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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
276 <sect id="definitions">
277 <heading>Definitions</heading>
280 The following terms are used in this Policy Manual:
284 The character encoding specified by ANSI X3.4-1986 and its
285 predecessor standards, referred to in MIME as US-ASCII, and
286 corresponding to an encoding in eight bits per character of
287 the first 128 <url id="http://www.unicode.org/"
288 name="Unicode"> characters, with the eighth bit always zero.
292 The transformation format (sometimes called encoding) of
293 <url id="http://www.unicode.org/" name="Unicode"> defined by
294 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
295 name="RFC 3629">. UTF-8 has the useful property of having
296 ASCII as a subset, so any text encoded in ASCII is trivially
306 <heading>The Debian Archive</heading>
309 The Debian GNU/Linux system is maintained and distributed as a
310 collection of <em>packages</em>. Since there are so many of
311 them (currently well over 15000), they are split into
312 <em>sections</em> and given <em>priorities</em> to simplify
313 the handling of them.
317 The effort of the Debian project is to build a free operating
318 system, but not every package we want to make accessible is
319 <em>free</em> in our sense (see the Debian Free Software
320 Guidelines, below), or may be imported/exported without
321 restrictions. Thus, the archive is split into areas<footnote>
322 The Debian archive software uses the term "component" internally
323 and in the Release file format to refer to the division of an
324 archive. The Debian Social Contract simply refers to "areas."
325 This document uses terminology similar to the Social Contract.
326 </footnote> based on their licenses and other restrictions.
330 The aims of this are:
332 <list compact="compact">
333 <item>to allow us to make as much software available as we can</item>
334 <item>to allow us to encourage everyone to write free software,
336 <item>to allow us to make it easy for people to produce
337 CD-ROMs of our system without violating any licenses,
338 import/export restrictions, or any other laws.</item>
343 The <em>main</em> archive area forms the <em>Debian GNU/Linux
348 Packages in the other archive areas (<tt>contrib</tt>,
349 <tt>non-free</tt>) are not considered to be part of the Debian
350 distribution, although we support their use and provide
351 infrastructure for them (such as our bug-tracking system and
352 mailing lists). This Debian Policy Manual applies to these
357 <heading>The Debian Free Software Guidelines</heading>
359 The Debian Free Software Guidelines (DFSG) form our
360 definition of "free software". These are:
362 <tag>Free Redistribution
365 The license of a Debian component may not restrict any
366 party from selling or giving away the software as a
367 component of an aggregate software distribution
368 containing programs from several different
369 sources. The license may not require a royalty or
370 other fee for such sale.
375 The program must include source code, and must allow
376 distribution in source code as well as compiled form.
381 The license must allow modifications and derived
382 works, and must allow them to be distributed under the
383 same terms as the license of the original software.
385 <tag>Integrity of The Author's Source Code
388 The license may restrict source-code from being
389 distributed in modified form <em>only</em> if the
390 license allows the distribution of "patch files"
391 with the source code for the purpose of modifying the
392 program at build time. The license must explicitly
393 permit distribution of software built from modified
394 source code. The license may require derived works to
395 carry a different name or version number from the
396 original software. (This is a compromise. The Debian
397 Project encourages all authors to not restrict any
398 files, source or binary, from being modified.)
400 <tag>No Discrimination Against Persons or Groups
403 The license must not discriminate against any person
406 <tag>No Discrimination Against Fields of Endeavor
409 The license must not restrict anyone from making use
410 of the program in a specific field of endeavor. For
411 example, it may not restrict the program from being
412 used in a business, or from being used for genetic
415 <tag>Distribution of License
418 The rights attached to the program must apply to all
419 to whom the program is redistributed without the need
420 for execution of an additional license by those
423 <tag>License Must Not Be Specific to Debian
426 The rights attached to the program must not depend on
427 the program's being part of a Debian system. If the
428 program is extracted from Debian and used or
429 distributed without Debian but otherwise within the
430 terms of the program's license, all parties to whom
431 the program is redistributed must have the same
432 rights as those that are granted in conjunction with
435 <tag>License Must Not Contaminate Other Software
438 The license must not place restrictions on other
439 software that is distributed along with the licensed
440 software. For example, the license must not insist
441 that all other programs distributed on the same medium
442 must be free software.
444 <tag>Example Licenses
447 The "GPL," "BSD," and "Artistic" licenses are examples of
448 licenses that we consider <em>free</em>.
455 <heading>Archive areas</heading>
458 <heading>The main archive area</heading>
461 Every package in <em>main</em> must comply with the DFSG
462 (Debian Free Software Guidelines).
466 In addition, the packages in <em>main</em>
467 <list compact="compact">
469 must not require a package outside of <em>main</em>
470 for compilation or execution (thus, the package must
471 not declare a "Depends", "Recommends", or
472 "Build-Depends" relationship on a non-<em>main</em>
476 must not be so buggy that we refuse to support them,
480 must meet all policy requirements presented in this
489 <heading>The contrib archive area</heading>
492 Every package in <em>contrib</em> must comply with the DFSG.
496 In addition, the packages in <em>contrib</em>
497 <list compact="compact">
499 must not be so buggy that we refuse to support them,
503 must meet all policy requirements presented in this
511 Examples of packages which would be included in
512 <em>contrib</em> are:
513 <list compact="compact">
515 free packages which require <em>contrib</em>,
516 <em>non-free</em> packages or packages which are not
517 in our archive at all for compilation or execution,
521 wrapper packages or other sorts of free accessories for
528 <sect1 id="non-free">
529 <heading>The non-free archive area</heading>
532 Packages must be placed in <em>non-free</em> if they are
533 not compliant with the DFSG or are encumbered by patents
534 or other legal issues that make their distribution
539 In addition, the packages in <em>non-free</em>
540 <list compact="compact">
542 must not be so buggy that we refuse to support them,
546 must meet all policy requirements presented in this
547 manual that it is possible for them to meet.
549 It is possible that there are policy
550 requirements which the package is unable to
551 meet, for example, if the source is
552 unavailable. These situations will need to be
553 handled on a case-by-case basis.
562 <sect id="pkgcopyright">
563 <heading>Copyright considerations</heading>
566 Every package must be accompanied by a verbatim copy of
567 its copyright and distribution license in the file
568 <file>/usr/share/doc/<var>package</var>/copyright</file>
569 (see <ref id="copyrightfile"> for further details).
573 We reserve the right to restrict files from being included
574 anywhere in our archives if
575 <list compact="compact">
577 their use or distribution would break a law,
580 there is an ethical conflict in their distribution or
584 we would have to sign a license for them, or
587 their distribution would conflict with other project
594 Programs whose authors encourage the user to make
595 donations are fine for the main distribution, provided
596 that the authors do not claim that not donating is
597 immoral, unethical, illegal or something similar; in such
598 a case they must go in <em>non-free</em>.
602 Packages whose copyright permission notices (or patent
603 problems) do not even allow redistribution of binaries
604 only, and where no special permission has been obtained,
605 must not be placed on the Debian FTP site and its mirrors
610 Note that under international copyright law (this applies
611 in the United States, too), <em>no</em> distribution or
612 modification of a work is allowed without an explicit
613 notice saying so. Therefore a program without a copyright
614 notice <em>is</em> copyrighted and you may not do anything
615 to it without risking being sued! Likewise if a program
616 has a copyright notice but no statement saying what is
617 permitted then nothing is permitted.
621 Many authors are unaware of the problems that restrictive
622 copyrights (or lack of copyright notices) can cause for
623 the users of their supposedly-free software. It is often
624 worthwhile contacting such authors diplomatically to ask
625 them to modify their license terms. However, this can be a
626 politically difficult thing to do and you should ask for
627 advice on the <tt>debian-legal</tt> mailing list first, as
632 When in doubt about a copyright, send mail to
633 <email>debian-legal@lists.debian.org</email>. Be prepared
634 to provide us with the copyright statement. Software
635 covered by the GPL, public domain software and BSD-like
636 copyrights are safe; be wary of the phrases "commercial
637 use prohibited" and "distribution restricted".
641 <sect id="subsections">
642 <heading>Sections</heading>
645 The packages in the archive areas <em>main</em>,
646 <em>contrib</em> and <em>non-free</em> are grouped further into
647 <em>sections</em> to simplify handling.
651 The archive area and section for each package should be
652 specified in the package's <tt>Section</tt> control record (see
653 <ref id="f-Section">). However, the maintainer of the Debian
654 archive may override this selection to ensure the consistency of
655 the Debian distribution. The <tt>Section</tt> field should be
657 <list compact="compact">
659 <em>section</em> if the package is in the
660 <em>main</em> archive area,
663 <em>area/section</em> if the package is in
664 the <em>contrib</em> or <em>non-free</em>
671 The Debian archive maintainers provide the authoritative
672 list of sections. At present, they are:
673 <em>admin</em>, <em>comm</em>,
674 <em>devel</em>, <em>doc</em>,
675 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
676 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
677 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
678 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
679 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
681 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
682 <em>science</em>, <em>shells</em>,
683 <em>sound</em>, <em>tex</em>, <em>text</em>,
684 <em>utils</em>, <em>web</em>, <em>x11</em>.
688 <sect id="priorities">
689 <heading>Priorities</heading>
692 Each package should have a <em>priority</em> value, which is
693 included in the package's <em>control record</em>
694 (see <ref id="f-Priority">).
695 This information is used by the Debian package management tools to
696 separate high-priority packages from less-important packages.
700 The following <em>priority levels</em> are recognized by the
701 Debian package management tools.
703 <tag><tt>required</tt></tag>
705 Packages which are necessary for the proper
706 functioning of the system (usually, this means that
707 dpkg functionality depends on these packages).
708 Removing a <tt>required</tt> package may cause your
709 system to become totally broken and you may not even
710 be able to use <prgn>dpkg</prgn> to put things back,
711 so only do so if you know what you are doing. Systems
712 with only the <tt>required</tt> packages are probably
713 unusable, but they do have enough functionality to
714 allow the sysadmin to boot and install more software.
716 <tag><tt>important</tt></tag>
718 Important programs, including those which one would
719 expect to find on any Unix-like system. If the
720 expectation is that an experienced Unix person who
721 found it missing would say "What on earth is going on,
722 where is <prgn>foo</prgn>?", it must be an
723 <tt>important</tt> package.<footnote>
724 This is an important criterion because we are
725 trying to produce, amongst other things, a free
728 Other packages without which the system will not run
729 well or be usable must also have priority
730 <tt>important</tt>. This does
731 <em>not</em> include Emacs, the X Window System, TeX
732 or any other large applications. The
733 <tt>important</tt> packages are just a bare minimum of
734 commonly-expected and necessary tools.
736 <tag><tt>standard</tt></tag>
738 These packages provide a reasonably small but not too
739 limited character-mode system. This is what will be
740 installed by default if the user doesn't select anything
741 else. It doesn't include many large applications.
743 <tag><tt>optional</tt></tag>
745 (In a sense everything that isn't required is
746 optional, but that's not what is meant here.) This is
747 all the software that you might reasonably want to
748 install if you didn't know what it was and don't have
749 specialized requirements. This is a much larger system
750 and includes the X Window System, a full TeX
751 distribution, and many applications. Note that
752 optional packages should not conflict with each other.
754 <tag><tt>extra</tt></tag>
756 This contains all packages that conflict with others
757 with required, important, standard or optional
758 priorities, or are only likely to be useful if you
759 already know what they are or have specialized
760 requirements (such as packages containing only detached
767 Packages must not depend on packages with lower priority
768 values (excluding build-time dependencies). In order to
769 ensure this, the priorities of one or more packages may need
778 <heading>Binary packages</heading>
781 The Debian GNU/Linux distribution is based on the Debian
782 package management system, called <prgn>dpkg</prgn>. Thus,
783 all packages in the Debian distribution must be provided
784 in the <tt>.deb</tt> file format.
788 <heading>The package name</heading>
791 Every package must have a name that's unique within the Debian
796 The package name is included in the control field
797 <tt>Package</tt>, the format of which is described
798 in <ref id="f-Package">.
799 The package name is also included as a part of the file name
800 of the <tt>.deb</tt> file.
805 <heading>The version of a package</heading>
808 Every package has a version number recorded in its
809 <tt>Version</tt> control file field, described in
810 <ref id="f-Version">.
814 The package management system imposes an ordering on version
815 numbers, so that it can tell whether packages are being up- or
816 downgraded and so that package system front end applications
817 can tell whether a package it finds available is newer than
818 the one installed on the system. The version number format
819 has the most significant parts (as far as comparison is
820 concerned) at the beginning.
824 If an upstream package has problematic version numbers they
825 should be converted to a sane form for use in the
826 <tt>Version</tt> field.
830 <heading>Version numbers based on dates</heading>
833 In general, Debian packages should use the same version
834 numbers as the upstream sources.
838 However, in some cases where the upstream version number is
839 based on a date (e.g., a development "snapshot" release) the
840 package management system cannot handle these version
841 numbers without epochs. For example, dpkg will consider
842 "96May01" to be greater than "96Dec24".
846 To prevent having to use epochs for every new upstream
847 version, the date based portion of the version number
848 should be changed to the following format in such cases:
849 "19960501", "19961224". It is up to the maintainer whether
850 they want to bother the upstream maintainer to change
851 the version numbers upstream, too.
855 Note that other version formats based on dates which are
856 parsed correctly by the package management system should
857 <em>not</em> be changed.
861 Native Debian packages (i.e., packages which have been
862 written especially for Debian) whose version numbers include
863 dates should always use the "YYYYMMDD" format.
870 <heading>The maintainer of a package</heading>
873 Every package must have a Debian maintainer (the
874 maintainer may be one person or a group of people
875 reachable from a common email address, such as a mailing
876 list). The maintainer is responsible for ensuring that
877 the package is placed in the appropriate distributions.
881 The maintainer must be specified in the
882 <tt>Maintainer</tt> control field with their correct name
883 and a working email address. If one person maintains
884 several packages, they should try to avoid having
885 different forms of their name and email address in
886 the <tt>Maintainer</tt> fields of those packages.
890 The format of the <tt>Maintainer</tt> control field is
891 described in <ref id="f-Maintainer">.
895 If the maintainer of a package quits from the Debian
896 project, "Debian QA Group"
897 <email>packages@qa.debian.org</email> takes over the
898 maintainer-ship of the package until someone else
899 volunteers for that task. These packages are called
900 <em>orphaned packages</em>.<footnote>
901 The detailed procedure for doing this gracefully can
902 be found in the Debian Developer's Reference,
903 see <ref id="related">.
908 <sect id="descriptions">
909 <heading>The description of a package</heading>
912 Every Debian package must have an extended description
913 stored in the appropriate field of the control record.
914 The technical information about the format of the
915 <tt>Description</tt> field is in <ref id="f-Description">.
919 The description should describe the package (the program) to a
920 user (system administrator) who has never met it before so that
921 they have enough information to decide whether they want to
922 install it. This description should not just be copied verbatim
923 from the program's documentation.
927 Put important information first, both in the synopsis and
928 extended description. Sometimes only the first part of the
929 synopsis or of the description will be displayed. You can
930 assume that there will usually be a way to see the whole
931 extended description.
935 The description should also give information about the
936 significant dependencies and conflicts between this package
937 and others, so that the user knows why these dependencies and
938 conflicts have been declared.
942 Instructions for configuring or using the package should
943 not be included (that is what installation scripts,
944 manual pages, info files, etc., are for). Copyright
945 statements and other administrivia should not be included
946 either (that is what the copyright file is for).
949 <sect1 id="synopsis"><heading>The single line synopsis</heading>
952 The single line synopsis should be kept brief - certainly
957 Do not include the package name in the synopsis line. The
958 display software knows how to display this already, and you
959 do not need to state it. Remember that in many situations
960 the user may only see the synopsis line - make it as
961 informative as you can.
966 <sect1 id="extendeddesc"><heading>The extended description</heading>
969 Do not try to continue the single line synopsis into the
970 extended description. This will not work correctly when
971 the full description is displayed, and makes no sense
972 where only the summary (the single line synopsis) is
977 The extended description should describe what the package
978 does and how it relates to the rest of the system (in terms
979 of, for example, which subsystem it is which part of).
983 The description field needs to make sense to anyone, even
984 people who have no idea about any of the things the
985 package deals with.<footnote>
986 The blurb that comes with a program in its
987 announcements and/or <prgn>README</prgn> files is
988 rarely suitable for use in a description. It is
989 usually aimed at people who are already in the
990 community where the package is used.
999 <heading>Dependencies</heading>
1002 Every package must specify the dependency information
1003 about other packages that are required for the first to
1008 For example, a dependency entry must be provided for any
1009 shared libraries required by a dynamically-linked executable
1010 binary in a package.
1014 Packages are not required to declare any dependencies they
1015 have on other packages which are marked <tt>Essential</tt>
1016 (see below), and should not do so unless they depend on a
1017 particular version of that package.<footnote>
1019 Essential is needed in part to avoid unresolvable dependency
1020 loops on upgrade. If packages add unnecessary dependencies
1021 on packages in this set, the chances that there
1022 <strong>will</strong> be an unresolvable dependency loop
1023 caused by forcing these Essential packages to be configured
1024 first before they need to be is greatly increased. It also
1025 increases the chances that frontends will be unable to
1026 <strong>calculate</strong> an upgrade path, even if one
1030 Also, functionality is rarely ever removed from the
1031 Essential set, but <em>packages</em> have been removed from
1032 the Essential set when the functionality moved to a
1033 different package. So depending on these packages <em>just
1034 in case</em> they stop being essential does way more harm
1041 Sometimes, a package requires another package to be installed
1042 <em>and</em> configured before it can be installed. In this
1043 case, you must specify a <tt>Pre-Depends</tt> entry for
1048 You should not specify a <tt>Pre-Depends</tt> entry for a
1049 package before this has been discussed on the
1050 <tt>debian-devel</tt> mailing list and a consensus about
1051 doing that has been reached.
1055 The format of the package interrelationship control fields is
1056 described in <ref id="relationships">.
1060 <sect id="virtual_pkg">
1061 <heading>Virtual packages</heading>
1064 Sometimes, there are several packages which offer
1065 more-or-less the same functionality. In this case, it's
1066 useful to define a <em>virtual package</em> whose name
1067 describes that common functionality. (The virtual
1068 packages only exist logically, not physically; that's why
1069 they are called <em>virtual</em>.) The packages with this
1070 particular function will then <em>provide</em> the virtual
1071 package. Thus, any other package requiring that function
1072 can simply depend on the virtual package without having to
1073 specify all possible packages individually.
1077 All packages should use virtual package names where
1078 appropriate, and arrange to create new ones if necessary.
1079 They should not use virtual package names (except privately,
1080 amongst a cooperating group of packages) unless they have
1081 been agreed upon and appear in the list of virtual package
1082 names. (See also <ref id="virtual">)
1086 The latest version of the authoritative list of virtual
1087 package names can be found in the <tt>debian-policy</tt> package.
1088 It is also available from the Debian web mirrors at
1089 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1090 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1094 The procedure for updating the list is described in the preface
1101 <heading>Base system</heading>
1104 The <tt>base system</tt> is a minimum subset of the Debian
1105 GNU/Linux system that is installed before everything else
1106 on a new system. Only very few packages are allowed to form
1107 part of the base system, in order to keep the required disk
1112 The base system consists of all those packages with priority
1113 <tt>required</tt> or <tt>important</tt>. Many of them will
1114 be tagged <tt>essential</tt> (see below).
1119 <heading>Essential packages</heading>
1122 Essential is defined as the minimal set of functionality that
1123 must be available and usable on the system at all times, even
1124 when packages are in an unconfigured (but unpacked) state.
1125 Packages are tagged <tt>essential</tt> for a system using the
1126 <tt>Essential</tt> control file field. The format of the
1127 <tt>Essential</tt> control field is described in <ref
1132 Since these packages cannot be easily removed (one has to
1133 specify an extra <em>force option</em> to
1134 <prgn>dpkg</prgn> to do so), this flag must not be used
1135 unless absolutely necessary. A shared library package
1136 must not be tagged <tt>essential</tt>; dependencies will
1137 prevent its premature removal, and we need to be able to
1138 remove it when it has been superseded.
1142 Since dpkg will not prevent upgrading of other packages
1143 while an <tt>essential</tt> package is in an unconfigured
1144 state, all <tt>essential</tt> packages must supply all of
1145 their core functionality even when unconfigured. If the
1146 package cannot satisfy this requirement it must not be
1147 tagged as essential, and any packages depending on this
1148 package must instead have explicit dependency fields as
1153 Maintainers should take great care in adding any programs,
1154 interfaces, or functionality to <tt>essential</tt> packages.
1155 Packages may assume that functionality provided by
1156 <tt>essential</tt> packages is always available without
1157 declaring explicit dependencies, which means that removing
1158 functionality from the Essential set is very difficult and is
1159 almost never done. Any capability added to an
1160 <tt>essential</tt> package therefore creates an obligation to
1161 support that capability as part of the Essential set in
1166 You must not tag any packages <tt>essential</tt> before
1167 this has been discussed on the <tt>debian-devel</tt>
1168 mailing list and a consensus about doing that has been
1173 <sect id="maintscripts">
1174 <heading>Maintainer Scripts</heading>
1177 The package installation scripts should avoid producing
1178 output which is unnecessary for the user to see and
1179 should rely on <prgn>dpkg</prgn> to stave off boredom on
1180 the part of a user installing many packages. This means,
1181 amongst other things, using the <tt>--quiet</tt> option on
1182 <prgn>install-info</prgn>.
1186 Errors which occur during the execution of an installation
1187 script must be checked and the installation must not
1188 continue after an error.
1192 Note that in general <ref id="scripts"> applies to package
1193 maintainer scripts, too.
1197 You should not use <prgn>dpkg-divert</prgn> on a file
1198 belonging to another package without consulting the
1199 maintainer of that package first.
1203 All packages which supply an instance of a common command
1204 name (or, in general, filename) should generally use
1205 <prgn>update-alternatives</prgn>, so that they may be
1206 installed together. If <prgn>update-alternatives</prgn>
1207 is not used, then each package must use
1208 <tt>Conflicts</tt> to ensure that other packages are
1209 de-installed. (In this case, it may be appropriate to
1210 specify a conflict against earlier versions of something
1211 that previously did not use
1212 <prgn>update-alternatives</prgn>; this is an exception to
1213 the usual rule that versioned conflicts should be
1217 <sect1 id="maintscriptprompt">
1218 <heading>Prompting in maintainer scripts</heading>
1220 Package maintainer scripts may prompt the user if
1221 necessary. Prompting must be done by communicating
1222 through a program, such as <prgn>debconf</prgn>, which
1223 conforms to the Debian Configuration Management
1224 Specification, version 2 or higher.
1228 Packages which are essential, or which are dependencies of
1229 essential packages, may fall back on another prompting method
1230 if no such interface is available when they are executed.
1234 The Debian Configuration Management Specification is included
1235 in the <file>debconf_specification</file> files in the
1236 <package>debian-policy</package> package.
1237 It is also available from the Debian web mirrors at
1238 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1239 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1243 Packages which use the Debian Configuration Management
1244 Specification may contain an additional
1245 <prgn>config</prgn> script and a <tt>templates</tt>
1246 file in their control archive<footnote>
1247 The control.tar.gz inside the .deb.
1248 See <manref name="deb" section="5">.
1250 The <prgn>config</prgn> script might be run before the
1251 <prgn>preinst</prgn> script, and before the package is unpacked
1252 or any of its dependencies or pre-dependencies are satisfied.
1253 Therefore it must work using only the tools present in
1254 <em>essential</em> packages.<footnote>
1255 <package>Debconf</package> or another tool that
1256 implements the Debian Configuration Management
1257 Specification will also be installed, and any
1258 versioned dependencies on it will be satisfied
1259 before preconfiguration begins.
1264 Packages which use the Debian Configuration Management
1265 Specification must allow for translation of their user-visible
1266 messages by using a gettext-based system such as the one
1267 provided by the <package>po-debconf</package> package.
1271 Packages should try to minimize the amount of prompting
1272 they need to do, and they should ensure that the user
1273 will only ever be asked each question once. This means
1274 that packages should try to use appropriate shared
1275 configuration files (such as <file>/etc/papersize</file> and
1276 <file>/etc/news/server</file>), and shared
1277 <package>debconf</package> variables rather than each
1278 prompting for their own list of required pieces of
1283 It also means that an upgrade should not ask the same
1284 questions again, unless the user has used
1285 <tt>dpkg --purge</tt> to remove the package's configuration.
1286 The answers to configuration questions should be stored in an
1287 appropriate place in <file>/etc</file> so that the user can
1288 modify them, and how this has been done should be
1293 If a package has a vitally important piece of
1294 information to pass to the user (such as "don't run me
1295 as I am, you must edit the following configuration files
1296 first or you risk your system emitting badly-formatted
1297 messages"), it should display this in the
1298 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1299 prompt the user to hit return to acknowledge the
1300 message. Copyright messages do not count as vitally
1301 important (they belong in
1302 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1303 neither do instructions on how to use a program (these
1304 should be in on-line documentation, where all the users
1309 Any necessary prompting should almost always be confined
1310 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1311 script. If it is done in the <prgn>postinst</prgn>, it
1312 should be protected with a conditional so that
1313 unnecessary prompting doesn't happen if a package's
1314 installation fails and the <prgn>postinst</prgn> is
1315 called with <tt>abort-upgrade</tt>,
1316 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1326 <heading>Source packages</heading>
1328 <sect id="standardsversion">
1329 <heading>Standards conformance</heading>
1332 Source packages should specify the most recent version number
1333 of this policy document with which your package complied
1334 when it was last updated.
1338 This information may be used to file bug reports
1339 automatically if your package becomes too much out of date.
1343 The version is specified in the <tt>Standards-Version</tt>
1345 The format of the <tt>Standards-Version</tt> field is
1346 described in <ref id="f-Standards-Version">.
1350 You should regularly, and especially if your package has
1351 become out of date, check for the newest Policy Manual
1352 available and update your package, if necessary. When your
1353 package complies with the new standards you should update the
1354 <tt>Standards-Version</tt> source package field and
1355 release it.<footnote>
1356 See the file <file>upgrading-checklist</file> for
1357 information about policy which has changed between
1358 different versions of this document.
1364 <sect id="pkg-relations">
1365 <heading>Package relationships</heading>
1368 Source packages should specify which binary packages they
1369 require to be installed or not to be installed in order to
1370 build correctly. For example, if building a package
1371 requires a certain compiler, then the compiler should be
1372 specified as a build-time dependency.
1376 It is not necessary to explicitly specify build-time
1377 relationships on a minimal set of packages that are always
1378 needed to compile, link and put in a Debian package a
1379 standard "Hello World!" program written in C or C++. The
1380 required packages are called <em>build-essential</em>, and
1381 an informational list can be found in
1382 <file>/usr/share/doc/build-essential/list</file> (which is
1383 contained in the <tt>build-essential</tt>
1386 <list compact="compact">
1388 This allows maintaining the list separately
1389 from the policy documents (the list does not
1390 need the kind of control that the policy
1394 Having a separate package allows one to install
1395 the build-essential packages on a machine, as
1396 well as allowing other packages such as tasks to
1397 require installation of the build-essential
1398 packages using the depends relation.
1401 The separate package allows bug reports against
1402 the list to be categorized separately from
1403 the policy management process in the BTS.
1410 When specifying the set of build-time dependencies, one
1411 should list only those packages explicitly required by the
1412 build. It is not necessary to list packages which are
1413 required merely because some other package in the list of
1414 build-time dependencies depends on them.<footnote>
1415 The reason for this is that dependencies change, and
1416 you should list all those packages, and <em>only</em>
1417 those packages that <em>you</em> need directly. What
1418 others need is their business. For example, if you
1419 only link against <file>libimlib</file>, you will need to
1420 build-depend on <package>libimlib2-dev</package> but
1421 not against any <tt>libjpeg*</tt> packages, even
1422 though <tt>libimlib2-dev</tt> currently depends on
1423 them: installation of <package>libimlib2-dev</package>
1424 will automatically ensure that all of its run-time
1425 dependencies are satisfied.
1430 If build-time dependencies are specified, it must be
1431 possible to build the package and produce working binaries
1432 on a system with only essential and build-essential
1433 packages installed and also those required to satisfy the
1434 build-time relationships (including any implied
1435 relationships). In particular, this means that version
1436 clauses should be used rigorously in build-time
1437 relationships so that one cannot produce bad or
1438 inconsistently configured packages when the relationships
1439 are properly satisfied.
1443 <ref id="relationships"> explains the technical details.
1448 <heading>Changes to the upstream sources</heading>
1451 If changes to the source code are made that are not
1452 specific to the needs of the Debian system, they should be
1453 sent to the upstream authors in whatever form they prefer
1454 so as to be included in the upstream version of the
1459 If you need to configure the package differently for
1460 Debian or for Linux, and the upstream source doesn't
1461 provide a way to do so, you should add such configuration
1462 facilities (for example, a new <prgn>autoconf</prgn> test
1463 or <tt>#define</tt>) and send the patch to the upstream
1464 authors, with the default set to the way they originally
1465 had it. You can then easily override the default in your
1466 <file>debian/rules</file> or wherever is appropriate.
1470 You should make sure that the <prgn>configure</prgn> utility
1471 detects the correct architecture specification string
1472 (refer to <ref id="arch-spec"> for details).
1476 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1477 <prgn>configure</prgn> scripts are used, you should edit the
1478 <file>.in</file> files rather than editing the
1479 <prgn>Makefile</prgn> directly. This allows the user to
1480 reconfigure the package if necessary. You should
1481 <em>not</em> configure the package and edit the generated
1482 <prgn>Makefile</prgn>! This makes it impossible for someone
1483 else to later reconfigure the package without losing the
1489 <sect id="dpkgchangelog">
1490 <heading>Debian changelog: <file>debian/changelog</file></heading>
1493 Changes in the Debian version of the package should be
1494 briefly explained in the Debian changelog file
1495 <file>debian/changelog</file>.<footnote>
1497 Mistakes in changelogs are usually best rectified by
1498 making a new changelog entry rather than "rewriting
1499 history" by editing old changelog entries.
1502 This includes modifications
1503 made in the Debian package compared to the upstream one
1504 as well as other changes and updates to the package.
1506 Although there is nothing stopping an author who is also
1507 the Debian maintainer from using this changelog for all
1508 their changes, it will have to be renamed if the Debian
1509 and upstream maintainers become different people. In such
1510 a case, however, it might be better to maintain the package
1511 as a non-native package.
1516 The format of the <file>debian/changelog</file> allows the
1517 package building tools to discover which version of the package
1518 is being built and find out other release-specific information.
1522 That format is a series of entries like this:
1524 <example compact="compact">
1525 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1527 [optional blank line(s), stripped]
1529 * <var>change details</var>
1530 <var>more change details</var>
1532 [blank line(s), included in output of dpkg-parsechangelog]
1534 * <var>even more change details</var>
1536 [optional blank line(s), stripped]
1538 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1543 <var>package</var> and <var>version</var> are the source
1544 package name and version number.
1548 <var>distribution(s)</var> lists the distributions where
1549 this version should be installed when it is uploaded - it
1550 is copied to the <tt>Distribution</tt> field in the
1551 <file>.changes</file> file. See <ref id="f-Distribution">.
1555 <var>urgency</var> is the value for the <tt>Urgency</tt>
1556 field in the <file>.changes</file> file for the upload
1557 (see <ref id="f-Urgency">). It is not possible to specify
1558 an urgency containing commas; commas are used to separate
1559 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1560 <prgn>dpkg</prgn> changelog format (though there is
1561 currently only one useful <var>keyword</var>,
1566 The change details may in fact be any series of lines
1567 starting with at least two spaces, but conventionally each
1568 change starts with an asterisk and a separating space and
1569 continuation lines are indented so as to bring them in
1570 line with the start of the text above. Blank lines may be
1571 used here to separate groups of changes, if desired.
1575 If this upload resolves bugs recorded in the Bug Tracking
1576 System (BTS), they may be automatically closed on the
1577 inclusion of this package into the Debian archive by
1578 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1579 in the change details.<footnote>
1580 To be precise, the string should match the following
1581 Perl regular expression:
1583 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1585 Then all of the bug numbers listed will be closed by the
1586 archive maintenance script (<prgn>katie</prgn>) using the
1587 <var>version</var> of the changelog entry.
1589 This information is conveyed via the <tt>Closes</tt> field
1590 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1594 The maintainer name and email address used in the changelog
1595 should be the details of the person uploading <em>this</em>
1596 version. They are <em>not</em> necessarily those of the
1597 usual package maintainer. The information here will be
1598 copied to the <tt>Changed-By</tt> field in the
1599 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1600 and then later used to send an acknowledgement when the
1601 upload has been installed.
1605 The <var>date</var> must be in RFC822 format<footnote>
1606 This is generated by <tt>date -R</tt>.
1607 </footnote>; it must include the time zone specified
1608 numerically, with the time zone name or abbreviation
1609 optionally present as a comment in parentheses.
1613 The first "title" line with the package name must start
1614 at the left hand margin. The "trailer" line with the
1615 maintainer and date details must be preceded by exactly
1616 one space. The maintainer details and the date must be
1617 separated by exactly two spaces.
1621 The entire changelog must be encoded in UTF-8.
1625 For more information on placement of the changelog files
1626 within binary packages, please see <ref id="changelogs">.
