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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 belonging
1216 to another package without consulting the maintainer of that
1217 package first. When adding or removing diversions, package
1218 maintainer scripts must provide the <tt>--package</tt> flag
1219 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1223 All packages which supply an instance of a common command
1224 name (or, in general, filename) should generally use
1225 <prgn>update-alternatives</prgn>, so that they may be
1226 installed together. If <prgn>update-alternatives</prgn>
1227 is not used, then each package must use
1228 <tt>Conflicts</tt> to ensure that other packages are
1229 de-installed. (In this case, it may be appropriate to
1230 specify a conflict against earlier versions of something
1231 that previously did not use
1232 <prgn>update-alternatives</prgn>; this is an exception to
1233 the usual rule that versioned conflicts should be
1237 <sect1 id="maintscriptprompt">
1238 <heading>Prompting in maintainer scripts</heading>
1240 Package maintainer scripts may prompt the user if
1241 necessary. Prompting must be done by communicating
1242 through a program, such as <prgn>debconf</prgn>, which
1243 conforms to the Debian Configuration Management
1244 Specification, version 2 or higher.
1248 Packages which are essential, or which are dependencies of
1249 essential packages, may fall back on another prompting method
1250 if no such interface is available when they are executed.
1254 The Debian Configuration Management Specification is included
1255 in the <file>debconf_specification</file> files in the
1256 <package>debian-policy</package> package.
1257 It is also available from the Debian web mirrors at
1258 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1259 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1263 Packages which use the Debian Configuration Management
1264 Specification may contain an additional
1265 <prgn>config</prgn> script and a <tt>templates</tt>
1266 file in their control archive<footnote>
1267 The control.tar.gz inside the .deb.
1268 See <manref name="deb" section="5">.
1270 The <prgn>config</prgn> script might be run before the
1271 <prgn>preinst</prgn> script, and before the package is unpacked
1272 or any of its dependencies or pre-dependencies are satisfied.
1273 Therefore it must work using only the tools present in
1274 <em>essential</em> packages.<footnote>
1275 <package>Debconf</package> or another tool that
1276 implements the Debian Configuration Management
1277 Specification will also be installed, and any
1278 versioned dependencies on it will be satisfied
1279 before preconfiguration begins.
1284 Packages which use the Debian Configuration Management
1285 Specification must allow for translation of their user-visible
1286 messages by using a gettext-based system such as the one
1287 provided by the <package>po-debconf</package> package.
1291 Packages should try to minimize the amount of prompting
1292 they need to do, and they should ensure that the user
1293 will only ever be asked each question once. This means
1294 that packages should try to use appropriate shared
1295 configuration files (such as <file>/etc/papersize</file> and
1296 <file>/etc/news/server</file>), and shared
1297 <package>debconf</package> variables rather than each
1298 prompting for their own list of required pieces of
1303 It also means that an upgrade should not ask the same
1304 questions again, unless the user has used
1305 <tt>dpkg --purge</tt> to remove the package's configuration.
1306 The answers to configuration questions should be stored in an
1307 appropriate place in <file>/etc</file> so that the user can
1308 modify them, and how this has been done should be
1313 If a package has a vitally important piece of
1314 information to pass to the user (such as "don't run me
1315 as I am, you must edit the following configuration files
1316 first or you risk your system emitting badly-formatted
1317 messages"), it should display this in the
1318 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1319 prompt the user to hit return to acknowledge the
1320 message. Copyright messages do not count as vitally
1321 important (they belong in
1322 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1323 neither do instructions on how to use a program (these
1324 should be in on-line documentation, where all the users
1329 Any necessary prompting should almost always be confined
1330 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1331 script. If it is done in the <prgn>postinst</prgn>, it
1332 should be protected with a conditional so that
1333 unnecessary prompting doesn't happen if a package's
1334 installation fails and the <prgn>postinst</prgn> is
1335 called with <tt>abort-upgrade</tt>,
1336 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1346 <heading>Source packages</heading>
1348 <sect id="standardsversion">
1349 <heading>Standards conformance</heading>
1352 Source packages should specify the most recent version number
1353 of this policy document with which your package complied
1354 when it was last updated.
1358 This information may be used to file bug reports
1359 automatically if your package becomes too much out of date.
1363 The version is specified in the <tt>Standards-Version</tt>
1365 The format of the <tt>Standards-Version</tt> field is
1366 described in <ref id="f-Standards-Version">.
1370 You should regularly, and especially if your package has
1371 become out of date, check for the newest Policy Manual
1372 available and update your package, if necessary. When your
1373 package complies with the new standards you should update the
1374 <tt>Standards-Version</tt> source package field and
1375 release it.<footnote>
1376 See the file <file>upgrading-checklist</file> for
1377 information about policy which has changed between
1378 different versions of this document.
