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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 <sect1 id="f-Maintainer">
2594 <heading><tt>Maintainer</tt></heading>
2597 The package maintainer's name and email address. The name
2598 should come first, then the email address inside angle
2599 brackets <tt><></tt> (in RFC822 format).
2603 If the maintainer's name contains a full stop then the
2604 whole field will not work directly as an email address due
2605 to a misfeature in the syntax specified in RFC822; a
2606 program using this field as an address must check for this
2607 and correct the problem if necessary (for example by
2608 putting the name in round brackets and moving it to the
2609 end, and bringing the email address forward).
2613 <sect1 id="f-Uploaders">
2614 <heading><tt>Uploaders</tt></heading>
2617 List of the names and email addresses of co-maintainers of
2618 the package, if any. If the package has other maintainers
2619 beside the one named in the
2620 <qref id="f-Maintainer">Maintainer field</qref>, their
2621 names and email addresses should be listed here. The
2622 format is the same as that of the Maintainer tag, and
2623 multiple entries should be comma separated. Currently,
2624 this field is restricted to a single line of data. This
2625 is an optional field.
2628 Any parser that interprets the Uploaders field in
2629 <file>debian/control</file> must permit it to span multiple
2630 lines. Line breaks in an Uploaders field that spans multiple
2631 lines are not significant and the semantics of the field are
2632 the same as if the line breaks had not been present.
2636 <sect1 id="f-Changed-By">
2637 <heading><tt>Changed-By</tt></heading>
2640 The name and email address of the person who changed the
2641 said package. Usually the name of the maintainer.
2642 All the rules for the Maintainer field apply here, too.
2646 <sect1 id="f-Section">
2647 <heading><tt>Section</tt></heading>
2650 This field specifies an application area into which the package
2651 has been classified. See <ref id="subsections">.
2655 When it appears in the <file>debian/control</file> file,
2656 it gives the value for the subfield of the same name in
2657 the <tt>Files</tt> field of the <file>.changes</file> file.
2658 It also gives the default for the same field in the binary
2663 <sect1 id="f-Priority">
2664 <heading><tt>Priority</tt></heading>
2667 This field represents how important that it is that the user
2668 have the package installed. See <ref id="priorities">.
2672 When it appears in the <file>debian/control</file> file,
2673 it gives the value for the subfield of the same name in
2674 the <tt>Files</tt> field of the <file>.changes</file> file.
2675 It also gives the default for the same field in the binary
2680 <sect1 id="f-Package">
2681 <heading><tt>Package</tt></heading>
2684 The name of the binary package.
2688 Package names must consist only of lower case letters
2689 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2690 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2691 They must be at least two characters long and must start
2692 with an alphanumeric character.
2696 <sect1 id="f-Architecture">
2697 <heading><tt>Architecture</tt></heading>
2700 Depending on context and the control file used, the
2701 <tt>Architecture</tt> field can include the following sets of
2704 <item>A unique single word identifying a Debian machine
2705 architecture, see <ref id="arch-spec">.
2706 <item><tt>all</tt>, which indicates an
2707 architecture-independent package.
2708 <item><tt>any</tt>, which indicates a package available
2709 for building on any architecture.
2710 <item><tt>source</tt>, which indicates a source package.
2715 In the main <file>debian/control</file> file in the source
2716 package, or in the source package control file
2717 <file>.dsc</file>, one may specify a list of architectures
2718 separated by spaces, or the special values <tt>any</tt> or
2723 Specifying <tt>any</tt> indicates that the source package
2724 isn't dependent on any particular architecture and should
2725 compile fine on any one. The produced binary package(s)
2726 will be specific to whatever the current build architecture
2728 This is the most often used setting, and is recommended
2729 for new packages that aren't <tt>Architecture: all</tt>.
2734 Specifying a list of architectures indicates that the source
2735 will build an architecture-dependent package, and will only
2736 work correctly on the listed architectures.<footnote>
2737 This is a setting used for a minority of cases where the
2738 program is not portable. Generally, it should not be used
2744 In a <file>.changes</file> file, the <tt>Architecture</tt>
2745 field lists the architecture(s) of the package(s)
2746 currently being uploaded. This will be a list; if the
2747 source for the package is also being uploaded, the special
2748 entry <tt>source</tt> is also present.
2752 See <ref id="debianrules"> for information how to get the
2753 architecture for the build process.
2757 <sect1 id="f-Essential">
2758 <heading><tt>Essential</tt></heading>
2761 This is a boolean field which may occur only in the
2762 control file of a binary package or in a per-package fields
2763 paragraph of a main source control data file.
2767 If set to <tt>yes</tt> then the package management system
2768 will refuse to remove the package (upgrading and replacing
2769 it is still possible). The other possible value is <tt>no</tt>,
2770 which is the same as not having the field at all.
2775 <heading>Package interrelationship fields:
2776 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2777 <tt>Recommends</tt>, <tt>Suggests</tt>,
2778 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2779 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2783 These fields describe the package's relationships with
2784 other packages. Their syntax and semantics are described
2785 in <ref id="relationships">.</p>
2788 <sect1 id="f-Standards-Version">
2789 <heading><tt>Standards-Version</tt></heading>
2792 The most recent version of the standards (the policy
2793 manual and associated texts) with which the package
2798 The version number has four components: major and minor
2799 version number and major and minor patch level. When the
2800 standards change in a way that requires every package to
2801 change the major number will be changed. Significant
2802 changes that will require work in many packages will be
2803 signaled by a change to the minor number. The major patch
2804 level will be changed for any change to the meaning of the
2805 standards, however small; the minor patch level will be
2806 changed when only cosmetic, typographical or other edits
2807 are made which neither change the meaning of the document
2808 nor affect the contents of packages.
2812 Thus only the first three components of the policy version
2813 are significant in the <em>Standards-Version</em> control
2814 field, and so either these three components or the all
2815 four components may be specified.<footnote>
2816 In the past, people specified the full version number
2817 in the Standards-Version field, for example "2.3.0.0".
2818 Since minor patch-level changes don't introduce new
2819 policy, it was thought it would be better to relax
2820 policy and only require the first 3 components to be
2821 specified, in this example "2.3.0". All four
2822 components may still be used if someone wishes to do so.
2828 <sect1 id="f-Version">
2829 <heading><tt>Version</tt></heading>
2832 The version number of a package. The format is:
2833 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2837 The three components here are:
2839 <tag><var>epoch</var></tag>
2842 This is a single (generally small) unsigned integer. It
2843 may be omitted, in which case zero is assumed. If it is
2844 omitted then the <var>upstream_version</var> may not
2849 It is provided to allow mistakes in the version numbers
2850 of older versions of a package, and also a package's
2851 previous version numbering schemes, to be left behind.
2855 <tag><var>upstream_version</var></tag>
2858 This is the main part of the version number. It is
2859 usually the version number of the original ("upstream")
2860 package from which the <file>.deb</file> file has been made,
2861 if this is applicable. Usually this will be in the same
2862 format as that specified by the upstream author(s);
2863 however, it may need to be reformatted to fit into the
2864 package management system's format and comparison
2869 The comparison behavior of the package management system
2870 with respect to the <var>upstream_version</var> is
2871 described below. The <var>upstream_version</var>
2872 portion of the version number is mandatory.
2876 The <var>upstream_version</var> may contain only
2877 alphanumerics<footnote>
2878 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2880 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2881 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2882 tilde) and should start with a digit. If there is no
2883 <var>debian_revision</var> then hyphens are not allowed;
2884 if there is no <var>epoch</var> then colons are not
2889 <tag><var>debian_revision</var></tag>
2892 This part of the version number specifies the version of
2893 the Debian package based on the upstream version. It
2894 may contain only alphanumerics and the characters
2895 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2896 tilde) and is compared in the same way as the
2897 <var>upstream_version</var> is.
2901 It is optional; if it isn't present then the
2902 <var>upstream_version</var> may not contain a hyphen.
2903 This format represents the case where a piece of
2904 software was written specifically to be turned into a
2905 Debian package, and so there is only one "debianisation"
2906 of it and therefore no revision indication is required.
2910 It is conventional to restart the
2911 <var>debian_revision</var> at <tt>1</tt> each time the
2912 <var>upstream_version</var> is increased.
2916 The package management system will break the version
2917 number apart at the last hyphen in the string (if there
2918 is one) to determine the <var>upstream_version</var> and
2919 <var>debian_revision</var>. The absence of a
2920 <var>debian_revision</var> is equivalent to a
2921 <var>debian_revision</var> of <tt>0</tt>.
2928 When comparing two version numbers, first the <var>epoch</var>
2929 of each are compared, then the <var>upstream_version</var> if
2930 <var>epoch</var> is equal, and then <var>debian_revision</var>
2931 if <var>upstream_version</var> is also equal.
2932 <var>epoch</var> is compared numerically. The
2933 <var>upstream_version</var> and <var>debian_revision</var>
2934 parts are compared by the package management system using the
2935 following algorithm:
2939 The strings are compared from left to right.
2943 First the initial part of each string consisting entirely of
2944 non-digit characters is determined. These two parts (one of
2945 which may be empty) are compared lexically. If a difference
2946 is found it is returned. The lexical comparison is a
2947 comparison of ASCII values modified so that all the letters
2948 sort earlier than all the non-letters and so that a tilde
2949 sorts before anything, even the end of a part. For example,
2950 the following parts are in sorted order from earliest to
2951 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2952 <tt>a</tt>.<footnote>
2953 One common use of <tt>~</tt> is for upstream pre-releases.
2954 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2955 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2960 Then the initial part of the remainder of each string which
2961 consists entirely of digit characters is determined. The
2962 numerical values of these two parts are compared, and any
2963 difference found is returned as the result of the comparison.
2964 For these purposes an empty string (which can only occur at
2965 the end of one or both version strings being compared) counts
2970 These two steps (comparing and removing initial non-digit
2971 strings and initial digit strings) are repeated until a
2972 difference is found or both strings are exhausted.
2976 Note that the purpose of epochs is to allow us to leave behind
2977 mistakes in version numbering, and to cope with situations
2978 where the version numbering scheme changes. It is
2979 <em>not</em> intended to cope with version numbers containing
2980 strings of letters which the package management system cannot
2981 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2982 silly orderings (the author of this manual has heard of a
2983 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2984 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2985 <tt>2</tt> and so forth).
2989 <sect1 id="f-Description">
2990 <heading><tt>Description</tt></heading>
2993 In a source or binary control file, the <tt>Description</tt>
2994 field contains a description of the binary package, consisting
2995 of two parts, the synopsis or the short description, and the
2996 long description. The field's format is as follows:
3001 Description: <single line synopsis>
3002 <extended description over several lines>
3007 The lines in the extended description can have these formats:
3013 Those starting with a single space are part of a paragraph.
3014 Successive lines of this form will be word-wrapped when
3015 displayed. The leading space will usually be stripped off.
3019 Those starting with two or more spaces. These will be
3020 displayed verbatim. If the display cannot be panned
3021 horizontally, the displaying program will line wrap them "hard"
3022 (i.e., without taking account of word breaks). If it can they
3023 will be allowed to trail off to the right. None, one or two
3024 initial spaces may be deleted, but the number of spaces
3025 deleted from each line will be the same (so that you can have
3026 indenting work correctly, for example).
3030 Those containing a single space followed by a single full stop
3031 character. These are rendered as blank lines. This is the
3032 <em>only</em> way to get a blank line<footnote>
3033 Completely empty lines will not be rendered as blank lines.
3034 Instead, they will cause the parser to think you're starting
3035 a whole new record in the control file, and will therefore
3036 likely abort with an error.
3041 Those containing a space, a full stop and some more characters.
3042 These are for future expansion. Do not use them.
3048 Do not use tab characters. Their effect is not predictable.
3052 See <ref id="descriptions"> for further information on this.
3056 In a <file>.changes</file> file, the <tt>Description</tt> field
3057 contains a summary of the descriptions for the packages being
3062 The part of the field before the first newline is empty;
3063 thereafter each line has the name of a binary package and
3064 the summary description line from that binary package.
3065 Each line is indented by one space.
3070 <sect1 id="f-Distribution">
3071 <heading><tt>Distribution</tt></heading>
3074 In a <file>.changes</file> file or parsed changelog output
3075 this contains the (space-separated) name(s) of the
3076 distribution(s) where this version of the package should
3077 be installed. Valid distributions are determined by the
3078 archive maintainers.<footnote>
3079 Current distribution names are:
3080 <taglist compact="compact">
3081 <tag><em>stable</em></tag>
3083 This is the current "released" version of Debian
3084 GNU/Linux. Once the distribution is
3085 <em>stable</em> only security fixes and other
3086 major bug fixes are allowed. When changes are
3087 made to this distribution, the release number is
3088 increased (for example: 2.2r1 becomes 2.2r2 then
3092 <tag><em>unstable</em></tag>
3094 This distribution value refers to the
3095 <em>developmental</em> part of the Debian
3096 distribution tree. New packages, new upstream
3097 versions of packages and bug fixes go into the
3098 <em>unstable</em> directory tree. Download from
3099 this distribution at your own risk.
3102 <tag><em>testing</em></tag>
3104 This distribution value refers to the
3105 <em>testing</em> part of the Debian distribution
3106 tree. It receives its packages from the
3107 unstable distribution after a short time lag to
3108 ensure that there are no major issues with the
3109 unstable packages. It is less prone to breakage
3110 than unstable, but still risky. It is not
3111 possible to upload packages directly to
3115 <tag><em>frozen</em></tag>
3117 From time to time, the <em>testing</em>
3118 distribution enters a state of "code-freeze" in
3119 anticipation of release as a <em>stable</em>
3120 version. During this period of testing only
3121 fixes for existing or newly-discovered bugs will
3122 be allowed. The exact details of this stage are
3123 determined by the Release Manager.
3126 <tag><em>experimental</em></tag>
3128 The packages with this distribution value are
3129 deemed by their maintainers to be high
3130 risk. Oftentimes they represent early beta or
3131 developmental packages from various sources that
3132 the maintainers want people to try, but are not
3133 ready to be a part of the other parts of the
3134 Debian distribution tree. Download at your own
3140 You should list <em>all</em> distributions that the
3141 package should be installed into.
3145 More information is available in the Debian Developer's
3146 Reference, section "The Debian archive".
3153 <heading><tt>Date</tt></heading>
3156 This field includes the date the package was built or last edited.
3160 The value of this field is usually extracted from the
3161 <file>debian/changelog</file> file - see
3162 <ref id="dpkgchangelog">).
3166 <sect1 id="f-Format">
3167 <heading><tt>Format</tt></heading>
3170 This field specifies a format revision for the file.
3171 The most current format described in the Policy Manual
3172 is version <strong>1.5</strong>. The syntax of the
3173 format value is the same as that of a package version
3174 number except that no epoch or Debian revision is allowed
3175 - see <ref id="f-Version">.
3179 <sect1 id="f-Urgency">
3180 <heading><tt>Urgency</tt></heading>
3183 This is a description of how important it is to upgrade to
3184 this version from previous ones. It consists of a single
3185 keyword taking one of the values <tt>low</tt>,
3186 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3187 <tt>critical</tt><footnote>
3188 Other urgency values are supported with configuration
3189 changes in the archive software but are not used in Debian.
3190 The urgency affects how quickly a package will be considered
3191 for inclusion into the <tt>testing</tt> distribution and
3192 gives an indication of the importance of any fixes included
3193 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3194 treated as synonymous.
3195 </footnote> (not case-sensitive) followed by an optional
3196 commentary (separated by a space) which is usually in
3197 parentheses. For example:
3200 Urgency: low (HIGH for users of diversions)
3206 The value of this field is usually extracted from the
3207 <file>debian/changelog</file> file - see
3208 <ref id="dpkgchangelog">.
3212 <sect1 id="f-Changes">
3213 <heading><tt>Changes</tt></heading>
3216 This field contains the human-readable changes data, describing
3217 the differences between the last version and the current one.
3221 There should be nothing in this field before the first
3222 newline; all the subsequent lines must be indented by at
3223 least one space; blank lines must be represented by a line
3224 consisting only of a space and a full stop.
3228 The value of this field is usually extracted from the
3229 <file>debian/changelog</file> file - see
3230 <ref id="dpkgchangelog">).
3234 Each version's change information should be preceded by a
3235 "title" line giving at least the version, distribution(s)
3236 and urgency, in a human-readable way.
3240 If data from several versions is being returned the entry
3241 for the most recent version should be returned first, and
3242 entries should be separated by the representation of a
3243 blank line (the "title" line may also be followed by the
3244 representation of blank line).
3248 <sect1 id="f-Binary">
3249 <heading><tt>Binary</tt></heading>
3252 This field is a list of binary packages.
3256 When it appears in the <file>.dsc</file> file it is the list
3257 of binary packages which a source package can produce. It
3258 does not necessarily produce all of these binary packages
3259 for every architecture. The source control file doesn't
3260 contain details of which architectures are appropriate for
3261 which of the binary packages.
3265 When it appears in a <file>.changes</file> file it lists the
3266 names of the binary packages actually being uploaded.
3270 The syntax is a list of binary packages separated by
3272 A space after each comma is conventional.
3273 </footnote>. Currently the packages must be separated using
3274 only spaces in the <file>.changes</file> file.
3278 <sect1 id="f-Installed-Size">
3279 <heading><tt>Installed-Size</tt></heading>
3282 This field appears in the control files of binary
3283 packages, and in the <file>Packages</file> files. It gives
3284 the total amount of disk space required to install the
3289 The disk space is represented in kilobytes as a simple
3294 <sect1 id="f-Files">
3295 <heading><tt>Files</tt></heading>
3298 This field contains a list of files with information about
3299 each one. The exact information and syntax varies with
3300 the context. In all cases the part of the field
3301 contents on the same line as the field name is empty. The
3302 remainder of the field is one line per file, each line
3303 being indented by one space and containing a number of
3304 sub-fields separated by spaces.
3308 In the <file>.dsc</file> file, each line contains the MD5
3309 checksum, size and filename of the tar file and (if applicable)
3310 diff file which make up the remainder of the source
3312 That is, the parts which are not the <tt>.dsc</tt>.
3314 The exact forms of the filenames are described
3315 in <ref id="pkg-sourcearchives">.
3319 In the <file>.changes</file> file this contains one line per
3320 file being uploaded. Each line contains the MD5 checksum,
3321 size, section and priority and the filename.
3322 The <qref id="f-Section">section</qref>
3323 and <qref id="f-Priority">priority</qref>
3324 are the values of the corresponding fields in
3325 the main source control file. If no section or priority is
3326 specified then <tt>-</tt> should be used, though section
3327 and priority values must be specified for new packages to
3328 be installed properly.
3332 The special value <tt>byhand</tt> for the section in a
3333 <tt>.changes</tt> file indicates that the file in question
3334 is not an ordinary package file and must by installed by
3335 hand by the distribution maintainers. If the section is
3336 <tt>byhand</tt> the priority should be <tt>-</tt>.
3340 If a new Debian revision of a package is being shipped and
3341 no new original source archive is being distributed the
3342 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3343 entry for the original source archive
3344 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3345 but the <file>.changes</file> file should leave it out. In
3346 this case the original source archive on the distribution
3347 site must match exactly, byte-for-byte, the original
3348 source archive which was used to generate the
3349 <file>.dsc</file> file and diff which are being uploaded.</p>
3352 <sect1 id="f-Closes">
3353 <heading><tt>Closes</tt></heading>
3356 A space-separated list of bug report numbers that the upload
3357 governed by the .changes file closes.
3361 <sect1 id="f-Homepage">
3362 <heading><tt>Homepage</tt></heading>
3365 The URL of the web site for this package, preferably (when
3366 applicable) the site from which the original source can be
3367 obtained and any additional upstream documentation or
3368 information may be found. The content of this field is a
3369 simple URL without any surrounding characters such as
3377 <heading>User-defined fields</heading>
3380 Additional user-defined fields may be added to the
3381 source package control file. Such fields will be
3382 ignored, and not copied to (for example) binary or
3383 source package control files or upload control files.
3387 If you wish to add additional unsupported fields to
3388 these output files you should use the mechanism
3393 Fields in the main source control information file with
3394 names starting <tt>X</tt>, followed by one or more of
3395 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3396 be copied to the output files. Only the part of the
3397 field name after the hyphen will be used in the output
3398 file. Where the letter <tt>B</tt> is used the field
3399 will appear in binary package control files, where the
3400 letter <tt>S</tt> is used in source package control
3401 files and where <tt>C</tt> is used in upload control
3402 (<tt>.changes</tt>) files.
3406 For example, if the main source information control file
3409 XBS-Comment: I stand between the candle and the star.
3411 then the binary and source package control files will contain the
3414 Comment: I stand between the candle and the star.
3423 <chapt id="maintainerscripts">
3424 <heading>Package maintainer scripts and installation procedure</heading>
3427 <heading>Introduction to package maintainer scripts</heading>
3430 It is possible to supply scripts as part of a package which
3431 the package management system will run for you when your
3432 package is installed, upgraded or removed.
3436 These scripts are the files <prgn>preinst</prgn>,
3437 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3438 <prgn>postrm</prgn> in the control area of the package.
3439 They must be proper executable files; if they are scripts
3440 (which is recommended), they must start with the usual
3441 <tt>#!</tt> convention. They should be readable and
3442 executable by anyone, and must not be world-writable.
3446 The package management system looks at the exit status from
3447 these scripts. It is important that they exit with a
3448 non-zero status if there is an error, so that the package
3449 management system can stop its processing. For shell
3450 scripts this means that you <em>almost always</em> need to
3451 use <tt>set -e</tt> (this is usually true when writing shell
3452 scripts, in fact). It is also important, of course, that
3453 they exit with a zero status if everything went well.
3457 Additionally, packages interacting with users using
3458 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3459 install a <prgn>config</prgn> script in the control area,
3460 see <ref id="maintscriptprompt"> for details.
3464 When a package is upgraded a combination of the scripts from
3465 the old and new packages is called during the upgrade
3466 procedure. If your scripts are going to be at all
3467 complicated you need to be aware of this, and may need to
3468 check the arguments to your scripts.
3472 Broadly speaking the <prgn>preinst</prgn> is called before
3473 (a particular version of) a package is installed, and the
3474 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3475 before (a version of) a package is removed and the
3476 <prgn>postrm</prgn> afterwards.
3480 Programs called from maintainer scripts should not normally
3481 have a path prepended to them. Before installation is
3482 started, the package management system checks to see if the
3483 programs <prgn>ldconfig</prgn>,
3484 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3485 and <prgn>update-rc.d</prgn> can be found via the
3486 <tt>PATH</tt> environment variable. Those programs, and any
3487 other program that one would expect to be in the
3488 <tt>PATH</tt>, should thus be invoked without an absolute
3489 pathname. Maintainer scripts should also not reset the
3490 <tt>PATH</tt>, though they might choose to modify it by
3491 prepending or appending package-specific directories. These
3492 considerations really apply to all shell scripts.</p>
3495 <sect id="idempotency">
3496 <heading>Maintainer scripts idempotency</heading>
3499 It is necessary for the error recovery procedures that the
3500 scripts be idempotent. This means that if it is run
3501 successfully, and then it is called again, it doesn't bomb
3502 out or cause any harm, but just ensures that everything is
3503 the way it ought to be. If the first call failed, or
3504 aborted half way through for some reason, the second call
3505 should merely do the things that were left undone the first
3506 time, if any, and exit with a success status if everything
3508 This is so that if an error occurs, the user interrupts
3509 <prgn>dpkg</prgn> or some other unforeseen circumstance
3510 happens you don't leave the user with a badly-broken
3511 package when <prgn>dpkg</prgn> attempts to repeat the
3517 <sect id="controllingterminal">
3518 <heading>Controlling terminal for maintainer scripts</heading>
3521 The maintainer scripts are guaranteed to run with a
3522 controlling terminal and can interact with the user.
3523 Because these scripts may be executed with standard output
3524 redirected into a pipe for logging purposes, Perl scripts
3525 should set unbuffered output by setting <tt>$|=1</tt> so
3526 that the output is printed immediately rather than being
3530 <sect id="exitstatus">
3531 <heading>Exit status</heading>
3534 Each script must return a zero exit status for
3535 success, or a nonzero one for failure, since the package
3536 management system looks for the exit status of these scripts
3537 and determines what action to take next based on that datum.
3541 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3546 <list compact="compact">
3548 <var>new-preinst</var> <tt>install</tt>
3551 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3554 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3557 <var>old-preinst</var> <tt>abort-upgrade</tt>
3558 <var>new-version</var>
3563 <list compact="compact">
3565 <var>postinst</var> <tt>configure</tt>
3566 <var>most-recently-configured-version</var>
3569 <var>old-postinst</var> <tt>abort-upgrade</tt>
3570 <var>new-version</var>
3573 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3574 <tt>in-favour</tt> <var>package</var>
3575 <var>new-version</var>
3578 <var>postinst</var> <tt>abort-remove</tt>
3581 <var>deconfigured's-postinst</var>
3582 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3583 <var>failed-install-package</var> <var>version</var>
3584 [<tt>removing</tt> <var>conflicting-package</var>
3590 <list compact="compact">
3592 <var>prerm</var> <tt>remove</tt>
3595 <var>old-prerm</var> <tt>upgrade</tt>
3596 <var>new-version</var>
3599 <var>new-prerm</var> <tt>failed-upgrade</tt>
3600 <var>old-version</var>
3603 <var>conflictor's-prerm</var> <tt>remove</tt>
3604 <tt>in-favour</tt> <var>package</var>
3605 <var>new-version</var>
3608 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3609 <tt>in-favour</tt> <var>package-being-installed</var>
3610 <var>version</var> [<tt>removing</tt>
3611 <var>conflicting-package</var>
3617 <list compact="compact">
3619 <var>postrm</var> <tt>remove</tt>
3622 <var>postrm</var> <tt>purge</tt>
3625 <var>old-postrm</var> <tt>upgrade</tt>
3626 <var>new-version</var>
3629 <var>new-postrm</var> <tt>failed-upgrade</tt>
3630 <var>old-version</var>
3633 <var>new-postrm</var> <tt>abort-install</tt>
3636 <var>new-postrm</var> <tt>abort-install</tt>
3637 <var>old-version</var>
3640 <var>new-postrm</var> <tt>abort-upgrade</tt>
3641 <var>old-version</var>
3644 <var>disappearer's-postrm</var> <tt>disappear</tt>
3645 <var>overwriter</var>
3646 <var>overwriter-version</var>
3652 <sect id="unpackphase">
3653 <heading>Details of unpack phase of installation or upgrade</heading>
3656 The procedure on installation/upgrade/overwrite/disappear
3657 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3658 stage of <tt>dpkg --install</tt>) is as follows. In each
3659 case, if a major error occurs (unless listed below) the
3660 actions are, in general, run backwards - this means that the
3661 maintainer scripts are run with different arguments in
3662 reverse order. These are the "error unwind" calls listed
3669 If a version of the package is already installed, call
3670 <example compact="compact">
3671 <var>old-prerm</var> upgrade <var>new-version</var>
3675 If the script runs but exits with a non-zero
3676 exit status, <prgn>dpkg</prgn> will attempt:
3677 <example compact="compact">
3678 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3680 If this works, the upgrade continues. If this
3681 does not work, the error unwind:
3682 <example compact="compact">
3683 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3685 If this works, then the old-version is
3686 "Installed", if not, the old version is in a
3687 "Failed-Config" state.
