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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
276 <sect id="definitions">
277 <heading>Definitions</heading>
280 The following terms are used in this Policy Manual:
284 The character encoding specified by ANSI X3.4-1986 and its
285 predecessor standards, referred to in MIME as US-ASCII, and
286 corresponding to an encoding in eight bits per character of
287 the first 128 <url id="http://www.unicode.org/"
288 name="Unicode"> characters, with the eighth bit always zero.
292 The transformation format (sometimes called encoding) of
293 <url id="http://www.unicode.org/" name="Unicode"> defined by
294 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
295 name="RFC 3629">. UTF-8 has the useful property of having
296 ASCII as a subset, so any text encoded in ASCII is trivially
306 <heading>The Debian Archive</heading>
309 The Debian GNU/Linux system is maintained and distributed as a
310 collection of <em>packages</em>. Since there are so many of
311 them (currently well over 15000), they are split into
312 <em>sections</em> and given <em>priorities</em> to simplify
313 the handling of them.
317 The effort of the Debian project is to build a free operating
318 system, but not every package we want to make accessible is
319 <em>free</em> in our sense (see the Debian Free Software
320 Guidelines, below), or may be imported/exported without
321 restrictions. Thus, the archive is split into the distribution
322 areas or categories based on their licenses and other restrictions.
326 The aims of this are:
328 <list compact="compact">
329 <item>to allow us to make as much software available as we can</item>
330 <item>to allow us to encourage everyone to write free software,
332 <item>to allow us to make it easy for people to produce
333 CD-ROMs of our system without violating any licenses,
334 import/export restrictions, or any other laws.</item>
339 The <em>main</em> category forms the
340 <em>Debian GNU/Linux distribution</em>.
344 Packages in the other distribution areas (<tt>contrib</tt>,
345 <tt>non-free</tt>) are not considered to be part of the Debian
346 distribution, although we support their use and provide
347 infrastructure for them (such as our bug-tracking system and
348 mailing lists). This Debian Policy Manual applies to these
353 <heading>The Debian Free Software Guidelines</heading>
355 The Debian Free Software Guidelines (DFSG) form our
356 definition of "free software". These are:
358 <tag>Free Redistribution
361 The license of a Debian component may not restrict any
362 party from selling or giving away the software as a
363 component of an aggregate software distribution
364 containing programs from several different
365 sources. The license may not require a royalty or
366 other fee for such sale.
371 The program must include source code, and must allow
372 distribution in source code as well as compiled form.
377 The license must allow modifications and derived
378 works, and must allow them to be distributed under the
379 same terms as the license of the original software.
381 <tag>Integrity of The Author's Source Code
384 The license may restrict source-code from being
385 distributed in modified form <em>only</em> if the
386 license allows the distribution of "patch files"
387 with the source code for the purpose of modifying the
388 program at build time. The license must explicitly
389 permit distribution of software built from modified
390 source code. The license may require derived works to
391 carry a different name or version number from the
392 original software. (This is a compromise. The Debian
393 Project encourages all authors to not restrict any
394 files, source or binary, from being modified.)
396 <tag>No Discrimination Against Persons or Groups
399 The license must not discriminate against any person
402 <tag>No Discrimination Against Fields of Endeavor
405 The license must not restrict anyone from making use
406 of the program in a specific field of endeavor. For
407 example, it may not restrict the program from being
408 used in a business, or from being used for genetic
411 <tag>Distribution of License
414 The rights attached to the program must apply to all
415 to whom the program is redistributed without the need
416 for execution of an additional license by those
419 <tag>License Must Not Be Specific to Debian
422 The rights attached to the program must not depend on
423 the program's being part of a Debian system. If the
424 program is extracted from Debian and used or
425 distributed without Debian but otherwise within the
426 terms of the program's license, all parties to whom
427 the program is redistributed must have the same
428 rights as those that are granted in conjunction with
431 <tag>License Must Not Contaminate Other Software
434 The license must not place restrictions on other
435 software that is distributed along with the licensed
436 software. For example, the license must not insist
437 that all other programs distributed on the same medium
438 must be free software.
440 <tag>Example Licenses
443 The "GPL," "BSD," and "Artistic" licenses are examples of
444 licenses that we consider <em>free</em>.
451 <heading>Categories</heading>
454 <heading>The main category</heading>
457 Every package in <em>main</em> must comply with the DFSG
458 (Debian Free Software Guidelines).
462 In addition, the packages in <em>main</em>
463 <list compact="compact">
465 must not require a package outside of <em>main</em>
466 for compilation or execution (thus, the package must
467 not declare a "Depends", "Recommends", or
468 "Build-Depends" relationship on a non-<em>main</em>
472 must not be so buggy that we refuse to support them,
476 must meet all policy requirements presented in this
485 <heading>The contrib category</heading>
488 Every package in <em>contrib</em> must comply with the DFSG.
492 In addition, the packages in <em>contrib</em>
493 <list compact="compact">
495 must not be so buggy that we refuse to support them,
499 must meet all policy requirements presented in this
507 Examples of packages which would be included in
508 <em>contrib</em> are:
509 <list compact="compact">
511 free packages which require <em>contrib</em>,
512 <em>non-free</em> packages or packages which are not
513 in our archive at all for compilation or execution,
517 wrapper packages or other sorts of free accessories for
524 <sect1 id="non-free">
525 <heading>The non-free category</heading>
528 Packages must be placed in <em>non-free</em> if they are
529 not compliant with the DFSG or are encumbered by patents
530 or other legal issues that make their distribution
535 In addition, the packages in <em>non-free</em>
536 <list compact="compact">
538 must not be so buggy that we refuse to support them,
542 must meet all policy requirements presented in this
543 manual that it is possible for them to meet.
545 It is possible that there are policy
546 requirements which the package is unable to
547 meet, for example, if the source is
548 unavailable. These situations will need to be
549 handled on a case-by-case basis.
558 <sect id="pkgcopyright">
559 <heading>Copyright considerations</heading>
562 Every package must be accompanied by a verbatim copy of
563 its copyright and distribution license in the file
564 <file>/usr/share/doc/<var>package</var>/copyright</file>
565 (see <ref id="copyrightfile"> for further details).
569 We reserve the right to restrict files from being included
570 anywhere in our archives if
571 <list compact="compact">
573 their use or distribution would break a law,
576 there is an ethical conflict in their distribution or
580 we would have to sign a license for them, or
583 their distribution would conflict with other project
590 Programs whose authors encourage the user to make
591 donations are fine for the main distribution, provided
592 that the authors do not claim that not donating is
593 immoral, unethical, illegal or something similar; in such
594 a case they must go in <em>non-free</em>.
598 Packages whose copyright permission notices (or patent
599 problems) do not even allow redistribution of binaries
600 only, and where no special permission has been obtained,
601 must not be placed on the Debian FTP site and its mirrors
606 Note that under international copyright law (this applies
607 in the United States, too), <em>no</em> distribution or
608 modification of a work is allowed without an explicit
609 notice saying so. Therefore a program without a copyright
610 notice <em>is</em> copyrighted and you may not do anything
611 to it without risking being sued! Likewise if a program
612 has a copyright notice but no statement saying what is
613 permitted then nothing is permitted.
617 Many authors are unaware of the problems that restrictive
618 copyrights (or lack of copyright notices) can cause for
619 the users of their supposedly-free software. It is often
620 worthwhile contacting such authors diplomatically to ask
621 them to modify their license terms. However, this can be a
622 politically difficult thing to do and you should ask for
623 advice on the <tt>debian-legal</tt> mailing list first, as
628 When in doubt about a copyright, send mail to
629 <email>debian-legal@lists.debian.org</email>. Be prepared
630 to provide us with the copyright statement. Software
631 covered by the GPL, public domain software and BSD-like
632 copyrights are safe; be wary of the phrases "commercial
633 use prohibited" and "distribution restricted".
637 <sect id="subsections">
638 <heading>Sections</heading>
641 The packages in the categories <em>main</em>,
642 <em>contrib</em> and <em>non-free</em> are grouped further
643 into <em>sections</em> to simplify handling.
647 The category and section for each package should be
648 specified in the package's <tt>Section</tt> control record
649 (see <ref id="f-Section">). However, the maintainer of the
650 Debian archive may override this selection to ensure the
651 consistency of the Debian distribution. The
652 <tt>Section</tt> field should be of the form:
653 <list compact="compact">
655 <em>section</em> if the package is in the
656 <em>main</em> category,
659 <em>segment/section</em> if the package is in
660 the <em>contrib</em> or <em>non-free</em>
667 The Debian archive maintainers provide the authoritative
668 list of sections. At present, they are:
669 <em>admin</em>, <em>comm</em>,
670 <em>devel</em>, <em>doc</em>,
671 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
672 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
673 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
674 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
675 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
677 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
678 <em>science</em>, <em>shells</em>,
679 <em>sound</em>, <em>tex</em>, <em>text</em>,
680 <em>utils</em>, <em>web</em>, <em>x11</em>.
684 <sect id="priorities">
685 <heading>Priorities</heading>
688 Each package should have a <em>priority</em> value, which is
689 included in the package's <em>control record</em>
690 (see <ref id="f-Priority">).
691 This information is used by the Debian package management tools to
692 separate high-priority packages from less-important packages.
696 The following <em>priority levels</em> are recognized by the
697 Debian package management tools.
699 <tag><tt>required</tt></tag>
701 Packages which are necessary for the proper
702 functioning of the system (usually, this means that
703 dpkg functionality depends on these packages).
704 Removing a <tt>required</tt> package may cause your
705 system to become totally broken and you may not even
706 be able to use <prgn>dpkg</prgn> to put things back,
707 so only do so if you know what you are doing. Systems
708 with only the <tt>required</tt> packages are probably
709 unusable, but they do have enough functionality to
710 allow the sysadmin to boot and install more software.
712 <tag><tt>important</tt></tag>
714 Important programs, including those which one would
715 expect to find on any Unix-like system. If the
716 expectation is that an experienced Unix person who
717 found it missing would say "What on earth is going on,
718 where is <prgn>foo</prgn>?", it must be an
719 <tt>important</tt> package.<footnote>
720 This is an important criterion because we are
721 trying to produce, amongst other things, a free
724 Other packages without which the system will not run
725 well or be usable must also have priority
726 <tt>important</tt>. This does
727 <em>not</em> include Emacs, the X Window System, TeX
728 or any other large applications. The
729 <tt>important</tt> packages are just a bare minimum of
730 commonly-expected and necessary tools.
732 <tag><tt>standard</tt></tag>
734 These packages provide a reasonably small but not too
735 limited character-mode system. This is what will be
736 installed by default if the user doesn't select anything
737 else. It doesn't include many large applications.
739 <tag><tt>optional</tt></tag>
741 (In a sense everything that isn't required is
742 optional, but that's not what is meant here.) This is
743 all the software that you might reasonably want to
744 install if you didn't know what it was and don't have
745 specialized requirements. This is a much larger system
746 and includes the X Window System, a full TeX
747 distribution, and many applications. Note that
748 optional packages should not conflict with each other.
750 <tag><tt>extra</tt></tag>
752 This contains all packages that conflict with others
753 with required, important, standard or optional
754 priorities, or are only likely to be useful if you
755 already know what they are or have specialized
756 requirements (such as packages containing only detached
763 Packages must not depend on packages with lower priority
764 values (excluding build-time dependencies). In order to
765 ensure this, the priorities of one or more packages may need
774 <heading>Binary packages</heading>
777 The Debian GNU/Linux distribution is based on the Debian
778 package management system, called <prgn>dpkg</prgn>. Thus,
779 all packages in the Debian distribution must be provided
780 in the <tt>.deb</tt> file format.
784 <heading>The package name</heading>
787 Every package must have a name that's unique within the Debian
792 The package name is included in the control field
793 <tt>Package</tt>, the format of which is described
794 in <ref id="f-Package">.
795 The package name is also included as a part of the file name
796 of the <tt>.deb</tt> file.
801 <heading>The version of a package</heading>
804 Every package has a version number recorded in its
805 <tt>Version</tt> control file field, described in
806 <ref id="f-Version">.
810 The package management system imposes an ordering on version
811 numbers, so that it can tell whether packages are being up- or
812 downgraded and so that package system front end applications
813 can tell whether a package it finds available is newer than
814 the one installed on the system. The version number format
815 has the most significant parts (as far as comparison is
816 concerned) at the beginning.
820 If an upstream package has problematic version numbers they
821 should be converted to a sane form for use in the
822 <tt>Version</tt> field.
826 <heading>Version numbers based on dates</heading>
829 In general, Debian packages should use the same version
830 numbers as the upstream sources.
834 However, in some cases where the upstream version number is
835 based on a date (e.g., a development "snapshot" release) the
836 package management system cannot handle these version
837 numbers without epochs. For example, dpkg will consider
838 "96May01" to be greater than "96Dec24".
842 To prevent having to use epochs for every new upstream
843 version, the date based portion of the version number
844 should be changed to the following format in such cases:
845 "19960501", "19961224". It is up to the maintainer whether
846 they want to bother the upstream maintainer to change
847 the version numbers upstream, too.
851 Note that other version formats based on dates which are
852 parsed correctly by the package management system should
853 <em>not</em> be changed.
857 Native Debian packages (i.e., packages which have been
858 written especially for Debian) whose version numbers include
859 dates should always use the "YYYYMMDD" format.
866 <heading>The maintainer of a package</heading>
869 Every package must have a Debian maintainer (the
870 maintainer may be one person or a group of people
871 reachable from a common email address, such as a mailing
872 list). The maintainer is responsible for ensuring that
873 the package is placed in the appropriate distributions.
877 The maintainer must be specified in the
878 <tt>Maintainer</tt> control field with their correct name
879 and a working email address. If one person maintains
880 several packages, they should try to avoid having
881 different forms of their name and email address in
882 the <tt>Maintainer</tt> fields of those packages.
886 The format of the <tt>Maintainer</tt> control field is
887 described in <ref id="f-Maintainer">.
891 If the maintainer of a package quits from the Debian
892 project, "Debian QA Group"
893 <email>packages@qa.debian.org</email> takes over the
894 maintainer-ship of the package until someone else
895 volunteers for that task. These packages are called
896 <em>orphaned packages</em>.<footnote>
897 The detailed procedure for doing this gracefully can
898 be found in the Debian Developer's Reference,
899 see <ref id="related">.
904 <sect id="descriptions">
905 <heading>The description of a package</heading>
908 Every Debian package must have an extended description
909 stored in the appropriate field of the control record.
910 The technical information about the format of the
911 <tt>Description</tt> field is in <ref id="f-Description">.
915 The description should describe the package (the program) to a
916 user (system administrator) who has never met it before so that
917 they have enough information to decide whether they want to
918 install it. This description should not just be copied verbatim
919 from the program's documentation.
923 Put important information first, both in the synopsis and
924 extended description. Sometimes only the first part of the
925 synopsis or of the description will be displayed. You can
926 assume that there will usually be a way to see the whole
927 extended description.
931 The description should also give information about the
932 significant dependencies and conflicts between this package
933 and others, so that the user knows why these dependencies and
934 conflicts have been declared.
938 Instructions for configuring or using the package should
939 not be included (that is what installation scripts,
940 manual pages, info files, etc., are for). Copyright
941 statements and other administrivia should not be included
942 either (that is what the copyright file is for).
945 <sect1 id="synopsis"><heading>The single line synopsis</heading>
948 The single line synopsis should be kept brief - certainly
953 Do not include the package name in the synopsis line. The
954 display software knows how to display this already, and you
955 do not need to state it. Remember that in many situations
956 the user may only see the synopsis line - make it as
957 informative as you can.
962 <sect1 id="extendeddesc"><heading>The extended description</heading>
965 Do not try to continue the single line synopsis into the
966 extended description. This will not work correctly when
967 the full description is displayed, and makes no sense
968 where only the summary (the single line synopsis) is
973 The extended description should describe what the package
974 does and how it relates to the rest of the system (in terms
975 of, for example, which subsystem it is which part of).
979 The description field needs to make sense to anyone, even
980 people who have no idea about any of the things the
981 package deals with.<footnote>
982 The blurb that comes with a program in its
983 announcements and/or <prgn>README</prgn> files is
984 rarely suitable for use in a description. It is
985 usually aimed at people who are already in the
986 community where the package is used.
995 <heading>Dependencies</heading>
998 Every package must specify the dependency information
999 about other packages that are required for the first to
1004 For example, a dependency entry must be provided for any
1005 shared libraries required by a dynamically-linked executable
1006 binary in a package.
1010 Packages are not required to declare any dependencies they
1011 have on other packages which are marked <tt>Essential</tt>
1012 (see below), and should not do so unless they depend on a
1013 particular version of that package.<footnote>
1015 Essential is needed in part to avoid unresolvable dependency
1016 loops on upgrade. If packages add unnecessary dependencies
1017 on packages in this set, the chances that there
1018 <strong>will</strong> be an unresolvable dependency loop
1019 caused by forcing these Essential packages to be configured
1020 first before they need to be is greatly increased. It also
1021 increases the chances that frontends will be unable to
1022 <strong>calculate</strong> an upgrade path, even if one
1026 Also, functionality is rarely ever removed from the
1027 Essential set, but <em>packages</em> have been removed from
1028 the Essential set when the functionality moved to a
1029 different package. So depending on these packages <em>just
1030 in case</em> they stop being essential does way more harm
1037 Sometimes, a package requires another package to be installed
1038 <em>and</em> configured before it can be installed. In this
1039 case, you must specify a <tt>Pre-Depends</tt> entry for
1044 You should not specify a <tt>Pre-Depends</tt> entry for a
1045 package before this has been discussed on the
1046 <tt>debian-devel</tt> mailing list and a consensus about
1047 doing that has been reached.
1051 The format of the package interrelationship control fields is
1052 described in <ref id="relationships">.
1056 <sect id="virtual_pkg">
1057 <heading>Virtual packages</heading>
1060 Sometimes, there are several packages which offer
1061 more-or-less the same functionality. In this case, it's
1062 useful to define a <em>virtual package</em> whose name
1063 describes that common functionality. (The virtual
1064 packages only exist logically, not physically; that's why
1065 they are called <em>virtual</em>.) The packages with this
1066 particular function will then <em>provide</em> the virtual
1067 package. Thus, any other package requiring that function
1068 can simply depend on the virtual package without having to
1069 specify all possible packages individually.
1073 All packages should use virtual package names where
1074 appropriate, and arrange to create new ones if necessary.
1075 They should not use virtual package names (except privately,
1076 amongst a cooperating group of packages) unless they have
1077 been agreed upon and appear in the list of virtual package
1078 names. (See also <ref id="virtual">)
1082 The latest version of the authoritative list of virtual
1083 package names can be found in the <tt>debian-policy</tt> package.
1084 It is also available from the Debian web mirrors at
1085 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1086 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1090 The procedure for updating the list is described in the preface
1097 <heading>Base system</heading>
1100 The <tt>base system</tt> is a minimum subset of the Debian
1101 GNU/Linux system that is installed before everything else
1102 on a new system. Only very few packages are allowed to form
1103 part of the base system, in order to keep the required disk
1108 The base system consists of all those packages with priority
1109 <tt>required</tt> or <tt>important</tt>. Many of them will
1110 be tagged <tt>essential</tt> (see below).
1115 <heading>Essential packages</heading>
1118 Essential is defined as the minimal set of functionality that
1119 must be available and usable on the system at all times, even
1120 when packages are in an unconfigured (but unpacked) state.
1121 Packages are tagged <tt>essential</tt> for a system using the
1122 <tt>Essential</tt> control file field. The format of the
1123 <tt>Essential</tt> control field is described in <ref
1128 Since these packages cannot be easily removed (one has to
1129 specify an extra <em>force option</em> to
1130 <prgn>dpkg</prgn> to do so), this flag must not be used
1131 unless absolutely necessary. A shared library package
1132 must not be tagged <tt>essential</tt>; dependencies will
1133 prevent its premature removal, and we need to be able to
1134 remove it when it has been superseded.
1138 Since dpkg will not prevent upgrading of other packages
1139 while an <tt>essential</tt> package is in an unconfigured
1140 state, all <tt>essential</tt> packages must supply all of
1141 their core functionality even when unconfigured. If the
1142 package cannot satisfy this requirement it must not be
1143 tagged as essential, and any packages depending on this
1144 package must instead have explicit dependency fields as
1149 Maintainers should take great care in adding any programs,
1150 interfaces, or functionality to <tt>essential</tt> packages.
1151 Packages may assume that functionality provided by
1152 <tt>essential</tt> packages is always available without
1153 declaring explicit dependencies, which means that removing
1154 functionality from the Essential set is very difficult and is
1155 almost never done. Any capability added to an
1156 <tt>essential</tt> package therefore creates an obligation to
1157 support that capability as part of the Essential set in
1162 You must not tag any packages <tt>essential</tt> before
1163 this has been discussed on the <tt>debian-devel</tt>
1164 mailing list and a consensus about doing that has been
1169 <sect id="maintscripts">
1170 <heading>Maintainer Scripts</heading>
1173 The package installation scripts should avoid producing
1174 output which is unnecessary for the user to see and
1175 should rely on <prgn>dpkg</prgn> to stave off boredom on
1176 the part of a user installing many packages. This means,
1177 amongst other things, using the <tt>--quiet</tt> option on
1178 <prgn>install-info</prgn>.
1182 Errors which occur during the execution of an installation
1183 script must be checked and the installation must not
1184 continue after an error.
1188 Note that in general <ref id="scripts"> applies to package
1189 maintainer scripts, too.
1193 You should not use <prgn>dpkg-divert</prgn> on a file
1194 belonging to another package without consulting the
1195 maintainer of that package first.
1199 All packages which supply an instance of a common command
1200 name (or, in general, filename) should generally use
1201 <prgn>update-alternatives</prgn>, so that they may be
1202 installed together. If <prgn>update-alternatives</prgn>
1203 is not used, then each package must use
1204 <tt>Conflicts</tt> to ensure that other packages are
1205 de-installed. (In this case, it may be appropriate to
1206 specify a conflict against earlier versions of something
1207 that previously did not use
1208 <prgn>update-alternatives</prgn>; this is an exception to
1209 the usual rule that versioned conflicts should be
1213 <sect1 id="maintscriptprompt">
1214 <heading>Prompting in maintainer scripts</heading>
1216 Package maintainer scripts may prompt the user if
1217 necessary. Prompting should be done by communicating
1218 through a program, such as <prgn>debconf</prgn>, which
1219 conforms to the Debian Configuration Management
1220 Specification, version 2 or higher. Prompting the user by
1221 other means, such as by hand<footnote>
1222 From the Jargon file: by hand 2. By extension,
1223 writing code which does something in an explicit or
1224 low-level way for which a presupplied library
1225 (<em>debconf, in this instance</em>) routine ought
1226 to have been available.
1227 </footnote>, is now deprecated.
1231 The Debian Configuration Management Specification is included
1232 in the <file>debconf_specification</file> files in the
1233 <package>debian-policy</package> package.
1234 It is also available from the Debian web mirrors at
1235 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1236 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1240 Packages which use the Debian Configuration Management
1241 Specification may contain an additional
1242 <prgn>config</prgn> script and a <tt>templates</tt>
1243 file in their control archive<footnote>
1244 The control.tar.gz inside the .deb.
1245 See <manref name="deb" section="5">.
1247 The <prgn>config</prgn> script might be run before the
1248 <prgn>preinst</prgn> script, and before the package is unpacked
1249 or any of its dependencies or pre-dependencies are satisfied.
1250 Therefore it must work using only the tools present in
1251 <em>essential</em> packages.<footnote>
1252 <package>Debconf</package> or another tool that
1253 implements the Debian Configuration Management
1254 Specification will also be installed, and any
1255 versioned dependencies on it will be satisfied
1256 before preconfiguration begins.
1261 Packages which use the Debian Configuration Management
1262 Specification must allow for translation of their user-visible
1263 messages by using a gettext-based system such as the one
1264 provided by the <package>po-debconf</package> package.
1268 Packages should try to minimize the amount of prompting
1269 they need to do, and they should ensure that the user
1270 will only ever be asked each question once. This means
1271 that packages should try to use appropriate shared
1272 configuration files (such as <file>/etc/papersize</file> and
1273 <file>/etc/news/server</file>), and shared
1274 <package>debconf</package> variables rather than each
1275 prompting for their own list of required pieces of
1280 It also means that an upgrade should not ask the same
1281 questions again, unless the user has used
1282 <tt>dpkg --purge</tt> to remove the package's configuration.
1283 The answers to configuration questions should be stored in an
1284 appropriate place in <file>/etc</file> so that the user can
1285 modify them, and how this has been done should be
1290 If a package has a vitally important piece of
1291 information to pass to the user (such as "don't run me
1292 as I am, you must edit the following configuration files
1293 first or you risk your system emitting badly-formatted
1294 messages"), it should display this in the
1295 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1296 prompt the user to hit return to acknowledge the
1297 message. Copyright messages do not count as vitally
1298 important (they belong in
1299 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1300 neither do instructions on how to use a program (these
1301 should be in on-line documentation, where all the users
1306 Any necessary prompting should almost always be confined
1307 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1308 script. If it is done in the <prgn>postinst</prgn>, it
1309 should be protected with a conditional so that
1310 unnecessary prompting doesn't happen if a package's
1311 installation fails and the <prgn>postinst</prgn> is
1312 called with <tt>abort-upgrade</tt>,
1313 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1323 <heading>Source packages</heading>
1325 <sect id="standardsversion">
1326 <heading>Standards conformance</heading>
1329 Source packages should specify the most recent version number
1330 of this policy document with which your package complied
1331 when it was last updated.
1335 This information may be used to file bug reports
1336 automatically if your package becomes too much out of date.
1340 The version is specified in the <tt>Standards-Version</tt>
1342 The format of the <tt>Standards-Version</tt> field is
1343 described in <ref id="f-Standards-Version">.
1347 You should regularly, and especially if your package has
1348 become out of date, check for the newest Policy Manual
1349 available and update your package, if necessary. When your
1350 package complies with the new standards you should update the
1351 <tt>Standards-Version</tt> source package field and
1352 release it.<footnote>
1353 See the file <file>upgrading-checklist</file> for
1354 information about policy which has changed between
1355 different versions of this document.
1361 <sect id="pkg-relations">
1362 <heading>Package relationships</heading>
1365 Source packages should specify which binary packages they
1366 require to be installed or not to be installed in order to
1367 build correctly. For example, if building a package
1368 requires a certain compiler, then the compiler should be
1369 specified as a build-time dependency.
1373 It is not necessary to explicitly specify build-time
1374 relationships on a minimal set of packages that are always
1375 needed to compile, link and put in a Debian package a
1376 standard "Hello World!" program written in C or C++. The
1377 required packages are called <em>build-essential</em>, and
1378 an informational list can be found in
1379 <file>/usr/share/doc/build-essential/list</file> (which is
1380 contained in the <tt>build-essential</tt>
1383 <list compact="compact">
1385 This allows maintaining the list separately
1386 from the policy documents (the list does not
1387 need the kind of control that the policy
1391 Having a separate package allows one to install
1392 the build-essential packages on a machine, as
1393 well as allowing other packages such as tasks to
1394 require installation of the build-essential
1395 packages using the depends relation.
1398 The separate package allows bug reports against
1399 the list to be categorized separately from
1400 the policy management process in the BTS.
1407 When specifying the set of build-time dependencies, one
1408 should list only those packages explicitly required by the
1409 build. It is not necessary to list packages which are
1410 required merely because some other package in the list of
1411 build-time dependencies depends on them.<footnote>
1412 The reason for this is that dependencies change, and
1413 you should list all those packages, and <em>only</em>
1414 those packages that <em>you</em> need directly. What
1415 others need is their business. For example, if you
1416 only link against <file>libimlib</file>, you will need to
1417 build-depend on <package>libimlib2-dev</package> but
1418 not against any <tt>libjpeg*</tt> packages, even
1419 though <tt>libimlib2-dev</tt> currently depends on
1420 them: installation of <package>libimlib2-dev</package>
1421 will automatically ensure that all of its run-time
1422 dependencies are satisfied.
1427 If build-time dependencies are specified, it must be
1428 possible to build the package and produce working binaries
1429 on a system with only essential and build-essential
1430 packages installed and also those required to satisfy the
1431 build-time relationships (including any implied
1432 relationships). In particular, this means that version
1433 clauses should be used rigorously in build-time
1434 relationships so that one cannot produce bad or
1435 inconsistently configured packages when the relationships
1436 are properly satisfied.
1440 <ref id="relationships"> explains the technical details.
1445 <heading>Changes to the upstream sources</heading>
1448 If changes to the source code are made that are not
1449 specific to the needs of the Debian system, they should be
1450 sent to the upstream authors in whatever form they prefer
1451 so as to be included in the upstream version of the
1456 If you need to configure the package differently for
1457 Debian or for Linux, and the upstream source doesn't
1458 provide a way to do so, you should add such configuration
1459 facilities (for example, a new <prgn>autoconf</prgn> test
1460 or <tt>#define</tt>) and send the patch to the upstream
1461 authors, with the default set to the way they originally
1462 had it. You can then easily override the default in your
1463 <file>debian/rules</file> or wherever is appropriate.
1467 You should make sure that the <prgn>configure</prgn> utility
1468 detects the correct architecture specification string
1469 (refer to <ref id="arch-spec"> for details).
1473 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1474 <prgn>configure</prgn> scripts are used, you should edit the
1475 <file>.in</file> files rather than editing the
1476 <prgn>Makefile</prgn> directly. This allows the user to
1477 reconfigure the package if necessary. You should
1478 <em>not</em> configure the package and edit the generated
1479 <prgn>Makefile</prgn>! This makes it impossible for someone
1480 else to later reconfigure the package without losing the
1486 <sect id="dpkgchangelog">
1487 <heading>Debian changelog: <file>debian/changelog</file></heading>
1490 Changes in the Debian version of the package should be
1491 briefly explained in the Debian changelog file
1492 <file>debian/changelog</file>.<footnote>
1494 Mistakes in changelogs are usually best rectified by
1495 making a new changelog entry rather than "rewriting
1496 history" by editing old changelog entries.
1499 This includes modifications
1500 made in the Debian package compared to the upstream one
1501 as well as other changes and updates to the package.
1503 Although there is nothing stopping an author who is also
1504 the Debian maintainer from using this changelog for all
1505 their changes, it will have to be renamed if the Debian
1506 and upstream maintainers become different people. In such
1507 a case, however, it might be better to maintain the package
1508 as a non-native package.
1513 The format of the <file>debian/changelog</file> allows the
1514 package building tools to discover which version of the package
1515 is being built and find out other release-specific information.
1519 That format is a series of entries like this:
1521 <example compact="compact">
1522 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1524 [optional blank line(s), stripped]
1526 * <var>change details</var>
1527 <var>more change details</var>
1529 [blank line(s), included in output of dpkg-parsechangelog]
1531 * <var>even more change details</var>
1533 [optional blank line(s), stripped]
1535 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1540 <var>package</var> and <var>version</var> are the source
1541 package name and version number.
1545 <var>distribution(s)</var> lists the distributions where
1546 this version should be installed when it is uploaded - it
1547 is copied to the <tt>Distribution</tt> field in the
1548 <file>.changes</file> file. See <ref id="f-Distribution">.
1552 <var>urgency</var> is the value for the <tt>Urgency</tt>
1553 field in the <file>.changes</file> file for the upload
1554 (see <ref id="f-Urgency">). It is not possible to specify
1555 an urgency containing commas; commas are used to separate
1556 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1557 <prgn>dpkg</prgn> changelog format (though there is
1558 currently only one useful <var>keyword</var>,
1563 The change details may in fact be any series of lines
1564 starting with at least two spaces, but conventionally each
1565 change starts with an asterisk and a separating space and
1566 continuation lines are indented so as to bring them in
1567 line with the start of the text above. Blank lines may be
1568 used here to separate groups of changes, if desired.
1572 If this upload resolves bugs recorded in the Bug Tracking
1573 System (BTS), they may be automatically closed on the
1574 inclusion of this package into the Debian archive by
1575 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1576 in the change details.<footnote>
1577 To be precise, the string should match the following
1578 Perl regular expression:
1580 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1582 Then all of the bug numbers listed will be closed by the
1583 archive maintenance script (<prgn>katie</prgn>) using the
1584 <var>version</var> of the changelog entry.
1586 This information is conveyed via the <tt>Closes</tt> field
1587 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1591 The maintainer name and email address used in the changelog
1592 should be the details of the person uploading <em>this</em>
1593 version. They are <em>not</em> necessarily those of the
1594 usual package maintainer. The information here will be
1595 copied to the <tt>Changed-By</tt> field in the
1596 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1597 and then later used to send an acknowledgement when the
1598 upload has been installed.
1602 The <var>date</var> must be in RFC822 format<footnote>
1603 This is generated by <tt>date -R</tt>.
1604 </footnote>; it must include the time zone specified
1605 numerically, with the time zone name or abbreviation
1606 optionally present as a comment in parentheses.
1610 The first "title" line with the package name must start
1611 at the left hand margin. The "trailer" line with the
1612 maintainer and date details must be preceded by exactly
1613 one space. The maintainer details and the date must be
1614 separated by exactly two spaces.
1618 The entire changelog must be encoded in UTF-8.
1622 For more information on placement of the changelog files
1623 within binary packages, please see <ref id="changelogs">.
