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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.
1482 The format of the <file>debian/changelog</file> allows the
1483 package building tools to discover which version of the package
1484 is being built and find out other release-specific information.
1488 That format is a series of entries like this:
1490 <example compact="compact">
1491 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1493 [optional blank line(s), stripped]
1495 * <var>change details</var>
1496 <var>more change details</var>
1498 [blank line(s), included in output of dpkg-parsechangelog]
1500 * <var>even more change details</var>
1502 [optional blank line(s), stripped]
1504 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1509 <var>package</var> and <var>version</var> are the source
1510 package name and version number.
1514 <var>distribution(s)</var> lists the distributions where
1515 this version should be installed when it is uploaded - it
1516 is copied to the <tt>Distribution</tt> field in the
1517 <file>.changes</file> file. See <ref id="f-Distribution">.
1521 <var>urgency</var> is the value for the <tt>Urgency</tt>
1522 field in the <file>.changes</file> file for the upload
1523 (see <ref id="f-Urgency">). It is not possible to specify
1524 an urgency containing commas; commas are used to separate
1525 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1526 <prgn>dpkg</prgn> changelog format (though there is
1527 currently only one useful <var>keyword</var>,
1532 The change details may in fact be any series of lines
1533 starting with at least two spaces, but conventionally each
1534 change starts with an asterisk and a separating space and
1535 continuation lines are indented so as to bring them in
1536 line with the start of the text above. Blank lines may be
1537 used here to separate groups of changes, if desired.
1541 If this upload resolves bugs recorded in the Bug Tracking
1542 System (BTS), they may be automatically closed on the
1543 inclusion of this package into the Debian archive by
1544 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1545 in the change details.<footnote>
1546 To be precise, the string should match the following
1547 Perl regular expression:
1549 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1551 Then all of the bug numbers listed will be closed by the
1552 archive maintenance script (<prgn>katie</prgn>) using the
1553 <var>version</var> of the changelog entry.
1555 This information is conveyed via the <tt>Closes</tt> field
1556 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1560 The maintainer name and email address used in the changelog
1561 should be the details of the person uploading <em>this</em>
1562 version. They are <em>not</em> necessarily those of the
1563 usual package maintainer. The information here will be
1564 copied to the <tt>Changed-By</tt> field in the
1565 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1566 and then later used to send an acknowledgement when the
1567 upload has been installed.
1571 The <var>date</var> must be in RFC822 format<footnote>
1572 This is generated by <tt>date -R</tt>.
1573 </footnote>; it must include the time zone specified
1574 numerically, with the time zone name or abbreviation
1575 optionally present as a comment in parentheses.
1579 The first "title" line with the package name must start
1580 at the left hand margin. The "trailer" line with the
1581 maintainer and date details must be preceded by exactly
1582 one space. The maintainer details and the date must be
1583 separated by exactly two spaces.
1587 For more information on placement of the changelog files
1588 within binary packages, please see <ref id="changelogs">.
1592 <sect id="dpkgcopyright">
1593 <heading>Copyright: <file>debian/copyright</file></heading>
1595 Every package must be accompanied by a verbatim copy of
1596 its copyright and distribution license in the file
1597 <file>/usr/share/doc/<var>package</var>/copyright</file>
1598 (see <ref id="copyrightfile"> for further details). Also see
1599 <ref id="pkgcopyright"> for further considerations relayed
1600 to copyrights for packages.
1604 <heading>Error trapping in makefiles</heading>
1607 When <prgn>make</prgn> invokes a command in a makefile
1608 (including your package's upstream makefiles and
1609 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1610 means that <prgn>sh</prgn>'s usual bad error handling
1611 properties apply: if you include a miniature script as one
1612 of the commands in your makefile you'll find that if you
1613 don't do anything about it then errors are not detected
1614 and <prgn>make</prgn> will blithely continue after
1619 Every time you put more than one shell command (this
1620 includes using a loop) in a makefile command you
1621 must make sure that errors are trapped. For
1622 simple compound commands, such as changing directory and
1623 then running a program, using <tt>&&</tt> rather
1624 than semicolon as a command separator is sufficient. For
1625 more complex commands including most loops and
1626 conditionals you should include a separate <tt>set -e</tt>
1627 command at the start of every makefile command that's
1628 actually one of these miniature shell scripts.
1632 <sect id="timestamps">
1633 <heading>Time Stamps</heading>
1635 Maintainers should preserve the modification times of the
1636 upstream source files in a package, as far as is reasonably
1638 The rationale is that there is some information conveyed
1639 by knowing the age of the file, for example, you could
1640 recognize that some documentation is very old by looking
1641 at the modification time, so it would be nice if the
1642 modification time of the upstream source would be
1648 <sect id="restrictions">
1649 <heading>Restrictions on objects in source packages</heading>
1652 The source package may not contain any hard links<footnote>
1654 This is not currently detected when building source
1655 packages, but only when extracting
1659 Hard links may be permitted at some point in the
1660 future, but would require a fair amount of
1663 </footnote>, device special files, sockets or setuid or
1664 setgid files.<footnote>
1665 Setgid directories are allowed.
1670 <sect id="debianrules">
1671 <heading>Main building script: <file>debian/rules</file></heading>
1674 This file must be an executable makefile, and contains the
1675 package-specific recipes for compiling the package and
1676 building binary package(s) from the source.
1680 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1681 so that it can be invoked by saying its name rather than
1682 invoking <prgn>make</prgn> explicitly.
1686 Since an interactive <file>debian/rules</file> script makes it
1687 impossible to auto-compile that package and also makes it
1688 hard for other people to reproduce the same binary
1689 package, all <em>required targets</em> MUST be
1690 non-interactive. At a minimum, required targets are the
1691 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1692 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1693 <em>binary-indep</em>, and <em>build</em>. It also follows
1694 that any target that these targets depend on must also be
1699 The targets are as follows (required unless stated otherwise):
1701 <tag><tt>build</tt></tag>
1704 The <tt>build</tt> target should perform all the
1705 configuration and compilation of the package.
1706 If a package has an interactive pre-build
1707 configuration routine, the Debianized source package
1708 must either be built after this has taken place (so
1709 that the binary package can be built without rerunning
1710 the configuration) or the configuration routine
1711 modified to become non-interactive. (The latter is
1712 preferable if there are architecture-specific features
1713 detected by the configuration routine.)
1717 For some packages, notably ones where the same
1718 source tree is compiled in different ways to produce
1719 two binary packages, the <tt>build</tt> target
1720 does not make much sense. For these packages it is
1721 good enough to provide two (or more) targets
1722 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1723 for each of the ways of building the package, and a
1724 <tt>build</tt> target that does nothing. The
1725 <tt>binary</tt> target will have to build the
1726 package in each of the possible ways and make the
1727 binary package out of each.
1731 The <tt>build</tt> target must not do anything
1732 that might require root privilege.
1736 The <tt>build</tt> target may need to run the
1737 <tt>clean</tt> target first - see below.
1741 When a package has a configuration and build routine
1742 which takes a long time, or when the makefiles are
1743 poorly designed, or when <tt>build</tt> needs to
1744 run <tt>clean</tt> first, it is a good idea to
1745 <tt>touch build</tt> when the build process is
1746 complete. This will ensure that if <tt>debian/rules
1747 build</tt> is run again it will not rebuild the whole
1749 Another common way to do this is for <tt>build</tt>
1750 to depend on <prgn>build-stamp</prgn> and to do
1751 nothing else, and for the <prgn>build-stamp</prgn>
1752 target to do the building and to <tt>touch
1753 build-stamp</tt> on completion. This is
1754 especially useful if the build routine creates a
1755 file or directory called <tt>build</tt>; in such a
1756 case, <tt>build</tt> will need to be listed as
1757 a phony target (i.e., as a dependency of the
1758 <tt>.PHONY</tt> target). See the documentation of
1759 <prgn>make</prgn> for more information on phony
1765 <tag><tt>build-arch</tt> (optional),
1766 <tt>build-indep</tt> (optional)
1770 A package may also provide both of the targets
1771 <tt>build-arch</tt> and <tt>build-indep</tt>.
1772 The <tt>build-arch</tt> target, if provided, should
1773 perform all the configuration and compilation required
1774 for producing all architecture-dependant binary packages
1775 (those packages for which the body of the
1776 <tt>Architecture</tt> field in <tt>debian/control</tt>
1777 is not <tt>all</tt>).
1778 Similarly, the <tt>build-indep</tt> target, if
1779 provided, should perform all the configuration and
1780 compilation required for producing all
1781 architecture-independent binary packages
1782 (those packages for which the body of the
1783 <tt>Architecture</tt> field in <tt>debian/control</tt>
1785 The <tt>build</tt> target should depend on those of the
1786 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1787 are provided in the rules file.
1791 If one or both of the targets <tt>build-arch</tt> and
1792 <tt>build-indep</tt> are not provided, then invoking
1793 <file>debian/rules</file> with one of the not-provided
1794 targets as arguments should produce a exit status code
1795 of 2. Usually this is provided automatically by make
1796 if the target is missing.
1800 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1801 must not do anything that might require root privilege.
1805 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1806 <tt>binary-indep</tt>
1810 The <tt>binary</tt> target must be all that is
1811 necessary for the user to build the binary package(s)
1812 produced from this source package. It is
1813 split into two parts: <prgn>binary-arch</prgn> builds
1814 the binary packages which are specific to a particular
1815 architecture, and <tt>binary-indep</tt> builds
1816 those which are not.
1819 <tt>binary</tt> may be (and commonly is) a target with
1820 no commands which simply depends on
1821 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1824 Both <tt>binary-*</tt> targets should depend on the
1825 <tt>build</tt> target, or on the appropriate
1826 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1827 provided, so that the package is built if it has not
1828 been already. It should then create the relevant
1829 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1830 make their control files and <prgn>dpkg-deb</prgn> to
1831 build them and place them in the parent of the top
1836 Both the <tt>binary-arch</tt> and
1837 <tt>binary-indep</tt> targets <em>must</em> exist.
1838 If one of them has nothing to do (which will always be
1839 the case if the source generates only a single binary
1840 package, whether architecture-dependent or not), it
1841 must still exist and must always succeed.
1845 The <tt>binary</tt> targets must be invoked as
1847 The <prgn>fakeroot</prgn> package often allows one
1848 to build a package correctly even without being
1854 <tag><tt>clean</tt></tag>
1857 This must undo any effects that the <tt>build</tt>
1858 and <tt>binary</tt> targets may have had, except
1859 that it should leave alone any output files created in
1860 the parent directory by a run of a <tt>binary</tt>
1865 If a <tt>build</tt> file is touched at the end of
1866 the <tt>build</tt> target, as suggested above, it
1867 should be removed as the first action that
1868 <tt>clean</tt> performs, so that running
1869 <tt>build</tt> again after an interrupted
1870 <tt>clean</tt> doesn't think that everything is
1875 The <tt>clean</tt> target may need to be
1876 invoked as root if <tt>binary</tt> has been
1877 invoked since the last <tt>clean</tt>, or if
1878 <tt>build</tt> has been invoked as root (since
1879 <tt>build</tt> may create directories, for
1884 <tag><tt>get-orig-source</tt> (optional)</tag>
1887 This target fetches the most recent version of the
1888 original source package from a canonical archive site
1889 (via FTP or WWW, for example), does any necessary
1890 rearrangement to turn it into the original source
1891 tar file format described below, and leaves it in the
1896 This target may be invoked in any directory, and
1897 should take care to clean up any temporary files it
1902 This target is optional, but providing it if
1903 possible is a good idea.
1907 <tag><tt>patch</tt> (optional)</tag>
1910 This target performs whatever additional actions are
1911 required to make the source ready for editing (unpacking
1912 additional upstream archives, applying patches, etc.).
1913 It is recommended to be implemented for any package where
1914 <tt>dpkg-source -x</tt> does not result in source ready
1915 for additional modification. See
1916 <ref id="readmesource">.
1922 The <tt>build</tt>, <tt>binary</tt> and
1923 <tt>clean</tt> targets must be invoked with the current
1924 directory being the package's top-level directory.
1929 Additional targets may exist in <file>debian/rules</file>,
1930 either as published or undocumented interfaces or for the
1931 package's internal use.
1935 The architectures we build on and build for are determined
1936 by <prgn>make</prgn> variables using the utility
1937 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1938 You can determine the
1939 Debian architecture and the GNU style architecture
1940 specification string for the build machine (the machine type
1941 we are building on) as well as for the host machine (the
1942 machine type we are building for). Here is a list of
1943 supported <prgn>make</prgn> variables:
1944 <list compact="compact">
1946 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1949 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1950 specification string)
1953 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1954 <tt>DEB_*_GNU_TYPE</tt>)
1957 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1958 <tt>DEB_*_GNU_TYPE</tt>)
1960 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1961 the build machine or <tt>HOST</tt> for specification of the
1966 Backward compatibility can be provided in the rules file
1967 by setting the needed variables to suitable default
1968 values; please refer to the documentation of
1969 <prgn>dpkg-architecture</prgn> for details.
1973 It is important to understand that the <tt>DEB_*_ARCH</tt>
1974 string only determines which Debian architecture we are
1975 building on or for. It should not be used to get the CPU
1976 or system information; the GNU style variables should be
1980 <sect1 id="debianrules-options">
1981 <heading><file>debian/rules</file> and
1982 <tt>DEB_BUILD_OPTIONS</tt></heading>
1985 Supporting the standardized environment variable
1986 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
1987 contain several flags to change how a package is compiled and
1988 built. Each flag must be in the form <var>flag</var> or
1989 <var>flag</var>=<var>options</var>. If multiple flags are
1990 given, they must be separated by whitespace.<footnote>
1991 Some packages support any delimiter, but whitespace is the
1992 easiest to parse inside a makefile and avoids ambiguity with
1993 flag values that contain commas.
1995 <var>flag</var> must start with a lowercase letter
1996 (<tt>a-z</tt>) and consist only of lowercase letters,
1997 numbers (<tt>0-9</tt>), and the characters
1998 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
1999 <var>options</var> must not contain whitespace. The same
2000 tag should not be given multiple times with conflicting
2001 values. Package maintainers may assume that
2002 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2006 The meaning of the following tags has been standardized:
2010 The presence of this tag means that the package should
2011 be compiled with a minimum of optimization. For C
2012 programs, it is best to add <tt>-O0</tt> to
2013 <tt>CFLAGS</tt> (although this is usually the default).
2014 Some programs might fail to build or run at this level
2015 of optimization; it may be necessary to use
2016 <tt>-O1</tt>, for example.
2020 This tag means that the debugging symbols should not be
2021 stripped from the binary during installation, so that
2022 debugging information may be included in the package.
2024 <tag>parallel=n</tag>
2026 This tag means that the package should be built using up
2027 to <tt>n</tt> parallel processes if the package build
2028 system supports this.<footnote>
2029 Packages built with <tt>make</tt> can often implement
2030 this by passing the <tt>-j</tt><var>n</var> option to
2033 If the package build system does not support parallel
2034 builds, this string must be ignored. If the package
2035 build system only supports a lower level of concurrency
2036 than <var>n</var>, the package should be built using as
2037 many parallel processes as the package build system
2038 supports. It is up to the package maintainer to decide
2039 whether the package build times are long enough and the
2040 package build system is robust enough to make supporting
2041 parallel builds worthwhile.
2047 Unknown flags must be ignored by <file>debian/rules</file>.
2051 The following makefile snippet is an example of how one may
2052 implement the build options; you will probably have to
2053 massage this example in order to make it work for your
2055 <example compact="compact">
2058 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2059 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2060 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2061 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2063 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2068 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2069 INSTALL_PROGRAM += -s
2071 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2072 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2073 MAKEFLAGS += -j$(NUMJOBS)
2080 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2081 <sect id="substvars">
2082 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2085 When <prgn>dpkg-gencontrol</prgn>,
2086 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2087 generate control files they perform variable substitutions
2088 on their output just before writing it. Variable
2089 substitutions have the form <tt>${<var>variable</var>}</tt>.
2090 The optional file <file>debian/substvars</file> contains
2091 variable substitutions to be used; variables can also be set
2092 directly from <file>debian/rules</file> using the <tt>-V</tt>
2093 option to the source packaging commands, and certain
2094 predefined variables are also available.
2098 The <file>debian/substvars</file> file is usually generated and
2099 modified dynamically by <file>debian/rules</file> targets, in
2100 which case it must be removed by the <tt>clean</tt> target.
2104 See <manref name="deb-substvars" section="5"> for full
2105 details about source variable substitutions, including the
2106 format of <file>debian/substvars</file>.</p>
2109 <sect id="debianwatch">
2110 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2113 This is an optional, recommended control file for the
2114 <tt>uscan</tt> utility which defines how to automatically
2115 scan ftp or http sites for newly available updates of the
2116 package. This is used by <url id="
2117 http://dehs.alioth.debian.org/"> and other Debian QA tools
2118 to help with quality control and maintenance of the
2119 distribution as a whole.
2124 <sect id="debianfiles">
2125 <heading>Generated files list: <file>debian/files</file></heading>
2128 This file is not a permanent part of the source tree; it
2129 is used while building packages to record which files are
2130 being generated. <prgn>dpkg-genchanges</prgn> uses it
2131 when it generates a <file>.changes</file> file.
2135 It should not exist in a shipped source package, and so it
2136 (and any backup files or temporary files such as
2137 <file>files.new</file><footnote>
2138 <file>files.new</file> is used as a temporary file by
2139 <prgn>dpkg-gencontrol</prgn> and
2140 <prgn>dpkg-distaddfile</prgn> - they write a new
2141 version of <tt>files</tt> here before renaming it,
2142 to avoid leaving a corrupted copy if an error
2144 </footnote>) should be removed by the
2145 <tt>clean</tt> target. It may also be wise to
2146 ensure a fresh start by emptying or removing it at the
2147 start of the <tt>binary</tt> target.
2151 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2152 package, it adds an entry to <file>debian/files</file> for the
2153 <file>.deb</file> file that will be created when <tt>dpkg-deb
2154 --build</tt> is run for that binary package. So for most
2155 packages all that needs to be done with this file is to
2156 delete it in the <tt>clean</tt> target.
2160 If a package upload includes files besides the source
2161 package and any binary packages whose control files were
2162 made with <prgn>dpkg-gencontrol</prgn> then they should be
2163 placed in the parent of the package's top-level directory
2164 and <prgn>dpkg-distaddfile</prgn> should be called to add
2165 the file to the list in <file>debian/files</file>.</p>
2168 <sect id="embeddedfiles">
2169 <heading>Convenience copies of code</heading>
2172 Some software packages include in their distribution convenience
2173 copies of code from other software packages, generally so that
2174 users compiling from source don't have to download multiple
2175 packages. Debian packages should not make use of these
2176 convenience copies unless the included package is explicitly
2177 intended to be used in this way.<footnote>
2178 For example, parts of the GNU build system work like this.
2180 If the included code is already in the Debian archive in the
2181 form of a library, the Debian packaging should ensure that
2182 binary packages reference the libraries already in Debian and
2183 the convenience copy is not used. If the included code is not
2184 already in Debian, it should be packaged separately as a
2185 prerequisite if possible.
2187 Having multiple copies of the same code in Debian is
2188 inefficient, often creates either static linking or shared
2189 library conflicts, and, most importantly, increases the
2190 difficulty of handling security vulnerabilities in the
2196 <sect id="readmesource">
2197 <heading>Source package handling:
2198 <file>debian/README.source</file></heading>
2201 If running <prgn>dpkg-source -x</prgn> on a source package
2202 doesn't produce the source of the package, ready for editing,
2203 and allow one to make changes and run
2204 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2205 without taking any additional steps, creating a
2206 <file>debian/README.source</file> documentation file is
2207 recommended. This file should explain how to do all of the
2210 <item>Generate the fully patched source, in a form ready for
2211 editing, that would be built to create Debian
2212 packages. Doing this with a <tt>patch</tt> target in
2213 <file>debian/rules</file> is recommended; see
2214 <ref id="debianrules">.</item>
2215 <item>Modify the source and save those modifications so that
2216 they will be applied when building the package.</item>
2217 <item>Remove source modifications that are currently being
2218 applied when building the package.</item>
2219 <item>Optionally, document what steps are necessary to
2220 upgrade the Debian source package to a new upstream version,
2221 if applicable.</item>
2223 This explanation should include specific commands and mention
2224 any additional required Debian packages. It should not assume
2225 familiarity with any specific Debian packaging system or patch
2230 This explanation may refer to a documentation file installed by
2231 one of the package's build dependencies provided that the
2232 referenced documentation clearly explains these tasks and is not
2233 a general reference manual.
2237 <file>debian/README.source</file> may also include any other
2238 information that would be helpful to someone modifying the
2239 source package. Even if the package doesn't fit the above
2240 description, maintainers are encouraged to document in a
2241 <file>debian/README.source</file> file any source package with a
2242 particularly complex or unintuitive source layout or build
2243 system (for example, a package that builds the same source
2244 multiple times to generate different binary packages).
2250 <chapt id="controlfields">
2251 <heading>Control files and their fields</heading>
2254 The package management system manipulates data represented in
2255 a common format, known as <em>control data</em>, stored in
2256 <em>control files</em>.
2257 Control files are used for source packages, binary packages and
2258 the <file>.changes</file> files which control the installation
2259 of uploaded files<footnote>
2260 <prgn>dpkg</prgn>'s internal databases are in a similar
2265 <sect id="controlsyntax">
2266 <heading>Syntax of control files</heading>
2269 A control file consists of one or more paragraphs of
2271 The paragraphs are also sometimes referred to as stanzas.
2273 The paragraphs are separated by blank lines. Some control
2274 files allow only one paragraph; others allow several, in
2275 which case each paragraph usually refers to a different
2276 package. (For example, in source packages, the first
2277 paragraph refers to the source package, and later paragraphs
2278 refer to binary packages generated from the source.)
2282 Each paragraph consists of a series of data fields; each
2283 field consists of the field name, followed by a colon and
2284 then the data/value associated with that field. It ends at
2285 the end of the (logical) line. Horizontal whitespace
2286 (spaces and tabs) may occur immediately before or after the
2287 value and is ignored there; it is conventional to put a
2288 single space after the colon. For example, a field might
2290 <example compact="compact">
2293 the field name is <tt>Package</tt> and the field value
2298 Many fields' values may span several lines; in this case
2299 each continuation line must start with a space or a tab.
2300 Any trailing spaces or tabs at the end of individual
2301 lines of a field value are ignored.
2305 In fields where it is specified that lines may not wrap,
2306 only a single line of data is allowed and whitespace is not
2307 significant in a field body. Whitespace must not appear
2308 inside names (of packages, architectures, files or anything
2309 else) or version numbers, or between the characters of
2310 multi-character version relationships.
2314 Field names are not case-sensitive, but it is usual to
2315 capitalize the field names using mixed case as shown below.
2319 Blank lines, or lines consisting only of spaces and tabs,
2320 are not allowed within field values or between fields - that
2321 would mean a new paragraph.
2326 <sect id="sourcecontrolfiles">
2327 <heading>Source package control files -- <file>debian/control</file></heading>
2330 The <file>debian/control</file> file contains the most vital
2331 (and version-independent) information about the source package
2332 and about the binary packages it creates.
2336 The first paragraph of the control file contains information about
2337 the source package in general. The subsequent sets each describe a
2338 binary package that the source tree builds.
2342 The fields in the general paragraph (the first one, for the source
2345 <list compact="compact">
2346 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2347 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2348 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2349 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2350 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2351 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2352 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2353 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2358 The fields in the binary package paragraphs are:
2360 <list compact="compact">
2361 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2362 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2363 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2364 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2365 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2366 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2367 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2368 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2373 The syntax and semantics of the fields are described below.
2379 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2380 generate control files for binary packages (see below), by
2381 <prgn>dpkg-genchanges</prgn> to generate the
2382 <tt>.changes</tt> file to accompany the upload, and by
2383 <prgn>dpkg-source</prgn> when it creates the
2384 <file>.dsc</file> source control file as part of a source
2385 archive. Many fields are permitted to span multiple lines in
2386 <file>debian/control</file> but not in any other control
2387 file. These tools are responsible for removing the line
2388 breaks from such fields when using fields from
2389 <file>debian/control</file> to generate other control files.
2393 The fields here may contain variable references - their
2394 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2395 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2396 when they generate output control files.
2397 See <ref id="substvars"> for details.
2402 <sect id="binarycontrolfiles">
2403 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2406 The <file>DEBIAN/control</file> file contains the most vital
2407 (and version-dependent) information about a binary package.
2411 The fields in this file are:
2413 <list compact="compact">
2414 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2415 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2416 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2417 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2418 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2419 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2420 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2421 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2422 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2423 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2424 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2425 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2430 <sect id="debiansourcecontrolfiles">
2431 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2434 This file contains a series of fields, identified and
2435 separated just like the fields in the control file of
2436 a binary package. The fields are listed below; their
2437 syntax is described above, in <ref id="pkg-controlfields">.
2439 <list compact="compact">
2440 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2441 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2442 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2443 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2444 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2445 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2446 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2447 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2448 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2449 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2450 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2455 The source package control file is generated by
2456 <prgn>dpkg-source</prgn> when it builds the source
2457 archive, from other files in the source package,
2458 described above. When unpacking, it is checked against
2459 the files and directories in the other parts of the
2465 <sect id="debianchangesfiles">
2466 <heading>Debian changes files -- <file>.changes</file></heading>
2469 The .changes files are used by the Debian archive maintenance
2470 software to process updates to packages. They contain one
2471 paragraph which contains information from the
2472 <tt>debian/control</tt> file and other data about the
2473 source package gathered via <tt>debian/changelog</tt>
2474 and <tt>debian/rules</tt>.
2478 The fields in this file are:
2480 <list compact="compact">
2481 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2482 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2483 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2484 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2485 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2486 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2487 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2489 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2490 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2491 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2492 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2493 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2494 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2499 <sect id="controlfieldslist">
2500 <heading>List of fields</heading>
2502 <sect1 id="f-Source">
2503 <heading><tt>Source</tt></heading>
2506 This field identifies the source package name.
2510 In <file>debian/control</file> or a <file>.dsc</file> file,
2511 this field must contain only the name of the source package.
2515 In a binary package control file or a <file>.changes</file>
2516 file, the source package name may be followed by a version
2517 number in parentheses<footnote>
2518 It is customary to leave a space after the package name
2519 if a version number is specified.
2521 This version number may be omitted (and is, by
2522 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2523 the <tt>Version</tt> field of the binary package in
2524 question. The field itself may be omitted from a binary
2525 package control file when the source package has the same
2526 name and version as the binary package.
2530 <sect1 id="f-Maintainer">
2531 <heading><tt>Maintainer</tt></heading>
2534 The package maintainer's name and email address. The name
2535 should come first, then the email address inside angle
2536 brackets <tt><></tt> (in RFC822 format).
2540 If the maintainer's name contains a full stop then the
2541 whole field will not work directly as an email address due
2542 to a misfeature in the syntax specified in RFC822; a
2543 program using this field as an address must check for this
2544 and correct the problem if necessary (for example by
2545 putting the name in round brackets and moving it to the
2546 end, and bringing the email address forward).
2550 <sect1 id="f-Uploaders">
2551 <heading><tt>Uploaders</tt></heading>
2554 List of the names and email addresses of co-maintainers of
2555 the package, if any. If the package has other maintainers
2556 beside the one named in the
2557 <qref id="f-Maintainer">Maintainer field</qref>, their
2558 names and email addresses should be listed here. The
2559 format is the same as that of the Maintainer tag, and
2560 multiple entries should be comma separated. Currently,
2561 this field is restricted to a single line of data. This
2562 is an optional field.
2565 Any parser that interprets the Uploaders field in
2566 <file>debian/control</file> must permit it to span multiple
2567 lines. Line breaks in an Uploaders field that spans multiple
2568 lines are not significant and the semantics of the field are
2569 the same as if the line breaks had not been present.
2573 <sect1 id="f-Changed-By">
2574 <heading><tt>Changed-By</tt></heading>
2577 The name and email address of the person who changed the
2578 said package. Usually the name of the maintainer.
2579 All the rules for the Maintainer field apply here, too.
2583 <sect1 id="f-Section">
2584 <heading><tt>Section</tt></heading>
2587 This field specifies an application area into which the package
2588 has been classified. See <ref id="subsections">.
2592 When it appears in the <file>debian/control</file> file,
2593 it gives the value for the subfield of the same name in
2594 the <tt>Files</tt> field of the <file>.changes</file> file.
2595 It also gives the default for the same field in the binary
2600 <sect1 id="f-Priority">
2601 <heading><tt>Priority</tt></heading>
2604 This field represents how important that it is that the user
2605 have the package installed. See <ref id="priorities">.
2609 When it appears in the <file>debian/control</file> file,
2610 it gives the value for the subfield of the same name in
2611 the <tt>Files</tt> field of the <file>.changes</file> file.
2612 It also gives the default for the same field in the binary
2617 <sect1 id="f-Package">
2618 <heading><tt>Package</tt></heading>
2621 The name of the binary package.
2625 Package names must consist only of lower case letters
2626 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2627 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2628 They must be at least two characters long and must start
2629 with an alphanumeric character.
2633 <sect1 id="f-Architecture">
2634 <heading><tt>Architecture</tt></heading>
2637 Depending on context and the control file used, the
2638 <tt>Architecture</tt> field can include the following sets of
2641 <item>A unique single word identifying a Debian machine
2642 architecture, see <ref id="arch-spec">.