1384 <sect id="pkg-relations">
1385 <heading>Package relationships</heading>
1388 Source packages should specify which binary packages they
1389 require to be installed or not to be installed in order to
1390 build correctly. For example, if building a package
1391 requires a certain compiler, then the compiler should be
1392 specified as a build-time dependency.
1396 It is not necessary to explicitly specify build-time
1397 relationships on a minimal set of packages that are always
1398 needed to compile, link and put in a Debian package a
1399 standard "Hello World!" program written in C or C++. The
1400 required packages are called <em>build-essential</em>, and
1401 an informational list can be found in
1402 <file>/usr/share/doc/build-essential/list</file> (which is
1403 contained in the <tt>build-essential</tt>
1406 <list compact="compact">
1408 This allows maintaining the list separately
1409 from the policy documents (the list does not
1410 need the kind of control that the policy
1414 Having a separate package allows one to install
1415 the build-essential packages on a machine, as
1416 well as allowing other packages such as tasks to
1417 require installation of the build-essential
1418 packages using the depends relation.
1421 The separate package allows bug reports against
1422 the list to be categorized separately from
1423 the policy management process in the BTS.
1430 When specifying the set of build-time dependencies, one
1431 should list only those packages explicitly required by the
1432 build. It is not necessary to list packages which are
1433 required merely because some other package in the list of
1434 build-time dependencies depends on them.<footnote>
1435 The reason for this is that dependencies change, and
1436 you should list all those packages, and <em>only</em>
1437 those packages that <em>you</em> need directly. What
1438 others need is their business. For example, if you
1439 only link against <file>libimlib</file>, you will need to
1440 build-depend on <package>libimlib2-dev</package> but
1441 not against any <tt>libjpeg*</tt> packages, even
1442 though <tt>libimlib2-dev</tt> currently depends on
1443 them: installation of <package>libimlib2-dev</package>
1444 will automatically ensure that all of its run-time
1445 dependencies are satisfied.
1450 If build-time dependencies are specified, it must be
1451 possible to build the package and produce working binaries
1452 on a system with only essential and build-essential
1453 packages installed and also those required to satisfy the
1454 build-time relationships (including any implied
1455 relationships). In particular, this means that version
1456 clauses should be used rigorously in build-time
1457 relationships so that one cannot produce bad or
1458 inconsistently configured packages when the relationships
1459 are properly satisfied.
1463 <ref id="relationships"> explains the technical details.
1468 <heading>Changes to the upstream sources</heading>
1471 If changes to the source code are made that are not
1472 specific to the needs of the Debian system, they should be
1473 sent to the upstream authors in whatever form they prefer
1474 so as to be included in the upstream version of the
1479 If you need to configure the package differently for
1480 Debian or for Linux, and the upstream source doesn't
1481 provide a way to do so, you should add such configuration
1482 facilities (for example, a new <prgn>autoconf</prgn> test
1483 or <tt>#define</tt>) and send the patch to the upstream
1484 authors, with the default set to the way they originally
1485 had it. You can then easily override the default in your
1486 <file>debian/rules</file> or wherever is appropriate.
1490 You should make sure that the <prgn>configure</prgn> utility
1491 detects the correct architecture specification string
1492 (refer to <ref id="arch-spec"> for details).
1496 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1497 <prgn>configure</prgn> scripts are used, you should edit the
1498 <file>.in</file> files rather than editing the
1499 <prgn>Makefile</prgn> directly. This allows the user to
1500 reconfigure the package if necessary. You should
1501 <em>not</em> configure the package and edit the generated
1502 <prgn>Makefile</prgn>! This makes it impossible for someone
1503 else to later reconfigure the package without losing the
1509 <sect id="dpkgchangelog">
1510 <heading>Debian changelog: <file>debian/changelog</file></heading>
1513 Changes in the Debian version of the package should be
1514 briefly explained in the Debian changelog file
1515 <file>debian/changelog</file>.<footnote>
1517 Mistakes in changelogs are usually best rectified by
1518 making a new changelog entry rather than "rewriting
1519 history" by editing old changelog entries.
1522 This includes modifications
1523 made in the Debian package compared to the upstream one
1524 as well as other changes and updates to the package.
1526 Although there is nothing stopping an author who is also
1527 the Debian maintainer from using this changelog for all
1528 their changes, it will have to be renamed if the Debian
1529 and upstream maintainers become different people. In such
1530 a case, however, it might be better to maintain the package
1531 as a non-native package.
1536 The format of the <file>debian/changelog</file> allows the
1537 package building tools to discover which version of the package
1538 is being built and find out other release-specific information.
1542 That format is a series of entries like this:
1544 <example compact="compact">
1545 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1547 [optional blank line(s), stripped]
1549 * <var>change details</var>
1550 <var>more change details</var>
1552 [blank line(s), included in output of dpkg-parsechangelog]
1554 * <var>even more change details</var>
1556 [optional blank line(s), stripped]
1558 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1563 <var>package</var> and <var>version</var> are the source
1564 package name and version number.