1627 <sect id="dpkgcopyright">
1628 <heading>Copyright: <file>debian/copyright</file></heading>
1630 Every package must be accompanied by a verbatim copy of
1631 its copyright and distribution license in the file
1632 <file>/usr/share/doc/<var>package</var>/copyright</file>
1633 (see <ref id="copyrightfile"> for further details). Also see
1634 <ref id="pkgcopyright"> for further considerations relayed
1635 to copyrights for packages.
1639 <heading>Error trapping in makefiles</heading>
1642 When <prgn>make</prgn> invokes a command in a makefile
1643 (including your package's upstream makefiles and
1644 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1645 means that <prgn>sh</prgn>'s usual bad error handling
1646 properties apply: if you include a miniature script as one
1647 of the commands in your makefile you'll find that if you
1648 don't do anything about it then errors are not detected
1649 and <prgn>make</prgn> will blithely continue after
1654 Every time you put more than one shell command (this
1655 includes using a loop) in a makefile command you
1656 must make sure that errors are trapped. For
1657 simple compound commands, such as changing directory and
1658 then running a program, using <tt>&&</tt> rather
1659 than semicolon as a command separator is sufficient. For
1660 more complex commands including most loops and
1661 conditionals you should include a separate <tt>set -e</tt>
1662 command at the start of every makefile command that's
1663 actually one of these miniature shell scripts.
1667 <sect id="timestamps">
1668 <heading>Time Stamps</heading>
1670 Maintainers should preserve the modification times of the
1671 upstream source files in a package, as far as is reasonably
1673 The rationale is that there is some information conveyed
1674 by knowing the age of the file, for example, you could
1675 recognize that some documentation is very old by looking
1676 at the modification time, so it would be nice if the
1677 modification time of the upstream source would be
1683 <sect id="restrictions">
1684 <heading>Restrictions on objects in source packages</heading>
1687 The source package may not contain any hard links<footnote>
1689 This is not currently detected when building source
1690 packages, but only when extracting
1694 Hard links may be permitted at some point in the
1695 future, but would require a fair amount of
1698 </footnote>, device special files, sockets or setuid or
1699 setgid files.<footnote>
1700 Setgid directories are allowed.
1705 <sect id="debianrules">
1706 <heading>Main building script: <file>debian/rules</file></heading>
1709 This file must be an executable makefile, and contains the
1710 package-specific recipes for compiling the package and
1711 building binary package(s) from the source.
1715 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1716 so that it can be invoked by saying its name rather than
1717 invoking <prgn>make</prgn> explicitly.
1721 Since an interactive <file>debian/rules</file> script makes it
1722 impossible to auto-compile that package and also makes it
1723 hard for other people to reproduce the same binary
1724 package, all <em>required targets</em> MUST be
1725 non-interactive. At a minimum, required targets are the
1726 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1727 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1728 <em>binary-indep</em>, and <em>build</em>. It also follows
1729 that any target that these targets depend on must also be
1734 The targets are as follows (required unless stated otherwise):
1736 <tag><tt>build</tt></tag>
1739 The <tt>build</tt> target should perform all the
1740 configuration and compilation of the package.
1741 If a package has an interactive pre-build
1742 configuration routine, the Debianized source package
1743 must either be built after this has taken place (so
1744 that the binary package can be built without rerunning
1745 the configuration) or the configuration routine
1746 modified to become non-interactive. (The latter is
1747 preferable if there are architecture-specific features
1748 detected by the configuration routine.)
1752 For some packages, notably ones where the same
1753 source tree is compiled in different ways to produce
1754 two binary packages, the <tt>build</tt> target
1755 does not make much sense. For these packages it is
1756 good enough to provide two (or more) targets
1757 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1758 for each of the ways of building the package, and a
1759 <tt>build</tt> target that does nothing. The
1760 <tt>binary</tt> target will have to build the
1761 package in each of the possible ways and make the
1762 binary package out of each.
1766 The <tt>build</tt> target must not do anything
1767 that might require root privilege.
1771 The <tt>build</tt> target may need to run the
1772 <tt>clean</tt> target first - see below.
1776 When a package has a configuration and build routine
1777 which takes a long time, or when the makefiles are
1778 poorly designed, or when <tt>build</tt> needs to
1779 run <tt>clean</tt> first, it is a good idea to
1780 <tt>touch build</tt> when the build process is
1781 complete. This will ensure that if <tt>debian/rules
1782 build</tt> is run again it will not rebuild the whole
1784 Another common way to do this is for <tt>build</tt>
1785 to depend on <prgn>build-stamp</prgn> and to do
1786 nothing else, and for the <prgn>build-stamp</prgn>
1787 target to do the building and to <tt>touch
1788 build-stamp</tt> on completion. This is
1789 especially useful if the build routine creates a
1790 file or directory called <tt>build</tt>; in such a
1791 case, <tt>build</tt> will need to be listed as
1792 a phony target (i.e., as a dependency of the
1793 <tt>.PHONY</tt> target). See the documentation of
1794 <prgn>make</prgn> for more information on phony
1800 <tag><tt>build-arch</tt> (optional),
1801 <tt>build-indep</tt> (optional)
1805 A package may also provide both of the targets
1806 <tt>build-arch</tt> and <tt>build-indep</tt>.
1807 The <tt>build-arch</tt> target, if provided, should
1808 perform all the configuration and compilation required
1809 for producing all architecture-dependant binary packages
1810 (those packages for which the body of the
1811 <tt>Architecture</tt> field in <tt>debian/control</tt>
1812 is not <tt>all</tt>).
1813 Similarly, the <tt>build-indep</tt> target, if
1814 provided, should perform all the configuration and
1815 compilation required for producing all
1816 architecture-independent binary packages
1817 (those packages for which the body of the
1818 <tt>Architecture</tt> field in <tt>debian/control</tt>
1820 The <tt>build</tt> target should depend on those of the
1821 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1822 are provided in the rules file.
1826 If one or both of the targets <tt>build-arch</tt> and
1827 <tt>build-indep</tt> are not provided, then invoking
1828 <file>debian/rules</file> with one of the not-provided
1829 targets as arguments should produce a exit status code
1830 of 2. Usually this is provided automatically by make
1831 if the target is missing.
1835 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1836 must not do anything that might require root privilege.
1840 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1841 <tt>binary-indep</tt>
1845 The <tt>binary</tt> target must be all that is
1846 necessary for the user to build the binary package(s)
1847 produced from this source package. It is
1848 split into two parts: <prgn>binary-arch</prgn> builds
1849 the binary packages which are specific to a particular
1850 architecture, and <tt>binary-indep</tt> builds
1851 those which are not.
1854 <tt>binary</tt> may be (and commonly is) a target with
1855 no commands which simply depends on
1856 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1859 Both <tt>binary-*</tt> targets should depend on the
1860 <tt>build</tt> target, or on the appropriate
1861 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1862 provided, so that the package is built if it has not
1863 been already. It should then create the relevant
1864 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1865 make their control files and <prgn>dpkg-deb</prgn> to
1866 build them and place them in the parent of the top
1871 Both the <tt>binary-arch</tt> and
1872 <tt>binary-indep</tt> targets <em>must</em> exist.
1873 If one of them has nothing to do (which will always be
1874 the case if the source generates only a single binary
1875 package, whether architecture-dependent or not), it
1876 must still exist and must always succeed.
1880 The <tt>binary</tt> targets must be invoked as
1882 The <prgn>fakeroot</prgn> package often allows one
1883 to build a package correctly even without being
1889 <tag><tt>clean</tt></tag>
1892 This must undo any effects that the <tt>build</tt>
1893 and <tt>binary</tt> targets may have had, except
1894 that it should leave alone any output files created in
1895 the parent directory by a run of a <tt>binary</tt>
1900 If a <tt>build</tt> file is touched at the end of
1901 the <tt>build</tt> target, as suggested above, it
1902 should be removed as the first action that
1903 <tt>clean</tt> performs, so that running
1904 <tt>build</tt> again after an interrupted
1905 <tt>clean</tt> doesn't think that everything is
1910 The <tt>clean</tt> target may need to be
1911 invoked as root if <tt>binary</tt> has been
1912 invoked since the last <tt>clean</tt>, or if
1913 <tt>build</tt> has been invoked as root (since
1914 <tt>build</tt> may create directories, for
1919 <tag><tt>get-orig-source</tt> (optional)</tag>
1922 This target fetches the most recent version of the
1923 original source package from a canonical archive site
1924 (via FTP or WWW, for example), does any necessary
1925 rearrangement to turn it into the original source
1926 tar file format described below, and leaves it in the
1931 This target may be invoked in any directory, and
1932 should take care to clean up any temporary files it
1937 This target is optional, but providing it if
1938 possible is a good idea.
1942 <tag><tt>patch</tt> (optional)</tag>
1945 This target performs whatever additional actions are
1946 required to make the source ready for editing (unpacking
1947 additional upstream archives, applying patches, etc.).
1948 It is recommended to be implemented for any package where
1949 <tt>dpkg-source -x</tt> does not result in source ready
1950 for additional modification. See
1951 <ref id="readmesource">.
1957 The <tt>build</tt>, <tt>binary</tt> and
1958 <tt>clean</tt> targets must be invoked with the current
1959 directory being the package's top-level directory.
1964 Additional targets may exist in <file>debian/rules</file>,
1965 either as published or undocumented interfaces or for the
1966 package's internal use.
1970 The architectures we build on and build for are determined
1971 by <prgn>make</prgn> variables using the utility
1972 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1973 You can determine the
1974 Debian architecture and the GNU style architecture
1975 specification string for the build machine (the machine type
1976 we are building on) as well as for the host machine (the
1977 machine type we are building for). Here is a list of
1978 supported <prgn>make</prgn> variables:
1979 <list compact="compact">
1981 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1984 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1985 specification string)
1988 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1989 <tt>DEB_*_GNU_TYPE</tt>)
1992 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1993 <tt>DEB_*_GNU_TYPE</tt>)
1995 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1996 the build machine or <tt>HOST</tt> for specification of the
2001 Backward compatibility can be provided in the rules file
2002 by setting the needed variables to suitable default
2003 values; please refer to the documentation of
2004 <prgn>dpkg-architecture</prgn> for details.
2008 It is important to understand that the <tt>DEB_*_ARCH</tt>
2009 string only determines which Debian architecture we are
2010 building on or for. It should not be used to get the CPU
2011 or system information; the GNU style variables should be
2015 <sect1 id="debianrules-options">
2016 <heading><file>debian/rules</file> and
2017 <tt>DEB_BUILD_OPTIONS</tt></heading>
2020 Supporting the standardized environment variable
2021 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2022 contain several flags to change how a package is compiled and
2023 built. Each flag must be in the form <var>flag</var> or
2024 <var>flag</var>=<var>options</var>. If multiple flags are
2025 given, they must be separated by whitespace.<footnote>
2026 Some packages support any delimiter, but whitespace is the
2027 easiest to parse inside a makefile and avoids ambiguity with
2028 flag values that contain commas.
2030 <var>flag</var> must start with a lowercase letter
2031 (<tt>a-z</tt>) and consist only of lowercase letters,
2032 numbers (<tt>0-9</tt>), and the characters
2033 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2034 <var>options</var> must not contain whitespace. The same
2035 tag should not be given multiple times with conflicting
2036 values. Package maintainers may assume that
2037 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2041 The meaning of the following tags has been standardized:
2045 This tag says to not run any build-time test suite
2046 provided by the package.
2050 The presence of this tag means that the package should
2051 be compiled with a minimum of optimization. For C
2052 programs, it is best to add <tt>-O0</tt> to
2053 <tt>CFLAGS</tt> (although this is usually the default).
2054 Some programs might fail to build or run at this level
2055 of optimization; it may be necessary to use
2056 <tt>-O1</tt>, for example.
2060 This tag means that the debugging symbols should not be
2061 stripped from the binary during installation, so that
2062 debugging information may be included in the package.
2064 <tag>parallel=n</tag>
2066 This tag means that the package should be built using up
2067 to <tt>n</tt> parallel processes if the package build
2068 system supports this.<footnote>
2069 Packages built with <tt>make</tt> can often implement
2070 this by passing the <tt>-j</tt><var>n</var> option to
2073 If the package build system does not support parallel
2074 builds, this string must be ignored. If the package
2075 build system only supports a lower level of concurrency
2076 than <var>n</var>, the package should be built using as
2077 many parallel processes as the package build system
2078 supports. It is up to the package maintainer to decide
2079 whether the package build times are long enough and the
2080 package build system is robust enough to make supporting
2081 parallel builds worthwhile.
2087 Unknown flags must be ignored by <file>debian/rules</file>.
2091 The following makefile snippet is an example of how one may
2092 implement the build options; you will probably have to
2093 massage this example in order to make it work for your
2095 <example compact="compact">
2098 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2099 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2100 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2101 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2103 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2108 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2109 INSTALL_PROGRAM += -s
2111 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2112 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2113 MAKEFLAGS += -j$(NUMJOBS)
2118 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2119 # Code to run the package test suite.
2126 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2127 <sect id="substvars">
2128 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2131 When <prgn>dpkg-gencontrol</prgn>,
2132 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2133 generate control files they perform variable substitutions
2134 on their output just before writing it. Variable
2135 substitutions have the form <tt>${<var>variable</var>}</tt>.
2136 The optional file <file>debian/substvars</file> contains
2137 variable substitutions to be used; variables can also be set
2138 directly from <file>debian/rules</file> using the <tt>-V</tt>
2139 option to the source packaging commands, and certain
2140 predefined variables are also available.
2144 The <file>debian/substvars</file> file is usually generated and
2145 modified dynamically by <file>debian/rules</file> targets, in
2146 which case it must be removed by the <tt>clean</tt> target.
2150 See <manref name="deb-substvars" section="5"> for full
2151 details about source variable substitutions, including the
2152 format of <file>debian/substvars</file>.</p>
2155 <sect id="debianwatch">
2156 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2159 This is an optional, recommended control file for the
2160 <tt>uscan</tt> utility which defines how to automatically
2161 scan ftp or http sites for newly available updates of the
2162 package. This is used by <url id="
2163 http://dehs.alioth.debian.org/"> and other Debian QA tools
2164 to help with quality control and maintenance of the
2165 distribution as a whole.
2170 <sect id="debianfiles">
2171 <heading>Generated files list: <file>debian/files</file></heading>
2174 This file is not a permanent part of the source tree; it
2175 is used while building packages to record which files are
2176 being generated. <prgn>dpkg-genchanges</prgn> uses it
2177 when it generates a <file>.changes</file> file.
2181 It should not exist in a shipped source package, and so it
2182 (and any backup files or temporary files such as
2183 <file>files.new</file><footnote>
2184 <file>files.new</file> is used as a temporary file by
2185 <prgn>dpkg-gencontrol</prgn> and
2186 <prgn>dpkg-distaddfile</prgn> - they write a new
2187 version of <tt>files</tt> here before renaming it,
2188 to avoid leaving a corrupted copy if an error
2190 </footnote>) should be removed by the
2191 <tt>clean</tt> target. It may also be wise to
2192 ensure a fresh start by emptying or removing it at the
2193 start of the <tt>binary</tt> target.
2197 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2198 package, it adds an entry to <file>debian/files</file> for the
2199 <file>.deb</file> file that will be created when <tt>dpkg-deb
2200 --build</tt> is run for that binary package. So for most
2201 packages all that needs to be done with this file is to
2202 delete it in the <tt>clean</tt> target.
2206 If a package upload includes files besides the source
2207 package and any binary packages whose control files were
2208 made with <prgn>dpkg-gencontrol</prgn> then they should be
2209 placed in the parent of the package's top-level directory
2210 and <prgn>dpkg-distaddfile</prgn> should be called to add
2211 the file to the list in <file>debian/files</file>.</p>
2214 <sect id="embeddedfiles">
2215 <heading>Convenience copies of code</heading>
2218 Some software packages include in their distribution convenience
2219 copies of code from other software packages, generally so that
2220 users compiling from source don't have to download multiple
2221 packages. Debian packages should not make use of these
2222 convenience copies unless the included package is explicitly
2223 intended to be used in this way.<footnote>
2224 For example, parts of the GNU build system work like this.
2226 If the included code is already in the Debian archive in the
2227 form of a library, the Debian packaging should ensure that
2228 binary packages reference the libraries already in Debian and
2229 the convenience copy is not used. If the included code is not
2230 already in Debian, it should be packaged separately as a
2231 prerequisite if possible.
2233 Having multiple copies of the same code in Debian is
2234 inefficient, often creates either static linking or shared
2235 library conflicts, and, most importantly, increases the
2236 difficulty of handling security vulnerabilities in the
2242 <sect id="readmesource">
2243 <heading>Source package handling:
2244 <file>debian/README.source</file></heading>
2247 If running <prgn>dpkg-source -x</prgn> on a source package
2248 doesn't produce the source of the package, ready for editing,
2249 and allow one to make changes and run
2250 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2251 without taking any additional steps, creating a
2252 <file>debian/README.source</file> documentation file is
2253 recommended. This file should explain how to do all of the
2256 <item>Generate the fully patched source, in a form ready for
2257 editing, that would be built to create Debian
2258 packages. Doing this with a <tt>patch</tt> target in
2259 <file>debian/rules</file> is recommended; see
2260 <ref id="debianrules">.</item>
2261 <item>Modify the source and save those modifications so that
2262 they will be applied when building the package.</item>
2263 <item>Remove source modifications that are currently being
2264 applied when building the package.</item>
2265 <item>Optionally, document what steps are necessary to
2266 upgrade the Debian source package to a new upstream version,
2267 if applicable.</item>
2269 This explanation should include specific commands and mention
2270 any additional required Debian packages. It should not assume
2271 familiarity with any specific Debian packaging system or patch
2276 This explanation may refer to a documentation file installed by
2277 one of the package's build dependencies provided that the
2278 referenced documentation clearly explains these tasks and is not
2279 a general reference manual.
2283 <file>debian/README.source</file> may also include any other
2284 information that would be helpful to someone modifying the
2285 source package. Even if the package doesn't fit the above
2286 description, maintainers are encouraged to document in a
2287 <file>debian/README.source</file> file any source package with a
2288 particularly complex or unintuitive source layout or build
2289 system (for example, a package that builds the same source
2290 multiple times to generate different binary packages).
2296 <chapt id="controlfields">
2297 <heading>Control files and their fields</heading>
2300 The package management system manipulates data represented in
2301 a common format, known as <em>control data</em>, stored in
2302 <em>control files</em>.
2303 Control files are used for source packages, binary packages and
2304 the <file>.changes</file> files which control the installation
2305 of uploaded files<footnote>
2306 <prgn>dpkg</prgn>'s internal databases are in a similar
2311 <sect id="controlsyntax">
2312 <heading>Syntax of control files</heading>
2315 A control file consists of one or more paragraphs of
2317 The paragraphs are also sometimes referred to as stanzas.
2319 The paragraphs are separated by blank lines. Some control
2320 files allow only one paragraph; others allow several, in
2321 which case each paragraph usually refers to a different
2322 package. (For example, in source packages, the first
2323 paragraph refers to the source package, and later paragraphs
2324 refer to binary packages generated from the source.)
2328 Each paragraph consists of a series of data fields; each
2329 field consists of the field name, followed by a colon and
2330 then the data/value associated with that field. It ends at
2331 the end of the (logical) line. Horizontal whitespace
2332 (spaces and tabs) may occur immediately before or after the
2333 value and is ignored there; it is conventional to put a
2334 single space after the colon. For example, a field might
2336 <example compact="compact">
2339 the field name is <tt>Package</tt> and the field value
2344 Many fields' values may span several lines; in this case
2345 each continuation line must start with a space or a tab.
2346 Any trailing spaces or tabs at the end of individual
2347 lines of a field value are ignored.
2351 In fields where it is specified that lines may not wrap,
2352 only a single line of data is allowed and whitespace is not
2353 significant in a field body. Whitespace must not appear
2354 inside names (of packages, architectures, files or anything
2355 else) or version numbers, or between the characters of
2356 multi-character version relationships.
2360 Field names are not case-sensitive, but it is usual to
2361 capitalize the field names using mixed case as shown below.
2365 Blank lines, or lines consisting only of spaces and tabs,
2366 are not allowed within field values or between fields - that
2367 would mean a new paragraph.
2371 All control files must be encoded in UTF-8.
2375 <sect id="sourcecontrolfiles">
2376 <heading>Source package control files -- <file>debian/control</file></heading>
2379 The <file>debian/control</file> file contains the most vital
2380 (and version-independent) information about the source package
2381 and about the binary packages it creates.
2385 The first paragraph of the control file contains information about
2386 the source package in general. The subsequent sets each describe a
2387 binary package that the source tree builds.
2391 The fields in the general paragraph (the first one, for the source
2394 <list compact="compact">
2395 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2396 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2397 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2398 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2399 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2400 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2401 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2402 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2407 The fields in the binary package paragraphs are:
2409 <list compact="compact">
2410 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2411 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2412 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2413 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2414 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2415 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2416 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2417 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2422 The syntax and semantics of the fields are described below.
2428 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2429 generate control files for binary packages (see below), by
2430 <prgn>dpkg-genchanges</prgn> to generate the
2431 <tt>.changes</tt> file to accompany the upload, and by
2432 <prgn>dpkg-source</prgn> when it creates the
2433 <file>.dsc</file> source control file as part of a source
2434 archive. Many fields are permitted to span multiple lines in
2435 <file>debian/control</file> but not in any other control
2436 file. These tools are responsible for removing the line
2437 breaks from such fields when using fields from
2438 <file>debian/control</file> to generate other control files.
2442 The fields here may contain variable references - their
2443 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2444 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2445 when they generate output control files.
2446 See <ref id="substvars"> for details.
2451 <sect id="binarycontrolfiles">
2452 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2455 The <file>DEBIAN/control</file> file contains the most vital
2456 (and version-dependent) information about a binary package.
2460 The fields in this file are:
2462 <list compact="compact">
2463 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2464 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2465 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2466 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2467 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2468 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2469 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2470 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2471 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2472 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2473 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2474 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2479 <sect id="debiansourcecontrolfiles">
2480 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2483 This file contains a series of fields, identified and
2484 separated just like the fields in the control file of
2485 a binary package. The fields are listed below; their
2486 syntax is described above, in <ref id="pkg-controlfields">.
2488 <list compact="compact">
2489 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2490 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2491 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2492 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2493 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2494 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2495 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2496 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2497 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2498 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2499 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2504 The source package control file is generated by
2505 <prgn>dpkg-source</prgn> when it builds the source
2506 archive, from other files in the source package,
2507 described above. When unpacking, it is checked against
2508 the files and directories in the other parts of the
2514 <sect id="debianchangesfiles">
2515 <heading>Debian changes files -- <file>.changes</file></heading>
2518 The .changes files are used by the Debian archive maintenance
2519 software to process updates to packages. They contain one
2520 paragraph which contains information from the
2521 <tt>debian/control</tt> file and other data about the
2522 source package gathered via <tt>debian/changelog</tt>
2523 and <tt>debian/rules</tt>.
2527 The fields in this file are:
2529 <list compact="compact">
2530 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2531 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2532 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2533 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2534 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2535 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2536 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2537 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2538 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2539 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2540 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2541 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2542 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2543 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2548 <sect id="controlfieldslist">
2549 <heading>List of fields</heading>
2551 <sect1 id="f-Source">
2552 <heading><tt>Source</tt></heading>
2555 This field identifies the source package name.
2559 In <file>debian/control</file> or a <file>.dsc</file> file,
2560 this field must contain only the name of the source package.
2564 In a binary package control file or a <file>.changes</file>
2565 file, the source package name may be followed by a version
2566 number in parentheses<footnote>
2567 It is customary to leave a space after the package name
2568 if a version number is specified.
2570 This version number may be omitted (and is, by
2571 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2572 the <tt>Version</tt> field of the binary package in
2573 question. The field itself may be omitted from a binary
2574 package control file when the source package has the same
2575 name and version as the binary package.
2579 <sect1 id="f-Maintainer">
2580 <heading><tt>Maintainer</tt></heading>
2583 The package maintainer's name and email address. The name
2584 should come first, then the email address inside angle
2585 brackets <tt><></tt> (in RFC822 format).
2589 If the maintainer's name contains a full stop then the
2590 whole field will not work directly as an email address due
2591 to a misfeature in the syntax specified in RFC822; a
2592 program using this field as an address must check for this
2593 and correct the problem if necessary (for example by
2594 putting the name in round brackets and moving it to the
2595 end, and bringing the email address forward).
2599 <sect1 id="f-Uploaders">
2600 <heading><tt>Uploaders</tt></heading>
2603 List of the names and email addresses of co-maintainers of
2604 the package, if any. If the package has other maintainers
2605 beside the one named in the
2606 <qref id="f-Maintainer">Maintainer field</qref>, their
2607 names and email addresses should be listed here. The
2608 format is the same as that of the Maintainer tag, and
2609 multiple entries should be comma separated. Currently,
2610 this field is restricted to a single line of data. This
2611 is an optional field.
2614 Any parser that interprets the Uploaders field in
2615 <file>debian/control</file> must permit it to span multiple
2616 lines. Line breaks in an Uploaders field that spans multiple
2617 lines are not significant and the semantics of the field are
2618 the same as if the line breaks had not been present.
2622 <sect1 id="f-Changed-By">
2623 <heading><tt>Changed-By</tt></heading>
2626 The name and email address of the person who changed the
2627 said package. Usually the name of the maintainer.
2628 All the rules for the Maintainer field apply here, too.
2632 <sect1 id="f-Section">
2633 <heading><tt>Section</tt></heading>
2636 This field specifies an application area into which the package
2637 has been classified. See <ref id="subsections">.
2641 When it appears in the <file>debian/control</file> file,
2642 it gives the value for the subfield of the same name in
2643 the <tt>Files</tt> field of the <file>.changes</file> file.
2644 It also gives the default for the same field in the binary
2649 <sect1 id="f-Priority">
2650 <heading><tt>Priority</tt></heading>
2653 This field represents how important that it is that the user
2654 have the package installed. See <ref id="priorities">.
2658 When it appears in the <file>debian/control</file> file,
2659 it gives the value for the subfield of the same name in
2660 the <tt>Files</tt> field of the <file>.changes</file> file.
2661 It also gives the default for the same field in the binary
2666 <sect1 id="f-Package">
2667 <heading><tt>Package</tt></heading>
2670 The name of the binary package.
2674 Package names must consist only of lower case letters
2675 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2676 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2677 They must be at least two characters long and must start
2678 with an alphanumeric character.
2682 <sect1 id="f-Architecture">
2683 <heading><tt>Architecture</tt></heading>
2686 Depending on context and the control file used, the
2687 <tt>Architecture</tt> field can include the following sets of
2690 <item>A unique single word identifying a Debian machine
2691 architecture, see <ref id="arch-spec">.
2692 <item><tt>all</tt>, which indicates an
2693 architecture-independent package.
2694 <item><tt>any</tt>, which indicates a package available
2695 for building on any architecture.
2696 <item><tt>source</tt>, which indicates a source package.
2701 In the main <file>debian/control</file> file in the source
2702 package, or in the source package control file
2703 <file>.dsc</file>, one may specify a list of architectures
2704 separated by spaces, or the special values <tt>any</tt> or
2709 Specifying <tt>any</tt> indicates that the source package
2710 isn't dependent on any particular architecture and should
2711 compile fine on any one. The produced binary package(s)
2712 will be specific to whatever the current build architecture
2714 This is the most often used setting, and is recommended
2715 for new packages that aren't <tt>Architecture: all</tt>.
2720 Specifying a list of architectures indicates that the source
2721 will build an architecture-dependent package, and will only
2722 work correctly on the listed architectures.<footnote>
2723 This is a setting used for a minority of cases where the
2724 program is not portable. Generally, it should not be used
2730 In a <file>.changes</file> file, the <tt>Architecture</tt>
2731 field lists the architecture(s) of the package(s)
2732 currently being uploaded. This will be a list; if the
2733 source for the package is also being uploaded, the special
2734 entry <tt>source</tt> is also present.
2738 See <ref id="debianrules"> for information how to get the
2739 architecture for the build process.
2743 <sect1 id="f-Essential">
2744 <heading><tt>Essential</tt></heading>
2747 This is a boolean field which may occur only in the
2748 control file of a binary package or in a per-package fields
2749 paragraph of a main source control data file.
2753 If set to <tt>yes</tt> then the package management system
2754 will refuse to remove the package (upgrading and replacing
2755 it is still possible). The other possible value is <tt>no</tt>,
2756 which is the same as not having the field at all.
2761 <heading>Package interrelationship fields:
2762 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2763 <tt>Recommends</tt>, <tt>Suggests</tt>,
2764 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2765 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2769 These fields describe the package's relationships with
2770 other packages. Their syntax and semantics are described
2771 in <ref id="relationships">.</p>
2774 <sect1 id="f-Standards-Version">
2775 <heading><tt>Standards-Version</tt></heading>
2778 The most recent version of the standards (the policy
2779 manual and associated texts) with which the package
2784 The version number has four components: major and minor
2785 version number and major and minor patch level. When the
2786 standards change in a way that requires every package to
2787 change the major number will be changed. Significant
2788 changes that will require work in many packages will be
2789 signaled by a change to the minor number. The major patch
2790 level will be changed for any change to the meaning of the
2791 standards, however small; the minor patch level will be
2792 changed when only cosmetic, typographical or other edits
2793 are made which neither change the meaning of the document
2794 nor affect the contents of packages.
2798 Thus only the first three components of the policy version
2799 are significant in the <em>Standards-Version</em> control
2800 field, and so either these three components or the all
2801 four components may be specified.<footnote>
2802 In the past, people specified the full version number
2803 in the Standards-Version field, for example "2.3.0.0".
2804 Since minor patch-level changes don't introduce new
2805 policy, it was thought it would be better to relax
2806 policy and only require the first 3 components to be
2807 specified, in this example "2.3.0". All four
2808 components may still be used if someone wishes to do so.
2814 <sect1 id="f-Version">
2815 <heading><tt>Version</tt></heading>
2818 The version number of a package. The format is:
2819 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2823 The three components here are:
2825 <tag><var>epoch</var></tag>
2828 This is a single (generally small) unsigned integer. It
2829 may be omitted, in which case zero is assumed. If it is
2830 omitted then the <var>upstream_version</var> may not
2835 It is provided to allow mistakes in the version numbers
2836 of older versions of a package, and also a package's
2837 previous version numbering schemes, to be left behind.
2841 <tag><var>upstream_version</var></tag>
2844 This is the main part of the version number. It is
2845 usually the version number of the original ("upstream")
2846 package from which the <file>.deb</file> file has been made,
2847 if this is applicable. Usually this will be in the same
2848 format as that specified by the upstream author(s);
2849 however, it may need to be reformatted to fit into the
2850 package management system's format and comparison
2855 The comparison behavior of the package management system
2856 with respect to the <var>upstream_version</var> is
2857 described below. The <var>upstream_version</var>
2858 portion of the version number is mandatory.
2862 The <var>upstream_version</var> may contain only
2863 alphanumerics<footnote>
2864 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2866 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2867 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2868 tilde) and should start with a digit. If there is no
2869 <var>debian_revision</var> then hyphens are not allowed;
2870 if there is no <var>epoch</var> then colons are not
2875 <tag><var>debian_revision</var></tag>
2878 This part of the version number specifies the version of
2879 the Debian package based on the upstream version. It
2880 may contain only alphanumerics and the characters
2881 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2882 tilde) and is compared in the same way as the
2883 <var>upstream_version</var> is.
2887 It is optional; if it isn't present then the
2888 <var>upstream_version</var> may not contain a hyphen.
2889 This format represents the case where a piece of
2890 software was written specifically to be turned into a
2891 Debian package, and so there is only one "debianisation"
2892 of it and therefore no revision indication is required.
2896 It is conventional to restart the
2897 <var>debian_revision</var> at <tt>1</tt> each time the
2898 <var>upstream_version</var> is increased.
2902 The package management system will break the version
2903 number apart at the last hyphen in the string (if there
2904 is one) to determine the <var>upstream_version</var> and
2905 <var>debian_revision</var>. The absence of a
2906 <var>debian_revision</var> is equivalent to a
2907 <var>debian_revision</var> of <tt>0</tt>.
2914 When comparing two version numbers, first the <var>epoch</var>
2915 of each are compared, then the <var>upstream_version</var> if
2916 <var>epoch</var> is equal, and then <var>debian_revision</var>
2917 if <var>upstream_version</var> is also equal.
2918 <var>epoch</var> is compared numerically. The
2919 <var>upstream_version</var> and <var>debian_revision</var>
2920 parts are compared by the package management system using the
2921 following algorithm:
2925 The strings are compared from left to right.
2929 First the initial part of each string consisting entirely of
2930 non-digit characters is determined. These two parts (one of
2931 which may be empty) are compared lexically. If a difference
2932 is found it is returned. The lexical comparison is a
2933 comparison of ASCII values modified so that all the letters
2934 sort earlier than all the non-letters and so that a tilde
2935 sorts before anything, even the end of a part. For example,
2936 the following parts are in sorted order from earliest to
2937 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2938 <tt>a</tt>.<footnote>
2939 One common use of <tt>~</tt> is for upstream pre-releases.
2940 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2941 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2946 Then the initial part of the remainder of each string which
2947 consists entirely of digit characters is determined. The
2948 numerical values of these two parts are compared, and any
2949 difference found is returned as the result of the comparison.
