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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> distribution area,
663 <em>area/section</em> if the package is in
664 the <em>contrib</em> or <em>non-free</em>
671 The Debian archive maintainers provide the authoritative
672 list of sections. At present, they are:
673 <em>admin</em>, <em>comm</em>,
674 <em>devel</em>, <em>doc</em>,
675 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
676 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
677 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
678 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
679 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
681 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
682 <em>science</em>, <em>shells</em>,
683 <em>sound</em>, <em>tex</em>, <em>text</em>,
684 <em>utils</em>, <em>web</em>, <em>x11</em>.
688 <sect id="priorities">
689 <heading>Priorities</heading>
692 Each package should have a <em>priority</em> value, which is
693 included in the package's <em>control record</em>
694 (see <ref id="f-Priority">).
695 This information is used by the Debian package management tools to
696 separate high-priority packages from less-important packages.
700 The following <em>priority levels</em> are recognized by the
701 Debian package management tools.
703 <tag><tt>required</tt></tag>
705 Packages which are necessary for the proper
706 functioning of the system (usually, this means that
707 dpkg functionality depends on these packages).
708 Removing a <tt>required</tt> package may cause your
709 system to become totally broken and you may not even
710 be able to use <prgn>dpkg</prgn> to put things back,
711 so only do so if you know what you are doing. Systems
712 with only the <tt>required</tt> packages are probably
713 unusable, but they do have enough functionality to
714 allow the sysadmin to boot and install more software.
716 <tag><tt>important</tt></tag>
718 Important programs, including those which one would
719 expect to find on any Unix-like system. If the
720 expectation is that an experienced Unix person who
721 found it missing would say "What on earth is going on,
722 where is <prgn>foo</prgn>?", it must be an
723 <tt>important</tt> package.<footnote>
724 This is an important criterion because we are
725 trying to produce, amongst other things, a free
728 Other packages without which the system will not run
729 well or be usable must also have priority
730 <tt>important</tt>. This does
731 <em>not</em> include Emacs, the X Window System, TeX
732 or any other large applications. The
733 <tt>important</tt> packages are just a bare minimum of
734 commonly-expected and necessary tools.
736 <tag><tt>standard</tt></tag>
738 These packages provide a reasonably small but not too
739 limited character-mode system. This is what will be
740 installed by default if the user doesn't select anything
741 else. It doesn't include many large applications.
743 <tag><tt>optional</tt></tag>
745 (In a sense everything that isn't required is
746 optional, but that's not what is meant here.) This is
747 all the software that you might reasonably want to
748 install if you didn't know what it was and don't have
749 specialized requirements. This is a much larger system
750 and includes the X Window System, a full TeX
751 distribution, and many applications. Note that
752 optional packages should not conflict with each other.
754 <tag><tt>extra</tt></tag>
756 This contains all packages that conflict with others
757 with required, important, standard or optional
758 priorities, or are only likely to be useful if you
759 already know what they are or have specialized
760 requirements (such as packages containing only detached
767 Packages must not depend on packages with lower priority
768 values (excluding build-time dependencies). In order to
769 ensure this, the priorities of one or more packages may need
778 <heading>Binary packages</heading>
781 The Debian GNU/Linux distribution is based on the Debian
782 package management system, called <prgn>dpkg</prgn>. Thus,
783 all packages in the Debian distribution must be provided
784 in the <tt>.deb</tt> file format.
788 <heading>The package name</heading>
791 Every package must have a name that's unique within the Debian
796 The package name is included in the control field
797 <tt>Package</tt>, the format of which is described
798 in <ref id="f-Package">.
799 The package name is also included as a part of the file name
800 of the <tt>.deb</tt> file.
805 <heading>The version of a package</heading>
808 Every package has a version number recorded in its
809 <tt>Version</tt> control file field, described in
810 <ref id="f-Version">.
814 The package management system imposes an ordering on version
815 numbers, so that it can tell whether packages are being up- or
816 downgraded and so that package system front end applications
817 can tell whether a package it finds available is newer than
818 the one installed on the system. The version number format
819 has the most significant parts (as far as comparison is
820 concerned) at the beginning.
824 If an upstream package has problematic version numbers they
825 should be converted to a sane form for use in the
826 <tt>Version</tt> field.
830 <heading>Version numbers based on dates</heading>
833 In general, Debian packages should use the same version
834 numbers as the upstream sources.
838 However, in some cases where the upstream version number is
839 based on a date (e.g., a development "snapshot" release) the
840 package management system cannot handle these version
841 numbers without epochs. For example, dpkg will consider
842 "96May01" to be greater than "96Dec24".
846 To prevent having to use epochs for every new upstream
847 version, the date based portion of the version number
848 should be changed to the following format in such cases:
849 "19960501", "19961224". It is up to the maintainer whether
850 they want to bother the upstream maintainer to change
851 the version numbers upstream, too.
855 Note that other version formats based on dates which are
856 parsed correctly by the package management system should
857 <em>not</em> be changed.
861 Native Debian packages (i.e., packages which have been
862 written especially for Debian) whose version numbers include
863 dates should always use the "YYYYMMDD" format.
870 <heading>The maintainer of a package</heading>
873 Every package must have a Debian maintainer (the
874 maintainer may be one person or a group of people
875 reachable from a common email address, such as a mailing
876 list). The maintainer is responsible for ensuring that
877 the package is placed in the appropriate distributions.
881 The maintainer must be specified in the
882 <tt>Maintainer</tt> control field with their correct name
883 and a working email address. If one person maintains
884 several packages, they should try to avoid having
885 different forms of their name and email address in
886 the <tt>Maintainer</tt> fields of those packages.
890 The format of the <tt>Maintainer</tt> control field is
891 described in <ref id="f-Maintainer">.
895 If the maintainer of a package quits from the Debian
896 project, "Debian QA Group"
897 <email>packages@qa.debian.org</email> takes over the
898 maintainer-ship of the package until someone else
899 volunteers for that task. These packages are called
900 <em>orphaned packages</em>.<footnote>
901 The detailed procedure for doing this gracefully can
902 be found in the Debian Developer's Reference,
903 see <ref id="related">.
908 <sect id="descriptions">
909 <heading>The description of a package</heading>
912 Every Debian package must have an extended description
913 stored in the appropriate field of the control record.
914 The technical information about the format of the
915 <tt>Description</tt> field is in <ref id="f-Description">.
919 The description should describe the package (the program) to a
920 user (system administrator) who has never met it before so that
921 they have enough information to decide whether they want to
922 install it. This description should not just be copied verbatim
923 from the program's documentation.
927 Put important information first, both in the synopsis and
928 extended description. Sometimes only the first part of the
929 synopsis or of the description will be displayed. You can
930 assume that there will usually be a way to see the whole
931 extended description.
935 The description should also give information about the
936 significant dependencies and conflicts between this package
937 and others, so that the user knows why these dependencies and
938 conflicts have been declared.
942 Instructions for configuring or using the package should
943 not be included (that is what installation scripts,
944 manual pages, info files, etc., are for). Copyright
945 statements and other administrivia should not be included
946 either (that is what the copyright file is for).
949 <sect1 id="synopsis"><heading>The single line synopsis</heading>
952 The single line synopsis should be kept brief - certainly
957 Do not include the package name in the synopsis line. The
958 display software knows how to display this already, and you
959 do not need to state it. Remember that in many situations
960 the user may only see the synopsis line - make it as
961 informative as you can.
966 <sect1 id="extendeddesc"><heading>The extended description</heading>
969 Do not try to continue the single line synopsis into the
970 extended description. This will not work correctly when
971 the full description is displayed, and makes no sense
972 where only the summary (the single line synopsis) is
977 The extended description should describe what the package
978 does and how it relates to the rest of the system (in terms
979 of, for example, which subsystem it is which part of).
983 The description field needs to make sense to anyone, even
984 people who have no idea about any of the things the
985 package deals with.<footnote>
986 The blurb that comes with a program in its
987 announcements and/or <prgn>README</prgn> files is
988 rarely suitable for use in a description. It is
989 usually aimed at people who are already in the
990 community where the package is used.
999 <heading>Dependencies</heading>
1002 Every package must specify the dependency information
1003 about other packages that are required for the first to
1008 For example, a dependency entry must be provided for any
1009 shared libraries required by a dynamically-linked executable
1010 binary in a package.
1014 Packages are not required to declare any dependencies they
1015 have on other packages which are marked <tt>Essential</tt>
1016 (see below), and should not do so unless they depend on a
1017 particular version of that package.<footnote>
1019 Essential is needed in part to avoid unresolvable dependency
1020 loops on upgrade. If packages add unnecessary dependencies
1021 on packages in this set, the chances that there
1022 <strong>will</strong> be an unresolvable dependency loop
1023 caused by forcing these Essential packages to be configured
1024 first before they need to be is greatly increased. It also
1025 increases the chances that frontends will be unable to
1026 <strong>calculate</strong> an upgrade path, even if one
1030 Also, functionality is rarely ever removed from the
1031 Essential set, but <em>packages</em> have been removed from
1032 the Essential set when the functionality moved to a
1033 different package. So depending on these packages <em>just
1034 in case</em> they stop being essential does way more harm
1041 Sometimes, a package requires another package to be installed
1042 <em>and</em> configured before it can be installed. In this
1043 case, you must specify a <tt>Pre-Depends</tt> entry for
1048 You should not specify a <tt>Pre-Depends</tt> entry for a
1049 package before this has been discussed on the
1050 <tt>debian-devel</tt> mailing list and a consensus about
1051 doing that has been reached.
1055 The format of the package interrelationship control fields is
1056 described in <ref id="relationships">.
1060 <sect id="virtual_pkg">
1061 <heading>Virtual packages</heading>
1064 Sometimes, there are several packages which offer
1065 more-or-less the same functionality. In this case, it's
1066 useful to define a <em>virtual package</em> whose name
1067 describes that common functionality. (The virtual
1068 packages only exist logically, not physically; that's why
1069 they are called <em>virtual</em>.) The packages with this
1070 particular function will then <em>provide</em> the virtual
1071 package. Thus, any other package requiring that function
1072 can simply depend on the virtual package without having to
1073 specify all possible packages individually.
1077 All packages should use virtual package names where
1078 appropriate, and arrange to create new ones if necessary.
1079 They should not use virtual package names (except privately,
1080 amongst a cooperating group of packages) unless they have
1081 been agreed upon and appear in the list of virtual package
1082 names. (See also <ref id="virtual">)
1086 The latest version of the authoritative list of virtual
1087 package names can be found in the <tt>debian-policy</tt> package.
1088 It is also available from the Debian web mirrors at
1089 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1090 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1094 The procedure for updating the list is described in the preface
1101 <heading>Base system</heading>
1104 The <tt>base system</tt> is a minimum subset of the Debian
1105 GNU/Linux system that is installed before everything else
1106 on a new system. Only very few packages are allowed to form
1107 part of the base system, in order to keep the required disk
1112 The base system consists of all those packages with priority
1113 <tt>required</tt> or <tt>important</tt>. Many of them will
1114 be tagged <tt>essential</tt> (see below).
1119 <heading>Essential packages</heading>
1122 Essential is defined as the minimal set of functionality that
1123 must be available and usable on the system at all times, even
1124 when packages are in an unconfigured (but unpacked) state.
1125 Packages are tagged <tt>essential</tt> for a system using the
1126 <tt>Essential</tt> control file field. The format of the
1127 <tt>Essential</tt> control field is described in <ref
1132 Since these packages cannot be easily removed (one has to
1133 specify an extra <em>force option</em> to
1134 <prgn>dpkg</prgn> to do so), this flag must not be used
1135 unless absolutely necessary. A shared library package
1136 must not be tagged <tt>essential</tt>; dependencies will
1137 prevent its premature removal, and we need to be able to
1138 remove it when it has been superseded.
1142 Since dpkg will not prevent upgrading of other packages
1143 while an <tt>essential</tt> package is in an unconfigured
1144 state, all <tt>essential</tt> packages must supply all of
1145 their core functionality even when unconfigured. If the
1146 package cannot satisfy this requirement it must not be
1147 tagged as essential, and any packages depending on this
1148 package must instead have explicit dependency fields as
1153 Maintainers should take great care in adding any programs,
1154 interfaces, or functionality to <tt>essential</tt> packages.
1155 Packages may assume that functionality provided by
1156 <tt>essential</tt> packages is always available without
1157 declaring explicit dependencies, which means that removing
1158 functionality from the Essential set is very difficult and is
1159 almost never done. Any capability added to an
1160 <tt>essential</tt> package therefore creates an obligation to
1161 support that capability as part of the Essential set in
1166 You must not tag any packages <tt>essential</tt> before
1167 this has been discussed on the <tt>debian-devel</tt>
1168 mailing list and a consensus about doing that has been
1173 <sect id="maintscripts">
1174 <heading>Maintainer Scripts</heading>
1177 The package installation scripts should avoid producing
1178 output which is unnecessary for the user to see and
1179 should rely on <prgn>dpkg</prgn> to stave off boredom on
1180 the part of a user installing many packages. This means,
1181 amongst other things, using the <tt>--quiet</tt> option on
1182 <prgn>install-info</prgn>.
1186 Errors which occur during the execution of an installation
1187 script must be checked and the installation must not
1188 continue after an error.
1192 Note that in general <ref id="scripts"> applies to package
1193 maintainer scripts, too.
1197 You should not use <prgn>dpkg-divert</prgn> on a file
1198 belonging to another package without consulting the
1199 maintainer of that package first.
1203 All packages which supply an instance of a common command
1204 name (or, in general, filename) should generally use
1205 <prgn>update-alternatives</prgn>, so that they may be
1206 installed together. If <prgn>update-alternatives</prgn>
1207 is not used, then each package must use
1208 <tt>Conflicts</tt> to ensure that other packages are
1209 de-installed. (In this case, it may be appropriate to
1210 specify a conflict against earlier versions of something
1211 that previously did not use
1212 <prgn>update-alternatives</prgn>; this is an exception to
1213 the usual rule that versioned conflicts should be
1217 <sect1 id="maintscriptprompt">
1218 <heading>Prompting in maintainer scripts</heading>
1220 Package maintainer scripts may prompt the user if
1221 necessary. Prompting should be done by communicating
1222 through a program, such as <prgn>debconf</prgn>, which
1223 conforms to the Debian Configuration Management
1224 Specification, version 2 or higher. Prompting the user by
1225 other means, such as by hand<footnote>
1226 From the Jargon file: by hand 2. By extension,
1227 writing code which does something in an explicit or
1228 low-level way for which a presupplied library
1229 (<em>debconf, in this instance</em>) routine ought
1230 to have been available.
1231 </footnote>, is now deprecated.
1235 The Debian Configuration Management Specification is included
1236 in the <file>debconf_specification</file> files in the
1237 <package>debian-policy</package> package.
1238 It is also available from the Debian web mirrors at
1239 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1240 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1244 Packages which use the Debian Configuration Management
1245 Specification may contain an additional
1246 <prgn>config</prgn> script and a <tt>templates</tt>
1247 file in their control archive<footnote>
1248 The control.tar.gz inside the .deb.
1249 See <manref name="deb" section="5">.
1251 The <prgn>config</prgn> script might be run before the
1252 <prgn>preinst</prgn> script, and before the package is unpacked
1253 or any of its dependencies or pre-dependencies are satisfied.
1254 Therefore it must work using only the tools present in
1255 <em>essential</em> packages.<footnote>
1256 <package>Debconf</package> or another tool that
1257 implements the Debian Configuration Management
1258 Specification will also be installed, and any
1259 versioned dependencies on it will be satisfied
1260 before preconfiguration begins.
1265 Packages which use the Debian Configuration Management
1266 Specification must allow for translation of their user-visible
1267 messages by using a gettext-based system such as the one
1268 provided by the <package>po-debconf</package> package.
1272 Packages should try to minimize the amount of prompting
1273 they need to do, and they should ensure that the user
1274 will only ever be asked each question once. This means
1275 that packages should try to use appropriate shared
1276 configuration files (such as <file>/etc/papersize</file> and
1277 <file>/etc/news/server</file>), and shared
1278 <package>debconf</package> variables rather than each
1279 prompting for their own list of required pieces of
1284 It also means that an upgrade should not ask the same
1285 questions again, unless the user has used
1286 <tt>dpkg --purge</tt> to remove the package's configuration.
1287 The answers to configuration questions should be stored in an
1288 appropriate place in <file>/etc</file> so that the user can
1289 modify them, and how this has been done should be
1294 If a package has a vitally important piece of
1295 information to pass to the user (such as "don't run me
1296 as I am, you must edit the following configuration files
1297 first or you risk your system emitting badly-formatted
1298 messages"), it should display this in the
1299 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1300 prompt the user to hit return to acknowledge the
1301 message. Copyright messages do not count as vitally
1302 important (they belong in
1303 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1304 neither do instructions on how to use a program (these
1305 should be in on-line documentation, where all the users
1310 Any necessary prompting should almost always be confined
1311 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1312 script. If it is done in the <prgn>postinst</prgn>, it
1313 should be protected with a conditional so that
1314 unnecessary prompting doesn't happen if a package's
1315 installation fails and the <prgn>postinst</prgn> is
1316 called with <tt>abort-upgrade</tt>,
1317 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1327 <heading>Source packages</heading>
1329 <sect id="standardsversion">
1330 <heading>Standards conformance</heading>
1333 Source packages should specify the most recent version number
1334 of this policy document with which your package complied
1335 when it was last updated.
1339 This information may be used to file bug reports
1340 automatically if your package becomes too much out of date.
1344 The version is specified in the <tt>Standards-Version</tt>
1346 The format of the <tt>Standards-Version</tt> field is
1347 described in <ref id="f-Standards-Version">.
1351 You should regularly, and especially if your package has
1352 become out of date, check for the newest Policy Manual
1353 available and update your package, if necessary. When your
1354 package complies with the new standards you should update the
1355 <tt>Standards-Version</tt> source package field and
1356 release it.<footnote>
1357 See the file <file>upgrading-checklist</file> for
1358 information about policy which has changed between
1359 different versions of this document.
1365 <sect id="pkg-relations">
1366 <heading>Package relationships</heading>
1369 Source packages should specify which binary packages they
1370 require to be installed or not to be installed in order to
1371 build correctly. For example, if building a package
1372 requires a certain compiler, then the compiler should be
1373 specified as a build-time dependency.
1377 It is not necessary to explicitly specify build-time
1378 relationships on a minimal set of packages that are always
1379 needed to compile, link and put in a Debian package a
1380 standard "Hello World!" program written in C or C++. The
1381 required packages are called <em>build-essential</em>, and
1382 an informational list can be found in
1383 <file>/usr/share/doc/build-essential/list</file> (which is
1384 contained in the <tt>build-essential</tt>
1387 <list compact="compact">
1389 This allows maintaining the list separately
1390 from the policy documents (the list does not
1391 need the kind of control that the policy
1395 Having a separate package allows one to install
1396 the build-essential packages on a machine, as
1397 well as allowing other packages such as tasks to
1398 require installation of the build-essential
1399 packages using the depends relation.
1402 The separate package allows bug reports against
1403 the list to be categorized separately from
1404 the policy management process in the BTS.
1411 When specifying the set of build-time dependencies, one
1412 should list only those packages explicitly required by the
1413 build. It is not necessary to list packages which are
1414 required merely because some other package in the list of
1415 build-time dependencies depends on them.<footnote>
1416 The reason for this is that dependencies change, and
1417 you should list all those packages, and <em>only</em>
1418 those packages that <em>you</em> need directly. What
1419 others need is their business. For example, if you
1420 only link against <file>libimlib</file>, you will need to
1421 build-depend on <package>libimlib2-dev</package> but
1422 not against any <tt>libjpeg*</tt> packages, even
1423 though <tt>libimlib2-dev</tt> currently depends on
1424 them: installation of <package>libimlib2-dev</package>
1425 will automatically ensure that all of its run-time
1426 dependencies are satisfied.
1431 If build-time dependencies are specified, it must be
1432 possible to build the package and produce working binaries
1433 on a system with only essential and build-essential
1434 packages installed and also those required to satisfy the
1435 build-time relationships (including any implied
1436 relationships). In particular, this means that version
1437 clauses should be used rigorously in build-time
1438 relationships so that one cannot produce bad or
1439 inconsistently configured packages when the relationships
1440 are properly satisfied.
1444 <ref id="relationships"> explains the technical details.
1449 <heading>Changes to the upstream sources</heading>
1452 If changes to the source code are made that are not
1453 specific to the needs of the Debian system, they should be
1454 sent to the upstream authors in whatever form they prefer
1455 so as to be included in the upstream version of the
1460 If you need to configure the package differently for
1461 Debian or for Linux, and the upstream source doesn't
1462 provide a way to do so, you should add such configuration
1463 facilities (for example, a new <prgn>autoconf</prgn> test
1464 or <tt>#define</tt>) and send the patch to the upstream
1465 authors, with the default set to the way they originally
1466 had it. You can then easily override the default in your
1467 <file>debian/rules</file> or wherever is appropriate.
1471 You should make sure that the <prgn>configure</prgn> utility
1472 detects the correct architecture specification string
1473 (refer to <ref id="arch-spec"> for details).
1477 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1478 <prgn>configure</prgn> scripts are used, you should edit the
1479 <file>.in</file> files rather than editing the
1480 <prgn>Makefile</prgn> directly. This allows the user to
1481 reconfigure the package if necessary. You should
1482 <em>not</em> configure the package and edit the generated
1483 <prgn>Makefile</prgn>! This makes it impossible for someone
1484 else to later reconfigure the package without losing the
1490 <sect id="dpkgchangelog">
1491 <heading>Debian changelog: <file>debian/changelog</file></heading>
1494 Changes in the Debian version of the package should be
1495 briefly explained in the Debian changelog file
1496 <file>debian/changelog</file>.<footnote>
1498 Mistakes in changelogs are usually best rectified by
1499 making a new changelog entry rather than "rewriting
1500 history" by editing old changelog entries.
1503 This includes modifications
1504 made in the Debian package compared to the upstream one
1505 as well as other changes and updates to the package.
1507 Although there is nothing stopping an author who is also
1508 the Debian maintainer from using this changelog for all
1509 their changes, it will have to be renamed if the Debian
1510 and upstream maintainers become different people. In such
1511 a case, however, it might be better to maintain the package
1512 as a non-native package.
1517 The format of the <file>debian/changelog</file> allows the
1518 package building tools to discover which version of the package
1519 is being built and find out other release-specific information.
1523 That format is a series of entries like this:
1525 <example compact="compact">
1526 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1528 [optional blank line(s), stripped]
1530 * <var>change details</var>
1531 <var>more change details</var>
1533 [blank line(s), included in output of dpkg-parsechangelog]
1535 * <var>even more change details</var>
1537 [optional blank line(s), stripped]
1539 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1544 <var>package</var> and <var>version</var> are the source
1545 package name and version number.
1549 <var>distribution(s)</var> lists the distributions where
1550 this version should be installed when it is uploaded - it
1551 is copied to the <tt>Distribution</tt> field in the
1552 <file>.changes</file> file. See <ref id="f-Distribution">.
1556 <var>urgency</var> is the value for the <tt>Urgency</tt>
1557 field in the <file>.changes</file> file for the upload
1558 (see <ref id="f-Urgency">). It is not possible to specify
1559 an urgency containing commas; commas are used to separate
1560 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1561 <prgn>dpkg</prgn> changelog format (though there is
1562 currently only one useful <var>keyword</var>,
1567 The change details may in fact be any series of lines
1568 starting with at least two spaces, but conventionally each
1569 change starts with an asterisk and a separating space and
1570 continuation lines are indented so as to bring them in
1571 line with the start of the text above. Blank lines may be
1572 used here to separate groups of changes, if desired.
1576 If this upload resolves bugs recorded in the Bug Tracking
1577 System (BTS), they may be automatically closed on the
1578 inclusion of this package into the Debian archive by
1579 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1580 in the change details.<footnote>
1581 To be precise, the string should match the following
1582 Perl regular expression:
1584 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1586 Then all of the bug numbers listed will be closed by the
1587 archive maintenance script (<prgn>katie</prgn>) using the
1588 <var>version</var> of the changelog entry.
1590 This information is conveyed via the <tt>Closes</tt> field
1591 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1595 The maintainer name and email address used in the changelog
1596 should be the details of the person uploading <em>this</em>
1597 version. They are <em>not</em> necessarily those of the
1598 usual package maintainer. The information here will be
1599 copied to the <tt>Changed-By</tt> field in the
1600 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1601 and then later used to send an acknowledgement when the
1602 upload has been installed.
1606 The <var>date</var> must be in RFC822 format<footnote>
1607 This is generated by <tt>date -R</tt>.
1608 </footnote>; it must include the time zone specified
1609 numerically, with the time zone name or abbreviation
1610 optionally present as a comment in parentheses.
1614 The first "title" line with the package name must start
1615 at the left hand margin. The "trailer" line with the
1616 maintainer and date details must be preceded by exactly
1617 one space. The maintainer details and the date must be
1618 separated by exactly two spaces.
1622 The entire changelog must be encoded in UTF-8.
1626 For more information on placement of the changelog files
1627 within binary packages, please see <ref id="changelogs">.
1631 <sect id="dpkgcopyright">
1632 <heading>Copyright: <file>debian/copyright</file></heading>
1634 Every package must be accompanied by a verbatim copy of
1635 its copyright and distribution license in the file
1636 <file>/usr/share/doc/<var>package</var>/copyright</file>
1637 (see <ref id="copyrightfile"> for further details). Also see
1638 <ref id="pkgcopyright"> for further considerations relayed
1639 to copyrights for packages.
1643 <heading>Error trapping in makefiles</heading>
1646 When <prgn>make</prgn> invokes a command in a makefile
1647 (including your package's upstream makefiles and
1648 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1649 means that <prgn>sh</prgn>'s usual bad error handling
1650 properties apply: if you include a miniature script as one
1651 of the commands in your makefile you'll find that if you
1652 don't do anything about it then errors are not detected
1653 and <prgn>make</prgn> will blithely continue after
1658 Every time you put more than one shell command (this
1659 includes using a loop) in a makefile command you
1660 must make sure that errors are trapped. For
1661 simple compound commands, such as changing directory and
1662 then running a program, using <tt>&&</tt> rather
1663 than semicolon as a command separator is sufficient. For
1664 more complex commands including most loops and
1665 conditionals you should include a separate <tt>set -e</tt>
1666 command at the start of every makefile command that's
1667 actually one of these miniature shell scripts.
1671 <sect id="timestamps">
1672 <heading>Time Stamps</heading>
1674 Maintainers should preserve the modification times of the
1675 upstream source files in a package, as far as is reasonably
1677 The rationale is that there is some information conveyed
1678 by knowing the age of the file, for example, you could
1679 recognize that some documentation is very old by looking
1680 at the modification time, so it would be nice if the
1681 modification time of the upstream source would be
1687 <sect id="restrictions">
1688 <heading>Restrictions on objects in source packages</heading>
1691 The source package may not contain any hard links<footnote>
1693 This is not currently detected when building source
1694 packages, but only when extracting
1698 Hard links may be permitted at some point in the
1699 future, but would require a fair amount of
1702 </footnote>, device special files, sockets or setuid or
1703 setgid files.<footnote>
1704 Setgid directories are allowed.
1709 <sect id="debianrules">
1710 <heading>Main building script: <file>debian/rules</file></heading>
1713 This file must be an executable makefile, and contains the
1714 package-specific recipes for compiling the package and
1715 building binary package(s) from the source.
1719 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1720 so that it can be invoked by saying its name rather than
1721 invoking <prgn>make</prgn> explicitly.
1725 Since an interactive <file>debian/rules</file> script makes it
1726 impossible to auto-compile that package and also makes it
1727 hard for other people to reproduce the same binary
1728 package, all <em>required targets</em> MUST be
1729 non-interactive. At a minimum, required targets are the
1730 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1731 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1732 <em>binary-indep</em>, and <em>build</em>. It also follows
1733 that any target that these targets depend on must also be
1738 The targets are as follows (required unless stated otherwise):
1740 <tag><tt>build</tt></tag>
1743 The <tt>build</tt> target should perform all the
1744 configuration and compilation of the package.
1745 If a package has an interactive pre-build
1746 configuration routine, the Debianized source package
1747 must either be built after this has taken place (so
1748 that the binary package can be built without rerunning
1749 the configuration) or the configuration routine
1750 modified to become non-interactive. (The latter is
1751 preferable if there are architecture-specific features
1752 detected by the configuration routine.)
1756 For some packages, notably ones where the same
1757 source tree is compiled in different ways to produce
1758 two binary packages, the <tt>build</tt> target
1759 does not make much sense. For these packages it is
1760 good enough to provide two (or more) targets
1761 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1762 for each of the ways of building the package, and a
1763 <tt>build</tt> target that does nothing. The
1764 <tt>binary</tt> target will have to build the
1765 package in each of the possible ways and make the
1766 binary package out of each.
1770 The <tt>build</tt> target must not do anything
1771 that might require root privilege.
1775 The <tt>build</tt> target may need to run the
1776 <tt>clean</tt> target first - see below.
1780 When a package has a configuration and build routine
1781 which takes a long time, or when the makefiles are
1782 poorly designed, or when <tt>build</tt> needs to
1783 run <tt>clean</tt> first, it is a good idea to
1784 <tt>touch build</tt> when the build process is
1785 complete. This will ensure that if <tt>debian/rules
1786 build</tt> is run again it will not rebuild the whole
1788 Another common way to do this is for <tt>build</tt>
1789 to depend on <prgn>build-stamp</prgn> and to do
1790 nothing else, and for the <prgn>build-stamp</prgn>
1791 target to do the building and to <tt>touch
1792 build-stamp</tt> on completion. This is
1793 especially useful if the build routine creates a
1794 file or directory called <tt>build</tt>; in such a
1795 case, <tt>build</tt> will need to be listed as
1796 a phony target (i.e., as a dependency of the
1797 <tt>.PHONY</tt> target). See the documentation of
1798 <prgn>make</prgn> for more information on phony
1804 <tag><tt>build-arch</tt> (optional),
1805 <tt>build-indep</tt> (optional)
1809 A package may also provide both of the targets
1810 <tt>build-arch</tt> and <tt>build-indep</tt>.
1811 The <tt>build-arch</tt> target, if provided, should
1812 perform all the configuration and compilation required
1813 for producing all architecture-dependant binary packages
1814 (those packages for which the body of the
1815 <tt>Architecture</tt> field in <tt>debian/control</tt>
1816 is not <tt>all</tt>).
1817 Similarly, the <tt>build-indep</tt> target, if
1818 provided, should perform all the configuration and
1819 compilation required for producing all
1820 architecture-independent binary packages
1821 (those packages for which the body of the
1822 <tt>Architecture</tt> field in <tt>debian/control</tt>
1824 The <tt>build</tt> target should depend on those of the
1825 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1826 are provided in the rules file.
1830 If one or both of the targets <tt>build-arch</tt> and
1831 <tt>build-indep</tt> are not provided, then invoking
1832 <file>debian/rules</file> with one of the not-provided
1833 targets as arguments should produce a exit status code
1834 of 2. Usually this is provided automatically by make
1835 if the target is missing.
1839 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1840 must not do anything that might require root privilege.
1844 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1845 <tt>binary-indep</tt>
1849 The <tt>binary</tt> target must be all that is
1850 necessary for the user to build the binary package(s)
1851 produced from this source package. It is
1852 split into two parts: <prgn>binary-arch</prgn> builds
1853 the binary packages which are specific to a particular
1854 architecture, and <tt>binary-indep</tt> builds
1855 those which are not.
1858 <tt>binary</tt> may be (and commonly is) a target with
1859 no commands which simply depends on
1860 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1863 Both <tt>binary-*</tt> targets should depend on the
1864 <tt>build</tt> target, or on the appropriate
1865 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1866 provided, so that the package is built if it has not
1867 been already. It should then create the relevant
1868 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1869 make their control files and <prgn>dpkg-deb</prgn> to
1870 build them and place them in the parent of the top
1875 Both the <tt>binary-arch</tt> and
1876 <tt>binary-indep</tt> targets <em>must</em> exist.
1877 If one of them has nothing to do (which will always be
1878 the case if the source generates only a single binary
1879 package, whether architecture-dependent or not), it
1880 must still exist and must always succeed.
