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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
762 Packages must not depend on packages with lower priority
763 values (excluding build-time dependencies). In order to
764 ensure this, the priorities of one or more packages may need
773 <heading>Binary packages</heading>
776 The Debian GNU/Linux distribution is based on the Debian
777 package management system, called <prgn>dpkg</prgn>. Thus,
778 all packages in the Debian distribution must be provided
779 in the <tt>.deb</tt> file format.
783 <heading>The package name</heading>
786 Every package must have a name that's unique within the Debian
791 The package name is included in the control field
792 <tt>Package</tt>, the format of which is described
793 in <ref id="f-Package">.
794 The package name is also included as a part of the file name
795 of the <tt>.deb</tt> file.
800 <heading>The version of a package</heading>
803 Every package has a version number recorded in its
804 <tt>Version</tt> control file field, described in
805 <ref id="f-Version">.
809 The package management system imposes an ordering on version
810 numbers, so that it can tell whether packages are being up- or
811 downgraded and so that package system front end applications
812 can tell whether a package it finds available is newer than
813 the one installed on the system. The version number format
814 has the most significant parts (as far as comparison is
815 concerned) at the beginning.
819 If an upstream package has problematic version numbers they
820 should be converted to a sane form for use in the
821 <tt>Version</tt> field.
825 <heading>Version numbers based on dates</heading>
828 In general, Debian packages should use the same version
829 numbers as the upstream sources.
833 However, in some cases where the upstream version number is
834 based on a date (e.g., a development "snapshot" release) the
835 package management system cannot handle these version
836 numbers without epochs. For example, dpkg will consider
837 "96May01" to be greater than "96Dec24".
841 To prevent having to use epochs for every new upstream
842 version, the date based portion of the version number
843 should be changed to the following format in such cases:
844 "19960501", "19961224". It is up to the maintainer whether
845 they want to bother the upstream maintainer to change
846 the version numbers upstream, too.
850 Note that other version formats based on dates which are
851 parsed correctly by the package management system should
852 <em>not</em> be changed.
856 Native Debian packages (i.e., packages which have been
857 written especially for Debian) whose version numbers include
858 dates should always use the "YYYYMMDD" format.
865 <heading>The maintainer of a package</heading>
868 Every package must have a Debian maintainer (the
869 maintainer may be one person or a group of people
870 reachable from a common email address, such as a mailing
871 list). The maintainer is responsible for ensuring that
872 the package is placed in the appropriate distributions.
876 The maintainer must be specified in the
877 <tt>Maintainer</tt> control field with their correct name
878 and a working email address. If one person maintains
879 several packages, they should try to avoid having
880 different forms of their name and email address in
881 the <tt>Maintainer</tt> fields of those packages.
885 The format of the <tt>Maintainer</tt> control field is
886 described in <ref id="f-Maintainer">.
890 If the maintainer of a package quits from the Debian
891 project, "Debian QA Group"
892 <email>packages@qa.debian.org</email> takes over the
893 maintainer-ship of the package until someone else
894 volunteers for that task. These packages are called
895 <em>orphaned packages</em>.<footnote>
896 The detailed procedure for doing this gracefully can
897 be found in the Debian Developer's Reference,
898 see <ref id="related">.
903 <sect id="descriptions">
904 <heading>The description of a package</heading>
907 Every Debian package must have an extended description
908 stored in the appropriate field of the control record.
909 The technical information about the format of the
910 <tt>Description</tt> field is in <ref id="f-Description">.
914 The description should describe the package (the program) to a
915 user (system administrator) who has never met it before so that
916 they have enough information to decide whether they want to
917 install it. This description should not just be copied verbatim
918 from the program's documentation.
922 Put important information first, both in the synopsis and
923 extended description. Sometimes only the first part of the
924 synopsis or of the description will be displayed. You can
925 assume that there will usually be a way to see the whole
926 extended description.
930 The description should also give information about the
931 significant dependencies and conflicts between this package
932 and others, so that the user knows why these dependencies and
933 conflicts have been declared.
937 Instructions for configuring or using the package should
938 not be included (that is what installation scripts,
939 manual pages, info files, etc., are for). Copyright
940 statements and other administrivia should not be included
941 either (that is what the copyright file is for).
944 <sect1 id="synopsis"><heading>The single line synopsis</heading>
947 The single line synopsis should be kept brief - certainly
952 Do not include the package name in the synopsis line. The
953 display software knows how to display this already, and you
954 do not need to state it. Remember that in many situations
955 the user may only see the synopsis line - make it as
956 informative as you can.
961 <sect1 id="extendeddesc"><heading>The extended description</heading>
964 Do not try to continue the single line synopsis into the
965 extended description. This will not work correctly when
966 the full description is displayed, and makes no sense
967 where only the summary (the single line synopsis) is
972 The extended description should describe what the package
973 does and how it relates to the rest of the system (in terms
974 of, for example, which subsystem it is which part of).
978 The description field needs to make sense to anyone, even
979 people who have no idea about any of the things the
980 package deals with.<footnote>
981 The blurb that comes with a program in its
982 announcements and/or <prgn>README</prgn> files is
983 rarely suitable for use in a description. It is
984 usually aimed at people who are already in the
985 community where the package is used.
994 <heading>Dependencies</heading>
997 Every package must specify the dependency information
998 about other packages that are required for the first to
1003 For example, a dependency entry must be provided for any
1004 shared libraries required by a dynamically-linked executable
1005 binary in a package.
1009 Packages are not required to declare any dependencies they
1010 have on other packages which are marked <tt>Essential</tt>
1011 (see below), and should not do so unless they depend on a
1012 particular version of that package.<footnote>
1014 Essential is defined as the minimal set of functionality
1015 that must be available and usable on the system even
1016 when packages are in an unconfigured (but unpacked)
1017 state. This is needed to avoid unresolvable dependency
1018 loops on upgrade. If packages add unnecessary
1019 dependencies on packages in this set, the chances that
1020 there <strong>will</strong> be an unresolvable
1021 dependency loop caused by forcing these Essential
1022 packages to be configured first before they need to be
1023 is greatly increased. It also increases the chances
1024 that frontends will be unable to
1025 <strong>calculate</strong> an upgrade path, even if one
1029 Also, it's pretty unlikely that functionality from
1030 Essential shall ever be removed (which is one reason why
1031 care must be taken before adding to the Essential
1032 packages set), but <em>packages</em> have been removed
1033 from the Essential set when the functionality moved to a
1034 different package. So depending on these packages
1035 <em>just in case</em> they stop being essential does way
1036 more harm than good.
1042 Sometimes, a package requires another package to be installed
1043 <em>and</em> configured before it can be installed. In this
1044 case, you must specify a <tt>Pre-Depends</tt> entry for
1049 You should not specify a <tt>Pre-Depends</tt> entry for a
1050 package before this has been discussed on the
1051 <tt>debian-devel</tt> mailing list and a consensus about
1052 doing that has been reached.
1056 The format of the package interrelationship control fields is
1057 described in <ref id="relationships">.
1061 <sect id="virtual_pkg">
1062 <heading>Virtual packages</heading>
1065 Sometimes, there are several packages which offer
1066 more-or-less the same functionality. In this case, it's
1067 useful to define a <em>virtual package</em> whose name
1068 describes that common functionality. (The virtual
1069 packages only exist logically, not physically; that's why
1070 they are called <em>virtual</em>.) The packages with this
1071 particular function will then <em>provide</em> the virtual
1072 package. Thus, any other package requiring that function
1073 can simply depend on the virtual package without having to
1074 specify all possible packages individually.
1078 All packages should use virtual package names where
1079 appropriate, and arrange to create new ones if necessary.
1080 They should not use virtual package names (except privately,
1081 amongst a cooperating group of packages) unless they have
1082 been agreed upon and appear in the list of virtual package
1083 names. (See also <ref id="virtual">)
1087 The latest version of the authoritative list of virtual
1088 package names can be found in the <tt>debian-policy</tt> package.
1089 It is also available from the Debian web mirrors at
1090 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1091 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1095 The procedure for updating the list is described in the preface
1102 <heading>Base system</heading>
1105 The <tt>base system</tt> is a minimum subset of the Debian
1106 GNU/Linux system that is installed before everything else
1107 on a new system. Only very few packages are allowed to form
1108 part of the base system, in order to keep the required disk
1113 The base system consists of all those packages with priority
1114 <tt>required</tt> or <tt>important</tt>. Many of them will
1115 be tagged <tt>essential</tt> (see below).
1120 <heading>Essential packages</heading>
1123 Some packages are tagged <tt>essential</tt> for a system
1124 using the <tt>Essential</tt> control file field.
1125 The format of the <tt>Essential</tt> control field is
1126 described in <ref id="f-Essential">.
1130 Since these packages cannot be easily removed (one has to
1131 specify an extra <em>force option</em> to
1132 <prgn>dpkg</prgn> to do so), this flag must not be used
1133 unless absolutely necessary. A shared library package
1134 must not be tagged <tt>essential</tt>; dependencies will
1135 prevent its premature removal, and we need to be able to
1136 remove it when it has been superseded.
1140 Since dpkg will not prevent upgrading of other packages
1141 while an <tt>essential</tt> package is in an unconfigured
1142 state, all <tt>essential</tt> packages must supply all of
1143 their core functionality even when unconfigured. If the
1144 package cannot satisfy this requirement it must not be
1145 tagged as essential, and any packages depending on this
1146 package must instead have explicit dependency fields as
1151 You must not tag any packages <tt>essential</tt> before
1152 this has been discussed on the <tt>debian-devel</tt>
1153 mailing list and a consensus about doing that has been
1158 <sect id="maintscripts">
1159 <heading>Maintainer Scripts</heading>
1162 The package installation scripts should avoid producing
1163 output which is unnecessary for the user to see and
1164 should rely on <prgn>dpkg</prgn> to stave off boredom on
1165 the part of a user installing many packages. This means,
1166 amongst other things, using the <tt>--quiet</tt> option on
1167 <prgn>install-info</prgn>.
1171 Errors which occur during the execution of an installation
1172 script must be checked and the installation must not
1173 continue after an error.
1177 Note that in general <ref id="scripts"> applies to package
1178 maintainer scripts, too.
1182 You should not use <prgn>dpkg-divert</prgn> on a file
1183 belonging to another package without consulting the
1184 maintainer of that package first.
1188 All packages which supply an instance of a common command
1189 name (or, in general, filename) should generally use
1190 <prgn>update-alternatives</prgn>, so that they may be
1191 installed together. If <prgn>update-alternatives</prgn>
1192 is not used, then each package must use
1193 <tt>Conflicts</tt> to ensure that other packages are
1194 de-installed. (In this case, it may be appropriate to
1195 specify a conflict against earlier versions of something
1196 that previously did not use
1197 <prgn>update-alternatives</prgn>; this is an exception to
1198 the usual rule that versioned conflicts should be
1202 <sect1 id="maintscriptprompt">
1203 <heading>Prompting in maintainer scripts</heading>
1205 Package maintainer scripts may prompt the user if
1206 necessary. Prompting should be done by communicating
1207 through a program, such as <prgn>debconf</prgn>, which
1208 conforms to the Debian Configuration management
1209 specification, version 2 or higher. Prompting the user by
1210 other means, such as by hand<footnote>
1211 From the Jargon file: by hand 2. By extension,
1212 writing code which does something in an explicit or
1213 low-level way for which a presupplied library
1214 (<em>debconf, in this instance</em>) routine ought
1215 to have been available.
1216 </footnote>, is now deprecated.
1220 The Debian Configuration management specification is included
1221 in the <file>debconf_specification</file> files in the
1222 <package>debian-policy</package> package.
1223 It is also available from the Debian web mirrors at
1224 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1225 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1229 Packages which use the Debian Configuration management
1230 specification may contain an additional
1231 <prgn>config</prgn> script and a <tt>templates</tt>
1232 file in their control archive<footnote>
1233 The control.tar.gz inside the .deb.
1234 See <manref name="deb" section="5">.
1236 The <prgn>config</prgn> script might be run before the
1237 <prgn>preinst</prgn> script, and before the package is unpacked
1238 or any of its dependencies or pre-dependencies are satisfied.
1239 Therefore it must work using only the tools present in
1240 <em>essential</em> packages.<footnote>
1241 <package>Debconf</package> or another tool that
1242 implements the Debian Configuration management
1243 specification will also be installed, and any
1244 versioned dependencies on it will be satisfied
1245 before preconfiguration begins.
1250 Packages which use the Debian Configuration management
1251 specification must allow for translation of their messages
1252 by using a gettext-based system such as the one provided by
1253 the <package>po-debconf</package> package.
1257 Packages should try to minimize the amount of prompting
1258 they need to do, and they should ensure that the user
1259 will only ever be asked each question once. This means
1260 that packages should try to use appropriate shared
1261 configuration files (such as <file>/etc/papersize</file> and
1262 <file>/etc/news/server</file>), and shared
1263 <package>debconf</package> variables rather than each
1264 prompting for their own list of required pieces of
1269 It also means that an upgrade should not ask the same
1270 questions again, unless the user has used
1271 <tt>dpkg --purge</tt> to remove the package's configuration.
1272 The answers to configuration questions should be stored in an
1273 appropriate place in <file>/etc</file> so that the user can
1274 modify them, and how this has been done should be
1279 If a package has a vitally important piece of
1280 information to pass to the user (such as "don't run me
1281 as I am, you must edit the following configuration files
1282 first or you risk your system emitting badly-formatted
1283 messages"), it should display this in the
1284 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1285 prompt the user to hit return to acknowledge the
1286 message. Copyright messages do not count as vitally
1287 important (they belong in
1288 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1289 neither do instructions on how to use a program (these
1290 should be in on-line documentation, where all the users
1295 Any necessary prompting should almost always be confined
1296 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1297 script. If it is done in the <prgn>postinst</prgn>, it
1298 should be protected with a conditional so that
1299 unnecessary prompting doesn't happen if a package's
1300 installation fails and the <prgn>postinst</prgn> is
1301 called with <tt>abort-upgrade</tt>,
1302 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1312 <heading>Source packages</heading>
1314 <sect id="standardsversion">
1315 <heading>Standards conformance</heading>
1318 Source packages should specify the most recent version number
1319 of this policy document with which your package complied
1320 when it was last updated.
1324 This information may be used to file bug reports
1325 automatically if your package becomes too much out of date.
1329 The version is specified in the <tt>Standards-Version</tt>
1331 The format of the <tt>Standards-Version</tt> field is
1332 described in <ref id="f-Standards-Version">.
1336 You should regularly, and especially if your package has
1337 become out of date, check for the newest Policy Manual
1338 available and update your package, if necessary. When your
1339 package complies with the new standards you should update the
1340 <tt>Standards-Version</tt> source package field and
1341 release it.<footnote>
1342 See the file <file>upgrading-checklist</file> for
1343 information about policy which has changed between
1344 different versions of this document.
1350 <sect id="pkg-relations">
1351 <heading>Package relationships</heading>
1354 Source packages should specify which binary packages they
1355 require to be installed or not to be installed in order to
1356 build correctly. For example, if building a package
1357 requires a certain compiler, then the compiler should be
1358 specified as a build-time dependency.
1362 It is not necessary to explicitly specify build-time
1363 relationships on a minimal set of packages that are always
1364 needed to compile, link and put in a Debian package a
1365 standard "Hello World!" program written in C or C++. The
1366 required packages are called <em>build-essential</em>, and
1367 an informational list can be found in
1368 <file>/usr/share/doc/build-essential/list</file> (which is
1369 contained in the <tt>build-essential</tt>
1372 <list compact="compact">
1374 This allows maintaining the list separately
1375 from the policy documents (the list does not
1376 need the kind of control that the policy
1380 Having a separate package allows one to install
1381 the build-essential packages on a machine, as
1382 well as allowing other packages such as tasks to
1383 require installation of the build-essential
1384 packages using the depends relation.
1387 The separate package allows bug reports against
1388 the list to be categorized separately from
1389 the policy management process in the BTS.
1396 When specifying the set of build-time dependencies, one
1397 should list only those packages explicitly required by the
1398 build. It is not necessary to list packages which are
1399 required merely because some other package in the list of
1400 build-time dependencies depends on them.<footnote>
1401 The reason for this is that dependencies change, and
1402 you should list all those packages, and <em>only</em>
1403 those packages that <em>you</em> need directly. What
1404 others need is their business. For example, if you
1405 only link against <file>libimlib</file>, you will need to
1406 build-depend on <package>libimlib2-dev</package> but
1407 not against any <tt>libjpeg*</tt> packages, even
1408 though <tt>libimlib2-dev</tt> currently depends on
1409 them: installation of <package>libimlib2-dev</package>
1410 will automatically ensure that all of its run-time
1411 dependencies are satisfied.
1416 If build-time dependencies are specified, it must be
1417 possible to build the package and produce working binaries
1418 on a system with only essential and build-essential
1419 packages installed and also those required to satisfy the
1420 build-time relationships (including any implied
1421 relationships). In particular, this means that version
1422 clauses should be used rigorously in build-time
1423 relationships so that one cannot produce bad or
1424 inconsistently configured packages when the relationships
1425 are properly satisfied.
1429 <ref id="relationships"> explains the technical details.
1434 <heading>Changes to the upstream sources</heading>
1437 If changes to the source code are made that are not
1438 specific to the needs of the Debian system, they should be
1439 sent to the upstream authors in whatever form they prefer
1440 so as to be included in the upstream version of the
1445 If you need to configure the package differently for
1446 Debian or for Linux, and the upstream source doesn't
1447 provide a way to do so, you should add such configuration
1448 facilities (for example, a new <prgn>autoconf</prgn> test
1449 or <tt>#define</tt>) and send the patch to the upstream
1450 authors, with the default set to the way they originally
1451 had it. You can then easily override the default in your
1452 <file>debian/rules</file> or wherever is appropriate.
1456 You should make sure that the <prgn>configure</prgn> utility
1457 detects the correct architecture specification string
1458 (refer to <ref id="arch-spec"> for details).
1462 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1463 <prgn>configure</prgn> scripts are used, you should edit the
1464 <file>.in</file> files rather than editing the
1465 <prgn>Makefile</prgn> directly. This allows the user to
1466 reconfigure the package if necessary. You should
1467 <em>not</em> configure the package and edit the generated
1468 <prgn>Makefile</prgn>! This makes it impossible for someone
1469 else to later reconfigure the package without losing the
1475 <sect id="dpkgchangelog">
1476 <heading>Debian changelog: <file>debian/changelog</file></heading>
1479 Changes in the Debian version of the package should be
1480 briefly explained in the Debian changelog file
1481 <file>debian/changelog</file>.<footnote>
1483 Mistakes in changelogs are usually best rectified by
1484 making a new changelog entry rather than "rewriting
1485 history" by editing old changelog entries.
1488 This includes modifications
1489 made in the Debian package compared to the upstream one
1490 as well as other changes and updates to the package.
1492 Although there is nothing stopping an author who is also
1493 the Debian maintainer from using this changelog for all
1494 their changes, it will have to be renamed if the Debian
1495 and upstream maintainers become different people. In such
1496 a case, however, it might be better to maintain the package
1497 as a non-native package.
1502 The format of the <file>debian/changelog</file> allows the
1503 package building tools to discover which version of the package
1504 is being built and find out other release-specific information.
1508 That format is a series of entries like this:
1510 <example compact="compact">
1511 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1513 [optional blank line(s), stripped]
1515 * <var>change details</var>
1516 <var>more change details</var>
1518 [blank line(s), included in output of dpkg-parsechangelog]
1520 * <var>even more change details</var>
1522 [optional blank line(s), stripped]
1524 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1529 <var>package</var> and <var>version</var> are the source
1530 package name and version number.
1534 <var>distribution(s)</var> lists the distributions where
1535 this version should be installed when it is uploaded - it
1536 is copied to the <tt>Distribution</tt> field in the
1537 <file>.changes</file> file. See <ref id="f-Distribution">.
1541 <var>urgency</var> is the value for the <tt>Urgency</tt>
1542 field in the <file>.changes</file> file for the upload
1543 (see <ref id="f-Urgency">). It is not possible to specify
1544 an urgency containing commas; commas are used to separate
1545 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1546 <prgn>dpkg</prgn> changelog format (though there is
1547 currently only one useful <var>keyword</var>,
1552 The change details may in fact be any series of lines
1553 starting with at least two spaces, but conventionally each
1554 change starts with an asterisk and a separating space and
1555 continuation lines are indented so as to bring them in
1556 line with the start of the text above. Blank lines may be
1557 used here to separate groups of changes, if desired.
1561 If this upload resolves bugs recorded in the Bug Tracking
1562 System (BTS), they may be automatically closed on the
1563 inclusion of this package into the Debian archive by
1564 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1565 in the change details.<footnote>
1566 To be precise, the string should match the following
1567 Perl regular expression:
1569 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1571 Then all of the bug numbers listed will be closed by the
1572 archive maintenance script (<prgn>katie</prgn>) using the
1573 <var>version</var> of the changelog entry.
1575 This information is conveyed via the <tt>Closes</tt> field
1576 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1580 The maintainer name and email address used in the changelog
1581 should be the details of the person uploading <em>this</em>
1582 version. They are <em>not</em> necessarily those of the
1583 usual package maintainer. The information here will be
1584 copied to the <tt>Changed-By</tt> field in the
1585 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1586 and then later used to send an acknowledgement when the
1587 upload has been installed.
1591 The <var>date</var> must be in RFC822 format<footnote>
1592 This is generated by <tt>date -R</tt>.
1593 </footnote>; it must include the time zone specified
1594 numerically, with the time zone name or abbreviation
1595 optionally present as a comment in parentheses.
1599 The first "title" line with the package name must start
1600 at the left hand margin. The "trailer" line with the
1601 maintainer and date details must be preceded by exactly
1602 one space. The maintainer details and the date must be
1603 separated by exactly two spaces.
1607 The entire changelog must be encoded in UTF-8.
1611 For more information on placement of the changelog files
1612 within binary packages, please see <ref id="changelogs">.
1616 <sect id="dpkgcopyright">
1617 <heading>Copyright: <file>debian/copyright</file></heading>
1619 Every package must be accompanied by a verbatim copy of
1620 its copyright and distribution license in the file
1621 <file>/usr/share/doc/<var>package</var>/copyright</file>
1622 (see <ref id="copyrightfile"> for further details). Also see
1623 <ref id="pkgcopyright"> for further considerations relayed
1624 to copyrights for packages.
1628 <heading>Error trapping in makefiles</heading>
1631 When <prgn>make</prgn> invokes a command in a makefile
1632 (including your package's upstream makefiles and
1633 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1634 means that <prgn>sh</prgn>'s usual bad error handling
1635 properties apply: if you include a miniature script as one
1636 of the commands in your makefile you'll find that if you
1637 don't do anything about it then errors are not detected
1638 and <prgn>make</prgn> will blithely continue after
1643 Every time you put more than one shell command (this
1644 includes using a loop) in a makefile command you
1645 must make sure that errors are trapped. For
1646 simple compound commands, such as changing directory and
1647 then running a program, using <tt>&&</tt> rather
1648 than semicolon as a command separator is sufficient. For
1649 more complex commands including most loops and
1650 conditionals you should include a separate <tt>set -e</tt>
1651 command at the start of every makefile command that's
1652 actually one of these miniature shell scripts.
1656 <sect id="timestamps">
1657 <heading>Time Stamps</heading>
1659 Maintainers should preserve the modification times of the
1660 upstream source files in a package, as far as is reasonably
1662 The rationale is that there is some information conveyed
1663 by knowing the age of the file, for example, you could
1664 recognize that some documentation is very old by looking
1665 at the modification time, so it would be nice if the
1666 modification time of the upstream source would be
1672 <sect id="restrictions">
1673 <heading>Restrictions on objects in source packages</heading>
1676 The source package may not contain any hard links<footnote>
1678 This is not currently detected when building source
1679 packages, but only when extracting
1683 Hard links may be permitted at some point in the
1684 future, but would require a fair amount of
1687 </footnote>, device special files, sockets or setuid or
1688 setgid files.<footnote>
1689 Setgid directories are allowed.
1694 <sect id="debianrules">
1695 <heading>Main building script: <file>debian/rules</file></heading>
1698 This file must be an executable makefile, and contains the
1699 package-specific recipes for compiling the package and
1700 building binary package(s) from the source.
1704 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1705 so that it can be invoked by saying its name rather than
1706 invoking <prgn>make</prgn> explicitly.
1710 Since an interactive <file>debian/rules</file> script makes it
1711 impossible to auto-compile that package and also makes it
1712 hard for other people to reproduce the same binary
1713 package, all <em>required targets</em> MUST be
1714 non-interactive. At a minimum, required targets are the
1715 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1716 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1717 <em>binary-indep</em>, and <em>build</em>. It also follows
1718 that any target that these targets depend on must also be
1723 The targets are as follows (required unless stated otherwise):
1725 <tag><tt>build</tt></tag>
1728 The <tt>build</tt> target should perform all the
1729 configuration and compilation of the package.
1730 If a package has an interactive pre-build
1731 configuration routine, the Debianized source package
1732 must either be built after this has taken place (so
1733 that the binary package can be built without rerunning
1734 the configuration) or the configuration routine
1735 modified to become non-interactive. (The latter is
1736 preferable if there are architecture-specific features
1737 detected by the configuration routine.)
1741 For some packages, notably ones where the same
1742 source tree is compiled in different ways to produce
1743 two binary packages, the <tt>build</tt> target
1744 does not make much sense. For these packages it is
1745 good enough to provide two (or more) targets
1746 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1747 for each of the ways of building the package, and a
1748 <tt>build</tt> target that does nothing. The
1749 <tt>binary</tt> target will have to build the
1750 package in each of the possible ways and make the
1751 binary package out of each.
1755 The <tt>build</tt> target must not do anything
1756 that might require root privilege.
1760 The <tt>build</tt> target may need to run the
1761 <tt>clean</tt> target first - see below.
1765 When a package has a configuration and build routine
1766 which takes a long time, or when the makefiles are
1767 poorly designed, or when <tt>build</tt> needs to
1768 run <tt>clean</tt> first, it is a good idea to
1769 <tt>touch build</tt> when the build process is
1770 complete. This will ensure that if <tt>debian/rules
1771 build</tt> is run again it will not rebuild the whole
1773 Another common way to do this is for <tt>build</tt>
1774 to depend on <prgn>build-stamp</prgn> and to do
1775 nothing else, and for the <prgn>build-stamp</prgn>
1776 target to do the building and to <tt>touch
1777 build-stamp</tt> on completion. This is
1778 especially useful if the build routine creates a
1779 file or directory called <tt>build</tt>; in such a
1780 case, <tt>build</tt> will need to be listed as
1781 a phony target (i.e., as a dependency of the
1782 <tt>.PHONY</tt> target). See the documentation of
1783 <prgn>make</prgn> for more information on phony
1789 <tag><tt>build-arch</tt> (optional),
1790 <tt>build-indep</tt> (optional)
1794 A package may also provide both of the targets
1795 <tt>build-arch</tt> and <tt>build-indep</tt>.
1796 The <tt>build-arch</tt> target, if provided, should
1797 perform all the configuration and compilation required
1798 for producing all architecture-dependant binary packages
1799 (those packages for which the body of the
1800 <tt>Architecture</tt> field in <tt>debian/control</tt>
1801 is not <tt>all</tt>).
1802 Similarly, the <tt>build-indep</tt> target, if
1803 provided, should perform all the configuration and
1804 compilation required for producing all
1805 architecture-independent binary packages
1806 (those packages for which the body of the
1807 <tt>Architecture</tt> field in <tt>debian/control</tt>
1809 The <tt>build</tt> target should depend on those of the
1810 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1811 are provided in the rules file.
1815 If one or both of the targets <tt>build-arch</tt> and
1816 <tt>build-indep</tt> are not provided, then invoking
1817 <file>debian/rules</file> with one of the not-provided
1818 targets as arguments should produce a exit status code
1819 of 2. Usually this is provided automatically by make
1820 if the target is missing.
1824 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1825 must not do anything that might require root privilege.
1829 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1830 <tt>binary-indep</tt>
1834 The <tt>binary</tt> target must be all that is
1835 necessary for the user to build the binary package(s)
1836 produced from this source package. It is
1837 split into two parts: <prgn>binary-arch</prgn> builds
1838 the binary packages which are specific to a particular
1839 architecture, and <tt>binary-indep</tt> builds
1840 those which are not.
1843 <tt>binary</tt> may be (and commonly is) a target with
1844 no commands which simply depends on
1845 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1848 Both <tt>binary-*</tt> targets should depend on the
1849 <tt>build</tt> target, or on the appropriate
1850 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1851 provided, so that the package is built if it has not
1852 been already. It should then create the relevant
1853 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1854 make their control files and <prgn>dpkg-deb</prgn> to
1855 build them and place them in the parent of the top
1860 Both the <tt>binary-arch</tt> and
1861 <tt>binary-indep</tt> targets <em>must</em> exist.
1862 If one of them has nothing to do (which will always be
1863 the case if the source generates only a single binary
1864 package, whether architecture-dependent or not), it
1865 must still exist and must always succeed.
1869 The <tt>binary</tt> targets must be invoked as
1871 The <prgn>fakeroot</prgn> package often allows one
1872 to build a package correctly even without being
1878 <tag><tt>clean</tt></tag>
1881 This must undo any effects that the <tt>build</tt>
1882 and <tt>binary</tt> targets may have had, except
1883 that it should leave alone any output files created in
1884 the parent directory by a run of a <tt>binary</tt>
1889 If a <tt>build</tt> file is touched at the end of
1890 the <tt>build</tt> target, as suggested above, it
1891 should be removed as the first action that
1892 <tt>clean</tt> performs, so that running
1893 <tt>build</tt> again after an interrupted
1894 <tt>clean</tt> doesn't think that everything is
1899 The <tt>clean</tt> target may need to be
1900 invoked as root if <tt>binary</tt> has been
1901 invoked since the last <tt>clean</tt>, or if
1902 <tt>build</tt> has been invoked as root (since
1903 <tt>build</tt> may create directories, for
1908 <tag><tt>get-orig-source</tt> (optional)</tag>
1911 This target fetches the most recent version of the
1912 original source package from a canonical archive site
1913 (via FTP or WWW, for example), does any necessary
1914 rearrangement to turn it into the original source
1915 tar file format described below, and leaves it in the
1920 This target may be invoked in any directory, and
1921 should take care to clean up any temporary files it
1926 This target is optional, but providing it if
1927 possible is a good idea.
1931 <tag><tt>patch</tt> (optional)</tag>
1934 This target performs whatever additional actions are
1935 required to make the source ready for editing (unpacking
1936 additional upstream archives, applying patches, etc.).
1937 It is recommended to be implemented for any package where
1938 <tt>dpkg-source -x</tt> does not result in source ready
1939 for additional modification. See
1940 <ref id="readmesource">.
1946 The <tt>build</tt>, <tt>binary</tt> and
1947 <tt>clean</tt> targets must be invoked with the current
1948 directory being the package's top-level directory.
1953 Additional targets may exist in <file>debian/rules</file>,
1954 either as published or undocumented interfaces or for the
1955 package's internal use.
1959 The architectures we build on and build for are determined
1960 by <prgn>make</prgn> variables using the utility
1961 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1962 You can determine the
1963 Debian architecture and the GNU style architecture
1964 specification string for the build machine (the machine type
1965 we are building on) as well as for the host machine (the
1966 machine type we are building for). Here is a list of
1967 supported <prgn>make</prgn> variables:
1968 <list compact="compact">
1970 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1973 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1974 specification string)
1977 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1978 <tt>DEB_*_GNU_TYPE</tt>)
1981 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1982 <tt>DEB_*_GNU_TYPE</tt>)
1984 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1985 the build machine or <tt>HOST</tt> for specification of the
1990 Backward compatibility can be provided in the rules file
1991 by setting the needed variables to suitable default
1992 values; please refer to the documentation of
1993 <prgn>dpkg-architecture</prgn> for details.
