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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 defined as the minimal set of functionality
1016 that must be available and usable on the system even
1017 when packages are in an unconfigured (but unpacked)
1018 state. This is needed to avoid unresolvable dependency
1019 loops on upgrade. If packages add unnecessary
1020 dependencies on packages in this set, the chances that
1021 there <strong>will</strong> be an unresolvable
1022 dependency loop caused by forcing these Essential
1023 packages to be configured first before they need to be
1024 is greatly increased. It also increases the chances
1025 that frontends will be unable to
1026 <strong>calculate</strong> an upgrade path, even if one
1030 Also, it's pretty unlikely that functionality from
1031 Essential shall ever be removed (which is one reason why
1032 care must be taken before adding to the Essential
1033 packages set), but <em>packages</em> have been removed
1034 from the Essential set when the functionality moved to a
1035 different package. So depending on these packages
1036 <em>just in case</em> they stop being essential does way
1037 more harm than good.
1043 Sometimes, a package requires another package to be installed
1044 <em>and</em> configured before it can be installed. In this
1045 case, you must specify a <tt>Pre-Depends</tt> entry for
1050 You should not specify a <tt>Pre-Depends</tt> entry for a
1051 package before this has been discussed on the
1052 <tt>debian-devel</tt> mailing list and a consensus about
1053 doing that has been reached.
1057 The format of the package interrelationship control fields is
1058 described in <ref id="relationships">.
1062 <sect id="virtual_pkg">
1063 <heading>Virtual packages</heading>
1066 Sometimes, there are several packages which offer
1067 more-or-less the same functionality. In this case, it's
1068 useful to define a <em>virtual package</em> whose name
1069 describes that common functionality. (The virtual
1070 packages only exist logically, not physically; that's why
1071 they are called <em>virtual</em>.) The packages with this
1072 particular function will then <em>provide</em> the virtual
1073 package. Thus, any other package requiring that function
1074 can simply depend on the virtual package without having to
1075 specify all possible packages individually.
1079 All packages should use virtual package names where
1080 appropriate, and arrange to create new ones if necessary.
1081 They should not use virtual package names (except privately,
1082 amongst a cooperating group of packages) unless they have
1083 been agreed upon and appear in the list of virtual package
1084 names. (See also <ref id="virtual">)
1088 The latest version of the authoritative list of virtual
1089 package names can be found in the <tt>debian-policy</tt> package.
1090 It is also available from the Debian web mirrors at
1091 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1092 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1096 The procedure for updating the list is described in the preface
1103 <heading>Base system</heading>
1106 The <tt>base system</tt> is a minimum subset of the Debian
1107 GNU/Linux system that is installed before everything else
1108 on a new system. Only very few packages are allowed to form
1109 part of the base system, in order to keep the required disk
1114 The base system consists of all those packages with priority
1115 <tt>required</tt> or <tt>important</tt>. Many of them will
1116 be tagged <tt>essential</tt> (see below).
1121 <heading>Essential packages</heading>
1124 Some packages are tagged <tt>essential</tt> for a system
1125 using the <tt>Essential</tt> control file field.
1126 The format of the <tt>Essential</tt> control field is
1127 described in <ref id="f-Essential">.
1131 Since these packages cannot be easily removed (one has to
1132 specify an extra <em>force option</em> to
1133 <prgn>dpkg</prgn> to do so), this flag must not be used
1134 unless absolutely necessary. A shared library package
1135 must not be tagged <tt>essential</tt>; dependencies will
1136 prevent its premature removal, and we need to be able to
1137 remove it when it has been superseded.
1141 Since dpkg will not prevent upgrading of other packages
1142 while an <tt>essential</tt> package is in an unconfigured
1143 state, all <tt>essential</tt> packages must supply all of
1144 their core functionality even when unconfigured. If the
1145 package cannot satisfy this requirement it must not be
1146 tagged as essential, and any packages depending on this
1147 package must instead have explicit dependency fields as
1152 You must not tag any packages <tt>essential</tt> before
1153 this has been discussed on the <tt>debian-devel</tt>
1154 mailing list and a consensus about doing that has been
1159 <sect id="maintscripts">
1160 <heading>Maintainer Scripts</heading>
1163 The package installation scripts should avoid producing
1164 output which is unnecessary for the user to see and
1165 should rely on <prgn>dpkg</prgn> to stave off boredom on
1166 the part of a user installing many packages. This means,
1167 amongst other things, using the <tt>--quiet</tt> option on
1168 <prgn>install-info</prgn>.
1172 Errors which occur during the execution of an installation
1173 script must be checked and the installation must not
1174 continue after an error.
1178 Note that in general <ref id="scripts"> applies to package
1179 maintainer scripts, too.
1183 You should not use <prgn>dpkg-divert</prgn> on a file
1184 belonging to another package without consulting the
1185 maintainer of that package first.
1189 All packages which supply an instance of a common command
1190 name (or, in general, filename) should generally use
1191 <prgn>update-alternatives</prgn>, so that they may be
1192 installed together. If <prgn>update-alternatives</prgn>
1193 is not used, then each package must use
1194 <tt>Conflicts</tt> to ensure that other packages are
1195 de-installed. (In this case, it may be appropriate to
1196 specify a conflict against earlier versions of something
1197 that previously did not use
1198 <prgn>update-alternatives</prgn>; this is an exception to
1199 the usual rule that versioned conflicts should be
1203 <sect1 id="maintscriptprompt">
1204 <heading>Prompting in maintainer scripts</heading>
1206 Package maintainer scripts may prompt the user if
1207 necessary. Prompting should be done by communicating
1208 through a program, such as <prgn>debconf</prgn>, which
1209 conforms to the Debian Configuration Management
1210 Specification, version 2 or higher. Prompting the user by
1211 other means, such as by hand<footnote>
1212 From the Jargon file: by hand 2. By extension,
1213 writing code which does something in an explicit or
1214 low-level way for which a presupplied library
1215 (<em>debconf, in this instance</em>) routine ought
1216 to have been available.
1217 </footnote>, is now deprecated.
1221 The Debian Configuration Management Specification is included
1222 in the <file>debconf_specification</file> files in the
1223 <package>debian-policy</package> package.
1224 It is also available from the Debian web mirrors at
1225 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1226 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1230 Packages which use the Debian Configuration Management
1231 Specification may contain an additional
1232 <prgn>config</prgn> script and a <tt>templates</tt>
1233 file in their control archive<footnote>
1234 The control.tar.gz inside the .deb.
1235 See <manref name="deb" section="5">.
1237 The <prgn>config</prgn> script might be run before the
1238 <prgn>preinst</prgn> script, and before the package is unpacked
1239 or any of its dependencies or pre-dependencies are satisfied.
1240 Therefore it must work using only the tools present in
1241 <em>essential</em> packages.<footnote>
1242 <package>Debconf</package> or another tool that
1243 implements the Debian Configuration Management
1244 Specification will also be installed, and any
1245 versioned dependencies on it will be satisfied
1246 before preconfiguration begins.
1251 Packages which use the Debian Configuration Management
1252 Specification must allow for translation of their user-visible
1253 messages by using a gettext-based system such as the one
1254 provided by the <package>po-debconf</package> package.
1258 Packages should try to minimize the amount of prompting
1259 they need to do, and they should ensure that the user
1260 will only ever be asked each question once. This means
1261 that packages should try to use appropriate shared
1262 configuration files (such as <file>/etc/papersize</file> and
1263 <file>/etc/news/server</file>), and shared
1264 <package>debconf</package> variables rather than each
1265 prompting for their own list of required pieces of
1270 It also means that an upgrade should not ask the same
1271 questions again, unless the user has used
1272 <tt>dpkg --purge</tt> to remove the package's configuration.
1273 The answers to configuration questions should be stored in an
1274 appropriate place in <file>/etc</file> so that the user can
1275 modify them, and how this has been done should be
1280 If a package has a vitally important piece of
1281 information to pass to the user (such as "don't run me
1282 as I am, you must edit the following configuration files
1283 first or you risk your system emitting badly-formatted
1284 messages"), it should display this in the
1285 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1286 prompt the user to hit return to acknowledge the
1287 message. Copyright messages do not count as vitally
1288 important (they belong in
1289 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1290 neither do instructions on how to use a program (these
1291 should be in on-line documentation, where all the users
1296 Any necessary prompting should almost always be confined
1297 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1298 script. If it is done in the <prgn>postinst</prgn>, it
1299 should be protected with a conditional so that
1300 unnecessary prompting doesn't happen if a package's
1301 installation fails and the <prgn>postinst</prgn> is
1302 called with <tt>abort-upgrade</tt>,
1303 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1313 <heading>Source packages</heading>
1315 <sect id="standardsversion">
1316 <heading>Standards conformance</heading>
1319 Source packages should specify the most recent version number
1320 of this policy document with which your package complied
1321 when it was last updated.
1325 This information may be used to file bug reports
1326 automatically if your package becomes too much out of date.
1330 The version is specified in the <tt>Standards-Version</tt>
1332 The format of the <tt>Standards-Version</tt> field is
1333 described in <ref id="f-Standards-Version">.
1337 You should regularly, and especially if your package has
1338 become out of date, check for the newest Policy Manual
1339 available and update your package, if necessary. When your
1340 package complies with the new standards you should update the
1341 <tt>Standards-Version</tt> source package field and
1342 release it.<footnote>
1343 See the file <file>upgrading-checklist</file> for
1344 information about policy which has changed between
1345 different versions of this document.
1351 <sect id="pkg-relations">
1352 <heading>Package relationships</heading>
1355 Source packages should specify which binary packages they
1356 require to be installed or not to be installed in order to
1357 build correctly. For example, if building a package
1358 requires a certain compiler, then the compiler should be
1359 specified as a build-time dependency.
1363 It is not necessary to explicitly specify build-time
1364 relationships on a minimal set of packages that are always
1365 needed to compile, link and put in a Debian package a
1366 standard "Hello World!" program written in C or C++. The
1367 required packages are called <em>build-essential</em>, and
1368 an informational list can be found in
1369 <file>/usr/share/doc/build-essential/list</file> (which is
1370 contained in the <tt>build-essential</tt>
1373 <list compact="compact">
1375 This allows maintaining the list separately
1376 from the policy documents (the list does not
1377 need the kind of control that the policy
1381 Having a separate package allows one to install
1382 the build-essential packages on a machine, as
1383 well as allowing other packages such as tasks to
1384 require installation of the build-essential
1385 packages using the depends relation.
1388 The separate package allows bug reports against
1389 the list to be categorized separately from
1390 the policy management process in the BTS.
1397 When specifying the set of build-time dependencies, one
1398 should list only those packages explicitly required by the
1399 build. It is not necessary to list packages which are
1400 required merely because some other package in the list of
1401 build-time dependencies depends on them.<footnote>
1402 The reason for this is that dependencies change, and
1403 you should list all those packages, and <em>only</em>
1404 those packages that <em>you</em> need directly. What
1405 others need is their business. For example, if you
1406 only link against <file>libimlib</file>, you will need to
1407 build-depend on <package>libimlib2-dev</package> but
1408 not against any <tt>libjpeg*</tt> packages, even
1409 though <tt>libimlib2-dev</tt> currently depends on
1410 them: installation of <package>libimlib2-dev</package>
1411 will automatically ensure that all of its run-time
1412 dependencies are satisfied.
1417 If build-time dependencies are specified, it must be
1418 possible to build the package and produce working binaries
1419 on a system with only essential and build-essential
1420 packages installed and also those required to satisfy the
1421 build-time relationships (including any implied
1422 relationships). In particular, this means that version
1423 clauses should be used rigorously in build-time
1424 relationships so that one cannot produce bad or
1425 inconsistently configured packages when the relationships
1426 are properly satisfied.
1430 <ref id="relationships"> explains the technical details.
1435 <heading>Changes to the upstream sources</heading>
1438 If changes to the source code are made that are not
1439 specific to the needs of the Debian system, they should be
1440 sent to the upstream authors in whatever form they prefer
1441 so as to be included in the upstream version of the
1446 If you need to configure the package differently for
1447 Debian or for Linux, and the upstream source doesn't
1448 provide a way to do so, you should add such configuration
1449 facilities (for example, a new <prgn>autoconf</prgn> test
1450 or <tt>#define</tt>) and send the patch to the upstream
1451 authors, with the default set to the way they originally
1452 had it. You can then easily override the default in your
1453 <file>debian/rules</file> or wherever is appropriate.
1457 You should make sure that the <prgn>configure</prgn> utility
1458 detects the correct architecture specification string
1459 (refer to <ref id="arch-spec"> for details).
1463 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1464 <prgn>configure</prgn> scripts are used, you should edit the
1465 <file>.in</file> files rather than editing the
1466 <prgn>Makefile</prgn> directly. This allows the user to
1467 reconfigure the package if necessary. You should
1468 <em>not</em> configure the package and edit the generated
1469 <prgn>Makefile</prgn>! This makes it impossible for someone
1470 else to later reconfigure the package without losing the
1476 <sect id="dpkgchangelog">
1477 <heading>Debian changelog: <file>debian/changelog</file></heading>
1480 Changes in the Debian version of the package should be
1481 briefly explained in the Debian changelog file
1482 <file>debian/changelog</file>.<footnote>
1484 Mistakes in changelogs are usually best rectified by
1485 making a new changelog entry rather than "rewriting
1486 history" by editing old changelog entries.
1489 This includes modifications
1490 made in the Debian package compared to the upstream one
1491 as well as other changes and updates to the package.
1493 Although there is nothing stopping an author who is also
1494 the Debian maintainer from using this changelog for all
1495 their changes, it will have to be renamed if the Debian
1496 and upstream maintainers become different people. In such
1497 a case, however, it might be better to maintain the package
1498 as a non-native package.
1503 The format of the <file>debian/changelog</file> allows the
1504 package building tools to discover which version of the package
1505 is being built and find out other release-specific information.
1509 That format is a series of entries like this:
1511 <example compact="compact">
1512 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1514 [optional blank line(s), stripped]
1516 * <var>change details</var>
1517 <var>more change details</var>
1519 [blank line(s), included in output of dpkg-parsechangelog]
1521 * <var>even more change details</var>
1523 [optional blank line(s), stripped]
1525 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1530 <var>package</var> and <var>version</var> are the source
1531 package name and version number.
1535 <var>distribution(s)</var> lists the distributions where
1536 this version should be installed when it is uploaded - it
1537 is copied to the <tt>Distribution</tt> field in the
1538 <file>.changes</file> file. See <ref id="f-Distribution">.
1542 <var>urgency</var> is the value for the <tt>Urgency</tt>
1543 field in the <file>.changes</file> file for the upload
1544 (see <ref id="f-Urgency">). It is not possible to specify
1545 an urgency containing commas; commas are used to separate
1546 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1547 <prgn>dpkg</prgn> changelog format (though there is
1548 currently only one useful <var>keyword</var>,
1553 The change details may in fact be any series of lines
1554 starting with at least two spaces, but conventionally each
1555 change starts with an asterisk and a separating space and
1556 continuation lines are indented so as to bring them in
1557 line with the start of the text above. Blank lines may be
1558 used here to separate groups of changes, if desired.
1562 If this upload resolves bugs recorded in the Bug Tracking
1563 System (BTS), they may be automatically closed on the
1564 inclusion of this package into the Debian archive by
1565 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1566 in the change details.<footnote>
1567 To be precise, the string should match the following
1568 Perl regular expression:
1570 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1572 Then all of the bug numbers listed will be closed by the
1573 archive maintenance script (<prgn>katie</prgn>) using the
1574 <var>version</var> of the changelog entry.
1576 This information is conveyed via the <tt>Closes</tt> field
1577 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1581 The maintainer name and email address used in the changelog
1582 should be the details of the person uploading <em>this</em>
1583 version. They are <em>not</em> necessarily those of the
1584 usual package maintainer. The information here will be
1585 copied to the <tt>Changed-By</tt> field in the
1586 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1587 and then later used to send an acknowledgement when the
1588 upload has been installed.
1592 The <var>date</var> must be in RFC822 format<footnote>
1593 This is generated by <tt>date -R</tt>.
1594 </footnote>; it must include the time zone specified
1595 numerically, with the time zone name or abbreviation
1596 optionally present as a comment in parentheses.
1600 The first "title" line with the package name must start
1601 at the left hand margin. The "trailer" line with the
1602 maintainer and date details must be preceded by exactly
1603 one space. The maintainer details and the date must be
1604 separated by exactly two spaces.
1608 The entire changelog must be encoded in UTF-8.
1612 For more information on placement of the changelog files
1613 within binary packages, please see <ref id="changelogs">.
1617 <sect id="dpkgcopyright">
1618 <heading>Copyright: <file>debian/copyright</file></heading>
1620 Every package must be accompanied by a verbatim copy of
1621 its copyright and distribution license in the file
1622 <file>/usr/share/doc/<var>package</var>/copyright</file>
1623 (see <ref id="copyrightfile"> for further details). Also see
1624 <ref id="pkgcopyright"> for further considerations relayed
1625 to copyrights for packages.
1629 <heading>Error trapping in makefiles</heading>
1632 When <prgn>make</prgn> invokes a command in a makefile
1633 (including your package's upstream makefiles and
1634 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1635 means that <prgn>sh</prgn>'s usual bad error handling
1636 properties apply: if you include a miniature script as one
1637 of the commands in your makefile you'll find that if you
1638 don't do anything about it then errors are not detected
1639 and <prgn>make</prgn> will blithely continue after
1644 Every time you put more than one shell command (this
1645 includes using a loop) in a makefile command you
1646 must make sure that errors are trapped. For
1647 simple compound commands, such as changing directory and
1648 then running a program, using <tt>&&</tt> rather
1649 than semicolon as a command separator is sufficient. For
1650 more complex commands including most loops and
1651 conditionals you should include a separate <tt>set -e</tt>
1652 command at the start of every makefile command that's
1653 actually one of these miniature shell scripts.
1657 <sect id="timestamps">
1658 <heading>Time Stamps</heading>
1660 Maintainers should preserve the modification times of the
1661 upstream source files in a package, as far as is reasonably
1663 The rationale is that there is some information conveyed
1664 by knowing the age of the file, for example, you could
1665 recognize that some documentation is very old by looking
1666 at the modification time, so it would be nice if the
1667 modification time of the upstream source would be
1673 <sect id="restrictions">
1674 <heading>Restrictions on objects in source packages</heading>
1677 The source package may not contain any hard links<footnote>
1679 This is not currently detected when building source
1680 packages, but only when extracting
1684 Hard links may be permitted at some point in the
1685 future, but would require a fair amount of
1688 </footnote>, device special files, sockets or setuid or
1689 setgid files.<footnote>
1690 Setgid directories are allowed.
1695 <sect id="debianrules">
1696 <heading>Main building script: <file>debian/rules</file></heading>
1699 This file must be an executable makefile, and contains the
1700 package-specific recipes for compiling the package and
1701 building binary package(s) from the source.
1705 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1706 so that it can be invoked by saying its name rather than
1707 invoking <prgn>make</prgn> explicitly.
1711 Since an interactive <file>debian/rules</file> script makes it
1712 impossible to auto-compile that package and also makes it
1713 hard for other people to reproduce the same binary
1714 package, all <em>required targets</em> MUST be
1715 non-interactive. At a minimum, required targets are the
1716 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1717 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1718 <em>binary-indep</em>, and <em>build</em>. It also follows
1719 that any target that these targets depend on must also be
1724 The targets are as follows (required unless stated otherwise):
1726 <tag><tt>build</tt></tag>
1729 The <tt>build</tt> target should perform all the
1730 configuration and compilation of the package.
1731 If a package has an interactive pre-build
1732 configuration routine, the Debianized source package
1733 must either be built after this has taken place (so
1734 that the binary package can be built without rerunning
1735 the configuration) or the configuration routine
1736 modified to become non-interactive. (The latter is
1737 preferable if there are architecture-specific features
1738 detected by the configuration routine.)
1742 For some packages, notably ones where the same
1743 source tree is compiled in different ways to produce
1744 two binary packages, the <tt>build</tt> target
1745 does not make much sense. For these packages it is
1746 good enough to provide two (or more) targets
1747 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1748 for each of the ways of building the package, and a
1749 <tt>build</tt> target that does nothing. The
1750 <tt>binary</tt> target will have to build the
1751 package in each of the possible ways and make the
1752 binary package out of each.
1756 The <tt>build</tt> target must not do anything
1757 that might require root privilege.
1761 The <tt>build</tt> target may need to run the
1762 <tt>clean</tt> target first - see below.
1766 When a package has a configuration and build routine
1767 which takes a long time, or when the makefiles are
1768 poorly designed, or when <tt>build</tt> needs to
1769 run <tt>clean</tt> first, it is a good idea to
1770 <tt>touch build</tt> when the build process is
1771 complete. This will ensure that if <tt>debian/rules
1772 build</tt> is run again it will not rebuild the whole
1774 Another common way to do this is for <tt>build</tt>
1775 to depend on <prgn>build-stamp</prgn> and to do
1776 nothing else, and for the <prgn>build-stamp</prgn>
1777 target to do the building and to <tt>touch
1778 build-stamp</tt> on completion. This is
1779 especially useful if the build routine creates a
1780 file or directory called <tt>build</tt>; in such a
1781 case, <tt>build</tt> will need to be listed as
1782 a phony target (i.e., as a dependency of the
1783 <tt>.PHONY</tt> target). See the documentation of
1784 <prgn>make</prgn> for more information on phony
1790 <tag><tt>build-arch</tt> (optional),
1791 <tt>build-indep</tt> (optional)
1795 A package may also provide both of the targets
1796 <tt>build-arch</tt> and <tt>build-indep</tt>.
1797 The <tt>build-arch</tt> target, if provided, should
1798 perform all the configuration and compilation required
1799 for producing all architecture-dependant binary packages
1800 (those packages for which the body of the
1801 <tt>Architecture</tt> field in <tt>debian/control</tt>
1802 is not <tt>all</tt>).
1803 Similarly, the <tt>build-indep</tt> target, if
1804 provided, should perform all the configuration and
1805 compilation required for producing all
1806 architecture-independent binary packages
1807 (those packages for which the body of the
1808 <tt>Architecture</tt> field in <tt>debian/control</tt>
1810 The <tt>build</tt> target should depend on those of the
1811 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1812 are provided in the rules file.
1816 If one or both of the targets <tt>build-arch</tt> and
1817 <tt>build-indep</tt> are not provided, then invoking
1818 <file>debian/rules</file> with one of the not-provided
1819 targets as arguments should produce a exit status code
1820 of 2. Usually this is provided automatically by make
1821 if the target is missing.
1825 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1826 must not do anything that might require root privilege.
1830 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1831 <tt>binary-indep</tt>
1835 The <tt>binary</tt> target must be all that is
1836 necessary for the user to build the binary package(s)
1837 produced from this source package. It is
1838 split into two parts: <prgn>binary-arch</prgn> builds
1839 the binary packages which are specific to a particular
1840 architecture, and <tt>binary-indep</tt> builds
1841 those which are not.
1844 <tt>binary</tt> may be (and commonly is) a target with
1845 no commands which simply depends on
1846 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1849 Both <tt>binary-*</tt> targets should depend on the
1850 <tt>build</tt> target, or on the appropriate
1851 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1852 provided, so that the package is built if it has not
1853 been already. It should then create the relevant
1854 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1855 make their control files and <prgn>dpkg-deb</prgn> to
1856 build them and place them in the parent of the top
1861 Both the <tt>binary-arch</tt> and
1862 <tt>binary-indep</tt> targets <em>must</em> exist.
1863 If one of them has nothing to do (which will always be
1864 the case if the source generates only a single binary
1865 package, whether architecture-dependent or not), it
1866 must still exist and must always succeed.
1870 The <tt>binary</tt> targets must be invoked as
1872 The <prgn>fakeroot</prgn> package often allows one
1873 to build a package correctly even without being
1879 <tag><tt>clean</tt></tag>
1882 This must undo any effects that the <tt>build</tt>
1883 and <tt>binary</tt> targets may have had, except
1884 that it should leave alone any output files created in
1885 the parent directory by a run of a <tt>binary</tt>
1890 If a <tt>build</tt> file is touched at the end of
1891 the <tt>build</tt> target, as suggested above, it
1892 should be removed as the first action that
1893 <tt>clean</tt> performs, so that running
1894 <tt>build</tt> again after an interrupted
1895 <tt>clean</tt> doesn't think that everything is
1900 The <tt>clean</tt> target may need to be
1901 invoked as root if <tt>binary</tt> has been
1902 invoked since the last <tt>clean</tt>, or if
1903 <tt>build</tt> has been invoked as root (since
1904 <tt>build</tt> may create directories, for
1909 <tag><tt>get-orig-source</tt> (optional)</tag>
1912 This target fetches the most recent version of the
1913 original source package from a canonical archive site
1914 (via FTP or WWW, for example), does any necessary
1915 rearrangement to turn it into the original source
1916 tar file format described below, and leaves it in the
1921 This target may be invoked in any directory, and
1922 should take care to clean up any temporary files it
1927 This target is optional, but providing it if
1928 possible is a good idea.
1932 <tag><tt>patch</tt> (optional)</tag>
1935 This target performs whatever additional actions are
1936 required to make the source ready for editing (unpacking
1937 additional upstream archives, applying patches, etc.).
1938 It is recommended to be implemented for any package where
1939 <tt>dpkg-source -x</tt> does not result in source ready
1940 for additional modification. See
1941 <ref id="readmesource">.
1947 The <tt>build</tt>, <tt>binary</tt> and
1948 <tt>clean</tt> targets must be invoked with the current
1949 directory being the package's top-level directory.
1954 Additional targets may exist in <file>debian/rules</file>,
1955 either as published or undocumented interfaces or for the
1956 package's internal use.
1960 The architectures we build on and build for are determined
1961 by <prgn>make</prgn> variables using the utility
1962 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1963 You can determine the
1964 Debian architecture and the GNU style architecture
1965 specification string for the build machine (the machine type
1966 we are building on) as well as for the host machine (the
1967 machine type we are building for). Here is a list of
1968 supported <prgn>make</prgn> variables:
1969 <list compact="compact">
1971 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1974 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1975 specification string)
1978 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1979 <tt>DEB_*_GNU_TYPE</tt>)
1982 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1983 <tt>DEB_*_GNU_TYPE</tt>)
1985 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1986 the build machine or <tt>HOST</tt> for specification of the
1991 Backward compatibility can be provided in the rules file
1992 by setting the needed variables to suitable default
1993 values; please refer to the documentation of
1994 <prgn>dpkg-architecture</prgn> for details.
1998 It is important to understand that the <tt>DEB_*_ARCH</tt>
1999 string only determines which Debian architecture we are
2000 building on or for. It should not be used to get the CPU
2001 or system information; the GNU style variables should be
2005 <sect1 id="debianrules-options">
2006 <heading><file>debian/rules</file> and
2007 <tt>DEB_BUILD_OPTIONS</tt></heading>
2010 Supporting the standardized environment variable
2011 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2012 contain several flags to change how a package is compiled and
2013 built. Each flag must be in the form <var>flag</var> or
2014 <var>flag</var>=<var>options</var>. If multiple flags are
2015 given, they must be separated by whitespace.<footnote>
2016 Some packages support any delimiter, but whitespace is the
2017 easiest to parse inside a makefile and avoids ambiguity with
2018 flag values that contain commas.
2020 <var>flag</var> must start with a lowercase letter
2021 (<tt>a-z</tt>) and consist only of lowercase letters,
2022 numbers (<tt>0-9</tt>), and the characters
2023 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2024 <var>options</var> must not contain whitespace. The same
2025 tag should not be given multiple times with conflicting
2026 values. Package maintainers may assume that
2027 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2031 The meaning of the following tags has been standardized:
2035 This tag says to not run any build-time test suite
2036 provided by the package.
2040 The presence of this tag means that the package should
2041 be compiled with a minimum of optimization. For C
2042 programs, it is best to add <tt>-O0</tt> to
2043 <tt>CFLAGS</tt> (although this is usually the default).
2044 Some programs might fail to build or run at this level
2045 of optimization; it may be necessary to use
2046 <tt>-O1</tt>, for example.
2050 This tag means that the debugging symbols should not be
2051 stripped from the binary during installation, so that
2052 debugging information may be included in the package.
2054 <tag>parallel=n</tag>
2056 This tag means that the package should be built using up
2057 to <tt>n</tt> parallel processes if the package build
2058 system supports this.<footnote>
2059 Packages built with <tt>make</tt> can often implement
2060 this by passing the <tt>-j</tt><var>n</var> option to
2063 If the package build system does not support parallel
2064 builds, this string must be ignored. If the package
2065 build system only supports a lower level of concurrency
2066 than <var>n</var>, the package should be built using as
2067 many parallel processes as the package build system
2068 supports. It is up to the package maintainer to decide
2069 whether the package build times are long enough and the
2070 package build system is robust enough to make supporting
2071 parallel builds worthwhile.
2077 Unknown flags must be ignored by <file>debian/rules</file>.
2081 The following makefile snippet is an example of how one may
2082 implement the build options; you will probably have to
2083 massage this example in order to make it work for your
2085 <example compact="compact">
2088 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2089 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2090 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2091 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2093 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2098 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2099 INSTALL_PROGRAM += -s
2101 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2102 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2103 MAKEFLAGS += -j$(NUMJOBS)
2108 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2109 # Code to run the package test suite.
2116 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2117 <sect id="substvars">
2118 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2121 When <prgn>dpkg-gencontrol</prgn>,
2122 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2123 generate control files they perform variable substitutions
2124 on their output just before writing it. Variable
2125 substitutions have the form <tt>${<var>variable</var>}</tt>.
2126 The optional file <file>debian/substvars</file> contains
2127 variable substitutions to be used; variables can also be set
2128 directly from <file>debian/rules</file> using the <tt>-V</tt>
2129 option to the source packaging commands, and certain
2130 predefined variables are also available.
2134 The <file>debian/substvars</file> file is usually generated and
2135 modified dynamically by <file>debian/rules</file> targets, in
2136 which case it must be removed by the <tt>clean</tt> target.
2140 See <manref name="deb-substvars" section="5"> for full
2141 details about source variable substitutions, including the
2142 format of <file>debian/substvars</file>.</p>
2145 <sect id="debianwatch">
2146 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2149 This is an optional, recommended control file for the
2150 <tt>uscan</tt> utility which defines how to automatically
2151 scan ftp or http sites for newly available updates of the
2152 package. This is used by <url id="
2153 http://dehs.alioth.debian.org/"> and other Debian QA tools
2154 to help with quality control and maintenance of the
2155 distribution as a whole.
2160 <sect id="debianfiles">
2161 <heading>Generated files list: <file>debian/files</file></heading>
2164 This file is not a permanent part of the source tree; it
2165 is used while building packages to record which files are
2166 being generated. <prgn>dpkg-genchanges</prgn> uses it
2167 when it generates a <file>.changes</file> file.
2171 It should not exist in a shipped source package, and so it
2172 (and any backup files or temporary files such as
2173 <file>files.new</file><footnote>
2174 <file>files.new</file> is used as a temporary file by
2175 <prgn>dpkg-gencontrol</prgn> and
2176 <prgn>dpkg-distaddfile</prgn> - they write a new
2177 version of <tt>files</tt> here before renaming it,
2178 to avoid leaving a corrupted copy if an error
2180 </footnote>) should be removed by the
2181 <tt>clean</tt> target. It may also be wise to
2182 ensure a fresh start by emptying or removing it at the
2183 start of the <tt>binary</tt> target.