1630 <sect id="dpkgcopyright">
1631 <heading>Copyright: <file>debian/copyright</file></heading>
1633 Every package must be accompanied by a verbatim copy of
1634 its copyright and distribution license in the file
1635 <file>/usr/share/doc/<var>package</var>/copyright</file>
1636 (see <ref id="copyrightfile"> for further details). Also see
1637 <ref id="pkgcopyright"> for further considerations relayed
1638 to copyrights for packages.
1642 <heading>Error trapping in makefiles</heading>
1645 When <prgn>make</prgn> invokes a command in a makefile
1646 (including your package's upstream makefiles and
1647 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1648 means that <prgn>sh</prgn>'s usual bad error handling
1649 properties apply: if you include a miniature script as one
1650 of the commands in your makefile you'll find that if you
1651 don't do anything about it then errors are not detected
1652 and <prgn>make</prgn> will blithely continue after
1657 Every time you put more than one shell command (this
1658 includes using a loop) in a makefile command you
1659 must make sure that errors are trapped. For
1660 simple compound commands, such as changing directory and
1661 then running a program, using <tt>&&</tt> rather
1662 than semicolon as a command separator is sufficient. For
1663 more complex commands including most loops and
1664 conditionals you should include a separate <tt>set -e</tt>
1665 command at the start of every makefile command that's
1666 actually one of these miniature shell scripts.
1670 <sect id="timestamps">
1671 <heading>Time Stamps</heading>
1673 Maintainers should preserve the modification times of the
1674 upstream source files in a package, as far as is reasonably
1676 The rationale is that there is some information conveyed
1677 by knowing the age of the file, for example, you could
1678 recognize that some documentation is very old by looking
1679 at the modification time, so it would be nice if the
1680 modification time of the upstream source would be
1686 <sect id="restrictions">
1687 <heading>Restrictions on objects in source packages</heading>
1690 The source package may not contain any hard links<footnote>
1692 This is not currently detected when building source
1693 packages, but only when extracting
1697 Hard links may be permitted at some point in the
1698 future, but would require a fair amount of
1701 </footnote>, device special files, sockets or setuid or
1702 setgid files.<footnote>
1703 Setgid directories are allowed.
1708 <sect id="debianrules">
1709 <heading>Main building script: <file>debian/rules</file></heading>
1712 This file must be an executable makefile, and contains the
1713 package-specific recipes for compiling the package and
1714 building binary package(s) from the source.
1718 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1719 so that it can be invoked by saying its name rather than
1720 invoking <prgn>make</prgn> explicitly.
1724 Since an interactive <file>debian/rules</file> script makes it
1725 impossible to auto-compile that package and also makes it
1726 hard for other people to reproduce the same binary
1727 package, all <em>required targets</em> MUST be
1728 non-interactive. At a minimum, required targets are the
1729 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1730 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1731 <em>binary-indep</em>, and <em>build</em>. It also follows
1732 that any target that these targets depend on must also be
1737 The targets are as follows (required unless stated otherwise):
1739 <tag><tt>build</tt></tag>
1742 The <tt>build</tt> target should perform all the
1743 configuration and compilation of the package.
1744 If a package has an interactive pre-build
1745 configuration routine, the Debianized source package
1746 must either be built after this has taken place (so
1747 that the binary package can be built without rerunning
1748 the configuration) or the configuration routine
1749 modified to become non-interactive. (The latter is
1750 preferable if there are architecture-specific features
1751 detected by the configuration routine.)
1755 For some packages, notably ones where the same
1756 source tree is compiled in different ways to produce
1757 two binary packages, the <tt>build</tt> target
1758 does not make much sense. For these packages it is
1759 good enough to provide two (or more) targets
1760 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1761 for each of the ways of building the package, and a
1762 <tt>build</tt> target that does nothing. The
1763 <tt>binary</tt> target will have to build the
1764 package in each of the possible ways and make the
1765 binary package out of each.
1769 The <tt>build</tt> target must not do anything
1770 that might require root privilege.
1774 The <tt>build</tt> target may need to run the
1775 <tt>clean</tt> target first - see below.
1779 When a package has a configuration and build routine
1780 which takes a long time, or when the makefiles are
1781 poorly designed, or when <tt>build</tt> needs to
1782 run <tt>clean</tt> first, it is a good idea to
1783 <tt>touch build</tt> when the build process is
1784 complete. This will ensure that if <tt>debian/rules
1785 build</tt> is run again it will not rebuild the whole
1787 Another common way to do this is for <tt>build</tt>
1788 to depend on <prgn>build-stamp</prgn> and to do
1789 nothing else, and for the <prgn>build-stamp</prgn>
1790 target to do the building and to <tt>touch
1791 build-stamp</tt> on completion. This is
1792 especially useful if the build routine creates a
1793 file or directory called <tt>build</tt>; in such a
1794 case, <tt>build</tt> will need to be listed as
1795 a phony target (i.e., as a dependency of the
1796 <tt>.PHONY</tt> target). See the documentation of
1797 <prgn>make</prgn> for more information on phony
1803 <tag><tt>build-arch</tt> (optional),
1804 <tt>build-indep</tt> (optional)
1808 A package may also provide both of the targets
1809 <tt>build-arch</tt> and <tt>build-indep</tt>.
1810 The <tt>build-arch</tt> target, if provided, should
1811 perform all the configuration and compilation required
1812 for producing all architecture-dependant binary packages
1813 (those packages for which the body of the
1814 <tt>Architecture</tt> field in <tt>debian/control</tt>
1815 is not <tt>all</tt>).
1816 Similarly, the <tt>build-indep</tt> target, if
1817 provided, should perform all the configuration and
1818 compilation required for producing all
1819 architecture-independent binary packages
1820 (those packages for which the body of the
1821 <tt>Architecture</tt> field in <tt>debian/control</tt>
1823 The <tt>build</tt> target should depend on those of the
1824 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1825 are provided in the rules file.
1829 If one or both of the targets <tt>build-arch</tt> and
1830 <tt>build-indep</tt> are not provided, then invoking
1831 <file>debian/rules</file> with one of the not-provided
1832 targets as arguments should produce a exit status code
1833 of 2. Usually this is provided automatically by make
1834 if the target is missing.
1838 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1839 must not do anything that might require root privilege.
1843 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1844 <tt>binary-indep</tt>
1848 The <tt>binary</tt> target must be all that is
1849 necessary for the user to build the binary package(s)
1850 produced from this source package. It is
1851 split into two parts: <prgn>binary-arch</prgn> builds
1852 the binary packages which are specific to a particular
1853 architecture, and <tt>binary-indep</tt> builds
1854 those which are not.
1857 <tt>binary</tt> may be (and commonly is) a target with
1858 no commands which simply depends on
1859 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1862 Both <tt>binary-*</tt> targets should depend on the
1863 <tt>build</tt> target, or on the appropriate
1864 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1865 provided, so that the package is built if it has not
1866 been already. It should then create the relevant
1867 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1868 make their control files and <prgn>dpkg-deb</prgn> to
1869 build them and place them in the parent of the top
1874 Both the <tt>binary-arch</tt> and
1875 <tt>binary-indep</tt> targets <em>must</em> exist.
1876 If one of them has nothing to do (which will always be
1877 the case if the source generates only a single binary
1878 package, whether architecture-dependent or not), it
1879 must still exist and must always succeed.
1883 The <tt>binary</tt> targets must be invoked as
1885 The <prgn>fakeroot</prgn> package often allows one
1886 to build a package correctly even without being
1892 <tag><tt>clean</tt></tag>
1895 This must undo any effects that the <tt>build</tt>
1896 and <tt>binary</tt> targets may have had, except
1897 that it should leave alone any output files created in
1898 the parent directory by a run of a <tt>binary</tt>
1903 If a <tt>build</tt> file is touched at the end of
1904 the <tt>build</tt> target, as suggested above, it
1905 should be removed as the first action that
1906 <tt>clean</tt> performs, so that running
1907 <tt>build</tt> again after an interrupted
1908 <tt>clean</tt> doesn't think that everything is
1913 The <tt>clean</tt> target may need to be
1914 invoked as root if <tt>binary</tt> has been
1915 invoked since the last <tt>clean</tt>, or if
1916 <tt>build</tt> has been invoked as root (since
1917 <tt>build</tt> may create directories, for
1922 <tag><tt>get-orig-source</tt> (optional)</tag>
1925 This target fetches the most recent version of the
1926 original source package from a canonical archive site
1927 (via FTP or WWW, for example), does any necessary
1928 rearrangement to turn it into the original source
1929 tar file format described below, and leaves it in the
1934 This target may be invoked in any directory, and
1935 should take care to clean up any temporary files it
1940 This target is optional, but providing it if
1941 possible is a good idea.
1945 <tag><tt>patch</tt> (optional)</tag>
1948 This target performs whatever additional actions are
1949 required to make the source ready for editing (unpacking
1950 additional upstream archives, applying patches, etc.).
1951 It is recommended to be implemented for any package where
1952 <tt>dpkg-source -x</tt> does not result in source ready
1953 for additional modification. See
1954 <ref id="readmesource">.
1960 The <tt>build</tt>, <tt>binary</tt> and
1961 <tt>clean</tt> targets must be invoked with the current
1962 directory being the package's top-level directory.
1967 Additional targets may exist in <file>debian/rules</file>,
1968 either as published or undocumented interfaces or for the
1969 package's internal use.
1973 The architectures we build on and build for are determined
1974 by <prgn>make</prgn> variables using the utility
1975 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1976 You can determine the
1977 Debian architecture and the GNU style architecture
1978 specification string for the build machine (the machine type
1979 we are building on) as well as for the host machine (the
1980 machine type we are building for). Here is a list of
1981 supported <prgn>make</prgn> variables:
1982 <list compact="compact">
1984 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1987 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1988 specification string)
1991 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1992 <tt>DEB_*_GNU_TYPE</tt>)
1995 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1996 <tt>DEB_*_GNU_TYPE</tt>)
1998 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1999 the build machine or <tt>HOST</tt> for specification of the
2004 Backward compatibility can be provided in the rules file
2005 by setting the needed variables to suitable default
2006 values; please refer to the documentation of
2007 <prgn>dpkg-architecture</prgn> for details.
2011 It is important to understand that the <tt>DEB_*_ARCH</tt>
2012 string only determines which Debian architecture we are
2013 building on or for. It should not be used to get the CPU
2014 or system information; the GNU style variables should be
2018 <sect1 id="debianrules-options">
2019 <heading><file>debian/rules</file> and
2020 <tt>DEB_BUILD_OPTIONS</tt></heading>
2023 Supporting the standardized environment variable
2024 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2025 contain several flags to change how a package is compiled and
2026 built. Each flag must be in the form <var>flag</var> or
2027 <var>flag</var>=<var>options</var>. If multiple flags are
2028 given, they must be separated by whitespace.<footnote>
2029 Some packages support any delimiter, but whitespace is the
2030 easiest to parse inside a makefile and avoids ambiguity with
2031 flag values that contain commas.
2033 <var>flag</var> must start with a lowercase letter
2034 (<tt>a-z</tt>) and consist only of lowercase letters,
2035 numbers (<tt>0-9</tt>), and the characters
2036 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2037 <var>options</var> must not contain whitespace. The same
2038 tag should not be given multiple times with conflicting
2039 values. Package maintainers may assume that
2040 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2044 The meaning of the following tags has been standardized:
2048 This tag says to not run any build-time test suite
2049 provided by the package.
2053 The presence of this tag means that the package should
2054 be compiled with a minimum of optimization. For C
2055 programs, it is best to add <tt>-O0</tt> to
2056 <tt>CFLAGS</tt> (although this is usually the default).
2057 Some programs might fail to build or run at this level
2058 of optimization; it may be necessary to use
2059 <tt>-O1</tt>, for example.
2063 This tag means that the debugging symbols should not be
2064 stripped from the binary during installation, so that
2065 debugging information may be included in the package.
2067 <tag>parallel=n</tag>
2069 This tag means that the package should be built using up
2070 to <tt>n</tt> parallel processes if the package build
2071 system supports this.<footnote>
2072 Packages built with <tt>make</tt> can often implement
2073 this by passing the <tt>-j</tt><var>n</var> option to
2076 If the package build system does not support parallel
2077 builds, this string must be ignored. If the package
2078 build system only supports a lower level of concurrency
2079 than <var>n</var>, the package should be built using as
2080 many parallel processes as the package build system
2081 supports. It is up to the package maintainer to decide
2082 whether the package build times are long enough and the
2083 package build system is robust enough to make supporting
2084 parallel builds worthwhile.
2090 Unknown flags must be ignored by <file>debian/rules</file>.
2094 The following makefile snippet is an example of how one may
2095 implement the build options; you will probably have to
2096 massage this example in order to make it work for your
2098 <example compact="compact">
2101 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2102 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2103 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2104 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2106 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2111 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2112 INSTALL_PROGRAM += -s
2114 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2115 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2116 MAKEFLAGS += -j$(NUMJOBS)
2121 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2122 # Code to run the package test suite.
2129 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2130 <sect id="substvars">
2131 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2134 When <prgn>dpkg-gencontrol</prgn>,
2135 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2136 generate control files they perform variable substitutions
2137 on their output just before writing it. Variable
2138 substitutions have the form <tt>${<var>variable</var>}</tt>.
2139 The optional file <file>debian/substvars</file> contains
2140 variable substitutions to be used; variables can also be set
2141 directly from <file>debian/rules</file> using the <tt>-V</tt>
2142 option to the source packaging commands, and certain
2143 predefined variables are also available.
2147 The <file>debian/substvars</file> file is usually generated and
2148 modified dynamically by <file>debian/rules</file> targets, in
2149 which case it must be removed by the <tt>clean</tt> target.
2153 See <manref name="deb-substvars" section="5"> for full
2154 details about source variable substitutions, including the
2155 format of <file>debian/substvars</file>.</p>
2158 <sect id="debianwatch">
2159 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2162 This is an optional, recommended control file for the
2163 <tt>uscan</tt> utility which defines how to automatically
2164 scan ftp or http sites for newly available updates of the
2165 package. This is used by <url id="
2166 http://dehs.alioth.debian.org/"> and other Debian QA tools
2167 to help with quality control and maintenance of the
2168 distribution as a whole.
2173 <sect id="debianfiles">
2174 <heading>Generated files list: <file>debian/files</file></heading>
2177 This file is not a permanent part of the source tree; it
2178 is used while building packages to record which files are
2179 being generated. <prgn>dpkg-genchanges</prgn> uses it
2180 when it generates a <file>.changes</file> file.
2184 It should not exist in a shipped source package, and so it
2185 (and any backup files or temporary files such as
2186 <file>files.new</file><footnote>
2187 <file>files.new</file> is used as a temporary file by
2188 <prgn>dpkg-gencontrol</prgn> and
2189 <prgn>dpkg-distaddfile</prgn> - they write a new
2190 version of <tt>files</tt> here before renaming it,
2191 to avoid leaving a corrupted copy if an error
2193 </footnote>) should be removed by the
2194 <tt>clean</tt> target. It may also be wise to
2195 ensure a fresh start by emptying or removing it at the
2196 start of the <tt>binary</tt> target.
2200 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2201 package, it adds an entry to <file>debian/files</file> for the
2202 <file>.deb</file> file that will be created when <tt>dpkg-deb
2203 --build</tt> is run for that binary package. So for most
2204 packages all that needs to be done with this file is to
2205 delete it in the <tt>clean</tt> target.
2209 If a package upload includes files besides the source
2210 package and any binary packages whose control files were
2211 made with <prgn>dpkg-gencontrol</prgn> then they should be
2212 placed in the parent of the package's top-level directory
2213 and <prgn>dpkg-distaddfile</prgn> should be called to add
2214 the file to the list in <file>debian/files</file>.</p>
2217 <sect id="embeddedfiles">
2218 <heading>Convenience copies of code</heading>
2221 Some software packages include in their distribution convenience
2222 copies of code from other software packages, generally so that
2223 users compiling from source don't have to download multiple
2224 packages. Debian packages should not make use of these
2225 convenience copies unless the included package is explicitly
2226 intended to be used in this way.<footnote>
2227 For example, parts of the GNU build system work like this.
2229 If the included code is already in the Debian archive in the
2230 form of a library, the Debian packaging should ensure that
2231 binary packages reference the libraries already in Debian and
2232 the convenience copy is not used. If the included code is not
2233 already in Debian, it should be packaged separately as a
2234 prerequisite if possible.
2236 Having multiple copies of the same code in Debian is
2237 inefficient, often creates either static linking or shared
2238 library conflicts, and, most importantly, increases the
2239 difficulty of handling security vulnerabilities in the
2245 <sect id="readmesource">
2246 <heading>Source package handling:
2247 <file>debian/README.source</file></heading>
2250 If running <prgn>dpkg-source -x</prgn> on a source package
2251 doesn't produce the source of the package, ready for editing,
2252 and allow one to make changes and run
2253 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2254 without taking any additional steps, creating a
2255 <file>debian/README.source</file> documentation file is
2256 recommended. This file should explain how to do all of the
2259 <item>Generate the fully patched source, in a form ready for
2260 editing, that would be built to create Debian
2261 packages. Doing this with a <tt>patch</tt> target in
2262 <file>debian/rules</file> is recommended; see
2263 <ref id="debianrules">.</item>
2264 <item>Modify the source and save those modifications so that
2265 they will be applied when building the package.</item>
2266 <item>Remove source modifications that are currently being
2267 applied when building the package.</item>
2268 <item>Optionally, document what steps are necessary to
2269 upgrade the Debian source package to a new upstream version,
2270 if applicable.</item>
2272 This explanation should include specific commands and mention
2273 any additional required Debian packages. It should not assume
2274 familiarity with any specific Debian packaging system or patch
2279 This explanation may refer to a documentation file installed by
2280 one of the package's build dependencies provided that the
2281 referenced documentation clearly explains these tasks and is not
2282 a general reference manual.
2286 <file>debian/README.source</file> may also include any other
2287 information that would be helpful to someone modifying the
2288 source package. Even if the package doesn't fit the above
2289 description, maintainers are encouraged to document in a
2290 <file>debian/README.source</file> file any source package with a
2291 particularly complex or unintuitive source layout or build
2292 system (for example, a package that builds the same source
2293 multiple times to generate different binary packages).
2299 <chapt id="controlfields">
2300 <heading>Control files and their fields</heading>
2303 The package management system manipulates data represented in
2304 a common format, known as <em>control data</em>, stored in
2305 <em>control files</em>.
2306 Control files are used for source packages, binary packages and
2307 the <file>.changes</file> files which control the installation
2308 of uploaded files<footnote>
2309 <prgn>dpkg</prgn>'s internal databases are in a similar
2314 <sect id="controlsyntax">
2315 <heading>Syntax of control files</heading>
2318 A control file consists of one or more paragraphs of
2320 The paragraphs are also sometimes referred to as stanzas.
2322 The paragraphs are separated by blank lines. Some control
2323 files allow only one paragraph; others allow several, in
2324 which case each paragraph usually refers to a different
2325 package. (For example, in source packages, the first
2326 paragraph refers to the source package, and later paragraphs
2327 refer to binary packages generated from the source.)
2331 Each paragraph consists of a series of data fields; each
2332 field consists of the field name, followed by a colon and
2333 then the data/value associated with that field. It ends at
2334 the end of the (logical) line. Horizontal whitespace
2335 (spaces and tabs) may occur immediately before or after the
2336 value and is ignored there; it is conventional to put a
2337 single space after the colon. For example, a field might
2339 <example compact="compact">
2342 the field name is <tt>Package</tt> and the field value
2347 Many fields' values may span several lines; in this case
2348 each continuation line must start with a space or a tab.
2349 Any trailing spaces or tabs at the end of individual
2350 lines of a field value are ignored.
2354 In fields where it is specified that lines may not wrap,
2355 only a single line of data is allowed and whitespace is not
2356 significant in a field body. Whitespace must not appear
2357 inside names (of packages, architectures, files or anything
2358 else) or version numbers, or between the characters of
2359 multi-character version relationships.
2363 Field names are not case-sensitive, but it is usual to
2364 capitalize the field names using mixed case as shown below.
2368 Blank lines, or lines consisting only of spaces and tabs,
2369 are not allowed within field values or between fields - that
2370 would mean a new paragraph.
2374 All control files must be encoded in UTF-8.
2378 <sect id="sourcecontrolfiles">
2379 <heading>Source package control files -- <file>debian/control</file></heading>
2382 The <file>debian/control</file> file contains the most vital
2383 (and version-independent) information about the source package
2384 and about the binary packages it creates.
2388 The first paragraph of the control file contains information about
2389 the source package in general. The subsequent sets each describe a
2390 binary package that the source tree builds.
2394 The fields in the general paragraph (the first one, for the source
2397 <list compact="compact">
2398 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2399 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2400 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2401 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2402 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2403 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2404 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2405 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2410 The fields in the binary package paragraphs are:
2412 <list compact="compact">
2413 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2414 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2415 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2416 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2417 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2418 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2419 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2420 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2425 The syntax and semantics of the fields are described below.
2431 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2432 generate control files for binary packages (see below), by
2433 <prgn>dpkg-genchanges</prgn> to generate the
2434 <tt>.changes</tt> file to accompany the upload, and by
2435 <prgn>dpkg-source</prgn> when it creates the
2436 <file>.dsc</file> source control file as part of a source
2437 archive. Many fields are permitted to span multiple lines in
2438 <file>debian/control</file> but not in any other control
2439 file. These tools are responsible for removing the line
2440 breaks from such fields when using fields from
2441 <file>debian/control</file> to generate other control files.
2445 The fields here may contain variable references - their
2446 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2447 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2448 when they generate output control files.
2449 See <ref id="substvars"> for details.
2453 In addition to the control file syntax described <qref
2454 id="controlsyntax">above</qref>, this file may also contain
2455 comment lines starting with <tt>#</tt> without any preceding
2456 whitespace. All such lines are ignored, even in the middle of
2457 continuation lines for a multiline field, and do not end a
2463 <sect id="binarycontrolfiles">
2464 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2467 The <file>DEBIAN/control</file> file contains the most vital
2468 (and version-dependent) information about a binary package.
2472 The fields in this file are:
2474 <list compact="compact">
2475 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2476 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2477 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2478 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2479 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2480 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2481 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2482 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2483 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2484 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2485 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2486 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2491 <sect id="debiansourcecontrolfiles">
2492 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2495 This file contains a series of fields, identified and
2496 separated just like the fields in the control file of
2497 a binary package. The fields are listed below; their
2498 syntax is described above, in <ref id="pkg-controlfields">.
2500 <list compact="compact">
2501 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2502 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2503 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2504 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2505 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2506 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2507 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2508 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2509 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2510 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2511 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2516 The source package control file is generated by
2517 <prgn>dpkg-source</prgn> when it builds the source
2518 archive, from other files in the source package,
2519 described above. When unpacking, it is checked against
2520 the files and directories in the other parts of the
2526 <sect id="debianchangesfiles">
2527 <heading>Debian changes files -- <file>.changes</file></heading>
2530 The .changes files are used by the Debian archive maintenance
2531 software to process updates to packages. They contain one
2532 paragraph which contains information from the
2533 <tt>debian/control</tt> file and other data about the
2534 source package gathered via <tt>debian/changelog</tt>
2535 and <tt>debian/rules</tt>.
2539 The fields in this file are:
2541 <list compact="compact">
2542 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2543 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2544 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2545 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2546 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2548 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2550 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2551 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2552 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2553 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2554 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2555 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2560 <sect id="controlfieldslist">
2561 <heading>List of fields</heading>
2563 <sect1 id="f-Source">
2564 <heading><tt>Source</tt></heading>
2567 This field identifies the source package name.
2571 In <file>debian/control</file> or a <file>.dsc</file> file,
2572 this field must contain only the name of the source package.
2576 In a binary package control file or a <file>.changes</file>
2577 file, the source package name may be followed by a version
2578 number in parentheses<footnote>
2579 It is customary to leave a space after the package name
2580 if a version number is specified.
2582 This version number may be omitted (and is, by
2583 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2584 the <tt>Version</tt> field of the binary package in
2585 question. The field itself may be omitted from a binary
2586 package control file when the source package has the same
2587 name and version as the binary package.
2591 <sect1 id="f-Maintainer">
2592 <heading><tt>Maintainer</tt></heading>
2595 The package maintainer's name and email address. The name
2596 should come first, then the email address inside angle
2597 brackets <tt><></tt> (in RFC822 format).
2601 If the maintainer's name contains a full stop then the
2602 whole field will not work directly as an email address due
2603 to a misfeature in the syntax specified in RFC822; a
2604 program using this field as an address must check for this
2605 and correct the problem if necessary (for example by
2606 putting the name in round brackets and moving it to the
2607 end, and bringing the email address forward).
2611 <sect1 id="f-Uploaders">
2612 <heading><tt>Uploaders</tt></heading>
2615 List of the names and email addresses of co-maintainers of
2616 the package, if any. If the package has other maintainers
2617 beside the one named in the
2618 <qref id="f-Maintainer">Maintainer field</qref>, their
2619 names and email addresses should be listed here. The
2620 format is the same as that of the Maintainer tag, and
2621 multiple entries should be comma separated. Currently,
2622 this field is restricted to a single line of data. This
2623 is an optional field.
2626 Any parser that interprets the Uploaders field in
2627 <file>debian/control</file> must permit it to span multiple
2628 lines. Line breaks in an Uploaders field that spans multiple
2629 lines are not significant and the semantics of the field are
2630 the same as if the line breaks had not been present.
2634 <sect1 id="f-Changed-By">
2635 <heading><tt>Changed-By</tt></heading>
2638 The name and email address of the person who changed the
2639 said package. Usually the name of the maintainer.
2640 All the rules for the Maintainer field apply here, too.
2644 <sect1 id="f-Section">
2645 <heading><tt>Section</tt></heading>
2648 This field specifies an application area into which the package
2649 has been classified. See <ref id="subsections">.
2653 When it appears in the <file>debian/control</file> file,
2654 it gives the value for the subfield of the same name in
2655 the <tt>Files</tt> field of the <file>.changes</file> file.
2656 It also gives the default for the same field in the binary
2661 <sect1 id="f-Priority">
2662 <heading><tt>Priority</tt></heading>
2665 This field represents how important that it is that the user
2666 have the package installed. See <ref id="priorities">.
2670 When it appears in the <file>debian/control</file> file,
2671 it gives the value for the subfield of the same name in
2672 the <tt>Files</tt> field of the <file>.changes</file> file.
2673 It also gives the default for the same field in the binary
2678 <sect1 id="f-Package">
2679 <heading><tt>Package</tt></heading>
2682 The name of the binary package.
2686 Package names must consist only of lower case letters
2687 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2688 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2689 They must be at least two characters long and must start
2690 with an alphanumeric character.
2694 <sect1 id="f-Architecture">
2695 <heading><tt>Architecture</tt></heading>
2698 Depending on context and the control file used, the
2699 <tt>Architecture</tt> field can include the following sets of
2702 <item>A unique single word identifying a Debian machine
2703 architecture, see <ref id="arch-spec">.
2704 <item><tt>all</tt>, which indicates an
2705 architecture-independent package.
2706 <item><tt>any</tt>, which indicates a package available
2707 for building on any architecture.
2708 <item><tt>source</tt>, which indicates a source package.
2713 In the main <file>debian/control</file> file in the source
2714 package, or in the source package control file
2715 <file>.dsc</file>, one may specify a list of architectures
2716 separated by spaces, or the special values <tt>any</tt> or
2721 Specifying <tt>any</tt> indicates that the source package
2722 isn't dependent on any particular architecture and should
2723 compile fine on any one. The produced binary package(s)
2724 will be specific to whatever the current build architecture
2726 This is the most often used setting, and is recommended
2727 for new packages that aren't <tt>Architecture: all</tt>.
2732 Specifying a list of architectures indicates that the source
2733 will build an architecture-dependent package, and will only
2734 work correctly on the listed architectures.<footnote>
2735 This is a setting used for a minority of cases where the
2736 program is not portable. Generally, it should not be used
2742 In a <file>.changes</file> file, the <tt>Architecture</tt>
2743 field lists the architecture(s) of the package(s)
2744 currently being uploaded. This will be a list; if the
2745 source for the package is also being uploaded, the special
2746 entry <tt>source</tt> is also present.
2750 See <ref id="debianrules"> for information how to get the
2751 architecture for the build process.
2755 <sect1 id="f-Essential">
2756 <heading><tt>Essential</tt></heading>
2759 This is a boolean field which may occur only in the
2760 control file of a binary package or in a per-package fields
2761 paragraph of a main source control data file.
2765 If set to <tt>yes</tt> then the package management system
2766 will refuse to remove the package (upgrading and replacing
2767 it is still possible). The other possible value is <tt>no</tt>,
2768 which is the same as not having the field at all.
2773 <heading>Package interrelationship fields:
2774 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2775 <tt>Recommends</tt>, <tt>Suggests</tt>,
2776 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2777 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2781 These fields describe the package's relationships with
2782 other packages. Their syntax and semantics are described
2783 in <ref id="relationships">.</p>
2786 <sect1 id="f-Standards-Version">
2787 <heading><tt>Standards-Version</tt></heading>
2790 The most recent version of the standards (the policy
2791 manual and associated texts) with which the package
2796 The version number has four components: major and minor
2797 version number and major and minor patch level. When the
2798 standards change in a way that requires every package to
2799 change the major number will be changed. Significant
2800 changes that will require work in many packages will be
2801 signaled by a change to the minor number. The major patch
2802 level will be changed for any change to the meaning of the
2803 standards, however small; the minor patch level will be
2804 changed when only cosmetic, typographical or other edits
2805 are made which neither change the meaning of the document
2806 nor affect the contents of packages.
2810 Thus only the first three components of the policy version
2811 are significant in the <em>Standards-Version</em> control
2812 field, and so either these three components or the all
2813 four components may be specified.<footnote>
2814 In the past, people specified the full version number
2815 in the Standards-Version field, for example "2.3.0.0".
2816 Since minor patch-level changes don't introduce new
2817 policy, it was thought it would be better to relax
2818 policy and only require the first 3 components to be
2819 specified, in this example "2.3.0". All four
2820 components may still be used if someone wishes to do so.
2826 <sect1 id="f-Version">
2827 <heading><tt>Version</tt></heading>
2830 The version number of a package. The format is:
2831 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2835 The three components here are:
2837 <tag><var>epoch</var></tag>
2840 This is a single (generally small) unsigned integer. It
2841 may be omitted, in which case zero is assumed. If it is
2842 omitted then the <var>upstream_version</var> may not
2847 It is provided to allow mistakes in the version numbers
2848 of older versions of a package, and also a package's
2849 previous version numbering schemes, to be left behind.
2853 <tag><var>upstream_version</var></tag>
2856 This is the main part of the version number. It is
2857 usually the version number of the original ("upstream")
2858 package from which the <file>.deb</file> file has been made,
2859 if this is applicable. Usually this will be in the same
2860 format as that specified by the upstream author(s);
2861 however, it may need to be reformatted to fit into the
2862 package management system's format and comparison
2867 The comparison behavior of the package management system
2868 with respect to the <var>upstream_version</var> is
2869 described below. The <var>upstream_version</var>
2870 portion of the version number is mandatory.
2874 The <var>upstream_version</var> may contain only
2875 alphanumerics<footnote>
2876 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2878 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2879 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2880 tilde) and should start with a digit. If there is no
2881 <var>debian_revision</var> then hyphens are not allowed;
2882 if there is no <var>epoch</var> then colons are not
2887 <tag><var>debian_revision</var></tag>
2890 This part of the version number specifies the version of
2891 the Debian package based on the upstream version. It
2892 may contain only alphanumerics and the characters
2893 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2894 tilde) and is compared in the same way as the
2895 <var>upstream_version</var> is.
2899 It is optional; if it isn't present then the
2900 <var>upstream_version</var> may not contain a hyphen.
2901 This format represents the case where a piece of
2902 software was written specifically to be turned into a
2903 Debian package, and so there is only one "debianisation"
2904 of it and therefore no revision indication is required.
2908 It is conventional to restart the
2909 <var>debian_revision</var> at <tt>1</tt> each time the
2910 <var>upstream_version</var> is increased.
2914 The package management system will break the version
2915 number apart at the last hyphen in the string (if there
2916 is one) to determine the <var>upstream_version</var> and
2917 <var>debian_revision</var>. The absence of a
2918 <var>debian_revision</var> is equivalent to a
2919 <var>debian_revision</var> of <tt>0</tt>.
2926 When comparing two version numbers, first the <var>epoch</var>
2927 of each are compared, then the <var>upstream_version</var> if
2928 <var>epoch</var> is equal, and then <var>debian_revision</var>
2929 if <var>upstream_version</var> is also equal.
2930 <var>epoch</var> is compared numerically. The
2931 <var>upstream_version</var> and <var>debian_revision</var>
2932 parts are compared by the package management system using the
2933 following algorithm:
2937 The strings are compared from left to right.
2941 First the initial part of each string consisting entirely of
2942 non-digit characters is determined. These two parts (one of
2943 which may be empty) are compared lexically. If a difference
2944 is found it is returned. The lexical comparison is a
2945 comparison of ASCII values modified so that all the letters
2946 sort earlier than all the non-letters and so that a tilde
2947 sorts before anything, even the end of a part. For example,
2948 the following parts are in sorted order from earliest to
2949 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2950 <tt>a</tt>.<footnote>
2951 One common use of <tt>~</tt> is for upstream pre-releases.
2952 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2953 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2958 Then the initial part of the remainder of each string which
2959 consists entirely of digit characters is determined. The
2960 numerical values of these two parts are compared, and any
2961 difference found is returned as the result of the comparison.