2950 For these purposes an empty string (which can only occur at
2951 the end of one or both version strings being compared) counts
2956 These two steps (comparing and removing initial non-digit
2957 strings and initial digit strings) are repeated until a
2958 difference is found or both strings are exhausted.
2962 Note that the purpose of epochs is to allow us to leave behind
2963 mistakes in version numbering, and to cope with situations
2964 where the version numbering scheme changes. It is
2965 <em>not</em> intended to cope with version numbers containing
2966 strings of letters which the package management system cannot
2967 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2968 silly orderings (the author of this manual has heard of a
2969 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2970 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2971 <tt>2</tt> and so forth).
2975 <sect1 id="f-Description">
2976 <heading><tt>Description</tt></heading>
2979 In a source or binary control file, the <tt>Description</tt>
2980 field contains a description of the binary package, consisting
2981 of two parts, the synopsis or the short description, and the
2982 long description. The field's format is as follows:
2987 Description: <single line synopsis>
2988 <extended description over several lines>
2993 The lines in the extended description can have these formats:
2999 Those starting with a single space are part of a paragraph.
3000 Successive lines of this form will be word-wrapped when
3001 displayed. The leading space will usually be stripped off.
3005 Those starting with two or more spaces. These will be
3006 displayed verbatim. If the display cannot be panned
3007 horizontally, the displaying program will line wrap them "hard"
3008 (i.e., without taking account of word breaks). If it can they
3009 will be allowed to trail off to the right. None, one or two
3010 initial spaces may be deleted, but the number of spaces
3011 deleted from each line will be the same (so that you can have
3012 indenting work correctly, for example).
3016 Those containing a single space followed by a single full stop
3017 character. These are rendered as blank lines. This is the
3018 <em>only</em> way to get a blank line<footnote>
3019 Completely empty lines will not be rendered as blank lines.
3020 Instead, they will cause the parser to think you're starting
3021 a whole new record in the control file, and will therefore
3022 likely abort with an error.
3027 Those containing a space, a full stop and some more characters.
3028 These are for future expansion. Do not use them.
3034 Do not use tab characters. Their effect is not predictable.
3038 See <ref id="descriptions"> for further information on this.
3042 In a <file>.changes</file> file, the <tt>Description</tt> field
3043 contains a summary of the descriptions for the packages being
3048 The part of the field before the first newline is empty;
3049 thereafter each line has the name of a binary package and
3050 the summary description line from that binary package.
3051 Each line is indented by one space.
3056 <sect1 id="f-Distribution">
3057 <heading><tt>Distribution</tt></heading>
3060 In a <file>.changes</file> file or parsed changelog output
3061 this contains the (space-separated) name(s) of the
3062 distribution(s) where this version of the package should
3063 be installed. Valid distributions are determined by the
3064 archive maintainers.<footnote>
3065 Current distribution names are:
3066 <taglist compact="compact">
3067 <tag><em>stable</em></tag>
3069 This is the current "released" version of Debian
3070 GNU/Linux. Once the distribution is
3071 <em>stable</em> only security fixes and other
3072 major bug fixes are allowed. When changes are
3073 made to this distribution, the release number is
3074 increased (for example: 2.2r1 becomes 2.2r2 then
3078 <tag><em>unstable</em></tag>
3080 This distribution value refers to the
3081 <em>developmental</em> part of the Debian
3082 distribution tree. New packages, new upstream
3083 versions of packages and bug fixes go into the
3084 <em>unstable</em> directory tree. Download from
3085 this distribution at your own risk.
3088 <tag><em>testing</em></tag>
3090 This distribution value refers to the
3091 <em>testing</em> part of the Debian distribution
3092 tree. It receives its packages from the
3093 unstable distribution after a short time lag to
3094 ensure that there are no major issues with the
3095 unstable packages. It is less prone to breakage
3096 than unstable, but still risky. It is not
3097 possible to upload packages directly to
3101 <tag><em>frozen</em></tag>
3103 From time to time, the <em>testing</em>
3104 distribution enters a state of "code-freeze" in
3105 anticipation of release as a <em>stable</em>
3106 version. During this period of testing only
3107 fixes for existing or newly-discovered bugs will
3108 be allowed. The exact details of this stage are
3109 determined by the Release Manager.
3112 <tag><em>experimental</em></tag>
3114 The packages with this distribution value are
3115 deemed by their maintainers to be high
3116 risk. Oftentimes they represent early beta or
3117 developmental packages from various sources that
3118 the maintainers want people to try, but are not
3119 ready to be a part of the other parts of the
3120 Debian distribution tree. Download at your own
3126 You should list <em>all</em> distributions that the
3127 package should be installed into.
3131 More information is available in the Debian Developer's
3132 Reference, section "The Debian archive".
3139 <heading><tt>Date</tt></heading>
3142 This field includes the date the package was built or last edited.
3146 The value of this field is usually extracted from the
3147 <file>debian/changelog</file> file - see
3148 <ref id="dpkgchangelog">).
3152 <sect1 id="f-Format">
3153 <heading><tt>Format</tt></heading>
3156 This field specifies a format revision for the file.
3157 The most current format described in the Policy Manual
3158 is version <strong>1.5</strong>. The syntax of the
3159 format value is the same as that of a package version
3160 number except that no epoch or Debian revision is allowed
3161 - see <ref id="f-Version">.
3165 <sect1 id="f-Urgency">
3166 <heading><tt>Urgency</tt></heading>
3169 This is a description of how important it is to upgrade to
3170 this version from previous ones. It consists of a single
3171 keyword taking one of the values <tt>low</tt>,
3172 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3173 <tt>critical</tt><footnote>
3174 Other urgency values are supported with configuration
3175 changes in the archive software but are not used in Debian.
3176 The urgency affects how quickly a package will be considered
3177 for inclusion into the <tt>testing</tt> distribution and
3178 gives an indication of the importance of any fixes included
3179 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3180 treated as synonymous.
3181 </footnote> (not case-sensitive) followed by an optional
3182 commentary (separated by a space) which is usually in
3183 parentheses. For example:
3186 Urgency: low (HIGH for users of diversions)
3192 The value of this field is usually extracted from the
3193 <file>debian/changelog</file> file - see
3194 <ref id="dpkgchangelog">.
3198 <sect1 id="f-Changes">
3199 <heading><tt>Changes</tt></heading>
3202 This field contains the human-readable changes data, describing
3203 the differences between the last version and the current one.
3207 There should be nothing in this field before the first
3208 newline; all the subsequent lines must be indented by at
3209 least one space; blank lines must be represented by a line
3210 consisting only of a space and a full stop.
3214 The value of this field is usually extracted from the
3215 <file>debian/changelog</file> file - see
3216 <ref id="dpkgchangelog">).
3220 Each version's change information should be preceded by a
3221 "title" line giving at least the version, distribution(s)
3222 and urgency, in a human-readable way.
3226 If data from several versions is being returned the entry
3227 for the most recent version should be returned first, and
3228 entries should be separated by the representation of a
3229 blank line (the "title" line may also be followed by the
3230 representation of blank line).
3234 <sect1 id="f-Binary">
3235 <heading><tt>Binary</tt></heading>
3238 This field is a list of binary packages.
3242 When it appears in the <file>.dsc</file> file it is the list
3243 of binary packages which a source package can produce. It
3244 does not necessarily produce all of these binary packages
3245 for every architecture. The source control file doesn't
3246 contain details of which architectures are appropriate for
3247 which of the binary packages.
3251 When it appears in a <file>.changes</file> file it lists the
3252 names of the binary packages actually being uploaded.
3256 The syntax is a list of binary packages separated by
3258 A space after each comma is conventional.
3259 </footnote>. Currently the packages must be separated using
3260 only spaces in the <file>.changes</file> file.
3264 <sect1 id="f-Installed-Size">
3265 <heading><tt>Installed-Size</tt></heading>
3268 This field appears in the control files of binary
3269 packages, and in the <file>Packages</file> files. It gives
3270 the total amount of disk space required to install the
3275 The disk space is represented in kilobytes as a simple
3280 <sect1 id="f-Files">
3281 <heading><tt>Files</tt></heading>
3284 This field contains a list of files with information about
3285 each one. The exact information and syntax varies with
3286 the context. In all cases the part of the field
3287 contents on the same line as the field name is empty. The
3288 remainder of the field is one line per file, each line
3289 being indented by one space and containing a number of
3290 sub-fields separated by spaces.
3294 In the <file>.dsc</file> file, each line contains the MD5
3295 checksum, size and filename of the tar file and (if applicable)
3296 diff file which make up the remainder of the source
3298 That is, the parts which are not the <tt>.dsc</tt>.
3300 The exact forms of the filenames are described
3301 in <ref id="pkg-sourcearchives">.
3305 In the <file>.changes</file> file this contains one line per
3306 file being uploaded. Each line contains the MD5 checksum,
3307 size, section and priority and the filename.
3308 The <qref id="f-Section">section</qref>
3309 and <qref id="f-Priority">priority</qref>
3310 are the values of the corresponding fields in
3311 the main source control file. If no section or priority is
3312 specified then <tt>-</tt> should be used, though section
3313 and priority values must be specified for new packages to
3314 be installed properly.
3318 The special value <tt>byhand</tt> for the section in a
3319 <tt>.changes</tt> file indicates that the file in question
3320 is not an ordinary package file and must by installed by
3321 hand by the distribution maintainers. If the section is
3322 <tt>byhand</tt> the priority should be <tt>-</tt>.
3326 If a new Debian revision of a package is being shipped and
3327 no new original source archive is being distributed the
3328 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3329 entry for the original source archive
3330 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3331 but the <file>.changes</file> file should leave it out. In
3332 this case the original source archive on the distribution
3333 site must match exactly, byte-for-byte, the original
3334 source archive which was used to generate the
3335 <file>.dsc</file> file and diff which are being uploaded.</p>
3338 <sect1 id="f-Closes">
3339 <heading><tt>Closes</tt></heading>
3342 A space-separated list of bug report numbers that the upload
3343 governed by the .changes file closes.
3347 <sect1 id="f-Homepage">
3348 <heading><tt>Homepage</tt></heading>
3351 The URL of the web site for this package, preferably (when
3352 applicable) the site from which the original source can be
3353 obtained and any additional upstream documentation or
3354 information may be found. The content of this field is a
3355 simple URL without any surrounding characters such as
3363 <heading>User-defined fields</heading>
3366 Additional user-defined fields may be added to the
3367 source package control file. Such fields will be
3368 ignored, and not copied to (for example) binary or
3369 source package control files or upload control files.
3373 If you wish to add additional unsupported fields to
3374 these output files you should use the mechanism
3379 Fields in the main source control information file with
3380 names starting <tt>X</tt>, followed by one or more of
3381 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3382 be copied to the output files. Only the part of the
3383 field name after the hyphen will be used in the output
3384 file. Where the letter <tt>B</tt> is used the field
3385 will appear in binary package control files, where the
3386 letter <tt>S</tt> is used in source package control
3387 files and where <tt>C</tt> is used in upload control
3388 (<tt>.changes</tt>) files.
3392 For example, if the main source information control file
3395 XBS-Comment: I stand between the candle and the star.
3397 then the binary and source package control files will contain the
3400 Comment: I stand between the candle and the star.
3409 <chapt id="maintainerscripts">
3410 <heading>Package maintainer scripts and installation procedure</heading>
3413 <heading>Introduction to package maintainer scripts</heading>
3416 It is possible to supply scripts as part of a package which
3417 the package management system will run for you when your
3418 package is installed, upgraded or removed.
3422 These scripts are the files <prgn>preinst</prgn>,
3423 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3424 <prgn>postrm</prgn> in the control area of the package.
3425 They must be proper executable files; if they are scripts
3426 (which is recommended), they must start with the usual
3427 <tt>#!</tt> convention. They should be readable and
3428 executable by anyone, and must not be world-writable.
3432 The package management system looks at the exit status from
3433 these scripts. It is important that they exit with a
3434 non-zero status if there is an error, so that the package
3435 management system can stop its processing. For shell
3436 scripts this means that you <em>almost always</em> need to
3437 use <tt>set -e</tt> (this is usually true when writing shell
3438 scripts, in fact). It is also important, of course, that
3439 they don't exit with a non-zero status if everything went
3444 Additionally, packages interacting with users using
3445 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3446 install a <prgn>config</prgn> script in the control area,
3447 see <ref id="maintscriptprompt"> for details.
3451 When a package is upgraded a combination of the scripts from
3452 the old and new packages is called during the upgrade
3453 procedure. If your scripts are going to be at all
3454 complicated you need to be aware of this, and may need to
3455 check the arguments to your scripts.
3459 Broadly speaking the <prgn>preinst</prgn> is called before
3460 (a particular version of) a package is installed, and the
3461 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3462 before (a version of) a package is removed and the
3463 <prgn>postrm</prgn> afterwards.
3467 Programs called from maintainer scripts should not normally
3468 have a path prepended to them. Before installation is
3469 started, the package management system checks to see if the
3470 programs <prgn>ldconfig</prgn>,
3471 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3472 and <prgn>update-rc.d</prgn> can be found via the
3473 <tt>PATH</tt> environment variable. Those programs, and any
3474 other program that one would expect to be in the
3475 <tt>PATH</tt>, should thus be invoked without an absolute
3476 pathname. Maintainer scripts should also not reset the
3477 <tt>PATH</tt>, though they might choose to modify it by
3478 prepending or appending package-specific directories. These
3479 considerations really apply to all shell scripts.</p>
3482 <sect id="idempotency">
3483 <heading>Maintainer scripts idempotency</heading>
3486 It is necessary for the error recovery procedures that the
3487 scripts be idempotent. This means that if it is run
3488 successfully, and then it is called again, it doesn't bomb
3489 out or cause any harm, but just ensures that everything is
3490 the way it ought to be. If the first call failed, or
3491 aborted half way through for some reason, the second call
3492 should merely do the things that were left undone the first
3493 time, if any, and exit with a success status if everything
3495 This is so that if an error occurs, the user interrupts
3496 <prgn>dpkg</prgn> or some other unforeseen circumstance
3497 happens you don't leave the user with a badly-broken
3498 package when <prgn>dpkg</prgn> attempts to repeat the
3504 <sect id="controllingterminal">
3505 <heading>Controlling terminal for maintainer scripts</heading>
3508 The maintainer scripts are guaranteed to run with a
3509 controlling terminal and can interact with the user.
3510 Because these scripts may be executed with standard output
3511 redirected into a pipe for logging purposes, Perl scripts
3512 should set unbuffered output by setting <tt>$|=1</tt> so
3513 that the output is printed immediately rather than being
3517 <sect id="exitstatus">
3518 <heading>Exit status</heading>
3521 Each script must return a zero exit status for
3522 success, or a nonzero one for failure, since the package
3523 management system looks for the exit status of these scripts
3524 and determines what action to take next based on that datum.
3528 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3533 <list compact="compact">
3535 <var>new-preinst</var> <tt>install</tt>
3538 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3541 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3544 <var>old-preinst</var> <tt>abort-upgrade</tt>
3545 <var>new-version</var>
3550 <list compact="compact">
3552 <var>postinst</var> <tt>configure</tt>
3553 <var>most-recently-configured-version</var>
3556 <var>old-postinst</var> <tt>abort-upgrade</tt>
3557 <var>new-version</var>
3560 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3561 <tt>in-favour</tt> <var>package</var>
3562 <var>new-version</var>
3565 <var>postinst</var> <tt>abort-remove</tt>
3568 <var>deconfigured's-postinst</var>
3569 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3570 <var>failed-install-package</var> <var>version</var>
3571 [<tt>removing</tt> <var>conflicting-package</var>
3577 <list compact="compact">
3579 <var>prerm</var> <tt>remove</tt>
3582 <var>old-prerm</var> <tt>upgrade</tt>
3583 <var>new-version</var>
3586 <var>new-prerm</var> <tt>failed-upgrade</tt>
3587 <var>old-version</var>
3590 <var>conflictor's-prerm</var> <tt>remove</tt>
3591 <tt>in-favour</tt> <var>package</var>
3592 <var>new-version</var>
3595 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3596 <tt>in-favour</tt> <var>package-being-installed</var>
3597 <var>version</var> [<tt>removing</tt>
3598 <var>conflicting-package</var>
3604 <list compact="compact">
3606 <var>postrm</var> <tt>remove</tt>
3609 <var>postrm</var> <tt>purge</tt>
3612 <var>old-postrm</var> <tt>upgrade</tt>
3613 <var>new-version</var>
3616 <var>new-postrm</var> <tt>failed-upgrade</tt>
3617 <var>old-version</var>
3620 <var>new-postrm</var> <tt>abort-install</tt>
3623 <var>new-postrm</var> <tt>abort-install</tt>
3624 <var>old-version</var>
3627 <var>new-postrm</var> <tt>abort-upgrade</tt>
3628 <var>old-version</var>
3631 <var>disappearer's-postrm</var> <tt>disappear</tt>
3632 <var>overwriter</var>
3633 <var>overwriter-version</var>
3639 <sect id="unpackphase">
3640 <heading>Details of unpack phase of installation or upgrade</heading>
3643 The procedure on installation/upgrade/overwrite/disappear
3644 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3645 stage of <tt>dpkg --install</tt>) is as follows. In each
3646 case, if a major error occurs (unless listed below) the
3647 actions are, in general, run backwards - this means that the
3648 maintainer scripts are run with different arguments in
3649 reverse order. These are the "error unwind" calls listed
3656 If a version of the package is already installed, call
3657 <example compact="compact">
3658 <var>old-prerm</var> upgrade <var>new-version</var>
3662 If the script runs but exits with a non-zero
3663 exit status, <prgn>dpkg</prgn> will attempt:
3664 <example compact="compact">
3665 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3667 If this works, the upgrade continues. If this
3668 does not work, the error unwind:
3669 <example compact="compact">
3670 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3672 If this works, then the old-version is
3673 "Installed", if not, the old version is in a
3674 "Failed-Config" state.
3680 If a "conflicting" package is being removed at the same time,
3681 or if any package will be broken (due to <tt>Breaks</tt>):
3684 If <tt>--auto-deconfigure</tt> is
3685 specified, call, for each package to be deconfigured
3686 due to <tt>Breaks</tt>:
3687 <example compact="compact">
3688 <var>deconfigured's-prerm</var> deconfigure \
3689 in-favour <var>package-being-installed</var> <var>version</var>
3692 <example compact="compact">
3693 <var>deconfigured's-postinst</var> abort-deconfigure \
3694 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3696 The deconfigured packages are marked as
3697 requiring configuration, so that if
3698 <tt>--install</tt> is used they will be
3699 configured again if possible.
3702 If any packages depended on a conflicting
3703 package being removed and <tt>--auto-deconfigure</tt> is
3704 specified, call, for each such package:
3705 <example compact="compact">
3706 <var>deconfigured's-prerm</var> deconfigure \
3707 in-favour <var>package-being-installed</var> <var>version</var> \
3708 removing <var>conflicting-package</var> <var>version</var>
3711 <example compact="compact">
3712 <var>deconfigured's-postinst</var> abort-deconfigure \
3713 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3714 removing <var>conflicting-package</var> <var>version</var>
3716 The deconfigured packages are marked as
3717 requiring configuration, so that if
3718 <tt>--install</tt> is used they will be
3719 configured again if possible.
3722 To prepare for removal of each conflicting package, call:
3723 <example compact="compact">
3724 <var>conflictor's-prerm</var> remove \
3725 in-favour <var>package</var> <var>new-version</var>
3728 <example compact="compact">
3729 <var>conflictor's-postinst</var> abort-remove \
3730 in-favour <var>package</var> <var>new-version</var>
3739 If the package is being upgraded, call:
3740 <example compact="compact">
3741 <var>new-preinst</var> upgrade <var>old-version</var>
3743 If this fails, we call:
3745 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3752 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3754 is called. If this works, then the old version
3755 is in an "Installed" state, or else it is left
3756 in an "Unpacked" state.
3761 If it fails, then the old version is left
3762 in an "Half-Installed" state.
3769 Otherwise, if the package had some configuration
3770 files from a previous version installed (i.e., it
3771 is in the "configuration files only" state):
3772 <example compact="compact">
3773 <var>new-preinst</var> install <var>old-version</var>
3777 <var>new-postrm</var> abort-install <var>old-version</var>
3779 If this fails, the package is left in a
3780 "Half-Installed" state, which requires a
3781 reinstall. If it works, the packages is left in
3782 a "Config Files" state.
3785 Otherwise (i.e., the package was completely purged):
3786 <example compact="compact">
3787 <var>new-preinst</var> install
3790 <example compact="compact">
3791 <var>new-postrm</var> abort-install
3793 If the error-unwind fails, the package is in a
3794 "Half Installed" phase, and requires a
3795 reinstall. If the error unwind works, the
3796 package is in a not installed state.
3803 The new package's files are unpacked, overwriting any
3804 that may be on the system already, for example any
3805 from the old version of the same package or from
3806 another package. Backups of the old files are kept
3807 temporarily, and if anything goes wrong the package
3808 management system will attempt to put them back as
3809 part of the error unwind.
3813 It is an error for a package to contain files which
3814 are on the system in another package, unless
3815 <tt>Replaces</tt> is used (see <ref id="replaces">).
3817 The following paragraph is not currently the case:
3818 Currently the <tt>- - force-overwrite</tt> flag is
3819 enabled, downgrading it to a warning, but this may not
3825 It is a more serious error for a package to contain a
3826 plain file or other kind of non-directory where another
3827 package has a directory (again, unless
3828 <tt>Replaces</tt> is used). This error can be
3829 overridden if desired using
3830 <tt>--force-overwrite-dir</tt>, but this is not
3835 Packages which overwrite each other's files produce
3836 behavior which, though deterministic, is hard for the
3837 system administrator to understand. It can easily
3838 lead to "missing" programs if, for example, a package
3839 is installed which overwrites a file from another
3840 package, and is then removed again.<footnote>
3841 Part of the problem is due to what is arguably a
3842 bug in <prgn>dpkg</prgn>.
3847 A directory will never be replaced by a symbolic link
3848 to a directory or vice versa; instead, the existing
3849 state (symlink or not) will be left alone and
3850 <prgn>dpkg</prgn> will follow the symlink if there is
3859 If the package is being upgraded, call
3860 <example compact="compact">
3861 <var>old-postrm</var> upgrade <var>new-version</var>
3865 If this fails, <prgn>dpkg</prgn> will attempt:
3866 <example compact="compact">
3867 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3869 If this works, installation continues. If not,
3871 <example compact="compact">
3872 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3874 If this fails, the old version is left in an
3875 "Half Installed" state. If it works, dpkg now
3877 <example compact="compact">
3878 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3880 If this fails, the old version is left in an
3881 "Half Installed" state. If it works, dpkg now
3883 <example compact="compact">
3884 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3886 If this fails, the old version is in an
3893 This is the point of no return - if
3894 <prgn>dpkg</prgn> gets this far, it won't back off
3895 past this point if an error occurs. This will
3896 leave the package in a fairly bad state, which
3897 will require a successful re-installation to clear
3898 up, but it's when <prgn>dpkg</prgn> starts doing
3899 things that are irreversible.
3904 Any files which were in the old version of the package
3905 but not in the new are removed.
3909 The new file list replaces the old.
3913 The new maintainer scripts replace the old.
3917 Any packages all of whose files have been overwritten
3918 during the installation, and which aren't required for
3919 dependencies, are considered to have been removed.
3920 For each such package
3923 <prgn>dpkg</prgn> calls:
3924 <example compact="compact">
3925 <var>disappearer's-postrm</var> disappear \
3926 <var>overwriter</var> <var>overwriter-version</var>
3930 The package's maintainer scripts are removed.
3933 It is noted in the status database as being in a
3934 sane state, namely not installed (any conffiles
3935 it may have are ignored, rather than being
3936 removed by <prgn>dpkg</prgn>). Note that
3937 disappearing packages do not have their prerm
3938 called, because <prgn>dpkg</prgn> doesn't know
3939 in advance that the package is going to
3946 Any files in the package we're unpacking that are also
3947 listed in the file lists of other packages are removed
3948 from those lists. (This will lobotomize the file list
3949 of the "conflicting" package if there is one.)
3953 The backup files made during installation, above, are
3959 The new package's status is now sane, and recorded as
3964 Here is another point of no return - if the
3965 conflicting package's removal fails we do not unwind
3966 the rest of the installation; the conflicting package
3967 is left in a half-removed limbo.
3972 If there was a conflicting package we go and do the
3973 removal actions (described below), starting with the
3974 removal of the conflicting package's files (any that
3975 are also in the package being installed have already
3976 been removed from the conflicting package's file list,
3977 and so do not get removed now).
3983 <sect id="configdetails"><heading>Details of configuration</heading>
3986 When we configure a package (this happens with <tt>dpkg
3987 --install</tt> and <tt>dpkg --configure</tt>), we first
3988 update any <tt>conffile</tt>s and then call:
3989 <example compact="compact">
3990 <var>postinst</var> configure <var>most-recently-configured-version</var>
3995 No attempt is made to unwind after errors during
3996 configuration. If the configuration fails, the package is in
3997 a "Failed Config" state, and an error message is generated.
4001 If there is no most recently configured version
4002 <prgn>dpkg</prgn> will pass a null argument.
4005 Historical note: Truly ancient (pre-1997) versions of
4006 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4007 (including the angle brackets) in this case. Even older
4008 ones did not pass a second argument at all, under any
4009 circumstance. Note that upgrades using such an old dpkg
4010 version are unlikely to work for other reasons, even if
4011 this old argument behavior is handled by your postinst script.
4017 <sect id="removedetails"><heading>Details of removal and/or
4018 configuration purging</heading>
4024 <example compact="compact">
4025 <var>prerm</var> remove
4029 If prerm fails during replacement due to conflict
4031 <var>conflictor's-postinst</var> abort-remove \
4032 in-favour <var>package</var> <var>new-version</var>
4036 <var>postinst</var> abort-remove
4040 If this fails, the package is in a "Failed-Config"
4041 state, or else it remains "Installed".
4045 The package's files are removed (except <tt>conffile</tt>s).
4048 <example compact="compact">
4049 <var>postrm</var> remove
4053 If it fails, there's no error unwind, and the package is in
4054 an "Half-Installed" state.
4059 All the maintainer scripts except the <prgn>postrm</prgn>
4064 If we aren't purging the package we stop here. Note
4065 that packages which have no <prgn>postrm</prgn> and no
4066 <tt>conffile</tt>s are automatically purged when
4067 removed, as there is no difference except for the
4068 <prgn>dpkg</prgn> status.
4072 The <tt>conffile</tt>s and any backup files
4073 (<tt>~</tt>-files, <tt>#*#</tt> files,
4074 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4079 <example compact="compact">
4080 <var>postrm</var> purge
4084 If this fails, the package remains in a "Config-Files"
4089 The package's file list is removed.
4098 <chapt id="relationships">
4099 <heading>Declaring relationships between packages</heading>
4101 <sect id="depsyntax">
4102 <heading>Syntax of relationship fields</heading>
4105 These fields all have a uniform syntax. They are a list of
4106 package names separated by commas.
4110 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4111 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4112 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4113 control file fields of the package, which declare
4114 dependencies on other packages, the package names listed may
4115 also include lists of alternative package names, separated
4116 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4117 if any one of the alternative packages is installed, that
4118 part of the dependency is considered to be satisfied.
4122 All of the fields except for <tt>Provides</tt> may restrict
4123 their applicability to particular versions of each named
4124 package. This is done in parentheses after each individual
4125 package name; the parentheses should contain a relation from
4126 the list below followed by a version number, in the format
4127 described in <ref id="f-Version">.
4131 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4132 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4133 strictly earlier, earlier or equal, exactly equal, later or
4134 equal and strictly later, respectively. The deprecated
4135 forms <tt><</tt> and <tt>></tt> were used to mean
4136 earlier/later or equal, rather than strictly earlier/later,
4137 so they should not appear in new packages (though
4138 <prgn>dpkg</prgn> still supports them).
4142 Whitespace may appear at any point in the version
4143 specification subject to the rules in <ref
4144 id="controlsyntax">, and must appear where it's necessary to
4145 disambiguate; it is not otherwise significant. All of the
4146 relationship fields may span multiple lines. For
4147 consistency and in case of future changes to
4148 <prgn>dpkg</prgn> it is recommended that a single space be
4149 used after a version relationship and before a version
4150 number; it is also conventional to put a single space after
4151 each comma, on either side of each vertical bar, and before
4152 each open parenthesis. When wrapping a relationship field, it
4153 is conventional to do so after a comma and before the space
4154 following that comma.
4158 For example, a list of dependencies might appear as:
4159 <example compact="compact">
4162 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4167 All fields that specify build-time relationships
4168 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4169 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4170 may be restricted to a certain set of architectures. This
4171 is indicated in brackets after each individual package name and
4172 the optional version specification. The brackets enclose a
4173 list of Debian architecture names separated by whitespace.
4174 Exclamation marks may be prepended to each of the names.
4175 (It is not permitted for some names to be prepended with
4176 exclamation marks while others aren't.) If the current Debian
4177 host architecture is not in this list and there are no
4178 exclamation marks in the list, or it is in the list with a
4179 prepended exclamation mark, the package name and the
4180 associated version specification are ignored completely for
4181 the purposes of defining the relationships.
4186 <example compact="compact">
4188 Build-Depends-Indep: texinfo
4189 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4190 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4195 Note that the binary package relationship fields such as
4196 <tt>Depends</tt> appear in one of the binary package
4197 sections of the control file, whereas the build-time
4198 relationships such as <tt>Build-Depends</tt> appear in the
4199 source package section of the control file (which is the
4204 <sect id="binarydeps">
4205 <heading>Binary Dependencies - <tt>Depends</tt>,
4206 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4207 <tt>Pre-Depends</tt>
4211 Packages can declare in their control file that they have
4212 certain relationships to other packages - for example, that
4213 they may not be installed at the same time as certain other
4214 packages, and/or that they depend on the presence of others.
4218 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4219 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4220 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4224 These seven fields are used to declare a dependency
4225 relationship by one package on another. Except for
4226 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4227 depending (binary) package's control file.
4228 (<tt>Enhances</tt> appears in the recommending package's
4229 control file, and <tt>Breaks</tt> appears in the version of
4230 depended-on package which causes the named package to
4235 A <tt>Depends</tt> field takes effect <em>only</em> when a
4236 package is to be configured. It does not prevent a package
4237 being on the system in an unconfigured state while its
4238 dependencies are unsatisfied, and it is possible to replace
4239 a package whose dependencies are satisfied and which is
4240 properly installed with a different version whose
4241 dependencies are not and cannot be satisfied; when this is
4242 done the depending package will be left unconfigured (since
4243 attempts to configure it will give errors) and will not
4244 function properly. If it is necessary, a
4245 <tt>Pre-Depends</tt> field can be used, which has a partial
4246 effect even when a package is being unpacked, as explained
4247 in detail below. (The other three dependency fields,
4248 <tt>Recommends</tt>, <tt>Suggests</tt> and
4249 <tt>Enhances</tt>, are only used by the various front-ends
4250 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4251 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4255 For this reason packages in an installation run are usually
4256 all unpacked first and all configured later; this gives
4257 later versions of packages with dependencies on later
4258 versions of other packages the opportunity to have their
4259 dependencies satisfied.
4263 In case of circular dependencies, since installation or
4264 removal order honoring the dependency order can't be
4265 established, dependency loops are broken at some point
4266 (based on rules below), and some packages may not be able to
4267 rely on their dependencies being present when being
4268 installed or removed, depending on which side of the break
4269 of the circular dependency loop they happen to be on. If one
4270 of the packages in the loop has no postinst script, then the
4271 cycle will be broken at that package, so as to ensure that
4272 all postinst scripts run with the dependencies properly
4273 configured if this is possible. Otherwise the breaking point
4278 The <tt>Depends</tt> field thus allows package maintainers
4279 to impose an order in which packages should be configured.
4283 The meaning of the five dependency fields is as follows:
4285 <tag><tt>Depends</tt></tag>
4288 This declares an absolute dependency. A package will
4289 not be configured unless all of the packages listed in
4290 its <tt>Depends</tt> field have been correctly
4295 The <tt>Depends</tt> field should be used if the
4296 depended-on package is required for the depending
4297 package to provide a significant amount of
4302 The <tt>Depends</tt> field should also be used if the
4303 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4304 <prgn>postrm</prgn> scripts require the package to be
4305 present in order to run. Note, however, that the
4306 <prgn>postrm</prgn> cannot rely on any non-essential
4307 packages to be present during the <tt>purge</tt>
4311 <tag><tt>Recommends</tt></tag>
4314 This declares a strong, but not absolute, dependency.
4318 The <tt>Recommends</tt> field should list packages
4319 that would be found together with this one in all but
4320 unusual installations.
4324 <tag><tt>Suggests</tt></tag>
4326 This is used to declare that one package may be more
4327 useful with one or more others. Using this field
4328 tells the packaging system and the user that the
4329 listed packages are related to this one and can
4330 perhaps enhance its usefulness, but that installing
4331 this one without them is perfectly reasonable.
