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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 The presence of this tag means that the package should
2035 be compiled with a minimum of optimization. For C
2036 programs, it is best to add <tt>-O0</tt> to
2037 <tt>CFLAGS</tt> (although this is usually the default).
2038 Some programs might fail to build or run at this level
2039 of optimization; it may be necessary to use
2040 <tt>-O1</tt>, for example.
2044 This tag means that the debugging symbols should not be
2045 stripped from the binary during installation, so that
2046 debugging information may be included in the package.
2048 <tag>parallel=n</tag>
2050 This tag means that the package should be built using up
2051 to <tt>n</tt> parallel processes if the package build
2052 system supports this.<footnote>
2053 Packages built with <tt>make</tt> can often implement
2054 this by passing the <tt>-j</tt><var>n</var> option to
2057 If the package build system does not support parallel
2058 builds, this string must be ignored. If the package
2059 build system only supports a lower level of concurrency
2060 than <var>n</var>, the package should be built using as
2061 many parallel processes as the package build system
2062 supports. It is up to the package maintainer to decide
2063 whether the package build times are long enough and the
2064 package build system is robust enough to make supporting
2065 parallel builds worthwhile.
2071 Unknown flags must be ignored by <file>debian/rules</file>.
2075 The following makefile snippet is an example of how one may
2076 implement the build options; you will probably have to
2077 massage this example in order to make it work for your
2079 <example compact="compact">
2082 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2083 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2084 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2085 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2087 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2092 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2093 INSTALL_PROGRAM += -s
2095 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2096 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2097 MAKEFLAGS += -j$(NUMJOBS)
2104 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2105 <sect id="substvars">
2106 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2109 When <prgn>dpkg-gencontrol</prgn>,
2110 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2111 generate control files they perform variable substitutions
2112 on their output just before writing it. Variable
2113 substitutions have the form <tt>${<var>variable</var>}</tt>.
2114 The optional file <file>debian/substvars</file> contains
2115 variable substitutions to be used; variables can also be set
2116 directly from <file>debian/rules</file> using the <tt>-V</tt>
2117 option to the source packaging commands, and certain
2118 predefined variables are also available.
2122 The <file>debian/substvars</file> file is usually generated and
2123 modified dynamically by <file>debian/rules</file> targets, in
2124 which case it must be removed by the <tt>clean</tt> target.
2128 See <manref name="deb-substvars" section="5"> for full
2129 details about source variable substitutions, including the
2130 format of <file>debian/substvars</file>.</p>
2133 <sect id="debianwatch">
2134 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2137 This is an optional, recommended control file for the
2138 <tt>uscan</tt> utility which defines how to automatically
2139 scan ftp or http sites for newly available updates of the
2140 package. This is used by <url id="
2141 http://dehs.alioth.debian.org/"> and other Debian QA tools
2142 to help with quality control and maintenance of the
2143 distribution as a whole.
2148 <sect id="debianfiles">
2149 <heading>Generated files list: <file>debian/files</file></heading>
2152 This file is not a permanent part of the source tree; it
2153 is used while building packages to record which files are
2154 being generated. <prgn>dpkg-genchanges</prgn> uses it
2155 when it generates a <file>.changes</file> file.
2159 It should not exist in a shipped source package, and so it
2160 (and any backup files or temporary files such as
2161 <file>files.new</file><footnote>
2162 <file>files.new</file> is used as a temporary file by
2163 <prgn>dpkg-gencontrol</prgn> and
2164 <prgn>dpkg-distaddfile</prgn> - they write a new
2165 version of <tt>files</tt> here before renaming it,
2166 to avoid leaving a corrupted copy if an error
2168 </footnote>) should be removed by the
2169 <tt>clean</tt> target. It may also be wise to
2170 ensure a fresh start by emptying or removing it at the
2171 start of the <tt>binary</tt> target.
2175 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2176 package, it adds an entry to <file>debian/files</file> for the
2177 <file>.deb</file> file that will be created when <tt>dpkg-deb
2178 --build</tt> is run for that binary package. So for most
2179 packages all that needs to be done with this file is to
2180 delete it in the <tt>clean</tt> target.
2184 If a package upload includes files besides the source
2185 package and any binary packages whose control files were
2186 made with <prgn>dpkg-gencontrol</prgn> then they should be
2187 placed in the parent of the package's top-level directory
2188 and <prgn>dpkg-distaddfile</prgn> should be called to add
2189 the file to the list in <file>debian/files</file>.</p>
2192 <sect id="embeddedfiles">
2193 <heading>Convenience copies of code</heading>
2196 Some software packages include in their distribution convenience
2197 copies of code from other software packages, generally so that
2198 users compiling from source don't have to download multiple
2199 packages. Debian packages should not make use of these
2200 convenience copies unless the included package is explicitly
2201 intended to be used in this way.<footnote>
2202 For example, parts of the GNU build system work like this.
2204 If the included code is already in the Debian archive in the
2205 form of a library, the Debian packaging should ensure that
2206 binary packages reference the libraries already in Debian and
2207 the convenience copy is not used. If the included code is not
2208 already in Debian, it should be packaged separately as a
2209 prerequisite if possible.
2211 Having multiple copies of the same code in Debian is
2212 inefficient, often creates either static linking or shared
2213 library conflicts, and, most importantly, increases the
2214 difficulty of handling security vulnerabilities in the
2220 <sect id="readmesource">
2221 <heading>Source package handling:
2222 <file>debian/README.source</file></heading>
2225 If running <prgn>dpkg-source -x</prgn> on a source package
2226 doesn't produce the source of the package, ready for editing,
2227 and allow one to make changes and run
2228 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2229 without taking any additional steps, creating a
2230 <file>debian/README.source</file> documentation file is
2231 recommended. This file should explain how to do all of the
2234 <item>Generate the fully patched source, in a form ready for
2235 editing, that would be built to create Debian
2236 packages. Doing this with a <tt>patch</tt> target in
2237 <file>debian/rules</file> is recommended; see
2238 <ref id="debianrules">.</item>
2239 <item>Modify the source and save those modifications so that
2240 they will be applied when building the package.</item>
2241 <item>Remove source modifications that are currently being
2242 applied when building the package.</item>
2243 <item>Optionally, document what steps are necessary to
2244 upgrade the Debian source package to a new upstream version,
2245 if applicable.</item>
2247 This explanation should include specific commands and mention
2248 any additional required Debian packages. It should not assume
2249 familiarity with any specific Debian packaging system or patch
2254 This explanation may refer to a documentation file installed by
2255 one of the package's build dependencies provided that the
2256 referenced documentation clearly explains these tasks and is not
2257 a general reference manual.
2261 <file>debian/README.source</file> may also include any other
2262 information that would be helpful to someone modifying the
2263 source package. Even if the package doesn't fit the above
2264 description, maintainers are encouraged to document in a
2265 <file>debian/README.source</file> file any source package with a
2266 particularly complex or unintuitive source layout or build
2267 system (for example, a package that builds the same source
2268 multiple times to generate different binary packages).
2274 <chapt id="controlfields">
2275 <heading>Control files and their fields</heading>
2278 The package management system manipulates data represented in
2279 a common format, known as <em>control data</em>, stored in
2280 <em>control files</em>.
2281 Control files are used for source packages, binary packages and
2282 the <file>.changes</file> files which control the installation
2283 of uploaded files<footnote>
2284 <prgn>dpkg</prgn>'s internal databases are in a similar
2289 <sect id="controlsyntax">
2290 <heading>Syntax of control files</heading>
2293 A control file consists of one or more paragraphs of
2295 The paragraphs are also sometimes referred to as stanzas.
2297 The paragraphs are separated by blank lines. Some control
2298 files allow only one paragraph; others allow several, in
2299 which case each paragraph usually refers to a different
2300 package. (For example, in source packages, the first
2301 paragraph refers to the source package, and later paragraphs
2302 refer to binary packages generated from the source.)
2306 Each paragraph consists of a series of data fields; each
2307 field consists of the field name, followed by a colon and
2308 then the data/value associated with that field. It ends at
2309 the end of the (logical) line. Horizontal whitespace
2310 (spaces and tabs) may occur immediately before or after the
2311 value and is ignored there; it is conventional to put a
2312 single space after the colon. For example, a field might
2314 <example compact="compact">
2317 the field name is <tt>Package</tt> and the field value
2322 Many fields' values may span several lines; in this case
2323 each continuation line must start with a space or a tab.
2324 Any trailing spaces or tabs at the end of individual
2325 lines of a field value are ignored.
2329 In fields where it is specified that lines may not wrap,
2330 only a single line of data is allowed and whitespace is not
2331 significant in a field body. Whitespace must not appear
2332 inside names (of packages, architectures, files or anything
2333 else) or version numbers, or between the characters of
2334 multi-character version relationships.
2338 Field names are not case-sensitive, but it is usual to
2339 capitalize the field names using mixed case as shown below.
2343 Blank lines, or lines consisting only of spaces and tabs,
2344 are not allowed within field values or between fields - that
2345 would mean a new paragraph.
2349 All control files must be encoded in UTF-8.
2353 <sect id="sourcecontrolfiles">
2354 <heading>Source package control files -- <file>debian/control</file></heading>
2357 The <file>debian/control</file> file contains the most vital
2358 (and version-independent) information about the source package
2359 and about the binary packages it creates.
2363 The first paragraph of the control file contains information about
2364 the source package in general. The subsequent sets each describe a
2365 binary package that the source tree builds.
2369 The fields in the general paragraph (the first one, for the source
2372 <list compact="compact">
2373 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2374 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2375 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2376 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2377 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2378 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2379 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2380 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2385 The fields in the binary package paragraphs are:
2387 <list compact="compact">
2388 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2389 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2390 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2391 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2392 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2393 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2394 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2395 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2400 The syntax and semantics of the fields are described below.
2406 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2407 generate control files for binary packages (see below), by
2408 <prgn>dpkg-genchanges</prgn> to generate the
2409 <tt>.changes</tt> file to accompany the upload, and by
2410 <prgn>dpkg-source</prgn> when it creates the
2411 <file>.dsc</file> source control file as part of a source
2412 archive. Many fields are permitted to span multiple lines in
2413 <file>debian/control</file> but not in any other control
2414 file. These tools are responsible for removing the line
2415 breaks from such fields when using fields from
2416 <file>debian/control</file> to generate other control files.
2420 The fields here may contain variable references - their
2421 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2422 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2423 when they generate output control files.
2424 See <ref id="substvars"> for details.
2429 <sect id="binarycontrolfiles">
2430 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2433 The <file>DEBIAN/control</file> file contains the most vital
2434 (and version-dependent) information about a binary package.
2438 The fields in this file are:
2440 <list compact="compact">
2441 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2442 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2443 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2444 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2445 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2446 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2447 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2448 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2449 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2450 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2451 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2452 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2457 <sect id="debiansourcecontrolfiles">
2458 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2461 This file contains a series of fields, identified and
2462 separated just like the fields in the control file of
2463 a binary package. The fields are listed below; their
2464 syntax is described above, in <ref id="pkg-controlfields">.
2466 <list compact="compact">
2467 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2468 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2469 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2470 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2471 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2472 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2473 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2474 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2475 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2476 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2477 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2482 The source package control file is generated by
2483 <prgn>dpkg-source</prgn> when it builds the source
2484 archive, from other files in the source package,
2485 described above. When unpacking, it is checked against
2486 the files and directories in the other parts of the
2492 <sect id="debianchangesfiles">
2493 <heading>Debian changes files -- <file>.changes</file></heading>
2496 The .changes files are used by the Debian archive maintenance
2497 software to process updates to packages. They contain one
2498 paragraph which contains information from the
2499 <tt>debian/control</tt> file and other data about the
2500 source package gathered via <tt>debian/changelog</tt>
2501 and <tt>debian/rules</tt>.
2505 The fields in this file are:
2507 <list compact="compact">
2508 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2509 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2510 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2511 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2512 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2513 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2514 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2515 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2516 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2518 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2519 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2520 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2521 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2526 <sect id="controlfieldslist">
2527 <heading>List of fields</heading>
2529 <sect1 id="f-Source">
2530 <heading><tt>Source</tt></heading>
2533 This field identifies the source package name.
2537 In <file>debian/control</file> or a <file>.dsc</file> file,
2538 this field must contain only the name of the source package.
2542 In a binary package control file or a <file>.changes</file>
2543 file, the source package name may be followed by a version
2544 number in parentheses<footnote>
2545 It is customary to leave a space after the package name
2546 if a version number is specified.
2548 This version number may be omitted (and is, by
2549 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2550 the <tt>Version</tt> field of the binary package in
2551 question. The field itself may be omitted from a binary
2552 package control file when the source package has the same
2553 name and version as the binary package.
2557 <sect1 id="f-Maintainer">
2558 <heading><tt>Maintainer</tt></heading>
2561 The package maintainer's name and email address. The name
2562 should come first, then the email address inside angle
2563 brackets <tt><></tt> (in RFC822 format).
2567 If the maintainer's name contains a full stop then the
2568 whole field will not work directly as an email address due
2569 to a misfeature in the syntax specified in RFC822; a
2570 program using this field as an address must check for this
2571 and correct the problem if necessary (for example by
2572 putting the name in round brackets and moving it to the
2573 end, and bringing the email address forward).
2577 <sect1 id="f-Uploaders">
2578 <heading><tt>Uploaders</tt></heading>
2581 List of the names and email addresses of co-maintainers of
2582 the package, if any. If the package has other maintainers
2583 beside the one named in the
2584 <qref id="f-Maintainer">Maintainer field</qref>, their
2585 names and email addresses should be listed here. The
2586 format is the same as that of the Maintainer tag, and
2587 multiple entries should be comma separated. Currently,
2588 this field is restricted to a single line of data. This
2589 is an optional field.
2592 Any parser that interprets the Uploaders field in
2593 <file>debian/control</file> must permit it to span multiple
2594 lines. Line breaks in an Uploaders field that spans multiple
2595 lines are not significant and the semantics of the field are
2596 the same as if the line breaks had not been present.
2600 <sect1 id="f-Changed-By">
2601 <heading><tt>Changed-By</tt></heading>
2604 The name and email address of the person who changed the
2605 said package. Usually the name of the maintainer.
2606 All the rules for the Maintainer field apply here, too.
2610 <sect1 id="f-Section">
2611 <heading><tt>Section</tt></heading>
2614 This field specifies an application area into which the package
2615 has been classified. See <ref id="subsections">.
2619 When it appears in the <file>debian/control</file> file,
2620 it gives the value for the subfield of the same name in
2621 the <tt>Files</tt> field of the <file>.changes</file> file.
2622 It also gives the default for the same field in the binary
2627 <sect1 id="f-Priority">
2628 <heading><tt>Priority</tt></heading>
2631 This field represents how important that it is that the user
2632 have the package installed. See <ref id="priorities">.
2636 When it appears in the <file>debian/control</file> file,
2637 it gives the value for the subfield of the same name in
2638 the <tt>Files</tt> field of the <file>.changes</file> file.
2639 It also gives the default for the same field in the binary
2644 <sect1 id="f-Package">
2645 <heading><tt>Package</tt></heading>
2648 The name of the binary package.
2652 Package names must consist only of lower case letters
2653 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2654 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2655 They must be at least two characters long and must start
2656 with an alphanumeric character.
2660 <sect1 id="f-Architecture">
2661 <heading><tt>Architecture</tt></heading>
2664 Depending on context and the control file used, the
2665 <tt>Architecture</tt> field can include the following sets of
2668 <item>A unique single word identifying a Debian machine
2669 architecture, see <ref id="arch-spec">.
2670 <item><tt>all</tt>, which indicates an
2671 architecture-independent package.
2672 <item><tt>any</tt>, which indicates a package available
2673 for building on any architecture.
2674 <item><tt>source</tt>, which indicates a source package.
2679 In the main <file>debian/control</file> file in the source
2680 package, or in the source package control file
2681 <file>.dsc</file>, one may specify a list of architectures
2682 separated by spaces, or the special values <tt>any</tt> or
2687 Specifying <tt>any</tt> indicates that the source package
2688 isn't dependent on any particular architecture and should
2689 compile fine on any one. The produced binary package(s)
2690 will be specific to whatever the current build architecture
2692 This is the most often used setting, and is recommended
2693 for new packages that aren't <tt>Architecture: all</tt>.
2698 Specifying a list of architectures indicates that the source
2699 will build an architecture-dependent package, and will only
2700 work correctly on the listed architectures.<footnote>
2701 This is a setting used for a minority of cases where the
2702 program is not portable. Generally, it should not be used
2708 In a <file>.changes</file> file, the <tt>Architecture</tt>
2709 field lists the architecture(s) of the package(s)
2710 currently being uploaded. This will be a list; if the
2711 source for the package is also being uploaded, the special
2712 entry <tt>source</tt> is also present.
2716 See <ref id="debianrules"> for information how to get the
2717 architecture for the build process.
2721 <sect1 id="f-Essential">
2722 <heading><tt>Essential</tt></heading>
2725 This is a boolean field which may occur only in the
2726 control file of a binary package or in a per-package fields
2727 paragraph of a main source control data file.
2731 If set to <tt>yes</tt> then the package management system
2732 will refuse to remove the package (upgrading and replacing
2733 it is still possible). The other possible value is <tt>no</tt>,
2734 which is the same as not having the field at all.
2739 <heading>Package interrelationship fields:
2740 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2741 <tt>Recommends</tt>, <tt>Suggests</tt>,
2742 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2743 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2747 These fields describe the package's relationships with
2748 other packages. Their syntax and semantics are described
2749 in <ref id="relationships">.</p>
2752 <sect1 id="f-Standards-Version">
2753 <heading><tt>Standards-Version</tt></heading>
2756 The most recent version of the standards (the policy
2757 manual and associated texts) with which the package
2762 The version number has four components: major and minor
2763 version number and major and minor patch level. When the
2764 standards change in a way that requires every package to
2765 change the major number will be changed. Significant
2766 changes that will require work in many packages will be
2767 signaled by a change to the minor number. The major patch
2768 level will be changed for any change to the meaning of the
2769 standards, however small; the minor patch level will be
2770 changed when only cosmetic, typographical or other edits
2771 are made which neither change the meaning of the document
2772 nor affect the contents of packages.
2776 Thus only the first three components of the policy version
2777 are significant in the <em>Standards-Version</em> control
2778 field, and so either these three components or the all
2779 four components may be specified.<footnote>
2780 In the past, people specified the full version number
2781 in the Standards-Version field, for example "2.3.0.0".
2782 Since minor patch-level changes don't introduce new
2783 policy, it was thought it would be better to relax
2784 policy and only require the first 3 components to be
2785 specified, in this example "2.3.0". All four
2786 components may still be used if someone wishes to do so.
2792 <sect1 id="f-Version">
2793 <heading><tt>Version</tt></heading>
2796 The version number of a package. The format is:
2797 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2801 The three components here are:
2803 <tag><var>epoch</var></tag>
2806 This is a single (generally small) unsigned integer. It
2807 may be omitted, in which case zero is assumed. If it is
2808 omitted then the <var>upstream_version</var> may not
2813 It is provided to allow mistakes in the version numbers
2814 of older versions of a package, and also a package's
2815 previous version numbering schemes, to be left behind.
2819 <tag><var>upstream_version</var></tag>
2822 This is the main part of the version number. It is
2823 usually the version number of the original ("upstream")
2824 package from which the <file>.deb</file> file has been made,
2825 if this is applicable. Usually this will be in the same
2826 format as that specified by the upstream author(s);
2827 however, it may need to be reformatted to fit into the
2828 package management system's format and comparison
2833 The comparison behavior of the package management system
2834 with respect to the <var>upstream_version</var> is
2835 described below. The <var>upstream_version</var>
2836 portion of the version number is mandatory.
2840 The <var>upstream_version</var> may contain only
2841 alphanumerics<footnote>
2842 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2844 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2845 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2846 tilde) and should start with a digit. If there is no
2847 <var>debian_revision</var> then hyphens are not allowed;
2848 if there is no <var>epoch</var> then colons are not
2853 <tag><var>debian_revision</var></tag>
2856 This part of the version number specifies the version of
2857 the Debian package based on the upstream version. It
2858 may contain only alphanumerics and the characters
2859 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2860 tilde) and is compared in the same way as the
2861 <var>upstream_version</var> is.
2865 It is optional; if it isn't present then the
2866 <var>upstream_version</var> may not contain a hyphen.
2867 This format represents the case where a piece of
2868 software was written specifically to be turned into a
2869 Debian package, and so there is only one "debianisation"
2870 of it and therefore no revision indication is required.
2874 It is conventional to restart the
2875 <var>debian_revision</var> at <tt>1</tt> each time the
2876 <var>upstream_version</var> is increased.
2880 The package management system will break the version
2881 number apart at the last hyphen in the string (if there
2882 is one) to determine the <var>upstream_version</var> and
2883 <var>debian_revision</var>. The absence of a
2884 <var>debian_revision</var> is equivalent to a
2885 <var>debian_revision</var> of <tt>0</tt>.
2892 When comparing two version numbers, first the <var>epoch</var>
2893 of each are compared, then the <var>upstream_version</var> if
2894 <var>epoch</var> is equal, and then <var>debian_revision</var>
2895 if <var>upstream_version</var> is also equal.
2896 <var>epoch</var> is compared numerically. The
2897 <var>upstream_version</var> and <var>debian_revision</var>
2898 parts are compared by the package management system using the
2899 following algorithm:
2903 The strings are compared from left to right.
2907 First the initial part of each string consisting entirely of
2908 non-digit characters is determined. These two parts (one of
2909 which may be empty) are compared lexically. If a difference
2910 is found it is returned. The lexical comparison is a
2911 comparison of ASCII values modified so that all the letters
2912 sort earlier than all the non-letters and so that a tilde
2913 sorts before anything, even the end of a part. For example,
2914 the following parts are in sorted order from earliest to
2915 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2916 <tt>a</tt>.<footnote>
2917 One common use of <tt>~</tt> is for upstream pre-releases.
2918 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2919 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2924 Then the initial part of the remainder of each string which
2925 consists entirely of digit characters is determined. The
2926 numerical values of these two parts are compared, and any
2927 difference found is returned as the result of the comparison.
2928 For these purposes an empty string (which can only occur at
2929 the end of one or both version strings being compared) counts
2934 These two steps (comparing and removing initial non-digit
2935 strings and initial digit strings) are repeated until a
2936 difference is found or both strings are exhausted.
2940 Note that the purpose of epochs is to allow us to leave behind
2941 mistakes in version numbering, and to cope with situations
2942 where the version numbering scheme changes. It is
2943 <em>not</em> intended to cope with version numbers containing
2944 strings of letters which the package management system cannot
2945 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2946 silly orderings (the author of this manual has heard of a
2947 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2948 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2949 <tt>2</tt> and so forth).
2953 <sect1 id="f-Description">
2954 <heading><tt>Description</tt></heading>
2957 In a source or binary control file, the <tt>Description</tt>
2958 field contains a description of the binary package, consisting
2959 of two parts, the synopsis or the short description, and the
2960 long description. The field's format is as follows:
2965 Description: <single line synopsis>
2966 <extended description over several lines>
2971 The lines in the extended description can have these formats:
2977 Those starting with a single space are part of a paragraph.
2978 Successive lines of this form will be word-wrapped when
2979 displayed. The leading space will usually be stripped off.
2983 Those starting with two or more spaces. These will be
2984 displayed verbatim. If the display cannot be panned
2985 horizontally, the displaying program will line wrap them "hard"
2986 (i.e., without taking account of word breaks). If it can they
2987 will be allowed to trail off to the right. None, one or two
2988 initial spaces may be deleted, but the number of spaces
2989 deleted from each line will be the same (so that you can have
2990 indenting work correctly, for example).
2994 Those containing a single space followed by a single full stop
2995 character. These are rendered as blank lines. This is the
2996 <em>only</em> way to get a blank line<footnote>
2997 Completely empty lines will not be rendered as blank lines.
2998 Instead, they will cause the parser to think you're starting
2999 a whole new record in the control file, and will therefore
3000 likely abort with an error.
3005 Those containing a space, a full stop and some more characters.
3006 These are for future expansion. Do not use them.
3012 Do not use tab characters. Their effect is not predictable.
3016 See <ref id="descriptions"> for further information on this.
3020 In a <file>.changes</file> file, the <tt>Description</tt> field
3021 contains a summary of the descriptions for the packages being
3026 The part of the field before the first newline is empty;
3027 thereafter each line has the name of a binary package and
3028 the summary description line from that binary package.
3029 Each line is indented by one space.
3034 <sect1 id="f-Distribution">
3035 <heading><tt>Distribution</tt></heading>
3038 In a <file>.changes</file> file or parsed changelog output
3039 this contains the (space-separated) name(s) of the
3040 distribution(s) where this version of the package should
3041 be installed. Valid distributions are determined by the
3042 archive maintainers.<footnote>
3043 Current distribution names are:
3044 <taglist compact="compact">
3045 <tag><em>stable</em></tag>
3047 This is the current "released" version of Debian
3048 GNU/Linux. Once the distribution is
3049 <em>stable</em> only security fixes and other
3050 major bug fixes are allowed. When changes are
3051 made to this distribution, the release number is
3052 increased (for example: 2.2r1 becomes 2.2r2 then
3056 <tag><em>unstable</em></tag>
3058 This distribution value refers to the
3059 <em>developmental</em> part of the Debian
3060 distribution tree. New packages, new upstream
3061 versions of packages and bug fixes go into the
3062 <em>unstable</em> directory tree. Download from
3063 this distribution at your own risk.
3066 <tag><em>testing</em></tag>
3068 This distribution value refers to the
3069 <em>testing</em> part of the Debian distribution
3070 tree. It receives its packages from the
3071 unstable distribution after a short time lag to
3072 ensure that there are no major issues with the
3073 unstable packages. It is less prone to breakage
3074 than unstable, but still risky. It is not
3075 possible to upload packages directly to
3079 <tag><em>frozen</em></tag>
3081 From time to time, the <em>testing</em>
3082 distribution enters a state of "code-freeze" in
3083 anticipation of release as a <em>stable</em>
3084 version. During this period of testing only
3085 fixes for existing or newly-discovered bugs will
3086 be allowed. The exact details of this stage are
3087 determined by the Release Manager.
3090 <tag><em>experimental</em></tag>
3092 The packages with this distribution value are
3093 deemed by their maintainers to be high
3094 risk. Oftentimes they represent early beta or
3095 developmental packages from various sources that
3096 the maintainers want people to try, but are not
3097 ready to be a part of the other parts of the
3098 Debian distribution tree. Download at your own
3104 You should list <em>all</em> distributions that the
3105 package should be installed into.
3109 More information is available in the Debian Developer's
3110 Reference, section "The Debian archive".
3117 <heading><tt>Date</tt></heading>
3120 This field includes the date the package was built or last edited.
3124 The value of this field is usually extracted from the
3125 <file>debian/changelog</file> file - see
3126 <ref id="dpkgchangelog">).
3130 <sect1 id="f-Format">
3131 <heading><tt>Format</tt></heading>
3134 This field specifies a format revision for the file.
3135 The most current format described in the Policy Manual
3136 is version <strong>1.5</strong>. The syntax of the
3137 format value is the same as that of a package version
3138 number except that no epoch or Debian revision is allowed
3139 - see <ref id="f-Version">.
3143 <sect1 id="f-Urgency">
3144 <heading><tt>Urgency</tt></heading>
3147 This is a description of how important it is to upgrade to
3148 this version from previous ones. It consists of a single
3149 keyword taking one of the values <tt>low</tt>,
3150 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3151 <tt>critical</tt><footnote>
3152 Other urgency values are supported with configuration
3153 changes in the archive software but are not used in Debian.