1568 <var>distribution(s)</var> lists the distributions where
1569 this version should be installed when it is uploaded - it
1570 is copied to the <tt>Distribution</tt> field in the
1571 <file>.changes</file> file. See <ref id="f-Distribution">.
1575 <var>urgency</var> is the value for the <tt>Urgency</tt>
1576 field in the <file>.changes</file> file for the upload
1577 (see <ref id="f-Urgency">). It is not possible to specify
1578 an urgency containing commas; commas are used to separate
1579 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1580 <prgn>dpkg</prgn> changelog format (though there is
1581 currently only one useful <var>keyword</var>,
1586 The change details may in fact be any series of lines
1587 starting with at least two spaces, but conventionally each
1588 change starts with an asterisk and a separating space and
1589 continuation lines are indented so as to bring them in
1590 line with the start of the text above. Blank lines may be
1591 used here to separate groups of changes, if desired.
1595 If this upload resolves bugs recorded in the Bug Tracking
1596 System (BTS), they may be automatically closed on the
1597 inclusion of this package into the Debian archive by
1598 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1599 in the change details.<footnote>
1600 To be precise, the string should match the following
1601 Perl regular expression:
1603 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1605 Then all of the bug numbers listed will be closed by the
1606 archive maintenance script (<prgn>katie</prgn>) using the
1607 <var>version</var> of the changelog entry.
1609 This information is conveyed via the <tt>Closes</tt> field
1610 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1614 The maintainer name and email address used in the changelog
1615 should be the details of the person uploading <em>this</em>
1616 version. They are <em>not</em> necessarily those of the
1617 usual package maintainer. The information here will be
1618 copied to the <tt>Changed-By</tt> field in the
1619 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1620 and then later used to send an acknowledgement when the
1621 upload has been installed.
1625 The <var>date</var> has the following format<footnote>
1626 This is the same as the format generated by <tt>date
1628 </footnote> (compatible and with the same semantics of
1629 RFC 2822 and RFC 5322):
1630 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1632 <list compact="compact">
1634 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1637 dd is a one- or two-digit day of the month (01-31)
1640 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1643 <item>yyyy is the four-digit year (e.g. 2010)</item>
1644 <item>hh is the two-digit hour (00-23)</item>
1645 <item>mm is the two-digit minutes (00-59)</item>
1646 <item>ss is the two-digit seconds (00-60)</item>
1648 +zzzz or -zzzz is the the time zone offset from Coordinated
1649 Universal Time (UTC). "+" indicates that the time is ahead
1650 of (i.e., east of) UTC and "-" indicates that the time is
1651 behind (i.e., west of) UTC. The first two digits indicate
1652 the hour difference from UTC and the last two digits
1653 indicate the number of additional minutes difference from
1654 UTC. The last two digits must be in the range 00-59.
1660 The first "title" line with the package name must start
1661 at the left hand margin. The "trailer" line with the
1662 maintainer and date details must be preceded by exactly
1663 one space. The maintainer details and the date must be
1664 separated by exactly two spaces.
1668 The entire changelog must be encoded in UTF-8.
1672 For more information on placement of the changelog files
1673 within binary packages, please see <ref id="changelogs">.
1677 <sect id="dpkgcopyright">
1678 <heading>Copyright: <file>debian/copyright</file></heading>
1680 Every package must be accompanied by a verbatim copy of its
1681 copyright information and distribution license in the file
1682 <file>/usr/share/doc/<var>package</var>/copyright</file>
1683 (see <ref id="copyrightfile"> for further details). Also see
1684 <ref id="pkgcopyright"> for further considerations related
1685 to copyrights for packages.
1689 <heading>Error trapping in makefiles</heading>
1692 When <prgn>make</prgn> invokes a command in a makefile
1693 (including your package's upstream makefiles and
1694 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1695 means that <prgn>sh</prgn>'s usual bad error handling
1696 properties apply: if you include a miniature script as one
1697 of the commands in your makefile you'll find that if you
1698 don't do anything about it then errors are not detected
1699 and <prgn>make</prgn> will blithely continue after
1704 Every time you put more than one shell command (this
1705 includes using a loop) in a makefile command you
1706 must make sure that errors are trapped. For
1707 simple compound commands, such as changing directory and
1708 then running a program, using <tt>&&</tt> rather
1709 than semicolon as a command separator is sufficient. For
1710 more complex commands including most loops and
1711 conditionals you should include a separate <tt>set -e</tt>
1712 command at the start of every makefile command that's
1713 actually one of these miniature shell scripts.