4334 <tag><tt>Enhances</tt></tag>
4336 This field is similar to Suggests but works in the
4337 opposite direction. It is used to declare that a
4338 package can enhance the functionality of another
4342 <tag><tt>Pre-Depends</tt></tag>
4345 This field is like <tt>Depends</tt>, except that it
4346 also forces <prgn>dpkg</prgn> to complete installation
4347 of the packages named before even starting the
4348 installation of the package which declares the
4349 pre-dependency, as follows:
4353 When a package declaring a pre-dependency is about to
4354 be <em>unpacked</em> the pre-dependency can be
4355 satisfied if the depended-on package is either fully
4356 configured, <em>or even if</em> the depended-on
4357 package(s) are only unpacked or half-configured,
4358 provided that they have been configured correctly at
4359 some point in the past (and not removed or partially
4360 removed since). In this case, both the
4361 previously-configured and currently unpacked or
4362 half-configured versions must satisfy any version
4363 clause in the <tt>Pre-Depends</tt> field.
4367 When the package declaring a pre-dependency is about
4368 to be <em>configured</em>, the pre-dependency will be
4369 treated as a normal <tt>Depends</tt>, that is, it will
4370 be considered satisfied only if the depended-on
4371 package has been correctly configured.
4375 <tt>Pre-Depends</tt> should be used sparingly,
4376 preferably only by packages whose premature upgrade or
4377 installation would hamper the ability of the system to
4378 continue with any upgrade that might be in progress.
4382 <tt>Pre-Depends</tt> are also required if the
4383 <prgn>preinst</prgn> script depends on the named
4384 package. It is best to avoid this situation if
4392 When selecting which level of dependency to use you should
4393 consider how important the depended-on package is to the
4394 functionality of the one declaring the dependency. Some
4395 packages are composed of components of varying degrees of
4396 importance. Such a package should list using
4397 <tt>Depends</tt> the package(s) which are required by the
4398 more important components. The other components'
4399 requirements may be mentioned as Suggestions or
4400 Recommendations, as appropriate to the components' relative
4406 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4409 Using <tt>Breaks</tt> may cause problems for upgrades from older
4410 versions of Debian and should not be used until the stable
4411 release of Debian supports <tt>Breaks</tt>.
4415 When one binary package declares that it breaks another,
4416 <prgn>dpkg</prgn> will refuse to allow the package which
4417 declares <tt>Breaks</tt> be installed unless the broken
4418 package is deconfigured first, and it will refuse to
4419 allow the broken package to be reconfigured.
4423 A package will not be regarded as causing breakage merely
4424 because its configuration files are still installed; it must
4425 be at least half-installed.
4429 A special exception is made for packages which declare that
4430 they break their own package name or a virtual package which
4431 they provide (see below): this does not count as a real
4436 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4437 version clause; such a <tt>Breaks</tt> is introduced in the
4438 version of an (implicit or explicit) dependency which
4439 violates an assumption or reveals a bug in earlier versions
4440 of the broken package. This use of <tt>Breaks</tt> will
4441 inform higher-level package management tools that broken
4442 package must be upgraded before the new one.
4446 If the breaking package also overwrites some files from the
4447 older package, it should use <tt>Replaces</tt> (not
4448 <tt>Conflicts</tt>) to ensure this goes smoothly.
4452 <sect id="conflicts">
4453 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4456 When one binary package declares a conflict with another
4457 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4458 refuse to allow them to be installed on the system at the
4463 If one package is to be installed, the other must be removed
4464 first - if the package being installed is marked as
4465 replacing (see <ref id="replaces">) the one on the system,
4466 or the one on the system is marked as deselected, or both
4467 packages are marked <tt>Essential</tt>, then
4468 <prgn>dpkg</prgn> will automatically remove the package
4469 which is causing the conflict, otherwise it will halt the
4470 installation of the new package with an error. This
4471 mechanism is specifically designed to produce an error when
4472 the installed package is <tt>Essential</tt>, but the new
4477 A package will not cause a conflict merely because its
4478 configuration files are still installed; it must be at least
4483 A special exception is made for packages which declare a
4484 conflict with their own package name, or with a virtual
4485 package which they provide (see below): this does not
4486 prevent their installation, and allows a package to conflict
4487 with others providing a replacement for it. You use this
4488 feature when you want the package in question to be the only
4489 package providing some feature.
4493 A <tt>Conflicts</tt> entry should almost never have an
4494 "earlier than" version clause. This would prevent
4495 <prgn>dpkg</prgn> from upgrading or installing the package
4496 which declared such a conflict until the upgrade or removal
4497 of the conflicted-with package had been completed. Instead,
4498 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4499 by the stable release of Debian).
4503 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4507 As well as the names of actual ("concrete") packages, the
4508 package relationship fields <tt>Depends</tt>,
4509 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4510 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4511 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4512 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4513 may mention "virtual packages".
4517 A <em>virtual package</em> is one which appears in the
4518 <tt>Provides</tt> control file field of another package.
4519 The effect is as if the package(s) which provide a
4520 particular virtual package name had been listed by name
4521 everywhere the virtual package name appears. (See also <ref
4526 If there are both concrete and virtual packages of the same
4527 name, then the dependency may be satisfied (or the conflict
4528 caused) by either the concrete package with the name in
4529 question or any other concrete package which provides the
4530 virtual package with the name in question. This is so that,
4531 for example, supposing we have
4532 <example compact="compact">
4535 </example> and someone else releases an enhanced version of
4536 the <tt>bar</tt> package they can say:
4537 <example compact="compact">
4541 and the <tt>bar-plus</tt> package will now also satisfy the
4542 dependency for the <tt>foo</tt> package.
4546 If a relationship field has a version number attached
4547 then only real packages will be considered to see whether
4548 the relationship is satisfied (or the prohibition violated,
4549 for a conflict or breakage) - it is assumed that a real
4550 package which provides the virtual package is not of the
4551 "right" version. So, a <tt>Provides</tt> field may not
4552 contain version numbers, and the version number of the
4553 concrete package which provides a particular virtual package
4554 will not be looked at when considering a dependency on or
4555 conflict with the virtual package name.
4559 It is likely that the ability will be added in a future
4560 release of <prgn>dpkg</prgn> to specify a version number for
4561 each virtual package it provides. This feature is not yet
4562 present, however, and is expected to be used only
4567 If you want to specify which of a set of real packages
4568 should be the default to satisfy a particular dependency on
4569 a virtual package, you should list the real package as an
4570 alternative before the virtual one.
4575 <sect id="replaces"><heading>Overwriting files and replacing
4576 packages - <tt>Replaces</tt></heading>
4579 Packages can declare in their control file that they should
4580 overwrite files in certain other packages, or completely
4581 replace other packages. The <tt>Replaces</tt> control file
4582 field has these two distinct purposes.
4585 <sect1><heading>Overwriting files in other packages</heading>
4588 Firstly, as mentioned before, it is usually an error for a
4589 package to contain files which are on the system in
4594 However, if the overwriting package declares that it
4595 <tt>Replaces</tt> the one containing the file being
4596 overwritten, then <prgn>dpkg</prgn> will replace the file
4597 from the old package with that from the new. The file
4598 will no longer be listed as "owned" by the old package.
4602 If a package is completely replaced in this way, so that
4603 <prgn>dpkg</prgn> does not know of any files it still
4604 contains, it is considered to have "disappeared". It will
4605 be marked as not wanted on the system (selected for
4606 removal) and not installed. Any <tt>conffile</tt>s
4607 details noted for the package will be ignored, as they
4608 will have been taken over by the overwriting package. The
4609 package's <prgn>postrm</prgn> script will be run with a
4610 special argument to allow the package to do any final
4611 cleanup required. See <ref id="mscriptsinstact">.
4614 Replaces is a one way relationship -- you have to
4615 install the replacing package after the replaced
4622 For this usage of <tt>Replaces</tt>, virtual packages (see
4623 <ref id="virtual">) are not considered when looking at a
4624 <tt>Replaces</tt> field - the packages declared as being
4625 replaced must be mentioned by their real names.
4629 Furthermore, this usage of <tt>Replaces</tt> only takes
4630 effect when both packages are at least partially on the
4631 system at once, so that it can only happen if they do not
4632 conflict or if the conflict has been overridden.
4637 <sect1><heading>Replacing whole packages, forcing their
4641 Secondly, <tt>Replaces</tt> allows the packaging system to
4642 resolve which package should be removed when there is a
4643 conflict - see <ref id="conflicts">. This usage only
4644 takes effect when the two packages <em>do</em> conflict,
4645 so that the two usages of this field do not interfere with
4650 In this situation, the package declared as being replaced
4651 can be a virtual package, so for example, all mail
4652 transport agents (MTAs) would have the following fields in
4653 their control files:
4654 <example compact="compact">
4655 Provides: mail-transport-agent
4656 Conflicts: mail-transport-agent
4657 Replaces: mail-transport-agent
4659 ensuring that only one MTA can be installed at any one
4664 <sect id="sourcebinarydeps">
4665 <heading>Relationships between source and binary packages -
4666 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4667 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4671 Source packages that require certain binary packages to be
4672 installed or absent at the time of building the package
4673 can declare relationships to those binary packages.
4677 This is done using the <tt>Build-Depends</tt>,
4678 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4679 <tt>Build-Conflicts-Indep</tt> control file fields.
4683 Build-dependencies on "build-essential" binary packages can be
4684 omitted. Please see <ref id="pkg-relations"> for more information.
4688 The dependencies and conflicts they define must be satisfied
4689 (as defined earlier for binary packages) in order to invoke
4690 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4692 If you make "build-arch" or "binary-arch", you need
4693 Build-Depends. If you make "build-indep" or
4694 "binary-indep", you need Build-Depends and
4695 Build-Depends-Indep. If you make "build" or "binary",
4699 There is no Build-Depends-Arch; this role is essentially
4700 met with Build-Depends. Anyone building the
4701 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4702 is basically assumed to be building the whole package
4703 anyway and so installs all build dependencies. The
4704 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4705 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4706 does not yet know how to check for its existence) and
4707 <tt>binary-arch</tt>.
4710 The purpose of the original split, I recall, was so that
4711 the autobuilders wouldn't need to install extra packages
4712 needed only for the binary-indep targets. But without a
4713 build-arch/build-indep split, this didn't work, since
4714 most of the work is done in the build target, not in the
4720 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4722 The <tt>Build-Depends</tt> and
4723 <tt>Build-Conflicts</tt> fields must be satisfied when
4724 any of the following targets is invoked:
4725 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4726 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4727 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4729 <tag><tt>Build-Depends-Indep</tt>,
4730 <tt>Build-Conflicts-Indep</tt></tag>
4732 The <tt>Build-Depends-Indep</tt> and
4733 <tt>Build-Conflicts-Indep</tt> fields must be
4734 satisfied when any of the following targets is
4735 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4736 <tt>binary</tt> and <tt>binary-indep</tt>.
4746 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4749 Packages containing shared libraries must be constructed with
4750 a little care to make sure that the shared library is always
4751 available. This is especially important for packages whose
4752 shared libraries are vitally important, such as the C library
4753 (currently <tt>libc6</tt>).
4757 Packages involving shared libraries should be split up into
4758 several binary packages. This section mostly deals with how
4759 this separation is to be accomplished; rules for files within
4760 the shared library packages are in <ref id="libraries"> instead.
4763 <sect id="sharedlibs-runtime">
4764 <heading>Run-time shared libraries</heading>
4767 The run-time shared library needs to be placed in a package
4768 whose name changes whenever the shared object version
4771 Since it is common place to install several versions of a
4772 package that just provides shared libraries, it is a
4773 good idea that the library package should not
4774 contain any extraneous non-versioned files, unless they
4775 happen to be in versioned directories.</p>
4777 The most common mechanism is to place it in a package
4779 <package><var>libraryname</var><var>soversion</var></package>,
4780 where <file><var>soversion</var></file> is the version number
4781 in the soname of the shared library<footnote>
4782 The soname is the shared object name: it's the thing
4783 that has to match exactly between building an executable
4784 and running it for the dynamic linker to be able run the
4785 program. For example, if the soname of the library is
4786 <file>libfoo.so.6</file>, the library package would be
4787 called <file>libfoo6</file>.
4789 Alternatively, if it would be confusing to directly append
4790 <var>soversion</var> to <var>libraryname</var> (e.g. because
4791 <var>libraryname</var> itself ends in a number), you may use
4792 <package><var>libraryname</var>-<var>soversion</var></package> and
4793 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4798 If you have several shared libraries built from the same
4799 source tree you may lump them all together into a single
4800 shared library package, provided that you change all of
4801 their sonames at once (so that you don't get filename
4802 clashes if you try to install different versions of the
4803 combined shared libraries package).
4807 The package should install the shared libraries under
4808 their normal names. For example, the <package>libgdbm3</package>
4809 package should install <file>libgdbm.so.3.0.0</file> as
4810 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4811 renamed or re-linked by any <prgn>prerm</prgn> or
4812 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4813 of renaming things safely without affecting running programs,
4814 and attempts to interfere with this are likely to lead to
4819 Shared libraries should not be installed executable, since
4820 the dynamic linker does not require this and trying to
4821 execute a shared library usually results in a core dump.
4825 The run-time library package should include the symbolic link that
4826 <prgn>ldconfig</prgn> would create for the shared libraries.
4827 For example, the <package>libgdbm3</package> package should include
4828 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4829 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4830 linker (for example <prgn>ld.so</prgn> or
4831 <prgn>ld-linux.so.*</prgn>) can find the library between the
4832 time that <prgn>dpkg</prgn> installs it and the time that
4833 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4835 The package management system requires the library to be
4836 placed before the symbolic link pointing to it in the
4837 <file>.deb</file> file. This is so that when
4838 <prgn>dpkg</prgn> comes to install the symlink
4839 (overwriting the previous symlink pointing at an older
4840 version of the library), the new shared library is already
4841 in place. In the past, this was achieved by creating the
4842 library in the temporary packaging directory before
4843 creating the symlink. Unfortunately, this was not always
4844 effective, since the building of the tar file in the
4845 <file>.deb</file> depended on the behavior of the underlying
4846 file system. Some file systems (such as reiserfs) reorder
4847 the files so that the order of creation is forgotten.
4848 Since version 1.7.0, <prgn>dpkg</prgn>
4849 reorders the files itself as necessary when building a
4850 package. Thus it is no longer important to concern
4851 oneself with the order of file creation.
4855 <sect1 id="ldconfig">
4856 <heading><tt>ldconfig</tt></heading>
4859 Any package installing shared libraries in one of the default
4860 library directories of the dynamic linker (which are currently
4861 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4862 listed in <file>/etc/ld.so.conf</file><footnote>
4864 <list compact="compact">
4865 <item>/usr/local/lib</item>
4866 <item>/usr/lib/libc5-compat</item>
4867 <item>/lib/libc5-compat</item>
4870 must use <prgn>ldconfig</prgn> to update the shared library
4875 The package maintainer scripts must only call
4876 <prgn>ldconfig</prgn> under these circumstances:
4877 <list compact="compact">
4878 <item>When the <prgn>postinst</prgn> script is run with a
4879 first argument of <tt>configure</tt>, the script must call
4880 <prgn>ldconfig</prgn>, and may optionally invoke
4881 <prgn>ldconfig</prgn> at other times.
4883 <item>When the <prgn>postrm</prgn> script is run with a
4884 first argument of <tt>remove</tt>, the script should call
4885 <prgn>ldconfig</prgn>.
4890 During install or upgrade, the preinst is called before
4891 the new files are installed, so calling "ldconfig" is
4892 pointless. The preinst of an existing package can also be
4893 called if an upgrade fails. However, this happens during
4894 the critical time when a shared libs may exist on-disk
4895 under a temporary name. Thus, it is dangerous and
4896 forbidden by current policy to call "ldconfig" at this
4901 When a package is installed or upgraded, "postinst
4902 configure" runs after the new files are safely on-disk.
4903 Since it is perfectly safe to invoke ldconfig
4904 unconditionally in a postinst, it is OK for a package to
4905 simply put ldconfig in its postinst without checking the
4906 argument. The postinst can also be called to recover from
4907 a failed upgrade. This happens before any new files are
4908 unpacked, so there is no reason to call "ldconfig" at this
4913 For a package that is being removed, prerm is
4914 called with all the files intact, so calling ldconfig is
4915 useless. The other calls to "prerm" happen in the case of
4916 upgrade at a time when all the files of the old package
4917 are on-disk, so again calling "ldconfig" is pointless.
4921 postrm, on the other hand, is called with the "remove"
4922 argument just after the files are removed, so this is
4923 the proper time to call "ldconfig" to notify the system
4924 of the fact that the shared libraries from the package
4925 are removed. The postrm can be called at several other
4926 times. At the time of "postrm purge", "postrm
4927 abort-install", or "postrm abort-upgrade", calling
4928 "ldconfig" is useless because the shared lib files are
4929 not on-disk. However, when "postrm" is invoked with
4930 arguments "upgrade", "failed-upgrade", or "disappear", a
4931 shared lib may exist on-disk under a temporary filename.
4939 <sect id="sharedlibs-support-files">
4940 <heading>Shared library support files</heading>
4943 If your package contains files whose names do not change with
4944 each change in the library shared object version, you must not
4945 put them in the shared library package. Otherwise, several
4946 versions of the shared library cannot be installed at the same
4947 time without filename clashes, making upgrades and transitions
4948 unnecessarily difficult.
4952 It is recommended that supporting files and run-time support
4953 programs that do not need to be invoked manually by users, but
4954 are nevertheless required for the package to function, be placed
4955 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4956 preferably under <file>/usr/lib/</file><var>package-name</var>.
4957 If the program or file is architecture independent, the
4958 recommendation is for it to be placed in a subdirectory of
4959 <file>/usr/share</file> instead, preferably under
4960 <file>/usr/share/</file><var>package-name</var>. Following the
4961 <var>package-name</var> naming convention ensures that the file
4962 names change when the shared object version changes.
4966 Run-time support programs that use the shared library but are
4967 not required for the library to function or files used by the
4968 shared library that can be used by any version of the shared
4969 library package should instead be put in a separate package.
4970 This package might typically be named
4971 <package><var>libraryname</var>-tools</package>; note the
4972 absence of the <var>soversion</var> in the package name.
4976 Files and support programs only useful when compiling software
4977 against the library should be included in the development
4978 package for the library.<footnote>
4979 For example, a <file><var>package-name</var>-config</file>
4980 script or <package>pkg-config</package> configuration files.
4985 <sect id="sharedlibs-static">
4986 <heading>Static libraries</heading>
4989 The static library (<file><var>libraryname.a</var></file>)
4990 is usually provided in addition to the shared version.
4991 It is placed into the development package (see below).
4995 In some cases, it is acceptable for a library to be
4996 available in static form only; these cases include:
4998 <item>libraries for languages whose shared library support
4999 is immature or unstable</item>
5000 <item>libraries whose interfaces are in flux or under
5001 development (commonly the case when the library's
5002 major version number is zero, or where the ABI breaks
5003 across patchlevels)</item>
5004 <item>libraries which are explicitly intended to be
5005 available only in static form by their upstream
5010 <sect id="sharedlibs-dev">
5011 <heading>Development files</heading>
5014 The development files associated to a shared library need to be
5015 placed in a package called
5016 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5017 or if you prefer only to support one development version at a
5018 time, <package><var>libraryname</var>-dev</package>.
5022 In case several development versions of a library exist, you may
5023 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5024 <ref id="conflicts">) to ensure that the user only installs one
5025 development version at a time (as different development versions are
5026 likely to have the same header files in them, which would cause a
5027 filename clash if both were installed).
5031 The development package should contain a symlink for the associated
5032 shared library without a version number. For example, the
5033 <package>libgdbm-dev</package> package should include a symlink
5034 from <file>/usr/lib/libgdbm.so</file> to
5035 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5036 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5037 <file>libgdbm.so</file> when compiling dynamically.
5041 <sect id="sharedlibs-intradeps">
5042 <heading>Dependencies between the packages of the same library</heading>
5045 Typically the development version should have an exact
5046 version dependency on the runtime library, to make sure that
5047 compilation and linking happens correctly. The
5048 <tt>${binary:Version}</tt> substitution variable can be
5049 useful for this purpose.
5051 Previously, <tt>${Source-Version}</tt> was used, but its name
5052 was confusing and it has been deprecated since dpkg 1.13.19.
5057 <sect id="sharedlibs-shlibdeps">
5058 <heading>Dependencies between the library and other packages -
5059 the <tt>shlibs</tt> system</heading>
5062 If a package contains a binary or library which links to a
5063 shared library, we must ensure that when the package is
5064 installed on the system, all of the libraries needed are
5065 also installed. This requirement led to the creation of the
5066 <tt>shlibs</tt> system, which is very simple in its design:
5067 any package which <em>provides</em> a shared library also
5068 provides information on the package dependencies required to
5069 ensure the presence of this library, and any package which
5070 <em>uses</em> a shared library uses this information to
5071 determine the dependencies it requires. The files which
5072 contain the mapping from shared libraries to the necessary
5073 dependency information are called <file>shlibs</file> files.
5077 Thus, when a package is built which contains any shared
5078 libraries, it must provide a <file>shlibs</file> file for other
5079 packages to use, and when a package is built which contains
5080 any shared libraries or compiled binaries, it must run
5081 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5082 on these to determine the libraries used and hence the
5083 dependencies needed by this package.<footnote>
5085 In the past, the shared libraries linked to were
5086 determined by calling <prgn>ldd</prgn>, but now
5087 <prgn>objdump</prgn> is used to do this. The only
5088 change this makes to package building is that
5089 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5090 libraries, whereas in the past this was unnecessary.
5091 The rest of this footnote explains the advantage that
5096 We say that a binary <tt>foo</tt> <em>directly</em> uses
5097 a library <tt>libbar</tt> if it is explicitly linked
5098 with that library (that is, it uses the flag
5099 <tt>-lbar</tt> during the linking stage). Other
5100 libraries that are needed by <tt>libbar</tt> are linked
5101 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5102 linker will load them automatically when it loads
5103 <tt>libbar</tt>. A package should depend on
5104 the libraries it directly uses, and the dependencies for
5105 those libraries should automatically pull in the other
5110 Unfortunately, the <prgn>ldd</prgn> program shows both
5111 the directly and indirectly used libraries, meaning that
5112 the dependencies determined included both direct and
5113 indirect dependencies. The use of <prgn>objdump</prgn>
5114 avoids this problem by determining only the directly
5119 A good example of where this helps is the following. We
5120 could update <tt>libimlib</tt> with a new version that
5121 supports a new graphics format called dgf (but retaining
5122 the same major version number). If we used the old
5123 <prgn>ldd</prgn> method, every package that uses
5124 <tt>libimlib</tt> would need to be recompiled so it
5125 would also depend on <tt>libdgf</tt> or it wouldn't run
5126 due to missing symbols. However with the new system,
5127 packages using <tt>libimlib</tt> can rely on
5128 <tt>libimlib</tt> itself having the dependency on
5129 <tt>libdgf</tt> and so they would not need rebuilding.
5135 In the following sections, we will first describe where the
5136 various <tt>shlibs</tt> files are to be found, then how to
5137 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5138 file format and how to create them if your package contains a
5143 <heading>The <tt>shlibs</tt> files present on the system</heading>
5146 There are several places where <tt>shlibs</tt> files are
5147 found. The following list gives them in the order in which
5149 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5150 (The first one which gives the required information is used.)
5156 <p><file>debian/shlibs.local</file></p>
5159 This lists overrides for this package. Its use is
5160 described below (see <ref id="shlibslocal">).
5165 <p><file>/etc/dpkg/shlibs.override</file></p>
5168 This lists global overrides. This list is normally
5169 empty. It is maintained by the local system
5175 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5178 When packages are being built, any
5179 <file>debian/shlibs</file> files are copied into the
5180 control file area of the temporary build directory and
5181 given the name <file>shlibs</file>. These files give
5182 details of any shared libraries included in the
5184 An example may help here. Let us say that the
5185 source package <tt>foo</tt> generates two binary
5186 packages, <tt>libfoo2</tt> and
5187 <tt>foo-runtime</tt>. When building the binary
5188 packages, the two packages are created in the
5189 directories <file>debian/libfoo2</file> and
5190 <file>debian/foo-runtime</file> respectively.
5191 (<file>debian/tmp</file> could be used instead of one
5192 of these.) Since <tt>libfoo2</tt> provides the
5193 <tt>libfoo</tt> shared library, it will require a
5194 <tt>shlibs</tt> file, which will be installed in
5195 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5197 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5198 when <prgn>dpkg-shlibdeps</prgn> is run on the
5200 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5202 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5203 determine whether <tt>foo-prog</tt>'s library
5204 dependencies are satisfied by any of the libraries
5205 provided by <tt>libfoo2</tt>. For this reason,
5206 <prgn>dpkg-shlibdeps</prgn> must only be run once
5207 all of the individual binary packages'
5208 <tt>shlibs</tt> files have been installed into the
5215 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5218 These are the <file>shlibs</file> files corresponding to
5219 all of the packages installed on the system, and are
5220 maintained by the relevant package maintainers.
5225 <p><file>/etc/dpkg/shlibs.default</file></p>
5228 This file lists any shared libraries whose packages
5229 have failed to provide correct <file>shlibs</file> files.
5230 It was used when the <file>shlibs</file> setup was first
5231 introduced, but it is now normally empty. It is
5232 maintained by the <tt>dpkg</tt> maintainer.
5240 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5241 <file>shlibs</file> files</heading>
5245 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5246 into your <file>debian/rules</file> file. If your package
5247 contains only compiled binaries and libraries (but no scripts),
5248 you can use a command such as:
5249 <example compact="compact">
5250 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5251 debian/tmp/usr/lib/*
5253 Otherwise, you will need to explicitly list the compiled
5254 binaries and libraries.<footnote>
5255 If you are using <tt>debhelper</tt>, the
5256 <prgn>dh_shlibdeps</prgn> program will do this work for
5257 you. It will also correctly handle multi-binary
5263 This command puts the dependency information into the
5264 <file>debian/substvars</file> file, which is then used by
5265 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5266 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5267 field in the control file for this to work.
5271 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5272 done. If it does complain you might need to create your own
5273 <file>debian/shlibs.local</file> file, as explained below (see
5274 <ref id="shlibslocal">).
5278 If you have multiple binary packages, you will need to call
5279 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5280 compiled libraries or binaries. In such a case, you will
5281 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5282 utilities to specify a different <file>substvars</file> file.
5286 If you are creating a udeb for use in the Debian Installer, you
5287 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5288 the dependency line of type <tt>udeb</tt> by adding
5289 <tt>-tudeb</tt> as option<footnote>
5290 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5291 will automatically add this option if it knows it is
5293 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5294 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5295 fall back to the regular dependency line.
5299 For more details on dpkg-shlibdeps, please see
5300 <ref id="pkg-dpkg-shlibdeps"> and
5301 <manref name="dpkg-shlibdeps" section="1">.
5306 <heading>The <file>shlibs</file> File Format</heading>
5309 Each <file>shlibs</file> file has the same format. Lines
5310 beginning with <tt>#</tt> are considered to be comments and
5311 are ignored. Each line is of the form:
5312 <example compact="compact">
5313 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5318 We will explain this by reference to the example of the
5319 <tt>zlib1g</tt> package, which (at the time of writing)
5320 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5324 <var>type</var> is an optional element that indicates the type
5325 of package for which the line is valid. The only type currently
5326 in use is <tt>udeb</tt>. The colon and space after the type are
5331 <var>library-name</var> is the name of the shared library,
5332 in this case <tt>libz</tt>. (This must match the name part
5333 of the soname, see below.)
5337 <var>soname-version</var> is the version part of the soname of
5338 the library. The soname is the thing that must exactly match
5339 for the library to be recognized by the dynamic linker, and is
5341 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5342 example, <tt>libz.so.1</tt>.<footnote>
5343 This can be determined using the command
5344 <example compact="compact">
5345 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5348 The version part is the part which comes after
5349 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5353 <var>dependencies</var> has the same syntax as a dependency
5354 field in a binary package control file. It should give
5355 details of which packages are required to satisfy a binary
5356 built against the version of the library contained in the
5357 package. See <ref id="depsyntax"> for details.
5361 In our example, if the first version of the <tt>zlib1g</tt>
5362 package which contained a minor number of at least
5363 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5364 <tt>shlibs</tt> entry for this library could say:
5365 <example compact="compact">
5366 libz 1 zlib1g (>= 1:1.1.3)
5368 The version-specific dependency is to avoid warnings from
5369 the dynamic linker about using older shared libraries with
5374 As zlib1g also provides a udeb containing the shared library,
5375 there would also be a second line:
5376 <example compact="compact">
5377 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5383 <heading>Providing a <file>shlibs</file> file</heading>
5386 If your package provides a shared library, you need to create
5387 a <file>shlibs</file> file following the format described above.
5388 It is usual to call this file <file>debian/shlibs</file> (but if
5389 you have multiple binary packages, you might want to call it
5390 <file>debian/shlibs.<var>package</var></file> instead). Then
5391 let <file>debian/rules</file> install it in the control area:
5392 <example compact="compact">
5393 install -m644 debian/shlibs debian/tmp/DEBIAN
5395 or, in the case of a multi-binary package:
5396 <example compact="compact">
5397 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5399 An alternative way of doing this is to create the
5400 <file>shlibs</file> file in the control area directly from
5401 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5402 file at all,<footnote>
5403 This is what <prgn>dh_makeshlibs</prgn> in the
5404 <tt>debhelper</tt> suite does. If your package also has a udeb
5405 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5406 automatically generate the <tt>udeb:</tt> lines if you specify
5407 the name of the udeb with the <tt>--add-udeb</tt> option.
5409 since the <file>debian/shlibs</file> file itself is ignored by
5410 <prgn>dpkg-shlibdeps</prgn>.
5414 As <prgn>dpkg-shlibdeps</prgn> reads the
5415 <file>DEBIAN/shlibs</file> files in all of the binary packages
5416 being built from this source package, all of the
5417 <file>DEBIAN/shlibs</file> files should be installed before
5418 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5423 <sect1 id="shlibslocal">
5424 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5427 This file is intended only as a <em>temporary</em> fix if
5428 your binaries or libraries depend on a library whose package
5429 does not yet provide a correct <file>shlibs</file> file.
5433 We will assume that you are trying to package a binary
5434 <tt>foo</tt>. When you try running
5435 <prgn>dpkg-shlibdeps</prgn> you get the following error
5436 message (<tt>-O</tt> displays the dependency information on
5437 <tt>stdout</tt> instead of writing it to
5438 <tt>debian/substvars</tt>, and the lines have been wrapped
5439 for ease of reading):
5440 <example compact="compact">
5441 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5442 dpkg-shlibdeps: warning: unable to find dependency
5443 information for shared library libbar (soname 1,
5444 path /usr/lib/libbar.so.1, dependency field Depends)
5445 shlibs:Depends=libc6 (>= 2.2.2-2)
5447 You can then run <prgn>ldd</prgn> on the binary to find the
5448 full location of the library concerned:
5449 <example compact="compact">
5451 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5452 libc.so.6 => /lib/libc.so.6 (0x40032000)
5453 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5455 So the <prgn>foo</prgn> binary depends on the
5456 <prgn>libbar</prgn> shared library, but no package seems to
5457 provide a <file>*.shlibs</file> file handling
5458 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5459 determine the package responsible:
5460 <example compact="compact">
5461 $ dpkg -S /usr/lib/libbar.so.1
5462 bar1: /usr/lib/libbar.so.1
5463 $ dpkg -s bar1 | grep Version
5466 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5467 is the one we are using. Now we can file a bug against the
5468 <tt>bar1</tt> package and create our own
5469 <file>debian/shlibs.local</file> to locally fix the problem.
5470 Including the following line into your
5471 <file>debian/shlibs.local</file> file:
5472 <example compact="compact">
5473 libbar 1 bar1 (>= 1.0-1)
5475 should allow the package build to work.
5479 As soon as the maintainer of <tt>bar1</tt> provides a
5480 correct <file>shlibs</file> file, you should remove this line
5481 from your <file>debian/shlibs.local</file> file. (You should
5482 probably also then have a versioned <tt>Build-Depends</tt>
5483 on <tt>bar1</tt> to help ensure that others do not have the
5484 same problem building your package.)
5493 <chapt id="opersys"><heading>The Operating System</heading>
5496 <heading>File system hierarchy</heading>
5500 <heading>File system Structure</heading>
5503 The location of all installed files and directories must
5504 comply with the File system Hierarchy Standard (FHS),
5505 version 2.3, with the exceptions noted below, and except
5506 where doing so would violate other terms of Debian
5507 Policy. The following exceptions to the FHS apply:
5512 Legacy XFree86 servers are permitted to retain the
5513 configuration file location
5514 <file>/etc/X11/XF86Config-4</file>.
5519 The optional rules related to user specific
5520 configuration files for applications are stored in
5521 the user's home directory are relaxed. It is
5522 recommended that such files start with the
5523 '<tt>.</tt>' character (a "dot file"), and if an
5524 application needs to create more than one dot file
5525 then the preferred placement is in a subdirectory
5526 with a name starting with a '.' character, (a "dot
5527 directory"). In this case it is recommended the
5528 configuration files not start with the '.'
5534 The requirement for amd64 to use <file>/lib64</file>
5535 for 64 bit binaries is removed.