1884 The <tt>binary</tt> targets must be invoked as
1886 The <prgn>fakeroot</prgn> package often allows one
1887 to build a package correctly even without being
1893 <tag><tt>clean</tt></tag>
1896 This must undo any effects that the <tt>build</tt>
1897 and <tt>binary</tt> targets may have had, except
1898 that it should leave alone any output files created in
1899 the parent directory by a run of a <tt>binary</tt>
1904 If a <tt>build</tt> file is touched at the end of
1905 the <tt>build</tt> target, as suggested above, it
1906 should be removed as the first action that
1907 <tt>clean</tt> performs, so that running
1908 <tt>build</tt> again after an interrupted
1909 <tt>clean</tt> doesn't think that everything is
1914 The <tt>clean</tt> target may need to be
1915 invoked as root if <tt>binary</tt> has been
1916 invoked since the last <tt>clean</tt>, or if
1917 <tt>build</tt> has been invoked as root (since
1918 <tt>build</tt> may create directories, for
1923 <tag><tt>get-orig-source</tt> (optional)</tag>
1926 This target fetches the most recent version of the
1927 original source package from a canonical archive site
1928 (via FTP or WWW, for example), does any necessary
1929 rearrangement to turn it into the original source
1930 tar file format described below, and leaves it in the
1935 This target may be invoked in any directory, and
1936 should take care to clean up any temporary files it
1941 This target is optional, but providing it if
1942 possible is a good idea.
1946 <tag><tt>patch</tt> (optional)</tag>
1949 This target performs whatever additional actions are
1950 required to make the source ready for editing (unpacking
1951 additional upstream archives, applying patches, etc.).
1952 It is recommended to be implemented for any package where
1953 <tt>dpkg-source -x</tt> does not result in source ready
1954 for additional modification. See
1955 <ref id="readmesource">.
1961 The <tt>build</tt>, <tt>binary</tt> and
1962 <tt>clean</tt> targets must be invoked with the current
1963 directory being the package's top-level directory.
1968 Additional targets may exist in <file>debian/rules</file>,
1969 either as published or undocumented interfaces or for the
1970 package's internal use.
1974 The architectures we build on and build for are determined
1975 by <prgn>make</prgn> variables using the utility
1976 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1977 You can determine the
1978 Debian architecture and the GNU style architecture
1979 specification string for the build machine (the machine type
1980 we are building on) as well as for the host machine (the
1981 machine type we are building for). Here is a list of
1982 supported <prgn>make</prgn> variables:
1983 <list compact="compact">
1985 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1988 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1989 specification string)
1992 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1993 <tt>DEB_*_GNU_TYPE</tt>)
1996 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1997 <tt>DEB_*_GNU_TYPE</tt>)
1999 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2000 the build machine or <tt>HOST</tt> for specification of the
2005 Backward compatibility can be provided in the rules file
2006 by setting the needed variables to suitable default
2007 values; please refer to the documentation of
2008 <prgn>dpkg-architecture</prgn> for details.
2012 It is important to understand that the <tt>DEB_*_ARCH</tt>
2013 string only determines which Debian architecture we are
2014 building on or for. It should not be used to get the CPU
2015 or system information; the GNU style variables should be
2019 <sect1 id="debianrules-options">
2020 <heading><file>debian/rules</file> and
2021 <tt>DEB_BUILD_OPTIONS</tt></heading>
2024 Supporting the standardized environment variable
2025 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2026 contain several flags to change how a package is compiled and
2027 built. Each flag must be in the form <var>flag</var> or
2028 <var>flag</var>=<var>options</var>. If multiple flags are
2029 given, they must be separated by whitespace.<footnote>
2030 Some packages support any delimiter, but whitespace is the
2031 easiest to parse inside a makefile and avoids ambiguity with
2032 flag values that contain commas.
2034 <var>flag</var> must start with a lowercase letter
2035 (<tt>a-z</tt>) and consist only of lowercase letters,
2036 numbers (<tt>0-9</tt>), and the characters
2037 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2038 <var>options</var> must not contain whitespace. The same
2039 tag should not be given multiple times with conflicting
2040 values. Package maintainers may assume that
2041 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2045 The meaning of the following tags has been standardized:
2049 This tag says to not run any build-time test suite
2050 provided by the package.
2054 The presence of this tag means that the package should
2055 be compiled with a minimum of optimization. For C
2056 programs, it is best to add <tt>-O0</tt> to
2057 <tt>CFLAGS</tt> (although this is usually the default).
2058 Some programs might fail to build or run at this level
2059 of optimization; it may be necessary to use
2060 <tt>-O1</tt>, for example.
2064 This tag means that the debugging symbols should not be
2065 stripped from the binary during installation, so that
2066 debugging information may be included in the package.
2068 <tag>parallel=n</tag>
2070 This tag means that the package should be built using up
2071 to <tt>n</tt> parallel processes if the package build
2072 system supports this.<footnote>
2073 Packages built with <tt>make</tt> can often implement
2074 this by passing the <tt>-j</tt><var>n</var> option to
2077 If the package build system does not support parallel
2078 builds, this string must be ignored. If the package
2079 build system only supports a lower level of concurrency
2080 than <var>n</var>, the package should be built using as
2081 many parallel processes as the package build system
2082 supports. It is up to the package maintainer to decide
2083 whether the package build times are long enough and the
2084 package build system is robust enough to make supporting
2085 parallel builds worthwhile.
2091 Unknown flags must be ignored by <file>debian/rules</file>.
2095 The following makefile snippet is an example of how one may
2096 implement the build options; you will probably have to
2097 massage this example in order to make it work for your
2099 <example compact="compact">
2102 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2103 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2104 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2105 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2107 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2112 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2113 INSTALL_PROGRAM += -s
2115 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2116 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2117 MAKEFLAGS += -j$(NUMJOBS)
2122 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2123 # Code to run the package test suite.
2130 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2131 <sect id="substvars">
2132 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2135 When <prgn>dpkg-gencontrol</prgn>,
2136 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2137 generate control files they perform variable substitutions
2138 on their output just before writing it. Variable
2139 substitutions have the form <tt>${<var>variable</var>}</tt>.
2140 The optional file <file>debian/substvars</file> contains
2141 variable substitutions to be used; variables can also be set
2142 directly from <file>debian/rules</file> using the <tt>-V</tt>
2143 option to the source packaging commands, and certain
2144 predefined variables are also available.
2148 The <file>debian/substvars</file> file is usually generated and
2149 modified dynamically by <file>debian/rules</file> targets, in
2150 which case it must be removed by the <tt>clean</tt> target.
2154 See <manref name="deb-substvars" section="5"> for full
2155 details about source variable substitutions, including the
2156 format of <file>debian/substvars</file>.</p>
2159 <sect id="debianwatch">
2160 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2163 This is an optional, recommended control file for the
2164 <tt>uscan</tt> utility which defines how to automatically
2165 scan ftp or http sites for newly available updates of the
2166 package. This is used by <url id="
2167 http://dehs.alioth.debian.org/"> and other Debian QA tools
2168 to help with quality control and maintenance of the
2169 distribution as a whole.
2174 <sect id="debianfiles">
2175 <heading>Generated files list: <file>debian/files</file></heading>
2178 This file is not a permanent part of the source tree; it
2179 is used while building packages to record which files are
2180 being generated. <prgn>dpkg-genchanges</prgn> uses it
2181 when it generates a <file>.changes</file> file.
2185 It should not exist in a shipped source package, and so it
2186 (and any backup files or temporary files such as
2187 <file>files.new</file><footnote>
2188 <file>files.new</file> is used as a temporary file by
2189 <prgn>dpkg-gencontrol</prgn> and
2190 <prgn>dpkg-distaddfile</prgn> - they write a new
2191 version of <tt>files</tt> here before renaming it,
2192 to avoid leaving a corrupted copy if an error
2194 </footnote>) should be removed by the
2195 <tt>clean</tt> target. It may also be wise to
2196 ensure a fresh start by emptying or removing it at the
2197 start of the <tt>binary</tt> target.
2201 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2202 package, it adds an entry to <file>debian/files</file> for the
2203 <file>.deb</file> file that will be created when <tt>dpkg-deb
2204 --build</tt> is run for that binary package. So for most
2205 packages all that needs to be done with this file is to
2206 delete it in the <tt>clean</tt> target.
2210 If a package upload includes files besides the source
2211 package and any binary packages whose control files were
2212 made with <prgn>dpkg-gencontrol</prgn> then they should be
2213 placed in the parent of the package's top-level directory
2214 and <prgn>dpkg-distaddfile</prgn> should be called to add
2215 the file to the list in <file>debian/files</file>.</p>
2218 <sect id="embeddedfiles">
2219 <heading>Convenience copies of code</heading>
2222 Some software packages include in their distribution convenience
2223 copies of code from other software packages, generally so that
2224 users compiling from source don't have to download multiple
2225 packages. Debian packages should not make use of these
2226 convenience copies unless the included package is explicitly
2227 intended to be used in this way.<footnote>
2228 For example, parts of the GNU build system work like this.
2230 If the included code is already in the Debian archive in the
2231 form of a library, the Debian packaging should ensure that
2232 binary packages reference the libraries already in Debian and
2233 the convenience copy is not used. If the included code is not
2234 already in Debian, it should be packaged separately as a
2235 prerequisite if possible.
2237 Having multiple copies of the same code in Debian is
2238 inefficient, often creates either static linking or shared
2239 library conflicts, and, most importantly, increases the
2240 difficulty of handling security vulnerabilities in the
2246 <sect id="readmesource">
2247 <heading>Source package handling:
2248 <file>debian/README.source</file></heading>
2251 If running <prgn>dpkg-source -x</prgn> on a source package
2252 doesn't produce the source of the package, ready for editing,
2253 and allow one to make changes and run
2254 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2255 without taking any additional steps, creating a
2256 <file>debian/README.source</file> documentation file is
2257 recommended. This file should explain how to do all of the
2260 <item>Generate the fully patched source, in a form ready for
2261 editing, that would be built to create Debian
2262 packages. Doing this with a <tt>patch</tt> target in
2263 <file>debian/rules</file> is recommended; see
2264 <ref id="debianrules">.</item>
2265 <item>Modify the source and save those modifications so that
2266 they will be applied when building the package.</item>
2267 <item>Remove source modifications that are currently being
2268 applied when building the package.</item>
2269 <item>Optionally, document what steps are necessary to
2270 upgrade the Debian source package to a new upstream version,
2271 if applicable.</item>
2273 This explanation should include specific commands and mention
2274 any additional required Debian packages. It should not assume
2275 familiarity with any specific Debian packaging system or patch
2280 This explanation may refer to a documentation file installed by
2281 one of the package's build dependencies provided that the
2282 referenced documentation clearly explains these tasks and is not
2283 a general reference manual.
2287 <file>debian/README.source</file> may also include any other
2288 information that would be helpful to someone modifying the
2289 source package. Even if the package doesn't fit the above
2290 description, maintainers are encouraged to document in a
2291 <file>debian/README.source</file> file any source package with a
2292 particularly complex or unintuitive source layout or build
2293 system (for example, a package that builds the same source
2294 multiple times to generate different binary packages).
2300 <chapt id="controlfields">
2301 <heading>Control files and their fields</heading>
2304 The package management system manipulates data represented in
2305 a common format, known as <em>control data</em>, stored in
2306 <em>control files</em>.
2307 Control files are used for source packages, binary packages and
2308 the <file>.changes</file> files which control the installation
2309 of uploaded files<footnote>
2310 <prgn>dpkg</prgn>'s internal databases are in a similar
2315 <sect id="controlsyntax">
2316 <heading>Syntax of control files</heading>
2319 A control file consists of one or more paragraphs of
2321 The paragraphs are also sometimes referred to as stanzas.
2323 The paragraphs are separated by blank lines. Some control
2324 files allow only one paragraph; others allow several, in
2325 which case each paragraph usually refers to a different
2326 package. (For example, in source packages, the first
2327 paragraph refers to the source package, and later paragraphs
2328 refer to binary packages generated from the source.)
2332 Each paragraph consists of a series of data fields; each
2333 field consists of the field name, followed by a colon and
2334 then the data/value associated with that field. It ends at
2335 the end of the (logical) line. Horizontal whitespace
2336 (spaces and tabs) may occur immediately before or after the
2337 value and is ignored there; it is conventional to put a
2338 single space after the colon. For example, a field might
2340 <example compact="compact">
2343 the field name is <tt>Package</tt> and the field value
2348 Many fields' values may span several lines; in this case
2349 each continuation line must start with a space or a tab.
2350 Any trailing spaces or tabs at the end of individual
2351 lines of a field value are ignored.
2355 In fields where it is specified that lines may not wrap,
2356 only a single line of data is allowed and whitespace is not
2357 significant in a field body. Whitespace must not appear
2358 inside names (of packages, architectures, files or anything
2359 else) or version numbers, or between the characters of
2360 multi-character version relationships.
2364 Field names are not case-sensitive, but it is usual to
2365 capitalize the field names using mixed case as shown below.
2369 Blank lines, or lines consisting only of spaces and tabs,
2370 are not allowed within field values or between fields - that
2371 would mean a new paragraph.
2375 All control files must be encoded in UTF-8.
2379 <sect id="sourcecontrolfiles">
2380 <heading>Source package control files -- <file>debian/control</file></heading>
2383 The <file>debian/control</file> file contains the most vital
2384 (and version-independent) information about the source package
2385 and about the binary packages it creates.
2389 The first paragraph of the control file contains information about
2390 the source package in general. The subsequent sets each describe a
2391 binary package that the source tree builds.
2395 The fields in the general paragraph (the first one, for the source
2398 <list compact="compact">
2399 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2400 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2401 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2402 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2403 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2404 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2405 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2406 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2411 The fields in the binary package paragraphs are:
2413 <list compact="compact">
2414 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2415 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2416 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2417 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2418 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2419 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2420 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2421 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2426 The syntax and semantics of the fields are described below.
2432 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2433 generate control files for binary packages (see below), by
2434 <prgn>dpkg-genchanges</prgn> to generate the
2435 <tt>.changes</tt> file to accompany the upload, and by
2436 <prgn>dpkg-source</prgn> when it creates the
2437 <file>.dsc</file> source control file as part of a source
2438 archive. Many fields are permitted to span multiple lines in
2439 <file>debian/control</file> but not in any other control
2440 file. These tools are responsible for removing the line
2441 breaks from such fields when using fields from
2442 <file>debian/control</file> to generate other control files.
2446 The fields here may contain variable references - their
2447 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2448 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2449 when they generate output control files.
2450 See <ref id="substvars"> for details.
2455 <sect id="binarycontrolfiles">
2456 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2459 The <file>DEBIAN/control</file> file contains the most vital
2460 (and version-dependent) information about a binary package.
2464 The fields in this file are:
2466 <list compact="compact">
2467 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2468 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2469 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2470 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2471 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2472 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2473 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2474 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2475 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2476 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2477 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2478 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2483 <sect id="debiansourcecontrolfiles">
2484 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2487 This file contains a series of fields, identified and
2488 separated just like the fields in the control file of
2489 a binary package. The fields are listed below; their
2490 syntax is described above, in <ref id="pkg-controlfields">.
2492 <list compact="compact">
2493 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2494 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2495 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2496 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2497 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2498 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2499 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2500 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2501 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2502 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2503 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2508 The source package control file is generated by
2509 <prgn>dpkg-source</prgn> when it builds the source
2510 archive, from other files in the source package,
2511 described above. When unpacking, it is checked against
2512 the files and directories in the other parts of the
2518 <sect id="debianchangesfiles">
2519 <heading>Debian changes files -- <file>.changes</file></heading>
2522 The .changes files are used by the Debian archive maintenance
2523 software to process updates to packages. They contain one
2524 paragraph which contains information from the
2525 <tt>debian/control</tt> file and other data about the
2526 source package gathered via <tt>debian/changelog</tt>
2527 and <tt>debian/rules</tt>.
2531 The fields in this file are:
2533 <list compact="compact">
2534 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2535 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2536 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2537 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2538 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2539 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2540 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2541 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2542 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2543 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2544 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2545 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2546 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2552 <sect id="controlfieldslist">
2553 <heading>List of fields</heading>
2555 <sect1 id="f-Source">
2556 <heading><tt>Source</tt></heading>
2559 This field identifies the source package name.
2563 In <file>debian/control</file> or a <file>.dsc</file> file,
2564 this field must contain only the name of the source package.
2568 In a binary package control file or a <file>.changes</file>
2569 file, the source package name may be followed by a version
2570 number in parentheses<footnote>
2571 It is customary to leave a space after the package name
2572 if a version number is specified.
2574 This version number may be omitted (and is, by
2575 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2576 the <tt>Version</tt> field of the binary package in
2577 question. The field itself may be omitted from a binary
2578 package control file when the source package has the same
2579 name and version as the binary package.
2583 <sect1 id="f-Maintainer">
2584 <heading><tt>Maintainer</tt></heading>
2587 The package maintainer's name and email address. The name
2588 should come first, then the email address inside angle
2589 brackets <tt><></tt> (in RFC822 format).
2593 If the maintainer's name contains a full stop then the
2594 whole field will not work directly as an email address due
2595 to a misfeature in the syntax specified in RFC822; a
2596 program using this field as an address must check for this
2597 and correct the problem if necessary (for example by
2598 putting the name in round brackets and moving it to the
2599 end, and bringing the email address forward).
2603 <sect1 id="f-Uploaders">
2604 <heading><tt>Uploaders</tt></heading>
2607 List of the names and email addresses of co-maintainers of
2608 the package, if any. If the package has other maintainers
2609 beside the one named in the
2610 <qref id="f-Maintainer">Maintainer field</qref>, their
2611 names and email addresses should be listed here. The
2612 format is the same as that of the Maintainer tag, and
2613 multiple entries should be comma separated. Currently,
2614 this field is restricted to a single line of data. This
2615 is an optional field.
2618 Any parser that interprets the Uploaders field in
2619 <file>debian/control</file> must permit it to span multiple
2620 lines. Line breaks in an Uploaders field that spans multiple
2621 lines are not significant and the semantics of the field are
2622 the same as if the line breaks had not been present.
2626 <sect1 id="f-Changed-By">
2627 <heading><tt>Changed-By</tt></heading>
2630 The name and email address of the person who changed the
2631 said package. Usually the name of the maintainer.
2632 All the rules for the Maintainer field apply here, too.
2636 <sect1 id="f-Section">
2637 <heading><tt>Section</tt></heading>
2640 This field specifies an application area into which the package
2641 has been classified. See <ref id="subsections">.
2645 When it appears in the <file>debian/control</file> file,
2646 it gives the value for the subfield of the same name in
2647 the <tt>Files</tt> field of the <file>.changes</file> file.
2648 It also gives the default for the same field in the binary
2653 <sect1 id="f-Priority">
2654 <heading><tt>Priority</tt></heading>
2657 This field represents how important that it is that the user
2658 have the package installed. See <ref id="priorities">.
2662 When it appears in the <file>debian/control</file> file,
2663 it gives the value for the subfield of the same name in
2664 the <tt>Files</tt> field of the <file>.changes</file> file.
2665 It also gives the default for the same field in the binary
2670 <sect1 id="f-Package">
2671 <heading><tt>Package</tt></heading>
2674 The name of the binary package.
2678 Package names must consist only of lower case letters
2679 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2680 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2681 They must be at least two characters long and must start
2682 with an alphanumeric character.
2686 <sect1 id="f-Architecture">
2687 <heading><tt>Architecture</tt></heading>
2690 Depending on context and the control file used, the
2691 <tt>Architecture</tt> field can include the following sets of
2694 <item>A unique single word identifying a Debian machine
2695 architecture, see <ref id="arch-spec">.
2696 <item><tt>all</tt>, which indicates an
2697 architecture-independent package.
2698 <item><tt>any</tt>, which indicates a package available
2699 for building on any architecture.
2700 <item><tt>source</tt>, which indicates a source package.
2705 In the main <file>debian/control</file> file in the source
2706 package, or in the source package control file
2707 <file>.dsc</file>, one may specify a list of architectures
2708 separated by spaces, or the special values <tt>any</tt> or
2713 Specifying <tt>any</tt> indicates that the source package
2714 isn't dependent on any particular architecture and should
2715 compile fine on any one. The produced binary package(s)
2716 will be specific to whatever the current build architecture
2718 This is the most often used setting, and is recommended
2719 for new packages that aren't <tt>Architecture: all</tt>.
2724 Specifying a list of architectures indicates that the source
2725 will build an architecture-dependent package, and will only
2726 work correctly on the listed architectures.<footnote>
2727 This is a setting used for a minority of cases where the
2728 program is not portable. Generally, it should not be used
2734 In a <file>.changes</file> file, the <tt>Architecture</tt>
2735 field lists the architecture(s) of the package(s)
2736 currently being uploaded. This will be a list; if the
2737 source for the package is also being uploaded, the special
2738 entry <tt>source</tt> is also present.
2742 See <ref id="debianrules"> for information how to get the
2743 architecture for the build process.
2747 <sect1 id="f-Essential">
2748 <heading><tt>Essential</tt></heading>
2751 This is a boolean field which may occur only in the
2752 control file of a binary package or in a per-package fields
2753 paragraph of a main source control data file.
2757 If set to <tt>yes</tt> then the package management system
2758 will refuse to remove the package (upgrading and replacing
2759 it is still possible). The other possible value is <tt>no</tt>,
2760 which is the same as not having the field at all.
2765 <heading>Package interrelationship fields:
2766 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2767 <tt>Recommends</tt>, <tt>Suggests</tt>,
2768 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2769 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2773 These fields describe the package's relationships with
2774 other packages. Their syntax and semantics are described
2775 in <ref id="relationships">.</p>
2778 <sect1 id="f-Standards-Version">
2779 <heading><tt>Standards-Version</tt></heading>
2782 The most recent version of the standards (the policy
2783 manual and associated texts) with which the package
2788 The version number has four components: major and minor
2789 version number and major and minor patch level. When the
2790 standards change in a way that requires every package to
2791 change the major number will be changed. Significant
2792 changes that will require work in many packages will be
2793 signaled by a change to the minor number. The major patch
2794 level will be changed for any change to the meaning of the
2795 standards, however small; the minor patch level will be
2796 changed when only cosmetic, typographical or other edits
2797 are made which neither change the meaning of the document
2798 nor affect the contents of packages.
2802 Thus only the first three components of the policy version
2803 are significant in the <em>Standards-Version</em> control
2804 field, and so either these three components or the all
2805 four components may be specified.<footnote>
2806 In the past, people specified the full version number
2807 in the Standards-Version field, for example "2.3.0.0".
2808 Since minor patch-level changes don't introduce new
2809 policy, it was thought it would be better to relax
2810 policy and only require the first 3 components to be
2811 specified, in this example "2.3.0". All four
2812 components may still be used if someone wishes to do so.
2818 <sect1 id="f-Version">
2819 <heading><tt>Version</tt></heading>
2822 The version number of a package. The format is:
2823 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2827 The three components here are:
2829 <tag><var>epoch</var></tag>
2832 This is a single (generally small) unsigned integer. It
2833 may be omitted, in which case zero is assumed. If it is
2834 omitted then the <var>upstream_version</var> may not
2839 It is provided to allow mistakes in the version numbers
2840 of older versions of a package, and also a package's
2841 previous version numbering schemes, to be left behind.
2845 <tag><var>upstream_version</var></tag>
2848 This is the main part of the version number. It is
2849 usually the version number of the original ("upstream")
2850 package from which the <file>.deb</file> file has been made,
2851 if this is applicable. Usually this will be in the same
2852 format as that specified by the upstream author(s);
2853 however, it may need to be reformatted to fit into the
2854 package management system's format and comparison
2859 The comparison behavior of the package management system
2860 with respect to the <var>upstream_version</var> is
2861 described below. The <var>upstream_version</var>
2862 portion of the version number is mandatory.
2866 The <var>upstream_version</var> may contain only
2867 alphanumerics<footnote>
2868 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2870 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2871 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2872 tilde) and should start with a digit. If there is no
2873 <var>debian_revision</var> then hyphens are not allowed;
2874 if there is no <var>epoch</var> then colons are not
2879 <tag><var>debian_revision</var></tag>
2882 This part of the version number specifies the version of
2883 the Debian package based on the upstream version. It
2884 may contain only alphanumerics and the characters
2885 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2886 tilde) and is compared in the same way as the
2887 <var>upstream_version</var> is.
2891 It is optional; if it isn't present then the
2892 <var>upstream_version</var> may not contain a hyphen.
2893 This format represents the case where a piece of
2894 software was written specifically to be turned into a
2895 Debian package, and so there is only one "debianisation"
2896 of it and therefore no revision indication is required.
2900 It is conventional to restart the
2901 <var>debian_revision</var> at <tt>1</tt> each time the
2902 <var>upstream_version</var> is increased.
2906 The package management system will break the version
2907 number apart at the last hyphen in the string (if there
2908 is one) to determine the <var>upstream_version</var> and
2909 <var>debian_revision</var>. The absence of a
2910 <var>debian_revision</var> is equivalent to a
2911 <var>debian_revision</var> of <tt>0</tt>.
2918 When comparing two version numbers, first the <var>epoch</var>
2919 of each are compared, then the <var>upstream_version</var> if
2920 <var>epoch</var> is equal, and then <var>debian_revision</var>
2921 if <var>upstream_version</var> is also equal.
2922 <var>epoch</var> is compared numerically. The
2923 <var>upstream_version</var> and <var>debian_revision</var>
2924 parts are compared by the package management system using the
2925 following algorithm:
2929 The strings are compared from left to right.
2933 First the initial part of each string consisting entirely of
2934 non-digit characters is determined. These two parts (one of
2935 which may be empty) are compared lexically. If a difference
2936 is found it is returned. The lexical comparison is a
2937 comparison of ASCII values modified so that all the letters
2938 sort earlier than all the non-letters and so that a tilde
2939 sorts before anything, even the end of a part. For example,
2940 the following parts are in sorted order from earliest to
2941 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2942 <tt>a</tt>.<footnote>
2943 One common use of <tt>~</tt> is for upstream pre-releases.
2944 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2945 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2950 Then the initial part of the remainder of each string which
2951 consists entirely of digit characters is determined. The
2952 numerical values of these two parts are compared, and any
2953 difference found is returned as the result of the comparison.
2954 For these purposes an empty string (which can only occur at
2955 the end of one or both version strings being compared) counts
2960 These two steps (comparing and removing initial non-digit
2961 strings and initial digit strings) are repeated until a
2962 difference is found or both strings are exhausted.
2966 Note that the purpose of epochs is to allow us to leave behind
2967 mistakes in version numbering, and to cope with situations
2968 where the version numbering scheme changes. It is
2969 <em>not</em> intended to cope with version numbers containing
2970 strings of letters which the package management system cannot
2971 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2972 silly orderings (the author of this manual has heard of a
2973 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2974 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2975 <tt>2</tt> and so forth).
2979 <sect1 id="f-Description">
2980 <heading><tt>Description</tt></heading>
2983 In a source or binary control file, the <tt>Description</tt>
2984 field contains a description of the binary package, consisting
2985 of two parts, the synopsis or the short description, and the
2986 long description. The field's format is as follows:
2991 Description: <single line synopsis>
2992 <extended description over several lines>
2997 The lines in the extended description can have these formats:
3003 Those starting with a single space are part of a paragraph.
3004 Successive lines of this form will be word-wrapped when
3005 displayed. The leading space will usually be stripped off.
3009 Those starting with two or more spaces. These will be
3010 displayed verbatim. If the display cannot be panned
3011 horizontally, the displaying program will line wrap them "hard"
3012 (i.e., without taking account of word breaks). If it can they
3013 will be allowed to trail off to the right. None, one or two
3014 initial spaces may be deleted, but the number of spaces
3015 deleted from each line will be the same (so that you can have
3016 indenting work correctly, for example).
3020 Those containing a single space followed by a single full stop
3021 character. These are rendered as blank lines. This is the
3022 <em>only</em> way to get a blank line<footnote>
3023 Completely empty lines will not be rendered as blank lines.
3024 Instead, they will cause the parser to think you're starting
3025 a whole new record in the control file, and will therefore
3026 likely abort with an error.
3031 Those containing a space, a full stop and some more characters.
3032 These are for future expansion. Do not use them.
3038 Do not use tab characters. Their effect is not predictable.
3042 See <ref id="descriptions"> for further information on this.
3046 In a <file>.changes</file> file, the <tt>Description</tt> field
3047 contains a summary of the descriptions for the packages being
3052 The part of the field before the first newline is empty;
3053 thereafter each line has the name of a binary package and
3054 the summary description line from that binary package.
3055 Each line is indented by one space.
3060 <sect1 id="f-Distribution">
3061 <heading><tt>Distribution</tt></heading>
3064 In a <file>.changes</file> file or parsed changelog output
3065 this contains the (space-separated) name(s) of the
3066 distribution(s) where this version of the package should
3067 be installed. Valid distributions are determined by the
3068 archive maintainers.<footnote>
3069 Current distribution names are:
3070 <taglist compact="compact">
3071 <tag><em>stable</em></tag>
3073 This is the current "released" version of Debian
3074 GNU/Linux. Once the distribution is
3075 <em>stable</em> only security fixes and other
3076 major bug fixes are allowed. When changes are
3077 made to this distribution, the release number is
3078 increased (for example: 2.2r1 becomes 2.2r2 then
3082 <tag><em>unstable</em></tag>
3084 This distribution value refers to the
3085 <em>developmental</em> part of the Debian
3086 distribution tree. New packages, new upstream
3087 versions of packages and bug fixes go into the
3088 <em>unstable</em> directory tree. Download from
3089 this distribution at your own risk.
3092 <tag><em>testing</em></tag>
3094 This distribution value refers to the
3095 <em>testing</em> part of the Debian distribution
3096 tree. It receives its packages from the
3097 unstable distribution after a short time lag to
3098 ensure that there are no major issues with the
3099 unstable packages. It is less prone to breakage
3100 than unstable, but still risky. It is not
3101 possible to upload packages directly to
3105 <tag><em>frozen</em></tag>
3107 From time to time, the <em>testing</em>
3108 distribution enters a state of "code-freeze" in
3109 anticipation of release as a <em>stable</em>
3110 version. During this period of testing only
3111 fixes for existing or newly-discovered bugs will
3112 be allowed. The exact details of this stage are
3113 determined by the Release Manager.
3116 <tag><em>experimental</em></tag>
3118 The packages with this distribution value are
3119 deemed by their maintainers to be high
3120 risk. Oftentimes they represent early beta or
3121 developmental packages from various sources that
3122 the maintainers want people to try, but are not
3123 ready to be a part of the other parts of the
3124 Debian distribution tree. Download at your own
3130 You should list <em>all</em> distributions that the
3131 package should be installed into.
3135 More information is available in the Debian Developer's
3136 Reference, section "The Debian archive".
3143 <heading><tt>Date</tt></heading>
3146 This field includes the date the package was built or last edited.
3150 The value of this field is usually extracted from the
3151 <file>debian/changelog</file> file - see
3152 <ref id="dpkgchangelog">).
3156 <sect1 id="f-Format">
3157 <heading><tt>Format</tt></heading>
3160 This field specifies a format revision for the file.
3161 The most current format described in the Policy Manual
3162 is version <strong>1.5</strong>. The syntax of the
3163 format value is the same as that of a package version
3164 number except that no epoch or Debian revision is allowed
3165 - see <ref id="f-Version">.
3169 <sect1 id="f-Urgency">
3170 <heading><tt>Urgency</tt></heading>
3173 This is a description of how important it is to upgrade to
3174 this version from previous ones. It consists of a single
3175 keyword taking one of the values <tt>low</tt>,
3176 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3177 <tt>critical</tt><footnote>
3178 Other urgency values are supported with configuration
3179 changes in the archive software but are not used in Debian.
3180 The urgency affects how quickly a package will be considered
3181 for inclusion into the <tt>testing</tt> distribution and
3182 gives an indication of the importance of any fixes included
3183 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3184 treated as synonymous.
3185 </footnote> (not case-sensitive) followed by an optional
3186 commentary (separated by a space) which is usually in
3187 parentheses. For example:
3190 Urgency: low (HIGH for users of diversions)
3196 The value of this field is usually extracted from the
3197 <file>debian/changelog</file> file - see
3198 <ref id="dpkgchangelog">.