3693 If a "conflicting" package is being removed at the same time,
3694 or if any package will be broken (due to <tt>Breaks</tt>):
3697 If <tt>--auto-deconfigure</tt> is
3698 specified, call, for each package to be deconfigured
3699 due to <tt>Breaks</tt>:
3700 <example compact="compact">
3701 <var>deconfigured's-prerm</var> deconfigure \
3702 in-favour <var>package-being-installed</var> <var>version</var>
3705 <example compact="compact">
3706 <var>deconfigured's-postinst</var> abort-deconfigure \
3707 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3709 The deconfigured packages are marked as
3710 requiring configuration, so that if
3711 <tt>--install</tt> is used they will be
3712 configured again if possible.
3715 If any packages depended on a conflicting
3716 package being removed and <tt>--auto-deconfigure</tt> is
3717 specified, call, for each such package:
3718 <example compact="compact">
3719 <var>deconfigured's-prerm</var> deconfigure \
3720 in-favour <var>package-being-installed</var> <var>version</var> \
3721 removing <var>conflicting-package</var> <var>version</var>
3724 <example compact="compact">
3725 <var>deconfigured's-postinst</var> abort-deconfigure \
3726 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3727 removing <var>conflicting-package</var> <var>version</var>
3729 The deconfigured packages are marked as
3730 requiring configuration, so that if
3731 <tt>--install</tt> is used they will be
3732 configured again if possible.
3735 To prepare for removal of each conflicting package, call:
3736 <example compact="compact">
3737 <var>conflictor's-prerm</var> remove \
3738 in-favour <var>package</var> <var>new-version</var>
3741 <example compact="compact">
3742 <var>conflictor's-postinst</var> abort-remove \
3743 in-favour <var>package</var> <var>new-version</var>
3752 If the package is being upgraded, call:
3753 <example compact="compact">
3754 <var>new-preinst</var> upgrade <var>old-version</var>
3756 If this fails, we call:
3758 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3765 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3767 is called. If this works, then the old version
3768 is in an "Installed" state, or else it is left
3769 in an "Unpacked" state.
3774 If it fails, then the old version is left
3775 in an "Half-Installed" state.
3782 Otherwise, if the package had some configuration
3783 files from a previous version installed (i.e., it
3784 is in the "configuration files only" state):
3785 <example compact="compact">
3786 <var>new-preinst</var> install <var>old-version</var>
3790 <var>new-postrm</var> abort-install <var>old-version</var>
3792 If this fails, the package is left in a
3793 "Half-Installed" state, which requires a
3794 reinstall. If it works, the packages is left in
3795 a "Config Files" state.
3798 Otherwise (i.e., the package was completely purged):
3799 <example compact="compact">
3800 <var>new-preinst</var> install
3803 <example compact="compact">
3804 <var>new-postrm</var> abort-install
3806 If the error-unwind fails, the package is in a
3807 "Half Installed" phase, and requires a
3808 reinstall. If the error unwind works, the
3809 package is in a not installed state.
3816 The new package's files are unpacked, overwriting any
3817 that may be on the system already, for example any
3818 from the old version of the same package or from
3819 another package. Backups of the old files are kept
3820 temporarily, and if anything goes wrong the package
3821 management system will attempt to put them back as
3822 part of the error unwind.
3826 It is an error for a package to contain files which
3827 are on the system in another package, unless
3828 <tt>Replaces</tt> is used (see <ref id="replaces">).
3830 The following paragraph is not currently the case:
3831 Currently the <tt>- - force-overwrite</tt> flag is
3832 enabled, downgrading it to a warning, but this may not
3838 It is a more serious error for a package to contain a
3839 plain file or other kind of non-directory where another
3840 package has a directory (again, unless
3841 <tt>Replaces</tt> is used). This error can be
3842 overridden if desired using
3843 <tt>--force-overwrite-dir</tt>, but this is not
3848 Packages which overwrite each other's files produce
3849 behavior which, though deterministic, is hard for the
3850 system administrator to understand. It can easily
3851 lead to "missing" programs if, for example, a package
3852 is installed which overwrites a file from another
3853 package, and is then removed again.<footnote>
3854 Part of the problem is due to what is arguably a
3855 bug in <prgn>dpkg</prgn>.
3860 A directory will never be replaced by a symbolic link
3861 to a directory or vice versa; instead, the existing
3862 state (symlink or not) will be left alone and
3863 <prgn>dpkg</prgn> will follow the symlink if there is
3872 If the package is being upgraded, call
3873 <example compact="compact">
3874 <var>old-postrm</var> upgrade <var>new-version</var>
3878 If this fails, <prgn>dpkg</prgn> will attempt:
3879 <example compact="compact">
3880 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3882 If this works, installation continues. If not,
3884 <example compact="compact">
3885 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3887 If this fails, the old version is left in an
3888 "Half Installed" state. If it works, dpkg now
3890 <example compact="compact">
3891 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3893 If this fails, the old version is left in an
3894 "Half Installed" state. If it works, dpkg now
3896 <example compact="compact">
3897 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3899 If this fails, the old version is in an
3906 This is the point of no return - if
3907 <prgn>dpkg</prgn> gets this far, it won't back off
3908 past this point if an error occurs. This will
3909 leave the package in a fairly bad state, which
3910 will require a successful re-installation to clear
3911 up, but it's when <prgn>dpkg</prgn> starts doing
3912 things that are irreversible.
3917 Any files which were in the old version of the package
3918 but not in the new are removed.
3922 The new file list replaces the old.
3926 The new maintainer scripts replace the old.
3930 Any packages all of whose files have been overwritten
3931 during the installation, and which aren't required for
3932 dependencies, are considered to have been removed.
3933 For each such package
3936 <prgn>dpkg</prgn> calls:
3937 <example compact="compact">
3938 <var>disappearer's-postrm</var> disappear \
3939 <var>overwriter</var> <var>overwriter-version</var>
3943 The package's maintainer scripts are removed.
3946 It is noted in the status database as being in a
3947 sane state, namely not installed (any conffiles
3948 it may have are ignored, rather than being
3949 removed by <prgn>dpkg</prgn>). Note that
3950 disappearing packages do not have their prerm
3951 called, because <prgn>dpkg</prgn> doesn't know
3952 in advance that the package is going to
3959 Any files in the package we're unpacking that are also
3960 listed in the file lists of other packages are removed
3961 from those lists. (This will lobotomize the file list
3962 of the "conflicting" package if there is one.)
3966 The backup files made during installation, above, are
3972 The new package's status is now sane, and recorded as
3977 Here is another point of no return - if the
3978 conflicting package's removal fails we do not unwind
3979 the rest of the installation; the conflicting package
3980 is left in a half-removed limbo.
3985 If there was a conflicting package we go and do the
3986 removal actions (described below), starting with the
3987 removal of the conflicting package's files (any that
3988 are also in the package being installed have already
3989 been removed from the conflicting package's file list,
3990 and so do not get removed now).
3996 <sect id="configdetails"><heading>Details of configuration</heading>
3999 When we configure a package (this happens with <tt>dpkg
4000 --install</tt> and <tt>dpkg --configure</tt>), we first
4001 update any <tt>conffile</tt>s and then call:
4002 <example compact="compact">
4003 <var>postinst</var> configure <var>most-recently-configured-version</var>
4008 No attempt is made to unwind after errors during
4009 configuration. If the configuration fails, the package is in
4010 a "Failed Config" state, and an error message is generated.
4014 If there is no most recently configured version
4015 <prgn>dpkg</prgn> will pass a null argument.
4018 Historical note: Truly ancient (pre-1997) versions of
4019 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4020 (including the angle brackets) in this case. Even older
4021 ones did not pass a second argument at all, under any
4022 circumstance. Note that upgrades using such an old dpkg
4023 version are unlikely to work for other reasons, even if
4024 this old argument behavior is handled by your postinst script.
4030 <sect id="removedetails"><heading>Details of removal and/or
4031 configuration purging</heading>
4037 <example compact="compact">
4038 <var>prerm</var> remove
4042 If prerm fails during replacement due to conflict
4044 <var>conflictor's-postinst</var> abort-remove \
4045 in-favour <var>package</var> <var>new-version</var>
4049 <var>postinst</var> abort-remove
4053 If this fails, the package is in a "Failed-Config"
4054 state, or else it remains "Installed".
4058 The package's files are removed (except <tt>conffile</tt>s).
4061 <example compact="compact">
4062 <var>postrm</var> remove
4066 If it fails, there's no error unwind, and the package is in
4067 an "Half-Installed" state.
4072 All the maintainer scripts except the <prgn>postrm</prgn>
4077 If we aren't purging the package we stop here. Note
4078 that packages which have no <prgn>postrm</prgn> and no
4079 <tt>conffile</tt>s are automatically purged when
4080 removed, as there is no difference except for the
4081 <prgn>dpkg</prgn> status.
4085 The <tt>conffile</tt>s and any backup files
4086 (<tt>~</tt>-files, <tt>#*#</tt> files,
4087 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4092 <example compact="compact">
4093 <var>postrm</var> purge
4097 If this fails, the package remains in a "Config-Files"
4102 The package's file list is removed.
4111 <chapt id="relationships">
4112 <heading>Declaring relationships between packages</heading>
4114 <sect id="depsyntax">
4115 <heading>Syntax of relationship fields</heading>
4118 These fields all have a uniform syntax. They are a list of
4119 package names separated by commas.
4123 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4124 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4125 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4126 control file fields of the package, which declare
4127 dependencies on other packages, the package names listed may
4128 also include lists of alternative package names, separated
4129 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4130 if any one of the alternative packages is installed, that
4131 part of the dependency is considered to be satisfied.
4135 All of the fields except for <tt>Provides</tt> may restrict
4136 their applicability to particular versions of each named
4137 package. This is done in parentheses after each individual
4138 package name; the parentheses should contain a relation from
4139 the list below followed by a version number, in the format
4140 described in <ref id="f-Version">.
4144 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4145 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4146 strictly earlier, earlier or equal, exactly equal, later or
4147 equal and strictly later, respectively. The deprecated
4148 forms <tt><</tt> and <tt>></tt> were used to mean
4149 earlier/later or equal, rather than strictly earlier/later,
4150 so they should not appear in new packages (though
4151 <prgn>dpkg</prgn> still supports them).
4155 Whitespace may appear at any point in the version
4156 specification subject to the rules in <ref
4157 id="controlsyntax">, and must appear where it's necessary to
4158 disambiguate; it is not otherwise significant. All of the
4159 relationship fields may span multiple lines. For
4160 consistency and in case of future changes to
4161 <prgn>dpkg</prgn> it is recommended that a single space be
4162 used after a version relationship and before a version
4163 number; it is also conventional to put a single space after
4164 each comma, on either side of each vertical bar, and before
4165 each open parenthesis. When wrapping a relationship field, it
4166 is conventional to do so after a comma and before the space
4167 following that comma.
4171 For example, a list of dependencies might appear as:
4172 <example compact="compact">
4175 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4180 All fields that specify build-time relationships
4181 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4182 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4183 may be restricted to a certain set of architectures. This
4184 is indicated in brackets after each individual package name and
4185 the optional version specification. The brackets enclose a
4186 list of Debian architecture names separated by whitespace.
4187 Exclamation marks may be prepended to each of the names.
4188 (It is not permitted for some names to be prepended with
4189 exclamation marks while others aren't.) If the current Debian
4190 host architecture is not in this list and there are no
4191 exclamation marks in the list, or it is in the list with a
4192 prepended exclamation mark, the package name and the
4193 associated version specification are ignored completely for
4194 the purposes of defining the relationships.
4199 <example compact="compact">
4201 Build-Depends-Indep: texinfo
4202 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4203 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4205 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4206 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4207 <tt>gnumach-dev</tt> only on hurd-i386.
4211 If the architecture-restricted dependency is part of a set of
4212 alternatives using <tt>|</tt>, that alternative is ignored
4213 completely on architectures that do not match the restriction.
4215 <example compact="compact">
4216 Build-Depends: foo [!i386] | bar [!amd64]
4218 is equivalent to <tt>bar</tt> on the i386 architecture, to
4219 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4220 bar</tt> on all other architectures.
4224 Note that the binary package relationship fields such as
4225 <tt>Depends</tt> appear in one of the binary package
4226 sections of the control file, whereas the build-time
4227 relationships such as <tt>Build-Depends</tt> appear in the
4228 source package section of the control file (which is the
4233 <sect id="binarydeps">
4234 <heading>Binary Dependencies - <tt>Depends</tt>,
4235 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4236 <tt>Pre-Depends</tt>
4240 Packages can declare in their control file that they have
4241 certain relationships to other packages - for example, that
4242 they may not be installed at the same time as certain other
4243 packages, and/or that they depend on the presence of others.
4247 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4248 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4249 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4253 These seven fields are used to declare a dependency
4254 relationship by one package on another. Except for
4255 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4256 depending (binary) package's control file.
4257 (<tt>Enhances</tt> appears in the recommending package's
4258 control file, and <tt>Breaks</tt> appears in the version of
4259 depended-on package which causes the named package to
4264 A <tt>Depends</tt> field takes effect <em>only</em> when a
4265 package is to be configured. It does not prevent a package
4266 being on the system in an unconfigured state while its
4267 dependencies are unsatisfied, and it is possible to replace
4268 a package whose dependencies are satisfied and which is
4269 properly installed with a different version whose
4270 dependencies are not and cannot be satisfied; when this is
4271 done the depending package will be left unconfigured (since
4272 attempts to configure it will give errors) and will not
4273 function properly. If it is necessary, a
4274 <tt>Pre-Depends</tt> field can be used, which has a partial
4275 effect even when a package is being unpacked, as explained
4276 in detail below. (The other three dependency fields,
4277 <tt>Recommends</tt>, <tt>Suggests</tt> and
4278 <tt>Enhances</tt>, are only used by the various front-ends
4279 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4280 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4284 For this reason packages in an installation run are usually
4285 all unpacked first and all configured later; this gives
4286 later versions of packages with dependencies on later
4287 versions of other packages the opportunity to have their
4288 dependencies satisfied.
4292 In case of circular dependencies, since installation or
4293 removal order honoring the dependency order can't be
4294 established, dependency loops are broken at some point
4295 (based on rules below), and some packages may not be able to
4296 rely on their dependencies being present when being
4297 installed or removed, depending on which side of the break
4298 of the circular dependency loop they happen to be on. If one
4299 of the packages in the loop has no postinst script, then the
4300 cycle will be broken at that package, so as to ensure that
4301 all postinst scripts run with the dependencies properly
4302 configured if this is possible. Otherwise the breaking point
4307 The <tt>Depends</tt> field thus allows package maintainers
4308 to impose an order in which packages should be configured.
4312 The meaning of the five dependency fields is as follows:
4314 <tag><tt>Depends</tt></tag>
4317 This declares an absolute dependency. A package will
4318 not be configured unless all of the packages listed in
4319 its <tt>Depends</tt> field have been correctly
4324 The <tt>Depends</tt> field should be used if the
4325 depended-on package is required for the depending
4326 package to provide a significant amount of
4331 The <tt>Depends</tt> field should also be used if the
4332 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4333 <prgn>postrm</prgn> scripts require the package to be
4334 present in order to run. Note, however, that the
4335 <prgn>postrm</prgn> cannot rely on any non-essential
4336 packages to be present during the <tt>purge</tt>
4340 <tag><tt>Recommends</tt></tag>
4343 This declares a strong, but not absolute, dependency.
4347 The <tt>Recommends</tt> field should list packages
4348 that would be found together with this one in all but
4349 unusual installations.
4353 <tag><tt>Suggests</tt></tag>
4355 This is used to declare that one package may be more
4356 useful with one or more others. Using this field
4357 tells the packaging system and the user that the
4358 listed packages are related to this one and can
4359 perhaps enhance its usefulness, but that installing
4360 this one without them is perfectly reasonable.
4363 <tag><tt>Enhances</tt></tag>
4365 This field is similar to Suggests but works in the
4366 opposite direction. It is used to declare that a
4367 package can enhance the functionality of another
4371 <tag><tt>Pre-Depends</tt></tag>
4374 This field is like <tt>Depends</tt>, except that it
4375 also forces <prgn>dpkg</prgn> to complete installation
4376 of the packages named before even starting the
4377 installation of the package which declares the
4378 pre-dependency, as follows:
4382 When a package declaring a pre-dependency is about to
4383 be <em>unpacked</em> the pre-dependency can be
4384 satisfied if the depended-on package is either fully
4385 configured, <em>or even if</em> the depended-on
4386 package(s) are only unpacked or half-configured,
4387 provided that they have been configured correctly at
4388 some point in the past (and not removed or partially
4389 removed since). In this case, both the
4390 previously-configured and currently unpacked or
4391 half-configured versions must satisfy any version
4392 clause in the <tt>Pre-Depends</tt> field.
4396 When the package declaring a pre-dependency is about
4397 to be <em>configured</em>, the pre-dependency will be
4398 treated as a normal <tt>Depends</tt>, that is, it will
4399 be considered satisfied only if the depended-on
4400 package has been correctly configured.
4404 <tt>Pre-Depends</tt> should be used sparingly,
4405 preferably only by packages whose premature upgrade or
4406 installation would hamper the ability of the system to
4407 continue with any upgrade that might be in progress.
4411 <tt>Pre-Depends</tt> are also required if the
4412 <prgn>preinst</prgn> script depends on the named
4413 package. It is best to avoid this situation if
4421 When selecting which level of dependency to use you should
4422 consider how important the depended-on package is to the
4423 functionality of the one declaring the dependency. Some
4424 packages are composed of components of varying degrees of
4425 importance. Such a package should list using
4426 <tt>Depends</tt> the package(s) which are required by the
4427 more important components. The other components'
4428 requirements may be mentioned as Suggestions or
4429 Recommendations, as appropriate to the components' relative
4435 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4438 Using <tt>Breaks</tt> may cause problems for upgrades from older
4439 versions of Debian and should not be used until the stable
4440 release of Debian supports <tt>Breaks</tt>.
4444 When one binary package declares that it breaks another,
4445 <prgn>dpkg</prgn> will refuse to allow the package which
4446 declares <tt>Breaks</tt> be installed unless the broken
4447 package is deconfigured first, and it will refuse to
4448 allow the broken package to be reconfigured.
4452 A package will not be regarded as causing breakage merely
4453 because its configuration files are still installed; it must
4454 be at least half-installed.
4458 A special exception is made for packages which declare that
4459 they break their own package name or a virtual package which
4460 they provide (see below): this does not count as a real
4465 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4466 version clause; such a <tt>Breaks</tt> is introduced in the
4467 version of an (implicit or explicit) dependency which
4468 violates an assumption or reveals a bug in earlier versions
4469 of the broken package. This use of <tt>Breaks</tt> will
4470 inform higher-level package management tools that broken
4471 package must be upgraded before the new one.
4475 If the breaking package also overwrites some files from the
4476 older package, it should use <tt>Replaces</tt> (not
4477 <tt>Conflicts</tt>) to ensure this goes smoothly.
4481 <sect id="conflicts">
4482 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4485 When one binary package declares a conflict with another
4486 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4487 refuse to allow them to be installed on the system at the
4492 If one package is to be installed, the other must be removed
4493 first - if the package being installed is marked as
4494 replacing (see <ref id="replaces">) the one on the system,
4495 or the one on the system is marked as deselected, or both
4496 packages are marked <tt>Essential</tt>, then
4497 <prgn>dpkg</prgn> will automatically remove the package
4498 which is causing the conflict, otherwise it will halt the
4499 installation of the new package with an error. This
4500 mechanism is specifically designed to produce an error when
4501 the installed package is <tt>Essential</tt>, but the new
4506 A package will not cause a conflict merely because its
4507 configuration files are still installed; it must be at least
4512 A special exception is made for packages which declare a
4513 conflict with their own package name, or with a virtual
4514 package which they provide (see below): this does not
4515 prevent their installation, and allows a package to conflict
4516 with others providing a replacement for it. You use this
4517 feature when you want the package in question to be the only
4518 package providing some feature.
4522 A <tt>Conflicts</tt> entry should almost never have an
4523 "earlier than" version clause. This would prevent
4524 <prgn>dpkg</prgn> from upgrading or installing the package
4525 which declared such a conflict until the upgrade or removal
4526 of the conflicted-with package had been completed. Instead,
4527 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4528 by the stable release of Debian).
4532 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4536 As well as the names of actual ("concrete") packages, the
4537 package relationship fields <tt>Depends</tt>,
4538 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4539 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4540 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4541 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4542 may mention "virtual packages".
4546 A <em>virtual package</em> is one which appears in the
4547 <tt>Provides</tt> control file field of another package.
4548 The effect is as if the package(s) which provide a
4549 particular virtual package name had been listed by name
4550 everywhere the virtual package name appears. (See also <ref
4555 If there are both concrete and virtual packages of the same
4556 name, then the dependency may be satisfied (or the conflict
4557 caused) by either the concrete package with the name in
4558 question or any other concrete package which provides the
4559 virtual package with the name in question. This is so that,
4560 for example, supposing we have
4561 <example compact="compact">
4564 </example> and someone else releases an enhanced version of
4565 the <tt>bar</tt> package they can say:
4566 <example compact="compact">
4570 and the <tt>bar-plus</tt> package will now also satisfy the
4571 dependency for the <tt>foo</tt> package.
4575 If a relationship field has a version number attached
4576 then only real packages will be considered to see whether
4577 the relationship is satisfied (or the prohibition violated,
4578 for a conflict or breakage) - it is assumed that a real
4579 package which provides the virtual package is not of the
4580 "right" version. So, a <tt>Provides</tt> field may not
4581 contain version numbers, and the version number of the
4582 concrete package which provides a particular virtual package
4583 will not be looked at when considering a dependency on or
4584 conflict with the virtual package name.
4588 It is likely that the ability will be added in a future
4589 release of <prgn>dpkg</prgn> to specify a version number for
4590 each virtual package it provides. This feature is not yet
4591 present, however, and is expected to be used only
4596 If you want to specify which of a set of real packages
4597 should be the default to satisfy a particular dependency on
4598 a virtual package, you should list the real package as an
4599 alternative before the virtual one.
4604 <sect id="replaces"><heading>Overwriting files and replacing
4605 packages - <tt>Replaces</tt></heading>
4608 Packages can declare in their control file that they should
4609 overwrite files in certain other packages, or completely
4610 replace other packages. The <tt>Replaces</tt> control file
4611 field has these two distinct purposes.
4614 <sect1><heading>Overwriting files in other packages</heading>
4617 Firstly, as mentioned before, it is usually an error for a
4618 package to contain files which are on the system in
4623 However, if the overwriting package declares that it
4624 <tt>Replaces</tt> the one containing the file being
4625 overwritten, then <prgn>dpkg</prgn> will replace the file
4626 from the old package with that from the new. The file
4627 will no longer be listed as "owned" by the old package.
4631 If a package is completely replaced in this way, so that
4632 <prgn>dpkg</prgn> does not know of any files it still
4633 contains, it is considered to have "disappeared". It will
4634 be marked as not wanted on the system (selected for
4635 removal) and not installed. Any <tt>conffile</tt>s
4636 details noted for the package will be ignored, as they
4637 will have been taken over by the overwriting package. The
4638 package's <prgn>postrm</prgn> script will be run with a
4639 special argument to allow the package to do any final
4640 cleanup required. See <ref id="mscriptsinstact">.
4643 Replaces is a one way relationship -- you have to
4644 install the replacing package after the replaced
4651 For this usage of <tt>Replaces</tt>, virtual packages (see
4652 <ref id="virtual">) are not considered when looking at a
4653 <tt>Replaces</tt> field - the packages declared as being
4654 replaced must be mentioned by their real names.
4658 Furthermore, this usage of <tt>Replaces</tt> only takes
4659 effect when both packages are at least partially on the
4660 system at once, so that it can only happen if they do not
4661 conflict or if the conflict has been overridden.
4666 <sect1><heading>Replacing whole packages, forcing their
4670 Secondly, <tt>Replaces</tt> allows the packaging system to
4671 resolve which package should be removed when there is a
4672 conflict - see <ref id="conflicts">. This usage only
4673 takes effect when the two packages <em>do</em> conflict,
4674 so that the two usages of this field do not interfere with
4679 In this situation, the package declared as being replaced
4680 can be a virtual package, so for example, all mail
4681 transport agents (MTAs) would have the following fields in
4682 their control files:
4683 <example compact="compact">
4684 Provides: mail-transport-agent
4685 Conflicts: mail-transport-agent
4686 Replaces: mail-transport-agent
4688 ensuring that only one MTA can be installed at any one
4693 <sect id="sourcebinarydeps">
4694 <heading>Relationships between source and binary packages -
4695 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4696 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4700 Source packages that require certain binary packages to be
4701 installed or absent at the time of building the package
4702 can declare relationships to those binary packages.
4706 This is done using the <tt>Build-Depends</tt>,
4707 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4708 <tt>Build-Conflicts-Indep</tt> control file fields.
4712 Build-dependencies on "build-essential" binary packages can be
4713 omitted. Please see <ref id="pkg-relations"> for more information.
