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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 the distribution
322 areas or components<footnote>
323 The Debian archive software uses the term "component" internally
324 and in the Release file format to refer to the division of an
325 archive. The Debian Social Contract refers to distribution
326 areas. This document uses the same terminology as the Social
328 </footnote> based on their licenses and other restrictions.
332 The aims of this are:
334 <list compact="compact">
335 <item>to allow us to make as much software available as we can</item>
336 <item>to allow us to encourage everyone to write free software,
338 <item>to allow us to make it easy for people to produce
339 CD-ROMs of our system without violating any licenses,
340 import/export restrictions, or any other laws.</item>
345 The <em>main</em> distribution area forms the <em>Debian GNU/Linux
350 Packages in the other distribution areas (<tt>contrib</tt>,
351 <tt>non-free</tt>) are not considered to be part of the Debian
352 distribution, although we support their use and provide
353 infrastructure for them (such as our bug-tracking system and
354 mailing lists). This Debian Policy Manual applies to these
359 <heading>The Debian Free Software Guidelines</heading>
361 The Debian Free Software Guidelines (DFSG) form our
362 definition of "free software". These are:
364 <tag>Free Redistribution
367 The license of a Debian component may not restrict any
368 party from selling or giving away the software as a
369 component of an aggregate software distribution
370 containing programs from several different
371 sources. The license may not require a royalty or
372 other fee for such sale.
377 The program must include source code, and must allow
378 distribution in source code as well as compiled form.
383 The license must allow modifications and derived
384 works, and must allow them to be distributed under the
385 same terms as the license of the original software.
387 <tag>Integrity of The Author's Source Code
390 The license may restrict source-code from being
391 distributed in modified form <em>only</em> if the
392 license allows the distribution of "patch files"
393 with the source code for the purpose of modifying the
394 program at build time. The license must explicitly
395 permit distribution of software built from modified
396 source code. The license may require derived works to
397 carry a different name or version number from the
398 original software. (This is a compromise. The Debian
399 Project encourages all authors to not restrict any
400 files, source or binary, from being modified.)
402 <tag>No Discrimination Against Persons or Groups
405 The license must not discriminate against any person
408 <tag>No Discrimination Against Fields of Endeavor
411 The license must not restrict anyone from making use
412 of the program in a specific field of endeavor. For
413 example, it may not restrict the program from being
414 used in a business, or from being used for genetic
417 <tag>Distribution of License
420 The rights attached to the program must apply to all
421 to whom the program is redistributed without the need
422 for execution of an additional license by those
425 <tag>License Must Not Be Specific to Debian
428 The rights attached to the program must not depend on
429 the program's being part of a Debian system. If the
430 program is extracted from Debian and used or
431 distributed without Debian but otherwise within the
432 terms of the program's license, all parties to whom
433 the program is redistributed must have the same
434 rights as those that are granted in conjunction with
437 <tag>License Must Not Contaminate Other Software
440 The license must not place restrictions on other
441 software that is distributed along with the licensed
442 software. For example, the license must not insist
443 that all other programs distributed on the same medium
444 must be free software.
446 <tag>Example Licenses
449 The "GPL," "BSD," and "Artistic" licenses are examples of
450 licenses that we consider <em>free</em>.
457 <heading>Distribution areas</heading>
460 <heading>The main distribution area</heading>
463 Every package in <em>main</em> must comply with the DFSG
464 (Debian Free Software Guidelines).
468 In addition, the packages in <em>main</em>
469 <list compact="compact">
471 must not require a package outside of <em>main</em>
472 for compilation or execution (thus, the package must
473 not declare a "Depends", "Recommends", or
474 "Build-Depends" relationship on a non-<em>main</em>
478 must not be so buggy that we refuse to support them,
482 must meet all policy requirements presented in this
491 <heading>The contrib distribution area</heading>
494 Every package in <em>contrib</em> must comply with the DFSG.
498 In addition, the packages in <em>contrib</em>
499 <list compact="compact">
501 must not be so buggy that we refuse to support them,
505 must meet all policy requirements presented in this
513 Examples of packages which would be included in
514 <em>contrib</em> are:
515 <list compact="compact">
517 free packages which require <em>contrib</em>,
518 <em>non-free</em> packages or packages which are not
519 in our archive at all for compilation or execution,
523 wrapper packages or other sorts of free accessories for
530 <sect1 id="non-free">
531 <heading>The non-free distribution area</heading>
534 Packages must be placed in <em>non-free</em> if they are
535 not compliant with the DFSG or are encumbered by patents
536 or other legal issues that make their distribution
541 In addition, the packages in <em>non-free</em>
542 <list compact="compact">
544 must not be so buggy that we refuse to support them,
548 must meet all policy requirements presented in this
549 manual that it is possible for them to meet.
551 It is possible that there are policy
552 requirements which the package is unable to
553 meet, for example, if the source is
554 unavailable. These situations will need to be
555 handled on a case-by-case basis.
564 <sect id="pkgcopyright">
565 <heading>Copyright considerations</heading>
568 Every package must be accompanied by a verbatim copy of
569 its copyright and distribution license in the file
570 <file>/usr/share/doc/<var>package</var>/copyright</file>
571 (see <ref id="copyrightfile"> for further details).
575 We reserve the right to restrict files from being included
576 anywhere in our archives if
577 <list compact="compact">
579 their use or distribution would break a law,
582 there is an ethical conflict in their distribution or
586 we would have to sign a license for them, or
589 their distribution would conflict with other project
596 Programs whose authors encourage the user to make
597 donations are fine for the main distribution, provided
598 that the authors do not claim that not donating is
599 immoral, unethical, illegal or something similar; in such
600 a case they must go in <em>non-free</em>.
604 Packages whose copyright permission notices (or patent
605 problems) do not even allow redistribution of binaries
606 only, and where no special permission has been obtained,
607 must not be placed on the Debian FTP site and its mirrors
612 Note that under international copyright law (this applies
613 in the United States, too), <em>no</em> distribution or
614 modification of a work is allowed without an explicit
615 notice saying so. Therefore a program without a copyright
616 notice <em>is</em> copyrighted and you may not do anything
617 to it without risking being sued! Likewise if a program
618 has a copyright notice but no statement saying what is
619 permitted then nothing is permitted.
623 Many authors are unaware of the problems that restrictive
624 copyrights (or lack of copyright notices) can cause for
625 the users of their supposedly-free software. It is often
626 worthwhile contacting such authors diplomatically to ask
627 them to modify their license terms. However, this can be a
628 politically difficult thing to do and you should ask for
629 advice on the <tt>debian-legal</tt> mailing list first, as
634 When in doubt about a copyright, send mail to
635 <email>debian-legal@lists.debian.org</email>. Be prepared
636 to provide us with the copyright statement. Software
637 covered by the GPL, public domain software and BSD-like
638 copyrights are safe; be wary of the phrases "commercial
639 use prohibited" and "distribution restricted".
643 <sect id="subsections">
644 <heading>Sections</heading>
647 The packages in the distribution areas <em>main</em>,
648 <em>contrib</em> and <em>non-free</em> are grouped further
649 into <em>sections</em> to simplify handling.
653 The distribution area and section for each package should be
654 specified in the package's <tt>Section</tt> control record
655 (see <ref id="f-Section">). However, the maintainer of the
656 Debian archive may override this selection to ensure the
657 consistency of the Debian distribution. The
658 <tt>Section</tt> field should be of the form:
659 <list compact="compact">
661 <em>section</em> if the package is in the
662 <em>main</em> distribution area,
665 <em>area/section</em> if the package is in
666 the <em>contrib</em> or <em>non-free</em>
673 The Debian archive maintainers provide the authoritative
674 list of sections. At present, they are:
675 <em>admin</em>, <em>comm</em>,
676 <em>devel</em>, <em>doc</em>,
677 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
678 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
679 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
680 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
681 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
683 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
684 <em>science</em>, <em>shells</em>,
685 <em>sound</em>, <em>tex</em>, <em>text</em>,
686 <em>utils</em>, <em>web</em>, <em>x11</em>.
690 <sect id="priorities">
691 <heading>Priorities</heading>
694 Each package should have a <em>priority</em> value, which is
695 included in the package's <em>control record</em>
696 (see <ref id="f-Priority">).
697 This information is used by the Debian package management tools to
698 separate high-priority packages from less-important packages.
702 The following <em>priority levels</em> are recognized by the
703 Debian package management tools.
705 <tag><tt>required</tt></tag>
707 Packages which are necessary for the proper
708 functioning of the system (usually, this means that
709 dpkg functionality depends on these packages).
710 Removing a <tt>required</tt> package may cause your
711 system to become totally broken and you may not even
712 be able to use <prgn>dpkg</prgn> to put things back,
713 so only do so if you know what you are doing. Systems
714 with only the <tt>required</tt> packages are probably
715 unusable, but they do have enough functionality to
716 allow the sysadmin to boot and install more software.
718 <tag><tt>important</tt></tag>
720 Important programs, including those which one would
721 expect to find on any Unix-like system. If the
722 expectation is that an experienced Unix person who
723 found it missing would say "What on earth is going on,
724 where is <prgn>foo</prgn>?", it must be an
725 <tt>important</tt> package.<footnote>
726 This is an important criterion because we are
727 trying to produce, amongst other things, a free
730 Other packages without which the system will not run
731 well or be usable must also have priority
732 <tt>important</tt>. This does
733 <em>not</em> include Emacs, the X Window System, TeX
734 or any other large applications. The
735 <tt>important</tt> packages are just a bare minimum of
736 commonly-expected and necessary tools.
738 <tag><tt>standard</tt></tag>
740 These packages provide a reasonably small but not too
741 limited character-mode system. This is what will be
742 installed by default if the user doesn't select anything
743 else. It doesn't include many large applications.
745 <tag><tt>optional</tt></tag>
747 (In a sense everything that isn't required is
748 optional, but that's not what is meant here.) This is
749 all the software that you might reasonably want to
750 install if you didn't know what it was and don't have
751 specialized requirements. This is a much larger system
752 and includes the X Window System, a full TeX
753 distribution, and many applications. Note that
754 optional packages should not conflict with each other.
756 <tag><tt>extra</tt></tag>
758 This contains all packages that conflict with others
759 with required, important, standard or optional
760 priorities, or are only likely to be useful if you
761 already know what they are or have specialized
762 requirements (such as packages containing only detached
769 Packages must not depend on packages with lower priority
770 values (excluding build-time dependencies). In order to
771 ensure this, the priorities of one or more packages may need
780 <heading>Binary packages</heading>
783 The Debian GNU/Linux distribution is based on the Debian
784 package management system, called <prgn>dpkg</prgn>. Thus,
785 all packages in the Debian distribution must be provided
786 in the <tt>.deb</tt> file format.
790 <heading>The package name</heading>
793 Every package must have a name that's unique within the Debian
798 The package name is included in the control field
799 <tt>Package</tt>, the format of which is described
800 in <ref id="f-Package">.
801 The package name is also included as a part of the file name
802 of the <tt>.deb</tt> file.
807 <heading>The version of a package</heading>
810 Every package has a version number recorded in its
811 <tt>Version</tt> control file field, described in
812 <ref id="f-Version">.
816 The package management system imposes an ordering on version
817 numbers, so that it can tell whether packages are being up- or
818 downgraded and so that package system front end applications
819 can tell whether a package it finds available is newer than
820 the one installed on the system. The version number format
821 has the most significant parts (as far as comparison is
822 concerned) at the beginning.
826 If an upstream package has problematic version numbers they
827 should be converted to a sane form for use in the
828 <tt>Version</tt> field.
832 <heading>Version numbers based on dates</heading>
835 In general, Debian packages should use the same version
836 numbers as the upstream sources.
840 However, in some cases where the upstream version number is
841 based on a date (e.g., a development "snapshot" release) the
842 package management system cannot handle these version
843 numbers without epochs. For example, dpkg will consider
844 "96May01" to be greater than "96Dec24".
848 To prevent having to use epochs for every new upstream
849 version, the date based portion of the version number
850 should be changed to the following format in such cases:
851 "19960501", "19961224". It is up to the maintainer whether
852 they want to bother the upstream maintainer to change
853 the version numbers upstream, too.
857 Note that other version formats based on dates which are
858 parsed correctly by the package management system should
859 <em>not</em> be changed.
863 Native Debian packages (i.e., packages which have been
864 written especially for Debian) whose version numbers include
865 dates should always use the "YYYYMMDD" format.
872 <heading>The maintainer of a package</heading>
875 Every package must have a Debian maintainer (the
876 maintainer may be one person or a group of people
877 reachable from a common email address, such as a mailing
878 list). The maintainer is responsible for ensuring that
879 the package is placed in the appropriate distributions.
883 The maintainer must be specified in the
884 <tt>Maintainer</tt> control field with their correct name
885 and a working email address. If one person maintains
886 several packages, they should try to avoid having
887 different forms of their name and email address in
888 the <tt>Maintainer</tt> fields of those packages.
892 The format of the <tt>Maintainer</tt> control field is
893 described in <ref id="f-Maintainer">.
897 If the maintainer of a package quits from the Debian
898 project, "Debian QA Group"
899 <email>packages@qa.debian.org</email> takes over the
900 maintainer-ship of the package until someone else
901 volunteers for that task. These packages are called
902 <em>orphaned packages</em>.<footnote>
903 The detailed procedure for doing this gracefully can
904 be found in the Debian Developer's Reference,
905 see <ref id="related">.
910 <sect id="descriptions">
911 <heading>The description of a package</heading>
914 Every Debian package must have an extended description
915 stored in the appropriate field of the control record.
916 The technical information about the format of the
917 <tt>Description</tt> field is in <ref id="f-Description">.
921 The description should describe the package (the program) to a
922 user (system administrator) who has never met it before so that
923 they have enough information to decide whether they want to
924 install it. This description should not just be copied verbatim
925 from the program's documentation.
929 Put important information first, both in the synopsis and
930 extended description. Sometimes only the first part of the
931 synopsis or of the description will be displayed. You can
932 assume that there will usually be a way to see the whole
933 extended description.
937 The description should also give information about the
938 significant dependencies and conflicts between this package
939 and others, so that the user knows why these dependencies and
940 conflicts have been declared.
944 Instructions for configuring or using the package should
945 not be included (that is what installation scripts,
946 manual pages, info files, etc., are for). Copyright
947 statements and other administrivia should not be included
948 either (that is what the copyright file is for).
951 <sect1 id="synopsis"><heading>The single line synopsis</heading>
954 The single line synopsis should be kept brief - certainly
959 Do not include the package name in the synopsis line. The
960 display software knows how to display this already, and you
961 do not need to state it. Remember that in many situations
962 the user may only see the synopsis line - make it as
963 informative as you can.
968 <sect1 id="extendeddesc"><heading>The extended description</heading>
971 Do not try to continue the single line synopsis into the
972 extended description. This will not work correctly when
973 the full description is displayed, and makes no sense
974 where only the summary (the single line synopsis) is
979 The extended description should describe what the package
980 does and how it relates to the rest of the system (in terms
981 of, for example, which subsystem it is which part of).
985 The description field needs to make sense to anyone, even
986 people who have no idea about any of the things the
987 package deals with.<footnote>
988 The blurb that comes with a program in its
989 announcements and/or <prgn>README</prgn> files is
990 rarely suitable for use in a description. It is
991 usually aimed at people who are already in the
992 community where the package is used.
1001 <heading>Dependencies</heading>
1004 Every package must specify the dependency information
1005 about other packages that are required for the first to
1010 For example, a dependency entry must be provided for any
1011 shared libraries required by a dynamically-linked executable
1012 binary in a package.
1016 Packages are not required to declare any dependencies they
1017 have on other packages which are marked <tt>Essential</tt>
1018 (see below), and should not do so unless they depend on a
1019 particular version of that package.<footnote>
1021 Essential is needed in part to avoid unresolvable dependency
1022 loops on upgrade. If packages add unnecessary dependencies
1023 on packages in this set, the chances that there
1024 <strong>will</strong> be an unresolvable dependency loop
1025 caused by forcing these Essential packages to be configured
1026 first before they need to be is greatly increased. It also
1027 increases the chances that frontends will be unable to
1028 <strong>calculate</strong> an upgrade path, even if one
1032 Also, functionality is rarely ever removed from the
1033 Essential set, but <em>packages</em> have been removed from
1034 the Essential set when the functionality moved to a
1035 different package. So depending on these packages <em>just
1036 in case</em> they stop being essential does way more harm
1043 Sometimes, a package requires another package to be installed
1044 <em>and</em> configured before it can be installed. In this
1045 case, you must specify a <tt>Pre-Depends</tt> entry for
1050 You should not specify a <tt>Pre-Depends</tt> entry for a
1051 package before this has been discussed on the
1052 <tt>debian-devel</tt> mailing list and a consensus about
1053 doing that has been reached.
1057 The format of the package interrelationship control fields is
1058 described in <ref id="relationships">.
1062 <sect id="virtual_pkg">
1063 <heading>Virtual packages</heading>
1066 Sometimes, there are several packages which offer
1067 more-or-less the same functionality. In this case, it's
1068 useful to define a <em>virtual package</em> whose name
1069 describes that common functionality. (The virtual
1070 packages only exist logically, not physically; that's why
1071 they are called <em>virtual</em>.) The packages with this
1072 particular function will then <em>provide</em> the virtual
1073 package. Thus, any other package requiring that function
1074 can simply depend on the virtual package without having to
1075 specify all possible packages individually.
1079 All packages should use virtual package names where
1080 appropriate, and arrange to create new ones if necessary.
1081 They should not use virtual package names (except privately,
1082 amongst a cooperating group of packages) unless they have
1083 been agreed upon and appear in the list of virtual package
1084 names. (See also <ref id="virtual">)
1088 The latest version of the authoritative list of virtual
1089 package names can be found in the <tt>debian-policy</tt> package.
1090 It is also available from the Debian web mirrors at
1091 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1092 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1096 The procedure for updating the list is described in the preface
1103 <heading>Base system</heading>
1106 The <tt>base system</tt> is a minimum subset of the Debian
1107 GNU/Linux system that is installed before everything else
1108 on a new system. Only very few packages are allowed to form
1109 part of the base system, in order to keep the required disk
1114 The base system consists of all those packages with priority
1115 <tt>required</tt> or <tt>important</tt>. Many of them will
1116 be tagged <tt>essential</tt> (see below).
1121 <heading>Essential packages</heading>
1124 Essential is defined as the minimal set of functionality that
1125 must be available and usable on the system at all times, even
1126 when packages are in an unconfigured (but unpacked) state.
1127 Packages are tagged <tt>essential</tt> for a system using the
1128 <tt>Essential</tt> control file field. The format of the
1129 <tt>Essential</tt> control field is described in <ref
1134 Since these packages cannot be easily removed (one has to
1135 specify an extra <em>force option</em> to
1136 <prgn>dpkg</prgn> to do so), this flag must not be used
1137 unless absolutely necessary. A shared library package
1138 must not be tagged <tt>essential</tt>; dependencies will
1139 prevent its premature removal, and we need to be able to
1140 remove it when it has been superseded.
1144 Since dpkg will not prevent upgrading of other packages
1145 while an <tt>essential</tt> package is in an unconfigured
1146 state, all <tt>essential</tt> packages must supply all of
1147 their core functionality even when unconfigured. If the
1148 package cannot satisfy this requirement it must not be
1149 tagged as essential, and any packages depending on this
1150 package must instead have explicit dependency fields as
1155 Maintainers should take great care in adding any programs,
1156 interfaces, or functionality to <tt>essential</tt> packages.
1157 Packages may assume that functionality provided by
1158 <tt>essential</tt> packages is always available without
1159 declaring explicit dependencies, which means that removing
1160 functionality from the Essential set is very difficult and is
1161 almost never done. Any capability added to an
1162 <tt>essential</tt> package therefore creates an obligation to
1163 support that capability as part of the Essential set in
1168 You must not tag any packages <tt>essential</tt> before
1169 this has been discussed on the <tt>debian-devel</tt>
1170 mailing list and a consensus about doing that has been
1175 <sect id="maintscripts">
1176 <heading>Maintainer Scripts</heading>
1179 The package installation scripts should avoid producing
1180 output which is unnecessary for the user to see and
1181 should rely on <prgn>dpkg</prgn> to stave off boredom on
1182 the part of a user installing many packages. This means,
1183 amongst other things, using the <tt>--quiet</tt> option on
1184 <prgn>install-info</prgn>.
1188 Errors which occur during the execution of an installation
1189 script must be checked and the installation must not
1190 continue after an error.
1194 Note that in general <ref id="scripts"> applies to package
1195 maintainer scripts, too.
1199 You should not use <prgn>dpkg-divert</prgn> on a file
1200 belonging to another package without consulting the
1201 maintainer of that package first.
1205 All packages which supply an instance of a common command
1206 name (or, in general, filename) should generally use
1207 <prgn>update-alternatives</prgn>, so that they may be
1208 installed together. If <prgn>update-alternatives</prgn>
1209 is not used, then each package must use
1210 <tt>Conflicts</tt> to ensure that other packages are
1211 de-installed. (In this case, it may be appropriate to
1212 specify a conflict against earlier versions of something
1213 that previously did not use
1214 <prgn>update-alternatives</prgn>; this is an exception to
1215 the usual rule that versioned conflicts should be
1219 <sect1 id="maintscriptprompt">
1220 <heading>Prompting in maintainer scripts</heading>
1222 Package maintainer scripts may prompt the user if
1223 necessary. Prompting should be done by communicating
1224 through a program, such as <prgn>debconf</prgn>, which
1225 conforms to the Debian Configuration Management
1226 Specification, version 2 or higher. Prompting the user by
1227 other means, such as by hand<footnote>
1228 From the Jargon file: by hand 2. By extension,
1229 writing code which does something in an explicit or
1230 low-level way for which a presupplied library
1231 (<em>debconf, in this instance</em>) routine ought
1232 to have been available.
1233 </footnote>, is now deprecated.
1237 The Debian Configuration Management Specification is included
1238 in the <file>debconf_specification</file> files in the
1239 <package>debian-policy</package> package.
1240 It is also available from the Debian web mirrors at
1241 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1242 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1246 Packages which use the Debian Configuration Management
1247 Specification may contain an additional
1248 <prgn>config</prgn> script and a <tt>templates</tt>
1249 file in their control archive<footnote>
1250 The control.tar.gz inside the .deb.
1251 See <manref name="deb" section="5">.
1253 The <prgn>config</prgn> script might be run before the
1254 <prgn>preinst</prgn> script, and before the package is unpacked
1255 or any of its dependencies or pre-dependencies are satisfied.
1256 Therefore it must work using only the tools present in
1257 <em>essential</em> packages.<footnote>
1258 <package>Debconf</package> or another tool that
1259 implements the Debian Configuration Management
1260 Specification will also be installed, and any
1261 versioned dependencies on it will be satisfied
1262 before preconfiguration begins.
1267 Packages which use the Debian Configuration Management
1268 Specification must allow for translation of their user-visible
1269 messages by using a gettext-based system such as the one
1270 provided by the <package>po-debconf</package> package.
1274 Packages should try to minimize the amount of prompting
1275 they need to do, and they should ensure that the user
1276 will only ever be asked each question once. This means
1277 that packages should try to use appropriate shared
1278 configuration files (such as <file>/etc/papersize</file> and
1279 <file>/etc/news/server</file>), and shared
1280 <package>debconf</package> variables rather than each
1281 prompting for their own list of required pieces of
1286 It also means that an upgrade should not ask the same
1287 questions again, unless the user has used
1288 <tt>dpkg --purge</tt> to remove the package's configuration.
1289 The answers to configuration questions should be stored in an
1290 appropriate place in <file>/etc</file> so that the user can
1291 modify them, and how this has been done should be
1296 If a package has a vitally important piece of
1297 information to pass to the user (such as "don't run me
1298 as I am, you must edit the following configuration files
1299 first or you risk your system emitting badly-formatted
1300 messages"), it should display this in the
1301 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1302 prompt the user to hit return to acknowledge the
1303 message. Copyright messages do not count as vitally
1304 important (they belong in
1305 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1306 neither do instructions on how to use a program (these
1307 should be in on-line documentation, where all the users
1312 Any necessary prompting should almost always be confined
1313 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1314 script. If it is done in the <prgn>postinst</prgn>, it
1315 should be protected with a conditional so that
1316 unnecessary prompting doesn't happen if a package's
1317 installation fails and the <prgn>postinst</prgn> is
1318 called with <tt>abort-upgrade</tt>,
1319 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1329 <heading>Source packages</heading>
1331 <sect id="standardsversion">
1332 <heading>Standards conformance</heading>
1335 Source packages should specify the most recent version number
1336 of this policy document with which your package complied
1337 when it was last updated.
1341 This information may be used to file bug reports
1342 automatically if your package becomes too much out of date.
1346 The version is specified in the <tt>Standards-Version</tt>
1348 The format of the <tt>Standards-Version</tt> field is
1349 described in <ref id="f-Standards-Version">.
1353 You should regularly, and especially if your package has
1354 become out of date, check for the newest Policy Manual
1355 available and update your package, if necessary. When your
1356 package complies with the new standards you should update the
1357 <tt>Standards-Version</tt> source package field and
1358 release it.<footnote>
1359 See the file <file>upgrading-checklist</file> for
1360 information about policy which has changed between
1361 different versions of this document.
1367 <sect id="pkg-relations">
1368 <heading>Package relationships</heading>
1371 Source packages should specify which binary packages they
1372 require to be installed or not to be installed in order to
1373 build correctly. For example, if building a package
1374 requires a certain compiler, then the compiler should be
1375 specified as a build-time dependency.
1379 It is not necessary to explicitly specify build-time
1380 relationships on a minimal set of packages that are always
1381 needed to compile, link and put in a Debian package a
1382 standard "Hello World!" program written in C or C++. The
1383 required packages are called <em>build-essential</em>, and
1384 an informational list can be found in
1385 <file>/usr/share/doc/build-essential/list</file> (which is
1386 contained in the <tt>build-essential</tt>
1389 <list compact="compact">
1391 This allows maintaining the list separately
1392 from the policy documents (the list does not
1393 need the kind of control that the policy
1397 Having a separate package allows one to install
1398 the build-essential packages on a machine, as
1399 well as allowing other packages such as tasks to
1400 require installation of the build-essential
1401 packages using the depends relation.
1404 The separate package allows bug reports against
1405 the list to be categorized separately from
1406 the policy management process in the BTS.
1413 When specifying the set of build-time dependencies, one
1414 should list only those packages explicitly required by the
1415 build. It is not necessary to list packages which are
1416 required merely because some other package in the list of
1417 build-time dependencies depends on them.<footnote>
1418 The reason for this is that dependencies change, and
1419 you should list all those packages, and <em>only</em>
1420 those packages that <em>you</em> need directly. What
1421 others need is their business. For example, if you
1422 only link against <file>libimlib</file>, you will need to
1423 build-depend on <package>libimlib2-dev</package> but
1424 not against any <tt>libjpeg*</tt> packages, even
1425 though <tt>libimlib2-dev</tt> currently depends on
1426 them: installation of <package>libimlib2-dev</package>
1427 will automatically ensure that all of its run-time
1428 dependencies are satisfied.
1433 If build-time dependencies are specified, it must be
1434 possible to build the package and produce working binaries
1435 on a system with only essential and build-essential
1436 packages installed and also those required to satisfy the
1437 build-time relationships (including any implied
1438 relationships). In particular, this means that version
1439 clauses should be used rigorously in build-time
1440 relationships so that one cannot produce bad or
1441 inconsistently configured packages when the relationships
1442 are properly satisfied.
1446 <ref id="relationships"> explains the technical details.
1451 <heading>Changes to the upstream sources</heading>
1454 If changes to the source code are made that are not
1455 specific to the needs of the Debian system, they should be
1456 sent to the upstream authors in whatever form they prefer
1457 so as to be included in the upstream version of the
1462 If you need to configure the package differently for
1463 Debian or for Linux, and the upstream source doesn't
1464 provide a way to do so, you should add such configuration
1465 facilities (for example, a new <prgn>autoconf</prgn> test
1466 or <tt>#define</tt>) and send the patch to the upstream
1467 authors, with the default set to the way they originally
1468 had it. You can then easily override the default in your
1469 <file>debian/rules</file> or wherever is appropriate.
1473 You should make sure that the <prgn>configure</prgn> utility
1474 detects the correct architecture specification string
1475 (refer to <ref id="arch-spec"> for details).
1479 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1480 <prgn>configure</prgn> scripts are used, you should edit the
1481 <file>.in</file> files rather than editing the
1482 <prgn>Makefile</prgn> directly. This allows the user to
1483 reconfigure the package if necessary. You should
1484 <em>not</em> configure the package and edit the generated
1485 <prgn>Makefile</prgn>! This makes it impossible for someone
1486 else to later reconfigure the package without losing the
1492 <sect id="dpkgchangelog">
1493 <heading>Debian changelog: <file>debian/changelog</file></heading>
1496 Changes in the Debian version of the package should be
1497 briefly explained in the Debian changelog file
1498 <file>debian/changelog</file>.<footnote>
1500 Mistakes in changelogs are usually best rectified by
1501 making a new changelog entry rather than "rewriting
1502 history" by editing old changelog entries.
1505 This includes modifications
1506 made in the Debian package compared to the upstream one
1507 as well as other changes and updates to the package.
1509 Although there is nothing stopping an author who is also
1510 the Debian maintainer from using this changelog for all
1511 their changes, it will have to be renamed if the Debian
1512 and upstream maintainers become different people. In such
1513 a case, however, it might be better to maintain the package
1514 as a non-native package.
1519 The format of the <file>debian/changelog</file> allows the
1520 package building tools to discover which version of the package
1521 is being built and find out other release-specific information.
1525 That format is a series of entries like this:
1527 <example compact="compact">
1528 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1530 [optional blank line(s), stripped]
1532 * <var>change details</var>
1533 <var>more change details</var>
1535 [blank line(s), included in output of dpkg-parsechangelog]
1537 * <var>even more change details</var>
1539 [optional blank line(s), stripped]
1541 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1546 <var>package</var> and <var>version</var> are the source
1547 package name and version number.
1551 <var>distribution(s)</var> lists the distributions where
1552 this version should be installed when it is uploaded - it
1553 is copied to the <tt>Distribution</tt> field in the
1554 <file>.changes</file> file. See <ref id="f-Distribution">.
1558 <var>urgency</var> is the value for the <tt>Urgency</tt>
1559 field in the <file>.changes</file> file for the upload
1560 (see <ref id="f-Urgency">). It is not possible to specify
1561 an urgency containing commas; commas are used to separate
1562 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1563 <prgn>dpkg</prgn> changelog format (though there is
1564 currently only one useful <var>keyword</var>,
1569 The change details may in fact be any series of lines
1570 starting with at least two spaces, but conventionally each
1571 change starts with an asterisk and a separating space and
1572 continuation lines are indented so as to bring them in
1573 line with the start of the text above. Blank lines may be
1574 used here to separate groups of changes, if desired.
1578 If this upload resolves bugs recorded in the Bug Tracking
1579 System (BTS), they may be automatically closed on the
1580 inclusion of this package into the Debian archive by
1581 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1582 in the change details.<footnote>
1583 To be precise, the string should match the following
1584 Perl regular expression:
1586 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1588 Then all of the bug numbers listed will be closed by the
1589 archive maintenance script (<prgn>katie</prgn>) using the
1590 <var>version</var> of the changelog entry.
1592 This information is conveyed via the <tt>Closes</tt> field
1593 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1597 The maintainer name and email address used in the changelog
1598 should be the details of the person uploading <em>this</em>
1599 version. They are <em>not</em> necessarily those of the
1600 usual package maintainer. The information here will be
1601 copied to the <tt>Changed-By</tt> field in the
1602 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1603 and then later used to send an acknowledgement when the
1604 upload has been installed.
1608 The <var>date</var> must be in RFC822 format<footnote>
1609 This is generated by <tt>date -R</tt>.
1610 </footnote>; it must include the time zone specified
1611 numerically, with the time zone name or abbreviation
1612 optionally present as a comment in parentheses.
1616 The first "title" line with the package name must start
1617 at the left hand margin. The "trailer" line with the
1618 maintainer and date details must be preceded by exactly
1619 one space. The maintainer details and the date must be
1620 separated by exactly two spaces.
1624 The entire changelog must be encoded in UTF-8.
1628 For more information on placement of the changelog files
1629 within binary packages, please see <ref id="changelogs">.
1633 <sect id="dpkgcopyright">
1634 <heading>Copyright: <file>debian/copyright</file></heading>
1636 Every package must be accompanied by a verbatim copy of
1637 its copyright and distribution license in the file
1638 <file>/usr/share/doc/<var>package</var>/copyright</file>
1639 (see <ref id="copyrightfile"> for further details). Also see
1640 <ref id="pkgcopyright"> for further considerations relayed
1641 to copyrights for packages.
