7465 modifier program is available or accept gracefully
7466 that they cannot modify the configuration file if it
7467 is not. (This is in addition to the fact that the
7468 configuration file may not even be present in the
7475 Sometimes it's appropriate to create a new package which
7476 provides the basic infrastructure for the other packages
7477 and which manages the shared configuration files. (The
7478 <tt>sgml-base</tt> package is a good example.)
7483 <heading>User configuration files ("dotfiles")</heading>
7486 The files in <file>/etc/skel</file> will automatically be
7487 copied into new user accounts by <prgn>adduser</prgn>.
7488 No other program should reference the files in
7489 <file>/etc/skel</file>.
7493 Therefore, if a program needs a dotfile to exist in
7494 advance in <file>$HOME</file> to work sensibly, that dotfile
7495 should be installed in <file>/etc/skel</file> and treated as a
7500 However, programs that require dotfiles in order to
7501 operate sensibly are a bad thing, unless they do create
7502 the dotfiles themselves automatically.
7506 Furthermore, programs should be configured by the Debian
7507 default installation to behave as closely to the upstream
7508 default behavior as possible.
7512 Therefore, if a program in a Debian package needs to be
7513 configured in some way in order to operate sensibly, that
7514 should be done using a site-wide configuration file placed
7515 in <file>/etc</file>. Only if the program doesn't support a
7516 site-wide default configuration and the package maintainer
7517 doesn't have time to add it may a default per-user file be
7518 placed in <file>/etc/skel</file>.
7522 <file>/etc/skel</file> should be as empty as we can make it.
7523 This is particularly true because there is no easy (or
7524 necessarily desirable) mechanism for ensuring that the
7525 appropriate dotfiles are copied into the accounts of
7526 existing users when a package is installed.
7532 <heading>Log files</heading>
7534 Log files should usually be named
7535 <file>/var/log/<var>package</var>.log</file>. If you have many
7536 log files, or need a separate directory for permission
7537 reasons (<file>/var/log</file> is writable only by
7538 <file>root</file>), you should usually create a directory named
7539 <file>/var/log/<var>package</var></file> and place your log
7544 Log files must be rotated occasionally so that they don't
7545 grow indefinitely; the best way to do this is to drop a log
7546 rotation configuration file into the directory
7547 <file>/etc/logrotate.d</file> and use the facilities provided by
7548 logrotate.<footnote>
7550 The traditional approach to log files has been to set up
7551 <em>ad hoc</em> log rotation schemes using simple shell
7552 scripts and cron. While this approach is highly
7553 customizable, it requires quite a lot of sysadmin work.
7554 Even though the original Debian system helped a little
7555 by automatically installing a system which can be used
7556 as a template, this was deemed not enough.
7560 The use of <prgn>logrotate</prgn>, a program developed
7561 by Red Hat, is better, as it centralizes log management.
7562 It has both a configuration file
7563 (<file>/etc/logrotate.conf</file>) and a directory where
7564 packages can drop their individual log rotation
7565 configurations (<file>/etc/logrotate.d</file>).
7568 Here is a good example for a logrotate config
7569 file (for more information see <manref name="logrotate"
7571 <example compact="compact">
7572 /var/log/foo/*.log {
7577 /etc/init.d/foo force-reload
7581 This rotates all files under <file>/var/log/foo</file>, saves 12
7582 compressed generations, and forces the daemon to reload its
7583 configuration information after the log rotation.
7587 Log files should be removed when the package is
7588 purged (but not when it is only removed). This should be
7589 done by the <prgn>postrm</prgn> script when it is called
7590 with the argument <tt>purge</tt> (see <ref
7591 id="removedetails">).
7596 <heading>Permissions and owners</heading>
7599 The rules in this section are guidelines for general use.
7600 If necessary you may deviate from the details below.
7601 However, if you do so you must make sure that what is done
7602 is secure and you should try to be as consistent as possible
7603 with the rest of the system. You should probably also
7604 discuss it on <prgn>debian-devel</prgn> first.
7608 Files should be owned by <tt>root:root</tt>, and made
7609 writable only by the owner and universally readable (and
7610 executable, if appropriate), that is mode 644 or 755.
7614 Directories should be mode 755 or (for group-writability)
7615 mode 2775. The ownership of the directory should be
7616 consistent with its mode: if a directory is mode 2775, it
7617 should be owned by the group that needs write access to
7620 When a package is upgraded, and the owner or permissions
7621 of a file included in the package has changed, dpkg
7622 arranges for the ownership and permissions to be
7623 correctly set upon installation. However, this does not
7624 extend to directories; the permissions and ownership of
7625 directories already on the system does not change on
7626 install or upgrade of packages. This makes sense, since
7627 otherwise common directories like <tt>/usr</tt> would
7628 always be in flux. To correctly change permissions of a
7629 directory the package owns, explicit action is required,
7630 usually in the <tt>postinst</tt> script. Care must be
7631 taken to handle downgrades as well, in that case.
7638 Setuid and setgid executables should be mode 4755 or 2755
7639 respectively, and owned by the appropriate user or group.
7640 They should not be made unreadable (modes like 4711 or
7641 2711 or even 4111); doing so achieves no extra security,
7642 because anyone can find the binary in the freely available
7643 Debian package; it is merely inconvenient. For the same
7644 reason you should not restrict read or execute permissions
7645 on non-set-id executables.
7649 Some setuid programs need to be restricted to particular
7650 sets of users, using file permissions. In this case they
7651 should be owned by the uid to which they are set-id, and by
7652 the group which should be allowed to execute them. They
7653 should have mode 4754; again there is no point in making
7654 them unreadable to those users who must not be allowed to
7659 It is possible to arrange that the system administrator can
7660 reconfigure the package to correspond to their local
7661 security policy by changing the permissions on a binary:
7662 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7663 described below.<footnote>
7664 Ordinary files installed by <prgn>dpkg</prgn> (as
7665 opposed to <tt>conffile</tt>s and other similar objects)
7666 normally have their permissions reset to the distributed
7667 permissions when the package is reinstalled. However,
7668 the use of <prgn>dpkg-statoverride</prgn> overrides this
7669 default behavior. If you use this method, you should
7670 remember to describe <prgn>dpkg-statoverride</prgn> in
7671 the package documentation; being a relatively new
7672 addition to Debian, it is probably not yet well-known.
7674 Another method you should consider is to create a group for
7675 people allowed to use the program(s) and make any setuid
7676 executables executable only by that group.
7680 If you need to create a new user or group for your package
7681 there are two possibilities. Firstly, you may need to
7682 make some files in the binary package be owned by this
7683 user or group, or you may need to compile the user or
7684 group id (rather than just the name) into the binary
7685 (though this latter should be avoided if possible, as in
7686 this case you need a statically allocated id).</p>
7689 If you need a statically allocated id, you must ask for a
7690 user or group id from the <tt>base-passwd</tt> maintainer,
7691 and must not release the package until you have been
7692 allocated one. Once you have been allocated one you must
7693 either make the package depend on a version of the
7694 <tt>base-passwd</tt> package with the id present in
7695 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7696 your package to create the user or group itself with the
7697 correct id (using <tt>adduser</tt>) in its
7698 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7699 the <prgn>postinst</prgn> is to be preferred if it is
7700 possible, otherwise a pre-dependency will be needed on the
7701 <tt>adduser</tt> package.)
7705 On the other hand, the program might be able to determine
7706 the uid or gid from the user or group name at runtime, so
7707 that a dynamically allocated id can be used. In this case
7708 you should choose an appropriate user or group name,
7709 discussing this on <prgn>debian-devel</prgn> and checking
7710 with the <package/base-passwd/ maintainer that it is unique and that
7711 they do not wish you to use a statically allocated id
7712 instead. When this has been checked you must arrange for
7713 your package to create the user or group if necessary using
7714 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7715 <prgn>postinst</prgn> script (again, the latter is to be
7716 preferred if it is possible).
7720 Note that changing the numeric value of an id associated
7721 with a name is very difficult, and involves searching the
7722 file system for all appropriate files. You need to think
7723 carefully whether a static or dynamic id is required, since
7724 changing your mind later will cause problems.
7727 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7729 This section is not intended as policy, but as a
7730 description of the use of <prgn>dpkg-statoverride</prgn>.
7734 If a system administrator wishes to have a file (or
7735 directory or other such thing) installed with owner and
7736 permissions different from those in the distributed Debian
7737 package, they can use the <prgn>dpkg-statoverride</prgn>
7738 program to instruct <prgn>dpkg</prgn> to use the different
7739 settings every time the file is installed. Thus the
7740 package maintainer should distribute the files with their
7741 normal permissions, and leave it for the system
7742 administrator to make any desired changes. For example, a
7743 daemon which is normally required to be setuid root, but
7744 in certain situations could be used without being setuid,
7745 should be installed setuid in the <tt>.deb</tt>. Then the
7746 local system administrator can change this if they wish.
7747 If there are two standard ways of doing it, the package
7748 maintainer can use <tt>debconf</tt> to find out the
7749 preference, and call <prgn>dpkg-statoverride</prgn> in the
7750 maintainer script if necessary to accommodate the system
7751 administrator's choice. Care must be taken during
7752 upgrades to not override an existing setting.
7756 Given the above, <prgn>dpkg-statoverride</prgn> is
7757 essentially a tool for system administrators and would not
7758 normally be needed in the maintainer scripts. There is
7759 one type of situation, though, where calls to
7760 <prgn>dpkg-statoverride</prgn> would be needed in the
7761 maintainer scripts, and that involves packages which use
7762 dynamically allocated user or group ids. In such a
7763 situation, something like the following idiom can be very
7764 helpful in the package's <prgn>postinst</prgn>, where
7765 <tt>sysuser</tt> is a dynamically allocated id:
7767 for i in /usr/bin/foo /usr/sbin/bar
7769 # only do something when no setting exists
7770 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7772 #include: debconf processing, question about foo and bar
7773 if [ "$RET" = "true" ] ; then
7774 dpkg-statoverride --update --add sysuser root 4755 $i
7779 The corresponding <tt>dpkg-statoverride --remove</tt>
7780 calls can then be made unconditionally when the package is
7788 <chapt id="customized-programs">
7789 <heading>Customized programs</heading>
7791 <sect id="arch-spec">
7792 <heading>Architecture specification strings</heading>
7795 If a program needs to specify an <em>architecture specification
7796 string</em> in some place, it should select one of the
7797 strings provided by <tt>dpkg-architecture -L</tt>. The
7798 strings are in the format
7799 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7800 is sometimes elided, as when the OS is Linux.<footnote>
7801 <p>Currently, the strings are:
7802 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7803 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7804 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7805 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7806 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7807 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7808 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7809 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7810 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7811 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7812 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7813 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7814 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7815 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7816 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7817 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7818 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7819 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7820 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7821 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7822 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7823 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7824 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7825 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7826 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7827 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7828 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7829 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7830 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7831 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7832 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7833 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7834 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7835 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7836 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7837 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7838 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7844 Note that we don't want to use
7845 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7846 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7847 since this would make our programs incompatible with other
7848 Linux distributions. We also don't use something like
7849 <tt><var>arch</var>-unknown-linux</tt>, since the
7850 <tt>unknown</tt> does not look very good.
