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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>.
280 <heading>The Debian Archive</heading>
283 The Debian GNU/Linux system is maintained and distributed as a
284 collection of <em>packages</em>. Since there are so many of
285 them (currently well over 15000), they are split into
286 <em>sections</em> and given <em>priorities</em> to simplify
287 the handling of them.
291 The effort of the Debian project is to build a free operating
292 system, but not every package we want to make accessible is
293 <em>free</em> in our sense (see the Debian Free Software
294 Guidelines, below), or may be imported/exported without
295 restrictions. Thus, the archive is split into the distribution
296 areas or components<footnote>
297 The Debian archive software uses the term "component" internally
298 and in the Release file format to refer to the division of an
299 archive. The Debian Social Contract refers to distribution
300 areas. This document uses the same terminology as the Social
302 </footnote> based on their licenses and other restrictions.
306 The aims of this are:
308 <list compact="compact">
309 <item>to allow us to make as much software available as we can</item>
310 <item>to allow us to encourage everyone to write free software,
312 <item>to allow us to make it easy for people to produce
313 CD-ROMs of our system without violating any licenses,
314 import/export restrictions, or any other laws.</item>
319 The <em>main</em> distribution area forms the <em>Debian GNU/Linux
324 Packages in the other distribution areas (<tt>contrib</tt>,
325 <tt>non-free</tt>) are not considered to be part of the Debian
326 distribution, although we support their use and provide
327 infrastructure for them (such as our bug-tracking system and
328 mailing lists). This Debian Policy Manual applies to these
333 <heading>The Debian Free Software Guidelines</heading>
335 The Debian Free Software Guidelines (DFSG) form our
336 definition of "free software". These are:
338 <tag>Free Redistribution
341 The license of a Debian component may not restrict any
342 party from selling or giving away the software as a
343 component of an aggregate software distribution
344 containing programs from several different
345 sources. The license may not require a royalty or
346 other fee for such sale.
351 The program must include source code, and must allow
352 distribution in source code as well as compiled form.
357 The license must allow modifications and derived
358 works, and must allow them to be distributed under the
359 same terms as the license of the original software.
361 <tag>Integrity of The Author's Source Code
364 The license may restrict source-code from being
365 distributed in modified form <em>only</em> if the
366 license allows the distribution of "patch files"
367 with the source code for the purpose of modifying the
368 program at build time. The license must explicitly
369 permit distribution of software built from modified
370 source code. The license may require derived works to
371 carry a different name or version number from the
372 original software. (This is a compromise. The Debian
373 Project encourages all authors to not restrict any
374 files, source or binary, from being modified.)
376 <tag>No Discrimination Against Persons or Groups
379 The license must not discriminate against any person
382 <tag>No Discrimination Against Fields of Endeavor
385 The license must not restrict anyone from making use
386 of the program in a specific field of endeavor. For
387 example, it may not restrict the program from being
388 used in a business, or from being used for genetic
391 <tag>Distribution of License
394 The rights attached to the program must apply to all
395 to whom the program is redistributed without the need
396 for execution of an additional license by those
399 <tag>License Must Not Be Specific to Debian
402 The rights attached to the program must not depend on
403 the program's being part of a Debian system. If the
404 program is extracted from Debian and used or
405 distributed without Debian but otherwise within the
406 terms of the program's license, all parties to whom
407 the program is redistributed must have the same
408 rights as those that are granted in conjunction with
411 <tag>License Must Not Contaminate Other Software
414 The license must not place restrictions on other
415 software that is distributed along with the licensed
416 software. For example, the license must not insist
417 that all other programs distributed on the same medium
418 must be free software.
420 <tag>Example Licenses
423 The "GPL," "BSD," and "Artistic" licenses are examples of
424 licenses that we consider <em>free</em>.
431 <heading>Distribution areas</heading>
434 <heading>The main distribution area</heading>
437 Every package in <em>main</em> must comply with the DFSG
438 (Debian Free Software Guidelines).
442 In addition, the packages in <em>main</em>
443 <list compact="compact">
445 must not require a package outside of <em>main</em>
446 for compilation or execution (thus, the package must
447 not declare a "Depends", "Recommends", or
448 "Build-Depends" relationship on a non-<em>main</em>
452 must not be so buggy that we refuse to support them,
456 must meet all policy requirements presented in this
465 <heading>The contrib distribution area</heading>
468 Every package in <em>contrib</em> must comply with the DFSG.
472 In addition, the packages in <em>contrib</em>
473 <list compact="compact">
475 must not be so buggy that we refuse to support them,
479 must meet all policy requirements presented in this
487 Examples of packages which would be included in
488 <em>contrib</em> are:
489 <list compact="compact">
491 free packages which require <em>contrib</em>,
492 <em>non-free</em> packages or packages which are not
493 in our archive at all for compilation or execution,
497 wrapper packages or other sorts of free accessories for
504 <sect1 id="non-free">
505 <heading>The non-free distribution area</heading>
508 Packages must be placed in <em>non-free</em> if they are
509 not compliant with the DFSG or are encumbered by patents
510 or other legal issues that make their distribution
515 In addition, the packages in <em>non-free</em>
516 <list compact="compact">
518 must not be so buggy that we refuse to support them,
522 must meet all policy requirements presented in this
523 manual that it is possible for them to meet.
525 It is possible that there are policy
526 requirements which the package is unable to
527 meet, for example, if the source is
528 unavailable. These situations will need to be
529 handled on a case-by-case basis.
538 <sect id="pkgcopyright">
539 <heading>Copyright considerations</heading>
542 Every package must be accompanied by a verbatim copy of
543 its copyright and distribution license in the file
544 <file>/usr/share/doc/<var>package</var>/copyright</file>
545 (see <ref id="copyrightfile"> for further details).
549 We reserve the right to restrict files from being included
550 anywhere in our archives if
551 <list compact="compact">
553 their use or distribution would break a law,
556 there is an ethical conflict in their distribution or
560 we would have to sign a license for them, or
563 their distribution would conflict with other project
570 Programs whose authors encourage the user to make
571 donations are fine for the main distribution, provided
572 that the authors do not claim that not donating is
573 immoral, unethical, illegal or something similar; in such
574 a case they must go in <em>non-free</em>.
578 Packages whose copyright permission notices (or patent
579 problems) do not even allow redistribution of binaries
580 only, and where no special permission has been obtained,
581 must not be placed on the Debian FTP site and its mirrors
586 Note that under international copyright law (this applies
587 in the United States, too), <em>no</em> distribution or
588 modification of a work is allowed without an explicit
589 notice saying so. Therefore a program without a copyright
590 notice <em>is</em> copyrighted and you may not do anything
591 to it without risking being sued! Likewise if a program
592 has a copyright notice but no statement saying what is
593 permitted then nothing is permitted.
597 Many authors are unaware of the problems that restrictive
598 copyrights (or lack of copyright notices) can cause for
599 the users of their supposedly-free software. It is often
600 worthwhile contacting such authors diplomatically to ask
601 them to modify their license terms. However, this can be a
602 politically difficult thing to do and you should ask for
603 advice on the <tt>debian-legal</tt> mailing list first, as
608 When in doubt about a copyright, send mail to
609 <email>debian-legal@lists.debian.org</email>. Be prepared
610 to provide us with the copyright statement. Software
611 covered by the GPL, public domain software and BSD-like
612 copyrights are safe; be wary of the phrases "commercial
613 use prohibited" and "distribution restricted".
617 <sect id="subsections">
618 <heading>Sections</heading>
621 The packages in the distribution areas <em>main</em>,
622 <em>contrib</em> and <em>non-free</em> are grouped further
623 into <em>sections</em> to simplify handling.
627 The distribution area and section for each package should be
628 specified in the package's <tt>Section</tt> control record
629 (see <ref id="f-Section">). However, the maintainer of the
630 Debian archive may override this selection to ensure the
631 consistency of the Debian distribution. The
632 <tt>Section</tt> field should be of the form:
633 <list compact="compact">
635 <em>section</em> if the package is in the
636 <em>main</em> distribution area,
639 <em>area/section</em> if the package is in
640 the <em>contrib</em> or <em>non-free</em>
647 The Debian archive maintainers provide the authoritative
648 list of sections. At present, they are:
649 <em>admin</em>, <em>comm</em>,
650 <em>devel</em>, <em>doc</em>,
651 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
652 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
653 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
654 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
655 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
657 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
658 <em>science</em>, <em>shells</em>,
659 <em>sound</em>, <em>tex</em>, <em>text</em>,
660 <em>utils</em>, <em>web</em>, <em>x11</em>.
664 <sect id="priorities">
665 <heading>Priorities</heading>
668 Each package should have a <em>priority</em> value, which is
669 included in the package's <em>control record</em>
670 (see <ref id="f-Priority">).
671 This information is used by the Debian package management tools to
672 separate high-priority packages from less-important packages.
676 The following <em>priority levels</em> are recognized by the
677 Debian package management tools.
679 <tag><tt>required</tt></tag>
681 Packages which are necessary for the proper
682 functioning of the system (usually, this means that
683 dpkg functionality depends on these packages).
684 Removing a <tt>required</tt> package may cause your
685 system to become totally broken and you may not even
686 be able to use <prgn>dpkg</prgn> to put things back,
687 so only do so if you know what you are doing. Systems
688 with only the <tt>required</tt> packages are probably
689 unusable, but they do have enough functionality to
690 allow the sysadmin to boot and install more software.
692 <tag><tt>important</tt></tag>
694 Important programs, including those which one would
695 expect to find on any Unix-like system. If the
696 expectation is that an experienced Unix person who
697 found it missing would say "What on earth is going on,
698 where is <prgn>foo</prgn>?", it must be an
699 <tt>important</tt> package.<footnote>
700 This is an important criterion because we are
701 trying to produce, amongst other things, a free
704 Other packages without which the system will not run
705 well or be usable must also have priority
706 <tt>important</tt>. This does
707 <em>not</em> include Emacs, the X Window System, TeX
708 or any other large applications. The
709 <tt>important</tt> packages are just a bare minimum of
710 commonly-expected and necessary tools.
712 <tag><tt>standard</tt></tag>
714 These packages provide a reasonably small but not too
715 limited character-mode system. This is what will be
716 installed by default if the user doesn't select anything
717 else. It doesn't include many large applications.
719 <tag><tt>optional</tt></tag>
721 (In a sense everything that isn't required is
722 optional, but that's not what is meant here.) This is
723 all the software that you might reasonably want to
724 install if you didn't know what it was and don't have
725 specialized requirements. This is a much larger system
726 and includes the X Window System, a full TeX
727 distribution, and many applications. Note that
728 optional packages should not conflict with each other.
730 <tag><tt>extra</tt></tag>
732 This contains all packages that conflict with others
733 with required, important, standard or optional
734 priorities, or are only likely to be useful if you
735 already know what they are or have specialized
742 Packages must not depend on packages with lower priority
743 values (excluding build-time dependencies). In order to
744 ensure this, the priorities of one or more packages may need
753 <heading>Binary packages</heading>
756 The Debian GNU/Linux distribution is based on the Debian
757 package management system, called <prgn>dpkg</prgn>. Thus,
758 all packages in the Debian distribution must be provided
759 in the <tt>.deb</tt> file format.
763 <heading>The package name</heading>
766 Every package must have a name that's unique within the Debian
771 The package name is included in the control field
772 <tt>Package</tt>, the format of which is described
773 in <ref id="f-Package">.
774 The package name is also included as a part of the file name
775 of the <tt>.deb</tt> file.
780 <heading>The version of a package</heading>
783 Every package has a version number recorded in its
784 <tt>Version</tt> control file field, described in
785 <ref id="f-Version">.
789 The package management system imposes an ordering on version
790 numbers, so that it can tell whether packages are being up- or
791 downgraded and so that package system front end applications
792 can tell whether a package it finds available is newer than
793 the one installed on the system. The version number format
794 has the most significant parts (as far as comparison is
795 concerned) at the beginning.
799 If an upstream package has problematic version numbers they
800 should be converted to a sane form for use in the
801 <tt>Version</tt> field.
805 <heading>Version numbers based on dates</heading>
808 In general, Debian packages should use the same version
809 numbers as the upstream sources.
813 However, in some cases where the upstream version number is
814 based on a date (e.g., a development "snapshot" release) the
815 package management system cannot handle these version
816 numbers without epochs. For example, dpkg will consider
817 "96May01" to be greater than "96Dec24".
821 To prevent having to use epochs for every new upstream
822 version, the date based portion of the version number
823 should be changed to the following format in such cases:
824 "19960501", "19961224". It is up to the maintainer whether
825 they want to bother the upstream maintainer to change
826 the version numbers upstream, too.
830 Note that other version formats based on dates which are
831 parsed correctly by the package management system should
832 <em>not</em> be changed.
836 Native Debian packages (i.e., packages which have been
837 written especially for Debian) whose version numbers include
838 dates should always use the "YYYYMMDD" format.
845 <heading>The maintainer of a package</heading>
848 Every package must have a Debian maintainer (the
849 maintainer may be one person or a group of people
850 reachable from a common email address, such as a mailing
851 list). The maintainer is responsible for ensuring that
852 the package is placed in the appropriate distributions.
856 The maintainer must be specified in the
857 <tt>Maintainer</tt> control field with their correct name
858 and a working email address. If one person maintains
859 several packages, they should try to avoid having
860 different forms of their name and email address in
861 the <tt>Maintainer</tt> fields of those packages.
865 The format of the <tt>Maintainer</tt> control field is
866 described in <ref id="f-Maintainer">.
870 If the maintainer of a package quits from the Debian
871 project, "Debian QA Group"
872 <email>packages@qa.debian.org</email> takes over the
873 maintainer-ship of the package until someone else
874 volunteers for that task. These packages are called
875 <em>orphaned packages</em>.<footnote>
876 The detailed procedure for doing this gracefully can
877 be found in the Debian Developer's Reference,
878 see <ref id="related">.
883 <sect id="descriptions">
884 <heading>The description of a package</heading>
887 Every Debian package must have an extended description
888 stored in the appropriate field of the control record.
889 The technical information about the format of the
890 <tt>Description</tt> field is in <ref id="f-Description">.
894 The description should describe the package (the program) to a
895 user (system administrator) who has never met it before so that
896 they have enough information to decide whether they want to
897 install it. This description should not just be copied verbatim
898 from the program's documentation.
902 Put important information first, both in the synopsis and
903 extended description. Sometimes only the first part of the
904 synopsis or of the description will be displayed. You can
905 assume that there will usually be a way to see the whole
906 extended description.
910 The description should also give information about the
911 significant dependencies and conflicts between this package
912 and others, so that the user knows why these dependencies and
913 conflicts have been declared.
917 Instructions for configuring or using the package should
918 not be included (that is what installation scripts,
919 manual pages, info files, etc., are for). Copyright
920 statements and other administrivia should not be included
921 either (that is what the copyright file is for).
924 <sect1 id="synopsis"><heading>The single line synopsis</heading>
927 The single line synopsis should be kept brief - certainly
932 Do not include the package name in the synopsis line. The
933 display software knows how to display this already, and you
934 do not need to state it. Remember that in many situations
935 the user may only see the synopsis line - make it as
936 informative as you can.
941 <sect1 id="extendeddesc"><heading>The extended description</heading>
944 Do not try to continue the single line synopsis into the
945 extended description. This will not work correctly when
946 the full description is displayed, and makes no sense
947 where only the summary (the single line synopsis) is
952 The extended description should describe what the package
953 does and how it relates to the rest of the system (in terms
954 of, for example, which subsystem it is which part of).
958 The description field needs to make sense to anyone, even
959 people who have no idea about any of the things the
960 package deals with.<footnote>
961 The blurb that comes with a program in its
962 announcements and/or <prgn>README</prgn> files is
963 rarely suitable for use in a description. It is
964 usually aimed at people who are already in the
965 community where the package is used.
974 <heading>Dependencies</heading>
977 Every package must specify the dependency information
978 about other packages that are required for the first to
983 For example, a dependency entry must be provided for any
984 shared libraries required by a dynamically-linked executable
989 Packages are not required to declare any dependencies they
990 have on other packages which are marked <tt>Essential</tt>
991 (see below), and should not do so unless they depend on a
992 particular version of that package.<footnote>
994 Essential is defined as the minimal set of functionality
995 that must be available and usable on the system even
996 when packages are in an unconfigured (but unpacked)
997 state. This is needed to avoid unresolvable dependency
998 loops on upgrade. If packages add unnecessary
999 dependencies on packages in this set, the chances that
1000 there <strong>will</strong> be an unresolvable
1001 dependency loop caused by forcing these Essential
1002 packages to be configured first before they need to be
1003 is greatly increased. It also increases the chances
1004 that frontends will be unable to
1005 <strong>calculate</strong> an upgrade path, even if one
1009 Also, it's pretty unlikely that functionality from
1010 Essential shall ever be removed (which is one reason why
1011 care must be taken before adding to the Essential
1012 packages set), but <em>packages</em> have been removed
1013 from the Essential set when the functionality moved to a
1014 different package. So depending on these packages
1015 <em>just in case</em> they stop being essential does way
1016 more harm than good.
1022 Sometimes, a package requires another package to be installed
1023 <em>and</em> configured before it can be installed. In this
1024 case, you must specify a <tt>Pre-Depends</tt> entry for
1029 You should not specify a <tt>Pre-Depends</tt> entry for a
1030 package before this has been discussed on the
1031 <tt>debian-devel</tt> mailing list and a consensus about
1032 doing that has been reached.
1036 The format of the package interrelationship control fields is
1037 described in <ref id="relationships">.
1041 <sect id="virtual_pkg">
1042 <heading>Virtual packages</heading>
1045 Sometimes, there are several packages which offer
1046 more-or-less the same functionality. In this case, it's
1047 useful to define a <em>virtual package</em> whose name
1048 describes that common functionality. (The virtual
1049 packages only exist logically, not physically; that's why
1050 they are called <em>virtual</em>.) The packages with this
1051 particular function will then <em>provide</em> the virtual
1052 package. Thus, any other package requiring that function
1053 can simply depend on the virtual package without having to
1054 specify all possible packages individually.
1058 All packages should use virtual package names where
1059 appropriate, and arrange to create new ones if necessary.
1060 They should not use virtual package names (except privately,
1061 amongst a cooperating group of packages) unless they have
1062 been agreed upon and appear in the list of virtual package
1063 names. (See also <ref id="virtual">)
1067 The latest version of the authoritative list of virtual
1068 package names can be found in the <tt>debian-policy</tt> package.
1069 It is also available from the Debian web mirrors at
1070 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1071 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1075 The procedure for updating the list is described in the preface
1082 <heading>Base system</heading>
1085 The <tt>base system</tt> is a minimum subset of the Debian
1086 GNU/Linux system that is installed before everything else
1087 on a new system. Only very few packages are allowed to form
1088 part of the base system, in order to keep the required disk
1093 The base system consists of all those packages with priority
1094 <tt>required</tt> or <tt>important</tt>. Many of them will
1095 be tagged <tt>essential</tt> (see below).
1100 <heading>Essential packages</heading>
1103 Some packages are tagged <tt>essential</tt> for a system
1104 using the <tt>Essential</tt> control file field.
1105 The format of the <tt>Essential</tt> control field is
1106 described in <ref id="f-Essential">.
1110 Since these packages cannot be easily removed (one has to
1111 specify an extra <em>force option</em> to
1112 <prgn>dpkg</prgn> to do so), this flag must not be used
1113 unless absolutely necessary. A shared library package
1114 must not be tagged <tt>essential</tt>; dependencies will
1115 prevent its premature removal, and we need to be able to
1116 remove it when it has been superseded.
1120 Since dpkg will not prevent upgrading of other packages
1121 while an <tt>essential</tt> package is in an unconfigured
1122 state, all <tt>essential</tt> packages must supply all of
1123 their core functionality even when unconfigured. If the
1124 package cannot satisfy this requirement it must not be
1125 tagged as essential, and any packages depending on this
1126 package must instead have explicit dependency fields as
1131 You must not tag any packages <tt>essential</tt> before
1132 this has been discussed on the <tt>debian-devel</tt>
1133 mailing list and a consensus about doing that has been
1138 <sect id="maintscripts">
1139 <heading>Maintainer Scripts</heading>
1142 The package installation scripts should avoid producing
1143 output which is unnecessary for the user to see and
1144 should rely on <prgn>dpkg</prgn> to stave off boredom on
1145 the part of a user installing many packages. This means,
1146 amongst other things, using the <tt>--quiet</tt> option on
1147 <prgn>install-info</prgn>.
1151 Errors which occur during the execution of an installation
1152 script must be checked and the installation must not
1153 continue after an error.
1157 Note that in general <ref id="scripts"> applies to package
1158 maintainer scripts, too.
1162 You should not use <prgn>dpkg-divert</prgn> on a file
1163 belonging to another package without consulting the
1164 maintainer of that package first.
1168 All packages which supply an instance of a common command
1169 name (or, in general, filename) should generally use
1170 <prgn>update-alternatives</prgn>, so that they may be
1171 installed together. If <prgn>update-alternatives</prgn>
1172 is not used, then each package must use
1173 <tt>Conflicts</tt> to ensure that other packages are
1174 de-installed. (In this case, it may be appropriate to
1175 specify a conflict against earlier versions of something
1176 that previously did not use
1177 <prgn>update-alternatives</prgn>; this is an exception to
1178 the usual rule that versioned conflicts should be
1182 <sect1 id="maintscriptprompt">
1183 <heading>Prompting in maintainer scripts</heading>
1185 Package maintainer scripts may prompt the user if
1186 necessary. Prompting should be done by communicating
1187 through a program, such as <prgn>debconf</prgn>, which
1188 conforms to the Debian Configuration management
1189 specification, version 2 or higher. Prompting the user by
1190 other means, such as by hand<footnote>
1191 From the Jargon file: by hand 2. By extension,
1192 writing code which does something in an explicit or
1193 low-level way for which a presupplied library
1194 (<em>debconf, in this instance</em>) routine ought
1195 to have been available.
1196 </footnote>, is now deprecated.
1200 The Debian Configuration management specification is included
1201 in the <file>debconf_specification</file> files in the
1202 <package>debian-policy</package> package.
1203 It is also available from the Debian web mirrors at
1204 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1205 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1209 Packages which use the Debian Configuration management
1210 specification may contain an additional
1211 <prgn>config</prgn> script and a <tt>templates</tt>
1212 file in their control archive<footnote>
1213 The control.tar.gz inside the .deb.
1214 See <manref name="deb" section="5">.
1216 The <prgn>config</prgn> script might be run before the
1217 <prgn>preinst</prgn> script, and before the package is unpacked
1218 or any of its dependencies or pre-dependencies are satisfied.
1219 Therefore it must work using only the tools present in
1220 <em>essential</em> packages.<footnote>
1221 <package>Debconf</package> or another tool that
1222 implements the Debian Configuration management
1223 specification will also be installed, and any
1224 versioned dependencies on it will be satisfied
1225 before preconfiguration begins.
1230 Packages which use the Debian Configuration management
1231 specification must allow for translation of their messages
1232 by using a gettext-based system such as the one provided by
1233 the <package>po-debconf</package> package.
1237 Packages should try to minimize the amount of prompting
1238 they need to do, and they should ensure that the user
1239 will only ever be asked each question once. This means
1240 that packages should try to use appropriate shared
1241 configuration files (such as <file>/etc/papersize</file> and
1242 <file>/etc/news/server</file>), and shared
1243 <package>debconf</package> variables rather than each
1244 prompting for their own list of required pieces of
1249 It also means that an upgrade should not ask the same
1250 questions again, unless the user has used
1251 <tt>dpkg --purge</tt> to remove the package's configuration.
1252 The answers to configuration questions should be stored in an
1253 appropriate place in <file>/etc</file> so that the user can
1254 modify them, and how this has been done should be
1259 If a package has a vitally important piece of
1260 information to pass to the user (such as "don't run me
1261 as I am, you must edit the following configuration files
1262 first or you risk your system emitting badly-formatted
1263 messages"), it should display this in the
1264 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1265 prompt the user to hit return to acknowledge the
1266 message. Copyright messages do not count as vitally
1267 important (they belong in
1268 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1269 neither do instructions on how to use a program (these
1270 should be in on-line documentation, where all the users
1275 Any necessary prompting should almost always be confined
1276 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1277 script. If it is done in the <prgn>postinst</prgn>, it
1278 should be protected with a conditional so that
1279 unnecessary prompting doesn't happen if a package's
1280 installation fails and the <prgn>postinst</prgn> is
1281 called with <tt>abort-upgrade</tt>,
1282 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1292 <heading>Source packages</heading>
1294 <sect id="standardsversion">
1295 <heading>Standards conformance</heading>
1298 Source packages should specify the most recent version number
1299 of this policy document with which your package complied
1300 when it was last updated.
1304 This information may be used to file bug reports
1305 automatically if your package becomes too much out of date.
1309 The version is specified in the <tt>Standards-Version</tt>
1311 The format of the <tt>Standards-Version</tt> field is
1312 described in <ref id="f-Standards-Version">.
1316 You should regularly, and especially if your package has
1317 become out of date, check for the newest Policy Manual
1318 available and update your package, if necessary. When your
1319 package complies with the new standards you should update the
1320 <tt>Standards-Version</tt> source package field and
1321 release it.<footnote>
1322 See the file <file>upgrading-checklist</file> for
1323 information about policy which has changed between
1324 different versions of this document.
1330 <sect id="pkg-relations">
1331 <heading>Package relationships</heading>
1334 Source packages should specify which binary packages they
1335 require to be installed or not to be installed in order to
1336 build correctly. For example, if building a package
1337 requires a certain compiler, then the compiler should be
1338 specified as a build-time dependency.
1342 It is not necessary to explicitly specify build-time
1343 relationships on a minimal set of packages that are always
1344 needed to compile, link and put in a Debian package a
1345 standard "Hello World!" program written in C or C++. The
1346 required packages are called <em>build-essential</em>, and
1347 an informational list can be found in
1348 <file>/usr/share/doc/build-essential/list</file> (which is
1349 contained in the <tt>build-essential</tt>
1352 <list compact="compact">
1354 This allows maintaining the list separately
1355 from the policy documents (the list does not
1356 need the kind of control that the policy
1360 Having a separate package allows one to install
1361 the build-essential packages on a machine, as
1362 well as allowing other packages such as tasks to
1363 require installation of the build-essential
1364 packages using the depends relation.
1367 The separate package allows bug reports against
1368 the list to be categorized separately from
1369 the policy management process in the BTS.
1376 When specifying the set of build-time dependencies, one
1377 should list only those packages explicitly required by the
1378 build. It is not necessary to list packages which are
1379 required merely because some other package in the list of
1380 build-time dependencies depends on them.<footnote>
1381 The reason for this is that dependencies change, and
1382 you should list all those packages, and <em>only</em>
1383 those packages that <em>you</em> need directly. What
1384 others need is their business. For example, if you
1385 only link against <file>libimlib</file>, you will need to
1386 build-depend on <package>libimlib2-dev</package> but
1387 not against any <tt>libjpeg*</tt> packages, even
1388 though <tt>libimlib2-dev</tt> currently depends on
1389 them: installation of <package>libimlib2-dev</package>
1390 will automatically ensure that all of its run-time
1391 dependencies are satisfied.
1396 If build-time dependencies are specified, it must be
1397 possible to build the package and produce working binaries
1398 on a system with only essential and build-essential
1399 packages installed and also those required to satisfy the
1400 build-time relationships (including any implied
1401 relationships). In particular, this means that version
1402 clauses should be used rigorously in build-time
1403 relationships so that one cannot produce bad or
1404 inconsistently configured packages when the relationships
1405 are properly satisfied.
1409 <ref id="relationships"> explains the technical details.
1414 <heading>Changes to the upstream sources</heading>
1417 If changes to the source code are made that are not
1418 specific to the needs of the Debian system, they should be
1419 sent to the upstream authors in whatever form they prefer
1420 so as to be included in the upstream version of the
1425 If you need to configure the package differently for
1426 Debian or for Linux, and the upstream source doesn't
1427 provide a way to do so, you should add such configuration
1428 facilities (for example, a new <prgn>autoconf</prgn> test
1429 or <tt>#define</tt>) and send the patch to the upstream
1430 authors, with the default set to the way they originally
1431 had it. You can then easily override the default in your
1432 <file>debian/rules</file> or wherever is appropriate.
1436 You should make sure that the <prgn>configure</prgn> utility
1437 detects the correct architecture specification string
1438 (refer to <ref id="arch-spec"> for details).
1442 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1443 <prgn>configure</prgn> scripts are used, you should edit the
1444 <file>.in</file> files rather than editing the
1445 <prgn>Makefile</prgn> directly. This allows the user to
1446 reconfigure the package if necessary. You should
1447 <em>not</em> configure the package and edit the generated
1448 <prgn>Makefile</prgn>! This makes it impossible for someone
1449 else to later reconfigure the package without losing the
1455 <sect id="dpkgchangelog">
1456 <heading>Debian changelog: <file>debian/changelog</file></heading>
1459 Changes in the Debian version of the package should be
1460 briefly explained in the Debian changelog file
1461 <file>debian/changelog</file>.<footnote>
1463 Mistakes in changelogs are usually best rectified by
1464 making a new changelog entry rather than "rewriting
1465 history" by editing old changelog entries.
1468 This includes modifications
1469 made in the Debian package compared to the upstream one
1470 as well as other changes and updates to the package.
1472 Although there is nothing stopping an author who is also
1473 the Debian maintainer from using this changelog for all
1474 their changes, it will have to be renamed if the Debian
1475 and upstream maintainers become different people. In such
1476 a case, however, it might be better to maintain the package
1477 as a non-native package.
1486 The format of the <file>debian/changelog</file> allows the
1487 package building tools to discover which version of the package
1488 is being built and find out other release-specific information.
1492 That format is a series of entries like this:
1494 <example compact="compact">
1495 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1497 [optional blank line(s), stripped]
1499 * <var>change details</var>
1500 <var>more change details</var>
1502 [blank line(s), included in output of dpkg-parsechangelog]
1504 * <var>even more change details</var>
1506 [optional blank line(s), stripped]
1508 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1513 <var>package</var> and <var>version</var> are the source
1514 package name and version number.
1518 <var>distribution(s)</var> lists the distributions where
1519 this version should be installed when it is uploaded - it
1520 is copied to the <tt>Distribution</tt> field in the
1521 <file>.changes</file> file. See <ref id="f-Distribution">.
1525 <var>urgency</var> is the value for the <tt>Urgency</tt>
1526 field in the <file>.changes</file> file for the upload
1527 (see <ref id="f-Urgency">). It is not possible to specify
1528 an urgency containing commas; commas are used to separate
1529 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1530 <prgn>dpkg</prgn> changelog format (though there is
1531 currently only one useful <var>keyword</var>,
1536 The change details may in fact be any series of lines
1537 starting with at least two spaces, but conventionally each
1538 change starts with an asterisk and a separating space and
1539 continuation lines are indented so as to bring them in
1540 line with the start of the text above. Blank lines may be
1541 used here to separate groups of changes, if desired.
1545 If this upload resolves bugs recorded in the Bug Tracking
1546 System (BTS), they may be automatically closed on the
1547 inclusion of this package into the Debian archive by
1548 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1549 in the change details.<footnote>
1550 To be precise, the string should match the following
1551 Perl regular expression:
1553 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1555 Then all of the bug numbers listed will be closed by the
1556 archive maintenance script (<prgn>katie</prgn>) using the
1557 <var>version</var> of the changelog entry.
1559 This information is conveyed via the <tt>Closes</tt> field
1560 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1564 The maintainer name and email address used in the changelog
1565 should be the details of the person uploading <em>this</em>
1566 version. They are <em>not</em> necessarily those of the
1567 usual package maintainer. The information here will be
1568 copied to the <tt>Changed-By</tt> field in the
1569 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1570 and then later used to send an acknowledgement when the
1571 upload has been installed.
1575 The <var>date</var> should be in RFC822 format<footnote>
1576 This is generated by <tt>date -R</tt>.
1577 </footnote>; it should include the time zone specified
1578 numerically, with the time zone name or abbreviation
1579 optionally present as a comment in parentheses.
1583 The first "title" line with the package name should start
1584 at the left hand margin; the "trailer" line with the
1585 maintainer and date details should be preceded by exactly
1586 one space. The maintainer details and the date must be
1587 separated by exactly two spaces.
1591 For more information on placement of the changelog files
1592 within binary packages, please see <ref id="changelogs">.
1595 <sect1><heading>Alternative changelog formats</heading>
1598 In non-experimental packages you must use a format for
1599 <file>debian/changelog</file> which is supported by the most
1600 recent released version of <prgn>dpkg</prgn>.
1604 It is possible to use a format different from the standard
1605 one by providing a changelog parser for the format you wish
1606 to use. The parser must have an API compatible with that
1607 expected by <prgn>dpkg-genchanges</prgn> and
1608 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1611 If there is general interest in the new format, you should
1612 contact the <package>dpkg</package> maintainer to have the
1613 parser script for it included in the <prgn>dpkg</prgn>
1614 package. (You will need to agree that the parser and its
1615 man page may be distributed under the GNU GPL, just as the rest
1616 of <prgn>dpkg</prgn> is.)