1645 <heading>Error trapping in makefiles</heading>
1648 When <prgn>make</prgn> invokes a command in a makefile
1649 (including your package's upstream makefiles and
1650 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1651 means that <prgn>sh</prgn>'s usual bad error handling
1652 properties apply: if you include a miniature script as one
1653 of the commands in your makefile you'll find that if you
1654 don't do anything about it then errors are not detected
1655 and <prgn>make</prgn> will blithely continue after
1660 Every time you put more than one shell command (this
1661 includes using a loop) in a makefile command you
1662 must make sure that errors are trapped. For
1663 simple compound commands, such as changing directory and
1664 then running a program, using <tt>&&</tt> rather
1665 than semicolon as a command separator is sufficient. For
1666 more complex commands including most loops and
1667 conditionals you should include a separate <tt>set -e</tt>
1668 command at the start of every makefile command that's
1669 actually one of these miniature shell scripts.
1673 <sect id="timestamps">
1674 <heading>Time Stamps</heading>
1676 Maintainers should preserve the modification times of the
1677 upstream source files in a package, as far as is reasonably
1679 The rationale is that there is some information conveyed
1680 by knowing the age of the file, for example, you could
1681 recognize that some documentation is very old by looking
1682 at the modification time, so it would be nice if the
1683 modification time of the upstream source would be
1689 <sect id="restrictions">
1690 <heading>Restrictions on objects in source packages</heading>
1693 The source package may not contain any hard links<footnote>
1695 This is not currently detected when building source
1696 packages, but only when extracting
1700 Hard links may be permitted at some point in the
1701 future, but would require a fair amount of
1704 </footnote>, device special files, sockets or setuid or
1705 setgid files.<footnote>
1706 Setgid directories are allowed.
1711 <sect id="debianrules">
1712 <heading>Main building script: <file>debian/rules</file></heading>
1715 This file must be an executable makefile, and contains the
1716 package-specific recipes for compiling the package and
1717 building binary package(s) from the source.
1721 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1722 so that it can be invoked by saying its name rather than
1723 invoking <prgn>make</prgn> explicitly.
1727 Since an interactive <file>debian/rules</file> script makes it
1728 impossible to auto-compile that package and also makes it
1729 hard for other people to reproduce the same binary
1730 package, all <em>required targets</em> MUST be
1731 non-interactive. At a minimum, required targets are the
1732 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1733 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1734 <em>binary-indep</em>, and <em>build</em>. It also follows
1735 that any target that these targets depend on must also be
1740 The targets are as follows (required unless stated otherwise):
1742 <tag><tt>build</tt></tag>
1745 The <tt>build</tt> target should perform all the
1746 configuration and compilation of the package.
1747 If a package has an interactive pre-build
1748 configuration routine, the Debianized source package
1749 must either be built after this has taken place (so
1750 that the binary package can be built without rerunning
1751 the configuration) or the configuration routine
1752 modified to become non-interactive. (The latter is
1753 preferable if there are architecture-specific features
1754 detected by the configuration routine.)
1758 For some packages, notably ones where the same
1759 source tree is compiled in different ways to produce
1760 two binary packages, the <tt>build</tt> target
1761 does not make much sense. For these packages it is
1762 good enough to provide two (or more) targets
1763 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1764 for each of the ways of building the package, and a
1765 <tt>build</tt> target that does nothing. The
1766 <tt>binary</tt> target will have to build the
1767 package in each of the possible ways and make the
1768 binary package out of each.
1772 The <tt>build</tt> target must not do anything
1773 that might require root privilege.
1777 The <tt>build</tt> target may need to run the
1778 <tt>clean</tt> target first - see below.
1782 When a package has a configuration and build routine
1783 which takes a long time, or when the makefiles are
1784 poorly designed, or when <tt>build</tt> needs to
1785 run <tt>clean</tt> first, it is a good idea to
1786 <tt>touch build</tt> when the build process is
1787 complete. This will ensure that if <tt>debian/rules
1788 build</tt> is run again it will not rebuild the whole
1790 Another common way to do this is for <tt>build</tt>
1791 to depend on <prgn>build-stamp</prgn> and to do
1792 nothing else, and for the <prgn>build-stamp</prgn>
1793 target to do the building and to <tt>touch
1794 build-stamp</tt> on completion. This is
1795 especially useful if the build routine creates a
1796 file or directory called <tt>build</tt>; in such a
1797 case, <tt>build</tt> will need to be listed as
1798 a phony target (i.e., as a dependency of the
1799 <tt>.PHONY</tt> target). See the documentation of
1800 <prgn>make</prgn> for more information on phony
1806 <tag><tt>build-arch</tt> (optional),
1807 <tt>build-indep</tt> (optional)
1811 A package may also provide both of the targets
1812 <tt>build-arch</tt> and <tt>build-indep</tt>.
1813 The <tt>build-arch</tt> target, if provided, should
1814 perform all the configuration and compilation required
1815 for producing all architecture-dependant binary packages
1816 (those packages for which the body of the
1817 <tt>Architecture</tt> field in <tt>debian/control</tt>
1818 is not <tt>all</tt>).
1819 Similarly, the <tt>build-indep</tt> target, if
1820 provided, should perform all the configuration and
1821 compilation required for producing all
1822 architecture-independent binary packages
1823 (those packages for which the body of the
1824 <tt>Architecture</tt> field in <tt>debian/control</tt>
1826 The <tt>build</tt> target should depend on those of the
1827 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1828 are provided in the rules file.
1832 If one or both of the targets <tt>build-arch</tt> and
1833 <tt>build-indep</tt> are not provided, then invoking
1834 <file>debian/rules</file> with one of the not-provided
1835 targets as arguments should produce a exit status code
1836 of 2. Usually this is provided automatically by make
1837 if the target is missing.
1841 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1842 must not do anything that might require root privilege.
1846 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1847 <tt>binary-indep</tt>
1851 The <tt>binary</tt> target must be all that is
1852 necessary for the user to build the binary package(s)
1853 produced from this source package. It is
1854 split into two parts: <prgn>binary-arch</prgn> builds
1855 the binary packages which are specific to a particular
1856 architecture, and <tt>binary-indep</tt> builds
1857 those which are not.
1860 <tt>binary</tt> may be (and commonly is) a target with
1861 no commands which simply depends on
1862 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1865 Both <tt>binary-*</tt> targets should depend on the
1866 <tt>build</tt> target, or on the appropriate
1867 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1868 provided, so that the package is built if it has not
1869 been already. It should then create the relevant
1870 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1871 make their control files and <prgn>dpkg-deb</prgn> to
1872 build them and place them in the parent of the top
1877 Both the <tt>binary-arch</tt> and
1878 <tt>binary-indep</tt> targets <em>must</em> exist.
1879 If one of them has nothing to do (which will always be
1880 the case if the source generates only a single binary
1881 package, whether architecture-dependent or not), it
1882 must still exist and must always succeed.
1886 The <tt>binary</tt> targets must be invoked as
1888 The <prgn>fakeroot</prgn> package often allows one
1889 to build a package correctly even without being
1895 <tag><tt>clean</tt></tag>
1898 This must undo any effects that the <tt>build</tt>
1899 and <tt>binary</tt> targets may have had, except
1900 that it should leave alone any output files created in
1901 the parent directory by a run of a <tt>binary</tt>
1906 If a <tt>build</tt> file is touched at the end of
1907 the <tt>build</tt> target, as suggested above, it
1908 should be removed as the first action that
1909 <tt>clean</tt> performs, so that running
1910 <tt>build</tt> again after an interrupted
1911 <tt>clean</tt> doesn't think that everything is
1916 The <tt>clean</tt> target may need to be
1917 invoked as root if <tt>binary</tt> has been
1918 invoked since the last <tt>clean</tt>, or if
1919 <tt>build</tt> has been invoked as root (since
1920 <tt>build</tt> may create directories, for
1925 <tag><tt>get-orig-source</tt> (optional)</tag>
1928 This target fetches the most recent version of the
1929 original source package from a canonical archive site
1930 (via FTP or WWW, for example), does any necessary
1931 rearrangement to turn it into the original source
1932 tar file format described below, and leaves it in the
1937 This target may be invoked in any directory, and
1938 should take care to clean up any temporary files it
1943 This target is optional, but providing it if
1944 possible is a good idea.
1948 <tag><tt>patch</tt> (optional)</tag>
1951 This target performs whatever additional actions are
1952 required to make the source ready for editing (unpacking
1953 additional upstream archives, applying patches, etc.).
1954 It is recommended to be implemented for any package where
1955 <tt>dpkg-source -x</tt> does not result in source ready
1956 for additional modification. See
1957 <ref id="readmesource">.
1963 The <tt>build</tt>, <tt>binary</tt> and
1964 <tt>clean</tt> targets must be invoked with the current
1965 directory being the package's top-level directory.
1970 Additional targets may exist in <file>debian/rules</file>,
1971 either as published or undocumented interfaces or for the
1972 package's internal use.
1976 The architectures we build on and build for are determined
1977 by <prgn>make</prgn> variables using the utility
1978 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1979 You can determine the
1980 Debian architecture and the GNU style architecture
1981 specification string for the build machine (the machine type
1982 we are building on) as well as for the host machine (the
1983 machine type we are building for). Here is a list of
1984 supported <prgn>make</prgn> variables:
1985 <list compact="compact">
1987 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1990 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1991 specification string)
1994 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1995 <tt>DEB_*_GNU_TYPE</tt>)
1998 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1999 <tt>DEB_*_GNU_TYPE</tt>)
2001 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2002 the build machine or <tt>HOST</tt> for specification of the
2007 Backward compatibility can be provided in the rules file
2008 by setting the needed variables to suitable default
2009 values; please refer to the documentation of
2010 <prgn>dpkg-architecture</prgn> for details.
2014 It is important to understand that the <tt>DEB_*_ARCH</tt>
2015 string only determines which Debian architecture we are
2016 building on or for. It should not be used to get the CPU
2017 or system information; the GNU style variables should be
2021 <sect1 id="debianrules-options">
2022 <heading><file>debian/rules</file> and
2023 <tt>DEB_BUILD_OPTIONS</tt></heading>
2026 Supporting the standardized environment variable
2027 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2028 contain several flags to change how a package is compiled and
2029 built. Each flag must be in the form <var>flag</var> or
2030 <var>flag</var>=<var>options</var>. If multiple flags are
2031 given, they must be separated by whitespace.<footnote>
2032 Some packages support any delimiter, but whitespace is the
2033 easiest to parse inside a makefile and avoids ambiguity with
2034 flag values that contain commas.
2036 <var>flag</var> must start with a lowercase letter
2037 (<tt>a-z</tt>) and consist only of lowercase letters,
2038 numbers (<tt>0-9</tt>), and the characters
2039 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2040 <var>options</var> must not contain whitespace. The same
2041 tag should not be given multiple times with conflicting
2042 values. Package maintainers may assume that
2043 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2047 The meaning of the following tags has been standardized:
2051 This tag says to not run any build-time test suite
2052 provided by the package.
2056 The presence of this tag means that the package should
2057 be compiled with a minimum of optimization. For C
2058 programs, it is best to add <tt>-O0</tt> to
2059 <tt>CFLAGS</tt> (although this is usually the default).
2060 Some programs might fail to build or run at this level
2061 of optimization; it may be necessary to use
2062 <tt>-O1</tt>, for example.
2066 This tag means that the debugging symbols should not be
2067 stripped from the binary during installation, so that
2068 debugging information may be included in the package.
2070 <tag>parallel=n</tag>
2072 This tag means that the package should be built using up
2073 to <tt>n</tt> parallel processes if the package build
2074 system supports this.<footnote>
2075 Packages built with <tt>make</tt> can often implement
2076 this by passing the <tt>-j</tt><var>n</var> option to
2079 If the package build system does not support parallel
2080 builds, this string must be ignored. If the package
2081 build system only supports a lower level of concurrency
2082 than <var>n</var>, the package should be built using as
2083 many parallel processes as the package build system
2084 supports. It is up to the package maintainer to decide
2085 whether the package build times are long enough and the
2086 package build system is robust enough to make supporting
2087 parallel builds worthwhile.
2093 Unknown flags must be ignored by <file>debian/rules</file>.
2097 The following makefile snippet is an example of how one may
2098 implement the build options; you will probably have to
2099 massage this example in order to make it work for your
2101 <example compact="compact">
2104 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2105 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2106 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2107 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2109 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2114 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2115 INSTALL_PROGRAM += -s
2117 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2118 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2119 MAKEFLAGS += -j$(NUMJOBS)
2124 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2125 # Code to run the package test suite.
2132 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2133 <sect id="substvars">
2134 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2137 When <prgn>dpkg-gencontrol</prgn>,
2138 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2139 generate control files they perform variable substitutions
2140 on their output just before writing it. Variable
2141 substitutions have the form <tt>${<var>variable</var>}</tt>.
2142 The optional file <file>debian/substvars</file> contains
2143 variable substitutions to be used; variables can also be set
2144 directly from <file>debian/rules</file> using the <tt>-V</tt>
2145 option to the source packaging commands, and certain
2146 predefined variables are also available.
2150 The <file>debian/substvars</file> file is usually generated and
2151 modified dynamically by <file>debian/rules</file> targets, in
2152 which case it must be removed by the <tt>clean</tt> target.
2156 See <manref name="deb-substvars" section="5"> for full
2157 details about source variable substitutions, including the
2158 format of <file>debian/substvars</file>.</p>
2161 <sect id="debianwatch">
2162 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2165 This is an optional, recommended control file for the
2166 <tt>uscan</tt> utility which defines how to automatically
2167 scan ftp or http sites for newly available updates of the
2168 package. This is used by <url id="
2169 http://dehs.alioth.debian.org/"> and other Debian QA tools
2170 to help with quality control and maintenance of the
2171 distribution as a whole.
2176 <sect id="debianfiles">
2177 <heading>Generated files list: <file>debian/files</file></heading>
2180 This file is not a permanent part of the source tree; it
2181 is used while building packages to record which files are
2182 being generated. <prgn>dpkg-genchanges</prgn> uses it
2183 when it generates a <file>.changes</file> file.
2187 It should not exist in a shipped source package, and so it
2188 (and any backup files or temporary files such as
2189 <file>files.new</file><footnote>
2190 <file>files.new</file> is used as a temporary file by
2191 <prgn>dpkg-gencontrol</prgn> and
2192 <prgn>dpkg-distaddfile</prgn> - they write a new
2193 version of <tt>files</tt> here before renaming it,
2194 to avoid leaving a corrupted copy if an error
2196 </footnote>) should be removed by the
2197 <tt>clean</tt> target. It may also be wise to
2198 ensure a fresh start by emptying or removing it at the
2199 start of the <tt>binary</tt> target.
2203 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2204 package, it adds an entry to <file>debian/files</file> for the
2205 <file>.deb</file> file that will be created when <tt>dpkg-deb
2206 --build</tt> is run for that binary package. So for most
2207 packages all that needs to be done with this file is to
2208 delete it in the <tt>clean</tt> target.
2212 If a package upload includes files besides the source
2213 package and any binary packages whose control files were
2214 made with <prgn>dpkg-gencontrol</prgn> then they should be
2215 placed in the parent of the package's top-level directory
2216 and <prgn>dpkg-distaddfile</prgn> should be called to add
2217 the file to the list in <file>debian/files</file>.</p>
2220 <sect id="embeddedfiles">
2221 <heading>Convenience copies of code</heading>
2224 Some software packages include in their distribution convenience
2225 copies of code from other software packages, generally so that
2226 users compiling from source don't have to download multiple
2227 packages. Debian packages should not make use of these
2228 convenience copies unless the included package is explicitly
2229 intended to be used in this way.<footnote>
2230 For example, parts of the GNU build system work like this.
2232 If the included code is already in the Debian archive in the
2233 form of a library, the Debian packaging should ensure that
2234 binary packages reference the libraries already in Debian and
2235 the convenience copy is not used. If the included code is not
2236 already in Debian, it should be packaged separately as a
2237 prerequisite if possible.
2239 Having multiple copies of the same code in Debian is
2240 inefficient, often creates either static linking or shared
2241 library conflicts, and, most importantly, increases the
2242 difficulty of handling security vulnerabilities in the
2248 <sect id="readmesource">
2249 <heading>Source package handling:
2250 <file>debian/README.source</file></heading>
2253 If running <prgn>dpkg-source -x</prgn> on a source package
2254 doesn't produce the source of the package, ready for editing,
2255 and allow one to make changes and run
2256 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2257 without taking any additional steps, creating a
2258 <file>debian/README.source</file> documentation file is
2259 recommended. This file should explain how to do all of the
2262 <item>Generate the fully patched source, in a form ready for
2263 editing, that would be built to create Debian
2264 packages. Doing this with a <tt>patch</tt> target in
2265 <file>debian/rules</file> is recommended; see
2266 <ref id="debianrules">.</item>
2267 <item>Modify the source and save those modifications so that
2268 they will be applied when building the package.</item>
2269 <item>Remove source modifications that are currently being
2270 applied when building the package.</item>
2271 <item>Optionally, document what steps are necessary to
2272 upgrade the Debian source package to a new upstream version,
2273 if applicable.</item>
2275 This explanation should include specific commands and mention
2276 any additional required Debian packages. It should not assume
2277 familiarity with any specific Debian packaging system or patch
2282 This explanation may refer to a documentation file installed by
2283 one of the package's build dependencies provided that the
2284 referenced documentation clearly explains these tasks and is not
2285 a general reference manual.
2289 <file>debian/README.source</file> may also include any other
2290 information that would be helpful to someone modifying the
2291 source package. Even if the package doesn't fit the above
2292 description, maintainers are encouraged to document in a
2293 <file>debian/README.source</file> file any source package with a
2294 particularly complex or unintuitive source layout or build
2295 system (for example, a package that builds the same source
2296 multiple times to generate different binary packages).
2302 <chapt id="controlfields">
2303 <heading>Control files and their fields</heading>
2306 The package management system manipulates data represented in
2307 a common format, known as <em>control data</em>, stored in
2308 <em>control files</em>.
2309 Control files are used for source packages, binary packages and
2310 the <file>.changes</file> files which control the installation
2311 of uploaded files<footnote>
2312 <prgn>dpkg</prgn>'s internal databases are in a similar
2317 <sect id="controlsyntax">
2318 <heading>Syntax of control files</heading>
2321 A control file consists of one or more paragraphs of
2323 The paragraphs are also sometimes referred to as stanzas.
2325 The paragraphs are separated by blank lines. Some control
2326 files allow only one paragraph; others allow several, in
2327 which case each paragraph usually refers to a different
2328 package. (For example, in source packages, the first
2329 paragraph refers to the source package, and later paragraphs
2330 refer to binary packages generated from the source.)
2334 Each paragraph consists of a series of data fields; each
2335 field consists of the field name, followed by a colon and
2336 then the data/value associated with that field. It ends at
2337 the end of the (logical) line. Horizontal whitespace
2338 (spaces and tabs) may occur immediately before or after the
2339 value and is ignored there; it is conventional to put a
2340 single space after the colon. For example, a field might
2342 <example compact="compact">
2345 the field name is <tt>Package</tt> and the field value
2350 Many fields' values may span several lines; in this case
2351 each continuation line must start with a space or a tab.
2352 Any trailing spaces or tabs at the end of individual
2353 lines of a field value are ignored.
2357 In fields where it is specified that lines may not wrap,
2358 only a single line of data is allowed and whitespace is not
2359 significant in a field body. Whitespace must not appear
2360 inside names (of packages, architectures, files or anything
2361 else) or version numbers, or between the characters of
2362 multi-character version relationships.
2366 Field names are not case-sensitive, but it is usual to
2367 capitalize the field names using mixed case as shown below.
2371 Blank lines, or lines consisting only of spaces and tabs,
2372 are not allowed within field values or between fields - that
2373 would mean a new paragraph.
2377 All control files must be encoded in UTF-8.
2381 <sect id="sourcecontrolfiles">
2382 <heading>Source package control files -- <file>debian/control</file></heading>
2385 The <file>debian/control</file> file contains the most vital
2386 (and version-independent) information about the source package
2387 and about the binary packages it creates.
2391 The first paragraph of the control file contains information about
2392 the source package in general. The subsequent sets each describe a
2393 binary package that the source tree builds.
2397 The fields in the general paragraph (the first one, for the source
2400 <list compact="compact">
2401 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2402 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2403 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2404 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2405 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2406 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2407 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2408 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2413 The fields in the binary package paragraphs are:
2415 <list compact="compact">
2416 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2417 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2418 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2419 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2420 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2421 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2422 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2423 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2428 The syntax and semantics of the fields are described below.
2434 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2435 generate control files for binary packages (see below), by
2436 <prgn>dpkg-genchanges</prgn> to generate the
2437 <tt>.changes</tt> file to accompany the upload, and by
2438 <prgn>dpkg-source</prgn> when it creates the
2439 <file>.dsc</file> source control file as part of a source
2440 archive. Many fields are permitted to span multiple lines in
2441 <file>debian/control</file> but not in any other control
2442 file. These tools are responsible for removing the line
2443 breaks from such fields when using fields from
2444 <file>debian/control</file> to generate other control files.
2448 The fields here may contain variable references - their
2449 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2450 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2451 when they generate output control files.
2452 See <ref id="substvars"> for details.
2457 <sect id="binarycontrolfiles">
2458 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2461 The <file>DEBIAN/control</file> file contains the most vital
2462 (and version-dependent) information about a binary package.
2466 The fields in this file are:
2468 <list compact="compact">
2469 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2470 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2471 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2472 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2473 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2474 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2475 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2476 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2477 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2478 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2479 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2480 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2485 <sect id="debiansourcecontrolfiles">
2486 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2489 This file contains a series of fields, identified and
2490 separated just like the fields in the control file of
2491 a binary package. The fields are listed below; their
2492 syntax is described above, in <ref id="pkg-controlfields">.
2494 <list compact="compact">
2495 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2496 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2497 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2498 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2499 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2500 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2501 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2502 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2503 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2504 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2505 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2510 The source package control file is generated by
2511 <prgn>dpkg-source</prgn> when it builds the source
2512 archive, from other files in the source package,
2513 described above. When unpacking, it is checked against
2514 the files and directories in the other parts of the
2520 <sect id="debianchangesfiles">
2521 <heading>Debian changes files -- <file>.changes</file></heading>
2524 The .changes files are used by the Debian archive maintenance
2525 software to process updates to packages. They contain one
2526 paragraph which contains information from the
2527 <tt>debian/control</tt> file and other data about the
2528 source package gathered via <tt>debian/changelog</tt>
2529 and <tt>debian/rules</tt>.
2533 The fields in this file are:
2535 <list compact="compact">
2536 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2537 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2538 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2539 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2540 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2541 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2542 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2543 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2544 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2545 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2546 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2548 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2554 <sect id="controlfieldslist">
2555 <heading>List of fields</heading>
2557 <sect1 id="f-Source">
2558 <heading><tt>Source</tt></heading>
2561 This field identifies the source package name.
2565 In <file>debian/control</file> or a <file>.dsc</file> file,
2566 this field must contain only the name of the source package.
2570 In a binary package control file or a <file>.changes</file>
2571 file, the source package name may be followed by a version
2572 number in parentheses<footnote>
2573 It is customary to leave a space after the package name
2574 if a version number is specified.
2576 This version number may be omitted (and is, by
2577 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2578 the <tt>Version</tt> field of the binary package in
2579 question. The field itself may be omitted from a binary
2580 package control file when the source package has the same
2581 name and version as the binary package.
2585 <sect1 id="f-Maintainer">
2586 <heading><tt>Maintainer</tt></heading>
2589 The package maintainer's name and email address. The name
2590 should come first, then the email address inside angle
2591 brackets <tt><></tt> (in RFC822 format).
2595 If the maintainer's name contains a full stop then the
2596 whole field will not work directly as an email address due
2597 to a misfeature in the syntax specified in RFC822; a
2598 program using this field as an address must check for this
2599 and correct the problem if necessary (for example by
2600 putting the name in round brackets and moving it to the
2601 end, and bringing the email address forward).
2605 <sect1 id="f-Uploaders">
2606 <heading><tt>Uploaders</tt></heading>
2609 List of the names and email addresses of co-maintainers of
2610 the package, if any. If the package has other maintainers
2611 beside the one named in the
2612 <qref id="f-Maintainer">Maintainer field</qref>, their
2613 names and email addresses should be listed here. The
2614 format is the same as that of the Maintainer tag, and
2615 multiple entries should be comma separated. Currently,
2616 this field is restricted to a single line of data. This
2617 is an optional field.
2620 Any parser that interprets the Uploaders field in
2621 <file>debian/control</file> must permit it to span multiple
2622 lines. Line breaks in an Uploaders field that spans multiple
2623 lines are not significant and the semantics of the field are
2624 the same as if the line breaks had not been present.
2628 <sect1 id="f-Changed-By">
2629 <heading><tt>Changed-By</tt></heading>
2632 The name and email address of the person who changed the
2633 said package. Usually the name of the maintainer.
2634 All the rules for the Maintainer field apply here, too.
2638 <sect1 id="f-Section">
2639 <heading><tt>Section</tt></heading>
2642 This field specifies an application area into which the package
2643 has been classified. See <ref id="subsections">.
2647 When it appears in the <file>debian/control</file> file,
2648 it gives the value for the subfield of the same name in
2649 the <tt>Files</tt> field of the <file>.changes</file> file.
2650 It also gives the default for the same field in the binary
2655 <sect1 id="f-Priority">
2656 <heading><tt>Priority</tt></heading>
2659 This field represents how important that it is that the user
2660 have the package installed. See <ref id="priorities">.
2664 When it appears in the <file>debian/control</file> file,
2665 it gives the value for the subfield of the same name in
2666 the <tt>Files</tt> field of the <file>.changes</file> file.
2667 It also gives the default for the same field in the binary
2672 <sect1 id="f-Package">
2673 <heading><tt>Package</tt></heading>
2676 The name of the binary package.
2680 Package names must consist only of lower case letters
2681 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2682 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2683 They must be at least two characters long and must start
2684 with an alphanumeric character.
2688 <sect1 id="f-Architecture">
2689 <heading><tt>Architecture</tt></heading>
2692 Depending on context and the control file used, the
2693 <tt>Architecture</tt> field can include the following sets of
2696 <item>A unique single word identifying a Debian machine
2697 architecture, see <ref id="arch-spec">.
2698 <item><tt>all</tt>, which indicates an
2699 architecture-independent package.
2700 <item><tt>any</tt>, which indicates a package available
2701 for building on any architecture.
2702 <item><tt>source</tt>, which indicates a source package.
2707 In the main <file>debian/control</file> file in the source
2708 package, or in the source package control file
2709 <file>.dsc</file>, one may specify a list of architectures
2710 separated by spaces, or the special values <tt>any</tt> or
2715 Specifying <tt>any</tt> indicates that the source package
2716 isn't dependent on any particular architecture and should
2717 compile fine on any one. The produced binary package(s)
2718 will be specific to whatever the current build architecture
2720 This is the most often used setting, and is recommended
2721 for new packages that aren't <tt>Architecture: all</tt>.
2726 Specifying a list of architectures indicates that the source
2727 will build an architecture-dependent package, and will only
2728 work correctly on the listed architectures.<footnote>
2729 This is a setting used for a minority of cases where the
2730 program is not portable. Generally, it should not be used
2736 In a <file>.changes</file> file, the <tt>Architecture</tt>
2737 field lists the architecture(s) of the package(s)
2738 currently being uploaded. This will be a list; if the
2739 source for the package is also being uploaded, the special
2740 entry <tt>source</tt> is also present.
2744 See <ref id="debianrules"> for information how to get the
2745 architecture for the build process.
2749 <sect1 id="f-Essential">
2750 <heading><tt>Essential</tt></heading>
2753 This is a boolean field which may occur only in the
2754 control file of a binary package or in a per-package fields
2755 paragraph of a main source control data file.
2759 If set to <tt>yes</tt> then the package management system
2760 will refuse to remove the package (upgrading and replacing
2761 it is still possible). The other possible value is <tt>no</tt>,
2762 which is the same as not having the field at all.
2767 <heading>Package interrelationship fields:
2768 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2769 <tt>Recommends</tt>, <tt>Suggests</tt>,
2770 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2771 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2775 These fields describe the package's relationships with
2776 other packages. Their syntax and semantics are described
2777 in <ref id="relationships">.</p>
2780 <sect1 id="f-Standards-Version">
2781 <heading><tt>Standards-Version</tt></heading>
2784 The most recent version of the standards (the policy
2785 manual and associated texts) with which the package
2790 The version number has four components: major and minor
2791 version number and major and minor patch level. When the
2792 standards change in a way that requires every package to
2793 change the major number will be changed. Significant
2794 changes that will require work in many packages will be
2795 signaled by a change to the minor number. The major patch
2796 level will be changed for any change to the meaning of the
2797 standards, however small; the minor patch level will be
2798 changed when only cosmetic, typographical or other edits
2799 are made which neither change the meaning of the document
2800 nor affect the contents of packages.
2804 Thus only the first three components of the policy version
2805 are significant in the <em>Standards-Version</em> control
2806 field, and so either these three components or the all
2807 four components may be specified.<footnote>
2808 In the past, people specified the full version number
2809 in the Standards-Version field, for example "2.3.0.0".
2810 Since minor patch-level changes don't introduce new
2811 policy, it was thought it would be better to relax
2812 policy and only require the first 3 components to be
2813 specified, in this example "2.3.0". All four
2814 components may still be used if someone wishes to do so.
2820 <sect1 id="f-Version">
2821 <heading><tt>Version</tt></heading>
2824 The version number of a package. The format is:
2825 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2829 The three components here are:
2831 <tag><var>epoch</var></tag>
2834 This is a single (generally small) unsigned integer. It
2835 may be omitted, in which case zero is assumed. If it is
2836 omitted then the <var>upstream_version</var> may not
2841 It is provided to allow mistakes in the version numbers
2842 of older versions of a package, and also a package's
2843 previous version numbering schemes, to be left behind.
2847 <tag><var>upstream_version</var></tag>
2850 This is the main part of the version number. It is
2851 usually the version number of the original ("upstream")
2852 package from which the <file>.deb</file> file has been made,
2853 if this is applicable. Usually this will be in the same
2854 format as that specified by the upstream author(s);
2855 however, it may need to be reformatted to fit into the
2856 package management system's format and comparison
2861 The comparison behavior of the package management system
2862 with respect to the <var>upstream_version</var> is
2863 described below. The <var>upstream_version</var>
2864 portion of the version number is mandatory.
2868 The <var>upstream_version</var> may contain only
2869 alphanumerics<footnote>
2870 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2872 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2873 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2874 tilde) and should start with a digit. If there is no
2875 <var>debian_revision</var> then hyphens are not allowed;
2876 if there is no <var>epoch</var> then colons are not
2881 <tag><var>debian_revision</var></tag>
2884 This part of the version number specifies the version of
2885 the Debian package based on the upstream version. It
2886 may contain only alphanumerics and the characters
2887 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2888 tilde) and is compared in the same way as the
2889 <var>upstream_version</var> is.
2893 It is optional; if it isn't present then the
2894 <var>upstream_version</var> may not contain a hyphen.
2895 This format represents the case where a piece of
2896 software was written specifically to be turned into a
2897 Debian package, and so there is only one "debianisation"
2898 of it and therefore no revision indication is required.
2902 It is conventional to restart the
2903 <var>debian_revision</var> at <tt>1</tt> each time the
2904 <var>upstream_version</var> is increased.
2908 The package management system will break the version
2909 number apart at the last hyphen in the string (if there
2910 is one) to determine the <var>upstream_version</var> and
2911 <var>debian_revision</var>. The absence of a
2912 <var>debian_revision</var> is equivalent to a
2913 <var>debian_revision</var> of <tt>0</tt>.
2920 When comparing two version numbers, first the <var>epoch</var>
2921 of each are compared, then the <var>upstream_version</var> if
2922 <var>epoch</var> is equal, and then <var>debian_revision</var>
2923 if <var>upstream_version</var> is also equal.
2924 <var>epoch</var> is compared numerically. The
2925 <var>upstream_version</var> and <var>debian_revision</var>
2926 parts are compared by the package management system using the
2927 following algorithm:
2931 The strings are compared from left to right.
2935 First the initial part of each string consisting entirely of
2936 non-digit characters is determined. These two parts (one of
2937 which may be empty) are compared lexically. If a difference
2938 is found it is returned. The lexical comparison is a
2939 comparison of ASCII values modified so that all the letters
2940 sort earlier than all the non-letters and so that a tilde
2941 sorts before anything, even the end of a part. For example,
2942 the following parts are in sorted order from earliest to
2943 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2944 <tt>a</tt>.<footnote>
2945 One common use of <tt>~</tt> is for upstream pre-releases.
2946 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2947 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2952 Then the initial part of the remainder of each string which
2953 consists entirely of digit characters is determined. The
2954 numerical values of these two parts are compared, and any
2955 difference found is returned as the result of the comparison.