5540 The requirement that
5541 <file>/usr/local/share/man</file> be "synonymous"
5542 with <file>/usr/local/man</file> is relaxed to a
5547 The requirement that windowmanagers with a single
5548 configuration file call it <file>system.*wmrc</file>
5549 is removed, as is the restriction that the window
5550 manager subdirectory be named identically to the
5551 window manager name itself.
5556 The requirement that boot manager configuration
5557 files live in <file>/etc</file>, or at least are
5558 symlinked there, is relaxed to a recommendation.
5565 The version of this document referred here can be
5566 found in the <tt>debian-policy</tt> package or on <url
5567 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5568 name="FHS (Debian copy)"> alongside this manual (or, if
5569 you have the <package>debian-policy</package> installed,
5571 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5572 (local copy)">). The
5573 latest version, which may be a more recent version, may
5575 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5576 Specific questions about following the standard may be
5577 asked on the <tt>debian-devel</tt> mailing list, or
5578 referred to the FHS mailing list (see the
5579 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5585 <heading>Site-specific programs</heading>
5588 As mandated by the FHS, packages must not place any
5589 files in <file>/usr/local</file>, either by putting them in
5590 the file system archive to be unpacked by <prgn>dpkg</prgn>
5591 or by manipulating them in their maintainer scripts.
5595 However, the package may create empty directories below
5596 <file>/usr/local</file> so that the system administrator knows
5597 where to place site-specific files. These are not
5598 directories <em>in</em> <file>/usr/local</file>, but are
5599 children of directories in <file>/usr/local</file>. These
5600 directories (<file>/usr/local/*/dir/</file>)
5601 should be removed on package removal if they are
5606 Note, that this applies only to directories <em>below</em>
5607 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5608 Packages must not create sub-directories in the directory
5609 <file>/usr/local</file> itself, except those listed in FHS,
5610 section 4.5. However, you may create directories below
5611 them as you wish. You must not remove any of the
5612 directories listed in 4.5, even if you created them.
5616 Since <file>/usr/local</file> can be mounted read-only from a
5617 remote server, these directories must be created and
5618 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5619 maintainer scripts and not be included in the
5620 <file>.deb</file> archive. These scripts must not fail if
5621 either of these operations fail.
5625 For example, the <tt>emacsen-common</tt> package could
5626 contain something like
5627 <example compact="compact">
5628 if [ ! -e /usr/local/share/emacs ]
5630 if mkdir /usr/local/share/emacs 2>/dev/null
5632 chown root:staff /usr/local/share/emacs
5633 chmod 2775 /usr/local/share/emacs
5637 in its <prgn>postinst</prgn> script, and
5638 <example compact="compact">
5639 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5640 rmdir /usr/local/share/emacs 2>/dev/null || true
5642 in the <prgn>prerm</prgn> script. (Note that this form is
5643 used to ensure that if the script is interrupted, the
5644 directory <file>/usr/local/share/emacs</file> will still be
5649 If you do create a directory in <file>/usr/local</file> for
5650 local additions to a package, you should ensure that
5651 settings in <file>/usr/local</file> take precedence over the
5652 equivalents in <file>/usr</file>.
5656 However, because <file>/usr/local</file> and its contents are
5657 for exclusive use of the local administrator, a package
5658 must not rely on the presence or absence of files or
5659 directories in <file>/usr/local</file> for normal operation.
5663 The <file>/usr/local</file> directory itself and all the
5664 subdirectories created by the package should (by default) have
5665 permissions 2775 (group-writable and set-group-id) and be
5666 owned by <tt>root:staff</tt>.
5671 <heading>The system-wide mail directory</heading>
5673 The system-wide mail directory is <file>/var/mail</file>. This
5674 directory is part of the base system and should not owned
5675 by any particular mail agents. The use of the old
5676 location <file>/var/spool/mail</file> is deprecated, even
5677 though the spool may still be physically located there.
5678 To maintain partial upgrade compatibility for systems
5679 which have <file>/var/spool/mail</file> as their physical mail
5680 spool, packages using <file>/var/mail</file> must depend on
5681 either <package>libc6</package> (>= 2.1.3-13), or on
5682 <package>base-files</package> (>= 2.2.0), or on later
5683 versions of either one of these packages.
5689 <heading>Users and groups</heading>
5692 <heading>Introduction</heading>
5694 The Debian system can be configured to use either plain or
5699 Some user ids (UIDs) and group ids (GIDs) are reserved
5700 globally for use by certain packages. Because some
5701 packages need to include files which are owned by these
5702 users or groups, or need the ids compiled into binaries,
5703 these ids must be used on any Debian system only for the
5704 purpose for which they are allocated. This is a serious
5705 restriction, and we should avoid getting in the way of
5706 local administration policies. In particular, many sites
5707 allocate users and/or local system groups starting at 100.
5711 Apart from this we should have dynamically allocated ids,
5712 which should by default be arranged in some sensible
5713 order, but the behavior should be configurable.
5717 Packages other than <tt>base-passwd</tt> must not modify
5718 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5719 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5724 <heading>UID and GID classes</heading>
5726 The UID and GID numbers are divided into classes as
5732 Globally allocated by the Debian project, the same
5733 on every Debian system. These ids will appear in
5734 the <file>passwd</file> and <file>group</file> files of all
5735 Debian systems, new ids in this range being added
5736 automatically as the <tt>base-passwd</tt> package is
5741 Packages which need a single statically allocated
5742 uid or gid should use one of these; their
5743 maintainers should ask the <tt>base-passwd</tt>
5751 Dynamically allocated system users and groups.
5752 Packages which need a user or group, but can have
5753 this user or group allocated dynamically and
5754 differently on each system, should use <tt>adduser
5755 --system</tt> to create the group and/or user.
5756 <prgn>adduser</prgn> will check for the existence of
5757 the user or group, and if necessary choose an unused
5758 id based on the ranges specified in
5759 <file>adduser.conf</file>.
5763 <tag>1000-29999:</tag>
5766 Dynamically allocated user accounts. By default
5767 <prgn>adduser</prgn> will choose UIDs and GIDs for
5768 user accounts in this range, though
5769 <file>adduser.conf</file> may be used to modify this
5774 <tag>30000-59999:</tag>
5779 <tag>60000-64999:</tag>
5782 Globally allocated by the Debian project, but only
5783 created on demand. The ids are allocated centrally
5784 and statically, but the actual accounts are only
5785 created on users' systems on demand.
5789 These ids are for packages which are obscure or
5790 which require many statically-allocated ids. These
5791 packages should check for and create the accounts in
5792 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5793 <prgn>adduser</prgn> if it has this facility) if
5794 necessary. Packages which are likely to require
5795 further allocations should have a "hole" left after
5796 them in the allocation, to give them room to
5801 <tag>65000-65533:</tag>
5809 User <tt>nobody</tt>. The corresponding gid refers
5810 to the group <tt>nogroup</tt>.
5817 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5818 not</em> be used, because it is the error return
5827 <sect id="sysvinit">
5828 <heading>System run levels and <file>init.d</file> scripts</heading>
5830 <sect1 id="/etc/init.d">
5831 <heading>Introduction</heading>
5834 The <file>/etc/init.d</file> directory contains the scripts
5835 executed by <prgn>init</prgn> at boot time and when the
5836 init state (or "runlevel") is changed (see <manref
5837 name="init" section="8">).
5841 There are at least two different, yet functionally
5842 equivalent, ways of handling these scripts. For the sake
5843 of simplicity, this document describes only the symbolic
5844 link method. However, it must not be assumed by maintainer
5845 scripts that this method is being used, and any automated
5846 manipulation of the various runlevel behaviors by
5847 maintainer scripts must be performed using
5848 <prgn>update-rc.d</prgn> as described below and not by
5849 manually installing or removing symlinks. For information
5850 on the implementation details of the other method,
5851 implemented in the <tt>file-rc</tt> package, please refer
5852 to the documentation of that package.
5856 These scripts are referenced by symbolic links in the
5857 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5858 runlevels, <prgn>init</prgn> looks in the directory
5859 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5860 execute, where <tt><var>n</var></tt> is the runlevel that
5861 is being changed to, or <tt>S</tt> for the boot-up
5866 The names of the links all have the form
5867 <file>S<var>mm</var><var>script</var></file> or
5868 <file>K<var>mm</var><var>script</var></file> where
5869 <var>mm</var> is a two-digit number and <var>script</var>
5870 is the name of the script (this should be the same as the
5871 name of the actual script in <file>/etc/init.d</file>).
5875 When <prgn>init</prgn> changes runlevel first the targets
5876 of the links whose names start with a <tt>K</tt> are
5877 executed, each with the single argument <tt>stop</tt>,
5878 followed by the scripts prefixed with an <tt>S</tt>, each
5879 with the single argument <tt>start</tt>. (The links are
5880 those in the <file>/etc/rc<var>n</var>.d</file> directory
5881 corresponding to the new runlevel.) The <tt>K</tt> links
5882 are responsible for killing services and the <tt>S</tt>
5883 link for starting services upon entering the runlevel.
5887 For example, if we are changing from runlevel 2 to
5888 runlevel 3, init will first execute all of the <tt>K</tt>
5889 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5890 all of the <tt>S</tt> prefixed scripts in that directory.
5891 The links starting with <tt>K</tt> will cause the
5892 referred-to file to be executed with an argument of
5893 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5898 The two-digit number <var>mm</var> is used to determine
5899 the order in which to run the scripts: low-numbered links
5900 have their scripts run first. For example, the
5901 <tt>K20</tt> scripts will be executed before the
5902 <tt>K30</tt> scripts. This is used when a certain service
5903 must be started before another. For example, the name
5904 server <prgn>bind</prgn> might need to be started before
5905 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5906 can set up its access lists. In this case, the script
5907 that starts <prgn>bind</prgn> would have a lower number
5908 than the script that starts <prgn>inn</prgn> so that it
5910 <example compact="compact">
5917 The two runlevels 0 (halt) and 6 (reboot) are slightly
5918 different. In these runlevels, the links with an
5919 <tt>S</tt> prefix are still called after those with a
5920 <tt>K</tt> prefix, but they too are called with the single
5921 argument <tt>stop</tt>.
5925 Also, if the script name ends in <tt>.sh</tt>, the script
5926 will be sourced in runlevel <tt>S</tt> rather than being
5927 run in a forked subprocess, but will be explicitly run by
5928 <prgn>sh</prgn> in all other runlevels.
5933 <heading>Writing the scripts</heading>
5936 Packages that include daemons for system services should
5937 place scripts in <file>/etc/init.d</file> to start or stop
5938 services at boot time or during a change of runlevel.
5939 These scripts should be named
5940 <file>/etc/init.d/<var>package</var></file>, and they should
5941 accept one argument, saying what to do:
5944 <tag><tt>start</tt></tag>
5945 <item>start the service,</item>
5947 <tag><tt>stop</tt></tag>
5948 <item>stop the service,</item>
5950 <tag><tt>restart</tt></tag>
5951 <item>stop and restart the service if it's already running,
5952 otherwise start the service</item>
5954 <tag><tt>reload</tt></tag>
5955 <item><p>cause the configuration of the service to be
5956 reloaded without actually stopping and restarting
5959 <tag><tt>force-reload</tt></tag>
5960 <item>cause the configuration to be reloaded if the
5961 service supports this, otherwise restart the
5965 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5966 <tt>force-reload</tt> options should be supported by all
5967 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5972 The <file>init.d</file> scripts must ensure that they will
5973 behave sensibly (i.e., returning success and not starting
5974 multiple copies of a service) if invoked with <tt>start</tt>
5975 when the service is already running, or with <tt>stop</tt>
5976 when it isn't, and that they don't kill unfortunately-named
5977 user processes. The best way to achieve this is usually to
5978 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5983 If a service reloads its configuration automatically (as
5984 in the case of <prgn>cron</prgn>, for example), the
5985 <tt>reload</tt> option of the <file>init.d</file> script
5986 should behave as if the configuration has been reloaded
5991 The <file>/etc/init.d</file> scripts must be treated as
5992 configuration files, either (if they are present in the
5993 package, that is, in the .deb file) by marking them as
5994 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5995 by managing them correctly in the maintainer scripts (see
5996 <ref id="config-files">). This is important since we want
5997 to give the local system administrator the chance to adapt
5998 the scripts to the local system, e.g., to disable a
5999 service without de-installing the package, or to specify
6000 some special command line options when starting a service,
6001 while making sure their changes aren't lost during the next
6006 These scripts should not fail obscurely when the
6007 configuration files remain but the package has been
6008 removed, as configuration files remain on the system after
6009 the package has been removed. Only when <prgn>dpkg</prgn>
6010 is executed with the <tt>--purge</tt> option will
6011 configuration files be removed. In particular, as the
6012 <file>/etc/init.d/<var>package</var></file> script itself is
6013 usually a <tt>conffile</tt>, it will remain on the system
6014 if the package is removed but not purged. Therefore, you
6015 should include a <tt>test</tt> statement at the top of the
6017 <example compact="compact">
6018 test -f <var>program-executed-later-in-script</var> || exit 0
6023 Often there are some variables in the <file>init.d</file>
6024 scripts whose values control the behavior of the scripts,
6025 and which a system administrator is likely to want to
6026 change. As the scripts themselves are frequently
6027 <tt>conffile</tt>s, modifying them requires that the
6028 administrator merge in their changes each time the package
6029 is upgraded and the <tt>conffile</tt> changes. To ease
6030 the burden on the system administrator, such configurable
6031 values should not be placed directly in the script.
6032 Instead, they should be placed in a file in
6033 <file>/etc/default</file>, which typically will have the same
6034 base name as the <file>init.d</file> script. This extra file
6035 should be sourced by the script when the script runs. It
6036 must contain only variable settings and comments in SUSv3
6037 <prgn>sh</prgn> format. It may either be a
6038 <tt>conffile</tt> or a configuration file maintained by
6039 the package maintainer scripts. See <ref id="config-files">
6044 To ensure that vital configurable values are always
6045 available, the <file>init.d</file> script should set default
6046 values for each of the shell variables it uses, either
6047 before sourcing the <file>/etc/default/</file> file or
6048 afterwards using something like the <tt>:
6049 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6050 script must behave sensibly and not fail if the
6051 <file>/etc/default</file> file is deleted.
6056 <heading>Interfacing with the initscript system</heading>
6059 Maintainers should use the abstraction layer provided by
6060 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6061 programs to deal with initscripts in their packages'
6062 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6063 and <prgn>postrm</prgn>.
6067 Directly managing the /etc/rc?.d links and directly
6068 invoking the <file>/etc/init.d/</file> initscripts should
6069 be done only by packages providing the initscript
6070 subsystem (such as <prgn>sysv-rc</prgn> and
6071 <prgn>file-rc</prgn>).
6075 <heading>Managing the links</heading>
6078 The program <prgn>update-rc.d</prgn> is provided for
6079 package maintainers to arrange for the proper creation and
6080 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6081 or their functional equivalent if another method is being
6082 used. This may be used by maintainers in their packages'
6083 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6087 You must not include any <file>/etc/rc<var>n</var>.d</file>
6088 symbolic links in the actual archive or manually create or
6089 remove the symbolic links in maintainer scripts; you must
6090 use the <prgn>update-rc.d</prgn> program instead. (The
6091 former will fail if an alternative method of maintaining
6092 runlevel information is being used.) You must not include
6093 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6094 in the archive either. (Only the <tt>sysvinit</tt>
6099 By default <prgn>update-rc.d</prgn> will start services in
6100 each of the multi-user state runlevels (2, 3, 4, and 5)
6101 and stop them in the halt runlevel (0), the single-user
6102 runlevel (1) and the reboot runlevel (6). The system
6103 administrator will have the opportunity to customize
6104 runlevels by simply adding, moving, or removing the
6105 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6106 symbolic links are being used, or by modifying
6107 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6112 To get the default behavior for your package, put in your
6113 <prgn>postinst</prgn> script
6114 <example compact="compact">
6115 update-rc.d <var>package</var> defaults
6117 and in your <prgn>postrm</prgn>
6118 <example compact="compact">
6119 if [ "$1" = purge ]; then
6120 update-rc.d <var>package</var> remove
6122 </example>. Note that if your package changes runlevels
6123 or priority, you may have to remove and recreate the links,
6124 since otherwise the old links may persist. Refer to the
6125 documentation of <prgn>update-rc.d</prgn>.
6129 This will use a default sequence number of 20. If it does
6130 not matter when or in which order the <file>init.d</file>
6131 script is run, use this default. If it does, then you
6132 should talk to the maintainer of the <prgn>sysvinit</prgn>
6133 package or post to <tt>debian-devel</tt>, and they will
6134 help you choose a number.
6138 For more information about using <tt>update-rc.d</tt>,
6139 please consult its man page <manref name="update-rc.d"
6145 <heading>Running initscripts</heading>
6147 The program <prgn>invoke-rc.d</prgn> is provided to make
6148 it easier for package maintainers to properly invoke an
6149 initscript, obeying runlevel and other locally-defined
6150 constraints that might limit a package's right to start,
6151 stop and otherwise manage services. This program may be
6152 used by maintainers in their packages' scripts.
6156 The package maintainer scripts must use
6157 <prgn>invoke-rc.d</prgn> to invoke the
6158 <file>/etc/init.d/*</file> initscripts, instead of
6159 calling them directly.
6163 By default, <prgn>invoke-rc.d</prgn> will pass any
6164 action requests (start, stop, reload, restart...) to the
6165 <file>/etc/init.d</file> script, filtering out requests
6166 to start or restart a service out of its intended
6171 Most packages will simply need to change:
6172 <example compact="compact">/etc/init.d/<package>
6173 <action></example> in their <prgn>postinst</prgn>
6174 and <prgn>prerm</prgn> scripts to:
6175 <example compact="compact">
6176 if which invoke-rc.d >/dev/null 2>&1; then
6177 invoke-rc.d <var>package</var> <action>
6179 /etc/init.d/<var>package</var> <action>
6185 A package should register its initscript services using
6186 <prgn>update-rc.d</prgn> before it tries to invoke them
6187 using <prgn>invoke-rc.d</prgn>. Invocation of
6188 unregistered services may fail.
6192 For more information about using
6193 <prgn>invoke-rc.d</prgn>, please consult its man page
6194 <manref name="invoke-rc.d" section="8">.
6200 <heading>Boot-time initialization</heading>
6203 There used to be another directory, <file>/etc/rc.boot</file>,
6204 which contained scripts which were run once per machine
6205 boot. This has been deprecated in favour of links from
6206 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6207 described in <ref id="/etc/init.d">. Packages must not
6208 place files in <file>/etc/rc.boot</file>.
6213 <heading>Example</heading>
6216 An example on which you can base your
6217 <file>/etc/init.d</file> scripts is found in
6218 <file>/etc/init.d/skeleton</file>.
6225 <heading>Console messages from <file>init.d</file> scripts</heading>
6228 This section describes the formats to be used for messages
6229 written to standard output by the <file>/etc/init.d</file>
6230 scripts. The intent is to improve the consistency of
6231 Debian's startup and shutdown look and feel. For this
6232 reason, please look very carefully at the details. We want
6233 the messages to have the same format in terms of wording,
6234 spaces, punctuation and case of letters.
6238 Here is a list of overall rules that should be used for
6239 messages generated by <file>/etc/init.d</file> scripts.
6245 The message should fit in one line (fewer than 80
6246 characters), start with a capital letter and end with
6247 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6251 If the script is performing some time consuming task in
6252 the background (not merely starting or stopping a
6253 program, for instance), an ellipsis (three dots:
6254 <tt>...</tt>) should be output to the screen, with no
6255 leading or tailing whitespace or line feeds.
6259 The messages should appear as if the computer is telling
6260 the user what it is doing (politely :-), but should not
6261 mention "it" directly. For example, instead of:
6262 <example compact="compact">
6263 I'm starting network daemons: nfsd mountd.
6265 the message should say
6266 <example compact="compact">
6267 Starting network daemons: nfsd mountd.
6274 <tt>init.d</tt> script should use the following standard
6275 message formats for the situations enumerated below.
6281 <p>When daemons are started</p>
6284 If the script starts one or more daemons, the output
6285 should look like this (a single line, no leading
6287 <example compact="compact">
6288 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6290 The <var>description</var> should describe the
6291 subsystem the daemon or set of daemons are part of,
6292 while <var>daemon-1</var> up to <var>daemon-n</var>
6293 denote each daemon's name (typically the file name of
6298 For example, the output of <file>/etc/init.d/lpd</file>
6300 <example compact="compact">
6301 Starting printer spooler: lpd.
6306 This can be achieved by saying
6307 <example compact="compact">
6308 echo -n "Starting printer spooler: lpd"
6309 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6312 in the script. If there are more than one daemon to
6313 start, the output should look like this:
6314 <example compact="compact">
6315 echo -n "Starting remote file system services:"
6316 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6317 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6318 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6321 This makes it possible for the user to see what is
6322 happening and when the final daemon has been started.
6323 Care should be taken in the placement of white spaces:
6324 in the example above the system administrators can
6325 easily comment out a line if they don't want to start
6326 a specific daemon, while the displayed message still
6332 <p>When a system parameter is being set</p>
6335 If you have to set up different system parameters
6336 during the system boot, you should use this format:
6337 <example compact="compact">
6338 Setting <var>parameter</var> to "<var>value</var>".
6343 You can use a statement such as the following to get
6345 <example compact="compact">
6346 echo "Setting DNS domainname to \"$domainname\"."
6351 Note that the same symbol (<tt>"</tt>) is used for the left
6352 and right quotation marks. A grave accent (<tt>`</tt>) is
6353 not a quote character; neither is an apostrophe
6359 <p>When a daemon is stopped or restarted</p>
6362 When you stop or restart a daemon, you should issue a
6363 message identical to the startup message, except that
6364 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6365 or <tt>Restarting</tt> respectively.
6369 For example, stopping the printer daemon will look like
6371 <example compact="compact">
6372 Stopping printer spooler: lpd.
6378 <p>When something is executed</p>
6381 There are several examples where you have to run a
6382 program at system startup or shutdown to perform a
6383 specific task, for example, setting the system's clock
6384 using <prgn>netdate</prgn> or killing all processes
6385 when the system shuts down. Your message should look
6387 <example compact="compact">
6388 Doing something very useful...done.
6390 You should print the <tt>done.</tt> immediately after
6391 the job has been completed, so that the user is
6392 informed why they have to wait. You can get this
6394 <example compact="compact">
6395 echo -n "Doing something very useful..."
6404 <p>When the configuration is reloaded</p>
6407 When a daemon is forced to reload its configuration
6408 files you should use the following format:
6409 <example compact="compact">
6410 Reloading <var>description</var> configuration...done.
6412 where <var>description</var> is the same as in the
6413 daemon starting message.
6421 <heading>Cron jobs</heading>
6424 Packages must not modify the configuration file
6425 <file>/etc/crontab</file>, and they must not modify the files in
6426 <file>/var/spool/cron/crontabs</file>.</p>
6429 If a package wants to install a job that has to be executed
6430 via cron, it should place a file with the name of the
6431 package in one or more of the following directories:
6432 <example compact="compact">
6438 As these directory names imply, the files within them are
6439 executed on an hourly, daily, weekly, or monthly basis,
6440 respectively. The exact times are listed in
6441 <file>/etc/crontab</file>.</p>
6444 All files installed in any of these directories must be
6445 scripts (e.g., shell scripts or Perl scripts) so that they
6446 can easily be modified by the local system administrator.
6447 In addition, they must be treated as configuration files.
6451 If a certain job has to be executed at some other frequency or
6452 at a specific time, the package should install a file
6453 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6454 same syntax as <file>/etc/crontab</file> and is processed by
6455 <prgn>cron</prgn> automatically. The file must also be
6456 treated as a configuration file. (Note that entries in the
6457 <file>/etc/cron.d</file> directory are not handled by
6458 <prgn>anacron</prgn>. Thus, you should only use this
6459 directory for jobs which may be skipped if the system is not
6463 The scripts or crontab entries in these directories should
6464 check if all necessary programs are installed before they
6465 try to execute them. Otherwise, problems will arise when a
6466 package was removed but not purged since configuration files
6467 are kept on the system in this situation.</p>
6471 <heading>Menus</heading>
6474 The Debian <tt>menu</tt> package provides a standard
6475 interface between packages providing applications and
6476 <em>menu programs</em> (either X window managers or
6477 text-based menu programs such as <prgn>pdmenu</prgn>).
6481 All packages that provide applications that need not be
6482 passed any special command line arguments for normal
6483 operation should register a menu entry for those
6484 applications, so that users of the <tt>menu</tt> package
6485 will automatically get menu entries in their window
6486 managers, as well in shells like <tt>pdmenu</tt>.
6490 Menu entries should follow the current menu policy.
6494 The menu policy can be found in the <tt>menu-policy</tt>
6495 files in the <tt>debian-policy</tt> package.
6496 It is also available from the Debian web mirrors at
6497 <tt><url name="/doc/packaging-manuals/menu-policy/"
6498 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6502 Please also refer to the <em>Debian Menu System</em>
6503 documentation that comes with the <package>menu</package>
6504 package for information about how to register your
6510 <heading>Multimedia handlers</heading>
6513 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6514 is a mechanism for encoding files and data streams and
6515 providing meta-information about them, in particular their
6516 type (e.g. audio or video) and format (e.g. PNG, HTML,
6521 Registration of MIME type handlers allows programs like mail
6522 user agents and web browsers to invoke these handlers to
6523 view, edit or display MIME types they don't support directly.
6527 Packages which provide the ability to view/show/play,
6528 compose, edit or print MIME types should register themselves
6529 as such following the current MIME support policy.
6533 The MIME support policy can be found in the <tt>mime-policy</tt>
6534 files in the <tt>debian-policy</tt> package.
6535 It is also available from the Debian web mirrors at
6536 <tt><url name="/doc/packaging-manuals/mime-policy/"
6537 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6543 <heading>Keyboard configuration</heading>
6546 To achieve a consistent keyboard configuration so that all
6547 applications interpret a keyboard event the same way, all
6548 programs in the Debian distribution must be configured to
6549 comply with the following guidelines.
6553 The following keys must have the specified interpretations:
6556 <tag><tt><--</tt></tag>
6557 <item>delete the character to the left of the cursor</item>
6559 <tag><tt>Delete</tt></tag>
6560 <item>delete the character to the right of the cursor</item>
6562 <tag><tt>Control+H</tt></tag>
6563 <item>emacs: the help prefix</item>
6566 The interpretation of any keyboard events should be
6567 independent of the terminal that is used, be it a virtual
6568 console, an X terminal emulator, an rlogin/telnet session,
6573 The following list explains how the different programs
6574 should be set up to achieve this:
6580 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6584 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6588 X translations are set up to make
6589 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6590 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6591 is the vt220 escape code for the "delete character"
6592 key). This must be done by loading the X resources
6593 using <prgn>xrdb</prgn> on all local X displays, not
6594 using the application defaults, so that the
6595 translation resources used correspond to the
6596 <prgn>xmodmap</prgn> settings.
6600 The Linux console is configured to make
6601 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6602 generate <tt>ESC [ 3 ~</tt>.
6606 X applications are configured so that <tt><</tt>
6607 deletes left, and <tt>Delete</tt> deletes right. Motif
6608 applications already work like this.
6612 Terminals should have <tt>stty erase ^?</tt> .
6616 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6617 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6618 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6622 Emacs is programmed to map <tt>KB_Backspace</tt> or
6623 the <tt>stty erase</tt> character to
6624 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6625 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6626 <tt>^H</tt> to <tt>help</tt> as always.
6630 Other applications use the <tt>stty erase</tt>
6631 character and <tt>kdch1</tt> for the two delete keys,
6632 with ASCII DEL being "delete previous character" and
6633 <tt>kdch1</tt> being "delete character under
6641 This will solve the problem except for the following
6648 Some terminals have a <tt><--</tt> key that cannot
6649 be made to produce anything except <tt>^H</tt>. On
6650 these terminals Emacs help will be unavailable on
6651 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6652 character takes precedence in Emacs, and has been set
6653 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6654 available) can be used instead.
6658 Some operating systems use <tt>^H</tt> for <tt>stty
6659 erase</tt>. However, modern telnet versions and all
6660 rlogin versions propagate <tt>stty</tt> settings, and
6661 almost all UNIX versions honour <tt>stty erase</tt>.
6662 Where the <tt>stty</tt> settings are not propagated
6663 correctly, things can be made to work by using
6664 <tt>stty</tt> manually.
6668 Some systems (including previous Debian versions) use
6669 <prgn>xmodmap</prgn> to arrange for both
6670 <tt><--</tt> and <tt>Delete</tt> to generate
6671 <tt>KB_Delete</tt>. We can change the behavior of
6672 their X clients using the same X resources that we use
6673 to do it for our own clients, or configure our clients
6674 using their resources when things are the other way
6675 around. On displays configured like this
6676 <tt>Delete</tt> will not work, but <tt><--</tt>
6681 Some operating systems have different <tt>kdch1</tt>
6682 settings in their <tt>terminfo</tt> database for
6683 <tt>xterm</tt> and others. On these systems the
6684 <tt>Delete</tt> key will not work correctly when you
6685 log in from a system conforming to our policy, but
6686 <tt><--</tt> will.
6693 <heading>Environment variables</heading>
6696 A program must not depend on environment variables to get
6697 reasonable defaults. (That's because these environment
6698 variables would have to be set in a system-wide
6699 configuration file like <file>/etc/profile</file>, which is not
6700 supported by all shells.)
6704 If a program usually depends on environment variables for its
6705 configuration, the program should be changed to fall back to
6706 a reasonable default configuration if these environment
6707 variables are not present. If this cannot be done easily
6708 (e.g., if the source code of a non-free program is not
6709 available), the program must be replaced by a small
6710 "wrapper" shell script which sets the environment variables
6711 if they are not already defined, and calls the original program.
6715 Here is an example of a wrapper script for this purpose:
6717 <example compact="compact">
6719 BAR=${BAR:-/var/lib/fubar}
6721 exec /usr/lib/foo/foo "$@"
6726 Furthermore, as <file>/etc/profile</file> is a configuration
6727 file of the <prgn>base-files</prgn> package, other packages must
6728 not put any environment variables or other commands into that
6733 <sect id="doc-base">
6734 <heading>Registering Documents using doc-base</heading>
6737 The <package>doc-base</package> package implements a
6738 flexible mechanism for handling and presenting
6739 documentation. The recommended practice is for every Debian
6740 package that provides online documentation (other than just
6741 manual pages) to register these documents with
6742 <package>doc-base</package> by installing a
6743 <package>doc-base</package> control file via the
6744 <prgn/install-docs/ script at installation time and
6745 de-register the manuals again when the package is removed.
6748 Please refer to the documentation that comes with the
6749 <package>doc-base</package> package for information and
6758 <heading>Files</heading>
6761 <heading>Binaries</heading>
6764 Two different packages must not install programs with
6765 different functionality but with the same filenames. (The
6766 case of two programs having the same functionality but
6767 different implementations is handled via "alternatives" or
6768 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6769 <ref id="conflicts"> respectively.) If this case happens,
6770 one of the programs must be renamed. The maintainers should
6771 report this to the <tt>debian-devel</tt> mailing list and
6772 try to find a consensus about which program will have to be
6773 renamed. If a consensus cannot be reached, <em>both</em>
6774 programs must be renamed.
6778 By default, when a package is being built, any binaries
6779 created should include debugging information, as well as
6780 being compiled with optimization. You should also turn on
6781 as many reasonable compilation warnings as possible; this
6782 makes life easier for porters, who can then look at build
6783 logs for possible problems. For the C programming language,
6784 this means the following compilation parameters should be
6786 <example compact="compact">
6788 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6790 INSTALL = install -s # (or use strip on the files in debian/tmp)
6795 Note that by default all installed binaries should be stripped,
6796 either by using the <tt>-s</tt> flag to
6797 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6798 the binaries after they have been copied into
6799 <file>debian/tmp</file> but before the tree is made into a
6804 Although binaries in the build tree should be compiled with
6805 debugging information by default, it can often be difficult to
6806 debug programs if they are also subjected to compiler
6807 optimization. For this reason, it is recommended to support the
6808 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6809 (see <ref id="debianrules-options">). This variable can contain
6810 several flags to change how a package is compiled and built.
6814 It is up to the package maintainer to decide what
6815 compilation options are best for the package. Certain
6816 binaries (such as computationally-intensive programs) will
6817 function better with certain flags (<tt>-O3</tt>, for
6818 example); feel free to use them. Please use good judgment
6819 here. Don't use flags for the sake of it; only use them
6820 if there is good reason to do so. Feel free to override
6821 the upstream author's ideas about which compilation
6822 options are best: they are often inappropriate for our
6828 <sect id="libraries">
6829 <heading>Libraries</heading>
6832 If the package is <strong>architecture: any</strong>, then
6833 the shared library compilation and linking flags must have
6834 <tt>-fPIC</tt>, or the package shall not build on some of
6835 the supported architectures<footnote>
6837 If you are using GCC, <tt>-fPIC</tt> produces code with
6838 relocatable position independent code, which is required for
6839 most architectures to create a shared library, with i386 and
6840 perhaps some others where non position independent code is
6841 permitted in a shared library.