2187 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2188 package, it adds an entry to <file>debian/files</file> for the
2189 <file>.deb</file> file that will be created when <tt>dpkg-deb
2190 --build</tt> is run for that binary package. So for most
2191 packages all that needs to be done with this file is to
2192 delete it in the <tt>clean</tt> target.
2196 If a package upload includes files besides the source
2197 package and any binary packages whose control files were
2198 made with <prgn>dpkg-gencontrol</prgn> then they should be
2199 placed in the parent of the package's top-level directory
2200 and <prgn>dpkg-distaddfile</prgn> should be called to add
2201 the file to the list in <file>debian/files</file>.</p>
2204 <sect id="embeddedfiles">
2205 <heading>Convenience copies of code</heading>
2208 Some software packages include in their distribution convenience
2209 copies of code from other software packages, generally so that
2210 users compiling from source don't have to download multiple
2211 packages. Debian packages should not make use of these
2212 convenience copies unless the included package is explicitly
2213 intended to be used in this way.<footnote>
2214 For example, parts of the GNU build system work like this.
2216 If the included code is already in the Debian archive in the
2217 form of a library, the Debian packaging should ensure that
2218 binary packages reference the libraries already in Debian and
2219 the convenience copy is not used. If the included code is not
2220 already in Debian, it should be packaged separately as a
2221 prerequisite if possible.
2223 Having multiple copies of the same code in Debian is
2224 inefficient, often creates either static linking or shared
2225 library conflicts, and, most importantly, increases the
2226 difficulty of handling security vulnerabilities in the
2232 <sect id="readmesource">
2233 <heading>Source package handling:
2234 <file>debian/README.source</file></heading>
2237 If running <prgn>dpkg-source -x</prgn> on a source package
2238 doesn't produce the source of the package, ready for editing,
2239 and allow one to make changes and run
2240 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2241 without taking any additional steps, creating a
2242 <file>debian/README.source</file> documentation file is
2243 recommended. This file should explain how to do all of the
2246 <item>Generate the fully patched source, in a form ready for
2247 editing, that would be built to create Debian
2248 packages. Doing this with a <tt>patch</tt> target in
2249 <file>debian/rules</file> is recommended; see
2250 <ref id="debianrules">.</item>
2251 <item>Modify the source and save those modifications so that
2252 they will be applied when building the package.</item>
2253 <item>Remove source modifications that are currently being
2254 applied when building the package.</item>
2255 <item>Optionally, document what steps are necessary to
2256 upgrade the Debian source package to a new upstream version,
2257 if applicable.</item>
2259 This explanation should include specific commands and mention
2260 any additional required Debian packages. It should not assume
2261 familiarity with any specific Debian packaging system or patch
2266 This explanation may refer to a documentation file installed by
2267 one of the package's build dependencies provided that the
2268 referenced documentation clearly explains these tasks and is not
2269 a general reference manual.
2273 <file>debian/README.source</file> may also include any other
2274 information that would be helpful to someone modifying the
2275 source package. Even if the package doesn't fit the above
2276 description, maintainers are encouraged to document in a
2277 <file>debian/README.source</file> file any source package with a
2278 particularly complex or unintuitive source layout or build
2279 system (for example, a package that builds the same source
2280 multiple times to generate different binary packages).
2286 <chapt id="controlfields">
2287 <heading>Control files and their fields</heading>
2290 The package management system manipulates data represented in
2291 a common format, known as <em>control data</em>, stored in
2292 <em>control files</em>.
2293 Control files are used for source packages, binary packages and
2294 the <file>.changes</file> files which control the installation
2295 of uploaded files<footnote>
2296 <prgn>dpkg</prgn>'s internal databases are in a similar
2301 <sect id="controlsyntax">
2302 <heading>Syntax of control files</heading>
2305 A control file consists of one or more paragraphs of
2307 The paragraphs are also sometimes referred to as stanzas.
2309 The paragraphs are separated by blank lines. Some control
2310 files allow only one paragraph; others allow several, in
2311 which case each paragraph usually refers to a different
2312 package. (For example, in source packages, the first
2313 paragraph refers to the source package, and later paragraphs
2314 refer to binary packages generated from the source.)
2318 Each paragraph consists of a series of data fields; each
2319 field consists of the field name, followed by a colon and
2320 then the data/value associated with that field. It ends at
2321 the end of the (logical) line. Horizontal whitespace
2322 (spaces and tabs) may occur immediately before or after the
2323 value and is ignored there; it is conventional to put a
2324 single space after the colon. For example, a field might
2326 <example compact="compact">
2329 the field name is <tt>Package</tt> and the field value
2334 Many fields' values may span several lines; in this case
2335 each continuation line must start with a space or a tab.
2336 Any trailing spaces or tabs at the end of individual
2337 lines of a field value are ignored.
2341 In fields where it is specified that lines may not wrap,
2342 only a single line of data is allowed and whitespace is not
2343 significant in a field body. Whitespace must not appear
2344 inside names (of packages, architectures, files or anything
2345 else) or version numbers, or between the characters of
2346 multi-character version relationships.
2350 Field names are not case-sensitive, but it is usual to
2351 capitalize the field names using mixed case as shown below.
2355 Blank lines, or lines consisting only of spaces and tabs,
2356 are not allowed within field values or between fields - that
2357 would mean a new paragraph.
2361 All control files must be encoded in UTF-8.
2365 <sect id="sourcecontrolfiles">
2366 <heading>Source package control files -- <file>debian/control</file></heading>
2369 The <file>debian/control</file> file contains the most vital
2370 (and version-independent) information about the source package
2371 and about the binary packages it creates.
2375 The first paragraph of the control file contains information about
2376 the source package in general. The subsequent sets each describe a
2377 binary package that the source tree builds.
2381 The fields in the general paragraph (the first one, for the source
2384 <list compact="compact">
2385 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2386 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2387 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2388 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2389 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2390 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2391 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2392 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2397 The fields in the binary package paragraphs are:
2399 <list compact="compact">
2400 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2401 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2402 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2403 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2404 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2405 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2406 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2407 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2412 The syntax and semantics of the fields are described below.
2418 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2419 generate control files for binary packages (see below), by
2420 <prgn>dpkg-genchanges</prgn> to generate the
2421 <tt>.changes</tt> file to accompany the upload, and by
2422 <prgn>dpkg-source</prgn> when it creates the
2423 <file>.dsc</file> source control file as part of a source
2424 archive. Many fields are permitted to span multiple lines in
2425 <file>debian/control</file> but not in any other control
2426 file. These tools are responsible for removing the line
2427 breaks from such fields when using fields from
2428 <file>debian/control</file> to generate other control files.
2432 The fields here may contain variable references - their
2433 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2434 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2435 when they generate output control files.
2436 See <ref id="substvars"> for details.
2441 <sect id="binarycontrolfiles">
2442 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2445 The <file>DEBIAN/control</file> file contains the most vital
2446 (and version-dependent) information about a binary package.
2450 The fields in this file are:
2452 <list compact="compact">
2453 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2454 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2455 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2456 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2457 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2458 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2459 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2460 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2461 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2462 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2463 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2464 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2469 <sect id="debiansourcecontrolfiles">
2470 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2473 This file contains a series of fields, identified and
2474 separated just like the fields in the control file of
2475 a binary package. The fields are listed below; their
2476 syntax is described above, in <ref id="pkg-controlfields">.
2478 <list compact="compact">
2479 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2480 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2481 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2482 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2483 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2484 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2485 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2486 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2487 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2488 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2489 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2494 The source package control file is generated by
2495 <prgn>dpkg-source</prgn> when it builds the source
2496 archive, from other files in the source package,
2497 described above. When unpacking, it is checked against
2498 the files and directories in the other parts of the
2504 <sect id="debianchangesfiles">
2505 <heading>Debian changes files -- <file>.changes</file></heading>
2508 The .changes files are used by the Debian archive maintenance
2509 software to process updates to packages. They contain one
2510 paragraph which contains information from the
2511 <tt>debian/control</tt> file and other data about the
2512 source package gathered via <tt>debian/changelog</tt>
2513 and <tt>debian/rules</tt>.
2517 The fields in this file are:
2519 <list compact="compact">
2520 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2521 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2522 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2523 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2524 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2525 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2526 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2527 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2528 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2529 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2530 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2531 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2532 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2533 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2538 <sect id="controlfieldslist">
2539 <heading>List of fields</heading>
2541 <sect1 id="f-Source">
2542 <heading><tt>Source</tt></heading>
2545 This field identifies the source package name.
2549 In <file>debian/control</file> or a <file>.dsc</file> file,
2550 this field must contain only the name of the source package.
2554 In a binary package control file or a <file>.changes</file>
2555 file, the source package name may be followed by a version
2556 number in parentheses<footnote>
2557 It is customary to leave a space after the package name
2558 if a version number is specified.
2560 This version number may be omitted (and is, by
2561 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2562 the <tt>Version</tt> field of the binary package in
2563 question. The field itself may be omitted from a binary
2564 package control file when the source package has the same
2565 name and version as the binary package.
2569 <sect1 id="f-Maintainer">
2570 <heading><tt>Maintainer</tt></heading>
2573 The package maintainer's name and email address. The name
2574 should come first, then the email address inside angle
2575 brackets <tt><></tt> (in RFC822 format).
2579 If the maintainer's name contains a full stop then the
2580 whole field will not work directly as an email address due
2581 to a misfeature in the syntax specified in RFC822; a
2582 program using this field as an address must check for this
2583 and correct the problem if necessary (for example by
2584 putting the name in round brackets and moving it to the
2585 end, and bringing the email address forward).
2589 <sect1 id="f-Uploaders">
2590 <heading><tt>Uploaders</tt></heading>
2593 List of the names and email addresses of co-maintainers of
2594 the package, if any. If the package has other maintainers
2595 beside the one named in the
2596 <qref id="f-Maintainer">Maintainer field</qref>, their
2597 names and email addresses should be listed here. The
2598 format is the same as that of the Maintainer tag, and
2599 multiple entries should be comma separated. Currently,
2600 this field is restricted to a single line of data. This
2601 is an optional field.
2604 Any parser that interprets the Uploaders field in
2605 <file>debian/control</file> must permit it to span multiple
2606 lines. Line breaks in an Uploaders field that spans multiple
2607 lines are not significant and the semantics of the field are
2608 the same as if the line breaks had not been present.
2612 <sect1 id="f-Changed-By">
2613 <heading><tt>Changed-By</tt></heading>
2616 The name and email address of the person who changed the
2617 said package. Usually the name of the maintainer.
2618 All the rules for the Maintainer field apply here, too.
2622 <sect1 id="f-Section">
2623 <heading><tt>Section</tt></heading>
2626 This field specifies an application area into which the package
2627 has been classified. See <ref id="subsections">.
2631 When it appears in the <file>debian/control</file> file,
2632 it gives the value for the subfield of the same name in
2633 the <tt>Files</tt> field of the <file>.changes</file> file.
2634 It also gives the default for the same field in the binary
2639 <sect1 id="f-Priority">
2640 <heading><tt>Priority</tt></heading>
2643 This field represents how important that it is that the user
2644 have the package installed. See <ref id="priorities">.
2648 When it appears in the <file>debian/control</file> file,
2649 it gives the value for the subfield of the same name in
2650 the <tt>Files</tt> field of the <file>.changes</file> file.
2651 It also gives the default for the same field in the binary
2656 <sect1 id="f-Package">
2657 <heading><tt>Package</tt></heading>
2660 The name of the binary package.
2664 Package names must consist only of lower case letters
2665 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2666 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2667 They must be at least two characters long and must start
2668 with an alphanumeric character.
2672 <sect1 id="f-Architecture">
2673 <heading><tt>Architecture</tt></heading>
2676 Depending on context and the control file used, the
2677 <tt>Architecture</tt> field can include the following sets of
2680 <item>A unique single word identifying a Debian machine
2681 architecture, see <ref id="arch-spec">.
2682 <item><tt>all</tt>, which indicates an
2683 architecture-independent package.
2684 <item><tt>any</tt>, which indicates a package available
2685 for building on any architecture.
2686 <item><tt>source</tt>, which indicates a source package.
2691 In the main <file>debian/control</file> file in the source
2692 package, or in the source package control file
2693 <file>.dsc</file>, one may specify a list of architectures
2694 separated by spaces, or the special values <tt>any</tt> or
2699 Specifying <tt>any</tt> indicates that the source package
2700 isn't dependent on any particular architecture and should
2701 compile fine on any one. The produced binary package(s)
2702 will be specific to whatever the current build architecture
2704 This is the most often used setting, and is recommended
2705 for new packages that aren't <tt>Architecture: all</tt>.
2710 Specifying a list of architectures indicates that the source
2711 will build an architecture-dependent package, and will only
2712 work correctly on the listed architectures.<footnote>
2713 This is a setting used for a minority of cases where the
2714 program is not portable. Generally, it should not be used
2720 In a <file>.changes</file> file, the <tt>Architecture</tt>
2721 field lists the architecture(s) of the package(s)
2722 currently being uploaded. This will be a list; if the
2723 source for the package is also being uploaded, the special
2724 entry <tt>source</tt> is also present.
2728 See <ref id="debianrules"> for information how to get the
2729 architecture for the build process.
2733 <sect1 id="f-Essential">
2734 <heading><tt>Essential</tt></heading>
2737 This is a boolean field which may occur only in the
2738 control file of a binary package or in a per-package fields
2739 paragraph of a main source control data file.
2743 If set to <tt>yes</tt> then the package management system
2744 will refuse to remove the package (upgrading and replacing
2745 it is still possible). The other possible value is <tt>no</tt>,
2746 which is the same as not having the field at all.
2751 <heading>Package interrelationship fields:
2752 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2753 <tt>Recommends</tt>, <tt>Suggests</tt>,
2754 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2755 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2759 These fields describe the package's relationships with
2760 other packages. Their syntax and semantics are described
2761 in <ref id="relationships">.</p>
2764 <sect1 id="f-Standards-Version">
2765 <heading><tt>Standards-Version</tt></heading>
2768 The most recent version of the standards (the policy
2769 manual and associated texts) with which the package
2774 The version number has four components: major and minor
2775 version number and major and minor patch level. When the
2776 standards change in a way that requires every package to
2777 change the major number will be changed. Significant
2778 changes that will require work in many packages will be
2779 signaled by a change to the minor number. The major patch
2780 level will be changed for any change to the meaning of the
2781 standards, however small; the minor patch level will be
2782 changed when only cosmetic, typographical or other edits
2783 are made which neither change the meaning of the document
2784 nor affect the contents of packages.
2788 Thus only the first three components of the policy version
2789 are significant in the <em>Standards-Version</em> control
2790 field, and so either these three components or the all
2791 four components may be specified.<footnote>
2792 In the past, people specified the full version number
2793 in the Standards-Version field, for example "2.3.0.0".
2794 Since minor patch-level changes don't introduce new
2795 policy, it was thought it would be better to relax
2796 policy and only require the first 3 components to be
2797 specified, in this example "2.3.0". All four
2798 components may still be used if someone wishes to do so.
2804 <sect1 id="f-Version">
2805 <heading><tt>Version</tt></heading>
2808 The version number of a package. The format is:
2809 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2813 The three components here are:
2815 <tag><var>epoch</var></tag>
2818 This is a single (generally small) unsigned integer. It
2819 may be omitted, in which case zero is assumed. If it is
2820 omitted then the <var>upstream_version</var> may not
2825 It is provided to allow mistakes in the version numbers
2826 of older versions of a package, and also a package's
2827 previous version numbering schemes, to be left behind.
2831 <tag><var>upstream_version</var></tag>
2834 This is the main part of the version number. It is
2835 usually the version number of the original ("upstream")
2836 package from which the <file>.deb</file> file has been made,
2837 if this is applicable. Usually this will be in the same
2838 format as that specified by the upstream author(s);
2839 however, it may need to be reformatted to fit into the
2840 package management system's format and comparison
2845 The comparison behavior of the package management system
2846 with respect to the <var>upstream_version</var> is
2847 described below. The <var>upstream_version</var>
2848 portion of the version number is mandatory.
2852 The <var>upstream_version</var> may contain only
2853 alphanumerics<footnote>
2854 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2856 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2857 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2858 tilde) and should start with a digit. If there is no
2859 <var>debian_revision</var> then hyphens are not allowed;
2860 if there is no <var>epoch</var> then colons are not
2865 <tag><var>debian_revision</var></tag>
2868 This part of the version number specifies the version of
2869 the Debian package based on the upstream version. It
2870 may contain only alphanumerics and the characters
2871 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2872 tilde) and is compared in the same way as the
2873 <var>upstream_version</var> is.
2877 It is optional; if it isn't present then the
2878 <var>upstream_version</var> may not contain a hyphen.
2879 This format represents the case where a piece of
2880 software was written specifically to be turned into a
2881 Debian package, and so there is only one "debianisation"
2882 of it and therefore no revision indication is required.
2886 It is conventional to restart the
2887 <var>debian_revision</var> at <tt>1</tt> each time the
2888 <var>upstream_version</var> is increased.
2892 The package management system will break the version
2893 number apart at the last hyphen in the string (if there
2894 is one) to determine the <var>upstream_version</var> and
2895 <var>debian_revision</var>. The absence of a
2896 <var>debian_revision</var> is equivalent to a
2897 <var>debian_revision</var> of <tt>0</tt>.
2904 When comparing two version numbers, first the <var>epoch</var>
2905 of each are compared, then the <var>upstream_version</var> if
2906 <var>epoch</var> is equal, and then <var>debian_revision</var>
2907 if <var>upstream_version</var> is also equal.
2908 <var>epoch</var> is compared numerically. The
2909 <var>upstream_version</var> and <var>debian_revision</var>
2910 parts are compared by the package management system using the
2911 following algorithm:
2915 The strings are compared from left to right.
2919 First the initial part of each string consisting entirely of
2920 non-digit characters is determined. These two parts (one of
2921 which may be empty) are compared lexically. If a difference
2922 is found it is returned. The lexical comparison is a
2923 comparison of ASCII values modified so that all the letters
2924 sort earlier than all the non-letters and so that a tilde
2925 sorts before anything, even the end of a part. For example,
2926 the following parts are in sorted order from earliest to
2927 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2928 <tt>a</tt>.<footnote>
2929 One common use of <tt>~</tt> is for upstream pre-releases.
2930 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2931 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2936 Then the initial part of the remainder of each string which
2937 consists entirely of digit characters is determined. The
2938 numerical values of these two parts are compared, and any
2939 difference found is returned as the result of the comparison.
2940 For these purposes an empty string (which can only occur at
2941 the end of one or both version strings being compared) counts
2946 These two steps (comparing and removing initial non-digit
2947 strings and initial digit strings) are repeated until a
2948 difference is found or both strings are exhausted.
2952 Note that the purpose of epochs is to allow us to leave behind
2953 mistakes in version numbering, and to cope with situations
2954 where the version numbering scheme changes. It is
2955 <em>not</em> intended to cope with version numbers containing
2956 strings of letters which the package management system cannot
2957 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2958 silly orderings (the author of this manual has heard of a
2959 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2960 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2961 <tt>2</tt> and so forth).
2965 <sect1 id="f-Description">
2966 <heading><tt>Description</tt></heading>
2969 In a source or binary control file, the <tt>Description</tt>
2970 field contains a description of the binary package, consisting
2971 of two parts, the synopsis or the short description, and the
2972 long description. The field's format is as follows:
2977 Description: <single line synopsis>
2978 <extended description over several lines>
2983 The lines in the extended description can have these formats:
2989 Those starting with a single space are part of a paragraph.
2990 Successive lines of this form will be word-wrapped when
2991 displayed. The leading space will usually be stripped off.
2995 Those starting with two or more spaces. These will be
2996 displayed verbatim. If the display cannot be panned
2997 horizontally, the displaying program will line wrap them "hard"
2998 (i.e., without taking account of word breaks). If it can they
2999 will be allowed to trail off to the right. None, one or two
3000 initial spaces may be deleted, but the number of spaces
3001 deleted from each line will be the same (so that you can have
3002 indenting work correctly, for example).
3006 Those containing a single space followed by a single full stop
3007 character. These are rendered as blank lines. This is the
3008 <em>only</em> way to get a blank line<footnote>
3009 Completely empty lines will not be rendered as blank lines.
3010 Instead, they will cause the parser to think you're starting
3011 a whole new record in the control file, and will therefore
3012 likely abort with an error.
3017 Those containing a space, a full stop and some more characters.
3018 These are for future expansion. Do not use them.
3024 Do not use tab characters. Their effect is not predictable.
3028 See <ref id="descriptions"> for further information on this.
3032 In a <file>.changes</file> file, the <tt>Description</tt> field
3033 contains a summary of the descriptions for the packages being
3038 The part of the field before the first newline is empty;
3039 thereafter each line has the name of a binary package and
3040 the summary description line from that binary package.
3041 Each line is indented by one space.
3046 <sect1 id="f-Distribution">
3047 <heading><tt>Distribution</tt></heading>
3050 In a <file>.changes</file> file or parsed changelog output
3051 this contains the (space-separated) name(s) of the
3052 distribution(s) where this version of the package should
3053 be installed. Valid distributions are determined by the
3054 archive maintainers.<footnote>
3055 Current distribution names are:
3056 <taglist compact="compact">
3057 <tag><em>stable</em></tag>
3059 This is the current "released" version of Debian
3060 GNU/Linux. Once the distribution is
3061 <em>stable</em> only security fixes and other
3062 major bug fixes are allowed. When changes are
3063 made to this distribution, the release number is
3064 increased (for example: 2.2r1 becomes 2.2r2 then
3068 <tag><em>unstable</em></tag>
3070 This distribution value refers to the
3071 <em>developmental</em> part of the Debian
3072 distribution tree. New packages, new upstream
3073 versions of packages and bug fixes go into the
3074 <em>unstable</em> directory tree. Download from
3075 this distribution at your own risk.
3078 <tag><em>testing</em></tag>
3080 This distribution value refers to the
3081 <em>testing</em> part of the Debian distribution
3082 tree. It receives its packages from the
3083 unstable distribution after a short time lag to
3084 ensure that there are no major issues with the
3085 unstable packages. It is less prone to breakage
3086 than unstable, but still risky. It is not
3087 possible to upload packages directly to
3091 <tag><em>frozen</em></tag>
3093 From time to time, the <em>testing</em>
3094 distribution enters a state of "code-freeze" in
3095 anticipation of release as a <em>stable</em>
3096 version. During this period of testing only
3097 fixes for existing or newly-discovered bugs will
3098 be allowed. The exact details of this stage are
3099 determined by the Release Manager.
3102 <tag><em>experimental</em></tag>
3104 The packages with this distribution value are
3105 deemed by their maintainers to be high
3106 risk. Oftentimes they represent early beta or
3107 developmental packages from various sources that
3108 the maintainers want people to try, but are not
3109 ready to be a part of the other parts of the
3110 Debian distribution tree. Download at your own
3116 You should list <em>all</em> distributions that the
3117 package should be installed into.
3121 More information is available in the Debian Developer's
3122 Reference, section "The Debian archive".
3129 <heading><tt>Date</tt></heading>
3132 This field includes the date the package was built or last edited.
3136 The value of this field is usually extracted from the
3137 <file>debian/changelog</file> file - see
3138 <ref id="dpkgchangelog">).
3142 <sect1 id="f-Format">
3143 <heading><tt>Format</tt></heading>
3146 This field specifies a format revision for the file.
3147 The most current format described in the Policy Manual
3148 is version <strong>1.5</strong>. The syntax of the
3149 format value is the same as that of a package version
3150 number except that no epoch or Debian revision is allowed
3151 - see <ref id="f-Version">.
3155 <sect1 id="f-Urgency">
3156 <heading><tt>Urgency</tt></heading>
3159 This is a description of how important it is to upgrade to
3160 this version from previous ones. It consists of a single
3161 keyword taking one of the values <tt>low</tt>,
3162 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3163 <tt>critical</tt><footnote>
3164 Other urgency values are supported with configuration
3165 changes in the archive software but are not used in Debian.
3166 The urgency affects how quickly a package will be considered
3167 for inclusion into the <tt>testing</tt> distribution and
3168 gives an indication of the importance of any fixes included
3169 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3170 treated as synonymous.
3171 </footnote> (not case-sensitive) followed by an optional
3172 commentary (separated by a space) which is usually in
3173 parentheses. For example:
3176 Urgency: low (HIGH for users of diversions)
3182 The value of this field is usually extracted from the
3183 <file>debian/changelog</file> file - see
3184 <ref id="dpkgchangelog">.
3188 <sect1 id="f-Changes">
3189 <heading><tt>Changes</tt></heading>
3192 This field contains the human-readable changes data, describing
3193 the differences between the last version and the current one.
3197 There should be nothing in this field before the first
3198 newline; all the subsequent lines must be indented by at
3199 least one space; blank lines must be represented by a line
3200 consisting only of a space and a full stop.
3204 The value of this field is usually extracted from the
3205 <file>debian/changelog</file> file - see
3206 <ref id="dpkgchangelog">).
3210 Each version's change information should be preceded by a
3211 "title" line giving at least the version, distribution(s)
3212 and urgency, in a human-readable way.
3216 If data from several versions is being returned the entry
3217 for the most recent version should be returned first, and
3218 entries should be separated by the representation of a
3219 blank line (the "title" line may also be followed by the
3220 representation of blank line).
3224 <sect1 id="f-Binary">
3225 <heading><tt>Binary</tt></heading>
3228 This field is a list of binary packages.
3232 When it appears in the <file>.dsc</file> file it is the list
3233 of binary packages which a source package can produce. It
3234 does not necessarily produce all of these binary packages
3235 for every architecture. The source control file doesn't
3236 contain details of which architectures are appropriate for
3237 which of the binary packages.
3241 When it appears in a <file>.changes</file> file it lists the
3242 names of the binary packages actually being uploaded.
3246 The syntax is a list of binary packages separated by
3248 A space after each comma is conventional.
3249 </footnote>. Currently the packages must be separated using
3250 only spaces in the <file>.changes</file> file.
3254 <sect1 id="f-Installed-Size">
3255 <heading><tt>Installed-Size</tt></heading>
3258 This field appears in the control files of binary
3259 packages, and in the <file>Packages</file> files. It gives
3260 the total amount of disk space required to install the
3265 The disk space is represented in kilobytes as a simple
3270 <sect1 id="f-Files">
3271 <heading><tt>Files</tt></heading>
3274 This field contains a list of files with information about
3275 each one. The exact information and syntax varies with
3276 the context. In all cases the part of the field
3277 contents on the same line as the field name is empty. The
3278 remainder of the field is one line per file, each line
3279 being indented by one space and containing a number of
3280 sub-fields separated by spaces.
3284 In the <file>.dsc</file> file, each line contains the MD5
3285 checksum, size and filename of the tar file and (if applicable)
3286 diff file which make up the remainder of the source
3288 That is, the parts which are not the <tt>.dsc</tt>.
3290 The exact forms of the filenames are described
3291 in <ref id="pkg-sourcearchives">.
3295 In the <file>.changes</file> file this contains one line per
3296 file being uploaded. Each line contains the MD5 checksum,
3297 size, section and priority and the filename.
3298 The <qref id="f-Section">section</qref>
3299 and <qref id="f-Priority">priority</qref>
3300 are the values of the corresponding fields in
3301 the main source control file. If no section or priority is
3302 specified then <tt>-</tt> should be used, though section
3303 and priority values must be specified for new packages to
3304 be installed properly.
3308 The special value <tt>byhand</tt> for the section in a
3309 <tt>.changes</tt> file indicates that the file in question
3310 is not an ordinary package file and must by installed by
3311 hand by the distribution maintainers. If the section is
3312 <tt>byhand</tt> the priority should be <tt>-</tt>.
3316 If a new Debian revision of a package is being shipped and
3317 no new original source archive is being distributed the
3318 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3319 entry for the original source archive
3320 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3321 but the <file>.changes</file> file should leave it out. In
3322 this case the original source archive on the distribution
3323 site must match exactly, byte-for-byte, the original
3324 source archive which was used to generate the
3325 <file>.dsc</file> file and diff which are being uploaded.</p>
3328 <sect1 id="f-Closes">
3329 <heading><tt>Closes</tt></heading>
3332 A space-separated list of bug report numbers that the upload
3333 governed by the .changes file closes.
3337 <sect1 id="f-Homepage">
3338 <heading><tt>Homepage</tt></heading>
3341 The URL of the web site for this package, preferably (when
3342 applicable) the site from which the original source can be
3343 obtained and any additional upstream documentation or
3344 information may be found. The content of this field is a
3345 simple URL without any surrounding characters such as
3353 <heading>User-defined fields</heading>
3356 Additional user-defined fields may be added to the
3357 source package control file. Such fields will be
3358 ignored, and not copied to (for example) binary or
3359 source package control files or upload control files.
3363 If you wish to add additional unsupported fields to
3364 these output files you should use the mechanism
3369 Fields in the main source control information file with
3370 names starting <tt>X</tt>, followed by one or more of
3371 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3372 be copied to the output files. Only the part of the
3373 field name after the hyphen will be used in the output
3374 file. Where the letter <tt>B</tt> is used the field
3375 will appear in binary package control files, where the
3376 letter <tt>S</tt> is used in source package control
3377 files and where <tt>C</tt> is used in upload control
3378 (<tt>.changes</tt>) files.
3382 For example, if the main source information control file
3385 XBS-Comment: I stand between the candle and the star.
3387 then the binary and source package control files will contain the
3390 Comment: I stand between the candle and the star.
3399 <chapt id="maintainerscripts">
3400 <heading>Package maintainer scripts and installation procedure</heading>
3403 <heading>Introduction to package maintainer scripts</heading>
3406 It is possible to supply scripts as part of a package which
3407 the package management system will run for you when your
3408 package is installed, upgraded or removed.
3412 These scripts are the files <prgn>preinst</prgn>,
3413 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3414 <prgn>postrm</prgn> in the control area of the package.
3415 They must be proper executable files; if they are scripts
3416 (which is recommended), they must start with the usual
3417 <tt>#!</tt> convention. They should be readable and
3418 executable by anyone, and must not be world-writable.
3422 The package management system looks at the exit status from
3423 these scripts. It is important that they exit with a
3424 non-zero status if there is an error, so that the package
3425 management system can stop its processing. For shell
3426 scripts this means that you <em>almost always</em> need to
3427 use <tt>set -e</tt> (this is usually true when writing shell
3428 scripts, in fact). It is also important, of course, that
3429 they don't exit with a non-zero status if everything went
3434 Additionally, packages interacting with users using
3435 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3436 install a <prgn>config</prgn> script in the control area,
3437 see <ref id="maintscriptprompt"> for details.
3441 When a package is upgraded a combination of the scripts from
3442 the old and new packages is called during the upgrade
3443 procedure. If your scripts are going to be at all
3444 complicated you need to be aware of this, and may need to
3445 check the arguments to your scripts.