2643 <item><tt>all</tt>, which indicates an
2644 architecture-independent package.
2645 <item><tt>any</tt>, which indicates a package available
2646 for building on any architecture.
2647 <item><tt>source</tt>, which indicates a source package.
2652 In the main <file>debian/control</file> file in the source
2653 package, or in the source package control file
2654 <file>.dsc</file>, one may specify a list of architectures
2655 separated by spaces, or the special values <tt>any</tt> or
2660 Specifying <tt>any</tt> indicates that the source package
2661 isn't dependent on any particular architecture and should
2662 compile fine on any one. The produced binary package(s)
2663 will be specific to whatever the current build architecture
2665 This is the most often used setting, and is recommended
2666 for new packages that aren't <tt>Architecture: all</tt>.
2671 Specifying a list of architectures indicates that the source
2672 will build an architecture-dependent package, and will only
2673 work correctly on the listed architectures.<footnote>
2674 This is a setting used for a minority of cases where the
2675 program is not portable. Generally, it should not be used
2681 In a <file>.changes</file> file, the <tt>Architecture</tt>
2682 field lists the architecture(s) of the package(s)
2683 currently being uploaded. This will be a list; if the
2684 source for the package is also being uploaded, the special
2685 entry <tt>source</tt> is also present.
2689 See <ref id="debianrules"> for information how to get the
2690 architecture for the build process.
2694 <sect1 id="f-Essential">
2695 <heading><tt>Essential</tt></heading>
2698 This is a boolean field which may occur only in the
2699 control file of a binary package or in a per-package fields
2700 paragraph of a main source control data file.
2704 If set to <tt>yes</tt> then the package management system
2705 will refuse to remove the package (upgrading and replacing
2706 it is still possible). The other possible value is <tt>no</tt>,
2707 which is the same as not having the field at all.
2712 <heading>Package interrelationship fields:
2713 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2714 <tt>Recommends</tt>, <tt>Suggests</tt>,
2715 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2716 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2720 These fields describe the package's relationships with
2721 other packages. Their syntax and semantics are described
2722 in <ref id="relationships">.</p>
2725 <sect1 id="f-Standards-Version">
2726 <heading><tt>Standards-Version</tt></heading>
2729 The most recent version of the standards (the policy
2730 manual and associated texts) with which the package
2735 The version number has four components: major and minor
2736 version number and major and minor patch level. When the
2737 standards change in a way that requires every package to
2738 change the major number will be changed. Significant
2739 changes that will require work in many packages will be
2740 signaled by a change to the minor number. The major patch
2741 level will be changed for any change to the meaning of the
2742 standards, however small; the minor patch level will be
2743 changed when only cosmetic, typographical or other edits
2744 are made which neither change the meaning of the document
2745 nor affect the contents of packages.
2749 Thus only the first three components of the policy version
2750 are significant in the <em>Standards-Version</em> control
2751 field, and so either these three components or the all
2752 four components may be specified.<footnote>
2753 In the past, people specified the full version number
2754 in the Standards-Version field, for example "2.3.0.0".
2755 Since minor patch-level changes don't introduce new
2756 policy, it was thought it would be better to relax
2757 policy and only require the first 3 components to be
2758 specified, in this example "2.3.0". All four
2759 components may still be used if someone wishes to do so.
2765 <sect1 id="f-Version">
2766 <heading><tt>Version</tt></heading>
2769 The version number of a package. The format is:
2770 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2774 The three components here are:
2776 <tag><var>epoch</var></tag>
2779 This is a single (generally small) unsigned integer. It
2780 may be omitted, in which case zero is assumed. If it is
2781 omitted then the <var>upstream_version</var> may not
2786 It is provided to allow mistakes in the version numbers
2787 of older versions of a package, and also a package's
2788 previous version numbering schemes, to be left behind.
2792 <tag><var>upstream_version</var></tag>
2795 This is the main part of the version number. It is
2796 usually the version number of the original ("upstream")
2797 package from which the <file>.deb</file> file has been made,
2798 if this is applicable. Usually this will be in the same
2799 format as that specified by the upstream author(s);
2800 however, it may need to be reformatted to fit into the
2801 package management system's format and comparison
2806 The comparison behavior of the package management system
2807 with respect to the <var>upstream_version</var> is
2808 described below. The <var>upstream_version</var>
2809 portion of the version number is mandatory.
2813 The <var>upstream_version</var> may contain only
2814 alphanumerics<footnote>
2815 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2817 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2818 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2819 tilde) and should start with a digit. If there is no
2820 <var>debian_revision</var> then hyphens are not allowed;
2821 if there is no <var>epoch</var> then colons are not
2826 <tag><var>debian_revision</var></tag>
2829 This part of the version number specifies the version of
2830 the Debian package based on the upstream version. It
2831 may contain only alphanumerics and the characters
2832 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2833 tilde) and is compared in the same way as the
2834 <var>upstream_version</var> is.
2838 It is optional; if it isn't present then the
2839 <var>upstream_version</var> may not contain a hyphen.
2840 This format represents the case where a piece of
2841 software was written specifically to be turned into a
2842 Debian package, and so there is only one "debianisation"
2843 of it and therefore no revision indication is required.
2847 It is conventional to restart the
2848 <var>debian_revision</var> at <tt>1</tt> each time the
2849 <var>upstream_version</var> is increased.
2853 The package management system will break the version
2854 number apart at the last hyphen in the string (if there
2855 is one) to determine the <var>upstream_version</var> and
2856 <var>debian_revision</var>. The absence of a
2857 <var>debian_revision</var> is equivalent to a
2858 <var>debian_revision</var> of <tt>0</tt>.
2865 When comparing two version numbers, first the <var>epoch</var>
2866 of each are compared, then the <var>upstream_version</var> if
2867 <var>epoch</var> is equal, and then <var>debian_revision</var>
2868 if <var>upstream_version</var> is also equal.
2869 <var>epoch</var> is compared numerically. The
2870 <var>upstream_version</var> and <var>debian_revision</var>
2871 parts are compared by the package management system using the
2872 following algorithm:
2876 The strings are compared from left to right.
2880 First the initial part of each string consisting entirely of
2881 non-digit characters is determined. These two parts (one of
2882 which may be empty) are compared lexically. If a difference
2883 is found it is returned. The lexical comparison is a
2884 comparison of ASCII values modified so that all the letters
2885 sort earlier than all the non-letters and so that a tilde
2886 sorts before anything, even the end of a part. For example,
2887 the following parts are in sorted order from earliest to
2888 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2889 <tt>a</tt>.<footnote>
2890 One common use of <tt>~</tt> is for upstream pre-releases.
2891 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2892 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2897 Then the initial part of the remainder of each string which
2898 consists entirely of digit characters is determined. The
2899 numerical values of these two parts are compared, and any
2900 difference found is returned as the result of the comparison.
2901 For these purposes an empty string (which can only occur at
2902 the end of one or both version strings being compared) counts
2907 These two steps (comparing and removing initial non-digit
2908 strings and initial digit strings) are repeated until a
2909 difference is found or both strings are exhausted.
2913 Note that the purpose of epochs is to allow us to leave behind
2914 mistakes in version numbering, and to cope with situations
2915 where the version numbering scheme changes. It is
2916 <em>not</em> intended to cope with version numbers containing
2917 strings of letters which the package management system cannot
2918 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2919 silly orderings (the author of this manual has heard of a
2920 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2921 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2922 <tt>2</tt> and so forth).
2926 <sect1 id="f-Description">
2927 <heading><tt>Description</tt></heading>
2930 In a source or binary control file, the <tt>Description</tt>
2931 field contains a description of the binary package, consisting
2932 of two parts, the synopsis or the short description, and the
2933 long description. The field's format is as follows:
2938 Description: <single line synopsis>
2939 <extended description over several lines>
2944 The lines in the extended description can have these formats:
2950 Those starting with a single space are part of a paragraph.
2951 Successive lines of this form will be word-wrapped when
2952 displayed. The leading space will usually be stripped off.
2956 Those starting with two or more spaces. These will be
2957 displayed verbatim. If the display cannot be panned
2958 horizontally, the displaying program will line wrap them "hard"
2959 (i.e., without taking account of word breaks). If it can they
2960 will be allowed to trail off to the right. None, one or two
2961 initial spaces may be deleted, but the number of spaces
2962 deleted from each line will be the same (so that you can have
2963 indenting work correctly, for example).
2967 Those containing a single space followed by a single full stop
2968 character. These are rendered as blank lines. This is the
2969 <em>only</em> way to get a blank line<footnote>
2970 Completely empty lines will not be rendered as blank lines.
2971 Instead, they will cause the parser to think you're starting
2972 a whole new record in the control file, and will therefore
2973 likely abort with an error.
2978 Those containing a space, a full stop and some more characters.
2979 These are for future expansion. Do not use them.
2985 Do not use tab characters. Their effect is not predictable.
2989 See <ref id="descriptions"> for further information on this.
2993 In a <file>.changes</file> file, the <tt>Description</tt> field
2994 contains a summary of the descriptions for the packages being
2999 The part of the field before the first newline is empty;
3000 thereafter each line has the name of a binary package and
3001 the summary description line from that binary package.
3002 Each line is indented by one space.
3007 <sect1 id="f-Distribution">
3008 <heading><tt>Distribution</tt></heading>
3011 In a <file>.changes</file> file or parsed changelog output
3012 this contains the (space-separated) name(s) of the
3013 distribution(s) where this version of the package should
3014 be installed. Valid distributions are determined by the
3015 archive maintainers.<footnote>
3016 Current distribution names are:
3017 <taglist compact="compact">
3018 <tag><em>stable</em></tag>
3020 This is the current "released" version of Debian
3021 GNU/Linux. Once the distribution is
3022 <em>stable</em> only security fixes and other
3023 major bug fixes are allowed. When changes are
3024 made to this distribution, the release number is
3025 increased (for example: 2.2r1 becomes 2.2r2 then
3029 <tag><em>unstable</em></tag>
3031 This distribution value refers to the
3032 <em>developmental</em> part of the Debian
3033 distribution tree. New packages, new upstream
3034 versions of packages and bug fixes go into the
3035 <em>unstable</em> directory tree. Download from
3036 this distribution at your own risk.
3039 <tag><em>testing</em></tag>
3041 This distribution value refers to the
3042 <em>testing</em> part of the Debian distribution
3043 tree. It receives its packages from the
3044 unstable distribution after a short time lag to
3045 ensure that there are no major issues with the
3046 unstable packages. It is less prone to breakage
3047 than unstable, but still risky. It is not
3048 possible to upload packages directly to
3052 <tag><em>frozen</em></tag>
3054 From time to time, the <em>testing</em>
3055 distribution enters a state of "code-freeze" in
3056 anticipation of release as a <em>stable</em>
3057 version. During this period of testing only
3058 fixes for existing or newly-discovered bugs will
3059 be allowed. The exact details of this stage are
3060 determined by the Release Manager.
3063 <tag><em>experimental</em></tag>
3065 The packages with this distribution value are
3066 deemed by their maintainers to be high
3067 risk. Oftentimes they represent early beta or
3068 developmental packages from various sources that
3069 the maintainers want people to try, but are not
3070 ready to be a part of the other parts of the
3071 Debian distribution tree. Download at your own
3077 You should list <em>all</em> distributions that the
3078 package should be installed into.
3082 More information is available in the Debian Developer's
3083 Reference, section "The Debian archive".
3090 <heading><tt>Date</tt></heading>
3093 This field includes the date the package was built or last edited.
3097 The value of this field is usually extracted from the
3098 <file>debian/changelog</file> file - see
3099 <ref id="dpkgchangelog">).
3103 <sect1 id="f-Format">
3104 <heading><tt>Format</tt></heading>
3107 This field specifies a format revision for the file.
3108 The most current format described in the Policy Manual
3109 is version <strong>1.5</strong>. The syntax of the
3110 format value is the same as that of a package version
3111 number except that no epoch or Debian revision is allowed
3112 - see <ref id="f-Version">.
3116 <sect1 id="f-Urgency">
3117 <heading><tt>Urgency</tt></heading>
3120 This is a description of how important it is to upgrade to
3121 this version from previous ones. It consists of a single
3122 keyword taking one of the values <tt>low</tt>,
3123 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3124 <tt>critical</tt><footnote>
3125 Other urgency values are supported with configuration
3126 changes in the archive software but are not used in Debian.
3127 The urgency affects how quickly a package will be considered
3128 for inclusion into the <tt>testing</tt> distribution and
3129 gives an indication of the importance of any fixes included
3130 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3131 treated as synonymous.
3132 </footnote> (not case-sensitive) followed by an optional
3133 commentary (separated by a space) which is usually in
3134 parentheses. For example:
3137 Urgency: low (HIGH for users of diversions)
3143 The value of this field is usually extracted from the
3144 <file>debian/changelog</file> file - see
3145 <ref id="dpkgchangelog">.
3149 <sect1 id="f-Changes">
3150 <heading><tt>Changes</tt></heading>
3153 This field contains the human-readable changes data, describing
3154 the differences between the last version and the current one.
3158 There should be nothing in this field before the first
3159 newline; all the subsequent lines must be indented by at
3160 least one space; blank lines must be represented by a line
3161 consisting only of a space and a full stop.
3165 The value of this field is usually extracted from the
3166 <file>debian/changelog</file> file - see
3167 <ref id="dpkgchangelog">).
3171 Each version's change information should be preceded by a
3172 "title" line giving at least the version, distribution(s)
3173 and urgency, in a human-readable way.
3177 If data from several versions is being returned the entry
3178 for the most recent version should be returned first, and
3179 entries should be separated by the representation of a
3180 blank line (the "title" line may also be followed by the
3181 representation of blank line).
3185 <sect1 id="f-Binary">
3186 <heading><tt>Binary</tt></heading>
3189 This field is a list of binary packages.
3193 When it appears in the <file>.dsc</file> file it is the list
3194 of binary packages which a source package can produce. It
3195 does not necessarily produce all of these binary packages
3196 for every architecture. The source control file doesn't
3197 contain details of which architectures are appropriate for
3198 which of the binary packages.
3202 When it appears in a <file>.changes</file> file it lists the
3203 names of the binary packages actually being uploaded.
3207 The syntax is a list of binary packages separated by
3209 A space after each comma is conventional.
3210 </footnote>. Currently the packages must be separated using
3211 only spaces in the <file>.changes</file> file.
3215 <sect1 id="f-Installed-Size">
3216 <heading><tt>Installed-Size</tt></heading>
3219 This field appears in the control files of binary
3220 packages, and in the <file>Packages</file> files. It gives
3221 the total amount of disk space required to install the
3226 The disk space is represented in kilobytes as a simple
3231 <sect1 id="f-Files">
3232 <heading><tt>Files</tt></heading>
3235 This field contains a list of files with information about
3236 each one. The exact information and syntax varies with
3237 the context. In all cases the part of the field
3238 contents on the same line as the field name is empty. The
3239 remainder of the field is one line per file, each line
3240 being indented by one space and containing a number of
3241 sub-fields separated by spaces.
3245 In the <file>.dsc</file> file, each line contains the MD5
3246 checksum, size and filename of the tar file and (if applicable)
3247 diff file which make up the remainder of the source
3249 That is, the parts which are not the <tt>.dsc</tt>.
3251 The exact forms of the filenames are described
3252 in <ref id="pkg-sourcearchives">.
3256 In the <file>.changes</file> file this contains one line per
3257 file being uploaded. Each line contains the MD5 checksum,
3258 size, section and priority and the filename.
3259 The <qref id="f-Section">section</qref>
3260 and <qref id="f-Priority">priority</qref>
3261 are the values of the corresponding fields in
3262 the main source control file. If no section or priority is
3263 specified then <tt>-</tt> should be used, though section
3264 and priority values must be specified for new packages to
3265 be installed properly.
3269 The special value <tt>byhand</tt> for the section in a
3270 <tt>.changes</tt> file indicates that the file in question
3271 is not an ordinary package file and must by installed by
3272 hand by the distribution maintainers. If the section is
3273 <tt>byhand</tt> the priority should be <tt>-</tt>.
3277 If a new Debian revision of a package is being shipped and
3278 no new original source archive is being distributed the
3279 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3280 entry for the original source archive
3281 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3282 but the <file>.changes</file> file should leave it out. In
3283 this case the original source archive on the distribution
3284 site must match exactly, byte-for-byte, the original
3285 source archive which was used to generate the
3286 <file>.dsc</file> file and diff which are being uploaded.</p>
3289 <sect1 id="f-Closes">
3290 <heading><tt>Closes</tt></heading>
3293 A space-separated list of bug report numbers that the upload
3294 governed by the .changes file closes.
3298 <sect1 id="f-Homepage">
3299 <heading><tt>Homepage</tt></heading>
3302 The URL of the web site for this package, preferably (when
3303 applicable) the site from which the original source can be
3304 obtained and any additional upstream documentation or
3305 information may be found. The content of this field is a
3306 simple URL without any surrounding characters such as
3314 <heading>User-defined fields</heading>
3317 Additional user-defined fields may be added to the
3318 source package control file. Such fields will be
3319 ignored, and not copied to (for example) binary or
3320 source package control files or upload control files.
3324 If you wish to add additional unsupported fields to
3325 these output files you should use the mechanism
3330 Fields in the main source control information file with
3331 names starting <tt>X</tt>, followed by one or more of
3332 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3333 be copied to the output files. Only the part of the
3334 field name after the hyphen will be used in the output
3335 file. Where the letter <tt>B</tt> is used the field
3336 will appear in binary package control files, where the
3337 letter <tt>S</tt> is used in source package control
3338 files and where <tt>C</tt> is used in upload control
3339 (<tt>.changes</tt>) files.
3343 For example, if the main source information control file
3346 XBS-Comment: I stand between the candle and the star.
3348 then the binary and source package control files will contain the
3351 Comment: I stand between the candle and the star.
3360 <chapt id="maintainerscripts">
3361 <heading>Package maintainer scripts and installation procedure</heading>
3364 <heading>Introduction to package maintainer scripts</heading>
3367 It is possible to supply scripts as part of a package which
3368 the package management system will run for you when your
3369 package is installed, upgraded or removed.
3373 These scripts are the files <prgn>preinst</prgn>,
3374 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3375 <prgn>postrm</prgn> in the control area of the package.
3376 They must be proper executable files; if they are scripts
3377 (which is recommended), they must start with the usual
3378 <tt>#!</tt> convention. They should be readable and
3379 executable by anyone, and must not be world-writable.
3383 The package management system looks at the exit status from
3384 these scripts. It is important that they exit with a
3385 non-zero status if there is an error, so that the package
3386 management system can stop its processing. For shell
3387 scripts this means that you <em>almost always</em> need to
3388 use <tt>set -e</tt> (this is usually true when writing shell
3389 scripts, in fact). It is also important, of course, that
3390 they don't exit with a non-zero status if everything went
3395 Additionally, packages interacting with users using
3396 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3397 install a <prgn>config</prgn> script in the control area,
3398 see <ref id="maintscriptprompt"> for details.
3402 When a package is upgraded a combination of the scripts from
3403 the old and new packages is called during the upgrade
3404 procedure. If your scripts are going to be at all
3405 complicated you need to be aware of this, and may need to
3406 check the arguments to your scripts.
3410 Broadly speaking the <prgn>preinst</prgn> is called before
3411 (a particular version of) a package is installed, and the
3412 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3413 before (a version of) a package is removed and the
3414 <prgn>postrm</prgn> afterwards.
3418 Programs called from maintainer scripts should not normally
3419 have a path prepended to them. Before installation is
3420 started, the package management system checks to see if the
3421 programs <prgn>ldconfig</prgn>,
3422 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3423 and <prgn>update-rc.d</prgn> can be found via the
3424 <tt>PATH</tt> environment variable. Those programs, and any
3425 other program that one would expect to be in the
3426 <tt>PATH</tt>, should thus be invoked without an absolute
3427 pathname. Maintainer scripts should also not reset the
3428 <tt>PATH</tt>, though they might choose to modify it by
3429 prepending or appending package-specific directories. These
3430 considerations really apply to all shell scripts.</p>
3433 <sect id="idempotency">
3434 <heading>Maintainer scripts idempotency</heading>
3437 It is necessary for the error recovery procedures that the
3438 scripts be idempotent. This means that if it is run
3439 successfully, and then it is called again, it doesn't bomb
3440 out or cause any harm, but just ensures that everything is
3441 the way it ought to be. If the first call failed, or
3442 aborted half way through for some reason, the second call
3443 should merely do the things that were left undone the first
3444 time, if any, and exit with a success status if everything
3446 This is so that if an error occurs, the user interrupts
3447 <prgn>dpkg</prgn> or some other unforeseen circumstance
3448 happens you don't leave the user with a badly-broken
3449 package when <prgn>dpkg</prgn> attempts to repeat the
3455 <sect id="controllingterminal">
3456 <heading>Controlling terminal for maintainer scripts</heading>
3459 The maintainer scripts are guaranteed to run with a
3460 controlling terminal and can interact with the user.
3461 Because these scripts may be executed with standard output
3462 redirected into a pipe for logging purposes, Perl scripts
3463 should set unbuffered output by setting <tt>$|=1</tt> so
3464 that the output is printed immediately rather than being
3468 <sect id="exitstatus">
3469 <heading>Exit status</heading>
3472 Each script must return a zero exit status for
3473 success, or a nonzero one for failure, since the package
3474 management system looks for the exit status of these scripts
3475 and determines what action to take next based on that datum.
3479 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3484 <list compact="compact">
3486 <var>new-preinst</var> <tt>install</tt>
3489 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3492 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3495 <var>old-preinst</var> <tt>abort-upgrade</tt>
3496 <var>new-version</var>
3501 <list compact="compact">
3503 <var>postinst</var> <tt>configure</tt>
3504 <var>most-recently-configured-version</var>
3507 <var>old-postinst</var> <tt>abort-upgrade</tt>
3508 <var>new-version</var>
3511 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3512 <tt>in-favour</tt> <var>package</var>
3513 <var>new-version</var>
3516 <var>postinst</var> <tt>abort-remove</tt>
3519 <var>deconfigured's-postinst</var>
3520 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3521 <var>failed-install-package</var> <var>version</var>
3522 [<tt>removing</tt> <var>conflicting-package</var>
3528 <list compact="compact">
3530 <var>prerm</var> <tt>remove</tt>
3533 <var>old-prerm</var> <tt>upgrade</tt>
3534 <var>new-version</var>
3537 <var>new-prerm</var> <tt>failed-upgrade</tt>
3538 <var>old-version</var>
3541 <var>conflictor's-prerm</var> <tt>remove</tt>
3542 <tt>in-favour</tt> <var>package</var>
3543 <var>new-version</var>
3546 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3547 <tt>in-favour</tt> <var>package-being-installed</var>
3548 <var>version</var> [<tt>removing</tt>
3549 <var>conflicting-package</var>
3555 <list compact="compact">
3557 <var>postrm</var> <tt>remove</tt>
3560 <var>postrm</var> <tt>purge</tt>
3563 <var>old-postrm</var> <tt>upgrade</tt>
3564 <var>new-version</var>
3567 <var>new-postrm</var> <tt>failed-upgrade</tt>
3568 <var>old-version</var>
3571 <var>new-postrm</var> <tt>abort-install</tt>
3574 <var>new-postrm</var> <tt>abort-install</tt>
3575 <var>old-version</var>
3578 <var>new-postrm</var> <tt>abort-upgrade</tt>
3579 <var>old-version</var>
3582 <var>disappearer's-postrm</var> <tt>disappear</tt>
3583 <var>overwriter</var>
3584 <var>overwriter-version</var>
3590 <sect id="unpackphase">
3591 <heading>Details of unpack phase of installation or upgrade</heading>
3594 The procedure on installation/upgrade/overwrite/disappear
3595 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3596 stage of <tt>dpkg --install</tt>) is as follows. In each
3597 case, if a major error occurs (unless listed below) the
3598 actions are, in general, run backwards - this means that the
3599 maintainer scripts are run with different arguments in
3600 reverse order. These are the "error unwind" calls listed
3607 If a version of the package is already installed, call
3608 <example compact="compact">
3609 <var>old-prerm</var> upgrade <var>new-version</var>
3613 If the script runs but exits with a non-zero
3614 exit status, <prgn>dpkg</prgn> will attempt:
3615 <example compact="compact">
3616 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3618 If this works, the upgrade continues. If this
3619 does not work, the error unwind:
3620 <example compact="compact">
3621 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3623 If this works, then the old-version is
3624 "Installed", if not, the old version is in a
3625 "Failed-Config" state.
3631 If a "conflicting" package is being removed at the same time,
3632 or if any package will be broken (due to <tt>Breaks</tt>):
3635 If <tt>--auto-deconfigure</tt> is
3636 specified, call, for each package to be deconfigured
3637 due to <tt>Breaks</tt>:
3638 <example compact="compact">
3639 <var>deconfigured's-prerm</var> deconfigure \
3640 in-favour <var>package-being-installed</var> <var>version</var>
3643 <example compact="compact">
3644 <var>deconfigured's-postinst</var> abort-deconfigure \
3645 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3647 The deconfigured packages are marked as
3648 requiring configuration, so that if
3649 <tt>--install</tt> is used they will be
3650 configured again if possible.
3653 If any packages depended on a conflicting
3654 package being removed and <tt>--auto-deconfigure</tt> is
3655 specified, call, for each such package:
3656 <example compact="compact">
3657 <var>deconfigured's-prerm</var> deconfigure \
3658 in-favour <var>package-being-installed</var> <var>version</var> \
3659 removing <var>conflicting-package</var> <var>version</var>
3662 <example compact="compact">
3663 <var>deconfigured's-postinst</var> abort-deconfigure \
3664 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3665 removing <var>conflicting-package</var> <var>version</var>
3667 The deconfigured packages are marked as
3668 requiring configuration, so that if
3669 <tt>--install</tt> is used they will be
3670 configured again if possible.
3673 To prepare for removal of each conflicting package, call:
3674 <example compact="compact">
3675 <var>conflictor's-prerm</var> remove \
3676 in-favour <var>package</var> <var>new-version</var>
3679 <example compact="compact">
3680 <var>conflictor's-postinst</var> abort-remove \
3681 in-favour <var>package</var> <var>new-version</var>
3690 If the package is being upgraded, call:
3691 <example compact="compact">
3692 <var>new-preinst</var> upgrade <var>old-version</var>
3694 If this fails, we call:
3696 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3703 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3705 is called. If this works, then the old version
3706 is in an "Installed" state, or else it is left
3707 in an "Unpacked" state.
3712 If it fails, then the old version is left
3713 in an "Half-Installed" state.
3720 Otherwise, if the package had some configuration
3721 files from a previous version installed (i.e., it
3722 is in the "configuration files only" state):
3723 <example compact="compact">
3724 <var>new-preinst</var> install <var>old-version</var>
3728 <var>new-postrm</var> abort-install <var>old-version</var>
3730 If this fails, the package is left in a
3731 "Half-Installed" state, which requires a
3732 reinstall. If it works, the packages is left in
3733 a "Config Files" state.
3736 Otherwise (i.e., the package was completely purged):
3737 <example compact="compact">
3738 <var>new-preinst</var> install
3741 <example compact="compact">
3742 <var>new-postrm</var> abort-install
3744 If the error-unwind fails, the package is in a
3745 "Half Installed" phase, and requires a
3746 reinstall. If the error unwind works, the
3747 package is in a not installed state.
3754 The new package's files are unpacked, overwriting any
3755 that may be on the system already, for example any
3756 from the old version of the same package or from
3757 another package. Backups of the old files are kept
3758 temporarily, and if anything goes wrong the package
3759 management system will attempt to put them back as
3760 part of the error unwind.
3764 It is an error for a package to contain files which
3765 are on the system in another package, unless
3766 <tt>Replaces</tt> is used (see <ref id="replaces">).
3768 The following paragraph is not currently the case:
3769 Currently the <tt>- - force-overwrite</tt> flag is
3770 enabled, downgrading it to a warning, but this may not
3776 It is a more serious error for a package to contain a
3777 plain file or other kind of non-directory where another
3778 package has a directory (again, unless
3779 <tt>Replaces</tt> is used). This error can be
3780 overridden if desired using
3781 <tt>--force-overwrite-dir</tt>, but this is not
3786 Packages which overwrite each other's files produce
3787 behavior which, though deterministic, is hard for the
3788 system administrator to understand. It can easily
3789 lead to "missing" programs if, for example, a package
3790 is installed which overwrites a file from another
3791 package, and is then removed again.<footnote>
3792 Part of the problem is due to what is arguably a
3793 bug in <prgn>dpkg</prgn>.
3798 A directory will never be replaced by a symbolic link
3799 to a directory or vice versa; instead, the existing
3800 state (symlink or not) will be left alone and
3801 <prgn>dpkg</prgn> will follow the symlink if there is
3810 If the package is being upgraded, call
3811 <example compact="compact">
3812 <var>old-postrm</var> upgrade <var>new-version</var>
3816 If this fails, <prgn>dpkg</prgn> will attempt:
3817 <example compact="compact">
3818 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3820 If this works, installation continues. If not,
3822 <example compact="compact">
3823 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3825 If this fails, the old version is left in an
3826 "Half Installed" state. If it works, dpkg now
3828 <example compact="compact">
3829 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3831 If this fails, the old version is left in an
3832 "Half Installed" state. If it works, dpkg now
3834 <example compact="compact">
3835 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3837 If this fails, the old version is in an
3844 This is the point of no return - if
3845 <prgn>dpkg</prgn> gets this far, it won't back off
3846 past this point if an error occurs. This will
3847 leave the package in a fairly bad state, which
3848 will require a successful re-installation to clear
3849 up, but it's when <prgn>dpkg</prgn> starts doing
3850 things that are irreversible.