1621 <sect id="dpkgcopyright">
1622 <heading>Copyright: <file>debian/copyright</file></heading>
1624 Every package must be accompanied by a verbatim copy of
1625 its copyright and distribution license in the file
1626 <file>/usr/share/doc/<var>package</var>/copyright</file>
1627 (see <ref id="copyrightfile"> for further details). Also see
1628 <ref id="pkgcopyright"> for further considerations relayed
1629 to copyrights for packages.
1633 <heading>Error trapping in makefiles</heading>
1636 When <prgn>make</prgn> invokes a command in a makefile
1637 (including your package's upstream makefiles and
1638 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1639 means that <prgn>sh</prgn>'s usual bad error handling
1640 properties apply: if you include a miniature script as one
1641 of the commands in your makefile you'll find that if you
1642 don't do anything about it then errors are not detected
1643 and <prgn>make</prgn> will blithely continue after
1648 Every time you put more than one shell command (this
1649 includes using a loop) in a makefile command you
1650 must make sure that errors are trapped. For
1651 simple compound commands, such as changing directory and
1652 then running a program, using <tt>&&</tt> rather
1653 than semicolon as a command separator is sufficient. For
1654 more complex commands including most loops and
1655 conditionals you should include a separate <tt>set -e</tt>
1656 command at the start of every makefile command that's
1657 actually one of these miniature shell scripts.
1661 <sect id="timestamps">
1662 <heading>Time Stamps</heading>
1664 Maintainers should preserve the modification times of the
1665 upstream source files in a package, as far as is reasonably
1667 The rationale is that there is some information conveyed
1668 by knowing the age of the file, for example, you could
1669 recognize that some documentation is very old by looking
1670 at the modification time, so it would be nice if the
1671 modification time of the upstream source would be
1677 <sect id="restrictions">
1678 <heading>Restrictions on objects in source packages</heading>
1681 The source package may not contain any hard links<footnote>
1683 This is not currently detected when building source
1684 packages, but only when extracting
1688 Hard links may be permitted at some point in the
1689 future, but would require a fair amount of
1692 </footnote>, device special files, sockets or setuid or
1693 setgid files.<footnote>
1694 Setgid directories are allowed.
1699 <sect id="debianrules">
1700 <heading>Main building script: <file>debian/rules</file></heading>
1703 This file must be an executable makefile, and contains the
1704 package-specific recipes for compiling the package and
1705 building binary package(s) from the source.
1709 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1710 so that it can be invoked by saying its name rather than
1711 invoking <prgn>make</prgn> explicitly.
1715 Since an interactive <file>debian/rules</file> script makes it
1716 impossible to auto-compile that package and also makes it
1717 hard for other people to reproduce the same binary
1718 package, all <em>required targets</em> MUST be
1719 non-interactive. At a minimum, required targets are the
1720 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1721 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1722 <em>binary-indep</em>, and <em>build</em>. It also follows
1723 that any target that these targets depend on must also be
1728 The targets are as follows (required unless stated otherwise):
1730 <tag><tt>build</tt></tag>
1733 The <tt>build</tt> target should perform all the
1734 configuration and compilation of the package.
1735 If a package has an interactive pre-build
1736 configuration routine, the Debianized source package
1737 must either be built after this has taken place (so
1738 that the binary package can be built without rerunning
1739 the configuration) or the configuration routine
1740 modified to become non-interactive. (The latter is
1741 preferable if there are architecture-specific features
1742 detected by the configuration routine.)
1746 For some packages, notably ones where the same
1747 source tree is compiled in different ways to produce
1748 two binary packages, the <tt>build</tt> target
1749 does not make much sense. For these packages it is
1750 good enough to provide two (or more) targets
1751 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1752 for each of the ways of building the package, and a
1753 <tt>build</tt> target that does nothing. The
1754 <tt>binary</tt> target will have to build the
1755 package in each of the possible ways and make the
1756 binary package out of each.
1760 The <tt>build</tt> target must not do anything
1761 that might require root privilege.
1765 The <tt>build</tt> target may need to run the
1766 <tt>clean</tt> target first - see below.
1770 When a package has a configuration and build routine
1771 which takes a long time, or when the makefiles are
1772 poorly designed, or when <tt>build</tt> needs to
1773 run <tt>clean</tt> first, it is a good idea to
1774 <tt>touch build</tt> when the build process is
1775 complete. This will ensure that if <tt>debian/rules
1776 build</tt> is run again it will not rebuild the whole
1778 Another common way to do this is for <tt>build</tt>
1779 to depend on <prgn>build-stamp</prgn> and to do
1780 nothing else, and for the <prgn>build-stamp</prgn>
1781 target to do the building and to <tt>touch
1782 build-stamp</tt> on completion. This is
1783 especially useful if the build routine creates a
1784 file or directory called <tt>build</tt>; in such a
1785 case, <tt>build</tt> will need to be listed as
1786 a phony target (i.e., as a dependency of the
1787 <tt>.PHONY</tt> target). See the documentation of
1788 <prgn>make</prgn> for more information on phony
1794 <tag><tt>build-arch</tt> (optional),
1795 <tt>build-indep</tt> (optional)
1799 A package may also provide both of the targets
1800 <tt>build-arch</tt> and <tt>build-indep</tt>.
1801 The <tt>build-arch</tt> target, if provided, should
1802 perform all the configuration and compilation required
1803 for producing all architecture-dependant binary packages
1804 (those packages for which the body of the
1805 <tt>Architecture</tt> field in <tt>debian/control</tt>
1806 is not <tt>all</tt>).
1807 Similarly, the <tt>build-indep</tt> target, if
1808 provided, should perform all the configuration and
1809 compilation required for producing all
1810 architecture-independent binary packages
1811 (those packages for which the body of the
1812 <tt>Architecture</tt> field in <tt>debian/control</tt>
1814 The <tt>build</tt> target should depend on those of the
1815 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1816 are provided in the rules file.
1820 If one or both of the targets <tt>build-arch</tt> and
1821 <tt>build-indep</tt> are not provided, then invoking
1822 <file>debian/rules</file> with one of the not-provided
1823 targets as arguments should produce a exit status code
1824 of 2. Usually this is provided automatically by make
1825 if the target is missing.
1829 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1830 must not do anything that might require root privilege.
1834 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1835 <tt>binary-indep</tt>
1839 The <tt>binary</tt> target must be all that is
1840 necessary for the user to build the binary package(s)
1841 produced from this source package. It is
1842 split into two parts: <prgn>binary-arch</prgn> builds
1843 the binary packages which are specific to a particular
1844 architecture, and <tt>binary-indep</tt> builds
1845 those which are not.
1848 <tt>binary</tt> may be (and commonly is) a target with
1849 no commands which simply depends on
1850 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1853 Both <tt>binary-*</tt> targets should depend on the
1854 <tt>build</tt> target, or on the appropriate
1855 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1856 provided, so that the package is built if it has not
1857 been already. It should then create the relevant
1858 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1859 make their control files and <prgn>dpkg-deb</prgn> to
1860 build them and place them in the parent of the top
1865 Both the <tt>binary-arch</tt> and
1866 <tt>binary-indep</tt> targets <em>must</em> exist.
1867 If one of them has nothing to do (which will always be
1868 the case if the source generates only a single binary
1869 package, whether architecture-dependent or not), it
1870 must still exist and must always succeed.
1874 The <tt>binary</tt> targets must be invoked as
1876 The <prgn>fakeroot</prgn> package often allows one
1877 to build a package correctly even without being
1883 <tag><tt>clean</tt></tag>
1886 This must undo any effects that the <tt>build</tt>
1887 and <tt>binary</tt> targets may have had, except
1888 that it should leave alone any output files created in
1889 the parent directory by a run of a <tt>binary</tt>
1894 If a <tt>build</tt> file is touched at the end of
1895 the <tt>build</tt> target, as suggested above, it
1896 should be removed as the first action that
1897 <tt>clean</tt> performs, so that running
1898 <tt>build</tt> again after an interrupted
1899 <tt>clean</tt> doesn't think that everything is
1904 The <tt>clean</tt> target may need to be
1905 invoked as root if <tt>binary</tt> has been
1906 invoked since the last <tt>clean</tt>, or if
1907 <tt>build</tt> has been invoked as root (since
1908 <tt>build</tt> may create directories, for
1913 <tag><tt>get-orig-source</tt> (optional)</tag>
1916 This target fetches the most recent version of the
1917 original source package from a canonical archive site
1918 (via FTP or WWW, for example), does any necessary
1919 rearrangement to turn it into the original source
1920 tar file format described below, and leaves it in the
1925 This target may be invoked in any directory, and
1926 should take care to clean up any temporary files it
1931 This target is optional, but providing it if
1932 possible is a good idea.
1936 <tag><tt>patch</tt> (optional)</tag>
1939 This target performs whatever additional actions are
1940 required to make the source ready for editing (unpacking
1941 additional upstream archives, applying patches, etc.).
1942 It is recommended to be implemented for any package where
1943 <tt>dpkg-source -x</tt> does not result in source ready
1944 for additional modification. See
1945 <ref id="readmesource">.
1951 The <tt>build</tt>, <tt>binary</tt> and
1952 <tt>clean</tt> targets must be invoked with the current
1953 directory being the package's top-level directory.
1958 Additional targets may exist in <file>debian/rules</file>,
1959 either as published or undocumented interfaces or for the
1960 package's internal use.
1964 The architectures we build on and build for are determined
1965 by <prgn>make</prgn> variables using the utility
1966 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1967 You can determine the
1968 Debian architecture and the GNU style architecture
1969 specification string for the build machine (the machine type
1970 we are building on) as well as for the host machine (the
1971 machine type we are building for). Here is a list of
1972 supported <prgn>make</prgn> variables:
1973 <list compact="compact">
1975 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1978 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1979 specification string)
1982 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1983 <tt>DEB_*_GNU_TYPE</tt>)
1986 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1987 <tt>DEB_*_GNU_TYPE</tt>)
1989 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1990 the build machine or <tt>HOST</tt> for specification of the
1995 Backward compatibility can be provided in the rules file
1996 by setting the needed variables to suitable default
1997 values; please refer to the documentation of
1998 <prgn>dpkg-architecture</prgn> for details.
2002 It is important to understand that the <tt>DEB_*_ARCH</tt>
2003 string only determines which Debian architecture we are
2004 building on or for. It should not be used to get the CPU
2005 or system information; the GNU style variables should be
2009 <sect1 id="debianrules-options">
2010 <heading><file>debian/rules</file> and
2011 <tt>DEB_BUILD_OPTIONS</tt></heading>
2014 Supporting the standardized environment variable
2015 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2016 contain several flags to change how a package is compiled and
2017 built. Each flag must be in the form <var>flag</var> or
2018 <var>flag</var>=<var>options</var>. If multiple flags are
2019 given, they must be separated by whitespace.<footnote>
2020 Some packages support any delimiter, but whitespace is the
2021 easiest to parse inside a makefile and avoids ambiguity with
2022 flag values that contain commas.
2024 <var>flag</var> must start with a lowercase letter
2025 (<tt>a-z</tt>) and consist only of lowercase letters,
2026 numbers (<tt>0-9</tt>), and the characters
2027 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2028 <var>options</var> must not contain whitespace. The same
2029 tag should not be given multiple times with conflicting
2030 values. Package maintainers may assume that
2031 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2035 The meaning of the following tags has been standardized:
2039 The presence of this tag means that the package should
2040 be compiled with a minimum of optimization. For C
2041 programs, it is best to add <tt>-O0</tt> to
2042 <tt>CFLAGS</tt> (although this is usually the default).
2043 Some programs might fail to build or run at this level
2044 of optimization; it may be necessary to use
2045 <tt>-O1</tt>, for example.
2049 This tag means that the debugging symbols should not be
2050 stripped from the binary during installation, so that
2051 debugging information may be included in the package.
2053 <tag>parallel=n</tag>
2055 This tag means that the package should be built using up
2056 to <tt>n</tt> parallel processes if the package build
2057 system supports this.<footnote>
2058 Packages built with <tt>make</tt> can often implement
2059 this by passing the <tt>-j</tt><var>n</var> option to
2062 If the package build system does not support parallel
2063 builds, this string must be ignored. If the package
2064 build system only supports a lower level of concurrency
2065 than <var>n</var>, the package should be built using as
2066 many parallel processes as the package build system
2067 supports. It is up to the package maintainer to decide
2068 whether the package build times are long enough and the
2069 package build system is robust enough to make supporting
2070 parallel builds worthwhile.
2076 Unknown flags must be ignored by <file>debian/rules</file>.
2080 The following makefile snippet is an example of how one may
2081 implement the build options; you will probably have to
2082 massage this example in order to make it work for your
2084 <example compact="compact">
2087 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2088 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2089 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2090 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2092 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2097 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2098 INSTALL_PROGRAM += -s
2100 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2101 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2102 MAKEFLAGS += -j$(NUMJOBS)
2109 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2110 <sect id="substvars">
2111 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2114 When <prgn>dpkg-gencontrol</prgn>,
2115 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2116 generate control files they perform variable substitutions
2117 on their output just before writing it. Variable
2118 substitutions have the form <tt>${<var>variable</var>}</tt>.
2119 The optional file <file>debian/substvars</file> contains
2120 variable substitutions to be used; variables can also be set
2121 directly from <file>debian/rules</file> using the <tt>-V</tt>
2122 option to the source packaging commands, and certain
2123 predefined variables are also available.
2127 The <file>debian/substvars</file> file is usually generated and
2128 modified dynamically by <file>debian/rules</file> targets, in
2129 which case it must be removed by the <tt>clean</tt> target.
2133 See <manref name="deb-substvars" section="5"> for full
2134 details about source variable substitutions, including the
2135 format of <file>debian/substvars</file>.</p>
2138 <sect id="debianwatch">
2139 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2142 This is an optional, recommended control file for the
2143 <tt>uscan</tt> utility which defines how to automatically
2144 scan ftp or http sites for newly available updates of the
2145 package. This is used by <url id="
2146 http://dehs.alioth.debian.org/"> and other Debian QA tools
2147 to help with quality control and maintenance of the
2148 distribution as a whole.
2153 <sect id="debianfiles">
2154 <heading>Generated files list: <file>debian/files</file></heading>
2157 This file is not a permanent part of the source tree; it
2158 is used while building packages to record which files are
2159 being generated. <prgn>dpkg-genchanges</prgn> uses it
2160 when it generates a <file>.changes</file> file.
2164 It should not exist in a shipped source package, and so it
2165 (and any backup files or temporary files such as
2166 <file>files.new</file><footnote>
2167 <file>files.new</file> is used as a temporary file by
2168 <prgn>dpkg-gencontrol</prgn> and
2169 <prgn>dpkg-distaddfile</prgn> - they write a new
2170 version of <tt>files</tt> here before renaming it,
2171 to avoid leaving a corrupted copy if an error
2173 </footnote>) should be removed by the
2174 <tt>clean</tt> target. It may also be wise to
2175 ensure a fresh start by emptying or removing it at the
2176 start of the <tt>binary</tt> target.
2180 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2181 package, it adds an entry to <file>debian/files</file> for the
2182 <file>.deb</file> file that will be created when <tt>dpkg-deb
2183 --build</tt> is run for that binary package. So for most
2184 packages all that needs to be done with this file is to
2185 delete it in the <tt>clean</tt> target.
2189 If a package upload includes files besides the source
2190 package and any binary packages whose control files were
2191 made with <prgn>dpkg-gencontrol</prgn> then they should be
2192 placed in the parent of the package's top-level directory
2193 and <prgn>dpkg-distaddfile</prgn> should be called to add
2194 the file to the list in <file>debian/files</file>.</p>
2197 <sect id="embeddedfiles">
2198 <heading>Convenience copies of code</heading>
2201 Some software packages include in their distribution convenience
2202 copies of code from other software packages, generally so that
2203 users compiling from source don't have to download multiple
2204 packages. Debian packages should not make use of these
2205 convenience copies unless the included package is explicitly
2206 intended to be used in this way.<footnote>
2207 For example, parts of the GNU build system work like this.
2209 If the included code is already in the Debian archive in the
2210 form of a library, the Debian packaging should ensure that
2211 binary packages reference the libraries already in Debian and
2212 the convenience copy is not used. If the included code is not
2213 already in Debian, it should be packaged separately as a
2214 prerequisite if possible.
2216 Having multiple copies of the same code in Debian is
2217 inefficient, often creates either static linking or shared
2218 library conflicts, and, most importantly, increases the
2219 difficulty of handling security vulnerabilities in the
2225 <sect id="readmesource">
2226 <heading>Source package handling:
2227 <file>debian/README.source</file></heading>
2230 If running <prgn>dpkg-source -x</prgn> on a source package
2231 doesn't produce the source of the package, ready for editing,
2232 and allow one to make changes and run
2233 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2234 without taking any additional steps, creating a
2235 <file>debian/README.source</file> documentation file is
2236 recommended. This file should explain how to do all of the
2239 <item>Generate the fully patched source, in a form ready for
2240 editing, that would be built to create Debian
2241 packages. Doing this with a <tt>patch</tt> target in
2242 <file>debian/rules</file> is recommended; see
2243 <ref id="debianrules">.</item>
2244 <item>Modify the source and save those modifications so that
2245 they will be applied when building the package.</item>
2246 <item>Remove source modifications that are currently being
2247 applied when building the package.</item>
2248 <item>Optionally, document what steps are necessary to
2249 upgrade the Debian source package to a new upstream version,
2250 if applicable.</item>
2252 This explanation should include specific commands and mention
2253 any additional required Debian packages. It should not assume
2254 familiarity with any specific Debian packaging system or patch
2259 This explanation may refer to a documentation file installed by
2260 one of the package's build dependencies provided that the
2261 referenced documentation clearly explains these tasks and is not
2262 a general reference manual.
2266 <file>debian/README.source</file> may also include any other
2267 information that would be helpful to someone modifying the
2268 source package. Even if the package doesn't fit the above
2269 description, maintainers are encouraged to document in a
2270 <file>debian/README.source</file> file any source package with a
2271 particularly complex or unintuitive source layout or build
2272 system (for example, a package that builds the same source
2273 multiple times to generate different binary packages).
2279 <chapt id="controlfields">
2280 <heading>Control files and their fields</heading>
2283 The package management system manipulates data represented in
2284 a common format, known as <em>control data</em>, stored in
2285 <em>control files</em>.
2286 Control files are used for source packages, binary packages and
2287 the <file>.changes</file> files which control the installation
2288 of uploaded files<footnote>
2289 <prgn>dpkg</prgn>'s internal databases are in a similar
2294 <sect id="controlsyntax">
2295 <heading>Syntax of control files</heading>
2298 A control file consists of one or more paragraphs of
2300 The paragraphs are also sometimes referred to as stanzas.
2302 The paragraphs are separated by blank lines. Some control
2303 files allow only one paragraph; others allow several, in
2304 which case each paragraph usually refers to a different
2305 package. (For example, in source packages, the first
2306 paragraph refers to the source package, and later paragraphs
2307 refer to binary packages generated from the source.)
2311 Each paragraph consists of a series of data fields; each
2312 field consists of the field name, followed by a colon and
2313 then the data/value associated with that field. It ends at
2314 the end of the (logical) line. Horizontal whitespace
2315 (spaces and tabs) may occur immediately before or after the
2316 value and is ignored there; it is conventional to put a
2317 single space after the colon. For example, a field might
2319 <example compact="compact">
2322 the field name is <tt>Package</tt> and the field value
2327 Many fields' values may span several lines; in this case
2328 each continuation line must start with a space or a tab.
2329 Any trailing spaces or tabs at the end of individual
2330 lines of a field value are ignored.
2334 In fields where it is specified that lines may not wrap,
2335 only a single line of data is allowed and whitespace is not
2336 significant in a field body. Whitespace must not appear
2337 inside names (of packages, architectures, files or anything
2338 else) or version numbers, or between the characters of
2339 multi-character version relationships.
2343 Field names are not case-sensitive, but it is usual to
2344 capitalize the field names using mixed case as shown below.
2348 Blank lines, or lines consisting only of spaces and tabs,
2349 are not allowed within field values or between fields - that
2350 would mean a new paragraph.
2355 <sect id="sourcecontrolfiles">
2356 <heading>Source package control files -- <file>debian/control</file></heading>
2359 The <file>debian/control</file> file contains the most vital
2360 (and version-independent) information about the source package
2361 and about the binary packages it creates.
2365 The first paragraph of the control file contains information about
2366 the source package in general. The subsequent sets each describe a
2367 binary package that the source tree builds.
2371 The fields in the general paragraph (the first one, for the source
2374 <list compact="compact">
2375 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2376 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2377 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2378 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2379 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2380 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2381 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2382 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2387 The fields in the binary package paragraphs are:
2389 <list compact="compact">
2390 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2391 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2392 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2393 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2394 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2395 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2396 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2397 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2402 The syntax and semantics of the fields are described below.
2408 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2409 generate control files for binary packages (see below), by
2410 <prgn>dpkg-genchanges</prgn> to generate the
2411 <tt>.changes</tt> file to accompany the upload, and by
2412 <prgn>dpkg-source</prgn> when it creates the
2413 <file>.dsc</file> source control file as part of a source
2414 archive. Many fields are permitted to span multiple lines in
2415 <file>debian/control</file> but not in any other control
2416 file. These tools are responsible for removing the line
2417 breaks from such fields when using fields from
2418 <file>debian/control</file> to generate other control files.
2422 The fields here may contain variable references - their
2423 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2424 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2425 when they generate output control files.
2426 See <ref id="substvars"> for details.
2431 <sect id="binarycontrolfiles">
2432 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2435 The <file>DEBIAN/control</file> file contains the most vital
2436 (and version-dependent) information about a binary package.
2440 The fields in this file are:
2442 <list compact="compact">
2443 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2444 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2445 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2446 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2447 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2448 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2449 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2450 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2451 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2452 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2453 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2454 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2459 <sect id="debiansourcecontrolfiles">
2460 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2463 This file contains a series of fields, identified and
2464 separated just like the fields in the control file of
2465 a binary package. The fields are listed below; their
2466 syntax is described above, in <ref id="pkg-controlfields">.
2468 <list compact="compact">
2469 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2470 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2471 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2472 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2473 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2474 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2475 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2476 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2477 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2478 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2479 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2484 The source package control file is generated by
2485 <prgn>dpkg-source</prgn> when it builds the source
2486 archive, from other files in the source package,
2487 described above. When unpacking, it is checked against
2488 the files and directories in the other parts of the
2494 <sect id="debianchangesfiles">
2495 <heading>Debian changes files -- <file>.changes</file></heading>
2498 The .changes files are used by the Debian archive maintenance
2499 software to process updates to packages. They contain one
2500 paragraph which contains information from the
2501 <tt>debian/control</tt> file and other data about the
2502 source package gathered via <tt>debian/changelog</tt>
2503 and <tt>debian/rules</tt>.
2507 The fields in this file are:
2509 <list compact="compact">
2510 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2511 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2512 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2513 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2514 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2515 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2516 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2518 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2519 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2520 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2521 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2522 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2523 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2528 <sect id="controlfieldslist">
2529 <heading>List of fields</heading>
2531 <sect1 id="f-Source">
2532 <heading><tt>Source</tt></heading>
2535 This field identifies the source package name.
2539 In <file>debian/control</file> or a <file>.dsc</file> file,
2540 this field must contain only the name of the source package.
2544 In a binary package control file or a <file>.changes</file>
2545 file, the source package name may be followed by a version
2546 number in parentheses<footnote>
2547 It is customary to leave a space after the package name
2548 if a version number is specified.
2550 This version number may be omitted (and is, by
2551 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2552 the <tt>Version</tt> field of the binary package in
2553 question. The field itself may be omitted from a binary
2554 package control file when the source package has the same
2555 name and version as the binary package.
2559 <sect1 id="f-Maintainer">
2560 <heading><tt>Maintainer</tt></heading>
2563 The package maintainer's name and email address. The name
2564 should come first, then the email address inside angle
2565 brackets <tt><></tt> (in RFC822 format).
2569 If the maintainer's name contains a full stop then the
2570 whole field will not work directly as an email address due
2571 to a misfeature in the syntax specified in RFC822; a
2572 program using this field as an address must check for this
2573 and correct the problem if necessary (for example by
2574 putting the name in round brackets and moving it to the
2575 end, and bringing the email address forward).
2579 <sect1 id="f-Uploaders">
2580 <heading><tt>Uploaders</tt></heading>
2583 List of the names and email addresses of co-maintainers of
2584 the package, if any. If the package has other maintainers
2585 beside the one named in the
2586 <qref id="f-Maintainer">Maintainer field</qref>, their
2587 names and email addresses should be listed here. The
2588 format is the same as that of the Maintainer tag, and
2589 multiple entries should be comma separated. Currently,
2590 this field is restricted to a single line of data. This
2591 is an optional field.
2594 Any parser that interprets the Uploaders field in
2595 <file>debian/control</file> must permit it to span multiple
2596 lines. Line breaks in an Uploaders field that spans multiple
2597 lines are not significant and the semantics of the field are
2598 the same as if the line breaks had not been present.
2602 <sect1 id="f-Changed-By">
2603 <heading><tt>Changed-By</tt></heading>
2606 The name and email address of the person who changed the
2607 said package. Usually the name of the maintainer.
2608 All the rules for the Maintainer field apply here, too.
2612 <sect1 id="f-Section">
2613 <heading><tt>Section</tt></heading>
2616 This field specifies an application area into which the package
2617 has been classified. See <ref id="subsections">.
2621 When it appears in the <file>debian/control</file> file,
2622 it gives the value for the subfield of the same name in
2623 the <tt>Files</tt> field of the <file>.changes</file> file.
2624 It also gives the default for the same field in the binary
2629 <sect1 id="f-Priority">
2630 <heading><tt>Priority</tt></heading>
2633 This field represents how important that it is that the user
2634 have the package installed. See <ref id="priorities">.
2638 When it appears in the <file>debian/control</file> file,
2639 it gives the value for the subfield of the same name in
2640 the <tt>Files</tt> field of the <file>.changes</file> file.
2641 It also gives the default for the same field in the binary
2646 <sect1 id="f-Package">
2647 <heading><tt>Package</tt></heading>
2650 The name of the binary package.
2654 Package names must consist only of lower case letters
2655 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2656 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2657 They must be at least two characters long and must start
2658 with an alphanumeric character.
2662 <sect1 id="f-Architecture">
2663 <heading><tt>Architecture</tt></heading>
2666 Depending on context and the control file used, the
2667 <tt>Architecture</tt> field can include the following sets of
2670 <item>A unique single word identifying a Debian machine
2671 architecture, see <ref id="arch-spec">.
2672 <item><tt>all</tt>, which indicates an
2673 architecture-independent package.
2674 <item><tt>any</tt>, which indicates a package available
2675 for building on any architecture.
2676 <item><tt>source</tt>, which indicates a source package.
2681 In the main <file>debian/control</file> file in the source
2682 package, or in the source package control file
2683 <file>.dsc</file>, one may specify a list of architectures
2684 separated by spaces, or the special values <tt>any</tt> or
2689 Specifying <tt>any</tt> indicates that the source package
2690 isn't dependent on any particular architecture and should
2691 compile fine on any one. The produced binary package(s)
2692 will be specific to whatever the current build architecture
2694 This is the most often used setting, and is recommended
2695 for new packages that aren't <tt>Architecture: all</tt>.
2700 Specifying a list of architectures indicates that the source
2701 will build an architecture-dependent package, and will only
2702 work correctly on the listed architectures.<footnote>
2703 This is a setting used for a minority of cases where the
2704 program is not portable. Generally, it should not be used
2710 In a <file>.changes</file> file, the <tt>Architecture</tt>
2711 field lists the architecture(s) of the package(s)
2712 currently being uploaded. This will be a list; if the
2713 source for the package is also being uploaded, the special
2714 entry <tt>source</tt> is also present.
2718 See <ref id="debianrules"> for information how to get the
2719 architecture for the build process.
2723 <sect1 id="f-Essential">
2724 <heading><tt>Essential</tt></heading>
2727 This is a boolean field which may occur only in the
2728 control file of a binary package or in a per-package fields
2729 paragraph of a main source control data file.
2733 If set to <tt>yes</tt> then the package management system
2734 will refuse to remove the package (upgrading and replacing
2735 it is still possible). The other possible value is <tt>no</tt>,
2736 which is the same as not having the field at all.
2741 <heading>Package interrelationship fields:
2742 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2743 <tt>Recommends</tt>, <tt>Suggests</tt>,
2744 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2745 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2749 These fields describe the package's relationships with
2750 other packages. Their syntax and semantics are described
2751 in <ref id="relationships">.</p>
2754 <sect1 id="f-Standards-Version">
2755 <heading><tt>Standards-Version</tt></heading>
2758 The most recent version of the standards (the policy
2759 manual and associated texts) with which the package
2764 The version number has four components: major and minor
2765 version number and major and minor patch level. When the
2766 standards change in a way that requires every package to
2767 change the major number will be changed. Significant
2768 changes that will require work in many packages will be
2769 signaled by a change to the minor number. The major patch
2770 level will be changed for any change to the meaning of the
2771 standards, however small; the minor patch level will be
2772 changed when only cosmetic, typographical or other edits
2773 are made which neither change the meaning of the document
2774 nor affect the contents of packages.
2778 Thus only the first three components of the policy version
2779 are significant in the <em>Standards-Version</em> control
2780 field, and so either these three components or the all
2781 four components may be specified.<footnote>
2782 In the past, people specified the full version number
2783 in the Standards-Version field, for example "2.3.0.0".
2784 Since minor patch-level changes don't introduce new
2785 policy, it was thought it would be better to relax
2786 policy and only require the first 3 components to be
2787 specified, in this example "2.3.0". All four
2788 components may still be used if someone wishes to do so.
2794 <sect1 id="f-Version">
2795 <heading><tt>Version</tt></heading>
2798 The version number of a package. The format is:
2799 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2803 The three components here are:
2805 <tag><var>epoch</var></tag>
2808 This is a single (generally small) unsigned integer. It
2809 may be omitted, in which case zero is assumed. If it is
2810 omitted then the <var>upstream_version</var> may not
2815 It is provided to allow mistakes in the version numbers
2816 of older versions of a package, and also a package's
2817 previous version numbering schemes, to be left behind.
2821 <tag><var>upstream_version</var></tag>
2824 This is the main part of the version number. It is
2825 usually the version number of the original ("upstream")
2826 package from which the <file>.deb</file> file has been made,
2827 if this is applicable. Usually this will be in the same
2828 format as that specified by the upstream author(s);
2829 however, it may need to be reformatted to fit into the
2830 package management system's format and comparison
2835 The comparison behavior of the package management system
2836 with respect to the <var>upstream_version</var> is
2837 described below. The <var>upstream_version</var>
2838 portion of the version number is mandatory.
2842 The <var>upstream_version</var> may contain only
2843 alphanumerics<footnote>
2844 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2846 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2847 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2848 tilde) and should start with a digit. If there is no
2849 <var>debian_revision</var> then hyphens are not allowed;
2850 if there is no <var>epoch</var> then colons are not
2855 <tag><var>debian_revision</var></tag>
2858 This part of the version number specifies the version of
2859 the Debian package based on the upstream version. It
2860 may contain only alphanumerics and the characters
2861 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2862 tilde) and is compared in the same way as the
2863 <var>upstream_version</var> is.
2867 It is optional; if it isn't present then the
2868 <var>upstream_version</var> may not contain a hyphen.
2869 This format represents the case where a piece of
2870 software was written specifically to be turned into a
2871 Debian package, and so there is only one "debianisation"
2872 of it and therefore no revision indication is required.
2876 It is conventional to restart the
2877 <var>debian_revision</var> at <tt>1</tt> each time the
2878 <var>upstream_version</var> is increased.
2882 The package management system will break the version
2883 number apart at the last hyphen in the string (if there
2884 is one) to determine the <var>upstream_version</var> and
2885 <var>debian_revision</var>. The absence of a
2886 <var>debian_revision</var> is equivalent to a
2887 <var>debian_revision</var> of <tt>0</tt>.
2894 When comparing two version numbers, first the <var>epoch</var>
2895 of each are compared, then the <var>upstream_version</var> if
2896 <var>epoch</var> is equal, and then <var>debian_revision</var>
2897 if <var>upstream_version</var> is also equal.
2898 <var>epoch</var> is compared numerically. The
2899 <var>upstream_version</var> and <var>debian_revision</var>
2900 parts are compared by the package management system using the
2901 following algorithm:
2905 The strings are compared from left to right.
2909 First the initial part of each string consisting entirely of
2910 non-digit characters is determined. These two parts (one of
2911 which may be empty) are compared lexically. If a difference
2912 is found it is returned. The lexical comparison is a
2913 comparison of ASCII values modified so that all the letters
2914 sort earlier than all the non-letters and so that a tilde
2915 sorts before anything, even the end of a part. For example,
2916 the following parts are in sorted order from earliest to
2917 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2918 <tt>a</tt>.<footnote>
2919 One common use of <tt>~</tt> is for upstream pre-releases.
2920 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2921 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2926 Then the initial part of the remainder of each string which
2927 consists entirely of digit characters is determined. The
2928 numerical values of these two parts are compared, and any
2929 difference found is returned as the result of the comparison.