2956 For these purposes an empty string (which can only occur at
2957 the end of one or both version strings being compared) counts
2962 These two steps (comparing and removing initial non-digit
2963 strings and initial digit strings) are repeated until a
2964 difference is found or both strings are exhausted.
2968 Note that the purpose of epochs is to allow us to leave behind
2969 mistakes in version numbering, and to cope with situations
2970 where the version numbering scheme changes. It is
2971 <em>not</em> intended to cope with version numbers containing
2972 strings of letters which the package management system cannot
2973 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2974 silly orderings (the author of this manual has heard of a
2975 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2976 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2977 <tt>2</tt> and so forth).
2981 <sect1 id="f-Description">
2982 <heading><tt>Description</tt></heading>
2985 In a source or binary control file, the <tt>Description</tt>
2986 field contains a description of the binary package, consisting
2987 of two parts, the synopsis or the short description, and the
2988 long description. The field's format is as follows:
2993 Description: <single line synopsis>
2994 <extended description over several lines>
2999 The lines in the extended description can have these formats:
3005 Those starting with a single space are part of a paragraph.
3006 Successive lines of this form will be word-wrapped when
3007 displayed. The leading space will usually be stripped off.
3011 Those starting with two or more spaces. These will be
3012 displayed verbatim. If the display cannot be panned
3013 horizontally, the displaying program will line wrap them "hard"
3014 (i.e., without taking account of word breaks). If it can they
3015 will be allowed to trail off to the right. None, one or two
3016 initial spaces may be deleted, but the number of spaces
3017 deleted from each line will be the same (so that you can have
3018 indenting work correctly, for example).
3022 Those containing a single space followed by a single full stop
3023 character. These are rendered as blank lines. This is the
3024 <em>only</em> way to get a blank line<footnote>
3025 Completely empty lines will not be rendered as blank lines.
3026 Instead, they will cause the parser to think you're starting
3027 a whole new record in the control file, and will therefore
3028 likely abort with an error.
3033 Those containing a space, a full stop and some more characters.
3034 These are for future expansion. Do not use them.
3040 Do not use tab characters. Their effect is not predictable.
3044 See <ref id="descriptions"> for further information on this.
3048 In a <file>.changes</file> file, the <tt>Description</tt> field
3049 contains a summary of the descriptions for the packages being
3054 The part of the field before the first newline is empty;
3055 thereafter each line has the name of a binary package and
3056 the summary description line from that binary package.
3057 Each line is indented by one space.
3062 <sect1 id="f-Distribution">
3063 <heading><tt>Distribution</tt></heading>
3066 In a <file>.changes</file> file or parsed changelog output
3067 this contains the (space-separated) name(s) of the
3068 distribution(s) where this version of the package should
3069 be installed. Valid distributions are determined by the
3070 archive maintainers.<footnote>
3071 Current distribution names are:
3072 <taglist compact="compact">
3073 <tag><em>stable</em></tag>
3075 This is the current "released" version of Debian
3076 GNU/Linux. Once the distribution is
3077 <em>stable</em> only security fixes and other
3078 major bug fixes are allowed. When changes are
3079 made to this distribution, the release number is
3080 increased (for example: 2.2r1 becomes 2.2r2 then
3084 <tag><em>unstable</em></tag>
3086 This distribution value refers to the
3087 <em>developmental</em> part of the Debian
3088 distribution tree. New packages, new upstream
3089 versions of packages and bug fixes go into the
3090 <em>unstable</em> directory tree. Download from
3091 this distribution at your own risk.
3094 <tag><em>testing</em></tag>
3096 This distribution value refers to the
3097 <em>testing</em> part of the Debian distribution
3098 tree. It receives its packages from the
3099 unstable distribution after a short time lag to
3100 ensure that there are no major issues with the
3101 unstable packages. It is less prone to breakage
3102 than unstable, but still risky. It is not
3103 possible to upload packages directly to
3107 <tag><em>frozen</em></tag>
3109 From time to time, the <em>testing</em>
3110 distribution enters a state of "code-freeze" in
3111 anticipation of release as a <em>stable</em>
3112 version. During this period of testing only
3113 fixes for existing or newly-discovered bugs will
3114 be allowed. The exact details of this stage are
3115 determined by the Release Manager.
3118 <tag><em>experimental</em></tag>
3120 The packages with this distribution value are
3121 deemed by their maintainers to be high
3122 risk. Oftentimes they represent early beta or
3123 developmental packages from various sources that
3124 the maintainers want people to try, but are not
3125 ready to be a part of the other parts of the
3126 Debian distribution tree. Download at your own
3132 You should list <em>all</em> distributions that the
3133 package should be installed into.
3137 More information is available in the Debian Developer's
3138 Reference, section "The Debian archive".
3145 <heading><tt>Date</tt></heading>
3148 This field includes the date the package was built or last edited.
3152 The value of this field is usually extracted from the
3153 <file>debian/changelog</file> file - see
3154 <ref id="dpkgchangelog">).
3158 <sect1 id="f-Format">
3159 <heading><tt>Format</tt></heading>
3162 This field specifies a format revision for the file.
3163 The most current format described in the Policy Manual
3164 is version <strong>1.5</strong>. The syntax of the
3165 format value is the same as that of a package version
3166 number except that no epoch or Debian revision is allowed
3167 - see <ref id="f-Version">.
3171 <sect1 id="f-Urgency">
3172 <heading><tt>Urgency</tt></heading>
3175 This is a description of how important it is to upgrade to
3176 this version from previous ones. It consists of a single
3177 keyword taking one of the values <tt>low</tt>,
3178 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3179 <tt>critical</tt><footnote>
3180 Other urgency values are supported with configuration
3181 changes in the archive software but are not used in Debian.
3182 The urgency affects how quickly a package will be considered
3183 for inclusion into the <tt>testing</tt> distribution and
3184 gives an indication of the importance of any fixes included
3185 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3186 treated as synonymous.
3187 </footnote> (not case-sensitive) followed by an optional
3188 commentary (separated by a space) which is usually in
3189 parentheses. For example:
3192 Urgency: low (HIGH for users of diversions)
3198 The value of this field is usually extracted from the
3199 <file>debian/changelog</file> file - see
3200 <ref id="dpkgchangelog">.
3204 <sect1 id="f-Changes">
3205 <heading><tt>Changes</tt></heading>
3208 This field contains the human-readable changes data, describing
3209 the differences between the last version and the current one.
3213 There should be nothing in this field before the first
3214 newline; all the subsequent lines must be indented by at
3215 least one space; blank lines must be represented by a line
3216 consisting only of a space and a full stop.
3220 The value of this field is usually extracted from the
3221 <file>debian/changelog</file> file - see
3222 <ref id="dpkgchangelog">).
3226 Each version's change information should be preceded by a
3227 "title" line giving at least the version, distribution(s)
3228 and urgency, in a human-readable way.
3232 If data from several versions is being returned the entry
3233 for the most recent version should be returned first, and
3234 entries should be separated by the representation of a
3235 blank line (the "title" line may also be followed by the
3236 representation of blank line).
3240 <sect1 id="f-Binary">
3241 <heading><tt>Binary</tt></heading>
3244 This field is a list of binary packages.
3248 When it appears in the <file>.dsc</file> file it is the list
3249 of binary packages which a source package can produce. It
3250 does not necessarily produce all of these binary packages
3251 for every architecture. The source control file doesn't
3252 contain details of which architectures are appropriate for
3253 which of the binary packages.
3257 When it appears in a <file>.changes</file> file it lists the
3258 names of the binary packages actually being uploaded.
3262 The syntax is a list of binary packages separated by
3264 A space after each comma is conventional.
3265 </footnote>. Currently the packages must be separated using
3266 only spaces in the <file>.changes</file> file.
3270 <sect1 id="f-Installed-Size">
3271 <heading><tt>Installed-Size</tt></heading>
3274 This field appears in the control files of binary
3275 packages, and in the <file>Packages</file> files. It gives
3276 the total amount of disk space required to install the
3281 The disk space is represented in kilobytes as a simple
3286 <sect1 id="f-Files">
3287 <heading><tt>Files</tt></heading>
3290 This field contains a list of files with information about
3291 each one. The exact information and syntax varies with
3292 the context. In all cases the part of the field
3293 contents on the same line as the field name is empty. The
3294 remainder of the field is one line per file, each line
3295 being indented by one space and containing a number of
3296 sub-fields separated by spaces.
3300 In the <file>.dsc</file> file, each line contains the MD5
3301 checksum, size and filename of the tar file and (if applicable)
3302 diff file which make up the remainder of the source
3304 That is, the parts which are not the <tt>.dsc</tt>.
3306 The exact forms of the filenames are described
3307 in <ref id="pkg-sourcearchives">.
3311 In the <file>.changes</file> file this contains one line per
3312 file being uploaded. Each line contains the MD5 checksum,
3313 size, section and priority and the filename.
3314 The <qref id="f-Section">section</qref>
3315 and <qref id="f-Priority">priority</qref>
3316 are the values of the corresponding fields in
3317 the main source control file. If no section or priority is
3318 specified then <tt>-</tt> should be used, though section
3319 and priority values must be specified for new packages to
3320 be installed properly.
3324 The special value <tt>byhand</tt> for the section in a
3325 <tt>.changes</tt> file indicates that the file in question
3326 is not an ordinary package file and must by installed by
3327 hand by the distribution maintainers. If the section is
3328 <tt>byhand</tt> the priority should be <tt>-</tt>.
3332 If a new Debian revision of a package is being shipped and
3333 no new original source archive is being distributed the
3334 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3335 entry for the original source archive
3336 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3337 but the <file>.changes</file> file should leave it out. In
3338 this case the original source archive on the distribution
3339 site must match exactly, byte-for-byte, the original
3340 source archive which was used to generate the
3341 <file>.dsc</file> file and diff which are being uploaded.</p>
3344 <sect1 id="f-Closes">
3345 <heading><tt>Closes</tt></heading>
3348 A space-separated list of bug report numbers that the upload
3349 governed by the .changes file closes.
3353 <sect1 id="f-Homepage">
3354 <heading><tt>Homepage</tt></heading>
3357 The URL of the web site for this package, preferably (when
3358 applicable) the site from which the original source can be
3359 obtained and any additional upstream documentation or
3360 information may be found. The content of this field is a
3361 simple URL without any surrounding characters such as
3369 <heading>User-defined fields</heading>
3372 Additional user-defined fields may be added to the
3373 source package control file. Such fields will be
3374 ignored, and not copied to (for example) binary or
3375 source package control files or upload control files.
3379 If you wish to add additional unsupported fields to
3380 these output files you should use the mechanism
3385 Fields in the main source control information file with
3386 names starting <tt>X</tt>, followed by one or more of
3387 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3388 be copied to the output files. Only the part of the
3389 field name after the hyphen will be used in the output
3390 file. Where the letter <tt>B</tt> is used the field
3391 will appear in binary package control files, where the
3392 letter <tt>S</tt> is used in source package control
3393 files and where <tt>C</tt> is used in upload control
3394 (<tt>.changes</tt>) files.
3398 For example, if the main source information control file
3401 XBS-Comment: I stand between the candle and the star.
3403 then the binary and source package control files will contain the
3406 Comment: I stand between the candle and the star.
3415 <chapt id="maintainerscripts">
3416 <heading>Package maintainer scripts and installation procedure</heading>
3419 <heading>Introduction to package maintainer scripts</heading>
3422 It is possible to supply scripts as part of a package which
3423 the package management system will run for you when your
3424 package is installed, upgraded or removed.
3428 These scripts are the files <prgn>preinst</prgn>,
3429 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3430 <prgn>postrm</prgn> in the control area of the package.
3431 They must be proper executable files; if they are scripts
3432 (which is recommended), they must start with the usual
3433 <tt>#!</tt> convention. They should be readable and
3434 executable by anyone, and must not be world-writable.
3438 The package management system looks at the exit status from
3439 these scripts. It is important that they exit with a
3440 non-zero status if there is an error, so that the package
3441 management system can stop its processing. For shell
3442 scripts this means that you <em>almost always</em> need to
3443 use <tt>set -e</tt> (this is usually true when writing shell
3444 scripts, in fact). It is also important, of course, that
3445 they exit with a zero status if everything went well.
3449 Additionally, packages interacting with users using
3450 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3451 install a <prgn>config</prgn> script in the control area,
3452 see <ref id="maintscriptprompt"> for details.
3456 When a package is upgraded a combination of the scripts from
3457 the old and new packages is called during the upgrade
3458 procedure. If your scripts are going to be at all
3459 complicated you need to be aware of this, and may need to
3460 check the arguments to your scripts.
3464 Broadly speaking the <prgn>preinst</prgn> is called before
3465 (a particular version of) a package is installed, and the
3466 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3467 before (a version of) a package is removed and the
3468 <prgn>postrm</prgn> afterwards.
3472 Programs called from maintainer scripts should not normally
3473 have a path prepended to them. Before installation is
3474 started, the package management system checks to see if the
3475 programs <prgn>ldconfig</prgn>,
3476 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3477 and <prgn>update-rc.d</prgn> can be found via the
3478 <tt>PATH</tt> environment variable. Those programs, and any
3479 other program that one would expect to be in the
3480 <tt>PATH</tt>, should thus be invoked without an absolute
3481 pathname. Maintainer scripts should also not reset the
3482 <tt>PATH</tt>, though they might choose to modify it by
3483 prepending or appending package-specific directories. These
3484 considerations really apply to all shell scripts.</p>
3487 <sect id="idempotency">
3488 <heading>Maintainer scripts idempotency</heading>
3491 It is necessary for the error recovery procedures that the
3492 scripts be idempotent. This means that if it is run
3493 successfully, and then it is called again, it doesn't bomb
3494 out or cause any harm, but just ensures that everything is
3495 the way it ought to be. If the first call failed, or
3496 aborted half way through for some reason, the second call
3497 should merely do the things that were left undone the first
3498 time, if any, and exit with a success status if everything
3500 This is so that if an error occurs, the user interrupts
3501 <prgn>dpkg</prgn> or some other unforeseen circumstance
3502 happens you don't leave the user with a badly-broken
3503 package when <prgn>dpkg</prgn> attempts to repeat the
3509 <sect id="controllingterminal">
3510 <heading>Controlling terminal for maintainer scripts</heading>
3513 The maintainer scripts are guaranteed to run with a
3514 controlling terminal and can interact with the user.
3515 Because these scripts may be executed with standard output
3516 redirected into a pipe for logging purposes, Perl scripts
3517 should set unbuffered output by setting <tt>$|=1</tt> so
3518 that the output is printed immediately rather than being
3522 <sect id="exitstatus">
3523 <heading>Exit status</heading>
3526 Each script must return a zero exit status for
3527 success, or a nonzero one for failure, since the package
3528 management system looks for the exit status of these scripts
3529 and determines what action to take next based on that datum.
3533 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3538 <list compact="compact">
3540 <var>new-preinst</var> <tt>install</tt>
3543 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3546 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3549 <var>old-preinst</var> <tt>abort-upgrade</tt>
3550 <var>new-version</var>
3555 <list compact="compact">
3557 <var>postinst</var> <tt>configure</tt>
3558 <var>most-recently-configured-version</var>
3561 <var>old-postinst</var> <tt>abort-upgrade</tt>
3562 <var>new-version</var>
3565 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3566 <tt>in-favour</tt> <var>package</var>
3567 <var>new-version</var>
3570 <var>postinst</var> <tt>abort-remove</tt>
3573 <var>deconfigured's-postinst</var>
3574 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3575 <var>failed-install-package</var> <var>version</var>
3576 [<tt>removing</tt> <var>conflicting-package</var>
3582 <list compact="compact">
3584 <var>prerm</var> <tt>remove</tt>
3587 <var>old-prerm</var> <tt>upgrade</tt>
3588 <var>new-version</var>
3591 <var>new-prerm</var> <tt>failed-upgrade</tt>
3592 <var>old-version</var>
3595 <var>conflictor's-prerm</var> <tt>remove</tt>
3596 <tt>in-favour</tt> <var>package</var>
3597 <var>new-version</var>
3600 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3601 <tt>in-favour</tt> <var>package-being-installed</var>
3602 <var>version</var> [<tt>removing</tt>
3603 <var>conflicting-package</var>
3609 <list compact="compact">
3611 <var>postrm</var> <tt>remove</tt>
3614 <var>postrm</var> <tt>purge</tt>
3617 <var>old-postrm</var> <tt>upgrade</tt>
3618 <var>new-version</var>
3621 <var>new-postrm</var> <tt>failed-upgrade</tt>
3622 <var>old-version</var>
3625 <var>new-postrm</var> <tt>abort-install</tt>
3628 <var>new-postrm</var> <tt>abort-install</tt>
3629 <var>old-version</var>
3632 <var>new-postrm</var> <tt>abort-upgrade</tt>
3633 <var>old-version</var>
3636 <var>disappearer's-postrm</var> <tt>disappear</tt>
3637 <var>overwriter</var>
3638 <var>overwriter-version</var>
3644 <sect id="unpackphase">
3645 <heading>Details of unpack phase of installation or upgrade</heading>
3648 The procedure on installation/upgrade/overwrite/disappear
3649 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3650 stage of <tt>dpkg --install</tt>) is as follows. In each
3651 case, if a major error occurs (unless listed below) the
3652 actions are, in general, run backwards - this means that the
3653 maintainer scripts are run with different arguments in
3654 reverse order. These are the "error unwind" calls listed
3661 If a version of the package is already installed, call
3662 <example compact="compact">
3663 <var>old-prerm</var> upgrade <var>new-version</var>
3667 If the script runs but exits with a non-zero
3668 exit status, <prgn>dpkg</prgn> will attempt:
3669 <example compact="compact">
3670 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3672 If this works, the upgrade continues. If this
3673 does not work, the error unwind:
3674 <example compact="compact">
3675 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3677 If this works, then the old-version is
3678 "Installed", if not, the old version is in a
3679 "Failed-Config" state.
3685 If a "conflicting" package is being removed at the same time,
3686 or if any package will be broken (due to <tt>Breaks</tt>):
3689 If <tt>--auto-deconfigure</tt> is
3690 specified, call, for each package to be deconfigured
3691 due to <tt>Breaks</tt>:
3692 <example compact="compact">
3693 <var>deconfigured's-prerm</var> deconfigure \
3694 in-favour <var>package-being-installed</var> <var>version</var>
3697 <example compact="compact">
3698 <var>deconfigured's-postinst</var> abort-deconfigure \
3699 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3701 The deconfigured packages are marked as
3702 requiring configuration, so that if
3703 <tt>--install</tt> is used they will be
3704 configured again if possible.
3707 If any packages depended on a conflicting
3708 package being removed and <tt>--auto-deconfigure</tt> is
3709 specified, call, for each such package:
3710 <example compact="compact">
3711 <var>deconfigured's-prerm</var> deconfigure \
3712 in-favour <var>package-being-installed</var> <var>version</var> \
3713 removing <var>conflicting-package</var> <var>version</var>
3716 <example compact="compact">
3717 <var>deconfigured's-postinst</var> abort-deconfigure \
3718 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3719 removing <var>conflicting-package</var> <var>version</var>
3721 The deconfigured packages are marked as
3722 requiring configuration, so that if
3723 <tt>--install</tt> is used they will be
3724 configured again if possible.
3727 To prepare for removal of each conflicting package, call:
3728 <example compact="compact">
3729 <var>conflictor's-prerm</var> remove \
3730 in-favour <var>package</var> <var>new-version</var>
3733 <example compact="compact">
3734 <var>conflictor's-postinst</var> abort-remove \
3735 in-favour <var>package</var> <var>new-version</var>
3744 If the package is being upgraded, call:
3745 <example compact="compact">
3746 <var>new-preinst</var> upgrade <var>old-version</var>
3748 If this fails, we call:
3750 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3757 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3759 is called. If this works, then the old version
3760 is in an "Installed" state, or else it is left
3761 in an "Unpacked" state.
3766 If it fails, then the old version is left
3767 in an "Half-Installed" state.
3774 Otherwise, if the package had some configuration
3775 files from a previous version installed (i.e., it
3776 is in the "configuration files only" state):
3777 <example compact="compact">
3778 <var>new-preinst</var> install <var>old-version</var>
3782 <var>new-postrm</var> abort-install <var>old-version</var>
3784 If this fails, the package is left in a
3785 "Half-Installed" state, which requires a
3786 reinstall. If it works, the packages is left in
3787 a "Config Files" state.
3790 Otherwise (i.e., the package was completely purged):
3791 <example compact="compact">
3792 <var>new-preinst</var> install
3795 <example compact="compact">
3796 <var>new-postrm</var> abort-install
3798 If the error-unwind fails, the package is in a
3799 "Half Installed" phase, and requires a
3800 reinstall. If the error unwind works, the
3801 package is in a not installed state.
3808 The new package's files are unpacked, overwriting any
3809 that may be on the system already, for example any
3810 from the old version of the same package or from
3811 another package. Backups of the old files are kept
3812 temporarily, and if anything goes wrong the package
3813 management system will attempt to put them back as
3814 part of the error unwind.
3818 It is an error for a package to contain files which
3819 are on the system in another package, unless
3820 <tt>Replaces</tt> is used (see <ref id="replaces">).
3822 The following paragraph is not currently the case:
3823 Currently the <tt>- - force-overwrite</tt> flag is
3824 enabled, downgrading it to a warning, but this may not
3830 It is a more serious error for a package to contain a
3831 plain file or other kind of non-directory where another
3832 package has a directory (again, unless
3833 <tt>Replaces</tt> is used). This error can be
3834 overridden if desired using
3835 <tt>--force-overwrite-dir</tt>, but this is not
3840 Packages which overwrite each other's files produce
3841 behavior which, though deterministic, is hard for the
3842 system administrator to understand. It can easily
3843 lead to "missing" programs if, for example, a package
3844 is installed which overwrites a file from another
3845 package, and is then removed again.<footnote>
3846 Part of the problem is due to what is arguably a
3847 bug in <prgn>dpkg</prgn>.
3852 A directory will never be replaced by a symbolic link
3853 to a directory or vice versa; instead, the existing
3854 state (symlink or not) will be left alone and
3855 <prgn>dpkg</prgn> will follow the symlink if there is
3864 If the package is being upgraded, call
3865 <example compact="compact">
3866 <var>old-postrm</var> upgrade <var>new-version</var>
3870 If this fails, <prgn>dpkg</prgn> will attempt:
3871 <example compact="compact">
3872 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3874 If this works, installation continues. If not,
3876 <example compact="compact">
3877 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3879 If this fails, the old version is left in an
3880 "Half Installed" state. If it works, dpkg now
3882 <example compact="compact">
3883 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3885 If this fails, the old version is left in an
3886 "Half Installed" state. If it works, dpkg now
3888 <example compact="compact">
3889 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3891 If this fails, the old version is in an
3898 This is the point of no return - if
3899 <prgn>dpkg</prgn> gets this far, it won't back off
3900 past this point if an error occurs. This will
3901 leave the package in a fairly bad state, which
3902 will require a successful re-installation to clear
3903 up, but it's when <prgn>dpkg</prgn> starts doing
3904 things that are irreversible.
3909 Any files which were in the old version of the package
3910 but not in the new are removed.
3914 The new file list replaces the old.
3918 The new maintainer scripts replace the old.
3922 Any packages all of whose files have been overwritten
3923 during the installation, and which aren't required for
3924 dependencies, are considered to have been removed.
3925 For each such package
3928 <prgn>dpkg</prgn> calls:
3929 <example compact="compact">
3930 <var>disappearer's-postrm</var> disappear \
3931 <var>overwriter</var> <var>overwriter-version</var>
3935 The package's maintainer scripts are removed.
3938 It is noted in the status database as being in a
3939 sane state, namely not installed (any conffiles
3940 it may have are ignored, rather than being
3941 removed by <prgn>dpkg</prgn>). Note that
3942 disappearing packages do not have their prerm
3943 called, because <prgn>dpkg</prgn> doesn't know
3944 in advance that the package is going to
3951 Any files in the package we're unpacking that are also
3952 listed in the file lists of other packages are removed
3953 from those lists. (This will lobotomize the file list
3954 of the "conflicting" package if there is one.)
3958 The backup files made during installation, above, are
3964 The new package's status is now sane, and recorded as
3969 Here is another point of no return - if the
3970 conflicting package's removal fails we do not unwind
3971 the rest of the installation; the conflicting package
3972 is left in a half-removed limbo.
3977 If there was a conflicting package we go and do the
3978 removal actions (described below), starting with the
3979 removal of the conflicting package's files (any that
3980 are also in the package being installed have already
3981 been removed from the conflicting package's file list,
3982 and so do not get removed now).
3988 <sect id="configdetails"><heading>Details of configuration</heading>
3991 When we configure a package (this happens with <tt>dpkg
3992 --install</tt> and <tt>dpkg --configure</tt>), we first
3993 update any <tt>conffile</tt>s and then call:
3994 <example compact="compact">
3995 <var>postinst</var> configure <var>most-recently-configured-version</var>
4000 No attempt is made to unwind after errors during
4001 configuration. If the configuration fails, the package is in
4002 a "Failed Config" state, and an error message is generated.
4006 If there is no most recently configured version
4007 <prgn>dpkg</prgn> will pass a null argument.
4010 Historical note: Truly ancient (pre-1997) versions of
4011 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4012 (including the angle brackets) in this case. Even older
4013 ones did not pass a second argument at all, under any
4014 circumstance. Note that upgrades using such an old dpkg
4015 version are unlikely to work for other reasons, even if
4016 this old argument behavior is handled by your postinst script.
4022 <sect id="removedetails"><heading>Details of removal and/or
4023 configuration purging</heading>
4029 <example compact="compact">
4030 <var>prerm</var> remove
4034 If prerm fails during replacement due to conflict
4036 <var>conflictor's-postinst</var> abort-remove \
4037 in-favour <var>package</var> <var>new-version</var>
4041 <var>postinst</var> abort-remove
4045 If this fails, the package is in a "Failed-Config"
4046 state, or else it remains "Installed".
4050 The package's files are removed (except <tt>conffile</tt>s).
4053 <example compact="compact">
4054 <var>postrm</var> remove
4058 If it fails, there's no error unwind, and the package is in
4059 an "Half-Installed" state.
4064 All the maintainer scripts except the <prgn>postrm</prgn>
4069 If we aren't purging the package we stop here. Note
4070 that packages which have no <prgn>postrm</prgn> and no
4071 <tt>conffile</tt>s are automatically purged when
4072 removed, as there is no difference except for the
4073 <prgn>dpkg</prgn> status.
4077 The <tt>conffile</tt>s and any backup files
4078 (<tt>~</tt>-files, <tt>#*#</tt> files,
4079 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4084 <example compact="compact">
4085 <var>postrm</var> purge
4089 If this fails, the package remains in a "Config-Files"
4094 The package's file list is removed.
4103 <chapt id="relationships">
4104 <heading>Declaring relationships between packages</heading>
4106 <sect id="depsyntax">
4107 <heading>Syntax of relationship fields</heading>
4110 These fields all have a uniform syntax. They are a list of
4111 package names separated by commas.
4115 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4116 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4117 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4118 control file fields of the package, which declare
4119 dependencies on other packages, the package names listed may
4120 also include lists of alternative package names, separated
4121 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4122 if any one of the alternative packages is installed, that
4123 part of the dependency is considered to be satisfied.
4127 All of the fields except for <tt>Provides</tt> may restrict
4128 their applicability to particular versions of each named
4129 package. This is done in parentheses after each individual
4130 package name; the parentheses should contain a relation from
4131 the list below followed by a version number, in the format
4132 described in <ref id="f-Version">.
4136 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4137 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4138 strictly earlier, earlier or equal, exactly equal, later or
4139 equal and strictly later, respectively. The deprecated
4140 forms <tt><</tt> and <tt>></tt> were used to mean
4141 earlier/later or equal, rather than strictly earlier/later,
4142 so they should not appear in new packages (though
4143 <prgn>dpkg</prgn> still supports them).
4147 Whitespace may appear at any point in the version
4148 specification subject to the rules in <ref
4149 id="controlsyntax">, and must appear where it's necessary to
4150 disambiguate; it is not otherwise significant. All of the
4151 relationship fields may span multiple lines. For
4152 consistency and in case of future changes to
4153 <prgn>dpkg</prgn> it is recommended that a single space be
4154 used after a version relationship and before a version
4155 number; it is also conventional to put a single space after
4156 each comma, on either side of each vertical bar, and before
4157 each open parenthesis. When wrapping a relationship field, it
4158 is conventional to do so after a comma and before the space
4159 following that comma.
4163 For example, a list of dependencies might appear as:
4164 <example compact="compact">
4167 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4172 All fields that specify build-time relationships
4173 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4174 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4175 may be restricted to a certain set of architectures. This
4176 is indicated in brackets after each individual package name and
4177 the optional version specification. The brackets enclose a
4178 list of Debian architecture names separated by whitespace.
4179 Exclamation marks may be prepended to each of the names.
4180 (It is not permitted for some names to be prepended with
4181 exclamation marks while others aren't.) If the current Debian
4182 host architecture is not in this list and there are no
4183 exclamation marks in the list, or it is in the list with a
4184 prepended exclamation mark, the package name and the
4185 associated version specification are ignored completely for
4186 the purposes of defining the relationships.
4191 <example compact="compact">
4193 Build-Depends-Indep: texinfo
4194 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4195 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4197 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4198 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4199 <tt>gnumach-dev</tt> only on hurd-i386.
4203 If the architecture-restricted dependency is part of a set of
4204 alternatives using <tt>|</tt>, that alternative is ignored
4205 completely on architectures that do not match the restriction.
4207 <example compact="compact">
4208 Build-Depends: foo [!i386] | bar [!amd64]
4210 is equivalent to <tt>bar</tt> on the i386 architecture, to
4211 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4212 bar</tt> on all other architectures.
4216 Note that the binary package relationship fields such as
4217 <tt>Depends</tt> appear in one of the binary package
4218 sections of the control file, whereas the build-time
4219 relationships such as <tt>Build-Depends</tt> appear in the
4220 source package section of the control file (which is the
4225 <sect id="binarydeps">
4226 <heading>Binary Dependencies - <tt>Depends</tt>,
4227 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4228 <tt>Pre-Depends</tt>
4232 Packages can declare in their control file that they have
4233 certain relationships to other packages - for example, that
4234 they may not be installed at the same time as certain other
4235 packages, and/or that they depend on the presence of others.
4239 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4240 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4241 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4245 These seven fields are used to declare a dependency
4246 relationship by one package on another. Except for
4247 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4248 depending (binary) package's control file.
4249 (<tt>Enhances</tt> appears in the recommending package's
4250 control file, and <tt>Breaks</tt> appears in the version of
4251 depended-on package which causes the named package to
4256 A <tt>Depends</tt> field takes effect <em>only</em> when a
4257 package is to be configured. It does not prevent a package
4258 being on the system in an unconfigured state while its
4259 dependencies are unsatisfied, and it is possible to replace
4260 a package whose dependencies are satisfied and which is
4261 properly installed with a different version whose
4262 dependencies are not and cannot be satisfied; when this is
4263 done the depending package will be left unconfigured (since
4264 attempts to configure it will give errors) and will not
4265 function properly. If it is necessary, a
4266 <tt>Pre-Depends</tt> field can be used, which has a partial
4267 effect even when a package is being unpacked, as explained
4268 in detail below. (The other three dependency fields,
4269 <tt>Recommends</tt>, <tt>Suggests</tt> and
4270 <tt>Enhances</tt>, are only used by the various front-ends
4271 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4272 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4276 For this reason packages in an installation run are usually
4277 all unpacked first and all configured later; this gives
4278 later versions of packages with dependencies on later
4279 versions of other packages the opportunity to have their
4280 dependencies satisfied.
4284 In case of circular dependencies, since installation or
4285 removal order honoring the dependency order can't be
4286 established, dependency loops are broken at some point
4287 (based on rules below), and some packages may not be able to
4288 rely on their dependencies being present when being
4289 installed or removed, depending on which side of the break
4290 of the circular dependency loop they happen to be on. If one
4291 of the packages in the loop has no postinst script, then the
4292 cycle will be broken at that package, so as to ensure that
4293 all postinst scripts run with the dependencies properly
4294 configured if this is possible. Otherwise the breaking point
4299 The <tt>Depends</tt> field thus allows package maintainers
4300 to impose an order in which packages should be configured.
