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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 <heading>The package name</heading>
809 Every package must have a name that's unique within the Debian
814 The package name is included in the control field
815 <tt>Package</tt>, the format of which is described
816 in <ref id="f-Package">.
817 The package name is also included as a part of the file name
818 of the <tt>.deb</tt> file.
823 <heading>The version of a package</heading>
826 Every package has a version number recorded in its
827 <tt>Version</tt> control file field, described in
828 <ref id="f-Version">.
832 The package management system imposes an ordering on version
833 numbers, so that it can tell whether packages are being up- or
834 downgraded and so that package system front end applications
835 can tell whether a package it finds available is newer than
836 the one installed on the system. The version number format
837 has the most significant parts (as far as comparison is
838 concerned) at the beginning.
842 If an upstream package has problematic version numbers they
843 should be converted to a sane form for use in the
844 <tt>Version</tt> field.
848 <heading>Version numbers based on dates</heading>
851 In general, Debian packages should use the same version
852 numbers as the upstream sources.
856 However, in some cases where the upstream version number is
857 based on a date (e.g., a development "snapshot" release) the
858 package management system cannot handle these version
859 numbers without epochs. For example, dpkg will consider
860 "96May01" to be greater than "96Dec24".
864 To prevent having to use epochs for every new upstream
865 version, the date based portion of the version number
866 should be changed to the following format in such cases:
867 "19960501", "19961224". It is up to the maintainer whether
868 they want to bother the upstream maintainer to change
869 the version numbers upstream, too.
873 Note that other version formats based on dates which are
874 parsed correctly by the package management system should
875 <em>not</em> be changed.
879 Native Debian packages (i.e., packages which have been
880 written especially for Debian) whose version numbers include
881 dates should always use the "YYYYMMDD" format.
888 <heading>The maintainer of a package</heading>
891 Every package must have a Debian maintainer (the
892 maintainer may be one person or a group of people
893 reachable from a common email address, such as a mailing
894 list). The maintainer is responsible for ensuring that
895 the package is placed in the appropriate distributions.
899 The maintainer must be specified in the
900 <tt>Maintainer</tt> control field with their correct name
901 and a working email address. If one person maintains
902 several packages, they should try to avoid having
903 different forms of their name and email address in
904 the <tt>Maintainer</tt> fields of those packages.
908 The format of the <tt>Maintainer</tt> control field is
909 described in <ref id="f-Maintainer">.
913 If the maintainer of a package quits from the Debian
914 project, "Debian QA Group"
915 <email>packages@qa.debian.org</email> takes over the
916 maintainer-ship of the package until someone else
917 volunteers for that task. These packages are called
918 <em>orphaned packages</em>.<footnote>
919 The detailed procedure for doing this gracefully can
920 be found in the Debian Developer's Reference,
921 see <ref id="related">.
926 <sect id="descriptions">
927 <heading>The description of a package</heading>
930 Every Debian package must have an extended description
931 stored in the appropriate field of the control record.
932 The technical information about the format of the
933 <tt>Description</tt> field is in <ref id="f-Description">.
937 The description should describe the package (the program) to a
938 user (system administrator) who has never met it before so that
939 they have enough information to decide whether they want to
940 install it. This description should not just be copied verbatim
941 from the program's documentation.
945 Put important information first, both in the synopsis and
946 extended description. Sometimes only the first part of the
947 synopsis or of the description will be displayed. You can
948 assume that there will usually be a way to see the whole
949 extended description.
953 The description should also give information about the
954 significant dependencies and conflicts between this package
955 and others, so that the user knows why these dependencies and
956 conflicts have been declared.
960 Instructions for configuring or using the package should
961 not be included (that is what installation scripts,
962 manual pages, info files, etc., are for). Copyright
963 statements and other administrivia should not be included
964 either (that is what the copyright file is for).
967 <sect1 id="synopsis"><heading>The single line synopsis</heading>
970 The single line synopsis should be kept brief - certainly
975 Do not include the package name in the synopsis line. The
976 display software knows how to display this already, and you
977 do not need to state it. Remember that in many situations
978 the user may only see the synopsis line - make it as
979 informative as you can.
984 <sect1 id="extendeddesc"><heading>The extended description</heading>
987 Do not try to continue the single line synopsis into the
988 extended description. This will not work correctly when
989 the full description is displayed, and makes no sense
990 where only the summary (the single line synopsis) is
995 The extended description should describe what the package
996 does and how it relates to the rest of the system (in terms
997 of, for example, which subsystem it is which part of).
1001 The description field needs to make sense to anyone, even
1002 people who have no idea about any of the things the
1003 package deals with.<footnote>
1004 The blurb that comes with a program in its
1005 announcements and/or <prgn>README</prgn> files is
1006 rarely suitable for use in a description. It is
1007 usually aimed at people who are already in the
1008 community where the package is used.
1017 <heading>Dependencies</heading>
1020 Every package must specify the dependency information
1021 about other packages that are required for the first to
1026 For example, a dependency entry must be provided for any
1027 shared libraries required by a dynamically-linked executable
1028 binary in a package.
1032 Packages are not required to declare any dependencies they
1033 have on other packages which are marked <tt>Essential</tt>
1034 (see below), and should not do so unless they depend on a
1035 particular version of that package.<footnote>
1037 Essential is needed in part to avoid unresolvable dependency
1038 loops on upgrade. If packages add unnecessary dependencies
1039 on packages in this set, the chances that there
1040 <strong>will</strong> be an unresolvable dependency loop
1041 caused by forcing these Essential packages to be configured
1042 first before they need to be is greatly increased. It also
1043 increases the chances that frontends will be unable to
1044 <strong>calculate</strong> an upgrade path, even if one
1048 Also, functionality is rarely ever removed from the
1049 Essential set, but <em>packages</em> have been removed from
1050 the Essential set when the functionality moved to a
1051 different package. So depending on these packages <em>just
1052 in case</em> they stop being essential does way more harm
1059 Sometimes, a package requires another package to be installed
1060 <em>and</em> configured before it can be installed. In this
1061 case, you must specify a <tt>Pre-Depends</tt> entry for
1066 You should not specify a <tt>Pre-Depends</tt> entry for a
1067 package before this has been discussed on the
1068 <tt>debian-devel</tt> mailing list and a consensus about
1069 doing that has been reached.
1073 The format of the package interrelationship control fields is
1074 described in <ref id="relationships">.
1078 <sect id="virtual_pkg">
1079 <heading>Virtual packages</heading>
1082 Sometimes, there are several packages which offer
1083 more-or-less the same functionality. In this case, it's
1084 useful to define a <em>virtual package</em> whose name
1085 describes that common functionality. (The virtual
1086 packages only exist logically, not physically; that's why
1087 they are called <em>virtual</em>.) The packages with this
1088 particular function will then <em>provide</em> the virtual
1089 package. Thus, any other package requiring that function
1090 can simply depend on the virtual package without having to
1091 specify all possible packages individually.
1095 All packages should use virtual package names where
1096 appropriate, and arrange to create new ones if necessary.
1097 They should not use virtual package names (except privately,
1098 amongst a cooperating group of packages) unless they have
1099 been agreed upon and appear in the list of virtual package
1100 names. (See also <ref id="virtual">)
1104 The latest version of the authoritative list of virtual
1105 package names can be found in the <tt>debian-policy</tt> package.
1106 It is also available from the Debian web mirrors at
1107 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1108 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1112 The procedure for updating the list is described in the preface
1119 <heading>Base system</heading>
1122 The <tt>base system</tt> is a minimum subset of the Debian
1123 GNU/Linux system that is installed before everything else
1124 on a new system. Only very few packages are allowed to form
1125 part of the base system, in order to keep the required disk
1130 The base system consists of all those packages with priority
1131 <tt>required</tt> or <tt>important</tt>. Many of them will
1132 be tagged <tt>essential</tt> (see below).
1137 <heading>Essential packages</heading>
1140 Essential is defined as the minimal set of functionality that
1141 must be available and usable on the system at all times, even
1142 when packages are in an unconfigured (but unpacked) state.
1143 Packages are tagged <tt>essential</tt> for a system using the
1144 <tt>Essential</tt> control file field. The format of the
1145 <tt>Essential</tt> control field is described in <ref
1150 Since these packages cannot be easily removed (one has to
1151 specify an extra <em>force option</em> to
1152 <prgn>dpkg</prgn> to do so), this flag must not be used
1153 unless absolutely necessary. A shared library package
1154 must not be tagged <tt>essential</tt>; dependencies will
1155 prevent its premature removal, and we need to be able to
1156 remove it when it has been superseded.
1160 Since dpkg will not prevent upgrading of other packages
1161 while an <tt>essential</tt> package is in an unconfigured
1162 state, all <tt>essential</tt> packages must supply all of
1163 their core functionality even when unconfigured. If the
1164 package cannot satisfy this requirement it must not be
1165 tagged as essential, and any packages depending on this
1166 package must instead have explicit dependency fields as
1171 Maintainers should take great care in adding any programs,
1172 interfaces, or functionality to <tt>essential</tt> packages.
1173 Packages may assume that functionality provided by
1174 <tt>essential</tt> packages is always available without
1175 declaring explicit dependencies, which means that removing
1176 functionality from the Essential set is very difficult and is
1177 almost never done. Any capability added to an
1178 <tt>essential</tt> package therefore creates an obligation to
1179 support that capability as part of the Essential set in
1184 You must not tag any packages <tt>essential</tt> before
1185 this has been discussed on the <tt>debian-devel</tt>
1186 mailing list and a consensus about doing that has been
1191 <sect id="maintscripts">
1192 <heading>Maintainer Scripts</heading>
1195 The package installation scripts should avoid producing
1196 output which is unnecessary for the user to see and
1197 should rely on <prgn>dpkg</prgn> to stave off boredom on
1198 the part of a user installing many packages. This means,
1199 amongst other things, using the <tt>--quiet</tt> option on
1200 <prgn>install-info</prgn>.
1204 Errors which occur during the execution of an installation
1205 script must be checked and the installation must not
1206 continue after an error.
1210 Note that in general <ref id="scripts"> applies to package
1211 maintainer scripts, too.
1215 You should not use <prgn>dpkg-divert</prgn> on a file
1216 belonging to another package without consulting the
1217 maintainer of that package first.
1221 All packages which supply an instance of a common command
1222 name (or, in general, filename) should generally use
1223 <prgn>update-alternatives</prgn>, so that they may be
1224 installed together. If <prgn>update-alternatives</prgn>
1225 is not used, then each package must use
1226 <tt>Conflicts</tt> to ensure that other packages are
1227 de-installed. (In this case, it may be appropriate to
1228 specify a conflict against earlier versions of something
1229 that previously did not use
1230 <prgn>update-alternatives</prgn>; this is an exception to
1231 the usual rule that versioned conflicts should be
1235 <sect1 id="maintscriptprompt">
1236 <heading>Prompting in maintainer scripts</heading>
1238 Package maintainer scripts may prompt the user if
1239 necessary. Prompting must be done by communicating
1240 through a program, such as <prgn>debconf</prgn>, which
1241 conforms to the Debian Configuration Management
1242 Specification, version 2 or higher.
1246 Packages which are essential, or which are dependencies of
1247 essential packages, may fall back on another prompting method
1248 if no such interface is available when they are executed.
1252 The Debian Configuration Management Specification is included
1253 in the <file>debconf_specification</file> files in the
1254 <package>debian-policy</package> package.
1255 It is also available from the Debian web mirrors at
1256 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1257 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1261 Packages which use the Debian Configuration Management
1262 Specification may contain an additional
1263 <prgn>config</prgn> script and a <tt>templates</tt>
1264 file in their control archive<footnote>
1265 The control.tar.gz inside the .deb.
1266 See <manref name="deb" section="5">.
1268 The <prgn>config</prgn> script might be run before the
1269 <prgn>preinst</prgn> script, and before the package is unpacked
1270 or any of its dependencies or pre-dependencies are satisfied.
1271 Therefore it must work using only the tools present in
1272 <em>essential</em> packages.<footnote>
1273 <package>Debconf</package> or another tool that
1274 implements the Debian Configuration Management
1275 Specification will also be installed, and any
1276 versioned dependencies on it will be satisfied
1277 before preconfiguration begins.
1282 Packages which use the Debian Configuration Management
1283 Specification must allow for translation of their user-visible
1284 messages by using a gettext-based system such as the one
1285 provided by the <package>po-debconf</package> package.
1289 Packages should try to minimize the amount of prompting
1290 they need to do, and they should ensure that the user
1291 will only ever be asked each question once. This means
1292 that packages should try to use appropriate shared
1293 configuration files (such as <file>/etc/papersize</file> and
1294 <file>/etc/news/server</file>), and shared
1295 <package>debconf</package> variables rather than each
1296 prompting for their own list of required pieces of
1301 It also means that an upgrade should not ask the same
1302 questions again, unless the user has used
1303 <tt>dpkg --purge</tt> to remove the package's configuration.
1304 The answers to configuration questions should be stored in an
1305 appropriate place in <file>/etc</file> so that the user can
1306 modify them, and how this has been done should be
1311 If a package has a vitally important piece of
1312 information to pass to the user (such as "don't run me
1313 as I am, you must edit the following configuration files
1314 first or you risk your system emitting badly-formatted
1315 messages"), it should display this in the
1316 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1317 prompt the user to hit return to acknowledge the
1318 message. Copyright messages do not count as vitally
1319 important (they belong in
1320 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1321 neither do instructions on how to use a program (these
1322 should be in on-line documentation, where all the users
1327 Any necessary prompting should almost always be confined
1328 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1329 script. If it is done in the <prgn>postinst</prgn>, it
1330 should be protected with a conditional so that
1331 unnecessary prompting doesn't happen if a package's
1332 installation fails and the <prgn>postinst</prgn> is
1333 called with <tt>abort-upgrade</tt>,
1334 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1344 <heading>Source packages</heading>
1346 <sect id="standardsversion">
1347 <heading>Standards conformance</heading>
1350 Source packages should specify the most recent version number
1351 of this policy document with which your package complied
1352 when it was last updated.
1356 This information may be used to file bug reports
1357 automatically if your package becomes too much out of date.
1361 The version is specified in the <tt>Standards-Version</tt>
1363 The format of the <tt>Standards-Version</tt> field is
1364 described in <ref id="f-Standards-Version">.
1368 You should regularly, and especially if your package has
1369 become out of date, check for the newest Policy Manual
1370 available and update your package, if necessary. When your
1371 package complies with the new standards you should update the
1372 <tt>Standards-Version</tt> source package field and
1373 release it.<footnote>
1374 See the file <file>upgrading-checklist</file> for
1375 information about policy which has changed between
1376 different versions of this document.
1382 <sect id="pkg-relations">
1383 <heading>Package relationships</heading>
1386 Source packages should specify which binary packages they
1387 require to be installed or not to be installed in order to
1388 build correctly. For example, if building a package
1389 requires a certain compiler, then the compiler should be
1390 specified as a build-time dependency.
1394 It is not necessary to explicitly specify build-time
1395 relationships on a minimal set of packages that are always
1396 needed to compile, link and put in a Debian package a
1397 standard "Hello World!" program written in C or C++. The
1398 required packages are called <em>build-essential</em>, and
1399 an informational list can be found in
1400 <file>/usr/share/doc/build-essential/list</file> (which is
1401 contained in the <tt>build-essential</tt>
1404 <list compact="compact">
1406 This allows maintaining the list separately
1407 from the policy documents (the list does not
1408 need the kind of control that the policy
1412 Having a separate package allows one to install
1413 the build-essential packages on a machine, as
1414 well as allowing other packages such as tasks to
1415 require installation of the build-essential
1416 packages using the depends relation.
1419 The separate package allows bug reports against
1420 the list to be categorized separately from
1421 the policy management process in the BTS.
1428 When specifying the set of build-time dependencies, one
1429 should list only those packages explicitly required by the
1430 build. It is not necessary to list packages which are
1431 required merely because some other package in the list of
1432 build-time dependencies depends on them.<footnote>
1433 The reason for this is that dependencies change, and
1434 you should list all those packages, and <em>only</em>
1435 those packages that <em>you</em> need directly. What
1436 others need is their business. For example, if you
1437 only link against <file>libimlib</file>, you will need to
1438 build-depend on <package>libimlib2-dev</package> but
1439 not against any <tt>libjpeg*</tt> packages, even
1440 though <tt>libimlib2-dev</tt> currently depends on
1441 them: installation of <package>libimlib2-dev</package>
1442 will automatically ensure that all of its run-time
1443 dependencies are satisfied.
1448 If build-time dependencies are specified, it must be
1449 possible to build the package and produce working binaries
1450 on a system with only essential and build-essential
1451 packages installed and also those required to satisfy the
1452 build-time relationships (including any implied
1453 relationships). In particular, this means that version
1454 clauses should be used rigorously in build-time
1455 relationships so that one cannot produce bad or
1456 inconsistently configured packages when the relationships
1457 are properly satisfied.
1461 <ref id="relationships"> explains the technical details.
1466 <heading>Changes to the upstream sources</heading>
1469 If changes to the source code are made that are not
1470 specific to the needs of the Debian system, they should be
1471 sent to the upstream authors in whatever form they prefer
1472 so as to be included in the upstream version of the
1477 If you need to configure the package differently for
1478 Debian or for Linux, and the upstream source doesn't
1479 provide a way to do so, you should add such configuration
1480 facilities (for example, a new <prgn>autoconf</prgn> test
1481 or <tt>#define</tt>) and send the patch to the upstream
1482 authors, with the default set to the way they originally
1483 had it. You can then easily override the default in your
1484 <file>debian/rules</file> or wherever is appropriate.
1488 You should make sure that the <prgn>configure</prgn> utility
1489 detects the correct architecture specification string
1490 (refer to <ref id="arch-spec"> for details).
1494 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1495 <prgn>configure</prgn> scripts are used, you should edit the
1496 <file>.in</file> files rather than editing the
1497 <prgn>Makefile</prgn> directly. This allows the user to
1498 reconfigure the package if necessary. You should
1499 <em>not</em> configure the package and edit the generated
1500 <prgn>Makefile</prgn>! This makes it impossible for someone
1501 else to later reconfigure the package without losing the
1507 <sect id="dpkgchangelog">
1508 <heading>Debian changelog: <file>debian/changelog</file></heading>
1511 Changes in the Debian version of the package should be
1512 briefly explained in the Debian changelog file
1513 <file>debian/changelog</file>.<footnote>
1515 Mistakes in changelogs are usually best rectified by
1516 making a new changelog entry rather than "rewriting
1517 history" by editing old changelog entries.
1520 This includes modifications
1521 made in the Debian package compared to the upstream one
1522 as well as other changes and updates to the package.
1524 Although there is nothing stopping an author who is also
1525 the Debian maintainer from using this changelog for all
1526 their changes, it will have to be renamed if the Debian
1527 and upstream maintainers become different people. In such
1528 a case, however, it might be better to maintain the package
1529 as a non-native package.
1534 The format of the <file>debian/changelog</file> allows the
1535 package building tools to discover which version of the package
1536 is being built and find out other release-specific information.
1540 That format is a series of entries like this:
1542 <example compact="compact">
1543 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1545 [optional blank line(s), stripped]
1547 * <var>change details</var>
1548 <var>more change details</var>
1550 [blank line(s), included in output of dpkg-parsechangelog]
1552 * <var>even more change details</var>
1554 [optional blank line(s), stripped]
1556 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1561 <var>package</var> and <var>version</var> are the source
1562 package name and version number.
1566 <var>distribution(s)</var> lists the distributions where
1567 this version should be installed when it is uploaded - it
1568 is copied to the <tt>Distribution</tt> field in the
1569 <file>.changes</file> file. See <ref id="f-Distribution">.
1573 <var>urgency</var> is the value for the <tt>Urgency</tt>
1574 field in the <file>.changes</file> file for the upload
1575 (see <ref id="f-Urgency">). It is not possible to specify
1576 an urgency containing commas; commas are used to separate
1577 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1578 <prgn>dpkg</prgn> changelog format (though there is
1579 currently only one useful <var>keyword</var>,
1584 The change details may in fact be any series of lines
1585 starting with at least two spaces, but conventionally each
1586 change starts with an asterisk and a separating space and
1587 continuation lines are indented so as to bring them in
1588 line with the start of the text above. Blank lines may be
1589 used here to separate groups of changes, if desired.
1593 If this upload resolves bugs recorded in the Bug Tracking
1594 System (BTS), they may be automatically closed on the
1595 inclusion of this package into the Debian archive by
1596 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1597 in the change details.<footnote>
1598 To be precise, the string should match the following
1599 Perl regular expression:
1601 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1603 Then all of the bug numbers listed will be closed by the
1604 archive maintenance script (<prgn>katie</prgn>) using the
1605 <var>version</var> of the changelog entry.
1607 This information is conveyed via the <tt>Closes</tt> field
1608 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1612 The maintainer name and email address used in the changelog
1613 should be the details of the person uploading <em>this</em>
1614 version. They are <em>not</em> necessarily those of the
1615 usual package maintainer. The information here will be
1616 copied to the <tt>Changed-By</tt> field in the
1617 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1618 and then later used to send an acknowledgement when the
1619 upload has been installed.
1623 The <var>date</var> has the following format<footnote>
1624 This is the same as the format generated by <tt>date
1626 </footnote> (compatible and with the same semantics of
1627 RFC 2822 and RFC 5322):
1628 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1630 <list compact="compact">
1632 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1635 dd is a one- or two-digit day of the month (01-31)
1638 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1641 <item>yyyy is the four-digit year (e.g. 2010)</item>
1642 <item>hh is the two-digit hour (00-23)</item>
1643 <item>mm is the two-digit minutes (00-59)</item>
1644 <item>ss is the two-digit seconds (00-60)</item>
1646 +zzzz or -zzzz is the the time zone offset from Coordinated
1647 Universal Time (UTC). "+" indicates that the time is ahead
1648 of (i.e., east of) UTC and "-" indicates that the time is
1649 behind (i.e., west of) UTC. The first two digits indicate
1650 the hour difference from UTC and the last two digits
1651 indicate the number of additional minutes difference from
1652 UTC. The last two digits must be in the range 00-59.
1658 The first "title" line with the package name must start
1659 at the left hand margin. The "trailer" line with the
1660 maintainer and date details must be preceded by exactly
1661 one space. The maintainer details and the date must be
1662 separated by exactly two spaces.
1666 The entire changelog must be encoded in UTF-8.
1670 For more information on placement of the changelog files
1671 within binary packages, please see <ref id="changelogs">.
1675 <sect id="dpkgcopyright">
1676 <heading>Copyright: <file>debian/copyright</file></heading>
1678 Every package must be accompanied by a verbatim copy of its
1679 copyright information and distribution license in the file
1680 <file>/usr/share/doc/<var>package</var>/copyright</file>
1681 (see <ref id="copyrightfile"> for further details). Also see
1682 <ref id="pkgcopyright"> for further considerations related
1683 to copyrights for packages.
1687 <heading>Error trapping in makefiles</heading>
1690 When <prgn>make</prgn> invokes a command in a makefile
1691 (including your package's upstream makefiles and
1692 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1693 means that <prgn>sh</prgn>'s usual bad error handling
1694 properties apply: if you include a miniature script as one
1695 of the commands in your makefile you'll find that if you
1696 don't do anything about it then errors are not detected
1697 and <prgn>make</prgn> will blithely continue after
1702 Every time you put more than one shell command (this
1703 includes using a loop) in a makefile command you
1704 must make sure that errors are trapped. For
1705 simple compound commands, such as changing directory and
1706 then running a program, using <tt>&&</tt> rather
1707 than semicolon as a command separator is sufficient. For
1708 more complex commands including most loops and
1709 conditionals you should include a separate <tt>set -e</tt>
1710 command at the start of every makefile command that's
1711 actually one of these miniature shell scripts.
1715 <sect id="timestamps">
1716 <heading>Time Stamps</heading>
1718 Maintainers should preserve the modification times of the
1719 upstream source files in a package, as far as is reasonably
1721 The rationale is that there is some information conveyed
1722 by knowing the age of the file, for example, you could
1723 recognize that some documentation is very old by looking
1724 at the modification time, so it would be nice if the
1725 modification time of the upstream source would be
1731 <sect id="restrictions">
1732 <heading>Restrictions on objects in source packages</heading>
1735 The source package may not contain any hard links<footnote>
1737 This is not currently detected when building source
1738 packages, but only when extracting
1742 Hard links may be permitted at some point in the
1743 future, but would require a fair amount of
1746 </footnote>, device special files, sockets or setuid or
1747 setgid files.<footnote>
1748 Setgid directories are allowed.
1753 <sect id="debianrules">
1754 <heading>Main building script: <file>debian/rules</file></heading>
1757 This file must be an executable makefile, and contains the
1758 package-specific recipes for compiling the package and
1759 building binary package(s) from the source.
1763 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1764 so that it can be invoked by saying its name rather than
1765 invoking <prgn>make</prgn> explicitly. That is, invoking
1766 either of <tt>make -f debian/rules <em>args...</em></tt>
1767 or <tt>./debian/rules <em>args...</em></tt> must result in
1772 Since an interactive <file>debian/rules</file> script makes it
1773 impossible to auto-compile that package and also makes it
1774 hard for other people to reproduce the same binary
1775 package, all <em>required targets</em> must be
1776 non-interactive. At a minimum, required targets are the
1777 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1778 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1779 <em>binary-indep</em>, and <em>build</em>. It also follows
1780 that any target that these targets depend on must also be
1785 The targets are as follows (required unless stated otherwise):
1787 <tag><tt>build</tt></tag>
1790 The <tt>build</tt> target should perform all the
1791 configuration and compilation of the package.
1792 If a package has an interactive pre-build
1793 configuration routine, the Debian source package
1794 must either be built after this has taken place (so
1795 that the binary package can be built without rerunning
1796 the configuration) or the configuration routine
1797 modified to become non-interactive. (The latter is
1798 preferable if there are architecture-specific features
1799 detected by the configuration routine.)
1803 For some packages, notably ones where the same
1804 source tree is compiled in different ways to produce
1805 two binary packages, the <tt>build</tt> target
1806 does not make much sense. For these packages it is
1807 good enough to provide two (or more) targets
1808 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1809 for each of the ways of building the package, and a
1810 <tt>build</tt> target that does nothing. The
1811 <tt>binary</tt> target will have to build the
1812 package in each of the possible ways and make the
1813 binary package out of each.
1817 The <tt>build</tt> target must not do anything
1818 that might require root privilege.
1822 The <tt>build</tt> target may need to run the
1823 <tt>clean</tt> target first - see below.
1827 When a package has a configuration and build routine
1828 which takes a long time, or when the makefiles are
1829 poorly designed, or when <tt>build</tt> needs to
1830 run <tt>clean</tt> first, it is a good idea to
1831 <tt>touch build</tt> when the build process is
1832 complete. This will ensure that if <tt>debian/rules
1833 build</tt> is run again it will not rebuild the whole
1835 Another common way to do this is for <tt>build</tt>
1836 to depend on <prgn>build-stamp</prgn> and to do
1837 nothing else, and for the <prgn>build-stamp</prgn>
1838 target to do the building and to <tt>touch
1839 build-stamp</tt> on completion. This is
1840 especially useful if the build routine creates a
1841 file or directory called <tt>build</tt>; in such a
1842 case, <tt>build</tt> will need to be listed as
1843 a phony target (i.e., as a dependency of the
1844 <tt>.PHONY</tt> target). See the documentation of
1845 <prgn>make</prgn> for more information on phony
1851 <tag><tt>build-arch</tt> (optional),
1852 <tt>build-indep</tt> (optional)
1856 A package may also provide both of the targets
1857 <tt>build-arch</tt> and <tt>build-indep</tt>.
1858 The <tt>build-arch</tt> target, if provided, should
1859 perform all the configuration and compilation required for
1860 producing all architecture-dependant binary packages
1861 (those packages for which the body of the
1862 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1863 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1864 target, if provided, should perform all the configuration
1865 and compilation required for producing all
1866 architecture-independent binary packages (those packages
1867 for which the body of the <tt>Architecture</tt> field
1868 in <tt>debian/control</tt> is <tt>all</tt>).
1869 The <tt>build</tt> target should depend on those of the
1870 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1871 are provided in the rules file.<footnote>
1872 The intent of this split is so that binary-only builds
1873 need not install the dependencies required for
1874 the <tt>build-indep</tt> target. However, this is not
1875 yet used in practice since <tt>dpkg-buildpackage
1876 -B</tt>, and therefore the autobuilders,
1877 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1878 due to the difficulties in determining whether the
1879 optional <tt>build-arch</tt> target exists.
1884 If one or both of the targets <tt>build-arch</tt> and
1885 <tt>build-indep</tt> are not provided, then invoking
1886 <file>debian/rules</file> with one of the not-provided
1887 targets as arguments should produce a exit status code
1888 of 2. Usually this is provided automatically by make
1889 if the target is missing.
1893 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1894 must not do anything that might require root privilege.
1898 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1899 <tt>binary-indep</tt>
1903 The <tt>binary</tt> target must be all that is
1904 necessary for the user to build the binary package(s)
1905 produced from this source package. It is
1906 split into two parts: <prgn>binary-arch</prgn> builds
1907 the binary packages which are specific to a particular
1908 architecture, and <tt>binary-indep</tt> builds
1909 those which are not.
1912 <tt>binary</tt> may be (and commonly is) a target with
1913 no commands which simply depends on
1914 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1917 Both <tt>binary-*</tt> targets should depend on the
1918 <tt>build</tt> target, or on the appropriate
1919 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1920 provided, so that the package is built if it has not
1921 been already. It should then create the relevant
1922 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1923 make their control files and <prgn>dpkg-deb</prgn> to
1924 build them and place them in the parent of the top
1929 Both the <tt>binary-arch</tt> and
1930 <tt>binary-indep</tt> targets <em>must</em> exist.
1931 If one of them has nothing to do (which will always be
1932 the case if the source generates only a single binary
1933 package, whether architecture-dependent or not), it
1934 must still exist and must always succeed.
1938 The <tt>binary</tt> targets must be invoked as
1940 The <prgn>fakeroot</prgn> package often allows one
1941 to build a package correctly even without being
1947 <tag><tt>clean</tt></tag>
1950 This must undo any effects that the <tt>build</tt>
1951 and <tt>binary</tt> targets may have had, except
1952 that it should leave alone any output files created in
1953 the parent directory by a run of a <tt>binary</tt>
1958 If a <tt>build</tt> file is touched at the end of
1959 the <tt>build</tt> target, as suggested above, it
1960 should be removed as the first action that
1961 <tt>clean</tt> performs, so that running
1962 <tt>build</tt> again after an interrupted
1963 <tt>clean</tt> doesn't think that everything is
1968 The <tt>clean</tt> target may need to be
1969 invoked as root if <tt>binary</tt> has been
1970 invoked since the last <tt>clean</tt>, or if
1971 <tt>build</tt> has been invoked as root (since
1972 <tt>build</tt> may create directories, for
1977 <tag><tt>get-orig-source</tt> (optional)</tag>
1980 This target fetches the most recent version of the
1981 original source package from a canonical archive site
1982 (via FTP or WWW, for example), does any necessary
1983 rearrangement to turn it into the original source
1984 tar file format described below, and leaves it in the
1989 This target may be invoked in any directory, and
1990 should take care to clean up any temporary files it
1995 This target is optional, but providing it if
1996 possible is a good idea.
2000 <tag><tt>patch</tt> (optional)</tag>
2003 This target performs whatever additional actions are
2004 required to make the source ready for editing (unpacking
2005 additional upstream archives, applying patches, etc.).
2006 It is recommended to be implemented for any package where
2007 <tt>dpkg-source -x</tt> does not result in source ready
2008 for additional modification. See
2009 <ref id="readmesource">.
2015 The <tt>build</tt>, <tt>binary</tt> and
2016 <tt>clean</tt> targets must be invoked with the current
2017 directory being the package's top-level directory.
2022 Additional targets may exist in <file>debian/rules</file>,
2023 either as published or undocumented interfaces or for the
2024 package's internal use.
2028 The architectures we build on and build for are determined
2029 by <prgn>make</prgn> variables using the utility
2030 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2031 You can determine the
2032 Debian architecture and the GNU style architecture
2033 specification string for the build machine (the machine type
2034 we are building on) as well as for the host machine (the
2035 machine type we are building for). Here is a list of
2036 supported <prgn>make</prgn> variables:
2037 <list compact="compact">
2039 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2042 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2045 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2048 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2049 specification string)
2052 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2053 <tt>DEB_*_GNU_TYPE</tt>)
2056 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2057 <tt>DEB_*_GNU_TYPE</tt>)
2059 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2060 the build machine or <tt>HOST</tt> for specification of the
2065 Backward compatibility can be provided in the rules file
2066 by setting the needed variables to suitable default
2067 values; please refer to the documentation of
2068 <prgn>dpkg-architecture</prgn> for details.
2072 It is important to understand that the <tt>DEB_*_ARCH</tt>
2073 string only determines which Debian architecture we are
2074 building on or for. It should not be used to get the CPU
2075 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2076 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2077 GNU style variables should generally only be used with upstream
2081 <sect1 id="debianrules-options">
2082 <heading><file>debian/rules</file> and
2083 <tt>DEB_BUILD_OPTIONS</tt></heading>
2086 Supporting the standardized environment variable
2087 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2088 contain several flags to change how a package is compiled and
2089 built. Each flag must be in the form <var>flag</var> or
2090 <var>flag</var>=<var>options</var>. If multiple flags are
2091 given, they must be separated by whitespace.<footnote>
2092 Some packages support any delimiter, but whitespace is the
2093 easiest to parse inside a makefile and avoids ambiguity with
2094 flag values that contain commas.