3154 The urgency affects how quickly a package will be considered
3155 for inclusion into the <tt>testing</tt> distribution and
3156 gives an indication of the importance of any fixes included
3157 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3158 treated as synonymous.
3159 </footnote> (not case-sensitive) followed by an optional
3160 commentary (separated by a space) which is usually in
3161 parentheses. For example:
3164 Urgency: low (HIGH for users of diversions)
3170 The value of this field is usually extracted from the
3171 <file>debian/changelog</file> file - see
3172 <ref id="dpkgchangelog">.
3176 <sect1 id="f-Changes">
3177 <heading><tt>Changes</tt></heading>
3180 This field contains the human-readable changes data, describing
3181 the differences between the last version and the current one.
3185 There should be nothing in this field before the first
3186 newline; all the subsequent lines must be indented by at
3187 least one space; blank lines must be represented by a line
3188 consisting only of a space and a full stop.
3192 The value of this field is usually extracted from the
3193 <file>debian/changelog</file> file - see
3194 <ref id="dpkgchangelog">).
3198 Each version's change information should be preceded by a
3199 "title" line giving at least the version, distribution(s)
3200 and urgency, in a human-readable way.
3204 If data from several versions is being returned the entry
3205 for the most recent version should be returned first, and
3206 entries should be separated by the representation of a
3207 blank line (the "title" line may also be followed by the
3208 representation of blank line).
3212 <sect1 id="f-Binary">
3213 <heading><tt>Binary</tt></heading>
3216 This field is a list of binary packages.
3220 When it appears in the <file>.dsc</file> file it is the list
3221 of binary packages which a source package can produce. It
3222 does not necessarily produce all of these binary packages
3223 for every architecture. The source control file doesn't
3224 contain details of which architectures are appropriate for
3225 which of the binary packages.
3229 When it appears in a <file>.changes</file> file it lists the
3230 names of the binary packages actually being uploaded.
3234 The syntax is a list of binary packages separated by
3236 A space after each comma is conventional.
3237 </footnote>. Currently the packages must be separated using
3238 only spaces in the <file>.changes</file> file.
3242 <sect1 id="f-Installed-Size">
3243 <heading><tt>Installed-Size</tt></heading>
3246 This field appears in the control files of binary
3247 packages, and in the <file>Packages</file> files. It gives
3248 the total amount of disk space required to install the
3253 The disk space is represented in kilobytes as a simple
3258 <sect1 id="f-Files">
3259 <heading><tt>Files</tt></heading>
3262 This field contains a list of files with information about
3263 each one. The exact information and syntax varies with
3264 the context. In all cases the part of the field
3265 contents on the same line as the field name is empty. The
3266 remainder of the field is one line per file, each line
3267 being indented by one space and containing a number of
3268 sub-fields separated by spaces.
3272 In the <file>.dsc</file> file, each line contains the MD5
3273 checksum, size and filename of the tar file and (if applicable)
3274 diff file which make up the remainder of the source
3276 That is, the parts which are not the <tt>.dsc</tt>.
3278 The exact forms of the filenames are described
3279 in <ref id="pkg-sourcearchives">.
3283 In the <file>.changes</file> file this contains one line per
3284 file being uploaded. Each line contains the MD5 checksum,
3285 size, section and priority and the filename.
3286 The <qref id="f-Section">section</qref>
3287 and <qref id="f-Priority">priority</qref>
3288 are the values of the corresponding fields in
3289 the main source control file. If no section or priority is
3290 specified then <tt>-</tt> should be used, though section
3291 and priority values must be specified for new packages to
3292 be installed properly.
3296 The special value <tt>byhand</tt> for the section in a
3297 <tt>.changes</tt> file indicates that the file in question
3298 is not an ordinary package file and must by installed by
3299 hand by the distribution maintainers. If the section is
3300 <tt>byhand</tt> the priority should be <tt>-</tt>.
3304 If a new Debian revision of a package is being shipped and
3305 no new original source archive is being distributed the
3306 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3307 entry for the original source archive
3308 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3309 but the <file>.changes</file> file should leave it out. In
3310 this case the original source archive on the distribution
3311 site must match exactly, byte-for-byte, the original
3312 source archive which was used to generate the
3313 <file>.dsc</file> file and diff which are being uploaded.</p>
3316 <sect1 id="f-Closes">
3317 <heading><tt>Closes</tt></heading>
3320 A space-separated list of bug report numbers that the upload
3321 governed by the .changes file closes.
3325 <sect1 id="f-Homepage">
3326 <heading><tt>Homepage</tt></heading>
3329 The URL of the web site for this package, preferably (when
3330 applicable) the site from which the original source can be
3331 obtained and any additional upstream documentation or
3332 information may be found. The content of this field is a
3333 simple URL without any surrounding characters such as
3341 <heading>User-defined fields</heading>
3344 Additional user-defined fields may be added to the
3345 source package control file. Such fields will be
3346 ignored, and not copied to (for example) binary or
3347 source package control files or upload control files.
3351 If you wish to add additional unsupported fields to
3352 these output files you should use the mechanism
3357 Fields in the main source control information file with
3358 names starting <tt>X</tt>, followed by one or more of
3359 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3360 be copied to the output files. Only the part of the
3361 field name after the hyphen will be used in the output
3362 file. Where the letter <tt>B</tt> is used the field
3363 will appear in binary package control files, where the
3364 letter <tt>S</tt> is used in source package control
3365 files and where <tt>C</tt> is used in upload control
3366 (<tt>.changes</tt>) files.
3370 For example, if the main source information control file
3373 XBS-Comment: I stand between the candle and the star.
3375 then the binary and source package control files will contain the
3378 Comment: I stand between the candle and the star.
3387 <chapt id="maintainerscripts">
3388 <heading>Package maintainer scripts and installation procedure</heading>
3391 <heading>Introduction to package maintainer scripts</heading>
3394 It is possible to supply scripts as part of a package which
3395 the package management system will run for you when your
3396 package is installed, upgraded or removed.
3400 These scripts are the files <prgn>preinst</prgn>,
3401 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3402 <prgn>postrm</prgn> in the control area of the package.
3403 They must be proper executable files; if they are scripts
3404 (which is recommended), they must start with the usual
3405 <tt>#!</tt> convention. They should be readable and
3406 executable by anyone, and must not be world-writable.
3410 The package management system looks at the exit status from
3411 these scripts. It is important that they exit with a
3412 non-zero status if there is an error, so that the package
3413 management system can stop its processing. For shell
3414 scripts this means that you <em>almost always</em> need to
3415 use <tt>set -e</tt> (this is usually true when writing shell
3416 scripts, in fact). It is also important, of course, that
3417 they don't exit with a non-zero status if everything went
3422 Additionally, packages interacting with users using
3423 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3424 install a <prgn>config</prgn> script in the control area,
3425 see <ref id="maintscriptprompt"> for details.
3429 When a package is upgraded a combination of the scripts from
3430 the old and new packages is called during the upgrade
3431 procedure. If your scripts are going to be at all
3432 complicated you need to be aware of this, and may need to
3433 check the arguments to your scripts.
3437 Broadly speaking the <prgn>preinst</prgn> is called before
3438 (a particular version of) a package is installed, and the
3439 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3440 before (a version of) a package is removed and the
3441 <prgn>postrm</prgn> afterwards.
3445 Programs called from maintainer scripts should not normally
3446 have a path prepended to them. Before installation is
3447 started, the package management system checks to see if the
3448 programs <prgn>ldconfig</prgn>,
3449 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3450 and <prgn>update-rc.d</prgn> can be found via the
3451 <tt>PATH</tt> environment variable. Those programs, and any
3452 other program that one would expect to be in the
3453 <tt>PATH</tt>, should thus be invoked without an absolute
3454 pathname. Maintainer scripts should also not reset the
3455 <tt>PATH</tt>, though they might choose to modify it by
3456 prepending or appending package-specific directories. These
3457 considerations really apply to all shell scripts.</p>
3460 <sect id="idempotency">
3461 <heading>Maintainer scripts idempotency</heading>
3464 It is necessary for the error recovery procedures that the
3465 scripts be idempotent. This means that if it is run
3466 successfully, and then it is called again, it doesn't bomb
3467 out or cause any harm, but just ensures that everything is
3468 the way it ought to be. If the first call failed, or
3469 aborted half way through for some reason, the second call
3470 should merely do the things that were left undone the first
3471 time, if any, and exit with a success status if everything
3473 This is so that if an error occurs, the user interrupts
3474 <prgn>dpkg</prgn> or some other unforeseen circumstance
3475 happens you don't leave the user with a badly-broken
3476 package when <prgn>dpkg</prgn> attempts to repeat the
3482 <sect id="controllingterminal">
3483 <heading>Controlling terminal for maintainer scripts</heading>
3486 The maintainer scripts are guaranteed to run with a
3487 controlling terminal and can interact with the user.
3488 Because these scripts may be executed with standard output
3489 redirected into a pipe for logging purposes, Perl scripts
3490 should set unbuffered output by setting <tt>$|=1</tt> so
3491 that the output is printed immediately rather than being
3495 <sect id="exitstatus">
3496 <heading>Exit status</heading>
3499 Each script must return a zero exit status for
3500 success, or a nonzero one for failure, since the package
3501 management system looks for the exit status of these scripts
3502 and determines what action to take next based on that datum.
3506 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3511 <list compact="compact">
3513 <var>new-preinst</var> <tt>install</tt>
3516 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3519 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3522 <var>old-preinst</var> <tt>abort-upgrade</tt>
3523 <var>new-version</var>
3528 <list compact="compact">
3530 <var>postinst</var> <tt>configure</tt>
3531 <var>most-recently-configured-version</var>
3534 <var>old-postinst</var> <tt>abort-upgrade</tt>
3535 <var>new-version</var>
3538 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3539 <tt>in-favour</tt> <var>package</var>
3540 <var>new-version</var>
3543 <var>postinst</var> <tt>abort-remove</tt>
3546 <var>deconfigured's-postinst</var>
3547 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3548 <var>failed-install-package</var> <var>version</var>
3549 [<tt>removing</tt> <var>conflicting-package</var>
3555 <list compact="compact">
3557 <var>prerm</var> <tt>remove</tt>
3560 <var>old-prerm</var> <tt>upgrade</tt>
3561 <var>new-version</var>
3564 <var>new-prerm</var> <tt>failed-upgrade</tt>
3565 <var>old-version</var>
3568 <var>conflictor's-prerm</var> <tt>remove</tt>
3569 <tt>in-favour</tt> <var>package</var>
3570 <var>new-version</var>
3573 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3574 <tt>in-favour</tt> <var>package-being-installed</var>
3575 <var>version</var> [<tt>removing</tt>
3576 <var>conflicting-package</var>
3582 <list compact="compact">
3584 <var>postrm</var> <tt>remove</tt>
3587 <var>postrm</var> <tt>purge</tt>
3590 <var>old-postrm</var> <tt>upgrade</tt>
3591 <var>new-version</var>
3594 <var>new-postrm</var> <tt>failed-upgrade</tt>
3595 <var>old-version</var>
3598 <var>new-postrm</var> <tt>abort-install</tt>
3601 <var>new-postrm</var> <tt>abort-install</tt>
3602 <var>old-version</var>
3605 <var>new-postrm</var> <tt>abort-upgrade</tt>
3606 <var>old-version</var>
3609 <var>disappearer's-postrm</var> <tt>disappear</tt>
3610 <var>overwriter</var>
3611 <var>overwriter-version</var>
3617 <sect id="unpackphase">
3618 <heading>Details of unpack phase of installation or upgrade</heading>
3621 The procedure on installation/upgrade/overwrite/disappear
3622 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3623 stage of <tt>dpkg --install</tt>) is as follows. In each
3624 case, if a major error occurs (unless listed below) the
3625 actions are, in general, run backwards - this means that the
3626 maintainer scripts are run with different arguments in
3627 reverse order. These are the "error unwind" calls listed
3634 If a version of the package is already installed, call
3635 <example compact="compact">
3636 <var>old-prerm</var> upgrade <var>new-version</var>
3640 If the script runs but exits with a non-zero
3641 exit status, <prgn>dpkg</prgn> will attempt:
3642 <example compact="compact">
3643 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3645 If this works, the upgrade continues. If this
3646 does not work, the error unwind:
3647 <example compact="compact">
3648 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3650 If this works, then the old-version is
3651 "Installed", if not, the old version is in a
3652 "Failed-Config" state.
3658 If a "conflicting" package is being removed at the same time,
3659 or if any package will be broken (due to <tt>Breaks</tt>):
3662 If <tt>--auto-deconfigure</tt> is
3663 specified, call, for each package to be deconfigured
3664 due to <tt>Breaks</tt>:
3665 <example compact="compact">
3666 <var>deconfigured's-prerm</var> deconfigure \
3667 in-favour <var>package-being-installed</var> <var>version</var>
3670 <example compact="compact">
3671 <var>deconfigured's-postinst</var> abort-deconfigure \
3672 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3674 The deconfigured packages are marked as
3675 requiring configuration, so that if
3676 <tt>--install</tt> is used they will be
3677 configured again if possible.
3680 If any packages depended on a conflicting
3681 package being removed and <tt>--auto-deconfigure</tt> is
3682 specified, call, for each such package:
3683 <example compact="compact">
3684 <var>deconfigured's-prerm</var> deconfigure \
3685 in-favour <var>package-being-installed</var> <var>version</var> \
3686 removing <var>conflicting-package</var> <var>version</var>
3689 <example compact="compact">
3690 <var>deconfigured's-postinst</var> abort-deconfigure \
3691 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3692 removing <var>conflicting-package</var> <var>version</var>
3694 The deconfigured packages are marked as
3695 requiring configuration, so that if
3696 <tt>--install</tt> is used they will be
3697 configured again if possible.
3700 To prepare for removal of each conflicting package, call:
3701 <example compact="compact">
3702 <var>conflictor's-prerm</var> remove \
3703 in-favour <var>package</var> <var>new-version</var>
3706 <example compact="compact">
3707 <var>conflictor's-postinst</var> abort-remove \
3708 in-favour <var>package</var> <var>new-version</var>
3717 If the package is being upgraded, call:
3718 <example compact="compact">
3719 <var>new-preinst</var> upgrade <var>old-version</var>
3721 If this fails, we call:
3723 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3730 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3732 is called. If this works, then the old version
3733 is in an "Installed" state, or else it is left
3734 in an "Unpacked" state.
3739 If it fails, then the old version is left
3740 in an "Half-Installed" state.
3747 Otherwise, if the package had some configuration
3748 files from a previous version installed (i.e., it
3749 is in the "configuration files only" state):
3750 <example compact="compact">
3751 <var>new-preinst</var> install <var>old-version</var>
3755 <var>new-postrm</var> abort-install <var>old-version</var>
3757 If this fails, the package is left in a
3758 "Half-Installed" state, which requires a
3759 reinstall. If it works, the packages is left in
3760 a "Config Files" state.
3763 Otherwise (i.e., the package was completely purged):
3764 <example compact="compact">
3765 <var>new-preinst</var> install
3768 <example compact="compact">
3769 <var>new-postrm</var> abort-install
3771 If the error-unwind fails, the package is in a
3772 "Half Installed" phase, and requires a
3773 reinstall. If the error unwind works, the
3774 package is in a not installed state.
3781 The new package's files are unpacked, overwriting any
3782 that may be on the system already, for example any
3783 from the old version of the same package or from
3784 another package. Backups of the old files are kept
3785 temporarily, and if anything goes wrong the package
3786 management system will attempt to put them back as
3787 part of the error unwind.
3791 It is an error for a package to contain files which
3792 are on the system in another package, unless
3793 <tt>Replaces</tt> is used (see <ref id="replaces">).
3795 The following paragraph is not currently the case:
3796 Currently the <tt>- - force-overwrite</tt> flag is
3797 enabled, downgrading it to a warning, but this may not
3803 It is a more serious error for a package to contain a
3804 plain file or other kind of non-directory where another
3805 package has a directory (again, unless
3806 <tt>Replaces</tt> is used). This error can be
3807 overridden if desired using
3808 <tt>--force-overwrite-dir</tt>, but this is not
3813 Packages which overwrite each other's files produce
3814 behavior which, though deterministic, is hard for the
3815 system administrator to understand. It can easily
3816 lead to "missing" programs if, for example, a package
3817 is installed which overwrites a file from another
3818 package, and is then removed again.<footnote>
3819 Part of the problem is due to what is arguably a
3820 bug in <prgn>dpkg</prgn>.
3825 A directory will never be replaced by a symbolic link
3826 to a directory or vice versa; instead, the existing
3827 state (symlink or not) will be left alone and
3828 <prgn>dpkg</prgn> will follow the symlink if there is
3837 If the package is being upgraded, call
3838 <example compact="compact">
3839 <var>old-postrm</var> upgrade <var>new-version</var>
3843 If this fails, <prgn>dpkg</prgn> will attempt:
3844 <example compact="compact">
3845 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3847 If this works, installation continues. If not,
3849 <example compact="compact">
3850 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3852 If this fails, the old version is left in an
3853 "Half Installed" state. If it works, dpkg now
3855 <example compact="compact">
3856 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3858 If this fails, the old version is left in an
3859 "Half Installed" state. If it works, dpkg now
3861 <example compact="compact">
3862 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3864 If this fails, the old version is in an
3871 This is the point of no return - if
3872 <prgn>dpkg</prgn> gets this far, it won't back off
3873 past this point if an error occurs. This will
3874 leave the package in a fairly bad state, which
3875 will require a successful re-installation to clear
3876 up, but it's when <prgn>dpkg</prgn> starts doing
3877 things that are irreversible.
3882 Any files which were in the old version of the package
3883 but not in the new are removed.
3887 The new file list replaces the old.
3891 The new maintainer scripts replace the old.
3895 Any packages all of whose files have been overwritten
3896 during the installation, and which aren't required for
3897 dependencies, are considered to have been removed.
3898 For each such package
3901 <prgn>dpkg</prgn> calls:
3902 <example compact="compact">
3903 <var>disappearer's-postrm</var> disappear \
3904 <var>overwriter</var> <var>overwriter-version</var>
3908 The package's maintainer scripts are removed.
3911 It is noted in the status database as being in a
3912 sane state, namely not installed (any conffiles
3913 it may have are ignored, rather than being
3914 removed by <prgn>dpkg</prgn>). Note that
3915 disappearing packages do not have their prerm
3916 called, because <prgn>dpkg</prgn> doesn't know
3917 in advance that the package is going to
3924 Any files in the package we're unpacking that are also
3925 listed in the file lists of other packages are removed
3926 from those lists. (This will lobotomize the file list
3927 of the "conflicting" package if there is one.)
3931 The backup files made during installation, above, are
3937 The new package's status is now sane, and recorded as
3942 Here is another point of no return - if the
3943 conflicting package's removal fails we do not unwind
3944 the rest of the installation; the conflicting package
3945 is left in a half-removed limbo.
3950 If there was a conflicting package we go and do the
3951 removal actions (described below), starting with the
3952 removal of the conflicting package's files (any that
3953 are also in the package being installed have already
3954 been removed from the conflicting package's file list,
3955 and so do not get removed now).
3961 <sect id="configdetails"><heading>Details of configuration</heading>
3964 When we configure a package (this happens with <tt>dpkg
3965 --install</tt> and <tt>dpkg --configure</tt>), we first
3966 update any <tt>conffile</tt>s and then call:
3967 <example compact="compact">
3968 <var>postinst</var> configure <var>most-recently-configured-version</var>
3973 No attempt is made to unwind after errors during
3974 configuration. If the configuration fails, the package is in
3975 a "Failed Config" state, and an error message is generated.
3979 If there is no most recently configured version
3980 <prgn>dpkg</prgn> will pass a null argument.
3983 Historical note: Truly ancient (pre-1997) versions of
3984 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3985 (including the angle brackets) in this case. Even older
3986 ones did not pass a second argument at all, under any
3987 circumstance. Note that upgrades using such an old dpkg
3988 version are unlikely to work for other reasons, even if
3989 this old argument behavior is handled by your postinst script.
3995 <sect id="removedetails"><heading>Details of removal and/or
3996 configuration purging</heading>
4002 <example compact="compact">
4003 <var>prerm</var> remove
4007 If prerm fails during replacement due to conflict
4009 <var>conflictor's-postinst</var> abort-remove \
4010 in-favour <var>package</var> <var>new-version</var>
4014 <var>postinst</var> abort-remove
4018 If this fails, the package is in a "Failed-Config"
4019 state, or else it remains "Installed".
4023 The package's files are removed (except <tt>conffile</tt>s).
4026 <example compact="compact">
4027 <var>postrm</var> remove
4031 If it fails, there's no error unwind, and the package is in
4032 an "Half-Installed" state.
4037 All the maintainer scripts except the <prgn>postrm</prgn>
4042 If we aren't purging the package we stop here. Note
4043 that packages which have no <prgn>postrm</prgn> and no
4044 <tt>conffile</tt>s are automatically purged when
4045 removed, as there is no difference except for the
4046 <prgn>dpkg</prgn> status.
4050 The <tt>conffile</tt>s and any backup files
4051 (<tt>~</tt>-files, <tt>#*#</tt> files,
4052 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4057 <example compact="compact">
4058 <var>postrm</var> purge
4062 If this fails, the package remains in a "Config-Files"
4067 The package's file list is removed.
4076 <chapt id="relationships">
4077 <heading>Declaring relationships between packages</heading>
4079 <sect id="depsyntax">
4080 <heading>Syntax of relationship fields</heading>
4083 These fields all have a uniform syntax. They are a list of
4084 package names separated by commas.
4088 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4089 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4090 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4091 control file fields of the package, which declare
4092 dependencies on other packages, the package names listed may
4093 also include lists of alternative package names, separated
4094 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4095 if any one of the alternative packages is installed, that
4096 part of the dependency is considered to be satisfied.
4100 All of the fields except for <tt>Provides</tt> may restrict
4101 their applicability to particular versions of each named
4102 package. This is done in parentheses after each individual
4103 package name; the parentheses should contain a relation from
4104 the list below followed by a version number, in the format
4105 described in <ref id="f-Version">.
4109 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4110 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4111 strictly earlier, earlier or equal, exactly equal, later or
4112 equal and strictly later, respectively. The deprecated
4113 forms <tt><</tt> and <tt>></tt> were used to mean
4114 earlier/later or equal, rather than strictly earlier/later,
4115 so they should not appear in new packages (though
4116 <prgn>dpkg</prgn> still supports them).
4120 Whitespace may appear at any point in the version
4121 specification subject to the rules in <ref
4122 id="controlsyntax">, and must appear where it's necessary to
4123 disambiguate; it is not otherwise significant. All of the
4124 relationship fields may span multiple lines. For
4125 consistency and in case of future changes to
4126 <prgn>dpkg</prgn> it is recommended that a single space be
4127 used after a version relationship and before a version
4128 number; it is also conventional to put a single space after
4129 each comma, on either side of each vertical bar, and before
4130 each open parenthesis. When wrapping a relationship field, it
4131 is conventional to do so after a comma and before the space
4132 following that comma.
4136 For example, a list of dependencies might appear as:
4137 <example compact="compact">
4140 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4145 All fields that specify build-time relationships
4146 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4147 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4148 may be restricted to a certain set of architectures. This
4149 is indicated in brackets after each individual package name and
4150 the optional version specification. The brackets enclose a
4151 list of Debian architecture names separated by whitespace.
4152 Exclamation marks may be prepended to each of the names.
4153 (It is not permitted for some names to be prepended with
4154 exclamation marks while others aren't.) If the current Debian
4155 host architecture is not in this list and there are no
4156 exclamation marks in the list, or it is in the list with a
4157 prepended exclamation mark, the package name and the
4158 associated version specification are ignored completely for
4159 the purposes of defining the relationships.
4164 <example compact="compact">
4166 Build-Depends-Indep: texinfo
4167 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4168 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4173 Note that the binary package relationship fields such as
4174 <tt>Depends</tt> appear in one of the binary package
4175 sections of the control file, whereas the build-time
4176 relationships such as <tt>Build-Depends</tt> appear in the
4177 source package section of the control file (which is the
4182 <sect id="binarydeps">
4183 <heading>Binary Dependencies - <tt>Depends</tt>,
4184 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4185 <tt>Pre-Depends</tt>
4189 Packages can declare in their control file that they have
4190 certain relationships to other packages - for example, that
4191 they may not be installed at the same time as certain other
4192 packages, and/or that they depend on the presence of others.
4196 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4197 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4198 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4202 These seven fields are used to declare a dependency
4203 relationship by one package on another. Except for
4204 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4205 depending (binary) package's control file.
4206 (<tt>Enhances</tt> appears in the recommending package's
4207 control file, and <tt>Breaks</tt> appears in the version of
4208 depended-on package which causes the named package to
4213 A <tt>Depends</tt> field takes effect <em>only</em> when a
4214 package is to be configured. It does not prevent a package
4215 being on the system in an unconfigured state while its
4216 dependencies are unsatisfied, and it is possible to replace
4217 a package whose dependencies are satisfied and which is
4218 properly installed with a different version whose
4219 dependencies are not and cannot be satisfied; when this is
4220 done the depending package will be left unconfigured (since
4221 attempts to configure it will give errors) and will not
4222 function properly. If it is necessary, a
4223 <tt>Pre-Depends</tt> field can be used, which has a partial
4224 effect even when a package is being unpacked, as explained
4225 in detail below. (The other three dependency fields,
4226 <tt>Recommends</tt>, <tt>Suggests</tt> and
4227 <tt>Enhances</tt>, are only used by the various front-ends
4228 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4229 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4233 For this reason packages in an installation run are usually
4234 all unpacked first and all configured later; this gives
4235 later versions of packages with dependencies on later
4236 versions of other packages the opportunity to have their
4237 dependencies satisfied.
4241 In case of circular dependencies, since installation or
4242 removal order honoring the dependency order can't be
4243 established, dependency loops are broken at some point
4244 (based on rules below), and some packages may not be able to
4245 rely on their dependencies being present when being
4246 installed or removed, depending on which side of the break
4247 of the circular dependency loop they happen to be on. If one
4248 of the packages in the loop has no postinst script, then the
4249 cycle will be broken at that package, so as to ensure that
4250 all postinst scripts run with the dependencies properly
4251 configured if this is possible. Otherwise the breaking point
4256 The <tt>Depends</tt> field thus allows package maintainers
4257 to impose an order in which packages should be configured.
4261 The meaning of the five dependency fields is as follows:
4263 <tag><tt>Depends</tt></tag>
4266 This declares an absolute dependency. A package will
4267 not be configured unless all of the packages listed in
4268 its <tt>Depends</tt> field have been correctly
4273 The <tt>Depends</tt> field should be used if the
4274 depended-on package is required for the depending
4275 package to provide a significant amount of
4280 The <tt>Depends</tt> field should also be used if the
4281 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4282 <prgn>postrm</prgn> scripts require the package to be
4283 present in order to run. Note, however, that the
4284 <prgn>postrm</prgn> cannot rely on any non-essential
4285 packages to be present during the <tt>purge</tt>
4289 <tag><tt>Recommends</tt></tag>
4292 This declares a strong, but not absolute, dependency.
4296 The <tt>Recommends</tt> field should list packages
4297 that would be found together with this one in all but
4298 unusual installations.