2962 For these purposes an empty string (which can only occur at
2963 the end of one or both version strings being compared) counts
2968 These two steps (comparing and removing initial non-digit
2969 strings and initial digit strings) are repeated until a
2970 difference is found or both strings are exhausted.
2974 Note that the purpose of epochs is to allow us to leave behind
2975 mistakes in version numbering, and to cope with situations
2976 where the version numbering scheme changes. It is
2977 <em>not</em> intended to cope with version numbers containing
2978 strings of letters which the package management system cannot
2979 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2980 silly orderings (the author of this manual has heard of a
2981 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2982 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2983 <tt>2</tt> and so forth).
2987 <sect1 id="f-Description">
2988 <heading><tt>Description</tt></heading>
2991 In a source or binary control file, the <tt>Description</tt>
2992 field contains a description of the binary package, consisting
2993 of two parts, the synopsis or the short description, and the
2994 long description. The field's format is as follows:
2999 Description: <single line synopsis>
3000 <extended description over several lines>
3005 The lines in the extended description can have these formats:
3011 Those starting with a single space are part of a paragraph.
3012 Successive lines of this form will be word-wrapped when
3013 displayed. The leading space will usually be stripped off.
3017 Those starting with two or more spaces. These will be
3018 displayed verbatim. If the display cannot be panned
3019 horizontally, the displaying program will line wrap them "hard"
3020 (i.e., without taking account of word breaks). If it can they
3021 will be allowed to trail off to the right. None, one or two
3022 initial spaces may be deleted, but the number of spaces
3023 deleted from each line will be the same (so that you can have
3024 indenting work correctly, for example).
3028 Those containing a single space followed by a single full stop
3029 character. These are rendered as blank lines. This is the
3030 <em>only</em> way to get a blank line<footnote>
3031 Completely empty lines will not be rendered as blank lines.
3032 Instead, they will cause the parser to think you're starting
3033 a whole new record in the control file, and will therefore
3034 likely abort with an error.
3039 Those containing a space, a full stop and some more characters.
3040 These are for future expansion. Do not use them.
3046 Do not use tab characters. Their effect is not predictable.
3050 See <ref id="descriptions"> for further information on this.
3054 In a <file>.changes</file> file, the <tt>Description</tt> field
3055 contains a summary of the descriptions for the packages being
3060 The part of the field before the first newline is empty;
3061 thereafter each line has the name of a binary package and
3062 the summary description line from that binary package.
3063 Each line is indented by one space.
3068 <sect1 id="f-Distribution">
3069 <heading><tt>Distribution</tt></heading>
3072 In a <file>.changes</file> file or parsed changelog output
3073 this contains the (space-separated) name(s) of the
3074 distribution(s) where this version of the package should
3075 be installed. Valid distributions are determined by the
3076 archive maintainers.<footnote>
3077 Current distribution names are:
3078 <taglist compact="compact">
3079 <tag><em>stable</em></tag>
3081 This is the current "released" version of Debian
3082 GNU/Linux. Once the distribution is
3083 <em>stable</em> only security fixes and other
3084 major bug fixes are allowed. When changes are
3085 made to this distribution, the release number is
3086 increased (for example: 2.2r1 becomes 2.2r2 then
3090 <tag><em>unstable</em></tag>
3092 This distribution value refers to the
3093 <em>developmental</em> part of the Debian
3094 distribution tree. New packages, new upstream
3095 versions of packages and bug fixes go into the
3096 <em>unstable</em> directory tree. Download from
3097 this distribution at your own risk.
3100 <tag><em>testing</em></tag>
3102 This distribution value refers to the
3103 <em>testing</em> part of the Debian distribution
3104 tree. It receives its packages from the
3105 unstable distribution after a short time lag to
3106 ensure that there are no major issues with the
3107 unstable packages. It is less prone to breakage
3108 than unstable, but still risky. It is not
3109 possible to upload packages directly to
3113 <tag><em>frozen</em></tag>
3115 From time to time, the <em>testing</em>
3116 distribution enters a state of "code-freeze" in
3117 anticipation of release as a <em>stable</em>
3118 version. During this period of testing only
3119 fixes for existing or newly-discovered bugs will
3120 be allowed. The exact details of this stage are
3121 determined by the Release Manager.
3124 <tag><em>experimental</em></tag>
3126 The packages with this distribution value are
3127 deemed by their maintainers to be high
3128 risk. Oftentimes they represent early beta or
3129 developmental packages from various sources that
3130 the maintainers want people to try, but are not
3131 ready to be a part of the other parts of the
3132 Debian distribution tree. Download at your own
3138 You should list <em>all</em> distributions that the
3139 package should be installed into.
3143 More information is available in the Debian Developer's
3144 Reference, section "The Debian archive".
3151 <heading><tt>Date</tt></heading>
3154 This field includes the date the package was built or last edited.
3158 The value of this field is usually extracted from the
3159 <file>debian/changelog</file> file - see
3160 <ref id="dpkgchangelog">).
3164 <sect1 id="f-Format">
3165 <heading><tt>Format</tt></heading>
3168 This field specifies a format revision for the file.
3169 The most current format described in the Policy Manual
3170 is version <strong>1.5</strong>. The syntax of the
3171 format value is the same as that of a package version
3172 number except that no epoch or Debian revision is allowed
3173 - see <ref id="f-Version">.
3177 <sect1 id="f-Urgency">
3178 <heading><tt>Urgency</tt></heading>
3181 This is a description of how important it is to upgrade to
3182 this version from previous ones. It consists of a single
3183 keyword taking one of the values <tt>low</tt>,
3184 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3185 <tt>critical</tt><footnote>
3186 Other urgency values are supported with configuration
3187 changes in the archive software but are not used in Debian.
3188 The urgency affects how quickly a package will be considered
3189 for inclusion into the <tt>testing</tt> distribution and
3190 gives an indication of the importance of any fixes included
3191 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3192 treated as synonymous.
3193 </footnote> (not case-sensitive) followed by an optional
3194 commentary (separated by a space) which is usually in
3195 parentheses. For example:
3198 Urgency: low (HIGH for users of diversions)
3204 The value of this field is usually extracted from the
3205 <file>debian/changelog</file> file - see
3206 <ref id="dpkgchangelog">.
3210 <sect1 id="f-Changes">
3211 <heading><tt>Changes</tt></heading>
3214 This field contains the human-readable changes data, describing
3215 the differences between the last version and the current one.
3219 There should be nothing in this field before the first
3220 newline; all the subsequent lines must be indented by at
3221 least one space; blank lines must be represented by a line
3222 consisting only of a space and a full stop.
3226 The value of this field is usually extracted from the
3227 <file>debian/changelog</file> file - see
3228 <ref id="dpkgchangelog">).
3232 Each version's change information should be preceded by a
3233 "title" line giving at least the version, distribution(s)
3234 and urgency, in a human-readable way.
3238 If data from several versions is being returned the entry
3239 for the most recent version should be returned first, and
3240 entries should be separated by the representation of a
3241 blank line (the "title" line may also be followed by the
3242 representation of blank line).
3246 <sect1 id="f-Binary">
3247 <heading><tt>Binary</tt></heading>
3250 This field is a list of binary packages.
3254 When it appears in the <file>.dsc</file> file it is the list
3255 of binary packages which a source package can produce. It
3256 does not necessarily produce all of these binary packages
3257 for every architecture. The source control file doesn't
3258 contain details of which architectures are appropriate for
3259 which of the binary packages.
3263 When it appears in a <file>.changes</file> file it lists the
3264 names of the binary packages actually being uploaded.
3268 The syntax is a list of binary packages separated by
3270 A space after each comma is conventional.
3271 </footnote>. Currently the packages must be separated using
3272 only spaces in the <file>.changes</file> file.
3276 <sect1 id="f-Installed-Size">
3277 <heading><tt>Installed-Size</tt></heading>
3280 This field appears in the control files of binary
3281 packages, and in the <file>Packages</file> files. It gives
3282 the total amount of disk space required to install the
3287 The disk space is represented in kilobytes as a simple
3292 <sect1 id="f-Files">
3293 <heading><tt>Files</tt></heading>
3296 This field contains a list of files with information about
3297 each one. The exact information and syntax varies with
3298 the context. In all cases the part of the field
3299 contents on the same line as the field name is empty. The
3300 remainder of the field is one line per file, each line
3301 being indented by one space and containing a number of
3302 sub-fields separated by spaces.
3306 In the <file>.dsc</file> file, each line contains the MD5
3307 checksum, size and filename of the tar file and (if applicable)
3308 diff file which make up the remainder of the source
3310 That is, the parts which are not the <tt>.dsc</tt>.
3312 The exact forms of the filenames are described
3313 in <ref id="pkg-sourcearchives">.
3317 In the <file>.changes</file> file this contains one line per
3318 file being uploaded. Each line contains the MD5 checksum,
3319 size, section and priority and the filename.
3320 The <qref id="f-Section">section</qref>
3321 and <qref id="f-Priority">priority</qref>
3322 are the values of the corresponding fields in
3323 the main source control file. If no section or priority is
3324 specified then <tt>-</tt> should be used, though section
3325 and priority values must be specified for new packages to
3326 be installed properly.
3330 The special value <tt>byhand</tt> for the section in a
3331 <tt>.changes</tt> file indicates that the file in question
3332 is not an ordinary package file and must by installed by
3333 hand by the distribution maintainers. If the section is
3334 <tt>byhand</tt> the priority should be <tt>-</tt>.
3338 If a new Debian revision of a package is being shipped and
3339 no new original source archive is being distributed the
3340 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3341 entry for the original source archive
3342 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3343 but the <file>.changes</file> file should leave it out. In
3344 this case the original source archive on the distribution
3345 site must match exactly, byte-for-byte, the original
3346 source archive which was used to generate the
3347 <file>.dsc</file> file and diff which are being uploaded.</p>
3350 <sect1 id="f-Closes">
3351 <heading><tt>Closes</tt></heading>
3354 A space-separated list of bug report numbers that the upload
3355 governed by the .changes file closes.
3359 <sect1 id="f-Homepage">
3360 <heading><tt>Homepage</tt></heading>
3363 The URL of the web site for this package, preferably (when
3364 applicable) the site from which the original source can be
3365 obtained and any additional upstream documentation or
3366 information may be found. The content of this field is a
3367 simple URL without any surrounding characters such as
3375 <heading>User-defined fields</heading>
3378 Additional user-defined fields may be added to the
3379 source package control file. Such fields will be
3380 ignored, and not copied to (for example) binary or
3381 source package control files or upload control files.
3385 If you wish to add additional unsupported fields to
3386 these output files you should use the mechanism
3391 Fields in the main source control information file with
3392 names starting <tt>X</tt>, followed by one or more of
3393 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3394 be copied to the output files. Only the part of the
3395 field name after the hyphen will be used in the output
3396 file. Where the letter <tt>B</tt> is used the field
3397 will appear in binary package control files, where the
3398 letter <tt>S</tt> is used in source package control
3399 files and where <tt>C</tt> is used in upload control
3400 (<tt>.changes</tt>) files.
3404 For example, if the main source information control file
3407 XBS-Comment: I stand between the candle and the star.
3409 then the binary and source package control files will contain the
3412 Comment: I stand between the candle and the star.
3421 <chapt id="maintainerscripts">
3422 <heading>Package maintainer scripts and installation procedure</heading>
3425 <heading>Introduction to package maintainer scripts</heading>
3428 It is possible to supply scripts as part of a package which
3429 the package management system will run for you when your
3430 package is installed, upgraded or removed.
3434 These scripts are the files <prgn>preinst</prgn>,
3435 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3436 <prgn>postrm</prgn> in the control area of the package.
3437 They must be proper executable files; if they are scripts
3438 (which is recommended), they must start with the usual
3439 <tt>#!</tt> convention. They should be readable and
3440 executable by anyone, and must not be world-writable.
3444 The package management system looks at the exit status from
3445 these scripts. It is important that they exit with a
3446 non-zero status if there is an error, so that the package
3447 management system can stop its processing. For shell
3448 scripts this means that you <em>almost always</em> need to
3449 use <tt>set -e</tt> (this is usually true when writing shell
3450 scripts, in fact). It is also important, of course, that
3451 they exit with a zero status if everything went well.
3455 Additionally, packages interacting with users using
3456 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3457 install a <prgn>config</prgn> script in the control area,
3458 see <ref id="maintscriptprompt"> for details.
3462 When a package is upgraded a combination of the scripts from
3463 the old and new packages is called during the upgrade
3464 procedure. If your scripts are going to be at all
3465 complicated you need to be aware of this, and may need to
3466 check the arguments to your scripts.
3470 Broadly speaking the <prgn>preinst</prgn> is called before
3471 (a particular version of) a package is installed, and the
3472 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3473 before (a version of) a package is removed and the
3474 <prgn>postrm</prgn> afterwards.
3478 Programs called from maintainer scripts should not normally
3479 have a path prepended to them. Before installation is
3480 started, the package management system checks to see if the
3481 programs <prgn>ldconfig</prgn>,
3482 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3483 and <prgn>update-rc.d</prgn> can be found via the
3484 <tt>PATH</tt> environment variable. Those programs, and any
3485 other program that one would expect to be in the
3486 <tt>PATH</tt>, should thus be invoked without an absolute
3487 pathname. Maintainer scripts should also not reset the
3488 <tt>PATH</tt>, though they might choose to modify it by
3489 prepending or appending package-specific directories. These
3490 considerations really apply to all shell scripts.</p>
3493 <sect id="idempotency">
3494 <heading>Maintainer scripts idempotency</heading>
3497 It is necessary for the error recovery procedures that the
3498 scripts be idempotent. This means that if it is run
3499 successfully, and then it is called again, it doesn't bomb
3500 out or cause any harm, but just ensures that everything is
3501 the way it ought to be. If the first call failed, or
3502 aborted half way through for some reason, the second call
3503 should merely do the things that were left undone the first
3504 time, if any, and exit with a success status if everything
3506 This is so that if an error occurs, the user interrupts
3507 <prgn>dpkg</prgn> or some other unforeseen circumstance
3508 happens you don't leave the user with a badly-broken
3509 package when <prgn>dpkg</prgn> attempts to repeat the
3515 <sect id="controllingterminal">
3516 <heading>Controlling terminal for maintainer scripts</heading>
3519 The maintainer scripts are guaranteed to run with a
3520 controlling terminal and can interact with the user.
3521 Because these scripts may be executed with standard output
3522 redirected into a pipe for logging purposes, Perl scripts
3523 should set unbuffered output by setting <tt>$|=1</tt> so
3524 that the output is printed immediately rather than being
3528 <sect id="exitstatus">
3529 <heading>Exit status</heading>
3532 Each script must return a zero exit status for
3533 success, or a nonzero one for failure, since the package
3534 management system looks for the exit status of these scripts
3535 and determines what action to take next based on that datum.
3539 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3544 <list compact="compact">
3546 <var>new-preinst</var> <tt>install</tt>
3549 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3552 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3555 <var>old-preinst</var> <tt>abort-upgrade</tt>
3556 <var>new-version</var>
3561 <list compact="compact">
3563 <var>postinst</var> <tt>configure</tt>
3564 <var>most-recently-configured-version</var>
3567 <var>old-postinst</var> <tt>abort-upgrade</tt>
3568 <var>new-version</var>
3571 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3572 <tt>in-favour</tt> <var>package</var>
3573 <var>new-version</var>
3576 <var>postinst</var> <tt>abort-remove</tt>
3579 <var>deconfigured's-postinst</var>
3580 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3581 <var>failed-install-package</var> <var>version</var>
3582 [<tt>removing</tt> <var>conflicting-package</var>
3588 <list compact="compact">
3590 <var>prerm</var> <tt>remove</tt>
3593 <var>old-prerm</var> <tt>upgrade</tt>
3594 <var>new-version</var>
3597 <var>new-prerm</var> <tt>failed-upgrade</tt>
3598 <var>old-version</var>
3601 <var>conflictor's-prerm</var> <tt>remove</tt>
3602 <tt>in-favour</tt> <var>package</var>
3603 <var>new-version</var>
3606 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3607 <tt>in-favour</tt> <var>package-being-installed</var>
3608 <var>version</var> [<tt>removing</tt>
3609 <var>conflicting-package</var>
3615 <list compact="compact">
3617 <var>postrm</var> <tt>remove</tt>
3620 <var>postrm</var> <tt>purge</tt>
3623 <var>old-postrm</var> <tt>upgrade</tt>
3624 <var>new-version</var>
3627 <var>new-postrm</var> <tt>failed-upgrade</tt>
3628 <var>old-version</var>
3631 <var>new-postrm</var> <tt>abort-install</tt>
3634 <var>new-postrm</var> <tt>abort-install</tt>
3635 <var>old-version</var>
3638 <var>new-postrm</var> <tt>abort-upgrade</tt>
3639 <var>old-version</var>
3642 <var>disappearer's-postrm</var> <tt>disappear</tt>
3643 <var>overwriter</var>
3644 <var>overwriter-version</var>
3650 <sect id="unpackphase">
3651 <heading>Details of unpack phase of installation or upgrade</heading>
3654 The procedure on installation/upgrade/overwrite/disappear
3655 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3656 stage of <tt>dpkg --install</tt>) is as follows. In each
3657 case, if a major error occurs (unless listed below) the
3658 actions are, in general, run backwards - this means that the
3659 maintainer scripts are run with different arguments in
3660 reverse order. These are the "error unwind" calls listed
3667 If a version of the package is already installed, call
3668 <example compact="compact">
3669 <var>old-prerm</var> upgrade <var>new-version</var>
3673 If the script runs but exits with a non-zero
3674 exit status, <prgn>dpkg</prgn> will attempt:
3675 <example compact="compact">
3676 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3678 If this works, the upgrade continues. If this
3679 does not work, the error unwind:
3680 <example compact="compact">
3681 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3683 If this works, then the old-version is
3684 "Installed", if not, the old version is in a
3685 "Failed-Config" state.
3691 If a "conflicting" package is being removed at the same time,
3692 or if any package will be broken (due to <tt>Breaks</tt>):
3695 If <tt>--auto-deconfigure</tt> is
3696 specified, call, for each package to be deconfigured
3697 due to <tt>Breaks</tt>:
3698 <example compact="compact">
3699 <var>deconfigured's-prerm</var> deconfigure \
3700 in-favour <var>package-being-installed</var> <var>version</var>
3703 <example compact="compact">
3704 <var>deconfigured's-postinst</var> abort-deconfigure \
3705 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3707 The deconfigured packages are marked as
3708 requiring configuration, so that if
3709 <tt>--install</tt> is used they will be
3710 configured again if possible.
3713 If any packages depended on a conflicting
3714 package being removed and <tt>--auto-deconfigure</tt> is
3715 specified, call, for each such package:
3716 <example compact="compact">
3717 <var>deconfigured's-prerm</var> deconfigure \
3718 in-favour <var>package-being-installed</var> <var>version</var> \
3719 removing <var>conflicting-package</var> <var>version</var>
3722 <example compact="compact">
3723 <var>deconfigured's-postinst</var> abort-deconfigure \
3724 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3725 removing <var>conflicting-package</var> <var>version</var>
3727 The deconfigured packages are marked as
3728 requiring configuration, so that if
3729 <tt>--install</tt> is used they will be
3730 configured again if possible.
3733 To prepare for removal of each conflicting package, call:
3734 <example compact="compact">
3735 <var>conflictor's-prerm</var> remove \
3736 in-favour <var>package</var> <var>new-version</var>
3739 <example compact="compact">
3740 <var>conflictor's-postinst</var> abort-remove \
3741 in-favour <var>package</var> <var>new-version</var>
3750 If the package is being upgraded, call:
3751 <example compact="compact">
3752 <var>new-preinst</var> upgrade <var>old-version</var>
3754 If this fails, we call:
3756 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3763 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3765 is called. If this works, then the old version
3766 is in an "Installed" state, or else it is left
3767 in an "Unpacked" state.
3772 If it fails, then the old version is left
3773 in an "Half-Installed" state.
3780 Otherwise, if the package had some configuration
3781 files from a previous version installed (i.e., it
3782 is in the "configuration files only" state):
3783 <example compact="compact">
3784 <var>new-preinst</var> install <var>old-version</var>
3788 <var>new-postrm</var> abort-install <var>old-version</var>
3790 If this fails, the package is left in a
3791 "Half-Installed" state, which requires a
3792 reinstall. If it works, the packages is left in
3793 a "Config Files" state.
3796 Otherwise (i.e., the package was completely purged):
3797 <example compact="compact">
3798 <var>new-preinst</var> install
3801 <example compact="compact">
3802 <var>new-postrm</var> abort-install
3804 If the error-unwind fails, the package is in a
3805 "Half Installed" phase, and requires a
3806 reinstall. If the error unwind works, the
3807 package is in a not installed state.
3814 The new package's files are unpacked, overwriting any
3815 that may be on the system already, for example any
3816 from the old version of the same package or from
3817 another package. Backups of the old files are kept
3818 temporarily, and if anything goes wrong the package
3819 management system will attempt to put them back as
3820 part of the error unwind.
3824 It is an error for a package to contain files which
3825 are on the system in another package, unless
3826 <tt>Replaces</tt> is used (see <ref id="replaces">).
3828 The following paragraph is not currently the case:
3829 Currently the <tt>- - force-overwrite</tt> flag is
3830 enabled, downgrading it to a warning, but this may not
3836 It is a more serious error for a package to contain a
3837 plain file or other kind of non-directory where another
3838 package has a directory (again, unless
3839 <tt>Replaces</tt> is used). This error can be
3840 overridden if desired using
3841 <tt>--force-overwrite-dir</tt>, but this is not
3846 Packages which overwrite each other's files produce
3847 behavior which, though deterministic, is hard for the
3848 system administrator to understand. It can easily
3849 lead to "missing" programs if, for example, a package
3850 is installed which overwrites a file from another
3851 package, and is then removed again.<footnote>
3852 Part of the problem is due to what is arguably a
3853 bug in <prgn>dpkg</prgn>.
3858 A directory will never be replaced by a symbolic link
3859 to a directory or vice versa; instead, the existing
3860 state (symlink or not) will be left alone and
3861 <prgn>dpkg</prgn> will follow the symlink if there is
3870 If the package is being upgraded, call
3871 <example compact="compact">
3872 <var>old-postrm</var> upgrade <var>new-version</var>
3876 If this fails, <prgn>dpkg</prgn> will attempt:
3877 <example compact="compact">
3878 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3880 If this works, installation continues. If not,
3882 <example compact="compact">
3883 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3885 If this fails, the old version is left in an
3886 "Half Installed" state. If it works, dpkg now
3888 <example compact="compact">
3889 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3891 If this fails, the old version is left in an
3892 "Half Installed" state. If it works, dpkg now
3894 <example compact="compact">
3895 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3897 If this fails, the old version is in an
3904 This is the point of no return - if
3905 <prgn>dpkg</prgn> gets this far, it won't back off
3906 past this point if an error occurs. This will
3907 leave the package in a fairly bad state, which
3908 will require a successful re-installation to clear
3909 up, but it's when <prgn>dpkg</prgn> starts doing
3910 things that are irreversible.
3915 Any files which were in the old version of the package
3916 but not in the new are removed.
3920 The new file list replaces the old.
3924 The new maintainer scripts replace the old.
3928 Any packages all of whose files have been overwritten
3929 during the installation, and which aren't required for
3930 dependencies, are considered to have been removed.
3931 For each such package
3934 <prgn>dpkg</prgn> calls:
3935 <example compact="compact">
3936 <var>disappearer's-postrm</var> disappear \
3937 <var>overwriter</var> <var>overwriter-version</var>
3941 The package's maintainer scripts are removed.
3944 It is noted in the status database as being in a
3945 sane state, namely not installed (any conffiles
3946 it may have are ignored, rather than being
3947 removed by <prgn>dpkg</prgn>). Note that
3948 disappearing packages do not have their prerm
3949 called, because <prgn>dpkg</prgn> doesn't know
3950 in advance that the package is going to
3957 Any files in the package we're unpacking that are also
3958 listed in the file lists of other packages are removed
3959 from those lists. (This will lobotomize the file list
3960 of the "conflicting" package if there is one.)
3964 The backup files made during installation, above, are
3970 The new package's status is now sane, and recorded as
3975 Here is another point of no return - if the
3976 conflicting package's removal fails we do not unwind
3977 the rest of the installation; the conflicting package
3978 is left in a half-removed limbo.
3983 If there was a conflicting package we go and do the
3984 removal actions (described below), starting with the
3985 removal of the conflicting package's files (any that
3986 are also in the package being installed have already
3987 been removed from the conflicting package's file list,
3988 and so do not get removed now).
3994 <sect id="configdetails"><heading>Details of configuration</heading>
3997 When we configure a package (this happens with <tt>dpkg
3998 --install</tt> and <tt>dpkg --configure</tt>), we first
3999 update any <tt>conffile</tt>s and then call:
4000 <example compact="compact">
4001 <var>postinst</var> configure <var>most-recently-configured-version</var>
4006 No attempt is made to unwind after errors during
4007 configuration. If the configuration fails, the package is in
4008 a "Failed Config" state, and an error message is generated.
4012 If there is no most recently configured version
4013 <prgn>dpkg</prgn> will pass a null argument.
4016 Historical note: Truly ancient (pre-1997) versions of
4017 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4018 (including the angle brackets) in this case. Even older
4019 ones did not pass a second argument at all, under any
4020 circumstance. Note that upgrades using such an old dpkg
4021 version are unlikely to work for other reasons, even if
4022 this old argument behavior is handled by your postinst script.
4028 <sect id="removedetails"><heading>Details of removal and/or
4029 configuration purging</heading>
4035 <example compact="compact">
4036 <var>prerm</var> remove
4040 If prerm fails during replacement due to conflict
4042 <var>conflictor's-postinst</var> abort-remove \
4043 in-favour <var>package</var> <var>new-version</var>
4047 <var>postinst</var> abort-remove
4051 If this fails, the package is in a "Failed-Config"
4052 state, or else it remains "Installed".
4056 The package's files are removed (except <tt>conffile</tt>s).
4059 <example compact="compact">
4060 <var>postrm</var> remove
4064 If it fails, there's no error unwind, and the package is in
4065 an "Half-Installed" state.
4070 All the maintainer scripts except the <prgn>postrm</prgn>
4075 If we aren't purging the package we stop here. Note
4076 that packages which have no <prgn>postrm</prgn> and no
4077 <tt>conffile</tt>s are automatically purged when
4078 removed, as there is no difference except for the
4079 <prgn>dpkg</prgn> status.
4083 The <tt>conffile</tt>s and any backup files
4084 (<tt>~</tt>-files, <tt>#*#</tt> files,
4085 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4090 <example compact="compact">
4091 <var>postrm</var> purge
4095 If this fails, the package remains in a "Config-Files"
4100 The package's file list is removed.
4109 <chapt id="relationships">
4110 <heading>Declaring relationships between packages</heading>
4112 <sect id="depsyntax">
4113 <heading>Syntax of relationship fields</heading>
4116 These fields all have a uniform syntax. They are a list of
4117 package names separated by commas.
4121 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4122 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4123 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4124 control file fields of the package, which declare
4125 dependencies on other packages, the package names listed may
4126 also include lists of alternative package names, separated
4127 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4128 if any one of the alternative packages is installed, that
4129 part of the dependency is considered to be satisfied.
4133 All of the fields except for <tt>Provides</tt> may restrict
4134 their applicability to particular versions of each named
4135 package. This is done in parentheses after each individual
4136 package name; the parentheses should contain a relation from
4137 the list below followed by a version number, in the format
4138 described in <ref id="f-Version">.
4142 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4143 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4144 strictly earlier, earlier or equal, exactly equal, later or
4145 equal and strictly later, respectively. The deprecated
4146 forms <tt><</tt> and <tt>></tt> were used to mean
4147 earlier/later or equal, rather than strictly earlier/later,
4148 so they should not appear in new packages (though
4149 <prgn>dpkg</prgn> still supports them).
4153 Whitespace may appear at any point in the version
4154 specification subject to the rules in <ref
4155 id="controlsyntax">, and must appear where it's necessary to
4156 disambiguate; it is not otherwise significant. All of the
4157 relationship fields may span multiple lines. For
4158 consistency and in case of future changes to
4159 <prgn>dpkg</prgn> it is recommended that a single space be
4160 used after a version relationship and before a version
4161 number; it is also conventional to put a single space after
4162 each comma, on either side of each vertical bar, and before
4163 each open parenthesis. When wrapping a relationship field, it
4164 is conventional to do so after a comma and before the space
4165 following that comma.
4169 For example, a list of dependencies might appear as:
4170 <example compact="compact">
4173 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4178 All fields that specify build-time relationships
4179 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4180 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4181 may be restricted to a certain set of architectures. This
4182 is indicated in brackets after each individual package name and
4183 the optional version specification. The brackets enclose a
4184 list of Debian architecture names separated by whitespace.
4185 Exclamation marks may be prepended to each of the names.
4186 (It is not permitted for some names to be prepended with
4187 exclamation marks while others aren't.) If the current Debian
4188 host architecture is not in this list and there are no
4189 exclamation marks in the list, or it is in the list with a
4190 prepended exclamation mark, the package name and the
4191 associated version specification are ignored completely for
4192 the purposes of defining the relationships.
4197 <example compact="compact">
4199 Build-Depends-Indep: texinfo
4200 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4201 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4203 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4204 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4205 <tt>gnumach-dev</tt> only on hurd-i386.
4209 If the architecture-restricted dependency is part of a set of
4210 alternatives using <tt>|</tt>, that alternative is ignored
4211 completely on architectures that do not match the restriction.
4213 <example compact="compact">
4214 Build-Depends: foo [!i386] | bar [!amd64]
4216 is equivalent to <tt>bar</tt> on the i386 architecture, to
4217 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4218 bar</tt> on all other architectures.
4222 Note that the binary package relationship fields such as
4223 <tt>Depends</tt> appear in one of the binary package
4224 sections of the control file, whereas the build-time
4225 relationships such as <tt>Build-Depends</tt> appear in the
4226 source package section of the control file (which is the
4231 <sect id="binarydeps">
4232 <heading>Binary Dependencies - <tt>Depends</tt>,
4233 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4234 <tt>Pre-Depends</tt>
4238 Packages can declare in their control file that they have
4239 certain relationships to other packages - for example, that
4240 they may not be installed at the same time as certain other
4241 packages, and/or that they depend on the presence of others.
4245 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4246 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4247 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4251 These seven fields are used to declare a dependency
4252 relationship by one package on another. Except for
4253 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4254 depending (binary) package's control file.
4255 (<tt>Enhances</tt> appears in the recommending package's
4256 control file, and <tt>Breaks</tt> appears in the version of
4257 depended-on package which causes the named package to
4262 A <tt>Depends</tt> field takes effect <em>only</em> when a
4263 package is to be configured. It does not prevent a package
4264 being on the system in an unconfigured state while its
4265 dependencies are unsatisfied, and it is possible to replace
4266 a package whose dependencies are satisfied and which is
4267 properly installed with a different version whose
4268 dependencies are not and cannot be satisfied; when this is
4269 done the depending package will be left unconfigured (since
4270 attempts to configure it will give errors) and will not
4271 function properly. If it is necessary, a
4272 <tt>Pre-Depends</tt> field can be used, which has a partial
4273 effect even when a package is being unpacked, as explained
4274 in detail below. (The other three dependency fields,
4275 <tt>Recommends</tt>, <tt>Suggests</tt> and
4276 <tt>Enhances</tt>, are only used by the various front-ends
4277 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4278 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4282 For this reason packages in an installation run are usually
4283 all unpacked first and all configured later; this gives
4284 later versions of packages with dependencies on later
4285 versions of other packages the opportunity to have their
4286 dependencies satisfied.
4290 In case of circular dependencies, since installation or
4291 removal order honoring the dependency order can't be
4292 established, dependency loops are broken at some point
4293 (based on rules below), and some packages may not be able to
4294 rely on their dependencies being present when being
4295 installed or removed, depending on which side of the break
4296 of the circular dependency loop they happen to be on. If one
4297 of the packages in the loop has no postinst script, then the
4298 cycle will be broken at that package, so as to ensure that
4299 all postinst scripts run with the dependencies properly
4300 configured if this is possible. Otherwise the breaking point
4305 The <tt>Depends</tt> field thus allows package maintainers
4306 to impose an order in which packages should be configured.
4310 The meaning of the five dependency fields is as follows:
4312 <tag><tt>Depends</tt></tag>
4315 This declares an absolute dependency. A package will
4316 not be configured unless all of the packages listed in
4317 its <tt>Depends</tt> field have been correctly
4322 The <tt>Depends</tt> field should be used if the
4323 depended-on package is required for the depending
4324 package to provide a significant amount of
4329 The <tt>Depends</tt> field should also be used if the
4330 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4331 <prgn>postrm</prgn> scripts require the package to be
4332 present in order to run. Note, however, that the
4333 <prgn>postrm</prgn> cannot rely on any non-essential
4334 packages to be present during the <tt>purge</tt>
4338 <tag><tt>Recommends</tt></tag>
4341 This declares a strong, but not absolute, dependency.
4345 The <tt>Recommends</tt> field should list packages
4346 that would be found together with this one in all but
4347 unusual installations.