1997 It is important to understand that the <tt>DEB_*_ARCH</tt>
1998 string only determines which Debian architecture we are
1999 building on or for. It should not be used to get the CPU
2000 or system information; the GNU style variables should be
2004 <sect1 id="debianrules-options">
2005 <heading><file>debian/rules</file> and
2006 <tt>DEB_BUILD_OPTIONS</tt></heading>
2009 Supporting the standardized environment variable
2010 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2011 contain several flags to change how a package is compiled and
2012 built. Each flag must be in the form <var>flag</var> or
2013 <var>flag</var>=<var>options</var>. If multiple flags are
2014 given, they must be separated by whitespace.<footnote>
2015 Some packages support any delimiter, but whitespace is the
2016 easiest to parse inside a makefile and avoids ambiguity with
2017 flag values that contain commas.
2019 <var>flag</var> must start with a lowercase letter
2020 (<tt>a-z</tt>) and consist only of lowercase letters,
2021 numbers (<tt>0-9</tt>), and the characters
2022 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2023 <var>options</var> must not contain whitespace. The same
2024 tag should not be given multiple times with conflicting
2025 values. Package maintainers may assume that
2026 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2030 The meaning of the following tags has been standardized:
2034 This tag says to not run any build-time test suite
2035 provided by the package.
2039 The presence of this tag means that the package should
2040 be compiled with a minimum of optimization. For C
2041 programs, it is best to add <tt>-O0</tt> to
2042 <tt>CFLAGS</tt> (although this is usually the default).
2043 Some programs might fail to build or run at this level
2044 of optimization; it may be necessary to use
2045 <tt>-O1</tt>, for example.
2049 This tag means that the debugging symbols should not be
2050 stripped from the binary during installation, so that
2051 debugging information may be included in the package.
2053 <tag>parallel=n</tag>
2055 This tag means that the package should be built using up
2056 to <tt>n</tt> parallel processes if the package build
2057 system supports this.<footnote>
2058 Packages built with <tt>make</tt> can often implement
2059 this by passing the <tt>-j</tt><var>n</var> option to
2062 If the package build system does not support parallel
2063 builds, this string must be ignored. If the package
2064 build system only supports a lower level of concurrency
2065 than <var>n</var>, the package should be built using as
2066 many parallel processes as the package build system
2067 supports. It is up to the package maintainer to decide
2068 whether the package build times are long enough and the
2069 package build system is robust enough to make supporting
2070 parallel builds worthwhile.
2076 Unknown flags must be ignored by <file>debian/rules</file>.
2080 The following makefile snippet is an example of how one may
2081 implement the build options; you will probably have to
2082 massage this example in order to make it work for your
2084 <example compact="compact">
2087 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2088 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2089 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2090 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2092 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2097 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2098 INSTALL_PROGRAM += -s
2100 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2101 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2102 MAKEFLAGS += -j$(NUMJOBS)
2107 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2108 # Code to run the package test suite.
2115 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2116 <sect id="substvars">
2117 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2120 When <prgn>dpkg-gencontrol</prgn>,
2121 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2122 generate control files they perform variable substitutions
2123 on their output just before writing it. Variable
2124 substitutions have the form <tt>${<var>variable</var>}</tt>.
2125 The optional file <file>debian/substvars</file> contains
2126 variable substitutions to be used; variables can also be set
2127 directly from <file>debian/rules</file> using the <tt>-V</tt>
2128 option to the source packaging commands, and certain
2129 predefined variables are also available.
2133 The <file>debian/substvars</file> file is usually generated and
2134 modified dynamically by <file>debian/rules</file> targets, in
2135 which case it must be removed by the <tt>clean</tt> target.
2139 See <manref name="deb-substvars" section="5"> for full
2140 details about source variable substitutions, including the
2141 format of <file>debian/substvars</file>.</p>
2144 <sect id="debianwatch">
2145 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2148 This is an optional, recommended control file for the
2149 <tt>uscan</tt> utility which defines how to automatically
2150 scan ftp or http sites for newly available updates of the
2151 package. This is used by <url id="
2152 http://dehs.alioth.debian.org/"> and other Debian QA tools
2153 to help with quality control and maintenance of the
2154 distribution as a whole.
2159 <sect id="debianfiles">
2160 <heading>Generated files list: <file>debian/files</file></heading>
2163 This file is not a permanent part of the source tree; it
2164 is used while building packages to record which files are
2165 being generated. <prgn>dpkg-genchanges</prgn> uses it
2166 when it generates a <file>.changes</file> file.
2170 It should not exist in a shipped source package, and so it
2171 (and any backup files or temporary files such as
2172 <file>files.new</file><footnote>
2173 <file>files.new</file> is used as a temporary file by
2174 <prgn>dpkg-gencontrol</prgn> and
2175 <prgn>dpkg-distaddfile</prgn> - they write a new
2176 version of <tt>files</tt> here before renaming it,
2177 to avoid leaving a corrupted copy if an error
2179 </footnote>) should be removed by the
2180 <tt>clean</tt> target. It may also be wise to
2181 ensure a fresh start by emptying or removing it at the
2182 start of the <tt>binary</tt> target.
2186 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2187 package, it adds an entry to <file>debian/files</file> for the
2188 <file>.deb</file> file that will be created when <tt>dpkg-deb
2189 --build</tt> is run for that binary package. So for most
2190 packages all that needs to be done with this file is to
2191 delete it in the <tt>clean</tt> target.
2195 If a package upload includes files besides the source
2196 package and any binary packages whose control files were
2197 made with <prgn>dpkg-gencontrol</prgn> then they should be
2198 placed in the parent of the package's top-level directory
2199 and <prgn>dpkg-distaddfile</prgn> should be called to add
2200 the file to the list in <file>debian/files</file>.</p>
2203 <sect id="embeddedfiles">
2204 <heading>Convenience copies of code</heading>
2207 Some software packages include in their distribution convenience
2208 copies of code from other software packages, generally so that
2209 users compiling from source don't have to download multiple
2210 packages. Debian packages should not make use of these
2211 convenience copies unless the included package is explicitly
2212 intended to be used in this way.<footnote>
2213 For example, parts of the GNU build system work like this.
2215 If the included code is already in the Debian archive in the
2216 form of a library, the Debian packaging should ensure that
2217 binary packages reference the libraries already in Debian and
2218 the convenience copy is not used. If the included code is not
2219 already in Debian, it should be packaged separately as a
2220 prerequisite if possible.
2222 Having multiple copies of the same code in Debian is
2223 inefficient, often creates either static linking or shared
2224 library conflicts, and, most importantly, increases the
2225 difficulty of handling security vulnerabilities in the
2231 <sect id="readmesource">
2232 <heading>Source package handling:
2233 <file>debian/README.source</file></heading>
2236 If running <prgn>dpkg-source -x</prgn> on a source package
2237 doesn't produce the source of the package, ready for editing,
2238 and allow one to make changes and run
2239 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2240 without taking any additional steps, creating a
2241 <file>debian/README.source</file> documentation file is
2242 recommended. This file should explain how to do all of the
2245 <item>Generate the fully patched source, in a form ready for
2246 editing, that would be built to create Debian
2247 packages. Doing this with a <tt>patch</tt> target in
2248 <file>debian/rules</file> is recommended; see
2249 <ref id="debianrules">.</item>
2250 <item>Modify the source and save those modifications so that
2251 they will be applied when building the package.</item>
2252 <item>Remove source modifications that are currently being
2253 applied when building the package.</item>
2254 <item>Optionally, document what steps are necessary to
2255 upgrade the Debian source package to a new upstream version,
2256 if applicable.</item>
2258 This explanation should include specific commands and mention
2259 any additional required Debian packages. It should not assume
2260 familiarity with any specific Debian packaging system or patch
2265 This explanation may refer to a documentation file installed by
2266 one of the package's build dependencies provided that the
2267 referenced documentation clearly explains these tasks and is not
2268 a general reference manual.
2272 <file>debian/README.source</file> may also include any other
2273 information that would be helpful to someone modifying the
2274 source package. Even if the package doesn't fit the above
2275 description, maintainers are encouraged to document in a
2276 <file>debian/README.source</file> file any source package with a
2277 particularly complex or unintuitive source layout or build
2278 system (for example, a package that builds the same source
2279 multiple times to generate different binary packages).
2285 <chapt id="controlfields">
2286 <heading>Control files and their fields</heading>
2289 The package management system manipulates data represented in
2290 a common format, known as <em>control data</em>, stored in
2291 <em>control files</em>.
2292 Control files are used for source packages, binary packages and
2293 the <file>.changes</file> files which control the installation
2294 of uploaded files<footnote>
2295 <prgn>dpkg</prgn>'s internal databases are in a similar
2300 <sect id="controlsyntax">
2301 <heading>Syntax of control files</heading>
2304 A control file consists of one or more paragraphs of
2306 The paragraphs are also sometimes referred to as stanzas.
2308 The paragraphs are separated by blank lines. Some control
2309 files allow only one paragraph; others allow several, in
2310 which case each paragraph usually refers to a different
2311 package. (For example, in source packages, the first
2312 paragraph refers to the source package, and later paragraphs
2313 refer to binary packages generated from the source.)
2317 Each paragraph consists of a series of data fields; each
2318 field consists of the field name, followed by a colon and
2319 then the data/value associated with that field. It ends at
2320 the end of the (logical) line. Horizontal whitespace
2321 (spaces and tabs) may occur immediately before or after the
2322 value and is ignored there; it is conventional to put a
2323 single space after the colon. For example, a field might
2325 <example compact="compact">
2328 the field name is <tt>Package</tt> and the field value
2333 Many fields' values may span several lines; in this case
2334 each continuation line must start with a space or a tab.
2335 Any trailing spaces or tabs at the end of individual
2336 lines of a field value are ignored.
2340 In fields where it is specified that lines may not wrap,
2341 only a single line of data is allowed and whitespace is not
2342 significant in a field body. Whitespace must not appear
2343 inside names (of packages, architectures, files or anything
2344 else) or version numbers, or between the characters of
2345 multi-character version relationships.
2349 Field names are not case-sensitive, but it is usual to
2350 capitalize the field names using mixed case as shown below.
2354 Blank lines, or lines consisting only of spaces and tabs,
2355 are not allowed within field values or between fields - that
2356 would mean a new paragraph.
2360 All control files must be encoded in UTF-8.
2364 <sect id="sourcecontrolfiles">
2365 <heading>Source package control files -- <file>debian/control</file></heading>
2368 The <file>debian/control</file> file contains the most vital
2369 (and version-independent) information about the source package
2370 and about the binary packages it creates.
2374 The first paragraph of the control file contains information about
2375 the source package in general. The subsequent sets each describe a
2376 binary package that the source tree builds.
2380 The fields in the general paragraph (the first one, for the source
2383 <list compact="compact">
2384 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2385 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2386 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2387 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2388 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2389 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2390 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2391 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2396 The fields in the binary package paragraphs are:
2398 <list compact="compact">
2399 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2400 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2401 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2402 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2403 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2404 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2405 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2406 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2411 The syntax and semantics of the fields are described below.
2417 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2418 generate control files for binary packages (see below), by
2419 <prgn>dpkg-genchanges</prgn> to generate the
2420 <tt>.changes</tt> file to accompany the upload, and by
2421 <prgn>dpkg-source</prgn> when it creates the
2422 <file>.dsc</file> source control file as part of a source
2423 archive. Many fields are permitted to span multiple lines in
2424 <file>debian/control</file> but not in any other control
2425 file. These tools are responsible for removing the line
2426 breaks from such fields when using fields from
2427 <file>debian/control</file> to generate other control files.
2431 The fields here may contain variable references - their
2432 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2433 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2434 when they generate output control files.
2435 See <ref id="substvars"> for details.
2440 <sect id="binarycontrolfiles">
2441 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2444 The <file>DEBIAN/control</file> file contains the most vital
2445 (and version-dependent) information about a binary package.
2449 The fields in this file are:
2451 <list compact="compact">
2452 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2453 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2454 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2455 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2456 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2457 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2458 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2459 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2460 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2461 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2462 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2463 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2468 <sect id="debiansourcecontrolfiles">
2469 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2472 This file contains a series of fields, identified and
2473 separated just like the fields in the control file of
2474 a binary package. The fields are listed below; their
2475 syntax is described above, in <ref id="pkg-controlfields">.
2477 <list compact="compact">
2478 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2479 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2480 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2481 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2482 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2483 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2484 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2485 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2486 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2487 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2493 The source package control file is generated by
2494 <prgn>dpkg-source</prgn> when it builds the source
2495 archive, from other files in the source package,
2496 described above. When unpacking, it is checked against
2497 the files and directories in the other parts of the
2503 <sect id="debianchangesfiles">
2504 <heading>Debian changes files -- <file>.changes</file></heading>
2507 The .changes files are used by the Debian archive maintenance
2508 software to process updates to packages. They contain one
2509 paragraph which contains information from the
2510 <tt>debian/control</tt> file and other data about the
2511 source package gathered via <tt>debian/changelog</tt>
2512 and <tt>debian/rules</tt>.
2516 The fields in this file are:
2518 <list compact="compact">
2519 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2520 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2521 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2522 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2523 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2524 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2525 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2526 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2527 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2528 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2529 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2530 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2531 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2532 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2537 <sect id="controlfieldslist">
2538 <heading>List of fields</heading>
2540 <sect1 id="f-Source">
2541 <heading><tt>Source</tt></heading>
2544 This field identifies the source package name.
2548 In <file>debian/control</file> or a <file>.dsc</file> file,
2549 this field must contain only the name of the source package.
2553 In a binary package control file or a <file>.changes</file>
2554 file, the source package name may be followed by a version
2555 number in parentheses<footnote>
2556 It is customary to leave a space after the package name
2557 if a version number is specified.
2559 This version number may be omitted (and is, by
2560 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2561 the <tt>Version</tt> field of the binary package in
2562 question. The field itself may be omitted from a binary
2563 package control file when the source package has the same
2564 name and version as the binary package.
2568 <sect1 id="f-Maintainer">
2569 <heading><tt>Maintainer</tt></heading>
2572 The package maintainer's name and email address. The name
2573 should come first, then the email address inside angle
2574 brackets <tt><></tt> (in RFC822 format).
2578 If the maintainer's name contains a full stop then the
2579 whole field will not work directly as an email address due
2580 to a misfeature in the syntax specified in RFC822; a
2581 program using this field as an address must check for this
2582 and correct the problem if necessary (for example by
2583 putting the name in round brackets and moving it to the
2584 end, and bringing the email address forward).
2588 <sect1 id="f-Uploaders">
2589 <heading><tt>Uploaders</tt></heading>
2592 List of the names and email addresses of co-maintainers of
2593 the package, if any. If the package has other maintainers
2594 beside the one named in the
2595 <qref id="f-Maintainer">Maintainer field</qref>, their
2596 names and email addresses should be listed here. The
2597 format is the same as that of the Maintainer tag, and
2598 multiple entries should be comma separated. Currently,
2599 this field is restricted to a single line of data. This
2600 is an optional field.
2603 Any parser that interprets the Uploaders field in
2604 <file>debian/control</file> must permit it to span multiple
2605 lines. Line breaks in an Uploaders field that spans multiple
2606 lines are not significant and the semantics of the field are
2607 the same as if the line breaks had not been present.
2611 <sect1 id="f-Changed-By">
2612 <heading><tt>Changed-By</tt></heading>
2615 The name and email address of the person who changed the
2616 said package. Usually the name of the maintainer.
2617 All the rules for the Maintainer field apply here, too.
2621 <sect1 id="f-Section">
2622 <heading><tt>Section</tt></heading>
2625 This field specifies an application area into which the package
2626 has been classified. See <ref id="subsections">.
2630 When it appears in the <file>debian/control</file> file,
2631 it gives the value for the subfield of the same name in
2632 the <tt>Files</tt> field of the <file>.changes</file> file.
2633 It also gives the default for the same field in the binary
2638 <sect1 id="f-Priority">
2639 <heading><tt>Priority</tt></heading>
2642 This field represents how important that it is that the user
2643 have the package installed. See <ref id="priorities">.
2647 When it appears in the <file>debian/control</file> file,
2648 it gives the value for the subfield of the same name in
2649 the <tt>Files</tt> field of the <file>.changes</file> file.
2650 It also gives the default for the same field in the binary
2655 <sect1 id="f-Package">
2656 <heading><tt>Package</tt></heading>
2659 The name of the binary package.
2663 Package names must consist only of lower case letters
2664 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2665 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2666 They must be at least two characters long and must start
2667 with an alphanumeric character.
2671 <sect1 id="f-Architecture">
2672 <heading><tt>Architecture</tt></heading>
2675 Depending on context and the control file used, the
2676 <tt>Architecture</tt> field can include the following sets of
2679 <item>A unique single word identifying a Debian machine
2680 architecture, see <ref id="arch-spec">.
2681 <item><tt>all</tt>, which indicates an
2682 architecture-independent package.
2683 <item><tt>any</tt>, which indicates a package available
2684 for building on any architecture.
2685 <item><tt>source</tt>, which indicates a source package.
2690 In the main <file>debian/control</file> file in the source
2691 package, or in the source package control file
2692 <file>.dsc</file>, one may specify a list of architectures
2693 separated by spaces, or the special values <tt>any</tt> or
2698 Specifying <tt>any</tt> indicates that the source package
2699 isn't dependent on any particular architecture and should
2700 compile fine on any one. The produced binary package(s)
2701 will be specific to whatever the current build architecture
2703 This is the most often used setting, and is recommended
2704 for new packages that aren't <tt>Architecture: all</tt>.
2709 Specifying a list of architectures indicates that the source
2710 will build an architecture-dependent package, and will only
2711 work correctly on the listed architectures.<footnote>
2712 This is a setting used for a minority of cases where the
2713 program is not portable. Generally, it should not be used
2719 In a <file>.changes</file> file, the <tt>Architecture</tt>
2720 field lists the architecture(s) of the package(s)
2721 currently being uploaded. This will be a list; if the
2722 source for the package is also being uploaded, the special
2723 entry <tt>source</tt> is also present.
2727 See <ref id="debianrules"> for information how to get the
2728 architecture for the build process.
2732 <sect1 id="f-Essential">
2733 <heading><tt>Essential</tt></heading>
2736 This is a boolean field which may occur only in the
2737 control file of a binary package or in a per-package fields
2738 paragraph of a main source control data file.
2742 If set to <tt>yes</tt> then the package management system
2743 will refuse to remove the package (upgrading and replacing
2744 it is still possible). The other possible value is <tt>no</tt>,
2745 which is the same as not having the field at all.
2750 <heading>Package interrelationship fields:
2751 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2752 <tt>Recommends</tt>, <tt>Suggests</tt>,
2753 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2754 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2758 These fields describe the package's relationships with
2759 other packages. Their syntax and semantics are described
2760 in <ref id="relationships">.</p>
2763 <sect1 id="f-Standards-Version">
2764 <heading><tt>Standards-Version</tt></heading>
2767 The most recent version of the standards (the policy
2768 manual and associated texts) with which the package
2773 The version number has four components: major and minor
2774 version number and major and minor patch level. When the
2775 standards change in a way that requires every package to
2776 change the major number will be changed. Significant
2777 changes that will require work in many packages will be
2778 signaled by a change to the minor number. The major patch
2779 level will be changed for any change to the meaning of the
2780 standards, however small; the minor patch level will be
2781 changed when only cosmetic, typographical or other edits
2782 are made which neither change the meaning of the document
2783 nor affect the contents of packages.
2787 Thus only the first three components of the policy version
2788 are significant in the <em>Standards-Version</em> control
2789 field, and so either these three components or the all
2790 four components may be specified.<footnote>
2791 In the past, people specified the full version number
2792 in the Standards-Version field, for example "2.3.0.0".
2793 Since minor patch-level changes don't introduce new
2794 policy, it was thought it would be better to relax
2795 policy and only require the first 3 components to be
2796 specified, in this example "2.3.0". All four
2797 components may still be used if someone wishes to do so.
2803 <sect1 id="f-Version">
2804 <heading><tt>Version</tt></heading>
2807 The version number of a package. The format is:
2808 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2812 The three components here are:
2814 <tag><var>epoch</var></tag>
2817 This is a single (generally small) unsigned integer. It
2818 may be omitted, in which case zero is assumed. If it is
2819 omitted then the <var>upstream_version</var> may not
2824 It is provided to allow mistakes in the version numbers
2825 of older versions of a package, and also a package's
2826 previous version numbering schemes, to be left behind.
2830 <tag><var>upstream_version</var></tag>
2833 This is the main part of the version number. It is
2834 usually the version number of the original ("upstream")
2835 package from which the <file>.deb</file> file has been made,
2836 if this is applicable. Usually this will be in the same
2837 format as that specified by the upstream author(s);
2838 however, it may need to be reformatted to fit into the
2839 package management system's format and comparison
2844 The comparison behavior of the package management system
2845 with respect to the <var>upstream_version</var> is
2846 described below. The <var>upstream_version</var>
2847 portion of the version number is mandatory.
2851 The <var>upstream_version</var> may contain only
2852 alphanumerics<footnote>
2853 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2855 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2856 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2857 tilde) and should start with a digit. If there is no
2858 <var>debian_revision</var> then hyphens are not allowed;
2859 if there is no <var>epoch</var> then colons are not
2864 <tag><var>debian_revision</var></tag>
2867 This part of the version number specifies the version of
2868 the Debian package based on the upstream version. It
2869 may contain only alphanumerics and the characters
2870 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2871 tilde) and is compared in the same way as the
2872 <var>upstream_version</var> is.
2876 It is optional; if it isn't present then the
2877 <var>upstream_version</var> may not contain a hyphen.
2878 This format represents the case where a piece of
2879 software was written specifically to be turned into a
2880 Debian package, and so there is only one "debianisation"
2881 of it and therefore no revision indication is required.
2885 It is conventional to restart the
2886 <var>debian_revision</var> at <tt>1</tt> each time the
2887 <var>upstream_version</var> is increased.
2891 The package management system will break the version
2892 number apart at the last hyphen in the string (if there
2893 is one) to determine the <var>upstream_version</var> and
2894 <var>debian_revision</var>. The absence of a
2895 <var>debian_revision</var> is equivalent to a
2896 <var>debian_revision</var> of <tt>0</tt>.
2903 When comparing two version numbers, first the <var>epoch</var>
2904 of each are compared, then the <var>upstream_version</var> if
2905 <var>epoch</var> is equal, and then <var>debian_revision</var>
2906 if <var>upstream_version</var> is also equal.
2907 <var>epoch</var> is compared numerically. The
2908 <var>upstream_version</var> and <var>debian_revision</var>
2909 parts are compared by the package management system using the
2910 following algorithm:
2914 The strings are compared from left to right.
2918 First the initial part of each string consisting entirely of
2919 non-digit characters is determined. These two parts (one of
2920 which may be empty) are compared lexically. If a difference
2921 is found it is returned. The lexical comparison is a
2922 comparison of ASCII values modified so that all the letters
2923 sort earlier than all the non-letters and so that a tilde
2924 sorts before anything, even the end of a part. For example,
2925 the following parts are in sorted order from earliest to
2926 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2927 <tt>a</tt>.<footnote>
2928 One common use of <tt>~</tt> is for upstream pre-releases.
2929 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2930 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2935 Then the initial part of the remainder of each string which
2936 consists entirely of digit characters is determined. The
2937 numerical values of these two parts are compared, and any
2938 difference found is returned as the result of the comparison.
2939 For these purposes an empty string (which can only occur at
2940 the end of one or both version strings being compared) counts
2945 These two steps (comparing and removing initial non-digit
2946 strings and initial digit strings) are repeated until a
2947 difference is found or both strings are exhausted.
2951 Note that the purpose of epochs is to allow us to leave behind
2952 mistakes in version numbering, and to cope with situations
2953 where the version numbering scheme changes. It is
2954 <em>not</em> intended to cope with version numbers containing
2955 strings of letters which the package management system cannot
2956 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2957 silly orderings (the author of this manual has heard of a
2958 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2959 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2960 <tt>2</tt> and so forth).
2964 <sect1 id="f-Description">
2965 <heading><tt>Description</tt></heading>
2968 In a source or binary control file, the <tt>Description</tt>
2969 field contains a description of the binary package, consisting
2970 of two parts, the synopsis or the short description, and the
2971 long description. The field's format is as follows:
2976 Description: <single line synopsis>
2977 <extended description over several lines>
2982 The lines in the extended description can have these formats:
2988 Those starting with a single space are part of a paragraph.
2989 Successive lines of this form will be word-wrapped when
2990 displayed. The leading space will usually be stripped off.
2994 Those starting with two or more spaces. These will be
2995 displayed verbatim. If the display cannot be panned
2996 horizontally, the displaying program will line wrap them "hard"
2997 (i.e., without taking account of word breaks). If it can they
2998 will be allowed to trail off to the right. None, one or two
2999 initial spaces may be deleted, but the number of spaces
3000 deleted from each line will be the same (so that you can have
3001 indenting work correctly, for example).
3005 Those containing a single space followed by a single full stop
3006 character. These are rendered as blank lines. This is the
3007 <em>only</em> way to get a blank line<footnote>
3008 Completely empty lines will not be rendered as blank lines.
3009 Instead, they will cause the parser to think you're starting
3010 a whole new record in the control file, and will therefore
3011 likely abort with an error.
3016 Those containing a space, a full stop and some more characters.
3017 These are for future expansion. Do not use them.
3023 Do not use tab characters. Their effect is not predictable.
3027 See <ref id="descriptions"> for further information on this.
3031 In a <file>.changes</file> file, the <tt>Description</tt> field
3032 contains a summary of the descriptions for the packages being
3037 The part of the field before the first newline is empty;
3038 thereafter each line has the name of a binary package and
3039 the summary description line from that binary package.
3040 Each line is indented by one space.
3045 <sect1 id="f-Distribution">
3046 <heading><tt>Distribution</tt></heading>
3049 In a <file>.changes</file> file or parsed changelog output
3050 this contains the (space-separated) name(s) of the
3051 distribution(s) where this version of the package should
3052 be installed. Valid distributions are determined by the
3053 archive maintainers.<footnote>
3054 Current distribution names are:
3055 <taglist compact="compact">
3056 <tag><em>stable</em></tag>
3058 This is the current "released" version of Debian
3059 GNU/Linux. Once the distribution is
3060 <em>stable</em> only security fixes and other
3061 major bug fixes are allowed. When changes are
3062 made to this distribution, the release number is
3063 increased (for example: 2.2r1 becomes 2.2r2 then
3067 <tag><em>unstable</em></tag>
3069 This distribution value refers to the
3070 <em>developmental</em> part of the Debian
3071 distribution tree. New packages, new upstream
3072 versions of packages and bug fixes go into the
3073 <em>unstable</em> directory tree. Download from
3074 this distribution at your own risk.
3077 <tag><em>testing</em></tag>
3079 This distribution value refers to the
3080 <em>testing</em> part of the Debian distribution
3081 tree. It receives its packages from the
3082 unstable distribution after a short time lag to
3083 ensure that there are no major issues with the
3084 unstable packages. It is less prone to breakage
3085 than unstable, but still risky. It is not
3086 possible to upload packages directly to
3090 <tag><em>frozen</em></tag>
3092 From time to time, the <em>testing</em>
3093 distribution enters a state of "code-freeze" in
3094 anticipation of release as a <em>stable</em>
3095 version. During this period of testing only
3096 fixes for existing or newly-discovered bugs will
3097 be allowed. The exact details of this stage are
3098 determined by the Release Manager.
3101 <tag><em>experimental</em></tag>
3103 The packages with this distribution value are
3104 deemed by their maintainers to be high
3105 risk. Oftentimes they represent early beta or
3106 developmental packages from various sources that
3107 the maintainers want people to try, but are not
3108 ready to be a part of the other parts of the
3109 Debian distribution tree. Download at your own
3115 You should list <em>all</em> distributions that the
3116 package should be installed into.
3120 More information is available in the Debian Developer's
3121 Reference, section "The Debian archive".
3128 <heading><tt>Date</tt></heading>
3131 This field includes the date the package was built or last edited.
3135 The value of this field is usually extracted from the
3136 <file>debian/changelog</file> file - see
3137 <ref id="dpkgchangelog">).
3141 <sect1 id="f-Format">
3142 <heading><tt>Format</tt></heading>
3145 This field specifies a format revision for the file.
3146 The most current format described in the Policy Manual
3147 is version <strong>1.5</strong>. The syntax of the
3148 format value is the same as that of a package version
3149 number except that no epoch or Debian revision is allowed
3150 - see <ref id="f-Version">.
3154 <sect1 id="f-Urgency">
3155 <heading><tt>Urgency</tt></heading>
3158 This is a description of how important it is to upgrade to
3159 this version from previous ones. It consists of a single
3160 keyword taking one of the values <tt>low</tt>,
3161 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3162 <tt>critical</tt><footnote>
3163 Other urgency values are supported with configuration
3164 changes in the archive software but are not used in Debian.
3165 The urgency affects how quickly a package will be considered
3166 for inclusion into the <tt>testing</tt> distribution and
3167 gives an indication of the importance of any fixes included
3168 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3169 treated as synonymous.
3170 </footnote> (not case-sensitive) followed by an optional
3171 commentary (separated by a space) which is usually in
3172 parentheses. For example:
3175 Urgency: low (HIGH for users of diversions)
3181 The value of this field is usually extracted from the
3182 <file>debian/changelog</file> file - see
3183 <ref id="dpkgchangelog">.
3187 <sect1 id="f-Changes">
3188 <heading><tt>Changes</tt></heading>
3191 This field contains the human-readable changes data, describing
3192 the differences between the last version and the current one.
3196 There should be nothing in this field before the first
3197 newline; all the subsequent lines must be indented by at
3198 least one space; blank lines must be represented by a line
3199 consisting only of a space and a full stop.
3203 The value of this field is usually extracted from the
3204 <file>debian/changelog</file> file - see
3205 <ref id="dpkgchangelog">).
3209 Each version's change information should be preceded by a
3210 "title" line giving at least the version, distribution(s)
3211 and urgency, in a human-readable way.
3215 If data from several versions is being returned the entry
3216 for the most recent version should be returned first, and
3217 entries should be separated by the representation of a
3218 blank line (the "title" line may also be followed by the
3219 representation of blank line).
3223 <sect1 id="f-Binary">
3224 <heading><tt>Binary</tt></heading>
3227 This field is a list of binary packages.
3231 When it appears in the <file>.dsc</file> file it is the list
3232 of binary packages which a source package can produce. It
3233 does not necessarily produce all of these binary packages
3234 for every architecture. The source control file doesn't
3235 contain details of which architectures are appropriate for
3236 which of the binary packages.
3240 When it appears in a <file>.changes</file> file it lists the
3241 names of the binary packages actually being uploaded.
3245 The syntax is a list of binary packages separated by
3247 A space after each comma is conventional.
3248 </footnote>. Currently the packages must be separated using
3249 only spaces in the <file>.changes</file> file.
3253 <sect1 id="f-Installed-Size">
3254 <heading><tt>Installed-Size</tt></heading>
3257 This field appears in the control files of binary
3258 packages, and in the <file>Packages</file> files. It gives
3259 the total amount of disk space required to install the
3264 The disk space is represented in kilobytes as a simple
3269 <sect1 id="f-Files">
3270 <heading><tt>Files</tt></heading>
3273 This field contains a list of files with information about
3274 each one. The exact information and syntax varies with
3275 the context. In all cases the part of the field
3276 contents on the same line as the field name is empty. The
3277 remainder of the field is one line per file, each line
3278 being indented by one space and containing a number of
3279 sub-fields separated by spaces.