4304 The meaning of the five dependency fields is as follows:
4306 <tag><tt>Depends</tt></tag>
4309 This declares an absolute dependency. A package will
4310 not be configured unless all of the packages listed in
4311 its <tt>Depends</tt> field have been correctly
4316 The <tt>Depends</tt> field should be used if the
4317 depended-on package is required for the depending
4318 package to provide a significant amount of
4323 The <tt>Depends</tt> field should also be used if the
4324 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4325 <prgn>postrm</prgn> scripts require the package to be
4326 present in order to run. Note, however, that the
4327 <prgn>postrm</prgn> cannot rely on any non-essential
4328 packages to be present during the <tt>purge</tt>
4332 <tag><tt>Recommends</tt></tag>
4335 This declares a strong, but not absolute, dependency.
4339 The <tt>Recommends</tt> field should list packages
4340 that would be found together with this one in all but
4341 unusual installations.
4345 <tag><tt>Suggests</tt></tag>
4347 This is used to declare that one package may be more
4348 useful with one or more others. Using this field
4349 tells the packaging system and the user that the
4350 listed packages are related to this one and can
4351 perhaps enhance its usefulness, but that installing
4352 this one without them is perfectly reasonable.
4355 <tag><tt>Enhances</tt></tag>
4357 This field is similar to Suggests but works in the
4358 opposite direction. It is used to declare that a
4359 package can enhance the functionality of another
4363 <tag><tt>Pre-Depends</tt></tag>
4366 This field is like <tt>Depends</tt>, except that it
4367 also forces <prgn>dpkg</prgn> to complete installation
4368 of the packages named before even starting the
4369 installation of the package which declares the
4370 pre-dependency, as follows:
4374 When a package declaring a pre-dependency is about to
4375 be <em>unpacked</em> the pre-dependency can be
4376 satisfied if the depended-on package is either fully
4377 configured, <em>or even if</em> the depended-on
4378 package(s) are only unpacked or half-configured,
4379 provided that they have been configured correctly at
4380 some point in the past (and not removed or partially
4381 removed since). In this case, both the
4382 previously-configured and currently unpacked or
4383 half-configured versions must satisfy any version
4384 clause in the <tt>Pre-Depends</tt> field.
4388 When the package declaring a pre-dependency is about
4389 to be <em>configured</em>, the pre-dependency will be
4390 treated as a normal <tt>Depends</tt>, that is, it will
4391 be considered satisfied only if the depended-on
4392 package has been correctly configured.
4396 <tt>Pre-Depends</tt> should be used sparingly,
4397 preferably only by packages whose premature upgrade or
4398 installation would hamper the ability of the system to
4399 continue with any upgrade that might be in progress.
4403 <tt>Pre-Depends</tt> are also required if the
4404 <prgn>preinst</prgn> script depends on the named
4405 package. It is best to avoid this situation if
4413 When selecting which level of dependency to use you should
4414 consider how important the depended-on package is to the
4415 functionality of the one declaring the dependency. Some
4416 packages are composed of components of varying degrees of
4417 importance. Such a package should list using
4418 <tt>Depends</tt> the package(s) which are required by the
4419 more important components. The other components'
4420 requirements may be mentioned as Suggestions or
4421 Recommendations, as appropriate to the components' relative
4427 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4430 Using <tt>Breaks</tt> may cause problems for upgrades from older
4431 versions of Debian and should not be used until the stable
4432 release of Debian supports <tt>Breaks</tt>.
4436 When one binary package declares that it breaks another,
4437 <prgn>dpkg</prgn> will refuse to allow the package which
4438 declares <tt>Breaks</tt> be installed unless the broken
4439 package is deconfigured first, and it will refuse to
4440 allow the broken package to be reconfigured.
4444 A package will not be regarded as causing breakage merely
4445 because its configuration files are still installed; it must
4446 be at least half-installed.
4450 A special exception is made for packages which declare that
4451 they break their own package name or a virtual package which
4452 they provide (see below): this does not count as a real
4457 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4458 version clause; such a <tt>Breaks</tt> is introduced in the
4459 version of an (implicit or explicit) dependency which
4460 violates an assumption or reveals a bug in earlier versions
4461 of the broken package. This use of <tt>Breaks</tt> will
4462 inform higher-level package management tools that broken
4463 package must be upgraded before the new one.
4467 If the breaking package also overwrites some files from the
4468 older package, it should use <tt>Replaces</tt> (not
4469 <tt>Conflicts</tt>) to ensure this goes smoothly.
4473 <sect id="conflicts">
4474 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4477 When one binary package declares a conflict with another
4478 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4479 refuse to allow them to be installed on the system at the
4484 If one package is to be installed, the other must be removed
4485 first - if the package being installed is marked as
4486 replacing (see <ref id="replaces">) the one on the system,
4487 or the one on the system is marked as deselected, or both
4488 packages are marked <tt>Essential</tt>, then
4489 <prgn>dpkg</prgn> will automatically remove the package
4490 which is causing the conflict, otherwise it will halt the
4491 installation of the new package with an error. This
4492 mechanism is specifically designed to produce an error when
4493 the installed package is <tt>Essential</tt>, but the new
4498 A package will not cause a conflict merely because its
4499 configuration files are still installed; it must be at least
4504 A special exception is made for packages which declare a
4505 conflict with their own package name, or with a virtual
4506 package which they provide (see below): this does not
4507 prevent their installation, and allows a package to conflict
4508 with others providing a replacement for it. You use this
4509 feature when you want the package in question to be the only
4510 package providing some feature.
4514 A <tt>Conflicts</tt> entry should almost never have an
4515 "earlier than" version clause. This would prevent
4516 <prgn>dpkg</prgn> from upgrading or installing the package
4517 which declared such a conflict until the upgrade or removal
4518 of the conflicted-with package had been completed. Instead,
4519 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4520 by the stable release of Debian).
4524 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4528 As well as the names of actual ("concrete") packages, the
4529 package relationship fields <tt>Depends</tt>,
4530 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4531 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4532 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4533 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4534 may mention "virtual packages".
4538 A <em>virtual package</em> is one which appears in the
4539 <tt>Provides</tt> control file field of another package.
4540 The effect is as if the package(s) which provide a
4541 particular virtual package name had been listed by name
4542 everywhere the virtual package name appears. (See also <ref
4547 If there are both concrete and virtual packages of the same
4548 name, then the dependency may be satisfied (or the conflict
4549 caused) by either the concrete package with the name in
4550 question or any other concrete package which provides the
4551 virtual package with the name in question. This is so that,
4552 for example, supposing we have
4553 <example compact="compact">
4556 </example> and someone else releases an enhanced version of
4557 the <tt>bar</tt> package they can say:
4558 <example compact="compact">
4562 and the <tt>bar-plus</tt> package will now also satisfy the
4563 dependency for the <tt>foo</tt> package.
4567 If a relationship field has a version number attached
4568 then only real packages will be considered to see whether
4569 the relationship is satisfied (or the prohibition violated,
4570 for a conflict or breakage) - it is assumed that a real
4571 package which provides the virtual package is not of the
4572 "right" version. So, a <tt>Provides</tt> field may not
4573 contain version numbers, and the version number of the
4574 concrete package which provides a particular virtual package
4575 will not be looked at when considering a dependency on or
4576 conflict with the virtual package name.
4580 It is likely that the ability will be added in a future
4581 release of <prgn>dpkg</prgn> to specify a version number for
4582 each virtual package it provides. This feature is not yet
4583 present, however, and is expected to be used only
4588 If you want to specify which of a set of real packages
4589 should be the default to satisfy a particular dependency on
4590 a virtual package, you should list the real package as an
4591 alternative before the virtual one.
4596 <sect id="replaces"><heading>Overwriting files and replacing
4597 packages - <tt>Replaces</tt></heading>
4600 Packages can declare in their control file that they should
4601 overwrite files in certain other packages, or completely
4602 replace other packages. The <tt>Replaces</tt> control file
4603 field has these two distinct purposes.
4606 <sect1><heading>Overwriting files in other packages</heading>
4609 Firstly, as mentioned before, it is usually an error for a
4610 package to contain files which are on the system in
4615 However, if the overwriting package declares that it
4616 <tt>Replaces</tt> the one containing the file being
4617 overwritten, then <prgn>dpkg</prgn> will replace the file
4618 from the old package with that from the new. The file
4619 will no longer be listed as "owned" by the old package.
4623 If a package is completely replaced in this way, so that
4624 <prgn>dpkg</prgn> does not know of any files it still
4625 contains, it is considered to have "disappeared". It will
4626 be marked as not wanted on the system (selected for
4627 removal) and not installed. Any <tt>conffile</tt>s
4628 details noted for the package will be ignored, as they
4629 will have been taken over by the overwriting package. The
4630 package's <prgn>postrm</prgn> script will be run with a
4631 special argument to allow the package to do any final
4632 cleanup required. See <ref id="mscriptsinstact">.
4635 Replaces is a one way relationship -- you have to
4636 install the replacing package after the replaced
4643 For this usage of <tt>Replaces</tt>, virtual packages (see
4644 <ref id="virtual">) are not considered when looking at a
4645 <tt>Replaces</tt> field - the packages declared as being
4646 replaced must be mentioned by their real names.
4650 Furthermore, this usage of <tt>Replaces</tt> only takes
4651 effect when both packages are at least partially on the
4652 system at once, so that it can only happen if they do not
4653 conflict or if the conflict has been overridden.
4658 <sect1><heading>Replacing whole packages, forcing their
4662 Secondly, <tt>Replaces</tt> allows the packaging system to
4663 resolve which package should be removed when there is a
4664 conflict - see <ref id="conflicts">. This usage only
4665 takes effect when the two packages <em>do</em> conflict,
4666 so that the two usages of this field do not interfere with
4671 In this situation, the package declared as being replaced
4672 can be a virtual package, so for example, all mail
4673 transport agents (MTAs) would have the following fields in
4674 their control files:
4675 <example compact="compact">
4676 Provides: mail-transport-agent
4677 Conflicts: mail-transport-agent
4678 Replaces: mail-transport-agent
4680 ensuring that only one MTA can be installed at any one
4685 <sect id="sourcebinarydeps">
4686 <heading>Relationships between source and binary packages -
4687 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4688 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4692 Source packages that require certain binary packages to be
4693 installed or absent at the time of building the package
4694 can declare relationships to those binary packages.
4698 This is done using the <tt>Build-Depends</tt>,
4699 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4700 <tt>Build-Conflicts-Indep</tt> control file fields.
4704 Build-dependencies on "build-essential" binary packages can be
4705 omitted. Please see <ref id="pkg-relations"> for more information.
4709 The dependencies and conflicts they define must be satisfied
4710 (as defined earlier for binary packages) in order to invoke
4711 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4713 If you make "build-arch" or "binary-arch", you need
4714 Build-Depends. If you make "build-indep" or
4715 "binary-indep", you need Build-Depends and
4716 Build-Depends-Indep. If you make "build" or "binary",
4720 There is no Build-Depends-Arch; this role is essentially
4721 met with Build-Depends. Anyone building the
4722 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4723 is basically assumed to be building the whole package
4724 anyway and so installs all build dependencies. The
4725 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4726 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4727 does not yet know how to check for its existence) and
4728 <tt>binary-arch</tt>.
4731 The purpose of the original split, I recall, was so that
4732 the autobuilders wouldn't need to install extra packages
4733 needed only for the binary-indep targets. But without a
4734 build-arch/build-indep split, this didn't work, since
4735 most of the work is done in the build target, not in the
4741 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4743 The <tt>Build-Depends</tt> and
4744 <tt>Build-Conflicts</tt> fields must be satisfied when
4745 any of the following targets is invoked:
4746 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4747 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4748 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4750 <tag><tt>Build-Depends-Indep</tt>,
4751 <tt>Build-Conflicts-Indep</tt></tag>
4753 The <tt>Build-Depends-Indep</tt> and
4754 <tt>Build-Conflicts-Indep</tt> fields must be
4755 satisfied when any of the following targets is
4756 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4757 <tt>binary</tt> and <tt>binary-indep</tt>.
4767 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4770 Packages containing shared libraries must be constructed with
4771 a little care to make sure that the shared library is always
4772 available. This is especially important for packages whose
4773 shared libraries are vitally important, such as the C library
4774 (currently <tt>libc6</tt>).
4778 Packages involving shared libraries should be split up into
4779 several binary packages. This section mostly deals with how
4780 this separation is to be accomplished; rules for files within
4781 the shared library packages are in <ref id="libraries"> instead.
4784 <sect id="sharedlibs-runtime">
4785 <heading>Run-time shared libraries</heading>
4788 The run-time shared library needs to be placed in a package
4789 whose name changes whenever the shared object version
4792 Since it is common place to install several versions of a
4793 package that just provides shared libraries, it is a
4794 good idea that the library package should not
4795 contain any extraneous non-versioned files, unless they
4796 happen to be in versioned directories.</p>
4798 The most common mechanism is to place it in a package
4800 <package><var>libraryname</var><var>soversion</var></package>,
4801 where <file><var>soversion</var></file> is the version number
4802 in the soname of the shared library<footnote>
4803 The soname is the shared object name: it's the thing
4804 that has to match exactly between building an executable
4805 and running it for the dynamic linker to be able run the
4806 program. For example, if the soname of the library is
4807 <file>libfoo.so.6</file>, the library package would be
4808 called <file>libfoo6</file>.
4810 Alternatively, if it would be confusing to directly append
4811 <var>soversion</var> to <var>libraryname</var> (e.g. because
4812 <var>libraryname</var> itself ends in a number), you may use
4813 <package><var>libraryname</var>-<var>soversion</var></package> and
4814 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4819 If you have several shared libraries built from the same
4820 source tree you may lump them all together into a single
4821 shared library package, provided that you change all of
4822 their sonames at once (so that you don't get filename
4823 clashes if you try to install different versions of the
4824 combined shared libraries package).
4828 The package should install the shared libraries under
4829 their normal names. For example, the <package>libgdbm3</package>
4830 package should install <file>libgdbm.so.3.0.0</file> as
4831 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4832 renamed or re-linked by any <prgn>prerm</prgn> or
4833 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4834 of renaming things safely without affecting running programs,
4835 and attempts to interfere with this are likely to lead to
4840 Shared libraries should not be installed executable, since
4841 the dynamic linker does not require this and trying to
4842 execute a shared library usually results in a core dump.
4846 The run-time library package should include the symbolic link that
4847 <prgn>ldconfig</prgn> would create for the shared libraries.
4848 For example, the <package>libgdbm3</package> package should include
4849 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4850 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4851 linker (for example <prgn>ld.so</prgn> or
4852 <prgn>ld-linux.so.*</prgn>) can find the library between the
4853 time that <prgn>dpkg</prgn> installs it and the time that
4854 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4856 The package management system requires the library to be
4857 placed before the symbolic link pointing to it in the
4858 <file>.deb</file> file. This is so that when
4859 <prgn>dpkg</prgn> comes to install the symlink
4860 (overwriting the previous symlink pointing at an older
4861 version of the library), the new shared library is already
4862 in place. In the past, this was achieved by creating the
4863 library in the temporary packaging directory before
4864 creating the symlink. Unfortunately, this was not always
4865 effective, since the building of the tar file in the
4866 <file>.deb</file> depended on the behavior of the underlying
4867 file system. Some file systems (such as reiserfs) reorder
4868 the files so that the order of creation is forgotten.
4869 Since version 1.7.0, <prgn>dpkg</prgn>
4870 reorders the files itself as necessary when building a
4871 package. Thus it is no longer important to concern
4872 oneself with the order of file creation.
4876 <sect1 id="ldconfig">
4877 <heading><tt>ldconfig</tt></heading>
4880 Any package installing shared libraries in one of the default
4881 library directories of the dynamic linker (which are currently
4882 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4883 listed in <file>/etc/ld.so.conf</file><footnote>
4885 <list compact="compact">
4886 <item>/usr/local/lib</item>
4887 <item>/usr/lib/libc5-compat</item>
4888 <item>/lib/libc5-compat</item>
4891 must use <prgn>ldconfig</prgn> to update the shared library
4896 The package maintainer scripts must only call
4897 <prgn>ldconfig</prgn> under these circumstances:
4898 <list compact="compact">
4899 <item>When the <prgn>postinst</prgn> script is run with a
4900 first argument of <tt>configure</tt>, the script must call
4901 <prgn>ldconfig</prgn>, and may optionally invoke
4902 <prgn>ldconfig</prgn> at other times.
4904 <item>When the <prgn>postrm</prgn> script is run with a
4905 first argument of <tt>remove</tt>, the script should call
4906 <prgn>ldconfig</prgn>.
4911 During install or upgrade, the preinst is called before
4912 the new files are installed, so calling "ldconfig" is
4913 pointless. The preinst of an existing package can also be
4914 called if an upgrade fails. However, this happens during
4915 the critical time when a shared libs may exist on-disk
4916 under a temporary name. Thus, it is dangerous and
4917 forbidden by current policy to call "ldconfig" at this
4922 When a package is installed or upgraded, "postinst
4923 configure" runs after the new files are safely on-disk.
4924 Since it is perfectly safe to invoke ldconfig
4925 unconditionally in a postinst, it is OK for a package to
4926 simply put ldconfig in its postinst without checking the
4927 argument. The postinst can also be called to recover from
4928 a failed upgrade. This happens before any new files are
4929 unpacked, so there is no reason to call "ldconfig" at this
4934 For a package that is being removed, prerm is
4935 called with all the files intact, so calling ldconfig is
4936 useless. The other calls to "prerm" happen in the case of
4937 upgrade at a time when all the files of the old package
4938 are on-disk, so again calling "ldconfig" is pointless.
4942 postrm, on the other hand, is called with the "remove"
4943 argument just after the files are removed, so this is
4944 the proper time to call "ldconfig" to notify the system
4945 of the fact that the shared libraries from the package
4946 are removed. The postrm can be called at several other
4947 times. At the time of "postrm purge", "postrm
4948 abort-install", or "postrm abort-upgrade", calling
4949 "ldconfig" is useless because the shared lib files are
4950 not on-disk. However, when "postrm" is invoked with
4951 arguments "upgrade", "failed-upgrade", or "disappear", a
4952 shared lib may exist on-disk under a temporary filename.
4960 <sect id="sharedlibs-support-files">
4961 <heading>Shared library support files</heading>
4964 If your package contains files whose names do not change with
4965 each change in the library shared object version, you must not
4966 put them in the shared library package. Otherwise, several
4967 versions of the shared library cannot be installed at the same
4968 time without filename clashes, making upgrades and transitions
4969 unnecessarily difficult.
4973 It is recommended that supporting files and run-time support
4974 programs that do not need to be invoked manually by users, but
4975 are nevertheless required for the package to function, be placed
4976 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4977 preferably under <file>/usr/lib/</file><var>package-name</var>.
4978 If the program or file is architecture independent, the
4979 recommendation is for it to be placed in a subdirectory of
4980 <file>/usr/share</file> instead, preferably under
4981 <file>/usr/share/</file><var>package-name</var>. Following the
4982 <var>package-name</var> naming convention ensures that the file
4983 names change when the shared object version changes.
4987 Run-time support programs that use the shared library but are
4988 not required for the library to function or files used by the
4989 shared library that can be used by any version of the shared
4990 library package should instead be put in a separate package.
4991 This package might typically be named
4992 <package><var>libraryname</var>-tools</package>; note the
4993 absence of the <var>soversion</var> in the package name.
4997 Files and support programs only useful when compiling software
4998 against the library should be included in the development
4999 package for the library.<footnote>
5000 For example, a <file><var>package-name</var>-config</file>
5001 script or <package>pkg-config</package> configuration files.
5006 <sect id="sharedlibs-static">
5007 <heading>Static libraries</heading>
5010 The static library (<file><var>libraryname.a</var></file>)
5011 is usually provided in addition to the shared version.
5012 It is placed into the development package (see below).
5016 In some cases, it is acceptable for a library to be
5017 available in static form only; these cases include:
5019 <item>libraries for languages whose shared library support
5020 is immature or unstable</item>
5021 <item>libraries whose interfaces are in flux or under
5022 development (commonly the case when the library's
5023 major version number is zero, or where the ABI breaks
5024 across patchlevels)</item>
5025 <item>libraries which are explicitly intended to be
5026 available only in static form by their upstream
5031 <sect id="sharedlibs-dev">
5032 <heading>Development files</heading>
5035 The development files associated to a shared library need to be
5036 placed in a package called
5037 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5038 or if you prefer only to support one development version at a
5039 time, <package><var>libraryname</var>-dev</package>.
5043 In case several development versions of a library exist, you may
5044 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5045 <ref id="conflicts">) to ensure that the user only installs one
5046 development version at a time (as different development versions are
5047 likely to have the same header files in them, which would cause a
5048 filename clash if both were installed).
5052 The development package should contain a symlink for the associated
5053 shared library without a version number. For example, the
5054 <package>libgdbm-dev</package> package should include a symlink
5055 from <file>/usr/lib/libgdbm.so</file> to
5056 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5057 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5058 <file>libgdbm.so</file> when compiling dynamically.
5062 <sect id="sharedlibs-intradeps">
5063 <heading>Dependencies between the packages of the same library</heading>
5066 Typically the development version should have an exact
5067 version dependency on the runtime library, to make sure that
5068 compilation and linking happens correctly. The
5069 <tt>${binary:Version}</tt> substitution variable can be
5070 useful for this purpose.
5072 Previously, <tt>${Source-Version}</tt> was used, but its name
5073 was confusing and it has been deprecated since dpkg 1.13.19.
5078 <sect id="sharedlibs-shlibdeps">
5079 <heading>Dependencies between the library and other packages -
5080 the <tt>shlibs</tt> system</heading>
5083 If a package contains a binary or library which links to a
5084 shared library, we must ensure that when the package is
5085 installed on the system, all of the libraries needed are
5086 also installed. This requirement led to the creation of the
5087 <tt>shlibs</tt> system, which is very simple in its design:
5088 any package which <em>provides</em> a shared library also
5089 provides information on the package dependencies required to
5090 ensure the presence of this library, and any package which
5091 <em>uses</em> a shared library uses this information to
5092 determine the dependencies it requires. The files which
5093 contain the mapping from shared libraries to the necessary
5094 dependency information are called <file>shlibs</file> files.
5098 Thus, when a package is built which contains any shared
5099 libraries, it must provide a <file>shlibs</file> file for other
5100 packages to use, and when a package is built which contains
5101 any shared libraries or compiled binaries, it must run
5102 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5103 on these to determine the libraries used and hence the
5104 dependencies needed by this package.<footnote>
5106 In the past, the shared libraries linked to were
5107 determined by calling <prgn>ldd</prgn>, but now
5108 <prgn>objdump</prgn> is used to do this. The only
5109 change this makes to package building is that
5110 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5111 libraries, whereas in the past this was unnecessary.
5112 The rest of this footnote explains the advantage that
5117 We say that a binary <tt>foo</tt> <em>directly</em> uses
5118 a library <tt>libbar</tt> if it is explicitly linked
5119 with that library (that is, it uses the flag
5120 <tt>-lbar</tt> during the linking stage). Other
5121 libraries that are needed by <tt>libbar</tt> are linked
5122 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5123 linker will load them automatically when it loads
5124 <tt>libbar</tt>. A package should depend on
5125 the libraries it directly uses, and the dependencies for
5126 those libraries should automatically pull in the other
5131 Unfortunately, the <prgn>ldd</prgn> program shows both
5132 the directly and indirectly used libraries, meaning that
5133 the dependencies determined included both direct and
5134 indirect dependencies. The use of <prgn>objdump</prgn>
5135 avoids this problem by determining only the directly
5140 A good example of where this helps is the following. We
5141 could update <tt>libimlib</tt> with a new version that
5142 supports a new graphics format called dgf (but retaining
5143 the same major version number). If we used the old
5144 <prgn>ldd</prgn> method, every package that uses
5145 <tt>libimlib</tt> would need to be recompiled so it
5146 would also depend on <tt>libdgf</tt> or it wouldn't run
5147 due to missing symbols. However with the new system,
5148 packages using <tt>libimlib</tt> can rely on
5149 <tt>libimlib</tt> itself having the dependency on
5150 <tt>libdgf</tt> and so they would not need rebuilding.
5156 In the following sections, we will first describe where the
5157 various <tt>shlibs</tt> files are to be found, then how to
5158 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5159 file format and how to create them if your package contains a
5164 <heading>The <tt>shlibs</tt> files present on the system</heading>
5167 There are several places where <tt>shlibs</tt> files are
5168 found. The following list gives them in the order in which
5170 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5171 (The first one which gives the required information is used.)
5177 <p><file>debian/shlibs.local</file></p>
5180 This lists overrides for this package. Its use is
5181 described below (see <ref id="shlibslocal">).
5186 <p><file>/etc/dpkg/shlibs.override</file></p>
5189 This lists global overrides. This list is normally
5190 empty. It is maintained by the local system
5196 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5199 When packages are being built, any
5200 <file>debian/shlibs</file> files are copied into the
5201 control file area of the temporary build directory and
5202 given the name <file>shlibs</file>. These files give
5203 details of any shared libraries included in the
5205 An example may help here. Let us say that the
5206 source package <tt>foo</tt> generates two binary
5207 packages, <tt>libfoo2</tt> and
5208 <tt>foo-runtime</tt>. When building the binary
5209 packages, the two packages are created in the
5210 directories <file>debian/libfoo2</file> and
5211 <file>debian/foo-runtime</file> respectively.
5212 (<file>debian/tmp</file> could be used instead of one
5213 of these.) Since <tt>libfoo2</tt> provides the
5214 <tt>libfoo</tt> shared library, it will require a
5215 <tt>shlibs</tt> file, which will be installed in
5216 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5218 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5219 when <prgn>dpkg-shlibdeps</prgn> is run on the
5221 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5223 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5224 determine whether <tt>foo-prog</tt>'s library
5225 dependencies are satisfied by any of the libraries
5226 provided by <tt>libfoo2</tt>. For this reason,
5227 <prgn>dpkg-shlibdeps</prgn> must only be run once
5228 all of the individual binary packages'
5229 <tt>shlibs</tt> files have been installed into the
5236 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5239 These are the <file>shlibs</file> files corresponding to
5240 all of the packages installed on the system, and are
5241 maintained by the relevant package maintainers.
5246 <p><file>/etc/dpkg/shlibs.default</file></p>
5249 This file lists any shared libraries whose packages
5250 have failed to provide correct <file>shlibs</file> files.
5251 It was used when the <file>shlibs</file> setup was first
5252 introduced, but it is now normally empty. It is
5253 maintained by the <tt>dpkg</tt> maintainer.
5261 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5262 <file>shlibs</file> files</heading>
5266 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5267 into your <file>debian/rules</file> file. If your package
5268 contains only compiled binaries and libraries (but no scripts),
5269 you can use a command such as:
5270 <example compact="compact">
5271 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5272 debian/tmp/usr/lib/*
5274 Otherwise, you will need to explicitly list the compiled
5275 binaries and libraries.<footnote>
5276 If you are using <tt>debhelper</tt>, the
5277 <prgn>dh_shlibdeps</prgn> program will do this work for
5278 you. It will also correctly handle multi-binary
5284 This command puts the dependency information into the
5285 <file>debian/substvars</file> file, which is then used by
5286 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5287 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5288 field in the control file for this to work.
5292 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5293 done. If it does complain you might need to create your own
5294 <file>debian/shlibs.local</file> file, as explained below (see
5295 <ref id="shlibslocal">).
5299 If you have multiple binary packages, you will need to call
5300 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5301 compiled libraries or binaries. In such a case, you will
5302 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5303 utilities to specify a different <file>substvars</file> file.
5307 If you are creating a udeb for use in the Debian Installer, you
5308 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5309 the dependency line of type <tt>udeb</tt> by adding
5310 <tt>-tudeb</tt> as option<footnote>
5311 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5312 will automatically add this option if it knows it is
5314 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5315 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5316 fall back to the regular dependency line.
5320 For more details on dpkg-shlibdeps, please see
5321 <ref id="pkg-dpkg-shlibdeps"> and
5322 <manref name="dpkg-shlibdeps" section="1">.
5327 <heading>The <file>shlibs</file> File Format</heading>
5330 Each <file>shlibs</file> file has the same format. Lines
5331 beginning with <tt>#</tt> are considered to be comments and
5332 are ignored. Each line is of the form:
5333 <example compact="compact">
5334 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5339 We will explain this by reference to the example of the
5340 <tt>zlib1g</tt> package, which (at the time of writing)
5341 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5345 <var>type</var> is an optional element that indicates the type
5346 of package for which the line is valid. The only type currently
5347 in use is <tt>udeb</tt>. The colon and space after the type are
5352 <var>library-name</var> is the name of the shared library,
5353 in this case <tt>libz</tt>. (This must match the name part
5354 of the soname, see below.)
5358 <var>soname-version</var> is the version part of the soname of
5359 the library. The soname is the thing that must exactly match
5360 for the library to be recognized by the dynamic linker, and is
5362 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5363 example, <tt>libz.so.1</tt>.<footnote>
5364 This can be determined using the command
5365 <example compact="compact">
5366 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5369 The version part is the part which comes after
5370 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5374 <var>dependencies</var> has the same syntax as a dependency
5375 field in a binary package control file. It should give
5376 details of which packages are required to satisfy a binary
5377 built against the version of the library contained in the
5378 package. See <ref id="depsyntax"> for details.
5382 In our example, if the first version of the <tt>zlib1g</tt>
5383 package which contained a minor number of at least
5384 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5385 <tt>shlibs</tt> entry for this library could say:
5386 <example compact="compact">
5387 libz 1 zlib1g (>= 1:1.1.3)
5389 The version-specific dependency is to avoid warnings from
5390 the dynamic linker about using older shared libraries with
5395 As zlib1g also provides a udeb containing the shared library,
5396 there would also be a second line:
5397 <example compact="compact">
5398 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5404 <heading>Providing a <file>shlibs</file> file</heading>
5407 If your package provides a shared library, you need to create
5408 a <file>shlibs</file> file following the format described above.
5409 It is usual to call this file <file>debian/shlibs</file> (but if
5410 you have multiple binary packages, you might want to call it
5411 <file>debian/shlibs.<var>package</var></file> instead). Then
5412 let <file>debian/rules</file> install it in the control area:
5413 <example compact="compact">
5414 install -m644 debian/shlibs debian/tmp/DEBIAN
5416 or, in the case of a multi-binary package:
5417 <example compact="compact">
5418 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5420 An alternative way of doing this is to create the
5421 <file>shlibs</file> file in the control area directly from
5422 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5423 file at all,<footnote>
5424 This is what <prgn>dh_makeshlibs</prgn> in the
5425 <tt>debhelper</tt> suite does. If your package also has a udeb
5426 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5427 automatically generate the <tt>udeb:</tt> lines if you specify
5428 the name of the udeb with the <tt>--add-udeb</tt> option.
5430 since the <file>debian/shlibs</file> file itself is ignored by
5431 <prgn>dpkg-shlibdeps</prgn>.
5435 As <prgn>dpkg-shlibdeps</prgn> reads the
5436 <file>DEBIAN/shlibs</file> files in all of the binary packages
5437 being built from this source package, all of the
5438 <file>DEBIAN/shlibs</file> files should be installed before
5439 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5444 <sect1 id="shlibslocal">
5445 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5448 This file is intended only as a <em>temporary</em> fix if
5449 your binaries or libraries depend on a library whose package
5450 does not yet provide a correct <file>shlibs</file> file.
5454 We will assume that you are trying to package a binary
5455 <tt>foo</tt>. When you try running
5456 <prgn>dpkg-shlibdeps</prgn> you get the following error
5457 message (<tt>-O</tt> displays the dependency information on
5458 <tt>stdout</tt> instead of writing it to
5459 <tt>debian/substvars</tt>, and the lines have been wrapped
5460 for ease of reading):
5461 <example compact="compact">
5462 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5463 dpkg-shlibdeps: warning: unable to find dependency
5464 information for shared library libbar (soname 1,
5465 path /usr/lib/libbar.so.1, dependency field Depends)
5466 shlibs:Depends=libc6 (>= 2.2.2-2)
5468 You can then run <prgn>ldd</prgn> on the binary to find the
5469 full location of the library concerned:
5470 <example compact="compact">
5472 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5473 libc.so.6 => /lib/libc.so.6 (0x40032000)
5474 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5476 So the <prgn>foo</prgn> binary depends on the
5477 <prgn>libbar</prgn> shared library, but no package seems to
5478 provide a <file>*.shlibs</file> file handling
5479 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5480 determine the package responsible:
5481 <example compact="compact">
5482 $ dpkg -S /usr/lib/libbar.so.1
5483 bar1: /usr/lib/libbar.so.1
5484 $ dpkg -s bar1 | grep Version
5487 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5488 is the one we are using. Now we can file a bug against the
5489 <tt>bar1</tt> package and create our own
5490 <file>debian/shlibs.local</file> to locally fix the problem.