2930 For these purposes an empty string (which can only occur at
2931 the end of one or both version strings being compared) counts
2936 These two steps (comparing and removing initial non-digit
2937 strings and initial digit strings) are repeated until a
2938 difference is found or both strings are exhausted.
2942 Note that the purpose of epochs is to allow us to leave behind
2943 mistakes in version numbering, and to cope with situations
2944 where the version numbering scheme changes. It is
2945 <em>not</em> intended to cope with version numbers containing
2946 strings of letters which the package management system cannot
2947 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2948 silly orderings (the author of this manual has heard of a
2949 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2950 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2951 <tt>2</tt> and so forth).
2955 <sect1 id="f-Description">
2956 <heading><tt>Description</tt></heading>
2959 In a source or binary control file, the <tt>Description</tt>
2960 field contains a description of the binary package, consisting
2961 of two parts, the synopsis or the short description, and the
2962 long description. The field's format is as follows:
2967 Description: <single line synopsis>
2968 <extended description over several lines>
2973 The lines in the extended description can have these formats:
2979 Those starting with a single space are part of a paragraph.
2980 Successive lines of this form will be word-wrapped when
2981 displayed. The leading space will usually be stripped off.
2985 Those starting with two or more spaces. These will be
2986 displayed verbatim. If the display cannot be panned
2987 horizontally, the displaying program will line wrap them "hard"
2988 (i.e., without taking account of word breaks). If it can they
2989 will be allowed to trail off to the right. None, one or two
2990 initial spaces may be deleted, but the number of spaces
2991 deleted from each line will be the same (so that you can have
2992 indenting work correctly, for example).
2996 Those containing a single space followed by a single full stop
2997 character. These are rendered as blank lines. This is the
2998 <em>only</em> way to get a blank line<footnote>
2999 Completely empty lines will not be rendered as blank lines.
3000 Instead, they will cause the parser to think you're starting
3001 a whole new record in the control file, and will therefore
3002 likely abort with an error.
3007 Those containing a space, a full stop and some more characters.
3008 These are for future expansion. Do not use them.
3014 Do not use tab characters. Their effect is not predictable.
3018 See <ref id="descriptions"> for further information on this.
3022 In a <file>.changes</file> file, the <tt>Description</tt> field
3023 contains a summary of the descriptions for the packages being
3028 The part of the field before the first newline is empty;
3029 thereafter each line has the name of a binary package and
3030 the summary description line from that binary package.
3031 Each line is indented by one space.
3036 <sect1 id="f-Distribution">
3037 <heading><tt>Distribution</tt></heading>
3040 In a <file>.changes</file> file or parsed changelog output
3041 this contains the (space-separated) name(s) of the
3042 distribution(s) where this version of the package should
3043 be installed. Valid distributions are determined by the
3044 archive maintainers.<footnote>
3045 Current distribution names are:
3046 <taglist compact="compact">
3047 <tag><em>stable</em></tag>
3049 This is the current "released" version of Debian
3050 GNU/Linux. Once the distribution is
3051 <em>stable</em> only security fixes and other
3052 major bug fixes are allowed. When changes are
3053 made to this distribution, the release number is
3054 increased (for example: 2.2r1 becomes 2.2r2 then
3058 <tag><em>unstable</em></tag>
3060 This distribution value refers to the
3061 <em>developmental</em> part of the Debian
3062 distribution tree. New packages, new upstream
3063 versions of packages and bug fixes go into the
3064 <em>unstable</em> directory tree. Download from
3065 this distribution at your own risk.
3068 <tag><em>testing</em></tag>
3070 This distribution value refers to the
3071 <em>testing</em> part of the Debian distribution
3072 tree. It receives its packages from the
3073 unstable distribution after a short time lag to
3074 ensure that there are no major issues with the
3075 unstable packages. It is less prone to breakage
3076 than unstable, but still risky. It is not
3077 possible to upload packages directly to
3081 <tag><em>frozen</em></tag>
3083 From time to time, the <em>testing</em>
3084 distribution enters a state of "code-freeze" in
3085 anticipation of release as a <em>stable</em>
3086 version. During this period of testing only
3087 fixes for existing or newly-discovered bugs will
3088 be allowed. The exact details of this stage are
3089 determined by the Release Manager.
3092 <tag><em>experimental</em></tag>
3094 The packages with this distribution value are
3095 deemed by their maintainers to be high
3096 risk. Oftentimes they represent early beta or
3097 developmental packages from various sources that
3098 the maintainers want people to try, but are not
3099 ready to be a part of the other parts of the
3100 Debian distribution tree. Download at your own
3106 You should list <em>all</em> distributions that the
3107 package should be installed into.
3111 More information is available in the Debian Developer's
3112 Reference, section "The Debian archive".
3119 <heading><tt>Date</tt></heading>
3122 This field includes the date the package was built or last edited.
3126 The value of this field is usually extracted from the
3127 <file>debian/changelog</file> file - see
3128 <ref id="dpkgchangelog">).
3132 <sect1 id="f-Format">
3133 <heading><tt>Format</tt></heading>
3136 This field specifies a format revision for the file.
3137 The most current format described in the Policy Manual
3138 is version <strong>1.5</strong>. The syntax of the
3139 format value is the same as that of a package version
3140 number except that no epoch or Debian revision is allowed
3141 - see <ref id="f-Version">.
3145 <sect1 id="f-Urgency">
3146 <heading><tt>Urgency</tt></heading>
3149 This is a description of how important it is to upgrade to
3150 this version from previous ones. It consists of a single
3151 keyword taking one of the values <tt>low</tt>,
3152 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3153 <tt>critical</tt><footnote>
3154 Other urgency values are supported with configuration
3155 changes in the archive software but are not used in Debian.
3156 The urgency affects how quickly a package will be considered
3157 for inclusion into the <tt>testing</tt> distribution and
3158 gives an indication of the importance of any fixes included
3159 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3160 treated as synonymous.
3161 </footnote> (not case-sensitive) followed by an optional
3162 commentary (separated by a space) which is usually in
3163 parentheses. For example:
3166 Urgency: low (HIGH for users of diversions)
3172 The value of this field is usually extracted from the
3173 <file>debian/changelog</file> file - see
3174 <ref id="dpkgchangelog">.
3178 <sect1 id="f-Changes">
3179 <heading><tt>Changes</tt></heading>
3182 This field contains the human-readable changes data, describing
3183 the differences between the last version and the current one.
3187 There should be nothing in this field before the first
3188 newline; all the subsequent lines must be indented by at
3189 least one space; blank lines must be represented by a line
3190 consisting only of a space and a full stop.
3194 The value of this field is usually extracted from the
3195 <file>debian/changelog</file> file - see
3196 <ref id="dpkgchangelog">).
3200 Each version's change information should be preceded by a
3201 "title" line giving at least the version, distribution(s)
3202 and urgency, in a human-readable way.
3206 If data from several versions is being returned the entry
3207 for the most recent version should be returned first, and
3208 entries should be separated by the representation of a
3209 blank line (the "title" line may also be followed by the
3210 representation of blank line).
3214 <sect1 id="f-Binary">
3215 <heading><tt>Binary</tt></heading>
3218 This field is a list of binary packages.
3222 When it appears in the <file>.dsc</file> file it is the list
3223 of binary packages which a source package can produce. It
3224 does not necessarily produce all of these binary packages
3225 for every architecture. The source control file doesn't
3226 contain details of which architectures are appropriate for
3227 which of the binary packages.
3231 When it appears in a <file>.changes</file> file it lists the
3232 names of the binary packages actually being uploaded.
3236 The syntax is a list of binary packages separated by
3238 A space after each comma is conventional.
3239 </footnote>. Currently the packages must be separated using
3240 only spaces in the <file>.changes</file> file.
3244 <sect1 id="f-Installed-Size">
3245 <heading><tt>Installed-Size</tt></heading>
3248 This field appears in the control files of binary
3249 packages, and in the <file>Packages</file> files. It gives
3250 the total amount of disk space required to install the
3255 The disk space is represented in kilobytes as a simple
3260 <sect1 id="f-Files">
3261 <heading><tt>Files</tt></heading>
3264 This field contains a list of files with information about
3265 each one. The exact information and syntax varies with
3266 the context. In all cases the part of the field
3267 contents on the same line as the field name is empty. The
3268 remainder of the field is one line per file, each line
3269 being indented by one space and containing a number of
3270 sub-fields separated by spaces.
3274 In the <file>.dsc</file> file, each line contains the MD5
3275 checksum, size and filename of the tar file and (if applicable)
3276 diff file which make up the remainder of the source
3278 That is, the parts which are not the <tt>.dsc</tt>.
3280 The exact forms of the filenames are described
3281 in <ref id="pkg-sourcearchives">.
3285 In the <file>.changes</file> file this contains one line per
3286 file being uploaded. Each line contains the MD5 checksum,
3287 size, section and priority and the filename.
3288 The <qref id="f-Section">section</qref>
3289 and <qref id="f-Priority">priority</qref>
3290 are the values of the corresponding fields in
3291 the main source control file. If no section or priority is
3292 specified then <tt>-</tt> should be used, though section
3293 and priority values must be specified for new packages to
3294 be installed properly.
3298 The special value <tt>byhand</tt> for the section in a
3299 <tt>.changes</tt> file indicates that the file in question
3300 is not an ordinary package file and must by installed by
3301 hand by the distribution maintainers. If the section is
3302 <tt>byhand</tt> the priority should be <tt>-</tt>.
3306 If a new Debian revision of a package is being shipped and
3307 no new original source archive is being distributed the
3308 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3309 entry for the original source archive
3310 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3311 but the <file>.changes</file> file should leave it out. In
3312 this case the original source archive on the distribution
3313 site must match exactly, byte-for-byte, the original
3314 source archive which was used to generate the
3315 <file>.dsc</file> file and diff which are being uploaded.</p>
3318 <sect1 id="f-Closes">
3319 <heading><tt>Closes</tt></heading>
3322 A space-separated list of bug report numbers that the upload
3323 governed by the .changes file closes.
3327 <sect1 id="f-Homepage">
3328 <heading><tt>Homepage</tt></heading>
3331 The URL of the web site for this package, preferably (when
3332 applicable) the site from which the original source can be
3333 obtained and any additional upstream documentation or
3334 information may be found. The content of this field is a
3335 simple URL without any surrounding characters such as
3343 <heading>User-defined fields</heading>
3346 Additional user-defined fields may be added to the
3347 source package control file. Such fields will be
3348 ignored, and not copied to (for example) binary or
3349 source package control files or upload control files.
3353 If you wish to add additional unsupported fields to
3354 these output files you should use the mechanism
3359 Fields in the main source control information file with
3360 names starting <tt>X</tt>, followed by one or more of
3361 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3362 be copied to the output files. Only the part of the
3363 field name after the hyphen will be used in the output
3364 file. Where the letter <tt>B</tt> is used the field
3365 will appear in binary package control files, where the
3366 letter <tt>S</tt> is used in source package control
3367 files and where <tt>C</tt> is used in upload control
3368 (<tt>.changes</tt>) files.
3372 For example, if the main source information control file
3375 XBS-Comment: I stand between the candle and the star.
3377 then the binary and source package control files will contain the
3380 Comment: I stand between the candle and the star.
3389 <chapt id="maintainerscripts">
3390 <heading>Package maintainer scripts and installation procedure</heading>
3393 <heading>Introduction to package maintainer scripts</heading>
3396 It is possible to supply scripts as part of a package which
3397 the package management system will run for you when your
3398 package is installed, upgraded or removed.
3402 These scripts are the files <prgn>preinst</prgn>,
3403 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3404 <prgn>postrm</prgn> in the control area of the package.
3405 They must be proper executable files; if they are scripts
3406 (which is recommended), they must start with the usual
3407 <tt>#!</tt> convention. They should be readable and
3408 executable by anyone, and must not be world-writable.
3412 The package management system looks at the exit status from
3413 these scripts. It is important that they exit with a
3414 non-zero status if there is an error, so that the package
3415 management system can stop its processing. For shell
3416 scripts this means that you <em>almost always</em> need to
3417 use <tt>set -e</tt> (this is usually true when writing shell
3418 scripts, in fact). It is also important, of course, that
3419 they don't exit with a non-zero status if everything went
3424 Additionally, packages interacting with users using
3425 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3426 install a <prgn>config</prgn> script in the control area,
3427 see <ref id="maintscriptprompt"> for details.
3431 When a package is upgraded a combination of the scripts from
3432 the old and new packages is called during the upgrade
3433 procedure. If your scripts are going to be at all
3434 complicated you need to be aware of this, and may need to
3435 check the arguments to your scripts.
3439 Broadly speaking the <prgn>preinst</prgn> is called before
3440 (a particular version of) a package is installed, and the
3441 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3442 before (a version of) a package is removed and the
3443 <prgn>postrm</prgn> afterwards.
3447 Programs called from maintainer scripts should not normally
3448 have a path prepended to them. Before installation is
3449 started, the package management system checks to see if the
3450 programs <prgn>ldconfig</prgn>,
3451 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3452 and <prgn>update-rc.d</prgn> can be found via the
3453 <tt>PATH</tt> environment variable. Those programs, and any
3454 other program that one would expect to be in the
3455 <tt>PATH</tt>, should thus be invoked without an absolute
3456 pathname. Maintainer scripts should also not reset the
3457 <tt>PATH</tt>, though they might choose to modify it by
3458 prepending or appending package-specific directories. These
3459 considerations really apply to all shell scripts.</p>
3462 <sect id="idempotency">
3463 <heading>Maintainer scripts idempotency</heading>
3466 It is necessary for the error recovery procedures that the
3467 scripts be idempotent. This means that if it is run
3468 successfully, and then it is called again, it doesn't bomb
3469 out or cause any harm, but just ensures that everything is
3470 the way it ought to be. If the first call failed, or
3471 aborted half way through for some reason, the second call
3472 should merely do the things that were left undone the first
3473 time, if any, and exit with a success status if everything
3475 This is so that if an error occurs, the user interrupts
3476 <prgn>dpkg</prgn> or some other unforeseen circumstance
3477 happens you don't leave the user with a badly-broken
3478 package when <prgn>dpkg</prgn> attempts to repeat the
3484 <sect id="controllingterminal">
3485 <heading>Controlling terminal for maintainer scripts</heading>
3488 The maintainer scripts are guaranteed to run with a
3489 controlling terminal and can interact with the user.
3490 Because these scripts may be executed with standard output
3491 redirected into a pipe for logging purposes, Perl scripts
3492 should set unbuffered output by setting <tt>$|=1</tt> so
3493 that the output is printed immediately rather than being
3497 <sect id="exitstatus">
3498 <heading>Exit status</heading>
3501 Each script must return a zero exit status for
3502 success, or a nonzero one for failure, since the package
3503 management system looks for the exit status of these scripts
3504 and determines what action to take next based on that datum.
3508 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3513 <list compact="compact">
3515 <var>new-preinst</var> <tt>install</tt>
3518 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3521 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3524 <var>old-preinst</var> <tt>abort-upgrade</tt>
3525 <var>new-version</var>
3530 <list compact="compact">
3532 <var>postinst</var> <tt>configure</tt>
3533 <var>most-recently-configured-version</var>
3536 <var>old-postinst</var> <tt>abort-upgrade</tt>
3537 <var>new-version</var>
3540 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3541 <tt>in-favour</tt> <var>package</var>
3542 <var>new-version</var>
3545 <var>postinst</var> <tt>abort-remove</tt>
3548 <var>deconfigured's-postinst</var>
3549 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3550 <var>failed-install-package</var> <var>version</var>
3551 [<tt>removing</tt> <var>conflicting-package</var>
3557 <list compact="compact">
3559 <var>prerm</var> <tt>remove</tt>
3562 <var>old-prerm</var> <tt>upgrade</tt>
3563 <var>new-version</var>
3566 <var>new-prerm</var> <tt>failed-upgrade</tt>
3567 <var>old-version</var>
3570 <var>conflictor's-prerm</var> <tt>remove</tt>
3571 <tt>in-favour</tt> <var>package</var>
3572 <var>new-version</var>
3575 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3576 <tt>in-favour</tt> <var>package-being-installed</var>
3577 <var>version</var> [<tt>removing</tt>
3578 <var>conflicting-package</var>
3584 <list compact="compact">
3586 <var>postrm</var> <tt>remove</tt>
3589 <var>postrm</var> <tt>purge</tt>
3592 <var>old-postrm</var> <tt>upgrade</tt>
3593 <var>new-version</var>
3596 <var>new-postrm</var> <tt>failed-upgrade</tt>
3597 <var>old-version</var>
3600 <var>new-postrm</var> <tt>abort-install</tt>
3603 <var>new-postrm</var> <tt>abort-install</tt>
3604 <var>old-version</var>
3607 <var>new-postrm</var> <tt>abort-upgrade</tt>
3608 <var>old-version</var>
3611 <var>disappearer's-postrm</var> <tt>disappear</tt>
3612 <var>overwriter</var>
3613 <var>overwriter-version</var>
3619 <sect id="unpackphase">
3620 <heading>Details of unpack phase of installation or upgrade</heading>
3623 The procedure on installation/upgrade/overwrite/disappear
3624 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3625 stage of <tt>dpkg --install</tt>) is as follows. In each
3626 case, if a major error occurs (unless listed below) the
3627 actions are, in general, run backwards - this means that the
3628 maintainer scripts are run with different arguments in
3629 reverse order. These are the "error unwind" calls listed
3636 If a version of the package is already installed, call
3637 <example compact="compact">
3638 <var>old-prerm</var> upgrade <var>new-version</var>
3642 If the script runs but exits with a non-zero
3643 exit status, <prgn>dpkg</prgn> will attempt:
3644 <example compact="compact">
3645 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3647 If this works, the upgrade continues. If this
3648 does not work, the error unwind:
3649 <example compact="compact">
3650 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3652 If this works, then the old-version is
3653 "Installed", if not, the old version is in a
3654 "Failed-Config" state.
3660 If a "conflicting" package is being removed at the same time,
3661 or if any package will be broken (due to <tt>Breaks</tt>):
3664 If <tt>--auto-deconfigure</tt> is
3665 specified, call, for each package to be deconfigured
3666 due to <tt>Breaks</tt>:
3667 <example compact="compact">
3668 <var>deconfigured's-prerm</var> deconfigure \
3669 in-favour <var>package-being-installed</var> <var>version</var>
3672 <example compact="compact">
3673 <var>deconfigured's-postinst</var> abort-deconfigure \
3674 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3676 The deconfigured packages are marked as
3677 requiring configuration, so that if
3678 <tt>--install</tt> is used they will be
3679 configured again if possible.
3682 If any packages depended on a conflicting
3683 package being removed and <tt>--auto-deconfigure</tt> is
3684 specified, call, for each such package:
3685 <example compact="compact">
3686 <var>deconfigured's-prerm</var> deconfigure \
3687 in-favour <var>package-being-installed</var> <var>version</var> \
3688 removing <var>conflicting-package</var> <var>version</var>
3691 <example compact="compact">
3692 <var>deconfigured's-postinst</var> abort-deconfigure \
3693 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3694 removing <var>conflicting-package</var> <var>version</var>
3696 The deconfigured packages are marked as
3697 requiring configuration, so that if
3698 <tt>--install</tt> is used they will be
3699 configured again if possible.
3702 To prepare for removal of each conflicting package, call:
3703 <example compact="compact">
3704 <var>conflictor's-prerm</var> remove \
3705 in-favour <var>package</var> <var>new-version</var>
3708 <example compact="compact">
3709 <var>conflictor's-postinst</var> abort-remove \
3710 in-favour <var>package</var> <var>new-version</var>
3719 If the package is being upgraded, call:
3720 <example compact="compact">
3721 <var>new-preinst</var> upgrade <var>old-version</var>
3723 If this fails, we call:
3725 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3732 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3734 is called. If this works, then the old version
3735 is in an "Installed" state, or else it is left
3736 in an "Unpacked" state.
3741 If it fails, then the old version is left
3742 in an "Half-Installed" state.
3749 Otherwise, if the package had some configuration
3750 files from a previous version installed (i.e., it
3751 is in the "configuration files only" state):
3752 <example compact="compact">
3753 <var>new-preinst</var> install <var>old-version</var>
3757 <var>new-postrm</var> abort-install <var>old-version</var>
3759 If this fails, the package is left in a
3760 "Half-Installed" state, which requires a
3761 reinstall. If it works, the packages is left in
3762 a "Config Files" state.
3765 Otherwise (i.e., the package was completely purged):
3766 <example compact="compact">
3767 <var>new-preinst</var> install
3770 <example compact="compact">
3771 <var>new-postrm</var> abort-install
3773 If the error-unwind fails, the package is in a
3774 "Half Installed" phase, and requires a
3775 reinstall. If the error unwind works, the
3776 package is in a not installed state.
3783 The new package's files are unpacked, overwriting any
3784 that may be on the system already, for example any
3785 from the old version of the same package or from
3786 another package. Backups of the old files are kept
3787 temporarily, and if anything goes wrong the package
3788 management system will attempt to put them back as
3789 part of the error unwind.
3793 It is an error for a package to contain files which
3794 are on the system in another package, unless
3795 <tt>Replaces</tt> is used (see <ref id="replaces">).
3797 The following paragraph is not currently the case:
3798 Currently the <tt>- - force-overwrite</tt> flag is
3799 enabled, downgrading it to a warning, but this may not
3805 It is a more serious error for a package to contain a
3806 plain file or other kind of non-directory where another
3807 package has a directory (again, unless
3808 <tt>Replaces</tt> is used). This error can be
3809 overridden if desired using
3810 <tt>--force-overwrite-dir</tt>, but this is not
3815 Packages which overwrite each other's files produce
3816 behavior which, though deterministic, is hard for the
3817 system administrator to understand. It can easily
3818 lead to "missing" programs if, for example, a package
3819 is installed which overwrites a file from another
3820 package, and is then removed again.<footnote>
3821 Part of the problem is due to what is arguably a
3822 bug in <prgn>dpkg</prgn>.
3827 A directory will never be replaced by a symbolic link
3828 to a directory or vice versa; instead, the existing
3829 state (symlink or not) will be left alone and
3830 <prgn>dpkg</prgn> will follow the symlink if there is
3839 If the package is being upgraded, call
3840 <example compact="compact">
3841 <var>old-postrm</var> upgrade <var>new-version</var>
3845 If this fails, <prgn>dpkg</prgn> will attempt:
3846 <example compact="compact">
3847 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3849 If this works, installation continues. If not,
3851 <example compact="compact">
3852 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3854 If this fails, the old version is left in an
3855 "Half Installed" state. If it works, dpkg now
3857 <example compact="compact">
3858 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3860 If this fails, the old version is left in an
3861 "Half Installed" state. If it works, dpkg now
3863 <example compact="compact">
3864 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3866 If this fails, the old version is in an
3873 This is the point of no return - if
3874 <prgn>dpkg</prgn> gets this far, it won't back off
3875 past this point if an error occurs. This will
3876 leave the package in a fairly bad state, which
3877 will require a successful re-installation to clear
3878 up, but it's when <prgn>dpkg</prgn> starts doing
3879 things that are irreversible.
3884 Any files which were in the old version of the package
3885 but not in the new are removed.
3889 The new file list replaces the old.
3893 The new maintainer scripts replace the old.
3897 Any packages all of whose files have been overwritten
3898 during the installation, and which aren't required for
3899 dependencies, are considered to have been removed.
3900 For each such package
3903 <prgn>dpkg</prgn> calls:
3904 <example compact="compact">
3905 <var>disappearer's-postrm</var> disappear \
3906 <var>overwriter</var> <var>overwriter-version</var>
3910 The package's maintainer scripts are removed.
3913 It is noted in the status database as being in a
3914 sane state, namely not installed (any conffiles
3915 it may have are ignored, rather than being
3916 removed by <prgn>dpkg</prgn>). Note that
3917 disappearing packages do not have their prerm
3918 called, because <prgn>dpkg</prgn> doesn't know
3919 in advance that the package is going to
3926 Any files in the package we're unpacking that are also
3927 listed in the file lists of other packages are removed
3928 from those lists. (This will lobotomize the file list
3929 of the "conflicting" package if there is one.)
3933 The backup files made during installation, above, are
3939 The new package's status is now sane, and recorded as
3944 Here is another point of no return - if the
3945 conflicting package's removal fails we do not unwind
3946 the rest of the installation; the conflicting package
3947 is left in a half-removed limbo.
3952 If there was a conflicting package we go and do the
3953 removal actions (described below), starting with the
3954 removal of the conflicting package's files (any that
3955 are also in the package being installed have already
3956 been removed from the conflicting package's file list,
3957 and so do not get removed now).
3963 <sect id="configdetails"><heading>Details of configuration</heading>
3966 When we configure a package (this happens with <tt>dpkg
3967 --install</tt> and <tt>dpkg --configure</tt>), we first
3968 update any <tt>conffile</tt>s and then call:
3969 <example compact="compact">
3970 <var>postinst</var> configure <var>most-recently-configured-version</var>
3975 No attempt is made to unwind after errors during
3976 configuration. If the configuration fails, the package is in
3977 a "Failed Config" state, and an error message is generated.
3981 If there is no most recently configured version
3982 <prgn>dpkg</prgn> will pass a null argument.
3985 Historical note: Truly ancient (pre-1997) versions of
3986 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3987 (including the angle brackets) in this case. Even older
3988 ones did not pass a second argument at all, under any
3989 circumstance. Note that upgrades using such an old dpkg
3990 version are unlikely to work for other reasons, even if
3991 this old argument behavior is handled by your postinst script.
3997 <sect id="removedetails"><heading>Details of removal and/or
3998 configuration purging</heading>
4004 <example compact="compact">
4005 <var>prerm</var> remove
4009 If prerm fails during replacement due to conflict
4011 <var>conflictor's-postinst</var> abort-remove \
4012 in-favour <var>package</var> <var>new-version</var>
4016 <var>postinst</var> abort-remove
4020 If this fails, the package is in a "Failed-Config"
4021 state, or else it remains "Installed".
4025 The package's files are removed (except <tt>conffile</tt>s).
4028 <example compact="compact">
4029 <var>postrm</var> remove
4033 If it fails, there's no error unwind, and the package is in
4034 an "Half-Installed" state.
4039 All the maintainer scripts except the <prgn>postrm</prgn>
4044 If we aren't purging the package we stop here. Note
4045 that packages which have no <prgn>postrm</prgn> and no
4046 <tt>conffile</tt>s are automatically purged when
4047 removed, as there is no difference except for the
4048 <prgn>dpkg</prgn> status.
4052 The <tt>conffile</tt>s and any backup files
4053 (<tt>~</tt>-files, <tt>#*#</tt> files,
4054 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4059 <example compact="compact">
4060 <var>postrm</var> purge
4064 If this fails, the package remains in a "Config-Files"
4069 The package's file list is removed.
4078 <chapt id="relationships">
4079 <heading>Declaring relationships between packages</heading>
4081 <sect id="depsyntax">
4082 <heading>Syntax of relationship fields</heading>
4085 These fields all have a uniform syntax. They are a list of
4086 package names separated by commas.
4090 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4091 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4092 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4093 control file fields of the package, which declare
4094 dependencies on other packages, the package names listed may
4095 also include lists of alternative package names, separated
4096 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4097 if any one of the alternative packages is installed, that
4098 part of the dependency is considered to be satisfied.
4102 All of the fields except for <tt>Provides</tt> may restrict
4103 their applicability to particular versions of each named
4104 package. This is done in parentheses after each individual
4105 package name; the parentheses should contain a relation from
4106 the list below followed by a version number, in the format
4107 described in <ref id="f-Version">.
4111 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4112 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4113 strictly earlier, earlier or equal, exactly equal, later or
4114 equal and strictly later, respectively. The deprecated
4115 forms <tt><</tt> and <tt>></tt> were used to mean
4116 earlier/later or equal, rather than strictly earlier/later,
4117 so they should not appear in new packages (though
4118 <prgn>dpkg</prgn> still supports them).
4122 Whitespace may appear at any point in the version
4123 specification subject to the rules in <ref
4124 id="controlsyntax">, and must appear where it's necessary to
4125 disambiguate; it is not otherwise significant. All of the
4126 relationship fields may span multiple lines. For
4127 consistency and in case of future changes to
4128 <prgn>dpkg</prgn> it is recommended that a single space be
4129 used after a version relationship and before a version
4130 number; it is also conventional to put a single space after
4131 each comma, on either side of each vertical bar, and before
4132 each open parenthesis. When wrapping a relationship field, it
4133 is conventional to do so after a comma and before the space
4134 following that comma.
4138 For example, a list of dependencies might appear as:
4139 <example compact="compact">
4142 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4147 All fields that specify build-time relationships
4148 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4149 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4150 may be restricted to a certain set of architectures. This
4151 is indicated in brackets after each individual package name and
4152 the optional version specification. The brackets enclose a
4153 list of Debian architecture names separated by whitespace.
4154 Exclamation marks may be prepended to each of the names.
4155 (It is not permitted for some names to be prepended with
4156 exclamation marks while others aren't.) If the current Debian
4157 host architecture is not in this list and there are no
4158 exclamation marks in the list, or it is in the list with a
4159 prepended exclamation mark, the package name and the
4160 associated version specification are ignored completely for
4161 the purposes of defining the relationships.
4166 <example compact="compact">
4168 Build-Depends-Indep: texinfo
4169 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4170 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4175 Note that the binary package relationship fields such as
4176 <tt>Depends</tt> appear in one of the binary package
4177 sections of the control file, whereas the build-time
4178 relationships such as <tt>Build-Depends</tt> appear in the
4179 source package section of the control file (which is the
4184 <sect id="binarydeps">
4185 <heading>Binary Dependencies - <tt>Depends</tt>,
4186 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4187 <tt>Pre-Depends</tt>
4191 Packages can declare in their control file that they have
4192 certain relationships to other packages - for example, that
4193 they may not be installed at the same time as certain other
4194 packages, and/or that they depend on the presence of others.
4198 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4199 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4200 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4204 These seven fields are used to declare a dependency
4205 relationship by one package on another. Except for
4206 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4207 depending (binary) package's control file.
4208 (<tt>Enhances</tt> appears in the recommending package's
4209 control file, and <tt>Breaks</tt> appears in the version of
4210 depended-on package which causes the named package to
4215 A <tt>Depends</tt> field takes effect <em>only</em> when a
4216 package is to be configured. It does not prevent a package
4217 being on the system in an unconfigured state while its
4218 dependencies are unsatisfied, and it is possible to replace
4219 a package whose dependencies are satisfied and which is
4220 properly installed with a different version whose
4221 dependencies are not and cannot be satisfied; when this is
4222 done the depending package will be left unconfigured (since
4223 attempts to configure it will give errors) and will not
4224 function properly. If it is necessary, a
4225 <tt>Pre-Depends</tt> field can be used, which has a partial
4226 effect even when a package is being unpacked, as explained
4227 in detail below. (The other three dependency fields,
4228 <tt>Recommends</tt>, <tt>Suggests</tt> and
4229 <tt>Enhances</tt>, are only used by the various front-ends
4230 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4231 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4235 For this reason packages in an installation run are usually
4236 all unpacked first and all configured later; this gives
4237 later versions of packages with dependencies on later
4238 versions of other packages the opportunity to have their
4239 dependencies satisfied.
4243 In case of circular dependencies, since installation or
4244 removal order honoring the dependency order can't be
4245 established, dependency loops are broken at some point
4246 (based on rules below), and some packages may not be able to
4247 rely on their dependencies being present when being
4248 installed or removed, depending on which side of the break
4249 of the circular dependency loop they happen to be on. If one
4250 of the packages in the loop has no postinst script, then the
4251 cycle will be broken at that package, so as to ensure that
4252 all postinst scripts run with the dependencies properly
4253 configured if this is possible. Otherwise the breaking point
4258 The <tt>Depends</tt> field thus allows package maintainers
4259 to impose an order in which packages should be configured.
4263 The meaning of the five dependency fields is as follows:
4265 <tag><tt>Depends</tt></tag>
4268 This declares an absolute dependency. A package will
4269 not be configured unless all of the packages listed in
4270 its <tt>Depends</tt> field have been correctly
4275 The <tt>Depends</tt> field should be used if the
4276 depended-on package is required for the depending
4277 package to provide a significant amount of
4282 The <tt>Depends</tt> field should also be used if the
4283 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4284 <prgn>postrm</prgn> scripts require the package to be
4285 present in order to run. Note, however, that the
4286 <prgn>postrm</prgn> cannot rely on any non-essential
4287 packages to be present during the <tt>purge</tt>
4291 <tag><tt>Recommends</tt></tag>
4294 This declares a strong, but not absolute, dependency.
4298 The <tt>Recommends</tt> field should list packages
4299 that would be found together with this one in all but
4300 unusual installations.
4304 <tag><tt>Suggests</tt></tag>
4306 This is used to declare that one package may be more
4307 useful with one or more others. Using this field
4308 tells the packaging system and the user that the
4309 listed packages are related to this one and can
4310 perhaps enhance its usefulness, but that installing
4311 this one without them is perfectly reasonable.