4351 <tag><tt>Suggests</tt></tag>
4353 This is used to declare that one package may be more
4354 useful with one or more others. Using this field
4355 tells the packaging system and the user that the
4356 listed packages are related to this one and can
4357 perhaps enhance its usefulness, but that installing
4358 this one without them is perfectly reasonable.
4361 <tag><tt>Enhances</tt></tag>
4363 This field is similar to Suggests but works in the
4364 opposite direction. It is used to declare that a
4365 package can enhance the functionality of another
4369 <tag><tt>Pre-Depends</tt></tag>
4372 This field is like <tt>Depends</tt>, except that it
4373 also forces <prgn>dpkg</prgn> to complete installation
4374 of the packages named before even starting the
4375 installation of the package which declares the
4376 pre-dependency, as follows:
4380 When a package declaring a pre-dependency is about to
4381 be <em>unpacked</em> the pre-dependency can be
4382 satisfied if the depended-on package is either fully
4383 configured, <em>or even if</em> the depended-on
4384 package(s) are only unpacked or half-configured,
4385 provided that they have been configured correctly at
4386 some point in the past (and not removed or partially
4387 removed since). In this case, both the
4388 previously-configured and currently unpacked or
4389 half-configured versions must satisfy any version
4390 clause in the <tt>Pre-Depends</tt> field.
4394 When the package declaring a pre-dependency is about
4395 to be <em>configured</em>, the pre-dependency will be
4396 treated as a normal <tt>Depends</tt>, that is, it will
4397 be considered satisfied only if the depended-on
4398 package has been correctly configured.
4402 <tt>Pre-Depends</tt> should be used sparingly,
4403 preferably only by packages whose premature upgrade or
4404 installation would hamper the ability of the system to
4405 continue with any upgrade that might be in progress.
4409 <tt>Pre-Depends</tt> are also required if the
4410 <prgn>preinst</prgn> script depends on the named
4411 package. It is best to avoid this situation if
4419 When selecting which level of dependency to use you should
4420 consider how important the depended-on package is to the
4421 functionality of the one declaring the dependency. Some
4422 packages are composed of components of varying degrees of
4423 importance. Such a package should list using
4424 <tt>Depends</tt> the package(s) which are required by the
4425 more important components. The other components'
4426 requirements may be mentioned as Suggestions or
4427 Recommendations, as appropriate to the components' relative
4433 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4436 Using <tt>Breaks</tt> may cause problems for upgrades from older
4437 versions of Debian and should not be used until the stable
4438 release of Debian supports <tt>Breaks</tt>.
4442 When one binary package declares that it breaks another,
4443 <prgn>dpkg</prgn> will refuse to allow the package which
4444 declares <tt>Breaks</tt> be installed unless the broken
4445 package is deconfigured first, and it will refuse to
4446 allow the broken package to be reconfigured.
4450 A package will not be regarded as causing breakage merely
4451 because its configuration files are still installed; it must
4452 be at least half-installed.
4456 A special exception is made for packages which declare that
4457 they break their own package name or a virtual package which
4458 they provide (see below): this does not count as a real
4463 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4464 version clause; such a <tt>Breaks</tt> is introduced in the
4465 version of an (implicit or explicit) dependency which
4466 violates an assumption or reveals a bug in earlier versions
4467 of the broken package. This use of <tt>Breaks</tt> will
4468 inform higher-level package management tools that broken
4469 package must be upgraded before the new one.
4473 If the breaking package also overwrites some files from the
4474 older package, it should use <tt>Replaces</tt> (not
4475 <tt>Conflicts</tt>) to ensure this goes smoothly.
4479 <sect id="conflicts">
4480 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4483 When one binary package declares a conflict with another
4484 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4485 refuse to allow them to be installed on the system at the
4490 If one package is to be installed, the other must be removed
4491 first - if the package being installed is marked as
4492 replacing (see <ref id="replaces">) the one on the system,
4493 or the one on the system is marked as deselected, or both
4494 packages are marked <tt>Essential</tt>, then
4495 <prgn>dpkg</prgn> will automatically remove the package
4496 which is causing the conflict, otherwise it will halt the
4497 installation of the new package with an error. This
4498 mechanism is specifically designed to produce an error when
4499 the installed package is <tt>Essential</tt>, but the new
4504 A package will not cause a conflict merely because its
4505 configuration files are still installed; it must be at least
4510 A special exception is made for packages which declare a
4511 conflict with their own package name, or with a virtual
4512 package which they provide (see below): this does not
4513 prevent their installation, and allows a package to conflict
4514 with others providing a replacement for it. You use this
4515 feature when you want the package in question to be the only
4516 package providing some feature.
4520 A <tt>Conflicts</tt> entry should almost never have an
4521 "earlier than" version clause. This would prevent
4522 <prgn>dpkg</prgn> from upgrading or installing the package
4523 which declared such a conflict until the upgrade or removal
4524 of the conflicted-with package had been completed. Instead,
4525 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4526 by the stable release of Debian).
4530 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4534 As well as the names of actual ("concrete") packages, the
4535 package relationship fields <tt>Depends</tt>,
4536 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4537 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4538 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4539 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4540 may mention "virtual packages".
4544 A <em>virtual package</em> is one which appears in the
4545 <tt>Provides</tt> control file field of another package.
4546 The effect is as if the package(s) which provide a
4547 particular virtual package name had been listed by name
4548 everywhere the virtual package name appears. (See also <ref
4553 If there are both concrete and virtual packages of the same
4554 name, then the dependency may be satisfied (or the conflict
4555 caused) by either the concrete package with the name in
4556 question or any other concrete package which provides the
4557 virtual package with the name in question. This is so that,
4558 for example, supposing we have
4559 <example compact="compact">
4562 </example> and someone else releases an enhanced version of
4563 the <tt>bar</tt> package they can say:
4564 <example compact="compact">
4568 and the <tt>bar-plus</tt> package will now also satisfy the
4569 dependency for the <tt>foo</tt> package.
4573 If a relationship field has a version number attached
4574 then only real packages will be considered to see whether
4575 the relationship is satisfied (or the prohibition violated,
4576 for a conflict or breakage) - it is assumed that a real
4577 package which provides the virtual package is not of the
4578 "right" version. So, a <tt>Provides</tt> field may not
4579 contain version numbers, and the version number of the
4580 concrete package which provides a particular virtual package
4581 will not be looked at when considering a dependency on or
4582 conflict with the virtual package name.
4586 It is likely that the ability will be added in a future
4587 release of <prgn>dpkg</prgn> to specify a version number for
4588 each virtual package it provides. This feature is not yet
4589 present, however, and is expected to be used only
4594 If you want to specify which of a set of real packages
4595 should be the default to satisfy a particular dependency on
4596 a virtual package, you should list the real package as an
4597 alternative before the virtual one.
4602 <sect id="replaces"><heading>Overwriting files and replacing
4603 packages - <tt>Replaces</tt></heading>
4606 Packages can declare in their control file that they should
4607 overwrite files in certain other packages, or completely
4608 replace other packages. The <tt>Replaces</tt> control file
4609 field has these two distinct purposes.
4612 <sect1><heading>Overwriting files in other packages</heading>
4615 Firstly, as mentioned before, it is usually an error for a
4616 package to contain files which are on the system in
4621 However, if the overwriting package declares that it
4622 <tt>Replaces</tt> the one containing the file being
4623 overwritten, then <prgn>dpkg</prgn> will replace the file
4624 from the old package with that from the new. The file
4625 will no longer be listed as "owned" by the old package.
4629 If a package is completely replaced in this way, so that
4630 <prgn>dpkg</prgn> does not know of any files it still
4631 contains, it is considered to have "disappeared". It will
4632 be marked as not wanted on the system (selected for
4633 removal) and not installed. Any <tt>conffile</tt>s
4634 details noted for the package will be ignored, as they
4635 will have been taken over by the overwriting package. The
4636 package's <prgn>postrm</prgn> script will be run with a
4637 special argument to allow the package to do any final
4638 cleanup required. See <ref id="mscriptsinstact">.
4641 Replaces is a one way relationship -- you have to
4642 install the replacing package after the replaced
4649 For this usage of <tt>Replaces</tt>, virtual packages (see
4650 <ref id="virtual">) are not considered when looking at a
4651 <tt>Replaces</tt> field - the packages declared as being
4652 replaced must be mentioned by their real names.
4656 Furthermore, this usage of <tt>Replaces</tt> only takes
4657 effect when both packages are at least partially on the
4658 system at once, so that it can only happen if they do not
4659 conflict or if the conflict has been overridden.
4664 <sect1><heading>Replacing whole packages, forcing their
4668 Secondly, <tt>Replaces</tt> allows the packaging system to
4669 resolve which package should be removed when there is a
4670 conflict - see <ref id="conflicts">. This usage only
4671 takes effect when the two packages <em>do</em> conflict,
4672 so that the two usages of this field do not interfere with
4677 In this situation, the package declared as being replaced
4678 can be a virtual package, so for example, all mail
4679 transport agents (MTAs) would have the following fields in
4680 their control files:
4681 <example compact="compact">
4682 Provides: mail-transport-agent
4683 Conflicts: mail-transport-agent
4684 Replaces: mail-transport-agent
4686 ensuring that only one MTA can be installed at any one
4691 <sect id="sourcebinarydeps">
4692 <heading>Relationships between source and binary packages -
4693 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4694 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4698 Source packages that require certain binary packages to be
4699 installed or absent at the time of building the package
4700 can declare relationships to those binary packages.
4704 This is done using the <tt>Build-Depends</tt>,
4705 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4706 <tt>Build-Conflicts-Indep</tt> control file fields.
4710 Build-dependencies on "build-essential" binary packages can be
4711 omitted. Please see <ref id="pkg-relations"> for more information.
4715 The dependencies and conflicts they define must be satisfied
4716 (as defined earlier for binary packages) in order to invoke
4717 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4719 If you make "build-arch" or "binary-arch", you need
4720 Build-Depends. If you make "build-indep" or
4721 "binary-indep", you need Build-Depends and
4722 Build-Depends-Indep. If you make "build" or "binary",
4726 There is no Build-Depends-Arch; this role is essentially
4727 met with Build-Depends. Anyone building the
4728 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4729 is basically assumed to be building the whole package
4730 anyway and so installs all build dependencies. The
4731 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4732 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4733 does not yet know how to check for its existence) and
4734 <tt>binary-arch</tt>.
4737 The purpose of the original split, I recall, was so that
4738 the autobuilders wouldn't need to install extra packages
4739 needed only for the binary-indep targets. But without a
4740 build-arch/build-indep split, this didn't work, since
4741 most of the work is done in the build target, not in the
4747 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4749 The <tt>Build-Depends</tt> and
4750 <tt>Build-Conflicts</tt> fields must be satisfied when
4751 any of the following targets is invoked:
4752 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4753 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4754 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4756 <tag><tt>Build-Depends-Indep</tt>,
4757 <tt>Build-Conflicts-Indep</tt></tag>
4759 The <tt>Build-Depends-Indep</tt> and
4760 <tt>Build-Conflicts-Indep</tt> fields must be
4761 satisfied when any of the following targets is
4762 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4763 <tt>binary</tt> and <tt>binary-indep</tt>.
4773 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4776 Packages containing shared libraries must be constructed with
4777 a little care to make sure that the shared library is always
4778 available. This is especially important for packages whose
4779 shared libraries are vitally important, such as the C library
4780 (currently <tt>libc6</tt>).
4784 Packages involving shared libraries should be split up into
4785 several binary packages. This section mostly deals with how
4786 this separation is to be accomplished; rules for files within
4787 the shared library packages are in <ref id="libraries"> instead.
4790 <sect id="sharedlibs-runtime">
4791 <heading>Run-time shared libraries</heading>
4794 The run-time shared library needs to be placed in a package
4795 whose name changes whenever the shared object version
4798 Since it is common place to install several versions of a
4799 package that just provides shared libraries, it is a
4800 good idea that the library package should not
4801 contain any extraneous non-versioned files, unless they
4802 happen to be in versioned directories.</p>
4804 The most common mechanism is to place it in a package
4806 <package><var>libraryname</var><var>soversion</var></package>,
4807 where <file><var>soversion</var></file> is the version number
4808 in the soname of the shared library<footnote>
4809 The soname is the shared object name: it's the thing
4810 that has to match exactly between building an executable
4811 and running it for the dynamic linker to be able run the
4812 program. For example, if the soname of the library is
4813 <file>libfoo.so.6</file>, the library package would be
4814 called <file>libfoo6</file>.
4816 Alternatively, if it would be confusing to directly append
4817 <var>soversion</var> to <var>libraryname</var> (e.g. because
4818 <var>libraryname</var> itself ends in a number), you may use
4819 <package><var>libraryname</var>-<var>soversion</var></package> and
4820 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4825 If you have several shared libraries built from the same
4826 source tree you may lump them all together into a single
4827 shared library package, provided that you change all of
4828 their sonames at once (so that you don't get filename
4829 clashes if you try to install different versions of the
4830 combined shared libraries package).
4834 The package should install the shared libraries under
4835 their normal names. For example, the <package>libgdbm3</package>
4836 package should install <file>libgdbm.so.3.0.0</file> as
4837 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4838 renamed or re-linked by any <prgn>prerm</prgn> or
4839 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4840 of renaming things safely without affecting running programs,
4841 and attempts to interfere with this are likely to lead to
4846 Shared libraries should not be installed executable, since
4847 the dynamic linker does not require this and trying to
4848 execute a shared library usually results in a core dump.
4852 The run-time library package should include the symbolic link that
4853 <prgn>ldconfig</prgn> would create for the shared libraries.
4854 For example, the <package>libgdbm3</package> package should include
4855 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4856 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4857 linker (for example <prgn>ld.so</prgn> or
4858 <prgn>ld-linux.so.*</prgn>) can find the library between the
4859 time that <prgn>dpkg</prgn> installs it and the time that
4860 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4862 The package management system requires the library to be
4863 placed before the symbolic link pointing to it in the
4864 <file>.deb</file> file. This is so that when
4865 <prgn>dpkg</prgn> comes to install the symlink
4866 (overwriting the previous symlink pointing at an older
4867 version of the library), the new shared library is already
4868 in place. In the past, this was achieved by creating the
4869 library in the temporary packaging directory before
4870 creating the symlink. Unfortunately, this was not always
4871 effective, since the building of the tar file in the
4872 <file>.deb</file> depended on the behavior of the underlying
4873 file system. Some file systems (such as reiserfs) reorder
4874 the files so that the order of creation is forgotten.
4875 Since version 1.7.0, <prgn>dpkg</prgn>
4876 reorders the files itself as necessary when building a
4877 package. Thus it is no longer important to concern
4878 oneself with the order of file creation.
4882 <sect1 id="ldconfig">
4883 <heading><tt>ldconfig</tt></heading>
4886 Any package installing shared libraries in one of the default
4887 library directories of the dynamic linker (which are currently
4888 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4889 listed in <file>/etc/ld.so.conf</file><footnote>
4891 <list compact="compact">
4892 <item>/usr/local/lib</item>
4893 <item>/usr/lib/libc5-compat</item>
4894 <item>/lib/libc5-compat</item>
4897 must use <prgn>ldconfig</prgn> to update the shared library
4902 The package maintainer scripts must only call
4903 <prgn>ldconfig</prgn> under these circumstances:
4904 <list compact="compact">
4905 <item>When the <prgn>postinst</prgn> script is run with a
4906 first argument of <tt>configure</tt>, the script must call
4907 <prgn>ldconfig</prgn>, and may optionally invoke
4908 <prgn>ldconfig</prgn> at other times.
4910 <item>When the <prgn>postrm</prgn> script is run with a
4911 first argument of <tt>remove</tt>, the script should call
4912 <prgn>ldconfig</prgn>.
4917 During install or upgrade, the preinst is called before
4918 the new files are installed, so calling "ldconfig" is
4919 pointless. The preinst of an existing package can also be
4920 called if an upgrade fails. However, this happens during
4921 the critical time when a shared libs may exist on-disk
4922 under a temporary name. Thus, it is dangerous and
4923 forbidden by current policy to call "ldconfig" at this
4928 When a package is installed or upgraded, "postinst
4929 configure" runs after the new files are safely on-disk.
4930 Since it is perfectly safe to invoke ldconfig
4931 unconditionally in a postinst, it is OK for a package to
4932 simply put ldconfig in its postinst without checking the
4933 argument. The postinst can also be called to recover from
4934 a failed upgrade. This happens before any new files are
4935 unpacked, so there is no reason to call "ldconfig" at this
4940 For a package that is being removed, prerm is
4941 called with all the files intact, so calling ldconfig is
4942 useless. The other calls to "prerm" happen in the case of
4943 upgrade at a time when all the files of the old package
4944 are on-disk, so again calling "ldconfig" is pointless.
4948 postrm, on the other hand, is called with the "remove"
4949 argument just after the files are removed, so this is
4950 the proper time to call "ldconfig" to notify the system
4951 of the fact that the shared libraries from the package
4952 are removed. The postrm can be called at several other
4953 times. At the time of "postrm purge", "postrm
4954 abort-install", or "postrm abort-upgrade", calling
4955 "ldconfig" is useless because the shared lib files are
4956 not on-disk. However, when "postrm" is invoked with
4957 arguments "upgrade", "failed-upgrade", or "disappear", a
4958 shared lib may exist on-disk under a temporary filename.
4966 <sect id="sharedlibs-support-files">
4967 <heading>Shared library support files</heading>
4970 If your package contains files whose names do not change with
4971 each change in the library shared object version, you must not
4972 put them in the shared library package. Otherwise, several
4973 versions of the shared library cannot be installed at the same
4974 time without filename clashes, making upgrades and transitions
4975 unnecessarily difficult.
4979 It is recommended that supporting files and run-time support
4980 programs that do not need to be invoked manually by users, but
4981 are nevertheless required for the package to function, be placed
4982 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4983 preferably under <file>/usr/lib/</file><var>package-name</var>.
4984 If the program or file is architecture independent, the
4985 recommendation is for it to be placed in a subdirectory of
4986 <file>/usr/share</file> instead, preferably under
4987 <file>/usr/share/</file><var>package-name</var>. Following the
4988 <var>package-name</var> naming convention ensures that the file
4989 names change when the shared object version changes.
4993 Run-time support programs that use the shared library but are
4994 not required for the library to function or files used by the
4995 shared library that can be used by any version of the shared
4996 library package should instead be put in a separate package.
4997 This package might typically be named
4998 <package><var>libraryname</var>-tools</package>; note the
4999 absence of the <var>soversion</var> in the package name.
5003 Files and support programs only useful when compiling software
5004 against the library should be included in the development
5005 package for the library.<footnote>
5006 For example, a <file><var>package-name</var>-config</file>
5007 script or <package>pkg-config</package> configuration files.
5012 <sect id="sharedlibs-static">
5013 <heading>Static libraries</heading>
5016 The static library (<file><var>libraryname.a</var></file>)
5017 is usually provided in addition to the shared version.
5018 It is placed into the development package (see below).
5022 In some cases, it is acceptable for a library to be
5023 available in static form only; these cases include:
5025 <item>libraries for languages whose shared library support
5026 is immature or unstable</item>
5027 <item>libraries whose interfaces are in flux or under
5028 development (commonly the case when the library's
5029 major version number is zero, or where the ABI breaks
5030 across patchlevels)</item>
5031 <item>libraries which are explicitly intended to be
5032 available only in static form by their upstream
5037 <sect id="sharedlibs-dev">
5038 <heading>Development files</heading>
5041 The development files associated to a shared library need to be
5042 placed in a package called
5043 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5044 or if you prefer only to support one development version at a
5045 time, <package><var>libraryname</var>-dev</package>.
5049 In case several development versions of a library exist, you may
5050 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5051 <ref id="conflicts">) to ensure that the user only installs one
5052 development version at a time (as different development versions are
5053 likely to have the same header files in them, which would cause a
5054 filename clash if both were installed).
5058 The development package should contain a symlink for the associated
5059 shared library without a version number. For example, the
5060 <package>libgdbm-dev</package> package should include a symlink
5061 from <file>/usr/lib/libgdbm.so</file> to
5062 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5063 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5064 <file>libgdbm.so</file> when compiling dynamically.
5068 <sect id="sharedlibs-intradeps">
5069 <heading>Dependencies between the packages of the same library</heading>
5072 Typically the development version should have an exact
5073 version dependency on the runtime library, to make sure that
5074 compilation and linking happens correctly. The
5075 <tt>${binary:Version}</tt> substitution variable can be
5076 useful for this purpose.
5078 Previously, <tt>${Source-Version}</tt> was used, but its name
5079 was confusing and it has been deprecated since dpkg 1.13.19.
5084 <sect id="sharedlibs-shlibdeps">
5085 <heading>Dependencies between the library and other packages -
5086 the <tt>shlibs</tt> system</heading>
5089 If a package contains a binary or library which links to a
5090 shared library, we must ensure that when the package is
5091 installed on the system, all of the libraries needed are
5092 also installed. This requirement led to the creation of the
5093 <tt>shlibs</tt> system, which is very simple in its design:
5094 any package which <em>provides</em> a shared library also
5095 provides information on the package dependencies required to
5096 ensure the presence of this library, and any package which
5097 <em>uses</em> a shared library uses this information to
5098 determine the dependencies it requires. The files which
5099 contain the mapping from shared libraries to the necessary
5100 dependency information are called <file>shlibs</file> files.
5104 Thus, when a package is built which contains any shared
5105 libraries, it must provide a <file>shlibs</file> file for other
5106 packages to use, and when a package is built which contains
5107 any shared libraries or compiled binaries, it must run
5108 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5109 on these to determine the libraries used and hence the
5110 dependencies needed by this package.<footnote>
5112 In the past, the shared libraries linked to were
5113 determined by calling <prgn>ldd</prgn>, but now
5114 <prgn>objdump</prgn> is used to do this. The only
5115 change this makes to package building is that
5116 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5117 libraries, whereas in the past this was unnecessary.
5118 The rest of this footnote explains the advantage that
5123 We say that a binary <tt>foo</tt> <em>directly</em> uses
5124 a library <tt>libbar</tt> if it is explicitly linked
5125 with that library (that is, it uses the flag
5126 <tt>-lbar</tt> during the linking stage). Other
5127 libraries that are needed by <tt>libbar</tt> are linked
5128 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5129 linker will load them automatically when it loads
5130 <tt>libbar</tt>. A package should depend on
5131 the libraries it directly uses, and the dependencies for
5132 those libraries should automatically pull in the other
5137 Unfortunately, the <prgn>ldd</prgn> program shows both
5138 the directly and indirectly used libraries, meaning that
5139 the dependencies determined included both direct and
5140 indirect dependencies. The use of <prgn>objdump</prgn>
5141 avoids this problem by determining only the directly
5146 A good example of where this helps is the following. We
5147 could update <tt>libimlib</tt> with a new version that
5148 supports a new graphics format called dgf (but retaining
5149 the same major version number). If we used the old
5150 <prgn>ldd</prgn> method, every package that uses
5151 <tt>libimlib</tt> would need to be recompiled so it
5152 would also depend on <tt>libdgf</tt> or it wouldn't run
5153 due to missing symbols. However with the new system,
5154 packages using <tt>libimlib</tt> can rely on
5155 <tt>libimlib</tt> itself having the dependency on
5156 <tt>libdgf</tt> and so they would not need rebuilding.
5162 In the following sections, we will first describe where the
5163 various <tt>shlibs</tt> files are to be found, then how to
5164 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5165 file format and how to create them if your package contains a
5170 <heading>The <tt>shlibs</tt> files present on the system</heading>
5173 There are several places where <tt>shlibs</tt> files are
5174 found. The following list gives them in the order in which
5176 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5177 (The first one which gives the required information is used.)
5183 <p><file>debian/shlibs.local</file></p>
5186 This lists overrides for this package. Its use is
5187 described below (see <ref id="shlibslocal">).
5192 <p><file>/etc/dpkg/shlibs.override</file></p>
5195 This lists global overrides. This list is normally
5196 empty. It is maintained by the local system
5202 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5205 When packages are being built, any
5206 <file>debian/shlibs</file> files are copied into the
5207 control file area of the temporary build directory and
5208 given the name <file>shlibs</file>. These files give
5209 details of any shared libraries included in the
5211 An example may help here. Let us say that the
5212 source package <tt>foo</tt> generates two binary
5213 packages, <tt>libfoo2</tt> and
5214 <tt>foo-runtime</tt>. When building the binary
5215 packages, the two packages are created in the
5216 directories <file>debian/libfoo2</file> and
5217 <file>debian/foo-runtime</file> respectively.
5218 (<file>debian/tmp</file> could be used instead of one
5219 of these.) Since <tt>libfoo2</tt> provides the
5220 <tt>libfoo</tt> shared library, it will require a
5221 <tt>shlibs</tt> file, which will be installed in
5222 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5224 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5225 when <prgn>dpkg-shlibdeps</prgn> is run on the
5227 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5229 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5230 determine whether <tt>foo-prog</tt>'s library
5231 dependencies are satisfied by any of the libraries
5232 provided by <tt>libfoo2</tt>. For this reason,
5233 <prgn>dpkg-shlibdeps</prgn> must only be run once
5234 all of the individual binary packages'
5235 <tt>shlibs</tt> files have been installed into the
5242 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5245 These are the <file>shlibs</file> files corresponding to
5246 all of the packages installed on the system, and are
5247 maintained by the relevant package maintainers.
5252 <p><file>/etc/dpkg/shlibs.default</file></p>
5255 This file lists any shared libraries whose packages
5256 have failed to provide correct <file>shlibs</file> files.
5257 It was used when the <file>shlibs</file> setup was first
5258 introduced, but it is now normally empty. It is
5259 maintained by the <tt>dpkg</tt> maintainer.
5267 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5268 <file>shlibs</file> files</heading>
5272 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5273 into your <file>debian/rules</file> file. If your package
5274 contains only compiled binaries and libraries (but no scripts),
5275 you can use a command such as:
5276 <example compact="compact">
5277 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5278 debian/tmp/usr/lib/*
5280 Otherwise, you will need to explicitly list the compiled
5281 binaries and libraries.<footnote>
5282 If you are using <tt>debhelper</tt>, the
5283 <prgn>dh_shlibdeps</prgn> program will do this work for
5284 you. It will also correctly handle multi-binary
5290 This command puts the dependency information into the
5291 <file>debian/substvars</file> file, which is then used by
5292 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5293 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5294 field in the control file for this to work.
5298 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5299 done. If it does complain you might need to create your own
5300 <file>debian/shlibs.local</file> file, as explained below (see
5301 <ref id="shlibslocal">).
5305 If you have multiple binary packages, you will need to call
5306 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5307 compiled libraries or binaries. In such a case, you will
5308 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5309 utilities to specify a different <file>substvars</file> file.
5313 If you are creating a udeb for use in the Debian Installer, you
5314 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5315 the dependency line of type <tt>udeb</tt> by adding
5316 <tt>-tudeb</tt> as option<footnote>
5317 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5318 will automatically add this option if it knows it is
5320 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5321 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5322 fall back to the regular dependency line.
5326 For more details on dpkg-shlibdeps, please see
5327 <ref id="pkg-dpkg-shlibdeps"> and
5328 <manref name="dpkg-shlibdeps" section="1">.
5333 <heading>The <file>shlibs</file> File Format</heading>
5336 Each <file>shlibs</file> file has the same format. Lines
5337 beginning with <tt>#</tt> are considered to be comments and
5338 are ignored. Each line is of the form:
5339 <example compact="compact">
5340 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5345 We will explain this by reference to the example of the
5346 <tt>zlib1g</tt> package, which (at the time of writing)
5347 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5351 <var>type</var> is an optional element that indicates the type
5352 of package for which the line is valid. The only type currently
5353 in use is <tt>udeb</tt>. The colon and space after the type are
5358 <var>library-name</var> is the name of the shared library,
5359 in this case <tt>libz</tt>. (This must match the name part
5360 of the soname, see below.)
5364 <var>soname-version</var> is the version part of the soname of
5365 the library. The soname is the thing that must exactly match
5366 for the library to be recognized by the dynamic linker, and is
5368 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5369 example, <tt>libz.so.1</tt>.<footnote>
5370 This can be determined using the command
5371 <example compact="compact">
5372 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5375 The version part is the part which comes after
5376 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5380 <var>dependencies</var> has the same syntax as a dependency
5381 field in a binary package control file. It should give
5382 details of which packages are required to satisfy a binary
5383 built against the version of the library contained in the
5384 package. See <ref id="depsyntax"> for details.
5388 In our example, if the first version of the <tt>zlib1g</tt>
5389 package which contained a minor number of at least
5390 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5391 <tt>shlibs</tt> entry for this library could say:
5392 <example compact="compact">
5393 libz 1 zlib1g (>= 1:1.1.3)
5395 The version-specific dependency is to avoid warnings from
5396 the dynamic linker about using older shared libraries with
5401 As zlib1g also provides a udeb containing the shared library,
5402 there would also be a second line:
5403 <example compact="compact">
5404 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5410 <heading>Providing a <file>shlibs</file> file</heading>
5413 If your package provides a shared library, you need to create
5414 a <file>shlibs</file> file following the format described above.
5415 It is usual to call this file <file>debian/shlibs</file> (but if
5416 you have multiple binary packages, you might want to call it
5417 <file>debian/shlibs.<var>package</var></file> instead). Then
5418 let <file>debian/rules</file> install it in the control area:
5419 <example compact="compact">
5420 install -m644 debian/shlibs debian/tmp/DEBIAN
5422 or, in the case of a multi-binary package:
5423 <example compact="compact">
5424 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5426 An alternative way of doing this is to create the
5427 <file>shlibs</file> file in the control area directly from
5428 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5429 file at all,<footnote>
5430 This is what <prgn>dh_makeshlibs</prgn> in the
5431 <tt>debhelper</tt> suite does. If your package also has a udeb
5432 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5433 automatically generate the <tt>udeb:</tt> lines if you specify
5434 the name of the udeb with the <tt>--add-udeb</tt> option.
5436 since the <file>debian/shlibs</file> file itself is ignored by
5437 <prgn>dpkg-shlibdeps</prgn>.
5441 As <prgn>dpkg-shlibdeps</prgn> reads the
5442 <file>DEBIAN/shlibs</file> files in all of the binary packages
5443 being built from this source package, all of the
5444 <file>DEBIAN/shlibs</file> files should be installed before
5445 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5450 <sect1 id="shlibslocal">
5451 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5454 This file is intended only as a <em>temporary</em> fix if
5455 your binaries or libraries depend on a library whose package
5456 does not yet provide a correct <file>shlibs</file> file.
5460 We will assume that you are trying to package a binary
5461 <tt>foo</tt>. When you try running
5462 <prgn>dpkg-shlibdeps</prgn> you get the following error
5463 message (<tt>-O</tt> displays the dependency information on
5464 <tt>stdout</tt> instead of writing it to
5465 <tt>debian/substvars</tt>, and the lines have been wrapped
5466 for ease of reading):
5467 <example compact="compact">
5468 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5469 dpkg-shlibdeps: warning: unable to find dependency
5470 information for shared library libbar (soname 1,
5471 path /usr/lib/libbar.so.1, dependency field Depends)
5472 shlibs:Depends=libc6 (>= 2.2.2-2)
5474 You can then run <prgn>ldd</prgn> on the binary to find the
5475 full location of the library concerned:
5476 <example compact="compact">
5478 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5479 libc.so.6 => /lib/libc.so.6 (0x40032000)
5480 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5482 So the <prgn>foo</prgn> binary depends on the
5483 <prgn>libbar</prgn> shared library, but no package seems to
5484 provide a <file>*.shlibs</file> file handling
5485 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5486 determine the package responsible:
5487 <example compact="compact">
5488 $ dpkg -S /usr/lib/libbar.so.1
5489 bar1: /usr/lib/libbar.so.1
5490 $ dpkg -s bar1 | grep Version
5493 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5494 is the one we are using. Now we can file a bug against the
5495 <tt>bar1</tt> package and create our own
5496 <file>debian/shlibs.local</file> to locally fix the problem.
5497 Including the following line into your
5498 <file>debian/shlibs.local</file> file:
5499 <example compact="compact">
5500 libbar 1 bar1 (>= 1.0-1)
5502 should allow the package build to work.
5506 As soon as the maintainer of <tt>bar1</tt> provides a
5507 correct <file>shlibs</file> file, you should remove this line
5508 from your <file>debian/shlibs.local</file> file. (You should
5509 probably also then have a versioned <tt>Build-Depends</tt>
5510 on <tt>bar1</tt> to help ensure that others do not have the
5511 same problem building your package.)
5520 <chapt id="opersys"><heading>The Operating System</heading>
5523 <heading>File system hierarchy</heading>
5527 <heading>File system Structure</heading>
5530 The location of all installed files and directories must
5531 comply with the File system Hierarchy Standard (FHS),
5532 version 2.3, with the exceptions noted below, and except
5533 where doing so would violate other terms of Debian
5534 Policy. The following exceptions to the FHS apply:
5539 Legacy XFree86 servers are permitted to retain the
5540 configuration file location
5541 <file>/etc/X11/XF86Config-4</file>.
5546 The optional rules related to user specific
5547 configuration files for applications are stored in
5548 the user's home directory are relaxed. It is
5549 recommended that such files start with the
5550 '<tt>.</tt>' character (a "dot file"), and if an
5551 application needs to create more than one dot file
5552 then the preferred placement is in a subdirectory
5553 with a name starting with a '.' character, (a "dot
5554 directory"). In this case it is recommended the
5555 configuration files not start with the '.'
