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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
276 <sect id="definitions">
277 <heading>Definitions</heading>
280 The following terms are used in this Policy Manual:
284 The character encoding specified by ANSI X3.4-1986 and its
285 predecessor standards, referred to in MIME as US-ASCII, and
286 corresponding to an encoding in eight bits per character of
287 the first 128 <url id="http://www.unicode.org/"
288 name="Unicode"> characters, with the eighth bit always zero.
292 The transformation format (sometimes called encoding) of
293 <url id="http://www.unicode.org/" name="Unicode"> defined by
294 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
295 name="RFC 3629">. UTF-8 has the useful property of having
296 ASCII as a subset, so any text encoded in ASCII is trivially
306 <heading>The Debian Archive</heading>
309 The Debian GNU/Linux system is maintained and distributed as a
310 collection of <em>packages</em>. Since there are so many of
311 them (currently well over 15000), they are split into
312 <em>sections</em> and given <em>priorities</em> to simplify
313 the handling of them.
317 The effort of the Debian project is to build a free operating
318 system, but not every package we want to make accessible is
319 <em>free</em> in our sense (see the Debian Free Software
320 Guidelines, below), or may be imported/exported without
321 restrictions. Thus, the archive is split into areas<footnote>
322 The Debian archive software uses the term "component" internally
323 and in the Release file format to refer to the division of an
324 archive. The Debian Social Contract simply refers to "areas."
325 This document uses terminology similar to the Social Contract.
326 </footnote> based on their licenses and other restrictions.
330 The aims of this are:
332 <list compact="compact">
333 <item>to allow us to make as much software available as we can</item>
334 <item>to allow us to encourage everyone to write free software,
336 <item>to allow us to make it easy for people to produce
337 CD-ROMs of our system without violating any licenses,
338 import/export restrictions, or any other laws.</item>
343 The <em>main</em> archive area forms the <em>Debian GNU/Linux
348 Packages in the other archive areas (<tt>contrib</tt>,
349 <tt>non-free</tt>) are not considered to be part of the Debian
350 distribution, although we support their use and provide
351 infrastructure for them (such as our bug-tracking system and
352 mailing lists). This Debian Policy Manual applies to these
357 <heading>The Debian Free Software Guidelines</heading>
359 The Debian Free Software Guidelines (DFSG) form our
360 definition of "free software". These are:
362 <tag>Free Redistribution
365 The license of a Debian component may not restrict any
366 party from selling or giving away the software as a
367 component of an aggregate software distribution
368 containing programs from several different
369 sources. The license may not require a royalty or
370 other fee for such sale.
375 The program must include source code, and must allow
376 distribution in source code as well as compiled form.
381 The license must allow modifications and derived
382 works, and must allow them to be distributed under the
383 same terms as the license of the original software.
385 <tag>Integrity of The Author's Source Code
388 The license may restrict source-code from being
389 distributed in modified form <em>only</em> if the
390 license allows the distribution of "patch files"
391 with the source code for the purpose of modifying the
392 program at build time. The license must explicitly
393 permit distribution of software built from modified
394 source code. The license may require derived works to
395 carry a different name or version number from the
396 original software. (This is a compromise. The Debian
397 Project encourages all authors to not restrict any
398 files, source or binary, from being modified.)
400 <tag>No Discrimination Against Persons or Groups
403 The license must not discriminate against any person
406 <tag>No Discrimination Against Fields of Endeavor
409 The license must not restrict anyone from making use
410 of the program in a specific field of endeavor. For
411 example, it may not restrict the program from being
412 used in a business, or from being used for genetic
415 <tag>Distribution of License
418 The rights attached to the program must apply to all
419 to whom the program is redistributed without the need
420 for execution of an additional license by those
423 <tag>License Must Not Be Specific to Debian
426 The rights attached to the program must not depend on
427 the program's being part of a Debian system. If the
428 program is extracted from Debian and used or
429 distributed without Debian but otherwise within the
430 terms of the program's license, all parties to whom
431 the program is redistributed must have the same
432 rights as those that are granted in conjunction with
435 <tag>License Must Not Contaminate Other Software
438 The license must not place restrictions on other
439 software that is distributed along with the licensed
440 software. For example, the license must not insist
441 that all other programs distributed on the same medium
442 must be free software.
444 <tag>Example Licenses
447 The "GPL," "BSD," and "Artistic" licenses are examples of
448 licenses that we consider <em>free</em>.
455 <heading>Archive areas</heading>
458 <heading>The main archive area</heading>
461 Every package in <em>main</em> must comply with the DFSG
462 (Debian Free Software Guidelines).
466 In addition, the packages in <em>main</em>
467 <list compact="compact">
469 must not require a package outside of <em>main</em>
470 for compilation or execution (thus, the package must
471 not declare a "Depends", "Recommends", or
472 "Build-Depends" relationship on a non-<em>main</em>
476 must not be so buggy that we refuse to support them,
480 must meet all policy requirements presented in this
489 <heading>The contrib archive area</heading>
492 Every package in <em>contrib</em> must comply with the DFSG.
496 In addition, the packages in <em>contrib</em>
497 <list compact="compact">
499 must not be so buggy that we refuse to support them,
503 must meet all policy requirements presented in this
511 Examples of packages which would be included in
512 <em>contrib</em> are:
513 <list compact="compact">
515 free packages which require <em>contrib</em>,
516 <em>non-free</em> packages or packages which are not
517 in our archive at all for compilation or execution,
521 wrapper packages or other sorts of free accessories for
528 <sect1 id="non-free">
529 <heading>The non-free archive area</heading>
532 Packages must be placed in <em>non-free</em> if they are
533 not compliant with the DFSG or are encumbered by patents
534 or other legal issues that make their distribution
539 In addition, the packages in <em>non-free</em>
540 <list compact="compact">
542 must not be so buggy that we refuse to support them,
546 must meet all policy requirements presented in this
547 manual that it is possible for them to meet.
549 It is possible that there are policy
550 requirements which the package is unable to
551 meet, for example, if the source is
552 unavailable. These situations will need to be
553 handled on a case-by-case basis.
562 <sect id="pkgcopyright">
563 <heading>Copyright considerations</heading>
566 Every package must be accompanied by a verbatim copy of
567 its copyright and distribution license in the file
568 <file>/usr/share/doc/<var>package</var>/copyright</file>
569 (see <ref id="copyrightfile"> for further details).
573 We reserve the right to restrict files from being included
574 anywhere in our archives if
575 <list compact="compact">
577 their use or distribution would break a law,
580 there is an ethical conflict in their distribution or
584 we would have to sign a license for them, or
587 their distribution would conflict with other project
594 Programs whose authors encourage the user to make
595 donations are fine for the main distribution, provided
596 that the authors do not claim that not donating is
597 immoral, unethical, illegal or something similar; in such
598 a case they must go in <em>non-free</em>.
602 Packages whose copyright permission notices (or patent
603 problems) do not even allow redistribution of binaries
604 only, and where no special permission has been obtained,
605 must not be placed on the Debian FTP site and its mirrors
610 Note that under international copyright law (this applies
611 in the United States, too), <em>no</em> distribution or
612 modification of a work is allowed without an explicit
613 notice saying so. Therefore a program without a copyright
614 notice <em>is</em> copyrighted and you may not do anything
615 to it without risking being sued! Likewise if a program
616 has a copyright notice but no statement saying what is
617 permitted then nothing is permitted.
621 Many authors are unaware of the problems that restrictive
622 copyrights (or lack of copyright notices) can cause for
623 the users of their supposedly-free software. It is often
624 worthwhile contacting such authors diplomatically to ask
625 them to modify their license terms. However, this can be a
626 politically difficult thing to do and you should ask for
627 advice on the <tt>debian-legal</tt> mailing list first, as
632 When in doubt about a copyright, send mail to
633 <email>debian-legal@lists.debian.org</email>. Be prepared
634 to provide us with the copyright statement. Software
635 covered by the GPL, public domain software and BSD-like
636 copyrights are safe; be wary of the phrases "commercial
637 use prohibited" and "distribution restricted".
641 <sect id="subsections">
642 <heading>Sections</heading>
645 The packages in the archive areas <em>main</em>,
646 <em>contrib</em> and <em>non-free</em> are grouped further into
647 <em>sections</em> to simplify handling.
651 The archive area and section for each package should be
652 specified in the package's <tt>Section</tt> control record (see
653 <ref id="f-Section">). However, the maintainer of the Debian
654 archive may override this selection to ensure the consistency of
655 the Debian distribution. The <tt>Section</tt> field should be
657 <list compact="compact">
659 <em>section</em> if the package is in the
660 <em>main</em> archive area,
663 <em>area/section</em> if the package is in
664 the <em>contrib</em> or <em>non-free</em>
671 The Debian archive maintainers provide the authoritative
672 list of sections. At present, they are:
673 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
674 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
675 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
676 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
677 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
678 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
679 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
680 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
681 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
682 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
683 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
684 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
685 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</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 must 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.
1230 Packages which are essential, or which are dependencies of
1231 essential packages, may fall back on another prompting method
1232 if no such interface is available when they are executed.
1236 The Debian Configuration Management Specification is included
1237 in the <file>debconf_specification</file> files in the
1238 <package>debian-policy</package> package.
1239 It is also available from the Debian web mirrors at
1240 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1241 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1245 Packages which use the Debian Configuration Management
1246 Specification may contain an additional
1247 <prgn>config</prgn> script and a <tt>templates</tt>
1248 file in their control archive<footnote>
1249 The control.tar.gz inside the .deb.
1250 See <manref name="deb" section="5">.
1252 The <prgn>config</prgn> script might be run before the
1253 <prgn>preinst</prgn> script, and before the package is unpacked
1254 or any of its dependencies or pre-dependencies are satisfied.
1255 Therefore it must work using only the tools present in
1256 <em>essential</em> packages.<footnote>
1257 <package>Debconf</package> or another tool that
1258 implements the Debian Configuration Management
1259 Specification will also be installed, and any
1260 versioned dependencies on it will be satisfied
1261 before preconfiguration begins.
1266 Packages which use the Debian Configuration Management
1267 Specification must allow for translation of their user-visible
1268 messages by using a gettext-based system such as the one
1269 provided by the <package>po-debconf</package> package.
1273 Packages should try to minimize the amount of prompting
1274 they need to do, and they should ensure that the user
1275 will only ever be asked each question once. This means
1276 that packages should try to use appropriate shared
1277 configuration files (such as <file>/etc/papersize</file> and
1278 <file>/etc/news/server</file>), and shared
1279 <package>debconf</package> variables rather than each
1280 prompting for their own list of required pieces of
1285 It also means that an upgrade should not ask the same
1286 questions again, unless the user has used
1287 <tt>dpkg --purge</tt> to remove the package's configuration.
1288 The answers to configuration questions should be stored in an
1289 appropriate place in <file>/etc</file> so that the user can
1290 modify them, and how this has been done should be
1295 If a package has a vitally important piece of
1296 information to pass to the user (such as "don't run me
1297 as I am, you must edit the following configuration files
1298 first or you risk your system emitting badly-formatted
1299 messages"), it should display this in the
1300 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1301 prompt the user to hit return to acknowledge the
1302 message. Copyright messages do not count as vitally
1303 important (they belong in
1304 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1305 neither do instructions on how to use a program (these
1306 should be in on-line documentation, where all the users
1311 Any necessary prompting should almost always be confined
1312 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1313 script. If it is done in the <prgn>postinst</prgn>, it
1314 should be protected with a conditional so that
1315 unnecessary prompting doesn't happen if a package's
1316 installation fails and the <prgn>postinst</prgn> is
1317 called with <tt>abort-upgrade</tt>,
1318 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1328 <heading>Source packages</heading>
1330 <sect id="standardsversion">
1331 <heading>Standards conformance</heading>
1334 Source packages should specify the most recent version number
1335 of this policy document with which your package complied
1336 when it was last updated.
1340 This information may be used to file bug reports
1341 automatically if your package becomes too much out of date.
1345 The version is specified in the <tt>Standards-Version</tt>
1347 The format of the <tt>Standards-Version</tt> field is
1348 described in <ref id="f-Standards-Version">.
1352 You should regularly, and especially if your package has
1353 become out of date, check for the newest Policy Manual
1354 available and update your package, if necessary. When your
1355 package complies with the new standards you should update the
1356 <tt>Standards-Version</tt> source package field and
1357 release it.<footnote>
1358 See the file <file>upgrading-checklist</file> for
1359 information about policy which has changed between
1360 different versions of this document.
1366 <sect id="pkg-relations">
1367 <heading>Package relationships</heading>
1370 Source packages should specify which binary packages they
1371 require to be installed or not to be installed in order to
1372 build correctly. For example, if building a package
1373 requires a certain compiler, then the compiler should be
1374 specified as a build-time dependency.
1378 It is not necessary to explicitly specify build-time
1379 relationships on a minimal set of packages that are always
1380 needed to compile, link and put in a Debian package a
1381 standard "Hello World!" program written in C or C++. The
1382 required packages are called <em>build-essential</em>, and
1383 an informational list can be found in
1384 <file>/usr/share/doc/build-essential/list</file> (which is
1385 contained in the <tt>build-essential</tt>
1388 <list compact="compact">
1390 This allows maintaining the list separately
1391 from the policy documents (the list does not
1392 need the kind of control that the policy
1396 Having a separate package allows one to install
1397 the build-essential packages on a machine, as
1398 well as allowing other packages such as tasks to
1399 require installation of the build-essential
1400 packages using the depends relation.
1403 The separate package allows bug reports against
1404 the list to be categorized separately from
1405 the policy management process in the BTS.
1412 When specifying the set of build-time dependencies, one
1413 should list only those packages explicitly required by the
1414 build. It is not necessary to list packages which are
1415 required merely because some other package in the list of
1416 build-time dependencies depends on them.<footnote>
1417 The reason for this is that dependencies change, and
1418 you should list all those packages, and <em>only</em>
1419 those packages that <em>you</em> need directly. What
1420 others need is their business. For example, if you
1421 only link against <file>libimlib</file>, you will need to
1422 build-depend on <package>libimlib2-dev</package> but
1423 not against any <tt>libjpeg*</tt> packages, even
1424 though <tt>libimlib2-dev</tt> currently depends on
1425 them: installation of <package>libimlib2-dev</package>
1426 will automatically ensure that all of its run-time
1427 dependencies are satisfied.
1432 If build-time dependencies are specified, it must be
1433 possible to build the package and produce working binaries
1434 on a system with only essential and build-essential
1435 packages installed and also those required to satisfy the
1436 build-time relationships (including any implied
1437 relationships). In particular, this means that version
1438 clauses should be used rigorously in build-time
1439 relationships so that one cannot produce bad or
1440 inconsistently configured packages when the relationships
1441 are properly satisfied.
1445 <ref id="relationships"> explains the technical details.
1450 <heading>Changes to the upstream sources</heading>
1453 If changes to the source code are made that are not
1454 specific to the needs of the Debian system, they should be
1455 sent to the upstream authors in whatever form they prefer
1456 so as to be included in the upstream version of the
1461 If you need to configure the package differently for
1462 Debian or for Linux, and the upstream source doesn't
1463 provide a way to do so, you should add such configuration
1464 facilities (for example, a new <prgn>autoconf</prgn> test
1465 or <tt>#define</tt>) and send the patch to the upstream
1466 authors, with the default set to the way they originally
1467 had it. You can then easily override the default in your
1468 <file>debian/rules</file> or wherever is appropriate.
1472 You should make sure that the <prgn>configure</prgn> utility
1473 detects the correct architecture specification string
1474 (refer to <ref id="arch-spec"> for details).
1478 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1479 <prgn>configure</prgn> scripts are used, you should edit the
1480 <file>.in</file> files rather than editing the
1481 <prgn>Makefile</prgn> directly. This allows the user to
1482 reconfigure the package if necessary. You should
1483 <em>not</em> configure the package and edit the generated
1484 <prgn>Makefile</prgn>! This makes it impossible for someone
1485 else to later reconfigure the package without losing the
1491 <sect id="dpkgchangelog">
1492 <heading>Debian changelog: <file>debian/changelog</file></heading>
1495 Changes in the Debian version of the package should be
1496 briefly explained in the Debian changelog file
1497 <file>debian/changelog</file>.<footnote>
1499 Mistakes in changelogs are usually best rectified by
1500 making a new changelog entry rather than "rewriting
1501 history" by editing old changelog entries.
1504 This includes modifications
1505 made in the Debian package compared to the upstream one
1506 as well as other changes and updates to the package.
1508 Although there is nothing stopping an author who is also
1509 the Debian maintainer from using this changelog for all
1510 their changes, it will have to be renamed if the Debian
1511 and upstream maintainers become different people. In such
1512 a case, however, it might be better to maintain the package
1513 as a non-native package.
1518 The format of the <file>debian/changelog</file> allows the
1519 package building tools to discover which version of the package
1520 is being built and find out other release-specific information.
1524 That format is a series of entries like this:
1526 <example compact="compact">
1527 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1529 [optional blank line(s), stripped]
1531 * <var>change details</var>
1532 <var>more change details</var>
1534 [blank line(s), included in output of dpkg-parsechangelog]
1536 * <var>even more change details</var>
1538 [optional blank line(s), stripped]
1540 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1545 <var>package</var> and <var>version</var> are the source
1546 package name and version number.
1550 <var>distribution(s)</var> lists the distributions where
1551 this version should be installed when it is uploaded - it
1552 is copied to the <tt>Distribution</tt> field in the
1553 <file>.changes</file> file. See <ref id="f-Distribution">.
1557 <var>urgency</var> is the value for the <tt>Urgency</tt>
1558 field in the <file>.changes</file> file for the upload
1559 (see <ref id="f-Urgency">). It is not possible to specify
1560 an urgency containing commas; commas are used to separate
1561 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1562 <prgn>dpkg</prgn> changelog format (though there is
1563 currently only one useful <var>keyword</var>,
1568 The change details may in fact be any series of lines
1569 starting with at least two spaces, but conventionally each
1570 change starts with an asterisk and a separating space and
1571 continuation lines are indented so as to bring them in
1572 line with the start of the text above. Blank lines may be
1573 used here to separate groups of changes, if desired.
1577 If this upload resolves bugs recorded in the Bug Tracking
1578 System (BTS), they may be automatically closed on the
1579 inclusion of this package into the Debian archive by
1580 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1581 in the change details.<footnote>
1582 To be precise, the string should match the following
1583 Perl regular expression:
1585 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1587 Then all of the bug numbers listed will be closed by the
1588 archive maintenance script (<prgn>katie</prgn>) using the
1589 <var>version</var> of the changelog entry.
1591 This information is conveyed via the <tt>Closes</tt> field
1592 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1596 The maintainer name and email address used in the changelog
1597 should be the details of the person uploading <em>this</em>
1598 version. They are <em>not</em> necessarily those of the
1599 usual package maintainer. The information here will be
1600 copied to the <tt>Changed-By</tt> field in the
1601 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1602 and then later used to send an acknowledgement when the
1603 upload has been installed.
1607 The <var>date</var> must be in RFC822 format<footnote>
1608 This is generated by <tt>date -R</tt>.
1609 </footnote>; it must include the time zone specified
1610 numerically, with the time zone name or abbreviation
1611 optionally present as a comment in parentheses.
1615 The first "title" line with the package name must start
1616 at the left hand margin. The "trailer" line with the
1617 maintainer and date details must be preceded by exactly
1618 one space. The maintainer details and the date must be
1619 separated by exactly two spaces.
1623 The entire changelog must be encoded in UTF-8.
1627 For more information on placement of the changelog files
1628 within binary packages, please see <ref id="changelogs">.
1632 <sect id="dpkgcopyright">
1633 <heading>Copyright: <file>debian/copyright</file></heading>
1635 Every package must be accompanied by a verbatim copy of
1636 its copyright and distribution license in the file
1637 <file>/usr/share/doc/<var>package</var>/copyright</file>
1638 (see <ref id="copyrightfile"> for further details). Also see
1639 <ref id="pkgcopyright"> for further considerations relayed
1640 to copyrights for packages.
1644 <heading>Error trapping in makefiles</heading>
1647 When <prgn>make</prgn> invokes a command in a makefile
1648 (including your package's upstream makefiles and
1649 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1650 means that <prgn>sh</prgn>'s usual bad error handling
1651 properties apply: if you include a miniature script as one
1652 of the commands in your makefile you'll find that if you
1653 don't do anything about it then errors are not detected
1654 and <prgn>make</prgn> will blithely continue after
1659 Every time you put more than one shell command (this
1660 includes using a loop) in a makefile command you
1661 must make sure that errors are trapped. For
1662 simple compound commands, such as changing directory and
1663 then running a program, using <tt>&&</tt> rather
1664 than semicolon as a command separator is sufficient. For
1665 more complex commands including most loops and
1666 conditionals you should include a separate <tt>set -e</tt>
1667 command at the start of every makefile command that's
1668 actually one of these miniature shell scripts.
1672 <sect id="timestamps">
1673 <heading>Time Stamps</heading>
1675 Maintainers should preserve the modification times of the
1676 upstream source files in a package, as far as is reasonably
1678 The rationale is that there is some information conveyed
1679 by knowing the age of the file, for example, you could
1680 recognize that some documentation is very old by looking
1681 at the modification time, so it would be nice if the
1682 modification time of the upstream source would be
1688 <sect id="restrictions">
1689 <heading>Restrictions on objects in source packages</heading>
1692 The source package may not contain any hard links<footnote>
1694 This is not currently detected when building source
1695 packages, but only when extracting
1699 Hard links may be permitted at some point in the
1700 future, but would require a fair amount of
1703 </footnote>, device special files, sockets or setuid or
1704 setgid files.<footnote>
1705 Setgid directories are allowed.
1710 <sect id="debianrules">
1711 <heading>Main building script: <file>debian/rules</file></heading>
1714 This file must be an executable makefile, and contains the
1715 package-specific recipes for compiling the package and
1716 building binary package(s) from the source.
1720 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1721 so that it can be invoked by saying its name rather than
1722 invoking <prgn>make</prgn> explicitly.
1726 Since an interactive <file>debian/rules</file> script makes it
1727 impossible to auto-compile that package and also makes it
1728 hard for other people to reproduce the same binary
1729 package, all <em>required targets</em> MUST be
1730 non-interactive. At a minimum, required targets are the
1731 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1732 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1733 <em>binary-indep</em>, and <em>build</em>. It also follows
1734 that any target that these targets depend on must also be
1739 The targets are as follows (required unless stated otherwise):
1741 <tag><tt>build</tt></tag>
1744 The <tt>build</tt> target should perform all the
1745 configuration and compilation of the package.
1746 If a package has an interactive pre-build
1747 configuration routine, the Debianized source package
1748 must either be built after this has taken place (so
1749 that the binary package can be built without rerunning
1750 the configuration) or the configuration routine
1751 modified to become non-interactive. (The latter is
1752 preferable if there are architecture-specific features
1753 detected by the configuration routine.)
1757 For some packages, notably ones where the same
1758 source tree is compiled in different ways to produce
1759 two binary packages, the <tt>build</tt> target
1760 does not make much sense. For these packages it is
1761 good enough to provide two (or more) targets
1762 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1763 for each of the ways of building the package, and a
1764 <tt>build</tt> target that does nothing. The
1765 <tt>binary</tt> target will have to build the
1766 package in each of the possible ways and make the
1767 binary package out of each.
1771 The <tt>build</tt> target must not do anything
1772 that might require root privilege.
1776 The <tt>build</tt> target may need to run the
1777 <tt>clean</tt> target first - see below.
1781 When a package has a configuration and build routine
1782 which takes a long time, or when the makefiles are
1783 poorly designed, or when <tt>build</tt> needs to
1784 run <tt>clean</tt> first, it is a good idea to
1785 <tt>touch build</tt> when the build process is
1786 complete. This will ensure that if <tt>debian/rules
1787 build</tt> is run again it will not rebuild the whole
1789 Another common way to do this is for <tt>build</tt>
1790 to depend on <prgn>build-stamp</prgn> and to do
1791 nothing else, and for the <prgn>build-stamp</prgn>
1792 target to do the building and to <tt>touch
1793 build-stamp</tt> on completion. This is
1794 especially useful if the build routine creates a
1795 file or directory called <tt>build</tt>; in such a
1796 case, <tt>build</tt> will need to be listed as
1797 a phony target (i.e., as a dependency of the
1798 <tt>.PHONY</tt> target). See the documentation of
1799 <prgn>make</prgn> for more information on phony
1805 <tag><tt>build-arch</tt> (optional),
1806 <tt>build-indep</tt> (optional)
1810 A package may also provide both of the targets
1811 <tt>build-arch</tt> and <tt>build-indep</tt>.
1812 The <tt>build-arch</tt> target, if provided, should
1813 perform all the configuration and compilation required
1814 for producing all architecture-dependant binary packages
1815 (those packages for which the body of the
1816 <tt>Architecture</tt> field in <tt>debian/control</tt>
1817 is not <tt>all</tt>).
1818 Similarly, the <tt>build-indep</tt> target, if
1819 provided, should perform all the configuration and
1820 compilation required for producing all
1821 architecture-independent binary packages
1822 (those packages for which the body of the
1823 <tt>Architecture</tt> field in <tt>debian/control</tt>
1825 The <tt>build</tt> target should depend on those of the
1826 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1827 are provided in the rules file.
1831 If one or both of the targets <tt>build-arch</tt> and
1832 <tt>build-indep</tt> are not provided, then invoking
1833 <file>debian/rules</file> with one of the not-provided
1834 targets as arguments should produce a exit status code
1835 of 2. Usually this is provided automatically by make
1836 if the target is missing.
1840 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1841 must not do anything that might require root privilege.
1845 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1846 <tt>binary-indep</tt>
1850 The <tt>binary</tt> target must be all that is
1851 necessary for the user to build the binary package(s)
1852 produced from this source package. It is
1853 split into two parts: <prgn>binary-arch</prgn> builds
1854 the binary packages which are specific to a particular
1855 architecture, and <tt>binary-indep</tt> builds
1856 those which are not.
1859 <tt>binary</tt> may be (and commonly is) a target with
1860 no commands which simply depends on
1861 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1864 Both <tt>binary-*</tt> targets should depend on the
1865 <tt>build</tt> target, or on the appropriate
1866 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1867 provided, so that the package is built if it has not
1868 been already. It should then create the relevant
1869 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1870 make their control files and <prgn>dpkg-deb</prgn> to
1871 build them and place them in the parent of the top
1876 Both the <tt>binary-arch</tt> and
1877 <tt>binary-indep</tt> targets <em>must</em> exist.
1878 If one of them has nothing to do (which will always be
1879 the case if the source generates only a single binary
1880 package, whether architecture-dependent or not), it
1881 must still exist and must always succeed.