6844 Position independent code may have a performance penalty,
6845 especially on <tt>i386</tt>. However, in most cases the
6846 speed penalty must be measured against the memory wasted on
6847 the few architectures where non position independent code is
6850 </footnote>. Any exception to this rule must be discussed on
6851 the mailing list <em>debian-devel@lists.debian.org</em>, and
6852 a rough consensus obtained. The reasons for not compiling
6853 with <tt>-fPIC</tt> flag must be recorded in the file
6854 <tt>README.Debian</tt>, and care must be taken to either
6855 restrict the architecture or arrange for <tt>-fPIC</tt> to
6856 be used on architectures where it is required.<footnote>
6858 Some of the reasons why this might be required is if the
6859 library contains hand crafted assembly code that is not
6860 relocatable, the speed penalty is excessive for compute
6861 intensive libs, and similar reasons.
6866 As to the static libraries, the common case is not to have
6867 relocatable code, since there is no benefit, unless in specific
6868 cases; therefore the static version must not be compiled
6869 with the <tt>-fPIC</tt> flag. Any exception to this rule
6870 should be discussed on the mailing list
6871 <em>debian-devel@lists.debian.org</em>, and the reasons for
6872 compiling with the <tt>-fPIC</tt> flag must be recorded in
6873 the file <tt>README.Debian</tt>. <footnote>
6875 Some of the reasons for linking static libraries with
6876 the <tt>-fPIC</tt> flag are if, for example, one needs a
6877 Perl API for a library that is under rapid development,
6878 and has an unstable API, so shared libraries are
6879 pointless at this phase of the library's development. In
6880 that case, since Perl needs a library with relocatable
6881 code, it may make sense to create a static library with
6882 relocatable code. Another reason cited is if you are
6883 distilling various libraries into a common shared
6884 library, like <tt>mklibs</tt> does in the Debian
6890 In other words, if both a shared and a static library is
6891 being built, each source unit (<tt>*.c</tt>, for example,
6892 for C files) will need to be compiled twice, for the normal
6896 You must specify the gcc option <tt>-D_REENTRANT</tt>
6897 when building a library (either static or shared) to make
6898 the library compatible with LinuxThreads.
6902 Although not enforced by the build tools, shared libraries
6903 must be linked against all libraries that they use symbols from
6904 in the same way that binaries are. This ensures the correct
6905 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6906 system and guarantees that all libraries can be safely opened
6907 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6908 option <tt>-Wl,-z,defs</tt> when building a shared library.
6909 Since this option enforces symbol resolution at build time,
6910 a missing library reference will be caught early as a fatal
6915 All installed shared libraries should be stripped with
6916 <example compact="compact">
6917 strip --strip-unneeded <var>your-lib</var>
6919 (The option <tt>--strip-unneeded</tt> makes
6920 <prgn>strip</prgn> remove only the symbols which aren't
6921 needed for relocation processing.) Shared libraries can
6922 function perfectly well when stripped, since the symbols for
6923 dynamic linking are in a separate part of the ELF object
6925 You might also want to use the options
6926 <tt>--remove-section=.comment</tt> and
6927 <tt>--remove-section=.note</tt> on both shared libraries
6928 and executables, and <tt>--strip-debug</tt> on static
6934 Note that under some circumstances it may be useful to
6935 install a shared library unstripped, for example when
6936 building a separate package to support debugging.
6940 Shared object files (often <file>.so</file> files) that are not
6941 public libraries, that is, they are not meant to be linked
6942 to by third party executables (binaries of other packages),
6943 should be installed in subdirectories of the
6944 <file>/usr/lib</file> directory. Such files are exempt from the
6945 rules that govern ordinary shared libraries, except that
6946 they must not be installed executable and should be
6948 A common example are the so-called "plug-ins",
6949 internal shared objects that are dynamically loaded by
6950 programs using <manref name="dlopen" section="3">.
6955 Packages containing shared libraries that may be linked to
6956 by other packages' binaries, but which for some
6957 <em>compelling</em> reason can not be installed in
6958 <file>/usr/lib</file> directory, may install the shared library
6959 files in subdirectories of the <file>/usr/lib</file> directory,
6960 in which case they should arrange to add that directory in
6961 <file>/etc/ld.so.conf</file> in the package's post-installation
6962 script, and remove it in the package's post-removal script.
6966 An ever increasing number of packages are using
6967 <prgn>libtool</prgn> to do their linking. The latest GNU
6968 libtools (>= 1.3a) can take advantage of the metadata in the
6969 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6970 files). The main advantage of <prgn>libtool</prgn>'s
6971 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6972 store and subsequently access metadata with respect to the
6973 libraries it builds. <prgn>libtool</prgn> will search for
6974 those files, which contain a lot of useful information about
6975 a library (such as library dependency information for static
6976 linking). Also, they're <em>essential</em> for programs
6977 using <tt>libltdl</tt>.<footnote>
6978 Although <prgn>libtool</prgn> is fully capable of
6979 linking against shared libraries which don't have
6980 <tt>.la</tt> files, as it is a mere shell script it can
6981 add considerably to the build time of a
6982 <prgn>libtool</prgn>-using package if that shell script
6983 has to derive all this information from first principles
6984 for each library every time it is linked. With the
6985 advent of <prgn>libtool</prgn> version 1.4 (and to a
6986 lesser extent <prgn>libtool</prgn> version 1.3), the
6987 <file>.la</file> files also store information about
6988 inter-library dependencies which cannot necessarily be
6989 derived after the <file>.la</file> file is deleted.
6994 Packages that use <prgn>libtool</prgn> to create shared
6995 libraries should include the <file>.la</file> files in the
6996 <tt>-dev</tt> package, unless the package relies on
6997 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6998 the <tt>.la</tt> files must go in the run-time library
7003 You must make sure that you use only released versions of
7004 shared libraries to build your packages; otherwise other
7005 users will not be able to run your binaries
7006 properly. Producing source packages that depend on
7007 unreleased compilers is also usually a bad
7014 <heading>Shared libraries</heading>
7016 This section has moved to <ref id="sharedlibs">.
7022 <heading>Scripts</heading>
7025 All command scripts, including the package maintainer
7026 scripts inside the package and used by <prgn>dpkg</prgn>,
7027 should have a <tt>#!</tt> line naming the shell to be used
7032 In the case of Perl scripts this should be
7033 <tt>#!/usr/bin/perl</tt>.
7037 When scripts are installed into a directory in the system
7038 PATH, the script name should not include an extension such
7039 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7040 language currently used to implement it.
7043 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7044 should almost certainly start with <tt>set -e</tt> so that
7045 errors are detected. Every script should use
7046 <tt>set -e</tt> or check the exit status of <em>every</em>
7051 Scripts may assume that <file>/bin/sh</file> implements the
7052 SUSv3 Shell Command Language<footnote>
7053 Single UNIX Specification, version 3, which is also IEEE
7054 1003.1-2004 (POSIX), and is available on the World Wide Web
7055 from <url id="http://www.unix.org/version3/online.html"
7056 name="The Open Group"> after free
7057 registration.</footnote>
7058 plus the following additional features not mandated by
7060 These features are in widespread use in the Linux community
7061 and are implemented in all of bash, dash, and ksh, the most
7062 common shells users may wish to use as <file>/bin/sh</file>.
7065 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7066 must not generate a newline.</item>
7067 <item><tt>test</tt>, if implemented as a shell built-in, must
7068 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7070 <item><tt>local</tt> to create a scoped variable must be
7071 supported, including listing multiple variables in a single
7072 local command and assigning a value to a variable at the
7073 same time as localizing it. <tt>local</tt> may or
7074 may not preserve the variable value from an outer scope if
7075 no assignment is present. Uses such as:
7079 # ... use a, b, c, d ...
7082 must be supported and must set the value of <tt>c</tt> to
7086 If a shell script requires non-SUSv3 features from the shell
7087 interpreter other than those listed above, the appropriate shell
7088 must be specified in the first line of the script (e.g.,
7089 <tt>#!/bin/bash</tt>) and the package must depend on the package
7090 providing the shell (unless the shell package is marked
7091 "Essential", as in the case of <prgn>bash</prgn>).
7095 You may wish to restrict your script to SUSv3 features plus the
7096 above set when possible so that it may use <file>/bin/sh</file>
7097 as its interpreter. If your script works with <prgn>dash</prgn>
7098 (originally called <prgn>ash</prgn>), it probably complies with
7099 the above requirements, but if you are in doubt, use
7100 <file>/bin/bash</file>.
7104 Perl scripts should check for errors when making any
7105 system calls, including <tt>open</tt>, <tt>print</tt>,
7106 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7110 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7111 scripting languages. See <em>Csh Programming Considered
7112 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7113 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7114 If an upstream package comes with <prgn>csh</prgn> scripts
7115 then you must make sure that they start with
7116 <tt>#!/bin/csh</tt> and make your package depend on the
7117 <prgn>c-shell</prgn> virtual package.
7121 Any scripts which create files in world-writeable
7122 directories (e.g., in <file>/tmp</file>) must use a
7123 mechanism which will fail atomically if a file with the same
7124 name already exists.
7128 The Debian base system provides the <prgn>tempfile</prgn>
7129 and <prgn>mktemp</prgn> utilities for use by scripts for
7136 <heading>Symbolic links</heading>
7139 In general, symbolic links within a top-level directory
7140 should be relative, and symbolic links pointing from one
7141 top-level directory into another should be absolute. (A
7142 top-level directory is a sub-directory of the root
7143 directory <file>/</file>.)
7147 In addition, symbolic links should be specified as short as
7148 possible, i.e., link targets like <file>foo/../bar</file> are
7153 Note that when creating a relative link using
7154 <prgn>ln</prgn> it is not necessary for the target of the
7155 link to exist relative to the working directory you're
7156 running <prgn>ln</prgn> from, nor is it necessary to change
7157 directory to the directory where the link is to be made.
7158 Simply include the string that should appear as the target
7159 of the link (this will be a pathname relative to the
7160 directory in which the link resides) as the first argument
7165 For example, in your <prgn>Makefile</prgn> or
7166 <file>debian/rules</file>, you can do things like:
7167 <example compact="compact">
7168 ln -fs gcc $(prefix)/bin/cc
7169 ln -fs gcc debian/tmp/usr/bin/cc
7170 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7171 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7176 A symbolic link pointing to a compressed file should always
7177 have the same file extension as the referenced file. (For
7178 example, if a file <file>foo.gz</file> is referenced by a
7179 symbolic link, the filename of the link has to end with
7180 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7185 <heading>Device files</heading>
7188 Packages must not include device files in the package file
7193 If a package needs any special device files that are not
7194 included in the base system, it must call
7195 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7196 after notifying the user<footnote>
7197 This notification could be done via a (low-priority)
7198 debconf message, or an echo (printf) statement.
7203 Packages must not remove any device files in the
7204 <prgn>postrm</prgn> or any other script. This is left to the
7205 system administrator.
7209 Debian uses the serial devices
7210 <file>/dev/ttyS*</file>. Programs using the old
7211 <file>/dev/cu*</file> devices should be changed to use
7212 <file>/dev/ttyS*</file>.
7216 <sect id="config-files">
7217 <heading>Configuration files</heading>
7220 <heading>Definitions</heading>
7224 <tag>configuration file</tag>
7226 A file that affects the operation of a program, or
7227 provides site- or host-specific information, or
7228 otherwise customizes the behavior of a program.
7229 Typically, configuration files are intended to be
7230 modified by the system administrator (if needed or
7231 desired) to conform to local policy or to provide
7232 more useful site-specific behavior.
7235 <tag><tt>conffile</tt></tag>
7237 A file listed in a package's <tt>conffiles</tt>
7238 file, and is treated specially by <prgn>dpkg</prgn>
7239 (see <ref id="configdetails">).
7245 The distinction between these two is important; they are
7246 not interchangeable concepts. Almost all
7247 <tt>conffile</tt>s are configuration files, but many
7248 configuration files are not <tt>conffiles</tt>.
7252 As noted elsewhere, <file>/etc/init.d</file> scripts,
7253 <file>/etc/default</file> files, scripts installed in
7254 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7255 configuration installed in <file>/etc/cron.d</file> must be
7256 treated as configuration files. In general, any script that
7257 embeds configuration information is de-facto a configuration
7258 file and should be treated as such.
7263 <heading>Location</heading>
7266 Any configuration files created or used by your package
7267 must reside in <file>/etc</file>. If there are several,
7268 consider creating a subdirectory of <file>/etc</file>
7269 named after your package.
7273 If your package creates or uses configuration files
7274 outside of <file>/etc</file>, and it is not feasible to modify
7275 the package to use <file>/etc</file> directly, put the files
7276 in <file>/etc</file> and create symbolic links to those files
7277 from the location that the package requires.
7282 <heading>Behavior</heading>
7285 Configuration file handling must conform to the following
7287 <list compact="compact">
7289 local changes must be preserved during a package
7293 configuration files must be preserved when the
7294 package is removed, and only deleted when the
7301 The easy way to achieve this behavior is to make the
7302 configuration file a <tt>conffile</tt>. This is
7303 appropriate only if it is possible to distribute a default
7304 version that will work for most installations, although
7305 some system administrators may choose to modify it. This
7306 implies that the default version will be part of the
7307 package distribution, and must not be modified by the
7308 maintainer scripts during installation (or at any other
7313 In order to ensure that local changes are preserved
7314 correctly, no package may contain or make hard links to
7315 conffiles.<footnote>
7316 Rationale: There are two problems with hard links.
7317 The first is that some editors break the link while
7318 editing one of the files, so that the two files may
7319 unwittingly become unlinked and different. The second
7320 is that <prgn>dpkg</prgn> might break the hard link
7321 while upgrading <tt>conffile</tt>s.
7326 The other way to do it is via the maintainer scripts. In
7327 this case, the configuration file must not be listed as a
7328 <tt>conffile</tt> and must not be part of the package
7329 distribution. If the existence of a file is required for
7330 the package to be sensibly configured it is the
7331 responsibility of the package maintainer to provide
7332 maintainer scripts which correctly create, update and
7333 maintain the file and remove it on purge. (See <ref
7334 id="maintainerscripts"> for more information.) These
7335 scripts must be idempotent (i.e., must work correctly if
7336 <prgn>dpkg</prgn> needs to re-run them due to errors
7337 during installation or removal), must cope with all the
7338 variety of ways <prgn>dpkg</prgn> can call maintainer
7339 scripts, must not overwrite or otherwise mangle the user's
7340 configuration without asking, must not ask unnecessary
7341 questions (particularly during upgrades), and must
7342 otherwise be good citizens.
7346 The scripts are not required to configure every possible
7347 option for the package, but only those necessary to get
7348 the package running on a given system. Ideally the
7349 sysadmin should not have to do any configuration other
7350 than that done (semi-)automatically by the
7351 <prgn>postinst</prgn> script.
7355 A common practice is to create a script called
7356 <file><var>package</var>-configure</file> and have the
7357 package's <prgn>postinst</prgn> call it if and only if the
7358 configuration file does not already exist. In certain
7359 cases it is useful for there to be an example or template
7360 file which the maintainer scripts use. Such files should
7361 be in <file>/usr/share/<var>package</var></file> or
7362 <file>/usr/lib/<var>package</var></file> (depending on whether
7363 they are architecture-independent or not). There should
7364 be symbolic links to them from
7365 <file>/usr/share/doc/<var>package</var>/examples</file> if
7366 they are examples, and should be perfectly ordinary
7367 <prgn>dpkg</prgn>-handled files (<em>not</em>
7368 configuration files).
7372 These two styles of configuration file handling must
7373 not be mixed, for that way lies madness:
7374 <prgn>dpkg</prgn> will ask about overwriting the file
7375 every time the package is upgraded.
7380 <heading>Sharing configuration files</heading>
7383 Packages which specify the same file as a
7384 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7385 with each other. (This is an instance of the general rule
7386 about not sharing files. Note that neither alternatives
7387 nor diversions are likely to be appropriate in this case;
7388 in particular, <prgn>dpkg</prgn> does not handle diverted
7389 <tt>conffile</tt>s well.)
7393 The maintainer scripts must not alter a <tt>conffile</tt>
7394 of <em>any</em> package, including the one the scripts
7399 If two or more packages use the same configuration file
7400 and it is reasonable for both to be installed at the same
7401 time, one of these packages must be defined as
7402 <em>owner</em> of the configuration file, i.e., it will be
7403 the package which handles that file as a configuration
7404 file. Other packages that use the configuration file must
7405 depend on the owning package if they require the
7406 configuration file to operate. If the other package will
7407 use the configuration file if present, but is capable of
7408 operating without it, no dependency need be declared.
7412 If it is desirable for two or more related packages to
7413 share a configuration file <em>and</em> for all of the
7414 related packages to be able to modify that configuration
7415 file, then the following should be done:
7416 <enumlist compact="compact">
7418 One of the related packages (the "owning" package)
7419 will manage the configuration file with maintainer
7420 scripts as described in the previous section.
7423 The owning package should also provide a program
7424 that the other packages may use to modify the
7428 The related packages must use the provided program
7429 to make any desired modifications to the
7430 configuration file. They should either depend on
7431 the core package to guarantee that the configuration
7432 modifier program is available or accept gracefully
7433 that they cannot modify the configuration file if it
7434 is not. (This is in addition to the fact that the
7435 configuration file may not even be present in the
7442 Sometimes it's appropriate to create a new package which
7443 provides the basic infrastructure for the other packages
7444 and which manages the shared configuration files. (The
7445 <tt>sgml-base</tt> package is a good example.)
7450 <heading>User configuration files ("dotfiles")</heading>
7453 The files in <file>/etc/skel</file> will automatically be
7454 copied into new user accounts by <prgn>adduser</prgn>.
7455 No other program should reference the files in
7456 <file>/etc/skel</file>.
7460 Therefore, if a program needs a dotfile to exist in
7461 advance in <file>$HOME</file> to work sensibly, that dotfile
7462 should be installed in <file>/etc/skel</file> and treated as a
7467 However, programs that require dotfiles in order to
7468 operate sensibly are a bad thing, unless they do create
7469 the dotfiles themselves automatically.
7473 Furthermore, programs should be configured by the Debian
7474 default installation to behave as closely to the upstream
7475 default behavior as possible.
7479 Therefore, if a program in a Debian package needs to be
7480 configured in some way in order to operate sensibly, that
7481 should be done using a site-wide configuration file placed
7482 in <file>/etc</file>. Only if the program doesn't support a
7483 site-wide default configuration and the package maintainer
7484 doesn't have time to add it may a default per-user file be
7485 placed in <file>/etc/skel</file>.
7489 <file>/etc/skel</file> should be as empty as we can make it.
7490 This is particularly true because there is no easy (or
7491 necessarily desirable) mechanism for ensuring that the
7492 appropriate dotfiles are copied into the accounts of
7493 existing users when a package is installed.
7499 <heading>Log files</heading>
7501 Log files should usually be named
7502 <file>/var/log/<var>package</var>.log</file>. If you have many
7503 log files, or need a separate directory for permission
7504 reasons (<file>/var/log</file> is writable only by
7505 <file>root</file>), you should usually create a directory named
7506 <file>/var/log/<var>package</var></file> and place your log
7511 Log files must be rotated occasionally so that they don't
7512 grow indefinitely; the best way to do this is to drop a log
7513 rotation configuration file into the directory
7514 <file>/etc/logrotate.d</file> and use the facilities provided by
7515 logrotate.<footnote>
7517 The traditional approach to log files has been to set up
7518 <em>ad hoc</em> log rotation schemes using simple shell
7519 scripts and cron. While this approach is highly
7520 customizable, it requires quite a lot of sysadmin work.
7521 Even though the original Debian system helped a little
7522 by automatically installing a system which can be used
7523 as a template, this was deemed not enough.
7527 The use of <prgn>logrotate</prgn>, a program developed
7528 by Red Hat, is better, as it centralizes log management.
7529 It has both a configuration file
7530 (<file>/etc/logrotate.conf</file>) and a directory where
7531 packages can drop their individual log rotation
7532 configurations (<file>/etc/logrotate.d</file>).
7535 Here is a good example for a logrotate config
7536 file (for more information see <manref name="logrotate"
7538 <example compact="compact">
7539 /var/log/foo/*.log {
7544 /etc/init.d/foo force-reload
7548 This rotates all files under <file>/var/log/foo</file>, saves 12
7549 compressed generations, and forces the daemon to reload its
7550 configuration information after the log rotation.
7554 Log files should be removed when the package is
7555 purged (but not when it is only removed). This should be
7556 done by the <prgn>postrm</prgn> script when it is called
7557 with the argument <tt>purge</tt> (see <ref
7558 id="removedetails">).
7563 <heading>Permissions and owners</heading>
7566 The rules in this section are guidelines for general use.
7567 If necessary you may deviate from the details below.
7568 However, if you do so you must make sure that what is done
7569 is secure and you should try to be as consistent as possible
7570 with the rest of the system. You should probably also
7571 discuss it on <prgn>debian-devel</prgn> first.
7575 Files should be owned by <tt>root:root</tt>, and made
7576 writable only by the owner and universally readable (and
7577 executable, if appropriate), that is mode 644 or 755.
7581 Directories should be mode 755 or (for group-writability)
7582 mode 2775. The ownership of the directory should be
7583 consistent with its mode: if a directory is mode 2775, it
7584 should be owned by the group that needs write access to
7587 When a package is upgraded, and the owner or permissions
7588 of a file included in the package has changed, dpkg
7589 arranges for the ownership and permissions to be
7590 correctly set upon installation. However, this does not
7591 extend to directories; the permissions and ownership of
7592 directories already on the system does not change on
7593 install or upgrade of packages. This makes sense, since
7594 otherwise common directories like <tt>/usr</tt> would
7595 always be in flux. To correctly change permissions of a
7596 directory the package owns, explicit action is required,
7597 usually in the <tt>postinst</tt> script. Care must be
7598 taken to handle downgrades as well, in that case.
7605 Setuid and setgid executables should be mode 4755 or 2755
7606 respectively, and owned by the appropriate user or group.
7607 They should not be made unreadable (modes like 4711 or
7608 2711 or even 4111); doing so achieves no extra security,
7609 because anyone can find the binary in the freely available
7610 Debian package; it is merely inconvenient. For the same
7611 reason you should not restrict read or execute permissions
7612 on non-set-id executables.
7616 Some setuid programs need to be restricted to particular
7617 sets of users, using file permissions. In this case they
7618 should be owned by the uid to which they are set-id, and by
7619 the group which should be allowed to execute them. They
7620 should have mode 4754; again there is no point in making
7621 them unreadable to those users who must not be allowed to
7626 It is possible to arrange that the system administrator can
7627 reconfigure the package to correspond to their local
7628 security policy by changing the permissions on a binary:
7629 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7630 described below.<footnote>
7631 Ordinary files installed by <prgn>dpkg</prgn> (as
7632 opposed to <tt>conffile</tt>s and other similar objects)
7633 normally have their permissions reset to the distributed
7634 permissions when the package is reinstalled. However,
7635 the use of <prgn>dpkg-statoverride</prgn> overrides this
7636 default behavior. If you use this method, you should
7637 remember to describe <prgn>dpkg-statoverride</prgn> in
7638 the package documentation; being a relatively new
7639 addition to Debian, it is probably not yet well-known.
7641 Another method you should consider is to create a group for
7642 people allowed to use the program(s) and make any setuid
7643 executables executable only by that group.
7647 If you need to create a new user or group for your package
7648 there are two possibilities. Firstly, you may need to
7649 make some files in the binary package be owned by this
7650 user or group, or you may need to compile the user or
7651 group id (rather than just the name) into the binary
7652 (though this latter should be avoided if possible, as in
7653 this case you need a statically allocated id).</p>
7656 If you need a statically allocated id, you must ask for a
7657 user or group id from the <tt>base-passwd</tt> maintainer,
7658 and must not release the package until you have been
7659 allocated one. Once you have been allocated one you must
7660 either make the package depend on a version of the
7661 <tt>base-passwd</tt> package with the id present in
7662 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7663 your package to create the user or group itself with the
7664 correct id (using <tt>adduser</tt>) in its
7665 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7666 the <prgn>postinst</prgn> is to be preferred if it is
7667 possible, otherwise a pre-dependency will be needed on the
7668 <tt>adduser</tt> package.)
7672 On the other hand, the program might be able to determine
7673 the uid or gid from the user or group name at runtime, so
7674 that a dynamically allocated id can be used. In this case
7675 you should choose an appropriate user or group name,
7676 discussing this on <prgn>debian-devel</prgn> and checking
7677 with the <package/base-passwd/ maintainer that it is unique and that
7678 they do not wish you to use a statically allocated id
7679 instead. When this has been checked you must arrange for
7680 your package to create the user or group if necessary using
7681 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7682 <prgn>postinst</prgn> script (again, the latter is to be
7683 preferred if it is possible).
7687 Note that changing the numeric value of an id associated
7688 with a name is very difficult, and involves searching the
7689 file system for all appropriate files. You need to think
7690 carefully whether a static or dynamic id is required, since
7691 changing your mind later will cause problems.
7694 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7696 This section is not intended as policy, but as a
7697 description of the use of <prgn>dpkg-statoverride</prgn>.
7701 If a system administrator wishes to have a file (or
7702 directory or other such thing) installed with owner and
7703 permissions different from those in the distributed Debian
7704 package, they can use the <prgn>dpkg-statoverride</prgn>
7705 program to instruct <prgn>dpkg</prgn> to use the different
7706 settings every time the file is installed. Thus the
7707 package maintainer should distribute the files with their
7708 normal permissions, and leave it for the system
7709 administrator to make any desired changes. For example, a
7710 daemon which is normally required to be setuid root, but
7711 in certain situations could be used without being setuid,
7712 should be installed setuid in the <tt>.deb</tt>. Then the
7713 local system administrator can change this if they wish.
7714 If there are two standard ways of doing it, the package
7715 maintainer can use <tt>debconf</tt> to find out the
7716 preference, and call <prgn>dpkg-statoverride</prgn> in the
7717 maintainer script if necessary to accommodate the system
7718 administrator's choice. Care must be taken during
7719 upgrades to not override an existing setting.
7723 Given the above, <prgn>dpkg-statoverride</prgn> is
7724 essentially a tool for system administrators and would not
7725 normally be needed in the maintainer scripts. There is
7726 one type of situation, though, where calls to
7727 <prgn>dpkg-statoverride</prgn> would be needed in the
7728 maintainer scripts, and that involves packages which use
7729 dynamically allocated user or group ids. In such a
7730 situation, something like the following idiom can be very
7731 helpful in the package's <prgn>postinst</prgn>, where
7732 <tt>sysuser</tt> is a dynamically allocated id:
7734 for i in /usr/bin/foo /usr/sbin/bar
7736 # only do something when no setting exists
7737 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7739 #include: debconf processing, question about foo and bar
7740 if [ "$RET" = "true" ] ; then
7741 dpkg-statoverride --update --add sysuser root 4755 $i
7746 The corresponding <tt>dpkg-statoverride --remove</tt>
7747 calls can then be made unconditionally when the package is
7755 <chapt id="customized-programs">
7756 <heading>Customized programs</heading>
7758 <sect id="arch-spec">
7759 <heading>Architecture specification strings</heading>
7762 If a program needs to specify an <em>architecture specification
7763 string</em> in some place, it should select one of the
7764 strings provided by <tt>dpkg-architecture -L</tt>. The
7765 strings are in the format
7766 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7767 is sometimes elided, as when the OS is Linux.<footnote>
7768 <p>Currently, the strings are:
7769 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7770 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7771 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7772 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7773 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7774 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7775 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7776 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7777 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7778 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7779 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7780 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7781 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7782 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7783 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7784 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7785 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7786 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7787 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7788 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7789 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7790 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7791 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7792 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7793 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7794 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7795 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7796 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7797 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7798 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7799 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7800 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7801 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7802 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7803 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7804 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7805 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7811 Note that we don't want to use
7812 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7813 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7814 since this would make our programs incompatible with other
7815 Linux distributions. We also don't use something like
7816 <tt><var>arch</var>-unknown-linux</tt>, since the
7817 <tt>unknown</tt> does not look very good.
7822 <heading>Daemons</heading>
7825 The configuration files <file>/etc/services</file>,
7826 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7827 by the <prgn>netbase</prgn> package and must not be modified
7832 If a package requires a new entry in one of these files, the
7833 maintainer should get in contact with the
7834 <prgn>netbase</prgn> maintainer, who will add the entries
7835 and release a new version of the <prgn>netbase</prgn>
7840 The configuration file <file>/etc/inetd.conf</file> must not be
7841 modified by the package's scripts except via the
7842 <prgn>update-inetd</prgn> script or the
7843 <file>DebianNet.pm</file> Perl module. See their documentation
7844 for details on how to add entries.
7848 If a package wants to install an example entry into
7849 <file>/etc/inetd.conf</file>, the entry must be preceded with
7850 exactly one hash character (<tt>#</tt>). Such lines are
7851 treated as "commented out by user" by the
7852 <prgn>update-inetd</prgn> script and are not changed or
7853 activated during package updates.
7858 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7862 Some programs need to create pseudo-ttys. This should be done
7863 using Unix98 ptys if the C library supports it. The resulting
7864 program must not be installed setuid root, unless that
7865 is required for other functionality.
7869 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7870 <file>/var/log/lastlog</file> must be installed writable by
7871 group <tt>utmp</tt>. Programs which need to modify those
7872 files must be installed setgid <tt>utmp</tt>.
7877 <heading>Editors and pagers</heading>
7880 Some programs have the ability to launch an editor or pager
7881 program to edit or display a text document. Since there are
7882 lots of different editors and pagers available in the Debian
7883 distribution, the system administrator and each user should
7884 have the possibility to choose their preferred editor and
7889 In addition, every program should choose a good default
7890 editor/pager if none is selected by the user or system
7895 Thus, every program that launches an editor or pager must
7896 use the EDITOR or PAGER environment variable to determine
7897 the editor or pager the user wishes to use. If these
7898 variables are not set, the programs <file>/usr/bin/editor</file>
7899 and <file>/usr/bin/pager</file> should be used, respectively.
7903 These two files are managed through the <prgn>dpkg</prgn>
7904 "alternatives" mechanism. Thus every package providing an
7905 editor or pager must call the
7906 <prgn>update-alternatives</prgn> script to register these
7911 If it is very hard to adapt a program to make use of the
7912 EDITOR or PAGER variables, that program may be configured to
7913 use <file>/usr/bin/sensible-editor</file> and
7914 <file>/usr/bin/sensible-pager</file> as the editor or pager
7915 program respectively. These are two scripts provided in the
7916 Debian base system that check the EDITOR and PAGER variables
7917 and launch the appropriate program, and fall back to
7918 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7919 variable is not set.
7923 A program may also use the VISUAL environment variable to
7924 determine the user's choice of editor. If it exists, it
7925 should take precedence over EDITOR. This is in fact what
7926 <file>/usr/bin/sensible-editor</file> does.
7930 It is not required for a package to depend on
7931 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7932 package to provide such virtual packages.<footnote>
7933 The Debian base system already provides an editor and a
7939 <sect id="web-appl">
7940 <heading>Web servers and applications</heading>
7943 This section describes the locations and URLs that should
7944 be used by all web servers and web applications in the
7951 Cgi-bin executable files are installed in the
7953 <example compact="compact">
7954 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7956 and should be referred to as
7957 <example compact="compact">
7958 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7964 <p>Access to HTML documents</p>
7967 HTML documents for a package are stored in
7968 <file>/usr/share/doc/<var>package</var></file>
7969 and can be referred to as
7970 <example compact="compact">
7971 http://localhost/doc/<var>package</var>/<var>filename</var>
7976 The web server should restrict access to the document
7977 tree so that only clients on the same host can read
7978 the documents. If the web server does not support such
7979 access controls, then it should not provide access at
7980 all, or ask about providing access during installation.
7985 <p>Access to images</p>
7987 It is recommended that images for a package be stored
7988 in <tt>/usr/share/images/<var>package</var></tt> and
7989 may be referred to through an alias <tt>/images/</tt>
7992 http://localhost/images/<package>/<filename>
7999 <p>Web Document Root</p>
8002 Web Applications should try to avoid storing files in
8003 the Web Document Root. Instead they should use the
8004 /usr/share/doc/<var>package</var> directory for
8005 documents and register the Web Application via the
8006 <package>doc-base</package> package. If access to the
8007 web document root is unavoidable then use
8008 <example compact="compact">
8011 as the Document Root. This might be just a symbolic
8012 link to the location where the system administrator
8013 has put the real document root.
8016 <item><p>Providing httpd and/or httpd-cgi</p>
8018 All web servers should provide the virtual package
8019 <tt>httpd</tt>. If a web server has CGI support it should
8020 provide <tt>httpd-cgi</tt> additionally.
8023 All web applications which do not contain CGI scripts should
8024 depend on <tt>httpd</tt>, all those web applications which
8025 <tt>do</tt> contain CGI scripts, should depend on
8033 <sect id="mail-transport-agents">
8034 <heading>Mail transport, delivery and user agents</heading>
8037 Debian packages which process electronic mail, whether mail
8038 user agents (MUAs) or mail transport agents (MTAs), must
8039 ensure that they are compatible with the configuration
8040 decisions below. Failure to do this may result in lost
8041 mail, broken <tt>From:</tt> lines, and other serious brain
8046 The mail spool is <file>/var/mail</file> and the interface to
8047 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8048 the FHS). On older systems, the mail spool may be
8049 physically located in <file>/var/spool/mail</file>, but all
8050 access to the mail spool should be via the
8051 <file>/var/mail</file> symlink. The mail spool is part of the
8052 base system and not part of the MTA package.