2096 <var>flag</var> must start with a lowercase letter
2097 (<tt>a-z</tt>) and consist only of lowercase letters,
2098 numbers (<tt>0-9</tt>), and the characters
2099 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2100 <var>options</var> must not contain whitespace. The same
2101 tag should not be given multiple times with conflicting
2102 values. Package maintainers may assume that
2103 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2107 The meaning of the following tags has been standardized:
2111 This tag says to not run any build-time test suite
2112 provided by the package.
2116 The presence of this tag means that the package should
2117 be compiled with a minimum of optimization. For C
2118 programs, it is best to add <tt>-O0</tt> to
2119 <tt>CFLAGS</tt> (although this is usually the default).
2120 Some programs might fail to build or run at this level
2121 of optimization; it may be necessary to use
2122 <tt>-O1</tt>, for example.
2126 This tag means that the debugging symbols should not be
2127 stripped from the binary during installation, so that
2128 debugging information may be included in the package.
2130 <tag>parallel=n</tag>
2132 This tag means that the package should be built using up
2133 to <tt>n</tt> parallel processes if the package build
2134 system supports this.<footnote>
2135 Packages built with <tt>make</tt> can often implement
2136 this by passing the <tt>-j</tt><var>n</var> option to
2139 If the package build system does not support parallel
2140 builds, this string must be ignored. If the package
2141 build system only supports a lower level of concurrency
2142 than <var>n</var>, the package should be built using as
2143 many parallel processes as the package build system
2144 supports. It is up to the package maintainer to decide
2145 whether the package build times are long enough and the
2146 package build system is robust enough to make supporting
2147 parallel builds worthwhile.
2153 Unknown flags must be ignored by <file>debian/rules</file>.
2157 The following makefile snippet is an example of how one may
2158 implement the build options; you will probably have to
2159 massage this example in order to make it work for your
2161 <example compact="compact">
2164 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2165 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2166 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2167 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2169 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2174 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2175 INSTALL_PROGRAM += -s
2177 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2178 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2179 MAKEFLAGS += -j$(NUMJOBS)
2184 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2185 # Code to run the package test suite.
2192 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2193 <sect id="substvars">
2194 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2197 When <prgn>dpkg-gencontrol</prgn>,
2198 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2199 generate control files they perform variable substitutions
2200 on their output just before writing it. Variable
2201 substitutions have the form <tt>${<var>variable</var>}</tt>.
2202 The optional file <file>debian/substvars</file> contains
2203 variable substitutions to be used; variables can also be set
2204 directly from <file>debian/rules</file> using the <tt>-V</tt>
2205 option to the source packaging commands, and certain
2206 predefined variables are also available.
2210 The <file>debian/substvars</file> file is usually generated and
2211 modified dynamically by <file>debian/rules</file> targets, in
2212 which case it must be removed by the <tt>clean</tt> target.
2216 See <manref name="deb-substvars" section="5"> for full
2217 details about source variable substitutions, including the
2218 format of <file>debian/substvars</file>.</p>
2221 <sect id="debianwatch">
2222 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2225 This is an optional, recommended control file for the
2226 <tt>uscan</tt> utility which defines how to automatically
2227 scan ftp or http sites for newly available updates of the
2228 package. This is used by <url id="
2229 http://dehs.alioth.debian.org/"> and other Debian QA tools
2230 to help with quality control and maintenance of the
2231 distribution as a whole.
2236 <sect id="debianfiles">
2237 <heading>Generated files list: <file>debian/files</file></heading>
2240 This file is not a permanent part of the source tree; it
2241 is used while building packages to record which files are
2242 being generated. <prgn>dpkg-genchanges</prgn> uses it
2243 when it generates a <file>.changes</file> file.
2247 It should not exist in a shipped source package, and so it
2248 (and any backup files or temporary files such as
2249 <file>files.new</file><footnote>
2250 <file>files.new</file> is used as a temporary file by
2251 <prgn>dpkg-gencontrol</prgn> and
2252 <prgn>dpkg-distaddfile</prgn> - they write a new
2253 version of <tt>files</tt> here before renaming it,
2254 to avoid leaving a corrupted copy if an error
2256 </footnote>) should be removed by the
2257 <tt>clean</tt> target. It may also be wise to
2258 ensure a fresh start by emptying or removing it at the
2259 start of the <tt>binary</tt> target.
2263 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2264 package, it adds an entry to <file>debian/files</file> for the
2265 <file>.deb</file> file that will be created when <tt>dpkg-deb
2266 --build</tt> is run for that binary package. So for most
2267 packages all that needs to be done with this file is to
2268 delete it in the <tt>clean</tt> target.
2272 If a package upload includes files besides the source
2273 package and any binary packages whose control files were
2274 made with <prgn>dpkg-gencontrol</prgn> then they should be
2275 placed in the parent of the package's top-level directory
2276 and <prgn>dpkg-distaddfile</prgn> should be called to add
2277 the file to the list in <file>debian/files</file>.</p>
2280 <sect id="embeddedfiles">
2281 <heading>Convenience copies of code</heading>
2284 Some software packages include in their distribution convenience
2285 copies of code from other software packages, generally so that
2286 users compiling from source don't have to download multiple
2287 packages. Debian packages should not make use of these
2288 convenience copies unless the included package is explicitly
2289 intended to be used in this way.<footnote>
2290 For example, parts of the GNU build system work like this.
2292 If the included code is already in the Debian archive in the
2293 form of a library, the Debian packaging should ensure that
2294 binary packages reference the libraries already in Debian and
2295 the convenience copy is not used. If the included code is not
2296 already in Debian, it should be packaged separately as a
2297 prerequisite if possible.
2299 Having multiple copies of the same code in Debian is
2300 inefficient, often creates either static linking or shared
2301 library conflicts, and, most importantly, increases the
2302 difficulty of handling security vulnerabilities in the
2308 <sect id="readmesource">
2309 <heading>Source package handling:
2310 <file>debian/README.source</file></heading>
2313 If running <prgn>dpkg-source -x</prgn> on a source package
2314 doesn't produce the source of the package, ready for editing,
2315 and allow one to make changes and run
2316 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2317 without taking any additional steps, creating a
2318 <file>debian/README.source</file> documentation file is
2319 recommended. This file should explain how to do all of the
2322 <item>Generate the fully patched source, in a form ready for
2323 editing, that would be built to create Debian
2324 packages. Doing this with a <tt>patch</tt> target in
2325 <file>debian/rules</file> is recommended; see
2326 <ref id="debianrules">.</item>
2327 <item>Modify the source and save those modifications so that
2328 they will be applied when building the package.</item>
2329 <item>Remove source modifications that are currently being
2330 applied when building the package.</item>
2331 <item>Optionally, document what steps are necessary to
2332 upgrade the Debian source package to a new upstream version,
2333 if applicable.</item>
2335 This explanation should include specific commands and mention
2336 any additional required Debian packages. It should not assume
2337 familiarity with any specific Debian packaging system or patch
2342 This explanation may refer to a documentation file installed by
2343 one of the package's build dependencies provided that the
2344 referenced documentation clearly explains these tasks and is not
2345 a general reference manual.
2349 <file>debian/README.source</file> may also include any other
2350 information that would be helpful to someone modifying the
2351 source package. Even if the package doesn't fit the above
2352 description, maintainers are encouraged to document in a
2353 <file>debian/README.source</file> file any source package with a
2354 particularly complex or unintuitive source layout or build
2355 system (for example, a package that builds the same source
2356 multiple times to generate different binary packages).
2362 <chapt id="controlfields">
2363 <heading>Control files and their fields</heading>
2366 The package management system manipulates data represented in
2367 a common format, known as <em>control data</em>, stored in
2368 <em>control files</em>.
2369 Control files are used for source packages, binary packages and
2370 the <file>.changes</file> files which control the installation
2371 of uploaded files<footnote>
2372 <prgn>dpkg</prgn>'s internal databases are in a similar
2377 <sect id="controlsyntax">
2378 <heading>Syntax of control files</heading>
2381 A control file consists of one or more paragraphs of
2383 The paragraphs are also sometimes referred to as stanzas.
2385 The paragraphs are separated by blank lines. Some control
2386 files allow only one paragraph; others allow several, in
2387 which case each paragraph usually refers to a different
2388 package. (For example, in source packages, the first
2389 paragraph refers to the source package, and later paragraphs
2390 refer to binary packages generated from the source.)
2394 Each paragraph consists of a series of data fields; each
2395 field consists of the field name, followed by a colon and
2396 then the data/value associated with that field. It ends at
2397 the end of the (logical) line. Horizontal whitespace
2398 (spaces and tabs) may occur immediately before or after the
2399 value and is ignored there; it is conventional to put a
2400 single space after the colon. For example, a field might
2402 <example compact="compact">
2405 the field name is <tt>Package</tt> and the field value
2410 A paragraph must not contain more than one instance of a
2411 particular field name.
2415 Many fields' values may span several lines; in this case
2416 each continuation line must start with a space or a tab.
2417 Any trailing spaces or tabs at the end of individual
2418 lines of a field value are ignored.
2422 In fields where it is specified that lines may not wrap,
2423 only a single line of data is allowed and whitespace is not
2424 significant in a field body. Whitespace must not appear
2425 inside names (of packages, architectures, files or anything
2426 else) or version numbers, or between the characters of
2427 multi-character version relationships.
2431 Field names are not case-sensitive, but it is usual to
2432 capitalize the field names using mixed case as shown below.
2433 Field values are case-sensitive unless the description of the
2434 field says otherwise.
2438 Blank lines, or lines consisting only of spaces and tabs,
2439 are not allowed within field values or between fields - that
2440 would mean a new paragraph.
2444 All control files must be encoded in UTF-8.
2448 <sect id="sourcecontrolfiles">
2449 <heading>Source package control files -- <file>debian/control</file></heading>
2452 The <file>debian/control</file> file contains the most vital
2453 (and version-independent) information about the source package
2454 and about the binary packages it creates.
2458 The first paragraph of the control file contains information about
2459 the source package in general. The subsequent sets each describe a
2460 binary package that the source tree builds.
2464 The fields in the general paragraph (the first one, for the source
2467 <list compact="compact">
2468 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2469 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2470 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2471 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2472 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2473 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2474 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2475 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2480 The fields in the binary package paragraphs are:
2482 <list compact="compact">
2483 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2484 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2485 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2486 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2487 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2488 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2489 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2490 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2495 The syntax and semantics of the fields are described below.
2499 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2500 generate control files for binary packages (see below), by
2501 <prgn>dpkg-genchanges</prgn> to generate the
2502 <file>.changes</file> file to accompany the upload, and by
2503 <prgn>dpkg-source</prgn> when it creates the
2504 <file>.dsc</file> source control file as part of a source
2505 archive. Many fields are permitted to span multiple lines in
2506 <file>debian/control</file> but not in any other control
2507 file. These tools are responsible for removing the line
2508 breaks from such fields when using fields from
2509 <file>debian/control</file> to generate other control files.
2513 The fields here may contain variable references - their
2514 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2515 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2516 when they generate output control files.
2517 See <ref id="substvars"> for details.
2521 In addition to the control file syntax described <qref
2522 id="controlsyntax">above</qref>, this file may also contain
2523 comment lines starting with <tt>#</tt> without any preceding
2524 whitespace. All such lines are ignored, even in the middle of
2525 continuation lines for a multiline field, and do not end a
2531 <sect id="binarycontrolfiles">
2532 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2535 The <file>DEBIAN/control</file> file contains the most vital
2536 (and version-dependent) information about a binary package. It
2537 consists of a single paragraph.
2541 The fields in this file are:
2543 <list compact="compact">
2544 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2545 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2546 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2548 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2549 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2550 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2551 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2552 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2553 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2554 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2555 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2560 <sect id="debiansourcecontrolfiles">
2561 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2564 This file consists of a single paragraph, possibly surrounded by
2565 a PGP signature. The fields of that paragraph are listed below.
2566 Their syntax is described above, in <ref id="pkg-controlfields">.
2568 <list compact="compact">
2569 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2570 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2571 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2572 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2573 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2575 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2576 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2577 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2578 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2579 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2580 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2581 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2586 The source package control file is generated by
2587 <prgn>dpkg-source</prgn> when it builds the source
2588 archive, from other files in the source package,
2589 described above. When unpacking, it is checked against
2590 the files and directories in the other parts of the
2596 <sect id="debianchangesfiles">
2597 <heading>Debian changes files -- <file>.changes</file></heading>
2600 The <file>.changes</file> files are used by the Debian archive
2601 maintenance software to process updates to packages. They
2602 consist of a single paragraph, possibly surrounded by a PGP
2603 signature. That paragraph contains information from the
2604 <file>debian/control</file> file and other data about the
2605 source package gathered via <file>debian/changelog</file>
2606 and <file>debian/rules</file>.
2610 <file>.changes</file> files have a format version that is
2611 incremented whenever the documented fields or their meaning
2612 change. This document describes format &changesversion;.
2616 The fields in this file are:
2618 <list compact="compact">
2619 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2620 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2621 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2623 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2624 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2625 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2627 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2629 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2630 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2631 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2632 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2633 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2634 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2639 <sect id="controlfieldslist">
2640 <heading>List of fields</heading>
2642 <sect1 id="f-Source">
2643 <heading><tt>Source</tt></heading>
2646 This field identifies the source package name.
2650 In <file>debian/control</file> or a <file>.dsc</file> file,
2651 this field must contain only the name of the source package.
2655 In a binary package control file or a <file>.changes</file>
2656 file, the source package name may be followed by a version
2657 number in parentheses<footnote>
2658 It is customary to leave a space after the package name
2659 if a version number is specified.
2661 This version number may be omitted (and is, by
2662 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2663 the <tt>Version</tt> field of the binary package in
2664 question. The field itself may be omitted from a binary
2665 package control file when the source package has the same
2666 name and version as the binary package.
2670 Package names (both source and binary,
2671 see <ref id="f-Package">) must consist only of lower case
2672 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2673 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2674 (<tt>.</tt>). They must be at least two characters long and
2675 must start with an alphanumeric character.
2679 <sect1 id="f-Maintainer">
2680 <heading><tt>Maintainer</tt></heading>
2683 The package maintainer's name and email address. The name
2684 must come first, then the email address inside angle
2685 brackets <tt><></tt> (in RFC822 format).
2689 If the maintainer's name contains a full stop then the
2690 whole field will not work directly as an email address due
2691 to a misfeature in the syntax specified in RFC822; a
2692 program using this field as an address must check for this
2693 and correct the problem if necessary (for example by
2694 putting the name in round brackets and moving it to the
2695 end, and bringing the email address forward).
2699 <sect1 id="f-Uploaders">
2700 <heading><tt>Uploaders</tt></heading>
2703 List of the names and email addresses of co-maintainers of
2704 the package, if any. If the package has other maintainers
2705 beside the one named in the
2706 <qref id="f-Maintainer">Maintainer field</qref>, their names
2707 and email addresses should be listed here. The format of each
2708 entry is the same as that of the Maintainer field, and
2709 multiple entries must be comma separated. This is an optional
2714 Any parser that interprets the Uploaders field in
2715 <file>debian/control</file> must permit it to span multiple
2716 lines. Line breaks in an Uploaders field that spans multiple
2717 lines are not significant and the semantics of the field are
2718 the same as if the line breaks had not been present.
2722 <sect1 id="f-Changed-By">
2723 <heading><tt>Changed-By</tt></heading>
2726 The name and email address of the person who prepared this
2727 version of the package, usually a maintainer. The syntax is
2728 the same as for the <qref id="f-Maintainer">Maintainer
2733 <sect1 id="f-Section">
2734 <heading><tt>Section</tt></heading>
2737 This field specifies an application area into which the package
2738 has been classified. See <ref id="subsections">.
2742 When it appears in the <file>debian/control</file> file,
2743 it gives the value for the subfield of the same name in
2744 the <tt>Files</tt> field of the <file>.changes</file> file.
2745 It also gives the default for the same field in the binary
2750 <sect1 id="f-Priority">
2751 <heading><tt>Priority</tt></heading>
2754 This field represents how important it is that the user
2755 have the package installed. See <ref id="priorities">.
2759 When it appears in the <file>debian/control</file> file,
2760 it gives the value for the subfield of the same name in
2761 the <tt>Files</tt> field of the <file>.changes</file> file.
2762 It also gives the default for the same field in the binary
2767 <sect1 id="f-Package">
2768 <heading><tt>Package</tt></heading>
2771 The name of the binary package.
2775 Binary package names must follow the same syntax and
2776 restrictions as source package names. See <ref id="f-Source">
2781 <sect1 id="f-Architecture">
2782 <heading><tt>Architecture</tt></heading>
2785 Depending on context and the control file used, the
2786 <tt>Architecture</tt> field can include the following sets of
2790 A unique single word identifying a Debian machine
2791 architecture as described in <ref id="arch-spec">.
2794 An architecture wildcard identifying a set of Debian
2795 machine architectures, see <ref id="arch-wildcard-spec">.
2796 <tt>any</tt> matches all Debian machine architectures
2797 and is the most frequently used.
2800 <tt>all</tt>, which indicates an
2801 architecture-independent package.
2804 <tt>source</tt>, which indicates a source package.
2810 In the main <file>debian/control</file> file in the source
2811 package, this field may contain the special
2812 value <tt>all</tt>, the special architecture
2813 wildcard <tt>any</tt>, or a list of specific and wildcard
2814 architectures separated by spaces. If <tt>all</tt>
2815 or <tt>any</tt> appears, that value must be the entire
2816 contents of the field. Most packages will use
2817 either <tt>all</tt> or <tt>any</tt>.
2821 Specifying a specific list of architectures indicates that the
2822 source will build an architecture-dependent package only on
2823 architectures included in the list. Specifying a list of
2824 architecture wildcards indicates that the source will build an
2825 architecture-dependent package on only those architectures
2826 that match any of the specified architecture wildcards.
2827 Specifying a list of architectures or architecture wildcards
2828 other than <tt>any</tt> is for the minority of cases where a
2829 program is not portable or is not useful on some
2830 architectures. Where possible, the program should be made
2835 In the source package control file <file>.dsc</file>, this
2836 field may contain either the architecture
2837 wildcard <tt>any</tt> or a list of architectures and
2838 architecture wildcards separated by spaces. If a list is
2839 given, it may include (or consist solely of) the special
2840 value <tt>all</tt>. In other words, in <file>.dsc</file>
2841 files unlike the <file>debian/control</file>, <tt>all</tt> may
2842 occur in combination with specific architectures.
2843 The <tt>Architecture</tt> field in the source package control
2844 file <file>.dsc</file> is generally constructed from
2845 the <tt>Architecture</tt> fields in
2846 the <file>debian/control</file> in the source package.
2850 Specifying <tt>any</tt> indicates that the source package
2851 isn't dependent on any particular architecture and should
2852 compile fine on any one. The produced binary package(s)
2853 will either be specific to whatever the current build
2854 architecture is or will be architecture-independent.
2858 Specifying only <tt>all</tt> indicates that the source package
2859 will only build architecture-independent packages. If this is
2860 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2861 <tt>any</tt> implies that the source package will build at
2862 least one architecture-dependent package.
2866 Specifying a list of architectures or architecture wildcards
2867 indicates that the source will build an architecture-dependent
2868 package, and will only work correctly on the listed or
2869 matching architectures. If the source package also builds at
2870 least one architecture-independent package, <tt>all</tt> will
2871 also be included in the list.
2875 In a <file>.changes</file> file, the <tt>Architecture</tt>
2876 field lists the architecture(s) of the package(s) currently
2877 being uploaded. This will be a list; if the source for the
2878 package is also being uploaded, the special
2879 entry <tt>source</tt> is also present. <tt>all</tt> will be
2880 present if any architecture-independent packages are being
2881 uploaded. Architecture wildcards such as <tt>any</tt> must
2882 never occur in the <tt>Architecture</tt> field in
2883 the <file>.changes</file> file.
2887 See <ref id="debianrules"> for information on how to get
2888 the architecture for the build process.
2892 <sect1 id="f-Essential">
2893 <heading><tt>Essential</tt></heading>
2896 This is a boolean field which may occur only in the
2897 control file of a binary package or in a per-package fields
2898 paragraph of a main source control data file.
2902 If set to <tt>yes</tt> then the package management system
2903 will refuse to remove the package (upgrading and replacing
2904 it is still possible). The other possible value is <tt>no</tt>,
2905 which is the same as not having the field at all.
2910 <heading>Package interrelationship fields:
2911 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2912 <tt>Recommends</tt>, <tt>Suggests</tt>,
2913 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2914 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2918 These fields describe the package's relationships with
2919 other packages. Their syntax and semantics are described
2920 in <ref id="relationships">.</p>
2923 <sect1 id="f-Standards-Version">
2924 <heading><tt>Standards-Version</tt></heading>
2927 The most recent version of the standards (the policy
2928 manual and associated texts) with which the package
2933 The version number has four components: major and minor
2934 version number and major and minor patch level. When the
2935 standards change in a way that requires every package to
2936 change the major number will be changed. Significant
2937 changes that will require work in many packages will be
2938 signaled by a change to the minor number. The major patch
2939 level will be changed for any change to the meaning of the
2940 standards, however small; the minor patch level will be
2941 changed when only cosmetic, typographical or other edits
2942 are made which neither change the meaning of the document
2943 nor affect the contents of packages.
2947 Thus only the first three components of the policy version
2948 are significant in the <em>Standards-Version</em> control
2949 field, and so either these three components or all four
2950 components may be specified.<footnote>
2951 In the past, people specified the full version number
2952 in the Standards-Version field, for example "2.3.0.0".
2953 Since minor patch-level changes don't introduce new
2954 policy, it was thought it would be better to relax
2955 policy and only require the first 3 components to be
2956 specified, in this example "2.3.0". All four
2957 components may still be used if someone wishes to do so.
2963 <sect1 id="f-Version">
2964 <heading><tt>Version</tt></heading>
2967 The version number of a package. The format is:
2968 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2972 The three components here are:
2974 <tag><var>epoch</var></tag>
2977 This is a single (generally small) unsigned integer. It
2978 may be omitted, in which case zero is assumed. If it is
2979 omitted then the <var>upstream_version</var> may not
2984 It is provided to allow mistakes in the version numbers
2985 of older versions of a package, and also a package's
2986 previous version numbering schemes, to be left behind.
2990 <tag><var>upstream_version</var></tag>
2993 This is the main part of the version number. It is
2994 usually the version number of the original ("upstream")
2995 package from which the <file>.deb</file> file has been made,
2996 if this is applicable. Usually this will be in the same
2997 format as that specified by the upstream author(s);
2998 however, it may need to be reformatted to fit into the
2999 package management system's format and comparison
3004 The comparison behavior of the package management system
3005 with respect to the <var>upstream_version</var> is
3006 described below. The <var>upstream_version</var>
3007 portion of the version number is mandatory.
3011 The <var>upstream_version</var> may contain only
3012 alphanumerics<footnote>
3013 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3015 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3016 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3017 tilde) and should start with a digit. If there is no
3018 <var>debian_revision</var> then hyphens are not allowed;
3019 if there is no <var>epoch</var> then colons are not
3024 <tag><var>debian_revision</var></tag>
3027 This part of the version number specifies the version of
3028 the Debian package based on the upstream version. It
3029 may contain only alphanumerics and the characters
3030 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3031 tilde) and is compared in the same way as the
3032 <var>upstream_version</var> is.
3036 It is optional; if it isn't present then the
3037 <var>upstream_version</var> may not contain a hyphen.
3038 This format represents the case where a piece of
3039 software was written specifically to be a Debian
3040 package, where the Debian package source must always
3041 be identical to the pristine source and therefore no
3042 revision indication is required.
3046 It is conventional to restart the
3047 <var>debian_revision</var> at <tt>1</tt> each time the
3048 <var>upstream_version</var> is increased.
3052 The package management system will break the version
3053 number apart at the last hyphen in the string (if there
3054 is one) to determine the <var>upstream_version</var> and
3055 <var>debian_revision</var>. The absence of a
3056 <var>debian_revision</var> is equivalent to a
3057 <var>debian_revision</var> of <tt>0</tt>.
3064 When comparing two version numbers, first the <var>epoch</var>
3065 of each are compared, then the <var>upstream_version</var> if
3066 <var>epoch</var> is equal, and then <var>debian_revision</var>
3067 if <var>upstream_version</var> is also equal.
3068 <var>epoch</var> is compared numerically. The
3069 <var>upstream_version</var> and <var>debian_revision</var>
3070 parts are compared by the package management system using the
3071 following algorithm:
3075 The strings are compared from left to right.
3079 First the initial part of each string consisting entirely of
3080 non-digit characters is determined. These two parts (one of
3081 which may be empty) are compared lexically. If a difference
3082 is found it is returned. The lexical comparison is a
3083 comparison of ASCII values modified so that all the letters
3084 sort earlier than all the non-letters and so that a tilde
3085 sorts before anything, even the end of a part. For example,
3086 the following parts are in sorted order from earliest to
3087 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3088 <tt>a</tt>.<footnote>
3089 One common use of <tt>~</tt> is for upstream pre-releases.
3090 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3091 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3096 Then the initial part of the remainder of each string which
3097 consists entirely of digit characters is determined. The
3098 numerical values of these two parts are compared, and any
3099 difference found is returned as the result of the comparison.
3100 For these purposes an empty string (which can only occur at
3101 the end of one or both version strings being compared) counts
3106 These two steps (comparing and removing initial non-digit
3107 strings and initial digit strings) are repeated until a
3108 difference is found or both strings are exhausted.
3112 Note that the purpose of epochs is to allow us to leave behind
3113 mistakes in version numbering, and to cope with situations
3114 where the version numbering scheme changes. It is
3115 <em>not</em> intended to cope with version numbers containing
3116 strings of letters which the package management system cannot
3117 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3118 silly orderings.<footnote>
3119 The author of this manual has heard of a package whose
3120 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3121 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3127 <sect1 id="f-Description">
3128 <heading><tt>Description</tt></heading>
3131 In a source or binary control file, the <tt>Description</tt>
3132 field contains a description of the binary package, consisting
3133 of two parts, the synopsis or the short description, and the
3134 long description. The field's format is as follows:
3139 Description: <single line synopsis>
3140 <extended description over several lines>
3145 The lines in the extended description can have these formats:
3151 Those starting with a single space are part of a paragraph.
3152 Successive lines of this form will be word-wrapped when
3153 displayed. The leading space will usually be stripped off.
3157 Those starting with two or more spaces. These will be
3158 displayed verbatim. If the display cannot be panned
3159 horizontally, the displaying program will line wrap them "hard"
3160 (i.e., without taking account of word breaks). If it can they
3161 will be allowed to trail off to the right. None, one or two
3162 initial spaces may be deleted, but the number of spaces
3163 deleted from each line will be the same (so that you can have
3164 indenting work correctly, for example).
3168 Those containing a single space followed by a single full stop
3169 character. These are rendered as blank lines. This is the
3170 <em>only</em> way to get a blank line<footnote>
3171 Completely empty lines will not be rendered as blank lines.
3172 Instead, they will cause the parser to think you're starting
3173 a whole new record in the control file, and will therefore
3174 likely abort with an error.
3179 Those containing a space, a full stop and some more characters.
3180 These are for future expansion. Do not use them.
3186 Do not use tab characters. Their effect is not predictable.
3190 See <ref id="descriptions"> for further information on this.
3194 In a <file>.changes</file> file, the <tt>Description</tt>
3195 field contains a summary of the descriptions for the packages
3196 being uploaded. For this case, the first line of the field
3197 value (the part on the same line as <tt>Description:</tt>) is
3198 always empty. The content of the field is expressed as
3199 continuation lines, one line per package. Each line is
3200 indented by one space and contains the name of a binary
3201 package, a space, a hyphen (<tt>-</tt>), a space, and the
3202 short description line from that package.
3206 <sect1 id="f-Distribution">
3207 <heading><tt>Distribution</tt></heading>
3210 In a <file>.changes</file> file or parsed changelog output
3211 this contains the (space-separated) name(s) of the
3212 distribution(s) where this version of the package should
3213 be installed. Valid distributions are determined by the
3214 archive maintainers.<footnote>
3215 Example distribution names in the Debian archive used in
3216 <file>.changes</file> files are:
3217 <taglist compact="compact">
3218 <tag><em>unstable</em></tag>
3220 This distribution value refers to the
3221 <em>developmental</em> part of the Debian distribution
3222 tree. Most new packages, new upstream versions of
3223 packages and bug fixes go into the <em>unstable</em>
3227 <tag><em>experimental</em></tag>
3229 The packages with this distribution value are deemed
3230 by their maintainers to be high risk. Oftentimes they
3231 represent early beta or developmental packages from
3232 various sources that the maintainers want people to
3233 try, but are not ready to be a part of the other parts
3234 of the Debian distribution tree.
3239 Others are used for updating stable releases or for
3240 security uploads. More information is available in the
3241 Debian Developer's Reference, section "The Debian
3245 The Debian archive software only supports listing a single
3246 distribution. Migration of packages to other distributions is
3247 handled outside of the upload process.
3252 <heading><tt>Date</tt></heading>
3255 This field includes the date the package was built or last
3256 edited. It must be in the same format as the <var>date</var>
3257 in a <file>debian/changelog</file> entry.
3261 The value of this field is usually extracted from the
3262 <file>debian/changelog</file> file - see
3263 <ref id="dpkgchangelog">).
3267 <sect1 id="f-Format">
3268 <heading><tt>Format</tt></heading>
3271 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3272 files, this field declares the format version of that file.
3273 The syntax of the field value is the same as that of
3274 a <qref id="f-Version">package version number</qref> except
3275 that no epoch or Debian revision is allowed. The format
3276 described in this document is <tt>&changesversion;</tt>.
3280 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3281 Debian source control</qref> files, this field declares the
3282 format of the source package. The field value is used by
3283 programs acting on a source package to interpret the list of
3284 files in the source package and determine how to unpack it.
3285 The syntax of the field value is a numeric major revision, a
3286 period, a numeric minor revision, and then an optional subtype
3287 after whitespace, which if specified is an alphanumeric word
3288 in parentheses. The subtype is optional in the syntax but may
3289 be mandatory for particular source format revisions.
3291 The source formats currently supported by the Debian archive
3292 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3293 and <tt>3.0 (quilt)</tt>.
3298 <sect1 id="f-Urgency">
3299 <heading><tt>Urgency</tt></heading>
3302 This is a description of how important it is to upgrade to
3303 this version from previous ones. It consists of a single
3304 keyword taking one of the values <tt>low</tt>,
3305 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3306 <tt>critical</tt><footnote>
3307 Other urgency values are supported with configuration
3308 changes in the archive software but are not used in Debian.
3309 The urgency affects how quickly a package will be considered
3310 for inclusion into the <tt>testing</tt> distribution and
3311 gives an indication of the importance of any fixes included
3312 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3313 treated as synonymous.
3314 </footnote> (not case-sensitive) followed by an optional
3315 commentary (separated by a space) which is usually in
3316 parentheses. For example:
3319 Urgency: low (HIGH for users of diversions)
3325 The value of this field is usually extracted from the
3326 <file>debian/changelog</file> file - see
3327 <ref id="dpkgchangelog">.
3331 <sect1 id="f-Changes">
3332 <heading><tt>Changes</tt></heading>
3335 This field contains the human-readable changes data, describing
3336 the differences between the last version and the current one.
3340 The first line of the field value (the part on the same line
3341 as <tt>Changes:</tt>) is always empty. The content of the
3342 field is expressed as continuation lines, with each line
3343 indented by at least one space. Blank lines must be
3344 represented by a line consisting only of a space and a full
3349 The value of this field is usually extracted from the
3350 <file>debian/changelog</file> file - see
3351 <ref id="dpkgchangelog">).
3355 Each version's change information should be preceded by a
3356 "title" line giving at least the version, distribution(s)
3357 and urgency, in a human-readable way.
3361 If data from several versions is being returned the entry
3362 for the most recent version should be returned first, and
3363 entries should be separated by the representation of a
3364 blank line (the "title" line may also be followed by the
3365 representation of a blank line).
3369 <sect1 id="f-Binary">
3370 <heading><tt>Binary</tt></heading>
3373 This field is a list of binary packages. Its syntax and
3374 meaning varies depending on the control file in which it
3379 When it appears in the <file>.dsc</file> file, it lists binary
3380 packages which a source package can produce, separated by
3382 A space after each comma is conventional.
3383 </footnote>. It may span multiple lines. The source package
3384 does not necessarily produce all of these binary packages for
3385 every architecture. The source control file doesn't contain
3386 details of which architectures are appropriate for which of
3387 the binary packages.
3391 When it appears in a <file>.changes</file> file, it lists the
3392 names of the binary packages being uploaded, separated by
3393 whitespace (not commas). It may span multiple lines.