1885 The <tt>binary</tt> targets must be invoked as
1887 The <prgn>fakeroot</prgn> package often allows one
1888 to build a package correctly even without being
1894 <tag><tt>clean</tt></tag>
1897 This must undo any effects that the <tt>build</tt>
1898 and <tt>binary</tt> targets may have had, except
1899 that it should leave alone any output files created in
1900 the parent directory by a run of a <tt>binary</tt>
1905 If a <tt>build</tt> file is touched at the end of
1906 the <tt>build</tt> target, as suggested above, it
1907 should be removed as the first action that
1908 <tt>clean</tt> performs, so that running
1909 <tt>build</tt> again after an interrupted
1910 <tt>clean</tt> doesn't think that everything is
1915 The <tt>clean</tt> target may need to be
1916 invoked as root if <tt>binary</tt> has been
1917 invoked since the last <tt>clean</tt>, or if
1918 <tt>build</tt> has been invoked as root (since
1919 <tt>build</tt> may create directories, for
1924 <tag><tt>get-orig-source</tt> (optional)</tag>
1927 This target fetches the most recent version of the
1928 original source package from a canonical archive site
1929 (via FTP or WWW, for example), does any necessary
1930 rearrangement to turn it into the original source
1931 tar file format described below, and leaves it in the
1936 This target may be invoked in any directory, and
1937 should take care to clean up any temporary files it
1942 This target is optional, but providing it if
1943 possible is a good idea.
1947 <tag><tt>patch</tt> (optional)</tag>
1950 This target performs whatever additional actions are
1951 required to make the source ready for editing (unpacking
1952 additional upstream archives, applying patches, etc.).
1953 It is recommended to be implemented for any package where
1954 <tt>dpkg-source -x</tt> does not result in source ready
1955 for additional modification. See
1956 <ref id="readmesource">.
1962 The <tt>build</tt>, <tt>binary</tt> and
1963 <tt>clean</tt> targets must be invoked with the current
1964 directory being the package's top-level directory.
1969 Additional targets may exist in <file>debian/rules</file>,
1970 either as published or undocumented interfaces or for the
1971 package's internal use.
1975 The architectures we build on and build for are determined
1976 by <prgn>make</prgn> variables using the utility
1977 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1978 You can determine the
1979 Debian architecture and the GNU style architecture
1980 specification string for the build machine (the machine type
1981 we are building on) as well as for the host machine (the
1982 machine type we are building for). Here is a list of
1983 supported <prgn>make</prgn> variables:
1984 <list compact="compact">
1986 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1989 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1990 specification string)
1993 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1994 <tt>DEB_*_GNU_TYPE</tt>)
1997 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1998 <tt>DEB_*_GNU_TYPE</tt>)
2000 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2001 the build machine or <tt>HOST</tt> for specification of the
2006 Backward compatibility can be provided in the rules file
2007 by setting the needed variables to suitable default
2008 values; please refer to the documentation of
2009 <prgn>dpkg-architecture</prgn> for details.
2013 It is important to understand that the <tt>DEB_*_ARCH</tt>
2014 string only determines which Debian architecture we are
2015 building on or for. It should not be used to get the CPU
2016 or system information; the GNU style variables should be
2020 <sect1 id="debianrules-options">
2021 <heading><file>debian/rules</file> and
2022 <tt>DEB_BUILD_OPTIONS</tt></heading>
2025 Supporting the standardized environment variable
2026 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2027 contain several flags to change how a package is compiled and
2028 built. Each flag must be in the form <var>flag</var> or
2029 <var>flag</var>=<var>options</var>. If multiple flags are
2030 given, they must be separated by whitespace.<footnote>
2031 Some packages support any delimiter, but whitespace is the
2032 easiest to parse inside a makefile and avoids ambiguity with
2033 flag values that contain commas.
2035 <var>flag</var> must start with a lowercase letter
2036 (<tt>a-z</tt>) and consist only of lowercase letters,
2037 numbers (<tt>0-9</tt>), and the characters
2038 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2039 <var>options</var> must not contain whitespace. The same
2040 tag should not be given multiple times with conflicting
2041 values. Package maintainers may assume that
2042 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2046 The meaning of the following tags has been standardized:
2050 This tag says to not run any build-time test suite
2051 provided by the package.
2055 The presence of this tag means that the package should
2056 be compiled with a minimum of optimization. For C
2057 programs, it is best to add <tt>-O0</tt> to
2058 <tt>CFLAGS</tt> (although this is usually the default).
2059 Some programs might fail to build or run at this level
2060 of optimization; it may be necessary to use
2061 <tt>-O1</tt>, for example.
2065 This tag means that the debugging symbols should not be
2066 stripped from the binary during installation, so that
2067 debugging information may be included in the package.
2069 <tag>parallel=n</tag>
2071 This tag means that the package should be built using up
2072 to <tt>n</tt> parallel processes if the package build
2073 system supports this.<footnote>
2074 Packages built with <tt>make</tt> can often implement
2075 this by passing the <tt>-j</tt><var>n</var> option to
2078 If the package build system does not support parallel
2079 builds, this string must be ignored. If the package
2080 build system only supports a lower level of concurrency
2081 than <var>n</var>, the package should be built using as
2082 many parallel processes as the package build system
2083 supports. It is up to the package maintainer to decide
2084 whether the package build times are long enough and the
2085 package build system is robust enough to make supporting
2086 parallel builds worthwhile.
2092 Unknown flags must be ignored by <file>debian/rules</file>.
2096 The following makefile snippet is an example of how one may
2097 implement the build options; you will probably have to
2098 massage this example in order to make it work for your
2100 <example compact="compact">
2103 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2104 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2105 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2106 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2108 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2113 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2114 INSTALL_PROGRAM += -s
2116 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2117 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2118 MAKEFLAGS += -j$(NUMJOBS)
2123 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2124 # Code to run the package test suite.
2131 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2132 <sect id="substvars">
2133 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2136 When <prgn>dpkg-gencontrol</prgn>,
2137 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2138 generate control files they perform variable substitutions
2139 on their output just before writing it. Variable
2140 substitutions have the form <tt>${<var>variable</var>}</tt>.
2141 The optional file <file>debian/substvars</file> contains
2142 variable substitutions to be used; variables can also be set
2143 directly from <file>debian/rules</file> using the <tt>-V</tt>
2144 option to the source packaging commands, and certain
2145 predefined variables are also available.
2149 The <file>debian/substvars</file> file is usually generated and
2150 modified dynamically by <file>debian/rules</file> targets, in
2151 which case it must be removed by the <tt>clean</tt> target.
2155 See <manref name="deb-substvars" section="5"> for full
2156 details about source variable substitutions, including the
2157 format of <file>debian/substvars</file>.</p>
2160 <sect id="debianwatch">
2161 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2164 This is an optional, recommended control file for the
2165 <tt>uscan</tt> utility which defines how to automatically
2166 scan ftp or http sites for newly available updates of the
2167 package. This is used by <url id="
2168 http://dehs.alioth.debian.org/"> and other Debian QA tools
2169 to help with quality control and maintenance of the
2170 distribution as a whole.
2175 <sect id="debianfiles">
2176 <heading>Generated files list: <file>debian/files</file></heading>
2179 This file is not a permanent part of the source tree; it
2180 is used while building packages to record which files are
2181 being generated. <prgn>dpkg-genchanges</prgn> uses it
2182 when it generates a <file>.changes</file> file.
2186 It should not exist in a shipped source package, and so it
2187 (and any backup files or temporary files such as
2188 <file>files.new</file><footnote>
2189 <file>files.new</file> is used as a temporary file by
2190 <prgn>dpkg-gencontrol</prgn> and
2191 <prgn>dpkg-distaddfile</prgn> - they write a new
2192 version of <tt>files</tt> here before renaming it,
2193 to avoid leaving a corrupted copy if an error
2195 </footnote>) should be removed by the
2196 <tt>clean</tt> target. It may also be wise to
2197 ensure a fresh start by emptying or removing it at the
2198 start of the <tt>binary</tt> target.
2202 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2203 package, it adds an entry to <file>debian/files</file> for the
2204 <file>.deb</file> file that will be created when <tt>dpkg-deb
2205 --build</tt> is run for that binary package. So for most
2206 packages all that needs to be done with this file is to
2207 delete it in the <tt>clean</tt> target.
2211 If a package upload includes files besides the source
2212 package and any binary packages whose control files were
2213 made with <prgn>dpkg-gencontrol</prgn> then they should be
2214 placed in the parent of the package's top-level directory
2215 and <prgn>dpkg-distaddfile</prgn> should be called to add
2216 the file to the list in <file>debian/files</file>.</p>
2219 <sect id="embeddedfiles">
2220 <heading>Convenience copies of code</heading>
2223 Some software packages include in their distribution convenience
2224 copies of code from other software packages, generally so that
2225 users compiling from source don't have to download multiple
2226 packages. Debian packages should not make use of these
2227 convenience copies unless the included package is explicitly
2228 intended to be used in this way.<footnote>
2229 For example, parts of the GNU build system work like this.
2231 If the included code is already in the Debian archive in the
2232 form of a library, the Debian packaging should ensure that
2233 binary packages reference the libraries already in Debian and
2234 the convenience copy is not used. If the included code is not
2235 already in Debian, it should be packaged separately as a
2236 prerequisite if possible.
2238 Having multiple copies of the same code in Debian is
2239 inefficient, often creates either static linking or shared
2240 library conflicts, and, most importantly, increases the
2241 difficulty of handling security vulnerabilities in the
2247 <sect id="readmesource">
2248 <heading>Source package handling:
2249 <file>debian/README.source</file></heading>
2252 If running <prgn>dpkg-source -x</prgn> on a source package
2253 doesn't produce the source of the package, ready for editing,
2254 and allow one to make changes and run
2255 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2256 without taking any additional steps, creating a
2257 <file>debian/README.source</file> documentation file is
2258 recommended. This file should explain how to do all of the
2261 <item>Generate the fully patched source, in a form ready for
2262 editing, that would be built to create Debian
2263 packages. Doing this with a <tt>patch</tt> target in
2264 <file>debian/rules</file> is recommended; see
2265 <ref id="debianrules">.</item>
2266 <item>Modify the source and save those modifications so that
2267 they will be applied when building the package.</item>
2268 <item>Remove source modifications that are currently being
2269 applied when building the package.</item>
2270 <item>Optionally, document what steps are necessary to
2271 upgrade the Debian source package to a new upstream version,
2272 if applicable.</item>
2274 This explanation should include specific commands and mention
2275 any additional required Debian packages. It should not assume
2276 familiarity with any specific Debian packaging system or patch
2281 This explanation may refer to a documentation file installed by
2282 one of the package's build dependencies provided that the
2283 referenced documentation clearly explains these tasks and is not
2284 a general reference manual.
2288 <file>debian/README.source</file> may also include any other
2289 information that would be helpful to someone modifying the
2290 source package. Even if the package doesn't fit the above
2291 description, maintainers are encouraged to document in a
2292 <file>debian/README.source</file> file any source package with a
2293 particularly complex or unintuitive source layout or build
2294 system (for example, a package that builds the same source
2295 multiple times to generate different binary packages).
2301 <chapt id="controlfields">
2302 <heading>Control files and their fields</heading>
2305 The package management system manipulates data represented in
2306 a common format, known as <em>control data</em>, stored in
2307 <em>control files</em>.
2308 Control files are used for source packages, binary packages and
2309 the <file>.changes</file> files which control the installation
2310 of uploaded files<footnote>
2311 <prgn>dpkg</prgn>'s internal databases are in a similar
2316 <sect id="controlsyntax">
2317 <heading>Syntax of control files</heading>
2320 A control file consists of one or more paragraphs of
2322 The paragraphs are also sometimes referred to as stanzas.
2324 The paragraphs are separated by blank lines. Some control
2325 files allow only one paragraph; others allow several, in
2326 which case each paragraph usually refers to a different
2327 package. (For example, in source packages, the first
2328 paragraph refers to the source package, and later paragraphs
2329 refer to binary packages generated from the source.)
2333 Each paragraph consists of a series of data fields; each
2334 field consists of the field name, followed by a colon and
2335 then the data/value associated with that field. It ends at
2336 the end of the (logical) line. Horizontal whitespace
2337 (spaces and tabs) may occur immediately before or after the
2338 value and is ignored there; it is conventional to put a
2339 single space after the colon. For example, a field might
2341 <example compact="compact">
2344 the field name is <tt>Package</tt> and the field value
2349 Many fields' values may span several lines; in this case
2350 each continuation line must start with a space or a tab.
2351 Any trailing spaces or tabs at the end of individual
2352 lines of a field value are ignored.
2356 In fields where it is specified that lines may not wrap,
2357 only a single line of data is allowed and whitespace is not
2358 significant in a field body. Whitespace must not appear
2359 inside names (of packages, architectures, files or anything
2360 else) or version numbers, or between the characters of
2361 multi-character version relationships.
2365 Field names are not case-sensitive, but it is usual to
2366 capitalize the field names using mixed case as shown below.
2370 Blank lines, or lines consisting only of spaces and tabs,
2371 are not allowed within field values or between fields - that
2372 would mean a new paragraph.
2376 All control files must be encoded in UTF-8.
2380 <sect id="sourcecontrolfiles">
2381 <heading>Source package control files -- <file>debian/control</file></heading>
2384 The <file>debian/control</file> file contains the most vital
2385 (and version-independent) information about the source package
2386 and about the binary packages it creates.
2390 The first paragraph of the control file contains information about
2391 the source package in general. The subsequent sets each describe a
2392 binary package that the source tree builds.
2396 The fields in the general paragraph (the first one, for the source
2399 <list compact="compact">
2400 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2401 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2402 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2403 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2404 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2405 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2406 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2407 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2412 The fields in the binary package paragraphs are:
2414 <list compact="compact">
2415 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2416 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2417 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2418 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2419 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2420 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2421 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2422 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2427 The syntax and semantics of the fields are described below.
2433 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2434 generate control files for binary packages (see below), by
2435 <prgn>dpkg-genchanges</prgn> to generate the
2436 <tt>.changes</tt> file to accompany the upload, and by
2437 <prgn>dpkg-source</prgn> when it creates the
2438 <file>.dsc</file> source control file as part of a source
2439 archive. Many fields are permitted to span multiple lines in
2440 <file>debian/control</file> but not in any other control
2441 file. These tools are responsible for removing the line
2442 breaks from such fields when using fields from
2443 <file>debian/control</file> to generate other control files.
2447 The fields here may contain variable references - their
2448 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2449 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2450 when they generate output control files.
2451 See <ref id="substvars"> for details.
2455 In addition to the control file syntax described <qref
2456 id="controlsyntax">above</qref>, this file may also contain
2457 comment lines starting with <tt>#</tt> without any preceding
2458 whitespace. All such lines are ignored, even in the middle of
2459 continuation lines for a multiline field, and do not end a
2465 <sect id="binarycontrolfiles">
2466 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2469 The <file>DEBIAN/control</file> file contains the most vital
2470 (and version-dependent) information about a binary package.
2474 The fields in this file are:
2476 <list compact="compact">
2477 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2478 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2479 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2480 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2481 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2482 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2483 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2484 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2485 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2486 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2487 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2493 <sect id="debiansourcecontrolfiles">
2494 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2497 This file contains a series of fields, identified and
2498 separated just like the fields in the control file of
2499 a binary package. The fields are listed below; their
2500 syntax is described above, in <ref id="pkg-controlfields">.
2502 <list compact="compact">
2503 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2504 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2505 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2506 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2507 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2508 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2509 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2510 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2511 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2512 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2513 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2518 The source package control file is generated by
2519 <prgn>dpkg-source</prgn> when it builds the source
2520 archive, from other files in the source package,
2521 described above. When unpacking, it is checked against
2522 the files and directories in the other parts of the
2528 <sect id="debianchangesfiles">
2529 <heading>Debian changes files -- <file>.changes</file></heading>
2532 The .changes files are used by the Debian archive maintenance
2533 software to process updates to packages. They contain one
2534 paragraph which contains information from the
2535 <tt>debian/control</tt> file and other data about the
2536 source package gathered via <tt>debian/changelog</tt>
2537 and <tt>debian/rules</tt>.
2541 The fields in this file are:
2543 <list compact="compact">
2544 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2545 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2546 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2548 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2550 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2551 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2552 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2553 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2554 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2555 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2556 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2557 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2562 <sect id="controlfieldslist">
2563 <heading>List of fields</heading>
2565 <sect1 id="f-Source">
2566 <heading><tt>Source</tt></heading>
2569 This field identifies the source package name.
2573 In <file>debian/control</file> or a <file>.dsc</file> file,
2574 this field must contain only the name of the source package.
2578 In a binary package control file or a <file>.changes</file>
2579 file, the source package name may be followed by a version
2580 number in parentheses<footnote>
2581 It is customary to leave a space after the package name
2582 if a version number is specified.
2584 This version number may be omitted (and is, by
2585 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2586 the <tt>Version</tt> field of the binary package in
2587 question. The field itself may be omitted from a binary
2588 package control file when the source package has the same
2589 name and version as the binary package.
2593 Package names must consist only of lower case letters
2594 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2595 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2596 They must be at least two characters long and must start
2597 with an alphanumeric character.
2601 <sect1 id="f-Maintainer">
2602 <heading><tt>Maintainer</tt></heading>
2605 The package maintainer's name and email address. The name
2606 should come first, then the email address inside angle
2607 brackets <tt><></tt> (in RFC822 format).
2611 If the maintainer's name contains a full stop then the
2612 whole field will not work directly as an email address due
2613 to a misfeature in the syntax specified in RFC822; a
2614 program using this field as an address must check for this
2615 and correct the problem if necessary (for example by
2616 putting the name in round brackets and moving it to the
2617 end, and bringing the email address forward).
2621 <sect1 id="f-Uploaders">
2622 <heading><tt>Uploaders</tt></heading>
2625 List of the names and email addresses of co-maintainers of
2626 the package, if any. If the package has other maintainers
2627 beside the one named in the
2628 <qref id="f-Maintainer">Maintainer field</qref>, their
2629 names and email addresses should be listed here. The
2630 format is the same as that of the Maintainer tag, and
2631 multiple entries should be comma separated. Currently,
2632 this field is restricted to a single line of data. This
2633 is an optional field.
2636 Any parser that interprets the Uploaders field in
2637 <file>debian/control</file> must permit it to span multiple
2638 lines. Line breaks in an Uploaders field that spans multiple
2639 lines are not significant and the semantics of the field are
2640 the same as if the line breaks had not been present.
2644 <sect1 id="f-Changed-By">
2645 <heading><tt>Changed-By</tt></heading>
2648 The name and email address of the person who changed the
2649 said package. Usually the name of the maintainer.
2650 All the rules for the Maintainer field apply here, too.
2654 <sect1 id="f-Section">
2655 <heading><tt>Section</tt></heading>
2658 This field specifies an application area into which the package
2659 has been classified. See <ref id="subsections">.
2663 When it appears in the <file>debian/control</file> file,
2664 it gives the value for the subfield of the same name in
2665 the <tt>Files</tt> field of the <file>.changes</file> file.
2666 It also gives the default for the same field in the binary
2671 <sect1 id="f-Priority">
2672 <heading><tt>Priority</tt></heading>
2675 This field represents how important that it is that the user
2676 have the package installed. See <ref id="priorities">.
2680 When it appears in the <file>debian/control</file> file,
2681 it gives the value for the subfield of the same name in
2682 the <tt>Files</tt> field of the <file>.changes</file> file.
2683 It also gives the default for the same field in the binary
2688 <sect1 id="f-Package">
2689 <heading><tt>Package</tt></heading>
2692 The name of the binary package.
2696 Package names must consist only of lower case letters
2697 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2698 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2699 They must be at least two characters long and must start
2700 with an alphanumeric character.
2704 <sect1 id="f-Architecture">
2705 <heading><tt>Architecture</tt></heading>
2708 Depending on context and the control file used, the
2709 <tt>Architecture</tt> field can include the following sets of
2712 <item>A unique single word identifying a Debian machine
2713 architecture, see <ref id="arch-spec">.
2714 <item><tt>all</tt>, which indicates an
2715 architecture-independent package.
2716 <item><tt>any</tt>, which indicates a package available
2717 for building on any architecture.
2718 <item><tt>source</tt>, which indicates a source package.
2723 In the main <file>debian/control</file> file in the source
2724 package, or in the source package control file
2725 <file>.dsc</file>, one may specify a list of architectures
2726 separated by spaces, or the special values <tt>any</tt> or
2731 Specifying <tt>any</tt> indicates that the source package
2732 isn't dependent on any particular architecture and should
2733 compile fine on any one. The produced binary package(s)
2734 will be specific to whatever the current build architecture
2736 This is the most often used setting, and is recommended
2737 for new packages that aren't <tt>Architecture: all</tt>.
2742 Specifying a list of architectures indicates that the source
2743 will build an architecture-dependent package, and will only
2744 work correctly on the listed architectures.<footnote>
2745 This is a setting used for a minority of cases where the
2746 program is not portable. Generally, it should not be used
2752 In a <file>.changes</file> file, the <tt>Architecture</tt>
2753 field lists the architecture(s) of the package(s)
2754 currently being uploaded. This will be a list; if the
2755 source for the package is also being uploaded, the special
2756 entry <tt>source</tt> is also present.
2760 See <ref id="debianrules"> for information how to get the
2761 architecture for the build process.
2765 <sect1 id="f-Essential">
2766 <heading><tt>Essential</tt></heading>
2769 This is a boolean field which may occur only in the
2770 control file of a binary package or in a per-package fields
2771 paragraph of a main source control data file.
2775 If set to <tt>yes</tt> then the package management system
2776 will refuse to remove the package (upgrading and replacing
2777 it is still possible). The other possible value is <tt>no</tt>,
2778 which is the same as not having the field at all.
2783 <heading>Package interrelationship fields:
2784 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2785 <tt>Recommends</tt>, <tt>Suggests</tt>,
2786 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2787 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2791 These fields describe the package's relationships with
2792 other packages. Their syntax and semantics are described
2793 in <ref id="relationships">.</p>
2796 <sect1 id="f-Standards-Version">
2797 <heading><tt>Standards-Version</tt></heading>
2800 The most recent version of the standards (the policy
2801 manual and associated texts) with which the package
2806 The version number has four components: major and minor
2807 version number and major and minor patch level. When the
2808 standards change in a way that requires every package to
2809 change the major number will be changed. Significant
2810 changes that will require work in many packages will be
2811 signaled by a change to the minor number. The major patch
2812 level will be changed for any change to the meaning of the
2813 standards, however small; the minor patch level will be
2814 changed when only cosmetic, typographical or other edits
2815 are made which neither change the meaning of the document
2816 nor affect the contents of packages.
2820 Thus only the first three components of the policy version
2821 are significant in the <em>Standards-Version</em> control
2822 field, and so either these three components or the all
2823 four components may be specified.<footnote>
2824 In the past, people specified the full version number
2825 in the Standards-Version field, for example "2.3.0.0".
2826 Since minor patch-level changes don't introduce new
2827 policy, it was thought it would be better to relax
2828 policy and only require the first 3 components to be
2829 specified, in this example "2.3.0". All four
2830 components may still be used if someone wishes to do so.
2836 <sect1 id="f-Version">
2837 <heading><tt>Version</tt></heading>
2840 The version number of a package. The format is:
2841 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2845 The three components here are:
2847 <tag><var>epoch</var></tag>
2850 This is a single (generally small) unsigned integer. It
2851 may be omitted, in which case zero is assumed. If it is
2852 omitted then the <var>upstream_version</var> may not
2857 It is provided to allow mistakes in the version numbers
2858 of older versions of a package, and also a package's
2859 previous version numbering schemes, to be left behind.
2863 <tag><var>upstream_version</var></tag>
2866 This is the main part of the version number. It is
2867 usually the version number of the original ("upstream")
2868 package from which the <file>.deb</file> file has been made,
2869 if this is applicable. Usually this will be in the same
2870 format as that specified by the upstream author(s);
2871 however, it may need to be reformatted to fit into the
2872 package management system's format and comparison
2877 The comparison behavior of the package management system
2878 with respect to the <var>upstream_version</var> is
2879 described below. The <var>upstream_version</var>
2880 portion of the version number is mandatory.
2884 The <var>upstream_version</var> may contain only
2885 alphanumerics<footnote>
2886 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2888 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2889 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2890 tilde) and should start with a digit. If there is no
2891 <var>debian_revision</var> then hyphens are not allowed;
2892 if there is no <var>epoch</var> then colons are not
2897 <tag><var>debian_revision</var></tag>
2900 This part of the version number specifies the version of
2901 the Debian package based on the upstream version. It
2902 may contain only alphanumerics and the characters
2903 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2904 tilde) and is compared in the same way as the
2905 <var>upstream_version</var> is.
2909 It is optional; if it isn't present then the
2910 <var>upstream_version</var> may not contain a hyphen.
2911 This format represents the case where a piece of
2912 software was written specifically to be turned into a
2913 Debian package, and so there is only one "debianisation"
2914 of it and therefore no revision indication is required.
2918 It is conventional to restart the
2919 <var>debian_revision</var> at <tt>1</tt> each time the
2920 <var>upstream_version</var> is increased.
2924 The package management system will break the version
2925 number apart at the last hyphen in the string (if there
2926 is one) to determine the <var>upstream_version</var> and
2927 <var>debian_revision</var>. The absence of a
2928 <var>debian_revision</var> is equivalent to a
2929 <var>debian_revision</var> of <tt>0</tt>.
2936 When comparing two version numbers, first the <var>epoch</var>
2937 of each are compared, then the <var>upstream_version</var> if
2938 <var>epoch</var> is equal, and then <var>debian_revision</var>
2939 if <var>upstream_version</var> is also equal.
2940 <var>epoch</var> is compared numerically. The
2941 <var>upstream_version</var> and <var>debian_revision</var>
2942 parts are compared by the package management system using the
2943 following algorithm:
2947 The strings are compared from left to right.
2951 First the initial part of each string consisting entirely of
2952 non-digit characters is determined. These two parts (one of
2953 which may be empty) are compared lexically. If a difference
2954 is found it is returned. The lexical comparison is a
2955 comparison of ASCII values modified so that all the letters
2956 sort earlier than all the non-letters and so that a tilde
2957 sorts before anything, even the end of a part. For example,
2958 the following parts are in sorted order from earliest to
2959 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2960 <tt>a</tt>.<footnote>
2961 One common use of <tt>~</tt> is for upstream pre-releases.
2962 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2963 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2968 Then the initial part of the remainder of each string which
2969 consists entirely of digit characters is determined. The
2970 numerical values of these two parts are compared, and any
2971 difference found is returned as the result of the comparison.
2972 For these purposes an empty string (which can only occur at
2973 the end of one or both version strings being compared) counts
2978 These two steps (comparing and removing initial non-digit
2979 strings and initial digit strings) are repeated until a
2980 difference is found or both strings are exhausted.