7855 <heading>Daemons</heading>
7858 The configuration files <file>/etc/services</file>,
7859 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7860 by the <prgn>netbase</prgn> package and must not be modified
7865 If a package requires a new entry in one of these files, the
7866 maintainer should get in contact with the
7867 <prgn>netbase</prgn> maintainer, who will add the entries
7868 and release a new version of the <prgn>netbase</prgn>
7873 The configuration file <file>/etc/inetd.conf</file> must not be
7874 modified by the package's scripts except via the
7875 <prgn>update-inetd</prgn> script or the
7876 <file>DebianNet.pm</file> Perl module. See their documentation
7877 for details on how to add entries.
7881 If a package wants to install an example entry into
7882 <file>/etc/inetd.conf</file>, the entry must be preceded with
7883 exactly one hash character (<tt>#</tt>). Such lines are
7884 treated as "commented out by user" by the
7885 <prgn>update-inetd</prgn> script and are not changed or
7886 activated during package updates.
7891 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7895 Some programs need to create pseudo-ttys. This should be done
7896 using Unix98 ptys if the C library supports it. The resulting
7897 program must not be installed setuid root, unless that
7898 is required for other functionality.
7902 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7903 <file>/var/log/lastlog</file> must be installed writable by
7904 group <tt>utmp</tt>. Programs which need to modify those
7905 files must be installed setgid <tt>utmp</tt>.
7910 <heading>Editors and pagers</heading>
7913 Some programs have the ability to launch an editor or pager
7914 program to edit or display a text document. Since there are
7915 lots of different editors and pagers available in the Debian
7916 distribution, the system administrator and each user should
7917 have the possibility to choose their preferred editor and
7922 In addition, every program should choose a good default
7923 editor/pager if none is selected by the user or system
7928 Thus, every program that launches an editor or pager must
7929 use the EDITOR or PAGER environment variable to determine
7930 the editor or pager the user wishes to use. If these
7931 variables are not set, the programs <file>/usr/bin/editor</file>
7932 and <file>/usr/bin/pager</file> should be used, respectively.
7936 These two files are managed through the <prgn>dpkg</prgn>
7937 "alternatives" mechanism. Thus every package providing an
7938 editor or pager must call the
7939 <prgn>update-alternatives</prgn> script to register these
7944 If it is very hard to adapt a program to make use of the
7945 EDITOR or PAGER variables, that program may be configured to
7946 use <file>/usr/bin/sensible-editor</file> and
7947 <file>/usr/bin/sensible-pager</file> as the editor or pager
7948 program respectively. These are two scripts provided in the
7949 Debian base system that check the EDITOR and PAGER variables
7950 and launch the appropriate program, and fall back to
7951 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7952 variable is not set.
7956 A program may also use the VISUAL environment variable to
7957 determine the user's choice of editor. If it exists, it
7958 should take precedence over EDITOR. This is in fact what
7959 <file>/usr/bin/sensible-editor</file> does.
7963 It is not required for a package to depend on
7964 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7965 package to provide such virtual packages.<footnote>
7966 The Debian base system already provides an editor and a
7972 <sect id="web-appl">
7973 <heading>Web servers and applications</heading>
7976 This section describes the locations and URLs that should
7977 be used by all web servers and web applications in the
7984 Cgi-bin executable files are installed in the
7986 <example compact="compact">
7987 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7989 and should be referred to as
7990 <example compact="compact">
7991 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7997 <p>Access to HTML documents</p>
8000 HTML documents for a package are stored in
8001 <file>/usr/share/doc/<var>package</var></file>
8002 and can be referred to as
8003 <example compact="compact">
8004 http://localhost/doc/<var>package</var>/<var>filename</var>
8009 The web server should restrict access to the document
8010 tree so that only clients on the same host can read
8011 the documents. If the web server does not support such
8012 access controls, then it should not provide access at
8013 all, or ask about providing access during installation.
8018 <p>Access to images</p>
8020 It is recommended that images for a package be stored
8021 in <tt>/usr/share/images/<var>package</var></tt> and
8022 may be referred to through an alias <tt>/images/</tt>
8025 http://localhost/images/<package>/<filename>
8032 <p>Web Document Root</p>
8035 Web Applications should try to avoid storing files in
8036 the Web Document Root. Instead they should use the
8037 /usr/share/doc/<var>package</var> directory for
8038 documents and register the Web Application via the
8039 <package>doc-base</package> package. If access to the
8040 web document root is unavoidable then use
8041 <example compact="compact">
8044 as the Document Root. This might be just a symbolic
8045 link to the location where the system administrator
8046 has put the real document root.
8049 <item><p>Providing httpd and/or httpd-cgi</p>
8051 All web servers should provide the virtual package
8052 <tt>httpd</tt>. If a web server has CGI support it should
8053 provide <tt>httpd-cgi</tt> additionally.
8056 All web applications which do not contain CGI scripts should
8057 depend on <tt>httpd</tt>, all those web applications which
8058 <tt>do</tt> contain CGI scripts, should depend on
8066 <sect id="mail-transport-agents">
8067 <heading>Mail transport, delivery and user agents</heading>
8070 Debian packages which process electronic mail, whether mail
8071 user agents (MUAs) or mail transport agents (MTAs), must
8072 ensure that they are compatible with the configuration
8073 decisions below. Failure to do this may result in lost
8074 mail, broken <tt>From:</tt> lines, and other serious brain
8079 The mail spool is <file>/var/mail</file> and the interface to
8080 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8081 the FHS). On older systems, the mail spool may be
8082 physically located in <file>/var/spool/mail</file>, but all
8083 access to the mail spool should be via the
8084 <file>/var/mail</file> symlink. The mail spool is part of the
8085 base system and not part of the MTA package.
8089 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8090 programs (such as IMAP daemons) must lock the mailbox in an
8091 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8092 be combined with dot locking. To avoid deadlocks, a program
8093 should use <tt>fcntl()</tt> first and dot locking after
8094 this, or alternatively implement the two locking methods in
8095 a non blocking way<footnote>
8096 If it is not possible to establish both locks, the
8097 system shouldn't wait for the second lock to be
8098 established, but remove the first lock, wait a (random)
8099 time, and start over locking again.
8100 </footnote>. Using the functions <tt>maillock</tt> and
8101 <tt>mailunlock</tt> provided by the
8102 <tt>liblockfile*</tt><footnote>
8103 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8104 to use these functions.
8105 </footnote> packages is the recommended way to realize this.
8109 Mailboxes are generally either mode 600 and owned by
8110 <var>user</var> or mode 660 and owned by
8111 <tt><var>user</var>:mail</tt><footnote>
8112 There are two traditional permission schemes for mail spools:
8113 mode 600 with all mail delivery done by processes running as
8114 the destination user, or mode 660 and owned by group mail with
8115 mail delivery done by a process running as a system user in
8116 group mail. Historically, Debian required mode 660 mail
8117 spools to enable the latter model, but that model has become
8118 increasingly uncommon and the principle of least privilege
8119 indicates that mail systems that use the first model should
8120 use permissions of 600. If delivery to programs is permitted,
8121 it's easier to keep the mail system secure if the delivery
8122 agent runs as the destination user. Debian Policy therefore
8123 permits either scheme.
8124 </footnote>. The local system administrator may choose a
8125 different permission scheme; packages should not make
8126 assumptions about the permission and ownership of mailboxes
8127 unless required (such as when creating a new mailbox). A MUA
8128 may remove a mailbox (unless it has nonstandard permissions) in
8129 which case the MTA or another MUA must recreate it if needed.
8133 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8134 be setgid mail to do the locking mentioned above (and
8135 must obviously avoid accessing other users' mailboxes
8136 using this privilege).</p>
8139 <file>/etc/aliases</file> is the source file for the system mail
8140 aliases (e.g., postmaster, usenet, etc.), it is the one
8141 which the sysadmin and <prgn>postinst</prgn> scripts may
8142 edit. After <file>/etc/aliases</file> is edited the program or
8143 human editing it must call <prgn>newaliases</prgn>. All MTA
8144 packages must come with a <prgn>newaliases</prgn> program,
8145 even if it does nothing, but older MTA packages did not do
8146 this so programs should not fail if <prgn>newaliases</prgn>
8147 cannot be found. Note that because of this, all MTA
8148 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8149 <tt>Replaces: mail-transport-agent</tt> control file
8154 The convention of writing <tt>forward to
8155 <var>address</var></tt> in the mailbox itself is not
8156 supported. Use a <tt>.forward</tt> file instead.</p>
8159 The <prgn>rmail</prgn> program used by UUCP
8160 for incoming mail should be <file>/usr/sbin/rmail</file>.
8161 Likewise, <prgn>rsmtp</prgn>, for receiving
8162 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8166 If your package needs to know what hostname to use on (for
8167 example) outgoing news and mail messages which are generated
8168 locally, you should use the file <file>/etc/mailname</file>. It
8169 will contain the portion after the username and <tt>@</tt>
8170 (at) sign for email addresses of users on the machine
8171 (followed by a newline).