3855 Any files which were in the old version of the package
3856 but not in the new are removed.
3860 The new file list replaces the old.
3864 The new maintainer scripts replace the old.
3868 Any packages all of whose files have been overwritten
3869 during the installation, and which aren't required for
3870 dependencies, are considered to have been removed.
3871 For each such package
3874 <prgn>dpkg</prgn> calls:
3875 <example compact="compact">
3876 <var>disappearer's-postrm</var> disappear \
3877 <var>overwriter</var> <var>overwriter-version</var>
3881 The package's maintainer scripts are removed.
3884 It is noted in the status database as being in a
3885 sane state, namely not installed (any conffiles
3886 it may have are ignored, rather than being
3887 removed by <prgn>dpkg</prgn>). Note that
3888 disappearing packages do not have their prerm
3889 called, because <prgn>dpkg</prgn> doesn't know
3890 in advance that the package is going to
3897 Any files in the package we're unpacking that are also
3898 listed in the file lists of other packages are removed
3899 from those lists. (This will lobotomize the file list
3900 of the "conflicting" package if there is one.)
3904 The backup files made during installation, above, are
3910 The new package's status is now sane, and recorded as
3915 Here is another point of no return - if the
3916 conflicting package's removal fails we do not unwind
3917 the rest of the installation; the conflicting package
3918 is left in a half-removed limbo.
3923 If there was a conflicting package we go and do the
3924 removal actions (described below), starting with the
3925 removal of the conflicting package's files (any that
3926 are also in the package being installed have already
3927 been removed from the conflicting package's file list,
3928 and so do not get removed now).
3934 <sect id="configdetails"><heading>Details of configuration</heading>
3937 When we configure a package (this happens with <tt>dpkg
3938 --install</tt> and <tt>dpkg --configure</tt>), we first
3939 update any <tt>conffile</tt>s and then call:
3940 <example compact="compact">
3941 <var>postinst</var> configure <var>most-recently-configured-version</var>
3946 No attempt is made to unwind after errors during
3947 configuration. If the configuration fails, the package is in
3948 a "Failed Config" state, and an error message is generated.
3952 If there is no most recently configured version
3953 <prgn>dpkg</prgn> will pass a null argument.
3956 Historical note: Truly ancient (pre-1997) versions of
3957 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3958 (including the angle brackets) in this case. Even older
3959 ones did not pass a second argument at all, under any
3960 circumstance. Note that upgrades using such an old dpkg
3961 version are unlikely to work for other reasons, even if
3962 this old argument behavior is handled by your postinst script.
3968 <sect id="removedetails"><heading>Details of removal and/or
3969 configuration purging</heading>
3975 <example compact="compact">
3976 <var>prerm</var> remove
3980 If prerm fails during replacement due to conflict
3982 <var>conflictor's-postinst</var> abort-remove \
3983 in-favour <var>package</var> <var>new-version</var>
3987 <var>postinst</var> abort-remove
3991 If this fails, the package is in a "Failed-Config"
3992 state, or else it remains "Installed".
3996 The package's files are removed (except <tt>conffile</tt>s).
3999 <example compact="compact">
4000 <var>postrm</var> remove
4004 If it fails, there's no error unwind, and the package is in
4005 an "Half-Installed" state.
4010 All the maintainer scripts except the <prgn>postrm</prgn>
4015 If we aren't purging the package we stop here. Note
4016 that packages which have no <prgn>postrm</prgn> and no
4017 <tt>conffile</tt>s are automatically purged when
4018 removed, as there is no difference except for the
4019 <prgn>dpkg</prgn> status.
4023 The <tt>conffile</tt>s and any backup files
4024 (<tt>~</tt>-files, <tt>#*#</tt> files,
4025 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4030 <example compact="compact">
4031 <var>postrm</var> purge
4035 If this fails, the package remains in a "Config-Files"
4040 The package's file list is removed.
4049 <chapt id="relationships">
4050 <heading>Declaring relationships between packages</heading>
4052 <sect id="depsyntax">
4053 <heading>Syntax of relationship fields</heading>
4056 These fields all have a uniform syntax. They are a list of
4057 package names separated by commas.
4061 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4062 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4063 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4064 control file fields of the package, which declare
4065 dependencies on other packages, the package names listed may
4066 also include lists of alternative package names, separated
4067 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4068 if any one of the alternative packages is installed, that
4069 part of the dependency is considered to be satisfied.
4073 All of the fields except for <tt>Provides</tt> may restrict
4074 their applicability to particular versions of each named
4075 package. This is done in parentheses after each individual
4076 package name; the parentheses should contain a relation from
4077 the list below followed by a version number, in the format
4078 described in <ref id="f-Version">.
4082 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4083 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4084 strictly earlier, earlier or equal, exactly equal, later or
4085 equal and strictly later, respectively. The deprecated
4086 forms <tt><</tt> and <tt>></tt> were used to mean
4087 earlier/later or equal, rather than strictly earlier/later,
4088 so they should not appear in new packages (though
4089 <prgn>dpkg</prgn> still supports them).
4093 Whitespace may appear at any point in the version
4094 specification subject to the rules in <ref
4095 id="controlsyntax">, and must appear where it's necessary to
4096 disambiguate; it is not otherwise significant. All of the
4097 relationship fields may span multiple lines. For
4098 consistency and in case of future changes to
4099 <prgn>dpkg</prgn> it is recommended that a single space be
4100 used after a version relationship and before a version
4101 number; it is also conventional to put a single space after
4102 each comma, on either side of each vertical bar, and before
4103 each open parenthesis. When wrapping a relationship field, it
4104 is conventional to do so after a comma and before the space
4105 following that comma.
4109 For example, a list of dependencies might appear as:
4110 <example compact="compact">
4113 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4118 All fields that specify build-time relationships
4119 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4120 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4121 may be restricted to a certain set of architectures. This
4122 is indicated in brackets after each individual package name and
4123 the optional version specification. The brackets enclose a
4124 list of Debian architecture names separated by whitespace.
4125 Exclamation marks may be prepended to each of the names.
4126 (It is not permitted for some names to be prepended with
4127 exclamation marks while others aren't.) If the current Debian
4128 host architecture is not in this list and there are no
4129 exclamation marks in the list, or it is in the list with a
4130 prepended exclamation mark, the package name and the
4131 associated version specification are ignored completely for
4132 the purposes of defining the relationships.
4137 <example compact="compact">
4139 Build-Depends-Indep: texinfo
4140 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4141 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4146 Note that the binary package relationship fields such as
4147 <tt>Depends</tt> appear in one of the binary package
4148 sections of the control file, whereas the build-time
4149 relationships such as <tt>Build-Depends</tt> appear in the
4150 source package section of the control file (which is the
4155 <sect id="binarydeps">
4156 <heading>Binary Dependencies - <tt>Depends</tt>,
4157 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4158 <tt>Pre-Depends</tt>
4162 Packages can declare in their control file that they have
4163 certain relationships to other packages - for example, that
4164 they may not be installed at the same time as certain other
4165 packages, and/or that they depend on the presence of others.
4169 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4170 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4171 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4175 These seven fields are used to declare a dependency
4176 relationship by one package on another. Except for
4177 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4178 depending (binary) package's control file.
4179 (<tt>Enhances</tt> appears in the recommending package's
4180 control file, and <tt>Breaks</tt> appears in the version of
4181 depended-on package which causes the named package to
4186 A <tt>Depends</tt> field takes effect <em>only</em> when a
4187 package is to be configured. It does not prevent a package
4188 being on the system in an unconfigured state while its
4189 dependencies are unsatisfied, and it is possible to replace
4190 a package whose dependencies are satisfied and which is
4191 properly installed with a different version whose
4192 dependencies are not and cannot be satisfied; when this is
4193 done the depending package will be left unconfigured (since
4194 attempts to configure it will give errors) and will not
4195 function properly. If it is necessary, a
4196 <tt>Pre-Depends</tt> field can be used, which has a partial
4197 effect even when a package is being unpacked, as explained
4198 in detail below. (The other three dependency fields,
4199 <tt>Recommends</tt>, <tt>Suggests</tt> and
4200 <tt>Enhances</tt>, are only used by the various front-ends
4201 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4202 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4206 For this reason packages in an installation run are usually
4207 all unpacked first and all configured later; this gives
4208 later versions of packages with dependencies on later
4209 versions of other packages the opportunity to have their
4210 dependencies satisfied.
4214 In case of circular dependencies, since installation or
4215 removal order honoring the dependency order can't be
4216 established, dependency loops are broken at some point
4217 (based on rules below), and some packages may not be able to
4218 rely on their dependencies being present when being
4219 installed or removed, depending on which side of the break
4220 of the circular dependency loop they happen to be on. If one
4221 of the packages in the loop has no postinst script, then the
4222 cycle will be broken at that package, so as to ensure that
4223 all postinst scripts run with the dependencies properly
4224 configured if this is possible. Otherwise the breaking point
4229 The <tt>Depends</tt> field thus allows package maintainers
4230 to impose an order in which packages should be configured.
4234 The meaning of the five dependency fields is as follows:
4236 <tag><tt>Depends</tt></tag>
4239 This declares an absolute dependency. A package will
4240 not be configured unless all of the packages listed in
4241 its <tt>Depends</tt> field have been correctly
4246 The <tt>Depends</tt> field should be used if the
4247 depended-on package is required for the depending
4248 package to provide a significant amount of
4253 The <tt>Depends</tt> field should also be used if the
4254 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4255 <prgn>postrm</prgn> scripts require the package to be
4256 present in order to run. Note, however, that the
4257 <prgn>postrm</prgn> cannot rely on any non-essential
4258 packages to be present during the <tt>purge</tt>
4262 <tag><tt>Recommends</tt></tag>
4265 This declares a strong, but not absolute, dependency.
4269 The <tt>Recommends</tt> field should list packages
4270 that would be found together with this one in all but
4271 unusual installations.
4275 <tag><tt>Suggests</tt></tag>
4277 This is used to declare that one package may be more
4278 useful with one or more others. Using this field
4279 tells the packaging system and the user that the
4280 listed packages are related to this one and can
4281 perhaps enhance its usefulness, but that installing
4282 this one without them is perfectly reasonable.
4285 <tag><tt>Enhances</tt></tag>
4287 This field is similar to Suggests but works in the
4288 opposite direction. It is used to declare that a
4289 package can enhance the functionality of another
4293 <tag><tt>Pre-Depends</tt></tag>
4296 This field is like <tt>Depends</tt>, except that it
4297 also forces <prgn>dpkg</prgn> to complete installation
4298 of the packages named before even starting the
4299 installation of the package which declares the
4300 pre-dependency, as follows:
4304 When a package declaring a pre-dependency is about to
4305 be <em>unpacked</em> the pre-dependency can be
4306 satisfied if the depended-on package is either fully
4307 configured, <em>or even if</em> the depended-on
4308 package(s) are only unpacked or half-configured,
4309 provided that they have been configured correctly at
4310 some point in the past (and not removed or partially
4311 removed since). In this case, both the
4312 previously-configured and currently unpacked or
4313 half-configured versions must satisfy any version
4314 clause in the <tt>Pre-Depends</tt> field.
4318 When the package declaring a pre-dependency is about
4319 to be <em>configured</em>, the pre-dependency will be
4320 treated as a normal <tt>Depends</tt>, that is, it will
4321 be considered satisfied only if the depended-on
4322 package has been correctly configured.
4326 <tt>Pre-Depends</tt> should be used sparingly,
4327 preferably only by packages whose premature upgrade or
4328 installation would hamper the ability of the system to
4329 continue with any upgrade that might be in progress.
4333 <tt>Pre-Depends</tt> are also required if the
4334 <prgn>preinst</prgn> script depends on the named
4335 package. It is best to avoid this situation if
4343 When selecting which level of dependency to use you should
4344 consider how important the depended-on package is to the
4345 functionality of the one declaring the dependency. Some
4346 packages are composed of components of varying degrees of
4347 importance. Such a package should list using
4348 <tt>Depends</tt> the package(s) which are required by the
4349 more important components. The other components'
4350 requirements may be mentioned as Suggestions or
4351 Recommendations, as appropriate to the components' relative
4357 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4360 Using <tt>Breaks</tt> may cause problems for upgrades from older
4361 versions of Debian and should not be used until the stable
4362 release of Debian supports <tt>Breaks</tt>.
4366 When one binary package declares that it breaks another,
4367 <prgn>dpkg</prgn> will refuse to allow the package which
4368 declares <tt>Breaks</tt> be installed unless the broken
4369 package is deconfigured first, and it will refuse to
4370 allow the broken package to be reconfigured.
4374 A package will not be regarded as causing breakage merely
4375 because its configuration files are still installed; it must
4376 be at least half-installed.
4380 A special exception is made for packages which declare that
4381 they break their own package name or a virtual package which
4382 they provide (see below): this does not count as a real
4387 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4388 version clause; such a <tt>Breaks</tt> is introduced in the
4389 version of an (implicit or explicit) dependency which
4390 violates an assumption or reveals a bug in earlier versions
4391 of the broken package. This use of <tt>Breaks</tt> will
4392 inform higher-level package management tools that broken
4393 package must be upgraded before the new one.
4397 If the breaking package also overwrites some files from the
4398 older package, it should use <tt>Replaces</tt> (not
4399 <tt>Conflicts</tt>) to ensure this goes smoothly.
4403 <sect id="conflicts">
4404 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4407 When one binary package declares a conflict with another
4408 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4409 refuse to allow them to be installed on the system at the
4414 If one package is to be installed, the other must be removed
4415 first - if the package being installed is marked as
4416 replacing (see <ref id="replaces">) the one on the system,
4417 or the one on the system is marked as deselected, or both
4418 packages are marked <tt>Essential</tt>, then
4419 <prgn>dpkg</prgn> will automatically remove the package
4420 which is causing the conflict, otherwise it will halt the
4421 installation of the new package with an error. This
4422 mechanism is specifically designed to produce an error when
4423 the installed package is <tt>Essential</tt>, but the new
4428 A package will not cause a conflict merely because its
4429 configuration files are still installed; it must be at least
4434 A special exception is made for packages which declare a
4435 conflict with their own package name, or with a virtual
4436 package which they provide (see below): this does not
4437 prevent their installation, and allows a package to conflict
4438 with others providing a replacement for it. You use this
4439 feature when you want the package in question to be the only
4440 package providing some feature.
4444 A <tt>Conflicts</tt> entry should almost never have an
4445 "earlier than" version clause. This would prevent
4446 <prgn>dpkg</prgn> from upgrading or installing the package
4447 which declared such a conflict until the upgrade or removal
4448 of the conflicted-with package had been completed. Instead,
4449 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4450 by the stable release of Debian).
4454 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4458 As well as the names of actual ("concrete") packages, the
4459 package relationship fields <tt>Depends</tt>,
4460 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4461 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4462 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4463 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4464 may mention "virtual packages".
4468 A <em>virtual package</em> is one which appears in the
4469 <tt>Provides</tt> control file field of another package.
4470 The effect is as if the package(s) which provide a
4471 particular virtual package name had been listed by name
4472 everywhere the virtual package name appears. (See also <ref
4477 If there are both concrete and virtual packages of the same
4478 name, then the dependency may be satisfied (or the conflict
4479 caused) by either the concrete package with the name in
4480 question or any other concrete package which provides the
4481 virtual package with the name in question. This is so that,
4482 for example, supposing we have
4483 <example compact="compact">
4486 </example> and someone else releases an enhanced version of
4487 the <tt>bar</tt> package they can say:
4488 <example compact="compact">
4492 and the <tt>bar-plus</tt> package will now also satisfy the
4493 dependency for the <tt>foo</tt> package.
4497 If a relationship field has a version number attached
4498 then only real packages will be considered to see whether
4499 the relationship is satisfied (or the prohibition violated,
4500 for a conflict or breakage) - it is assumed that a real
4501 package which provides the virtual package is not of the
4502 "right" version. So, a <tt>Provides</tt> field may not
4503 contain version numbers, and the version number of the
4504 concrete package which provides a particular virtual package
4505 will not be looked at when considering a dependency on or
4506 conflict with the virtual package name.
4510 It is likely that the ability will be added in a future
4511 release of <prgn>dpkg</prgn> to specify a version number for
4512 each virtual package it provides. This feature is not yet
4513 present, however, and is expected to be used only
4518 If you want to specify which of a set of real packages
4519 should be the default to satisfy a particular dependency on
4520 a virtual package, you should list the real package as an
4521 alternative before the virtual one.
4526 <sect id="replaces"><heading>Overwriting files and replacing
4527 packages - <tt>Replaces</tt></heading>
4530 Packages can declare in their control file that they should
4531 overwrite files in certain other packages, or completely
4532 replace other packages. The <tt>Replaces</tt> control file
4533 field has these two distinct purposes.
4536 <sect1><heading>Overwriting files in other packages</heading>
4539 Firstly, as mentioned before, it is usually an error for a
4540 package to contain files which are on the system in
4545 However, if the overwriting package declares that it
4546 <tt>Replaces</tt> the one containing the file being
4547 overwritten, then <prgn>dpkg</prgn> will replace the file
4548 from the old package with that from the new. The file
4549 will no longer be listed as "owned" by the old package.
4553 If a package is completely replaced in this way, so that
4554 <prgn>dpkg</prgn> does not know of any files it still
4555 contains, it is considered to have "disappeared". It will
4556 be marked as not wanted on the system (selected for
4557 removal) and not installed. Any <tt>conffile</tt>s
4558 details noted for the package will be ignored, as they
4559 will have been taken over by the overwriting package. The
4560 package's <prgn>postrm</prgn> script will be run with a
4561 special argument to allow the package to do any final
4562 cleanup required. See <ref id="mscriptsinstact">.
4565 Replaces is a one way relationship -- you have to
4566 install the replacing package after the replaced
4573 For this usage of <tt>Replaces</tt>, virtual packages (see
4574 <ref id="virtual">) are not considered when looking at a
4575 <tt>Replaces</tt> field - the packages declared as being
4576 replaced must be mentioned by their real names.
4580 Furthermore, this usage of <tt>Replaces</tt> only takes
4581 effect when both packages are at least partially on the
4582 system at once, so that it can only happen if they do not
4583 conflict or if the conflict has been overridden.
4588 <sect1><heading>Replacing whole packages, forcing their
4592 Secondly, <tt>Replaces</tt> allows the packaging system to
4593 resolve which package should be removed when there is a
4594 conflict - see <ref id="conflicts">. This usage only
4595 takes effect when the two packages <em>do</em> conflict,
4596 so that the two usages of this field do not interfere with
4601 In this situation, the package declared as being replaced
4602 can be a virtual package, so for example, all mail
4603 transport agents (MTAs) would have the following fields in
4604 their control files:
4605 <example compact="compact">
4606 Provides: mail-transport-agent
4607 Conflicts: mail-transport-agent
4608 Replaces: mail-transport-agent
4610 ensuring that only one MTA can be installed at any one
4615 <sect id="sourcebinarydeps">
4616 <heading>Relationships between source and binary packages -
4617 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4618 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4622 Source packages that require certain binary packages to be
4623 installed or absent at the time of building the package
4624 can declare relationships to those binary packages.
4628 This is done using the <tt>Build-Depends</tt>,
4629 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4630 <tt>Build-Conflicts-Indep</tt> control file fields.
4634 Build-dependencies on "build-essential" binary packages can be
4635 omitted. Please see <ref id="pkg-relations"> for more information.
4639 The dependencies and conflicts they define must be satisfied
4640 (as defined earlier for binary packages) in order to invoke
4641 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4643 If you make "build-arch" or "binary-arch", you need
4644 Build-Depends. If you make "build-indep" or
4645 "binary-indep", you need Build-Depends and
4646 Build-Depends-Indep. If you make "build" or "binary",
4650 There is no Build-Depends-Arch; this role is essentially
4651 met with Build-Depends. Anyone building the
4652 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4653 is basically assumed to be building the whole package
4654 anyway and so installs all build dependencies. The
4655 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4656 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4657 does not yet know how to check for its existence) and
4658 <tt>binary-arch</tt>.
4661 The purpose of the original split, I recall, was so that
4662 the autobuilders wouldn't need to install extra packages
4663 needed only for the binary-indep targets. But without a
4664 build-arch/build-indep split, this didn't work, since
4665 most of the work is done in the build target, not in the
4671 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4673 The <tt>Build-Depends</tt> and
4674 <tt>Build-Conflicts</tt> fields must be satisfied when
4675 any of the following targets is invoked:
4676 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4677 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4678 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4680 <tag><tt>Build-Depends-Indep</tt>,
4681 <tt>Build-Conflicts-Indep</tt></tag>
4683 The <tt>Build-Depends-Indep</tt> and
4684 <tt>Build-Conflicts-Indep</tt> fields must be
4685 satisfied when any of the following targets is
4686 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4687 <tt>binary</tt> and <tt>binary-indep</tt>.
4697 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4700 Packages containing shared libraries must be constructed with
4701 a little care to make sure that the shared library is always
4702 available. This is especially important for packages whose
4703 shared libraries are vitally important, such as the C library
4704 (currently <tt>libc6</tt>).
4708 Packages involving shared libraries should be split up into
4709 several binary packages. This section mostly deals with how
4710 this separation is to be accomplished; rules for files within
4711 the shared library packages are in <ref id="libraries"> instead.
4714 <sect id="sharedlibs-runtime">
4715 <heading>Run-time shared libraries</heading>
4718 The run-time shared library needs to be placed in a package
4719 whose name changes whenever the shared object version
4722 Since it is common place to install several versions of a
4723 package that just provides shared libraries, it is a
4724 good idea that the library package should not
4725 contain any extraneous non-versioned files, unless they
4726 happen to be in versioned directories.</p>
4728 The most common mechanism is to place it in a package
4730 <package><var>libraryname</var><var>soversion</var></package>,
4731 where <file><var>soversion</var></file> is the version number
4732 in the soname of the shared library<footnote>
4733 The soname is the shared object name: it's the thing
4734 that has to match exactly between building an executable
4735 and running it for the dynamic linker to be able run the
4736 program. For example, if the soname of the library is
4737 <file>libfoo.so.6</file>, the library package would be
4738 called <file>libfoo6</file>.
4740 Alternatively, if it would be confusing to directly append
4741 <var>soversion</var> to <var>libraryname</var> (e.g. because
4742 <var>libraryname</var> itself ends in a number), you may use
4743 <package><var>libraryname</var>-<var>soversion</var></package> and
4744 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4749 If you have several shared libraries built from the same
4750 source tree you may lump them all together into a single
4751 shared library package, provided that you change all of
4752 their sonames at once (so that you don't get filename
4753 clashes if you try to install different versions of the
4754 combined shared libraries package).
4758 The package should install the shared libraries under
4759 their normal names. For example, the <package>libgdbm3</package>
4760 package should install <file>libgdbm.so.3.0.0</file> as
4761 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4762 renamed or re-linked by any <prgn>prerm</prgn> or
4763 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4764 of renaming things safely without affecting running programs,
4765 and attempts to interfere with this are likely to lead to
4770 Shared libraries should not be installed executable, since
4771 the dynamic linker does not require this and trying to
4772 execute a shared library usually results in a core dump.
4776 The run-time library package should include the symbolic link that
4777 <prgn>ldconfig</prgn> would create for the shared libraries.
4778 For example, the <package>libgdbm3</package> package should include
4779 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4780 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4781 linker (for example <prgn>ld.so</prgn> or
4782 <prgn>ld-linux.so.*</prgn>) can find the library between the
4783 time that <prgn>dpkg</prgn> installs it and the time that
4784 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4786 The package management system requires the library to be
4787 placed before the symbolic link pointing to it in the
4788 <file>.deb</file> file. This is so that when
4789 <prgn>dpkg</prgn> comes to install the symlink
4790 (overwriting the previous symlink pointing at an older
4791 version of the library), the new shared library is already
4792 in place. In the past, this was achieved by creating the
4793 library in the temporary packaging directory before
4794 creating the symlink. Unfortunately, this was not always
4795 effective, since the building of the tar file in the
4796 <file>.deb</file> depended on the behavior of the underlying
4797 file system. Some file systems (such as reiserfs) reorder
4798 the files so that the order of creation is forgotten.
4799 Since version 1.7.0, <prgn>dpkg</prgn>
4800 reorders the files itself as necessary when building a
4801 package. Thus it is no longer important to concern
4802 oneself with the order of file creation.
4806 <sect1 id="ldconfig">
4807 <heading><tt>ldconfig</tt></heading>
4810 Any package installing shared libraries in one of the default
4811 library directories of the dynamic linker (which are currently
4812 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4813 listed in <file>/etc/ld.so.conf</file><footnote>
4815 <list compact="compact">
4816 <item>/usr/local/lib</item>
4817 <item>/usr/lib/libc5-compat</item>
4818 <item>/lib/libc5-compat</item>
4821 must use <prgn>ldconfig</prgn> to update the shared library
4826 The package maintainer scripts must only call
4827 <prgn>ldconfig</prgn> under these circumstances:
4828 <list compact="compact">
4829 <item>When the <prgn>postinst</prgn> script is run with a
4830 first argument of <tt>configure</tt>, the script must call
4831 <prgn>ldconfig</prgn>, and may optionally invoke
4832 <prgn>ldconfig</prgn> at other times.
4834 <item>When the <prgn>postrm</prgn> script is run with a
4835 first argument of <tt>remove</tt>, the script should call
4836 <prgn>ldconfig</prgn>.
4841 During install or upgrade, the preinst is called before
4842 the new files are installed, so calling "ldconfig" is
4843 pointless. The preinst of an existing package can also be
4844 called if an upgrade fails. However, this happens during
4845 the critical time when a shared libs may exist on-disk
4846 under a temporary name. Thus, it is dangerous and
4847 forbidden by current policy to call "ldconfig" at this
4852 When a package is installed or upgraded, "postinst
4853 configure" runs after the new files are safely on-disk.
4854 Since it is perfectly safe to invoke ldconfig
4855 unconditionally in a postinst, it is OK for a package to
4856 simply put ldconfig in its postinst without checking the
4857 argument. The postinst can also be called to recover from
4858 a failed upgrade. This happens before any new files are
4859 unpacked, so there is no reason to call "ldconfig" at this
4864 For a package that is being removed, prerm is
4865 called with all the files intact, so calling ldconfig is
4866 useless. The other calls to "prerm" happen in the case of
4867 upgrade at a time when all the files of the old package
4868 are on-disk, so again calling "ldconfig" is pointless.
4872 postrm, on the other hand, is called with the "remove"
4873 argument just after the files are removed, so this is
4874 the proper time to call "ldconfig" to notify the system
4875 of the fact that the shared libraries from the package
4876 are removed. The postrm can be called at several other
4877 times. At the time of "postrm purge", "postrm
4878 abort-install", or "postrm abort-upgrade", calling
4879 "ldconfig" is useless because the shared lib files are
4880 not on-disk. However, when "postrm" is invoked with
4881 arguments "upgrade", "failed-upgrade", or "disappear", a
4882 shared lib may exist on-disk under a temporary filename.
4890 <sect id="sharedlibs-support-files">
4891 <heading>Shared library support files</heading>
4894 If your package contains files whose names do not change with
4895 each change in the library shared object version, you must not
4896 put them in the shared library package. Otherwise, several
4897 versions of the shared library cannot be installed at the same
4898 time without filename clashes, making upgrades and transitions
4899 unnecessarily difficult.
4903 It is recommended that supporting files and run-time support
4904 programs that do not need to be invoked manually by users, but
4905 are nevertheless required for the package to function, be placed
4906 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
4907 preferably under <file>/usr/lib/</file><var>package-name</var>.
4908 If the program or file is architecture independent, the
4909 recommendation is for it to be placed in a subdirectory of
4910 <file>/usr/share</file> instead, preferably under
4911 <file>/usr/share/</file><var>package-name</var>. Following the
4912 <var>package-name</var> naming convention ensures that the file
4913 names change when the shared object version changes.
4917 Run-time support programs that use the shared library but are
4918 not required for the library to function or files used by the
4919 shared library that can be used by any version of the shared
4920 library package should instead be put in a separate package.
4921 This package might typically be named
4922 <package><var>libraryname</var>-tools</package>; note the
4923 absence of the <var>soversion</var> in the package name.
4927 Files and support programs only useful when compiling software
4928 against the library should be included in the development
4929 package for the library.<footnote>
4930 For example, a <file><var>package-name</var>-config</file>
4931 script or <package>pkg-config</package> configuration files.
4936 <sect id="sharedlibs-static">
4937 <heading>Static libraries</heading>
4940 The static library (<file><var>libraryname.a</var></file>)
4941 is usually provided in addition to the shared version.