4717 The dependencies and conflicts they define must be satisfied
4718 (as defined earlier for binary packages) in order to invoke
4719 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4721 If you make "build-arch" or "binary-arch", you need
4722 Build-Depends. If you make "build-indep" or
4723 "binary-indep", you need Build-Depends and
4724 Build-Depends-Indep. If you make "build" or "binary",
4728 There is no Build-Depends-Arch; this role is essentially
4729 met with Build-Depends. Anyone building the
4730 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4731 is basically assumed to be building the whole package
4732 anyway and so installs all build dependencies. The
4733 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4734 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4735 does not yet know how to check for its existence) and
4736 <tt>binary-arch</tt>.
4739 The purpose of the original split, I recall, was so that
4740 the autobuilders wouldn't need to install extra packages
4741 needed only for the binary-indep targets. But without a
4742 build-arch/build-indep split, this didn't work, since
4743 most of the work is done in the build target, not in the
4749 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4751 The <tt>Build-Depends</tt> and
4752 <tt>Build-Conflicts</tt> fields must be satisfied when
4753 any of the following targets is invoked:
4754 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4755 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4756 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4758 <tag><tt>Build-Depends-Indep</tt>,
4759 <tt>Build-Conflicts-Indep</tt></tag>
4761 The <tt>Build-Depends-Indep</tt> and
4762 <tt>Build-Conflicts-Indep</tt> fields must be
4763 satisfied when any of the following targets is
4764 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4765 <tt>binary</tt> and <tt>binary-indep</tt>.
4775 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4778 Packages containing shared libraries must be constructed with
4779 a little care to make sure that the shared library is always
4780 available. This is especially important for packages whose
4781 shared libraries are vitally important, such as the C library
4782 (currently <tt>libc6</tt>).
4786 Packages involving shared libraries should be split up into
4787 several binary packages. This section mostly deals with how
4788 this separation is to be accomplished; rules for files within
4789 the shared library packages are in <ref id="libraries"> instead.
4792 <sect id="sharedlibs-runtime">
4793 <heading>Run-time shared libraries</heading>
4796 The run-time shared library needs to be placed in a package
4797 whose name changes whenever the shared object version
4800 Since it is common place to install several versions of a
4801 package that just provides shared libraries, it is a
4802 good idea that the library package should not
4803 contain any extraneous non-versioned files, unless they
4804 happen to be in versioned directories.</p>
4806 The most common mechanism is to place it in a package
4808 <package><var>libraryname</var><var>soversion</var></package>,
4809 where <file><var>soversion</var></file> is the version number
4810 in the soname of the shared library<footnote>
4811 The soname is the shared object name: it's the thing
4812 that has to match exactly between building an executable
4813 and running it for the dynamic linker to be able run the
4814 program. For example, if the soname of the library is
4815 <file>libfoo.so.6</file>, the library package would be
4816 called <file>libfoo6</file>.
4818 Alternatively, if it would be confusing to directly append
4819 <var>soversion</var> to <var>libraryname</var> (e.g. because
4820 <var>libraryname</var> itself ends in a number), you may use
4821 <package><var>libraryname</var>-<var>soversion</var></package> and
4822 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4827 If you have several shared libraries built from the same
4828 source tree you may lump them all together into a single
4829 shared library package, provided that you change all of
4830 their sonames at once (so that you don't get filename
4831 clashes if you try to install different versions of the
4832 combined shared libraries package).
4836 The package should install the shared libraries under
4837 their normal names. For example, the <package>libgdbm3</package>
4838 package should install <file>libgdbm.so.3.0.0</file> as
4839 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4840 renamed or re-linked by any <prgn>prerm</prgn> or
4841 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4842 of renaming things safely without affecting running programs,
4843 and attempts to interfere with this are likely to lead to
4848 Shared libraries should not be installed executable, since
4849 the dynamic linker does not require this and trying to
4850 execute a shared library usually results in a core dump.
4854 The run-time library package should include the symbolic link that
4855 <prgn>ldconfig</prgn> would create for the shared libraries.
4856 For example, the <package>libgdbm3</package> package should include
4857 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4858 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4859 linker (for example <prgn>ld.so</prgn> or
4860 <prgn>ld-linux.so.*</prgn>) can find the library between the
4861 time that <prgn>dpkg</prgn> installs it and the time that
4862 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4864 The package management system requires the library to be
4865 placed before the symbolic link pointing to it in the
4866 <file>.deb</file> file. This is so that when
4867 <prgn>dpkg</prgn> comes to install the symlink
4868 (overwriting the previous symlink pointing at an older
4869 version of the library), the new shared library is already
4870 in place. In the past, this was achieved by creating the
4871 library in the temporary packaging directory before
4872 creating the symlink. Unfortunately, this was not always
4873 effective, since the building of the tar file in the
4874 <file>.deb</file> depended on the behavior of the underlying
4875 file system. Some file systems (such as reiserfs) reorder
4876 the files so that the order of creation is forgotten.
4877 Since version 1.7.0, <prgn>dpkg</prgn>
4878 reorders the files itself as necessary when building a
4879 package. Thus it is no longer important to concern
4880 oneself with the order of file creation.
4884 <sect1 id="ldconfig">
4885 <heading><tt>ldconfig</tt></heading>
4888 Any package installing shared libraries in one of the default
4889 library directories of the dynamic linker (which are currently
4890 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4891 listed in <file>/etc/ld.so.conf</file><footnote>
4893 <list compact="compact">
4894 <item>/usr/local/lib</item>
4895 <item>/usr/lib/libc5-compat</item>
4896 <item>/lib/libc5-compat</item>
4899 must use <prgn>ldconfig</prgn> to update the shared library
4904 The package maintainer scripts must only call
4905 <prgn>ldconfig</prgn> under these circumstances:
4906 <list compact="compact">
4907 <item>When the <prgn>postinst</prgn> script is run with a
4908 first argument of <tt>configure</tt>, the script must call
4909 <prgn>ldconfig</prgn>, and may optionally invoke
4910 <prgn>ldconfig</prgn> at other times.
4912 <item>When the <prgn>postrm</prgn> script is run with a
4913 first argument of <tt>remove</tt>, the script should call
4914 <prgn>ldconfig</prgn>.
4919 During install or upgrade, the preinst is called before
4920 the new files are installed, so calling "ldconfig" is
4921 pointless. The preinst of an existing package can also be
4922 called if an upgrade fails. However, this happens during
4923 the critical time when a shared libs may exist on-disk
4924 under a temporary name. Thus, it is dangerous and
4925 forbidden by current policy to call "ldconfig" at this
4930 When a package is installed or upgraded, "postinst
4931 configure" runs after the new files are safely on-disk.
4932 Since it is perfectly safe to invoke ldconfig
4933 unconditionally in a postinst, it is OK for a package to
4934 simply put ldconfig in its postinst without checking the
4935 argument. The postinst can also be called to recover from
4936 a failed upgrade. This happens before any new files are
4937 unpacked, so there is no reason to call "ldconfig" at this
4942 For a package that is being removed, prerm is
4943 called with all the files intact, so calling ldconfig is
4944 useless. The other calls to "prerm" happen in the case of
4945 upgrade at a time when all the files of the old package
4946 are on-disk, so again calling "ldconfig" is pointless.
4950 postrm, on the other hand, is called with the "remove"
4951 argument just after the files are removed, so this is
4952 the proper time to call "ldconfig" to notify the system
4953 of the fact that the shared libraries from the package
4954 are removed. The postrm can be called at several other
4955 times. At the time of "postrm purge", "postrm
4956 abort-install", or "postrm abort-upgrade", calling
4957 "ldconfig" is useless because the shared lib files are
4958 not on-disk. However, when "postrm" is invoked with
4959 arguments "upgrade", "failed-upgrade", or "disappear", a
4960 shared lib may exist on-disk under a temporary filename.
4968 <sect id="sharedlibs-support-files">
4969 <heading>Shared library support files</heading>
4972 If your package contains files whose names do not change with
4973 each change in the library shared object version, you must not
4974 put them in the shared library package. Otherwise, several
4975 versions of the shared library cannot be installed at the same
4976 time without filename clashes, making upgrades and transitions
4977 unnecessarily difficult.
4981 It is recommended that supporting files and run-time support
4982 programs that do not need to be invoked manually by users, but
4983 are nevertheless required for the package to function, be placed
4984 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4985 preferably under <file>/usr/lib/</file><var>package-name</var>.
4986 If the program or file is architecture independent, the
4987 recommendation is for it to be placed in a subdirectory of
4988 <file>/usr/share</file> instead, preferably under
4989 <file>/usr/share/</file><var>package-name</var>. Following the
4990 <var>package-name</var> naming convention ensures that the file
4991 names change when the shared object version changes.
4995 Run-time support programs that use the shared library but are
4996 not required for the library to function or files used by the
4997 shared library that can be used by any version of the shared
4998 library package should instead be put in a separate package.
4999 This package might typically be named
5000 <package><var>libraryname</var>-tools</package>; note the
5001 absence of the <var>soversion</var> in the package name.
5005 Files and support programs only useful when compiling software
5006 against the library should be included in the development
5007 package for the library.<footnote>
5008 For example, a <file><var>package-name</var>-config</file>
5009 script or <package>pkg-config</package> configuration files.
5014 <sect id="sharedlibs-static">
5015 <heading>Static libraries</heading>
5018 The static library (<file><var>libraryname.a</var></file>)
5019 is usually provided in addition to the shared version.
5020 It is placed into the development package (see below).
5024 In some cases, it is acceptable for a library to be
5025 available in static form only; these cases include:
5027 <item>libraries for languages whose shared library support
5028 is immature or unstable</item>
5029 <item>libraries whose interfaces are in flux or under
5030 development (commonly the case when the library's
5031 major version number is zero, or where the ABI breaks
5032 across patchlevels)</item>
5033 <item>libraries which are explicitly intended to be
5034 available only in static form by their upstream
5039 <sect id="sharedlibs-dev">
5040 <heading>Development files</heading>
5043 The development files associated to a shared library need to be
5044 placed in a package called
5045 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5046 or if you prefer only to support one development version at a
5047 time, <package><var>libraryname</var>-dev</package>.
5051 In case several development versions of a library exist, you may
5052 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5053 <ref id="conflicts">) to ensure that the user only installs one
5054 development version at a time (as different development versions are
5055 likely to have the same header files in them, which would cause a
5056 filename clash if both were installed).
5060 The development package should contain a symlink for the associated
5061 shared library without a version number. For example, the
5062 <package>libgdbm-dev</package> package should include a symlink
5063 from <file>/usr/lib/libgdbm.so</file> to
5064 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5065 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5066 <file>libgdbm.so</file> when compiling dynamically.
5070 <sect id="sharedlibs-intradeps">
5071 <heading>Dependencies between the packages of the same library</heading>
5074 Typically the development version should have an exact
5075 version dependency on the runtime library, to make sure that
5076 compilation and linking happens correctly. The
5077 <tt>${binary:Version}</tt> substitution variable can be
5078 useful for this purpose.
5080 Previously, <tt>${Source-Version}</tt> was used, but its name
5081 was confusing and it has been deprecated since dpkg 1.13.19.
5086 <sect id="sharedlibs-shlibdeps">
5087 <heading>Dependencies between the library and other packages -
5088 the <tt>shlibs</tt> system</heading>
5091 If a package contains a binary or library which links to a
5092 shared library, we must ensure that when the package is
5093 installed on the system, all of the libraries needed are
5094 also installed. This requirement led to the creation of the
5095 <tt>shlibs</tt> system, which is very simple in its design:
5096 any package which <em>provides</em> a shared library also
5097 provides information on the package dependencies required to
5098 ensure the presence of this library, and any package which
5099 <em>uses</em> a shared library uses this information to
5100 determine the dependencies it requires. The files which
5101 contain the mapping from shared libraries to the necessary
5102 dependency information are called <file>shlibs</file> files.
5106 Thus, when a package is built which contains any shared
5107 libraries, it must provide a <file>shlibs</file> file for other
5108 packages to use, and when a package is built which contains
5109 any shared libraries or compiled binaries, it must run
5110 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5111 on these to determine the libraries used and hence the
5112 dependencies needed by this package.<footnote>
5114 In the past, the shared libraries linked to were
5115 determined by calling <prgn>ldd</prgn>, but now
5116 <prgn>objdump</prgn> is used to do this. The only
5117 change this makes to package building is that
5118 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5119 libraries, whereas in the past this was unnecessary.
5120 The rest of this footnote explains the advantage that
5125 We say that a binary <tt>foo</tt> <em>directly</em> uses
5126 a library <tt>libbar</tt> if it is explicitly linked
5127 with that library (that is, it uses the flag
5128 <tt>-lbar</tt> during the linking stage). Other
5129 libraries that are needed by <tt>libbar</tt> are linked
5130 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5131 linker will load them automatically when it loads
5132 <tt>libbar</tt>. A package should depend on
5133 the libraries it directly uses, and the dependencies for
5134 those libraries should automatically pull in the other
5139 Unfortunately, the <prgn>ldd</prgn> program shows both
5140 the directly and indirectly used libraries, meaning that
5141 the dependencies determined included both direct and
5142 indirect dependencies. The use of <prgn>objdump</prgn>
5143 avoids this problem by determining only the directly
5148 A good example of where this helps is the following. We
5149 could update <tt>libimlib</tt> with a new version that
5150 supports a new graphics format called dgf (but retaining
5151 the same major version number). If we used the old
5152 <prgn>ldd</prgn> method, every package that uses
5153 <tt>libimlib</tt> would need to be recompiled so it
5154 would also depend on <tt>libdgf</tt> or it wouldn't run
5155 due to missing symbols. However with the new system,
5156 packages using <tt>libimlib</tt> can rely on
5157 <tt>libimlib</tt> itself having the dependency on
5158 <tt>libdgf</tt> and so they would not need rebuilding.
5164 In the following sections, we will first describe where the
5165 various <tt>shlibs</tt> files are to be found, then how to
5166 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5167 file format and how to create them if your package contains a
5172 <heading>The <tt>shlibs</tt> files present on the system</heading>
5175 There are several places where <tt>shlibs</tt> files are
5176 found. The following list gives them in the order in which
5178 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5179 (The first one which gives the required information is used.)
5185 <p><file>debian/shlibs.local</file></p>
5188 This lists overrides for this package. Its use is
5189 described below (see <ref id="shlibslocal">).
5194 <p><file>/etc/dpkg/shlibs.override</file></p>
5197 This lists global overrides. This list is normally
5198 empty. It is maintained by the local system
5204 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5207 When packages are being built, any
5208 <file>debian/shlibs</file> files are copied into the
5209 control file area of the temporary build directory and
5210 given the name <file>shlibs</file>. These files give
5211 details of any shared libraries included in the
5213 An example may help here. Let us say that the
5214 source package <tt>foo</tt> generates two binary
5215 packages, <tt>libfoo2</tt> and
5216 <tt>foo-runtime</tt>. When building the binary
5217 packages, the two packages are created in the
5218 directories <file>debian/libfoo2</file> and
5219 <file>debian/foo-runtime</file> respectively.
5220 (<file>debian/tmp</file> could be used instead of one
5221 of these.) Since <tt>libfoo2</tt> provides the
5222 <tt>libfoo</tt> shared library, it will require a
5223 <tt>shlibs</tt> file, which will be installed in
5224 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5226 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5227 when <prgn>dpkg-shlibdeps</prgn> is run on the
5229 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5231 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5232 determine whether <tt>foo-prog</tt>'s library
5233 dependencies are satisfied by any of the libraries
5234 provided by <tt>libfoo2</tt>. For this reason,
5235 <prgn>dpkg-shlibdeps</prgn> must only be run once
5236 all of the individual binary packages'
5237 <tt>shlibs</tt> files have been installed into the
5244 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5247 These are the <file>shlibs</file> files corresponding to
5248 all of the packages installed on the system, and are
5249 maintained by the relevant package maintainers.
5254 <p><file>/etc/dpkg/shlibs.default</file></p>
5257 This file lists any shared libraries whose packages
5258 have failed to provide correct <file>shlibs</file> files.
5259 It was used when the <file>shlibs</file> setup was first
5260 introduced, but it is now normally empty. It is
5261 maintained by the <tt>dpkg</tt> maintainer.
5269 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5270 <file>shlibs</file> files</heading>
5274 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5275 into your <file>debian/rules</file> file. If your package
5276 contains only compiled binaries and libraries (but no scripts),
5277 you can use a command such as:
5278 <example compact="compact">
5279 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5280 debian/tmp/usr/lib/*
5282 Otherwise, you will need to explicitly list the compiled
5283 binaries and libraries.<footnote>
5284 If you are using <tt>debhelper</tt>, the
5285 <prgn>dh_shlibdeps</prgn> program will do this work for
5286 you. It will also correctly handle multi-binary
5292 This command puts the dependency information into the
5293 <file>debian/substvars</file> file, which is then used by
5294 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5295 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5296 field in the control file for this to work.
5300 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5301 done. If it does complain you might need to create your own
5302 <file>debian/shlibs.local</file> file, as explained below (see
5303 <ref id="shlibslocal">).
5307 If you have multiple binary packages, you will need to call
5308 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5309 compiled libraries or binaries. In such a case, you will
5310 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5311 utilities to specify a different <file>substvars</file> file.
5315 If you are creating a udeb for use in the Debian Installer, you
5316 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5317 the dependency line of type <tt>udeb</tt> by adding
5318 <tt>-tudeb</tt> as option<footnote>
5319 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5320 will automatically add this option if it knows it is
5322 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5323 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5324 fall back to the regular dependency line.
5328 For more details on dpkg-shlibdeps, please see
5329 <ref id="pkg-dpkg-shlibdeps"> and
5330 <manref name="dpkg-shlibdeps" section="1">.
5335 <heading>The <file>shlibs</file> File Format</heading>
5338 Each <file>shlibs</file> file has the same format. Lines
5339 beginning with <tt>#</tt> are considered to be comments and
5340 are ignored. Each line is of the form:
5341 <example compact="compact">
5342 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5347 We will explain this by reference to the example of the
5348 <tt>zlib1g</tt> package, which (at the time of writing)
5349 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5353 <var>type</var> is an optional element that indicates the type
5354 of package for which the line is valid. The only type currently
5355 in use is <tt>udeb</tt>. The colon and space after the type are
5360 <var>library-name</var> is the name of the shared library,
5361 in this case <tt>libz</tt>. (This must match the name part
5362 of the soname, see below.)
5366 <var>soname-version</var> is the version part of the soname of
5367 the library. The soname is the thing that must exactly match
5368 for the library to be recognized by the dynamic linker, and is
5370 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5371 example, <tt>libz.so.1</tt>.<footnote>
5372 This can be determined using the command
5373 <example compact="compact">
5374 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5377 The version part is the part which comes after
5378 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5382 <var>dependencies</var> has the same syntax as a dependency
5383 field in a binary package control file. It should give
5384 details of which packages are required to satisfy a binary
5385 built against the version of the library contained in the
5386 package. See <ref id="depsyntax"> for details.
5390 In our example, if the first version of the <tt>zlib1g</tt>
5391 package which contained a minor number of at least
5392 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5393 <tt>shlibs</tt> entry for this library could say:
5394 <example compact="compact">
5395 libz 1 zlib1g (>= 1:1.1.3)
5397 The version-specific dependency is to avoid warnings from
5398 the dynamic linker about using older shared libraries with
5403 As zlib1g also provides a udeb containing the shared library,
5404 there would also be a second line:
5405 <example compact="compact">
5406 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5412 <heading>Providing a <file>shlibs</file> file</heading>
5415 If your package provides a shared library, you need to create
5416 a <file>shlibs</file> file following the format described above.
5417 It is usual to call this file <file>debian/shlibs</file> (but if
5418 you have multiple binary packages, you might want to call it
5419 <file>debian/shlibs.<var>package</var></file> instead). Then
5420 let <file>debian/rules</file> install it in the control area:
5421 <example compact="compact">
5422 install -m644 debian/shlibs debian/tmp/DEBIAN
5424 or, in the case of a multi-binary package:
5425 <example compact="compact">
5426 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5428 An alternative way of doing this is to create the
5429 <file>shlibs</file> file in the control area directly from
5430 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5431 file at all,<footnote>
5432 This is what <prgn>dh_makeshlibs</prgn> in the
5433 <tt>debhelper</tt> suite does. If your package also has a udeb
5434 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5435 automatically generate the <tt>udeb:</tt> lines if you specify
5436 the name of the udeb with the <tt>--add-udeb</tt> option.
5438 since the <file>debian/shlibs</file> file itself is ignored by
5439 <prgn>dpkg-shlibdeps</prgn>.
5443 As <prgn>dpkg-shlibdeps</prgn> reads the
5444 <file>DEBIAN/shlibs</file> files in all of the binary packages
5445 being built from this source package, all of the
5446 <file>DEBIAN/shlibs</file> files should be installed before
5447 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5452 <sect1 id="shlibslocal">
5453 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5456 This file is intended only as a <em>temporary</em> fix if
5457 your binaries or libraries depend on a library whose package
5458 does not yet provide a correct <file>shlibs</file> file.
5462 We will assume that you are trying to package a binary
5463 <tt>foo</tt>. When you try running
5464 <prgn>dpkg-shlibdeps</prgn> you get the following error
5465 message (<tt>-O</tt> displays the dependency information on
5466 <tt>stdout</tt> instead of writing it to
5467 <tt>debian/substvars</tt>, and the lines have been wrapped
5468 for ease of reading):
5469 <example compact="compact">
5470 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5471 dpkg-shlibdeps: warning: unable to find dependency
5472 information for shared library libbar (soname 1,
5473 path /usr/lib/libbar.so.1, dependency field Depends)
5474 shlibs:Depends=libc6 (>= 2.2.2-2)
5476 You can then run <prgn>ldd</prgn> on the binary to find the
5477 full location of the library concerned:
5478 <example compact="compact">
5480 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5481 libc.so.6 => /lib/libc.so.6 (0x40032000)
5482 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5484 So the <prgn>foo</prgn> binary depends on the
5485 <prgn>libbar</prgn> shared library, but no package seems to
5486 provide a <file>*.shlibs</file> file handling
5487 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5488 determine the package responsible:
5489 <example compact="compact">
5490 $ dpkg -S /usr/lib/libbar.so.1
5491 bar1: /usr/lib/libbar.so.1
5492 $ dpkg -s bar1 | grep Version
5495 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5496 is the one we are using. Now we can file a bug against the
5497 <tt>bar1</tt> package and create our own
5498 <file>debian/shlibs.local</file> to locally fix the problem.
5499 Including the following line into your
5500 <file>debian/shlibs.local</file> file:
5501 <example compact="compact">
5502 libbar 1 bar1 (>= 1.0-1)
5504 should allow the package build to work.
5508 As soon as the maintainer of <tt>bar1</tt> provides a
5509 correct <file>shlibs</file> file, you should remove this line
5510 from your <file>debian/shlibs.local</file> file. (You should
5511 probably also then have a versioned <tt>Build-Depends</tt>
5512 on <tt>bar1</tt> to help ensure that others do not have the
5513 same problem building your package.)
5522 <chapt id="opersys"><heading>The Operating System</heading>
5525 <heading>File system hierarchy</heading>
5529 <heading>File system Structure</heading>
5532 The location of all installed files and directories must
5533 comply with the File system Hierarchy Standard (FHS),
5534 version 2.3, with the exceptions noted below, and except
5535 where doing so would violate other terms of Debian
5536 Policy. The following exceptions to the FHS apply:
5541 The optional rules related to user specific
5542 configuration files for applications are stored in
5543 the user's home directory are relaxed. It is
5544 recommended that such files start with the
5545 '<tt>.</tt>' character (a "dot file"), and if an
5546 application needs to create more than one dot file
5547 then the preferred placement is in a subdirectory
5548 with a name starting with a '.' character, (a "dot
5549 directory"). In this case it is recommended the
5550 configuration files not start with the '.'
5556 The requirement for amd64 to use <file>/lib64</file>
5557 for 64 bit binaries is removed.
5562 The requirement that
5563 <file>/usr/local/share/man</file> be "synonymous"
5564 with <file>/usr/local/man</file> is relaxed to a
5569 The requirement that windowmanagers with a single
5570 configuration file call it <file>system.*wmrc</file>
5571 is removed, as is the restriction that the window
5572 manager subdirectory be named identically to the
5573 window manager name itself.
5578 The requirement that boot manager configuration
5579 files live in <file>/etc</file>, or at least are
5580 symlinked there, is relaxed to a recommendation.
5587 The version of this document referred here can be
5588 found in the <tt>debian-policy</tt> package or on <url
5589 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5590 name="FHS (Debian copy)"> alongside this manual (or, if
5591 you have the <package>debian-policy</package> installed,
5593 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5594 (local copy)">). The
5595 latest version, which may be a more recent version, may
5597 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5598 Specific questions about following the standard may be
5599 asked on the <tt>debian-devel</tt> mailing list, or
5600 referred to the FHS mailing list (see the
5601 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5607 <heading>Site-specific programs</heading>
5610 As mandated by the FHS, packages must not place any
5611 files in <file>/usr/local</file>, either by putting them in
5612 the file system archive to be unpacked by <prgn>dpkg</prgn>
5613 or by manipulating them in their maintainer scripts.
5617 However, the package may create empty directories below
5618 <file>/usr/local</file> so that the system administrator knows
5619 where to place site-specific files. These are not
5620 directories <em>in</em> <file>/usr/local</file>, but are
5621 children of directories in <file>/usr/local</file>. These
5622 directories (<file>/usr/local/*/dir/</file>)
5623 should be removed on package removal if they are
5628 Note, that this applies only to directories <em>below</em>
5629 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5630 Packages must not create sub-directories in the directory
5631 <file>/usr/local</file> itself, except those listed in FHS,
5632 section 4.5. However, you may create directories below
5633 them as you wish. You must not remove any of the
5634 directories listed in 4.5, even if you created them.
5638 Since <file>/usr/local</file> can be mounted read-only from a
5639 remote server, these directories must be created and
5640 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5641 maintainer scripts and not be included in the
5642 <file>.deb</file> archive. These scripts must not fail if
5643 either of these operations fail.