5561 The requirement for amd64 to use <file>/lib64</file>
5562 for 64 bit binaries is removed.
5567 The requirement that
5568 <file>/usr/local/share/man</file> be "synonymous"
5569 with <file>/usr/local/man</file> is relaxed to a
5574 The requirement that windowmanagers with a single
5575 configuration file call it <file>system.*wmrc</file>
5576 is removed, as is the restriction that the window
5577 manager subdirectory be named identically to the
5578 window manager name itself.
5583 The requirement that boot manager configuration
5584 files live in <file>/etc</file>, or at least are
5585 symlinked there, is relaxed to a recommendation.
5592 The version of this document referred here can be
5593 found in the <tt>debian-policy</tt> package or on <url
5594 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5595 name="FHS (Debian copy)"> alongside this manual (or, if
5596 you have the <package>debian-policy</package> installed,
5598 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5599 (local copy)">). The
5600 latest version, which may be a more recent version, may
5602 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5603 Specific questions about following the standard may be
5604 asked on the <tt>debian-devel</tt> mailing list, or
5605 referred to the FHS mailing list (see the
5606 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5612 <heading>Site-specific programs</heading>
5615 As mandated by the FHS, packages must not place any
5616 files in <file>/usr/local</file>, either by putting them in
5617 the file system archive to be unpacked by <prgn>dpkg</prgn>
5618 or by manipulating them in their maintainer scripts.
5622 However, the package may create empty directories below
5623 <file>/usr/local</file> so that the system administrator knows
5624 where to place site-specific files. These are not
5625 directories <em>in</em> <file>/usr/local</file>, but are
5626 children of directories in <file>/usr/local</file>. These
5627 directories (<file>/usr/local/*/dir/</file>)
5628 should be removed on package removal if they are
5633 Note, that this applies only to directories <em>below</em>
5634 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5635 Packages must not create sub-directories in the directory
5636 <file>/usr/local</file> itself, except those listed in FHS,
5637 section 4.5. However, you may create directories below
5638 them as you wish. You must not remove any of the
5639 directories listed in 4.5, even if you created them.
5643 Since <file>/usr/local</file> can be mounted read-only from a
5644 remote server, these directories must be created and
5645 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5646 maintainer scripts and not be included in the
5647 <file>.deb</file> archive. These scripts must not fail if
5648 either of these operations fail.
5652 For example, the <tt>emacsen-common</tt> package could
5653 contain something like
5654 <example compact="compact">
5655 if [ ! -e /usr/local/share/emacs ]
5657 if mkdir /usr/local/share/emacs 2>/dev/null
5659 chown root:staff /usr/local/share/emacs
5660 chmod 2775 /usr/local/share/emacs
5664 in its <prgn>postinst</prgn> script, and
5665 <example compact="compact">
5666 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5667 rmdir /usr/local/share/emacs 2>/dev/null || true
5669 in the <prgn>prerm</prgn> script. (Note that this form is
5670 used to ensure that if the script is interrupted, the
5671 directory <file>/usr/local/share/emacs</file> will still be
5676 If you do create a directory in <file>/usr/local</file> for
5677 local additions to a package, you should ensure that
5678 settings in <file>/usr/local</file> take precedence over the
5679 equivalents in <file>/usr</file>.
5683 However, because <file>/usr/local</file> and its contents are
5684 for exclusive use of the local administrator, a package
5685 must not rely on the presence or absence of files or
5686 directories in <file>/usr/local</file> for normal operation.
5690 The <file>/usr/local</file> directory itself and all the
5691 subdirectories created by the package should (by default) have
5692 permissions 2775 (group-writable and set-group-id) and be
5693 owned by <tt>root:staff</tt>.
5698 <heading>The system-wide mail directory</heading>
5700 The system-wide mail directory is <file>/var/mail</file>. This
5701 directory is part of the base system and should not owned
5702 by any particular mail agents. The use of the old
5703 location <file>/var/spool/mail</file> is deprecated, even
5704 though the spool may still be physically located there.
5705 To maintain partial upgrade compatibility for systems
5706 which have <file>/var/spool/mail</file> as their physical mail
5707 spool, packages using <file>/var/mail</file> must depend on
5708 either <package>libc6</package> (>= 2.1.3-13), or on
5709 <package>base-files</package> (>= 2.2.0), or on later
5710 versions of either one of these packages.
5716 <heading>Users and groups</heading>
5719 <heading>Introduction</heading>
5721 The Debian system can be configured to use either plain or
5726 Some user ids (UIDs) and group ids (GIDs) are reserved
5727 globally for use by certain packages. Because some
5728 packages need to include files which are owned by these
5729 users or groups, or need the ids compiled into binaries,
5730 these ids must be used on any Debian system only for the
5731 purpose for which they are allocated. This is a serious
5732 restriction, and we should avoid getting in the way of
5733 local administration policies. In particular, many sites
5734 allocate users and/or local system groups starting at 100.
5738 Apart from this we should have dynamically allocated ids,
5739 which should by default be arranged in some sensible
5740 order, but the behavior should be configurable.
5744 Packages other than <tt>base-passwd</tt> must not modify
5745 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5746 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5751 <heading>UID and GID classes</heading>
5753 The UID and GID numbers are divided into classes as
5759 Globally allocated by the Debian project, the same
5760 on every Debian system. These ids will appear in
5761 the <file>passwd</file> and <file>group</file> files of all
5762 Debian systems, new ids in this range being added
5763 automatically as the <tt>base-passwd</tt> package is
5768 Packages which need a single statically allocated
5769 uid or gid should use one of these; their
5770 maintainers should ask the <tt>base-passwd</tt>
5778 Dynamically allocated system users and groups.
5779 Packages which need a user or group, but can have
5780 this user or group allocated dynamically and
5781 differently on each system, should use <tt>adduser
5782 --system</tt> to create the group and/or user.
5783 <prgn>adduser</prgn> will check for the existence of
5784 the user or group, and if necessary choose an unused
5785 id based on the ranges specified in
5786 <file>adduser.conf</file>.
5790 <tag>1000-29999:</tag>
5793 Dynamically allocated user accounts. By default
5794 <prgn>adduser</prgn> will choose UIDs and GIDs for
5795 user accounts in this range, though
5796 <file>adduser.conf</file> may be used to modify this
5801 <tag>30000-59999:</tag>
5806 <tag>60000-64999:</tag>
5809 Globally allocated by the Debian project, but only
5810 created on demand. The ids are allocated centrally
5811 and statically, but the actual accounts are only
5812 created on users' systems on demand.
5816 These ids are for packages which are obscure or
5817 which require many statically-allocated ids. These
5818 packages should check for and create the accounts in
5819 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5820 <prgn>adduser</prgn> if it has this facility) if
5821 necessary. Packages which are likely to require
5822 further allocations should have a "hole" left after
5823 them in the allocation, to give them room to
5828 <tag>65000-65533:</tag>
5836 User <tt>nobody</tt>. The corresponding gid refers
5837 to the group <tt>nogroup</tt>.
5844 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5845 not</em> be used, because it is the error return
5854 <sect id="sysvinit">
5855 <heading>System run levels and <file>init.d</file> scripts</heading>
5857 <sect1 id="/etc/init.d">
5858 <heading>Introduction</heading>
5861 The <file>/etc/init.d</file> directory contains the scripts
5862 executed by <prgn>init</prgn> at boot time and when the
5863 init state (or "runlevel") is changed (see <manref
5864 name="init" section="8">).
5868 There are at least two different, yet functionally
5869 equivalent, ways of handling these scripts. For the sake
5870 of simplicity, this document describes only the symbolic
5871 link method. However, it must not be assumed by maintainer
5872 scripts that this method is being used, and any automated
5873 manipulation of the various runlevel behaviors by
5874 maintainer scripts must be performed using
5875 <prgn>update-rc.d</prgn> as described below and not by
5876 manually installing or removing symlinks. For information
5877 on the implementation details of the other method,
5878 implemented in the <tt>file-rc</tt> package, please refer
5879 to the documentation of that package.
5883 These scripts are referenced by symbolic links in the
5884 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5885 runlevels, <prgn>init</prgn> looks in the directory
5886 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5887 execute, where <tt><var>n</var></tt> is the runlevel that
5888 is being changed to, or <tt>S</tt> for the boot-up
5893 The names of the links all have the form
5894 <file>S<var>mm</var><var>script</var></file> or
5895 <file>K<var>mm</var><var>script</var></file> where
5896 <var>mm</var> is a two-digit number and <var>script</var>
5897 is the name of the script (this should be the same as the
5898 name of the actual script in <file>/etc/init.d</file>).
5902 When <prgn>init</prgn> changes runlevel first the targets
5903 of the links whose names start with a <tt>K</tt> are
5904 executed, each with the single argument <tt>stop</tt>,
5905 followed by the scripts prefixed with an <tt>S</tt>, each
5906 with the single argument <tt>start</tt>. (The links are
5907 those in the <file>/etc/rc<var>n</var>.d</file> directory
5908 corresponding to the new runlevel.) The <tt>K</tt> links
5909 are responsible for killing services and the <tt>S</tt>
5910 link for starting services upon entering the runlevel.
5914 For example, if we are changing from runlevel 2 to
5915 runlevel 3, init will first execute all of the <tt>K</tt>
5916 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5917 all of the <tt>S</tt> prefixed scripts in that directory.
5918 The links starting with <tt>K</tt> will cause the
5919 referred-to file to be executed with an argument of
5920 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5925 The two-digit number <var>mm</var> is used to determine
5926 the order in which to run the scripts: low-numbered links
5927 have their scripts run first. For example, the
5928 <tt>K20</tt> scripts will be executed before the
5929 <tt>K30</tt> scripts. This is used when a certain service
5930 must be started before another. For example, the name
5931 server <prgn>bind</prgn> might need to be started before
5932 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5933 can set up its access lists. In this case, the script
5934 that starts <prgn>bind</prgn> would have a lower number
5935 than the script that starts <prgn>inn</prgn> so that it
5937 <example compact="compact">
5944 The two runlevels 0 (halt) and 6 (reboot) are slightly
5945 different. In these runlevels, the links with an
5946 <tt>S</tt> prefix are still called after those with a
5947 <tt>K</tt> prefix, but they too are called with the single
5948 argument <tt>stop</tt>.
5953 <heading>Writing the scripts</heading>
5956 Packages that include daemons for system services should
5957 place scripts in <file>/etc/init.d</file> to start or stop
5958 services at boot time or during a change of runlevel.
5959 These scripts should be named
5960 <file>/etc/init.d/<var>package</var></file>, and they should
5961 accept one argument, saying what to do:
5964 <tag><tt>start</tt></tag>
5965 <item>start the service,</item>
5967 <tag><tt>stop</tt></tag>
5968 <item>stop the service,</item>
5970 <tag><tt>restart</tt></tag>
5971 <item>stop and restart the service if it's already running,
5972 otherwise start the service</item>
5974 <tag><tt>reload</tt></tag>
5975 <item><p>cause the configuration of the service to be
5976 reloaded without actually stopping and restarting
5979 <tag><tt>force-reload</tt></tag>
5980 <item>cause the configuration to be reloaded if the
5981 service supports this, otherwise restart the
5985 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5986 <tt>force-reload</tt> options should be supported by all
5987 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5992 The <file>init.d</file> scripts must ensure that they will
5993 behave sensibly (i.e., returning success and not starting
5994 multiple copies of a service) if invoked with <tt>start</tt>
5995 when the service is already running, or with <tt>stop</tt>
5996 when it isn't, and that they don't kill unfortunately-named
5997 user processes. The best way to achieve this is usually to
5998 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6003 If a service reloads its configuration automatically (as
6004 in the case of <prgn>cron</prgn>, for example), the
6005 <tt>reload</tt> option of the <file>init.d</file> script
6006 should behave as if the configuration has been reloaded
6011 The <file>/etc/init.d</file> scripts must be treated as
6012 configuration files, either (if they are present in the
6013 package, that is, in the .deb file) by marking them as
6014 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6015 by managing them correctly in the maintainer scripts (see
6016 <ref id="config-files">). This is important since we want
6017 to give the local system administrator the chance to adapt
6018 the scripts to the local system, e.g., to disable a
6019 service without de-installing the package, or to specify
6020 some special command line options when starting a service,
6021 while making sure their changes aren't lost during the next
6026 These scripts should not fail obscurely when the
6027 configuration files remain but the package has been
6028 removed, as configuration files remain on the system after
6029 the package has been removed. Only when <prgn>dpkg</prgn>
6030 is executed with the <tt>--purge</tt> option will
6031 configuration files be removed. In particular, as the
6032 <file>/etc/init.d/<var>package</var></file> script itself is
6033 usually a <tt>conffile</tt>, it will remain on the system
6034 if the package is removed but not purged. Therefore, you
6035 should include a <tt>test</tt> statement at the top of the
6037 <example compact="compact">
6038 test -f <var>program-executed-later-in-script</var> || exit 0
6043 Often there are some variables in the <file>init.d</file>
6044 scripts whose values control the behavior of the scripts,
6045 and which a system administrator is likely to want to
6046 change. As the scripts themselves are frequently
6047 <tt>conffile</tt>s, modifying them requires that the
6048 administrator merge in their changes each time the package
6049 is upgraded and the <tt>conffile</tt> changes. To ease
6050 the burden on the system administrator, such configurable
6051 values should not be placed directly in the script.
6052 Instead, they should be placed in a file in
6053 <file>/etc/default</file>, which typically will have the same
6054 base name as the <file>init.d</file> script. This extra file
6055 should be sourced by the script when the script runs. It
6056 must contain only variable settings and comments in SUSv3
6057 <prgn>sh</prgn> format. It may either be a
6058 <tt>conffile</tt> or a configuration file maintained by
6059 the package maintainer scripts. See <ref id="config-files">
6064 To ensure that vital configurable values are always
6065 available, the <file>init.d</file> script should set default
6066 values for each of the shell variables it uses, either
6067 before sourcing the <file>/etc/default/</file> file or
6068 afterwards using something like the <tt>:
6069 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6070 script must behave sensibly and not fail if the
6071 <file>/etc/default</file> file is deleted.
6075 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6076 as temporary filesystems<footnote>
6077 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6078 options in <file>/etc/default/rcS</file>.
6079 </footnote>, so the <file>init.d</file> scripts must handle this
6080 correctly. This will typically amount to creating any required
6081 subdirectories dynamically when the <file>init.d</file> script
6082 is run, rather than including them in the package and relying on
6083 <prgn>dpkg</prgn> to create them.
6088 <heading>Interfacing with the initscript system</heading>
6091 Maintainers should use the abstraction layer provided by
6092 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6093 programs to deal with initscripts in their packages'
6094 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6095 and <prgn>postrm</prgn>.
6099 Directly managing the /etc/rc?.d links and directly
6100 invoking the <file>/etc/init.d/</file> initscripts should
6101 be done only by packages providing the initscript
6102 subsystem (such as <prgn>sysv-rc</prgn> and
6103 <prgn>file-rc</prgn>).
6107 <heading>Managing the links</heading>
6110 The program <prgn>update-rc.d</prgn> is provided for
6111 package maintainers to arrange for the proper creation and
6112 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6113 or their functional equivalent if another method is being
6114 used. This may be used by maintainers in their packages'
6115 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6119 You must not include any <file>/etc/rc<var>n</var>.d</file>
6120 symbolic links in the actual archive or manually create or
6121 remove the symbolic links in maintainer scripts; you must
6122 use the <prgn>update-rc.d</prgn> program instead. (The
6123 former will fail if an alternative method of maintaining
6124 runlevel information is being used.) You must not include
6125 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6126 in the archive either. (Only the <tt>sysvinit</tt>
6131 By default <prgn>update-rc.d</prgn> will start services in
6132 each of the multi-user state runlevels (2, 3, 4, and 5)
6133 and stop them in the halt runlevel (0), the single-user
6134 runlevel (1) and the reboot runlevel (6). The system
6135 administrator will have the opportunity to customize
6136 runlevels by simply adding, moving, or removing the
6137 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6138 symbolic links are being used, or by modifying
6139 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6144 To get the default behavior for your package, put in your
6145 <prgn>postinst</prgn> script
6146 <example compact="compact">
6147 update-rc.d <var>package</var> defaults
6149 and in your <prgn>postrm</prgn>
6150 <example compact="compact">
6151 if [ "$1" = purge ]; then
6152 update-rc.d <var>package</var> remove
6154 </example>. Note that if your package changes runlevels
6155 or priority, you may have to remove and recreate the links,
6156 since otherwise the old links may persist. Refer to the
6157 documentation of <prgn>update-rc.d</prgn>.
6161 This will use a default sequence number of 20. If it does
6162 not matter when or in which order the <file>init.d</file>
6163 script is run, use this default. If it does, then you
6164 should talk to the maintainer of the <prgn>sysvinit</prgn>
6165 package or post to <tt>debian-devel</tt>, and they will
6166 help you choose a number.
6170 For more information about using <tt>update-rc.d</tt>,
6171 please consult its man page <manref name="update-rc.d"
6177 <heading>Running initscripts</heading>
6179 The program <prgn>invoke-rc.d</prgn> is provided to make
6180 it easier for package maintainers to properly invoke an
6181 initscript, obeying runlevel and other locally-defined
6182 constraints that might limit a package's right to start,
6183 stop and otherwise manage services. This program may be
6184 used by maintainers in their packages' scripts.
6188 The package maintainer scripts must use
6189 <prgn>invoke-rc.d</prgn> to invoke the
6190 <file>/etc/init.d/*</file> initscripts, instead of
6191 calling them directly.
6195 By default, <prgn>invoke-rc.d</prgn> will pass any
6196 action requests (start, stop, reload, restart...) to the
6197 <file>/etc/init.d</file> script, filtering out requests
6198 to start or restart a service out of its intended
6203 Most packages will simply need to change:
6204 <example compact="compact">/etc/init.d/<package>
6205 <action></example> in their <prgn>postinst</prgn>
6206 and <prgn>prerm</prgn> scripts to:
6207 <example compact="compact">
6208 if which invoke-rc.d >/dev/null 2>&1; then
6209 invoke-rc.d <var>package</var> <action>
6211 /etc/init.d/<var>package</var> <action>
6217 A package should register its initscript services using
6218 <prgn>update-rc.d</prgn> before it tries to invoke them
6219 using <prgn>invoke-rc.d</prgn>. Invocation of
6220 unregistered services may fail.
6224 For more information about using
6225 <prgn>invoke-rc.d</prgn>, please consult its man page
6226 <manref name="invoke-rc.d" section="8">.
6232 <heading>Boot-time initialization</heading>
6235 There used to be another directory, <file>/etc/rc.boot</file>,
6236 which contained scripts which were run once per machine
6237 boot. This has been deprecated in favour of links from
6238 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6239 described in <ref id="/etc/init.d">. Packages must not
6240 place files in <file>/etc/rc.boot</file>.
6245 <heading>Example</heading>
6248 An example on which you can base your
6249 <file>/etc/init.d</file> scripts is found in
6250 <file>/etc/init.d/skeleton</file>.
6257 <heading>Console messages from <file>init.d</file> scripts</heading>
6260 This section describes the formats to be used for messages
6261 written to standard output by the <file>/etc/init.d</file>
6262 scripts. The intent is to improve the consistency of
6263 Debian's startup and shutdown look and feel. For this
6264 reason, please look very carefully at the details. We want
6265 the messages to have the same format in terms of wording,
6266 spaces, punctuation and case of letters.
6270 Here is a list of overall rules that should be used for
6271 messages generated by <file>/etc/init.d</file> scripts.
6277 The message should fit in one line (fewer than 80
6278 characters), start with a capital letter and end with
6279 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6283 If the script is performing some time consuming task in
6284 the background (not merely starting or stopping a
6285 program, for instance), an ellipsis (three dots:
6286 <tt>...</tt>) should be output to the screen, with no
6287 leading or tailing whitespace or line feeds.
6291 The messages should appear as if the computer is telling
6292 the user what it is doing (politely :-), but should not
6293 mention "it" directly. For example, instead of:
6294 <example compact="compact">
6295 I'm starting network daemons: nfsd mountd.
6297 the message should say
6298 <example compact="compact">
6299 Starting network daemons: nfsd mountd.
6306 <tt>init.d</tt> script should use the following standard
6307 message formats for the situations enumerated below.
6313 <p>When daemons are started</p>
6316 If the script starts one or more daemons, the output
6317 should look like this (a single line, no leading
6319 <example compact="compact">
6320 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6322 The <var>description</var> should describe the
6323 subsystem the daemon or set of daemons are part of,
6324 while <var>daemon-1</var> up to <var>daemon-n</var>
6325 denote each daemon's name (typically the file name of
6330 For example, the output of <file>/etc/init.d/lpd</file>
6332 <example compact="compact">
6333 Starting printer spooler: lpd.
6338 This can be achieved by saying
6339 <example compact="compact">
6340 echo -n "Starting printer spooler: lpd"
6341 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6344 in the script. If there are more than one daemon to
6345 start, the output should look like this:
6346 <example compact="compact">
6347 echo -n "Starting remote file system services:"
6348 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6349 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6350 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6353 This makes it possible for the user to see what is
6354 happening and when the final daemon has been started.
6355 Care should be taken in the placement of white spaces:
6356 in the example above the system administrators can
6357 easily comment out a line if they don't want to start
6358 a specific daemon, while the displayed message still
6364 <p>When a system parameter is being set</p>
6367 If you have to set up different system parameters
6368 during the system boot, you should use this format:
6369 <example compact="compact">
6370 Setting <var>parameter</var> to "<var>value</var>".
6375 You can use a statement such as the following to get
6377 <example compact="compact">
6378 echo "Setting DNS domainname to \"$domainname\"."
6383 Note that the same symbol (<tt>"</tt>) is used for the left
6384 and right quotation marks. A grave accent (<tt>`</tt>) is
6385 not a quote character; neither is an apostrophe
6391 <p>When a daemon is stopped or restarted</p>
6394 When you stop or restart a daemon, you should issue a
6395 message identical to the startup message, except that
6396 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6397 or <tt>Restarting</tt> respectively.
6401 For example, stopping the printer daemon will look like
6403 <example compact="compact">
6404 Stopping printer spooler: lpd.
6410 <p>When something is executed</p>
6413 There are several examples where you have to run a
6414 program at system startup or shutdown to perform a
6415 specific task, for example, setting the system's clock
6416 using <prgn>netdate</prgn> or killing all processes
6417 when the system shuts down. Your message should look
6419 <example compact="compact">
6420 Doing something very useful...done.
6422 You should print the <tt>done.</tt> immediately after
6423 the job has been completed, so that the user is
6424 informed why they have to wait. You can get this
6426 <example compact="compact">
6427 echo -n "Doing something very useful..."
6436 <p>When the configuration is reloaded</p>
6439 When a daemon is forced to reload its configuration
6440 files you should use the following format:
6441 <example compact="compact">
6442 Reloading <var>description</var> configuration...done.
6444 where <var>description</var> is the same as in the
6445 daemon starting message.
6453 <heading>Cron jobs</heading>
6456 Packages must not modify the configuration file
6457 <file>/etc/crontab</file>, and they must not modify the files in
6458 <file>/var/spool/cron/crontabs</file>.</p>
6461 If a package wants to install a job that has to be executed
6462 via cron, it should place a file with the name of the
6463 package in one or more of the following directories:
6464 <example compact="compact">
6470 As these directory names imply, the files within them are
6471 executed on an hourly, daily, weekly, or monthly basis,
6472 respectively. The exact times are listed in
6473 <file>/etc/crontab</file>.</p>
6476 All files installed in any of these directories must be
6477 scripts (e.g., shell scripts or Perl scripts) so that they
6478 can easily be modified by the local system administrator.
6479 In addition, they must be treated as configuration files.
6483 If a certain job has to be executed at some other frequency or
6484 at a specific time, the package should install a file
6485 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6486 same syntax as <file>/etc/crontab</file> and is processed by
6487 <prgn>cron</prgn> automatically. The file must also be
6488 treated as a configuration file. (Note that entries in the
6489 <file>/etc/cron.d</file> directory are not handled by
6490 <prgn>anacron</prgn>. Thus, you should only use this
6491 directory for jobs which may be skipped if the system is not
6495 The scripts or crontab entries in these directories should
6496 check if all necessary programs are installed before they
6497 try to execute them. Otherwise, problems will arise when a
6498 package was removed but not purged since configuration files
6499 are kept on the system in this situation.</p>
6503 <heading>Menus</heading>
6506 The Debian <tt>menu</tt> package provides a standard
6507 interface between packages providing applications and
6508 <em>menu programs</em> (either X window managers or
6509 text-based menu programs such as <prgn>pdmenu</prgn>).
6513 All packages that provide applications that need not be
6514 passed any special command line arguments for normal
6515 operation should register a menu entry for those
6516 applications, so that users of the <tt>menu</tt> package
6517 will automatically get menu entries in their window
6518 managers, as well in shells like <tt>pdmenu</tt>.
6522 Menu entries should follow the current menu policy.
6526 The menu policy can be found in the <tt>menu-policy</tt>
6527 files in the <tt>debian-policy</tt> package.
6528 It is also available from the Debian web mirrors at
6529 <tt><url name="/doc/packaging-manuals/menu-policy/"
6530 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6534 Please also refer to the <em>Debian Menu System</em>
6535 documentation that comes with the <package>menu</package>
6536 package for information about how to register your
6542 <heading>Multimedia handlers</heading>
6545 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6546 is a mechanism for encoding files and data streams and
6547 providing meta-information about them, in particular their
6548 type (e.g. audio or video) and format (e.g. PNG, HTML,
6553 Registration of MIME type handlers allows programs like mail
6554 user agents and web browsers to invoke these handlers to
6555 view, edit or display MIME types they don't support directly.
6559 Packages which provide the ability to view/show/play,
6560 compose, edit or print MIME types should register themselves
6561 as such following the current MIME support policy.
6565 The MIME support policy can be found in the <tt>mime-policy</tt>
6566 files in the <tt>debian-policy</tt> package.
6567 It is also available from the Debian web mirrors at
6568 <tt><url name="/doc/packaging-manuals/mime-policy/"
6569 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6575 <heading>Keyboard configuration</heading>
6578 To achieve a consistent keyboard configuration so that all
6579 applications interpret a keyboard event the same way, all
6580 programs in the Debian distribution must be configured to
6581 comply with the following guidelines.
6585 The following keys must have the specified interpretations:
6588 <tag><tt><--</tt></tag>
6589 <item>delete the character to the left of the cursor</item>
6591 <tag><tt>Delete</tt></tag>
6592 <item>delete the character to the right of the cursor</item>
6594 <tag><tt>Control+H</tt></tag>
6595 <item>emacs: the help prefix</item>
6598 The interpretation of any keyboard events should be
6599 independent of the terminal that is used, be it a virtual
6600 console, an X terminal emulator, an rlogin/telnet session,
6605 The following list explains how the different programs
6606 should be set up to achieve this:
6612 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6616 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6620 X translations are set up to make
6621 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6622 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6623 is the vt220 escape code for the "delete character"
6624 key). This must be done by loading the X resources
6625 using <prgn>xrdb</prgn> on all local X displays, not
6626 using the application defaults, so that the
6627 translation resources used correspond to the
6628 <prgn>xmodmap</prgn> settings.
6632 The Linux console is configured to make
6633 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6634 generate <tt>ESC [ 3 ~</tt>.
6638 X applications are configured so that <tt><</tt>
6639 deletes left, and <tt>Delete</tt> deletes right. Motif
6640 applications already work like this.
6644 Terminals should have <tt>stty erase ^?</tt> .
6648 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6649 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6650 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6654 Emacs is programmed to map <tt>KB_Backspace</tt> or
6655 the <tt>stty erase</tt> character to
6656 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6657 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6658 <tt>^H</tt> to <tt>help</tt> as always.
6662 Other applications use the <tt>stty erase</tt>
6663 character and <tt>kdch1</tt> for the two delete keys,
6664 with ASCII DEL being "delete previous character" and
6665 <tt>kdch1</tt> being "delete character under
6673 This will solve the problem except for the following
6680 Some terminals have a <tt><--</tt> key that cannot
6681 be made to produce anything except <tt>^H</tt>. On
6682 these terminals Emacs help will be unavailable on
6683 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6684 character takes precedence in Emacs, and has been set
6685 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6686 available) can be used instead.
6690 Some operating systems use <tt>^H</tt> for <tt>stty
6691 erase</tt>. However, modern telnet versions and all
6692 rlogin versions propagate <tt>stty</tt> settings, and
6693 almost all UNIX versions honour <tt>stty erase</tt>.
6694 Where the <tt>stty</tt> settings are not propagated
6695 correctly, things can be made to work by using
6696 <tt>stty</tt> manually.
6700 Some systems (including previous Debian versions) use
6701 <prgn>xmodmap</prgn> to arrange for both
6702 <tt><--</tt> and <tt>Delete</tt> to generate
6703 <tt>KB_Delete</tt>. We can change the behavior of
6704 their X clients using the same X resources that we use
6705 to do it for our own clients, or configure our clients
6706 using their resources when things are the other way
6707 around. On displays configured like this
6708 <tt>Delete</tt> will not work, but <tt><--</tt>
6713 Some operating systems have different <tt>kdch1</tt>
6714 settings in their <tt>terminfo</tt> database for
6715 <tt>xterm</tt> and others. On these systems the
6716 <tt>Delete</tt> key will not work correctly when you
6717 log in from a system conforming to our policy, but
6718 <tt><--</tt> will.
6725 <heading>Environment variables</heading>
6728 A program must not depend on environment variables to get
6729 reasonable defaults. (That's because these environment
6730 variables would have to be set in a system-wide
6731 configuration file like <file>/etc/profile</file>, which is not
6732 supported by all shells.)
6736 If a program usually depends on environment variables for its
6737 configuration, the program should be changed to fall back to
6738 a reasonable default configuration if these environment
6739 variables are not present. If this cannot be done easily
6740 (e.g., if the source code of a non-free program is not
6741 available), the program must be replaced by a small
6742 "wrapper" shell script which sets the environment variables
6743 if they are not already defined, and calls the original program.
6747 Here is an example of a wrapper script for this purpose:
6749 <example compact="compact">
6751 BAR=${BAR:-/var/lib/fubar}
6753 exec /usr/lib/foo/foo "$@"
6758 Furthermore, as <file>/etc/profile</file> is a configuration
6759 file of the <prgn>base-files</prgn> package, other packages must
6760 not put any environment variables or other commands into that
6765 <sect id="doc-base">
6766 <heading>Registering Documents using doc-base</heading>
6769 The <package>doc-base</package> package implements a
6770 flexible mechanism for handling and presenting
6771 documentation. The recommended practice is for every Debian
6772 package that provides online documentation (other than just
6773 manual pages) to register these documents with
6774 <package>doc-base</package> by installing a
6775 <package>doc-base</package> control file via the
6776 <prgn/install-docs/ script at installation time and
6777 de-register the manuals again when the package is removed.
6780 Please refer to the documentation that comes with the
6781 <package>doc-base</package> package for information and
6790 <heading>Files</heading>
6793 <heading>Binaries</heading>
6796 Two different packages must not install programs with
6797 different functionality but with the same filenames. (The
6798 case of two programs having the same functionality but
6799 different implementations is handled via "alternatives" or
6800 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6801 <ref id="conflicts"> respectively.) If this case happens,
6802 one of the programs must be renamed. The maintainers should
6803 report this to the <tt>debian-devel</tt> mailing list and
6804 try to find a consensus about which program will have to be
6805 renamed. If a consensus cannot be reached, <em>both</em>
6806 programs must be renamed.
6810 By default, when a package is being built, any binaries
6811 created should include debugging information, as well as
6812 being compiled with optimization. You should also turn on
6813 as many reasonable compilation warnings as possible; this
6814 makes life easier for porters, who can then look at build
6815 logs for possible problems. For the C programming language,
6816 this means the following compilation parameters should be
6818 <example compact="compact">
6820 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6822 INSTALL = install -s # (or use strip on the files in debian/tmp)
6827 Note that by default all installed binaries should be stripped,
6828 either by using the <tt>-s</tt> flag to
6829 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6830 the binaries after they have been copied into
6831 <file>debian/tmp</file> but before the tree is made into a
6836 Although binaries in the build tree should be compiled with
6837 debugging information by default, it can often be difficult to
6838 debug programs if they are also subjected to compiler
6839 optimization. For this reason, it is recommended to support the
6840 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6841 (see <ref id="debianrules-options">). This variable can contain
6842 several flags to change how a package is compiled and built.
6846 It is up to the package maintainer to decide what
6847 compilation options are best for the package. Certain
6848 binaries (such as computationally-intensive programs) will
6849 function better with certain flags (<tt>-O3</tt>, for
6850 example); feel free to use them. Please use good judgment
6851 here. Don't use flags for the sake of it; only use them
6852 if there is good reason to do so. Feel free to override
6853 the upstream author's ideas about which compilation
6854 options are best: they are often inappropriate for our
6860 <sect id="libraries">
6861 <heading>Libraries</heading>
6864 If the package is <strong>architecture: any</strong>, then
6865 the shared library compilation and linking flags must have
6866 <tt>-fPIC</tt>, or the package shall not build on some of
6867 the supported architectures<footnote>
6869 If you are using GCC, <tt>-fPIC</tt> produces code with
6870 relocatable position independent code, which is required for
6871 most architectures to create a shared library, with i386 and
6872 perhaps some others where non position independent code is
6873 permitted in a shared library.