3449 Broadly speaking the <prgn>preinst</prgn> is called before
3450 (a particular version of) a package is installed, and the
3451 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3452 before (a version of) a package is removed and the
3453 <prgn>postrm</prgn> afterwards.
3457 Programs called from maintainer scripts should not normally
3458 have a path prepended to them. Before installation is
3459 started, the package management system checks to see if the
3460 programs <prgn>ldconfig</prgn>,
3461 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3462 and <prgn>update-rc.d</prgn> can be found via the
3463 <tt>PATH</tt> environment variable. Those programs, and any
3464 other program that one would expect to be in the
3465 <tt>PATH</tt>, should thus be invoked without an absolute
3466 pathname. Maintainer scripts should also not reset the
3467 <tt>PATH</tt>, though they might choose to modify it by
3468 prepending or appending package-specific directories. These
3469 considerations really apply to all shell scripts.</p>
3472 <sect id="idempotency">
3473 <heading>Maintainer scripts idempotency</heading>
3476 It is necessary for the error recovery procedures that the
3477 scripts be idempotent. This means that if it is run
3478 successfully, and then it is called again, it doesn't bomb
3479 out or cause any harm, but just ensures that everything is
3480 the way it ought to be. If the first call failed, or
3481 aborted half way through for some reason, the second call
3482 should merely do the things that were left undone the first
3483 time, if any, and exit with a success status if everything
3485 This is so that if an error occurs, the user interrupts
3486 <prgn>dpkg</prgn> or some other unforeseen circumstance
3487 happens you don't leave the user with a badly-broken
3488 package when <prgn>dpkg</prgn> attempts to repeat the
3494 <sect id="controllingterminal">
3495 <heading>Controlling terminal for maintainer scripts</heading>
3498 The maintainer scripts are guaranteed to run with a
3499 controlling terminal and can interact with the user.
3500 Because these scripts may be executed with standard output
3501 redirected into a pipe for logging purposes, Perl scripts
3502 should set unbuffered output by setting <tt>$|=1</tt> so
3503 that the output is printed immediately rather than being
3507 <sect id="exitstatus">
3508 <heading>Exit status</heading>
3511 Each script must return a zero exit status for
3512 success, or a nonzero one for failure, since the package
3513 management system looks for the exit status of these scripts
3514 and determines what action to take next based on that datum.
3518 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3523 <list compact="compact">
3525 <var>new-preinst</var> <tt>install</tt>
3528 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3531 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3534 <var>old-preinst</var> <tt>abort-upgrade</tt>
3535 <var>new-version</var>
3540 <list compact="compact">
3542 <var>postinst</var> <tt>configure</tt>
3543 <var>most-recently-configured-version</var>
3546 <var>old-postinst</var> <tt>abort-upgrade</tt>
3547 <var>new-version</var>
3550 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3551 <tt>in-favour</tt> <var>package</var>
3552 <var>new-version</var>
3555 <var>postinst</var> <tt>abort-remove</tt>
3558 <var>deconfigured's-postinst</var>
3559 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3560 <var>failed-install-package</var> <var>version</var>
3561 [<tt>removing</tt> <var>conflicting-package</var>
3567 <list compact="compact">
3569 <var>prerm</var> <tt>remove</tt>
3572 <var>old-prerm</var> <tt>upgrade</tt>
3573 <var>new-version</var>
3576 <var>new-prerm</var> <tt>failed-upgrade</tt>
3577 <var>old-version</var>
3580 <var>conflictor's-prerm</var> <tt>remove</tt>
3581 <tt>in-favour</tt> <var>package</var>
3582 <var>new-version</var>
3585 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3586 <tt>in-favour</tt> <var>package-being-installed</var>
3587 <var>version</var> [<tt>removing</tt>
3588 <var>conflicting-package</var>
3594 <list compact="compact">
3596 <var>postrm</var> <tt>remove</tt>
3599 <var>postrm</var> <tt>purge</tt>
3602 <var>old-postrm</var> <tt>upgrade</tt>
3603 <var>new-version</var>
3606 <var>new-postrm</var> <tt>failed-upgrade</tt>
3607 <var>old-version</var>
3610 <var>new-postrm</var> <tt>abort-install</tt>
3613 <var>new-postrm</var> <tt>abort-install</tt>
3614 <var>old-version</var>
3617 <var>new-postrm</var> <tt>abort-upgrade</tt>
3618 <var>old-version</var>
3621 <var>disappearer's-postrm</var> <tt>disappear</tt>
3622 <var>overwriter</var>
3623 <var>overwriter-version</var>
3629 <sect id="unpackphase">
3630 <heading>Details of unpack phase of installation or upgrade</heading>
3633 The procedure on installation/upgrade/overwrite/disappear
3634 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3635 stage of <tt>dpkg --install</tt>) is as follows. In each
3636 case, if a major error occurs (unless listed below) the
3637 actions are, in general, run backwards - this means that the
3638 maintainer scripts are run with different arguments in
3639 reverse order. These are the "error unwind" calls listed
3646 If a version of the package is already installed, call
3647 <example compact="compact">
3648 <var>old-prerm</var> upgrade <var>new-version</var>
3652 If the script runs but exits with a non-zero
3653 exit status, <prgn>dpkg</prgn> will attempt:
3654 <example compact="compact">
3655 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3657 If this works, the upgrade continues. If this
3658 does not work, the error unwind:
3659 <example compact="compact">
3660 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3662 If this works, then the old-version is
3663 "Installed", if not, the old version is in a
3664 "Failed-Config" state.
3670 If a "conflicting" package is being removed at the same time,
3671 or if any package will be broken (due to <tt>Breaks</tt>):
3674 If <tt>--auto-deconfigure</tt> is
3675 specified, call, for each package to be deconfigured
3676 due to <tt>Breaks</tt>:
3677 <example compact="compact">
3678 <var>deconfigured's-prerm</var> deconfigure \
3679 in-favour <var>package-being-installed</var> <var>version</var>
3682 <example compact="compact">
3683 <var>deconfigured's-postinst</var> abort-deconfigure \
3684 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3686 The deconfigured packages are marked as
3687 requiring configuration, so that if
3688 <tt>--install</tt> is used they will be
3689 configured again if possible.
3692 If any packages depended on a conflicting
3693 package being removed and <tt>--auto-deconfigure</tt> is
3694 specified, call, for each such package:
3695 <example compact="compact">
3696 <var>deconfigured's-prerm</var> deconfigure \
3697 in-favour <var>package-being-installed</var> <var>version</var> \
3698 removing <var>conflicting-package</var> <var>version</var>
3701 <example compact="compact">
3702 <var>deconfigured's-postinst</var> abort-deconfigure \
3703 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3704 removing <var>conflicting-package</var> <var>version</var>
3706 The deconfigured packages are marked as
3707 requiring configuration, so that if
3708 <tt>--install</tt> is used they will be
3709 configured again if possible.
3712 To prepare for removal of each conflicting package, call:
3713 <example compact="compact">
3714 <var>conflictor's-prerm</var> remove \
3715 in-favour <var>package</var> <var>new-version</var>
3718 <example compact="compact">
3719 <var>conflictor's-postinst</var> abort-remove \
3720 in-favour <var>package</var> <var>new-version</var>
3729 If the package is being upgraded, call:
3730 <example compact="compact">
3731 <var>new-preinst</var> upgrade <var>old-version</var>
3733 If this fails, we call:
3735 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3742 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3744 is called. If this works, then the old version
3745 is in an "Installed" state, or else it is left
3746 in an "Unpacked" state.
3751 If it fails, then the old version is left
3752 in an "Half-Installed" state.
3759 Otherwise, if the package had some configuration
3760 files from a previous version installed (i.e., it
3761 is in the "configuration files only" state):
3762 <example compact="compact">
3763 <var>new-preinst</var> install <var>old-version</var>
3767 <var>new-postrm</var> abort-install <var>old-version</var>
3769 If this fails, the package is left in a
3770 "Half-Installed" state, which requires a
3771 reinstall. If it works, the packages is left in
3772 a "Config Files" state.
3775 Otherwise (i.e., the package was completely purged):
3776 <example compact="compact">
3777 <var>new-preinst</var> install
3780 <example compact="compact">
3781 <var>new-postrm</var> abort-install
3783 If the error-unwind fails, the package is in a
3784 "Half Installed" phase, and requires a
3785 reinstall. If the error unwind works, the
3786 package is in a not installed state.
3793 The new package's files are unpacked, overwriting any
3794 that may be on the system already, for example any
3795 from the old version of the same package or from
3796 another package. Backups of the old files are kept
3797 temporarily, and if anything goes wrong the package
3798 management system will attempt to put them back as
3799 part of the error unwind.
3803 It is an error for a package to contain files which
3804 are on the system in another package, unless
3805 <tt>Replaces</tt> is used (see <ref id="replaces">).
3807 The following paragraph is not currently the case:
3808 Currently the <tt>- - force-overwrite</tt> flag is
3809 enabled, downgrading it to a warning, but this may not
3815 It is a more serious error for a package to contain a
3816 plain file or other kind of non-directory where another
3817 package has a directory (again, unless
3818 <tt>Replaces</tt> is used). This error can be
3819 overridden if desired using
3820 <tt>--force-overwrite-dir</tt>, but this is not
3825 Packages which overwrite each other's files produce
3826 behavior which, though deterministic, is hard for the
3827 system administrator to understand. It can easily
3828 lead to "missing" programs if, for example, a package
3829 is installed which overwrites a file from another
3830 package, and is then removed again.<footnote>
3831 Part of the problem is due to what is arguably a
3832 bug in <prgn>dpkg</prgn>.
3837 A directory will never be replaced by a symbolic link
3838 to a directory or vice versa; instead, the existing
3839 state (symlink or not) will be left alone and
3840 <prgn>dpkg</prgn> will follow the symlink if there is
3849 If the package is being upgraded, call
3850 <example compact="compact">
3851 <var>old-postrm</var> upgrade <var>new-version</var>
3855 If this fails, <prgn>dpkg</prgn> will attempt:
3856 <example compact="compact">
3857 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3859 If this works, installation continues. If not,
3861 <example compact="compact">
3862 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3864 If this fails, the old version is left in an
3865 "Half Installed" state. If it works, dpkg now
3867 <example compact="compact">
3868 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3870 If this fails, the old version is left in an
3871 "Half Installed" state. If it works, dpkg now
3873 <example compact="compact">
3874 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3876 If this fails, the old version is in an
3883 This is the point of no return - if
3884 <prgn>dpkg</prgn> gets this far, it won't back off
3885 past this point if an error occurs. This will
3886 leave the package in a fairly bad state, which
3887 will require a successful re-installation to clear
3888 up, but it's when <prgn>dpkg</prgn> starts doing
3889 things that are irreversible.
3894 Any files which were in the old version of the package
3895 but not in the new are removed.
3899 The new file list replaces the old.
3903 The new maintainer scripts replace the old.
3907 Any packages all of whose files have been overwritten
3908 during the installation, and which aren't required for
3909 dependencies, are considered to have been removed.
3910 For each such package
3913 <prgn>dpkg</prgn> calls:
3914 <example compact="compact">
3915 <var>disappearer's-postrm</var> disappear \
3916 <var>overwriter</var> <var>overwriter-version</var>
3920 The package's maintainer scripts are removed.
3923 It is noted in the status database as being in a
3924 sane state, namely not installed (any conffiles
3925 it may have are ignored, rather than being
3926 removed by <prgn>dpkg</prgn>). Note that
3927 disappearing packages do not have their prerm
3928 called, because <prgn>dpkg</prgn> doesn't know
3929 in advance that the package is going to
3936 Any files in the package we're unpacking that are also
3937 listed in the file lists of other packages are removed
3938 from those lists. (This will lobotomize the file list
3939 of the "conflicting" package if there is one.)
3943 The backup files made during installation, above, are
3949 The new package's status is now sane, and recorded as
3954 Here is another point of no return - if the
3955 conflicting package's removal fails we do not unwind
3956 the rest of the installation; the conflicting package
3957 is left in a half-removed limbo.
3962 If there was a conflicting package we go and do the
3963 removal actions (described below), starting with the
3964 removal of the conflicting package's files (any that
3965 are also in the package being installed have already
3966 been removed from the conflicting package's file list,
3967 and so do not get removed now).
3973 <sect id="configdetails"><heading>Details of configuration</heading>
3976 When we configure a package (this happens with <tt>dpkg
3977 --install</tt> and <tt>dpkg --configure</tt>), we first
3978 update any <tt>conffile</tt>s and then call:
3979 <example compact="compact">
3980 <var>postinst</var> configure <var>most-recently-configured-version</var>
3985 No attempt is made to unwind after errors during
3986 configuration. If the configuration fails, the package is in
3987 a "Failed Config" state, and an error message is generated.
3991 If there is no most recently configured version
3992 <prgn>dpkg</prgn> will pass a null argument.
3995 Historical note: Truly ancient (pre-1997) versions of
3996 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3997 (including the angle brackets) in this case. Even older
3998 ones did not pass a second argument at all, under any
3999 circumstance. Note that upgrades using such an old dpkg
4000 version are unlikely to work for other reasons, even if
4001 this old argument behavior is handled by your postinst script.
4007 <sect id="removedetails"><heading>Details of removal and/or
4008 configuration purging</heading>
4014 <example compact="compact">
4015 <var>prerm</var> remove
4019 If prerm fails during replacement due to conflict
4021 <var>conflictor's-postinst</var> abort-remove \
4022 in-favour <var>package</var> <var>new-version</var>
4026 <var>postinst</var> abort-remove
4030 If this fails, the package is in a "Failed-Config"
4031 state, or else it remains "Installed".
4035 The package's files are removed (except <tt>conffile</tt>s).
4038 <example compact="compact">
4039 <var>postrm</var> remove
4043 If it fails, there's no error unwind, and the package is in
4044 an "Half-Installed" state.
4049 All the maintainer scripts except the <prgn>postrm</prgn>
4054 If we aren't purging the package we stop here. Note
4055 that packages which have no <prgn>postrm</prgn> and no
4056 <tt>conffile</tt>s are automatically purged when
4057 removed, as there is no difference except for the
4058 <prgn>dpkg</prgn> status.
4062 The <tt>conffile</tt>s and any backup files
4063 (<tt>~</tt>-files, <tt>#*#</tt> files,
4064 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4069 <example compact="compact">
4070 <var>postrm</var> purge
4074 If this fails, the package remains in a "Config-Files"
4079 The package's file list is removed.
4088 <chapt id="relationships">
4089 <heading>Declaring relationships between packages</heading>
4091 <sect id="depsyntax">
4092 <heading>Syntax of relationship fields</heading>
4095 These fields all have a uniform syntax. They are a list of
4096 package names separated by commas.
4100 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4101 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4102 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4103 control file fields of the package, which declare
4104 dependencies on other packages, the package names listed may
4105 also include lists of alternative package names, separated
4106 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4107 if any one of the alternative packages is installed, that
4108 part of the dependency is considered to be satisfied.
4112 All of the fields except for <tt>Provides</tt> may restrict
4113 their applicability to particular versions of each named
4114 package. This is done in parentheses after each individual
4115 package name; the parentheses should contain a relation from
4116 the list below followed by a version number, in the format
4117 described in <ref id="f-Version">.
4121 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4122 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4123 strictly earlier, earlier or equal, exactly equal, later or
4124 equal and strictly later, respectively. The deprecated
4125 forms <tt><</tt> and <tt>></tt> were used to mean
4126 earlier/later or equal, rather than strictly earlier/later,
4127 so they should not appear in new packages (though
4128 <prgn>dpkg</prgn> still supports them).
4132 Whitespace may appear at any point in the version
4133 specification subject to the rules in <ref
4134 id="controlsyntax">, and must appear where it's necessary to
4135 disambiguate; it is not otherwise significant. All of the
4136 relationship fields may span multiple lines. For
4137 consistency and in case of future changes to
4138 <prgn>dpkg</prgn> it is recommended that a single space be
4139 used after a version relationship and before a version
4140 number; it is also conventional to put a single space after
4141 each comma, on either side of each vertical bar, and before
4142 each open parenthesis. When wrapping a relationship field, it
4143 is conventional to do so after a comma and before the space
4144 following that comma.
4148 For example, a list of dependencies might appear as:
4149 <example compact="compact">
4152 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4157 All fields that specify build-time relationships
4158 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4159 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4160 may be restricted to a certain set of architectures. This
4161 is indicated in brackets after each individual package name and
4162 the optional version specification. The brackets enclose a
4163 list of Debian architecture names separated by whitespace.
4164 Exclamation marks may be prepended to each of the names.
4165 (It is not permitted for some names to be prepended with
4166 exclamation marks while others aren't.) If the current Debian
4167 host architecture is not in this list and there are no
4168 exclamation marks in the list, or it is in the list with a
4169 prepended exclamation mark, the package name and the
4170 associated version specification are ignored completely for
4171 the purposes of defining the relationships.
4176 <example compact="compact">
4178 Build-Depends-Indep: texinfo
4179 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4180 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4185 Note that the binary package relationship fields such as
4186 <tt>Depends</tt> appear in one of the binary package
4187 sections of the control file, whereas the build-time
4188 relationships such as <tt>Build-Depends</tt> appear in the
4189 source package section of the control file (which is the
4194 <sect id="binarydeps">
4195 <heading>Binary Dependencies - <tt>Depends</tt>,
4196 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4197 <tt>Pre-Depends</tt>
4201 Packages can declare in their control file that they have
4202 certain relationships to other packages - for example, that
4203 they may not be installed at the same time as certain other
4204 packages, and/or that they depend on the presence of others.
4208 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4209 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4210 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4214 These seven fields are used to declare a dependency
4215 relationship by one package on another. Except for
4216 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4217 depending (binary) package's control file.
4218 (<tt>Enhances</tt> appears in the recommending package's
4219 control file, and <tt>Breaks</tt> appears in the version of
4220 depended-on package which causes the named package to
4225 A <tt>Depends</tt> field takes effect <em>only</em> when a
4226 package is to be configured. It does not prevent a package
4227 being on the system in an unconfigured state while its
4228 dependencies are unsatisfied, and it is possible to replace
4229 a package whose dependencies are satisfied and which is
4230 properly installed with a different version whose
4231 dependencies are not and cannot be satisfied; when this is
4232 done the depending package will be left unconfigured (since
4233 attempts to configure it will give errors) and will not
4234 function properly. If it is necessary, a
4235 <tt>Pre-Depends</tt> field can be used, which has a partial
4236 effect even when a package is being unpacked, as explained
4237 in detail below. (The other three dependency fields,
4238 <tt>Recommends</tt>, <tt>Suggests</tt> and
4239 <tt>Enhances</tt>, are only used by the various front-ends
4240 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4241 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4245 For this reason packages in an installation run are usually
4246 all unpacked first and all configured later; this gives
4247 later versions of packages with dependencies on later
4248 versions of other packages the opportunity to have their
4249 dependencies satisfied.
4253 In case of circular dependencies, since installation or
4254 removal order honoring the dependency order can't be
4255 established, dependency loops are broken at some point
4256 (based on rules below), and some packages may not be able to
4257 rely on their dependencies being present when being
4258 installed or removed, depending on which side of the break
4259 of the circular dependency loop they happen to be on. If one
4260 of the packages in the loop has no postinst script, then the
4261 cycle will be broken at that package, so as to ensure that
4262 all postinst scripts run with the dependencies properly
4263 configured if this is possible. Otherwise the breaking point
4268 The <tt>Depends</tt> field thus allows package maintainers
4269 to impose an order in which packages should be configured.
4273 The meaning of the five dependency fields is as follows:
4275 <tag><tt>Depends</tt></tag>
4278 This declares an absolute dependency. A package will
4279 not be configured unless all of the packages listed in
4280 its <tt>Depends</tt> field have been correctly
4285 The <tt>Depends</tt> field should be used if the
4286 depended-on package is required for the depending
4287 package to provide a significant amount of
4292 The <tt>Depends</tt> field should also be used if the
4293 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4294 <prgn>postrm</prgn> scripts require the package to be
4295 present in order to run. Note, however, that the
4296 <prgn>postrm</prgn> cannot rely on any non-essential
4297 packages to be present during the <tt>purge</tt>
4301 <tag><tt>Recommends</tt></tag>
4304 This declares a strong, but not absolute, dependency.
4308 The <tt>Recommends</tt> field should list packages
4309 that would be found together with this one in all but
4310 unusual installations.
4314 <tag><tt>Suggests</tt></tag>
4316 This is used to declare that one package may be more
4317 useful with one or more others. Using this field
4318 tells the packaging system and the user that the
4319 listed packages are related to this one and can
4320 perhaps enhance its usefulness, but that installing
4321 this one without them is perfectly reasonable.
4324 <tag><tt>Enhances</tt></tag>
4326 This field is similar to Suggests but works in the
4327 opposite direction. It is used to declare that a
4328 package can enhance the functionality of another
4332 <tag><tt>Pre-Depends</tt></tag>
4335 This field is like <tt>Depends</tt>, except that it
4336 also forces <prgn>dpkg</prgn> to complete installation
4337 of the packages named before even starting the
4338 installation of the package which declares the
4339 pre-dependency, as follows:
4343 When a package declaring a pre-dependency is about to
4344 be <em>unpacked</em> the pre-dependency can be
4345 satisfied if the depended-on package is either fully
4346 configured, <em>or even if</em> the depended-on
4347 package(s) are only unpacked or half-configured,
4348 provided that they have been configured correctly at
4349 some point in the past (and not removed or partially
4350 removed since). In this case, both the
4351 previously-configured and currently unpacked or
4352 half-configured versions must satisfy any version
4353 clause in the <tt>Pre-Depends</tt> field.
4357 When the package declaring a pre-dependency is about
4358 to be <em>configured</em>, the pre-dependency will be
4359 treated as a normal <tt>Depends</tt>, that is, it will
4360 be considered satisfied only if the depended-on
4361 package has been correctly configured.
4365 <tt>Pre-Depends</tt> should be used sparingly,
4366 preferably only by packages whose premature upgrade or
4367 installation would hamper the ability of the system to
4368 continue with any upgrade that might be in progress.
4372 <tt>Pre-Depends</tt> are also required if the
4373 <prgn>preinst</prgn> script depends on the named
4374 package. It is best to avoid this situation if
4382 When selecting which level of dependency to use you should
4383 consider how important the depended-on package is to the
4384 functionality of the one declaring the dependency. Some
4385 packages are composed of components of varying degrees of
4386 importance. Such a package should list using
4387 <tt>Depends</tt> the package(s) which are required by the
4388 more important components. The other components'
4389 requirements may be mentioned as Suggestions or
4390 Recommendations, as appropriate to the components' relative
4396 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4399 Using <tt>Breaks</tt> may cause problems for upgrades from older
4400 versions of Debian and should not be used until the stable
4401 release of Debian supports <tt>Breaks</tt>.
4405 When one binary package declares that it breaks another,
4406 <prgn>dpkg</prgn> will refuse to allow the package which
4407 declares <tt>Breaks</tt> be installed unless the broken
4408 package is deconfigured first, and it will refuse to
4409 allow the broken package to be reconfigured.
4413 A package will not be regarded as causing breakage merely
4414 because its configuration files are still installed; it must
4415 be at least half-installed.
4419 A special exception is made for packages which declare that
4420 they break their own package name or a virtual package which
4421 they provide (see below): this does not count as a real
4426 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4427 version clause; such a <tt>Breaks</tt> is introduced in the
4428 version of an (implicit or explicit) dependency which
4429 violates an assumption or reveals a bug in earlier versions
4430 of the broken package. This use of <tt>Breaks</tt> will
4431 inform higher-level package management tools that broken
4432 package must be upgraded before the new one.
4436 If the breaking package also overwrites some files from the
4437 older package, it should use <tt>Replaces</tt> (not
4438 <tt>Conflicts</tt>) to ensure this goes smoothly.
4442 <sect id="conflicts">
4443 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4446 When one binary package declares a conflict with another
4447 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4448 refuse to allow them to be installed on the system at the
4453 If one package is to be installed, the other must be removed
4454 first - if the package being installed is marked as
4455 replacing (see <ref id="replaces">) the one on the system,
4456 or the one on the system is marked as deselected, or both
4457 packages are marked <tt>Essential</tt>, then
4458 <prgn>dpkg</prgn> will automatically remove the package
4459 which is causing the conflict, otherwise it will halt the
4460 installation of the new package with an error. This
4461 mechanism is specifically designed to produce an error when
4462 the installed package is <tt>Essential</tt>, but the new
4467 A package will not cause a conflict merely because its
4468 configuration files are still installed; it must be at least
4473 A special exception is made for packages which declare a
4474 conflict with their own package name, or with a virtual
4475 package which they provide (see below): this does not
4476 prevent their installation, and allows a package to conflict
4477 with others providing a replacement for it. You use this
4478 feature when you want the package in question to be the only
4479 package providing some feature.
4483 A <tt>Conflicts</tt> entry should almost never have an
4484 "earlier than" version clause. This would prevent
4485 <prgn>dpkg</prgn> from upgrading or installing the package
4486 which declared such a conflict until the upgrade or removal
4487 of the conflicted-with package had been completed. Instead,
4488 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4489 by the stable release of Debian).
4493 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4497 As well as the names of actual ("concrete") packages, the
4498 package relationship fields <tt>Depends</tt>,
4499 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4500 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4501 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4502 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4503 may mention "virtual packages".
4507 A <em>virtual package</em> is one which appears in the
4508 <tt>Provides</tt> control file field of another package.
4509 The effect is as if the package(s) which provide a
4510 particular virtual package name had been listed by name
4511 everywhere the virtual package name appears. (See also <ref
4516 If there are both concrete and virtual packages of the same
4517 name, then the dependency may be satisfied (or the conflict
4518 caused) by either the concrete package with the name in
4519 question or any other concrete package which provides the
4520 virtual package with the name in question. This is so that,
4521 for example, supposing we have
4522 <example compact="compact">
4525 </example> and someone else releases an enhanced version of
4526 the <tt>bar</tt> package they can say:
4527 <example compact="compact">
4531 and the <tt>bar-plus</tt> package will now also satisfy the
4532 dependency for the <tt>foo</tt> package.
4536 If a relationship field has a version number attached
4537 then only real packages will be considered to see whether
4538 the relationship is satisfied (or the prohibition violated,
4539 for a conflict or breakage) - it is assumed that a real
4540 package which provides the virtual package is not of the
4541 "right" version. So, a <tt>Provides</tt> field may not
4542 contain version numbers, and the version number of the
4543 concrete package which provides a particular virtual package
4544 will not be looked at when considering a dependency on or
4545 conflict with the virtual package name.
4549 It is likely that the ability will be added in a future
4550 release of <prgn>dpkg</prgn> to specify a version number for
4551 each virtual package it provides. This feature is not yet
4552 present, however, and is expected to be used only
4557 If you want to specify which of a set of real packages
4558 should be the default to satisfy a particular dependency on
4559 a virtual package, you should list the real package as an
4560 alternative before the virtual one.
4565 <sect id="replaces"><heading>Overwriting files and replacing
4566 packages - <tt>Replaces</tt></heading>
4569 Packages can declare in their control file that they should
4570 overwrite files in certain other packages, or completely
4571 replace other packages. The <tt>Replaces</tt> control file
4572 field has these two distinct purposes.
4575 <sect1><heading>Overwriting files in other packages</heading>
4578 Firstly, as mentioned before, it is usually an error for a
4579 package to contain files which are on the system in
4584 However, if the overwriting package declares that it
4585 <tt>Replaces</tt> the one containing the file being
4586 overwritten, then <prgn>dpkg</prgn> will replace the file
4587 from the old package with that from the new. The file
4588 will no longer be listed as "owned" by the old package.
4592 If a package is completely replaced in this way, so that
4593 <prgn>dpkg</prgn> does not know of any files it still
4594 contains, it is considered to have "disappeared". It will
4595 be marked as not wanted on the system (selected for
4596 removal) and not installed. Any <tt>conffile</tt>s
4597 details noted for the package will be ignored, as they
4598 will have been taken over by the overwriting package. The
4599 package's <prgn>postrm</prgn> script will be run with a
4600 special argument to allow the package to do any final
4601 cleanup required. See <ref id="mscriptsinstact">.
4604 Replaces is a one way relationship -- you have to
4605 install the replacing package after the replaced
4612 For this usage of <tt>Replaces</tt>, virtual packages (see
4613 <ref id="virtual">) are not considered when looking at a
4614 <tt>Replaces</tt> field - the packages declared as being
4615 replaced must be mentioned by their real names.
4619 Furthermore, this usage of <tt>Replaces</tt> only takes
4620 effect when both packages are at least partially on the
4621 system at once, so that it can only happen if they do not
4622 conflict or if the conflict has been overridden.
4627 <sect1><heading>Replacing whole packages, forcing their
4631 Secondly, <tt>Replaces</tt> allows the packaging system to
4632 resolve which package should be removed when there is a
4633 conflict - see <ref id="conflicts">. This usage only
4634 takes effect when the two packages <em>do</em> conflict,
4635 so that the two usages of this field do not interfere with
4640 In this situation, the package declared as being replaced
4641 can be a virtual package, so for example, all mail
4642 transport agents (MTAs) would have the following fields in
4643 their control files:
4644 <example compact="compact">
4645 Provides: mail-transport-agent
4646 Conflicts: mail-transport-agent
4647 Replaces: mail-transport-agent
4649 ensuring that only one MTA can be installed at any one
4654 <sect id="sourcebinarydeps">
4655 <heading>Relationships between source and binary packages -
4656 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4657 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4661 Source packages that require certain binary packages to be
4662 installed or absent at the time of building the package
4663 can declare relationships to those binary packages.
4667 This is done using the <tt>Build-Depends</tt>,
4668 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4669 <tt>Build-Conflicts-Indep</tt> control file fields.
4673 Build-dependencies on "build-essential" binary packages can be
4674 omitted. Please see <ref id="pkg-relations"> for more information.
4678 The dependencies and conflicts they define must be satisfied
4679 (as defined earlier for binary packages) in order to invoke
4680 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4682 If you make "build-arch" or "binary-arch", you need
4683 Build-Depends. If you make "build-indep" or
4684 "binary-indep", you need Build-Depends and
4685 Build-Depends-Indep. If you make "build" or "binary",
4689 There is no Build-Depends-Arch; this role is essentially
4690 met with Build-Depends. Anyone building the
4691 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4692 is basically assumed to be building the whole package
4693 anyway and so installs all build dependencies. The
4694 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4695 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4696 does not yet know how to check for its existence) and
4697 <tt>binary-arch</tt>.
4700 The purpose of the original split, I recall, was so that
4701 the autobuilders wouldn't need to install extra packages
4702 needed only for the binary-indep targets. But without a
4703 build-arch/build-indep split, this didn't work, since
4704 most of the work is done in the build target, not in the
4710 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4712 The <tt>Build-Depends</tt> and
4713 <tt>Build-Conflicts</tt> fields must be satisfied when
4714 any of the following targets is invoked:
4715 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4716 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4717 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4719 <tag><tt>Build-Depends-Indep</tt>,
4720 <tt>Build-Conflicts-Indep</tt></tag>
4722 The <tt>Build-Depends-Indep</tt> and
4723 <tt>Build-Conflicts-Indep</tt> fields must be
4724 satisfied when any of the following targets is
4725 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4726 <tt>binary</tt> and <tt>binary-indep</tt>.