3397 <sect1 id="f-Installed-Size">
3398 <heading><tt>Installed-Size</tt></heading>
3401 This field appears in the control files of binary packages,
3402 and in the <file>Packages</file> files. It gives an estimate
3403 of the total amount of disk space required to install the
3404 named package. Actual installed size may vary based on block
3405 size, file system properties, or actions taken by package
3410 The disk space is given as the integer value of the estimated
3411 installed size in bytes, divided by 1024 and rounded up.
3415 <sect1 id="f-Files">
3416 <heading><tt>Files</tt></heading>
3419 This field contains a list of files with information about
3420 each one. The exact information and syntax varies with
3425 In all cases, Files is a multiline field. The first line of
3426 the field value (the part on the same line as <tt>Files:</tt>)
3427 is always empty. The content of the field is expressed as
3428 continuation lines, one line per file. Each line must be
3429 indented by one space and contain a number of sub-fields,
3430 separated by spaces, as described below.
3434 In the <file>.dsc</file> file, each line contains the MD5
3435 checksum, size and filename of the tar file and (if
3436 applicable) diff file which make up the remainder of the
3437 source package<footnote>
3438 That is, the parts which are not the <tt>.dsc</tt>.
3439 </footnote>. For example:
3442 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3443 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3445 The exact forms of the filenames are described
3446 in <ref id="pkg-sourcearchives">.
3450 In the <file>.changes</file> file this contains one line per
3451 file being uploaded. Each line contains the MD5 checksum,
3452 size, section and priority and the filename. For example:
3455 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3456 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3457 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3458 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3460 The <qref id="f-Section">section</qref>
3461 and <qref id="f-Priority">priority</qref> are the values of
3462 the corresponding fields in the main source control file. If
3463 no section or priority is specified then <tt>-</tt> should be
3464 used, though section and priority values must be specified for
3465 new packages to be installed properly.
3469 The special value <tt>byhand</tt> for the section in a
3470 <tt>.changes</tt> file indicates that the file in question
3471 is not an ordinary package file and must by installed by
3472 hand by the distribution maintainers. If the section is
3473 <tt>byhand</tt> the priority should be <tt>-</tt>.
3477 If a new Debian revision of a package is being shipped and
3478 no new original source archive is being distributed the
3479 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3480 entry for the original source archive
3481 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3482 but the <file>.changes</file> file should leave it out. In
3483 this case the original source archive on the distribution
3484 site must match exactly, byte-for-byte, the original
3485 source archive which was used to generate the
3486 <file>.dsc</file> file and diff which are being uploaded.</p>
3489 <sect1 id="f-Closes">
3490 <heading><tt>Closes</tt></heading>
3493 A space-separated list of bug report numbers that the upload
3494 governed by the .changes file closes.
3498 <sect1 id="f-Homepage">
3499 <heading><tt>Homepage</tt></heading>
3502 The URL of the web site for this package, preferably (when
3503 applicable) the site from which the original source can be
3504 obtained and any additional upstream documentation or
3505 information may be found. The content of this field is a
3506 simple URL without any surrounding characters such as
3511 <sect1 id="f-Checksums">
3512 <heading><tt>Checksums-Sha1</tt>
3513 and <tt>Checksums-Sha256</tt></heading>
3516 These fields contain a list of files with a checksum and size
3517 for each one. Both <tt>Checksums-Sha1</tt>
3518 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3519 only in the checksum algorithm used: SHA-1
3520 for <tt>Checksums-Sha1</tt> and SHA-256
3521 for <tt>Checksums-Sha256</tt>.
3525 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3526 multiline fields. The first line of the field value (the part
3527 on the same line as <tt>Checksums-Sha1:</tt>
3528 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3529 of the field is expressed as continuation lines, one line per
3530 file. Each line consists of the checksum, a space, the file
3531 size, a space, and the file name. For example (from
3532 a <file>.changes</file> file):
3535 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3536 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3537 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3538 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3540 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3541 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3542 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3543 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3548 In the <file>.dsc</file> file, these fields should list all
3549 files that make up the source package. In
3550 the <file>.changes</file> file, these fields should list all
3551 files being uploaded. The list of files in these fields
3552 must match the list of files in the <tt>Files</tt> field.
3558 <heading>User-defined fields</heading>
3561 Additional user-defined fields may be added to the
3562 source package control file. Such fields will be
3563 ignored, and not copied to (for example) binary or
3564 source package control files or upload control files.
3568 If you wish to add additional unsupported fields to
3569 these output files you should use the mechanism
3574 Fields in the main source control information file with
3575 names starting <tt>X</tt>, followed by one or more of
3576 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3577 be copied to the output files. Only the part of the
3578 field name after the hyphen will be used in the output
3579 file. Where the letter <tt>B</tt> is used the field
3580 will appear in binary package control files, where the
3581 letter <tt>S</tt> is used in source package control
3582 files and where <tt>C</tt> is used in upload control
3583 (<tt>.changes</tt>) files.
3587 For example, if the main source information control file
3590 XBS-Comment: I stand between the candle and the star.
3592 then the binary and source package control files will contain the
3595 Comment: I stand between the candle and the star.
3604 <chapt id="maintainerscripts">
3605 <heading>Package maintainer scripts and installation procedure</heading>
3608 <heading>Introduction to package maintainer scripts</heading>
3611 It is possible to supply scripts as part of a package which
3612 the package management system will run for you when your
3613 package is installed, upgraded or removed.
3617 These scripts are the files <prgn>preinst</prgn>,
3618 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3619 <prgn>postrm</prgn> in the control area of the package.
3620 They must be proper executable files; if they are scripts
3621 (which is recommended), they must start with the usual
3622 <tt>#!</tt> convention. They should be readable and
3623 executable by anyone, and must not be world-writable.
3627 The package management system looks at the exit status from
3628 these scripts. It is important that they exit with a
3629 non-zero status if there is an error, so that the package
3630 management system can stop its processing. For shell
3631 scripts this means that you <em>almost always</em> need to
3632 use <tt>set -e</tt> (this is usually true when writing shell
3633 scripts, in fact). It is also important, of course, that
3634 they exit with a zero status if everything went well.
3638 Additionally, packages interacting with users using
3639 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3640 install a <prgn>config</prgn> script in the control area,
3641 see <ref id="maintscriptprompt"> for details.
3645 When a package is upgraded a combination of the scripts from
3646 the old and new packages is called during the upgrade
3647 procedure. If your scripts are going to be at all
3648 complicated you need to be aware of this, and may need to
3649 check the arguments to your scripts.
3653 Broadly speaking the <prgn>preinst</prgn> is called before
3654 (a particular version of) a package is installed, and the
3655 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3656 before (a version of) a package is removed and the
3657 <prgn>postrm</prgn> afterwards.
3661 Programs called from maintainer scripts should not normally
3662 have a path prepended to them. Before installation is
3663 started, the package management system checks to see if the
3664 programs <prgn>ldconfig</prgn>,
3665 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3666 and <prgn>update-rc.d</prgn> can be found via the
3667 <tt>PATH</tt> environment variable. Those programs, and any
3668 other program that one would expect to be in the
3669 <tt>PATH</tt>, should thus be invoked without an absolute
3670 pathname. Maintainer scripts should also not reset the
3671 <tt>PATH</tt>, though they might choose to modify it by
3672 prepending or appending package-specific directories. These
3673 considerations really apply to all shell scripts.</p>
3676 <sect id="idempotency">
3677 <heading>Maintainer scripts idempotency</heading>
3680 It is necessary for the error recovery procedures that the
3681 scripts be idempotent. This means that if it is run
3682 successfully, and then it is called again, it doesn't bomb
3683 out or cause any harm, but just ensures that everything is
3684 the way it ought to be. If the first call failed, or
3685 aborted half way through for some reason, the second call
3686 should merely do the things that were left undone the first
3687 time, if any, and exit with a success status if everything
3689 This is so that if an error occurs, the user interrupts
3690 <prgn>dpkg</prgn> or some other unforeseen circumstance
3691 happens you don't leave the user with a badly-broken
3692 package when <prgn>dpkg</prgn> attempts to repeat the
3698 <sect id="controllingterminal">
3699 <heading>Controlling terminal for maintainer scripts</heading>
3702 Maintainer scripts are not guaranteed to run with a controlling
3703 terminal and may not be able to interact with the user. They
3704 must be able to fall back to noninteractive behavior if no
3705 controlling terminal is available. Maintainer scripts that
3706 prompt via a program conforming to the Debian Configuration
3707 Management Specification (see <ref id="maintscriptprompt">) may
3708 assume that program will handle falling back to noninteractive
3713 For high-priority prompts without a reasonable default answer,
3714 maintainer scripts may abort if there is no controlling
3715 terminal. However, this situation should be avoided if at all
3716 possible, since it prevents automated or unattended installs.
3717 In most cases, users will consider this to be a bug in the
3722 <sect id="exitstatus">
3723 <heading>Exit status</heading>
3726 Each script must return a zero exit status for
3727 success, or a nonzero one for failure, since the package
3728 management system looks for the exit status of these scripts
3729 and determines what action to take next based on that datum.
3733 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3738 <list compact="compact">
3740 <var>new-preinst</var> <tt>install</tt>
3743 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3746 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3749 <var>old-preinst</var> <tt>abort-upgrade</tt>
3750 <var>new-version</var>
3755 <list compact="compact">
3757 <var>postinst</var> <tt>configure</tt>
3758 <var>most-recently-configured-version</var>
3761 <var>old-postinst</var> <tt>abort-upgrade</tt>
3762 <var>new-version</var>
3765 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3766 <tt>in-favour</tt> <var>package</var>
3767 <var>new-version</var>
3770 <var>postinst</var> <tt>abort-remove</tt>
3773 <var>deconfigured's-postinst</var>
3774 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3775 <var>failed-install-package</var> <var>version</var>
3776 [<tt>removing</tt> <var>conflicting-package</var>
3782 <list compact="compact">
3784 <var>prerm</var> <tt>remove</tt>
3787 <var>old-prerm</var> <tt>upgrade</tt>
3788 <var>new-version</var>
3791 <var>new-prerm</var> <tt>failed-upgrade</tt>
3792 <var>old-version</var>
3795 <var>conflictor's-prerm</var> <tt>remove</tt>
3796 <tt>in-favour</tt> <var>package</var>
3797 <var>new-version</var>
3800 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3801 <tt>in-favour</tt> <var>package-being-installed</var>
3802 <var>version</var> [<tt>removing</tt>
3803 <var>conflicting-package</var>
3809 <list compact="compact">
3811 <var>postrm</var> <tt>remove</tt>
3814 <var>postrm</var> <tt>purge</tt>
3817 <var>old-postrm</var> <tt>upgrade</tt>
3818 <var>new-version</var>
3821 <var>new-postrm</var> <tt>failed-upgrade</tt>
3822 <var>old-version</var>
3825 <var>new-postrm</var> <tt>abort-install</tt>
3828 <var>new-postrm</var> <tt>abort-install</tt>
3829 <var>old-version</var>
3832 <var>new-postrm</var> <tt>abort-upgrade</tt>
3833 <var>old-version</var>
3836 <var>disappearer's-postrm</var> <tt>disappear</tt>
3837 <var>overwriter</var>
3838 <var>overwriter-version</var>
3844 <sect id="unpackphase">
3845 <heading>Details of unpack phase of installation or upgrade</heading>
3848 The procedure on installation/upgrade/overwrite/disappear
3849 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3850 stage of <tt>dpkg --install</tt>) is as follows. In each
3851 case, if a major error occurs (unless listed below) the
3852 actions are, in general, run backwards - this means that the
3853 maintainer scripts are run with different arguments in
3854 reverse order. These are the "error unwind" calls listed
3861 If a version of the package is already installed, call
3862 <example compact="compact">
3863 <var>old-prerm</var> upgrade <var>new-version</var>
3867 If the script runs but exits with a non-zero
3868 exit status, <prgn>dpkg</prgn> will attempt:
3869 <example compact="compact">
3870 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3872 If this works, the upgrade continues. If this
3873 does not work, the error unwind:
3874 <example compact="compact">
3875 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3877 If this works, then the old-version is
3878 "Installed", if not, the old version is in a
3879 "Half-Configured" state.
3885 If a "conflicting" package is being removed at the same time,
3886 or if any package will be broken (due to <tt>Breaks</tt>):
3889 If <tt>--auto-deconfigure</tt> is
3890 specified, call, for each package to be deconfigured
3891 due to <tt>Breaks</tt>:
3892 <example compact="compact">
3893 <var>deconfigured's-prerm</var> deconfigure \
3894 in-favour <var>package-being-installed</var> <var>version</var>
3897 <example compact="compact">
3898 <var>deconfigured's-postinst</var> abort-deconfigure \
3899 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3901 The deconfigured packages are marked as
3902 requiring configuration, so that if
3903 <tt>--install</tt> is used they will be
3904 configured again if possible.
3907 If any packages depended on a conflicting
3908 package being removed and <tt>--auto-deconfigure</tt> is
3909 specified, call, for each such package:
3910 <example compact="compact">
3911 <var>deconfigured's-prerm</var> deconfigure \
3912 in-favour <var>package-being-installed</var> <var>version</var> \
3913 removing <var>conflicting-package</var> <var>version</var>
3916 <example compact="compact">
3917 <var>deconfigured's-postinst</var> abort-deconfigure \
3918 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3919 removing <var>conflicting-package</var> <var>version</var>
3921 The deconfigured packages are marked as
3922 requiring configuration, so that if
3923 <tt>--install</tt> is used they will be
3924 configured again if possible.
3927 To prepare for removal of each conflicting package, call:
3928 <example compact="compact">
3929 <var>conflictor's-prerm</var> remove \
3930 in-favour <var>package</var> <var>new-version</var>
3933 <example compact="compact">
3934 <var>conflictor's-postinst</var> abort-remove \
3935 in-favour <var>package</var> <var>new-version</var>
3944 If the package is being upgraded, call:
3945 <example compact="compact">
3946 <var>new-preinst</var> upgrade <var>old-version</var>
3948 If this fails, we call:
3950 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3957 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3959 is called. If this works, then the old version
3960 is in an "Installed" state, or else it is left
3961 in an "Unpacked" state.
3966 If it fails, then the old version is left
3967 in an "Half-Installed" state.
3974 Otherwise, if the package had some configuration
3975 files from a previous version installed (i.e., it
3976 is in the "configuration files only" state):
3977 <example compact="compact">
3978 <var>new-preinst</var> install <var>old-version</var>
3982 <var>new-postrm</var> abort-install <var>old-version</var>
3984 If this fails, the package is left in a
3985 "Half-Installed" state, which requires a
3986 reinstall. If it works, the packages is left in
3987 a "Config-Files" state.
3990 Otherwise (i.e., the package was completely purged):
3991 <example compact="compact">
3992 <var>new-preinst</var> install
3995 <example compact="compact">
3996 <var>new-postrm</var> abort-install
3998 If the error-unwind fails, the package is in a
3999 "Half-Installed" phase, and requires a
4000 reinstall. If the error unwind works, the
4001 package is in a not installed state.
4008 The new package's files are unpacked, overwriting any
4009 that may be on the system already, for example any
4010 from the old version of the same package or from
4011 another package. Backups of the old files are kept
4012 temporarily, and if anything goes wrong the package
4013 management system will attempt to put them back as
4014 part of the error unwind.
4018 It is an error for a package to contain files which
4019 are on the system in another package, unless
4020 <tt>Replaces</tt> is used (see <ref id="replaces">).
4022 The following paragraph is not currently the case:
4023 Currently the <tt>- - force-overwrite</tt> flag is
4024 enabled, downgrading it to a warning, but this may not
4030 It is a more serious error for a package to contain a
4031 plain file or other kind of non-directory where another
4032 package has a directory (again, unless
4033 <tt>Replaces</tt> is used). This error can be
4034 overridden if desired using
4035 <tt>--force-overwrite-dir</tt>, but this is not
4040 Packages which overwrite each other's files produce
4041 behavior which, though deterministic, is hard for the
4042 system administrator to understand. It can easily
4043 lead to "missing" programs if, for example, a package
4044 is installed which overwrites a file from another
4045 package, and is then removed again.<footnote>
4046 Part of the problem is due to what is arguably a
4047 bug in <prgn>dpkg</prgn>.
4052 A directory will never be replaced by a symbolic link
4053 to a directory or vice versa; instead, the existing
4054 state (symlink or not) will be left alone and
4055 <prgn>dpkg</prgn> will follow the symlink if there is
4064 If the package is being upgraded, call
4065 <example compact="compact">
4066 <var>old-postrm</var> upgrade <var>new-version</var>
4070 If this fails, <prgn>dpkg</prgn> will attempt:
4071 <example compact="compact">
4072 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4074 If this works, installation continues. If not,
4076 <example compact="compact">
4077 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4079 If this fails, the old version is left in a
4080 "Half-Installed" state. If it works, dpkg now
4082 <example compact="compact">
4083 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4085 If this fails, the old version is left in a
4086 "Half-Installed" state. If it works, dpkg now
4088 <example compact="compact">
4089 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4091 If this fails, the old version is in an
4098 This is the point of no return - if
4099 <prgn>dpkg</prgn> gets this far, it won't back off
4100 past this point if an error occurs. This will
4101 leave the package in a fairly bad state, which
4102 will require a successful re-installation to clear
4103 up, but it's when <prgn>dpkg</prgn> starts doing
4104 things that are irreversible.
4109 Any files which were in the old version of the package
4110 but not in the new are removed.
4114 The new file list replaces the old.
4118 The new maintainer scripts replace the old.
4122 Any packages all of whose files have been overwritten
4123 during the installation, and which aren't required for
4124 dependencies, are considered to have been removed.
4125 For each such package
4128 <prgn>dpkg</prgn> calls:
4129 <example compact="compact">
4130 <var>disappearer's-postrm</var> disappear \
4131 <var>overwriter</var> <var>overwriter-version</var>
4135 The package's maintainer scripts are removed.
4138 It is noted in the status database as being in a
4139 sane state, namely not installed (any conffiles
4140 it may have are ignored, rather than being
4141 removed by <prgn>dpkg</prgn>). Note that
4142 disappearing packages do not have their prerm
4143 called, because <prgn>dpkg</prgn> doesn't know
4144 in advance that the package is going to
4151 Any files in the package we're unpacking that are also
4152 listed in the file lists of other packages are removed
4153 from those lists. (This will lobotomize the file list
4154 of the "conflicting" package if there is one.)
4158 The backup files made during installation, above, are
4164 The new package's status is now sane, and recorded as
4169 Here is another point of no return - if the
4170 conflicting package's removal fails we do not unwind
4171 the rest of the installation; the conflicting package
4172 is left in a half-removed limbo.
4177 If there was a conflicting package we go and do the
4178 removal actions (described below), starting with the
4179 removal of the conflicting package's files (any that
4180 are also in the package being installed have already
4181 been removed from the conflicting package's file list,
4182 and so do not get removed now).
4188 <sect id="configdetails"><heading>Details of configuration</heading>
4191 When we configure a package (this happens with <tt>dpkg
4192 --install</tt> and <tt>dpkg --configure</tt>), we first
4193 update any <tt>conffile</tt>s and then call:
4194 <example compact="compact">
4195 <var>postinst</var> configure <var>most-recently-configured-version</var>
4200 No attempt is made to unwind after errors during
4201 configuration. If the configuration fails, the package is in
4202 a "Failed Config" state, and an error message is generated.
4206 If there is no most recently configured version
4207 <prgn>dpkg</prgn> will pass a null argument.
4210 Historical note: Truly ancient (pre-1997) versions of
4211 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4212 (including the angle brackets) in this case. Even older
4213 ones did not pass a second argument at all, under any
4214 circumstance. Note that upgrades using such an old dpkg
4215 version are unlikely to work for other reasons, even if
4216 this old argument behavior is handled by your postinst script.
4222 <sect id="removedetails"><heading>Details of removal and/or
4223 configuration purging</heading>
4229 <example compact="compact">
4230 <var>prerm</var> remove
4234 If prerm fails during replacement due to conflict
4236 <var>conflictor's-postinst</var> abort-remove \
4237 in-favour <var>package</var> <var>new-version</var>
4241 <var>postinst</var> abort-remove
4245 If this fails, the package is in a "Half-Configured"
4246 state, or else it remains "Installed".
4250 The package's files are removed (except <tt>conffile</tt>s).
4253 <example compact="compact">
4254 <var>postrm</var> remove
4258 If it fails, there's no error unwind, and the package is in
4259 an "Half-Installed" state.
4264 All the maintainer scripts except the <prgn>postrm</prgn>
4269 If we aren't purging the package we stop here. Note
4270 that packages which have no <prgn>postrm</prgn> and no
4271 <tt>conffile</tt>s are automatically purged when
4272 removed, as there is no difference except for the
4273 <prgn>dpkg</prgn> status.
4277 The <tt>conffile</tt>s and any backup files
4278 (<tt>~</tt>-files, <tt>#*#</tt> files,
4279 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4284 <example compact="compact">
4285 <var>postrm</var> purge
4289 If this fails, the package remains in a "Config-Files"
4294 The package's file list is removed.
4303 <chapt id="relationships">
4304 <heading>Declaring relationships between packages</heading>
4306 <sect id="depsyntax">
4307 <heading>Syntax of relationship fields</heading>
4310 These fields all have a uniform syntax. They are a list of
4311 package names separated by commas.
4315 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4316 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4317 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4318 control file fields of the package, which declare
4319 dependencies on other packages, the package names listed may
4320 also include lists of alternative package names, separated
4321 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4322 if any one of the alternative packages is installed, that
4323 part of the dependency is considered to be satisfied.
4327 All of the fields except for <tt>Provides</tt> may restrict
4328 their applicability to particular versions of each named
4329 package. This is done in parentheses after each individual
4330 package name; the parentheses should contain a relation from
4331 the list below followed by a version number, in the format
4332 described in <ref id="f-Version">.
4336 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4337 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4338 strictly earlier, earlier or equal, exactly equal, later or
4339 equal and strictly later, respectively. The deprecated
4340 forms <tt><</tt> and <tt>></tt> were used to mean
4341 earlier/later or equal, rather than strictly earlier/later,
4342 so they should not appear in new packages (though
4343 <prgn>dpkg</prgn> still supports them).
4347 Whitespace may appear at any point in the version
4348 specification subject to the rules in <ref
4349 id="controlsyntax">, and must appear where it's necessary to
4350 disambiguate; it is not otherwise significant. All of the
4351 relationship fields may span multiple lines. For
4352 consistency and in case of future changes to
4353 <prgn>dpkg</prgn> it is recommended that a single space be
4354 used after a version relationship and before a version
4355 number; it is also conventional to put a single space after
4356 each comma, on either side of each vertical bar, and before
4357 each open parenthesis. When wrapping a relationship field, it
4358 is conventional to do so after a comma and before the space
4359 following that comma.
4363 For example, a list of dependencies might appear as:
4364 <example compact="compact">
4367 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4372 All fields that specify build-time relationships
4373 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4374 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4375 may be restricted to a certain set of architectures. This
4376 is indicated in brackets after each individual package name and
4377 the optional version specification. The brackets enclose a
4378 list of Debian architecture names separated by whitespace.
4379 Exclamation marks may be prepended to each of the names.
4380 (It is not permitted for some names to be prepended with
4381 exclamation marks while others aren't.) If the current Debian
4382 host architecture is not in this list and there are no
4383 exclamation marks in the list, or it is in the list with a
4384 prepended exclamation mark, the package name and the
4385 associated version specification are ignored completely for
4386 the purposes of defining the relationships.
4391 <example compact="compact">
4393 Build-Depends-Indep: texinfo
4394 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4395 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4397 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4398 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4399 <tt>gnumach-dev</tt> only on hurd-i386.
4403 If the architecture-restricted dependency is part of a set of
4404 alternatives using <tt>|</tt>, that alternative is ignored
4405 completely on architectures that do not match the restriction.
4407 <example compact="compact">
4408 Build-Depends: foo [!i386] | bar [!amd64]
4410 is equivalent to <tt>bar</tt> on the i386 architecture, to
4411 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4412 bar</tt> on all other architectures.
4416 All fields that specify build-time relationships may also be
4417 restricted to a certain set of architectures using architecture
4418 wildcards. The syntax for declaring such restrictions is the
4419 same as declaring restrictions using a certain set of
4420 architectures without architecture wildcards. For example:
4421 <example compact="compact">
4422 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4424 is equivalent to <tt>foo</tt> on architectures using the Linux
4425 kernel and any cpu, <tt>bar</tt> on architectures using any
4426 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4427 using a kernel other than Linux.
4431 Note that the binary package relationship fields such as
4432 <tt>Depends</tt> appear in one of the binary package
4433 sections of the control file, whereas the build-time
4434 relationships such as <tt>Build-Depends</tt> appear in the
4435 source package section of the control file (which is the
4440 <sect id="binarydeps">
4441 <heading>Binary Dependencies - <tt>Depends</tt>,
4442 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4443 <tt>Pre-Depends</tt>
4447 Packages can declare in their control file that they have
4448 certain relationships to other packages - for example, that
4449 they may not be installed at the same time as certain other
4450 packages, and/or that they depend on the presence of others.
4454 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4455 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4456 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4457 <tt>Breaks</tt> is described in <ref id="breaks">, and
4458 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4459 rest are described below.
4463 These seven fields are used to declare a dependency
4464 relationship by one package on another. Except for
4465 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4466 depending (binary) package's control file.
4467 (<tt>Enhances</tt> appears in the recommending package's
4468 control file, and <tt>Breaks</tt> appears in the version of
4469 depended-on package which causes the named package to
4474 A <tt>Depends</tt> field takes effect <em>only</em> when a
4475 package is to be configured. It does not prevent a package
4476 being on the system in an unconfigured state while its
4477 dependencies are unsatisfied, and it is possible to replace
4478 a package whose dependencies are satisfied and which is
4479 properly installed with a different version whose
4480 dependencies are not and cannot be satisfied; when this is
4481 done the depending package will be left unconfigured (since
4482 attempts to configure it will give errors) and will not
4483 function properly. If it is necessary, a
4484 <tt>Pre-Depends</tt> field can be used, which has a partial
4485 effect even when a package is being unpacked, as explained
4486 in detail below. (The other three dependency fields,
4487 <tt>Recommends</tt>, <tt>Suggests</tt> and
4488 <tt>Enhances</tt>, are only used by the various front-ends
4489 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4490 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4494 For this reason packages in an installation run are usually
4495 all unpacked first and all configured later; this gives
4496 later versions of packages with dependencies on later
4497 versions of other packages the opportunity to have their
4498 dependencies satisfied.
4502 In case of circular dependencies, since installation or
4503 removal order honoring the dependency order can't be
4504 established, dependency loops are broken at some point
4505 (based on rules below), and some packages may not be able to
4506 rely on their dependencies being present when being
4507 installed or removed, depending on which side of the break
4508 of the circular dependency loop they happen to be on. If one
4509 of the packages in the loop has no postinst script, then the
4510 cycle will be broken at that package, so as to ensure that
4511 all postinst scripts run with the dependencies properly
4512 configured if this is possible. Otherwise the breaking point
4517 The <tt>Depends</tt> field thus allows package maintainers
4518 to impose an order in which packages should be configured.
4522 The meaning of the five dependency fields is as follows:
4524 <tag><tt>Depends</tt></tag>
4527 This declares an absolute dependency. A package will
4528 not be configured unless all of the packages listed in
4529 its <tt>Depends</tt> field have been correctly
4534 The <tt>Depends</tt> field should be used if the
4535 depended-on package is required for the depending
4536 package to provide a significant amount of
4541 The <tt>Depends</tt> field should also be used if the
4542 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4543 <prgn>postrm</prgn> scripts require the package to be
4544 present in order to run. Note, however, that the
4545 <prgn>postrm</prgn> cannot rely on any non-essential
4546 packages to be present during the <tt>purge</tt>
4550 <tag><tt>Recommends</tt></tag>
4553 This declares a strong, but not absolute, dependency.
4557 The <tt>Recommends</tt> field should list packages
4558 that would be found together with this one in all but
4559 unusual installations.
4563 <tag><tt>Suggests</tt></tag>
4565 This is used to declare that one package may be more
4566 useful with one or more others. Using this field
4567 tells the packaging system and the user that the
4568 listed packages are related to this one and can
4569 perhaps enhance its usefulness, but that installing
4570 this one without them is perfectly reasonable.
4573 <tag><tt>Enhances</tt></tag>
4575 This field is similar to Suggests but works in the
4576 opposite direction. It is used to declare that a
4577 package can enhance the functionality of another
4581 <tag><tt>Pre-Depends</tt></tag>
4584 This field is like <tt>Depends</tt>, except that it
4585 also forces <prgn>dpkg</prgn> to complete installation
4586 of the packages named before even starting the
4587 installation of the package which declares the
4588 pre-dependency, as follows:
4592 When a package declaring a pre-dependency is about to
4593 be <em>unpacked</em> the pre-dependency can be
4594 satisfied if the depended-on package is either fully
4595 configured, <em>or even if</em> the depended-on
4596 package(s) are only unpacked or in the "Half-Configured"
4597 state, provided that they have been configured
4598 correctly at some point in the past (and not removed
4599 or partially removed since). In this case, both the
4600 previously-configured and currently unpacked or
4601 "Half-Configured" versions must satisfy any version
4602 clause in the <tt>Pre-Depends</tt> field.
4606 When the package declaring a pre-dependency is about
4607 to be <em>configured</em>, the pre-dependency will be
4608 treated as a normal <tt>Depends</tt>, that is, it will
4609 be considered satisfied only if the depended-on
4610 package has been correctly configured.
4614 <tt>Pre-Depends</tt> should be used sparingly,
4615 preferably only by packages whose premature upgrade or
4616 installation would hamper the ability of the system to
4617 continue with any upgrade that might be in progress.
4621 <tt>Pre-Depends</tt> are also required if the
4622 <prgn>preinst</prgn> script depends on the named
4623 package. It is best to avoid this situation if
4631 When selecting which level of dependency to use you should
4632 consider how important the depended-on package is to the
4633 functionality of the one declaring the dependency. Some
4634 packages are composed of components of varying degrees of
4635 importance. Such a package should list using
4636 <tt>Depends</tt> the package(s) which are required by the
4637 more important components. The other components'
4638 requirements may be mentioned as Suggestions or
4639 Recommendations, as appropriate to the components' relative
4645 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4648 When one binary package declares that it breaks another,
4649 <prgn>dpkg</prgn> will refuse to allow the package which
4650 declares <tt>Breaks</tt> be installed unless the broken
4651 package is deconfigured first, and it will refuse to
4652 allow the broken package to be reconfigured.
4656 A package will not be regarded as causing breakage merely
4657 because its configuration files are still installed; it must
4658 be at least "Half-Installed".
4662 A special exception is made for packages which declare that
4663 they break their own package name or a virtual package which
4664 they provide (see below): this does not count as a real
4669 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4670 version clause; such a <tt>Breaks</tt> is introduced in the
4671 version of an (implicit or explicit) dependency which violates
4672 an assumption or reveals a bug in earlier versions of the broken
4673 package, or which takes over a file from earlier versions of the
4674 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4675 will inform higher-level package management tools that the
4676 broken package must be upgraded before the new one.
4680 If the breaking package also overwrites some files from the
4681 older package, it should use <tt>Replaces</tt> to ensure this
4682 goes smoothly. See <ref id="replaces"> for a full discussion
4683 of taking over files from other packages, including how to
4684 use <tt>Breaks</tt> in those cases.
4688 Many of the cases where <tt>Breaks</tt> should be used were
4689 previously handled with <tt>Conflicts</tt>
4690 because <tt>Breaks</tt> did not yet exist.
4691 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4692 See <ref id="conflicts"> for more information about the
4697 <sect id="conflicts">
4698 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4701 When one binary package declares a conflict with another
4702 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4703 refuse to allow them to be installed on the system at the
4704 same time. This is a stronger restriction than <tt>Breaks</tt>,
4705 which just prevents both packages from being configured at the
4706 same time. Conflicting packages cannot be unpacked on the
4707 system at the same time.
4711 If one package is to be installed, the other must be removed
4712 first. If the package being installed is marked as replacing
4713 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4714 normally be used in this case) the one on the system, or the one
4715 on the system is marked as deselected, or both packages are
4716 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4717 automatically remove the package which is causing the conflict.
4718 Otherwise, it will halt the installation of the new package with
4719 an error. This mechanism is specifically designed to produce an
4720 error when the installed package is <tt>Essential</tt>, but the
4725 A package will not cause a conflict merely because its
4726 configuration files are still installed; it must be at least
4731 A special exception is made for packages which declare a
4732 conflict with their own package name, or with a virtual
4733 package which they provide (see below): this does not
4734 prevent their installation, and allows a package to conflict
4735 with others providing a replacement for it. You use this
4736 feature when you want the package in question to be the only
4737 package providing some feature.
4741 Normally, <tt>Breaks</tt> should be used instead
4742 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4743 stronger restriction on the ordering of package installation or
4744 upgrade and can make it more difficult for the package manager
4745 to find a correct solution to an upgrade or installation
4746 problem. <tt>Breaks</tt> should be used
4748 <item>when moving a file from one package to another (see
4749 <ref id="replaces">),</item>
4750 <item>when splitting a package (a special case of the previous
4752 <item>when the breaking package exposes a bug in or interacts
4753 badly with particular versions of the broken
4756 <tt>Conflicts</tt> should be used
4758 <item>when two packages provide the same file and will
4759 continue to do so,</item>
4760 <item>in conjunction with <tt>Provides</tt> when only one
4761 package providing a given virtual facility may be installed
4762 at a time (see <ref id="virtual">),</item>
4763 <item>in other cases where one must prevent simultaneous
4764 installation of two packages for reasons that are ongoing
4765 (not fixed in a later version of one of the packages) or
4766 that must prevent both packages from being unpacked at the
4767 same time, not just configured.</item>
4769 Be aware that adding <tt>Conflicts</tt> is normally not the best
4770 solution when two packages provide the same files. Depending on
4771 the reason for that conflict, using alternatives or renaming the
4772 files is often a better approach. See, for
4773 example, <ref id="binaries">.