5491 Including the following line into your
5492 <file>debian/shlibs.local</file> file:
5493 <example compact="compact">
5494 libbar 1 bar1 (>= 1.0-1)
5496 should allow the package build to work.
5500 As soon as the maintainer of <tt>bar1</tt> provides a
5501 correct <file>shlibs</file> file, you should remove this line
5502 from your <file>debian/shlibs.local</file> file. (You should
5503 probably also then have a versioned <tt>Build-Depends</tt>
5504 on <tt>bar1</tt> to help ensure that others do not have the
5505 same problem building your package.)
5514 <chapt id="opersys"><heading>The Operating System</heading>
5517 <heading>File system hierarchy</heading>
5521 <heading>File system Structure</heading>
5524 The location of all installed files and directories must
5525 comply with the File system Hierarchy Standard (FHS),
5526 version 2.3, with the exceptions noted below, and except
5527 where doing so would violate other terms of Debian
5528 Policy. The following exceptions to the FHS apply:
5533 Legacy XFree86 servers are permitted to retain the
5534 configuration file location
5535 <file>/etc/X11/XF86Config-4</file>.
5540 The optional rules related to user specific
5541 configuration files for applications are stored in
5542 the user's home directory are relaxed. It is
5543 recommended that such files start with the
5544 '<tt>.</tt>' character (a "dot file"), and if an
5545 application needs to create more than one dot file
5546 then the preferred placement is in a subdirectory
5547 with a name starting with a '.' character, (a "dot
5548 directory"). In this case it is recommended the
5549 configuration files not start with the '.'
5555 The requirement for amd64 to use <file>/lib64</file>
5556 for 64 bit binaries is removed.
5561 The requirement that
5562 <file>/usr/local/share/man</file> be "synonymous"
5563 with <file>/usr/local/man</file> is relaxed to a
5568 The requirement that windowmanagers with a single
5569 configuration file call it <file>system.*wmrc</file>
5570 is removed, as is the restriction that the window
5571 manager subdirectory be named identically to the
5572 window manager name itself.
5577 The requirement that boot manager configuration
5578 files live in <file>/etc</file>, or at least are
5579 symlinked there, is relaxed to a recommendation.
5586 The version of this document referred here can be
5587 found in the <tt>debian-policy</tt> package or on <url
5588 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5589 name="FHS (Debian copy)"> alongside this manual (or, if
5590 you have the <package>debian-policy</package> installed,
5592 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5593 (local copy)">). The
5594 latest version, which may be a more recent version, may
5596 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5597 Specific questions about following the standard may be
5598 asked on the <tt>debian-devel</tt> mailing list, or
5599 referred to the FHS mailing list (see the
5600 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5606 <heading>Site-specific programs</heading>
5609 As mandated by the FHS, packages must not place any
5610 files in <file>/usr/local</file>, either by putting them in
5611 the file system archive to be unpacked by <prgn>dpkg</prgn>
5612 or by manipulating them in their maintainer scripts.
5616 However, the package may create empty directories below
5617 <file>/usr/local</file> so that the system administrator knows
5618 where to place site-specific files. These are not
5619 directories <em>in</em> <file>/usr/local</file>, but are
5620 children of directories in <file>/usr/local</file>. These
5621 directories (<file>/usr/local/*/dir/</file>)
5622 should be removed on package removal if they are
5627 Note, that this applies only to directories <em>below</em>
5628 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5629 Packages must not create sub-directories in the directory
5630 <file>/usr/local</file> itself, except those listed in FHS,
5631 section 4.5. However, you may create directories below
5632 them as you wish. You must not remove any of the
5633 directories listed in 4.5, even if you created them.
5637 Since <file>/usr/local</file> can be mounted read-only from a
5638 remote server, these directories must be created and
5639 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5640 maintainer scripts and not be included in the
5641 <file>.deb</file> archive. These scripts must not fail if
5642 either of these operations fail.
5646 For example, the <tt>emacsen-common</tt> package could
5647 contain something like
5648 <example compact="compact">
5649 if [ ! -e /usr/local/share/emacs ]
5651 if mkdir /usr/local/share/emacs 2>/dev/null
5653 chown root:staff /usr/local/share/emacs
5654 chmod 2775 /usr/local/share/emacs
5658 in its <prgn>postinst</prgn> script, and
5659 <example compact="compact">
5660 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5661 rmdir /usr/local/share/emacs 2>/dev/null || true
5663 in the <prgn>prerm</prgn> script. (Note that this form is
5664 used to ensure that if the script is interrupted, the
5665 directory <file>/usr/local/share/emacs</file> will still be
5670 If you do create a directory in <file>/usr/local</file> for
5671 local additions to a package, you should ensure that
5672 settings in <file>/usr/local</file> take precedence over the
5673 equivalents in <file>/usr</file>.
5677 However, because <file>/usr/local</file> and its contents are
5678 for exclusive use of the local administrator, a package
5679 must not rely on the presence or absence of files or
5680 directories in <file>/usr/local</file> for normal operation.
5684 The <file>/usr/local</file> directory itself and all the
5685 subdirectories created by the package should (by default) have
5686 permissions 2775 (group-writable and set-group-id) and be
5687 owned by <tt>root:staff</tt>.
5692 <heading>The system-wide mail directory</heading>
5694 The system-wide mail directory is <file>/var/mail</file>. This
5695 directory is part of the base system and should not owned
5696 by any particular mail agents. The use of the old
5697 location <file>/var/spool/mail</file> is deprecated, even
5698 though the spool may still be physically located there.
5699 To maintain partial upgrade compatibility for systems
5700 which have <file>/var/spool/mail</file> as their physical mail
5701 spool, packages using <file>/var/mail</file> must depend on
5702 either <package>libc6</package> (>= 2.1.3-13), or on
5703 <package>base-files</package> (>= 2.2.0), or on later
5704 versions of either one of these packages.
5710 <heading>Users and groups</heading>
5713 <heading>Introduction</heading>
5715 The Debian system can be configured to use either plain or
5720 Some user ids (UIDs) and group ids (GIDs) are reserved
5721 globally for use by certain packages. Because some
5722 packages need to include files which are owned by these
5723 users or groups, or need the ids compiled into binaries,
5724 these ids must be used on any Debian system only for the
5725 purpose for which they are allocated. This is a serious
5726 restriction, and we should avoid getting in the way of
5727 local administration policies. In particular, many sites
5728 allocate users and/or local system groups starting at 100.
5732 Apart from this we should have dynamically allocated ids,
5733 which should by default be arranged in some sensible
5734 order, but the behavior should be configurable.
5738 Packages other than <tt>base-passwd</tt> must not modify
5739 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5740 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5745 <heading>UID and GID classes</heading>
5747 The UID and GID numbers are divided into classes as
5753 Globally allocated by the Debian project, the same
5754 on every Debian system. These ids will appear in
5755 the <file>passwd</file> and <file>group</file> files of all
5756 Debian systems, new ids in this range being added
5757 automatically as the <tt>base-passwd</tt> package is
5762 Packages which need a single statically allocated
5763 uid or gid should use one of these; their
5764 maintainers should ask the <tt>base-passwd</tt>
5772 Dynamically allocated system users and groups.
5773 Packages which need a user or group, but can have
5774 this user or group allocated dynamically and
5775 differently on each system, should use <tt>adduser
5776 --system</tt> to create the group and/or user.
5777 <prgn>adduser</prgn> will check for the existence of
5778 the user or group, and if necessary choose an unused
5779 id based on the ranges specified in
5780 <file>adduser.conf</file>.
5784 <tag>1000-29999:</tag>
5787 Dynamically allocated user accounts. By default
5788 <prgn>adduser</prgn> will choose UIDs and GIDs for
5789 user accounts in this range, though
5790 <file>adduser.conf</file> may be used to modify this
5795 <tag>30000-59999:</tag>
5800 <tag>60000-64999:</tag>
5803 Globally allocated by the Debian project, but only
5804 created on demand. The ids are allocated centrally
5805 and statically, but the actual accounts are only
5806 created on users' systems on demand.
5810 These ids are for packages which are obscure or
5811 which require many statically-allocated ids. These
5812 packages should check for and create the accounts in
5813 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5814 <prgn>adduser</prgn> if it has this facility) if
5815 necessary. Packages which are likely to require
5816 further allocations should have a "hole" left after
5817 them in the allocation, to give them room to
5822 <tag>65000-65533:</tag>
5830 User <tt>nobody</tt>. The corresponding gid refers
5831 to the group <tt>nogroup</tt>.
5838 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5839 not</em> be used, because it is the error return
5848 <sect id="sysvinit">
5849 <heading>System run levels and <file>init.d</file> scripts</heading>
5851 <sect1 id="/etc/init.d">
5852 <heading>Introduction</heading>
5855 The <file>/etc/init.d</file> directory contains the scripts
5856 executed by <prgn>init</prgn> at boot time and when the
5857 init state (or "runlevel") is changed (see <manref
5858 name="init" section="8">).
5862 There are at least two different, yet functionally
5863 equivalent, ways of handling these scripts. For the sake
5864 of simplicity, this document describes only the symbolic
5865 link method. However, it must not be assumed by maintainer
5866 scripts that this method is being used, and any automated
5867 manipulation of the various runlevel behaviors by
5868 maintainer scripts must be performed using
5869 <prgn>update-rc.d</prgn> as described below and not by
5870 manually installing or removing symlinks. For information
5871 on the implementation details of the other method,
5872 implemented in the <tt>file-rc</tt> package, please refer
5873 to the documentation of that package.
5877 These scripts are referenced by symbolic links in the
5878 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5879 runlevels, <prgn>init</prgn> looks in the directory
5880 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5881 execute, where <tt><var>n</var></tt> is the runlevel that
5882 is being changed to, or <tt>S</tt> for the boot-up
5887 The names of the links all have the form
5888 <file>S<var>mm</var><var>script</var></file> or
5889 <file>K<var>mm</var><var>script</var></file> where
5890 <var>mm</var> is a two-digit number and <var>script</var>
5891 is the name of the script (this should be the same as the
5892 name of the actual script in <file>/etc/init.d</file>).
5896 When <prgn>init</prgn> changes runlevel first the targets
5897 of the links whose names start with a <tt>K</tt> are
5898 executed, each with the single argument <tt>stop</tt>,
5899 followed by the scripts prefixed with an <tt>S</tt>, each
5900 with the single argument <tt>start</tt>. (The links are
5901 those in the <file>/etc/rc<var>n</var>.d</file> directory
5902 corresponding to the new runlevel.) The <tt>K</tt> links
5903 are responsible for killing services and the <tt>S</tt>
5904 link for starting services upon entering the runlevel.
5908 For example, if we are changing from runlevel 2 to
5909 runlevel 3, init will first execute all of the <tt>K</tt>
5910 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5911 all of the <tt>S</tt> prefixed scripts in that directory.
5912 The links starting with <tt>K</tt> will cause the
5913 referred-to file to be executed with an argument of
5914 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5919 The two-digit number <var>mm</var> is used to determine
5920 the order in which to run the scripts: low-numbered links
5921 have their scripts run first. For example, the
5922 <tt>K20</tt> scripts will be executed before the
5923 <tt>K30</tt> scripts. This is used when a certain service
5924 must be started before another. For example, the name
5925 server <prgn>bind</prgn> might need to be started before
5926 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5927 can set up its access lists. In this case, the script
5928 that starts <prgn>bind</prgn> would have a lower number
5929 than the script that starts <prgn>inn</prgn> so that it
5931 <example compact="compact">
5938 The two runlevels 0 (halt) and 6 (reboot) are slightly
5939 different. In these runlevels, the links with an
5940 <tt>S</tt> prefix are still called after those with a
5941 <tt>K</tt> prefix, but they too are called with the single
5942 argument <tt>stop</tt>.
5946 Also, if the script name ends in <tt>.sh</tt>, the script
5947 will be sourced in runlevel <tt>S</tt> rather than being
5948 run in a forked subprocess, but will be explicitly run by
5949 <prgn>sh</prgn> in all other runlevels.
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.
6077 <heading>Interfacing with the initscript system</heading>
6080 Maintainers should use the abstraction layer provided by
6081 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6082 programs to deal with initscripts in their packages'
6083 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6084 and <prgn>postrm</prgn>.
6088 Directly managing the /etc/rc?.d links and directly
6089 invoking the <file>/etc/init.d/</file> initscripts should
6090 be done only by packages providing the initscript
6091 subsystem (such as <prgn>sysv-rc</prgn> and
6092 <prgn>file-rc</prgn>).
6096 <heading>Managing the links</heading>
6099 The program <prgn>update-rc.d</prgn> is provided for
6100 package maintainers to arrange for the proper creation and
6101 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6102 or their functional equivalent if another method is being
6103 used. This may be used by maintainers in their packages'
6104 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6108 You must not include any <file>/etc/rc<var>n</var>.d</file>
6109 symbolic links in the actual archive or manually create or
6110 remove the symbolic links in maintainer scripts; you must
6111 use the <prgn>update-rc.d</prgn> program instead. (The
6112 former will fail if an alternative method of maintaining
6113 runlevel information is being used.) You must not include
6114 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6115 in the archive either. (Only the <tt>sysvinit</tt>
6120 By default <prgn>update-rc.d</prgn> will start services in
6121 each of the multi-user state runlevels (2, 3, 4, and 5)
6122 and stop them in the halt runlevel (0), the single-user
6123 runlevel (1) and the reboot runlevel (6). The system
6124 administrator will have the opportunity to customize
6125 runlevels by simply adding, moving, or removing the
6126 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6127 symbolic links are being used, or by modifying
6128 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6133 To get the default behavior for your package, put in your
6134 <prgn>postinst</prgn> script
6135 <example compact="compact">
6136 update-rc.d <var>package</var> defaults
6138 and in your <prgn>postrm</prgn>
6139 <example compact="compact">
6140 if [ "$1" = purge ]; then
6141 update-rc.d <var>package</var> remove
6143 </example>. Note that if your package changes runlevels
6144 or priority, you may have to remove and recreate the links,
6145 since otherwise the old links may persist. Refer to the
6146 documentation of <prgn>update-rc.d</prgn>.
6150 This will use a default sequence number of 20. If it does
6151 not matter when or in which order the <file>init.d</file>
6152 script is run, use this default. If it does, then you
6153 should talk to the maintainer of the <prgn>sysvinit</prgn>
6154 package or post to <tt>debian-devel</tt>, and they will
6155 help you choose a number.
6159 For more information about using <tt>update-rc.d</tt>,
6160 please consult its man page <manref name="update-rc.d"
6166 <heading>Running initscripts</heading>
6168 The program <prgn>invoke-rc.d</prgn> is provided to make
6169 it easier for package maintainers to properly invoke an
6170 initscript, obeying runlevel and other locally-defined
6171 constraints that might limit a package's right to start,
6172 stop and otherwise manage services. This program may be
6173 used by maintainers in their packages' scripts.
6177 The package maintainer scripts must use
6178 <prgn>invoke-rc.d</prgn> to invoke the
6179 <file>/etc/init.d/*</file> initscripts, instead of
6180 calling them directly.
6184 By default, <prgn>invoke-rc.d</prgn> will pass any
6185 action requests (start, stop, reload, restart...) to the
6186 <file>/etc/init.d</file> script, filtering out requests
6187 to start or restart a service out of its intended
6192 Most packages will simply need to change:
6193 <example compact="compact">/etc/init.d/<package>
6194 <action></example> in their <prgn>postinst</prgn>
6195 and <prgn>prerm</prgn> scripts to:
6196 <example compact="compact">
6197 if which invoke-rc.d >/dev/null 2>&1; then
6198 invoke-rc.d <var>package</var> <action>
6200 /etc/init.d/<var>package</var> <action>
6206 A package should register its initscript services using
6207 <prgn>update-rc.d</prgn> before it tries to invoke them
6208 using <prgn>invoke-rc.d</prgn>. Invocation of
6209 unregistered services may fail.
6213 For more information about using
6214 <prgn>invoke-rc.d</prgn>, please consult its man page
6215 <manref name="invoke-rc.d" section="8">.
6221 <heading>Boot-time initialization</heading>
6224 There used to be another directory, <file>/etc/rc.boot</file>,
6225 which contained scripts which were run once per machine
6226 boot. This has been deprecated in favour of links from
6227 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6228 described in <ref id="/etc/init.d">. Packages must not
6229 place files in <file>/etc/rc.boot</file>.
6234 <heading>Example</heading>
6237 An example on which you can base your
6238 <file>/etc/init.d</file> scripts is found in
6239 <file>/etc/init.d/skeleton</file>.
6246 <heading>Console messages from <file>init.d</file> scripts</heading>
6249 This section describes the formats to be used for messages
6250 written to standard output by the <file>/etc/init.d</file>
6251 scripts. The intent is to improve the consistency of
6252 Debian's startup and shutdown look and feel. For this
6253 reason, please look very carefully at the details. We want
6254 the messages to have the same format in terms of wording,
6255 spaces, punctuation and case of letters.
6259 Here is a list of overall rules that should be used for
6260 messages generated by <file>/etc/init.d</file> scripts.
6266 The message should fit in one line (fewer than 80
6267 characters), start with a capital letter and end with
6268 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6272 If the script is performing some time consuming task in
6273 the background (not merely starting or stopping a
6274 program, for instance), an ellipsis (three dots:
6275 <tt>...</tt>) should be output to the screen, with no
6276 leading or tailing whitespace or line feeds.
6280 The messages should appear as if the computer is telling
6281 the user what it is doing (politely :-), but should not
6282 mention "it" directly. For example, instead of:
6283 <example compact="compact">
6284 I'm starting network daemons: nfsd mountd.
6286 the message should say
6287 <example compact="compact">
6288 Starting network daemons: nfsd mountd.
6295 <tt>init.d</tt> script should use the following standard
6296 message formats for the situations enumerated below.
6302 <p>When daemons are started</p>
6305 If the script starts one or more daemons, the output
6306 should look like this (a single line, no leading
6308 <example compact="compact">
6309 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6311 The <var>description</var> should describe the
6312 subsystem the daemon or set of daemons are part of,
6313 while <var>daemon-1</var> up to <var>daemon-n</var>
6314 denote each daemon's name (typically the file name of
6319 For example, the output of <file>/etc/init.d/lpd</file>
6321 <example compact="compact">
6322 Starting printer spooler: lpd.
6327 This can be achieved by saying
6328 <example compact="compact">
6329 echo -n "Starting printer spooler: lpd"
6330 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6333 in the script. If there are more than one daemon to
6334 start, the output should look like this:
6335 <example compact="compact">
6336 echo -n "Starting remote file system services:"
6337 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6338 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6339 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6342 This makes it possible for the user to see what is
6343 happening and when the final daemon has been started.
6344 Care should be taken in the placement of white spaces:
6345 in the example above the system administrators can
6346 easily comment out a line if they don't want to start
6347 a specific daemon, while the displayed message still
6353 <p>When a system parameter is being set</p>
6356 If you have to set up different system parameters
6357 during the system boot, you should use this format:
6358 <example compact="compact">
6359 Setting <var>parameter</var> to "<var>value</var>".
6364 You can use a statement such as the following to get
6366 <example compact="compact">
6367 echo "Setting DNS domainname to \"$domainname\"."
6372 Note that the same symbol (<tt>"</tt>) is used for the left
6373 and right quotation marks. A grave accent (<tt>`</tt>) is
6374 not a quote character; neither is an apostrophe
6380 <p>When a daemon is stopped or restarted</p>
6383 When you stop or restart a daemon, you should issue a
6384 message identical to the startup message, except that
6385 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6386 or <tt>Restarting</tt> respectively.
6390 For example, stopping the printer daemon will look like
6392 <example compact="compact">
6393 Stopping printer spooler: lpd.
6399 <p>When something is executed</p>
6402 There are several examples where you have to run a
6403 program at system startup or shutdown to perform a
6404 specific task, for example, setting the system's clock
6405 using <prgn>netdate</prgn> or killing all processes
6406 when the system shuts down. Your message should look
6408 <example compact="compact">
6409 Doing something very useful...done.
6411 You should print the <tt>done.</tt> immediately after
6412 the job has been completed, so that the user is
6413 informed why they have to wait. You can get this
6415 <example compact="compact">
6416 echo -n "Doing something very useful..."
6425 <p>When the configuration is reloaded</p>
6428 When a daemon is forced to reload its configuration
6429 files you should use the following format:
6430 <example compact="compact">
6431 Reloading <var>description</var> configuration...done.
6433 where <var>description</var> is the same as in the
6434 daemon starting message.
6442 <heading>Cron jobs</heading>
6445 Packages must not modify the configuration file
6446 <file>/etc/crontab</file>, and they must not modify the files in
6447 <file>/var/spool/cron/crontabs</file>.</p>
6450 If a package wants to install a job that has to be executed
6451 via cron, it should place a file with the name of the
6452 package in one or more of the following directories:
6453 <example compact="compact">
6459 As these directory names imply, the files within them are
6460 executed on an hourly, daily, weekly, or monthly basis,
6461 respectively. The exact times are listed in
6462 <file>/etc/crontab</file>.</p>
6465 All files installed in any of these directories must be
6466 scripts (e.g., shell scripts or Perl scripts) so that they
6467 can easily be modified by the local system administrator.
6468 In addition, they must be treated as configuration files.
6472 If a certain job has to be executed at some other frequency or
6473 at a specific time, the package should install a file
6474 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6475 same syntax as <file>/etc/crontab</file> and is processed by
6476 <prgn>cron</prgn> automatically. The file must also be
6477 treated as a configuration file. (Note that entries in the
6478 <file>/etc/cron.d</file> directory are not handled by
6479 <prgn>anacron</prgn>. Thus, you should only use this
6480 directory for jobs which may be skipped if the system is not
6484 The scripts or crontab entries in these directories should
6485 check if all necessary programs are installed before they
6486 try to execute them. Otherwise, problems will arise when a
6487 package was removed but not purged since configuration files
6488 are kept on the system in this situation.</p>
6492 <heading>Menus</heading>
6495 The Debian <tt>menu</tt> package provides a standard
6496 interface between packages providing applications and
6497 <em>menu programs</em> (either X window managers or
6498 text-based menu programs such as <prgn>pdmenu</prgn>).
6502 All packages that provide applications that need not be
6503 passed any special command line arguments for normal
6504 operation should register a menu entry for those
6505 applications, so that users of the <tt>menu</tt> package
6506 will automatically get menu entries in their window
6507 managers, as well in shells like <tt>pdmenu</tt>.
6511 Menu entries should follow the current menu policy.
6515 The menu policy can be found in the <tt>menu-policy</tt>
6516 files in the <tt>debian-policy</tt> package.
6517 It is also available from the Debian web mirrors at
6518 <tt><url name="/doc/packaging-manuals/menu-policy/"
6519 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6523 Please also refer to the <em>Debian Menu System</em>
6524 documentation that comes with the <package>menu</package>
6525 package for information about how to register your
6531 <heading>Multimedia handlers</heading>
6534 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6535 is a mechanism for encoding files and data streams and
6536 providing meta-information about them, in particular their
6537 type (e.g. audio or video) and format (e.g. PNG, HTML,
6542 Registration of MIME type handlers allows programs like mail
6543 user agents and web browsers to invoke these handlers to
6544 view, edit or display MIME types they don't support directly.
6548 Packages which provide the ability to view/show/play,
6549 compose, edit or print MIME types should register themselves
6550 as such following the current MIME support policy.
6554 The MIME support policy can be found in the <tt>mime-policy</tt>
6555 files in the <tt>debian-policy</tt> package.
6556 It is also available from the Debian web mirrors at
6557 <tt><url name="/doc/packaging-manuals/mime-policy/"
6558 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6564 <heading>Keyboard configuration</heading>
6567 To achieve a consistent keyboard configuration so that all
6568 applications interpret a keyboard event the same way, all
6569 programs in the Debian distribution must be configured to
6570 comply with the following guidelines.
6574 The following keys must have the specified interpretations:
6577 <tag><tt><--</tt></tag>
6578 <item>delete the character to the left of the cursor</item>
6580 <tag><tt>Delete</tt></tag>
6581 <item>delete the character to the right of the cursor</item>
6583 <tag><tt>Control+H</tt></tag>
6584 <item>emacs: the help prefix</item>
6587 The interpretation of any keyboard events should be
6588 independent of the terminal that is used, be it a virtual
6589 console, an X terminal emulator, an rlogin/telnet session,
6594 The following list explains how the different programs
6595 should be set up to achieve this:
6601 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6605 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6609 X translations are set up to make
6610 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6611 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6612 is the vt220 escape code for the "delete character"
6613 key). This must be done by loading the X resources
6614 using <prgn>xrdb</prgn> on all local X displays, not
6615 using the application defaults, so that the
6616 translation resources used correspond to the
6617 <prgn>xmodmap</prgn> settings.
6621 The Linux console is configured to make
6622 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6623 generate <tt>ESC [ 3 ~</tt>.
6627 X applications are configured so that <tt><</tt>
6628 deletes left, and <tt>Delete</tt> deletes right. Motif
6629 applications already work like this.
6633 Terminals should have <tt>stty erase ^?</tt> .
6637 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6638 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6639 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6643 Emacs is programmed to map <tt>KB_Backspace</tt> or
6644 the <tt>stty erase</tt> character to
6645 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6646 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6647 <tt>^H</tt> to <tt>help</tt> as always.
6651 Other applications use the <tt>stty erase</tt>
6652 character and <tt>kdch1</tt> for the two delete keys,
6653 with ASCII DEL being "delete previous character" and
6654 <tt>kdch1</tt> being "delete character under
6662 This will solve the problem except for the following
6669 Some terminals have a <tt><--</tt> key that cannot
6670 be made to produce anything except <tt>^H</tt>. On
6671 these terminals Emacs help will be unavailable on
6672 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6673 character takes precedence in Emacs, and has been set
6674 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6675 available) can be used instead.
6679 Some operating systems use <tt>^H</tt> for <tt>stty
6680 erase</tt>. However, modern telnet versions and all
6681 rlogin versions propagate <tt>stty</tt> settings, and
6682 almost all UNIX versions honour <tt>stty erase</tt>.
6683 Where the <tt>stty</tt> settings are not propagated
6684 correctly, things can be made to work by using
6685 <tt>stty</tt> manually.
6689 Some systems (including previous Debian versions) use
6690 <prgn>xmodmap</prgn> to arrange for both
6691 <tt><--</tt> and <tt>Delete</tt> to generate
6692 <tt>KB_Delete</tt>. We can change the behavior of
6693 their X clients using the same X resources that we use
6694 to do it for our own clients, or configure our clients
6695 using their resources when things are the other way
6696 around. On displays configured like this
6697 <tt>Delete</tt> will not work, but <tt><--</tt>
6702 Some operating systems have different <tt>kdch1</tt>
6703 settings in their <tt>terminfo</tt> database for
6704 <tt>xterm</tt> and others. On these systems the
6705 <tt>Delete</tt> key will not work correctly when you
6706 log in from a system conforming to our policy, but
6707 <tt><--</tt> will.
6714 <heading>Environment variables</heading>
6717 A program must not depend on environment variables to get
6718 reasonable defaults. (That's because these environment
6719 variables would have to be set in a system-wide
6720 configuration file like <file>/etc/profile</file>, which is not
6721 supported by all shells.)
6725 If a program usually depends on environment variables for its
6726 configuration, the program should be changed to fall back to
6727 a reasonable default configuration if these environment
6728 variables are not present. If this cannot be done easily
6729 (e.g., if the source code of a non-free program is not
6730 available), the program must be replaced by a small
6731 "wrapper" shell script which sets the environment variables
6732 if they are not already defined, and calls the original program.
6736 Here is an example of a wrapper script for this purpose:
6738 <example compact="compact">
6740 BAR=${BAR:-/var/lib/fubar}
6742 exec /usr/lib/foo/foo "$@"
6747 Furthermore, as <file>/etc/profile</file> is a configuration
6748 file of the <prgn>base-files</prgn> package, other packages must
6749 not put any environment variables or other commands into that
6754 <sect id="doc-base">
6755 <heading>Registering Documents using doc-base</heading>
6758 The <package>doc-base</package> package implements a
6759 flexible mechanism for handling and presenting
6760 documentation. The recommended practice is for every Debian
6761 package that provides online documentation (other than just
6762 manual pages) to register these documents with
6763 <package>doc-base</package> by installing a
6764 <package>doc-base</package> control file via the
6765 <prgn/install-docs/ script at installation time and
6766 de-register the manuals again when the package is removed.
6769 Please refer to the documentation that comes with the
6770 <package>doc-base</package> package for information and
6779 <heading>Files</heading>
6782 <heading>Binaries</heading>
6785 Two different packages must not install programs with
6786 different functionality but with the same filenames. (The
6787 case of two programs having the same functionality but
6788 different implementations is handled via "alternatives" or
6789 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6790 <ref id="conflicts"> respectively.) If this case happens,
6791 one of the programs must be renamed. The maintainers should
6792 report this to the <tt>debian-devel</tt> mailing list and
6793 try to find a consensus about which program will have to be
6794 renamed. If a consensus cannot be reached, <em>both</em>
6795 programs must be renamed.
6799 By default, when a package is being built, any binaries
6800 created should include debugging information, as well as
6801 being compiled with optimization. You should also turn on
6802 as many reasonable compilation warnings as possible; this
6803 makes life easier for porters, who can then look at build
6804 logs for possible problems. For the C programming language,
6805 this means the following compilation parameters should be
6807 <example compact="compact">
6809 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6811 INSTALL = install -s # (or use strip on the files in debian/tmp)
6816 Note that by default all installed binaries should be stripped,
6817 either by using the <tt>-s</tt> flag to
6818 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6819 the binaries after they have been copied into
6820 <file>debian/tmp</file> but before the tree is made into a
6825 Although binaries in the build tree should be compiled with
6826 debugging information by default, it can often be difficult to
6827 debug programs if they are also subjected to compiler
6828 optimization. For this reason, it is recommended to support the
6829 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6830 (see <ref id="debianrules-options">). This variable can contain
6831 several flags to change how a package is compiled and built.
6835 It is up to the package maintainer to decide what
6836 compilation options are best for the package. Certain
6837 binaries (such as computationally-intensive programs) will
6838 function better with certain flags (<tt>-O3</tt>, for
6839 example); feel free to use them. Please use good judgment
6840 here. Don't use flags for the sake of it; only use them
6841 if there is good reason to do so. Feel free to override
6842 the upstream author's ideas about which compilation
6843 options are best: they are often inappropriate for our
6849 <sect id="libraries">
6850 <heading>Libraries</heading>
6853 If the package is <strong>architecture: any</strong>, then
6854 the shared library compilation and linking flags must have
6855 <tt>-fPIC</tt>, or the package shall not build on some of
6856 the supported architectures<footnote>
6858 If you are using GCC, <tt>-fPIC</tt> produces code with
6859 relocatable position independent code, which is required for
6860 most architectures to create a shared library, with i386 and
6861 perhaps some others where non position independent code is
6862 permitted in a shared library.
6865 Position independent code may have a performance penalty,
6866 especially on <tt>i386</tt>. However, in most cases the
6867 speed penalty must be measured against the memory wasted on
6868 the few architectures where non position independent code is
6871 </footnote>. Any exception to this rule must be discussed on
6872 the mailing list <em>debian-devel@lists.debian.org</em>, and
6873 a rough consensus obtained. The reasons for not compiling
6874 with <tt>-fPIC</tt> flag must be recorded in the file
6875 <tt>README.Debian</tt>, and care must be taken to either
6876 restrict the architecture or arrange for <tt>-fPIC</tt> to
6877 be used on architectures where it is required.<footnote>
6879 Some of the reasons why this might be required is if the
6880 library contains hand crafted assembly code that is not
6881 relocatable, the speed penalty is excessive for compute
6882 intensive libs, and similar reasons.
6887 As to the static libraries, the common case is not to have
6888 relocatable code, since there is no benefit, unless in specific
6889 cases; therefore the static version must not be compiled
6890 with the <tt>-fPIC</tt> flag. Any exception to this rule
6891 should be discussed on the mailing list
6892 <em>debian-devel@lists.debian.org</em>, and the reasons for
6893 compiling with the <tt>-fPIC</tt> flag must be recorded in
6894 the file <tt>README.Debian</tt>. <footnote>
6896 Some of the reasons for linking static libraries with
6897 the <tt>-fPIC</tt> flag are if, for example, one needs a
6898 Perl API for a library that is under rapid development,
6899 and has an unstable API, so shared libraries are
6900 pointless at this phase of the library's development. In
6901 that case, since Perl needs a library with relocatable
6902 code, it may make sense to create a static library with
6903 relocatable code. Another reason cited is if you are
6904 distilling various libraries into a common shared
6905 library, like <tt>mklibs</tt> does in the Debian
6911 In other words, if both a shared and a static library is
6912 being built, each source unit (<tt>*.c</tt>, for example,
6913 for C files) will need to be compiled twice, for the normal
6917 You must specify the gcc option <tt>-D_REENTRANT</tt>
6918 when building a library (either static or shared) to make
6919 the library compatible with LinuxThreads.