5647 For example, the <tt>emacsen-common</tt> package could
5648 contain something like
5649 <example compact="compact">
5650 if [ ! -e /usr/local/share/emacs ]
5652 if mkdir /usr/local/share/emacs 2>/dev/null
5654 chown root:staff /usr/local/share/emacs
5655 chmod 2775 /usr/local/share/emacs
5659 in its <prgn>postinst</prgn> script, and
5660 <example compact="compact">
5661 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5662 rmdir /usr/local/share/emacs 2>/dev/null || true
5664 in the <prgn>prerm</prgn> script. (Note that this form is
5665 used to ensure that if the script is interrupted, the
5666 directory <file>/usr/local/share/emacs</file> will still be
5671 If you do create a directory in <file>/usr/local</file> for
5672 local additions to a package, you should ensure that
5673 settings in <file>/usr/local</file> take precedence over the
5674 equivalents in <file>/usr</file>.
5678 However, because <file>/usr/local</file> and its contents are
5679 for exclusive use of the local administrator, a package
5680 must not rely on the presence or absence of files or
5681 directories in <file>/usr/local</file> for normal operation.
5685 The <file>/usr/local</file> directory itself and all the
5686 subdirectories created by the package should (by default) have
5687 permissions 2775 (group-writable and set-group-id) and be
5688 owned by <tt>root:staff</tt>.
5693 <heading>The system-wide mail directory</heading>
5695 The system-wide mail directory is <file>/var/mail</file>. This
5696 directory is part of the base system and should not owned
5697 by any particular mail agents. The use of the old
5698 location <file>/var/spool/mail</file> is deprecated, even
5699 though the spool may still be physically located there.
5705 <heading>Users and groups</heading>
5708 <heading>Introduction</heading>
5710 The Debian system can be configured to use either plain or
5715 Some user ids (UIDs) and group ids (GIDs) are reserved
5716 globally for use by certain packages. Because some
5717 packages need to include files which are owned by these
5718 users or groups, or need the ids compiled into binaries,
5719 these ids must be used on any Debian system only for the
5720 purpose for which they are allocated. This is a serious
5721 restriction, and we should avoid getting in the way of
5722 local administration policies. In particular, many sites
5723 allocate users and/or local system groups starting at 100.
5727 Apart from this we should have dynamically allocated ids,
5728 which should by default be arranged in some sensible
5729 order, but the behavior should be configurable.
5733 Packages other than <tt>base-passwd</tt> must not modify
5734 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5735 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5740 <heading>UID and GID classes</heading>
5742 The UID and GID numbers are divided into classes as
5748 Globally allocated by the Debian project, the same
5749 on every Debian system. These ids will appear in
5750 the <file>passwd</file> and <file>group</file> files of all
5751 Debian systems, new ids in this range being added
5752 automatically as the <tt>base-passwd</tt> package is
5757 Packages which need a single statically allocated
5758 uid or gid should use one of these; their
5759 maintainers should ask the <tt>base-passwd</tt>
5767 Dynamically allocated system users and groups.
5768 Packages which need a user or group, but can have
5769 this user or group allocated dynamically and
5770 differently on each system, should use <tt>adduser
5771 --system</tt> to create the group and/or user.
5772 <prgn>adduser</prgn> will check for the existence of
5773 the user or group, and if necessary choose an unused
5774 id based on the ranges specified in
5775 <file>adduser.conf</file>.
5779 <tag>1000-29999:</tag>
5782 Dynamically allocated user accounts. By default
5783 <prgn>adduser</prgn> will choose UIDs and GIDs for
5784 user accounts in this range, though
5785 <file>adduser.conf</file> may be used to modify this
5790 <tag>30000-59999:</tag>
5795 <tag>60000-64999:</tag>
5798 Globally allocated by the Debian project, but only
5799 created on demand. The ids are allocated centrally
5800 and statically, but the actual accounts are only
5801 created on users' systems on demand.
5805 These ids are for packages which are obscure or
5806 which require many statically-allocated ids. These
5807 packages should check for and create the accounts in
5808 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5809 <prgn>adduser</prgn> if it has this facility) if
5810 necessary. Packages which are likely to require
5811 further allocations should have a "hole" left after
5812 them in the allocation, to give them room to
5817 <tag>65000-65533:</tag>
5825 User <tt>nobody</tt>. The corresponding gid refers
5826 to the group <tt>nogroup</tt>.
5833 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5834 not</em> be used, because it is the error return
5843 <sect id="sysvinit">
5844 <heading>System run levels and <file>init.d</file> scripts</heading>
5846 <sect1 id="/etc/init.d">
5847 <heading>Introduction</heading>
5850 The <file>/etc/init.d</file> directory contains the scripts
5851 executed by <prgn>init</prgn> at boot time and when the
5852 init state (or "runlevel") is changed (see <manref
5853 name="init" section="8">).
5857 There are at least two different, yet functionally
5858 equivalent, ways of handling these scripts. For the sake
5859 of simplicity, this document describes only the symbolic
5860 link method. However, it must not be assumed by maintainer
5861 scripts that this method is being used, and any automated
5862 manipulation of the various runlevel behaviors by
5863 maintainer scripts must be performed using
5864 <prgn>update-rc.d</prgn> as described below and not by
5865 manually installing or removing symlinks. For information
5866 on the implementation details of the other method,
5867 implemented in the <tt>file-rc</tt> package, please refer
5868 to the documentation of that package.
5872 These scripts are referenced by symbolic links in the
5873 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5874 runlevels, <prgn>init</prgn> looks in the directory
5875 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5876 execute, where <tt><var>n</var></tt> is the runlevel that
5877 is being changed to, or <tt>S</tt> for the boot-up
5882 The names of the links all have the form
5883 <file>S<var>mm</var><var>script</var></file> or
5884 <file>K<var>mm</var><var>script</var></file> where
5885 <var>mm</var> is a two-digit number and <var>script</var>
5886 is the name of the script (this should be the same as the
5887 name of the actual script in <file>/etc/init.d</file>).
5891 When <prgn>init</prgn> changes runlevel first the targets
5892 of the links whose names start with a <tt>K</tt> are
5893 executed, each with the single argument <tt>stop</tt>,
5894 followed by the scripts prefixed with an <tt>S</tt>, each
5895 with the single argument <tt>start</tt>. (The links are
5896 those in the <file>/etc/rc<var>n</var>.d</file> directory
5897 corresponding to the new runlevel.) The <tt>K</tt> links
5898 are responsible for killing services and the <tt>S</tt>
5899 link for starting services upon entering the runlevel.
5903 For example, if we are changing from runlevel 2 to
5904 runlevel 3, init will first execute all of the <tt>K</tt>
5905 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5906 all of the <tt>S</tt> prefixed scripts in that directory.
5907 The links starting with <tt>K</tt> will cause the
5908 referred-to file to be executed with an argument of
5909 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5914 The two-digit number <var>mm</var> is used to determine
5915 the order in which to run the scripts: low-numbered links
5916 have their scripts run first. For example, the
5917 <tt>K20</tt> scripts will be executed before the
5918 <tt>K30</tt> scripts. This is used when a certain service
5919 must be started before another. For example, the name
5920 server <prgn>bind</prgn> might need to be started before
5921 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5922 can set up its access lists. In this case, the script
5923 that starts <prgn>bind</prgn> would have a lower number
5924 than the script that starts <prgn>inn</prgn> so that it
5926 <example compact="compact">
5933 The two runlevels 0 (halt) and 6 (reboot) are slightly
5934 different. In these runlevels, the links with an
5935 <tt>S</tt> prefix are still called after those with a
5936 <tt>K</tt> prefix, but they too are called with the single
5937 argument <tt>stop</tt>.
5942 <heading>Writing the scripts</heading>
5945 Packages that include daemons for system services should
5946 place scripts in <file>/etc/init.d</file> to start or stop
5947 services at boot time or during a change of runlevel.
5948 These scripts should be named
5949 <file>/etc/init.d/<var>package</var></file>, and they should
5950 accept one argument, saying what to do:
5953 <tag><tt>start</tt></tag>
5954 <item>start the service,</item>
5956 <tag><tt>stop</tt></tag>
5957 <item>stop the service,</item>
5959 <tag><tt>restart</tt></tag>
5960 <item>stop and restart the service if it's already running,
5961 otherwise start the service</item>
5963 <tag><tt>reload</tt></tag>
5964 <item><p>cause the configuration of the service to be
5965 reloaded without actually stopping and restarting
5968 <tag><tt>force-reload</tt></tag>
5969 <item>cause the configuration to be reloaded if the
5970 service supports this, otherwise restart the
5974 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5975 <tt>force-reload</tt> options should be supported by all
5976 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5981 The <file>init.d</file> scripts must ensure that they will
5982 behave sensibly (i.e., returning success and not starting
5983 multiple copies of a service) if invoked with <tt>start</tt>
5984 when the service is already running, or with <tt>stop</tt>
5985 when it isn't, and that they don't kill unfortunately-named
5986 user processes. The best way to achieve this is usually to
5987 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5992 If a service reloads its configuration automatically (as
5993 in the case of <prgn>cron</prgn>, for example), the
5994 <tt>reload</tt> option of the <file>init.d</file> script
5995 should behave as if the configuration has been reloaded
6000 The <file>/etc/init.d</file> scripts must be treated as
6001 configuration files, either (if they are present in the
6002 package, that is, in the .deb file) by marking them as
6003 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6004 by managing them correctly in the maintainer scripts (see
6005 <ref id="config-files">). This is important since we want
6006 to give the local system administrator the chance to adapt
6007 the scripts to the local system, e.g., to disable a
6008 service without de-installing the package, or to specify
6009 some special command line options when starting a service,
6010 while making sure their changes aren't lost during the next
6015 These scripts should not fail obscurely when the
6016 configuration files remain but the package has been
6017 removed, as configuration files remain on the system after
6018 the package has been removed. Only when <prgn>dpkg</prgn>
6019 is executed with the <tt>--purge</tt> option will
6020 configuration files be removed. In particular, as the
6021 <file>/etc/init.d/<var>package</var></file> script itself is
6022 usually a <tt>conffile</tt>, it will remain on the system
6023 if the package is removed but not purged. Therefore, you
6024 should include a <tt>test</tt> statement at the top of the
6026 <example compact="compact">
6027 test -f <var>program-executed-later-in-script</var> || exit 0
6032 Often there are some variables in the <file>init.d</file>
6033 scripts whose values control the behavior of the scripts,
6034 and which a system administrator is likely to want to
6035 change. As the scripts themselves are frequently
6036 <tt>conffile</tt>s, modifying them requires that the
6037 administrator merge in their changes each time the package
6038 is upgraded and the <tt>conffile</tt> changes. To ease
6039 the burden on the system administrator, such configurable
6040 values should not be placed directly in the script.
6041 Instead, they should be placed in a file in
6042 <file>/etc/default</file>, which typically will have the same
6043 base name as the <file>init.d</file> script. This extra file
6044 should be sourced by the script when the script runs. It
6045 must contain only variable settings and comments in SUSv3
6046 <prgn>sh</prgn> format. It may either be a
6047 <tt>conffile</tt> or a configuration file maintained by
6048 the package maintainer scripts. See <ref id="config-files">
6053 To ensure that vital configurable values are always
6054 available, the <file>init.d</file> script should set default
6055 values for each of the shell variables it uses, either
6056 before sourcing the <file>/etc/default/</file> file or
6057 afterwards using something like the <tt>:
6058 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6059 script must behave sensibly and not fail if the
6060 <file>/etc/default</file> file is deleted.
6064 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6065 as temporary filesystems<footnote>
6066 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6067 options in <file>/etc/default/rcS</file>.
6068 </footnote>, so the <file>init.d</file> scripts must handle this
6069 correctly. This will typically amount to creating any required
6070 subdirectories dynamically when the <file>init.d</file> script
6071 is run, rather than including them in the package and relying on
6072 <prgn>dpkg</prgn> to create them.
6077 <heading>Interfacing with the initscript system</heading>
6080 Maintainers should use the abstraction layer provided by
6081 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6082 programs to deal with initscripts in their packages'
6083 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6084 and <prgn>postrm</prgn>.
6088 Directly managing the /etc/rc?.d links and directly
6089 invoking the <file>/etc/init.d/</file> initscripts should
6090 be done only by packages providing the initscript
6091 subsystem (such as <prgn>sysv-rc</prgn> and
6092 <prgn>file-rc</prgn>).
6096 <heading>Managing the links</heading>
6099 The program <prgn>update-rc.d</prgn> is provided for
6100 package maintainers to arrange for the proper creation and
6101 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6102 or their functional equivalent if another method is being
6103 used. This may be used by maintainers in their packages'
6104 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6108 You must not include any <file>/etc/rc<var>n</var>.d</file>
6109 symbolic links in the actual archive or manually create or
6110 remove the symbolic links in maintainer scripts; you must
6111 use the <prgn>update-rc.d</prgn> program instead. (The
6112 former will fail if an alternative method of maintaining
6113 runlevel information is being used.) You must not include
6114 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6115 in the archive either. (Only the <tt>sysvinit</tt>
6120 By default <prgn>update-rc.d</prgn> will start services in
6121 each of the multi-user state runlevels (2, 3, 4, and 5)
6122 and stop them in the halt runlevel (0), the single-user
6123 runlevel (1) and the reboot runlevel (6). The system
6124 administrator will have the opportunity to customize
6125 runlevels by simply adding, moving, or removing the
6126 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6127 symbolic links are being used, or by modifying
6128 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6133 To get the default behavior for your package, put in your
6134 <prgn>postinst</prgn> script
6135 <example compact="compact">
6136 update-rc.d <var>package</var> defaults
6138 and in your <prgn>postrm</prgn>
6139 <example compact="compact">
6140 if [ "$1" = purge ]; then
6141 update-rc.d <var>package</var> remove
6143 </example>. Note that if your package changes runlevels
6144 or priority, you may have to remove and recreate the links,
6145 since otherwise the old links may persist. Refer to the
6146 documentation of <prgn>update-rc.d</prgn>.
6150 This will use a default sequence number of 20. If it does
6151 not matter when or in which order the <file>init.d</file>
6152 script is run, use this default. If it does, then you
6153 should talk to the maintainer of the <prgn>sysvinit</prgn>
6154 package or post to <tt>debian-devel</tt>, and they will
6155 help you choose a number.
6159 For more information about using <tt>update-rc.d</tt>,
6160 please consult its man page <manref name="update-rc.d"
6166 <heading>Running initscripts</heading>
6168 The program <prgn>invoke-rc.d</prgn> is provided to make
6169 it easier for package maintainers to properly invoke an
6170 initscript, obeying runlevel and other locally-defined
6171 constraints that might limit a package's right to start,
6172 stop and otherwise manage services. This program may be
6173 used by maintainers in their packages' scripts.
6177 The package maintainer scripts must use
6178 <prgn>invoke-rc.d</prgn> to invoke the
6179 <file>/etc/init.d/*</file> initscripts, instead of
6180 calling them directly.
6184 By default, <prgn>invoke-rc.d</prgn> will pass any
6185 action requests (start, stop, reload, restart...) to the
6186 <file>/etc/init.d</file> script, filtering out requests
6187 to start or restart a service out of its intended
6192 Most packages will simply need to change:
6193 <example compact="compact">/etc/init.d/<package>
6194 <action></example> in their <prgn>postinst</prgn>
6195 and <prgn>prerm</prgn> scripts to:
6196 <example compact="compact">
6197 if which invoke-rc.d >/dev/null 2>&1; then
6198 invoke-rc.d <var>package</var> <action>
6200 /etc/init.d/<var>package</var> <action>
6206 A package should register its initscript services using
6207 <prgn>update-rc.d</prgn> before it tries to invoke them
6208 using <prgn>invoke-rc.d</prgn>. Invocation of
6209 unregistered services may fail.
6213 For more information about using
6214 <prgn>invoke-rc.d</prgn>, please consult its man page
6215 <manref name="invoke-rc.d" section="8">.
6221 <heading>Boot-time initialization</heading>
6224 There used to be another directory, <file>/etc/rc.boot</file>,
6225 which contained scripts which were run once per machine
6226 boot. This has been deprecated in favour of links from
6227 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6228 described in <ref id="/etc/init.d">. Packages must not
6229 place files in <file>/etc/rc.boot</file>.
6234 <heading>Example</heading>
6237 An example on which you can base your
6238 <file>/etc/init.d</file> scripts is found in
6239 <file>/etc/init.d/skeleton</file>.
6246 <heading>Console messages from <file>init.d</file> scripts</heading>
6249 This section describes the formats to be used for messages
6250 written to standard output by the <file>/etc/init.d</file>
6251 scripts. The intent is to improve the consistency of
6252 Debian's startup and shutdown look and feel. For this
6253 reason, please look very carefully at the details. We want
6254 the messages to have the same format in terms of wording,
6255 spaces, punctuation and case of letters.
6259 Here is a list of overall rules that should be used for
6260 messages generated by <file>/etc/init.d</file> scripts.
6266 The message should fit in one line (fewer than 80
6267 characters), start with a capital letter and end with
6268 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6272 If the script is performing some time consuming task in
6273 the background (not merely starting or stopping a
6274 program, for instance), an ellipsis (three dots:
6275 <tt>...</tt>) should be output to the screen, with no
6276 leading or tailing whitespace or line feeds.
6280 The messages should appear as if the computer is telling
6281 the user what it is doing (politely :-), but should not
6282 mention "it" directly. For example, instead of:
6283 <example compact="compact">
6284 I'm starting network daemons: nfsd mountd.
6286 the message should say
6287 <example compact="compact">
6288 Starting network daemons: nfsd mountd.
6295 <tt>init.d</tt> script should use the following standard
6296 message formats for the situations enumerated below.
6302 <p>When daemons are started</p>
6305 If the script starts one or more daemons, the output
6306 should look like this (a single line, no leading
6308 <example compact="compact">
6309 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6311 The <var>description</var> should describe the
6312 subsystem the daemon or set of daemons are part of,
6313 while <var>daemon-1</var> up to <var>daemon-n</var>
6314 denote each daemon's name (typically the file name of
6319 For example, the output of <file>/etc/init.d/lpd</file>
6321 <example compact="compact">
6322 Starting printer spooler: lpd.
6327 This can be achieved by saying
6328 <example compact="compact">
6329 echo -n "Starting printer spooler: lpd"
6330 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6333 in the script. If there are more than one daemon to
6334 start, the output should look like this:
6335 <example compact="compact">
6336 echo -n "Starting remote file system services:"
6337 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6338 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6339 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6342 This makes it possible for the user to see what is
6343 happening and when the final daemon has been started.
6344 Care should be taken in the placement of white spaces:
6345 in the example above the system administrators can
6346 easily comment out a line if they don't want to start
6347 a specific daemon, while the displayed message still
6353 <p>When a system parameter is being set</p>
6356 If you have to set up different system parameters
6357 during the system boot, you should use this format:
6358 <example compact="compact">
6359 Setting <var>parameter</var> to "<var>value</var>".
6364 You can use a statement such as the following to get
6366 <example compact="compact">
6367 echo "Setting DNS domainname to \"$domainname\"."
6372 Note that the same symbol (<tt>"</tt>) is used for the left
6373 and right quotation marks. A grave accent (<tt>`</tt>) is
6374 not a quote character; neither is an apostrophe
6380 <p>When a daemon is stopped or restarted</p>
6383 When you stop or restart a daemon, you should issue a
6384 message identical to the startup message, except that
6385 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6386 or <tt>Restarting</tt> respectively.
6390 For example, stopping the printer daemon will look like
6392 <example compact="compact">
6393 Stopping printer spooler: lpd.
6399 <p>When something is executed</p>
6402 There are several examples where you have to run a
6403 program at system startup or shutdown to perform a
6404 specific task, for example, setting the system's clock
6405 using <prgn>netdate</prgn> or killing all processes
6406 when the system shuts down. Your message should look
6408 <example compact="compact">
6409 Doing something very useful...done.
6411 You should print the <tt>done.</tt> immediately after
6412 the job has been completed, so that the user is
6413 informed why they have to wait. You can get this
6415 <example compact="compact">
6416 echo -n "Doing something very useful..."
6425 <p>When the configuration is reloaded</p>
6428 When a daemon is forced to reload its configuration
6429 files you should use the following format:
6430 <example compact="compact">
6431 Reloading <var>description</var> configuration...done.
6433 where <var>description</var> is the same as in the
6434 daemon starting message.
6442 <heading>Cron jobs</heading>
6445 Packages must not modify the configuration file
6446 <file>/etc/crontab</file>, and they must not modify the files in
6447 <file>/var/spool/cron/crontabs</file>.</p>
6450 If a package wants to install a job that has to be executed
6451 via cron, it should place a file with the name of the
6452 package in one or more of the following directories:
6453 <example compact="compact">
6459 As these directory names imply, the files within them are
6460 executed on an hourly, daily, weekly, or monthly basis,
6461 respectively. The exact times are listed in
6462 <file>/etc/crontab</file>.</p>
6465 All files installed in any of these directories must be
6466 scripts (e.g., shell scripts or Perl scripts) so that they
6467 can easily be modified by the local system administrator.
6468 In addition, they must be treated as configuration files.
6472 If a certain job has to be executed at some other frequency or
6473 at a specific time, the package should install a file
6474 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6475 same syntax as <file>/etc/crontab</file> and is processed by
6476 <prgn>cron</prgn> automatically. The file must also be
6477 treated as a configuration file. (Note that entries in the
6478 <file>/etc/cron.d</file> directory are not handled by
6479 <prgn>anacron</prgn>. Thus, you should only use this
6480 directory for jobs which may be skipped if the system is not
6484 The scripts or crontab entries in these directories should
6485 check if all necessary programs are installed before they
6486 try to execute them. Otherwise, problems will arise when a
6487 package was removed but not purged since configuration files
6488 are kept on the system in this situation.</p>
6492 <heading>Menus</heading>
6495 The Debian <tt>menu</tt> package provides a standard
6496 interface between packages providing applications and
6497 <em>menu programs</em> (either X window managers or
6498 text-based menu programs such as <prgn>pdmenu</prgn>).
6502 All packages that provide applications that need not be
6503 passed any special command line arguments for normal
6504 operation should register a menu entry for those
6505 applications, so that users of the <tt>menu</tt> package
6506 will automatically get menu entries in their window
6507 managers, as well in shells like <tt>pdmenu</tt>.
6511 Menu entries should follow the current menu policy.
6515 The menu policy can be found in the <tt>menu-policy</tt>
6516 files in the <tt>debian-policy</tt> package.
6517 It is also available from the Debian web mirrors at
6518 <tt><url name="/doc/packaging-manuals/menu-policy/"
6519 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6523 Please also refer to the <em>Debian Menu System</em>
6524 documentation that comes with the <package>menu</package>
6525 package for information about how to register your
6531 <heading>Multimedia handlers</heading>
6534 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6535 is a mechanism for encoding files and data streams and
6536 providing meta-information about them, in particular their
6537 type (e.g. audio or video) and format (e.g. PNG, HTML,
6542 Registration of MIME type handlers allows programs like mail
6543 user agents and web browsers to invoke these handlers to
6544 view, edit or display MIME types they don't support directly.
6548 Packages which provide the ability to view/show/play,
6549 compose, edit or print MIME types should register themselves
6550 as such following the current MIME support policy.
6554 The MIME support policy can be found in the <tt>mime-policy</tt>
6555 files in the <tt>debian-policy</tt> package.
6556 It is also available from the Debian web mirrors at
6557 <tt><url name="/doc/packaging-manuals/mime-policy/"
6558 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6564 <heading>Keyboard configuration</heading>
6567 To achieve a consistent keyboard configuration so that all
6568 applications interpret a keyboard event the same way, all
6569 programs in the Debian distribution must be configured to
6570 comply with the following guidelines.
6574 The following keys must have the specified interpretations:
6577 <tag><tt><--</tt></tag>
6578 <item>delete the character to the left of the cursor</item>
6580 <tag><tt>Delete</tt></tag>
6581 <item>delete the character to the right of the cursor</item>
6583 <tag><tt>Control+H</tt></tag>
6584 <item>emacs: the help prefix</item>
6587 The interpretation of any keyboard events should be
6588 independent of the terminal that is used, be it a virtual
6589 console, an X terminal emulator, an rlogin/telnet session,
6594 The following list explains how the different programs
6595 should be set up to achieve this:
6601 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6605 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6609 X translations are set up to make
6610 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6611 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6612 is the vt220 escape code for the "delete character"
6613 key). This must be done by loading the X resources
6614 using <prgn>xrdb</prgn> on all local X displays, not
6615 using the application defaults, so that the
6616 translation resources used correspond to the
6617 <prgn>xmodmap</prgn> settings.
6621 The Linux console is configured to make
6622 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6623 generate <tt>ESC [ 3 ~</tt>.
6627 X applications are configured so that <tt><</tt>
6628 deletes left, and <tt>Delete</tt> deletes right. Motif
6629 applications already work like this.
6633 Terminals should have <tt>stty erase ^?</tt> .
6637 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6638 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6639 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6643 Emacs is programmed to map <tt>KB_Backspace</tt> or
6644 the <tt>stty erase</tt> character to
6645 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6646 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6647 <tt>^H</tt> to <tt>help</tt> as always.
6651 Other applications use the <tt>stty erase</tt>
6652 character and <tt>kdch1</tt> for the two delete keys,
6653 with ASCII DEL being "delete previous character" and
6654 <tt>kdch1</tt> being "delete character under
6662 This will solve the problem except for the following
6669 Some terminals have a <tt><--</tt> key that cannot
6670 be made to produce anything except <tt>^H</tt>. On
6671 these terminals Emacs help will be unavailable on
6672 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6673 character takes precedence in Emacs, and has been set
6674 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6675 available) can be used instead.
6679 Some operating systems use <tt>^H</tt> for <tt>stty
6680 erase</tt>. However, modern telnet versions and all
6681 rlogin versions propagate <tt>stty</tt> settings, and
6682 almost all UNIX versions honour <tt>stty erase</tt>.
6683 Where the <tt>stty</tt> settings are not propagated
6684 correctly, things can be made to work by using
6685 <tt>stty</tt> manually.