6876 Position independent code may have a performance penalty,
6877 especially on <tt>i386</tt>. However, in most cases the
6878 speed penalty must be measured against the memory wasted on
6879 the few architectures where non position independent code is
6882 </footnote>. Any exception to this rule must be discussed on
6883 the mailing list <em>debian-devel@lists.debian.org</em>, and
6884 a rough consensus obtained. The reasons for not compiling
6885 with <tt>-fPIC</tt> flag must be recorded in the file
6886 <tt>README.Debian</tt>, and care must be taken to either
6887 restrict the architecture or arrange for <tt>-fPIC</tt> to
6888 be used on architectures where it is required.<footnote>
6890 Some of the reasons why this might be required is if the
6891 library contains hand crafted assembly code that is not
6892 relocatable, the speed penalty is excessive for compute
6893 intensive libs, and similar reasons.
6898 As to the static libraries, the common case is not to have
6899 relocatable code, since there is no benefit, unless in specific
6900 cases; therefore the static version must not be compiled
6901 with the <tt>-fPIC</tt> flag. Any exception to this rule
6902 should be discussed on the mailing list
6903 <em>debian-devel@lists.debian.org</em>, and the reasons for
6904 compiling with the <tt>-fPIC</tt> flag must be recorded in
6905 the file <tt>README.Debian</tt>. <footnote>
6907 Some of the reasons for linking static libraries with
6908 the <tt>-fPIC</tt> flag are if, for example, one needs a
6909 Perl API for a library that is under rapid development,
6910 and has an unstable API, so shared libraries are
6911 pointless at this phase of the library's development. In
6912 that case, since Perl needs a library with relocatable
6913 code, it may make sense to create a static library with
6914 relocatable code. Another reason cited is if you are
6915 distilling various libraries into a common shared
6916 library, like <tt>mklibs</tt> does in the Debian
6922 In other words, if both a shared and a static library is
6923 being built, each source unit (<tt>*.c</tt>, for example,
6924 for C files) will need to be compiled twice, for the normal
6928 You must specify the gcc option <tt>-D_REENTRANT</tt>
6929 when building a library (either static or shared) to make
6930 the library compatible with LinuxThreads.
6934 Although not enforced by the build tools, shared libraries
6935 must be linked against all libraries that they use symbols from
6936 in the same way that binaries are. This ensures the correct
6937 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6938 system and guarantees that all libraries can be safely opened
6939 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6940 option <tt>-Wl,-z,defs</tt> when building a shared library.
6941 Since this option enforces symbol resolution at build time,
6942 a missing library reference will be caught early as a fatal
6947 All installed shared libraries should be stripped with
6948 <example compact="compact">
6949 strip --strip-unneeded <var>your-lib</var>
6951 (The option <tt>--strip-unneeded</tt> makes
6952 <prgn>strip</prgn> remove only the symbols which aren't
6953 needed for relocation processing.) Shared libraries can
6954 function perfectly well when stripped, since the symbols for
6955 dynamic linking are in a separate part of the ELF object
6957 You might also want to use the options
6958 <tt>--remove-section=.comment</tt> and
6959 <tt>--remove-section=.note</tt> on both shared libraries
6960 and executables, and <tt>--strip-debug</tt> on static
6966 Note that under some circumstances it may be useful to
6967 install a shared library unstripped, for example when
6968 building a separate package to support debugging.
6972 Shared object files (often <file>.so</file> files) that are not
6973 public libraries, that is, they are not meant to be linked
6974 to by third party executables (binaries of other packages),
6975 should be installed in subdirectories of the
6976 <file>/usr/lib</file> directory. Such files are exempt from the
6977 rules that govern ordinary shared libraries, except that
6978 they must not be installed executable and should be
6980 A common example are the so-called "plug-ins",
6981 internal shared objects that are dynamically loaded by
6982 programs using <manref name="dlopen" section="3">.
6987 Packages containing shared libraries that may be linked to
6988 by other packages' binaries, but which for some
6989 <em>compelling</em> reason can not be installed in
6990 <file>/usr/lib</file> directory, may install the shared library
6991 files in subdirectories of the <file>/usr/lib</file> directory,
6992 in which case they should arrange to add that directory in
6993 <file>/etc/ld.so.conf</file> in the package's post-installation
6994 script, and remove it in the package's post-removal script.
6998 An ever increasing number of packages are using
6999 <prgn>libtool</prgn> to do their linking. The latest GNU
7000 libtools (>= 1.3a) can take advantage of the metadata in the
7001 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7002 files). The main advantage of <prgn>libtool</prgn>'s
7003 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7004 store and subsequently access metadata with respect to the
7005 libraries it builds. <prgn>libtool</prgn> will search for
7006 those files, which contain a lot of useful information about
7007 a library (such as library dependency information for static
7008 linking). Also, they're <em>essential</em> for programs
7009 using <tt>libltdl</tt>.<footnote>
7010 Although <prgn>libtool</prgn> is fully capable of
7011 linking against shared libraries which don't have
7012 <tt>.la</tt> files, as it is a mere shell script it can
7013 add considerably to the build time of a
7014 <prgn>libtool</prgn>-using package if that shell script
7015 has to derive all this information from first principles
7016 for each library every time it is linked. With the
7017 advent of <prgn>libtool</prgn> version 1.4 (and to a
7018 lesser extent <prgn>libtool</prgn> version 1.3), the
7019 <file>.la</file> files also store information about
7020 inter-library dependencies which cannot necessarily be
7021 derived after the <file>.la</file> file is deleted.
7026 Packages that use <prgn>libtool</prgn> to create shared
7027 libraries should include the <file>.la</file> files in the
7028 <tt>-dev</tt> package, unless the package relies on
7029 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7030 the <tt>.la</tt> files must go in the run-time library
7035 You must make sure that you use only released versions of
7036 shared libraries to build your packages; otherwise other
7037 users will not be able to run your binaries
7038 properly. Producing source packages that depend on
7039 unreleased compilers is also usually a bad
7046 <heading>Shared libraries</heading>
7048 This section has moved to <ref id="sharedlibs">.
7054 <heading>Scripts</heading>
7057 All command scripts, including the package maintainer
7058 scripts inside the package and used by <prgn>dpkg</prgn>,
7059 should have a <tt>#!</tt> line naming the shell to be used
7064 In the case of Perl scripts this should be
7065 <tt>#!/usr/bin/perl</tt>.
7069 When scripts are installed into a directory in the system
7070 PATH, the script name should not include an extension such
7071 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7072 language currently used to implement it.
7075 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7076 should almost certainly start with <tt>set -e</tt> so that
7077 errors are detected. Every script should use
7078 <tt>set -e</tt> or check the exit status of <em>every</em>
7083 Scripts may assume that <file>/bin/sh</file> implements the
7084 SUSv3 Shell Command Language<footnote>
7085 Single UNIX Specification, version 3, which is also IEEE
7086 1003.1-2004 (POSIX), and is available on the World Wide Web
7087 from <url id="http://www.unix.org/version3/online.html"
7088 name="The Open Group"> after free
7089 registration.</footnote>
7090 plus the following additional features not mandated by
7092 These features are in widespread use in the Linux community
7093 and are implemented in all of bash, dash, and ksh, the most
7094 common shells users may wish to use as <file>/bin/sh</file>.
7097 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7098 must not generate a newline.</item>
7099 <item><tt>test</tt>, if implemented as a shell built-in, must
7100 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7102 <item><tt>local</tt> to create a scoped variable must be
7103 supported, including listing multiple variables in a single
7104 local command and assigning a value to a variable at the
7105 same time as localizing it. <tt>local</tt> may or
7106 may not preserve the variable value from an outer scope if
7107 no assignment is present. Uses such as:
7111 # ... use a, b, c, d ...
7114 must be supported and must set the value of <tt>c</tt> to
7118 If a shell script requires non-SUSv3 features from the shell
7119 interpreter other than those listed above, the appropriate shell
7120 must be specified in the first line of the script (e.g.,
7121 <tt>#!/bin/bash</tt>) and the package must depend on the package
7122 providing the shell (unless the shell package is marked
7123 "Essential", as in the case of <prgn>bash</prgn>).
7127 You may wish to restrict your script to SUSv3 features plus the
7128 above set when possible so that it may use <file>/bin/sh</file>
7129 as its interpreter. If your script works with <prgn>dash</prgn>
7130 (originally called <prgn>ash</prgn>), it probably complies with
7131 the above requirements, but if you are in doubt, use
7132 <file>/bin/bash</file>.
7136 Perl scripts should check for errors when making any
7137 system calls, including <tt>open</tt>, <tt>print</tt>,
7138 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7142 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7143 scripting languages. See <em>Csh Programming Considered
7144 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7145 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7146 If an upstream package comes with <prgn>csh</prgn> scripts
7147 then you must make sure that they start with
7148 <tt>#!/bin/csh</tt> and make your package depend on the
7149 <prgn>c-shell</prgn> virtual package.
7153 Any scripts which create files in world-writeable
7154 directories (e.g., in <file>/tmp</file>) must use a
7155 mechanism which will fail atomically if a file with the same
7156 name already exists.
7160 The Debian base system provides the <prgn>tempfile</prgn>
7161 and <prgn>mktemp</prgn> utilities for use by scripts for
7168 <heading>Symbolic links</heading>
7171 In general, symbolic links within a top-level directory
7172 should be relative, and symbolic links pointing from one
7173 top-level directory into another should be absolute. (A
7174 top-level directory is a sub-directory of the root
7175 directory <file>/</file>.)
7179 In addition, symbolic links should be specified as short as
7180 possible, i.e., link targets like <file>foo/../bar</file> are
7185 Note that when creating a relative link using
7186 <prgn>ln</prgn> it is not necessary for the target of the
7187 link to exist relative to the working directory you're
7188 running <prgn>ln</prgn> from, nor is it necessary to change
7189 directory to the directory where the link is to be made.
7190 Simply include the string that should appear as the target
7191 of the link (this will be a pathname relative to the
7192 directory in which the link resides) as the first argument
7197 For example, in your <prgn>Makefile</prgn> or
7198 <file>debian/rules</file>, you can do things like:
7199 <example compact="compact">
7200 ln -fs gcc $(prefix)/bin/cc
7201 ln -fs gcc debian/tmp/usr/bin/cc
7202 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7203 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7208 A symbolic link pointing to a compressed file should always
7209 have the same file extension as the referenced file. (For
7210 example, if a file <file>foo.gz</file> is referenced by a
7211 symbolic link, the filename of the link has to end with
7212 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7217 <heading>Device files</heading>
7220 Packages must not include device files in the package file
7225 If a package needs any special device files that are not
7226 included in the base system, it must call
7227 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7228 after notifying the user<footnote>
7229 This notification could be done via a (low-priority)
7230 debconf message, or an echo (printf) statement.
7235 Packages must not remove any device files in the
7236 <prgn>postrm</prgn> or any other script. This is left to the
7237 system administrator.
7241 Debian uses the serial devices
7242 <file>/dev/ttyS*</file>. Programs using the old
7243 <file>/dev/cu*</file> devices should be changed to use
7244 <file>/dev/ttyS*</file>.
7248 <sect id="config-files">
7249 <heading>Configuration files</heading>
7252 <heading>Definitions</heading>
7256 <tag>configuration file</tag>
7258 A file that affects the operation of a program, or
7259 provides site- or host-specific information, or
7260 otherwise customizes the behavior of a program.
7261 Typically, configuration files are intended to be
7262 modified by the system administrator (if needed or
7263 desired) to conform to local policy or to provide
7264 more useful site-specific behavior.
7267 <tag><tt>conffile</tt></tag>
7269 A file listed in a package's <tt>conffiles</tt>
7270 file, and is treated specially by <prgn>dpkg</prgn>
7271 (see <ref id="configdetails">).
7277 The distinction between these two is important; they are
7278 not interchangeable concepts. Almost all
7279 <tt>conffile</tt>s are configuration files, but many
7280 configuration files are not <tt>conffiles</tt>.
7284 As noted elsewhere, <file>/etc/init.d</file> scripts,
7285 <file>/etc/default</file> files, scripts installed in
7286 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7287 configuration installed in <file>/etc/cron.d</file> must be
7288 treated as configuration files. In general, any script that
7289 embeds configuration information is de-facto a configuration
7290 file and should be treated as such.
7295 <heading>Location</heading>
7298 Any configuration files created or used by your package
7299 must reside in <file>/etc</file>. If there are several,
7300 consider creating a subdirectory of <file>/etc</file>
7301 named after your package.
7305 If your package creates or uses configuration files
7306 outside of <file>/etc</file>, and it is not feasible to modify
7307 the package to use <file>/etc</file> directly, put the files
7308 in <file>/etc</file> and create symbolic links to those files
7309 from the location that the package requires.
7314 <heading>Behavior</heading>
7317 Configuration file handling must conform to the following
7319 <list compact="compact">
7321 local changes must be preserved during a package
7325 configuration files must be preserved when the
7326 package is removed, and only deleted when the
7333 The easy way to achieve this behavior is to make the
7334 configuration file a <tt>conffile</tt>. This is
7335 appropriate only if it is possible to distribute a default
7336 version that will work for most installations, although
7337 some system administrators may choose to modify it. This
7338 implies that the default version will be part of the
7339 package distribution, and must not be modified by the
7340 maintainer scripts during installation (or at any other
7345 In order to ensure that local changes are preserved
7346 correctly, no package may contain or make hard links to
7347 conffiles.<footnote>
7348 Rationale: There are two problems with hard links.
7349 The first is that some editors break the link while
7350 editing one of the files, so that the two files may
7351 unwittingly become unlinked and different. The second
7352 is that <prgn>dpkg</prgn> might break the hard link
7353 while upgrading <tt>conffile</tt>s.
7358 The other way to do it is via the maintainer scripts. In
7359 this case, the configuration file must not be listed as a
7360 <tt>conffile</tt> and must not be part of the package
7361 distribution. If the existence of a file is required for
7362 the package to be sensibly configured it is the
7363 responsibility of the package maintainer to provide
7364 maintainer scripts which correctly create, update and
7365 maintain the file and remove it on purge. (See <ref
7366 id="maintainerscripts"> for more information.) These
7367 scripts must be idempotent (i.e., must work correctly if
7368 <prgn>dpkg</prgn> needs to re-run them due to errors
7369 during installation or removal), must cope with all the
7370 variety of ways <prgn>dpkg</prgn> can call maintainer
7371 scripts, must not overwrite or otherwise mangle the user's
7372 configuration without asking, must not ask unnecessary
7373 questions (particularly during upgrades), and must
7374 otherwise be good citizens.
7378 The scripts are not required to configure every possible
7379 option for the package, but only those necessary to get
7380 the package running on a given system. Ideally the
7381 sysadmin should not have to do any configuration other
7382 than that done (semi-)automatically by the
7383 <prgn>postinst</prgn> script.
7387 A common practice is to create a script called
7388 <file><var>package</var>-configure</file> and have the
7389 package's <prgn>postinst</prgn> call it if and only if the
7390 configuration file does not already exist. In certain
7391 cases it is useful for there to be an example or template
7392 file which the maintainer scripts use. Such files should
7393 be in <file>/usr/share/<var>package</var></file> or
7394 <file>/usr/lib/<var>package</var></file> (depending on whether
7395 they are architecture-independent or not). There should
7396 be symbolic links to them from
7397 <file>/usr/share/doc/<var>package</var>/examples</file> if
7398 they are examples, and should be perfectly ordinary
7399 <prgn>dpkg</prgn>-handled files (<em>not</em>
7400 configuration files).
7404 These two styles of configuration file handling must
7405 not be mixed, for that way lies madness:
7406 <prgn>dpkg</prgn> will ask about overwriting the file
7407 every time the package is upgraded.
7412 <heading>Sharing configuration files</heading>
7415 Packages which specify the same file as a
7416 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7417 with each other. (This is an instance of the general rule
7418 about not sharing files. Note that neither alternatives
7419 nor diversions are likely to be appropriate in this case;
7420 in particular, <prgn>dpkg</prgn> does not handle diverted
7421 <tt>conffile</tt>s well.)
7425 The maintainer scripts must not alter a <tt>conffile</tt>
7426 of <em>any</em> package, including the one the scripts
7431 If two or more packages use the same configuration file
7432 and it is reasonable for both to be installed at the same
7433 time, one of these packages must be defined as
7434 <em>owner</em> of the configuration file, i.e., it will be
7435 the package which handles that file as a configuration
7436 file. Other packages that use the configuration file must
7437 depend on the owning package if they require the
7438 configuration file to operate. If the other package will
7439 use the configuration file if present, but is capable of
7440 operating without it, no dependency need be declared.
7444 If it is desirable for two or more related packages to
7445 share a configuration file <em>and</em> for all of the
7446 related packages to be able to modify that configuration
7447 file, then the following should be done:
7448 <enumlist compact="compact">
7450 One of the related packages (the "owning" package)
7451 will manage the configuration file with maintainer
7452 scripts as described in the previous section.
7455 The owning package should also provide a program
7456 that the other packages may use to modify the
7460 The related packages must use the provided program
7461 to make any desired modifications to the
7462 configuration file. They should either depend on
7463 the core package to guarantee that the configuration
7464 modifier program is available or accept gracefully
7465 that they cannot modify the configuration file if it
7466 is not. (This is in addition to the fact that the
7467 configuration file may not even be present in the
7474 Sometimes it's appropriate to create a new package which
7475 provides the basic infrastructure for the other packages
7476 and which manages the shared configuration files. (The
7477 <tt>sgml-base</tt> package is a good example.)
7482 <heading>User configuration files ("dotfiles")</heading>
7485 The files in <file>/etc/skel</file> will automatically be
7486 copied into new user accounts by <prgn>adduser</prgn>.
7487 No other program should reference the files in
7488 <file>/etc/skel</file>.
7492 Therefore, if a program needs a dotfile to exist in
7493 advance in <file>$HOME</file> to work sensibly, that dotfile
7494 should be installed in <file>/etc/skel</file> and treated as a
7499 However, programs that require dotfiles in order to
7500 operate sensibly are a bad thing, unless they do create
7501 the dotfiles themselves automatically.
7505 Furthermore, programs should be configured by the Debian
7506 default installation to behave as closely to the upstream
7507 default behavior as possible.
7511 Therefore, if a program in a Debian package needs to be
7512 configured in some way in order to operate sensibly, that
7513 should be done using a site-wide configuration file placed
7514 in <file>/etc</file>. Only if the program doesn't support a
7515 site-wide default configuration and the package maintainer
7516 doesn't have time to add it may a default per-user file be
7517 placed in <file>/etc/skel</file>.
7521 <file>/etc/skel</file> should be as empty as we can make it.
7522 This is particularly true because there is no easy (or
7523 necessarily desirable) mechanism for ensuring that the
7524 appropriate dotfiles are copied into the accounts of
7525 existing users when a package is installed.
7531 <heading>Log files</heading>
7533 Log files should usually be named
7534 <file>/var/log/<var>package</var>.log</file>. If you have many
7535 log files, or need a separate directory for permission
7536 reasons (<file>/var/log</file> is writable only by
7537 <file>root</file>), you should usually create a directory named
7538 <file>/var/log/<var>package</var></file> and place your log
7543 Log files must be rotated occasionally so that they don't
7544 grow indefinitely; the best way to do this is to drop a log
7545 rotation configuration file into the directory
7546 <file>/etc/logrotate.d</file> and use the facilities provided by
7547 logrotate.<footnote>
7549 The traditional approach to log files has been to set up
7550 <em>ad hoc</em> log rotation schemes using simple shell
7551 scripts and cron. While this approach is highly
7552 customizable, it requires quite a lot of sysadmin work.
7553 Even though the original Debian system helped a little
7554 by automatically installing a system which can be used
7555 as a template, this was deemed not enough.
7559 The use of <prgn>logrotate</prgn>, a program developed
7560 by Red Hat, is better, as it centralizes log management.
7561 It has both a configuration file
7562 (<file>/etc/logrotate.conf</file>) and a directory where
7563 packages can drop their individual log rotation
7564 configurations (<file>/etc/logrotate.d</file>).
7567 Here is a good example for a logrotate config
7568 file (for more information see <manref name="logrotate"
7570 <example compact="compact">
7571 /var/log/foo/*.log {
7576 /etc/init.d/foo force-reload
7580 This rotates all files under <file>/var/log/foo</file>, saves 12
7581 compressed generations, and forces the daemon to reload its
7582 configuration information after the log rotation.
7586 Log files should be removed when the package is
7587 purged (but not when it is only removed). This should be
7588 done by the <prgn>postrm</prgn> script when it is called
7589 with the argument <tt>purge</tt> (see <ref
7590 id="removedetails">).
7595 <heading>Permissions and owners</heading>
7598 The rules in this section are guidelines for general use.
7599 If necessary you may deviate from the details below.
7600 However, if you do so you must make sure that what is done
7601 is secure and you should try to be as consistent as possible
7602 with the rest of the system. You should probably also
7603 discuss it on <prgn>debian-devel</prgn> first.
7607 Files should be owned by <tt>root:root</tt>, and made
7608 writable only by the owner and universally readable (and
7609 executable, if appropriate), that is mode 644 or 755.
7613 Directories should be mode 755 or (for group-writability)
7614 mode 2775. The ownership of the directory should be
7615 consistent with its mode: if a directory is mode 2775, it
7616 should be owned by the group that needs write access to
7619 When a package is upgraded, and the owner or permissions
7620 of a file included in the package has changed, dpkg
7621 arranges for the ownership and permissions to be
7622 correctly set upon installation. However, this does not
7623 extend to directories; the permissions and ownership of
7624 directories already on the system does not change on
7625 install or upgrade of packages. This makes sense, since
7626 otherwise common directories like <tt>/usr</tt> would
7627 always be in flux. To correctly change permissions of a
7628 directory the package owns, explicit action is required,
7629 usually in the <tt>postinst</tt> script. Care must be
7630 taken to handle downgrades as well, in that case.
7637 Setuid and setgid executables should be mode 4755 or 2755
7638 respectively, and owned by the appropriate user or group.
7639 They should not be made unreadable (modes like 4711 or
7640 2711 or even 4111); doing so achieves no extra security,
7641 because anyone can find the binary in the freely available
7642 Debian package; it is merely inconvenient. For the same
7643 reason you should not restrict read or execute permissions
7644 on non-set-id executables.
7648 Some setuid programs need to be restricted to particular
7649 sets of users, using file permissions. In this case they
7650 should be owned by the uid to which they are set-id, and by
7651 the group which should be allowed to execute them. They
7652 should have mode 4754; again there is no point in making
7653 them unreadable to those users who must not be allowed to
7658 It is possible to arrange that the system administrator can
7659 reconfigure the package to correspond to their local
7660 security policy by changing the permissions on a binary:
7661 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7662 described below.<footnote>
7663 Ordinary files installed by <prgn>dpkg</prgn> (as
7664 opposed to <tt>conffile</tt>s and other similar objects)
7665 normally have their permissions reset to the distributed
7666 permissions when the package is reinstalled. However,
7667 the use of <prgn>dpkg-statoverride</prgn> overrides this
7668 default behavior. If you use this method, you should
7669 remember to describe <prgn>dpkg-statoverride</prgn> in
7670 the package documentation; being a relatively new
7671 addition to Debian, it is probably not yet well-known.
7673 Another method you should consider is to create a group for
7674 people allowed to use the program(s) and make any setuid
7675 executables executable only by that group.
7679 If you need to create a new user or group for your package
7680 there are two possibilities. Firstly, you may need to
7681 make some files in the binary package be owned by this
7682 user or group, or you may need to compile the user or
7683 group id (rather than just the name) into the binary
7684 (though this latter should be avoided if possible, as in
7685 this case you need a statically allocated id).</p>
7688 If you need a statically allocated id, you must ask for a
7689 user or group id from the <tt>base-passwd</tt> maintainer,
7690 and must not release the package until you have been
7691 allocated one. Once you have been allocated one you must
7692 either make the package depend on a version of the
7693 <tt>base-passwd</tt> package with the id present in
7694 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7695 your package to create the user or group itself with the
7696 correct id (using <tt>adduser</tt>) in its
7697 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7698 the <prgn>postinst</prgn> is to be preferred if it is
7699 possible, otherwise a pre-dependency will be needed on the
7700 <tt>adduser</tt> package.)
7704 On the other hand, the program might be able to determine
7705 the uid or gid from the user or group name at runtime, so
7706 that a dynamically allocated id can be used. In this case
7707 you should choose an appropriate user or group name,
7708 discussing this on <prgn>debian-devel</prgn> and checking
7709 with the <package/base-passwd/ maintainer that it is unique and that
7710 they do not wish you to use a statically allocated id
7711 instead. When this has been checked you must arrange for
7712 your package to create the user or group if necessary using
7713 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7714 <prgn>postinst</prgn> script (again, the latter is to be
7715 preferred if it is possible).
7719 Note that changing the numeric value of an id associated
7720 with a name is very difficult, and involves searching the
7721 file system for all appropriate files. You need to think
7722 carefully whether a static or dynamic id is required, since
7723 changing your mind later will cause problems.
7726 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7728 This section is not intended as policy, but as a
7729 description of the use of <prgn>dpkg-statoverride</prgn>.
7733 If a system administrator wishes to have a file (or
7734 directory or other such thing) installed with owner and
7735 permissions different from those in the distributed Debian
7736 package, they can use the <prgn>dpkg-statoverride</prgn>
7737 program to instruct <prgn>dpkg</prgn> to use the different
7738 settings every time the file is installed. Thus the
7739 package maintainer should distribute the files with their
7740 normal permissions, and leave it for the system
7741 administrator to make any desired changes. For example, a
7742 daemon which is normally required to be setuid root, but
7743 in certain situations could be used without being setuid,
7744 should be installed setuid in the <tt>.deb</tt>. Then the
7745 local system administrator can change this if they wish.
7746 If there are two standard ways of doing it, the package
7747 maintainer can use <tt>debconf</tt> to find out the
7748 preference, and call <prgn>dpkg-statoverride</prgn> in the
7749 maintainer script if necessary to accommodate the system
7750 administrator's choice. Care must be taken during
7751 upgrades to not override an existing setting.
7755 Given the above, <prgn>dpkg-statoverride</prgn> is
7756 essentially a tool for system administrators and would not
7757 normally be needed in the maintainer scripts. There is
7758 one type of situation, though, where calls to
7759 <prgn>dpkg-statoverride</prgn> would be needed in the
7760 maintainer scripts, and that involves packages which use
7761 dynamically allocated user or group ids. In such a
7762 situation, something like the following idiom can be very
7763 helpful in the package's <prgn>postinst</prgn>, where
7764 <tt>sysuser</tt> is a dynamically allocated id:
7766 for i in /usr/bin/foo /usr/sbin/bar
7768 # only do something when no setting exists
7769 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7771 #include: debconf processing, question about foo and bar
7772 if [ "$RET" = "true" ] ; then
7773 dpkg-statoverride --update --add sysuser root 4755 $i
7778 The corresponding <tt>dpkg-statoverride --remove</tt>
7779 calls can then be made unconditionally when the package is
7787 <chapt id="customized-programs">
7788 <heading>Customized programs</heading>
7790 <sect id="arch-spec">
7791 <heading>Architecture specification strings</heading>
7794 If a program needs to specify an <em>architecture specification
7795 string</em> in some place, it should select one of the
7796 strings provided by <tt>dpkg-architecture -L</tt>. The
7797 strings are in the format
7798 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7799 is sometimes elided, as when the OS is Linux.<footnote>
7800 <p>Currently, the strings are:
7801 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7802 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7803 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7804 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7805 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7806 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7807 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7808 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7809 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7810 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7811 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7812 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7813 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7814 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7815 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7816 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7817 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7818 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7819 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7820 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7821 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7822 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7823 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7824 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7825 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7826 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7827 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7828 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7829 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7830 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7831 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7832 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7833 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7834 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7835 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7836 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7837 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7843 Note that we don't want to use
7844 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7845 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7846 since this would make our programs incompatible with other
7847 Linux distributions. We also don't use something like
7848 <tt><var>arch</var>-unknown-linux</tt>, since the
7849 <tt>unknown</tt> does not look very good.
7854 <heading>Daemons</heading>
7857 The configuration files <file>/etc/services</file>,
7858 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7859 by the <prgn>netbase</prgn> package and must not be modified
7864 If a package requires a new entry in one of these files, the
7865 maintainer should get in contact with the
7866 <prgn>netbase</prgn> maintainer, who will add the entries
7867 and release a new version of the <prgn>netbase</prgn>
7872 The configuration file <file>/etc/inetd.conf</file> must not be
7873 modified by the package's scripts except via the
7874 <prgn>update-inetd</prgn> script or the
7875 <file>DebianNet.pm</file> Perl module. See their documentation
7876 for details on how to add entries.
7880 If a package wants to install an example entry into
7881 <file>/etc/inetd.conf</file>, the entry must be preceded with
7882 exactly one hash character (<tt>#</tt>). Such lines are
7883 treated as "commented out by user" by the
7884 <prgn>update-inetd</prgn> script and are not changed or
7885 activated during package updates.
7890 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7894 Some programs need to create pseudo-ttys. This should be done
7895 using Unix98 ptys if the C library supports it. The resulting
7896 program must not be installed setuid root, unless that
7897 is required for other functionality.
7901 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7902 <file>/var/log/lastlog</file> must be installed writable by
7903 group <tt>utmp</tt>. Programs which need to modify those
7904 files must be installed setgid <tt>utmp</tt>.
7909 <heading>Editors and pagers</heading>
7912 Some programs have the ability to launch an editor or pager
7913 program to edit or display a text document. Since there are
7914 lots of different editors and pagers available in the Debian
7915 distribution, the system administrator and each user should
7916 have the possibility to choose their preferred editor and
7921 In addition, every program should choose a good default
7922 editor/pager if none is selected by the user or system
7927 Thus, every program that launches an editor or pager must
7928 use the EDITOR or PAGER environment variable to determine
7929 the editor or pager the user wishes to use. If these
7930 variables are not set, the programs <file>/usr/bin/editor</file>
7931 and <file>/usr/bin/pager</file> should be used, respectively.
7935 These two files are managed through the <prgn>dpkg</prgn>
7936 "alternatives" mechanism. Thus every package providing an
7937 editor or pager must call the
7938 <prgn>update-alternatives</prgn> script to register these
7943 If it is very hard to adapt a program to make use of the
7944 EDITOR or PAGER variables, that program may be configured to
7945 use <file>/usr/bin/sensible-editor</file> and
7946 <file>/usr/bin/sensible-pager</file> as the editor or pager
7947 program respectively. These are two scripts provided in the
7948 Debian base system that check the EDITOR and PAGER variables
7949 and launch the appropriate program, and fall back to
7950 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7951 variable is not set.
7955 A program may also use the VISUAL environment variable to
7956 determine the user's choice of editor. If it exists, it
7957 should take precedence over EDITOR. This is in fact what
7958 <file>/usr/bin/sensible-editor</file> does.
7962 It is not required for a package to depend on
7963 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7964 package to provide such virtual packages.<footnote>
7965 The Debian base system already provides an editor and a
7971 <sect id="web-appl">
7972 <heading>Web servers and applications</heading>
7975 This section describes the locations and URLs that should
7976 be used by all web servers and web applications in the
7983 Cgi-bin executable files are installed in the
7985 <example compact="compact">
7986 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7988 and should be referred to as
7989 <example compact="compact">
7990 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7996 <p>Access to HTML documents</p>
7999 HTML documents for a package are stored in
8000 <file>/usr/share/doc/<var>package</var></file>
8001 and can be referred to as
8002 <example compact="compact">
8003 http://localhost/doc/<var>package</var>/<var>filename</var>
8008 The web server should restrict access to the document
8009 tree so that only clients on the same host can read
8010 the documents. If the web server does not support such
8011 access controls, then it should not provide access at
8012 all, or ask about providing access during installation.
8017 <p>Access to images</p>
8019 It is recommended that images for a package be stored
8020 in <tt>/usr/share/images/<var>package</var></tt> and
8021 may be referred to through an alias <tt>/images/</tt>
8024 http://localhost/images/<package>/<filename>
8031 <p>Web Document Root</p>
8034 Web Applications should try to avoid storing files in
8035 the Web Document Root. Instead they should use the
8036 /usr/share/doc/<var>package</var> directory for
8037 documents and register the Web Application via the
8038 <package>doc-base</package> package. If access to the
8039 web document root is unavoidable then use
8040 <example compact="compact">
8043 as the Document Root. This might be just a symbolic
8044 link to the location where the system administrator
8045 has put the real document root.
8048 <item><p>Providing httpd and/or httpd-cgi</p>
8050 All web servers should provide the virtual package
8051 <tt>httpd</tt>. If a web server has CGI support it should
8052 provide <tt>httpd-cgi</tt> additionally.
8055 All web applications which do not contain CGI scripts should
8056 depend on <tt>httpd</tt>, all those web applications which
8057 <tt>do</tt> contain CGI scripts, should depend on
8065 <sect id="mail-transport-agents">
8066 <heading>Mail transport, delivery and user agents</heading>
8069 Debian packages which process electronic mail, whether mail
8070 user agents (MUAs) or mail transport agents (MTAs), must
8071 ensure that they are compatible with the configuration
8072 decisions below. Failure to do this may result in lost
8073 mail, broken <tt>From:</tt> lines, and other serious brain
8078 The mail spool is <file>/var/mail</file> and the interface to
8079 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8080 the FHS). On older systems, the mail spool may be
8081 physically located in <file>/var/spool/mail</file>, but all
8082 access to the mail spool should be via the
8083 <file>/var/mail</file> symlink. The mail spool is part of the
8084 base system and not part of the MTA package.