1717 <sect id="timestamps">
1718 <heading>Time Stamps</heading>
1720 Maintainers should preserve the modification times of the
1721 upstream source files in a package, as far as is reasonably
1723 The rationale is that there is some information conveyed
1724 by knowing the age of the file, for example, you could
1725 recognize that some documentation is very old by looking
1726 at the modification time, so it would be nice if the
1727 modification time of the upstream source would be
1733 <sect id="restrictions">
1734 <heading>Restrictions on objects in source packages</heading>
1737 The source package may not contain any hard links<footnote>
1739 This is not currently detected when building source
1740 packages, but only when extracting
1744 Hard links may be permitted at some point in the
1745 future, but would require a fair amount of
1748 </footnote>, device special files, sockets or setuid or
1749 setgid files.<footnote>
1750 Setgid directories are allowed.
1755 <sect id="debianrules">
1756 <heading>Main building script: <file>debian/rules</file></heading>
1759 This file must be an executable makefile, and contains the
1760 package-specific recipes for compiling the package and
1761 building binary package(s) from the source.
1765 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1766 so that it can be invoked by saying its name rather than
1767 invoking <prgn>make</prgn> explicitly. That is, invoking
1768 either of <tt>make -f debian/rules <em>args...</em></tt>
1769 or <tt>./debian/rules <em>args...</em></tt> must result in
1774 Since an interactive <file>debian/rules</file> script makes it
1775 impossible to auto-compile that package and also makes it
1776 hard for other people to reproduce the same binary
1777 package, all <em>required targets</em> must be
1778 non-interactive. At a minimum, required targets are the
1779 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1780 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1781 <em>binary-indep</em>, and <em>build</em>. It also follows
1782 that any target that these targets depend on must also be
1787 The targets are as follows (required unless stated otherwise):
1789 <tag><tt>build</tt></tag>
1792 The <tt>build</tt> target should perform all the
1793 configuration and compilation of the package.
1794 If a package has an interactive pre-build
1795 configuration routine, the Debian source package
1796 must either be built after this has taken place (so
1797 that the binary package can be built without rerunning
1798 the configuration) or the configuration routine
1799 modified to become non-interactive. (The latter is
1800 preferable if there are architecture-specific features
1801 detected by the configuration routine.)
1805 For some packages, notably ones where the same
1806 source tree is compiled in different ways to produce
1807 two binary packages, the <tt>build</tt> target
1808 does not make much sense. For these packages it is
1809 good enough to provide two (or more) targets
1810 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1811 for each of the ways of building the package, and a
1812 <tt>build</tt> target that does nothing. The
1813 <tt>binary</tt> target will have to build the
1814 package in each of the possible ways and make the
1815 binary package out of each.
1819 The <tt>build</tt> target must not do anything
1820 that might require root privilege.
1824 The <tt>build</tt> target may need to run the
1825 <tt>clean</tt> target first - see below.
1829 When a package has a configuration and build routine
1830 which takes a long time, or when the makefiles are
1831 poorly designed, or when <tt>build</tt> needs to
1832 run <tt>clean</tt> first, it is a good idea to
1833 <tt>touch build</tt> when the build process is
1834 complete. This will ensure that if <tt>debian/rules
1835 build</tt> is run again it will not rebuild the whole
1837 Another common way to do this is for <tt>build</tt>
1838 to depend on <prgn>build-stamp</prgn> and to do
1839 nothing else, and for the <prgn>build-stamp</prgn>
1840 target to do the building and to <tt>touch
1841 build-stamp</tt> on completion. This is
1842 especially useful if the build routine creates a
1843 file or directory called <tt>build</tt>; in such a
1844 case, <tt>build</tt> will need to be listed as
1845 a phony target (i.e., as a dependency of the
1846 <tt>.PHONY</tt> target). See the documentation of
1847 <prgn>make</prgn> for more information on phony
1853 <tag><tt>build-arch</tt> (optional),
1854 <tt>build-indep</tt> (optional)
1858 A package may also provide both of the targets
1859 <tt>build-arch</tt> and <tt>build-indep</tt>.
1860 The <tt>build-arch</tt> target, if provided, should
1861 perform all the configuration and compilation required for
1862 producing all architecture-dependant binary packages
1863 (those packages for which the body of the
1864 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1865 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1866 target, if provided, should perform all the configuration
1867 and compilation required for producing all
1868 architecture-independent binary packages (those packages
1869 for which the body of the <tt>Architecture</tt> field
1870 in <tt>debian/control</tt> is <tt>all</tt>).
1871 The <tt>build</tt> target should depend on those of the
1872 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1873 are provided in the rules file.<footnote>
1874 The intent of this split is so that binary-only builds
1875 need not install the dependencies required for
1876 the <tt>build-indep</tt> target. However, this is not
1877 yet used in practice since <tt>dpkg-buildpackage
1878 -B</tt>, and therefore the autobuilders,
1879 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1880 due to the difficulties in determining whether the
1881 optional <tt>build-arch</tt> target exists.
1886 If one or both of the targets <tt>build-arch</tt> and
1887 <tt>build-indep</tt> are not provided, then invoking
1888 <file>debian/rules</file> with one of the not-provided
1889 targets as arguments should produce a exit status code
1890 of 2. Usually this is provided automatically by make
1891 if the target is missing.
1895 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1896 must not do anything that might require root privilege.