4777 A <tt>Conflicts</tt> entry may have an "earlier than" version
4778 clause if the reason for the conflict is corrected in a later
4779 version of one of the packages. However, normally the presence
4780 of an "earlier than" version clause is a sign
4781 that <tt>Breaks</tt> should have been used instead. An "earlier
4782 than" version clause in <tt>Conflicts</tt>
4783 prevents <prgn>dpkg</prgn> from upgrading or installing the
4784 package which declares such a conflict until the upgrade or
4785 removal of the conflicted-with package has been completed, which
4786 is a strong restriction.
4790 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4794 As well as the names of actual ("concrete") packages, the
4795 package relationship fields <tt>Depends</tt>,
4796 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4797 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4798 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4799 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4800 may mention "virtual packages".
4804 A <em>virtual package</em> is one which appears in the
4805 <tt>Provides</tt> control file field of another package.
4806 The effect is as if the package(s) which provide a
4807 particular virtual package name had been listed by name
4808 everywhere the virtual package name appears. (See also <ref
4813 If there are both concrete and virtual packages of the same
4814 name, then the dependency may be satisfied (or the conflict
4815 caused) by either the concrete package with the name in
4816 question or any other concrete package which provides the
4817 virtual package with the name in question. This is so that,
4818 for example, supposing we have
4819 <example compact="compact">
4822 </example> and someone else releases an enhanced version of
4823 the <tt>bar</tt> package they can say:
4824 <example compact="compact">
4828 and the <tt>bar-plus</tt> package will now also satisfy the
4829 dependency for the <tt>foo</tt> package.
4833 If a relationship field has a version number attached, only real
4834 packages will be considered to see whether the relationship is
4835 satisfied (or the prohibition violated, for a conflict or
4836 breakage). In other words, if a version number is specified,
4837 this is a request to ignore all <tt>Provides</tt> for that
4838 package name and consider only real packages. The package
4839 manager will assume that a package providing that virtual
4840 package is not of the "right" version. A <tt>Provides</tt>
4841 field may not contain version numbers, and the version number of
4842 the concrete package which provides a particular virtual package
4843 will not be considered when considering a dependency on or
4844 conflict with the virtual package name.<footnote>
4845 It is possible that a future release of <prgn>dpkg</prgn> may
4846 add the ability to specify a version number for each virtual
4847 package it provides. This feature is not yet present,
4848 however, and is expected to be used only infrequently.
4853 To specify which of a set of real packages should be the default
4854 to satisfy a particular dependency on a virtual package, list
4855 the real package as an alternative before the virtual one.
4859 If the virtual package represents a facility that can only be
4860 provided by one real package at a time, such as
4861 the <package>mail-transport-agent</package> virtual package that
4862 requires installation of a binary that would conflict with all
4863 other providers of that virtual package (see
4864 <ref id="mail-transport-agents">), all packages providing that
4865 virtual package should also declare a conflict with it
4866 using <tt>Conflicts</tt>. This will ensure that at most one
4867 provider of that virtual package is unpacked or installed at a
4872 <sect id="replaces"><heading>Overwriting files and replacing
4873 packages - <tt>Replaces</tt></heading>
4876 Packages can declare in their control file that they should
4877 overwrite files in certain other packages, or completely
4878 replace other packages. The <tt>Replaces</tt> control file
4879 field has these two distinct purposes.
4882 <sect1><heading>Overwriting files in other packages</heading>
4885 It is usually an error for a package to contain files which
4886 are on the system in another package. However, if the
4887 overwriting package declares that it <tt>Replaces</tt> the one
4888 containing the file being overwritten, then <prgn>dpkg</prgn>
4889 will replace the file from the old package with that from the
4890 new. The file will no longer be listed as "owned" by the old
4891 package and will be taken over by the new package.
4892 Normally, <tt>Breaks</tt> should be used in conjunction
4893 with <tt>Replaces</tt>.<footnote>
4894 To see why <tt>Breaks</tt> is normally needed in addition
4895 to <tt>Replaces</tt>, consider the case of a file in the
4896 package <package>foo</package> being taken over by the
4897 package <package>foo-data</package>.
4898 <tt>Replaces</tt> will allow <package>foo-data</package> to
4899 be installed and take over that file. However,
4900 without <tt>Breaks</tt>, nothing
4901 requires <package>foo</package> to be upgraded to a newer
4902 version that knows it does not include that file and instead
4903 depends on <package>foo-data</package>. Nothing would
4904 prevent the new <package>foo-data</package> package from
4905 being installed and then removed, removing the file that it
4906 took over from <package>foo</package>. After that
4907 operation, the package manager would think the system was in
4908 a consistent state, but the <package>foo</package> package
4909 would be missing one of its files.
4914 For example, if a package <package>foo</package> is split
4915 into <package>foo</package> and <package>foo-data</package>
4916 starting at version 1.2-3, <package>foo-data</package> would
4918 <example compact="compact">
4919 Replaces: foo (<< 1.2-3)
4920 Breaks: foo (<< 1.2-3)
4922 in its control file. The new version of the
4923 package <package>foo</package> would normally have the field
4924 <example compact="compact">
4925 Depends: foo-data (>= 1.2-3)
4927 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4928 the files moved into <package>foo-data</package> are not
4929 required for normal operation).
4933 If a package is completely replaced in this way, so that
4934 <prgn>dpkg</prgn> does not know of any files it still
4935 contains, it is considered to have "disappeared". It will
4936 be marked as not wanted on the system (selected for
4937 removal) and not installed. Any <tt>conffile</tt>s
4938 details noted for the package will be ignored, as they
4939 will have been taken over by the overwriting package. The
4940 package's <prgn>postrm</prgn> script will be run with a
4941 special argument to allow the package to do any final
4942 cleanup required. See <ref id="mscriptsinstact">.
4944 Replaces is a one way relationship. You have to install
4945 the replacing package after the replaced package.
4950 For this usage of <tt>Replaces</tt>, virtual packages (see
4951 <ref id="virtual">) are not considered when looking at a
4952 <tt>Replaces</tt> field. The packages declared as being
4953 replaced must be mentioned by their real names.
4957 This usage of <tt>Replaces</tt> only takes effect when both
4958 packages are at least partially on the system at once. It is
4959 not relevant if the packages conflict unless the conflict has
4964 <sect1><heading>Replacing whole packages, forcing their
4968 Second, <tt>Replaces</tt> allows the packaging system to
4969 resolve which package should be removed when there is a
4970 conflict (see <ref id="conflicts">). This usage only takes
4971 effect when the two packages <em>do</em> conflict, so that the
4972 two usages of this field do not interfere with each other.
4976 In this situation, the package declared as being replaced
4977 can be a virtual package, so for example, all mail
4978 transport agents (MTAs) would have the following fields in
4979 their control files:
4980 <example compact="compact">
4981 Provides: mail-transport-agent
4982 Conflicts: mail-transport-agent
4983 Replaces: mail-transport-agent
4985 ensuring that only one MTA can be installed at any one
4986 time. See <ref id="virtual"> for more information about this
4991 <sect id="sourcebinarydeps">
4992 <heading>Relationships between source and binary packages -
4993 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4994 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4998 Source packages that require certain binary packages to be
4999 installed or absent at the time of building the package
5000 can declare relationships to those binary packages.
5004 This is done using the <tt>Build-Depends</tt>,
5005 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5006 <tt>Build-Conflicts-Indep</tt> control file fields.
5010 Build-dependencies on "build-essential" binary packages can be
5011 omitted. Please see <ref id="pkg-relations"> for more information.
5015 The dependencies and conflicts they define must be satisfied
5016 (as defined earlier for binary packages) in order to invoke
5017 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5019 There is no Build-Depends-Arch; this role is essentially
5020 met with Build-Depends. Anyone building the
5021 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5022 assumed to be building the whole package, and therefore
5023 installation of all build dependencies is required.
5026 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5027 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5028 not yet know how to check for its existence, and
5029 <tt>binary-arch</tt>. The purpose of the original split
5030 between <tt>Build-Depends</tt> and
5031 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5032 wouldn't need to install extra packages needed only for the
5033 binary-indep targets. But without a build-arch/build-indep
5034 split, this didn't work, since most of the work is done in
5035 the build target, not in the binary target.
5039 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5040 <tt>binary-arch</tt></tag>
5042 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5043 fields must be satisfied when these targets are invoked.
5045 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5046 and <tt>binary-indep</tt></tag>
5048 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5049 <tt>Build-Depends-Indep</tt>, and
5050 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5051 these targets are invoked.
5059 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5062 Packages containing shared libraries must be constructed with
5063 a little care to make sure that the shared library is always
5064 available. This is especially important for packages whose
5065 shared libraries are vitally important, such as the C library
5066 (currently <tt>libc6</tt>).
5070 Packages involving shared libraries should be split up into
5071 several binary packages. This section mostly deals with how
5072 this separation is to be accomplished; rules for files within
5073 the shared library packages are in <ref id="libraries"> instead.
5076 <sect id="sharedlibs-runtime">
5077 <heading>Run-time shared libraries</heading>
5080 The run-time shared library needs to be placed in a package
5081 whose name changes whenever the shared object version
5084 Since it is common place to install several versions of a
5085 package that just provides shared libraries, it is a
5086 good idea that the library package should not
5087 contain any extraneous non-versioned files, unless they
5088 happen to be in versioned directories.</p>
5090 The most common mechanism is to place it in a package
5092 <package><var>libraryname</var><var>soversion</var></package>,
5093 where <file><var>soversion</var></file> is the version number
5094 in the soname of the shared library<footnote>
5095 The soname is the shared object name: it's the thing
5096 that has to match exactly between building an executable
5097 and running it for the dynamic linker to be able run the
5098 program. For example, if the soname of the library is
5099 <file>libfoo.so.6</file>, the library package would be
5100 called <file>libfoo6</file>.
5102 Alternatively, if it would be confusing to directly append
5103 <var>soversion</var> to <var>libraryname</var> (e.g. because
5104 <var>libraryname</var> itself ends in a number), you may use
5105 <package><var>libraryname</var>-<var>soversion</var></package> and
5106 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5111 If you have several shared libraries built from the same
5112 source tree you may lump them all together into a single
5113 shared library package, provided that you change all of
5114 their sonames at once (so that you don't get filename
5115 clashes if you try to install different versions of the
5116 combined shared libraries package).
5120 The package should install the shared libraries under
5121 their normal names. For example, the <package>libgdbm3</package>
5122 package should install <file>libgdbm.so.3.0.0</file> as
5123 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5124 renamed or re-linked by any <prgn>prerm</prgn> or
5125 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5126 of renaming things safely without affecting running programs,
5127 and attempts to interfere with this are likely to lead to
5132 Shared libraries should not be installed executable, since
5133 the dynamic linker does not require this and trying to
5134 execute a shared library usually results in a core dump.
5138 The run-time library package should include the symbolic link that
5139 <prgn>ldconfig</prgn> would create for the shared libraries.
5140 For example, the <package>libgdbm3</package> package should include
5141 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5142 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5143 linker (for example <prgn>ld.so</prgn> or
5144 <prgn>ld-linux.so.*</prgn>) can find the library between the
5145 time that <prgn>dpkg</prgn> installs it and the time that
5146 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5148 The package management system requires the library to be
5149 placed before the symbolic link pointing to it in the
5150 <file>.deb</file> file. This is so that when
5151 <prgn>dpkg</prgn> comes to install the symlink
5152 (overwriting the previous symlink pointing at an older
5153 version of the library), the new shared library is already
5154 in place. In the past, this was achieved by creating the
5155 library in the temporary packaging directory before
5156 creating the symlink. Unfortunately, this was not always
5157 effective, since the building of the tar file in the
5158 <file>.deb</file> depended on the behavior of the underlying
5159 file system. Some file systems (such as reiserfs) reorder
5160 the files so that the order of creation is forgotten.
5161 Since version 1.7.0, <prgn>dpkg</prgn>
5162 reorders the files itself as necessary when building a
5163 package. Thus it is no longer important to concern
5164 oneself with the order of file creation.
5168 <sect1 id="ldconfig">
5169 <heading><tt>ldconfig</tt></heading>
5172 Any package installing shared libraries in one of the default
5173 library directories of the dynamic linker (which are currently
5174 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5175 listed in <file>/etc/ld.so.conf</file><footnote>
5177 <list compact="compact">
5178 <item>/usr/local/lib</item>
5179 <item>/usr/lib/libc5-compat</item>
5180 <item>/lib/libc5-compat</item>
5183 must use <prgn>ldconfig</prgn> to update the shared library
5188 The package maintainer scripts must only call
5189 <prgn>ldconfig</prgn> under these circumstances:
5190 <list compact="compact">
5191 <item>When the <prgn>postinst</prgn> script is run with a
5192 first argument of <tt>configure</tt>, the script must call
5193 <prgn>ldconfig</prgn>, and may optionally invoke
5194 <prgn>ldconfig</prgn> at other times.
5196 <item>When the <prgn>postrm</prgn> script is run with a
5197 first argument of <tt>remove</tt>, the script should call
5198 <prgn>ldconfig</prgn>.
5203 During install or upgrade, the preinst is called before
5204 the new files are installed, so calling "ldconfig" is
5205 pointless. The preinst of an existing package can also be
5206 called if an upgrade fails. However, this happens during
5207 the critical time when a shared libs may exist on-disk
5208 under a temporary name. Thus, it is dangerous and
5209 forbidden by current policy to call "ldconfig" at this
5214 When a package is installed or upgraded, "postinst
5215 configure" runs after the new files are safely on-disk.
5216 Since it is perfectly safe to invoke ldconfig
5217 unconditionally in a postinst, it is OK for a package to
5218 simply put ldconfig in its postinst without checking the
5219 argument. The postinst can also be called to recover from
5220 a failed upgrade. This happens before any new files are
5221 unpacked, so there is no reason to call "ldconfig" at this
5226 For a package that is being removed, prerm is
5227 called with all the files intact, so calling ldconfig is
5228 useless. The other calls to "prerm" happen in the case of
5229 upgrade at a time when all the files of the old package
5230 are on-disk, so again calling "ldconfig" is pointless.
5234 postrm, on the other hand, is called with the "remove"
5235 argument just after the files are removed, so this is
5236 the proper time to call "ldconfig" to notify the system
5237 of the fact that the shared libraries from the package
5238 are removed. The postrm can be called at several other
5239 times. At the time of "postrm purge", "postrm
5240 abort-install", or "postrm abort-upgrade", calling
5241 "ldconfig" is useless because the shared lib files are
5242 not on-disk. However, when "postrm" is invoked with
5243 arguments "upgrade", "failed-upgrade", or "disappear", a
5244 shared lib may exist on-disk under a temporary filename.
5252 <sect id="sharedlibs-support-files">
5253 <heading>Shared library support files</heading>
5256 If your package contains files whose names do not change with
5257 each change in the library shared object version, you must not
5258 put them in the shared library package. Otherwise, several
5259 versions of the shared library cannot be installed at the same
5260 time without filename clashes, making upgrades and transitions
5261 unnecessarily difficult.
5265 It is recommended that supporting files and run-time support
5266 programs that do not need to be invoked manually by users, but
5267 are nevertheless required for the package to function, be placed
5268 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5269 preferably under <file>/usr/lib/</file><var>package-name</var>.
5270 If the program or file is architecture independent, the
5271 recommendation is for it to be placed in a subdirectory of
5272 <file>/usr/share</file> instead, preferably under
5273 <file>/usr/share/</file><var>package-name</var>. Following the
5274 <var>package-name</var> naming convention ensures that the file
5275 names change when the shared object version changes.
5279 Run-time support programs that use the shared library but are
5280 not required for the library to function or files used by the
5281 shared library that can be used by any version of the shared
5282 library package should instead be put in a separate package.
5283 This package might typically be named
5284 <package><var>libraryname</var>-tools</package>; note the
5285 absence of the <var>soversion</var> in the package name.
5289 Files and support programs only useful when compiling software
5290 against the library should be included in the development
5291 package for the library.<footnote>
5292 For example, a <file><var>package-name</var>-config</file>
5293 script or <package>pkg-config</package> configuration files.
5298 <sect id="sharedlibs-static">
5299 <heading>Static libraries</heading>
5302 The static library (<file><var>libraryname.a</var></file>)
5303 is usually provided in addition to the shared version.
5304 It is placed into the development package (see below).
5308 In some cases, it is acceptable for a library to be
5309 available in static form only; these cases include:
5311 <item>libraries for languages whose shared library support
5312 is immature or unstable</item>
5313 <item>libraries whose interfaces are in flux or under
5314 development (commonly the case when the library's
5315 major version number is zero, or where the ABI breaks
5316 across patchlevels)</item>
5317 <item>libraries which are explicitly intended to be
5318 available only in static form by their upstream
5323 <sect id="sharedlibs-dev">
5324 <heading>Development files</heading>
5327 If there are development files associated with a shared library,
5328 the source package needs to generate a binary development package
5329 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5330 or if you prefer only to support one development version at a
5331 time, <package><var>libraryname</var>-dev</package>. Installing
5332 the development package must result in installation of all the
5333 development files necessary for compiling programs against that
5334 shared library.<footnote>
5335 This wording allows the development files to be split into
5336 several packages, such as a separate architecture-independent
5337 <package><var>libraryname</var>-headers</package>, provided that
5338 the development package depends on all the required additional
5344 In case several development versions of a library exist, you may
5345 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5346 <ref id="conflicts">) to ensure that the user only installs one
5347 development version at a time (as different development versions are
5348 likely to have the same header files in them, which would cause a
5349 filename clash if both were installed).
5353 The development package should contain a symlink for the associated
5354 shared library without a version number. For example, the
5355 <package>libgdbm-dev</package> package should include a symlink
5356 from <file>/usr/lib/libgdbm.so</file> to
5357 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5358 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5359 <file>libgdbm.so</file> when compiling dynamically.
5363 <sect id="sharedlibs-intradeps">
5364 <heading>Dependencies between the packages of the same library</heading>
5367 Typically the development version should have an exact
5368 version dependency on the runtime library, to make sure that
5369 compilation and linking happens correctly. The
5370 <tt>${binary:Version}</tt> substitution variable can be
5371 useful for this purpose.
5373 Previously, <tt>${Source-Version}</tt> was used, but its name
5374 was confusing and it has been deprecated since dpkg 1.13.19.
5379 <sect id="sharedlibs-shlibdeps">
5380 <heading>Dependencies between the library and other packages -
5381 the <tt>shlibs</tt> system</heading>
5384 If a package contains a binary or library which links to a
5385 shared library, we must ensure that when the package is
5386 installed on the system, all of the libraries needed are
5387 also installed. This requirement led to the creation of the
5388 <tt>shlibs</tt> system, which is very simple in its design:
5389 any package which <em>provides</em> a shared library also
5390 provides information on the package dependencies required to
5391 ensure the presence of this library, and any package which
5392 <em>uses</em> a shared library uses this information to
5393 determine the dependencies it requires. The files which
5394 contain the mapping from shared libraries to the necessary
5395 dependency information are called <file>shlibs</file> files.
5399 Thus, when a package is built which contains any shared
5400 libraries, it must provide a <file>shlibs</file> file for other
5401 packages to use, and when a package is built which contains
5402 any shared libraries or compiled binaries, it must run
5403 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5404 on these to determine the libraries used and hence the
5405 dependencies needed by this package.<footnote>
5407 In the past, the shared libraries linked to were
5408 determined by calling <prgn>ldd</prgn>, but now
5409 <prgn>objdump</prgn> is used to do this. The only
5410 change this makes to package building is that
5411 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5412 libraries, whereas in the past this was unnecessary.
5413 The rest of this footnote explains the advantage that
5418 We say that a binary <tt>foo</tt> <em>directly</em> uses
5419 a library <tt>libbar</tt> if it is explicitly linked
5420 with that library (that is, it uses the flag
5421 <tt>-lbar</tt> during the linking stage). Other
5422 libraries that are needed by <tt>libbar</tt> are linked
5423 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5424 linker will load them automatically when it loads
5425 <tt>libbar</tt>. A package should depend on
5426 the libraries it directly uses, and the dependencies for
5427 those libraries should automatically pull in the other
5432 Unfortunately, the <prgn>ldd</prgn> program shows both
5433 the directly and indirectly used libraries, meaning that
5434 the dependencies determined included both direct and
5435 indirect dependencies. The use of <prgn>objdump</prgn>
5436 avoids this problem by determining only the directly
5441 A good example of where this helps is the following. We
5442 could update <tt>libimlib</tt> with a new version that
5443 supports a new graphics format called dgf (but retaining
5444 the same major version number). If we used the old
5445 <prgn>ldd</prgn> method, every package that uses
5446 <tt>libimlib</tt> would need to be recompiled so it
5447 would also depend on <tt>libdgf</tt> or it wouldn't run
5448 due to missing symbols. However with the new system,
5449 packages using <tt>libimlib</tt> can rely on
5450 <tt>libimlib</tt> itself having the dependency on
5451 <tt>libdgf</tt> and so they would not need rebuilding.
5457 In the following sections, we will first describe where the
5458 various <tt>shlibs</tt> files are to be found, then how to
5459 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5460 file format and how to create them if your package contains a
5465 <heading>The <tt>shlibs</tt> files present on the system</heading>
5468 There are several places where <tt>shlibs</tt> files are
5469 found. The following list gives them in the order in which
5471 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5472 (The first one which gives the required information is used.)
5478 <p><file>debian/shlibs.local</file></p>
5481 This lists overrides for this package. Its use is
5482 described below (see <ref id="shlibslocal">).
5487 <p><file>/etc/dpkg/shlibs.override</file></p>
5490 This lists global overrides. This list is normally
5491 empty. It is maintained by the local system
5497 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5500 When packages are being built, any
5501 <file>debian/shlibs</file> files are copied into the
5502 control file area of the temporary build directory and
5503 given the name <file>shlibs</file>. These files give
5504 details of any shared libraries included in the
5506 An example may help here. Let us say that the
5507 source package <tt>foo</tt> generates two binary
5508 packages, <tt>libfoo2</tt> and
5509 <tt>foo-runtime</tt>. When building the binary
5510 packages, the two packages are created in the
5511 directories <file>debian/libfoo2</file> and
5512 <file>debian/foo-runtime</file> respectively.
5513 (<file>debian/tmp</file> could be used instead of one
5514 of these.) Since <tt>libfoo2</tt> provides the
5515 <tt>libfoo</tt> shared library, it will require a
5516 <tt>shlibs</tt> file, which will be installed in
5517 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5519 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5520 when <prgn>dpkg-shlibdeps</prgn> is run on the
5522 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5524 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5525 determine whether <tt>foo-prog</tt>'s library
5526 dependencies are satisfied by any of the libraries
5527 provided by <tt>libfoo2</tt>. For this reason,
5528 <prgn>dpkg-shlibdeps</prgn> must only be run once
5529 all of the individual binary packages'
5530 <tt>shlibs</tt> files have been installed into the
5537 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5540 These are the <file>shlibs</file> files corresponding to
5541 all of the packages installed on the system, and are
5542 maintained by the relevant package maintainers.
5547 <p><file>/etc/dpkg/shlibs.default</file></p>
5550 This file lists any shared libraries whose packages
5551 have failed to provide correct <file>shlibs</file> files.
5552 It was used when the <file>shlibs</file> setup was first
5553 introduced, but it is now normally empty. It is
5554 maintained by the <tt>dpkg</tt> maintainer.
5562 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5563 <file>shlibs</file> files</heading>
5567 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5568 into your <file>debian/rules</file> file. If your package
5569 contains only compiled binaries and libraries (but no scripts),
5570 you can use a command such as:
5571 <example compact="compact">
5572 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5573 debian/tmp/usr/lib/*
5575 Otherwise, you will need to explicitly list the compiled
5576 binaries and libraries.<footnote>
5577 If you are using <tt>debhelper</tt>, the
5578 <prgn>dh_shlibdeps</prgn> program will do this work for
5579 you. It will also correctly handle multi-binary
5585 This command puts the dependency information into the
5586 <file>debian/substvars</file> file, which is then used by
5587 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5588 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5589 field in the control file for this to work.
5593 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5594 done. If it does complain you might need to create your own
5595 <file>debian/shlibs.local</file> file, as explained below (see
5596 <ref id="shlibslocal">).
5600 If you have multiple binary packages, you will need to call
5601 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5602 compiled libraries or binaries. In such a case, you will
5603 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5604 utilities to specify a different <file>substvars</file> file.
5608 If you are creating a udeb for use in the Debian Installer,
5609 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5610 should use the dependency line of type <tt>udeb</tt> by
5611 adding the <tt>-tudeb</tt> option<footnote>
5612 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5613 will automatically add this option if it knows it is
5615 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5616 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5617 fall back to the regular dependency line.
5621 For more details on dpkg-shlibdeps, please see
5622 <ref id="pkg-dpkg-shlibdeps"> and
5623 <manref name="dpkg-shlibdeps" section="1">.
5628 <heading>The <file>shlibs</file> File Format</heading>
5631 Each <file>shlibs</file> file has the same format. Lines
5632 beginning with <tt>#</tt> are considered to be comments and
5633 are ignored. Each line is of the form:
5634 <example compact="compact">
5635 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5640 We will explain this by reference to the example of the
5641 <tt>zlib1g</tt> package, which (at the time of writing)
5642 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5646 <var>type</var> is an optional element that indicates the type
5647 of package for which the line is valid. The only type currently
5648 in use is <tt>udeb</tt>. The colon and space after the type are
5653 <var>library-name</var> is the name of the shared library,
5654 in this case <tt>libz</tt>. (This must match the name part
5655 of the soname, see below.)
5659 <var>soname-version</var> is the version part of the soname of
5660 the library. The soname is the thing that must exactly match
5661 for the library to be recognized by the dynamic linker, and is
5663 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5664 example, <tt>libz.so.1</tt>.<footnote>
5665 This can be determined using the command
5666 <example compact="compact">
5667 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5670 The version part is the part which comes after
5671 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5675 <var>dependencies</var> has the same syntax as a dependency
5676 field in a binary package control file. It should give
5677 details of which packages are required to satisfy a binary
5678 built against the version of the library contained in the
5679 package. See <ref id="depsyntax"> for details.
5683 In our example, if the first version of the <tt>zlib1g</tt>
5684 package which contained a minor number of at least
5685 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5686 <tt>shlibs</tt> entry for this library could say:
5687 <example compact="compact">
5688 libz 1 zlib1g (>= 1:1.1.3)
5690 The version-specific dependency is to avoid warnings from
5691 the dynamic linker about using older shared libraries with
5696 As zlib1g also provides a udeb containing the shared library,
5697 there would also be a second line:
5698 <example compact="compact">
5699 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5705 <heading>Providing a <file>shlibs</file> file</heading>
5708 If your package provides a shared library, you need to create
5709 a <file>shlibs</file> file following the format described above.
5710 It is usual to call this file <file>debian/shlibs</file> (but if
5711 you have multiple binary packages, you might want to call it
5712 <file>debian/shlibs.<var>package</var></file> instead). Then
5713 let <file>debian/rules</file> install it in the control area:
5714 <example compact="compact">
5715 install -m644 debian/shlibs debian/tmp/DEBIAN
5717 or, in the case of a multi-binary package:
5718 <example compact="compact">
5719 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5721 An alternative way of doing this is to create the
5722 <file>shlibs</file> file in the control area directly from
5723 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5724 file at all,<footnote>
5725 This is what <prgn>dh_makeshlibs</prgn> in the
5726 <tt>debhelper</tt> suite does. If your package also has a udeb
5727 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5728 automatically generate the <tt>udeb:</tt> lines if you specify
5729 the name of the udeb with the <tt>--add-udeb</tt> option.
5731 since the <file>debian/shlibs</file> file itself is ignored by
5732 <prgn>dpkg-shlibdeps</prgn>.
5736 As <prgn>dpkg-shlibdeps</prgn> reads the
5737 <file>DEBIAN/shlibs</file> files in all of the binary packages
5738 being built from this source package, all of the
5739 <file>DEBIAN/shlibs</file> files should be installed before
5740 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5745 <sect1 id="shlibslocal">
5746 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5749 This file is intended only as a <em>temporary</em> fix if
5750 your binaries or libraries depend on a library whose package
5751 does not yet provide a correct <file>shlibs</file> file.
5755 We will assume that you are trying to package a binary
5756 <tt>foo</tt>. When you try running
5757 <prgn>dpkg-shlibdeps</prgn> you get the following error
5758 message (<tt>-O</tt> displays the dependency information on
5759 <tt>stdout</tt> instead of writing it to
5760 <tt>debian/substvars</tt>, and the lines have been wrapped
5761 for ease of reading):
5762 <example compact="compact">
5763 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5764 dpkg-shlibdeps: warning: unable to find dependency
5765 information for shared library libbar (soname 1,
5766 path /usr/lib/libbar.so.1, dependency field Depends)
5767 shlibs:Depends=libc6 (>= 2.2.2-2)
5769 You can then run <prgn>ldd</prgn> on the binary to find the
5770 full location of the library concerned:
5771 <example compact="compact">
5773 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5774 libc.so.6 => /lib/libc.so.6 (0x40032000)
5775 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5777 So the <prgn>foo</prgn> binary depends on the
5778 <prgn>libbar</prgn> shared library, but no package seems to
5779 provide a <file>*.shlibs</file> file handling
5780 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5781 determine the package responsible:
5782 <example compact="compact">
5783 $ dpkg -S /usr/lib/libbar.so.1
5784 bar1: /usr/lib/libbar.so.1
5785 $ dpkg -s bar1 | grep Version
5788 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5789 is the one we are using. Now we can file a bug against the
5790 <tt>bar1</tt> package and create our own
5791 <file>debian/shlibs.local</file> to locally fix the problem.
5792 Including the following line into your
5793 <file>debian/shlibs.local</file> file:
5794 <example compact="compact">
5795 libbar 1 bar1 (>= 1.0-1)
5797 should allow the package build to work.
5801 As soon as the maintainer of <tt>bar1</tt> provides a
5802 correct <file>shlibs</file> file, you should remove this line
5803 from your <file>debian/shlibs.local</file> file. (You should
5804 probably also then have a versioned <tt>Build-Depends</tt>
5805 on <tt>bar1</tt> to help ensure that others do not have the
5806 same problem building your package.)
5815 <chapt id="opersys"><heading>The Operating System</heading>
5818 <heading>File system hierarchy</heading>
5822 <heading>File System Structure</heading>
5825 The location of all installed files and directories must
5826 comply with the Filesystem Hierarchy Standard (FHS),
5827 version 2.3, with the exceptions noted below, and except
5828 where doing so would violate other terms of Debian
5829 Policy. The following exceptions to the FHS apply:
5834 The optional rules related to user specific
5835 configuration files for applications are stored in
5836 the user's home directory are relaxed. It is
5837 recommended that such files start with the
5838 '<tt>.</tt>' character (a "dot file"), and if an
5839 application needs to create more than one dot file
5840 then the preferred placement is in a subdirectory
5841 with a name starting with a '.' character, (a "dot
5842 directory"). In this case it is recommended the
5843 configuration files not start with the '.'
5849 The requirement for amd64 to use <file>/lib64</file>
5850 for 64 bit binaries is removed.
5855 The requirement for object files, internal binaries, and
5856 libraries, including <file>libc.so.*</file>, to be located
5857 directly under <file>/lib{,32}</file> and
5858 <file>/usr/lib{,32}</file> is amended, permitting files
5859 to instead be installed to
5860 <file>/lib/<var>triplet</var></file> and
5861 <file>/usr/lib/<var>triplet</var></file>, where
5862 <tt><var>triplet</var></tt> is the value returned by
5863 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5864 architecture of the package. Packages may <em>not</em>
5865 install files to any <var>triplet</var> path other
5866 than the one matching the architecture of that package;
5867 for instance, an <tt>Architecture: amd64</tt> package
5868 containing 32-bit x86 libraries may not install these
5869 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5871 This is necessary in order to reserve the directories for
5872 use in cross-installation of library packages from other
5873 architectures, as part of the planned deployment of
5878 Applications may also use a single subdirectory under
5879 <file>/usr/lib/<var>triplet</var></file>.
5882 The execution time linker/loader, ld*, must still be made
5883 available in the existing location under /lib or /lib64
5884 since this is part of the ELF ABI for the architecture.
5889 The requirement that
5890 <file>/usr/local/share/man</file> be "synonymous"
5891 with <file>/usr/local/man</file> is relaxed to a
5896 The requirement that windowmanagers with a single
5897 configuration file call it <file>system.*wmrc</file>
5898 is removed, as is the restriction that the window
5899 manager subdirectory be named identically to the
5900 window manager name itself.
5905 The requirement that boot manager configuration
5906 files live in <file>/etc</file>, or at least are
5907 symlinked there, is relaxed to a recommendation.