8175 Such a package should check for the existence of this file
8176 when it is being configured. If it exists, it should be
8177 used without comment, although an MTA's configuration script
8178 may wish to prompt the user even if it finds that this file
8179 exists. If the file does not exist, the package should
8180 prompt the user for the value (preferably using
8181 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8182 as well as using it in the package's configuration. The
8183 prompt should make it clear that the name will not just be
8184 used by that package. For example, in this situation the
8185 <tt>inn</tt> package could say something like:
8186 <example compact="compact">
8187 Please enter the "mail name" of your system. This is the
8188 hostname portion of the address to be shown on outgoing
8189 news and mail messages. The default is
8190 <var>syshostname</var>, your system's host name. Mail
8191 name ["<var>syshostname</var>"]:
8193 where <var>syshostname</var> is the output of <tt>hostname
8199 <heading>News system configuration</heading>
8202 All the configuration files related to the NNTP (news)
8203 servers and clients should be located under
8204 <file>/etc/news</file>.</p>
8207 There are some configuration issues that apply to a number
8208 of news clients and server packages on the machine. These
8212 <tag><file>/etc/news/organization</file></tag>
8214 A string which should appear as the
8215 organization header for all messages posted
8216 by NNTP clients on the machine
8219 <tag><file>/etc/news/server</file></tag>
8221 Contains the FQDN of the upstream NNTP
8222 server, or localhost if the local machine is
8227 Other global files may be added as required for cross-package news
8234 <heading>Programs for the X Window System</heading>
8237 <heading>Providing X support and package priorities</heading>
8240 Programs that can be configured with support for the X
8241 Window System must be configured to do so and must declare
8242 any package dependencies necessary to satisfy their
8243 runtime requirements when using the X Window System. If
8244 such a package is of higher priority than the X packages
8245 on which it depends, it is required that either the
8246 X-specific components be split into a separate package, or
8247 that an alternative version of the package, which includes
8248 X support, be provided, or that the package's priority be
8254 <heading>Packages providing an X server</heading>
8257 Packages that provide an X server that, directly or
8258 indirectly, communicates with real input and display
8259 hardware should declare in their control data that they
8260 provide the virtual package <tt>xserver</tt>.<footnote>
8261 This implements current practice, and provides an
8262 actual policy for usage of the <tt>xserver</tt>
8263 virtual package which appears in the virtual packages
8264 list. In a nutshell, X servers that interface
8265 directly with the display and input hardware or via
8266 another subsystem (e.g., GGI) should provide
8267 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8268 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8274 <heading>Packages providing a terminal emulator</heading>
8277 Packages that provide a terminal emulator for the X Window
8278 System which meet the criteria listed below should declare
8279 in their control data that they provide the virtual
8280 package <tt>x-terminal-emulator</tt>. They should also
8281 register themselves as an alternative for
8282 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8287 To be an <tt>x-terminal-emulator</tt>, a program must:
8288 <list compact="compact">
8290 Be able to emulate a DEC VT100 terminal, or a
8291 compatible terminal.
8295 Support the command-line option <tt>-e
8296 <var>command</var></tt>, which creates a new
8297 terminal window<footnote>
8298 "New terminal window" does not necessarily mean
8299 a new top-level X window directly parented by
8300 the window manager; it could, if the terminal
8301 emulator application were so coded, be a new
8302 "view" in a multiple-document interface (MDI).
8304 and runs the specified <var>command</var>,
8305 interpreting the entirety of the rest of the command
8306 line as a command to pass straight to exec, in the
8307 manner that <tt>xterm</tt> does.
8311 Support the command-line option <tt>-T
8312 <var>title</var></tt>, which creates a new terminal
8313 window with the window title <var>title</var>.
8320 <heading>Packages providing a window manager</heading>
8323 Packages that provide a window manager should declare in
8324 their control data that they provide the virtual package
8325 <tt>x-window-manager</tt>. They should also register
8326 themselves as an alternative for
8327 <file>/usr/bin/x-window-manager</file>, with a priority
8328 calculated as follows:
8329 <list compact="compact">
8331 Start with a priority of 20.
8335 If the window manager supports the Debian menu
8336 system, add 20 points if this support is available
8337 in the package's default configuration (i.e., no
8338 configuration files belonging to the system or user
8339 have to be edited to activate the feature); if
8340 configuration files must be modified, add only 10
8346 If the window manager complies with <url
8347 id="http://www.freedesktop.org/Standards/wm-spec"
8348 name="The Window Manager Specification Project">,
8349 written by the <url id="http://www.freedesktop.org/"
8350 name="Free Desktop Group">, add 40 points.
8354 If the window manager permits the X session to be
8355 restarted using a <em>different</em> window manager
8356 (without killing the X server) in its default
8357 configuration, add 10 points; otherwise add none.
8364 <heading>Packages providing fonts</heading>
8367 Packages that provide fonts for the X Window
8369 For the purposes of Debian Policy, a "font for the X
8370 Window System" is one which is accessed via X protocol
8371 requests. Fonts for the Linux console, for PostScript
8372 renderer, or any other purpose, do not fit this
8373 definition. Any tool which makes such fonts available
8374 to the X Window System, however, must abide by this
8377 must do a number of things to ensure that they are both
8378 available without modification of the X or font server
8379 configuration, and that they do not corrupt files used by
8380 other font packages to register information about
8384 Fonts of any type supported by the X Window System
8385 must be in a separate binary package from any
8386 executables, libraries, or documentation (except
8387 that specific to the fonts shipped, such as their
8388 license information). If one or more of the fonts
8389 so packaged are necessary for proper operation of
8390 the package with which they are associated the font
8391 package may be Recommended; if the fonts merely
8392 provide an enhancement, a Suggests relationship may
8393 be used. Packages must not Depend on font
8395 This is because the X server may retrieve fonts
8396 from the local file system or over the network
8397 from an X font server; the Debian package system
8398 is empowered to deal only with the local
8404 BDF fonts must be converted to PCF fonts with the
8405 <prgn>bdftopcf</prgn> utility (available in the
8406 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8407 placed in a directory that corresponds to their
8409 <list compact="compact">
8411 100 dpi fonts must be placed in
8412 <file>/usr/share/fonts/X11/100dpi/</file>.
8416 75 dpi fonts must be placed in
8417 <file>/usr/share/fonts/X11/75dpi/</file>.
8421 Character-cell fonts, cursor fonts, and other
8422 low-resolution fonts must be placed in
8423 <file>/usr/share/fonts/X11/misc/</file>.
8429 Speedo fonts must be placed in
8430 <file>/usr/share/fonts/X11/Speedo/</file>.
8434 Type 1 fonts must be placed in
8435 <file>/usr/share/fonts/X11/Type1/</file>. If font
8436 metric files are available, they must be placed here
8441 Subdirectories of <file>/usr/share/fonts/X11/</file>
8442 other than those listed above must be neither
8443 created nor used. (The <file>PEX</file>, <file>CID</file>,
8444 and <file>cyrillic</file> directories are excepted for
8445 historical reasons, but installation of files into
8446 these directories remains discouraged.)
8450 Font packages may, instead of placing files directly
8451 in the X font directories listed above, provide
8452 symbolic links in that font directory pointing to
8453 the files' actual location in the filesystem. Such
8454 a location must comply with the FHS.
8458 Font packages should not contain both 75dpi and
8459 100dpi versions of a font. If both are available,
8460 they should be provided in separate binary packages
8461 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8462 the names of the packages containing the
8463 corresponding fonts.
8467 Fonts destined for the <file>misc</file> subdirectory
8468 should not be included in the same package as 75dpi
8469 or 100dpi fonts; instead, they should be provided in
8470 a separate package with <tt>-misc</tt> appended to
8475 Font packages must not provide the files
8476 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8477 <file>fonts.scale</file> in a font directory:
8480 <file>fonts.dir</file> files must not be provided at all.
8484 <file>fonts.alias</file> and <file>fonts.scale</file>
8485 files, if needed, should be provided in the
8487 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8488 where <var>fontdir</var> is the name of the
8490 <file>/usr/share/fonts/X11/</file> where the
8491 package's corresponding fonts are stored
8492 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8493 <var>package</var> is the name of the package
8494 that provides these fonts, and
8495 <var>extension</var> is either <tt>scale</tt>
8496 or <tt>alias</tt>, whichever corresponds to
8503 Font packages must declare a dependency on
8504 <tt>xfonts-utils</tt> in their control
8509 Font packages that provide one or more
8510 <file>fonts.scale</file> files as described above must
8511 invoke <prgn>update-fonts-scale</prgn> on each
8512 directory into which they installed fonts
8513 <em>before</em> invoking
8514 <prgn>update-fonts-dir</prgn> on that directory.
8515 This invocation must occur in both the
8516 <prgn>postinst</prgn> (for all arguments) and
8517 <prgn>postrm</prgn> (for all arguments except
8518 <tt>upgrade</tt>) scripts.
8522 Font packages that provide one or more
8523 <file>fonts.alias</file> files as described above must
8524 invoke <prgn>update-fonts-alias</prgn> on each
8525 directory into which they installed fonts. This
8526 invocation must occur in both the
8527 <prgn>postinst</prgn> (for all arguments) and
8528 <prgn>postrm</prgn> (for all arguments except
8529 <tt>upgrade</tt>) scripts.
8533 Font packages must invoke
8534 <prgn>update-fonts-dir</prgn> on each directory into
8535 which they installed fonts. This invocation must
8536 occur in both the <prgn>postinst</prgn> (for all
8537 arguments) and <prgn>postrm</prgn> (for all
8538 arguments except <tt>upgrade</tt>) scripts.
8542 Font packages must not provide alias names for the
8543 fonts they include which collide with alias names
8544 already in use by fonts already packaged.
8548 Font packages must not provide fonts with the same
8549 XLFD registry name as another font already packaged.
8556 <heading>Application defaults files</heading>
8559 Application defaults files must be installed in the
8560 directory <file>/etc/X11/app-defaults/</file> (use of a
8561 localized subdirectory of <file>/etc/X11/</file> as described
8562 in the <em>X Toolkit Intrinsics - C Language
8563 Interface</em> manual is also permitted). They must be
8564 registered as <tt>conffile</tt>s or handled as
8565 configuration files.
8569 Customization of programs' X resources may also be
8570 supported with the provision of a file with the same name
8571 as that of the package placed in the
8572 <file>/etc/X11/Xresources/</file> directory, which must
8573 registered as a <tt>conffile</tt> or handled as a
8574 configuration file.<footnote>
8575 Note that this mechanism is not the same as using
8576 app-defaults; app-defaults are tied to the client
8577 binary on the local file system, whereas X resources
8578 are stored in the X server and affect all connecting
8585 <heading>Installation directory issues</heading>
8588 Packages using the X Window System should not be
8589 configured to install files under the
8590 <file>/usr/X11R6/</file> directory. The
8591 <file>/usr/X11R6/</file> directory hierarchy should be
8592 regarded as obsolete.