4736 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4739 Packages containing shared libraries must be constructed with
4740 a little care to make sure that the shared library is always
4741 available. This is especially important for packages whose
4742 shared libraries are vitally important, such as the C library
4743 (currently <tt>libc6</tt>).
4747 Packages involving shared libraries should be split up into
4748 several binary packages. This section mostly deals with how
4749 this separation is to be accomplished; rules for files within
4750 the shared library packages are in <ref id="libraries"> instead.
4753 <sect id="sharedlibs-runtime">
4754 <heading>Run-time shared libraries</heading>
4757 The run-time shared library needs to be placed in a package
4758 whose name changes whenever the shared object version
4761 Since it is common place to install several versions of a
4762 package that just provides shared libraries, it is a
4763 good idea that the library package should not
4764 contain any extraneous non-versioned files, unless they
4765 happen to be in versioned directories.</p>
4767 The most common mechanism is to place it in a package
4769 <package><var>libraryname</var><var>soversion</var></package>,
4770 where <file><var>soversion</var></file> is the version number
4771 in the soname of the shared library<footnote>
4772 The soname is the shared object name: it's the thing
4773 that has to match exactly between building an executable
4774 and running it for the dynamic linker to be able run the
4775 program. For example, if the soname of the library is
4776 <file>libfoo.so.6</file>, the library package would be
4777 called <file>libfoo6</file>.
4779 Alternatively, if it would be confusing to directly append
4780 <var>soversion</var> to <var>libraryname</var> (e.g. because
4781 <var>libraryname</var> itself ends in a number), you may use
4782 <package><var>libraryname</var>-<var>soversion</var></package> and
4783 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4788 If you have several shared libraries built from the same
4789 source tree you may lump them all together into a single
4790 shared library package, provided that you change all of
4791 their sonames at once (so that you don't get filename
4792 clashes if you try to install different versions of the
4793 combined shared libraries package).
4797 The package should install the shared libraries under
4798 their normal names. For example, the <package>libgdbm3</package>
4799 package should install <file>libgdbm.so.3.0.0</file> as
4800 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4801 renamed or re-linked by any <prgn>prerm</prgn> or
4802 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4803 of renaming things safely without affecting running programs,
4804 and attempts to interfere with this are likely to lead to
4809 Shared libraries should not be installed executable, since
4810 the dynamic linker does not require this and trying to
4811 execute a shared library usually results in a core dump.
4815 The run-time library package should include the symbolic link that
4816 <prgn>ldconfig</prgn> would create for the shared libraries.
4817 For example, the <package>libgdbm3</package> package should include
4818 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4819 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4820 linker (for example <prgn>ld.so</prgn> or
4821 <prgn>ld-linux.so.*</prgn>) can find the library between the
4822 time that <prgn>dpkg</prgn> installs it and the time that
4823 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4825 The package management system requires the library to be
4826 placed before the symbolic link pointing to it in the
4827 <file>.deb</file> file. This is so that when
4828 <prgn>dpkg</prgn> comes to install the symlink
4829 (overwriting the previous symlink pointing at an older
4830 version of the library), the new shared library is already
4831 in place. In the past, this was achieved by creating the
4832 library in the temporary packaging directory before
4833 creating the symlink. Unfortunately, this was not always
4834 effective, since the building of the tar file in the
4835 <file>.deb</file> depended on the behavior of the underlying
4836 file system. Some file systems (such as reiserfs) reorder
4837 the files so that the order of creation is forgotten.
4838 Since version 1.7.0, <prgn>dpkg</prgn>
4839 reorders the files itself as necessary when building a
4840 package. Thus it is no longer important to concern
4841 oneself with the order of file creation.
4845 <sect1 id="ldconfig">
4846 <heading><tt>ldconfig</tt></heading>
4849 Any package installing shared libraries in one of the default
4850 library directories of the dynamic linker (which are currently
4851 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4852 listed in <file>/etc/ld.so.conf</file><footnote>
4854 <list compact="compact">
4855 <item>/usr/local/lib</item>
4856 <item>/usr/lib/libc5-compat</item>
4857 <item>/lib/libc5-compat</item>
4860 must use <prgn>ldconfig</prgn> to update the shared library
4865 The package maintainer scripts must only call
4866 <prgn>ldconfig</prgn> under these circumstances:
4867 <list compact="compact">
4868 <item>When the <prgn>postinst</prgn> script is run with a
4869 first argument of <tt>configure</tt>, the script must call
4870 <prgn>ldconfig</prgn>, and may optionally invoke
4871 <prgn>ldconfig</prgn> at other times.
4873 <item>When the <prgn>postrm</prgn> script is run with a
4874 first argument of <tt>remove</tt>, the script should call
4875 <prgn>ldconfig</prgn>.
4880 During install or upgrade, the preinst is called before
4881 the new files are installed, so calling "ldconfig" is
4882 pointless. The preinst of an existing package can also be
4883 called if an upgrade fails. However, this happens during
4884 the critical time when a shared libs may exist on-disk
4885 under a temporary name. Thus, it is dangerous and
4886 forbidden by current policy to call "ldconfig" at this
4891 When a package is installed or upgraded, "postinst
4892 configure" runs after the new files are safely on-disk.
4893 Since it is perfectly safe to invoke ldconfig
4894 unconditionally in a postinst, it is OK for a package to
4895 simply put ldconfig in its postinst without checking the
4896 argument. The postinst can also be called to recover from
4897 a failed upgrade. This happens before any new files are
4898 unpacked, so there is no reason to call "ldconfig" at this
4903 For a package that is being removed, prerm is
4904 called with all the files intact, so calling ldconfig is
4905 useless. The other calls to "prerm" happen in the case of
4906 upgrade at a time when all the files of the old package
4907 are on-disk, so again calling "ldconfig" is pointless.
4911 postrm, on the other hand, is called with the "remove"
4912 argument just after the files are removed, so this is
4913 the proper time to call "ldconfig" to notify the system
4914 of the fact that the shared libraries from the package
4915 are removed. The postrm can be called at several other
4916 times. At the time of "postrm purge", "postrm
4917 abort-install", or "postrm abort-upgrade", calling
4918 "ldconfig" is useless because the shared lib files are
4919 not on-disk. However, when "postrm" is invoked with
4920 arguments "upgrade", "failed-upgrade", or "disappear", a
4921 shared lib may exist on-disk under a temporary filename.
4929 <sect id="sharedlibs-support-files">
4930 <heading>Shared library support files</heading>
4933 If your package contains files whose names do not change with
4934 each change in the library shared object version, you must not
4935 put them in the shared library package. Otherwise, several
4936 versions of the shared library cannot be installed at the same
4937 time without filename clashes, making upgrades and transitions
4938 unnecessarily difficult.
4942 It is recommended that supporting files and run-time support
4943 programs that do not need to be invoked manually by users, but
4944 are nevertheless required for the package to function, be placed
4945 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4946 preferably under <file>/usr/lib/</file><var>package-name</var>.
4947 If the program or file is architecture independent, the
4948 recommendation is for it to be placed in a subdirectory of
4949 <file>/usr/share</file> instead, preferably under
4950 <file>/usr/share/</file><var>package-name</var>. Following the
4951 <var>package-name</var> naming convention ensures that the file
4952 names change when the shared object version changes.
4956 Run-time support programs that use the shared library but are
4957 not required for the library to function or files used by the
4958 shared library that can be used by any version of the shared
4959 library package should instead be put in a separate package.
4960 This package might typically be named
4961 <package><var>libraryname</var>-tools</package>; note the
4962 absence of the <var>soversion</var> in the package name.
4966 Files and support programs only useful when compiling software
4967 against the library should be included in the development
4968 package for the library.<footnote>
4969 For example, a <file><var>package-name</var>-config</file>
4970 script or <package>pkg-config</package> configuration files.
4975 <sect id="sharedlibs-static">
4976 <heading>Static libraries</heading>
4979 The static library (<file><var>libraryname.a</var></file>)
4980 is usually provided in addition to the shared version.
4981 It is placed into the development package (see below).
4985 In some cases, it is acceptable for a library to be
4986 available in static form only; these cases include:
4988 <item>libraries for languages whose shared library support
4989 is immature or unstable</item>
4990 <item>libraries whose interfaces are in flux or under
4991 development (commonly the case when the library's
4992 major version number is zero, or where the ABI breaks
4993 across patchlevels)</item>
4994 <item>libraries which are explicitly intended to be
4995 available only in static form by their upstream
5000 <sect id="sharedlibs-dev">
5001 <heading>Development files</heading>
5004 The development files associated to a shared library need to be
5005 placed in a package called
5006 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5007 or if you prefer only to support one development version at a
5008 time, <package><var>libraryname</var>-dev</package>.
5012 In case several development versions of a library exist, you may
5013 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5014 <ref id="conflicts">) to ensure that the user only installs one
5015 development version at a time (as different development versions are
5016 likely to have the same header files in them, which would cause a
5017 filename clash if both were installed).
5021 The development package should contain a symlink for the associated
5022 shared library without a version number. For example, the
5023 <package>libgdbm-dev</package> package should include a symlink
5024 from <file>/usr/lib/libgdbm.so</file> to
5025 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5026 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5027 <file>libgdbm.so</file> when compiling dynamically.
5031 <sect id="sharedlibs-intradeps">
5032 <heading>Dependencies between the packages of the same library</heading>
5035 Typically the development version should have an exact
5036 version dependency on the runtime library, to make sure that
5037 compilation and linking happens correctly. The
5038 <tt>${binary:Version}</tt> substitution variable can be
5039 useful for this purpose.
5041 Previously, <tt>${Source-Version}</tt> was used, but its name
5042 was confusing and it has been deprecated since dpkg 1.13.19.
5047 <sect id="sharedlibs-shlibdeps">
5048 <heading>Dependencies between the library and other packages -
5049 the <tt>shlibs</tt> system</heading>
5052 If a package contains a binary or library which links to a
5053 shared library, we must ensure that when the package is
5054 installed on the system, all of the libraries needed are
5055 also installed. This requirement led to the creation of the
5056 <tt>shlibs</tt> system, which is very simple in its design:
5057 any package which <em>provides</em> a shared library also
5058 provides information on the package dependencies required to
5059 ensure the presence of this library, and any package which
5060 <em>uses</em> a shared library uses this information to
5061 determine the dependencies it requires. The files which
5062 contain the mapping from shared libraries to the necessary
5063 dependency information are called <file>shlibs</file> files.
5067 Thus, when a package is built which contains any shared
5068 libraries, it must provide a <file>shlibs</file> file for other
5069 packages to use, and when a package is built which contains
5070 any shared libraries or compiled binaries, it must run
5071 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5072 on these to determine the libraries used and hence the
5073 dependencies needed by this package.<footnote>
5075 In the past, the shared libraries linked to were
5076 determined by calling <prgn>ldd</prgn>, but now
5077 <prgn>objdump</prgn> is used to do this. The only
5078 change this makes to package building is that
5079 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5080 libraries, whereas in the past this was unnecessary.
5081 The rest of this footnote explains the advantage that
5086 We say that a binary <tt>foo</tt> <em>directly</em> uses
5087 a library <tt>libbar</tt> if it is explicitly linked
5088 with that library (that is, it uses the flag
5089 <tt>-lbar</tt> during the linking stage). Other
5090 libraries that are needed by <tt>libbar</tt> are linked
5091 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5092 linker will load them automatically when it loads
5093 <tt>libbar</tt>. A package should depend on
5094 the libraries it directly uses, and the dependencies for
5095 those libraries should automatically pull in the other
5100 Unfortunately, the <prgn>ldd</prgn> program shows both
5101 the directly and indirectly used libraries, meaning that
5102 the dependencies determined included both direct and
5103 indirect dependencies. The use of <prgn>objdump</prgn>
5104 avoids this problem by determining only the directly
5109 A good example of where this helps is the following. We
5110 could update <tt>libimlib</tt> with a new version that
5111 supports a new graphics format called dgf (but retaining
5112 the same major version number). If we used the old
5113 <prgn>ldd</prgn> method, every package that uses
5114 <tt>libimlib</tt> would need to be recompiled so it
5115 would also depend on <tt>libdgf</tt> or it wouldn't run
5116 due to missing symbols. However with the new system,
5117 packages using <tt>libimlib</tt> can rely on
5118 <tt>libimlib</tt> itself having the dependency on
5119 <tt>libdgf</tt> and so they would not need rebuilding.
5125 In the following sections, we will first describe where the
5126 various <tt>shlibs</tt> files are to be found, then how to
5127 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5128 file format and how to create them if your package contains a
5133 <heading>The <tt>shlibs</tt> files present on the system</heading>
5136 There are several places where <tt>shlibs</tt> files are
5137 found. The following list gives them in the order in which
5139 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5140 (The first one which gives the required information is used.)
5146 <p><file>debian/shlibs.local</file></p>
5149 This lists overrides for this package. Its use is
5150 described below (see <ref id="shlibslocal">).
5155 <p><file>/etc/dpkg/shlibs.override</file></p>
5158 This lists global overrides. This list is normally
5159 empty. It is maintained by the local system
5165 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5168 When packages are being built, any
5169 <file>debian/shlibs</file> files are copied into the
5170 control file area of the temporary build directory and
5171 given the name <file>shlibs</file>. These files give
5172 details of any shared libraries included in the
5174 An example may help here. Let us say that the
5175 source package <tt>foo</tt> generates two binary
5176 packages, <tt>libfoo2</tt> and
5177 <tt>foo-runtime</tt>. When building the binary
5178 packages, the two packages are created in the
5179 directories <file>debian/libfoo2</file> and
5180 <file>debian/foo-runtime</file> respectively.
5181 (<file>debian/tmp</file> could be used instead of one
5182 of these.) Since <tt>libfoo2</tt> provides the
5183 <tt>libfoo</tt> shared library, it will require a
5184 <tt>shlibs</tt> file, which will be installed in
5185 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5187 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5188 when <prgn>dpkg-shlibdeps</prgn> is run on the
5190 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5192 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5193 determine whether <tt>foo-prog</tt>'s library
5194 dependencies are satisfied by any of the libraries
5195 provided by <tt>libfoo2</tt>. For this reason,
5196 <prgn>dpkg-shlibdeps</prgn> must only be run once
5197 all of the individual binary packages'
5198 <tt>shlibs</tt> files have been installed into the
5205 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5208 These are the <file>shlibs</file> files corresponding to
5209 all of the packages installed on the system, and are
5210 maintained by the relevant package maintainers.
5215 <p><file>/etc/dpkg/shlibs.default</file></p>
5218 This file lists any shared libraries whose packages
5219 have failed to provide correct <file>shlibs</file> files.
5220 It was used when the <file>shlibs</file> setup was first
5221 introduced, but it is now normally empty. It is
5222 maintained by the <tt>dpkg</tt> maintainer.
5230 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5231 <file>shlibs</file> files</heading>
5235 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5236 into your <file>debian/rules</file> file. If your package
5237 contains only compiled binaries and libraries (but no scripts),
5238 you can use a command such as:
5239 <example compact="compact">
5240 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5241 debian/tmp/usr/lib/*
5243 Otherwise, you will need to explicitly list the compiled
5244 binaries and libraries.<footnote>
5245 If you are using <tt>debhelper</tt>, the
5246 <prgn>dh_shlibdeps</prgn> program will do this work for
5247 you. It will also correctly handle multi-binary
5253 This command puts the dependency information into the
5254 <file>debian/substvars</file> file, which is then used by
5255 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5256 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5257 field in the control file for this to work.
5261 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5262 done. If it does complain you might need to create your own
5263 <file>debian/shlibs.local</file> file, as explained below (see
5264 <ref id="shlibslocal">).
5268 If you have multiple binary packages, you will need to call
5269 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5270 compiled libraries or binaries. In such a case, you will
5271 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5272 utilities to specify a different <file>substvars</file> file.
5276 If you are creating a udeb for use in the Debian Installer, you
5277 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5278 the dependency line of type <tt>udeb</tt> by adding
5279 <tt>-tudeb</tt> as option<footnote>
5280 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5281 will automatically add this option if it knows it is
5283 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5284 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5285 fall back to the regular dependency line.
5289 For more details on dpkg-shlibdeps, please see
5290 <ref id="pkg-dpkg-shlibdeps"> and
5291 <manref name="dpkg-shlibdeps" section="1">.
5296 <heading>The <file>shlibs</file> File Format</heading>
5299 Each <file>shlibs</file> file has the same format. Lines
5300 beginning with <tt>#</tt> are considered to be comments and
5301 are ignored. Each line is of the form:
5302 <example compact="compact">
5303 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5308 We will explain this by reference to the example of the
5309 <tt>zlib1g</tt> package, which (at the time of writing)
5310 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5314 <var>type</var> is an optional element that indicates the type
5315 of package for which the line is valid. The only type currently
5316 in use is <tt>udeb</tt>. The colon and space after the type are
5321 <var>library-name</var> is the name of the shared library,
5322 in this case <tt>libz</tt>. (This must match the name part
5323 of the soname, see below.)
5327 <var>soname-version</var> is the version part of the soname of
5328 the library. The soname is the thing that must exactly match
5329 for the library to be recognized by the dynamic linker, and is
5331 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5332 example, <tt>libz.so.1</tt>.<footnote>
5333 This can be determined using the command
5334 <example compact="compact">
5335 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5338 The version part is the part which comes after
5339 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5343 <var>dependencies</var> has the same syntax as a dependency
5344 field in a binary package control file. It should give
5345 details of which packages are required to satisfy a binary
5346 built against the version of the library contained in the
5347 package. See <ref id="depsyntax"> for details.
5351 In our example, if the first version of the <tt>zlib1g</tt>
5352 package which contained a minor number of at least
5353 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5354 <tt>shlibs</tt> entry for this library could say:
5355 <example compact="compact">
5356 libz 1 zlib1g (>= 1:1.1.3)
5358 The version-specific dependency is to avoid warnings from
5359 the dynamic linker about using older shared libraries with
5364 As zlib1g also provides a udeb containing the shared library,
5365 there would also be a second line:
5366 <example compact="compact">
5367 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5373 <heading>Providing a <file>shlibs</file> file</heading>
5376 If your package provides a shared library, you need to create
5377 a <file>shlibs</file> file following the format described above.
5378 It is usual to call this file <file>debian/shlibs</file> (but if
5379 you have multiple binary packages, you might want to call it
5380 <file>debian/shlibs.<var>package</var></file> instead). Then
5381 let <file>debian/rules</file> install it in the control area:
5382 <example compact="compact">
5383 install -m644 debian/shlibs debian/tmp/DEBIAN
5385 or, in the case of a multi-binary package:
5386 <example compact="compact">
5387 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5389 An alternative way of doing this is to create the
5390 <file>shlibs</file> file in the control area directly from
5391 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5392 file at all,<footnote>
5393 This is what <prgn>dh_makeshlibs</prgn> in the
5394 <tt>debhelper</tt> suite does. If your package also has a udeb
5395 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5396 automatically generate the <tt>udeb:</tt> lines if you specify
5397 the name of the udeb with the <tt>--add-udeb</tt> option.
5399 since the <file>debian/shlibs</file> file itself is ignored by
5400 <prgn>dpkg-shlibdeps</prgn>.
5404 As <prgn>dpkg-shlibdeps</prgn> reads the
5405 <file>DEBIAN/shlibs</file> files in all of the binary packages
5406 being built from this source package, all of the
5407 <file>DEBIAN/shlibs</file> files should be installed before
5408 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5413 <sect1 id="shlibslocal">
5414 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5417 This file is intended only as a <em>temporary</em> fix if
5418 your binaries or libraries depend on a library whose package
5419 does not yet provide a correct <file>shlibs</file> file.
5423 We will assume that you are trying to package a binary
5424 <tt>foo</tt>. When you try running
5425 <prgn>dpkg-shlibdeps</prgn> you get the following error
5426 message (<tt>-O</tt> displays the dependency information on
5427 <tt>stdout</tt> instead of writing it to
5428 <tt>debian/substvars</tt>, and the lines have been wrapped
5429 for ease of reading):
5430 <example compact="compact">
5431 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5432 dpkg-shlibdeps: warning: unable to find dependency
5433 information for shared library libbar (soname 1,
5434 path /usr/lib/libbar.so.1, dependency field Depends)
5435 shlibs:Depends=libc6 (>= 2.2.2-2)
5437 You can then run <prgn>ldd</prgn> on the binary to find the
5438 full location of the library concerned:
5439 <example compact="compact">
5441 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5442 libc.so.6 => /lib/libc.so.6 (0x40032000)
5443 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5445 So the <prgn>foo</prgn> binary depends on the
5446 <prgn>libbar</prgn> shared library, but no package seems to
5447 provide a <file>*.shlibs</file> file handling
5448 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5449 determine the package responsible:
5450 <example compact="compact">
5451 $ dpkg -S /usr/lib/libbar.so.1
5452 bar1: /usr/lib/libbar.so.1
5453 $ dpkg -s bar1 | grep Version
5456 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5457 is the one we are using. Now we can file a bug against the
5458 <tt>bar1</tt> package and create our own
5459 <file>debian/shlibs.local</file> to locally fix the problem.
5460 Including the following line into your
5461 <file>debian/shlibs.local</file> file:
5462 <example compact="compact">
5463 libbar 1 bar1 (>= 1.0-1)
5465 should allow the package build to work.
5469 As soon as the maintainer of <tt>bar1</tt> provides a
5470 correct <file>shlibs</file> file, you should remove this line
5471 from your <file>debian/shlibs.local</file> file. (You should
5472 probably also then have a versioned <tt>Build-Depends</tt>
5473 on <tt>bar1</tt> to help ensure that others do not have the
5474 same problem building your package.)
5483 <chapt id="opersys"><heading>The Operating System</heading>
5486 <heading>File system hierarchy</heading>
5490 <heading>File system Structure</heading>
5493 The location of all installed files and directories must
5494 comply with the File system Hierarchy Standard (FHS),
5495 version 2.3, with the exceptions noted below, and except
5496 where doing so would violate other terms of Debian
5497 Policy. The following exceptions to the FHS apply:
5502 Legacy XFree86 servers are permitted to retain the
5503 configuration file location
5504 <file>/etc/X11/XF86Config-4</file>.
5509 The optional rules related to user specific
5510 configuration files for applications are stored in
5511 the user's home directory are relaxed. It is
5512 recommended that such files start with the
5513 '<tt>.</tt>' character (a "dot file"), and if an
5514 application needs to create more than one dot file
5515 then the preferred placement is in a subdirectory
5516 with a name starting with a '.' character, (a "dot
5517 directory"). In this case it is recommended the
5518 configuration files not start with the '.'
5524 The requirement for amd64 to use <file>/lib64</file>
5525 for 64 bit binaries is removed.
5530 The requirement that
5531 <file>/usr/local/share/man</file> be "synonymous"
5532 with <file>/usr/local/man</file> is relaxed to a
5537 The requirement that windowmanagers with a single
5538 configuration file call it <file>system.*wmrc</file>
5539 is removed, as is the restriction that the window
5540 manager subdirectory be named identically to the
5541 window manager name itself.
5546 The requirement that boot manager configuration
5547 files live in <file>/etc</file>, or at least are
5548 symlinked there, is relaxed to a recommendation.
5555 The version of this document referred here can be
5556 found in the <tt>debian-policy</tt> package or on <url
5557 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5558 name="FHS (Debian copy)"> alongside this manual (or, if
5559 you have the <package>debian-policy</package> installed,
5561 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5562 (local copy)">). The
5563 latest version, which may be a more recent version, may
5565 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5566 Specific questions about following the standard may be
5567 asked on the <tt>debian-devel</tt> mailing list, or
5568 referred to the FHS mailing list (see the
5569 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5575 <heading>Site-specific programs</heading>
5578 As mandated by the FHS, packages must not place any
5579 files in <file>/usr/local</file>, either by putting them in
5580 the file system archive to be unpacked by <prgn>dpkg</prgn>
5581 or by manipulating them in their maintainer scripts.
5585 However, the package may create empty directories below
5586 <file>/usr/local</file> so that the system administrator knows
5587 where to place site-specific files. These are not
5588 directories <em>in</em> <file>/usr/local</file>, but are
5589 children of directories in <file>/usr/local</file>. These
5590 directories (<file>/usr/local/*/dir/</file>)
5591 should be removed on package removal if they are
5596 Note, that this applies only to directories <em>below</em>
5597 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5598 Packages must not create sub-directories in the directory
5599 <file>/usr/local</file> itself, except those listed in FHS,
5600 section 4.5. However, you may create directories below
5601 them as you wish. You must not remove any of the
5602 directories listed in 4.5, even if you created them.
5606 Since <file>/usr/local</file> can be mounted read-only from a
5607 remote server, these directories must be created and
5608 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5609 maintainer scripts and not be included in the
5610 <file>.deb</file> archive. These scripts must not fail if
5611 either of these operations fail.
5615 For example, the <tt>emacsen-common</tt> package could
5616 contain something like
5617 <example compact="compact">
5618 if [ ! -e /usr/local/share/emacs ]
5620 if mkdir /usr/local/share/emacs 2>/dev/null
5622 chown root:staff /usr/local/share/emacs
5623 chmod 2775 /usr/local/share/emacs
5627 in its <prgn>postinst</prgn> script, and
5628 <example compact="compact">
5629 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5630 rmdir /usr/local/share/emacs 2>/dev/null || true
5632 in the <prgn>prerm</prgn> script. (Note that this form is
5633 used to ensure that if the script is interrupted, the
5634 directory <file>/usr/local/share/emacs</file> will still be
5639 If you do create a directory in <file>/usr/local</file> for
5640 local additions to a package, you should ensure that
5641 settings in <file>/usr/local</file> take precedence over the
5642 equivalents in <file>/usr</file>.
5646 However, because <file>/usr/local</file> and its contents are
5647 for exclusive use of the local administrator, a package
5648 must not rely on the presence or absence of files or
5649 directories in <file>/usr/local</file> for normal operation.
5653 The <file>/usr/local</file> directory itself and all the
5654 subdirectories created by the package should (by default) have
5655 permissions 2775 (group-writable and set-group-id) and be
5656 owned by <tt>root:staff</tt>.
5661 <heading>The system-wide mail directory</heading>
5663 The system-wide mail directory is <file>/var/mail</file>. This
5664 directory is part of the base system and should not owned
5665 by any particular mail agents. The use of the old
5666 location <file>/var/spool/mail</file> is deprecated, even
5667 though the spool may still be physically located there.
5668 To maintain partial upgrade compatibility for systems
5669 which have <file>/var/spool/mail</file> as their physical mail
5670 spool, packages using <file>/var/mail</file> must depend on
5671 either <package>libc6</package> (>= 2.1.3-13), or on
5672 <package>base-files</package> (>= 2.2.0), or on later
5673 versions of either one of these packages.
5679 <heading>Users and groups</heading>
5682 <heading>Introduction</heading>
5684 The Debian system can be configured to use either plain or
5689 Some user ids (UIDs) and group ids (GIDs) are reserved
5690 globally for use by certain packages. Because some
5691 packages need to include files which are owned by these
5692 users or groups, or need the ids compiled into binaries,
5693 these ids must be used on any Debian system only for the
5694 purpose for which they are allocated. This is a serious
5695 restriction, and we should avoid getting in the way of
5696 local administration policies. In particular, many sites
5697 allocate users and/or local system groups starting at 100.
5701 Apart from this we should have dynamically allocated ids,
5702 which should by default be arranged in some sensible
5703 order, but the behavior should be configurable.
5707 Packages other than <tt>base-passwd</tt> must not modify
5708 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5709 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5714 <heading>UID and GID classes</heading>
5716 The UID and GID numbers are divided into classes as
5722 Globally allocated by the Debian project, the same
5723 on every Debian system. These ids will appear in
5724 the <file>passwd</file> and <file>group</file> files of all
5725 Debian systems, new ids in this range being added
5726 automatically as the <tt>base-passwd</tt> package is
5731 Packages which need a single statically allocated
5732 uid or gid should use one of these; their
5733 maintainers should ask the <tt>base-passwd</tt>
5741 Dynamically allocated system users and groups.
5742 Packages which need a user or group, but can have
5743 this user or group allocated dynamically and
5744 differently on each system, should use <tt>adduser
5745 --system</tt> to create the group and/or user.
5746 <prgn>adduser</prgn> will check for the existence of
5747 the user or group, and if necessary choose an unused
5748 id based on the ranges specified in
5749 <file>adduser.conf</file>.
5753 <tag>1000-29999:</tag>
5756 Dynamically allocated user accounts. By default
5757 <prgn>adduser</prgn> will choose UIDs and GIDs for
5758 user accounts in this range, though
5759 <file>adduser.conf</file> may be used to modify this
5764 <tag>30000-59999:</tag>
5769 <tag>60000-64999:</tag>
5772 Globally allocated by the Debian project, but only
5773 created on demand. The ids are allocated centrally
5774 and statically, but the actual accounts are only
5775 created on users' systems on demand.
5779 These ids are for packages which are obscure or
5780 which require many statically-allocated ids. These
5781 packages should check for and create the accounts in
5782 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5783 <prgn>adduser</prgn> if it has this facility) if
5784 necessary. Packages which are likely to require
5785 further allocations should have a "hole" left after
5786 them in the allocation, to give them room to
5791 <tag>65000-65533:</tag>
5799 User <tt>nobody</tt>. The corresponding gid refers
5800 to the group <tt>nogroup</tt>.
5807 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5808 not</em> be used, because it is the error return
5817 <sect id="sysvinit">
5818 <heading>System run levels and <file>init.d</file> scripts</heading>
5820 <sect1 id="/etc/init.d">
5821 <heading>Introduction</heading>
5824 The <file>/etc/init.d</file> directory contains the scripts
5825 executed by <prgn>init</prgn> at boot time and when the
5826 init state (or "runlevel") is changed (see <manref
5827 name="init" section="8">).
5831 There are at least two different, yet functionally
5832 equivalent, ways of handling these scripts. For the sake
5833 of simplicity, this document describes only the symbolic
5834 link method. However, it must not be assumed by maintainer
5835 scripts that this method is being used, and any automated
5836 manipulation of the various runlevel behaviors by
5837 maintainer scripts must be performed using
5838 <prgn>update-rc.d</prgn> as described below and not by
5839 manually installing or removing symlinks. For information
5840 on the implementation details of the other method,
5841 implemented in the <tt>file-rc</tt> package, please refer
5842 to the documentation of that package.
5846 These scripts are referenced by symbolic links in the
5847 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5848 runlevels, <prgn>init</prgn> looks in the directory
5849 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5850 execute, where <tt><var>n</var></tt> is the runlevel that
5851 is being changed to, or <tt>S</tt> for the boot-up
5856 The names of the links all have the form
5857 <file>S<var>mm</var><var>script</var></file> or
5858 <file>K<var>mm</var><var>script</var></file> where
5859 <var>mm</var> is a two-digit number and <var>script</var>
5860 is the name of the script (this should be the same as the
5861 name of the actual script in <file>/etc/init.d</file>).