4942 It is placed into the development package (see below).
4946 In some cases, it is acceptable for a library to be
4947 available in static form only; these cases include:
4949 <item>libraries for languages whose shared library support
4950 is immature or unstable</item>
4951 <item>libraries whose interfaces are in flux or under
4952 development (commonly the case when the library's
4953 major version number is zero, or where the ABI breaks
4954 across patchlevels)</item>
4955 <item>libraries which are explicitly intended to be
4956 available only in static form by their upstream
4961 <sect id="sharedlibs-dev">
4962 <heading>Development files</heading>
4965 The development files associated to a shared library need to be
4966 placed in a package called
4967 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4968 or if you prefer only to support one development version at a
4969 time, <package><var>libraryname</var>-dev</package>.
4973 In case several development versions of a library exist, you may
4974 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4975 <ref id="conflicts">) to ensure that the user only installs one
4976 development version at a time (as different development versions are
4977 likely to have the same header files in them, which would cause a
4978 filename clash if both were installed).
4982 The development package should contain a symlink for the associated
4983 shared library without a version number. For example, the
4984 <package>libgdbm-dev</package> package should include a symlink
4985 from <file>/usr/lib/libgdbm.so</file> to
4986 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4987 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4988 <file>libgdbm.so</file> when compiling dynamically.
4992 <sect id="sharedlibs-intradeps">
4993 <heading>Dependencies between the packages of the same library</heading>
4996 Typically the development version should have an exact
4997 version dependency on the runtime library, to make sure that
4998 compilation and linking happens correctly. The
4999 <tt>${binary:Version}</tt> substitution variable can be
5000 useful for this purpose.
5002 Previously, <tt>${Source-Version}</tt> was used, but its name
5003 was confusing and it has been deprecated since dpkg 1.13.19.
5008 <sect id="sharedlibs-shlibdeps">
5009 <heading>Dependencies between the library and other packages -
5010 the <tt>shlibs</tt> system</heading>
5013 If a package contains a binary or library which links to a
5014 shared library, we must ensure that when the package is
5015 installed on the system, all of the libraries needed are
5016 also installed. This requirement led to the creation of the
5017 <tt>shlibs</tt> system, which is very simple in its design:
5018 any package which <em>provides</em> a shared library also
5019 provides information on the package dependencies required to
5020 ensure the presence of this library, and any package which
5021 <em>uses</em> a shared library uses this information to
5022 determine the dependencies it requires. The files which
5023 contain the mapping from shared libraries to the necessary
5024 dependency information are called <file>shlibs</file> files.
5028 Thus, when a package is built which contains any shared
5029 libraries, it must provide a <file>shlibs</file> file for other
5030 packages to use, and when a package is built which contains
5031 any shared libraries or compiled binaries, it must run
5032 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5033 on these to determine the libraries used and hence the
5034 dependencies needed by this package.<footnote>
5036 In the past, the shared libraries linked to were
5037 determined by calling <prgn>ldd</prgn>, but now
5038 <prgn>objdump</prgn> is used to do this. The only
5039 change this makes to package building is that
5040 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5041 libraries, whereas in the past this was unnecessary.
5042 The rest of this footnote explains the advantage that
5047 We say that a binary <tt>foo</tt> <em>directly</em> uses
5048 a library <tt>libbar</tt> if it is explicitly linked
5049 with that library (that is, it uses the flag
5050 <tt>-lbar</tt> during the linking stage). Other
5051 libraries that are needed by <tt>libbar</tt> are linked
5052 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5053 linker will load them automatically when it loads
5054 <tt>libbar</tt>. A package should depend on
5055 the libraries it directly uses, and the dependencies for
5056 those libraries should automatically pull in the other
5061 Unfortunately, the <prgn>ldd</prgn> program shows both
5062 the directly and indirectly used libraries, meaning that
5063 the dependencies determined included both direct and
5064 indirect dependencies. The use of <prgn>objdump</prgn>
5065 avoids this problem by determining only the directly
5070 A good example of where this helps is the following. We
5071 could update <tt>libimlib</tt> with a new version that
5072 supports a new graphics format called dgf (but retaining
5073 the same major version number). If we used the old
5074 <prgn>ldd</prgn> method, every package that uses
5075 <tt>libimlib</tt> would need to be recompiled so it
5076 would also depend on <tt>libdgf</tt> or it wouldn't run
5077 due to missing symbols. However with the new system,
5078 packages using <tt>libimlib</tt> can rely on
5079 <tt>libimlib</tt> itself having the dependency on
5080 <tt>libdgf</tt> and so they would not need rebuilding.
5086 In the following sections, we will first describe where the
5087 various <tt>shlibs</tt> files are to be found, then how to
5088 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5089 file format and how to create them if your package contains a
5094 <heading>The <tt>shlibs</tt> files present on the system</heading>
5097 There are several places where <tt>shlibs</tt> files are
5098 found. The following list gives them in the order in which
5100 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5101 (The first one which gives the required information is used.)
5107 <p><file>debian/shlibs.local</file></p>
5110 This lists overrides for this package. Its use is
5111 described below (see <ref id="shlibslocal">).
5116 <p><file>/etc/dpkg/shlibs.override</file></p>
5119 This lists global overrides. This list is normally
5120 empty. It is maintained by the local system
5126 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5129 When packages are being built, any
5130 <file>debian/shlibs</file> files are copied into the
5131 control file area of the temporary build directory and
5132 given the name <file>shlibs</file>. These files give
5133 details of any shared libraries included in the
5135 An example may help here. Let us say that the
5136 source package <tt>foo</tt> generates two binary
5137 packages, <tt>libfoo2</tt> and
5138 <tt>foo-runtime</tt>. When building the binary
5139 packages, the two packages are created in the
5140 directories <file>debian/libfoo2</file> and
5141 <file>debian/foo-runtime</file> respectively.
5142 (<file>debian/tmp</file> could be used instead of one
5143 of these.) Since <tt>libfoo2</tt> provides the
5144 <tt>libfoo</tt> shared library, it will require a
5145 <tt>shlibs</tt> file, which will be installed in
5146 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5148 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5149 when <prgn>dpkg-shlibdeps</prgn> is run on the
5151 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5153 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5154 determine whether <tt>foo-prog</tt>'s library
5155 dependencies are satisfied by any of the libraries
5156 provided by <tt>libfoo2</tt>. For this reason,
5157 <prgn>dpkg-shlibdeps</prgn> must only be run once
5158 all of the individual binary packages'
5159 <tt>shlibs</tt> files have been installed into the
5166 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5169 These are the <file>shlibs</file> files corresponding to
5170 all of the packages installed on the system, and are
5171 maintained by the relevant package maintainers.
5176 <p><file>/etc/dpkg/shlibs.default</file></p>
5179 This file lists any shared libraries whose packages
5180 have failed to provide correct <file>shlibs</file> files.
5181 It was used when the <file>shlibs</file> setup was first
5182 introduced, but it is now normally empty. It is
5183 maintained by the <tt>dpkg</tt> maintainer.
5191 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5192 <file>shlibs</file> files</heading>
5196 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5197 into your <file>debian/rules</file> file. If your package
5198 contains only compiled binaries and libraries (but no scripts),
5199 you can use a command such as:
5200 <example compact="compact">
5201 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5202 debian/tmp/usr/lib/*
5204 Otherwise, you will need to explicitly list the compiled
5205 binaries and libraries.<footnote>
5206 If you are using <tt>debhelper</tt>, the
5207 <prgn>dh_shlibdeps</prgn> program will do this work for
5208 you. It will also correctly handle multi-binary
5214 This command puts the dependency information into the
5215 <file>debian/substvars</file> file, which is then used by
5216 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5217 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5218 field in the control file for this to work.
5222 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5223 done. If it does complain you might need to create your own
5224 <file>debian/shlibs.local</file> file, as explained below (see
5225 <ref id="shlibslocal">).
5229 If you have multiple binary packages, you will need to call
5230 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5231 compiled libraries or binaries. In such a case, you will
5232 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5233 utilities to specify a different <file>substvars</file> file.
5237 If you are creating a udeb for use in the Debian Installer, you
5238 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5239 the dependency line of type <tt>udeb</tt> by adding
5240 <tt>-tudeb</tt> as option<footnote>
5241 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5242 will automatically add this option if it knows it is
5244 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5245 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5246 fall back to the regular dependency line.
5250 For more details on dpkg-shlibdeps, please see
5251 <ref id="pkg-dpkg-shlibdeps"> and
5252 <manref name="dpkg-shlibdeps" section="1">.
5257 <heading>The <file>shlibs</file> File Format</heading>
5260 Each <file>shlibs</file> file has the same format. Lines
5261 beginning with <tt>#</tt> are considered to be comments and
5262 are ignored. Each line is of the form:
5263 <example compact="compact">
5264 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5269 We will explain this by reference to the example of the
5270 <tt>zlib1g</tt> package, which (at the time of writing)
5271 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5275 <var>type</var> is an optional element that indicates the type
5276 of package for which the line is valid. The only type currently
5277 in use is <tt>udeb</tt>. The colon and space after the type are
5282 <var>library-name</var> is the name of the shared library,
5283 in this case <tt>libz</tt>. (This must match the name part
5284 of the soname, see below.)
5288 <var>soname-version</var> is the version part of the soname of
5289 the library. The soname is the thing that must exactly match
5290 for the library to be recognized by the dynamic linker, and is
5292 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5293 example, <tt>libz.so.1</tt>.<footnote>
5294 This can be determined using the command
5295 <example compact="compact">
5296 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5299 The version part is the part which comes after
5300 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5304 <var>dependencies</var> has the same syntax as a dependency
5305 field in a binary package control file. It should give
5306 details of which packages are required to satisfy a binary
5307 built against the version of the library contained in the
5308 package. See <ref id="depsyntax"> for details.
5312 In our example, if the first version of the <tt>zlib1g</tt>
5313 package which contained a minor number of at least
5314 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5315 <tt>shlibs</tt> entry for this library could say:
5316 <example compact="compact">
5317 libz 1 zlib1g (>= 1:1.1.3)
5319 The version-specific dependency is to avoid warnings from
5320 the dynamic linker about using older shared libraries with
5325 As zlib1g also provides a udeb containing the shared library,
5326 there would also be a second line:
5327 <example compact="compact">
5328 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5334 <heading>Providing a <file>shlibs</file> file</heading>
5337 If your package provides a shared library, you need to create
5338 a <file>shlibs</file> file following the format described above.
5339 It is usual to call this file <file>debian/shlibs</file> (but if
5340 you have multiple binary packages, you might want to call it
5341 <file>debian/shlibs.<var>package</var></file> instead). Then
5342 let <file>debian/rules</file> install it in the control area:
5343 <example compact="compact">
5344 install -m644 debian/shlibs debian/tmp/DEBIAN
5346 or, in the case of a multi-binary package:
5347 <example compact="compact">
5348 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5350 An alternative way of doing this is to create the
5351 <file>shlibs</file> file in the control area directly from
5352 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5353 file at all,<footnote>
5354 This is what <prgn>dh_makeshlibs</prgn> in the
5355 <tt>debhelper</tt> suite does. If your package also has a udeb
5356 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5357 automatically generate the <tt>udeb:</tt> lines if you specify
5358 the name of the udeb with the <tt>--add-udeb</tt> option.
5360 since the <file>debian/shlibs</file> file itself is ignored by
5361 <prgn>dpkg-shlibdeps</prgn>.
5365 As <prgn>dpkg-shlibdeps</prgn> reads the
5366 <file>DEBIAN/shlibs</file> files in all of the binary packages
5367 being built from this source package, all of the
5368 <file>DEBIAN/shlibs</file> files should be installed before
5369 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5374 <sect1 id="shlibslocal">
5375 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5378 This file is intended only as a <em>temporary</em> fix if
5379 your binaries or libraries depend on a library whose package
5380 does not yet provide a correct <file>shlibs</file> file.
5384 We will assume that you are trying to package a binary
5385 <tt>foo</tt>. When you try running
5386 <prgn>dpkg-shlibdeps</prgn> you get the following error
5387 message (<tt>-O</tt> displays the dependency information on
5388 <tt>stdout</tt> instead of writing it to
5389 <tt>debian/substvars</tt>, and the lines have been wrapped
5390 for ease of reading):
5391 <example compact="compact">
5392 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5393 dpkg-shlibdeps: warning: unable to find dependency
5394 information for shared library libbar (soname 1,
5395 path /usr/lib/libbar.so.1, dependency field Depends)
5396 shlibs:Depends=libc6 (>= 2.2.2-2)
5398 You can then run <prgn>ldd</prgn> on the binary to find the
5399 full location of the library concerned:
5400 <example compact="compact">
5402 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5403 libc.so.6 => /lib/libc.so.6 (0x40032000)
5404 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5406 So the <prgn>foo</prgn> binary depends on the
5407 <prgn>libbar</prgn> shared library, but no package seems to
5408 provide a <file>*.shlibs</file> file handling
5409 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5410 determine the package responsible:
5411 <example compact="compact">
5412 $ dpkg -S /usr/lib/libbar.so.1
5413 bar1: /usr/lib/libbar.so.1
5414 $ dpkg -s bar1 | grep Version
5417 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5418 is the one we are using. Now we can file a bug against the
5419 <tt>bar1</tt> package and create our own
5420 <file>debian/shlibs.local</file> to locally fix the problem.
5421 Including the following line into your
5422 <file>debian/shlibs.local</file> file:
5423 <example compact="compact">
5424 libbar 1 bar1 (>= 1.0-1)
5426 should allow the package build to work.
5430 As soon as the maintainer of <tt>bar1</tt> provides a
5431 correct <file>shlibs</file> file, you should remove this line
5432 from your <file>debian/shlibs.local</file> file. (You should
5433 probably also then have a versioned <tt>Build-Depends</tt>
5434 on <tt>bar1</tt> to help ensure that others do not have the
5435 same problem building your package.)
5444 <chapt id="opersys"><heading>The Operating System</heading>
5447 <heading>File system hierarchy</heading>
5451 <heading>File system Structure</heading>
5454 The location of all installed files and directories must
5455 comply with the File system Hierarchy Standard (FHS),
5456 version 2.3, with the exceptions noted below, and except
5457 where doing so would violate other terms of Debian
5458 Policy. The following exceptions to the FHS apply:
5463 Legacy XFree86 servers are permitted to retain the
5464 configuration file location
5465 <file>/etc/X11/XF86Config-4</file>.
5470 The optional rules related to user specific
5471 configuration files for applications are stored in
5472 the user's home directory are relaxed. It is
5473 recommended that such files start with the
5474 '<tt>.</tt>' character (a "dot file"), and if an
5475 application needs to create more than one dot file
5476 then the preferred placement is in a subdirectory
5477 with a name starting with a '.' character, (a "dot
5478 directory"). In this case it is recommended the
5479 configuration files not start with the '.'
5485 The requirement for amd64 to use <file>/lib64</file>
5486 for 64 bit binaries is removed.
5491 The requirement that
5492 <file>/usr/local/share/man</file> be "synonymous"
5493 with <file>/usr/local/man</file> is relaxed to a
5498 The requirement that windowmanagers with a single
5499 configuration file call it <file>system.*wmrc</file>
5500 is removed, as is the restriction that the window
5501 manager subdirectory be named identically to the
5502 window manager name itself.
5507 The requirement that boot manager configuration
5508 files live in <file>/etc</file>, or at least are
5509 symlinked there, is relaxed to a recommendation.
5516 The version of this document referred here can be
5517 found in the <tt>debian-policy</tt> package or on <url
5518 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5519 name="FHS (Debian copy)"> alongside this manual (or, if
5520 you have the <package>debian-policy</package> installed,
5522 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5523 (local copy)">). The
5524 latest version, which may be a more recent version, may
5526 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5527 Specific questions about following the standard may be
5528 asked on the <tt>debian-devel</tt> mailing list, or
5529 referred to the FHS mailing list (see the
5530 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5536 <heading>Site-specific programs</heading>
5539 As mandated by the FHS, packages must not place any
5540 files in <file>/usr/local</file>, either by putting them in
5541 the file system archive to be unpacked by <prgn>dpkg</prgn>
5542 or by manipulating them in their maintainer scripts.
5546 However, the package may create empty directories below
5547 <file>/usr/local</file> so that the system administrator knows
5548 where to place site-specific files. These are not
5549 directories <em>in</em> <file>/usr/local</file>, but are
5550 children of directories in <file>/usr/local</file>. These
5551 directories (<file>/usr/local/*/dir/</file>)
5552 should be removed on package removal if they are
5557 Note, that this applies only to directories <em>below</em>
5558 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5559 Packages must not create sub-directories in the directory
5560 <file>/usr/local</file> itself, except those listed in FHS,
5561 section 4.5. However, you may create directories below
5562 them as you wish. You must not remove any of the
5563 directories listed in 4.5, even if you created them.
5567 Since <file>/usr/local</file> can be mounted read-only from a
5568 remote server, these directories must be created and
5569 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5570 maintainer scripts and not be included in the
5571 <file>.deb</file> archive. These scripts must not fail if
5572 either of these operations fail.
5576 For example, the <tt>emacsen-common</tt> package could
5577 contain something like
5578 <example compact="compact">
5579 if [ ! -e /usr/local/share/emacs ]
5581 if mkdir /usr/local/share/emacs 2>/dev/null
5583 chown root:staff /usr/local/share/emacs
5584 chmod 2775 /usr/local/share/emacs
5588 in its <prgn>postinst</prgn> script, and
5589 <example compact="compact">
5590 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5591 rmdir /usr/local/share/emacs 2>/dev/null || true
5593 in the <prgn>prerm</prgn> script. (Note that this form is
5594 used to ensure that if the script is interrupted, the
5595 directory <file>/usr/local/share/emacs</file> will still be
5600 If you do create a directory in <file>/usr/local</file> for
5601 local additions to a package, you should ensure that
5602 settings in <file>/usr/local</file> take precedence over the
5603 equivalents in <file>/usr</file>.
5607 However, because <file>/usr/local</file> and its contents are
5608 for exclusive use of the local administrator, a package
5609 must not rely on the presence or absence of files or
5610 directories in <file>/usr/local</file> for normal operation.
5614 The <file>/usr/local</file> directory itself and all the
5615 subdirectories created by the package should (by default) have
5616 permissions 2775 (group-writable and set-group-id) and be
5617 owned by <tt>root:staff</tt>.
5622 <heading>The system-wide mail directory</heading>
5624 The system-wide mail directory is <file>/var/mail</file>. This
5625 directory is part of the base system and should not owned
5626 by any particular mail agents. The use of the old
5627 location <file>/var/spool/mail</file> is deprecated, even
5628 though the spool may still be physically located there.
5629 To maintain partial upgrade compatibility for systems
5630 which have <file>/var/spool/mail</file> as their physical mail
5631 spool, packages using <file>/var/mail</file> must depend on
5632 either <package>libc6</package> (>= 2.1.3-13), or on
5633 <package>base-files</package> (>= 2.2.0), or on later
5634 versions of either one of these packages.
5640 <heading>Users and groups</heading>
5643 <heading>Introduction</heading>
5645 The Debian system can be configured to use either plain or
5650 Some user ids (UIDs) and group ids (GIDs) are reserved
5651 globally for use by certain packages. Because some
5652 packages need to include files which are owned by these
5653 users or groups, or need the ids compiled into binaries,
5654 these ids must be used on any Debian system only for the
5655 purpose for which they are allocated. This is a serious
5656 restriction, and we should avoid getting in the way of
5657 local administration policies. In particular, many sites
5658 allocate users and/or local system groups starting at 100.
5662 Apart from this we should have dynamically allocated ids,
5663 which should by default be arranged in some sensible
5664 order, but the behavior should be configurable.
5668 Packages other than <tt>base-passwd</tt> must not modify
5669 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5670 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5675 <heading>UID and GID classes</heading>
5677 The UID and GID numbers are divided into classes as
5683 Globally allocated by the Debian project, the same
5684 on every Debian system. These ids will appear in
5685 the <file>passwd</file> and <file>group</file> files of all
5686 Debian systems, new ids in this range being added
5687 automatically as the <tt>base-passwd</tt> package is
5692 Packages which need a single statically allocated
5693 uid or gid should use one of these; their
5694 maintainers should ask the <tt>base-passwd</tt>
5702 Dynamically allocated system users and groups.
5703 Packages which need a user or group, but can have
5704 this user or group allocated dynamically and
5705 differently on each system, should use <tt>adduser
5706 --system</tt> to create the group and/or user.
5707 <prgn>adduser</prgn> will check for the existence of
5708 the user or group, and if necessary choose an unused
5709 id based on the ranges specified in
5710 <file>adduser.conf</file>.
5714 <tag>1000-29999:</tag>
5717 Dynamically allocated user accounts. By default
5718 <prgn>adduser</prgn> will choose UIDs and GIDs for
5719 user accounts in this range, though
5720 <file>adduser.conf</file> may be used to modify this
5725 <tag>30000-59999:</tag>
5730 <tag>60000-64999:</tag>
5733 Globally allocated by the Debian project, but only
5734 created on demand. The ids are allocated centrally
5735 and statically, but the actual accounts are only
5736 created on users' systems on demand.
5740 These ids are for packages which are obscure or
5741 which require many statically-allocated ids. These
5742 packages should check for and create the accounts in
5743 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5744 <prgn>adduser</prgn> if it has this facility) if
5745 necessary. Packages which are likely to require
5746 further allocations should have a "hole" left after
5747 them in the allocation, to give them room to
5752 <tag>65000-65533:</tag>
5760 User <tt>nobody</tt>. The corresponding gid refers
5761 to the group <tt>nogroup</tt>.
5768 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5769 not</em> be used, because it is the error return
5778 <sect id="sysvinit">
5779 <heading>System run levels and <file>init.d</file> scripts</heading>
5781 <sect1 id="/etc/init.d">
5782 <heading>Introduction</heading>
5785 The <file>/etc/init.d</file> directory contains the scripts
5786 executed by <prgn>init</prgn> at boot time and when the
5787 init state (or "runlevel") is changed (see <manref
5788 name="init" section="8">).
5792 There are at least two different, yet functionally
5793 equivalent, ways of handling these scripts. For the sake
5794 of simplicity, this document describes only the symbolic
5795 link method. However, it must not be assumed by maintainer
5796 scripts that this method is being used, and any automated
5797 manipulation of the various runlevel behaviors by
5798 maintainer scripts must be performed using
5799 <prgn>update-rc.d</prgn> as described below and not by
5800 manually installing or removing symlinks. For information
5801 on the implementation details of the other method,
5802 implemented in the <tt>file-rc</tt> package, please refer
5803 to the documentation of that package.
5807 These scripts are referenced by symbolic links in the
5808 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5809 runlevels, <prgn>init</prgn> looks in the directory
5810 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5811 execute, where <tt><var>n</var></tt> is the runlevel that
5812 is being changed to, or <tt>S</tt> for the boot-up
5817 The names of the links all have the form
5818 <file>S<var>mm</var><var>script</var></file> or
5819 <file>K<var>mm</var><var>script</var></file> where
5820 <var>mm</var> is a two-digit number and <var>script</var>
5821 is the name of the script (this should be the same as the
5822 name of the actual script in <file>/etc/init.d</file>).
5826 When <prgn>init</prgn> changes runlevel first the targets
5827 of the links whose names start with a <tt>K</tt> are
5828 executed, each with the single argument <tt>stop</tt>,
5829 followed by the scripts prefixed with an <tt>S</tt>, each
5830 with the single argument <tt>start</tt>. (The links are
5831 those in the <file>/etc/rc<var>n</var>.d</file> directory
5832 corresponding to the new runlevel.) The <tt>K</tt> links
5833 are responsible for killing services and the <tt>S</tt>
5834 link for starting services upon entering the runlevel.
5838 For example, if we are changing from runlevel 2 to
5839 runlevel 3, init will first execute all of the <tt>K</tt>
5840 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5841 all of the <tt>S</tt> prefixed scripts in that directory.
5842 The links starting with <tt>K</tt> will cause the
5843 referred-to file to be executed with an argument of
5844 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5849 The two-digit number <var>mm</var> is used to determine
5850 the order in which to run the scripts: low-numbered links
5851 have their scripts run first. For example, the
5852 <tt>K20</tt> scripts will be executed before the
5853 <tt>K30</tt> scripts. This is used when a certain service
5854 must be started before another. For example, the name
5855 server <prgn>bind</prgn> might need to be started before
5856 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5857 can set up its access lists. In this case, the script
5858 that starts <prgn>bind</prgn> would have a lower number
5859 than the script that starts <prgn>inn</prgn> so that it
5861 <example compact="compact">
5868 The two runlevels 0 (halt) and 6 (reboot) are slightly
5869 different. In these runlevels, the links with an
5870 <tt>S</tt> prefix are still called after those with a
5871 <tt>K</tt> prefix, but they too are called with the single
5872 argument <tt>stop</tt>.
5876 Also, if the script name ends in <tt>.sh</tt>, the script
5877 will be sourced in runlevel <tt>S</tt> rather than being
5878 run in a forked subprocess, but will be explicitly run by
5879 <prgn>sh</prgn> in all other runlevels.
5884 <heading>Writing the scripts</heading>
5887 Packages that include daemons for system services should
5888 place scripts in <file>/etc/init.d</file> to start or stop
5889 services at boot time or during a change of runlevel.
5890 These scripts should be named
5891 <file>/etc/init.d/<var>package</var></file>, and they should
5892 accept one argument, saying what to do:
5895 <tag><tt>start</tt></tag>
5896 <item>start the service,</item>
5898 <tag><tt>stop</tt></tag>
5899 <item>stop the service,</item>
5901 <tag><tt>restart</tt></tag>
5902 <item>stop and restart the service if it's already running,
5903 otherwise start the service</item>
5905 <tag><tt>reload</tt></tag>
5906 <item><p>cause the configuration of the service to be
5907 reloaded without actually stopping and restarting
5910 <tag><tt>force-reload</tt></tag>
5911 <item>cause the configuration to be reloaded if the
5912 service supports this, otherwise restart the
5916 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5917 <tt>force-reload</tt> options should be supported by all
5918 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5923 The <file>init.d</file> scripts must ensure that they will
5924 behave sensibly (i.e., returning success and not starting
5925 multiple copies of a service) if invoked with <tt>start</tt>
5926 when the service is already running, or with <tt>stop</tt>
5927 when it isn't, and that they don't kill unfortunately-named
5928 user processes. The best way to achieve this is usually to
5929 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
5934 If a service reloads its configuration automatically (as
5935 in the case of <prgn>cron</prgn>, for example), the
5936 <tt>reload</tt> option of the <file>init.d</file> script
5937 should behave as if the configuration has been reloaded
5942 The <file>/etc/init.d</file> scripts must be treated as
5943 configuration files, either (if they are present in the
5944 package, that is, in the .deb file) by marking them as
5945 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5946 by managing them correctly in the maintainer scripts (see
5947 <ref id="config-files">). This is important since we want
5948 to give the local system administrator the chance to adapt
5949 the scripts to the local system, e.g., to disable a
5950 service without de-installing the package, or to specify
5951 some special command line options when starting a service,
5952 while making sure their changes aren't lost during the next
5957 These scripts should not fail obscurely when the
5958 configuration files remain but the package has been
5959 removed, as configuration files remain on the system after
5960 the package has been removed. Only when <prgn>dpkg</prgn>
5961 is executed with the <tt>--purge</tt> option will
5962 configuration files be removed. In particular, as the
5963 <file>/etc/init.d/<var>package</var></file> script itself is
5964 usually a <tt>conffile</tt>, it will remain on the system
5965 if the package is removed but not purged. Therefore, you
5966 should include a <tt>test</tt> statement at the top of the
5968 <example compact="compact">
5969 test -f <var>program-executed-later-in-script</var> || exit 0
5974 Often there are some variables in the <file>init.d</file>
5975 scripts whose values control the behavior of the scripts,
5976 and which a system administrator is likely to want to
5977 change. As the scripts themselves are frequently
5978 <tt>conffile</tt>s, modifying them requires that the
5979 administrator merge in their changes each time the package
5980 is upgraded and the <tt>conffile</tt> changes. To ease
5981 the burden on the system administrator, such configurable
5982 values should not be placed directly in the script.
5983 Instead, they should be placed in a file in
5984 <file>/etc/default</file>, which typically will have the same
5985 base name as the <file>init.d</file> script. This extra file
5986 should be sourced by the script when the script runs. It
5987 must contain only variable settings and comments in SUSv3
5988 <prgn>sh</prgn> format. It may either be a
5989 <tt>conffile</tt> or a configuration file maintained by
5990 the package maintainer scripts. See <ref id="config-files">
5995 To ensure that vital configurable values are always
5996 available, the <file>init.d</file> script should set default
5997 values for each of the shell variables it uses, either
5998 before sourcing the <file>/etc/default/</file> file or
5999 afterwards using something like the <tt>:
6000 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6001 script must behave sensibly and not fail if the
6002 <file>/etc/default</file> file is deleted.
6007 <heading>Interfacing with the initscript system</heading>
6010 Maintainers should use the abstraction layer provided by
6011 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6012 programs to deal with initscripts in their packages'
6013 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6014 and <prgn>postrm</prgn>.
6018 Directly managing the /etc/rc?.d links and directly
6019 invoking the <file>/etc/init.d/</file> initscripts should
6020 be done only by packages providing the initscript
6021 subsystem (such as <prgn>sysv-rc</prgn> and
6022 <prgn>file-rc</prgn>).