4314 <tag><tt>Enhances</tt></tag>
4316 This field is similar to Suggests but works in the
4317 opposite direction. It is used to declare that a
4318 package can enhance the functionality of another
4322 <tag><tt>Pre-Depends</tt></tag>
4325 This field is like <tt>Depends</tt>, except that it
4326 also forces <prgn>dpkg</prgn> to complete installation
4327 of the packages named before even starting the
4328 installation of the package which declares the
4329 pre-dependency, as follows:
4333 When a package declaring a pre-dependency is about to
4334 be <em>unpacked</em> the pre-dependency can be
4335 satisfied if the depended-on package is either fully
4336 configured, <em>or even if</em> the depended-on
4337 package(s) are only unpacked or half-configured,
4338 provided that they have been configured correctly at
4339 some point in the past (and not removed or partially
4340 removed since). In this case, both the
4341 previously-configured and currently unpacked or
4342 half-configured versions must satisfy any version
4343 clause in the <tt>Pre-Depends</tt> field.
4347 When the package declaring a pre-dependency is about
4348 to be <em>configured</em>, the pre-dependency will be
4349 treated as a normal <tt>Depends</tt>, that is, it will
4350 be considered satisfied only if the depended-on
4351 package has been correctly configured.
4355 <tt>Pre-Depends</tt> should be used sparingly,
4356 preferably only by packages whose premature upgrade or
4357 installation would hamper the ability of the system to
4358 continue with any upgrade that might be in progress.
4362 <tt>Pre-Depends</tt> are also required if the
4363 <prgn>preinst</prgn> script depends on the named
4364 package. It is best to avoid this situation if
4372 When selecting which level of dependency to use you should
4373 consider how important the depended-on package is to the
4374 functionality of the one declaring the dependency. Some
4375 packages are composed of components of varying degrees of
4376 importance. Such a package should list using
4377 <tt>Depends</tt> the package(s) which are required by the
4378 more important components. The other components'
4379 requirements may be mentioned as Suggestions or
4380 Recommendations, as appropriate to the components' relative
4386 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4389 Using <tt>Breaks</tt> may cause problems for upgrades from older
4390 versions of Debian and should not be used until the stable
4391 release of Debian supports <tt>Breaks</tt>.
4395 When one binary package declares that it breaks another,
4396 <prgn>dpkg</prgn> will refuse to allow the package which
4397 declares <tt>Breaks</tt> be installed unless the broken
4398 package is deconfigured first, and it will refuse to
4399 allow the broken package to be reconfigured.
4403 A package will not be regarded as causing breakage merely
4404 because its configuration files are still installed; it must
4405 be at least half-installed.
4409 A special exception is made for packages which declare that
4410 they break their own package name or a virtual package which
4411 they provide (see below): this does not count as a real
4416 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4417 version clause; such a <tt>Breaks</tt> is introduced in the
4418 version of an (implicit or explicit) dependency which
4419 violates an assumption or reveals a bug in earlier versions
4420 of the broken package. This use of <tt>Breaks</tt> will
4421 inform higher-level package management tools that broken
4422 package must be upgraded before the new one.
4426 If the breaking package also overwrites some files from the
4427 older package, it should use <tt>Replaces</tt> (not
4428 <tt>Conflicts</tt>) to ensure this goes smoothly.
4432 <sect id="conflicts">
4433 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4436 When one binary package declares a conflict with another
4437 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4438 refuse to allow them to be installed on the system at the
4443 If one package is to be installed, the other must be removed
4444 first - if the package being installed is marked as
4445 replacing (see <ref id="replaces">) the one on the system,
4446 or the one on the system is marked as deselected, or both
4447 packages are marked <tt>Essential</tt>, then
4448 <prgn>dpkg</prgn> will automatically remove the package
4449 which is causing the conflict, otherwise it will halt the
4450 installation of the new package with an error. This
4451 mechanism is specifically designed to produce an error when
4452 the installed package is <tt>Essential</tt>, but the new
4457 A package will not cause a conflict merely because its
4458 configuration files are still installed; it must be at least
4463 A special exception is made for packages which declare a
4464 conflict with their own package name, or with a virtual
4465 package which they provide (see below): this does not
4466 prevent their installation, and allows a package to conflict
4467 with others providing a replacement for it. You use this
4468 feature when you want the package in question to be the only
4469 package providing some feature.
4473 A <tt>Conflicts</tt> entry should almost never have an
4474 "earlier than" version clause. This would prevent
4475 <prgn>dpkg</prgn> from upgrading or installing the package
4476 which declared such a conflict until the upgrade or removal
4477 of the conflicted-with package had been completed. Instead,
4478 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4479 by the stable release of Debian).
4483 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4487 As well as the names of actual ("concrete") packages, the
4488 package relationship fields <tt>Depends</tt>,
4489 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4490 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4491 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4492 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4493 may mention "virtual packages".
4497 A <em>virtual package</em> is one which appears in the
4498 <tt>Provides</tt> control file field of another package.
4499 The effect is as if the package(s) which provide a
4500 particular virtual package name had been listed by name
4501 everywhere the virtual package name appears. (See also <ref
4506 If there are both concrete and virtual packages of the same
4507 name, then the dependency may be satisfied (or the conflict
4508 caused) by either the concrete package with the name in
4509 question or any other concrete package which provides the
4510 virtual package with the name in question. This is so that,
4511 for example, supposing we have
4512 <example compact="compact">
4515 </example> and someone else releases an enhanced version of
4516 the <tt>bar</tt> package they can say:
4517 <example compact="compact">
4521 and the <tt>bar-plus</tt> package will now also satisfy the
4522 dependency for the <tt>foo</tt> package.
4526 If a relationship field has a version number attached
4527 then only real packages will be considered to see whether
4528 the relationship is satisfied (or the prohibition violated,
4529 for a conflict or breakage) - it is assumed that a real
4530 package which provides the virtual package is not of the
4531 "right" version. So, a <tt>Provides</tt> field may not
4532 contain version numbers, and the version number of the
4533 concrete package which provides a particular virtual package
4534 will not be looked at when considering a dependency on or
4535 conflict with the virtual package name.
4539 It is likely that the ability will be added in a future
4540 release of <prgn>dpkg</prgn> to specify a version number for
4541 each virtual package it provides. This feature is not yet
4542 present, however, and is expected to be used only
4547 If you want to specify which of a set of real packages
4548 should be the default to satisfy a particular dependency on
4549 a virtual package, you should list the real package as an
4550 alternative before the virtual one.
4555 <sect id="replaces"><heading>Overwriting files and replacing
4556 packages - <tt>Replaces</tt></heading>
4559 Packages can declare in their control file that they should
4560 overwrite files in certain other packages, or completely
4561 replace other packages. The <tt>Replaces</tt> control file
4562 field has these two distinct purposes.
4565 <sect1><heading>Overwriting files in other packages</heading>
4568 Firstly, as mentioned before, it is usually an error for a
4569 package to contain files which are on the system in
4574 However, if the overwriting package declares that it
4575 <tt>Replaces</tt> the one containing the file being
4576 overwritten, then <prgn>dpkg</prgn> will replace the file
4577 from the old package with that from the new. The file
4578 will no longer be listed as "owned" by the old package.
4582 If a package is completely replaced in this way, so that
4583 <prgn>dpkg</prgn> does not know of any files it still
4584 contains, it is considered to have "disappeared". It will
4585 be marked as not wanted on the system (selected for
4586 removal) and not installed. Any <tt>conffile</tt>s
4587 details noted for the package will be ignored, as they
4588 will have been taken over by the overwriting package. The
4589 package's <prgn>postrm</prgn> script will be run with a
4590 special argument to allow the package to do any final
4591 cleanup required. See <ref id="mscriptsinstact">.
4594 Replaces is a one way relationship -- you have to
4595 install the replacing package after the replaced
4602 For this usage of <tt>Replaces</tt>, virtual packages (see
4603 <ref id="virtual">) are not considered when looking at a
4604 <tt>Replaces</tt> field - the packages declared as being
4605 replaced must be mentioned by their real names.
4609 Furthermore, this usage of <tt>Replaces</tt> only takes
4610 effect when both packages are at least partially on the
4611 system at once, so that it can only happen if they do not
4612 conflict or if the conflict has been overridden.
4617 <sect1><heading>Replacing whole packages, forcing their
4621 Secondly, <tt>Replaces</tt> allows the packaging system to
4622 resolve which package should be removed when there is a
4623 conflict - see <ref id="conflicts">. This usage only
4624 takes effect when the two packages <em>do</em> conflict,
4625 so that the two usages of this field do not interfere with
4630 In this situation, the package declared as being replaced
4631 can be a virtual package, so for example, all mail
4632 transport agents (MTAs) would have the following fields in
4633 their control files:
4634 <example compact="compact">
4635 Provides: mail-transport-agent
4636 Conflicts: mail-transport-agent
4637 Replaces: mail-transport-agent
4639 ensuring that only one MTA can be installed at any one
4644 <sect id="sourcebinarydeps">
4645 <heading>Relationships between source and binary packages -
4646 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4647 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4651 Source packages that require certain binary packages to be
4652 installed or absent at the time of building the package
4653 can declare relationships to those binary packages.
4657 This is done using the <tt>Build-Depends</tt>,
4658 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4659 <tt>Build-Conflicts-Indep</tt> control file fields.
4663 Build-dependencies on "build-essential" binary packages can be
4664 omitted. Please see <ref id="pkg-relations"> for more information.
4668 The dependencies and conflicts they define must be satisfied
4669 (as defined earlier for binary packages) in order to invoke
4670 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4672 If you make "build-arch" or "binary-arch", you need
4673 Build-Depends. If you make "build-indep" or
4674 "binary-indep", you need Build-Depends and
4675 Build-Depends-Indep. If you make "build" or "binary",
4679 There is no Build-Depends-Arch; this role is essentially
4680 met with Build-Depends. Anyone building the
4681 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4682 is basically assumed to be building the whole package
4683 anyway and so installs all build dependencies. The
4684 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4685 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4686 does not yet know how to check for its existence) and
4687 <tt>binary-arch</tt>.
4690 The purpose of the original split, I recall, was so that
4691 the autobuilders wouldn't need to install extra packages
4692 needed only for the binary-indep targets. But without a
4693 build-arch/build-indep split, this didn't work, since
4694 most of the work is done in the build target, not in the
4700 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4702 The <tt>Build-Depends</tt> and
4703 <tt>Build-Conflicts</tt> fields must be satisfied when
4704 any of the following targets is invoked:
4705 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4706 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4707 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4709 <tag><tt>Build-Depends-Indep</tt>,
4710 <tt>Build-Conflicts-Indep</tt></tag>
4712 The <tt>Build-Depends-Indep</tt> and
4713 <tt>Build-Conflicts-Indep</tt> fields must be
4714 satisfied when any of the following targets is
4715 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4716 <tt>binary</tt> and <tt>binary-indep</tt>.
4726 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4729 Packages containing shared libraries must be constructed with
4730 a little care to make sure that the shared library is always
4731 available. This is especially important for packages whose
4732 shared libraries are vitally important, such as the C library
4733 (currently <tt>libc6</tt>).
4737 Packages involving shared libraries should be split up into
4738 several binary packages. This section mostly deals with how
4739 this separation is to be accomplished; rules for files within
4740 the shared library packages are in <ref id="libraries"> instead.
4743 <sect id="sharedlibs-runtime">
4744 <heading>Run-time shared libraries</heading>
4747 The run-time shared library needs to be placed in a package
4748 whose name changes whenever the shared object version
4751 Since it is common place to install several versions of a
4752 package that just provides shared libraries, it is a
4753 good idea that the library package should not
4754 contain any extraneous non-versioned files, unless they
4755 happen to be in versioned directories.</p>
4757 The most common mechanism is to place it in a package
4759 <package><var>libraryname</var><var>soversion</var></package>,
4760 where <file><var>soversion</var></file> is the version number
4761 in the soname of the shared library<footnote>
4762 The soname is the shared object name: it's the thing
4763 that has to match exactly between building an executable
4764 and running it for the dynamic linker to be able run the
4765 program. For example, if the soname of the library is
4766 <file>libfoo.so.6</file>, the library package would be
4767 called <file>libfoo6</file>.
4769 Alternatively, if it would be confusing to directly append
4770 <var>soversion</var> to <var>libraryname</var> (e.g. because
4771 <var>libraryname</var> itself ends in a number), you may use
4772 <package><var>libraryname</var>-<var>soversion</var></package> and
4773 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4778 If you have several shared libraries built from the same
4779 source tree you may lump them all together into a single
4780 shared library package, provided that you change all of
4781 their sonames at once (so that you don't get filename
4782 clashes if you try to install different versions of the
4783 combined shared libraries package).
4787 The package should install the shared libraries under
4788 their normal names. For example, the <package>libgdbm3</package>
4789 package should install <file>libgdbm.so.3.0.0</file> as
4790 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4791 renamed or re-linked by any <prgn>prerm</prgn> or
4792 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4793 of renaming things safely without affecting running programs,
4794 and attempts to interfere with this are likely to lead to
4799 Shared libraries should not be installed executable, since
4800 the dynamic linker does not require this and trying to
4801 execute a shared library usually results in a core dump.
4805 The run-time library package should include the symbolic link that
4806 <prgn>ldconfig</prgn> would create for the shared libraries.
4807 For example, the <package>libgdbm3</package> package should include
4808 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4809 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4810 linker (for example <prgn>ld.so</prgn> or
4811 <prgn>ld-linux.so.*</prgn>) can find the library between the
4812 time that <prgn>dpkg</prgn> installs it and the time that
4813 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4815 The package management system requires the library to be
4816 placed before the symbolic link pointing to it in the
4817 <file>.deb</file> file. This is so that when
4818 <prgn>dpkg</prgn> comes to install the symlink
4819 (overwriting the previous symlink pointing at an older
4820 version of the library), the new shared library is already
4821 in place. In the past, this was achieved by creating the
4822 library in the temporary packaging directory before
4823 creating the symlink. Unfortunately, this was not always
4824 effective, since the building of the tar file in the
4825 <file>.deb</file> depended on the behavior of the underlying
4826 file system. Some file systems (such as reiserfs) reorder
4827 the files so that the order of creation is forgotten.
4828 Since version 1.7.0, <prgn>dpkg</prgn>
4829 reorders the files itself as necessary when building a
4830 package. Thus it is no longer important to concern
4831 oneself with the order of file creation.
4835 <sect1 id="ldconfig">
4836 <heading><tt>ldconfig</tt></heading>
4839 Any package installing shared libraries in one of the default
4840 library directories of the dynamic linker (which are currently
4841 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4842 listed in <file>/etc/ld.so.conf</file><footnote>
4844 <list compact="compact">
4845 <item>/usr/local/lib</item>
4846 <item>/usr/lib/libc5-compat</item>
4847 <item>/lib/libc5-compat</item>
4850 must use <prgn>ldconfig</prgn> to update the shared library
4855 The package maintainer scripts must only call
4856 <prgn>ldconfig</prgn> under these circumstances:
4857 <list compact="compact">
4858 <item>When the <prgn>postinst</prgn> script is run with a
4859 first argument of <tt>configure</tt>, the script must call
4860 <prgn>ldconfig</prgn>, and may optionally invoke
4861 <prgn>ldconfig</prgn> at other times.
4863 <item>When the <prgn>postrm</prgn> script is run with a
4864 first argument of <tt>remove</tt>, the script should call
4865 <prgn>ldconfig</prgn>.
4870 During install or upgrade, the preinst is called before
4871 the new files are installed, so calling "ldconfig" is
4872 pointless. The preinst of an existing package can also be
4873 called if an upgrade fails. However, this happens during
4874 the critical time when a shared libs may exist on-disk
4875 under a temporary name. Thus, it is dangerous and
4876 forbidden by current policy to call "ldconfig" at this
4881 When a package is installed or upgraded, "postinst
4882 configure" runs after the new files are safely on-disk.
4883 Since it is perfectly safe to invoke ldconfig
4884 unconditionally in a postinst, it is OK for a package to
4885 simply put ldconfig in its postinst without checking the
4886 argument. The postinst can also be called to recover from
4887 a failed upgrade. This happens before any new files are
4888 unpacked, so there is no reason to call "ldconfig" at this
4893 For a package that is being removed, prerm is
4894 called with all the files intact, so calling ldconfig is
4895 useless. The other calls to "prerm" happen in the case of
4896 upgrade at a time when all the files of the old package
4897 are on-disk, so again calling "ldconfig" is pointless.
4901 postrm, on the other hand, is called with the "remove"
4902 argument just after the files are removed, so this is
4903 the proper time to call "ldconfig" to notify the system
4904 of the fact that the shared libraries from the package
4905 are removed. The postrm can be called at several other
4906 times. At the time of "postrm purge", "postrm
4907 abort-install", or "postrm abort-upgrade", calling
4908 "ldconfig" is useless because the shared lib files are
4909 not on-disk. However, when "postrm" is invoked with
4910 arguments "upgrade", "failed-upgrade", or "disappear", a
4911 shared lib may exist on-disk under a temporary filename.
4919 <sect id="sharedlibs-support-files">
4920 <heading>Shared library support files</heading>
4923 If your package contains files whose names do not change with
4924 each change in the library shared object version, you must not
4925 put them in the shared library package. Otherwise, several
4926 versions of the shared library cannot be installed at the same
4927 time without filename clashes, making upgrades and transitions
4928 unnecessarily difficult.
4932 It is recommended that supporting files and run-time support
4933 programs that do not need to be invoked manually by users, but
4934 are nevertheless required for the package to function, be placed
4935 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4936 preferably under <file>/usr/lib/</file><var>package-name</var>.
4937 If the program or file is architecture independent, the
4938 recommendation is for it to be placed in a subdirectory of
4939 <file>/usr/share</file> instead, preferably under
4940 <file>/usr/share/</file><var>package-name</var>. Following the
4941 <var>package-name</var> naming convention ensures that the file
4942 names change when the shared object version changes.
4946 Run-time support programs that use the shared library but are
4947 not required for the library to function or files used by the
4948 shared library that can be used by any version of the shared
4949 library package should instead be put in a separate package.
4950 This package might typically be named
4951 <package><var>libraryname</var>-tools</package>; note the
4952 absence of the <var>soversion</var> in the package name.
4956 Files and support programs only useful when compiling software
4957 against the library should be included in the development
4958 package for the library.<footnote>
4959 For example, a <file><var>package-name</var>-config</file>
4960 script or <package>pkg-config</package> configuration files.
4965 <sect id="sharedlibs-static">
4966 <heading>Static libraries</heading>
4969 The static library (<file><var>libraryname.a</var></file>)
4970 is usually provided in addition to the shared version.
4971 It is placed into the development package (see below).
4975 In some cases, it is acceptable for a library to be
4976 available in static form only; these cases include:
4978 <item>libraries for languages whose shared library support
4979 is immature or unstable</item>
4980 <item>libraries whose interfaces are in flux or under
4981 development (commonly the case when the library's
4982 major version number is zero, or where the ABI breaks
4983 across patchlevels)</item>
4984 <item>libraries which are explicitly intended to be
4985 available only in static form by their upstream
4990 <sect id="sharedlibs-dev">
4991 <heading>Development files</heading>
4994 The development files associated to a shared library need to be
4995 placed in a package called
4996 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4997 or if you prefer only to support one development version at a
4998 time, <package><var>libraryname</var>-dev</package>.
5002 In case several development versions of a library exist, you may
5003 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5004 <ref id="conflicts">) to ensure that the user only installs one
5005 development version at a time (as different development versions are
5006 likely to have the same header files in them, which would cause a
5007 filename clash if both were installed).
5011 The development package should contain a symlink for the associated
5012 shared library without a version number. For example, the
5013 <package>libgdbm-dev</package> package should include a symlink
5014 from <file>/usr/lib/libgdbm.so</file> to
5015 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5016 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5017 <file>libgdbm.so</file> when compiling dynamically.
5021 <sect id="sharedlibs-intradeps">
5022 <heading>Dependencies between the packages of the same library</heading>
5025 Typically the development version should have an exact
5026 version dependency on the runtime library, to make sure that
5027 compilation and linking happens correctly. The
5028 <tt>${binary:Version}</tt> substitution variable can be
5029 useful for this purpose.
5031 Previously, <tt>${Source-Version}</tt> was used, but its name
5032 was confusing and it has been deprecated since dpkg 1.13.19.
5037 <sect id="sharedlibs-shlibdeps">
5038 <heading>Dependencies between the library and other packages -
5039 the <tt>shlibs</tt> system</heading>
5042 If a package contains a binary or library which links to a
5043 shared library, we must ensure that when the package is
5044 installed on the system, all of the libraries needed are
5045 also installed. This requirement led to the creation of the
5046 <tt>shlibs</tt> system, which is very simple in its design:
5047 any package which <em>provides</em> a shared library also
5048 provides information on the package dependencies required to
5049 ensure the presence of this library, and any package which
5050 <em>uses</em> a shared library uses this information to
5051 determine the dependencies it requires. The files which
5052 contain the mapping from shared libraries to the necessary
5053 dependency information are called <file>shlibs</file> files.
5057 Thus, when a package is built which contains any shared
5058 libraries, it must provide a <file>shlibs</file> file for other
5059 packages to use, and when a package is built which contains
5060 any shared libraries or compiled binaries, it must run
5061 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5062 on these to determine the libraries used and hence the
5063 dependencies needed by this package.<footnote>
5065 In the past, the shared libraries linked to were
5066 determined by calling <prgn>ldd</prgn>, but now
5067 <prgn>objdump</prgn> is used to do this. The only
5068 change this makes to package building is that
5069 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5070 libraries, whereas in the past this was unnecessary.
5071 The rest of this footnote explains the advantage that
5076 We say that a binary <tt>foo</tt> <em>directly</em> uses
5077 a library <tt>libbar</tt> if it is explicitly linked
5078 with that library (that is, it uses the flag
5079 <tt>-lbar</tt> during the linking stage). Other
5080 libraries that are needed by <tt>libbar</tt> are linked
5081 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5082 linker will load them automatically when it loads
5083 <tt>libbar</tt>. A package should depend on
5084 the libraries it directly uses, and the dependencies for
5085 those libraries should automatically pull in the other
5090 Unfortunately, the <prgn>ldd</prgn> program shows both
5091 the directly and indirectly used libraries, meaning that
5092 the dependencies determined included both direct and
5093 indirect dependencies. The use of <prgn>objdump</prgn>
5094 avoids this problem by determining only the directly
5099 A good example of where this helps is the following. We
5100 could update <tt>libimlib</tt> with a new version that
5101 supports a new graphics format called dgf (but retaining
5102 the same major version number). If we used the old
5103 <prgn>ldd</prgn> method, every package that uses
5104 <tt>libimlib</tt> would need to be recompiled so it
5105 would also depend on <tt>libdgf</tt> or it wouldn't run
5106 due to missing symbols. However with the new system,
5107 packages using <tt>libimlib</tt> can rely on
5108 <tt>libimlib</tt> itself having the dependency on
5109 <tt>libdgf</tt> and so they would not need rebuilding.
5115 In the following sections, we will first describe where the
5116 various <tt>shlibs</tt> files are to be found, then how to
5117 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5118 file format and how to create them if your package contains a
5123 <heading>The <tt>shlibs</tt> files present on the system</heading>
5126 There are several places where <tt>shlibs</tt> files are
5127 found. The following list gives them in the order in which
5129 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5130 (The first one which gives the required information is used.)
5136 <p><file>debian/shlibs.local</file></p>
5139 This lists overrides for this package. Its use is
5140 described below (see <ref id="shlibslocal">).
5145 <p><file>/etc/dpkg/shlibs.override</file></p>
5148 This lists global overrides. This list is normally
5149 empty. It is maintained by the local system
5155 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5158 When packages are being built, any
5159 <file>debian/shlibs</file> files are copied into the
5160 control file area of the temporary build directory and
5161 given the name <file>shlibs</file>. These files give
5162 details of any shared libraries included in the
5164 An example may help here. Let us say that the
5165 source package <tt>foo</tt> generates two binary
5166 packages, <tt>libfoo2</tt> and
5167 <tt>foo-runtime</tt>. When building the binary
5168 packages, the two packages are created in the
5169 directories <file>debian/libfoo2</file> and
5170 <file>debian/foo-runtime</file> respectively.
5171 (<file>debian/tmp</file> could be used instead of one
5172 of these.) Since <tt>libfoo2</tt> provides the
5173 <tt>libfoo</tt> shared library, it will require a
5174 <tt>shlibs</tt> file, which will be installed in
5175 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5177 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5178 when <prgn>dpkg-shlibdeps</prgn> is run on the
5180 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5182 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5183 determine whether <tt>foo-prog</tt>'s library
5184 dependencies are satisfied by any of the libraries
5185 provided by <tt>libfoo2</tt>. For this reason,
5186 <prgn>dpkg-shlibdeps</prgn> must only be run once
5187 all of the individual binary packages'
5188 <tt>shlibs</tt> files have been installed into the
5195 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5198 These are the <file>shlibs</file> files corresponding to
5199 all of the packages installed on the system, and are
5200 maintained by the relevant package maintainers.
5205 <p><file>/etc/dpkg/shlibs.default</file></p>
5208 This file lists any shared libraries whose packages
5209 have failed to provide correct <file>shlibs</file> files.
5210 It was used when the <file>shlibs</file> setup was first
5211 introduced, but it is now normally empty. It is
5212 maintained by the <tt>dpkg</tt> maintainer.
5220 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5221 <file>shlibs</file> files</heading>
5225 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5226 into your <file>debian/rules</file> file. If your package
5227 contains only compiled binaries and libraries (but no scripts),
5228 you can use a command such as:
5229 <example compact="compact">
5230 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5231 debian/tmp/usr/lib/*
5233 Otherwise, you will need to explicitly list the compiled
5234 binaries and libraries.<footnote>
5235 If you are using <tt>debhelper</tt>, the
5236 <prgn>dh_shlibdeps</prgn> program will do this work for
5237 you. It will also correctly handle multi-binary
5243 This command puts the dependency information into the
5244 <file>debian/substvars</file> file, which is then used by
5245 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5246 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5247 field in the control file for this to work.
5251 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5252 done. If it does complain you might need to create your own
5253 <file>debian/shlibs.local</file> file, as explained below (see
5254 <ref id="shlibslocal">).
5258 If you have multiple binary packages, you will need to call
5259 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5260 compiled libraries or binaries. In such a case, you will
5261 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5262 utilities to specify a different <file>substvars</file> file.
5266 If you are creating a udeb for use in the Debian Installer, you
5267 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5268 the dependency line of type <tt>udeb</tt> by adding
5269 <tt>-tudeb</tt> as option<footnote>
5270 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5271 will automatically add this option if it knows it is
5273 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5274 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5275 fall back to the regular dependency line.
5279 For more details on dpkg-shlibdeps, please see
5280 <ref id="pkg-dpkg-shlibdeps"> and
5281 <manref name="dpkg-shlibdeps" section="1">.
5286 <heading>The <file>shlibs</file> File Format</heading>
5289 Each <file>shlibs</file> file has the same format. Lines
5290 beginning with <tt>#</tt> are considered to be comments and
5291 are ignored. Each line is of the form:
5292 <example compact="compact">
5293 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5298 We will explain this by reference to the example of the
5299 <tt>zlib1g</tt> package, which (at the time of writing)
5300 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5304 <var>type</var> is an optional element that indicates the type
5305 of package for which the line is valid. The only type currently
5306 in use is <tt>udeb</tt>. The colon and space after the type are
5311 <var>library-name</var> is the name of the shared library,
5312 in this case <tt>libz</tt>. (This must match the name part
5313 of the soname, see below.)
5317 <var>soname-version</var> is the version part of the soname of
5318 the library. The soname is the thing that must exactly match
5319 for the library to be recognized by the dynamic linker, and is
5321 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5322 example, <tt>libz.so.1</tt>.<footnote>
5323 This can be determined using the command
5324 <example compact="compact">
5325 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5328 The version part is the part which comes after
5329 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5333 <var>dependencies</var> has the same syntax as a dependency
5334 field in a binary package control file. It should give
5335 details of which packages are required to satisfy a binary
5336 built against the version of the library contained in the
5337 package. See <ref id="depsyntax"> for details.
5341 In our example, if the first version of the <tt>zlib1g</tt>
5342 package which contained a minor number of at least
5343 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5344 <tt>shlibs</tt> entry for this library could say:
5345 <example compact="compact">
5346 libz 1 zlib1g (>= 1:1.1.3)
5348 The version-specific dependency is to avoid warnings from
5349 the dynamic linker about using older shared libraries with
5354 As zlib1g also provides a udeb containing the shared library,
5355 there would also be a second line:
5356 <example compact="compact">
5357 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5363 <heading>Providing a <file>shlibs</file> file</heading>
5366 If your package provides a shared library, you need to create
5367 a <file>shlibs</file> file following the format described above.
5368 It is usual to call this file <file>debian/shlibs</file> (but if
5369 you have multiple binary packages, you might want to call it
5370 <file>debian/shlibs.<var>package</var></file> instead). Then
5371 let <file>debian/rules</file> install it in the control area:
5372 <example compact="compact">
5373 install -m644 debian/shlibs debian/tmp/DEBIAN
5375 or, in the case of a multi-binary package:
5376 <example compact="compact">
5377 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5379 An alternative way of doing this is to create the
5380 <file>shlibs</file> file in the control area directly from
5381 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5382 file at all,<footnote>
5383 This is what <prgn>dh_makeshlibs</prgn> in the
5384 <tt>debhelper</tt> suite does. If your package also has a udeb
5385 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5386 automatically generate the <tt>udeb:</tt> lines if you specify
5387 the name of the udeb with the <tt>--add-udeb</tt> option.
5389 since the <file>debian/shlibs</file> file itself is ignored by
5390 <prgn>dpkg-shlibdeps</prgn>.
5394 As <prgn>dpkg-shlibdeps</prgn> reads the
5395 <file>DEBIAN/shlibs</file> files in all of the binary packages
5396 being built from this source package, all of the
5397 <file>DEBIAN/shlibs</file> files should be installed before
5398 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5403 <sect1 id="shlibslocal">
5404 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5407 This file is intended only as a <em>temporary</em> fix if
5408 your binaries or libraries depend on a library whose package
5409 does not yet provide a correct <file>shlibs</file> file.
5413 We will assume that you are trying to package a binary
5414 <tt>foo</tt>. When you try running
5415 <prgn>dpkg-shlibdeps</prgn> you get the following error
5416 message (<tt>-O</tt> displays the dependency information on
5417 <tt>stdout</tt> instead of writing it to
5418 <tt>debian/substvars</tt>, and the lines have been wrapped
5419 for ease of reading):
5420 <example compact="compact">
5421 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5422 dpkg-shlibdeps: warning: unable to find dependency
5423 information for shared library libbar (soname 1,
5424 path /usr/lib/libbar.so.1, dependency field Depends)
5425 shlibs:Depends=libc6 (>= 2.2.2-2)
5427 You can then run <prgn>ldd</prgn> on the binary to find the
5428 full location of the library concerned:
5429 <example compact="compact">
5431 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5432 libc.so.6 => /lib/libc.so.6 (0x40032000)
5433 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5435 So the <prgn>foo</prgn> binary depends on the
5436 <prgn>libbar</prgn> shared library, but no package seems to
5437 provide a <file>*.shlibs</file> file handling
5438 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5439 determine the package responsible:
5440 <example compact="compact">
5441 $ dpkg -S /usr/lib/libbar.so.1
5442 bar1: /usr/lib/libbar.so.1
5443 $ dpkg -s bar1 | grep Version
5446 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5447 is the one we are using. Now we can file a bug against the
5448 <tt>bar1</tt> package and create our own
5449 <file>debian/shlibs.local</file> to locally fix the problem.
5450 Including the following line into your
5451 <file>debian/shlibs.local</file> file:
5452 <example compact="compact">
5453 libbar 1 bar1 (>= 1.0-1)
5455 should allow the package build to work.
5459 As soon as the maintainer of <tt>bar1</tt> provides a
5460 correct <file>shlibs</file> file, you should remove this line
5461 from your <file>debian/shlibs.local</file> file. (You should
5462 probably also then have a versioned <tt>Build-Depends</tt>
5463 on <tt>bar1</tt> to help ensure that others do not have the
5464 same problem building your package.)
5473 <chapt id="opersys"><heading>The Operating System</heading>
5476 <heading>File system hierarchy</heading>
5480 <heading>File system Structure</heading>
5483 The location of all installed files and directories must
5484 comply with the File system Hierarchy Standard (FHS),
5485 version 2.3, with the exceptions noted below, and except
5486 where doing so would violate other terms of Debian
5487 Policy. The following exceptions to the FHS apply:
5492 Legacy XFree86 servers are permitted to retain the
5493 configuration file location
5494 <file>/etc/X11/XF86Config-4</file>.