3202 <sect1 id="f-Changes">
3203 <heading><tt>Changes</tt></heading>
3206 This field contains the human-readable changes data, describing
3207 the differences between the last version and the current one.
3211 There should be nothing in this field before the first
3212 newline; all the subsequent lines must be indented by at
3213 least one space; blank lines must be represented by a line
3214 consisting only of a space and a full stop.
3218 The value of this field is usually extracted from the
3219 <file>debian/changelog</file> file - see
3220 <ref id="dpkgchangelog">).
3224 Each version's change information should be preceded by a
3225 "title" line giving at least the version, distribution(s)
3226 and urgency, in a human-readable way.
3230 If data from several versions is being returned the entry
3231 for the most recent version should be returned first, and
3232 entries should be separated by the representation of a
3233 blank line (the "title" line may also be followed by the
3234 representation of blank line).
3238 <sect1 id="f-Binary">
3239 <heading><tt>Binary</tt></heading>
3242 This field is a list of binary packages.
3246 When it appears in the <file>.dsc</file> file it is the list
3247 of binary packages which a source package can produce. It
3248 does not necessarily produce all of these binary packages
3249 for every architecture. The source control file doesn't
3250 contain details of which architectures are appropriate for
3251 which of the binary packages.
3255 When it appears in a <file>.changes</file> file it lists the
3256 names of the binary packages actually being uploaded.
3260 The syntax is a list of binary packages separated by
3262 A space after each comma is conventional.
3263 </footnote>. Currently the packages must be separated using
3264 only spaces in the <file>.changes</file> file.
3268 <sect1 id="f-Installed-Size">
3269 <heading><tt>Installed-Size</tt></heading>
3272 This field appears in the control files of binary
3273 packages, and in the <file>Packages</file> files. It gives
3274 the total amount of disk space required to install the
3279 The disk space is represented in kilobytes as a simple
3284 <sect1 id="f-Files">
3285 <heading><tt>Files</tt></heading>
3288 This field contains a list of files with information about
3289 each one. The exact information and syntax varies with
3290 the context. In all cases the part of the field
3291 contents on the same line as the field name is empty. The
3292 remainder of the field is one line per file, each line
3293 being indented by one space and containing a number of
3294 sub-fields separated by spaces.
3298 In the <file>.dsc</file> file, each line contains the MD5
3299 checksum, size and filename of the tar file and (if applicable)
3300 diff file which make up the remainder of the source
3302 That is, the parts which are not the <tt>.dsc</tt>.
3304 The exact forms of the filenames are described
3305 in <ref id="pkg-sourcearchives">.
3309 In the <file>.changes</file> file this contains one line per
3310 file being uploaded. Each line contains the MD5 checksum,
3311 size, section and priority and the filename.
3312 The <qref id="f-Section">section</qref>
3313 and <qref id="f-Priority">priority</qref>
3314 are the values of the corresponding fields in
3315 the main source control file. If no section or priority is
3316 specified then <tt>-</tt> should be used, though section
3317 and priority values must be specified for new packages to
3318 be installed properly.
3322 The special value <tt>byhand</tt> for the section in a
3323 <tt>.changes</tt> file indicates that the file in question
3324 is not an ordinary package file and must by installed by
3325 hand by the distribution maintainers. If the section is
3326 <tt>byhand</tt> the priority should be <tt>-</tt>.
3330 If a new Debian revision of a package is being shipped and
3331 no new original source archive is being distributed the
3332 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3333 entry for the original source archive
3334 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3335 but the <file>.changes</file> file should leave it out. In
3336 this case the original source archive on the distribution
3337 site must match exactly, byte-for-byte, the original
3338 source archive which was used to generate the
3339 <file>.dsc</file> file and diff which are being uploaded.</p>
3342 <sect1 id="f-Closes">
3343 <heading><tt>Closes</tt></heading>
3346 A space-separated list of bug report numbers that the upload
3347 governed by the .changes file closes.
3351 <sect1 id="f-Homepage">
3352 <heading><tt>Homepage</tt></heading>
3355 The URL of the web site for this package, preferably (when
3356 applicable) the site from which the original source can be
3357 obtained and any additional upstream documentation or
3358 information may be found. The content of this field is a
3359 simple URL without any surrounding characters such as
3367 <heading>User-defined fields</heading>
3370 Additional user-defined fields may be added to the
3371 source package control file. Such fields will be
3372 ignored, and not copied to (for example) binary or
3373 source package control files or upload control files.
3377 If you wish to add additional unsupported fields to
3378 these output files you should use the mechanism
3383 Fields in the main source control information file with
3384 names starting <tt>X</tt>, followed by one or more of
3385 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3386 be copied to the output files. Only the part of the
3387 field name after the hyphen will be used in the output
3388 file. Where the letter <tt>B</tt> is used the field
3389 will appear in binary package control files, where the
3390 letter <tt>S</tt> is used in source package control
3391 files and where <tt>C</tt> is used in upload control
3392 (<tt>.changes</tt>) files.
3396 For example, if the main source information control file
3399 XBS-Comment: I stand between the candle and the star.
3401 then the binary and source package control files will contain the
3404 Comment: I stand between the candle and the star.
3413 <chapt id="maintainerscripts">
3414 <heading>Package maintainer scripts and installation procedure</heading>
3417 <heading>Introduction to package maintainer scripts</heading>
3420 It is possible to supply scripts as part of a package which
3421 the package management system will run for you when your
3422 package is installed, upgraded or removed.
3426 These scripts are the files <prgn>preinst</prgn>,
3427 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3428 <prgn>postrm</prgn> in the control area of the package.
3429 They must be proper executable files; if they are scripts
3430 (which is recommended), they must start with the usual
3431 <tt>#!</tt> convention. They should be readable and
3432 executable by anyone, and must not be world-writable.
3436 The package management system looks at the exit status from
3437 these scripts. It is important that they exit with a
3438 non-zero status if there is an error, so that the package
3439 management system can stop its processing. For shell
3440 scripts this means that you <em>almost always</em> need to
3441 use <tt>set -e</tt> (this is usually true when writing shell
3442 scripts, in fact). It is also important, of course, that
3443 they exit with a zero status if everything went well.
3447 Additionally, packages interacting with users using
3448 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3449 install a <prgn>config</prgn> script in the control area,
3450 see <ref id="maintscriptprompt"> for details.
3454 When a package is upgraded a combination of the scripts from
3455 the old and new packages is called during the upgrade
3456 procedure. If your scripts are going to be at all
3457 complicated you need to be aware of this, and may need to
3458 check the arguments to your scripts.
3462 Broadly speaking the <prgn>preinst</prgn> is called before
3463 (a particular version of) a package is installed, and the
3464 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3465 before (a version of) a package is removed and the
3466 <prgn>postrm</prgn> afterwards.
3470 Programs called from maintainer scripts should not normally
3471 have a path prepended to them. Before installation is
3472 started, the package management system checks to see if the
3473 programs <prgn>ldconfig</prgn>,
3474 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3475 and <prgn>update-rc.d</prgn> can be found via the
3476 <tt>PATH</tt> environment variable. Those programs, and any
3477 other program that one would expect to be in the
3478 <tt>PATH</tt>, should thus be invoked without an absolute
3479 pathname. Maintainer scripts should also not reset the
3480 <tt>PATH</tt>, though they might choose to modify it by
3481 prepending or appending package-specific directories. These
3482 considerations really apply to all shell scripts.</p>
3485 <sect id="idempotency">
3486 <heading>Maintainer scripts idempotency</heading>
3489 It is necessary for the error recovery procedures that the
3490 scripts be idempotent. This means that if it is run
3491 successfully, and then it is called again, it doesn't bomb
3492 out or cause any harm, but just ensures that everything is
3493 the way it ought to be. If the first call failed, or
3494 aborted half way through for some reason, the second call
3495 should merely do the things that were left undone the first
3496 time, if any, and exit with a success status if everything
3498 This is so that if an error occurs, the user interrupts
3499 <prgn>dpkg</prgn> or some other unforeseen circumstance
3500 happens you don't leave the user with a badly-broken
3501 package when <prgn>dpkg</prgn> attempts to repeat the
3507 <sect id="controllingterminal">
3508 <heading>Controlling terminal for maintainer scripts</heading>
3511 The maintainer scripts are guaranteed to run with a
3512 controlling terminal and can interact with the user.
3513 Because these scripts may be executed with standard output
3514 redirected into a pipe for logging purposes, Perl scripts
3515 should set unbuffered output by setting <tt>$|=1</tt> so
3516 that the output is printed immediately rather than being
3520 <sect id="exitstatus">
3521 <heading>Exit status</heading>
3524 Each script must return a zero exit status for
3525 success, or a nonzero one for failure, since the package
3526 management system looks for the exit status of these scripts
3527 and determines what action to take next based on that datum.
3531 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3536 <list compact="compact">
3538 <var>new-preinst</var> <tt>install</tt>
3541 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3544 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3547 <var>old-preinst</var> <tt>abort-upgrade</tt>
3548 <var>new-version</var>
3553 <list compact="compact">
3555 <var>postinst</var> <tt>configure</tt>
3556 <var>most-recently-configured-version</var>
3559 <var>old-postinst</var> <tt>abort-upgrade</tt>
3560 <var>new-version</var>
3563 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3564 <tt>in-favour</tt> <var>package</var>
3565 <var>new-version</var>
3568 <var>postinst</var> <tt>abort-remove</tt>
3571 <var>deconfigured's-postinst</var>
3572 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3573 <var>failed-install-package</var> <var>version</var>
3574 [<tt>removing</tt> <var>conflicting-package</var>
3580 <list compact="compact">
3582 <var>prerm</var> <tt>remove</tt>
3585 <var>old-prerm</var> <tt>upgrade</tt>
3586 <var>new-version</var>
3589 <var>new-prerm</var> <tt>failed-upgrade</tt>
3590 <var>old-version</var>
3593 <var>conflictor's-prerm</var> <tt>remove</tt>
3594 <tt>in-favour</tt> <var>package</var>
3595 <var>new-version</var>
3598 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3599 <tt>in-favour</tt> <var>package-being-installed</var>
3600 <var>version</var> [<tt>removing</tt>
3601 <var>conflicting-package</var>
3607 <list compact="compact">
3609 <var>postrm</var> <tt>remove</tt>
3612 <var>postrm</var> <tt>purge</tt>
3615 <var>old-postrm</var> <tt>upgrade</tt>
3616 <var>new-version</var>
3619 <var>new-postrm</var> <tt>failed-upgrade</tt>
3620 <var>old-version</var>
3623 <var>new-postrm</var> <tt>abort-install</tt>
3626 <var>new-postrm</var> <tt>abort-install</tt>
3627 <var>old-version</var>
3630 <var>new-postrm</var> <tt>abort-upgrade</tt>
3631 <var>old-version</var>
3634 <var>disappearer's-postrm</var> <tt>disappear</tt>
3635 <var>overwriter</var>
3636 <var>overwriter-version</var>
3642 <sect id="unpackphase">
3643 <heading>Details of unpack phase of installation or upgrade</heading>
3646 The procedure on installation/upgrade/overwrite/disappear
3647 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3648 stage of <tt>dpkg --install</tt>) is as follows. In each
3649 case, if a major error occurs (unless listed below) the
3650 actions are, in general, run backwards - this means that the
3651 maintainer scripts are run with different arguments in
3652 reverse order. These are the "error unwind" calls listed
3659 If a version of the package is already installed, call
3660 <example compact="compact">
3661 <var>old-prerm</var> upgrade <var>new-version</var>
3665 If the script runs but exits with a non-zero
3666 exit status, <prgn>dpkg</prgn> will attempt:
3667 <example compact="compact">
3668 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3670 If this works, the upgrade continues. If this
3671 does not work, the error unwind:
3672 <example compact="compact">
3673 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3675 If this works, then the old-version is
3676 "Installed", if not, the old version is in a
3677 "Failed-Config" state.
3683 If a "conflicting" package is being removed at the same time,
3684 or if any package will be broken (due to <tt>Breaks</tt>):
3687 If <tt>--auto-deconfigure</tt> is
3688 specified, call, for each package to be deconfigured
3689 due to <tt>Breaks</tt>:
3690 <example compact="compact">
3691 <var>deconfigured's-prerm</var> deconfigure \
3692 in-favour <var>package-being-installed</var> <var>version</var>
3695 <example compact="compact">
3696 <var>deconfigured's-postinst</var> abort-deconfigure \
3697 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3699 The deconfigured packages are marked as
3700 requiring configuration, so that if
3701 <tt>--install</tt> is used they will be
3702 configured again if possible.
3705 If any packages depended on a conflicting
3706 package being removed and <tt>--auto-deconfigure</tt> is
3707 specified, call, for each such package:
3708 <example compact="compact">
3709 <var>deconfigured's-prerm</var> deconfigure \
3710 in-favour <var>package-being-installed</var> <var>version</var> \
3711 removing <var>conflicting-package</var> <var>version</var>
3714 <example compact="compact">
3715 <var>deconfigured's-postinst</var> abort-deconfigure \
3716 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3717 removing <var>conflicting-package</var> <var>version</var>
3719 The deconfigured packages are marked as
3720 requiring configuration, so that if
3721 <tt>--install</tt> is used they will be
3722 configured again if possible.
3725 To prepare for removal of each conflicting package, call:
3726 <example compact="compact">
3727 <var>conflictor's-prerm</var> remove \
3728 in-favour <var>package</var> <var>new-version</var>
3731 <example compact="compact">
3732 <var>conflictor's-postinst</var> abort-remove \
3733 in-favour <var>package</var> <var>new-version</var>
3742 If the package is being upgraded, call:
3743 <example compact="compact">
3744 <var>new-preinst</var> upgrade <var>old-version</var>
3746 If this fails, we call:
3748 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3755 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3757 is called. If this works, then the old version
3758 is in an "Installed" state, or else it is left
3759 in an "Unpacked" state.
3764 If it fails, then the old version is left
3765 in an "Half-Installed" state.
3772 Otherwise, if the package had some configuration
3773 files from a previous version installed (i.e., it
3774 is in the "configuration files only" state):
3775 <example compact="compact">
3776 <var>new-preinst</var> install <var>old-version</var>
3780 <var>new-postrm</var> abort-install <var>old-version</var>
3782 If this fails, the package is left in a
3783 "Half-Installed" state, which requires a
3784 reinstall. If it works, the packages is left in
3785 a "Config Files" state.
3788 Otherwise (i.e., the package was completely purged):
3789 <example compact="compact">
3790 <var>new-preinst</var> install
3793 <example compact="compact">
3794 <var>new-postrm</var> abort-install
3796 If the error-unwind fails, the package is in a
3797 "Half Installed" phase, and requires a
3798 reinstall. If the error unwind works, the
3799 package is in a not installed state.
3806 The new package's files are unpacked, overwriting any
3807 that may be on the system already, for example any
3808 from the old version of the same package or from
3809 another package. Backups of the old files are kept
3810 temporarily, and if anything goes wrong the package
3811 management system will attempt to put them back as
3812 part of the error unwind.
3816 It is an error for a package to contain files which
3817 are on the system in another package, unless
3818 <tt>Replaces</tt> is used (see <ref id="replaces">).
3820 The following paragraph is not currently the case:
3821 Currently the <tt>- - force-overwrite</tt> flag is
3822 enabled, downgrading it to a warning, but this may not
3828 It is a more serious error for a package to contain a
3829 plain file or other kind of non-directory where another
3830 package has a directory (again, unless
3831 <tt>Replaces</tt> is used). This error can be
3832 overridden if desired using
3833 <tt>--force-overwrite-dir</tt>, but this is not
3838 Packages which overwrite each other's files produce
3839 behavior which, though deterministic, is hard for the
3840 system administrator to understand. It can easily
3841 lead to "missing" programs if, for example, a package
3842 is installed which overwrites a file from another
3843 package, and is then removed again.<footnote>
3844 Part of the problem is due to what is arguably a
3845 bug in <prgn>dpkg</prgn>.
3850 A directory will never be replaced by a symbolic link
3851 to a directory or vice versa; instead, the existing
3852 state (symlink or not) will be left alone and
3853 <prgn>dpkg</prgn> will follow the symlink if there is
3862 If the package is being upgraded, call
3863 <example compact="compact">
3864 <var>old-postrm</var> upgrade <var>new-version</var>
3868 If this fails, <prgn>dpkg</prgn> will attempt:
3869 <example compact="compact">
3870 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3872 If this works, installation continues. If not,
3874 <example compact="compact">
3875 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3877 If this fails, the old version is left in an
3878 "Half Installed" state. If it works, dpkg now
3880 <example compact="compact">
3881 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3883 If this fails, the old version is left in an
3884 "Half Installed" state. If it works, dpkg now
3886 <example compact="compact">
3887 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3889 If this fails, the old version is in an
3896 This is the point of no return - if
3897 <prgn>dpkg</prgn> gets this far, it won't back off
3898 past this point if an error occurs. This will
3899 leave the package in a fairly bad state, which
3900 will require a successful re-installation to clear
3901 up, but it's when <prgn>dpkg</prgn> starts doing
3902 things that are irreversible.
3907 Any files which were in the old version of the package
3908 but not in the new are removed.
3912 The new file list replaces the old.
3916 The new maintainer scripts replace the old.
3920 Any packages all of whose files have been overwritten
3921 during the installation, and which aren't required for
3922 dependencies, are considered to have been removed.
3923 For each such package
3926 <prgn>dpkg</prgn> calls:
3927 <example compact="compact">
3928 <var>disappearer's-postrm</var> disappear \
3929 <var>overwriter</var> <var>overwriter-version</var>
3933 The package's maintainer scripts are removed.
3936 It is noted in the status database as being in a
3937 sane state, namely not installed (any conffiles
3938 it may have are ignored, rather than being
3939 removed by <prgn>dpkg</prgn>). Note that
3940 disappearing packages do not have their prerm
3941 called, because <prgn>dpkg</prgn> doesn't know
3942 in advance that the package is going to
3949 Any files in the package we're unpacking that are also
3950 listed in the file lists of other packages are removed
3951 from those lists. (This will lobotomize the file list
3952 of the "conflicting" package if there is one.)
3956 The backup files made during installation, above, are
3962 The new package's status is now sane, and recorded as
3967 Here is another point of no return - if the
3968 conflicting package's removal fails we do not unwind
3969 the rest of the installation; the conflicting package
3970 is left in a half-removed limbo.
3975 If there was a conflicting package we go and do the
3976 removal actions (described below), starting with the
3977 removal of the conflicting package's files (any that
3978 are also in the package being installed have already
3979 been removed from the conflicting package's file list,
3980 and so do not get removed now).
3986 <sect id="configdetails"><heading>Details of configuration</heading>
3989 When we configure a package (this happens with <tt>dpkg
3990 --install</tt> and <tt>dpkg --configure</tt>), we first
3991 update any <tt>conffile</tt>s and then call:
3992 <example compact="compact">
3993 <var>postinst</var> configure <var>most-recently-configured-version</var>
3998 No attempt is made to unwind after errors during
3999 configuration. If the configuration fails, the package is in
4000 a "Failed Config" state, and an error message is generated.
4004 If there is no most recently configured version
4005 <prgn>dpkg</prgn> will pass a null argument.
4008 Historical note: Truly ancient (pre-1997) versions of
4009 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4010 (including the angle brackets) in this case. Even older
4011 ones did not pass a second argument at all, under any
4012 circumstance. Note that upgrades using such an old dpkg
4013 version are unlikely to work for other reasons, even if
4014 this old argument behavior is handled by your postinst script.
4020 <sect id="removedetails"><heading>Details of removal and/or
4021 configuration purging</heading>
4027 <example compact="compact">
4028 <var>prerm</var> remove
4032 If prerm fails during replacement due to conflict
4034 <var>conflictor's-postinst</var> abort-remove \
4035 in-favour <var>package</var> <var>new-version</var>
4039 <var>postinst</var> abort-remove
4043 If this fails, the package is in a "Failed-Config"
4044 state, or else it remains "Installed".
4048 The package's files are removed (except <tt>conffile</tt>s).
4051 <example compact="compact">
4052 <var>postrm</var> remove
4056 If it fails, there's no error unwind, and the package is in
4057 an "Half-Installed" state.
4062 All the maintainer scripts except the <prgn>postrm</prgn>
4067 If we aren't purging the package we stop here. Note
4068 that packages which have no <prgn>postrm</prgn> and no
4069 <tt>conffile</tt>s are automatically purged when
4070 removed, as there is no difference except for the
4071 <prgn>dpkg</prgn> status.
4075 The <tt>conffile</tt>s and any backup files
4076 (<tt>~</tt>-files, <tt>#*#</tt> files,
4077 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4082 <example compact="compact">
4083 <var>postrm</var> purge
4087 If this fails, the package remains in a "Config-Files"
4092 The package's file list is removed.
4101 <chapt id="relationships">
4102 <heading>Declaring relationships between packages</heading>
4104 <sect id="depsyntax">
4105 <heading>Syntax of relationship fields</heading>
4108 These fields all have a uniform syntax. They are a list of
4109 package names separated by commas.
4113 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4114 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4115 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4116 control file fields of the package, which declare
4117 dependencies on other packages, the package names listed may
4118 also include lists of alternative package names, separated
4119 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4120 if any one of the alternative packages is installed, that
4121 part of the dependency is considered to be satisfied.
4125 All of the fields except for <tt>Provides</tt> may restrict
4126 their applicability to particular versions of each named
4127 package. This is done in parentheses after each individual
4128 package name; the parentheses should contain a relation from
4129 the list below followed by a version number, in the format
4130 described in <ref id="f-Version">.
4134 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4135 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4136 strictly earlier, earlier or equal, exactly equal, later or
4137 equal and strictly later, respectively. The deprecated
4138 forms <tt><</tt> and <tt>></tt> were used to mean
4139 earlier/later or equal, rather than strictly earlier/later,
4140 so they should not appear in new packages (though
4141 <prgn>dpkg</prgn> still supports them).
4145 Whitespace may appear at any point in the version
4146 specification subject to the rules in <ref
4147 id="controlsyntax">, and must appear where it's necessary to
4148 disambiguate; it is not otherwise significant. All of the
4149 relationship fields may span multiple lines. For
4150 consistency and in case of future changes to
4151 <prgn>dpkg</prgn> it is recommended that a single space be
4152 used after a version relationship and before a version
4153 number; it is also conventional to put a single space after
4154 each comma, on either side of each vertical bar, and before
4155 each open parenthesis. When wrapping a relationship field, it
4156 is conventional to do so after a comma and before the space
4157 following that comma.
4161 For example, a list of dependencies might appear as:
4162 <example compact="compact">
4165 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4170 All fields that specify build-time relationships
4171 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4172 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4173 may be restricted to a certain set of architectures. This
4174 is indicated in brackets after each individual package name and
4175 the optional version specification. The brackets enclose a
4176 list of Debian architecture names separated by whitespace.
4177 Exclamation marks may be prepended to each of the names.
4178 (It is not permitted for some names to be prepended with
4179 exclamation marks while others aren't.) If the current Debian
4180 host architecture is not in this list and there are no
4181 exclamation marks in the list, or it is in the list with a
4182 prepended exclamation mark, the package name and the
4183 associated version specification are ignored completely for
4184 the purposes of defining the relationships.
4189 <example compact="compact">
4191 Build-Depends-Indep: texinfo
4192 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4193 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4195 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4196 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4197 <tt>gnumach-dev</tt> only on hurd-i386.
4201 If the architecture-restricted dependency is part of a set of
4202 alternatives using <tt>|</tt>, that alternative is ignored
4203 completely on architectures that do not match the restriction.
4205 <example compact="compact">
4206 Build-Depends: foo [!i386] | bar [!amd64]
4208 is equivalent to <tt>bar</tt> on the i386 architecture, to
4209 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4210 bar</tt> on all other architectures.
4214 Note that the binary package relationship fields such as
4215 <tt>Depends</tt> appear in one of the binary package
4216 sections of the control file, whereas the build-time
4217 relationships such as <tt>Build-Depends</tt> appear in the
4218 source package section of the control file (which is the
4223 <sect id="binarydeps">
4224 <heading>Binary Dependencies - <tt>Depends</tt>,
4225 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4226 <tt>Pre-Depends</tt>
4230 Packages can declare in their control file that they have
4231 certain relationships to other packages - for example, that
4232 they may not be installed at the same time as certain other
4233 packages, and/or that they depend on the presence of others.
4237 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4238 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4239 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4243 These seven fields are used to declare a dependency
4244 relationship by one package on another. Except for
4245 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4246 depending (binary) package's control file.
4247 (<tt>Enhances</tt> appears in the recommending package's
4248 control file, and <tt>Breaks</tt> appears in the version of
4249 depended-on package which causes the named package to
4254 A <tt>Depends</tt> field takes effect <em>only</em> when a
4255 package is to be configured. It does not prevent a package
4256 being on the system in an unconfigured state while its
4257 dependencies are unsatisfied, and it is possible to replace
4258 a package whose dependencies are satisfied and which is
4259 properly installed with a different version whose
4260 dependencies are not and cannot be satisfied; when this is
4261 done the depending package will be left unconfigured (since
4262 attempts to configure it will give errors) and will not
4263 function properly. If it is necessary, a
4264 <tt>Pre-Depends</tt> field can be used, which has a partial
4265 effect even when a package is being unpacked, as explained
4266 in detail below. (The other three dependency fields,
4267 <tt>Recommends</tt>, <tt>Suggests</tt> and
4268 <tt>Enhances</tt>, are only used by the various front-ends
4269 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4270 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4274 For this reason packages in an installation run are usually
4275 all unpacked first and all configured later; this gives
4276 later versions of packages with dependencies on later
4277 versions of other packages the opportunity to have their
4278 dependencies satisfied.
4282 In case of circular dependencies, since installation or
4283 removal order honoring the dependency order can't be
4284 established, dependency loops are broken at some point
4285 (based on rules below), and some packages may not be able to
4286 rely on their dependencies being present when being
4287 installed or removed, depending on which side of the break
4288 of the circular dependency loop they happen to be on. If one
4289 of the packages in the loop has no postinst script, then the
4290 cycle will be broken at that package, so as to ensure that
4291 all postinst scripts run with the dependencies properly
4292 configured if this is possible. Otherwise the breaking point
4297 The <tt>Depends</tt> field thus allows package maintainers
4298 to impose an order in which packages should be configured.
4302 The meaning of the five dependency fields is as follows:
4304 <tag><tt>Depends</tt></tag>
4307 This declares an absolute dependency. A package will
4308 not be configured unless all of the packages listed in
4309 its <tt>Depends</tt> field have been correctly
4314 The <tt>Depends</tt> field should be used if the
4315 depended-on package is required for the depending
4316 package to provide a significant amount of
4321 The <tt>Depends</tt> field should also be used if the
4322 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4323 <prgn>postrm</prgn> scripts require the package to be
4324 present in order to run. Note, however, that the
4325 <prgn>postrm</prgn> cannot rely on any non-essential
4326 packages to be present during the <tt>purge</tt>
4330 <tag><tt>Recommends</tt></tag>
4333 This declares a strong, but not absolute, dependency.
4337 The <tt>Recommends</tt> field should list packages
4338 that would be found together with this one in all but
4339 unusual installations.
4343 <tag><tt>Suggests</tt></tag>
4345 This is used to declare that one package may be more
4346 useful with one or more others. Using this field
4347 tells the packaging system and the user that the
4348 listed packages are related to this one and can
4349 perhaps enhance its usefulness, but that installing
4350 this one without them is perfectly reasonable.
4353 <tag><tt>Enhances</tt></tag>
4355 This field is similar to Suggests but works in the
4356 opposite direction. It is used to declare that a
4357 package can enhance the functionality of another
4361 <tag><tt>Pre-Depends</tt></tag>
4364 This field is like <tt>Depends</tt>, except that it
4365 also forces <prgn>dpkg</prgn> to complete installation
4366 of the packages named before even starting the
4367 installation of the package which declares the
4368 pre-dependency, as follows:
4372 When a package declaring a pre-dependency is about to
4373 be <em>unpacked</em> the pre-dependency can be
4374 satisfied if the depended-on package is either fully
4375 configured, <em>or even if</em> the depended-on
4376 package(s) are only unpacked or half-configured,
4377 provided that they have been configured correctly at
4378 some point in the past (and not removed or partially
4379 removed since). In this case, both the
4380 previously-configured and currently unpacked or
4381 half-configured versions must satisfy any version
4382 clause in the <tt>Pre-Depends</tt> field.
4386 When the package declaring a pre-dependency is about
4387 to be <em>configured</em>, the pre-dependency will be
4388 treated as a normal <tt>Depends</tt>, that is, it will
4389 be considered satisfied only if the depended-on
4390 package has been correctly configured.
4394 <tt>Pre-Depends</tt> should be used sparingly,
4395 preferably only by packages whose premature upgrade or
4396 installation would hamper the ability of the system to
4397 continue with any upgrade that might be in progress.
4401 <tt>Pre-Depends</tt> are also required if the
4402 <prgn>preinst</prgn> script depends on the named
4403 package. It is best to avoid this situation if
4411 When selecting which level of dependency to use you should
4412 consider how important the depended-on package is to the
4413 functionality of the one declaring the dependency. Some
4414 packages are composed of components of varying degrees of
4415 importance. Such a package should list using
4416 <tt>Depends</tt> the package(s) which are required by the
4417 more important components. The other components'
4418 requirements may be mentioned as Suggestions or
4419 Recommendations, as appropriate to the components' relative
4425 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4428 Using <tt>Breaks</tt> may cause problems for upgrades from older
4429 versions of Debian and should not be used until the stable
4430 release of Debian supports <tt>Breaks</tt>.
4434 When one binary package declares that it breaks another,
4435 <prgn>dpkg</prgn> will refuse to allow the package which
4436 declares <tt>Breaks</tt> be installed unless the broken
4437 package is deconfigured first, and it will refuse to
4438 allow the broken package to be reconfigured.
4442 A package will not be regarded as causing breakage merely
4443 because its configuration files are still installed; it must
4444 be at least half-installed.
4448 A special exception is made for packages which declare that
4449 they break their own package name or a virtual package which
4450 they provide (see below): this does not count as a real
4455 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4456 version clause; such a <tt>Breaks</tt> is introduced in the
4457 version of an (implicit or explicit) dependency which
4458 violates an assumption or reveals a bug in earlier versions
4459 of the broken package. This use of <tt>Breaks</tt> will
4460 inform higher-level package management tools that broken
4461 package must be upgraded before the new one.
4465 If the breaking package also overwrites some files from the
4466 older package, it should use <tt>Replaces</tt> (not
4467 <tt>Conflicts</tt>) to ensure this goes smoothly.
4471 <sect id="conflicts">
4472 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4475 When one binary package declares a conflict with another
4476 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4477 refuse to allow them to be installed on the system at the
4482 If one package is to be installed, the other must be removed
4483 first - if the package being installed is marked as
4484 replacing (see <ref id="replaces">) the one on the system,
4485 or the one on the system is marked as deselected, or both
4486 packages are marked <tt>Essential</tt>, then
4487 <prgn>dpkg</prgn> will automatically remove the package
4488 which is causing the conflict, otherwise it will halt the
4489 installation of the new package with an error. This
4490 mechanism is specifically designed to produce an error when
4491 the installed package is <tt>Essential</tt>, but the new
4496 A package will not cause a conflict merely because its
4497 configuration files are still installed; it must be at least
4502 A special exception is made for packages which declare a
4503 conflict with their own package name, or with a virtual
4504 package which they provide (see below): this does not
4505 prevent their installation, and allows a package to conflict
4506 with others providing a replacement for it. You use this
4507 feature when you want the package in question to be the only
4508 package providing some feature.
4512 A <tt>Conflicts</tt> entry should almost never have an
4513 "earlier than" version clause. This would prevent
4514 <prgn>dpkg</prgn> from upgrading or installing the package
4515 which declared such a conflict until the upgrade or removal
4516 of the conflicted-with package had been completed. Instead,
4517 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4518 by the stable release of Debian).
4522 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4526 As well as the names of actual ("concrete") packages, the
4527 package relationship fields <tt>Depends</tt>,
4528 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4529 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4530 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4531 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4532 may mention "virtual packages".
4536 A <em>virtual package</em> is one which appears in the
4537 <tt>Provides</tt> control file field of another package.