1900 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1901 <tt>binary-indep</tt>
1905 The <tt>binary</tt> target must be all that is
1906 necessary for the user to build the binary package(s)
1907 produced from this source package. It is
1908 split into two parts: <prgn>binary-arch</prgn> builds
1909 the binary packages which are specific to a particular
1910 architecture, and <tt>binary-indep</tt> builds
1911 those which are not.
1914 <tt>binary</tt> may be (and commonly is) a target with
1915 no commands which simply depends on
1916 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1919 Both <tt>binary-*</tt> targets should depend on the
1920 <tt>build</tt> target, or on the appropriate
1921 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1922 provided, so that the package is built if it has not
1923 been already. It should then create the relevant
1924 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1925 make their control files and <prgn>dpkg-deb</prgn> to
1926 build them and place them in the parent of the top
1931 Both the <tt>binary-arch</tt> and
1932 <tt>binary-indep</tt> targets <em>must</em> exist.
1933 If one of them has nothing to do (which will always be
1934 the case if the source generates only a single binary
1935 package, whether architecture-dependent or not), it
1936 must still exist and must always succeed.
1940 The <tt>binary</tt> targets must be invoked as
1942 The <prgn>fakeroot</prgn> package often allows one
1943 to build a package correctly even without being
1949 <tag><tt>clean</tt></tag>
1952 This must undo any effects that the <tt>build</tt>
1953 and <tt>binary</tt> targets may have had, except
1954 that it should leave alone any output files created in
1955 the parent directory by a run of a <tt>binary</tt>
1960 If a <tt>build</tt> file is touched at the end of
1961 the <tt>build</tt> target, as suggested above, it
1962 should be removed as the first action that
1963 <tt>clean</tt> performs, so that running
1964 <tt>build</tt> again after an interrupted
1965 <tt>clean</tt> doesn't think that everything is
1970 The <tt>clean</tt> target may need to be
1971 invoked as root if <tt>binary</tt> has been
1972 invoked since the last <tt>clean</tt>, or if
1973 <tt>build</tt> has been invoked as root (since
1974 <tt>build</tt> may create directories, for
1979 <tag><tt>get-orig-source</tt> (optional)</tag>
1982 This target fetches the most recent version of the
1983 original source package from a canonical archive site
1984 (via FTP or WWW, for example), does any necessary
1985 rearrangement to turn it into the original source
1986 tar file format described below, and leaves it in the
1991 This target may be invoked in any directory, and
1992 should take care to clean up any temporary files it
1997 This target is optional, but providing it if
1998 possible is a good idea.
2002 <tag><tt>patch</tt> (optional)</tag>
2005 This target performs whatever additional actions are
2006 required to make the source ready for editing (unpacking
2007 additional upstream archives, applying patches, etc.).
2008 It is recommended to be implemented for any package where
2009 <tt>dpkg-source -x</tt> does not result in source ready
2010 for additional modification. See
2011 <ref id="readmesource">.
2017 The <tt>build</tt>, <tt>binary</tt> and
2018 <tt>clean</tt> targets must be invoked with the current
2019 directory being the package's top-level directory.
2024 Additional targets may exist in <file>debian/rules</file>,
2025 either as published or undocumented interfaces or for the
2026 package's internal use.
2030 The architectures we build on and build for are determined
2031 by <prgn>make</prgn> variables using the utility
2032 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2033 You can determine the
2034 Debian architecture and the GNU style architecture
2035 specification string for the build machine (the machine type
2036 we are building on) as well as for the host machine (the
2037 machine type we are building for). Here is a list of
2038 supported <prgn>make</prgn> variables:
2039 <list compact="compact">
2041 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2044 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2047 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2050 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2051 specification string)
2054 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2055 <tt>DEB_*_GNU_TYPE</tt>)
2058 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2059 <tt>DEB_*_GNU_TYPE</tt>)
2061 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2062 the build machine or <tt>HOST</tt> for specification of the
2067 Backward compatibility can be provided in the rules file
2068 by setting the needed variables to suitable default
2069 values; please refer to the documentation of
2070 <prgn>dpkg-architecture</prgn> for details.
2074 It is important to understand that the <tt>DEB_*_ARCH</tt>
2075 string only determines which Debian architecture we are
2076 building on or for. It should not be used to get the CPU
2077 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2078 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2079 GNU style variables should generally only be used with upstream
2083 <sect1 id="debianrules-options">
2084 <heading><file>debian/rules</file> and
2085 <tt>DEB_BUILD_OPTIONS</tt></heading>
2088 Supporting the standardized environment variable
2089 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2090 contain several flags to change how a package is compiled and
2091 built. Each flag must be in the form <var>flag</var> or
2092 <var>flag</var>=<var>options</var>. If multiple flags are
2093 given, they must be separated by whitespace.<footnote>
2094 Some packages support any delimiter, but whitespace is the
2095 easiest to parse inside a makefile and avoids ambiguity with
2096 flag values that contain commas.