4302 <tag><tt>Suggests</tt></tag>
4304 This is used to declare that one package may be more
4305 useful with one or more others. Using this field
4306 tells the packaging system and the user that the
4307 listed packages are related to this one and can
4308 perhaps enhance its usefulness, but that installing
4309 this one without them is perfectly reasonable.
4312 <tag><tt>Enhances</tt></tag>
4314 This field is similar to Suggests but works in the
4315 opposite direction. It is used to declare that a
4316 package can enhance the functionality of another
4320 <tag><tt>Pre-Depends</tt></tag>
4323 This field is like <tt>Depends</tt>, except that it
4324 also forces <prgn>dpkg</prgn> to complete installation
4325 of the packages named before even starting the
4326 installation of the package which declares the
4327 pre-dependency, as follows:
4331 When a package declaring a pre-dependency is about to
4332 be <em>unpacked</em> the pre-dependency can be
4333 satisfied if the depended-on package is either fully
4334 configured, <em>or even if</em> the depended-on
4335 package(s) are only unpacked or half-configured,
4336 provided that they have been configured correctly at
4337 some point in the past (and not removed or partially
4338 removed since). In this case, both the
4339 previously-configured and currently unpacked or
4340 half-configured versions must satisfy any version
4341 clause in the <tt>Pre-Depends</tt> field.
4345 When the package declaring a pre-dependency is about
4346 to be <em>configured</em>, the pre-dependency will be
4347 treated as a normal <tt>Depends</tt>, that is, it will
4348 be considered satisfied only if the depended-on
4349 package has been correctly configured.
4353 <tt>Pre-Depends</tt> should be used sparingly,
4354 preferably only by packages whose premature upgrade or
4355 installation would hamper the ability of the system to
4356 continue with any upgrade that might be in progress.
4360 <tt>Pre-Depends</tt> are also required if the
4361 <prgn>preinst</prgn> script depends on the named
4362 package. It is best to avoid this situation if
4370 When selecting which level of dependency to use you should
4371 consider how important the depended-on package is to the
4372 functionality of the one declaring the dependency. Some
4373 packages are composed of components of varying degrees of
4374 importance. Such a package should list using
4375 <tt>Depends</tt> the package(s) which are required by the
4376 more important components. The other components'
4377 requirements may be mentioned as Suggestions or
4378 Recommendations, as appropriate to the components' relative
4384 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4387 Using <tt>Breaks</tt> may cause problems for upgrades from older
4388 versions of Debian and should not be used until the stable
4389 release of Debian supports <tt>Breaks</tt>.
4393 When one binary package declares that it breaks another,
4394 <prgn>dpkg</prgn> will refuse to allow the package which
4395 declares <tt>Breaks</tt> be installed unless the broken
4396 package is deconfigured first, and it will refuse to
4397 allow the broken package to be reconfigured.
4401 A package will not be regarded as causing breakage merely
4402 because its configuration files are still installed; it must
4403 be at least half-installed.
4407 A special exception is made for packages which declare that
4408 they break their own package name or a virtual package which
4409 they provide (see below): this does not count as a real
4414 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4415 version clause; such a <tt>Breaks</tt> is introduced in the
4416 version of an (implicit or explicit) dependency which
4417 violates an assumption or reveals a bug in earlier versions
4418 of the broken package. This use of <tt>Breaks</tt> will
4419 inform higher-level package management tools that broken
4420 package must be upgraded before the new one.
4424 If the breaking package also overwrites some files from the
4425 older package, it should use <tt>Replaces</tt> (not
4426 <tt>Conflicts</tt>) to ensure this goes smoothly.
4430 <sect id="conflicts">
4431 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4434 When one binary package declares a conflict with another
4435 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4436 refuse to allow them to be installed on the system at the
4441 If one package is to be installed, the other must be removed
4442 first - if the package being installed is marked as
4443 replacing (see <ref id="replaces">) the one on the system,
4444 or the one on the system is marked as deselected, or both
4445 packages are marked <tt>Essential</tt>, then
4446 <prgn>dpkg</prgn> will automatically remove the package
4447 which is causing the conflict, otherwise it will halt the
4448 installation of the new package with an error. This
4449 mechanism is specifically designed to produce an error when
4450 the installed package is <tt>Essential</tt>, but the new
4455 A package will not cause a conflict merely because its
4456 configuration files are still installed; it must be at least
4461 A special exception is made for packages which declare a
4462 conflict with their own package name, or with a virtual
4463 package which they provide (see below): this does not
4464 prevent their installation, and allows a package to conflict
4465 with others providing a replacement for it. You use this
4466 feature when you want the package in question to be the only
4467 package providing some feature.
4471 A <tt>Conflicts</tt> entry should almost never have an
4472 "earlier than" version clause. This would prevent
4473 <prgn>dpkg</prgn> from upgrading or installing the package
4474 which declared such a conflict until the upgrade or removal
4475 of the conflicted-with package had been completed. Instead,
4476 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4477 by the stable release of Debian).
4481 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4485 As well as the names of actual ("concrete") packages, the
4486 package relationship fields <tt>Depends</tt>,
4487 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4488 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4489 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4490 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4491 may mention "virtual packages".
4495 A <em>virtual package</em> is one which appears in the
4496 <tt>Provides</tt> control file field of another package.
4497 The effect is as if the package(s) which provide a
4498 particular virtual package name had been listed by name
4499 everywhere the virtual package name appears. (See also <ref
4504 If there are both concrete and virtual packages of the same
4505 name, then the dependency may be satisfied (or the conflict
4506 caused) by either the concrete package with the name in
4507 question or any other concrete package which provides the
4508 virtual package with the name in question. This is so that,
4509 for example, supposing we have
4510 <example compact="compact">
4513 </example> and someone else releases an enhanced version of
4514 the <tt>bar</tt> package they can say:
4515 <example compact="compact">
4519 and the <tt>bar-plus</tt> package will now also satisfy the
4520 dependency for the <tt>foo</tt> package.
4524 If a relationship field has a version number attached
4525 then only real packages will be considered to see whether
4526 the relationship is satisfied (or the prohibition violated,
4527 for a conflict or breakage) - it is assumed that a real
4528 package which provides the virtual package is not of the
4529 "right" version. So, a <tt>Provides</tt> field may not
4530 contain version numbers, and the version number of the
4531 concrete package which provides a particular virtual package
4532 will not be looked at when considering a dependency on or
4533 conflict with the virtual package name.
4537 It is likely that the ability will be added in a future
4538 release of <prgn>dpkg</prgn> to specify a version number for
4539 each virtual package it provides. This feature is not yet
4540 present, however, and is expected to be used only
4545 If you want to specify which of a set of real packages
4546 should be the default to satisfy a particular dependency on
4547 a virtual package, you should list the real package as an
4548 alternative before the virtual one.
4553 <sect id="replaces"><heading>Overwriting files and replacing
4554 packages - <tt>Replaces</tt></heading>
4557 Packages can declare in their control file that they should
4558 overwrite files in certain other packages, or completely
4559 replace other packages. The <tt>Replaces</tt> control file
4560 field has these two distinct purposes.
4563 <sect1><heading>Overwriting files in other packages</heading>
4566 Firstly, as mentioned before, it is usually an error for a
4567 package to contain files which are on the system in
4572 However, if the overwriting package declares that it
4573 <tt>Replaces</tt> the one containing the file being
4574 overwritten, then <prgn>dpkg</prgn> will replace the file
4575 from the old package with that from the new. The file
4576 will no longer be listed as "owned" by the old package.
4580 If a package is completely replaced in this way, so that
4581 <prgn>dpkg</prgn> does not know of any files it still
4582 contains, it is considered to have "disappeared". It will
4583 be marked as not wanted on the system (selected for
4584 removal) and not installed. Any <tt>conffile</tt>s
4585 details noted for the package will be ignored, as they
4586 will have been taken over by the overwriting package. The
4587 package's <prgn>postrm</prgn> script will be run with a
4588 special argument to allow the package to do any final
4589 cleanup required. See <ref id="mscriptsinstact">.
4592 Replaces is a one way relationship -- you have to
4593 install the replacing package after the replaced
4600 For this usage of <tt>Replaces</tt>, virtual packages (see
4601 <ref id="virtual">) are not considered when looking at a
4602 <tt>Replaces</tt> field - the packages declared as being
4603 replaced must be mentioned by their real names.
4607 Furthermore, this usage of <tt>Replaces</tt> only takes
4608 effect when both packages are at least partially on the
4609 system at once, so that it can only happen if they do not
4610 conflict or if the conflict has been overridden.
4615 <sect1><heading>Replacing whole packages, forcing their
4619 Secondly, <tt>Replaces</tt> allows the packaging system to
4620 resolve which package should be removed when there is a
4621 conflict - see <ref id="conflicts">. This usage only
4622 takes effect when the two packages <em>do</em> conflict,
4623 so that the two usages of this field do not interfere with
4628 In this situation, the package declared as being replaced
4629 can be a virtual package, so for example, all mail
4630 transport agents (MTAs) would have the following fields in
4631 their control files:
4632 <example compact="compact">
4633 Provides: mail-transport-agent
4634 Conflicts: mail-transport-agent
4635 Replaces: mail-transport-agent
4637 ensuring that only one MTA can be installed at any one
4642 <sect id="sourcebinarydeps">
4643 <heading>Relationships between source and binary packages -
4644 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4645 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4649 Source packages that require certain binary packages to be
4650 installed or absent at the time of building the package
4651 can declare relationships to those binary packages.
4655 This is done using the <tt>Build-Depends</tt>,
4656 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4657 <tt>Build-Conflicts-Indep</tt> control file fields.
4661 Build-dependencies on "build-essential" binary packages can be
4662 omitted. Please see <ref id="pkg-relations"> for more information.
4666 The dependencies and conflicts they define must be satisfied
4667 (as defined earlier for binary packages) in order to invoke
4668 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4670 If you make "build-arch" or "binary-arch", you need
4671 Build-Depends. If you make "build-indep" or
4672 "binary-indep", you need Build-Depends and
4673 Build-Depends-Indep. If you make "build" or "binary",
4677 There is no Build-Depends-Arch; this role is essentially
4678 met with Build-Depends. Anyone building the
4679 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4680 is basically assumed to be building the whole package
4681 anyway and so installs all build dependencies. The
4682 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4683 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4684 does not yet know how to check for its existence) and
4685 <tt>binary-arch</tt>.
4688 The purpose of the original split, I recall, was so that
4689 the autobuilders wouldn't need to install extra packages
4690 needed only for the binary-indep targets. But without a
4691 build-arch/build-indep split, this didn't work, since
4692 most of the work is done in the build target, not in the
4698 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4700 The <tt>Build-Depends</tt> and
4701 <tt>Build-Conflicts</tt> fields must be satisfied when
4702 any of the following targets is invoked:
4703 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4704 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4705 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4707 <tag><tt>Build-Depends-Indep</tt>,
4708 <tt>Build-Conflicts-Indep</tt></tag>
4710 The <tt>Build-Depends-Indep</tt> and
4711 <tt>Build-Conflicts-Indep</tt> fields must be
4712 satisfied when any of the following targets is
4713 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4714 <tt>binary</tt> and <tt>binary-indep</tt>.
4724 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4727 Packages containing shared libraries must be constructed with
4728 a little care to make sure that the shared library is always
4729 available. This is especially important for packages whose
4730 shared libraries are vitally important, such as the C library
4731 (currently <tt>libc6</tt>).
4735 Packages involving shared libraries should be split up into
4736 several binary packages. This section mostly deals with how
4737 this separation is to be accomplished; rules for files within
4738 the shared library packages are in <ref id="libraries"> instead.
4741 <sect id="sharedlibs-runtime">
4742 <heading>Run-time shared libraries</heading>
4745 The run-time shared library needs to be placed in a package
4746 whose name changes whenever the shared object version
4749 Since it is common place to install several versions of a
4750 package that just provides shared libraries, it is a
4751 good idea that the library package should not
4752 contain any extraneous non-versioned files, unless they
4753 happen to be in versioned directories.</p>
4755 The most common mechanism is to place it in a package
4757 <package><var>libraryname</var><var>soversion</var></package>,
4758 where <file><var>soversion</var></file> is the version number
4759 in the soname of the shared library<footnote>
4760 The soname is the shared object name: it's the thing
4761 that has to match exactly between building an executable
4762 and running it for the dynamic linker to be able run the
4763 program. For example, if the soname of the library is
4764 <file>libfoo.so.6</file>, the library package would be
4765 called <file>libfoo6</file>.
4767 Alternatively, if it would be confusing to directly append
4768 <var>soversion</var> to <var>libraryname</var> (e.g. because
4769 <var>libraryname</var> itself ends in a number), you may use
4770 <package><var>libraryname</var>-<var>soversion</var></package> and
4771 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4776 If you have several shared libraries built from the same
4777 source tree you may lump them all together into a single
4778 shared library package, provided that you change all of
4779 their sonames at once (so that you don't get filename
4780 clashes if you try to install different versions of the
4781 combined shared libraries package).
4785 The package should install the shared libraries under
4786 their normal names. For example, the <package>libgdbm3</package>
4787 package should install <file>libgdbm.so.3.0.0</file> as
4788 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4789 renamed or re-linked by any <prgn>prerm</prgn> or
4790 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4791 of renaming things safely without affecting running programs,
4792 and attempts to interfere with this are likely to lead to
4797 Shared libraries should not be installed executable, since
4798 the dynamic linker does not require this and trying to
4799 execute a shared library usually results in a core dump.
4803 The run-time library package should include the symbolic link that
4804 <prgn>ldconfig</prgn> would create for the shared libraries.
4805 For example, the <package>libgdbm3</package> package should include
4806 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4807 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4808 linker (for example <prgn>ld.so</prgn> or
4809 <prgn>ld-linux.so.*</prgn>) can find the library between the
4810 time that <prgn>dpkg</prgn> installs it and the time that
4811 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4813 The package management system requires the library to be
4814 placed before the symbolic link pointing to it in the
4815 <file>.deb</file> file. This is so that when
4816 <prgn>dpkg</prgn> comes to install the symlink
4817 (overwriting the previous symlink pointing at an older
4818 version of the library), the new shared library is already
4819 in place. In the past, this was achieved by creating the
4820 library in the temporary packaging directory before
4821 creating the symlink. Unfortunately, this was not always
4822 effective, since the building of the tar file in the
4823 <file>.deb</file> depended on the behavior of the underlying
4824 file system. Some file systems (such as reiserfs) reorder
4825 the files so that the order of creation is forgotten.
4826 Since version 1.7.0, <prgn>dpkg</prgn>
4827 reorders the files itself as necessary when building a
4828 package. Thus it is no longer important to concern
4829 oneself with the order of file creation.
4833 <sect1 id="ldconfig">
4834 <heading><tt>ldconfig</tt></heading>
4837 Any package installing shared libraries in one of the default
4838 library directories of the dynamic linker (which are currently
4839 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4840 listed in <file>/etc/ld.so.conf</file><footnote>
4842 <list compact="compact">
4843 <item>/usr/local/lib</item>
4844 <item>/usr/lib/libc5-compat</item>
4845 <item>/lib/libc5-compat</item>
4848 must use <prgn>ldconfig</prgn> to update the shared library
4853 The package maintainer scripts must only call
4854 <prgn>ldconfig</prgn> under these circumstances:
4855 <list compact="compact">
4856 <item>When the <prgn>postinst</prgn> script is run with a
4857 first argument of <tt>configure</tt>, the script must call
4858 <prgn>ldconfig</prgn>, and may optionally invoke
4859 <prgn>ldconfig</prgn> at other times.
4861 <item>When the <prgn>postrm</prgn> script is run with a
4862 first argument of <tt>remove</tt>, the script should call
4863 <prgn>ldconfig</prgn>.
4868 During install or upgrade, the preinst is called before
4869 the new files are installed, so calling "ldconfig" is
4870 pointless. The preinst of an existing package can also be
4871 called if an upgrade fails. However, this happens during
4872 the critical time when a shared libs may exist on-disk
4873 under a temporary name. Thus, it is dangerous and
4874 forbidden by current policy to call "ldconfig" at this
4879 When a package is installed or upgraded, "postinst
4880 configure" runs after the new files are safely on-disk.
4881 Since it is perfectly safe to invoke ldconfig
4882 unconditionally in a postinst, it is OK for a package to
4883 simply put ldconfig in its postinst without checking the
4884 argument. The postinst can also be called to recover from
4885 a failed upgrade. This happens before any new files are
4886 unpacked, so there is no reason to call "ldconfig" at this
4891 For a package that is being removed, prerm is
4892 called with all the files intact, so calling ldconfig is
4893 useless. The other calls to "prerm" happen in the case of
4894 upgrade at a time when all the files of the old package
4895 are on-disk, so again calling "ldconfig" is pointless.
4899 postrm, on the other hand, is called with the "remove"
4900 argument just after the files are removed, so this is
4901 the proper time to call "ldconfig" to notify the system
4902 of the fact that the shared libraries from the package
4903 are removed. The postrm can be called at several other
4904 times. At the time of "postrm purge", "postrm
4905 abort-install", or "postrm abort-upgrade", calling
4906 "ldconfig" is useless because the shared lib files are
4907 not on-disk. However, when "postrm" is invoked with
4908 arguments "upgrade", "failed-upgrade", or "disappear", a
4909 shared lib may exist on-disk under a temporary filename.
4917 <sect id="sharedlibs-support-files">
4918 <heading>Shared library support files</heading>
4921 If your package contains files whose names do not change with
4922 each change in the library shared object version, you must not
4923 put them in the shared library package. Otherwise, several
4924 versions of the shared library cannot be installed at the same
4925 time without filename clashes, making upgrades and transitions
4926 unnecessarily difficult.
4930 It is recommended that supporting files and run-time support
4931 programs that do not need to be invoked manually by users, but
4932 are nevertheless required for the package to function, be placed
4933 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4934 preferably under <file>/usr/lib/</file><var>package-name</var>.
4935 If the program or file is architecture independent, the
4936 recommendation is for it to be placed in a subdirectory of
4937 <file>/usr/share</file> instead, preferably under
4938 <file>/usr/share/</file><var>package-name</var>. Following the
4939 <var>package-name</var> naming convention ensures that the file
4940 names change when the shared object version changes.
4944 Run-time support programs that use the shared library but are
4945 not required for the library to function or files used by the
4946 shared library that can be used by any version of the shared
4947 library package should instead be put in a separate package.
4948 This package might typically be named
4949 <package><var>libraryname</var>-tools</package>; note the
4950 absence of the <var>soversion</var> in the package name.
4954 Files and support programs only useful when compiling software
4955 against the library should be included in the development
4956 package for the library.<footnote>
4957 For example, a <file><var>package-name</var>-config</file>
4958 script or <package>pkg-config</package> configuration files.
4963 <sect id="sharedlibs-static">
4964 <heading>Static libraries</heading>
4967 The static library (<file><var>libraryname.a</var></file>)
4968 is usually provided in addition to the shared version.
4969 It is placed into the development package (see below).
4973 In some cases, it is acceptable for a library to be
4974 available in static form only; these cases include:
4976 <item>libraries for languages whose shared library support
4977 is immature or unstable</item>
4978 <item>libraries whose interfaces are in flux or under
4979 development (commonly the case when the library's
4980 major version number is zero, or where the ABI breaks
4981 across patchlevels)</item>
4982 <item>libraries which are explicitly intended to be
4983 available only in static form by their upstream
4988 <sect id="sharedlibs-dev">
4989 <heading>Development files</heading>
4992 The development files associated to a shared library need to be
4993 placed in a package called
4994 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4995 or if you prefer only to support one development version at a
4996 time, <package><var>libraryname</var>-dev</package>.
5000 In case several development versions of a library exist, you may
5001 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5002 <ref id="conflicts">) to ensure that the user only installs one
5003 development version at a time (as different development versions are
5004 likely to have the same header files in them, which would cause a
5005 filename clash if both were installed).
5009 The development package should contain a symlink for the associated
5010 shared library without a version number. For example, the
5011 <package>libgdbm-dev</package> package should include a symlink
5012 from <file>/usr/lib/libgdbm.so</file> to
5013 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5014 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5015 <file>libgdbm.so</file> when compiling dynamically.
5019 <sect id="sharedlibs-intradeps">
5020 <heading>Dependencies between the packages of the same library</heading>
5023 Typically the development version should have an exact
5024 version dependency on the runtime library, to make sure that
5025 compilation and linking happens correctly. The
5026 <tt>${binary:Version}</tt> substitution variable can be
5027 useful for this purpose.
5029 Previously, <tt>${Source-Version}</tt> was used, but its name
5030 was confusing and it has been deprecated since dpkg 1.13.19.
5035 <sect id="sharedlibs-shlibdeps">
5036 <heading>Dependencies between the library and other packages -
5037 the <tt>shlibs</tt> system</heading>
5040 If a package contains a binary or library which links to a
5041 shared library, we must ensure that when the package is
5042 installed on the system, all of the libraries needed are
5043 also installed. This requirement led to the creation of the
5044 <tt>shlibs</tt> system, which is very simple in its design:
5045 any package which <em>provides</em> a shared library also
5046 provides information on the package dependencies required to
5047 ensure the presence of this library, and any package which
5048 <em>uses</em> a shared library uses this information to
5049 determine the dependencies it requires. The files which
5050 contain the mapping from shared libraries to the necessary
5051 dependency information are called <file>shlibs</file> files.
5055 Thus, when a package is built which contains any shared
5056 libraries, it must provide a <file>shlibs</file> file for other
5057 packages to use, and when a package is built which contains
5058 any shared libraries or compiled binaries, it must run
5059 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5060 on these to determine the libraries used and hence the
5061 dependencies needed by this package.<footnote>
5063 In the past, the shared libraries linked to were
5064 determined by calling <prgn>ldd</prgn>, but now
5065 <prgn>objdump</prgn> is used to do this. The only
5066 change this makes to package building is that
5067 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5068 libraries, whereas in the past this was unnecessary.
5069 The rest of this footnote explains the advantage that
5074 We say that a binary <tt>foo</tt> <em>directly</em> uses
5075 a library <tt>libbar</tt> if it is explicitly linked
5076 with that library (that is, it uses the flag
5077 <tt>-lbar</tt> during the linking stage). Other
5078 libraries that are needed by <tt>libbar</tt> are linked
5079 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5080 linker will load them automatically when it loads
5081 <tt>libbar</tt>. A package should depend on
5082 the libraries it directly uses, and the dependencies for
5083 those libraries should automatically pull in the other
5088 Unfortunately, the <prgn>ldd</prgn> program shows both
5089 the directly and indirectly used libraries, meaning that
5090 the dependencies determined included both direct and
5091 indirect dependencies. The use of <prgn>objdump</prgn>
5092 avoids this problem by determining only the directly
5097 A good example of where this helps is the following. We
5098 could update <tt>libimlib</tt> with a new version that
5099 supports a new graphics format called dgf (but retaining
5100 the same major version number). If we used the old
5101 <prgn>ldd</prgn> method, every package that uses
5102 <tt>libimlib</tt> would need to be recompiled so it
5103 would also depend on <tt>libdgf</tt> or it wouldn't run
5104 due to missing symbols. However with the new system,
5105 packages using <tt>libimlib</tt> can rely on
5106 <tt>libimlib</tt> itself having the dependency on
5107 <tt>libdgf</tt> and so they would not need rebuilding.
5113 In the following sections, we will first describe where the
5114 various <tt>shlibs</tt> files are to be found, then how to
5115 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5116 file format and how to create them if your package contains a
5121 <heading>The <tt>shlibs</tt> files present on the system</heading>
5124 There are several places where <tt>shlibs</tt> files are
5125 found. The following list gives them in the order in which
5127 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5128 (The first one which gives the required information is used.)
5134 <p><file>debian/shlibs.local</file></p>
5137 This lists overrides for this package. Its use is
5138 described below (see <ref id="shlibslocal">).
5143 <p><file>/etc/dpkg/shlibs.override</file></p>
5146 This lists global overrides. This list is normally
5147 empty. It is maintained by the local system
5153 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5156 When packages are being built, any
5157 <file>debian/shlibs</file> files are copied into the
5158 control file area of the temporary build directory and
5159 given the name <file>shlibs</file>. These files give
5160 details of any shared libraries included in the
5162 An example may help here. Let us say that the
5163 source package <tt>foo</tt> generates two binary
5164 packages, <tt>libfoo2</tt> and
5165 <tt>foo-runtime</tt>. When building the binary
5166 packages, the two packages are created in the
5167 directories <file>debian/libfoo2</file> and
5168 <file>debian/foo-runtime</file> respectively.
5169 (<file>debian/tmp</file> could be used instead of one
5170 of these.) Since <tt>libfoo2</tt> provides the
5171 <tt>libfoo</tt> shared library, it will require a
5172 <tt>shlibs</tt> file, which will be installed in
5173 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5175 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5176 when <prgn>dpkg-shlibdeps</prgn> is run on the
5178 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5180 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5181 determine whether <tt>foo-prog</tt>'s library
5182 dependencies are satisfied by any of the libraries
5183 provided by <tt>libfoo2</tt>. For this reason,
5184 <prgn>dpkg-shlibdeps</prgn> must only be run once
5185 all of the individual binary packages'
5186 <tt>shlibs</tt> files have been installed into the
5193 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5196 These are the <file>shlibs</file> files corresponding to
5197 all of the packages installed on the system, and are
5198 maintained by the relevant package maintainers.
5203 <p><file>/etc/dpkg/shlibs.default</file></p>
5206 This file lists any shared libraries whose packages
5207 have failed to provide correct <file>shlibs</file> files.
5208 It was used when the <file>shlibs</file> setup was first
5209 introduced, but it is now normally empty. It is
5210 maintained by the <tt>dpkg</tt> maintainer.
5218 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5219 <file>shlibs</file> files</heading>
5223 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5224 into your <file>debian/rules</file> file. If your package
5225 contains only compiled binaries and libraries (but no scripts),
5226 you can use a command such as:
5227 <example compact="compact">
5228 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5229 debian/tmp/usr/lib/*
5231 Otherwise, you will need to explicitly list the compiled
5232 binaries and libraries.<footnote>
5233 If you are using <tt>debhelper</tt>, the
5234 <prgn>dh_shlibdeps</prgn> program will do this work for
5235 you. It will also correctly handle multi-binary
5241 This command puts the dependency information into the
5242 <file>debian/substvars</file> file, which is then used by
5243 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5244 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5245 field in the control file for this to work.
5249 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5250 done. If it does complain you might need to create your own
5251 <file>debian/shlibs.local</file> file, as explained below (see
5252 <ref id="shlibslocal">).
5256 If you have multiple binary packages, you will need to call
5257 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5258 compiled libraries or binaries. In such a case, you will
5259 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5260 utilities to specify a different <file>substvars</file> file.
5264 If you are creating a udeb for use in the Debian Installer, you
5265 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5266 the dependency line of type <tt>udeb</tt> by adding
5267 <tt>-tudeb</tt> as option<footnote>
5268 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5269 will automatically add this option if it knows it is
5271 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5272 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5273 fall back to the regular dependency line.
5277 For more details on dpkg-shlibdeps, please see
5278 <ref id="pkg-dpkg-shlibdeps"> and
5279 <manref name="dpkg-shlibdeps" section="1">.
5284 <heading>The <file>shlibs</file> File Format</heading>
5287 Each <file>shlibs</file> file has the same format. Lines
5288 beginning with <tt>#</tt> are considered to be comments and
5289 are ignored. Each line is of the form:
5290 <example compact="compact">
5291 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5296 We will explain this by reference to the example of the
5297 <tt>zlib1g</tt> package, which (at the time of writing)
5298 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5302 <var>type</var> is an optional element that indicates the type
5303 of package for which the line is valid. The only type currently
5304 in use is <tt>udeb</tt>. The colon and space after the type are
5309 <var>library-name</var> is the name of the shared library,
5310 in this case <tt>libz</tt>. (This must match the name part
5311 of the soname, see below.)