5865 When <prgn>init</prgn> changes runlevel first the targets
5866 of the links whose names start with a <tt>K</tt> are
5867 executed, each with the single argument <tt>stop</tt>,
5868 followed by the scripts prefixed with an <tt>S</tt>, each
5869 with the single argument <tt>start</tt>. (The links are
5870 those in the <file>/etc/rc<var>n</var>.d</file> directory
5871 corresponding to the new runlevel.) The <tt>K</tt> links
5872 are responsible for killing services and the <tt>S</tt>
5873 link for starting services upon entering the runlevel.
5877 For example, if we are changing from runlevel 2 to
5878 runlevel 3, init will first execute all of the <tt>K</tt>
5879 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5880 all of the <tt>S</tt> prefixed scripts in that directory.
5881 The links starting with <tt>K</tt> will cause the
5882 referred-to file to be executed with an argument of
5883 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5888 The two-digit number <var>mm</var> is used to determine
5889 the order in which to run the scripts: low-numbered links
5890 have their scripts run first. For example, the
5891 <tt>K20</tt> scripts will be executed before the
5892 <tt>K30</tt> scripts. This is used when a certain service
5893 must be started before another. For example, the name
5894 server <prgn>bind</prgn> might need to be started before
5895 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5896 can set up its access lists. In this case, the script
5897 that starts <prgn>bind</prgn> would have a lower number
5898 than the script that starts <prgn>inn</prgn> so that it
5900 <example compact="compact">
5907 The two runlevels 0 (halt) and 6 (reboot) are slightly
5908 different. In these runlevels, the links with an
5909 <tt>S</tt> prefix are still called after those with a
5910 <tt>K</tt> prefix, but they too are called with the single
5911 argument <tt>stop</tt>.
5915 Also, if the script name ends in <tt>.sh</tt>, the script
5916 will be sourced in runlevel <tt>S</tt> rather than being
5917 run in a forked subprocess, but will be explicitly run by
5918 <prgn>sh</prgn> in all other runlevels.
5923 <heading>Writing the scripts</heading>
5926 Packages that include daemons for system services should
5927 place scripts in <file>/etc/init.d</file> to start or stop
5928 services at boot time or during a change of runlevel.
5929 These scripts should be named
5930 <file>/etc/init.d/<var>package</var></file>, and they should
5931 accept one argument, saying what to do:
5934 <tag><tt>start</tt></tag>
5935 <item>start the service,</item>
5937 <tag><tt>stop</tt></tag>
5938 <item>stop the service,</item>
5940 <tag><tt>restart</tt></tag>
5941 <item>stop and restart the service if it's already running,
5942 otherwise start the service</item>
5944 <tag><tt>reload</tt></tag>
5945 <item><p>cause the configuration of the service to be
5946 reloaded without actually stopping and restarting
5949 <tag><tt>force-reload</tt></tag>
5950 <item>cause the configuration to be reloaded if the
5951 service supports this, otherwise restart the
5955 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5956 <tt>force-reload</tt> options should be supported by all
5957 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5962 The <file>init.d</file> scripts must ensure that they will
5963 behave sensibly (i.e., returning success and not starting
5964 multiple copies of a service) if invoked with <tt>start</tt>
5965 when the service is already running, or with <tt>stop</tt>
5966 when it isn't, and that they don't kill unfortunately-named
5967 user processes. The best way to achieve this is usually to
5968 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5973 If a service reloads its configuration automatically (as
5974 in the case of <prgn>cron</prgn>, for example), the
5975 <tt>reload</tt> option of the <file>init.d</file> script
5976 should behave as if the configuration has been reloaded
5981 The <file>/etc/init.d</file> scripts must be treated as
5982 configuration files, either (if they are present in the
5983 package, that is, in the .deb file) by marking them as
5984 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5985 by managing them correctly in the maintainer scripts (see
5986 <ref id="config-files">). This is important since we want
5987 to give the local system administrator the chance to adapt
5988 the scripts to the local system, e.g., to disable a
5989 service without de-installing the package, or to specify
5990 some special command line options when starting a service,
5991 while making sure their changes aren't lost during the next
5996 These scripts should not fail obscurely when the
5997 configuration files remain but the package has been
5998 removed, as configuration files remain on the system after
5999 the package has been removed. Only when <prgn>dpkg</prgn>
6000 is executed with the <tt>--purge</tt> option will
6001 configuration files be removed. In particular, as the
6002 <file>/etc/init.d/<var>package</var></file> script itself is
6003 usually a <tt>conffile</tt>, it will remain on the system
6004 if the package is removed but not purged. Therefore, you
6005 should include a <tt>test</tt> statement at the top of the
6007 <example compact="compact">
6008 test -f <var>program-executed-later-in-script</var> || exit 0
6013 Often there are some variables in the <file>init.d</file>
6014 scripts whose values control the behavior of the scripts,
6015 and which a system administrator is likely to want to
6016 change. As the scripts themselves are frequently
6017 <tt>conffile</tt>s, modifying them requires that the
6018 administrator merge in their changes each time the package
6019 is upgraded and the <tt>conffile</tt> changes. To ease
6020 the burden on the system administrator, such configurable
6021 values should not be placed directly in the script.
6022 Instead, they should be placed in a file in
6023 <file>/etc/default</file>, which typically will have the same
6024 base name as the <file>init.d</file> script. This extra file
6025 should be sourced by the script when the script runs. It
6026 must contain only variable settings and comments in SUSv3
6027 <prgn>sh</prgn> format. It may either be a
6028 <tt>conffile</tt> or a configuration file maintained by
6029 the package maintainer scripts. See <ref id="config-files">
6034 To ensure that vital configurable values are always
6035 available, the <file>init.d</file> script should set default
6036 values for each of the shell variables it uses, either
6037 before sourcing the <file>/etc/default/</file> file or
6038 afterwards using something like the <tt>:
6039 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6040 script must behave sensibly and not fail if the
6041 <file>/etc/default</file> file is deleted.
6046 <heading>Interfacing with the initscript system</heading>
6049 Maintainers should use the abstraction layer provided by
6050 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6051 programs to deal with initscripts in their packages'
6052 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6053 and <prgn>postrm</prgn>.
6057 Directly managing the /etc/rc?.d links and directly
6058 invoking the <file>/etc/init.d/</file> initscripts should
6059 be done only by packages providing the initscript
6060 subsystem (such as <prgn>sysv-rc</prgn> and
6061 <prgn>file-rc</prgn>).
6065 <heading>Managing the links</heading>
6068 The program <prgn>update-rc.d</prgn> is provided for
6069 package maintainers to arrange for the proper creation and
6070 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6071 or their functional equivalent if another method is being
6072 used. This may be used by maintainers in their packages'
6073 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6077 You must not include any <file>/etc/rc<var>n</var>.d</file>
6078 symbolic links in the actual archive or manually create or
6079 remove the symbolic links in maintainer scripts; you must
6080 use the <prgn>update-rc.d</prgn> program instead. (The
6081 former will fail if an alternative method of maintaining
6082 runlevel information is being used.) You must not include
6083 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6084 in the archive either. (Only the <tt>sysvinit</tt>
6089 By default <prgn>update-rc.d</prgn> will start services in
6090 each of the multi-user state runlevels (2, 3, 4, and 5)
6091 and stop them in the halt runlevel (0), the single-user
6092 runlevel (1) and the reboot runlevel (6). The system
6093 administrator will have the opportunity to customize
6094 runlevels by simply adding, moving, or removing the
6095 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6096 symbolic links are being used, or by modifying
6097 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6102 To get the default behavior for your package, put in your
6103 <prgn>postinst</prgn> script
6104 <example compact="compact">
6105 update-rc.d <var>package</var> defaults
6107 and in your <prgn>postrm</prgn>
6108 <example compact="compact">
6109 if [ "$1" = purge ]; then
6110 update-rc.d <var>package</var> remove
6112 </example>. Note that if your package changes runlevels
6113 or priority, you may have to remove and recreate the links,
6114 since otherwise the old links may persist. Refer to the
6115 documentation of <prgn>update-rc.d</prgn>.
6119 This will use a default sequence number of 20. If it does
6120 not matter when or in which order the <file>init.d</file>
6121 script is run, use this default. If it does, then you
6122 should talk to the maintainer of the <prgn>sysvinit</prgn>
6123 package or post to <tt>debian-devel</tt>, and they will
6124 help you choose a number.
6128 For more information about using <tt>update-rc.d</tt>,
6129 please consult its man page <manref name="update-rc.d"
6135 <heading>Running initscripts</heading>
6137 The program <prgn>invoke-rc.d</prgn> is provided to make
6138 it easier for package maintainers to properly invoke an
6139 initscript, obeying runlevel and other locally-defined
6140 constraints that might limit a package's right to start,
6141 stop and otherwise manage services. This program may be
6142 used by maintainers in their packages' scripts.
6146 The package maintainer scripts must use
6147 <prgn>invoke-rc.d</prgn> to invoke the
6148 <file>/etc/init.d/*</file> initscripts, instead of
6149 calling them directly.
6153 By default, <prgn>invoke-rc.d</prgn> will pass any
6154 action requests (start, stop, reload, restart...) to the
6155 <file>/etc/init.d</file> script, filtering out requests
6156 to start or restart a service out of its intended
6161 Most packages will simply need to change:
6162 <example compact="compact">/etc/init.d/<package>
6163 <action></example> in their <prgn>postinst</prgn>
6164 and <prgn>prerm</prgn> scripts to:
6165 <example compact="compact">
6166 if which invoke-rc.d >/dev/null 2>&1; then
6167 invoke-rc.d <var>package</var> <action>
6169 /etc/init.d/<var>package</var> <action>
6175 A package should register its initscript services using
6176 <prgn>update-rc.d</prgn> before it tries to invoke them
6177 using <prgn>invoke-rc.d</prgn>. Invocation of
6178 unregistered services may fail.
6182 For more information about using
6183 <prgn>invoke-rc.d</prgn>, please consult its man page
6184 <manref name="invoke-rc.d" section="8">.
6190 <heading>Boot-time initialization</heading>
6193 There used to be another directory, <file>/etc/rc.boot</file>,
6194 which contained scripts which were run once per machine
6195 boot. This has been deprecated in favour of links from
6196 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6197 described in <ref id="/etc/init.d">. Packages must not
6198 place files in <file>/etc/rc.boot</file>.
6203 <heading>Example</heading>
6206 An example on which you can base your
6207 <file>/etc/init.d</file> scripts is found in
6208 <file>/etc/init.d/skeleton</file>.
6215 <heading>Console messages from <file>init.d</file> scripts</heading>
6218 This section describes the formats to be used for messages
6219 written to standard output by the <file>/etc/init.d</file>
6220 scripts. The intent is to improve the consistency of
6221 Debian's startup and shutdown look and feel. For this
6222 reason, please look very carefully at the details. We want
6223 the messages to have the same format in terms of wording,
6224 spaces, punctuation and case of letters.
6228 Here is a list of overall rules that should be used for
6229 messages generated by <file>/etc/init.d</file> scripts.
6235 The message should fit in one line (fewer than 80
6236 characters), start with a capital letter and end with
6237 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6241 If the script is performing some time consuming task in
6242 the background (not merely starting or stopping a
6243 program, for instance), an ellipsis (three dots:
6244 <tt>...</tt>) should be output to the screen, with no
6245 leading or tailing whitespace or line feeds.
6249 The messages should appear as if the computer is telling
6250 the user what it is doing (politely :-), but should not
6251 mention "it" directly. For example, instead of:
6252 <example compact="compact">
6253 I'm starting network daemons: nfsd mountd.
6255 the message should say
6256 <example compact="compact">
6257 Starting network daemons: nfsd mountd.
6264 <tt>init.d</tt> script should use the following standard
6265 message formats for the situations enumerated below.
6271 <p>When daemons are started</p>
6274 If the script starts one or more daemons, the output
6275 should look like this (a single line, no leading
6277 <example compact="compact">
6278 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6280 The <var>description</var> should describe the
6281 subsystem the daemon or set of daemons are part of,
6282 while <var>daemon-1</var> up to <var>daemon-n</var>
6283 denote each daemon's name (typically the file name of
6288 For example, the output of <file>/etc/init.d/lpd</file>
6290 <example compact="compact">
6291 Starting printer spooler: lpd.
6296 This can be achieved by saying
6297 <example compact="compact">
6298 echo -n "Starting printer spooler: lpd"
6299 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6302 in the script. If there are more than one daemon to
6303 start, the output should look like this:
6304 <example compact="compact">
6305 echo -n "Starting remote file system services:"
6306 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6307 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6308 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6311 This makes it possible for the user to see what is
6312 happening and when the final daemon has been started.
6313 Care should be taken in the placement of white spaces:
6314 in the example above the system administrators can
6315 easily comment out a line if they don't want to start
6316 a specific daemon, while the displayed message still
6322 <p>When a system parameter is being set</p>
6325 If you have to set up different system parameters
6326 during the system boot, you should use this format:
6327 <example compact="compact">
6328 Setting <var>parameter</var> to "<var>value</var>".
6333 You can use a statement such as the following to get
6335 <example compact="compact">
6336 echo "Setting DNS domainname to \"$domainname\"."
6341 Note that the same symbol (<tt>"</tt>) is used for the left
6342 and right quotation marks. A grave accent (<tt>`</tt>) is
6343 not a quote character; neither is an apostrophe
6349 <p>When a daemon is stopped or restarted</p>
6352 When you stop or restart a daemon, you should issue a
6353 message identical to the startup message, except that
6354 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6355 or <tt>Restarting</tt> respectively.
6359 For example, stopping the printer daemon will look like
6361 <example compact="compact">
6362 Stopping printer spooler: lpd.
6368 <p>When something is executed</p>
6371 There are several examples where you have to run a
6372 program at system startup or shutdown to perform a
6373 specific task, for example, setting the system's clock
6374 using <prgn>netdate</prgn> or killing all processes
6375 when the system shuts down. Your message should look
6377 <example compact="compact">
6378 Doing something very useful...done.
6380 You should print the <tt>done.</tt> immediately after
6381 the job has been completed, so that the user is
6382 informed why they have to wait. You can get this
6384 <example compact="compact">
6385 echo -n "Doing something very useful..."
6394 <p>When the configuration is reloaded</p>
6397 When a daemon is forced to reload its configuration
6398 files you should use the following format:
6399 <example compact="compact">
6400 Reloading <var>description</var> configuration...done.
6402 where <var>description</var> is the same as in the
6403 daemon starting message.
6411 <heading>Cron jobs</heading>
6414 Packages must not modify the configuration file
6415 <file>/etc/crontab</file>, and they must not modify the files in
6416 <file>/var/spool/cron/crontabs</file>.</p>
6419 If a package wants to install a job that has to be executed
6420 via cron, it should place a file with the name of the
6421 package in one or more of the following directories:
6422 <example compact="compact">
6428 As these directory names imply, the files within them are
6429 executed on an hourly, daily, weekly, or monthly basis,
6430 respectively. The exact times are listed in
6431 <file>/etc/crontab</file>.</p>
6434 All files installed in any of these directories must be
6435 scripts (e.g., shell scripts or Perl scripts) so that they
6436 can easily be modified by the local system administrator.
6437 In addition, they must be treated as configuration files.
6441 If a certain job has to be executed at some other frequency or
6442 at a specific time, the package should install a file
6443 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6444 same syntax as <file>/etc/crontab</file> and is processed by
6445 <prgn>cron</prgn> automatically. The file must also be
6446 treated as a configuration file. (Note that entries in the
6447 <file>/etc/cron.d</file> directory are not handled by
6448 <prgn>anacron</prgn>. Thus, you should only use this
6449 directory for jobs which may be skipped if the system is not
6453 The scripts or crontab entries in these directories should
6454 check if all necessary programs are installed before they
6455 try to execute them. Otherwise, problems will arise when a
6456 package was removed but not purged since configuration files
6457 are kept on the system in this situation.</p>
6461 <heading>Menus</heading>
6464 The Debian <tt>menu</tt> package provides a standard
6465 interface between packages providing applications and
6466 <em>menu programs</em> (either X window managers or
6467 text-based menu programs such as <prgn>pdmenu</prgn>).
6471 All packages that provide applications that need not be
6472 passed any special command line arguments for normal
6473 operation should register a menu entry for those
6474 applications, so that users of the <tt>menu</tt> package
6475 will automatically get menu entries in their window
6476 managers, as well in shells like <tt>pdmenu</tt>.
6480 Menu entries should follow the current menu policy.
6484 The menu policy can be found in the <tt>menu-policy</tt>
6485 files in the <tt>debian-policy</tt> package.
6486 It is also available from the Debian web mirrors at
6487 <tt><url name="/doc/packaging-manuals/menu-policy/"
6488 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6492 Please also refer to the <em>Debian Menu System</em>
6493 documentation that comes with the <package>menu</package>
6494 package for information about how to register your
6500 <heading>Multimedia handlers</heading>
6503 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6504 is a mechanism for encoding files and data streams and
6505 providing meta-information about them, in particular their
6506 type (e.g. audio or video) and format (e.g. PNG, HTML,
6511 Registration of MIME type handlers allows programs like mail
6512 user agents and web browsers to invoke these handlers to
6513 view, edit or display MIME types they don't support directly.
6517 Packages which provide the ability to view/show/play,
6518 compose, edit or print MIME types should register themselves
6519 as such following the current MIME support policy.
6523 The MIME support policy can be found in the <tt>mime-policy</tt>
6524 files in the <tt>debian-policy</tt> package.
6525 It is also available from the Debian web mirrors at
6526 <tt><url name="/doc/packaging-manuals/mime-policy/"
6527 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6533 <heading>Keyboard configuration</heading>
6536 To achieve a consistent keyboard configuration so that all
6537 applications interpret a keyboard event the same way, all
6538 programs in the Debian distribution must be configured to
6539 comply with the following guidelines.
6543 The following keys must have the specified interpretations:
6546 <tag><tt><--</tt></tag>
6547 <item>delete the character to the left of the cursor</item>
6549 <tag><tt>Delete</tt></tag>
6550 <item>delete the character to the right of the cursor</item>
6552 <tag><tt>Control+H</tt></tag>
6553 <item>emacs: the help prefix</item>
6556 The interpretation of any keyboard events should be
6557 independent of the terminal that is used, be it a virtual
6558 console, an X terminal emulator, an rlogin/telnet session,
6563 The following list explains how the different programs
6564 should be set up to achieve this:
6570 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6574 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6578 X translations are set up to make
6579 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6580 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6581 is the vt220 escape code for the "delete character"
6582 key). This must be done by loading the X resources
6583 using <prgn>xrdb</prgn> on all local X displays, not
6584 using the application defaults, so that the
6585 translation resources used correspond to the
6586 <prgn>xmodmap</prgn> settings.
6590 The Linux console is configured to make
6591 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6592 generate <tt>ESC [ 3 ~</tt>.
6596 X applications are configured so that <tt><</tt>
6597 deletes left, and <tt>Delete</tt> deletes right. Motif
6598 applications already work like this.
6602 Terminals should have <tt>stty erase ^?</tt> .
6606 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6607 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6608 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6612 Emacs is programmed to map <tt>KB_Backspace</tt> or
6613 the <tt>stty erase</tt> character to
6614 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6615 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6616 <tt>^H</tt> to <tt>help</tt> as always.
6620 Other applications use the <tt>stty erase</tt>
6621 character and <tt>kdch1</tt> for the two delete keys,
6622 with ASCII DEL being "delete previous character" and
6623 <tt>kdch1</tt> being "delete character under
6631 This will solve the problem except for the following
6638 Some terminals have a <tt><--</tt> key that cannot
6639 be made to produce anything except <tt>^H</tt>. On
6640 these terminals Emacs help will be unavailable on
6641 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6642 character takes precedence in Emacs, and has been set
6643 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6644 available) can be used instead.
6648 Some operating systems use <tt>^H</tt> for <tt>stty
6649 erase</tt>. However, modern telnet versions and all
6650 rlogin versions propagate <tt>stty</tt> settings, and
6651 almost all UNIX versions honour <tt>stty erase</tt>.
6652 Where the <tt>stty</tt> settings are not propagated
6653 correctly, things can be made to work by using
6654 <tt>stty</tt> manually.
6658 Some systems (including previous Debian versions) use
6659 <prgn>xmodmap</prgn> to arrange for both
6660 <tt><--</tt> and <tt>Delete</tt> to generate
6661 <tt>KB_Delete</tt>. We can change the behavior of
6662 their X clients using the same X resources that we use
6663 to do it for our own clients, or configure our clients
6664 using their resources when things are the other way
6665 around. On displays configured like this
6666 <tt>Delete</tt> will not work, but <tt><--</tt>
6671 Some operating systems have different <tt>kdch1</tt>
6672 settings in their <tt>terminfo</tt> database for
6673 <tt>xterm</tt> and others. On these systems the
6674 <tt>Delete</tt> key will not work correctly when you
6675 log in from a system conforming to our policy, but
6676 <tt><--</tt> will.
6683 <heading>Environment variables</heading>
6686 A program must not depend on environment variables to get
6687 reasonable defaults. (That's because these environment
6688 variables would have to be set in a system-wide
6689 configuration file like <file>/etc/profile</file>, which is not
6690 supported by all shells.)
6694 If a program usually depends on environment variables for its
6695 configuration, the program should be changed to fall back to
6696 a reasonable default configuration if these environment
6697 variables are not present. If this cannot be done easily
6698 (e.g., if the source code of a non-free program is not
6699 available), the program must be replaced by a small
6700 "wrapper" shell script which sets the environment variables
6701 if they are not already defined, and calls the original program.
6705 Here is an example of a wrapper script for this purpose:
6707 <example compact="compact">
6709 BAR=${BAR:-/var/lib/fubar}
6711 exec /usr/lib/foo/foo "$@"
6716 Furthermore, as <file>/etc/profile</file> is a configuration
6717 file of the <prgn>base-files</prgn> package, other packages must
6718 not put any environment variables or other commands into that
6723 <sect id="doc-base">
6724 <heading>Registering Documents using doc-base</heading>
6727 The <package>doc-base</package> package implements a
6728 flexible mechanism for handling and presenting
6729 documentation. The recommended practice is for every Debian
6730 package that provides online documentation (other than just
6731 manual pages) to register these documents with
6732 <package>doc-base</package> by installing a
6733 <package>doc-base</package> control file via the
6734 <prgn/install-docs/ script at installation time and
6735 de-register the manuals again when the package is removed.
6738 Please refer to the documentation that comes with the
6739 <package>doc-base</package> package for information and
6748 <heading>Files</heading>
6751 <heading>Binaries</heading>
6754 Two different packages must not install programs with
6755 different functionality but with the same filenames. (The
6756 case of two programs having the same functionality but
6757 different implementations is handled via "alternatives" or
6758 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6759 <ref id="conflicts"> respectively.) If this case happens,
6760 one of the programs must be renamed. The maintainers should
6761 report this to the <tt>debian-devel</tt> mailing list and
6762 try to find a consensus about which program will have to be
6763 renamed. If a consensus cannot be reached, <em>both</em>
6764 programs must be renamed.
6768 By default, when a package is being built, any binaries
6769 created should include debugging information, as well as
6770 being compiled with optimization. You should also turn on
6771 as many reasonable compilation warnings as possible; this
6772 makes life easier for porters, who can then look at build
6773 logs for possible problems. For the C programming language,
6774 this means the following compilation parameters should be
6776 <example compact="compact">
6778 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6780 INSTALL = install -s # (or use strip on the files in debian/tmp)
6785 Note that by default all installed binaries should be stripped,
6786 either by using the <tt>-s</tt> flag to
6787 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6788 the binaries after they have been copied into
6789 <file>debian/tmp</file> but before the tree is made into a
6794 Although binaries in the build tree should be compiled with
6795 debugging information by default, it can often be difficult to
6796 debug programs if they are also subjected to compiler
6797 optimization. For this reason, it is recommended to support the
6798 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6799 (see <ref id="debianrules-options">). This variable can contain
6800 several flags to change how a package is compiled and built.
6804 It is up to the package maintainer to decide what
6805 compilation options are best for the package. Certain
6806 binaries (such as computationally-intensive programs) will
6807 function better with certain flags (<tt>-O3</tt>, for
6808 example); feel free to use them. Please use good judgment
6809 here. Don't use flags for the sake of it; only use them
6810 if there is good reason to do so. Feel free to override
6811 the upstream author's ideas about which compilation
6812 options are best: they are often inappropriate for our
6818 <sect id="libraries">
6819 <heading>Libraries</heading>
6822 If the package is <strong>architecture: any</strong>, then
6823 the shared library compilation and linking flags must have
6824 <tt>-fPIC</tt>, or the package shall not build on some of
6825 the supported architectures<footnote>
6827 If you are using GCC, <tt>-fPIC</tt> produces code with
6828 relocatable position independent code, which is required for
6829 most architectures to create a shared library, with i386 and
6830 perhaps some others where non position independent code is
6831 permitted in a shared library.
6834 Position independent code may have a performance penalty,
6835 especially on <tt>i386</tt>. However, in most cases the
6836 speed penalty must be measured against the memory wasted on
6837 the few architectures where non position independent code is
6840 </footnote>. Any exception to this rule must be discussed on
6841 the mailing list <em>debian-devel@lists.debian.org</em>, and
6842 a rough consensus obtained. The reasons for not compiling
6843 with <tt>-fPIC</tt> flag must be recorded in the file
6844 <tt>README.Debian</tt>, and care must be taken to either
6845 restrict the architecture or arrange for <tt>-fPIC</tt> to
6846 be used on architectures where it is required.<footnote>
6848 Some of the reasons why this might be required is if the
6849 library contains hand crafted assembly code that is not
6850 relocatable, the speed penalty is excessive for compute
6851 intensive libs, and similar reasons.
6856 As to the static libraries, the common case is not to have
6857 relocatable code, since there is no benefit, unless in specific
6858 cases; therefore the static version must not be compiled
6859 with the <tt>-fPIC</tt> flag. Any exception to this rule
6860 should be discussed on the mailing list
6861 <em>debian-devel@lists.debian.org</em>, and the reasons for
6862 compiling with the <tt>-fPIC</tt> flag must be recorded in
6863 the file <tt>README.Debian</tt>. <footnote>
6865 Some of the reasons for linking static libraries with
6866 the <tt>-fPIC</tt> flag are if, for example, one needs a
6867 Perl API for a library that is under rapid development,
6868 and has an unstable API, so shared libraries are
6869 pointless at this phase of the library's development. In
6870 that case, since Perl needs a library with relocatable
6871 code, it may make sense to create a static library with
6872 relocatable code. Another reason cited is if you are
6873 distilling various libraries into a common shared
6874 library, like <tt>mklibs</tt> does in the Debian
6880 In other words, if both a shared and a static library is
6881 being built, each source unit (<tt>*.c</tt>, for example,
6882 for C files) will need to be compiled twice, for the normal
6886 You must specify the gcc option <tt>-D_REENTRANT</tt>
6887 when building a library (either static or shared) to make
6888 the library compatible with LinuxThreads.
6892 Although not enforced by the build tools, shared libraries
6893 must be linked against all libraries that they use symbols from
6894 in the same way that binaries are. This ensures the correct
6895 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6896 system and guarantees that all libraries can be safely opened
6897 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6898 option <tt>-Wl,-z,defs</tt> when building a shared library.
6899 Since this option enforces symbol resolution at build time,
6900 a missing library reference will be caught early as a fatal
6905 All installed shared libraries should be stripped with
6906 <example compact="compact">
6907 strip --strip-unneeded <var>your-lib</var>
6909 (The option <tt>--strip-unneeded</tt> makes
6910 <prgn>strip</prgn> remove only the symbols which aren't
6911 needed for relocation processing.) Shared libraries can
6912 function perfectly well when stripped, since the symbols for
6913 dynamic linking are in a separate part of the ELF object
6915 You might also want to use the options
6916 <tt>--remove-section=.comment</tt> and
6917 <tt>--remove-section=.note</tt> on both shared libraries
6918 and executables, and <tt>--strip-debug</tt> on static
6924 Note that under some circumstances it may be useful to
6925 install a shared library unstripped, for example when
6926 building a separate package to support debugging.
6930 Shared object files (often <file>.so</file> files) that are not
6931 public libraries, that is, they are not meant to be linked
6932 to by third party executables (binaries of other packages),
6933 should be installed in subdirectories of the
6934 <file>/usr/lib</file> directory. Such files are exempt from the
6935 rules that govern ordinary shared libraries, except that
6936 they must not be installed executable and should be
6938 A common example are the so-called "plug-ins",
6939 internal shared objects that are dynamically loaded by
6940 programs using <manref name="dlopen" section="3">.
6945 Packages containing shared libraries that may be linked to
6946 by other packages' binaries, but which for some
6947 <em>compelling</em> reason can not be installed in
6948 <file>/usr/lib</file> directory, may install the shared library
6949 files in subdirectories of the <file>/usr/lib</file> directory,
6950 in which case they should arrange to add that directory in
6951 <file>/etc/ld.so.conf</file> in the package's post-installation
6952 script, and remove it in the package's post-removal script.
6956 An ever increasing number of packages are using
6957 <prgn>libtool</prgn> to do their linking. The latest GNU
6958 libtools (>= 1.3a) can take advantage of the metadata in the
6959 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6960 files). The main advantage of <prgn>libtool</prgn>'s
6961 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6962 store and subsequently access metadata with respect to the
6963 libraries it builds. <prgn>libtool</prgn> will search for
6964 those files, which contain a lot of useful information about
6965 a library (such as library dependency information for static
6966 linking). Also, they're <em>essential</em> for programs
6967 using <tt>libltdl</tt>.<footnote>
6968 Although <prgn>libtool</prgn> is fully capable of
6969 linking against shared libraries which don't have
6970 <tt>.la</tt> files, as it is a mere shell script it can
6971 add considerably to the build time of a
6972 <prgn>libtool</prgn>-using package if that shell script
6973 has to derive all this information from first principles
6974 for each library every time it is linked. With the
6975 advent of <prgn>libtool</prgn> version 1.4 (and to a
6976 lesser extent <prgn>libtool</prgn> version 1.3), the
6977 <file>.la</file> files also store information about
6978 inter-library dependencies which cannot necessarily be
6979 derived after the <file>.la</file> file is deleted.
6984 Packages that use <prgn>libtool</prgn> to create shared
6985 libraries should include the <file>.la</file> files in the
6986 <tt>-dev</tt> package, unless the package relies on
6987 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6988 the <tt>.la</tt> files must go in the run-time library
6993 You must make sure that you use only released versions of
6994 shared libraries to build your packages; otherwise other
6995 users will not be able to run your binaries
6996 properly. Producing source packages that depend on
6997 unreleased compilers is also usually a bad
7004 <heading>Shared libraries</heading>
7006 This section has moved to <ref id="sharedlibs">.
7012 <heading>Scripts</heading>
7015 All command scripts, including the package maintainer
7016 scripts inside the package and used by <prgn>dpkg</prgn>,
7017 should have a <tt>#!</tt> line naming the shell to be used
7022 In the case of Perl scripts this should be
7023 <tt>#!/usr/bin/perl</tt>.
7027 When scripts are installed into a directory in the system
7028 PATH, the script name should not include an extension such
7029 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7030 language currently used to implement it.