6923 Although not enforced by the build tools, shared libraries
6924 must be linked against all libraries that they use symbols from
6925 in the same way that binaries are. This ensures the correct
6926 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6927 system and guarantees that all libraries can be safely opened
6928 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6929 option <tt>-Wl,-z,defs</tt> when building a shared library.
6930 Since this option enforces symbol resolution at build time,
6931 a missing library reference will be caught early as a fatal
6936 All installed shared libraries should be stripped with
6937 <example compact="compact">
6938 strip --strip-unneeded <var>your-lib</var>
6940 (The option <tt>--strip-unneeded</tt> makes
6941 <prgn>strip</prgn> remove only the symbols which aren't
6942 needed for relocation processing.) Shared libraries can
6943 function perfectly well when stripped, since the symbols for
6944 dynamic linking are in a separate part of the ELF object
6946 You might also want to use the options
6947 <tt>--remove-section=.comment</tt> and
6948 <tt>--remove-section=.note</tt> on both shared libraries
6949 and executables, and <tt>--strip-debug</tt> on static
6955 Note that under some circumstances it may be useful to
6956 install a shared library unstripped, for example when
6957 building a separate package to support debugging.
6961 Shared object files (often <file>.so</file> files) that are not
6962 public libraries, that is, they are not meant to be linked
6963 to by third party executables (binaries of other packages),
6964 should be installed in subdirectories of the
6965 <file>/usr/lib</file> directory. Such files are exempt from the
6966 rules that govern ordinary shared libraries, except that
6967 they must not be installed executable and should be
6969 A common example are the so-called "plug-ins",
6970 internal shared objects that are dynamically loaded by
6971 programs using <manref name="dlopen" section="3">.
6976 Packages containing shared libraries that may be linked to
6977 by other packages' binaries, but which for some
6978 <em>compelling</em> reason can not be installed in
6979 <file>/usr/lib</file> directory, may install the shared library
6980 files in subdirectories of the <file>/usr/lib</file> directory,
6981 in which case they should arrange to add that directory in
6982 <file>/etc/ld.so.conf</file> in the package's post-installation
6983 script, and remove it in the package's post-removal script.
6987 An ever increasing number of packages are using
6988 <prgn>libtool</prgn> to do their linking. The latest GNU
6989 libtools (>= 1.3a) can take advantage of the metadata in the
6990 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6991 files). The main advantage of <prgn>libtool</prgn>'s
6992 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6993 store and subsequently access metadata with respect to the
6994 libraries it builds. <prgn>libtool</prgn> will search for
6995 those files, which contain a lot of useful information about
6996 a library (such as library dependency information for static
6997 linking). Also, they're <em>essential</em> for programs
6998 using <tt>libltdl</tt>.<footnote>
6999 Although <prgn>libtool</prgn> is fully capable of
7000 linking against shared libraries which don't have
7001 <tt>.la</tt> files, as it is a mere shell script it can
7002 add considerably to the build time of a
7003 <prgn>libtool</prgn>-using package if that shell script
7004 has to derive all this information from first principles
7005 for each library every time it is linked. With the
7006 advent of <prgn>libtool</prgn> version 1.4 (and to a
7007 lesser extent <prgn>libtool</prgn> version 1.3), the
7008 <file>.la</file> files also store information about
7009 inter-library dependencies which cannot necessarily be
7010 derived after the <file>.la</file> file is deleted.
7015 Packages that use <prgn>libtool</prgn> to create shared
7016 libraries should include the <file>.la</file> files in the
7017 <tt>-dev</tt> package, unless the package relies on
7018 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7019 the <tt>.la</tt> files must go in the run-time library
7024 You must make sure that you use only released versions of
7025 shared libraries to build your packages; otherwise other
7026 users will not be able to run your binaries
7027 properly. Producing source packages that depend on
7028 unreleased compilers is also usually a bad
7035 <heading>Shared libraries</heading>
7037 This section has moved to <ref id="sharedlibs">.
7043 <heading>Scripts</heading>
7046 All command scripts, including the package maintainer
7047 scripts inside the package and used by <prgn>dpkg</prgn>,
7048 should have a <tt>#!</tt> line naming the shell to be used
7053 In the case of Perl scripts this should be
7054 <tt>#!/usr/bin/perl</tt>.
7058 When scripts are installed into a directory in the system
7059 PATH, the script name should not include an extension such
7060 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7061 language currently used to implement it.
7064 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7065 should almost certainly start with <tt>set -e</tt> so that
7066 errors are detected. Every script should use
7067 <tt>set -e</tt> or check the exit status of <em>every</em>
7072 Scripts may assume that <file>/bin/sh</file> implements the
7073 SUSv3 Shell Command Language<footnote>
7074 Single UNIX Specification, version 3, which is also IEEE
7075 1003.1-2004 (POSIX), and is available on the World Wide Web
7076 from <url id="http://www.unix.org/version3/online.html"
7077 name="The Open Group"> after free
7078 registration.</footnote>
7079 plus the following additional features not mandated by
7081 These features are in widespread use in the Linux community
7082 and are implemented in all of bash, dash, and ksh, the most
7083 common shells users may wish to use as <file>/bin/sh</file>.
7086 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7087 must not generate a newline.</item>
7088 <item><tt>test</tt>, if implemented as a shell built-in, must
7089 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7091 <item><tt>local</tt> to create a scoped variable must be
7092 supported, including listing multiple variables in a single
7093 local command and assigning a value to a variable at the
7094 same time as localizing it. <tt>local</tt> may or
7095 may not preserve the variable value from an outer scope if
7096 no assignment is present. Uses such as:
7100 # ... use a, b, c, d ...
7103 must be supported and must set the value of <tt>c</tt> to
7107 If a shell script requires non-SUSv3 features from the shell
7108 interpreter other than those listed above, the appropriate shell
7109 must be specified in the first line of the script (e.g.,
7110 <tt>#!/bin/bash</tt>) and the package must depend on the package
7111 providing the shell (unless the shell package is marked
7112 "Essential", as in the case of <prgn>bash</prgn>).
7116 You may wish to restrict your script to SUSv3 features plus the
7117 above set when possible so that it may use <file>/bin/sh</file>
7118 as its interpreter. If your script works with <prgn>dash</prgn>
7119 (originally called <prgn>ash</prgn>), it probably complies with
7120 the above requirements, but if you are in doubt, use
7121 <file>/bin/bash</file>.
7125 Perl scripts should check for errors when making any
7126 system calls, including <tt>open</tt>, <tt>print</tt>,
7127 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7131 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7132 scripting languages. See <em>Csh Programming Considered
7133 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7134 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7135 If an upstream package comes with <prgn>csh</prgn> scripts
7136 then you must make sure that they start with
7137 <tt>#!/bin/csh</tt> and make your package depend on the
7138 <prgn>c-shell</prgn> virtual package.
7142 Any scripts which create files in world-writeable
7143 directories (e.g., in <file>/tmp</file>) must use a
7144 mechanism which will fail atomically if a file with the same
7145 name already exists.
7149 The Debian base system provides the <prgn>tempfile</prgn>
7150 and <prgn>mktemp</prgn> utilities for use by scripts for
7157 <heading>Symbolic links</heading>
7160 In general, symbolic links within a top-level directory
7161 should be relative, and symbolic links pointing from one
7162 top-level directory into another should be absolute. (A
7163 top-level directory is a sub-directory of the root
7164 directory <file>/</file>.)
7168 In addition, symbolic links should be specified as short as
7169 possible, i.e., link targets like <file>foo/../bar</file> are
7174 Note that when creating a relative link using
7175 <prgn>ln</prgn> it is not necessary for the target of the
7176 link to exist relative to the working directory you're
7177 running <prgn>ln</prgn> from, nor is it necessary to change
7178 directory to the directory where the link is to be made.
7179 Simply include the string that should appear as the target
7180 of the link (this will be a pathname relative to the
7181 directory in which the link resides) as the first argument
7186 For example, in your <prgn>Makefile</prgn> or
7187 <file>debian/rules</file>, you can do things like:
7188 <example compact="compact">
7189 ln -fs gcc $(prefix)/bin/cc
7190 ln -fs gcc debian/tmp/usr/bin/cc
7191 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7192 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7197 A symbolic link pointing to a compressed file should always
7198 have the same file extension as the referenced file. (For
7199 example, if a file <file>foo.gz</file> is referenced by a
7200 symbolic link, the filename of the link has to end with
7201 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7206 <heading>Device files</heading>
7209 Packages must not include device files in the package file
7214 If a package needs any special device files that are not
7215 included in the base system, it must call
7216 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7217 after notifying the user<footnote>
7218 This notification could be done via a (low-priority)
7219 debconf message, or an echo (printf) statement.
7224 Packages must not remove any device files in the
7225 <prgn>postrm</prgn> or any other script. This is left to the
7226 system administrator.
7230 Debian uses the serial devices
7231 <file>/dev/ttyS*</file>. Programs using the old
7232 <file>/dev/cu*</file> devices should be changed to use
7233 <file>/dev/ttyS*</file>.
7237 <sect id="config-files">
7238 <heading>Configuration files</heading>
7241 <heading>Definitions</heading>
7245 <tag>configuration file</tag>
7247 A file that affects the operation of a program, or
7248 provides site- or host-specific information, or
7249 otherwise customizes the behavior of a program.
7250 Typically, configuration files are intended to be
7251 modified by the system administrator (if needed or
7252 desired) to conform to local policy or to provide
7253 more useful site-specific behavior.
7256 <tag><tt>conffile</tt></tag>
7258 A file listed in a package's <tt>conffiles</tt>
7259 file, and is treated specially by <prgn>dpkg</prgn>
7260 (see <ref id="configdetails">).
7266 The distinction between these two is important; they are
7267 not interchangeable concepts. Almost all
7268 <tt>conffile</tt>s are configuration files, but many
7269 configuration files are not <tt>conffiles</tt>.
7273 As noted elsewhere, <file>/etc/init.d</file> scripts,
7274 <file>/etc/default</file> files, scripts installed in
7275 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7276 configuration installed in <file>/etc/cron.d</file> must be
7277 treated as configuration files. In general, any script that
7278 embeds configuration information is de-facto a configuration
7279 file and should be treated as such.
7284 <heading>Location</heading>
7287 Any configuration files created or used by your package
7288 must reside in <file>/etc</file>. If there are several,
7289 consider creating a subdirectory of <file>/etc</file>
7290 named after your package.
7294 If your package creates or uses configuration files
7295 outside of <file>/etc</file>, and it is not feasible to modify
7296 the package to use <file>/etc</file> directly, put the files
7297 in <file>/etc</file> and create symbolic links to those files
7298 from the location that the package requires.
7303 <heading>Behavior</heading>
7306 Configuration file handling must conform to the following
7308 <list compact="compact">
7310 local changes must be preserved during a package
7314 configuration files must be preserved when the
7315 package is removed, and only deleted when the
7322 The easy way to achieve this behavior is to make the
7323 configuration file a <tt>conffile</tt>. This is
7324 appropriate only if it is possible to distribute a default
7325 version that will work for most installations, although
7326 some system administrators may choose to modify it. This
7327 implies that the default version will be part of the
7328 package distribution, and must not be modified by the
7329 maintainer scripts during installation (or at any other
7334 In order to ensure that local changes are preserved
7335 correctly, no package may contain or make hard links to
7336 conffiles.<footnote>
7337 Rationale: There are two problems with hard links.
7338 The first is that some editors break the link while
7339 editing one of the files, so that the two files may
7340 unwittingly become unlinked and different. The second
7341 is that <prgn>dpkg</prgn> might break the hard link
7342 while upgrading <tt>conffile</tt>s.
7347 The other way to do it is via the maintainer scripts. In
7348 this case, the configuration file must not be listed as a
7349 <tt>conffile</tt> and must not be part of the package
7350 distribution. If the existence of a file is required for
7351 the package to be sensibly configured it is the
7352 responsibility of the package maintainer to provide
7353 maintainer scripts which correctly create, update and
7354 maintain the file and remove it on purge. (See <ref
7355 id="maintainerscripts"> for more information.) These
7356 scripts must be idempotent (i.e., must work correctly if
7357 <prgn>dpkg</prgn> needs to re-run them due to errors
7358 during installation or removal), must cope with all the
7359 variety of ways <prgn>dpkg</prgn> can call maintainer
7360 scripts, must not overwrite or otherwise mangle the user's
7361 configuration without asking, must not ask unnecessary
7362 questions (particularly during upgrades), and must
7363 otherwise be good citizens.
7367 The scripts are not required to configure every possible
7368 option for the package, but only those necessary to get
7369 the package running on a given system. Ideally the
7370 sysadmin should not have to do any configuration other
7371 than that done (semi-)automatically by the
7372 <prgn>postinst</prgn> script.
7376 A common practice is to create a script called
7377 <file><var>package</var>-configure</file> and have the
7378 package's <prgn>postinst</prgn> call it if and only if the
7379 configuration file does not already exist. In certain
7380 cases it is useful for there to be an example or template
7381 file which the maintainer scripts use. Such files should
7382 be in <file>/usr/share/<var>package</var></file> or
7383 <file>/usr/lib/<var>package</var></file> (depending on whether
7384 they are architecture-independent or not). There should
7385 be symbolic links to them from
7386 <file>/usr/share/doc/<var>package</var>/examples</file> if
7387 they are examples, and should be perfectly ordinary
7388 <prgn>dpkg</prgn>-handled files (<em>not</em>
7389 configuration files).
7393 These two styles of configuration file handling must
7394 not be mixed, for that way lies madness:
7395 <prgn>dpkg</prgn> will ask about overwriting the file
7396 every time the package is upgraded.
7401 <heading>Sharing configuration files</heading>
7404 Packages which specify the same file as a
7405 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7406 with each other. (This is an instance of the general rule
7407 about not sharing files. Note that neither alternatives
7408 nor diversions are likely to be appropriate in this case;
7409 in particular, <prgn>dpkg</prgn> does not handle diverted
7410 <tt>conffile</tt>s well.)
7414 The maintainer scripts must not alter a <tt>conffile</tt>
7415 of <em>any</em> package, including the one the scripts
7420 If two or more packages use the same configuration file
7421 and it is reasonable for both to be installed at the same
7422 time, one of these packages must be defined as
7423 <em>owner</em> of the configuration file, i.e., it will be
7424 the package which handles that file as a configuration
7425 file. Other packages that use the configuration file must
7426 depend on the owning package if they require the
7427 configuration file to operate. If the other package will
7428 use the configuration file if present, but is capable of
7429 operating without it, no dependency need be declared.
7433 If it is desirable for two or more related packages to
7434 share a configuration file <em>and</em> for all of the
7435 related packages to be able to modify that configuration
7436 file, then the following should be done:
7437 <enumlist compact="compact">
7439 One of the related packages (the "owning" package)
7440 will manage the configuration file with maintainer
7441 scripts as described in the previous section.
7444 The owning package should also provide a program
7445 that the other packages may use to modify the
7449 The related packages must use the provided program
7450 to make any desired modifications to the
7451 configuration file. They should either depend on
7452 the core package to guarantee that the configuration
7453 modifier program is available or accept gracefully
7454 that they cannot modify the configuration file if it
7455 is not. (This is in addition to the fact that the
7456 configuration file may not even be present in the
7463 Sometimes it's appropriate to create a new package which
7464 provides the basic infrastructure for the other packages
7465 and which manages the shared configuration files. (The
7466 <tt>sgml-base</tt> package is a good example.)
7471 <heading>User configuration files ("dotfiles")</heading>
7474 The files in <file>/etc/skel</file> will automatically be
7475 copied into new user accounts by <prgn>adduser</prgn>.
7476 No other program should reference the files in
7477 <file>/etc/skel</file>.
7481 Therefore, if a program needs a dotfile to exist in
7482 advance in <file>$HOME</file> to work sensibly, that dotfile
7483 should be installed in <file>/etc/skel</file> and treated as a
7488 However, programs that require dotfiles in order to
7489 operate sensibly are a bad thing, unless they do create
7490 the dotfiles themselves automatically.
7494 Furthermore, programs should be configured by the Debian
7495 default installation to behave as closely to the upstream
7496 default behavior as possible.
7500 Therefore, if a program in a Debian package needs to be
7501 configured in some way in order to operate sensibly, that
7502 should be done using a site-wide configuration file placed
7503 in <file>/etc</file>. Only if the program doesn't support a
7504 site-wide default configuration and the package maintainer
7505 doesn't have time to add it may a default per-user file be
7506 placed in <file>/etc/skel</file>.
7510 <file>/etc/skel</file> should be as empty as we can make it.
7511 This is particularly true because there is no easy (or
7512 necessarily desirable) mechanism for ensuring that the
7513 appropriate dotfiles are copied into the accounts of
7514 existing users when a package is installed.
7520 <heading>Log files</heading>
7522 Log files should usually be named
7523 <file>/var/log/<var>package</var>.log</file>. If you have many
7524 log files, or need a separate directory for permission
7525 reasons (<file>/var/log</file> is writable only by
7526 <file>root</file>), you should usually create a directory named
7527 <file>/var/log/<var>package</var></file> and place your log
7532 Log files must be rotated occasionally so that they don't
7533 grow indefinitely; the best way to do this is to drop a log
7534 rotation configuration file into the directory
7535 <file>/etc/logrotate.d</file> and use the facilities provided by
7536 logrotate.<footnote>
7538 The traditional approach to log files has been to set up
7539 <em>ad hoc</em> log rotation schemes using simple shell
7540 scripts and cron. While this approach is highly
7541 customizable, it requires quite a lot of sysadmin work.
7542 Even though the original Debian system helped a little
7543 by automatically installing a system which can be used
7544 as a template, this was deemed not enough.
7548 The use of <prgn>logrotate</prgn>, a program developed
7549 by Red Hat, is better, as it centralizes log management.
7550 It has both a configuration file
7551 (<file>/etc/logrotate.conf</file>) and a directory where
7552 packages can drop their individual log rotation
7553 configurations (<file>/etc/logrotate.d</file>).
7556 Here is a good example for a logrotate config
7557 file (for more information see <manref name="logrotate"
7559 <example compact="compact">
7560 /var/log/foo/*.log {
7565 /etc/init.d/foo force-reload
7569 This rotates all files under <file>/var/log/foo</file>, saves 12
7570 compressed generations, and forces the daemon to reload its
7571 configuration information after the log rotation.
7575 Log files should be removed when the package is
7576 purged (but not when it is only removed). This should be
7577 done by the <prgn>postrm</prgn> script when it is called
7578 with the argument <tt>purge</tt> (see <ref
7579 id="removedetails">).
7584 <heading>Permissions and owners</heading>
7587 The rules in this section are guidelines for general use.
7588 If necessary you may deviate from the details below.
7589 However, if you do so you must make sure that what is done
7590 is secure and you should try to be as consistent as possible
7591 with the rest of the system. You should probably also
7592 discuss it on <prgn>debian-devel</prgn> first.
7596 Files should be owned by <tt>root:root</tt>, and made
7597 writable only by the owner and universally readable (and
7598 executable, if appropriate), that is mode 644 or 755.
7602 Directories should be mode 755 or (for group-writability)
7603 mode 2775. The ownership of the directory should be
7604 consistent with its mode: if a directory is mode 2775, it
7605 should be owned by the group that needs write access to
7608 When a package is upgraded, and the owner or permissions
7609 of a file included in the package has changed, dpkg
7610 arranges for the ownership and permissions to be
7611 correctly set upon installation. However, this does not
7612 extend to directories; the permissions and ownership of
7613 directories already on the system does not change on
7614 install or upgrade of packages. This makes sense, since
7615 otherwise common directories like <tt>/usr</tt> would
7616 always be in flux. To correctly change permissions of a
7617 directory the package owns, explicit action is required,
7618 usually in the <tt>postinst</tt> script. Care must be
7619 taken to handle downgrades as well, in that case.
7626 Setuid and setgid executables should be mode 4755 or 2755
7627 respectively, and owned by the appropriate user or group.
7628 They should not be made unreadable (modes like 4711 or
7629 2711 or even 4111); doing so achieves no extra security,
7630 because anyone can find the binary in the freely available
7631 Debian package; it is merely inconvenient. For the same
7632 reason you should not restrict read or execute permissions
7633 on non-set-id executables.
7637 Some setuid programs need to be restricted to particular
7638 sets of users, using file permissions. In this case they
7639 should be owned by the uid to which they are set-id, and by
7640 the group which should be allowed to execute them. They
7641 should have mode 4754; again there is no point in making
7642 them unreadable to those users who must not be allowed to
7647 It is possible to arrange that the system administrator can
7648 reconfigure the package to correspond to their local
7649 security policy by changing the permissions on a binary:
7650 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7651 described below.<footnote>
7652 Ordinary files installed by <prgn>dpkg</prgn> (as
7653 opposed to <tt>conffile</tt>s and other similar objects)
7654 normally have their permissions reset to the distributed
7655 permissions when the package is reinstalled. However,
7656 the use of <prgn>dpkg-statoverride</prgn> overrides this
7657 default behavior. If you use this method, you should
7658 remember to describe <prgn>dpkg-statoverride</prgn> in
7659 the package documentation; being a relatively new
7660 addition to Debian, it is probably not yet well-known.
7662 Another method you should consider is to create a group for
7663 people allowed to use the program(s) and make any setuid
7664 executables executable only by that group.
7668 If you need to create a new user or group for your package
7669 there are two possibilities. Firstly, you may need to
7670 make some files in the binary package be owned by this
7671 user or group, or you may need to compile the user or
7672 group id (rather than just the name) into the binary
7673 (though this latter should be avoided if possible, as in
7674 this case you need a statically allocated id).</p>
7677 If you need a statically allocated id, you must ask for a
7678 user or group id from the <tt>base-passwd</tt> maintainer,
7679 and must not release the package until you have been
7680 allocated one. Once you have been allocated one you must
7681 either make the package depend on a version of the
7682 <tt>base-passwd</tt> package with the id present in
7683 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7684 your package to create the user or group itself with the
7685 correct id (using <tt>adduser</tt>) in its
7686 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7687 the <prgn>postinst</prgn> is to be preferred if it is
7688 possible, otherwise a pre-dependency will be needed on the
7689 <tt>adduser</tt> package.)
7693 On the other hand, the program might be able to determine
7694 the uid or gid from the user or group name at runtime, so
7695 that a dynamically allocated id can be used. In this case
7696 you should choose an appropriate user or group name,
7697 discussing this on <prgn>debian-devel</prgn> and checking
7698 with the <package/base-passwd/ maintainer that it is unique and that
7699 they do not wish you to use a statically allocated id
7700 instead. When this has been checked you must arrange for
7701 your package to create the user or group if necessary using
7702 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7703 <prgn>postinst</prgn> script (again, the latter is to be
7704 preferred if it is possible).
7708 Note that changing the numeric value of an id associated
7709 with a name is very difficult, and involves searching the
7710 file system for all appropriate files. You need to think
7711 carefully whether a static or dynamic id is required, since
7712 changing your mind later will cause problems.
7715 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7717 This section is not intended as policy, but as a
7718 description of the use of <prgn>dpkg-statoverride</prgn>.
7722 If a system administrator wishes to have a file (or
7723 directory or other such thing) installed with owner and
7724 permissions different from those in the distributed Debian
7725 package, they can use the <prgn>dpkg-statoverride</prgn>
7726 program to instruct <prgn>dpkg</prgn> to use the different
7727 settings every time the file is installed. Thus the
7728 package maintainer should distribute the files with their
7729 normal permissions, and leave it for the system
7730 administrator to make any desired changes. For example, a
7731 daemon which is normally required to be setuid root, but
7732 in certain situations could be used without being setuid,
7733 should be installed setuid in the <tt>.deb</tt>. Then the
7734 local system administrator can change this if they wish.
7735 If there are two standard ways of doing it, the package
7736 maintainer can use <tt>debconf</tt> to find out the
7737 preference, and call <prgn>dpkg-statoverride</prgn> in the
7738 maintainer script if necessary to accommodate the system
7739 administrator's choice. Care must be taken during
7740 upgrades to not override an existing setting.
7744 Given the above, <prgn>dpkg-statoverride</prgn> is
7745 essentially a tool for system administrators and would not
7746 normally be needed in the maintainer scripts. There is
7747 one type of situation, though, where calls to
7748 <prgn>dpkg-statoverride</prgn> would be needed in the
7749 maintainer scripts, and that involves packages which use
7750 dynamically allocated user or group ids. In such a
7751 situation, something like the following idiom can be very
7752 helpful in the package's <prgn>postinst</prgn>, where
7753 <tt>sysuser</tt> is a dynamically allocated id:
7755 for i in /usr/bin/foo /usr/sbin/bar
7757 # only do something when no setting exists
7758 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7760 #include: debconf processing, question about foo and bar
7761 if [ "$RET" = "true" ] ; then
7762 dpkg-statoverride --update --add sysuser root 4755 $i
7767 The corresponding <tt>dpkg-statoverride --remove</tt>
7768 calls can then be made unconditionally when the package is
7776 <chapt id="customized-programs">
7777 <heading>Customized programs</heading>
7779 <sect id="arch-spec">
7780 <heading>Architecture specification strings</heading>
7783 If a program needs to specify an <em>architecture specification
7784 string</em> in some place, it should select one of the
7785 strings provided by <tt>dpkg-architecture -L</tt>. The
7786 strings are in the format
7787 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7788 is sometimes elided, as when the OS is Linux.<footnote>
7789 <p>Currently, the strings are:
7790 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7791 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7792 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7793 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7794 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7795 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7796 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7797 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7798 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7799 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7800 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7801 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7802 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7803 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7804 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7805 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7806 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7807 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7808 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7809 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7810 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7811 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7812 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7813 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7814 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7815 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7816 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7817 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7818 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7819 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7820 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7821 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7822 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7823 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7824 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7825 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7826 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7832 Note that we don't want to use
7833 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7834 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7835 since this would make our programs incompatible with other
7836 Linux distributions. We also don't use something like
7837 <tt><var>arch</var>-unknown-linux</tt>, since the
7838 <tt>unknown</tt> does not look very good.
7843 <heading>Daemons</heading>
7846 The configuration files <file>/etc/services</file>,
7847 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7848 by the <prgn>netbase</prgn> package and must not be modified
7853 If a package requires a new entry in one of these files, the
7854 maintainer should get in contact with the
7855 <prgn>netbase</prgn> maintainer, who will add the entries
7856 and release a new version of the <prgn>netbase</prgn>
7861 The configuration file <file>/etc/inetd.conf</file> must not be
7862 modified by the package's scripts except via the
7863 <prgn>update-inetd</prgn> script or the
7864 <file>DebianNet.pm</file> Perl module. See their documentation
7865 for details on how to add entries.
7869 If a package wants to install an example entry into
7870 <file>/etc/inetd.conf</file>, the entry must be preceded with
7871 exactly one hash character (<tt>#</tt>). Such lines are
7872 treated as "commented out by user" by the
7873 <prgn>update-inetd</prgn> script and are not changed or
7874 activated during package updates.
7879 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7883 Some programs need to create pseudo-ttys. This should be done
7884 using Unix98 ptys if the C library supports it. The resulting
7885 program must not be installed setuid root, unless that
7886 is required for other functionality.
7890 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7891 <file>/var/log/lastlog</file> must be installed writable by
7892 group <tt>utmp</tt>. Programs which need to modify those
7893 files must be installed setgid <tt>utmp</tt>.
7898 <heading>Editors and pagers</heading>
7901 Some programs have the ability to launch an editor or pager
7902 program to edit or display a text document. Since there are
7903 lots of different editors and pagers available in the Debian
7904 distribution, the system administrator and each user should
7905 have the possibility to choose their preferred editor and
7910 In addition, every program should choose a good default
7911 editor/pager if none is selected by the user or system
7916 Thus, every program that launches an editor or pager must
7917 use the EDITOR or PAGER environment variable to determine
7918 the editor or pager the user wishes to use. If these
7919 variables are not set, the programs <file>/usr/bin/editor</file>
7920 and <file>/usr/bin/pager</file> should be used, respectively.
7924 These two files are managed through the <prgn>dpkg</prgn>
7925 "alternatives" mechanism. Thus every package providing an
7926 editor or pager must call the
7927 <prgn>update-alternatives</prgn> script to register these
7932 If it is very hard to adapt a program to make use of the
7933 EDITOR or PAGER variables, that program may be configured to
7934 use <file>/usr/bin/sensible-editor</file> and
7935 <file>/usr/bin/sensible-pager</file> as the editor or pager
7936 program respectively. These are two scripts provided in the
7937 Debian base system that check the EDITOR and PAGER variables
7938 and launch the appropriate program, and fall back to
7939 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7940 variable is not set.
7944 A program may also use the VISUAL environment variable to
7945 determine the user's choice of editor. If it exists, it
7946 should take precedence over EDITOR. This is in fact what
7947 <file>/usr/bin/sensible-editor</file> does.
7951 It is not required for a package to depend on
7952 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7953 package to provide such virtual packages.<footnote>
7954 The Debian base system already provides an editor and a
7960 <sect id="web-appl">
7961 <heading>Web servers and applications</heading>
7964 This section describes the locations and URLs that should
7965 be used by all web servers and web applications in the
7972 Cgi-bin executable files are installed in the
7974 <example compact="compact">
7975 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7977 and should be referred to as
7978 <example compact="compact">
7979 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7985 <p>Access to HTML documents</p>
7988 HTML documents for a package are stored in
7989 <file>/usr/share/doc/<var>package</var></file>
7990 and can be referred to as
7991 <example compact="compact">
7992 http://localhost/doc/<var>package</var>/<var>filename</var>
7997 The web server should restrict access to the document
7998 tree so that only clients on the same host can read
7999 the documents. If the web server does not support such
8000 access controls, then it should not provide access at
8001 all, or ask about providing access during installation.
8006 <p>Access to images</p>
8008 It is recommended that images for a package be stored
8009 in <tt>/usr/share/images/<var>package</var></tt> and
8010 may be referred to through an alias <tt>/images/</tt>
8013 http://localhost/images/<package>/<filename>
8020 <p>Web Document Root</p>
8023 Web Applications should try to avoid storing files in
8024 the Web Document Root. Instead they should use the
8025 /usr/share/doc/<var>package</var> directory for
8026 documents and register the Web Application via the
8027 <package>doc-base</package> package. If access to the
8028 web document root is unavoidable then use
8029 <example compact="compact">
8032 as the Document Root. This might be just a symbolic
8033 link to the location where the system administrator
8034 has put the real document root.
8037 <item><p>Providing httpd and/or httpd-cgi</p>
8039 All web servers should provide the virtual package
8040 <tt>httpd</tt>. If a web server has CGI support it should
8041 provide <tt>httpd-cgi</tt> additionally.
8044 All web applications which do not contain CGI scripts should
8045 depend on <tt>httpd</tt>, all those web applications which
8046 <tt>do</tt> contain CGI scripts, should depend on
8054 <sect id="mail-transport-agents">
8055 <heading>Mail transport, delivery and user agents</heading>
8058 Debian packages which process electronic mail, whether mail
8059 user agents (MUAs) or mail transport agents (MTAs), must
8060 ensure that they are compatible with the configuration
8061 decisions below. Failure to do this may result in lost
8062 mail, broken <tt>From:</tt> lines, and other serious brain
8067 The mail spool is <file>/var/mail</file> and the interface to
8068 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8069 the FHS). On older systems, the mail spool may be
8070 physically located in <file>/var/spool/mail</file>, but all
8071 access to the mail spool should be via the
8072 <file>/var/mail</file> symlink. The mail spool is part of the
8073 base system and not part of the MTA package.
8077 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8078 programs (such as IMAP daemons) must lock the mailbox in an
8079 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8080 be combined with dot locking. To avoid deadlocks, a program
8081 should use <tt>fcntl()</tt> first and dot locking after
8082 this, or alternatively implement the two locking methods in
8083 a non blocking way<footnote>
8084 If it is not possible to establish both locks, the
8085 system shouldn't wait for the second lock to be
8086 established, but remove the first lock, wait a (random)
8087 time, and start over locking again.
8088 </footnote>. Using the functions <tt>maillock</tt> and
8089 <tt>mailunlock</tt> provided by the
8090 <tt>liblockfile*</tt><footnote>
8091 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8092 to use these functions.
8093 </footnote> packages is the recommended way to realize this.