2984 Note that the purpose of epochs is to allow us to leave behind
2985 mistakes in version numbering, and to cope with situations
2986 where the version numbering scheme changes. It is
2987 <em>not</em> intended to cope with version numbers containing
2988 strings of letters which the package management system cannot
2989 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2990 silly orderings (the author of this manual has heard of a
2991 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2992 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2993 <tt>2</tt> and so forth).
2997 <sect1 id="f-Description">
2998 <heading><tt>Description</tt></heading>
3001 In a source or binary control file, the <tt>Description</tt>
3002 field contains a description of the binary package, consisting
3003 of two parts, the synopsis or the short description, and the
3004 long description. The field's format is as follows:
3009 Description: <single line synopsis>
3010 <extended description over several lines>
3015 The lines in the extended description can have these formats:
3021 Those starting with a single space are part of a paragraph.
3022 Successive lines of this form will be word-wrapped when
3023 displayed. The leading space will usually be stripped off.
3027 Those starting with two or more spaces. These will be
3028 displayed verbatim. If the display cannot be panned
3029 horizontally, the displaying program will line wrap them "hard"
3030 (i.e., without taking account of word breaks). If it can they
3031 will be allowed to trail off to the right. None, one or two
3032 initial spaces may be deleted, but the number of spaces
3033 deleted from each line will be the same (so that you can have
3034 indenting work correctly, for example).
3038 Those containing a single space followed by a single full stop
3039 character. These are rendered as blank lines. This is the
3040 <em>only</em> way to get a blank line<footnote>
3041 Completely empty lines will not be rendered as blank lines.
3042 Instead, they will cause the parser to think you're starting
3043 a whole new record in the control file, and will therefore
3044 likely abort with an error.
3049 Those containing a space, a full stop and some more characters.
3050 These are for future expansion. Do not use them.
3056 Do not use tab characters. Their effect is not predictable.
3060 See <ref id="descriptions"> for further information on this.
3064 In a <file>.changes</file> file, the <tt>Description</tt> field
3065 contains a summary of the descriptions for the packages being
3070 The part of the field before the first newline is empty;
3071 thereafter each line has the name of a binary package and
3072 the summary description line from that binary package.
3073 Each line is indented by one space.
3078 <sect1 id="f-Distribution">
3079 <heading><tt>Distribution</tt></heading>
3082 In a <file>.changes</file> file or parsed changelog output
3083 this contains the (space-separated) name(s) of the
3084 distribution(s) where this version of the package should
3085 be installed. Valid distributions are determined by the
3086 archive maintainers.<footnote>
3087 Current distribution names are:
3088 <taglist compact="compact">
3089 <tag><em>stable</em></tag>
3091 This is the current "released" version of Debian
3092 GNU/Linux. Once the distribution is
3093 <em>stable</em> only security fixes and other
3094 major bug fixes are allowed. When changes are
3095 made to this distribution, the release number is
3096 increased (for example: 2.2r1 becomes 2.2r2 then
3100 <tag><em>unstable</em></tag>
3102 This distribution value refers to the
3103 <em>developmental</em> part of the Debian
3104 distribution tree. New packages, new upstream
3105 versions of packages and bug fixes go into the
3106 <em>unstable</em> directory tree. Download from
3107 this distribution at your own risk.
3110 <tag><em>testing</em></tag>
3112 This distribution value refers to the
3113 <em>testing</em> part of the Debian distribution
3114 tree. It receives its packages from the
3115 unstable distribution after a short time lag to
3116 ensure that there are no major issues with the
3117 unstable packages. It is less prone to breakage
3118 than unstable, but still risky. It is not
3119 possible to upload packages directly to
3123 <tag><em>frozen</em></tag>
3125 From time to time, the <em>testing</em>
3126 distribution enters a state of "code-freeze" in
3127 anticipation of release as a <em>stable</em>
3128 version. During this period of testing only
3129 fixes for existing or newly-discovered bugs will
3130 be allowed. The exact details of this stage are
3131 determined by the Release Manager.
3134 <tag><em>experimental</em></tag>
3136 The packages with this distribution value are
3137 deemed by their maintainers to be high
3138 risk. Oftentimes they represent early beta or
3139 developmental packages from various sources that
3140 the maintainers want people to try, but are not
3141 ready to be a part of the other parts of the
3142 Debian distribution tree. Download at your own
3148 You should list <em>all</em> distributions that the
3149 package should be installed into.
3153 More information is available in the Debian Developer's
3154 Reference, section "The Debian archive".
3161 <heading><tt>Date</tt></heading>
3164 This field includes the date the package was built or last edited.
3168 The value of this field is usually extracted from the
3169 <file>debian/changelog</file> file - see
3170 <ref id="dpkgchangelog">).
3174 <sect1 id="f-Format">
3175 <heading><tt>Format</tt></heading>
3178 This field specifies a format revision for the file.
3179 The most current format described in the Policy Manual
3180 is version <strong>1.5</strong>. The syntax of the
3181 format value is the same as that of a package version
3182 number except that no epoch or Debian revision is allowed
3183 - see <ref id="f-Version">.
3187 <sect1 id="f-Urgency">
3188 <heading><tt>Urgency</tt></heading>
3191 This is a description of how important it is to upgrade to
3192 this version from previous ones. It consists of a single
3193 keyword taking one of the values <tt>low</tt>,
3194 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3195 <tt>critical</tt><footnote>
3196 Other urgency values are supported with configuration
3197 changes in the archive software but are not used in Debian.
3198 The urgency affects how quickly a package will be considered
3199 for inclusion into the <tt>testing</tt> distribution and
3200 gives an indication of the importance of any fixes included
3201 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3202 treated as synonymous.
3203 </footnote> (not case-sensitive) followed by an optional
3204 commentary (separated by a space) which is usually in
3205 parentheses. For example:
3208 Urgency: low (HIGH for users of diversions)
3214 The value of this field is usually extracted from the
3215 <file>debian/changelog</file> file - see
3216 <ref id="dpkgchangelog">.
3220 <sect1 id="f-Changes">
3221 <heading><tt>Changes</tt></heading>
3224 This field contains the human-readable changes data, describing
3225 the differences between the last version and the current one.
3229 There should be nothing in this field before the first
3230 newline; all the subsequent lines must be indented by at
3231 least one space; blank lines must be represented by a line
3232 consisting only of a space and a full stop.
3236 The value of this field is usually extracted from the
3237 <file>debian/changelog</file> file - see
3238 <ref id="dpkgchangelog">).
3242 Each version's change information should be preceded by a
3243 "title" line giving at least the version, distribution(s)
3244 and urgency, in a human-readable way.
3248 If data from several versions is being returned the entry
3249 for the most recent version should be returned first, and
3250 entries should be separated by the representation of a
3251 blank line (the "title" line may also be followed by the
3252 representation of blank line).
3256 <sect1 id="f-Binary">
3257 <heading><tt>Binary</tt></heading>
3260 This field is a list of binary packages.
3264 When it appears in the <file>.dsc</file> file it is the list
3265 of binary packages which a source package can produce. It
3266 does not necessarily produce all of these binary packages
3267 for every architecture. The source control file doesn't
3268 contain details of which architectures are appropriate for
3269 which of the binary packages.
3273 When it appears in a <file>.changes</file> file it lists the
3274 names of the binary packages actually being uploaded.
3278 The syntax is a list of binary packages separated by
3280 A space after each comma is conventional.
3281 </footnote>. Currently the packages must be separated using
3282 only spaces in the <file>.changes</file> file.
3286 <sect1 id="f-Installed-Size">
3287 <heading><tt>Installed-Size</tt></heading>
3290 This field appears in the control files of binary
3291 packages, and in the <file>Packages</file> files. It gives
3292 the total amount of disk space required to install the
3297 The disk space is represented in kilobytes as a simple
3302 <sect1 id="f-Files">
3303 <heading><tt>Files</tt></heading>
3306 This field contains a list of files with information about
3307 each one. The exact information and syntax varies with
3308 the context. In all cases the part of the field
3309 contents on the same line as the field name is empty. The
3310 remainder of the field is one line per file, each line
3311 being indented by one space and containing a number of
3312 sub-fields separated by spaces.
3316 In the <file>.dsc</file> file, each line contains the MD5
3317 checksum, size and filename of the tar file and (if applicable)
3318 diff file which make up the remainder of the source
3320 That is, the parts which are not the <tt>.dsc</tt>.
3322 The exact forms of the filenames are described
3323 in <ref id="pkg-sourcearchives">.
3327 In the <file>.changes</file> file this contains one line per
3328 file being uploaded. Each line contains the MD5 checksum,
3329 size, section and priority and the filename.
3330 The <qref id="f-Section">section</qref>
3331 and <qref id="f-Priority">priority</qref>
3332 are the values of the corresponding fields in
3333 the main source control file. If no section or priority is
3334 specified then <tt>-</tt> should be used, though section
3335 and priority values must be specified for new packages to
3336 be installed properly.
3340 The special value <tt>byhand</tt> for the section in a
3341 <tt>.changes</tt> file indicates that the file in question
3342 is not an ordinary package file and must by installed by
3343 hand by the distribution maintainers. If the section is
3344 <tt>byhand</tt> the priority should be <tt>-</tt>.
3348 If a new Debian revision of a package is being shipped and
3349 no new original source archive is being distributed the
3350 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3351 entry for the original source archive
3352 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3353 but the <file>.changes</file> file should leave it out. In
3354 this case the original source archive on the distribution
3355 site must match exactly, byte-for-byte, the original
3356 source archive which was used to generate the
3357 <file>.dsc</file> file and diff which are being uploaded.</p>
3360 <sect1 id="f-Closes">
3361 <heading><tt>Closes</tt></heading>
3364 A space-separated list of bug report numbers that the upload
3365 governed by the .changes file closes.
3369 <sect1 id="f-Homepage">
3370 <heading><tt>Homepage</tt></heading>
3373 The URL of the web site for this package, preferably (when
3374 applicable) the site from which the original source can be
3375 obtained and any additional upstream documentation or
3376 information may be found. The content of this field is a
3377 simple URL without any surrounding characters such as
3385 <heading>User-defined fields</heading>
3388 Additional user-defined fields may be added to the
3389 source package control file. Such fields will be
3390 ignored, and not copied to (for example) binary or
3391 source package control files or upload control files.
3395 If you wish to add additional unsupported fields to
3396 these output files you should use the mechanism
3401 Fields in the main source control information file with
3402 names starting <tt>X</tt>, followed by one or more of
3403 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3404 be copied to the output files. Only the part of the
3405 field name after the hyphen will be used in the output
3406 file. Where the letter <tt>B</tt> is used the field
3407 will appear in binary package control files, where the
3408 letter <tt>S</tt> is used in source package control
3409 files and where <tt>C</tt> is used in upload control
3410 (<tt>.changes</tt>) files.
3414 For example, if the main source information control file
3417 XBS-Comment: I stand between the candle and the star.
3419 then the binary and source package control files will contain the
3422 Comment: I stand between the candle and the star.
3431 <chapt id="maintainerscripts">
3432 <heading>Package maintainer scripts and installation procedure</heading>
3435 <heading>Introduction to package maintainer scripts</heading>
3438 It is possible to supply scripts as part of a package which
3439 the package management system will run for you when your
3440 package is installed, upgraded or removed.
3444 These scripts are the files <prgn>preinst</prgn>,
3445 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3446 <prgn>postrm</prgn> in the control area of the package.
3447 They must be proper executable files; if they are scripts
3448 (which is recommended), they must start with the usual
3449 <tt>#!</tt> convention. They should be readable and
3450 executable by anyone, and must not be world-writable.
3454 The package management system looks at the exit status from
3455 these scripts. It is important that they exit with a
3456 non-zero status if there is an error, so that the package
3457 management system can stop its processing. For shell
3458 scripts this means that you <em>almost always</em> need to
3459 use <tt>set -e</tt> (this is usually true when writing shell
3460 scripts, in fact). It is also important, of course, that
3461 they exit with a zero status if everything went well.
3465 Additionally, packages interacting with users using
3466 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3467 install a <prgn>config</prgn> script in the control area,
3468 see <ref id="maintscriptprompt"> for details.
3472 When a package is upgraded a combination of the scripts from
3473 the old and new packages is called during the upgrade
3474 procedure. If your scripts are going to be at all
3475 complicated you need to be aware of this, and may need to
3476 check the arguments to your scripts.
3480 Broadly speaking the <prgn>preinst</prgn> is called before
3481 (a particular version of) a package is installed, and the
3482 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3483 before (a version of) a package is removed and the
3484 <prgn>postrm</prgn> afterwards.
3488 Programs called from maintainer scripts should not normally
3489 have a path prepended to them. Before installation is
3490 started, the package management system checks to see if the
3491 programs <prgn>ldconfig</prgn>,
3492 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3493 and <prgn>update-rc.d</prgn> can be found via the
3494 <tt>PATH</tt> environment variable. Those programs, and any
3495 other program that one would expect to be in the
3496 <tt>PATH</tt>, should thus be invoked without an absolute
3497 pathname. Maintainer scripts should also not reset the
3498 <tt>PATH</tt>, though they might choose to modify it by
3499 prepending or appending package-specific directories. These
3500 considerations really apply to all shell scripts.</p>
3503 <sect id="idempotency">
3504 <heading>Maintainer scripts idempotency</heading>
3507 It is necessary for the error recovery procedures that the
3508 scripts be idempotent. This means that if it is run
3509 successfully, and then it is called again, it doesn't bomb
3510 out or cause any harm, but just ensures that everything is
3511 the way it ought to be. If the first call failed, or
3512 aborted half way through for some reason, the second call
3513 should merely do the things that were left undone the first
3514 time, if any, and exit with a success status if everything
3516 This is so that if an error occurs, the user interrupts
3517 <prgn>dpkg</prgn> or some other unforeseen circumstance
3518 happens you don't leave the user with a badly-broken
3519 package when <prgn>dpkg</prgn> attempts to repeat the
3525 <sect id="controllingterminal">
3526 <heading>Controlling terminal for maintainer scripts</heading>
3529 The maintainer scripts are guaranteed to run with a
3530 controlling terminal and can interact with the user.
3531 Because these scripts may be executed with standard output
3532 redirected into a pipe for logging purposes, Perl scripts
3533 should set unbuffered output by setting <tt>$|=1</tt> so
3534 that the output is printed immediately rather than being
3538 <sect id="exitstatus">
3539 <heading>Exit status</heading>
3542 Each script must return a zero exit status for
3543 success, or a nonzero one for failure, since the package
3544 management system looks for the exit status of these scripts
3545 and determines what action to take next based on that datum.
3549 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3554 <list compact="compact">
3556 <var>new-preinst</var> <tt>install</tt>
3559 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3562 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3565 <var>old-preinst</var> <tt>abort-upgrade</tt>
3566 <var>new-version</var>
3571 <list compact="compact">
3573 <var>postinst</var> <tt>configure</tt>
3574 <var>most-recently-configured-version</var>
3577 <var>old-postinst</var> <tt>abort-upgrade</tt>
3578 <var>new-version</var>
3581 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3582 <tt>in-favour</tt> <var>package</var>
3583 <var>new-version</var>
3586 <var>postinst</var> <tt>abort-remove</tt>
3589 <var>deconfigured's-postinst</var>
3590 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3591 <var>failed-install-package</var> <var>version</var>
3592 [<tt>removing</tt> <var>conflicting-package</var>
3598 <list compact="compact">
3600 <var>prerm</var> <tt>remove</tt>
3603 <var>old-prerm</var> <tt>upgrade</tt>
3604 <var>new-version</var>
3607 <var>new-prerm</var> <tt>failed-upgrade</tt>
3608 <var>old-version</var>
3611 <var>conflictor's-prerm</var> <tt>remove</tt>
3612 <tt>in-favour</tt> <var>package</var>
3613 <var>new-version</var>
3616 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3617 <tt>in-favour</tt> <var>package-being-installed</var>
3618 <var>version</var> [<tt>removing</tt>
3619 <var>conflicting-package</var>
3625 <list compact="compact">
3627 <var>postrm</var> <tt>remove</tt>
3630 <var>postrm</var> <tt>purge</tt>
3633 <var>old-postrm</var> <tt>upgrade</tt>
3634 <var>new-version</var>
3637 <var>new-postrm</var> <tt>failed-upgrade</tt>
3638 <var>old-version</var>
3641 <var>new-postrm</var> <tt>abort-install</tt>
3644 <var>new-postrm</var> <tt>abort-install</tt>
3645 <var>old-version</var>
3648 <var>new-postrm</var> <tt>abort-upgrade</tt>
3649 <var>old-version</var>
3652 <var>disappearer's-postrm</var> <tt>disappear</tt>
3653 <var>overwriter</var>
3654 <var>overwriter-version</var>
3660 <sect id="unpackphase">
3661 <heading>Details of unpack phase of installation or upgrade</heading>
3664 The procedure on installation/upgrade/overwrite/disappear
3665 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3666 stage of <tt>dpkg --install</tt>) is as follows. In each
3667 case, if a major error occurs (unless listed below) the
3668 actions are, in general, run backwards - this means that the
3669 maintainer scripts are run with different arguments in
3670 reverse order. These are the "error unwind" calls listed
3677 If a version of the package is already installed, call
3678 <example compact="compact">
3679 <var>old-prerm</var> upgrade <var>new-version</var>
3683 If the script runs but exits with a non-zero
3684 exit status, <prgn>dpkg</prgn> will attempt:
3685 <example compact="compact">
3686 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3688 If this works, the upgrade continues. If this
3689 does not work, the error unwind:
3690 <example compact="compact">
3691 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3693 If this works, then the old-version is
3694 "Installed", if not, the old version is in a
3695 "Failed-Config" state.
3701 If a "conflicting" package is being removed at the same time,
3702 or if any package will be broken (due to <tt>Breaks</tt>):
3705 If <tt>--auto-deconfigure</tt> is
3706 specified, call, for each package to be deconfigured
3707 due to <tt>Breaks</tt>:
3708 <example compact="compact">
3709 <var>deconfigured's-prerm</var> deconfigure \
3710 in-favour <var>package-being-installed</var> <var>version</var>
3713 <example compact="compact">
3714 <var>deconfigured's-postinst</var> abort-deconfigure \
3715 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3717 The deconfigured packages are marked as
3718 requiring configuration, so that if
3719 <tt>--install</tt> is used they will be
3720 configured again if possible.
3723 If any packages depended on a conflicting
3724 package being removed and <tt>--auto-deconfigure</tt> is
3725 specified, call, for each such package:
3726 <example compact="compact">
3727 <var>deconfigured's-prerm</var> deconfigure \
3728 in-favour <var>package-being-installed</var> <var>version</var> \
3729 removing <var>conflicting-package</var> <var>version</var>
3732 <example compact="compact">
3733 <var>deconfigured's-postinst</var> abort-deconfigure \
3734 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3735 removing <var>conflicting-package</var> <var>version</var>
3737 The deconfigured packages are marked as
3738 requiring configuration, so that if
3739 <tt>--install</tt> is used they will be
3740 configured again if possible.
3743 To prepare for removal of each conflicting package, call:
3744 <example compact="compact">
3745 <var>conflictor's-prerm</var> remove \
3746 in-favour <var>package</var> <var>new-version</var>
3749 <example compact="compact">
3750 <var>conflictor's-postinst</var> abort-remove \
3751 in-favour <var>package</var> <var>new-version</var>
3760 If the package is being upgraded, call:
3761 <example compact="compact">
3762 <var>new-preinst</var> upgrade <var>old-version</var>
3764 If this fails, we call:
3766 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3773 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3775 is called. If this works, then the old version
3776 is in an "Installed" state, or else it is left
3777 in an "Unpacked" state.
3782 If it fails, then the old version is left
3783 in an "Half-Installed" state.
3790 Otherwise, if the package had some configuration
3791 files from a previous version installed (i.e., it
3792 is in the "configuration files only" state):
3793 <example compact="compact">
3794 <var>new-preinst</var> install <var>old-version</var>
3798 <var>new-postrm</var> abort-install <var>old-version</var>
3800 If this fails, the package is left in a
3801 "Half-Installed" state, which requires a
3802 reinstall. If it works, the packages is left in
3803 a "Config Files" state.
3806 Otherwise (i.e., the package was completely purged):
3807 <example compact="compact">
3808 <var>new-preinst</var> install
3811 <example compact="compact">
3812 <var>new-postrm</var> abort-install
3814 If the error-unwind fails, the package is in a
3815 "Half Installed" phase, and requires a
3816 reinstall. If the error unwind works, the
3817 package is in a not installed state.
3824 The new package's files are unpacked, overwriting any
3825 that may be on the system already, for example any
3826 from the old version of the same package or from
3827 another package. Backups of the old files are kept
3828 temporarily, and if anything goes wrong the package
3829 management system will attempt to put them back as
3830 part of the error unwind.
3834 It is an error for a package to contain files which
3835 are on the system in another package, unless
3836 <tt>Replaces</tt> is used (see <ref id="replaces">).
3838 The following paragraph is not currently the case:
3839 Currently the <tt>- - force-overwrite</tt> flag is
3840 enabled, downgrading it to a warning, but this may not
3846 It is a more serious error for a package to contain a
3847 plain file or other kind of non-directory where another
3848 package has a directory (again, unless
3849 <tt>Replaces</tt> is used). This error can be
3850 overridden if desired using
3851 <tt>--force-overwrite-dir</tt>, but this is not
3856 Packages which overwrite each other's files produce
3857 behavior which, though deterministic, is hard for the
3858 system administrator to understand. It can easily
3859 lead to "missing" programs if, for example, a package
3860 is installed which overwrites a file from another
3861 package, and is then removed again.<footnote>
3862 Part of the problem is due to what is arguably a
3863 bug in <prgn>dpkg</prgn>.
3868 A directory will never be replaced by a symbolic link
3869 to a directory or vice versa; instead, the existing
3870 state (symlink or not) will be left alone and
3871 <prgn>dpkg</prgn> will follow the symlink if there is
3880 If the package is being upgraded, call
3881 <example compact="compact">
3882 <var>old-postrm</var> upgrade <var>new-version</var>
3886 If this fails, <prgn>dpkg</prgn> will attempt:
3887 <example compact="compact">
3888 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3890 If this works, installation continues. If not,
3892 <example compact="compact">
3893 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3895 If this fails, the old version is left in an
3896 "Half Installed" state. If it works, dpkg now
3898 <example compact="compact">
3899 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3901 If this fails, the old version is left in an
3902 "Half Installed" state. If it works, dpkg now
3904 <example compact="compact">
3905 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3907 If this fails, the old version is in an
3914 This is the point of no return - if
3915 <prgn>dpkg</prgn> gets this far, it won't back off
3916 past this point if an error occurs. This will
3917 leave the package in a fairly bad state, which
3918 will require a successful re-installation to clear
3919 up, but it's when <prgn>dpkg</prgn> starts doing
3920 things that are irreversible.
3925 Any files which were in the old version of the package
3926 but not in the new are removed.
3930 The new file list replaces the old.
3934 The new maintainer scripts replace the old.
3938 Any packages all of whose files have been overwritten
3939 during the installation, and which aren't required for
3940 dependencies, are considered to have been removed.
3941 For each such package
3944 <prgn>dpkg</prgn> calls:
3945 <example compact="compact">
3946 <var>disappearer's-postrm</var> disappear \
3947 <var>overwriter</var> <var>overwriter-version</var>
3951 The package's maintainer scripts are removed.
3954 It is noted in the status database as being in a
3955 sane state, namely not installed (any conffiles
3956 it may have are ignored, rather than being
3957 removed by <prgn>dpkg</prgn>). Note that
3958 disappearing packages do not have their prerm
3959 called, because <prgn>dpkg</prgn> doesn't know
3960 in advance that the package is going to
3967 Any files in the package we're unpacking that are also
3968 listed in the file lists of other packages are removed
3969 from those lists. (This will lobotomize the file list
3970 of the "conflicting" package if there is one.)
3974 The backup files made during installation, above, are
3980 The new package's status is now sane, and recorded as
3985 Here is another point of no return - if the
3986 conflicting package's removal fails we do not unwind
3987 the rest of the installation; the conflicting package
3988 is left in a half-removed limbo.
3993 If there was a conflicting package we go and do the
3994 removal actions (described below), starting with the
3995 removal of the conflicting package's files (any that
3996 are also in the package being installed have already
3997 been removed from the conflicting package's file list,
3998 and so do not get removed now).
4004 <sect id="configdetails"><heading>Details of configuration</heading>
4007 When we configure a package (this happens with <tt>dpkg
4008 --install</tt> and <tt>dpkg --configure</tt>), we first
4009 update any <tt>conffile</tt>s and then call:
4010 <example compact="compact">
4011 <var>postinst</var> configure <var>most-recently-configured-version</var>
4016 No attempt is made to unwind after errors during
4017 configuration. If the configuration fails, the package is in
4018 a "Failed Config" state, and an error message is generated.
4022 If there is no most recently configured version
4023 <prgn>dpkg</prgn> will pass a null argument.
4026 Historical note: Truly ancient (pre-1997) versions of
4027 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4028 (including the angle brackets) in this case. Even older
4029 ones did not pass a second argument at all, under any
4030 circumstance. Note that upgrades using such an old dpkg
4031 version are unlikely to work for other reasons, even if
4032 this old argument behavior is handled by your postinst script.
4038 <sect id="removedetails"><heading>Details of removal and/or
4039 configuration purging</heading>
4045 <example compact="compact">
4046 <var>prerm</var> remove
4050 If prerm fails during replacement due to conflict
4052 <var>conflictor's-postinst</var> abort-remove \
4053 in-favour <var>package</var> <var>new-version</var>
4057 <var>postinst</var> abort-remove
4061 If this fails, the package is in a "Failed-Config"
4062 state, or else it remains "Installed".
4066 The package's files are removed (except <tt>conffile</tt>s).
4069 <example compact="compact">
4070 <var>postrm</var> remove
4074 If it fails, there's no error unwind, and the package is in
4075 an "Half-Installed" state.
4080 All the maintainer scripts except the <prgn>postrm</prgn>
4085 If we aren't purging the package we stop here. Note
4086 that packages which have no <prgn>postrm</prgn> and no
4087 <tt>conffile</tt>s are automatically purged when
4088 removed, as there is no difference except for the
4089 <prgn>dpkg</prgn> status.
4093 The <tt>conffile</tt>s and any backup files
4094 (<tt>~</tt>-files, <tt>#*#</tt> files,
4095 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4100 <example compact="compact">
4101 <var>postrm</var> purge
4105 If this fails, the package remains in a "Config-Files"
4110 The package's file list is removed.
4119 <chapt id="relationships">
4120 <heading>Declaring relationships between packages</heading>
4122 <sect id="depsyntax">
4123 <heading>Syntax of relationship fields</heading>
4126 These fields all have a uniform syntax. They are a list of
4127 package names separated by commas.