2098 <var>flag</var> must start with a lowercase letter
2099 (<tt>a-z</tt>) and consist only of lowercase letters,
2100 numbers (<tt>0-9</tt>), and the characters
2101 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2102 <var>options</var> must not contain whitespace. The same
2103 tag should not be given multiple times with conflicting
2104 values. Package maintainers may assume that
2105 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2109 The meaning of the following tags has been standardized:
2113 This tag says to not run any build-time test suite
2114 provided by the package.
2118 The presence of this tag means that the package should
2119 be compiled with a minimum of optimization. For C
2120 programs, it is best to add <tt>-O0</tt> to
2121 <tt>CFLAGS</tt> (although this is usually the default).
2122 Some programs might fail to build or run at this level
2123 of optimization; it may be necessary to use
2124 <tt>-O1</tt>, for example.
2128 This tag means that the debugging symbols should not be
2129 stripped from the binary during installation, so that
2130 debugging information may be included in the package.
2132 <tag>parallel=n</tag>
2134 This tag means that the package should be built using up
2135 to <tt>n</tt> parallel processes if the package build
2136 system supports this.<footnote>
2137 Packages built with <tt>make</tt> can often implement
2138 this by passing the <tt>-j</tt><var>n</var> option to
2141 If the package build system does not support parallel
2142 builds, this string must be ignored. If the package
2143 build system only supports a lower level of concurrency
2144 than <var>n</var>, the package should be built using as
2145 many parallel processes as the package build system
2146 supports. It is up to the package maintainer to decide
2147 whether the package build times are long enough and the
2148 package build system is robust enough to make supporting
2149 parallel builds worthwhile.
2155 Unknown flags must be ignored by <file>debian/rules</file>.
2159 The following makefile snippet is an example of how one may
2160 implement the build options; you will probably have to
2161 massage this example in order to make it work for your
2163 <example compact="compact">
2166 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2167 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2168 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2169 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2171 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2176 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2177 INSTALL_PROGRAM += -s
2179 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2180 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2181 MAKEFLAGS += -j$(NUMJOBS)
2186 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2187 # Code to run the package test suite.
2194 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2195 <sect id="substvars">
2196 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2199 When <prgn>dpkg-gencontrol</prgn>,
2200 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2201 generate control files they perform variable substitutions
2202 on their output just before writing it. Variable
2203 substitutions have the form <tt>${<var>variable</var>}</tt>.
2204 The optional file <file>debian/substvars</file> contains
2205 variable substitutions to be used; variables can also be set
2206 directly from <file>debian/rules</file> using the <tt>-V</tt>
2207 option to the source packaging commands, and certain
2208 predefined variables are also available.
2212 The <file>debian/substvars</file> file is usually generated and
2213 modified dynamically by <file>debian/rules</file> targets, in
2214 which case it must be removed by the <tt>clean</tt> target.
2218 See <manref name="deb-substvars" section="5"> for full
2219 details about source variable substitutions, including the
2220 format of <file>debian/substvars</file>.</p>
2223 <sect id="debianwatch">
2224 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2227 This is an optional, recommended control file for the
2228 <tt>uscan</tt> utility which defines how to automatically
2229 scan ftp or http sites for newly available updates of the
2230 package. This is used by <url id="
2231 http://dehs.alioth.debian.org/"> and other Debian QA tools
2232 to help with quality control and maintenance of the
2233 distribution as a whole.
2238 <sect id="debianfiles">
2239 <heading>Generated files list: <file>debian/files</file></heading>
2242 This file is not a permanent part of the source tree; it
2243 is used while building packages to record which files are
2244 being generated. <prgn>dpkg-genchanges</prgn> uses it
2245 when it generates a <file>.changes</file> file.
2249 It should not exist in a shipped source package, and so it
2250 (and any backup files or temporary files such as
2251 <file>files.new</file><footnote>
2252 <file>files.new</file> is used as a temporary file by
2253 <prgn>dpkg-gencontrol</prgn> and
2254 <prgn>dpkg-distaddfile</prgn> - they write a new
2255 version of <tt>files</tt> here before renaming it,
2256 to avoid leaving a corrupted copy if an error
2258 </footnote>) should be removed by the
2259 <tt>clean</tt> target. It may also be wise to
2260 ensure a fresh start by emptying or removing it at the
2261 start of the <tt>binary</tt> target.
2265 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2266 package, it adds an entry to <file>debian/files</file> for the
2267 <file>.deb</file> file that will be created when <tt>dpkg-deb
2268 --build</tt> is run for that binary package. So for most
2269 packages all that needs to be done with this file is to
2270 delete it in the <tt>clean</tt> target.