8596 Programs that use GNU <prgn>autoconf</prgn> and
8597 <prgn>automake</prgn> are usually easily configured at
8598 compile time to use <file>/usr/</file> instead of
8599 <file>/usr/X11R6/</file>, and this should be done whenever
8600 possible. Configuration files for window managers and
8601 display managers should be placed in a subdirectory of
8602 <file>/etc/X11/</file> corresponding to the package name due
8603 to these programs' tight integration with the mechanisms
8604 of the X Window System. Application-level programs should
8605 use the <file>/etc/</file> directory unless otherwise mandated
8610 The installation of files into subdirectories
8611 of <file>/usr/X11R6/include/X11/</file> and
8612 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8613 package maintainers should determine if subdirectories of
8614 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8619 Packages should install any relevant files into the
8620 directories <file>/usr/include/X11/</file> and
8621 <file>/usr/lib/X11/</file>, but if they do so, they must
8622 pre-depend on <tt>x11-common (>=
8623 1:7.0.0)</tt><footnote>
8625 These libraries used to be all symbolic
8626 links. However, with <tt>X11R7</tt>,
8627 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8628 are now real directories, and packages
8629 <strong>should</strong> ship their files here instead
8630 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8631 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8632 responsible for converting these symlinks into
8640 <heading>The OSF/Motif and OpenMotif libraries</heading>
8643 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8644 OpenMotif libraries</em><footnote>
8645 OSF/Motif and OpenMotif are collectively referred to as
8646 "Motif" in this policy document.
8648 should be compiled against and tested with LessTif (a free
8649 re-implementation of Motif) instead. If the maintainer
8650 judges that the program or programs do not work
8651 sufficiently well with LessTif to be distributed and
8652 supported, but do so when compiled against Motif, then two
8653 versions of the package should be created; one linked
8654 statically against Motif and with <tt>-smotif</tt>
8655 appended to the package name, and one linked dynamically
8656 against Motif and with <tt>-dmotif</tt> appended to the
8661 Both Motif-linked versions are dependent
8662 upon non-DFSG-compliant software and thus cannot be
8663 uploaded to the <em>main</em> distribution; if the
8664 software is itself DFSG-compliant it may be uploaded to
8665 the <em>contrib</em> distribution. While known existing
8666 versions of Motif permit unlimited redistribution of
8667 binaries linked against the library (whether statically or
8668 dynamically), it is the package maintainer's
8669 responsibility to determine whether this is permitted by
8670 the license of the copy of Motif in their possession.
8676 <heading>Perl programs and modules</heading>
8679 Perl programs and modules should follow the current Perl policy.
8683 The Perl policy can be found in the <tt>perl-policy</tt>
8684 files in the <tt>debian-policy</tt> package.
8685 It is also available from the Debian web mirrors at
8686 <tt><url name="/doc/packaging-manuals/perl-policy/"
8687 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8692 <heading>Emacs lisp programs</heading>
8695 Please refer to the "Debian Emacs Policy" for details of how to
8696 package emacs lisp programs.
8700 The Emacs policy is available in
8701 <file>debian-emacs-policy.gz</file> of the
8702 <package>emacsen-common</package> package.
8703 It is also available from the Debian web mirrors at
8704 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8705 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8710 <heading>Games</heading>
8713 The permissions on <file>/var/games</file> are mode 755, owner
8714 <tt>root</tt> and group <tt>root</tt>.
8718 Each game decides on its own security policy.</p>
8721 Games which require protected, privileged access to
8722 high-score files, saved games, etc., may be made
8723 set-<em>group</em>-id (mode 2755) and owned by
8724 <tt>root:games</tt>, and use files and directories with
8725 appropriate permissions (770 <tt>root:games</tt>, for
8726 example). They must not be made
8727 set-<em>user</em>-id, as this causes security problems. (If
8728 an attacker can subvert any set-user-id game they can
8729 overwrite the executable of any other, causing other players
8730 of these games to run a Trojan horse program. With a
8731 set-group-id game the attacker only gets access to less
8732 important game data, and if they can get at the other
8733 players' accounts at all it will take considerably more
8737 Some packages, for example some fortune cookie programs, are
8738 configured by the upstream authors to install with their
8739 data files or other static information made unreadable so
8740 that they can only be accessed through set-id programs
8741 provided. You should not do this in a Debian package: anyone can
8742 download the <file>.deb</file> file and read the data from it,
8743 so there is no point making the files unreadable. Not
8744 making the files unreadable also means that you don't have
8745 to make so many programs set-id, which reduces the risk of a
8749 As described in the FHS, binaries of games should be
8750 installed in the directory <file>/usr/games</file>. This also
8751 applies to games that use the X Window System. Manual pages
8752 for games (X and non-X games) should be installed in
8753 <file>/usr/share/man/man6</file>.</p>
8759 <heading>Documentation</heading>
8762 <heading>Manual pages</heading>
8765 You should install manual pages in <prgn>nroff</prgn> source
8766 form, in appropriate places under <file>/usr/share/man</file>.
8767 You should only use sections 1 to 9 (see the FHS for more
8768 details). You must not install a pre-formatted "cat page".
8772 Each program, utility, and function should have an
8773 associated manual page included in the same package. It is
8774 suggested that all configuration files also have a manual
8775 page included as well. Manual pages for protocols and other
8776 auxiliary things are optional.
8780 If no manual page is available, this is considered as a bug
8781 and should be reported to the Debian Bug Tracking System (the
8782 maintainer of the package is allowed to write this bug report
8783 themselves, if they so desire). Do not close the bug report
8784 until a proper man page is available.<footnote>
8785 It is not very hard to write a man page. See the
8786 <url id="http://www.schweikhardt.net/man_page_howto.html"
8787 name="Man-Page-HOWTO">,
8788 <manref name="man" section="7">, the examples
8789 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8790 the helper programs <prgn>help2man</prgn>, or the
8791 directory <file>/usr/share/doc/man-db/examples</file>.
8796 You may forward a complaint about a missing man page to the
8797 upstream authors, and mark the bug as forwarded in the
8798 Debian bug tracking system. Even though the GNU Project do
8799 not in general consider the lack of a man page to be a bug,
8800 we do; if they tell you that they don't consider it a bug
8801 you should leave the bug in our bug tracking system open
8806 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8810 If one man page needs to be accessible via several names it
8811 is better to use a symbolic link than the <file>.so</file>
8812 feature, but there is no need to fiddle with the relevant
8813 parts of the upstream source to change from <file>.so</file> to
8814 symlinks: don't do it unless it's easy. You should not
8815 create hard links in the manual page directories, nor put
8816 absolute filenames in <file>.so</file> directives. The filename
8817 in a <file>.so</file> in a man page should be relative to the
8818 base of the man page tree (usually
8819 <file>/usr/share/man</file>). If you do not create any links
8820 (whether symlinks, hard links, or <tt>.so</tt> directives)
8821 in the file system to the alternate names of the man page,
8822 then you should not rely on <prgn>man</prgn> finding your
8823 man page under those names based solely on the information in
8824 the man page's header.<footnote>
8825 Supporting this in <prgn>man</prgn> often requires
8826 unreasonable processing time to find a manual page or to
8827 report that none exists, and moves knowledge into man's
8828 database that would be better left in the file system.
8829 This support is therefore deprecated and will cease to
8830 be present in the future.
8835 Manual pages in locale-specific subdirectories of
8836 <file>/usr/share/man</file> should use either UTF-8 or the usual
8837 legacy encoding for that language (normally the one corresponding
8838 to the shortest relevant locale name in
8839 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8840 <file>/usr/share/man/fr</file> should use either UTF-8 or
8841 ISO-8859-1.<footnote>
8842 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8843 use. In future, all manual pages will be required to use
8849 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8850 included in the subdirectory name unless it indicates a
8851 significant difference in the language, as this excludes
8852 speakers of the language in other countries.<footnote>
8853 At the time of writing, Chinese and Portuguese are the main
8854 languages with such differences, so <file>pt_BR</file>,
8855 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8860 Due to limitations in current implementations, all characters
8861 in the manual page source should be representable in the usual
8862 legacy encoding for that language, even if the file is
8863 actually encoded in UTF-8. Safe alternative ways to write many
8864 characters outside that range may be found in
8865 <manref name="groff_char" section="7">.
8870 <heading>Info documents</heading>
8873 Info documents should be installed in <file>/usr/share/info</file>.
8874 They should be compressed with <tt>gzip -9</tt>.
8878 Your package should call <prgn>install-info</prgn> to update
8879 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8880 script when called with a <tt>configure</tt> argument, for
8882 <example compact="compact">
8883 install-info --quiet --section Development Development \
8884 /usr/share/info/foobar.info
8888 It is a good idea to specify a section for the location of
8889 your program; this is done with the <tt>--section</tt>
8890 switch. To determine which section to use, you should look
8891 at <file>/usr/share/info/dir</file> on your system and choose the most
8892 relevant (or create a new section if none of the current
8893 sections are relevant). Note that the <tt>--section</tt>
8894 flag takes two arguments; the first is a regular expression
8895 to match (case-insensitively) against an existing section,
8896 the second is used when creating a new one.</p>
8899 You should remove the entries in the <prgn>prerm</prgn>
8900 script when called with a <tt>remove</tt> argument:
8901 <example compact="compact">
8902 install-info --quiet --remove /usr/share/info/foobar.info
8906 If <prgn>install-info</prgn> cannot find a description entry
8907 in the Info file you must supply one. See <manref
8908 name="install-info" section="8"> for details.</p>
8912 <heading>Additional documentation</heading>
8915 Any additional documentation that comes with the package may
8916 be installed at the discretion of the package maintainer.
8917 Plain text documentation should be installed in the directory
8918 <file>/usr/share/doc/<var>package</var></file>, where
8919 <var>package</var> is the name of the package, and
8920 compressed with <tt>gzip -9</tt> unless it is small.
8924 If a package comes with large amounts of documentation which
8925 many users of the package will not require you should create
8926 a separate binary package to contain it, so that it does not
8927 take up disk space on the machines of users who do not need
8928 or want it installed.</p>
8931 It is often a good idea to put text information files
8932 (<file>README</file>s, changelogs, and so forth) that come with
8933 the source package in <file>/usr/share/doc/<var>package</var></file>
8934 in the binary package. However, you don't need to install
8935 the instructions for building and installing the package, of
8939 Packages must not require the existence of any files in
8940 <file>/usr/share/doc/</file> in order to function
8942 The system administrator should be able to
8943 delete files in <file>/usr/share/doc/</file> without causing
8944 any programs to break.
8946 Any files that are referenced by programs but are also
8947 useful as stand alone documentation should be installed under
8948 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8949 <file>/usr/share/doc/<var>package</var></file>.