5912 The following directories in the root filesystem are
5913 additionally allowed: <file>/sys</file> and
5914 <file>/selinux</file>. <footnote>These directories
5915 are used as mount points to mount virtual filesystems
5916 to get access to kernel information.</footnote>
5923 The version of this document referred here can be
5924 found in the <tt>debian-policy</tt> package or on <url
5925 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5926 name="FHS (Debian copy)"> alongside this manual (or, if
5927 you have the <package>debian-policy</package> installed,
5929 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5930 (local copy)">). The
5931 latest version, which may be a more recent version, may
5933 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5934 Specific questions about following the standard may be
5935 asked on the <tt>debian-devel</tt> mailing list, or
5936 referred to the FHS mailing list (see the
5937 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5943 <heading>Site-specific programs</heading>
5946 As mandated by the FHS, packages must not place any
5947 files in <file>/usr/local</file>, either by putting them in
5948 the file system archive to be unpacked by <prgn>dpkg</prgn>
5949 or by manipulating them in their maintainer scripts.
5953 However, the package may create empty directories below
5954 <file>/usr/local</file> so that the system administrator knows
5955 where to place site-specific files. These are not
5956 directories <em>in</em> <file>/usr/local</file>, but are
5957 children of directories in <file>/usr/local</file>. These
5958 directories (<file>/usr/local/*/dir/</file>)
5959 should be removed on package removal if they are
5964 Note that this applies only to
5965 directories <em>below</em> <file>/usr/local</file>,
5966 not <em>in</em> <file>/usr/local</file>. Packages must
5967 not create sub-directories in the
5968 directory <file>/usr/local</file> itself, except those
5969 listed in FHS, section 4.5. However, you may create
5970 directories below them as you wish. You must not remove
5971 any of the directories listed in 4.5, even if you created
5976 Since <file>/usr/local</file> can be mounted read-only from a
5977 remote server, these directories must be created and
5978 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5979 maintainer scripts and not be included in the
5980 <file>.deb</file> archive. These scripts must not fail if
5981 either of these operations fail.
5985 For example, the <tt>emacsen-common</tt> package could
5986 contain something like
5987 <example compact="compact">
5988 if [ ! -e /usr/local/share/emacs ]
5990 if mkdir /usr/local/share/emacs 2>/dev/null
5992 chown root:staff /usr/local/share/emacs
5993 chmod 2775 /usr/local/share/emacs
5997 in its <prgn>postinst</prgn> script, and
5998 <example compact="compact">
5999 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6000 rmdir /usr/local/share/emacs 2>/dev/null || true
6002 in the <prgn>prerm</prgn> script. (Note that this form is
6003 used to ensure that if the script is interrupted, the
6004 directory <file>/usr/local/share/emacs</file> will still be
6009 If you do create a directory in <file>/usr/local</file> for
6010 local additions to a package, you should ensure that
6011 settings in <file>/usr/local</file> take precedence over the
6012 equivalents in <file>/usr</file>.
6016 However, because <file>/usr/local</file> and its contents are
6017 for exclusive use of the local administrator, a package
6018 must not rely on the presence or absence of files or
6019 directories in <file>/usr/local</file> for normal operation.
6023 The <file>/usr/local</file> directory itself and all the
6024 subdirectories created by the package should (by default) have
6025 permissions 2775 (group-writable and set-group-id) and be
6026 owned by <tt>root:staff</tt>.
6031 <heading>The system-wide mail directory</heading>
6033 The system-wide mail directory
6034 is <file>/var/mail</file>. This directory is part of the
6035 base system and should not be owned by any particular mail
6036 agents. The use of the old
6037 location <file>/var/spool/mail</file> is deprecated, even
6038 though the spool may still be physically located there.
6044 <heading>Users and groups</heading>
6047 <heading>Introduction</heading>
6049 The Debian system can be configured to use either plain or
6054 Some user ids (UIDs) and group ids (GIDs) are reserved
6055 globally for use by certain packages. Because some
6056 packages need to include files which are owned by these
6057 users or groups, or need the ids compiled into binaries,
6058 these ids must be used on any Debian system only for the
6059 purpose for which they are allocated. This is a serious
6060 restriction, and we should avoid getting in the way of
6061 local administration policies. In particular, many sites
6062 allocate users and/or local system groups starting at 100.
6066 Apart from this we should have dynamically allocated ids,
6067 which should by default be arranged in some sensible
6068 order, but the behavior should be configurable.
6072 Packages other than <tt>base-passwd</tt> must not modify
6073 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6074 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6079 <heading>UID and GID classes</heading>
6081 The UID and GID numbers are divided into classes as
6087 Globally allocated by the Debian project, the same
6088 on every Debian system. These ids will appear in
6089 the <file>passwd</file> and <file>group</file> files of all
6090 Debian systems, new ids in this range being added
6091 automatically as the <tt>base-passwd</tt> package is
6096 Packages which need a single statically allocated
6097 uid or gid should use one of these; their
6098 maintainers should ask the <tt>base-passwd</tt>
6106 Dynamically allocated system users and groups.
6107 Packages which need a user or group, but can have
6108 this user or group allocated dynamically and
6109 differently on each system, should use <tt>adduser
6110 --system</tt> to create the group and/or user.
6111 <prgn>adduser</prgn> will check for the existence of
6112 the user or group, and if necessary choose an unused
6113 id based on the ranges specified in
6114 <file>adduser.conf</file>.
6118 <tag>1000-59999:</tag>
6121 Dynamically allocated user accounts. By default
6122 <prgn>adduser</prgn> will choose UIDs and GIDs for
6123 user accounts in this range, though
6124 <file>adduser.conf</file> may be used to modify this
6129 <tag>60000-64999:</tag>
6132 Globally allocated by the Debian project, but only
6133 created on demand. The ids are allocated centrally
6134 and statically, but the actual accounts are only
6135 created on users' systems on demand.
6139 These ids are for packages which are obscure or
6140 which require many statically-allocated ids. These
6141 packages should check for and create the accounts in
6142 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6143 <prgn>adduser</prgn> if it has this facility) if
6144 necessary. Packages which are likely to require
6145 further allocations should have a "hole" left after
6146 them in the allocation, to give them room to
6151 <tag>65000-65533:</tag>
6159 User <tt>nobody</tt>. The corresponding gid refers
6160 to the group <tt>nogroup</tt>.
6167 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6168 not</em> be used, because it is the error return
6177 <sect id="sysvinit">
6178 <heading>System run levels and <file>init.d</file> scripts</heading>
6180 <sect1 id="/etc/init.d">
6181 <heading>Introduction</heading>
6184 The <file>/etc/init.d</file> directory contains the scripts
6185 executed by <prgn>init</prgn> at boot time and when the
6186 init state (or "runlevel") is changed (see <manref
6187 name="init" section="8">).
6191 There are at least two different, yet functionally
6192 equivalent, ways of handling these scripts. For the sake
6193 of simplicity, this document describes only the symbolic
6194 link method. However, it must not be assumed by maintainer
6195 scripts that this method is being used, and any automated
6196 manipulation of the various runlevel behaviors by
6197 maintainer scripts must be performed using
6198 <prgn>update-rc.d</prgn> as described below and not by
6199 manually installing or removing symlinks. For information
6200 on the implementation details of the other method,
6201 implemented in the <tt>file-rc</tt> package, please refer
6202 to the documentation of that package.
6206 These scripts are referenced by symbolic links in the
6207 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6208 runlevels, <prgn>init</prgn> looks in the directory
6209 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6210 execute, where <tt><var>n</var></tt> is the runlevel that
6211 is being changed to, or <tt>S</tt> for the boot-up
6216 The names of the links all have the form
6217 <file>S<var>mm</var><var>script</var></file> or
6218 <file>K<var>mm</var><var>script</var></file> where
6219 <var>mm</var> is a two-digit number and <var>script</var>
6220 is the name of the script (this should be the same as the
6221 name of the actual script in <file>/etc/init.d</file>).
6225 When <prgn>init</prgn> changes runlevel first the targets
6226 of the links whose names start with a <tt>K</tt> are
6227 executed, each with the single argument <tt>stop</tt>,
6228 followed by the scripts prefixed with an <tt>S</tt>, each
6229 with the single argument <tt>start</tt>. (The links are
6230 those in the <file>/etc/rc<var>n</var>.d</file> directory
6231 corresponding to the new runlevel.) The <tt>K</tt> links
6232 are responsible for killing services and the <tt>S</tt>
6233 link for starting services upon entering the runlevel.
6237 For example, if we are changing from runlevel 2 to
6238 runlevel 3, init will first execute all of the <tt>K</tt>
6239 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6240 all of the <tt>S</tt> prefixed scripts in that directory.
6241 The links starting with <tt>K</tt> will cause the
6242 referred-to file to be executed with an argument of
6243 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6248 The two-digit number <var>mm</var> is used to determine
6249 the order in which to run the scripts: low-numbered links
6250 have their scripts run first. For example, the
6251 <tt>K20</tt> scripts will be executed before the
6252 <tt>K30</tt> scripts. This is used when a certain service
6253 must be started before another. For example, the name
6254 server <prgn>bind</prgn> might need to be started before
6255 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6256 can set up its access lists. In this case, the script
6257 that starts <prgn>bind</prgn> would have a lower number
6258 than the script that starts <prgn>inn</prgn> so that it
6260 <example compact="compact">
6267 The two runlevels 0 (halt) and 6 (reboot) are slightly
6268 different. In these runlevels, the links with an
6269 <tt>S</tt> prefix are still called after those with a
6270 <tt>K</tt> prefix, but they too are called with the single
6271 argument <tt>stop</tt>.
6275 <sect1 id="writing-init">
6276 <heading>Writing the scripts</heading>
6279 Packages that include daemons for system services should
6280 place scripts in <file>/etc/init.d</file> to start or stop
6281 services at boot time or during a change of runlevel.
6282 These scripts should be named
6283 <file>/etc/init.d/<var>package</var></file>, and they should
6284 accept one argument, saying what to do:
6287 <tag><tt>start</tt></tag>
6288 <item>start the service,</item>
6290 <tag><tt>stop</tt></tag>
6291 <item>stop the service,</item>
6293 <tag><tt>restart</tt></tag>
6294 <item>stop and restart the service if it's already running,
6295 otherwise start the service</item>
6297 <tag><tt>reload</tt></tag>
6298 <item><p>cause the configuration of the service to be
6299 reloaded without actually stopping and restarting
6302 <tag><tt>force-reload</tt></tag>
6303 <item>cause the configuration to be reloaded if the
6304 service supports this, otherwise restart the
6308 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6309 <tt>force-reload</tt> options should be supported by all
6310 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6315 The <file>init.d</file> scripts must ensure that they will
6316 behave sensibly (i.e., returning success and not starting
6317 multiple copies of a service) if invoked with <tt>start</tt>
6318 when the service is already running, or with <tt>stop</tt>
6319 when it isn't, and that they don't kill unfortunately-named
6320 user processes. The best way to achieve this is usually to
6321 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6326 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6327 scripts. Writing correct <file>init.d</file> scripts requires
6328 accepting various error exit statuses when daemons are already
6329 running or already stopped without aborting
6330 the <file>init.d</file> script, and common <file>init.d</file>
6331 function libraries are not safe to call with <tt>set -e</tt>
6333 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6334 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6335 in effect and echoing status messages to the console fails,
6337 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6338 to not use <tt>set -e</tt> and instead check the result of
6339 each command separately.
6343 If a service reloads its configuration automatically (as
6344 in the case of <prgn>cron</prgn>, for example), the
6345 <tt>reload</tt> option of the <file>init.d</file> script
6346 should behave as if the configuration has been reloaded
6351 The <file>/etc/init.d</file> scripts must be treated as
6352 configuration files, either (if they are present in the
6353 package, that is, in the .deb file) by marking them as
6354 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6355 by managing them correctly in the maintainer scripts (see
6356 <ref id="config-files">). This is important since we want
6357 to give the local system administrator the chance to adapt
6358 the scripts to the local system, e.g., to disable a
6359 service without de-installing the package, or to specify
6360 some special command line options when starting a service,
6361 while making sure their changes aren't lost during the next
6366 These scripts should not fail obscurely when the
6367 configuration files remain but the package has been
6368 removed, as configuration files remain on the system after
6369 the package has been removed. Only when <prgn>dpkg</prgn>
6370 is executed with the <tt>--purge</tt> option will
6371 configuration files be removed. In particular, as the
6372 <file>/etc/init.d/<var>package</var></file> script itself is
6373 usually a <tt>conffile</tt>, it will remain on the system
6374 if the package is removed but not purged. Therefore, you
6375 should include a <tt>test</tt> statement at the top of the
6377 <example compact="compact">
6378 test -f <var>program-executed-later-in-script</var> || exit 0
6383 Often there are some variables in the <file>init.d</file>
6384 scripts whose values control the behavior of the scripts,
6385 and which a system administrator is likely to want to
6386 change. As the scripts themselves are frequently
6387 <tt>conffile</tt>s, modifying them requires that the
6388 administrator merge in their changes each time the package
6389 is upgraded and the <tt>conffile</tt> changes. To ease
6390 the burden on the system administrator, such configurable
6391 values should not be placed directly in the script.
6392 Instead, they should be placed in a file in
6393 <file>/etc/default</file>, which typically will have the same
6394 base name as the <file>init.d</file> script. This extra file
6395 should be sourced by the script when the script runs. It
6396 must contain only variable settings and comments in SUSv3
6397 <prgn>sh</prgn> format. It may either be a
6398 <tt>conffile</tt> or a configuration file maintained by
6399 the package maintainer scripts. See <ref id="config-files">
6404 To ensure that vital configurable values are always
6405 available, the <file>init.d</file> script should set default
6406 values for each of the shell variables it uses, either
6407 before sourcing the <file>/etc/default/</file> file or
6408 afterwards using something like the <tt>:
6409 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6410 script must behave sensibly and not fail if the
6411 <file>/etc/default</file> file is deleted.
6415 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6416 as temporary filesystems<footnote>
6417 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6418 options in <file>/etc/default/rcS</file>.
6419 </footnote>, so the <file>init.d</file> scripts must handle this
6420 correctly. This will typically amount to creating any required
6421 subdirectories dynamically when the <file>init.d</file> script
6422 is run, rather than including them in the package and relying on
6423 <prgn>dpkg</prgn> to create them.
6428 <heading>Interfacing with the initscript system</heading>
6431 Maintainers should use the abstraction layer provided by
6432 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6433 programs to deal with initscripts in their packages'
6434 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6435 and <prgn>postrm</prgn>.
6439 Directly managing the /etc/rc?.d links and directly
6440 invoking the <file>/etc/init.d/</file> initscripts should
6441 be done only by packages providing the initscript
6442 subsystem (such as <prgn>sysv-rc</prgn> and
6443 <prgn>file-rc</prgn>).
6447 <heading>Managing the links</heading>
6450 The program <prgn>update-rc.d</prgn> is provided for
6451 package maintainers to arrange for the proper creation and
6452 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6453 or their functional equivalent if another method is being
6454 used. This may be used by maintainers in their packages'
6455 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6459 You must not include any <file>/etc/rc<var>n</var>.d</file>
6460 symbolic links in the actual archive or manually create or
6461 remove the symbolic links in maintainer scripts; you must
6462 use the <prgn>update-rc.d</prgn> program instead. (The
6463 former will fail if an alternative method of maintaining
6464 runlevel information is being used.) You must not include
6465 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6466 in the archive either. (Only the <tt>sysvinit</tt>
6471 By default <prgn>update-rc.d</prgn> will start services in
6472 each of the multi-user state runlevels (2, 3, 4, and 5)
6473 and stop them in the halt runlevel (0), the single-user
6474 runlevel (1) and the reboot runlevel (6). The system
6475 administrator will have the opportunity to customize
6476 runlevels by simply adding, moving, or removing the
6477 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6478 symbolic links are being used, or by modifying
6479 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6484 To get the default behavior for your package, put in your
6485 <prgn>postinst</prgn> script
6486 <example compact="compact">
6487 update-rc.d <var>package</var> defaults
6489 and in your <prgn>postrm</prgn>
6490 <example compact="compact">
6491 if [ "$1" = purge ]; then
6492 update-rc.d <var>package</var> remove
6494 </example>. Note that if your package changes runlevels
6495 or priority, you may have to remove and recreate the links,
6496 since otherwise the old links may persist. Refer to the
6497 documentation of <prgn>update-rc.d</prgn>.
6501 This will use a default sequence number of 20. If it does
6502 not matter when or in which order the <file>init.d</file>
6503 script is run, use this default. If it does, then you
6504 should talk to the maintainer of the <prgn>sysvinit</prgn>
6505 package or post to <tt>debian-devel</tt>, and they will
6506 help you choose a number.
6510 For more information about using <tt>update-rc.d</tt>,
6511 please consult its man page <manref name="update-rc.d"
6517 <heading>Running initscripts</heading>
6519 The program <prgn>invoke-rc.d</prgn> is provided to make
6520 it easier for package maintainers to properly invoke an
6521 initscript, obeying runlevel and other locally-defined
6522 constraints that might limit a package's right to start,
6523 stop and otherwise manage services. This program may be
6524 used by maintainers in their packages' scripts.
6528 The package maintainer scripts must use
6529 <prgn>invoke-rc.d</prgn> to invoke the
6530 <file>/etc/init.d/*</file> initscripts, instead of
6531 calling them directly.
6535 By default, <prgn>invoke-rc.d</prgn> will pass any
6536 action requests (start, stop, reload, restart...) to the
6537 <file>/etc/init.d</file> script, filtering out requests
6538 to start or restart a service out of its intended
6543 Most packages will simply need to change:
6544 <example compact="compact">/etc/init.d/<package>
6545 <action></example> in their <prgn>postinst</prgn>
6546 and <prgn>prerm</prgn> scripts to:
6547 <example compact="compact">
6548 if which invoke-rc.d >/dev/null 2>&1; then
6549 invoke-rc.d <var>package</var> <action>
6551 /etc/init.d/<var>package</var> <action>
6557 A package should register its initscript services using
6558 <prgn>update-rc.d</prgn> before it tries to invoke them
6559 using <prgn>invoke-rc.d</prgn>. Invocation of
6560 unregistered services may fail.
6564 For more information about using
6565 <prgn>invoke-rc.d</prgn>, please consult its man page
6566 <manref name="invoke-rc.d" section="8">.
6572 <heading>Boot-time initialization</heading>
6575 There used to be another directory, <file>/etc/rc.boot</file>,
6576 which contained scripts which were run once per machine
6577 boot. This has been deprecated in favour of links from
6578 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6579 described in <ref id="/etc/init.d">. Packages must not
6580 place files in <file>/etc/rc.boot</file>.
6585 <heading>Example</heading>
6588 An example on which you can base your
6589 <file>/etc/init.d</file> scripts is found in
6590 <file>/etc/init.d/skeleton</file>.
6597 <heading>Console messages from <file>init.d</file> scripts</heading>
6600 This section describes the formats to be used for messages
6601 written to standard output by the <file>/etc/init.d</file>
6602 scripts. The intent is to improve the consistency of
6603 Debian's startup and shutdown look and feel. For this
6604 reason, please look very carefully at the details. We want
6605 the messages to have the same format in terms of wording,
6606 spaces, punctuation and case of letters.
6610 Here is a list of overall rules that should be used for
6611 messages generated by <file>/etc/init.d</file> scripts.
6617 The message should fit in one line (fewer than 80
6618 characters), start with a capital letter and end with
6619 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6623 If the script is performing some time consuming task in
6624 the background (not merely starting or stopping a
6625 program, for instance), an ellipsis (three dots:
6626 <tt>...</tt>) should be output to the screen, with no
6627 leading or tailing whitespace or line feeds.
6631 The messages should appear as if the computer is telling
6632 the user what it is doing (politely :-), but should not
6633 mention "it" directly. For example, instead of:
6634 <example compact="compact">
6635 I'm starting network daemons: nfsd mountd.
6637 the message should say
6638 <example compact="compact">
6639 Starting network daemons: nfsd mountd.
6646 <tt>init.d</tt> script should use the following standard
6647 message formats for the situations enumerated below.
6653 <p>When daemons are started</p>
6656 If the script starts one or more daemons, the output
6657 should look like this (a single line, no leading
6659 <example compact="compact">
6660 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6662 The <var>description</var> should describe the
6663 subsystem the daemon or set of daemons are part of,
6664 while <var>daemon-1</var> up to <var>daemon-n</var>
6665 denote each daemon's name (typically the file name of
6670 For example, the output of <file>/etc/init.d/lpd</file>
6672 <example compact="compact">
6673 Starting printer spooler: lpd.
6678 This can be achieved by saying
6679 <example compact="compact">
6680 echo -n "Starting printer spooler: lpd"
6681 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6684 in the script. If there are more than one daemon to
6685 start, the output should look like this:
6686 <example compact="compact">
6687 echo -n "Starting remote file system services:"
6688 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6689 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6690 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6693 This makes it possible for the user to see what is
6694 happening and when the final daemon has been started.
6695 Care should be taken in the placement of white spaces:
6696 in the example above the system administrators can
6697 easily comment out a line if they don't want to start
6698 a specific daemon, while the displayed message still
6704 <p>When a system parameter is being set</p>
6707 If you have to set up different system parameters
6708 during the system boot, you should use this format:
6709 <example compact="compact">
6710 Setting <var>parameter</var> to "<var>value</var>".
6715 You can use a statement such as the following to get
6717 <example compact="compact">
6718 echo "Setting DNS domainname to \"$domainname\"."
6723 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6724 for the left and right quotation marks. A grave accent
6725 (<tt>`</tt>) is not a quote character; neither is an
6726 apostrophe (<tt>'</tt>).
6731 <p>When a daemon is stopped or restarted</p>
6734 When you stop or restart a daemon, you should issue a
6735 message identical to the startup message, except that
6736 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6737 or <tt>Restarting</tt> respectively.
6741 For example, stopping the printer daemon will look like
6743 <example compact="compact">
6744 Stopping printer spooler: lpd.
6750 <p>When something is executed</p>
6753 There are several examples where you have to run a
6754 program at system startup or shutdown to perform a
6755 specific task, for example, setting the system's clock
6756 using <prgn>netdate</prgn> or killing all processes
6757 when the system shuts down. Your message should look
6759 <example compact="compact">
6760 Doing something very useful...done.
6762 You should print the <tt>done.</tt> immediately after
6763 the job has been completed, so that the user is
6764 informed why they have to wait. You can get this
6766 <example compact="compact">
6767 echo -n "Doing something very useful..."
6776 <p>When the configuration is reloaded</p>
6779 When a daemon is forced to reload its configuration
6780 files you should use the following format:
6781 <example compact="compact">
6782 Reloading <var>description</var> configuration...done.
6784 where <var>description</var> is the same as in the
6785 daemon starting message.
6793 <heading>Cron jobs</heading>
6796 Packages must not modify the configuration file
6797 <file>/etc/crontab</file>, and they must not modify the files in
6798 <file>/var/spool/cron/crontabs</file>.</p>
6801 If a package wants to install a job that has to be executed
6802 via cron, it should place a file with the name of the
6803 package in one or more of the following directories:
6804 <example compact="compact">
6810 As these directory names imply, the files within them are
6811 executed on an hourly, daily, weekly, or monthly basis,
6812 respectively. The exact times are listed in
6813 <file>/etc/crontab</file>.</p>
6816 All files installed in any of these directories must be
6817 scripts (e.g., shell scripts or Perl scripts) so that they
6818 can easily be modified by the local system administrator.
6819 In addition, they must be treated as configuration files.
6823 If a certain job has to be executed at some other frequency or
6824 at a specific time, the package should install a file
6825 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6826 same syntax as <file>/etc/crontab</file> and is processed by
6827 <prgn>cron</prgn> automatically. The file must also be
6828 treated as a configuration file. (Note that entries in the
6829 <file>/etc/cron.d</file> directory are not handled by
6830 <prgn>anacron</prgn>. Thus, you should only use this
6831 directory for jobs which may be skipped if the system is not
6834 Unlike <file>crontab</file> files described in the IEEE Std
6835 1003.1-2008 (POSIX.1) available from
6836 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6837 name="The Open Group">, the files in
6838 <file>/etc/cron.d</file> and the file
6839 <file>/etc/crontab</file> have seven fields; namely:
6841 <item>Minute [0,59]</item>
6842 <item>Hour [0,23]</item>
6843 <item>Day of the month [1,31]</item>
6844 <item>Month of the year [1,12]</item>
6845 <item>Day of the week ([0,6] with 0=Sunday)</item>
6846 <item>Username</item>
6847 <item>Command to be run</item>
6849 Ranges of numbers are allowed. Ranges are two numbers
6850 separated with a hyphen. The specified range is inclusive.
6851 Lists are allowed. A list is a set of numbers (or ranges)
6852 separated by commas. Step values can be used in conjunction
6857 The scripts or <tt>crontab</tt> entries in these directories should
6858 check if all necessary programs are installed before they
6859 try to execute them. Otherwise, problems will arise when a
6860 package was removed but not purged since configuration files
6861 are kept on the system in this situation.
6865 Any <tt>cron</tt> daemon must provide
6866 <file>/usr/bin/crontab</file> and support normal
6867 <tt>crontab</tt> entries as specified in POSIX. The daemon
6868 must also support names for days and months, ranges, and
6869 step values. It has to support <file>/etc/crontab</file>,
6870 and correctly execute the scripts in
6871 <file>/etc/cron.d</file>. The daemon must also correctly
6873 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6878 <heading>Menus</heading>
6881 The Debian <tt>menu</tt> package provides a standard
6882 interface between packages providing applications and
6883 <em>menu programs</em> (either X window managers or
6884 text-based menu programs such as <prgn>pdmenu</prgn>).
6888 All packages that provide applications that need not be
6889 passed any special command line arguments for normal
6890 operation should register a menu entry for those
6891 applications, so that users of the <tt>menu</tt> package
6892 will automatically get menu entries in their window
6893 managers, as well in shells like <tt>pdmenu</tt>.
6897 Menu entries should follow the current menu policy.
6901 The menu policy can be found in the <tt>menu-policy</tt>
6902 files in the <tt>debian-policy</tt> package.
6903 It is also available from the Debian web mirrors at
6904 <tt><url name="/doc/packaging-manuals/menu-policy/"
6905 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6909 Please also refer to the <em>Debian Menu System</em>
6910 documentation that comes with the <package>menu</package>
6911 package for information about how to register your
6917 <heading>Multimedia handlers</heading>
6920 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6921 is a mechanism for encoding files and data streams and
6922 providing meta-information about them, in particular their
6923 type (e.g. audio or video) and format (e.g. PNG, HTML,
6928 Registration of MIME type handlers allows programs like mail
6929 user agents and web browsers to invoke these handlers to
6930 view, edit or display MIME types they don't support directly.
6934 Packages which provide the ability to view/show/play,
6935 compose, edit or print MIME types should register themselves
6936 as such following the current MIME support policy.
6940 The MIME support policy can be found in the <tt>mime-policy</tt>
6941 files in the <tt>debian-policy</tt> package.
6942 It is also available from the Debian web mirrors at
6943 <tt><url name="/doc/packaging-manuals/mime-policy/"
6944 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6950 <heading>Keyboard configuration</heading>
6953 To achieve a consistent keyboard configuration so that all
6954 applications interpret a keyboard event the same way, all
6955 programs in the Debian distribution must be configured to
6956 comply with the following guidelines.
6960 The following keys must have the specified interpretations:
6963 <tag><tt><--</tt></tag>
6964 <item>delete the character to the left of the cursor</item>
6966 <tag><tt>Delete</tt></tag>
6967 <item>delete the character to the right of the cursor</item>
6969 <tag><tt>Control+H</tt></tag>
6970 <item>emacs: the help prefix</item>
6973 The interpretation of any keyboard events should be
6974 independent of the terminal that is used, be it a virtual
6975 console, an X terminal emulator, an rlogin/telnet session,
6980 The following list explains how the different programs
6981 should be set up to achieve this:
6987 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6991 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6995 X translations are set up to make
6996 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6997 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6998 is the vt220 escape code for the "delete character"
6999 key). This must be done by loading the X resources
7000 using <prgn>xrdb</prgn> on all local X displays, not
7001 using the application defaults, so that the
7002 translation resources used correspond to the
7003 <prgn>xmodmap</prgn> settings.
7007 The Linux console is configured to make
7008 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7009 generate <tt>ESC [ 3 ~</tt>.
7013 X applications are configured so that <tt><</tt>
7014 deletes left, and <tt>Delete</tt> deletes right. Motif
7015 applications already work like this.
7019 Terminals should have <tt>stty erase ^?</tt> .
7023 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7024 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7025 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7029 Emacs is programmed to map <tt>KB_Backspace</tt> or
7030 the <tt>stty erase</tt> character to
7031 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7032 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7033 <tt>^H</tt> to <tt>help</tt> as always.
7037 Other applications use the <tt>stty erase</tt>
7038 character and <tt>kdch1</tt> for the two delete keys,
7039 with ASCII DEL being "delete previous character" and
7040 <tt>kdch1</tt> being "delete character under
7048 This will solve the problem except for the following
7055 Some terminals have a <tt><--</tt> key that cannot
7056 be made to produce anything except <tt>^H</tt>. On
7057 these terminals Emacs help will be unavailable on
7058 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7059 character takes precedence in Emacs, and has been set
7060 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7061 available) can be used instead.
7065 Some operating systems use <tt>^H</tt> for <tt>stty
7066 erase</tt>. However, modern telnet versions and all
7067 rlogin versions propagate <tt>stty</tt> settings, and
7068 almost all UNIX versions honour <tt>stty erase</tt>.
7069 Where the <tt>stty</tt> settings are not propagated
7070 correctly, things can be made to work by using
7071 <tt>stty</tt> manually.
7075 Some systems (including previous Debian versions) use
7076 <prgn>xmodmap</prgn> to arrange for both
7077 <tt><--</tt> and <tt>Delete</tt> to generate
7078 <tt>KB_Delete</tt>. We can change the behavior of
7079 their X clients using the same X resources that we use
7080 to do it for our own clients, or configure our clients
7081 using their resources when things are the other way
7082 around. On displays configured like this
7083 <tt>Delete</tt> will not work, but <tt><--</tt>
7088 Some operating systems have different <tt>kdch1</tt>
7089 settings in their <tt>terminfo</tt> database for
7090 <tt>xterm</tt> and others. On these systems the
7091 <tt>Delete</tt> key will not work correctly when you
7092 log in from a system conforming to our policy, but
7093 <tt><--</tt> will.
7100 <heading>Environment variables</heading>
7103 A program must not depend on environment variables to get
7104 reasonable defaults. (That's because these environment
7105 variables would have to be set in a system-wide
7106 configuration file like <file>/etc/profile</file>, which is not
7107 supported by all shells.)
7111 If a program usually depends on environment variables for its
7112 configuration, the program should be changed to fall back to
7113 a reasonable default configuration if these environment
7114 variables are not present. If this cannot be done easily
7115 (e.g., if the source code of a non-free program is not
7116 available), the program must be replaced by a small
7117 "wrapper" shell script which sets the environment variables
7118 if they are not already defined, and calls the original program.
7122 Here is an example of a wrapper script for this purpose:
7124 <example compact="compact">
7126 BAR=${BAR:-/var/lib/fubar}
7128 exec /usr/lib/foo/foo "$@"
7133 Furthermore, as <file>/etc/profile</file> is a configuration
7134 file of the <prgn>base-files</prgn> package, other packages must
7135 not put any environment variables or other commands into that
7140 <sect id="doc-base">
7141 <heading>Registering Documents using doc-base</heading>
7144 The <package>doc-base</package> package implements a
7145 flexible mechanism for handling and presenting
7146 documentation. The recommended practice is for every Debian
7147 package that provides online documentation (other than just
7148 manual pages) to register these documents with
7149 <package>doc-base</package> by installing a
7150 <package>doc-base</package> control file via the
7151 <prgn/install-docs/ script at installation time and
7152 de-register the manuals again when the package is removed.
7155 Please refer to the documentation that comes with the
7156 <package>doc-base</package> package for information and
7165 <heading>Files</heading>
7167 <sect id="binaries">
7168 <heading>Binaries</heading>
7171 Two different packages must not install programs with
7172 different functionality but with the same filenames. (The
7173 case of two programs having the same functionality but
7174 different implementations is handled via "alternatives" or
7175 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7176 <ref id="conflicts"> respectively.) If this case happens,
7177 one of the programs must be renamed. The maintainers should
7178 report this to the <tt>debian-devel</tt> mailing list and
7179 try to find a consensus about which program will have to be
7180 renamed. If a consensus cannot be reached, <em>both</em>
7181 programs must be renamed.
7185 By default, when a package is being built, any binaries
7186 created should include debugging information, as well as
7187 being compiled with optimization. You should also turn on
7188 as many reasonable compilation warnings as possible; this
7189 makes life easier for porters, who can then look at build
7190 logs for possible problems. For the C programming language,
7191 this means the following compilation parameters should be
7193 <example compact="compact">
7195 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7197 INSTALL = install -s # (or use strip on the files in debian/tmp)
7202 Note that by default all installed binaries should be stripped,
7203 either by using the <tt>-s</tt> flag to
7204 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7205 the binaries after they have been copied into
7206 <file>debian/tmp</file> but before the tree is made into a
7211 Although binaries in the build tree should be compiled with
7212 debugging information by default, it can often be difficult to
7213 debug programs if they are also subjected to compiler
7214 optimization. For this reason, it is recommended to support the
7215 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7216 (see <ref id="debianrules-options">). This variable can contain
7217 several flags to change how a package is compiled and built.