5499 The optional rules related to user specific
5500 configuration files for applications are stored in
5501 the user's home directory are relaxed. It is
5502 recommended that such files start with the
5503 '<tt>.</tt>' character (a "dot file"), and if an
5504 application needs to create more than one dot file
5505 then the preferred placement is in a subdirectory
5506 with a name starting with a '.' character, (a "dot
5507 directory"). In this case it is recommended the
5508 configuration files not start with the '.'
5514 The requirement for amd64 to use <file>/lib64</file>
5515 for 64 bit binaries is removed.
5520 The requirement that
5521 <file>/usr/local/share/man</file> be "synonymous"
5522 with <file>/usr/local/man</file> is relaxed to a
5527 The requirement that windowmanagers with a single
5528 configuration file call it <file>system.*wmrc</file>
5529 is removed, as is the restriction that the window
5530 manager subdirectory be named identically to the
5531 window manager name itself.
5536 The requirement that boot manager configuration
5537 files live in <file>/etc</file>, or at least are
5538 symlinked there, is relaxed to a recommendation.
5545 The version of this document referred here can be
5546 found in the <tt>debian-policy</tt> package or on <url
5547 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5548 name="FHS (Debian copy)"> alongside this manual (or, if
5549 you have the <package>debian-policy</package> installed,
5551 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5552 (local copy)">). The
5553 latest version, which may be a more recent version, may
5555 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5556 Specific questions about following the standard may be
5557 asked on the <tt>debian-devel</tt> mailing list, or
5558 referred to the FHS mailing list (see the
5559 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5565 <heading>Site-specific programs</heading>
5568 As mandated by the FHS, packages must not place any
5569 files in <file>/usr/local</file>, either by putting them in
5570 the file system archive to be unpacked by <prgn>dpkg</prgn>
5571 or by manipulating them in their maintainer scripts.
5575 However, the package may create empty directories below
5576 <file>/usr/local</file> so that the system administrator knows
5577 where to place site-specific files. These are not
5578 directories <em>in</em> <file>/usr/local</file>, but are
5579 children of directories in <file>/usr/local</file>. These
5580 directories (<file>/usr/local/*/dir/</file>)
5581 should be removed on package removal if they are
5586 Note, that this applies only to directories <em>below</em>
5587 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5588 Packages must not create sub-directories in the directory
5589 <file>/usr/local</file> itself, except those listed in FHS,
5590 section 4.5. However, you may create directories below
5591 them as you wish. You must not remove any of the
5592 directories listed in 4.5, even if you created them.
5596 Since <file>/usr/local</file> can be mounted read-only from a
5597 remote server, these directories must be created and
5598 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5599 maintainer scripts and not be included in the
5600 <file>.deb</file> archive. These scripts must not fail if
5601 either of these operations fail.
5605 For example, the <tt>emacsen-common</tt> package could
5606 contain something like
5607 <example compact="compact">
5608 if [ ! -e /usr/local/share/emacs ]
5610 if mkdir /usr/local/share/emacs 2>/dev/null
5612 chown root:staff /usr/local/share/emacs
5613 chmod 2775 /usr/local/share/emacs
5617 in its <prgn>postinst</prgn> script, and
5618 <example compact="compact">
5619 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5620 rmdir /usr/local/share/emacs 2>/dev/null || true
5622 in the <prgn>prerm</prgn> script. (Note that this form is
5623 used to ensure that if the script is interrupted, the
5624 directory <file>/usr/local/share/emacs</file> will still be
5629 If you do create a directory in <file>/usr/local</file> for
5630 local additions to a package, you should ensure that
5631 settings in <file>/usr/local</file> take precedence over the
5632 equivalents in <file>/usr</file>.
5636 However, because <file>/usr/local</file> and its contents are
5637 for exclusive use of the local administrator, a package
5638 must not rely on the presence or absence of files or
5639 directories in <file>/usr/local</file> for normal operation.
5643 The <file>/usr/local</file> directory itself and all the
5644 subdirectories created by the package should (by default) have
5645 permissions 2775 (group-writable and set-group-id) and be
5646 owned by <tt>root:staff</tt>.
5651 <heading>The system-wide mail directory</heading>
5653 The system-wide mail directory is <file>/var/mail</file>. This
5654 directory is part of the base system and should not owned
5655 by any particular mail agents. The use of the old
5656 location <file>/var/spool/mail</file> is deprecated, even
5657 though the spool may still be physically located there.
5658 To maintain partial upgrade compatibility for systems
5659 which have <file>/var/spool/mail</file> as their physical mail
5660 spool, packages using <file>/var/mail</file> must depend on
5661 either <package>libc6</package> (>= 2.1.3-13), or on
5662 <package>base-files</package> (>= 2.2.0), or on later
5663 versions of either one of these packages.
5669 <heading>Users and groups</heading>
5672 <heading>Introduction</heading>
5674 The Debian system can be configured to use either plain or
5679 Some user ids (UIDs) and group ids (GIDs) are reserved
5680 globally for use by certain packages. Because some
5681 packages need to include files which are owned by these
5682 users or groups, or need the ids compiled into binaries,
5683 these ids must be used on any Debian system only for the
5684 purpose for which they are allocated. This is a serious
5685 restriction, and we should avoid getting in the way of
5686 local administration policies. In particular, many sites
5687 allocate users and/or local system groups starting at 100.
5691 Apart from this we should have dynamically allocated ids,
5692 which should by default be arranged in some sensible
5693 order, but the behavior should be configurable.
5697 Packages other than <tt>base-passwd</tt> must not modify
5698 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5699 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5704 <heading>UID and GID classes</heading>
5706 The UID and GID numbers are divided into classes as
5712 Globally allocated by the Debian project, the same
5713 on every Debian system. These ids will appear in
5714 the <file>passwd</file> and <file>group</file> files of all
5715 Debian systems, new ids in this range being added
5716 automatically as the <tt>base-passwd</tt> package is
5721 Packages which need a single statically allocated
5722 uid or gid should use one of these; their
5723 maintainers should ask the <tt>base-passwd</tt>
5731 Dynamically allocated system users and groups.
5732 Packages which need a user or group, but can have
5733 this user or group allocated dynamically and
5734 differently on each system, should use <tt>adduser
5735 --system</tt> to create the group and/or user.
5736 <prgn>adduser</prgn> will check for the existence of
5737 the user or group, and if necessary choose an unused
5738 id based on the ranges specified in
5739 <file>adduser.conf</file>.
5743 <tag>1000-29999:</tag>
5746 Dynamically allocated user accounts. By default
5747 <prgn>adduser</prgn> will choose UIDs and GIDs for
5748 user accounts in this range, though
5749 <file>adduser.conf</file> may be used to modify this
5754 <tag>30000-59999:</tag>
5759 <tag>60000-64999:</tag>
5762 Globally allocated by the Debian project, but only
5763 created on demand. The ids are allocated centrally
5764 and statically, but the actual accounts are only
5765 created on users' systems on demand.
5769 These ids are for packages which are obscure or
5770 which require many statically-allocated ids. These
5771 packages should check for and create the accounts in
5772 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5773 <prgn>adduser</prgn> if it has this facility) if
5774 necessary. Packages which are likely to require
5775 further allocations should have a "hole" left after
5776 them in the allocation, to give them room to
5781 <tag>65000-65533:</tag>
5789 User <tt>nobody</tt>. The corresponding gid refers
5790 to the group <tt>nogroup</tt>.
5797 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5798 not</em> be used, because it is the error return
5807 <sect id="sysvinit">
5808 <heading>System run levels and <file>init.d</file> scripts</heading>
5810 <sect1 id="/etc/init.d">
5811 <heading>Introduction</heading>
5814 The <file>/etc/init.d</file> directory contains the scripts
5815 executed by <prgn>init</prgn> at boot time and when the
5816 init state (or "runlevel") is changed (see <manref
5817 name="init" section="8">).
5821 There are at least two different, yet functionally
5822 equivalent, ways of handling these scripts. For the sake
5823 of simplicity, this document describes only the symbolic
5824 link method. However, it must not be assumed by maintainer
5825 scripts that this method is being used, and any automated
5826 manipulation of the various runlevel behaviors by
5827 maintainer scripts must be performed using
5828 <prgn>update-rc.d</prgn> as described below and not by
5829 manually installing or removing symlinks. For information
5830 on the implementation details of the other method,
5831 implemented in the <tt>file-rc</tt> package, please refer
5832 to the documentation of that package.
5836 These scripts are referenced by symbolic links in the
5837 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5838 runlevels, <prgn>init</prgn> looks in the directory
5839 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5840 execute, where <tt><var>n</var></tt> is the runlevel that
5841 is being changed to, or <tt>S</tt> for the boot-up
5846 The names of the links all have the form
5847 <file>S<var>mm</var><var>script</var></file> or
5848 <file>K<var>mm</var><var>script</var></file> where
5849 <var>mm</var> is a two-digit number and <var>script</var>
5850 is the name of the script (this should be the same as the
5851 name of the actual script in <file>/etc/init.d</file>).
5855 When <prgn>init</prgn> changes runlevel first the targets
5856 of the links whose names start with a <tt>K</tt> are
5857 executed, each with the single argument <tt>stop</tt>,
5858 followed by the scripts prefixed with an <tt>S</tt>, each
5859 with the single argument <tt>start</tt>. (The links are
5860 those in the <file>/etc/rc<var>n</var>.d</file> directory
5861 corresponding to the new runlevel.) The <tt>K</tt> links
5862 are responsible for killing services and the <tt>S</tt>
5863 link for starting services upon entering the runlevel.
5867 For example, if we are changing from runlevel 2 to
5868 runlevel 3, init will first execute all of the <tt>K</tt>
5869 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5870 all of the <tt>S</tt> prefixed scripts in that directory.
5871 The links starting with <tt>K</tt> will cause the
5872 referred-to file to be executed with an argument of
5873 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5878 The two-digit number <var>mm</var> is used to determine
5879 the order in which to run the scripts: low-numbered links
5880 have their scripts run first. For example, the
5881 <tt>K20</tt> scripts will be executed before the
5882 <tt>K30</tt> scripts. This is used when a certain service
5883 must be started before another. For example, the name
5884 server <prgn>bind</prgn> might need to be started before
5885 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5886 can set up its access lists. In this case, the script
5887 that starts <prgn>bind</prgn> would have a lower number
5888 than the script that starts <prgn>inn</prgn> so that it
5890 <example compact="compact">
5897 The two runlevels 0 (halt) and 6 (reboot) are slightly
5898 different. In these runlevels, the links with an
5899 <tt>S</tt> prefix are still called after those with a
5900 <tt>K</tt> prefix, but they too are called with the single
5901 argument <tt>stop</tt>.
5905 Also, if the script name ends in <tt>.sh</tt>, the script
5906 will be sourced in runlevel <tt>S</tt> rather than being
5907 run in a forked subprocess, but will be explicitly run by
5908 <prgn>sh</prgn> in all other runlevels.
5913 <heading>Writing the scripts</heading>
5916 Packages that include daemons for system services should
5917 place scripts in <file>/etc/init.d</file> to start or stop
5918 services at boot time or during a change of runlevel.
5919 These scripts should be named
5920 <file>/etc/init.d/<var>package</var></file>, and they should
5921 accept one argument, saying what to do:
5924 <tag><tt>start</tt></tag>
5925 <item>start the service,</item>
5927 <tag><tt>stop</tt></tag>
5928 <item>stop the service,</item>
5930 <tag><tt>restart</tt></tag>
5931 <item>stop and restart the service if it's already running,
5932 otherwise start the service</item>
5934 <tag><tt>reload</tt></tag>
5935 <item><p>cause the configuration of the service to be
5936 reloaded without actually stopping and restarting
5939 <tag><tt>force-reload</tt></tag>
5940 <item>cause the configuration to be reloaded if the
5941 service supports this, otherwise restart the
5945 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5946 <tt>force-reload</tt> options should be supported by all
5947 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5952 The <file>init.d</file> scripts must ensure that they will
5953 behave sensibly (i.e., returning success and not starting
5954 multiple copies of a service) if invoked with <tt>start</tt>
5955 when the service is already running, or with <tt>stop</tt>
5956 when it isn't, and that they don't kill unfortunately-named
5957 user processes. The best way to achieve this is usually to
5958 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5963 If a service reloads its configuration automatically (as
5964 in the case of <prgn>cron</prgn>, for example), the
5965 <tt>reload</tt> option of the <file>init.d</file> script
5966 should behave as if the configuration has been reloaded
5971 The <file>/etc/init.d</file> scripts must be treated as
5972 configuration files, either (if they are present in the
5973 package, that is, in the .deb file) by marking them as
5974 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5975 by managing them correctly in the maintainer scripts (see
5976 <ref id="config-files">). This is important since we want
5977 to give the local system administrator the chance to adapt
5978 the scripts to the local system, e.g., to disable a
5979 service without de-installing the package, or to specify
5980 some special command line options when starting a service,
5981 while making sure their changes aren't lost during the next
5986 These scripts should not fail obscurely when the
5987 configuration files remain but the package has been
5988 removed, as configuration files remain on the system after
5989 the package has been removed. Only when <prgn>dpkg</prgn>
5990 is executed with the <tt>--purge</tt> option will
5991 configuration files be removed. In particular, as the
5992 <file>/etc/init.d/<var>package</var></file> script itself is
5993 usually a <tt>conffile</tt>, it will remain on the system
5994 if the package is removed but not purged. Therefore, you
5995 should include a <tt>test</tt> statement at the top of the
5997 <example compact="compact">
5998 test -f <var>program-executed-later-in-script</var> || exit 0
6003 Often there are some variables in the <file>init.d</file>
6004 scripts whose values control the behavior of the scripts,
6005 and which a system administrator is likely to want to
6006 change. As the scripts themselves are frequently
6007 <tt>conffile</tt>s, modifying them requires that the
6008 administrator merge in their changes each time the package
6009 is upgraded and the <tt>conffile</tt> changes. To ease
6010 the burden on the system administrator, such configurable
6011 values should not be placed directly in the script.
6012 Instead, they should be placed in a file in
6013 <file>/etc/default</file>, which typically will have the same
6014 base name as the <file>init.d</file> script. This extra file
6015 should be sourced by the script when the script runs. It
6016 must contain only variable settings and comments in SUSv3
6017 <prgn>sh</prgn> format. It may either be a
6018 <tt>conffile</tt> or a configuration file maintained by
6019 the package maintainer scripts. See <ref id="config-files">
6024 To ensure that vital configurable values are always
6025 available, the <file>init.d</file> script should set default
6026 values for each of the shell variables it uses, either
6027 before sourcing the <file>/etc/default/</file> file or
6028 afterwards using something like the <tt>:
6029 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6030 script must behave sensibly and not fail if the
6031 <file>/etc/default</file> file is deleted.
6036 <heading>Interfacing with the initscript system</heading>
6039 Maintainers should use the abstraction layer provided by
6040 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6041 programs to deal with initscripts in their packages'
6042 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6043 and <prgn>postrm</prgn>.
6047 Directly managing the /etc/rc?.d links and directly
6048 invoking the <file>/etc/init.d/</file> initscripts should
6049 be done only by packages providing the initscript
6050 subsystem (such as <prgn>sysv-rc</prgn> and
6051 <prgn>file-rc</prgn>).
6055 <heading>Managing the links</heading>
6058 The program <prgn>update-rc.d</prgn> is provided for
6059 package maintainers to arrange for the proper creation and
6060 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6061 or their functional equivalent if another method is being
6062 used. This may be used by maintainers in their packages'
6063 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6067 You must not include any <file>/etc/rc<var>n</var>.d</file>
6068 symbolic links in the actual archive or manually create or
6069 remove the symbolic links in maintainer scripts; you must
6070 use the <prgn>update-rc.d</prgn> program instead. (The
6071 former will fail if an alternative method of maintaining
6072 runlevel information is being used.) You must not include
6073 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6074 in the archive either. (Only the <tt>sysvinit</tt>
6079 By default <prgn>update-rc.d</prgn> will start services in
6080 each of the multi-user state runlevels (2, 3, 4, and 5)
6081 and stop them in the halt runlevel (0), the single-user
6082 runlevel (1) and the reboot runlevel (6). The system
6083 administrator will have the opportunity to customize
6084 runlevels by simply adding, moving, or removing the
6085 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6086 symbolic links are being used, or by modifying
6087 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6092 To get the default behavior for your package, put in your
6093 <prgn>postinst</prgn> script
6094 <example compact="compact">
6095 update-rc.d <var>package</var> defaults
6097 and in your <prgn>postrm</prgn>
6098 <example compact="compact">
6099 if [ "$1" = purge ]; then
6100 update-rc.d <var>package</var> remove
6102 </example>. Note that if your package changes runlevels
6103 or priority, you may have to remove and recreate the links,
6104 since otherwise the old links may persist. Refer to the
6105 documentation of <prgn>update-rc.d</prgn>.
6109 This will use a default sequence number of 20. If it does
6110 not matter when or in which order the <file>init.d</file>
6111 script is run, use this default. If it does, then you
6112 should talk to the maintainer of the <prgn>sysvinit</prgn>
6113 package or post to <tt>debian-devel</tt>, and they will
6114 help you choose a number.
6118 For more information about using <tt>update-rc.d</tt>,
6119 please consult its man page <manref name="update-rc.d"
6125 <heading>Running initscripts</heading>
6127 The program <prgn>invoke-rc.d</prgn> is provided to make
6128 it easier for package maintainers to properly invoke an
6129 initscript, obeying runlevel and other locally-defined
6130 constraints that might limit a package's right to start,
6131 stop and otherwise manage services. This program may be
6132 used by maintainers in their packages' scripts.
6136 The package maintainer scripts must use
6137 <prgn>invoke-rc.d</prgn> to invoke the
6138 <file>/etc/init.d/*</file> initscripts, instead of
6139 calling them directly.
6143 By default, <prgn>invoke-rc.d</prgn> will pass any
6144 action requests (start, stop, reload, restart...) to the
6145 <file>/etc/init.d</file> script, filtering out requests
6146 to start or restart a service out of its intended
6151 Most packages will simply need to change:
6152 <example compact="compact">/etc/init.d/<package>
6153 <action></example> in their <prgn>postinst</prgn>
6154 and <prgn>prerm</prgn> scripts to:
6155 <example compact="compact">
6156 if which invoke-rc.d >/dev/null 2>&1; then
6157 invoke-rc.d <var>package</var> <action>
6159 /etc/init.d/<var>package</var> <action>
6165 A package should register its initscript services using
6166 <prgn>update-rc.d</prgn> before it tries to invoke them
6167 using <prgn>invoke-rc.d</prgn>. Invocation of
6168 unregistered services may fail.
6172 For more information about using
6173 <prgn>invoke-rc.d</prgn>, please consult its man page
6174 <manref name="invoke-rc.d" section="8">.
6180 <heading>Boot-time initialization</heading>
6183 There used to be another directory, <file>/etc/rc.boot</file>,
6184 which contained scripts which were run once per machine
6185 boot. This has been deprecated in favour of links from
6186 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6187 described in <ref id="/etc/init.d">. Packages must not
6188 place files in <file>/etc/rc.boot</file>.
6193 <heading>Example</heading>
6196 An example on which you can base your
6197 <file>/etc/init.d</file> scripts is found in
6198 <file>/etc/init.d/skeleton</file>.
6205 <heading>Console messages from <file>init.d</file> scripts</heading>
6208 This section describes the formats to be used for messages
6209 written to standard output by the <file>/etc/init.d</file>
6210 scripts. The intent is to improve the consistency of
6211 Debian's startup and shutdown look and feel. For this
6212 reason, please look very carefully at the details. We want
6213 the messages to have the same format in terms of wording,
6214 spaces, punctuation and case of letters.
6218 Here is a list of overall rules that should be used for
6219 messages generated by <file>/etc/init.d</file> scripts.
6225 The message should fit in one line (fewer than 80
6226 characters), start with a capital letter and end with
6227 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6231 If the script is performing some time consuming task in
6232 the background (not merely starting or stopping a
6233 program, for instance), an ellipsis (three dots:
6234 <tt>...</tt>) should be output to the screen, with no
6235 leading or tailing whitespace or line feeds.
6239 The messages should appear as if the computer is telling
6240 the user what it is doing (politely :-), but should not
6241 mention "it" directly. For example, instead of:
6242 <example compact="compact">
6243 I'm starting network daemons: nfsd mountd.
6245 the message should say
6246 <example compact="compact">
6247 Starting network daemons: nfsd mountd.
6254 <tt>init.d</tt> script should use the following standard
6255 message formats for the situations enumerated below.
6261 <p>When daemons are started</p>
6264 If the script starts one or more daemons, the output
6265 should look like this (a single line, no leading
6267 <example compact="compact">
6268 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6270 The <var>description</var> should describe the
6271 subsystem the daemon or set of daemons are part of,
6272 while <var>daemon-1</var> up to <var>daemon-n</var>
6273 denote each daemon's name (typically the file name of
6278 For example, the output of <file>/etc/init.d/lpd</file>
6280 <example compact="compact">
6281 Starting printer spooler: lpd.
6286 This can be achieved by saying
6287 <example compact="compact">
6288 echo -n "Starting printer spooler: lpd"
6289 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6292 in the script. If there are more than one daemon to
6293 start, the output should look like this:
6294 <example compact="compact">
6295 echo -n "Starting remote file system services:"
6296 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6297 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6298 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6301 This makes it possible for the user to see what is
6302 happening and when the final daemon has been started.
6303 Care should be taken in the placement of white spaces:
6304 in the example above the system administrators can
6305 easily comment out a line if they don't want to start
6306 a specific daemon, while the displayed message still
6312 <p>When a system parameter is being set</p>
6315 If you have to set up different system parameters
6316 during the system boot, you should use this format:
6317 <example compact="compact">
6318 Setting <var>parameter</var> to "<var>value</var>".
6323 You can use a statement such as the following to get
6325 <example compact="compact">
6326 echo "Setting DNS domainname to \"$domainname\"."
6331 Note that the same symbol (<tt>"</tt>) is used for the left
6332 and right quotation marks. A grave accent (<tt>`</tt>) is
6333 not a quote character; neither is an apostrophe
6339 <p>When a daemon is stopped or restarted</p>
6342 When you stop or restart a daemon, you should issue a
6343 message identical to the startup message, except that
6344 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6345 or <tt>Restarting</tt> respectively.
6349 For example, stopping the printer daemon will look like
6351 <example compact="compact">
6352 Stopping printer spooler: lpd.
6358 <p>When something is executed</p>
6361 There are several examples where you have to run a
6362 program at system startup or shutdown to perform a
6363 specific task, for example, setting the system's clock
6364 using <prgn>netdate</prgn> or killing all processes
6365 when the system shuts down. Your message should look
6367 <example compact="compact">
6368 Doing something very useful...done.
6370 You should print the <tt>done.</tt> immediately after
6371 the job has been completed, so that the user is
6372 informed why they have to wait. You can get this
6374 <example compact="compact">
6375 echo -n "Doing something very useful..."
6384 <p>When the configuration is reloaded</p>
6387 When a daemon is forced to reload its configuration
6388 files you should use the following format:
6389 <example compact="compact">
6390 Reloading <var>description</var> configuration...done.
6392 where <var>description</var> is the same as in the
6393 daemon starting message.
6401 <heading>Cron jobs</heading>
6404 Packages must not modify the configuration file
6405 <file>/etc/crontab</file>, and they must not modify the files in
6406 <file>/var/spool/cron/crontabs</file>.</p>
6409 If a package wants to install a job that has to be executed
6410 via cron, it should place a file with the name of the
6411 package in one or more of the following directories:
6412 <example compact="compact">
6418 As these directory names imply, the files within them are
6419 executed on an hourly, daily, weekly, or monthly basis,
6420 respectively. The exact times are listed in
6421 <file>/etc/crontab</file>.</p>
6424 All files installed in any of these directories must be
6425 scripts (e.g., shell scripts or Perl scripts) so that they
6426 can easily be modified by the local system administrator.
6427 In addition, they must be treated as configuration files.
6431 If a certain job has to be executed at some other frequency or
6432 at a specific time, the package should install a file
6433 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6434 same syntax as <file>/etc/crontab</file> and is processed by
6435 <prgn>cron</prgn> automatically. The file must also be
6436 treated as a configuration file. (Note that entries in the
6437 <file>/etc/cron.d</file> directory are not handled by
6438 <prgn>anacron</prgn>. Thus, you should only use this
6439 directory for jobs which may be skipped if the system is not
6443 The scripts or crontab entries in these directories should
6444 check if all necessary programs are installed before they
6445 try to execute them. Otherwise, problems will arise when a
6446 package was removed but not purged since configuration files
6447 are kept on the system in this situation.</p>
6451 <heading>Menus</heading>
6454 The Debian <tt>menu</tt> package provides a standard
6455 interface between packages providing applications and
6456 <em>menu programs</em> (either X window managers or
6457 text-based menu programs such as <prgn>pdmenu</prgn>).
6461 All packages that provide applications that need not be
6462 passed any special command line arguments for normal
6463 operation should register a menu entry for those
6464 applications, so that users of the <tt>menu</tt> package
6465 will automatically get menu entries in their window
6466 managers, as well in shells like <tt>pdmenu</tt>.
6470 Menu entries should follow the current menu policy.
6474 The menu policy can be found in the <tt>menu-policy</tt>
6475 files in the <tt>debian-policy</tt> package.
6476 It is also available from the Debian web mirrors at
6477 <tt><url name="/doc/packaging-manuals/menu-policy/"
6478 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6482 Please also refer to the <em>Debian Menu System</em>
6483 documentation that comes with the <package>menu</package>
6484 package for information about how to register your
6490 <heading>Multimedia handlers</heading>
6493 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6494 is a mechanism for encoding files and data streams and
6495 providing meta-information about them, in particular their
6496 type (e.g. audio or video) and format (e.g. PNG, HTML,
6501 Registration of MIME type handlers allows programs like mail
6502 user agents and web browsers to invoke these handlers to
6503 view, edit or display MIME types they don't support directly.
6507 Packages which provide the ability to view/show/play,
6508 compose, edit or print MIME types should register themselves
6509 as such following the current MIME support policy.
6513 The MIME support policy can be found in the <tt>mime-policy</tt>
6514 files in the <tt>debian-policy</tt> package.
6515 It is also available from the Debian web mirrors at
6516 <tt><url name="/doc/packaging-manuals/mime-policy/"
6517 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6523 <heading>Keyboard configuration</heading>
6526 To achieve a consistent keyboard configuration so that all
6527 applications interpret a keyboard event the same way, all
6528 programs in the Debian distribution must be configured to
6529 comply with the following guidelines.
6533 The following keys must have the specified interpretations:
6536 <tag><tt><--</tt></tag>
6537 <item>delete the character to the left of the cursor</item>
6539 <tag><tt>Delete</tt></tag>
6540 <item>delete the character to the right of the cursor</item>
6542 <tag><tt>Control+H</tt></tag>
6543 <item>emacs: the help prefix</item>
6546 The interpretation of any keyboard events should be
6547 independent of the terminal that is used, be it a virtual
6548 console, an X terminal emulator, an rlogin/telnet session,
6553 The following list explains how the different programs
6554 should be set up to achieve this:
6560 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6564 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6568 X translations are set up to make
6569 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6570 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6571 is the vt220 escape code for the "delete character"
6572 key). This must be done by loading the X resources
6573 using <prgn>xrdb</prgn> on all local X displays, not
6574 using the application defaults, so that the
6575 translation resources used correspond to the
6576 <prgn>xmodmap</prgn> settings.
6580 The Linux console is configured to make
6581 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6582 generate <tt>ESC [ 3 ~</tt>.
6586 X applications are configured so that <tt><</tt>
6587 deletes left, and <tt>Delete</tt> deletes right. Motif
6588 applications already work like this.
6592 Terminals should have <tt>stty erase ^?</tt> .
6596 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6597 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6598 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6602 Emacs is programmed to map <tt>KB_Backspace</tt> or
6603 the <tt>stty erase</tt> character to
6604 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6605 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6606 <tt>^H</tt> to <tt>help</tt> as always.
6610 Other applications use the <tt>stty erase</tt>
6611 character and <tt>kdch1</tt> for the two delete keys,
6612 with ASCII DEL being "delete previous character" and
6613 <tt>kdch1</tt> being "delete character under
6621 This will solve the problem except for the following
6628 Some terminals have a <tt><--</tt> key that cannot
6629 be made to produce anything except <tt>^H</tt>. On
6630 these terminals Emacs help will be unavailable on
6631 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6632 character takes precedence in Emacs, and has been set
6633 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6634 available) can be used instead.
6638 Some operating systems use <tt>^H</tt> for <tt>stty
6639 erase</tt>. However, modern telnet versions and all
6640 rlogin versions propagate <tt>stty</tt> settings, and
6641 almost all UNIX versions honour <tt>stty erase</tt>.
6642 Where the <tt>stty</tt> settings are not propagated
6643 correctly, things can be made to work by using
6644 <tt>stty</tt> manually.
6648 Some systems (including previous Debian versions) use
6649 <prgn>xmodmap</prgn> to arrange for both
6650 <tt><--</tt> and <tt>Delete</tt> to generate
6651 <tt>KB_Delete</tt>. We can change the behavior of
6652 their X clients using the same X resources that we use
6653 to do it for our own clients, or configure our clients
6654 using their resources when things are the other way
6655 around. On displays configured like this
6656 <tt>Delete</tt> will not work, but <tt><--</tt>
6661 Some operating systems have different <tt>kdch1</tt>
6662 settings in their <tt>terminfo</tt> database for
6663 <tt>xterm</tt> and others. On these systems the
6664 <tt>Delete</tt> key will not work correctly when you
6665 log in from a system conforming to our policy, but
6666 <tt><--</tt> will.
6673 <heading>Environment variables</heading>
6676 A program must not depend on environment variables to get
6677 reasonable defaults. (That's because these environment
6678 variables would have to be set in a system-wide
6679 configuration file like <file>/etc/profile</file>, which is not
6680 supported by all shells.)
6684 If a program usually depends on environment variables for its
6685 configuration, the program should be changed to fall back to
6686 a reasonable default configuration if these environment
6687 variables are not present. If this cannot be done easily
6688 (e.g., if the source code of a non-free program is not
6689 available), the program must be replaced by a small
6690 "wrapper" shell script which sets the environment variables
6691 if they are not already defined, and calls the original program.
6695 Here is an example of a wrapper script for this purpose:
6697 <example compact="compact">
6699 BAR=${BAR:-/var/lib/fubar}
6701 exec /usr/lib/foo/foo "$@"
6706 Furthermore, as <file>/etc/profile</file> is a configuration
6707 file of the <prgn>base-files</prgn> package, other packages must
6708 not put any environment variables or other commands into that
6713 <sect id="doc-base">
6714 <heading>Registering Documents using doc-base</heading>
6717 The <package>doc-base</package> package implements a
6718 flexible mechanism for handling and presenting
6719 documentation. The recommended practice is for every Debian
6720 package that provides online documentation (other than just
6721 manual pages) to register these documents with
6722 <package>doc-base</package> by installing a
6723 <package>doc-base</package> control file via the
6724 <prgn/install-docs/ script at installation time and
6725 de-register the manuals again when the package is removed.
6728 Please refer to the documentation that comes with the
6729 <package>doc-base</package> package for information and
6738 <heading>Files</heading>
6741 <heading>Binaries</heading>
6744 Two different packages must not install programs with
6745 different functionality but with the same filenames. (The
6746 case of two programs having the same functionality but
6747 different implementations is handled via "alternatives" or
6748 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6749 <ref id="conflicts"> respectively.) If this case happens,
6750 one of the programs must be renamed. The maintainers should
6751 report this to the <tt>debian-devel</tt> mailing list and
6752 try to find a consensus about which program will have to be
6753 renamed. If a consensus cannot be reached, <em>both</em>
6754 programs must be renamed.
6758 By default, when a package is being built, any binaries
6759 created should include debugging information, as well as
6760 being compiled with optimization. You should also turn on
6761 as many reasonable compilation warnings as possible; this
6762 makes life easier for porters, who can then look at build
6763 logs for possible problems. For the C programming language,
6764 this means the following compilation parameters should be
6766 <example compact="compact">
6768 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6770 INSTALL = install -s # (or use strip on the files in debian/tmp)
6775 Note that by default all installed binaries should be stripped,
6776 either by using the <tt>-s</tt> flag to
6777 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6778 the binaries after they have been copied into
6779 <file>debian/tmp</file> but before the tree is made into a
6784 Although binaries in the build tree should be compiled with
6785 debugging information by default, it can often be difficult to
6786 debug programs if they are also subjected to compiler
6787 optimization. For this reason, it is recommended to support the
6788 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6789 (see <ref id="debianrules-options">). This variable can contain
6790 several flags to change how a package is compiled and built.
6794 It is up to the package maintainer to decide what
6795 compilation options are best for the package. Certain
6796 binaries (such as computationally-intensive programs) will
6797 function better with certain flags (<tt>-O3</tt>, for
6798 example); feel free to use them. Please use good judgment
6799 here. Don't use flags for the sake of it; only use them
6800 if there is good reason to do so. Feel free to override
6801 the upstream author's ideas about which compilation
6802 options are best: they are often inappropriate for our
6808 <sect id="libraries">
6809 <heading>Libraries</heading>
6812 If the package is <strong>architecture: any</strong>, then
6813 the shared library compilation and linking flags must have
6814 <tt>-fPIC</tt>, or the package shall not build on some of
6815 the supported architectures<footnote>
6817 If you are using GCC, <tt>-fPIC</tt> produces code with
6818 relocatable position independent code, which is required for
6819 most architectures to create a shared library, with i386 and
6820 perhaps some others where non position independent code is
6821 permitted in a shared library.