6026 <heading>Managing the links</heading>
6029 The program <prgn>update-rc.d</prgn> is provided for
6030 package maintainers to arrange for the proper creation and
6031 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6032 or their functional equivalent if another method is being
6033 used. This may be used by maintainers in their packages'
6034 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6038 You must not include any <file>/etc/rc<var>n</var>.d</file>
6039 symbolic links in the actual archive or manually create or
6040 remove the symbolic links in maintainer scripts; you must
6041 use the <prgn>update-rc.d</prgn> program instead. (The
6042 former will fail if an alternative method of maintaining
6043 runlevel information is being used.) You must not include
6044 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6045 in the archive either. (Only the <tt>sysvinit</tt>
6050 By default <prgn>update-rc.d</prgn> will start services in
6051 each of the multi-user state runlevels (2, 3, 4, and 5)
6052 and stop them in the halt runlevel (0), the single-user
6053 runlevel (1) and the reboot runlevel (6). The system
6054 administrator will have the opportunity to customize
6055 runlevels by simply adding, moving, or removing the
6056 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6057 symbolic links are being used, or by modifying
6058 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6063 To get the default behavior for your package, put in your
6064 <prgn>postinst</prgn> script
6065 <example compact="compact">
6066 update-rc.d <var>package</var> defaults
6068 and in your <prgn>postrm</prgn>
6069 <example compact="compact">
6070 if [ "$1" = purge ]; then
6071 update-rc.d <var>package</var> remove
6073 </example>. Note that if your package changes runlevels
6074 or priority, you may have to remove and recreate the links,
6075 since otherwise the old links may persist. Refer to the
6076 documentation of <prgn>update-rc.d</prgn>.
6080 This will use a default sequence number of 20. If it does
6081 not matter when or in which order the <file>init.d</file>
6082 script is run, use this default. If it does, then you
6083 should talk to the maintainer of the <prgn>sysvinit</prgn>
6084 package or post to <tt>debian-devel</tt>, and they will
6085 help you choose a number.
6089 For more information about using <tt>update-rc.d</tt>,
6090 please consult its man page <manref name="update-rc.d"
6096 <heading>Running initscripts</heading>
6098 The program <prgn>invoke-rc.d</prgn> is provided to make
6099 it easier for package maintainers to properly invoke an
6100 initscript, obeying runlevel and other locally-defined
6101 constraints that might limit a package's right to start,
6102 stop and otherwise manage services. This program may be
6103 used by maintainers in their packages' scripts.
6107 The package maintainer scripts must use
6108 <prgn>invoke-rc.d</prgn> to invoke the
6109 <file>/etc/init.d/*</file> initscripts, instead of
6110 calling them directly.
6114 By default, <prgn>invoke-rc.d</prgn> will pass any
6115 action requests (start, stop, reload, restart...) to the
6116 <file>/etc/init.d</file> script, filtering out requests
6117 to start or restart a service out of its intended
6122 Most packages will simply need to change:
6123 <example compact="compact">/etc/init.d/<package>
6124 <action></example> in their <prgn>postinst</prgn>
6125 and <prgn>prerm</prgn> scripts to:
6126 <example compact="compact">
6127 if which invoke-rc.d >/dev/null 2>&1; then
6128 invoke-rc.d <var>package</var> <action>
6130 /etc/init.d/<var>package</var> <action>
6136 A package should register its initscript services using
6137 <prgn>update-rc.d</prgn> before it tries to invoke them
6138 using <prgn>invoke-rc.d</prgn>. Invocation of
6139 unregistered services may fail.
6143 For more information about using
6144 <prgn>invoke-rc.d</prgn>, please consult its man page
6145 <manref name="invoke-rc.d" section="8">.
6151 <heading>Boot-time initialization</heading>
6154 There used to be another directory, <file>/etc/rc.boot</file>,
6155 which contained scripts which were run once per machine
6156 boot. This has been deprecated in favour of links from
6157 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6158 described in <ref id="/etc/init.d">. Packages must not
6159 place files in <file>/etc/rc.boot</file>.
6164 <heading>Example</heading>
6167 An example on which you can base your
6168 <file>/etc/init.d</file> scripts is found in
6169 <file>/etc/init.d/skeleton</file>.
6176 <heading>Console messages from <file>init.d</file> scripts</heading>
6179 This section describes the formats to be used for messages
6180 written to standard output by the <file>/etc/init.d</file>
6181 scripts. The intent is to improve the consistency of
6182 Debian's startup and shutdown look and feel. For this
6183 reason, please look very carefully at the details. We want
6184 the messages to have the same format in terms of wording,
6185 spaces, punctuation and case of letters.
6189 Here is a list of overall rules that should be used for
6190 messages generated by <file>/etc/init.d</file> scripts.
6196 The message should fit in one line (fewer than 80
6197 characters), start with a capital letter and end with
6198 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6202 If the script is performing some time consuming task in
6203 the background (not merely starting or stopping a
6204 program, for instance), an ellipsis (three dots:
6205 <tt>...</tt>) should be output to the screen, with no
6206 leading or tailing whitespace or line feeds.
6210 The messages should appear as if the computer is telling
6211 the user what it is doing (politely :-), but should not
6212 mention "it" directly. For example, instead of:
6213 <example compact="compact">
6214 I'm starting network daemons: nfsd mountd.
6216 the message should say
6217 <example compact="compact">
6218 Starting network daemons: nfsd mountd.
6225 <tt>init.d</tt> script should use the following standard
6226 message formats for the situations enumerated below.
6232 <p>When daemons are started</p>
6235 If the script starts one or more daemons, the output
6236 should look like this (a single line, no leading
6238 <example compact="compact">
6239 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6241 The <var>description</var> should describe the
6242 subsystem the daemon or set of daemons are part of,
6243 while <var>daemon-1</var> up to <var>daemon-n</var>
6244 denote each daemon's name (typically the file name of
6249 For example, the output of <file>/etc/init.d/lpd</file>
6251 <example compact="compact">
6252 Starting printer spooler: lpd.
6257 This can be achieved by saying
6258 <example compact="compact">
6259 echo -n "Starting printer spooler: lpd"
6260 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6263 in the script. If there are more than one daemon to
6264 start, the output should look like this:
6265 <example compact="compact">
6266 echo -n "Starting remote file system services:"
6267 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6268 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6269 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6272 This makes it possible for the user to see what is
6273 happening and when the final daemon has been started.
6274 Care should be taken in the placement of white spaces:
6275 in the example above the system administrators can
6276 easily comment out a line if they don't want to start
6277 a specific daemon, while the displayed message still
6283 <p>When a system parameter is being set</p>
6286 If you have to set up different system parameters
6287 during the system boot, you should use this format:
6288 <example compact="compact">
6289 Setting <var>parameter</var> to "<var>value</var>".
6294 You can use a statement such as the following to get
6296 <example compact="compact">
6297 echo "Setting DNS domainname to \"$domainname\"."
6302 Note that the same symbol (<tt>"</tt>) is used for the left
6303 and right quotation marks. A grave accent (<tt>`</tt>) is
6304 not a quote character; neither is an apostrophe
6310 <p>When a daemon is stopped or restarted</p>
6313 When you stop or restart a daemon, you should issue a
6314 message identical to the startup message, except that
6315 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6316 or <tt>Restarting</tt> respectively.
6320 For example, stopping the printer daemon will look like
6322 <example compact="compact">
6323 Stopping printer spooler: lpd.
6329 <p>When something is executed</p>
6332 There are several examples where you have to run a
6333 program at system startup or shutdown to perform a
6334 specific task, for example, setting the system's clock
6335 using <prgn>netdate</prgn> or killing all processes
6336 when the system shuts down. Your message should look
6338 <example compact="compact">
6339 Doing something very useful...done.
6341 You should print the <tt>done.</tt> immediately after
6342 the job has been completed, so that the user is
6343 informed why they have to wait. You can get this
6345 <example compact="compact">
6346 echo -n "Doing something very useful..."
6355 <p>When the configuration is reloaded</p>
6358 When a daemon is forced to reload its configuration
6359 files you should use the following format:
6360 <example compact="compact">
6361 Reloading <var>description</var> configuration...done.
6363 where <var>description</var> is the same as in the
6364 daemon starting message.
6372 <heading>Cron jobs</heading>
6375 Packages must not modify the configuration file
6376 <file>/etc/crontab</file>, and they must not modify the files in
6377 <file>/var/spool/cron/crontabs</file>.</p>
6380 If a package wants to install a job that has to be executed
6381 via cron, it should place a file with the name of the
6382 package in one or more of the following directories:
6383 <example compact="compact">
6389 As these directory names imply, the files within them are
6390 executed on an hourly, daily, weekly, or monthly basis,
6391 respectively. The exact times are listed in
6392 <file>/etc/crontab</file>.</p>
6395 All files installed in any of these directories must be
6396 scripts (e.g., shell scripts or Perl scripts) so that they
6397 can easily be modified by the local system administrator.
6398 In addition, they must be treated as configuration files.
6402 If a certain job has to be executed at some other frequency or
6403 at a specific time, the package should install a file
6404 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6405 same syntax as <file>/etc/crontab</file> and is processed by
6406 <prgn>cron</prgn> automatically. The file must also be
6407 treated as a configuration file. (Note that entries in the
6408 <file>/etc/cron.d</file> directory are not handled by
6409 <prgn>anacron</prgn>. Thus, you should only use this
6410 directory for jobs which may be skipped if the system is not
6414 The scripts or crontab entries in these directories should
6415 check if all necessary programs are installed before they
6416 try to execute them. Otherwise, problems will arise when a
6417 package was removed but not purged since configuration files
6418 are kept on the system in this situation.</p>
6422 <heading>Menus</heading>
6425 The Debian <tt>menu</tt> package provides a standard
6426 interface between packages providing applications and
6427 <em>menu programs</em> (either X window managers or
6428 text-based menu programs such as <prgn>pdmenu</prgn>).
6432 All packages that provide applications that need not be
6433 passed any special command line arguments for normal
6434 operation should register a menu entry for those
6435 applications, so that users of the <tt>menu</tt> package
6436 will automatically get menu entries in their window
6437 managers, as well in shells like <tt>pdmenu</tt>.
6441 Menu entries should follow the current menu policy.
6445 The menu policy can be found in the <tt>menu-policy</tt>
6446 files in the <tt>debian-policy</tt> package.
6447 It is also available from the Debian web mirrors at
6448 <tt><url name="/doc/packaging-manuals/menu-policy/"
6449 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6453 Please also refer to the <em>Debian Menu System</em>
6454 documentation that comes with the <package>menu</package>
6455 package for information about how to register your
6461 <heading>Multimedia handlers</heading>
6464 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6465 is a mechanism for encoding files and data streams and
6466 providing meta-information about them, in particular their
6467 type (e.g. audio or video) and format (e.g. PNG, HTML,
6472 Registration of MIME type handlers allows programs like mail
6473 user agents and web browsers to invoke these handlers to
6474 view, edit or display MIME types they don't support directly.
6478 Packages which provide the ability to view/show/play,
6479 compose, edit or print MIME types should register themselves
6480 as such following the current MIME support policy.
6484 The MIME support policy can be found in the <tt>mime-policy</tt>
6485 files in the <tt>debian-policy</tt> package.
6486 It is also available from the Debian web mirrors at
6487 <tt><url name="/doc/packaging-manuals/mime-policy/"
6488 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6494 <heading>Keyboard configuration</heading>
6497 To achieve a consistent keyboard configuration so that all
6498 applications interpret a keyboard event the same way, all
6499 programs in the Debian distribution must be configured to
6500 comply with the following guidelines.
6504 The following keys must have the specified interpretations:
6507 <tag><tt><--</tt></tag>
6508 <item>delete the character to the left of the cursor</item>
6510 <tag><tt>Delete</tt></tag>
6511 <item>delete the character to the right of the cursor</item>
6513 <tag><tt>Control+H</tt></tag>
6514 <item>emacs: the help prefix</item>
6517 The interpretation of any keyboard events should be
6518 independent of the terminal that is used, be it a virtual
6519 console, an X terminal emulator, an rlogin/telnet session,
6524 The following list explains how the different programs
6525 should be set up to achieve this:
6531 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6535 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6539 X translations are set up to make
6540 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6541 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6542 is the vt220 escape code for the "delete character"
6543 key). This must be done by loading the X resources
6544 using <prgn>xrdb</prgn> on all local X displays, not
6545 using the application defaults, so that the
6546 translation resources used correspond to the
6547 <prgn>xmodmap</prgn> settings.
6551 The Linux console is configured to make
6552 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6553 generate <tt>ESC [ 3 ~</tt>.
6557 X applications are configured so that <tt><</tt>
6558 deletes left, and <tt>Delete</tt> deletes right. Motif
6559 applications already work like this.
6563 Terminals should have <tt>stty erase ^?</tt> .
6567 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6568 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6569 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6573 Emacs is programmed to map <tt>KB_Backspace</tt> or
6574 the <tt>stty erase</tt> character to
6575 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6576 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6577 <tt>^H</tt> to <tt>help</tt> as always.
6581 Other applications use the <tt>stty erase</tt>
6582 character and <tt>kdch1</tt> for the two delete keys,
6583 with ASCII DEL being "delete previous character" and
6584 <tt>kdch1</tt> being "delete character under
6592 This will solve the problem except for the following
6599 Some terminals have a <tt><--</tt> key that cannot
6600 be made to produce anything except <tt>^H</tt>. On
6601 these terminals Emacs help will be unavailable on
6602 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6603 character takes precedence in Emacs, and has been set
6604 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6605 available) can be used instead.
6609 Some operating systems use <tt>^H</tt> for <tt>stty
6610 erase</tt>. However, modern telnet versions and all
6611 rlogin versions propagate <tt>stty</tt> settings, and
6612 almost all UNIX versions honour <tt>stty erase</tt>.
6613 Where the <tt>stty</tt> settings are not propagated
6614 correctly, things can be made to work by using
6615 <tt>stty</tt> manually.
6619 Some systems (including previous Debian versions) use
6620 <prgn>xmodmap</prgn> to arrange for both
6621 <tt><--</tt> and <tt>Delete</tt> to generate
6622 <tt>KB_Delete</tt>. We can change the behavior of
6623 their X clients using the same X resources that we use
6624 to do it for our own clients, or configure our clients
6625 using their resources when things are the other way
6626 around. On displays configured like this
6627 <tt>Delete</tt> will not work, but <tt><--</tt>
6632 Some operating systems have different <tt>kdch1</tt>
6633 settings in their <tt>terminfo</tt> database for
6634 <tt>xterm</tt> and others. On these systems the
6635 <tt>Delete</tt> key will not work correctly when you
6636 log in from a system conforming to our policy, but
6637 <tt><--</tt> will.
6644 <heading>Environment variables</heading>
6647 A program must not depend on environment variables to get
6648 reasonable defaults. (That's because these environment
6649 variables would have to be set in a system-wide
6650 configuration file like <file>/etc/profile</file>, which is not
6651 supported by all shells.)
6655 If a program usually depends on environment variables for its
6656 configuration, the program should be changed to fall back to
6657 a reasonable default configuration if these environment
6658 variables are not present. If this cannot be done easily
6659 (e.g., if the source code of a non-free program is not
6660 available), the program must be replaced by a small
6661 "wrapper" shell script which sets the environment variables
6662 if they are not already defined, and calls the original program.
6666 Here is an example of a wrapper script for this purpose:
6668 <example compact="compact">
6670 BAR=${BAR:-/var/lib/fubar}
6672 exec /usr/lib/foo/foo "$@"
6677 Furthermore, as <file>/etc/profile</file> is a configuration
6678 file of the <prgn>base-files</prgn> package, other packages must
6679 not put any environment variables or other commands into that
6684 <sect id="doc-base">
6685 <heading>Registering Documents using doc-base</heading>
6688 The <package>doc-base</package> package implements a
6689 flexible mechanism for handling and presenting
6690 documentation. The recommended practice is for every Debian
6691 package that provides online documentation (other than just
6692 manual pages) to register these documents with
6693 <package>doc-base</package> by installing a
6694 <package>doc-base</package> control file via the
6695 <prgn/install-docs/ script at installation time and
6696 de-register the manuals again when the package is removed.
6699 Please refer to the documentation that comes with the
6700 <package>doc-base</package> package for information and
6709 <heading>Files</heading>
6712 <heading>Binaries</heading>
6715 Two different packages must not install programs with
6716 different functionality but with the same filenames. (The
6717 case of two programs having the same functionality but
6718 different implementations is handled via "alternatives" or
6719 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6720 <ref id="conflicts"> respectively.) If this case happens,
6721 one of the programs must be renamed. The maintainers should
6722 report this to the <tt>debian-devel</tt> mailing list and
6723 try to find a consensus about which program will have to be
6724 renamed. If a consensus cannot be reached, <em>both</em>
6725 programs must be renamed.
6729 By default, when a package is being built, any binaries
6730 created should include debugging information, as well as
6731 being compiled with optimization. You should also turn on
6732 as many reasonable compilation warnings as possible; this
6733 makes life easier for porters, who can then look at build
6734 logs for possible problems. For the C programming language,
6735 this means the following compilation parameters should be
6737 <example compact="compact">
6739 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6741 INSTALL = install -s # (or use strip on the files in debian/tmp)
6746 Note that by default all installed binaries should be stripped,
6747 either by using the <tt>-s</tt> flag to
6748 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6749 the binaries after they have been copied into
6750 <file>debian/tmp</file> but before the tree is made into a
6755 Although binaries in the build tree should be compiled with
6756 debugging information by default, it can often be difficult to
6757 debug programs if they are also subjected to compiler
6758 optimization. For this reason, it is recommended to support the
6759 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6760 (see <ref id="debianrules-options">). This variable can contain
6761 several flags to change how a package is compiled and built.
6765 It is up to the package maintainer to decide what
6766 compilation options are best for the package. Certain
6767 binaries (such as computationally-intensive programs) will
6768 function better with certain flags (<tt>-O3</tt>, for
6769 example); feel free to use them. Please use good judgment
6770 here. Don't use flags for the sake of it; only use them
6771 if there is good reason to do so. Feel free to override
6772 the upstream author's ideas about which compilation
6773 options are best: they are often inappropriate for our
6779 <sect id="libraries">
6780 <heading>Libraries</heading>
6783 If the package is <strong>architecture: any</strong>, then
6784 the shared library compilation and linking flags must have
6785 <tt>-fPIC</tt>, or the package shall not build on some of
6786 the supported architectures<footnote>
6788 If you are using GCC, <tt>-fPIC</tt> produces code with
6789 relocatable position independent code, which is required for
6790 most architectures to create a shared library, with i386 and
6791 perhaps some others where non position independent code is
6792 permitted in a shared library.
6795 Position independent code may have a performance penalty,
6796 especially on <tt>i386</tt>. However, in most cases the
6797 speed penalty must be measured against the memory wasted on
6798 the few architectures where non position independent code is
6801 </footnote>. Any exception to this rule must be discussed on
6802 the mailing list <em>debian-devel@lists.debian.org</em>, and
6803 a rough consensus obtained. The reasons for not compiling
6804 with <tt>-fPIC</tt> flag must be recorded in the file
6805 <tt>README.Debian</tt>, and care must be taken to either
6806 restrict the architecture or arrange for <tt>-fPIC</tt> to
6807 be used on architectures where it is required.<footnote>
6809 Some of the reasons why this might be required is if the
6810 library contains hand crafted assembly code that is not
6811 relocatable, the speed penalty is excessive for compute
6812 intensive libs, and similar reasons.
6817 As to the static libraries, the common case is not to have
6818 relocatable code, since there is no benefit, unless in specific
6819 cases; therefore the static version must not be compiled
6820 with the <tt>-fPIC</tt> flag. Any exception to this rule
6821 should be discussed on the mailing list
6822 <em>debian-devel@lists.debian.org</em>, and the reasons for
6823 compiling with the <tt>-fPIC</tt> flag must be recorded in
6824 the file <tt>README.Debian</tt>. <footnote>
6826 Some of the reasons for linking static libraries with
6827 the <tt>-fPIC</tt> flag are if, for example, one needs a
6828 Perl API for a library that is under rapid development,
6829 and has an unstable API, so shared libraries are
6830 pointless at this phase of the library's development. In
6831 that case, since Perl needs a library with relocatable
6832 code, it may make sense to create a static library with
6833 relocatable code. Another reason cited is if you are
6834 distilling various libraries into a common shared
6835 library, like <tt>mklibs</tt> does in the Debian
6841 In other words, if both a shared and a static library is
6842 being built, each source unit (<tt>*.c</tt>, for example,
6843 for C files) will need to be compiled twice, for the normal
6847 You must specify the gcc option <tt>-D_REENTRANT</tt>
6848 when building a library (either static or shared) to make
6849 the library compatible with LinuxThreads.
6853 Although not enforced by the build tools, shared libraries
6854 must be linked against all libraries that they use symbols from
6855 in the same way that binaries are. This ensures the correct
6856 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6857 system and guarantees that all libraries can be safely opened
6858 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6859 option <tt>-Wl,-z,defs</tt> when building a shared library.
6860 Since this option enforces symbol resolution at build time,
6861 a missing library reference will be caught early as a fatal
6866 All installed shared libraries should be stripped with
6867 <example compact="compact">
6868 strip --strip-unneeded <var>your-lib</var>
6870 (The option <tt>--strip-unneeded</tt> makes
6871 <prgn>strip</prgn> remove only the symbols which aren't
6872 needed for relocation processing.) Shared libraries can
6873 function perfectly well when stripped, since the symbols for
6874 dynamic linking are in a separate part of the ELF object
6876 You might also want to use the options
6877 <tt>--remove-section=.comment</tt> and
6878 <tt>--remove-section=.note</tt> on both shared libraries
6879 and executables, and <tt>--strip-debug</tt> on static
6885 Note that under some circumstances it may be useful to
6886 install a shared library unstripped, for example when
6887 building a separate package to support debugging.
6891 Shared object files (often <file>.so</file> files) that are not
6892 public libraries, that is, they are not meant to be linked
6893 to by third party executables (binaries of other packages),
6894 should be installed in subdirectories of the
6895 <file>/usr/lib</file> directory. Such files are exempt from the
6896 rules that govern ordinary shared libraries, except that
6897 they must not be installed executable and should be
6899 A common example are the so-called "plug-ins",
6900 internal shared objects that are dynamically loaded by
6901 programs using <manref name="dlopen" section="3">.
6906 Packages containing shared libraries that may be linked to
6907 by other packages' binaries, but which for some
6908 <em>compelling</em> reason can not be installed in
6909 <file>/usr/lib</file> directory, may install the shared library
6910 files in subdirectories of the <file>/usr/lib</file> directory,
6911 in which case they should arrange to add that directory in
6912 <file>/etc/ld.so.conf</file> in the package's post-installation
6913 script, and remove it in the package's post-removal script.
6917 An ever increasing number of packages are using
6918 <prgn>libtool</prgn> to do their linking. The latest GNU
6919 libtools (>= 1.3a) can take advantage of the metadata in the
6920 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6921 files). The main advantage of <prgn>libtool</prgn>'s
6922 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6923 store and subsequently access metadata with respect to the
6924 libraries it builds. <prgn>libtool</prgn> will search for
6925 those files, which contain a lot of useful information about
6926 a library (such as library dependency information for static
6927 linking). Also, they're <em>essential</em> for programs
6928 using <tt>libltdl</tt>.<footnote>
6929 Although <prgn>libtool</prgn> is fully capable of
6930 linking against shared libraries which don't have
6931 <tt>.la</tt> files, as it is a mere shell script it can
6932 add considerably to the build time of a
6933 <prgn>libtool</prgn>-using package if that shell script
6934 has to derive all this information from first principles
6935 for each library every time it is linked. With the
6936 advent of <prgn>libtool</prgn> version 1.4 (and to a
6937 lesser extent <prgn>libtool</prgn> version 1.3), the
6938 <file>.la</file> files also store information about
6939 inter-library dependencies which cannot necessarily be
6940 derived after the <file>.la</file> file is deleted.
6945 Packages that use <prgn>libtool</prgn> to create shared
6946 libraries should include the <file>.la</file> files in the
6947 <tt>-dev</tt> package, unless the package relies on
6948 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6949 the <tt>.la</tt> files must go in the run-time library
6954 You must make sure that you use only released versions of
6955 shared libraries to build your packages; otherwise other
6956 users will not be able to run your binaries
6957 properly. Producing source packages that depend on
6958 unreleased compilers is also usually a bad
6965 <heading>Shared libraries</heading>
6967 This section has moved to <ref id="sharedlibs">.
6973 <heading>Scripts</heading>
6976 All command scripts, including the package maintainer
6977 scripts inside the package and used by <prgn>dpkg</prgn>,
6978 should have a <tt>#!</tt> line naming the shell to be used
6983 In the case of Perl scripts this should be
6984 <tt>#!/usr/bin/perl</tt>.
6988 When scripts are installed into a directory in the system
6989 PATH, the script name should not include an extension such
6990 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6991 language currently used to implement it.
6994 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6995 should almost certainly start with <tt>set -e</tt> so that
6996 errors are detected. Every script should use
6997 <tt>set -e</tt> or check the exit status of <em>every</em>
7002 Scripts may assume that <file>/bin/sh</file> implements the
7003 SUSv3 Shell Command Language<footnote>
7004 Single UNIX Specification, version 3, which is also IEEE
7005 1003.1-2004 (POSIX), and is available on the World Wide Web
7006 from <url id="http://www.unix.org/version3/online.html"
7007 name="The Open Group"> after free
7008 registration.</footnote>
7009 plus the following additional features not mandated by
7011 These features are in widespread use in the Linux community
7012 and are implemented in all of bash, dash, and ksh, the most
7013 common shells users may wish to use as <file>/bin/sh</file>.
7016 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7017 must not generate a newline.</item>
7018 <item><tt>test</tt>, if implemented as a shell built-in, must
7019 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7021 <item><tt>local</tt> to create a scoped variable must be
7022 supported; however, <tt>local</tt> may or may not preserve
7023 the variable value from an outer scope and may or may not
7024 support arguments more complex than simple variables. Only
7036 If a shell script requires non-SUSv3 features from the shell
7037 interpreter other than those listed above, the appropriate shell
7038 must be specified in the first line of the script (e.g.,
7039 <tt>#!/bin/bash</tt>) and the package must depend on the package
7040 providing the shell (unless the shell package is marked
7041 "Essential", as in the case of <prgn>bash</prgn>).
7045 You may wish to restrict your script to SUSv3 features plus the
7046 above set when possible so that it may use <file>/bin/sh</file>
7047 as its interpreter. If your script works with <prgn>dash</prgn>
7048 (originally called <prgn>ash</prgn>), it probably complies with
7049 the above requirements, but if you are in doubt, use
7050 <file>/bin/bash</file>.
7054 Perl scripts should check for errors when making any
7055 system calls, including <tt>open</tt>, <tt>print</tt>,
7056 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7060 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7061 scripting languages. See <em>Csh Programming Considered
7062 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7063 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7064 If an upstream package comes with <prgn>csh</prgn> scripts
7065 then you must make sure that they start with
7066 <tt>#!/bin/csh</tt> and make your package depend on the
7067 <prgn>c-shell</prgn> virtual package.
7071 Any scripts which create files in world-writeable
7072 directories (e.g., in <file>/tmp</file>) must use a
7073 mechanism which will fail atomically if a file with the same
7074 name already exists.
7078 The Debian base system provides the <prgn>tempfile</prgn>
7079 and <prgn>mktemp</prgn> utilities for use by scripts for
7086 <heading>Symbolic links</heading>
7089 In general, symbolic links within a top-level directory
7090 should be relative, and symbolic links pointing from one
7091 top-level directory into another should be absolute. (A
7092 top-level directory is a sub-directory of the root
7093 directory <file>/</file>.)
7097 In addition, symbolic links should be specified as short as
7098 possible, i.e., link targets like <file>foo/../bar</file> are
7103 Note that when creating a relative link using
7104 <prgn>ln</prgn> it is not necessary for the target of the
7105 link to exist relative to the working directory you're
7106 running <prgn>ln</prgn> from, nor is it necessary to change
7107 directory to the directory where the link is to be made.
7108 Simply include the string that should appear as the target
7109 of the link (this will be a pathname relative to the
7110 directory in which the link resides) as the first argument
7115 For example, in your <prgn>Makefile</prgn> or
7116 <file>debian/rules</file>, you can do things like:
7117 <example compact="compact">
7118 ln -fs gcc $(prefix)/bin/cc
7119 ln -fs gcc debian/tmp/usr/bin/cc
7120 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7121 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7126 A symbolic link pointing to a compressed file should always
7127 have the same file extension as the referenced file. (For
7128 example, if a file <file>foo.gz</file> is referenced by a
7129 symbolic link, the filename of the link has to end with
7130 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7135 <heading>Device files</heading>
7138 Packages must not include device files in the package file
7143 If a package needs any special device files that are not
7144 included in the base system, it must call
7145 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7146 after notifying the user<footnote>
7147 This notification could be done via a (low-priority)
7148 debconf message, or an echo (printf) statement.
7153 Packages must not remove any device files in the
7154 <prgn>postrm</prgn> or any other script. This is left to the
7155 system administrator.
7159 Debian uses the serial devices
7160 <file>/dev/ttyS*</file>. Programs using the old
7161 <file>/dev/cu*</file> devices should be changed to use
7162 <file>/dev/ttyS*</file>.
7166 <sect id="config-files">
7167 <heading>Configuration files</heading>
7170 <heading>Definitions</heading>
7174 <tag>configuration file</tag>
7176 A file that affects the operation of a program, or
7177 provides site- or host-specific information, or
7178 otherwise customizes the behavior of a program.