6689 Some systems (including previous Debian versions) use
6690 <prgn>xmodmap</prgn> to arrange for both
6691 <tt><--</tt> and <tt>Delete</tt> to generate
6692 <tt>KB_Delete</tt>. We can change the behavior of
6693 their X clients using the same X resources that we use
6694 to do it for our own clients, or configure our clients
6695 using their resources when things are the other way
6696 around. On displays configured like this
6697 <tt>Delete</tt> will not work, but <tt><--</tt>
6702 Some operating systems have different <tt>kdch1</tt>
6703 settings in their <tt>terminfo</tt> database for
6704 <tt>xterm</tt> and others. On these systems the
6705 <tt>Delete</tt> key will not work correctly when you
6706 log in from a system conforming to our policy, but
6707 <tt><--</tt> will.
6714 <heading>Environment variables</heading>
6717 A program must not depend on environment variables to get
6718 reasonable defaults. (That's because these environment
6719 variables would have to be set in a system-wide
6720 configuration file like <file>/etc/profile</file>, which is not
6721 supported by all shells.)
6725 If a program usually depends on environment variables for its
6726 configuration, the program should be changed to fall back to
6727 a reasonable default configuration if these environment
6728 variables are not present. If this cannot be done easily
6729 (e.g., if the source code of a non-free program is not
6730 available), the program must be replaced by a small
6731 "wrapper" shell script which sets the environment variables
6732 if they are not already defined, and calls the original program.
6736 Here is an example of a wrapper script for this purpose:
6738 <example compact="compact">
6740 BAR=${BAR:-/var/lib/fubar}
6742 exec /usr/lib/foo/foo "$@"
6747 Furthermore, as <file>/etc/profile</file> is a configuration
6748 file of the <prgn>base-files</prgn> package, other packages must
6749 not put any environment variables or other commands into that
6754 <sect id="doc-base">
6755 <heading>Registering Documents using doc-base</heading>
6758 The <package>doc-base</package> package implements a
6759 flexible mechanism for handling and presenting
6760 documentation. The recommended practice is for every Debian
6761 package that provides online documentation (other than just
6762 manual pages) to register these documents with
6763 <package>doc-base</package> by installing a
6764 <package>doc-base</package> control file via the
6765 <prgn/install-docs/ script at installation time and
6766 de-register the manuals again when the package is removed.
6769 Please refer to the documentation that comes with the
6770 <package>doc-base</package> package for information and
6779 <heading>Files</heading>
6782 <heading>Binaries</heading>
6785 Two different packages must not install programs with
6786 different functionality but with the same filenames. (The
6787 case of two programs having the same functionality but
6788 different implementations is handled via "alternatives" or
6789 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6790 <ref id="conflicts"> respectively.) If this case happens,
6791 one of the programs must be renamed. The maintainers should
6792 report this to the <tt>debian-devel</tt> mailing list and
6793 try to find a consensus about which program will have to be
6794 renamed. If a consensus cannot be reached, <em>both</em>
6795 programs must be renamed.
6799 By default, when a package is being built, any binaries
6800 created should include debugging information, as well as
6801 being compiled with optimization. You should also turn on
6802 as many reasonable compilation warnings as possible; this
6803 makes life easier for porters, who can then look at build
6804 logs for possible problems. For the C programming language,
6805 this means the following compilation parameters should be
6807 <example compact="compact">
6809 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6811 INSTALL = install -s # (or use strip on the files in debian/tmp)
6816 Note that by default all installed binaries should be stripped,
6817 either by using the <tt>-s</tt> flag to
6818 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6819 the binaries after they have been copied into
6820 <file>debian/tmp</file> but before the tree is made into a
6825 Although binaries in the build tree should be compiled with
6826 debugging information by default, it can often be difficult to
6827 debug programs if they are also subjected to compiler
6828 optimization. For this reason, it is recommended to support the
6829 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6830 (see <ref id="debianrules-options">). This variable can contain
6831 several flags to change how a package is compiled and built.
6835 It is up to the package maintainer to decide what
6836 compilation options are best for the package. Certain
6837 binaries (such as computationally-intensive programs) will
6838 function better with certain flags (<tt>-O3</tt>, for
6839 example); feel free to use them. Please use good judgment
6840 here. Don't use flags for the sake of it; only use them
6841 if there is good reason to do so. Feel free to override
6842 the upstream author's ideas about which compilation
6843 options are best: they are often inappropriate for our
6849 <sect id="libraries">
6850 <heading>Libraries</heading>
6853 If the package is <strong>architecture: any</strong>, then
6854 the shared library compilation and linking flags must have
6855 <tt>-fPIC</tt>, or the package shall not build on some of
6856 the supported architectures<footnote>
6858 If you are using GCC, <tt>-fPIC</tt> produces code with
6859 relocatable position independent code, which is required for
6860 most architectures to create a shared library, with i386 and
6861 perhaps some others where non position independent code is
6862 permitted in a shared library.
6865 Position independent code may have a performance penalty,
6866 especially on <tt>i386</tt>. However, in most cases the
6867 speed penalty must be measured against the memory wasted on
6868 the few architectures where non position independent code is
6871 </footnote>. Any exception to this rule must be discussed on
6872 the mailing list <em>debian-devel@lists.debian.org</em>, and
6873 a rough consensus obtained. The reasons for not compiling
6874 with <tt>-fPIC</tt> flag must be recorded in the file
6875 <tt>README.Debian</tt>, and care must be taken to either
6876 restrict the architecture or arrange for <tt>-fPIC</tt> to
6877 be used on architectures where it is required.<footnote>
6879 Some of the reasons why this might be required is if the
6880 library contains hand crafted assembly code that is not
6881 relocatable, the speed penalty is excessive for compute
6882 intensive libs, and similar reasons.
6887 As to the static libraries, the common case is not to have
6888 relocatable code, since there is no benefit, unless in specific
6889 cases; therefore the static version must not be compiled
6890 with the <tt>-fPIC</tt> flag. Any exception to this rule
6891 should be discussed on the mailing list
6892 <em>debian-devel@lists.debian.org</em>, and the reasons for
6893 compiling with the <tt>-fPIC</tt> flag must be recorded in
6894 the file <tt>README.Debian</tt>. <footnote>
6896 Some of the reasons for linking static libraries with
6897 the <tt>-fPIC</tt> flag are if, for example, one needs a
6898 Perl API for a library that is under rapid development,
6899 and has an unstable API, so shared libraries are
6900 pointless at this phase of the library's development. In
6901 that case, since Perl needs a library with relocatable
6902 code, it may make sense to create a static library with
6903 relocatable code. Another reason cited is if you are
6904 distilling various libraries into a common shared
6905 library, like <tt>mklibs</tt> does in the Debian
6911 In other words, if both a shared and a static library is
6912 being built, each source unit (<tt>*.c</tt>, for example,
6913 for C files) will need to be compiled twice, for the normal
6917 You must specify the gcc option <tt>-D_REENTRANT</tt>
6918 when building a library (either static or shared) to make
6919 the library compatible with LinuxThreads.
6923 Although not enforced by the build tools, shared libraries
6924 must be linked against all libraries that they use symbols from
6925 in the same way that binaries are. This ensures the correct
6926 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6927 system and guarantees that all libraries can be safely opened
6928 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6929 option <tt>-Wl,-z,defs</tt> when building a shared library.
6930 Since this option enforces symbol resolution at build time,
6931 a missing library reference will be caught early as a fatal
6936 All installed shared libraries should be stripped with
6937 <example compact="compact">
6938 strip --strip-unneeded <var>your-lib</var>
6940 (The option <tt>--strip-unneeded</tt> makes
6941 <prgn>strip</prgn> remove only the symbols which aren't
6942 needed for relocation processing.) Shared libraries can
6943 function perfectly well when stripped, since the symbols for
6944 dynamic linking are in a separate part of the ELF object
6946 You might also want to use the options
6947 <tt>--remove-section=.comment</tt> and
6948 <tt>--remove-section=.note</tt> on both shared libraries
6949 and executables, and <tt>--strip-debug</tt> on static
6955 Note that under some circumstances it may be useful to
6956 install a shared library unstripped, for example when
6957 building a separate package to support debugging.
6961 Shared object files (often <file>.so</file> files) that are not
6962 public libraries, that is, they are not meant to be linked
6963 to by third party executables (binaries of other packages),
6964 should be installed in subdirectories of the
6965 <file>/usr/lib</file> directory. Such files are exempt from the
6966 rules that govern ordinary shared libraries, except that
6967 they must not be installed executable and should be
6969 A common example are the so-called "plug-ins",
6970 internal shared objects that are dynamically loaded by
6971 programs using <manref name="dlopen" section="3">.
6976 Packages containing shared libraries that may be linked to
6977 by other packages' binaries, but which for some
6978 <em>compelling</em> reason can not be installed in
6979 <file>/usr/lib</file> directory, may install the shared library
6980 files in subdirectories of the <file>/usr/lib</file> directory,
6981 in which case they should arrange to add that directory in
6982 <file>/etc/ld.so.conf</file> in the package's post-installation
6983 script, and remove it in the package's post-removal script.
6987 An ever increasing number of packages are using
6988 <prgn>libtool</prgn> to do their linking. The latest GNU
6989 libtools (>= 1.3a) can take advantage of the metadata in the
6990 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6991 files). The main advantage of <prgn>libtool</prgn>'s
6992 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6993 store and subsequently access metadata with respect to the
6994 libraries it builds. <prgn>libtool</prgn> will search for
6995 those files, which contain a lot of useful information about
6996 a library (such as library dependency information for static
6997 linking). Also, they're <em>essential</em> for programs
6998 using <tt>libltdl</tt>.<footnote>
6999 Although <prgn>libtool</prgn> is fully capable of
7000 linking against shared libraries which don't have
7001 <tt>.la</tt> files, as it is a mere shell script it can
7002 add considerably to the build time of a
7003 <prgn>libtool</prgn>-using package if that shell script
7004 has to derive all this information from first principles
7005 for each library every time it is linked. With the
7006 advent of <prgn>libtool</prgn> version 1.4 (and to a
7007 lesser extent <prgn>libtool</prgn> version 1.3), the
7008 <file>.la</file> files also store information about
7009 inter-library dependencies which cannot necessarily be
7010 derived after the <file>.la</file> file is deleted.
7015 Packages that use <prgn>libtool</prgn> to create shared
7016 libraries should include the <file>.la</file> files in the
7017 <tt>-dev</tt> package, unless the package relies on
7018 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7019 the <tt>.la</tt> files must go in the run-time library
7024 You must make sure that you use only released versions of
7025 shared libraries to build your packages; otherwise other
7026 users will not be able to run your binaries
7027 properly. Producing source packages that depend on
7028 unreleased compilers is also usually a bad
7035 <heading>Shared libraries</heading>
7037 This section has moved to <ref id="sharedlibs">.
7043 <heading>Scripts</heading>
7046 All command scripts, including the package maintainer
7047 scripts inside the package and used by <prgn>dpkg</prgn>,
7048 should have a <tt>#!</tt> line naming the shell to be used
7053 In the case of Perl scripts this should be
7054 <tt>#!/usr/bin/perl</tt>.
7058 When scripts are installed into a directory in the system
7059 PATH, the script name should not include an extension such
7060 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7061 language currently used to implement it.
7064 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7065 should almost certainly start with <tt>set -e</tt> so that
7066 errors are detected. Every script should use
7067 <tt>set -e</tt> or check the exit status of <em>every</em>
7072 Scripts may assume that <file>/bin/sh</file> implements the
7073 SUSv3 Shell Command Language<footnote>
7074 Single UNIX Specification, version 3, which is also IEEE
7075 1003.1-2004 (POSIX), and is available on the World Wide Web
7076 from <url id="http://www.unix.org/version3/online.html"
7077 name="The Open Group"> after free
7078 registration.</footnote>
7079 plus the following additional features not mandated by
7081 These features are in widespread use in the Linux community
7082 and are implemented in all of bash, dash, and ksh, the most
7083 common shells users may wish to use as <file>/bin/sh</file>.
7086 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7087 must not generate a newline.</item>
7088 <item><tt>test</tt>, if implemented as a shell built-in, must
7089 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7091 <item><tt>local</tt> to create a scoped variable must be
7092 supported, including listing multiple variables in a single
7093 local command and assigning a value to a variable at the
7094 same time as localizing it. <tt>local</tt> may or
7095 may not preserve the variable value from an outer scope if
7096 no assignment is present. Uses such as:
7100 # ... use a, b, c, d ...
7103 must be supported and must set the value of <tt>c</tt> to
7107 If a shell script requires non-SUSv3 features from the shell
7108 interpreter other than those listed above, the appropriate shell
7109 must be specified in the first line of the script (e.g.,
7110 <tt>#!/bin/bash</tt>) and the package must depend on the package
7111 providing the shell (unless the shell package is marked
7112 "Essential", as in the case of <prgn>bash</prgn>).
7116 You may wish to restrict your script to SUSv3 features plus the
7117 above set when possible so that it may use <file>/bin/sh</file>
7118 as its interpreter. If your script works with <prgn>dash</prgn>
7119 (originally called <prgn>ash</prgn>), it probably complies with
7120 the above requirements, but if you are in doubt, use
7121 <file>/bin/bash</file>.
7125 Perl scripts should check for errors when making any
7126 system calls, including <tt>open</tt>, <tt>print</tt>,
7127 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7131 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7132 scripting languages. See <em>Csh Programming Considered
7133 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7134 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7135 If an upstream package comes with <prgn>csh</prgn> scripts
7136 then you must make sure that they start with
7137 <tt>#!/bin/csh</tt> and make your package depend on the
7138 <prgn>c-shell</prgn> virtual package.
7142 Any scripts which create files in world-writeable
7143 directories (e.g., in <file>/tmp</file>) must use a
7144 mechanism which will fail atomically if a file with the same
7145 name already exists.
7149 The Debian base system provides the <prgn>tempfile</prgn>
7150 and <prgn>mktemp</prgn> utilities for use by scripts for
7157 <heading>Symbolic links</heading>
7160 In general, symbolic links within a top-level directory
7161 should be relative, and symbolic links pointing from one
7162 top-level directory into another should be absolute. (A
7163 top-level directory is a sub-directory of the root
7164 directory <file>/</file>.)
7168 In addition, symbolic links should be specified as short as
7169 possible, i.e., link targets like <file>foo/../bar</file> are
7174 Note that when creating a relative link using
7175 <prgn>ln</prgn> it is not necessary for the target of the
7176 link to exist relative to the working directory you're
7177 running <prgn>ln</prgn> from, nor is it necessary to change
7178 directory to the directory where the link is to be made.
7179 Simply include the string that should appear as the target
7180 of the link (this will be a pathname relative to the
7181 directory in which the link resides) as the first argument
7186 For example, in your <prgn>Makefile</prgn> or
7187 <file>debian/rules</file>, you can do things like:
7188 <example compact="compact">
7189 ln -fs gcc $(prefix)/bin/cc
7190 ln -fs gcc debian/tmp/usr/bin/cc
7191 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7192 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7197 A symbolic link pointing to a compressed file should always
7198 have the same file extension as the referenced file. (For
7199 example, if a file <file>foo.gz</file> is referenced by a
7200 symbolic link, the filename of the link has to end with
7201 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7206 <heading>Device files</heading>
7209 Packages must not include device files in the package file
7214 If a package needs any special device files that are not
7215 included in the base system, it must call
7216 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7217 after notifying the user<footnote>
7218 This notification could be done via a (low-priority)
7219 debconf message, or an echo (printf) statement.
7224 Packages must not remove any device files in the
7225 <prgn>postrm</prgn> or any other script. This is left to the
7226 system administrator.
7230 Debian uses the serial devices
7231 <file>/dev/ttyS*</file>. Programs using the old
7232 <file>/dev/cu*</file> devices should be changed to use
7233 <file>/dev/ttyS*</file>.
7237 <sect id="config-files">
7238 <heading>Configuration files</heading>
7241 <heading>Definitions</heading>
7245 <tag>configuration file</tag>
7247 A file that affects the operation of a program, or
7248 provides site- or host-specific information, or
7249 otherwise customizes the behavior of a program.
7250 Typically, configuration files are intended to be
7251 modified by the system administrator (if needed or
7252 desired) to conform to local policy or to provide
7253 more useful site-specific behavior.
7256 <tag><tt>conffile</tt></tag>
7258 A file listed in a package's <tt>conffiles</tt>
7259 file, and is treated specially by <prgn>dpkg</prgn>
7260 (see <ref id="configdetails">).
7266 The distinction between these two is important; they are
7267 not interchangeable concepts. Almost all
7268 <tt>conffile</tt>s are configuration files, but many
7269 configuration files are not <tt>conffiles</tt>.
7273 As noted elsewhere, <file>/etc/init.d</file> scripts,
7274 <file>/etc/default</file> files, scripts installed in
7275 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7276 configuration installed in <file>/etc/cron.d</file> must be
7277 treated as configuration files. In general, any script that
7278 embeds configuration information is de-facto a configuration
7279 file and should be treated as such.
7284 <heading>Location</heading>
7287 Any configuration files created or used by your package
7288 must reside in <file>/etc</file>. If there are several,
7289 consider creating a subdirectory of <file>/etc</file>
7290 named after your package.
7294 If your package creates or uses configuration files
7295 outside of <file>/etc</file>, and it is not feasible to modify
7296 the package to use <file>/etc</file> directly, put the files
7297 in <file>/etc</file> and create symbolic links to those files
7298 from the location that the package requires.
7303 <heading>Behavior</heading>
7306 Configuration file handling must conform to the following
7308 <list compact="compact">
7310 local changes must be preserved during a package
7314 configuration files must be preserved when the
7315 package is removed, and only deleted when the
7322 The easy way to achieve this behavior is to make the
7323 configuration file a <tt>conffile</tt>. This is
7324 appropriate only if it is possible to distribute a default
7325 version that will work for most installations, although
7326 some system administrators may choose to modify it. This
7327 implies that the default version will be part of the
7328 package distribution, and must not be modified by the
7329 maintainer scripts during installation (or at any other
7334 In order to ensure that local changes are preserved
7335 correctly, no package may contain or make hard links to
7336 conffiles.<footnote>
7337 Rationale: There are two problems with hard links.
7338 The first is that some editors break the link while
7339 editing one of the files, so that the two files may
7340 unwittingly become unlinked and different. The second
7341 is that <prgn>dpkg</prgn> might break the hard link
7342 while upgrading <tt>conffile</tt>s.
7347 The other way to do it is via the maintainer scripts. In
7348 this case, the configuration file must not be listed as a
7349 <tt>conffile</tt> and must not be part of the package
7350 distribution. If the existence of a file is required for
7351 the package to be sensibly configured it is the
7352 responsibility of the package maintainer to provide
7353 maintainer scripts which correctly create, update and
7354 maintain the file and remove it on purge. (See <ref
7355 id="maintainerscripts"> for more information.) These
7356 scripts must be idempotent (i.e., must work correctly if
7357 <prgn>dpkg</prgn> needs to re-run them due to errors
7358 during installation or removal), must cope with all the
7359 variety of ways <prgn>dpkg</prgn> can call maintainer
7360 scripts, must not overwrite or otherwise mangle the user's
7361 configuration without asking, must not ask unnecessary
7362 questions (particularly during upgrades), and must
7363 otherwise be good citizens.
7367 The scripts are not required to configure every possible
7368 option for the package, but only those necessary to get
7369 the package running on a given system. Ideally the
7370 sysadmin should not have to do any configuration other
7371 than that done (semi-)automatically by the
7372 <prgn>postinst</prgn> script.
7376 A common practice is to create a script called
7377 <file><var>package</var>-configure</file> and have the
7378 package's <prgn>postinst</prgn> call it if and only if the
7379 configuration file does not already exist. In certain
7380 cases it is useful for there to be an example or template
7381 file which the maintainer scripts use. Such files should
7382 be in <file>/usr/share/<var>package</var></file> or
7383 <file>/usr/lib/<var>package</var></file> (depending on whether
7384 they are architecture-independent or not). There should
7385 be symbolic links to them from
7386 <file>/usr/share/doc/<var>package</var>/examples</file> if
7387 they are examples, and should be perfectly ordinary
7388 <prgn>dpkg</prgn>-handled files (<em>not</em>
7389 configuration files).
7393 These two styles of configuration file handling must
7394 not be mixed, for that way lies madness:
7395 <prgn>dpkg</prgn> will ask about overwriting the file
7396 every time the package is upgraded.
7401 <heading>Sharing configuration files</heading>
7404 Packages which specify the same file as a
7405 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7406 with each other. (This is an instance of the general rule
7407 about not sharing files. Note that neither alternatives
7408 nor diversions are likely to be appropriate in this case;
7409 in particular, <prgn>dpkg</prgn> does not handle diverted
7410 <tt>conffile</tt>s well.)
7414 The maintainer scripts must not alter a <tt>conffile</tt>
7415 of <em>any</em> package, including the one the scripts
7420 If two or more packages use the same configuration file
7421 and it is reasonable for both to be installed at the same
7422 time, one of these packages must be defined as
7423 <em>owner</em> of the configuration file, i.e., it will be
7424 the package which handles that file as a configuration
7425 file. Other packages that use the configuration file must
7426 depend on the owning package if they require the
7427 configuration file to operate. If the other package will
7428 use the configuration file if present, but is capable of
7429 operating without it, no dependency need be declared.
7433 If it is desirable for two or more related packages to
7434 share a configuration file <em>and</em> for all of the
7435 related packages to be able to modify that configuration
7436 file, then the following should be done:
7437 <enumlist compact="compact">
7439 One of the related packages (the "owning" package)
7440 will manage the configuration file with maintainer
7441 scripts as described in the previous section.
7444 The owning package should also provide a program
7445 that the other packages may use to modify the
7449 The related packages must use the provided program
7450 to make any desired modifications to the
7451 configuration file. They should either depend on
7452 the core package to guarantee that the configuration
7453 modifier program is available or accept gracefully
7454 that they cannot modify the configuration file if it
7455 is not. (This is in addition to the fact that the
7456 configuration file may not even be present in the
7463 Sometimes it's appropriate to create a new package which
7464 provides the basic infrastructure for the other packages
7465 and which manages the shared configuration files. (The
7466 <tt>sgml-base</tt> package is a good example.)
7471 <heading>User configuration files ("dotfiles")</heading>
7474 The files in <file>/etc/skel</file> will automatically be
7475 copied into new user accounts by <prgn>adduser</prgn>.
7476 No other program should reference the files in
7477 <file>/etc/skel</file>.
7481 Therefore, if a program needs a dotfile to exist in
7482 advance in <file>$HOME</file> to work sensibly, that dotfile
7483 should be installed in <file>/etc/skel</file> and treated as a
7488 However, programs that require dotfiles in order to
7489 operate sensibly are a bad thing, unless they do create
7490 the dotfiles themselves automatically.
7494 Furthermore, programs should be configured by the Debian
7495 default installation to behave as closely to the upstream
7496 default behavior as possible.
7500 Therefore, if a program in a Debian package needs to be
7501 configured in some way in order to operate sensibly, that
7502 should be done using a site-wide configuration file placed
7503 in <file>/etc</file>. Only if the program doesn't support a
7504 site-wide default configuration and the package maintainer
7505 doesn't have time to add it may a default per-user file be
7506 placed in <file>/etc/skel</file>.
7510 <file>/etc/skel</file> should be as empty as we can make it.
7511 This is particularly true because there is no easy (or
7512 necessarily desirable) mechanism for ensuring that the
7513 appropriate dotfiles are copied into the accounts of
7514 existing users when a package is installed.
7520 <heading>Log files</heading>
7522 Log files should usually be named
7523 <file>/var/log/<var>package</var>.log</file>. If you have many
7524 log files, or need a separate directory for permission
7525 reasons (<file>/var/log</file> is writable only by
7526 <file>root</file>), you should usually create a directory named
7527 <file>/var/log/<var>package</var></file> and place your log
7532 Log files must be rotated occasionally so that they don't
7533 grow indefinitely; the best way to do this is to drop a log
7534 rotation configuration file into the directory
7535 <file>/etc/logrotate.d</file> and use the facilities provided by
7536 logrotate.<footnote>
7538 The traditional approach to log files has been to set up
7539 <em>ad hoc</em> log rotation schemes using simple shell
7540 scripts and cron. While this approach is highly
7541 customizable, it requires quite a lot of sysadmin work.
7542 Even though the original Debian system helped a little
7543 by automatically installing a system which can be used
7544 as a template, this was deemed not enough.
7548 The use of <prgn>logrotate</prgn>, a program developed
7549 by Red Hat, is better, as it centralizes log management.
7550 It has both a configuration file
7551 (<file>/etc/logrotate.conf</file>) and a directory where
7552 packages can drop their individual log rotation
7553 configurations (<file>/etc/logrotate.d</file>).
7556 Here is a good example for a logrotate config
7557 file (for more information see <manref name="logrotate"
7559 <example compact="compact">
7560 /var/log/foo/*.log {
7565 /etc/init.d/foo force-reload
7569 This rotates all files under <file>/var/log/foo</file>, saves 12
7570 compressed generations, and forces the daemon to reload its
7571 configuration information after the log rotation.
7575 Log files should be removed when the package is
7576 purged (but not when it is only removed). This should be
7577 done by the <prgn>postrm</prgn> script when it is called
7578 with the argument <tt>purge</tt> (see <ref
7579 id="removedetails">).
7584 <heading>Permissions and owners</heading>
7587 The rules in this section are guidelines for general use.
7588 If necessary you may deviate from the details below.
7589 However, if you do so you must make sure that what is done
7590 is secure and you should try to be as consistent as possible
7591 with the rest of the system. You should probably also
7592 discuss it on <prgn>debian-devel</prgn> first.
7596 Files should be owned by <tt>root:root</tt>, and made
7597 writable only by the owner and universally readable (and
7598 executable, if appropriate), that is mode 644 or 755.
7602 Directories should be mode 755 or (for group-writability)
7603 mode 2775. The ownership of the directory should be
7604 consistent with its mode: if a directory is mode 2775, it
7605 should be owned by the group that needs write access to
7608 When a package is upgraded, and the owner or permissions
7609 of a file included in the package has changed, dpkg
7610 arranges for the ownership and permissions to be
7611 correctly set upon installation. However, this does not
7612 extend to directories; the permissions and ownership of
7613 directories already on the system does not change on
7614 install or upgrade of packages. This makes sense, since
7615 otherwise common directories like <tt>/usr</tt> would
7616 always be in flux. To correctly change permissions of a
7617 directory the package owns, explicit action is required,
7618 usually in the <tt>postinst</tt> script. Care must be
7619 taken to handle downgrades as well, in that case.