4131 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4132 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4133 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4134 control file fields of the package, which declare
4135 dependencies on other packages, the package names listed may
4136 also include lists of alternative package names, separated
4137 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4138 if any one of the alternative packages is installed, that
4139 part of the dependency is considered to be satisfied.
4143 All of the fields except for <tt>Provides</tt> may restrict
4144 their applicability to particular versions of each named
4145 package. This is done in parentheses after each individual
4146 package name; the parentheses should contain a relation from
4147 the list below followed by a version number, in the format
4148 described in <ref id="f-Version">.
4152 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4153 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4154 strictly earlier, earlier or equal, exactly equal, later or
4155 equal and strictly later, respectively. The deprecated
4156 forms <tt><</tt> and <tt>></tt> were used to mean
4157 earlier/later or equal, rather than strictly earlier/later,
4158 so they should not appear in new packages (though
4159 <prgn>dpkg</prgn> still supports them).
4163 Whitespace may appear at any point in the version
4164 specification subject to the rules in <ref
4165 id="controlsyntax">, and must appear where it's necessary to
4166 disambiguate; it is not otherwise significant. All of the
4167 relationship fields may span multiple lines. For
4168 consistency and in case of future changes to
4169 <prgn>dpkg</prgn> it is recommended that a single space be
4170 used after a version relationship and before a version
4171 number; it is also conventional to put a single space after
4172 each comma, on either side of each vertical bar, and before
4173 each open parenthesis. When wrapping a relationship field, it
4174 is conventional to do so after a comma and before the space
4175 following that comma.
4179 For example, a list of dependencies might appear as:
4180 <example compact="compact">
4183 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4188 All fields that specify build-time relationships
4189 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4190 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4191 may be restricted to a certain set of architectures. This
4192 is indicated in brackets after each individual package name and
4193 the optional version specification. The brackets enclose a
4194 list of Debian architecture names separated by whitespace.
4195 Exclamation marks may be prepended to each of the names.
4196 (It is not permitted for some names to be prepended with
4197 exclamation marks while others aren't.) If the current Debian
4198 host architecture is not in this list and there are no
4199 exclamation marks in the list, or it is in the list with a
4200 prepended exclamation mark, the package name and the
4201 associated version specification are ignored completely for
4202 the purposes of defining the relationships.
4207 <example compact="compact">
4209 Build-Depends-Indep: texinfo
4210 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4211 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4213 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4214 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4215 <tt>gnumach-dev</tt> only on hurd-i386.
4219 If the architecture-restricted dependency is part of a set of
4220 alternatives using <tt>|</tt>, that alternative is ignored
4221 completely on architectures that do not match the restriction.
4223 <example compact="compact">
4224 Build-Depends: foo [!i386] | bar [!amd64]
4226 is equivalent to <tt>bar</tt> on the i386 architecture, to
4227 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4228 bar</tt> on all other architectures.
4232 Note that the binary package relationship fields such as
4233 <tt>Depends</tt> appear in one of the binary package
4234 sections of the control file, whereas the build-time
4235 relationships such as <tt>Build-Depends</tt> appear in the
4236 source package section of the control file (which is the
4241 <sect id="binarydeps">
4242 <heading>Binary Dependencies - <tt>Depends</tt>,
4243 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4244 <tt>Pre-Depends</tt>
4248 Packages can declare in their control file that they have
4249 certain relationships to other packages - for example, that
4250 they may not be installed at the same time as certain other
4251 packages, and/or that they depend on the presence of others.
4255 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4256 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4257 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4258 <tt>Breaks</tt> is described in <ref id="breaks">, and
4259 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4260 rest are described below.
4264 These seven fields are used to declare a dependency
4265 relationship by one package on another. Except for
4266 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4267 depending (binary) package's control file.
4268 (<tt>Enhances</tt> appears in the recommending package's
4269 control file, and <tt>Breaks</tt> appears in the version of
4270 depended-on package which causes the named package to
4275 A <tt>Depends</tt> field takes effect <em>only</em> when a
4276 package is to be configured. It does not prevent a package
4277 being on the system in an unconfigured state while its
4278 dependencies are unsatisfied, and it is possible to replace
4279 a package whose dependencies are satisfied and which is
4280 properly installed with a different version whose
4281 dependencies are not and cannot be satisfied; when this is
4282 done the depending package will be left unconfigured (since
4283 attempts to configure it will give errors) and will not
4284 function properly. If it is necessary, a
4285 <tt>Pre-Depends</tt> field can be used, which has a partial
4286 effect even when a package is being unpacked, as explained
4287 in detail below. (The other three dependency fields,
4288 <tt>Recommends</tt>, <tt>Suggests</tt> and
4289 <tt>Enhances</tt>, are only used by the various front-ends
4290 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4291 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4295 For this reason packages in an installation run are usually
4296 all unpacked first and all configured later; this gives
4297 later versions of packages with dependencies on later
4298 versions of other packages the opportunity to have their
4299 dependencies satisfied.
4303 In case of circular dependencies, since installation or
4304 removal order honoring the dependency order can't be
4305 established, dependency loops are broken at some point
4306 (based on rules below), and some packages may not be able to
4307 rely on their dependencies being present when being
4308 installed or removed, depending on which side of the break
4309 of the circular dependency loop they happen to be on. If one
4310 of the packages in the loop has no postinst script, then the
4311 cycle will be broken at that package, so as to ensure that
4312 all postinst scripts run with the dependencies properly
4313 configured if this is possible. Otherwise the breaking point
4318 The <tt>Depends</tt> field thus allows package maintainers
4319 to impose an order in which packages should be configured.
4323 The meaning of the five dependency fields is as follows:
4325 <tag><tt>Depends</tt></tag>
4328 This declares an absolute dependency. A package will
4329 not be configured unless all of the packages listed in
4330 its <tt>Depends</tt> field have been correctly
4335 The <tt>Depends</tt> field should be used if the
4336 depended-on package is required for the depending
4337 package to provide a significant amount of
4342 The <tt>Depends</tt> field should also be used if the
4343 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4344 <prgn>postrm</prgn> scripts require the package to be
4345 present in order to run. Note, however, that the
4346 <prgn>postrm</prgn> cannot rely on any non-essential
4347 packages to be present during the <tt>purge</tt>
4351 <tag><tt>Recommends</tt></tag>
4354 This declares a strong, but not absolute, dependency.
4358 The <tt>Recommends</tt> field should list packages
4359 that would be found together with this one in all but
4360 unusual installations.
4364 <tag><tt>Suggests</tt></tag>
4366 This is used to declare that one package may be more
4367 useful with one or more others. Using this field
4368 tells the packaging system and the user that the
4369 listed packages are related to this one and can
4370 perhaps enhance its usefulness, but that installing
4371 this one without them is perfectly reasonable.
4374 <tag><tt>Enhances</tt></tag>
4376 This field is similar to Suggests but works in the
4377 opposite direction. It is used to declare that a
4378 package can enhance the functionality of another
4382 <tag><tt>Pre-Depends</tt></tag>
4385 This field is like <tt>Depends</tt>, except that it
4386 also forces <prgn>dpkg</prgn> to complete installation
4387 of the packages named before even starting the
4388 installation of the package which declares the
4389 pre-dependency, as follows:
4393 When a package declaring a pre-dependency is about to
4394 be <em>unpacked</em> the pre-dependency can be
4395 satisfied if the depended-on package is either fully
4396 configured, <em>or even if</em> the depended-on
4397 package(s) are only unpacked or half-configured,
4398 provided that they have been configured correctly at
4399 some point in the past (and not removed or partially
4400 removed since). In this case, both the
4401 previously-configured and currently unpacked or
4402 half-configured versions must satisfy any version
4403 clause in the <tt>Pre-Depends</tt> field.
4407 When the package declaring a pre-dependency is about
4408 to be <em>configured</em>, the pre-dependency will be
4409 treated as a normal <tt>Depends</tt>, that is, it will
4410 be considered satisfied only if the depended-on
4411 package has been correctly configured.
4415 <tt>Pre-Depends</tt> should be used sparingly,
4416 preferably only by packages whose premature upgrade or
4417 installation would hamper the ability of the system to
4418 continue with any upgrade that might be in progress.
4422 <tt>Pre-Depends</tt> are also required if the
4423 <prgn>preinst</prgn> script depends on the named
4424 package. It is best to avoid this situation if
4432 When selecting which level of dependency to use you should
4433 consider how important the depended-on package is to the
4434 functionality of the one declaring the dependency. Some
4435 packages are composed of components of varying degrees of
4436 importance. Such a package should list using
4437 <tt>Depends</tt> the package(s) which are required by the
4438 more important components. The other components'
4439 requirements may be mentioned as Suggestions or
4440 Recommendations, as appropriate to the components' relative
4446 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4449 When one binary package declares that it breaks another,
4450 <prgn>dpkg</prgn> will refuse to allow the package which
4451 declares <tt>Breaks</tt> be installed unless the broken
4452 package is deconfigured first, and it will refuse to
4453 allow the broken package to be reconfigured.
4457 A package will not be regarded as causing breakage merely
4458 because its configuration files are still installed; it must
4459 be at least half-installed.
4463 A special exception is made for packages which declare that
4464 they break their own package name or a virtual package which
4465 they provide (see below): this does not count as a real
4470 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4471 version clause; such a <tt>Breaks</tt> is introduced in the
4472 version of an (implicit or explicit) dependency which
4473 violates an assumption or reveals a bug in earlier versions
4474 of the broken package. This use of <tt>Breaks</tt> will
4475 inform higher-level package management tools that broken
4476 package must be upgraded before the new one.
4480 If the breaking package also overwrites some files from the
4481 older package, it should use <tt>Replaces</tt> (not
4482 <tt>Conflicts</tt>) to ensure this goes smoothly.
4486 <sect id="conflicts">
4487 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4490 When one binary package declares a conflict with another
4491 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4492 refuse to allow them to be installed on the system at the
4497 If one package is to be installed, the other must be removed
4498 first - if the package being installed is marked as
4499 replacing (see <ref id="replaces">) the one on the system,
4500 or the one on the system is marked as deselected, or both
4501 packages are marked <tt>Essential</tt>, then
4502 <prgn>dpkg</prgn> will automatically remove the package
4503 which is causing the conflict, otherwise it will halt the
4504 installation of the new package with an error. This
4505 mechanism is specifically designed to produce an error when
4506 the installed package is <tt>Essential</tt>, but the new
4511 A package will not cause a conflict merely because its
4512 configuration files are still installed; it must be at least
4517 A special exception is made for packages which declare a
4518 conflict with their own package name, or with a virtual
4519 package which they provide (see below): this does not
4520 prevent their installation, and allows a package to conflict
4521 with others providing a replacement for it. You use this
4522 feature when you want the package in question to be the only
4523 package providing some feature.
4527 A <tt>Conflicts</tt> entry should almost never have an
4528 "earlier than" version clause. This would prevent
4529 <prgn>dpkg</prgn> from upgrading or installing the package
4530 which declared such a conflict until the upgrade or removal
4531 of the conflicted-with package had been completed. Instead,
4532 <tt>Breaks</tt> may be used.
4536 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4540 As well as the names of actual ("concrete") packages, the
4541 package relationship fields <tt>Depends</tt>,
4542 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4543 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4544 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4545 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4546 may mention "virtual packages".
4550 A <em>virtual package</em> is one which appears in the
4551 <tt>Provides</tt> control file field of another package.
4552 The effect is as if the package(s) which provide a
4553 particular virtual package name had been listed by name
4554 everywhere the virtual package name appears. (See also <ref
4559 If there are both concrete and virtual packages of the same
4560 name, then the dependency may be satisfied (or the conflict
4561 caused) by either the concrete package with the name in
4562 question or any other concrete package which provides the
4563 virtual package with the name in question. This is so that,
4564 for example, supposing we have
4565 <example compact="compact">
4568 </example> and someone else releases an enhanced version of
4569 the <tt>bar</tt> package they can say:
4570 <example compact="compact">
4574 and the <tt>bar-plus</tt> package will now also satisfy the
4575 dependency for the <tt>foo</tt> package.
4579 If a relationship field has a version number attached
4580 then only real packages will be considered to see whether
4581 the relationship is satisfied (or the prohibition violated,
4582 for a conflict or breakage) - it is assumed that a real
4583 package which provides the virtual package is not of the
4584 "right" version. So, a <tt>Provides</tt> field may not
4585 contain version numbers, and the version number of the
4586 concrete package which provides a particular virtual package
4587 will not be looked at when considering a dependency on or
4588 conflict with the virtual package name.
4592 It is likely that the ability will be added in a future
4593 release of <prgn>dpkg</prgn> to specify a version number for
4594 each virtual package it provides. This feature is not yet
4595 present, however, and is expected to be used only
4600 If you want to specify which of a set of real packages
4601 should be the default to satisfy a particular dependency on
4602 a virtual package, you should list the real package as an
4603 alternative before the virtual one.
4608 <sect id="replaces"><heading>Overwriting files and replacing
4609 packages - <tt>Replaces</tt></heading>
4612 Packages can declare in their control file that they should
4613 overwrite files in certain other packages, or completely
4614 replace other packages. The <tt>Replaces</tt> control file
4615 field has these two distinct purposes.
4618 <sect1><heading>Overwriting files in other packages</heading>
4621 Firstly, as mentioned before, it is usually an error for a
4622 package to contain files which are on the system in
4627 However, if the overwriting package declares that it
4628 <tt>Replaces</tt> the one containing the file being
4629 overwritten, then <prgn>dpkg</prgn> will replace the file
4630 from the old package with that from the new. The file
4631 will no longer be listed as "owned" by the old package.
4635 If a package is completely replaced in this way, so that
4636 <prgn>dpkg</prgn> does not know of any files it still
4637 contains, it is considered to have "disappeared". It will
4638 be marked as not wanted on the system (selected for
4639 removal) and not installed. Any <tt>conffile</tt>s
4640 details noted for the package will be ignored, as they
4641 will have been taken over by the overwriting package. The
4642 package's <prgn>postrm</prgn> script will be run with a
4643 special argument to allow the package to do any final
4644 cleanup required. See <ref id="mscriptsinstact">.
4647 Replaces is a one way relationship -- you have to
4648 install the replacing package after the replaced
4655 For this usage of <tt>Replaces</tt>, virtual packages (see
4656 <ref id="virtual">) are not considered when looking at a
4657 <tt>Replaces</tt> field - the packages declared as being
4658 replaced must be mentioned by their real names.
4662 Furthermore, this usage of <tt>Replaces</tt> only takes
4663 effect when both packages are at least partially on the
4664 system at once, so that it can only happen if they do not
4665 conflict or if the conflict has been overridden.
4670 <sect1><heading>Replacing whole packages, forcing their
4674 Secondly, <tt>Replaces</tt> allows the packaging system to
4675 resolve which package should be removed when there is a
4676 conflict - see <ref id="conflicts">. This usage only
4677 takes effect when the two packages <em>do</em> conflict,
4678 so that the two usages of this field do not interfere with
4683 In this situation, the package declared as being replaced
4684 can be a virtual package, so for example, all mail
4685 transport agents (MTAs) would have the following fields in
4686 their control files:
4687 <example compact="compact">
4688 Provides: mail-transport-agent
4689 Conflicts: mail-transport-agent
4690 Replaces: mail-transport-agent
4692 ensuring that only one MTA can be installed at any one
4697 <sect id="sourcebinarydeps">
4698 <heading>Relationships between source and binary packages -
4699 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4700 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4704 Source packages that require certain binary packages to be
4705 installed or absent at the time of building the package
4706 can declare relationships to those binary packages.
4710 This is done using the <tt>Build-Depends</tt>,
4711 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4712 <tt>Build-Conflicts-Indep</tt> control file fields.
4716 Build-dependencies on "build-essential" binary packages can be
4717 omitted. Please see <ref id="pkg-relations"> for more information.
4721 The dependencies and conflicts they define must be satisfied
4722 (as defined earlier for binary packages) in order to invoke
4723 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4725 If you make "build-arch" or "binary-arch", you need
4726 Build-Depends. If you make "build-indep" or
4727 "binary-indep", you need Build-Depends and
4728 Build-Depends-Indep. If you make "build" or "binary",
4732 There is no Build-Depends-Arch; this role is essentially
4733 met with Build-Depends. Anyone building the
4734 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4735 is basically assumed to be building the whole package
4736 anyway and so installs all build dependencies. The
4737 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4738 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4739 does not yet know how to check for its existence) and
4740 <tt>binary-arch</tt>.
4743 The purpose of the original split, I recall, was so that
4744 the autobuilders wouldn't need to install extra packages
4745 needed only for the binary-indep targets. But without a
4746 build-arch/build-indep split, this didn't work, since
4747 most of the work is done in the build target, not in the
4753 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4755 The <tt>Build-Depends</tt> and
4756 <tt>Build-Conflicts</tt> fields must be satisfied when
4757 any of the following targets is invoked:
4758 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4759 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4760 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4762 <tag><tt>Build-Depends-Indep</tt>,
4763 <tt>Build-Conflicts-Indep</tt></tag>
4765 The <tt>Build-Depends-Indep</tt> and
4766 <tt>Build-Conflicts-Indep</tt> fields must be
4767 satisfied when any of the following targets is
4768 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4769 <tt>binary</tt> and <tt>binary-indep</tt>.
4779 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4782 Packages containing shared libraries must be constructed with
4783 a little care to make sure that the shared library is always
4784 available. This is especially important for packages whose
4785 shared libraries are vitally important, such as the C library
4786 (currently <tt>libc6</tt>).
4790 Packages involving shared libraries should be split up into
4791 several binary packages. This section mostly deals with how
4792 this separation is to be accomplished; rules for files within
4793 the shared library packages are in <ref id="libraries"> instead.
4796 <sect id="sharedlibs-runtime">
4797 <heading>Run-time shared libraries</heading>
4800 The run-time shared library needs to be placed in a package
4801 whose name changes whenever the shared object version
4804 Since it is common place to install several versions of a
4805 package that just provides shared libraries, it is a
4806 good idea that the library package should not
4807 contain any extraneous non-versioned files, unless they
4808 happen to be in versioned directories.</p>
4810 The most common mechanism is to place it in a package
4812 <package><var>libraryname</var><var>soversion</var></package>,
4813 where <file><var>soversion</var></file> is the version number
4814 in the soname of the shared library<footnote>
4815 The soname is the shared object name: it's the thing
4816 that has to match exactly between building an executable
4817 and running it for the dynamic linker to be able run the
4818 program. For example, if the soname of the library is
4819 <file>libfoo.so.6</file>, the library package would be
4820 called <file>libfoo6</file>.
4822 Alternatively, if it would be confusing to directly append
4823 <var>soversion</var> to <var>libraryname</var> (e.g. because
4824 <var>libraryname</var> itself ends in a number), you may use
4825 <package><var>libraryname</var>-<var>soversion</var></package> and
4826 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4831 If you have several shared libraries built from the same
4832 source tree you may lump them all together into a single
4833 shared library package, provided that you change all of
4834 their sonames at once (so that you don't get filename
4835 clashes if you try to install different versions of the
4836 combined shared libraries package).
4840 The package should install the shared libraries under
4841 their normal names. For example, the <package>libgdbm3</package>
4842 package should install <file>libgdbm.so.3.0.0</file> as
4843 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4844 renamed or re-linked by any <prgn>prerm</prgn> or
4845 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4846 of renaming things safely without affecting running programs,
4847 and attempts to interfere with this are likely to lead to
4852 Shared libraries should not be installed executable, since
4853 the dynamic linker does not require this and trying to
4854 execute a shared library usually results in a core dump.
4858 The run-time library package should include the symbolic link that
4859 <prgn>ldconfig</prgn> would create for the shared libraries.
4860 For example, the <package>libgdbm3</package> package should include
4861 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4862 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4863 linker (for example <prgn>ld.so</prgn> or
4864 <prgn>ld-linux.so.*</prgn>) can find the library between the
4865 time that <prgn>dpkg</prgn> installs it and the time that
4866 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4868 The package management system requires the library to be
4869 placed before the symbolic link pointing to it in the
4870 <file>.deb</file> file. This is so that when
4871 <prgn>dpkg</prgn> comes to install the symlink
4872 (overwriting the previous symlink pointing at an older
4873 version of the library), the new shared library is already
4874 in place. In the past, this was achieved by creating the
4875 library in the temporary packaging directory before
4876 creating the symlink. Unfortunately, this was not always
4877 effective, since the building of the tar file in the
4878 <file>.deb</file> depended on the behavior of the underlying
4879 file system. Some file systems (such as reiserfs) reorder
4880 the files so that the order of creation is forgotten.
4881 Since version 1.7.0, <prgn>dpkg</prgn>
4882 reorders the files itself as necessary when building a
4883 package. Thus it is no longer important to concern
4884 oneself with the order of file creation.
4888 <sect1 id="ldconfig">
4889 <heading><tt>ldconfig</tt></heading>
4892 Any package installing shared libraries in one of the default
4893 library directories of the dynamic linker (which are currently
4894 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4895 listed in <file>/etc/ld.so.conf</file><footnote>
4897 <list compact="compact">
4898 <item>/usr/local/lib</item>
4899 <item>/usr/lib/libc5-compat</item>
4900 <item>/lib/libc5-compat</item>
4903 must use <prgn>ldconfig</prgn> to update the shared library
4908 The package maintainer scripts must only call
4909 <prgn>ldconfig</prgn> under these circumstances:
4910 <list compact="compact">
4911 <item>When the <prgn>postinst</prgn> script is run with a
4912 first argument of <tt>configure</tt>, the script must call
4913 <prgn>ldconfig</prgn>, and may optionally invoke
4914 <prgn>ldconfig</prgn> at other times.
4916 <item>When the <prgn>postrm</prgn> script is run with a
4917 first argument of <tt>remove</tt>, the script should call
4918 <prgn>ldconfig</prgn>.
4923 During install or upgrade, the preinst is called before
4924 the new files are installed, so calling "ldconfig" is
4925 pointless. The preinst of an existing package can also be
4926 called if an upgrade fails. However, this happens during
4927 the critical time when a shared libs may exist on-disk
4928 under a temporary name. Thus, it is dangerous and
4929 forbidden by current policy to call "ldconfig" at this
4934 When a package is installed or upgraded, "postinst
4935 configure" runs after the new files are safely on-disk.
4936 Since it is perfectly safe to invoke ldconfig
4937 unconditionally in a postinst, it is OK for a package to
4938 simply put ldconfig in its postinst without checking the
4939 argument. The postinst can also be called to recover from
4940 a failed upgrade. This happens before any new files are
4941 unpacked, so there is no reason to call "ldconfig" at this
4946 For a package that is being removed, prerm is
4947 called with all the files intact, so calling ldconfig is
4948 useless. The other calls to "prerm" happen in the case of
4949 upgrade at a time when all the files of the old package
4950 are on-disk, so again calling "ldconfig" is pointless.
4954 postrm, on the other hand, is called with the "remove"
4955 argument just after the files are removed, so this is
4956 the proper time to call "ldconfig" to notify the system
4957 of the fact that the shared libraries from the package
4958 are removed. The postrm can be called at several other
4959 times. At the time of "postrm purge", "postrm
4960 abort-install", or "postrm abort-upgrade", calling
4961 "ldconfig" is useless because the shared lib files are
4962 not on-disk. However, when "postrm" is invoked with
4963 arguments "upgrade", "failed-upgrade", or "disappear", a
4964 shared lib may exist on-disk under a temporary filename.
4972 <sect id="sharedlibs-support-files">
4973 <heading>Shared library support files</heading>
4976 If your package contains files whose names do not change with
4977 each change in the library shared object version, you must not
4978 put them in the shared library package. Otherwise, several
4979 versions of the shared library cannot be installed at the same
4980 time without filename clashes, making upgrades and transitions
4981 unnecessarily difficult.
4985 It is recommended that supporting files and run-time support
4986 programs that do not need to be invoked manually by users, but
4987 are nevertheless required for the package to function, be placed
4988 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4989 preferably under <file>/usr/lib/</file><var>package-name</var>.
4990 If the program or file is architecture independent, the
4991 recommendation is for it to be placed in a subdirectory of
4992 <file>/usr/share</file> instead, preferably under
4993 <file>/usr/share/</file><var>package-name</var>. Following the
4994 <var>package-name</var> naming convention ensures that the file
4995 names change when the shared object version changes.
4999 Run-time support programs that use the shared library but are
5000 not required for the library to function or files used by the
5001 shared library that can be used by any version of the shared
5002 library package should instead be put in a separate package.
5003 This package might typically be named
5004 <package><var>libraryname</var>-tools</package>; note the
5005 absence of the <var>soversion</var> in the package name.
5009 Files and support programs only useful when compiling software
5010 against the library should be included in the development
5011 package for the library.<footnote>
5012 For example, a <file><var>package-name</var>-config</file>
5013 script or <package>pkg-config</package> configuration files.
5018 <sect id="sharedlibs-static">
5019 <heading>Static libraries</heading>
5022 The static library (<file><var>libraryname.a</var></file>)
5023 is usually provided in addition to the shared version.
5024 It is placed into the development package (see below).
5028 In some cases, it is acceptable for a library to be
5029 available in static form only; these cases include:
5031 <item>libraries for languages whose shared library support
5032 is immature or unstable</item>
5033 <item>libraries whose interfaces are in flux or under
5034 development (commonly the case when the library's
5035 major version number is zero, or where the ABI breaks
5036 across patchlevels)</item>
5037 <item>libraries which are explicitly intended to be
5038 available only in static form by their upstream
5043 <sect id="sharedlibs-dev">
5044 <heading>Development files</heading>
5047 The development files associated to a shared library need to be
5048 placed in a package called
5049 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5050 or if you prefer only to support one development version at a
5051 time, <package><var>libraryname</var>-dev</package>.
5055 In case several development versions of a library exist, you may
5056 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5057 <ref id="conflicts">) to ensure that the user only installs one
5058 development version at a time (as different development versions are
5059 likely to have the same header files in them, which would cause a
5060 filename clash if both were installed).
5064 The development package should contain a symlink for the associated
5065 shared library without a version number. For example, the
5066 <package>libgdbm-dev</package> package should include a symlink
5067 from <file>/usr/lib/libgdbm.so</file> to
5068 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5069 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5070 <file>libgdbm.so</file> when compiling dynamically.
5074 <sect id="sharedlibs-intradeps">
5075 <heading>Dependencies between the packages of the same library</heading>
5078 Typically the development version should have an exact
5079 version dependency on the runtime library, to make sure that
5080 compilation and linking happens correctly. The
5081 <tt>${binary:Version}</tt> substitution variable can be
5082 useful for this purpose.
5084 Previously, <tt>${Source-Version}</tt> was used, but its name
5085 was confusing and it has been deprecated since dpkg 1.13.19.