7033 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7034 should almost certainly start with <tt>set -e</tt> so that
7035 errors are detected. Every script should use
7036 <tt>set -e</tt> or check the exit status of <em>every</em>
7041 Scripts may assume that <file>/bin/sh</file> implements the
7042 SUSv3 Shell Command Language<footnote>
7043 Single UNIX Specification, version 3, which is also IEEE
7044 1003.1-2004 (POSIX), and is available on the World Wide Web
7045 from <url id="http://www.unix.org/version3/online.html"
7046 name="The Open Group"> after free
7047 registration.</footnote>
7048 plus the following additional features not mandated by
7050 These features are in widespread use in the Linux community
7051 and are implemented in all of bash, dash, and ksh, the most
7052 common shells users may wish to use as <file>/bin/sh</file>.
7055 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7056 must not generate a newline.</item>
7057 <item><tt>test</tt>, if implemented as a shell built-in, must
7058 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7060 <item><tt>local</tt> to create a scoped variable must be
7061 supported, including listing multiple variables in a single
7062 local command and assigning a value to a variable at the
7063 same time as localizing it. <tt>local</tt> may or
7064 may not preserve the variable value from an outer scope if
7065 no assignment is present. Uses such as:
7069 # ... use a, b, c, d ...
7072 must be supported and must set the value of <tt>c</tt> to
7076 If a shell script requires non-SUSv3 features from the shell
7077 interpreter other than those listed above, the appropriate shell
7078 must be specified in the first line of the script (e.g.,
7079 <tt>#!/bin/bash</tt>) and the package must depend on the package
7080 providing the shell (unless the shell package is marked
7081 "Essential", as in the case of <prgn>bash</prgn>).
7085 You may wish to restrict your script to SUSv3 features plus the
7086 above set when possible so that it may use <file>/bin/sh</file>
7087 as its interpreter. If your script works with <prgn>dash</prgn>
7088 (originally called <prgn>ash</prgn>), it probably complies with
7089 the above requirements, but if you are in doubt, use
7090 <file>/bin/bash</file>.
7094 Perl scripts should check for errors when making any
7095 system calls, including <tt>open</tt>, <tt>print</tt>,
7096 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7100 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7101 scripting languages. See <em>Csh Programming Considered
7102 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7103 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7104 If an upstream package comes with <prgn>csh</prgn> scripts
7105 then you must make sure that they start with
7106 <tt>#!/bin/csh</tt> and make your package depend on the
7107 <prgn>c-shell</prgn> virtual package.
7111 Any scripts which create files in world-writeable
7112 directories (e.g., in <file>/tmp</file>) must use a
7113 mechanism which will fail atomically if a file with the same
7114 name already exists.
7118 The Debian base system provides the <prgn>tempfile</prgn>
7119 and <prgn>mktemp</prgn> utilities for use by scripts for
7126 <heading>Symbolic links</heading>
7129 In general, symbolic links within a top-level directory
7130 should be relative, and symbolic links pointing from one
7131 top-level directory into another should be absolute. (A
7132 top-level directory is a sub-directory of the root
7133 directory <file>/</file>.)
7137 In addition, symbolic links should be specified as short as
7138 possible, i.e., link targets like <file>foo/../bar</file> are
7143 Note that when creating a relative link using
7144 <prgn>ln</prgn> it is not necessary for the target of the
7145 link to exist relative to the working directory you're
7146 running <prgn>ln</prgn> from, nor is it necessary to change
7147 directory to the directory where the link is to be made.
7148 Simply include the string that should appear as the target
7149 of the link (this will be a pathname relative to the
7150 directory in which the link resides) as the first argument
7155 For example, in your <prgn>Makefile</prgn> or
7156 <file>debian/rules</file>, you can do things like:
7157 <example compact="compact">
7158 ln -fs gcc $(prefix)/bin/cc
7159 ln -fs gcc debian/tmp/usr/bin/cc
7160 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7161 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7166 A symbolic link pointing to a compressed file should always
7167 have the same file extension as the referenced file. (For
7168 example, if a file <file>foo.gz</file> is referenced by a
7169 symbolic link, the filename of the link has to end with
7170 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7175 <heading>Device files</heading>
7178 Packages must not include device files in the package file
7183 If a package needs any special device files that are not
7184 included in the base system, it must call
7185 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7186 after notifying the user<footnote>
7187 This notification could be done via a (low-priority)
7188 debconf message, or an echo (printf) statement.
7193 Packages must not remove any device files in the
7194 <prgn>postrm</prgn> or any other script. This is left to the
7195 system administrator.
7199 Debian uses the serial devices
7200 <file>/dev/ttyS*</file>. Programs using the old
7201 <file>/dev/cu*</file> devices should be changed to use
7202 <file>/dev/ttyS*</file>.
7206 <sect id="config-files">
7207 <heading>Configuration files</heading>
7210 <heading>Definitions</heading>
7214 <tag>configuration file</tag>
7216 A file that affects the operation of a program, or
7217 provides site- or host-specific information, or
7218 otherwise customizes the behavior of a program.
7219 Typically, configuration files are intended to be
7220 modified by the system administrator (if needed or
7221 desired) to conform to local policy or to provide
7222 more useful site-specific behavior.
7225 <tag><tt>conffile</tt></tag>
7227 A file listed in a package's <tt>conffiles</tt>
7228 file, and is treated specially by <prgn>dpkg</prgn>
7229 (see <ref id="configdetails">).
7235 The distinction between these two is important; they are
7236 not interchangeable concepts. Almost all
7237 <tt>conffile</tt>s are configuration files, but many
7238 configuration files are not <tt>conffiles</tt>.
7242 As noted elsewhere, <file>/etc/init.d</file> scripts,
7243 <file>/etc/default</file> files, scripts installed in
7244 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7245 configuration installed in <file>/etc/cron.d</file> must be
7246 treated as configuration files. In general, any script that
7247 embeds configuration information is de-facto a configuration
7248 file and should be treated as such.
7253 <heading>Location</heading>
7256 Any configuration files created or used by your package
7257 must reside in <file>/etc</file>. If there are several,
7258 consider creating a subdirectory of <file>/etc</file>
7259 named after your package.
7263 If your package creates or uses configuration files
7264 outside of <file>/etc</file>, and it is not feasible to modify
7265 the package to use <file>/etc</file> directly, put the files
7266 in <file>/etc</file> and create symbolic links to those files
7267 from the location that the package requires.
7272 <heading>Behavior</heading>
7275 Configuration file handling must conform to the following
7277 <list compact="compact">
7279 local changes must be preserved during a package
7283 configuration files must be preserved when the
7284 package is removed, and only deleted when the
7291 The easy way to achieve this behavior is to make the
7292 configuration file a <tt>conffile</tt>. This is
7293 appropriate only if it is possible to distribute a default
7294 version that will work for most installations, although
7295 some system administrators may choose to modify it. This
7296 implies that the default version will be part of the
7297 package distribution, and must not be modified by the
7298 maintainer scripts during installation (or at any other
7303 In order to ensure that local changes are preserved
7304 correctly, no package may contain or make hard links to
7305 conffiles.<footnote>
7306 Rationale: There are two problems with hard links.
7307 The first is that some editors break the link while
7308 editing one of the files, so that the two files may
7309 unwittingly become unlinked and different. The second
7310 is that <prgn>dpkg</prgn> might break the hard link
7311 while upgrading <tt>conffile</tt>s.
7316 The other way to do it is via the maintainer scripts. In
7317 this case, the configuration file must not be listed as a
7318 <tt>conffile</tt> and must not be part of the package
7319 distribution. If the existence of a file is required for
7320 the package to be sensibly configured it is the
7321 responsibility of the package maintainer to provide
7322 maintainer scripts which correctly create, update and
7323 maintain the file and remove it on purge. (See <ref
7324 id="maintainerscripts"> for more information.) These
7325 scripts must be idempotent (i.e., must work correctly if
7326 <prgn>dpkg</prgn> needs to re-run them due to errors
7327 during installation or removal), must cope with all the
7328 variety of ways <prgn>dpkg</prgn> can call maintainer
7329 scripts, must not overwrite or otherwise mangle the user's
7330 configuration without asking, must not ask unnecessary
7331 questions (particularly during upgrades), and must
7332 otherwise be good citizens.
7336 The scripts are not required to configure every possible
7337 option for the package, but only those necessary to get
7338 the package running on a given system. Ideally the
7339 sysadmin should not have to do any configuration other
7340 than that done (semi-)automatically by the
7341 <prgn>postinst</prgn> script.
7345 A common practice is to create a script called
7346 <file><var>package</var>-configure</file> and have the
7347 package's <prgn>postinst</prgn> call it if and only if the
7348 configuration file does not already exist. In certain
7349 cases it is useful for there to be an example or template
7350 file which the maintainer scripts use. Such files should
7351 be in <file>/usr/share/<var>package</var></file> or
7352 <file>/usr/lib/<var>package</var></file> (depending on whether
7353 they are architecture-independent or not). There should
7354 be symbolic links to them from
7355 <file>/usr/share/doc/<var>package</var>/examples</file> if
7356 they are examples, and should be perfectly ordinary
7357 <prgn>dpkg</prgn>-handled files (<em>not</em>
7358 configuration files).
7362 These two styles of configuration file handling must
7363 not be mixed, for that way lies madness:
7364 <prgn>dpkg</prgn> will ask about overwriting the file
7365 every time the package is upgraded.
7370 <heading>Sharing configuration files</heading>
7373 Packages which specify the same file as a
7374 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7375 with each other. (This is an instance of the general rule
7376 about not sharing files. Note that neither alternatives
7377 nor diversions are likely to be appropriate in this case;
7378 in particular, <prgn>dpkg</prgn> does not handle diverted
7379 <tt>conffile</tt>s well.)
7383 The maintainer scripts must not alter a <tt>conffile</tt>
7384 of <em>any</em> package, including the one the scripts
7389 If two or more packages use the same configuration file
7390 and it is reasonable for both to be installed at the same
7391 time, one of these packages must be defined as
7392 <em>owner</em> of the configuration file, i.e., it will be
7393 the package which handles that file as a configuration
7394 file. Other packages that use the configuration file must
7395 depend on the owning package if they require the
7396 configuration file to operate. If the other package will
7397 use the configuration file if present, but is capable of
7398 operating without it, no dependency need be declared.
7402 If it is desirable for two or more related packages to
7403 share a configuration file <em>and</em> for all of the
7404 related packages to be able to modify that configuration
7405 file, then the following should be done:
7406 <enumlist compact="compact">
7408 One of the related packages (the "owning" package)
7409 will manage the configuration file with maintainer
7410 scripts as described in the previous section.
7413 The owning package should also provide a program
7414 that the other packages may use to modify the
7418 The related packages must use the provided program
7419 to make any desired modifications to the
7420 configuration file. They should either depend on
7421 the core package to guarantee that the configuration
7422 modifier program is available or accept gracefully
7423 that they cannot modify the configuration file if it
7424 is not. (This is in addition to the fact that the
7425 configuration file may not even be present in the
7432 Sometimes it's appropriate to create a new package which
7433 provides the basic infrastructure for the other packages
7434 and which manages the shared configuration files. (The
7435 <tt>sgml-base</tt> package is a good example.)
7440 <heading>User configuration files ("dotfiles")</heading>
7443 The files in <file>/etc/skel</file> will automatically be
7444 copied into new user accounts by <prgn>adduser</prgn>.
7445 No other program should reference the files in
7446 <file>/etc/skel</file>.
7450 Therefore, if a program needs a dotfile to exist in
7451 advance in <file>$HOME</file> to work sensibly, that dotfile
7452 should be installed in <file>/etc/skel</file> and treated as a
7457 However, programs that require dotfiles in order to
7458 operate sensibly are a bad thing, unless they do create
7459 the dotfiles themselves automatically.
7463 Furthermore, programs should be configured by the Debian
7464 default installation to behave as closely to the upstream
7465 default behavior as possible.
7469 Therefore, if a program in a Debian package needs to be
7470 configured in some way in order to operate sensibly, that
7471 should be done using a site-wide configuration file placed
7472 in <file>/etc</file>. Only if the program doesn't support a
7473 site-wide default configuration and the package maintainer
7474 doesn't have time to add it may a default per-user file be
7475 placed in <file>/etc/skel</file>.
7479 <file>/etc/skel</file> should be as empty as we can make it.
7480 This is particularly true because there is no easy (or
7481 necessarily desirable) mechanism for ensuring that the
7482 appropriate dotfiles are copied into the accounts of
7483 existing users when a package is installed.
7489 <heading>Log files</heading>
7491 Log files should usually be named
7492 <file>/var/log/<var>package</var>.log</file>. If you have many
7493 log files, or need a separate directory for permission
7494 reasons (<file>/var/log</file> is writable only by
7495 <file>root</file>), you should usually create a directory named
7496 <file>/var/log/<var>package</var></file> and place your log
7501 Log files must be rotated occasionally so that they don't
7502 grow indefinitely; the best way to do this is to drop a log
7503 rotation configuration file into the directory
7504 <file>/etc/logrotate.d</file> and use the facilities provided by
7505 logrotate.<footnote>
7507 The traditional approach to log files has been to set up
7508 <em>ad hoc</em> log rotation schemes using simple shell
7509 scripts and cron. While this approach is highly
7510 customizable, it requires quite a lot of sysadmin work.
7511 Even though the original Debian system helped a little
7512 by automatically installing a system which can be used
7513 as a template, this was deemed not enough.
7517 The use of <prgn>logrotate</prgn>, a program developed
7518 by Red Hat, is better, as it centralizes log management.
7519 It has both a configuration file
7520 (<file>/etc/logrotate.conf</file>) and a directory where
7521 packages can drop their individual log rotation
7522 configurations (<file>/etc/logrotate.d</file>).
7525 Here is a good example for a logrotate config
7526 file (for more information see <manref name="logrotate"
7528 <example compact="compact">
7529 /var/log/foo/*.log {
7534 /etc/init.d/foo force-reload
7538 This rotates all files under <file>/var/log/foo</file>, saves 12
7539 compressed generations, and forces the daemon to reload its
7540 configuration information after the log rotation.
7544 Log files should be removed when the package is
7545 purged (but not when it is only removed). This should be
7546 done by the <prgn>postrm</prgn> script when it is called
7547 with the argument <tt>purge</tt> (see <ref
7548 id="removedetails">).
7553 <heading>Permissions and owners</heading>
7556 The rules in this section are guidelines for general use.
7557 If necessary you may deviate from the details below.
7558 However, if you do so you must make sure that what is done
7559 is secure and you should try to be as consistent as possible
7560 with the rest of the system. You should probably also
7561 discuss it on <prgn>debian-devel</prgn> first.
7565 Files should be owned by <tt>root:root</tt>, and made
7566 writable only by the owner and universally readable (and
7567 executable, if appropriate), that is mode 644 or 755.
7571 Directories should be mode 755 or (for group-writability)
7572 mode 2775. The ownership of the directory should be
7573 consistent with its mode: if a directory is mode 2775, it
7574 should be owned by the group that needs write access to
7577 When a package is upgraded, and the owner or permissions
7578 of a file included in the package has changed, dpkg
7579 arranges for the ownership and permissions to be
7580 correctly set upon installation. However, this does not
7581 extend to directories; the permissions and ownership of
7582 directories already on the system does not change on
7583 install or upgrade of packages. This makes sense, since
7584 otherwise common directories like <tt>/usr</tt> would
7585 always be in flux. To correctly change permissions of a
7586 directory the package owns, explicit action is required,
7587 usually in the <tt>postinst</tt> script. Care must be
7588 taken to handle downgrades as well, in that case.
7595 Setuid and setgid executables should be mode 4755 or 2755
7596 respectively, and owned by the appropriate user or group.
7597 They should not be made unreadable (modes like 4711 or
7598 2711 or even 4111); doing so achieves no extra security,
7599 because anyone can find the binary in the freely available
7600 Debian package; it is merely inconvenient. For the same
7601 reason you should not restrict read or execute permissions
7602 on non-set-id executables.
7606 Some setuid programs need to be restricted to particular
7607 sets of users, using file permissions. In this case they
7608 should be owned by the uid to which they are set-id, and by
7609 the group which should be allowed to execute them. They
7610 should have mode 4754; again there is no point in making
7611 them unreadable to those users who must not be allowed to
7616 It is possible to arrange that the system administrator can
7617 reconfigure the package to correspond to their local
7618 security policy by changing the permissions on a binary:
7619 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7620 described below.<footnote>
7621 Ordinary files installed by <prgn>dpkg</prgn> (as
7622 opposed to <tt>conffile</tt>s and other similar objects)
7623 normally have their permissions reset to the distributed
7624 permissions when the package is reinstalled. However,
7625 the use of <prgn>dpkg-statoverride</prgn> overrides this
7626 default behavior. If you use this method, you should
7627 remember to describe <prgn>dpkg-statoverride</prgn> in
7628 the package documentation; being a relatively new
7629 addition to Debian, it is probably not yet well-known.
7631 Another method you should consider is to create a group for
7632 people allowed to use the program(s) and make any setuid
7633 executables executable only by that group.
7637 If you need to create a new user or group for your package
7638 there are two possibilities. Firstly, you may need to
7639 make some files in the binary package be owned by this
7640 user or group, or you may need to compile the user or
7641 group id (rather than just the name) into the binary
7642 (though this latter should be avoided if possible, as in
7643 this case you need a statically allocated id).</p>
7646 If you need a statically allocated id, you must ask for a
7647 user or group id from the <tt>base-passwd</tt> maintainer,
7648 and must not release the package until you have been
7649 allocated one. Once you have been allocated one you must
7650 either make the package depend on a version of the
7651 <tt>base-passwd</tt> package with the id present in
7652 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7653 your package to create the user or group itself with the
7654 correct id (using <tt>adduser</tt>) in its
7655 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7656 the <prgn>postinst</prgn> is to be preferred if it is
7657 possible, otherwise a pre-dependency will be needed on the
7658 <tt>adduser</tt> package.)
7662 On the other hand, the program might be able to determine
7663 the uid or gid from the user or group name at runtime, so
7664 that a dynamically allocated id can be used. In this case
7665 you should choose an appropriate user or group name,
7666 discussing this on <prgn>debian-devel</prgn> and checking
7667 with the <package/base-passwd/ maintainer that it is unique and that
7668 they do not wish you to use a statically allocated id
7669 instead. When this has been checked you must arrange for
7670 your package to create the user or group if necessary using
7671 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7672 <prgn>postinst</prgn> script (again, the latter is to be
7673 preferred if it is possible).
7677 Note that changing the numeric value of an id associated
7678 with a name is very difficult, and involves searching the
7679 file system for all appropriate files. You need to think
7680 carefully whether a static or dynamic id is required, since
7681 changing your mind later will cause problems.
7684 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7686 This section is not intended as policy, but as a
7687 description of the use of <prgn>dpkg-statoverride</prgn>.
7691 If a system administrator wishes to have a file (or
7692 directory or other such thing) installed with owner and
7693 permissions different from those in the distributed Debian
7694 package, they can use the <prgn>dpkg-statoverride</prgn>
7695 program to instruct <prgn>dpkg</prgn> to use the different
7696 settings every time the file is installed. Thus the
7697 package maintainer should distribute the files with their
7698 normal permissions, and leave it for the system
7699 administrator to make any desired changes. For example, a
7700 daemon which is normally required to be setuid root, but
7701 in certain situations could be used without being setuid,
7702 should be installed setuid in the <tt>.deb</tt>. Then the
7703 local system administrator can change this if they wish.
7704 If there are two standard ways of doing it, the package
7705 maintainer can use <tt>debconf</tt> to find out the
7706 preference, and call <prgn>dpkg-statoverride</prgn> in the
7707 maintainer script if necessary to accommodate the system
7708 administrator's choice. Care must be taken during
7709 upgrades to not override an existing setting.
7713 Given the above, <prgn>dpkg-statoverride</prgn> is
7714 essentially a tool for system administrators and would not
7715 normally be needed in the maintainer scripts. There is
7716 one type of situation, though, where calls to
7717 <prgn>dpkg-statoverride</prgn> would be needed in the
7718 maintainer scripts, and that involves packages which use
7719 dynamically allocated user or group ids. In such a
7720 situation, something like the following idiom can be very
7721 helpful in the package's <prgn>postinst</prgn>, where
7722 <tt>sysuser</tt> is a dynamically allocated id:
7724 for i in /usr/bin/foo /usr/sbin/bar
7726 # only do something when no setting exists
7727 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7729 #include: debconf processing, question about foo and bar
7730 if [ "$RET" = "true" ] ; then
7731 dpkg-statoverride --update --add sysuser root 4755 $i
7736 The corresponding <tt>dpkg-statoverride --remove</tt>
7737 calls can then be made unconditionally when the package is
7745 <chapt id="customized-programs">
7746 <heading>Customized programs</heading>
7748 <sect id="arch-spec">
7749 <heading>Architecture specification strings</heading>
7752 If a program needs to specify an <em>architecture specification
7753 string</em> in some place, it should select one of the
7754 strings provided by <tt>dpkg-architecture -L</tt>. The
7755 strings are in the format
7756 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7757 is sometimes elided, as when the OS is Linux.<footnote>
7758 <p>Currently, the strings are:
7759 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7760 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7761 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7762 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7763 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7764 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7765 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7766 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7767 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7768 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7769 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7770 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7771 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7772 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7773 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7774 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7775 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7776 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7777 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7778 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7779 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7780 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7781 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7782 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7783 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7784 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7785 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7786 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7787 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7788 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7789 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7790 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7791 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7792 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7793 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7794 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7795 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7801 Note that we don't want to use
7802 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7803 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7804 since this would make our programs incompatible with other
7805 Linux distributions. We also don't use something like
7806 <tt><var>arch</var>-unknown-linux</tt>, since the
7807 <tt>unknown</tt> does not look very good.
7812 <heading>Daemons</heading>
7815 The configuration files <file>/etc/services</file>,
7816 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7817 by the <prgn>netbase</prgn> package and must not be modified
7822 If a package requires a new entry in one of these files, the
7823 maintainer should get in contact with the
7824 <prgn>netbase</prgn> maintainer, who will add the entries
7825 and release a new version of the <prgn>netbase</prgn>
7830 The configuration file <file>/etc/inetd.conf</file> must not be
7831 modified by the package's scripts except via the
7832 <prgn>update-inetd</prgn> script or the
7833 <file>DebianNet.pm</file> Perl module. See their documentation
7834 for details on how to add entries.
7838 If a package wants to install an example entry into
7839 <file>/etc/inetd.conf</file>, the entry must be preceded with
7840 exactly one hash character (<tt>#</tt>). Such lines are
7841 treated as "commented out by user" by the
7842 <prgn>update-inetd</prgn> script and are not changed or
7843 activated during package updates.
7848 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7852 Some programs need to create pseudo-ttys. This should be done
7853 using Unix98 ptys if the C library supports it. The resulting
7854 program must not be installed setuid root, unless that
7855 is required for other functionality.
7859 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7860 <file>/var/log/lastlog</file> must be installed writable by
7861 group <tt>utmp</tt>. Programs which need to modify those
7862 files must be installed setgid <tt>utmp</tt>.
7867 <heading>Editors and pagers</heading>
7870 Some programs have the ability to launch an editor or pager
7871 program to edit or display a text document. Since there are
7872 lots of different editors and pagers available in the Debian
7873 distribution, the system administrator and each user should
7874 have the possibility to choose their preferred editor and
7879 In addition, every program should choose a good default
7880 editor/pager if none is selected by the user or system
7885 Thus, every program that launches an editor or pager must
7886 use the EDITOR or PAGER environment variable to determine
7887 the editor or pager the user wishes to use. If these
7888 variables are not set, the programs <file>/usr/bin/editor</file>
7889 and <file>/usr/bin/pager</file> should be used, respectively.
7893 These two files are managed through the <prgn>dpkg</prgn>
7894 "alternatives" mechanism. Thus every package providing an
7895 editor or pager must call the
7896 <prgn>update-alternatives</prgn> script to register these
7901 If it is very hard to adapt a program to make use of the
7902 EDITOR or PAGER variables, that program may be configured to
7903 use <file>/usr/bin/sensible-editor</file> and
7904 <file>/usr/bin/sensible-pager</file> as the editor or pager
7905 program respectively. These are two scripts provided in the
7906 Debian base system that check the EDITOR and PAGER variables
7907 and launch the appropriate program, and fall back to
7908 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7909 variable is not set.
7913 A program may also use the VISUAL environment variable to
7914 determine the user's choice of editor. If it exists, it
7915 should take precedence over EDITOR. This is in fact what
7916 <file>/usr/bin/sensible-editor</file> does.
7920 It is not required for a package to depend on
7921 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7922 package to provide such virtual packages.<footnote>
7923 The Debian base system already provides an editor and a
7929 <sect id="web-appl">
7930 <heading>Web servers and applications</heading>
7933 This section describes the locations and URLs that should
7934 be used by all web servers and web applications in the
7941 Cgi-bin executable files are installed in the
7943 <example compact="compact">
7944 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7946 and should be referred to as
7947 <example compact="compact">
7948 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7954 <p>Access to HTML documents</p>
7957 HTML documents for a package are stored in
7958 <file>/usr/share/doc/<var>package</var></file>
7959 and can be referred to as
7960 <example compact="compact">
7961 http://localhost/doc/<var>package</var>/<var>filename</var>
7966 The web server should restrict access to the document
7967 tree so that only clients on the same host can read
7968 the documents. If the web server does not support such
7969 access controls, then it should not provide access at
7970 all, or ask about providing access during installation.
7975 <p>Access to images</p>
7977 It is recommended that images for a package be stored
7978 in <tt>/usr/share/images/<var>package</var></tt> and
7979 may be referred to through an alias <tt>/images/</tt>
7982 http://localhost/images/<package>/<filename>
7989 <p>Web Document Root</p>
7992 Web Applications should try to avoid storing files in
7993 the Web Document Root. Instead they should use the
7994 /usr/share/doc/<var>package</var> directory for
7995 documents and register the Web Application via the
7996 <package>doc-base</package> package. If access to the
7997 web document root is unavoidable then use
7998 <example compact="compact">
8001 as the Document Root. This might be just a symbolic
8002 link to the location where the system administrator
8003 has put the real document root.
8006 <item><p>Providing httpd and/or httpd-cgi</p>
8008 All web servers should provide the virtual package
8009 <tt>httpd</tt>. If a web server has CGI support it should
8010 provide <tt>httpd-cgi</tt> additionally.
8013 All web applications which do not contain CGI scripts should
8014 depend on <tt>httpd</tt>, all those web applications which
8015 <tt>do</tt> contain CGI scripts, should depend on
8023 <sect id="mail-transport-agents">
8024 <heading>Mail transport, delivery and user agents</heading>
8027 Debian packages which process electronic mail, whether mail
8028 user agents (MUAs) or mail transport agents (MTAs), must
8029 ensure that they are compatible with the configuration
8030 decisions below. Failure to do this may result in lost
8031 mail, broken <tt>From:</tt> lines, and other serious brain
8036 The mail spool is <file>/var/mail</file> and the interface to
8037 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8038 the FHS). On older systems, the mail spool may be
8039 physically located in <file>/var/spool/mail</file>, but all
8040 access to the mail spool should be via the
8041 <file>/var/mail</file> symlink. The mail spool is part of the
8042 base system and not part of the MTA package.
8046 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8047 programs (such as IMAP daemons) must lock the mailbox in an
8048 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8049 be combined with dot locking. To avoid deadlocks, a program
8050 should use <tt>fcntl()</tt> first and dot locking after
8051 this, or alternatively implement the two locking methods in
8052 a non blocking way<footnote>
8053 If it is not possible to establish both locks, the
8054 system shouldn't wait for the second lock to be
8055 established, but remove the first lock, wait a (random)
8056 time, and start over locking again.
8057 </footnote>. Using the functions <tt>maillock</tt> and
8058 <tt>mailunlock</tt> provided by the
8059 <tt>liblockfile*</tt><footnote>
8060 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8061 to use these functions.
8062 </footnote> packages is the recommended way to realize this.
8066 Mailboxes are generally either mode 600 and owned by
8067 <var>user</var> or mode 660 and owned by
8068 <tt><var>user</var>:mail</tt><footnote>
8069 There are two traditional permission schemes for mail spools:
8070 mode 600 with all mail delivery done by processes running as
8071 the destination user, or mode 660 and owned by group mail with
8072 mail delivery done by a process running as a system user in
8073 group mail. Historically, Debian required mode 660 mail
8074 spools to enable the latter model, but that model has become
8075 increasingly uncommon and the principle of least privilege
8076 indicates that mail systems that use the first model should
8077 use permissions of 600. If delivery to programs is permitted,
8078 it's easier to keep the mail system secure if the delivery
8079 agent runs as the destination user. Debian Policy therefore
8080 permits either scheme.
8081 </footnote>. The local system administrator may choose a
8082 different permission scheme; packages should not make
8083 assumptions about the permission and ownership of mailboxes
8084 unless required (such as when creating a new mailbox). A MUA
8085 may remove a mailbox (unless it has nonstandard permissions) in
8086 which case the MTA or another MUA must recreate it if needed.
8090 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8091 be setgid mail to do the locking mentioned above (and
8092 must obviously avoid accessing other users' mailboxes
8093 using this privilege).</p>
8096 <file>/etc/aliases</file> is the source file for the system mail
8097 aliases (e.g., postmaster, usenet, etc.), it is the one
8098 which the sysadmin and <prgn>postinst</prgn> scripts may
8099 edit. After <file>/etc/aliases</file> is edited the program or
8100 human editing it must call <prgn>newaliases</prgn>. All MTA
8101 packages must come with a <prgn>newaliases</prgn> program,
8102 even if it does nothing, but older MTA packages did not do
8103 this so programs should not fail if <prgn>newaliases</prgn>
8104 cannot be found. Note that because of this, all MTA
8105 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8106 <tt>Replaces: mail-transport-agent</tt> control file
8111 The convention of writing <tt>forward to
8112 <var>address</var></tt> in the mailbox itself is not
8113 supported. Use a <tt>.forward</tt> file instead.</p>
8116 The <prgn>rmail</prgn> program used by UUCP
8117 for incoming mail should be <file>/usr/sbin/rmail</file>.
8118 Likewise, <prgn>rsmtp</prgn>, for receiving
8119 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8123 If your package needs to know what hostname to use on (for
8124 example) outgoing news and mail messages which are generated
8125 locally, you should use the file <file>/etc/mailname</file>. It
8126 will contain the portion after the username and <tt>@</tt>
8127 (at) sign for email addresses of users on the machine
8128 (followed by a newline).