3283 In the <file>.dsc</file> file, each line contains the MD5
3284 checksum, size and filename of the tar file and (if applicable)
3285 diff file which make up the remainder of the source
3287 That is, the parts which are not the <tt>.dsc</tt>.
3289 The exact forms of the filenames are described
3290 in <ref id="pkg-sourcearchives">.
3294 In the <file>.changes</file> file this contains one line per
3295 file being uploaded. Each line contains the MD5 checksum,
3296 size, section and priority and the filename.
3297 The <qref id="f-Section">section</qref>
3298 and <qref id="f-Priority">priority</qref>
3299 are the values of the corresponding fields in
3300 the main source control file. If no section or priority is
3301 specified then <tt>-</tt> should be used, though section
3302 and priority values must be specified for new packages to
3303 be installed properly.
3307 The special value <tt>byhand</tt> for the section in a
3308 <tt>.changes</tt> file indicates that the file in question
3309 is not an ordinary package file and must by installed by
3310 hand by the distribution maintainers. If the section is
3311 <tt>byhand</tt> the priority should be <tt>-</tt>.
3315 If a new Debian revision of a package is being shipped and
3316 no new original source archive is being distributed the
3317 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3318 entry for the original source archive
3319 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3320 but the <file>.changes</file> file should leave it out. In
3321 this case the original source archive on the distribution
3322 site must match exactly, byte-for-byte, the original
3323 source archive which was used to generate the
3324 <file>.dsc</file> file and diff which are being uploaded.</p>
3327 <sect1 id="f-Closes">
3328 <heading><tt>Closes</tt></heading>
3331 A space-separated list of bug report numbers that the upload
3332 governed by the .changes file closes.
3336 <sect1 id="f-Homepage">
3337 <heading><tt>Homepage</tt></heading>
3340 The URL of the web site for this package, preferably (when
3341 applicable) the site from which the original source can be
3342 obtained and any additional upstream documentation or
3343 information may be found. The content of this field is a
3344 simple URL without any surrounding characters such as
3352 <heading>User-defined fields</heading>
3355 Additional user-defined fields may be added to the
3356 source package control file. Such fields will be
3357 ignored, and not copied to (for example) binary or
3358 source package control files or upload control files.
3362 If you wish to add additional unsupported fields to
3363 these output files you should use the mechanism
3368 Fields in the main source control information file with
3369 names starting <tt>X</tt>, followed by one or more of
3370 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3371 be copied to the output files. Only the part of the
3372 field name after the hyphen will be used in the output
3373 file. Where the letter <tt>B</tt> is used the field
3374 will appear in binary package control files, where the
3375 letter <tt>S</tt> is used in source package control
3376 files and where <tt>C</tt> is used in upload control
3377 (<tt>.changes</tt>) files.
3381 For example, if the main source information control file
3384 XBS-Comment: I stand between the candle and the star.
3386 then the binary and source package control files will contain the
3389 Comment: I stand between the candle and the star.
3398 <chapt id="maintainerscripts">
3399 <heading>Package maintainer scripts and installation procedure</heading>
3402 <heading>Introduction to package maintainer scripts</heading>
3405 It is possible to supply scripts as part of a package which
3406 the package management system will run for you when your
3407 package is installed, upgraded or removed.
3411 These scripts are the files <prgn>preinst</prgn>,
3412 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3413 <prgn>postrm</prgn> in the control area of the package.
3414 They must be proper executable files; if they are scripts
3415 (which is recommended), they must start with the usual
3416 <tt>#!</tt> convention. They should be readable and
3417 executable by anyone, and must not be world-writable.
3421 The package management system looks at the exit status from
3422 these scripts. It is important that they exit with a
3423 non-zero status if there is an error, so that the package
3424 management system can stop its processing. For shell
3425 scripts this means that you <em>almost always</em> need to
3426 use <tt>set -e</tt> (this is usually true when writing shell
3427 scripts, in fact). It is also important, of course, that
3428 they don't exit with a non-zero status if everything went
3433 Additionally, packages interacting with users using
3434 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3435 install a <prgn>config</prgn> script in the control area,
3436 see <ref id="maintscriptprompt"> for details.
3440 When a package is upgraded a combination of the scripts from
3441 the old and new packages is called during the upgrade
3442 procedure. If your scripts are going to be at all
3443 complicated you need to be aware of this, and may need to
3444 check the arguments to your scripts.
3448 Broadly speaking the <prgn>preinst</prgn> is called before
3449 (a particular version of) a package is installed, and the
3450 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3451 before (a version of) a package is removed and the
3452 <prgn>postrm</prgn> afterwards.
3456 Programs called from maintainer scripts should not normally
3457 have a path prepended to them. Before installation is
3458 started, the package management system checks to see if the
3459 programs <prgn>ldconfig</prgn>,
3460 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3461 and <prgn>update-rc.d</prgn> can be found via the
3462 <tt>PATH</tt> environment variable. Those programs, and any
3463 other program that one would expect to be in the
3464 <tt>PATH</tt>, should thus be invoked without an absolute
3465 pathname. Maintainer scripts should also not reset the
3466 <tt>PATH</tt>, though they might choose to modify it by
3467 prepending or appending package-specific directories. These
3468 considerations really apply to all shell scripts.</p>
3471 <sect id="idempotency">
3472 <heading>Maintainer scripts idempotency</heading>
3475 It is necessary for the error recovery procedures that the
3476 scripts be idempotent. This means that if it is run
3477 successfully, and then it is called again, it doesn't bomb
3478 out or cause any harm, but just ensures that everything is
3479 the way it ought to be. If the first call failed, or
3480 aborted half way through for some reason, the second call
3481 should merely do the things that were left undone the first
3482 time, if any, and exit with a success status if everything
3484 This is so that if an error occurs, the user interrupts
3485 <prgn>dpkg</prgn> or some other unforeseen circumstance
3486 happens you don't leave the user with a badly-broken
3487 package when <prgn>dpkg</prgn> attempts to repeat the
3493 <sect id="controllingterminal">
3494 <heading>Controlling terminal for maintainer scripts</heading>
3497 The maintainer scripts are guaranteed to run with a
3498 controlling terminal and can interact with the user.
3499 Because these scripts may be executed with standard output
3500 redirected into a pipe for logging purposes, Perl scripts
3501 should set unbuffered output by setting <tt>$|=1</tt> so
3502 that the output is printed immediately rather than being
3506 <sect id="exitstatus">
3507 <heading>Exit status</heading>
3510 Each script must return a zero exit status for
3511 success, or a nonzero one for failure, since the package
3512 management system looks for the exit status of these scripts
3513 and determines what action to take next based on that datum.
3517 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3522 <list compact="compact">
3524 <var>new-preinst</var> <tt>install</tt>
3527 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3530 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3533 <var>old-preinst</var> <tt>abort-upgrade</tt>
3534 <var>new-version</var>
3539 <list compact="compact">
3541 <var>postinst</var> <tt>configure</tt>
3542 <var>most-recently-configured-version</var>
3545 <var>old-postinst</var> <tt>abort-upgrade</tt>
3546 <var>new-version</var>
3549 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3550 <tt>in-favour</tt> <var>package</var>
3551 <var>new-version</var>
3554 <var>postinst</var> <tt>abort-remove</tt>
3557 <var>deconfigured's-postinst</var>
3558 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3559 <var>failed-install-package</var> <var>version</var>
3560 [<tt>removing</tt> <var>conflicting-package</var>
3566 <list compact="compact">
3568 <var>prerm</var> <tt>remove</tt>
3571 <var>old-prerm</var> <tt>upgrade</tt>
3572 <var>new-version</var>
3575 <var>new-prerm</var> <tt>failed-upgrade</tt>
3576 <var>old-version</var>
3579 <var>conflictor's-prerm</var> <tt>remove</tt>
3580 <tt>in-favour</tt> <var>package</var>
3581 <var>new-version</var>
3584 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3585 <tt>in-favour</tt> <var>package-being-installed</var>
3586 <var>version</var> [<tt>removing</tt>
3587 <var>conflicting-package</var>
3593 <list compact="compact">
3595 <var>postrm</var> <tt>remove</tt>
3598 <var>postrm</var> <tt>purge</tt>
3601 <var>old-postrm</var> <tt>upgrade</tt>
3602 <var>new-version</var>
3605 <var>new-postrm</var> <tt>failed-upgrade</tt>
3606 <var>old-version</var>
3609 <var>new-postrm</var> <tt>abort-install</tt>
3612 <var>new-postrm</var> <tt>abort-install</tt>
3613 <var>old-version</var>
3616 <var>new-postrm</var> <tt>abort-upgrade</tt>
3617 <var>old-version</var>
3620 <var>disappearer's-postrm</var> <tt>disappear</tt>
3621 <var>overwriter</var>
3622 <var>overwriter-version</var>
3628 <sect id="unpackphase">
3629 <heading>Details of unpack phase of installation or upgrade</heading>
3632 The procedure on installation/upgrade/overwrite/disappear
3633 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3634 stage of <tt>dpkg --install</tt>) is as follows. In each
3635 case, if a major error occurs (unless listed below) the
3636 actions are, in general, run backwards - this means that the
3637 maintainer scripts are run with different arguments in
3638 reverse order. These are the "error unwind" calls listed
3645 If a version of the package is already installed, call
3646 <example compact="compact">
3647 <var>old-prerm</var> upgrade <var>new-version</var>
3651 If the script runs but exits with a non-zero
3652 exit status, <prgn>dpkg</prgn> will attempt:
3653 <example compact="compact">
3654 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3656 If this works, the upgrade continues. If this
3657 does not work, the error unwind:
3658 <example compact="compact">
3659 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3661 If this works, then the old-version is
3662 "Installed", if not, the old version is in a
3663 "Failed-Config" state.
3669 If a "conflicting" package is being removed at the same time,
3670 or if any package will be broken (due to <tt>Breaks</tt>):
3673 If <tt>--auto-deconfigure</tt> is
3674 specified, call, for each package to be deconfigured
3675 due to <tt>Breaks</tt>:
3676 <example compact="compact">
3677 <var>deconfigured's-prerm</var> deconfigure \
3678 in-favour <var>package-being-installed</var> <var>version</var>
3681 <example compact="compact">
3682 <var>deconfigured's-postinst</var> abort-deconfigure \
3683 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3685 The deconfigured packages are marked as
3686 requiring configuration, so that if
3687 <tt>--install</tt> is used they will be
3688 configured again if possible.
3691 If any packages depended on a conflicting
3692 package being removed and <tt>--auto-deconfigure</tt> is
3693 specified, call, for each such package:
3694 <example compact="compact">
3695 <var>deconfigured's-prerm</var> deconfigure \
3696 in-favour <var>package-being-installed</var> <var>version</var> \
3697 removing <var>conflicting-package</var> <var>version</var>
3700 <example compact="compact">
3701 <var>deconfigured's-postinst</var> abort-deconfigure \
3702 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3703 removing <var>conflicting-package</var> <var>version</var>
3705 The deconfigured packages are marked as
3706 requiring configuration, so that if
3707 <tt>--install</tt> is used they will be
3708 configured again if possible.
3711 To prepare for removal of each conflicting package, call:
3712 <example compact="compact">
3713 <var>conflictor's-prerm</var> remove \
3714 in-favour <var>package</var> <var>new-version</var>
3717 <example compact="compact">
3718 <var>conflictor's-postinst</var> abort-remove \
3719 in-favour <var>package</var> <var>new-version</var>
3728 If the package is being upgraded, call:
3729 <example compact="compact">
3730 <var>new-preinst</var> upgrade <var>old-version</var>
3732 If this fails, we call:
3734 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3741 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3743 is called. If this works, then the old version
3744 is in an "Installed" state, or else it is left
3745 in an "Unpacked" state.
3750 If it fails, then the old version is left
3751 in an "Half-Installed" state.
3758 Otherwise, if the package had some configuration
3759 files from a previous version installed (i.e., it
3760 is in the "configuration files only" state):
3761 <example compact="compact">
3762 <var>new-preinst</var> install <var>old-version</var>
3766 <var>new-postrm</var> abort-install <var>old-version</var>
3768 If this fails, the package is left in a
3769 "Half-Installed" state, which requires a
3770 reinstall. If it works, the packages is left in
3771 a "Config Files" state.
3774 Otherwise (i.e., the package was completely purged):
3775 <example compact="compact">
3776 <var>new-preinst</var> install
3779 <example compact="compact">
3780 <var>new-postrm</var> abort-install
3782 If the error-unwind fails, the package is in a
3783 "Half Installed" phase, and requires a
3784 reinstall. If the error unwind works, the
3785 package is in a not installed state.
3792 The new package's files are unpacked, overwriting any
3793 that may be on the system already, for example any
3794 from the old version of the same package or from
3795 another package. Backups of the old files are kept
3796 temporarily, and if anything goes wrong the package
3797 management system will attempt to put them back as
3798 part of the error unwind.
3802 It is an error for a package to contain files which
3803 are on the system in another package, unless
3804 <tt>Replaces</tt> is used (see <ref id="replaces">).
3806 The following paragraph is not currently the case:
3807 Currently the <tt>- - force-overwrite</tt> flag is
3808 enabled, downgrading it to a warning, but this may not
3814 It is a more serious error for a package to contain a
3815 plain file or other kind of non-directory where another
3816 package has a directory (again, unless
3817 <tt>Replaces</tt> is used). This error can be
3818 overridden if desired using
3819 <tt>--force-overwrite-dir</tt>, but this is not
3824 Packages which overwrite each other's files produce
3825 behavior which, though deterministic, is hard for the
3826 system administrator to understand. It can easily
3827 lead to "missing" programs if, for example, a package
3828 is installed which overwrites a file from another
3829 package, and is then removed again.<footnote>
3830 Part of the problem is due to what is arguably a
3831 bug in <prgn>dpkg</prgn>.
3836 A directory will never be replaced by a symbolic link
3837 to a directory or vice versa; instead, the existing
3838 state (symlink or not) will be left alone and
3839 <prgn>dpkg</prgn> will follow the symlink if there is
3848 If the package is being upgraded, call
3849 <example compact="compact">
3850 <var>old-postrm</var> upgrade <var>new-version</var>
3854 If this fails, <prgn>dpkg</prgn> will attempt:
3855 <example compact="compact">
3856 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3858 If this works, installation continues. If not,
3860 <example compact="compact">
3861 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3863 If this fails, the old version is left in an
3864 "Half Installed" state. If it works, dpkg now
3866 <example compact="compact">
3867 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3869 If this fails, the old version is left in an
3870 "Half Installed" state. If it works, dpkg now
3872 <example compact="compact">
3873 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3875 If this fails, the old version is in an
3882 This is the point of no return - if
3883 <prgn>dpkg</prgn> gets this far, it won't back off
3884 past this point if an error occurs. This will
3885 leave the package in a fairly bad state, which
3886 will require a successful re-installation to clear
3887 up, but it's when <prgn>dpkg</prgn> starts doing
3888 things that are irreversible.
3893 Any files which were in the old version of the package
3894 but not in the new are removed.
3898 The new file list replaces the old.
3902 The new maintainer scripts replace the old.
3906 Any packages all of whose files have been overwritten
3907 during the installation, and which aren't required for
3908 dependencies, are considered to have been removed.
3909 For each such package
3912 <prgn>dpkg</prgn> calls:
3913 <example compact="compact">
3914 <var>disappearer's-postrm</var> disappear \
3915 <var>overwriter</var> <var>overwriter-version</var>
3919 The package's maintainer scripts are removed.
3922 It is noted in the status database as being in a
3923 sane state, namely not installed (any conffiles
3924 it may have are ignored, rather than being
3925 removed by <prgn>dpkg</prgn>). Note that
3926 disappearing packages do not have their prerm
3927 called, because <prgn>dpkg</prgn> doesn't know
3928 in advance that the package is going to
3935 Any files in the package we're unpacking that are also
3936 listed in the file lists of other packages are removed
3937 from those lists. (This will lobotomize the file list
3938 of the "conflicting" package if there is one.)
3942 The backup files made during installation, above, are
3948 The new package's status is now sane, and recorded as
3953 Here is another point of no return - if the
3954 conflicting package's removal fails we do not unwind
3955 the rest of the installation; the conflicting package
3956 is left in a half-removed limbo.
3961 If there was a conflicting package we go and do the
3962 removal actions (described below), starting with the
3963 removal of the conflicting package's files (any that
3964 are also in the package being installed have already
3965 been removed from the conflicting package's file list,
3966 and so do not get removed now).
3972 <sect id="configdetails"><heading>Details of configuration</heading>
3975 When we configure a package (this happens with <tt>dpkg
3976 --install</tt> and <tt>dpkg --configure</tt>), we first
3977 update any <tt>conffile</tt>s and then call:
3978 <example compact="compact">
3979 <var>postinst</var> configure <var>most-recently-configured-version</var>
3984 No attempt is made to unwind after errors during
3985 configuration. If the configuration fails, the package is in
3986 a "Failed Config" state, and an error message is generated.
3990 If there is no most recently configured version
3991 <prgn>dpkg</prgn> will pass a null argument.
3994 Historical note: Truly ancient (pre-1997) versions of
3995 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3996 (including the angle brackets) in this case. Even older
3997 ones did not pass a second argument at all, under any
3998 circumstance. Note that upgrades using such an old dpkg
3999 version are unlikely to work for other reasons, even if
4000 this old argument behavior is handled by your postinst script.
4006 <sect id="removedetails"><heading>Details of removal and/or
4007 configuration purging</heading>
4013 <example compact="compact">
4014 <var>prerm</var> remove
4018 If prerm fails during replacement due to conflict
4020 <var>conflictor's-postinst</var> abort-remove \
4021 in-favour <var>package</var> <var>new-version</var>
4025 <var>postinst</var> abort-remove
4029 If this fails, the package is in a "Failed-Config"
4030 state, or else it remains "Installed".
4034 The package's files are removed (except <tt>conffile</tt>s).
4037 <example compact="compact">
4038 <var>postrm</var> remove
4042 If it fails, there's no error unwind, and the package is in
4043 an "Half-Installed" state.
4048 All the maintainer scripts except the <prgn>postrm</prgn>
4053 If we aren't purging the package we stop here. Note
4054 that packages which have no <prgn>postrm</prgn> and no
4055 <tt>conffile</tt>s are automatically purged when
4056 removed, as there is no difference except for the
4057 <prgn>dpkg</prgn> status.
4061 The <tt>conffile</tt>s and any backup files
4062 (<tt>~</tt>-files, <tt>#*#</tt> files,
4063 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4068 <example compact="compact">
4069 <var>postrm</var> purge
4073 If this fails, the package remains in a "Config-Files"
4078 The package's file list is removed.
4087 <chapt id="relationships">
4088 <heading>Declaring relationships between packages</heading>
4090 <sect id="depsyntax">
4091 <heading>Syntax of relationship fields</heading>
4094 These fields all have a uniform syntax. They are a list of
4095 package names separated by commas.
4099 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4100 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4101 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4102 control file fields of the package, which declare
4103 dependencies on other packages, the package names listed may
4104 also include lists of alternative package names, separated
4105 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4106 if any one of the alternative packages is installed, that
4107 part of the dependency is considered to be satisfied.
4111 All of the fields except for <tt>Provides</tt> may restrict
4112 their applicability to particular versions of each named
4113 package. This is done in parentheses after each individual
4114 package name; the parentheses should contain a relation from
4115 the list below followed by a version number, in the format
4116 described in <ref id="f-Version">.
4120 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4121 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4122 strictly earlier, earlier or equal, exactly equal, later or
4123 equal and strictly later, respectively. The deprecated
4124 forms <tt><</tt> and <tt>></tt> were used to mean
4125 earlier/later or equal, rather than strictly earlier/later,
4126 so they should not appear in new packages (though
4127 <prgn>dpkg</prgn> still supports them).
4131 Whitespace may appear at any point in the version
4132 specification subject to the rules in <ref
4133 id="controlsyntax">, and must appear where it's necessary to
4134 disambiguate; it is not otherwise significant. All of the
4135 relationship fields may span multiple lines. For
4136 consistency and in case of future changes to
4137 <prgn>dpkg</prgn> it is recommended that a single space be
4138 used after a version relationship and before a version
4139 number; it is also conventional to put a single space after
4140 each comma, on either side of each vertical bar, and before
4141 each open parenthesis. When wrapping a relationship field, it
4142 is conventional to do so after a comma and before the space
4143 following that comma.
4147 For example, a list of dependencies might appear as:
4148 <example compact="compact">
4151 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4156 All fields that specify build-time relationships
4157 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4158 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4159 may be restricted to a certain set of architectures. This
4160 is indicated in brackets after each individual package name and
4161 the optional version specification. The brackets enclose a
4162 list of Debian architecture names separated by whitespace.
4163 Exclamation marks may be prepended to each of the names.
4164 (It is not permitted for some names to be prepended with
4165 exclamation marks while others aren't.) If the current Debian
4166 host architecture is not in this list and there are no
4167 exclamation marks in the list, or it is in the list with a
4168 prepended exclamation mark, the package name and the
4169 associated version specification are ignored completely for
4170 the purposes of defining the relationships.
4175 <example compact="compact">
4177 Build-Depends-Indep: texinfo
4178 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4179 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4184 Note that the binary package relationship fields such as
4185 <tt>Depends</tt> appear in one of the binary package
4186 sections of the control file, whereas the build-time
4187 relationships such as <tt>Build-Depends</tt> appear in the
4188 source package section of the control file (which is the
4193 <sect id="binarydeps">
4194 <heading>Binary Dependencies - <tt>Depends</tt>,
4195 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4196 <tt>Pre-Depends</tt>
4200 Packages can declare in their control file that they have
4201 certain relationships to other packages - for example, that
4202 they may not be installed at the same time as certain other
4203 packages, and/or that they depend on the presence of others.
4207 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4208 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4209 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4213 These seven fields are used to declare a dependency
4214 relationship by one package on another. Except for
4215 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4216 depending (binary) package's control file.
4217 (<tt>Enhances</tt> appears in the recommending package's
4218 control file, and <tt>Breaks</tt> appears in the version of
4219 depended-on package which causes the named package to
4224 A <tt>Depends</tt> field takes effect <em>only</em> when a
4225 package is to be configured. It does not prevent a package
4226 being on the system in an unconfigured state while its
4227 dependencies are unsatisfied, and it is possible to replace
4228 a package whose dependencies are satisfied and which is
4229 properly installed with a different version whose
4230 dependencies are not and cannot be satisfied; when this is
4231 done the depending package will be left unconfigured (since
4232 attempts to configure it will give errors) and will not
4233 function properly. If it is necessary, a
4234 <tt>Pre-Depends</tt> field can be used, which has a partial
4235 effect even when a package is being unpacked, as explained
4236 in detail below. (The other three dependency fields,
4237 <tt>Recommends</tt>, <tt>Suggests</tt> and
4238 <tt>Enhances</tt>, are only used by the various front-ends
4239 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4240 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4244 For this reason packages in an installation run are usually
4245 all unpacked first and all configured later; this gives
4246 later versions of packages with dependencies on later
4247 versions of other packages the opportunity to have their
4248 dependencies satisfied.
4252 In case of circular dependencies, since installation or
4253 removal order honoring the dependency order can't be
4254 established, dependency loops are broken at some point
4255 (based on rules below), and some packages may not be able to
4256 rely on their dependencies being present when being
4257 installed or removed, depending on which side of the break
4258 of the circular dependency loop they happen to be on. If one
4259 of the packages in the loop has no postinst script, then the
4260 cycle will be broken at that package, so as to ensure that
4261 all postinst scripts run with the dependencies properly
4262 configured if this is possible. Otherwise the breaking point
4267 The <tt>Depends</tt> field thus allows package maintainers
4268 to impose an order in which packages should be configured.
4272 The meaning of the five dependency fields is as follows:
4274 <tag><tt>Depends</tt></tag>
4277 This declares an absolute dependency. A package will
4278 not be configured unless all of the packages listed in
4279 its <tt>Depends</tt> field have been correctly
4284 The <tt>Depends</tt> field should be used if the
4285 depended-on package is required for the depending
4286 package to provide a significant amount of
4291 The <tt>Depends</tt> field should also be used if the
4292 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4293 <prgn>postrm</prgn> scripts require the package to be
4294 present in order to run. Note, however, that the
4295 <prgn>postrm</prgn> cannot rely on any non-essential
4296 packages to be present during the <tt>purge</tt>
4300 <tag><tt>Recommends</tt></tag>
4303 This declares a strong, but not absolute, dependency.
4307 The <tt>Recommends</tt> field should list packages
4308 that would be found together with this one in all but
4309 unusual installations.
4313 <tag><tt>Suggests</tt></tag>
4315 This is used to declare that one package may be more
4316 useful with one or more others. Using this field
4317 tells the packaging system and the user that the
4318 listed packages are related to this one and can
4319 perhaps enhance its usefulness, but that installing
4320 this one without them is perfectly reasonable.
4323 <tag><tt>Enhances</tt></tag>
4325 This field is similar to Suggests but works in the
4326 opposite direction. It is used to declare that a
4327 package can enhance the functionality of another
4331 <tag><tt>Pre-Depends</tt></tag>
4334 This field is like <tt>Depends</tt>, except that it
4335 also forces <prgn>dpkg</prgn> to complete installation
4336 of the packages named before even starting the
4337 installation of the package which declares the
4338 pre-dependency, as follows:
4342 When a package declaring a pre-dependency is about to
4343 be <em>unpacked</em> the pre-dependency can be
4344 satisfied if the depended-on package is either fully
4345 configured, <em>or even if</em> the depended-on
4346 package(s) are only unpacked or half-configured,
4347 provided that they have been configured correctly at
4348 some point in the past (and not removed or partially
4349 removed since). In this case, both the
4350 previously-configured and currently unpacked or
4351 half-configured versions must satisfy any version
4352 clause in the <tt>Pre-Depends</tt> field.
4356 When the package declaring a pre-dependency is about
4357 to be <em>configured</em>, the pre-dependency will be
4358 treated as a normal <tt>Depends</tt>, that is, it will
4359 be considered satisfied only if the depended-on
4360 package has been correctly configured.
4364 <tt>Pre-Depends</tt> should be used sparingly,
4365 preferably only by packages whose premature upgrade or
4366 installation would hamper the ability of the system to
4367 continue with any upgrade that might be in progress.
4371 <tt>Pre-Depends</tt> are also required if the
4372 <prgn>preinst</prgn> script depends on the named
4373 package. It is best to avoid this situation if
4381 When selecting which level of dependency to use you should
4382 consider how important the depended-on package is to the
4383 functionality of the one declaring the dependency. Some
4384 packages are composed of components of varying degrees of
4385 importance. Such a package should list using
4386 <tt>Depends</tt> the package(s) which are required by the
4387 more important components. The other components'
4388 requirements may be mentioned as Suggestions or
4389 Recommendations, as appropriate to the components' relative
4395 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4398 Using <tt>Breaks</tt> may cause problems for upgrades from older
4399 versions of Debian and should not be used until the stable
4400 release of Debian supports <tt>Breaks</tt>.
4404 When one binary package declares that it breaks another,
4405 <prgn>dpkg</prgn> will refuse to allow the package which
4406 declares <tt>Breaks</tt> be installed unless the broken
4407 package is deconfigured first, and it will refuse to
4408 allow the broken package to be reconfigured.
4412 A package will not be regarded as causing breakage merely
4413 because its configuration files are still installed; it must
4414 be at least half-installed.
4418 A special exception is made for packages which declare that
4419 they break their own package name or a virtual package which
4420 they provide (see below): this does not count as a real
4425 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4426 version clause; such a <tt>Breaks</tt> is introduced in the
4427 version of an (implicit or explicit) dependency which
4428 violates an assumption or reveals a bug in earlier versions
4429 of the broken package. This use of <tt>Breaks</tt> will
4430 inform higher-level package management tools that broken
4431 package must be upgraded before the new one.
4435 If the breaking package also overwrites some files from the
4436 older package, it should use <tt>Replaces</tt> (not
4437 <tt>Conflicts</tt>) to ensure this goes smoothly.
4441 <sect id="conflicts">
4442 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4445 When one binary package declares a conflict with another
4446 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4447 refuse to allow them to be installed on the system at the
4452 If one package is to be installed, the other must be removed
4453 first - if the package being installed is marked as
4454 replacing (see <ref id="replaces">) the one on the system,
4455 or the one on the system is marked as deselected, or both
4456 packages are marked <tt>Essential</tt>, then
4457 <prgn>dpkg</prgn> will automatically remove the package
4458 which is causing the conflict, otherwise it will halt the
4459 installation of the new package with an error. This
4460 mechanism is specifically designed to produce an error when
4461 the installed package is <tt>Essential</tt>, but the new
4466 A package will not cause a conflict merely because its
4467 configuration files are still installed; it must be at least
4472 A special exception is made for packages which declare a
4473 conflict with their own package name, or with a virtual
4474 package which they provide (see below): this does not
4475 prevent their installation, and allows a package to conflict
4476 with others providing a replacement for it. You use this
4477 feature when you want the package in question to be the only
4478 package providing some feature.
4482 A <tt>Conflicts</tt> entry should almost never have an
4483 "earlier than" version clause. This would prevent
4484 <prgn>dpkg</prgn> from upgrading or installing the package
4485 which declared such a conflict until the upgrade or removal
4486 of the conflicted-with package had been completed. Instead,
4487 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4488 by the stable release of Debian).
4492 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4496 As well as the names of actual ("concrete") packages, the
4497 package relationship fields <tt>Depends</tt>,
4498 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4499 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4500 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4501 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4502 may mention "virtual packages".
4506 A <em>virtual package</em> is one which appears in the
4507 <tt>Provides</tt> control file field of another package.
4508 The effect is as if the package(s) which provide a
4509 particular virtual package name had been listed by name
4510 everywhere the virtual package name appears. (See also <ref
4515 If there are both concrete and virtual packages of the same
4516 name, then the dependency may be satisfied (or the conflict
4517 caused) by either the concrete package with the name in
4518 question or any other concrete package which provides the
4519 virtual package with the name in question. This is so that,
4520 for example, supposing we have
4521 <example compact="compact">
4524 </example> and someone else releases an enhanced version of
4525 the <tt>bar</tt> package they can say:
4526 <example compact="compact">
4530 and the <tt>bar-plus</tt> package will now also satisfy the
4531 dependency for the <tt>foo</tt> package.
4535 If a relationship field has a version number attached
4536 then only real packages will be considered to see whether
4537 the relationship is satisfied (or the prohibition violated,
4538 for a conflict or breakage) - it is assumed that a real
4539 package which provides the virtual package is not of the
4540 "right" version. So, a <tt>Provides</tt> field may not
4541 contain version numbers, and the version number of the
4542 concrete package which provides a particular virtual package
4543 will not be looked at when considering a dependency on or
4544 conflict with the virtual package name.
4548 It is likely that the ability will be added in a future
4549 release of <prgn>dpkg</prgn> to specify a version number for
4550 each virtual package it provides. This feature is not yet
4551 present, however, and is expected to be used only
4556 If you want to specify which of a set of real packages
4557 should be the default to satisfy a particular dependency on
4558 a virtual package, you should list the real package as an
4559 alternative before the virtual one.
4564 <sect id="replaces"><heading>Overwriting files and replacing
4565 packages - <tt>Replaces</tt></heading>
4568 Packages can declare in their control file that they should
4569 overwrite files in certain other packages, or completely
4570 replace other packages. The <tt>Replaces</tt> control file
4571 field has these two distinct purposes.
4574 <sect1><heading>Overwriting files in other packages</heading>
4577 Firstly, as mentioned before, it is usually an error for a
4578 package to contain files which are on the system in
4583 However, if the overwriting package declares that it
4584 <tt>Replaces</tt> the one containing the file being
4585 overwritten, then <prgn>dpkg</prgn> will replace the file
4586 from the old package with that from the new. The file
4587 will no longer be listed as "owned" by the old package.