4538 The effect is as if the package(s) which provide a
4539 particular virtual package name had been listed by name
4540 everywhere the virtual package name appears. (See also <ref
4545 If there are both concrete and virtual packages of the same
4546 name, then the dependency may be satisfied (or the conflict
4547 caused) by either the concrete package with the name in
4548 question or any other concrete package which provides the
4549 virtual package with the name in question. This is so that,
4550 for example, supposing we have
4551 <example compact="compact">
4554 </example> and someone else releases an enhanced version of
4555 the <tt>bar</tt> package they can say:
4556 <example compact="compact">
4560 and the <tt>bar-plus</tt> package will now also satisfy the
4561 dependency for the <tt>foo</tt> package.
4565 If a relationship field has a version number attached
4566 then only real packages will be considered to see whether
4567 the relationship is satisfied (or the prohibition violated,
4568 for a conflict or breakage) - it is assumed that a real
4569 package which provides the virtual package is not of the
4570 "right" version. So, a <tt>Provides</tt> field may not
4571 contain version numbers, and the version number of the
4572 concrete package which provides a particular virtual package
4573 will not be looked at when considering a dependency on or
4574 conflict with the virtual package name.
4578 It is likely that the ability will be added in a future
4579 release of <prgn>dpkg</prgn> to specify a version number for
4580 each virtual package it provides. This feature is not yet
4581 present, however, and is expected to be used only
4586 If you want to specify which of a set of real packages
4587 should be the default to satisfy a particular dependency on
4588 a virtual package, you should list the real package as an
4589 alternative before the virtual one.
4594 <sect id="replaces"><heading>Overwriting files and replacing
4595 packages - <tt>Replaces</tt></heading>
4598 Packages can declare in their control file that they should
4599 overwrite files in certain other packages, or completely
4600 replace other packages. The <tt>Replaces</tt> control file
4601 field has these two distinct purposes.
4604 <sect1><heading>Overwriting files in other packages</heading>
4607 Firstly, as mentioned before, it is usually an error for a
4608 package to contain files which are on the system in
4613 However, if the overwriting package declares that it
4614 <tt>Replaces</tt> the one containing the file being
4615 overwritten, then <prgn>dpkg</prgn> will replace the file
4616 from the old package with that from the new. The file
4617 will no longer be listed as "owned" by the old package.
4621 If a package is completely replaced in this way, so that
4622 <prgn>dpkg</prgn> does not know of any files it still
4623 contains, it is considered to have "disappeared". It will
4624 be marked as not wanted on the system (selected for
4625 removal) and not installed. Any <tt>conffile</tt>s
4626 details noted for the package will be ignored, as they
4627 will have been taken over by the overwriting package. The
4628 package's <prgn>postrm</prgn> script will be run with a
4629 special argument to allow the package to do any final
4630 cleanup required. See <ref id="mscriptsinstact">.
4633 Replaces is a one way relationship -- you have to
4634 install the replacing package after the replaced
4641 For this usage of <tt>Replaces</tt>, virtual packages (see
4642 <ref id="virtual">) are not considered when looking at a
4643 <tt>Replaces</tt> field - the packages declared as being
4644 replaced must be mentioned by their real names.
4648 Furthermore, this usage of <tt>Replaces</tt> only takes
4649 effect when both packages are at least partially on the
4650 system at once, so that it can only happen if they do not
4651 conflict or if the conflict has been overridden.
4656 <sect1><heading>Replacing whole packages, forcing their
4660 Secondly, <tt>Replaces</tt> allows the packaging system to
4661 resolve which package should be removed when there is a
4662 conflict - see <ref id="conflicts">. This usage only
4663 takes effect when the two packages <em>do</em> conflict,
4664 so that the two usages of this field do not interfere with
4669 In this situation, the package declared as being replaced
4670 can be a virtual package, so for example, all mail
4671 transport agents (MTAs) would have the following fields in
4672 their control files:
4673 <example compact="compact">
4674 Provides: mail-transport-agent
4675 Conflicts: mail-transport-agent
4676 Replaces: mail-transport-agent
4678 ensuring that only one MTA can be installed at any one
4683 <sect id="sourcebinarydeps">
4684 <heading>Relationships between source and binary packages -
4685 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4686 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4690 Source packages that require certain binary packages to be
4691 installed or absent at the time of building the package
4692 can declare relationships to those binary packages.
4696 This is done using the <tt>Build-Depends</tt>,
4697 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4698 <tt>Build-Conflicts-Indep</tt> control file fields.
4702 Build-dependencies on "build-essential" binary packages can be
4703 omitted. Please see <ref id="pkg-relations"> for more information.
4707 The dependencies and conflicts they define must be satisfied
4708 (as defined earlier for binary packages) in order to invoke
4709 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4711 If you make "build-arch" or "binary-arch", you need
4712 Build-Depends. If you make "build-indep" or
4713 "binary-indep", you need Build-Depends and
4714 Build-Depends-Indep. If you make "build" or "binary",
4718 There is no Build-Depends-Arch; this role is essentially
4719 met with Build-Depends. Anyone building the
4720 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4721 is basically assumed to be building the whole package
4722 anyway and so installs all build dependencies. The
4723 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4724 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4725 does not yet know how to check for its existence) and
4726 <tt>binary-arch</tt>.
4729 The purpose of the original split, I recall, was so that
4730 the autobuilders wouldn't need to install extra packages
4731 needed only for the binary-indep targets. But without a
4732 build-arch/build-indep split, this didn't work, since
4733 most of the work is done in the build target, not in the
4739 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4741 The <tt>Build-Depends</tt> and
4742 <tt>Build-Conflicts</tt> fields must be satisfied when
4743 any of the following targets is invoked:
4744 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4745 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4746 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4748 <tag><tt>Build-Depends-Indep</tt>,
4749 <tt>Build-Conflicts-Indep</tt></tag>
4751 The <tt>Build-Depends-Indep</tt> and
4752 <tt>Build-Conflicts-Indep</tt> fields must be
4753 satisfied when any of the following targets is
4754 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4755 <tt>binary</tt> and <tt>binary-indep</tt>.
4765 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4768 Packages containing shared libraries must be constructed with
4769 a little care to make sure that the shared library is always
4770 available. This is especially important for packages whose
4771 shared libraries are vitally important, such as the C library
4772 (currently <tt>libc6</tt>).
4776 Packages involving shared libraries should be split up into
4777 several binary packages. This section mostly deals with how
4778 this separation is to be accomplished; rules for files within
4779 the shared library packages are in <ref id="libraries"> instead.
4782 <sect id="sharedlibs-runtime">
4783 <heading>Run-time shared libraries</heading>
4786 The run-time shared library needs to be placed in a package
4787 whose name changes whenever the shared object version
4790 Since it is common place to install several versions of a
4791 package that just provides shared libraries, it is a
4792 good idea that the library package should not
4793 contain any extraneous non-versioned files, unless they
4794 happen to be in versioned directories.</p>
4796 The most common mechanism is to place it in a package
4798 <package><var>libraryname</var><var>soversion</var></package>,
4799 where <file><var>soversion</var></file> is the version number
4800 in the soname of the shared library<footnote>
4801 The soname is the shared object name: it's the thing
4802 that has to match exactly between building an executable
4803 and running it for the dynamic linker to be able run the
4804 program. For example, if the soname of the library is
4805 <file>libfoo.so.6</file>, the library package would be
4806 called <file>libfoo6</file>.
4808 Alternatively, if it would be confusing to directly append
4809 <var>soversion</var> to <var>libraryname</var> (e.g. because
4810 <var>libraryname</var> itself ends in a number), you may use
4811 <package><var>libraryname</var>-<var>soversion</var></package> and
4812 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4817 If you have several shared libraries built from the same
4818 source tree you may lump them all together into a single
4819 shared library package, provided that you change all of
4820 their sonames at once (so that you don't get filename
4821 clashes if you try to install different versions of the
4822 combined shared libraries package).
4826 The package should install the shared libraries under
4827 their normal names. For example, the <package>libgdbm3</package>
4828 package should install <file>libgdbm.so.3.0.0</file> as
4829 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4830 renamed or re-linked by any <prgn>prerm</prgn> or
4831 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4832 of renaming things safely without affecting running programs,
4833 and attempts to interfere with this are likely to lead to
4838 Shared libraries should not be installed executable, since
4839 the dynamic linker does not require this and trying to
4840 execute a shared library usually results in a core dump.
4844 The run-time library package should include the symbolic link that
4845 <prgn>ldconfig</prgn> would create for the shared libraries.
4846 For example, the <package>libgdbm3</package> package should include
4847 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4848 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4849 linker (for example <prgn>ld.so</prgn> or
4850 <prgn>ld-linux.so.*</prgn>) can find the library between the
4851 time that <prgn>dpkg</prgn> installs it and the time that
4852 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4854 The package management system requires the library to be
4855 placed before the symbolic link pointing to it in the
4856 <file>.deb</file> file. This is so that when
4857 <prgn>dpkg</prgn> comes to install the symlink
4858 (overwriting the previous symlink pointing at an older
4859 version of the library), the new shared library is already
4860 in place. In the past, this was achieved by creating the
4861 library in the temporary packaging directory before
4862 creating the symlink. Unfortunately, this was not always
4863 effective, since the building of the tar file in the
4864 <file>.deb</file> depended on the behavior of the underlying
4865 file system. Some file systems (such as reiserfs) reorder
4866 the files so that the order of creation is forgotten.
4867 Since version 1.7.0, <prgn>dpkg</prgn>
4868 reorders the files itself as necessary when building a
4869 package. Thus it is no longer important to concern
4870 oneself with the order of file creation.
4874 <sect1 id="ldconfig">
4875 <heading><tt>ldconfig</tt></heading>
4878 Any package installing shared libraries in one of the default
4879 library directories of the dynamic linker (which are currently
4880 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4881 listed in <file>/etc/ld.so.conf</file><footnote>
4883 <list compact="compact">
4884 <item>/usr/local/lib</item>
4885 <item>/usr/lib/libc5-compat</item>
4886 <item>/lib/libc5-compat</item>
4889 must use <prgn>ldconfig</prgn> to update the shared library
4894 The package maintainer scripts must only call
4895 <prgn>ldconfig</prgn> under these circumstances:
4896 <list compact="compact">
4897 <item>When the <prgn>postinst</prgn> script is run with a
4898 first argument of <tt>configure</tt>, the script must call
4899 <prgn>ldconfig</prgn>, and may optionally invoke
4900 <prgn>ldconfig</prgn> at other times.
4902 <item>When the <prgn>postrm</prgn> script is run with a
4903 first argument of <tt>remove</tt>, the script should call
4904 <prgn>ldconfig</prgn>.
4909 During install or upgrade, the preinst is called before
4910 the new files are installed, so calling "ldconfig" is
4911 pointless. The preinst of an existing package can also be
4912 called if an upgrade fails. However, this happens during
4913 the critical time when a shared libs may exist on-disk
4914 under a temporary name. Thus, it is dangerous and
4915 forbidden by current policy to call "ldconfig" at this
4920 When a package is installed or upgraded, "postinst
4921 configure" runs after the new files are safely on-disk.
4922 Since it is perfectly safe to invoke ldconfig
4923 unconditionally in a postinst, it is OK for a package to
4924 simply put ldconfig in its postinst without checking the
4925 argument. The postinst can also be called to recover from
4926 a failed upgrade. This happens before any new files are
4927 unpacked, so there is no reason to call "ldconfig" at this
4932 For a package that is being removed, prerm is
4933 called with all the files intact, so calling ldconfig is
4934 useless. The other calls to "prerm" happen in the case of
4935 upgrade at a time when all the files of the old package
4936 are on-disk, so again calling "ldconfig" is pointless.
4940 postrm, on the other hand, is called with the "remove"
4941 argument just after the files are removed, so this is
4942 the proper time to call "ldconfig" to notify the system
4943 of the fact that the shared libraries from the package
4944 are removed. The postrm can be called at several other
4945 times. At the time of "postrm purge", "postrm
4946 abort-install", or "postrm abort-upgrade", calling
4947 "ldconfig" is useless because the shared lib files are
4948 not on-disk. However, when "postrm" is invoked with
4949 arguments "upgrade", "failed-upgrade", or "disappear", a
4950 shared lib may exist on-disk under a temporary filename.
4958 <sect id="sharedlibs-support-files">
4959 <heading>Shared library support files</heading>
4962 If your package contains files whose names do not change with
4963 each change in the library shared object version, you must not
4964 put them in the shared library package. Otherwise, several
4965 versions of the shared library cannot be installed at the same
4966 time without filename clashes, making upgrades and transitions
4967 unnecessarily difficult.
4971 It is recommended that supporting files and run-time support
4972 programs that do not need to be invoked manually by users, but
4973 are nevertheless required for the package to function, be placed
4974 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4975 preferably under <file>/usr/lib/</file><var>package-name</var>.
4976 If the program or file is architecture independent, the
4977 recommendation is for it to be placed in a subdirectory of
4978 <file>/usr/share</file> instead, preferably under
4979 <file>/usr/share/</file><var>package-name</var>. Following the
4980 <var>package-name</var> naming convention ensures that the file
4981 names change when the shared object version changes.
4985 Run-time support programs that use the shared library but are
4986 not required for the library to function or files used by the
4987 shared library that can be used by any version of the shared
4988 library package should instead be put in a separate package.
4989 This package might typically be named
4990 <package><var>libraryname</var>-tools</package>; note the
4991 absence of the <var>soversion</var> in the package name.
4995 Files and support programs only useful when compiling software
4996 against the library should be included in the development
4997 package for the library.<footnote>
4998 For example, a <file><var>package-name</var>-config</file>
4999 script or <package>pkg-config</package> configuration files.
5004 <sect id="sharedlibs-static">
5005 <heading>Static libraries</heading>
5008 The static library (<file><var>libraryname.a</var></file>)
5009 is usually provided in addition to the shared version.
5010 It is placed into the development package (see below).
5014 In some cases, it is acceptable for a library to be
5015 available in static form only; these cases include:
5017 <item>libraries for languages whose shared library support
5018 is immature or unstable</item>
5019 <item>libraries whose interfaces are in flux or under
5020 development (commonly the case when the library's
5021 major version number is zero, or where the ABI breaks
5022 across patchlevels)</item>
5023 <item>libraries which are explicitly intended to be
5024 available only in static form by their upstream
5029 <sect id="sharedlibs-dev">
5030 <heading>Development files</heading>
5033 The development files associated to a shared library need to be
5034 placed in a package called
5035 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5036 or if you prefer only to support one development version at a
5037 time, <package><var>libraryname</var>-dev</package>.
5041 In case several development versions of a library exist, you may
5042 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5043 <ref id="conflicts">) to ensure that the user only installs one
5044 development version at a time (as different development versions are
5045 likely to have the same header files in them, which would cause a
5046 filename clash if both were installed).
5050 The development package should contain a symlink for the associated
5051 shared library without a version number. For example, the
5052 <package>libgdbm-dev</package> package should include a symlink
5053 from <file>/usr/lib/libgdbm.so</file> to
5054 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5055 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5056 <file>libgdbm.so</file> when compiling dynamically.
5060 <sect id="sharedlibs-intradeps">
5061 <heading>Dependencies between the packages of the same library</heading>
5064 Typically the development version should have an exact
5065 version dependency on the runtime library, to make sure that
5066 compilation and linking happens correctly. The
5067 <tt>${binary:Version}</tt> substitution variable can be
5068 useful for this purpose.
5070 Previously, <tt>${Source-Version}</tt> was used, but its name
5071 was confusing and it has been deprecated since dpkg 1.13.19.
5076 <sect id="sharedlibs-shlibdeps">
5077 <heading>Dependencies between the library and other packages -
5078 the <tt>shlibs</tt> system</heading>
5081 If a package contains a binary or library which links to a
5082 shared library, we must ensure that when the package is
5083 installed on the system, all of the libraries needed are
5084 also installed. This requirement led to the creation of the
5085 <tt>shlibs</tt> system, which is very simple in its design:
5086 any package which <em>provides</em> a shared library also
5087 provides information on the package dependencies required to
5088 ensure the presence of this library, and any package which
5089 <em>uses</em> a shared library uses this information to
5090 determine the dependencies it requires. The files which
5091 contain the mapping from shared libraries to the necessary
5092 dependency information are called <file>shlibs</file> files.
5096 Thus, when a package is built which contains any shared
5097 libraries, it must provide a <file>shlibs</file> file for other
5098 packages to use, and when a package is built which contains
5099 any shared libraries or compiled binaries, it must run
5100 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5101 on these to determine the libraries used and hence the
5102 dependencies needed by this package.<footnote>
5104 In the past, the shared libraries linked to were
5105 determined by calling <prgn>ldd</prgn>, but now
5106 <prgn>objdump</prgn> is used to do this. The only
5107 change this makes to package building is that
5108 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5109 libraries, whereas in the past this was unnecessary.
5110 The rest of this footnote explains the advantage that
5115 We say that a binary <tt>foo</tt> <em>directly</em> uses
5116 a library <tt>libbar</tt> if it is explicitly linked
5117 with that library (that is, it uses the flag
5118 <tt>-lbar</tt> during the linking stage). Other
5119 libraries that are needed by <tt>libbar</tt> are linked
5120 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5121 linker will load them automatically when it loads
5122 <tt>libbar</tt>. A package should depend on
5123 the libraries it directly uses, and the dependencies for
5124 those libraries should automatically pull in the other
5129 Unfortunately, the <prgn>ldd</prgn> program shows both
5130 the directly and indirectly used libraries, meaning that
5131 the dependencies determined included both direct and
5132 indirect dependencies. The use of <prgn>objdump</prgn>
5133 avoids this problem by determining only the directly
5138 A good example of where this helps is the following. We
5139 could update <tt>libimlib</tt> with a new version that
5140 supports a new graphics format called dgf (but retaining
5141 the same major version number). If we used the old
5142 <prgn>ldd</prgn> method, every package that uses
5143 <tt>libimlib</tt> would need to be recompiled so it
5144 would also depend on <tt>libdgf</tt> or it wouldn't run
5145 due to missing symbols. However with the new system,
5146 packages using <tt>libimlib</tt> can rely on
5147 <tt>libimlib</tt> itself having the dependency on
5148 <tt>libdgf</tt> and so they would not need rebuilding.
5154 In the following sections, we will first describe where the
5155 various <tt>shlibs</tt> files are to be found, then how to
5156 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5157 file format and how to create them if your package contains a
5162 <heading>The <tt>shlibs</tt> files present on the system</heading>
5165 There are several places where <tt>shlibs</tt> files are
5166 found. The following list gives them in the order in which
5168 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5169 (The first one which gives the required information is used.)
5175 <p><file>debian/shlibs.local</file></p>
5178 This lists overrides for this package. Its use is
5179 described below (see <ref id="shlibslocal">).
5184 <p><file>/etc/dpkg/shlibs.override</file></p>
5187 This lists global overrides. This list is normally
5188 empty. It is maintained by the local system
5194 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5197 When packages are being built, any
5198 <file>debian/shlibs</file> files are copied into the
5199 control file area of the temporary build directory and
5200 given the name <file>shlibs</file>. These files give
5201 details of any shared libraries included in the
5203 An example may help here. Let us say that the
5204 source package <tt>foo</tt> generates two binary
5205 packages, <tt>libfoo2</tt> and
5206 <tt>foo-runtime</tt>. When building the binary
5207 packages, the two packages are created in the
5208 directories <file>debian/libfoo2</file> and
5209 <file>debian/foo-runtime</file> respectively.
5210 (<file>debian/tmp</file> could be used instead of one
5211 of these.) Since <tt>libfoo2</tt> provides the
5212 <tt>libfoo</tt> shared library, it will require a
5213 <tt>shlibs</tt> file, which will be installed in
5214 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5216 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5217 when <prgn>dpkg-shlibdeps</prgn> is run on the
5219 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5221 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5222 determine whether <tt>foo-prog</tt>'s library
5223 dependencies are satisfied by any of the libraries
5224 provided by <tt>libfoo2</tt>. For this reason,
5225 <prgn>dpkg-shlibdeps</prgn> must only be run once
5226 all of the individual binary packages'
5227 <tt>shlibs</tt> files have been installed into the
5234 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5237 These are the <file>shlibs</file> files corresponding to
5238 all of the packages installed on the system, and are
5239 maintained by the relevant package maintainers.
5244 <p><file>/etc/dpkg/shlibs.default</file></p>
5247 This file lists any shared libraries whose packages
5248 have failed to provide correct <file>shlibs</file> files.
5249 It was used when the <file>shlibs</file> setup was first
5250 introduced, but it is now normally empty. It is
5251 maintained by the <tt>dpkg</tt> maintainer.
5259 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5260 <file>shlibs</file> files</heading>
5264 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5265 into your <file>debian/rules</file> file. If your package
5266 contains only compiled binaries and libraries (but no scripts),
5267 you can use a command such as:
5268 <example compact="compact">
5269 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5270 debian/tmp/usr/lib/*
5272 Otherwise, you will need to explicitly list the compiled
5273 binaries and libraries.<footnote>
5274 If you are using <tt>debhelper</tt>, the
5275 <prgn>dh_shlibdeps</prgn> program will do this work for
5276 you. It will also correctly handle multi-binary
5282 This command puts the dependency information into the
5283 <file>debian/substvars</file> file, which is then used by
5284 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5285 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5286 field in the control file for this to work.
5290 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5291 done. If it does complain you might need to create your own
5292 <file>debian/shlibs.local</file> file, as explained below (see
5293 <ref id="shlibslocal">).
5297 If you have multiple binary packages, you will need to call
5298 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5299 compiled libraries or binaries. In such a case, you will
5300 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5301 utilities to specify a different <file>substvars</file> file.
5305 If you are creating a udeb for use in the Debian Installer, you
5306 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5307 the dependency line of type <tt>udeb</tt> by adding
5308 <tt>-tudeb</tt> as option<footnote>
5309 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5310 will automatically add this option if it knows it is
5312 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5313 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5314 fall back to the regular dependency line.
5318 For more details on dpkg-shlibdeps, please see
5319 <ref id="pkg-dpkg-shlibdeps"> and
5320 <manref name="dpkg-shlibdeps" section="1">.
5325 <heading>The <file>shlibs</file> File Format</heading>
5328 Each <file>shlibs</file> file has the same format. Lines
5329 beginning with <tt>#</tt> are considered to be comments and
5330 are ignored. Each line is of the form:
5331 <example compact="compact">
5332 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5337 We will explain this by reference to the example of the
5338 <tt>zlib1g</tt> package, which (at the time of writing)
5339 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5343 <var>type</var> is an optional element that indicates the type
5344 of package for which the line is valid. The only type currently
5345 in use is <tt>udeb</tt>. The colon and space after the type are
5350 <var>library-name</var> is the name of the shared library,
5351 in this case <tt>libz</tt>. (This must match the name part
5352 of the soname, see below.)
5356 <var>soname-version</var> is the version part of the soname of
5357 the library. The soname is the thing that must exactly match
5358 for the library to be recognized by the dynamic linker, and is
5360 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5361 example, <tt>libz.so.1</tt>.<footnote>
5362 This can be determined using the command
5363 <example compact="compact">
5364 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5367 The version part is the part which comes after
5368 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5372 <var>dependencies</var> has the same syntax as a dependency
5373 field in a binary package control file. It should give
5374 details of which packages are required to satisfy a binary
5375 built against the version of the library contained in the
5376 package. See <ref id="depsyntax"> for details.
5380 In our example, if the first version of the <tt>zlib1g</tt>
5381 package which contained a minor number of at least
5382 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5383 <tt>shlibs</tt> entry for this library could say:
5384 <example compact="compact">
5385 libz 1 zlib1g (>= 1:1.1.3)
5387 The version-specific dependency is to avoid warnings from
5388 the dynamic linker about using older shared libraries with
5393 As zlib1g also provides a udeb containing the shared library,
5394 there would also be a second line:
5395 <example compact="compact">
5396 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5402 <heading>Providing a <file>shlibs</file> file</heading>
5405 If your package provides a shared library, you need to create
5406 a <file>shlibs</file> file following the format described above.
5407 It is usual to call this file <file>debian/shlibs</file> (but if
5408 you have multiple binary packages, you might want to call it
5409 <file>debian/shlibs.<var>package</var></file> instead). Then
5410 let <file>debian/rules</file> install it in the control area:
5411 <example compact="compact">
5412 install -m644 debian/shlibs debian/tmp/DEBIAN
5414 or, in the case of a multi-binary package:
5415 <example compact="compact">
5416 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5418 An alternative way of doing this is to create the
5419 <file>shlibs</file> file in the control area directly from
5420 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5421 file at all,<footnote>
5422 This is what <prgn>dh_makeshlibs</prgn> in the
5423 <tt>debhelper</tt> suite does. If your package also has a udeb
5424 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5425 automatically generate the <tt>udeb:</tt> lines if you specify
5426 the name of the udeb with the <tt>--add-udeb</tt> option.
5428 since the <file>debian/shlibs</file> file itself is ignored by
5429 <prgn>dpkg-shlibdeps</prgn>.
5433 As <prgn>dpkg-shlibdeps</prgn> reads the
5434 <file>DEBIAN/shlibs</file> files in all of the binary packages
5435 being built from this source package, all of the
5436 <file>DEBIAN/shlibs</file> files should be installed before
5437 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5442 <sect1 id="shlibslocal">
5443 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5446 This file is intended only as a <em>temporary</em> fix if
5447 your binaries or libraries depend on a library whose package
5448 does not yet provide a correct <file>shlibs</file> file.
5452 We will assume that you are trying to package a binary
5453 <tt>foo</tt>. When you try running
5454 <prgn>dpkg-shlibdeps</prgn> you get the following error
5455 message (<tt>-O</tt> displays the dependency information on
5456 <tt>stdout</tt> instead of writing it to
5457 <tt>debian/substvars</tt>, and the lines have been wrapped
5458 for ease of reading):
5459 <example compact="compact">
5460 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5461 dpkg-shlibdeps: warning: unable to find dependency
5462 information for shared library libbar (soname 1,
5463 path /usr/lib/libbar.so.1, dependency field Depends)
5464 shlibs:Depends=libc6 (>= 2.2.2-2)
5466 You can then run <prgn>ldd</prgn> on the binary to find the
5467 full location of the library concerned:
5468 <example compact="compact">
5470 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5471 libc.so.6 => /lib/libc.so.6 (0x40032000)
5472 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5474 So the <prgn>foo</prgn> binary depends on the
5475 <prgn>libbar</prgn> shared library, but no package seems to
5476 provide a <file>*.shlibs</file> file handling
5477 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5478 determine the package responsible:
5479 <example compact="compact">
5480 $ dpkg -S /usr/lib/libbar.so.1
5481 bar1: /usr/lib/libbar.so.1
5482 $ dpkg -s bar1 | grep Version
5485 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5486 is the one we are using. Now we can file a bug against the
5487 <tt>bar1</tt> package and create our own
5488 <file>debian/shlibs.local</file> to locally fix the problem.
5489 Including the following line into your
5490 <file>debian/shlibs.local</file> file:
5491 <example compact="compact">
5492 libbar 1 bar1 (>= 1.0-1)
5494 should allow the package build to work.
5498 As soon as the maintainer of <tt>bar1</tt> provides a
5499 correct <file>shlibs</file> file, you should remove this line
5500 from your <file>debian/shlibs.local</file> file. (You should
5501 probably also then have a versioned <tt>Build-Depends</tt>
5502 on <tt>bar1</tt> to help ensure that others do not have the
5503 same problem building your package.)
5512 <chapt id="opersys"><heading>The Operating System</heading>
5515 <heading>File system hierarchy</heading>
5519 <heading>File system Structure</heading>
5522 The location of all installed files and directories must
5523 comply with the File system Hierarchy Standard (FHS),
5524 version 2.3, with the exceptions noted below, and except
5525 where doing so would violate other terms of Debian
5526 Policy. The following exceptions to the FHS apply:
5531 Legacy XFree86 servers are permitted to retain the
5532 configuration file location
5533 <file>/etc/X11/XF86Config-4</file>.
5538 The optional rules related to user specific
5539 configuration files for applications are stored in
5540 the user's home directory are relaxed. It is
5541 recommended that such files start with the
5542 '<tt>.</tt>' character (a "dot file"), and if an
5543 application needs to create more than one dot file
5544 then the preferred placement is in a subdirectory
5545 with a name starting with a '.' character, (a "dot
5546 directory"). In this case it is recommended the
5547 configuration files not start with the '.'
5553 The requirement for amd64 to use <file>/lib64</file>
5554 for 64 bit binaries is removed.
5559 The requirement that
5560 <file>/usr/local/share/man</file> be "synonymous"
5561 with <file>/usr/local/man</file> is relaxed to a
5566 The requirement that windowmanagers with a single
5567 configuration file call it <file>system.*wmrc</file>
5568 is removed, as is the restriction that the window
5569 manager subdirectory be named identically to the
5570 window manager name itself.
5575 The requirement that boot manager configuration
5576 files live in <file>/etc</file>, or at least are
5577 symlinked there, is relaxed to a recommendation.
5584 The version of this document referred here can be
5585 found in the <tt>debian-policy</tt> package or on <url
5586 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5587 name="FHS (Debian copy)"> alongside this manual (or, if
5588 you have the <package>debian-policy</package> installed,
5590 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5591 (local copy)">). The
5592 latest version, which may be a more recent version, may
5594 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5595 Specific questions about following the standard may be
5596 asked on the <tt>debian-devel</tt> mailing list, or
5597 referred to the FHS mailing list (see the
5598 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5604 <heading>Site-specific programs</heading>
5607 As mandated by the FHS, packages must not place any
5608 files in <file>/usr/local</file>, either by putting them in
5609 the file system archive to be unpacked by <prgn>dpkg</prgn>
5610 or by manipulating them in their maintainer scripts.
5614 However, the package may create empty directories below
5615 <file>/usr/local</file> so that the system administrator knows
5616 where to place site-specific files. These are not
5617 directories <em>in</em> <file>/usr/local</file>, but are
5618 children of directories in <file>/usr/local</file>. These
5619 directories (<file>/usr/local/*/dir/</file>)
5620 should be removed on package removal if they are
5625 Note, that this applies only to directories <em>below</em>
5626 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5627 Packages must not create sub-directories in the directory
5628 <file>/usr/local</file> itself, except those listed in FHS,
5629 section 4.5. However, you may create directories below
5630 them as you wish. You must not remove any of the
5631 directories listed in 4.5, even if you created them.
5635 Since <file>/usr/local</file> can be mounted read-only from a
5636 remote server, these directories must be created and
5637 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5638 maintainer scripts and not be included in the
5639 <file>.deb</file> archive. These scripts must not fail if
5640 either of these operations fail.
5644 For example, the <tt>emacsen-common</tt> package could
5645 contain something like
5646 <example compact="compact">
5647 if [ ! -e /usr/local/share/emacs ]
5649 if mkdir /usr/local/share/emacs 2>/dev/null
5651 chown root:staff /usr/local/share/emacs
5652 chmod 2775 /usr/local/share/emacs
5656 in its <prgn>postinst</prgn> script, and
5657 <example compact="compact">
5658 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5659 rmdir /usr/local/share/emacs 2>/dev/null || true
5661 in the <prgn>prerm</prgn> script. (Note that this form is
5662 used to ensure that if the script is interrupted, the
5663 directory <file>/usr/local/share/emacs</file> will still be
5668 If you do create a directory in <file>/usr/local</file> for
5669 local additions to a package, you should ensure that
5670 settings in <file>/usr/local</file> take precedence over the
5671 equivalents in <file>/usr</file>.
5675 However, because <file>/usr/local</file> and its contents are
5676 for exclusive use of the local administrator, a package
5677 must not rely on the presence or absence of files or
5678 directories in <file>/usr/local</file> for normal operation.
5682 The <file>/usr/local</file> directory itself and all the
5683 subdirectories created by the package should (by default) have
5684 permissions 2775 (group-writable and set-group-id) and be
5685 owned by <tt>root:staff</tt>.
5690 <heading>The system-wide mail directory</heading>
5692 The system-wide mail directory is <file>/var/mail</file>. This
5693 directory is part of the base system and should not owned
5694 by any particular mail agents. The use of the old
5695 location <file>/var/spool/mail</file> is deprecated, even
5696 though the spool may still be physically located there.