8953 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8954 link to another directory in <file>/usr/share/doc</file> only if
8955 the two packages both come from the same source and the
8956 first package Depends on the second.<footnote>
8958 Please note that this does not override the section on
8959 changelog files below, so the file
8960 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8961 must refer to the changelog for the current version of
8962 <var>package</var> in question. In practice, this means
8963 that the sources of the target and the destination of the
8964 symlink must be the same (same source package and
8971 Former Debian releases placed all additional documentation
8972 in <file>/usr/doc/<var>package</var></file>. This has been
8973 changed to <file>/usr/share/doc/<var>package</var></file>,
8974 and packages must not put documentation in the directory
8975 <file>/usr/doc/<var>package</var></file>. <footnote>
8976 At this phase of the transition, we no longer require a
8977 symbolic link in <file>/usr/doc/</file>. At a later point,
8978 policy shall change to make the symbolic links a bug.
8984 <heading>Preferred documentation formats</heading>
8987 The unification of Debian documentation is being carried out
8991 If your package comes with extensive documentation in a
8992 markup format that can be converted to various other formats
8993 you should if possible ship HTML versions in a binary
8994 package, in the directory
8995 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8996 its subdirectories.<footnote>
8997 The rationale: The important thing here is that HTML
8998 docs should be available in <em>some</em> package, not
8999 necessarily in the main binary package.
9004 Other formats such as PostScript may be provided at the
9005 package maintainer's discretion.
9009 <sect id="copyrightfile">
9010 <heading>Copyright information</heading>
9013 Every package must be accompanied by a verbatim copy of its
9014 copyright and distribution license in the file
9015 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9016 file must neither be compressed nor be a symbolic link.
9020 In addition, the copyright file must say where the upstream
9021 sources (if any) were obtained. It should name the original
9022 authors of the package and the Debian maintainer(s) who were
9023 involved with its creation.
9027 Packages in the <em>contrib</em> or <em>non-free</em> archive
9028 areas should state in the copyright file that the package is not
9029 part of the Debian GNU/Linux distribution and briefly explain
9034 A copy of the file which will be installed in
9035 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9036 be in <file>debian/copyright</file> in the source package.
9040 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9041 link to another directory in <file>/usr/share/doc</file> only if
9042 the two packages both come from the same source and the
9043 first package Depends on the second. These rules are
9044 important because copyrights must be extractable by
9049 Packages distributed under the UCB BSD license, the Apache
9050 license (version 2.0), the Artistic license, the GNU GPL
9051 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
9052 the GNU FDL (version 1.2) should refer to the corresponding
9053 files under <file>/usr/share/common-licenses</file>,<footnote>
9056 <file>/usr/share/common-licenses/BSD</file>,
9057 <file>/usr/share/common-licenses/Apache-2.0</file>,
9058 <file>/usr/share/common-licenses/Artistic</file>,
9059 <file>/usr/share/common-licenses/GPL-2</file>,
9060 <file>/usr/share/common-licenses/GPL-3</file>,
9061 <file>/usr/share/common-licenses/LGPL-2</file>,
9062 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9063 <file>/usr/share/common-licenses/LGPL-3</file>, and
9064 <file>/usr/share/common-licenses/GFDL-1.2</file>
9067 </footnote> rather than quoting them in the copyright
9072 You should not use the copyright file as a general <file>README</file>
9073 file. If your package has such a file it should be
9074 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9075 <file>README.Debian</file> or some other appropriate place.</p>
9079 <heading>Examples</heading>
9082 Any examples (configurations, source files, whatever),
9083 should be installed in a directory
9084 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9085 files should not be referenced by any program: they're there
9086 for the benefit of the system administrator and users as
9087 documentation only. Architecture-specific example files
9088 should be installed in a directory
9089 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9091 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9092 latter directory itself may be a symbolic link to the
9097 If the purpose of a package is to provide examples, then the
9098 example files may be installed into
9099 <file>/usr/share/doc/<var>package</var></file>.
9103 <sect id="changelogs">
9104 <heading>Changelog files</heading>
9107 Packages that are not Debian-native must contain a
9108 compressed copy of the <file>debian/changelog</file> file from
9109 the Debian source tree in
9110 <file>/usr/share/doc/<var>package</var></file> with the name
9111 <file>changelog.Debian.gz</file>.
9115 If an upstream changelog is available, it should be accessible as
9116 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9117 plain text. If the upstream changelog is distributed in
9118 HTML, it should be made available in that form as
9119 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9120 and a plain text <file>changelog.gz</file> should be generated
9121 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9122 the upstream changelog files do not already conform to this
9123 naming convention, then this may be achieved either by
9124 renaming the files, or by adding a symbolic link, at the
9125 maintainer's discretion.<footnote>
9126 Rationale: People should not have to look in places for
9127 upstream changelogs merely because they are given
9128 different names or are distributed in HTML format.
9133 All of these files should be installed compressed using
9134 <tt>gzip -9</tt>, as they will become large with time even
9135 if they start out small.
9139 If the package has only one changelog which is used both as
9140 the Debian changelog and the upstream one because there is
9141 no separate upstream maintainer then that changelog should
9142 usually be installed as
9143 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9144 there is a separate upstream maintainer, but no upstream
9145 changelog, then the Debian changelog should still be called
9146 <file>changelog.Debian.gz</file>.
9150 For details about the format and contents of the Debian
9151 changelog file, please see <ref id="dpkgchangelog">.
9156 <appendix id="pkg-scope">
9157 <heading>Introduction and scope of these appendices</heading>
9160 These appendices are taken essentially verbatim from the
9161 now-deprecated Packaging Manual, version 3.2.1.0. They are
9162 the chapters which are likely to be of use to package
9163 maintainers and which have not already been included in the
9164 policy document itself. Most of these sections are very likely
9165 not relevant to policy; they should be treated as
9166 documentation for the packaging system. Please note that these
9167 appendices are included for convenience, and for historical
9168 reasons: they used to be part of policy package, and they have
9169 not yet been incorporated into dpkg documentation. However,
9170 they still have value, and hence they are presented here.
9174 They have not yet been checked to ensure that they are
9175 compatible with the contents of policy, and if there are any
9176 contradictions, the version in the main policy document takes
9177 precedence. The remaining chapters of the old Packaging
9178 Manual have also not been read in detail to ensure that there
9179 are not parts which have been left out. Both of these will be
9184 Certain parts of the Packaging manual were integrated into the
9185 Policy Manual proper, and removed from the appendices. Links
9186 have been placed from the old locations to the new ones.
9190 <prgn>dpkg</prgn> is a suite of programs for creating binary
9191 package files and installing and removing them on Unix
9193 <prgn>dpkg</prgn> is targeted primarily at Debian
9194 GNU/Linux, but may work on or be ported to other
9200 The binary packages are designed for the management of
9201 installed executable programs (usually compiled binaries) and
9202 their associated data, though source code examples and
9203 documentation are provided as part of some packages.</p>
9206 This manual describes the technical aspects of creating Debian
9207 binary packages (<file>.deb</file> files). It documents the
9208 behavior of the package management programs
9209 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9210 they interact with packages.</p>
9213 It also documents the interaction between
9214 <prgn>dselect</prgn>'s core and the access method scripts it
9215 uses to actually install the selected packages, and describes
9216 how to create a new access method.</p>
9219 This manual does not go into detail about the options and
9220 usage of the package building and installation tools. It
9221 should therefore be read in conjunction with those programs'
9226 The utility programs which are provided with <prgn>dpkg</prgn>
9227 for managing various system configuration and similar issues,
9228 such as <prgn>update-rc.d</prgn> and
9229 <prgn>install-info</prgn>, are not described in detail here -
9230 please see their man pages.
9234 It is assumed that the reader is reasonably familiar with the
9235 <prgn>dpkg</prgn> System Administrators' manual.
9236 Unfortunately this manual does not yet exist.
9240 The Debian version of the FSF's GNU hello program is provided
9241 as an example for people wishing to create Debian
9242 packages. The Debian <prgn>debmake</prgn> package is
9243 recommended as a very helpful tool in creating and maintaining
9244 Debian packages. However, while the tools and examples are
9245 helpful, they do not replace the need to read and follow the
9246 Policy and Programmer's Manual.</p>
9249 <appendix id="pkg-binarypkg">
9250 <heading>Binary packages (from old Packaging Manual)</heading>
9253 The binary package has two main sections. The first part
9254 consists of various control information files and scripts used
9255 by <prgn>dpkg</prgn> when installing and removing. See <ref
9256 id="pkg-controlarea">.
9260 The second part is an archive containing the files and
9261 directories to be installed.
9265 In the future binary packages may also contain other
9266 components, such as checksums and digital signatures. The
9267 format for the archive is described in full in the
9268 <file>deb(5)</file> man page.
9272 <sect id="pkg-bincreating"><heading>Creating package files -
9273 <prgn>dpkg-deb</prgn>
9277 All manipulation of binary package files is done by
9278 <prgn>dpkg-deb</prgn>; it's the only program that has
9279 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9280 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9281 will spot that the options requested are appropriate to
9282 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9287 In order to create a binary package you must make a
9288 directory tree which contains all the files and directories
9289 you want to have in the file system data part of the package.
9290 In Debian-format source packages this directory is usually
9291 <file>debian/tmp</file>, relative to the top of the package's
9296 They should have the locations (relative to the root of the
9297 directory tree you're constructing) ownerships and
9298 permissions which you want them to have on the system when
9303 With current versions of <prgn>dpkg</prgn> the uid/username
9304 and gid/groupname mappings for the users and groups being
9305 used should be the same on the system where the package is
9306 built and the one where it is installed.
9310 You need to add one special directory to the root of the
9311 miniature file system tree you're creating:
9312 <prgn>DEBIAN</prgn>. It should contain the control
9313 information files, notably the binary package control file
9314 (see <ref id="pkg-controlfile">).
9318 The <prgn>DEBIAN</prgn> directory will not appear in the
9319 file system archive of the package, and so won't be installed
9320 by <prgn>dpkg</prgn> when the package is installed.
9324 When you've prepared the package, you should invoke:
9326 dpkg --build <var>directory</var>
9331 This will build the package in
9332 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9333 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9334 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9339 See the man page <manref name="dpkg-deb" section="8"> for details of how
9340 to examine the contents of this newly-created file. You may find the
9341 output of following commands enlightening:
9343 dpkg-deb --info <var>filename</var>.deb
9344 dpkg-deb --contents <var>filename</var>.deb
9345 dpkg --contents <var>filename</var>.deb
9347 To view the copyright file for a package you could use this command:
9349 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9354 <sect id="pkg-controlarea">
9355 <heading>Package control information files</heading>
9358 The control information portion of a binary package is a
9359 collection of files with names known to <prgn>dpkg</prgn>.