7221 It is up to the package maintainer to decide what
7222 compilation options are best for the package. Certain
7223 binaries (such as computationally-intensive programs) will
7224 function better with certain flags (<tt>-O3</tt>, for
7225 example); feel free to use them. Please use good judgment
7226 here. Don't use flags for the sake of it; only use them
7227 if there is good reason to do so. Feel free to override
7228 the upstream author's ideas about which compilation
7229 options are best: they are often inappropriate for our
7235 <sect id="libraries">
7236 <heading>Libraries</heading>
7239 If the package is <strong>architecture: any</strong>, then
7240 the shared library compilation and linking flags must have
7241 <tt>-fPIC</tt>, or the package shall not build on some of
7242 the supported architectures<footnote>
7244 If you are using GCC, <tt>-fPIC</tt> produces code with
7245 relocatable position independent code, which is required for
7246 most architectures to create a shared library, with i386 and
7247 perhaps some others where non position independent code is
7248 permitted in a shared library.
7251 Position independent code may have a performance penalty,
7252 especially on <tt>i386</tt>. However, in most cases the
7253 speed penalty must be measured against the memory wasted on
7254 the few architectures where non position independent code is
7257 </footnote>. Any exception to this rule must be discussed on
7258 the mailing list <em>debian-devel@lists.debian.org</em>, and
7259 a rough consensus obtained. The reasons for not compiling
7260 with <tt>-fPIC</tt> flag must be recorded in the file
7261 <tt>README.Debian</tt>, and care must be taken to either
7262 restrict the architecture or arrange for <tt>-fPIC</tt> to
7263 be used on architectures where it is required.<footnote>
7265 Some of the reasons why this might be required is if the
7266 library contains hand crafted assembly code that is not
7267 relocatable, the speed penalty is excessive for compute
7268 intensive libs, and similar reasons.
7273 As to the static libraries, the common case is not to have
7274 relocatable code, since there is no benefit, unless in specific
7275 cases; therefore the static version must not be compiled
7276 with the <tt>-fPIC</tt> flag. Any exception to this rule
7277 should be discussed on the mailing list
7278 <em>debian-devel@lists.debian.org</em>, and the reasons for
7279 compiling with the <tt>-fPIC</tt> flag must be recorded in
7280 the file <tt>README.Debian</tt>. <footnote>
7282 Some of the reasons for linking static libraries with
7283 the <tt>-fPIC</tt> flag are if, for example, one needs a
7284 Perl API for a library that is under rapid development,
7285 and has an unstable API, so shared libraries are
7286 pointless at this phase of the library's development. In
7287 that case, since Perl needs a library with relocatable
7288 code, it may make sense to create a static library with
7289 relocatable code. Another reason cited is if you are
7290 distilling various libraries into a common shared
7291 library, like <tt>mklibs</tt> does in the Debian
7297 In other words, if both a shared and a static library is
7298 being built, each source unit (<tt>*.c</tt>, for example,
7299 for C files) will need to be compiled twice, for the normal
7303 You must specify the gcc option <tt>-D_REENTRANT</tt>
7304 when building a library (either static or shared) to make
7305 the library compatible with LinuxThreads.
7309 Although not enforced by the build tools, shared libraries
7310 must be linked against all libraries that they use symbols from
7311 in the same way that binaries are. This ensures the correct
7312 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7313 system and guarantees that all libraries can be safely opened
7314 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7315 option <tt>-Wl,-z,defs</tt> when building a shared library.
7316 Since this option enforces symbol resolution at build time,
7317 a missing library reference will be caught early as a fatal
7322 All installed shared libraries should be stripped with
7323 <example compact="compact">
7324 strip --strip-unneeded <var>your-lib</var>
7326 (The option <tt>--strip-unneeded</tt> makes
7327 <prgn>strip</prgn> remove only the symbols which aren't
7328 needed for relocation processing.) Shared libraries can
7329 function perfectly well when stripped, since the symbols for
7330 dynamic linking are in a separate part of the ELF object
7332 You might also want to use the options
7333 <tt>--remove-section=.comment</tt> and
7334 <tt>--remove-section=.note</tt> on both shared libraries
7335 and executables, and <tt>--strip-debug</tt> on static
7341 Note that under some circumstances it may be useful to
7342 install a shared library unstripped, for example when
7343 building a separate package to support debugging.
7347 Shared object files (often <file>.so</file> files) that are not
7348 public libraries, that is, they are not meant to be linked
7349 to by third party executables (binaries of other packages),
7350 should be installed in subdirectories of the
7351 <file>/usr/lib</file> directory. Such files are exempt from the
7352 rules that govern ordinary shared libraries, except that
7353 they must not be installed executable and should be
7355 A common example are the so-called "plug-ins",
7356 internal shared objects that are dynamically loaded by
7357 programs using <manref name="dlopen" section="3">.
7362 An ever increasing number of packages are using
7363 <prgn>libtool</prgn> to do their linking. The latest GNU
7364 libtools (>= 1.3a) can take advantage of the metadata in the
7365 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7366 files). The main advantage of <prgn>libtool</prgn>'s
7367 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7368 store and subsequently access metadata with respect to the
7369 libraries it builds. <prgn>libtool</prgn> will search for
7370 those files, which contain a lot of useful information about
7371 a library (such as library dependency information for static
7372 linking). Also, they're <em>essential</em> for programs
7373 using <tt>libltdl</tt>.<footnote>
7374 Although <prgn>libtool</prgn> is fully capable of
7375 linking against shared libraries which don't have
7376 <tt>.la</tt> files, as it is a mere shell script it can
7377 add considerably to the build time of a
7378 <prgn>libtool</prgn>-using package if that shell script
7379 has to derive all this information from first principles
7380 for each library every time it is linked. With the
7381 advent of <prgn>libtool</prgn> version 1.4 (and to a
7382 lesser extent <prgn>libtool</prgn> version 1.3), the
7383 <file>.la</file> files also store information about
7384 inter-library dependencies which cannot necessarily be
7385 derived after the <file>.la</file> file is deleted.
7390 Packages that use <prgn>libtool</prgn> to create shared
7391 libraries should include the <file>.la</file> files in the
7392 <tt>-dev</tt> package, unless the package relies on
7393 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7394 the <tt>.la</tt> files must go in the run-time library
7399 You must make sure that you use only released versions of
7400 shared libraries to build your packages; otherwise other
7401 users will not be able to run your binaries
7402 properly. Producing source packages that depend on
7403 unreleased compilers is also usually a bad
7410 <heading>Shared libraries</heading>
7412 This section has moved to <ref id="sharedlibs">.
7418 <heading>Scripts</heading>
7421 All command scripts, including the package maintainer
7422 scripts inside the package and used by <prgn>dpkg</prgn>,
7423 should have a <tt>#!</tt> line naming the shell to be used
7428 In the case of Perl scripts this should be
7429 <tt>#!/usr/bin/perl</tt>.
7433 When scripts are installed into a directory in the system
7434 PATH, the script name should not include an extension such
7435 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7436 language currently used to implement it.
7439 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7440 <file>init.d</file> scripts should almost certainly start
7441 with <tt>set -e</tt> so that errors are detected.
7442 <file>init.d</file> scripts are something of a special case, due
7443 to how frequently they need to call commands that are allowed to
7444 fail, and it may instead be easier to check the exit status of
7445 commands directly. See <ref id="writing-init"> for more
7446 information about writing <file>init.d</file> scripts.
7449 Every script should use <tt>set -e</tt> or check the exit status
7450 of <em>every</em> command.
7453 Scripts may assume that <file>/bin/sh</file> implements the
7454 SUSv3 Shell Command Language<footnote>
7455 Single UNIX Specification, version 3, which is also IEEE
7456 1003.1-2004 (POSIX), and is available on the World Wide Web
7457 from <url id="http://www.unix.org/version3/online.html"
7458 name="The Open Group"> after free
7459 registration.</footnote>
7460 plus the following additional features not mandated by
7462 These features are in widespread use in the Linux community
7463 and are implemented in all of bash, dash, and ksh, the most
7464 common shells users may wish to use as <file>/bin/sh</file>.
7467 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7468 must not generate a newline.</item>
7469 <item><tt>test</tt>, if implemented as a shell built-in, must
7470 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7472 <item><tt>local</tt> to create a scoped variable must be
7473 supported, including listing multiple variables in a single
7474 local command and assigning a value to a variable at the
7475 same time as localizing it. <tt>local</tt> may or
7476 may not preserve the variable value from an outer scope if
7477 no assignment is present. Uses such as:
7481 # ... use a, b, c, d ...
7484 must be supported and must set the value of <tt>c</tt> to
7488 If a shell script requires non-SUSv3 features from the shell
7489 interpreter other than those listed above, the appropriate shell
7490 must be specified in the first line of the script (e.g.,
7491 <tt>#!/bin/bash</tt>) and the package must depend on the package
7492 providing the shell (unless the shell package is marked
7493 "Essential", as in the case of <prgn>bash</prgn>).
7497 You may wish to restrict your script to SUSv3 features plus the
7498 above set when possible so that it may use <file>/bin/sh</file>
7499 as its interpreter. If your script works with <prgn>dash</prgn>
7500 (originally called <prgn>ash</prgn>), it probably complies with
7501 the above requirements, but if you are in doubt, use
7502 <file>/bin/bash</file>.
7506 Perl scripts should check for errors when making any
7507 system calls, including <tt>open</tt>, <tt>print</tt>,
7508 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7512 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7513 scripting languages. See <em>Csh Programming Considered
7514 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7515 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7516 If an upstream package comes with <prgn>csh</prgn> scripts
7517 then you must make sure that they start with
7518 <tt>#!/bin/csh</tt> and make your package depend on the
7519 <prgn>c-shell</prgn> virtual package.
7523 Any scripts which create files in world-writeable
7524 directories (e.g., in <file>/tmp</file>) must use a
7525 mechanism which will fail atomically if a file with the same
7526 name already exists.
7530 The Debian base system provides the <prgn>tempfile</prgn>
7531 and <prgn>mktemp</prgn> utilities for use by scripts for
7538 <heading>Symbolic links</heading>
7541 In general, symbolic links within a top-level directory
7542 should be relative, and symbolic links pointing from one
7543 top-level directory into another should be absolute. (A
7544 top-level directory is a sub-directory of the root
7545 directory <file>/</file>.)
7549 In addition, symbolic links should be specified as short as
7550 possible, i.e., link targets like <file>foo/../bar</file> are
7555 Note that when creating a relative link using
7556 <prgn>ln</prgn> it is not necessary for the target of the
7557 link to exist relative to the working directory you're
7558 running <prgn>ln</prgn> from, nor is it necessary to change
7559 directory to the directory where the link is to be made.
7560 Simply include the string that should appear as the target
7561 of the link (this will be a pathname relative to the
7562 directory in which the link resides) as the first argument
7567 For example, in your <prgn>Makefile</prgn> or
7568 <file>debian/rules</file>, you can do things like:
7569 <example compact="compact">
7570 ln -fs gcc $(prefix)/bin/cc
7571 ln -fs gcc debian/tmp/usr/bin/cc
7572 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7573 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7578 A symbolic link pointing to a compressed file should always
7579 have the same file extension as the referenced file. (For
7580 example, if a file <file>foo.gz</file> is referenced by a
7581 symbolic link, the filename of the link has to end with
7582 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7587 <heading>Device files</heading>
7590 Packages must not include device files or named pipes in the
7595 If a package needs any special device files that are not
7596 included in the base system, it must call
7597 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7598 after notifying the user<footnote>
7599 This notification could be done via a (low-priority)
7600 debconf message, or an echo (printf) statement.
7605 Packages must not remove any device files in the
7606 <prgn>postrm</prgn> or any other script. This is left to the
7607 system administrator.
7611 Debian uses the serial devices
7612 <file>/dev/ttyS*</file>. Programs using the old
7613 <file>/dev/cu*</file> devices should be changed to use
7614 <file>/dev/ttyS*</file>.
7618 Named pipes needed by the package must be created in
7619 the <prgn>postinst</prgn> script<footnote>
7620 It's better to use <prgn>mkfifo</prgn> rather
7621 than <prgn>mknod</prgn> to create named pipes so that
7622 automated checks for packages incorrectly creating device
7623 files with <prgn>mknod</prgn> won't have false positives.
7624 </footnote> and removed in
7625 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7630 <sect id="config-files">
7631 <heading>Configuration files</heading>
7634 <heading>Definitions</heading>
7638 <tag>configuration file</tag>
7640 A file that affects the operation of a program, or
7641 provides site- or host-specific information, or
7642 otherwise customizes the behavior of a program.
7643 Typically, configuration files are intended to be
7644 modified by the system administrator (if needed or
7645 desired) to conform to local policy or to provide
7646 more useful site-specific behavior.
7649 <tag><tt>conffile</tt></tag>
7651 A file listed in a package's <tt>conffiles</tt>
7652 file, and is treated specially by <prgn>dpkg</prgn>
7653 (see <ref id="configdetails">).
7659 The distinction between these two is important; they are
7660 not interchangeable concepts. Almost all
7661 <tt>conffile</tt>s are configuration files, but many
7662 configuration files are not <tt>conffiles</tt>.
7666 As noted elsewhere, <file>/etc/init.d</file> scripts,
7667 <file>/etc/default</file> files, scripts installed in
7668 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7669 configuration installed in <file>/etc/cron.d</file> must be
7670 treated as configuration files. In general, any script that
7671 embeds configuration information is de-facto a configuration
7672 file and should be treated as such.
7677 <heading>Location</heading>
7680 Any configuration files created or used by your package
7681 must reside in <file>/etc</file>. If there are several,
7682 consider creating a subdirectory of <file>/etc</file>
7683 named after your package.
7687 If your package creates or uses configuration files
7688 outside of <file>/etc</file>, and it is not feasible to modify
7689 the package to use <file>/etc</file> directly, put the files
7690 in <file>/etc</file> and create symbolic links to those files
7691 from the location that the package requires.
7696 <heading>Behavior</heading>
7699 Configuration file handling must conform to the following
7701 <list compact="compact">
7703 local changes must be preserved during a package
7707 configuration files must be preserved when the
7708 package is removed, and only deleted when the
7712 Obsolete configuration files without local changes may be
7713 removed by the package during upgrade.
7717 The easy way to achieve this behavior is to make the
7718 configuration file a <tt>conffile</tt>. This is
7719 appropriate only if it is possible to distribute a default
7720 version that will work for most installations, although
7721 some system administrators may choose to modify it. This
7722 implies that the default version will be part of the
7723 package distribution, and must not be modified by the
7724 maintainer scripts during installation (or at any other
7729 In order to ensure that local changes are preserved
7730 correctly, no package may contain or make hard links to
7731 conffiles.<footnote>
7732 Rationale: There are two problems with hard links.
7733 The first is that some editors break the link while
7734 editing one of the files, so that the two files may
7735 unwittingly become unlinked and different. The second
7736 is that <prgn>dpkg</prgn> might break the hard link
7737 while upgrading <tt>conffile</tt>s.
7742 The other way to do it is via the maintainer scripts. In
7743 this case, the configuration file must not be listed as a
7744 <tt>conffile</tt> and must not be part of the package
7745 distribution. If the existence of a file is required for
7746 the package to be sensibly configured it is the
7747 responsibility of the package maintainer to provide
7748 maintainer scripts which correctly create, update and
7749 maintain the file and remove it on purge. (See <ref
7750 id="maintainerscripts"> for more information.) These
7751 scripts must be idempotent (i.e., must work correctly if
7752 <prgn>dpkg</prgn> needs to re-run them due to errors
7753 during installation or removal), must cope with all the
7754 variety of ways <prgn>dpkg</prgn> can call maintainer
7755 scripts, must not overwrite or otherwise mangle the user's
7756 configuration without asking, must not ask unnecessary
7757 questions (particularly during upgrades), and must
7758 otherwise be good citizens.
7762 The scripts are not required to configure every possible
7763 option for the package, but only those necessary to get
7764 the package running on a given system. Ideally the
7765 sysadmin should not have to do any configuration other
7766 than that done (semi-)automatically by the
7767 <prgn>postinst</prgn> script.
7771 A common practice is to create a script called
7772 <file><var>package</var>-configure</file> and have the
7773 package's <prgn>postinst</prgn> call it if and only if the
7774 configuration file does not already exist. In certain
7775 cases it is useful for there to be an example or template
7776 file which the maintainer scripts use. Such files should
7777 be in <file>/usr/share/<var>package</var></file> or
7778 <file>/usr/lib/<var>package</var></file> (depending on whether
7779 they are architecture-independent or not). There should
7780 be symbolic links to them from
7781 <file>/usr/share/doc/<var>package</var>/examples</file> if
7782 they are examples, and should be perfectly ordinary
7783 <prgn>dpkg</prgn>-handled files (<em>not</em>
7784 configuration files).
7788 These two styles of configuration file handling must
7789 not be mixed, for that way lies madness:
7790 <prgn>dpkg</prgn> will ask about overwriting the file
7791 every time the package is upgraded.
7796 <heading>Sharing configuration files</heading>
7799 Packages which specify the same file as a
7800 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7801 with each other. (This is an instance of the general rule
7802 about not sharing files. Note that neither alternatives
7803 nor diversions are likely to be appropriate in this case;
7804 in particular, <prgn>dpkg</prgn> does not handle diverted
7805 <tt>conffile</tt>s well.)
7809 The maintainer scripts must not alter a <tt>conffile</tt>
7810 of <em>any</em> package, including the one the scripts
7815 If two or more packages use the same configuration file
7816 and it is reasonable for both to be installed at the same
7817 time, one of these packages must be defined as
7818 <em>owner</em> of the configuration file, i.e., it will be
7819 the package which handles that file as a configuration
7820 file. Other packages that use the configuration file must
7821 depend on the owning package if they require the
7822 configuration file to operate. If the other package will
7823 use the configuration file if present, but is capable of
7824 operating without it, no dependency need be declared.
7828 If it is desirable for two or more related packages to
7829 share a configuration file <em>and</em> for all of the
7830 related packages to be able to modify that configuration
7831 file, then the following should be done:
7832 <enumlist compact="compact">
7834 One of the related packages (the "owning" package)
7835 will manage the configuration file with maintainer
7836 scripts as described in the previous section.
7839 The owning package should also provide a program
7840 that the other packages may use to modify the
7844 The related packages must use the provided program
7845 to make any desired modifications to the
7846 configuration file. They should either depend on
7847 the core package to guarantee that the configuration
7848 modifier program is available or accept gracefully
7849 that they cannot modify the configuration file if it
7850 is not. (This is in addition to the fact that the
7851 configuration file may not even be present in the
7858 Sometimes it's appropriate to create a new package which
7859 provides the basic infrastructure for the other packages
7860 and which manages the shared configuration files. (The
7861 <tt>sgml-base</tt> package is a good example.)
7866 <heading>User configuration files ("dotfiles")</heading>
7869 The files in <file>/etc/skel</file> will automatically be
7870 copied into new user accounts by <prgn>adduser</prgn>.
7871 No other program should reference the files in
7872 <file>/etc/skel</file>.
7876 Therefore, if a program needs a dotfile to exist in
7877 advance in <file>$HOME</file> to work sensibly, that dotfile
7878 should be installed in <file>/etc/skel</file> and treated as a
7883 However, programs that require dotfiles in order to
7884 operate sensibly are a bad thing, unless they do create
7885 the dotfiles themselves automatically.
7889 Furthermore, programs should be configured by the Debian
7890 default installation to behave as closely to the upstream
7891 default behavior as possible.
7895 Therefore, if a program in a Debian package needs to be
7896 configured in some way in order to operate sensibly, that
7897 should be done using a site-wide configuration file placed
7898 in <file>/etc</file>. Only if the program doesn't support a
7899 site-wide default configuration and the package maintainer
7900 doesn't have time to add it may a default per-user file be
7901 placed in <file>/etc/skel</file>.
7905 <file>/etc/skel</file> should be as empty as we can make it.
7906 This is particularly true because there is no easy (or
7907 necessarily desirable) mechanism for ensuring that the
7908 appropriate dotfiles are copied into the accounts of
7909 existing users when a package is installed.
7915 <heading>Log files</heading>
7917 Log files should usually be named
7918 <file>/var/log/<var>package</var>.log</file>. If you have many
7919 log files, or need a separate directory for permission
7920 reasons (<file>/var/log</file> is writable only by
7921 <file>root</file>), you should usually create a directory named
7922 <file>/var/log/<var>package</var></file> and place your log
7927 Log files must be rotated occasionally so that they don't
7928 grow indefinitely; the best way to do this is to drop a log
7929 rotation configuration file into the directory
7930 <file>/etc/logrotate.d</file> and use the facilities provided by
7931 logrotate.<footnote>
7933 The traditional approach to log files has been to set up
7934 <em>ad hoc</em> log rotation schemes using simple shell
7935 scripts and cron. While this approach is highly
7936 customizable, it requires quite a lot of sysadmin work.
7937 Even though the original Debian system helped a little
7938 by automatically installing a system which can be used
7939 as a template, this was deemed not enough.
7943 The use of <prgn>logrotate</prgn>, a program developed
7944 by Red Hat, is better, as it centralizes log management.
7945 It has both a configuration file
7946 (<file>/etc/logrotate.conf</file>) and a directory where
7947 packages can drop their individual log rotation
7948 configurations (<file>/etc/logrotate.d</file>).
7951 Here is a good example for a logrotate config
7952 file (for more information see <manref name="logrotate"
7954 <example compact="compact">
7955 /var/log/foo/*.log {
7960 /etc/init.d/foo force-reload
7964 This rotates all files under <file>/var/log/foo</file>, saves 12
7965 compressed generations, and forces the daemon to reload its
7966 configuration information after the log rotation.
7970 Log files should be removed when the package is
7971 purged (but not when it is only removed). This should be
7972 done by the <prgn>postrm</prgn> script when it is called
7973 with the argument <tt>purge</tt> (see <ref
7974 id="removedetails">).
7979 <heading>Permissions and owners</heading>
7982 The rules in this section are guidelines for general use.
7983 If necessary you may deviate from the details below.
7984 However, if you do so you must make sure that what is done
7985 is secure and you should try to be as consistent as possible
7986 with the rest of the system. You should probably also
7987 discuss it on <prgn>debian-devel</prgn> first.
7991 Files should be owned by <tt>root:root</tt>, and made
7992 writable only by the owner and universally readable (and
7993 executable, if appropriate), that is mode 644 or 755.
7997 Directories should be mode 755 or (for group-writability)
7998 mode 2775. The ownership of the directory should be
7999 consistent with its mode: if a directory is mode 2775, it
8000 should be owned by the group that needs write access to
8003 When a package is upgraded, and the owner or permissions
8004 of a file included in the package has changed, dpkg
8005 arranges for the ownership and permissions to be
8006 correctly set upon installation. However, this does not
8007 extend to directories; the permissions and ownership of
8008 directories already on the system does not change on
8009 install or upgrade of packages. This makes sense, since
8010 otherwise common directories like <tt>/usr</tt> would
8011 always be in flux. To correctly change permissions of a
8012 directory the package owns, explicit action is required,
8013 usually in the <tt>postinst</tt> script. Care must be
8014 taken to handle downgrades as well, in that case.
8021 Setuid and setgid executables should be mode 4755 or 2755
8022 respectively, and owned by the appropriate user or group.
8023 They should not be made unreadable (modes like 4711 or
8024 2711 or even 4111); doing so achieves no extra security,
8025 because anyone can find the binary in the freely available
8026 Debian package; it is merely inconvenient. For the same
8027 reason you should not restrict read or execute permissions
8028 on non-set-id executables.
8032 Some setuid programs need to be restricted to particular
8033 sets of users, using file permissions. In this case they
8034 should be owned by the uid to which they are set-id, and by
8035 the group which should be allowed to execute them. They
8036 should have mode 4754; again there is no point in making
8037 them unreadable to those users who must not be allowed to
8042 It is possible to arrange that the system administrator can
8043 reconfigure the package to correspond to their local
8044 security policy by changing the permissions on a binary:
8045 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8046 described below.<footnote>
8047 Ordinary files installed by <prgn>dpkg</prgn> (as
8048 opposed to <tt>conffile</tt>s and other similar objects)
8049 normally have their permissions reset to the distributed
8050 permissions when the package is reinstalled. However,
8051 the use of <prgn>dpkg-statoverride</prgn> overrides this
8054 Another method you should consider is to create a group for
8055 people allowed to use the program(s) and make any setuid
8056 executables executable only by that group.
8060 If you need to create a new user or group for your package
8061 there are two possibilities. Firstly, you may need to
8062 make some files in the binary package be owned by this
8063 user or group, or you may need to compile the user or
8064 group id (rather than just the name) into the binary
8065 (though this latter should be avoided if possible, as in
8066 this case you need a statically allocated id).</p>
8069 If you need a statically allocated id, you must ask for a
8070 user or group id from the <tt>base-passwd</tt> maintainer,
8071 and must not release the package until you have been
8072 allocated one. Once you have been allocated one you must
8073 either make the package depend on a version of the
8074 <tt>base-passwd</tt> package with the id present in
8075 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8076 your package to create the user or group itself with the
8077 correct id (using <tt>adduser</tt>) in its
8078 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8079 the <prgn>postinst</prgn> is to be preferred if it is
8080 possible, otherwise a pre-dependency will be needed on the
8081 <tt>adduser</tt> package.)
8085 On the other hand, the program might be able to determine
8086 the uid or gid from the user or group name at runtime, so
8087 that a dynamically allocated id can be used. In this case
8088 you should choose an appropriate user or group name,
8089 discussing this on <prgn>debian-devel</prgn> and checking
8090 with the <package/base-passwd/ maintainer that it is unique and that
8091 they do not wish you to use a statically allocated id
8092 instead. When this has been checked you must arrange for
8093 your package to create the user or group if necessary using
8094 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8095 <prgn>postinst</prgn> script (again, the latter is to be
8096 preferred if it is possible).
8100 Note that changing the numeric value of an id associated
8101 with a name is very difficult, and involves searching the
8102 file system for all appropriate files. You need to think
8103 carefully whether a static or dynamic id is required, since
8104 changing your mind later will cause problems.
8107 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8109 This section is not intended as policy, but as a
8110 description of the use of <prgn>dpkg-statoverride</prgn>.
8114 If a system administrator wishes to have a file (or
8115 directory or other such thing) installed with owner and
8116 permissions different from those in the distributed Debian
8117 package, they can use the <prgn>dpkg-statoverride</prgn>
8118 program to instruct <prgn>dpkg</prgn> to use the different
8119 settings every time the file is installed. Thus the
8120 package maintainer should distribute the files with their
8121 normal permissions, and leave it for the system
8122 administrator to make any desired changes. For example, a
8123 daemon which is normally required to be setuid root, but
8124 in certain situations could be used without being setuid,
8125 should be installed setuid in the <tt>.deb</tt>. Then the
8126 local system administrator can change this if they wish.
8127 If there are two standard ways of doing it, the package
8128 maintainer can use <tt>debconf</tt> to find out the
8129 preference, and call <prgn>dpkg-statoverride</prgn> in the
8130 maintainer script if necessary to accommodate the system
8131 administrator's choice. Care must be taken during
8132 upgrades to not override an existing setting.
8136 Given the above, <prgn>dpkg-statoverride</prgn> is
8137 essentially a tool for system administrators and would not
8138 normally be needed in the maintainer scripts. There is
8139 one type of situation, though, where calls to
8140 <prgn>dpkg-statoverride</prgn> would be needed in the
8141 maintainer scripts, and that involves packages which use
8142 dynamically allocated user or group ids. In such a
8143 situation, something like the following idiom can be very
8144 helpful in the package's <prgn>postinst</prgn>, where
8145 <tt>sysuser</tt> is a dynamically allocated id:
8147 for i in /usr/bin/foo /usr/sbin/bar
8149 # only do something when no setting exists
8150 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8152 #include: debconf processing, question about foo and bar
8153 if [ "$RET" = "true" ] ; then
8154 dpkg-statoverride --update --add sysuser root 4755 $i
8159 The corresponding code to remove the override when the package
8162 for i in /usr/bin/foo /usr/sbin/bar
8164 if dpkg-statoverride --list $i >/dev/null 2>&1
8166 dpkg-statoverride --remove $i
8176 <chapt id="customized-programs">
8177 <heading>Customized programs</heading>
8179 <sect id="arch-spec">
8180 <heading>Architecture specification strings</heading>
8183 If a program needs to specify an <em>architecture specification
8184 string</em> in some place, it should select one of the strings
8185 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8186 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8187 part is sometimes elided, as when the OS is Linux.
8191 Note that we don't want to use
8192 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8193 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8194 since this would make our programs incompatible with other
8195 Linux distributions. We also don't use something like
8196 <tt><var>arch</var>-unknown-linux</tt>, since the
8197 <tt>unknown</tt> does not look very good.
8200 <sect1 id="arch-wildcard-spec">
8201 <heading>Architecture wildcards</heading>
8204 A package may specify an architecture wildcard. Architecture
8205 wildcards are in the format <tt>any</tt> (which matches every
8206 architecture), <tt><var>os</var></tt>-any, or
8207 any-<tt><var>cpu</var></tt>. <footnote>
8208 Internally, the package system normalizes the GNU triplets
8209 and the Debian arches into Debian arch triplets (which are
8210 kind of inverted GNU triplets), with the first component of
8211 the triplet representing the libc and ABI in use, and then
8212 does matching against those triplets. However, such
8213 triplets are an internal implementation detail that should
8214 not be used by packages directly. The libc and ABI portion
8215 is handled internally by the package system based on
8216 the <var>os</var> and <var>cpu</var>.
8223 <heading>Daemons</heading>
8226 The configuration files <file>/etc/services</file>,
8227 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8228 by the <prgn>netbase</prgn> package and must not be modified
8233 If a package requires a new entry in one of these files, the
8234 maintainer should get in contact with the
8235 <prgn>netbase</prgn> maintainer, who will add the entries
8236 and release a new version of the <prgn>netbase</prgn>
8241 The configuration file <file>/etc/inetd.conf</file> must not be
8242 modified by the package's scripts except via the
8243 <prgn>update-inetd</prgn> script or the
8244 <file>DebianNet.pm</file> Perl module. See their documentation
8245 for details on how to add entries.
8249 If a package wants to install an example entry into
8250 <file>/etc/inetd.conf</file>, the entry must be preceded with
8251 exactly one hash character (<tt>#</tt>). Such lines are
8252 treated as "commented out by user" by the
8253 <prgn>update-inetd</prgn> script and are not changed or
8254 activated during package updates.
8259 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8263 Some programs need to create pseudo-ttys. This should be done
8264 using Unix98 ptys if the C library supports it. The resulting
8265 program must not be installed setuid root, unless that
8266 is required for other functionality.
8270 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8271 <file>/var/log/lastlog</file> must be installed writable by
8272 group <tt>utmp</tt>. Programs which need to modify those
8273 files must be installed setgid <tt>utmp</tt>.
8278 <heading>Editors and pagers</heading>
8281 Some programs have the ability to launch an editor or pager
8282 program to edit or display a text document. Since there are
8283 lots of different editors and pagers available in the Debian
8284 distribution, the system administrator and each user should
8285 have the possibility to choose their preferred editor and
8290 In addition, every program should choose a good default
8291 editor/pager if none is selected by the user or system
8296 Thus, every program that launches an editor or pager must
8297 use the EDITOR or PAGER environment variable to determine
8298 the editor or pager the user wishes to use. If these
8299 variables are not set, the programs <file>/usr/bin/editor</file>
8300 and <file>/usr/bin/pager</file> should be used, respectively.
8304 These two files are managed through the <prgn>dpkg</prgn>
8305 "alternatives" mechanism. Thus every package providing an
8306 editor or pager must call the
8307 <prgn>update-alternatives</prgn> script to register these
8312 If it is very hard to adapt a program to make use of the
8313 EDITOR or PAGER variables, that program may be configured to
8314 use <file>/usr/bin/sensible-editor</file> and
8315 <file>/usr/bin/sensible-pager</file> as the editor or pager
8316 program respectively. These are two scripts provided in the
8317 <package>sensible-utils</package> package that check the EDITOR
8318 and PAGER variables and launch the appropriate program, and fall
8319 back to <file>/usr/bin/editor</file>
8320 and <file>/usr/bin/pager</file> if the variable is not set.
8324 A program may also use the VISUAL environment variable to
8325 determine the user's choice of editor. If it exists, it
8326 should take precedence over EDITOR. This is in fact what
8327 <file>/usr/bin/sensible-editor</file> does.
8331 It is not required for a package to depend on
8332 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8333 package to provide such virtual packages.<footnote>
8334 The Debian base system already provides an editor and a
8340 <sect id="web-appl">
8341 <heading>Web servers and applications</heading>
8344 This section describes the locations and URLs that should
8345 be used by all web servers and web applications in the
8352 Cgi-bin executable files are installed in the
8354 <example compact="compact">
8355 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8357 and should be referred to as
8358 <example compact="compact">
8359 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8365 <p>Access to HTML documents</p>
8368 HTML documents for a package are stored in
8369 <file>/usr/share/doc/<var>package</var></file>
8370 and can be referred to as
8371 <example compact="compact">
8372 http://localhost/doc/<var>package</var>/<var>filename</var>
8377 The web server should restrict access to the document
8378 tree so that only clients on the same host can read
8379 the documents. If the web server does not support such
8380 access controls, then it should not provide access at
8381 all, or ask about providing access during installation.