5315 <var>soname-version</var> is the version part of the soname of
5316 the library. The soname is the thing that must exactly match
5317 for the library to be recognized by the dynamic linker, and is
5319 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5320 example, <tt>libz.so.1</tt>.<footnote>
5321 This can be determined using the command
5322 <example compact="compact">
5323 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5326 The version part is the part which comes after
5327 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5331 <var>dependencies</var> has the same syntax as a dependency
5332 field in a binary package control file. It should give
5333 details of which packages are required to satisfy a binary
5334 built against the version of the library contained in the
5335 package. See <ref id="depsyntax"> for details.
5339 In our example, if the first version of the <tt>zlib1g</tt>
5340 package which contained a minor number of at least
5341 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5342 <tt>shlibs</tt> entry for this library could say:
5343 <example compact="compact">
5344 libz 1 zlib1g (>= 1:1.1.3)
5346 The version-specific dependency is to avoid warnings from
5347 the dynamic linker about using older shared libraries with
5352 As zlib1g also provides a udeb containing the shared library,
5353 there would also be a second line:
5354 <example compact="compact">
5355 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5361 <heading>Providing a <file>shlibs</file> file</heading>
5364 If your package provides a shared library, you need to create
5365 a <file>shlibs</file> file following the format described above.
5366 It is usual to call this file <file>debian/shlibs</file> (but if
5367 you have multiple binary packages, you might want to call it
5368 <file>debian/shlibs.<var>package</var></file> instead). Then
5369 let <file>debian/rules</file> install it in the control area:
5370 <example compact="compact">
5371 install -m644 debian/shlibs debian/tmp/DEBIAN
5373 or, in the case of a multi-binary package:
5374 <example compact="compact">
5375 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5377 An alternative way of doing this is to create the
5378 <file>shlibs</file> file in the control area directly from
5379 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5380 file at all,<footnote>
5381 This is what <prgn>dh_makeshlibs</prgn> in the
5382 <tt>debhelper</tt> suite does. If your package also has a udeb
5383 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5384 automatically generate the <tt>udeb:</tt> lines if you specify
5385 the name of the udeb with the <tt>--add-udeb</tt> option.
5387 since the <file>debian/shlibs</file> file itself is ignored by
5388 <prgn>dpkg-shlibdeps</prgn>.
5392 As <prgn>dpkg-shlibdeps</prgn> reads the
5393 <file>DEBIAN/shlibs</file> files in all of the binary packages
5394 being built from this source package, all of the
5395 <file>DEBIAN/shlibs</file> files should be installed before
5396 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5401 <sect1 id="shlibslocal">
5402 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5405 This file is intended only as a <em>temporary</em> fix if
5406 your binaries or libraries depend on a library whose package
5407 does not yet provide a correct <file>shlibs</file> file.
5411 We will assume that you are trying to package a binary
5412 <tt>foo</tt>. When you try running
5413 <prgn>dpkg-shlibdeps</prgn> you get the following error
5414 message (<tt>-O</tt> displays the dependency information on
5415 <tt>stdout</tt> instead of writing it to
5416 <tt>debian/substvars</tt>, and the lines have been wrapped
5417 for ease of reading):
5418 <example compact="compact">
5419 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5420 dpkg-shlibdeps: warning: unable to find dependency
5421 information for shared library libbar (soname 1,
5422 path /usr/lib/libbar.so.1, dependency field Depends)
5423 shlibs:Depends=libc6 (>= 2.2.2-2)
5425 You can then run <prgn>ldd</prgn> on the binary to find the
5426 full location of the library concerned:
5427 <example compact="compact">
5429 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5430 libc.so.6 => /lib/libc.so.6 (0x40032000)
5431 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5433 So the <prgn>foo</prgn> binary depends on the
5434 <prgn>libbar</prgn> shared library, but no package seems to
5435 provide a <file>*.shlibs</file> file handling
5436 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5437 determine the package responsible:
5438 <example compact="compact">
5439 $ dpkg -S /usr/lib/libbar.so.1
5440 bar1: /usr/lib/libbar.so.1
5441 $ dpkg -s bar1 | grep Version
5444 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5445 is the one we are using. Now we can file a bug against the
5446 <tt>bar1</tt> package and create our own
5447 <file>debian/shlibs.local</file> to locally fix the problem.
5448 Including the following line into your
5449 <file>debian/shlibs.local</file> file:
5450 <example compact="compact">
5451 libbar 1 bar1 (>= 1.0-1)
5453 should allow the package build to work.
5457 As soon as the maintainer of <tt>bar1</tt> provides a
5458 correct <file>shlibs</file> file, you should remove this line
5459 from your <file>debian/shlibs.local</file> file. (You should
5460 probably also then have a versioned <tt>Build-Depends</tt>
5461 on <tt>bar1</tt> to help ensure that others do not have the
5462 same problem building your package.)
5471 <chapt id="opersys"><heading>The Operating System</heading>
5474 <heading>File system hierarchy</heading>
5478 <heading>File system Structure</heading>
5481 The location of all installed files and directories must
5482 comply with the File system Hierarchy Standard (FHS),
5483 version 2.3, with the exceptions noted below, and except
5484 where doing so would violate other terms of Debian
5485 Policy. The following exceptions to the FHS apply:
5490 Legacy XFree86 servers are permitted to retain the
5491 configuration file location
5492 <file>/etc/X11/XF86Config-4</file>.
5497 The optional rules related to user specific
5498 configuration files for applications are stored in
5499 the user's home directory are relaxed. It is
5500 recommended that such files start with the
5501 '<tt>.</tt>' character (a "dot file"), and if an
5502 application needs to create more than one dot file
5503 then the preferred placement is in a subdirectory
5504 with a name starting with a '.' character, (a "dot
5505 directory"). In this case it is recommended the
5506 configuration files not start with the '.'
5512 The requirement for amd64 to use <file>/lib64</file>
5513 for 64 bit binaries is removed.
5518 The requirement that
5519 <file>/usr/local/share/man</file> be "synonymous"
5520 with <file>/usr/local/man</file> is relaxed to a
5525 The requirement that windowmanagers with a single
5526 configuration file call it <file>system.*wmrc</file>
5527 is removed, as is the restriction that the window
5528 manager subdirectory be named identically to the
5529 window manager name itself.
5534 The requirement that boot manager configuration
5535 files live in <file>/etc</file>, or at least are
5536 symlinked there, is relaxed to a recommendation.
5543 The version of this document referred here can be
5544 found in the <tt>debian-policy</tt> package or on <url
5545 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5546 name="FHS (Debian copy)"> alongside this manual (or, if
5547 you have the <package>debian-policy</package> installed,
5549 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5550 (local copy)">). The
5551 latest version, which may be a more recent version, may
5553 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5554 Specific questions about following the standard may be
5555 asked on the <tt>debian-devel</tt> mailing list, or
5556 referred to the FHS mailing list (see the
5557 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5563 <heading>Site-specific programs</heading>
5566 As mandated by the FHS, packages must not place any
5567 files in <file>/usr/local</file>, either by putting them in
5568 the file system archive to be unpacked by <prgn>dpkg</prgn>
5569 or by manipulating them in their maintainer scripts.
5573 However, the package may create empty directories below
5574 <file>/usr/local</file> so that the system administrator knows
5575 where to place site-specific files. These are not
5576 directories <em>in</em> <file>/usr/local</file>, but are
5577 children of directories in <file>/usr/local</file>. These
5578 directories (<file>/usr/local/*/dir/</file>)
5579 should be removed on package removal if they are
5584 Note, that this applies only to directories <em>below</em>
5585 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5586 Packages must not create sub-directories in the directory
5587 <file>/usr/local</file> itself, except those listed in FHS,
5588 section 4.5. However, you may create directories below
5589 them as you wish. You must not remove any of the
5590 directories listed in 4.5, even if you created them.
5594 Since <file>/usr/local</file> can be mounted read-only from a
5595 remote server, these directories must be created and
5596 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5597 maintainer scripts and not be included in the
5598 <file>.deb</file> archive. These scripts must not fail if
5599 either of these operations fail.
5603 For example, the <tt>emacsen-common</tt> package could
5604 contain something like
5605 <example compact="compact">
5606 if [ ! -e /usr/local/share/emacs ]
5608 if mkdir /usr/local/share/emacs 2>/dev/null
5610 chown root:staff /usr/local/share/emacs
5611 chmod 2775 /usr/local/share/emacs
5615 in its <prgn>postinst</prgn> script, and
5616 <example compact="compact">
5617 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5618 rmdir /usr/local/share/emacs 2>/dev/null || true
5620 in the <prgn>prerm</prgn> script. (Note that this form is
5621 used to ensure that if the script is interrupted, the
5622 directory <file>/usr/local/share/emacs</file> will still be
5627 If you do create a directory in <file>/usr/local</file> for
5628 local additions to a package, you should ensure that
5629 settings in <file>/usr/local</file> take precedence over the
5630 equivalents in <file>/usr</file>.
5634 However, because <file>/usr/local</file> and its contents are
5635 for exclusive use of the local administrator, a package
5636 must not rely on the presence or absence of files or
5637 directories in <file>/usr/local</file> for normal operation.
5641 The <file>/usr/local</file> directory itself and all the
5642 subdirectories created by the package should (by default) have
5643 permissions 2775 (group-writable and set-group-id) and be
5644 owned by <tt>root:staff</tt>.
5649 <heading>The system-wide mail directory</heading>
5651 The system-wide mail directory is <file>/var/mail</file>. This
5652 directory is part of the base system and should not owned
5653 by any particular mail agents. The use of the old
5654 location <file>/var/spool/mail</file> is deprecated, even
5655 though the spool may still be physically located there.
5656 To maintain partial upgrade compatibility for systems
5657 which have <file>/var/spool/mail</file> as their physical mail
5658 spool, packages using <file>/var/mail</file> must depend on
5659 either <package>libc6</package> (>= 2.1.3-13), or on
5660 <package>base-files</package> (>= 2.2.0), or on later
5661 versions of either one of these packages.
5667 <heading>Users and groups</heading>
5670 <heading>Introduction</heading>
5672 The Debian system can be configured to use either plain or
5677 Some user ids (UIDs) and group ids (GIDs) are reserved
5678 globally for use by certain packages. Because some
5679 packages need to include files which are owned by these
5680 users or groups, or need the ids compiled into binaries,
5681 these ids must be used on any Debian system only for the
5682 purpose for which they are allocated. This is a serious
5683 restriction, and we should avoid getting in the way of
5684 local administration policies. In particular, many sites
5685 allocate users and/or local system groups starting at 100.
5689 Apart from this we should have dynamically allocated ids,
5690 which should by default be arranged in some sensible
5691 order, but the behavior should be configurable.
5695 Packages other than <tt>base-passwd</tt> must not modify
5696 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5697 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5702 <heading>UID and GID classes</heading>
5704 The UID and GID numbers are divided into classes as
5710 Globally allocated by the Debian project, the same
5711 on every Debian system. These ids will appear in
5712 the <file>passwd</file> and <file>group</file> files of all
5713 Debian systems, new ids in this range being added
5714 automatically as the <tt>base-passwd</tt> package is
5719 Packages which need a single statically allocated
5720 uid or gid should use one of these; their
5721 maintainers should ask the <tt>base-passwd</tt>
5729 Dynamically allocated system users and groups.
5730 Packages which need a user or group, but can have
5731 this user or group allocated dynamically and
5732 differently on each system, should use <tt>adduser
5733 --system</tt> to create the group and/or user.
5734 <prgn>adduser</prgn> will check for the existence of
5735 the user or group, and if necessary choose an unused
5736 id based on the ranges specified in
5737 <file>adduser.conf</file>.
5741 <tag>1000-29999:</tag>
5744 Dynamically allocated user accounts. By default
5745 <prgn>adduser</prgn> will choose UIDs and GIDs for
5746 user accounts in this range, though
5747 <file>adduser.conf</file> may be used to modify this
5752 <tag>30000-59999:</tag>
5757 <tag>60000-64999:</tag>
5760 Globally allocated by the Debian project, but only
5761 created on demand. The ids are allocated centrally
5762 and statically, but the actual accounts are only
5763 created on users' systems on demand.
5767 These ids are for packages which are obscure or
5768 which require many statically-allocated ids. These
5769 packages should check for and create the accounts in
5770 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5771 <prgn>adduser</prgn> if it has this facility) if
5772 necessary. Packages which are likely to require
5773 further allocations should have a "hole" left after
5774 them in the allocation, to give them room to
5779 <tag>65000-65533:</tag>
5787 User <tt>nobody</tt>. The corresponding gid refers
5788 to the group <tt>nogroup</tt>.
5795 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5796 not</em> be used, because it is the error return
5805 <sect id="sysvinit">
5806 <heading>System run levels and <file>init.d</file> scripts</heading>
5808 <sect1 id="/etc/init.d">
5809 <heading>Introduction</heading>
5812 The <file>/etc/init.d</file> directory contains the scripts
5813 executed by <prgn>init</prgn> at boot time and when the
5814 init state (or "runlevel") is changed (see <manref
5815 name="init" section="8">).
5819 There are at least two different, yet functionally
5820 equivalent, ways of handling these scripts. For the sake
5821 of simplicity, this document describes only the symbolic
5822 link method. However, it must not be assumed by maintainer
5823 scripts that this method is being used, and any automated
5824 manipulation of the various runlevel behaviors by
5825 maintainer scripts must be performed using
5826 <prgn>update-rc.d</prgn> as described below and not by
5827 manually installing or removing symlinks. For information
5828 on the implementation details of the other method,
5829 implemented in the <tt>file-rc</tt> package, please refer
5830 to the documentation of that package.
5834 These scripts are referenced by symbolic links in the
5835 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5836 runlevels, <prgn>init</prgn> looks in the directory
5837 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5838 execute, where <tt><var>n</var></tt> is the runlevel that
5839 is being changed to, or <tt>S</tt> for the boot-up
5844 The names of the links all have the form
5845 <file>S<var>mm</var><var>script</var></file> or
5846 <file>K<var>mm</var><var>script</var></file> where
5847 <var>mm</var> is a two-digit number and <var>script</var>
5848 is the name of the script (this should be the same as the
5849 name of the actual script in <file>/etc/init.d</file>).
5853 When <prgn>init</prgn> changes runlevel first the targets
5854 of the links whose names start with a <tt>K</tt> are
5855 executed, each with the single argument <tt>stop</tt>,
5856 followed by the scripts prefixed with an <tt>S</tt>, each
5857 with the single argument <tt>start</tt>. (The links are
5858 those in the <file>/etc/rc<var>n</var>.d</file> directory
5859 corresponding to the new runlevel.) The <tt>K</tt> links
5860 are responsible for killing services and the <tt>S</tt>
5861 link for starting services upon entering the runlevel.
5865 For example, if we are changing from runlevel 2 to
5866 runlevel 3, init will first execute all of the <tt>K</tt>
5867 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5868 all of the <tt>S</tt> prefixed scripts in that directory.
5869 The links starting with <tt>K</tt> will cause the
5870 referred-to file to be executed with an argument of
5871 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5876 The two-digit number <var>mm</var> is used to determine
5877 the order in which to run the scripts: low-numbered links
5878 have their scripts run first. For example, the
5879 <tt>K20</tt> scripts will be executed before the
5880 <tt>K30</tt> scripts. This is used when a certain service
5881 must be started before another. For example, the name
5882 server <prgn>bind</prgn> might need to be started before
5883 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5884 can set up its access lists. In this case, the script
5885 that starts <prgn>bind</prgn> would have a lower number
5886 than the script that starts <prgn>inn</prgn> so that it
5888 <example compact="compact">
5895 The two runlevels 0 (halt) and 6 (reboot) are slightly
5896 different. In these runlevels, the links with an
5897 <tt>S</tt> prefix are still called after those with a
5898 <tt>K</tt> prefix, but they too are called with the single
5899 argument <tt>stop</tt>.
5903 Also, if the script name ends in <tt>.sh</tt>, the script
5904 will be sourced in runlevel <tt>S</tt> rather than being
5905 run in a forked subprocess, but will be explicitly run by
5906 <prgn>sh</prgn> in all other runlevels.
5911 <heading>Writing the scripts</heading>
5914 Packages that include daemons for system services should
5915 place scripts in <file>/etc/init.d</file> to start or stop
5916 services at boot time or during a change of runlevel.
5917 These scripts should be named
5918 <file>/etc/init.d/<var>package</var></file>, and they should
5919 accept one argument, saying what to do:
5922 <tag><tt>start</tt></tag>
5923 <item>start the service,</item>
5925 <tag><tt>stop</tt></tag>
5926 <item>stop the service,</item>
5928 <tag><tt>restart</tt></tag>
5929 <item>stop and restart the service if it's already running,
5930 otherwise start the service</item>
5932 <tag><tt>reload</tt></tag>
5933 <item><p>cause the configuration of the service to be
5934 reloaded without actually stopping and restarting
5937 <tag><tt>force-reload</tt></tag>
5938 <item>cause the configuration to be reloaded if the
5939 service supports this, otherwise restart the
5943 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5944 <tt>force-reload</tt> options should be supported by all
5945 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5950 The <file>init.d</file> scripts must ensure that they will
5951 behave sensibly (i.e., returning success and not starting
5952 multiple copies of a service) if invoked with <tt>start</tt>
5953 when the service is already running, or with <tt>stop</tt>
5954 when it isn't, and that they don't kill unfortunately-named
5955 user processes. The best way to achieve this is usually to
5956 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5961 If a service reloads its configuration automatically (as
5962 in the case of <prgn>cron</prgn>, for example), the
5963 <tt>reload</tt> option of the <file>init.d</file> script
5964 should behave as if the configuration has been reloaded
5969 The <file>/etc/init.d</file> scripts must be treated as
5970 configuration files, either (if they are present in the
5971 package, that is, in the .deb file) by marking them as
5972 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5973 by managing them correctly in the maintainer scripts (see
5974 <ref id="config-files">). This is important since we want
5975 to give the local system administrator the chance to adapt
5976 the scripts to the local system, e.g., to disable a
5977 service without de-installing the package, or to specify
5978 some special command line options when starting a service,
5979 while making sure their changes aren't lost during the next
5984 These scripts should not fail obscurely when the
5985 configuration files remain but the package has been
5986 removed, as configuration files remain on the system after
5987 the package has been removed. Only when <prgn>dpkg</prgn>
5988 is executed with the <tt>--purge</tt> option will
5989 configuration files be removed. In particular, as the
5990 <file>/etc/init.d/<var>package</var></file> script itself is
5991 usually a <tt>conffile</tt>, it will remain on the system
5992 if the package is removed but not purged. Therefore, you
5993 should include a <tt>test</tt> statement at the top of the
5995 <example compact="compact">
5996 test -f <var>program-executed-later-in-script</var> || exit 0
6001 Often there are some variables in the <file>init.d</file>
6002 scripts whose values control the behavior of the scripts,
6003 and which a system administrator is likely to want to
6004 change. As the scripts themselves are frequently
6005 <tt>conffile</tt>s, modifying them requires that the
6006 administrator merge in their changes each time the package
6007 is upgraded and the <tt>conffile</tt> changes. To ease
6008 the burden on the system administrator, such configurable
6009 values should not be placed directly in the script.
6010 Instead, they should be placed in a file in
6011 <file>/etc/default</file>, which typically will have the same
6012 base name as the <file>init.d</file> script. This extra file
6013 should be sourced by the script when the script runs. It
6014 must contain only variable settings and comments in SUSv3
6015 <prgn>sh</prgn> format. It may either be a
6016 <tt>conffile</tt> or a configuration file maintained by
6017 the package maintainer scripts. See <ref id="config-files">
6022 To ensure that vital configurable values are always
6023 available, the <file>init.d</file> script should set default
6024 values for each of the shell variables it uses, either
6025 before sourcing the <file>/etc/default/</file> file or
6026 afterwards using something like the <tt>:
6027 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6028 script must behave sensibly and not fail if the
6029 <file>/etc/default</file> file is deleted.
6034 <heading>Interfacing with the initscript system</heading>
6037 Maintainers should use the abstraction layer provided by
6038 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6039 programs to deal with initscripts in their packages'
6040 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6041 and <prgn>postrm</prgn>.
6045 Directly managing the /etc/rc?.d links and directly
6046 invoking the <file>/etc/init.d/</file> initscripts should
6047 be done only by packages providing the initscript
6048 subsystem (such as <prgn>sysv-rc</prgn> and
6049 <prgn>file-rc</prgn>).
6053 <heading>Managing the links</heading>
6056 The program <prgn>update-rc.d</prgn> is provided for
6057 package maintainers to arrange for the proper creation and
6058 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6059 or their functional equivalent if another method is being
6060 used. This may be used by maintainers in their packages'
6061 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6065 You must not include any <file>/etc/rc<var>n</var>.d</file>
6066 symbolic links in the actual archive or manually create or
6067 remove the symbolic links in maintainer scripts; you must
6068 use the <prgn>update-rc.d</prgn> program instead. (The
6069 former will fail if an alternative method of maintaining
6070 runlevel information is being used.) You must not include
6071 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6072 in the archive either. (Only the <tt>sysvinit</tt>
6077 By default <prgn>update-rc.d</prgn> will start services in
6078 each of the multi-user state runlevels (2, 3, 4, and 5)
6079 and stop them in the halt runlevel (0), the single-user
6080 runlevel (1) and the reboot runlevel (6). The system
6081 administrator will have the opportunity to customize
6082 runlevels by simply adding, moving, or removing the
6083 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6084 symbolic links are being used, or by modifying
6085 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6090 To get the default behavior for your package, put in your
6091 <prgn>postinst</prgn> script
6092 <example compact="compact">
6093 update-rc.d <var>package</var> defaults
6095 and in your <prgn>postrm</prgn>
6096 <example compact="compact">
6097 if [ "$1" = purge ]; then
6098 update-rc.d <var>package</var> remove
6100 </example>. Note that if your package changes runlevels
6101 or priority, you may have to remove and recreate the links,
6102 since otherwise the old links may persist. Refer to the
6103 documentation of <prgn>update-rc.d</prgn>.
6107 This will use a default sequence number of 20. If it does
6108 not matter when or in which order the <file>init.d</file>
6109 script is run, use this default. If it does, then you
6110 should talk to the maintainer of the <prgn>sysvinit</prgn>
6111 package or post to <tt>debian-devel</tt>, and they will
6112 help you choose a number.
6116 For more information about using <tt>update-rc.d</tt>,
6117 please consult its man page <manref name="update-rc.d"
6123 <heading>Running initscripts</heading>
6125 The program <prgn>invoke-rc.d</prgn> is provided to make
6126 it easier for package maintainers to properly invoke an
6127 initscript, obeying runlevel and other locally-defined
6128 constraints that might limit a package's right to start,
6129 stop and otherwise manage services. This program may be
6130 used by maintainers in their packages' scripts.
6134 The package maintainer scripts must use
6135 <prgn>invoke-rc.d</prgn> to invoke the
6136 <file>/etc/init.d/*</file> initscripts, instead of
6137 calling them directly.
6141 By default, <prgn>invoke-rc.d</prgn> will pass any
6142 action requests (start, stop, reload, restart...) to the
6143 <file>/etc/init.d</file> script, filtering out requests
6144 to start or restart a service out of its intended
6149 Most packages will simply need to change:
6150 <example compact="compact">/etc/init.d/<package>
6151 <action></example> in their <prgn>postinst</prgn>
6152 and <prgn>prerm</prgn> scripts to:
6153 <example compact="compact">
6154 if which invoke-rc.d >/dev/null 2>&1; then
6155 invoke-rc.d <var>package</var> <action>
6157 /etc/init.d/<var>package</var> <action>
6163 A package should register its initscript services using
6164 <prgn>update-rc.d</prgn> before it tries to invoke them
6165 using <prgn>invoke-rc.d</prgn>. Invocation of
6166 unregistered services may fail.
6170 For more information about using
6171 <prgn>invoke-rc.d</prgn>, please consult its man page
6172 <manref name="invoke-rc.d" section="8">.
6178 <heading>Boot-time initialization</heading>
6181 There used to be another directory, <file>/etc/rc.boot</file>,
6182 which contained scripts which were run once per machine
6183 boot. This has been deprecated in favour of links from
6184 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6185 described in <ref id="/etc/init.d">. Packages must not
6186 place files in <file>/etc/rc.boot</file>.
6191 <heading>Example</heading>
6194 An example on which you can base your
6195 <file>/etc/init.d</file> scripts is found in
6196 <file>/etc/init.d/skeleton</file>.
6203 <heading>Console messages from <file>init.d</file> scripts</heading>
6206 This section describes the formats to be used for messages
6207 written to standard output by the <file>/etc/init.d</file>
6208 scripts. The intent is to improve the consistency of
6209 Debian's startup and shutdown look and feel. For this
6210 reason, please look very carefully at the details. We want
6211 the messages to have the same format in terms of wording,
6212 spaces, punctuation and case of letters.
6216 Here is a list of overall rules that should be used for
6217 messages generated by <file>/etc/init.d</file> scripts.
6223 The message should fit in one line (fewer than 80
6224 characters), start with a capital letter and end with
6225 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6229 If the script is performing some time consuming task in
6230 the background (not merely starting or stopping a
6231 program, for instance), an ellipsis (three dots:
6232 <tt>...</tt>) should be output to the screen, with no
6233 leading or tailing whitespace or line feeds.
6237 The messages should appear as if the computer is telling
6238 the user what it is doing (politely :-), but should not
6239 mention "it" directly. For example, instead of:
6240 <example compact="compact">
6241 I'm starting network daemons: nfsd mountd.
6243 the message should say
6244 <example compact="compact">
6245 Starting network daemons: nfsd mountd.
6252 <tt>init.d</tt> script should use the following standard
6253 message formats for the situations enumerated below.
6259 <p>When daemons are started</p>
6262 If the script starts one or more daemons, the output
6263 should look like this (a single line, no leading
6265 <example compact="compact">
6266 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6268 The <var>description</var> should describe the
6269 subsystem the daemon or set of daemons are part of,
6270 while <var>daemon-1</var> up to <var>daemon-n</var>
6271 denote each daemon's name (typically the file name of
6276 For example, the output of <file>/etc/init.d/lpd</file>
6278 <example compact="compact">
6279 Starting printer spooler: lpd.
6284 This can be achieved by saying
6285 <example compact="compact">
6286 echo -n "Starting printer spooler: lpd"
6287 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6290 in the script. If there are more than one daemon to
6291 start, the output should look like this:
6292 <example compact="compact">
6293 echo -n "Starting remote file system services:"
6294 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6295 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6296 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6299 This makes it possible for the user to see what is
6300 happening and when the final daemon has been started.
6301 Care should be taken in the placement of white spaces:
6302 in the example above the system administrators can
6303 easily comment out a line if they don't want to start
6304 a specific daemon, while the displayed message still
6310 <p>When a system parameter is being set</p>
6313 If you have to set up different system parameters
6314 during the system boot, you should use this format:
6315 <example compact="compact">
6316 Setting <var>parameter</var> to "<var>value</var>".
6321 You can use a statement such as the following to get
6323 <example compact="compact">
6324 echo "Setting DNS domainname to \"$domainname\"."