8097 Mailboxes are generally either mode 600 and owned by
8098 <var>user</var> or mode 660 and owned by
8099 <tt><var>user</var>:mail</tt><footnote>
8100 There are two traditional permission schemes for mail spools:
8101 mode 600 with all mail delivery done by processes running as
8102 the destination user, or mode 660 and owned by group mail with
8103 mail delivery done by a process running as a system user in
8104 group mail. Historically, Debian required mode 660 mail
8105 spools to enable the latter model, but that model has become
8106 increasingly uncommon and the principle of least privilege
8107 indicates that mail systems that use the first model should
8108 use permissions of 600. If delivery to programs is permitted,
8109 it's easier to keep the mail system secure if the delivery
8110 agent runs as the destination user. Debian Policy therefore
8111 permits either scheme.
8112 </footnote>. The local system administrator may choose a
8113 different permission scheme; packages should not make
8114 assumptions about the permission and ownership of mailboxes
8115 unless required (such as when creating a new mailbox). A MUA
8116 may remove a mailbox (unless it has nonstandard permissions) in
8117 which case the MTA or another MUA must recreate it if needed.
8121 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8122 be setgid mail to do the locking mentioned above (and
8123 must obviously avoid accessing other users' mailboxes
8124 using this privilege).</p>
8127 <file>/etc/aliases</file> is the source file for the system mail
8128 aliases (e.g., postmaster, usenet, etc.), it is the one
8129 which the sysadmin and <prgn>postinst</prgn> scripts may
8130 edit. After <file>/etc/aliases</file> is edited the program or
8131 human editing it must call <prgn>newaliases</prgn>. All MTA
8132 packages must come with a <prgn>newaliases</prgn> program,
8133 even if it does nothing, but older MTA packages did not do
8134 this so programs should not fail if <prgn>newaliases</prgn>
8135 cannot be found. Note that because of this, all MTA
8136 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8137 <tt>Replaces: mail-transport-agent</tt> control file
8142 The convention of writing <tt>forward to
8143 <var>address</var></tt> in the mailbox itself is not
8144 supported. Use a <tt>.forward</tt> file instead.</p>
8147 The <prgn>rmail</prgn> program used by UUCP
8148 for incoming mail should be <file>/usr/sbin/rmail</file>.
8149 Likewise, <prgn>rsmtp</prgn>, for receiving
8150 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8154 If your package needs to know what hostname to use on (for
8155 example) outgoing news and mail messages which are generated
8156 locally, you should use the file <file>/etc/mailname</file>. It
8157 will contain the portion after the username and <tt>@</tt>
8158 (at) sign for email addresses of users on the machine
8159 (followed by a newline).
8163 Such a package should check for the existence of this file
8164 when it is being configured. If it exists, it should be
8165 used without comment, although an MTA's configuration script
8166 may wish to prompt the user even if it finds that this file
8167 exists. If the file does not exist, the package should
8168 prompt the user for the value (preferably using
8169 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8170 as well as using it in the package's configuration. The
8171 prompt should make it clear that the name will not just be
8172 used by that package. For example, in this situation the
8173 <tt>inn</tt> package could say something like:
8174 <example compact="compact">
8175 Please enter the "mail name" of your system. This is the
8176 hostname portion of the address to be shown on outgoing
8177 news and mail messages. The default is
8178 <var>syshostname</var>, your system's host name. Mail
8179 name ["<var>syshostname</var>"]:
8181 where <var>syshostname</var> is the output of <tt>hostname
8187 <heading>News system configuration</heading>
8190 All the configuration files related to the NNTP (news)
8191 servers and clients should be located under
8192 <file>/etc/news</file>.</p>
8195 There are some configuration issues that apply to a number
8196 of news clients and server packages on the machine. These
8200 <tag><file>/etc/news/organization</file></tag>
8202 A string which should appear as the
8203 organization header for all messages posted
8204 by NNTP clients on the machine
8207 <tag><file>/etc/news/server</file></tag>
8209 Contains the FQDN of the upstream NNTP
8210 server, or localhost if the local machine is
8215 Other global files may be added as required for cross-package news
8222 <heading>Programs for the X Window System</heading>
8225 <heading>Providing X support and package priorities</heading>
8228 Programs that can be configured with support for the X
8229 Window System must be configured to do so and must declare
8230 any package dependencies necessary to satisfy their
8231 runtime requirements when using the X Window System. If
8232 such a package is of higher priority than the X packages
8233 on which it depends, it is required that either the
8234 X-specific components be split into a separate package, or
8235 that an alternative version of the package, which includes
8236 X support, be provided, or that the package's priority be
8242 <heading>Packages providing an X server</heading>
8245 Packages that provide an X server that, directly or
8246 indirectly, communicates with real input and display
8247 hardware should declare in their control data that they
8248 provide the virtual package <tt>xserver</tt>.<footnote>
8249 This implements current practice, and provides an
8250 actual policy for usage of the <tt>xserver</tt>
8251 virtual package which appears in the virtual packages
8252 list. In a nutshell, X servers that interface
8253 directly with the display and input hardware or via
8254 another subsystem (e.g., GGI) should provide
8255 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8256 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8262 <heading>Packages providing a terminal emulator</heading>
8265 Packages that provide a terminal emulator for the X Window
8266 System which meet the criteria listed below should declare
8267 in their control data that they provide the virtual
8268 package <tt>x-terminal-emulator</tt>. They should also
8269 register themselves as an alternative for
8270 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8275 To be an <tt>x-terminal-emulator</tt>, a program must:
8276 <list compact="compact">
8278 Be able to emulate a DEC VT100 terminal, or a
8279 compatible terminal.
8283 Support the command-line option <tt>-e
8284 <var>command</var></tt>, which creates a new
8285 terminal window<footnote>
8286 "New terminal window" does not necessarily mean
8287 a new top-level X window directly parented by
8288 the window manager; it could, if the terminal
8289 emulator application were so coded, be a new
8290 "view" in a multiple-document interface (MDI).
8292 and runs the specified <var>command</var>,
8293 interpreting the entirety of the rest of the command
8294 line as a command to pass straight to exec, in the
8295 manner that <tt>xterm</tt> does.
8299 Support the command-line option <tt>-T
8300 <var>title</var></tt>, which creates a new terminal
8301 window with the window title <var>title</var>.
8308 <heading>Packages providing a window manager</heading>
8311 Packages that provide a window manager should declare in
8312 their control data that they provide the virtual package
8313 <tt>x-window-manager</tt>. They should also register
8314 themselves as an alternative for
8315 <file>/usr/bin/x-window-manager</file>, with a priority
8316 calculated as follows:
8317 <list compact="compact">
8319 Start with a priority of 20.
8323 If the window manager supports the Debian menu
8324 system, add 20 points if this support is available
8325 in the package's default configuration (i.e., no
8326 configuration files belonging to the system or user
8327 have to be edited to activate the feature); if
8328 configuration files must be modified, add only 10
8334 If the window manager complies with <url
8335 id="http://www.freedesktop.org/Standards/wm-spec"
8336 name="The Window Manager Specification Project">,
8337 written by the <url id="http://www.freedesktop.org/"
8338 name="Free Desktop Group">, add 40 points.
8342 If the window manager permits the X session to be
8343 restarted using a <em>different</em> window manager
8344 (without killing the X server) in its default
8345 configuration, add 10 points; otherwise add none.
8352 <heading>Packages providing fonts</heading>
8355 Packages that provide fonts for the X Window
8357 For the purposes of Debian Policy, a "font for the X
8358 Window System" is one which is accessed via X protocol
8359 requests. Fonts for the Linux console, for PostScript
8360 renderer, or any other purpose, do not fit this
8361 definition. Any tool which makes such fonts available
8362 to the X Window System, however, must abide by this
8365 must do a number of things to ensure that they are both
8366 available without modification of the X or font server
8367 configuration, and that they do not corrupt files used by
8368 other font packages to register information about
8372 Fonts of any type supported by the X Window System
8373 must be in a separate binary package from any
8374 executables, libraries, or documentation (except
8375 that specific to the fonts shipped, such as their
8376 license information). If one or more of the fonts
8377 so packaged are necessary for proper operation of
8378 the package with which they are associated the font
8379 package may be Recommended; if the fonts merely
8380 provide an enhancement, a Suggests relationship may
8381 be used. Packages must not Depend on font
8383 This is because the X server may retrieve fonts
8384 from the local file system or over the network
8385 from an X font server; the Debian package system
8386 is empowered to deal only with the local
8392 BDF fonts must be converted to PCF fonts with the
8393 <prgn>bdftopcf</prgn> utility (available in the
8394 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8395 placed in a directory that corresponds to their
8397 <list compact="compact">
8399 100 dpi fonts must be placed in
8400 <file>/usr/share/fonts/X11/100dpi/</file>.
8404 75 dpi fonts must be placed in
8405 <file>/usr/share/fonts/X11/75dpi/</file>.
8409 Character-cell fonts, cursor fonts, and other
8410 low-resolution fonts must be placed in
8411 <file>/usr/share/fonts/X11/misc/</file>.
8417 Speedo fonts must be placed in
8418 <file>/usr/share/fonts/X11/Speedo/</file>.
8422 Type 1 fonts must be placed in
8423 <file>/usr/share/fonts/X11/Type1/</file>. If font
8424 metric files are available, they must be placed here
8429 Subdirectories of <file>/usr/share/fonts/X11/</file>
8430 other than those listed above must be neither
8431 created nor used. (The <file>PEX</file>, <file>CID</file>,
8432 and <file>cyrillic</file> directories are excepted for
8433 historical reasons, but installation of files into
8434 these directories remains discouraged.)
8438 Font packages may, instead of placing files directly
8439 in the X font directories listed above, provide
8440 symbolic links in that font directory pointing to
8441 the files' actual location in the filesystem. Such
8442 a location must comply with the FHS.
8446 Font packages should not contain both 75dpi and
8447 100dpi versions of a font. If both are available,
8448 they should be provided in separate binary packages
8449 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8450 the names of the packages containing the
8451 corresponding fonts.
8455 Fonts destined for the <file>misc</file> subdirectory
8456 should not be included in the same package as 75dpi
8457 or 100dpi fonts; instead, they should be provided in
8458 a separate package with <tt>-misc</tt> appended to
8463 Font packages must not provide the files
8464 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8465 <file>fonts.scale</file> in a font directory:
8468 <file>fonts.dir</file> files must not be provided at all.
8472 <file>fonts.alias</file> and <file>fonts.scale</file>
8473 files, if needed, should be provided in the
8475 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8476 where <var>fontdir</var> is the name of the
8478 <file>/usr/share/fonts/X11/</file> where the
8479 package's corresponding fonts are stored
8480 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8481 <var>package</var> is the name of the package
8482 that provides these fonts, and
8483 <var>extension</var> is either <tt>scale</tt>
8484 or <tt>alias</tt>, whichever corresponds to
8491 Font packages must declare a dependency on
8492 <tt>xfonts-utils</tt> in their control
8497 Font packages that provide one or more
8498 <file>fonts.scale</file> files as described above must
8499 invoke <prgn>update-fonts-scale</prgn> on each
8500 directory into which they installed fonts
8501 <em>before</em> invoking
8502 <prgn>update-fonts-dir</prgn> on that directory.
8503 This invocation must occur in both the
8504 <prgn>postinst</prgn> (for all arguments) and
8505 <prgn>postrm</prgn> (for all arguments except
8506 <tt>upgrade</tt>) scripts.
8510 Font packages that provide one or more
8511 <file>fonts.alias</file> files as described above must
8512 invoke <prgn>update-fonts-alias</prgn> on each
8513 directory into which they installed fonts. This
8514 invocation must occur in both the
8515 <prgn>postinst</prgn> (for all arguments) and
8516 <prgn>postrm</prgn> (for all arguments except
8517 <tt>upgrade</tt>) scripts.
8521 Font packages must invoke
8522 <prgn>update-fonts-dir</prgn> on each directory into
8523 which they installed fonts. This invocation must
8524 occur in both the <prgn>postinst</prgn> (for all
8525 arguments) and <prgn>postrm</prgn> (for all
8526 arguments except <tt>upgrade</tt>) scripts.
8530 Font packages must not provide alias names for the
8531 fonts they include which collide with alias names
8532 already in use by fonts already packaged.
8536 Font packages must not provide fonts with the same
8537 XLFD registry name as another font already packaged.
8544 <heading>Application defaults files</heading>
8547 Application defaults files must be installed in the
8548 directory <file>/etc/X11/app-defaults/</file> (use of a
8549 localized subdirectory of <file>/etc/X11/</file> as described
8550 in the <em>X Toolkit Intrinsics - C Language
8551 Interface</em> manual is also permitted). They must be
8552 registered as <tt>conffile</tt>s or handled as
8553 configuration files.
8557 Customization of programs' X resources may also be
8558 supported with the provision of a file with the same name
8559 as that of the package placed in the
8560 <file>/etc/X11/Xresources/</file> directory, which must
8561 registered as a <tt>conffile</tt> or handled as a
8562 configuration file.<footnote>
8563 Note that this mechanism is not the same as using
8564 app-defaults; app-defaults are tied to the client
8565 binary on the local file system, whereas X resources
8566 are stored in the X server and affect all connecting
8573 <heading>Installation directory issues</heading>
8576 Packages using the X Window System should not be
8577 configured to install files under the
8578 <file>/usr/X11R6/</file> directory. The
8579 <file>/usr/X11R6/</file> directory hierarchy should be
8580 regarded as obsolete.
8584 Programs that use GNU <prgn>autoconf</prgn> and
8585 <prgn>automake</prgn> are usually easily configured at
8586 compile time to use <file>/usr/</file> instead of
8587 <file>/usr/X11R6/</file>, and this should be done whenever
8588 possible. Configuration files for window managers and
8589 display managers should be placed in a subdirectory of
8590 <file>/etc/X11/</file> corresponding to the package name due
8591 to these programs' tight integration with the mechanisms
8592 of the X Window System. Application-level programs should
8593 use the <file>/etc/</file> directory unless otherwise mandated
8598 The installation of files into subdirectories
8599 of <file>/usr/X11R6/include/X11/</file> and
8600 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8601 package maintainers should determine if subdirectories of
8602 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8607 Packages should install any relevant files into the
8608 directories <file>/usr/include/X11/</file> and
8609 <file>/usr/lib/X11/</file>, but if they do so, they must
8610 pre-depend on <tt>x11-common (>=
8611 1:7.0.0)</tt><footnote>
8613 These libraries used to be all symbolic
8614 links. However, with <tt>X11R7</tt>,
8615 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8616 are now real directories, and packages
8617 <strong>should</strong> ship their files here instead
8618 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8619 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8620 responsible for converting these symlinks into
8628 <heading>The OSF/Motif and OpenMotif libraries</heading>
8631 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8632 OpenMotif libraries</em><footnote>
8633 OSF/Motif and OpenMotif are collectively referred to as
8634 "Motif" in this policy document.
8636 should be compiled against and tested with LessTif (a free
8637 re-implementation of Motif) instead. If the maintainer
8638 judges that the program or programs do not work
8639 sufficiently well with LessTif to be distributed and
8640 supported, but do so when compiled against Motif, then two
8641 versions of the package should be created; one linked
8642 statically against Motif and with <tt>-smotif</tt>
8643 appended to the package name, and one linked dynamically
8644 against Motif and with <tt>-dmotif</tt> appended to the
8649 Both Motif-linked versions are dependent
8650 upon non-DFSG-compliant software and thus cannot be
8651 uploaded to the <em>main</em> distribution; if the
8652 software is itself DFSG-compliant it may be uploaded to
8653 the <em>contrib</em> distribution. While known existing
8654 versions of Motif permit unlimited redistribution of
8655 binaries linked against the library (whether statically or
8656 dynamically), it is the package maintainer's
8657 responsibility to determine whether this is permitted by
8658 the license of the copy of Motif in their possession.
8664 <heading>Perl programs and modules</heading>
8667 Perl programs and modules should follow the current Perl policy.
8671 The Perl policy can be found in the <tt>perl-policy</tt>
8672 files in the <tt>debian-policy</tt> package.
8673 It is also available from the Debian web mirrors at
8674 <tt><url name="/doc/packaging-manuals/perl-policy/"
8675 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8680 <heading>Emacs lisp programs</heading>
8683 Please refer to the "Debian Emacs Policy" for details of how to
8684 package emacs lisp programs.
8688 The Emacs policy is available in
8689 <file>debian-emacs-policy.gz</file> of the
8690 <package>emacsen-common</package> package.
8691 It is also available from the Debian web mirrors at
8692 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8693 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8698 <heading>Games</heading>
8701 The permissions on <file>/var/games</file> are mode 755, owner
8702 <tt>root</tt> and group <tt>root</tt>.
8706 Each game decides on its own security policy.</p>
8709 Games which require protected, privileged access to
8710 high-score files, saved games, etc., may be made
8711 set-<em>group</em>-id (mode 2755) and owned by
8712 <tt>root:games</tt>, and use files and directories with
8713 appropriate permissions (770 <tt>root:games</tt>, for
8714 example). They must not be made
8715 set-<em>user</em>-id, as this causes security problems. (If
8716 an attacker can subvert any set-user-id game they can
8717 overwrite the executable of any other, causing other players
8718 of these games to run a Trojan horse program. With a
8719 set-group-id game the attacker only gets access to less
8720 important game data, and if they can get at the other
8721 players' accounts at all it will take considerably more
8725 Some packages, for example some fortune cookie programs, are
8726 configured by the upstream authors to install with their
8727 data files or other static information made unreadable so
8728 that they can only be accessed through set-id programs
8729 provided. You should not do this in a Debian package: anyone can
8730 download the <file>.deb</file> file and read the data from it,
8731 so there is no point making the files unreadable. Not
8732 making the files unreadable also means that you don't have
8733 to make so many programs set-id, which reduces the risk of a
8737 As described in the FHS, binaries of games should be
8738 installed in the directory <file>/usr/games</file>. This also
8739 applies to games that use the X Window System. Manual pages
8740 for games (X and non-X games) should be installed in
8741 <file>/usr/share/man/man6</file>.</p>
8747 <heading>Documentation</heading>
8750 <heading>Manual pages</heading>
8753 You should install manual pages in <prgn>nroff</prgn> source
8754 form, in appropriate places under <file>/usr/share/man</file>.
8755 You should only use sections 1 to 9 (see the FHS for more
8756 details). You must not install a pre-formatted "cat page".
8760 Each program, utility, and function should have an
8761 associated manual page included in the same package. It is
8762 suggested that all configuration files also have a manual
8763 page included as well. Manual pages for protocols and other
8764 auxiliary things are optional.
8768 If no manual page is available, this is considered as a bug
8769 and should be reported to the Debian Bug Tracking System (the
8770 maintainer of the package is allowed to write this bug report
8771 themselves, if they so desire). Do not close the bug report
8772 until a proper man page is available.<footnote>
8773 It is not very hard to write a man page. See the
8774 <url id="http://www.schweikhardt.net/man_page_howto.html"
8775 name="Man-Page-HOWTO">,
8776 <manref name="man" section="7">, the examples
8777 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8778 the helper programs <prgn>help2man</prgn>, or the
8779 directory <file>/usr/share/doc/man-db/examples</file>.
8784 You may forward a complaint about a missing man page to the
8785 upstream authors, and mark the bug as forwarded in the
8786 Debian bug tracking system. Even though the GNU Project do
8787 not in general consider the lack of a man page to be a bug,
8788 we do; if they tell you that they don't consider it a bug
8789 you should leave the bug in our bug tracking system open
8794 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8798 If one man page needs to be accessible via several names it
8799 is better to use a symbolic link than the <file>.so</file>
8800 feature, but there is no need to fiddle with the relevant
8801 parts of the upstream source to change from <file>.so</file> to
8802 symlinks: don't do it unless it's easy. You should not
8803 create hard links in the manual page directories, nor put
8804 absolute filenames in <file>.so</file> directives. The filename
8805 in a <file>.so</file> in a man page should be relative to the
8806 base of the man page tree (usually
8807 <file>/usr/share/man</file>). If you do not create any links
8808 (whether symlinks, hard links, or <tt>.so</tt> directives)
8809 in the file system to the alternate names of the man page,
8810 then you should not rely on <prgn>man</prgn> finding your
8811 man page under those names based solely on the information in
8812 the man page's header.<footnote>
8813 Supporting this in <prgn>man</prgn> often requires
8814 unreasonable processing time to find a manual page or to
8815 report that none exists, and moves knowledge into man's
8816 database that would be better left in the file system.
8817 This support is therefore deprecated and will cease to
8818 be present in the future.
8823 Manual pages in locale-specific subdirectories of
8824 <file>/usr/share/man</file> should use either UTF-8 or the usual
8825 legacy encoding for that language (normally the one corresponding
8826 to the shortest relevant locale name in
8827 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8828 <file>/usr/share/man/fr</file> should use either UTF-8 or
8829 ISO-8859-1.<footnote>
8830 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8831 use. In future, all manual pages will be required to use
8837 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8838 included in the subdirectory name unless it indicates a
8839 significant difference in the language, as this excludes
8840 speakers of the language in other countries.<footnote>
8841 At the time of writing, Chinese and Portuguese are the main
8842 languages with such differences, so <file>pt_BR</file>,
8843 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8848 Due to limitations in current implementations, all characters
8849 in the manual page source should be representable in the usual
8850 legacy encoding for that language, even if the file is
8851 actually encoded in UTF-8. Safe alternative ways to write many
8852 characters outside that range may be found in
8853 <manref name="groff_char" section="7">.
8858 <heading>Info documents</heading>
8861 Info documents should be installed in <file>/usr/share/info</file>.
8862 They should be compressed with <tt>gzip -9</tt>.
8866 Your package should call <prgn>install-info</prgn> to update
8867 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8868 script when called with a <tt>configure</tt> argument, for
8870 <example compact="compact">
8871 install-info --quiet --section Development Development \
8872 /usr/share/info/foobar.info
8876 It is a good idea to specify a section for the location of
8877 your program; this is done with the <tt>--section</tt>
8878 switch. To determine which section to use, you should look
8879 at <file>/usr/share/info/dir</file> on your system and choose the most
8880 relevant (or create a new section if none of the current
8881 sections are relevant). Note that the <tt>--section</tt>
8882 flag takes two arguments; the first is a regular expression
8883 to match (case-insensitively) against an existing section,
8884 the second is used when creating a new one.</p>
8887 You should remove the entries in the <prgn>prerm</prgn>
8888 script when called with a <tt>remove</tt> argument:
8889 <example compact="compact">
8890 install-info --quiet --remove /usr/share/info/foobar.info
8894 If <prgn>install-info</prgn> cannot find a description entry
8895 in the Info file you must supply one. See <manref
8896 name="install-info" section="8"> for details.</p>
8900 <heading>Additional documentation</heading>
8903 Any additional documentation that comes with the package may
8904 be installed at the discretion of the package maintainer.
8905 Plain text documentation should be installed in the directory
8906 <file>/usr/share/doc/<var>package</var></file>, where
8907 <var>package</var> is the name of the package, and
8908 compressed with <tt>gzip -9</tt> unless it is small.
8912 If a package comes with large amounts of documentation which
8913 many users of the package will not require you should create
8914 a separate binary package to contain it, so that it does not
8915 take up disk space on the machines of users who do not need
8916 or want it installed.</p>
8919 It is often a good idea to put text information files
8920 (<file>README</file>s, changelogs, and so forth) that come with
8921 the source package in <file>/usr/share/doc/<var>package</var></file>
8922 in the binary package. However, you don't need to install
8923 the instructions for building and installing the package, of
8927 Packages must not require the existence of any files in
8928 <file>/usr/share/doc/</file> in order to function
8930 The system administrator should be able to
8931 delete files in <file>/usr/share/doc/</file> without causing
8932 any programs to break.
8934 Any files that are referenced by programs but are also
8935 useful as stand alone documentation should be installed under
8936 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8937 <file>/usr/share/doc/<var>package</var></file>.
8941 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8942 link to another directory in <file>/usr/share/doc</file> only if
8943 the two packages both come from the same source and the
8944 first package Depends on the second.<footnote>
8946 Please note that this does not override the section on
8947 changelog files below, so the file
8948 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8949 must refer to the changelog for the current version of
8950 <var>package</var> in question. In practice, this means
8951 that the sources of the target and the destination of the
8952 symlink must be the same (same source package and
8959 Former Debian releases placed all additional documentation
8960 in <file>/usr/doc/<var>package</var></file>. This has been
8961 changed to <file>/usr/share/doc/<var>package</var></file>,
8962 and packages must not put documentation in the directory
8963 <file>/usr/doc/<var>package</var></file>. <footnote>
8964 At this phase of the transition, we no longer require a
8965 symbolic link in <file>/usr/doc/</file>. At a later point,
8966 policy shall change to make the symbolic links a bug.
8972 <heading>Preferred documentation formats</heading>
8975 The unification of Debian documentation is being carried out
8979 If your package comes with extensive documentation in a
8980 markup format that can be converted to various other formats
8981 you should if possible ship HTML versions in a binary
8982 package, in the directory
8983 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8984 its subdirectories.<footnote>
8985 The rationale: The important thing here is that HTML
8986 docs should be available in <em>some</em> package, not
8987 necessarily in the main binary package.
8992 Other formats such as PostScript may be provided at the
8993 package maintainer's discretion.
8997 <sect id="copyrightfile">
8998 <heading>Copyright information</heading>
9001 Every package must be accompanied by a verbatim copy of its
9002 copyright and distribution license in the file
9003 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9004 file must neither be compressed nor be a symbolic link.
9008 In addition, the copyright file must say where the upstream
9009 sources (if any) were obtained. It should name the original
9010 authors of the package and the Debian maintainer(s) who were
9011 involved with its creation.
9015 Packages in the <em>contrib</em> or <em>non-free</em>
9016 distribution areas should state in the copyright file that the
9017 package is not part of the Debian GNU/Linux distribution and
9018 briefly explain why.
9022 A copy of the file which will be installed in
9023 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9024 be in <file>debian/copyright</file> in the source package.
9028 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9029 link to another directory in <file>/usr/share/doc</file> only if
9030 the two packages both come from the same source and the
9031 first package Depends on the second. These rules are
9032 important because copyrights must be extractable by
9037 Packages distributed under the UCB BSD license, the Apache
9038 license (version 2.0), the Artistic license, the GNU GPL
9039 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
9040 the GNU FDL (version 1.2) should refer to the corresponding
9041 files under <file>/usr/share/common-licenses</file>,<footnote>
9044 <file>/usr/share/common-licenses/BSD</file>,
9045 <file>/usr/share/common-licenses/Apache-2.0</file>,
9046 <file>/usr/share/common-licenses/Artistic</file>,
9047 <file>/usr/share/common-licenses/GPL-2</file>,
9048 <file>/usr/share/common-licenses/GPL-3</file>,
9049 <file>/usr/share/common-licenses/LGPL-2</file>,
9050 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9051 <file>/usr/share/common-licenses/LGPL-3</file>, and
9052 <file>/usr/share/common-licenses/GFDL-1.2</file>
9055 </footnote> rather than quoting them in the copyright
9060 You should not use the copyright file as a general <file>README</file>
9061 file. If your package has such a file it should be
9062 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9063 <file>README.Debian</file> or some other appropriate place.</p>
9067 <heading>Examples</heading>
9070 Any examples (configurations, source files, whatever),
9071 should be installed in a directory
9072 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9073 files should not be referenced by any program: they're there
9074 for the benefit of the system administrator and users as
9075 documentation only. Architecture-specific example files
9076 should be installed in a directory
9077 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9079 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9080 latter directory itself may be a symbolic link to the
9085 If the purpose of a package is to provide examples, then the
9086 example files may be installed into
9087 <file>/usr/share/doc/<var>package</var></file>.
9091 <sect id="changelogs">
9092 <heading>Changelog files</heading>
9095 Packages that are not Debian-native must contain a
9096 compressed copy of the <file>debian/changelog</file> file from
9097 the Debian source tree in
9098 <file>/usr/share/doc/<var>package</var></file> with the name
9099 <file>changelog.Debian.gz</file>.
9103 If an upstream changelog is available, it should be accessible as
9104 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9105 plain text. If the upstream changelog is distributed in
9106 HTML, it should be made available in that form as
9107 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9108 and a plain text <file>changelog.gz</file> should be generated
9109 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9110 the upstream changelog files do not already conform to this
9111 naming convention, then this may be achieved either by
9112 renaming the files, or by adding a symbolic link, at the
9113 maintainer's discretion.<footnote>
9114 Rationale: People should not have to look in places for
9115 upstream changelogs merely because they are given
9116 different names or are distributed in HTML format.
9121 All of these files should be installed compressed using
9122 <tt>gzip -9</tt>, as they will become large with time even
9123 if they start out small.
9127 If the package has only one changelog which is used both as
9128 the Debian changelog and the upstream one because there is
9129 no separate upstream maintainer then that changelog should
9130 usually be installed as
9131 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9132 there is a separate upstream maintainer, but no upstream
9133 changelog, then the Debian changelog should still be called
9134 <file>changelog.Debian.gz</file>.
9138 For details about the format and contents of the Debian
9139 changelog file, please see <ref id="dpkgchangelog">.
9144 <appendix id="pkg-scope">
9145 <heading>Introduction and scope of these appendices</heading>
9148 These appendices are taken essentially verbatim from the
9149 now-deprecated Packaging Manual, version 3.2.1.0. They are
9150 the chapters which are likely to be of use to package
9151 maintainers and which have not already been included in the
9152 policy document itself. Most of these sections are very likely
9153 not relevant to policy; they should be treated as
9154 documentation for the packaging system. Please note that these
9155 appendices are included for convenience, and for historical
9156 reasons: they used to be part of policy package, and they have
9157 not yet been incorporated into dpkg documentation. However,
9158 they still have value, and hence they are presented here.
9162 They have not yet been checked to ensure that they are
9163 compatible with the contents of policy, and if there are any
9164 contradictions, the version in the main policy document takes
9165 precedence. The remaining chapters of the old Packaging
9166 Manual have also not been read in detail to ensure that there
9167 are not parts which have been left out. Both of these will be
9172 Certain parts of the Packaging manual were integrated into the
9173 Policy Manual proper, and removed from the appendices. Links
9174 have been placed from the old locations to the new ones.
9178 <prgn>dpkg</prgn> is a suite of programs for creating binary
9179 package files and installing and removing them on Unix
9181 <prgn>dpkg</prgn> is targeted primarily at Debian
9182 GNU/Linux, but may work on or be ported to other
9188 The binary packages are designed for the management of
9189 installed executable programs (usually compiled binaries) and
9190 their associated data, though source code examples and
9191 documentation are provided as part of some packages.</p>
9194 This manual describes the technical aspects of creating Debian
9195 binary packages (<file>.deb</file> files). It documents the
9196 behavior of the package management programs
9197 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9198 they interact with packages.</p>
9201 It also documents the interaction between
9202 <prgn>dselect</prgn>'s core and the access method scripts it
9203 uses to actually install the selected packages, and describes
9204 how to create a new access method.</p>
9207 This manual does not go into detail about the options and
9208 usage of the package building and installation tools. It
9209 should therefore be read in conjunction with those programs'
9214 The utility programs which are provided with <prgn>dpkg</prgn>
9215 for managing various system configuration and similar issues,
9216 such as <prgn>update-rc.d</prgn> and
9217 <prgn>install-info</prgn>, are not described in detail here -
9218 please see their man pages.
9222 It is assumed that the reader is reasonably familiar with the
9223 <prgn>dpkg</prgn> System Administrators' manual.
9224 Unfortunately this manual does not yet exist.
9228 The Debian version of the FSF's GNU hello program is provided
9229 as an example for people wishing to create Debian
9230 packages. The Debian <prgn>debmake</prgn> package is
9231 recommended as a very helpful tool in creating and maintaining
9232 Debian packages. However, while the tools and examples are
9233 helpful, they do not replace the need to read and follow the
9234 Policy and Programmer's Manual.</p>
9237 <appendix id="pkg-binarypkg">
9238 <heading>Binary packages (from old Packaging Manual)</heading>
9241 The binary package has two main sections. The first part
9242 consists of various control information files and scripts used
9243 by <prgn>dpkg</prgn> when installing and removing. See <ref
9244 id="pkg-controlarea">.
9248 The second part is an archive containing the files and
9249 directories to be installed.
9253 In the future binary packages may also contain other
9254 components, such as checksums and digital signatures. The
9255 format for the archive is described in full in the
9256 <file>deb(5)</file> man page.
9260 <sect id="pkg-bincreating"><heading>Creating package files -
9261 <prgn>dpkg-deb</prgn>
9265 All manipulation of binary package files is done by
9266 <prgn>dpkg-deb</prgn>; it's the only program that has
9267 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9268 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9269 will spot that the options requested are appropriate to
9270 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9275 In order to create a binary package you must make a
9276 directory tree which contains all the files and directories
9277 you want to have in the file system data part of the package.