8386 <p>Access to images</p>
8388 It is recommended that images for a package be stored
8389 in <tt>/usr/share/images/<var>package</var></tt> and
8390 may be referred to through an alias <tt>/images/</tt>
8393 http://localhost/images/<package>/<filename>
8400 <p>Web Document Root</p>
8403 Web Applications should try to avoid storing files in
8404 the Web Document Root. Instead they should use the
8405 /usr/share/doc/<var>package</var> directory for
8406 documents and register the Web Application via the
8407 <package>doc-base</package> package. If access to the
8408 web document root is unavoidable then use
8409 <example compact="compact">
8412 as the Document Root. This might be just a symbolic
8413 link to the location where the system administrator
8414 has put the real document root.
8417 <item><p>Providing httpd and/or httpd-cgi</p>
8419 All web servers should provide the virtual package
8420 <tt>httpd</tt>. If a web server has CGI support it should
8421 provide <tt>httpd-cgi</tt> additionally.
8424 All web applications which do not contain CGI scripts should
8425 depend on <tt>httpd</tt>, all those web applications which
8426 <tt>do</tt> contain CGI scripts, should depend on
8434 <sect id="mail-transport-agents">
8435 <heading>Mail transport, delivery and user agents</heading>
8438 Debian packages which process electronic mail, whether mail
8439 user agents (MUAs) or mail transport agents (MTAs), must
8440 ensure that they are compatible with the configuration
8441 decisions below. Failure to do this may result in lost
8442 mail, broken <tt>From:</tt> lines, and other serious brain
8447 The mail spool is <file>/var/mail</file> and the interface to
8448 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8449 the FHS). On older systems, the mail spool may be
8450 physically located in <file>/var/spool/mail</file>, but all
8451 access to the mail spool should be via the
8452 <file>/var/mail</file> symlink. The mail spool is part of the
8453 base system and not part of the MTA package.
8457 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8458 programs (such as IMAP daemons) must lock the mailbox in an
8459 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8460 be combined with dot locking. To avoid deadlocks, a program
8461 should use <tt>fcntl()</tt> first and dot locking after
8462 this, or alternatively implement the two locking methods in
8463 a non blocking way<footnote>
8464 If it is not possible to establish both locks, the
8465 system shouldn't wait for the second lock to be
8466 established, but remove the first lock, wait a (random)
8467 time, and start over locking again.
8468 </footnote>. Using the functions <tt>maillock</tt> and
8469 <tt>mailunlock</tt> provided by the
8470 <tt>liblockfile*</tt><footnote>
8471 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8472 to use these functions.
8473 </footnote> packages is the recommended way to realize this.
8477 Mailboxes are generally either mode 600 and owned by
8478 <var>user</var> or mode 660 and owned by
8479 <tt><var>user</var>:mail</tt><footnote>
8480 There are two traditional permission schemes for mail spools:
8481 mode 600 with all mail delivery done by processes running as
8482 the destination user, or mode 660 and owned by group mail with
8483 mail delivery done by a process running as a system user in
8484 group mail. Historically, Debian required mode 660 mail
8485 spools to enable the latter model, but that model has become
8486 increasingly uncommon and the principle of least privilege
8487 indicates that mail systems that use the first model should
8488 use permissions of 600. If delivery to programs is permitted,
8489 it's easier to keep the mail system secure if the delivery
8490 agent runs as the destination user. Debian Policy therefore
8491 permits either scheme.
8492 </footnote>. The local system administrator may choose a
8493 different permission scheme; packages should not make
8494 assumptions about the permission and ownership of mailboxes
8495 unless required (such as when creating a new mailbox). A MUA
8496 may remove a mailbox (unless it has nonstandard permissions) in
8497 which case the MTA or another MUA must recreate it if needed.
8501 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8502 be setgid mail to do the locking mentioned above (and
8503 must obviously avoid accessing other users' mailboxes
8504 using this privilege).</p>
8507 <file>/etc/aliases</file> is the source file for the system mail
8508 aliases (e.g., postmaster, usenet, etc.), it is the one
8509 which the sysadmin and <prgn>postinst</prgn> scripts may
8510 edit. After <file>/etc/aliases</file> is edited the program or
8511 human editing it must call <prgn>newaliases</prgn>. All MTA
8512 packages must come with a <prgn>newaliases</prgn> program,
8513 even if it does nothing, but older MTA packages did not do
8514 this so programs should not fail if <prgn>newaliases</prgn>
8515 cannot be found. Note that because of this, all MTA
8516 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8517 <tt>Replaces: mail-transport-agent</tt> control file
8522 The convention of writing <tt>forward to
8523 <var>address</var></tt> in the mailbox itself is not
8524 supported. Use a <tt>.forward</tt> file instead.</p>
8527 The <prgn>rmail</prgn> program used by UUCP
8528 for incoming mail should be <file>/usr/sbin/rmail</file>.
8529 Likewise, <prgn>rsmtp</prgn>, for receiving
8530 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8534 If your package needs to know what hostname to use on (for
8535 example) outgoing news and mail messages which are generated
8536 locally, you should use the file <file>/etc/mailname</file>. It
8537 will contain the portion after the username and <tt>@</tt>
8538 (at) sign for email addresses of users on the machine
8539 (followed by a newline).
8543 Such a package should check for the existence of this file
8544 when it is being configured. If it exists, it should be
8545 used without comment, although an MTA's configuration script
8546 may wish to prompt the user even if it finds that this file
8547 exists. If the file does not exist, the package should
8548 prompt the user for the value (preferably using
8549 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8550 as well as using it in the package's configuration. The
8551 prompt should make it clear that the name will not just be
8552 used by that package. For example, in this situation the
8553 <tt>inn</tt> package could say something like:
8554 <example compact="compact">
8555 Please enter the "mail name" of your system. This is the
8556 hostname portion of the address to be shown on outgoing
8557 news and mail messages. The default is
8558 <var>syshostname</var>, your system's host name. Mail
8559 name ["<var>syshostname</var>"]:
8561 where <var>syshostname</var> is the output of <tt>hostname
8567 <heading>News system configuration</heading>
8570 All the configuration files related to the NNTP (news)
8571 servers and clients should be located under
8572 <file>/etc/news</file>.</p>
8575 There are some configuration issues that apply to a number
8576 of news clients and server packages on the machine. These
8580 <tag><file>/etc/news/organization</file></tag>
8582 A string which should appear as the
8583 organization header for all messages posted
8584 by NNTP clients on the machine
8587 <tag><file>/etc/news/server</file></tag>
8589 Contains the FQDN of the upstream NNTP
8590 server, or localhost if the local machine is
8595 Other global files may be added as required for cross-package news
8602 <heading>Programs for the X Window System</heading>
8605 <heading>Providing X support and package priorities</heading>
8608 Programs that can be configured with support for the X
8609 Window System must be configured to do so and must declare
8610 any package dependencies necessary to satisfy their
8611 runtime requirements when using the X Window System. If
8612 such a package is of higher priority than the X packages
8613 on which it depends, it is required that either the
8614 X-specific components be split into a separate package, or
8615 that an alternative version of the package, which includes
8616 X support, be provided, or that the package's priority be
8622 <heading>Packages providing an X server</heading>
8625 Packages that provide an X server that, directly or
8626 indirectly, communicates with real input and display
8627 hardware should declare in their control data that they
8628 provide the virtual package <tt>xserver</tt>.<footnote>
8629 This implements current practice, and provides an
8630 actual policy for usage of the <tt>xserver</tt>
8631 virtual package which appears in the virtual packages
8632 list. In a nutshell, X servers that interface
8633 directly with the display and input hardware or via
8634 another subsystem (e.g., GGI) should provide
8635 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8636 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8642 <heading>Packages providing a terminal emulator</heading>
8645 Packages that provide a terminal emulator for the X Window
8646 System which meet the criteria listed below should declare
8647 in their control data that they provide the virtual
8648 package <tt>x-terminal-emulator</tt>. They should also
8649 register themselves as an alternative for
8650 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8655 To be an <tt>x-terminal-emulator</tt>, a program must:
8656 <list compact="compact">
8658 Be able to emulate a DEC VT100 terminal, or a
8659 compatible terminal.
8663 Support the command-line option <tt>-e
8664 <var>command</var></tt>, which creates a new
8665 terminal window<footnote>
8666 "New terminal window" does not necessarily mean
8667 a new top-level X window directly parented by
8668 the window manager; it could, if the terminal
8669 emulator application were so coded, be a new
8670 "view" in a multiple-document interface (MDI).
8672 and runs the specified <var>command</var>,
8673 interpreting the entirety of the rest of the command
8674 line as a command to pass straight to exec, in the
8675 manner that <tt>xterm</tt> does.
8679 Support the command-line option <tt>-T
8680 <var>title</var></tt>, which creates a new terminal
8681 window with the window title <var>title</var>.
8688 <heading>Packages providing a window manager</heading>
8691 Packages that provide a window manager should declare in
8692 their control data that they provide the virtual package
8693 <tt>x-window-manager</tt>. They should also register
8694 themselves as an alternative for
8695 <file>/usr/bin/x-window-manager</file>, with a priority
8696 calculated as follows:
8697 <list compact="compact">
8699 Start with a priority of 20.
8703 If the window manager supports the Debian menu
8704 system, add 20 points if this support is available
8705 in the package's default configuration (i.e., no
8706 configuration files belonging to the system or user
8707 have to be edited to activate the feature); if
8708 configuration files must be modified, add only 10
8714 If the window manager complies with <url
8715 id="http://www.freedesktop.org/Standards/wm-spec"
8716 name="The Window Manager Specification Project">,
8717 written by the <url id="http://www.freedesktop.org/"
8718 name="Free Desktop Group">, add 40 points.
8722 If the window manager permits the X session to be
8723 restarted using a <em>different</em> window manager
8724 (without killing the X server) in its default
8725 configuration, add 10 points; otherwise add none.
8732 <heading>Packages providing fonts</heading>
8735 Packages that provide fonts for the X Window
8737 For the purposes of Debian Policy, a "font for the X
8738 Window System" is one which is accessed via X protocol
8739 requests. Fonts for the Linux console, for PostScript
8740 renderer, or any other purpose, do not fit this
8741 definition. Any tool which makes such fonts available
8742 to the X Window System, however, must abide by this
8745 must do a number of things to ensure that they are both
8746 available without modification of the X or font server
8747 configuration, and that they do not corrupt files used by
8748 other font packages to register information about
8752 Fonts of any type supported by the X Window System
8753 must be in a separate binary package from any
8754 executables, libraries, or documentation (except
8755 that specific to the fonts shipped, such as their
8756 license information). If one or more of the fonts
8757 so packaged are necessary for proper operation of
8758 the package with which they are associated the font
8759 package may be Recommended; if the fonts merely
8760 provide an enhancement, a Suggests relationship may
8761 be used. Packages must not Depend on font
8763 This is because the X server may retrieve fonts
8764 from the local file system or over the network
8765 from an X font server; the Debian package system
8766 is empowered to deal only with the local
8772 BDF fonts must be converted to PCF fonts with the
8773 <prgn>bdftopcf</prgn> utility (available in the
8774 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8775 placed in a directory that corresponds to their
8777 <list compact="compact">
8779 100 dpi fonts must be placed in
8780 <file>/usr/share/fonts/X11/100dpi/</file>.
8784 75 dpi fonts must be placed in
8785 <file>/usr/share/fonts/X11/75dpi/</file>.
8789 Character-cell fonts, cursor fonts, and other
8790 low-resolution fonts must be placed in
8791 <file>/usr/share/fonts/X11/misc/</file>.
8797 Type 1 fonts must be placed in
8798 <file>/usr/share/fonts/X11/Type1/</file>. If font
8799 metric files are available, they must be placed here
8804 Subdirectories of <file>/usr/share/fonts/X11/</file>
8805 other than those listed above must be neither
8806 created nor used. (The <file>PEX</file>, <file>CID</file>,
8807 <file>Speedo</file>, and <file>cyrillic</file> directories
8808 are excepted for historical reasons, but installation of
8809 files into these directories remains discouraged.)
8813 Font packages may, instead of placing files directly
8814 in the X font directories listed above, provide
8815 symbolic links in that font directory pointing to
8816 the files' actual location in the filesystem. Such
8817 a location must comply with the FHS.
8821 Font packages should not contain both 75dpi and
8822 100dpi versions of a font. If both are available,
8823 they should be provided in separate binary packages
8824 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8825 the names of the packages containing the
8826 corresponding fonts.
8830 Fonts destined for the <file>misc</file> subdirectory
8831 should not be included in the same package as 75dpi
8832 or 100dpi fonts; instead, they should be provided in
8833 a separate package with <tt>-misc</tt> appended to
8838 Font packages must not provide the files
8839 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8840 <file>fonts.scale</file> in a font directory:
8843 <file>fonts.dir</file> files must not be provided at all.
8847 <file>fonts.alias</file> and <file>fonts.scale</file>
8848 files, if needed, should be provided in the
8850 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8851 where <var>fontdir</var> is the name of the
8853 <file>/usr/share/fonts/X11/</file> where the
8854 package's corresponding fonts are stored
8855 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8856 <var>package</var> is the name of the package
8857 that provides these fonts, and
8858 <var>extension</var> is either <tt>scale</tt>
8859 or <tt>alias</tt>, whichever corresponds to
8866 Font packages must declare a dependency on
8867 <tt>xfonts-utils</tt> in their control
8872 Font packages that provide one or more
8873 <file>fonts.scale</file> files as described above must
8874 invoke <prgn>update-fonts-scale</prgn> on each
8875 directory into which they installed fonts
8876 <em>before</em> invoking
8877 <prgn>update-fonts-dir</prgn> on that directory.
8878 This invocation must occur in both the
8879 <prgn>postinst</prgn> (for all arguments) and
8880 <prgn>postrm</prgn> (for all arguments except
8881 <tt>upgrade</tt>) scripts.
8885 Font packages that provide one or more
8886 <file>fonts.alias</file> files as described above must
8887 invoke <prgn>update-fonts-alias</prgn> on each
8888 directory into which they installed fonts. This
8889 invocation must occur in both the
8890 <prgn>postinst</prgn> (for all arguments) and
8891 <prgn>postrm</prgn> (for all arguments except
8892 <tt>upgrade</tt>) scripts.
8896 Font packages must invoke
8897 <prgn>update-fonts-dir</prgn> on each directory into
8898 which they installed fonts. This invocation must
8899 occur in both the <prgn>postinst</prgn> (for all
8900 arguments) and <prgn>postrm</prgn> (for all
8901 arguments except <tt>upgrade</tt>) scripts.
8905 Font packages must not provide alias names for the
8906 fonts they include which collide with alias names
8907 already in use by fonts already packaged.
8911 Font packages must not provide fonts with the same
8912 XLFD registry name as another font already packaged.
8918 <sect1 id="appdefaults">
8919 <heading>Application defaults files</heading>
8922 Application defaults files must be installed in the
8923 directory <file>/etc/X11/app-defaults/</file> (use of a
8924 localized subdirectory of <file>/etc/X11/</file> as described
8925 in the <em>X Toolkit Intrinsics - C Language
8926 Interface</em> manual is also permitted). They must be
8927 registered as <tt>conffile</tt>s or handled as
8928 configuration files.
8932 Customization of programs' X resources may also be
8933 supported with the provision of a file with the same name
8934 as that of the package placed in
8935 the <file>/etc/X11/Xresources/</file> directory, which
8936 must be registered as a <tt>conffile</tt> or handled as a
8937 configuration file.<footnote>
8938 Note that this mechanism is not the same as using
8939 app-defaults; app-defaults are tied to the client
8940 binary on the local file system, whereas X resources
8941 are stored in the X server and affect all connecting
8948 <heading>Installation directory issues</heading>
8951 Historically, packages using the X Window System used a
8952 separate set of installation directories from other packages.
8953 This practice has been discontinued and packages using the X
8954 Window System should now generally be installed in the same
8955 directories as any other package. Specifically, packages must
8956 not install files under the <file>/usr/X11R6/</file> directory
8957 and the <file>/usr/X11R6/</file> directory hierarchy should be
8958 regarded as obsolete.
8962 Include files previously installed under
8963 <file>/usr/X11R6/include/X11/</file> should be installed into
8964 <file>/usr/include/X11/</file>. For files previously
8965 installed into subdirectories of
8966 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8967 determine if subdirectories of <file>/usr/lib/</file> and
8968 <file>/usr/share/</file> can be used. If not, a subdirectory
8969 of <file>/usr/lib/X11/</file> should be used.
8973 Configuration files for window, display, or session managers
8974 or other applications that are tightly integrated with the X
8975 Window System may be placed in a subdirectory
8976 of <file>/etc/X11/</file> corresponding to the package name.
8977 Other X Window System applications should use
8978 the <file>/etc/</file> directory unless otherwise mandated by
8979 policy (such as for <ref id="appdefaults">).
8984 <heading>The OSF/Motif and OpenMotif libraries</heading>
8987 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8988 OpenMotif libraries</em><footnote>
8989 OSF/Motif and OpenMotif are collectively referred to as
8990 "Motif" in this policy document.
8992 should be compiled against and tested with LessTif (a free
8993 re-implementation of Motif) instead. If the maintainer
8994 judges that the program or programs do not work
8995 sufficiently well with LessTif to be distributed and
8996 supported, but do so when compiled against Motif, then two
8997 versions of the package should be created; one linked
8998 statically against Motif and with <tt>-smotif</tt>
8999 appended to the package name, and one linked dynamically
9000 against Motif and with <tt>-dmotif</tt> appended to the
9005 Both Motif-linked versions are dependent
9006 upon non-DFSG-compliant software and thus cannot be
9007 uploaded to the <em>main</em> distribution; if the
9008 software is itself DFSG-compliant it may be uploaded to
9009 the <em>contrib</em> distribution. While known existing
9010 versions of Motif permit unlimited redistribution of
9011 binaries linked against the library (whether statically or
9012 dynamically), it is the package maintainer's
9013 responsibility to determine whether this is permitted by
9014 the license of the copy of Motif in their possession.
9020 <heading>Perl programs and modules</heading>
9023 Perl programs and modules should follow the current Perl policy.
9027 The Perl policy can be found in the <tt>perl-policy</tt>
9028 files in the <tt>debian-policy</tt> package.
9029 It is also available from the Debian web mirrors at
9030 <tt><url name="/doc/packaging-manuals/perl-policy/"
9031 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9036 <heading>Emacs lisp programs</heading>
9039 Please refer to the "Debian Emacs Policy" for details of how to
9040 package emacs lisp programs.
9044 The Emacs policy is available in
9045 <file>debian-emacs-policy.gz</file> of the
9046 <package>emacsen-common</package> package.
9047 It is also available from the Debian web mirrors at
9048 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9049 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9054 <heading>Games</heading>
9057 The permissions on <file>/var/games</file> are mode 755, owner
9058 <tt>root</tt> and group <tt>root</tt>.
9062 Each game decides on its own security policy.</p>
9065 Games which require protected, privileged access to
9066 high-score files, saved games, etc., may be made
9067 set-<em>group</em>-id (mode 2755) and owned by
9068 <tt>root:games</tt>, and use files and directories with
9069 appropriate permissions (770 <tt>root:games</tt>, for
9070 example). They must not be made
9071 set-<em>user</em>-id, as this causes security problems. (If
9072 an attacker can subvert any set-user-id game they can
9073 overwrite the executable of any other, causing other players
9074 of these games to run a Trojan horse program. With a
9075 set-group-id game the attacker only gets access to less
9076 important game data, and if they can get at the other
9077 players' accounts at all it will take considerably more
9081 Some packages, for example some fortune cookie programs, are
9082 configured by the upstream authors to install with their
9083 data files or other static information made unreadable so
9084 that they can only be accessed through set-id programs
9085 provided. You should not do this in a Debian package: anyone can
9086 download the <file>.deb</file> file and read the data from it,
9087 so there is no point making the files unreadable. Not
9088 making the files unreadable also means that you don't have
9089 to make so many programs set-id, which reduces the risk of a
9093 As described in the FHS, binaries of games should be
9094 installed in the directory <file>/usr/games</file>. This also
9095 applies to games that use the X Window System. Manual pages
9096 for games (X and non-X games) should be installed in
9097 <file>/usr/share/man/man6</file>.</p>
9103 <heading>Documentation</heading>
9106 <heading>Manual pages</heading>
9109 You should install manual pages in <prgn>nroff</prgn> source
9110 form, in appropriate places under <file>/usr/share/man</file>.
9111 You should only use sections 1 to 9 (see the FHS for more
9112 details). You must not install a pre-formatted "cat page".
9116 Each program, utility, and function should have an
9117 associated manual page included in the same package. It is
9118 suggested that all configuration files also have a manual
9119 page included as well. Manual pages for protocols and other
9120 auxiliary things are optional.
9124 If no manual page is available, this is considered as a bug
9125 and should be reported to the Debian Bug Tracking System (the
9126 maintainer of the package is allowed to write this bug report
9127 themselves, if they so desire). Do not close the bug report
9128 until a proper man page is available.<footnote>
9129 It is not very hard to write a man page. See the
9130 <url id="http://www.schweikhardt.net/man_page_howto.html"
9131 name="Man-Page-HOWTO">,
9132 <manref name="man" section="7">, the examples
9133 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9134 the helper program <prgn>help2man</prgn>, or the
9135 directory <file>/usr/share/doc/man-db/examples</file>.
9140 You may forward a complaint about a missing man page to the
9141 upstream authors, and mark the bug as forwarded in the
9142 Debian bug tracking system. Even though the GNU Project do
9143 not in general consider the lack of a man page to be a bug,
9144 we do; if they tell you that they don't consider it a bug
9145 you should leave the bug in our bug tracking system open
9150 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9154 If one man page needs to be accessible via several names it
9155 is better to use a symbolic link than the <file>.so</file>
9156 feature, but there is no need to fiddle with the relevant
9157 parts of the upstream source to change from <file>.so</file> to
9158 symlinks: don't do it unless it's easy. You should not
9159 create hard links in the manual page directories, nor put
9160 absolute filenames in <file>.so</file> directives. The filename
9161 in a <file>.so</file> in a man page should be relative to the
9162 base of the man page tree (usually
9163 <file>/usr/share/man</file>). If you do not create any links
9164 (whether symlinks, hard links, or <tt>.so</tt> directives)
9165 in the file system to the alternate names of the man page,
9166 then you should not rely on <prgn>man</prgn> finding your
9167 man page under those names based solely on the information in
9168 the man page's header.<footnote>
9169 Supporting this in <prgn>man</prgn> often requires
9170 unreasonable processing time to find a manual page or to
9171 report that none exists, and moves knowledge into man's
9172 database that would be better left in the file system.
9173 This support is therefore deprecated and will cease to
9174 be present in the future.
9179 Manual pages in locale-specific subdirectories of
9180 <file>/usr/share/man</file> should use either UTF-8 or the usual
9181 legacy encoding for that language (normally the one corresponding
9182 to the shortest relevant locale name in
9183 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9184 <file>/usr/share/man/fr</file> should use either UTF-8 or
9185 ISO-8859-1.<footnote>
9186 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9187 use. In future, all manual pages will be required to use
9193 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9194 included in the subdirectory name unless it indicates a
9195 significant difference in the language, as this excludes
9196 speakers of the language in other countries.<footnote>
9197 At the time of writing, Chinese and Portuguese are the main
9198 languages with such differences, so <file>pt_BR</file>,
9199 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9204 If a localized version of a manual page is provided, it should
9205 either be up-to-date or it should be obvious to the reader that
9206 it is outdated and the original manual page should be used
9207 instead. This can be done either by a note at the beginning of
9208 the manual page or by showing the missing or changed portions in
9209 the original language instead of the target language.
9214 <heading>Info documents</heading>
9217 Info documents should be installed in <file>/usr/share/info</file>.
9218 They should be compressed with <tt>gzip -9</tt>.
9222 The <prgn>install-info</prgn> program maintains a directory of
9223 installed info documents in <file>/usr/share/info/dir</file> for
9224 the use of info readers.<footnote>
9225 It was previously necessary for packages installing info
9226 documents to run <prgn>install-info</prgn> from maintainer
9227 scripts. This is no longer necessary. The installation
9228 system now uses dpkg triggers.
9230 This file must not be included in packages. Packages containing
9231 info documents should depend on <tt>dpkg (>= 1.15.4) |
9232 install-info</tt> to ensure that the directory file is properly
9233 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9238 Info documents should contain section and directory entry
9239 information in the document for the use
9240 of <prgn>install-info</prgn>. The section should be specified
9241 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9242 space and the section of this info page. The directory entry or
9243 entries should be included between
9244 a <tt>START-INFO-DIR-ENTRY</tt> line and
9245 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9247 INFO-DIR-SECTION Individual utilities
9248 START-INFO-DIR-ENTRY
9249 * example: (example). An example info directory entry.
9252 To determine which section to use, you should look
9253 at <file>/usr/share/info/dir</file> on your system and choose
9254 the most relevant (or create a new section if none of the
9255 current sections are relevant).<footnote>
9256 Normally, info documents are generated from Texinfo source.
9257 To include this information in the generated info document, if
9258 it is absent, add commands like:
9260 @dircategory Individual utilities
9262 * example: (example). An example info directory entry.
9265 to the Texinfo source of the document and ensure that the info
9266 documents are rebuilt from source during the package build.
9272 <heading>Additional documentation</heading>
9275 Any additional documentation that comes with the package may
9276 be installed at the discretion of the package maintainer.
9277 Plain text documentation should be installed in the directory
9278 <file>/usr/share/doc/<var>package</var></file>, where
9279 <var>package</var> is the name of the package, and
9280 compressed with <tt>gzip -9</tt> unless it is small.
9284 If a package comes with large amounts of documentation which
9285 many users of the package will not require you should create
9286 a separate binary package to contain it, so that it does not
9287 take up disk space on the machines of users who do not need
9288 or want it installed.</p>
9291 It is often a good idea to put text information files
9292 (<file>README</file>s, changelogs, and so forth) that come with
9293 the source package in <file>/usr/share/doc/<var>package</var></file>
9294 in the binary package. However, you don't need to install
9295 the instructions for building and installing the package, of
9299 Packages must not require the existence of any files in
9300 <file>/usr/share/doc/</file> in order to function
9302 The system administrator should be able to
9303 delete files in <file>/usr/share/doc/</file> without causing
9304 any programs to break.
9306 Any files that are referenced by programs but are also
9307 useful as stand alone documentation should be installed under
9308 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9309 <file>/usr/share/doc/<var>package</var></file>.
9313 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9314 link to another directory in <file>/usr/share/doc</file> only if
9315 the two packages both come from the same source and the
9316 first package Depends on the second.<footnote>
9318 Please note that this does not override the section on
9319 changelog files below, so the file
9320 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9321 must refer to the changelog for the current version of
9322 <var>package</var> in question. In practice, this means
9323 that the sources of the target and the destination of the
9324 symlink must be the same (same source package and
9331 Former Debian releases placed all additional documentation
9332 in <file>/usr/doc/<var>package</var></file>. This has been
9333 changed to <file>/usr/share/doc/<var>package</var></file>,
9334 and packages must not put documentation in the directory
9335 <file>/usr/doc/<var>package</var></file>. <footnote>
9336 At this phase of the transition, we no longer require a
9337 symbolic link in <file>/usr/doc/</file>. At a later point,
9338 policy shall change to make the symbolic links a bug.
9344 <heading>Preferred documentation formats</heading>
9347 The unification of Debian documentation is being carried out
9351 If your package comes with extensive documentation in a
9352 markup format that can be converted to various other formats
9353 you should if possible ship HTML versions in a binary
9354 package, in the directory
9355 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9356 its subdirectories.<footnote>
9357 The rationale: The important thing here is that HTML
9358 docs should be available in <em>some</em> package, not
9359 necessarily in the main binary package.
9364 Other formats such as PostScript may be provided at the
9365 package maintainer's discretion.
9369 <sect id="copyrightfile">
9370 <heading>Copyright information</heading>
9373 Every package must be accompanied by a verbatim copy of its
9374 copyright information and distribution license in the file
9375 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9376 file must neither be compressed nor be a symbolic link.
9380 In addition, the copyright file must say where the upstream
9381 sources (if any) were obtained. It should name the original
9382 authors of the package and the Debian maintainer(s) who were
9383 involved with its creation.
9387 Packages in the <em>contrib</em> or <em>non-free</em> archive
9388 areas should state in the copyright file that the package is not
9389 part of the Debian GNU/Linux distribution and briefly explain
9394 A copy of the file which will be installed in
9395 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9396 be in <file>debian/copyright</file> in the source package.
9400 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9401 link to another directory in <file>/usr/share/doc</file> only if
9402 the two packages both come from the same source and the
9403 first package Depends on the second. These rules are
9404 important because copyrights must be extractable by
9409 Packages distributed under the Apache license (version 2.0), the
9410 Artistic license, the GNU GPL (version 2 or 3), the GNU LGPL
9411 (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or 1.3)
9412 should refer to the corresponding files
9413 under <file>/usr/share/common-licenses</file>,<footnote>
9416 <file>/usr/share/common-licenses/Apache-2.0</file>,
9417 <file>/usr/share/common-licenses/Artistic</file>,
9418 <file>/usr/share/common-licenses/GPL-2</file>,
9419 <file>/usr/share/common-licenses/GPL-3</file>,
9420 <file>/usr/share/common-licenses/LGPL-2</file>,
9421 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9422 <file>/usr/share/common-licenses/LGPL-3</file>,
9423 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9424 <file>/usr/share/common-licenses/GFDL-1.3</file>
9425 respectively. The University of California BSD license is
9426 also included in <package>base-files</package> as
9427 <file>/usr/share/common-licenses/BSD</file>, but given the
9428 brevity of this license, its specificity to code whose
9429 copyright is held by the Regents of the University of
9430 California, and the frequency of minor wording changes, its
9431 text should be included in the copyright file rather than
9432 referencing this file.
9434 </footnote> rather than quoting them in the copyright
9439 You should not use the copyright file as a general <file>README</file>
9440 file. If your package has such a file it should be
9441 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9442 <file>README.Debian</file> or some other appropriate place.</p>
9446 <heading>Examples</heading>
9449 Any examples (configurations, source files, whatever),
9450 should be installed in a directory
9451 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9452 files should not be referenced by any program: they're there
9453 for the benefit of the system administrator and users as
9454 documentation only. Architecture-specific example files
9455 should be installed in a directory
9456 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9458 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9459 latter directory itself may be a symbolic link to the
9464 If the purpose of a package is to provide examples, then the
9465 example files may be installed into
9466 <file>/usr/share/doc/<var>package</var></file>.
9470 <sect id="changelogs">
9471 <heading>Changelog files</heading>
9474 Packages that are not Debian-native must contain a
9475 compressed copy of the <file>debian/changelog</file> file from
9476 the Debian source tree in
9477 <file>/usr/share/doc/<var>package</var></file> with the name
9478 <file>changelog.Debian.gz</file>.
9482 If an upstream changelog is available, it should be accessible as
9483 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9484 plain text. If the upstream changelog is distributed in
9485 HTML, it should be made available in that form as
9486 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9487 and a plain text <file>changelog.gz</file> should be generated
9488 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9489 the upstream changelog files do not already conform to this
9490 naming convention, then this may be achieved either by
9491 renaming the files, or by adding a symbolic link, at the
9492 maintainer's discretion.<footnote>
9493 Rationale: People should not have to look in places for
9494 upstream changelogs merely because they are given
9495 different names or are distributed in HTML format.
9500 All of these files should be installed compressed using
9501 <tt>gzip -9</tt>, as they will become large with time even
9502 if they start out small.
9506 If the package has only one changelog which is used both as
9507 the Debian changelog and the upstream one because there is
9508 no separate upstream maintainer then that changelog should
9509 usually be installed as
9510 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9511 there is a separate upstream maintainer, but no upstream
9512 changelog, then the Debian changelog should still be called
9513 <file>changelog.Debian.gz</file>.
9517 For details about the format and contents of the Debian
9518 changelog file, please see <ref id="dpkgchangelog">.
9523 <appendix id="pkg-scope">
9524 <heading>Introduction and scope of these appendices</heading>
9527 These appendices are taken essentially verbatim from the
9528 now-deprecated Packaging Manual, version 3.2.1.0. They are
9529 the chapters which are likely to be of use to package
9530 maintainers and which have not already been included in the
9531 policy document itself. Most of these sections are very likely
9532 not relevant to policy; they should be treated as
9533 documentation for the packaging system. Please note that these
9534 appendices are included for convenience, and for historical
9535 reasons: they used to be part of policy package, and they have
9536 not yet been incorporated into dpkg documentation. However,
9537 they still have value, and hence they are presented here.
9541 They have not yet been checked to ensure that they are
9542 compatible with the contents of policy, and if there are any
9543 contradictions, the version in the main policy document takes
9544 precedence. The remaining chapters of the old Packaging
9545 Manual have also not been read in detail to ensure that there
9546 are not parts which have been left out. Both of these will be
9551 Certain parts of the Packaging manual were integrated into the
9552 Policy Manual proper, and removed from the appendices. Links
9553 have been placed from the old locations to the new ones.