5697 To maintain partial upgrade compatibility for systems
5698 which have <file>/var/spool/mail</file> as their physical mail
5699 spool, packages using <file>/var/mail</file> must depend on
5700 either <package>libc6</package> (>= 2.1.3-13), or on
5701 <package>base-files</package> (>= 2.2.0), or on later
5702 versions of either one of these packages.
5708 <heading>Users and groups</heading>
5711 <heading>Introduction</heading>
5713 The Debian system can be configured to use either plain or
5718 Some user ids (UIDs) and group ids (GIDs) are reserved
5719 globally for use by certain packages. Because some
5720 packages need to include files which are owned by these
5721 users or groups, or need the ids compiled into binaries,
5722 these ids must be used on any Debian system only for the
5723 purpose for which they are allocated. This is a serious
5724 restriction, and we should avoid getting in the way of
5725 local administration policies. In particular, many sites
5726 allocate users and/or local system groups starting at 100.
5730 Apart from this we should have dynamically allocated ids,
5731 which should by default be arranged in some sensible
5732 order, but the behavior should be configurable.
5736 Packages other than <tt>base-passwd</tt> must not modify
5737 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5738 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5743 <heading>UID and GID classes</heading>
5745 The UID and GID numbers are divided into classes as
5751 Globally allocated by the Debian project, the same
5752 on every Debian system. These ids will appear in
5753 the <file>passwd</file> and <file>group</file> files of all
5754 Debian systems, new ids in this range being added
5755 automatically as the <tt>base-passwd</tt> package is
5760 Packages which need a single statically allocated
5761 uid or gid should use one of these; their
5762 maintainers should ask the <tt>base-passwd</tt>
5770 Dynamically allocated system users and groups.
5771 Packages which need a user or group, but can have
5772 this user or group allocated dynamically and
5773 differently on each system, should use <tt>adduser
5774 --system</tt> to create the group and/or user.
5775 <prgn>adduser</prgn> will check for the existence of
5776 the user or group, and if necessary choose an unused
5777 id based on the ranges specified in
5778 <file>adduser.conf</file>.
5782 <tag>1000-29999:</tag>
5785 Dynamically allocated user accounts. By default
5786 <prgn>adduser</prgn> will choose UIDs and GIDs for
5787 user accounts in this range, though
5788 <file>adduser.conf</file> may be used to modify this
5793 <tag>30000-59999:</tag>
5798 <tag>60000-64999:</tag>
5801 Globally allocated by the Debian project, but only
5802 created on demand. The ids are allocated centrally
5803 and statically, but the actual accounts are only
5804 created on users' systems on demand.
5808 These ids are for packages which are obscure or
5809 which require many statically-allocated ids. These
5810 packages should check for and create the accounts in
5811 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5812 <prgn>adduser</prgn> if it has this facility) if
5813 necessary. Packages which are likely to require
5814 further allocations should have a "hole" left after
5815 them in the allocation, to give them room to
5820 <tag>65000-65533:</tag>
5828 User <tt>nobody</tt>. The corresponding gid refers
5829 to the group <tt>nogroup</tt>.
5836 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5837 not</em> be used, because it is the error return
5846 <sect id="sysvinit">
5847 <heading>System run levels and <file>init.d</file> scripts</heading>
5849 <sect1 id="/etc/init.d">
5850 <heading>Introduction</heading>
5853 The <file>/etc/init.d</file> directory contains the scripts
5854 executed by <prgn>init</prgn> at boot time and when the
5855 init state (or "runlevel") is changed (see <manref
5856 name="init" section="8">).
5860 There are at least two different, yet functionally
5861 equivalent, ways of handling these scripts. For the sake
5862 of simplicity, this document describes only the symbolic
5863 link method. However, it must not be assumed by maintainer
5864 scripts that this method is being used, and any automated
5865 manipulation of the various runlevel behaviors by
5866 maintainer scripts must be performed using
5867 <prgn>update-rc.d</prgn> as described below and not by
5868 manually installing or removing symlinks. For information
5869 on the implementation details of the other method,
5870 implemented in the <tt>file-rc</tt> package, please refer
5871 to the documentation of that package.
5875 These scripts are referenced by symbolic links in the
5876 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5877 runlevels, <prgn>init</prgn> looks in the directory
5878 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5879 execute, where <tt><var>n</var></tt> is the runlevel that
5880 is being changed to, or <tt>S</tt> for the boot-up
5885 The names of the links all have the form
5886 <file>S<var>mm</var><var>script</var></file> or
5887 <file>K<var>mm</var><var>script</var></file> where
5888 <var>mm</var> is a two-digit number and <var>script</var>
5889 is the name of the script (this should be the same as the
5890 name of the actual script in <file>/etc/init.d</file>).
5894 When <prgn>init</prgn> changes runlevel first the targets
5895 of the links whose names start with a <tt>K</tt> are
5896 executed, each with the single argument <tt>stop</tt>,
5897 followed by the scripts prefixed with an <tt>S</tt>, each
5898 with the single argument <tt>start</tt>. (The links are
5899 those in the <file>/etc/rc<var>n</var>.d</file> directory
5900 corresponding to the new runlevel.) The <tt>K</tt> links
5901 are responsible for killing services and the <tt>S</tt>
5902 link for starting services upon entering the runlevel.
5906 For example, if we are changing from runlevel 2 to
5907 runlevel 3, init will first execute all of the <tt>K</tt>
5908 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5909 all of the <tt>S</tt> prefixed scripts in that directory.
5910 The links starting with <tt>K</tt> will cause the
5911 referred-to file to be executed with an argument of
5912 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5917 The two-digit number <var>mm</var> is used to determine
5918 the order in which to run the scripts: low-numbered links
5919 have their scripts run first. For example, the
5920 <tt>K20</tt> scripts will be executed before the
5921 <tt>K30</tt> scripts. This is used when a certain service
5922 must be started before another. For example, the name
5923 server <prgn>bind</prgn> might need to be started before
5924 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5925 can set up its access lists. In this case, the script
5926 that starts <prgn>bind</prgn> would have a lower number
5927 than the script that starts <prgn>inn</prgn> so that it
5929 <example compact="compact">
5936 The two runlevels 0 (halt) and 6 (reboot) are slightly
5937 different. In these runlevels, the links with an
5938 <tt>S</tt> prefix are still called after those with a
5939 <tt>K</tt> prefix, but they too are called with the single
5940 argument <tt>stop</tt>.
5944 Also, if the script name ends in <tt>.sh</tt>, the script
5945 will be sourced in runlevel <tt>S</tt> rather than being
5946 run in a forked subprocess, but will be explicitly run by
5947 <prgn>sh</prgn> in all other runlevels.
5952 <heading>Writing the scripts</heading>
5955 Packages that include daemons for system services should
5956 place scripts in <file>/etc/init.d</file> to start or stop
5957 services at boot time or during a change of runlevel.
5958 These scripts should be named
5959 <file>/etc/init.d/<var>package</var></file>, and they should
5960 accept one argument, saying what to do:
5963 <tag><tt>start</tt></tag>
5964 <item>start the service,</item>
5966 <tag><tt>stop</tt></tag>
5967 <item>stop the service,</item>
5969 <tag><tt>restart</tt></tag>
5970 <item>stop and restart the service if it's already running,
5971 otherwise start the service</item>
5973 <tag><tt>reload</tt></tag>
5974 <item><p>cause the configuration of the service to be
5975 reloaded without actually stopping and restarting
5978 <tag><tt>force-reload</tt></tag>
5979 <item>cause the configuration to be reloaded if the
5980 service supports this, otherwise restart the
5984 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5985 <tt>force-reload</tt> options should be supported by all
5986 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5991 The <file>init.d</file> scripts must ensure that they will
5992 behave sensibly (i.e., returning success and not starting
5993 multiple copies of a service) if invoked with <tt>start</tt>
5994 when the service is already running, or with <tt>stop</tt>
5995 when it isn't, and that they don't kill unfortunately-named
5996 user processes. The best way to achieve this is usually to
5997 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6002 If a service reloads its configuration automatically (as
6003 in the case of <prgn>cron</prgn>, for example), the
6004 <tt>reload</tt> option of the <file>init.d</file> script
6005 should behave as if the configuration has been reloaded
6010 The <file>/etc/init.d</file> scripts must be treated as
6011 configuration files, either (if they are present in the
6012 package, that is, in the .deb file) by marking them as
6013 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6014 by managing them correctly in the maintainer scripts (see
6015 <ref id="config-files">). This is important since we want
6016 to give the local system administrator the chance to adapt
6017 the scripts to the local system, e.g., to disable a
6018 service without de-installing the package, or to specify
6019 some special command line options when starting a service,
6020 while making sure their changes aren't lost during the next
6025 These scripts should not fail obscurely when the
6026 configuration files remain but the package has been
6027 removed, as configuration files remain on the system after
6028 the package has been removed. Only when <prgn>dpkg</prgn>
6029 is executed with the <tt>--purge</tt> option will
6030 configuration files be removed. In particular, as the
6031 <file>/etc/init.d/<var>package</var></file> script itself is
6032 usually a <tt>conffile</tt>, it will remain on the system
6033 if the package is removed but not purged. Therefore, you
6034 should include a <tt>test</tt> statement at the top of the
6036 <example compact="compact">
6037 test -f <var>program-executed-later-in-script</var> || exit 0
6042 Often there are some variables in the <file>init.d</file>
6043 scripts whose values control the behavior of the scripts,
6044 and which a system administrator is likely to want to
6045 change. As the scripts themselves are frequently
6046 <tt>conffile</tt>s, modifying them requires that the
6047 administrator merge in their changes each time the package
6048 is upgraded and the <tt>conffile</tt> changes. To ease
6049 the burden on the system administrator, such configurable
6050 values should not be placed directly in the script.
6051 Instead, they should be placed in a file in
6052 <file>/etc/default</file>, which typically will have the same
6053 base name as the <file>init.d</file> script. This extra file
6054 should be sourced by the script when the script runs. It
6055 must contain only variable settings and comments in SUSv3
6056 <prgn>sh</prgn> format. It may either be a
6057 <tt>conffile</tt> or a configuration file maintained by
6058 the package maintainer scripts. See <ref id="config-files">
6063 To ensure that vital configurable values are always
6064 available, the <file>init.d</file> script should set default
6065 values for each of the shell variables it uses, either
6066 before sourcing the <file>/etc/default/</file> file or
6067 afterwards using something like the <tt>:
6068 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6069 script must behave sensibly and not fail if the
6070 <file>/etc/default</file> file is deleted.
6075 <heading>Interfacing with the initscript system</heading>
6078 Maintainers should use the abstraction layer provided by
6079 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6080 programs to deal with initscripts in their packages'
6081 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6082 and <prgn>postrm</prgn>.
6086 Directly managing the /etc/rc?.d links and directly
6087 invoking the <file>/etc/init.d/</file> initscripts should
6088 be done only by packages providing the initscript
6089 subsystem (such as <prgn>sysv-rc</prgn> and
6090 <prgn>file-rc</prgn>).
6094 <heading>Managing the links</heading>
6097 The program <prgn>update-rc.d</prgn> is provided for
6098 package maintainers to arrange for the proper creation and
6099 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6100 or their functional equivalent if another method is being
6101 used. This may be used by maintainers in their packages'
6102 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6106 You must not include any <file>/etc/rc<var>n</var>.d</file>
6107 symbolic links in the actual archive or manually create or
6108 remove the symbolic links in maintainer scripts; you must
6109 use the <prgn>update-rc.d</prgn> program instead. (The
6110 former will fail if an alternative method of maintaining
6111 runlevel information is being used.) You must not include
6112 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6113 in the archive either. (Only the <tt>sysvinit</tt>
6118 By default <prgn>update-rc.d</prgn> will start services in
6119 each of the multi-user state runlevels (2, 3, 4, and 5)
6120 and stop them in the halt runlevel (0), the single-user
6121 runlevel (1) and the reboot runlevel (6). The system
6122 administrator will have the opportunity to customize
6123 runlevels by simply adding, moving, or removing the
6124 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6125 symbolic links are being used, or by modifying
6126 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6131 To get the default behavior for your package, put in your
6132 <prgn>postinst</prgn> script
6133 <example compact="compact">
6134 update-rc.d <var>package</var> defaults
6136 and in your <prgn>postrm</prgn>
6137 <example compact="compact">
6138 if [ "$1" = purge ]; then
6139 update-rc.d <var>package</var> remove
6141 </example>. Note that if your package changes runlevels
6142 or priority, you may have to remove and recreate the links,
6143 since otherwise the old links may persist. Refer to the
6144 documentation of <prgn>update-rc.d</prgn>.
6148 This will use a default sequence number of 20. If it does
6149 not matter when or in which order the <file>init.d</file>
6150 script is run, use this default. If it does, then you
6151 should talk to the maintainer of the <prgn>sysvinit</prgn>
6152 package or post to <tt>debian-devel</tt>, and they will
6153 help you choose a number.
6157 For more information about using <tt>update-rc.d</tt>,
6158 please consult its man page <manref name="update-rc.d"
6164 <heading>Running initscripts</heading>
6166 The program <prgn>invoke-rc.d</prgn> is provided to make
6167 it easier for package maintainers to properly invoke an
6168 initscript, obeying runlevel and other locally-defined
6169 constraints that might limit a package's right to start,
6170 stop and otherwise manage services. This program may be
6171 used by maintainers in their packages' scripts.
6175 The package maintainer scripts must use
6176 <prgn>invoke-rc.d</prgn> to invoke the
6177 <file>/etc/init.d/*</file> initscripts, instead of
6178 calling them directly.
6182 By default, <prgn>invoke-rc.d</prgn> will pass any
6183 action requests (start, stop, reload, restart...) to the
6184 <file>/etc/init.d</file> script, filtering out requests
6185 to start or restart a service out of its intended
6190 Most packages will simply need to change:
6191 <example compact="compact">/etc/init.d/<package>
6192 <action></example> in their <prgn>postinst</prgn>
6193 and <prgn>prerm</prgn> scripts to:
6194 <example compact="compact">
6195 if which invoke-rc.d >/dev/null 2>&1; then
6196 invoke-rc.d <var>package</var> <action>
6198 /etc/init.d/<var>package</var> <action>
6204 A package should register its initscript services using
6205 <prgn>update-rc.d</prgn> before it tries to invoke them
6206 using <prgn>invoke-rc.d</prgn>. Invocation of
6207 unregistered services may fail.
6211 For more information about using
6212 <prgn>invoke-rc.d</prgn>, please consult its man page
6213 <manref name="invoke-rc.d" section="8">.
6219 <heading>Boot-time initialization</heading>
6222 There used to be another directory, <file>/etc/rc.boot</file>,
6223 which contained scripts which were run once per machine
6224 boot. This has been deprecated in favour of links from
6225 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6226 described in <ref id="/etc/init.d">. Packages must not
6227 place files in <file>/etc/rc.boot</file>.
6232 <heading>Example</heading>
6235 An example on which you can base your
6236 <file>/etc/init.d</file> scripts is found in
6237 <file>/etc/init.d/skeleton</file>.
6244 <heading>Console messages from <file>init.d</file> scripts</heading>
6247 This section describes the formats to be used for messages
6248 written to standard output by the <file>/etc/init.d</file>
6249 scripts. The intent is to improve the consistency of
6250 Debian's startup and shutdown look and feel. For this
6251 reason, please look very carefully at the details. We want
6252 the messages to have the same format in terms of wording,
6253 spaces, punctuation and case of letters.
6257 Here is a list of overall rules that should be used for
6258 messages generated by <file>/etc/init.d</file> scripts.
6264 The message should fit in one line (fewer than 80
6265 characters), start with a capital letter and end with
6266 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6270 If the script is performing some time consuming task in
6271 the background (not merely starting or stopping a
6272 program, for instance), an ellipsis (three dots:
6273 <tt>...</tt>) should be output to the screen, with no
6274 leading or tailing whitespace or line feeds.
6278 The messages should appear as if the computer is telling
6279 the user what it is doing (politely :-), but should not
6280 mention "it" directly. For example, instead of:
6281 <example compact="compact">
6282 I'm starting network daemons: nfsd mountd.
6284 the message should say
6285 <example compact="compact">
6286 Starting network daemons: nfsd mountd.
6293 <tt>init.d</tt> script should use the following standard
6294 message formats for the situations enumerated below.
6300 <p>When daemons are started</p>
6303 If the script starts one or more daemons, the output
6304 should look like this (a single line, no leading
6306 <example compact="compact">
6307 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6309 The <var>description</var> should describe the
6310 subsystem the daemon or set of daemons are part of,
6311 while <var>daemon-1</var> up to <var>daemon-n</var>
6312 denote each daemon's name (typically the file name of
6317 For example, the output of <file>/etc/init.d/lpd</file>
6319 <example compact="compact">
6320 Starting printer spooler: lpd.
6325 This can be achieved by saying
6326 <example compact="compact">
6327 echo -n "Starting printer spooler: lpd"
6328 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6331 in the script. If there are more than one daemon to
6332 start, the output should look like this:
6333 <example compact="compact">
6334 echo -n "Starting remote file system services:"
6335 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6336 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6337 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6340 This makes it possible for the user to see what is
6341 happening and when the final daemon has been started.
6342 Care should be taken in the placement of white spaces:
6343 in the example above the system administrators can
6344 easily comment out a line if they don't want to start
6345 a specific daemon, while the displayed message still
6351 <p>When a system parameter is being set</p>
6354 If you have to set up different system parameters
6355 during the system boot, you should use this format:
6356 <example compact="compact">
6357 Setting <var>parameter</var> to "<var>value</var>".
6362 You can use a statement such as the following to get
6364 <example compact="compact">
6365 echo "Setting DNS domainname to \"$domainname\"."
6370 Note that the same symbol (<tt>"</tt>) is used for the left
6371 and right quotation marks. A grave accent (<tt>`</tt>) is
6372 not a quote character; neither is an apostrophe
6378 <p>When a daemon is stopped or restarted</p>
6381 When you stop or restart a daemon, you should issue a
6382 message identical to the startup message, except that
6383 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6384 or <tt>Restarting</tt> respectively.
6388 For example, stopping the printer daemon will look like
6390 <example compact="compact">
6391 Stopping printer spooler: lpd.
6397 <p>When something is executed</p>
6400 There are several examples where you have to run a
6401 program at system startup or shutdown to perform a
6402 specific task, for example, setting the system's clock
6403 using <prgn>netdate</prgn> or killing all processes
6404 when the system shuts down. Your message should look
6406 <example compact="compact">
6407 Doing something very useful...done.
6409 You should print the <tt>done.</tt> immediately after
6410 the job has been completed, so that the user is
6411 informed why they have to wait. You can get this
6413 <example compact="compact">
6414 echo -n "Doing something very useful..."
6423 <p>When the configuration is reloaded</p>
6426 When a daemon is forced to reload its configuration
6427 files you should use the following format:
6428 <example compact="compact">
6429 Reloading <var>description</var> configuration...done.
6431 where <var>description</var> is the same as in the
6432 daemon starting message.
6440 <heading>Cron jobs</heading>
6443 Packages must not modify the configuration file
6444 <file>/etc/crontab</file>, and they must not modify the files in
6445 <file>/var/spool/cron/crontabs</file>.</p>
6448 If a package wants to install a job that has to be executed
6449 via cron, it should place a file with the name of the
6450 package in one or more of the following directories:
6451 <example compact="compact">
6457 As these directory names imply, the files within them are
6458 executed on an hourly, daily, weekly, or monthly basis,
6459 respectively. The exact times are listed in
6460 <file>/etc/crontab</file>.</p>
6463 All files installed in any of these directories must be
6464 scripts (e.g., shell scripts or Perl scripts) so that they
6465 can easily be modified by the local system administrator.
6466 In addition, they must be treated as configuration files.
6470 If a certain job has to be executed at some other frequency or
6471 at a specific time, the package should install a file
6472 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6473 same syntax as <file>/etc/crontab</file> and is processed by
6474 <prgn>cron</prgn> automatically. The file must also be
6475 treated as a configuration file. (Note that entries in the
6476 <file>/etc/cron.d</file> directory are not handled by
6477 <prgn>anacron</prgn>. Thus, you should only use this
6478 directory for jobs which may be skipped if the system is not
6482 The scripts or crontab entries in these directories should
6483 check if all necessary programs are installed before they
6484 try to execute them. Otherwise, problems will arise when a
6485 package was removed but not purged since configuration files
6486 are kept on the system in this situation.</p>
6490 <heading>Menus</heading>
6493 The Debian <tt>menu</tt> package provides a standard
6494 interface between packages providing applications and
6495 <em>menu programs</em> (either X window managers or
6496 text-based menu programs such as <prgn>pdmenu</prgn>).
6500 All packages that provide applications that need not be
6501 passed any special command line arguments for normal
6502 operation should register a menu entry for those
6503 applications, so that users of the <tt>menu</tt> package
6504 will automatically get menu entries in their window
6505 managers, as well in shells like <tt>pdmenu</tt>.
6509 Menu entries should follow the current menu policy.
6513 The menu policy can be found in the <tt>menu-policy</tt>
6514 files in the <tt>debian-policy</tt> package.
6515 It is also available from the Debian web mirrors at
6516 <tt><url name="/doc/packaging-manuals/menu-policy/"
6517 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6521 Please also refer to the <em>Debian Menu System</em>
6522 documentation that comes with the <package>menu</package>
6523 package for information about how to register your
6529 <heading>Multimedia handlers</heading>
6532 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6533 is a mechanism for encoding files and data streams and
6534 providing meta-information about them, in particular their
6535 type (e.g. audio or video) and format (e.g. PNG, HTML,
6540 Registration of MIME type handlers allows programs like mail
6541 user agents and web browsers to invoke these handlers to
6542 view, edit or display MIME types they don't support directly.
6546 Packages which provide the ability to view/show/play,
6547 compose, edit or print MIME types should register themselves
6548 as such following the current MIME support policy.
6552 The MIME support policy can be found in the <tt>mime-policy</tt>
6553 files in the <tt>debian-policy</tt> package.
6554 It is also available from the Debian web mirrors at
6555 <tt><url name="/doc/packaging-manuals/mime-policy/"
6556 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6562 <heading>Keyboard configuration</heading>
6565 To achieve a consistent keyboard configuration so that all
6566 applications interpret a keyboard event the same way, all
6567 programs in the Debian distribution must be configured to
6568 comply with the following guidelines.
6572 The following keys must have the specified interpretations:
6575 <tag><tt><--</tt></tag>
6576 <item>delete the character to the left of the cursor</item>
6578 <tag><tt>Delete</tt></tag>
6579 <item>delete the character to the right of the cursor</item>
6581 <tag><tt>Control+H</tt></tag>
6582 <item>emacs: the help prefix</item>
6585 The interpretation of any keyboard events should be
6586 independent of the terminal that is used, be it a virtual
6587 console, an X terminal emulator, an rlogin/telnet session,
6592 The following list explains how the different programs
6593 should be set up to achieve this:
6599 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6603 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6607 X translations are set up to make
6608 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6609 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6610 is the vt220 escape code for the "delete character"
6611 key). This must be done by loading the X resources
6612 using <prgn>xrdb</prgn> on all local X displays, not
6613 using the application defaults, so that the
6614 translation resources used correspond to the
6615 <prgn>xmodmap</prgn> settings.
6619 The Linux console is configured to make
6620 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6621 generate <tt>ESC [ 3 ~</tt>.
6625 X applications are configured so that <tt><</tt>
6626 deletes left, and <tt>Delete</tt> deletes right. Motif
6627 applications already work like this.
6631 Terminals should have <tt>stty erase ^?</tt> .
6635 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6636 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6637 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6641 Emacs is programmed to map <tt>KB_Backspace</tt> or
6642 the <tt>stty erase</tt> character to
6643 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6644 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6645 <tt>^H</tt> to <tt>help</tt> as always.
6649 Other applications use the <tt>stty erase</tt>
6650 character and <tt>kdch1</tt> for the two delete keys,
6651 with ASCII DEL being "delete previous character" and
6652 <tt>kdch1</tt> being "delete character under
6660 This will solve the problem except for the following
6667 Some terminals have a <tt><--</tt> key that cannot
6668 be made to produce anything except <tt>^H</tt>. On
6669 these terminals Emacs help will be unavailable on
6670 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6671 character takes precedence in Emacs, and has been set
6672 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6673 available) can be used instead.
6677 Some operating systems use <tt>^H</tt> for <tt>stty
6678 erase</tt>. However, modern telnet versions and all
6679 rlogin versions propagate <tt>stty</tt> settings, and
6680 almost all UNIX versions honour <tt>stty erase</tt>.
6681 Where the <tt>stty</tt> settings are not propagated
6682 correctly, things can be made to work by using
6683 <tt>stty</tt> manually.
6687 Some systems (including previous Debian versions) use
6688 <prgn>xmodmap</prgn> to arrange for both
6689 <tt><--</tt> and <tt>Delete</tt> to generate
6690 <tt>KB_Delete</tt>. We can change the behavior of
6691 their X clients using the same X resources that we use
6692 to do it for our own clients, or configure our clients
6693 using their resources when things are the other way
6694 around. On displays configured like this
6695 <tt>Delete</tt> will not work, but <tt><--</tt>
6700 Some operating systems have different <tt>kdch1</tt>
6701 settings in their <tt>terminfo</tt> database for
6702 <tt>xterm</tt> and others. On these systems the
6703 <tt>Delete</tt> key will not work correctly when you
6704 log in from a system conforming to our policy, but
6705 <tt><--</tt> will.
6712 <heading>Environment variables</heading>
6715 A program must not depend on environment variables to get
6716 reasonable defaults. (That's because these environment
6717 variables would have to be set in a system-wide
6718 configuration file like <file>/etc/profile</file>, which is not
6719 supported by all shells.)
6723 If a program usually depends on environment variables for its
6724 configuration, the program should be changed to fall back to
6725 a reasonable default configuration if these environment
6726 variables are not present. If this cannot be done easily
6727 (e.g., if the source code of a non-free program is not
6728 available), the program must be replaced by a small
6729 "wrapper" shell script which sets the environment variables
6730 if they are not already defined, and calls the original program.
6734 Here is an example of a wrapper script for this purpose:
6736 <example compact="compact">
6738 BAR=${BAR:-/var/lib/fubar}
6740 exec /usr/lib/foo/foo "$@"
6745 Furthermore, as <file>/etc/profile</file> is a configuration
6746 file of the <prgn>base-files</prgn> package, other packages must
6747 not put any environment variables or other commands into that
6752 <sect id="doc-base">
6753 <heading>Registering Documents using doc-base</heading>
6756 The <package>doc-base</package> package implements a
6757 flexible mechanism for handling and presenting
6758 documentation. The recommended practice is for every Debian
6759 package that provides online documentation (other than just
6760 manual pages) to register these documents with
6761 <package>doc-base</package> by installing a
6762 <package>doc-base</package> control file via the
6763 <prgn/install-docs/ script at installation time and
6764 de-register the manuals again when the package is removed.
6767 Please refer to the documentation that comes with the
6768 <package>doc-base</package> package for information and
6777 <heading>Files</heading>
6780 <heading>Binaries</heading>
6783 Two different packages must not install programs with
6784 different functionality but with the same filenames. (The
6785 case of two programs having the same functionality but
6786 different implementations is handled via "alternatives" or
6787 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6788 <ref id="conflicts"> respectively.) If this case happens,
6789 one of the programs must be renamed. The maintainers should
6790 report this to the <tt>debian-devel</tt> mailing list and
6791 try to find a consensus about which program will have to be
6792 renamed. If a consensus cannot be reached, <em>both</em>
6793 programs must be renamed.
6797 By default, when a package is being built, any binaries
6798 created should include debugging information, as well as
6799 being compiled with optimization. You should also turn on
6800 as many reasonable compilation warnings as possible; this
6801 makes life easier for porters, who can then look at build
6802 logs for possible problems. For the C programming language,
6803 this means the following compilation parameters should be
6805 <example compact="compact">
6807 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6809 INSTALL = install -s # (or use strip on the files in debian/tmp)
6814 Note that by default all installed binaries should be stripped,
6815 either by using the <tt>-s</tt> flag to
6816 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6817 the binaries after they have been copied into
6818 <file>debian/tmp</file> but before the tree is made into a
6823 Although binaries in the build tree should be compiled with
6824 debugging information by default, it can often be difficult to
6825 debug programs if they are also subjected to compiler
6826 optimization. For this reason, it is recommended to support the
6827 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6828 (see <ref id="debianrules-options">). This variable can contain
6829 several flags to change how a package is compiled and built.
6833 It is up to the package maintainer to decide what
6834 compilation options are best for the package. Certain
6835 binaries (such as computationally-intensive programs) will
6836 function better with certain flags (<tt>-O3</tt>, for
6837 example); feel free to use them. Please use good judgment
6838 here. Don't use flags for the sake of it; only use them
6839 if there is good reason to do so. Feel free to override
6840 the upstream author's ideas about which compilation
6841 options are best: they are often inappropriate for our
6847 <sect id="libraries">
6848 <heading>Libraries</heading>
6851 If the package is <strong>architecture: any</strong>, then
6852 the shared library compilation and linking flags must have
6853 <tt>-fPIC</tt>, or the package shall not build on some of
6854 the supported architectures<footnote>
6856 If you are using GCC, <tt>-fPIC</tt> produces code with
6857 relocatable position independent code, which is required for
6858 most architectures to create a shared library, with i386 and
6859 perhaps some others where non position independent code is
6860 permitted in a shared library.
6863 Position independent code may have a performance penalty,
6864 especially on <tt>i386</tt>. However, in most cases the
6865 speed penalty must be measured against the memory wasted on
6866 the few architectures where non position independent code is
6869 </footnote>. Any exception to this rule must be discussed on
6870 the mailing list <em>debian-devel@lists.debian.org</em>, and
6871 a rough consensus obtained. The reasons for not compiling
6872 with <tt>-fPIC</tt> flag must be recorded in the file
6873 <tt>README.Debian</tt>, and care must be taken to either
6874 restrict the architecture or arrange for <tt>-fPIC</tt> to
6875 be used on architectures where it is required.<footnote>
6877 Some of the reasons why this might be required is if the
6878 library contains hand crafted assembly code that is not
6879 relocatable, the speed penalty is excessive for compute
6880 intensive libs, and similar reasons.
6885 As to the static libraries, the common case is not to have
6886 relocatable code, since there is no benefit, unless in specific
6887 cases; therefore the static version must not be compiled
6888 with the <tt>-fPIC</tt> flag. Any exception to this rule
6889 should be discussed on the mailing list
6890 <em>debian-devel@lists.debian.org</em>, and the reasons for
6891 compiling with the <tt>-fPIC</tt> flag must be recorded in
6892 the file <tt>README.Debian</tt>. <footnote>
6894 Some of the reasons for linking static libraries with
6895 the <tt>-fPIC</tt> flag are if, for example, one needs a
6896 Perl API for a library that is under rapid development,
6897 and has an unstable API, so shared libraries are
6898 pointless at this phase of the library's development. In
6899 that case, since Perl needs a library with relocatable
6900 code, it may make sense to create a static library with
6901 relocatable code. Another reason cited is if you are
6902 distilling various libraries into a common shared
6903 library, like <tt>mklibs</tt> does in the Debian
6909 In other words, if both a shared and a static library is
6910 being built, each source unit (<tt>*.c</tt>, for example,
6911 for C files) will need to be compiled twice, for the normal
6915 You must specify the gcc option <tt>-D_REENTRANT</tt>
6916 when building a library (either static or shared) to make
6917 the library compatible with LinuxThreads.
6921 Although not enforced by the build tools, shared libraries
6922 must be linked against all libraries that they use symbols from
6923 in the same way that binaries are. This ensures the correct
6924 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6925 system and guarantees that all libraries can be safely opened
6926 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6927 option <tt>-Wl,-z,defs</tt> when building a shared library.
6928 Since this option enforces symbol resolution at build time,
6929 a missing library reference will be caught early as a fatal
6934 All installed shared libraries should be stripped with
6935 <example compact="compact">
6936 strip --strip-unneeded <var>your-lib</var>
6938 (The option <tt>--strip-unneeded</tt> makes
6939 <prgn>strip</prgn> remove only the symbols which aren't
6940 needed for relocation processing.) Shared libraries can
6941 function perfectly well when stripped, since the symbols for
6942 dynamic linking are in a separate part of the ELF object
6944 You might also want to use the options
6945 <tt>--remove-section=.comment</tt> and
6946 <tt>--remove-section=.note</tt> on both shared libraries
6947 and executables, and <tt>--strip-debug</tt> on static
6953 Note that under some circumstances it may be useful to
6954 install a shared library unstripped, for example when
6955 building a separate package to support debugging.