8132 Such a package should check for the existence of this file
8133 when it is being configured. If it exists, it should be
8134 used without comment, although an MTA's configuration script
8135 may wish to prompt the user even if it finds that this file
8136 exists. If the file does not exist, the package should
8137 prompt the user for the value (preferably using
8138 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8139 as well as using it in the package's configuration. The
8140 prompt should make it clear that the name will not just be
8141 used by that package. For example, in this situation the
8142 <tt>inn</tt> package could say something like:
8143 <example compact="compact">
8144 Please enter the "mail name" of your system. This is the
8145 hostname portion of the address to be shown on outgoing
8146 news and mail messages. The default is
8147 <var>syshostname</var>, your system's host name. Mail
8148 name ["<var>syshostname</var>"]:
8150 where <var>syshostname</var> is the output of <tt>hostname
8156 <heading>News system configuration</heading>
8159 All the configuration files related to the NNTP (news)
8160 servers and clients should be located under
8161 <file>/etc/news</file>.</p>
8164 There are some configuration issues that apply to a number
8165 of news clients and server packages on the machine. These
8169 <tag><file>/etc/news/organization</file></tag>
8171 A string which should appear as the
8172 organization header for all messages posted
8173 by NNTP clients on the machine
8176 <tag><file>/etc/news/server</file></tag>
8178 Contains the FQDN of the upstream NNTP
8179 server, or localhost if the local machine is
8184 Other global files may be added as required for cross-package news
8191 <heading>Programs for the X Window System</heading>
8194 <heading>Providing X support and package priorities</heading>
8197 Programs that can be configured with support for the X
8198 Window System must be configured to do so and must declare
8199 any package dependencies necessary to satisfy their
8200 runtime requirements when using the X Window System. If
8201 such a package is of higher priority than the X packages
8202 on which it depends, it is required that either the
8203 X-specific components be split into a separate package, or
8204 that an alternative version of the package, which includes
8205 X support, be provided, or that the package's priority be
8211 <heading>Packages providing an X server</heading>
8214 Packages that provide an X server that, directly or
8215 indirectly, communicates with real input and display
8216 hardware should declare in their control data that they
8217 provide the virtual package <tt>xserver</tt>.<footnote>
8218 This implements current practice, and provides an
8219 actual policy for usage of the <tt>xserver</tt>
8220 virtual package which appears in the virtual packages
8221 list. In a nutshell, X servers that interface
8222 directly with the display and input hardware or via
8223 another subsystem (e.g., GGI) should provide
8224 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8225 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8231 <heading>Packages providing a terminal emulator</heading>
8234 Packages that provide a terminal emulator for the X Window
8235 System which meet the criteria listed below should declare
8236 in their control data that they provide the virtual
8237 package <tt>x-terminal-emulator</tt>. They should also
8238 register themselves as an alternative for
8239 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8244 To be an <tt>x-terminal-emulator</tt>, a program must:
8245 <list compact="compact">
8247 Be able to emulate a DEC VT100 terminal, or a
8248 compatible terminal.
8252 Support the command-line option <tt>-e
8253 <var>command</var></tt>, which creates a new
8254 terminal window<footnote>
8255 "New terminal window" does not necessarily mean
8256 a new top-level X window directly parented by
8257 the window manager; it could, if the terminal
8258 emulator application were so coded, be a new
8259 "view" in a multiple-document interface (MDI).
8261 and runs the specified <var>command</var>,
8262 interpreting the entirety of the rest of the command
8263 line as a command to pass straight to exec, in the
8264 manner that <tt>xterm</tt> does.
8268 Support the command-line option <tt>-T
8269 <var>title</var></tt>, which creates a new terminal
8270 window with the window title <var>title</var>.
8277 <heading>Packages providing a window manager</heading>
8280 Packages that provide a window manager should declare in
8281 their control data that they provide the virtual package
8282 <tt>x-window-manager</tt>. They should also register
8283 themselves as an alternative for
8284 <file>/usr/bin/x-window-manager</file>, with a priority
8285 calculated as follows:
8286 <list compact="compact">
8288 Start with a priority of 20.
8292 If the window manager supports the Debian menu
8293 system, add 20 points if this support is available
8294 in the package's default configuration (i.e., no
8295 configuration files belonging to the system or user
8296 have to be edited to activate the feature); if
8297 configuration files must be modified, add only 10
8303 If the window manager complies with <url
8304 id="http://www.freedesktop.org/Standards/wm-spec"
8305 name="The Window Manager Specification Project">,
8306 written by the <url id="http://www.freedesktop.org/"
8307 name="Free Desktop Group">, add 40 points.
8311 If the window manager permits the X session to be
8312 restarted using a <em>different</em> window manager
8313 (without killing the X server) in its default
8314 configuration, add 10 points; otherwise add none.
8321 <heading>Packages providing fonts</heading>
8324 Packages that provide fonts for the X Window
8326 For the purposes of Debian Policy, a "font for the X
8327 Window System" is one which is accessed via X protocol
8328 requests. Fonts for the Linux console, for PostScript
8329 renderer, or any other purpose, do not fit this
8330 definition. Any tool which makes such fonts available
8331 to the X Window System, however, must abide by this
8334 must do a number of things to ensure that they are both
8335 available without modification of the X or font server
8336 configuration, and that they do not corrupt files used by
8337 other font packages to register information about
8341 Fonts of any type supported by the X Window System
8342 must be in a separate binary package from any
8343 executables, libraries, or documentation (except
8344 that specific to the fonts shipped, such as their
8345 license information). If one or more of the fonts
8346 so packaged are necessary for proper operation of
8347 the package with which they are associated the font
8348 package may be Recommended; if the fonts merely
8349 provide an enhancement, a Suggests relationship may
8350 be used. Packages must not Depend on font
8352 This is because the X server may retrieve fonts
8353 from the local file system or over the network
8354 from an X font server; the Debian package system
8355 is empowered to deal only with the local
8361 BDF fonts must be converted to PCF fonts with the
8362 <prgn>bdftopcf</prgn> utility (available in the
8363 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8364 placed in a directory that corresponds to their
8366 <list compact="compact">
8368 100 dpi fonts must be placed in
8369 <file>/usr/share/fonts/X11/100dpi/</file>.
8373 75 dpi fonts must be placed in
8374 <file>/usr/share/fonts/X11/75dpi/</file>.
8378 Character-cell fonts, cursor fonts, and other
8379 low-resolution fonts must be placed in
8380 <file>/usr/share/fonts/X11/misc/</file>.
8386 Speedo fonts must be placed in
8387 <file>/usr/share/fonts/X11/Speedo/</file>.
8391 Type 1 fonts must be placed in
8392 <file>/usr/share/fonts/X11/Type1/</file>. If font
8393 metric files are available, they must be placed here
8398 Subdirectories of <file>/usr/share/fonts/X11/</file>
8399 other than those listed above must be neither
8400 created nor used. (The <file>PEX</file>, <file>CID</file>,
8401 and <file>cyrillic</file> directories are excepted for
8402 historical reasons, but installation of files into
8403 these directories remains discouraged.)
8407 Font packages may, instead of placing files directly
8408 in the X font directories listed above, provide
8409 symbolic links in that font directory pointing to
8410 the files' actual location in the filesystem. Such
8411 a location must comply with the FHS.
8415 Font packages should not contain both 75dpi and
8416 100dpi versions of a font. If both are available,
8417 they should be provided in separate binary packages
8418 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8419 the names of the packages containing the
8420 corresponding fonts.
8424 Fonts destined for the <file>misc</file> subdirectory
8425 should not be included in the same package as 75dpi
8426 or 100dpi fonts; instead, they should be provided in
8427 a separate package with <tt>-misc</tt> appended to
8432 Font packages must not provide the files
8433 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8434 <file>fonts.scale</file> in a font directory:
8437 <file>fonts.dir</file> files must not be provided at all.
8441 <file>fonts.alias</file> and <file>fonts.scale</file>
8442 files, if needed, should be provided in the
8444 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8445 where <var>fontdir</var> is the name of the
8447 <file>/usr/share/fonts/X11/</file> where the
8448 package's corresponding fonts are stored
8449 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8450 <var>package</var> is the name of the package
8451 that provides these fonts, and
8452 <var>extension</var> is either <tt>scale</tt>
8453 or <tt>alias</tt>, whichever corresponds to
8460 Font packages must declare a dependency on
8461 <tt>xfonts-utils</tt> in their control
8466 Font packages that provide one or more
8467 <file>fonts.scale</file> files as described above must
8468 invoke <prgn>update-fonts-scale</prgn> on each
8469 directory into which they installed fonts
8470 <em>before</em> invoking
8471 <prgn>update-fonts-dir</prgn> on that directory.
8472 This invocation must occur in both the
8473 <prgn>postinst</prgn> (for all arguments) and
8474 <prgn>postrm</prgn> (for all arguments except
8475 <tt>upgrade</tt>) scripts.
8479 Font packages that provide one or more
8480 <file>fonts.alias</file> files as described above must
8481 invoke <prgn>update-fonts-alias</prgn> on each
8482 directory into which they installed fonts. This
8483 invocation must occur in both the
8484 <prgn>postinst</prgn> (for all arguments) and
8485 <prgn>postrm</prgn> (for all arguments except
8486 <tt>upgrade</tt>) scripts.
8490 Font packages must invoke
8491 <prgn>update-fonts-dir</prgn> on each directory into
8492 which they installed fonts. This invocation must
8493 occur in both the <prgn>postinst</prgn> (for all
8494 arguments) and <prgn>postrm</prgn> (for all
8495 arguments except <tt>upgrade</tt>) scripts.
8499 Font packages must not provide alias names for the
8500 fonts they include which collide with alias names
8501 already in use by fonts already packaged.
8505 Font packages must not provide fonts with the same
8506 XLFD registry name as another font already packaged.
8513 <heading>Application defaults files</heading>
8516 Application defaults files must be installed in the
8517 directory <file>/etc/X11/app-defaults/</file> (use of a
8518 localized subdirectory of <file>/etc/X11/</file> as described
8519 in the <em>X Toolkit Intrinsics - C Language
8520 Interface</em> manual is also permitted). They must be
8521 registered as <tt>conffile</tt>s or handled as
8522 configuration files.
8526 Customization of programs' X resources may also be
8527 supported with the provision of a file with the same name
8528 as that of the package placed in the
8529 <file>/etc/X11/Xresources/</file> directory, which must
8530 registered as a <tt>conffile</tt> or handled as a
8531 configuration file.<footnote>
8532 Note that this mechanism is not the same as using
8533 app-defaults; app-defaults are tied to the client
8534 binary on the local file system, whereas X resources
8535 are stored in the X server and affect all connecting
8542 <heading>Installation directory issues</heading>
8545 Packages using the X Window System should not be
8546 configured to install files under the
8547 <file>/usr/X11R6/</file> directory. The
8548 <file>/usr/X11R6/</file> directory hierarchy should be
8549 regarded as obsolete.
8553 Programs that use GNU <prgn>autoconf</prgn> and
8554 <prgn>automake</prgn> are usually easily configured at
8555 compile time to use <file>/usr/</file> instead of
8556 <file>/usr/X11R6/</file>, and this should be done whenever
8557 possible. Configuration files for window managers and
8558 display managers should be placed in a subdirectory of
8559 <file>/etc/X11/</file> corresponding to the package name due
8560 to these programs' tight integration with the mechanisms
8561 of the X Window System. Application-level programs should
8562 use the <file>/etc/</file> directory unless otherwise mandated
8567 The installation of files into subdirectories
8568 of <file>/usr/X11R6/include/X11/</file> and
8569 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8570 package maintainers should determine if subdirectories of
8571 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8576 Packages should install any relevant files into the
8577 directories <file>/usr/include/X11/</file> and
8578 <file>/usr/lib/X11/</file>, but if they do so, they must
8579 pre-depend on <tt>x11-common (>=
8580 1:7.0.0)</tt><footnote>
8582 These libraries used to be all symbolic
8583 links. However, with <tt>X11R7</tt>,
8584 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8585 are now real directories, and packages
8586 <strong>should</strong> ship their files here instead
8587 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8588 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8589 responsible for converting these symlinks into
8597 <heading>The OSF/Motif and OpenMotif libraries</heading>
8600 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8601 OpenMotif libraries</em><footnote>
8602 OSF/Motif and OpenMotif are collectively referred to as
8603 "Motif" in this policy document.
8605 should be compiled against and tested with LessTif (a free
8606 re-implementation of Motif) instead. If the maintainer
8607 judges that the program or programs do not work
8608 sufficiently well with LessTif to be distributed and
8609 supported, but do so when compiled against Motif, then two
8610 versions of the package should be created; one linked
8611 statically against Motif and with <tt>-smotif</tt>
8612 appended to the package name, and one linked dynamically
8613 against Motif and with <tt>-dmotif</tt> appended to the
8618 Both Motif-linked versions are dependent
8619 upon non-DFSG-compliant software and thus cannot be
8620 uploaded to the <em>main</em> distribution; if the
8621 software is itself DFSG-compliant it may be uploaded to
8622 the <em>contrib</em> distribution. While known existing
8623 versions of Motif permit unlimited redistribution of
8624 binaries linked against the library (whether statically or
8625 dynamically), it is the package maintainer's
8626 responsibility to determine whether this is permitted by
8627 the license of the copy of Motif in their possession.
8633 <heading>Perl programs and modules</heading>
8636 Perl programs and modules should follow the current Perl policy.
8640 The Perl policy can be found in the <tt>perl-policy</tt>
8641 files in the <tt>debian-policy</tt> package.
8642 It is also available from the Debian web mirrors at
8643 <tt><url name="/doc/packaging-manuals/perl-policy/"
8644 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8649 <heading>Emacs lisp programs</heading>
8652 Please refer to the "Debian Emacs Policy" for details of how to
8653 package emacs lisp programs.
8657 The Emacs policy is available in
8658 <file>debian-emacs-policy.gz</file> of the
8659 <package>emacsen-common</package> package.
8660 It is also available from the Debian web mirrors at
8661 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8662 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8667 <heading>Games</heading>
8670 The permissions on <file>/var/games</file> are mode 755, owner
8671 <tt>root</tt> and group <tt>root</tt>.
8675 Each game decides on its own security policy.</p>
8678 Games which require protected, privileged access to
8679 high-score files, saved games, etc., may be made
8680 set-<em>group</em>-id (mode 2755) and owned by
8681 <tt>root:games</tt>, and use files and directories with
8682 appropriate permissions (770 <tt>root:games</tt>, for
8683 example). They must not be made
8684 set-<em>user</em>-id, as this causes security problems. (If
8685 an attacker can subvert any set-user-id game they can
8686 overwrite the executable of any other, causing other players
8687 of these games to run a Trojan horse program. With a
8688 set-group-id game the attacker only gets access to less
8689 important game data, and if they can get at the other
8690 players' accounts at all it will take considerably more
8694 Some packages, for example some fortune cookie programs, are
8695 configured by the upstream authors to install with their
8696 data files or other static information made unreadable so
8697 that they can only be accessed through set-id programs
8698 provided. You should not do this in a Debian package: anyone can
8699 download the <file>.deb</file> file and read the data from it,
8700 so there is no point making the files unreadable. Not
8701 making the files unreadable also means that you don't have
8702 to make so many programs set-id, which reduces the risk of a
8706 As described in the FHS, binaries of games should be
8707 installed in the directory <file>/usr/games</file>. This also
8708 applies to games that use the X Window System. Manual pages
8709 for games (X and non-X games) should be installed in
8710 <file>/usr/share/man/man6</file>.</p>
8716 <heading>Documentation</heading>
8719 <heading>Manual pages</heading>
8722 You should install manual pages in <prgn>nroff</prgn> source
8723 form, in appropriate places under <file>/usr/share/man</file>.
8724 You should only use sections 1 to 9 (see the FHS for more
8725 details). You must not install a pre-formatted "cat page".
8729 Each program, utility, and function should have an
8730 associated manual page included in the same package. It is
8731 suggested that all configuration files also have a manual
8732 page included as well. Manual pages for protocols and other
8733 auxiliary things are optional.
8737 If no manual page is available, this is considered as a bug
8738 and should be reported to the Debian Bug Tracking System (the
8739 maintainer of the package is allowed to write this bug report
8740 themselves, if they so desire). Do not close the bug report
8741 until a proper man page is available.<footnote>
8742 It is not very hard to write a man page. See the
8743 <url id="http://www.schweikhardt.net/man_page_howto.html"
8744 name="Man-Page-HOWTO">,
8745 <manref name="man" section="7">, the examples
8746 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8747 the helper programs <prgn>help2man</prgn>, or the
8748 directory <file>/usr/share/doc/man-db/examples</file>.
8753 You may forward a complaint about a missing man page to the
8754 upstream authors, and mark the bug as forwarded in the
8755 Debian bug tracking system. Even though the GNU Project do
8756 not in general consider the lack of a man page to be a bug,
8757 we do; if they tell you that they don't consider it a bug
8758 you should leave the bug in our bug tracking system open
8763 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8767 If one man page needs to be accessible via several names it
8768 is better to use a symbolic link than the <file>.so</file>
8769 feature, but there is no need to fiddle with the relevant
8770 parts of the upstream source to change from <file>.so</file> to
8771 symlinks: don't do it unless it's easy. You should not
8772 create hard links in the manual page directories, nor put
8773 absolute filenames in <file>.so</file> directives. The filename
8774 in a <file>.so</file> in a man page should be relative to the
8775 base of the man page tree (usually
8776 <file>/usr/share/man</file>). If you do not create any links
8777 (whether symlinks, hard links, or <tt>.so</tt> directives)
8778 in the file system to the alternate names of the man page,
8779 then you should not rely on <prgn>man</prgn> finding your
8780 man page under those names based solely on the information in
8781 the man page's header.<footnote>
8782 Supporting this in <prgn>man</prgn> often requires
8783 unreasonable processing time to find a manual page or to
8784 report that none exists, and moves knowledge into man's
8785 database that would be better left in the file system.
8786 This support is therefore deprecated and will cease to
8787 be present in the future.
8792 Manual pages in locale-specific subdirectories of
8793 <file>/usr/share/man</file> should use either UTF-8 or the usual
8794 legacy encoding for that language (normally the one corresponding
8795 to the shortest relevant locale name in
8796 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8797 <file>/usr/share/man/fr</file> should use either UTF-8 or
8798 ISO-8859-1.<footnote>
8799 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8800 use. In future, all manual pages will be required to use
8806 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8807 included in the subdirectory name unless it indicates a
8808 significant difference in the language, as this excludes
8809 speakers of the language in other countries.<footnote>
8810 At the time of writing, Chinese and Portuguese are the main
8811 languages with such differences, so <file>pt_BR</file>,
8812 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8817 Due to limitations in current implementations, all characters
8818 in the manual page source should be representable in the usual
8819 legacy encoding for that language, even if the file is
8820 actually encoded in UTF-8. Safe alternative ways to write many
8821 characters outside that range may be found in
8822 <manref name="groff_char" section="7">.
8827 <heading>Info documents</heading>
8830 Info documents should be installed in <file>/usr/share/info</file>.
8831 They should be compressed with <tt>gzip -9</tt>.
8835 Your package should call <prgn>install-info</prgn> to update
8836 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8837 script when called with a <tt>configure</tt> argument, for
8839 <example compact="compact">
8840 install-info --quiet --section Development Development \
8841 /usr/share/info/foobar.info
8845 It is a good idea to specify a section for the location of
8846 your program; this is done with the <tt>--section</tt>
8847 switch. To determine which section to use, you should look
8848 at <file>/usr/share/info/dir</file> on your system and choose the most
8849 relevant (or create a new section if none of the current
8850 sections are relevant). Note that the <tt>--section</tt>
8851 flag takes two arguments; the first is a regular expression
8852 to match (case-insensitively) against an existing section,
8853 the second is used when creating a new one.</p>
8856 You should remove the entries in the <prgn>prerm</prgn>
8857 script when called with a <tt>remove</tt> argument:
8858 <example compact="compact">
8859 install-info --quiet --remove /usr/share/info/foobar.info
8863 If <prgn>install-info</prgn> cannot find a description entry
8864 in the Info file you must supply one. See <manref
8865 name="install-info" section="8"> for details.</p>
8869 <heading>Additional documentation</heading>
8872 Any additional documentation that comes with the package may
8873 be installed at the discretion of the package maintainer.
8874 Plain text documentation should be installed in the directory
8875 <file>/usr/share/doc/<var>package</var></file>, where
8876 <var>package</var> is the name of the package, and
8877 compressed with <tt>gzip -9</tt> unless it is small.
8881 If a package comes with large amounts of documentation which
8882 many users of the package will not require you should create
8883 a separate binary package to contain it, so that it does not
8884 take up disk space on the machines of users who do not need
8885 or want it installed.</p>
8888 It is often a good idea to put text information files
8889 (<file>README</file>s, changelogs, and so forth) that come with
8890 the source package in <file>/usr/share/doc/<var>package</var></file>
8891 in the binary package. However, you don't need to install
8892 the instructions for building and installing the package, of
8896 Packages must not require the existence of any files in
8897 <file>/usr/share/doc/</file> in order to function
8899 The system administrator should be able to
8900 delete files in <file>/usr/share/doc/</file> without causing
8901 any programs to break.
8903 Any files that are referenced by programs but are also
8904 useful as stand alone documentation should be installed under
8905 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8906 <file>/usr/share/doc/<var>package</var></file>.
8910 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8911 link to another directory in <file>/usr/share/doc</file> only if
8912 the two packages both come from the same source and the
8913 first package Depends on the second.<footnote>
8915 Please note that this does not override the section on
8916 changelog files below, so the file
8917 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8918 must refer to the changelog for the current version of
8919 <var>package</var> in question. In practice, this means
8920 that the sources of the target and the destination of the
8921 symlink must be the same (same source package and
8928 Former Debian releases placed all additional documentation
8929 in <file>/usr/doc/<var>package</var></file>. This has been
8930 changed to <file>/usr/share/doc/<var>package</var></file>,
8931 and packages must not put documentation in the directory
8932 <file>/usr/doc/<var>package</var></file>. <footnote>
8933 At this phase of the transition, we no longer require a
8934 symbolic link in <file>/usr/doc/</file>. At a later point,
8935 policy shall change to make the symbolic links a bug.
8941 <heading>Preferred documentation formats</heading>
8944 The unification of Debian documentation is being carried out
8948 If your package comes with extensive documentation in a
8949 markup format that can be converted to various other formats
8950 you should if possible ship HTML versions in a binary
8951 package, in the directory
8952 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8953 its subdirectories.<footnote>
8954 The rationale: The important thing here is that HTML
8955 docs should be available in <em>some</em> package, not
8956 necessarily in the main binary package.
8961 Other formats such as PostScript may be provided at the
8962 package maintainer's discretion.
8966 <sect id="copyrightfile">
8967 <heading>Copyright information</heading>
8970 Every package must be accompanied by a verbatim copy of its
8971 copyright and distribution license in the file
8972 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8973 file must neither be compressed nor be a symbolic link.
8977 In addition, the copyright file must say where the upstream
8978 sources (if any) were obtained. It should name the original
8979 authors of the package and the Debian maintainer(s) who were
8980 involved with its creation.
8984 Packages in the <em>contrib</em> or <em>non-free</em> categories
8985 should state in the copyright file that the package is not part
8986 of the Debian GNU/Linux distribution and briefly explain why.
8990 A copy of the file which will be installed in
8991 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8992 be in <file>debian/copyright</file> in the source package.
8996 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8997 link to another directory in <file>/usr/share/doc</file> only if
8998 the two packages both come from the same source and the
8999 first package Depends on the second. These rules are
9000 important because copyrights must be extractable by
9005 Packages distributed under the UCB BSD license, the Apache
9006 license (version 2.0), the Artistic license, the GNU GPL
9007 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
9008 the GNU FDL (version 1.2) should refer to the corresponding
9009 files under <file>/usr/share/common-licenses</file>,<footnote>
9012 <file>/usr/share/common-licenses/BSD</file>,
9013 <file>/usr/share/common-licenses/Apache-2.0</file>,
9014 <file>/usr/share/common-licenses/Artistic</file>,
9015 <file>/usr/share/common-licenses/GPL-2</file>,
9016 <file>/usr/share/common-licenses/GPL-3</file>,
9017 <file>/usr/share/common-licenses/LGPL-2</file>,
9018 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9019 <file>/usr/share/common-licenses/LGPL-3</file>, and
9020 <file>/usr/share/common-licenses/GFDL-1.2</file>
9023 </footnote> rather than quoting them in the copyright
9028 You should not use the copyright file as a general <file>README</file>
9029 file. If your package has such a file it should be
9030 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9031 <file>README.Debian</file> or some other appropriate place.</p>
9035 <heading>Examples</heading>
9038 Any examples (configurations, source files, whatever),
9039 should be installed in a directory
9040 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9041 files should not be referenced by any program: they're there
9042 for the benefit of the system administrator and users as
9043 documentation only. Architecture-specific example files
9044 should be installed in a directory
9045 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9047 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9048 latter directory itself may be a symbolic link to the
9053 If the purpose of a package is to provide examples, then the
9054 example files may be installed into
9055 <file>/usr/share/doc/<var>package</var></file>.
9059 <sect id="changelogs">
9060 <heading>Changelog files</heading>
9063 Packages that are not Debian-native must contain a
9064 compressed copy of the <file>debian/changelog</file> file from
9065 the Debian source tree in
9066 <file>/usr/share/doc/<var>package</var></file> with the name
9067 <file>changelog.Debian.gz</file>.
9071 If an upstream changelog is available, it should be accessible as
9072 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9073 plain text. If the upstream changelog is distributed in
9074 HTML, it should be made available in that form as
9075 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9076 and a plain text <file>changelog.gz</file> should be generated
9077 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9078 the upstream changelog files do not already conform to this
9079 naming convention, then this may be achieved either by
9080 renaming the files, or by adding a symbolic link, at the
9081 maintainer's discretion.<footnote>
9082 Rationale: People should not have to look in places for
9083 upstream changelogs merely because they are given
9084 different names or are distributed in HTML format.
9089 All of these files should be installed compressed using
9090 <tt>gzip -9</tt>, as they will become large with time even
9091 if they start out small.
9095 If the package has only one changelog which is used both as
9096 the Debian changelog and the upstream one because there is
9097 no separate upstream maintainer then that changelog should
9098 usually be installed as
9099 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9100 there is a separate upstream maintainer, but no upstream
9101 changelog, then the Debian changelog should still be called
9102 <file>changelog.Debian.gz</file>.
9106 For details about the format and contents of the Debian
9107 changelog file, please see <ref id="dpkgchangelog">.
9112 <appendix id="pkg-scope">
9113 <heading>Introduction and scope of these appendices</heading>
9116 These appendices are taken essentially verbatim from the
9117 now-deprecated Packaging Manual, version 3.2.1.0. They are
9118 the chapters which are likely to be of use to package
9119 maintainers and which have not already been included in the
9120 policy document itself. Most of these sections are very likely
9121 not relevant to policy; they should be treated as
9122 documentation for the packaging system. Please note that these
9123 appendices are included for convenience, and for historical
9124 reasons: they used to be part of policy package, and they have
9125 not yet been incorporated into dpkg documentation. However,
9126 they still have value, and hence they are presented here.
9130 They have not yet been checked to ensure that they are
9131 compatible with the contents of policy, and if there are any
9132 contradictions, the version in the main policy document takes
9133 precedence. The remaining chapters of the old Packaging
9134 Manual have also not been read in detail to ensure that there
9135 are not parts which have been left out. Both of these will be
9140 Certain parts of the Packaging manual were integrated into the
9141 Policy Manual proper, and removed from the appendices. Links
9142 have been placed from the old locations to the new ones.
9146 <prgn>dpkg</prgn> is a suite of programs for creating binary
9147 package files and installing and removing them on Unix
9149 <prgn>dpkg</prgn> is targeted primarily at Debian
9150 GNU/Linux, but may work on or be ported to other
9156 The binary packages are designed for the management of
9157 installed executable programs (usually compiled binaries) and
9158 their associated data, though source code examples and
9159 documentation are provided as part of some packages.</p>
9162 This manual describes the technical aspects of creating Debian
9163 binary packages (<file>.deb</file> files). It documents the
9164 behavior of the package management programs
9165 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9166 they interact with packages.</p>
9169 It also documents the interaction between
9170 <prgn>dselect</prgn>'s core and the access method scripts it
9171 uses to actually install the selected packages, and describes
9172 how to create a new access method.</p>
9175 This manual does not go into detail about the options and
9176 usage of the package building and installation tools. It
9177 should therefore be read in conjunction with those programs'
9182 The utility programs which are provided with <prgn>dpkg</prgn>
9183 for managing various system configuration and similar issues,
9184 such as <prgn>update-rc.d</prgn> and
9185 <prgn>install-info</prgn>, are not described in detail here -
9186 please see their man pages.
9190 It is assumed that the reader is reasonably familiar with the
9191 <prgn>dpkg</prgn> System Administrators' manual.
9192 Unfortunately this manual does not yet exist.
9196 The Debian version of the FSF's GNU hello program is provided
9197 as an example for people wishing to create Debian
9198 packages. The Debian <prgn>debmake</prgn> package is
9199 recommended as a very helpful tool in creating and maintaining
9200 Debian packages. However, while the tools and examples are
9201 helpful, they do not replace the need to read and follow the
9202 Policy and Programmer's Manual.</p>
9205 <appendix id="pkg-binarypkg">
9206 <heading>Binary packages (from old Packaging Manual)</heading>
9209 The binary package has two main sections. The first part
9210 consists of various control information files and scripts used
9211 by <prgn>dpkg</prgn> when installing and removing. See <ref
9212 id="pkg-controlarea">.
9216 The second part is an archive containing the files and
9217 directories to be installed.
9221 In the future binary packages may also contain other
9222 components, such as checksums and digital signatures. The
9223 format for the archive is described in full in the
9224 <file>deb(5)</file> man page.
9228 <sect id="pkg-bincreating"><heading>Creating package files -
9229 <prgn>dpkg-deb</prgn>
9233 All manipulation of binary package files is done by
9234 <prgn>dpkg-deb</prgn>; it's the only program that has
9235 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9236 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9237 will spot that the options requested are appropriate to
9238 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9243 In order to create a binary package you must make a
9244 directory tree which contains all the files and directories
9245 you want to have in the file system data part of the package.
9246 In Debian-format source packages this directory is usually
9247 <file>debian/tmp</file>, relative to the top of the package's
9252 They should have the locations (relative to the root of the
9253 directory tree you're constructing) ownerships and
9254 permissions which you want them to have on the system when
9259 With current versions of <prgn>dpkg</prgn> the uid/username
9260 and gid/groupname mappings for the users and groups being
9261 used should be the same on the system where the package is
9262 built and the one where it is installed.
9266 You need to add one special directory to the root of the
9267 miniature file system tree you're creating:
9268 <prgn>DEBIAN</prgn>. It should contain the control
9269 information files, notably the binary package control file
9270 (see <ref id="pkg-controlfile">).
9274 The <prgn>DEBIAN</prgn> directory will not appear in the
9275 file system archive of the package, and so won't be installed
9276 by <prgn>dpkg</prgn> when the package is installed.
9280 When you've prepared the package, you should invoke:
9282 dpkg --build <var>directory</var>
9287 This will build the package in
9288 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9289 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9290 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9295 See the man page <manref name="dpkg-deb" section="8"> for details of how
9296 to examine the contents of this newly-created file. You may find the
9297 output of following commands enlightening:
9299 dpkg-deb --info <var>filename</var>.deb
9300 dpkg-deb --contents <var>filename</var>.deb
9301 dpkg --contents <var>filename</var>.deb
9303 To view the copyright file for a package you could use this command:
9305 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9310 <sect id="pkg-controlarea">
9311 <heading>Package control information files</heading>
9314 The control information portion of a binary package is a
9315 collection of files with names known to <prgn>dpkg</prgn>.