5090 <sect id="sharedlibs-shlibdeps">
5091 <heading>Dependencies between the library and other packages -
5092 the <tt>shlibs</tt> system</heading>
5095 If a package contains a binary or library which links to a
5096 shared library, we must ensure that when the package is
5097 installed on the system, all of the libraries needed are
5098 also installed. This requirement led to the creation of the
5099 <tt>shlibs</tt> system, which is very simple in its design:
5100 any package which <em>provides</em> a shared library also
5101 provides information on the package dependencies required to
5102 ensure the presence of this library, and any package which
5103 <em>uses</em> a shared library uses this information to
5104 determine the dependencies it requires. The files which
5105 contain the mapping from shared libraries to the necessary
5106 dependency information are called <file>shlibs</file> files.
5110 Thus, when a package is built which contains any shared
5111 libraries, it must provide a <file>shlibs</file> file for other
5112 packages to use, and when a package is built which contains
5113 any shared libraries or compiled binaries, it must run
5114 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5115 on these to determine the libraries used and hence the
5116 dependencies needed by this package.<footnote>
5118 In the past, the shared libraries linked to were
5119 determined by calling <prgn>ldd</prgn>, but now
5120 <prgn>objdump</prgn> is used to do this. The only
5121 change this makes to package building is that
5122 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5123 libraries, whereas in the past this was unnecessary.
5124 The rest of this footnote explains the advantage that
5129 We say that a binary <tt>foo</tt> <em>directly</em> uses
5130 a library <tt>libbar</tt> if it is explicitly linked
5131 with that library (that is, it uses the flag
5132 <tt>-lbar</tt> during the linking stage). Other
5133 libraries that are needed by <tt>libbar</tt> are linked
5134 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5135 linker will load them automatically when it loads
5136 <tt>libbar</tt>. A package should depend on
5137 the libraries it directly uses, and the dependencies for
5138 those libraries should automatically pull in the other
5143 Unfortunately, the <prgn>ldd</prgn> program shows both
5144 the directly and indirectly used libraries, meaning that
5145 the dependencies determined included both direct and
5146 indirect dependencies. The use of <prgn>objdump</prgn>
5147 avoids this problem by determining only the directly
5152 A good example of where this helps is the following. We
5153 could update <tt>libimlib</tt> with a new version that
5154 supports a new graphics format called dgf (but retaining
5155 the same major version number). If we used the old
5156 <prgn>ldd</prgn> method, every package that uses
5157 <tt>libimlib</tt> would need to be recompiled so it
5158 would also depend on <tt>libdgf</tt> or it wouldn't run
5159 due to missing symbols. However with the new system,
5160 packages using <tt>libimlib</tt> can rely on
5161 <tt>libimlib</tt> itself having the dependency on
5162 <tt>libdgf</tt> and so they would not need rebuilding.
5168 In the following sections, we will first describe where the
5169 various <tt>shlibs</tt> files are to be found, then how to
5170 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5171 file format and how to create them if your package contains a
5176 <heading>The <tt>shlibs</tt> files present on the system</heading>
5179 There are several places where <tt>shlibs</tt> files are
5180 found. The following list gives them in the order in which
5182 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5183 (The first one which gives the required information is used.)
5189 <p><file>debian/shlibs.local</file></p>
5192 This lists overrides for this package. Its use is
5193 described below (see <ref id="shlibslocal">).
5198 <p><file>/etc/dpkg/shlibs.override</file></p>
5201 This lists global overrides. This list is normally
5202 empty. It is maintained by the local system
5208 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5211 When packages are being built, any
5212 <file>debian/shlibs</file> files are copied into the
5213 control file area of the temporary build directory and
5214 given the name <file>shlibs</file>. These files give
5215 details of any shared libraries included in the
5217 An example may help here. Let us say that the
5218 source package <tt>foo</tt> generates two binary
5219 packages, <tt>libfoo2</tt> and
5220 <tt>foo-runtime</tt>. When building the binary
5221 packages, the two packages are created in the
5222 directories <file>debian/libfoo2</file> and
5223 <file>debian/foo-runtime</file> respectively.
5224 (<file>debian/tmp</file> could be used instead of one
5225 of these.) Since <tt>libfoo2</tt> provides the
5226 <tt>libfoo</tt> shared library, it will require a
5227 <tt>shlibs</tt> file, which will be installed in
5228 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5230 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5231 when <prgn>dpkg-shlibdeps</prgn> is run on the
5233 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5235 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5236 determine whether <tt>foo-prog</tt>'s library
5237 dependencies are satisfied by any of the libraries
5238 provided by <tt>libfoo2</tt>. For this reason,
5239 <prgn>dpkg-shlibdeps</prgn> must only be run once
5240 all of the individual binary packages'
5241 <tt>shlibs</tt> files have been installed into the
5248 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5251 These are the <file>shlibs</file> files corresponding to
5252 all of the packages installed on the system, and are
5253 maintained by the relevant package maintainers.
5258 <p><file>/etc/dpkg/shlibs.default</file></p>
5261 This file lists any shared libraries whose packages
5262 have failed to provide correct <file>shlibs</file> files.
5263 It was used when the <file>shlibs</file> setup was first
5264 introduced, but it is now normally empty. It is
5265 maintained by the <tt>dpkg</tt> maintainer.
5273 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5274 <file>shlibs</file> files</heading>
5278 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5279 into your <file>debian/rules</file> file. If your package
5280 contains only compiled binaries and libraries (but no scripts),
5281 you can use a command such as:
5282 <example compact="compact">
5283 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5284 debian/tmp/usr/lib/*
5286 Otherwise, you will need to explicitly list the compiled
5287 binaries and libraries.<footnote>
5288 If you are using <tt>debhelper</tt>, the
5289 <prgn>dh_shlibdeps</prgn> program will do this work for
5290 you. It will also correctly handle multi-binary
5296 This command puts the dependency information into the
5297 <file>debian/substvars</file> file, which is then used by
5298 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5299 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5300 field in the control file for this to work.
5304 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5305 done. If it does complain you might need to create your own
5306 <file>debian/shlibs.local</file> file, as explained below (see
5307 <ref id="shlibslocal">).
5311 If you have multiple binary packages, you will need to call
5312 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5313 compiled libraries or binaries. In such a case, you will
5314 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5315 utilities to specify a different <file>substvars</file> file.
5319 If you are creating a udeb for use in the Debian Installer, you
5320 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5321 the dependency line of type <tt>udeb</tt> by adding
5322 <tt>-tudeb</tt> as option<footnote>
5323 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5324 will automatically add this option if it knows it is
5326 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5327 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5328 fall back to the regular dependency line.
5332 For more details on dpkg-shlibdeps, please see
5333 <ref id="pkg-dpkg-shlibdeps"> and
5334 <manref name="dpkg-shlibdeps" section="1">.
5339 <heading>The <file>shlibs</file> File Format</heading>
5342 Each <file>shlibs</file> file has the same format. Lines
5343 beginning with <tt>#</tt> are considered to be comments and
5344 are ignored. Each line is of the form:
5345 <example compact="compact">
5346 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5351 We will explain this by reference to the example of the
5352 <tt>zlib1g</tt> package, which (at the time of writing)
5353 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5357 <var>type</var> is an optional element that indicates the type
5358 of package for which the line is valid. The only type currently
5359 in use is <tt>udeb</tt>. The colon and space after the type are
5364 <var>library-name</var> is the name of the shared library,
5365 in this case <tt>libz</tt>. (This must match the name part
5366 of the soname, see below.)
5370 <var>soname-version</var> is the version part of the soname of
5371 the library. The soname is the thing that must exactly match
5372 for the library to be recognized by the dynamic linker, and is
5374 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5375 example, <tt>libz.so.1</tt>.<footnote>
5376 This can be determined using the command
5377 <example compact="compact">
5378 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5381 The version part is the part which comes after
5382 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5386 <var>dependencies</var> has the same syntax as a dependency
5387 field in a binary package control file. It should give
5388 details of which packages are required to satisfy a binary
5389 built against the version of the library contained in the
5390 package. See <ref id="depsyntax"> for details.
5394 In our example, if the first version of the <tt>zlib1g</tt>
5395 package which contained a minor number of at least
5396 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5397 <tt>shlibs</tt> entry for this library could say:
5398 <example compact="compact">
5399 libz 1 zlib1g (>= 1:1.1.3)
5401 The version-specific dependency is to avoid warnings from
5402 the dynamic linker about using older shared libraries with
5407 As zlib1g also provides a udeb containing the shared library,
5408 there would also be a second line:
5409 <example compact="compact">
5410 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5416 <heading>Providing a <file>shlibs</file> file</heading>
5419 If your package provides a shared library, you need to create
5420 a <file>shlibs</file> file following the format described above.
5421 It is usual to call this file <file>debian/shlibs</file> (but if
5422 you have multiple binary packages, you might want to call it
5423 <file>debian/shlibs.<var>package</var></file> instead). Then
5424 let <file>debian/rules</file> install it in the control area:
5425 <example compact="compact">
5426 install -m644 debian/shlibs debian/tmp/DEBIAN
5428 or, in the case of a multi-binary package:
5429 <example compact="compact">
5430 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5432 An alternative way of doing this is to create the
5433 <file>shlibs</file> file in the control area directly from
5434 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5435 file at all,<footnote>
5436 This is what <prgn>dh_makeshlibs</prgn> in the
5437 <tt>debhelper</tt> suite does. If your package also has a udeb
5438 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5439 automatically generate the <tt>udeb:</tt> lines if you specify
5440 the name of the udeb with the <tt>--add-udeb</tt> option.
5442 since the <file>debian/shlibs</file> file itself is ignored by
5443 <prgn>dpkg-shlibdeps</prgn>.
5447 As <prgn>dpkg-shlibdeps</prgn> reads the
5448 <file>DEBIAN/shlibs</file> files in all of the binary packages
5449 being built from this source package, all of the
5450 <file>DEBIAN/shlibs</file> files should be installed before
5451 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5456 <sect1 id="shlibslocal">
5457 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5460 This file is intended only as a <em>temporary</em> fix if
5461 your binaries or libraries depend on a library whose package
5462 does not yet provide a correct <file>shlibs</file> file.
5466 We will assume that you are trying to package a binary
5467 <tt>foo</tt>. When you try running
5468 <prgn>dpkg-shlibdeps</prgn> you get the following error
5469 message (<tt>-O</tt> displays the dependency information on
5470 <tt>stdout</tt> instead of writing it to
5471 <tt>debian/substvars</tt>, and the lines have been wrapped
5472 for ease of reading):
5473 <example compact="compact">
5474 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5475 dpkg-shlibdeps: warning: unable to find dependency
5476 information for shared library libbar (soname 1,
5477 path /usr/lib/libbar.so.1, dependency field Depends)
5478 shlibs:Depends=libc6 (>= 2.2.2-2)
5480 You can then run <prgn>ldd</prgn> on the binary to find the
5481 full location of the library concerned:
5482 <example compact="compact">
5484 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5485 libc.so.6 => /lib/libc.so.6 (0x40032000)
5486 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5488 So the <prgn>foo</prgn> binary depends on the
5489 <prgn>libbar</prgn> shared library, but no package seems to
5490 provide a <file>*.shlibs</file> file handling
5491 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5492 determine the package responsible:
5493 <example compact="compact">
5494 $ dpkg -S /usr/lib/libbar.so.1
5495 bar1: /usr/lib/libbar.so.1
5496 $ dpkg -s bar1 | grep Version
5499 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5500 is the one we are using. Now we can file a bug against the
5501 <tt>bar1</tt> package and create our own
5502 <file>debian/shlibs.local</file> to locally fix the problem.
5503 Including the following line into your
5504 <file>debian/shlibs.local</file> file:
5505 <example compact="compact">
5506 libbar 1 bar1 (>= 1.0-1)
5508 should allow the package build to work.
5512 As soon as the maintainer of <tt>bar1</tt> provides a
5513 correct <file>shlibs</file> file, you should remove this line
5514 from your <file>debian/shlibs.local</file> file. (You should
5515 probably also then have a versioned <tt>Build-Depends</tt>
5516 on <tt>bar1</tt> to help ensure that others do not have the
5517 same problem building your package.)
5526 <chapt id="opersys"><heading>The Operating System</heading>
5529 <heading>File system hierarchy</heading>
5533 <heading>File System Structure</heading>
5536 The location of all installed files and directories must
5537 comply with the Filesystem Hierarchy Standard (FHS),
5538 version 2.3, with the exceptions noted below, and except
5539 where doing so would violate other terms of Debian
5540 Policy. The following exceptions to the FHS apply:
5545 The optional rules related to user specific
5546 configuration files for applications are stored in
5547 the user's home directory are relaxed. It is
5548 recommended that such files start with the
5549 '<tt>.</tt>' character (a "dot file"), and if an
5550 application needs to create more than one dot file
5551 then the preferred placement is in a subdirectory
5552 with a name starting with a '.' character, (a "dot
5553 directory"). In this case it is recommended the
5554 configuration files not start with the '.'
5560 The requirement for amd64 to use <file>/lib64</file>
5561 for 64 bit binaries is removed.
5566 The requirement that
5567 <file>/usr/local/share/man</file> be "synonymous"
5568 with <file>/usr/local/man</file> is relaxed to a
5573 The requirement that windowmanagers with a single
5574 configuration file call it <file>system.*wmrc</file>
5575 is removed, as is the restriction that the window
5576 manager subdirectory be named identically to the
5577 window manager name itself.
5582 The requirement that boot manager configuration
5583 files live in <file>/etc</file>, or at least are
5584 symlinked there, is relaxed to a recommendation.
5591 The version of this document referred here can be
5592 found in the <tt>debian-policy</tt> package or on <url
5593 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5594 name="FHS (Debian copy)"> alongside this manual (or, if
5595 you have the <package>debian-policy</package> installed,
5597 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5598 (local copy)">). The
5599 latest version, which may be a more recent version, may
5601 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5602 Specific questions about following the standard may be
5603 asked on the <tt>debian-devel</tt> mailing list, or
5604 referred to the FHS mailing list (see the
5605 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5611 <heading>Site-specific programs</heading>
5614 As mandated by the FHS, packages must not place any
5615 files in <file>/usr/local</file>, either by putting them in
5616 the file system archive to be unpacked by <prgn>dpkg</prgn>
5617 or by manipulating them in their maintainer scripts.
5621 However, the package may create empty directories below
5622 <file>/usr/local</file> so that the system administrator knows
5623 where to place site-specific files. These are not
5624 directories <em>in</em> <file>/usr/local</file>, but are
5625 children of directories in <file>/usr/local</file>. These
5626 directories (<file>/usr/local/*/dir/</file>)
5627 should be removed on package removal if they are
5632 Note, that this applies only to directories <em>below</em>
5633 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5634 Packages must not create sub-directories in the directory
5635 <file>/usr/local</file> itself, except those listed in FHS,
5636 section 4.5. However, you may create directories below
5637 them as you wish. You must not remove any of the
5638 directories listed in 4.5, even if you created them.
5642 Since <file>/usr/local</file> can be mounted read-only from a
5643 remote server, these directories must be created and
5644 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5645 maintainer scripts and not be included in the
5646 <file>.deb</file> archive. These scripts must not fail if
5647 either of these operations fail.
5651 For example, the <tt>emacsen-common</tt> package could
5652 contain something like
5653 <example compact="compact">
5654 if [ ! -e /usr/local/share/emacs ]
5656 if mkdir /usr/local/share/emacs 2>/dev/null
5658 chown root:staff /usr/local/share/emacs
5659 chmod 2775 /usr/local/share/emacs
5663 in its <prgn>postinst</prgn> script, and
5664 <example compact="compact">
5665 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5666 rmdir /usr/local/share/emacs 2>/dev/null || true
5668 in the <prgn>prerm</prgn> script. (Note that this form is
5669 used to ensure that if the script is interrupted, the
5670 directory <file>/usr/local/share/emacs</file> will still be
5675 If you do create a directory in <file>/usr/local</file> for
5676 local additions to a package, you should ensure that
5677 settings in <file>/usr/local</file> take precedence over the
5678 equivalents in <file>/usr</file>.
5682 However, because <file>/usr/local</file> and its contents are
5683 for exclusive use of the local administrator, a package
5684 must not rely on the presence or absence of files or
5685 directories in <file>/usr/local</file> for normal operation.
5689 The <file>/usr/local</file> directory itself and all the
5690 subdirectories created by the package should (by default) have
5691 permissions 2775 (group-writable and set-group-id) and be
5692 owned by <tt>root:staff</tt>.
5697 <heading>The system-wide mail directory</heading>
5699 The system-wide mail directory is <file>/var/mail</file>. This
5700 directory is part of the base system and should not owned
5701 by any particular mail agents. The use of the old
5702 location <file>/var/spool/mail</file> is deprecated, even
5703 though the spool may still be physically located there.
5709 <heading>Users and groups</heading>
5712 <heading>Introduction</heading>
5714 The Debian system can be configured to use either plain or
5719 Some user ids (UIDs) and group ids (GIDs) are reserved
5720 globally for use by certain packages. Because some
5721 packages need to include files which are owned by these
5722 users or groups, or need the ids compiled into binaries,
5723 these ids must be used on any Debian system only for the
5724 purpose for which they are allocated. This is a serious
5725 restriction, and we should avoid getting in the way of
5726 local administration policies. In particular, many sites
5727 allocate users and/or local system groups starting at 100.
5731 Apart from this we should have dynamically allocated ids,
5732 which should by default be arranged in some sensible
5733 order, but the behavior should be configurable.
5737 Packages other than <tt>base-passwd</tt> must not modify
5738 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5739 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5744 <heading>UID and GID classes</heading>
5746 The UID and GID numbers are divided into classes as
5752 Globally allocated by the Debian project, the same
5753 on every Debian system. These ids will appear in
5754 the <file>passwd</file> and <file>group</file> files of all
5755 Debian systems, new ids in this range being added
5756 automatically as the <tt>base-passwd</tt> package is
5761 Packages which need a single statically allocated
5762 uid or gid should use one of these; their
5763 maintainers should ask the <tt>base-passwd</tt>
5771 Dynamically allocated system users and groups.
5772 Packages which need a user or group, but can have
5773 this user or group allocated dynamically and
5774 differently on each system, should use <tt>adduser
5775 --system</tt> to create the group and/or user.
5776 <prgn>adduser</prgn> will check for the existence of
5777 the user or group, and if necessary choose an unused
5778 id based on the ranges specified in
5779 <file>adduser.conf</file>.
5783 <tag>1000-29999:</tag>
5786 Dynamically allocated user accounts. By default
5787 <prgn>adduser</prgn> will choose UIDs and GIDs for
5788 user accounts in this range, though
5789 <file>adduser.conf</file> may be used to modify this
5794 <tag>30000-59999:</tag>
5799 <tag>60000-64999:</tag>
5802 Globally allocated by the Debian project, but only
5803 created on demand. The ids are allocated centrally
5804 and statically, but the actual accounts are only
5805 created on users' systems on demand.
5809 These ids are for packages which are obscure or
5810 which require many statically-allocated ids. These
5811 packages should check for and create the accounts in
5812 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5813 <prgn>adduser</prgn> if it has this facility) if
5814 necessary. Packages which are likely to require
5815 further allocations should have a "hole" left after
5816 them in the allocation, to give them room to
5821 <tag>65000-65533:</tag>
5829 User <tt>nobody</tt>. The corresponding gid refers
5830 to the group <tt>nogroup</tt>.
5837 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5838 not</em> be used, because it is the error return
5847 <sect id="sysvinit">
5848 <heading>System run levels and <file>init.d</file> scripts</heading>
5850 <sect1 id="/etc/init.d">
5851 <heading>Introduction</heading>
5854 The <file>/etc/init.d</file> directory contains the scripts
5855 executed by <prgn>init</prgn> at boot time and when the
5856 init state (or "runlevel") is changed (see <manref
5857 name="init" section="8">).
5861 There are at least two different, yet functionally
5862 equivalent, ways of handling these scripts. For the sake
5863 of simplicity, this document describes only the symbolic
5864 link method. However, it must not be assumed by maintainer
5865 scripts that this method is being used, and any automated
5866 manipulation of the various runlevel behaviors by
5867 maintainer scripts must be performed using
5868 <prgn>update-rc.d</prgn> as described below and not by
5869 manually installing or removing symlinks. For information
5870 on the implementation details of the other method,
5871 implemented in the <tt>file-rc</tt> package, please refer
5872 to the documentation of that package.
5876 These scripts are referenced by symbolic links in the
5877 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5878 runlevels, <prgn>init</prgn> looks in the directory
5879 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5880 execute, where <tt><var>n</var></tt> is the runlevel that
5881 is being changed to, or <tt>S</tt> for the boot-up
5886 The names of the links all have the form
5887 <file>S<var>mm</var><var>script</var></file> or
5888 <file>K<var>mm</var><var>script</var></file> where
5889 <var>mm</var> is a two-digit number and <var>script</var>
5890 is the name of the script (this should be the same as the
5891 name of the actual script in <file>/etc/init.d</file>).
5895 When <prgn>init</prgn> changes runlevel first the targets
5896 of the links whose names start with a <tt>K</tt> are
5897 executed, each with the single argument <tt>stop</tt>,
5898 followed by the scripts prefixed with an <tt>S</tt>, each
5899 with the single argument <tt>start</tt>. (The links are
5900 those in the <file>/etc/rc<var>n</var>.d</file> directory
5901 corresponding to the new runlevel.) The <tt>K</tt> links
5902 are responsible for killing services and the <tt>S</tt>
5903 link for starting services upon entering the runlevel.
5907 For example, if we are changing from runlevel 2 to
5908 runlevel 3, init will first execute all of the <tt>K</tt>
5909 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5910 all of the <tt>S</tt> prefixed scripts in that directory.
5911 The links starting with <tt>K</tt> will cause the
5912 referred-to file to be executed with an argument of
5913 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5918 The two-digit number <var>mm</var> is used to determine
5919 the order in which to run the scripts: low-numbered links
5920 have their scripts run first. For example, the
5921 <tt>K20</tt> scripts will be executed before the
5922 <tt>K30</tt> scripts. This is used when a certain service
5923 must be started before another. For example, the name
5924 server <prgn>bind</prgn> might need to be started before
5925 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5926 can set up its access lists. In this case, the script
5927 that starts <prgn>bind</prgn> would have a lower number
5928 than the script that starts <prgn>inn</prgn> so that it
5930 <example compact="compact">
5937 The two runlevels 0 (halt) and 6 (reboot) are slightly
5938 different. In these runlevels, the links with an
5939 <tt>S</tt> prefix are still called after those with a
5940 <tt>K</tt> prefix, but they too are called with the single
5941 argument <tt>stop</tt>.
5946 <heading>Writing the scripts</heading>
5949 Packages that include daemons for system services should
5950 place scripts in <file>/etc/init.d</file> to start or stop
5951 services at boot time or during a change of runlevel.
5952 These scripts should be named
5953 <file>/etc/init.d/<var>package</var></file>, and they should
5954 accept one argument, saying what to do:
5957 <tag><tt>start</tt></tag>
5958 <item>start the service,</item>
5960 <tag><tt>stop</tt></tag>
5961 <item>stop the service,</item>
5963 <tag><tt>restart</tt></tag>
5964 <item>stop and restart the service if it's already running,
5965 otherwise start the service</item>
5967 <tag><tt>reload</tt></tag>
5968 <item><p>cause the configuration of the service to be
5969 reloaded without actually stopping and restarting
5972 <tag><tt>force-reload</tt></tag>
5973 <item>cause the configuration to be reloaded if the
5974 service supports this, otherwise restart the
5978 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5979 <tt>force-reload</tt> options should be supported by all
5980 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5985 The <file>init.d</file> scripts must ensure that they will
5986 behave sensibly (i.e., returning success and not starting
5987 multiple copies of a service) if invoked with <tt>start</tt>
5988 when the service is already running, or with <tt>stop</tt>
5989 when it isn't, and that they don't kill unfortunately-named
5990 user processes. The best way to achieve this is usually to
5991 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5996 If a service reloads its configuration automatically (as
5997 in the case of <prgn>cron</prgn>, for example), the
5998 <tt>reload</tt> option of the <file>init.d</file> script
5999 should behave as if the configuration has been reloaded
6004 The <file>/etc/init.d</file> scripts must be treated as
6005 configuration files, either (if they are present in the
6006 package, that is, in the .deb file) by marking them as
6007 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6008 by managing them correctly in the maintainer scripts (see
6009 <ref id="config-files">). This is important since we want
6010 to give the local system administrator the chance to adapt
6011 the scripts to the local system, e.g., to disable a
6012 service without de-installing the package, or to specify
6013 some special command line options when starting a service,
6014 while making sure their changes aren't lost during the next
6019 These scripts should not fail obscurely when the
6020 configuration files remain but the package has been
6021 removed, as configuration files remain on the system after
6022 the package has been removed. Only when <prgn>dpkg</prgn>
6023 is executed with the <tt>--purge</tt> option will
6024 configuration files be removed. In particular, as the
6025 <file>/etc/init.d/<var>package</var></file> script itself is
6026 usually a <tt>conffile</tt>, it will remain on the system
6027 if the package is removed but not purged. Therefore, you
6028 should include a <tt>test</tt> statement at the top of the
6030 <example compact="compact">
6031 test -f <var>program-executed-later-in-script</var> || exit 0
6036 Often there are some variables in the <file>init.d</file>
6037 scripts whose values control the behavior of the scripts,
6038 and which a system administrator is likely to want to
6039 change. As the scripts themselves are frequently
6040 <tt>conffile</tt>s, modifying them requires that the
6041 administrator merge in their changes each time the package
6042 is upgraded and the <tt>conffile</tt> changes. To ease
6043 the burden on the system administrator, such configurable
6044 values should not be placed directly in the script.
6045 Instead, they should be placed in a file in
6046 <file>/etc/default</file>, which typically will have the same
6047 base name as the <file>init.d</file> script. This extra file
6048 should be sourced by the script when the script runs. It
6049 must contain only variable settings and comments in SUSv3
6050 <prgn>sh</prgn> format. It may either be a
6051 <tt>conffile</tt> or a configuration file maintained by
6052 the package maintainer scripts. See <ref id="config-files">
6057 To ensure that vital configurable values are always
6058 available, the <file>init.d</file> script should set default
6059 values for each of the shell variables it uses, either
6060 before sourcing the <file>/etc/default/</file> file or
6061 afterwards using something like the <tt>:
6062 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6063 script must behave sensibly and not fail if the
6064 <file>/etc/default</file> file is deleted.
6068 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6069 as temporary filesystems<footnote>
6070 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6071 options in <file>/etc/default/rcS</file>.
6072 </footnote>, so the <file>init.d</file> scripts must handle this
6073 correctly. This will typically amount to creating any required
6074 subdirectories dynamically when the <file>init.d</file> script
6075 is run, rather than including them in the package and relying on
6076 <prgn>dpkg</prgn> to create them.