8056 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8057 programs (such as IMAP daemons) must lock the mailbox in an
8058 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8059 be combined with dot locking. To avoid deadlocks, a program
8060 should use <tt>fcntl()</tt> first and dot locking after
8061 this, or alternatively implement the two locking methods in
8062 a non blocking way<footnote>
8063 If it is not possible to establish both locks, the
8064 system shouldn't wait for the second lock to be
8065 established, but remove the first lock, wait a (random)
8066 time, and start over locking again.
8067 </footnote>. Using the functions <tt>maillock</tt> and
8068 <tt>mailunlock</tt> provided by the
8069 <tt>liblockfile*</tt><footnote>
8070 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8071 to use these functions.
8072 </footnote> packages is the recommended way to realize this.
8076 Mailboxes are generally either mode 600 and owned by
8077 <var>user</var> or mode 660 and owned by
8078 <tt><var>user</var>:mail</tt><footnote>
8079 There are two traditional permission schemes for mail spools:
8080 mode 600 with all mail delivery done by processes running as
8081 the destination user, or mode 660 and owned by group mail with
8082 mail delivery done by a process running as a system user in
8083 group mail. Historically, Debian required mode 660 mail
8084 spools to enable the latter model, but that model has become
8085 increasingly uncommon and the principle of least privilege
8086 indicates that mail systems that use the first model should
8087 use permissions of 600. If delivery to programs is permitted,
8088 it's easier to keep the mail system secure if the delivery
8089 agent runs as the destination user. Debian Policy therefore
8090 permits either scheme.
8091 </footnote>. The local system administrator may choose a
8092 different permission scheme; packages should not make
8093 assumptions about the permission and ownership of mailboxes
8094 unless required (such as when creating a new mailbox). A MUA
8095 may remove a mailbox (unless it has nonstandard permissions) in
8096 which case the MTA or another MUA must recreate it if needed.
8100 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8101 be setgid mail to do the locking mentioned above (and
8102 must obviously avoid accessing other users' mailboxes
8103 using this privilege).</p>
8106 <file>/etc/aliases</file> is the source file for the system mail
8107 aliases (e.g., postmaster, usenet, etc.), it is the one
8108 which the sysadmin and <prgn>postinst</prgn> scripts may
8109 edit. After <file>/etc/aliases</file> is edited the program or
8110 human editing it must call <prgn>newaliases</prgn>. All MTA
8111 packages must come with a <prgn>newaliases</prgn> program,
8112 even if it does nothing, but older MTA packages did not do
8113 this so programs should not fail if <prgn>newaliases</prgn>
8114 cannot be found. Note that because of this, all MTA
8115 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8116 <tt>Replaces: mail-transport-agent</tt> control file
8121 The convention of writing <tt>forward to
8122 <var>address</var></tt> in the mailbox itself is not
8123 supported. Use a <tt>.forward</tt> file instead.</p>
8126 The <prgn>rmail</prgn> program used by UUCP
8127 for incoming mail should be <file>/usr/sbin/rmail</file>.
8128 Likewise, <prgn>rsmtp</prgn>, for receiving
8129 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8133 If your package needs to know what hostname to use on (for
8134 example) outgoing news and mail messages which are generated
8135 locally, you should use the file <file>/etc/mailname</file>. It
8136 will contain the portion after the username and <tt>@</tt>
8137 (at) sign for email addresses of users on the machine
8138 (followed by a newline).
8142 Such a package should check for the existence of this file
8143 when it is being configured. If it exists, it should be
8144 used without comment, although an MTA's configuration script
8145 may wish to prompt the user even if it finds that this file
8146 exists. If the file does not exist, the package should
8147 prompt the user for the value (preferably using
8148 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8149 as well as using it in the package's configuration. The
8150 prompt should make it clear that the name will not just be
8151 used by that package. For example, in this situation the
8152 <tt>inn</tt> package could say something like:
8153 <example compact="compact">
8154 Please enter the "mail name" of your system. This is the
8155 hostname portion of the address to be shown on outgoing
8156 news and mail messages. The default is
8157 <var>syshostname</var>, your system's host name. Mail
8158 name ["<var>syshostname</var>"]:
8160 where <var>syshostname</var> is the output of <tt>hostname
8166 <heading>News system configuration</heading>
8169 All the configuration files related to the NNTP (news)
8170 servers and clients should be located under
8171 <file>/etc/news</file>.</p>
8174 There are some configuration issues that apply to a number
8175 of news clients and server packages on the machine. These
8179 <tag><file>/etc/news/organization</file></tag>
8181 A string which should appear as the
8182 organization header for all messages posted
8183 by NNTP clients on the machine
8186 <tag><file>/etc/news/server</file></tag>
8188 Contains the FQDN of the upstream NNTP
8189 server, or localhost if the local machine is
8194 Other global files may be added as required for cross-package news
8201 <heading>Programs for the X Window System</heading>
8204 <heading>Providing X support and package priorities</heading>
8207 Programs that can be configured with support for the X
8208 Window System must be configured to do so and must declare
8209 any package dependencies necessary to satisfy their
8210 runtime requirements when using the X Window System. If
8211 such a package is of higher priority than the X packages
8212 on which it depends, it is required that either the
8213 X-specific components be split into a separate package, or
8214 that an alternative version of the package, which includes
8215 X support, be provided, or that the package's priority be
8221 <heading>Packages providing an X server</heading>
8224 Packages that provide an X server that, directly or
8225 indirectly, communicates with real input and display
8226 hardware should declare in their control data that they
8227 provide the virtual package <tt>xserver</tt>.<footnote>
8228 This implements current practice, and provides an
8229 actual policy for usage of the <tt>xserver</tt>
8230 virtual package which appears in the virtual packages
8231 list. In a nutshell, X servers that interface
8232 directly with the display and input hardware or via
8233 another subsystem (e.g., GGI) should provide
8234 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8235 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8241 <heading>Packages providing a terminal emulator</heading>
8244 Packages that provide a terminal emulator for the X Window
8245 System which meet the criteria listed below should declare
8246 in their control data that they provide the virtual
8247 package <tt>x-terminal-emulator</tt>. They should also
8248 register themselves as an alternative for
8249 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8254 To be an <tt>x-terminal-emulator</tt>, a program must:
8255 <list compact="compact">
8257 Be able to emulate a DEC VT100 terminal, or a
8258 compatible terminal.
8262 Support the command-line option <tt>-e
8263 <var>command</var></tt>, which creates a new
8264 terminal window<footnote>
8265 "New terminal window" does not necessarily mean
8266 a new top-level X window directly parented by
8267 the window manager; it could, if the terminal
8268 emulator application were so coded, be a new
8269 "view" in a multiple-document interface (MDI).
8271 and runs the specified <var>command</var>,
8272 interpreting the entirety of the rest of the command
8273 line as a command to pass straight to exec, in the
8274 manner that <tt>xterm</tt> does.
8278 Support the command-line option <tt>-T
8279 <var>title</var></tt>, which creates a new terminal
8280 window with the window title <var>title</var>.
8287 <heading>Packages providing a window manager</heading>
8290 Packages that provide a window manager should declare in
8291 their control data that they provide the virtual package
8292 <tt>x-window-manager</tt>. They should also register
8293 themselves as an alternative for
8294 <file>/usr/bin/x-window-manager</file>, with a priority
8295 calculated as follows:
8296 <list compact="compact">
8298 Start with a priority of 20.
8302 If the window manager supports the Debian menu
8303 system, add 20 points if this support is available
8304 in the package's default configuration (i.e., no
8305 configuration files belonging to the system or user
8306 have to be edited to activate the feature); if
8307 configuration files must be modified, add only 10
8313 If the window manager complies with <url
8314 id="http://www.freedesktop.org/Standards/wm-spec"
8315 name="The Window Manager Specification Project">,
8316 written by the <url id="http://www.freedesktop.org/"
8317 name="Free Desktop Group">, add 40 points.
8321 If the window manager permits the X session to be
8322 restarted using a <em>different</em> window manager
8323 (without killing the X server) in its default
8324 configuration, add 10 points; otherwise add none.
8331 <heading>Packages providing fonts</heading>
8334 Packages that provide fonts for the X Window
8336 For the purposes of Debian Policy, a "font for the X
8337 Window System" is one which is accessed via X protocol
8338 requests. Fonts for the Linux console, for PostScript
8339 renderer, or any other purpose, do not fit this
8340 definition. Any tool which makes such fonts available
8341 to the X Window System, however, must abide by this
8344 must do a number of things to ensure that they are both
8345 available without modification of the X or font server
8346 configuration, and that they do not corrupt files used by
8347 other font packages to register information about
8351 Fonts of any type supported by the X Window System
8352 must be in a separate binary package from any
8353 executables, libraries, or documentation (except
8354 that specific to the fonts shipped, such as their
8355 license information). If one or more of the fonts
8356 so packaged are necessary for proper operation of
8357 the package with which they are associated the font
8358 package may be Recommended; if the fonts merely
8359 provide an enhancement, a Suggests relationship may
8360 be used. Packages must not Depend on font
8362 This is because the X server may retrieve fonts
8363 from the local file system or over the network
8364 from an X font server; the Debian package system
8365 is empowered to deal only with the local
8371 BDF fonts must be converted to PCF fonts with the
8372 <prgn>bdftopcf</prgn> utility (available in the
8373 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8374 placed in a directory that corresponds to their
8376 <list compact="compact">
8378 100 dpi fonts must be placed in
8379 <file>/usr/share/fonts/X11/100dpi/</file>.
8383 75 dpi fonts must be placed in
8384 <file>/usr/share/fonts/X11/75dpi/</file>.
8388 Character-cell fonts, cursor fonts, and other
8389 low-resolution fonts must be placed in
8390 <file>/usr/share/fonts/X11/misc/</file>.
8396 Speedo fonts must be placed in
8397 <file>/usr/share/fonts/X11/Speedo/</file>.
8401 Type 1 fonts must be placed in
8402 <file>/usr/share/fonts/X11/Type1/</file>. If font
8403 metric files are available, they must be placed here
8408 Subdirectories of <file>/usr/share/fonts/X11/</file>
8409 other than those listed above must be neither
8410 created nor used. (The <file>PEX</file>, <file>CID</file>,
8411 and <file>cyrillic</file> directories are excepted for
8412 historical reasons, but installation of files into
8413 these directories remains discouraged.)
8417 Font packages may, instead of placing files directly
8418 in the X font directories listed above, provide
8419 symbolic links in that font directory pointing to
8420 the files' actual location in the filesystem. Such
8421 a location must comply with the FHS.
8425 Font packages should not contain both 75dpi and
8426 100dpi versions of a font. If both are available,
8427 they should be provided in separate binary packages
8428 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8429 the names of the packages containing the
8430 corresponding fonts.
8434 Fonts destined for the <file>misc</file> subdirectory
8435 should not be included in the same package as 75dpi
8436 or 100dpi fonts; instead, they should be provided in
8437 a separate package with <tt>-misc</tt> appended to
8442 Font packages must not provide the files
8443 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8444 <file>fonts.scale</file> in a font directory:
8447 <file>fonts.dir</file> files must not be provided at all.
8451 <file>fonts.alias</file> and <file>fonts.scale</file>
8452 files, if needed, should be provided in the
8454 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8455 where <var>fontdir</var> is the name of the
8457 <file>/usr/share/fonts/X11/</file> where the
8458 package's corresponding fonts are stored
8459 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8460 <var>package</var> is the name of the package
8461 that provides these fonts, and
8462 <var>extension</var> is either <tt>scale</tt>
8463 or <tt>alias</tt>, whichever corresponds to
8470 Font packages must declare a dependency on
8471 <tt>xfonts-utils</tt> in their control
8476 Font packages that provide one or more
8477 <file>fonts.scale</file> files as described above must
8478 invoke <prgn>update-fonts-scale</prgn> on each
8479 directory into which they installed fonts
8480 <em>before</em> invoking
8481 <prgn>update-fonts-dir</prgn> on that directory.
8482 This invocation must occur in both the
8483 <prgn>postinst</prgn> (for all arguments) and
8484 <prgn>postrm</prgn> (for all arguments except
8485 <tt>upgrade</tt>) scripts.
8489 Font packages that provide one or more
8490 <file>fonts.alias</file> files as described above must
8491 invoke <prgn>update-fonts-alias</prgn> on each
8492 directory into which they installed fonts. This
8493 invocation must occur in both the
8494 <prgn>postinst</prgn> (for all arguments) and
8495 <prgn>postrm</prgn> (for all arguments except
8496 <tt>upgrade</tt>) scripts.
8500 Font packages must invoke
8501 <prgn>update-fonts-dir</prgn> on each directory into
8502 which they installed fonts. This invocation must
8503 occur in both the <prgn>postinst</prgn> (for all
8504 arguments) and <prgn>postrm</prgn> (for all
8505 arguments except <tt>upgrade</tt>) scripts.
8509 Font packages must not provide alias names for the
8510 fonts they include which collide with alias names
8511 already in use by fonts already packaged.
8515 Font packages must not provide fonts with the same
8516 XLFD registry name as another font already packaged.
8523 <heading>Application defaults files</heading>
8526 Application defaults files must be installed in the
8527 directory <file>/etc/X11/app-defaults/</file> (use of a
8528 localized subdirectory of <file>/etc/X11/</file> as described
8529 in the <em>X Toolkit Intrinsics - C Language
8530 Interface</em> manual is also permitted). They must be
8531 registered as <tt>conffile</tt>s or handled as
8532 configuration files.
8536 Customization of programs' X resources may also be
8537 supported with the provision of a file with the same name
8538 as that of the package placed in the
8539 <file>/etc/X11/Xresources/</file> directory, which must
8540 registered as a <tt>conffile</tt> or handled as a
8541 configuration file.<footnote>
8542 Note that this mechanism is not the same as using
8543 app-defaults; app-defaults are tied to the client
8544 binary on the local file system, whereas X resources
8545 are stored in the X server and affect all connecting
8552 <heading>Installation directory issues</heading>
8555 Packages using the X Window System should not be
8556 configured to install files under the
8557 <file>/usr/X11R6/</file> directory. The
8558 <file>/usr/X11R6/</file> directory hierarchy should be
8559 regarded as obsolete.
8563 Programs that use GNU <prgn>autoconf</prgn> and
8564 <prgn>automake</prgn> are usually easily configured at
8565 compile time to use <file>/usr/</file> instead of
8566 <file>/usr/X11R6/</file>, and this should be done whenever
8567 possible. Configuration files for window managers and
8568 display managers should be placed in a subdirectory of
8569 <file>/etc/X11/</file> corresponding to the package name due
8570 to these programs' tight integration with the mechanisms
8571 of the X Window System. Application-level programs should
8572 use the <file>/etc/</file> directory unless otherwise mandated
8577 The installation of files into subdirectories
8578 of <file>/usr/X11R6/include/X11/</file> and
8579 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8580 package maintainers should determine if subdirectories of
8581 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8586 Packages should install any relevant files into the
8587 directories <file>/usr/include/X11/</file> and
8588 <file>/usr/lib/X11/</file>, but if they do so, they must
8589 pre-depend on <tt>x11-common (>=
8590 1:7.0.0)</tt><footnote>
8592 These libraries used to be all symbolic
8593 links. However, with <tt>X11R7</tt>,
8594 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8595 are now real directories, and packages
8596 <strong>should</strong> ship their files here instead
8597 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8598 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8599 responsible for converting these symlinks into
8607 <heading>The OSF/Motif and OpenMotif libraries</heading>
8610 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8611 OpenMotif libraries</em><footnote>
8612 OSF/Motif and OpenMotif are collectively referred to as
8613 "Motif" in this policy document.
8615 should be compiled against and tested with LessTif (a free
8616 re-implementation of Motif) instead. If the maintainer
8617 judges that the program or programs do not work
8618 sufficiently well with LessTif to be distributed and
8619 supported, but do so when compiled against Motif, then two
8620 versions of the package should be created; one linked
8621 statically against Motif and with <tt>-smotif</tt>
8622 appended to the package name, and one linked dynamically
8623 against Motif and with <tt>-dmotif</tt> appended to the
8628 Both Motif-linked versions are dependent
8629 upon non-DFSG-compliant software and thus cannot be
8630 uploaded to the <em>main</em> distribution; if the
8631 software is itself DFSG-compliant it may be uploaded to
8632 the <em>contrib</em> distribution. While known existing
8633 versions of Motif permit unlimited redistribution of
8634 binaries linked against the library (whether statically or
8635 dynamically), it is the package maintainer's
8636 responsibility to determine whether this is permitted by
8637 the license of the copy of Motif in their possession.
8643 <heading>Perl programs and modules</heading>
8646 Perl programs and modules should follow the current Perl policy.
8650 The Perl policy can be found in the <tt>perl-policy</tt>
8651 files in the <tt>debian-policy</tt> package.
8652 It is also available from the Debian web mirrors at
8653 <tt><url name="/doc/packaging-manuals/perl-policy/"
8654 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8659 <heading>Emacs lisp programs</heading>
8662 Please refer to the "Debian Emacs Policy" for details of how to
8663 package emacs lisp programs.
8667 The Emacs policy is available in
8668 <file>debian-emacs-policy.gz</file> of the
8669 <package>emacsen-common</package> package.
8670 It is also available from the Debian web mirrors at
8671 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8672 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8677 <heading>Games</heading>
8680 The permissions on <file>/var/games</file> are mode 755, owner
8681 <tt>root</tt> and group <tt>root</tt>.
8685 Each game decides on its own security policy.</p>
8688 Games which require protected, privileged access to
8689 high-score files, saved games, etc., may be made
8690 set-<em>group</em>-id (mode 2755) and owned by
8691 <tt>root:games</tt>, and use files and directories with
8692 appropriate permissions (770 <tt>root:games</tt>, for
8693 example). They must not be made
8694 set-<em>user</em>-id, as this causes security problems. (If
8695 an attacker can subvert any set-user-id game they can
8696 overwrite the executable of any other, causing other players
8697 of these games to run a Trojan horse program. With a
8698 set-group-id game the attacker only gets access to less
8699 important game data, and if they can get at the other
8700 players' accounts at all it will take considerably more
8704 Some packages, for example some fortune cookie programs, are
8705 configured by the upstream authors to install with their
8706 data files or other static information made unreadable so
8707 that they can only be accessed through set-id programs
8708 provided. You should not do this in a Debian package: anyone can
8709 download the <file>.deb</file> file and read the data from it,
8710 so there is no point making the files unreadable. Not
8711 making the files unreadable also means that you don't have
8712 to make so many programs set-id, which reduces the risk of a
8716 As described in the FHS, binaries of games should be
8717 installed in the directory <file>/usr/games</file>. This also
8718 applies to games that use the X Window System. Manual pages
8719 for games (X and non-X games) should be installed in
8720 <file>/usr/share/man/man6</file>.</p>
8726 <heading>Documentation</heading>
8729 <heading>Manual pages</heading>
8732 You should install manual pages in <prgn>nroff</prgn> source
8733 form, in appropriate places under <file>/usr/share/man</file>.
8734 You should only use sections 1 to 9 (see the FHS for more
8735 details). You must not install a pre-formatted "cat page".
8739 Each program, utility, and function should have an
8740 associated manual page included in the same package. It is
8741 suggested that all configuration files also have a manual
8742 page included as well. Manual pages for protocols and other
8743 auxiliary things are optional.
8747 If no manual page is available, this is considered as a bug
8748 and should be reported to the Debian Bug Tracking System (the
8749 maintainer of the package is allowed to write this bug report
8750 themselves, if they so desire). Do not close the bug report
8751 until a proper man page is available.<footnote>
8752 It is not very hard to write a man page. See the
8753 <url id="http://www.schweikhardt.net/man_page_howto.html"
8754 name="Man-Page-HOWTO">,
8755 <manref name="man" section="7">, the examples
8756 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8757 the helper programs <prgn>help2man</prgn>, or the
8758 directory <file>/usr/share/doc/man-db/examples</file>.
8763 You may forward a complaint about a missing man page to the
8764 upstream authors, and mark the bug as forwarded in the
8765 Debian bug tracking system. Even though the GNU Project do
8766 not in general consider the lack of a man page to be a bug,
8767 we do; if they tell you that they don't consider it a bug
8768 you should leave the bug in our bug tracking system open
8773 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8777 If one man page needs to be accessible via several names it
8778 is better to use a symbolic link than the <file>.so</file>
8779 feature, but there is no need to fiddle with the relevant
8780 parts of the upstream source to change from <file>.so</file> to
8781 symlinks: don't do it unless it's easy. You should not
8782 create hard links in the manual page directories, nor put
8783 absolute filenames in <file>.so</file> directives. The filename
8784 in a <file>.so</file> in a man page should be relative to the
8785 base of the man page tree (usually
8786 <file>/usr/share/man</file>). If you do not create any links
8787 (whether symlinks, hard links, or <tt>.so</tt> directives)
8788 in the file system to the alternate names of the man page,
8789 then you should not rely on <prgn>man</prgn> finding your
8790 man page under those names based solely on the information in
8791 the man page's header.<footnote>
8792 Supporting this in <prgn>man</prgn> often requires
8793 unreasonable processing time to find a manual page or to
8794 report that none exists, and moves knowledge into man's
8795 database that would be better left in the file system.
8796 This support is therefore deprecated and will cease to
8797 be present in the future.
8802 Manual pages in locale-specific subdirectories of
8803 <file>/usr/share/man</file> should use either UTF-8 or the usual
8804 legacy encoding for that language (normally the one corresponding
8805 to the shortest relevant locale name in
8806 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8807 <file>/usr/share/man/fr</file> should use either UTF-8 or
8808 ISO-8859-1.<footnote>
8809 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8810 use. In future, all manual pages will be required to use
8816 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8817 included in the subdirectory name unless it indicates a
8818 significant difference in the language, as this excludes
8819 speakers of the language in other countries.<footnote>
8820 At the time of writing, Chinese and Portuguese are the main
8821 languages with such differences, so <file>pt_BR</file>,
8822 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8827 Due to limitations in current implementations, all characters
8828 in the manual page source should be representable in the usual
8829 legacy encoding for that language, even if the file is
8830 actually encoded in UTF-8. Safe alternative ways to write many
8831 characters outside that range may be found in
8832 <manref name="groff_char" section="7">.
8837 <heading>Info documents</heading>
8840 Info documents should be installed in <file>/usr/share/info</file>.
8841 They should be compressed with <tt>gzip -9</tt>.
8845 Your package should call <prgn>install-info</prgn> to update
8846 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8847 script when called with a <tt>configure</tt> argument, for
8849 <example compact="compact">
8850 install-info --quiet --section Development Development \
8851 /usr/share/info/foobar.info
8855 It is a good idea to specify a section for the location of
8856 your program; this is done with the <tt>--section</tt>
8857 switch. To determine which section to use, you should look
8858 at <file>/usr/share/info/dir</file> on your system and choose the most
8859 relevant (or create a new section if none of the current
8860 sections are relevant). Note that the <tt>--section</tt>
8861 flag takes two arguments; the first is a regular expression
8862 to match (case-insensitively) against an existing section,
8863 the second is used when creating a new one.</p>
8866 You should remove the entries in the <prgn>prerm</prgn>
8867 script when called with a <tt>remove</tt> argument:
8868 <example compact="compact">
8869 install-info --quiet --remove /usr/share/info/foobar.info
8873 If <prgn>install-info</prgn> cannot find a description entry
8874 in the Info file you must supply one. See <manref
8875 name="install-info" section="8"> for details.</p>
8879 <heading>Additional documentation</heading>
8882 Any additional documentation that comes with the package may
8883 be installed at the discretion of the package maintainer.
8884 Plain text documentation should be installed in the directory
8885 <file>/usr/share/doc/<var>package</var></file>, where
8886 <var>package</var> is the name of the package, and
8887 compressed with <tt>gzip -9</tt> unless it is small.
8891 If a package comes with large amounts of documentation which
8892 many users of the package will not require you should create
8893 a separate binary package to contain it, so that it does not
8894 take up disk space on the machines of users who do not need
8895 or want it installed.</p>
8898 It is often a good idea to put text information files
8899 (<file>README</file>s, changelogs, and so forth) that come with
8900 the source package in <file>/usr/share/doc/<var>package</var></file>
8901 in the binary package. However, you don't need to install
8902 the instructions for building and installing the package, of
8906 Packages must not require the existence of any files in
8907 <file>/usr/share/doc/</file> in order to function
8909 The system administrator should be able to
8910 delete files in <file>/usr/share/doc/</file> without causing
8911 any programs to break.
8913 Any files that are referenced by programs but are also
8914 useful as stand alone documentation should be installed under
8915 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8916 <file>/usr/share/doc/<var>package</var></file>.
8920 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8921 link to another directory in <file>/usr/share/doc</file> only if
8922 the two packages both come from the same source and the
8923 first package Depends on the second.<footnote>
8925 Please note that this does not override the section on
8926 changelog files below, so the file
8927 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8928 must refer to the changelog for the current version of
8929 <var>package</var> in question. In practice, this means
8930 that the sources of the target and the destination of the
8931 symlink must be the same (same source package and
8938 Former Debian releases placed all additional documentation
8939 in <file>/usr/doc/<var>package</var></file>. This has been
8940 changed to <file>/usr/share/doc/<var>package</var></file>,
8941 and packages must not put documentation in the directory
8942 <file>/usr/doc/<var>package</var></file>. <footnote>
8943 At this phase of the transition, we no longer require a
8944 symbolic link in <file>/usr/doc/</file>. At a later point,
8945 policy shall change to make the symbolic links a bug.
8951 <heading>Preferred documentation formats</heading>
8954 The unification of Debian documentation is being carried out
8958 If your package comes with extensive documentation in a
8959 markup format that can be converted to various other formats
8960 you should if possible ship HTML versions in a binary
8961 package, in the directory
8962 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8963 its subdirectories.<footnote>
8964 The rationale: The important thing here is that HTML
8965 docs should be available in <em>some</em> package, not
8966 necessarily in the main binary package.
8971 Other formats such as PostScript may be provided at the
8972 package maintainer's discretion.
8976 <sect id="copyrightfile">
8977 <heading>Copyright information</heading>
8980 Every package must be accompanied by a verbatim copy of its
8981 copyright and distribution license in the file
8982 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8983 file must neither be compressed nor be a symbolic link.
8987 In addition, the copyright file must say where the upstream
8988 sources (if any) were obtained. It should name the original
8989 authors of the package and the Debian maintainer(s) who were
8990 involved with its creation.
8994 Packages in the <em>contrib</em> or <em>non-free</em> categories
8995 should state in the copyright file that the package is not part
8996 of the Debian GNU/Linux distribution and briefly explain why.
9000 A copy of the file which will be installed in
9001 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9002 be in <file>debian/copyright</file> in the source package.
9006 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9007 link to another directory in <file>/usr/share/doc</file> only if
9008 the two packages both come from the same source and the
9009 first package Depends on the second. These rules are
9010 important because copyrights must be extractable by
9015 Packages distributed under the UCB BSD license, the Apache
9016 license (version 2.0), the Artistic license, the GNU GPL
9017 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
9018 the GNU FDL (version 1.2) should refer to the corresponding
9019 files under <file>/usr/share/common-licenses</file>,<footnote>
9022 <file>/usr/share/common-licenses/BSD</file>,
9023 <file>/usr/share/common-licenses/Apache-2.0</file>,
9024 <file>/usr/share/common-licenses/Artistic</file>,
9025 <file>/usr/share/common-licenses/GPL-2</file>,
9026 <file>/usr/share/common-licenses/GPL-3</file>,
9027 <file>/usr/share/common-licenses/LGPL-2</file>,
9028 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9029 <file>/usr/share/common-licenses/LGPL-3</file>, and
9030 <file>/usr/share/common-licenses/GFDL-1.2</file>
9033 </footnote> rather than quoting them in the copyright
9038 You should not use the copyright file as a general <file>README</file>
9039 file. If your package has such a file it should be
9040 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9041 <file>README.Debian</file> or some other appropriate place.</p>
9045 <heading>Examples</heading>
9048 Any examples (configurations, source files, whatever),
9049 should be installed in a directory
9050 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9051 files should not be referenced by any program: they're there
9052 for the benefit of the system administrator and users as
9053 documentation only. Architecture-specific example files
9054 should be installed in a directory
9055 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9057 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9058 latter directory itself may be a symbolic link to the
9063 If the purpose of a package is to provide examples, then the
9064 example files may be installed into
9065 <file>/usr/share/doc/<var>package</var></file>.
9069 <sect id="changelogs">
9070 <heading>Changelog files</heading>
9073 Packages that are not Debian-native must contain a
9074 compressed copy of the <file>debian/changelog</file> file from
9075 the Debian source tree in
9076 <file>/usr/share/doc/<var>package</var></file> with the name
9077 <file>changelog.Debian.gz</file>.
9081 If an upstream changelog is available, it should be accessible as
9082 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9083 plain text. If the upstream changelog is distributed in
9084 HTML, it should be made available in that form as
9085 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9086 and a plain text <file>changelog.gz</file> should be generated
9087 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9088 the upstream changelog files do not already conform to this
9089 naming convention, then this may be achieved either by
9090 renaming the files, or by adding a symbolic link, at the
9091 maintainer's discretion.<footnote>
9092 Rationale: People should not have to look in places for
9093 upstream changelogs merely because they are given
9094 different names or are distributed in HTML format.
9099 All of these files should be installed compressed using
9100 <tt>gzip -9</tt>, as they will become large with time even
9101 if they start out small.
9105 If the package has only one changelog which is used both as
9106 the Debian changelog and the upstream one because there is
9107 no separate upstream maintainer then that changelog should
9108 usually be installed as
9109 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9110 there is a separate upstream maintainer, but no upstream
9111 changelog, then the Debian changelog should still be called
9112 <file>changelog.Debian.gz</file>.
9116 For details about the format and contents of the Debian
9117 changelog file, please see <ref id="dpkgchangelog">.
9122 <appendix id="pkg-scope">
9123 <heading>Introduction and scope of these appendices</heading>
9126 These appendices are taken essentially verbatim from the
9127 now-deprecated Packaging Manual, version 3.2.1.0. They are
9128 the chapters which are likely to be of use to package
9129 maintainers and which have not already been included in the
9130 policy document itself. Most of these sections are very likely
9131 not relevant to policy; they should be treated as
9132 documentation for the packaging system. Please note that these
9133 appendices are included for convenience, and for historical
9134 reasons: they used to be part of policy package, and they have
9135 not yet been incorporated into dpkg documentation. However,
9136 they still have value, and hence they are presented here.
9140 They have not yet been checked to ensure that they are
9141 compatible with the contents of policy, and if there are any
9142 contradictions, the version in the main policy document takes
9143 precedence. The remaining chapters of the old Packaging
9144 Manual have also not been read in detail to ensure that there
9145 are not parts which have been left out. Both of these will be
9150 Certain parts of the Packaging manual were integrated into the
9151 Policy Manual proper, and removed from the appendices. Links
9152 have been placed from the old locations to the new ones.
9156 <prgn>dpkg</prgn> is a suite of programs for creating binary
9157 package files and installing and removing them on Unix
9159 <prgn>dpkg</prgn> is targeted primarily at Debian
9160 GNU/Linux, but may work on or be ported to other
9166 The binary packages are designed for the management of
9167 installed executable programs (usually compiled binaries) and
9168 their associated data, though source code examples and
9169 documentation are provided as part of some packages.</p>
9172 This manual describes the technical aspects of creating Debian
9173 binary packages (<file>.deb</file> files). It documents the
9174 behavior of the package management programs
9175 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9176 they interact with packages.</p>
9179 It also documents the interaction between
9180 <prgn>dselect</prgn>'s core and the access method scripts it
9181 uses to actually install the selected packages, and describes
9182 how to create a new access method.</p>
9185 This manual does not go into detail about the options and
9186 usage of the package building and installation tools. It
9187 should therefore be read in conjunction with those programs'
9192 The utility programs which are provided with <prgn>dpkg</prgn>
9193 for managing various system configuration and similar issues,
9194 such as <prgn>update-rc.d</prgn> and
9195 <prgn>install-info</prgn>, are not described in detail here -
9196 please see their man pages.
9200 It is assumed that the reader is reasonably familiar with the
9201 <prgn>dpkg</prgn> System Administrators' manual.
9202 Unfortunately this manual does not yet exist.
9206 The Debian version of the FSF's GNU hello program is provided
9207 as an example for people wishing to create Debian
9208 packages. The Debian <prgn>debmake</prgn> package is
9209 recommended as a very helpful tool in creating and maintaining
9210 Debian packages. However, while the tools and examples are
9211 helpful, they do not replace the need to read and follow the
9212 Policy and Programmer's Manual.</p>
9215 <appendix id="pkg-binarypkg">
9216 <heading>Binary packages (from old Packaging Manual)</heading>
9219 The binary package has two main sections. The first part
9220 consists of various control information files and scripts used
9221 by <prgn>dpkg</prgn> when installing and removing. See <ref
9222 id="pkg-controlarea">.
9226 The second part is an archive containing the files and
9227 directories to be installed.