2274 If a package upload includes files besides the source
2275 package and any binary packages whose control files were
2276 made with <prgn>dpkg-gencontrol</prgn> then they should be
2277 placed in the parent of the package's top-level directory
2278 and <prgn>dpkg-distaddfile</prgn> should be called to add
2279 the file to the list in <file>debian/files</file>.</p>
2282 <sect id="embeddedfiles">
2283 <heading>Convenience copies of code</heading>
2286 Some software packages include in their distribution convenience
2287 copies of code from other software packages, generally so that
2288 users compiling from source don't have to download multiple
2289 packages. Debian packages should not make use of these
2290 convenience copies unless the included package is explicitly
2291 intended to be used in this way.<footnote>
2292 For example, parts of the GNU build system work like this.
2294 If the included code is already in the Debian archive in the
2295 form of a library, the Debian packaging should ensure that
2296 binary packages reference the libraries already in Debian and
2297 the convenience copy is not used. If the included code is not
2298 already in Debian, it should be packaged separately as a
2299 prerequisite if possible.
2301 Having multiple copies of the same code in Debian is
2302 inefficient, often creates either static linking or shared
2303 library conflicts, and, most importantly, increases the
2304 difficulty of handling security vulnerabilities in the
2310 <sect id="readmesource">
2311 <heading>Source package handling:
2312 <file>debian/README.source</file></heading>
2315 If running <prgn>dpkg-source -x</prgn> on a source package
2316 doesn't produce the source of the package, ready for editing,
2317 and allow one to make changes and run
2318 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2319 without taking any additional steps, creating a
2320 <file>debian/README.source</file> documentation file is
2321 recommended. This file should explain how to do all of the
2324 <item>Generate the fully patched source, in a form ready for
2325 editing, that would be built to create Debian
2326 packages. Doing this with a <tt>patch</tt> target in
2327 <file>debian/rules</file> is recommended; see
2328 <ref id="debianrules">.</item>
2329 <item>Modify the source and save those modifications so that
2330 they will be applied when building the package.</item>
2331 <item>Remove source modifications that are currently being
2332 applied when building the package.</item>
2333 <item>Optionally, document what steps are necessary to
2334 upgrade the Debian source package to a new upstream version,
2335 if applicable.</item>
2337 This explanation should include specific commands and mention
2338 any additional required Debian packages. It should not assume
2339 familiarity with any specific Debian packaging system or patch
2344 This explanation may refer to a documentation file installed by
2345 one of the package's build dependencies provided that the
2346 referenced documentation clearly explains these tasks and is not
2347 a general reference manual.
2351 <file>debian/README.source</file> may also include any other
2352 information that would be helpful to someone modifying the
2353 source package. Even if the package doesn't fit the above
2354 description, maintainers are encouraged to document in a
2355 <file>debian/README.source</file> file any source package with a
2356 particularly complex or unintuitive source layout or build
2357 system (for example, a package that builds the same source
2358 multiple times to generate different binary packages).
2364 <chapt id="controlfields">
2365 <heading>Control files and their fields</heading>
2368 The package management system manipulates data represented in
2369 a common format, known as <em>control data</em>, stored in
2370 <em>control files</em>.
2371 Control files are used for source packages, binary packages and
2372 the <file>.changes</file> files which control the installation
2373 of uploaded files<footnote>
2374 <prgn>dpkg</prgn>'s internal databases are in a similar
2379 <sect id="controlsyntax">
2380 <heading>Syntax of control files</heading>
2383 A control file consists of one or more paragraphs of
2385 The paragraphs are also sometimes referred to as stanzas.
2387 The paragraphs are separated by blank lines. Some control
2388 files allow only one paragraph; others allow several, in
2389 which case each paragraph usually refers to a different
2390 package. (For example, in source packages, the first
2391 paragraph refers to the source package, and later paragraphs
2392 refer to binary packages generated from the source.)
2396 Each paragraph consists of a series of data fields; each
2397 field consists of the field name, followed by a colon and
2398 then the data/value associated with that field. It ends at
2399 the end of the (logical) line. Horizontal whitespace
2400 (spaces and tabs) may occur immediately before or after the
2401 value and is ignored there; it is conventional to put a
2402 single space after the colon. For example, a field might
2404 <example compact="compact">
2407 the field name is <tt>Package</tt> and the field value
2412 A paragraph must not contain more than one instance of a
2413 particular field name.
2417 Many fields' values may span several lines; in this case
2418 each continuation line must start with a space or a tab.
2419 Any trailing spaces or tabs at the end of individual
2420 lines of a field value are ignored.
2424 In fields where it is specified that lines may not wrap,
2425 only a single line of data is allowed and whitespace is not
2426 significant in a field body. Whitespace must not appear
2427 inside names (of packages, architectures, files or anything
2428 else) or version numbers, or between the characters of
2429 multi-character version relationships.
2433 Field names are not case-sensitive, but it is usual to
2434 capitalize the field names using mixed case as shown below.
2435 Field values are case-sensitive unless the description of the
2436 field says otherwise.
2440 Blank lines, or lines consisting only of spaces and tabs,
2441 are not allowed within field values or between fields - that
2442 would mean a new paragraph.