6081 <heading>Interfacing with the initscript system</heading>
6084 Maintainers should use the abstraction layer provided by
6085 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6086 programs to deal with initscripts in their packages'
6087 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6088 and <prgn>postrm</prgn>.
6092 Directly managing the /etc/rc?.d links and directly
6093 invoking the <file>/etc/init.d/</file> initscripts should
6094 be done only by packages providing the initscript
6095 subsystem (such as <prgn>sysv-rc</prgn> and
6096 <prgn>file-rc</prgn>).
6100 <heading>Managing the links</heading>
6103 The program <prgn>update-rc.d</prgn> is provided for
6104 package maintainers to arrange for the proper creation and
6105 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6106 or their functional equivalent if another method is being
6107 used. This may be used by maintainers in their packages'
6108 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6112 You must not include any <file>/etc/rc<var>n</var>.d</file>
6113 symbolic links in the actual archive or manually create or
6114 remove the symbolic links in maintainer scripts; you must
6115 use the <prgn>update-rc.d</prgn> program instead. (The
6116 former will fail if an alternative method of maintaining
6117 runlevel information is being used.) You must not include
6118 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6119 in the archive either. (Only the <tt>sysvinit</tt>
6124 By default <prgn>update-rc.d</prgn> will start services in
6125 each of the multi-user state runlevels (2, 3, 4, and 5)
6126 and stop them in the halt runlevel (0), the single-user
6127 runlevel (1) and the reboot runlevel (6). The system
6128 administrator will have the opportunity to customize
6129 runlevels by simply adding, moving, or removing the
6130 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6131 symbolic links are being used, or by modifying
6132 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6137 To get the default behavior for your package, put in your
6138 <prgn>postinst</prgn> script
6139 <example compact="compact">
6140 update-rc.d <var>package</var> defaults
6142 and in your <prgn>postrm</prgn>
6143 <example compact="compact">
6144 if [ "$1" = purge ]; then
6145 update-rc.d <var>package</var> remove
6147 </example>. Note that if your package changes runlevels
6148 or priority, you may have to remove and recreate the links,
6149 since otherwise the old links may persist. Refer to the
6150 documentation of <prgn>update-rc.d</prgn>.
6154 This will use a default sequence number of 20. If it does
6155 not matter when or in which order the <file>init.d</file>
6156 script is run, use this default. If it does, then you
6157 should talk to the maintainer of the <prgn>sysvinit</prgn>
6158 package or post to <tt>debian-devel</tt>, and they will
6159 help you choose a number.
6163 For more information about using <tt>update-rc.d</tt>,
6164 please consult its man page <manref name="update-rc.d"
6170 <heading>Running initscripts</heading>
6172 The program <prgn>invoke-rc.d</prgn> is provided to make
6173 it easier for package maintainers to properly invoke an
6174 initscript, obeying runlevel and other locally-defined
6175 constraints that might limit a package's right to start,
6176 stop and otherwise manage services. This program may be
6177 used by maintainers in their packages' scripts.
6181 The package maintainer scripts must use
6182 <prgn>invoke-rc.d</prgn> to invoke the
6183 <file>/etc/init.d/*</file> initscripts, instead of
6184 calling them directly.
6188 By default, <prgn>invoke-rc.d</prgn> will pass any
6189 action requests (start, stop, reload, restart...) to the
6190 <file>/etc/init.d</file> script, filtering out requests
6191 to start or restart a service out of its intended
6196 Most packages will simply need to change:
6197 <example compact="compact">/etc/init.d/<package>
6198 <action></example> in their <prgn>postinst</prgn>
6199 and <prgn>prerm</prgn> scripts to:
6200 <example compact="compact">
6201 if which invoke-rc.d >/dev/null 2>&1; then
6202 invoke-rc.d <var>package</var> <action>
6204 /etc/init.d/<var>package</var> <action>
6210 A package should register its initscript services using
6211 <prgn>update-rc.d</prgn> before it tries to invoke them
6212 using <prgn>invoke-rc.d</prgn>. Invocation of
6213 unregistered services may fail.
6217 For more information about using
6218 <prgn>invoke-rc.d</prgn>, please consult its man page
6219 <manref name="invoke-rc.d" section="8">.
6225 <heading>Boot-time initialization</heading>
6228 There used to be another directory, <file>/etc/rc.boot</file>,
6229 which contained scripts which were run once per machine
6230 boot. This has been deprecated in favour of links from
6231 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6232 described in <ref id="/etc/init.d">. Packages must not
6233 place files in <file>/etc/rc.boot</file>.
6238 <heading>Example</heading>
6241 An example on which you can base your
6242 <file>/etc/init.d</file> scripts is found in
6243 <file>/etc/init.d/skeleton</file>.
6250 <heading>Console messages from <file>init.d</file> scripts</heading>
6253 This section describes the formats to be used for messages
6254 written to standard output by the <file>/etc/init.d</file>
6255 scripts. The intent is to improve the consistency of
6256 Debian's startup and shutdown look and feel. For this
6257 reason, please look very carefully at the details. We want
6258 the messages to have the same format in terms of wording,
6259 spaces, punctuation and case of letters.
6263 Here is a list of overall rules that should be used for
6264 messages generated by <file>/etc/init.d</file> scripts.
6270 The message should fit in one line (fewer than 80
6271 characters), start with a capital letter and end with
6272 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6276 If the script is performing some time consuming task in
6277 the background (not merely starting or stopping a
6278 program, for instance), an ellipsis (three dots:
6279 <tt>...</tt>) should be output to the screen, with no
6280 leading or tailing whitespace or line feeds.
6284 The messages should appear as if the computer is telling
6285 the user what it is doing (politely :-), but should not
6286 mention "it" directly. For example, instead of:
6287 <example compact="compact">
6288 I'm starting network daemons: nfsd mountd.
6290 the message should say
6291 <example compact="compact">
6292 Starting network daemons: nfsd mountd.
6299 <tt>init.d</tt> script should use the following standard
6300 message formats for the situations enumerated below.
6306 <p>When daemons are started</p>
6309 If the script starts one or more daemons, the output
6310 should look like this (a single line, no leading
6312 <example compact="compact">
6313 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6315 The <var>description</var> should describe the
6316 subsystem the daemon or set of daemons are part of,
6317 while <var>daemon-1</var> up to <var>daemon-n</var>
6318 denote each daemon's name (typically the file name of
6323 For example, the output of <file>/etc/init.d/lpd</file>
6325 <example compact="compact">
6326 Starting printer spooler: lpd.
6331 This can be achieved by saying
6332 <example compact="compact">
6333 echo -n "Starting printer spooler: lpd"
6334 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6337 in the script. If there are more than one daemon to
6338 start, the output should look like this:
6339 <example compact="compact">
6340 echo -n "Starting remote file system services:"
6341 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6342 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6343 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6346 This makes it possible for the user to see what is
6347 happening and when the final daemon has been started.
6348 Care should be taken in the placement of white spaces:
6349 in the example above the system administrators can
6350 easily comment out a line if they don't want to start
6351 a specific daemon, while the displayed message still
6357 <p>When a system parameter is being set</p>
6360 If you have to set up different system parameters
6361 during the system boot, you should use this format:
6362 <example compact="compact">
6363 Setting <var>parameter</var> to "<var>value</var>".
6368 You can use a statement such as the following to get
6370 <example compact="compact">
6371 echo "Setting DNS domainname to \"$domainname\"."
6376 Note that the same symbol (<tt>"</tt>) is used for the left
6377 and right quotation marks. A grave accent (<tt>`</tt>) is
6378 not a quote character; neither is an apostrophe
6384 <p>When a daemon is stopped or restarted</p>
6387 When you stop or restart a daemon, you should issue a
6388 message identical to the startup message, except that
6389 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6390 or <tt>Restarting</tt> respectively.
6394 For example, stopping the printer daemon will look like
6396 <example compact="compact">
6397 Stopping printer spooler: lpd.
6403 <p>When something is executed</p>
6406 There are several examples where you have to run a
6407 program at system startup or shutdown to perform a
6408 specific task, for example, setting the system's clock
6409 using <prgn>netdate</prgn> or killing all processes
6410 when the system shuts down. Your message should look
6412 <example compact="compact">
6413 Doing something very useful...done.
6415 You should print the <tt>done.</tt> immediately after
6416 the job has been completed, so that the user is
6417 informed why they have to wait. You can get this
6419 <example compact="compact">
6420 echo -n "Doing something very useful..."
6429 <p>When the configuration is reloaded</p>
6432 When a daemon is forced to reload its configuration
6433 files you should use the following format:
6434 <example compact="compact">
6435 Reloading <var>description</var> configuration...done.
6437 where <var>description</var> is the same as in the
6438 daemon starting message.
6446 <heading>Cron jobs</heading>
6449 Packages must not modify the configuration file
6450 <file>/etc/crontab</file>, and they must not modify the files in
6451 <file>/var/spool/cron/crontabs</file>.</p>
6454 If a package wants to install a job that has to be executed
6455 via cron, it should place a file with the name of the
6456 package in one or more of the following directories:
6457 <example compact="compact">
6463 As these directory names imply, the files within them are
6464 executed on an hourly, daily, weekly, or monthly basis,
6465 respectively. The exact times are listed in
6466 <file>/etc/crontab</file>.</p>
6469 All files installed in any of these directories must be
6470 scripts (e.g., shell scripts or Perl scripts) so that they
6471 can easily be modified by the local system administrator.
6472 In addition, they must be treated as configuration files.
6476 If a certain job has to be executed at some other frequency or
6477 at a specific time, the package should install a file
6478 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6479 same syntax as <file>/etc/crontab</file> and is processed by
6480 <prgn>cron</prgn> automatically. The file must also be
6481 treated as a configuration file. (Note that entries in the
6482 <file>/etc/cron.d</file> directory are not handled by
6483 <prgn>anacron</prgn>. Thus, you should only use this
6484 directory for jobs which may be skipped if the system is not
6488 The scripts or crontab entries in these directories should
6489 check if all necessary programs are installed before they
6490 try to execute them. Otherwise, problems will arise when a
6491 package was removed but not purged since configuration files
6492 are kept on the system in this situation.</p>
6496 <heading>Menus</heading>
6499 The Debian <tt>menu</tt> package provides a standard
6500 interface between packages providing applications and
6501 <em>menu programs</em> (either X window managers or
6502 text-based menu programs such as <prgn>pdmenu</prgn>).
6506 All packages that provide applications that need not be
6507 passed any special command line arguments for normal
6508 operation should register a menu entry for those
6509 applications, so that users of the <tt>menu</tt> package
6510 will automatically get menu entries in their window
6511 managers, as well in shells like <tt>pdmenu</tt>.
6515 Menu entries should follow the current menu policy.
6519 The menu policy can be found in the <tt>menu-policy</tt>
6520 files in the <tt>debian-policy</tt> package.
6521 It is also available from the Debian web mirrors at
6522 <tt><url name="/doc/packaging-manuals/menu-policy/"
6523 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6527 Please also refer to the <em>Debian Menu System</em>
6528 documentation that comes with the <package>menu</package>
6529 package for information about how to register your
6535 <heading>Multimedia handlers</heading>
6538 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6539 is a mechanism for encoding files and data streams and
6540 providing meta-information about them, in particular their
6541 type (e.g. audio or video) and format (e.g. PNG, HTML,
6546 Registration of MIME type handlers allows programs like mail
6547 user agents and web browsers to invoke these handlers to
6548 view, edit or display MIME types they don't support directly.
6552 Packages which provide the ability to view/show/play,
6553 compose, edit or print MIME types should register themselves
6554 as such following the current MIME support policy.
6558 The MIME support policy can be found in the <tt>mime-policy</tt>
6559 files in the <tt>debian-policy</tt> package.
6560 It is also available from the Debian web mirrors at
6561 <tt><url name="/doc/packaging-manuals/mime-policy/"
6562 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6568 <heading>Keyboard configuration</heading>
6571 To achieve a consistent keyboard configuration so that all
6572 applications interpret a keyboard event the same way, all
6573 programs in the Debian distribution must be configured to
6574 comply with the following guidelines.
6578 The following keys must have the specified interpretations:
6581 <tag><tt><--</tt></tag>
6582 <item>delete the character to the left of the cursor</item>
6584 <tag><tt>Delete</tt></tag>
6585 <item>delete the character to the right of the cursor</item>
6587 <tag><tt>Control+H</tt></tag>
6588 <item>emacs: the help prefix</item>
6591 The interpretation of any keyboard events should be
6592 independent of the terminal that is used, be it a virtual
6593 console, an X terminal emulator, an rlogin/telnet session,
6598 The following list explains how the different programs
6599 should be set up to achieve this:
6605 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6609 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6613 X translations are set up to make
6614 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6615 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6616 is the vt220 escape code for the "delete character"
6617 key). This must be done by loading the X resources
6618 using <prgn>xrdb</prgn> on all local X displays, not
6619 using the application defaults, so that the
6620 translation resources used correspond to the
6621 <prgn>xmodmap</prgn> settings.
6625 The Linux console is configured to make
6626 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6627 generate <tt>ESC [ 3 ~</tt>.
6631 X applications are configured so that <tt><</tt>
6632 deletes left, and <tt>Delete</tt> deletes right. Motif
6633 applications already work like this.
6637 Terminals should have <tt>stty erase ^?</tt> .
6641 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6642 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6643 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6647 Emacs is programmed to map <tt>KB_Backspace</tt> or
6648 the <tt>stty erase</tt> character to
6649 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6650 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6651 <tt>^H</tt> to <tt>help</tt> as always.
6655 Other applications use the <tt>stty erase</tt>
6656 character and <tt>kdch1</tt> for the two delete keys,
6657 with ASCII DEL being "delete previous character" and
6658 <tt>kdch1</tt> being "delete character under
6666 This will solve the problem except for the following
6673 Some terminals have a <tt><--</tt> key that cannot
6674 be made to produce anything except <tt>^H</tt>. On
6675 these terminals Emacs help will be unavailable on
6676 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6677 character takes precedence in Emacs, and has been set
6678 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6679 available) can be used instead.
6683 Some operating systems use <tt>^H</tt> for <tt>stty
6684 erase</tt>. However, modern telnet versions and all
6685 rlogin versions propagate <tt>stty</tt> settings, and
6686 almost all UNIX versions honour <tt>stty erase</tt>.
6687 Where the <tt>stty</tt> settings are not propagated
6688 correctly, things can be made to work by using
6689 <tt>stty</tt> manually.
6693 Some systems (including previous Debian versions) use
6694 <prgn>xmodmap</prgn> to arrange for both
6695 <tt><--</tt> and <tt>Delete</tt> to generate
6696 <tt>KB_Delete</tt>. We can change the behavior of
6697 their X clients using the same X resources that we use
6698 to do it for our own clients, or configure our clients
6699 using their resources when things are the other way
6700 around. On displays configured like this
6701 <tt>Delete</tt> will not work, but <tt><--</tt>
6706 Some operating systems have different <tt>kdch1</tt>
6707 settings in their <tt>terminfo</tt> database for
6708 <tt>xterm</tt> and others. On these systems the
6709 <tt>Delete</tt> key will not work correctly when you
6710 log in from a system conforming to our policy, but
6711 <tt><--</tt> will.
6718 <heading>Environment variables</heading>
6721 A program must not depend on environment variables to get
6722 reasonable defaults. (That's because these environment
6723 variables would have to be set in a system-wide
6724 configuration file like <file>/etc/profile</file>, which is not
6725 supported by all shells.)
6729 If a program usually depends on environment variables for its
6730 configuration, the program should be changed to fall back to
6731 a reasonable default configuration if these environment
6732 variables are not present. If this cannot be done easily
6733 (e.g., if the source code of a non-free program is not
6734 available), the program must be replaced by a small
6735 "wrapper" shell script which sets the environment variables
6736 if they are not already defined, and calls the original program.
6740 Here is an example of a wrapper script for this purpose:
6742 <example compact="compact">
6744 BAR=${BAR:-/var/lib/fubar}
6746 exec /usr/lib/foo/foo "$@"
6751 Furthermore, as <file>/etc/profile</file> is a configuration
6752 file of the <prgn>base-files</prgn> package, other packages must
6753 not put any environment variables or other commands into that
6758 <sect id="doc-base">
6759 <heading>Registering Documents using doc-base</heading>
6762 The <package>doc-base</package> package implements a
6763 flexible mechanism for handling and presenting
6764 documentation. The recommended practice is for every Debian
6765 package that provides online documentation (other than just
6766 manual pages) to register these documents with
6767 <package>doc-base</package> by installing a
6768 <package>doc-base</package> control file via the
6769 <prgn/install-docs/ script at installation time and
6770 de-register the manuals again when the package is removed.
6773 Please refer to the documentation that comes with the
6774 <package>doc-base</package> package for information and
6783 <heading>Files</heading>
6786 <heading>Binaries</heading>
6789 Two different packages must not install programs with
6790 different functionality but with the same filenames. (The
6791 case of two programs having the same functionality but
6792 different implementations is handled via "alternatives" or
6793 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6794 <ref id="conflicts"> respectively.) If this case happens,
6795 one of the programs must be renamed. The maintainers should
6796 report this to the <tt>debian-devel</tt> mailing list and
6797 try to find a consensus about which program will have to be
6798 renamed. If a consensus cannot be reached, <em>both</em>
6799 programs must be renamed.
6803 By default, when a package is being built, any binaries
6804 created should include debugging information, as well as
6805 being compiled with optimization. You should also turn on
6806 as many reasonable compilation warnings as possible; this
6807 makes life easier for porters, who can then look at build
6808 logs for possible problems. For the C programming language,
6809 this means the following compilation parameters should be
6811 <example compact="compact">
6813 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6815 INSTALL = install -s # (or use strip on the files in debian/tmp)
6820 Note that by default all installed binaries should be stripped,
6821 either by using the <tt>-s</tt> flag to
6822 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6823 the binaries after they have been copied into
6824 <file>debian/tmp</file> but before the tree is made into a
6829 Although binaries in the build tree should be compiled with
6830 debugging information by default, it can often be difficult to
6831 debug programs if they are also subjected to compiler
6832 optimization. For this reason, it is recommended to support the
6833 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6834 (see <ref id="debianrules-options">). This variable can contain
6835 several flags to change how a package is compiled and built.
6839 It is up to the package maintainer to decide what
6840 compilation options are best for the package. Certain
6841 binaries (such as computationally-intensive programs) will
6842 function better with certain flags (<tt>-O3</tt>, for
6843 example); feel free to use them. Please use good judgment
6844 here. Don't use flags for the sake of it; only use them
6845 if there is good reason to do so. Feel free to override
6846 the upstream author's ideas about which compilation
6847 options are best: they are often inappropriate for our
6853 <sect id="libraries">
6854 <heading>Libraries</heading>
6857 If the package is <strong>architecture: any</strong>, then
6858 the shared library compilation and linking flags must have
6859 <tt>-fPIC</tt>, or the package shall not build on some of
6860 the supported architectures<footnote>
6862 If you are using GCC, <tt>-fPIC</tt> produces code with
6863 relocatable position independent code, which is required for
6864 most architectures to create a shared library, with i386 and
6865 perhaps some others where non position independent code is
6866 permitted in a shared library.
6869 Position independent code may have a performance penalty,
6870 especially on <tt>i386</tt>. However, in most cases the
6871 speed penalty must be measured against the memory wasted on
6872 the few architectures where non position independent code is
6875 </footnote>. Any exception to this rule must be discussed on
6876 the mailing list <em>debian-devel@lists.debian.org</em>, and
6877 a rough consensus obtained. The reasons for not compiling
6878 with <tt>-fPIC</tt> flag must be recorded in the file
6879 <tt>README.Debian</tt>, and care must be taken to either
6880 restrict the architecture or arrange for <tt>-fPIC</tt> to
6881 be used on architectures where it is required.<footnote>
6883 Some of the reasons why this might be required is if the
6884 library contains hand crafted assembly code that is not
6885 relocatable, the speed penalty is excessive for compute
6886 intensive libs, and similar reasons.
6891 As to the static libraries, the common case is not to have
6892 relocatable code, since there is no benefit, unless in specific
6893 cases; therefore the static version must not be compiled
6894 with the <tt>-fPIC</tt> flag. Any exception to this rule
6895 should be discussed on the mailing list
6896 <em>debian-devel@lists.debian.org</em>, and the reasons for
6897 compiling with the <tt>-fPIC</tt> flag must be recorded in
6898 the file <tt>README.Debian</tt>. <footnote>
6900 Some of the reasons for linking static libraries with
6901 the <tt>-fPIC</tt> flag are if, for example, one needs a
6902 Perl API for a library that is under rapid development,
6903 and has an unstable API, so shared libraries are
6904 pointless at this phase of the library's development. In
6905 that case, since Perl needs a library with relocatable
6906 code, it may make sense to create a static library with
6907 relocatable code. Another reason cited is if you are
6908 distilling various libraries into a common shared
6909 library, like <tt>mklibs</tt> does in the Debian
6915 In other words, if both a shared and a static library is
6916 being built, each source unit (<tt>*.c</tt>, for example,
6917 for C files) will need to be compiled twice, for the normal
6921 You must specify the gcc option <tt>-D_REENTRANT</tt>
6922 when building a library (either static or shared) to make
6923 the library compatible with LinuxThreads.
6927 Although not enforced by the build tools, shared libraries
6928 must be linked against all libraries that they use symbols from
6929 in the same way that binaries are. This ensures the correct
6930 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6931 system and guarantees that all libraries can be safely opened
6932 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6933 option <tt>-Wl,-z,defs</tt> when building a shared library.
6934 Since this option enforces symbol resolution at build time,
6935 a missing library reference will be caught early as a fatal
6940 All installed shared libraries should be stripped with
6941 <example compact="compact">
6942 strip --strip-unneeded <var>your-lib</var>
6944 (The option <tt>--strip-unneeded</tt> makes
6945 <prgn>strip</prgn> remove only the symbols which aren't
6946 needed for relocation processing.) Shared libraries can
6947 function perfectly well when stripped, since the symbols for
6948 dynamic linking are in a separate part of the ELF object
6950 You might also want to use the options
6951 <tt>--remove-section=.comment</tt> and
6952 <tt>--remove-section=.note</tt> on both shared libraries
6953 and executables, and <tt>--strip-debug</tt> on static
6959 Note that under some circumstances it may be useful to
6960 install a shared library unstripped, for example when
6961 building a separate package to support debugging.
6965 Shared object files (often <file>.so</file> files) that are not
6966 public libraries, that is, they are not meant to be linked
6967 to by third party executables (binaries of other packages),
6968 should be installed in subdirectories of the
6969 <file>/usr/lib</file> directory. Such files are exempt from the
6970 rules that govern ordinary shared libraries, except that
6971 they must not be installed executable and should be
6973 A common example are the so-called "plug-ins",
6974 internal shared objects that are dynamically loaded by
6975 programs using <manref name="dlopen" section="3">.
6980 Packages containing shared libraries that may be linked to
6981 by other packages' binaries, but which for some
6982 <em>compelling</em> reason can not be installed in
6983 <file>/usr/lib</file> directory, may install the shared library
6984 files in subdirectories of the <file>/usr/lib</file> directory,
6985 in which case they should arrange to add that directory in
6986 <file>/etc/ld.so.conf</file> in the package's post-installation
6987 script, and remove it in the package's post-removal script.
6991 An ever increasing number of packages are using
6992 <prgn>libtool</prgn> to do their linking. The latest GNU
6993 libtools (>= 1.3a) can take advantage of the metadata in the
6994 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6995 files). The main advantage of <prgn>libtool</prgn>'s
6996 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6997 store and subsequently access metadata with respect to the
6998 libraries it builds. <prgn>libtool</prgn> will search for
6999 those files, which contain a lot of useful information about
7000 a library (such as library dependency information for static
7001 linking). Also, they're <em>essential</em> for programs
7002 using <tt>libltdl</tt>.<footnote>
7003 Although <prgn>libtool</prgn> is fully capable of
7004 linking against shared libraries which don't have
7005 <tt>.la</tt> files, as it is a mere shell script it can
7006 add considerably to the build time of a
7007 <prgn>libtool</prgn>-using package if that shell script
7008 has to derive all this information from first principles
7009 for each library every time it is linked. With the
7010 advent of <prgn>libtool</prgn> version 1.4 (and to a
7011 lesser extent <prgn>libtool</prgn> version 1.3), the
7012 <file>.la</file> files also store information about
7013 inter-library dependencies which cannot necessarily be
7014 derived after the <file>.la</file> file is deleted.
7019 Packages that use <prgn>libtool</prgn> to create shared
7020 libraries should include the <file>.la</file> files in the
7021 <tt>-dev</tt> package, unless the package relies on
7022 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7023 the <tt>.la</tt> files must go in the run-time library
7028 You must make sure that you use only released versions of
7029 shared libraries to build your packages; otherwise other
7030 users will not be able to run your binaries
7031 properly. Producing source packages that depend on
7032 unreleased compilers is also usually a bad
7039 <heading>Shared libraries</heading>
7041 This section has moved to <ref id="sharedlibs">.
7047 <heading>Scripts</heading>
7050 All command scripts, including the package maintainer
7051 scripts inside the package and used by <prgn>dpkg</prgn>,
7052 should have a <tt>#!</tt> line naming the shell to be used
7057 In the case of Perl scripts this should be
7058 <tt>#!/usr/bin/perl</tt>.
7062 When scripts are installed into a directory in the system
7063 PATH, the script name should not include an extension such
7064 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7065 language currently used to implement it.
7068 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7069 should almost certainly start with <tt>set -e</tt> so that
7070 errors are detected. Every script should use
7071 <tt>set -e</tt> or check the exit status of <em>every</em>
7076 Scripts may assume that <file>/bin/sh</file> implements the
7077 SUSv3 Shell Command Language<footnote>
7078 Single UNIX Specification, version 3, which is also IEEE
7079 1003.1-2004 (POSIX), and is available on the World Wide Web
7080 from <url id="http://www.unix.org/version3/online.html"
7081 name="The Open Group"> after free
7082 registration.</footnote>
7083 plus the following additional features not mandated by
7085 These features are in widespread use in the Linux community
7086 and are implemented in all of bash, dash, and ksh, the most
7087 common shells users may wish to use as <file>/bin/sh</file>.
7090 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7091 must not generate a newline.</item>
7092 <item><tt>test</tt>, if implemented as a shell built-in, must
7093 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7095 <item><tt>local</tt> to create a scoped variable must be
7096 supported, including listing multiple variables in a single
7097 local command and assigning a value to a variable at the
7098 same time as localizing it. <tt>local</tt> may or
7099 may not preserve the variable value from an outer scope if
7100 no assignment is present. Uses such as:
7104 # ... use a, b, c, d ...