7179 Typically, configuration files are intended to be
7180 modified by the system administrator (if needed or
7181 desired) to conform to local policy or to provide
7182 more useful site-specific behavior.
7185 <tag><tt>conffile</tt></tag>
7187 A file listed in a package's <tt>conffiles</tt>
7188 file, and is treated specially by <prgn>dpkg</prgn>
7189 (see <ref id="configdetails">).
7195 The distinction between these two is important; they are
7196 not interchangeable concepts. Almost all
7197 <tt>conffile</tt>s are configuration files, but many
7198 configuration files are not <tt>conffiles</tt>.
7202 As noted elsewhere, <file>/etc/init.d</file> scripts,
7203 <file>/etc/default</file> files, scripts installed in
7204 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7205 configuration installed in <file>/etc/cron.d</file> must be
7206 treated as configuration files. In general, any script that
7207 embeds configuration information is de-facto a configuration
7208 file and should be treated as such.
7213 <heading>Location</heading>
7216 Any configuration files created or used by your package
7217 must reside in <file>/etc</file>. If there are several,
7218 consider creating a subdirectory of <file>/etc</file>
7219 named after your package.
7223 If your package creates or uses configuration files
7224 outside of <file>/etc</file>, and it is not feasible to modify
7225 the package to use <file>/etc</file> directly, put the files
7226 in <file>/etc</file> and create symbolic links to those files
7227 from the location that the package requires.
7232 <heading>Behavior</heading>
7235 Configuration file handling must conform to the following
7237 <list compact="compact">
7239 local changes must be preserved during a package
7243 configuration files must be preserved when the
7244 package is removed, and only deleted when the
7251 The easy way to achieve this behavior is to make the
7252 configuration file a <tt>conffile</tt>. This is
7253 appropriate only if it is possible to distribute a default
7254 version that will work for most installations, although
7255 some system administrators may choose to modify it. This
7256 implies that the default version will be part of the
7257 package distribution, and must not be modified by the
7258 maintainer scripts during installation (or at any other
7263 In order to ensure that local changes are preserved
7264 correctly, no package may contain or make hard links to
7265 conffiles.<footnote>
7266 Rationale: There are two problems with hard links.
7267 The first is that some editors break the link while
7268 editing one of the files, so that the two files may
7269 unwittingly become unlinked and different. The second
7270 is that <prgn>dpkg</prgn> might break the hard link
7271 while upgrading <tt>conffile</tt>s.
7276 The other way to do it is via the maintainer scripts. In
7277 this case, the configuration file must not be listed as a
7278 <tt>conffile</tt> and must not be part of the package
7279 distribution. If the existence of a file is required for
7280 the package to be sensibly configured it is the
7281 responsibility of the package maintainer to provide
7282 maintainer scripts which correctly create, update and
7283 maintain the file and remove it on purge. (See <ref
7284 id="maintainerscripts"> for more information.) These
7285 scripts must be idempotent (i.e., must work correctly if
7286 <prgn>dpkg</prgn> needs to re-run them due to errors
7287 during installation or removal), must cope with all the
7288 variety of ways <prgn>dpkg</prgn> can call maintainer
7289 scripts, must not overwrite or otherwise mangle the user's
7290 configuration without asking, must not ask unnecessary
7291 questions (particularly during upgrades), and must
7292 otherwise be good citizens.
7296 The scripts are not required to configure every possible
7297 option for the package, but only those necessary to get
7298 the package running on a given system. Ideally the
7299 sysadmin should not have to do any configuration other
7300 than that done (semi-)automatically by the
7301 <prgn>postinst</prgn> script.
7305 A common practice is to create a script called
7306 <file><var>package</var>-configure</file> and have the
7307 package's <prgn>postinst</prgn> call it if and only if the
7308 configuration file does not already exist. In certain
7309 cases it is useful for there to be an example or template
7310 file which the maintainer scripts use. Such files should
7311 be in <file>/usr/share/<var>package</var></file> or
7312 <file>/usr/lib/<var>package</var></file> (depending on whether
7313 they are architecture-independent or not). There should
7314 be symbolic links to them from
7315 <file>/usr/share/doc/<var>package</var>/examples</file> if
7316 they are examples, and should be perfectly ordinary
7317 <prgn>dpkg</prgn>-handled files (<em>not</em>
7318 configuration files).
7322 These two styles of configuration file handling must
7323 not be mixed, for that way lies madness:
7324 <prgn>dpkg</prgn> will ask about overwriting the file
7325 every time the package is upgraded.
7330 <heading>Sharing configuration files</heading>
7333 Packages which specify the same file as a
7334 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7335 with each other. (This is an instance of the general rule
7336 about not sharing files. Note that neither alternatives
7337 nor diversions are likely to be appropriate in this case;
7338 in particular, <prgn>dpkg</prgn> does not handle diverted
7339 <tt>conffile</tt>s well.)
7343 The maintainer scripts must not alter a <tt>conffile</tt>
7344 of <em>any</em> package, including the one the scripts
7349 If two or more packages use the same configuration file
7350 and it is reasonable for both to be installed at the same
7351 time, one of these packages must be defined as
7352 <em>owner</em> of the configuration file, i.e., it will be
7353 the package which handles that file as a configuration
7354 file. Other packages that use the configuration file must
7355 depend on the owning package if they require the
7356 configuration file to operate. If the other package will
7357 use the configuration file if present, but is capable of
7358 operating without it, no dependency need be declared.
7362 If it is desirable for two or more related packages to
7363 share a configuration file <em>and</em> for all of the
7364 related packages to be able to modify that configuration
7365 file, then the following should be done:
7366 <enumlist compact="compact">
7368 One of the related packages (the "owning" package)
7369 will manage the configuration file with maintainer
7370 scripts as described in the previous section.
7373 The owning package should also provide a program
7374 that the other packages may use to modify the
7378 The related packages must use the provided program
7379 to make any desired modifications to the
7380 configuration file. They should either depend on
7381 the core package to guarantee that the configuration
7382 modifier program is available or accept gracefully
7383 that they cannot modify the configuration file if it
7384 is not. (This is in addition to the fact that the
7385 configuration file may not even be present in the
7392 Sometimes it's appropriate to create a new package which
7393 provides the basic infrastructure for the other packages
7394 and which manages the shared configuration files. (The
7395 <tt>sgml-base</tt> package is a good example.)
7400 <heading>User configuration files ("dotfiles")</heading>
7403 The files in <file>/etc/skel</file> will automatically be
7404 copied into new user accounts by <prgn>adduser</prgn>.
7405 No other program should reference the files in
7406 <file>/etc/skel</file>.
7410 Therefore, if a program needs a dotfile to exist in
7411 advance in <file>$HOME</file> to work sensibly, that dotfile
7412 should be installed in <file>/etc/skel</file> and treated as a
7417 However, programs that require dotfiles in order to
7418 operate sensibly are a bad thing, unless they do create
7419 the dotfiles themselves automatically.
7423 Furthermore, programs should be configured by the Debian
7424 default installation to behave as closely to the upstream
7425 default behavior as possible.
7429 Therefore, if a program in a Debian package needs to be
7430 configured in some way in order to operate sensibly, that
7431 should be done using a site-wide configuration file placed
7432 in <file>/etc</file>. Only if the program doesn't support a
7433 site-wide default configuration and the package maintainer
7434 doesn't have time to add it may a default per-user file be
7435 placed in <file>/etc/skel</file>.
7439 <file>/etc/skel</file> should be as empty as we can make it.
7440 This is particularly true because there is no easy (or
7441 necessarily desirable) mechanism for ensuring that the
7442 appropriate dotfiles are copied into the accounts of
7443 existing users when a package is installed.
7449 <heading>Log files</heading>
7451 Log files should usually be named
7452 <file>/var/log/<var>package</var>.log</file>. If you have many
7453 log files, or need a separate directory for permission
7454 reasons (<file>/var/log</file> is writable only by
7455 <file>root</file>), you should usually create a directory named
7456 <file>/var/log/<var>package</var></file> and place your log
7461 Log files must be rotated occasionally so that they don't
7462 grow indefinitely; the best way to do this is to drop a log
7463 rotation configuration file into the directory
7464 <file>/etc/logrotate.d</file> and use the facilities provided by
7465 logrotate.<footnote>
7467 The traditional approach to log files has been to set up
7468 <em>ad hoc</em> log rotation schemes using simple shell
7469 scripts and cron. While this approach is highly
7470 customizable, it requires quite a lot of sysadmin work.
7471 Even though the original Debian system helped a little
7472 by automatically installing a system which can be used
7473 as a template, this was deemed not enough.
7477 The use of <prgn>logrotate</prgn>, a program developed
7478 by Red Hat, is better, as it centralizes log management.
7479 It has both a configuration file
7480 (<file>/etc/logrotate.conf</file>) and a directory where
7481 packages can drop their individual log rotation
7482 configurations (<file>/etc/logrotate.d</file>).
7485 Here is a good example for a logrotate config
7486 file (for more information see <manref name="logrotate"
7488 <example compact="compact">
7489 /var/log/foo/*.log {
7494 /etc/init.d/foo force-reload
7498 This rotates all files under <file>/var/log/foo</file>, saves 12
7499 compressed generations, and forces the daemon to reload its
7500 configuration information after the log rotation.
7504 Log files should be removed when the package is
7505 purged (but not when it is only removed). This should be
7506 done by the <prgn>postrm</prgn> script when it is called
7507 with the argument <tt>purge</tt> (see <ref
7508 id="removedetails">).
7513 <heading>Permissions and owners</heading>
7516 The rules in this section are guidelines for general use.
7517 If necessary you may deviate from the details below.
7518 However, if you do so you must make sure that what is done
7519 is secure and you should try to be as consistent as possible
7520 with the rest of the system. You should probably also
7521 discuss it on <prgn>debian-devel</prgn> first.
7525 Files should be owned by <tt>root:root</tt>, and made
7526 writable only by the owner and universally readable (and
7527 executable, if appropriate), that is mode 644 or 755.
7531 Directories should be mode 755 or (for group-writability)
7532 mode 2775. The ownership of the directory should be
7533 consistent with its mode: if a directory is mode 2775, it
7534 should be owned by the group that needs write access to
7537 When a package is upgraded, and the owner or permissions
7538 of a file included in the package has changed, dpkg
7539 arranges for the ownership and permissions to be
7540 correctly set upon installation. However, this does not
7541 extend to directories; the permissions and ownership of
7542 directories already on the system does not change on
7543 install or upgrade of packages. This makes sense, since
7544 otherwise common directories like <tt>/usr</tt> would
7545 always be in flux. To correctly change permissions of a
7546 directory the package owns, explicit action is required,
7547 usually in the <tt>postinst</tt> script. Care must be
7548 taken to handle downgrades as well, in that case.
7555 Setuid and setgid executables should be mode 4755 or 2755
7556 respectively, and owned by the appropriate user or group.
7557 They should not be made unreadable (modes like 4711 or
7558 2711 or even 4111); doing so achieves no extra security,
7559 because anyone can find the binary in the freely available
7560 Debian package; it is merely inconvenient. For the same
7561 reason you should not restrict read or execute permissions
7562 on non-set-id executables.
7566 Some setuid programs need to be restricted to particular
7567 sets of users, using file permissions. In this case they
7568 should be owned by the uid to which they are set-id, and by
7569 the group which should be allowed to execute them. They
7570 should have mode 4754; again there is no point in making
7571 them unreadable to those users who must not be allowed to
7576 It is possible to arrange that the system administrator can
7577 reconfigure the package to correspond to their local
7578 security policy by changing the permissions on a binary:
7579 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7580 described below.<footnote>
7581 Ordinary files installed by <prgn>dpkg</prgn> (as
7582 opposed to <tt>conffile</tt>s and other similar objects)
7583 normally have their permissions reset to the distributed
7584 permissions when the package is reinstalled. However,
7585 the use of <prgn>dpkg-statoverride</prgn> overrides this
7586 default behavior. If you use this method, you should
7587 remember to describe <prgn>dpkg-statoverride</prgn> in
7588 the package documentation; being a relatively new
7589 addition to Debian, it is probably not yet well-known.
7591 Another method you should consider is to create a group for
7592 people allowed to use the program(s) and make any setuid
7593 executables executable only by that group.
7597 If you need to create a new user or group for your package
7598 there are two possibilities. Firstly, you may need to
7599 make some files in the binary package be owned by this
7600 user or group, or you may need to compile the user or
7601 group id (rather than just the name) into the binary
7602 (though this latter should be avoided if possible, as in
7603 this case you need a statically allocated id).</p>
7606 If you need a statically allocated id, you must ask for a
7607 user or group id from the <tt>base-passwd</tt> maintainer,
7608 and must not release the package until you have been
7609 allocated one. Once you have been allocated one you must
7610 either make the package depend on a version of the
7611 <tt>base-passwd</tt> package with the id present in
7612 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7613 your package to create the user or group itself with the
7614 correct id (using <tt>adduser</tt>) in its
7615 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7616 the <prgn>postinst</prgn> is to be preferred if it is
7617 possible, otherwise a pre-dependency will be needed on the
7618 <tt>adduser</tt> package.)
7622 On the other hand, the program might be able to determine
7623 the uid or gid from the user or group name at runtime, so
7624 that a dynamically allocated id can be used. In this case
7625 you should choose an appropriate user or group name,
7626 discussing this on <prgn>debian-devel</prgn> and checking
7627 with the <package/base-passwd/ maintainer that it is unique and that
7628 they do not wish you to use a statically allocated id
7629 instead. When this has been checked you must arrange for
7630 your package to create the user or group if necessary using
7631 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7632 <prgn>postinst</prgn> script (again, the latter is to be
7633 preferred if it is possible).
7637 Note that changing the numeric value of an id associated
7638 with a name is very difficult, and involves searching the
7639 file system for all appropriate files. You need to think
7640 carefully whether a static or dynamic id is required, since
7641 changing your mind later will cause problems.
7644 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7646 This section is not intended as policy, but as a
7647 description of the use of <prgn>dpkg-statoverride</prgn>.
7651 If a system administrator wishes to have a file (or
7652 directory or other such thing) installed with owner and
7653 permissions different from those in the distributed Debian
7654 package, they can use the <prgn>dpkg-statoverride</prgn>
7655 program to instruct <prgn>dpkg</prgn> to use the different
7656 settings every time the file is installed. Thus the
7657 package maintainer should distribute the files with their
7658 normal permissions, and leave it for the system
7659 administrator to make any desired changes. For example, a
7660 daemon which is normally required to be setuid root, but
7661 in certain situations could be used without being setuid,
7662 should be installed setuid in the <tt>.deb</tt>. Then the
7663 local system administrator can change this if they wish.
7664 If there are two standard ways of doing it, the package
7665 maintainer can use <tt>debconf</tt> to find out the
7666 preference, and call <prgn>dpkg-statoverride</prgn> in the
7667 maintainer script if necessary to accommodate the system
7668 administrator's choice. Care must be taken during
7669 upgrades to not override an existing setting.
7673 Given the above, <prgn>dpkg-statoverride</prgn> is
7674 essentially a tool for system administrators and would not
7675 normally be needed in the maintainer scripts. There is
7676 one type of situation, though, where calls to
7677 <prgn>dpkg-statoverride</prgn> would be needed in the
7678 maintainer scripts, and that involves packages which use
7679 dynamically allocated user or group ids. In such a
7680 situation, something like the following idiom can be very
7681 helpful in the package's <prgn>postinst</prgn>, where
7682 <tt>sysuser</tt> is a dynamically allocated id:
7684 for i in /usr/bin/foo /usr/sbin/bar
7686 # only do something when no setting exists
7687 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7689 #include: debconf processing, question about foo and bar
7690 if [ "$RET" = "true" ] ; then
7691 dpkg-statoverride --update --add sysuser root 4755 $i
7696 The corresponding <tt>dpkg-statoverride --remove</tt>
7697 calls can then be made unconditionally when the package is
7705 <chapt id="customized-programs">
7706 <heading>Customized programs</heading>
7708 <sect id="arch-spec">
7709 <heading>Architecture specification strings</heading>
7712 If a program needs to specify an <em>architecture specification
7713 string</em> in some place, it should select one of the
7714 strings provided by <tt>dpkg-architecture -L</tt>. The
7715 strings are in the format
7716 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7717 is sometimes elided, as when the OS is Linux.<footnote>
7718 <p>Currently, the strings are:
7719 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7720 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7721 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7722 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7723 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7724 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7725 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7726 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7727 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7728 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7729 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7730 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7731 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7732 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7733 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7734 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7735 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7736 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7737 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7738 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7739 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7740 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7741 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7742 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7743 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7744 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7745 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7746 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7747 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7748 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7749 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7750 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7751 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7752 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7753 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7754 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7755 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7761 Note that we don't want to use
7762 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7763 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7764 since this would make our programs incompatible with other
7765 Linux distributions. We also don't use something like
7766 <tt><var>arch</var>-unknown-linux</tt>, since the
7767 <tt>unknown</tt> does not look very good.
7772 <heading>Daemons</heading>
7775 The configuration files <file>/etc/services</file>,
7776 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7777 by the <prgn>netbase</prgn> package and must not be modified
7782 If a package requires a new entry in one of these files, the
7783 maintainer should get in contact with the
7784 <prgn>netbase</prgn> maintainer, who will add the entries
7785 and release a new version of the <prgn>netbase</prgn>
7790 The configuration file <file>/etc/inetd.conf</file> must not be
7791 modified by the package's scripts except via the
7792 <prgn>update-inetd</prgn> script or the
7793 <file>DebianNet.pm</file> Perl module. See their documentation
7794 for details on how to add entries.
7798 If a package wants to install an example entry into
7799 <file>/etc/inetd.conf</file>, the entry must be preceded with
7800 exactly one hash character (<tt>#</tt>). Such lines are
7801 treated as "commented out by user" by the
7802 <prgn>update-inetd</prgn> script and are not changed or
7803 activated during package updates.
7808 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7812 Some programs need to create pseudo-ttys. This should be done
7813 using Unix98 ptys if the C library supports it. The resulting
7814 program must not be installed setuid root, unless that
7815 is required for other functionality.
7819 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7820 <file>/var/log/lastlog</file> must be installed writable by
7821 group <tt>utmp</tt>. Programs which need to modify those
7822 files must be installed setgid <tt>utmp</tt>.
7827 <heading>Editors and pagers</heading>
7830 Some programs have the ability to launch an editor or pager
7831 program to edit or display a text document. Since there are
7832 lots of different editors and pagers available in the Debian
7833 distribution, the system administrator and each user should
7834 have the possibility to choose their preferred editor and
7839 In addition, every program should choose a good default
7840 editor/pager if none is selected by the user or system
7845 Thus, every program that launches an editor or pager must
7846 use the EDITOR or PAGER environment variable to determine
7847 the editor or pager the user wishes to use. If these
7848 variables are not set, the programs <file>/usr/bin/editor</file>
7849 and <file>/usr/bin/pager</file> should be used, respectively.
7853 These two files are managed through the <prgn>dpkg</prgn>
7854 "alternatives" mechanism. Thus every package providing an
7855 editor or pager must call the
7856 <prgn>update-alternatives</prgn> script to register these
7861 If it is very hard to adapt a program to make use of the
7862 EDITOR or PAGER variables, that program may be configured to
7863 use <file>/usr/bin/sensible-editor</file> and
7864 <file>/usr/bin/sensible-pager</file> as the editor or pager
7865 program respectively. These are two scripts provided in the
7866 Debian base system that check the EDITOR and PAGER variables
7867 and launch the appropriate program, and fall back to
7868 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7869 variable is not set.
7873 A program may also use the VISUAL environment variable to
7874 determine the user's choice of editor. If it exists, it
7875 should take precedence over EDITOR. This is in fact what
7876 <file>/usr/bin/sensible-editor</file> does.
7880 It is not required for a package to depend on
7881 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7882 package to provide such virtual packages.<footnote>
7883 The Debian base system already provides an editor and a
7889 <sect id="web-appl">
7890 <heading>Web servers and applications</heading>
7893 This section describes the locations and URLs that should
7894 be used by all web servers and web applications in the
7901 Cgi-bin executable files are installed in the
7903 <example compact="compact">
7904 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7906 and should be referred to as
7907 <example compact="compact">
7908 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7914 <p>Access to HTML documents</p>
7917 HTML documents for a package are stored in
7918 <file>/usr/share/doc/<var>package</var></file>
7919 and can be referred to as
7920 <example compact="compact">
7921 http://localhost/doc/<var>package</var>/<var>filename</var>
7926 The web server should restrict access to the document
7927 tree so that only clients on the same host can read
7928 the documents. If the web server does not support such
7929 access controls, then it should not provide access at
7930 all, or ask about providing access during installation.
7935 <p>Access to images</p>
7937 It is recommended that images for a package be stored
7938 in <tt>/usr/share/images/<var>package</var></tt> and
7939 may be referred to through an alias <tt>/images/</tt>
7942 http://localhost/images/<package>/<filename>
7949 <p>Web Document Root</p>
7952 Web Applications should try to avoid storing files in
7953 the Web Document Root. Instead they should use the
7954 /usr/share/doc/<var>package</var> directory for
7955 documents and register the Web Application via the
7956 <package>doc-base</package> package. If access to the
7957 web document root is unavoidable then use
7958 <example compact="compact">
7961 as the Document Root. This might be just a symbolic
7962 link to the location where the system administrator
7963 has put the real document root.
7966 <item><p>Providing httpd and/or httpd-cgi</p>
7968 All web servers should provide the virtual package
7969 <tt>httpd</tt>. If a web server has CGI support it should
7970 provide <tt>httpd-cgi</tt> additionally.
7973 All web applications which do not contain CGI scripts should
7974 depend on <tt>httpd</tt>, all those web applications which
7975 <tt>do</tt> contain CGI scripts, should depend on
7983 <sect id="mail-transport-agents">
7984 <heading>Mail transport, delivery and user agents</heading>
7987 Debian packages which process electronic mail, whether mail
7988 user agents (MUAs) or mail transport agents (MTAs), must
7989 ensure that they are compatible with the configuration
7990 decisions below. Failure to do this may result in lost
7991 mail, broken <tt>From:</tt> lines, and other serious brain
7996 The mail spool is <file>/var/mail</file> and the interface to
7997 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7998 the FHS). On older systems, the mail spool may be
7999 physically located in <file>/var/spool/mail</file>, but all
8000 access to the mail spool should be via the
8001 <file>/var/mail</file> symlink. The mail spool is part of the
8002 base system and not part of the MTA package.
8006 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8007 programs (such as IMAP daemons) must lock the mailbox in an
8008 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8009 be combined with dot locking. To avoid deadlocks, a program
8010 should use <tt>fcntl()</tt> first and dot locking after
8011 this, or alternatively implement the two locking methods in
8012 a non blocking way<footnote>
8013 If it is not possible to establish both locks, the
8014 system shouldn't wait for the second lock to be
8015 established, but remove the first lock, wait a (random)
8016 time, and start over locking again.
8017 </footnote>. Using the functions <tt>maillock</tt> and
8018 <tt>mailunlock</tt> provided by the
8019 <tt>liblockfile*</tt><footnote>
8020 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8021 to use these functions.
8022 </footnote> packages is the recommended way to realize this.
8026 Mailboxes are generally mode 660
8027 <tt><var>user</var>:mail</tt> unless the system
8028 administrator has chosen otherwise. A MUA may remove a
8029 mailbox (unless it has nonstandard permissions) in which
8030 case the MTA or another MUA must recreate it if needed.
8031 Mailboxes must be writable by group mail.
8035 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8036 be setgid mail to do the locking mentioned above (and
8037 must obviously avoid accessing other users' mailboxes
8038 using this privilege).</p>
8041 <file>/etc/aliases</file> is the source file for the system mail
8042 aliases (e.g., postmaster, usenet, etc.), it is the one
8043 which the sysadmin and <prgn>postinst</prgn> scripts may
8044 edit. After <file>/etc/aliases</file> is edited the program or
8045 human editing it must call <prgn>newaliases</prgn>. All MTA
8046 packages must come with a <prgn>newaliases</prgn> program,
8047 even if it does nothing, but older MTA packages did not do
8048 this so programs should not fail if <prgn>newaliases</prgn>
8049 cannot be found. Note that because of this, all MTA
8050 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8051 <tt>Replaces: mail-transport-agent</tt> control file
8056 The convention of writing <tt>forward to
8057 <var>address</var></tt> in the mailbox itself is not
8058 supported. Use a <tt>.forward</tt> file instead.</p>
8061 The <prgn>rmail</prgn> program used by UUCP
8062 for incoming mail should be <file>/usr/sbin/rmail</file>.
8063 Likewise, <prgn>rsmtp</prgn>, for receiving
8064 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8068 If your package needs to know what hostname to use on (for
8069 example) outgoing news and mail messages which are generated
8070 locally, you should use the file <file>/etc/mailname</file>. It
8071 will contain the portion after the username and <tt>@</tt>
8072 (at) sign for email addresses of users on the machine
8073 (followed by a newline).
8077 Such a package should check for the existence of this file
8078 when it is being configured. If it exists, it should be
8079 used without comment, although an MTA's configuration script
8080 may wish to prompt the user even if it finds that this file
8081 exists. If the file does not exist, the package should
8082 prompt the user for the value (preferably using
8083 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8084 as well as using it in the package's configuration. The
8085 prompt should make it clear that the name will not just be
8086 used by that package. For example, in this situation the
8087 <tt>inn</tt> package could say something like:
8088 <example compact="compact">
8089 Please enter the "mail name" of your system. This is the
8090 hostname portion of the address to be shown on outgoing
8091 news and mail messages. The default is
8092 <var>syshostname</var>, your system's host name. Mail
8093 name ["<var>syshostname</var>"]:
8095 where <var>syshostname</var> is the output of <tt>hostname
8101 <heading>News system configuration</heading>
8104 All the configuration files related to the NNTP (news)
8105 servers and clients should be located under
8106 <file>/etc/news</file>.</p>
8109 There are some configuration issues that apply to a number
8110 of news clients and server packages on the machine. These
8114 <tag><file>/etc/news/organization</file></tag>
8116 A string which should appear as the
8117 organization header for all messages posted
8118 by NNTP clients on the machine
8121 <tag><file>/etc/news/server</file></tag>
8123 Contains the FQDN of the upstream NNTP
8124 server, or localhost if the local machine is
8129 Other global files may be added as required for cross-package news
8136 <heading>Programs for the X Window System</heading>
8139 <heading>Providing X support and package priorities</heading>
8142 Programs that can be configured with support for the X
8143 Window System must be configured to do so and must declare
8144 any package dependencies necessary to satisfy their
8145 runtime requirements when using the X Window System. If
8146 such a package is of higher priority than the X packages
8147 on which it depends, it is required that either the
8148 X-specific components be split into a separate package, or
8149 that an alternative version of the package, which includes
8150 X support, be provided, or that the package's priority be
8156 <heading>Packages providing an X server</heading>
8159 Packages that provide an X server that, directly or
8160 indirectly, communicates with real input and display
8161 hardware should declare in their control data that they
8162 provide the virtual package <tt>xserver</tt>.<footnote>
8163 This implements current practice, and provides an
8164 actual policy for usage of the <tt>xserver</tt>
8165 virtual package which appears in the virtual packages
8166 list. In a nutshell, X servers that interface
8167 directly with the display and input hardware or via
8168 another subsystem (e.g., GGI) should provide
8169 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8170 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8176 <heading>Packages providing a terminal emulator</heading>
8179 Packages that provide a terminal emulator for the X Window
8180 System which meet the criteria listed below should declare
8181 in their control data that they provide the virtual
8182 package <tt>x-terminal-emulator</tt>. They should also
8183 register themselves as an alternative for
8184 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8189 To be an <tt>x-terminal-emulator</tt>, a program must:
8190 <list compact="compact">
8192 Be able to emulate a DEC VT100 terminal, or a
8193 compatible terminal.
8197 Support the command-line option <tt>-e
8198 <var>command</var></tt>, which creates a new
8199 terminal window<footnote>
8200 "New terminal window" does not necessarily mean
8201 a new top-level X window directly parented by
8202 the window manager; it could, if the terminal
8203 emulator application were so coded, be a new
8204 "view" in a multiple-document interface (MDI).
8206 and runs the specified <var>command</var>,
8207 interpreting the entirety of the rest of the command
8208 line as a command to pass straight to exec, in the
8209 manner that <tt>xterm</tt> does.
8213 Support the command-line option <tt>-T
8214 <var>title</var></tt>, which creates a new terminal
8215 window with the window title <var>title</var>.
8222 <heading>Packages providing a window manager</heading>
8225 Packages that provide a window manager should declare in
8226 their control data that they provide the virtual package
8227 <tt>x-window-manager</tt>. They should also register
8228 themselves as an alternative for
8229 <file>/usr/bin/x-window-manager</file>, with a priority
8230 calculated as follows:
8231 <list compact="compact">
8233 Start with a priority of 20.
8237 If the window manager supports the Debian menu
8238 system, add 20 points if this support is available
8239 in the package's default configuration (i.e., no
8240 configuration files belonging to the system or user
8241 have to be edited to activate the feature); if
8242 configuration files must be modified, add only 10
8248 If the window manager complies with <url
8249 id="http://www.freedesktop.org/Standards/wm-spec"
8250 name="The Window Manager Specification Project">,
8251 written by the <url id="http://www.freedesktop.org/"
8252 name="Free Desktop Group">, add 40 points.