6329 Note that the same symbol (<tt>"</tt>) is used for the left
6330 and right quotation marks. A grave accent (<tt>`</tt>) is
6331 not a quote character; neither is an apostrophe
6337 <p>When a daemon is stopped or restarted</p>
6340 When you stop or restart a daemon, you should issue a
6341 message identical to the startup message, except that
6342 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6343 or <tt>Restarting</tt> respectively.
6347 For example, stopping the printer daemon will look like
6349 <example compact="compact">
6350 Stopping printer spooler: lpd.
6356 <p>When something is executed</p>
6359 There are several examples where you have to run a
6360 program at system startup or shutdown to perform a
6361 specific task, for example, setting the system's clock
6362 using <prgn>netdate</prgn> or killing all processes
6363 when the system shuts down. Your message should look
6365 <example compact="compact">
6366 Doing something very useful...done.
6368 You should print the <tt>done.</tt> immediately after
6369 the job has been completed, so that the user is
6370 informed why they have to wait. You can get this
6372 <example compact="compact">
6373 echo -n "Doing something very useful..."
6382 <p>When the configuration is reloaded</p>
6385 When a daemon is forced to reload its configuration
6386 files you should use the following format:
6387 <example compact="compact">
6388 Reloading <var>description</var> configuration...done.
6390 where <var>description</var> is the same as in the
6391 daemon starting message.
6399 <heading>Cron jobs</heading>
6402 Packages must not modify the configuration file
6403 <file>/etc/crontab</file>, and they must not modify the files in
6404 <file>/var/spool/cron/crontabs</file>.</p>
6407 If a package wants to install a job that has to be executed
6408 via cron, it should place a file with the name of the
6409 package in one or more of the following directories:
6410 <example compact="compact">
6416 As these directory names imply, the files within them are
6417 executed on an hourly, daily, weekly, or monthly basis,
6418 respectively. The exact times are listed in
6419 <file>/etc/crontab</file>.</p>
6422 All files installed in any of these directories must be
6423 scripts (e.g., shell scripts or Perl scripts) so that they
6424 can easily be modified by the local system administrator.
6425 In addition, they must be treated as configuration files.
6429 If a certain job has to be executed at some other frequency or
6430 at a specific time, the package should install a file
6431 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6432 same syntax as <file>/etc/crontab</file> and is processed by
6433 <prgn>cron</prgn> automatically. The file must also be
6434 treated as a configuration file. (Note that entries in the
6435 <file>/etc/cron.d</file> directory are not handled by
6436 <prgn>anacron</prgn>. Thus, you should only use this
6437 directory for jobs which may be skipped if the system is not
6441 The scripts or crontab entries in these directories should
6442 check if all necessary programs are installed before they
6443 try to execute them. Otherwise, problems will arise when a
6444 package was removed but not purged since configuration files
6445 are kept on the system in this situation.</p>
6449 <heading>Menus</heading>
6452 The Debian <tt>menu</tt> package provides a standard
6453 interface between packages providing applications and
6454 <em>menu programs</em> (either X window managers or
6455 text-based menu programs such as <prgn>pdmenu</prgn>).
6459 All packages that provide applications that need not be
6460 passed any special command line arguments for normal
6461 operation should register a menu entry for those
6462 applications, so that users of the <tt>menu</tt> package
6463 will automatically get menu entries in their window
6464 managers, as well in shells like <tt>pdmenu</tt>.
6468 Menu entries should follow the current menu policy.
6472 The menu policy can be found in the <tt>menu-policy</tt>
6473 files in the <tt>debian-policy</tt> package.
6474 It is also available from the Debian web mirrors at
6475 <tt><url name="/doc/packaging-manuals/menu-policy/"
6476 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6480 Please also refer to the <em>Debian Menu System</em>
6481 documentation that comes with the <package>menu</package>
6482 package for information about how to register your
6488 <heading>Multimedia handlers</heading>
6491 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6492 is a mechanism for encoding files and data streams and
6493 providing meta-information about them, in particular their
6494 type (e.g. audio or video) and format (e.g. PNG, HTML,
6499 Registration of MIME type handlers allows programs like mail
6500 user agents and web browsers to invoke these handlers to
6501 view, edit or display MIME types they don't support directly.
6505 Packages which provide the ability to view/show/play,
6506 compose, edit or print MIME types should register themselves
6507 as such following the current MIME support policy.
6511 The MIME support policy can be found in the <tt>mime-policy</tt>
6512 files in the <tt>debian-policy</tt> package.
6513 It is also available from the Debian web mirrors at
6514 <tt><url name="/doc/packaging-manuals/mime-policy/"
6515 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6521 <heading>Keyboard configuration</heading>
6524 To achieve a consistent keyboard configuration so that all
6525 applications interpret a keyboard event the same way, all
6526 programs in the Debian distribution must be configured to
6527 comply with the following guidelines.
6531 The following keys must have the specified interpretations:
6534 <tag><tt><--</tt></tag>
6535 <item>delete the character to the left of the cursor</item>
6537 <tag><tt>Delete</tt></tag>
6538 <item>delete the character to the right of the cursor</item>
6540 <tag><tt>Control+H</tt></tag>
6541 <item>emacs: the help prefix</item>
6544 The interpretation of any keyboard events should be
6545 independent of the terminal that is used, be it a virtual
6546 console, an X terminal emulator, an rlogin/telnet session,
6551 The following list explains how the different programs
6552 should be set up to achieve this:
6558 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6562 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6566 X translations are set up to make
6567 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6568 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6569 is the vt220 escape code for the "delete character"
6570 key). This must be done by loading the X resources
6571 using <prgn>xrdb</prgn> on all local X displays, not
6572 using the application defaults, so that the
6573 translation resources used correspond to the
6574 <prgn>xmodmap</prgn> settings.
6578 The Linux console is configured to make
6579 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6580 generate <tt>ESC [ 3 ~</tt>.
6584 X applications are configured so that <tt><</tt>
6585 deletes left, and <tt>Delete</tt> deletes right. Motif
6586 applications already work like this.
6590 Terminals should have <tt>stty erase ^?</tt> .
6594 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6595 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6596 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6600 Emacs is programmed to map <tt>KB_Backspace</tt> or
6601 the <tt>stty erase</tt> character to
6602 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6603 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6604 <tt>^H</tt> to <tt>help</tt> as always.
6608 Other applications use the <tt>stty erase</tt>
6609 character and <tt>kdch1</tt> for the two delete keys,
6610 with ASCII DEL being "delete previous character" and
6611 <tt>kdch1</tt> being "delete character under
6619 This will solve the problem except for the following
6626 Some terminals have a <tt><--</tt> key that cannot
6627 be made to produce anything except <tt>^H</tt>. On
6628 these terminals Emacs help will be unavailable on
6629 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6630 character takes precedence in Emacs, and has been set
6631 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6632 available) can be used instead.
6636 Some operating systems use <tt>^H</tt> for <tt>stty
6637 erase</tt>. However, modern telnet versions and all
6638 rlogin versions propagate <tt>stty</tt> settings, and
6639 almost all UNIX versions honour <tt>stty erase</tt>.
6640 Where the <tt>stty</tt> settings are not propagated
6641 correctly, things can be made to work by using
6642 <tt>stty</tt> manually.
6646 Some systems (including previous Debian versions) use
6647 <prgn>xmodmap</prgn> to arrange for both
6648 <tt><--</tt> and <tt>Delete</tt> to generate
6649 <tt>KB_Delete</tt>. We can change the behavior of
6650 their X clients using the same X resources that we use
6651 to do it for our own clients, or configure our clients
6652 using their resources when things are the other way
6653 around. On displays configured like this
6654 <tt>Delete</tt> will not work, but <tt><--</tt>
6659 Some operating systems have different <tt>kdch1</tt>
6660 settings in their <tt>terminfo</tt> database for
6661 <tt>xterm</tt> and others. On these systems the
6662 <tt>Delete</tt> key will not work correctly when you
6663 log in from a system conforming to our policy, but
6664 <tt><--</tt> will.
6671 <heading>Environment variables</heading>
6674 A program must not depend on environment variables to get
6675 reasonable defaults. (That's because these environment
6676 variables would have to be set in a system-wide
6677 configuration file like <file>/etc/profile</file>, which is not
6678 supported by all shells.)
6682 If a program usually depends on environment variables for its
6683 configuration, the program should be changed to fall back to
6684 a reasonable default configuration if these environment
6685 variables are not present. If this cannot be done easily
6686 (e.g., if the source code of a non-free program is not
6687 available), the program must be replaced by a small
6688 "wrapper" shell script which sets the environment variables
6689 if they are not already defined, and calls the original program.
6693 Here is an example of a wrapper script for this purpose:
6695 <example compact="compact">
6697 BAR=${BAR:-/var/lib/fubar}
6699 exec /usr/lib/foo/foo "$@"
6704 Furthermore, as <file>/etc/profile</file> is a configuration
6705 file of the <prgn>base-files</prgn> package, other packages must
6706 not put any environment variables or other commands into that
6711 <sect id="doc-base">
6712 <heading>Registering Documents using doc-base</heading>
6715 The <package>doc-base</package> package implements a
6716 flexible mechanism for handling and presenting
6717 documentation. The recommended practice is for every Debian
6718 package that provides online documentation (other than just
6719 manual pages) to register these documents with
6720 <package>doc-base</package> by installing a
6721 <package>doc-base</package> control file via the
6722 <prgn/install-docs/ script at installation time and
6723 de-register the manuals again when the package is removed.
6726 Please refer to the documentation that comes with the
6727 <package>doc-base</package> package for information and
6736 <heading>Files</heading>
6739 <heading>Binaries</heading>
6742 Two different packages must not install programs with
6743 different functionality but with the same filenames. (The
6744 case of two programs having the same functionality but
6745 different implementations is handled via "alternatives" or
6746 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6747 <ref id="conflicts"> respectively.) If this case happens,
6748 one of the programs must be renamed. The maintainers should
6749 report this to the <tt>debian-devel</tt> mailing list and
6750 try to find a consensus about which program will have to be
6751 renamed. If a consensus cannot be reached, <em>both</em>
6752 programs must be renamed.
6756 By default, when a package is being built, any binaries
6757 created should include debugging information, as well as
6758 being compiled with optimization. You should also turn on
6759 as many reasonable compilation warnings as possible; this
6760 makes life easier for porters, who can then look at build
6761 logs for possible problems. For the C programming language,
6762 this means the following compilation parameters should be
6764 <example compact="compact">
6766 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6768 INSTALL = install -s # (or use strip on the files in debian/tmp)
6773 Note that by default all installed binaries should be stripped,
6774 either by using the <tt>-s</tt> flag to
6775 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6776 the binaries after they have been copied into
6777 <file>debian/tmp</file> but before the tree is made into a
6782 Although binaries in the build tree should be compiled with
6783 debugging information by default, it can often be difficult to
6784 debug programs if they are also subjected to compiler
6785 optimization. For this reason, it is recommended to support the
6786 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6787 (see <ref id="debianrules-options">). This variable can contain
6788 several flags to change how a package is compiled and built.
6792 It is up to the package maintainer to decide what
6793 compilation options are best for the package. Certain
6794 binaries (such as computationally-intensive programs) will
6795 function better with certain flags (<tt>-O3</tt>, for
6796 example); feel free to use them. Please use good judgment
6797 here. Don't use flags for the sake of it; only use them
6798 if there is good reason to do so. Feel free to override
6799 the upstream author's ideas about which compilation
6800 options are best: they are often inappropriate for our
6806 <sect id="libraries">
6807 <heading>Libraries</heading>
6810 If the package is <strong>architecture: any</strong>, then
6811 the shared library compilation and linking flags must have
6812 <tt>-fPIC</tt>, or the package shall not build on some of
6813 the supported architectures<footnote>
6815 If you are using GCC, <tt>-fPIC</tt> produces code with
6816 relocatable position independent code, which is required for
6817 most architectures to create a shared library, with i386 and
6818 perhaps some others where non position independent code is
6819 permitted in a shared library.
6822 Position independent code may have a performance penalty,
6823 especially on <tt>i386</tt>. However, in most cases the
6824 speed penalty must be measured against the memory wasted on
6825 the few architectures where non position independent code is
6828 </footnote>. Any exception to this rule must be discussed on
6829 the mailing list <em>debian-devel@lists.debian.org</em>, and
6830 a rough consensus obtained. The reasons for not compiling
6831 with <tt>-fPIC</tt> flag must be recorded in the file
6832 <tt>README.Debian</tt>, and care must be taken to either
6833 restrict the architecture or arrange for <tt>-fPIC</tt> to
6834 be used on architectures where it is required.<footnote>
6836 Some of the reasons why this might be required is if the
6837 library contains hand crafted assembly code that is not
6838 relocatable, the speed penalty is excessive for compute
6839 intensive libs, and similar reasons.
6844 As to the static libraries, the common case is not to have
6845 relocatable code, since there is no benefit, unless in specific
6846 cases; therefore the static version must not be compiled
6847 with the <tt>-fPIC</tt> flag. Any exception to this rule
6848 should be discussed on the mailing list
6849 <em>debian-devel@lists.debian.org</em>, and the reasons for
6850 compiling with the <tt>-fPIC</tt> flag must be recorded in
6851 the file <tt>README.Debian</tt>. <footnote>
6853 Some of the reasons for linking static libraries with
6854 the <tt>-fPIC</tt> flag are if, for example, one needs a
6855 Perl API for a library that is under rapid development,
6856 and has an unstable API, so shared libraries are
6857 pointless at this phase of the library's development. In
6858 that case, since Perl needs a library with relocatable
6859 code, it may make sense to create a static library with
6860 relocatable code. Another reason cited is if you are
6861 distilling various libraries into a common shared
6862 library, like <tt>mklibs</tt> does in the Debian
6868 In other words, if both a shared and a static library is
6869 being built, each source unit (<tt>*.c</tt>, for example,
6870 for C files) will need to be compiled twice, for the normal
6874 You must specify the gcc option <tt>-D_REENTRANT</tt>
6875 when building a library (either static or shared) to make
6876 the library compatible with LinuxThreads.
6880 Although not enforced by the build tools, shared libraries
6881 must be linked against all libraries that they use symbols from
6882 in the same way that binaries are. This ensures the correct
6883 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6884 system and guarantees that all libraries can be safely opened
6885 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6886 option <tt>-Wl,-z,defs</tt> when building a shared library.
6887 Since this option enforces symbol resolution at build time,
6888 a missing library reference will be caught early as a fatal
6893 All installed shared libraries should be stripped with
6894 <example compact="compact">
6895 strip --strip-unneeded <var>your-lib</var>
6897 (The option <tt>--strip-unneeded</tt> makes
6898 <prgn>strip</prgn> remove only the symbols which aren't
6899 needed for relocation processing.) Shared libraries can
6900 function perfectly well when stripped, since the symbols for
6901 dynamic linking are in a separate part of the ELF object
6903 You might also want to use the options
6904 <tt>--remove-section=.comment</tt> and
6905 <tt>--remove-section=.note</tt> on both shared libraries
6906 and executables, and <tt>--strip-debug</tt> on static
6912 Note that under some circumstances it may be useful to
6913 install a shared library unstripped, for example when
6914 building a separate package to support debugging.
6918 Shared object files (often <file>.so</file> files) that are not
6919 public libraries, that is, they are not meant to be linked
6920 to by third party executables (binaries of other packages),
6921 should be installed in subdirectories of the
6922 <file>/usr/lib</file> directory. Such files are exempt from the
6923 rules that govern ordinary shared libraries, except that
6924 they must not be installed executable and should be
6926 A common example are the so-called "plug-ins",
6927 internal shared objects that are dynamically loaded by
6928 programs using <manref name="dlopen" section="3">.
6933 Packages containing shared libraries that may be linked to
6934 by other packages' binaries, but which for some
6935 <em>compelling</em> reason can not be installed in
6936 <file>/usr/lib</file> directory, may install the shared library
6937 files in subdirectories of the <file>/usr/lib</file> directory,
6938 in which case they should arrange to add that directory in
6939 <file>/etc/ld.so.conf</file> in the package's post-installation
6940 script, and remove it in the package's post-removal script.
6944 An ever increasing number of packages are using
6945 <prgn>libtool</prgn> to do their linking. The latest GNU
6946 libtools (>= 1.3a) can take advantage of the metadata in the
6947 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6948 files). The main advantage of <prgn>libtool</prgn>'s
6949 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6950 store and subsequently access metadata with respect to the
6951 libraries it builds. <prgn>libtool</prgn> will search for
6952 those files, which contain a lot of useful information about
6953 a library (such as library dependency information for static
6954 linking). Also, they're <em>essential</em> for programs
6955 using <tt>libltdl</tt>.<footnote>
6956 Although <prgn>libtool</prgn> is fully capable of
6957 linking against shared libraries which don't have
6958 <tt>.la</tt> files, as it is a mere shell script it can
6959 add considerably to the build time of a
6960 <prgn>libtool</prgn>-using package if that shell script
6961 has to derive all this information from first principles
6962 for each library every time it is linked. With the
6963 advent of <prgn>libtool</prgn> version 1.4 (and to a
6964 lesser extent <prgn>libtool</prgn> version 1.3), the
6965 <file>.la</file> files also store information about
6966 inter-library dependencies which cannot necessarily be
6967 derived after the <file>.la</file> file is deleted.
6972 Packages that use <prgn>libtool</prgn> to create shared
6973 libraries should include the <file>.la</file> files in the
6974 <tt>-dev</tt> package, unless the package relies on
6975 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6976 the <tt>.la</tt> files must go in the run-time library
6981 You must make sure that you use only released versions of
6982 shared libraries to build your packages; otherwise other
6983 users will not be able to run your binaries
6984 properly. Producing source packages that depend on
6985 unreleased compilers is also usually a bad
6992 <heading>Shared libraries</heading>
6994 This section has moved to <ref id="sharedlibs">.
7000 <heading>Scripts</heading>
7003 All command scripts, including the package maintainer
7004 scripts inside the package and used by <prgn>dpkg</prgn>,
7005 should have a <tt>#!</tt> line naming the shell to be used
7010 In the case of Perl scripts this should be
7011 <tt>#!/usr/bin/perl</tt>.
7015 When scripts are installed into a directory in the system
7016 PATH, the script name should not include an extension such
7017 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7018 language currently used to implement it.
7021 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7022 should almost certainly start with <tt>set -e</tt> so that
7023 errors are detected. Every script should use
7024 <tt>set -e</tt> or check the exit status of <em>every</em>
7029 Scripts may assume that <file>/bin/sh</file> implements the
7030 SUSv3 Shell Command Language<footnote>
7031 Single UNIX Specification, version 3, which is also IEEE
7032 1003.1-2004 (POSIX), and is available on the World Wide Web
7033 from <url id="http://www.unix.org/version3/online.html"
7034 name="The Open Group"> after free
7035 registration.</footnote>
7036 plus the following additional features not mandated by
7038 These features are in widespread use in the Linux community
7039 and are implemented in all of bash, dash, and ksh, the most
7040 common shells users may wish to use as <file>/bin/sh</file>.
7043 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7044 must not generate a newline.</item>
7045 <item><tt>test</tt>, if implemented as a shell built-in, must
7046 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7048 <item><tt>local</tt> to create a scoped variable must be
7049 supported; however, <tt>local</tt> may or may not preserve
7050 the variable value from an outer scope and may or may not
7051 support arguments more complex than simple variables. Only
7063 If a shell script requires non-SUSv3 features from the shell
7064 interpreter other than those listed above, the appropriate shell
7065 must be specified in the first line of the script (e.g.,
7066 <tt>#!/bin/bash</tt>) and the package must depend on the package
7067 providing the shell (unless the shell package is marked
7068 "Essential", as in the case of <prgn>bash</prgn>).
7072 You may wish to restrict your script to SUSv3 features plus the
7073 above set when possible so that it may use <file>/bin/sh</file>
7074 as its interpreter. If your script works with <prgn>dash</prgn>
7075 (originally called <prgn>ash</prgn>), it probably complies with
7076 the above requirements, but if you are in doubt, use
7077 <file>/bin/bash</file>.
7081 Perl scripts should check for errors when making any
7082 system calls, including <tt>open</tt>, <tt>print</tt>,
7083 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7087 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7088 scripting languages. See <em>Csh Programming Considered
7089 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7090 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7091 If an upstream package comes with <prgn>csh</prgn> scripts
7092 then you must make sure that they start with
7093 <tt>#!/bin/csh</tt> and make your package depend on the
7094 <prgn>c-shell</prgn> virtual package.
7098 Any scripts which create files in world-writeable
7099 directories (e.g., in <file>/tmp</file>) must use a
7100 mechanism which will fail atomically if a file with the same
7101 name already exists.
7105 The Debian base system provides the <prgn>tempfile</prgn>
7106 and <prgn>mktemp</prgn> utilities for use by scripts for
7113 <heading>Symbolic links</heading>
7116 In general, symbolic links within a top-level directory
7117 should be relative, and symbolic links pointing from one
7118 top-level directory into another should be absolute. (A
7119 top-level directory is a sub-directory of the root
7120 directory <file>/</file>.)
7124 In addition, symbolic links should be specified as short as
7125 possible, i.e., link targets like <file>foo/../bar</file> are
7130 Note that when creating a relative link using
7131 <prgn>ln</prgn> it is not necessary for the target of the
7132 link to exist relative to the working directory you're
7133 running <prgn>ln</prgn> from, nor is it necessary to change
7134 directory to the directory where the link is to be made.
7135 Simply include the string that should appear as the target
7136 of the link (this will be a pathname relative to the
7137 directory in which the link resides) as the first argument
7142 For example, in your <prgn>Makefile</prgn> or
7143 <file>debian/rules</file>, you can do things like:
7144 <example compact="compact">
7145 ln -fs gcc $(prefix)/bin/cc
7146 ln -fs gcc debian/tmp/usr/bin/cc
7147 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7148 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7153 A symbolic link pointing to a compressed file should always
7154 have the same file extension as the referenced file. (For
7155 example, if a file <file>foo.gz</file> is referenced by a
7156 symbolic link, the filename of the link has to end with
7157 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7162 <heading>Device files</heading>
7165 Packages must not include device files in the package file
7170 If a package needs any special device files that are not
7171 included in the base system, it must call
7172 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7173 after notifying the user<footnote>
7174 This notification could be done via a (low-priority)
7175 debconf message, or an echo (printf) statement.
7180 Packages must not remove any device files in the
7181 <prgn>postrm</prgn> or any other script. This is left to the
7182 system administrator.
7186 Debian uses the serial devices
7187 <file>/dev/ttyS*</file>. Programs using the old
7188 <file>/dev/cu*</file> devices should be changed to use
7189 <file>/dev/ttyS*</file>.
7193 <sect id="config-files">
7194 <heading>Configuration files</heading>
7197 <heading>Definitions</heading>
7201 <tag>configuration file</tag>
7203 A file that affects the operation of a program, or
7204 provides site- or host-specific information, or
7205 otherwise customizes the behavior of a program.
7206 Typically, configuration files are intended to be
7207 modified by the system administrator (if needed or
7208 desired) to conform to local policy or to provide
7209 more useful site-specific behavior.
7212 <tag><tt>conffile</tt></tag>
7214 A file listed in a package's <tt>conffiles</tt>
7215 file, and is treated specially by <prgn>dpkg</prgn>
7216 (see <ref id="configdetails">).
7222 The distinction between these two is important; they are
7223 not interchangeable concepts. Almost all
7224 <tt>conffile</tt>s are configuration files, but many
7225 configuration files are not <tt>conffiles</tt>.
7229 As noted elsewhere, <file>/etc/init.d</file> scripts,
7230 <file>/etc/default</file> files, scripts installed in
7231 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7232 configuration installed in <file>/etc/cron.d</file> must be
7233 treated as configuration files. In general, any script that
7234 embeds configuration information is de-facto a configuration
7235 file and should be treated as such.
7240 <heading>Location</heading>
7243 Any configuration files created or used by your package
7244 must reside in <file>/etc</file>. If there are several,
7245 consider creating a subdirectory of <file>/etc</file>
7246 named after your package.
7250 If your package creates or uses configuration files
7251 outside of <file>/etc</file>, and it is not feasible to modify
7252 the package to use <file>/etc</file> directly, put the files
7253 in <file>/etc</file> and create symbolic links to those files
7254 from the location that the package requires.
7259 <heading>Behavior</heading>
7262 Configuration file handling must conform to the following
7264 <list compact="compact">
7266 local changes must be preserved during a package
7270 configuration files must be preserved when the
7271 package is removed, and only deleted when the
7278 The easy way to achieve this behavior is to make the
7279 configuration file a <tt>conffile</tt>. This is
7280 appropriate only if it is possible to distribute a default
7281 version that will work for most installations, although
7282 some system administrators may choose to modify it. This
7283 implies that the default version will be part of the
7284 package distribution, and must not be modified by the
7285 maintainer scripts during installation (or at any other
7290 In order to ensure that local changes are preserved
7291 correctly, no package may contain or make hard links to
7292 conffiles.<footnote>
7293 Rationale: There are two problems with hard links.
7294 The first is that some editors break the link while
7295 editing one of the files, so that the two files may
7296 unwittingly become unlinked and different. The second
7297 is that <prgn>dpkg</prgn> might break the hard link
7298 while upgrading <tt>conffile</tt>s.
7303 The other way to do it is via the maintainer scripts. In
7304 this case, the configuration file must not be listed as a
7305 <tt>conffile</tt> and must not be part of the package
7306 distribution. If the existence of a file is required for
7307 the package to be sensibly configured it is the
7308 responsibility of the package maintainer to provide
7309 maintainer scripts which correctly create, update and
7310 maintain the file and remove it on purge. (See <ref
7311 id="maintainerscripts"> for more information.) These
7312 scripts must be idempotent (i.e., must work correctly if
7313 <prgn>dpkg</prgn> needs to re-run them due to errors
7314 during installation or removal), must cope with all the
7315 variety of ways <prgn>dpkg</prgn> can call maintainer
7316 scripts, must not overwrite or otherwise mangle the user's
7317 configuration without asking, must not ask unnecessary
7318 questions (particularly during upgrades), and must
7319 otherwise be good citizens.
7323 The scripts are not required to configure every possible
7324 option for the package, but only those necessary to get
7325 the package running on a given system. Ideally the
7326 sysadmin should not have to do any configuration other
7327 than that done (semi-)automatically by the
7328 <prgn>postinst</prgn> script.
7332 A common practice is to create a script called
7333 <file><var>package</var>-configure</file> and have the
7334 package's <prgn>postinst</prgn> call it if and only if the
7335 configuration file does not already exist. In certain
7336 cases it is useful for there to be an example or template
7337 file which the maintainer scripts use. Such files should
7338 be in <file>/usr/share/<var>package</var></file> or
7339 <file>/usr/lib/<var>package</var></file> (depending on whether
7340 they are architecture-independent or not). There should
7341 be symbolic links to them from
7342 <file>/usr/share/doc/<var>package</var>/examples</file> if
7343 they are examples, and should be perfectly ordinary
7344 <prgn>dpkg</prgn>-handled files (<em>not</em>
7345 configuration files).
7349 These two styles of configuration file handling must
7350 not be mixed, for that way lies madness:
7351 <prgn>dpkg</prgn> will ask about overwriting the file
7352 every time the package is upgraded.
7357 <heading>Sharing configuration files</heading>
7360 Packages which specify the same file as a
7361 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7362 with each other. (This is an instance of the general rule
7363 about not sharing files. Note that neither alternatives
7364 nor diversions are likely to be appropriate in this case;
7365 in particular, <prgn>dpkg</prgn> does not handle diverted
7366 <tt>conffile</tt>s well.)