7107 must be supported and must set the value of <tt>c</tt> to
7111 If a shell script requires non-SUSv3 features from the shell
7112 interpreter other than those listed above, the appropriate shell
7113 must be specified in the first line of the script (e.g.,
7114 <tt>#!/bin/bash</tt>) and the package must depend on the package
7115 providing the shell (unless the shell package is marked
7116 "Essential", as in the case of <prgn>bash</prgn>).
7120 You may wish to restrict your script to SUSv3 features plus the
7121 above set when possible so that it may use <file>/bin/sh</file>
7122 as its interpreter. If your script works with <prgn>dash</prgn>
7123 (originally called <prgn>ash</prgn>), it probably complies with
7124 the above requirements, but if you are in doubt, use
7125 <file>/bin/bash</file>.
7129 Perl scripts should check for errors when making any
7130 system calls, including <tt>open</tt>, <tt>print</tt>,
7131 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7135 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7136 scripting languages. See <em>Csh Programming Considered
7137 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7138 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7139 If an upstream package comes with <prgn>csh</prgn> scripts
7140 then you must make sure that they start with
7141 <tt>#!/bin/csh</tt> and make your package depend on the
7142 <prgn>c-shell</prgn> virtual package.
7146 Any scripts which create files in world-writeable
7147 directories (e.g., in <file>/tmp</file>) must use a
7148 mechanism which will fail atomically if a file with the same
7149 name already exists.
7153 The Debian base system provides the <prgn>tempfile</prgn>
7154 and <prgn>mktemp</prgn> utilities for use by scripts for
7161 <heading>Symbolic links</heading>
7164 In general, symbolic links within a top-level directory
7165 should be relative, and symbolic links pointing from one
7166 top-level directory into another should be absolute. (A
7167 top-level directory is a sub-directory of the root
7168 directory <file>/</file>.)
7172 In addition, symbolic links should be specified as short as
7173 possible, i.e., link targets like <file>foo/../bar</file> are
7178 Note that when creating a relative link using
7179 <prgn>ln</prgn> it is not necessary for the target of the
7180 link to exist relative to the working directory you're
7181 running <prgn>ln</prgn> from, nor is it necessary to change
7182 directory to the directory where the link is to be made.
7183 Simply include the string that should appear as the target
7184 of the link (this will be a pathname relative to the
7185 directory in which the link resides) as the first argument
7190 For example, in your <prgn>Makefile</prgn> or
7191 <file>debian/rules</file>, you can do things like:
7192 <example compact="compact">
7193 ln -fs gcc $(prefix)/bin/cc
7194 ln -fs gcc debian/tmp/usr/bin/cc
7195 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7196 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7201 A symbolic link pointing to a compressed file should always
7202 have the same file extension as the referenced file. (For
7203 example, if a file <file>foo.gz</file> is referenced by a
7204 symbolic link, the filename of the link has to end with
7205 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7210 <heading>Device files</heading>
7213 Packages must not include device files in the package file
7218 If a package needs any special device files that are not
7219 included in the base system, it must call
7220 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7221 after notifying the user<footnote>
7222 This notification could be done via a (low-priority)
7223 debconf message, or an echo (printf) statement.
7228 Packages must not remove any device files in the
7229 <prgn>postrm</prgn> or any other script. This is left to the
7230 system administrator.
7234 Debian uses the serial devices
7235 <file>/dev/ttyS*</file>. Programs using the old
7236 <file>/dev/cu*</file> devices should be changed to use
7237 <file>/dev/ttyS*</file>.
7241 <sect id="config-files">
7242 <heading>Configuration files</heading>
7245 <heading>Definitions</heading>
7249 <tag>configuration file</tag>
7251 A file that affects the operation of a program, or
7252 provides site- or host-specific information, or
7253 otherwise customizes the behavior of a program.
7254 Typically, configuration files are intended to be
7255 modified by the system administrator (if needed or
7256 desired) to conform to local policy or to provide
7257 more useful site-specific behavior.
7260 <tag><tt>conffile</tt></tag>
7262 A file listed in a package's <tt>conffiles</tt>
7263 file, and is treated specially by <prgn>dpkg</prgn>
7264 (see <ref id="configdetails">).
7270 The distinction between these two is important; they are
7271 not interchangeable concepts. Almost all
7272 <tt>conffile</tt>s are configuration files, but many
7273 configuration files are not <tt>conffiles</tt>.
7277 As noted elsewhere, <file>/etc/init.d</file> scripts,
7278 <file>/etc/default</file> files, scripts installed in
7279 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7280 configuration installed in <file>/etc/cron.d</file> must be
7281 treated as configuration files. In general, any script that
7282 embeds configuration information is de-facto a configuration
7283 file and should be treated as such.
7288 <heading>Location</heading>
7291 Any configuration files created or used by your package
7292 must reside in <file>/etc</file>. If there are several,
7293 consider creating a subdirectory of <file>/etc</file>
7294 named after your package.
7298 If your package creates or uses configuration files
7299 outside of <file>/etc</file>, and it is not feasible to modify
7300 the package to use <file>/etc</file> directly, put the files
7301 in <file>/etc</file> and create symbolic links to those files
7302 from the location that the package requires.
7307 <heading>Behavior</heading>
7310 Configuration file handling must conform to the following
7312 <list compact="compact">
7314 local changes must be preserved during a package
7318 configuration files must be preserved when the
7319 package is removed, and only deleted when the
7326 The easy way to achieve this behavior is to make the
7327 configuration file a <tt>conffile</tt>. This is
7328 appropriate only if it is possible to distribute a default
7329 version that will work for most installations, although
7330 some system administrators may choose to modify it. This
7331 implies that the default version will be part of the
7332 package distribution, and must not be modified by the
7333 maintainer scripts during installation (or at any other
7338 In order to ensure that local changes are preserved
7339 correctly, no package may contain or make hard links to
7340 conffiles.<footnote>
7341 Rationale: There are two problems with hard links.
7342 The first is that some editors break the link while
7343 editing one of the files, so that the two files may
7344 unwittingly become unlinked and different. The second
7345 is that <prgn>dpkg</prgn> might break the hard link
7346 while upgrading <tt>conffile</tt>s.
7351 The other way to do it is via the maintainer scripts. In
7352 this case, the configuration file must not be listed as a
7353 <tt>conffile</tt> and must not be part of the package
7354 distribution. If the existence of a file is required for
7355 the package to be sensibly configured it is the
7356 responsibility of the package maintainer to provide
7357 maintainer scripts which correctly create, update and
7358 maintain the file and remove it on purge. (See <ref
7359 id="maintainerscripts"> for more information.) These
7360 scripts must be idempotent (i.e., must work correctly if
7361 <prgn>dpkg</prgn> needs to re-run them due to errors
7362 during installation or removal), must cope with all the
7363 variety of ways <prgn>dpkg</prgn> can call maintainer
7364 scripts, must not overwrite or otherwise mangle the user's
7365 configuration without asking, must not ask unnecessary
7366 questions (particularly during upgrades), and must
7367 otherwise be good citizens.
7371 The scripts are not required to configure every possible
7372 option for the package, but only those necessary to get
7373 the package running on a given system. Ideally the
7374 sysadmin should not have to do any configuration other
7375 than that done (semi-)automatically by the
7376 <prgn>postinst</prgn> script.
7380 A common practice is to create a script called
7381 <file><var>package</var>-configure</file> and have the
7382 package's <prgn>postinst</prgn> call it if and only if the
7383 configuration file does not already exist. In certain
7384 cases it is useful for there to be an example or template
7385 file which the maintainer scripts use. Such files should
7386 be in <file>/usr/share/<var>package</var></file> or
7387 <file>/usr/lib/<var>package</var></file> (depending on whether
7388 they are architecture-independent or not). There should
7389 be symbolic links to them from
7390 <file>/usr/share/doc/<var>package</var>/examples</file> if
7391 they are examples, and should be perfectly ordinary
7392 <prgn>dpkg</prgn>-handled files (<em>not</em>
7393 configuration files).
7397 These two styles of configuration file handling must
7398 not be mixed, for that way lies madness:
7399 <prgn>dpkg</prgn> will ask about overwriting the file
7400 every time the package is upgraded.
7405 <heading>Sharing configuration files</heading>
7408 Packages which specify the same file as a
7409 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7410 with each other. (This is an instance of the general rule
7411 about not sharing files. Note that neither alternatives
7412 nor diversions are likely to be appropriate in this case;
7413 in particular, <prgn>dpkg</prgn> does not handle diverted
7414 <tt>conffile</tt>s well.)
7418 The maintainer scripts must not alter a <tt>conffile</tt>
7419 of <em>any</em> package, including the one the scripts
7424 If two or more packages use the same configuration file
7425 and it is reasonable for both to be installed at the same
7426 time, one of these packages must be defined as
7427 <em>owner</em> of the configuration file, i.e., it will be
7428 the package which handles that file as a configuration
7429 file. Other packages that use the configuration file must
7430 depend on the owning package if they require the
7431 configuration file to operate. If the other package will
7432 use the configuration file if present, but is capable of
7433 operating without it, no dependency need be declared.
7437 If it is desirable for two or more related packages to
7438 share a configuration file <em>and</em> for all of the
7439 related packages to be able to modify that configuration
7440 file, then the following should be done:
7441 <enumlist compact="compact">
7443 One of the related packages (the "owning" package)
7444 will manage the configuration file with maintainer
7445 scripts as described in the previous section.
7448 The owning package should also provide a program
7449 that the other packages may use to modify the
7453 The related packages must use the provided program
7454 to make any desired modifications to the
7455 configuration file. They should either depend on
7456 the core package to guarantee that the configuration
7457 modifier program is available or accept gracefully
7458 that they cannot modify the configuration file if it
7459 is not. (This is in addition to the fact that the
7460 configuration file may not even be present in the
7467 Sometimes it's appropriate to create a new package which
7468 provides the basic infrastructure for the other packages
7469 and which manages the shared configuration files. (The
7470 <tt>sgml-base</tt> package is a good example.)
7475 <heading>User configuration files ("dotfiles")</heading>
7478 The files in <file>/etc/skel</file> will automatically be
7479 copied into new user accounts by <prgn>adduser</prgn>.
7480 No other program should reference the files in
7481 <file>/etc/skel</file>.
7485 Therefore, if a program needs a dotfile to exist in
7486 advance in <file>$HOME</file> to work sensibly, that dotfile
7487 should be installed in <file>/etc/skel</file> and treated as a
7492 However, programs that require dotfiles in order to
7493 operate sensibly are a bad thing, unless they do create
7494 the dotfiles themselves automatically.
7498 Furthermore, programs should be configured by the Debian
7499 default installation to behave as closely to the upstream
7500 default behavior as possible.
7504 Therefore, if a program in a Debian package needs to be
7505 configured in some way in order to operate sensibly, that
7506 should be done using a site-wide configuration file placed
7507 in <file>/etc</file>. Only if the program doesn't support a
7508 site-wide default configuration and the package maintainer
7509 doesn't have time to add it may a default per-user file be
7510 placed in <file>/etc/skel</file>.
7514 <file>/etc/skel</file> should be as empty as we can make it.
7515 This is particularly true because there is no easy (or
7516 necessarily desirable) mechanism for ensuring that the
7517 appropriate dotfiles are copied into the accounts of
7518 existing users when a package is installed.
7524 <heading>Log files</heading>
7526 Log files should usually be named
7527 <file>/var/log/<var>package</var>.log</file>. If you have many
7528 log files, or need a separate directory for permission
7529 reasons (<file>/var/log</file> is writable only by
7530 <file>root</file>), you should usually create a directory named
7531 <file>/var/log/<var>package</var></file> and place your log
7536 Log files must be rotated occasionally so that they don't
7537 grow indefinitely; the best way to do this is to drop a log
7538 rotation configuration file into the directory
7539 <file>/etc/logrotate.d</file> and use the facilities provided by
7540 logrotate.<footnote>
7542 The traditional approach to log files has been to set up
7543 <em>ad hoc</em> log rotation schemes using simple shell
7544 scripts and cron. While this approach is highly
7545 customizable, it requires quite a lot of sysadmin work.
7546 Even though the original Debian system helped a little
7547 by automatically installing a system which can be used
7548 as a template, this was deemed not enough.
7552 The use of <prgn>logrotate</prgn>, a program developed
7553 by Red Hat, is better, as it centralizes log management.
7554 It has both a configuration file
7555 (<file>/etc/logrotate.conf</file>) and a directory where
7556 packages can drop their individual log rotation
7557 configurations (<file>/etc/logrotate.d</file>).
7560 Here is a good example for a logrotate config
7561 file (for more information see <manref name="logrotate"
7563 <example compact="compact">
7564 /var/log/foo/*.log {
7569 /etc/init.d/foo force-reload
7573 This rotates all files under <file>/var/log/foo</file>, saves 12
7574 compressed generations, and forces the daemon to reload its
7575 configuration information after the log rotation.
7579 Log files should be removed when the package is
7580 purged (but not when it is only removed). This should be
7581 done by the <prgn>postrm</prgn> script when it is called
7582 with the argument <tt>purge</tt> (see <ref
7583 id="removedetails">).
7588 <heading>Permissions and owners</heading>
7591 The rules in this section are guidelines for general use.
7592 If necessary you may deviate from the details below.
7593 However, if you do so you must make sure that what is done
7594 is secure and you should try to be as consistent as possible
7595 with the rest of the system. You should probably also
7596 discuss it on <prgn>debian-devel</prgn> first.
7600 Files should be owned by <tt>root:root</tt>, and made
7601 writable only by the owner and universally readable (and
7602 executable, if appropriate), that is mode 644 or 755.
7606 Directories should be mode 755 or (for group-writability)
7607 mode 2775. The ownership of the directory should be
7608 consistent with its mode: if a directory is mode 2775, it
7609 should be owned by the group that needs write access to
7612 When a package is upgraded, and the owner or permissions
7613 of a file included in the package has changed, dpkg
7614 arranges for the ownership and permissions to be
7615 correctly set upon installation. However, this does not
7616 extend to directories; the permissions and ownership of
7617 directories already on the system does not change on
7618 install or upgrade of packages. This makes sense, since
7619 otherwise common directories like <tt>/usr</tt> would
7620 always be in flux. To correctly change permissions of a
7621 directory the package owns, explicit action is required,
7622 usually in the <tt>postinst</tt> script. Care must be
7623 taken to handle downgrades as well, in that case.
7630 Setuid and setgid executables should be mode 4755 or 2755
7631 respectively, and owned by the appropriate user or group.
7632 They should not be made unreadable (modes like 4711 or
7633 2711 or even 4111); doing so achieves no extra security,
7634 because anyone can find the binary in the freely available
7635 Debian package; it is merely inconvenient. For the same
7636 reason you should not restrict read or execute permissions
7637 on non-set-id executables.
7641 Some setuid programs need to be restricted to particular
7642 sets of users, using file permissions. In this case they
7643 should be owned by the uid to which they are set-id, and by
7644 the group which should be allowed to execute them. They
7645 should have mode 4754; again there is no point in making
7646 them unreadable to those users who must not be allowed to
7651 It is possible to arrange that the system administrator can
7652 reconfigure the package to correspond to their local
7653 security policy by changing the permissions on a binary:
7654 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7655 described below.<footnote>
7656 Ordinary files installed by <prgn>dpkg</prgn> (as
7657 opposed to <tt>conffile</tt>s and other similar objects)
7658 normally have their permissions reset to the distributed
7659 permissions when the package is reinstalled. However,
7660 the use of <prgn>dpkg-statoverride</prgn> overrides this
7661 default behavior. If you use this method, you should
7662 remember to describe <prgn>dpkg-statoverride</prgn> in
7663 the package documentation; being a relatively new
7664 addition to Debian, it is probably not yet well-known.
7666 Another method you should consider is to create a group for
7667 people allowed to use the program(s) and make any setuid
7668 executables executable only by that group.
7672 If you need to create a new user or group for your package
7673 there are two possibilities. Firstly, you may need to
7674 make some files in the binary package be owned by this
7675 user or group, or you may need to compile the user or
7676 group id (rather than just the name) into the binary
7677 (though this latter should be avoided if possible, as in
7678 this case you need a statically allocated id).</p>
7681 If you need a statically allocated id, you must ask for a
7682 user or group id from the <tt>base-passwd</tt> maintainer,
7683 and must not release the package until you have been
7684 allocated one. Once you have been allocated one you must
7685 either make the package depend on a version of the
7686 <tt>base-passwd</tt> package with the id present in
7687 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7688 your package to create the user or group itself with the
7689 correct id (using <tt>adduser</tt>) in its
7690 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7691 the <prgn>postinst</prgn> is to be preferred if it is
7692 possible, otherwise a pre-dependency will be needed on the
7693 <tt>adduser</tt> package.)
7697 On the other hand, the program might be able to determine
7698 the uid or gid from the user or group name at runtime, so
7699 that a dynamically allocated id can be used. In this case
7700 you should choose an appropriate user or group name,
7701 discussing this on <prgn>debian-devel</prgn> and checking
7702 with the <package/base-passwd/ maintainer that it is unique and that
7703 they do not wish you to use a statically allocated id
7704 instead. When this has been checked you must arrange for
7705 your package to create the user or group if necessary using
7706 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7707 <prgn>postinst</prgn> script (again, the latter is to be
7708 preferred if it is possible).
7712 Note that changing the numeric value of an id associated
7713 with a name is very difficult, and involves searching the
7714 file system for all appropriate files. You need to think
7715 carefully whether a static or dynamic id is required, since
7716 changing your mind later will cause problems.
7719 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7721 This section is not intended as policy, but as a
7722 description of the use of <prgn>dpkg-statoverride</prgn>.
7726 If a system administrator wishes to have a file (or
7727 directory or other such thing) installed with owner and
7728 permissions different from those in the distributed Debian
7729 package, they can use the <prgn>dpkg-statoverride</prgn>
7730 program to instruct <prgn>dpkg</prgn> to use the different
7731 settings every time the file is installed. Thus the
7732 package maintainer should distribute the files with their
7733 normal permissions, and leave it for the system
7734 administrator to make any desired changes. For example, a
7735 daemon which is normally required to be setuid root, but
7736 in certain situations could be used without being setuid,
7737 should be installed setuid in the <tt>.deb</tt>. Then the
7738 local system administrator can change this if they wish.
7739 If there are two standard ways of doing it, the package
7740 maintainer can use <tt>debconf</tt> to find out the
7741 preference, and call <prgn>dpkg-statoverride</prgn> in the
7742 maintainer script if necessary to accommodate the system
7743 administrator's choice. Care must be taken during
7744 upgrades to not override an existing setting.
7748 Given the above, <prgn>dpkg-statoverride</prgn> is
7749 essentially a tool for system administrators and would not
7750 normally be needed in the maintainer scripts. There is
7751 one type of situation, though, where calls to
7752 <prgn>dpkg-statoverride</prgn> would be needed in the
7753 maintainer scripts, and that involves packages which use
7754 dynamically allocated user or group ids. In such a
7755 situation, something like the following idiom can be very
7756 helpful in the package's <prgn>postinst</prgn>, where
7757 <tt>sysuser</tt> is a dynamically allocated id:
7759 for i in /usr/bin/foo /usr/sbin/bar
7761 # only do something when no setting exists
7762 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7764 #include: debconf processing, question about foo and bar
7765 if [ "$RET" = "true" ] ; then
7766 dpkg-statoverride --update --add sysuser root 4755 $i
7771 The corresponding <tt>dpkg-statoverride --remove</tt>
7772 calls can then be made unconditionally when the package is
7780 <chapt id="customized-programs">
7781 <heading>Customized programs</heading>
7783 <sect id="arch-spec">
7784 <heading>Architecture specification strings</heading>
7787 If a program needs to specify an <em>architecture specification
7788 string</em> in some place, it should select one of the
7789 strings provided by <tt>dpkg-architecture -L</tt>. The
7790 strings are in the format
7791 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7792 is sometimes elided, as when the OS is Linux.<footnote>
7793 <p>Currently, the strings are:
7794 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7795 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7796 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7797 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7798 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7799 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7800 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7801 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7802 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7803 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7804 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7805 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7806 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7807 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7808 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7809 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7810 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7811 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7812 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7813 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7814 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7815 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7816 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7817 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7818 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7819 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7820 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7821 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7822 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7823 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7824 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7825 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7826 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7827 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7828 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7829 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7830 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7836 Note that we don't want to use
7837 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7838 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7839 since this would make our programs incompatible with other
7840 Linux distributions. We also don't use something like
7841 <tt><var>arch</var>-unknown-linux</tt>, since the
7842 <tt>unknown</tt> does not look very good.
7847 <heading>Daemons</heading>
7850 The configuration files <file>/etc/services</file>,
7851 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7852 by the <prgn>netbase</prgn> package and must not be modified
7857 If a package requires a new entry in one of these files, the
7858 maintainer should get in contact with the
7859 <prgn>netbase</prgn> maintainer, who will add the entries
7860 and release a new version of the <prgn>netbase</prgn>
7865 The configuration file <file>/etc/inetd.conf</file> must not be
7866 modified by the package's scripts except via the
7867 <prgn>update-inetd</prgn> script or the
7868 <file>DebianNet.pm</file> Perl module. See their documentation
7869 for details on how to add entries.
7873 If a package wants to install an example entry into
7874 <file>/etc/inetd.conf</file>, the entry must be preceded with
7875 exactly one hash character (<tt>#</tt>). Such lines are
7876 treated as "commented out by user" by the
7877 <prgn>update-inetd</prgn> script and are not changed or
7878 activated during package updates.
7883 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7887 Some programs need to create pseudo-ttys. This should be done
7888 using Unix98 ptys if the C library supports it. The resulting
7889 program must not be installed setuid root, unless that
7890 is required for other functionality.
7894 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7895 <file>/var/log/lastlog</file> must be installed writable by
7896 group <tt>utmp</tt>. Programs which need to modify those
7897 files must be installed setgid <tt>utmp</tt>.
7902 <heading>Editors and pagers</heading>
7905 Some programs have the ability to launch an editor or pager
7906 program to edit or display a text document. Since there are
7907 lots of different editors and pagers available in the Debian
7908 distribution, the system administrator and each user should
7909 have the possibility to choose their preferred editor and
7914 In addition, every program should choose a good default
7915 editor/pager if none is selected by the user or system
7920 Thus, every program that launches an editor or pager must
7921 use the EDITOR or PAGER environment variable to determine
7922 the editor or pager the user wishes to use. If these
7923 variables are not set, the programs <file>/usr/bin/editor</file>
7924 and <file>/usr/bin/pager</file> should be used, respectively.
7928 These two files are managed through the <prgn>dpkg</prgn>
7929 "alternatives" mechanism. Thus every package providing an
7930 editor or pager must call the
7931 <prgn>update-alternatives</prgn> script to register these
7936 If it is very hard to adapt a program to make use of the
7937 EDITOR or PAGER variables, that program may be configured to
7938 use <file>/usr/bin/sensible-editor</file> and
7939 <file>/usr/bin/sensible-pager</file> as the editor or pager
7940 program respectively. These are two scripts provided in the
7941 Debian base system that check the EDITOR and PAGER variables
7942 and launch the appropriate program, and fall back to
7943 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7944 variable is not set.
7948 A program may also use the VISUAL environment variable to
7949 determine the user's choice of editor. If it exists, it
7950 should take precedence over EDITOR. This is in fact what
7951 <file>/usr/bin/sensible-editor</file> does.
7955 It is not required for a package to depend on
7956 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7957 package to provide such virtual packages.<footnote>
7958 The Debian base system already provides an editor and a
7964 <sect id="web-appl">
7965 <heading>Web servers and applications</heading>
7968 This section describes the locations and URLs that should
7969 be used by all web servers and web applications in the
7976 Cgi-bin executable files are installed in the
7978 <example compact="compact">
7979 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7981 and should be referred to as
7982 <example compact="compact">
7983 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7989 <p>Access to HTML documents</p>
7992 HTML documents for a package are stored in
7993 <file>/usr/share/doc/<var>package</var></file>
7994 and can be referred to as
7995 <example compact="compact">
7996 http://localhost/doc/<var>package</var>/<var>filename</var>
8001 The web server should restrict access to the document
8002 tree so that only clients on the same host can read
8003 the documents. If the web server does not support such
8004 access controls, then it should not provide access at
8005 all, or ask about providing access during installation.
8010 <p>Access to images</p>
8012 It is recommended that images for a package be stored
8013 in <tt>/usr/share/images/<var>package</var></tt> and
8014 may be referred to through an alias <tt>/images/</tt>
8017 http://localhost/images/<package>/<filename>
8024 <p>Web Document Root</p>
8027 Web Applications should try to avoid storing files in
8028 the Web Document Root. Instead they should use the
8029 /usr/share/doc/<var>package</var> directory for
8030 documents and register the Web Application via the
8031 <package>doc-base</package> package. If access to the
8032 web document root is unavoidable then use
8033 <example compact="compact">
8036 as the Document Root. This might be just a symbolic
8037 link to the location where the system administrator
8038 has put the real document root.
8041 <item><p>Providing httpd and/or httpd-cgi</p>
8043 All web servers should provide the virtual package
8044 <tt>httpd</tt>. If a web server has CGI support it should
8045 provide <tt>httpd-cgi</tt> additionally.
8048 All web applications which do not contain CGI scripts should
8049 depend on <tt>httpd</tt>, all those web applications which
8050 <tt>do</tt> contain CGI scripts, should depend on
8058 <sect id="mail-transport-agents">
8059 <heading>Mail transport, delivery and user agents</heading>
8062 Debian packages which process electronic mail, whether mail
8063 user agents (MUAs) or mail transport agents (MTAs), must
8064 ensure that they are compatible with the configuration
8065 decisions below. Failure to do this may result in lost
8066 mail, broken <tt>From:</tt> lines, and other serious brain
8071 The mail spool is <file>/var/mail</file> and the interface to
8072 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8073 the FHS). On older systems, the mail spool may be
8074 physically located in <file>/var/spool/mail</file>, but all
8075 access to the mail spool should be via the
8076 <file>/var/mail</file> symlink. The mail spool is part of the
8077 base system and not part of the MTA package.
8081 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8082 programs (such as IMAP daemons) must lock the mailbox in an
8083 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8084 be combined with dot locking. To avoid deadlocks, a program
8085 should use <tt>fcntl()</tt> first and dot locking after
8086 this, or alternatively implement the two locking methods in
8087 a non blocking way<footnote>
8088 If it is not possible to establish both locks, the
8089 system shouldn't wait for the second lock to be
8090 established, but remove the first lock, wait a (random)
8091 time, and start over locking again.
8092 </footnote>. Using the functions <tt>maillock</tt> and
8093 <tt>mailunlock</tt> provided by the
8094 <tt>liblockfile*</tt><footnote>
8095 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8096 to use these functions.
8097 </footnote> packages is the recommended way to realize this.