9360 It will treat the contents of these files specially - some
9361 of them contain information used by <prgn>dpkg</prgn> when
9362 installing or removing the package; others are scripts which
9363 the package maintainer wants <prgn>dpkg</prgn> to run.
9367 It is possible to put other files in the package control
9368 area, but this is not generally a good idea (though they
9369 will largely be ignored).
9373 Here is a brief list of the control info files supported by
9374 <prgn>dpkg</prgn> and a summary of what they're used for.
9379 <tag><tt>control</tt>
9382 This is the key description file used by
9383 <prgn>dpkg</prgn>. It specifies the package's name
9384 and version, gives its description for the user,
9385 states its relationships with other packages, and so
9386 forth. See <ref id="sourcecontrolfiles"> and
9387 <ref id="binarycontrolfiles">.
9391 It is usually generated automatically from information
9392 in the source package by the
9393 <prgn>dpkg-gencontrol</prgn> program, and with
9394 assistance from <prgn>dpkg-shlibdeps</prgn>.
9395 See <ref id="pkg-sourcetools">.
9399 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9404 These are executable files (usually scripts) which
9405 <prgn>dpkg</prgn> runs during installation, upgrade
9406 and removal of packages. They allow the package to
9407 deal with matters which are particular to that package
9408 or require more complicated processing than that
9409 provided by <prgn>dpkg</prgn>. Details of when and
9410 how they are called are in <ref id="maintainerscripts">.
9414 It is very important to make these scripts idempotent.
9415 See <ref id="idempotency">.
9419 The maintainer scripts are guaranteed to run with a
9420 controlling terminal and can interact with the user.
9421 See <ref id="controllingterminal">.
9425 <tag><tt>conffiles</tt>
9428 This file contains a list of configuration files which
9429 are to be handled automatically by <prgn>dpkg</prgn>
9430 (see <ref id="pkg-conffiles">). Note that not necessarily
9431 every configuration file should be listed here.
9434 <tag><tt>shlibs</tt>
9437 This file contains a list of the shared libraries
9438 supplied by the package, with dependency details for
9439 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9440 when it determines what dependencies are required in a
9441 package control file. The <tt>shlibs</tt> file format
9442 is described on <ref id="shlibs">.
9447 <sect id="pkg-controlfile">
9448 <heading>The main control information file: <tt>control</tt></heading>
9451 The most important control information file used by
9452 <prgn>dpkg</prgn> when it installs a package is
9453 <tt>control</tt>. It contains all the package's "vital
9458 The binary package control files of packages built from
9459 Debian sources are made by a special tool,
9460 <prgn>dpkg-gencontrol</prgn>, which reads
9461 <file>debian/control</file> and <file>debian/changelog</file> to
9462 find the information it needs. See <ref id="pkg-sourcepkg"> for
9467 The fields in binary package control files are listed in
9468 <ref id="binarycontrolfiles">.
9472 A description of the syntax of control files and the purpose
9473 of the fields is available in <ref id="controlfields">.
9478 <heading>Time Stamps</heading>
9481 See <ref id="timestamps">.
9486 <appendix id="pkg-sourcepkg">
9487 <heading>Source packages (from old Packaging Manual) </heading>
9490 The Debian binary packages in the distribution are generated
9491 from Debian sources, which are in a special format to assist
9492 the easy and automatic building of binaries.
9495 <sect id="pkg-sourcetools">
9496 <heading>Tools for processing source packages</heading>
9499 Various tools are provided for manipulating source packages;
9500 they pack and unpack sources and help build of binary
9501 packages and help manage the distribution of new versions.
9505 They are introduced and typical uses described here; see
9506 <manref name="dpkg-source" section="1"> for full
9507 documentation about their arguments and operation.
9511 For examples of how to construct a Debian source package,
9512 and how to use those utilities that are used by Debian
9513 source packages, please see the <prgn>hello</prgn> example
9517 <sect1 id="pkg-dpkg-source">
9519 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9524 This program is frequently used by hand, and is also
9525 called from package-independent automated building scripts
9526 such as <prgn>dpkg-buildpackage</prgn>.
9530 To unpack a package it is typically invoked with
9532 dpkg-source -x <var>.../path/to/filename</var>.dsc
9537 with the <file><var>filename</var>.tar.gz</file> and
9538 <file><var>filename</var>.diff.gz</file> (if applicable) in
9539 the same directory. It unpacks into
9540 <file><var>package</var>-<var>version</var></file>, and if
9542 <file><var>package</var>-<var>version</var>.orig</file>, in
9543 the current directory.
9547 To create a packed source archive it is typically invoked:
9549 dpkg-source -b <var>package</var>-<var>version</var>
9554 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9555 <file>.diff.gz</file> (if appropriate) in the current
9556 directory. <prgn>dpkg-source</prgn> does not clean the
9557 source tree first - this must be done separately if it is
9562 See also <ref id="pkg-sourcearchives">.</p>
9566 <sect1 id="pkg-dpkg-buildpackage">
9568 <prgn>dpkg-buildpackage</prgn> - overall package-building
9573 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9574 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9575 targets <tt>clean</tt>, <tt>build</tt> and
9576 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9577 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9578 source and binary package upload.
9582 It is usually invoked by hand from the top level of the
9583 built or unbuilt source directory. It may be invoked with
9584 no arguments; useful arguments include:
9585 <taglist compact="compact">
9586 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9589 Do not sign the <tt>.changes</tt> file or the
9590 source package <tt>.dsc</tt> file, respectively.</p>
9592 <tag><tt>-p<var>sign-command</var></tt></tag>
9595 Invoke <var>sign-command</var> instead of finding
9596 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9597 <var>sign-command</var> must behave just like
9598 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9600 <tag><tt>-r<var>root-command</var></tt></tag>
9603 When root privilege is required, invoke the command
9604 <var>root-command</var>. <var>root-command</var>
9605 should invoke its first argument as a command, from
9606 the <prgn>PATH</prgn> if necessary, and pass its
9607 second and subsequent arguments to the command it
9608 calls. If no <var>root-command</var> is supplied
9609 then <var>dpkg-buildpackage</var> will take no
9610 special action to gain root privilege, so that for
9611 most packages it will have to be invoked as root to
9614 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9617 Two types of binary-only build and upload - see
9618 <manref name="dpkg-source" section="1">.
9625 <sect1 id="pkg-dpkg-gencontrol">
9627 <prgn>dpkg-gencontrol</prgn> - generates binary package
9632 This program is usually called from <file>debian/rules</file>
9633 (see <ref id="pkg-sourcetree">) in the top level of the source
9638 This is usually done just before the files and directories in the
9639 temporary directory tree where the package is being built have their
9640 permissions and ownerships set and the package is constructed using
9641 <prgn>dpkg-deb/</prgn>
9643 This is so that the control file which is produced has
9644 the right permissions
9649 <prgn>dpkg-gencontrol</prgn> must be called after all the
9650 files which are to go into the package have been placed in
9651 the temporary build directory, so that its calculation of
9652 the installed size of a package is correct.
9656 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9657 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9658 variable substitutions created by
9659 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9664 For a package which generates only one binary package, and
9665 which builds it in <file>debian/tmp</file> relative to the top
9666 of the source package, it is usually sufficient to call
9667 <prgn>dpkg-gencontrol</prgn>.
9671 Sources which build several binaries will typically need
9674 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9675 </example> The <tt>-P</tt> tells
9676 <prgn>dpkg-gencontrol</prgn> that the package is being
9677 built in a non-default directory, and the <tt>-p</tt>
9678 tells it which package's control file should be generated.
9682 <prgn>dpkg-gencontrol</prgn> also adds information to the
9683 list of files in <file>debian/files</file>, for the benefit of
9684 (for example) a future invocation of
9685 <prgn>dpkg-genchanges</prgn>.</p>
9688 <sect1 id="pkg-dpkg-shlibdeps">
9690 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9695 This program is usually called from <file>debian/rules</file>
9696 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9697 id="pkg-sourcetree">), in the top level of the source tree.
9701 Its arguments are executables and shared libraries
9704 They may be specified either in the locations in the
9705 source tree where they are created or in the locations
9706 in the temporary build tree where they are installed
9707 prior to binary package creation.
9709 </footnote> for which shared library dependencies should
9710 be included in the binary package's control file.
9714 If some of the found shared libraries should only
9715 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9716 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9717 by using the <tt>-d<var>dependency-field</var></tt> option
9718 before those executable(s). (Each <tt>-d</tt> option
9719 takes effect until the next <tt>-d</tt>.)
9723 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9724 output control file to be modified. Instead by default it
9725 adds to the <file>debian/substvars</file> file variable
9726 settings like <tt>shlibs:Depends</tt>. These variable
9727 settings must be referenced in dependency fields in the
9728 appropriate per-binary-package sections of the source
9733 For example, a package that generates an essential part
9734 which requires dependencies, and optional parts that
9735 which only require a recommendation, would separate those
9736 two sets of dependencies into two different fields.<footnote>
9737 At the time of writing, an example for this was the
9738 <package/xmms/ package, with Depends used for the xmms
9739 executable, Recommends for the plug-ins and Suggests for
9740 even more optional features provided by unzip.
9742 It can say in its <file>debian/rules</file>:
9744 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9745 -dRecommends <var>optionalpart anotheroptionalpart</var>
9747 and then in its main control file <file>debian/control</file>:
9750 Depends: ${shlibs:Depends}
9751 Recommends: ${shlibs:Recommends}
9757 Sources which produce several binary packages with
9758 different shared library dependency requirements can use
9759 the <tt>-p<var>varnameprefix</var></tt> option to override
9760 the default <tt>shlibs:</tt> prefix (one invocation of
9761 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9762 They can thus produce several sets of dependency
9763 variables, each of the form
9764 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9765 which can be referred to in the appropriate parts of the
9766 binary package control files.
9771 <sect1 id="pkg-dpkg-distaddfile">
9773 <prgn>dpkg-distaddfile</prgn> - adds a file to
9774 <file>debian/files</file>
9778 Some packages' uploads need to include files other than
9779 the source and binary package files.
9783 <prgn>dpkg-distaddfile</prgn> adds a file to the
9784 <file>debian/files</file> file so that it will be included in
9785 the <file>.changes</file> file when
9786 <prgn>dpkg-genchanges</prgn> is run.
9790 It is usually invoked from the <tt>binary</tt> target of
9791 <file>debian/rules</file>:
9793 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9795 The <var>filename</var> is relative to the directory where
9796 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9797 is usually the directory above the top level of the source
9798 tree. The <file>debian/rules</file> target should put the
9799 file there just before or just after calling
9800 <prgn>dpkg-distaddfile</prgn>.