9557 <prgn>dpkg</prgn> is a suite of programs for creating binary
9558 package files and installing and removing them on Unix
9560 <prgn>dpkg</prgn> is targeted primarily at Debian
9561 GNU/Linux, but may work on or be ported to other
9567 The binary packages are designed for the management of
9568 installed executable programs (usually compiled binaries) and
9569 their associated data, though source code examples and
9570 documentation are provided as part of some packages.</p>
9573 This manual describes the technical aspects of creating Debian
9574 binary packages (<file>.deb</file> files). It documents the
9575 behavior of the package management programs
9576 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9577 they interact with packages.</p>
9580 It also documents the interaction between
9581 <prgn>dselect</prgn>'s core and the access method scripts it
9582 uses to actually install the selected packages, and describes
9583 how to create a new access method.</p>
9586 This manual does not go into detail about the options and
9587 usage of the package building and installation tools. It
9588 should therefore be read in conjunction with those programs'
9593 The utility programs which are provided with <prgn>dpkg</prgn>
9594 for managing various system configuration and similar issues,
9595 such as <prgn>update-rc.d</prgn> and
9596 <prgn>install-info</prgn>, are not described in detail here -
9597 please see their man pages.
9601 It is assumed that the reader is reasonably familiar with the
9602 <prgn>dpkg</prgn> System Administrators' manual.
9603 Unfortunately this manual does not yet exist.
9607 The Debian version of the FSF's GNU hello program is provided
9608 as an example for people wishing to create Debian
9609 packages. The Debian <prgn>debmake</prgn> package is
9610 recommended as a very helpful tool in creating and maintaining
9611 Debian packages. However, while the tools and examples are
9612 helpful, they do not replace the need to read and follow the
9613 Policy and Programmer's Manual.</p>
9616 <appendix id="pkg-binarypkg">
9617 <heading>Binary packages (from old Packaging Manual)</heading>
9620 The binary package has two main sections. The first part
9621 consists of various control information files and scripts used
9622 by <prgn>dpkg</prgn> when installing and removing. See <ref
9623 id="pkg-controlarea">.
9627 The second part is an archive containing the files and
9628 directories to be installed.
9632 In the future binary packages may also contain other
9633 components, such as checksums and digital signatures. The
9634 format for the archive is described in full in the
9635 <file>deb(5)</file> man page.
9639 <sect id="pkg-bincreating"><heading>Creating package files -
9640 <prgn>dpkg-deb</prgn>
9644 All manipulation of binary package files is done by
9645 <prgn>dpkg-deb</prgn>; it's the only program that has
9646 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9647 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9648 will spot that the options requested are appropriate to
9649 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9654 In order to create a binary package you must make a
9655 directory tree which contains all the files and directories
9656 you want to have in the file system data part of the package.
9657 In Debian-format source packages this directory is usually
9658 <file>debian/tmp</file>, relative to the top of the package's
9663 They should have the locations (relative to the root of the
9664 directory tree you're constructing) ownerships and
9665 permissions which you want them to have on the system when
9670 With current versions of <prgn>dpkg</prgn> the uid/username
9671 and gid/groupname mappings for the users and groups being
9672 used should be the same on the system where the package is
9673 built and the one where it is installed.
9677 You need to add one special directory to the root of the
9678 miniature file system tree you're creating:
9679 <prgn>DEBIAN</prgn>. It should contain the control
9680 information files, notably the binary package control file
9681 (see <ref id="pkg-controlfile">).
9685 The <prgn>DEBIAN</prgn> directory will not appear in the
9686 file system archive of the package, and so won't be installed
9687 by <prgn>dpkg</prgn> when the package is installed.
9691 When you've prepared the package, you should invoke:
9693 dpkg --build <var>directory</var>
9698 This will build the package in
9699 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9700 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9701 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9706 See the man page <manref name="dpkg-deb" section="8"> for details of how
9707 to examine the contents of this newly-created file. You may find the
9708 output of following commands enlightening:
9710 dpkg-deb --info <var>filename</var>.deb
9711 dpkg-deb --contents <var>filename</var>.deb
9712 dpkg --contents <var>filename</var>.deb
9714 To view the copyright file for a package you could use this command:
9716 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9721 <sect id="pkg-controlarea">
9722 <heading>Package control information files</heading>
9725 The control information portion of a binary package is a
9726 collection of files with names known to <prgn>dpkg</prgn>.
9727 It will treat the contents of these files specially - some
9728 of them contain information used by <prgn>dpkg</prgn> when
9729 installing or removing the package; others are scripts which
9730 the package maintainer wants <prgn>dpkg</prgn> to run.
9734 It is possible to put other files in the package control
9735 area, but this is not generally a good idea (though they
9736 will largely be ignored).
9740 Here is a brief list of the control info files supported by
9741 <prgn>dpkg</prgn> and a summary of what they're used for.
9746 <tag><tt>control</tt>
9749 This is the key description file used by
9750 <prgn>dpkg</prgn>. It specifies the package's name
9751 and version, gives its description for the user,
9752 states its relationships with other packages, and so
9753 forth. See <ref id="sourcecontrolfiles"> and
9754 <ref id="binarycontrolfiles">.
9758 It is usually generated automatically from information
9759 in the source package by the
9760 <prgn>dpkg-gencontrol</prgn> program, and with
9761 assistance from <prgn>dpkg-shlibdeps</prgn>.
9762 See <ref id="pkg-sourcetools">.
9766 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9771 These are executable files (usually scripts) which
9772 <prgn>dpkg</prgn> runs during installation, upgrade
9773 and removal of packages. They allow the package to
9774 deal with matters which are particular to that package
9775 or require more complicated processing than that
9776 provided by <prgn>dpkg</prgn>. Details of when and
9777 how they are called are in <ref id="maintainerscripts">.
9781 It is very important to make these scripts idempotent.
9782 See <ref id="idempotency">.
9786 The maintainer scripts are not guaranteed to run with a
9787 controlling terminal and may not be able to interact with
9788 the user. See <ref id="controllingterminal">.
9792 <tag><tt>conffiles</tt>
9795 This file contains a list of configuration files which
9796 are to be handled automatically by <prgn>dpkg</prgn>
9797 (see <ref id="pkg-conffiles">). Note that not necessarily
9798 every configuration file should be listed here.
9801 <tag><tt>shlibs</tt>
9804 This file contains a list of the shared libraries
9805 supplied by the package, with dependency details for
9806 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9807 when it determines what dependencies are required in a
9808 package control file. The <tt>shlibs</tt> file format
9809 is described on <ref id="shlibs">.
9814 <sect id="pkg-controlfile">
9815 <heading>The main control information file: <tt>control</tt></heading>
9818 The most important control information file used by
9819 <prgn>dpkg</prgn> when it installs a package is
9820 <tt>control</tt>. It contains all the package's "vital
9825 The binary package control files of packages built from
9826 Debian sources are made by a special tool,
9827 <prgn>dpkg-gencontrol</prgn>, which reads
9828 <file>debian/control</file> and <file>debian/changelog</file> to
9829 find the information it needs. See <ref id="pkg-sourcepkg"> for
9834 The fields in binary package control files are listed in
9835 <ref id="binarycontrolfiles">.
9839 A description of the syntax of control files and the purpose
9840 of the fields is available in <ref id="controlfields">.
9845 <heading>Time Stamps</heading>
9848 See <ref id="timestamps">.
9853 <appendix id="pkg-sourcepkg">
9854 <heading>Source packages (from old Packaging Manual) </heading>
9857 The Debian binary packages in the distribution are generated
9858 from Debian sources, which are in a special format to assist
9859 the easy and automatic building of binaries.
9862 <sect id="pkg-sourcetools">
9863 <heading>Tools for processing source packages</heading>
9866 Various tools are provided for manipulating source packages;
9867 they pack and unpack sources and help build of binary
9868 packages and help manage the distribution of new versions.
9872 They are introduced and typical uses described here; see
9873 <manref name="dpkg-source" section="1"> for full
9874 documentation about their arguments and operation.
9878 For examples of how to construct a Debian source package,
9879 and how to use those utilities that are used by Debian
9880 source packages, please see the <prgn>hello</prgn> example
9884 <sect1 id="pkg-dpkg-source">
9886 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9891 This program is frequently used by hand, and is also
9892 called from package-independent automated building scripts
9893 such as <prgn>dpkg-buildpackage</prgn>.
9897 To unpack a package it is typically invoked with
9899 dpkg-source -x <var>.../path/to/filename</var>.dsc
9904 with the <file><var>filename</var>.tar.gz</file> and
9905 <file><var>filename</var>.diff.gz</file> (if applicable) in
9906 the same directory. It unpacks into
9907 <file><var>package</var>-<var>version</var></file>, and if
9909 <file><var>package</var>-<var>version</var>.orig</file>, in
9910 the current directory.
9914 To create a packed source archive it is typically invoked:
9916 dpkg-source -b <var>package</var>-<var>version</var>
9921 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9922 <file>.diff.gz</file> (if appropriate) in the current
9923 directory. <prgn>dpkg-source</prgn> does not clean the
9924 source tree first - this must be done separately if it is
9929 See also <ref id="pkg-sourcearchives">.</p>
9933 <sect1 id="pkg-dpkg-buildpackage">
9935 <prgn>dpkg-buildpackage</prgn> - overall package-building
9940 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9941 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9942 targets <tt>clean</tt>, <tt>build</tt> and
9943 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9944 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9945 source and binary package upload.
9949 It is usually invoked by hand from the top level of the
9950 built or unbuilt source directory. It may be invoked with
9951 no arguments; useful arguments include:
9952 <taglist compact="compact">
9953 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9956 Do not sign the <tt>.changes</tt> file or the
9957 source package <tt>.dsc</tt> file, respectively.</p>
9959 <tag><tt>-p<var>sign-command</var></tt></tag>
9962 Invoke <var>sign-command</var> instead of finding
9963 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9964 <var>sign-command</var> must behave just like
9965 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9967 <tag><tt>-r<var>root-command</var></tt></tag>
9970 When root privilege is required, invoke the command
9971 <var>root-command</var>. <var>root-command</var>
9972 should invoke its first argument as a command, from
9973 the <prgn>PATH</prgn> if necessary, and pass its
9974 second and subsequent arguments to the command it
9975 calls. If no <var>root-command</var> is supplied
9976 then <var>dpkg-buildpackage</var> will take no
9977 special action to gain root privilege, so that for
9978 most packages it will have to be invoked as root to
9981 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9984 Two types of binary-only build and upload - see
9985 <manref name="dpkg-source" section="1">.
9992 <sect1 id="pkg-dpkg-gencontrol">
9994 <prgn>dpkg-gencontrol</prgn> - generates binary package
9999 This program is usually called from <file>debian/rules</file>
10000 (see <ref id="pkg-sourcetree">) in the top level of the source
10005 This is usually done just before the files and directories in the
10006 temporary directory tree where the package is being built have their
10007 permissions and ownerships set and the package is constructed using
10008 <prgn>dpkg-deb/</prgn>
10010 This is so that the control file which is produced has
10011 the right permissions
10016 <prgn>dpkg-gencontrol</prgn> must be called after all the
10017 files which are to go into the package have been placed in
10018 the temporary build directory, so that its calculation of
10019 the installed size of a package is correct.
10023 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10024 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10025 variable substitutions created by
10026 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10031 For a package which generates only one binary package, and
10032 which builds it in <file>debian/tmp</file> relative to the top
10033 of the source package, it is usually sufficient to call
10034 <prgn>dpkg-gencontrol</prgn>.
10038 Sources which build several binaries will typically need
10041 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10042 </example> The <tt>-P</tt> tells
10043 <prgn>dpkg-gencontrol</prgn> that the package is being
10044 built in a non-default directory, and the <tt>-p</tt>
10045 tells it which package's control file should be generated.
10049 <prgn>dpkg-gencontrol</prgn> also adds information to the
10050 list of files in <file>debian/files</file>, for the benefit of
10051 (for example) a future invocation of
10052 <prgn>dpkg-genchanges</prgn>.</p>
10055 <sect1 id="pkg-dpkg-shlibdeps">
10057 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10062 This program is usually called from <file>debian/rules</file>
10063 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10064 id="pkg-sourcetree">), in the top level of the source tree.
10068 Its arguments are executables and shared libraries
10071 They may be specified either in the locations in the
10072 source tree where they are created or in the locations
10073 in the temporary build tree where they are installed
10074 prior to binary package creation.
10076 </footnote> for which shared library dependencies should
10077 be included in the binary package's control file.
10081 If some of the found shared libraries should only
10082 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10083 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10084 by using the <tt>-d<var>dependency-field</var></tt> option
10085 before those executable(s). (Each <tt>-d</tt> option
10086 takes effect until the next <tt>-d</tt>.)
10090 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10091 output control file to be modified. Instead by default it
10092 adds to the <file>debian/substvars</file> file variable
10093 settings like <tt>shlibs:Depends</tt>. These variable
10094 settings must be referenced in dependency fields in the
10095 appropriate per-binary-package sections of the source
10100 For example, a package that generates an essential part
10101 which requires dependencies, and optional parts that
10102 which only require a recommendation, would separate those
10103 two sets of dependencies into two different fields.<footnote>
10104 At the time of writing, an example for this was the
10105 <package/xmms/ package, with Depends used for the xmms
10106 executable, Recommends for the plug-ins and Suggests for
10107 even more optional features provided by unzip.
10109 It can say in its <file>debian/rules</file>:
10111 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10112 -dRecommends <var>optionalpart anotheroptionalpart</var>
10114 and then in its main control file <file>debian/control</file>:
10117 Depends: ${shlibs:Depends}
10118 Recommends: ${shlibs:Recommends}
10124 Sources which produce several binary packages with
10125 different shared library dependency requirements can use
10126 the <tt>-p<var>varnameprefix</var></tt> option to override
10127 the default <tt>shlibs:</tt> prefix (one invocation of
10128 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10129 They can thus produce several sets of dependency
10130 variables, each of the form
10131 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10132 which can be referred to in the appropriate parts of the
10133 binary package control files.
10138 <sect1 id="pkg-dpkg-distaddfile">
10140 <prgn>dpkg-distaddfile</prgn> - adds a file to
10141 <file>debian/files</file>
10145 Some packages' uploads need to include files other than
10146 the source and binary package files.
10150 <prgn>dpkg-distaddfile</prgn> adds a file to the
10151 <file>debian/files</file> file so that it will be included in
10152 the <file>.changes</file> file when
10153 <prgn>dpkg-genchanges</prgn> is run.
10157 It is usually invoked from the <tt>binary</tt> target of
10158 <file>debian/rules</file>:
10160 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10162 The <var>filename</var> is relative to the directory where
10163 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10164 is usually the directory above the top level of the source
10165 tree. The <file>debian/rules</file> target should put the
10166 file there just before or just after calling
10167 <prgn>dpkg-distaddfile</prgn>.
10171 The <var>section</var> and <var>priority</var> are passed
10172 unchanged into the resulting <file>.changes</file> file.
10177 <sect1 id="pkg-dpkg-genchanges">
10179 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10180 upload control file
10184 This program is usually called by package-independent
10185 automatic building scripts such as
10186 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10191 It is usually called in the top level of a built source
10192 tree, and when invoked with no arguments will print out a
10193 straightforward <file>.changes</file> file based on the
10194 information in the source package's changelog and control
10195 file and the binary and source packages which should have
10201 <sect1 id="pkg-dpkg-parsechangelog">
10203 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10204 representation of a changelog
10208 This program is used internally by
10209 <prgn>dpkg-source</prgn> et al. It may also occasionally
10210 be useful in <file>debian/rules</file> and elsewhere. It
10211 parses a changelog, <file>debian/changelog</file> by default,
10212 and prints a control-file format representation of the
10213 information in it to standard output.
10217 <sect1 id="pkg-dpkg-architecture">
10219 <prgn>dpkg-architecture</prgn> - information about the build and
10224 This program can be used manually, but is also invoked by
10225 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10226 environment or make variables which specify the build and host
10227 architecture for the package building process.
10232 <sect id="pkg-sourcetree">
10233 <heading>The Debian package source tree</heading>
10236 The source archive scheme described later is intended to
10237 allow a Debian package source tree with some associated
10238 control information to be reproduced and transported easily.
10239 The Debian package source tree is a version of the original
10240 program with certain files added for the benefit of the
10241 packaging process, and with any other changes required
10242 made to the rest of the source code and installation
10247 The extra files created for Debian are in the subdirectory
10248 <file>debian</file> of the top level of the Debian package
10249 source tree. They are described below.
10252 <sect1 id="pkg-debianrules">
10253 <heading><file>debian/rules</file> - the main building script</heading>
10256 See <ref id="debianrules">.
10260 <sect1 id="pkg-srcsubstvars">
10261 <heading><file>debian/substvars</file> and variable substitutions</heading>
10264 See <ref id="substvars">.
10270 <heading><file>debian/files</file></heading>
10273 See <ref id="debianfiles">.
10277 <sect1><heading><file>debian/tmp</file>
10281 This is the canonical temporary location for the
10282 construction of binary packages by the <tt>binary</tt>
10283 target. The directory <file>tmp</file> serves as the root of
10284 the file system tree as it is being constructed (for
10285 example, by using the package's upstream makefiles install
10286 targets and redirecting the output there), and it also
10287 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10288 id="pkg-bincreating">.
10292 If several binary packages are generated from the same
10293 source tree it is usual to use several
10294 <file>debian/tmp<var>something</var></file> directories, for
10295 example <file>tmp-a</file> or <file>tmp-doc</file>.
10299 Whatever <file>tmp</file> directories are created and used by
10300 <tt>binary</tt> must of course be removed by the
10301 <tt>clean</tt> target.</p></sect1>
10305 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10309 As it exists on the FTP site, a Debian source package
10310 consists of three related files. You must have the right
10311 versions of all three to be able to use them.
10316 <tag>Debian source control file - <tt>.dsc</tt></tag>
10318 This file is a control file used by <prgn>dpkg-source</prgn>
10319 to extract a source package.
10320 See <ref id="debiansourcecontrolfiles">.
10324 Original source archive -
10326 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10332 This is a compressed (with <tt>gzip -9</tt>)
10333 <prgn>tar</prgn> file containing the source code from
10334 the upstream authors of the program.
10339 Debian package diff -
10341 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10347 This is a unified context diff (<tt>diff -u</tt>)
10348 giving the changes which are required to turn the
10349 original source into the Debian source. These changes
10350 may only include editing and creating plain files.
10351 The permissions of files, the targets of symbolic
10352 links and the characteristics of special files or
10353 pipes may not be changed and no files may be removed
10358 All the directories in the diff must exist, except the
10359 <file>debian</file> subdirectory of the top of the source
10360 tree, which will be created by
10361 <prgn>dpkg-source</prgn> if necessary when unpacking.
10365 The <prgn>dpkg-source</prgn> program will
10366 automatically make the <file>debian/rules</file> file
10367 executable (see below).</p></item>
10372 If there is no original source code - for example, if the
10373 package is specially prepared for Debian or the Debian
10374 maintainer is the same as the upstream maintainer - the
10375 format is slightly different: then there is no diff, and the
10377 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10378 and preferably contains a directory named
10379 <file><var>package</var>-<var>version</var></file>.
10384 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10387 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10388 Debian source package. However, if it is not available it
10389 is possible to unpack a Debian source archive as follows:
10390 <enumlist compact="compact">
10393 Untar the tarfile, which will create a <file>.orig</file>
10397 <p>Rename the <file>.orig</file> directory to
10398 <file><var>package</var>-<var>version</var></file>.</p>
10402 Create the subdirectory <file>debian</file> at the top of
10403 the source tree.</p>
10405 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10407 <item><p>Untar the tarfile again if you want a copy of the original
10408 source code alongside the Debian version.</p>
10413 It is not possible to generate a valid Debian source archive
10414 without using <prgn>dpkg-source</prgn>. In particular,
10415 attempting to use <prgn>diff</prgn> directly to generate the
10416 <file>.diff.gz</file> file will not work.
10420 <heading>Restrictions on objects in source packages</heading>
10423 The source package may not contain any hard links
10425 This is not currently detected when building source
10426 packages, but only when extracting
10430 Hard links may be permitted at some point in the
10431 future, but would require a fair amount of
10433 </footnote>, device special files, sockets or setuid or
10436 Setgid directories are allowed.
10441 The source packaging tools manage the changes between the
10442 original and Debian source using <prgn>diff</prgn> and
10443 <prgn>patch</prgn>. Turning the original source tree as
10444 included in the <file>.orig.tar.gz</file> into the Debian
10445 package source must not involve any changes which cannot be
10446 handled by these tools. Problematic changes which cause
10447 <prgn>dpkg-source</prgn> to halt with an error when
10448 building the source package are:
10449 <list compact="compact">
10450 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10452 <item><p>Changing the targets of symbolic links.</p>
10454 <item><p>Creating directories, other than <file>debian</file>.</p>
10456 <item><p>Changes to the contents of binary files.</p></item>
10457 </list> Changes which cause <prgn>dpkg-source</prgn> to
10458 print a warning but continue anyway are:
10459 <list compact="compact">
10462 Removing files, directories or symlinks.
10464 Renaming a file is not treated specially - it is
10465 seen as the removal of the old file (which
10466 generates a warning, but is otherwise ignored),
10467 and the creation of the new one.
10473 Changed text files which are missing the usual final
10474 newline (either in the original or the modified
10479 Changes which are not represented, but which are not detected by
10480 <prgn>dpkg-source</prgn>, are:
10481 <list compact="compact">
10482 <item><p>Changing the permissions of files (other than
10483 <file>debian/rules</file>) and directories.</p></item>
10488 The <file>debian</file> directory and <file>debian/rules</file>
10489 are handled specially by <prgn>dpkg-source</prgn> - before
10490 applying the changes it will create the <file>debian</file>
10491 directory, and afterwards it will make
10492 <file>debian/rules</file> world-executable.
10498 <appendix id="pkg-controlfields">
10499 <heading>Control files and their fields (from old Packaging Manual)</heading>
10502 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10503 data in a common format, known as control files. Binary and
10504 source packages have control data as do the <file>.changes</file>
10505 files which control the installation of uploaded files, and
10506 <prgn>dpkg</prgn>'s internal databases are in a similar
10511 <heading>Syntax of control files</heading>
10514 See <ref id="controlsyntax">.
10518 It is important to note that there are several fields which
10519 are optional as far as <prgn>dpkg</prgn> and the related
10520 tools are concerned, but which must appear in every Debian
10521 package, or whose omission may cause problems.
10526 <heading>List of fields</heading>
10529 See <ref id="controlfieldslist">.
10533 This section now contains only the fields that didn't belong
10534 to the Policy manual.
10537 <sect1 id="pkg-f-Filename">
10538 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10541 These fields in <tt>Packages</tt> files give the
10542 filename(s) of (the parts of) a package in the
10543 distribution directories, relative to the root of the
10544 Debian hierarchy. If the package has been split into
10545 several parts the parts are all listed in order, separated
10550 <sect1 id="pkg-f-Size">
10551 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10554 These fields in <file>Packages</file> files give the size (in
10555 bytes, expressed in decimal) and MD5 checksum of the
10556 file(s) which make(s) up a binary package in the
10557 distribution. If the package is split into several parts
10558 the values for the parts are listed in order, separated by
10563 <sect1 id="pkg-f-Status">
10564 <heading><tt>Status</tt></heading>
10567 This field in <prgn>dpkg</prgn>'s status file records
10568 whether the user wants a package installed, removed or
10569 left alone, whether it is broken (requiring
10570 re-installation) or not and what its current state on the
10571 system is. Each of these pieces of information is a
10576 <sect1 id="pkg-f-Config-Version">
10577 <heading><tt>Config-Version</tt></heading>
10580 If a package is not installed or not configured, this
10581 field in <prgn>dpkg</prgn>'s status file records the last
10582 version of the package which was successfully
10587 <sect1 id="pkg-f-Conffiles">
10588 <heading><tt>Conffiles</tt></heading>
10591 This field in <prgn>dpkg</prgn>'s status file contains
10592 information about the automatically-managed configuration
10593 files held by a package. This field should <em>not</em>
10594 appear anywhere in a package!
10599 <heading>Obsolete fields</heading>
10602 These are still recognized by <prgn>dpkg</prgn> but should
10603 not appear anywhere any more.
10605 <taglist compact="compact">
10607 <tag><tt>Revision</tt></tag>
10608 <tag><tt>Package-Revision</tt></tag>
10609 <tag><tt>Package_Revision</tt></tag>
10611 The Debian revision part of the package version was
10612 at one point in a separate control file field. This
10613 field went through several names.
10616 <tag><tt>Recommended</tt></tag>
10617 <item>Old name for <tt>Recommends</tt>.</item>
10619 <tag><tt>Optional</tt></tag>
10620 <item>Old name for <tt>Suggests</tt>.</item>
10622 <tag><tt>Class</tt></tag>
10623 <item>Old name for <tt>Priority</tt>.</item>
10632 <appendix id="pkg-conffiles">
10633 <heading>Configuration file handling (from old Packaging Manual)</heading>
10636 <prgn>dpkg</prgn> can do a certain amount of automatic
10637 handling of package configuration files.
10641 Whether this mechanism is appropriate depends on a number of
10642 factors, but basically there are two approaches to any
10643 particular configuration file.
10647 The easy method is to ship a best-effort configuration in the
10648 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10649 handle updates. If the user is unlikely to want to edit the
10650 file, but you need them to be able to without losing their
10651 changes, and a new package with a changed version of the file
10652 is only released infrequently, this is a good approach.
10656 The hard method is to build the configuration file from
10657 scratch in the <prgn>postinst</prgn> script, and to take the
10658 responsibility for fixing any mistakes made in earlier
10659 versions of the package automatically. This will be
10660 appropriate if the file is likely to need to be different on
10664 <sect><heading>Automatic handling of configuration files by
10669 A package may contain a control area file called
10670 <tt>conffiles</tt>. This file should be a list of filenames
10671 of configuration files needing automatic handling, separated
10672 by newlines. The filenames should be absolute pathnames,
10673 and the files referred to should actually exist in the
10678 When a package is upgraded <prgn>dpkg</prgn> will process
10679 the configuration files during the configuration stage,
10680 shortly before it runs the package's <prgn>postinst</prgn>
10685 For each file it checks to see whether the version of the
10686 file included in the package is the same as the one that was
10687 included in the last version of the package (the one that is
10688 being upgraded from); it also compares the version currently
10689 installed on the system with the one shipped with the last
10694 If neither the user nor the package maintainer has changed
10695 the file, it is left alone. If one or the other has changed
10696 their version, then the changed version is preferred - i.e.,
10697 if the user edits their file, but the package maintainer
10698 doesn't ship a different version, the user's changes will
10699 stay, silently, but if the maintainer ships a new version
10700 and the user hasn't edited it the new version will be
10701 installed (with an informative message). If both have
10702 changed their version the user is prompted about the problem
10703 and must resolve the differences themselves.
10707 The comparisons are done by calculating the MD5 message
10708 digests of the files, and storing the MD5 of the file as it
10709 was included in the most recent version of the package.
10713 When a package is installed for the first time
10714 <prgn>dpkg</prgn> will install the file that comes with it,
10715 unless that would mean overwriting a file already on the
10720 However, note that <prgn>dpkg</prgn> will <em>not</em>
10721 replace a conffile that was removed by the user (or by a
10722 script). This is necessary because with some programs a
10723 missing file produces an effect hard or impossible to
10724 achieve in another way, so that a missing file needs to be
10725 kept that way if the user did it.
10729 Note that a package should <em>not</em> modify a
10730 <prgn>dpkg</prgn>-handled conffile in its maintainer
10731 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10732 the user confusing and possibly dangerous options for
10733 conffile update when the package is upgraded.</p>
10736 <sect><heading>Fully-featured maintainer script configuration
10741 For files which contain site-specific information such as
10742 the hostname and networking details and so forth, it is
10743 better to create the file in the package's
10744 <prgn>postinst</prgn> script.
10748 This will typically involve examining the state of the rest
10749 of the system to determine values and other information, and
10750 may involve prompting the user for some information which
10751 can't be obtained some other way.
10755 When using this method there are a couple of important
10756 issues which should be considered:
10760 If you discover a bug in the program which generates the
10761 configuration file, or if the format of the file changes
10762 from one version to the next, you will have to arrange for
10763 the postinst script to do something sensible - usually this
10764 will mean editing the installed configuration file to remove
10765 the problem or change the syntax. You will have to do this
10766 very carefully, since the user may have changed the file,
10767 perhaps to fix the very problem that your script is trying
10768 to deal with - you will have to detect these situations and
10769 deal with them correctly.
10773 If you do go down this route it's probably a good idea to
10774 make the program that generates the configuration file(s) a
10775 separate program in <file>/usr/sbin</file>, by convention called
10776 <file><var>package</var>config</file> and then run that if
10777 appropriate from the post-installation script. The
10778 <tt><var>package</var>config</tt> program should not
10779 unquestioningly overwrite an existing configuration - if its
10780 mode of operation is geared towards setting up a package for
10781 the first time (rather than any arbitrary reconfiguration
10782 later) you should have it check whether the configuration
10783 already exists, and require a <tt>--force</tt> flag to
10784 overwrite it.</p></sect>
10787 <appendix id="pkg-alternatives"><heading>Alternative versions of
10788 an interface - <prgn>update-alternatives</prgn> (from old
10793 When several packages all provide different versions of the
10794 same program or file it is useful to have the system select a
10795 default, but to allow the system administrator to change it
10796 and have their decisions respected.
10800 For example, there are several versions of the <prgn>vi</prgn>
10801 editor, and there is no reason to prevent all of them from
10802 being installed at once, each under their own name
10803 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10804 Nevertheless it is desirable to have the name <tt>vi</tt>
10805 refer to something, at least by default.
10809 If all the packages involved cooperate, this can be done with
10810 <prgn>update-alternatives</prgn>.
10814 Each package provides its own version under its own name, and
10815 calls <prgn>update-alternatives</prgn> in its postinst to
10816 register its version (and again in its prerm to deregister
10821 See the man page <manref name="update-alternatives"
10822 section="8"> for details.
10826 If <prgn>update-alternatives</prgn> does not seem appropriate
10827 you may wish to consider using diversions instead.</p>
10830 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10831 package's version of a file (from old Packaging Manual)
10835 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10836 when it reinstalls the package it belongs to, and to have it
10837 put the file from the package somewhere else instead.
10841 This can be used locally to override a package's version of a
10842 file, or by one package to override another's version (or
10843 provide a wrapper for it).
10847 Before deciding to use a diversion, read <ref
10848 id="pkg-alternatives"> to see if you really want a diversion
10849 rather than several alternative versions of a program.
10853 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10854 and updated by a special program <prgn>dpkg-divert</prgn>.
10855 Please see <manref name="dpkg-divert" section="8"> for full
10856 details of its operation.
10860 When a package wishes to divert a file from another, it should
10861 call <prgn>dpkg-divert</prgn> in its preinst to add the
10862 diversion and rename the existing file. For example,
10863 supposing that a <prgn>smailwrapper</prgn> package wishes to
10864 install a wrapper around <file>/usr/sbin/smail</file>:
10866 dpkg-divert --package smailwrapper --add --rename \
10867 --divert /usr/sbin/smail.real /usr/sbin/smail
10868 </example> The <tt>--package smailwrapper</tt> ensures that
10869 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10870 can bypass the diversion and get installed as the true version.
10871 It's safe to add the diversion unconditionally on upgrades since
10872 it will be left unchanged if it already exists, but
10873 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10874 message, make the command conditional on the version from which
10875 the package is being upgraded:
10877 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10878 dpkg-divert --package smailwrapper --add --rename \
10879 --divert /usr/sbin/smail.real /usr/sbin/smail
10881 </example> where <tt>1.0-2</tt> is the version at which the
10882 diversion was first added to the package. Running the command
10883 during abort-upgrade is pointless but harmless.
10887 The postrm has to do the reverse:
10889 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10890 dpkg-divert --package smailwrapper --remove --rename \
10891 --divert /usr/sbin/smail.real /usr/sbin/smail
10893 </example> If the diversion was added at a particular version, the
10894 postrm should also handle the failure case of upgrading from an
10895 older version (unless the older version is so old that direct
10896 upgrades are no longer supported):
10898 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10899 dpkg-divert --package smailwrapper --remove --rename \
10900 --divert /usr/sbin/smail.real /usr/sbin/smail
10902 </example> where <tt>1.02-2</tt> is the version at which the
10903 diversion was first added to the package. The postrm should not
10904 remove the diversion on upgrades both because there's no reason to
10905 remove the diversion only to immediately re-add it and since the
10906 postrm of the old package is run after unpacking so the removal of
10907 the diversion will fail.
10911 Do not attempt to divert a file which is vitally important for
10912 the system's operation - when using <prgn>dpkg-divert</prgn>
10913 there is a time, after it has been diverted but before
10914 <prgn>dpkg</prgn> has installed the new version, when the file
10915 does not exist.</p>
10920 <!-- Local variables: -->
10921 <!-- indent-tabs-mode: t -->
10923 <!-- vim:set ai et sts=2 sw=2 tw=76: -->