6824 Position independent code may have a performance penalty,
6825 especially on <tt>i386</tt>. However, in most cases the
6826 speed penalty must be measured against the memory wasted on
6827 the few architectures where non position independent code is
6830 </footnote>. Any exception to this rule must be discussed on
6831 the mailing list <em>debian-devel@lists.debian.org</em>, and
6832 a rough consensus obtained. The reasons for not compiling
6833 with <tt>-fPIC</tt> flag must be recorded in the file
6834 <tt>README.Debian</tt>, and care must be taken to either
6835 restrict the architecture or arrange for <tt>-fPIC</tt> to
6836 be used on architectures where it is required.<footnote>
6838 Some of the reasons why this might be required is if the
6839 library contains hand crafted assembly code that is not
6840 relocatable, the speed penalty is excessive for compute
6841 intensive libs, and similar reasons.
6846 As to the static libraries, the common case is not to have
6847 relocatable code, since there is no benefit, unless in specific
6848 cases; therefore the static version must not be compiled
6849 with the <tt>-fPIC</tt> flag. Any exception to this rule
6850 should be discussed on the mailing list
6851 <em>debian-devel@lists.debian.org</em>, and the reasons for
6852 compiling with the <tt>-fPIC</tt> flag must be recorded in
6853 the file <tt>README.Debian</tt>. <footnote>
6855 Some of the reasons for linking static libraries with
6856 the <tt>-fPIC</tt> flag are if, for example, one needs a
6857 Perl API for a library that is under rapid development,
6858 and has an unstable API, so shared libraries are
6859 pointless at this phase of the library's development. In
6860 that case, since Perl needs a library with relocatable
6861 code, it may make sense to create a static library with
6862 relocatable code. Another reason cited is if you are
6863 distilling various libraries into a common shared
6864 library, like <tt>mklibs</tt> does in the Debian
6870 In other words, if both a shared and a static library is
6871 being built, each source unit (<tt>*.c</tt>, for example,
6872 for C files) will need to be compiled twice, for the normal
6876 You must specify the gcc option <tt>-D_REENTRANT</tt>
6877 when building a library (either static or shared) to make
6878 the library compatible with LinuxThreads.
6882 Although not enforced by the build tools, shared libraries
6883 must be linked against all libraries that they use symbols from
6884 in the same way that binaries are. This ensures the correct
6885 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6886 system and guarantees that all libraries can be safely opened
6887 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6888 option <tt>-Wl,-z,defs</tt> when building a shared library.
6889 Since this option enforces symbol resolution at build time,
6890 a missing library reference will be caught early as a fatal
6895 All installed shared libraries should be stripped with
6896 <example compact="compact">
6897 strip --strip-unneeded <var>your-lib</var>
6899 (The option <tt>--strip-unneeded</tt> makes
6900 <prgn>strip</prgn> remove only the symbols which aren't
6901 needed for relocation processing.) Shared libraries can
6902 function perfectly well when stripped, since the symbols for
6903 dynamic linking are in a separate part of the ELF object
6905 You might also want to use the options
6906 <tt>--remove-section=.comment</tt> and
6907 <tt>--remove-section=.note</tt> on both shared libraries
6908 and executables, and <tt>--strip-debug</tt> on static
6914 Note that under some circumstances it may be useful to
6915 install a shared library unstripped, for example when
6916 building a separate package to support debugging.
6920 Shared object files (often <file>.so</file> files) that are not
6921 public libraries, that is, they are not meant to be linked
6922 to by third party executables (binaries of other packages),
6923 should be installed in subdirectories of the
6924 <file>/usr/lib</file> directory. Such files are exempt from the
6925 rules that govern ordinary shared libraries, except that
6926 they must not be installed executable and should be
6928 A common example are the so-called "plug-ins",
6929 internal shared objects that are dynamically loaded by
6930 programs using <manref name="dlopen" section="3">.
6935 Packages containing shared libraries that may be linked to
6936 by other packages' binaries, but which for some
6937 <em>compelling</em> reason can not be installed in
6938 <file>/usr/lib</file> directory, may install the shared library
6939 files in subdirectories of the <file>/usr/lib</file> directory,
6940 in which case they should arrange to add that directory in
6941 <file>/etc/ld.so.conf</file> in the package's post-installation
6942 script, and remove it in the package's post-removal script.
6946 An ever increasing number of packages are using
6947 <prgn>libtool</prgn> to do their linking. The latest GNU
6948 libtools (>= 1.3a) can take advantage of the metadata in the
6949 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6950 files). The main advantage of <prgn>libtool</prgn>'s
6951 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6952 store and subsequently access metadata with respect to the
6953 libraries it builds. <prgn>libtool</prgn> will search for
6954 those files, which contain a lot of useful information about
6955 a library (such as library dependency information for static
6956 linking). Also, they're <em>essential</em> for programs
6957 using <tt>libltdl</tt>.<footnote>
6958 Although <prgn>libtool</prgn> is fully capable of
6959 linking against shared libraries which don't have
6960 <tt>.la</tt> files, as it is a mere shell script it can
6961 add considerably to the build time of a
6962 <prgn>libtool</prgn>-using package if that shell script
6963 has to derive all this information from first principles
6964 for each library every time it is linked. With the
6965 advent of <prgn>libtool</prgn> version 1.4 (and to a
6966 lesser extent <prgn>libtool</prgn> version 1.3), the
6967 <file>.la</file> files also store information about
6968 inter-library dependencies which cannot necessarily be
6969 derived after the <file>.la</file> file is deleted.
6974 Packages that use <prgn>libtool</prgn> to create shared
6975 libraries should include the <file>.la</file> files in the
6976 <tt>-dev</tt> package, unless the package relies on
6977 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6978 the <tt>.la</tt> files must go in the run-time library
6983 You must make sure that you use only released versions of
6984 shared libraries to build your packages; otherwise other
6985 users will not be able to run your binaries
6986 properly. Producing source packages that depend on
6987 unreleased compilers is also usually a bad
6994 <heading>Shared libraries</heading>
6996 This section has moved to <ref id="sharedlibs">.
7002 <heading>Scripts</heading>
7005 All command scripts, including the package maintainer
7006 scripts inside the package and used by <prgn>dpkg</prgn>,
7007 should have a <tt>#!</tt> line naming the shell to be used
7012 In the case of Perl scripts this should be
7013 <tt>#!/usr/bin/perl</tt>.
7017 When scripts are installed into a directory in the system
7018 PATH, the script name should not include an extension such
7019 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7020 language currently used to implement it.
7023 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7024 should almost certainly start with <tt>set -e</tt> so that
7025 errors are detected. Every script should use
7026 <tt>set -e</tt> or check the exit status of <em>every</em>
7031 Scripts may assume that <file>/bin/sh</file> implements the
7032 SUSv3 Shell Command Language<footnote>
7033 Single UNIX Specification, version 3, which is also IEEE
7034 1003.1-2004 (POSIX), and is available on the World Wide Web
7035 from <url id="http://www.unix.org/version3/online.html"
7036 name="The Open Group"> after free
7037 registration.</footnote>
7038 plus the following additional features not mandated by
7040 These features are in widespread use in the Linux community
7041 and are implemented in all of bash, dash, and ksh, the most
7042 common shells users may wish to use as <file>/bin/sh</file>.
7045 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7046 must not generate a newline.</item>
7047 <item><tt>test</tt>, if implemented as a shell built-in, must
7048 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7050 <item><tt>local</tt> to create a scoped variable must be
7051 supported; however, <tt>local</tt> may or may not preserve
7052 the variable value from an outer scope and may or may not
7053 support arguments more complex than simple variables. Only
7065 If a shell script requires non-SUSv3 features from the shell
7066 interpreter other than those listed above, the appropriate shell
7067 must be specified in the first line of the script (e.g.,
7068 <tt>#!/bin/bash</tt>) and the package must depend on the package
7069 providing the shell (unless the shell package is marked
7070 "Essential", as in the case of <prgn>bash</prgn>).
7074 You may wish to restrict your script to SUSv3 features plus the
7075 above set when possible so that it may use <file>/bin/sh</file>
7076 as its interpreter. If your script works with <prgn>dash</prgn>
7077 (originally called <prgn>ash</prgn>), it probably complies with
7078 the above requirements, but if you are in doubt, use
7079 <file>/bin/bash</file>.
7083 Perl scripts should check for errors when making any
7084 system calls, including <tt>open</tt>, <tt>print</tt>,
7085 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7089 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7090 scripting languages. See <em>Csh Programming Considered
7091 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7092 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7093 If an upstream package comes with <prgn>csh</prgn> scripts
7094 then you must make sure that they start with
7095 <tt>#!/bin/csh</tt> and make your package depend on the
7096 <prgn>c-shell</prgn> virtual package.
7100 Any scripts which create files in world-writeable
7101 directories (e.g., in <file>/tmp</file>) must use a
7102 mechanism which will fail atomically if a file with the same
7103 name already exists.
7107 The Debian base system provides the <prgn>tempfile</prgn>
7108 and <prgn>mktemp</prgn> utilities for use by scripts for
7115 <heading>Symbolic links</heading>
7118 In general, symbolic links within a top-level directory
7119 should be relative, and symbolic links pointing from one
7120 top-level directory into another should be absolute. (A
7121 top-level directory is a sub-directory of the root
7122 directory <file>/</file>.)
7126 In addition, symbolic links should be specified as short as
7127 possible, i.e., link targets like <file>foo/../bar</file> are
7132 Note that when creating a relative link using
7133 <prgn>ln</prgn> it is not necessary for the target of the
7134 link to exist relative to the working directory you're
7135 running <prgn>ln</prgn> from, nor is it necessary to change
7136 directory to the directory where the link is to be made.
7137 Simply include the string that should appear as the target
7138 of the link (this will be a pathname relative to the
7139 directory in which the link resides) as the first argument
7144 For example, in your <prgn>Makefile</prgn> or
7145 <file>debian/rules</file>, you can do things like:
7146 <example compact="compact">
7147 ln -fs gcc $(prefix)/bin/cc
7148 ln -fs gcc debian/tmp/usr/bin/cc
7149 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7150 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7155 A symbolic link pointing to a compressed file should always
7156 have the same file extension as the referenced file. (For
7157 example, if a file <file>foo.gz</file> is referenced by a
7158 symbolic link, the filename of the link has to end with
7159 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7164 <heading>Device files</heading>
7167 Packages must not include device files in the package file
7172 If a package needs any special device files that are not
7173 included in the base system, it must call
7174 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7175 after notifying the user<footnote>
7176 This notification could be done via a (low-priority)
7177 debconf message, or an echo (printf) statement.
7182 Packages must not remove any device files in the
7183 <prgn>postrm</prgn> or any other script. This is left to the
7184 system administrator.
7188 Debian uses the serial devices
7189 <file>/dev/ttyS*</file>. Programs using the old
7190 <file>/dev/cu*</file> devices should be changed to use
7191 <file>/dev/ttyS*</file>.
7195 <sect id="config-files">
7196 <heading>Configuration files</heading>
7199 <heading>Definitions</heading>
7203 <tag>configuration file</tag>
7205 A file that affects the operation of a program, or
7206 provides site- or host-specific information, or
7207 otherwise customizes the behavior of a program.
7208 Typically, configuration files are intended to be
7209 modified by the system administrator (if needed or
7210 desired) to conform to local policy or to provide
7211 more useful site-specific behavior.
7214 <tag><tt>conffile</tt></tag>
7216 A file listed in a package's <tt>conffiles</tt>
7217 file, and is treated specially by <prgn>dpkg</prgn>
7218 (see <ref id="configdetails">).
7224 The distinction between these two is important; they are
7225 not interchangeable concepts. Almost all
7226 <tt>conffile</tt>s are configuration files, but many
7227 configuration files are not <tt>conffiles</tt>.
7231 As noted elsewhere, <file>/etc/init.d</file> scripts,
7232 <file>/etc/default</file> files, scripts installed in
7233 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7234 configuration installed in <file>/etc/cron.d</file> must be
7235 treated as configuration files. In general, any script that
7236 embeds configuration information is de-facto a configuration
7237 file and should be treated as such.
7242 <heading>Location</heading>
7245 Any configuration files created or used by your package
7246 must reside in <file>/etc</file>. If there are several,
7247 consider creating a subdirectory of <file>/etc</file>
7248 named after your package.
7252 If your package creates or uses configuration files
7253 outside of <file>/etc</file>, and it is not feasible to modify
7254 the package to use <file>/etc</file> directly, put the files
7255 in <file>/etc</file> and create symbolic links to those files
7256 from the location that the package requires.
7261 <heading>Behavior</heading>
7264 Configuration file handling must conform to the following
7266 <list compact="compact">
7268 local changes must be preserved during a package
7272 configuration files must be preserved when the
7273 package is removed, and only deleted when the
7280 The easy way to achieve this behavior is to make the
7281 configuration file a <tt>conffile</tt>. This is
7282 appropriate only if it is possible to distribute a default
7283 version that will work for most installations, although
7284 some system administrators may choose to modify it. This
7285 implies that the default version will be part of the
7286 package distribution, and must not be modified by the
7287 maintainer scripts during installation (or at any other
7292 In order to ensure that local changes are preserved
7293 correctly, no package may contain or make hard links to
7294 conffiles.<footnote>
7295 Rationale: There are two problems with hard links.
7296 The first is that some editors break the link while
7297 editing one of the files, so that the two files may
7298 unwittingly become unlinked and different. The second
7299 is that <prgn>dpkg</prgn> might break the hard link
7300 while upgrading <tt>conffile</tt>s.
7305 The other way to do it is via the maintainer scripts. In
7306 this case, the configuration file must not be listed as a
7307 <tt>conffile</tt> and must not be part of the package
7308 distribution. If the existence of a file is required for
7309 the package to be sensibly configured it is the
7310 responsibility of the package maintainer to provide
7311 maintainer scripts which correctly create, update and
7312 maintain the file and remove it on purge. (See <ref
7313 id="maintainerscripts"> for more information.) These
7314 scripts must be idempotent (i.e., must work correctly if
7315 <prgn>dpkg</prgn> needs to re-run them due to errors
7316 during installation or removal), must cope with all the
7317 variety of ways <prgn>dpkg</prgn> can call maintainer
7318 scripts, must not overwrite or otherwise mangle the user's
7319 configuration without asking, must not ask unnecessary
7320 questions (particularly during upgrades), and must
7321 otherwise be good citizens.
7325 The scripts are not required to configure every possible
7326 option for the package, but only those necessary to get
7327 the package running on a given system. Ideally the
7328 sysadmin should not have to do any configuration other
7329 than that done (semi-)automatically by the
7330 <prgn>postinst</prgn> script.
7334 A common practice is to create a script called
7335 <file><var>package</var>-configure</file> and have the
7336 package's <prgn>postinst</prgn> call it if and only if the
7337 configuration file does not already exist. In certain
7338 cases it is useful for there to be an example or template
7339 file which the maintainer scripts use. Such files should
7340 be in <file>/usr/share/<var>package</var></file> or
7341 <file>/usr/lib/<var>package</var></file> (depending on whether
7342 they are architecture-independent or not). There should
7343 be symbolic links to them from
7344 <file>/usr/share/doc/<var>package</var>/examples</file> if
7345 they are examples, and should be perfectly ordinary
7346 <prgn>dpkg</prgn>-handled files (<em>not</em>
7347 configuration files).
7351 These two styles of configuration file handling must
7352 not be mixed, for that way lies madness:
7353 <prgn>dpkg</prgn> will ask about overwriting the file
7354 every time the package is upgraded.
7359 <heading>Sharing configuration files</heading>
7362 Packages which specify the same file as a
7363 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7364 with each other. (This is an instance of the general rule
7365 about not sharing files. Note that neither alternatives
7366 nor diversions are likely to be appropriate in this case;
7367 in particular, <prgn>dpkg</prgn> does not handle diverted
7368 <tt>conffile</tt>s well.)
7372 The maintainer scripts must not alter a <tt>conffile</tt>
7373 of <em>any</em> package, including the one the scripts
7378 If two or more packages use the same configuration file
7379 and it is reasonable for both to be installed at the same
7380 time, one of these packages must be defined as
7381 <em>owner</em> of the configuration file, i.e., it will be
7382 the package which handles that file as a configuration
7383 file. Other packages that use the configuration file must
7384 depend on the owning package if they require the
7385 configuration file to operate. If the other package will
7386 use the configuration file if present, but is capable of
7387 operating without it, no dependency need be declared.
7391 If it is desirable for two or more related packages to
7392 share a configuration file <em>and</em> for all of the
7393 related packages to be able to modify that configuration
7394 file, then the following should be done:
7395 <enumlist compact="compact">
7397 One of the related packages (the "owning" package)
7398 will manage the configuration file with maintainer
7399 scripts as described in the previous section.
7402 The owning package should also provide a program
7403 that the other packages may use to modify the
7407 The related packages must use the provided program
7408 to make any desired modifications to the
7409 configuration file. They should either depend on
7410 the core package to guarantee that the configuration
7411 modifier program is available or accept gracefully
7412 that they cannot modify the configuration file if it
7413 is not. (This is in addition to the fact that the
7414 configuration file may not even be present in the
7421 Sometimes it's appropriate to create a new package which
7422 provides the basic infrastructure for the other packages
7423 and which manages the shared configuration files. (The
7424 <tt>sgml-base</tt> package is a good example.)
7429 <heading>User configuration files ("dotfiles")</heading>
7432 The files in <file>/etc/skel</file> will automatically be
7433 copied into new user accounts by <prgn>adduser</prgn>.
7434 No other program should reference the files in
7435 <file>/etc/skel</file>.
7439 Therefore, if a program needs a dotfile to exist in
7440 advance in <file>$HOME</file> to work sensibly, that dotfile
7441 should be installed in <file>/etc/skel</file> and treated as a
7446 However, programs that require dotfiles in order to
7447 operate sensibly are a bad thing, unless they do create
7448 the dotfiles themselves automatically.
7452 Furthermore, programs should be configured by the Debian
7453 default installation to behave as closely to the upstream
7454 default behavior as possible.
7458 Therefore, if a program in a Debian package needs to be
7459 configured in some way in order to operate sensibly, that
7460 should be done using a site-wide configuration file placed
7461 in <file>/etc</file>. Only if the program doesn't support a
7462 site-wide default configuration and the package maintainer
7463 doesn't have time to add it may a default per-user file be
7464 placed in <file>/etc/skel</file>.
7468 <file>/etc/skel</file> should be as empty as we can make it.
7469 This is particularly true because there is no easy (or
7470 necessarily desirable) mechanism for ensuring that the
7471 appropriate dotfiles are copied into the accounts of
7472 existing users when a package is installed.
7478 <heading>Log files</heading>
7480 Log files should usually be named
7481 <file>/var/log/<var>package</var>.log</file>. If you have many
7482 log files, or need a separate directory for permission
7483 reasons (<file>/var/log</file> is writable only by
7484 <file>root</file>), you should usually create a directory named
7485 <file>/var/log/<var>package</var></file> and place your log
7490 Log files must be rotated occasionally so that they don't
7491 grow indefinitely; the best way to do this is to drop a log
7492 rotation configuration file into the directory
7493 <file>/etc/logrotate.d</file> and use the facilities provided by
7494 logrotate.<footnote>
7496 The traditional approach to log files has been to set up
7497 <em>ad hoc</em> log rotation schemes using simple shell
7498 scripts and cron. While this approach is highly
7499 customizable, it requires quite a lot of sysadmin work.
7500 Even though the original Debian system helped a little
7501 by automatically installing a system which can be used
7502 as a template, this was deemed not enough.
7506 The use of <prgn>logrotate</prgn>, a program developed
7507 by Red Hat, is better, as it centralizes log management.
7508 It has both a configuration file
7509 (<file>/etc/logrotate.conf</file>) and a directory where
7510 packages can drop their individual log rotation
7511 configurations (<file>/etc/logrotate.d</file>).
7514 Here is a good example for a logrotate config
7515 file (for more information see <manref name="logrotate"
7517 <example compact="compact">
7518 /var/log/foo/*.log {
7523 /etc/init.d/foo force-reload
7527 This rotates all files under <file>/var/log/foo</file>, saves 12
7528 compressed generations, and forces the daemon to reload its
7529 configuration information after the log rotation.
7533 Log files should be removed when the package is
7534 purged (but not when it is only removed). This should be
7535 done by the <prgn>postrm</prgn> script when it is called
7536 with the argument <tt>purge</tt> (see <ref
7537 id="removedetails">).
7542 <heading>Permissions and owners</heading>
7545 The rules in this section are guidelines for general use.
7546 If necessary you may deviate from the details below.
7547 However, if you do so you must make sure that what is done
7548 is secure and you should try to be as consistent as possible
7549 with the rest of the system. You should probably also
7550 discuss it on <prgn>debian-devel</prgn> first.
7554 Files should be owned by <tt>root:root</tt>, and made
7555 writable only by the owner and universally readable (and
7556 executable, if appropriate), that is mode 644 or 755.
7560 Directories should be mode 755 or (for group-writability)
7561 mode 2775. The ownership of the directory should be
7562 consistent with its mode: if a directory is mode 2775, it
7563 should be owned by the group that needs write access to
7566 When a package is upgraded, and the owner or permissions
7567 of a file included in the package has changed, dpkg
7568 arranges for the ownership and permissions to be
7569 correctly set upon installation. However, this does not
7570 extend to directories; the permissions and ownership of
7571 directories already on the system does not change on
7572 install or upgrade of packages. This makes sense, since
7573 otherwise common directories like <tt>/usr</tt> would
7574 always be in flux. To correctly change permissions of a
7575 directory the package owns, explicit action is required,
7576 usually in the <tt>postinst</tt> script. Care must be
7577 taken to handle downgrades as well, in that case.
7584 Setuid and setgid executables should be mode 4755 or 2755
7585 respectively, and owned by the appropriate user or group.
7586 They should not be made unreadable (modes like 4711 or
7587 2711 or even 4111); doing so achieves no extra security,
7588 because anyone can find the binary in the freely available
7589 Debian package; it is merely inconvenient. For the same
7590 reason you should not restrict read or execute permissions
7591 on non-set-id executables.
7595 Some setuid programs need to be restricted to particular
7596 sets of users, using file permissions. In this case they
7597 should be owned by the uid to which they are set-id, and by
7598 the group which should be allowed to execute them. They
7599 should have mode 4754; again there is no point in making
7600 them unreadable to those users who must not be allowed to
7605 It is possible to arrange that the system administrator can
7606 reconfigure the package to correspond to their local
7607 security policy by changing the permissions on a binary:
7608 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7609 described below.<footnote>
7610 Ordinary files installed by <prgn>dpkg</prgn> (as
7611 opposed to <tt>conffile</tt>s and other similar objects)
7612 normally have their permissions reset to the distributed
7613 permissions when the package is reinstalled. However,
7614 the use of <prgn>dpkg-statoverride</prgn> overrides this
7615 default behavior. If you use this method, you should
7616 remember to describe <prgn>dpkg-statoverride</prgn> in
7617 the package documentation; being a relatively new
7618 addition to Debian, it is probably not yet well-known.
7620 Another method you should consider is to create a group for
7621 people allowed to use the program(s) and make any setuid
7622 executables executable only by that group.
7626 If you need to create a new user or group for your package
7627 there are two possibilities. Firstly, you may need to
7628 make some files in the binary package be owned by this
7629 user or group, or you may need to compile the user or
7630 group id (rather than just the name) into the binary
7631 (though this latter should be avoided if possible, as in
7632 this case you need a statically allocated id).</p>
7635 If you need a statically allocated id, you must ask for a
7636 user or group id from the <tt>base-passwd</tt> maintainer,
7637 and must not release the package until you have been
7638 allocated one. Once you have been allocated one you must
7639 either make the package depend on a version of the
7640 <tt>base-passwd</tt> package with the id present in
7641 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7642 your package to create the user or group itself with the
7643 correct id (using <tt>adduser</tt>) in its
7644 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7645 the <prgn>postinst</prgn> is to be preferred if it is
7646 possible, otherwise a pre-dependency will be needed on the
7647 <tt>adduser</tt> package.)
7651 On the other hand, the program might be able to determine
7652 the uid or gid from the user or group name at runtime, so
7653 that a dynamically allocated id can be used. In this case
7654 you should choose an appropriate user or group name,
7655 discussing this on <prgn>debian-devel</prgn> and checking
7656 with the <package/base-passwd/ maintainer that it is unique and that
7657 they do not wish you to use a statically allocated id
7658 instead. When this has been checked you must arrange for
7659 your package to create the user or group if necessary using
7660 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7661 <prgn>postinst</prgn> script (again, the latter is to be
7662 preferred if it is possible).
7666 Note that changing the numeric value of an id associated
7667 with a name is very difficult, and involves searching the
7668 file system for all appropriate files. You need to think
7669 carefully whether a static or dynamic id is required, since
7670 changing your mind later will cause problems.
7673 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7675 This section is not intended as policy, but as a
7676 description of the use of <prgn>dpkg-statoverride</prgn>.
7680 If a system administrator wishes to have a file (or
7681 directory or other such thing) installed with owner and
7682 permissions different from those in the distributed Debian
7683 package, they can use the <prgn>dpkg-statoverride</prgn>
7684 program to instruct <prgn>dpkg</prgn> to use the different
7685 settings every time the file is installed. Thus the
7686 package maintainer should distribute the files with their
7687 normal permissions, and leave it for the system
7688 administrator to make any desired changes. For example, a
7689 daemon which is normally required to be setuid root, but
7690 in certain situations could be used without being setuid,
7691 should be installed setuid in the <tt>.deb</tt>. Then the
7692 local system administrator can change this if they wish.
7693 If there are two standard ways of doing it, the package
7694 maintainer can use <tt>debconf</tt> to find out the
7695 preference, and call <prgn>dpkg-statoverride</prgn> in the
7696 maintainer script if necessary to accommodate the system
7697 administrator's choice. Care must be taken during
7698 upgrades to not override an existing setting.
7702 Given the above, <prgn>dpkg-statoverride</prgn> is
7703 essentially a tool for system administrators and would not
7704 normally be needed in the maintainer scripts. There is
7705 one type of situation, though, where calls to
7706 <prgn>dpkg-statoverride</prgn> would be needed in the
7707 maintainer scripts, and that involves packages which use
7708 dynamically allocated user or group ids. In such a
7709 situation, something like the following idiom can be very
7710 helpful in the package's <prgn>postinst</prgn>, where
7711 <tt>sysuser</tt> is a dynamically allocated id:
7713 for i in /usr/bin/foo /usr/sbin/bar
7715 # only do something when no setting exists
7716 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7718 #include: debconf processing, question about foo and bar
7719 if [ "$RET" = "true" ] ; then
7720 dpkg-statoverride --update --add sysuser root 4755 $i
7725 The corresponding <tt>dpkg-statoverride --remove</tt>
7726 calls can then be made unconditionally when the package is
7734 <chapt id="customized-programs">
7735 <heading>Customized programs</heading>
7737 <sect id="arch-spec">
7738 <heading>Architecture specification strings</heading>
7741 If a program needs to specify an <em>architecture specification
7742 string</em> in some place, it should select one of the
7743 strings provided by <tt>dpkg-architecture -L</tt>. The
7744 strings are in the format
7745 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7746 is sometimes elided, as when the OS is Linux.<footnote>
7747 <p>Currently, the strings are:
7748 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7749 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7750 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7751 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7752 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7753 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7754 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7755 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7756 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7757 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7758 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7759 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7760 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7761 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7762 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7763 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7764 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7765 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7766 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7767 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7768 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7769 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7770 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7771 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7772 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7773 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7774 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7775 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7776 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7777 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7778 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7779 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7780 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7781 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7782 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7783 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7784 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7790 Note that we don't want to use
7791 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7792 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7793 since this would make our programs incompatible with other
7794 Linux distributions. We also don't use something like
7795 <tt><var>arch</var>-unknown-linux</tt>, since the
7796 <tt>unknown</tt> does not look very good.
7801 <heading>Daemons</heading>
7804 The configuration files <file>/etc/services</file>,
7805 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7806 by the <prgn>netbase</prgn> package and must not be modified
7811 If a package requires a new entry in one of these files, the
7812 maintainer should get in contact with the
7813 <prgn>netbase</prgn> maintainer, who will add the entries
7814 and release a new version of the <prgn>netbase</prgn>
7819 The configuration file <file>/etc/inetd.conf</file> must not be
7820 modified by the package's scripts except via the
7821 <prgn>update-inetd</prgn> script or the
7822 <file>DebianNet.pm</file> Perl module. See their documentation
7823 for details on how to add entries.
7827 If a package wants to install an example entry into
7828 <file>/etc/inetd.conf</file>, the entry must be preceded with
7829 exactly one hash character (<tt>#</tt>). Such lines are
7830 treated as "commented out by user" by the
7831 <prgn>update-inetd</prgn> script and are not changed or
7832 activated during package updates.
7837 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7841 Some programs need to create pseudo-ttys. This should be done
7842 using Unix98 ptys if the C library supports it. The resulting
7843 program must not be installed setuid root, unless that
7844 is required for other functionality.
7848 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7849 <file>/var/log/lastlog</file> must be installed writable by
7850 group <tt>utmp</tt>. Programs which need to modify those
7851 files must be installed setgid <tt>utmp</tt>.
7856 <heading>Editors and pagers</heading>
7859 Some programs have the ability to launch an editor or pager
7860 program to edit or display a text document. Since there are
7861 lots of different editors and pagers available in the Debian
7862 distribution, the system administrator and each user should
7863 have the possibility to choose their preferred editor and
7868 In addition, every program should choose a good default
7869 editor/pager if none is selected by the user or system
7874 Thus, every program that launches an editor or pager must
7875 use the EDITOR or PAGER environment variable to determine
7876 the editor or pager the user wishes to use. If these
7877 variables are not set, the programs <file>/usr/bin/editor</file>
7878 and <file>/usr/bin/pager</file> should be used, respectively.
7882 These two files are managed through the <prgn>dpkg</prgn>
7883 "alternatives" mechanism. Thus every package providing an
7884 editor or pager must call the
7885 <prgn>update-alternatives</prgn> script to register these
7890 If it is very hard to adapt a program to make use of the
7891 EDITOR or PAGER variables, that program may be configured to
7892 use <file>/usr/bin/sensible-editor</file> and
7893 <file>/usr/bin/sensible-pager</file> as the editor or pager
7894 program respectively. These are two scripts provided in the
7895 Debian base system that check the EDITOR and PAGER variables
7896 and launch the appropriate program, and fall back to
7897 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7898 variable is not set.
7902 A program may also use the VISUAL environment variable to
7903 determine the user's choice of editor. If it exists, it
7904 should take precedence over EDITOR. This is in fact what
7905 <file>/usr/bin/sensible-editor</file> does.
7909 It is not required for a package to depend on
7910 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7911 package to provide such virtual packages.<footnote>
7912 The Debian base system already provides an editor and a
7918 <sect id="web-appl">
7919 <heading>Web servers and applications</heading>
7922 This section describes the locations and URLs that should
7923 be used by all web servers and web applications in the
7930 Cgi-bin executable files are installed in the
7932 <example compact="compact">
7933 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7935 and should be referred to as
7936 <example compact="compact">
7937 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7943 <p>Access to HTML documents</p>
7946 HTML documents for a package are stored in
7947 <file>/usr/share/doc/<var>package</var></file>
7948 and can be referred to as
7949 <example compact="compact">
7950 http://localhost/doc/<var>package</var>/<var>filename</var>
7955 The web server should restrict access to the document
7956 tree so that only clients on the same host can read
7957 the documents. If the web server does not support such
7958 access controls, then it should not provide access at
7959 all, or ask about providing access during installation.
7964 <p>Access to images</p>
7966 It is recommended that images for a package be stored
7967 in <tt>/usr/share/images/<var>package</var></tt> and
7968 may be referred to through an alias <tt>/images/</tt>
7971 http://localhost/images/<package>/<filename>
7978 <p>Web Document Root</p>
7981 Web Applications should try to avoid storing files in
7982 the Web Document Root. Instead they should use the
7983 /usr/share/doc/<var>package</var> directory for
7984 documents and register the Web Application via the
7985 <package>doc-base</package> package. If access to the
7986 web document root is unavoidable then use
7987 <example compact="compact">
7990 as the Document Root. This might be just a symbolic
7991 link to the location where the system administrator
7992 has put the real document root.
7995 <item><p>Providing httpd and/or httpd-cgi</p>
7997 All web servers should provide the virtual package
7998 <tt>httpd</tt>. If a web server has CGI support it should
7999 provide <tt>httpd-cgi</tt> additionally.