9316 It will treat the contents of these files specially - some
9317 of them contain information used by <prgn>dpkg</prgn> when
9318 installing or removing the package; others are scripts which
9319 the package maintainer wants <prgn>dpkg</prgn> to run.
9323 It is possible to put other files in the package control
9324 area, but this is not generally a good idea (though they
9325 will largely be ignored).
9329 Here is a brief list of the control info files supported by
9330 <prgn>dpkg</prgn> and a summary of what they're used for.
9335 <tag><tt>control</tt>
9338 This is the key description file used by
9339 <prgn>dpkg</prgn>. It specifies the package's name
9340 and version, gives its description for the user,
9341 states its relationships with other packages, and so
9342 forth. See <ref id="sourcecontrolfiles"> and
9343 <ref id="binarycontrolfiles">.
9347 It is usually generated automatically from information
9348 in the source package by the
9349 <prgn>dpkg-gencontrol</prgn> program, and with
9350 assistance from <prgn>dpkg-shlibdeps</prgn>.
9351 See <ref id="pkg-sourcetools">.
9355 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9360 These are executable files (usually scripts) which
9361 <prgn>dpkg</prgn> runs during installation, upgrade
9362 and removal of packages. They allow the package to
9363 deal with matters which are particular to that package
9364 or require more complicated processing than that
9365 provided by <prgn>dpkg</prgn>. Details of when and
9366 how they are called are in <ref id="maintainerscripts">.
9370 It is very important to make these scripts idempotent.
9371 See <ref id="idempotency">.
9375 The maintainer scripts are guaranteed to run with a
9376 controlling terminal and can interact with the user.
9377 See <ref id="controllingterminal">.
9381 <tag><tt>conffiles</tt>
9384 This file contains a list of configuration files which
9385 are to be handled automatically by <prgn>dpkg</prgn>
9386 (see <ref id="pkg-conffiles">). Note that not necessarily
9387 every configuration file should be listed here.
9390 <tag><tt>shlibs</tt>
9393 This file contains a list of the shared libraries
9394 supplied by the package, with dependency details for
9395 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9396 when it determines what dependencies are required in a
9397 package control file. The <tt>shlibs</tt> file format
9398 is described on <ref id="shlibs">.
9403 <sect id="pkg-controlfile">
9404 <heading>The main control information file: <tt>control</tt></heading>
9407 The most important control information file used by
9408 <prgn>dpkg</prgn> when it installs a package is
9409 <tt>control</tt>. It contains all the package's "vital
9414 The binary package control files of packages built from
9415 Debian sources are made by a special tool,
9416 <prgn>dpkg-gencontrol</prgn>, which reads
9417 <file>debian/control</file> and <file>debian/changelog</file> to
9418 find the information it needs. See <ref id="pkg-sourcepkg"> for
9423 The fields in binary package control files are listed in
9424 <ref id="binarycontrolfiles">.
9428 A description of the syntax of control files and the purpose
9429 of the fields is available in <ref id="controlfields">.
9434 <heading>Time Stamps</heading>
9437 See <ref id="timestamps">.
9442 <appendix id="pkg-sourcepkg">
9443 <heading>Source packages (from old Packaging Manual) </heading>
9446 The Debian binary packages in the distribution are generated
9447 from Debian sources, which are in a special format to assist
9448 the easy and automatic building of binaries.
9451 <sect id="pkg-sourcetools">
9452 <heading>Tools for processing source packages</heading>
9455 Various tools are provided for manipulating source packages;
9456 they pack and unpack sources and help build of binary
9457 packages and help manage the distribution of new versions.
9461 They are introduced and typical uses described here; see
9462 <manref name="dpkg-source" section="1"> for full
9463 documentation about their arguments and operation.
9467 For examples of how to construct a Debian source package,
9468 and how to use those utilities that are used by Debian
9469 source packages, please see the <prgn>hello</prgn> example
9473 <sect1 id="pkg-dpkg-source">
9475 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9480 This program is frequently used by hand, and is also
9481 called from package-independent automated building scripts
9482 such as <prgn>dpkg-buildpackage</prgn>.
9486 To unpack a package it is typically invoked with
9488 dpkg-source -x <var>.../path/to/filename</var>.dsc
9493 with the <file><var>filename</var>.tar.gz</file> and
9494 <file><var>filename</var>.diff.gz</file> (if applicable) in
9495 the same directory. It unpacks into
9496 <file><var>package</var>-<var>version</var></file>, and if
9498 <file><var>package</var>-<var>version</var>.orig</file>, in
9499 the current directory.
9503 To create a packed source archive it is typically invoked:
9505 dpkg-source -b <var>package</var>-<var>version</var>
9510 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9511 <file>.diff.gz</file> (if appropriate) in the current
9512 directory. <prgn>dpkg-source</prgn> does not clean the
9513 source tree first - this must be done separately if it is
9518 See also <ref id="pkg-sourcearchives">.</p>
9522 <sect1 id="pkg-dpkg-buildpackage">
9524 <prgn>dpkg-buildpackage</prgn> - overall package-building
9529 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9530 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9531 targets <tt>clean</tt>, <tt>build</tt> and
9532 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9533 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9534 source and binary package upload.
9538 It is usually invoked by hand from the top level of the
9539 built or unbuilt source directory. It may be invoked with
9540 no arguments; useful arguments include:
9541 <taglist compact="compact">
9542 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9545 Do not sign the <tt>.changes</tt> file or the
9546 source package <tt>.dsc</tt> file, respectively.</p>
9548 <tag><tt>-p<var>sign-command</var></tt></tag>
9551 Invoke <var>sign-command</var> instead of finding
9552 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9553 <var>sign-command</var> must behave just like
9554 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9556 <tag><tt>-r<var>root-command</var></tt></tag>
9559 When root privilege is required, invoke the command
9560 <var>root-command</var>. <var>root-command</var>
9561 should invoke its first argument as a command, from
9562 the <prgn>PATH</prgn> if necessary, and pass its
9563 second and subsequent arguments to the command it
9564 calls. If no <var>root-command</var> is supplied
9565 then <var>dpkg-buildpackage</var> will take no
9566 special action to gain root privilege, so that for
9567 most packages it will have to be invoked as root to
9570 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9573 Two types of binary-only build and upload - see
9574 <manref name="dpkg-source" section="1">.
9581 <sect1 id="pkg-dpkg-gencontrol">
9583 <prgn>dpkg-gencontrol</prgn> - generates binary package
9588 This program is usually called from <file>debian/rules</file>
9589 (see <ref id="pkg-sourcetree">) in the top level of the source
9594 This is usually done just before the files and directories in the
9595 temporary directory tree where the package is being built have their
9596 permissions and ownerships set and the package is constructed using
9597 <prgn>dpkg-deb/</prgn>
9599 This is so that the control file which is produced has
9600 the right permissions
9605 <prgn>dpkg-gencontrol</prgn> must be called after all the
9606 files which are to go into the package have been placed in
9607 the temporary build directory, so that its calculation of
9608 the installed size of a package is correct.
9612 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9613 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9614 variable substitutions created by
9615 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9620 For a package which generates only one binary package, and
9621 which builds it in <file>debian/tmp</file> relative to the top
9622 of the source package, it is usually sufficient to call
9623 <prgn>dpkg-gencontrol</prgn>.
9627 Sources which build several binaries will typically need
9630 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9631 </example> The <tt>-P</tt> tells
9632 <prgn>dpkg-gencontrol</prgn> that the package is being
9633 built in a non-default directory, and the <tt>-p</tt>
9634 tells it which package's control file should be generated.
9638 <prgn>dpkg-gencontrol</prgn> also adds information to the
9639 list of files in <file>debian/files</file>, for the benefit of
9640 (for example) a future invocation of
9641 <prgn>dpkg-genchanges</prgn>.</p>
9644 <sect1 id="pkg-dpkg-shlibdeps">
9646 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9651 This program is usually called from <file>debian/rules</file>
9652 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9653 id="pkg-sourcetree">), in the top level of the source tree.
9657 Its arguments are executables and shared libraries
9660 They may be specified either in the locations in the
9661 source tree where they are created or in the locations
9662 in the temporary build tree where they are installed
9663 prior to binary package creation.
9665 </footnote> for which shared library dependencies should
9666 be included in the binary package's control file.
9670 If some of the found shared libraries should only
9671 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9672 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9673 by using the <tt>-d<var>dependency-field</var></tt> option
9674 before those executable(s). (Each <tt>-d</tt> option
9675 takes effect until the next <tt>-d</tt>.)
9679 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9680 output control file to be modified. Instead by default it
9681 adds to the <file>debian/substvars</file> file variable
9682 settings like <tt>shlibs:Depends</tt>. These variable
9683 settings must be referenced in dependency fields in the
9684 appropriate per-binary-package sections of the source
9689 For example, a package that generates an essential part
9690 which requires dependencies, and optional parts that
9691 which only require a recommendation, would separate those
9692 two sets of dependencies into two different fields.<footnote>
9693 At the time of writing, an example for this was the
9694 <package/xmms/ package, with Depends used for the xmms
9695 executable, Recommends for the plug-ins and Suggests for
9696 even more optional features provided by unzip.
9698 It can say in its <file>debian/rules</file>:
9700 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9701 -dRecommends <var>optionalpart anotheroptionalpart</var>
9703 and then in its main control file <file>debian/control</file>:
9706 Depends: ${shlibs:Depends}
9707 Recommends: ${shlibs:Recommends}
9713 Sources which produce several binary packages with
9714 different shared library dependency requirements can use
9715 the <tt>-p<var>varnameprefix</var></tt> option to override
9716 the default <tt>shlibs:</tt> prefix (one invocation of
9717 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9718 They can thus produce several sets of dependency
9719 variables, each of the form
9720 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9721 which can be referred to in the appropriate parts of the
9722 binary package control files.
9727 <sect1 id="pkg-dpkg-distaddfile">
9729 <prgn>dpkg-distaddfile</prgn> - adds a file to
9730 <file>debian/files</file>
9734 Some packages' uploads need to include files other than
9735 the source and binary package files.
9739 <prgn>dpkg-distaddfile</prgn> adds a file to the
9740 <file>debian/files</file> file so that it will be included in
9741 the <file>.changes</file> file when
9742 <prgn>dpkg-genchanges</prgn> is run.
9746 It is usually invoked from the <tt>binary</tt> target of
9747 <file>debian/rules</file>:
9749 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9751 The <var>filename</var> is relative to the directory where
9752 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9753 is usually the directory above the top level of the source
9754 tree. The <file>debian/rules</file> target should put the
9755 file there just before or just after calling
9756 <prgn>dpkg-distaddfile</prgn>.
9760 The <var>section</var> and <var>priority</var> are passed
9761 unchanged into the resulting <file>.changes</file> file.
9766 <sect1 id="pkg-dpkg-genchanges">
9768 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9773 This program is usually called by package-independent
9774 automatic building scripts such as
9775 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9780 It is usually called in the top level of a built source
9781 tree, and when invoked with no arguments will print out a
9782 straightforward <file>.changes</file> file based on the
9783 information in the source package's changelog and control
9784 file and the binary and source packages which should have
9790 <sect1 id="pkg-dpkg-parsechangelog">
9792 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9793 representation of a changelog
9797 This program is used internally by
9798 <prgn>dpkg-source</prgn> et al. It may also occasionally
9799 be useful in <file>debian/rules</file> and elsewhere. It
9800 parses a changelog, <file>debian/changelog</file> by default,
9801 and prints a control-file format representation of the
9802 information in it to standard output.
9806 <sect1 id="pkg-dpkg-architecture">
9808 <prgn>dpkg-architecture</prgn> - information about the build and
9813 This program can be used manually, but is also invoked by
9814 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9815 environment or make variables which specify the build and host
9816 architecture for the package building process.
9821 <sect id="pkg-sourcetree">
9822 <heading>The Debianised source tree</heading>
9825 The source archive scheme described later is intended to
9826 allow a Debianised source tree with some associated control
9827 information to be reproduced and transported easily. The
9828 Debianised source tree is a version of the original program
9829 with certain files added for the benefit of the
9830 Debianisation process, and with any other changes required
9831 made to the rest of the source code and installation
9836 The extra files created for Debian are in the subdirectory
9837 <file>debian</file> of the top level of the Debianised source
9838 tree. They are described below.
9841 <sect1 id="pkg-debianrules">
9842 <heading><file>debian/rules</file> - the main building script</heading>
9845 See <ref id="debianrules">.
9850 <sect1 id="pkg-dpkgchangelog">
9851 <heading><file>debian/changelog</file></heading>
9854 See <ref id="dpkgchangelog">.
9857 <sect2><heading>Defining alternative changelog formats
9861 It is possible to use a different format to the standard
9862 one, by providing a parser for the format you wish to
9867 In order to have <tt>dpkg-parsechangelog</tt> run your
9868 parser, you must include a line within the last 40 lines
9869 of your file matching the Perl regular expression:
9870 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9871 parentheses should be the name of the format. For
9872 example, you might say:
9874 @@@ changelog-format: joebloggs @@@
9876 Changelog format names are non-empty strings of alphanumerics.
9880 If such a line exists then <tt>dpkg-parsechangelog</tt>
9881 will look for the parser as
9882 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9884 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9885 it is an error for it not to find it, or for it not to
9886 be an executable program. The default changelog format
9887 is <tt>dpkg</tt>, and a parser for it is provided with
9888 the <tt>dpkg</tt> package.
9892 The parser will be invoked with the changelog open on
9893 standard input at the start of the file. It should read
9894 the file (it may seek if it wishes) to determine the
9895 information required and return the parsed information
9896 to standard output in the form of a series of control
9897 fields in the standard format. By default it should
9898 return information about only the most recent version in
9899 the changelog; it should accept a
9900 <tt>-v<var>version</var></tt> option to return changes
9901 information from all versions present <em>strictly
9902 after</em> <var>version</var>, and it should then be an
9903 error for <var>version</var> not to be present in the
9909 <list compact="compact">
9910 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9911 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9912 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9913 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9914 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9915 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9916 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9921 If several versions are being returned (due to the use
9922 of <tt>-v</tt>), the urgency value should be of the
9923 highest urgency code listed at the start of any of the
9924 versions requested followed by the concatenated
9925 (space-separated) comments from all the versions
9926 requested; the maintainer, version, distribution and
9927 date should always be from the most recent version.
9931 For the format of the <tt>Changes</tt> field see
9932 <ref id="f-Changes">.
9936 If the changelog format which is being parsed always or
9937 almost always leaves a blank line between individual
9938 change notes these blank lines should be stripped out,
9939 so as to make the resulting output compact.
9943 If the changelog format does not contain date or package
9944 name information this information should be omitted from
9945 the output. The parser should not attempt to synthesize
9946 it or find it from other sources.
9950 If the changelog does not have the expected format the
9951 parser should exit with a nonzero exit status, rather
9952 than trying to muddle through and possibly generating
9957 A changelog parser may not interact with the user at
9963 <sect1 id="pkg-srcsubstvars">
9964 <heading><file>debian/substvars</file> and variable substitutions</heading>
9967 See <ref id="substvars">.
9973 <heading><file>debian/files</file></heading>
9976 See <ref id="debianfiles">.
9980 <sect1><heading><file>debian/tmp</file>
9984 This is the canonical temporary location for the
9985 construction of binary packages by the <tt>binary</tt>
9986 target. The directory <file>tmp</file> serves as the root of
9987 the file system tree as it is being constructed (for
9988 example, by using the package's upstream makefiles install
9989 targets and redirecting the output there), and it also
9990 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9991 id="pkg-bincreating">.
9995 If several binary packages are generated from the same
9996 source tree it is usual to use several
9997 <file>debian/tmp<var>something</var></file> directories, for
9998 example <file>tmp-a</file> or <file>tmp-doc</file>.
10002 Whatever <file>tmp</file> directories are created and used by
10003 <tt>binary</tt> must of course be removed by the
10004 <tt>clean</tt> target.</p></sect1>
10008 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10012 As it exists on the FTP site, a Debian source package
10013 consists of three related files. You must have the right
10014 versions of all three to be able to use them.
10019 <tag>Debian source control file - <tt>.dsc</tt></tag>
10021 This file is a control file used by <prgn>dpkg-source</prgn>
10022 to extract a source package.
10023 See <ref id="debiansourcecontrolfiles">.
10027 Original source archive -
10029 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10035 This is a compressed (with <tt>gzip -9</tt>)
10036 <prgn>tar</prgn> file containing the source code from
10037 the upstream authors of the program.
10042 Debianisation diff -
10044 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10050 This is a unified context diff (<tt>diff -u</tt>)
10051 giving the changes which are required to turn the
10052 original source into the Debian source. These changes
10053 may only include editing and creating plain files.
10054 The permissions of files, the targets of symbolic
10055 links and the characteristics of special files or
10056 pipes may not be changed and no files may be removed
10061 All the directories in the diff must exist, except the
10062 <file>debian</file> subdirectory of the top of the source
10063 tree, which will be created by
10064 <prgn>dpkg-source</prgn> if necessary when unpacking.
10068 The <prgn>dpkg-source</prgn> program will
10069 automatically make the <file>debian/rules</file> file
10070 executable (see below).</p></item>
10075 If there is no original source code - for example, if the
10076 package is specially prepared for Debian or the Debian
10077 maintainer is the same as the upstream maintainer - the
10078 format is slightly different: then there is no diff, and the
10080 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10081 and preferably contains a directory named
10082 <file><var>package</var>-<var>version</var></file>.
10087 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10090 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10091 Debian source package. However, if it is not available it
10092 is possible to unpack a Debian source archive as follows:
10093 <enumlist compact="compact">
10096 Untar the tarfile, which will create a <file>.orig</file>
10100 <p>Rename the <file>.orig</file> directory to
10101 <file><var>package</var>-<var>version</var></file>.</p>
10105 Create the subdirectory <file>debian</file> at the top of
10106 the source tree.</p>
10108 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10110 <item><p>Untar the tarfile again if you want a copy of the original
10111 source code alongside the Debianised version.</p>
10116 It is not possible to generate a valid Debian source archive
10117 without using <prgn>dpkg-source</prgn>. In particular,
10118 attempting to use <prgn>diff</prgn> directly to generate the
10119 <file>.diff.gz</file> file will not work.
10123 <heading>Restrictions on objects in source packages</heading>
10126 The source package may not contain any hard links
10128 This is not currently detected when building source
10129 packages, but only when extracting
10133 Hard links may be permitted at some point in the
10134 future, but would require a fair amount of
10136 </footnote>, device special files, sockets or setuid or
10139 Setgid directories are allowed.
10144 The source packaging tools manage the changes between the
10145 original and Debianised source using <prgn>diff</prgn> and
10146 <prgn>patch</prgn>. Turning the original source tree as
10147 included in the <file>.orig.tar.gz</file> into the debianised
10148 source must not involve any changes which cannot be
10149 handled by these tools. Problematic changes which cause
10150 <prgn>dpkg-source</prgn> to halt with an error when
10151 building the source package are:
10152 <list compact="compact">
10153 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10155 <item><p>Changing the targets of symbolic links.</p>
10157 <item><p>Creating directories, other than <file>debian</file>.</p>
10159 <item><p>Changes to the contents of binary files.</p></item>
10160 </list> Changes which cause <prgn>dpkg-source</prgn> to
10161 print a warning but continue anyway are:
10162 <list compact="compact">
10165 Removing files, directories or symlinks.
10167 Renaming a file is not treated specially - it is
10168 seen as the removal of the old file (which
10169 generates a warning, but is otherwise ignored),
10170 and the creation of the new one.
10176 Changed text files which are missing the usual final
10177 newline (either in the original or the modified
10182 Changes which are not represented, but which are not detected by
10183 <prgn>dpkg-source</prgn>, are:
10184 <list compact="compact">
10185 <item><p>Changing the permissions of files (other than
10186 <file>debian/rules</file>) and directories.</p></item>
10191 The <file>debian</file> directory and <file>debian/rules</file>
10192 are handled specially by <prgn>dpkg-source</prgn> - before
10193 applying the changes it will create the <file>debian</file>
10194 directory, and afterwards it will make
10195 <file>debian/rules</file> world-executable.
10201 <appendix id="pkg-controlfields">
10202 <heading>Control files and their fields (from old Packaging Manual)</heading>
10205 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10206 data in a common format, known as control files. Binary and
10207 source packages have control data as do the <file>.changes</file>
10208 files which control the installation of uploaded files, and
10209 <prgn>dpkg</prgn>'s internal databases are in a similar
10214 <heading>Syntax of control files</heading>
10217 See <ref id="controlsyntax">.
10221 It is important to note that there are several fields which
10222 are optional as far as <prgn>dpkg</prgn> and the related
10223 tools are concerned, but which must appear in every Debian
10224 package, or whose omission may cause problems.
10229 <heading>List of fields</heading>
10232 See <ref id="controlfieldslist">.
10236 This section now contains only the fields that didn't belong
10237 to the Policy manual.
10240 <sect1 id="pkg-f-Filename">
10241 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10244 These fields in <tt>Packages</tt> files give the
10245 filename(s) of (the parts of) a package in the
10246 distribution directories, relative to the root of the
10247 Debian hierarchy. If the package has been split into
10248 several parts the parts are all listed in order, separated
10253 <sect1 id="pkg-f-Size">
10254 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10257 These fields in <file>Packages</file> files give the size (in
10258 bytes, expressed in decimal) and MD5 checksum of the
10259 file(s) which make(s) up a binary package in the
10260 distribution. If the package is split into several parts
10261 the values for the parts are listed in order, separated by
10266 <sect1 id="pkg-f-Status">
10267 <heading><tt>Status</tt></heading>
10270 This field in <prgn>dpkg</prgn>'s status file records
10271 whether the user wants a package installed, removed or
10272 left alone, whether it is broken (requiring
10273 re-installation) or not and what its current state on the
10274 system is. Each of these pieces of information is a
10279 <sect1 id="pkg-f-Config-Version">
10280 <heading><tt>Config-Version</tt></heading>
10283 If a package is not installed or not configured, this
10284 field in <prgn>dpkg</prgn>'s status file records the last
10285 version of the package which was successfully
10290 <sect1 id="pkg-f-Conffiles">
10291 <heading><tt>Conffiles</tt></heading>
10294 This field in <prgn>dpkg</prgn>'s status file contains
10295 information about the automatically-managed configuration
10296 files held by a package. This field should <em>not</em>
10297 appear anywhere in a package!
10302 <heading>Obsolete fields</heading>
10305 These are still recognized by <prgn>dpkg</prgn> but should
10306 not appear anywhere any more.
10308 <taglist compact="compact">
10310 <tag><tt>Revision</tt></tag>
10311 <tag><tt>Package-Revision</tt></tag>
10312 <tag><tt>Package_Revision</tt></tag>
10314 The Debian revision part of the package version was
10315 at one point in a separate control file field. This
10316 field went through several names.
10319 <tag><tt>Recommended</tt></tag>
10320 <item>Old name for <tt>Recommends</tt>.</item>
10322 <tag><tt>Optional</tt></tag>
10323 <item>Old name for <tt>Suggests</tt>.</item>
10325 <tag><tt>Class</tt></tag>
10326 <item>Old name for <tt>Priority</tt>.</item>
10335 <appendix id="pkg-conffiles">
10336 <heading>Configuration file handling (from old Packaging Manual)</heading>
10339 <prgn>dpkg</prgn> can do a certain amount of automatic
10340 handling of package configuration files.
10344 Whether this mechanism is appropriate depends on a number of
10345 factors, but basically there are two approaches to any
10346 particular configuration file.
10350 The easy method is to ship a best-effort configuration in the
10351 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10352 handle updates. If the user is unlikely to want to edit the
10353 file, but you need them to be able to without losing their
10354 changes, and a new package with a changed version of the file
10355 is only released infrequently, this is a good approach.
10359 The hard method is to build the configuration file from
10360 scratch in the <prgn>postinst</prgn> script, and to take the
10361 responsibility for fixing any mistakes made in earlier
10362 versions of the package automatically. This will be
10363 appropriate if the file is likely to need to be different on
10367 <sect><heading>Automatic handling of configuration files by
10372 A package may contain a control area file called
10373 <tt>conffiles</tt>. This file should be a list of filenames
10374 of configuration files needing automatic handling, separated
10375 by newlines. The filenames should be absolute pathnames,
10376 and the files referred to should actually exist in the
10381 When a package is upgraded <prgn>dpkg</prgn> will process
10382 the configuration files during the configuration stage,
10383 shortly before it runs the package's <prgn>postinst</prgn>
10388 For each file it checks to see whether the version of the
10389 file included in the package is the same as the one that was
10390 included in the last version of the package (the one that is
10391 being upgraded from); it also compares the version currently
10392 installed on the system with the one shipped with the last
10397 If neither the user nor the package maintainer has changed
10398 the file, it is left alone. If one or the other has changed
10399 their version, then the changed version is preferred - i.e.,
10400 if the user edits their file, but the package maintainer
10401 doesn't ship a different version, the user's changes will
10402 stay, silently, but if the maintainer ships a new version
10403 and the user hasn't edited it the new version will be
10404 installed (with an informative message). If both have
10405 changed their version the user is prompted about the problem
10406 and must resolve the differences themselves.
10410 The comparisons are done by calculating the MD5 message
10411 digests of the files, and storing the MD5 of the file as it
10412 was included in the most recent version of the package.
10416 When a package is installed for the first time
10417 <prgn>dpkg</prgn> will install the file that comes with it,
10418 unless that would mean overwriting a file already on the
10423 However, note that <prgn>dpkg</prgn> will <em>not</em>
10424 replace a conffile that was removed by the user (or by a
10425 script). This is necessary because with some programs a
10426 missing file produces an effect hard or impossible to
10427 achieve in another way, so that a missing file needs to be
10428 kept that way if the user did it.
10432 Note that a package should <em>not</em> modify a
10433 <prgn>dpkg</prgn>-handled conffile in its maintainer
10434 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10435 the user confusing and possibly dangerous options for
10436 conffile update when the package is upgraded.</p>
10439 <sect><heading>Fully-featured maintainer script configuration
10444 For files which contain site-specific information such as
10445 the hostname and networking details and so forth, it is
10446 better to create the file in the package's
10447 <prgn>postinst</prgn> script.
10451 This will typically involve examining the state of the rest
10452 of the system to determine values and other information, and
10453 may involve prompting the user for some information which
10454 can't be obtained some other way.
10458 When using this method there are a couple of important
10459 issues which should be considered:
10463 If you discover a bug in the program which generates the
10464 configuration file, or if the format of the file changes
10465 from one version to the next, you will have to arrange for
10466 the postinst script to do something sensible - usually this
10467 will mean editing the installed configuration file to remove
10468 the problem or change the syntax. You will have to do this
10469 very carefully, since the user may have changed the file,
10470 perhaps to fix the very problem that your script is trying
10471 to deal with - you will have to detect these situations and
10472 deal with them correctly.
10476 If you do go down this route it's probably a good idea to
10477 make the program that generates the configuration file(s) a
10478 separate program in <file>/usr/sbin</file>, by convention called
10479 <file><var>package</var>config</file> and then run that if
10480 appropriate from the post-installation script. The
10481 <tt><var>package</var>config</tt> program should not
10482 unquestioningly overwrite an existing configuration - if its
10483 mode of operation is geared towards setting up a package for
10484 the first time (rather than any arbitrary reconfiguration
10485 later) you should have it check whether the configuration
10486 already exists, and require a <tt>--force</tt> flag to
10487 overwrite it.</p></sect>
10490 <appendix id="pkg-alternatives"><heading>Alternative versions of
10491 an interface - <prgn>update-alternatives</prgn> (from old
10496 When several packages all provide different versions of the
10497 same program or file it is useful to have the system select a
10498 default, but to allow the system administrator to change it
10499 and have their decisions respected.
10503 For example, there are several versions of the <prgn>vi</prgn>
10504 editor, and there is no reason to prevent all of them from
10505 being installed at once, each under their own name
10506 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10507 Nevertheless it is desirable to have the name <tt>vi</tt>
10508 refer to something, at least by default.
10512 If all the packages involved cooperate, this can be done with
10513 <prgn>update-alternatives</prgn>.
10517 Each package provides its own version under its own name, and
10518 calls <prgn>update-alternatives</prgn> in its postinst to
10519 register its version (and again in its prerm to deregister
10524 See the man page <manref name="update-alternatives"
10525 section="8"> for details.
10529 If <prgn>update-alternatives</prgn> does not seem appropriate
10530 you may wish to consider using diversions instead.</p>
10533 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10534 package's version of a file (from old Packaging Manual)
10538 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10539 when it reinstalls the package it belongs to, and to have it
10540 put the file from the package somewhere else instead.
10544 This can be used locally to override a package's version of a
10545 file, or by one package to override another's version (or
10546 provide a wrapper for it).
10550 Before deciding to use a diversion, read <ref
10551 id="pkg-alternatives"> to see if you really want a diversion
10552 rather than several alternative versions of a program.
10556 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10557 and updated by a special program <prgn>dpkg-divert</prgn>.
10558 Please see <manref name="dpkg-divert" section="8"> for full
10559 details of its operation.
10563 When a package wishes to divert a file from another, it should
10564 call <prgn>dpkg-divert</prgn> in its preinst to add the
10565 diversion and rename the existing file. For example,
10566 supposing that a <prgn>smailwrapper</prgn> package wishes to
10567 install a wrapper around <file>/usr/sbin/smail</file>:
10569 dpkg-divert --package smailwrapper --add --rename \
10570 --divert /usr/sbin/smail.real /usr/sbin/smail
10571 </example> The <tt>--package smailwrapper</tt> ensures that
10572 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10573 can bypass the diversion and get installed as the true version.
10574 It's safe to add the diversion unconditionally on upgrades since
10575 it will be left unchanged if it already exists, but
10576 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10577 message, make the command conditional on the version from which
10578 the package is being upgraded:
10580 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10581 dpkg-divert --package smailwrapper --add --rename \
10582 --divert /usr/sbin/smail.real /usr/sbin/smail
10584 </example> where <tt>1.0-2</tt> is the version at which the
10585 diversion was first added to the package. Running the command
10586 during abort-upgrade is pointless but harmless.
10590 The postrm has to do the reverse:
10592 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10593 dpkg-divert --package smailwrapper --remove --rename \
10594 --divert /usr/sbin/smail.real /usr/sbin/smail
10596 </example> If the diversion was added at a particular version, the
10597 postrm should also handle the failure case of upgrading from an
10598 older version (unless the older version is so old that direct
10599 upgrades are no longer supported):
10601 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10602 dpkg-divert --package smailwrapper --remove --rename \
10603 --divert /usr/sbin/smail.real /usr/sbin/smail
10605 </example> where <tt>1.02-2</tt> is the version at which the
10606 diversion was first added to the package. The postrm should not
10607 remove the diversion on upgrades both because there's no reason to
10608 remove the diversion only to immediately re-add it and since the
10609 postrm of the old package is run after unpacking so the removal of
10610 the diversion will fail.
10614 Do not attempt to divert a file which is vitally important for
10615 the system's operation - when using <prgn>dpkg-divert</prgn>
10616 there is a time, after it has been diverted but before
10617 <prgn>dpkg</prgn> has installed the new version, when the file
10618 does not exist.</p>
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