8088 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8089 programs (such as IMAP daemons) must lock the mailbox in an
8090 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8091 be combined with dot locking. To avoid deadlocks, a program
8092 should use <tt>fcntl()</tt> first and dot locking after
8093 this, or alternatively implement the two locking methods in
8094 a non blocking way<footnote>
8095 If it is not possible to establish both locks, the
8096 system shouldn't wait for the second lock to be
8097 established, but remove the first lock, wait a (random)
8098 time, and start over locking again.
8099 </footnote>. Using the functions <tt>maillock</tt> and
8100 <tt>mailunlock</tt> provided by the
8101 <tt>liblockfile*</tt><footnote>
8102 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8103 to use these functions.
8104 </footnote> packages is the recommended way to realize this.
8108 Mailboxes are generally either mode 600 and owned by
8109 <var>user</var> or mode 660 and owned by
8110 <tt><var>user</var>:mail</tt><footnote>
8111 There are two traditional permission schemes for mail spools:
8112 mode 600 with all mail delivery done by processes running as
8113 the destination user, or mode 660 and owned by group mail with
8114 mail delivery done by a process running as a system user in
8115 group mail. Historically, Debian required mode 660 mail
8116 spools to enable the latter model, but that model has become
8117 increasingly uncommon and the principle of least privilege
8118 indicates that mail systems that use the first model should
8119 use permissions of 600. If delivery to programs is permitted,
8120 it's easier to keep the mail system secure if the delivery
8121 agent runs as the destination user. Debian Policy therefore
8122 permits either scheme.
8123 </footnote>. The local system administrator may choose a
8124 different permission scheme; packages should not make
8125 assumptions about the permission and ownership of mailboxes
8126 unless required (such as when creating a new mailbox). A MUA
8127 may remove a mailbox (unless it has nonstandard permissions) in
8128 which case the MTA or another MUA must recreate it if needed.
8132 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8133 be setgid mail to do the locking mentioned above (and
8134 must obviously avoid accessing other users' mailboxes
8135 using this privilege).</p>
8138 <file>/etc/aliases</file> is the source file for the system mail
8139 aliases (e.g., postmaster, usenet, etc.), it is the one
8140 which the sysadmin and <prgn>postinst</prgn> scripts may
8141 edit. After <file>/etc/aliases</file> is edited the program or
8142 human editing it must call <prgn>newaliases</prgn>. All MTA
8143 packages must come with a <prgn>newaliases</prgn> program,
8144 even if it does nothing, but older MTA packages did not do
8145 this so programs should not fail if <prgn>newaliases</prgn>
8146 cannot be found. Note that because of this, all MTA
8147 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8148 <tt>Replaces: mail-transport-agent</tt> control file
8153 The convention of writing <tt>forward to
8154 <var>address</var></tt> in the mailbox itself is not
8155 supported. Use a <tt>.forward</tt> file instead.</p>
8158 The <prgn>rmail</prgn> program used by UUCP
8159 for incoming mail should be <file>/usr/sbin/rmail</file>.
8160 Likewise, <prgn>rsmtp</prgn>, for receiving
8161 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8165 If your package needs to know what hostname to use on (for
8166 example) outgoing news and mail messages which are generated
8167 locally, you should use the file <file>/etc/mailname</file>. It
8168 will contain the portion after the username and <tt>@</tt>
8169 (at) sign for email addresses of users on the machine
8170 (followed by a newline).
8174 Such a package should check for the existence of this file
8175 when it is being configured. If it exists, it should be
8176 used without comment, although an MTA's configuration script
8177 may wish to prompt the user even if it finds that this file
8178 exists. If the file does not exist, the package should
8179 prompt the user for the value (preferably using
8180 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8181 as well as using it in the package's configuration. The
8182 prompt should make it clear that the name will not just be
8183 used by that package. For example, in this situation the
8184 <tt>inn</tt> package could say something like:
8185 <example compact="compact">
8186 Please enter the "mail name" of your system. This is the
8187 hostname portion of the address to be shown on outgoing
8188 news and mail messages. The default is
8189 <var>syshostname</var>, your system's host name. Mail
8190 name ["<var>syshostname</var>"]:
8192 where <var>syshostname</var> is the output of <tt>hostname
8198 <heading>News system configuration</heading>
8201 All the configuration files related to the NNTP (news)
8202 servers and clients should be located under
8203 <file>/etc/news</file>.</p>
8206 There are some configuration issues that apply to a number
8207 of news clients and server packages on the machine. These
8211 <tag><file>/etc/news/organization</file></tag>
8213 A string which should appear as the
8214 organization header for all messages posted
8215 by NNTP clients on the machine
8218 <tag><file>/etc/news/server</file></tag>
8220 Contains the FQDN of the upstream NNTP
8221 server, or localhost if the local machine is
8226 Other global files may be added as required for cross-package news
8233 <heading>Programs for the X Window System</heading>
8236 <heading>Providing X support and package priorities</heading>
8239 Programs that can be configured with support for the X
8240 Window System must be configured to do so and must declare
8241 any package dependencies necessary to satisfy their
8242 runtime requirements when using the X Window System. If
8243 such a package is of higher priority than the X packages
8244 on which it depends, it is required that either the
8245 X-specific components be split into a separate package, or
8246 that an alternative version of the package, which includes
8247 X support, be provided, or that the package's priority be
8253 <heading>Packages providing an X server</heading>
8256 Packages that provide an X server that, directly or
8257 indirectly, communicates with real input and display
8258 hardware should declare in their control data that they
8259 provide the virtual package <tt>xserver</tt>.<footnote>
8260 This implements current practice, and provides an
8261 actual policy for usage of the <tt>xserver</tt>
8262 virtual package which appears in the virtual packages
8263 list. In a nutshell, X servers that interface
8264 directly with the display and input hardware or via
8265 another subsystem (e.g., GGI) should provide
8266 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8267 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8273 <heading>Packages providing a terminal emulator</heading>
8276 Packages that provide a terminal emulator for the X Window
8277 System which meet the criteria listed below should declare
8278 in their control data that they provide the virtual
8279 package <tt>x-terminal-emulator</tt>. They should also
8280 register themselves as an alternative for
8281 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8286 To be an <tt>x-terminal-emulator</tt>, a program must:
8287 <list compact="compact">
8289 Be able to emulate a DEC VT100 terminal, or a
8290 compatible terminal.
8294 Support the command-line option <tt>-e
8295 <var>command</var></tt>, which creates a new
8296 terminal window<footnote>
8297 "New terminal window" does not necessarily mean
8298 a new top-level X window directly parented by
8299 the window manager; it could, if the terminal
8300 emulator application were so coded, be a new
8301 "view" in a multiple-document interface (MDI).
8303 and runs the specified <var>command</var>,
8304 interpreting the entirety of the rest of the command
8305 line as a command to pass straight to exec, in the
8306 manner that <tt>xterm</tt> does.
8310 Support the command-line option <tt>-T
8311 <var>title</var></tt>, which creates a new terminal
8312 window with the window title <var>title</var>.
8319 <heading>Packages providing a window manager</heading>
8322 Packages that provide a window manager should declare in
8323 their control data that they provide the virtual package
8324 <tt>x-window-manager</tt>. They should also register
8325 themselves as an alternative for
8326 <file>/usr/bin/x-window-manager</file>, with a priority
8327 calculated as follows:
8328 <list compact="compact">
8330 Start with a priority of 20.
8334 If the window manager supports the Debian menu
8335 system, add 20 points if this support is available
8336 in the package's default configuration (i.e., no
8337 configuration files belonging to the system or user
8338 have to be edited to activate the feature); if
8339 configuration files must be modified, add only 10
8345 If the window manager complies with <url
8346 id="http://www.freedesktop.org/Standards/wm-spec"
8347 name="The Window Manager Specification Project">,
8348 written by the <url id="http://www.freedesktop.org/"
8349 name="Free Desktop Group">, add 40 points.
8353 If the window manager permits the X session to be
8354 restarted using a <em>different</em> window manager
8355 (without killing the X server) in its default
8356 configuration, add 10 points; otherwise add none.
8363 <heading>Packages providing fonts</heading>
8366 Packages that provide fonts for the X Window
8368 For the purposes of Debian Policy, a "font for the X
8369 Window System" is one which is accessed via X protocol
8370 requests. Fonts for the Linux console, for PostScript
8371 renderer, or any other purpose, do not fit this
8372 definition. Any tool which makes such fonts available
8373 to the X Window System, however, must abide by this
8376 must do a number of things to ensure that they are both
8377 available without modification of the X or font server
8378 configuration, and that they do not corrupt files used by
8379 other font packages to register information about
8383 Fonts of any type supported by the X Window System
8384 must be in a separate binary package from any
8385 executables, libraries, or documentation (except
8386 that specific to the fonts shipped, such as their
8387 license information). If one or more of the fonts
8388 so packaged are necessary for proper operation of
8389 the package with which they are associated the font
8390 package may be Recommended; if the fonts merely
8391 provide an enhancement, a Suggests relationship may
8392 be used. Packages must not Depend on font
8394 This is because the X server may retrieve fonts
8395 from the local file system or over the network
8396 from an X font server; the Debian package system
8397 is empowered to deal only with the local
8403 BDF fonts must be converted to PCF fonts with the
8404 <prgn>bdftopcf</prgn> utility (available in the
8405 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8406 placed in a directory that corresponds to their
8408 <list compact="compact">
8410 100 dpi fonts must be placed in
8411 <file>/usr/share/fonts/X11/100dpi/</file>.
8415 75 dpi fonts must be placed in
8416 <file>/usr/share/fonts/X11/75dpi/</file>.
8420 Character-cell fonts, cursor fonts, and other
8421 low-resolution fonts must be placed in
8422 <file>/usr/share/fonts/X11/misc/</file>.
8428 Speedo fonts must be placed in
8429 <file>/usr/share/fonts/X11/Speedo/</file>.
8433 Type 1 fonts must be placed in
8434 <file>/usr/share/fonts/X11/Type1/</file>. If font
8435 metric files are available, they must be placed here
8440 Subdirectories of <file>/usr/share/fonts/X11/</file>
8441 other than those listed above must be neither
8442 created nor used. (The <file>PEX</file>, <file>CID</file>,
8443 and <file>cyrillic</file> directories are excepted for
8444 historical reasons, but installation of files into
8445 these directories remains discouraged.)
8449 Font packages may, instead of placing files directly
8450 in the X font directories listed above, provide
8451 symbolic links in that font directory pointing to
8452 the files' actual location in the filesystem. Such
8453 a location must comply with the FHS.
8457 Font packages should not contain both 75dpi and
8458 100dpi versions of a font. If both are available,
8459 they should be provided in separate binary packages
8460 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8461 the names of the packages containing the
8462 corresponding fonts.
8466 Fonts destined for the <file>misc</file> subdirectory
8467 should not be included in the same package as 75dpi
8468 or 100dpi fonts; instead, they should be provided in
8469 a separate package with <tt>-misc</tt> appended to
8474 Font packages must not provide the files
8475 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8476 <file>fonts.scale</file> in a font directory:
8479 <file>fonts.dir</file> files must not be provided at all.
8483 <file>fonts.alias</file> and <file>fonts.scale</file>
8484 files, if needed, should be provided in the
8486 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8487 where <var>fontdir</var> is the name of the
8489 <file>/usr/share/fonts/X11/</file> where the
8490 package's corresponding fonts are stored
8491 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8492 <var>package</var> is the name of the package
8493 that provides these fonts, and
8494 <var>extension</var> is either <tt>scale</tt>
8495 or <tt>alias</tt>, whichever corresponds to
8502 Font packages must declare a dependency on
8503 <tt>xfonts-utils</tt> in their control
8508 Font packages that provide one or more
8509 <file>fonts.scale</file> files as described above must
8510 invoke <prgn>update-fonts-scale</prgn> on each
8511 directory into which they installed fonts
8512 <em>before</em> invoking
8513 <prgn>update-fonts-dir</prgn> on that directory.
8514 This invocation must occur in both the
8515 <prgn>postinst</prgn> (for all arguments) and
8516 <prgn>postrm</prgn> (for all arguments except
8517 <tt>upgrade</tt>) scripts.
8521 Font packages that provide one or more
8522 <file>fonts.alias</file> files as described above must
8523 invoke <prgn>update-fonts-alias</prgn> on each
8524 directory into which they installed fonts. This
8525 invocation must occur in both the
8526 <prgn>postinst</prgn> (for all arguments) and
8527 <prgn>postrm</prgn> (for all arguments except
8528 <tt>upgrade</tt>) scripts.
8532 Font packages must invoke
8533 <prgn>update-fonts-dir</prgn> on each directory into
8534 which they installed fonts. This invocation must
8535 occur in both the <prgn>postinst</prgn> (for all
8536 arguments) and <prgn>postrm</prgn> (for all
8537 arguments except <tt>upgrade</tt>) scripts.
8541 Font packages must not provide alias names for the
8542 fonts they include which collide with alias names
8543 already in use by fonts already packaged.
8547 Font packages must not provide fonts with the same
8548 XLFD registry name as another font already packaged.
8555 <heading>Application defaults files</heading>
8558 Application defaults files must be installed in the
8559 directory <file>/etc/X11/app-defaults/</file> (use of a
8560 localized subdirectory of <file>/etc/X11/</file> as described
8561 in the <em>X Toolkit Intrinsics - C Language
8562 Interface</em> manual is also permitted). They must be
8563 registered as <tt>conffile</tt>s or handled as
8564 configuration files.
8568 Customization of programs' X resources may also be
8569 supported with the provision of a file with the same name
8570 as that of the package placed in the
8571 <file>/etc/X11/Xresources/</file> directory, which must
8572 registered as a <tt>conffile</tt> or handled as a
8573 configuration file.<footnote>
8574 Note that this mechanism is not the same as using
8575 app-defaults; app-defaults are tied to the client
8576 binary on the local file system, whereas X resources
8577 are stored in the X server and affect all connecting
8584 <heading>Installation directory issues</heading>
8587 Packages using the X Window System should not be
8588 configured to install files under the
8589 <file>/usr/X11R6/</file> directory. The
8590 <file>/usr/X11R6/</file> directory hierarchy should be
8591 regarded as obsolete.
8595 Programs that use GNU <prgn>autoconf</prgn> and
8596 <prgn>automake</prgn> are usually easily configured at
8597 compile time to use <file>/usr/</file> instead of
8598 <file>/usr/X11R6/</file>, and this should be done whenever
8599 possible. Configuration files for window managers and
8600 display managers should be placed in a subdirectory of
8601 <file>/etc/X11/</file> corresponding to the package name due
8602 to these programs' tight integration with the mechanisms
8603 of the X Window System. Application-level programs should
8604 use the <file>/etc/</file> directory unless otherwise mandated
8609 The installation of files into subdirectories
8610 of <file>/usr/X11R6/include/X11/</file> and
8611 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8612 package maintainers should determine if subdirectories of
8613 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8618 Packages should install any relevant files into the
8619 directories <file>/usr/include/X11/</file> and
8620 <file>/usr/lib/X11/</file>, but if they do so, they must
8621 pre-depend on <tt>x11-common (>=
8622 1:7.0.0)</tt><footnote>
8624 These libraries used to be all symbolic
8625 links. However, with <tt>X11R7</tt>,
8626 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8627 are now real directories, and packages
8628 <strong>should</strong> ship their files here instead
8629 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8630 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8631 responsible for converting these symlinks into
8639 <heading>The OSF/Motif and OpenMotif libraries</heading>
8642 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8643 OpenMotif libraries</em><footnote>
8644 OSF/Motif and OpenMotif are collectively referred to as
8645 "Motif" in this policy document.
8647 should be compiled against and tested with LessTif (a free
8648 re-implementation of Motif) instead. If the maintainer
8649 judges that the program or programs do not work
8650 sufficiently well with LessTif to be distributed and
8651 supported, but do so when compiled against Motif, then two
8652 versions of the package should be created; one linked
8653 statically against Motif and with <tt>-smotif</tt>
8654 appended to the package name, and one linked dynamically
8655 against Motif and with <tt>-dmotif</tt> appended to the
8660 Both Motif-linked versions are dependent
8661 upon non-DFSG-compliant software and thus cannot be
8662 uploaded to the <em>main</em> distribution; if the
8663 software is itself DFSG-compliant it may be uploaded to
8664 the <em>contrib</em> distribution. While known existing
8665 versions of Motif permit unlimited redistribution of
8666 binaries linked against the library (whether statically or
8667 dynamically), it is the package maintainer's
8668 responsibility to determine whether this is permitted by
8669 the license of the copy of Motif in their possession.
8675 <heading>Perl programs and modules</heading>
8678 Perl programs and modules should follow the current Perl policy.
8682 The Perl policy can be found in the <tt>perl-policy</tt>
8683 files in the <tt>debian-policy</tt> package.
8684 It is also available from the Debian web mirrors at
8685 <tt><url name="/doc/packaging-manuals/perl-policy/"
8686 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8691 <heading>Emacs lisp programs</heading>
8694 Please refer to the "Debian Emacs Policy" for details of how to
8695 package emacs lisp programs.
8699 The Emacs policy is available in
8700 <file>debian-emacs-policy.gz</file> of the
8701 <package>emacsen-common</package> package.
8702 It is also available from the Debian web mirrors at
8703 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8704 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8709 <heading>Games</heading>
8712 The permissions on <file>/var/games</file> are mode 755, owner
8713 <tt>root</tt> and group <tt>root</tt>.
8717 Each game decides on its own security policy.</p>
8720 Games which require protected, privileged access to
8721 high-score files, saved games, etc., may be made
8722 set-<em>group</em>-id (mode 2755) and owned by
8723 <tt>root:games</tt>, and use files and directories with
8724 appropriate permissions (770 <tt>root:games</tt>, for
8725 example). They must not be made
8726 set-<em>user</em>-id, as this causes security problems. (If
8727 an attacker can subvert any set-user-id game they can
8728 overwrite the executable of any other, causing other players
8729 of these games to run a Trojan horse program. With a
8730 set-group-id game the attacker only gets access to less
8731 important game data, and if they can get at the other
8732 players' accounts at all it will take considerably more
8736 Some packages, for example some fortune cookie programs, are
8737 configured by the upstream authors to install with their
8738 data files or other static information made unreadable so
8739 that they can only be accessed through set-id programs
8740 provided. You should not do this in a Debian package: anyone can
8741 download the <file>.deb</file> file and read the data from it,
8742 so there is no point making the files unreadable. Not
8743 making the files unreadable also means that you don't have
8744 to make so many programs set-id, which reduces the risk of a
8748 As described in the FHS, binaries of games should be
8749 installed in the directory <file>/usr/games</file>. This also
8750 applies to games that use the X Window System. Manual pages
8751 for games (X and non-X games) should be installed in
8752 <file>/usr/share/man/man6</file>.</p>
8758 <heading>Documentation</heading>
8761 <heading>Manual pages</heading>
8764 You should install manual pages in <prgn>nroff</prgn> source
8765 form, in appropriate places under <file>/usr/share/man</file>.
8766 You should only use sections 1 to 9 (see the FHS for more
8767 details). You must not install a pre-formatted "cat page".
8771 Each program, utility, and function should have an
8772 associated manual page included in the same package. It is
8773 suggested that all configuration files also have a manual
8774 page included as well. Manual pages for protocols and other
8775 auxiliary things are optional.
8779 If no manual page is available, this is considered as a bug
8780 and should be reported to the Debian Bug Tracking System (the
8781 maintainer of the package is allowed to write this bug report
8782 themselves, if they so desire). Do not close the bug report
8783 until a proper man page is available.<footnote>
8784 It is not very hard to write a man page. See the
8785 <url id="http://www.schweikhardt.net/man_page_howto.html"
8786 name="Man-Page-HOWTO">,
8787 <manref name="man" section="7">, the examples
8788 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8789 the helper programs <prgn>help2man</prgn>, or the
8790 directory <file>/usr/share/doc/man-db/examples</file>.
8795 You may forward a complaint about a missing man page to the
8796 upstream authors, and mark the bug as forwarded in the
8797 Debian bug tracking system. Even though the GNU Project do
8798 not in general consider the lack of a man page to be a bug,
8799 we do; if they tell you that they don't consider it a bug
8800 you should leave the bug in our bug tracking system open
8805 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8809 If one man page needs to be accessible via several names it
8810 is better to use a symbolic link than the <file>.so</file>
8811 feature, but there is no need to fiddle with the relevant
8812 parts of the upstream source to change from <file>.so</file> to
8813 symlinks: don't do it unless it's easy. You should not
8814 create hard links in the manual page directories, nor put
8815 absolute filenames in <file>.so</file> directives. The filename
8816 in a <file>.so</file> in a man page should be relative to the
8817 base of the man page tree (usually
8818 <file>/usr/share/man</file>). If you do not create any links
8819 (whether symlinks, hard links, or <tt>.so</tt> directives)
8820 in the file system to the alternate names of the man page,
8821 then you should not rely on <prgn>man</prgn> finding your
8822 man page under those names based solely on the information in
8823 the man page's header.<footnote>
8824 Supporting this in <prgn>man</prgn> often requires
8825 unreasonable processing time to find a manual page or to
8826 report that none exists, and moves knowledge into man's
8827 database that would be better left in the file system.
8828 This support is therefore deprecated and will cease to
8829 be present in the future.
8834 Manual pages in locale-specific subdirectories of
8835 <file>/usr/share/man</file> should use either UTF-8 or the usual
8836 legacy encoding for that language (normally the one corresponding
8837 to the shortest relevant locale name in
8838 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8839 <file>/usr/share/man/fr</file> should use either UTF-8 or
8840 ISO-8859-1.<footnote>
8841 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8842 use. In future, all manual pages will be required to use
8848 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8849 included in the subdirectory name unless it indicates a
8850 significant difference in the language, as this excludes
8851 speakers of the language in other countries.<footnote>
8852 At the time of writing, Chinese and Portuguese are the main
8853 languages with such differences, so <file>pt_BR</file>,
8854 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8859 Due to limitations in current implementations, all characters
8860 in the manual page source should be representable in the usual
8861 legacy encoding for that language, even if the file is
8862 actually encoded in UTF-8. Safe alternative ways to write many
8863 characters outside that range may be found in
8864 <manref name="groff_char" section="7">.
8869 <heading>Info documents</heading>
8872 Info documents should be installed in <file>/usr/share/info</file>.
8873 They should be compressed with <tt>gzip -9</tt>.
8877 Your package should call <prgn>install-info</prgn> to update
8878 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8879 script when called with a <tt>configure</tt> argument, for
8881 <example compact="compact">
8882 install-info --quiet --section Development Development \
8883 /usr/share/info/foobar.info
8887 It is a good idea to specify a section for the location of
8888 your program; this is done with the <tt>--section</tt>
8889 switch. To determine which section to use, you should look
8890 at <file>/usr/share/info/dir</file> on your system and choose the most
8891 relevant (or create a new section if none of the current
8892 sections are relevant). Note that the <tt>--section</tt>
8893 flag takes two arguments; the first is a regular expression
8894 to match (case-insensitively) against an existing section,
8895 the second is used when creating a new one.</p>
8898 You should remove the entries in the <prgn>prerm</prgn>
8899 script when called with a <tt>remove</tt> argument:
8900 <example compact="compact">
8901 install-info --quiet --remove /usr/share/info/foobar.info
8905 If <prgn>install-info</prgn> cannot find a description entry
8906 in the Info file you must supply one. See <manref
8907 name="install-info" section="8"> for details.</p>
8911 <heading>Additional documentation</heading>
8914 Any additional documentation that comes with the package may
8915 be installed at the discretion of the package maintainer.
8916 Plain text documentation should be installed in the directory
8917 <file>/usr/share/doc/<var>package</var></file>, where
8918 <var>package</var> is the name of the package, and
8919 compressed with <tt>gzip -9</tt> unless it is small.
8923 If a package comes with large amounts of documentation which
8924 many users of the package will not require you should create
8925 a separate binary package to contain it, so that it does not
8926 take up disk space on the machines of users who do not need
8927 or want it installed.</p>
8930 It is often a good idea to put text information files
8931 (<file>README</file>s, changelogs, and so forth) that come with
8932 the source package in <file>/usr/share/doc/<var>package</var></file>
8933 in the binary package. However, you don't need to install
8934 the instructions for building and installing the package, of
8938 Packages must not require the existence of any files in
8939 <file>/usr/share/doc/</file> in order to function
8941 The system administrator should be able to
8942 delete files in <file>/usr/share/doc/</file> without causing
8943 any programs to break.
8945 Any files that are referenced by programs but are also
8946 useful as stand alone documentation should be installed under
8947 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8948 <file>/usr/share/doc/<var>package</var></file>.
8952 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8953 link to another directory in <file>/usr/share/doc</file> only if
8954 the two packages both come from the same source and the
8955 first package Depends on the second.<footnote>
8957 Please note that this does not override the section on
8958 changelog files below, so the file
8959 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8960 must refer to the changelog for the current version of
8961 <var>package</var> in question. In practice, this means
8962 that the sources of the target and the destination of the
8963 symlink must be the same (same source package and
8970 Former Debian releases placed all additional documentation
8971 in <file>/usr/doc/<var>package</var></file>. This has been
8972 changed to <file>/usr/share/doc/<var>package</var></file>,
8973 and packages must not put documentation in the directory
8974 <file>/usr/doc/<var>package</var></file>. <footnote>
8975 At this phase of the transition, we no longer require a
8976 symbolic link in <file>/usr/doc/</file>. At a later point,
8977 policy shall change to make the symbolic links a bug.
8983 <heading>Preferred documentation formats</heading>
8986 The unification of Debian documentation is being carried out
8990 If your package comes with extensive documentation in a
8991 markup format that can be converted to various other formats
8992 you should if possible ship HTML versions in a binary
8993 package, in the directory
8994 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8995 its subdirectories.<footnote>
8996 The rationale: The important thing here is that HTML
8997 docs should be available in <em>some</em> package, not
8998 necessarily in the main binary package.
9003 Other formats such as PostScript may be provided at the
9004 package maintainer's discretion.
9008 <sect id="copyrightfile">
9009 <heading>Copyright information</heading>
9012 Every package must be accompanied by a verbatim copy of its
9013 copyright and distribution license in the file
9014 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9015 file must neither be compressed nor be a symbolic link.
9019 In addition, the copyright file must say where the upstream
9020 sources (if any) were obtained. It should name the original
9021 authors of the package and the Debian maintainer(s) who were
9022 involved with its creation.
9026 Packages in the <em>contrib</em> or <em>non-free</em> archive
9027 areas should state in the copyright file that the package is not
9028 part of the Debian GNU/Linux distribution and briefly explain
9033 A copy of the file which will be installed in
9034 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9035 be in <file>debian/copyright</file> in the source package.
9039 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9040 link to another directory in <file>/usr/share/doc</file> only if
9041 the two packages both come from the same source and the
9042 first package Depends on the second. These rules are
9043 important because copyrights must be extractable by
9048 Packages distributed under the UCB BSD license, the Apache
9049 license (version 2.0), the Artistic license, the GNU GPL
9050 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
9051 the GNU FDL (version 1.2) should refer to the corresponding
9052 files under <file>/usr/share/common-licenses</file>,<footnote>
9055 <file>/usr/share/common-licenses/BSD</file>,
9056 <file>/usr/share/common-licenses/Apache-2.0</file>,
9057 <file>/usr/share/common-licenses/Artistic</file>,
9058 <file>/usr/share/common-licenses/GPL-2</file>,
9059 <file>/usr/share/common-licenses/GPL-3</file>,
9060 <file>/usr/share/common-licenses/LGPL-2</file>,
9061 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9062 <file>/usr/share/common-licenses/LGPL-3</file>, and
9063 <file>/usr/share/common-licenses/GFDL-1.2</file>
9066 </footnote> rather than quoting them in the copyright
9071 You should not use the copyright file as a general <file>README</file>
9072 file. If your package has such a file it should be
9073 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9074 <file>README.Debian</file> or some other appropriate place.</p>
9078 <heading>Examples</heading>
9081 Any examples (configurations, source files, whatever),
9082 should be installed in a directory
9083 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9084 files should not be referenced by any program: they're there
9085 for the benefit of the system administrator and users as
9086 documentation only. Architecture-specific example files
9087 should be installed in a directory
9088 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9090 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9091 latter directory itself may be a symbolic link to the
9096 If the purpose of a package is to provide examples, then the
9097 example files may be installed into
9098 <file>/usr/share/doc/<var>package</var></file>.
9102 <sect id="changelogs">
9103 <heading>Changelog files</heading>
9106 Packages that are not Debian-native must contain a
9107 compressed copy of the <file>debian/changelog</file> file from
9108 the Debian source tree in
9109 <file>/usr/share/doc/<var>package</var></file> with the name
9110 <file>changelog.Debian.gz</file>.
9114 If an upstream changelog is available, it should be accessible as
9115 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9116 plain text. If the upstream changelog is distributed in
9117 HTML, it should be made available in that form as
9118 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9119 and a plain text <file>changelog.gz</file> should be generated
9120 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9121 the upstream changelog files do not already conform to this
9122 naming convention, then this may be achieved either by
9123 renaming the files, or by adding a symbolic link, at the
9124 maintainer's discretion.<footnote>
9125 Rationale: People should not have to look in places for
9126 upstream changelogs merely because they are given
9127 different names or are distributed in HTML format.
9132 All of these files should be installed compressed using
9133 <tt>gzip -9</tt>, as they will become large with time even
9134 if they start out small.
9138 If the package has only one changelog which is used both as
9139 the Debian changelog and the upstream one because there is
9140 no separate upstream maintainer then that changelog should
9141 usually be installed as
9142 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9143 there is a separate upstream maintainer, but no upstream
9144 changelog, then the Debian changelog should still be called
9145 <file>changelog.Debian.gz</file>.
9149 For details about the format and contents of the Debian
9150 changelog file, please see <ref id="dpkgchangelog">.
9155 <appendix id="pkg-scope">
9156 <heading>Introduction and scope of these appendices</heading>
9159 These appendices are taken essentially verbatim from the
9160 now-deprecated Packaging Manual, version 3.2.1.0. They are
9161 the chapters which are likely to be of use to package
9162 maintainers and which have not already been included in the
9163 policy document itself. Most of these sections are very likely
9164 not relevant to policy; they should be treated as
9165 documentation for the packaging system. Please note that these
9166 appendices are included for convenience, and for historical
9167 reasons: they used to be part of policy package, and they have
9168 not yet been incorporated into dpkg documentation. However,
9169 they still have value, and hence they are presented here.
9173 They have not yet been checked to ensure that they are
9174 compatible with the contents of policy, and if there are any
9175 contradictions, the version in the main policy document takes
9176 precedence. The remaining chapters of the old Packaging
9177 Manual have also not been read in detail to ensure that there
9178 are not parts which have been left out. Both of these will be
9183 Certain parts of the Packaging manual were integrated into the
9184 Policy Manual proper, and removed from the appendices. Links
9185 have been placed from the old locations to the new ones.
9189 <prgn>dpkg</prgn> is a suite of programs for creating binary
9190 package files and installing and removing them on Unix
9192 <prgn>dpkg</prgn> is targeted primarily at Debian
9193 GNU/Linux, but may work on or be ported to other
9199 The binary packages are designed for the management of
9200 installed executable programs (usually compiled binaries) and
9201 their associated data, though source code examples and
9202 documentation are provided as part of some packages.</p>
9205 This manual describes the technical aspects of creating Debian
9206 binary packages (<file>.deb</file> files). It documents the
9207 behavior of the package management programs
9208 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9209 they interact with packages.</p>
9212 It also documents the interaction between
9213 <prgn>dselect</prgn>'s core and the access method scripts it
9214 uses to actually install the selected packages, and describes
9215 how to create a new access method.</p>
9218 This manual does not go into detail about the options and
9219 usage of the package building and installation tools. It
9220 should therefore be read in conjunction with those programs'
9225 The utility programs which are provided with <prgn>dpkg</prgn>
9226 for managing various system configuration and similar issues,
9227 such as <prgn>update-rc.d</prgn> and
9228 <prgn>install-info</prgn>, are not described in detail here -
9229 please see their man pages.
9233 It is assumed that the reader is reasonably familiar with the
9234 <prgn>dpkg</prgn> System Administrators' manual.
9235 Unfortunately this manual does not yet exist.
9239 The Debian version of the FSF's GNU hello program is provided
9240 as an example for people wishing to create Debian
9241 packages. The Debian <prgn>debmake</prgn> package is
9242 recommended as a very helpful tool in creating and maintaining
9243 Debian packages. However, while the tools and examples are
9244 helpful, they do not replace the need to read and follow the
9245 Policy and Programmer's Manual.</p>
9248 <appendix id="pkg-binarypkg">
9249 <heading>Binary packages (from old Packaging Manual)</heading>
9252 The binary package has two main sections. The first part
9253 consists of various control information files and scripts used
9254 by <prgn>dpkg</prgn> when installing and removing. See <ref
9255 id="pkg-controlarea">.
9259 The second part is an archive containing the files and
9260 directories to be installed.