9231 In the future binary packages may also contain other
9232 components, such as checksums and digital signatures. The
9233 format for the archive is described in full in the
9234 <file>deb(5)</file> man page.
9238 <sect id="pkg-bincreating"><heading>Creating package files -
9239 <prgn>dpkg-deb</prgn>
9243 All manipulation of binary package files is done by
9244 <prgn>dpkg-deb</prgn>; it's the only program that has
9245 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9246 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9247 will spot that the options requested are appropriate to
9248 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9253 In order to create a binary package you must make a
9254 directory tree which contains all the files and directories
9255 you want to have in the file system data part of the package.
9256 In Debian-format source packages this directory is usually
9257 <file>debian/tmp</file>, relative to the top of the package's
9262 They should have the locations (relative to the root of the
9263 directory tree you're constructing) ownerships and
9264 permissions which you want them to have on the system when
9269 With current versions of <prgn>dpkg</prgn> the uid/username
9270 and gid/groupname mappings for the users and groups being
9271 used should be the same on the system where the package is
9272 built and the one where it is installed.
9276 You need to add one special directory to the root of the
9277 miniature file system tree you're creating:
9278 <prgn>DEBIAN</prgn>. It should contain the control
9279 information files, notably the binary package control file
9280 (see <ref id="pkg-controlfile">).
9284 The <prgn>DEBIAN</prgn> directory will not appear in the
9285 file system archive of the package, and so won't be installed
9286 by <prgn>dpkg</prgn> when the package is installed.
9290 When you've prepared the package, you should invoke:
9292 dpkg --build <var>directory</var>
9297 This will build the package in
9298 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9299 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9300 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9305 See the man page <manref name="dpkg-deb" section="8"> for details of how
9306 to examine the contents of this newly-created file. You may find the
9307 output of following commands enlightening:
9309 dpkg-deb --info <var>filename</var>.deb
9310 dpkg-deb --contents <var>filename</var>.deb
9311 dpkg --contents <var>filename</var>.deb
9313 To view the copyright file for a package you could use this command:
9315 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9320 <sect id="pkg-controlarea">
9321 <heading>Package control information files</heading>
9324 The control information portion of a binary package is a
9325 collection of files with names known to <prgn>dpkg</prgn>.
9326 It will treat the contents of these files specially - some
9327 of them contain information used by <prgn>dpkg</prgn> when
9328 installing or removing the package; others are scripts which
9329 the package maintainer wants <prgn>dpkg</prgn> to run.
9333 It is possible to put other files in the package control
9334 area, but this is not generally a good idea (though they
9335 will largely be ignored).
9339 Here is a brief list of the control info files supported by
9340 <prgn>dpkg</prgn> and a summary of what they're used for.
9345 <tag><tt>control</tt>
9348 This is the key description file used by
9349 <prgn>dpkg</prgn>. It specifies the package's name
9350 and version, gives its description for the user,
9351 states its relationships with other packages, and so
9352 forth. See <ref id="sourcecontrolfiles"> and
9353 <ref id="binarycontrolfiles">.
9357 It is usually generated automatically from information
9358 in the source package by the
9359 <prgn>dpkg-gencontrol</prgn> program, and with
9360 assistance from <prgn>dpkg-shlibdeps</prgn>.
9361 See <ref id="pkg-sourcetools">.
9365 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9370 These are executable files (usually scripts) which
9371 <prgn>dpkg</prgn> runs during installation, upgrade
9372 and removal of packages. They allow the package to
9373 deal with matters which are particular to that package
9374 or require more complicated processing than that
9375 provided by <prgn>dpkg</prgn>. Details of when and
9376 how they are called are in <ref id="maintainerscripts">.
9380 It is very important to make these scripts idempotent.
9381 See <ref id="idempotency">.
9385 The maintainer scripts are guaranteed to run with a
9386 controlling terminal and can interact with the user.
9387 See <ref id="controllingterminal">.
9391 <tag><tt>conffiles</tt>
9394 This file contains a list of configuration files which
9395 are to be handled automatically by <prgn>dpkg</prgn>
9396 (see <ref id="pkg-conffiles">). Note that not necessarily
9397 every configuration file should be listed here.
9400 <tag><tt>shlibs</tt>
9403 This file contains a list of the shared libraries
9404 supplied by the package, with dependency details for
9405 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9406 when it determines what dependencies are required in a
9407 package control file. The <tt>shlibs</tt> file format
9408 is described on <ref id="shlibs">.
9413 <sect id="pkg-controlfile">
9414 <heading>The main control information file: <tt>control</tt></heading>
9417 The most important control information file used by
9418 <prgn>dpkg</prgn> when it installs a package is
9419 <tt>control</tt>. It contains all the package's "vital
9424 The binary package control files of packages built from
9425 Debian sources are made by a special tool,
9426 <prgn>dpkg-gencontrol</prgn>, which reads
9427 <file>debian/control</file> and <file>debian/changelog</file> to
9428 find the information it needs. See <ref id="pkg-sourcepkg"> for
9433 The fields in binary package control files are listed in
9434 <ref id="binarycontrolfiles">.
9438 A description of the syntax of control files and the purpose
9439 of the fields is available in <ref id="controlfields">.
9444 <heading>Time Stamps</heading>
9447 See <ref id="timestamps">.
9452 <appendix id="pkg-sourcepkg">
9453 <heading>Source packages (from old Packaging Manual) </heading>
9456 The Debian binary packages in the distribution are generated
9457 from Debian sources, which are in a special format to assist
9458 the easy and automatic building of binaries.
9461 <sect id="pkg-sourcetools">
9462 <heading>Tools for processing source packages</heading>
9465 Various tools are provided for manipulating source packages;
9466 they pack and unpack sources and help build of binary
9467 packages and help manage the distribution of new versions.
9471 They are introduced and typical uses described here; see
9472 <manref name="dpkg-source" section="1"> for full
9473 documentation about their arguments and operation.
9477 For examples of how to construct a Debian source package,
9478 and how to use those utilities that are used by Debian
9479 source packages, please see the <prgn>hello</prgn> example
9483 <sect1 id="pkg-dpkg-source">
9485 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9490 This program is frequently used by hand, and is also
9491 called from package-independent automated building scripts
9492 such as <prgn>dpkg-buildpackage</prgn>.
9496 To unpack a package it is typically invoked with
9498 dpkg-source -x <var>.../path/to/filename</var>.dsc
9503 with the <file><var>filename</var>.tar.gz</file> and
9504 <file><var>filename</var>.diff.gz</file> (if applicable) in
9505 the same directory. It unpacks into
9506 <file><var>package</var>-<var>version</var></file>, and if
9508 <file><var>package</var>-<var>version</var>.orig</file>, in
9509 the current directory.
9513 To create a packed source archive it is typically invoked:
9515 dpkg-source -b <var>package</var>-<var>version</var>
9520 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9521 <file>.diff.gz</file> (if appropriate) in the current
9522 directory. <prgn>dpkg-source</prgn> does not clean the
9523 source tree first - this must be done separately if it is
9528 See also <ref id="pkg-sourcearchives">.</p>
9532 <sect1 id="pkg-dpkg-buildpackage">
9534 <prgn>dpkg-buildpackage</prgn> - overall package-building
9539 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9540 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9541 targets <tt>clean</tt>, <tt>build</tt> and
9542 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9543 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9544 source and binary package upload.
9548 It is usually invoked by hand from the top level of the
9549 built or unbuilt source directory. It may be invoked with
9550 no arguments; useful arguments include:
9551 <taglist compact="compact">
9552 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9555 Do not sign the <tt>.changes</tt> file or the
9556 source package <tt>.dsc</tt> file, respectively.</p>
9558 <tag><tt>-p<var>sign-command</var></tt></tag>
9561 Invoke <var>sign-command</var> instead of finding
9562 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9563 <var>sign-command</var> must behave just like
9564 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9566 <tag><tt>-r<var>root-command</var></tt></tag>
9569 When root privilege is required, invoke the command
9570 <var>root-command</var>. <var>root-command</var>
9571 should invoke its first argument as a command, from
9572 the <prgn>PATH</prgn> if necessary, and pass its
9573 second and subsequent arguments to the command it
9574 calls. If no <var>root-command</var> is supplied
9575 then <var>dpkg-buildpackage</var> will take no
9576 special action to gain root privilege, so that for
9577 most packages it will have to be invoked as root to
9580 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9583 Two types of binary-only build and upload - see
9584 <manref name="dpkg-source" section="1">.
9591 <sect1 id="pkg-dpkg-gencontrol">
9593 <prgn>dpkg-gencontrol</prgn> - generates binary package
9598 This program is usually called from <file>debian/rules</file>
9599 (see <ref id="pkg-sourcetree">) in the top level of the source
9604 This is usually done just before the files and directories in the
9605 temporary directory tree where the package is being built have their
9606 permissions and ownerships set and the package is constructed using
9607 <prgn>dpkg-deb/</prgn>
9609 This is so that the control file which is produced has
9610 the right permissions
9615 <prgn>dpkg-gencontrol</prgn> must be called after all the
9616 files which are to go into the package have been placed in
9617 the temporary build directory, so that its calculation of
9618 the installed size of a package is correct.
9622 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9623 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9624 variable substitutions created by
9625 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9630 For a package which generates only one binary package, and
9631 which builds it in <file>debian/tmp</file> relative to the top
9632 of the source package, it is usually sufficient to call
9633 <prgn>dpkg-gencontrol</prgn>.
9637 Sources which build several binaries will typically need
9640 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9641 </example> The <tt>-P</tt> tells
9642 <prgn>dpkg-gencontrol</prgn> that the package is being
9643 built in a non-default directory, and the <tt>-p</tt>
9644 tells it which package's control file should be generated.
9648 <prgn>dpkg-gencontrol</prgn> also adds information to the
9649 list of files in <file>debian/files</file>, for the benefit of
9650 (for example) a future invocation of
9651 <prgn>dpkg-genchanges</prgn>.</p>
9654 <sect1 id="pkg-dpkg-shlibdeps">
9656 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9661 This program is usually called from <file>debian/rules</file>
9662 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9663 id="pkg-sourcetree">), in the top level of the source tree.
9667 Its arguments are executables and shared libraries
9670 They may be specified either in the locations in the
9671 source tree where they are created or in the locations
9672 in the temporary build tree where they are installed
9673 prior to binary package creation.
9675 </footnote> for which shared library dependencies should
9676 be included in the binary package's control file.
9680 If some of the found shared libraries should only
9681 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9682 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9683 by using the <tt>-d<var>dependency-field</var></tt> option
9684 before those executable(s). (Each <tt>-d</tt> option
9685 takes effect until the next <tt>-d</tt>.)
9689 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9690 output control file to be modified. Instead by default it
9691 adds to the <file>debian/substvars</file> file variable
9692 settings like <tt>shlibs:Depends</tt>. These variable
9693 settings must be referenced in dependency fields in the
9694 appropriate per-binary-package sections of the source
9699 For example, a package that generates an essential part
9700 which requires dependencies, and optional parts that
9701 which only require a recommendation, would separate those
9702 two sets of dependencies into two different fields.<footnote>
9703 At the time of writing, an example for this was the
9704 <package/xmms/ package, with Depends used for the xmms
9705 executable, Recommends for the plug-ins and Suggests for
9706 even more optional features provided by unzip.
9708 It can say in its <file>debian/rules</file>:
9710 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9711 -dRecommends <var>optionalpart anotheroptionalpart</var>
9713 and then in its main control file <file>debian/control</file>:
9716 Depends: ${shlibs:Depends}
9717 Recommends: ${shlibs:Recommends}
9723 Sources which produce several binary packages with
9724 different shared library dependency requirements can use
9725 the <tt>-p<var>varnameprefix</var></tt> option to override
9726 the default <tt>shlibs:</tt> prefix (one invocation of
9727 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9728 They can thus produce several sets of dependency
9729 variables, each of the form
9730 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9731 which can be referred to in the appropriate parts of the
9732 binary package control files.
9737 <sect1 id="pkg-dpkg-distaddfile">
9739 <prgn>dpkg-distaddfile</prgn> - adds a file to
9740 <file>debian/files</file>
9744 Some packages' uploads need to include files other than
9745 the source and binary package files.
9749 <prgn>dpkg-distaddfile</prgn> adds a file to the
9750 <file>debian/files</file> file so that it will be included in
9751 the <file>.changes</file> file when
9752 <prgn>dpkg-genchanges</prgn> is run.
9756 It is usually invoked from the <tt>binary</tt> target of
9757 <file>debian/rules</file>:
9759 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9761 The <var>filename</var> is relative to the directory where
9762 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9763 is usually the directory above the top level of the source
9764 tree. The <file>debian/rules</file> target should put the
9765 file there just before or just after calling
9766 <prgn>dpkg-distaddfile</prgn>.
9770 The <var>section</var> and <var>priority</var> are passed
9771 unchanged into the resulting <file>.changes</file> file.
9776 <sect1 id="pkg-dpkg-genchanges">
9778 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9783 This program is usually called by package-independent
9784 automatic building scripts such as
9785 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9790 It is usually called in the top level of a built source
9791 tree, and when invoked with no arguments will print out a
9792 straightforward <file>.changes</file> file based on the
9793 information in the source package's changelog and control
9794 file and the binary and source packages which should have
9800 <sect1 id="pkg-dpkg-parsechangelog">
9802 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9803 representation of a changelog
9807 This program is used internally by
9808 <prgn>dpkg-source</prgn> et al. It may also occasionally
9809 be useful in <file>debian/rules</file> and elsewhere. It
9810 parses a changelog, <file>debian/changelog</file> by default,
9811 and prints a control-file format representation of the
9812 information in it to standard output.
9816 <sect1 id="pkg-dpkg-architecture">
9818 <prgn>dpkg-architecture</prgn> - information about the build and
9823 This program can be used manually, but is also invoked by
9824 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9825 environment or make variables which specify the build and host
9826 architecture for the package building process.
9831 <sect id="pkg-sourcetree">
9832 <heading>The Debianised source tree</heading>
9835 The source archive scheme described later is intended to
9836 allow a Debianised source tree with some associated control
9837 information to be reproduced and transported easily. The
9838 Debianised source tree is a version of the original program
9839 with certain files added for the benefit of the
9840 Debianisation process, and with any other changes required
9841 made to the rest of the source code and installation
9846 The extra files created for Debian are in the subdirectory
9847 <file>debian</file> of the top level of the Debianised source
9848 tree. They are described below.
9851 <sect1 id="pkg-debianrules">
9852 <heading><file>debian/rules</file> - the main building script</heading>
9855 See <ref id="debianrules">.
9860 <sect1 id="pkg-dpkgchangelog">
9861 <heading><file>debian/changelog</file></heading>
9864 See <ref id="dpkgchangelog">.
9867 <sect2><heading>Defining alternative changelog formats
9871 It is possible to use a different format to the standard
9872 one, by providing a parser for the format you wish to
9877 In order to have <tt>dpkg-parsechangelog</tt> run your
9878 parser, you must include a line within the last 40 lines
9879 of your file matching the Perl regular expression:
9880 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9881 parentheses should be the name of the format. For
9882 example, you might say:
9884 @@@ changelog-format: joebloggs @@@
9886 Changelog format names are non-empty strings of alphanumerics.
9890 If such a line exists then <tt>dpkg-parsechangelog</tt>
9891 will look for the parser as
9892 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9894 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9895 it is an error for it not to find it, or for it not to
9896 be an executable program. The default changelog format
9897 is <tt>dpkg</tt>, and a parser for it is provided with
9898 the <tt>dpkg</tt> package.
9902 The parser will be invoked with the changelog open on
9903 standard input at the start of the file. It should read
9904 the file (it may seek if it wishes) to determine the
9905 information required and return the parsed information
9906 to standard output in the form of a series of control
9907 fields in the standard format. By default it should
9908 return information about only the most recent version in
9909 the changelog; it should accept a
9910 <tt>-v<var>version</var></tt> option to return changes
9911 information from all versions present <em>strictly
9912 after</em> <var>version</var>, and it should then be an
9913 error for <var>version</var> not to be present in the
9919 <list compact="compact">
9920 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9921 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9922 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9923 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9924 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9925 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9926 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9931 If several versions are being returned (due to the use
9932 of <tt>-v</tt>), the urgency value should be of the
9933 highest urgency code listed at the start of any of the
9934 versions requested followed by the concatenated
9935 (space-separated) comments from all the versions
9936 requested; the maintainer, version, distribution and
9937 date should always be from the most recent version.
9941 For the format of the <tt>Changes</tt> field see
9942 <ref id="f-Changes">.
9946 If the changelog format which is being parsed always or
9947 almost always leaves a blank line between individual
9948 change notes these blank lines should be stripped out,
9949 so as to make the resulting output compact.
9953 If the changelog format does not contain date or package
9954 name information this information should be omitted from
9955 the output. The parser should not attempt to synthesize
9956 it or find it from other sources.
9960 If the changelog does not have the expected format the
9961 parser should exit with a nonzero exit status, rather
9962 than trying to muddle through and possibly generating
9967 A changelog parser may not interact with the user at
9973 <sect1 id="pkg-srcsubstvars">
9974 <heading><file>debian/substvars</file> and variable substitutions</heading>
9977 See <ref id="substvars">.
9983 <heading><file>debian/files</file></heading>
9986 See <ref id="debianfiles">.
9990 <sect1><heading><file>debian/tmp</file>
9994 This is the canonical temporary location for the
9995 construction of binary packages by the <tt>binary</tt>
9996 target. The directory <file>tmp</file> serves as the root of
9997 the file system tree as it is being constructed (for
9998 example, by using the package's upstream makefiles install
9999 targets and redirecting the output there), and it also
10000 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10001 id="pkg-bincreating">.
10005 If several binary packages are generated from the same
10006 source tree it is usual to use several
10007 <file>debian/tmp<var>something</var></file> directories, for
10008 example <file>tmp-a</file> or <file>tmp-doc</file>.
10012 Whatever <file>tmp</file> directories are created and used by
10013 <tt>binary</tt> must of course be removed by the
10014 <tt>clean</tt> target.</p></sect1>
10018 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10022 As it exists on the FTP site, a Debian source package
10023 consists of three related files. You must have the right
10024 versions of all three to be able to use them.
10029 <tag>Debian source control file - <tt>.dsc</tt></tag>
10031 This file is a control file used by <prgn>dpkg-source</prgn>
10032 to extract a source package.
10033 See <ref id="debiansourcecontrolfiles">.
10037 Original source archive -
10039 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10045 This is a compressed (with <tt>gzip -9</tt>)
10046 <prgn>tar</prgn> file containing the source code from
10047 the upstream authors of the program.
10052 Debianisation diff -
10054 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10060 This is a unified context diff (<tt>diff -u</tt>)
10061 giving the changes which are required to turn the
10062 original source into the Debian source. These changes
10063 may only include editing and creating plain files.
10064 The permissions of files, the targets of symbolic
10065 links and the characteristics of special files or
10066 pipes may not be changed and no files may be removed
10071 All the directories in the diff must exist, except the
10072 <file>debian</file> subdirectory of the top of the source
10073 tree, which will be created by
10074 <prgn>dpkg-source</prgn> if necessary when unpacking.
10078 The <prgn>dpkg-source</prgn> program will
10079 automatically make the <file>debian/rules</file> file
10080 executable (see below).</p></item>
10085 If there is no original source code - for example, if the
10086 package is specially prepared for Debian or the Debian
10087 maintainer is the same as the upstream maintainer - the
10088 format is slightly different: then there is no diff, and the
10090 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10091 and preferably contains a directory named
10092 <file><var>package</var>-<var>version</var></file>.
10097 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10100 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10101 Debian source package. However, if it is not available it
10102 is possible to unpack a Debian source archive as follows:
10103 <enumlist compact="compact">
10106 Untar the tarfile, which will create a <file>.orig</file>
10110 <p>Rename the <file>.orig</file> directory to
10111 <file><var>package</var>-<var>version</var></file>.</p>
10115 Create the subdirectory <file>debian</file> at the top of
10116 the source tree.</p>
10118 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10120 <item><p>Untar the tarfile again if you want a copy of the original
10121 source code alongside the Debianised version.</p>
10126 It is not possible to generate a valid Debian source archive
10127 without using <prgn>dpkg-source</prgn>. In particular,
10128 attempting to use <prgn>diff</prgn> directly to generate the
10129 <file>.diff.gz</file> file will not work.
10133 <heading>Restrictions on objects in source packages</heading>
10136 The source package may not contain any hard links
10138 This is not currently detected when building source
10139 packages, but only when extracting
10143 Hard links may be permitted at some point in the
10144 future, but would require a fair amount of
10146 </footnote>, device special files, sockets or setuid or
10149 Setgid directories are allowed.
10154 The source packaging tools manage the changes between the
10155 original and Debianised source using <prgn>diff</prgn> and
10156 <prgn>patch</prgn>. Turning the original source tree as
10157 included in the <file>.orig.tar.gz</file> into the debianised
10158 source must not involve any changes which cannot be
10159 handled by these tools. Problematic changes which cause
10160 <prgn>dpkg-source</prgn> to halt with an error when
10161 building the source package are:
10162 <list compact="compact">
10163 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10165 <item><p>Changing the targets of symbolic links.</p>
10167 <item><p>Creating directories, other than <file>debian</file>.</p>
10169 <item><p>Changes to the contents of binary files.</p></item>
10170 </list> Changes which cause <prgn>dpkg-source</prgn> to
10171 print a warning but continue anyway are:
10172 <list compact="compact">
10175 Removing files, directories or symlinks.
10177 Renaming a file is not treated specially - it is
10178 seen as the removal of the old file (which
10179 generates a warning, but is otherwise ignored),
10180 and the creation of the new one.
10186 Changed text files which are missing the usual final
10187 newline (either in the original or the modified
10192 Changes which are not represented, but which are not detected by
10193 <prgn>dpkg-source</prgn>, are:
10194 <list compact="compact">
10195 <item><p>Changing the permissions of files (other than
10196 <file>debian/rules</file>) and directories.</p></item>
10201 The <file>debian</file> directory and <file>debian/rules</file>
10202 are handled specially by <prgn>dpkg-source</prgn> - before
10203 applying the changes it will create the <file>debian</file>
10204 directory, and afterwards it will make
10205 <file>debian/rules</file> world-executable.
10211 <appendix id="pkg-controlfields">
10212 <heading>Control files and their fields (from old Packaging Manual)</heading>
10215 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10216 data in a common format, known as control files. Binary and
10217 source packages have control data as do the <file>.changes</file>
10218 files which control the installation of uploaded files, and
10219 <prgn>dpkg</prgn>'s internal databases are in a similar
10224 <heading>Syntax of control files</heading>
10227 See <ref id="controlsyntax">.
10231 It is important to note that there are several fields which
10232 are optional as far as <prgn>dpkg</prgn> and the related
10233 tools are concerned, but which must appear in every Debian
10234 package, or whose omission may cause problems.
10239 <heading>List of fields</heading>
10242 See <ref id="controlfieldslist">.
10246 This section now contains only the fields that didn't belong
10247 to the Policy manual.
10250 <sect1 id="pkg-f-Filename">
10251 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10254 These fields in <tt>Packages</tt> files give the
10255 filename(s) of (the parts of) a package in the
10256 distribution directories, relative to the root of the
10257 Debian hierarchy. If the package has been split into
10258 several parts the parts are all listed in order, separated
10263 <sect1 id="pkg-f-Size">
10264 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10267 These fields in <file>Packages</file> files give the size (in
10268 bytes, expressed in decimal) and MD5 checksum of the
10269 file(s) which make(s) up a binary package in the
10270 distribution. If the package is split into several parts
10271 the values for the parts are listed in order, separated by
10276 <sect1 id="pkg-f-Status">
10277 <heading><tt>Status</tt></heading>
10280 This field in <prgn>dpkg</prgn>'s status file records
10281 whether the user wants a package installed, removed or
10282 left alone, whether it is broken (requiring
10283 re-installation) or not and what its current state on the
10284 system is. Each of these pieces of information is a
10289 <sect1 id="pkg-f-Config-Version">
10290 <heading><tt>Config-Version</tt></heading>
10293 If a package is not installed or not configured, this
10294 field in <prgn>dpkg</prgn>'s status file records the last
10295 version of the package which was successfully
10300 <sect1 id="pkg-f-Conffiles">
10301 <heading><tt>Conffiles</tt></heading>
10304 This field in <prgn>dpkg</prgn>'s status file contains
10305 information about the automatically-managed configuration
10306 files held by a package. This field should <em>not</em>
10307 appear anywhere in a package!
10312 <heading>Obsolete fields</heading>
10315 These are still recognized by <prgn>dpkg</prgn> but should
10316 not appear anywhere any more.
10318 <taglist compact="compact">
10320 <tag><tt>Revision</tt></tag>
10321 <tag><tt>Package-Revision</tt></tag>
10322 <tag><tt>Package_Revision</tt></tag>
10324 The Debian revision part of the package version was
10325 at one point in a separate control file field. This
10326 field went through several names.
10329 <tag><tt>Recommended</tt></tag>
10330 <item>Old name for <tt>Recommends</tt>.</item>
10332 <tag><tt>Optional</tt></tag>
10333 <item>Old name for <tt>Suggests</tt>.</item>
10335 <tag><tt>Class</tt></tag>
10336 <item>Old name for <tt>Priority</tt>.</item>
10345 <appendix id="pkg-conffiles">
10346 <heading>Configuration file handling (from old Packaging Manual)</heading>
10349 <prgn>dpkg</prgn> can do a certain amount of automatic
10350 handling of package configuration files.
10354 Whether this mechanism is appropriate depends on a number of
10355 factors, but basically there are two approaches to any
10356 particular configuration file.
10360 The easy method is to ship a best-effort configuration in the
10361 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10362 handle updates. If the user is unlikely to want to edit the
10363 file, but you need them to be able to without losing their
10364 changes, and a new package with a changed version of the file
10365 is only released infrequently, this is a good approach.
10369 The hard method is to build the configuration file from
10370 scratch in the <prgn>postinst</prgn> script, and to take the
10371 responsibility for fixing any mistakes made in earlier
10372 versions of the package automatically. This will be
10373 appropriate if the file is likely to need to be different on
10377 <sect><heading>Automatic handling of configuration files by
10382 A package may contain a control area file called
10383 <tt>conffiles</tt>. This file should be a list of filenames
10384 of configuration files needing automatic handling, separated
10385 by newlines. The filenames should be absolute pathnames,
10386 and the files referred to should actually exist in the
10391 When a package is upgraded <prgn>dpkg</prgn> will process
10392 the configuration files during the configuration stage,
10393 shortly before it runs the package's <prgn>postinst</prgn>
10398 For each file it checks to see whether the version of the
10399 file included in the package is the same as the one that was
10400 included in the last version of the package (the one that is
10401 being upgraded from); it also compares the version currently
10402 installed on the system with the one shipped with the last
10407 If neither the user nor the package maintainer has changed
10408 the file, it is left alone. If one or the other has changed
10409 their version, then the changed version is preferred - i.e.,
10410 if the user edits their file, but the package maintainer
10411 doesn't ship a different version, the user's changes will
10412 stay, silently, but if the maintainer ships a new version
10413 and the user hasn't edited it the new version will be
10414 installed (with an informative message). If both have
10415 changed their version the user is prompted about the problem
10416 and must resolve the differences themselves.
10420 The comparisons are done by calculating the MD5 message
10421 digests of the files, and storing the MD5 of the file as it
10422 was included in the most recent version of the package.
10426 When a package is installed for the first time
10427 <prgn>dpkg</prgn> will install the file that comes with it,
10428 unless that would mean overwriting a file already on the
10433 However, note that <prgn>dpkg</prgn> will <em>not</em>
10434 replace a conffile that was removed by the user (or by a
10435 script). This is necessary because with some programs a
10436 missing file produces an effect hard or impossible to
10437 achieve in another way, so that a missing file needs to be
10438 kept that way if the user did it.
10442 Note that a package should <em>not</em> modify a
10443 <prgn>dpkg</prgn>-handled conffile in its maintainer
10444 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10445 the user confusing and possibly dangerous options for
10446 conffile update when the package is upgraded.</p>
10449 <sect><heading>Fully-featured maintainer script configuration
10454 For files which contain site-specific information such as
10455 the hostname and networking details and so forth, it is
10456 better to create the file in the package's
10457 <prgn>postinst</prgn> script.
10461 This will typically involve examining the state of the rest
10462 of the system to determine values and other information, and
10463 may involve prompting the user for some information which
10464 can't be obtained some other way.
10468 When using this method there are a couple of important
10469 issues which should be considered:
10473 If you discover a bug in the program which generates the
10474 configuration file, or if the format of the file changes
10475 from one version to the next, you will have to arrange for
10476 the postinst script to do something sensible - usually this
10477 will mean editing the installed configuration file to remove
10478 the problem or change the syntax. You will have to do this
10479 very carefully, since the user may have changed the file,
10480 perhaps to fix the very problem that your script is trying
10481 to deal with - you will have to detect these situations and
10482 deal with them correctly.
10486 If you do go down this route it's probably a good idea to
10487 make the program that generates the configuration file(s) a
10488 separate program in <file>/usr/sbin</file>, by convention called
10489 <file><var>package</var>config</file> and then run that if
10490 appropriate from the post-installation script. The
10491 <tt><var>package</var>config</tt> program should not
10492 unquestioningly overwrite an existing configuration - if its
10493 mode of operation is geared towards setting up a package for
10494 the first time (rather than any arbitrary reconfiguration
10495 later) you should have it check whether the configuration
10496 already exists, and require a <tt>--force</tt> flag to
10497 overwrite it.</p></sect>
10500 <appendix id="pkg-alternatives"><heading>Alternative versions of
10501 an interface - <prgn>update-alternatives</prgn> (from old
10506 When several packages all provide different versions of the
10507 same program or file it is useful to have the system select a
10508 default, but to allow the system administrator to change it
10509 and have their decisions respected.
10513 For example, there are several versions of the <prgn>vi</prgn>
10514 editor, and there is no reason to prevent all of them from
10515 being installed at once, each under their own name
10516 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10517 Nevertheless it is desirable to have the name <tt>vi</tt>
10518 refer to something, at least by default.
10522 If all the packages involved cooperate, this can be done with
10523 <prgn>update-alternatives</prgn>.
10527 Each package provides its own version under its own name, and
10528 calls <prgn>update-alternatives</prgn> in its postinst to
10529 register its version (and again in its prerm to deregister
10534 See the man page <manref name="update-alternatives"
10535 section="8"> for details.
10539 If <prgn>update-alternatives</prgn> does not seem appropriate
10540 you may wish to consider using diversions instead.</p>
10543 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10544 package's version of a file (from old Packaging Manual)
10548 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10549 when it reinstalls the package it belongs to, and to have it
10550 put the file from the package somewhere else instead.
10554 This can be used locally to override a package's version of a
10555 file, or by one package to override another's version (or
10556 provide a wrapper for it).
10560 Before deciding to use a diversion, read <ref
10561 id="pkg-alternatives"> to see if you really want a diversion
10562 rather than several alternative versions of a program.
10566 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10567 and updated by a special program <prgn>dpkg-divert</prgn>.
10568 Please see <manref name="dpkg-divert" section="8"> for full
10569 details of its operation.
10573 When a package wishes to divert a file from another, it should
10574 call <prgn>dpkg-divert</prgn> in its preinst to add the
10575 diversion and rename the existing file. For example,
10576 supposing that a <prgn>smailwrapper</prgn> package wishes to
10577 install a wrapper around <file>/usr/sbin/smail</file>:
10579 dpkg-divert --package smailwrapper --add --rename \
10580 --divert /usr/sbin/smail.real /usr/sbin/smail
10581 </example> The <tt>--package smailwrapper</tt> ensures that
10582 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10583 can bypass the diversion and get installed as the true version.
10584 It's safe to add the diversion unconditionally on upgrades since
10585 it will be left unchanged if it already exists, but
10586 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10587 message, make the command conditional on the version from which
10588 the package is being upgraded:
10590 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10591 dpkg-divert --package smailwrapper --add --rename \
10592 --divert /usr/sbin/smail.real /usr/sbin/smail
10594 </example> where <tt>1.0-2</tt> is the version at which the
10595 diversion was first added to the package. Running the command
10596 during abort-upgrade is pointless but harmless.
10600 The postrm has to do the reverse:
10602 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10603 dpkg-divert --package smailwrapper --remove --rename \
10604 --divert /usr/sbin/smail.real /usr/sbin/smail
10606 </example> If the diversion was added at a particular version, the
10607 postrm should also handle the failure case of upgrading from an
10608 older version (unless the older version is so old that direct
10609 upgrades are no longer supported):
10611 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10612 dpkg-divert --package smailwrapper --remove --rename \
10613 --divert /usr/sbin/smail.real /usr/sbin/smail
10615 </example> where <tt>1.02-2</tt> is the version at which the
10616 diversion was first added to the package. The postrm should not
10617 remove the diversion on upgrades both because there's no reason to
10618 remove the diversion only to immediately re-add it and since the
10619 postrm of the old package is run after unpacking so the removal of
10620 the diversion will fail.
10624 Do not attempt to divert a file which is vitally important for
10625 the system's operation - when using <prgn>dpkg-divert</prgn>
10626 there is a time, after it has been diverted but before
10627 <prgn>dpkg</prgn> has installed the new version, when the file
10628 does not exist.</p>
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