8101 Mailboxes are generally either mode 600 and owned by
8102 <var>user</var> or mode 660 and owned by
8103 <tt><var>user</var>:mail</tt><footnote>
8104 There are two traditional permission schemes for mail spools:
8105 mode 600 with all mail delivery done by processes running as
8106 the destination user, or mode 660 and owned by group mail with
8107 mail delivery done by a process running as a system user in
8108 group mail. Historically, Debian required mode 660 mail
8109 spools to enable the latter model, but that model has become
8110 increasingly uncommon and the principle of least privilege
8111 indicates that mail systems that use the first model should
8112 use permissions of 600. If delivery to programs is permitted,
8113 it's easier to keep the mail system secure if the delivery
8114 agent runs as the destination user. Debian Policy therefore
8115 permits either scheme.
8116 </footnote>. The local system administrator may choose a
8117 different permission scheme; packages should not make
8118 assumptions about the permission and ownership of mailboxes
8119 unless required (such as when creating a new mailbox). A MUA
8120 may remove a mailbox (unless it has nonstandard permissions) in
8121 which case the MTA or another MUA must recreate it if needed.
8125 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8126 be setgid mail to do the locking mentioned above (and
8127 must obviously avoid accessing other users' mailboxes
8128 using this privilege).</p>
8131 <file>/etc/aliases</file> is the source file for the system mail
8132 aliases (e.g., postmaster, usenet, etc.), it is the one
8133 which the sysadmin and <prgn>postinst</prgn> scripts may
8134 edit. After <file>/etc/aliases</file> is edited the program or
8135 human editing it must call <prgn>newaliases</prgn>. All MTA
8136 packages must come with a <prgn>newaliases</prgn> program,
8137 even if it does nothing, but older MTA packages did not do
8138 this so programs should not fail if <prgn>newaliases</prgn>
8139 cannot be found. Note that because of this, all MTA
8140 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8141 <tt>Replaces: mail-transport-agent</tt> control file
8146 The convention of writing <tt>forward to
8147 <var>address</var></tt> in the mailbox itself is not
8148 supported. Use a <tt>.forward</tt> file instead.</p>
8151 The <prgn>rmail</prgn> program used by UUCP
8152 for incoming mail should be <file>/usr/sbin/rmail</file>.
8153 Likewise, <prgn>rsmtp</prgn>, for receiving
8154 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8158 If your package needs to know what hostname to use on (for
8159 example) outgoing news and mail messages which are generated
8160 locally, you should use the file <file>/etc/mailname</file>. It
8161 will contain the portion after the username and <tt>@</tt>
8162 (at) sign for email addresses of users on the machine
8163 (followed by a newline).
8167 Such a package should check for the existence of this file
8168 when it is being configured. If it exists, it should be
8169 used without comment, although an MTA's configuration script
8170 may wish to prompt the user even if it finds that this file
8171 exists. If the file does not exist, the package should
8172 prompt the user for the value (preferably using
8173 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8174 as well as using it in the package's configuration. The
8175 prompt should make it clear that the name will not just be
8176 used by that package. For example, in this situation the
8177 <tt>inn</tt> package could say something like:
8178 <example compact="compact">
8179 Please enter the "mail name" of your system. This is the
8180 hostname portion of the address to be shown on outgoing
8181 news and mail messages. The default is
8182 <var>syshostname</var>, your system's host name. Mail
8183 name ["<var>syshostname</var>"]:
8185 where <var>syshostname</var> is the output of <tt>hostname
8191 <heading>News system configuration</heading>
8194 All the configuration files related to the NNTP (news)
8195 servers and clients should be located under
8196 <file>/etc/news</file>.</p>
8199 There are some configuration issues that apply to a number
8200 of news clients and server packages on the machine. These
8204 <tag><file>/etc/news/organization</file></tag>
8206 A string which should appear as the
8207 organization header for all messages posted
8208 by NNTP clients on the machine
8211 <tag><file>/etc/news/server</file></tag>
8213 Contains the FQDN of the upstream NNTP
8214 server, or localhost if the local machine is
8219 Other global files may be added as required for cross-package news
8226 <heading>Programs for the X Window System</heading>
8229 <heading>Providing X support and package priorities</heading>
8232 Programs that can be configured with support for the X
8233 Window System must be configured to do so and must declare
8234 any package dependencies necessary to satisfy their
8235 runtime requirements when using the X Window System. If
8236 such a package is of higher priority than the X packages
8237 on which it depends, it is required that either the
8238 X-specific components be split into a separate package, or
8239 that an alternative version of the package, which includes
8240 X support, be provided, or that the package's priority be
8246 <heading>Packages providing an X server</heading>
8249 Packages that provide an X server that, directly or
8250 indirectly, communicates with real input and display
8251 hardware should declare in their control data that they
8252 provide the virtual package <tt>xserver</tt>.<footnote>
8253 This implements current practice, and provides an
8254 actual policy for usage of the <tt>xserver</tt>
8255 virtual package which appears in the virtual packages
8256 list. In a nutshell, X servers that interface
8257 directly with the display and input hardware or via
8258 another subsystem (e.g., GGI) should provide
8259 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8260 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8266 <heading>Packages providing a terminal emulator</heading>
8269 Packages that provide a terminal emulator for the X Window
8270 System which meet the criteria listed below should declare
8271 in their control data that they provide the virtual
8272 package <tt>x-terminal-emulator</tt>. They should also
8273 register themselves as an alternative for
8274 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8279 To be an <tt>x-terminal-emulator</tt>, a program must:
8280 <list compact="compact">
8282 Be able to emulate a DEC VT100 terminal, or a
8283 compatible terminal.
8287 Support the command-line option <tt>-e
8288 <var>command</var></tt>, which creates a new
8289 terminal window<footnote>
8290 "New terminal window" does not necessarily mean
8291 a new top-level X window directly parented by
8292 the window manager; it could, if the terminal
8293 emulator application were so coded, be a new
8294 "view" in a multiple-document interface (MDI).
8296 and runs the specified <var>command</var>,
8297 interpreting the entirety of the rest of the command
8298 line as a command to pass straight to exec, in the
8299 manner that <tt>xterm</tt> does.
8303 Support the command-line option <tt>-T
8304 <var>title</var></tt>, which creates a new terminal
8305 window with the window title <var>title</var>.
8312 <heading>Packages providing a window manager</heading>
8315 Packages that provide a window manager should declare in
8316 their control data that they provide the virtual package
8317 <tt>x-window-manager</tt>. They should also register
8318 themselves as an alternative for
8319 <file>/usr/bin/x-window-manager</file>, with a priority
8320 calculated as follows:
8321 <list compact="compact">
8323 Start with a priority of 20.
8327 If the window manager supports the Debian menu
8328 system, add 20 points if this support is available
8329 in the package's default configuration (i.e., no
8330 configuration files belonging to the system or user
8331 have to be edited to activate the feature); if
8332 configuration files must be modified, add only 10
8338 If the window manager complies with <url
8339 id="http://www.freedesktop.org/Standards/wm-spec"
8340 name="The Window Manager Specification Project">,
8341 written by the <url id="http://www.freedesktop.org/"
8342 name="Free Desktop Group">, add 40 points.
8346 If the window manager permits the X session to be
8347 restarted using a <em>different</em> window manager
8348 (without killing the X server) in its default
8349 configuration, add 10 points; otherwise add none.
8356 <heading>Packages providing fonts</heading>
8359 Packages that provide fonts for the X Window
8361 For the purposes of Debian Policy, a "font for the X
8362 Window System" is one which is accessed via X protocol
8363 requests. Fonts for the Linux console, for PostScript
8364 renderer, or any other purpose, do not fit this
8365 definition. Any tool which makes such fonts available
8366 to the X Window System, however, must abide by this
8369 must do a number of things to ensure that they are both
8370 available without modification of the X or font server
8371 configuration, and that they do not corrupt files used by
8372 other font packages to register information about
8376 Fonts of any type supported by the X Window System
8377 must be in a separate binary package from any
8378 executables, libraries, or documentation (except
8379 that specific to the fonts shipped, such as their
8380 license information). If one or more of the fonts
8381 so packaged are necessary for proper operation of
8382 the package with which they are associated the font
8383 package may be Recommended; if the fonts merely
8384 provide an enhancement, a Suggests relationship may
8385 be used. Packages must not Depend on font
8387 This is because the X server may retrieve fonts
8388 from the local file system or over the network
8389 from an X font server; the Debian package system
8390 is empowered to deal only with the local
8396 BDF fonts must be converted to PCF fonts with the
8397 <prgn>bdftopcf</prgn> utility (available in the
8398 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8399 placed in a directory that corresponds to their
8401 <list compact="compact">
8403 100 dpi fonts must be placed in
8404 <file>/usr/share/fonts/X11/100dpi/</file>.
8408 75 dpi fonts must be placed in
8409 <file>/usr/share/fonts/X11/75dpi/</file>.
8413 Character-cell fonts, cursor fonts, and other
8414 low-resolution fonts must be placed in
8415 <file>/usr/share/fonts/X11/misc/</file>.
8421 Type 1 fonts must be placed in
8422 <file>/usr/share/fonts/X11/Type1/</file>. If font
8423 metric files are available, they must be placed here
8428 Subdirectories of <file>/usr/share/fonts/X11/</file>
8429 other than those listed above must be neither
8430 created nor used. (The <file>PEX</file>, <file>CID</file>,
8431 <file>Speedo</file>, and <file>cyrillic</file> directories
8432 are excepted for historical reasons, but installation of
8433 files into these directories remains discouraged.)
8437 Font packages may, instead of placing files directly
8438 in the X font directories listed above, provide
8439 symbolic links in that font directory pointing to
8440 the files' actual location in the filesystem. Such
8441 a location must comply with the FHS.
8445 Font packages should not contain both 75dpi and
8446 100dpi versions of a font. If both are available,
8447 they should be provided in separate binary packages
8448 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8449 the names of the packages containing the
8450 corresponding fonts.
8454 Fonts destined for the <file>misc</file> subdirectory
8455 should not be included in the same package as 75dpi
8456 or 100dpi fonts; instead, they should be provided in
8457 a separate package with <tt>-misc</tt> appended to
8462 Font packages must not provide the files
8463 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8464 <file>fonts.scale</file> in a font directory:
8467 <file>fonts.dir</file> files must not be provided at all.
8471 <file>fonts.alias</file> and <file>fonts.scale</file>
8472 files, if needed, should be provided in the
8474 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8475 where <var>fontdir</var> is the name of the
8477 <file>/usr/share/fonts/X11/</file> where the
8478 package's corresponding fonts are stored
8479 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8480 <var>package</var> is the name of the package
8481 that provides these fonts, and
8482 <var>extension</var> is either <tt>scale</tt>
8483 or <tt>alias</tt>, whichever corresponds to
8490 Font packages must declare a dependency on
8491 <tt>xfonts-utils</tt> in their control
8496 Font packages that provide one or more
8497 <file>fonts.scale</file> files as described above must
8498 invoke <prgn>update-fonts-scale</prgn> on each
8499 directory into which they installed fonts
8500 <em>before</em> invoking
8501 <prgn>update-fonts-dir</prgn> on that directory.
8502 This invocation must occur in both the
8503 <prgn>postinst</prgn> (for all arguments) and
8504 <prgn>postrm</prgn> (for all arguments except
8505 <tt>upgrade</tt>) scripts.
8509 Font packages that provide one or more
8510 <file>fonts.alias</file> files as described above must
8511 invoke <prgn>update-fonts-alias</prgn> on each
8512 directory into which they installed fonts. This
8513 invocation must occur in both the
8514 <prgn>postinst</prgn> (for all arguments) and
8515 <prgn>postrm</prgn> (for all arguments except
8516 <tt>upgrade</tt>) scripts.
8520 Font packages must invoke
8521 <prgn>update-fonts-dir</prgn> on each directory into
8522 which they installed fonts. This invocation must
8523 occur in both the <prgn>postinst</prgn> (for all
8524 arguments) and <prgn>postrm</prgn> (for all
8525 arguments except <tt>upgrade</tt>) scripts.
8529 Font packages must not provide alias names for the
8530 fonts they include which collide with alias names
8531 already in use by fonts already packaged.
8535 Font packages must not provide fonts with the same
8536 XLFD registry name as another font already packaged.
8543 <heading>Application defaults files</heading>
8546 Application defaults files must be installed in the
8547 directory <file>/etc/X11/app-defaults/</file> (use of a
8548 localized subdirectory of <file>/etc/X11/</file> as described
8549 in the <em>X Toolkit Intrinsics - C Language
8550 Interface</em> manual is also permitted). They must be
8551 registered as <tt>conffile</tt>s or handled as
8552 configuration files.
8556 Customization of programs' X resources may also be
8557 supported with the provision of a file with the same name
8558 as that of the package placed in the
8559 <file>/etc/X11/Xresources/</file> directory, which must
8560 registered as a <tt>conffile</tt> or handled as a
8561 configuration file.<footnote>
8562 Note that this mechanism is not the same as using
8563 app-defaults; app-defaults are tied to the client
8564 binary on the local file system, whereas X resources
8565 are stored in the X server and affect all connecting
8572 <heading>Installation directory issues</heading>
8575 Packages using the X Window System should not be
8576 configured to install files under the
8577 <file>/usr/X11R6/</file> directory. The
8578 <file>/usr/X11R6/</file> directory hierarchy should be
8579 regarded as obsolete.
8583 Programs that use GNU <prgn>autoconf</prgn> and
8584 <prgn>automake</prgn> are usually easily configured at
8585 compile time to use <file>/usr/</file> instead of
8586 <file>/usr/X11R6/</file>, and this should be done whenever
8587 possible. Configuration files for window managers and
8588 display managers should be placed in a subdirectory of
8589 <file>/etc/X11/</file> corresponding to the package name due
8590 to these programs' tight integration with the mechanisms
8591 of the X Window System. Application-level programs should
8592 use the <file>/etc/</file> directory unless otherwise mandated
8597 The installation of files into subdirectories
8598 of <file>/usr/X11R6/include/X11/</file> and
8599 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8600 package maintainers should determine if subdirectories of
8601 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8606 Packages should install any relevant files into the
8607 directories <file>/usr/include/X11/</file> and
8608 <file>/usr/lib/X11/</file>, but if they do so, they must
8609 pre-depend on <tt>x11-common (>=
8610 1:7.0.0)</tt><footnote>
8612 These libraries used to be all symbolic
8613 links. However, with <tt>X11R7</tt>,
8614 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8615 are now real directories, and packages
8616 <strong>should</strong> ship their files here instead
8617 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8618 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8619 responsible for converting these symlinks into
8627 <heading>The OSF/Motif and OpenMotif libraries</heading>
8630 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8631 OpenMotif libraries</em><footnote>
8632 OSF/Motif and OpenMotif are collectively referred to as
8633 "Motif" in this policy document.
8635 should be compiled against and tested with LessTif (a free
8636 re-implementation of Motif) instead. If the maintainer
8637 judges that the program or programs do not work
8638 sufficiently well with LessTif to be distributed and
8639 supported, but do so when compiled against Motif, then two
8640 versions of the package should be created; one linked
8641 statically against Motif and with <tt>-smotif</tt>
8642 appended to the package name, and one linked dynamically
8643 against Motif and with <tt>-dmotif</tt> appended to the
8648 Both Motif-linked versions are dependent
8649 upon non-DFSG-compliant software and thus cannot be
8650 uploaded to the <em>main</em> distribution; if the
8651 software is itself DFSG-compliant it may be uploaded to
8652 the <em>contrib</em> distribution. While known existing
8653 versions of Motif permit unlimited redistribution of
8654 binaries linked against the library (whether statically or
8655 dynamically), it is the package maintainer's
8656 responsibility to determine whether this is permitted by
8657 the license of the copy of Motif in their possession.
8663 <heading>Perl programs and modules</heading>
8666 Perl programs and modules should follow the current Perl policy.
8670 The Perl policy can be found in the <tt>perl-policy</tt>
8671 files in the <tt>debian-policy</tt> package.
8672 It is also available from the Debian web mirrors at
8673 <tt><url name="/doc/packaging-manuals/perl-policy/"
8674 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8679 <heading>Emacs lisp programs</heading>
8682 Please refer to the "Debian Emacs Policy" for details of how to
8683 package emacs lisp programs.
8687 The Emacs policy is available in
8688 <file>debian-emacs-policy.gz</file> of the
8689 <package>emacsen-common</package> package.
8690 It is also available from the Debian web mirrors at
8691 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8692 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8697 <heading>Games</heading>
8700 The permissions on <file>/var/games</file> are mode 755, owner
8701 <tt>root</tt> and group <tt>root</tt>.
8705 Each game decides on its own security policy.</p>
8708 Games which require protected, privileged access to
8709 high-score files, saved games, etc., may be made
8710 set-<em>group</em>-id (mode 2755) and owned by
8711 <tt>root:games</tt>, and use files and directories with
8712 appropriate permissions (770 <tt>root:games</tt>, for
8713 example). They must not be made
8714 set-<em>user</em>-id, as this causes security problems. (If
8715 an attacker can subvert any set-user-id game they can
8716 overwrite the executable of any other, causing other players
8717 of these games to run a Trojan horse program. With a
8718 set-group-id game the attacker only gets access to less
8719 important game data, and if they can get at the other
8720 players' accounts at all it will take considerably more
8724 Some packages, for example some fortune cookie programs, are
8725 configured by the upstream authors to install with their
8726 data files or other static information made unreadable so
8727 that they can only be accessed through set-id programs
8728 provided. You should not do this in a Debian package: anyone can
8729 download the <file>.deb</file> file and read the data from it,
8730 so there is no point making the files unreadable. Not
8731 making the files unreadable also means that you don't have
8732 to make so many programs set-id, which reduces the risk of a
8736 As described in the FHS, binaries of games should be
8737 installed in the directory <file>/usr/games</file>. This also
8738 applies to games that use the X Window System. Manual pages
8739 for games (X and non-X games) should be installed in
8740 <file>/usr/share/man/man6</file>.</p>
8746 <heading>Documentation</heading>
8749 <heading>Manual pages</heading>
8752 You should install manual pages in <prgn>nroff</prgn> source
8753 form, in appropriate places under <file>/usr/share/man</file>.
8754 You should only use sections 1 to 9 (see the FHS for more
8755 details). You must not install a pre-formatted "cat page".
8759 Each program, utility, and function should have an
8760 associated manual page included in the same package. It is
8761 suggested that all configuration files also have a manual
8762 page included as well. Manual pages for protocols and other
8763 auxiliary things are optional.
8767 If no manual page is available, this is considered as a bug
8768 and should be reported to the Debian Bug Tracking System (the
8769 maintainer of the package is allowed to write this bug report
8770 themselves, if they so desire). Do not close the bug report
8771 until a proper man page is available.<footnote>
8772 It is not very hard to write a man page. See the
8773 <url id="http://www.schweikhardt.net/man_page_howto.html"
8774 name="Man-Page-HOWTO">,
8775 <manref name="man" section="7">, the examples
8776 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8777 the helper programs <prgn>help2man</prgn>, or the
8778 directory <file>/usr/share/doc/man-db/examples</file>.
8783 You may forward a complaint about a missing man page to the
8784 upstream authors, and mark the bug as forwarded in the
8785 Debian bug tracking system. Even though the GNU Project do
8786 not in general consider the lack of a man page to be a bug,
8787 we do; if they tell you that they don't consider it a bug
8788 you should leave the bug in our bug tracking system open
8793 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8797 If one man page needs to be accessible via several names it
8798 is better to use a symbolic link than the <file>.so</file>
8799 feature, but there is no need to fiddle with the relevant
8800 parts of the upstream source to change from <file>.so</file> to
8801 symlinks: don't do it unless it's easy. You should not
8802 create hard links in the manual page directories, nor put
8803 absolute filenames in <file>.so</file> directives. The filename
8804 in a <file>.so</file> in a man page should be relative to the
8805 base of the man page tree (usually
8806 <file>/usr/share/man</file>). If you do not create any links
8807 (whether symlinks, hard links, or <tt>.so</tt> directives)
8808 in the file system to the alternate names of the man page,
8809 then you should not rely on <prgn>man</prgn> finding your
8810 man page under those names based solely on the information in
8811 the man page's header.<footnote>
8812 Supporting this in <prgn>man</prgn> often requires
8813 unreasonable processing time to find a manual page or to
8814 report that none exists, and moves knowledge into man's
8815 database that would be better left in the file system.
8816 This support is therefore deprecated and will cease to
8817 be present in the future.
8822 Manual pages in locale-specific subdirectories of
8823 <file>/usr/share/man</file> should use either UTF-8 or the usual
8824 legacy encoding for that language (normally the one corresponding
8825 to the shortest relevant locale name in
8826 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8827 <file>/usr/share/man/fr</file> should use either UTF-8 or
8828 ISO-8859-1.<footnote>
8829 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8830 use. In future, all manual pages will be required to use
8836 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8837 included in the subdirectory name unless it indicates a
8838 significant difference in the language, as this excludes
8839 speakers of the language in other countries.<footnote>
8840 At the time of writing, Chinese and Portuguese are the main
8841 languages with such differences, so <file>pt_BR</file>,
8842 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8847 Due to limitations in current implementations, all characters
8848 in the manual page source should be representable in the usual
8849 legacy encoding for that language, even if the file is
8850 actually encoded in UTF-8. Safe alternative ways to write many
8851 characters outside that range may be found in
8852 <manref name="groff_char" section="7">.
8857 <heading>Info documents</heading>
8860 Info documents should be installed in <file>/usr/share/info</file>.
8861 They should be compressed with <tt>gzip -9</tt>.
8865 Your package should call <prgn>install-info</prgn> to update
8866 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8867 script when called with a <tt>configure</tt> argument, for
8869 <example compact="compact">
8870 install-info --quiet --section Development Development \
8871 /usr/share/info/foobar.info
8875 It is a good idea to specify a section for the location of
8876 your program; this is done with the <tt>--section</tt>
8877 switch. To determine which section to use, you should look
8878 at <file>/usr/share/info/dir</file> on your system and choose the most
8879 relevant (or create a new section if none of the current
8880 sections are relevant). Note that the <tt>--section</tt>
8881 flag takes two arguments; the first is a regular expression
8882 to match (case-insensitively) against an existing section,
8883 the second is used when creating a new one.</p>
8886 You should remove the entries in the <prgn>prerm</prgn>
8887 script when called with a <tt>remove</tt> argument:
8888 <example compact="compact">
8889 install-info --quiet --remove /usr/share/info/foobar.info
8893 If <prgn>install-info</prgn> cannot find a description entry
8894 in the Info file you must supply one. See <manref
8895 name="install-info" section="8"> for details.</p>
8899 <heading>Additional documentation</heading>
8902 Any additional documentation that comes with the package may
8903 be installed at the discretion of the package maintainer.
8904 Plain text documentation should be installed in the directory
8905 <file>/usr/share/doc/<var>package</var></file>, where
8906 <var>package</var> is the name of the package, and
8907 compressed with <tt>gzip -9</tt> unless it is small.
8911 If a package comes with large amounts of documentation which
8912 many users of the package will not require you should create
8913 a separate binary package to contain it, so that it does not
8914 take up disk space on the machines of users who do not need
8915 or want it installed.</p>
8918 It is often a good idea to put text information files
8919 (<file>README</file>s, changelogs, and so forth) that come with
8920 the source package in <file>/usr/share/doc/<var>package</var></file>
8921 in the binary package. However, you don't need to install
8922 the instructions for building and installing the package, of
8926 Packages must not require the existence of any files in
8927 <file>/usr/share/doc/</file> in order to function
8929 The system administrator should be able to
8930 delete files in <file>/usr/share/doc/</file> without causing
8931 any programs to break.
8933 Any files that are referenced by programs but are also
8934 useful as stand alone documentation should be installed under
8935 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8936 <file>/usr/share/doc/<var>package</var></file>.
8940 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8941 link to another directory in <file>/usr/share/doc</file> only if
8942 the two packages both come from the same source and the
8943 first package Depends on the second.<footnote>
8945 Please note that this does not override the section on
8946 changelog files below, so the file
8947 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8948 must refer to the changelog for the current version of
8949 <var>package</var> in question. In practice, this means
8950 that the sources of the target and the destination of the
8951 symlink must be the same (same source package and
8958 Former Debian releases placed all additional documentation
8959 in <file>/usr/doc/<var>package</var></file>. This has been
8960 changed to <file>/usr/share/doc/<var>package</var></file>,
8961 and packages must not put documentation in the directory
8962 <file>/usr/doc/<var>package</var></file>. <footnote>
8963 At this phase of the transition, we no longer require a
8964 symbolic link in <file>/usr/doc/</file>. At a later point,
8965 policy shall change to make the symbolic links a bug.
8971 <heading>Preferred documentation formats</heading>
8974 The unification of Debian documentation is being carried out
8978 If your package comes with extensive documentation in a
8979 markup format that can be converted to various other formats
8980 you should if possible ship HTML versions in a binary
8981 package, in the directory
8982 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8983 its subdirectories.<footnote>
8984 The rationale: The important thing here is that HTML
8985 docs should be available in <em>some</em> package, not
8986 necessarily in the main binary package.
8991 Other formats such as PostScript may be provided at the
8992 package maintainer's discretion.
8996 <sect id="copyrightfile">
8997 <heading>Copyright information</heading>
9000 Every package must be accompanied by a verbatim copy of its
9001 copyright and distribution license in the file
9002 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9003 file must neither be compressed nor be a symbolic link.
9007 In addition, the copyright file must say where the upstream
9008 sources (if any) were obtained. It should name the original
9009 authors of the package and the Debian maintainer(s) who were
9010 involved with its creation.
9014 Packages in the <em>contrib</em> or <em>non-free</em> archive
9015 areas should state in the copyright file that the package is not
9016 part of the Debian GNU/Linux distribution and briefly explain
9021 A copy of the file which will be installed in
9022 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9023 be in <file>debian/copyright</file> in the source package.
9027 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9028 link to another directory in <file>/usr/share/doc</file> only if
9029 the two packages both come from the same source and the
9030 first package Depends on the second. These rules are
9031 important because copyrights must be extractable by
9036 Packages distributed under the UCB BSD license, the Apache
9037 license (version 2.0), the Artistic license, the GNU GPL
9038 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and the
9039 GNU FDL (versions 1.2 or 1.3) should refer to the corresponding
9040 files under <file>/usr/share/common-licenses</file>,<footnote>
9043 <file>/usr/share/common-licenses/BSD</file>,
9044 <file>/usr/share/common-licenses/Apache-2.0</file>,
9045 <file>/usr/share/common-licenses/Artistic</file>,
9046 <file>/usr/share/common-licenses/GPL-2</file>,
9047 <file>/usr/share/common-licenses/GPL-3</file>,
9048 <file>/usr/share/common-licenses/LGPL-2</file>,
9049 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9050 <file>/usr/share/common-licenses/LGPL-3</file>,
9051 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9052 <file>/usr/share/common-licenses/GFDL-1.3</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>
10655 <!-- Local variables: -->
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