4591 If a package is completely replaced in this way, so that
4592 <prgn>dpkg</prgn> does not know of any files it still
4593 contains, it is considered to have "disappeared". It will
4594 be marked as not wanted on the system (selected for
4595 removal) and not installed. Any <tt>conffile</tt>s
4596 details noted for the package will be ignored, as they
4597 will have been taken over by the overwriting package. The
4598 package's <prgn>postrm</prgn> script will be run with a
4599 special argument to allow the package to do any final
4600 cleanup required. See <ref id="mscriptsinstact">.
4603 Replaces is a one way relationship -- you have to
4604 install the replacing package after the replaced
4611 For this usage of <tt>Replaces</tt>, virtual packages (see
4612 <ref id="virtual">) are not considered when looking at a
4613 <tt>Replaces</tt> field - the packages declared as being
4614 replaced must be mentioned by their real names.
4618 Furthermore, this usage of <tt>Replaces</tt> only takes
4619 effect when both packages are at least partially on the
4620 system at once, so that it can only happen if they do not
4621 conflict or if the conflict has been overridden.
4626 <sect1><heading>Replacing whole packages, forcing their
4630 Secondly, <tt>Replaces</tt> allows the packaging system to
4631 resolve which package should be removed when there is a
4632 conflict - see <ref id="conflicts">. This usage only
4633 takes effect when the two packages <em>do</em> conflict,
4634 so that the two usages of this field do not interfere with
4639 In this situation, the package declared as being replaced
4640 can be a virtual package, so for example, all mail
4641 transport agents (MTAs) would have the following fields in
4642 their control files:
4643 <example compact="compact">
4644 Provides: mail-transport-agent
4645 Conflicts: mail-transport-agent
4646 Replaces: mail-transport-agent
4648 ensuring that only one MTA can be installed at any one
4653 <sect id="sourcebinarydeps">
4654 <heading>Relationships between source and binary packages -
4655 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4656 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4660 Source packages that require certain binary packages to be
4661 installed or absent at the time of building the package
4662 can declare relationships to those binary packages.
4666 This is done using the <tt>Build-Depends</tt>,
4667 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4668 <tt>Build-Conflicts-Indep</tt> control file fields.
4672 Build-dependencies on "build-essential" binary packages can be
4673 omitted. Please see <ref id="pkg-relations"> for more information.
4677 The dependencies and conflicts they define must be satisfied
4678 (as defined earlier for binary packages) in order to invoke
4679 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4681 If you make "build-arch" or "binary-arch", you need
4682 Build-Depends. If you make "build-indep" or
4683 "binary-indep", you need Build-Depends and
4684 Build-Depends-Indep. If you make "build" or "binary",
4688 There is no Build-Depends-Arch; this role is essentially
4689 met with Build-Depends. Anyone building the
4690 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4691 is basically assumed to be building the whole package
4692 anyway and so installs all build dependencies. The
4693 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4694 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4695 does not yet know how to check for its existence) and
4696 <tt>binary-arch</tt>.
4699 The purpose of the original split, I recall, was so that
4700 the autobuilders wouldn't need to install extra packages
4701 needed only for the binary-indep targets. But without a
4702 build-arch/build-indep split, this didn't work, since
4703 most of the work is done in the build target, not in the
4709 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4711 The <tt>Build-Depends</tt> and
4712 <tt>Build-Conflicts</tt> fields must be satisfied when
4713 any of the following targets is invoked:
4714 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4715 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4716 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4718 <tag><tt>Build-Depends-Indep</tt>,
4719 <tt>Build-Conflicts-Indep</tt></tag>
4721 The <tt>Build-Depends-Indep</tt> and
4722 <tt>Build-Conflicts-Indep</tt> fields must be
4723 satisfied when any of the following targets is
4724 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4725 <tt>binary</tt> and <tt>binary-indep</tt>.
4735 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4738 Packages containing shared libraries must be constructed with
4739 a little care to make sure that the shared library is always
4740 available. This is especially important for packages whose
4741 shared libraries are vitally important, such as the C library
4742 (currently <tt>libc6</tt>).
4746 Packages involving shared libraries should be split up into
4747 several binary packages. This section mostly deals with how
4748 this separation is to be accomplished; rules for files within
4749 the shared library packages are in <ref id="libraries"> instead.
4752 <sect id="sharedlibs-runtime">
4753 <heading>Run-time shared libraries</heading>
4756 The run-time shared library needs to be placed in a package
4757 whose name changes whenever the shared object version
4760 Since it is common place to install several versions of a
4761 package that just provides shared libraries, it is a
4762 good idea that the library package should not
4763 contain any extraneous non-versioned files, unless they
4764 happen to be in versioned directories.</p>
4766 The most common mechanism is to place it in a package
4768 <package><var>libraryname</var><var>soversion</var></package>,
4769 where <file><var>soversion</var></file> is the version number
4770 in the soname of the shared library<footnote>
4771 The soname is the shared object name: it's the thing
4772 that has to match exactly between building an executable
4773 and running it for the dynamic linker to be able run the
4774 program. For example, if the soname of the library is
4775 <file>libfoo.so.6</file>, the library package would be
4776 called <file>libfoo6</file>.
4778 Alternatively, if it would be confusing to directly append
4779 <var>soversion</var> to <var>libraryname</var> (e.g. because
4780 <var>libraryname</var> itself ends in a number), you may use
4781 <package><var>libraryname</var>-<var>soversion</var></package> and
4782 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4787 If you have several shared libraries built from the same
4788 source tree you may lump them all together into a single
4789 shared library package, provided that you change all of
4790 their sonames at once (so that you don't get filename
4791 clashes if you try to install different versions of the
4792 combined shared libraries package).
4796 The package should install the shared libraries under
4797 their normal names. For example, the <package>libgdbm3</package>
4798 package should install <file>libgdbm.so.3.0.0</file> as
4799 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4800 renamed or re-linked by any <prgn>prerm</prgn> or
4801 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4802 of renaming things safely without affecting running programs,
4803 and attempts to interfere with this are likely to lead to
4808 Shared libraries should not be installed executable, since
4809 the dynamic linker does not require this and trying to
4810 execute a shared library usually results in a core dump.
4814 The run-time library package should include the symbolic link that
4815 <prgn>ldconfig</prgn> would create for the shared libraries.
4816 For example, the <package>libgdbm3</package> package should include
4817 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4818 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4819 linker (for example <prgn>ld.so</prgn> or
4820 <prgn>ld-linux.so.*</prgn>) can find the library between the
4821 time that <prgn>dpkg</prgn> installs it and the time that
4822 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4824 The package management system requires the library to be
4825 placed before the symbolic link pointing to it in the
4826 <file>.deb</file> file. This is so that when
4827 <prgn>dpkg</prgn> comes to install the symlink
4828 (overwriting the previous symlink pointing at an older
4829 version of the library), the new shared library is already
4830 in place. In the past, this was achieved by creating the
4831 library in the temporary packaging directory before
4832 creating the symlink. Unfortunately, this was not always
4833 effective, since the building of the tar file in the
4834 <file>.deb</file> depended on the behavior of the underlying
4835 file system. Some file systems (such as reiserfs) reorder
4836 the files so that the order of creation is forgotten.
4837 Since version 1.7.0, <prgn>dpkg</prgn>
4838 reorders the files itself as necessary when building a
4839 package. Thus it is no longer important to concern
4840 oneself with the order of file creation.
4844 <sect1 id="ldconfig">
4845 <heading><tt>ldconfig</tt></heading>
4848 Any package installing shared libraries in one of the default
4849 library directories of the dynamic linker (which are currently
4850 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4851 listed in <file>/etc/ld.so.conf</file><footnote>
4853 <list compact="compact">
4854 <item>/usr/local/lib</item>
4855 <item>/usr/lib/libc5-compat</item>
4856 <item>/lib/libc5-compat</item>
4859 must use <prgn>ldconfig</prgn> to update the shared library
4864 The package maintainer scripts must only call
4865 <prgn>ldconfig</prgn> under these circumstances:
4866 <list compact="compact">
4867 <item>When the <prgn>postinst</prgn> script is run with a
4868 first argument of <tt>configure</tt>, the script must call
4869 <prgn>ldconfig</prgn>, and may optionally invoke
4870 <prgn>ldconfig</prgn> at other times.
4872 <item>When the <prgn>postrm</prgn> script is run with a
4873 first argument of <tt>remove</tt>, the script should call
4874 <prgn>ldconfig</prgn>.
4879 During install or upgrade, the preinst is called before
4880 the new files are installed, so calling "ldconfig" is
4881 pointless. The preinst of an existing package can also be
4882 called if an upgrade fails. However, this happens during
4883 the critical time when a shared libs may exist on-disk
4884 under a temporary name. Thus, it is dangerous and
4885 forbidden by current policy to call "ldconfig" at this
4890 When a package is installed or upgraded, "postinst
4891 configure" runs after the new files are safely on-disk.
4892 Since it is perfectly safe to invoke ldconfig
4893 unconditionally in a postinst, it is OK for a package to
4894 simply put ldconfig in its postinst without checking the
4895 argument. The postinst can also be called to recover from
4896 a failed upgrade. This happens before any new files are
4897 unpacked, so there is no reason to call "ldconfig" at this
4902 For a package that is being removed, prerm is
4903 called with all the files intact, so calling ldconfig is
4904 useless. The other calls to "prerm" happen in the case of
4905 upgrade at a time when all the files of the old package
4906 are on-disk, so again calling "ldconfig" is pointless.
4910 postrm, on the other hand, is called with the "remove"
4911 argument just after the files are removed, so this is
4912 the proper time to call "ldconfig" to notify the system
4913 of the fact that the shared libraries from the package
4914 are removed. The postrm can be called at several other
4915 times. At the time of "postrm purge", "postrm
4916 abort-install", or "postrm abort-upgrade", calling
4917 "ldconfig" is useless because the shared lib files are
4918 not on-disk. However, when "postrm" is invoked with
4919 arguments "upgrade", "failed-upgrade", or "disappear", a
4920 shared lib may exist on-disk under a temporary filename.
4928 <sect id="sharedlibs-support-files">
4929 <heading>Shared library support files</heading>
4932 If your package contains files whose names do not change with
4933 each change in the library shared object version, you must not
4934 put them in the shared library package. Otherwise, several
4935 versions of the shared library cannot be installed at the same
4936 time without filename clashes, making upgrades and transitions
4937 unnecessarily difficult.
4941 It is recommended that supporting files and run-time support
4942 programs that do not need to be invoked manually by users, but
4943 are nevertheless required for the package to function, be placed
4944 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4945 preferably under <file>/usr/lib/</file><var>package-name</var>.
4946 If the program or file is architecture independent, the
4947 recommendation is for it to be placed in a subdirectory of
4948 <file>/usr/share</file> instead, preferably under
4949 <file>/usr/share/</file><var>package-name</var>. Following the
4950 <var>package-name</var> naming convention ensures that the file
4951 names change when the shared object version changes.
4955 Run-time support programs that use the shared library but are
4956 not required for the library to function or files used by the
4957 shared library that can be used by any version of the shared
4958 library package should instead be put in a separate package.
4959 This package might typically be named
4960 <package><var>libraryname</var>-tools</package>; note the
4961 absence of the <var>soversion</var> in the package name.
4965 Files and support programs only useful when compiling software
4966 against the library should be included in the development
4967 package for the library.<footnote>
4968 For example, a <file><var>package-name</var>-config</file>
4969 script or <package>pkg-config</package> configuration files.
4974 <sect id="sharedlibs-static">
4975 <heading>Static libraries</heading>
4978 The static library (<file><var>libraryname.a</var></file>)
4979 is usually provided in addition to the shared version.
4980 It is placed into the development package (see below).
4984 In some cases, it is acceptable for a library to be
4985 available in static form only; these cases include:
4987 <item>libraries for languages whose shared library support
4988 is immature or unstable</item>
4989 <item>libraries whose interfaces are in flux or under
4990 development (commonly the case when the library's
4991 major version number is zero, or where the ABI breaks
4992 across patchlevels)</item>
4993 <item>libraries which are explicitly intended to be
4994 available only in static form by their upstream
4999 <sect id="sharedlibs-dev">
5000 <heading>Development files</heading>
5003 The development files associated to a shared library need to be
5004 placed in a package called
5005 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5006 or if you prefer only to support one development version at a
5007 time, <package><var>libraryname</var>-dev</package>.
5011 In case several development versions of a library exist, you may
5012 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5013 <ref id="conflicts">) to ensure that the user only installs one
5014 development version at a time (as different development versions are
5015 likely to have the same header files in them, which would cause a
5016 filename clash if both were installed).
5020 The development package should contain a symlink for the associated
5021 shared library without a version number. For example, the
5022 <package>libgdbm-dev</package> package should include a symlink
5023 from <file>/usr/lib/libgdbm.so</file> to
5024 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5025 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5026 <file>libgdbm.so</file> when compiling dynamically.
5030 <sect id="sharedlibs-intradeps">
5031 <heading>Dependencies between the packages of the same library</heading>
5034 Typically the development version should have an exact
5035 version dependency on the runtime library, to make sure that
5036 compilation and linking happens correctly. The
5037 <tt>${binary:Version}</tt> substitution variable can be
5038 useful for this purpose.
5040 Previously, <tt>${Source-Version}</tt> was used, but its name
5041 was confusing and it has been deprecated since dpkg 1.13.19.
5046 <sect id="sharedlibs-shlibdeps">
5047 <heading>Dependencies between the library and other packages -
5048 the <tt>shlibs</tt> system</heading>
5051 If a package contains a binary or library which links to a
5052 shared library, we must ensure that when the package is
5053 installed on the system, all of the libraries needed are
5054 also installed. This requirement led to the creation of the
5055 <tt>shlibs</tt> system, which is very simple in its design:
5056 any package which <em>provides</em> a shared library also
5057 provides information on the package dependencies required to
5058 ensure the presence of this library, and any package which
5059 <em>uses</em> a shared library uses this information to
5060 determine the dependencies it requires. The files which
5061 contain the mapping from shared libraries to the necessary
5062 dependency information are called <file>shlibs</file> files.
5066 Thus, when a package is built which contains any shared
5067 libraries, it must provide a <file>shlibs</file> file for other
5068 packages to use, and when a package is built which contains
5069 any shared libraries or compiled binaries, it must run
5070 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5071 on these to determine the libraries used and hence the
5072 dependencies needed by this package.<footnote>
5074 In the past, the shared libraries linked to were
5075 determined by calling <prgn>ldd</prgn>, but now
5076 <prgn>objdump</prgn> is used to do this. The only
5077 change this makes to package building is that
5078 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5079 libraries, whereas in the past this was unnecessary.
5080 The rest of this footnote explains the advantage that
5085 We say that a binary <tt>foo</tt> <em>directly</em> uses
5086 a library <tt>libbar</tt> if it is explicitly linked
5087 with that library (that is, it uses the flag
5088 <tt>-lbar</tt> during the linking stage). Other
5089 libraries that are needed by <tt>libbar</tt> are linked
5090 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5091 linker will load them automatically when it loads
5092 <tt>libbar</tt>. A package should depend on
5093 the libraries it directly uses, and the dependencies for
5094 those libraries should automatically pull in the other
5099 Unfortunately, the <prgn>ldd</prgn> program shows both
5100 the directly and indirectly used libraries, meaning that
5101 the dependencies determined included both direct and
5102 indirect dependencies. The use of <prgn>objdump</prgn>
5103 avoids this problem by determining only the directly
5108 A good example of where this helps is the following. We
5109 could update <tt>libimlib</tt> with a new version that
5110 supports a new graphics format called dgf (but retaining
5111 the same major version number). If we used the old
5112 <prgn>ldd</prgn> method, every package that uses
5113 <tt>libimlib</tt> would need to be recompiled so it
5114 would also depend on <tt>libdgf</tt> or it wouldn't run
5115 due to missing symbols. However with the new system,
5116 packages using <tt>libimlib</tt> can rely on
5117 <tt>libimlib</tt> itself having the dependency on
5118 <tt>libdgf</tt> and so they would not need rebuilding.
5124 In the following sections, we will first describe where the
5125 various <tt>shlibs</tt> files are to be found, then how to
5126 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5127 file format and how to create them if your package contains a
5132 <heading>The <tt>shlibs</tt> files present on the system</heading>
5135 There are several places where <tt>shlibs</tt> files are
5136 found. The following list gives them in the order in which
5138 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5139 (The first one which gives the required information is used.)
5145 <p><file>debian/shlibs.local</file></p>
5148 This lists overrides for this package. Its use is
5149 described below (see <ref id="shlibslocal">).
5154 <p><file>/etc/dpkg/shlibs.override</file></p>
5157 This lists global overrides. This list is normally
5158 empty. It is maintained by the local system
5164 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5167 When packages are being built, any
5168 <file>debian/shlibs</file> files are copied into the
5169 control file area of the temporary build directory and
5170 given the name <file>shlibs</file>. These files give
5171 details of any shared libraries included in the
5173 An example may help here. Let us say that the
5174 source package <tt>foo</tt> generates two binary
5175 packages, <tt>libfoo2</tt> and
5176 <tt>foo-runtime</tt>. When building the binary
5177 packages, the two packages are created in the
5178 directories <file>debian/libfoo2</file> and
5179 <file>debian/foo-runtime</file> respectively.
5180 (<file>debian/tmp</file> could be used instead of one
5181 of these.) Since <tt>libfoo2</tt> provides the
5182 <tt>libfoo</tt> shared library, it will require a
5183 <tt>shlibs</tt> file, which will be installed in
5184 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5186 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5187 when <prgn>dpkg-shlibdeps</prgn> is run on the
5189 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5191 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5192 determine whether <tt>foo-prog</tt>'s library
5193 dependencies are satisfied by any of the libraries
5194 provided by <tt>libfoo2</tt>. For this reason,
5195 <prgn>dpkg-shlibdeps</prgn> must only be run once
5196 all of the individual binary packages'
5197 <tt>shlibs</tt> files have been installed into the
5204 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5207 These are the <file>shlibs</file> files corresponding to
5208 all of the packages installed on the system, and are
5209 maintained by the relevant package maintainers.
5214 <p><file>/etc/dpkg/shlibs.default</file></p>
5217 This file lists any shared libraries whose packages
5218 have failed to provide correct <file>shlibs</file> files.
5219 It was used when the <file>shlibs</file> setup was first
5220 introduced, but it is now normally empty. It is
5221 maintained by the <tt>dpkg</tt> maintainer.
5229 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5230 <file>shlibs</file> files</heading>
5234 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5235 into your <file>debian/rules</file> file. If your package
5236 contains only compiled binaries and libraries (but no scripts),
5237 you can use a command such as:
5238 <example compact="compact">
5239 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5240 debian/tmp/usr/lib/*
5242 Otherwise, you will need to explicitly list the compiled
5243 binaries and libraries.<footnote>
5244 If you are using <tt>debhelper</tt>, the
5245 <prgn>dh_shlibdeps</prgn> program will do this work for
5246 you. It will also correctly handle multi-binary
5252 This command puts the dependency information into the
5253 <file>debian/substvars</file> file, which is then used by
5254 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5255 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5256 field in the control file for this to work.
5260 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5261 done. If it does complain you might need to create your own
5262 <file>debian/shlibs.local</file> file, as explained below (see
5263 <ref id="shlibslocal">).
5267 If you have multiple binary packages, you will need to call
5268 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5269 compiled libraries or binaries. In such a case, you will
5270 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5271 utilities to specify a different <file>substvars</file> file.
5275 If you are creating a udeb for use in the Debian Installer, you
5276 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5277 the dependency line of type <tt>udeb</tt> by adding
5278 <tt>-tudeb</tt> as option<footnote>
5279 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5280 will automatically add this option if it knows it is
5282 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5283 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5284 fall back to the regular dependency line.
5288 For more details on dpkg-shlibdeps, please see
5289 <ref id="pkg-dpkg-shlibdeps"> and
5290 <manref name="dpkg-shlibdeps" section="1">.
5295 <heading>The <file>shlibs</file> File Format</heading>
5298 Each <file>shlibs</file> file has the same format. Lines
5299 beginning with <tt>#</tt> are considered to be comments and
5300 are ignored. Each line is of the form:
5301 <example compact="compact">
5302 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5307 We will explain this by reference to the example of the
5308 <tt>zlib1g</tt> package, which (at the time of writing)
5309 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5313 <var>type</var> is an optional element that indicates the type
5314 of package for which the line is valid. The only type currently
5315 in use is <tt>udeb</tt>. The colon and space after the type are
5320 <var>library-name</var> is the name of the shared library,
5321 in this case <tt>libz</tt>. (This must match the name part
5322 of the soname, see below.)
5326 <var>soname-version</var> is the version part of the soname of
5327 the library. The soname is the thing that must exactly match
5328 for the library to be recognized by the dynamic linker, and is
5330 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5331 example, <tt>libz.so.1</tt>.<footnote>
5332 This can be determined using the command
5333 <example compact="compact">
5334 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5337 The version part is the part which comes after
5338 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5342 <var>dependencies</var> has the same syntax as a dependency
5343 field in a binary package control file. It should give
5344 details of which packages are required to satisfy a binary
5345 built against the version of the library contained in the
5346 package. See <ref id="depsyntax"> for details.
5350 In our example, if the first version of the <tt>zlib1g</tt>
5351 package which contained a minor number of at least
5352 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5353 <tt>shlibs</tt> entry for this library could say:
5354 <example compact="compact">
5355 libz 1 zlib1g (>= 1:1.1.3)
5357 The version-specific dependency is to avoid warnings from
5358 the dynamic linker about using older shared libraries with
5363 As zlib1g also provides a udeb containing the shared library,
5364 there would also be a second line:
5365 <example compact="compact">
5366 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5372 <heading>Providing a <file>shlibs</file> file</heading>
5375 If your package provides a shared library, you need to create
5376 a <file>shlibs</file> file following the format described above.
5377 It is usual to call this file <file>debian/shlibs</file> (but if
5378 you have multiple binary packages, you might want to call it
5379 <file>debian/shlibs.<var>package</var></file> instead). Then
5380 let <file>debian/rules</file> install it in the control area:
5381 <example compact="compact">
5382 install -m644 debian/shlibs debian/tmp/DEBIAN
5384 or, in the case of a multi-binary package:
5385 <example compact="compact">
5386 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5388 An alternative way of doing this is to create the
5389 <file>shlibs</file> file in the control area directly from
5390 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5391 file at all,<footnote>
5392 This is what <prgn>dh_makeshlibs</prgn> in the
5393 <tt>debhelper</tt> suite does. If your package also has a udeb
5394 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5395 automatically generate the <tt>udeb:</tt> lines if you specify
5396 the name of the udeb with the <tt>--add-udeb</tt> option.
5398 since the <file>debian/shlibs</file> file itself is ignored by
5399 <prgn>dpkg-shlibdeps</prgn>.
5403 As <prgn>dpkg-shlibdeps</prgn> reads the
5404 <file>DEBIAN/shlibs</file> files in all of the binary packages
5405 being built from this source package, all of the
5406 <file>DEBIAN/shlibs</file> files should be installed before
5407 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5412 <sect1 id="shlibslocal">
5413 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5416 This file is intended only as a <em>temporary</em> fix if
5417 your binaries or libraries depend on a library whose package
5418 does not yet provide a correct <file>shlibs</file> file.
5422 We will assume that you are trying to package a binary
5423 <tt>foo</tt>. When you try running
5424 <prgn>dpkg-shlibdeps</prgn> you get the following error
5425 message (<tt>-O</tt> displays the dependency information on
5426 <tt>stdout</tt> instead of writing it to
5427 <tt>debian/substvars</tt>, and the lines have been wrapped
5428 for ease of reading):
5429 <example compact="compact">
5430 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5431 dpkg-shlibdeps: warning: unable to find dependency
5432 information for shared library libbar (soname 1,
5433 path /usr/lib/libbar.so.1, dependency field Depends)
5434 shlibs:Depends=libc6 (>= 2.2.2-2)
5436 You can then run <prgn>ldd</prgn> on the binary to find the
5437 full location of the library concerned:
5438 <example compact="compact">
5440 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5441 libc.so.6 => /lib/libc.so.6 (0x40032000)
5442 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5444 So the <prgn>foo</prgn> binary depends on the
5445 <prgn>libbar</prgn> shared library, but no package seems to
5446 provide a <file>*.shlibs</file> file handling
5447 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5448 determine the package responsible:
5449 <example compact="compact">
5450 $ dpkg -S /usr/lib/libbar.so.1
5451 bar1: /usr/lib/libbar.so.1
5452 $ dpkg -s bar1 | grep Version
5455 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5456 is the one we are using. Now we can file a bug against the
5457 <tt>bar1</tt> package and create our own
5458 <file>debian/shlibs.local</file> to locally fix the problem.
5459 Including the following line into your
5460 <file>debian/shlibs.local</file> file:
5461 <example compact="compact">
5462 libbar 1 bar1 (>= 1.0-1)
5464 should allow the package build to work.
5468 As soon as the maintainer of <tt>bar1</tt> provides a
5469 correct <file>shlibs</file> file, you should remove this line
5470 from your <file>debian/shlibs.local</file> file. (You should
5471 probably also then have a versioned <tt>Build-Depends</tt>
5472 on <tt>bar1</tt> to help ensure that others do not have the
5473 same problem building your package.)
5482 <chapt id="opersys"><heading>The Operating System</heading>
5485 <heading>File system hierarchy</heading>
5489 <heading>File system Structure</heading>
5492 The location of all installed files and directories must
5493 comply with the File system Hierarchy Standard (FHS),
5494 version 2.3, with the exceptions noted below, and except
5495 where doing so would violate other terms of Debian
5496 Policy. The following exceptions to the FHS apply:
5501 Legacy XFree86 servers are permitted to retain the
5502 configuration file location
5503 <file>/etc/X11/XF86Config-4</file>.
5508 The optional rules related to user specific
5509 configuration files for applications are stored in
5510 the user's home directory are relaxed. It is
5511 recommended that such files start with the
5512 '<tt>.</tt>' character (a "dot file"), and if an
5513 application needs to create more than one dot file
5514 then the preferred placement is in a subdirectory
5515 with a name starting with a '.' character, (a "dot
5516 directory"). In this case it is recommended the
5517 configuration files not start with the '.'
5523 The requirement for amd64 to use <file>/lib64</file>
5524 for 64 bit binaries is removed.
5529 The requirement that
5530 <file>/usr/local/share/man</file> be "synonymous"
5531 with <file>/usr/local/man</file> is relaxed to a
5536 The requirement that windowmanagers with a single
5537 configuration file call it <file>system.*wmrc</file>
5538 is removed, as is the restriction that the window
5539 manager subdirectory be named identically to the
5540 window manager name itself.
5545 The requirement that boot manager configuration
5546 files live in <file>/etc</file>, or at least are
5547 symlinked there, is relaxed to a recommendation.
5554 The version of this document referred here can be
5555 found in the <tt>debian-policy</tt> package or on <url
5556 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5557 name="FHS (Debian copy)"> alongside this manual (or, if
5558 you have the <package>debian-policy</package> installed,
5560 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5561 (local copy)">). The
5562 latest version, which may be a more recent version, may
5564 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5565 Specific questions about following the standard may be
5566 asked on the <tt>debian-devel</tt> mailing list, or
5567 referred to the FHS mailing list (see the
5568 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5574 <heading>Site-specific programs</heading>
5577 As mandated by the FHS, packages must not place any
5578 files in <file>/usr/local</file>, either by putting them in
5579 the file system archive to be unpacked by <prgn>dpkg</prgn>
5580 or by manipulating them in their maintainer scripts.
5584 However, the package may create empty directories below
5585 <file>/usr/local</file> so that the system administrator knows
5586 where to place site-specific files. These are not
5587 directories <em>in</em> <file>/usr/local</file>, but are
5588 children of directories in <file>/usr/local</file>. These
5589 directories (<file>/usr/local/*/dir/</file>)
5590 should be removed on package removal if they are
5595 Note, that this applies only to directories <em>below</em>
5596 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5597 Packages must not create sub-directories in the directory
5598 <file>/usr/local</file> itself, except those listed in FHS,
5599 section 4.5. However, you may create directories below
5600 them as you wish. You must not remove any of the
5601 directories listed in 4.5, even if you created them.
5605 Since <file>/usr/local</file> can be mounted read-only from a
5606 remote server, these directories must be created and
5607 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5608 maintainer scripts and not be included in the
5609 <file>.deb</file> archive. These scripts must not fail if
5610 either of these operations fail.
5614 For example, the <tt>emacsen-common</tt> package could
5615 contain something like
5616 <example compact="compact">
5617 if [ ! -e /usr/local/share/emacs ]
5619 if mkdir /usr/local/share/emacs 2>/dev/null
5621 chown root:staff /usr/local/share/emacs
5622 chmod 2775 /usr/local/share/emacs
5626 in its <prgn>postinst</prgn> script, and
5627 <example compact="compact">
5628 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5629 rmdir /usr/local/share/emacs 2>/dev/null || true
5631 in the <prgn>prerm</prgn> script. (Note that this form is
5632 used to ensure that if the script is interrupted, the
5633 directory <file>/usr/local/share/emacs</file> will still be
5638 If you do create a directory in <file>/usr/local</file> for
5639 local additions to a package, you should ensure that
5640 settings in <file>/usr/local</file> take precedence over the
5641 equivalents in <file>/usr</file>.
5645 However, because <file>/usr/local</file> and its contents are
5646 for exclusive use of the local administrator, a package
5647 must not rely on the presence or absence of files or
5648 directories in <file>/usr/local</file> for normal operation.
5652 The <file>/usr/local</file> directory itself and all the
5653 subdirectories created by the package should (by default) have
5654 permissions 2775 (group-writable and set-group-id) and be
5655 owned by <tt>root:staff</tt>.
5660 <heading>The system-wide mail directory</heading>
5662 The system-wide mail directory is <file>/var/mail</file>. This
5663 directory is part of the base system and should not owned
5664 by any particular mail agents. The use of the old
5665 location <file>/var/spool/mail</file> is deprecated, even
5666 though the spool may still be physically located there.
5667 To maintain partial upgrade compatibility for systems
5668 which have <file>/var/spool/mail</file> as their physical mail
5669 spool, packages using <file>/var/mail</file> must depend on
5670 either <package>libc6</package> (>= 2.1.3-13), or on
5671 <package>base-files</package> (>= 2.2.0), or on later
5672 versions of either one of these packages.
5678 <heading>Users and groups</heading>
5681 <heading>Introduction</heading>
5683 The Debian system can be configured to use either plain or
5688 Some user ids (UIDs) and group ids (GIDs) are reserved
5689 globally for use by certain packages. Because some
5690 packages need to include files which are owned by these
5691 users or groups, or need the ids compiled into binaries,
5692 these ids must be used on any Debian system only for the
5693 purpose for which they are allocated. This is a serious
5694 restriction, and we should avoid getting in the way of
5695 local administration policies. In particular, many sites
5696 allocate users and/or local system groups starting at 100.
5700 Apart from this we should have dynamically allocated ids,
5701 which should by default be arranged in some sensible
5702 order, but the behavior should be configurable.
5706 Packages other than <tt>base-passwd</tt> must not modify
5707 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5708 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5713 <heading>UID and GID classes</heading>
5715 The UID and GID numbers are divided into classes as
5721 Globally allocated by the Debian project, the same
5722 on every Debian system. These ids will appear in
5723 the <file>passwd</file> and <file>group</file> files of all
5724 Debian systems, new ids in this range being added
5725 automatically as the <tt>base-passwd</tt> package is
5730 Packages which need a single statically allocated
5731 uid or gid should use one of these; their
5732 maintainers should ask the <tt>base-passwd</tt>
5740 Dynamically allocated system users and groups.
5741 Packages which need a user or group, but can have
5742 this user or group allocated dynamically and
5743 differently on each system, should use <tt>adduser
5744 --system</tt> to create the group and/or user.