6959 Shared object files (often <file>.so</file> files) that are not
6960 public libraries, that is, they are not meant to be linked
6961 to by third party executables (binaries of other packages),
6962 should be installed in subdirectories of the
6963 <file>/usr/lib</file> directory. Such files are exempt from the
6964 rules that govern ordinary shared libraries, except that
6965 they must not be installed executable and should be
6967 A common example are the so-called "plug-ins",
6968 internal shared objects that are dynamically loaded by
6969 programs using <manref name="dlopen" section="3">.
6974 Packages containing shared libraries that may be linked to
6975 by other packages' binaries, but which for some
6976 <em>compelling</em> reason can not be installed in
6977 <file>/usr/lib</file> directory, may install the shared library
6978 files in subdirectories of the <file>/usr/lib</file> directory,
6979 in which case they should arrange to add that directory in
6980 <file>/etc/ld.so.conf</file> in the package's post-installation
6981 script, and remove it in the package's post-removal script.
6985 An ever increasing number of packages are using
6986 <prgn>libtool</prgn> to do their linking. The latest GNU
6987 libtools (>= 1.3a) can take advantage of the metadata in the
6988 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6989 files). The main advantage of <prgn>libtool</prgn>'s
6990 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6991 store and subsequently access metadata with respect to the
6992 libraries it builds. <prgn>libtool</prgn> will search for
6993 those files, which contain a lot of useful information about
6994 a library (such as library dependency information for static
6995 linking). Also, they're <em>essential</em> for programs
6996 using <tt>libltdl</tt>.<footnote>
6997 Although <prgn>libtool</prgn> is fully capable of
6998 linking against shared libraries which don't have
6999 <tt>.la</tt> files, as it is a mere shell script it can
7000 add considerably to the build time of a
7001 <prgn>libtool</prgn>-using package if that shell script
7002 has to derive all this information from first principles
7003 for each library every time it is linked. With the
7004 advent of <prgn>libtool</prgn> version 1.4 (and to a
7005 lesser extent <prgn>libtool</prgn> version 1.3), the
7006 <file>.la</file> files also store information about
7007 inter-library dependencies which cannot necessarily be
7008 derived after the <file>.la</file> file is deleted.
7013 Packages that use <prgn>libtool</prgn> to create shared
7014 libraries should include the <file>.la</file> files in the
7015 <tt>-dev</tt> package, unless the package relies on
7016 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7017 the <tt>.la</tt> files must go in the run-time library
7022 You must make sure that you use only released versions of
7023 shared libraries to build your packages; otherwise other
7024 users will not be able to run your binaries
7025 properly. Producing source packages that depend on
7026 unreleased compilers is also usually a bad
7033 <heading>Shared libraries</heading>
7035 This section has moved to <ref id="sharedlibs">.
7041 <heading>Scripts</heading>
7044 All command scripts, including the package maintainer
7045 scripts inside the package and used by <prgn>dpkg</prgn>,
7046 should have a <tt>#!</tt> line naming the shell to be used
7051 In the case of Perl scripts this should be
7052 <tt>#!/usr/bin/perl</tt>.
7056 When scripts are installed into a directory in the system
7057 PATH, the script name should not include an extension such
7058 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7059 language currently used to implement it.
7062 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7063 should almost certainly start with <tt>set -e</tt> so that
7064 errors are detected. Every script should use
7065 <tt>set -e</tt> or check the exit status of <em>every</em>
7070 Scripts may assume that <file>/bin/sh</file> implements the
7071 SUSv3 Shell Command Language<footnote>
7072 Single UNIX Specification, version 3, which is also IEEE
7073 1003.1-2004 (POSIX), and is available on the World Wide Web
7074 from <url id="http://www.unix.org/version3/online.html"
7075 name="The Open Group"> after free
7076 registration.</footnote>
7077 plus the following additional features not mandated by
7079 These features are in widespread use in the Linux community
7080 and are implemented in all of bash, dash, and ksh, the most
7081 common shells users may wish to use as <file>/bin/sh</file>.
7084 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7085 must not generate a newline.</item>
7086 <item><tt>test</tt>, if implemented as a shell built-in, must
7087 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7089 <item><tt>local</tt> to create a scoped variable must be
7090 supported, including listing multiple variables in a single
7091 local command and assigning a value to a variable at the
7092 same time as localizing it. <tt>local</tt> may or
7093 may not preserve the variable value from an outer scope if
7094 no assignment is present. Uses such as:
7098 # ... use a, b, c, d ...
7101 must be supported and must set the value of <tt>c</tt> to
7105 If a shell script requires non-SUSv3 features from the shell
7106 interpreter other than those listed above, the appropriate shell
7107 must be specified in the first line of the script (e.g.,
7108 <tt>#!/bin/bash</tt>) and the package must depend on the package
7109 providing the shell (unless the shell package is marked
7110 "Essential", as in the case of <prgn>bash</prgn>).
7114 You may wish to restrict your script to SUSv3 features plus the
7115 above set when possible so that it may use <file>/bin/sh</file>
7116 as its interpreter. If your script works with <prgn>dash</prgn>
7117 (originally called <prgn>ash</prgn>), it probably complies with
7118 the above requirements, but if you are in doubt, use
7119 <file>/bin/bash</file>.
7123 Perl scripts should check for errors when making any
7124 system calls, including <tt>open</tt>, <tt>print</tt>,
7125 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7129 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7130 scripting languages. See <em>Csh Programming Considered
7131 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7132 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7133 If an upstream package comes with <prgn>csh</prgn> scripts
7134 then you must make sure that they start with
7135 <tt>#!/bin/csh</tt> and make your package depend on the
7136 <prgn>c-shell</prgn> virtual package.
7140 Any scripts which create files in world-writeable
7141 directories (e.g., in <file>/tmp</file>) must use a
7142 mechanism which will fail atomically if a file with the same
7143 name already exists.
7147 The Debian base system provides the <prgn>tempfile</prgn>
7148 and <prgn>mktemp</prgn> utilities for use by scripts for
7155 <heading>Symbolic links</heading>
7158 In general, symbolic links within a top-level directory
7159 should be relative, and symbolic links pointing from one
7160 top-level directory into another should be absolute. (A
7161 top-level directory is a sub-directory of the root
7162 directory <file>/</file>.)
7166 In addition, symbolic links should be specified as short as
7167 possible, i.e., link targets like <file>foo/../bar</file> are
7172 Note that when creating a relative link using
7173 <prgn>ln</prgn> it is not necessary for the target of the
7174 link to exist relative to the working directory you're
7175 running <prgn>ln</prgn> from, nor is it necessary to change
7176 directory to the directory where the link is to be made.
7177 Simply include the string that should appear as the target
7178 of the link (this will be a pathname relative to the
7179 directory in which the link resides) as the first argument
7184 For example, in your <prgn>Makefile</prgn> or
7185 <file>debian/rules</file>, you can do things like:
7186 <example compact="compact">
7187 ln -fs gcc $(prefix)/bin/cc
7188 ln -fs gcc debian/tmp/usr/bin/cc
7189 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7190 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7195 A symbolic link pointing to a compressed file should always
7196 have the same file extension as the referenced file. (For
7197 example, if a file <file>foo.gz</file> is referenced by a
7198 symbolic link, the filename of the link has to end with
7199 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7204 <heading>Device files</heading>
7207 Packages must not include device files in the package file
7212 If a package needs any special device files that are not
7213 included in the base system, it must call
7214 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7215 after notifying the user<footnote>
7216 This notification could be done via a (low-priority)
7217 debconf message, or an echo (printf) statement.
7222 Packages must not remove any device files in the
7223 <prgn>postrm</prgn> or any other script. This is left to the
7224 system administrator.
7228 Debian uses the serial devices
7229 <file>/dev/ttyS*</file>. Programs using the old
7230 <file>/dev/cu*</file> devices should be changed to use
7231 <file>/dev/ttyS*</file>.
7235 <sect id="config-files">
7236 <heading>Configuration files</heading>
7239 <heading>Definitions</heading>
7243 <tag>configuration file</tag>
7245 A file that affects the operation of a program, or
7246 provides site- or host-specific information, or
7247 otherwise customizes the behavior of a program.
7248 Typically, configuration files are intended to be
7249 modified by the system administrator (if needed or
7250 desired) to conform to local policy or to provide
7251 more useful site-specific behavior.
7254 <tag><tt>conffile</tt></tag>
7256 A file listed in a package's <tt>conffiles</tt>
7257 file, and is treated specially by <prgn>dpkg</prgn>
7258 (see <ref id="configdetails">).
7264 The distinction between these two is important; they are
7265 not interchangeable concepts. Almost all
7266 <tt>conffile</tt>s are configuration files, but many
7267 configuration files are not <tt>conffiles</tt>.
7271 As noted elsewhere, <file>/etc/init.d</file> scripts,
7272 <file>/etc/default</file> files, scripts installed in
7273 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7274 configuration installed in <file>/etc/cron.d</file> must be
7275 treated as configuration files. In general, any script that
7276 embeds configuration information is de-facto a configuration
7277 file and should be treated as such.
7282 <heading>Location</heading>
7285 Any configuration files created or used by your package
7286 must reside in <file>/etc</file>. If there are several,
7287 consider creating a subdirectory of <file>/etc</file>
7288 named after your package.
7292 If your package creates or uses configuration files
7293 outside of <file>/etc</file>, and it is not feasible to modify
7294 the package to use <file>/etc</file> directly, put the files
7295 in <file>/etc</file> and create symbolic links to those files
7296 from the location that the package requires.
7301 <heading>Behavior</heading>
7304 Configuration file handling must conform to the following
7306 <list compact="compact">
7308 local changes must be preserved during a package
7312 configuration files must be preserved when the
7313 package is removed, and only deleted when the
7320 The easy way to achieve this behavior is to make the
7321 configuration file a <tt>conffile</tt>. This is
7322 appropriate only if it is possible to distribute a default
7323 version that will work for most installations, although
7324 some system administrators may choose to modify it. This
7325 implies that the default version will be part of the
7326 package distribution, and must not be modified by the
7327 maintainer scripts during installation (or at any other
7332 In order to ensure that local changes are preserved
7333 correctly, no package may contain or make hard links to
7334 conffiles.<footnote>
7335 Rationale: There are two problems with hard links.
7336 The first is that some editors break the link while
7337 editing one of the files, so that the two files may
7338 unwittingly become unlinked and different. The second
7339 is that <prgn>dpkg</prgn> might break the hard link
7340 while upgrading <tt>conffile</tt>s.
7345 The other way to do it is via the maintainer scripts. In
7346 this case, the configuration file must not be listed as a
7347 <tt>conffile</tt> and must not be part of the package
7348 distribution. If the existence of a file is required for
7349 the package to be sensibly configured it is the
7350 responsibility of the package maintainer to provide
7351 maintainer scripts which correctly create, update and
7352 maintain the file and remove it on purge. (See <ref
7353 id="maintainerscripts"> for more information.) These
7354 scripts must be idempotent (i.e., must work correctly if
7355 <prgn>dpkg</prgn> needs to re-run them due to errors
7356 during installation or removal), must cope with all the
7357 variety of ways <prgn>dpkg</prgn> can call maintainer
7358 scripts, must not overwrite or otherwise mangle the user's
7359 configuration without asking, must not ask unnecessary
7360 questions (particularly during upgrades), and must
7361 otherwise be good citizens.
7365 The scripts are not required to configure every possible
7366 option for the package, but only those necessary to get
7367 the package running on a given system. Ideally the
7368 sysadmin should not have to do any configuration other
7369 than that done (semi-)automatically by the
7370 <prgn>postinst</prgn> script.
7374 A common practice is to create a script called
7375 <file><var>package</var>-configure</file> and have the
7376 package's <prgn>postinst</prgn> call it if and only if the
7377 configuration file does not already exist. In certain
7378 cases it is useful for there to be an example or template
7379 file which the maintainer scripts use. Such files should
7380 be in <file>/usr/share/<var>package</var></file> or
7381 <file>/usr/lib/<var>package</var></file> (depending on whether
7382 they are architecture-independent or not). There should
7383 be symbolic links to them from
7384 <file>/usr/share/doc/<var>package</var>/examples</file> if
7385 they are examples, and should be perfectly ordinary
7386 <prgn>dpkg</prgn>-handled files (<em>not</em>
7387 configuration files).
7391 These two styles of configuration file handling must
7392 not be mixed, for that way lies madness:
7393 <prgn>dpkg</prgn> will ask about overwriting the file
7394 every time the package is upgraded.
7399 <heading>Sharing configuration files</heading>
7402 Packages which specify the same file as a
7403 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7404 with each other. (This is an instance of the general rule
7405 about not sharing files. Note that neither alternatives
7406 nor diversions are likely to be appropriate in this case;
7407 in particular, <prgn>dpkg</prgn> does not handle diverted
7408 <tt>conffile</tt>s well.)
7412 The maintainer scripts must not alter a <tt>conffile</tt>
7413 of <em>any</em> package, including the one the scripts
7418 If two or more packages use the same configuration file
7419 and it is reasonable for both to be installed at the same
7420 time, one of these packages must be defined as
7421 <em>owner</em> of the configuration file, i.e., it will be
7422 the package which handles that file as a configuration
7423 file. Other packages that use the configuration file must
7424 depend on the owning package if they require the
7425 configuration file to operate. If the other package will
7426 use the configuration file if present, but is capable of
7427 operating without it, no dependency need be declared.
7431 If it is desirable for two or more related packages to
7432 share a configuration file <em>and</em> for all of the
7433 related packages to be able to modify that configuration
7434 file, then the following should be done:
7435 <enumlist compact="compact">
7437 One of the related packages (the "owning" package)
7438 will manage the configuration file with maintainer
7439 scripts as described in the previous section.
7442 The owning package should also provide a program
7443 that the other packages may use to modify the
7447 The related packages must use the provided program
7448 to make any desired modifications to the
7449 configuration file. They should either depend on
7450 the core package to guarantee that the configuration
7451 modifier program is available or accept gracefully
7452 that they cannot modify the configuration file if it
7453 is not. (This is in addition to the fact that the
7454 configuration file may not even be present in the
7461 Sometimes it's appropriate to create a new package which
7462 provides the basic infrastructure for the other packages
7463 and which manages the shared configuration files. (The
7464 <tt>sgml-base</tt> package is a good example.)
7469 <heading>User configuration files ("dotfiles")</heading>
7472 The files in <file>/etc/skel</file> will automatically be
7473 copied into new user accounts by <prgn>adduser</prgn>.
7474 No other program should reference the files in
7475 <file>/etc/skel</file>.
7479 Therefore, if a program needs a dotfile to exist in
7480 advance in <file>$HOME</file> to work sensibly, that dotfile
7481 should be installed in <file>/etc/skel</file> and treated as a
7486 However, programs that require dotfiles in order to
7487 operate sensibly are a bad thing, unless they do create
7488 the dotfiles themselves automatically.
7492 Furthermore, programs should be configured by the Debian
7493 default installation to behave as closely to the upstream
7494 default behavior as possible.
7498 Therefore, if a program in a Debian package needs to be
7499 configured in some way in order to operate sensibly, that
7500 should be done using a site-wide configuration file placed
7501 in <file>/etc</file>. Only if the program doesn't support a
7502 site-wide default configuration and the package maintainer
7503 doesn't have time to add it may a default per-user file be
7504 placed in <file>/etc/skel</file>.
7508 <file>/etc/skel</file> should be as empty as we can make it.
7509 This is particularly true because there is no easy (or
7510 necessarily desirable) mechanism for ensuring that the
7511 appropriate dotfiles are copied into the accounts of
7512 existing users when a package is installed.
7518 <heading>Log files</heading>
7520 Log files should usually be named
7521 <file>/var/log/<var>package</var>.log</file>. If you have many
7522 log files, or need a separate directory for permission
7523 reasons (<file>/var/log</file> is writable only by
7524 <file>root</file>), you should usually create a directory named
7525 <file>/var/log/<var>package</var></file> and place your log
7530 Log files must be rotated occasionally so that they don't
7531 grow indefinitely; the best way to do this is to drop a log
7532 rotation configuration file into the directory
7533 <file>/etc/logrotate.d</file> and use the facilities provided by
7534 logrotate.<footnote>
7536 The traditional approach to log files has been to set up
7537 <em>ad hoc</em> log rotation schemes using simple shell
7538 scripts and cron. While this approach is highly
7539 customizable, it requires quite a lot of sysadmin work.
7540 Even though the original Debian system helped a little
7541 by automatically installing a system which can be used
7542 as a template, this was deemed not enough.
7546 The use of <prgn>logrotate</prgn>, a program developed
7547 by Red Hat, is better, as it centralizes log management.
7548 It has both a configuration file
7549 (<file>/etc/logrotate.conf</file>) and a directory where
7550 packages can drop their individual log rotation
7551 configurations (<file>/etc/logrotate.d</file>).
7554 Here is a good example for a logrotate config
7555 file (for more information see <manref name="logrotate"
7557 <example compact="compact">
7558 /var/log/foo/*.log {
7563 /etc/init.d/foo force-reload
7567 This rotates all files under <file>/var/log/foo</file>, saves 12
7568 compressed generations, and forces the daemon to reload its
7569 configuration information after the log rotation.
7573 Log files should be removed when the package is
7574 purged (but not when it is only removed). This should be
7575 done by the <prgn>postrm</prgn> script when it is called
7576 with the argument <tt>purge</tt> (see <ref
7577 id="removedetails">).
7582 <heading>Permissions and owners</heading>
7585 The rules in this section are guidelines for general use.
7586 If necessary you may deviate from the details below.
7587 However, if you do so you must make sure that what is done
7588 is secure and you should try to be as consistent as possible
7589 with the rest of the system. You should probably also
7590 discuss it on <prgn>debian-devel</prgn> first.
7594 Files should be owned by <tt>root:root</tt>, and made
7595 writable only by the owner and universally readable (and
7596 executable, if appropriate), that is mode 644 or 755.
7600 Directories should be mode 755 or (for group-writability)
7601 mode 2775. The ownership of the directory should be
7602 consistent with its mode: if a directory is mode 2775, it
7603 should be owned by the group that needs write access to
7606 When a package is upgraded, and the owner or permissions
7607 of a file included in the package has changed, dpkg
7608 arranges for the ownership and permissions to be
7609 correctly set upon installation. However, this does not
7610 extend to directories; the permissions and ownership of
7611 directories already on the system does not change on
7612 install or upgrade of packages. This makes sense, since
7613 otherwise common directories like <tt>/usr</tt> would
7614 always be in flux. To correctly change permissions of a
7615 directory the package owns, explicit action is required,
7616 usually in the <tt>postinst</tt> script. Care must be
7617 taken to handle downgrades as well, in that case.
7624 Setuid and setgid executables should be mode 4755 or 2755
7625 respectively, and owned by the appropriate user or group.
7626 They should not be made unreadable (modes like 4711 or
7627 2711 or even 4111); doing so achieves no extra security,
7628 because anyone can find the binary in the freely available
7629 Debian package; it is merely inconvenient. For the same
7630 reason you should not restrict read or execute permissions
7631 on non-set-id executables.
7635 Some setuid programs need to be restricted to particular
7636 sets of users, using file permissions. In this case they
7637 should be owned by the uid to which they are set-id, and by
7638 the group which should be allowed to execute them. They
7639 should have mode 4754; again there is no point in making
7640 them unreadable to those users who must not be allowed to
7645 It is possible to arrange that the system administrator can
7646 reconfigure the package to correspond to their local
7647 security policy by changing the permissions on a binary:
7648 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7649 described below.<footnote>
7650 Ordinary files installed by <prgn>dpkg</prgn> (as
7651 opposed to <tt>conffile</tt>s and other similar objects)
7652 normally have their permissions reset to the distributed
7653 permissions when the package is reinstalled. However,
7654 the use of <prgn>dpkg-statoverride</prgn> overrides this
7655 default behavior. If you use this method, you should
7656 remember to describe <prgn>dpkg-statoverride</prgn> in
7657 the package documentation; being a relatively new
7658 addition to Debian, it is probably not yet well-known.
7660 Another method you should consider is to create a group for
7661 people allowed to use the program(s) and make any setuid
7662 executables executable only by that group.
7666 If you need to create a new user or group for your package
7667 there are two possibilities. Firstly, you may need to
7668 make some files in the binary package be owned by this
7669 user or group, or you may need to compile the user or
7670 group id (rather than just the name) into the binary
7671 (though this latter should be avoided if possible, as in
7672 this case you need a statically allocated id).</p>
7675 If you need a statically allocated id, you must ask for a
7676 user or group id from the <tt>base-passwd</tt> maintainer,
7677 and must not release the package until you have been
7678 allocated one. Once you have been allocated one you must
7679 either make the package depend on a version of the
7680 <tt>base-passwd</tt> package with the id present in
7681 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7682 your package to create the user or group itself with the
7683 correct id (using <tt>adduser</tt>) in its
7684 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7685 the <prgn>postinst</prgn> is to be preferred if it is
7686 possible, otherwise a pre-dependency will be needed on the
7687 <tt>adduser</tt> package.)
7691 On the other hand, the program might be able to determine
7692 the uid or gid from the user or group name at runtime, so
7693 that a dynamically allocated id can be used. In this case
7694 you should choose an appropriate user or group name,
7695 discussing this on <prgn>debian-devel</prgn> and checking
7696 with the <package/base-passwd/ maintainer that it is unique and that
7697 they do not wish you to use a statically allocated id
7698 instead. When this has been checked you must arrange for
7699 your package to create the user or group if necessary using
7700 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7701 <prgn>postinst</prgn> script (again, the latter is to be
7702 preferred if it is possible).
7706 Note that changing the numeric value of an id associated
7707 with a name is very difficult, and involves searching the
7708 file system for all appropriate files. You need to think
7709 carefully whether a static or dynamic id is required, since
7710 changing your mind later will cause problems.
7713 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7715 This section is not intended as policy, but as a
7716 description of the use of <prgn>dpkg-statoverride</prgn>.
7720 If a system administrator wishes to have a file (or
7721 directory or other such thing) installed with owner and
7722 permissions different from those in the distributed Debian
7723 package, they can use the <prgn>dpkg-statoverride</prgn>
7724 program to instruct <prgn>dpkg</prgn> to use the different
7725 settings every time the file is installed. Thus the
7726 package maintainer should distribute the files with their
7727 normal permissions, and leave it for the system
7728 administrator to make any desired changes. For example, a
7729 daemon which is normally required to be setuid root, but
7730 in certain situations could be used without being setuid,
7731 should be installed setuid in the <tt>.deb</tt>. Then the
7732 local system administrator can change this if they wish.
7733 If there are two standard ways of doing it, the package
7734 maintainer can use <tt>debconf</tt> to find out the
7735 preference, and call <prgn>dpkg-statoverride</prgn> in the
7736 maintainer script if necessary to accommodate the system
7737 administrator's choice. Care must be taken during
7738 upgrades to not override an existing setting.
7742 Given the above, <prgn>dpkg-statoverride</prgn> is
7743 essentially a tool for system administrators and would not
7744 normally be needed in the maintainer scripts. There is
7745 one type of situation, though, where calls to
7746 <prgn>dpkg-statoverride</prgn> would be needed in the
7747 maintainer scripts, and that involves packages which use
7748 dynamically allocated user or group ids. In such a
7749 situation, something like the following idiom can be very
7750 helpful in the package's <prgn>postinst</prgn>, where
7751 <tt>sysuser</tt> is a dynamically allocated id:
7753 for i in /usr/bin/foo /usr/sbin/bar
7755 # only do something when no setting exists
7756 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7758 #include: debconf processing, question about foo and bar
7759 if [ "$RET" = "true" ] ; then
7760 dpkg-statoverride --update --add sysuser root 4755 $i
7765 The corresponding <tt>dpkg-statoverride --remove</tt>
7766 calls can then be made unconditionally when the package is
7774 <chapt id="customized-programs">
7775 <heading>Customized programs</heading>
7777 <sect id="arch-spec">
7778 <heading>Architecture specification strings</heading>
7781 If a program needs to specify an <em>architecture specification
7782 string</em> in some place, it should select one of the
7783 strings provided by <tt>dpkg-architecture -L</tt>. The
7784 strings are in the format
7785 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7786 is sometimes elided, as when the OS is Linux.<footnote>
7787 <p>Currently, the strings are:
7788 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7789 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7790 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7791 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7792 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7793 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7794 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7795 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7796 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7797 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7798 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7799 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7800 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7801 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7802 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7803 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7804 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7805 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7806 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7807 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7808 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7809 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7810 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7811 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7812 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7813 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7814 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7815 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7816 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7817 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7818 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7819 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7820 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7821 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7822 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7823 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7824 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7830 Note that we don't want to use
7831 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7832 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7833 since this would make our programs incompatible with other
7834 Linux distributions. We also don't use something like
7835 <tt><var>arch</var>-unknown-linux</tt>, since the
7836 <tt>unknown</tt> does not look very good.
7841 <heading>Daemons</heading>
7844 The configuration files <file>/etc/services</file>,
7845 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7846 by the <prgn>netbase</prgn> package and must not be modified
7851 If a package requires a new entry in one of these files, the
7852 maintainer should get in contact with the
7853 <prgn>netbase</prgn> maintainer, who will add the entries
7854 and release a new version of the <prgn>netbase</prgn>
7859 The configuration file <file>/etc/inetd.conf</file> must not be
7860 modified by the package's scripts except via the
7861 <prgn>update-inetd</prgn> script or the
7862 <file>DebianNet.pm</file> Perl module. See their documentation
7863 for details on how to add entries.
7867 If a package wants to install an example entry into
7868 <file>/etc/inetd.conf</file>, the entry must be preceded with
7869 exactly one hash character (<tt>#</tt>). Such lines are
7870 treated as "commented out by user" by the
7871 <prgn>update-inetd</prgn> script and are not changed or
7872 activated during package updates.
7877 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7881 Some programs need to create pseudo-ttys. This should be done
7882 using Unix98 ptys if the C library supports it. The resulting
7883 program must not be installed setuid root, unless that
7884 is required for other functionality.
7888 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7889 <file>/var/log/lastlog</file> must be installed writable by
7890 group <tt>utmp</tt>. Programs which need to modify those
7891 files must be installed setgid <tt>utmp</tt>.
7896 <heading>Editors and pagers</heading>
7899 Some programs have the ability to launch an editor or pager
7900 program to edit or display a text document. Since there are
7901 lots of different editors and pagers available in the Debian
7902 distribution, the system administrator and each user should
7903 have the possibility to choose their preferred editor and
7908 In addition, every program should choose a good default
7909 editor/pager if none is selected by the user or system
7914 Thus, every program that launches an editor or pager must
7915 use the EDITOR or PAGER environment variable to determine
7916 the editor or pager the user wishes to use. If these
7917 variables are not set, the programs <file>/usr/bin/editor</file>
7918 and <file>/usr/bin/pager</file> should be used, respectively.
7922 These two files are managed through the <prgn>dpkg</prgn>
7923 "alternatives" mechanism. Thus every package providing an
7924 editor or pager must call the
7925 <prgn>update-alternatives</prgn> script to register these
7930 If it is very hard to adapt a program to make use of the
7931 EDITOR or PAGER variables, that program may be configured to
7932 use <file>/usr/bin/sensible-editor</file> and
7933 <file>/usr/bin/sensible-pager</file> as the editor or pager
7934 program respectively. These are two scripts provided in the
7935 Debian base system that check the EDITOR and PAGER variables
7936 and launch the appropriate program, and fall back to
7937 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7938 variable is not set.
7942 A program may also use the VISUAL environment variable to
7943 determine the user's choice of editor. If it exists, it
7944 should take precedence over EDITOR. This is in fact what
7945 <file>/usr/bin/sensible-editor</file> does.
7949 It is not required for a package to depend on
7950 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7951 package to provide such virtual packages.<footnote>
7952 The Debian base system already provides an editor and a
7958 <sect id="web-appl">
7959 <heading>Web servers and applications</heading>
7962 This section describes the locations and URLs that should
7963 be used by all web servers and web applications in the
7970 Cgi-bin executable files are installed in the
7972 <example compact="compact">
7973 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7975 and should be referred to as
7976 <example compact="compact">
7977 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7983 <p>Access to HTML documents</p>
7986 HTML documents for a package are stored in
7987 <file>/usr/share/doc/<var>package</var></file>
7988 and can be referred to as
7989 <example compact="compact">
7990 http://localhost/doc/<var>package</var>/<var>filename</var>
7995 The web server should restrict access to the document
7996 tree so that only clients on the same host can read
7997 the documents. If the web server does not support such
7998 access controls, then it should not provide access at
7999 all, or ask about providing access during installation.
8004 <p>Access to images</p>
8006 It is recommended that images for a package be stored
8007 in <tt>/usr/share/images/<var>package</var></tt> and
8008 may be referred to through an alias <tt>/images/</tt>
8011 http://localhost/images/<package>/<filename>
8018 <p>Web Document Root</p>
8021 Web Applications should try to avoid storing files in
8022 the Web Document Root. Instead they should use the
8023 /usr/share/doc/<var>package</var> directory for
8024 documents and register the Web Application via the
8025 <package>doc-base</package> package. If access to the
8026 web document root is unavoidable then use
8027 <example compact="compact">
8030 as the Document Root. This might be just a symbolic
8031 link to the location where the system administrator
8032 has put the real document root.
8035 <item><p>Providing httpd and/or httpd-cgi</p>
8037 All web servers should provide the virtual package
8038 <tt>httpd</tt>. If a web server has CGI support it should
8039 provide <tt>httpd-cgi</tt> additionally.
8042 All web applications which do not contain CGI scripts should
8043 depend on <tt>httpd</tt>, all those web applications which
8044 <tt>do</tt> contain CGI scripts, should depend on
8052 <sect id="mail-transport-agents">
8053 <heading>Mail transport, delivery and user agents</heading>
8056 Debian packages which process electronic mail, whether mail
8057 user agents (MUAs) or mail transport agents (MTAs), must
8058 ensure that they are compatible with the configuration
8059 decisions below. Failure to do this may result in lost
8060 mail, broken <tt>From:</tt> lines, and other serious brain
8065 The mail spool is <file>/var/mail</file> and the interface to
8066 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8067 the FHS). On older systems, the mail spool may be
8068 physically located in <file>/var/spool/mail</file>, but all
8069 access to the mail spool should be via the
8070 <file>/var/mail</file> symlink. The mail spool is part of the
8071 base system and not part of the MTA package.
8075 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8076 programs (such as IMAP daemons) must lock the mailbox in an
8077 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8078 be combined with dot locking. To avoid deadlocks, a program
8079 should use <tt>fcntl()</tt> first and dot locking after
8080 this, or alternatively implement the two locking methods in
8081 a non blocking way<footnote>
8082 If it is not possible to establish both locks, the
8083 system shouldn't wait for the second lock to be
8084 established, but remove the first lock, wait a (random)
8085 time, and start over locking again.
8086 </footnote>. Using the functions <tt>maillock</tt> and
8087 <tt>mailunlock</tt> provided by the
8088 <tt>liblockfile*</tt><footnote>
8089 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8090 to use these functions.
8091 </footnote> packages is the recommended way to realize this.
8095 Mailboxes are generally either mode 600 and owned by
8096 <var>user</var> or mode 660 and owned by
8097 <tt><var>user</var>:mail</tt><footnote>
8098 There are two traditional permission schemes for mail spools:
8099 mode 600 with all mail delivery done by processes running as
8100 the destination user, or mode 660 and owned by group mail with
8101 mail delivery done by a process running as a system user in
8102 group mail. Historically, Debian required mode 660 mail
8103 spools to enable the latter model, but that model has become
8104 increasingly uncommon and the principle of least privilege
8105 indicates that mail systems that use the first model should
8106 use permissions of 600. If delivery to programs is permitted,
8107 it's easier to keep the mail system secure if the delivery
8108 agent runs as the destination user. Debian Policy therefore
8109 permits either scheme.
8110 </footnote>. The local system administrator may choose a
8111 different permission scheme; packages should not make
8112 assumptions about the permission and ownership of mailboxes
8113 unless required (such as when creating a new mailbox). A MUA
8114 may remove a mailbox (unless it has nonstandard permissions) in
8115 which case the MTA or another MUA must recreate it if needed.