9264 In the future binary packages may also contain other
9265 components, such as checksums and digital signatures. The
9266 format for the archive is described in full in the
9267 <file>deb(5)</file> man page.
9271 <sect id="pkg-bincreating"><heading>Creating package files -
9272 <prgn>dpkg-deb</prgn>
9276 All manipulation of binary package files is done by
9277 <prgn>dpkg-deb</prgn>; it's the only program that has
9278 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9279 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9280 will spot that the options requested are appropriate to
9281 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9286 In order to create a binary package you must make a
9287 directory tree which contains all the files and directories
9288 you want to have in the file system data part of the package.
9289 In Debian-format source packages this directory is usually
9290 <file>debian/tmp</file>, relative to the top of the package's
9295 They should have the locations (relative to the root of the
9296 directory tree you're constructing) ownerships and
9297 permissions which you want them to have on the system when
9302 With current versions of <prgn>dpkg</prgn> the uid/username
9303 and gid/groupname mappings for the users and groups being
9304 used should be the same on the system where the package is
9305 built and the one where it is installed.
9309 You need to add one special directory to the root of the
9310 miniature file system tree you're creating:
9311 <prgn>DEBIAN</prgn>. It should contain the control
9312 information files, notably the binary package control file
9313 (see <ref id="pkg-controlfile">).
9317 The <prgn>DEBIAN</prgn> directory will not appear in the
9318 file system archive of the package, and so won't be installed
9319 by <prgn>dpkg</prgn> when the package is installed.
9323 When you've prepared the package, you should invoke:
9325 dpkg --build <var>directory</var>
9330 This will build the package in
9331 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9332 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9333 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9338 See the man page <manref name="dpkg-deb" section="8"> for details of how
9339 to examine the contents of this newly-created file. You may find the
9340 output of following commands enlightening:
9342 dpkg-deb --info <var>filename</var>.deb
9343 dpkg-deb --contents <var>filename</var>.deb
9344 dpkg --contents <var>filename</var>.deb
9346 To view the copyright file for a package you could use this command:
9348 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9353 <sect id="pkg-controlarea">
9354 <heading>Package control information files</heading>
9357 The control information portion of a binary package is a
9358 collection of files with names known to <prgn>dpkg</prgn>.
9359 It will treat the contents of these files specially - some
9360 of them contain information used by <prgn>dpkg</prgn> when
9361 installing or removing the package; others are scripts which
9362 the package maintainer wants <prgn>dpkg</prgn> to run.
9366 It is possible to put other files in the package control
9367 area, but this is not generally a good idea (though they
9368 will largely be ignored).
9372 Here is a brief list of the control info files supported by
9373 <prgn>dpkg</prgn> and a summary of what they're used for.
9378 <tag><tt>control</tt>
9381 This is the key description file used by
9382 <prgn>dpkg</prgn>. It specifies the package's name
9383 and version, gives its description for the user,
9384 states its relationships with other packages, and so
9385 forth. See <ref id="sourcecontrolfiles"> and
9386 <ref id="binarycontrolfiles">.
9390 It is usually generated automatically from information
9391 in the source package by the
9392 <prgn>dpkg-gencontrol</prgn> program, and with
9393 assistance from <prgn>dpkg-shlibdeps</prgn>.
9394 See <ref id="pkg-sourcetools">.
9398 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9403 These are executable files (usually scripts) which
9404 <prgn>dpkg</prgn> runs during installation, upgrade
9405 and removal of packages. They allow the package to
9406 deal with matters which are particular to that package
9407 or require more complicated processing than that
9408 provided by <prgn>dpkg</prgn>. Details of when and
9409 how they are called are in <ref id="maintainerscripts">.
9413 It is very important to make these scripts idempotent.
9414 See <ref id="idempotency">.
9418 The maintainer scripts are guaranteed to run with a
9419 controlling terminal and can interact with the user.
9420 See <ref id="controllingterminal">.
9424 <tag><tt>conffiles</tt>
9427 This file contains a list of configuration files which
9428 are to be handled automatically by <prgn>dpkg</prgn>
9429 (see <ref id="pkg-conffiles">). Note that not necessarily
9430 every configuration file should be listed here.
9433 <tag><tt>shlibs</tt>
9436 This file contains a list of the shared libraries
9437 supplied by the package, with dependency details for
9438 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9439 when it determines what dependencies are required in a
9440 package control file. The <tt>shlibs</tt> file format
9441 is described on <ref id="shlibs">.
9446 <sect id="pkg-controlfile">
9447 <heading>The main control information file: <tt>control</tt></heading>
9450 The most important control information file used by
9451 <prgn>dpkg</prgn> when it installs a package is
9452 <tt>control</tt>. It contains all the package's "vital
9457 The binary package control files of packages built from
9458 Debian sources are made by a special tool,
9459 <prgn>dpkg-gencontrol</prgn>, which reads
9460 <file>debian/control</file> and <file>debian/changelog</file> to
9461 find the information it needs. See <ref id="pkg-sourcepkg"> for
9466 The fields in binary package control files are listed in
9467 <ref id="binarycontrolfiles">.
9471 A description of the syntax of control files and the purpose
9472 of the fields is available in <ref id="controlfields">.
9477 <heading>Time Stamps</heading>
9480 See <ref id="timestamps">.
9485 <appendix id="pkg-sourcepkg">
9486 <heading>Source packages (from old Packaging Manual) </heading>
9489 The Debian binary packages in the distribution are generated
9490 from Debian sources, which are in a special format to assist
9491 the easy and automatic building of binaries.
9494 <sect id="pkg-sourcetools">
9495 <heading>Tools for processing source packages</heading>
9498 Various tools are provided for manipulating source packages;
9499 they pack and unpack sources and help build of binary
9500 packages and help manage the distribution of new versions.
9504 They are introduced and typical uses described here; see
9505 <manref name="dpkg-source" section="1"> for full
9506 documentation about their arguments and operation.
9510 For examples of how to construct a Debian source package,
9511 and how to use those utilities that are used by Debian
9512 source packages, please see the <prgn>hello</prgn> example
9516 <sect1 id="pkg-dpkg-source">
9518 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9523 This program is frequently used by hand, and is also
9524 called from package-independent automated building scripts
9525 such as <prgn>dpkg-buildpackage</prgn>.
9529 To unpack a package it is typically invoked with
9531 dpkg-source -x <var>.../path/to/filename</var>.dsc
9536 with the <file><var>filename</var>.tar.gz</file> and
9537 <file><var>filename</var>.diff.gz</file> (if applicable) in
9538 the same directory. It unpacks into
9539 <file><var>package</var>-<var>version</var></file>, and if
9541 <file><var>package</var>-<var>version</var>.orig</file>, in
9542 the current directory.
9546 To create a packed source archive it is typically invoked:
9548 dpkg-source -b <var>package</var>-<var>version</var>
9553 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9554 <file>.diff.gz</file> (if appropriate) in the current
9555 directory. <prgn>dpkg-source</prgn> does not clean the
9556 source tree first - this must be done separately if it is
9561 See also <ref id="pkg-sourcearchives">.</p>
9565 <sect1 id="pkg-dpkg-buildpackage">
9567 <prgn>dpkg-buildpackage</prgn> - overall package-building
9572 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9573 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9574 targets <tt>clean</tt>, <tt>build</tt> and
9575 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9576 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9577 source and binary package upload.
9581 It is usually invoked by hand from the top level of the
9582 built or unbuilt source directory. It may be invoked with
9583 no arguments; useful arguments include:
9584 <taglist compact="compact">
9585 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9588 Do not sign the <tt>.changes</tt> file or the
9589 source package <tt>.dsc</tt> file, respectively.</p>
9591 <tag><tt>-p<var>sign-command</var></tt></tag>
9594 Invoke <var>sign-command</var> instead of finding
9595 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9596 <var>sign-command</var> must behave just like
9597 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9599 <tag><tt>-r<var>root-command</var></tt></tag>
9602 When root privilege is required, invoke the command
9603 <var>root-command</var>. <var>root-command</var>
9604 should invoke its first argument as a command, from
9605 the <prgn>PATH</prgn> if necessary, and pass its
9606 second and subsequent arguments to the command it
9607 calls. If no <var>root-command</var> is supplied
9608 then <var>dpkg-buildpackage</var> will take no
9609 special action to gain root privilege, so that for
9610 most packages it will have to be invoked as root to
9613 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9616 Two types of binary-only build and upload - see
9617 <manref name="dpkg-source" section="1">.
9624 <sect1 id="pkg-dpkg-gencontrol">
9626 <prgn>dpkg-gencontrol</prgn> - generates binary package
9631 This program is usually called from <file>debian/rules</file>
9632 (see <ref id="pkg-sourcetree">) in the top level of the source
9637 This is usually done just before the files and directories in the
9638 temporary directory tree where the package is being built have their
9639 permissions and ownerships set and the package is constructed using
9640 <prgn>dpkg-deb/</prgn>
9642 This is so that the control file which is produced has
9643 the right permissions
9648 <prgn>dpkg-gencontrol</prgn> must be called after all the
9649 files which are to go into the package have been placed in
9650 the temporary build directory, so that its calculation of
9651 the installed size of a package is correct.
9655 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9656 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9657 variable substitutions created by
9658 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9663 For a package which generates only one binary package, and
9664 which builds it in <file>debian/tmp</file> relative to the top
9665 of the source package, it is usually sufficient to call
9666 <prgn>dpkg-gencontrol</prgn>.
9670 Sources which build several binaries will typically need
9673 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9674 </example> The <tt>-P</tt> tells
9675 <prgn>dpkg-gencontrol</prgn> that the package is being
9676 built in a non-default directory, and the <tt>-p</tt>
9677 tells it which package's control file should be generated.
9681 <prgn>dpkg-gencontrol</prgn> also adds information to the
9682 list of files in <file>debian/files</file>, for the benefit of
9683 (for example) a future invocation of
9684 <prgn>dpkg-genchanges</prgn>.</p>
9687 <sect1 id="pkg-dpkg-shlibdeps">
9689 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9694 This program is usually called from <file>debian/rules</file>
9695 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9696 id="pkg-sourcetree">), in the top level of the source tree.
9700 Its arguments are executables and shared libraries
9703 They may be specified either in the locations in the
9704 source tree where they are created or in the locations
9705 in the temporary build tree where they are installed
9706 prior to binary package creation.
9708 </footnote> for which shared library dependencies should
9709 be included in the binary package's control file.
9713 If some of the found shared libraries should only
9714 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9715 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9716 by using the <tt>-d<var>dependency-field</var></tt> option
9717 before those executable(s). (Each <tt>-d</tt> option
9718 takes effect until the next <tt>-d</tt>.)
9722 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9723 output control file to be modified. Instead by default it
9724 adds to the <file>debian/substvars</file> file variable
9725 settings like <tt>shlibs:Depends</tt>. These variable
9726 settings must be referenced in dependency fields in the
9727 appropriate per-binary-package sections of the source
9732 For example, a package that generates an essential part
9733 which requires dependencies, and optional parts that
9734 which only require a recommendation, would separate those
9735 two sets of dependencies into two different fields.<footnote>
9736 At the time of writing, an example for this was the
9737 <package/xmms/ package, with Depends used for the xmms
9738 executable, Recommends for the plug-ins and Suggests for
9739 even more optional features provided by unzip.
9741 It can say in its <file>debian/rules</file>:
9743 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9744 -dRecommends <var>optionalpart anotheroptionalpart</var>
9746 and then in its main control file <file>debian/control</file>:
9749 Depends: ${shlibs:Depends}
9750 Recommends: ${shlibs:Recommends}
9756 Sources which produce several binary packages with
9757 different shared library dependency requirements can use
9758 the <tt>-p<var>varnameprefix</var></tt> option to override
9759 the default <tt>shlibs:</tt> prefix (one invocation of
9760 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9761 They can thus produce several sets of dependency
9762 variables, each of the form
9763 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9764 which can be referred to in the appropriate parts of the
9765 binary package control files.
9770 <sect1 id="pkg-dpkg-distaddfile">
9772 <prgn>dpkg-distaddfile</prgn> - adds a file to
9773 <file>debian/files</file>
9777 Some packages' uploads need to include files other than
9778 the source and binary package files.
9782 <prgn>dpkg-distaddfile</prgn> adds a file to the
9783 <file>debian/files</file> file so that it will be included in
9784 the <file>.changes</file> file when
9785 <prgn>dpkg-genchanges</prgn> is run.
9789 It is usually invoked from the <tt>binary</tt> target of
9790 <file>debian/rules</file>:
9792 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9794 The <var>filename</var> is relative to the directory where
9795 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9796 is usually the directory above the top level of the source
9797 tree. The <file>debian/rules</file> target should put the
9798 file there just before or just after calling
9799 <prgn>dpkg-distaddfile</prgn>.
9803 The <var>section</var> and <var>priority</var> are passed
9804 unchanged into the resulting <file>.changes</file> file.
9809 <sect1 id="pkg-dpkg-genchanges">
9811 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9816 This program is usually called by package-independent
9817 automatic building scripts such as
9818 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9823 It is usually called in the top level of a built source
9824 tree, and when invoked with no arguments will print out a
9825 straightforward <file>.changes</file> file based on the
9826 information in the source package's changelog and control
9827 file and the binary and source packages which should have
9833 <sect1 id="pkg-dpkg-parsechangelog">
9835 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9836 representation of a changelog
9840 This program is used internally by
9841 <prgn>dpkg-source</prgn> et al. It may also occasionally
9842 be useful in <file>debian/rules</file> and elsewhere. It
9843 parses a changelog, <file>debian/changelog</file> by default,
9844 and prints a control-file format representation of the
9845 information in it to standard output.
9849 <sect1 id="pkg-dpkg-architecture">
9851 <prgn>dpkg-architecture</prgn> - information about the build and
9856 This program can be used manually, but is also invoked by
9857 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9858 environment or make variables which specify the build and host
9859 architecture for the package building process.
9864 <sect id="pkg-sourcetree">
9865 <heading>The Debianised source tree</heading>
9868 The source archive scheme described later is intended to
9869 allow a Debianised source tree with some associated control
9870 information to be reproduced and transported easily. The
9871 Debianised source tree is a version of the original program
9872 with certain files added for the benefit of the
9873 Debianisation process, and with any other changes required
9874 made to the rest of the source code and installation
9879 The extra files created for Debian are in the subdirectory
9880 <file>debian</file> of the top level of the Debianised source
9881 tree. They are described below.
9884 <sect1 id="pkg-debianrules">
9885 <heading><file>debian/rules</file> - the main building script</heading>
9888 See <ref id="debianrules">.
9893 <sect1 id="pkg-dpkgchangelog">
9894 <heading><file>debian/changelog</file></heading>
9897 See <ref id="dpkgchangelog">.
9900 <sect2><heading>Defining alternative changelog formats
9904 It is possible to use a different format to the standard
9905 one, by providing a parser for the format you wish to
9910 In order to have <tt>dpkg-parsechangelog</tt> run your
9911 parser, you must include a line within the last 40 lines
9912 of your file matching the Perl regular expression:
9913 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9914 parentheses should be the name of the format. For
9915 example, you might say:
9917 @@@ changelog-format: joebloggs @@@
9919 Changelog format names are non-empty strings of alphanumerics.
9923 If such a line exists then <tt>dpkg-parsechangelog</tt>
9924 will look for the parser as
9925 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9927 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9928 it is an error for it not to find it, or for it not to
9929 be an executable program. The default changelog format
9930 is <tt>dpkg</tt>, and a parser for it is provided with
9931 the <tt>dpkg</tt> package.
9935 The parser will be invoked with the changelog open on
9936 standard input at the start of the file. It should read
9937 the file (it may seek if it wishes) to determine the
9938 information required and return the parsed information
9939 to standard output in the form of a series of control
9940 fields in the standard format. By default it should
9941 return information about only the most recent version in
9942 the changelog; it should accept a
9943 <tt>-v<var>version</var></tt> option to return changes
9944 information from all versions present <em>strictly
9945 after</em> <var>version</var>, and it should then be an
9946 error for <var>version</var> not to be present in the
9952 <list compact="compact">
9953 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9954 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9955 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9956 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9957 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9958 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9959 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9964 If several versions are being returned (due to the use
9965 of <tt>-v</tt>), the urgency value should be of the
9966 highest urgency code listed at the start of any of the
9967 versions requested followed by the concatenated
9968 (space-separated) comments from all the versions
9969 requested; the maintainer, version, distribution and
9970 date should always be from the most recent version.
9974 For the format of the <tt>Changes</tt> field see
9975 <ref id="f-Changes">.
9979 If the changelog format which is being parsed always or
9980 almost always leaves a blank line between individual
9981 change notes these blank lines should be stripped out,
9982 so as to make the resulting output compact.
9986 If the changelog format does not contain date or package
9987 name information this information should be omitted from
9988 the output. The parser should not attempt to synthesize
9989 it or find it from other sources.
9993 If the changelog does not have the expected format the
9994 parser should exit with a nonzero exit status, rather
9995 than trying to muddle through and possibly generating
10000 A changelog parser may not interact with the user at
10006 <sect1 id="pkg-srcsubstvars">
10007 <heading><file>debian/substvars</file> and variable substitutions</heading>
10010 See <ref id="substvars">.
10016 <heading><file>debian/files</file></heading>
10019 See <ref id="debianfiles">.
10023 <sect1><heading><file>debian/tmp</file>
10027 This is the canonical temporary location for the
10028 construction of binary packages by the <tt>binary</tt>
10029 target. The directory <file>tmp</file> serves as the root of
10030 the file system tree as it is being constructed (for
10031 example, by using the package's upstream makefiles install
10032 targets and redirecting the output there), and it also
10033 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10034 id="pkg-bincreating">.
10038 If several binary packages are generated from the same
10039 source tree it is usual to use several
10040 <file>debian/tmp<var>something</var></file> directories, for
10041 example <file>tmp-a</file> or <file>tmp-doc</file>.
10045 Whatever <file>tmp</file> directories are created and used by
10046 <tt>binary</tt> must of course be removed by the
10047 <tt>clean</tt> target.</p></sect1>
10051 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10055 As it exists on the FTP site, a Debian source package
10056 consists of three related files. You must have the right
10057 versions of all three to be able to use them.
10062 <tag>Debian source control file - <tt>.dsc</tt></tag>
10064 This file is a control file used by <prgn>dpkg-source</prgn>
10065 to extract a source package.
10066 See <ref id="debiansourcecontrolfiles">.
10070 Original source archive -
10072 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10078 This is a compressed (with <tt>gzip -9</tt>)
10079 <prgn>tar</prgn> file containing the source code from
10080 the upstream authors of the program.
10085 Debianisation diff -
10087 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10093 This is a unified context diff (<tt>diff -u</tt>)
10094 giving the changes which are required to turn the
10095 original source into the Debian source. These changes
10096 may only include editing and creating plain files.
10097 The permissions of files, the targets of symbolic
10098 links and the characteristics of special files or
10099 pipes may not be changed and no files may be removed
10104 All the directories in the diff must exist, except the
10105 <file>debian</file> subdirectory of the top of the source
10106 tree, which will be created by
10107 <prgn>dpkg-source</prgn> if necessary when unpacking.
10111 The <prgn>dpkg-source</prgn> program will
10112 automatically make the <file>debian/rules</file> file
10113 executable (see below).</p></item>
10118 If there is no original source code - for example, if the
10119 package is specially prepared for Debian or the Debian
10120 maintainer is the same as the upstream maintainer - the
10121 format is slightly different: then there is no diff, and the
10123 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10124 and preferably contains a directory named
10125 <file><var>package</var>-<var>version</var></file>.
10130 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10133 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10134 Debian source package. However, if it is not available it
10135 is possible to unpack a Debian source archive as follows:
10136 <enumlist compact="compact">
10139 Untar the tarfile, which will create a <file>.orig</file>
10143 <p>Rename the <file>.orig</file> directory to
10144 <file><var>package</var>-<var>version</var></file>.</p>
10148 Create the subdirectory <file>debian</file> at the top of
10149 the source tree.</p>
10151 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10153 <item><p>Untar the tarfile again if you want a copy of the original
10154 source code alongside the Debianised version.</p>
10159 It is not possible to generate a valid Debian source archive
10160 without using <prgn>dpkg-source</prgn>. In particular,
10161 attempting to use <prgn>diff</prgn> directly to generate the
10162 <file>.diff.gz</file> file will not work.
10166 <heading>Restrictions on objects in source packages</heading>
10169 The source package may not contain any hard links
10171 This is not currently detected when building source
10172 packages, but only when extracting
10176 Hard links may be permitted at some point in the
10177 future, but would require a fair amount of
10179 </footnote>, device special files, sockets or setuid or
10182 Setgid directories are allowed.
10187 The source packaging tools manage the changes between the
10188 original and Debianised source using <prgn>diff</prgn> and
10189 <prgn>patch</prgn>. Turning the original source tree as
10190 included in the <file>.orig.tar.gz</file> into the debianised
10191 source must not involve any changes which cannot be
10192 handled by these tools. Problematic changes which cause
10193 <prgn>dpkg-source</prgn> to halt with an error when
10194 building the source package are:
10195 <list compact="compact">
10196 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10198 <item><p>Changing the targets of symbolic links.</p>
10200 <item><p>Creating directories, other than <file>debian</file>.</p>
10202 <item><p>Changes to the contents of binary files.</p></item>
10203 </list> Changes which cause <prgn>dpkg-source</prgn> to
10204 print a warning but continue anyway are:
10205 <list compact="compact">
10208 Removing files, directories or symlinks.
10210 Renaming a file is not treated specially - it is
10211 seen as the removal of the old file (which
10212 generates a warning, but is otherwise ignored),
10213 and the creation of the new one.
10219 Changed text files which are missing the usual final
10220 newline (either in the original or the modified
10225 Changes which are not represented, but which are not detected by
10226 <prgn>dpkg-source</prgn>, are:
10227 <list compact="compact">
10228 <item><p>Changing the permissions of files (other than
10229 <file>debian/rules</file>) and directories.</p></item>
10234 The <file>debian</file> directory and <file>debian/rules</file>
10235 are handled specially by <prgn>dpkg-source</prgn> - before
10236 applying the changes it will create the <file>debian</file>
10237 directory, and afterwards it will make
10238 <file>debian/rules</file> world-executable.
10244 <appendix id="pkg-controlfields">
10245 <heading>Control files and their fields (from old Packaging Manual)</heading>
10248 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10249 data in a common format, known as control files. Binary and
10250 source packages have control data as do the <file>.changes</file>
10251 files which control the installation of uploaded files, and
10252 <prgn>dpkg</prgn>'s internal databases are in a similar
10257 <heading>Syntax of control files</heading>
10260 See <ref id="controlsyntax">.
10264 It is important to note that there are several fields which
10265 are optional as far as <prgn>dpkg</prgn> and the related
10266 tools are concerned, but which must appear in every Debian
10267 package, or whose omission may cause problems.
10272 <heading>List of fields</heading>
10275 See <ref id="controlfieldslist">.
10279 This section now contains only the fields that didn't belong
10280 to the Policy manual.
10283 <sect1 id="pkg-f-Filename">
10284 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10287 These fields in <tt>Packages</tt> files give the
10288 filename(s) of (the parts of) a package in the
10289 distribution directories, relative to the root of the
10290 Debian hierarchy. If the package has been split into
10291 several parts the parts are all listed in order, separated
10296 <sect1 id="pkg-f-Size">
10297 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10300 These fields in <file>Packages</file> files give the size (in
10301 bytes, expressed in decimal) and MD5 checksum of the
10302 file(s) which make(s) up a binary package in the
10303 distribution. If the package is split into several parts
10304 the values for the parts are listed in order, separated by
10309 <sect1 id="pkg-f-Status">
10310 <heading><tt>Status</tt></heading>
10313 This field in <prgn>dpkg</prgn>'s status file records
10314 whether the user wants a package installed, removed or
10315 left alone, whether it is broken (requiring
10316 re-installation) or not and what its current state on the
10317 system is. Each of these pieces of information is a
10322 <sect1 id="pkg-f-Config-Version">
10323 <heading><tt>Config-Version</tt></heading>
10326 If a package is not installed or not configured, this
10327 field in <prgn>dpkg</prgn>'s status file records the last
10328 version of the package which was successfully
10333 <sect1 id="pkg-f-Conffiles">
10334 <heading><tt>Conffiles</tt></heading>
10337 This field in <prgn>dpkg</prgn>'s status file contains
10338 information about the automatically-managed configuration
10339 files held by a package. This field should <em>not</em>
10340 appear anywhere in a package!
10345 <heading>Obsolete fields</heading>
10348 These are still recognized by <prgn>dpkg</prgn> but should
10349 not appear anywhere any more.
10351 <taglist compact="compact">
10353 <tag><tt>Revision</tt></tag>
10354 <tag><tt>Package-Revision</tt></tag>
10355 <tag><tt>Package_Revision</tt></tag>
10357 The Debian revision part of the package version was
10358 at one point in a separate control file field. This
10359 field went through several names.
10362 <tag><tt>Recommended</tt></tag>
10363 <item>Old name for <tt>Recommends</tt>.</item>
10365 <tag><tt>Optional</tt></tag>
10366 <item>Old name for <tt>Suggests</tt>.</item>
10368 <tag><tt>Class</tt></tag>
10369 <item>Old name for <tt>Priority</tt>.</item>
10378 <appendix id="pkg-conffiles">
10379 <heading>Configuration file handling (from old Packaging Manual)</heading>
10382 <prgn>dpkg</prgn> can do a certain amount of automatic
10383 handling of package configuration files.
10387 Whether this mechanism is appropriate depends on a number of
10388 factors, but basically there are two approaches to any
10389 particular configuration file.
10393 The easy method is to ship a best-effort configuration in the
10394 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10395 handle updates. If the user is unlikely to want to edit the
10396 file, but you need them to be able to without losing their
10397 changes, and a new package with a changed version of the file
10398 is only released infrequently, this is a good approach.
10402 The hard method is to build the configuration file from
10403 scratch in the <prgn>postinst</prgn> script, and to take the
10404 responsibility for fixing any mistakes made in earlier
10405 versions of the package automatically. This will be
10406 appropriate if the file is likely to need to be different on
10410 <sect><heading>Automatic handling of configuration files by
10415 A package may contain a control area file called
10416 <tt>conffiles</tt>. This file should be a list of filenames
10417 of configuration files needing automatic handling, separated
10418 by newlines. The filenames should be absolute pathnames,
10419 and the files referred to should actually exist in the
10424 When a package is upgraded <prgn>dpkg</prgn> will process
10425 the configuration files during the configuration stage,
10426 shortly before it runs the package's <prgn>postinst</prgn>
10431 For each file it checks to see whether the version of the
10432 file included in the package is the same as the one that was
10433 included in the last version of the package (the one that is
10434 being upgraded from); it also compares the version currently
10435 installed on the system with the one shipped with the last
10440 If neither the user nor the package maintainer has changed
10441 the file, it is left alone. If one or the other has changed
10442 their version, then the changed version is preferred - i.e.,
10443 if the user edits their file, but the package maintainer
10444 doesn't ship a different version, the user's changes will
10445 stay, silently, but if the maintainer ships a new version
10446 and the user hasn't edited it the new version will be
10447 installed (with an informative message). If both have
10448 changed their version the user is prompted about the problem
10449 and must resolve the differences themselves.
10453 The comparisons are done by calculating the MD5 message
10454 digests of the files, and storing the MD5 of the file as it
10455 was included in the most recent version of the package.
10459 When a package is installed for the first time
10460 <prgn>dpkg</prgn> will install the file that comes with it,
10461 unless that would mean overwriting a file already on the
10466 However, note that <prgn>dpkg</prgn> will <em>not</em>
10467 replace a conffile that was removed by the user (or by a
10468 script). This is necessary because with some programs a
10469 missing file produces an effect hard or impossible to
10470 achieve in another way, so that a missing file needs to be
10471 kept that way if the user did it.
10475 Note that a package should <em>not</em> modify a
10476 <prgn>dpkg</prgn>-handled conffile in its maintainer
10477 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10478 the user confusing and possibly dangerous options for
10479 conffile update when the package is upgraded.</p>
10482 <sect><heading>Fully-featured maintainer script configuration
10487 For files which contain site-specific information such as
10488 the hostname and networking details and so forth, it is
10489 better to create the file in the package's
10490 <prgn>postinst</prgn> script.
10494 This will typically involve examining the state of the rest
10495 of the system to determine values and other information, and
10496 may involve prompting the user for some information which
10497 can't be obtained some other way.
10501 When using this method there are a couple of important
10502 issues which should be considered:
10506 If you discover a bug in the program which generates the
10507 configuration file, or if the format of the file changes
10508 from one version to the next, you will have to arrange for
10509 the postinst script to do something sensible - usually this
10510 will mean editing the installed configuration file to remove
10511 the problem or change the syntax. You will have to do this
10512 very carefully, since the user may have changed the file,
10513 perhaps to fix the very problem that your script is trying
10514 to deal with - you will have to detect these situations and
10515 deal with them correctly.
10519 If you do go down this route it's probably a good idea to
10520 make the program that generates the configuration file(s) a
10521 separate program in <file>/usr/sbin</file>, by convention called
10522 <file><var>package</var>config</file> and then run that if
10523 appropriate from the post-installation script. The
10524 <tt><var>package</var>config</tt> program should not
10525 unquestioningly overwrite an existing configuration - if its
10526 mode of operation is geared towards setting up a package for
10527 the first time (rather than any arbitrary reconfiguration
10528 later) you should have it check whether the configuration
10529 already exists, and require a <tt>--force</tt> flag to
10530 overwrite it.</p></sect>
10533 <appendix id="pkg-alternatives"><heading>Alternative versions of
10534 an interface - <prgn>update-alternatives</prgn> (from old
10539 When several packages all provide different versions of the
10540 same program or file it is useful to have the system select a
10541 default, but to allow the system administrator to change it
10542 and have their decisions respected.
10546 For example, there are several versions of the <prgn>vi</prgn>
10547 editor, and there is no reason to prevent all of them from
10548 being installed at once, each under their own name
10549 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10550 Nevertheless it is desirable to have the name <tt>vi</tt>
10551 refer to something, at least by default.
10555 If all the packages involved cooperate, this can be done with
10556 <prgn>update-alternatives</prgn>.
10560 Each package provides its own version under its own name, and
10561 calls <prgn>update-alternatives</prgn> in its postinst to
10562 register its version (and again in its prerm to deregister
10567 See the man page <manref name="update-alternatives"
10568 section="8"> for details.
10572 If <prgn>update-alternatives</prgn> does not seem appropriate
10573 you may wish to consider using diversions instead.</p>
10576 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10577 package's version of a file (from old Packaging Manual)
10581 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10582 when it reinstalls the package it belongs to, and to have it
10583 put the file from the package somewhere else instead.
10587 This can be used locally to override a package's version of a
10588 file, or by one package to override another's version (or
10589 provide a wrapper for it).
10593 Before deciding to use a diversion, read <ref
10594 id="pkg-alternatives"> to see if you really want a diversion
10595 rather than several alternative versions of a program.
10599 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10600 and updated by a special program <prgn>dpkg-divert</prgn>.
10601 Please see <manref name="dpkg-divert" section="8"> for full
10602 details of its operation.
10606 When a package wishes to divert a file from another, it should
10607 call <prgn>dpkg-divert</prgn> in its preinst to add the
10608 diversion and rename the existing file. For example,
10609 supposing that a <prgn>smailwrapper</prgn> package wishes to
10610 install a wrapper around <file>/usr/sbin/smail</file>:
10612 dpkg-divert --package smailwrapper --add --rename \
10613 --divert /usr/sbin/smail.real /usr/sbin/smail
10614 </example> The <tt>--package smailwrapper</tt> ensures that
10615 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10616 can bypass the diversion and get installed as the true version.
10617 It's safe to add the diversion unconditionally on upgrades since
10618 it will be left unchanged if it already exists, but
10619 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10620 message, make the command conditional on the version from which
10621 the package is being upgraded:
10623 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10624 dpkg-divert --package smailwrapper --add --rename \
10625 --divert /usr/sbin/smail.real /usr/sbin/smail
10627 </example> where <tt>1.0-2</tt> is the version at which the
10628 diversion was first added to the package. Running the command
10629 during abort-upgrade is pointless but harmless.
10633 The postrm has to do the reverse:
10635 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10636 dpkg-divert --package smailwrapper --remove --rename \
10637 --divert /usr/sbin/smail.real /usr/sbin/smail
10639 </example> If the diversion was added at a particular version, the
10640 postrm should also handle the failure case of upgrading from an
10641 older version (unless the older version is so old that direct
10642 upgrades are no longer supported):
10644 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10645 dpkg-divert --package smailwrapper --remove --rename \
10646 --divert /usr/sbin/smail.real /usr/sbin/smail
10648 </example> where <tt>1.02-2</tt> is the version at which the
10649 diversion was first added to the package. The postrm should not
10650 remove the diversion on upgrades both because there's no reason to
10651 remove the diversion only to immediately re-add it and since the
10652 postrm of the old package is run after unpacking so the removal of
10653 the diversion will fail.
10657 Do not attempt to divert a file which is vitally important for
10658 the system's operation - when using <prgn>dpkg-divert</prgn>
10659 there is a time, after it has been diverted but before
10660 <prgn>dpkg</prgn> has installed the new version, when the file
10661 does not exist.</p>
10666 <!-- Local variables: -->
10667 <!-- indent-tabs-mode: t -->
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