8002 All web applications which do not contain CGI scripts should
8003 depend on <tt>httpd</tt>, all those web applications which
8004 <tt>do</tt> contain CGI scripts, should depend on
8012 <sect id="mail-transport-agents">
8013 <heading>Mail transport, delivery and user agents</heading>
8016 Debian packages which process electronic mail, whether mail
8017 user agents (MUAs) or mail transport agents (MTAs), must
8018 ensure that they are compatible with the configuration
8019 decisions below. Failure to do this may result in lost
8020 mail, broken <tt>From:</tt> lines, and other serious brain
8025 The mail spool is <file>/var/mail</file> and the interface to
8026 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8027 the FHS). On older systems, the mail spool may be
8028 physically located in <file>/var/spool/mail</file>, but all
8029 access to the mail spool should be via the
8030 <file>/var/mail</file> symlink. The mail spool is part of the
8031 base system and not part of the MTA package.
8035 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8036 programs (such as IMAP daemons) must lock the mailbox in an
8037 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8038 be combined with dot locking. To avoid deadlocks, a program
8039 should use <tt>fcntl()</tt> first and dot locking after
8040 this, or alternatively implement the two locking methods in
8041 a non blocking way<footnote>
8042 If it is not possible to establish both locks, the
8043 system shouldn't wait for the second lock to be
8044 established, but remove the first lock, wait a (random)
8045 time, and start over locking again.
8046 </footnote>. Using the functions <tt>maillock</tt> and
8047 <tt>mailunlock</tt> provided by the
8048 <tt>liblockfile*</tt><footnote>
8049 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8050 to use these functions.
8051 </footnote> packages is the recommended way to realize this.
8055 Mailboxes are generally mode 660
8056 <tt><var>user</var>:mail</tt> unless the system
8057 administrator has chosen otherwise. A MUA may remove a
8058 mailbox (unless it has nonstandard permissions) in which
8059 case the MTA or another MUA must recreate it if needed.
8060 Mailboxes must be writable by group mail.
8064 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8065 be setgid mail to do the locking mentioned above (and
8066 must obviously avoid accessing other users' mailboxes
8067 using this privilege).</p>
8070 <file>/etc/aliases</file> is the source file for the system mail
8071 aliases (e.g., postmaster, usenet, etc.), it is the one
8072 which the sysadmin and <prgn>postinst</prgn> scripts may
8073 edit. After <file>/etc/aliases</file> is edited the program or
8074 human editing it must call <prgn>newaliases</prgn>. All MTA
8075 packages must come with a <prgn>newaliases</prgn> program,
8076 even if it does nothing, but older MTA packages did not do
8077 this so programs should not fail if <prgn>newaliases</prgn>
8078 cannot be found. Note that because of this, all MTA
8079 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8080 <tt>Replaces: mail-transport-agent</tt> control file
8085 The convention of writing <tt>forward to
8086 <var>address</var></tt> in the mailbox itself is not
8087 supported. Use a <tt>.forward</tt> file instead.</p>
8090 The <prgn>rmail</prgn> program used by UUCP
8091 for incoming mail should be <file>/usr/sbin/rmail</file>.
8092 Likewise, <prgn>rsmtp</prgn>, for receiving
8093 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8097 If your package needs to know what hostname to use on (for
8098 example) outgoing news and mail messages which are generated
8099 locally, you should use the file <file>/etc/mailname</file>. It
8100 will contain the portion after the username and <tt>@</tt>
8101 (at) sign for email addresses of users on the machine
8102 (followed by a newline).
8106 Such a package should check for the existence of this file
8107 when it is being configured. If it exists, it should be
8108 used without comment, although an MTA's configuration script
8109 may wish to prompt the user even if it finds that this file
8110 exists. If the file does not exist, the package should
8111 prompt the user for the value (preferably using
8112 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8113 as well as using it in the package's configuration. The
8114 prompt should make it clear that the name will not just be
8115 used by that package. For example, in this situation the
8116 <tt>inn</tt> package could say something like:
8117 <example compact="compact">
8118 Please enter the "mail name" of your system. This is the
8119 hostname portion of the address to be shown on outgoing
8120 news and mail messages. The default is
8121 <var>syshostname</var>, your system's host name. Mail
8122 name ["<var>syshostname</var>"]:
8124 where <var>syshostname</var> is the output of <tt>hostname
8130 <heading>News system configuration</heading>
8133 All the configuration files related to the NNTP (news)
8134 servers and clients should be located under
8135 <file>/etc/news</file>.</p>
8138 There are some configuration issues that apply to a number
8139 of news clients and server packages on the machine. These
8143 <tag><file>/etc/news/organization</file></tag>
8145 A string which should appear as the
8146 organization header for all messages posted
8147 by NNTP clients on the machine
8150 <tag><file>/etc/news/server</file></tag>
8152 Contains the FQDN of the upstream NNTP
8153 server, or localhost if the local machine is
8158 Other global files may be added as required for cross-package news
8165 <heading>Programs for the X Window System</heading>
8168 <heading>Providing X support and package priorities</heading>
8171 Programs that can be configured with support for the X
8172 Window System must be configured to do so and must declare
8173 any package dependencies necessary to satisfy their
8174 runtime requirements when using the X Window System. If
8175 such a package is of higher priority than the X packages
8176 on which it depends, it is required that either the
8177 X-specific components be split into a separate package, or
8178 that an alternative version of the package, which includes
8179 X support, be provided, or that the package's priority be
8185 <heading>Packages providing an X server</heading>
8188 Packages that provide an X server that, directly or
8189 indirectly, communicates with real input and display
8190 hardware should declare in their control data that they
8191 provide the virtual package <tt>xserver</tt>.<footnote>
8192 This implements current practice, and provides an
8193 actual policy for usage of the <tt>xserver</tt>
8194 virtual package which appears in the virtual packages
8195 list. In a nutshell, X servers that interface
8196 directly with the display and input hardware or via
8197 another subsystem (e.g., GGI) should provide
8198 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8199 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8205 <heading>Packages providing a terminal emulator</heading>
8208 Packages that provide a terminal emulator for the X Window
8209 System which meet the criteria listed below should declare
8210 in their control data that they provide the virtual
8211 package <tt>x-terminal-emulator</tt>. They should also
8212 register themselves as an alternative for
8213 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8218 To be an <tt>x-terminal-emulator</tt>, a program must:
8219 <list compact="compact">
8221 Be able to emulate a DEC VT100 terminal, or a
8222 compatible terminal.
8226 Support the command-line option <tt>-e
8227 <var>command</var></tt>, which creates a new
8228 terminal window<footnote>
8229 "New terminal window" does not necessarily mean
8230 a new top-level X window directly parented by
8231 the window manager; it could, if the terminal
8232 emulator application were so coded, be a new
8233 "view" in a multiple-document interface (MDI).
8235 and runs the specified <var>command</var>,
8236 interpreting the entirety of the rest of the command
8237 line as a command to pass straight to exec, in the
8238 manner that <tt>xterm</tt> does.
8242 Support the command-line option <tt>-T
8243 <var>title</var></tt>, which creates a new terminal
8244 window with the window title <var>title</var>.
8251 <heading>Packages providing a window manager</heading>
8254 Packages that provide a window manager should declare in
8255 their control data that they provide the virtual package
8256 <tt>x-window-manager</tt>. They should also register
8257 themselves as an alternative for
8258 <file>/usr/bin/x-window-manager</file>, with a priority
8259 calculated as follows:
8260 <list compact="compact">
8262 Start with a priority of 20.
8266 If the window manager supports the Debian menu
8267 system, add 20 points if this support is available
8268 in the package's default configuration (i.e., no
8269 configuration files belonging to the system or user
8270 have to be edited to activate the feature); if
8271 configuration files must be modified, add only 10
8277 If the window manager complies with <url
8278 id="http://www.freedesktop.org/Standards/wm-spec"
8279 name="The Window Manager Specification Project">,
8280 written by the <url id="http://www.freedesktop.org/"
8281 name="Free Desktop Group">, add 40 points.
8285 If the window manager permits the X session to be
8286 restarted using a <em>different</em> window manager
8287 (without killing the X server) in its default
8288 configuration, add 10 points; otherwise add none.
8295 <heading>Packages providing fonts</heading>
8298 Packages that provide fonts for the X Window
8300 For the purposes of Debian Policy, a "font for the X
8301 Window System" is one which is accessed via X protocol
8302 requests. Fonts for the Linux console, for PostScript
8303 renderer, or any other purpose, do not fit this
8304 definition. Any tool which makes such fonts available
8305 to the X Window System, however, must abide by this
8308 must do a number of things to ensure that they are both
8309 available without modification of the X or font server
8310 configuration, and that they do not corrupt files used by
8311 other font packages to register information about
8315 Fonts of any type supported by the X Window System
8316 must be in a separate binary package from any
8317 executables, libraries, or documentation (except
8318 that specific to the fonts shipped, such as their
8319 license information). If one or more of the fonts
8320 so packaged are necessary for proper operation of
8321 the package with which they are associated the font
8322 package may be Recommended; if the fonts merely
8323 provide an enhancement, a Suggests relationship may
8324 be used. Packages must not Depend on font
8326 This is because the X server may retrieve fonts
8327 from the local file system or over the network
8328 from an X font server; the Debian package system
8329 is empowered to deal only with the local
8335 BDF fonts must be converted to PCF fonts with the
8336 <prgn>bdftopcf</prgn> utility (available in the
8337 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8338 placed in a directory that corresponds to their
8340 <list compact="compact">
8342 100 dpi fonts must be placed in
8343 <file>/usr/share/fonts/X11/100dpi/</file>.
8347 75 dpi fonts must be placed in
8348 <file>/usr/share/fonts/X11/75dpi/</file>.
8352 Character-cell fonts, cursor fonts, and other
8353 low-resolution fonts must be placed in
8354 <file>/usr/share/fonts/X11/misc/</file>.
8360 Speedo fonts must be placed in
8361 <file>/usr/share/fonts/X11/Speedo/</file>.
8365 Type 1 fonts must be placed in
8366 <file>/usr/share/fonts/X11/Type1/</file>. If font
8367 metric files are available, they must be placed here
8372 Subdirectories of <file>/usr/share/fonts/X11/</file>
8373 other than those listed above must be neither
8374 created nor used. (The <file>PEX</file>, <file>CID</file>,
8375 and <file>cyrillic</file> directories are excepted for
8376 historical reasons, but installation of files into
8377 these directories remains discouraged.)
8381 Font packages may, instead of placing files directly
8382 in the X font directories listed above, provide
8383 symbolic links in that font directory pointing to
8384 the files' actual location in the filesystem. Such
8385 a location must comply with the FHS.
8389 Font packages should not contain both 75dpi and
8390 100dpi versions of a font. If both are available,
8391 they should be provided in separate binary packages
8392 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8393 the names of the packages containing the
8394 corresponding fonts.
8398 Fonts destined for the <file>misc</file> subdirectory
8399 should not be included in the same package as 75dpi
8400 or 100dpi fonts; instead, they should be provided in
8401 a separate package with <tt>-misc</tt> appended to
8406 Font packages must not provide the files
8407 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8408 <file>fonts.scale</file> in a font directory:
8411 <file>fonts.dir</file> files must not be provided at all.
8415 <file>fonts.alias</file> and <file>fonts.scale</file>
8416 files, if needed, should be provided in the
8418 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8419 where <var>fontdir</var> is the name of the
8421 <file>/usr/share/fonts/X11/</file> where the
8422 package's corresponding fonts are stored
8423 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8424 <var>package</var> is the name of the package
8425 that provides these fonts, and
8426 <var>extension</var> is either <tt>scale</tt>
8427 or <tt>alias</tt>, whichever corresponds to
8434 Font packages must declare a dependency on
8435 <tt>xfonts-utils</tt> in their control
8440 Font packages that provide one or more
8441 <file>fonts.scale</file> files as described above must
8442 invoke <prgn>update-fonts-scale</prgn> on each
8443 directory into which they installed fonts
8444 <em>before</em> invoking
8445 <prgn>update-fonts-dir</prgn> on that directory.
8446 This invocation must occur in both the
8447 <prgn>postinst</prgn> (for all arguments) and
8448 <prgn>postrm</prgn> (for all arguments except
8449 <tt>upgrade</tt>) scripts.
8453 Font packages that provide one or more
8454 <file>fonts.alias</file> files as described above must
8455 invoke <prgn>update-fonts-alias</prgn> on each
8456 directory into which they installed fonts. This
8457 invocation must occur in both the
8458 <prgn>postinst</prgn> (for all arguments) and
8459 <prgn>postrm</prgn> (for all arguments except
8460 <tt>upgrade</tt>) scripts.
8464 Font packages must invoke
8465 <prgn>update-fonts-dir</prgn> on each directory into
8466 which they installed fonts. This invocation must
8467 occur in both the <prgn>postinst</prgn> (for all
8468 arguments) and <prgn>postrm</prgn> (for all
8469 arguments except <tt>upgrade</tt>) scripts.
8473 Font packages must not provide alias names for the
8474 fonts they include which collide with alias names
8475 already in use by fonts already packaged.
8479 Font packages must not provide fonts with the same
8480 XLFD registry name as another font already packaged.
8487 <heading>Application defaults files</heading>
8490 Application defaults files must be installed in the
8491 directory <file>/etc/X11/app-defaults/</file> (use of a
8492 localized subdirectory of <file>/etc/X11/</file> as described
8493 in the <em>X Toolkit Intrinsics - C Language
8494 Interface</em> manual is also permitted). They must be
8495 registered as <tt>conffile</tt>s or handled as
8496 configuration files.
8500 Customization of programs' X resources may also be
8501 supported with the provision of a file with the same name
8502 as that of the package placed in the
8503 <file>/etc/X11/Xresources/</file> directory, which must
8504 registered as a <tt>conffile</tt> or handled as a
8505 configuration file.<footnote>
8506 Note that this mechanism is not the same as using
8507 app-defaults; app-defaults are tied to the client
8508 binary on the local file system, whereas X resources
8509 are stored in the X server and affect all connecting
8516 <heading>Installation directory issues</heading>
8519 Packages using the X Window System should not be
8520 configured to install files under the
8521 <file>/usr/X11R6/</file> directory. The
8522 <file>/usr/X11R6/</file> directory hierarchy should be
8523 regarded as obsolete.
8527 Programs that use GNU <prgn>autoconf</prgn> and
8528 <prgn>automake</prgn> are usually easily configured at
8529 compile time to use <file>/usr/</file> instead of
8530 <file>/usr/X11R6/</file>, and this should be done whenever
8531 possible. Configuration files for window managers and
8532 display managers should be placed in a subdirectory of
8533 <file>/etc/X11/</file> corresponding to the package name due
8534 to these programs' tight integration with the mechanisms
8535 of the X Window System. Application-level programs should
8536 use the <file>/etc/</file> directory unless otherwise mandated
8541 The installation of files into subdirectories
8542 of <file>/usr/X11R6/include/X11/</file> and
8543 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8544 package maintainers should determine if subdirectories of
8545 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8550 Packages should install any relevant files into the
8551 directories <file>/usr/include/X11/</file> and
8552 <file>/usr/lib/X11/</file>, but if they do so, they must
8553 pre-depend on <tt>x11-common (>=
8554 1:7.0.0)</tt><footnote>
8556 These libraries used to be all symbolic
8557 links. However, with <tt>X11R7</tt>,
8558 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8559 are now real directories, and packages
8560 <strong>should</strong> ship their files here instead
8561 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8562 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8563 responsible for converting these symlinks into
8571 <heading>The OSF/Motif and OpenMotif libraries</heading>
8574 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8575 OpenMotif libraries</em><footnote>
8576 OSF/Motif and OpenMotif are collectively referred to as
8577 "Motif" in this policy document.
8579 should be compiled against and tested with LessTif (a free
8580 re-implementation of Motif) instead. If the maintainer
8581 judges that the program or programs do not work
8582 sufficiently well with LessTif to be distributed and
8583 supported, but do so when compiled against Motif, then two
8584 versions of the package should be created; one linked
8585 statically against Motif and with <tt>-smotif</tt>
8586 appended to the package name, and one linked dynamically
8587 against Motif and with <tt>-dmotif</tt> appended to the
8592 Both Motif-linked versions are dependent
8593 upon non-DFSG-compliant software and thus cannot be
8594 uploaded to the <em>main</em> distribution; if the
8595 software is itself DFSG-compliant it may be uploaded to
8596 the <em>contrib</em> distribution. While known existing
8597 versions of Motif permit unlimited redistribution of
8598 binaries linked against the library (whether statically or
8599 dynamically), it is the package maintainer's
8600 responsibility to determine whether this is permitted by
8601 the license of the copy of Motif in their possession.
8607 <heading>Perl programs and modules</heading>
8610 Perl programs and modules should follow the current Perl policy.
8614 The Perl policy can be found in the <tt>perl-policy</tt>
8615 files in the <tt>debian-policy</tt> package.
8616 It is also available from the Debian web mirrors at
8617 <tt><url name="/doc/packaging-manuals/perl-policy/"
8618 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8623 <heading>Emacs lisp programs</heading>
8626 Please refer to the "Debian Emacs Policy" for details of how to
8627 package emacs lisp programs.
8631 The Emacs policy is available in
8632 <file>debian-emacs-policy.gz</file> of the
8633 <package>emacsen-common</package> package.
8634 It is also available from the Debian web mirrors at
8635 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8636 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8641 <heading>Games</heading>
8644 The permissions on <file>/var/games</file> are mode 755, owner
8645 <tt>root</tt> and group <tt>root</tt>.
8649 Each game decides on its own security policy.</p>
8652 Games which require protected, privileged access to
8653 high-score files, saved games, etc., may be made
8654 set-<em>group</em>-id (mode 2755) and owned by
8655 <tt>root:games</tt>, and use files and directories with
8656 appropriate permissions (770 <tt>root:games</tt>, for
8657 example). They must not be made
8658 set-<em>user</em>-id, as this causes security problems. (If
8659 an attacker can subvert any set-user-id game they can
8660 overwrite the executable of any other, causing other players
8661 of these games to run a Trojan horse program. With a
8662 set-group-id game the attacker only gets access to less
8663 important game data, and if they can get at the other
8664 players' accounts at all it will take considerably more
8668 Some packages, for example some fortune cookie programs, are
8669 configured by the upstream authors to install with their
8670 data files or other static information made unreadable so
8671 that they can only be accessed through set-id programs
8672 provided. You should not do this in a Debian package: anyone can
8673 download the <file>.deb</file> file and read the data from it,
8674 so there is no point making the files unreadable. Not
8675 making the files unreadable also means that you don't have
8676 to make so many programs set-id, which reduces the risk of a
8680 As described in the FHS, binaries of games should be
8681 installed in the directory <file>/usr/games</file>. This also
8682 applies to games that use the X Window System. Manual pages
8683 for games (X and non-X games) should be installed in
8684 <file>/usr/share/man/man6</file>.</p>
8690 <heading>Documentation</heading>
8693 <heading>Manual pages</heading>
8696 You should install manual pages in <prgn>nroff</prgn> source
8697 form, in appropriate places under <file>/usr/share/man</file>.
8698 You should only use sections 1 to 9 (see the FHS for more
8699 details). You must not install a pre-formatted "cat page".
8703 Each program, utility, and function should have an
8704 associated manual page included in the same package. It is
8705 suggested that all configuration files also have a manual
8706 page included as well. Manual pages for protocols and other
8707 auxiliary things are optional.
8711 If no manual page is available, this is considered as a bug
8712 and should be reported to the Debian Bug Tracking System (the
8713 maintainer of the package is allowed to write this bug report
8714 themselves, if they so desire). Do not close the bug report
8715 until a proper man page is available.<footnote>
8716 It is not very hard to write a man page. See the
8717 <url id="http://www.schweikhardt.net/man_page_howto.html"
8718 name="Man-Page-HOWTO">,
8719 <manref name="man" section="7">, the examples
8720 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8721 the helper programs <prgn>help2man</prgn>, or the
8722 directory <file>/usr/share/doc/man-db/examples</file>.
8727 You may forward a complaint about a missing man page to the
8728 upstream authors, and mark the bug as forwarded in the
8729 Debian bug tracking system. Even though the GNU Project do
8730 not in general consider the lack of a man page to be a bug,
8731 we do; if they tell you that they don't consider it a bug
8732 you should leave the bug in our bug tracking system open
8737 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8741 If one man page needs to be accessible via several names it
8742 is better to use a symbolic link than the <file>.so</file>
8743 feature, but there is no need to fiddle with the relevant
8744 parts of the upstream source to change from <file>.so</file> to
8745 symlinks: don't do it unless it's easy. You should not
8746 create hard links in the manual page directories, nor put
8747 absolute filenames in <file>.so</file> directives. The filename
8748 in a <file>.so</file> in a man page should be relative to the
8749 base of the man page tree (usually
8750 <file>/usr/share/man</file>). If you do not create any links
8751 (whether symlinks, hard links, or <tt>.so</tt> directives)
8752 in the file system to the alternate names of the man page,
8753 then you should not rely on <prgn>man</prgn> finding your
8754 man page under those names based solely on the information in
8755 the man page's header.<footnote>
8756 Supporting this in <prgn>man</prgn> often requires
8757 unreasonable processing time to find a manual page or to
8758 report that none exists, and moves knowledge into man's
8759 database that would be better left in the file system.
8760 This support is therefore deprecated and will cease to
8761 be present in the future.
8766 Manual pages in locale-specific subdirectories of
8767 <file>/usr/share/man</file> should use either UTF-8 or the usual
8768 legacy encoding for that language (normally the one corresponding
8769 to the shortest relevant locale name in
8770 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8771 <file>/usr/share/man/fr</file> should use either UTF-8 or
8772 ISO-8859-1.<footnote>
8773 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8774 use. In future, all manual pages will be required to use
8780 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8781 included in the subdirectory name unless it indicates a
8782 significant difference in the language, as this excludes
8783 speakers of the language in other countries.<footnote>
8784 At the time of writing, Chinese and Portuguese are the main
8785 languages with such differences, so <file>pt_BR</file>,
8786 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8791 Due to limitations in current implementations, all characters
8792 in the manual page source should be representable in the usual
8793 legacy encoding for that language, even if the file is
8794 actually encoded in UTF-8. Safe alternative ways to write many
8795 characters outside that range may be found in
8796 <manref name="groff_char" section="7">.
8801 <heading>Info documents</heading>
8804 Info documents should be installed in <file>/usr/share/info</file>.
8805 They should be compressed with <tt>gzip -9</tt>.
8809 Your package should call <prgn>install-info</prgn> to update
8810 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8811 script when called with a <tt>configure</tt> argument, for
8813 <example compact="compact">
8814 install-info --quiet --section Development Development \
8815 /usr/share/info/foobar.info
8819 It is a good idea to specify a section for the location of
8820 your program; this is done with the <tt>--section</tt>
8821 switch. To determine which section to use, you should look
8822 at <file>/usr/share/info/dir</file> on your system and choose the most
8823 relevant (or create a new section if none of the current
8824 sections are relevant). Note that the <tt>--section</tt>
8825 flag takes two arguments; the first is a regular expression
8826 to match (case-insensitively) against an existing section,
8827 the second is used when creating a new one.</p>
8830 You should remove the entries in the <prgn>prerm</prgn>
8831 script when called with a <tt>remove</tt> argument:
8832 <example compact="compact">
8833 install-info --quiet --remove /usr/share/info/foobar.info
8837 If <prgn>install-info</prgn> cannot find a description entry
8838 in the Info file you must supply one. See <manref
8839 name="install-info" section="8"> for details.</p>
8843 <heading>Additional documentation</heading>
8846 Any additional documentation that comes with the package may
8847 be installed at the discretion of the package maintainer.
8848 Plain text documentation should be installed in the directory
8849 <file>/usr/share/doc/<var>package</var></file>, where
8850 <var>package</var> is the name of the package, and
8851 compressed with <tt>gzip -9</tt> unless it is small.
8855 If a package comes with large amounts of documentation which
8856 many users of the package will not require you should create
8857 a separate binary package to contain it, so that it does not
8858 take up disk space on the machines of users who do not need
8859 or want it installed.</p>
8862 It is often a good idea to put text information files
8863 (<file>README</file>s, changelogs, and so forth) that come with
8864 the source package in <file>/usr/share/doc/<var>package</var></file>
8865 in the binary package. However, you don't need to install
8866 the instructions for building and installing the package, of
8870 Packages must not require the existence of any files in
8871 <file>/usr/share/doc/</file> in order to function
8873 The system administrator should be able to
8874 delete files in <file>/usr/share/doc/</file> without causing
8875 any programs to break.
8877 Any files that are referenced by programs but are also
8878 useful as stand alone documentation should be installed under
8879 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8880 <file>/usr/share/doc/<var>package</var></file>.
8884 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8885 link to another directory in <file>/usr/share/doc</file> only if
8886 the two packages both come from the same source and the
8887 first package Depends on the second.<footnote>
8889 Please note that this does not override the section on
8890 changelog files below, so the file
8891 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8892 must refer to the changelog for the current version of
8893 <var>package</var> in question. In practice, this means
8894 that the sources of the target and the destination of the
8895 symlink must be the same (same source package and
8902 Former Debian releases placed all additional documentation
8903 in <file>/usr/doc/<var>package</var></file>. This has been
8904 changed to <file>/usr/share/doc/<var>package</var></file>,
8905 and packages must not put documentation in the directory
8906 <file>/usr/doc/<var>package</var></file>. <footnote>
8907 At this phase of the transition, we no longer require a
8908 symbolic link in <file>/usr/doc/</file>. At a later point,
8909 policy shall change to make the symbolic links a bug.
8915 <heading>Preferred documentation formats</heading>
8918 The unification of Debian documentation is being carried out
8922 If your package comes with extensive documentation in a
8923 markup format that can be converted to various other formats
8924 you should if possible ship HTML versions in a binary
8925 package, in the directory
8926 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8927 its subdirectories.<footnote>
8928 The rationale: The important thing here is that HTML
8929 docs should be available in <em>some</em> package, not
8930 necessarily in the main binary package.
8935 Other formats such as PostScript may be provided at the
8936 package maintainer's discretion.
8940 <sect id="copyrightfile">
8941 <heading>Copyright information</heading>
8944 Every package must be accompanied by a verbatim copy of its
8945 copyright and distribution license in the file
8946 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8947 file must neither be compressed nor be a symbolic link.
8951 In addition, the copyright file must say where the upstream
8952 sources (if any) were obtained. It should name the original
8953 authors of the package and the Debian maintainer(s) who were
8954 involved with its creation.
8958 Packages in the <em>contrib</em> or <em>non-free</em>
8959 distribution areas should state in the copyright file that the
8960 package is not part of the Debian GNU/Linux distribution and
8961 briefly explain why.
8965 A copy of the file which will be installed in
8966 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8967 be in <file>debian/copyright</file> in the source package.
8971 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8972 link to another directory in <file>/usr/share/doc</file> only if
8973 the two packages both come from the same source and the
8974 first package Depends on the second. These rules are
8975 important because copyrights must be extractable by
8980 Packages distributed under the UCB BSD license, the Apache
8981 license (version 2.0), the Artistic license, the GNU GPL
8982 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8983 the GNU FDL (version 1.2) should refer to the corresponding
8984 files under <file>/usr/share/common-licenses</file>,<footnote>
8987 <file>/usr/share/common-licenses/BSD</file>,
8988 <file>/usr/share/common-licenses/Apache-2.0</file>,
8989 <file>/usr/share/common-licenses/Artistic</file>,
8990 <file>/usr/share/common-licenses/GPL-2</file>,
8991 <file>/usr/share/common-licenses/GPL-3</file>,
8992 <file>/usr/share/common-licenses/LGPL-2</file>,
8993 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8994 <file>/usr/share/common-licenses/LGPL-3</file>, and
8995 <file>/usr/share/common-licenses/GFDL-1.2</file>
8998 </footnote> rather than quoting them in the copyright
9003 You should not use the copyright file as a general <file>README</file>
9004 file. If your package has such a file it should be
9005 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9006 <file>README.Debian</file> or some other appropriate place.</p>
9010 <heading>Examples</heading>
9013 Any examples (configurations, source files, whatever),
9014 should be installed in a directory
9015 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9016 files should not be referenced by any program: they're there
9017 for the benefit of the system administrator and users as
9018 documentation only. Architecture-specific example files
9019 should be installed in a directory
9020 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9022 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9023 latter directory itself may be a symbolic link to the
9028 If the purpose of a package is to provide examples, then the
9029 example files may be installed into
9030 <file>/usr/share/doc/<var>package</var></file>.
9034 <sect id="changelogs">
9035 <heading>Changelog files</heading>
9038 Packages that are not Debian-native must contain a
9039 compressed copy of the <file>debian/changelog</file> file from
9040 the Debian source tree in
9041 <file>/usr/share/doc/<var>package</var></file> with the name
9042 <file>changelog.Debian.gz</file>.
9046 If an upstream changelog is available, it should be accessible as
9047 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9048 plain text. If the upstream changelog is distributed in
9049 HTML, it should be made available in that form as
9050 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9051 and a plain text <file>changelog.gz</file> should be generated
9052 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9053 the upstream changelog files do not already conform to this
9054 naming convention, then this may be achieved either by
9055 renaming the files, or by adding a symbolic link, at the
9056 maintainer's discretion.<footnote>
9057 Rationale: People should not have to look in places for
9058 upstream changelogs merely because they are given
9059 different names or are distributed in HTML format.
9064 All of these files should be installed compressed using
9065 <tt>gzip -9</tt>, as they will become large with time even
9066 if they start out small.
9070 If the package has only one changelog which is used both as
9071 the Debian changelog and the upstream one because there is
9072 no separate upstream maintainer then that changelog should
9073 usually be installed as
9074 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9075 there is a separate upstream maintainer, but no upstream
9076 changelog, then the Debian changelog should still be called
9077 <file>changelog.Debian.gz</file>.
9081 For details about the format and contents of the Debian
9082 changelog file, please see <ref id="dpkgchangelog">.
9087 <appendix id="pkg-scope">
9088 <heading>Introduction and scope of these appendices</heading>
9091 These appendices are taken essentially verbatim from the
9092 now-deprecated Packaging Manual, version 3.2.1.0. They are
9093 the chapters which are likely to be of use to package
9094 maintainers and which have not already been included in the
9095 policy document itself. Most of these sections are very likely
9096 not relevant to policy; they should be treated as
9097 documentation for the packaging system. Please note that these
9098 appendices are included for convenience, and for historical
9099 reasons: they used to be part of policy package, and they have
9100 not yet been incorporated into dpkg documentation. However,
9101 they still have value, and hence they are presented here.
9105 They have not yet been checked to ensure that they are
9106 compatible with the contents of policy, and if there are any
9107 contradictions, the version in the main policy document takes
9108 precedence. The remaining chapters of the old Packaging
9109 Manual have also not been read in detail to ensure that there
9110 are not parts which have been left out. Both of these will be
9115 Certain parts of the Packaging manual were integrated into the
9116 Policy Manual proper, and removed from the appendices. Links
9117 have been placed from the old locations to the new ones.
9121 <prgn>dpkg</prgn> is a suite of programs for creating binary
9122 package files and installing and removing them on Unix
9124 <prgn>dpkg</prgn> is targeted primarily at Debian
9125 GNU/Linux, but may work on or be ported to other
9131 The binary packages are designed for the management of
9132 installed executable programs (usually compiled binaries) and
9133 their associated data, though source code examples and
9134 documentation are provided as part of some packages.</p>
9137 This manual describes the technical aspects of creating Debian
9138 binary packages (<file>.deb</file> files). It documents the
9139 behavior of the package management programs
9140 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9141 they interact with packages.</p>
9144 It also documents the interaction between
9145 <prgn>dselect</prgn>'s core and the access method scripts it
9146 uses to actually install the selected packages, and describes
9147 how to create a new access method.</p>
9150 This manual does not go into detail about the options and
9151 usage of the package building and installation tools. It
9152 should therefore be read in conjunction with those programs'
9157 The utility programs which are provided with <prgn>dpkg</prgn>
9158 for managing various system configuration and similar issues,
9159 such as <prgn>update-rc.d</prgn> and
9160 <prgn>install-info</prgn>, are not described in detail here -
9161 please see their man pages.
9165 It is assumed that the reader is reasonably familiar with the
9166 <prgn>dpkg</prgn> System Administrators' manual.
9167 Unfortunately this manual does not yet exist.
9171 The Debian version of the FSF's GNU hello program is provided
9172 as an example for people wishing to create Debian
9173 packages. The Debian <prgn>debmake</prgn> package is
9174 recommended as a very helpful tool in creating and maintaining
9175 Debian packages. However, while the tools and examples are
9176 helpful, they do not replace the need to read and follow the
9177 Policy and Programmer's Manual.</p>
9180 <appendix id="pkg-binarypkg">
9181 <heading>Binary packages (from old Packaging Manual)</heading>
9184 The binary package has two main sections. The first part
9185 consists of various control information files and scripts used
9186 by <prgn>dpkg</prgn> when installing and removing. See <ref
9187 id="pkg-controlarea">.
9191 The second part is an archive containing the files and
9192 directories to be installed.
9196 In the future binary packages may also contain other
9197 components, such as checksums and digital signatures. The
9198 format for the archive is described in full in the
9199 <file>deb(5)</file> man page.