7370 The maintainer scripts must not alter a <tt>conffile</tt>
7371 of <em>any</em> package, including the one the scripts
7376 If two or more packages use the same configuration file
7377 and it is reasonable for both to be installed at the same
7378 time, one of these packages must be defined as
7379 <em>owner</em> of the configuration file, i.e., it will be
7380 the package which handles that file as a configuration
7381 file. Other packages that use the configuration file must
7382 depend on the owning package if they require the
7383 configuration file to operate. If the other package will
7384 use the configuration file if present, but is capable of
7385 operating without it, no dependency need be declared.
7389 If it is desirable for two or more related packages to
7390 share a configuration file <em>and</em> for all of the
7391 related packages to be able to modify that configuration
7392 file, then the following should be done:
7393 <enumlist compact="compact">
7395 One of the related packages (the "owning" package)
7396 will manage the configuration file with maintainer
7397 scripts as described in the previous section.
7400 The owning package should also provide a program
7401 that the other packages may use to modify the
7405 The related packages must use the provided program
7406 to make any desired modifications to the
7407 configuration file. They should either depend on
7408 the core package to guarantee that the configuration
7409 modifier program is available or accept gracefully
7410 that they cannot modify the configuration file if it
7411 is not. (This is in addition to the fact that the
7412 configuration file may not even be present in the
7419 Sometimes it's appropriate to create a new package which
7420 provides the basic infrastructure for the other packages
7421 and which manages the shared configuration files. (The
7422 <tt>sgml-base</tt> package is a good example.)
7427 <heading>User configuration files ("dotfiles")</heading>
7430 The files in <file>/etc/skel</file> will automatically be
7431 copied into new user accounts by <prgn>adduser</prgn>.
7432 No other program should reference the files in
7433 <file>/etc/skel</file>.
7437 Therefore, if a program needs a dotfile to exist in
7438 advance in <file>$HOME</file> to work sensibly, that dotfile
7439 should be installed in <file>/etc/skel</file> and treated as a
7444 However, programs that require dotfiles in order to
7445 operate sensibly are a bad thing, unless they do create
7446 the dotfiles themselves automatically.
7450 Furthermore, programs should be configured by the Debian
7451 default installation to behave as closely to the upstream
7452 default behavior as possible.
7456 Therefore, if a program in a Debian package needs to be
7457 configured in some way in order to operate sensibly, that
7458 should be done using a site-wide configuration file placed
7459 in <file>/etc</file>. Only if the program doesn't support a
7460 site-wide default configuration and the package maintainer
7461 doesn't have time to add it may a default per-user file be
7462 placed in <file>/etc/skel</file>.
7466 <file>/etc/skel</file> should be as empty as we can make it.
7467 This is particularly true because there is no easy (or
7468 necessarily desirable) mechanism for ensuring that the
7469 appropriate dotfiles are copied into the accounts of
7470 existing users when a package is installed.
7476 <heading>Log files</heading>
7478 Log files should usually be named
7479 <file>/var/log/<var>package</var>.log</file>. If you have many
7480 log files, or need a separate directory for permission
7481 reasons (<file>/var/log</file> is writable only by
7482 <file>root</file>), you should usually create a directory named
7483 <file>/var/log/<var>package</var></file> and place your log
7488 Log files must be rotated occasionally so that they don't
7489 grow indefinitely; the best way to do this is to drop a log
7490 rotation configuration file into the directory
7491 <file>/etc/logrotate.d</file> and use the facilities provided by
7492 logrotate.<footnote>
7494 The traditional approach to log files has been to set up
7495 <em>ad hoc</em> log rotation schemes using simple shell
7496 scripts and cron. While this approach is highly
7497 customizable, it requires quite a lot of sysadmin work.
7498 Even though the original Debian system helped a little
7499 by automatically installing a system which can be used
7500 as a template, this was deemed not enough.
7504 The use of <prgn>logrotate</prgn>, a program developed
7505 by Red Hat, is better, as it centralizes log management.
7506 It has both a configuration file
7507 (<file>/etc/logrotate.conf</file>) and a directory where
7508 packages can drop their individual log rotation
7509 configurations (<file>/etc/logrotate.d</file>).
7512 Here is a good example for a logrotate config
7513 file (for more information see <manref name="logrotate"
7515 <example compact="compact">
7516 /var/log/foo/*.log {
7521 /etc/init.d/foo force-reload
7525 This rotates all files under <file>/var/log/foo</file>, saves 12
7526 compressed generations, and forces the daemon to reload its
7527 configuration information after the log rotation.
7531 Log files should be removed when the package is
7532 purged (but not when it is only removed). This should be
7533 done by the <prgn>postrm</prgn> script when it is called
7534 with the argument <tt>purge</tt> (see <ref
7535 id="removedetails">).
7540 <heading>Permissions and owners</heading>
7543 The rules in this section are guidelines for general use.
7544 If necessary you may deviate from the details below.
7545 However, if you do so you must make sure that what is done
7546 is secure and you should try to be as consistent as possible
7547 with the rest of the system. You should probably also
7548 discuss it on <prgn>debian-devel</prgn> first.
7552 Files should be owned by <tt>root:root</tt>, and made
7553 writable only by the owner and universally readable (and
7554 executable, if appropriate), that is mode 644 or 755.
7558 Directories should be mode 755 or (for group-writability)
7559 mode 2775. The ownership of the directory should be
7560 consistent with its mode: if a directory is mode 2775, it
7561 should be owned by the group that needs write access to
7564 When a package is upgraded, and the owner or permissions
7565 of a file included in the package has changed, dpkg
7566 arranges for the ownership and permissions to be
7567 correctly set upon installation. However, this does not
7568 extend to directories; the permissions and ownership of
7569 directories already on the system does not change on
7570 install or upgrade of packages. This makes sense, since
7571 otherwise common directories like <tt>/usr</tt> would
7572 always be in flux. To correctly change permissions of a
7573 directory the package owns, explicit action is required,
7574 usually in the <tt>postinst</tt> script. Care must be
7575 taken to handle downgrades as well, in that case.
7582 Setuid and setgid executables should be mode 4755 or 2755
7583 respectively, and owned by the appropriate user or group.
7584 They should not be made unreadable (modes like 4711 or
7585 2711 or even 4111); doing so achieves no extra security,
7586 because anyone can find the binary in the freely available
7587 Debian package; it is merely inconvenient. For the same
7588 reason you should not restrict read or execute permissions
7589 on non-set-id executables.
7593 Some setuid programs need to be restricted to particular
7594 sets of users, using file permissions. In this case they
7595 should be owned by the uid to which they are set-id, and by
7596 the group which should be allowed to execute them. They
7597 should have mode 4754; again there is no point in making
7598 them unreadable to those users who must not be allowed to
7603 It is possible to arrange that the system administrator can
7604 reconfigure the package to correspond to their local
7605 security policy by changing the permissions on a binary:
7606 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7607 described below.<footnote>
7608 Ordinary files installed by <prgn>dpkg</prgn> (as
7609 opposed to <tt>conffile</tt>s and other similar objects)
7610 normally have their permissions reset to the distributed
7611 permissions when the package is reinstalled. However,
7612 the use of <prgn>dpkg-statoverride</prgn> overrides this
7613 default behavior. If you use this method, you should
7614 remember to describe <prgn>dpkg-statoverride</prgn> in
7615 the package documentation; being a relatively new
7616 addition to Debian, it is probably not yet well-known.
7618 Another method you should consider is to create a group for
7619 people allowed to use the program(s) and make any setuid
7620 executables executable only by that group.
7624 If you need to create a new user or group for your package
7625 there are two possibilities. Firstly, you may need to
7626 make some files in the binary package be owned by this
7627 user or group, or you may need to compile the user or
7628 group id (rather than just the name) into the binary
7629 (though this latter should be avoided if possible, as in
7630 this case you need a statically allocated id).</p>
7633 If you need a statically allocated id, you must ask for a
7634 user or group id from the <tt>base-passwd</tt> maintainer,
7635 and must not release the package until you have been
7636 allocated one. Once you have been allocated one you must
7637 either make the package depend on a version of the
7638 <tt>base-passwd</tt> package with the id present in
7639 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7640 your package to create the user or group itself with the
7641 correct id (using <tt>adduser</tt>) in its
7642 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7643 the <prgn>postinst</prgn> is to be preferred if it is
7644 possible, otherwise a pre-dependency will be needed on the
7645 <tt>adduser</tt> package.)
7649 On the other hand, the program might be able to determine
7650 the uid or gid from the user or group name at runtime, so
7651 that a dynamically allocated id can be used. In this case
7652 you should choose an appropriate user or group name,
7653 discussing this on <prgn>debian-devel</prgn> and checking
7654 with the <package/base-passwd/ maintainer that it is unique and that
7655 they do not wish you to use a statically allocated id
7656 instead. When this has been checked you must arrange for
7657 your package to create the user or group if necessary using
7658 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7659 <prgn>postinst</prgn> script (again, the latter is to be
7660 preferred if it is possible).
7664 Note that changing the numeric value of an id associated
7665 with a name is very difficult, and involves searching the
7666 file system for all appropriate files. You need to think
7667 carefully whether a static or dynamic id is required, since
7668 changing your mind later will cause problems.
7671 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7673 This section is not intended as policy, but as a
7674 description of the use of <prgn>dpkg-statoverride</prgn>.
7678 If a system administrator wishes to have a file (or
7679 directory or other such thing) installed with owner and
7680 permissions different from those in the distributed Debian
7681 package, they can use the <prgn>dpkg-statoverride</prgn>
7682 program to instruct <prgn>dpkg</prgn> to use the different
7683 settings every time the file is installed. Thus the
7684 package maintainer should distribute the files with their
7685 normal permissions, and leave it for the system
7686 administrator to make any desired changes. For example, a
7687 daemon which is normally required to be setuid root, but
7688 in certain situations could be used without being setuid,
7689 should be installed setuid in the <tt>.deb</tt>. Then the
7690 local system administrator can change this if they wish.
7691 If there are two standard ways of doing it, the package
7692 maintainer can use <tt>debconf</tt> to find out the
7693 preference, and call <prgn>dpkg-statoverride</prgn> in the
7694 maintainer script if necessary to accommodate the system
7695 administrator's choice. Care must be taken during
7696 upgrades to not override an existing setting.
7700 Given the above, <prgn>dpkg-statoverride</prgn> is
7701 essentially a tool for system administrators and would not
7702 normally be needed in the maintainer scripts. There is
7703 one type of situation, though, where calls to
7704 <prgn>dpkg-statoverride</prgn> would be needed in the
7705 maintainer scripts, and that involves packages which use
7706 dynamically allocated user or group ids. In such a
7707 situation, something like the following idiom can be very
7708 helpful in the package's <prgn>postinst</prgn>, where
7709 <tt>sysuser</tt> is a dynamically allocated id:
7711 for i in /usr/bin/foo /usr/sbin/bar
7713 # only do something when no setting exists
7714 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7716 #include: debconf processing, question about foo and bar
7717 if [ "$RET" = "true" ] ; then
7718 dpkg-statoverride --update --add sysuser root 4755 $i
7723 The corresponding <tt>dpkg-statoverride --remove</tt>
7724 calls can then be made unconditionally when the package is
7732 <chapt id="customized-programs">
7733 <heading>Customized programs</heading>
7735 <sect id="arch-spec">
7736 <heading>Architecture specification strings</heading>
7739 If a program needs to specify an <em>architecture specification
7740 string</em> in some place, it should select one of the
7741 strings provided by <tt>dpkg-architecture -L</tt>. The
7742 strings are in the format
7743 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7744 is sometimes elided, as when the OS is Linux.<footnote>
7745 <p>Currently, the strings are:
7746 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7747 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7748 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7749 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7750 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7751 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7752 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7753 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7754 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7755 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7756 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7757 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7758 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7759 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7760 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7761 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7762 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7763 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7764 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7765 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7766 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7767 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7768 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7769 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7770 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7771 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7772 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7773 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7774 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7775 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7776 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7777 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7778 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7779 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7780 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7781 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7782 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7788 Note that we don't want to use
7789 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7790 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7791 since this would make our programs incompatible with other
7792 Linux distributions. We also don't use something like
7793 <tt><var>arch</var>-unknown-linux</tt>, since the
7794 <tt>unknown</tt> does not look very good.
7799 <heading>Daemons</heading>
7802 The configuration files <file>/etc/services</file>,
7803 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7804 by the <prgn>netbase</prgn> package and must not be modified
7809 If a package requires a new entry in one of these files, the
7810 maintainer should get in contact with the
7811 <prgn>netbase</prgn> maintainer, who will add the entries
7812 and release a new version of the <prgn>netbase</prgn>
7817 The configuration file <file>/etc/inetd.conf</file> must not be
7818 modified by the package's scripts except via the
7819 <prgn>update-inetd</prgn> script or the
7820 <file>DebianNet.pm</file> Perl module. See their documentation
7821 for details on how to add entries.
7825 If a package wants to install an example entry into
7826 <file>/etc/inetd.conf</file>, the entry must be preceded with
7827 exactly one hash character (<tt>#</tt>). Such lines are
7828 treated as "commented out by user" by the
7829 <prgn>update-inetd</prgn> script and are not changed or
7830 activated during package updates.
7835 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7839 Some programs need to create pseudo-ttys. This should be done
7840 using Unix98 ptys if the C library supports it. The resulting
7841 program must not be installed setuid root, unless that
7842 is required for other functionality.
7846 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7847 <file>/var/log/lastlog</file> must be installed writable by
7848 group <tt>utmp</tt>. Programs which need to modify those
7849 files must be installed setgid <tt>utmp</tt>.
7854 <heading>Editors and pagers</heading>
7857 Some programs have the ability to launch an editor or pager
7858 program to edit or display a text document. Since there are
7859 lots of different editors and pagers available in the Debian
7860 distribution, the system administrator and each user should
7861 have the possibility to choose their preferred editor and
7866 In addition, every program should choose a good default
7867 editor/pager if none is selected by the user or system
7872 Thus, every program that launches an editor or pager must
7873 use the EDITOR or PAGER environment variable to determine
7874 the editor or pager the user wishes to use. If these
7875 variables are not set, the programs <file>/usr/bin/editor</file>
7876 and <file>/usr/bin/pager</file> should be used, respectively.
7880 These two files are managed through the <prgn>dpkg</prgn>
7881 "alternatives" mechanism. Thus every package providing an
7882 editor or pager must call the
7883 <prgn>update-alternatives</prgn> script to register these
7888 If it is very hard to adapt a program to make use of the
7889 EDITOR or PAGER variables, that program may be configured to
7890 use <file>/usr/bin/sensible-editor</file> and
7891 <file>/usr/bin/sensible-pager</file> as the editor or pager
7892 program respectively. These are two scripts provided in the
7893 Debian base system that check the EDITOR and PAGER variables
7894 and launch the appropriate program, and fall back to
7895 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7896 variable is not set.
7900 A program may also use the VISUAL environment variable to
7901 determine the user's choice of editor. If it exists, it
7902 should take precedence over EDITOR. This is in fact what
7903 <file>/usr/bin/sensible-editor</file> does.
7907 It is not required for a package to depend on
7908 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7909 package to provide such virtual packages.<footnote>
7910 The Debian base system already provides an editor and a
7916 <sect id="web-appl">
7917 <heading>Web servers and applications</heading>
7920 This section describes the locations and URLs that should
7921 be used by all web servers and web applications in the
7928 Cgi-bin executable files are installed in the
7930 <example compact="compact">
7931 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7933 and should be referred to as
7934 <example compact="compact">
7935 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7941 <p>Access to HTML documents</p>
7944 HTML documents for a package are stored in
7945 <file>/usr/share/doc/<var>package</var></file>
7946 and can be referred to as
7947 <example compact="compact">
7948 http://localhost/doc/<var>package</var>/<var>filename</var>
7953 The web server should restrict access to the document
7954 tree so that only clients on the same host can read
7955 the documents. If the web server does not support such
7956 access controls, then it should not provide access at
7957 all, or ask about providing access during installation.
7962 <p>Access to images</p>
7964 It is recommended that images for a package be stored
7965 in <tt>/usr/share/images/<var>package</var></tt> and
7966 may be referred to through an alias <tt>/images/</tt>
7969 http://localhost/images/<package>/<filename>
7976 <p>Web Document Root</p>
7979 Web Applications should try to avoid storing files in
7980 the Web Document Root. Instead they should use the
7981 /usr/share/doc/<var>package</var> directory for
7982 documents and register the Web Application via the
7983 <package>doc-base</package> package. If access to the
7984 web document root is unavoidable then use
7985 <example compact="compact">
7988 as the Document Root. This might be just a symbolic
7989 link to the location where the system administrator
7990 has put the real document root.
7993 <item><p>Providing httpd and/or httpd-cgi</p>
7995 All web servers should provide the virtual package
7996 <tt>httpd</tt>. If a web server has CGI support it should
7997 provide <tt>httpd-cgi</tt> additionally.
8000 All web applications which do not contain CGI scripts should
8001 depend on <tt>httpd</tt>, all those web applications which
8002 <tt>do</tt> contain CGI scripts, should depend on
8010 <sect id="mail-transport-agents">
8011 <heading>Mail transport, delivery and user agents</heading>
8014 Debian packages which process electronic mail, whether mail
8015 user agents (MUAs) or mail transport agents (MTAs), must
8016 ensure that they are compatible with the configuration
8017 decisions below. Failure to do this may result in lost
8018 mail, broken <tt>From:</tt> lines, and other serious brain
8023 The mail spool is <file>/var/mail</file> and the interface to
8024 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8025 the FHS). On older systems, the mail spool may be
8026 physically located in <file>/var/spool/mail</file>, but all
8027 access to the mail spool should be via the
8028 <file>/var/mail</file> symlink. The mail spool is part of the
8029 base system and not part of the MTA package.
8033 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8034 programs (such as IMAP daemons) must lock the mailbox in an
8035 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8036 be combined with dot locking. To avoid deadlocks, a program
8037 should use <tt>fcntl()</tt> first and dot locking after
8038 this, or alternatively implement the two locking methods in
8039 a non blocking way<footnote>
8040 If it is not possible to establish both locks, the
8041 system shouldn't wait for the second lock to be
8042 established, but remove the first lock, wait a (random)
8043 time, and start over locking again.
8044 </footnote>. Using the functions <tt>maillock</tt> and
8045 <tt>mailunlock</tt> provided by the
8046 <tt>liblockfile*</tt><footnote>
8047 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8048 to use these functions.
8049 </footnote> packages is the recommended way to realize this.
8053 Mailboxes are generally mode 660
8054 <tt><var>user</var>:mail</tt> unless the system
8055 administrator has chosen otherwise. A MUA may remove a
8056 mailbox (unless it has nonstandard permissions) in which
8057 case the MTA or another MUA must recreate it if needed.
8058 Mailboxes must be writable by group mail.
8062 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8063 be setgid mail to do the locking mentioned above (and
8064 must obviously avoid accessing other users' mailboxes
8065 using this privilege).</p>
8068 <file>/etc/aliases</file> is the source file for the system mail
8069 aliases (e.g., postmaster, usenet, etc.), it is the one
8070 which the sysadmin and <prgn>postinst</prgn> scripts may
8071 edit. After <file>/etc/aliases</file> is edited the program or
8072 human editing it must call <prgn>newaliases</prgn>. All MTA
8073 packages must come with a <prgn>newaliases</prgn> program,
8074 even if it does nothing, but older MTA packages did not do
8075 this so programs should not fail if <prgn>newaliases</prgn>
8076 cannot be found. Note that because of this, all MTA
8077 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8078 <tt>Replaces: mail-transport-agent</tt> control file
8083 The convention of writing <tt>forward to
8084 <var>address</var></tt> in the mailbox itself is not
8085 supported. Use a <tt>.forward</tt> file instead.</p>
8088 The <prgn>rmail</prgn> program used by UUCP
8089 for incoming mail should be <file>/usr/sbin/rmail</file>.
8090 Likewise, <prgn>rsmtp</prgn>, for receiving
8091 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8095 If your package needs to know what hostname to use on (for
8096 example) outgoing news and mail messages which are generated
8097 locally, you should use the file <file>/etc/mailname</file>. It
8098 will contain the portion after the username and <tt>@</tt>
8099 (at) sign for email addresses of users on the machine
8100 (followed by a newline).
8104 Such a package should check for the existence of this file
8105 when it is being configured. If it exists, it should be
8106 used without comment, although an MTA's configuration script
8107 may wish to prompt the user even if it finds that this file
8108 exists. If the file does not exist, the package should
8109 prompt the user for the value (preferably using
8110 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8111 as well as using it in the package's configuration. The
8112 prompt should make it clear that the name will not just be
8113 used by that package. For example, in this situation the
8114 <tt>inn</tt> package could say something like:
8115 <example compact="compact">
8116 Please enter the "mail name" of your system. This is the
8117 hostname portion of the address to be shown on outgoing
8118 news and mail messages. The default is
8119 <var>syshostname</var>, your system's host name. Mail
8120 name ["<var>syshostname</var>"]:
8122 where <var>syshostname</var> is the output of <tt>hostname
8128 <heading>News system configuration</heading>
8131 All the configuration files related to the NNTP (news)
8132 servers and clients should be located under
8133 <file>/etc/news</file>.</p>
8136 There are some configuration issues that apply to a number
8137 of news clients and server packages on the machine. These
8141 <tag><file>/etc/news/organization</file></tag>
8143 A string which should appear as the
8144 organization header for all messages posted
8145 by NNTP clients on the machine
8148 <tag><file>/etc/news/server</file></tag>
8150 Contains the FQDN of the upstream NNTP
8151 server, or localhost if the local machine is
8156 Other global files may be added as required for cross-package news
8163 <heading>Programs for the X Window System</heading>
8166 <heading>Providing X support and package priorities</heading>
8169 Programs that can be configured with support for the X
8170 Window System must be configured to do so and must declare
8171 any package dependencies necessary to satisfy their
8172 runtime requirements when using the X Window System. If
8173 such a package is of higher priority than the X packages
8174 on which it depends, it is required that either the
8175 X-specific components be split into a separate package, or
8176 that an alternative version of the package, which includes
8177 X support, be provided, or that the package's priority be
8183 <heading>Packages providing an X server</heading>
8186 Packages that provide an X server that, directly or
8187 indirectly, communicates with real input and display
8188 hardware should declare in their control data that they
8189 provide the virtual package <tt>xserver</tt>.<footnote>
8190 This implements current practice, and provides an
8191 actual policy for usage of the <tt>xserver</tt>
8192 virtual package which appears in the virtual packages
8193 list. In a nutshell, X servers that interface
8194 directly with the display and input hardware or via
8195 another subsystem (e.g., GGI) should provide
8196 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8197 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8203 <heading>Packages providing a terminal emulator</heading>
8206 Packages that provide a terminal emulator for the X Window
8207 System which meet the criteria listed below should declare
8208 in their control data that they provide the virtual
8209 package <tt>x-terminal-emulator</tt>. They should also
8210 register themselves as an alternative for
8211 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8216 To be an <tt>x-terminal-emulator</tt>, a program must:
8217 <list compact="compact">
8219 Be able to emulate a DEC VT100 terminal, or a
8220 compatible terminal.
8224 Support the command-line option <tt>-e
8225 <var>command</var></tt>, which creates a new
8226 terminal window<footnote>
8227 "New terminal window" does not necessarily mean
8228 a new top-level X window directly parented by
8229 the window manager; it could, if the terminal
8230 emulator application were so coded, be a new
8231 "view" in a multiple-document interface (MDI).
8233 and runs the specified <var>command</var>,
8234 interpreting the entirety of the rest of the command
8235 line as a command to pass straight to exec, in the
8236 manner that <tt>xterm</tt> does.
8240 Support the command-line option <tt>-T
8241 <var>title</var></tt>, which creates a new terminal
8242 window with the window title <var>title</var>.
8249 <heading>Packages providing a window manager</heading>
8252 Packages that provide a window manager should declare in
8253 their control data that they provide the virtual package
8254 <tt>x-window-manager</tt>. They should also register
8255 themselves as an alternative for
8256 <file>/usr/bin/x-window-manager</file>, with a priority
8257 calculated as follows:
8258 <list compact="compact">
8260 Start with a priority of 20.
8264 If the window manager supports the Debian menu
8265 system, add 20 points if this support is available
8266 in the package's default configuration (i.e., no
8267 configuration files belonging to the system or user
8268 have to be edited to activate the feature); if
8269 configuration files must be modified, add only 10
8275 If the window manager complies with <url
8276 id="http://www.freedesktop.org/Standards/wm-spec"
8277 name="The Window Manager Specification Project">,
8278 written by the <url id="http://www.freedesktop.org/"
8279 name="Free Desktop Group">, add 40 points.
8283 If the window manager permits the X session to be
8284 restarted using a <em>different</em> window manager
8285 (without killing the X server) in its default
8286 configuration, add 10 points; otherwise add none.
8293 <heading>Packages providing fonts</heading>
8296 Packages that provide fonts for the X Window
8298 For the purposes of Debian Policy, a "font for the X
8299 Window System" is one which is accessed via X protocol
8300 requests. Fonts for the Linux console, for PostScript
8301 renderer, or any other purpose, do not fit this
8302 definition. Any tool which makes such fonts available
8303 to the X Window System, however, must abide by this
8306 must do a number of things to ensure that they are both
8307 available without modification of the X or font server
8308 configuration, and that they do not corrupt files used by
8309 other font packages to register information about
8313 Fonts of any type supported by the X Window System
8314 must be in a separate binary package from any
8315 executables, libraries, or documentation (except
8316 that specific to the fonts shipped, such as their
8317 license information). If one or more of the fonts
8318 so packaged are necessary for proper operation of
8319 the package with which they are associated the font
8320 package may be Recommended; if the fonts merely
8321 provide an enhancement, a Suggests relationship may
8322 be used. Packages must not Depend on font
8324 This is because the X server may retrieve fonts
8325 from the local file system or over the network
8326 from an X font server; the Debian package system
8327 is empowered to deal only with the local
8333 BDF fonts must be converted to PCF fonts with the
8334 <prgn>bdftopcf</prgn> utility (available in the
8335 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8336 placed in a directory that corresponds to their
8338 <list compact="compact">
8340 100 dpi fonts must be placed in
8341 <file>/usr/share/fonts/X11/100dpi/</file>.
8345 75 dpi fonts must be placed in
8346 <file>/usr/share/fonts/X11/75dpi/</file>.
8350 Character-cell fonts, cursor fonts, and other
8351 low-resolution fonts must be placed in
8352 <file>/usr/share/fonts/X11/misc/</file>.
8358 Speedo fonts must be placed in
8359 <file>/usr/share/fonts/X11/Speedo/</file>.
8363 Type 1 fonts must be placed in
8364 <file>/usr/share/fonts/X11/Type1/</file>. If font
8365 metric files are available, they must be placed here
8370 Subdirectories of <file>/usr/share/fonts/X11/</file>
8371 other than those listed above must be neither
8372 created nor used. (The <file>PEX</file>, <file>CID</file>,
8373 and <file>cyrillic</file> directories are excepted for
8374 historical reasons, but installation of files into
8375 these directories remains discouraged.)
8379 Font packages may, instead of placing files directly
8380 in the X font directories listed above, provide
8381 symbolic links in that font directory pointing to
8382 the files' actual location in the filesystem. Such
8383 a location must comply with the FHS.