8256 If the window manager permits the X session to be
8257 restarted using a <em>different</em> window manager
8258 (without killing the X server) in its default
8259 configuration, add 10 points; otherwise add none.
8266 <heading>Packages providing fonts</heading>
8269 Packages that provide fonts for the X Window
8271 For the purposes of Debian Policy, a "font for the X
8272 Window System" is one which is accessed via X protocol
8273 requests. Fonts for the Linux console, for PostScript
8274 renderer, or any other purpose, do not fit this
8275 definition. Any tool which makes such fonts available
8276 to the X Window System, however, must abide by this
8279 must do a number of things to ensure that they are both
8280 available without modification of the X or font server
8281 configuration, and that they do not corrupt files used by
8282 other font packages to register information about
8286 Fonts of any type supported by the X Window System
8287 must be in a separate binary package from any
8288 executables, libraries, or documentation (except
8289 that specific to the fonts shipped, such as their
8290 license information). If one or more of the fonts
8291 so packaged are necessary for proper operation of
8292 the package with which they are associated the font
8293 package may be Recommended; if the fonts merely
8294 provide an enhancement, a Suggests relationship may
8295 be used. Packages must not Depend on font
8297 This is because the X server may retrieve fonts
8298 from the local file system or over the network
8299 from an X font server; the Debian package system
8300 is empowered to deal only with the local
8306 BDF fonts must be converted to PCF fonts with the
8307 <prgn>bdftopcf</prgn> utility (available in the
8308 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8309 placed in a directory that corresponds to their
8311 <list compact="compact">
8313 100 dpi fonts must be placed in
8314 <file>/usr/share/fonts/X11/100dpi/</file>.
8318 75 dpi fonts must be placed in
8319 <file>/usr/share/fonts/X11/75dpi/</file>.
8323 Character-cell fonts, cursor fonts, and other
8324 low-resolution fonts must be placed in
8325 <file>/usr/share/fonts/X11/misc/</file>.
8331 Speedo fonts must be placed in
8332 <file>/usr/share/fonts/X11/Speedo/</file>.
8336 Type 1 fonts must be placed in
8337 <file>/usr/share/fonts/X11/Type1/</file>. If font
8338 metric files are available, they must be placed here
8343 Subdirectories of <file>/usr/share/fonts/X11/</file>
8344 other than those listed above must be neither
8345 created nor used. (The <file>PEX</file>, <file>CID</file>,
8346 and <file>cyrillic</file> directories are excepted for
8347 historical reasons, but installation of files into
8348 these directories remains discouraged.)
8352 Font packages may, instead of placing files directly
8353 in the X font directories listed above, provide
8354 symbolic links in that font directory pointing to
8355 the files' actual location in the filesystem. Such
8356 a location must comply with the FHS.
8360 Font packages should not contain both 75dpi and
8361 100dpi versions of a font. If both are available,
8362 they should be provided in separate binary packages
8363 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8364 the names of the packages containing the
8365 corresponding fonts.
8369 Fonts destined for the <file>misc</file> subdirectory
8370 should not be included in the same package as 75dpi
8371 or 100dpi fonts; instead, they should be provided in
8372 a separate package with <tt>-misc</tt> appended to
8377 Font packages must not provide the files
8378 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8379 <file>fonts.scale</file> in a font directory:
8382 <file>fonts.dir</file> files must not be provided at all.
8386 <file>fonts.alias</file> and <file>fonts.scale</file>
8387 files, if needed, should be provided in the
8389 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8390 where <var>fontdir</var> is the name of the
8392 <file>/usr/share/fonts/X11/</file> where the
8393 package's corresponding fonts are stored
8394 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8395 <var>package</var> is the name of the package
8396 that provides these fonts, and
8397 <var>extension</var> is either <tt>scale</tt>
8398 or <tt>alias</tt>, whichever corresponds to
8405 Font packages must declare a dependency on
8406 <tt>xfonts-utils</tt> in their control
8411 Font packages that provide one or more
8412 <file>fonts.scale</file> files as described above must
8413 invoke <prgn>update-fonts-scale</prgn> on each
8414 directory into which they installed fonts
8415 <em>before</em> invoking
8416 <prgn>update-fonts-dir</prgn> on that directory.
8417 This invocation must occur in both the
8418 <prgn>postinst</prgn> (for all arguments) and
8419 <prgn>postrm</prgn> (for all arguments except
8420 <tt>upgrade</tt>) scripts.
8424 Font packages that provide one or more
8425 <file>fonts.alias</file> files as described above must
8426 invoke <prgn>update-fonts-alias</prgn> on each
8427 directory into which they installed fonts. This
8428 invocation must occur in both the
8429 <prgn>postinst</prgn> (for all arguments) and
8430 <prgn>postrm</prgn> (for all arguments except
8431 <tt>upgrade</tt>) scripts.
8435 Font packages must invoke
8436 <prgn>update-fonts-dir</prgn> on each directory into
8437 which they installed fonts. This invocation must
8438 occur in both the <prgn>postinst</prgn> (for all
8439 arguments) and <prgn>postrm</prgn> (for all
8440 arguments except <tt>upgrade</tt>) scripts.
8444 Font packages must not provide alias names for the
8445 fonts they include which collide with alias names
8446 already in use by fonts already packaged.
8450 Font packages must not provide fonts with the same
8451 XLFD registry name as another font already packaged.
8458 <heading>Application defaults files</heading>
8461 Application defaults files must be installed in the
8462 directory <file>/etc/X11/app-defaults/</file> (use of a
8463 localized subdirectory of <file>/etc/X11/</file> as described
8464 in the <em>X Toolkit Intrinsics - C Language
8465 Interface</em> manual is also permitted). They must be
8466 registered as <tt>conffile</tt>s or handled as
8467 configuration files.
8471 Customization of programs' X resources may also be
8472 supported with the provision of a file with the same name
8473 as that of the package placed in the
8474 <file>/etc/X11/Xresources/</file> directory, which must
8475 registered as a <tt>conffile</tt> or handled as a
8476 configuration file.<footnote>
8477 Note that this mechanism is not the same as using
8478 app-defaults; app-defaults are tied to the client
8479 binary on the local file system, whereas X resources
8480 are stored in the X server and affect all connecting
8487 <heading>Installation directory issues</heading>
8490 Packages using the X Window System should not be
8491 configured to install files under the
8492 <file>/usr/X11R6/</file> directory. The
8493 <file>/usr/X11R6/</file> directory hierarchy should be
8494 regarded as obsolete.
8498 Programs that use GNU <prgn>autoconf</prgn> and
8499 <prgn>automake</prgn> are usually easily configured at
8500 compile time to use <file>/usr/</file> instead of
8501 <file>/usr/X11R6/</file>, and this should be done whenever
8502 possible. Configuration files for window managers and
8503 display managers should be placed in a subdirectory of
8504 <file>/etc/X11/</file> corresponding to the package name due
8505 to these programs' tight integration with the mechanisms
8506 of the X Window System. Application-level programs should
8507 use the <file>/etc/</file> directory unless otherwise mandated
8512 The installation of files into subdirectories
8513 of <file>/usr/X11R6/include/X11/</file> and
8514 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8515 package maintainers should determine if subdirectories of
8516 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8521 Packages should install any relevant files into the
8522 directories <file>/usr/include/X11/</file> and
8523 <file>/usr/lib/X11/</file>, but if they do so, they must
8524 pre-depend on <tt>x11-common (>=
8525 1:7.0.0)</tt><footnote>
8527 These libraries used to be all symbolic
8528 links. However, with <tt>X11R7</tt>,
8529 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8530 are now real directories, and packages
8531 <strong>should</strong> ship their files here instead
8532 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8533 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8534 responsible for converting these symlinks into
8542 <heading>The OSF/Motif and OpenMotif libraries</heading>
8545 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8546 OpenMotif libraries</em><footnote>
8547 OSF/Motif and OpenMotif are collectively referred to as
8548 "Motif" in this policy document.
8550 should be compiled against and tested with LessTif (a free
8551 re-implementation of Motif) instead. If the maintainer
8552 judges that the program or programs do not work
8553 sufficiently well with LessTif to be distributed and
8554 supported, but do so when compiled against Motif, then two
8555 versions of the package should be created; one linked
8556 statically against Motif and with <tt>-smotif</tt>
8557 appended to the package name, and one linked dynamically
8558 against Motif and with <tt>-dmotif</tt> appended to the
8563 Both Motif-linked versions are dependent
8564 upon non-DFSG-compliant software and thus cannot be
8565 uploaded to the <em>main</em> distribution; if the
8566 software is itself DFSG-compliant it may be uploaded to
8567 the <em>contrib</em> distribution. While known existing
8568 versions of Motif permit unlimited redistribution of
8569 binaries linked against the library (whether statically or
8570 dynamically), it is the package maintainer's
8571 responsibility to determine whether this is permitted by
8572 the license of the copy of Motif in their possession.
8578 <heading>Perl programs and modules</heading>
8581 Perl programs and modules should follow the current Perl policy.
8585 The Perl policy can be found in the <tt>perl-policy</tt>
8586 files in the <tt>debian-policy</tt> package.
8587 It is also available from the Debian web mirrors at
8588 <tt><url name="/doc/packaging-manuals/perl-policy/"
8589 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8594 <heading>Emacs lisp programs</heading>
8597 Please refer to the "Debian Emacs Policy" for details of how to
8598 package emacs lisp programs.
8602 The Emacs policy is available in
8603 <file>debian-emacs-policy.gz</file> of the
8604 <package>emacsen-common</package> package.
8605 It is also available from the Debian web mirrors at
8606 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8607 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8612 <heading>Games</heading>
8615 The permissions on <file>/var/games</file> are mode 755, owner
8616 <tt>root</tt> and group <tt>root</tt>.
8620 Each game decides on its own security policy.</p>
8623 Games which require protected, privileged access to
8624 high-score files, saved games, etc., may be made
8625 set-<em>group</em>-id (mode 2755) and owned by
8626 <tt>root:games</tt>, and use files and directories with
8627 appropriate permissions (770 <tt>root:games</tt>, for
8628 example). They must not be made
8629 set-<em>user</em>-id, as this causes security problems. (If
8630 an attacker can subvert any set-user-id game they can
8631 overwrite the executable of any other, causing other players
8632 of these games to run a Trojan horse program. With a
8633 set-group-id game the attacker only gets access to less
8634 important game data, and if they can get at the other
8635 players' accounts at all it will take considerably more
8639 Some packages, for example some fortune cookie programs, are
8640 configured by the upstream authors to install with their
8641 data files or other static information made unreadable so
8642 that they can only be accessed through set-id programs
8643 provided. You should not do this in a Debian package: anyone can
8644 download the <file>.deb</file> file and read the data from it,
8645 so there is no point making the files unreadable. Not
8646 making the files unreadable also means that you don't have
8647 to make so many programs set-id, which reduces the risk of a
8651 As described in the FHS, binaries of games should be
8652 installed in the directory <file>/usr/games</file>. This also
8653 applies to games that use the X Window System. Manual pages
8654 for games (X and non-X games) should be installed in
8655 <file>/usr/share/man/man6</file>.</p>
8661 <heading>Documentation</heading>
8664 <heading>Manual pages</heading>
8667 You should install manual pages in <prgn>nroff</prgn> source
8668 form, in appropriate places under <file>/usr/share/man</file>.
8669 You should only use sections 1 to 9 (see the FHS for more
8670 details). You must not install a pre-formatted "cat page".
8674 Each program, utility, and function should have an
8675 associated manual page included in the same package. It is
8676 suggested that all configuration files also have a manual
8677 page included as well. Manual pages for protocols and other
8678 auxiliary things are optional.
8682 If no manual page is available, this is considered as a bug
8683 and should be reported to the Debian Bug Tracking System (the
8684 maintainer of the package is allowed to write this bug report
8685 themselves, if they so desire). Do not close the bug report
8686 until a proper man page is available.<footnote>
8687 It is not very hard to write a man page. See the
8688 <url id="http://www.schweikhardt.net/man_page_howto.html"
8689 name="Man-Page-HOWTO">,
8690 <manref name="man" section="7">, the examples
8691 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8692 the helper programs <prgn>help2man</prgn>, or the
8693 directory <file>/usr/share/doc/man-db/examples</file>.
8698 You may forward a complaint about a missing man page to the
8699 upstream authors, and mark the bug as forwarded in the
8700 Debian bug tracking system. Even though the GNU Project do
8701 not in general consider the lack of a man page to be a bug,
8702 we do; if they tell you that they don't consider it a bug
8703 you should leave the bug in our bug tracking system open
8708 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8712 If one man page needs to be accessible via several names it
8713 is better to use a symbolic link than the <file>.so</file>
8714 feature, but there is no need to fiddle with the relevant
8715 parts of the upstream source to change from <file>.so</file> to
8716 symlinks: don't do it unless it's easy. You should not
8717 create hard links in the manual page directories, nor put
8718 absolute filenames in <file>.so</file> directives. The filename
8719 in a <file>.so</file> in a man page should be relative to the
8720 base of the man page tree (usually
8721 <file>/usr/share/man</file>). If you do not create any links
8722 (whether symlinks, hard links, or <tt>.so</tt> directives)
8723 in the file system to the alternate names of the man page,
8724 then you should not rely on <prgn>man</prgn> finding your
8725 man page under those names based solely on the information in
8726 the man page's header.<footnote>
8727 Supporting this in <prgn>man</prgn> often requires
8728 unreasonable processing time to find a manual page or to
8729 report that none exists, and moves knowledge into man's
8730 database that would be better left in the file system.
8731 This support is therefore deprecated and will cease to
8732 be present in the future.
8737 Manual pages in locale-specific subdirectories of
8738 <file>/usr/share/man</file> should use either UTF-8 or the usual
8739 legacy encoding for that language (normally the one corresponding
8740 to the shortest relevant locale name in
8741 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8742 <file>/usr/share/man/fr</file> should use either UTF-8 or
8743 ISO-8859-1.<footnote>
8744 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8745 use. In future, all manual pages will be required to use
8751 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8752 included in the subdirectory name unless it indicates a
8753 significant difference in the language, as this excludes
8754 speakers of the language in other countries.<footnote>
8755 At the time of writing, Chinese and Portuguese are the main
8756 languages with such differences, so <file>pt_BR</file>,
8757 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8762 Due to limitations in current implementations, all characters
8763 in the manual page source should be representable in the usual
8764 legacy encoding for that language, even if the file is
8765 actually encoded in UTF-8. Safe alternative ways to write many
8766 characters outside that range may be found in
8767 <manref name="groff_char" section="7">.
8772 <heading>Info documents</heading>
8775 Info documents should be installed in <file>/usr/share/info</file>.
8776 They should be compressed with <tt>gzip -9</tt>.
8780 Your package should call <prgn>install-info</prgn> to update
8781 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8782 script when called with a <tt>configure</tt> argument, for
8784 <example compact="compact">
8785 install-info --quiet --section Development Development \
8786 /usr/share/info/foobar.info
8790 It is a good idea to specify a section for the location of
8791 your program; this is done with the <tt>--section</tt>
8792 switch. To determine which section to use, you should look
8793 at <file>/usr/share/info/dir</file> on your system and choose the most
8794 relevant (or create a new section if none of the current
8795 sections are relevant). Note that the <tt>--section</tt>
8796 flag takes two arguments; the first is a regular expression
8797 to match (case-insensitively) against an existing section,
8798 the second is used when creating a new one.</p>
8801 You should remove the entries in the <prgn>prerm</prgn>
8802 script when called with a <tt>remove</tt> argument:
8803 <example compact="compact">
8804 install-info --quiet --remove /usr/share/info/foobar.info
8808 If <prgn>install-info</prgn> cannot find a description entry
8809 in the Info file you must supply one. See <manref
8810 name="install-info" section="8"> for details.</p>
8814 <heading>Additional documentation</heading>
8817 Any additional documentation that comes with the package may
8818 be installed at the discretion of the package maintainer.
8819 Plain text documentation should be installed in the directory
8820 <file>/usr/share/doc/<var>package</var></file>, where
8821 <var>package</var> is the name of the package, and
8822 compressed with <tt>gzip -9</tt> unless it is small.
8826 If a package comes with large amounts of documentation which
8827 many users of the package will not require you should create
8828 a separate binary package to contain it, so that it does not
8829 take up disk space on the machines of users who do not need
8830 or want it installed.</p>
8833 It is often a good idea to put text information files
8834 (<file>README</file>s, changelogs, and so forth) that come with
8835 the source package in <file>/usr/share/doc/<var>package</var></file>
8836 in the binary package. However, you don't need to install
8837 the instructions for building and installing the package, of
8841 Packages must not require the existence of any files in
8842 <file>/usr/share/doc/</file> in order to function
8844 The system administrator should be able to
8845 delete files in <file>/usr/share/doc/</file> without causing
8846 any programs to break.
8848 Any files that are referenced by programs but are also
8849 useful as stand alone documentation should be installed under
8850 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8851 <file>/usr/share/doc/<var>package</var></file>.
8855 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8856 link to another directory in <file>/usr/share/doc</file> only if
8857 the two packages both come from the same source and the
8858 first package Depends on the second.<footnote>
8860 Please note that this does not override the section on
8861 changelog files below, so the file
8862 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8863 must refer to the changelog for the current version of
8864 <var>package</var> in question. In practice, this means
8865 that the sources of the target and the destination of the
8866 symlink must be the same (same source package and
8873 Former Debian releases placed all additional documentation
8874 in <file>/usr/doc/<var>package</var></file>. This has been
8875 changed to <file>/usr/share/doc/<var>package</var></file>,
8876 and packages must not put documentation in the directory
8877 <file>/usr/doc/<var>package</var></file>. <footnote>
8878 At this phase of the transition, we no longer require a
8879 symbolic link in <file>/usr/doc/</file>. At a later point,
8880 policy shall change to make the symbolic links a bug.
8886 <heading>Preferred documentation formats</heading>
8889 The unification of Debian documentation is being carried out
8893 If your package comes with extensive documentation in a
8894 markup format that can be converted to various other formats
8895 you should if possible ship HTML versions in a binary
8896 package, in the directory
8897 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8898 its subdirectories.<footnote>
8899 The rationale: The important thing here is that HTML
8900 docs should be available in <em>some</em> package, not
8901 necessarily in the main binary package.
8906 Other formats such as PostScript may be provided at the
8907 package maintainer's discretion.
8911 <sect id="copyrightfile">
8912 <heading>Copyright information</heading>
8915 Every package must be accompanied by a verbatim copy of its
8916 copyright and distribution license in the file
8917 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8918 file must neither be compressed nor be a symbolic link.
8922 In addition, the copyright file must say where the upstream
8923 sources (if any) were obtained. It should name the original
8924 authors of the package and the Debian maintainer(s) who were
8925 involved with its creation.
8929 Packages in the <em>contrib</em> or <em>non-free</em>
8930 distribution areas should state in the copyright file that the
8931 package is not part of the Debian GNU/Linux distribution and
8932 briefly explain why.
8936 A copy of the file which will be installed in
8937 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8938 be in <file>debian/copyright</file> in the source package.
8942 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8943 link to another directory in <file>/usr/share/doc</file> only if
8944 the two packages both come from the same source and the
8945 first package Depends on the second. These rules are
8946 important because copyrights must be extractable by
8951 Packages distributed under the UCB BSD license, the Apache
8952 license (version 2.0), the Artistic license, the GNU GPL
8953 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8954 the GNU FDL (version 1.2) should refer to the corresponding
8955 files under <file>/usr/share/common-licenses</file>,<footnote>
8958 <file>/usr/share/common-licenses/BSD</file>,
8959 <file>/usr/share/common-licenses/Apache-2.0</file>,
8960 <file>/usr/share/common-licenses/Artistic</file>,
8961 <file>/usr/share/common-licenses/GPL-2</file>,
8962 <file>/usr/share/common-licenses/GPL-3</file>,
8963 <file>/usr/share/common-licenses/LGPL-2</file>,
8964 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8965 <file>/usr/share/common-licenses/LGPL-3</file>, and
8966 <file>/usr/share/common-licenses/GFDL-1.2</file>
8969 </footnote> rather than quoting them in the copyright
8974 You should not use the copyright file as a general <file>README</file>
8975 file. If your package has such a file it should be
8976 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8977 <file>README.Debian</file> or some other appropriate place.</p>
8981 <heading>Examples</heading>
8984 Any examples (configurations, source files, whatever),
8985 should be installed in a directory
8986 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8987 files should not be referenced by any program: they're there
8988 for the benefit of the system administrator and users as
8989 documentation only. Architecture-specific example files
8990 should be installed in a directory
8991 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8993 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8994 latter directory itself may be a symbolic link to the
8999 If the purpose of a package is to provide examples, then the
9000 example files may be installed into
9001 <file>/usr/share/doc/<var>package</var></file>.
9005 <sect id="changelogs">
9006 <heading>Changelog files</heading>
9009 Packages that are not Debian-native must contain a
9010 compressed copy of the <file>debian/changelog</file> file from
9011 the Debian source tree in
9012 <file>/usr/share/doc/<var>package</var></file> with the name
9013 <file>changelog.Debian.gz</file>.
9017 If an upstream changelog is available, it should be accessible as
9018 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9019 plain text. If the upstream changelog is distributed in
9020 HTML, it should be made available in that form as
9021 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9022 and a plain text <file>changelog.gz</file> should be generated
9023 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9024 the upstream changelog files do not already conform to this
9025 naming convention, then this may be achieved either by
9026 renaming the files, or by adding a symbolic link, at the
9027 maintainer's discretion.<footnote>
9028 Rationale: People should not have to look in places for
9029 upstream changelogs merely because they are given
9030 different names or are distributed in HTML format.
9035 All of these files should be installed compressed using
9036 <tt>gzip -9</tt>, as they will become large with time even
9037 if they start out small.
9041 If the package has only one changelog which is used both as
9042 the Debian changelog and the upstream one because there is
9043 no separate upstream maintainer then that changelog should
9044 usually be installed as
9045 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9046 there is a separate upstream maintainer, but no upstream
9047 changelog, then the Debian changelog should still be called
9048 <file>changelog.Debian.gz</file>.
9052 For details about the format and contents of the Debian
9053 changelog file, please see <ref id="dpkgchangelog">.
9058 <appendix id="pkg-scope">
9059 <heading>Introduction and scope of these appendices</heading>
9062 These appendices are taken essentially verbatim from the
9063 now-deprecated Packaging Manual, version 3.2.1.0. They are
9064 the chapters which are likely to be of use to package
9065 maintainers and which have not already been included in the
9066 policy document itself. Most of these sections are very likely
9067 not relevant to policy; they should be treated as
9068 documentation for the packaging system. Please note that these
9069 appendices are included for convenience, and for historical
9070 reasons: they used to be part of policy package, and they have
9071 not yet been incorporated into dpkg documentation. However,
9072 they still have value, and hence they are presented here.
9076 They have not yet been checked to ensure that they are
9077 compatible with the contents of policy, and if there are any
9078 contradictions, the version in the main policy document takes
9079 precedence. The remaining chapters of the old Packaging
9080 Manual have also not been read in detail to ensure that there
9081 are not parts which have been left out. Both of these will be
9086 Certain parts of the Packaging manual were integrated into the
9087 Policy Manual proper, and removed from the appendices. Links
9088 have been placed from the old locations to the new ones.
9092 <prgn>dpkg</prgn> is a suite of programs for creating binary
9093 package files and installing and removing them on Unix
9095 <prgn>dpkg</prgn> is targeted primarily at Debian
9096 GNU/Linux, but may work on or be ported to other
9102 The binary packages are designed for the management of
9103 installed executable programs (usually compiled binaries) and
9104 their associated data, though source code examples and
9105 documentation are provided as part of some packages.</p>
9108 This manual describes the technical aspects of creating Debian
9109 binary packages (<file>.deb</file> files). It documents the
9110 behavior of the package management programs
9111 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9112 they interact with packages.</p>
9115 It also documents the interaction between
9116 <prgn>dselect</prgn>'s core and the access method scripts it
9117 uses to actually install the selected packages, and describes
9118 how to create a new access method.</p>
9121 This manual does not go into detail about the options and
9122 usage of the package building and installation tools. It
9123 should therefore be read in conjunction with those programs'
9128 The utility programs which are provided with <prgn>dpkg</prgn>
9129 for managing various system configuration and similar issues,
9130 such as <prgn>update-rc.d</prgn> and
9131 <prgn>install-info</prgn>, are not described in detail here -
9132 please see their man pages.
9136 It is assumed that the reader is reasonably familiar with the
9137 <prgn>dpkg</prgn> System Administrators' manual.
9138 Unfortunately this manual does not yet exist.
9142 The Debian version of the FSF's GNU hello program is provided
9143 as an example for people wishing to create Debian
9144 packages. The Debian <prgn>debmake</prgn> package is
9145 recommended as a very helpful tool in creating and maintaining
9146 Debian packages. However, while the tools and examples are
9147 helpful, they do not replace the need to read and follow the
9148 Policy and Programmer's Manual.</p>
9151 <appendix id="pkg-binarypkg">
9152 <heading>Binary packages (from old Packaging Manual)</heading>
9155 The binary package has two main sections. The first part
9156 consists of various control information files and scripts used
9157 by <prgn>dpkg</prgn> when installing and removing. See <ref
9158 id="pkg-controlarea">.
9162 The second part is an archive containing the files and
9163 directories to be installed.
9167 In the future binary packages may also contain other
9168 components, such as checksums and digital signatures. The
9169 format for the archive is described in full in the
9170 <file>deb(5)</file> man page.
9174 <sect id="pkg-bincreating"><heading>Creating package files -
9175 <prgn>dpkg-deb</prgn>
9179 All manipulation of binary package files is done by
9180 <prgn>dpkg-deb</prgn>; it's the only program that has
9181 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9182 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9183 will spot that the options requested are appropriate to
9184 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9189 In order to create a binary package you must make a
9190 directory tree which contains all the files and directories
9191 you want to have in the file system data part of the package.
9192 In Debian-format source packages this directory is usually
9193 <file>debian/tmp</file>, relative to the top of the package's
9198 They should have the locations (relative to the root of the
9199 directory tree you're constructing) ownerships and
9200 permissions which you want them to have on the system when
9205 With current versions of <prgn>dpkg</prgn> the uid/username
9206 and gid/groupname mappings for the users and groups being
9207 used should be the same on the system where the package is
9208 built and the one where it is installed.
9212 You need to add one special directory to the root of the
9213 miniature file system tree you're creating:
9214 <prgn>DEBIAN</prgn>. It should contain the control
9215 information files, notably the binary package control file
9216 (see <ref id="pkg-controlfile">).
9220 The <prgn>DEBIAN</prgn> directory will not appear in the
9221 file system archive of the package, and so won't be installed
9222 by <prgn>dpkg</prgn> when the package is installed.
9226 When you've prepared the package, you should invoke:
9228 dpkg --build <var>directory</var>
9233 This will build the package in
9234 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9235 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9236 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9241 See the man page <manref name="dpkg-deb" section="8"> for details of how
9242 to examine the contents of this newly-created file. You may find the
9243 output of following commands enlightening:
9245 dpkg-deb --info <var>filename</var>.deb
9246 dpkg-deb --contents <var>filename</var>.deb
9247 dpkg --contents <var>filename</var>.deb
9249 To view the copyright file for a package you could use this command:
9251 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9256 <sect id="pkg-controlarea">
9257 <heading>Package control information files</heading>
9260 The control information portion of a binary package is a
9261 collection of files with names known to <prgn>dpkg</prgn>.
9262 It will treat the contents of these files specially - some
9263 of them contain information used by <prgn>dpkg</prgn> when
9264 installing or removing the package; others are scripts which
9265 the package maintainer wants <prgn>dpkg</prgn> to run.
9269 It is possible to put other files in the package control
9270 area, but this is not generally a good idea (though they
9271 will largely be ignored).
9275 Here is a brief list of the control info files supported by
9276 <prgn>dpkg</prgn> and a summary of what they're used for.
9281 <tag><tt>control</tt>
9284 This is the key description file used by
9285 <prgn>dpkg</prgn>. It specifies the package's name
9286 and version, gives its description for the user,
9287 states its relationships with other packages, and so
9288 forth. See <ref id="sourcecontrolfiles"> and
9289 <ref id="binarycontrolfiles">.
9293 It is usually generated automatically from information
9294 in the source package by the
9295 <prgn>dpkg-gencontrol</prgn> program, and with
9296 assistance from <prgn>dpkg-shlibdeps</prgn>.
9297 See <ref id="pkg-sourcetools">.
9301 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9306 These are executable files (usually scripts) which
9307 <prgn>dpkg</prgn> runs during installation, upgrade
9308 and removal of packages. They allow the package to
9309 deal with matters which are particular to that package
9310 or require more complicated processing than that
9311 provided by <prgn>dpkg</prgn>. Details of when and
9312 how they are called are in <ref id="maintainerscripts">.
9316 It is very important to make these scripts idempotent.
9317 See <ref id="idempotency">.
9321 The maintainer scripts are guaranteed to run with a
9322 controlling terminal and can interact with the user.
9323 See <ref id="controllingterminal">.
9327 <tag><tt>conffiles</tt>
9330 This file contains a list of configuration files which
9331 are to be handled automatically by <prgn>dpkg</prgn>
9332 (see <ref id="pkg-conffiles">). Note that not necessarily
9333 every configuration file should be listed here.