9804 The <var>section</var> and <var>priority</var> are passed
9805 unchanged into the resulting <file>.changes</file> file.
9810 <sect1 id="pkg-dpkg-genchanges">
9812 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9817 This program is usually called by package-independent
9818 automatic building scripts such as
9819 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9824 It is usually called in the top level of a built source
9825 tree, and when invoked with no arguments will print out a
9826 straightforward <file>.changes</file> file based on the
9827 information in the source package's changelog and control
9828 file and the binary and source packages which should have
9834 <sect1 id="pkg-dpkg-parsechangelog">
9836 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9837 representation of a changelog
9841 This program is used internally by
9842 <prgn>dpkg-source</prgn> et al. It may also occasionally
9843 be useful in <file>debian/rules</file> and elsewhere. It
9844 parses a changelog, <file>debian/changelog</file> by default,
9845 and prints a control-file format representation of the
9846 information in it to standard output.
9850 <sect1 id="pkg-dpkg-architecture">
9852 <prgn>dpkg-architecture</prgn> - information about the build and
9857 This program can be used manually, but is also invoked by
9858 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9859 environment or make variables which specify the build and host
9860 architecture for the package building process.
9865 <sect id="pkg-sourcetree">
9866 <heading>The Debianised source tree</heading>
9869 The source archive scheme described later is intended to
9870 allow a Debianised source tree with some associated control
9871 information to be reproduced and transported easily. The
9872 Debianised source tree is a version of the original program
9873 with certain files added for the benefit of the
9874 Debianisation process, and with any other changes required
9875 made to the rest of the source code and installation
9880 The extra files created for Debian are in the subdirectory
9881 <file>debian</file> of the top level of the Debianised source
9882 tree. They are described below.
9885 <sect1 id="pkg-debianrules">
9886 <heading><file>debian/rules</file> - the main building script</heading>
9889 See <ref id="debianrules">.
9894 <sect1 id="pkg-dpkgchangelog">
9895 <heading><file>debian/changelog</file></heading>
9898 See <ref id="dpkgchangelog">.
9901 <sect2><heading>Defining alternative changelog formats
9905 It is possible to use a different format to the standard
9906 one, by providing a parser for the format you wish to
9911 In order to have <tt>dpkg-parsechangelog</tt> run your
9912 parser, you must include a line within the last 40 lines
9913 of your file matching the Perl regular expression:
9914 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9915 parentheses should be the name of the format. For
9916 example, you might say:
9918 @@@ changelog-format: joebloggs @@@
9920 Changelog format names are non-empty strings of alphanumerics.
9924 If such a line exists then <tt>dpkg-parsechangelog</tt>
9925 will look for the parser as
9926 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9928 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9929 it is an error for it not to find it, or for it not to
9930 be an executable program. The default changelog format
9931 is <tt>dpkg</tt>, and a parser for it is provided with
9932 the <tt>dpkg</tt> package.
9936 The parser will be invoked with the changelog open on
9937 standard input at the start of the file. It should read
9938 the file (it may seek if it wishes) to determine the
9939 information required and return the parsed information
9940 to standard output in the form of a series of control
9941 fields in the standard format. By default it should
9942 return information about only the most recent version in
9943 the changelog; it should accept a
9944 <tt>-v<var>version</var></tt> option to return changes
9945 information from all versions present <em>strictly
9946 after</em> <var>version</var>, and it should then be an
9947 error for <var>version</var> not to be present in the
9953 <list compact="compact">
9954 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9955 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9956 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9957 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9958 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9959 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9960 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9965 If several versions are being returned (due to the use
9966 of <tt>-v</tt>), the urgency value should be of the
9967 highest urgency code listed at the start of any of the
9968 versions requested followed by the concatenated
9969 (space-separated) comments from all the versions
9970 requested; the maintainer, version, distribution and
9971 date should always be from the most recent version.
9975 For the format of the <tt>Changes</tt> field see
9976 <ref id="f-Changes">.
9980 If the changelog format which is being parsed always or
9981 almost always leaves a blank line between individual
9982 change notes these blank lines should be stripped out,
9983 so as to make the resulting output compact.
9987 If the changelog format does not contain date or package
9988 name information this information should be omitted from
9989 the output. The parser should not attempt to synthesize
9990 it or find it from other sources.
9994 If the changelog does not have the expected format the
9995 parser should exit with a nonzero exit status, rather
9996 than trying to muddle through and possibly generating
10001 A changelog parser may not interact with the user at
10007 <sect1 id="pkg-srcsubstvars">
10008 <heading><file>debian/substvars</file> and variable substitutions</heading>
10011 See <ref id="substvars">.
10017 <heading><file>debian/files</file></heading>
10020 See <ref id="debianfiles">.
10024 <sect1><heading><file>debian/tmp</file>
10028 This is the canonical temporary location for the
10029 construction of binary packages by the <tt>binary</tt>
10030 target. The directory <file>tmp</file> serves as the root of
10031 the file system tree as it is being constructed (for
10032 example, by using the package's upstream makefiles install
10033 targets and redirecting the output there), and it also
10034 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10035 id="pkg-bincreating">.
10039 If several binary packages are generated from the same
10040 source tree it is usual to use several
10041 <file>debian/tmp<var>something</var></file> directories, for
10042 example <file>tmp-a</file> or <file>tmp-doc</file>.
10046 Whatever <file>tmp</file> directories are created and used by
10047 <tt>binary</tt> must of course be removed by the
10048 <tt>clean</tt> target.</p></sect1>
10052 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10056 As it exists on the FTP site, a Debian source package
10057 consists of three related files. You must have the right
10058 versions of all three to be able to use them.
10063 <tag>Debian source control file - <tt>.dsc</tt></tag>
10065 This file is a control file used by <prgn>dpkg-source</prgn>
10066 to extract a source package.
10067 See <ref id="debiansourcecontrolfiles">.
10071 Original source archive -
10073 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10079 This is a compressed (with <tt>gzip -9</tt>)
10080 <prgn>tar</prgn> file containing the source code from
10081 the upstream authors of the program.
10086 Debianisation diff -
10088 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10094 This is a unified context diff (<tt>diff -u</tt>)
10095 giving the changes which are required to turn the
10096 original source into the Debian source. These changes
10097 may only include editing and creating plain files.
10098 The permissions of files, the targets of symbolic
10099 links and the characteristics of special files or
10100 pipes may not be changed and no files may be removed
10105 All the directories in the diff must exist, except the
10106 <file>debian</file> subdirectory of the top of the source
10107 tree, which will be created by
10108 <prgn>dpkg-source</prgn> if necessary when unpacking.
10112 The <prgn>dpkg-source</prgn> program will
10113 automatically make the <file>debian/rules</file> file
10114 executable (see below).</p></item>
10119 If there is no original source code - for example, if the
10120 package is specially prepared for Debian or the Debian
10121 maintainer is the same as the upstream maintainer - the
10122 format is slightly different: then there is no diff, and the
10124 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10125 and preferably contains a directory named
10126 <file><var>package</var>-<var>version</var></file>.
10131 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10134 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10135 Debian source package. However, if it is not available it
10136 is possible to unpack a Debian source archive as follows:
10137 <enumlist compact="compact">
10140 Untar the tarfile, which will create a <file>.orig</file>
10144 <p>Rename the <file>.orig</file> directory to
10145 <file><var>package</var>-<var>version</var></file>.</p>
10149 Create the subdirectory <file>debian</file> at the top of
10150 the source tree.</p>
10152 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10154 <item><p>Untar the tarfile again if you want a copy of the original
10155 source code alongside the Debianised version.</p>
10160 It is not possible to generate a valid Debian source archive
10161 without using <prgn>dpkg-source</prgn>. In particular,
10162 attempting to use <prgn>diff</prgn> directly to generate the
10163 <file>.diff.gz</file> file will not work.
10167 <heading>Restrictions on objects in source packages</heading>
10170 The source package may not contain any hard links
10172 This is not currently detected when building source
10173 packages, but only when extracting
10177 Hard links may be permitted at some point in the
10178 future, but would require a fair amount of
10180 </footnote>, device special files, sockets or setuid or
10183 Setgid directories are allowed.
10188 The source packaging tools manage the changes between the
10189 original and Debianised source using <prgn>diff</prgn> and
10190 <prgn>patch</prgn>. Turning the original source tree as
10191 included in the <file>.orig.tar.gz</file> into the debianised
10192 source must not involve any changes which cannot be
10193 handled by these tools. Problematic changes which cause
10194 <prgn>dpkg-source</prgn> to halt with an error when
10195 building the source package are:
10196 <list compact="compact">
10197 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10199 <item><p>Changing the targets of symbolic links.</p>
10201 <item><p>Creating directories, other than <file>debian</file>.</p>
10203 <item><p>Changes to the contents of binary files.</p></item>
10204 </list> Changes which cause <prgn>dpkg-source</prgn> to
10205 print a warning but continue anyway are:
10206 <list compact="compact">
10209 Removing files, directories or symlinks.
10211 Renaming a file is not treated specially - it is
10212 seen as the removal of the old file (which
10213 generates a warning, but is otherwise ignored),
10214 and the creation of the new one.
10220 Changed text files which are missing the usual final
10221 newline (either in the original or the modified
10226 Changes which are not represented, but which are not detected by
10227 <prgn>dpkg-source</prgn>, are:
10228 <list compact="compact">
10229 <item><p>Changing the permissions of files (other than
10230 <file>debian/rules</file>) and directories.</p></item>
10235 The <file>debian</file> directory and <file>debian/rules</file>
10236 are handled specially by <prgn>dpkg-source</prgn> - before
10237 applying the changes it will create the <file>debian</file>
10238 directory, and afterwards it will make
10239 <file>debian/rules</file> world-executable.
10245 <appendix id="pkg-controlfields">
10246 <heading>Control files and their fields (from old Packaging Manual)</heading>
10249 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10250 data in a common format, known as control files. Binary and
10251 source packages have control data as do the <file>.changes</file>
10252 files which control the installation of uploaded files, and
10253 <prgn>dpkg</prgn>'s internal databases are in a similar
10258 <heading>Syntax of control files</heading>
10261 See <ref id="controlsyntax">.
10265 It is important to note that there are several fields which
10266 are optional as far as <prgn>dpkg</prgn> and the related
10267 tools are concerned, but which must appear in every Debian
10268 package, or whose omission may cause problems.
10273 <heading>List of fields</heading>
10276 See <ref id="controlfieldslist">.
10280 This section now contains only the fields that didn't belong
10281 to the Policy manual.