7626 Setuid and setgid executables should be mode 4755 or 2755
7627 respectively, and owned by the appropriate user or group.
7628 They should not be made unreadable (modes like 4711 or
7629 2711 or even 4111); doing so achieves no extra security,
7630 because anyone can find the binary in the freely available
7631 Debian package; it is merely inconvenient. For the same
7632 reason you should not restrict read or execute permissions
7633 on non-set-id executables.
7637 Some setuid programs need to be restricted to particular
7638 sets of users, using file permissions. In this case they
7639 should be owned by the uid to which they are set-id, and by
7640 the group which should be allowed to execute them. They
7641 should have mode 4754; again there is no point in making
7642 them unreadable to those users who must not be allowed to
7647 It is possible to arrange that the system administrator can
7648 reconfigure the package to correspond to their local
7649 security policy by changing the permissions on a binary:
7650 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7651 described below.<footnote>
7652 Ordinary files installed by <prgn>dpkg</prgn> (as
7653 opposed to <tt>conffile</tt>s and other similar objects)
7654 normally have their permissions reset to the distributed
7655 permissions when the package is reinstalled. However,
7656 the use of <prgn>dpkg-statoverride</prgn> overrides this
7657 default behavior. If you use this method, you should
7658 remember to describe <prgn>dpkg-statoverride</prgn> in
7659 the package documentation; being a relatively new
7660 addition to Debian, it is probably not yet well-known.
7662 Another method you should consider is to create a group for
7663 people allowed to use the program(s) and make any setuid
7664 executables executable only by that group.
7668 If you need to create a new user or group for your package
7669 there are two possibilities. Firstly, you may need to
7670 make some files in the binary package be owned by this
7671 user or group, or you may need to compile the user or
7672 group id (rather than just the name) into the binary
7673 (though this latter should be avoided if possible, as in
7674 this case you need a statically allocated id).</p>
7677 If you need a statically allocated id, you must ask for a
7678 user or group id from the <tt>base-passwd</tt> maintainer,
7679 and must not release the package until you have been
7680 allocated one. Once you have been allocated one you must
7681 either make the package depend on a version of the
7682 <tt>base-passwd</tt> package with the id present in
7683 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7684 your package to create the user or group itself with the
7685 correct id (using <tt>adduser</tt>) in its
7686 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7687 the <prgn>postinst</prgn> is to be preferred if it is
7688 possible, otherwise a pre-dependency will be needed on the
7689 <tt>adduser</tt> package.)
7693 On the other hand, the program might be able to determine
7694 the uid or gid from the user or group name at runtime, so
7695 that a dynamically allocated id can be used. In this case
7696 you should choose an appropriate user or group name,
7697 discussing this on <prgn>debian-devel</prgn> and checking
7698 with the <package/base-passwd/ maintainer that it is unique and that
7699 they do not wish you to use a statically allocated id
7700 instead. When this has been checked you must arrange for
7701 your package to create the user or group if necessary using
7702 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7703 <prgn>postinst</prgn> script (again, the latter is to be
7704 preferred if it is possible).
7708 Note that changing the numeric value of an id associated
7709 with a name is very difficult, and involves searching the
7710 file system for all appropriate files. You need to think
7711 carefully whether a static or dynamic id is required, since
7712 changing your mind later will cause problems.
7715 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7717 This section is not intended as policy, but as a
7718 description of the use of <prgn>dpkg-statoverride</prgn>.
7722 If a system administrator wishes to have a file (or
7723 directory or other such thing) installed with owner and
7724 permissions different from those in the distributed Debian
7725 package, they can use the <prgn>dpkg-statoverride</prgn>
7726 program to instruct <prgn>dpkg</prgn> to use the different
7727 settings every time the file is installed. Thus the
7728 package maintainer should distribute the files with their
7729 normal permissions, and leave it for the system
7730 administrator to make any desired changes. For example, a
7731 daemon which is normally required to be setuid root, but
7732 in certain situations could be used without being setuid,
7733 should be installed setuid in the <tt>.deb</tt>. Then the
7734 local system administrator can change this if they wish.
7735 If there are two standard ways of doing it, the package
7736 maintainer can use <tt>debconf</tt> to find out the
7737 preference, and call <prgn>dpkg-statoverride</prgn> in the
7738 maintainer script if necessary to accommodate the system
7739 administrator's choice. Care must be taken during
7740 upgrades to not override an existing setting.
7744 Given the above, <prgn>dpkg-statoverride</prgn> is
7745 essentially a tool for system administrators and would not
7746 normally be needed in the maintainer scripts. There is
7747 one type of situation, though, where calls to
7748 <prgn>dpkg-statoverride</prgn> would be needed in the
7749 maintainer scripts, and that involves packages which use
7750 dynamically allocated user or group ids. In such a
7751 situation, something like the following idiom can be very
7752 helpful in the package's <prgn>postinst</prgn>, where
7753 <tt>sysuser</tt> is a dynamically allocated id:
7755 for i in /usr/bin/foo /usr/sbin/bar
7757 # only do something when no setting exists
7758 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7760 #include: debconf processing, question about foo and bar
7761 if [ "$RET" = "true" ] ; then
7762 dpkg-statoverride --update --add sysuser root 4755 $i
7767 The corresponding <tt>dpkg-statoverride --remove</tt>
7768 calls can then be made unconditionally when the package is
7776 <chapt id="customized-programs">
7777 <heading>Customized programs</heading>
7779 <sect id="arch-spec">
7780 <heading>Architecture specification strings</heading>
7783 If a program needs to specify an <em>architecture specification
7784 string</em> in some place, it should select one of the
7785 strings provided by <tt>dpkg-architecture -L</tt>. The
7786 strings are in the format
7787 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7788 is sometimes elided, as when the OS is Linux.<footnote>
7789 <p>Currently, the strings are:
7790 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7791 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7792 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7793 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7794 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7795 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7796 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7797 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7798 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7799 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7800 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7801 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7802 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7803 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7804 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7805 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7806 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7807 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7808 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7809 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7810 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7811 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7812 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7813 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7814 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7815 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7816 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7817 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7818 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7819 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7820 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7821 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7822 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7823 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7824 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7825 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7826 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7832 Note that we don't want to use
7833 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7834 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7835 since this would make our programs incompatible with other
7836 Linux distributions. We also don't use something like
7837 <tt><var>arch</var>-unknown-linux</tt>, since the
7838 <tt>unknown</tt> does not look very good.
7843 <heading>Daemons</heading>
7846 The configuration files <file>/etc/services</file>,
7847 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7848 by the <prgn>netbase</prgn> package and must not be modified
7853 If a package requires a new entry in one of these files, the
7854 maintainer should get in contact with the
7855 <prgn>netbase</prgn> maintainer, who will add the entries
7856 and release a new version of the <prgn>netbase</prgn>
7861 The configuration file <file>/etc/inetd.conf</file> must not be
7862 modified by the package's scripts except via the
7863 <prgn>update-inetd</prgn> script or the
7864 <file>DebianNet.pm</file> Perl module. See their documentation
7865 for details on how to add entries.
7869 If a package wants to install an example entry into
7870 <file>/etc/inetd.conf</file>, the entry must be preceded with
7871 exactly one hash character (<tt>#</tt>). Such lines are
7872 treated as "commented out by user" by the
7873 <prgn>update-inetd</prgn> script and are not changed or
7874 activated during package updates.
7879 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7883 Some programs need to create pseudo-ttys. This should be done
7884 using Unix98 ptys if the C library supports it. The resulting
7885 program must not be installed setuid root, unless that
7886 is required for other functionality.
7890 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7891 <file>/var/log/lastlog</file> must be installed writable by
7892 group <tt>utmp</tt>. Programs which need to modify those
7893 files must be installed setgid <tt>utmp</tt>.
7898 <heading>Editors and pagers</heading>
7901 Some programs have the ability to launch an editor or pager
7902 program to edit or display a text document. Since there are
7903 lots of different editors and pagers available in the Debian
7904 distribution, the system administrator and each user should
7905 have the possibility to choose their preferred editor and
7910 In addition, every program should choose a good default
7911 editor/pager if none is selected by the user or system
7916 Thus, every program that launches an editor or pager must
7917 use the EDITOR or PAGER environment variable to determine
7918 the editor or pager the user wishes to use. If these
7919 variables are not set, the programs <file>/usr/bin/editor</file>
7920 and <file>/usr/bin/pager</file> should be used, respectively.
7924 These two files are managed through the <prgn>dpkg</prgn>
7925 "alternatives" mechanism. Thus every package providing an
7926 editor or pager must call the
7927 <prgn>update-alternatives</prgn> script to register these
7932 If it is very hard to adapt a program to make use of the
7933 EDITOR or PAGER variables, that program may be configured to
7934 use <file>/usr/bin/sensible-editor</file> and
7935 <file>/usr/bin/sensible-pager</file> as the editor or pager
7936 program respectively. These are two scripts provided in the
7937 Debian base system that check the EDITOR and PAGER variables
7938 and launch the appropriate program, and fall back to
7939 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7940 variable is not set.
7944 A program may also use the VISUAL environment variable to
7945 determine the user's choice of editor. If it exists, it
7946 should take precedence over EDITOR. This is in fact what
7947 <file>/usr/bin/sensible-editor</file> does.
7951 It is not required for a package to depend on
7952 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7953 package to provide such virtual packages.<footnote>
7954 The Debian base system already provides an editor and a
7960 <sect id="web-appl">
7961 <heading>Web servers and applications</heading>
7964 This section describes the locations and URLs that should
7965 be used by all web servers and web applications in the
7972 Cgi-bin executable files are installed in the
7974 <example compact="compact">
7975 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7977 and should be referred to as
7978 <example compact="compact">
7979 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7985 <p>Access to HTML documents</p>
7988 HTML documents for a package are stored in
7989 <file>/usr/share/doc/<var>package</var></file>
7990 and can be referred to as
7991 <example compact="compact">
7992 http://localhost/doc/<var>package</var>/<var>filename</var>
7997 The web server should restrict access to the document
7998 tree so that only clients on the same host can read
7999 the documents. If the web server does not support such
8000 access controls, then it should not provide access at
8001 all, or ask about providing access during installation.
8006 <p>Access to images</p>
8008 It is recommended that images for a package be stored
8009 in <tt>/usr/share/images/<var>package</var></tt> and
8010 may be referred to through an alias <tt>/images/</tt>
8013 http://localhost/images/<package>/<filename>
8020 <p>Web Document Root</p>
8023 Web Applications should try to avoid storing files in
8024 the Web Document Root. Instead they should use the
8025 /usr/share/doc/<var>package</var> directory for
8026 documents and register the Web Application via the
8027 <package>doc-base</package> package. If access to the
8028 web document root is unavoidable then use
8029 <example compact="compact">
8032 as the Document Root. This might be just a symbolic
8033 link to the location where the system administrator
8034 has put the real document root.
8037 <item><p>Providing httpd and/or httpd-cgi</p>
8039 All web servers should provide the virtual package
8040 <tt>httpd</tt>. If a web server has CGI support it should
8041 provide <tt>httpd-cgi</tt> additionally.
8044 All web applications which do not contain CGI scripts should
8045 depend on <tt>httpd</tt>, all those web applications which
8046 <tt>do</tt> contain CGI scripts, should depend on
8054 <sect id="mail-transport-agents">
8055 <heading>Mail transport, delivery and user agents</heading>
8058 Debian packages which process electronic mail, whether mail
8059 user agents (MUAs) or mail transport agents (MTAs), must
8060 ensure that they are compatible with the configuration
8061 decisions below. Failure to do this may result in lost
8062 mail, broken <tt>From:</tt> lines, and other serious brain
8067 The mail spool is <file>/var/mail</file> and the interface to
8068 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8069 the FHS). On older systems, the mail spool may be
8070 physically located in <file>/var/spool/mail</file>, but all
8071 access to the mail spool should be via the
8072 <file>/var/mail</file> symlink. The mail spool is part of the
8073 base system and not part of the MTA package.
8077 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8078 programs (such as IMAP daemons) must lock the mailbox in an
8079 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8080 be combined with dot locking. To avoid deadlocks, a program
8081 should use <tt>fcntl()</tt> first and dot locking after
8082 this, or alternatively implement the two locking methods in
8083 a non blocking way<footnote>
8084 If it is not possible to establish both locks, the
8085 system shouldn't wait for the second lock to be
8086 established, but remove the first lock, wait a (random)
8087 time, and start over locking again.
8088 </footnote>. Using the functions <tt>maillock</tt> and
8089 <tt>mailunlock</tt> provided by the
8090 <tt>liblockfile*</tt><footnote>
8091 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8092 to use these functions.
8093 </footnote> packages is the recommended way to realize this.
8097 Mailboxes are generally either mode 600 and owned by
8098 <var>user</var> or mode 660 and owned by
8099 <tt><var>user</var>:mail</tt><footnote>
8100 There are two traditional permission schemes for mail spools:
8101 mode 600 with all mail delivery done by processes running as
8102 the destination user, or mode 660 and owned by group mail with
8103 mail delivery done by a process running as a system user in
8104 group mail. Historically, Debian required mode 660 mail
8105 spools to enable the latter model, but that model has become
8106 increasingly uncommon and the principle of least privilege
8107 indicates that mail systems that use the first model should
8108 use permissions of 600. If delivery to programs is permitted,
8109 it's easier to keep the mail system secure if the delivery
8110 agent runs as the destination user. Debian Policy therefore
8111 permits either scheme.
8112 </footnote>. The local system administrator may choose a
8113 different permission scheme; packages should not make
8114 assumptions about the permission and ownership of mailboxes
8115 unless required (such as when creating a new mailbox). A MUA
8116 may remove a mailbox (unless it has nonstandard permissions) in
8117 which case the MTA or another MUA must recreate it if needed.
8121 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8122 be setgid mail to do the locking mentioned above (and
8123 must obviously avoid accessing other users' mailboxes
8124 using this privilege).</p>
8127 <file>/etc/aliases</file> is the source file for the system mail
8128 aliases (e.g., postmaster, usenet, etc.), it is the one
8129 which the sysadmin and <prgn>postinst</prgn> scripts may
8130 edit. After <file>/etc/aliases</file> is edited the program or
8131 human editing it must call <prgn>newaliases</prgn>. All MTA
8132 packages must come with a <prgn>newaliases</prgn> program,
8133 even if it does nothing, but older MTA packages did not do
8134 this so programs should not fail if <prgn>newaliases</prgn>
8135 cannot be found. Note that because of this, all MTA
8136 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8137 <tt>Replaces: mail-transport-agent</tt> control file
8142 The convention of writing <tt>forward to
8143 <var>address</var></tt> in the mailbox itself is not
8144 supported. Use a <tt>.forward</tt> file instead.</p>
8147 The <prgn>rmail</prgn> program used by UUCP
8148 for incoming mail should be <file>/usr/sbin/rmail</file>.
8149 Likewise, <prgn>rsmtp</prgn>, for receiving
8150 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8154 If your package needs to know what hostname to use on (for
8155 example) outgoing news and mail messages which are generated
8156 locally, you should use the file <file>/etc/mailname</file>. It
8157 will contain the portion after the username and <tt>@</tt>
8158 (at) sign for email addresses of users on the machine
8159 (followed by a newline).
8163 Such a package should check for the existence of this file
8164 when it is being configured. If it exists, it should be
8165 used without comment, although an MTA's configuration script
8166 may wish to prompt the user even if it finds that this file
8167 exists. If the file does not exist, the package should
8168 prompt the user for the value (preferably using
8169 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8170 as well as using it in the package's configuration. The
8171 prompt should make it clear that the name will not just be
8172 used by that package. For example, in this situation the
8173 <tt>inn</tt> package could say something like:
8174 <example compact="compact">
8175 Please enter the "mail name" of your system. This is the
8176 hostname portion of the address to be shown on outgoing
8177 news and mail messages. The default is
8178 <var>syshostname</var>, your system's host name. Mail
8179 name ["<var>syshostname</var>"]:
8181 where <var>syshostname</var> is the output of <tt>hostname
8187 <heading>News system configuration</heading>
8190 All the configuration files related to the NNTP (news)
8191 servers and clients should be located under
8192 <file>/etc/news</file>.</p>
8195 There are some configuration issues that apply to a number
8196 of news clients and server packages on the machine. These
8200 <tag><file>/etc/news/organization</file></tag>
8202 A string which should appear as the
8203 organization header for all messages posted
8204 by NNTP clients on the machine
8207 <tag><file>/etc/news/server</file></tag>
8209 Contains the FQDN of the upstream NNTP
8210 server, or localhost if the local machine is
8215 Other global files may be added as required for cross-package news
8222 <heading>Programs for the X Window System</heading>
8225 <heading>Providing X support and package priorities</heading>
8228 Programs that can be configured with support for the X
8229 Window System must be configured to do so and must declare
8230 any package dependencies necessary to satisfy their
8231 runtime requirements when using the X Window System. If
8232 such a package is of higher priority than the X packages
8233 on which it depends, it is required that either the
8234 X-specific components be split into a separate package, or
8235 that an alternative version of the package, which includes
8236 X support, be provided, or that the package's priority be
8242 <heading>Packages providing an X server</heading>
8245 Packages that provide an X server that, directly or
8246 indirectly, communicates with real input and display
8247 hardware should declare in their control data that they
8248 provide the virtual package <tt>xserver</tt>.<footnote>
8249 This implements current practice, and provides an
8250 actual policy for usage of the <tt>xserver</tt>
8251 virtual package which appears in the virtual packages
8252 list. In a nutshell, X servers that interface
8253 directly with the display and input hardware or via
8254 another subsystem (e.g., GGI) should provide
8255 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8256 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8262 <heading>Packages providing a terminal emulator</heading>
8265 Packages that provide a terminal emulator for the X Window
8266 System which meet the criteria listed below should declare
8267 in their control data that they provide the virtual
8268 package <tt>x-terminal-emulator</tt>. They should also
8269 register themselves as an alternative for
8270 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8275 To be an <tt>x-terminal-emulator</tt>, a program must:
8276 <list compact="compact">
8278 Be able to emulate a DEC VT100 terminal, or a
8279 compatible terminal.
8283 Support the command-line option <tt>-e
8284 <var>command</var></tt>, which creates a new
8285 terminal window<footnote>
8286 "New terminal window" does not necessarily mean
8287 a new top-level X window directly parented by
8288 the window manager; it could, if the terminal
8289 emulator application were so coded, be a new
8290 "view" in a multiple-document interface (MDI).
8292 and runs the specified <var>command</var>,
8293 interpreting the entirety of the rest of the command
8294 line as a command to pass straight to exec, in the
8295 manner that <tt>xterm</tt> does.
8299 Support the command-line option <tt>-T
8300 <var>title</var></tt>, which creates a new terminal
8301 window with the window title <var>title</var>.
8308 <heading>Packages providing a window manager</heading>
8311 Packages that provide a window manager should declare in
8312 their control data that they provide the virtual package
8313 <tt>x-window-manager</tt>. They should also register
8314 themselves as an alternative for
8315 <file>/usr/bin/x-window-manager</file>, with a priority
8316 calculated as follows:
8317 <list compact="compact">
8319 Start with a priority of 20.
8323 If the window manager supports the Debian menu
8324 system, add 20 points if this support is available
8325 in the package's default configuration (i.e., no
8326 configuration files belonging to the system or user
8327 have to be edited to activate the feature); if
8328 configuration files must be modified, add only 10
8334 If the window manager complies with <url
8335 id="http://www.freedesktop.org/Standards/wm-spec"
8336 name="The Window Manager Specification Project">,
8337 written by the <url id="http://www.freedesktop.org/"
8338 name="Free Desktop Group">, add 40 points.
8342 If the window manager permits the X session to be
8343 restarted using a <em>different</em> window manager
8344 (without killing the X server) in its default
8345 configuration, add 10 points; otherwise add none.
8352 <heading>Packages providing fonts</heading>
8355 Packages that provide fonts for the X Window
8357 For the purposes of Debian Policy, a "font for the X
8358 Window System" is one which is accessed via X protocol
8359 requests. Fonts for the Linux console, for PostScript
8360 renderer, or any other purpose, do not fit this
8361 definition. Any tool which makes such fonts available
8362 to the X Window System, however, must abide by this
8365 must do a number of things to ensure that they are both
8366 available without modification of the X or font server
8367 configuration, and that they do not corrupt files used by
8368 other font packages to register information about
8372 Fonts of any type supported by the X Window System
8373 must be in a separate binary package from any
8374 executables, libraries, or documentation (except
8375 that specific to the fonts shipped, such as their
8376 license information). If one or more of the fonts
8377 so packaged are necessary for proper operation of
8378 the package with which they are associated the font
8379 package may be Recommended; if the fonts merely
8380 provide an enhancement, a Suggests relationship may
8381 be used. Packages must not Depend on font
8383 This is because the X server may retrieve fonts
8384 from the local file system or over the network
8385 from an X font server; the Debian package system
8386 is empowered to deal only with the local
8392 BDF fonts must be converted to PCF fonts with the
8393 <prgn>bdftopcf</prgn> utility (available in the
8394 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8395 placed in a directory that corresponds to their
8397 <list compact="compact">
8399 100 dpi fonts must be placed in
8400 <file>/usr/share/fonts/X11/100dpi/</file>.
8404 75 dpi fonts must be placed in
8405 <file>/usr/share/fonts/X11/75dpi/</file>.
8409 Character-cell fonts, cursor fonts, and other
8410 low-resolution fonts must be placed in
8411 <file>/usr/share/fonts/X11/misc/</file>.
8417 Type 1 fonts must be placed in
8418 <file>/usr/share/fonts/X11/Type1/</file>. If font
8419 metric files are available, they must be placed here
8424 Subdirectories of <file>/usr/share/fonts/X11/</file>
8425 other than those listed above must be neither
8426 created nor used. (The <file>PEX</file>, <file>CID</file>,
8427 <file>Speedo</file>, and <file>cyrillic</file> directories
8428 are excepted for historical reasons, but installation of
8429 files into these directories remains discouraged.)
8433 Font packages may, instead of placing files directly
8434 in the X font directories listed above, provide
8435 symbolic links in that font directory pointing to
8436 the files' actual location in the filesystem. Such
8437 a location must comply with the FHS.
8441 Font packages should not contain both 75dpi and
8442 100dpi versions of a font. If both are available,
8443 they should be provided in separate binary packages
8444 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8445 the names of the packages containing the
8446 corresponding fonts.
8450 Fonts destined for the <file>misc</file> subdirectory
8451 should not be included in the same package as 75dpi
8452 or 100dpi fonts; instead, they should be provided in
8453 a separate package with <tt>-misc</tt> appended to
8458 Font packages must not provide the files
8459 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8460 <file>fonts.scale</file> in a font directory:
8463 <file>fonts.dir</file> files must not be provided at all.
8467 <file>fonts.alias</file> and <file>fonts.scale</file>
8468 files, if needed, should be provided in the
8470 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8471 where <var>fontdir</var> is the name of the
8473 <file>/usr/share/fonts/X11/</file> where the
8474 package's corresponding fonts are stored
8475 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8476 <var>package</var> is the name of the package
8477 that provides these fonts, and
8478 <var>extension</var> is either <tt>scale</tt>
8479 or <tt>alias</tt>, whichever corresponds to
8486 Font packages must declare a dependency on
8487 <tt>xfonts-utils</tt> in their control
8492 Font packages that provide one or more
8493 <file>fonts.scale</file> files as described above must
8494 invoke <prgn>update-fonts-scale</prgn> on each
8495 directory into which they installed fonts
8496 <em>before</em> invoking
8497 <prgn>update-fonts-dir</prgn> on that directory.
8498 This invocation must occur in both the
8499 <prgn>postinst</prgn> (for all arguments) and
8500 <prgn>postrm</prgn> (for all arguments except
8501 <tt>upgrade</tt>) scripts.
8505 Font packages that provide one or more
8506 <file>fonts.alias</file> files as described above must
8507 invoke <prgn>update-fonts-alias</prgn> on each
8508 directory into which they installed fonts. This
8509 invocation must occur in both the
8510 <prgn>postinst</prgn> (for all arguments) and
8511 <prgn>postrm</prgn> (for all arguments except
8512 <tt>upgrade</tt>) scripts.
8516 Font packages must invoke
8517 <prgn>update-fonts-dir</prgn> on each directory into
8518 which they installed fonts. This invocation must
8519 occur in both the <prgn>postinst</prgn> (for all
8520 arguments) and <prgn>postrm</prgn> (for all
8521 arguments except <tt>upgrade</tt>) scripts.
8525 Font packages must not provide alias names for the
8526 fonts they include which collide with alias names
8527 already in use by fonts already packaged.
8531 Font packages must not provide fonts with the same
8532 XLFD registry name as another font already packaged.
8539 <heading>Application defaults files</heading>
8542 Application defaults files must be installed in the
8543 directory <file>/etc/X11/app-defaults/</file> (use of a
8544 localized subdirectory of <file>/etc/X11/</file> as described
8545 in the <em>X Toolkit Intrinsics - C Language
8546 Interface</em> manual is also permitted). They must be
8547 registered as <tt>conffile</tt>s or handled as
8548 configuration files.
8552 Customization of programs' X resources may also be
8553 supported with the provision of a file with the same name
8554 as that of the package placed in the
8555 <file>/etc/X11/Xresources/</file> directory, which must
8556 registered as a <tt>conffile</tt> or handled as a
8557 configuration file.<footnote>
8558 Note that this mechanism is not the same as using
8559 app-defaults; app-defaults are tied to the client
8560 binary on the local file system, whereas X resources
8561 are stored in the X server and affect all connecting
8568 <heading>Installation directory issues</heading>
8571 Packages using the X Window System should not be
8572 configured to install files under the
8573 <file>/usr/X11R6/</file> directory. The
8574 <file>/usr/X11R6/</file> directory hierarchy should be
8575 regarded as obsolete.