9336 <tag><tt>shlibs</tt>
9339 This file contains a list of the shared libraries
9340 supplied by the package, with dependency details for
9341 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9342 when it determines what dependencies are required in a
9343 package control file. The <tt>shlibs</tt> file format
9344 is described on <ref id="shlibs">.
9349 <sect id="pkg-controlfile">
9350 <heading>The main control information file: <tt>control</tt></heading>
9353 The most important control information file used by
9354 <prgn>dpkg</prgn> when it installs a package is
9355 <tt>control</tt>. It contains all the package's "vital
9360 The binary package control files of packages built from
9361 Debian sources are made by a special tool,
9362 <prgn>dpkg-gencontrol</prgn>, which reads
9363 <file>debian/control</file> and <file>debian/changelog</file> to
9364 find the information it needs. See <ref id="pkg-sourcepkg"> for
9369 The fields in binary package control files are listed in
9370 <ref id="binarycontrolfiles">.
9374 A description of the syntax of control files and the purpose
9375 of the fields is available in <ref id="controlfields">.
9380 <heading>Time Stamps</heading>
9383 See <ref id="timestamps">.
9388 <appendix id="pkg-sourcepkg">
9389 <heading>Source packages (from old Packaging Manual) </heading>
9392 The Debian binary packages in the distribution are generated
9393 from Debian sources, which are in a special format to assist
9394 the easy and automatic building of binaries.
9397 <sect id="pkg-sourcetools">
9398 <heading>Tools for processing source packages</heading>
9401 Various tools are provided for manipulating source packages;
9402 they pack and unpack sources and help build of binary
9403 packages and help manage the distribution of new versions.
9407 They are introduced and typical uses described here; see
9408 <manref name="dpkg-source" section="1"> for full
9409 documentation about their arguments and operation.
9413 For examples of how to construct a Debian source package,
9414 and how to use those utilities that are used by Debian
9415 source packages, please see the <prgn>hello</prgn> example
9419 <sect1 id="pkg-dpkg-source">
9421 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9426 This program is frequently used by hand, and is also
9427 called from package-independent automated building scripts
9428 such as <prgn>dpkg-buildpackage</prgn>.
9432 To unpack a package it is typically invoked with
9434 dpkg-source -x <var>.../path/to/filename</var>.dsc
9439 with the <file><var>filename</var>.tar.gz</file> and
9440 <file><var>filename</var>.diff.gz</file> (if applicable) in
9441 the same directory. It unpacks into
9442 <file><var>package</var>-<var>version</var></file>, and if
9444 <file><var>package</var>-<var>version</var>.orig</file>, in
9445 the current directory.
9449 To create a packed source archive it is typically invoked:
9451 dpkg-source -b <var>package</var>-<var>version</var>
9456 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9457 <file>.diff.gz</file> (if appropriate) in the current
9458 directory. <prgn>dpkg-source</prgn> does not clean the
9459 source tree first - this must be done separately if it is
9464 See also <ref id="pkg-sourcearchives">.</p>
9468 <sect1 id="pkg-dpkg-buildpackage">
9470 <prgn>dpkg-buildpackage</prgn> - overall package-building
9475 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9476 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9477 targets <tt>clean</tt>, <tt>build</tt> and
9478 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9479 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9480 source and binary package upload.
9484 It is usually invoked by hand from the top level of the
9485 built or unbuilt source directory. It may be invoked with
9486 no arguments; useful arguments include:
9487 <taglist compact="compact">
9488 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9491 Do not sign the <tt>.changes</tt> file or the
9492 source package <tt>.dsc</tt> file, respectively.</p>
9494 <tag><tt>-p<var>sign-command</var></tt></tag>
9497 Invoke <var>sign-command</var> instead of finding
9498 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9499 <var>sign-command</var> must behave just like
9500 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9502 <tag><tt>-r<var>root-command</var></tt></tag>
9505 When root privilege is required, invoke the command
9506 <var>root-command</var>. <var>root-command</var>
9507 should invoke its first argument as a command, from
9508 the <prgn>PATH</prgn> if necessary, and pass its
9509 second and subsequent arguments to the command it
9510 calls. If no <var>root-command</var> is supplied
9511 then <var>dpkg-buildpackage</var> will take no
9512 special action to gain root privilege, so that for
9513 most packages it will have to be invoked as root to
9516 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9519 Two types of binary-only build and upload - see
9520 <manref name="dpkg-source" section="1">.
9527 <sect1 id="pkg-dpkg-gencontrol">
9529 <prgn>dpkg-gencontrol</prgn> - generates binary package
9534 This program is usually called from <file>debian/rules</file>
9535 (see <ref id="pkg-sourcetree">) in the top level of the source
9540 This is usually done just before the files and directories in the
9541 temporary directory tree where the package is being built have their
9542 permissions and ownerships set and the package is constructed using
9543 <prgn>dpkg-deb/</prgn>
9545 This is so that the control file which is produced has
9546 the right permissions
9551 <prgn>dpkg-gencontrol</prgn> must be called after all the
9552 files which are to go into the package have been placed in
9553 the temporary build directory, so that its calculation of
9554 the installed size of a package is correct.
9558 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9559 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9560 variable substitutions created by
9561 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9566 For a package which generates only one binary package, and
9567 which builds it in <file>debian/tmp</file> relative to the top
9568 of the source package, it is usually sufficient to call
9569 <prgn>dpkg-gencontrol</prgn>.
9573 Sources which build several binaries will typically need
9576 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9577 </example> The <tt>-P</tt> tells
9578 <prgn>dpkg-gencontrol</prgn> that the package is being
9579 built in a non-default directory, and the <tt>-p</tt>
9580 tells it which package's control file should be generated.
9584 <prgn>dpkg-gencontrol</prgn> also adds information to the
9585 list of files in <file>debian/files</file>, for the benefit of
9586 (for example) a future invocation of
9587 <prgn>dpkg-genchanges</prgn>.</p>
9590 <sect1 id="pkg-dpkg-shlibdeps">
9592 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9597 This program is usually called from <file>debian/rules</file>
9598 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9599 id="pkg-sourcetree">), in the top level of the source tree.
9603 Its arguments are executables and shared libraries
9606 They may be specified either in the locations in the
9607 source tree where they are created or in the locations
9608 in the temporary build tree where they are installed
9609 prior to binary package creation.
9611 </footnote> for which shared library dependencies should
9612 be included in the binary package's control file.
9616 If some of the found shared libraries should only
9617 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9618 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9619 by using the <tt>-d<var>dependency-field</var></tt> option
9620 before those executable(s). (Each <tt>-d</tt> option
9621 takes effect until the next <tt>-d</tt>.)
9625 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9626 output control file to be modified. Instead by default it
9627 adds to the <file>debian/substvars</file> file variable
9628 settings like <tt>shlibs:Depends</tt>. These variable
9629 settings must be referenced in dependency fields in the
9630 appropriate per-binary-package sections of the source
9635 For example, a package that generates an essential part
9636 which requires dependencies, and optional parts that
9637 which only require a recommendation, would separate those
9638 two sets of dependencies into two different fields.<footnote>
9639 At the time of writing, an example for this was the
9640 <package/xmms/ package, with Depends used for the xmms
9641 executable, Recommends for the plug-ins and Suggests for
9642 even more optional features provided by unzip.
9644 It can say in its <file>debian/rules</file>:
9646 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9647 -dRecommends <var>optionalpart anotheroptionalpart</var>
9649 and then in its main control file <file>debian/control</file>:
9652 Depends: ${shlibs:Depends}
9653 Recommends: ${shlibs:Recommends}
9659 Sources which produce several binary packages with
9660 different shared library dependency requirements can use
9661 the <tt>-p<var>varnameprefix</var></tt> option to override
9662 the default <tt>shlibs:</tt> prefix (one invocation of
9663 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9664 They can thus produce several sets of dependency
9665 variables, each of the form
9666 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9667 which can be referred to in the appropriate parts of the
9668 binary package control files.
9673 <sect1 id="pkg-dpkg-distaddfile">
9675 <prgn>dpkg-distaddfile</prgn> - adds a file to
9676 <file>debian/files</file>
9680 Some packages' uploads need to include files other than
9681 the source and binary package files.
9685 <prgn>dpkg-distaddfile</prgn> adds a file to the
9686 <file>debian/files</file> file so that it will be included in
9687 the <file>.changes</file> file when
9688 <prgn>dpkg-genchanges</prgn> is run.
9692 It is usually invoked from the <tt>binary</tt> target of
9693 <file>debian/rules</file>:
9695 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9697 The <var>filename</var> is relative to the directory where
9698 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9699 is usually the directory above the top level of the source
9700 tree. The <file>debian/rules</file> target should put the
9701 file there just before or just after calling
9702 <prgn>dpkg-distaddfile</prgn>.
9706 The <var>section</var> and <var>priority</var> are passed
9707 unchanged into the resulting <file>.changes</file> file.
9712 <sect1 id="pkg-dpkg-genchanges">
9714 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9719 This program is usually called by package-independent
9720 automatic building scripts such as
9721 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9726 It is usually called in the top level of a built source
9727 tree, and when invoked with no arguments will print out a
9728 straightforward <file>.changes</file> file based on the
9729 information in the source package's changelog and control
9730 file and the binary and source packages which should have
9736 <sect1 id="pkg-dpkg-parsechangelog">
9738 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9739 representation of a changelog
9743 This program is used internally by
9744 <prgn>dpkg-source</prgn> et al. It may also occasionally
9745 be useful in <file>debian/rules</file> and elsewhere. It
9746 parses a changelog, <file>debian/changelog</file> by default,
9747 and prints a control-file format representation of the
9748 information in it to standard output.
9752 <sect1 id="pkg-dpkg-architecture">
9754 <prgn>dpkg-architecture</prgn> - information about the build and
9759 This program can be used manually, but is also invoked by
9760 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9761 environment or make variables which specify the build and host
9762 architecture for the package building process.
9767 <sect id="pkg-sourcetree">
9768 <heading>The Debianised source tree</heading>
9771 The source archive scheme described later is intended to
9772 allow a Debianised source tree with some associated control
9773 information to be reproduced and transported easily. The
9774 Debianised source tree is a version of the original program
9775 with certain files added for the benefit of the
9776 Debianisation process, and with any other changes required
9777 made to the rest of the source code and installation
9782 The extra files created for Debian are in the subdirectory
9783 <file>debian</file> of the top level of the Debianised source
9784 tree. They are described below.
9787 <sect1 id="pkg-debianrules">
9788 <heading><file>debian/rules</file> - the main building script</heading>
9791 See <ref id="debianrules">.
9796 <sect1 id="pkg-dpkgchangelog">
9797 <heading><file>debian/changelog</file></heading>
9800 See <ref id="dpkgchangelog">.
9804 It is recommended that the entire changelog be encoded in the
9805 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9807 <url id="http://www.unicode.org/"
9808 name="Unicode">.<footnote>
9810 I think it is fairly obvious that we need to
9811 eventually transition to UTF-8 for our package
9812 infrastructure; it is really the only sane char-set in
9813 an international environment. Now, we can't switch to
9814 using UTF-8 for package control fields and the like
9815 until dpkg has better support, but one thing we can
9816 start doing today is requesting that Debian changelogs
9817 are UTF-8 encoded. At some point in time, we can start
9818 requiring them to do so.
9821 Checking for non-UTF8 characters in a changelog is
9822 trivial. Dump the file through
9823 <example>iconv -f utf-8 -t ucs-4</example>
9824 discard the output, and check the return
9825 value. If there are any characters in the stream
9826 which are invalid UTF-8 sequences, iconv will exit
9827 with an error code; and this will be the case for the
9828 vast majority of other character sets.
9833 <sect2><heading>Defining alternative changelog formats
9837 It is possible to use a different format to the standard
9838 one, by providing a parser for the format you wish to
9843 In order to have <tt>dpkg-parsechangelog</tt> run your
9844 parser, you must include a line within the last 40 lines
9845 of your file matching the Perl regular expression:
9846 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9847 parentheses should be the name of the format. For
9848 example, you might say:
9850 @@@ changelog-format: joebloggs @@@
9852 Changelog format names are non-empty strings of alphanumerics.
9856 If such a line exists then <tt>dpkg-parsechangelog</tt>
9857 will look for the parser as
9858 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9860 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9861 it is an error for it not to find it, or for it not to
9862 be an executable program. The default changelog format
9863 is <tt>dpkg</tt>, and a parser for it is provided with
9864 the <tt>dpkg</tt> package.
9868 The parser will be invoked with the changelog open on
9869 standard input at the start of the file. It should read
9870 the file (it may seek if it wishes) to determine the
9871 information required and return the parsed information
9872 to standard output in the form of a series of control
9873 fields in the standard format. By default it should
9874 return information about only the most recent version in
9875 the changelog; it should accept a
9876 <tt>-v<var>version</var></tt> option to return changes
9877 information from all versions present <em>strictly
9878 after</em> <var>version</var>, and it should then be an
9879 error for <var>version</var> not to be present in the
9885 <list compact="compact">
9886 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9887 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9888 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9889 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9890 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9891 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9892 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9897 If several versions are being returned (due to the use
9898 of <tt>-v</tt>), the urgency value should be of the
9899 highest urgency code listed at the start of any of the
9900 versions requested followed by the concatenated
9901 (space-separated) comments from all the versions
9902 requested; the maintainer, version, distribution and
9903 date should always be from the most recent version.
9907 For the format of the <tt>Changes</tt> field see
9908 <ref id="f-Changes">.
9912 If the changelog format which is being parsed always or
9913 almost always leaves a blank line between individual
9914 change notes these blank lines should be stripped out,
9915 so as to make the resulting output compact.
9919 If the changelog format does not contain date or package
9920 name information this information should be omitted from
9921 the output. The parser should not attempt to synthesize
9922 it or find it from other sources.
9926 If the changelog does not have the expected format the
9927 parser should exit with a nonzero exit status, rather
9928 than trying to muddle through and possibly generating
9933 A changelog parser may not interact with the user at
9939 <sect1 id="pkg-srcsubstvars">
9940 <heading><file>debian/substvars</file> and variable substitutions</heading>
9943 See <ref id="substvars">.
9949 <heading><file>debian/files</file></heading>
9952 See <ref id="debianfiles">.
9956 <sect1><heading><file>debian/tmp</file>
9960 This is the canonical temporary location for the
9961 construction of binary packages by the <tt>binary</tt>
9962 target. The directory <file>tmp</file> serves as the root of
9963 the file system tree as it is being constructed (for
9964 example, by using the package's upstream makefiles install
9965 targets and redirecting the output there), and it also
9966 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9967 id="pkg-bincreating">.
9971 If several binary packages are generated from the same
9972 source tree it is usual to use several
9973 <file>debian/tmp<var>something</var></file> directories, for
9974 example <file>tmp-a</file> or <file>tmp-doc</file>.
9978 Whatever <file>tmp</file> directories are created and used by
9979 <tt>binary</tt> must of course be removed by the
9980 <tt>clean</tt> target.</p></sect1>
9984 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9988 As it exists on the FTP site, a Debian source package
9989 consists of three related files. You must have the right
9990 versions of all three to be able to use them.
9995 <tag>Debian source control file - <tt>.dsc</tt></tag>
9997 This file is a control file used by <prgn>dpkg-source</prgn>
9998 to extract a source package.
9999 See <ref id="debiansourcecontrolfiles">.
10003 Original source archive -
10005 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10011 This is a compressed (with <tt>gzip -9</tt>)
10012 <prgn>tar</prgn> file containing the source code from
10013 the upstream authors of the program.
10018 Debianisation diff -
10020 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10026 This is a unified context diff (<tt>diff -u</tt>)
10027 giving the changes which are required to turn the
10028 original source into the Debian source. These changes
10029 may only include editing and creating plain files.
10030 The permissions of files, the targets of symbolic
10031 links and the characteristics of special files or
10032 pipes may not be changed and no files may be removed
10037 All the directories in the diff must exist, except the
10038 <file>debian</file> subdirectory of the top of the source
10039 tree, which will be created by
10040 <prgn>dpkg-source</prgn> if necessary when unpacking.
10044 The <prgn>dpkg-source</prgn> program will
10045 automatically make the <file>debian/rules</file> file
10046 executable (see below).</p></item>
10051 If there is no original source code - for example, if the
10052 package is specially prepared for Debian or the Debian
10053 maintainer is the same as the upstream maintainer - the
10054 format is slightly different: then there is no diff, and the
10056 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10057 and preferably contains a directory named
10058 <file><var>package</var>-<var>version</var></file>.
10063 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10066 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10067 Debian source package. However, if it is not available it
10068 is possible to unpack a Debian source archive as follows:
10069 <enumlist compact="compact">
10072 Untar the tarfile, which will create a <file>.orig</file>
10076 <p>Rename the <file>.orig</file> directory to
10077 <file><var>package</var>-<var>version</var></file>.</p>
10081 Create the subdirectory <file>debian</file> at the top of
10082 the source tree.</p>
10084 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10086 <item><p>Untar the tarfile again if you want a copy of the original
10087 source code alongside the Debianised version.</p>
10092 It is not possible to generate a valid Debian source archive
10093 without using <prgn>dpkg-source</prgn>. In particular,
10094 attempting to use <prgn>diff</prgn> directly to generate the
10095 <file>.diff.gz</file> file will not work.
10099 <heading>Restrictions on objects in source packages</heading>
10102 The source package may not contain any hard links
10104 This is not currently detected when building source
10105 packages, but only when extracting
10109 Hard links may be permitted at some point in the
10110 future, but would require a fair amount of
10112 </footnote>, device special files, sockets or setuid or
10115 Setgid directories are allowed.
10120 The source packaging tools manage the changes between the
10121 original and Debianised source using <prgn>diff</prgn> and
10122 <prgn>patch</prgn>. Turning the original source tree as
10123 included in the <file>.orig.tar.gz</file> into the debianised
10124 source must not involve any changes which cannot be
10125 handled by these tools. Problematic changes which cause
10126 <prgn>dpkg-source</prgn> to halt with an error when
10127 building the source package are:
10128 <list compact="compact">
10129 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10131 <item><p>Changing the targets of symbolic links.</p>
10133 <item><p>Creating directories, other than <file>debian</file>.</p>
10135 <item><p>Changes to the contents of binary files.</p></item>
10136 </list> Changes which cause <prgn>dpkg-source</prgn> to
10137 print a warning but continue anyway are:
10138 <list compact="compact">
10141 Removing files, directories or symlinks.
10143 Renaming a file is not treated specially - it is
10144 seen as the removal of the old file (which
10145 generates a warning, but is otherwise ignored),
10146 and the creation of the new one.
10152 Changed text files which are missing the usual final
10153 newline (either in the original or the modified
10158 Changes which are not represented, but which are not detected by
10159 <prgn>dpkg-source</prgn>, are:
10160 <list compact="compact">
10161 <item><p>Changing the permissions of files (other than
10162 <file>debian/rules</file>) and directories.</p></item>
10167 The <file>debian</file> directory and <file>debian/rules</file>
10168 are handled specially by <prgn>dpkg-source</prgn> - before
10169 applying the changes it will create the <file>debian</file>
10170 directory, and afterwards it will make
10171 <file>debian/rules</file> world-executable.
10177 <appendix id="pkg-controlfields">
10178 <heading>Control files and their fields (from old Packaging Manual)</heading>
10181 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10182 data in a common format, known as control files. Binary and
10183 source packages have control data as do the <file>.changes</file>
10184 files which control the installation of uploaded files, and
10185 <prgn>dpkg</prgn>'s internal databases are in a similar
10190 <heading>Syntax of control files</heading>
10193 See <ref id="controlsyntax">.
10197 It is important to note that there are several fields which
10198 are optional as far as <prgn>dpkg</prgn> and the related
10199 tools are concerned, but which must appear in every Debian
10200 package, or whose omission may cause problems.
10205 <heading>List of fields</heading>
10208 See <ref id="controlfieldslist">.
10212 This section now contains only the fields that didn't belong
10213 to the Policy manual.
10216 <sect1 id="pkg-f-Filename">
10217 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10220 These fields in <tt>Packages</tt> files give the
10221 filename(s) of (the parts of) a package in the
10222 distribution directories, relative to the root of the
10223 Debian hierarchy. If the package has been split into
10224 several parts the parts are all listed in order, separated
10229 <sect1 id="pkg-f-Size">
10230 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10233 These fields in <file>Packages</file> files give the size (in
10234 bytes, expressed in decimal) and MD5 checksum of the
10235 file(s) which make(s) up a binary package in the
10236 distribution. If the package is split into several parts
10237 the values for the parts are listed in order, separated by
10242 <sect1 id="pkg-f-Status">
10243 <heading><tt>Status</tt></heading>
10246 This field in <prgn>dpkg</prgn>'s status file records
10247 whether the user wants a package installed, removed or
10248 left alone, whether it is broken (requiring
10249 re-installation) or not and what its current state on the
10250 system is. Each of these pieces of information is a
10255 <sect1 id="pkg-f-Config-Version">
10256 <heading><tt>Config-Version</tt></heading>
10259 If a package is not installed or not configured, this
10260 field in <prgn>dpkg</prgn>'s status file records the last
10261 version of the package which was successfully
10266 <sect1 id="pkg-f-Conffiles">
10267 <heading><tt>Conffiles</tt></heading>
10270 This field in <prgn>dpkg</prgn>'s status file contains
10271 information about the automatically-managed configuration
10272 files held by a package. This field should <em>not</em>
10273 appear anywhere in a package!
10278 <heading>Obsolete fields</heading>
10281 These are still recognized by <prgn>dpkg</prgn> but should
10282 not appear anywhere any more.
10284 <taglist compact="compact">
10286 <tag><tt>Revision</tt></tag>
10287 <tag><tt>Package-Revision</tt></tag>
10288 <tag><tt>Package_Revision</tt></tag>
10290 The Debian revision part of the package version was
10291 at one point in a separate control file field. This
10292 field went through several names.
10295 <tag><tt>Recommended</tt></tag>
10296 <item>Old name for <tt>Recommends</tt>.</item>
10298 <tag><tt>Optional</tt></tag>
10299 <item>Old name for <tt>Suggests</tt>.</item>
10301 <tag><tt>Class</tt></tag>
10302 <item>Old name for <tt>Priority</tt>.</item>
10311 <appendix id="pkg-conffiles">
10312 <heading>Configuration file handling (from old Packaging Manual)</heading>
10315 <prgn>dpkg</prgn> can do a certain amount of automatic
10316 handling of package configuration files.
10320 Whether this mechanism is appropriate depends on a number of
10321 factors, but basically there are two approaches to any
10322 particular configuration file.
10326 The easy method is to ship a best-effort configuration in the
10327 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10328 handle updates. If the user is unlikely to want to edit the
10329 file, but you need them to be able to without losing their
10330 changes, and a new package with a changed version of the file
10331 is only released infrequently, this is a good approach.
10335 The hard method is to build the configuration file from
10336 scratch in the <prgn>postinst</prgn> script, and to take the
10337 responsibility for fixing any mistakes made in earlier
10338 versions of the package automatically. This will be
10339 appropriate if the file is likely to need to be different on
10343 <sect><heading>Automatic handling of configuration files by
10348 A package may contain a control area file called
10349 <tt>conffiles</tt>. This file should be a list of filenames
10350 of configuration files needing automatic handling, separated
10351 by newlines. The filenames should be absolute pathnames,
10352 and the files referred to should actually exist in the
10357 When a package is upgraded <prgn>dpkg</prgn> will process
10358 the configuration files during the configuration stage,
10359 shortly before it runs the package's <prgn>postinst</prgn>
10364 For each file it checks to see whether the version of the
10365 file included in the package is the same as the one that was
10366 included in the last version of the package (the one that is
10367 being upgraded from); it also compares the version currently
10368 installed on the system with the one shipped with the last
10373 If neither the user nor the package maintainer has changed
10374 the file, it is left alone. If one or the other has changed
10375 their version, then the changed version is preferred - i.e.,
10376 if the user edits their file, but the package maintainer
10377 doesn't ship a different version, the user's changes will
10378 stay, silently, but if the maintainer ships a new version
10379 and the user hasn't edited it the new version will be
10380 installed (with an informative message). If both have
10381 changed their version the user is prompted about the problem
10382 and must resolve the differences themselves.
10386 The comparisons are done by calculating the MD5 message
10387 digests of the files, and storing the MD5 of the file as it
10388 was included in the most recent version of the package.
10392 When a package is installed for the first time
10393 <prgn>dpkg</prgn> will install the file that comes with it,
10394 unless that would mean overwriting a file already on the
10399 However, note that <prgn>dpkg</prgn> will <em>not</em>
10400 replace a conffile that was removed by the user (or by a
10401 script). This is necessary because with some programs a
10402 missing file produces an effect hard or impossible to
10403 achieve in another way, so that a missing file needs to be
10404 kept that way if the user did it.
10408 Note that a package should <em>not</em> modify a
10409 <prgn>dpkg</prgn>-handled conffile in its maintainer
10410 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10411 the user confusing and possibly dangerous options for
10412 conffile update when the package is upgraded.</p>
10415 <sect><heading>Fully-featured maintainer script configuration
10420 For files which contain site-specific information such as
10421 the hostname and networking details and so forth, it is
10422 better to create the file in the package's
10423 <prgn>postinst</prgn> script.
10427 This will typically involve examining the state of the rest
10428 of the system to determine values and other information, and
10429 may involve prompting the user for some information which
10430 can't be obtained some other way.
10434 When using this method there are a couple of important
10435 issues which should be considered:
10439 If you discover a bug in the program which generates the
10440 configuration file, or if the format of the file changes
10441 from one version to the next, you will have to arrange for
10442 the postinst script to do something sensible - usually this
10443 will mean editing the installed configuration file to remove
10444 the problem or change the syntax. You will have to do this
10445 very carefully, since the user may have changed the file,
10446 perhaps to fix the very problem that your script is trying
10447 to deal with - you will have to detect these situations and
10448 deal with them correctly.
10452 If you do go down this route it's probably a good idea to
10453 make the program that generates the configuration file(s) a
10454 separate program in <file>/usr/sbin</file>, by convention called
10455 <file><var>package</var>config</file> and then run that if
10456 appropriate from the post-installation script. The
10457 <tt><var>package</var>config</tt> program should not
10458 unquestioningly overwrite an existing configuration - if its
10459 mode of operation is geared towards setting up a package for
10460 the first time (rather than any arbitrary reconfiguration
10461 later) you should have it check whether the configuration
10462 already exists, and require a <tt>--force</tt> flag to
10463 overwrite it.</p></sect>
10466 <appendix id="pkg-alternatives"><heading>Alternative versions of
10467 an interface - <prgn>update-alternatives</prgn> (from old
10472 When several packages all provide different versions of the
10473 same program or file it is useful to have the system select a
10474 default, but to allow the system administrator to change it
10475 and have their decisions respected.
10479 For example, there are several versions of the <prgn>vi</prgn>
10480 editor, and there is no reason to prevent all of them from
10481 being installed at once, each under their own name
10482 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10483 Nevertheless it is desirable to have the name <tt>vi</tt>
10484 refer to something, at least by default.
10488 If all the packages involved cooperate, this can be done with
10489 <prgn>update-alternatives</prgn>.
10493 Each package provides its own version under its own name, and
10494 calls <prgn>update-alternatives</prgn> in its postinst to
10495 register its version (and again in its prerm to deregister
10500 See the man page <manref name="update-alternatives"
10501 section="8"> for details.
10505 If <prgn>update-alternatives</prgn> does not seem appropriate
10506 you may wish to consider using diversions instead.</p>
10509 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10510 package's version of a file (from old Packaging Manual)
10514 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10515 when it reinstalls the package it belongs to, and to have it
10516 put the file from the package somewhere else instead.
10520 This can be used locally to override a package's version of a
10521 file, or by one package to override another's version (or
10522 provide a wrapper for it).
10526 Before deciding to use a diversion, read <ref
10527 id="pkg-alternatives"> to see if you really want a diversion
10528 rather than several alternative versions of a program.
10532 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10533 and updated by a special program <prgn>dpkg-divert</prgn>.
10534 Please see <manref name="dpkg-divert" section="8"> for full
10535 details of its operation.
10539 When a package wishes to divert a file from another, it should
10540 call <prgn>dpkg-divert</prgn> in its preinst to add the
10541 diversion and rename the existing file. For example,
10542 supposing that a <prgn>smailwrapper</prgn> package wishes to
10543 install a wrapper around <file>/usr/sbin/smail</file>:
10545 if [ install = "$1" ]; then
10546 dpkg-divert --package smailwrapper --add --rename \
10547 --divert /usr/sbin/smail.real /usr/sbin/smail
10549 </example> Testing <tt>$1</tt> is necessary so that the script
10550 doesn't try to add the diversion again when
10551 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10552 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10553 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10554 get installed as the true version.
10558 The postrm has to do the reverse:
10560 if [ remove = "$1" ]; then
10561 dpkg-divert --package smailwrapper --remove --rename \
10562 --divert /usr/sbin/smail.real /usr/sbin/smail
10568 Do not attempt to divert a file which is vitally important for
10569 the system's operation - when using <prgn>dpkg-divert</prgn>
10570 there is a time, after it has been diverted but before
10571 <prgn>dpkg</prgn> has installed the new version, when the file
10572 does not exist.</p>
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