5745 <prgn>adduser</prgn> will check for the existence of
5746 the user or group, and if necessary choose an unused
5747 id based on the ranges specified in
5748 <file>adduser.conf</file>.
5752 <tag>1000-29999:</tag>
5755 Dynamically allocated user accounts. By default
5756 <prgn>adduser</prgn> will choose UIDs and GIDs for
5757 user accounts in this range, though
5758 <file>adduser.conf</file> may be used to modify this
5763 <tag>30000-59999:</tag>
5768 <tag>60000-64999:</tag>
5771 Globally allocated by the Debian project, but only
5772 created on demand. The ids are allocated centrally
5773 and statically, but the actual accounts are only
5774 created on users' systems on demand.
5778 These ids are for packages which are obscure or
5779 which require many statically-allocated ids. These
5780 packages should check for and create the accounts in
5781 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5782 <prgn>adduser</prgn> if it has this facility) if
5783 necessary. Packages which are likely to require
5784 further allocations should have a "hole" left after
5785 them in the allocation, to give them room to
5790 <tag>65000-65533:</tag>
5798 User <tt>nobody</tt>. The corresponding gid refers
5799 to the group <tt>nogroup</tt>.
5806 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5807 not</em> be used, because it is the error return
5816 <sect id="sysvinit">
5817 <heading>System run levels and <file>init.d</file> scripts</heading>
5819 <sect1 id="/etc/init.d">
5820 <heading>Introduction</heading>
5823 The <file>/etc/init.d</file> directory contains the scripts
5824 executed by <prgn>init</prgn> at boot time and when the
5825 init state (or "runlevel") is changed (see <manref
5826 name="init" section="8">).
5830 There are at least two different, yet functionally
5831 equivalent, ways of handling these scripts. For the sake
5832 of simplicity, this document describes only the symbolic
5833 link method. However, it must not be assumed by maintainer
5834 scripts that this method is being used, and any automated
5835 manipulation of the various runlevel behaviors by
5836 maintainer scripts must be performed using
5837 <prgn>update-rc.d</prgn> as described below and not by
5838 manually installing or removing symlinks. For information
5839 on the implementation details of the other method,
5840 implemented in the <tt>file-rc</tt> package, please refer
5841 to the documentation of that package.
5845 These scripts are referenced by symbolic links in the
5846 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5847 runlevels, <prgn>init</prgn> looks in the directory
5848 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5849 execute, where <tt><var>n</var></tt> is the runlevel that
5850 is being changed to, or <tt>S</tt> for the boot-up
5855 The names of the links all have the form
5856 <file>S<var>mm</var><var>script</var></file> or
5857 <file>K<var>mm</var><var>script</var></file> where
5858 <var>mm</var> is a two-digit number and <var>script</var>
5859 is the name of the script (this should be the same as the
5860 name of the actual script in <file>/etc/init.d</file>).
5864 When <prgn>init</prgn> changes runlevel first the targets
5865 of the links whose names start with a <tt>K</tt> are
5866 executed, each with the single argument <tt>stop</tt>,
5867 followed by the scripts prefixed with an <tt>S</tt>, each
5868 with the single argument <tt>start</tt>. (The links are
5869 those in the <file>/etc/rc<var>n</var>.d</file> directory
5870 corresponding to the new runlevel.) The <tt>K</tt> links
5871 are responsible for killing services and the <tt>S</tt>
5872 link for starting services upon entering the runlevel.
5876 For example, if we are changing from runlevel 2 to
5877 runlevel 3, init will first execute all of the <tt>K</tt>
5878 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5879 all of the <tt>S</tt> prefixed scripts in that directory.
5880 The links starting with <tt>K</tt> will cause the
5881 referred-to file to be executed with an argument of
5882 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5887 The two-digit number <var>mm</var> is used to determine
5888 the order in which to run the scripts: low-numbered links
5889 have their scripts run first. For example, the
5890 <tt>K20</tt> scripts will be executed before the
5891 <tt>K30</tt> scripts. This is used when a certain service
5892 must be started before another. For example, the name
5893 server <prgn>bind</prgn> might need to be started before
5894 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5895 can set up its access lists. In this case, the script
5896 that starts <prgn>bind</prgn> would have a lower number
5897 than the script that starts <prgn>inn</prgn> so that it
5899 <example compact="compact">
5906 The two runlevels 0 (halt) and 6 (reboot) are slightly
5907 different. In these runlevels, the links with an
5908 <tt>S</tt> prefix are still called after those with a
5909 <tt>K</tt> prefix, but they too are called with the single
5910 argument <tt>stop</tt>.
5914 Also, if the script name ends in <tt>.sh</tt>, the script
5915 will be sourced in runlevel <tt>S</tt> rather than being
5916 run in a forked subprocess, but will be explicitly run by
5917 <prgn>sh</prgn> in all other runlevels.
5922 <heading>Writing the scripts</heading>
5925 Packages that include daemons for system services should
5926 place scripts in <file>/etc/init.d</file> to start or stop
5927 services at boot time or during a change of runlevel.
5928 These scripts should be named
5929 <file>/etc/init.d/<var>package</var></file>, and they should
5930 accept one argument, saying what to do:
5933 <tag><tt>start</tt></tag>
5934 <item>start the service,</item>
5936 <tag><tt>stop</tt></tag>
5937 <item>stop the service,</item>
5939 <tag><tt>restart</tt></tag>
5940 <item>stop and restart the service if it's already running,
5941 otherwise start the service</item>
5943 <tag><tt>reload</tt></tag>
5944 <item><p>cause the configuration of the service to be
5945 reloaded without actually stopping and restarting
5948 <tag><tt>force-reload</tt></tag>
5949 <item>cause the configuration to be reloaded if the
5950 service supports this, otherwise restart the
5954 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5955 <tt>force-reload</tt> options should be supported by all
5956 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5961 The <file>init.d</file> scripts must ensure that they will
5962 behave sensibly (i.e., returning success and not starting
5963 multiple copies of a service) if invoked with <tt>start</tt>
5964 when the service is already running, or with <tt>stop</tt>
5965 when it isn't, and that they don't kill unfortunately-named
5966 user processes. The best way to achieve this is usually to
5967 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5972 If a service reloads its configuration automatically (as
5973 in the case of <prgn>cron</prgn>, for example), the
5974 <tt>reload</tt> option of the <file>init.d</file> script
5975 should behave as if the configuration has been reloaded
5980 The <file>/etc/init.d</file> scripts must be treated as
5981 configuration files, either (if they are present in the
5982 package, that is, in the .deb file) by marking them as
5983 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5984 by managing them correctly in the maintainer scripts (see
5985 <ref id="config-files">). This is important since we want
5986 to give the local system administrator the chance to adapt
5987 the scripts to the local system, e.g., to disable a
5988 service without de-installing the package, or to specify
5989 some special command line options when starting a service,
5990 while making sure their changes aren't lost during the next
5995 These scripts should not fail obscurely when the
5996 configuration files remain but the package has been
5997 removed, as configuration files remain on the system after
5998 the package has been removed. Only when <prgn>dpkg</prgn>
5999 is executed with the <tt>--purge</tt> option will
6000 configuration files be removed. In particular, as the
6001 <file>/etc/init.d/<var>package</var></file> script itself is
6002 usually a <tt>conffile</tt>, it will remain on the system
6003 if the package is removed but not purged. Therefore, you
6004 should include a <tt>test</tt> statement at the top of the
6006 <example compact="compact">
6007 test -f <var>program-executed-later-in-script</var> || exit 0
6012 Often there are some variables in the <file>init.d</file>
6013 scripts whose values control the behavior of the scripts,
6014 and which a system administrator is likely to want to
6015 change. As the scripts themselves are frequently
6016 <tt>conffile</tt>s, modifying them requires that the
6017 administrator merge in their changes each time the package
6018 is upgraded and the <tt>conffile</tt> changes. To ease
6019 the burden on the system administrator, such configurable
6020 values should not be placed directly in the script.
6021 Instead, they should be placed in a file in
6022 <file>/etc/default</file>, which typically will have the same
6023 base name as the <file>init.d</file> script. This extra file
6024 should be sourced by the script when the script runs. It
6025 must contain only variable settings and comments in SUSv3
6026 <prgn>sh</prgn> format. It may either be a
6027 <tt>conffile</tt> or a configuration file maintained by
6028 the package maintainer scripts. See <ref id="config-files">
6033 To ensure that vital configurable values are always
6034 available, the <file>init.d</file> script should set default
6035 values for each of the shell variables it uses, either
6036 before sourcing the <file>/etc/default/</file> file or
6037 afterwards using something like the <tt>:
6038 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6039 script must behave sensibly and not fail if the
6040 <file>/etc/default</file> file is deleted.
6045 <heading>Interfacing with the initscript system</heading>
6048 Maintainers should use the abstraction layer provided by
6049 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6050 programs to deal with initscripts in their packages'
6051 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6052 and <prgn>postrm</prgn>.
6056 Directly managing the /etc/rc?.d links and directly
6057 invoking the <file>/etc/init.d/</file> initscripts should
6058 be done only by packages providing the initscript
6059 subsystem (such as <prgn>sysv-rc</prgn> and
6060 <prgn>file-rc</prgn>).
6064 <heading>Managing the links</heading>
6067 The program <prgn>update-rc.d</prgn> is provided for
6068 package maintainers to arrange for the proper creation and
6069 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6070 or their functional equivalent if another method is being
6071 used. This may be used by maintainers in their packages'
6072 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6076 You must not include any <file>/etc/rc<var>n</var>.d</file>
6077 symbolic links in the actual archive or manually create or
6078 remove the symbolic links in maintainer scripts; you must
6079 use the <prgn>update-rc.d</prgn> program instead. (The
6080 former will fail if an alternative method of maintaining
6081 runlevel information is being used.) You must not include
6082 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6083 in the archive either. (Only the <tt>sysvinit</tt>
6088 By default <prgn>update-rc.d</prgn> will start services in
6089 each of the multi-user state runlevels (2, 3, 4, and 5)
6090 and stop them in the halt runlevel (0), the single-user
6091 runlevel (1) and the reboot runlevel (6). The system
6092 administrator will have the opportunity to customize
6093 runlevels by simply adding, moving, or removing the
6094 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6095 symbolic links are being used, or by modifying
6096 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6101 To get the default behavior for your package, put in your
6102 <prgn>postinst</prgn> script
6103 <example compact="compact">
6104 update-rc.d <var>package</var> defaults
6106 and in your <prgn>postrm</prgn>
6107 <example compact="compact">
6108 if [ "$1" = purge ]; then
6109 update-rc.d <var>package</var> remove
6111 </example>. Note that if your package changes runlevels
6112 or priority, you may have to remove and recreate the links,
6113 since otherwise the old links may persist. Refer to the
6114 documentation of <prgn>update-rc.d</prgn>.
6118 This will use a default sequence number of 20. If it does
6119 not matter when or in which order the <file>init.d</file>
6120 script is run, use this default. If it does, then you
6121 should talk to the maintainer of the <prgn>sysvinit</prgn>
6122 package or post to <tt>debian-devel</tt>, and they will
6123 help you choose a number.
6127 For more information about using <tt>update-rc.d</tt>,
6128 please consult its man page <manref name="update-rc.d"
6134 <heading>Running initscripts</heading>
6136 The program <prgn>invoke-rc.d</prgn> is provided to make
6137 it easier for package maintainers to properly invoke an
6138 initscript, obeying runlevel and other locally-defined
6139 constraints that might limit a package's right to start,
6140 stop and otherwise manage services. This program may be
6141 used by maintainers in their packages' scripts.
6145 The package maintainer scripts must use
6146 <prgn>invoke-rc.d</prgn> to invoke the
6147 <file>/etc/init.d/*</file> initscripts, instead of
6148 calling them directly.
6152 By default, <prgn>invoke-rc.d</prgn> will pass any
6153 action requests (start, stop, reload, restart...) to the
6154 <file>/etc/init.d</file> script, filtering out requests
6155 to start or restart a service out of its intended
6160 Most packages will simply need to change:
6161 <example compact="compact">/etc/init.d/<package>
6162 <action></example> in their <prgn>postinst</prgn>
6163 and <prgn>prerm</prgn> scripts to:
6164 <example compact="compact">
6165 if which invoke-rc.d >/dev/null 2>&1; then
6166 invoke-rc.d <var>package</var> <action>
6168 /etc/init.d/<var>package</var> <action>
6174 A package should register its initscript services using
6175 <prgn>update-rc.d</prgn> before it tries to invoke them
6176 using <prgn>invoke-rc.d</prgn>. Invocation of
6177 unregistered services may fail.
6181 For more information about using
6182 <prgn>invoke-rc.d</prgn>, please consult its man page
6183 <manref name="invoke-rc.d" section="8">.
6189 <heading>Boot-time initialization</heading>
6192 There used to be another directory, <file>/etc/rc.boot</file>,
6193 which contained scripts which were run once per machine
6194 boot. This has been deprecated in favour of links from
6195 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6196 described in <ref id="/etc/init.d">. Packages must not
6197 place files in <file>/etc/rc.boot</file>.
6202 <heading>Example</heading>
6205 An example on which you can base your
6206 <file>/etc/init.d</file> scripts is found in
6207 <file>/etc/init.d/skeleton</file>.
6214 <heading>Console messages from <file>init.d</file> scripts</heading>
6217 This section describes the formats to be used for messages
6218 written to standard output by the <file>/etc/init.d</file>
6219 scripts. The intent is to improve the consistency of
6220 Debian's startup and shutdown look and feel. For this
6221 reason, please look very carefully at the details. We want
6222 the messages to have the same format in terms of wording,
6223 spaces, punctuation and case of letters.
6227 Here is a list of overall rules that should be used for
6228 messages generated by <file>/etc/init.d</file> scripts.
6234 The message should fit in one line (fewer than 80
6235 characters), start with a capital letter and end with
6236 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6240 If the script is performing some time consuming task in
6241 the background (not merely starting or stopping a
6242 program, for instance), an ellipsis (three dots:
6243 <tt>...</tt>) should be output to the screen, with no
6244 leading or tailing whitespace or line feeds.
6248 The messages should appear as if the computer is telling
6249 the user what it is doing (politely :-), but should not
6250 mention "it" directly. For example, instead of:
6251 <example compact="compact">
6252 I'm starting network daemons: nfsd mountd.
6254 the message should say
6255 <example compact="compact">
6256 Starting network daemons: nfsd mountd.
6263 <tt>init.d</tt> script should use the following standard
6264 message formats for the situations enumerated below.
6270 <p>When daemons are started</p>
6273 If the script starts one or more daemons, the output
6274 should look like this (a single line, no leading
6276 <example compact="compact">
6277 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6279 The <var>description</var> should describe the
6280 subsystem the daemon or set of daemons are part of,
6281 while <var>daemon-1</var> up to <var>daemon-n</var>
6282 denote each daemon's name (typically the file name of
6287 For example, the output of <file>/etc/init.d/lpd</file>
6289 <example compact="compact">
6290 Starting printer spooler: lpd.
6295 This can be achieved by saying
6296 <example compact="compact">
6297 echo -n "Starting printer spooler: lpd"
6298 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6301 in the script. If there are more than one daemon to
6302 start, the output should look like this:
6303 <example compact="compact">
6304 echo -n "Starting remote file system services:"
6305 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6306 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6307 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6310 This makes it possible for the user to see what is
6311 happening and when the final daemon has been started.
6312 Care should be taken in the placement of white spaces:
6313 in the example above the system administrators can
6314 easily comment out a line if they don't want to start
6315 a specific daemon, while the displayed message still
6321 <p>When a system parameter is being set</p>
6324 If you have to set up different system parameters
6325 during the system boot, you should use this format:
6326 <example compact="compact">
6327 Setting <var>parameter</var> to "<var>value</var>".
6332 You can use a statement such as the following to get
6334 <example compact="compact">
6335 echo "Setting DNS domainname to \"$domainname\"."
6340 Note that the same symbol (<tt>"</tt>) is used for the left
6341 and right quotation marks. A grave accent (<tt>`</tt>) is
6342 not a quote character; neither is an apostrophe
6348 <p>When a daemon is stopped or restarted</p>
6351 When you stop or restart a daemon, you should issue a
6352 message identical to the startup message, except that
6353 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6354 or <tt>Restarting</tt> respectively.
6358 For example, stopping the printer daemon will look like
6360 <example compact="compact">
6361 Stopping printer spooler: lpd.
6367 <p>When something is executed</p>
6370 There are several examples where you have to run a
6371 program at system startup or shutdown to perform a
6372 specific task, for example, setting the system's clock
6373 using <prgn>netdate</prgn> or killing all processes
6374 when the system shuts down. Your message should look
6376 <example compact="compact">
6377 Doing something very useful...done.
6379 You should print the <tt>done.</tt> immediately after
6380 the job has been completed, so that the user is
6381 informed why they have to wait. You can get this
6383 <example compact="compact">
6384 echo -n "Doing something very useful..."
6393 <p>When the configuration is reloaded</p>
6396 When a daemon is forced to reload its configuration
6397 files you should use the following format:
6398 <example compact="compact">
6399 Reloading <var>description</var> configuration...done.
6401 where <var>description</var> is the same as in the
6402 daemon starting message.
6410 <heading>Cron jobs</heading>
6413 Packages must not modify the configuration file
6414 <file>/etc/crontab</file>, and they must not modify the files in
6415 <file>/var/spool/cron/crontabs</file>.</p>
6418 If a package wants to install a job that has to be executed
6419 via cron, it should place a file with the name of the
6420 package in one or more of the following directories:
6421 <example compact="compact">
6427 As these directory names imply, the files within them are
6428 executed on an hourly, daily, weekly, or monthly basis,
6429 respectively. The exact times are listed in
6430 <file>/etc/crontab</file>.</p>
6433 All files installed in any of these directories must be
6434 scripts (e.g., shell scripts or Perl scripts) so that they
6435 can easily be modified by the local system administrator.
6436 In addition, they must be treated as configuration files.
6440 If a certain job has to be executed at some other frequency or
6441 at a specific time, the package should install a file
6442 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6443 same syntax as <file>/etc/crontab</file> and is processed by
6444 <prgn>cron</prgn> automatically. The file must also be
6445 treated as a configuration file. (Note that entries in the
6446 <file>/etc/cron.d</file> directory are not handled by
6447 <prgn>anacron</prgn>. Thus, you should only use this
6448 directory for jobs which may be skipped if the system is not
6452 The scripts or crontab entries in these directories should
6453 check if all necessary programs are installed before they
6454 try to execute them. Otherwise, problems will arise when a
6455 package was removed but not purged since configuration files
6456 are kept on the system in this situation.</p>
6460 <heading>Menus</heading>
6463 The Debian <tt>menu</tt> package provides a standard
6464 interface between packages providing applications and
6465 <em>menu programs</em> (either X window managers or
6466 text-based menu programs such as <prgn>pdmenu</prgn>).
6470 All packages that provide applications that need not be
6471 passed any special command line arguments for normal
6472 operation should register a menu entry for those
6473 applications, so that users of the <tt>menu</tt> package
6474 will automatically get menu entries in their window
6475 managers, as well in shells like <tt>pdmenu</tt>.
6479 Menu entries should follow the current menu policy.
6483 The menu policy can be found in the <tt>menu-policy</tt>
6484 files in the <tt>debian-policy</tt> package.
6485 It is also available from the Debian web mirrors at
6486 <tt><url name="/doc/packaging-manuals/menu-policy/"
6487 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6491 Please also refer to the <em>Debian Menu System</em>
6492 documentation that comes with the <package>menu</package>
6493 package for information about how to register your
6499 <heading>Multimedia handlers</heading>
6502 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6503 is a mechanism for encoding files and data streams and
6504 providing meta-information about them, in particular their
6505 type (e.g. audio or video) and format (e.g. PNG, HTML,
6510 Registration of MIME type handlers allows programs like mail
6511 user agents and web browsers to invoke these handlers to
6512 view, edit or display MIME types they don't support directly.
6516 Packages which provide the ability to view/show/play,
6517 compose, edit or print MIME types should register themselves
6518 as such following the current MIME support policy.
6522 The MIME support policy can be found in the <tt>mime-policy</tt>
6523 files in the <tt>debian-policy</tt> package.
6524 It is also available from the Debian web mirrors at
6525 <tt><url name="/doc/packaging-manuals/mime-policy/"
6526 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6532 <heading>Keyboard configuration</heading>
6535 To achieve a consistent keyboard configuration so that all
6536 applications interpret a keyboard event the same way, all
6537 programs in the Debian distribution must be configured to
6538 comply with the following guidelines.
6542 The following keys must have the specified interpretations:
6545 <tag><tt><--</tt></tag>
6546 <item>delete the character to the left of the cursor</item>
6548 <tag><tt>Delete</tt></tag>
6549 <item>delete the character to the right of the cursor</item>
6551 <tag><tt>Control+H</tt></tag>
6552 <item>emacs: the help prefix</item>
6555 The interpretation of any keyboard events should be
6556 independent of the terminal that is used, be it a virtual
6557 console, an X terminal emulator, an rlogin/telnet session,
6562 The following list explains how the different programs
6563 should be set up to achieve this:
6569 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6573 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6577 X translations are set up to make
6578 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6579 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6580 is the vt220 escape code for the "delete character"
6581 key). This must be done by loading the X resources
6582 using <prgn>xrdb</prgn> on all local X displays, not
6583 using the application defaults, so that the
6584 translation resources used correspond to the
6585 <prgn>xmodmap</prgn> settings.
6589 The Linux console is configured to make
6590 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6591 generate <tt>ESC [ 3 ~</tt>.
6595 X applications are configured so that <tt><</tt>
6596 deletes left, and <tt>Delete</tt> deletes right. Motif
6597 applications already work like this.
6601 Terminals should have <tt>stty erase ^?</tt> .
6605 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6606 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6607 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6611 Emacs is programmed to map <tt>KB_Backspace</tt> or
6612 the <tt>stty erase</tt> character to
6613 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6614 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6615 <tt>^H</tt> to <tt>help</tt> as always.
6619 Other applications use the <tt>stty erase</tt>
6620 character and <tt>kdch1</tt> for the two delete keys,
6621 with ASCII DEL being "delete previous character" and
6622 <tt>kdch1</tt> being "delete character under
6630 This will solve the problem except for the following
6637 Some terminals have a <tt><--</tt> key that cannot
6638 be made to produce anything except <tt>^H</tt>. On
6639 these terminals Emacs help will be unavailable on
6640 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6641 character takes precedence in Emacs, and has been set
6642 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6643 available) can be used instead.
6647 Some operating systems use <tt>^H</tt> for <tt>stty
6648 erase</tt>. However, modern telnet versions and all
6649 rlogin versions propagate <tt>stty</tt> settings, and
6650 almost all UNIX versions honour <tt>stty erase</tt>.
6651 Where the <tt>stty</tt> settings are not propagated
6652 correctly, things can be made to work by using
6653 <tt>stty</tt> manually.
6657 Some systems (including previous Debian versions) use
6658 <prgn>xmodmap</prgn> to arrange for both
6659 <tt><--</tt> and <tt>Delete</tt> to generate
6660 <tt>KB_Delete</tt>. We can change the behavior of
6661 their X clients using the same X resources that we use
6662 to do it for our own clients, or configure our clients
6663 using their resources when things are the other way
6664 around. On displays configured like this
6665 <tt>Delete</tt> will not work, but <tt><--</tt>
6670 Some operating systems have different <tt>kdch1</tt>
6671 settings in their <tt>terminfo</tt> database for
6672 <tt>xterm</tt> and others. On these systems the
6673 <tt>Delete</tt> key will not work correctly when you
6674 log in from a system conforming to our policy, but
6675 <tt><--</tt> will.
6682 <heading>Environment variables</heading>
6685 A program must not depend on environment variables to get
6686 reasonable defaults. (That's because these environment
6687 variables would have to be set in a system-wide
6688 configuration file like <file>/etc/profile</file>, which is not
6689 supported by all shells.)
6693 If a program usually depends on environment variables for its
6694 configuration, the program should be changed to fall back to
6695 a reasonable default configuration if these environment
6696 variables are not present. If this cannot be done easily
6697 (e.g., if the source code of a non-free program is not
6698 available), the program must be replaced by a small
6699 "wrapper" shell script which sets the environment variables
6700 if they are not already defined, and calls the original program.
6704 Here is an example of a wrapper script for this purpose:
6706 <example compact="compact">
6708 BAR=${BAR:-/var/lib/fubar}
6710 exec /usr/lib/foo/foo "$@"
6715 Furthermore, as <file>/etc/profile</file> is a configuration
6716 file of the <prgn>base-files</prgn> package, other packages must
6717 not put any environment variables or other commands into that
6722 <sect id="doc-base">
6723 <heading>Registering Documents using doc-base</heading>
6726 The <package>doc-base</package> package implements a
6727 flexible mechanism for handling and presenting
6728 documentation. The recommended practice is for every Debian
6729 package that provides online documentation (other than just
6730 manual pages) to register these documents with
6731 <package>doc-base</package> by installing a
6732 <package>doc-base</package> control file via the
6733 <prgn/install-docs/ script at installation time and
6734 de-register the manuals again when the package is removed.
6737 Please refer to the documentation that comes with the
6738 <package>doc-base</package> package for information and
6747 <heading>Files</heading>
6750 <heading>Binaries</heading>
6753 Two different packages must not install programs with
6754 different functionality but with the same filenames. (The
6755 case of two programs having the same functionality but
6756 different implementations is handled via "alternatives" or
6757 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6758 <ref id="conflicts"> respectively.) If this case happens,
6759 one of the programs must be renamed. The maintainers should
6760 report this to the <tt>debian-devel</tt> mailing list and
6761 try to find a consensus about which program will have to be
6762 renamed. If a consensus cannot be reached, <em>both</em>
6763 programs must be renamed.
6767 By default, when a package is being built, any binaries
6768 created should include debugging information, as well as
6769 being compiled with optimization. You should also turn on
6770 as many reasonable compilation warnings as possible; this
6771 makes life easier for porters, who can then look at build
6772 logs for possible problems. For the C programming language,
6773 this means the following compilation parameters should be
6775 <example compact="compact">
6777 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6779 INSTALL = install -s # (or use strip on the files in debian/tmp)
6784 Note that by default all installed binaries should be stripped,
6785 either by using the <tt>-s</tt> flag to
6786 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6787 the binaries after they have been copied into
6788 <file>debian/tmp</file> but before the tree is made into a
6793 Although binaries in the build tree should be compiled with
6794 debugging information by default, it can often be difficult to
6795 debug programs if they are also subjected to compiler
6796 optimization. For this reason, it is recommended to support the
6797 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6798 (see <ref id="debianrules-options">). This variable can contain
6799 several flags to change how a package is compiled and built.
6803 It is up to the package maintainer to decide what
6804 compilation options are best for the package. Certain
6805 binaries (such as computationally-intensive programs) will
6806 function better with certain flags (<tt>-O3</tt>, for
6807 example); feel free to use them. Please use good judgment
6808 here. Don't use flags for the sake of it; only use them
6809 if there is good reason to do so. Feel free to override
6810 the upstream author's ideas about which compilation
6811 options are best: they are often inappropriate for our
6817 <sect id="libraries">
6818 <heading>Libraries</heading>
6821 If the package is <strong>architecture: any</strong>, then
6822 the shared library compilation and linking flags must have
6823 <tt>-fPIC</tt>, or the package shall not build on some of
6824 the supported architectures<footnote>
6826 If you are using GCC, <tt>-fPIC</tt> produces code with
6827 relocatable position independent code, which is required for
6828 most architectures to create a shared library, with i386 and
6829 perhaps some others where non position independent code is
6830 permitted in a shared library.
6833 Position independent code may have a performance penalty,
6834 especially on <tt>i386</tt>. However, in most cases the
6835 speed penalty must be measured against the memory wasted on
6836 the few architectures where non position independent code is
6839 </footnote>. Any exception to this rule must be discussed on
6840 the mailing list <em>debian-devel@lists.debian.org</em>, and
6841 a rough consensus obtained. The reasons for not compiling
6842 with <tt>-fPIC</tt> flag must be recorded in the file
6843 <tt>README.Debian</tt>, and care must be taken to either
6844 restrict the architecture or arrange for <tt>-fPIC</tt> to
6845 be used on architectures where it is required.<footnote>
6847 Some of the reasons why this might be required is if the
6848 library contains hand crafted assembly code that is not
6849 relocatable, the speed penalty is excessive for compute
6850 intensive libs, and similar reasons.
6855 As to the static libraries, the common case is not to have
6856 relocatable code, since there is no benefit, unless in specific
6857 cases; therefore the static version must not be compiled
6858 with the <tt>-fPIC</tt> flag. Any exception to this rule
6859 should be discussed on the mailing list
6860 <em>debian-devel@lists.debian.org</em>, and the reasons for
6861 compiling with the <tt>-fPIC</tt> flag must be recorded in
6862 the file <tt>README.Debian</tt>. <footnote>
6864 Some of the reasons for linking static libraries with
6865 the <tt>-fPIC</tt> flag are if, for example, one needs a
6866 Perl API for a library that is under rapid development,
6867 and has an unstable API, so shared libraries are
6868 pointless at this phase of the library's development. In
6869 that case, since Perl needs a library with relocatable
6870 code, it may make sense to create a static library with
6871 relocatable code. Another reason cited is if you are
6872 distilling various libraries into a common shared
6873 library, like <tt>mklibs</tt> does in the Debian
6879 In other words, if both a shared and a static library is
6880 being built, each source unit (<tt>*.c</tt>, for example,
6881 for C files) will need to be compiled twice, for the normal
6885 You must specify the gcc option <tt>-D_REENTRANT</tt>
6886 when building a library (either static or shared) to make
6887 the library compatible with LinuxThreads.
6891 Although not enforced by the build tools, shared libraries
6892 must be linked against all libraries that they use symbols from
6893 in the same way that binaries are. This ensures the correct
6894 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6895 system and guarantees that all libraries can be safely opened
6896 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6897 option <tt>-Wl,-z,defs</tt> when building a shared library.
6898 Since this option enforces symbol resolution at build time,
6899 a missing library reference will be caught early as a fatal
6904 All installed shared libraries should be stripped with
6905 <example compact="compact">
6906 strip --strip-unneeded <var>your-lib</var>
6908 (The option <tt>--strip-unneeded</tt> makes
6909 <prgn>strip</prgn> remove only the symbols which aren't
6910 needed for relocation processing.) Shared libraries can
6911 function perfectly well when stripped, since the symbols for
6912 dynamic linking are in a separate part of the ELF object
6914 You might also want to use the options
6915 <tt>--remove-section=.comment</tt> and
6916 <tt>--remove-section=.note</tt> on both shared libraries
6917 and executables, and <tt>--strip-debug</tt> on static
6923 Note that under some circumstances it may be useful to
6924 install a shared library unstripped, for example when
6925 building a separate package to support debugging.
6929 Shared object files (often <file>.so</file> files) that are not
6930 public libraries, that is, they are not meant to be linked
6931 to by third party executables (binaries of other packages),
6932 should be installed in subdirectories of the
6933 <file>/usr/lib</file> directory. Such files are exempt from the
6934 rules that govern ordinary shared libraries, except that
6935 they must not be installed executable and should be
6937 A common example are the so-called "plug-ins",
6938 internal shared objects that are dynamically loaded by
6939 programs using <manref name="dlopen" section="3">.