8387 Font packages should not contain both 75dpi and
8388 100dpi versions of a font. If both are available,
8389 they should be provided in separate binary packages
8390 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8391 the names of the packages containing the
8392 corresponding fonts.
8396 Fonts destined for the <file>misc</file> subdirectory
8397 should not be included in the same package as 75dpi
8398 or 100dpi fonts; instead, they should be provided in
8399 a separate package with <tt>-misc</tt> appended to
8404 Font packages must not provide the files
8405 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8406 <file>fonts.scale</file> in a font directory:
8409 <file>fonts.dir</file> files must not be provided at all.
8413 <file>fonts.alias</file> and <file>fonts.scale</file>
8414 files, if needed, should be provided in the
8416 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8417 where <var>fontdir</var> is the name of the
8419 <file>/usr/share/fonts/X11/</file> where the
8420 package's corresponding fonts are stored
8421 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8422 <var>package</var> is the name of the package
8423 that provides these fonts, and
8424 <var>extension</var> is either <tt>scale</tt>
8425 or <tt>alias</tt>, whichever corresponds to
8432 Font packages must declare a dependency on
8433 <tt>xfonts-utils</tt> in their control
8438 Font packages that provide one or more
8439 <file>fonts.scale</file> files as described above must
8440 invoke <prgn>update-fonts-scale</prgn> on each
8441 directory into which they installed fonts
8442 <em>before</em> invoking
8443 <prgn>update-fonts-dir</prgn> on that directory.
8444 This invocation must occur in both the
8445 <prgn>postinst</prgn> (for all arguments) and
8446 <prgn>postrm</prgn> (for all arguments except
8447 <tt>upgrade</tt>) scripts.
8451 Font packages that provide one or more
8452 <file>fonts.alias</file> files as described above must
8453 invoke <prgn>update-fonts-alias</prgn> on each
8454 directory into which they installed fonts. This
8455 invocation must occur in both the
8456 <prgn>postinst</prgn> (for all arguments) and
8457 <prgn>postrm</prgn> (for all arguments except
8458 <tt>upgrade</tt>) scripts.
8462 Font packages must invoke
8463 <prgn>update-fonts-dir</prgn> on each directory into
8464 which they installed fonts. This invocation must
8465 occur in both the <prgn>postinst</prgn> (for all
8466 arguments) and <prgn>postrm</prgn> (for all
8467 arguments except <tt>upgrade</tt>) scripts.
8471 Font packages must not provide alias names for the
8472 fonts they include which collide with alias names
8473 already in use by fonts already packaged.
8477 Font packages must not provide fonts with the same
8478 XLFD registry name as another font already packaged.
8485 <heading>Application defaults files</heading>
8488 Application defaults files must be installed in the
8489 directory <file>/etc/X11/app-defaults/</file> (use of a
8490 localized subdirectory of <file>/etc/X11/</file> as described
8491 in the <em>X Toolkit Intrinsics - C Language
8492 Interface</em> manual is also permitted). They must be
8493 registered as <tt>conffile</tt>s or handled as
8494 configuration files.
8498 Customization of programs' X resources may also be
8499 supported with the provision of a file with the same name
8500 as that of the package placed in the
8501 <file>/etc/X11/Xresources/</file> directory, which must
8502 registered as a <tt>conffile</tt> or handled as a
8503 configuration file.<footnote>
8504 Note that this mechanism is not the same as using
8505 app-defaults; app-defaults are tied to the client
8506 binary on the local file system, whereas X resources
8507 are stored in the X server and affect all connecting
8514 <heading>Installation directory issues</heading>
8517 Packages using the X Window System should not be
8518 configured to install files under the
8519 <file>/usr/X11R6/</file> directory. The
8520 <file>/usr/X11R6/</file> directory hierarchy should be
8521 regarded as obsolete.
8525 Programs that use GNU <prgn>autoconf</prgn> and
8526 <prgn>automake</prgn> are usually easily configured at
8527 compile time to use <file>/usr/</file> instead of
8528 <file>/usr/X11R6/</file>, and this should be done whenever
8529 possible. Configuration files for window managers and
8530 display managers should be placed in a subdirectory of
8531 <file>/etc/X11/</file> corresponding to the package name due
8532 to these programs' tight integration with the mechanisms
8533 of the X Window System. Application-level programs should
8534 use the <file>/etc/</file> directory unless otherwise mandated
8539 The installation of files into subdirectories
8540 of <file>/usr/X11R6/include/X11/</file> and
8541 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8542 package maintainers should determine if subdirectories of
8543 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8548 Packages should install any relevant files into the
8549 directories <file>/usr/include/X11/</file> and
8550 <file>/usr/lib/X11/</file>, but if they do so, they must
8551 pre-depend on <tt>x11-common (>=
8552 1:7.0.0)</tt><footnote>
8554 These libraries used to be all symbolic
8555 links. However, with <tt>X11R7</tt>,
8556 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8557 are now real directories, and packages
8558 <strong>should</strong> ship their files here instead
8559 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8560 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8561 responsible for converting these symlinks into
8569 <heading>The OSF/Motif and OpenMotif libraries</heading>
8572 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8573 OpenMotif libraries</em><footnote>
8574 OSF/Motif and OpenMotif are collectively referred to as
8575 "Motif" in this policy document.
8577 should be compiled against and tested with LessTif (a free
8578 re-implementation of Motif) instead. If the maintainer
8579 judges that the program or programs do not work
8580 sufficiently well with LessTif to be distributed and
8581 supported, but do so when compiled against Motif, then two
8582 versions of the package should be created; one linked
8583 statically against Motif and with <tt>-smotif</tt>
8584 appended to the package name, and one linked dynamically
8585 against Motif and with <tt>-dmotif</tt> appended to the
8590 Both Motif-linked versions are dependent
8591 upon non-DFSG-compliant software and thus cannot be
8592 uploaded to the <em>main</em> distribution; if the
8593 software is itself DFSG-compliant it may be uploaded to
8594 the <em>contrib</em> distribution. While known existing
8595 versions of Motif permit unlimited redistribution of
8596 binaries linked against the library (whether statically or
8597 dynamically), it is the package maintainer's
8598 responsibility to determine whether this is permitted by
8599 the license of the copy of Motif in their possession.
8605 <heading>Perl programs and modules</heading>
8608 Perl programs and modules should follow the current Perl policy.
8612 The Perl policy can be found in the <tt>perl-policy</tt>
8613 files in the <tt>debian-policy</tt> package.
8614 It is also available from the Debian web mirrors at
8615 <tt><url name="/doc/packaging-manuals/perl-policy/"
8616 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8621 <heading>Emacs lisp programs</heading>
8624 Please refer to the "Debian Emacs Policy" for details of how to
8625 package emacs lisp programs.
8629 The Emacs policy is available in
8630 <file>debian-emacs-policy.gz</file> of the
8631 <package>emacsen-common</package> package.
8632 It is also available from the Debian web mirrors at
8633 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8634 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8639 <heading>Games</heading>
8642 The permissions on <file>/var/games</file> are mode 755, owner
8643 <tt>root</tt> and group <tt>root</tt>.
8647 Each game decides on its own security policy.</p>
8650 Games which require protected, privileged access to
8651 high-score files, saved games, etc., may be made
8652 set-<em>group</em>-id (mode 2755) and owned by
8653 <tt>root:games</tt>, and use files and directories with
8654 appropriate permissions (770 <tt>root:games</tt>, for
8655 example). They must not be made
8656 set-<em>user</em>-id, as this causes security problems. (If
8657 an attacker can subvert any set-user-id game they can
8658 overwrite the executable of any other, causing other players
8659 of these games to run a Trojan horse program. With a
8660 set-group-id game the attacker only gets access to less
8661 important game data, and if they can get at the other
8662 players' accounts at all it will take considerably more
8666 Some packages, for example some fortune cookie programs, are
8667 configured by the upstream authors to install with their
8668 data files or other static information made unreadable so
8669 that they can only be accessed through set-id programs
8670 provided. You should not do this in a Debian package: anyone can
8671 download the <file>.deb</file> file and read the data from it,
8672 so there is no point making the files unreadable. Not
8673 making the files unreadable also means that you don't have
8674 to make so many programs set-id, which reduces the risk of a
8678 As described in the FHS, binaries of games should be
8679 installed in the directory <file>/usr/games</file>. This also
8680 applies to games that use the X Window System. Manual pages
8681 for games (X and non-X games) should be installed in
8682 <file>/usr/share/man/man6</file>.</p>
8688 <heading>Documentation</heading>
8691 <heading>Manual pages</heading>
8694 You should install manual pages in <prgn>nroff</prgn> source
8695 form, in appropriate places under <file>/usr/share/man</file>.
8696 You should only use sections 1 to 9 (see the FHS for more
8697 details). You must not install a pre-formatted "cat page".
8701 Each program, utility, and function should have an
8702 associated manual page included in the same package. It is
8703 suggested that all configuration files also have a manual
8704 page included as well. Manual pages for protocols and other
8705 auxiliary things are optional.
8709 If no manual page is available, this is considered as a bug
8710 and should be reported to the Debian Bug Tracking System (the
8711 maintainer of the package is allowed to write this bug report
8712 themselves, if they so desire). Do not close the bug report
8713 until a proper man page is available.<footnote>
8714 It is not very hard to write a man page. See the
8715 <url id="http://www.schweikhardt.net/man_page_howto.html"
8716 name="Man-Page-HOWTO">,
8717 <manref name="man" section="7">, the examples
8718 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8719 the helper programs <prgn>help2man</prgn>, or the
8720 directory <file>/usr/share/doc/man-db/examples</file>.
8725 You may forward a complaint about a missing man page to the
8726 upstream authors, and mark the bug as forwarded in the
8727 Debian bug tracking system. Even though the GNU Project do
8728 not in general consider the lack of a man page to be a bug,
8729 we do; if they tell you that they don't consider it a bug
8730 you should leave the bug in our bug tracking system open
8735 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8739 If one man page needs to be accessible via several names it
8740 is better to use a symbolic link than the <file>.so</file>
8741 feature, but there is no need to fiddle with the relevant
8742 parts of the upstream source to change from <file>.so</file> to
8743 symlinks: don't do it unless it's easy. You should not
8744 create hard links in the manual page directories, nor put
8745 absolute filenames in <file>.so</file> directives. The filename
8746 in a <file>.so</file> in a man page should be relative to the
8747 base of the man page tree (usually
8748 <file>/usr/share/man</file>). If you do not create any links
8749 (whether symlinks, hard links, or <tt>.so</tt> directives)
8750 in the file system to the alternate names of the man page,
8751 then you should not rely on <prgn>man</prgn> finding your
8752 man page under those names based solely on the information in
8753 the man page's header.<footnote>
8754 Supporting this in <prgn>man</prgn> often requires
8755 unreasonable processing time to find a manual page or to
8756 report that none exists, and moves knowledge into man's
8757 database that would be better left in the file system.
8758 This support is therefore deprecated and will cease to
8759 be present in the future.
8764 Manual pages in locale-specific subdirectories of
8765 <file>/usr/share/man</file> should use either UTF-8 or the usual
8766 legacy encoding for that language (normally the one corresponding
8767 to the shortest relevant locale name in
8768 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8769 <file>/usr/share/man/fr</file> should use either UTF-8 or
8770 ISO-8859-1.<footnote>
8771 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8772 use. In future, all manual pages will be required to use
8778 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8779 included in the subdirectory name unless it indicates a
8780 significant difference in the language, as this excludes
8781 speakers of the language in other countries.<footnote>
8782 At the time of writing, Chinese and Portuguese are the main
8783 languages with such differences, so <file>pt_BR</file>,
8784 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8789 Due to limitations in current implementations, all characters
8790 in the manual page source should be representable in the usual
8791 legacy encoding for that language, even if the file is
8792 actually encoded in UTF-8. Safe alternative ways to write many
8793 characters outside that range may be found in
8794 <manref name="groff_char" section="7">.
8799 <heading>Info documents</heading>
8802 Info documents should be installed in <file>/usr/share/info</file>.
8803 They should be compressed with <tt>gzip -9</tt>.
8807 Your package should call <prgn>install-info</prgn> to update
8808 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8809 script when called with a <tt>configure</tt> argument, for
8811 <example compact="compact">
8812 install-info --quiet --section Development Development \
8813 /usr/share/info/foobar.info
8817 It is a good idea to specify a section for the location of
8818 your program; this is done with the <tt>--section</tt>
8819 switch. To determine which section to use, you should look
8820 at <file>/usr/share/info/dir</file> on your system and choose the most
8821 relevant (or create a new section if none of the current
8822 sections are relevant). Note that the <tt>--section</tt>
8823 flag takes two arguments; the first is a regular expression
8824 to match (case-insensitively) against an existing section,
8825 the second is used when creating a new one.</p>
8828 You should remove the entries in the <prgn>prerm</prgn>
8829 script when called with a <tt>remove</tt> argument:
8830 <example compact="compact">
8831 install-info --quiet --remove /usr/share/info/foobar.info
8835 If <prgn>install-info</prgn> cannot find a description entry
8836 in the Info file you must supply one. See <manref
8837 name="install-info" section="8"> for details.</p>
8841 <heading>Additional documentation</heading>
8844 Any additional documentation that comes with the package may
8845 be installed at the discretion of the package maintainer.
8846 Plain text documentation should be installed in the directory
8847 <file>/usr/share/doc/<var>package</var></file>, where
8848 <var>package</var> is the name of the package, and
8849 compressed with <tt>gzip -9</tt> unless it is small.
8853 If a package comes with large amounts of documentation which
8854 many users of the package will not require you should create
8855 a separate binary package to contain it, so that it does not
8856 take up disk space on the machines of users who do not need
8857 or want it installed.</p>
8860 It is often a good idea to put text information files
8861 (<file>README</file>s, changelogs, and so forth) that come with
8862 the source package in <file>/usr/share/doc/<var>package</var></file>
8863 in the binary package. However, you don't need to install
8864 the instructions for building and installing the package, of
8868 Packages must not require the existence of any files in
8869 <file>/usr/share/doc/</file> in order to function
8871 The system administrator should be able to
8872 delete files in <file>/usr/share/doc/</file> without causing
8873 any programs to break.
8875 Any files that are referenced by programs but are also
8876 useful as stand alone documentation should be installed under
8877 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8878 <file>/usr/share/doc/<var>package</var></file>.
8882 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8883 link to another directory in <file>/usr/share/doc</file> only if
8884 the two packages both come from the same source and the
8885 first package Depends on the second.<footnote>
8887 Please note that this does not override the section on
8888 changelog files below, so the file
8889 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8890 must refer to the changelog for the current version of
8891 <var>package</var> in question. In practice, this means
8892 that the sources of the target and the destination of the
8893 symlink must be the same (same source package and
8900 Former Debian releases placed all additional documentation
8901 in <file>/usr/doc/<var>package</var></file>. This has been
8902 changed to <file>/usr/share/doc/<var>package</var></file>,
8903 and packages must not put documentation in the directory
8904 <file>/usr/doc/<var>package</var></file>. <footnote>
8905 At this phase of the transition, we no longer require a
8906 symbolic link in <file>/usr/doc/</file>. At a later point,
8907 policy shall change to make the symbolic links a bug.
8913 <heading>Preferred documentation formats</heading>
8916 The unification of Debian documentation is being carried out
8920 If your package comes with extensive documentation in a
8921 markup format that can be converted to various other formats
8922 you should if possible ship HTML versions in a binary
8923 package, in the directory
8924 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8925 its subdirectories.<footnote>
8926 The rationale: The important thing here is that HTML
8927 docs should be available in <em>some</em> package, not
8928 necessarily in the main binary package.
8933 Other formats such as PostScript may be provided at the
8934 package maintainer's discretion.
8938 <sect id="copyrightfile">
8939 <heading>Copyright information</heading>
8942 Every package must be accompanied by a verbatim copy of its
8943 copyright and distribution license in the file
8944 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8945 file must neither be compressed nor be a symbolic link.
8949 In addition, the copyright file must say where the upstream
8950 sources (if any) were obtained. It should name the original
8951 authors of the package and the Debian maintainer(s) who were
8952 involved with its creation.
8956 Packages in the <em>contrib</em> or <em>non-free</em> categories
8957 should state in the copyright file that the package is not part
8958 of the Debian GNU/Linux distribution and briefly explain why.
8962 A copy of the file which will be installed in
8963 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8964 be in <file>debian/copyright</file> in the source package.
8968 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8969 link to another directory in <file>/usr/share/doc</file> only if
8970 the two packages both come from the same source and the
8971 first package Depends on the second. These rules are
8972 important because copyrights must be extractable by
8977 Packages distributed under the UCB BSD license, the Apache
8978 license (version 2.0), the Artistic license, the GNU GPL
8979 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8980 the GNU FDL (version 1.2) should refer to the corresponding
8981 files under <file>/usr/share/common-licenses</file>,<footnote>
8984 <file>/usr/share/common-licenses/BSD</file>,
8985 <file>/usr/share/common-licenses/Apache-2.0</file>,
8986 <file>/usr/share/common-licenses/Artistic</file>,
8987 <file>/usr/share/common-licenses/GPL-2</file>,
8988 <file>/usr/share/common-licenses/GPL-3</file>,
8989 <file>/usr/share/common-licenses/LGPL-2</file>,
8990 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8991 <file>/usr/share/common-licenses/LGPL-3</file>, and
8992 <file>/usr/share/common-licenses/GFDL-1.2</file>
8995 </footnote> rather than quoting them in the copyright
9000 You should not use the copyright file as a general <file>README</file>
9001 file. If your package has such a file it should be
9002 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9003 <file>README.Debian</file> or some other appropriate place.</p>
9007 <heading>Examples</heading>
9010 Any examples (configurations, source files, whatever),
9011 should be installed in a directory
9012 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9013 files should not be referenced by any program: they're there
9014 for the benefit of the system administrator and users as
9015 documentation only. Architecture-specific example files
9016 should be installed in a directory
9017 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9019 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9020 latter directory itself may be a symbolic link to the
9025 If the purpose of a package is to provide examples, then the
9026 example files may be installed into
9027 <file>/usr/share/doc/<var>package</var></file>.
9031 <sect id="changelogs">
9032 <heading>Changelog files</heading>
9035 Packages that are not Debian-native must contain a
9036 compressed copy of the <file>debian/changelog</file> file from
9037 the Debian source tree in
9038 <file>/usr/share/doc/<var>package</var></file> with the name
9039 <file>changelog.Debian.gz</file>.
9043 If an upstream changelog is available, it should be accessible as
9044 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9045 plain text. If the upstream changelog is distributed in
9046 HTML, it should be made available in that form as
9047 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9048 and a plain text <file>changelog.gz</file> should be generated
9049 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9050 the upstream changelog files do not already conform to this
9051 naming convention, then this may be achieved either by
9052 renaming the files, or by adding a symbolic link, at the
9053 maintainer's discretion.<footnote>
9054 Rationale: People should not have to look in places for
9055 upstream changelogs merely because they are given
9056 different names or are distributed in HTML format.
9061 All of these files should be installed compressed using
9062 <tt>gzip -9</tt>, as they will become large with time even
9063 if they start out small.
9067 If the package has only one changelog which is used both as
9068 the Debian changelog and the upstream one because there is
9069 no separate upstream maintainer then that changelog should
9070 usually be installed as
9071 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9072 there is a separate upstream maintainer, but no upstream
9073 changelog, then the Debian changelog should still be called
9074 <file>changelog.Debian.gz</file>.
9078 For details about the format and contents of the Debian
9079 changelog file, please see <ref id="dpkgchangelog">.
9084 <appendix id="pkg-scope">
9085 <heading>Introduction and scope of these appendices</heading>
9088 These appendices are taken essentially verbatim from the
9089 now-deprecated Packaging Manual, version 3.2.1.0. They are
9090 the chapters which are likely to be of use to package
9091 maintainers and which have not already been included in the
9092 policy document itself. Most of these sections are very likely
9093 not relevant to policy; they should be treated as
9094 documentation for the packaging system. Please note that these
9095 appendices are included for convenience, and for historical
9096 reasons: they used to be part of policy package, and they have
9097 not yet been incorporated into dpkg documentation. However,
9098 they still have value, and hence they are presented here.
9102 They have not yet been checked to ensure that they are
9103 compatible with the contents of policy, and if there are any
9104 contradictions, the version in the main policy document takes
9105 precedence. The remaining chapters of the old Packaging
9106 Manual have also not been read in detail to ensure that there
9107 are not parts which have been left out. Both of these will be
9112 Certain parts of the Packaging manual were integrated into the
9113 Policy Manual proper, and removed from the appendices. Links
9114 have been placed from the old locations to the new ones.
9118 <prgn>dpkg</prgn> is a suite of programs for creating binary
9119 package files and installing and removing them on Unix
9121 <prgn>dpkg</prgn> is targeted primarily at Debian
9122 GNU/Linux, but may work on or be ported to other
9128 The binary packages are designed for the management of
9129 installed executable programs (usually compiled binaries) and
9130 their associated data, though source code examples and
9131 documentation are provided as part of some packages.</p>
9134 This manual describes the technical aspects of creating Debian
9135 binary packages (<file>.deb</file> files). It documents the
9136 behavior of the package management programs
9137 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9138 they interact with packages.</p>
9141 It also documents the interaction between
9142 <prgn>dselect</prgn>'s core and the access method scripts it
9143 uses to actually install the selected packages, and describes
9144 how to create a new access method.</p>
9147 This manual does not go into detail about the options and
9148 usage of the package building and installation tools. It
9149 should therefore be read in conjunction with those programs'
9154 The utility programs which are provided with <prgn>dpkg</prgn>
9155 for managing various system configuration and similar issues,
9156 such as <prgn>update-rc.d</prgn> and
9157 <prgn>install-info</prgn>, are not described in detail here -
9158 please see their man pages.
9162 It is assumed that the reader is reasonably familiar with the
9163 <prgn>dpkg</prgn> System Administrators' manual.
9164 Unfortunately this manual does not yet exist.
9168 The Debian version of the FSF's GNU hello program is provided
9169 as an example for people wishing to create Debian
9170 packages. The Debian <prgn>debmake</prgn> package is
9171 recommended as a very helpful tool in creating and maintaining
9172 Debian packages. However, while the tools and examples are
9173 helpful, they do not replace the need to read and follow the
9174 Policy and Programmer's Manual.</p>
9177 <appendix id="pkg-binarypkg">
9178 <heading>Binary packages (from old Packaging Manual)</heading>
9181 The binary package has two main sections. The first part
9182 consists of various control information files and scripts used
9183 by <prgn>dpkg</prgn> when installing and removing. See <ref
9184 id="pkg-controlarea">.
9188 The second part is an archive containing the files and
9189 directories to be installed.
9193 In the future binary packages may also contain other
9194 components, such as checksums and digital signatures. The
9195 format for the archive is described in full in the
9196 <file>deb(5)</file> man page.
9200 <sect id="pkg-bincreating"><heading>Creating package files -
9201 <prgn>dpkg-deb</prgn>
9205 All manipulation of binary package files is done by
9206 <prgn>dpkg-deb</prgn>; it's the only program that has
9207 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9208 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9209 will spot that the options requested are appropriate to
9210 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9215 In order to create a binary package you must make a
9216 directory tree which contains all the files and directories
9217 you want to have in the file system data part of the package.
9218 In Debian-format source packages this directory is usually
9219 <file>debian/tmp</file>, relative to the top of the package's
9224 They should have the locations (relative to the root of the
9225 directory tree you're constructing) ownerships and
9226 permissions which you want them to have on the system when
9231 With current versions of <prgn>dpkg</prgn> the uid/username
9232 and gid/groupname mappings for the users and groups being
9233 used should be the same on the system where the package is
9234 built and the one where it is installed.
9238 You need to add one special directory to the root of the
9239 miniature file system tree you're creating:
9240 <prgn>DEBIAN</prgn>. It should contain the control
9241 information files, notably the binary package control file
9242 (see <ref id="pkg-controlfile">).
9246 The <prgn>DEBIAN</prgn> directory will not appear in the
9247 file system archive of the package, and so won't be installed
9248 by <prgn>dpkg</prgn> when the package is installed.
9252 When you've prepared the package, you should invoke:
9254 dpkg --build <var>directory</var>
9259 This will build the package in
9260 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9261 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9262 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9267 See the man page <manref name="dpkg-deb" section="8"> for details of how
9268 to examine the contents of this newly-created file. You may find the
9269 output of following commands enlightening:
9271 dpkg-deb --info <var>filename</var>.deb
9272 dpkg-deb --contents <var>filename</var>.deb
9273 dpkg --contents <var>filename</var>.deb
9275 To view the copyright file for a package you could use this command:
9277 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9282 <sect id="pkg-controlarea">
9283 <heading>Package control information files</heading>
9286 The control information portion of a binary package is a
9287 collection of files with names known to <prgn>dpkg</prgn>.
9288 It will treat the contents of these files specially - some
9289 of them contain information used by <prgn>dpkg</prgn> when
9290 installing or removing the package; others are scripts which
9291 the package maintainer wants <prgn>dpkg</prgn> to run.
9295 It is possible to put other files in the package control
9296 area, but this is not generally a good idea (though they
9297 will largely be ignored).
9301 Here is a brief list of the control info files supported by
9302 <prgn>dpkg</prgn> and a summary of what they're used for.
9307 <tag><tt>control</tt>
9310 This is the key description file used by
9311 <prgn>dpkg</prgn>. It specifies the package's name
9312 and version, gives its description for the user,
9313 states its relationships with other packages, and so
9314 forth. See <ref id="sourcecontrolfiles"> and
9315 <ref id="binarycontrolfiles">.
9319 It is usually generated automatically from information
9320 in the source package by the
9321 <prgn>dpkg-gencontrol</prgn> program, and with
9322 assistance from <prgn>dpkg-shlibdeps</prgn>.
9323 See <ref id="pkg-sourcetools">.
9327 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9332 These are executable files (usually scripts) which
9333 <prgn>dpkg</prgn> runs during installation, upgrade
9334 and removal of packages. They allow the package to
9335 deal with matters which are particular to that package
9336 or require more complicated processing than that
9337 provided by <prgn>dpkg</prgn>. Details of when and
9338 how they are called are in <ref id="maintainerscripts">.
9342 It is very important to make these scripts idempotent.
9343 See <ref id="idempotency">.
9347 The maintainer scripts are guaranteed to run with a
9348 controlling terminal and can interact with the user.
9349 See <ref id="controllingterminal">.
9353 <tag><tt>conffiles</tt>
9356 This file contains a list of configuration files which
9357 are to be handled automatically by <prgn>dpkg</prgn>
9358 (see <ref id="pkg-conffiles">). Note that not necessarily
9359 every configuration file should be listed here.
9362 <tag><tt>shlibs</tt>
9365 This file contains a list of the shared libraries
9366 supplied by the package, with dependency details for
9367 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9368 when it determines what dependencies are required in a
9369 package control file. The <tt>shlibs</tt> file format
9370 is described on <ref id="shlibs">.
9375 <sect id="pkg-controlfile">
9376 <heading>The main control information file: <tt>control</tt></heading>
9379 The most important control information file used by
9380 <prgn>dpkg</prgn> when it installs a package is
9381 <tt>control</tt>. It contains all the package's "vital
9386 The binary package control files of packages built from
9387 Debian sources are made by a special tool,
9388 <prgn>dpkg-gencontrol</prgn>, which reads
9389 <file>debian/control</file> and <file>debian/changelog</file> to
9390 find the information it needs. See <ref id="pkg-sourcepkg"> for
9395 The fields in binary package control files are listed in
9396 <ref id="binarycontrolfiles">.