8119 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8120 be setgid mail to do the locking mentioned above (and
8121 must obviously avoid accessing other users' mailboxes
8122 using this privilege).</p>
8125 <file>/etc/aliases</file> is the source file for the system mail
8126 aliases (e.g., postmaster, usenet, etc.), it is the one
8127 which the sysadmin and <prgn>postinst</prgn> scripts may
8128 edit. After <file>/etc/aliases</file> is edited the program or
8129 human editing it must call <prgn>newaliases</prgn>. All MTA
8130 packages must come with a <prgn>newaliases</prgn> program,
8131 even if it does nothing, but older MTA packages did not do
8132 this so programs should not fail if <prgn>newaliases</prgn>
8133 cannot be found. Note that because of this, all MTA
8134 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8135 <tt>Replaces: mail-transport-agent</tt> control file
8140 The convention of writing <tt>forward to
8141 <var>address</var></tt> in the mailbox itself is not
8142 supported. Use a <tt>.forward</tt> file instead.</p>
8145 The <prgn>rmail</prgn> program used by UUCP
8146 for incoming mail should be <file>/usr/sbin/rmail</file>.
8147 Likewise, <prgn>rsmtp</prgn>, for receiving
8148 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8152 If your package needs to know what hostname to use on (for
8153 example) outgoing news and mail messages which are generated
8154 locally, you should use the file <file>/etc/mailname</file>. It
8155 will contain the portion after the username and <tt>@</tt>
8156 (at) sign for email addresses of users on the machine
8157 (followed by a newline).
8161 Such a package should check for the existence of this file
8162 when it is being configured. If it exists, it should be
8163 used without comment, although an MTA's configuration script
8164 may wish to prompt the user even if it finds that this file
8165 exists. If the file does not exist, the package should
8166 prompt the user for the value (preferably using
8167 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8168 as well as using it in the package's configuration. The
8169 prompt should make it clear that the name will not just be
8170 used by that package. For example, in this situation the
8171 <tt>inn</tt> package could say something like:
8172 <example compact="compact">
8173 Please enter the "mail name" of your system. This is the
8174 hostname portion of the address to be shown on outgoing
8175 news and mail messages. The default is
8176 <var>syshostname</var>, your system's host name. Mail
8177 name ["<var>syshostname</var>"]:
8179 where <var>syshostname</var> is the output of <tt>hostname
8185 <heading>News system configuration</heading>
8188 All the configuration files related to the NNTP (news)
8189 servers and clients should be located under
8190 <file>/etc/news</file>.</p>
8193 There are some configuration issues that apply to a number
8194 of news clients and server packages on the machine. These
8198 <tag><file>/etc/news/organization</file></tag>
8200 A string which should appear as the
8201 organization header for all messages posted
8202 by NNTP clients on the machine
8205 <tag><file>/etc/news/server</file></tag>
8207 Contains the FQDN of the upstream NNTP
8208 server, or localhost if the local machine is
8213 Other global files may be added as required for cross-package news
8220 <heading>Programs for the X Window System</heading>
8223 <heading>Providing X support and package priorities</heading>
8226 Programs that can be configured with support for the X
8227 Window System must be configured to do so and must declare
8228 any package dependencies necessary to satisfy their
8229 runtime requirements when using the X Window System. If
8230 such a package is of higher priority than the X packages
8231 on which it depends, it is required that either the
8232 X-specific components be split into a separate package, or
8233 that an alternative version of the package, which includes
8234 X support, be provided, or that the package's priority be
8240 <heading>Packages providing an X server</heading>
8243 Packages that provide an X server that, directly or
8244 indirectly, communicates with real input and display
8245 hardware should declare in their control data that they
8246 provide the virtual package <tt>xserver</tt>.<footnote>
8247 This implements current practice, and provides an
8248 actual policy for usage of the <tt>xserver</tt>
8249 virtual package which appears in the virtual packages
8250 list. In a nutshell, X servers that interface
8251 directly with the display and input hardware or via
8252 another subsystem (e.g., GGI) should provide
8253 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8254 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8260 <heading>Packages providing a terminal emulator</heading>
8263 Packages that provide a terminal emulator for the X Window
8264 System which meet the criteria listed below should declare
8265 in their control data that they provide the virtual
8266 package <tt>x-terminal-emulator</tt>. They should also
8267 register themselves as an alternative for
8268 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8273 To be an <tt>x-terminal-emulator</tt>, a program must:
8274 <list compact="compact">
8276 Be able to emulate a DEC VT100 terminal, or a
8277 compatible terminal.
8281 Support the command-line option <tt>-e
8282 <var>command</var></tt>, which creates a new
8283 terminal window<footnote>
8284 "New terminal window" does not necessarily mean
8285 a new top-level X window directly parented by
8286 the window manager; it could, if the terminal
8287 emulator application were so coded, be a new
8288 "view" in a multiple-document interface (MDI).
8290 and runs the specified <var>command</var>,
8291 interpreting the entirety of the rest of the command
8292 line as a command to pass straight to exec, in the
8293 manner that <tt>xterm</tt> does.
8297 Support the command-line option <tt>-T
8298 <var>title</var></tt>, which creates a new terminal
8299 window with the window title <var>title</var>.
8306 <heading>Packages providing a window manager</heading>
8309 Packages that provide a window manager should declare in
8310 their control data that they provide the virtual package
8311 <tt>x-window-manager</tt>. They should also register
8312 themselves as an alternative for
8313 <file>/usr/bin/x-window-manager</file>, with a priority
8314 calculated as follows:
8315 <list compact="compact">
8317 Start with a priority of 20.
8321 If the window manager supports the Debian menu
8322 system, add 20 points if this support is available
8323 in the package's default configuration (i.e., no
8324 configuration files belonging to the system or user
8325 have to be edited to activate the feature); if
8326 configuration files must be modified, add only 10
8332 If the window manager complies with <url
8333 id="http://www.freedesktop.org/Standards/wm-spec"
8334 name="The Window Manager Specification Project">,
8335 written by the <url id="http://www.freedesktop.org/"
8336 name="Free Desktop Group">, add 40 points.
8340 If the window manager permits the X session to be
8341 restarted using a <em>different</em> window manager
8342 (without killing the X server) in its default
8343 configuration, add 10 points; otherwise add none.
8350 <heading>Packages providing fonts</heading>
8353 Packages that provide fonts for the X Window
8355 For the purposes of Debian Policy, a "font for the X
8356 Window System" is one which is accessed via X protocol
8357 requests. Fonts for the Linux console, for PostScript
8358 renderer, or any other purpose, do not fit this
8359 definition. Any tool which makes such fonts available
8360 to the X Window System, however, must abide by this
8363 must do a number of things to ensure that they are both
8364 available without modification of the X or font server
8365 configuration, and that they do not corrupt files used by
8366 other font packages to register information about
8370 Fonts of any type supported by the X Window System
8371 must be in a separate binary package from any
8372 executables, libraries, or documentation (except
8373 that specific to the fonts shipped, such as their
8374 license information). If one or more of the fonts
8375 so packaged are necessary for proper operation of
8376 the package with which they are associated the font
8377 package may be Recommended; if the fonts merely
8378 provide an enhancement, a Suggests relationship may
8379 be used. Packages must not Depend on font
8381 This is because the X server may retrieve fonts
8382 from the local file system or over the network
8383 from an X font server; the Debian package system
8384 is empowered to deal only with the local
8390 BDF fonts must be converted to PCF fonts with the
8391 <prgn>bdftopcf</prgn> utility (available in the
8392 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8393 placed in a directory that corresponds to their
8395 <list compact="compact">
8397 100 dpi fonts must be placed in
8398 <file>/usr/share/fonts/X11/100dpi/</file>.
8402 75 dpi fonts must be placed in
8403 <file>/usr/share/fonts/X11/75dpi/</file>.
8407 Character-cell fonts, cursor fonts, and other
8408 low-resolution fonts must be placed in
8409 <file>/usr/share/fonts/X11/misc/</file>.
8415 Speedo fonts must be placed in
8416 <file>/usr/share/fonts/X11/Speedo/</file>.
8420 Type 1 fonts must be placed in
8421 <file>/usr/share/fonts/X11/Type1/</file>. If font
8422 metric files are available, they must be placed here
8427 Subdirectories of <file>/usr/share/fonts/X11/</file>
8428 other than those listed above must be neither
8429 created nor used. (The <file>PEX</file>, <file>CID</file>,
8430 and <file>cyrillic</file> directories are excepted for
8431 historical reasons, but installation of files into
8432 these directories remains discouraged.)
8436 Font packages may, instead of placing files directly
8437 in the X font directories listed above, provide
8438 symbolic links in that font directory pointing to
8439 the files' actual location in the filesystem. Such
8440 a location must comply with the FHS.
8444 Font packages should not contain both 75dpi and
8445 100dpi versions of a font. If both are available,
8446 they should be provided in separate binary packages
8447 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8448 the names of the packages containing the
8449 corresponding fonts.
8453 Fonts destined for the <file>misc</file> subdirectory
8454 should not be included in the same package as 75dpi
8455 or 100dpi fonts; instead, they should be provided in
8456 a separate package with <tt>-misc</tt> appended to
8461 Font packages must not provide the files
8462 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8463 <file>fonts.scale</file> in a font directory:
8466 <file>fonts.dir</file> files must not be provided at all.
8470 <file>fonts.alias</file> and <file>fonts.scale</file>
8471 files, if needed, should be provided in the
8473 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8474 where <var>fontdir</var> is the name of the
8476 <file>/usr/share/fonts/X11/</file> where the
8477 package's corresponding fonts are stored
8478 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8479 <var>package</var> is the name of the package
8480 that provides these fonts, and
8481 <var>extension</var> is either <tt>scale</tt>
8482 or <tt>alias</tt>, whichever corresponds to
8489 Font packages must declare a dependency on
8490 <tt>xfonts-utils</tt> in their control
8495 Font packages that provide one or more
8496 <file>fonts.scale</file> files as described above must
8497 invoke <prgn>update-fonts-scale</prgn> on each
8498 directory into which they installed fonts
8499 <em>before</em> invoking
8500 <prgn>update-fonts-dir</prgn> on that directory.
8501 This invocation must occur in both the
8502 <prgn>postinst</prgn> (for all arguments) and
8503 <prgn>postrm</prgn> (for all arguments except
8504 <tt>upgrade</tt>) scripts.
8508 Font packages that provide one or more
8509 <file>fonts.alias</file> files as described above must
8510 invoke <prgn>update-fonts-alias</prgn> on each
8511 directory into which they installed fonts. This
8512 invocation must occur in both the
8513 <prgn>postinst</prgn> (for all arguments) and
8514 <prgn>postrm</prgn> (for all arguments except
8515 <tt>upgrade</tt>) scripts.
8519 Font packages must invoke
8520 <prgn>update-fonts-dir</prgn> on each directory into
8521 which they installed fonts. This invocation must
8522 occur in both the <prgn>postinst</prgn> (for all
8523 arguments) and <prgn>postrm</prgn> (for all
8524 arguments except <tt>upgrade</tt>) scripts.
8528 Font packages must not provide alias names for the
8529 fonts they include which collide with alias names
8530 already in use by fonts already packaged.
8534 Font packages must not provide fonts with the same
8535 XLFD registry name as another font already packaged.
8542 <heading>Application defaults files</heading>
8545 Application defaults files must be installed in the
8546 directory <file>/etc/X11/app-defaults/</file> (use of a
8547 localized subdirectory of <file>/etc/X11/</file> as described
8548 in the <em>X Toolkit Intrinsics - C Language
8549 Interface</em> manual is also permitted). They must be
8550 registered as <tt>conffile</tt>s or handled as
8551 configuration files.
8555 Customization of programs' X resources may also be
8556 supported with the provision of a file with the same name
8557 as that of the package placed in the
8558 <file>/etc/X11/Xresources/</file> directory, which must
8559 registered as a <tt>conffile</tt> or handled as a
8560 configuration file.<footnote>
8561 Note that this mechanism is not the same as using
8562 app-defaults; app-defaults are tied to the client
8563 binary on the local file system, whereas X resources
8564 are stored in the X server and affect all connecting
8571 <heading>Installation directory issues</heading>
8574 Packages using the X Window System should not be
8575 configured to install files under the
8576 <file>/usr/X11R6/</file> directory. The
8577 <file>/usr/X11R6/</file> directory hierarchy should be
8578 regarded as obsolete.
8582 Programs that use GNU <prgn>autoconf</prgn> and
8583 <prgn>automake</prgn> are usually easily configured at
8584 compile time to use <file>/usr/</file> instead of
8585 <file>/usr/X11R6/</file>, and this should be done whenever
8586 possible. Configuration files for window managers and
8587 display managers should be placed in a subdirectory of
8588 <file>/etc/X11/</file> corresponding to the package name due
8589 to these programs' tight integration with the mechanisms
8590 of the X Window System. Application-level programs should
8591 use the <file>/etc/</file> directory unless otherwise mandated
8596 The installation of files into subdirectories
8597 of <file>/usr/X11R6/include/X11/</file> and
8598 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8599 package maintainers should determine if subdirectories of
8600 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8605 Packages should install any relevant files into the
8606 directories <file>/usr/include/X11/</file> and
8607 <file>/usr/lib/X11/</file>, but if they do so, they must
8608 pre-depend on <tt>x11-common (>=
8609 1:7.0.0)</tt><footnote>
8611 These libraries used to be all symbolic
8612 links. However, with <tt>X11R7</tt>,
8613 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8614 are now real directories, and packages
8615 <strong>should</strong> ship their files here instead
8616 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8617 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8618 responsible for converting these symlinks into
8626 <heading>The OSF/Motif and OpenMotif libraries</heading>
8629 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8630 OpenMotif libraries</em><footnote>
8631 OSF/Motif and OpenMotif are collectively referred to as
8632 "Motif" in this policy document.
8634 should be compiled against and tested with LessTif (a free
8635 re-implementation of Motif) instead. If the maintainer
8636 judges that the program or programs do not work
8637 sufficiently well with LessTif to be distributed and
8638 supported, but do so when compiled against Motif, then two
8639 versions of the package should be created; one linked
8640 statically against Motif and with <tt>-smotif</tt>
8641 appended to the package name, and one linked dynamically
8642 against Motif and with <tt>-dmotif</tt> appended to the
8647 Both Motif-linked versions are dependent
8648 upon non-DFSG-compliant software and thus cannot be
8649 uploaded to the <em>main</em> distribution; if the
8650 software is itself DFSG-compliant it may be uploaded to
8651 the <em>contrib</em> distribution. While known existing
8652 versions of Motif permit unlimited redistribution of
8653 binaries linked against the library (whether statically or
8654 dynamically), it is the package maintainer's
8655 responsibility to determine whether this is permitted by
8656 the license of the copy of Motif in their possession.
8662 <heading>Perl programs and modules</heading>
8665 Perl programs and modules should follow the current Perl policy.
8669 The Perl policy can be found in the <tt>perl-policy</tt>
8670 files in the <tt>debian-policy</tt> package.
8671 It is also available from the Debian web mirrors at
8672 <tt><url name="/doc/packaging-manuals/perl-policy/"
8673 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8678 <heading>Emacs lisp programs</heading>
8681 Please refer to the "Debian Emacs Policy" for details of how to
8682 package emacs lisp programs.
8686 The Emacs policy is available in
8687 <file>debian-emacs-policy.gz</file> of the
8688 <package>emacsen-common</package> package.
8689 It is also available from the Debian web mirrors at
8690 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8691 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8696 <heading>Games</heading>
8699 The permissions on <file>/var/games</file> are mode 755, owner
8700 <tt>root</tt> and group <tt>root</tt>.
8704 Each game decides on its own security policy.</p>
8707 Games which require protected, privileged access to
8708 high-score files, saved games, etc., may be made
8709 set-<em>group</em>-id (mode 2755) and owned by
8710 <tt>root:games</tt>, and use files and directories with
8711 appropriate permissions (770 <tt>root:games</tt>, for
8712 example). They must not be made
8713 set-<em>user</em>-id, as this causes security problems. (If
8714 an attacker can subvert any set-user-id game they can
8715 overwrite the executable of any other, causing other players
8716 of these games to run a Trojan horse program. With a
8717 set-group-id game the attacker only gets access to less
8718 important game data, and if they can get at the other
8719 players' accounts at all it will take considerably more
8723 Some packages, for example some fortune cookie programs, are
8724 configured by the upstream authors to install with their
8725 data files or other static information made unreadable so
8726 that they can only be accessed through set-id programs
8727 provided. You should not do this in a Debian package: anyone can
8728 download the <file>.deb</file> file and read the data from it,
8729 so there is no point making the files unreadable. Not
8730 making the files unreadable also means that you don't have
8731 to make so many programs set-id, which reduces the risk of a
8735 As described in the FHS, binaries of games should be
8736 installed in the directory <file>/usr/games</file>. This also
8737 applies to games that use the X Window System. Manual pages
8738 for games (X and non-X games) should be installed in
8739 <file>/usr/share/man/man6</file>.</p>
8745 <heading>Documentation</heading>
8748 <heading>Manual pages</heading>
8751 You should install manual pages in <prgn>nroff</prgn> source
8752 form, in appropriate places under <file>/usr/share/man</file>.
8753 You should only use sections 1 to 9 (see the FHS for more
8754 details). You must not install a pre-formatted "cat page".
8758 Each program, utility, and function should have an
8759 associated manual page included in the same package. It is
8760 suggested that all configuration files also have a manual
8761 page included as well. Manual pages for protocols and other
8762 auxiliary things are optional.
8766 If no manual page is available, this is considered as a bug
8767 and should be reported to the Debian Bug Tracking System (the
8768 maintainer of the package is allowed to write this bug report
8769 themselves, if they so desire). Do not close the bug report
8770 until a proper man page is available.<footnote>
8771 It is not very hard to write a man page. See the
8772 <url id="http://www.schweikhardt.net/man_page_howto.html"
8773 name="Man-Page-HOWTO">,
8774 <manref name="man" section="7">, the examples
8775 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8776 the helper programs <prgn>help2man</prgn>, or the
8777 directory <file>/usr/share/doc/man-db/examples</file>.
8782 You may forward a complaint about a missing man page to the
8783 upstream authors, and mark the bug as forwarded in the
8784 Debian bug tracking system. Even though the GNU Project do
8785 not in general consider the lack of a man page to be a bug,
8786 we do; if they tell you that they don't consider it a bug
8787 you should leave the bug in our bug tracking system open
8792 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8796 If one man page needs to be accessible via several names it
8797 is better to use a symbolic link than the <file>.so</file>
8798 feature, but there is no need to fiddle with the relevant
8799 parts of the upstream source to change from <file>.so</file> to
8800 symlinks: don't do it unless it's easy. You should not
8801 create hard links in the manual page directories, nor put
8802 absolute filenames in <file>.so</file> directives. The filename
8803 in a <file>.so</file> in a man page should be relative to the
8804 base of the man page tree (usually
8805 <file>/usr/share/man</file>). If you do not create any links
8806 (whether symlinks, hard links, or <tt>.so</tt> directives)
8807 in the file system to the alternate names of the man page,
8808 then you should not rely on <prgn>man</prgn> finding your
8809 man page under those names based solely on the information in
8810 the man page's header.<footnote>
8811 Supporting this in <prgn>man</prgn> often requires
8812 unreasonable processing time to find a manual page or to
8813 report that none exists, and moves knowledge into man's
8814 database that would be better left in the file system.
8815 This support is therefore deprecated and will cease to
8816 be present in the future.
8821 Manual pages in locale-specific subdirectories of
8822 <file>/usr/share/man</file> should use either UTF-8 or the usual
8823 legacy encoding for that language (normally the one corresponding
8824 to the shortest relevant locale name in
8825 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8826 <file>/usr/share/man/fr</file> should use either UTF-8 or
8827 ISO-8859-1.<footnote>
8828 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8829 use. In future, all manual pages will be required to use
8835 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8836 included in the subdirectory name unless it indicates a
8837 significant difference in the language, as this excludes
8838 speakers of the language in other countries.<footnote>
8839 At the time of writing, Chinese and Portuguese are the main
8840 languages with such differences, so <file>pt_BR</file>,
8841 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8846 Due to limitations in current implementations, all characters
8847 in the manual page source should be representable in the usual
8848 legacy encoding for that language, even if the file is
8849 actually encoded in UTF-8. Safe alternative ways to write many
8850 characters outside that range may be found in
8851 <manref name="groff_char" section="7">.
8856 <heading>Info documents</heading>
8859 Info documents should be installed in <file>/usr/share/info</file>.
8860 They should be compressed with <tt>gzip -9</tt>.
8864 Your package should call <prgn>install-info</prgn> to update
8865 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8866 script when called with a <tt>configure</tt> argument, for
8868 <example compact="compact">
8869 install-info --quiet --section Development Development \
8870 /usr/share/info/foobar.info
8874 It is a good idea to specify a section for the location of
8875 your program; this is done with the <tt>--section</tt>
8876 switch. To determine which section to use, you should look
8877 at <file>/usr/share/info/dir</file> on your system and choose the most
8878 relevant (or create a new section if none of the current
8879 sections are relevant). Note that the <tt>--section</tt>
8880 flag takes two arguments; the first is a regular expression
8881 to match (case-insensitively) against an existing section,
8882 the second is used when creating a new one.</p>
8885 You should remove the entries in the <prgn>prerm</prgn>
8886 script when called with a <tt>remove</tt> argument:
8887 <example compact="compact">
8888 install-info --quiet --remove /usr/share/info/foobar.info
8892 If <prgn>install-info</prgn> cannot find a description entry
8893 in the Info file you must supply one. See <manref
8894 name="install-info" section="8"> for details.</p>
8898 <heading>Additional documentation</heading>
8901 Any additional documentation that comes with the package may
8902 be installed at the discretion of the package maintainer.
8903 Plain text documentation should be installed in the directory
8904 <file>/usr/share/doc/<var>package</var></file>, where
8905 <var>package</var> is the name of the package, and
8906 compressed with <tt>gzip -9</tt> unless it is small.
8910 If a package comes with large amounts of documentation which
8911 many users of the package will not require you should create
8912 a separate binary package to contain it, so that it does not
8913 take up disk space on the machines of users who do not need
8914 or want it installed.</p>
8917 It is often a good idea to put text information files
8918 (<file>README</file>s, changelogs, and so forth) that come with
8919 the source package in <file>/usr/share/doc/<var>package</var></file>
8920 in the binary package. However, you don't need to install
8921 the instructions for building and installing the package, of
8925 Packages must not require the existence of any files in
8926 <file>/usr/share/doc/</file> in order to function
8928 The system administrator should be able to
8929 delete files in <file>/usr/share/doc/</file> without causing
8930 any programs to break.
8932 Any files that are referenced by programs but are also
8933 useful as stand alone documentation should be installed under
8934 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8935 <file>/usr/share/doc/<var>package</var></file>.
8939 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8940 link to another directory in <file>/usr/share/doc</file> only if
8941 the two packages both come from the same source and the
8942 first package Depends on the second.<footnote>
8944 Please note that this does not override the section on
8945 changelog files below, so the file
8946 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8947 must refer to the changelog for the current version of
8948 <var>package</var> in question. In practice, this means
8949 that the sources of the target and the destination of the
8950 symlink must be the same (same source package and
8957 Former Debian releases placed all additional documentation
8958 in <file>/usr/doc/<var>package</var></file>. This has been
8959 changed to <file>/usr/share/doc/<var>package</var></file>,
8960 and packages must not put documentation in the directory
8961 <file>/usr/doc/<var>package</var></file>. <footnote>
8962 At this phase of the transition, we no longer require a
8963 symbolic link in <file>/usr/doc/</file>. At a later point,
8964 policy shall change to make the symbolic links a bug.
8970 <heading>Preferred documentation formats</heading>
8973 The unification of Debian documentation is being carried out
8977 If your package comes with extensive documentation in a
8978 markup format that can be converted to various other formats
8979 you should if possible ship HTML versions in a binary
8980 package, in the directory
8981 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8982 its subdirectories.<footnote>
8983 The rationale: The important thing here is that HTML
8984 docs should be available in <em>some</em> package, not
8985 necessarily in the main binary package.
8990 Other formats such as PostScript may be provided at the
8991 package maintainer's discretion.
8995 <sect id="copyrightfile">
8996 <heading>Copyright information</heading>
8999 Every package must be accompanied by a verbatim copy of its
9000 copyright and distribution license in the file
9001 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9002 file must neither be compressed nor be a symbolic link.
9006 In addition, the copyright file must say where the upstream
9007 sources (if any) were obtained. It should name the original
9008 authors of the package and the Debian maintainer(s) who were
9009 involved with its creation.
9013 Packages in the <em>contrib</em> or <em>non-free</em> archive
9014 areas should state in the copyright file that the package is not
9015 part of the Debian GNU/Linux distribution and briefly explain
9020 A copy of the file which will be installed in
9021 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9022 be in <file>debian/copyright</file> in the source package.
9026 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9027 link to another directory in <file>/usr/share/doc</file> only if
9028 the two packages both come from the same source and the
9029 first package Depends on the second. These rules are
9030 important because copyrights must be extractable by
9035 Packages distributed under the UCB BSD license, the Apache
9036 license (version 2.0), the Artistic license, the GNU GPL
9037 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
9038 the GNU FDL (version 1.2) should refer to the corresponding
9039 files under <file>/usr/share/common-licenses</file>,<footnote>
9042 <file>/usr/share/common-licenses/BSD</file>,
9043 <file>/usr/share/common-licenses/Apache-2.0</file>,
9044 <file>/usr/share/common-licenses/Artistic</file>,
9045 <file>/usr/share/common-licenses/GPL-2</file>,
9046 <file>/usr/share/common-licenses/GPL-3</file>,
9047 <file>/usr/share/common-licenses/LGPL-2</file>,
9048 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9049 <file>/usr/share/common-licenses/LGPL-3</file>, and
9050 <file>/usr/share/common-licenses/GFDL-1.2</file>
9053 </footnote> rather than quoting them in the copyright
9058 You should not use the copyright file as a general <file>README</file>
9059 file. If your package has such a file it should be
9060 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9061 <file>README.Debian</file> or some other appropriate place.</p>
9065 <heading>Examples</heading>
9068 Any examples (configurations, source files, whatever),
9069 should be installed in a directory
9070 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9071 files should not be referenced by any program: they're there
9072 for the benefit of the system administrator and users as
9073 documentation only. Architecture-specific example files
9074 should be installed in a directory
9075 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9077 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9078 latter directory itself may be a symbolic link to the
9083 If the purpose of a package is to provide examples, then the
9084 example files may be installed into
9085 <file>/usr/share/doc/<var>package</var></file>.
9089 <sect id="changelogs">
9090 <heading>Changelog files</heading>
9093 Packages that are not Debian-native must contain a
9094 compressed copy of the <file>debian/changelog</file> file from
9095 the Debian source tree in
9096 <file>/usr/share/doc/<var>package</var></file> with the name
9097 <file>changelog.Debian.gz</file>.
9101 If an upstream changelog is available, it should be accessible as
9102 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9103 plain text. If the upstream changelog is distributed in
9104 HTML, it should be made available in that form as
9105 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9106 and a plain text <file>changelog.gz</file> should be generated
9107 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9108 the upstream changelog files do not already conform to this
9109 naming convention, then this may be achieved either by
9110 renaming the files, or by adding a symbolic link, at the
9111 maintainer's discretion.<footnote>
9112 Rationale: People should not have to look in places for
9113 upstream changelogs merely because they are given
9114 different names or are distributed in HTML format.
9119 All of these files should be installed compressed using
9120 <tt>gzip -9</tt>, as they will become large with time even
9121 if they start out small.
9125 If the package has only one changelog which is used both as
9126 the Debian changelog and the upstream one because there is
9127 no separate upstream maintainer then that changelog should
9128 usually be installed as
9129 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9130 there is a separate upstream maintainer, but no upstream
9131 changelog, then the Debian changelog should still be called
9132 <file>changelog.Debian.gz</file>.
9136 For details about the format and contents of the Debian
9137 changelog file, please see <ref id="dpkgchangelog">.
9142 <appendix id="pkg-scope">
9143 <heading>Introduction and scope of these appendices</heading>
9146 These appendices are taken essentially verbatim from the
9147 now-deprecated Packaging Manual, version 3.2.1.0. They are
9148 the chapters which are likely to be of use to package
9149 maintainers and which have not already been included in the
9150 policy document itself. Most of these sections are very likely
9151 not relevant to policy; they should be treated as
9152 documentation for the packaging system. Please note that these
9153 appendices are included for convenience, and for historical
9154 reasons: they used to be part of policy package, and they have
9155 not yet been incorporated into dpkg documentation. However,
9156 they still have value, and hence they are presented here.
9160 They have not yet been checked to ensure that they are
9161 compatible with the contents of policy, and if there are any
9162 contradictions, the version in the main policy document takes
9163 precedence. The remaining chapters of the old Packaging
9164 Manual have also not been read in detail to ensure that there
9165 are not parts which have been left out. Both of these will be
9170 Certain parts of the Packaging manual were integrated into the
9171 Policy Manual proper, and removed from the appendices. Links
9172 have been placed from the old locations to the new ones.
9176 <prgn>dpkg</prgn> is a suite of programs for creating binary
9177 package files and installing and removing them on Unix
9179 <prgn>dpkg</prgn> is targeted primarily at Debian
9180 GNU/Linux, but may work on or be ported to other
9186 The binary packages are designed for the management of
9187 installed executable programs (usually compiled binaries) and
9188 their associated data, though source code examples and
9189 documentation are provided as part of some packages.</p>
9192 This manual describes the technical aspects of creating Debian
9193 binary packages (<file>.deb</file> files). It documents the
9194 behavior of the package management programs
9195 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9196 they interact with packages.</p>
9199 It also documents the interaction between
9200 <prgn>dselect</prgn>'s core and the access method scripts it
9201 uses to actually install the selected packages, and describes
9202 how to create a new access method.</p>
9205 This manual does not go into detail about the options and
9206 usage of the package building and installation tools. It
9207 should therefore be read in conjunction with those programs'
9212 The utility programs which are provided with <prgn>dpkg</prgn>
9213 for managing various system configuration and similar issues,
9214 such as <prgn>update-rc.d</prgn> and
9215 <prgn>install-info</prgn>, are not described in detail here -
9216 please see their man pages.
9220 It is assumed that the reader is reasonably familiar with the
9221 <prgn>dpkg</prgn> System Administrators' manual.
9222 Unfortunately this manual does not yet exist.
9226 The Debian version of the FSF's GNU hello program is provided
9227 as an example for people wishing to create Debian
9228 packages. The Debian <prgn>debmake</prgn> package is
9229 recommended as a very helpful tool in creating and maintaining
9230 Debian packages. However, while the tools and examples are
9231 helpful, they do not replace the need to read and follow the
9232 Policy and Programmer's Manual.</p>
9235 <appendix id="pkg-binarypkg">
9236 <heading>Binary packages (from old Packaging Manual)</heading>
9239 The binary package has two main sections. The first part
9240 consists of various control information files and scripts used
9241 by <prgn>dpkg</prgn> when installing and removing. See <ref
9242 id="pkg-controlarea">.
9246 The second part is an archive containing the files and
9247 directories to be installed.
9251 In the future binary packages may also contain other
9252 components, such as checksums and digital signatures. The
9253 format for the archive is described in full in the
9254 <file>deb(5)</file> man page.
9258 <sect id="pkg-bincreating"><heading>Creating package files -
9259 <prgn>dpkg-deb</prgn>
9263 All manipulation of binary package files is done by
9264 <prgn>dpkg-deb</prgn>; it's the only program that has
9265 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9266 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9267 will spot that the options requested are appropriate to
9268 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9273 In order to create a binary package you must make a
9274 directory tree which contains all the files and directories
9275 you want to have in the file system data part of the package.
9276 In Debian-format source packages this directory is usually
9277 <file>debian/tmp</file>, relative to the top of the package's
9282 They should have the locations (relative to the root of the
9283 directory tree you're constructing) ownerships and
9284 permissions which you want them to have on the system when
9289 With current versions of <prgn>dpkg</prgn> the uid/username
9290 and gid/groupname mappings for the users and groups being
9291 used should be the same on the system where the package is
9292 built and the one where it is installed.