6944 Packages containing shared libraries that may be linked to
6945 by other packages' binaries, but which for some
6946 <em>compelling</em> reason can not be installed in
6947 <file>/usr/lib</file> directory, may install the shared library
6948 files in subdirectories of the <file>/usr/lib</file> directory,
6949 in which case they should arrange to add that directory in
6950 <file>/etc/ld.so.conf</file> in the package's post-installation
6951 script, and remove it in the package's post-removal script.
6955 An ever increasing number of packages are using
6956 <prgn>libtool</prgn> to do their linking. The latest GNU
6957 libtools (>= 1.3a) can take advantage of the metadata in the
6958 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6959 files). The main advantage of <prgn>libtool</prgn>'s
6960 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6961 store and subsequently access metadata with respect to the
6962 libraries it builds. <prgn>libtool</prgn> will search for
6963 those files, which contain a lot of useful information about
6964 a library (such as library dependency information for static
6965 linking). Also, they're <em>essential</em> for programs
6966 using <tt>libltdl</tt>.<footnote>
6967 Although <prgn>libtool</prgn> is fully capable of
6968 linking against shared libraries which don't have
6969 <tt>.la</tt> files, as it is a mere shell script it can
6970 add considerably to the build time of a
6971 <prgn>libtool</prgn>-using package if that shell script
6972 has to derive all this information from first principles
6973 for each library every time it is linked. With the
6974 advent of <prgn>libtool</prgn> version 1.4 (and to a
6975 lesser extent <prgn>libtool</prgn> version 1.3), the
6976 <file>.la</file> files also store information about
6977 inter-library dependencies which cannot necessarily be
6978 derived after the <file>.la</file> file is deleted.
6983 Packages that use <prgn>libtool</prgn> to create shared
6984 libraries should include the <file>.la</file> files in the
6985 <tt>-dev</tt> package, unless the package relies on
6986 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6987 the <tt>.la</tt> files must go in the run-time library
6992 You must make sure that you use only released versions of
6993 shared libraries to build your packages; otherwise other
6994 users will not be able to run your binaries
6995 properly. Producing source packages that depend on
6996 unreleased compilers is also usually a bad
7003 <heading>Shared libraries</heading>
7005 This section has moved to <ref id="sharedlibs">.
7011 <heading>Scripts</heading>
7014 All command scripts, including the package maintainer
7015 scripts inside the package and used by <prgn>dpkg</prgn>,
7016 should have a <tt>#!</tt> line naming the shell to be used
7021 In the case of Perl scripts this should be
7022 <tt>#!/usr/bin/perl</tt>.
7026 When scripts are installed into a directory in the system
7027 PATH, the script name should not include an extension such
7028 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7029 language currently used to implement it.
7032 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7033 should almost certainly start with <tt>set -e</tt> so that
7034 errors are detected. Every script should use
7035 <tt>set -e</tt> or check the exit status of <em>every</em>
7040 Scripts may assume that <file>/bin/sh</file> implements the
7041 SUSv3 Shell Command Language<footnote>
7042 Single UNIX Specification, version 3, which is also IEEE
7043 1003.1-2004 (POSIX), and is available on the World Wide Web
7044 from <url id="http://www.unix.org/version3/online.html"
7045 name="The Open Group"> after free
7046 registration.</footnote>
7047 plus the following additional features not mandated by
7049 These features are in widespread use in the Linux community
7050 and are implemented in all of bash, dash, and ksh, the most
7051 common shells users may wish to use as <file>/bin/sh</file>.
7054 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7055 must not generate a newline.</item>
7056 <item><tt>test</tt>, if implemented as a shell built-in, must
7057 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7059 <item><tt>local</tt> to create a scoped variable must be
7060 supported, including listing multiple variables in a single
7061 local command and assigning a value to a variable at the
7062 same time as localizing it. <tt>local</tt> may or
7063 may not preserve the variable value from an outer scope if
7064 no assignment is present. Uses such as:
7068 # ... use a, b, c, d ...
7071 must be supported and must set the value of <tt>c</tt> to
7075 If a shell script requires non-SUSv3 features from the shell
7076 interpreter other than those listed above, the appropriate shell
7077 must be specified in the first line of the script (e.g.,
7078 <tt>#!/bin/bash</tt>) and the package must depend on the package
7079 providing the shell (unless the shell package is marked
7080 "Essential", as in the case of <prgn>bash</prgn>).
7084 You may wish to restrict your script to SUSv3 features plus the
7085 above set when possible so that it may use <file>/bin/sh</file>
7086 as its interpreter. If your script works with <prgn>dash</prgn>
7087 (originally called <prgn>ash</prgn>), it probably complies with
7088 the above requirements, but if you are in doubt, use
7089 <file>/bin/bash</file>.
7093 Perl scripts should check for errors when making any
7094 system calls, including <tt>open</tt>, <tt>print</tt>,
7095 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7099 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7100 scripting languages. See <em>Csh Programming Considered
7101 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7102 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7103 If an upstream package comes with <prgn>csh</prgn> scripts
7104 then you must make sure that they start with
7105 <tt>#!/bin/csh</tt> and make your package depend on the
7106 <prgn>c-shell</prgn> virtual package.
7110 Any scripts which create files in world-writeable
7111 directories (e.g., in <file>/tmp</file>) must use a
7112 mechanism which will fail atomically if a file with the same
7113 name already exists.
7117 The Debian base system provides the <prgn>tempfile</prgn>
7118 and <prgn>mktemp</prgn> utilities for use by scripts for
7125 <heading>Symbolic links</heading>
7128 In general, symbolic links within a top-level directory
7129 should be relative, and symbolic links pointing from one
7130 top-level directory into another should be absolute. (A
7131 top-level directory is a sub-directory of the root
7132 directory <file>/</file>.)
7136 In addition, symbolic links should be specified as short as
7137 possible, i.e., link targets like <file>foo/../bar</file> are
7142 Note that when creating a relative link using
7143 <prgn>ln</prgn> it is not necessary for the target of the
7144 link to exist relative to the working directory you're
7145 running <prgn>ln</prgn> from, nor is it necessary to change
7146 directory to the directory where the link is to be made.
7147 Simply include the string that should appear as the target
7148 of the link (this will be a pathname relative to the
7149 directory in which the link resides) as the first argument
7154 For example, in your <prgn>Makefile</prgn> or
7155 <file>debian/rules</file>, you can do things like:
7156 <example compact="compact">
7157 ln -fs gcc $(prefix)/bin/cc
7158 ln -fs gcc debian/tmp/usr/bin/cc
7159 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7160 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7165 A symbolic link pointing to a compressed file should always
7166 have the same file extension as the referenced file. (For
7167 example, if a file <file>foo.gz</file> is referenced by a
7168 symbolic link, the filename of the link has to end with
7169 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7174 <heading>Device files</heading>
7177 Packages must not include device files in the package file
7182 If a package needs any special device files that are not
7183 included in the base system, it must call
7184 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7185 after notifying the user<footnote>
7186 This notification could be done via a (low-priority)
7187 debconf message, or an echo (printf) statement.
7192 Packages must not remove any device files in the
7193 <prgn>postrm</prgn> or any other script. This is left to the
7194 system administrator.
7198 Debian uses the serial devices
7199 <file>/dev/ttyS*</file>. Programs using the old
7200 <file>/dev/cu*</file> devices should be changed to use
7201 <file>/dev/ttyS*</file>.
7205 <sect id="config-files">
7206 <heading>Configuration files</heading>
7209 <heading>Definitions</heading>
7213 <tag>configuration file</tag>
7215 A file that affects the operation of a program, or
7216 provides site- or host-specific information, or
7217 otherwise customizes the behavior of a program.
7218 Typically, configuration files are intended to be
7219 modified by the system administrator (if needed or
7220 desired) to conform to local policy or to provide
7221 more useful site-specific behavior.
7224 <tag><tt>conffile</tt></tag>
7226 A file listed in a package's <tt>conffiles</tt>
7227 file, and is treated specially by <prgn>dpkg</prgn>
7228 (see <ref id="configdetails">).
7234 The distinction between these two is important; they are
7235 not interchangeable concepts. Almost all
7236 <tt>conffile</tt>s are configuration files, but many
7237 configuration files are not <tt>conffiles</tt>.
7241 As noted elsewhere, <file>/etc/init.d</file> scripts,
7242 <file>/etc/default</file> files, scripts installed in
7243 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7244 configuration installed in <file>/etc/cron.d</file> must be
7245 treated as configuration files. In general, any script that
7246 embeds configuration information is de-facto a configuration
7247 file and should be treated as such.
7252 <heading>Location</heading>
7255 Any configuration files created or used by your package
7256 must reside in <file>/etc</file>. If there are several,
7257 consider creating a subdirectory of <file>/etc</file>
7258 named after your package.
7262 If your package creates or uses configuration files
7263 outside of <file>/etc</file>, and it is not feasible to modify
7264 the package to use <file>/etc</file> directly, put the files
7265 in <file>/etc</file> and create symbolic links to those files
7266 from the location that the package requires.
7271 <heading>Behavior</heading>
7274 Configuration file handling must conform to the following
7276 <list compact="compact">
7278 local changes must be preserved during a package
7282 configuration files must be preserved when the
7283 package is removed, and only deleted when the
7290 The easy way to achieve this behavior is to make the
7291 configuration file a <tt>conffile</tt>. This is
7292 appropriate only if it is possible to distribute a default
7293 version that will work for most installations, although
7294 some system administrators may choose to modify it. This
7295 implies that the default version will be part of the
7296 package distribution, and must not be modified by the
7297 maintainer scripts during installation (or at any other
7302 In order to ensure that local changes are preserved
7303 correctly, no package may contain or make hard links to
7304 conffiles.<footnote>
7305 Rationale: There are two problems with hard links.
7306 The first is that some editors break the link while
7307 editing one of the files, so that the two files may
7308 unwittingly become unlinked and different. The second
7309 is that <prgn>dpkg</prgn> might break the hard link
7310 while upgrading <tt>conffile</tt>s.
7315 The other way to do it is via the maintainer scripts. In
7316 this case, the configuration file must not be listed as a
7317 <tt>conffile</tt> and must not be part of the package
7318 distribution. If the existence of a file is required for
7319 the package to be sensibly configured it is the
7320 responsibility of the package maintainer to provide
7321 maintainer scripts which correctly create, update and
7322 maintain the file and remove it on purge. (See <ref
7323 id="maintainerscripts"> for more information.) These
7324 scripts must be idempotent (i.e., must work correctly if
7325 <prgn>dpkg</prgn> needs to re-run them due to errors
7326 during installation or removal), must cope with all the
7327 variety of ways <prgn>dpkg</prgn> can call maintainer
7328 scripts, must not overwrite or otherwise mangle the user's
7329 configuration without asking, must not ask unnecessary
7330 questions (particularly during upgrades), and must
7331 otherwise be good citizens.
7335 The scripts are not required to configure every possible
7336 option for the package, but only those necessary to get
7337 the package running on a given system. Ideally the
7338 sysadmin should not have to do any configuration other
7339 than that done (semi-)automatically by the
7340 <prgn>postinst</prgn> script.
7344 A common practice is to create a script called
7345 <file><var>package</var>-configure</file> and have the
7346 package's <prgn>postinst</prgn> call it if and only if the
7347 configuration file does not already exist. In certain
7348 cases it is useful for there to be an example or template
7349 file which the maintainer scripts use. Such files should
7350 be in <file>/usr/share/<var>package</var></file> or
7351 <file>/usr/lib/<var>package</var></file> (depending on whether
7352 they are architecture-independent or not). There should
7353 be symbolic links to them from
7354 <file>/usr/share/doc/<var>package</var>/examples</file> if
7355 they are examples, and should be perfectly ordinary
7356 <prgn>dpkg</prgn>-handled files (<em>not</em>
7357 configuration files).
7361 These two styles of configuration file handling must
7362 not be mixed, for that way lies madness:
7363 <prgn>dpkg</prgn> will ask about overwriting the file
7364 every time the package is upgraded.
7369 <heading>Sharing configuration files</heading>
7372 Packages which specify the same file as a
7373 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7374 with each other. (This is an instance of the general rule
7375 about not sharing files. Note that neither alternatives
7376 nor diversions are likely to be appropriate in this case;
7377 in particular, <prgn>dpkg</prgn> does not handle diverted
7378 <tt>conffile</tt>s well.)
7382 The maintainer scripts must not alter a <tt>conffile</tt>
7383 of <em>any</em> package, including the one the scripts
7388 If two or more packages use the same configuration file
7389 and it is reasonable for both to be installed at the same
7390 time, one of these packages must be defined as
7391 <em>owner</em> of the configuration file, i.e., it will be
7392 the package which handles that file as a configuration
7393 file. Other packages that use the configuration file must
7394 depend on the owning package if they require the
7395 configuration file to operate. If the other package will
7396 use the configuration file if present, but is capable of
7397 operating without it, no dependency need be declared.
7401 If it is desirable for two or more related packages to
7402 share a configuration file <em>and</em> for all of the
7403 related packages to be able to modify that configuration
7404 file, then the following should be done:
7405 <enumlist compact="compact">
7407 One of the related packages (the "owning" package)
7408 will manage the configuration file with maintainer
7409 scripts as described in the previous section.
7412 The owning package should also provide a program
7413 that the other packages may use to modify the
7417 The related packages must use the provided program
7418 to make any desired modifications to the
7419 configuration file. They should either depend on
7420 the core package to guarantee that the configuration
7421 modifier program is available or accept gracefully
7422 that they cannot modify the configuration file if it
7423 is not. (This is in addition to the fact that the
7424 configuration file may not even be present in the
7431 Sometimes it's appropriate to create a new package which
7432 provides the basic infrastructure for the other packages
7433 and which manages the shared configuration files. (The
7434 <tt>sgml-base</tt> package is a good example.)
7439 <heading>User configuration files ("dotfiles")</heading>
7442 The files in <file>/etc/skel</file> will automatically be
7443 copied into new user accounts by <prgn>adduser</prgn>.
7444 No other program should reference the files in
7445 <file>/etc/skel</file>.
7449 Therefore, if a program needs a dotfile to exist in
7450 advance in <file>$HOME</file> to work sensibly, that dotfile
7451 should be installed in <file>/etc/skel</file> and treated as a
7456 However, programs that require dotfiles in order to
7457 operate sensibly are a bad thing, unless they do create
7458 the dotfiles themselves automatically.
7462 Furthermore, programs should be configured by the Debian
7463 default installation to behave as closely to the upstream
7464 default behavior as possible.
7468 Therefore, if a program in a Debian package needs to be
7469 configured in some way in order to operate sensibly, that
7470 should be done using a site-wide configuration file placed
7471 in <file>/etc</file>. Only if the program doesn't support a
7472 site-wide default configuration and the package maintainer
7473 doesn't have time to add it may a default per-user file be
7474 placed in <file>/etc/skel</file>.
7478 <file>/etc/skel</file> should be as empty as we can make it.
7479 This is particularly true because there is no easy (or
7480 necessarily desirable) mechanism for ensuring that the
7481 appropriate dotfiles are copied into the accounts of
7482 existing users when a package is installed.
7488 <heading>Log files</heading>
7490 Log files should usually be named
7491 <file>/var/log/<var>package</var>.log</file>. If you have many
7492 log files, or need a separate directory for permission
7493 reasons (<file>/var/log</file> is writable only by
7494 <file>root</file>), you should usually create a directory named
7495 <file>/var/log/<var>package</var></file> and place your log
7500 Log files must be rotated occasionally so that they don't
7501 grow indefinitely; the best way to do this is to drop a log
7502 rotation configuration file into the directory
7503 <file>/etc/logrotate.d</file> and use the facilities provided by
7504 logrotate.<footnote>
7506 The traditional approach to log files has been to set up
7507 <em>ad hoc</em> log rotation schemes using simple shell
7508 scripts and cron. While this approach is highly
7509 customizable, it requires quite a lot of sysadmin work.
7510 Even though the original Debian system helped a little
7511 by automatically installing a system which can be used
7512 as a template, this was deemed not enough.
7516 The use of <prgn>logrotate</prgn>, a program developed
7517 by Red Hat, is better, as it centralizes log management.
7518 It has both a configuration file
7519 (<file>/etc/logrotate.conf</file>) and a directory where
7520 packages can drop their individual log rotation
7521 configurations (<file>/etc/logrotate.d</file>).
7524 Here is a good example for a logrotate config
7525 file (for more information see <manref name="logrotate"
7527 <example compact="compact">
7528 /var/log/foo/*.log {
7533 /etc/init.d/foo force-reload
7537 This rotates all files under <file>/var/log/foo</file>, saves 12
7538 compressed generations, and forces the daemon to reload its
7539 configuration information after the log rotation.
7543 Log files should be removed when the package is
7544 purged (but not when it is only removed). This should be
7545 done by the <prgn>postrm</prgn> script when it is called
7546 with the argument <tt>purge</tt> (see <ref
7547 id="removedetails">).
7552 <heading>Permissions and owners</heading>
7555 The rules in this section are guidelines for general use.
7556 If necessary you may deviate from the details below.
7557 However, if you do so you must make sure that what is done
7558 is secure and you should try to be as consistent as possible
7559 with the rest of the system. You should probably also
7560 discuss it on <prgn>debian-devel</prgn> first.
7564 Files should be owned by <tt>root:root</tt>, and made
7565 writable only by the owner and universally readable (and
7566 executable, if appropriate), that is mode 644 or 755.
7570 Directories should be mode 755 or (for group-writability)
7571 mode 2775. The ownership of the directory should be
7572 consistent with its mode: if a directory is mode 2775, it
7573 should be owned by the group that needs write access to
7576 When a package is upgraded, and the owner or permissions
7577 of a file included in the package has changed, dpkg
7578 arranges for the ownership and permissions to be
7579 correctly set upon installation. However, this does not
7580 extend to directories; the permissions and ownership of
7581 directories already on the system does not change on
7582 install or upgrade of packages. This makes sense, since
7583 otherwise common directories like <tt>/usr</tt> would
7584 always be in flux. To correctly change permissions of a
7585 directory the package owns, explicit action is required,
7586 usually in the <tt>postinst</tt> script. Care must be
7587 taken to handle downgrades as well, in that case.
7594 Setuid and setgid executables should be mode 4755 or 2755
7595 respectively, and owned by the appropriate user or group.
7596 They should not be made unreadable (modes like 4711 or
7597 2711 or even 4111); doing so achieves no extra security,
7598 because anyone can find the binary in the freely available
7599 Debian package; it is merely inconvenient. For the same
7600 reason you should not restrict read or execute permissions
7601 on non-set-id executables.
7605 Some setuid programs need to be restricted to particular
7606 sets of users, using file permissions. In this case they
7607 should be owned by the uid to which they are set-id, and by
7608 the group which should be allowed to execute them. They
7609 should have mode 4754; again there is no point in making
7610 them unreadable to those users who must not be allowed to
7615 It is possible to arrange that the system administrator can
7616 reconfigure the package to correspond to their local
7617 security policy by changing the permissions on a binary:
7618 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7619 described below.<footnote>
7620 Ordinary files installed by <prgn>dpkg</prgn> (as
7621 opposed to <tt>conffile</tt>s and other similar objects)
7622 normally have their permissions reset to the distributed
7623 permissions when the package is reinstalled. However,
7624 the use of <prgn>dpkg-statoverride</prgn> overrides this
7625 default behavior. If you use this method, you should
7626 remember to describe <prgn>dpkg-statoverride</prgn> in
7627 the package documentation; being a relatively new
7628 addition to Debian, it is probably not yet well-known.
7630 Another method you should consider is to create a group for
7631 people allowed to use the program(s) and make any setuid
7632 executables executable only by that group.
7636 If you need to create a new user or group for your package
7637 there are two possibilities. Firstly, you may need to
7638 make some files in the binary package be owned by this
7639 user or group, or you may need to compile the user or
7640 group id (rather than just the name) into the binary
7641 (though this latter should be avoided if possible, as in
7642 this case you need a statically allocated id).</p>
7645 If you need a statically allocated id, you must ask for a
7646 user or group id from the <tt>base-passwd</tt> maintainer,
7647 and must not release the package until you have been
7648 allocated one. Once you have been allocated one you must
7649 either make the package depend on a version of the
7650 <tt>base-passwd</tt> package with the id present in
7651 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7652 your package to create the user or group itself with the
7653 correct id (using <tt>adduser</tt>) in its
7654 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7655 the <prgn>postinst</prgn> is to be preferred if it is
7656 possible, otherwise a pre-dependency will be needed on the
7657 <tt>adduser</tt> package.)
7661 On the other hand, the program might be able to determine
7662 the uid or gid from the user or group name at runtime, so
7663 that a dynamically allocated id can be used. In this case
7664 you should choose an appropriate user or group name,
7665 discussing this on <prgn>debian-devel</prgn> and checking
7666 with the <package/base-passwd/ maintainer that it is unique and that
7667 they do not wish you to use a statically allocated id
7668 instead. When this has been checked you must arrange for
7669 your package to create the user or group if necessary using
7670 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7671 <prgn>postinst</prgn> script (again, the latter is to be
7672 preferred if it is possible).
7676 Note that changing the numeric value of an id associated
7677 with a name is very difficult, and involves searching the
7678 file system for all appropriate files. You need to think
7679 carefully whether a static or dynamic id is required, since
7680 changing your mind later will cause problems.
7683 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7685 This section is not intended as policy, but as a
7686 description of the use of <prgn>dpkg-statoverride</prgn>.
7690 If a system administrator wishes to have a file (or
7691 directory or other such thing) installed with owner and
7692 permissions different from those in the distributed Debian
7693 package, they can use the <prgn>dpkg-statoverride</prgn>
7694 program to instruct <prgn>dpkg</prgn> to use the different
7695 settings every time the file is installed. Thus the
7696 package maintainer should distribute the files with their
7697 normal permissions, and leave it for the system
7698 administrator to make any desired changes. For example, a
7699 daemon which is normally required to be setuid root, but
7700 in certain situations could be used without being setuid,
7701 should be installed setuid in the <tt>.deb</tt>. Then the
7702 local system administrator can change this if they wish.
7703 If there are two standard ways of doing it, the package
7704 maintainer can use <tt>debconf</tt> to find out the
7705 preference, and call <prgn>dpkg-statoverride</prgn> in the
7706 maintainer script if necessary to accommodate the system
7707 administrator's choice. Care must be taken during
7708 upgrades to not override an existing setting.
7712 Given the above, <prgn>dpkg-statoverride</prgn> is
7713 essentially a tool for system administrators and would not
7714 normally be needed in the maintainer scripts. There is
7715 one type of situation, though, where calls to
7716 <prgn>dpkg-statoverride</prgn> would be needed in the
7717 maintainer scripts, and that involves packages which use
7718 dynamically allocated user or group ids. In such a
7719 situation, something like the following idiom can be very
7720 helpful in the package's <prgn>postinst</prgn>, where
7721 <tt>sysuser</tt> is a dynamically allocated id:
7723 for i in /usr/bin/foo /usr/sbin/bar
7725 # only do something when no setting exists
7726 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7728 #include: debconf processing, question about foo and bar
7729 if [ "$RET" = "true" ] ; then
7730 dpkg-statoverride --update --add sysuser root 4755 $i
7735 The corresponding <tt>dpkg-statoverride --remove</tt>
7736 calls can then be made unconditionally when the package is
7744 <chapt id="customized-programs">
7745 <heading>Customized programs</heading>
7747 <sect id="arch-spec">
7748 <heading>Architecture specification strings</heading>
7751 If a program needs to specify an <em>architecture specification
7752 string</em> in some place, it should select one of the
7753 strings provided by <tt>dpkg-architecture -L</tt>. The
7754 strings are in the format
7755 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7756 is sometimes elided, as when the OS is Linux.<footnote>
7757 <p>Currently, the strings are:
7758 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7759 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7760 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7761 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7762 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7763 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7764 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7765 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7766 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7767 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7768 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7769 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7770 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7771 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7772 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7773 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7774 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7775 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7776 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7777 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7778 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7779 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7780 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7781 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7782 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7783 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7784 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7785 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7786 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7787 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7788 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7789 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7790 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7791 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7792 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7793 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7794 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7800 Note that we don't want to use
7801 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7802 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7803 since this would make our programs incompatible with other
7804 Linux distributions. We also don't use something like
7805 <tt><var>arch</var>-unknown-linux</tt>, since the
7806 <tt>unknown</tt> does not look very good.
7811 <heading>Daemons</heading>
7814 The configuration files <file>/etc/services</file>,
7815 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7816 by the <prgn>netbase</prgn> package and must not be modified
7821 If a package requires a new entry in one of these files, the
7822 maintainer should get in contact with the
7823 <prgn>netbase</prgn> maintainer, who will add the entries
7824 and release a new version of the <prgn>netbase</prgn>
7829 The configuration file <file>/etc/inetd.conf</file> must not be
7830 modified by the package's scripts except via the
7831 <prgn>update-inetd</prgn> script or the
7832 <file>DebianNet.pm</file> Perl module. See their documentation
7833 for details on how to add entries.
7837 If a package wants to install an example entry into
7838 <file>/etc/inetd.conf</file>, the entry must be preceded with
7839 exactly one hash character (<tt>#</tt>). Such lines are
7840 treated as "commented out by user" by the
7841 <prgn>update-inetd</prgn> script and are not changed or
7842 activated during package updates.
7847 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7851 Some programs need to create pseudo-ttys. This should be done
7852 using Unix98 ptys if the C library supports it. The resulting
7853 program must not be installed setuid root, unless that
7854 is required for other functionality.
7858 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7859 <file>/var/log/lastlog</file> must be installed writable by
7860 group <tt>utmp</tt>. Programs which need to modify those
7861 files must be installed setgid <tt>utmp</tt>.
7866 <heading>Editors and pagers</heading>
7869 Some programs have the ability to launch an editor or pager
7870 program to edit or display a text document. Since there are
7871 lots of different editors and pagers available in the Debian
7872 distribution, the system administrator and each user should
7873 have the possibility to choose their preferred editor and
7878 In addition, every program should choose a good default
7879 editor/pager if none is selected by the user or system
7884 Thus, every program that launches an editor or pager must
7885 use the EDITOR or PAGER environment variable to determine
7886 the editor or pager the user wishes to use. If these
7887 variables are not set, the programs <file>/usr/bin/editor</file>
7888 and <file>/usr/bin/pager</file> should be used, respectively.
7892 These two files are managed through the <prgn>dpkg</prgn>
7893 "alternatives" mechanism. Thus every package providing an
7894 editor or pager must call the
7895 <prgn>update-alternatives</prgn> script to register these
7900 If it is very hard to adapt a program to make use of the
7901 EDITOR or PAGER variables, that program may be configured to
7902 use <file>/usr/bin/sensible-editor</file> and
7903 <file>/usr/bin/sensible-pager</file> as the editor or pager
7904 program respectively. These are two scripts provided in the
7905 Debian base system that check the EDITOR and PAGER variables
7906 and launch the appropriate program, and fall back to
7907 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7908 variable is not set.
7912 A program may also use the VISUAL environment variable to
7913 determine the user's choice of editor. If it exists, it
7914 should take precedence over EDITOR. This is in fact what
7915 <file>/usr/bin/sensible-editor</file> does.
7919 It is not required for a package to depend on
7920 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7921 package to provide such virtual packages.<footnote>
7922 The Debian base system already provides an editor and a
7928 <sect id="web-appl">
7929 <heading>Web servers and applications</heading>
7932 This section describes the locations and URLs that should
7933 be used by all web servers and web applications in the
7940 Cgi-bin executable files are installed in the
7942 <example compact="compact">
7943 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7945 and should be referred to as
7946 <example compact="compact">
7947 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7953 <p>Access to HTML documents</p>
7956 HTML documents for a package are stored in
7957 <file>/usr/share/doc/<var>package</var></file>
7958 and can be referred to as
7959 <example compact="compact">
7960 http://localhost/doc/<var>package</var>/<var>filename</var>
7965 The web server should restrict access to the document
7966 tree so that only clients on the same host can read
7967 the documents. If the web server does not support such
7968 access controls, then it should not provide access at
7969 all, or ask about providing access during installation.
7974 <p>Access to images</p>
7976 It is recommended that images for a package be stored
7977 in <tt>/usr/share/images/<var>package</var></tt> and
7978 may be referred to through an alias <tt>/images/</tt>
7981 http://localhost/images/<package>/<filename>
7988 <p>Web Document Root</p>
7991 Web Applications should try to avoid storing files in
7992 the Web Document Root. Instead they should use the
7993 /usr/share/doc/<var>package</var> directory for
7994 documents and register the Web Application via the
7995 <package>doc-base</package> package. If access to the
7996 web document root is unavoidable then use
7997 <example compact="compact">
8000 as the Document Root. This might be just a symbolic
8001 link to the location where the system administrator
8002 has put the real document root.
8005 <item><p>Providing httpd and/or httpd-cgi</p>
8007 All web servers should provide the virtual package
8008 <tt>httpd</tt>. If a web server has CGI support it should
8009 provide <tt>httpd-cgi</tt> additionally.
8012 All web applications which do not contain CGI scripts should
8013 depend on <tt>httpd</tt>, all those web applications which
8014 <tt>do</tt> contain CGI scripts, should depend on
8022 <sect id="mail-transport-agents">
8023 <heading>Mail transport, delivery and user agents</heading>
8026 Debian packages which process electronic mail, whether mail
8027 user agents (MUAs) or mail transport agents (MTAs), must
8028 ensure that they are compatible with the configuration
8029 decisions below. Failure to do this may result in lost
8030 mail, broken <tt>From:</tt> lines, and other serious brain
8035 The mail spool is <file>/var/mail</file> and the interface to
8036 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8037 the FHS). On older systems, the mail spool may be
8038 physically located in <file>/var/spool/mail</file>, but all
8039 access to the mail spool should be via the
8040 <file>/var/mail</file> symlink. The mail spool is part of the
8041 base system and not part of the MTA package.
8045 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8046 programs (such as IMAP daemons) must lock the mailbox in an
8047 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8048 be combined with dot locking. To avoid deadlocks, a program
8049 should use <tt>fcntl()</tt> first and dot locking after
8050 this, or alternatively implement the two locking methods in
8051 a non blocking way<footnote>
8052 If it is not possible to establish both locks, the
8053 system shouldn't wait for the second lock to be
8054 established, but remove the first lock, wait a (random)
8055 time, and start over locking again.
8056 </footnote>. Using the functions <tt>maillock</tt> and
8057 <tt>mailunlock</tt> provided by the
8058 <tt>liblockfile*</tt><footnote>
8059 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8060 to use these functions.
8061 </footnote> packages is the recommended way to realize this.
8065 Mailboxes are generally either mode 600 and owned by
8066 <var>user</var> or mode 660 and owned by
8067 <tt><var>user</var>:mail</tt><footnote>
8068 There are two traditional permission schemes for mail spools:
8069 mode 600 with all mail delivery done by processes running as
8070 the destination user, or mode 660 and owned by group mail with
8071 mail delivery done by a process running as a system user in
8072 group mail. Historically, Debian required mode 660 mail
8073 spools to enable the latter model, but that model has become
8074 increasingly uncommon and the principle of least privilege
8075 indicates that mail systems that use the first model should
8076 use permissions of 600. If delivery to programs is permitted,
8077 it's easier to keep the mail system secure if the delivery
8078 agent runs as the destination user. Debian Policy therefore
8079 permits either scheme.
8080 </footnote>. The local system administrator may choose a
8081 different permission scheme; packages should not make
8082 assumptions about the permission and ownership of mailboxes
8083 unless required (such as when creating a new mailbox). A MUA
8084 may remove a mailbox (unless it has nonstandard permissions) in
8085 which case the MTA or another MUA must recreate it if needed.