8579 Programs that use GNU <prgn>autoconf</prgn> and
8580 <prgn>automake</prgn> are usually easily configured at
8581 compile time to use <file>/usr/</file> instead of
8582 <file>/usr/X11R6/</file>, and this should be done whenever
8583 possible. Configuration files for window managers and
8584 display managers should be placed in a subdirectory of
8585 <file>/etc/X11/</file> corresponding to the package name due
8586 to these programs' tight integration with the mechanisms
8587 of the X Window System. Application-level programs should
8588 use the <file>/etc/</file> directory unless otherwise mandated
8593 The installation of files into subdirectories
8594 of <file>/usr/X11R6/include/X11/</file> and
8595 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8596 package maintainers should determine if subdirectories of
8597 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8602 Packages should install any relevant files into the
8603 directories <file>/usr/include/X11/</file> and
8604 <file>/usr/lib/X11/</file>, but if they do so, they must
8605 pre-depend on <tt>x11-common (>=
8606 1:7.0.0)</tt><footnote>
8608 These libraries used to be all symbolic
8609 links. However, with <tt>X11R7</tt>,
8610 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8611 are now real directories, and packages
8612 <strong>should</strong> ship their files here instead
8613 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8614 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8615 responsible for converting these symlinks into
8623 <heading>The OSF/Motif and OpenMotif libraries</heading>
8626 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8627 OpenMotif libraries</em><footnote>
8628 OSF/Motif and OpenMotif are collectively referred to as
8629 "Motif" in this policy document.
8631 should be compiled against and tested with LessTif (a free
8632 re-implementation of Motif) instead. If the maintainer
8633 judges that the program or programs do not work
8634 sufficiently well with LessTif to be distributed and
8635 supported, but do so when compiled against Motif, then two
8636 versions of the package should be created; one linked
8637 statically against Motif and with <tt>-smotif</tt>
8638 appended to the package name, and one linked dynamically
8639 against Motif and with <tt>-dmotif</tt> appended to the
8644 Both Motif-linked versions are dependent
8645 upon non-DFSG-compliant software and thus cannot be
8646 uploaded to the <em>main</em> distribution; if the
8647 software is itself DFSG-compliant it may be uploaded to
8648 the <em>contrib</em> distribution. While known existing
8649 versions of Motif permit unlimited redistribution of
8650 binaries linked against the library (whether statically or
8651 dynamically), it is the package maintainer's
8652 responsibility to determine whether this is permitted by
8653 the license of the copy of Motif in their possession.
8659 <heading>Perl programs and modules</heading>
8662 Perl programs and modules should follow the current Perl policy.
8666 The Perl policy can be found in the <tt>perl-policy</tt>
8667 files in the <tt>debian-policy</tt> package.
8668 It is also available from the Debian web mirrors at
8669 <tt><url name="/doc/packaging-manuals/perl-policy/"
8670 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8675 <heading>Emacs lisp programs</heading>
8678 Please refer to the "Debian Emacs Policy" for details of how to
8679 package emacs lisp programs.
8683 The Emacs policy is available in
8684 <file>debian-emacs-policy.gz</file> of the
8685 <package>emacsen-common</package> package.
8686 It is also available from the Debian web mirrors at
8687 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8688 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8693 <heading>Games</heading>
8696 The permissions on <file>/var/games</file> are mode 755, owner
8697 <tt>root</tt> and group <tt>root</tt>.
8701 Each game decides on its own security policy.</p>
8704 Games which require protected, privileged access to
8705 high-score files, saved games, etc., may be made
8706 set-<em>group</em>-id (mode 2755) and owned by
8707 <tt>root:games</tt>, and use files and directories with
8708 appropriate permissions (770 <tt>root:games</tt>, for
8709 example). They must not be made
8710 set-<em>user</em>-id, as this causes security problems. (If
8711 an attacker can subvert any set-user-id game they can
8712 overwrite the executable of any other, causing other players
8713 of these games to run a Trojan horse program. With a
8714 set-group-id game the attacker only gets access to less
8715 important game data, and if they can get at the other
8716 players' accounts at all it will take considerably more
8720 Some packages, for example some fortune cookie programs, are
8721 configured by the upstream authors to install with their
8722 data files or other static information made unreadable so
8723 that they can only be accessed through set-id programs
8724 provided. You should not do this in a Debian package: anyone can
8725 download the <file>.deb</file> file and read the data from it,
8726 so there is no point making the files unreadable. Not
8727 making the files unreadable also means that you don't have
8728 to make so many programs set-id, which reduces the risk of a
8732 As described in the FHS, binaries of games should be
8733 installed in the directory <file>/usr/games</file>. This also
8734 applies to games that use the X Window System. Manual pages
8735 for games (X and non-X games) should be installed in
8736 <file>/usr/share/man/man6</file>.</p>
8742 <heading>Documentation</heading>
8745 <heading>Manual pages</heading>
8748 You should install manual pages in <prgn>nroff</prgn> source
8749 form, in appropriate places under <file>/usr/share/man</file>.
8750 You should only use sections 1 to 9 (see the FHS for more
8751 details). You must not install a pre-formatted "cat page".
8755 Each program, utility, and function should have an
8756 associated manual page included in the same package. It is
8757 suggested that all configuration files also have a manual
8758 page included as well. Manual pages for protocols and other
8759 auxiliary things are optional.
8763 If no manual page is available, this is considered as a bug
8764 and should be reported to the Debian Bug Tracking System (the
8765 maintainer of the package is allowed to write this bug report
8766 themselves, if they so desire). Do not close the bug report
8767 until a proper man page is available.<footnote>
8768 It is not very hard to write a man page. See the
8769 <url id="http://www.schweikhardt.net/man_page_howto.html"
8770 name="Man-Page-HOWTO">,
8771 <manref name="man" section="7">, the examples
8772 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8773 the helper programs <prgn>help2man</prgn>, or the
8774 directory <file>/usr/share/doc/man-db/examples</file>.
8779 You may forward a complaint about a missing man page to the
8780 upstream authors, and mark the bug as forwarded in the
8781 Debian bug tracking system. Even though the GNU Project do
8782 not in general consider the lack of a man page to be a bug,
8783 we do; if they tell you that they don't consider it a bug
8784 you should leave the bug in our bug tracking system open
8789 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8793 If one man page needs to be accessible via several names it
8794 is better to use a symbolic link than the <file>.so</file>
8795 feature, but there is no need to fiddle with the relevant
8796 parts of the upstream source to change from <file>.so</file> to
8797 symlinks: don't do it unless it's easy. You should not
8798 create hard links in the manual page directories, nor put
8799 absolute filenames in <file>.so</file> directives. The filename
8800 in a <file>.so</file> in a man page should be relative to the
8801 base of the man page tree (usually
8802 <file>/usr/share/man</file>). If you do not create any links
8803 (whether symlinks, hard links, or <tt>.so</tt> directives)
8804 in the file system to the alternate names of the man page,
8805 then you should not rely on <prgn>man</prgn> finding your
8806 man page under those names based solely on the information in
8807 the man page's header.<footnote>
8808 Supporting this in <prgn>man</prgn> often requires
8809 unreasonable processing time to find a manual page or to
8810 report that none exists, and moves knowledge into man's
8811 database that would be better left in the file system.
8812 This support is therefore deprecated and will cease to
8813 be present in the future.
8818 Manual pages in locale-specific subdirectories of
8819 <file>/usr/share/man</file> should use either UTF-8 or the usual
8820 legacy encoding for that language (normally the one corresponding
8821 to the shortest relevant locale name in
8822 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8823 <file>/usr/share/man/fr</file> should use either UTF-8 or
8824 ISO-8859-1.<footnote>
8825 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8826 use. In future, all manual pages will be required to use
8832 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8833 included in the subdirectory name unless it indicates a
8834 significant difference in the language, as this excludes
8835 speakers of the language in other countries.<footnote>
8836 At the time of writing, Chinese and Portuguese are the main
8837 languages with such differences, so <file>pt_BR</file>,
8838 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8843 Due to limitations in current implementations, all characters
8844 in the manual page source should be representable in the usual
8845 legacy encoding for that language, even if the file is
8846 actually encoded in UTF-8. Safe alternative ways to write many
8847 characters outside that range may be found in
8848 <manref name="groff_char" section="7">.
8853 <heading>Info documents</heading>
8856 Info documents should be installed in <file>/usr/share/info</file>.
8857 They should be compressed with <tt>gzip -9</tt>.
8861 Your package should call <prgn>install-info</prgn> to update
8862 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8863 script when called with a <tt>configure</tt> argument, for
8865 <example compact="compact">
8866 install-info --quiet --section Development Development \
8867 /usr/share/info/foobar.info
8871 It is a good idea to specify a section for the location of
8872 your program; this is done with the <tt>--section</tt>
8873 switch. To determine which section to use, you should look
8874 at <file>/usr/share/info/dir</file> on your system and choose the most
8875 relevant (or create a new section if none of the current
8876 sections are relevant). Note that the <tt>--section</tt>
8877 flag takes two arguments; the first is a regular expression
8878 to match (case-insensitively) against an existing section,
8879 the second is used when creating a new one.</p>
8882 You should remove the entries in the <prgn>prerm</prgn>
8883 script when called with a <tt>remove</tt> argument:
8884 <example compact="compact">
8885 install-info --quiet --remove /usr/share/info/foobar.info
8889 If <prgn>install-info</prgn> cannot find a description entry
8890 in the Info file you must supply one. See <manref
8891 name="install-info" section="8"> for details.</p>
8895 <heading>Additional documentation</heading>
8898 Any additional documentation that comes with the package may
8899 be installed at the discretion of the package maintainer.
8900 Plain text documentation should be installed in the directory
8901 <file>/usr/share/doc/<var>package</var></file>, where
8902 <var>package</var> is the name of the package, and
8903 compressed with <tt>gzip -9</tt> unless it is small.
8907 If a package comes with large amounts of documentation which
8908 many users of the package will not require you should create
8909 a separate binary package to contain it, so that it does not
8910 take up disk space on the machines of users who do not need
8911 or want it installed.</p>
8914 It is often a good idea to put text information files
8915 (<file>README</file>s, changelogs, and so forth) that come with
8916 the source package in <file>/usr/share/doc/<var>package</var></file>
8917 in the binary package. However, you don't need to install
8918 the instructions for building and installing the package, of
8922 Packages must not require the existence of any files in
8923 <file>/usr/share/doc/</file> in order to function
8925 The system administrator should be able to
8926 delete files in <file>/usr/share/doc/</file> without causing
8927 any programs to break.
8929 Any files that are referenced by programs but are also
8930 useful as stand alone documentation should be installed under
8931 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8932 <file>/usr/share/doc/<var>package</var></file>.
8936 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8937 link to another directory in <file>/usr/share/doc</file> only if
8938 the two packages both come from the same source and the
8939 first package Depends on the second.<footnote>
8941 Please note that this does not override the section on
8942 changelog files below, so the file
8943 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8944 must refer to the changelog for the current version of
8945 <var>package</var> in question. In practice, this means
8946 that the sources of the target and the destination of the
8947 symlink must be the same (same source package and
8954 Former Debian releases placed all additional documentation
8955 in <file>/usr/doc/<var>package</var></file>. This has been
8956 changed to <file>/usr/share/doc/<var>package</var></file>,
8957 and packages must not put documentation in the directory
8958 <file>/usr/doc/<var>package</var></file>. <footnote>
8959 At this phase of the transition, we no longer require a
8960 symbolic link in <file>/usr/doc/</file>. At a later point,
8961 policy shall change to make the symbolic links a bug.
8967 <heading>Preferred documentation formats</heading>
8970 The unification of Debian documentation is being carried out
8974 If your package comes with extensive documentation in a
8975 markup format that can be converted to various other formats
8976 you should if possible ship HTML versions in a binary
8977 package, in the directory
8978 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8979 its subdirectories.<footnote>
8980 The rationale: The important thing here is that HTML
8981 docs should be available in <em>some</em> package, not
8982 necessarily in the main binary package.
8987 Other formats such as PostScript may be provided at the
8988 package maintainer's discretion.
8992 <sect id="copyrightfile">
8993 <heading>Copyright information</heading>
8996 Every package must be accompanied by a verbatim copy of its
8997 copyright and distribution license in the file
8998 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8999 file must neither be compressed nor be a symbolic link.
9003 In addition, the copyright file must say where the upstream
9004 sources (if any) were obtained. It should name the original
9005 authors of the package and the Debian maintainer(s) who were
9006 involved with its creation.
9010 Packages in the <em>contrib</em> or <em>non-free</em> archive
9011 areas should state in the copyright file that the package is not
9012 part of the Debian GNU/Linux distribution and briefly explain
9017 A copy of the file which will be installed in
9018 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9019 be in <file>debian/copyright</file> in the source package.
9023 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9024 link to another directory in <file>/usr/share/doc</file> only if
9025 the two packages both come from the same source and the
9026 first package Depends on the second. These rules are
9027 important because copyrights must be extractable by
9032 Packages distributed under the UCB BSD license, the Apache
9033 license (version 2.0), the Artistic license, the GNU GPL
9034 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and the
9035 GNU FDL (versions 1.2 or 1.3) should refer to the corresponding
9036 files under <file>/usr/share/common-licenses</file>,<footnote>
9039 <file>/usr/share/common-licenses/BSD</file>,
9040 <file>/usr/share/common-licenses/Apache-2.0</file>,
9041 <file>/usr/share/common-licenses/Artistic</file>,
9042 <file>/usr/share/common-licenses/GPL-2</file>,
9043 <file>/usr/share/common-licenses/GPL-3</file>,
9044 <file>/usr/share/common-licenses/LGPL-2</file>,
9045 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9046 <file>/usr/share/common-licenses/LGPL-3</file>,
9047 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9048 <file>/usr/share/common-licenses/GFDL-1.3</file>
9051 </footnote> rather than quoting them in the copyright
9056 You should not use the copyright file as a general <file>README</file>
9057 file. If your package has such a file it should be
9058 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9059 <file>README.Debian</file> or some other appropriate place.</p>
9063 <heading>Examples</heading>
9066 Any examples (configurations, source files, whatever),
9067 should be installed in a directory
9068 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9069 files should not be referenced by any program: they're there
9070 for the benefit of the system administrator and users as
9071 documentation only. Architecture-specific example files
9072 should be installed in a directory
9073 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9075 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9076 latter directory itself may be a symbolic link to the
9081 If the purpose of a package is to provide examples, then the
9082 example files may be installed into
9083 <file>/usr/share/doc/<var>package</var></file>.
9087 <sect id="changelogs">
9088 <heading>Changelog files</heading>
9091 Packages that are not Debian-native must contain a
9092 compressed copy of the <file>debian/changelog</file> file from
9093 the Debian source tree in
9094 <file>/usr/share/doc/<var>package</var></file> with the name
9095 <file>changelog.Debian.gz</file>.
9099 If an upstream changelog is available, it should be accessible as
9100 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9101 plain text. If the upstream changelog is distributed in
9102 HTML, it should be made available in that form as
9103 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9104 and a plain text <file>changelog.gz</file> should be generated
9105 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9106 the upstream changelog files do not already conform to this
9107 naming convention, then this may be achieved either by
9108 renaming the files, or by adding a symbolic link, at the
9109 maintainer's discretion.<footnote>
9110 Rationale: People should not have to look in places for
9111 upstream changelogs merely because they are given
9112 different names or are distributed in HTML format.
9117 All of these files should be installed compressed using
9118 <tt>gzip -9</tt>, as they will become large with time even
9119 if they start out small.
9123 If the package has only one changelog which is used both as
9124 the Debian changelog and the upstream one because there is
9125 no separate upstream maintainer then that changelog should
9126 usually be installed as
9127 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9128 there is a separate upstream maintainer, but no upstream
9129 changelog, then the Debian changelog should still be called
9130 <file>changelog.Debian.gz</file>.
9134 For details about the format and contents of the Debian
9135 changelog file, please see <ref id="dpkgchangelog">.
9140 <appendix id="pkg-scope">
9141 <heading>Introduction and scope of these appendices</heading>
9144 These appendices are taken essentially verbatim from the
9145 now-deprecated Packaging Manual, version 3.2.1.0. They are
9146 the chapters which are likely to be of use to package
9147 maintainers and which have not already been included in the
9148 policy document itself. Most of these sections are very likely
9149 not relevant to policy; they should be treated as
9150 documentation for the packaging system. Please note that these
9151 appendices are included for convenience, and for historical
9152 reasons: they used to be part of policy package, and they have
9153 not yet been incorporated into dpkg documentation. However,
9154 they still have value, and hence they are presented here.
9158 They have not yet been checked to ensure that they are
9159 compatible with the contents of policy, and if there are any
9160 contradictions, the version in the main policy document takes
9161 precedence. The remaining chapters of the old Packaging
9162 Manual have also not been read in detail to ensure that there
9163 are not parts which have been left out. Both of these will be
9168 Certain parts of the Packaging manual were integrated into the
9169 Policy Manual proper, and removed from the appendices. Links
9170 have been placed from the old locations to the new ones.
9174 <prgn>dpkg</prgn> is a suite of programs for creating binary
9175 package files and installing and removing them on Unix
9177 <prgn>dpkg</prgn> is targeted primarily at Debian
9178 GNU/Linux, but may work on or be ported to other
9184 The binary packages are designed for the management of
9185 installed executable programs (usually compiled binaries) and
9186 their associated data, though source code examples and
9187 documentation are provided as part of some packages.</p>
9190 This manual describes the technical aspects of creating Debian
9191 binary packages (<file>.deb</file> files). It documents the
9192 behavior of the package management programs
9193 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9194 they interact with packages.</p>
9197 It also documents the interaction between
9198 <prgn>dselect</prgn>'s core and the access method scripts it
9199 uses to actually install the selected packages, and describes
9200 how to create a new access method.</p>
9203 This manual does not go into detail about the options and
9204 usage of the package building and installation tools. It
9205 should therefore be read in conjunction with those programs'
9210 The utility programs which are provided with <prgn>dpkg</prgn>
9211 for managing various system configuration and similar issues,
9212 such as <prgn>update-rc.d</prgn> and
9213 <prgn>install-info</prgn>, are not described in detail here -
9214 please see their man pages.
9218 It is assumed that the reader is reasonably familiar with the
9219 <prgn>dpkg</prgn> System Administrators' manual.
9220 Unfortunately this manual does not yet exist.
9224 The Debian version of the FSF's GNU hello program is provided
9225 as an example for people wishing to create Debian
9226 packages. The Debian <prgn>debmake</prgn> package is
9227 recommended as a very helpful tool in creating and maintaining
9228 Debian packages. However, while the tools and examples are
9229 helpful, they do not replace the need to read and follow the
9230 Policy and Programmer's Manual.</p>
9233 <appendix id="pkg-binarypkg">
9234 <heading>Binary packages (from old Packaging Manual)</heading>
9237 The binary package has two main sections. The first part
9238 consists of various control information files and scripts used
9239 by <prgn>dpkg</prgn> when installing and removing. See <ref
9240 id="pkg-controlarea">.
9244 The second part is an archive containing the files and
9245 directories to be installed.
9249 In the future binary packages may also contain other
9250 components, such as checksums and digital signatures. The
9251 format for the archive is described in full in the
9252 <file>deb(5)</file> man page.
9256 <sect id="pkg-bincreating"><heading>Creating package files -
9257 <prgn>dpkg-deb</prgn>
9261 All manipulation of binary package files is done by
9262 <prgn>dpkg-deb</prgn>; it's the only program that has
9263 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9264 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9265 will spot that the options requested are appropriate to
9266 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9271 In order to create a binary package you must make a
9272 directory tree which contains all the files and directories
9273 you want to have in the file system data part of the package.
9274 In Debian-format source packages this directory is usually
9275 <file>debian/tmp</file>, relative to the top of the package's
9280 They should have the locations (relative to the root of the
9281 directory tree you're constructing) ownerships and
9282 permissions which you want them to have on the system when
9287 With current versions of <prgn>dpkg</prgn> the uid/username
9288 and gid/groupname mappings for the users and groups being
9289 used should be the same on the system where the package is
9290 built and the one where it is installed.
9294 You need to add one special directory to the root of the
9295 miniature file system tree you're creating:
9296 <prgn>DEBIAN</prgn>. It should contain the control
9297 information files, notably the binary package control file
9298 (see <ref id="pkg-controlfile">).
9302 The <prgn>DEBIAN</prgn> directory will not appear in the
9303 file system archive of the package, and so won't be installed
9304 by <prgn>dpkg</prgn> when the package is installed.
9308 When you've prepared the package, you should invoke:
9310 dpkg --build <var>directory</var>
9315 This will build the package in
9316 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9317 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9318 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9323 See the man page <manref name="dpkg-deb" section="8"> for details of how
9324 to examine the contents of this newly-created file. You may find the
9325 output of following commands enlightening:
9327 dpkg-deb --info <var>filename</var>.deb
9328 dpkg-deb --contents <var>filename</var>.deb
9329 dpkg --contents <var>filename</var>.deb
9331 To view the copyright file for a package you could use this command:
9333 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9338 <sect id="pkg-controlarea">
9339 <heading>Package control information files</heading>
9342 The control information portion of a binary package is a
9343 collection of files with names known to <prgn>dpkg</prgn>.
9344 It will treat the contents of these files specially - some
9345 of them contain information used by <prgn>dpkg</prgn> when
9346 installing or removing the package; others are scripts which
9347 the package maintainer wants <prgn>dpkg</prgn> to run.
9351 It is possible to put other files in the package control
9352 area, but this is not generally a good idea (though they
9353 will largely be ignored).
9357 Here is a brief list of the control info files supported by
9358 <prgn>dpkg</prgn> and a summary of what they're used for.
9363 <tag><tt>control</tt>
9366 This is the key description file used by
9367 <prgn>dpkg</prgn>. It specifies the package's name
9368 and version, gives its description for the user,
9369 states its relationships with other packages, and so
9370 forth. See <ref id="sourcecontrolfiles"> and
9371 <ref id="binarycontrolfiles">.
9375 It is usually generated automatically from information
9376 in the source package by the
9377 <prgn>dpkg-gencontrol</prgn> program, and with
9378 assistance from <prgn>dpkg-shlibdeps</prgn>.
9379 See <ref id="pkg-sourcetools">.
9383 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9388 These are executable files (usually scripts) which
9389 <prgn>dpkg</prgn> runs during installation, upgrade
9390 and removal of packages. They allow the package to
9391 deal with matters which are particular to that package
9392 or require more complicated processing than that
9393 provided by <prgn>dpkg</prgn>. Details of when and
9394 how they are called are in <ref id="maintainerscripts">.
9398 It is very important to make these scripts idempotent.
9399 See <ref id="idempotency">.
9403 The maintainer scripts are guaranteed to run with a
9404 controlling terminal and can interact with the user.
9405 See <ref id="controllingterminal">.
9409 <tag><tt>conffiles</tt>
9412 This file contains a list of configuration files which
9413 are to be handled automatically by <prgn>dpkg</prgn>
9414 (see <ref id="pkg-conffiles">). Note that not necessarily
9415 every configuration file should be listed here.
9418 <tag><tt>shlibs</tt>
9421 This file contains a list of the shared libraries
9422 supplied by the package, with dependency details for
9423 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9424 when it determines what dependencies are required in a
9425 package control file. The <tt>shlibs</tt> file format
9426 is described on <ref id="shlibs">.
9431 <sect id="pkg-controlfile">
9432 <heading>The main control information file: <tt>control</tt></heading>
9435 The most important control information file used by
9436 <prgn>dpkg</prgn> when it installs a package is
9437 <tt>control</tt>. It contains all the package's "vital
9442 The binary package control files of packages built from
9443 Debian sources are made by a special tool,
9444 <prgn>dpkg-gencontrol</prgn>, which reads
9445 <file>debian/control</file> and <file>debian/changelog</file> to
9446 find the information it needs. See <ref id="pkg-sourcepkg"> for
9451 The fields in binary package control files are listed in
9452 <ref id="binarycontrolfiles">.
9456 A description of the syntax of control files and the purpose
9457 of the fields is available in <ref id="controlfields">.
9462 <heading>Time Stamps</heading>
9465 See <ref id="timestamps">.
9470 <appendix id="pkg-sourcepkg">
9471 <heading>Source packages (from old Packaging Manual) </heading>
9474 The Debian binary packages in the distribution are generated
9475 from Debian sources, which are in a special format to assist
9476 the easy and automatic building of binaries.
9479 <sect id="pkg-sourcetools">
9480 <heading>Tools for processing source packages</heading>
9483 Various tools are provided for manipulating source packages;
9484 they pack and unpack sources and help build of binary
9485 packages and help manage the distribution of new versions.
9489 They are introduced and typical uses described here; see
9490 <manref name="dpkg-source" section="1"> for full
9491 documentation about their arguments and operation.
9495 For examples of how to construct a Debian source package,
9496 and how to use those utilities that are used by Debian
9497 source packages, please see the <prgn>hello</prgn> example
9501 <sect1 id="pkg-dpkg-source">
9503 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9508 This program is frequently used by hand, and is also
9509 called from package-independent automated building scripts
9510 such as <prgn>dpkg-buildpackage</prgn>.
9514 To unpack a package it is typically invoked with
9516 dpkg-source -x <var>.../path/to/filename</var>.dsc
9521 with the <file><var>filename</var>.tar.gz</file> and
9522 <file><var>filename</var>.diff.gz</file> (if applicable) in
9523 the same directory. It unpacks into
9524 <file><var>package</var>-<var>version</var></file>, and if
9526 <file><var>package</var>-<var>version</var>.orig</file>, in
9527 the current directory.
9531 To create a packed source archive it is typically invoked:
9533 dpkg-source -b <var>package</var>-<var>version</var>
9538 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9539 <file>.diff.gz</file> (if appropriate) in the current
9540 directory. <prgn>dpkg-source</prgn> does not clean the
9541 source tree first - this must be done separately if it is
9546 See also <ref id="pkg-sourcearchives">.</p>
9550 <sect1 id="pkg-dpkg-buildpackage">
9552 <prgn>dpkg-buildpackage</prgn> - overall package-building
9557 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9558 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9559 targets <tt>clean</tt>, <tt>build</tt> and
9560 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9561 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9562 source and binary package upload.