9203 <sect id="pkg-bincreating"><heading>Creating package files -
9204 <prgn>dpkg-deb</prgn>
9208 All manipulation of binary package files is done by
9209 <prgn>dpkg-deb</prgn>; it's the only program that has
9210 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9211 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9212 will spot that the options requested are appropriate to
9213 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9218 In order to create a binary package you must make a
9219 directory tree which contains all the files and directories
9220 you want to have in the file system data part of the package.
9221 In Debian-format source packages this directory is usually
9222 <file>debian/tmp</file>, relative to the top of the package's
9227 They should have the locations (relative to the root of the
9228 directory tree you're constructing) ownerships and
9229 permissions which you want them to have on the system when
9234 With current versions of <prgn>dpkg</prgn> the uid/username
9235 and gid/groupname mappings for the users and groups being
9236 used should be the same on the system where the package is
9237 built and the one where it is installed.
9241 You need to add one special directory to the root of the
9242 miniature file system tree you're creating:
9243 <prgn>DEBIAN</prgn>. It should contain the control
9244 information files, notably the binary package control file
9245 (see <ref id="pkg-controlfile">).
9249 The <prgn>DEBIAN</prgn> directory will not appear in the
9250 file system archive of the package, and so won't be installed
9251 by <prgn>dpkg</prgn> when the package is installed.
9255 When you've prepared the package, you should invoke:
9257 dpkg --build <var>directory</var>
9262 This will build the package in
9263 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9264 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9265 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9270 See the man page <manref name="dpkg-deb" section="8"> for details of how
9271 to examine the contents of this newly-created file. You may find the
9272 output of following commands enlightening:
9274 dpkg-deb --info <var>filename</var>.deb
9275 dpkg-deb --contents <var>filename</var>.deb
9276 dpkg --contents <var>filename</var>.deb
9278 To view the copyright file for a package you could use this command:
9280 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9285 <sect id="pkg-controlarea">
9286 <heading>Package control information files</heading>
9289 The control information portion of a binary package is a
9290 collection of files with names known to <prgn>dpkg</prgn>.
9291 It will treat the contents of these files specially - some
9292 of them contain information used by <prgn>dpkg</prgn> when
9293 installing or removing the package; others are scripts which
9294 the package maintainer wants <prgn>dpkg</prgn> to run.
9298 It is possible to put other files in the package control
9299 area, but this is not generally a good idea (though they
9300 will largely be ignored).
9304 Here is a brief list of the control info files supported by
9305 <prgn>dpkg</prgn> and a summary of what they're used for.
9310 <tag><tt>control</tt>
9313 This is the key description file used by
9314 <prgn>dpkg</prgn>. It specifies the package's name
9315 and version, gives its description for the user,
9316 states its relationships with other packages, and so
9317 forth. See <ref id="sourcecontrolfiles"> and
9318 <ref id="binarycontrolfiles">.
9322 It is usually generated automatically from information
9323 in the source package by the
9324 <prgn>dpkg-gencontrol</prgn> program, and with
9325 assistance from <prgn>dpkg-shlibdeps</prgn>.
9326 See <ref id="pkg-sourcetools">.
9330 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9335 These are executable files (usually scripts) which
9336 <prgn>dpkg</prgn> runs during installation, upgrade
9337 and removal of packages. They allow the package to
9338 deal with matters which are particular to that package
9339 or require more complicated processing than that
9340 provided by <prgn>dpkg</prgn>. Details of when and
9341 how they are called are in <ref id="maintainerscripts">.
9345 It is very important to make these scripts idempotent.
9346 See <ref id="idempotency">.
9350 The maintainer scripts are guaranteed to run with a
9351 controlling terminal and can interact with the user.
9352 See <ref id="controllingterminal">.
9356 <tag><tt>conffiles</tt>
9359 This file contains a list of configuration files which
9360 are to be handled automatically by <prgn>dpkg</prgn>
9361 (see <ref id="pkg-conffiles">). Note that not necessarily
9362 every configuration file should be listed here.
9365 <tag><tt>shlibs</tt>
9368 This file contains a list of the shared libraries
9369 supplied by the package, with dependency details for
9370 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9371 when it determines what dependencies are required in a
9372 package control file. The <tt>shlibs</tt> file format
9373 is described on <ref id="shlibs">.
9378 <sect id="pkg-controlfile">
9379 <heading>The main control information file: <tt>control</tt></heading>
9382 The most important control information file used by
9383 <prgn>dpkg</prgn> when it installs a package is
9384 <tt>control</tt>. It contains all the package's "vital
9389 The binary package control files of packages built from
9390 Debian sources are made by a special tool,
9391 <prgn>dpkg-gencontrol</prgn>, which reads
9392 <file>debian/control</file> and <file>debian/changelog</file> to
9393 find the information it needs. See <ref id="pkg-sourcepkg"> for
9398 The fields in binary package control files are listed in
9399 <ref id="binarycontrolfiles">.
9403 A description of the syntax of control files and the purpose
9404 of the fields is available in <ref id="controlfields">.
9409 <heading>Time Stamps</heading>
9412 See <ref id="timestamps">.
9417 <appendix id="pkg-sourcepkg">
9418 <heading>Source packages (from old Packaging Manual) </heading>
9421 The Debian binary packages in the distribution are generated
9422 from Debian sources, which are in a special format to assist
9423 the easy and automatic building of binaries.
9426 <sect id="pkg-sourcetools">
9427 <heading>Tools for processing source packages</heading>
9430 Various tools are provided for manipulating source packages;
9431 they pack and unpack sources and help build of binary
9432 packages and help manage the distribution of new versions.
9436 They are introduced and typical uses described here; see
9437 <manref name="dpkg-source" section="1"> for full
9438 documentation about their arguments and operation.
9442 For examples of how to construct a Debian source package,
9443 and how to use those utilities that are used by Debian
9444 source packages, please see the <prgn>hello</prgn> example
9448 <sect1 id="pkg-dpkg-source">
9450 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9455 This program is frequently used by hand, and is also
9456 called from package-independent automated building scripts
9457 such as <prgn>dpkg-buildpackage</prgn>.
9461 To unpack a package it is typically invoked with
9463 dpkg-source -x <var>.../path/to/filename</var>.dsc
9468 with the <file><var>filename</var>.tar.gz</file> and
9469 <file><var>filename</var>.diff.gz</file> (if applicable) in
9470 the same directory. It unpacks into
9471 <file><var>package</var>-<var>version</var></file>, and if
9473 <file><var>package</var>-<var>version</var>.orig</file>, in
9474 the current directory.
9478 To create a packed source archive it is typically invoked:
9480 dpkg-source -b <var>package</var>-<var>version</var>
9485 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9486 <file>.diff.gz</file> (if appropriate) in the current
9487 directory. <prgn>dpkg-source</prgn> does not clean the
9488 source tree first - this must be done separately if it is
9493 See also <ref id="pkg-sourcearchives">.</p>
9497 <sect1 id="pkg-dpkg-buildpackage">
9499 <prgn>dpkg-buildpackage</prgn> - overall package-building
9504 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9505 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9506 targets <tt>clean</tt>, <tt>build</tt> and
9507 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9508 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9509 source and binary package upload.
9513 It is usually invoked by hand from the top level of the
9514 built or unbuilt source directory. It may be invoked with
9515 no arguments; useful arguments include:
9516 <taglist compact="compact">
9517 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9520 Do not sign the <tt>.changes</tt> file or the
9521 source package <tt>.dsc</tt> file, respectively.</p>
9523 <tag><tt>-p<var>sign-command</var></tt></tag>
9526 Invoke <var>sign-command</var> instead of finding
9527 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9528 <var>sign-command</var> must behave just like
9529 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9531 <tag><tt>-r<var>root-command</var></tt></tag>
9534 When root privilege is required, invoke the command
9535 <var>root-command</var>. <var>root-command</var>
9536 should invoke its first argument as a command, from
9537 the <prgn>PATH</prgn> if necessary, and pass its
9538 second and subsequent arguments to the command it
9539 calls. If no <var>root-command</var> is supplied
9540 then <var>dpkg-buildpackage</var> will take no
9541 special action to gain root privilege, so that for
9542 most packages it will have to be invoked as root to
9545 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9548 Two types of binary-only build and upload - see
9549 <manref name="dpkg-source" section="1">.
9556 <sect1 id="pkg-dpkg-gencontrol">
9558 <prgn>dpkg-gencontrol</prgn> - generates binary package
9563 This program is usually called from <file>debian/rules</file>
9564 (see <ref id="pkg-sourcetree">) in the top level of the source
9569 This is usually done just before the files and directories in the
9570 temporary directory tree where the package is being built have their
9571 permissions and ownerships set and the package is constructed using
9572 <prgn>dpkg-deb/</prgn>
9574 This is so that the control file which is produced has
9575 the right permissions
9580 <prgn>dpkg-gencontrol</prgn> must be called after all the
9581 files which are to go into the package have been placed in
9582 the temporary build directory, so that its calculation of
9583 the installed size of a package is correct.
9587 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9588 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9589 variable substitutions created by
9590 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9595 For a package which generates only one binary package, and
9596 which builds it in <file>debian/tmp</file> relative to the top
9597 of the source package, it is usually sufficient to call
9598 <prgn>dpkg-gencontrol</prgn>.
9602 Sources which build several binaries will typically need
9605 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9606 </example> The <tt>-P</tt> tells
9607 <prgn>dpkg-gencontrol</prgn> that the package is being
9608 built in a non-default directory, and the <tt>-p</tt>
9609 tells it which package's control file should be generated.
9613 <prgn>dpkg-gencontrol</prgn> also adds information to the
9614 list of files in <file>debian/files</file>, for the benefit of
9615 (for example) a future invocation of
9616 <prgn>dpkg-genchanges</prgn>.</p>
9619 <sect1 id="pkg-dpkg-shlibdeps">
9621 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9626 This program is usually called from <file>debian/rules</file>
9627 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9628 id="pkg-sourcetree">), in the top level of the source tree.
9632 Its arguments are executables and shared libraries
9635 They may be specified either in the locations in the
9636 source tree where they are created or in the locations
9637 in the temporary build tree where they are installed
9638 prior to binary package creation.
9640 </footnote> for which shared library dependencies should
9641 be included in the binary package's control file.
9645 If some of the found shared libraries should only
9646 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9647 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9648 by using the <tt>-d<var>dependency-field</var></tt> option
9649 before those executable(s). (Each <tt>-d</tt> option
9650 takes effect until the next <tt>-d</tt>.)
9654 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9655 output control file to be modified. Instead by default it
9656 adds to the <file>debian/substvars</file> file variable
9657 settings like <tt>shlibs:Depends</tt>. These variable
9658 settings must be referenced in dependency fields in the
9659 appropriate per-binary-package sections of the source
9664 For example, a package that generates an essential part
9665 which requires dependencies, and optional parts that
9666 which only require a recommendation, would separate those
9667 two sets of dependencies into two different fields.<footnote>
9668 At the time of writing, an example for this was the
9669 <package/xmms/ package, with Depends used for the xmms
9670 executable, Recommends for the plug-ins and Suggests for
9671 even more optional features provided by unzip.
9673 It can say in its <file>debian/rules</file>:
9675 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9676 -dRecommends <var>optionalpart anotheroptionalpart</var>
9678 and then in its main control file <file>debian/control</file>:
9681 Depends: ${shlibs:Depends}
9682 Recommends: ${shlibs:Recommends}
9688 Sources which produce several binary packages with
9689 different shared library dependency requirements can use
9690 the <tt>-p<var>varnameprefix</var></tt> option to override
9691 the default <tt>shlibs:</tt> prefix (one invocation of
9692 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9693 They can thus produce several sets of dependency
9694 variables, each of the form
9695 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9696 which can be referred to in the appropriate parts of the
9697 binary package control files.
9702 <sect1 id="pkg-dpkg-distaddfile">
9704 <prgn>dpkg-distaddfile</prgn> - adds a file to
9705 <file>debian/files</file>
9709 Some packages' uploads need to include files other than
9710 the source and binary package files.
9714 <prgn>dpkg-distaddfile</prgn> adds a file to the
9715 <file>debian/files</file> file so that it will be included in
9716 the <file>.changes</file> file when
9717 <prgn>dpkg-genchanges</prgn> is run.
9721 It is usually invoked from the <tt>binary</tt> target of
9722 <file>debian/rules</file>:
9724 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9726 The <var>filename</var> is relative to the directory where
9727 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9728 is usually the directory above the top level of the source
9729 tree. The <file>debian/rules</file> target should put the
9730 file there just before or just after calling
9731 <prgn>dpkg-distaddfile</prgn>.
9735 The <var>section</var> and <var>priority</var> are passed
9736 unchanged into the resulting <file>.changes</file> file.
9741 <sect1 id="pkg-dpkg-genchanges">
9743 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9748 This program is usually called by package-independent
9749 automatic building scripts such as
9750 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9755 It is usually called in the top level of a built source
9756 tree, and when invoked with no arguments will print out a
9757 straightforward <file>.changes</file> file based on the
9758 information in the source package's changelog and control
9759 file and the binary and source packages which should have
9765 <sect1 id="pkg-dpkg-parsechangelog">
9767 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9768 representation of a changelog
9772 This program is used internally by
9773 <prgn>dpkg-source</prgn> et al. It may also occasionally
9774 be useful in <file>debian/rules</file> and elsewhere. It
9775 parses a changelog, <file>debian/changelog</file> by default,
9776 and prints a control-file format representation of the
9777 information in it to standard output.
9781 <sect1 id="pkg-dpkg-architecture">
9783 <prgn>dpkg-architecture</prgn> - information about the build and
9788 This program can be used manually, but is also invoked by
9789 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9790 environment or make variables which specify the build and host
9791 architecture for the package building process.
9796 <sect id="pkg-sourcetree">
9797 <heading>The Debianised source tree</heading>
9800 The source archive scheme described later is intended to
9801 allow a Debianised source tree with some associated control
9802 information to be reproduced and transported easily. The
9803 Debianised source tree is a version of the original program
9804 with certain files added for the benefit of the
9805 Debianisation process, and with any other changes required
9806 made to the rest of the source code and installation
9811 The extra files created for Debian are in the subdirectory
9812 <file>debian</file> of the top level of the Debianised source
9813 tree. They are described below.
9816 <sect1 id="pkg-debianrules">
9817 <heading><file>debian/rules</file> - the main building script</heading>
9820 See <ref id="debianrules">.
9825 <sect1 id="pkg-dpkgchangelog">
9826 <heading><file>debian/changelog</file></heading>
9829 See <ref id="dpkgchangelog">.
9833 It is recommended that the entire changelog be encoded in the
9834 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9836 <url id="http://www.unicode.org/"
9837 name="Unicode">.<footnote>
9839 I think it is fairly obvious that we need to
9840 eventually transition to UTF-8 for our package
9841 infrastructure; it is really the only sane char-set in
9842 an international environment. Now, we can't switch to
9843 using UTF-8 for package control fields and the like
9844 until dpkg has better support, but one thing we can
9845 start doing today is requesting that Debian changelogs
9846 are UTF-8 encoded. At some point in time, we can start
9847 requiring them to do so.
9850 Checking for non-UTF8 characters in a changelog is
9851 trivial. Dump the file through
9852 <example>iconv -f utf-8 -t ucs-4</example>
9853 discard the output, and check the return
9854 value. If there are any characters in the stream
9855 which are invalid UTF-8 sequences, iconv will exit
9856 with an error code; and this will be the case for the
9857 vast majority of other character sets.
9862 <sect2><heading>Defining alternative changelog formats
9866 It is possible to use a different format to the standard
9867 one, by providing a parser for the format you wish to
9872 In order to have <tt>dpkg-parsechangelog</tt> run your
9873 parser, you must include a line within the last 40 lines
9874 of your file matching the Perl regular expression:
9875 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9876 parentheses should be the name of the format. For
9877 example, you might say:
9879 @@@ changelog-format: joebloggs @@@
9881 Changelog format names are non-empty strings of alphanumerics.
9885 If such a line exists then <tt>dpkg-parsechangelog</tt>
9886 will look for the parser as
9887 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9889 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9890 it is an error for it not to find it, or for it not to
9891 be an executable program. The default changelog format
9892 is <tt>dpkg</tt>, and a parser for it is provided with
9893 the <tt>dpkg</tt> package.
9897 The parser will be invoked with the changelog open on
9898 standard input at the start of the file. It should read
9899 the file (it may seek if it wishes) to determine the
9900 information required and return the parsed information
9901 to standard output in the form of a series of control
9902 fields in the standard format. By default it should
9903 return information about only the most recent version in
9904 the changelog; it should accept a
9905 <tt>-v<var>version</var></tt> option to return changes
9906 information from all versions present <em>strictly
9907 after</em> <var>version</var>, and it should then be an
9908 error for <var>version</var> not to be present in the
9914 <list compact="compact">
9915 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9916 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9917 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9918 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9919 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9920 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9921 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9926 If several versions are being returned (due to the use
9927 of <tt>-v</tt>), the urgency value should be of the
9928 highest urgency code listed at the start of any of the
9929 versions requested followed by the concatenated
9930 (space-separated) comments from all the versions
9931 requested; the maintainer, version, distribution and
9932 date should always be from the most recent version.
9936 For the format of the <tt>Changes</tt> field see
9937 <ref id="f-Changes">.
9941 If the changelog format which is being parsed always or
9942 almost always leaves a blank line between individual
9943 change notes these blank lines should be stripped out,
9944 so as to make the resulting output compact.
9948 If the changelog format does not contain date or package
9949 name information this information should be omitted from
9950 the output. The parser should not attempt to synthesize
9951 it or find it from other sources.
9955 If the changelog does not have the expected format the
9956 parser should exit with a nonzero exit status, rather
9957 than trying to muddle through and possibly generating
9962 A changelog parser may not interact with the user at
9968 <sect1 id="pkg-srcsubstvars">
9969 <heading><file>debian/substvars</file> and variable substitutions</heading>
9972 See <ref id="substvars">.
9978 <heading><file>debian/files</file></heading>
9981 See <ref id="debianfiles">.
9985 <sect1><heading><file>debian/tmp</file>
9989 This is the canonical temporary location for the
9990 construction of binary packages by the <tt>binary</tt>
9991 target. The directory <file>tmp</file> serves as the root of
9992 the file system tree as it is being constructed (for
9993 example, by using the package's upstream makefiles install
9994 targets and redirecting the output there), and it also
9995 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9996 id="pkg-bincreating">.
10000 If several binary packages are generated from the same
10001 source tree it is usual to use several
10002 <file>debian/tmp<var>something</var></file> directories, for
10003 example <file>tmp-a</file> or <file>tmp-doc</file>.
10007 Whatever <file>tmp</file> directories are created and used by
10008 <tt>binary</tt> must of course be removed by the
10009 <tt>clean</tt> target.</p></sect1>
10013 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10017 As it exists on the FTP site, a Debian source package
10018 consists of three related files. You must have the right
10019 versions of all three to be able to use them.
10024 <tag>Debian source control file - <tt>.dsc</tt></tag>
10026 This file is a control file used by <prgn>dpkg-source</prgn>
10027 to extract a source package.
10028 See <ref id="debiansourcecontrolfiles">.
10032 Original source archive -
10034 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10040 This is a compressed (with <tt>gzip -9</tt>)
10041 <prgn>tar</prgn> file containing the source code from
10042 the upstream authors of the program.
10047 Debianisation diff -
10049 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10055 This is a unified context diff (<tt>diff -u</tt>)
10056 giving the changes which are required to turn the
10057 original source into the Debian source. These changes
10058 may only include editing and creating plain files.
10059 The permissions of files, the targets of symbolic
10060 links and the characteristics of special files or
10061 pipes may not be changed and no files may be removed
10066 All the directories in the diff must exist, except the
10067 <file>debian</file> subdirectory of the top of the source
10068 tree, which will be created by
10069 <prgn>dpkg-source</prgn> if necessary when unpacking.
10073 The <prgn>dpkg-source</prgn> program will
10074 automatically make the <file>debian/rules</file> file
10075 executable (see below).</p></item>
10080 If there is no original source code - for example, if the
10081 package is specially prepared for Debian or the Debian
10082 maintainer is the same as the upstream maintainer - the
10083 format is slightly different: then there is no diff, and the
10085 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10086 and preferably contains a directory named
10087 <file><var>package</var>-<var>version</var></file>.
10092 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10095 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10096 Debian source package. However, if it is not available it
10097 is possible to unpack a Debian source archive as follows:
10098 <enumlist compact="compact">
10101 Untar the tarfile, which will create a <file>.orig</file>
10105 <p>Rename the <file>.orig</file> directory to
10106 <file><var>package</var>-<var>version</var></file>.</p>
10110 Create the subdirectory <file>debian</file> at the top of
10111 the source tree.</p>
10113 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10115 <item><p>Untar the tarfile again if you want a copy of the original
10116 source code alongside the Debianised version.</p>
10121 It is not possible to generate a valid Debian source archive
10122 without using <prgn>dpkg-source</prgn>. In particular,
10123 attempting to use <prgn>diff</prgn> directly to generate the
10124 <file>.diff.gz</file> file will not work.
10128 <heading>Restrictions on objects in source packages</heading>
10131 The source package may not contain any hard links
10133 This is not currently detected when building source
10134 packages, but only when extracting
10138 Hard links may be permitted at some point in the
10139 future, but would require a fair amount of
10141 </footnote>, device special files, sockets or setuid or
10144 Setgid directories are allowed.
10149 The source packaging tools manage the changes between the
10150 original and Debianised source using <prgn>diff</prgn> and
10151 <prgn>patch</prgn>. Turning the original source tree as
10152 included in the <file>.orig.tar.gz</file> into the debianised
10153 source must not involve any changes which cannot be
10154 handled by these tools. Problematic changes which cause
10155 <prgn>dpkg-source</prgn> to halt with an error when
10156 building the source package are:
10157 <list compact="compact">
10158 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10160 <item><p>Changing the targets of symbolic links.</p>
10162 <item><p>Creating directories, other than <file>debian</file>.</p>
10164 <item><p>Changes to the contents of binary files.</p></item>
10165 </list> Changes which cause <prgn>dpkg-source</prgn> to
10166 print a warning but continue anyway are:
10167 <list compact="compact">
10170 Removing files, directories or symlinks.
10172 Renaming a file is not treated specially - it is
10173 seen as the removal of the old file (which
10174 generates a warning, but is otherwise ignored),
10175 and the creation of the new one.
10181 Changed text files which are missing the usual final
10182 newline (either in the original or the modified
10187 Changes which are not represented, but which are not detected by
10188 <prgn>dpkg-source</prgn>, are:
10189 <list compact="compact">
10190 <item><p>Changing the permissions of files (other than
10191 <file>debian/rules</file>) and directories.</p></item>
10196 The <file>debian</file> directory and <file>debian/rules</file>
10197 are handled specially by <prgn>dpkg-source</prgn> - before
10198 applying the changes it will create the <file>debian</file>
10199 directory, and afterwards it will make
10200 <file>debian/rules</file> world-executable.
10206 <appendix id="pkg-controlfields">
10207 <heading>Control files and their fields (from old Packaging Manual)</heading>
10210 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10211 data in a common format, known as control files. Binary and
10212 source packages have control data as do the <file>.changes</file>
10213 files which control the installation of uploaded files, and
10214 <prgn>dpkg</prgn>'s internal databases are in a similar
10219 <heading>Syntax of control files</heading>
10222 See <ref id="controlsyntax">.
10226 It is important to note that there are several fields which
10227 are optional as far as <prgn>dpkg</prgn> and the related
10228 tools are concerned, but which must appear in every Debian
10229 package, or whose omission may cause problems.
10234 <heading>List of fields</heading>
10237 See <ref id="controlfieldslist">.
10241 This section now contains only the fields that didn't belong
10242 to the Policy manual.
10245 <sect1 id="pkg-f-Filename">
10246 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10249 These fields in <tt>Packages</tt> files give the
10250 filename(s) of (the parts of) a package in the
10251 distribution directories, relative to the root of the
10252 Debian hierarchy. If the package has been split into
10253 several parts the parts are all listed in order, separated
10258 <sect1 id="pkg-f-Size">
10259 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10262 These fields in <file>Packages</file> files give the size (in
10263 bytes, expressed in decimal) and MD5 checksum of the
10264 file(s) which make(s) up a binary package in the
10265 distribution. If the package is split into several parts
10266 the values for the parts are listed in order, separated by
10271 <sect1 id="pkg-f-Status">
10272 <heading><tt>Status</tt></heading>
10275 This field in <prgn>dpkg</prgn>'s status file records
10276 whether the user wants a package installed, removed or
10277 left alone, whether it is broken (requiring
10278 re-installation) or not and what its current state on the
10279 system is. Each of these pieces of information is a
10284 <sect1 id="pkg-f-Config-Version">
10285 <heading><tt>Config-Version</tt></heading>
10288 If a package is not installed or not configured, this
10289 field in <prgn>dpkg</prgn>'s status file records the last
10290 version of the package which was successfully
10295 <sect1 id="pkg-f-Conffiles">
10296 <heading><tt>Conffiles</tt></heading>
10299 This field in <prgn>dpkg</prgn>'s status file contains
10300 information about the automatically-managed configuration
10301 files held by a package. This field should <em>not</em>
10302 appear anywhere in a package!
10307 <heading>Obsolete fields</heading>
10310 These are still recognized by <prgn>dpkg</prgn> but should
10311 not appear anywhere any more.
10313 <taglist compact="compact">
10315 <tag><tt>Revision</tt></tag>
10316 <tag><tt>Package-Revision</tt></tag>
10317 <tag><tt>Package_Revision</tt></tag>
10319 The Debian revision part of the package version was
10320 at one point in a separate control file field. This
10321 field went through several names.
10324 <tag><tt>Recommended</tt></tag>
10325 <item>Old name for <tt>Recommends</tt>.</item>
10327 <tag><tt>Optional</tt></tag>
10328 <item>Old name for <tt>Suggests</tt>.</item>
10330 <tag><tt>Class</tt></tag>
10331 <item>Old name for <tt>Priority</tt>.</item>
10340 <appendix id="pkg-conffiles">
10341 <heading>Configuration file handling (from old Packaging Manual)</heading>
10344 <prgn>dpkg</prgn> can do a certain amount of automatic
10345 handling of package configuration files.
10349 Whether this mechanism is appropriate depends on a number of
10350 factors, but basically there are two approaches to any
10351 particular configuration file.
10355 The easy method is to ship a best-effort configuration in the
10356 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10357 handle updates. If the user is unlikely to want to edit the
10358 file, but you need them to be able to without losing their
10359 changes, and a new package with a changed version of the file
10360 is only released infrequently, this is a good approach.
10364 The hard method is to build the configuration file from
10365 scratch in the <prgn>postinst</prgn> script, and to take the
10366 responsibility for fixing any mistakes made in earlier
10367 versions of the package automatically. This will be
10368 appropriate if the file is likely to need to be different on
10372 <sect><heading>Automatic handling of configuration files by
10377 A package may contain a control area file called
10378 <tt>conffiles</tt>. This file should be a list of filenames
10379 of configuration files needing automatic handling, separated
10380 by newlines. The filenames should be absolute pathnames,
10381 and the files referred to should actually exist in the
10386 When a package is upgraded <prgn>dpkg</prgn> will process
10387 the configuration files during the configuration stage,
10388 shortly before it runs the package's <prgn>postinst</prgn>
10393 For each file it checks to see whether the version of the
10394 file included in the package is the same as the one that was
10395 included in the last version of the package (the one that is
10396 being upgraded from); it also compares the version currently
10397 installed on the system with the one shipped with the last
10402 If neither the user nor the package maintainer has changed
10403 the file, it is left alone. If one or the other has changed
10404 their version, then the changed version is preferred - i.e.,
10405 if the user edits their file, but the package maintainer
10406 doesn't ship a different version, the user's changes will
10407 stay, silently, but if the maintainer ships a new version
10408 and the user hasn't edited it the new version will be
10409 installed (with an informative message). If both have
10410 changed their version the user is prompted about the problem
10411 and must resolve the differences themselves.
10415 The comparisons are done by calculating the MD5 message
10416 digests of the files, and storing the MD5 of the file as it
10417 was included in the most recent version of the package.
10421 When a package is installed for the first time
10422 <prgn>dpkg</prgn> will install the file that comes with it,
10423 unless that would mean overwriting a file already on the
10428 However, note that <prgn>dpkg</prgn> will <em>not</em>
10429 replace a conffile that was removed by the user (or by a
10430 script). This is necessary because with some programs a
10431 missing file produces an effect hard or impossible to
10432 achieve in another way, so that a missing file needs to be
10433 kept that way if the user did it.
10437 Note that a package should <em>not</em> modify a
10438 <prgn>dpkg</prgn>-handled conffile in its maintainer
10439 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10440 the user confusing and possibly dangerous options for
10441 conffile update when the package is upgraded.</p>
10444 <sect><heading>Fully-featured maintainer script configuration
10449 For files which contain site-specific information such as
10450 the hostname and networking details and so forth, it is
10451 better to create the file in the package's
10452 <prgn>postinst</prgn> script.
10456 This will typically involve examining the state of the rest
10457 of the system to determine values and other information, and
10458 may involve prompting the user for some information which
10459 can't be obtained some other way.
10463 When using this method there are a couple of important
10464 issues which should be considered:
10468 If you discover a bug in the program which generates the
10469 configuration file, or if the format of the file changes
10470 from one version to the next, you will have to arrange for
10471 the postinst script to do something sensible - usually this
10472 will mean editing the installed configuration file to remove
10473 the problem or change the syntax. You will have to do this
10474 very carefully, since the user may have changed the file,
10475 perhaps to fix the very problem that your script is trying
10476 to deal with - you will have to detect these situations and
10477 deal with them correctly.
10481 If you do go down this route it's probably a good idea to
10482 make the program that generates the configuration file(s) a
10483 separate program in <file>/usr/sbin</file>, by convention called
10484 <file><var>package</var>config</file> and then run that if
10485 appropriate from the post-installation script. The
10486 <tt><var>package</var>config</tt> program should not
10487 unquestioningly overwrite an existing configuration - if its
10488 mode of operation is geared towards setting up a package for
10489 the first time (rather than any arbitrary reconfiguration
10490 later) you should have it check whether the configuration
10491 already exists, and require a <tt>--force</tt> flag to
10492 overwrite it.</p></sect>
10495 <appendix id="pkg-alternatives"><heading>Alternative versions of
10496 an interface - <prgn>update-alternatives</prgn> (from old
10501 When several packages all provide different versions of the
10502 same program or file it is useful to have the system select a
10503 default, but to allow the system administrator to change it
10504 and have their decisions respected.
10508 For example, there are several versions of the <prgn>vi</prgn>
10509 editor, and there is no reason to prevent all of them from
10510 being installed at once, each under their own name
10511 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10512 Nevertheless it is desirable to have the name <tt>vi</tt>
10513 refer to something, at least by default.
10517 If all the packages involved cooperate, this can be done with
10518 <prgn>update-alternatives</prgn>.
10522 Each package provides its own version under its own name, and
10523 calls <prgn>update-alternatives</prgn> in its postinst to
10524 register its version (and again in its prerm to deregister
10529 See the man page <manref name="update-alternatives"
10530 section="8"> for details.
10534 If <prgn>update-alternatives</prgn> does not seem appropriate
10535 you may wish to consider using diversions instead.</p>
10538 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10539 package's version of a file (from old Packaging Manual)
10543 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10544 when it reinstalls the package it belongs to, and to have it
10545 put the file from the package somewhere else instead.
10549 This can be used locally to override a package's version of a
10550 file, or by one package to override another's version (or
10551 provide a wrapper for it).
10555 Before deciding to use a diversion, read <ref
10556 id="pkg-alternatives"> to see if you really want a diversion
10557 rather than several alternative versions of a program.
10561 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10562 and updated by a special program <prgn>dpkg-divert</prgn>.
10563 Please see <manref name="dpkg-divert" section="8"> for full
10564 details of its operation.
10568 When a package wishes to divert a file from another, it should
10569 call <prgn>dpkg-divert</prgn> in its preinst to add the
10570 diversion and rename the existing file. For example,
10571 supposing that a <prgn>smailwrapper</prgn> package wishes to
10572 install a wrapper around <file>/usr/sbin/smail</file>:
10574 if [ install = "$1" ]; then
10575 dpkg-divert --package smailwrapper --add --rename \
10576 --divert /usr/sbin/smail.real /usr/sbin/smail
10578 </example> Testing <tt>$1</tt> is necessary so that the script
10579 doesn't try to add the diversion again when
10580 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10581 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10582 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10583 get installed as the true version.
10587 The postrm has to do the reverse:
10589 if [ remove = "$1" ]; then
10590 dpkg-divert --package smailwrapper --remove --rename \
10591 --divert /usr/sbin/smail.real /usr/sbin/smail
10597 Do not attempt to divert a file which is vitally important for
10598 the system's operation - when using <prgn>dpkg-divert</prgn>
10599 there is a time, after it has been diverted but before
10600 <prgn>dpkg</prgn> has installed the new version, when the file
10601 does not exist.</p>
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