8089 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8090 be setgid mail to do the locking mentioned above (and
8091 must obviously avoid accessing other users' mailboxes
8092 using this privilege).</p>
8095 <file>/etc/aliases</file> is the source file for the system mail
8096 aliases (e.g., postmaster, usenet, etc.), it is the one
8097 which the sysadmin and <prgn>postinst</prgn> scripts may
8098 edit. After <file>/etc/aliases</file> is edited the program or
8099 human editing it must call <prgn>newaliases</prgn>. All MTA
8100 packages must come with a <prgn>newaliases</prgn> program,
8101 even if it does nothing, but older MTA packages did not do
8102 this so programs should not fail if <prgn>newaliases</prgn>
8103 cannot be found. Note that because of this, all MTA
8104 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8105 <tt>Replaces: mail-transport-agent</tt> control file
8110 The convention of writing <tt>forward to
8111 <var>address</var></tt> in the mailbox itself is not
8112 supported. Use a <tt>.forward</tt> file instead.</p>
8115 The <prgn>rmail</prgn> program used by UUCP
8116 for incoming mail should be <file>/usr/sbin/rmail</file>.
8117 Likewise, <prgn>rsmtp</prgn>, for receiving
8118 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8122 If your package needs to know what hostname to use on (for
8123 example) outgoing news and mail messages which are generated
8124 locally, you should use the file <file>/etc/mailname</file>. It
8125 will contain the portion after the username and <tt>@</tt>
8126 (at) sign for email addresses of users on the machine
8127 (followed by a newline).
8131 Such a package should check for the existence of this file
8132 when it is being configured. If it exists, it should be
8133 used without comment, although an MTA's configuration script
8134 may wish to prompt the user even if it finds that this file
8135 exists. If the file does not exist, the package should
8136 prompt the user for the value (preferably using
8137 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8138 as well as using it in the package's configuration. The
8139 prompt should make it clear that the name will not just be
8140 used by that package. For example, in this situation the
8141 <tt>inn</tt> package could say something like:
8142 <example compact="compact">
8143 Please enter the "mail name" of your system. This is the
8144 hostname portion of the address to be shown on outgoing
8145 news and mail messages. The default is
8146 <var>syshostname</var>, your system's host name. Mail
8147 name ["<var>syshostname</var>"]:
8149 where <var>syshostname</var> is the output of <tt>hostname
8155 <heading>News system configuration</heading>
8158 All the configuration files related to the NNTP (news)
8159 servers and clients should be located under
8160 <file>/etc/news</file>.</p>
8163 There are some configuration issues that apply to a number
8164 of news clients and server packages on the machine. These
8168 <tag><file>/etc/news/organization</file></tag>
8170 A string which should appear as the
8171 organization header for all messages posted
8172 by NNTP clients on the machine
8175 <tag><file>/etc/news/server</file></tag>
8177 Contains the FQDN of the upstream NNTP
8178 server, or localhost if the local machine is
8183 Other global files may be added as required for cross-package news
8190 <heading>Programs for the X Window System</heading>
8193 <heading>Providing X support and package priorities</heading>
8196 Programs that can be configured with support for the X
8197 Window System must be configured to do so and must declare
8198 any package dependencies necessary to satisfy their
8199 runtime requirements when using the X Window System. If
8200 such a package is of higher priority than the X packages
8201 on which it depends, it is required that either the
8202 X-specific components be split into a separate package, or
8203 that an alternative version of the package, which includes
8204 X support, be provided, or that the package's priority be
8210 <heading>Packages providing an X server</heading>
8213 Packages that provide an X server that, directly or
8214 indirectly, communicates with real input and display
8215 hardware should declare in their control data that they
8216 provide the virtual package <tt>xserver</tt>.<footnote>
8217 This implements current practice, and provides an
8218 actual policy for usage of the <tt>xserver</tt>
8219 virtual package which appears in the virtual packages
8220 list. In a nutshell, X servers that interface
8221 directly with the display and input hardware or via
8222 another subsystem (e.g., GGI) should provide
8223 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8224 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8230 <heading>Packages providing a terminal emulator</heading>
8233 Packages that provide a terminal emulator for the X Window
8234 System which meet the criteria listed below should declare
8235 in their control data that they provide the virtual
8236 package <tt>x-terminal-emulator</tt>. They should also
8237 register themselves as an alternative for
8238 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8243 To be an <tt>x-terminal-emulator</tt>, a program must:
8244 <list compact="compact">
8246 Be able to emulate a DEC VT100 terminal, or a
8247 compatible terminal.
8251 Support the command-line option <tt>-e
8252 <var>command</var></tt>, which creates a new
8253 terminal window<footnote>
8254 "New terminal window" does not necessarily mean
8255 a new top-level X window directly parented by
8256 the window manager; it could, if the terminal
8257 emulator application were so coded, be a new
8258 "view" in a multiple-document interface (MDI).
8260 and runs the specified <var>command</var>,
8261 interpreting the entirety of the rest of the command
8262 line as a command to pass straight to exec, in the
8263 manner that <tt>xterm</tt> does.
8267 Support the command-line option <tt>-T
8268 <var>title</var></tt>, which creates a new terminal
8269 window with the window title <var>title</var>.
8276 <heading>Packages providing a window manager</heading>
8279 Packages that provide a window manager should declare in
8280 their control data that they provide the virtual package
8281 <tt>x-window-manager</tt>. They should also register
8282 themselves as an alternative for
8283 <file>/usr/bin/x-window-manager</file>, with a priority
8284 calculated as follows:
8285 <list compact="compact">
8287 Start with a priority of 20.
8291 If the window manager supports the Debian menu
8292 system, add 20 points if this support is available
8293 in the package's default configuration (i.e., no
8294 configuration files belonging to the system or user
8295 have to be edited to activate the feature); if
8296 configuration files must be modified, add only 10
8302 If the window manager complies with <url
8303 id="http://www.freedesktop.org/Standards/wm-spec"
8304 name="The Window Manager Specification Project">,
8305 written by the <url id="http://www.freedesktop.org/"
8306 name="Free Desktop Group">, add 40 points.
8310 If the window manager permits the X session to be
8311 restarted using a <em>different</em> window manager
8312 (without killing the X server) in its default
8313 configuration, add 10 points; otherwise add none.
8320 <heading>Packages providing fonts</heading>
8323 Packages that provide fonts for the X Window
8325 For the purposes of Debian Policy, a "font for the X
8326 Window System" is one which is accessed via X protocol
8327 requests. Fonts for the Linux console, for PostScript
8328 renderer, or any other purpose, do not fit this
8329 definition. Any tool which makes such fonts available
8330 to the X Window System, however, must abide by this
8333 must do a number of things to ensure that they are both
8334 available without modification of the X or font server
8335 configuration, and that they do not corrupt files used by
8336 other font packages to register information about
8340 Fonts of any type supported by the X Window System
8341 must be in a separate binary package from any
8342 executables, libraries, or documentation (except
8343 that specific to the fonts shipped, such as their
8344 license information). If one or more of the fonts
8345 so packaged are necessary for proper operation of
8346 the package with which they are associated the font
8347 package may be Recommended; if the fonts merely
8348 provide an enhancement, a Suggests relationship may
8349 be used. Packages must not Depend on font
8351 This is because the X server may retrieve fonts
8352 from the local file system or over the network
8353 from an X font server; the Debian package system
8354 is empowered to deal only with the local
8360 BDF fonts must be converted to PCF fonts with the
8361 <prgn>bdftopcf</prgn> utility (available in the
8362 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8363 placed in a directory that corresponds to their
8365 <list compact="compact">
8367 100 dpi fonts must be placed in
8368 <file>/usr/share/fonts/X11/100dpi/</file>.
8372 75 dpi fonts must be placed in
8373 <file>/usr/share/fonts/X11/75dpi/</file>.
8377 Character-cell fonts, cursor fonts, and other
8378 low-resolution fonts must be placed in
8379 <file>/usr/share/fonts/X11/misc/</file>.
8385 Speedo fonts must be placed in
8386 <file>/usr/share/fonts/X11/Speedo/</file>.
8390 Type 1 fonts must be placed in
8391 <file>/usr/share/fonts/X11/Type1/</file>. If font
8392 metric files are available, they must be placed here
8397 Subdirectories of <file>/usr/share/fonts/X11/</file>
8398 other than those listed above must be neither
8399 created nor used. (The <file>PEX</file>, <file>CID</file>,
8400 and <file>cyrillic</file> directories are excepted for
8401 historical reasons, but installation of files into
8402 these directories remains discouraged.)
8406 Font packages may, instead of placing files directly
8407 in the X font directories listed above, provide
8408 symbolic links in that font directory pointing to
8409 the files' actual location in the filesystem. Such
8410 a location must comply with the FHS.
8414 Font packages should not contain both 75dpi and
8415 100dpi versions of a font. If both are available,
8416 they should be provided in separate binary packages
8417 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8418 the names of the packages containing the
8419 corresponding fonts.
8423 Fonts destined for the <file>misc</file> subdirectory
8424 should not be included in the same package as 75dpi
8425 or 100dpi fonts; instead, they should be provided in
8426 a separate package with <tt>-misc</tt> appended to
8431 Font packages must not provide the files
8432 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8433 <file>fonts.scale</file> in a font directory:
8436 <file>fonts.dir</file> files must not be provided at all.
8440 <file>fonts.alias</file> and <file>fonts.scale</file>
8441 files, if needed, should be provided in the
8443 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8444 where <var>fontdir</var> is the name of the
8446 <file>/usr/share/fonts/X11/</file> where the
8447 package's corresponding fonts are stored
8448 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8449 <var>package</var> is the name of the package
8450 that provides these fonts, and
8451 <var>extension</var> is either <tt>scale</tt>
8452 or <tt>alias</tt>, whichever corresponds to
8459 Font packages must declare a dependency on
8460 <tt>xfonts-utils</tt> in their control
8465 Font packages that provide one or more
8466 <file>fonts.scale</file> files as described above must
8467 invoke <prgn>update-fonts-scale</prgn> on each
8468 directory into which they installed fonts
8469 <em>before</em> invoking
8470 <prgn>update-fonts-dir</prgn> on that directory.
8471 This invocation must occur in both the
8472 <prgn>postinst</prgn> (for all arguments) and
8473 <prgn>postrm</prgn> (for all arguments except
8474 <tt>upgrade</tt>) scripts.
8478 Font packages that provide one or more
8479 <file>fonts.alias</file> files as described above must
8480 invoke <prgn>update-fonts-alias</prgn> on each
8481 directory into which they installed fonts. This
8482 invocation must occur in both the
8483 <prgn>postinst</prgn> (for all arguments) and
8484 <prgn>postrm</prgn> (for all arguments except
8485 <tt>upgrade</tt>) scripts.
8489 Font packages must invoke
8490 <prgn>update-fonts-dir</prgn> on each directory into
8491 which they installed fonts. This invocation must
8492 occur in both the <prgn>postinst</prgn> (for all
8493 arguments) and <prgn>postrm</prgn> (for all
8494 arguments except <tt>upgrade</tt>) scripts.
8498 Font packages must not provide alias names for the
8499 fonts they include which collide with alias names
8500 already in use by fonts already packaged.
8504 Font packages must not provide fonts with the same
8505 XLFD registry name as another font already packaged.
8512 <heading>Application defaults files</heading>
8515 Application defaults files must be installed in the
8516 directory <file>/etc/X11/app-defaults/</file> (use of a
8517 localized subdirectory of <file>/etc/X11/</file> as described
8518 in the <em>X Toolkit Intrinsics - C Language
8519 Interface</em> manual is also permitted). They must be
8520 registered as <tt>conffile</tt>s or handled as
8521 configuration files.
8525 Customization of programs' X resources may also be
8526 supported with the provision of a file with the same name
8527 as that of the package placed in the
8528 <file>/etc/X11/Xresources/</file> directory, which must
8529 registered as a <tt>conffile</tt> or handled as a
8530 configuration file.<footnote>
8531 Note that this mechanism is not the same as using
8532 app-defaults; app-defaults are tied to the client
8533 binary on the local file system, whereas X resources
8534 are stored in the X server and affect all connecting
8541 <heading>Installation directory issues</heading>
8544 Packages using the X Window System should not be
8545 configured to install files under the
8546 <file>/usr/X11R6/</file> directory. The
8547 <file>/usr/X11R6/</file> directory hierarchy should be
8548 regarded as obsolete.
8552 Programs that use GNU <prgn>autoconf</prgn> and
8553 <prgn>automake</prgn> are usually easily configured at
8554 compile time to use <file>/usr/</file> instead of
8555 <file>/usr/X11R6/</file>, and this should be done whenever
8556 possible. Configuration files for window managers and
8557 display managers should be placed in a subdirectory of
8558 <file>/etc/X11/</file> corresponding to the package name due
8559 to these programs' tight integration with the mechanisms
8560 of the X Window System. Application-level programs should
8561 use the <file>/etc/</file> directory unless otherwise mandated
8566 The installation of files into subdirectories
8567 of <file>/usr/X11R6/include/X11/</file> and
8568 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8569 package maintainers should determine if subdirectories of
8570 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8575 Packages should install any relevant files into the
8576 directories <file>/usr/include/X11/</file> and
8577 <file>/usr/lib/X11/</file>, but if they do so, they must
8578 pre-depend on <tt>x11-common (>=
8579 1:7.0.0)</tt><footnote>
8581 These libraries used to be all symbolic
8582 links. However, with <tt>X11R7</tt>,
8583 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8584 are now real directories, and packages
8585 <strong>should</strong> ship their files here instead
8586 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8587 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8588 responsible for converting these symlinks into
8596 <heading>The OSF/Motif and OpenMotif libraries</heading>
8599 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8600 OpenMotif libraries</em><footnote>
8601 OSF/Motif and OpenMotif are collectively referred to as
8602 "Motif" in this policy document.
8604 should be compiled against and tested with LessTif (a free
8605 re-implementation of Motif) instead. If the maintainer
8606 judges that the program or programs do not work
8607 sufficiently well with LessTif to be distributed and
8608 supported, but do so when compiled against Motif, then two
8609 versions of the package should be created; one linked
8610 statically against Motif and with <tt>-smotif</tt>
8611 appended to the package name, and one linked dynamically
8612 against Motif and with <tt>-dmotif</tt> appended to the
8617 Both Motif-linked versions are dependent
8618 upon non-DFSG-compliant software and thus cannot be
8619 uploaded to the <em>main</em> distribution; if the
8620 software is itself DFSG-compliant it may be uploaded to
8621 the <em>contrib</em> distribution. While known existing
8622 versions of Motif permit unlimited redistribution of
8623 binaries linked against the library (whether statically or
8624 dynamically), it is the package maintainer's
8625 responsibility to determine whether this is permitted by
8626 the license of the copy of Motif in their possession.
8632 <heading>Perl programs and modules</heading>
8635 Perl programs and modules should follow the current Perl policy.
8639 The Perl policy can be found in the <tt>perl-policy</tt>
8640 files in the <tt>debian-policy</tt> package.
8641 It is also available from the Debian web mirrors at
8642 <tt><url name="/doc/packaging-manuals/perl-policy/"
8643 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8648 <heading>Emacs lisp programs</heading>
8651 Please refer to the "Debian Emacs Policy" for details of how to
8652 package emacs lisp programs.
8656 The Emacs policy is available in
8657 <file>debian-emacs-policy.gz</file> of the
8658 <package>emacsen-common</package> package.
8659 It is also available from the Debian web mirrors at
8660 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8661 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8666 <heading>Games</heading>
8669 The permissions on <file>/var/games</file> are mode 755, owner
8670 <tt>root</tt> and group <tt>root</tt>.
8674 Each game decides on its own security policy.</p>
8677 Games which require protected, privileged access to
8678 high-score files, saved games, etc., may be made
8679 set-<em>group</em>-id (mode 2755) and owned by
8680 <tt>root:games</tt>, and use files and directories with
8681 appropriate permissions (770 <tt>root:games</tt>, for
8682 example). They must not be made
8683 set-<em>user</em>-id, as this causes security problems. (If
8684 an attacker can subvert any set-user-id game they can
8685 overwrite the executable of any other, causing other players
8686 of these games to run a Trojan horse program. With a
8687 set-group-id game the attacker only gets access to less
8688 important game data, and if they can get at the other
8689 players' accounts at all it will take considerably more
8693 Some packages, for example some fortune cookie programs, are
8694 configured by the upstream authors to install with their
8695 data files or other static information made unreadable so
8696 that they can only be accessed through set-id programs
8697 provided. You should not do this in a Debian package: anyone can
8698 download the <file>.deb</file> file and read the data from it,
8699 so there is no point making the files unreadable. Not
8700 making the files unreadable also means that you don't have
8701 to make so many programs set-id, which reduces the risk of a
8705 As described in the FHS, binaries of games should be
8706 installed in the directory <file>/usr/games</file>. This also
8707 applies to games that use the X Window System. Manual pages
8708 for games (X and non-X games) should be installed in
8709 <file>/usr/share/man/man6</file>.</p>
8715 <heading>Documentation</heading>
8718 <heading>Manual pages</heading>
8721 You should install manual pages in <prgn>nroff</prgn> source
8722 form, in appropriate places under <file>/usr/share/man</file>.
8723 You should only use sections 1 to 9 (see the FHS for more
8724 details). You must not install a pre-formatted "cat page".
8728 Each program, utility, and function should have an
8729 associated manual page included in the same package. It is
8730 suggested that all configuration files also have a manual
8731 page included as well. Manual pages for protocols and other
8732 auxiliary things are optional.
8736 If no manual page is available, this is considered as a bug
8737 and should be reported to the Debian Bug Tracking System (the
8738 maintainer of the package is allowed to write this bug report
8739 themselves, if they so desire). Do not close the bug report
8740 until a proper man page is available.<footnote>
8741 It is not very hard to write a man page. See the
8742 <url id="http://www.schweikhardt.net/man_page_howto.html"
8743 name="Man-Page-HOWTO">,
8744 <manref name="man" section="7">, the examples
8745 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8746 the helper programs <prgn>help2man</prgn>, or the
8747 directory <file>/usr/share/doc/man-db/examples</file>.
8752 You may forward a complaint about a missing man page to the
8753 upstream authors, and mark the bug as forwarded in the
8754 Debian bug tracking system. Even though the GNU Project do
8755 not in general consider the lack of a man page to be a bug,
8756 we do; if they tell you that they don't consider it a bug
8757 you should leave the bug in our bug tracking system open
8762 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8766 If one man page needs to be accessible via several names it
8767 is better to use a symbolic link than the <file>.so</file>
8768 feature, but there is no need to fiddle with the relevant
8769 parts of the upstream source to change from <file>.so</file> to
8770 symlinks: don't do it unless it's easy. You should not
8771 create hard links in the manual page directories, nor put
8772 absolute filenames in <file>.so</file> directives. The filename
8773 in a <file>.so</file> in a man page should be relative to the
8774 base of the man page tree (usually
8775 <file>/usr/share/man</file>). If you do not create any links
8776 (whether symlinks, hard links, or <tt>.so</tt> directives)
8777 in the file system to the alternate names of the man page,
8778 then you should not rely on <prgn>man</prgn> finding your
8779 man page under those names based solely on the information in
8780 the man page's header.<footnote>
8781 Supporting this in <prgn>man</prgn> often requires
8782 unreasonable processing time to find a manual page or to
8783 report that none exists, and moves knowledge into man's
8784 database that would be better left in the file system.
8785 This support is therefore deprecated and will cease to
8786 be present in the future.
8791 Manual pages in locale-specific subdirectories of
8792 <file>/usr/share/man</file> should use either UTF-8 or the usual
8793 legacy encoding for that language (normally the one corresponding
8794 to the shortest relevant locale name in
8795 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8796 <file>/usr/share/man/fr</file> should use either UTF-8 or
8797 ISO-8859-1.<footnote>
8798 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8799 use. In future, all manual pages will be required to use
8805 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8806 included in the subdirectory name unless it indicates a
8807 significant difference in the language, as this excludes
8808 speakers of the language in other countries.<footnote>
8809 At the time of writing, Chinese and Portuguese are the main
8810 languages with such differences, so <file>pt_BR</file>,
8811 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8816 Due to limitations in current implementations, all characters
8817 in the manual page source should be representable in the usual
8818 legacy encoding for that language, even if the file is
8819 actually encoded in UTF-8. Safe alternative ways to write many
8820 characters outside that range may be found in
8821 <manref name="groff_char" section="7">.
8826 <heading>Info documents</heading>
8829 Info documents should be installed in <file>/usr/share/info</file>.
8830 They should be compressed with <tt>gzip -9</tt>.
8834 Your package should call <prgn>install-info</prgn> to update
8835 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8836 script when called with a <tt>configure</tt> argument, for
8838 <example compact="compact">
8839 install-info --quiet --section Development Development \
8840 /usr/share/info/foobar.info
8844 It is a good idea to specify a section for the location of
8845 your program; this is done with the <tt>--section</tt>
8846 switch. To determine which section to use, you should look
8847 at <file>/usr/share/info/dir</file> on your system and choose the most
8848 relevant (or create a new section if none of the current
8849 sections are relevant). Note that the <tt>--section</tt>
8850 flag takes two arguments; the first is a regular expression
8851 to match (case-insensitively) against an existing section,
8852 the second is used when creating a new one.</p>
8855 You should remove the entries in the <prgn>prerm</prgn>
8856 script when called with a <tt>remove</tt> argument:
8857 <example compact="compact">
8858 install-info --quiet --remove /usr/share/info/foobar.info
8862 If <prgn>install-info</prgn> cannot find a description entry
8863 in the Info file you must supply one. See <manref
8864 name="install-info" section="8"> for details.</p>
8868 <heading>Additional documentation</heading>
8871 Any additional documentation that comes with the package may
8872 be installed at the discretion of the package maintainer.
8873 Plain text documentation should be installed in the directory
8874 <file>/usr/share/doc/<var>package</var></file>, where
8875 <var>package</var> is the name of the package, and
8876 compressed with <tt>gzip -9</tt> unless it is small.
8880 If a package comes with large amounts of documentation which
8881 many users of the package will not require you should create
8882 a separate binary package to contain it, so that it does not
8883 take up disk space on the machines of users who do not need
8884 or want it installed.</p>
8887 It is often a good idea to put text information files
8888 (<file>README</file>s, changelogs, and so forth) that come with
8889 the source package in <file>/usr/share/doc/<var>package</var></file>
8890 in the binary package. However, you don't need to install
8891 the instructions for building and installing the package, of
8895 Packages must not require the existence of any files in
8896 <file>/usr/share/doc/</file> in order to function
8898 The system administrator should be able to
8899 delete files in <file>/usr/share/doc/</file> without causing
8900 any programs to break.
8902 Any files that are referenced by programs but are also
8903 useful as stand alone documentation should be installed under
8904 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8905 <file>/usr/share/doc/<var>package</var></file>.
8909 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8910 link to another directory in <file>/usr/share/doc</file> only if
8911 the two packages both come from the same source and the
8912 first package Depends on the second.<footnote>
8914 Please note that this does not override the section on
8915 changelog files below, so the file
8916 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8917 must refer to the changelog for the current version of
8918 <var>package</var> in question. In practice, this means
8919 that the sources of the target and the destination of the
8920 symlink must be the same (same source package and
8927 Former Debian releases placed all additional documentation
8928 in <file>/usr/doc/<var>package</var></file>. This has been
8929 changed to <file>/usr/share/doc/<var>package</var></file>,
8930 and packages must not put documentation in the directory
8931 <file>/usr/doc/<var>package</var></file>. <footnote>
8932 At this phase of the transition, we no longer require a
8933 symbolic link in <file>/usr/doc/</file>. At a later point,
8934 policy shall change to make the symbolic links a bug.
8940 <heading>Preferred documentation formats</heading>
8943 The unification of Debian documentation is being carried out
8947 If your package comes with extensive documentation in a
8948 markup format that can be converted to various other formats
8949 you should if possible ship HTML versions in a binary
8950 package, in the directory
8951 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8952 its subdirectories.<footnote>
8953 The rationale: The important thing here is that HTML
8954 docs should be available in <em>some</em> package, not
8955 necessarily in the main binary package.
8960 Other formats such as PostScript may be provided at the
8961 package maintainer's discretion.
8965 <sect id="copyrightfile">
8966 <heading>Copyright information</heading>
8969 Every package must be accompanied by a verbatim copy of its
8970 copyright and distribution license in the file
8971 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8972 file must neither be compressed nor be a symbolic link.
8976 In addition, the copyright file must say where the upstream
8977 sources (if any) were obtained. It should name the original
8978 authors of the package and the Debian maintainer(s) who were
8979 involved with its creation.
8983 Packages in the <em>contrib</em> or <em>non-free</em> categories
8984 should state in the copyright file that the package is not part
8985 of the Debian GNU/Linux distribution and briefly explain why.
8989 A copy of the file which will be installed in
8990 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8991 be in <file>debian/copyright</file> in the source package.
8995 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8996 link to another directory in <file>/usr/share/doc</file> only if
8997 the two packages both come from the same source and the
8998 first package Depends on the second. These rules are
8999 important because copyrights must be extractable by
9004 Packages distributed under the UCB BSD license, the Apache
9005 license (version 2.0), the Artistic license, the GNU GPL
9006 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
9007 the GNU FDL (version 1.2) should refer to the corresponding
9008 files under <file>/usr/share/common-licenses</file>,<footnote>
9011 <file>/usr/share/common-licenses/BSD</file>,
9012 <file>/usr/share/common-licenses/Apache-2.0</file>,
9013 <file>/usr/share/common-licenses/Artistic</file>,
9014 <file>/usr/share/common-licenses/GPL-2</file>,
9015 <file>/usr/share/common-licenses/GPL-3</file>,
9016 <file>/usr/share/common-licenses/LGPL-2</file>,
9017 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9018 <file>/usr/share/common-licenses/LGPL-3</file>, and
9019 <file>/usr/share/common-licenses/GFDL-1.2</file>
9022 </footnote> rather than quoting them in the copyright
9027 You should not use the copyright file as a general <file>README</file>
9028 file. If your package has such a file it should be
9029 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9030 <file>README.Debian</file> or some other appropriate place.</p>
9034 <heading>Examples</heading>
9037 Any examples (configurations, source files, whatever),
9038 should be installed in a directory
9039 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9040 files should not be referenced by any program: they're there
9041 for the benefit of the system administrator and users as
9042 documentation only. Architecture-specific example files
9043 should be installed in a directory
9044 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9046 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9047 latter directory itself may be a symbolic link to the
9052 If the purpose of a package is to provide examples, then the
9053 example files may be installed into
9054 <file>/usr/share/doc/<var>package</var></file>.
9058 <sect id="changelogs">
9059 <heading>Changelog files</heading>
9062 Packages that are not Debian-native must contain a
9063 compressed copy of the <file>debian/changelog</file> file from
9064 the Debian source tree in
9065 <file>/usr/share/doc/<var>package</var></file> with the name
9066 <file>changelog.Debian.gz</file>.
9070 If an upstream changelog is available, it should be accessible as
9071 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9072 plain text. If the upstream changelog is distributed in
9073 HTML, it should be made available in that form as
9074 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9075 and a plain text <file>changelog.gz</file> should be generated
9076 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9077 the upstream changelog files do not already conform to this
9078 naming convention, then this may be achieved either by
9079 renaming the files, or by adding a symbolic link, at the
9080 maintainer's discretion.<footnote>
9081 Rationale: People should not have to look in places for
9082 upstream changelogs merely because they are given
9083 different names or are distributed in HTML format.
9088 All of these files should be installed compressed using
9089 <tt>gzip -9</tt>, as they will become large with time even
9090 if they start out small.
9094 If the package has only one changelog which is used both as
9095 the Debian changelog and the upstream one because there is
9096 no separate upstream maintainer then that changelog should
9097 usually be installed as
9098 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9099 there is a separate upstream maintainer, but no upstream
9100 changelog, then the Debian changelog should still be called
9101 <file>changelog.Debian.gz</file>.
9105 For details about the format and contents of the Debian
9106 changelog file, please see <ref id="dpkgchangelog">.
9111 <appendix id="pkg-scope">
9112 <heading>Introduction and scope of these appendices</heading>
9115 These appendices are taken essentially verbatim from the
9116 now-deprecated Packaging Manual, version 3.2.1.0. They are
9117 the chapters which are likely to be of use to package
9118 maintainers and which have not already been included in the
9119 policy document itself. Most of these sections are very likely
9120 not relevant to policy; they should be treated as
9121 documentation for the packaging system. Please note that these
9122 appendices are included for convenience, and for historical
9123 reasons: they used to be part of policy package, and they have
9124 not yet been incorporated into dpkg documentation. However,
9125 they still have value, and hence they are presented here.
9129 They have not yet been checked to ensure that they are
9130 compatible with the contents of policy, and if there are any
9131 contradictions, the version in the main policy document takes
9132 precedence. The remaining chapters of the old Packaging
9133 Manual have also not been read in detail to ensure that there
9134 are not parts which have been left out. Both of these will be
9139 Certain parts of the Packaging manual were integrated into the
9140 Policy Manual proper, and removed from the appendices. Links
9141 have been placed from the old locations to the new ones.
9145 <prgn>dpkg</prgn> is a suite of programs for creating binary
9146 package files and installing and removing them on Unix
9148 <prgn>dpkg</prgn> is targeted primarily at Debian
9149 GNU/Linux, but may work on or be ported to other
9155 The binary packages are designed for the management of
9156 installed executable programs (usually compiled binaries) and
9157 their associated data, though source code examples and
9158 documentation are provided as part of some packages.</p>
9161 This manual describes the technical aspects of creating Debian
9162 binary packages (<file>.deb</file> files). It documents the
9163 behavior of the package management programs
9164 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9165 they interact with packages.</p>
9168 It also documents the interaction between
9169 <prgn>dselect</prgn>'s core and the access method scripts it
9170 uses to actually install the selected packages, and describes
9171 how to create a new access method.</p>
9174 This manual does not go into detail about the options and
9175 usage of the package building and installation tools. It
9176 should therefore be read in conjunction with those programs'
9181 The utility programs which are provided with <prgn>dpkg</prgn>
9182 for managing various system configuration and similar issues,
9183 such as <prgn>update-rc.d</prgn> and
9184 <prgn>install-info</prgn>, are not described in detail here -
9185 please see their man pages.
9189 It is assumed that the reader is reasonably familiar with the
9190 <prgn>dpkg</prgn> System Administrators' manual.
9191 Unfortunately this manual does not yet exist.
9195 The Debian version of the FSF's GNU hello program is provided
9196 as an example for people wishing to create Debian
9197 packages. The Debian <prgn>debmake</prgn> package is
9198 recommended as a very helpful tool in creating and maintaining
9199 Debian packages. However, while the tools and examples are
9200 helpful, they do not replace the need to read and follow the
9201 Policy and Programmer's Manual.</p>
9204 <appendix id="pkg-binarypkg">
9205 <heading>Binary packages (from old Packaging Manual)</heading>
9208 The binary package has two main sections. The first part
9209 consists of various control information files and scripts used
9210 by <prgn>dpkg</prgn> when installing and removing. See <ref
9211 id="pkg-controlarea">.
9215 The second part is an archive containing the files and
9216 directories to be installed.
9220 In the future binary packages may also contain other
9221 components, such as checksums and digital signatures. The
9222 format for the archive is described in full in the
9223 <file>deb(5)</file> man page.
9227 <sect id="pkg-bincreating"><heading>Creating package files -
9228 <prgn>dpkg-deb</prgn>
9232 All manipulation of binary package files is done by
9233 <prgn>dpkg-deb</prgn>; it's the only program that has
9234 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9235 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9236 will spot that the options requested are appropriate to
9237 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9242 In order to create a binary package you must make a
9243 directory tree which contains all the files and directories
9244 you want to have in the file system data part of the package.