9566 It is usually invoked by hand from the top level of the
9567 built or unbuilt source directory. It may be invoked with
9568 no arguments; useful arguments include:
9569 <taglist compact="compact">
9570 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9573 Do not sign the <tt>.changes</tt> file or the
9574 source package <tt>.dsc</tt> file, respectively.</p>
9576 <tag><tt>-p<var>sign-command</var></tt></tag>
9579 Invoke <var>sign-command</var> instead of finding
9580 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9581 <var>sign-command</var> must behave just like
9582 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9584 <tag><tt>-r<var>root-command</var></tt></tag>
9587 When root privilege is required, invoke the command
9588 <var>root-command</var>. <var>root-command</var>
9589 should invoke its first argument as a command, from
9590 the <prgn>PATH</prgn> if necessary, and pass its
9591 second and subsequent arguments to the command it
9592 calls. If no <var>root-command</var> is supplied
9593 then <var>dpkg-buildpackage</var> will take no
9594 special action to gain root privilege, so that for
9595 most packages it will have to be invoked as root to
9598 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9601 Two types of binary-only build and upload - see
9602 <manref name="dpkg-source" section="1">.
9609 <sect1 id="pkg-dpkg-gencontrol">
9611 <prgn>dpkg-gencontrol</prgn> - generates binary package
9616 This program is usually called from <file>debian/rules</file>
9617 (see <ref id="pkg-sourcetree">) in the top level of the source
9622 This is usually done just before the files and directories in the
9623 temporary directory tree where the package is being built have their
9624 permissions and ownerships set and the package is constructed using
9625 <prgn>dpkg-deb/</prgn>
9627 This is so that the control file which is produced has
9628 the right permissions
9633 <prgn>dpkg-gencontrol</prgn> must be called after all the
9634 files which are to go into the package have been placed in
9635 the temporary build directory, so that its calculation of
9636 the installed size of a package is correct.
9640 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9641 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9642 variable substitutions created by
9643 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9648 For a package which generates only one binary package, and
9649 which builds it in <file>debian/tmp</file> relative to the top
9650 of the source package, it is usually sufficient to call
9651 <prgn>dpkg-gencontrol</prgn>.
9655 Sources which build several binaries will typically need
9658 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9659 </example> The <tt>-P</tt> tells
9660 <prgn>dpkg-gencontrol</prgn> that the package is being
9661 built in a non-default directory, and the <tt>-p</tt>
9662 tells it which package's control file should be generated.
9666 <prgn>dpkg-gencontrol</prgn> also adds information to the
9667 list of files in <file>debian/files</file>, for the benefit of
9668 (for example) a future invocation of
9669 <prgn>dpkg-genchanges</prgn>.</p>
9672 <sect1 id="pkg-dpkg-shlibdeps">
9674 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9679 This program is usually called from <file>debian/rules</file>
9680 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9681 id="pkg-sourcetree">), in the top level of the source tree.
9685 Its arguments are executables and shared libraries
9688 They may be specified either in the locations in the
9689 source tree where they are created or in the locations
9690 in the temporary build tree where they are installed
9691 prior to binary package creation.
9693 </footnote> for which shared library dependencies should
9694 be included in the binary package's control file.
9698 If some of the found shared libraries should only
9699 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9700 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9701 by using the <tt>-d<var>dependency-field</var></tt> option
9702 before those executable(s). (Each <tt>-d</tt> option
9703 takes effect until the next <tt>-d</tt>.)
9707 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9708 output control file to be modified. Instead by default it
9709 adds to the <file>debian/substvars</file> file variable
9710 settings like <tt>shlibs:Depends</tt>. These variable
9711 settings must be referenced in dependency fields in the
9712 appropriate per-binary-package sections of the source
9717 For example, a package that generates an essential part
9718 which requires dependencies, and optional parts that
9719 which only require a recommendation, would separate those
9720 two sets of dependencies into two different fields.<footnote>
9721 At the time of writing, an example for this was the
9722 <package/xmms/ package, with Depends used for the xmms
9723 executable, Recommends for the plug-ins and Suggests for
9724 even more optional features provided by unzip.
9726 It can say in its <file>debian/rules</file>:
9728 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9729 -dRecommends <var>optionalpart anotheroptionalpart</var>
9731 and then in its main control file <file>debian/control</file>:
9734 Depends: ${shlibs:Depends}
9735 Recommends: ${shlibs:Recommends}
9741 Sources which produce several binary packages with
9742 different shared library dependency requirements can use
9743 the <tt>-p<var>varnameprefix</var></tt> option to override
9744 the default <tt>shlibs:</tt> prefix (one invocation of
9745 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9746 They can thus produce several sets of dependency
9747 variables, each of the form
9748 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9749 which can be referred to in the appropriate parts of the
9750 binary package control files.
9755 <sect1 id="pkg-dpkg-distaddfile">
9757 <prgn>dpkg-distaddfile</prgn> - adds a file to
9758 <file>debian/files</file>
9762 Some packages' uploads need to include files other than
9763 the source and binary package files.
9767 <prgn>dpkg-distaddfile</prgn> adds a file to the
9768 <file>debian/files</file> file so that it will be included in
9769 the <file>.changes</file> file when
9770 <prgn>dpkg-genchanges</prgn> is run.
9774 It is usually invoked from the <tt>binary</tt> target of
9775 <file>debian/rules</file>:
9777 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9779 The <var>filename</var> is relative to the directory where
9780 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9781 is usually the directory above the top level of the source
9782 tree. The <file>debian/rules</file> target should put the
9783 file there just before or just after calling
9784 <prgn>dpkg-distaddfile</prgn>.
9788 The <var>section</var> and <var>priority</var> are passed
9789 unchanged into the resulting <file>.changes</file> file.
9794 <sect1 id="pkg-dpkg-genchanges">
9796 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9801 This program is usually called by package-independent
9802 automatic building scripts such as
9803 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9808 It is usually called in the top level of a built source
9809 tree, and when invoked with no arguments will print out a
9810 straightforward <file>.changes</file> file based on the
9811 information in the source package's changelog and control
9812 file and the binary and source packages which should have
9818 <sect1 id="pkg-dpkg-parsechangelog">
9820 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9821 representation of a changelog
9825 This program is used internally by
9826 <prgn>dpkg-source</prgn> et al. It may also occasionally
9827 be useful in <file>debian/rules</file> and elsewhere. It
9828 parses a changelog, <file>debian/changelog</file> by default,
9829 and prints a control-file format representation of the
9830 information in it to standard output.
9834 <sect1 id="pkg-dpkg-architecture">
9836 <prgn>dpkg-architecture</prgn> - information about the build and
9841 This program can be used manually, but is also invoked by
9842 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9843 environment or make variables which specify the build and host
9844 architecture for the package building process.
9849 <sect id="pkg-sourcetree">
9850 <heading>The Debianised source tree</heading>
9853 The source archive scheme described later is intended to
9854 allow a Debianised source tree with some associated control
9855 information to be reproduced and transported easily. The
9856 Debianised source tree is a version of the original program
9857 with certain files added for the benefit of the
9858 Debianisation process, and with any other changes required
9859 made to the rest of the source code and installation
9864 The extra files created for Debian are in the subdirectory
9865 <file>debian</file> of the top level of the Debianised source
9866 tree. They are described below.
9869 <sect1 id="pkg-debianrules">
9870 <heading><file>debian/rules</file> - the main building script</heading>
9873 See <ref id="debianrules">.
9878 <sect1 id="pkg-dpkgchangelog">
9879 <heading><file>debian/changelog</file></heading>
9882 See <ref id="dpkgchangelog">.
9885 <sect2><heading>Defining alternative changelog formats
9889 It is possible to use a different format to the standard
9890 one, by providing a parser for the format you wish to
9895 In order to have <tt>dpkg-parsechangelog</tt> run your
9896 parser, you must include a line within the last 40 lines
9897 of your file matching the Perl regular expression:
9898 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9899 parentheses should be the name of the format. For
9900 example, you might say:
9902 @@@ changelog-format: joebloggs @@@
9904 Changelog format names are non-empty strings of alphanumerics.
9908 If such a line exists then <tt>dpkg-parsechangelog</tt>
9909 will look for the parser as
9910 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9912 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9913 it is an error for it not to find it, or for it not to
9914 be an executable program. The default changelog format
9915 is <tt>dpkg</tt>, and a parser for it is provided with
9916 the <tt>dpkg</tt> package.
9920 The parser will be invoked with the changelog open on
9921 standard input at the start of the file. It should read
9922 the file (it may seek if it wishes) to determine the
9923 information required and return the parsed information
9924 to standard output in the form of a series of control
9925 fields in the standard format. By default it should
9926 return information about only the most recent version in
9927 the changelog; it should accept a
9928 <tt>-v<var>version</var></tt> option to return changes
9929 information from all versions present <em>strictly
9930 after</em> <var>version</var>, and it should then be an
9931 error for <var>version</var> not to be present in the
9937 <list compact="compact">
9938 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9939 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9940 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9941 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9942 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9943 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9944 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9949 If several versions are being returned (due to the use
9950 of <tt>-v</tt>), the urgency value should be of the
9951 highest urgency code listed at the start of any of the
9952 versions requested followed by the concatenated
9953 (space-separated) comments from all the versions
9954 requested; the maintainer, version, distribution and
9955 date should always be from the most recent version.
9959 For the format of the <tt>Changes</tt> field see
9960 <ref id="f-Changes">.
9964 If the changelog format which is being parsed always or
9965 almost always leaves a blank line between individual
9966 change notes these blank lines should be stripped out,
9967 so as to make the resulting output compact.
9971 If the changelog format does not contain date or package
9972 name information this information should be omitted from
9973 the output. The parser should not attempt to synthesize
9974 it or find it from other sources.
9978 If the changelog does not have the expected format the
9979 parser should exit with a nonzero exit status, rather
9980 than trying to muddle through and possibly generating
9985 A changelog parser may not interact with the user at
9991 <sect1 id="pkg-srcsubstvars">
9992 <heading><file>debian/substvars</file> and variable substitutions</heading>
9995 See <ref id="substvars">.
10001 <heading><file>debian/files</file></heading>
10004 See <ref id="debianfiles">.
10008 <sect1><heading><file>debian/tmp</file>
10012 This is the canonical temporary location for the
10013 construction of binary packages by the <tt>binary</tt>
10014 target. The directory <file>tmp</file> serves as the root of
10015 the file system tree as it is being constructed (for
10016 example, by using the package's upstream makefiles install
10017 targets and redirecting the output there), and it also
10018 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10019 id="pkg-bincreating">.
10023 If several binary packages are generated from the same
10024 source tree it is usual to use several
10025 <file>debian/tmp<var>something</var></file> directories, for
10026 example <file>tmp-a</file> or <file>tmp-doc</file>.
10030 Whatever <file>tmp</file> directories are created and used by
10031 <tt>binary</tt> must of course be removed by the
10032 <tt>clean</tt> target.</p></sect1>
10036 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10040 As it exists on the FTP site, a Debian source package
10041 consists of three related files. You must have the right
10042 versions of all three to be able to use them.
10047 <tag>Debian source control file - <tt>.dsc</tt></tag>
10049 This file is a control file used by <prgn>dpkg-source</prgn>
10050 to extract a source package.
10051 See <ref id="debiansourcecontrolfiles">.
10055 Original source archive -
10057 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10063 This is a compressed (with <tt>gzip -9</tt>)
10064 <prgn>tar</prgn> file containing the source code from
10065 the upstream authors of the program.
10070 Debianisation diff -
10072 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10078 This is a unified context diff (<tt>diff -u</tt>)
10079 giving the changes which are required to turn the
10080 original source into the Debian source. These changes
10081 may only include editing and creating plain files.
10082 The permissions of files, the targets of symbolic
10083 links and the characteristics of special files or
10084 pipes may not be changed and no files may be removed
10089 All the directories in the diff must exist, except the
10090 <file>debian</file> subdirectory of the top of the source
10091 tree, which will be created by
10092 <prgn>dpkg-source</prgn> if necessary when unpacking.
10096 The <prgn>dpkg-source</prgn> program will
10097 automatically make the <file>debian/rules</file> file
10098 executable (see below).</p></item>
10103 If there is no original source code - for example, if the
10104 package is specially prepared for Debian or the Debian
10105 maintainer is the same as the upstream maintainer - the
10106 format is slightly different: then there is no diff, and the
10108 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10109 and preferably contains a directory named
10110 <file><var>package</var>-<var>version</var></file>.
10115 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10118 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10119 Debian source package. However, if it is not available it
10120 is possible to unpack a Debian source archive as follows:
10121 <enumlist compact="compact">
10124 Untar the tarfile, which will create a <file>.orig</file>
10128 <p>Rename the <file>.orig</file> directory to
10129 <file><var>package</var>-<var>version</var></file>.</p>
10133 Create the subdirectory <file>debian</file> at the top of
10134 the source tree.</p>
10136 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10138 <item><p>Untar the tarfile again if you want a copy of the original
10139 source code alongside the Debianised version.</p>
10144 It is not possible to generate a valid Debian source archive
10145 without using <prgn>dpkg-source</prgn>. In particular,
10146 attempting to use <prgn>diff</prgn> directly to generate the
10147 <file>.diff.gz</file> file will not work.
10151 <heading>Restrictions on objects in source packages</heading>
10154 The source package may not contain any hard links
10156 This is not currently detected when building source
10157 packages, but only when extracting
10161 Hard links may be permitted at some point in the
10162 future, but would require a fair amount of
10164 </footnote>, device special files, sockets or setuid or
10167 Setgid directories are allowed.
10172 The source packaging tools manage the changes between the
10173 original and Debianised source using <prgn>diff</prgn> and
10174 <prgn>patch</prgn>. Turning the original source tree as
10175 included in the <file>.orig.tar.gz</file> into the debianised
10176 source must not involve any changes which cannot be
10177 handled by these tools. Problematic changes which cause
10178 <prgn>dpkg-source</prgn> to halt with an error when
10179 building the source package are:
10180 <list compact="compact">
10181 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10183 <item><p>Changing the targets of symbolic links.</p>
10185 <item><p>Creating directories, other than <file>debian</file>.</p>
10187 <item><p>Changes to the contents of binary files.</p></item>
10188 </list> Changes which cause <prgn>dpkg-source</prgn> to
10189 print a warning but continue anyway are:
10190 <list compact="compact">
10193 Removing files, directories or symlinks.
10195 Renaming a file is not treated specially - it is
10196 seen as the removal of the old file (which
10197 generates a warning, but is otherwise ignored),
10198 and the creation of the new one.
10204 Changed text files which are missing the usual final
10205 newline (either in the original or the modified
10210 Changes which are not represented, but which are not detected by
10211 <prgn>dpkg-source</prgn>, are:
10212 <list compact="compact">
10213 <item><p>Changing the permissions of files (other than
10214 <file>debian/rules</file>) and directories.</p></item>
10219 The <file>debian</file> directory and <file>debian/rules</file>
10220 are handled specially by <prgn>dpkg-source</prgn> - before
10221 applying the changes it will create the <file>debian</file>
10222 directory, and afterwards it will make
10223 <file>debian/rules</file> world-executable.
10229 <appendix id="pkg-controlfields">
10230 <heading>Control files and their fields (from old Packaging Manual)</heading>
10233 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10234 data in a common format, known as control files. Binary and
10235 source packages have control data as do the <file>.changes</file>
10236 files which control the installation of uploaded files, and
10237 <prgn>dpkg</prgn>'s internal databases are in a similar
10242 <heading>Syntax of control files</heading>
10245 See <ref id="controlsyntax">.
10249 It is important to note that there are several fields which
10250 are optional as far as <prgn>dpkg</prgn> and the related
10251 tools are concerned, but which must appear in every Debian
10252 package, or whose omission may cause problems.
10257 <heading>List of fields</heading>
10260 See <ref id="controlfieldslist">.
10264 This section now contains only the fields that didn't belong
10265 to the Policy manual.
10268 <sect1 id="pkg-f-Filename">
10269 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10272 These fields in <tt>Packages</tt> files give the
10273 filename(s) of (the parts of) a package in the
10274 distribution directories, relative to the root of the
10275 Debian hierarchy. If the package has been split into
10276 several parts the parts are all listed in order, separated
10281 <sect1 id="pkg-f-Size">
10282 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10285 These fields in <file>Packages</file> files give the size (in
10286 bytes, expressed in decimal) and MD5 checksum of the
10287 file(s) which make(s) up a binary package in the
10288 distribution. If the package is split into several parts
10289 the values for the parts are listed in order, separated by
10294 <sect1 id="pkg-f-Status">
10295 <heading><tt>Status</tt></heading>
10298 This field in <prgn>dpkg</prgn>'s status file records
10299 whether the user wants a package installed, removed or
10300 left alone, whether it is broken (requiring
10301 re-installation) or not and what its current state on the
10302 system is. Each of these pieces of information is a
10307 <sect1 id="pkg-f-Config-Version">
10308 <heading><tt>Config-Version</tt></heading>
10311 If a package is not installed or not configured, this
10312 field in <prgn>dpkg</prgn>'s status file records the last
10313 version of the package which was successfully
10318 <sect1 id="pkg-f-Conffiles">
10319 <heading><tt>Conffiles</tt></heading>
10322 This field in <prgn>dpkg</prgn>'s status file contains
10323 information about the automatically-managed configuration
10324 files held by a package. This field should <em>not</em>
10325 appear anywhere in a package!
10330 <heading>Obsolete fields</heading>
10333 These are still recognized by <prgn>dpkg</prgn> but should
10334 not appear anywhere any more.
10336 <taglist compact="compact">
10338 <tag><tt>Revision</tt></tag>
10339 <tag><tt>Package-Revision</tt></tag>
10340 <tag><tt>Package_Revision</tt></tag>
10342 The Debian revision part of the package version was
10343 at one point in a separate control file field. This
10344 field went through several names.
10347 <tag><tt>Recommended</tt></tag>
10348 <item>Old name for <tt>Recommends</tt>.</item>
10350 <tag><tt>Optional</tt></tag>
10351 <item>Old name for <tt>Suggests</tt>.</item>
10353 <tag><tt>Class</tt></tag>
10354 <item>Old name for <tt>Priority</tt>.</item>
10363 <appendix id="pkg-conffiles">
10364 <heading>Configuration file handling (from old Packaging Manual)</heading>
10367 <prgn>dpkg</prgn> can do a certain amount of automatic
10368 handling of package configuration files.
10372 Whether this mechanism is appropriate depends on a number of
10373 factors, but basically there are two approaches to any
10374 particular configuration file.
10378 The easy method is to ship a best-effort configuration in the
10379 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10380 handle updates. If the user is unlikely to want to edit the
10381 file, but you need them to be able to without losing their
10382 changes, and a new package with a changed version of the file
10383 is only released infrequently, this is a good approach.
10387 The hard method is to build the configuration file from
10388 scratch in the <prgn>postinst</prgn> script, and to take the
10389 responsibility for fixing any mistakes made in earlier
10390 versions of the package automatically. This will be
10391 appropriate if the file is likely to need to be different on
10395 <sect><heading>Automatic handling of configuration files by
10400 A package may contain a control area file called
10401 <tt>conffiles</tt>. This file should be a list of filenames
10402 of configuration files needing automatic handling, separated
10403 by newlines. The filenames should be absolute pathnames,
10404 and the files referred to should actually exist in the
10409 When a package is upgraded <prgn>dpkg</prgn> will process
10410 the configuration files during the configuration stage,
10411 shortly before it runs the package's <prgn>postinst</prgn>
10416 For each file it checks to see whether the version of the
10417 file included in the package is the same as the one that was
10418 included in the last version of the package (the one that is
10419 being upgraded from); it also compares the version currently
10420 installed on the system with the one shipped with the last
10425 If neither the user nor the package maintainer has changed
10426 the file, it is left alone. If one or the other has changed
10427 their version, then the changed version is preferred - i.e.,
10428 if the user edits their file, but the package maintainer
10429 doesn't ship a different version, the user's changes will
10430 stay, silently, but if the maintainer ships a new version
10431 and the user hasn't edited it the new version will be
10432 installed (with an informative message). If both have
10433 changed their version the user is prompted about the problem
10434 and must resolve the differences themselves.
10438 The comparisons are done by calculating the MD5 message
10439 digests of the files, and storing the MD5 of the file as it
10440 was included in the most recent version of the package.
10444 When a package is installed for the first time
10445 <prgn>dpkg</prgn> will install the file that comes with it,
10446 unless that would mean overwriting a file already on the
10451 However, note that <prgn>dpkg</prgn> will <em>not</em>
10452 replace a conffile that was removed by the user (or by a
10453 script). This is necessary because with some programs a
10454 missing file produces an effect hard or impossible to
10455 achieve in another way, so that a missing file needs to be
10456 kept that way if the user did it.
10460 Note that a package should <em>not</em> modify a
10461 <prgn>dpkg</prgn>-handled conffile in its maintainer
10462 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10463 the user confusing and possibly dangerous options for
10464 conffile update when the package is upgraded.</p>
10467 <sect><heading>Fully-featured maintainer script configuration
10472 For files which contain site-specific information such as
10473 the hostname and networking details and so forth, it is
10474 better to create the file in the package's
10475 <prgn>postinst</prgn> script.
10479 This will typically involve examining the state of the rest
10480 of the system to determine values and other information, and
10481 may involve prompting the user for some information which
10482 can't be obtained some other way.
10486 When using this method there are a couple of important
10487 issues which should be considered:
10491 If you discover a bug in the program which generates the
10492 configuration file, or if the format of the file changes
10493 from one version to the next, you will have to arrange for
10494 the postinst script to do something sensible - usually this
10495 will mean editing the installed configuration file to remove
10496 the problem or change the syntax. You will have to do this
10497 very carefully, since the user may have changed the file,
10498 perhaps to fix the very problem that your script is trying
10499 to deal with - you will have to detect these situations and
10500 deal with them correctly.
10504 If you do go down this route it's probably a good idea to
10505 make the program that generates the configuration file(s) a
10506 separate program in <file>/usr/sbin</file>, by convention called
10507 <file><var>package</var>config</file> and then run that if
10508 appropriate from the post-installation script. The
10509 <tt><var>package</var>config</tt> program should not
10510 unquestioningly overwrite an existing configuration - if its
10511 mode of operation is geared towards setting up a package for
10512 the first time (rather than any arbitrary reconfiguration
10513 later) you should have it check whether the configuration
10514 already exists, and require a <tt>--force</tt> flag to
10515 overwrite it.</p></sect>
10518 <appendix id="pkg-alternatives"><heading>Alternative versions of
10519 an interface - <prgn>update-alternatives</prgn> (from old
10524 When several packages all provide different versions of the
10525 same program or file it is useful to have the system select a
10526 default, but to allow the system administrator to change it
10527 and have their decisions respected.
10531 For example, there are several versions of the <prgn>vi</prgn>
10532 editor, and there is no reason to prevent all of them from
10533 being installed at once, each under their own name
10534 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10535 Nevertheless it is desirable to have the name <tt>vi</tt>
10536 refer to something, at least by default.
10540 If all the packages involved cooperate, this can be done with
10541 <prgn>update-alternatives</prgn>.
10545 Each package provides its own version under its own name, and
10546 calls <prgn>update-alternatives</prgn> in its postinst to
10547 register its version (and again in its prerm to deregister
10552 See the man page <manref name="update-alternatives"
10553 section="8"> for details.
10557 If <prgn>update-alternatives</prgn> does not seem appropriate
10558 you may wish to consider using diversions instead.</p>
10561 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10562 package's version of a file (from old Packaging Manual)
10566 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10567 when it reinstalls the package it belongs to, and to have it
10568 put the file from the package somewhere else instead.
10572 This can be used locally to override a package's version of a
10573 file, or by one package to override another's version (or
10574 provide a wrapper for it).
10578 Before deciding to use a diversion, read <ref
10579 id="pkg-alternatives"> to see if you really want a diversion
10580 rather than several alternative versions of a program.
10584 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10585 and updated by a special program <prgn>dpkg-divert</prgn>.
10586 Please see <manref name="dpkg-divert" section="8"> for full
10587 details of its operation.
10591 When a package wishes to divert a file from another, it should
10592 call <prgn>dpkg-divert</prgn> in its preinst to add the
10593 diversion and rename the existing file. For example,
10594 supposing that a <prgn>smailwrapper</prgn> package wishes to
10595 install a wrapper around <file>/usr/sbin/smail</file>:
10597 dpkg-divert --package smailwrapper --add --rename \
10598 --divert /usr/sbin/smail.real /usr/sbin/smail
10599 </example> The <tt>--package smailwrapper</tt> ensures that
10600 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10601 can bypass the diversion and get installed as the true version.
10602 It's safe to add the diversion unconditionally on upgrades since
10603 it will be left unchanged if it already exists, but
10604 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10605 message, make the command conditional on the version from which
10606 the package is being upgraded:
10608 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10609 dpkg-divert --package smailwrapper --add --rename \
10610 --divert /usr/sbin/smail.real /usr/sbin/smail
10612 </example> where <tt>1.0-2</tt> is the version at which the
10613 diversion was first added to the package. Running the command
10614 during abort-upgrade is pointless but harmless.
10618 The postrm has to do the reverse:
10620 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10621 dpkg-divert --package smailwrapper --remove --rename \
10622 --divert /usr/sbin/smail.real /usr/sbin/smail
10624 </example> If the diversion was added at a particular version, the
10625 postrm should also handle the failure case of upgrading from an
10626 older version (unless the older version is so old that direct
10627 upgrades are no longer supported):
10629 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10630 dpkg-divert --package smailwrapper --remove --rename \
10631 --divert /usr/sbin/smail.real /usr/sbin/smail
10633 </example> where <tt>1.02-2</tt> is the version at which the
10634 diversion was first added to the package. The postrm should not
10635 remove the diversion on upgrades both because there's no reason to
10636 remove the diversion only to immediately re-add it and since the
10637 postrm of the old package is run after unpacking so the removal of
10638 the diversion will fail.
10642 Do not attempt to divert a file which is vitally important for
10643 the system's operation - when using <prgn>dpkg-divert</prgn>
10644 there is a time, after it has been diverted but before
10645 <prgn>dpkg</prgn> has installed the new version, when the file
10646 does not exist.</p>
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