9400 A description of the syntax of control files and the purpose
9401 of the fields is available in <ref id="controlfields">.
9406 <heading>Time Stamps</heading>
9409 See <ref id="timestamps">.
9414 <appendix id="pkg-sourcepkg">
9415 <heading>Source packages (from old Packaging Manual) </heading>
9418 The Debian binary packages in the distribution are generated
9419 from Debian sources, which are in a special format to assist
9420 the easy and automatic building of binaries.
9423 <sect id="pkg-sourcetools">
9424 <heading>Tools for processing source packages</heading>
9427 Various tools are provided for manipulating source packages;
9428 they pack and unpack sources and help build of binary
9429 packages and help manage the distribution of new versions.
9433 They are introduced and typical uses described here; see
9434 <manref name="dpkg-source" section="1"> for full
9435 documentation about their arguments and operation.
9439 For examples of how to construct a Debian source package,
9440 and how to use those utilities that are used by Debian
9441 source packages, please see the <prgn>hello</prgn> example
9445 <sect1 id="pkg-dpkg-source">
9447 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9452 This program is frequently used by hand, and is also
9453 called from package-independent automated building scripts
9454 such as <prgn>dpkg-buildpackage</prgn>.
9458 To unpack a package it is typically invoked with
9460 dpkg-source -x <var>.../path/to/filename</var>.dsc
9465 with the <file><var>filename</var>.tar.gz</file> and
9466 <file><var>filename</var>.diff.gz</file> (if applicable) in
9467 the same directory. It unpacks into
9468 <file><var>package</var>-<var>version</var></file>, and if
9470 <file><var>package</var>-<var>version</var>.orig</file>, in
9471 the current directory.
9475 To create a packed source archive it is typically invoked:
9477 dpkg-source -b <var>package</var>-<var>version</var>
9482 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9483 <file>.diff.gz</file> (if appropriate) in the current
9484 directory. <prgn>dpkg-source</prgn> does not clean the
9485 source tree first - this must be done separately if it is
9490 See also <ref id="pkg-sourcearchives">.</p>
9494 <sect1 id="pkg-dpkg-buildpackage">
9496 <prgn>dpkg-buildpackage</prgn> - overall package-building
9501 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9502 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9503 targets <tt>clean</tt>, <tt>build</tt> and
9504 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9505 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9506 source and binary package upload.
9510 It is usually invoked by hand from the top level of the
9511 built or unbuilt source directory. It may be invoked with
9512 no arguments; useful arguments include:
9513 <taglist compact="compact">
9514 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9517 Do not sign the <tt>.changes</tt> file or the
9518 source package <tt>.dsc</tt> file, respectively.</p>
9520 <tag><tt>-p<var>sign-command</var></tt></tag>
9523 Invoke <var>sign-command</var> instead of finding
9524 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9525 <var>sign-command</var> must behave just like
9526 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9528 <tag><tt>-r<var>root-command</var></tt></tag>
9531 When root privilege is required, invoke the command
9532 <var>root-command</var>. <var>root-command</var>
9533 should invoke its first argument as a command, from
9534 the <prgn>PATH</prgn> if necessary, and pass its
9535 second and subsequent arguments to the command it
9536 calls. If no <var>root-command</var> is supplied
9537 then <var>dpkg-buildpackage</var> will take no
9538 special action to gain root privilege, so that for
9539 most packages it will have to be invoked as root to
9542 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9545 Two types of binary-only build and upload - see
9546 <manref name="dpkg-source" section="1">.
9553 <sect1 id="pkg-dpkg-gencontrol">
9555 <prgn>dpkg-gencontrol</prgn> - generates binary package
9560 This program is usually called from <file>debian/rules</file>
9561 (see <ref id="pkg-sourcetree">) in the top level of the source
9566 This is usually done just before the files and directories in the
9567 temporary directory tree where the package is being built have their
9568 permissions and ownerships set and the package is constructed using
9569 <prgn>dpkg-deb/</prgn>
9571 This is so that the control file which is produced has
9572 the right permissions
9577 <prgn>dpkg-gencontrol</prgn> must be called after all the
9578 files which are to go into the package have been placed in
9579 the temporary build directory, so that its calculation of
9580 the installed size of a package is correct.
9584 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9585 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9586 variable substitutions created by
9587 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9592 For a package which generates only one binary package, and
9593 which builds it in <file>debian/tmp</file> relative to the top
9594 of the source package, it is usually sufficient to call
9595 <prgn>dpkg-gencontrol</prgn>.
9599 Sources which build several binaries will typically need
9602 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9603 </example> The <tt>-P</tt> tells
9604 <prgn>dpkg-gencontrol</prgn> that the package is being
9605 built in a non-default directory, and the <tt>-p</tt>
9606 tells it which package's control file should be generated.
9610 <prgn>dpkg-gencontrol</prgn> also adds information to the
9611 list of files in <file>debian/files</file>, for the benefit of
9612 (for example) a future invocation of
9613 <prgn>dpkg-genchanges</prgn>.</p>
9616 <sect1 id="pkg-dpkg-shlibdeps">
9618 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9623 This program is usually called from <file>debian/rules</file>
9624 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9625 id="pkg-sourcetree">), in the top level of the source tree.
9629 Its arguments are executables and shared libraries
9632 They may be specified either in the locations in the
9633 source tree where they are created or in the locations
9634 in the temporary build tree where they are installed
9635 prior to binary package creation.
9637 </footnote> for which shared library dependencies should
9638 be included in the binary package's control file.
9642 If some of the found shared libraries should only
9643 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9644 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9645 by using the <tt>-d<var>dependency-field</var></tt> option
9646 before those executable(s). (Each <tt>-d</tt> option
9647 takes effect until the next <tt>-d</tt>.)
9651 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9652 output control file to be modified. Instead by default it
9653 adds to the <file>debian/substvars</file> file variable
9654 settings like <tt>shlibs:Depends</tt>. These variable
9655 settings must be referenced in dependency fields in the
9656 appropriate per-binary-package sections of the source
9661 For example, a package that generates an essential part
9662 which requires dependencies, and optional parts that
9663 which only require a recommendation, would separate those
9664 two sets of dependencies into two different fields.<footnote>
9665 At the time of writing, an example for this was the
9666 <package/xmms/ package, with Depends used for the xmms
9667 executable, Recommends for the plug-ins and Suggests for
9668 even more optional features provided by unzip.
9670 It can say in its <file>debian/rules</file>:
9672 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9673 -dRecommends <var>optionalpart anotheroptionalpart</var>
9675 and then in its main control file <file>debian/control</file>:
9678 Depends: ${shlibs:Depends}
9679 Recommends: ${shlibs:Recommends}
9685 Sources which produce several binary packages with
9686 different shared library dependency requirements can use
9687 the <tt>-p<var>varnameprefix</var></tt> option to override
9688 the default <tt>shlibs:</tt> prefix (one invocation of
9689 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9690 They can thus produce several sets of dependency
9691 variables, each of the form
9692 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9693 which can be referred to in the appropriate parts of the
9694 binary package control files.
9699 <sect1 id="pkg-dpkg-distaddfile">
9701 <prgn>dpkg-distaddfile</prgn> - adds a file to
9702 <file>debian/files</file>
9706 Some packages' uploads need to include files other than
9707 the source and binary package files.
9711 <prgn>dpkg-distaddfile</prgn> adds a file to the
9712 <file>debian/files</file> file so that it will be included in
9713 the <file>.changes</file> file when
9714 <prgn>dpkg-genchanges</prgn> is run.
9718 It is usually invoked from the <tt>binary</tt> target of
9719 <file>debian/rules</file>:
9721 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9723 The <var>filename</var> is relative to the directory where
9724 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9725 is usually the directory above the top level of the source
9726 tree. The <file>debian/rules</file> target should put the
9727 file there just before or just after calling
9728 <prgn>dpkg-distaddfile</prgn>.
9732 The <var>section</var> and <var>priority</var> are passed
9733 unchanged into the resulting <file>.changes</file> file.
9738 <sect1 id="pkg-dpkg-genchanges">
9740 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9745 This program is usually called by package-independent
9746 automatic building scripts such as
9747 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9752 It is usually called in the top level of a built source
9753 tree, and when invoked with no arguments will print out a
9754 straightforward <file>.changes</file> file based on the
9755 information in the source package's changelog and control
9756 file and the binary and source packages which should have
9762 <sect1 id="pkg-dpkg-parsechangelog">
9764 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9765 representation of a changelog
9769 This program is used internally by
9770 <prgn>dpkg-source</prgn> et al. It may also occasionally
9771 be useful in <file>debian/rules</file> and elsewhere. It
9772 parses a changelog, <file>debian/changelog</file> by default,
9773 and prints a control-file format representation of the
9774 information in it to standard output.
9778 <sect1 id="pkg-dpkg-architecture">
9780 <prgn>dpkg-architecture</prgn> - information about the build and
9785 This program can be used manually, but is also invoked by
9786 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9787 environment or make variables which specify the build and host
9788 architecture for the package building process.
9793 <sect id="pkg-sourcetree">
9794 <heading>The Debianised source tree</heading>
9797 The source archive scheme described later is intended to
9798 allow a Debianised source tree with some associated control
9799 information to be reproduced and transported easily. The
9800 Debianised source tree is a version of the original program
9801 with certain files added for the benefit of the
9802 Debianisation process, and with any other changes required
9803 made to the rest of the source code and installation
9808 The extra files created for Debian are in the subdirectory
9809 <file>debian</file> of the top level of the Debianised source
9810 tree. They are described below.
9813 <sect1 id="pkg-debianrules">
9814 <heading><file>debian/rules</file> - the main building script</heading>
9817 See <ref id="debianrules">.
9822 <sect1 id="pkg-dpkgchangelog">
9823 <heading><file>debian/changelog</file></heading>
9826 See <ref id="dpkgchangelog">.
9829 <sect2><heading>Defining alternative changelog formats
9833 It is possible to use a different format to the standard
9834 one, by providing a parser for the format you wish to
9839 In order to have <tt>dpkg-parsechangelog</tt> run your
9840 parser, you must include a line within the last 40 lines
9841 of your file matching the Perl regular expression:
9842 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9843 parentheses should be the name of the format. For
9844 example, you might say:
9846 @@@ changelog-format: joebloggs @@@
9848 Changelog format names are non-empty strings of alphanumerics.
9852 If such a line exists then <tt>dpkg-parsechangelog</tt>
9853 will look for the parser as
9854 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9856 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9857 it is an error for it not to find it, or for it not to
9858 be an executable program. The default changelog format
9859 is <tt>dpkg</tt>, and a parser for it is provided with
9860 the <tt>dpkg</tt> package.
9864 The parser will be invoked with the changelog open on
9865 standard input at the start of the file. It should read
9866 the file (it may seek if it wishes) to determine the
9867 information required and return the parsed information
9868 to standard output in the form of a series of control
9869 fields in the standard format. By default it should
9870 return information about only the most recent version in
9871 the changelog; it should accept a
9872 <tt>-v<var>version</var></tt> option to return changes
9873 information from all versions present <em>strictly
9874 after</em> <var>version</var>, and it should then be an
9875 error for <var>version</var> not to be present in the
9881 <list compact="compact">
9882 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9883 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9884 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9885 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9886 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9887 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9888 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9893 If several versions are being returned (due to the use
9894 of <tt>-v</tt>), the urgency value should be of the
9895 highest urgency code listed at the start of any of the
9896 versions requested followed by the concatenated
9897 (space-separated) comments from all the versions
9898 requested; the maintainer, version, distribution and
9899 date should always be from the most recent version.
9903 For the format of the <tt>Changes</tt> field see
9904 <ref id="f-Changes">.
9908 If the changelog format which is being parsed always or
9909 almost always leaves a blank line between individual
9910 change notes these blank lines should be stripped out,
9911 so as to make the resulting output compact.
9915 If the changelog format does not contain date or package
9916 name information this information should be omitted from
9917 the output. The parser should not attempt to synthesize
9918 it or find it from other sources.
9922 If the changelog does not have the expected format the
9923 parser should exit with a nonzero exit status, rather
9924 than trying to muddle through and possibly generating
9929 A changelog parser may not interact with the user at
9935 <sect1 id="pkg-srcsubstvars">
9936 <heading><file>debian/substvars</file> and variable substitutions</heading>
9939 See <ref id="substvars">.
9945 <heading><file>debian/files</file></heading>
9948 See <ref id="debianfiles">.
9952 <sect1><heading><file>debian/tmp</file>
9956 This is the canonical temporary location for the
9957 construction of binary packages by the <tt>binary</tt>
9958 target. The directory <file>tmp</file> serves as the root of
9959 the file system tree as it is being constructed (for
9960 example, by using the package's upstream makefiles install
9961 targets and redirecting the output there), and it also
9962 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9963 id="pkg-bincreating">.
9967 If several binary packages are generated from the same
9968 source tree it is usual to use several
9969 <file>debian/tmp<var>something</var></file> directories, for
9970 example <file>tmp-a</file> or <file>tmp-doc</file>.
9974 Whatever <file>tmp</file> directories are created and used by
9975 <tt>binary</tt> must of course be removed by the
9976 <tt>clean</tt> target.</p></sect1>
9980 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9984 As it exists on the FTP site, a Debian source package
9985 consists of three related files. You must have the right
9986 versions of all three to be able to use them.
9991 <tag>Debian source control file - <tt>.dsc</tt></tag>
9993 This file is a control file used by <prgn>dpkg-source</prgn>
9994 to extract a source package.
9995 See <ref id="debiansourcecontrolfiles">.
9999 Original source archive -
10001 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10007 This is a compressed (with <tt>gzip -9</tt>)
10008 <prgn>tar</prgn> file containing the source code from
10009 the upstream authors of the program.
10014 Debianisation diff -
10016 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10022 This is a unified context diff (<tt>diff -u</tt>)
10023 giving the changes which are required to turn the
10024 original source into the Debian source. These changes
10025 may only include editing and creating plain files.
10026 The permissions of files, the targets of symbolic
10027 links and the characteristics of special files or
10028 pipes may not be changed and no files may be removed
10033 All the directories in the diff must exist, except the
10034 <file>debian</file> subdirectory of the top of the source
10035 tree, which will be created by
10036 <prgn>dpkg-source</prgn> if necessary when unpacking.
10040 The <prgn>dpkg-source</prgn> program will
10041 automatically make the <file>debian/rules</file> file
10042 executable (see below).</p></item>
10047 If there is no original source code - for example, if the
10048 package is specially prepared for Debian or the Debian
10049 maintainer is the same as the upstream maintainer - the
10050 format is slightly different: then there is no diff, and the
10052 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10053 and preferably contains a directory named
10054 <file><var>package</var>-<var>version</var></file>.
10059 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10062 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10063 Debian source package. However, if it is not available it
10064 is possible to unpack a Debian source archive as follows:
10065 <enumlist compact="compact">
10068 Untar the tarfile, which will create a <file>.orig</file>
10072 <p>Rename the <file>.orig</file> directory to
10073 <file><var>package</var>-<var>version</var></file>.</p>
10077 Create the subdirectory <file>debian</file> at the top of
10078 the source tree.</p>
10080 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10082 <item><p>Untar the tarfile again if you want a copy of the original
10083 source code alongside the Debianised version.</p>
10088 It is not possible to generate a valid Debian source archive
10089 without using <prgn>dpkg-source</prgn>. In particular,
10090 attempting to use <prgn>diff</prgn> directly to generate the
10091 <file>.diff.gz</file> file will not work.
10095 <heading>Restrictions on objects in source packages</heading>
10098 The source package may not contain any hard links
10100 This is not currently detected when building source
10101 packages, but only when extracting
10105 Hard links may be permitted at some point in the
10106 future, but would require a fair amount of
10108 </footnote>, device special files, sockets or setuid or
10111 Setgid directories are allowed.
10116 The source packaging tools manage the changes between the
10117 original and Debianised source using <prgn>diff</prgn> and
10118 <prgn>patch</prgn>. Turning the original source tree as
10119 included in the <file>.orig.tar.gz</file> into the debianised
10120 source must not involve any changes which cannot be
10121 handled by these tools. Problematic changes which cause
10122 <prgn>dpkg-source</prgn> to halt with an error when
10123 building the source package are:
10124 <list compact="compact">
10125 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10127 <item><p>Changing the targets of symbolic links.</p>
10129 <item><p>Creating directories, other than <file>debian</file>.</p>
10131 <item><p>Changes to the contents of binary files.</p></item>
10132 </list> Changes which cause <prgn>dpkg-source</prgn> to
10133 print a warning but continue anyway are:
10134 <list compact="compact">
10137 Removing files, directories or symlinks.
10139 Renaming a file is not treated specially - it is
10140 seen as the removal of the old file (which
10141 generates a warning, but is otherwise ignored),
10142 and the creation of the new one.
10148 Changed text files which are missing the usual final
10149 newline (either in the original or the modified
10154 Changes which are not represented, but which are not detected by
10155 <prgn>dpkg-source</prgn>, are:
10156 <list compact="compact">
10157 <item><p>Changing the permissions of files (other than
10158 <file>debian/rules</file>) and directories.</p></item>
10163 The <file>debian</file> directory and <file>debian/rules</file>
10164 are handled specially by <prgn>dpkg-source</prgn> - before
10165 applying the changes it will create the <file>debian</file>
10166 directory, and afterwards it will make
10167 <file>debian/rules</file> world-executable.
10173 <appendix id="pkg-controlfields">
10174 <heading>Control files and their fields (from old Packaging Manual)</heading>
10177 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10178 data in a common format, known as control files. Binary and
10179 source packages have control data as do the <file>.changes</file>
10180 files which control the installation of uploaded files, and
10181 <prgn>dpkg</prgn>'s internal databases are in a similar
10186 <heading>Syntax of control files</heading>
10189 See <ref id="controlsyntax">.
10193 It is important to note that there are several fields which
10194 are optional as far as <prgn>dpkg</prgn> and the related
10195 tools are concerned, but which must appear in every Debian
10196 package, or whose omission may cause problems.
10201 <heading>List of fields</heading>
10204 See <ref id="controlfieldslist">.
10208 This section now contains only the fields that didn't belong
10209 to the Policy manual.
10212 <sect1 id="pkg-f-Filename">
10213 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10216 These fields in <tt>Packages</tt> files give the
10217 filename(s) of (the parts of) a package in the
10218 distribution directories, relative to the root of the
10219 Debian hierarchy. If the package has been split into
10220 several parts the parts are all listed in order, separated
10225 <sect1 id="pkg-f-Size">
10226 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10229 These fields in <file>Packages</file> files give the size (in
10230 bytes, expressed in decimal) and MD5 checksum of the
10231 file(s) which make(s) up a binary package in the
10232 distribution. If the package is split into several parts
10233 the values for the parts are listed in order, separated by
10238 <sect1 id="pkg-f-Status">
10239 <heading><tt>Status</tt></heading>
10242 This field in <prgn>dpkg</prgn>'s status file records
10243 whether the user wants a package installed, removed or
10244 left alone, whether it is broken (requiring
10245 re-installation) or not and what its current state on the
10246 system is. Each of these pieces of information is a
10251 <sect1 id="pkg-f-Config-Version">
10252 <heading><tt>Config-Version</tt></heading>
10255 If a package is not installed or not configured, this
10256 field in <prgn>dpkg</prgn>'s status file records the last
10257 version of the package which was successfully
10262 <sect1 id="pkg-f-Conffiles">
10263 <heading><tt>Conffiles</tt></heading>
10266 This field in <prgn>dpkg</prgn>'s status file contains
10267 information about the automatically-managed configuration
10268 files held by a package. This field should <em>not</em>
10269 appear anywhere in a package!
10274 <heading>Obsolete fields</heading>
10277 These are still recognized by <prgn>dpkg</prgn> but should
10278 not appear anywhere any more.
10280 <taglist compact="compact">
10282 <tag><tt>Revision</tt></tag>
10283 <tag><tt>Package-Revision</tt></tag>
10284 <tag><tt>Package_Revision</tt></tag>
10286 The Debian revision part of the package version was
10287 at one point in a separate control file field. This
10288 field went through several names.
10291 <tag><tt>Recommended</tt></tag>
10292 <item>Old name for <tt>Recommends</tt>.</item>
10294 <tag><tt>Optional</tt></tag>
10295 <item>Old name for <tt>Suggests</tt>.</item>
10297 <tag><tt>Class</tt></tag>
10298 <item>Old name for <tt>Priority</tt>.</item>
10307 <appendix id="pkg-conffiles">
10308 <heading>Configuration file handling (from old Packaging Manual)</heading>
10311 <prgn>dpkg</prgn> can do a certain amount of automatic
10312 handling of package configuration files.
10316 Whether this mechanism is appropriate depends on a number of
10317 factors, but basically there are two approaches to any
10318 particular configuration file.
10322 The easy method is to ship a best-effort configuration in the
10323 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10324 handle updates. If the user is unlikely to want to edit the
10325 file, but you need them to be able to without losing their
10326 changes, and a new package with a changed version of the file
10327 is only released infrequently, this is a good approach.
10331 The hard method is to build the configuration file from
10332 scratch in the <prgn>postinst</prgn> script, and to take the
10333 responsibility for fixing any mistakes made in earlier
10334 versions of the package automatically. This will be
10335 appropriate if the file is likely to need to be different on
10339 <sect><heading>Automatic handling of configuration files by
10344 A package may contain a control area file called
10345 <tt>conffiles</tt>. This file should be a list of filenames
10346 of configuration files needing automatic handling, separated
10347 by newlines. The filenames should be absolute pathnames,
10348 and the files referred to should actually exist in the
10353 When a package is upgraded <prgn>dpkg</prgn> will process
10354 the configuration files during the configuration stage,
10355 shortly before it runs the package's <prgn>postinst</prgn>
10360 For each file it checks to see whether the version of the
10361 file included in the package is the same as the one that was
10362 included in the last version of the package (the one that is
10363 being upgraded from); it also compares the version currently
10364 installed on the system with the one shipped with the last
10369 If neither the user nor the package maintainer has changed
10370 the file, it is left alone. If one or the other has changed
10371 their version, then the changed version is preferred - i.e.,
10372 if the user edits their file, but the package maintainer
10373 doesn't ship a different version, the user's changes will
10374 stay, silently, but if the maintainer ships a new version
10375 and the user hasn't edited it the new version will be
10376 installed (with an informative message). If both have
10377 changed their version the user is prompted about the problem
10378 and must resolve the differences themselves.
10382 The comparisons are done by calculating the MD5 message
10383 digests of the files, and storing the MD5 of the file as it
10384 was included in the most recent version of the package.
10388 When a package is installed for the first time
10389 <prgn>dpkg</prgn> will install the file that comes with it,
10390 unless that would mean overwriting a file already on the
10395 However, note that <prgn>dpkg</prgn> will <em>not</em>
10396 replace a conffile that was removed by the user (or by a
10397 script). This is necessary because with some programs a
10398 missing file produces an effect hard or impossible to
10399 achieve in another way, so that a missing file needs to be
10400 kept that way if the user did it.
10404 Note that a package should <em>not</em> modify a
10405 <prgn>dpkg</prgn>-handled conffile in its maintainer
10406 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10407 the user confusing and possibly dangerous options for
10408 conffile update when the package is upgraded.</p>
10411 <sect><heading>Fully-featured maintainer script configuration
10416 For files which contain site-specific information such as
10417 the hostname and networking details and so forth, it is
10418 better to create the file in the package's
10419 <prgn>postinst</prgn> script.
10423 This will typically involve examining the state of the rest
10424 of the system to determine values and other information, and
10425 may involve prompting the user for some information which
10426 can't be obtained some other way.
10430 When using this method there are a couple of important
10431 issues which should be considered:
10435 If you discover a bug in the program which generates the
10436 configuration file, or if the format of the file changes
10437 from one version to the next, you will have to arrange for
10438 the postinst script to do something sensible - usually this
10439 will mean editing the installed configuration file to remove
10440 the problem or change the syntax. You will have to do this
10441 very carefully, since the user may have changed the file,
10442 perhaps to fix the very problem that your script is trying
10443 to deal with - you will have to detect these situations and
10444 deal with them correctly.
10448 If you do go down this route it's probably a good idea to
10449 make the program that generates the configuration file(s) a
10450 separate program in <file>/usr/sbin</file>, by convention called
10451 <file><var>package</var>config</file> and then run that if
10452 appropriate from the post-installation script. The
10453 <tt><var>package</var>config</tt> program should not
10454 unquestioningly overwrite an existing configuration - if its
10455 mode of operation is geared towards setting up a package for
10456 the first time (rather than any arbitrary reconfiguration
10457 later) you should have it check whether the configuration
10458 already exists, and require a <tt>--force</tt> flag to
10459 overwrite it.</p></sect>
10462 <appendix id="pkg-alternatives"><heading>Alternative versions of
10463 an interface - <prgn>update-alternatives</prgn> (from old
10468 When several packages all provide different versions of the
10469 same program or file it is useful to have the system select a
10470 default, but to allow the system administrator to change it
10471 and have their decisions respected.
10475 For example, there are several versions of the <prgn>vi</prgn>
10476 editor, and there is no reason to prevent all of them from
10477 being installed at once, each under their own name
10478 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10479 Nevertheless it is desirable to have the name <tt>vi</tt>
10480 refer to something, at least by default.
10484 If all the packages involved cooperate, this can be done with
10485 <prgn>update-alternatives</prgn>.
10489 Each package provides its own version under its own name, and
10490 calls <prgn>update-alternatives</prgn> in its postinst to
10491 register its version (and again in its prerm to deregister
10496 See the man page <manref name="update-alternatives"
10497 section="8"> for details.
10501 If <prgn>update-alternatives</prgn> does not seem appropriate
10502 you may wish to consider using diversions instead.</p>
10505 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10506 package's version of a file (from old Packaging Manual)
10510 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10511 when it reinstalls the package it belongs to, and to have it
10512 put the file from the package somewhere else instead.
10516 This can be used locally to override a package's version of a
10517 file, or by one package to override another's version (or
10518 provide a wrapper for it).
10522 Before deciding to use a diversion, read <ref
10523 id="pkg-alternatives"> to see if you really want a diversion
10524 rather than several alternative versions of a program.
10528 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10529 and updated by a special program <prgn>dpkg-divert</prgn>.
10530 Please see <manref name="dpkg-divert" section="8"> for full
10531 details of its operation.
10535 When a package wishes to divert a file from another, it should
10536 call <prgn>dpkg-divert</prgn> in its preinst to add the
10537 diversion and rename the existing file. For example,
10538 supposing that a <prgn>smailwrapper</prgn> package wishes to
10539 install a wrapper around <file>/usr/sbin/smail</file>:
10541 if [ install = "$1" ]; then
10542 dpkg-divert --package smailwrapper --add --rename \
10543 --divert /usr/sbin/smail.real /usr/sbin/smail
10545 </example> Testing <tt>$1</tt> is necessary so that the script
10546 doesn't try to add the diversion again when
10547 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10548 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10549 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10550 get installed as the true version.
10554 The postrm has to do the reverse:
10556 if [ remove = "$1" ]; then
10557 dpkg-divert --package smailwrapper --remove --rename \
10558 --divert /usr/sbin/smail.real /usr/sbin/smail
10564 Do not attempt to divert a file which is vitally important for
10565 the system's operation - when using <prgn>dpkg-divert</prgn>
10566 there is a time, after it has been diverted but before
10567 <prgn>dpkg</prgn> has installed the new version, when the file
10568 does not exist.</p>
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