9245 In Debian-format source packages this directory is usually
9246 <file>debian/tmp</file>, relative to the top of the package's
9251 They should have the locations (relative to the root of the
9252 directory tree you're constructing) ownerships and
9253 permissions which you want them to have on the system when
9258 With current versions of <prgn>dpkg</prgn> the uid/username
9259 and gid/groupname mappings for the users and groups being
9260 used should be the same on the system where the package is
9261 built and the one where it is installed.
9265 You need to add one special directory to the root of the
9266 miniature file system tree you're creating:
9267 <prgn>DEBIAN</prgn>. It should contain the control
9268 information files, notably the binary package control file
9269 (see <ref id="pkg-controlfile">).
9273 The <prgn>DEBIAN</prgn> directory will not appear in the
9274 file system archive of the package, and so won't be installed
9275 by <prgn>dpkg</prgn> when the package is installed.
9279 When you've prepared the package, you should invoke:
9281 dpkg --build <var>directory</var>
9286 This will build the package in
9287 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9288 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9289 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9294 See the man page <manref name="dpkg-deb" section="8"> for details of how
9295 to examine the contents of this newly-created file. You may find the
9296 output of following commands enlightening:
9298 dpkg-deb --info <var>filename</var>.deb
9299 dpkg-deb --contents <var>filename</var>.deb
9300 dpkg --contents <var>filename</var>.deb
9302 To view the copyright file for a package you could use this command:
9304 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9309 <sect id="pkg-controlarea">
9310 <heading>Package control information files</heading>
9313 The control information portion of a binary package is a
9314 collection of files with names known to <prgn>dpkg</prgn>.
9315 It will treat the contents of these files specially - some
9316 of them contain information used by <prgn>dpkg</prgn> when
9317 installing or removing the package; others are scripts which
9318 the package maintainer wants <prgn>dpkg</prgn> to run.
9322 It is possible to put other files in the package control
9323 area, but this is not generally a good idea (though they
9324 will largely be ignored).
9328 Here is a brief list of the control info files supported by
9329 <prgn>dpkg</prgn> and a summary of what they're used for.
9334 <tag><tt>control</tt>
9337 This is the key description file used by
9338 <prgn>dpkg</prgn>. It specifies the package's name
9339 and version, gives its description for the user,
9340 states its relationships with other packages, and so
9341 forth. See <ref id="sourcecontrolfiles"> and
9342 <ref id="binarycontrolfiles">.
9346 It is usually generated automatically from information
9347 in the source package by the
9348 <prgn>dpkg-gencontrol</prgn> program, and with
9349 assistance from <prgn>dpkg-shlibdeps</prgn>.
9350 See <ref id="pkg-sourcetools">.
9354 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9359 These are executable files (usually scripts) which
9360 <prgn>dpkg</prgn> runs during installation, upgrade
9361 and removal of packages. They allow the package to
9362 deal with matters which are particular to that package
9363 or require more complicated processing than that
9364 provided by <prgn>dpkg</prgn>. Details of when and
9365 how they are called are in <ref id="maintainerscripts">.
9369 It is very important to make these scripts idempotent.
9370 See <ref id="idempotency">.
9374 The maintainer scripts are guaranteed to run with a
9375 controlling terminal and can interact with the user.
9376 See <ref id="controllingterminal">.
9380 <tag><tt>conffiles</tt>
9383 This file contains a list of configuration files which
9384 are to be handled automatically by <prgn>dpkg</prgn>
9385 (see <ref id="pkg-conffiles">). Note that not necessarily
9386 every configuration file should be listed here.
9389 <tag><tt>shlibs</tt>
9392 This file contains a list of the shared libraries
9393 supplied by the package, with dependency details for
9394 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9395 when it determines what dependencies are required in a
9396 package control file. The <tt>shlibs</tt> file format
9397 is described on <ref id="shlibs">.
9402 <sect id="pkg-controlfile">
9403 <heading>The main control information file: <tt>control</tt></heading>
9406 The most important control information file used by
9407 <prgn>dpkg</prgn> when it installs a package is
9408 <tt>control</tt>. It contains all the package's "vital
9413 The binary package control files of packages built from
9414 Debian sources are made by a special tool,
9415 <prgn>dpkg-gencontrol</prgn>, which reads
9416 <file>debian/control</file> and <file>debian/changelog</file> to
9417 find the information it needs. See <ref id="pkg-sourcepkg"> for
9422 The fields in binary package control files are listed in
9423 <ref id="binarycontrolfiles">.
9427 A description of the syntax of control files and the purpose
9428 of the fields is available in <ref id="controlfields">.
9433 <heading>Time Stamps</heading>
9436 See <ref id="timestamps">.
9441 <appendix id="pkg-sourcepkg">
9442 <heading>Source packages (from old Packaging Manual) </heading>
9445 The Debian binary packages in the distribution are generated
9446 from Debian sources, which are in a special format to assist
9447 the easy and automatic building of binaries.
9450 <sect id="pkg-sourcetools">
9451 <heading>Tools for processing source packages</heading>
9454 Various tools are provided for manipulating source packages;
9455 they pack and unpack sources and help build of binary
9456 packages and help manage the distribution of new versions.
9460 They are introduced and typical uses described here; see
9461 <manref name="dpkg-source" section="1"> for full
9462 documentation about their arguments and operation.
9466 For examples of how to construct a Debian source package,
9467 and how to use those utilities that are used by Debian
9468 source packages, please see the <prgn>hello</prgn> example
9472 <sect1 id="pkg-dpkg-source">
9474 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9479 This program is frequently used by hand, and is also
9480 called from package-independent automated building scripts
9481 such as <prgn>dpkg-buildpackage</prgn>.
9485 To unpack a package it is typically invoked with
9487 dpkg-source -x <var>.../path/to/filename</var>.dsc
9492 with the <file><var>filename</var>.tar.gz</file> and
9493 <file><var>filename</var>.diff.gz</file> (if applicable) in
9494 the same directory. It unpacks into
9495 <file><var>package</var>-<var>version</var></file>, and if
9497 <file><var>package</var>-<var>version</var>.orig</file>, in
9498 the current directory.
9502 To create a packed source archive it is typically invoked:
9504 dpkg-source -b <var>package</var>-<var>version</var>
9509 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9510 <file>.diff.gz</file> (if appropriate) in the current
9511 directory. <prgn>dpkg-source</prgn> does not clean the
9512 source tree first - this must be done separately if it is
9517 See also <ref id="pkg-sourcearchives">.</p>
9521 <sect1 id="pkg-dpkg-buildpackage">
9523 <prgn>dpkg-buildpackage</prgn> - overall package-building
9528 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9529 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9530 targets <tt>clean</tt>, <tt>build</tt> and
9531 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9532 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9533 source and binary package upload.
9537 It is usually invoked by hand from the top level of the
9538 built or unbuilt source directory. It may be invoked with
9539 no arguments; useful arguments include:
9540 <taglist compact="compact">
9541 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9544 Do not sign the <tt>.changes</tt> file or the
9545 source package <tt>.dsc</tt> file, respectively.</p>
9547 <tag><tt>-p<var>sign-command</var></tt></tag>
9550 Invoke <var>sign-command</var> instead of finding
9551 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9552 <var>sign-command</var> must behave just like
9553 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9555 <tag><tt>-r<var>root-command</var></tt></tag>
9558 When root privilege is required, invoke the command
9559 <var>root-command</var>. <var>root-command</var>
9560 should invoke its first argument as a command, from
9561 the <prgn>PATH</prgn> if necessary, and pass its
9562 second and subsequent arguments to the command it
9563 calls. If no <var>root-command</var> is supplied
9564 then <var>dpkg-buildpackage</var> will take no
9565 special action to gain root privilege, so that for
9566 most packages it will have to be invoked as root to
9569 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9572 Two types of binary-only build and upload - see
9573 <manref name="dpkg-source" section="1">.
9580 <sect1 id="pkg-dpkg-gencontrol">
9582 <prgn>dpkg-gencontrol</prgn> - generates binary package
9587 This program is usually called from <file>debian/rules</file>
9588 (see <ref id="pkg-sourcetree">) in the top level of the source
9593 This is usually done just before the files and directories in the
9594 temporary directory tree where the package is being built have their
9595 permissions and ownerships set and the package is constructed using
9596 <prgn>dpkg-deb/</prgn>
9598 This is so that the control file which is produced has
9599 the right permissions
9604 <prgn>dpkg-gencontrol</prgn> must be called after all the
9605 files which are to go into the package have been placed in
9606 the temporary build directory, so that its calculation of
9607 the installed size of a package is correct.
9611 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9612 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9613 variable substitutions created by
9614 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9619 For a package which generates only one binary package, and
9620 which builds it in <file>debian/tmp</file> relative to the top
9621 of the source package, it is usually sufficient to call
9622 <prgn>dpkg-gencontrol</prgn>.
9626 Sources which build several binaries will typically need
9629 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9630 </example> The <tt>-P</tt> tells
9631 <prgn>dpkg-gencontrol</prgn> that the package is being
9632 built in a non-default directory, and the <tt>-p</tt>
9633 tells it which package's control file should be generated.
9637 <prgn>dpkg-gencontrol</prgn> also adds information to the
9638 list of files in <file>debian/files</file>, for the benefit of
9639 (for example) a future invocation of
9640 <prgn>dpkg-genchanges</prgn>.</p>
9643 <sect1 id="pkg-dpkg-shlibdeps">
9645 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9650 This program is usually called from <file>debian/rules</file>
9651 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9652 id="pkg-sourcetree">), in the top level of the source tree.
9656 Its arguments are executables and shared libraries
9659 They may be specified either in the locations in the
9660 source tree where they are created or in the locations
9661 in the temporary build tree where they are installed
9662 prior to binary package creation.
9664 </footnote> for which shared library dependencies should
9665 be included in the binary package's control file.
9669 If some of the found shared libraries should only
9670 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9671 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9672 by using the <tt>-d<var>dependency-field</var></tt> option
9673 before those executable(s). (Each <tt>-d</tt> option
9674 takes effect until the next <tt>-d</tt>.)
9678 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9679 output control file to be modified. Instead by default it
9680 adds to the <file>debian/substvars</file> file variable
9681 settings like <tt>shlibs:Depends</tt>. These variable
9682 settings must be referenced in dependency fields in the
9683 appropriate per-binary-package sections of the source
9688 For example, a package that generates an essential part
9689 which requires dependencies, and optional parts that
9690 which only require a recommendation, would separate those
9691 two sets of dependencies into two different fields.<footnote>
9692 At the time of writing, an example for this was the
9693 <package/xmms/ package, with Depends used for the xmms
9694 executable, Recommends for the plug-ins and Suggests for
9695 even more optional features provided by unzip.
9697 It can say in its <file>debian/rules</file>:
9699 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9700 -dRecommends <var>optionalpart anotheroptionalpart</var>
9702 and then in its main control file <file>debian/control</file>:
9705 Depends: ${shlibs:Depends}
9706 Recommends: ${shlibs:Recommends}
9712 Sources which produce several binary packages with
9713 different shared library dependency requirements can use
9714 the <tt>-p<var>varnameprefix</var></tt> option to override
9715 the default <tt>shlibs:</tt> prefix (one invocation of
9716 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9717 They can thus produce several sets of dependency
9718 variables, each of the form
9719 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9720 which can be referred to in the appropriate parts of the
9721 binary package control files.
9726 <sect1 id="pkg-dpkg-distaddfile">
9728 <prgn>dpkg-distaddfile</prgn> - adds a file to
9729 <file>debian/files</file>
9733 Some packages' uploads need to include files other than
9734 the source and binary package files.
9738 <prgn>dpkg-distaddfile</prgn> adds a file to the
9739 <file>debian/files</file> file so that it will be included in
9740 the <file>.changes</file> file when
9741 <prgn>dpkg-genchanges</prgn> is run.
9745 It is usually invoked from the <tt>binary</tt> target of
9746 <file>debian/rules</file>:
9748 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9750 The <var>filename</var> is relative to the directory where
9751 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9752 is usually the directory above the top level of the source
9753 tree. The <file>debian/rules</file> target should put the
9754 file there just before or just after calling
9755 <prgn>dpkg-distaddfile</prgn>.
9759 The <var>section</var> and <var>priority</var> are passed
9760 unchanged into the resulting <file>.changes</file> file.
9765 <sect1 id="pkg-dpkg-genchanges">
9767 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9772 This program is usually called by package-independent
9773 automatic building scripts such as
9774 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9779 It is usually called in the top level of a built source
9780 tree, and when invoked with no arguments will print out a
9781 straightforward <file>.changes</file> file based on the
9782 information in the source package's changelog and control
9783 file and the binary and source packages which should have
9789 <sect1 id="pkg-dpkg-parsechangelog">
9791 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9792 representation of a changelog
9796 This program is used internally by
9797 <prgn>dpkg-source</prgn> et al. It may also occasionally
9798 be useful in <file>debian/rules</file> and elsewhere. It
9799 parses a changelog, <file>debian/changelog</file> by default,
9800 and prints a control-file format representation of the
9801 information in it to standard output.
9805 <sect1 id="pkg-dpkg-architecture">
9807 <prgn>dpkg-architecture</prgn> - information about the build and
9812 This program can be used manually, but is also invoked by
9813 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9814 environment or make variables which specify the build and host
9815 architecture for the package building process.
9820 <sect id="pkg-sourcetree">
9821 <heading>The Debianised source tree</heading>
9824 The source archive scheme described later is intended to
9825 allow a Debianised source tree with some associated control
9826 information to be reproduced and transported easily. The
9827 Debianised source tree is a version of the original program
9828 with certain files added for the benefit of the
9829 Debianisation process, and with any other changes required
9830 made to the rest of the source code and installation
9835 The extra files created for Debian are in the subdirectory
9836 <file>debian</file> of the top level of the Debianised source
9837 tree. They are described below.
9840 <sect1 id="pkg-debianrules">
9841 <heading><file>debian/rules</file> - the main building script</heading>
9844 See <ref id="debianrules">.
9849 <sect1 id="pkg-dpkgchangelog">
9850 <heading><file>debian/changelog</file></heading>
9853 See <ref id="dpkgchangelog">.
9856 <sect2><heading>Defining alternative changelog formats
9860 It is possible to use a different format to the standard
9861 one, by providing a parser for the format you wish to
9866 In order to have <tt>dpkg-parsechangelog</tt> run your
9867 parser, you must include a line within the last 40 lines
9868 of your file matching the Perl regular expression:
9869 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9870 parentheses should be the name of the format. For
9871 example, you might say:
9873 @@@ changelog-format: joebloggs @@@
9875 Changelog format names are non-empty strings of alphanumerics.
9879 If such a line exists then <tt>dpkg-parsechangelog</tt>
9880 will look for the parser as
9881 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9883 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9884 it is an error for it not to find it, or for it not to
9885 be an executable program. The default changelog format
9886 is <tt>dpkg</tt>, and a parser for it is provided with
9887 the <tt>dpkg</tt> package.
9891 The parser will be invoked with the changelog open on
9892 standard input at the start of the file. It should read
9893 the file (it may seek if it wishes) to determine the
9894 information required and return the parsed information
9895 to standard output in the form of a series of control
9896 fields in the standard format. By default it should
9897 return information about only the most recent version in
9898 the changelog; it should accept a
9899 <tt>-v<var>version</var></tt> option to return changes
9900 information from all versions present <em>strictly
9901 after</em> <var>version</var>, and it should then be an
9902 error for <var>version</var> not to be present in the
9908 <list compact="compact">
9909 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9910 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9911 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9912 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9913 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9914 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9915 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9920 If several versions are being returned (due to the use
9921 of <tt>-v</tt>), the urgency value should be of the
9922 highest urgency code listed at the start of any of the
9923 versions requested followed by the concatenated
9924 (space-separated) comments from all the versions
9925 requested; the maintainer, version, distribution and
9926 date should always be from the most recent version.
9930 For the format of the <tt>Changes</tt> field see
9931 <ref id="f-Changes">.
9935 If the changelog format which is being parsed always or
9936 almost always leaves a blank line between individual
9937 change notes these blank lines should be stripped out,
9938 so as to make the resulting output compact.
9942 If the changelog format does not contain date or package
9943 name information this information should be omitted from
9944 the output. The parser should not attempt to synthesize
9945 it or find it from other sources.
9949 If the changelog does not have the expected format the
9950 parser should exit with a nonzero exit status, rather
9951 than trying to muddle through and possibly generating
9956 A changelog parser may not interact with the user at
9962 <sect1 id="pkg-srcsubstvars">
9963 <heading><file>debian/substvars</file> and variable substitutions</heading>
9966 See <ref id="substvars">.
9972 <heading><file>debian/files</file></heading>
9975 See <ref id="debianfiles">.
9979 <sect1><heading><file>debian/tmp</file>
9983 This is the canonical temporary location for the
9984 construction of binary packages by the <tt>binary</tt>
9985 target. The directory <file>tmp</file> serves as the root of
9986 the file system tree as it is being constructed (for
9987 example, by using the package's upstream makefiles install
9988 targets and redirecting the output there), and it also
9989 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9990 id="pkg-bincreating">.
9994 If several binary packages are generated from the same
9995 source tree it is usual to use several
9996 <file>debian/tmp<var>something</var></file> directories, for
9997 example <file>tmp-a</file> or <file>tmp-doc</file>.
10001 Whatever <file>tmp</file> directories are created and used by
10002 <tt>binary</tt> must of course be removed by the
10003 <tt>clean</tt> target.</p></sect1>
10007 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10011 As it exists on the FTP site, a Debian source package
10012 consists of three related files. You must have the right
10013 versions of all three to be able to use them.
10018 <tag>Debian source control file - <tt>.dsc</tt></tag>
10020 This file is a control file used by <prgn>dpkg-source</prgn>
10021 to extract a source package.
10022 See <ref id="debiansourcecontrolfiles">.
10026 Original source archive -
10028 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10034 This is a compressed (with <tt>gzip -9</tt>)
10035 <prgn>tar</prgn> file containing the source code from
10036 the upstream authors of the program.
10041 Debianisation diff -
10043 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10049 This is a unified context diff (<tt>diff -u</tt>)
10050 giving the changes which are required to turn the
10051 original source into the Debian source. These changes
10052 may only include editing and creating plain files.
10053 The permissions of files, the targets of symbolic
10054 links and the characteristics of special files or
10055 pipes may not be changed and no files may be removed
10060 All the directories in the diff must exist, except the
10061 <file>debian</file> subdirectory of the top of the source
10062 tree, which will be created by
10063 <prgn>dpkg-source</prgn> if necessary when unpacking.
10067 The <prgn>dpkg-source</prgn> program will
10068 automatically make the <file>debian/rules</file> file
10069 executable (see below).</p></item>
10074 If there is no original source code - for example, if the
10075 package is specially prepared for Debian or the Debian
10076 maintainer is the same as the upstream maintainer - the
10077 format is slightly different: then there is no diff, and the
10079 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10080 and preferably contains a directory named
10081 <file><var>package</var>-<var>version</var></file>.
10086 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10089 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10090 Debian source package. However, if it is not available it
10091 is possible to unpack a Debian source archive as follows:
10092 <enumlist compact="compact">
10095 Untar the tarfile, which will create a <file>.orig</file>
10099 <p>Rename the <file>.orig</file> directory to
10100 <file><var>package</var>-<var>version</var></file>.</p>
10104 Create the subdirectory <file>debian</file> at the top of
10105 the source tree.</p>
10107 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10109 <item><p>Untar the tarfile again if you want a copy of the original
10110 source code alongside the Debianised version.</p>
10115 It is not possible to generate a valid Debian source archive
10116 without using <prgn>dpkg-source</prgn>. In particular,
10117 attempting to use <prgn>diff</prgn> directly to generate the
10118 <file>.diff.gz</file> file will not work.
10122 <heading>Restrictions on objects in source packages</heading>
10125 The source package may not contain any hard links
10127 This is not currently detected when building source
10128 packages, but only when extracting
10132 Hard links may be permitted at some point in the
10133 future, but would require a fair amount of
10135 </footnote>, device special files, sockets or setuid or
10138 Setgid directories are allowed.
10143 The source packaging tools manage the changes between the
10144 original and Debianised source using <prgn>diff</prgn> and
10145 <prgn>patch</prgn>. Turning the original source tree as
10146 included in the <file>.orig.tar.gz</file> into the debianised
10147 source must not involve any changes which cannot be
10148 handled by these tools. Problematic changes which cause
10149 <prgn>dpkg-source</prgn> to halt with an error when
10150 building the source package are:
10151 <list compact="compact">
10152 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10154 <item><p>Changing the targets of symbolic links.</p>
10156 <item><p>Creating directories, other than <file>debian</file>.</p>
10158 <item><p>Changes to the contents of binary files.</p></item>
10159 </list> Changes which cause <prgn>dpkg-source</prgn> to
10160 print a warning but continue anyway are:
10161 <list compact="compact">
10164 Removing files, directories or symlinks.
10166 Renaming a file is not treated specially - it is
10167 seen as the removal of the old file (which
10168 generates a warning, but is otherwise ignored),
10169 and the creation of the new one.
10175 Changed text files which are missing the usual final
10176 newline (either in the original or the modified
10181 Changes which are not represented, but which are not detected by
10182 <prgn>dpkg-source</prgn>, are:
10183 <list compact="compact">
10184 <item><p>Changing the permissions of files (other than
10185 <file>debian/rules</file>) and directories.</p></item>
10190 The <file>debian</file> directory and <file>debian/rules</file>
10191 are handled specially by <prgn>dpkg-source</prgn> - before
10192 applying the changes it will create the <file>debian</file>
10193 directory, and afterwards it will make
10194 <file>debian/rules</file> world-executable.
10200 <appendix id="pkg-controlfields">
10201 <heading>Control files and their fields (from old Packaging Manual)</heading>
10204 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10205 data in a common format, known as control files. Binary and
10206 source packages have control data as do the <file>.changes</file>
10207 files which control the installation of uploaded files, and
10208 <prgn>dpkg</prgn>'s internal databases are in a similar
10213 <heading>Syntax of control files</heading>
10216 See <ref id="controlsyntax">.
10220 It is important to note that there are several fields which
10221 are optional as far as <prgn>dpkg</prgn> and the related
10222 tools are concerned, but which must appear in every Debian
10223 package, or whose omission may cause problems.
10228 <heading>List of fields</heading>
10231 See <ref id="controlfieldslist">.
10235 This section now contains only the fields that didn't belong
10236 to the Policy manual.
10239 <sect1 id="pkg-f-Filename">
10240 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10243 These fields in <tt>Packages</tt> files give the
10244 filename(s) of (the parts of) a package in the
10245 distribution directories, relative to the root of the
10246 Debian hierarchy. If the package has been split into
10247 several parts the parts are all listed in order, separated
10252 <sect1 id="pkg-f-Size">
10253 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10256 These fields in <file>Packages</file> files give the size (in
10257 bytes, expressed in decimal) and MD5 checksum of the
10258 file(s) which make(s) up a binary package in the
10259 distribution. If the package is split into several parts
10260 the values for the parts are listed in order, separated by
10265 <sect1 id="pkg-f-Status">
10266 <heading><tt>Status</tt></heading>
10269 This field in <prgn>dpkg</prgn>'s status file records
10270 whether the user wants a package installed, removed or
10271 left alone, whether it is broken (requiring
10272 re-installation) or not and what its current state on the
10273 system is. Each of these pieces of information is a
10278 <sect1 id="pkg-f-Config-Version">
10279 <heading><tt>Config-Version</tt></heading>
10282 If a package is not installed or not configured, this
10283 field in <prgn>dpkg</prgn>'s status file records the last
10284 version of the package which was successfully
10289 <sect1 id="pkg-f-Conffiles">
10290 <heading><tt>Conffiles</tt></heading>
10293 This field in <prgn>dpkg</prgn>'s status file contains
10294 information about the automatically-managed configuration
10295 files held by a package. This field should <em>not</em>
10296 appear anywhere in a package!
10301 <heading>Obsolete fields</heading>
10304 These are still recognized by <prgn>dpkg</prgn> but should
10305 not appear anywhere any more.
10307 <taglist compact="compact">
10309 <tag><tt>Revision</tt></tag>
10310 <tag><tt>Package-Revision</tt></tag>
10311 <tag><tt>Package_Revision</tt></tag>
10313 The Debian revision part of the package version was
10314 at one point in a separate control file field. This
10315 field went through several names.
10318 <tag><tt>Recommended</tt></tag>
10319 <item>Old name for <tt>Recommends</tt>.</item>
10321 <tag><tt>Optional</tt></tag>
10322 <item>Old name for <tt>Suggests</tt>.</item>
10324 <tag><tt>Class</tt></tag>
10325 <item>Old name for <tt>Priority</tt>.</item>
10334 <appendix id="pkg-conffiles">
10335 <heading>Configuration file handling (from old Packaging Manual)</heading>
10338 <prgn>dpkg</prgn> can do a certain amount of automatic
10339 handling of package configuration files.
10343 Whether this mechanism is appropriate depends on a number of
10344 factors, but basically there are two approaches to any
10345 particular configuration file.
10349 The easy method is to ship a best-effort configuration in the
10350 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10351 handle updates. If the user is unlikely to want to edit the
10352 file, but you need them to be able to without losing their
10353 changes, and a new package with a changed version of the file
10354 is only released infrequently, this is a good approach.
10358 The hard method is to build the configuration file from
10359 scratch in the <prgn>postinst</prgn> script, and to take the
10360 responsibility for fixing any mistakes made in earlier
10361 versions of the package automatically. This will be
10362 appropriate if the file is likely to need to be different on
10366 <sect><heading>Automatic handling of configuration files by
10371 A package may contain a control area file called
10372 <tt>conffiles</tt>. This file should be a list of filenames
10373 of configuration files needing automatic handling, separated
10374 by newlines. The filenames should be absolute pathnames,
10375 and the files referred to should actually exist in the
10380 When a package is upgraded <prgn>dpkg</prgn> will process
10381 the configuration files during the configuration stage,
10382 shortly before it runs the package's <prgn>postinst</prgn>
10387 For each file it checks to see whether the version of the
10388 file included in the package is the same as the one that was
10389 included in the last version of the package (the one that is
10390 being upgraded from); it also compares the version currently
10391 installed on the system with the one shipped with the last
10396 If neither the user nor the package maintainer has changed
10397 the file, it is left alone. If one or the other has changed
10398 their version, then the changed version is preferred - i.e.,
10399 if the user edits their file, but the package maintainer
10400 doesn't ship a different version, the user's changes will
10401 stay, silently, but if the maintainer ships a new version
10402 and the user hasn't edited it the new version will be
10403 installed (with an informative message). If both have
10404 changed their version the user is prompted about the problem
10405 and must resolve the differences themselves.
10409 The comparisons are done by calculating the MD5 message
10410 digests of the files, and storing the MD5 of the file as it
10411 was included in the most recent version of the package.
10415 When a package is installed for the first time
10416 <prgn>dpkg</prgn> will install the file that comes with it,
10417 unless that would mean overwriting a file already on the
10422 However, note that <prgn>dpkg</prgn> will <em>not</em>
10423 replace a conffile that was removed by the user (or by a
10424 script). This is necessary because with some programs a
10425 missing file produces an effect hard or impossible to
10426 achieve in another way, so that a missing file needs to be
10427 kept that way if the user did it.
10431 Note that a package should <em>not</em> modify a
10432 <prgn>dpkg</prgn>-handled conffile in its maintainer
10433 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10434 the user confusing and possibly dangerous options for
10435 conffile update when the package is upgraded.</p>
10438 <sect><heading>Fully-featured maintainer script configuration
10443 For files which contain site-specific information such as
10444 the hostname and networking details and so forth, it is
10445 better to create the file in the package's
10446 <prgn>postinst</prgn> script.
10450 This will typically involve examining the state of the rest
10451 of the system to determine values and other information, and
10452 may involve prompting the user for some information which
10453 can't be obtained some other way.
10457 When using this method there are a couple of important
10458 issues which should be considered:
10462 If you discover a bug in the program which generates the
10463 configuration file, or if the format of the file changes
10464 from one version to the next, you will have to arrange for
10465 the postinst script to do something sensible - usually this
10466 will mean editing the installed configuration file to remove
10467 the problem or change the syntax. You will have to do this
10468 very carefully, since the user may have changed the file,
10469 perhaps to fix the very problem that your script is trying
10470 to deal with - you will have to detect these situations and
10471 deal with them correctly.
10475 If you do go down this route it's probably a good idea to
10476 make the program that generates the configuration file(s) a
10477 separate program in <file>/usr/sbin</file>, by convention called
10478 <file><var>package</var>config</file> and then run that if
10479 appropriate from the post-installation script. The
10480 <tt><var>package</var>config</tt> program should not
10481 unquestioningly overwrite an existing configuration - if its
10482 mode of operation is geared towards setting up a package for
10483 the first time (rather than any arbitrary reconfiguration
10484 later) you should have it check whether the configuration
10485 already exists, and require a <tt>--force</tt> flag to
10486 overwrite it.</p></sect>
10489 <appendix id="pkg-alternatives"><heading>Alternative versions of
10490 an interface - <prgn>update-alternatives</prgn> (from old
10495 When several packages all provide different versions of the
10496 same program or file it is useful to have the system select a
10497 default, but to allow the system administrator to change it
10498 and have their decisions respected.
10502 For example, there are several versions of the <prgn>vi</prgn>
10503 editor, and there is no reason to prevent all of them from
10504 being installed at once, each under their own name
10505 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10506 Nevertheless it is desirable to have the name <tt>vi</tt>
10507 refer to something, at least by default.
10511 If all the packages involved cooperate, this can be done with
10512 <prgn>update-alternatives</prgn>.
10516 Each package provides its own version under its own name, and
10517 calls <prgn>update-alternatives</prgn> in its postinst to
10518 register its version (and again in its prerm to deregister
10523 See the man page <manref name="update-alternatives"
10524 section="8"> for details.
10528 If <prgn>update-alternatives</prgn> does not seem appropriate
10529 you may wish to consider using diversions instead.</p>
10532 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10533 package's version of a file (from old Packaging Manual)
10537 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10538 when it reinstalls the package it belongs to, and to have it
10539 put the file from the package somewhere else instead.
10543 This can be used locally to override a package's version of a
10544 file, or by one package to override another's version (or
10545 provide a wrapper for it).
10549 Before deciding to use a diversion, read <ref
10550 id="pkg-alternatives"> to see if you really want a diversion
10551 rather than several alternative versions of a program.
10555 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10556 and updated by a special program <prgn>dpkg-divert</prgn>.
10557 Please see <manref name="dpkg-divert" section="8"> for full
10558 details of its operation.
10562 When a package wishes to divert a file from another, it should
10563 call <prgn>dpkg-divert</prgn> in its preinst to add the
10564 diversion and rename the existing file. For example,
10565 supposing that a <prgn>smailwrapper</prgn> package wishes to
10566 install a wrapper around <file>/usr/sbin/smail</file>:
10568 if [ install = "$1" ]; then
10569 dpkg-divert --package smailwrapper --add --rename \
10570 --divert /usr/sbin/smail.real /usr/sbin/smail
10572 </example> Testing <tt>$1</tt> is necessary so that the script
10573 doesn't try to add the diversion again when
10574 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10575 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10576 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10577 get installed as the true version.
10581 The postrm has to do the reverse:
10583 if [ remove = "$1" ]; then
10584 dpkg-divert --package smailwrapper --remove --rename \
10585 --divert /usr/sbin/smail.real /usr/sbin/smail
10591 Do not attempt to divert a file which is vitally important for
10592 the system's operation - when using <prgn>dpkg-divert</prgn>
10593 there is a time, after it has been diverted but before
10594 <prgn>dpkg</prgn> has installed the new version, when the file
10595 does not exist.</p>
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