9278 In Debian-format source packages this directory is usually
9279 <file>debian/tmp</file>, relative to the top of the package's
9284 They should have the locations (relative to the root of the
9285 directory tree you're constructing) ownerships and
9286 permissions which you want them to have on the system when
9291 With current versions of <prgn>dpkg</prgn> the uid/username
9292 and gid/groupname mappings for the users and groups being
9293 used should be the same on the system where the package is
9294 built and the one where it is installed.
9298 You need to add one special directory to the root of the
9299 miniature file system tree you're creating:
9300 <prgn>DEBIAN</prgn>. It should contain the control
9301 information files, notably the binary package control file
9302 (see <ref id="pkg-controlfile">).
9306 The <prgn>DEBIAN</prgn> directory will not appear in the
9307 file system archive of the package, and so won't be installed
9308 by <prgn>dpkg</prgn> when the package is installed.
9312 When you've prepared the package, you should invoke:
9314 dpkg --build <var>directory</var>
9319 This will build the package in
9320 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9321 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9322 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9327 See the man page <manref name="dpkg-deb" section="8"> for details of how
9328 to examine the contents of this newly-created file. You may find the
9329 output of following commands enlightening:
9331 dpkg-deb --info <var>filename</var>.deb
9332 dpkg-deb --contents <var>filename</var>.deb
9333 dpkg --contents <var>filename</var>.deb
9335 To view the copyright file for a package you could use this command:
9337 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9342 <sect id="pkg-controlarea">
9343 <heading>Package control information files</heading>
9346 The control information portion of a binary package is a
9347 collection of files with names known to <prgn>dpkg</prgn>.
9348 It will treat the contents of these files specially - some
9349 of them contain information used by <prgn>dpkg</prgn> when
9350 installing or removing the package; others are scripts which
9351 the package maintainer wants <prgn>dpkg</prgn> to run.
9355 It is possible to put other files in the package control
9356 area, but this is not generally a good idea (though they
9357 will largely be ignored).
9361 Here is a brief list of the control info files supported by
9362 <prgn>dpkg</prgn> and a summary of what they're used for.
9367 <tag><tt>control</tt>
9370 This is the key description file used by
9371 <prgn>dpkg</prgn>. It specifies the package's name
9372 and version, gives its description for the user,
9373 states its relationships with other packages, and so
9374 forth. See <ref id="sourcecontrolfiles"> and
9375 <ref id="binarycontrolfiles">.
9379 It is usually generated automatically from information
9380 in the source package by the
9381 <prgn>dpkg-gencontrol</prgn> program, and with
9382 assistance from <prgn>dpkg-shlibdeps</prgn>.
9383 See <ref id="pkg-sourcetools">.
9387 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9392 These are executable files (usually scripts) which
9393 <prgn>dpkg</prgn> runs during installation, upgrade
9394 and removal of packages. They allow the package to
9395 deal with matters which are particular to that package
9396 or require more complicated processing than that
9397 provided by <prgn>dpkg</prgn>. Details of when and
9398 how they are called are in <ref id="maintainerscripts">.
9402 It is very important to make these scripts idempotent.
9403 See <ref id="idempotency">.
9407 The maintainer scripts are guaranteed to run with a
9408 controlling terminal and can interact with the user.
9409 See <ref id="controllingterminal">.
9413 <tag><tt>conffiles</tt>
9416 This file contains a list of configuration files which
9417 are to be handled automatically by <prgn>dpkg</prgn>
9418 (see <ref id="pkg-conffiles">). Note that not necessarily
9419 every configuration file should be listed here.
9422 <tag><tt>shlibs</tt>
9425 This file contains a list of the shared libraries
9426 supplied by the package, with dependency details for
9427 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9428 when it determines what dependencies are required in a
9429 package control file. The <tt>shlibs</tt> file format
9430 is described on <ref id="shlibs">.
9435 <sect id="pkg-controlfile">
9436 <heading>The main control information file: <tt>control</tt></heading>
9439 The most important control information file used by
9440 <prgn>dpkg</prgn> when it installs a package is
9441 <tt>control</tt>. It contains all the package's "vital
9446 The binary package control files of packages built from
9447 Debian sources are made by a special tool,
9448 <prgn>dpkg-gencontrol</prgn>, which reads
9449 <file>debian/control</file> and <file>debian/changelog</file> to
9450 find the information it needs. See <ref id="pkg-sourcepkg"> for
9455 The fields in binary package control files are listed in
9456 <ref id="binarycontrolfiles">.
9460 A description of the syntax of control files and the purpose
9461 of the fields is available in <ref id="controlfields">.
9466 <heading>Time Stamps</heading>
9469 See <ref id="timestamps">.
9474 <appendix id="pkg-sourcepkg">
9475 <heading>Source packages (from old Packaging Manual) </heading>
9478 The Debian binary packages in the distribution are generated
9479 from Debian sources, which are in a special format to assist
9480 the easy and automatic building of binaries.
9483 <sect id="pkg-sourcetools">
9484 <heading>Tools for processing source packages</heading>
9487 Various tools are provided for manipulating source packages;
9488 they pack and unpack sources and help build of binary
9489 packages and help manage the distribution of new versions.
9493 They are introduced and typical uses described here; see
9494 <manref name="dpkg-source" section="1"> for full
9495 documentation about their arguments and operation.
9499 For examples of how to construct a Debian source package,
9500 and how to use those utilities that are used by Debian
9501 source packages, please see the <prgn>hello</prgn> example
9505 <sect1 id="pkg-dpkg-source">
9507 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9512 This program is frequently used by hand, and is also
9513 called from package-independent automated building scripts
9514 such as <prgn>dpkg-buildpackage</prgn>.
9518 To unpack a package it is typically invoked with
9520 dpkg-source -x <var>.../path/to/filename</var>.dsc
9525 with the <file><var>filename</var>.tar.gz</file> and
9526 <file><var>filename</var>.diff.gz</file> (if applicable) in
9527 the same directory. It unpacks into
9528 <file><var>package</var>-<var>version</var></file>, and if
9530 <file><var>package</var>-<var>version</var>.orig</file>, in
9531 the current directory.
9535 To create a packed source archive it is typically invoked:
9537 dpkg-source -b <var>package</var>-<var>version</var>
9542 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9543 <file>.diff.gz</file> (if appropriate) in the current
9544 directory. <prgn>dpkg-source</prgn> does not clean the
9545 source tree first - this must be done separately if it is
9550 See also <ref id="pkg-sourcearchives">.</p>
9554 <sect1 id="pkg-dpkg-buildpackage">
9556 <prgn>dpkg-buildpackage</prgn> - overall package-building
9561 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9562 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9563 targets <tt>clean</tt>, <tt>build</tt> and
9564 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9565 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9566 source and binary package upload.
9570 It is usually invoked by hand from the top level of the
9571 built or unbuilt source directory. It may be invoked with
9572 no arguments; useful arguments include:
9573 <taglist compact="compact">
9574 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9577 Do not sign the <tt>.changes</tt> file or the
9578 source package <tt>.dsc</tt> file, respectively.</p>
9580 <tag><tt>-p<var>sign-command</var></tt></tag>
9583 Invoke <var>sign-command</var> instead of finding
9584 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9585 <var>sign-command</var> must behave just like
9586 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9588 <tag><tt>-r<var>root-command</var></tt></tag>
9591 When root privilege is required, invoke the command
9592 <var>root-command</var>. <var>root-command</var>
9593 should invoke its first argument as a command, from
9594 the <prgn>PATH</prgn> if necessary, and pass its
9595 second and subsequent arguments to the command it
9596 calls. If no <var>root-command</var> is supplied
9597 then <var>dpkg-buildpackage</var> will take no
9598 special action to gain root privilege, so that for
9599 most packages it will have to be invoked as root to
9602 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9605 Two types of binary-only build and upload - see
9606 <manref name="dpkg-source" section="1">.
9613 <sect1 id="pkg-dpkg-gencontrol">
9615 <prgn>dpkg-gencontrol</prgn> - generates binary package
9620 This program is usually called from <file>debian/rules</file>
9621 (see <ref id="pkg-sourcetree">) in the top level of the source
9626 This is usually done just before the files and directories in the
9627 temporary directory tree where the package is being built have their
9628 permissions and ownerships set and the package is constructed using
9629 <prgn>dpkg-deb/</prgn>
9631 This is so that the control file which is produced has
9632 the right permissions
9637 <prgn>dpkg-gencontrol</prgn> must be called after all the
9638 files which are to go into the package have been placed in
9639 the temporary build directory, so that its calculation of
9640 the installed size of a package is correct.
9644 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9645 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9646 variable substitutions created by
9647 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9652 For a package which generates only one binary package, and
9653 which builds it in <file>debian/tmp</file> relative to the top
9654 of the source package, it is usually sufficient to call
9655 <prgn>dpkg-gencontrol</prgn>.
9659 Sources which build several binaries will typically need
9662 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9663 </example> The <tt>-P</tt> tells
9664 <prgn>dpkg-gencontrol</prgn> that the package is being
9665 built in a non-default directory, and the <tt>-p</tt>
9666 tells it which package's control file should be generated.
9670 <prgn>dpkg-gencontrol</prgn> also adds information to the
9671 list of files in <file>debian/files</file>, for the benefit of
9672 (for example) a future invocation of
9673 <prgn>dpkg-genchanges</prgn>.</p>
9676 <sect1 id="pkg-dpkg-shlibdeps">
9678 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9683 This program is usually called from <file>debian/rules</file>
9684 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9685 id="pkg-sourcetree">), in the top level of the source tree.
9689 Its arguments are executables and shared libraries
9692 They may be specified either in the locations in the
9693 source tree where they are created or in the locations
9694 in the temporary build tree where they are installed
9695 prior to binary package creation.
9697 </footnote> for which shared library dependencies should
9698 be included in the binary package's control file.
9702 If some of the found shared libraries should only
9703 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9704 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9705 by using the <tt>-d<var>dependency-field</var></tt> option
9706 before those executable(s). (Each <tt>-d</tt> option
9707 takes effect until the next <tt>-d</tt>.)
9711 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9712 output control file to be modified. Instead by default it
9713 adds to the <file>debian/substvars</file> file variable
9714 settings like <tt>shlibs:Depends</tt>. These variable
9715 settings must be referenced in dependency fields in the
9716 appropriate per-binary-package sections of the source
9721 For example, a package that generates an essential part
9722 which requires dependencies, and optional parts that
9723 which only require a recommendation, would separate those
9724 two sets of dependencies into two different fields.<footnote>
9725 At the time of writing, an example for this was the
9726 <package/xmms/ package, with Depends used for the xmms
9727 executable, Recommends for the plug-ins and Suggests for
9728 even more optional features provided by unzip.
9730 It can say in its <file>debian/rules</file>:
9732 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9733 -dRecommends <var>optionalpart anotheroptionalpart</var>
9735 and then in its main control file <file>debian/control</file>:
9738 Depends: ${shlibs:Depends}
9739 Recommends: ${shlibs:Recommends}
9745 Sources which produce several binary packages with
9746 different shared library dependency requirements can use
9747 the <tt>-p<var>varnameprefix</var></tt> option to override
9748 the default <tt>shlibs:</tt> prefix (one invocation of
9749 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9750 They can thus produce several sets of dependency
9751 variables, each of the form
9752 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9753 which can be referred to in the appropriate parts of the
9754 binary package control files.
9759 <sect1 id="pkg-dpkg-distaddfile">
9761 <prgn>dpkg-distaddfile</prgn> - adds a file to
9762 <file>debian/files</file>
9766 Some packages' uploads need to include files other than
9767 the source and binary package files.
9771 <prgn>dpkg-distaddfile</prgn> adds a file to the
9772 <file>debian/files</file> file so that it will be included in
9773 the <file>.changes</file> file when
9774 <prgn>dpkg-genchanges</prgn> is run.
9778 It is usually invoked from the <tt>binary</tt> target of
9779 <file>debian/rules</file>:
9781 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9783 The <var>filename</var> is relative to the directory where
9784 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9785 is usually the directory above the top level of the source
9786 tree. The <file>debian/rules</file> target should put the
9787 file there just before or just after calling
9788 <prgn>dpkg-distaddfile</prgn>.
9792 The <var>section</var> and <var>priority</var> are passed
9793 unchanged into the resulting <file>.changes</file> file.
9798 <sect1 id="pkg-dpkg-genchanges">
9800 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9805 This program is usually called by package-independent
9806 automatic building scripts such as
9807 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9812 It is usually called in the top level of a built source
9813 tree, and when invoked with no arguments will print out a
9814 straightforward <file>.changes</file> file based on the
9815 information in the source package's changelog and control
9816 file and the binary and source packages which should have
9822 <sect1 id="pkg-dpkg-parsechangelog">
9824 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9825 representation of a changelog
9829 This program is used internally by
9830 <prgn>dpkg-source</prgn> et al. It may also occasionally
9831 be useful in <file>debian/rules</file> and elsewhere. It
9832 parses a changelog, <file>debian/changelog</file> by default,
9833 and prints a control-file format representation of the
9834 information in it to standard output.
9838 <sect1 id="pkg-dpkg-architecture">
9840 <prgn>dpkg-architecture</prgn> - information about the build and
9845 This program can be used manually, but is also invoked by
9846 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9847 environment or make variables which specify the build and host
9848 architecture for the package building process.
9853 <sect id="pkg-sourcetree">
9854 <heading>The Debianised source tree</heading>
9857 The source archive scheme described later is intended to
9858 allow a Debianised source tree with some associated control
9859 information to be reproduced and transported easily. The
9860 Debianised source tree is a version of the original program
9861 with certain files added for the benefit of the
9862 Debianisation process, and with any other changes required
9863 made to the rest of the source code and installation
9868 The extra files created for Debian are in the subdirectory
9869 <file>debian</file> of the top level of the Debianised source
9870 tree. They are described below.
9873 <sect1 id="pkg-debianrules">
9874 <heading><file>debian/rules</file> - the main building script</heading>
9877 See <ref id="debianrules">.
9882 <sect1 id="pkg-dpkgchangelog">
9883 <heading><file>debian/changelog</file></heading>
9886 See <ref id="dpkgchangelog">.
9889 <sect2><heading>Defining alternative changelog formats
9893 It is possible to use a different format to the standard
9894 one, by providing a parser for the format you wish to
9899 In order to have <tt>dpkg-parsechangelog</tt> run your
9900 parser, you must include a line within the last 40 lines
9901 of your file matching the Perl regular expression:
9902 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9903 parentheses should be the name of the format. For
9904 example, you might say:
9906 @@@ changelog-format: joebloggs @@@
9908 Changelog format names are non-empty strings of alphanumerics.
9912 If such a line exists then <tt>dpkg-parsechangelog</tt>
9913 will look for the parser as
9914 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9916 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9917 it is an error for it not to find it, or for it not to
9918 be an executable program. The default changelog format
9919 is <tt>dpkg</tt>, and a parser for it is provided with
9920 the <tt>dpkg</tt> package.
9924 The parser will be invoked with the changelog open on
9925 standard input at the start of the file. It should read
9926 the file (it may seek if it wishes) to determine the
9927 information required and return the parsed information
9928 to standard output in the form of a series of control
9929 fields in the standard format. By default it should
9930 return information about only the most recent version in
9931 the changelog; it should accept a
9932 <tt>-v<var>version</var></tt> option to return changes
9933 information from all versions present <em>strictly
9934 after</em> <var>version</var>, and it should then be an
9935 error for <var>version</var> not to be present in the
9941 <list compact="compact">
9942 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9943 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9944 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9945 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9946 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9947 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9948 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9953 If several versions are being returned (due to the use
9954 of <tt>-v</tt>), the urgency value should be of the
9955 highest urgency code listed at the start of any of the
9956 versions requested followed by the concatenated
9957 (space-separated) comments from all the versions
9958 requested; the maintainer, version, distribution and
9959 date should always be from the most recent version.
9963 For the format of the <tt>Changes</tt> field see
9964 <ref id="f-Changes">.
9968 If the changelog format which is being parsed always or
9969 almost always leaves a blank line between individual
9970 change notes these blank lines should be stripped out,
9971 so as to make the resulting output compact.
9975 If the changelog format does not contain date or package
9976 name information this information should be omitted from
9977 the output. The parser should not attempt to synthesize
9978 it or find it from other sources.
9982 If the changelog does not have the expected format the
9983 parser should exit with a nonzero exit status, rather
9984 than trying to muddle through and possibly generating
9989 A changelog parser may not interact with the user at
9995 <sect1 id="pkg-srcsubstvars">
9996 <heading><file>debian/substvars</file> and variable substitutions</heading>
9999 See <ref id="substvars">.
10005 <heading><file>debian/files</file></heading>
10008 See <ref id="debianfiles">.
10012 <sect1><heading><file>debian/tmp</file>
10016 This is the canonical temporary location for the
10017 construction of binary packages by the <tt>binary</tt>
10018 target. The directory <file>tmp</file> serves as the root of
10019 the file system tree as it is being constructed (for
10020 example, by using the package's upstream makefiles install
10021 targets and redirecting the output there), and it also
10022 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10023 id="pkg-bincreating">.
10027 If several binary packages are generated from the same
10028 source tree it is usual to use several
10029 <file>debian/tmp<var>something</var></file> directories, for
10030 example <file>tmp-a</file> or <file>tmp-doc</file>.
10034 Whatever <file>tmp</file> directories are created and used by
10035 <tt>binary</tt> must of course be removed by the
10036 <tt>clean</tt> target.</p></sect1>
10040 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10044 As it exists on the FTP site, a Debian source package
10045 consists of three related files. You must have the right
10046 versions of all three to be able to use them.
10051 <tag>Debian source control file - <tt>.dsc</tt></tag>
10053 This file is a control file used by <prgn>dpkg-source</prgn>
10054 to extract a source package.
10055 See <ref id="debiansourcecontrolfiles">.
10059 Original source archive -
10061 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10067 This is a compressed (with <tt>gzip -9</tt>)
10068 <prgn>tar</prgn> file containing the source code from
10069 the upstream authors of the program.
10074 Debianisation diff -
10076 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10082 This is a unified context diff (<tt>diff -u</tt>)
10083 giving the changes which are required to turn the
10084 original source into the Debian source. These changes
10085 may only include editing and creating plain files.
10086 The permissions of files, the targets of symbolic
10087 links and the characteristics of special files or
10088 pipes may not be changed and no files may be removed
10093 All the directories in the diff must exist, except the
10094 <file>debian</file> subdirectory of the top of the source
10095 tree, which will be created by
10096 <prgn>dpkg-source</prgn> if necessary when unpacking.
10100 The <prgn>dpkg-source</prgn> program will
10101 automatically make the <file>debian/rules</file> file
10102 executable (see below).</p></item>
10107 If there is no original source code - for example, if the
10108 package is specially prepared for Debian or the Debian
10109 maintainer is the same as the upstream maintainer - the
10110 format is slightly different: then there is no diff, and the
10112 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10113 and preferably contains a directory named
10114 <file><var>package</var>-<var>version</var></file>.
10119 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10122 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10123 Debian source package. However, if it is not available it
10124 is possible to unpack a Debian source archive as follows:
10125 <enumlist compact="compact">
10128 Untar the tarfile, which will create a <file>.orig</file>
10132 <p>Rename the <file>.orig</file> directory to
10133 <file><var>package</var>-<var>version</var></file>.</p>
10137 Create the subdirectory <file>debian</file> at the top of
10138 the source tree.</p>
10140 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10142 <item><p>Untar the tarfile again if you want a copy of the original
10143 source code alongside the Debianised version.</p>
10148 It is not possible to generate a valid Debian source archive
10149 without using <prgn>dpkg-source</prgn>. In particular,
10150 attempting to use <prgn>diff</prgn> directly to generate the
10151 <file>.diff.gz</file> file will not work.
10155 <heading>Restrictions on objects in source packages</heading>
10158 The source package may not contain any hard links
10160 This is not currently detected when building source
10161 packages, but only when extracting
10165 Hard links may be permitted at some point in the
10166 future, but would require a fair amount of
10168 </footnote>, device special files, sockets or setuid or
10171 Setgid directories are allowed.
10176 The source packaging tools manage the changes between the
10177 original and Debianised source using <prgn>diff</prgn> and
10178 <prgn>patch</prgn>. Turning the original source tree as
10179 included in the <file>.orig.tar.gz</file> into the debianised
10180 source must not involve any changes which cannot be
10181 handled by these tools. Problematic changes which cause
10182 <prgn>dpkg-source</prgn> to halt with an error when
10183 building the source package are:
10184 <list compact="compact">
10185 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10187 <item><p>Changing the targets of symbolic links.</p>
10189 <item><p>Creating directories, other than <file>debian</file>.</p>
10191 <item><p>Changes to the contents of binary files.</p></item>
10192 </list> Changes which cause <prgn>dpkg-source</prgn> to
10193 print a warning but continue anyway are:
10194 <list compact="compact">
10197 Removing files, directories or symlinks.
10199 Renaming a file is not treated specially - it is
10200 seen as the removal of the old file (which
10201 generates a warning, but is otherwise ignored),
10202 and the creation of the new one.
10208 Changed text files which are missing the usual final
10209 newline (either in the original or the modified
10214 Changes which are not represented, but which are not detected by
10215 <prgn>dpkg-source</prgn>, are:
10216 <list compact="compact">
10217 <item><p>Changing the permissions of files (other than
10218 <file>debian/rules</file>) and directories.</p></item>
10223 The <file>debian</file> directory and <file>debian/rules</file>
10224 are handled specially by <prgn>dpkg-source</prgn> - before
10225 applying the changes it will create the <file>debian</file>
10226 directory, and afterwards it will make
10227 <file>debian/rules</file> world-executable.
10233 <appendix id="pkg-controlfields">
10234 <heading>Control files and their fields (from old Packaging Manual)</heading>
10237 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10238 data in a common format, known as control files. Binary and
10239 source packages have control data as do the <file>.changes</file>
10240 files which control the installation of uploaded files, and
10241 <prgn>dpkg</prgn>'s internal databases are in a similar
10246 <heading>Syntax of control files</heading>
10249 See <ref id="controlsyntax">.
10253 It is important to note that there are several fields which
10254 are optional as far as <prgn>dpkg</prgn> and the related
10255 tools are concerned, but which must appear in every Debian
10256 package, or whose omission may cause problems.
10261 <heading>List of fields</heading>
10264 See <ref id="controlfieldslist">.
10268 This section now contains only the fields that didn't belong
10269 to the Policy manual.
10272 <sect1 id="pkg-f-Filename">
10273 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10276 These fields in <tt>Packages</tt> files give the
10277 filename(s) of (the parts of) a package in the
10278 distribution directories, relative to the root of the
10279 Debian hierarchy. If the package has been split into
10280 several parts the parts are all listed in order, separated
10285 <sect1 id="pkg-f-Size">
10286 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10289 These fields in <file>Packages</file> files give the size (in
10290 bytes, expressed in decimal) and MD5 checksum of the
10291 file(s) which make(s) up a binary package in the
10292 distribution. If the package is split into several parts
10293 the values for the parts are listed in order, separated by
10298 <sect1 id="pkg-f-Status">
10299 <heading><tt>Status</tt></heading>
10302 This field in <prgn>dpkg</prgn>'s status file records
10303 whether the user wants a package installed, removed or
10304 left alone, whether it is broken (requiring
10305 re-installation) or not and what its current state on the
10306 system is. Each of these pieces of information is a
10311 <sect1 id="pkg-f-Config-Version">
10312 <heading><tt>Config-Version</tt></heading>
10315 If a package is not installed or not configured, this
10316 field in <prgn>dpkg</prgn>'s status file records the last
10317 version of the package which was successfully
10322 <sect1 id="pkg-f-Conffiles">
10323 <heading><tt>Conffiles</tt></heading>
10326 This field in <prgn>dpkg</prgn>'s status file contains
10327 information about the automatically-managed configuration
10328 files held by a package. This field should <em>not</em>
10329 appear anywhere in a package!
10334 <heading>Obsolete fields</heading>
10337 These are still recognized by <prgn>dpkg</prgn> but should
10338 not appear anywhere any more.
10340 <taglist compact="compact">
10342 <tag><tt>Revision</tt></tag>
10343 <tag><tt>Package-Revision</tt></tag>
10344 <tag><tt>Package_Revision</tt></tag>
10346 The Debian revision part of the package version was
10347 at one point in a separate control file field. This
10348 field went through several names.
10351 <tag><tt>Recommended</tt></tag>
10352 <item>Old name for <tt>Recommends</tt>.</item>
10354 <tag><tt>Optional</tt></tag>
10355 <item>Old name for <tt>Suggests</tt>.</item>
10357 <tag><tt>Class</tt></tag>
10358 <item>Old name for <tt>Priority</tt>.</item>
10367 <appendix id="pkg-conffiles">
10368 <heading>Configuration file handling (from old Packaging Manual)</heading>
10371 <prgn>dpkg</prgn> can do a certain amount of automatic
10372 handling of package configuration files.
10376 Whether this mechanism is appropriate depends on a number of
10377 factors, but basically there are two approaches to any
10378 particular configuration file.
10382 The easy method is to ship a best-effort configuration in the
10383 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10384 handle updates. If the user is unlikely to want to edit the
10385 file, but you need them to be able to without losing their
10386 changes, and a new package with a changed version of the file
10387 is only released infrequently, this is a good approach.
10391 The hard method is to build the configuration file from
10392 scratch in the <prgn>postinst</prgn> script, and to take the
10393 responsibility for fixing any mistakes made in earlier
10394 versions of the package automatically. This will be
10395 appropriate if the file is likely to need to be different on
10399 <sect><heading>Automatic handling of configuration files by
10404 A package may contain a control area file called
10405 <tt>conffiles</tt>. This file should be a list of filenames
10406 of configuration files needing automatic handling, separated
10407 by newlines. The filenames should be absolute pathnames,
10408 and the files referred to should actually exist in the
10413 When a package is upgraded <prgn>dpkg</prgn> will process
10414 the configuration files during the configuration stage,
10415 shortly before it runs the package's <prgn>postinst</prgn>
10420 For each file it checks to see whether the version of the
10421 file included in the package is the same as the one that was
10422 included in the last version of the package (the one that is
10423 being upgraded from); it also compares the version currently
10424 installed on the system with the one shipped with the last
10429 If neither the user nor the package maintainer has changed
10430 the file, it is left alone. If one or the other has changed
10431 their version, then the changed version is preferred - i.e.,
10432 if the user edits their file, but the package maintainer
10433 doesn't ship a different version, the user's changes will
10434 stay, silently, but if the maintainer ships a new version
10435 and the user hasn't edited it the new version will be
10436 installed (with an informative message). If both have
10437 changed their version the user is prompted about the problem
10438 and must resolve the differences themselves.
10442 The comparisons are done by calculating the MD5 message
10443 digests of the files, and storing the MD5 of the file as it
10444 was included in the most recent version of the package.
10448 When a package is installed for the first time
10449 <prgn>dpkg</prgn> will install the file that comes with it,
10450 unless that would mean overwriting a file already on the
10455 However, note that <prgn>dpkg</prgn> will <em>not</em>
10456 replace a conffile that was removed by the user (or by a
10457 script). This is necessary because with some programs a
10458 missing file produces an effect hard or impossible to
10459 achieve in another way, so that a missing file needs to be
10460 kept that way if the user did it.
10464 Note that a package should <em>not</em> modify a
10465 <prgn>dpkg</prgn>-handled conffile in its maintainer
10466 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10467 the user confusing and possibly dangerous options for
10468 conffile update when the package is upgraded.</p>
10471 <sect><heading>Fully-featured maintainer script configuration
10476 For files which contain site-specific information such as
10477 the hostname and networking details and so forth, it is
10478 better to create the file in the package's
10479 <prgn>postinst</prgn> script.
10483 This will typically involve examining the state of the rest
10484 of the system to determine values and other information, and
10485 may involve prompting the user for some information which
10486 can't be obtained some other way.
10490 When using this method there are a couple of important
10491 issues which should be considered:
10495 If you discover a bug in the program which generates the
10496 configuration file, or if the format of the file changes
10497 from one version to the next, you will have to arrange for
10498 the postinst script to do something sensible - usually this
10499 will mean editing the installed configuration file to remove
10500 the problem or change the syntax. You will have to do this
10501 very carefully, since the user may have changed the file,
10502 perhaps to fix the very problem that your script is trying
10503 to deal with - you will have to detect these situations and
10504 deal with them correctly.
10508 If you do go down this route it's probably a good idea to
10509 make the program that generates the configuration file(s) a
10510 separate program in <file>/usr/sbin</file>, by convention called
10511 <file><var>package</var>config</file> and then run that if
10512 appropriate from the post-installation script. The
10513 <tt><var>package</var>config</tt> program should not
10514 unquestioningly overwrite an existing configuration - if its
10515 mode of operation is geared towards setting up a package for
10516 the first time (rather than any arbitrary reconfiguration
10517 later) you should have it check whether the configuration
10518 already exists, and require a <tt>--force</tt> flag to
10519 overwrite it.</p></sect>
10522 <appendix id="pkg-alternatives"><heading>Alternative versions of
10523 an interface - <prgn>update-alternatives</prgn> (from old
10528 When several packages all provide different versions of the
10529 same program or file it is useful to have the system select a
10530 default, but to allow the system administrator to change it
10531 and have their decisions respected.
10535 For example, there are several versions of the <prgn>vi</prgn>
10536 editor, and there is no reason to prevent all of them from
10537 being installed at once, each under their own name
10538 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10539 Nevertheless it is desirable to have the name <tt>vi</tt>
10540 refer to something, at least by default.
10544 If all the packages involved cooperate, this can be done with
10545 <prgn>update-alternatives</prgn>.
10549 Each package provides its own version under its own name, and
10550 calls <prgn>update-alternatives</prgn> in its postinst to
10551 register its version (and again in its prerm to deregister
10556 See the man page <manref name="update-alternatives"
10557 section="8"> for details.
10561 If <prgn>update-alternatives</prgn> does not seem appropriate
10562 you may wish to consider using diversions instead.</p>
10565 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10566 package's version of a file (from old Packaging Manual)
10570 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10571 when it reinstalls the package it belongs to, and to have it
10572 put the file from the package somewhere else instead.
10576 This can be used locally to override a package's version of a
10577 file, or by one package to override another's version (or
10578 provide a wrapper for it).
10582 Before deciding to use a diversion, read <ref
10583 id="pkg-alternatives"> to see if you really want a diversion
10584 rather than several alternative versions of a program.
10588 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10589 and updated by a special program <prgn>dpkg-divert</prgn>.
10590 Please see <manref name="dpkg-divert" section="8"> for full
10591 details of its operation.
10595 When a package wishes to divert a file from another, it should
10596 call <prgn>dpkg-divert</prgn> in its preinst to add the
10597 diversion and rename the existing file. For example,
10598 supposing that a <prgn>smailwrapper</prgn> package wishes to
10599 install a wrapper around <file>/usr/sbin/smail</file>:
10601 dpkg-divert --package smailwrapper --add --rename \
10602 --divert /usr/sbin/smail.real /usr/sbin/smail
10603 </example> The <tt>--package smailwrapper</tt> ensures that
10604 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10605 can bypass the diversion and get installed as the true version.
10606 It's safe to add the diversion unconditionally on upgrades since
10607 it will be left unchanged if it already exists, but
10608 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10609 message, make the command conditional on the version from which
10610 the package is being upgraded:
10612 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10613 dpkg-divert --package smailwrapper --add --rename \
10614 --divert /usr/sbin/smail.real /usr/sbin/smail
10616 </example> where <tt>1.0-2</tt> is the version at which the
10617 diversion was first added to the package. Running the command
10618 during abort-upgrade is pointless but harmless.
10622 The postrm has to do the reverse:
10624 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10625 dpkg-divert --package smailwrapper --remove --rename \
10626 --divert /usr/sbin/smail.real /usr/sbin/smail
10628 </example> If the diversion was added at a particular version, the
10629 postrm should also handle the failure case of upgrading from an
10630 older version (unless the older version is so old that direct
10631 upgrades are no longer supported):
10633 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10634 dpkg-divert --package smailwrapper --remove --rename \
10635 --divert /usr/sbin/smail.real /usr/sbin/smail
10637 </example> where <tt>1.02-2</tt> is the version at which the
10638 diversion was first added to the package. The postrm should not
10639 remove the diversion on upgrades both because there's no reason to
10640 remove the diversion only to immediately re-add it and since the
10641 postrm of the old package is run after unpacking so the removal of
10642 the diversion will fail.
10646 Do not attempt to divert a file which is vitally important for
10647 the system's operation - when using <prgn>dpkg-divert</prgn>
10648 there is a time, after it has been diverted but before
10649 <prgn>dpkg</prgn> has installed the new version, when the file
10650 does not exist.</p>
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