9296 You need to add one special directory to the root of the
9297 miniature file system tree you're creating:
9298 <prgn>DEBIAN</prgn>. It should contain the control
9299 information files, notably the binary package control file
9300 (see <ref id="pkg-controlfile">).
9304 The <prgn>DEBIAN</prgn> directory will not appear in the
9305 file system archive of the package, and so won't be installed
9306 by <prgn>dpkg</prgn> when the package is installed.
9310 When you've prepared the package, you should invoke:
9312 dpkg --build <var>directory</var>
9317 This will build the package in
9318 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9319 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9320 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9325 See the man page <manref name="dpkg-deb" section="8"> for details of how
9326 to examine the contents of this newly-created file. You may find the
9327 output of following commands enlightening:
9329 dpkg-deb --info <var>filename</var>.deb
9330 dpkg-deb --contents <var>filename</var>.deb
9331 dpkg --contents <var>filename</var>.deb
9333 To view the copyright file for a package you could use this command:
9335 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9340 <sect id="pkg-controlarea">
9341 <heading>Package control information files</heading>
9344 The control information portion of a binary package is a
9345 collection of files with names known to <prgn>dpkg</prgn>.
9346 It will treat the contents of these files specially - some
9347 of them contain information used by <prgn>dpkg</prgn> when
9348 installing or removing the package; others are scripts which
9349 the package maintainer wants <prgn>dpkg</prgn> to run.
9353 It is possible to put other files in the package control
9354 area, but this is not generally a good idea (though they
9355 will largely be ignored).
9359 Here is a brief list of the control info files supported by
9360 <prgn>dpkg</prgn> and a summary of what they're used for.
9365 <tag><tt>control</tt>
9368 This is the key description file used by
9369 <prgn>dpkg</prgn>. It specifies the package's name
9370 and version, gives its description for the user,
9371 states its relationships with other packages, and so
9372 forth. See <ref id="sourcecontrolfiles"> and
9373 <ref id="binarycontrolfiles">.
9377 It is usually generated automatically from information
9378 in the source package by the
9379 <prgn>dpkg-gencontrol</prgn> program, and with
9380 assistance from <prgn>dpkg-shlibdeps</prgn>.
9381 See <ref id="pkg-sourcetools">.
9385 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9390 These are executable files (usually scripts) which
9391 <prgn>dpkg</prgn> runs during installation, upgrade
9392 and removal of packages. They allow the package to
9393 deal with matters which are particular to that package
9394 or require more complicated processing than that
9395 provided by <prgn>dpkg</prgn>. Details of when and
9396 how they are called are in <ref id="maintainerscripts">.
9400 It is very important to make these scripts idempotent.
9401 See <ref id="idempotency">.
9405 The maintainer scripts are guaranteed to run with a
9406 controlling terminal and can interact with the user.
9407 See <ref id="controllingterminal">.
9411 <tag><tt>conffiles</tt>
9414 This file contains a list of configuration files which
9415 are to be handled automatically by <prgn>dpkg</prgn>
9416 (see <ref id="pkg-conffiles">). Note that not necessarily
9417 every configuration file should be listed here.
9420 <tag><tt>shlibs</tt>
9423 This file contains a list of the shared libraries
9424 supplied by the package, with dependency details for
9425 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9426 when it determines what dependencies are required in a
9427 package control file. The <tt>shlibs</tt> file format
9428 is described on <ref id="shlibs">.
9433 <sect id="pkg-controlfile">
9434 <heading>The main control information file: <tt>control</tt></heading>
9437 The most important control information file used by
9438 <prgn>dpkg</prgn> when it installs a package is
9439 <tt>control</tt>. It contains all the package's "vital
9444 The binary package control files of packages built from
9445 Debian sources are made by a special tool,
9446 <prgn>dpkg-gencontrol</prgn>, which reads
9447 <file>debian/control</file> and <file>debian/changelog</file> to
9448 find the information it needs. See <ref id="pkg-sourcepkg"> for
9453 The fields in binary package control files are listed in
9454 <ref id="binarycontrolfiles">.
9458 A description of the syntax of control files and the purpose
9459 of the fields is available in <ref id="controlfields">.
9464 <heading>Time Stamps</heading>
9467 See <ref id="timestamps">.
9472 <appendix id="pkg-sourcepkg">
9473 <heading>Source packages (from old Packaging Manual) </heading>
9476 The Debian binary packages in the distribution are generated
9477 from Debian sources, which are in a special format to assist
9478 the easy and automatic building of binaries.
9481 <sect id="pkg-sourcetools">
9482 <heading>Tools for processing source packages</heading>
9485 Various tools are provided for manipulating source packages;
9486 they pack and unpack sources and help build of binary
9487 packages and help manage the distribution of new versions.
9491 They are introduced and typical uses described here; see
9492 <manref name="dpkg-source" section="1"> for full
9493 documentation about their arguments and operation.
9497 For examples of how to construct a Debian source package,
9498 and how to use those utilities that are used by Debian
9499 source packages, please see the <prgn>hello</prgn> example
9503 <sect1 id="pkg-dpkg-source">
9505 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9510 This program is frequently used by hand, and is also
9511 called from package-independent automated building scripts
9512 such as <prgn>dpkg-buildpackage</prgn>.
9516 To unpack a package it is typically invoked with
9518 dpkg-source -x <var>.../path/to/filename</var>.dsc
9523 with the <file><var>filename</var>.tar.gz</file> and
9524 <file><var>filename</var>.diff.gz</file> (if applicable) in
9525 the same directory. It unpacks into
9526 <file><var>package</var>-<var>version</var></file>, and if
9528 <file><var>package</var>-<var>version</var>.orig</file>, in
9529 the current directory.
9533 To create a packed source archive it is typically invoked:
9535 dpkg-source -b <var>package</var>-<var>version</var>
9540 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9541 <file>.diff.gz</file> (if appropriate) in the current
9542 directory. <prgn>dpkg-source</prgn> does not clean the
9543 source tree first - this must be done separately if it is
9548 See also <ref id="pkg-sourcearchives">.</p>
9552 <sect1 id="pkg-dpkg-buildpackage">
9554 <prgn>dpkg-buildpackage</prgn> - overall package-building
9559 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9560 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9561 targets <tt>clean</tt>, <tt>build</tt> and
9562 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9563 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9564 source and binary package upload.
9568 It is usually invoked by hand from the top level of the
9569 built or unbuilt source directory. It may be invoked with
9570 no arguments; useful arguments include:
9571 <taglist compact="compact">
9572 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9575 Do not sign the <tt>.changes</tt> file or the
9576 source package <tt>.dsc</tt> file, respectively.</p>
9578 <tag><tt>-p<var>sign-command</var></tt></tag>
9581 Invoke <var>sign-command</var> instead of finding
9582 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9583 <var>sign-command</var> must behave just like
9584 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9586 <tag><tt>-r<var>root-command</var></tt></tag>
9589 When root privilege is required, invoke the command
9590 <var>root-command</var>. <var>root-command</var>
9591 should invoke its first argument as a command, from
9592 the <prgn>PATH</prgn> if necessary, and pass its
9593 second and subsequent arguments to the command it
9594 calls. If no <var>root-command</var> is supplied
9595 then <var>dpkg-buildpackage</var> will take no
9596 special action to gain root privilege, so that for
9597 most packages it will have to be invoked as root to
9600 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9603 Two types of binary-only build and upload - see
9604 <manref name="dpkg-source" section="1">.
9611 <sect1 id="pkg-dpkg-gencontrol">
9613 <prgn>dpkg-gencontrol</prgn> - generates binary package
9618 This program is usually called from <file>debian/rules</file>
9619 (see <ref id="pkg-sourcetree">) in the top level of the source
9624 This is usually done just before the files and directories in the
9625 temporary directory tree where the package is being built have their
9626 permissions and ownerships set and the package is constructed using
9627 <prgn>dpkg-deb/</prgn>
9629 This is so that the control file which is produced has
9630 the right permissions
9635 <prgn>dpkg-gencontrol</prgn> must be called after all the
9636 files which are to go into the package have been placed in
9637 the temporary build directory, so that its calculation of
9638 the installed size of a package is correct.
9642 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9643 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9644 variable substitutions created by
9645 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9650 For a package which generates only one binary package, and
9651 which builds it in <file>debian/tmp</file> relative to the top
9652 of the source package, it is usually sufficient to call
9653 <prgn>dpkg-gencontrol</prgn>.
9657 Sources which build several binaries will typically need
9660 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9661 </example> The <tt>-P</tt> tells
9662 <prgn>dpkg-gencontrol</prgn> that the package is being
9663 built in a non-default directory, and the <tt>-p</tt>
9664 tells it which package's control file should be generated.
9668 <prgn>dpkg-gencontrol</prgn> also adds information to the
9669 list of files in <file>debian/files</file>, for the benefit of
9670 (for example) a future invocation of
9671 <prgn>dpkg-genchanges</prgn>.</p>
9674 <sect1 id="pkg-dpkg-shlibdeps">
9676 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9681 This program is usually called from <file>debian/rules</file>
9682 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9683 id="pkg-sourcetree">), in the top level of the source tree.
9687 Its arguments are executables and shared libraries
9690 They may be specified either in the locations in the
9691 source tree where they are created or in the locations
9692 in the temporary build tree where they are installed
9693 prior to binary package creation.
9695 </footnote> for which shared library dependencies should
9696 be included in the binary package's control file.
9700 If some of the found shared libraries should only
9701 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9702 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9703 by using the <tt>-d<var>dependency-field</var></tt> option
9704 before those executable(s). (Each <tt>-d</tt> option
9705 takes effect until the next <tt>-d</tt>.)
9709 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9710 output control file to be modified. Instead by default it
9711 adds to the <file>debian/substvars</file> file variable
9712 settings like <tt>shlibs:Depends</tt>. These variable
9713 settings must be referenced in dependency fields in the
9714 appropriate per-binary-package sections of the source
9719 For example, a package that generates an essential part
9720 which requires dependencies, and optional parts that
9721 which only require a recommendation, would separate those
9722 two sets of dependencies into two different fields.<footnote>
9723 At the time of writing, an example for this was the
9724 <package/xmms/ package, with Depends used for the xmms
9725 executable, Recommends for the plug-ins and Suggests for
9726 even more optional features provided by unzip.
9728 It can say in its <file>debian/rules</file>:
9730 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9731 -dRecommends <var>optionalpart anotheroptionalpart</var>
9733 and then in its main control file <file>debian/control</file>:
9736 Depends: ${shlibs:Depends}
9737 Recommends: ${shlibs:Recommends}
9743 Sources which produce several binary packages with
9744 different shared library dependency requirements can use
9745 the <tt>-p<var>varnameprefix</var></tt> option to override
9746 the default <tt>shlibs:</tt> prefix (one invocation of
9747 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9748 They can thus produce several sets of dependency
9749 variables, each of the form
9750 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9751 which can be referred to in the appropriate parts of the
9752 binary package control files.
9757 <sect1 id="pkg-dpkg-distaddfile">
9759 <prgn>dpkg-distaddfile</prgn> - adds a file to
9760 <file>debian/files</file>
9764 Some packages' uploads need to include files other than
9765 the source and binary package files.
9769 <prgn>dpkg-distaddfile</prgn> adds a file to the
9770 <file>debian/files</file> file so that it will be included in
9771 the <file>.changes</file> file when
9772 <prgn>dpkg-genchanges</prgn> is run.
9776 It is usually invoked from the <tt>binary</tt> target of
9777 <file>debian/rules</file>:
9779 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9781 The <var>filename</var> is relative to the directory where
9782 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9783 is usually the directory above the top level of the source
9784 tree. The <file>debian/rules</file> target should put the
9785 file there just before or just after calling
9786 <prgn>dpkg-distaddfile</prgn>.
9790 The <var>section</var> and <var>priority</var> are passed
9791 unchanged into the resulting <file>.changes</file> file.
9796 <sect1 id="pkg-dpkg-genchanges">
9798 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9803 This program is usually called by package-independent
9804 automatic building scripts such as
9805 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9810 It is usually called in the top level of a built source
9811 tree, and when invoked with no arguments will print out a
9812 straightforward <file>.changes</file> file based on the
9813 information in the source package's changelog and control
9814 file and the binary and source packages which should have
9820 <sect1 id="pkg-dpkg-parsechangelog">
9822 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9823 representation of a changelog
9827 This program is used internally by
9828 <prgn>dpkg-source</prgn> et al. It may also occasionally
9829 be useful in <file>debian/rules</file> and elsewhere. It
9830 parses a changelog, <file>debian/changelog</file> by default,
9831 and prints a control-file format representation of the
9832 information in it to standard output.
9836 <sect1 id="pkg-dpkg-architecture">
9838 <prgn>dpkg-architecture</prgn> - information about the build and
9843 This program can be used manually, but is also invoked by
9844 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9845 environment or make variables which specify the build and host
9846 architecture for the package building process.
9851 <sect id="pkg-sourcetree">
9852 <heading>The Debianised source tree</heading>
9855 The source archive scheme described later is intended to
9856 allow a Debianised source tree with some associated control
9857 information to be reproduced and transported easily. The
9858 Debianised source tree is a version of the original program
9859 with certain files added for the benefit of the
9860 Debianisation process, and with any other changes required
9861 made to the rest of the source code and installation
9866 The extra files created for Debian are in the subdirectory
9867 <file>debian</file> of the top level of the Debianised source
9868 tree. They are described below.
9871 <sect1 id="pkg-debianrules">
9872 <heading><file>debian/rules</file> - the main building script</heading>
9875 See <ref id="debianrules">.
9880 <sect1 id="pkg-dpkgchangelog">
9881 <heading><file>debian/changelog</file></heading>
9884 See <ref id="dpkgchangelog">.
9887 <sect2><heading>Defining alternative changelog formats
9891 It is possible to use a different format to the standard
9892 one, by providing a parser for the format you wish to
9897 In order to have <tt>dpkg-parsechangelog</tt> run your
9898 parser, you must include a line within the last 40 lines
9899 of your file matching the Perl regular expression:
9900 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9901 parentheses should be the name of the format. For
9902 example, you might say:
9904 @@@ changelog-format: joebloggs @@@
9906 Changelog format names are non-empty strings of alphanumerics.
9910 If such a line exists then <tt>dpkg-parsechangelog</tt>
9911 will look for the parser as
9912 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9914 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9915 it is an error for it not to find it, or for it not to
9916 be an executable program. The default changelog format
9917 is <tt>dpkg</tt>, and a parser for it is provided with
9918 the <tt>dpkg</tt> package.
9922 The parser will be invoked with the changelog open on
9923 standard input at the start of the file. It should read
9924 the file (it may seek if it wishes) to determine the
9925 information required and return the parsed information
9926 to standard output in the form of a series of control
9927 fields in the standard format. By default it should
9928 return information about only the most recent version in
9929 the changelog; it should accept a
9930 <tt>-v<var>version</var></tt> option to return changes
9931 information from all versions present <em>strictly
9932 after</em> <var>version</var>, and it should then be an
9933 error for <var>version</var> not to be present in the
9939 <list compact="compact">
9940 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9941 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9942 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9943 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9944 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9945 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9946 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9951 If several versions are being returned (due to the use
9952 of <tt>-v</tt>), the urgency value should be of the
9953 highest urgency code listed at the start of any of the
9954 versions requested followed by the concatenated
9955 (space-separated) comments from all the versions
9956 requested; the maintainer, version, distribution and
9957 date should always be from the most recent version.
9961 For the format of the <tt>Changes</tt> field see
9962 <ref id="f-Changes">.
9966 If the changelog format which is being parsed always or
9967 almost always leaves a blank line between individual
9968 change notes these blank lines should be stripped out,
9969 so as to make the resulting output compact.
9973 If the changelog format does not contain date or package
9974 name information this information should be omitted from
9975 the output. The parser should not attempt to synthesize
9976 it or find it from other sources.
9980 If the changelog does not have the expected format the
9981 parser should exit with a nonzero exit status, rather
9982 than trying to muddle through and possibly generating
9987 A changelog parser may not interact with the user at
9993 <sect1 id="pkg-srcsubstvars">
9994 <heading><file>debian/substvars</file> and variable substitutions</heading>
9997 See <ref id="substvars">.
10003 <heading><file>debian/files</file></heading>
10006 See <ref id="debianfiles">.
10010 <sect1><heading><file>debian/tmp</file>
10014 This is the canonical temporary location for the
10015 construction of binary packages by the <tt>binary</tt>
10016 target. The directory <file>tmp</file> serves as the root of
10017 the file system tree as it is being constructed (for
10018 example, by using the package's upstream makefiles install
10019 targets and redirecting the output there), and it also
10020 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10021 id="pkg-bincreating">.
10025 If several binary packages are generated from the same
10026 source tree it is usual to use several
10027 <file>debian/tmp<var>something</var></file> directories, for
10028 example <file>tmp-a</file> or <file>tmp-doc</file>.
10032 Whatever <file>tmp</file> directories are created and used by
10033 <tt>binary</tt> must of course be removed by the
10034 <tt>clean</tt> target.</p></sect1>
10038 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10042 As it exists on the FTP site, a Debian source package
10043 consists of three related files. You must have the right
10044 versions of all three to be able to use them.
10049 <tag>Debian source control file - <tt>.dsc</tt></tag>
10051 This file is a control file used by <prgn>dpkg-source</prgn>
10052 to extract a source package.
10053 See <ref id="debiansourcecontrolfiles">.
10057 Original source archive -
10059 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10065 This is a compressed (with <tt>gzip -9</tt>)
10066 <prgn>tar</prgn> file containing the source code from
10067 the upstream authors of the program.
10072 Debianisation diff -
10074 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10080 This is a unified context diff (<tt>diff -u</tt>)
10081 giving the changes which are required to turn the
10082 original source into the Debian source. These changes
10083 may only include editing and creating plain files.
10084 The permissions of files, the targets of symbolic
10085 links and the characteristics of special files or
10086 pipes may not be changed and no files may be removed
10091 All the directories in the diff must exist, except the
10092 <file>debian</file> subdirectory of the top of the source
10093 tree, which will be created by
10094 <prgn>dpkg-source</prgn> if necessary when unpacking.
10098 The <prgn>dpkg-source</prgn> program will
10099 automatically make the <file>debian/rules</file> file
10100 executable (see below).</p></item>
10105 If there is no original source code - for example, if the
10106 package is specially prepared for Debian or the Debian
10107 maintainer is the same as the upstream maintainer - the
10108 format is slightly different: then there is no diff, and the
10110 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10111 and preferably contains a directory named
10112 <file><var>package</var>-<var>version</var></file>.
10117 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10120 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10121 Debian source package. However, if it is not available it
10122 is possible to unpack a Debian source archive as follows:
10123 <enumlist compact="compact">
10126 Untar the tarfile, which will create a <file>.orig</file>
10130 <p>Rename the <file>.orig</file> directory to
10131 <file><var>package</var>-<var>version</var></file>.</p>
10135 Create the subdirectory <file>debian</file> at the top of
10136 the source tree.</p>
10138 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10140 <item><p>Untar the tarfile again if you want a copy of the original
10141 source code alongside the Debianised version.</p>
10146 It is not possible to generate a valid Debian source archive
10147 without using <prgn>dpkg-source</prgn>. In particular,
10148 attempting to use <prgn>diff</prgn> directly to generate the
10149 <file>.diff.gz</file> file will not work.
10153 <heading>Restrictions on objects in source packages</heading>
10156 The source package may not contain any hard links
10158 This is not currently detected when building source
10159 packages, but only when extracting
10163 Hard links may be permitted at some point in the
10164 future, but would require a fair amount of
10166 </footnote>, device special files, sockets or setuid or
10169 Setgid directories are allowed.
10174 The source packaging tools manage the changes between the
10175 original and Debianised source using <prgn>diff</prgn> and
10176 <prgn>patch</prgn>. Turning the original source tree as
10177 included in the <file>.orig.tar.gz</file> into the debianised
10178 source must not involve any changes which cannot be
10179 handled by these tools. Problematic changes which cause
10180 <prgn>dpkg-source</prgn> to halt with an error when
10181 building the source package are:
10182 <list compact="compact">
10183 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10185 <item><p>Changing the targets of symbolic links.</p>
10187 <item><p>Creating directories, other than <file>debian</file>.</p>
10189 <item><p>Changes to the contents of binary files.</p></item>
10190 </list> Changes which cause <prgn>dpkg-source</prgn> to
10191 print a warning but continue anyway are:
10192 <list compact="compact">
10195 Removing files, directories or symlinks.
10197 Renaming a file is not treated specially - it is
10198 seen as the removal of the old file (which
10199 generates a warning, but is otherwise ignored),
10200 and the creation of the new one.
10206 Changed text files which are missing the usual final
10207 newline (either in the original or the modified
10212 Changes which are not represented, but which are not detected by
10213 <prgn>dpkg-source</prgn>, are:
10214 <list compact="compact">
10215 <item><p>Changing the permissions of files (other than
10216 <file>debian/rules</file>) and directories.</p></item>
10221 The <file>debian</file> directory and <file>debian/rules</file>
10222 are handled specially by <prgn>dpkg-source</prgn> - before
10223 applying the changes it will create the <file>debian</file>
10224 directory, and afterwards it will make
10225 <file>debian/rules</file> world-executable.
10231 <appendix id="pkg-controlfields">
10232 <heading>Control files and their fields (from old Packaging Manual)</heading>
10235 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10236 data in a common format, known as control files. Binary and
10237 source packages have control data as do the <file>.changes</file>
10238 files which control the installation of uploaded files, and
10239 <prgn>dpkg</prgn>'s internal databases are in a similar
10244 <heading>Syntax of control files</heading>
10247 See <ref id="controlsyntax">.
10251 It is important to note that there are several fields which
10252 are optional as far as <prgn>dpkg</prgn> and the related
10253 tools are concerned, but which must appear in every Debian
10254 package, or whose omission may cause problems.
10259 <heading>List of fields</heading>
10262 See <ref id="controlfieldslist">.
10266 This section now contains only the fields that didn't belong
10267 to the Policy manual.
10270 <sect1 id="pkg-f-Filename">
10271 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10274 These fields in <tt>Packages</tt> files give the
10275 filename(s) of (the parts of) a package in the
10276 distribution directories, relative to the root of the
10277 Debian hierarchy. If the package has been split into
10278 several parts the parts are all listed in order, separated
10283 <sect1 id="pkg-f-Size">
10284 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10287 These fields in <file>Packages</file> files give the size (in
10288 bytes, expressed in decimal) and MD5 checksum of the
10289 file(s) which make(s) up a binary package in the
10290 distribution. If the package is split into several parts
10291 the values for the parts are listed in order, separated by
10296 <sect1 id="pkg-f-Status">
10297 <heading><tt>Status</tt></heading>
10300 This field in <prgn>dpkg</prgn>'s status file records
10301 whether the user wants a package installed, removed or
10302 left alone, whether it is broken (requiring
10303 re-installation) or not and what its current state on the
10304 system is. Each of these pieces of information is a
10309 <sect1 id="pkg-f-Config-Version">
10310 <heading><tt>Config-Version</tt></heading>
10313 If a package is not installed or not configured, this
10314 field in <prgn>dpkg</prgn>'s status file records the last
10315 version of the package which was successfully
10320 <sect1 id="pkg-f-Conffiles">
10321 <heading><tt>Conffiles</tt></heading>
10324 This field in <prgn>dpkg</prgn>'s status file contains
10325 information about the automatically-managed configuration
10326 files held by a package. This field should <em>not</em>
10327 appear anywhere in a package!
10332 <heading>Obsolete fields</heading>
10335 These are still recognized by <prgn>dpkg</prgn> but should
10336 not appear anywhere any more.
10338 <taglist compact="compact">
10340 <tag><tt>Revision</tt></tag>
10341 <tag><tt>Package-Revision</tt></tag>
10342 <tag><tt>Package_Revision</tt></tag>
10344 The Debian revision part of the package version was
10345 at one point in a separate control file field. This
10346 field went through several names.
10349 <tag><tt>Recommended</tt></tag>
10350 <item>Old name for <tt>Recommends</tt>.</item>
10352 <tag><tt>Optional</tt></tag>
10353 <item>Old name for <tt>Suggests</tt>.</item>
10355 <tag><tt>Class</tt></tag>
10356 <item>Old name for <tt>Priority</tt>.</item>
10365 <appendix id="pkg-conffiles">
10366 <heading>Configuration file handling (from old Packaging Manual)</heading>
10369 <prgn>dpkg</prgn> can do a certain amount of automatic
10370 handling of package configuration files.
10374 Whether this mechanism is appropriate depends on a number of
10375 factors, but basically there are two approaches to any
10376 particular configuration file.
10380 The easy method is to ship a best-effort configuration in the
10381 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10382 handle updates. If the user is unlikely to want to edit the
10383 file, but you need them to be able to without losing their
10384 changes, and a new package with a changed version of the file
10385 is only released infrequently, this is a good approach.
10389 The hard method is to build the configuration file from
10390 scratch in the <prgn>postinst</prgn> script, and to take the
10391 responsibility for fixing any mistakes made in earlier
10392 versions of the package automatically. This will be
10393 appropriate if the file is likely to need to be different on
10397 <sect><heading>Automatic handling of configuration files by
10402 A package may contain a control area file called
10403 <tt>conffiles</tt>. This file should be a list of filenames
10404 of configuration files needing automatic handling, separated
10405 by newlines. The filenames should be absolute pathnames,
10406 and the files referred to should actually exist in the
10411 When a package is upgraded <prgn>dpkg</prgn> will process
10412 the configuration files during the configuration stage,
10413 shortly before it runs the package's <prgn>postinst</prgn>
10418 For each file it checks to see whether the version of the
10419 file included in the package is the same as the one that was
10420 included in the last version of the package (the one that is
10421 being upgraded from); it also compares the version currently
10422 installed on the system with the one shipped with the last
10427 If neither the user nor the package maintainer has changed
10428 the file, it is left alone. If one or the other has changed
10429 their version, then the changed version is preferred - i.e.,
10430 if the user edits their file, but the package maintainer
10431 doesn't ship a different version, the user's changes will
10432 stay, silently, but if the maintainer ships a new version
10433 and the user hasn't edited it the new version will be
10434 installed (with an informative message). If both have
10435 changed their version the user is prompted about the problem
10436 and must resolve the differences themselves.
10440 The comparisons are done by calculating the MD5 message
10441 digests of the files, and storing the MD5 of the file as it
10442 was included in the most recent version of the package.
10446 When a package is installed for the first time
10447 <prgn>dpkg</prgn> will install the file that comes with it,
10448 unless that would mean overwriting a file already on the
10453 However, note that <prgn>dpkg</prgn> will <em>not</em>
10454 replace a conffile that was removed by the user (or by a
10455 script). This is necessary because with some programs a
10456 missing file produces an effect hard or impossible to
10457 achieve in another way, so that a missing file needs to be
10458 kept that way if the user did it.
10462 Note that a package should <em>not</em> modify a
10463 <prgn>dpkg</prgn>-handled conffile in its maintainer
10464 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10465 the user confusing and possibly dangerous options for
10466 conffile update when the package is upgraded.</p>
10469 <sect><heading>Fully-featured maintainer script configuration
10474 For files which contain site-specific information such as
10475 the hostname and networking details and so forth, it is
10476 better to create the file in the package's
10477 <prgn>postinst</prgn> script.
10481 This will typically involve examining the state of the rest
10482 of the system to determine values and other information, and
10483 may involve prompting the user for some information which
10484 can't be obtained some other way.
10488 When using this method there are a couple of important
10489 issues which should be considered:
10493 If you discover a bug in the program which generates the
10494 configuration file, or if the format of the file changes
10495 from one version to the next, you will have to arrange for
10496 the postinst script to do something sensible - usually this
10497 will mean editing the installed configuration file to remove
10498 the problem or change the syntax. You will have to do this
10499 very carefully, since the user may have changed the file,
10500 perhaps to fix the very problem that your script is trying
10501 to deal with - you will have to detect these situations and
10502 deal with them correctly.
10506 If you do go down this route it's probably a good idea to
10507 make the program that generates the configuration file(s) a
10508 separate program in <file>/usr/sbin</file>, by convention called
10509 <file><var>package</var>config</file> and then run that if
10510 appropriate from the post-installation script. The
10511 <tt><var>package</var>config</tt> program should not
10512 unquestioningly overwrite an existing configuration - if its
10513 mode of operation is geared towards setting up a package for
10514 the first time (rather than any arbitrary reconfiguration
10515 later) you should have it check whether the configuration
10516 already exists, and require a <tt>--force</tt> flag to
10517 overwrite it.</p></sect>
10520 <appendix id="pkg-alternatives"><heading>Alternative versions of
10521 an interface - <prgn>update-alternatives</prgn> (from old
10526 When several packages all provide different versions of the
10527 same program or file it is useful to have the system select a
10528 default, but to allow the system administrator to change it
10529 and have their decisions respected.
10533 For example, there are several versions of the <prgn>vi</prgn>
10534 editor, and there is no reason to prevent all of them from
10535 being installed at once, each under their own name
10536 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10537 Nevertheless it is desirable to have the name <tt>vi</tt>
10538 refer to something, at least by default.
10542 If all the packages involved cooperate, this can be done with
10543 <prgn>update-alternatives</prgn>.
10547 Each package provides its own version under its own name, and
10548 calls <prgn>update-alternatives</prgn> in its postinst to
10549 register its version (and again in its prerm to deregister
10554 See the man page <manref name="update-alternatives"
10555 section="8"> for details.
10559 If <prgn>update-alternatives</prgn> does not seem appropriate
10560 you may wish to consider using diversions instead.</p>
10563 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10564 package's version of a file (from old Packaging Manual)
10568 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10569 when it reinstalls the package it belongs to, and to have it
10570 put the file from the package somewhere else instead.
10574 This can be used locally to override a package's version of a
10575 file, or by one package to override another's version (or
10576 provide a wrapper for it).
10580 Before deciding to use a diversion, read <ref
10581 id="pkg-alternatives"> to see if you really want a diversion
10582 rather than several alternative versions of a program.
10586 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10587 and updated by a special program <prgn>dpkg-divert</prgn>.
10588 Please see <manref name="dpkg-divert" section="8"> for full
10589 details of its operation.
10593 When a package wishes to divert a file from another, it should
10594 call <prgn>dpkg-divert</prgn> in its preinst to add the
10595 diversion and rename the existing file. For example,
10596 supposing that a <prgn>smailwrapper</prgn> package wishes to
10597 install a wrapper around <file>/usr/sbin/smail</file>:
10599 dpkg-divert --package smailwrapper --add --rename \
10600 --divert /usr/sbin/smail.real /usr/sbin/smail
10601 </example> The <tt>--package smailwrapper</tt> ensures that
10602 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10603 can bypass the diversion and get installed as the true version.
10604 It's safe to add the diversion unconditionally on upgrades since
10605 it will be left unchanged if it already exists, but
10606 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10607 message, make the command conditional on the version from which
10608 the package is being upgraded:
10610 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10611 dpkg-divert --package smailwrapper --add --rename \
10612 --divert /usr/sbin/smail.real /usr/sbin/smail
10614 </example> where <tt>1.0-2</tt> is the version at which the
10615 diversion was first added to the package. Running the command
10616 during abort-upgrade is pointless but harmless.
10620 The postrm has to do the reverse:
10622 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10623 dpkg-divert --package smailwrapper --remove --rename \
10624 --divert /usr/sbin/smail.real /usr/sbin/smail
10626 </example> If the diversion was added at a particular version, the
10627 postrm should also handle the failure case of upgrading from an
10628 older version (unless the older version is so old that direct
10629 upgrades are no longer supported):
10631 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10632 dpkg-divert --package smailwrapper --remove --rename \
10633 --divert /usr/sbin/smail.real /usr/sbin/smail
10635 </example> where <tt>1.02-2</tt> is the version at which the
10636 diversion was first added to the package. The postrm should not
10637 remove the diversion on upgrades both because there's no reason to
10638 remove the diversion only to immediately re-add it and since the
10639 postrm of the old package is run after unpacking so the removal of
10640 the diversion will fail.
10644 Do not attempt to divert a file which is vitally important for
10645 the system's operation - when using <prgn>dpkg-divert</prgn>
10646 there is a time, after it has been diverted but before
10647 <prgn>dpkg</prgn> has installed the new version, when the file
10648 does not exist.</p>
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