10284 <sect1 id="pkg-f-Filename">
10285 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10288 These fields in <tt>Packages</tt> files give the
10289 filename(s) of (the parts of) a package in the
10290 distribution directories, relative to the root of the
10291 Debian hierarchy. If the package has been split into
10292 several parts the parts are all listed in order, separated
10297 <sect1 id="pkg-f-Size">
10298 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10301 These fields in <file>Packages</file> files give the size (in
10302 bytes, expressed in decimal) and MD5 checksum of the
10303 file(s) which make(s) up a binary package in the
10304 distribution. If the package is split into several parts
10305 the values for the parts are listed in order, separated by
10310 <sect1 id="pkg-f-Status">
10311 <heading><tt>Status</tt></heading>
10314 This field in <prgn>dpkg</prgn>'s status file records
10315 whether the user wants a package installed, removed or
10316 left alone, whether it is broken (requiring
10317 re-installation) or not and what its current state on the
10318 system is. Each of these pieces of information is a
10323 <sect1 id="pkg-f-Config-Version">
10324 <heading><tt>Config-Version</tt></heading>
10327 If a package is not installed or not configured, this
10328 field in <prgn>dpkg</prgn>'s status file records the last
10329 version of the package which was successfully
10334 <sect1 id="pkg-f-Conffiles">
10335 <heading><tt>Conffiles</tt></heading>
10338 This field in <prgn>dpkg</prgn>'s status file contains
10339 information about the automatically-managed configuration
10340 files held by a package. This field should <em>not</em>
10341 appear anywhere in a package!
10346 <heading>Obsolete fields</heading>
10349 These are still recognized by <prgn>dpkg</prgn> but should
10350 not appear anywhere any more.
10352 <taglist compact="compact">
10354 <tag><tt>Revision</tt></tag>
10355 <tag><tt>Package-Revision</tt></tag>
10356 <tag><tt>Package_Revision</tt></tag>
10358 The Debian revision part of the package version was
10359 at one point in a separate control file field. This
10360 field went through several names.
10363 <tag><tt>Recommended</tt></tag>
10364 <item>Old name for <tt>Recommends</tt>.</item>
10366 <tag><tt>Optional</tt></tag>
10367 <item>Old name for <tt>Suggests</tt>.</item>
10369 <tag><tt>Class</tt></tag>
10370 <item>Old name for <tt>Priority</tt>.</item>
10379 <appendix id="pkg-conffiles">
10380 <heading>Configuration file handling (from old Packaging Manual)</heading>
10383 <prgn>dpkg</prgn> can do a certain amount of automatic
10384 handling of package configuration files.
10388 Whether this mechanism is appropriate depends on a number of
10389 factors, but basically there are two approaches to any
10390 particular configuration file.
10394 The easy method is to ship a best-effort configuration in the
10395 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10396 handle updates. If the user is unlikely to want to edit the
10397 file, but you need them to be able to without losing their
10398 changes, and a new package with a changed version of the file
10399 is only released infrequently, this is a good approach.
10403 The hard method is to build the configuration file from
10404 scratch in the <prgn>postinst</prgn> script, and to take the
10405 responsibility for fixing any mistakes made in earlier
10406 versions of the package automatically. This will be
10407 appropriate if the file is likely to need to be different on
10411 <sect><heading>Automatic handling of configuration files by
10416 A package may contain a control area file called
10417 <tt>conffiles</tt>. This file should be a list of filenames
10418 of configuration files needing automatic handling, separated
10419 by newlines. The filenames should be absolute pathnames,
10420 and the files referred to should actually exist in the
10425 When a package is upgraded <prgn>dpkg</prgn> will process
10426 the configuration files during the configuration stage,
10427 shortly before it runs the package's <prgn>postinst</prgn>
10432 For each file it checks to see whether the version of the
10433 file included in the package is the same as the one that was
10434 included in the last version of the package (the one that is
10435 being upgraded from); it also compares the version currently
10436 installed on the system with the one shipped with the last
10441 If neither the user nor the package maintainer has changed
10442 the file, it is left alone. If one or the other has changed
10443 their version, then the changed version is preferred - i.e.,
10444 if the user edits their file, but the package maintainer
10445 doesn't ship a different version, the user's changes will
10446 stay, silently, but if the maintainer ships a new version
10447 and the user hasn't edited it the new version will be
10448 installed (with an informative message). If both have
10449 changed their version the user is prompted about the problem
10450 and must resolve the differences themselves.
10454 The comparisons are done by calculating the MD5 message
10455 digests of the files, and storing the MD5 of the file as it
10456 was included in the most recent version of the package.
10460 When a package is installed for the first time
10461 <prgn>dpkg</prgn> will install the file that comes with it,
10462 unless that would mean overwriting a file already on the
10467 However, note that <prgn>dpkg</prgn> will <em>not</em>
10468 replace a conffile that was removed by the user (or by a
10469 script). This is necessary because with some programs a
10470 missing file produces an effect hard or impossible to
10471 achieve in another way, so that a missing file needs to be
10472 kept that way if the user did it.
10476 Note that a package should <em>not</em> modify a
10477 <prgn>dpkg</prgn>-handled conffile in its maintainer
10478 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10479 the user confusing and possibly dangerous options for
10480 conffile update when the package is upgraded.</p>
10483 <sect><heading>Fully-featured maintainer script configuration
10488 For files which contain site-specific information such as
10489 the hostname and networking details and so forth, it is
10490 better to create the file in the package's
10491 <prgn>postinst</prgn> script.
10495 This will typically involve examining the state of the rest
10496 of the system to determine values and other information, and
10497 may involve prompting the user for some information which
10498 can't be obtained some other way.
10502 When using this method there are a couple of important
10503 issues which should be considered:
10507 If you discover a bug in the program which generates the
10508 configuration file, or if the format of the file changes
10509 from one version to the next, you will have to arrange for
10510 the postinst script to do something sensible - usually this
10511 will mean editing the installed configuration file to remove
10512 the problem or change the syntax. You will have to do this
10513 very carefully, since the user may have changed the file,
10514 perhaps to fix the very problem that your script is trying
10515 to deal with - you will have to detect these situations and
10516 deal with them correctly.
10520 If you do go down this route it's probably a good idea to
10521 make the program that generates the configuration file(s) a
10522 separate program in <file>/usr/sbin</file>, by convention called
10523 <file><var>package</var>config</file> and then run that if
10524 appropriate from the post-installation script. The
10525 <tt><var>package</var>config</tt> program should not
10526 unquestioningly overwrite an existing configuration - if its
10527 mode of operation is geared towards setting up a package for
10528 the first time (rather than any arbitrary reconfiguration
10529 later) you should have it check whether the configuration
10530 already exists, and require a <tt>--force</tt> flag to
10531 overwrite it.</p></sect>
10534 <appendix id="pkg-alternatives"><heading>Alternative versions of
10535 an interface - <prgn>update-alternatives</prgn> (from old
10540 When several packages all provide different versions of the
10541 same program or file it is useful to have the system select a
10542 default, but to allow the system administrator to change it
10543 and have their decisions respected.
10547 For example, there are several versions of the <prgn>vi</prgn>
10548 editor, and there is no reason to prevent all of them from
10549 being installed at once, each under their own name
10550 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10551 Nevertheless it is desirable to have the name <tt>vi</tt>
10552 refer to something, at least by default.
10556 If all the packages involved cooperate, this can be done with
10557 <prgn>update-alternatives</prgn>.
10561 Each package provides its own version under its own name, and
10562 calls <prgn>update-alternatives</prgn> in its postinst to
10563 register its version (and again in its prerm to deregister
10568 See the man page <manref name="update-alternatives"
10569 section="8"> for details.
10573 If <prgn>update-alternatives</prgn> does not seem appropriate
10574 you may wish to consider using diversions instead.</p>
10577 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10578 package's version of a file (from old Packaging Manual)
10582 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10583 when it reinstalls the package it belongs to, and to have it
10584 put the file from the package somewhere else instead.
10588 This can be used locally to override a package's version of a
10589 file, or by one package to override another's version (or
10590 provide a wrapper for it).
10594 Before deciding to use a diversion, read <ref
10595 id="pkg-alternatives"> to see if you really want a diversion
10596 rather than several alternative versions of a program.
10600 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10601 and updated by a special program <prgn>dpkg-divert</prgn>.
10602 Please see <manref name="dpkg-divert" section="8"> for full
10603 details of its operation.
10607 When a package wishes to divert a file from another, it should
10608 call <prgn>dpkg-divert</prgn> in its preinst to add the
10609 diversion and rename the existing file. For example,
10610 supposing that a <prgn>smailwrapper</prgn> package wishes to
10611 install a wrapper around <file>/usr/sbin/smail</file>:
10613 dpkg-divert --package smailwrapper --add --rename \
10614 --divert /usr/sbin/smail.real /usr/sbin/smail
10615 </example> The <tt>--package smailwrapper</tt> ensures that
10616 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10617 can bypass the diversion and get installed as the true version.
10618 It's safe to add the diversion unconditionally on upgrades since
10619 it will be left unchanged if it already exists, but
10620 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10621 message, make the command conditional on the version from which
10622 the package is being upgraded:
10624 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10625 dpkg-divert --package smailwrapper --add --rename \
10626 --divert /usr/sbin/smail.real /usr/sbin/smail
10628 </example> where <tt>1.0-2</tt> is the version at which the
10629 diversion was first added to the package. Running the command
10630 during abort-upgrade is pointless but harmless.
10634 The postrm has to do the reverse:
10636 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10637 dpkg-divert --package smailwrapper --remove --rename \
10638 --divert /usr/sbin/smail.real /usr/sbin/smail
10640 </example> If the diversion was added at a particular version, the
10641 postrm should also handle the failure case of upgrading from an
10642 older version (unless the older version is so old that direct
10643 upgrades are no longer supported):
10645 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10646 dpkg-divert --package smailwrapper --remove --rename \
10647 --divert /usr/sbin/smail.real /usr/sbin/smail
10649 </example> where <tt>1.02-2</tt> is the version at which the
10650 diversion was first added to the package. The postrm should not
10651 remove the diversion on upgrades both because there's no reason to
10652 remove the diversion only to immediately re-add it and since the
10653 postrm of the old package is run after unpacking so the removal of
10654 the diversion will fail.
10658 Do not attempt to divert a file which is vitally important for
10659 the system's operation - when using <prgn>dpkg-divert</prgn>
10660 there is a time, after it has been diverted but before
10661 <prgn>dpkg</prgn> has installed the new version, when the file
10662 does not exist.</p>
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