2446 All control files must be encoded in UTF-8.
2450 <sect id="sourcecontrolfiles">
2451 <heading>Source package control files -- <file>debian/control</file></heading>
2454 The <file>debian/control</file> file contains the most vital
2455 (and version-independent) information about the source package
2456 and about the binary packages it creates.
2460 The first paragraph of the control file contains information about
2461 the source package in general. The subsequent sets each describe a
2462 binary package that the source tree builds.
2466 The fields in the general paragraph (the first one, for the source
2469 <list compact="compact">
2470 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2471 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2472 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2473 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2474 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2475 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2476 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2477 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2482 The fields in the binary package paragraphs are:
2484 <list compact="compact">
2485 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2486 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2487 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2488 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2489 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2490 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2491 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2492 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2497 The syntax and semantics of the fields are described below.
2501 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2502 generate control files for binary packages (see below), by
2503 <prgn>dpkg-genchanges</prgn> to generate the
2504 <file>.changes</file> file to accompany the upload, and by
2505 <prgn>dpkg-source</prgn> when it creates the
2506 <file>.dsc</file> source control file as part of a source
2507 archive. Many fields are permitted to span multiple lines in
2508 <file>debian/control</file> but not in any other control
2509 file. These tools are responsible for removing the line
2510 breaks from such fields when using fields from
2511 <file>debian/control</file> to generate other control files.
2515 The fields here may contain variable references - their
2516 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2517 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2518 when they generate output control files.
2519 See <ref id="substvars"> for details.
2523 In addition to the control file syntax described <qref
2524 id="controlsyntax">above</qref>, this file may also contain
2525 comment lines starting with <tt>#</tt> without any preceding
2526 whitespace. All such lines are ignored, even in the middle of
2527 continuation lines for a multiline field, and do not end a
2533 <sect id="binarycontrolfiles">
2534 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2537 The <file>DEBIAN/control</file> file contains the most vital
2538 (and version-dependent) information about a binary package. It
2539 consists of a single paragraph.
2543 The fields in this file are:
2545 <list compact="compact">
2546 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2548 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2550 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2551 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2553 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2554 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2555 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2556 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2557 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2562 <sect id="debiansourcecontrolfiles">
2563 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2566 This file consists of a single paragraph, possibly surrounded by
2567 a PGP signature. The fields of that paragraph are listed below.
2568 Their syntax is described above, in <ref id="pkg-controlfields">.
2570 <list compact="compact">
2571 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2572 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2573 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2574 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2575 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2576 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2577 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2578 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2579 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2580 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2581 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2582 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2583 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2588 The source package control file is generated by
2589 <prgn>dpkg-source</prgn> when it builds the source
2590 archive, from other files in the source package,
2591 described above. When unpacking, it is checked against
2592 the files and directories in the other parts of the
2598 <sect id="debianchangesfiles">
2599 <heading>Debian changes files -- <file>.changes</file></heading>
2602 The <file>.changes</file> files are used by the Debian archive
2603 maintenance software to process updates to packages. They
2604 consist of a single paragraph, possibly surrounded by a PGP
2605 signature. That paragraph contains information from the
2606 <file>debian/control</file> file and other data about the
2607 source package gathered via <file>debian/changelog</file>
2608 and <file>debian/rules</file>.
2612 <file>.changes</file> files have a format version that is
2613 incremented whenever the documented fields or their meaning
2614 change. This document describes format &changesversion;.
2618 The fields in this file are:
2620 <list compact="compact">
2621 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2623 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2624 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2625 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2627 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2629 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2630 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2631 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2632 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2633 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2634 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2635 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2636 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2641 <sect id="controlfieldslist">
2642 <heading>List of fields</heading>
2644 <sect1 id="f-Source">
2645 <heading><tt>Source</tt></heading>
2648 This field identifies the source package name.
2652 In <file>debian/control</file> or a <file>.dsc</file> file,
2653 this field must contain only the name of the source package.
2657 In a binary package control file or a <file>.changes</file>
2658 file, the source package name may be followed by a version
2659 number in parentheses<footnote>
2660 It is customary to leave a space after the package name
2661 if a version number is specified.
2663 This version number may be omitted (and is, by
2664 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2665 the <tt>Version</tt> field of the binary package in
2666 question. The field itself may be omitted from a binary
2667 package control file when the source package has the same
2668 name and version as the binary package.
2672 Package names (both source and binary,
2673 see <ref id="f-Package">) must consist only of lower case
2674 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2675 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2676 (<tt>.</tt>). They must be at least two characters long and
2677 must start with an alphanumeric character.
2681 <sect1 id="f-Maintainer">
2682 <heading><tt>Maintainer</tt></heading>
2685 The package maintainer's name and email address. The name
2686 must come first, then the email address inside angle
2687 brackets <tt><></tt> (in RFC822 format).
2691 If the maintainer's name contains a full stop then the
2692 whole field will not work directly as an email address due
2693 to a misfeature in the syntax specified in RFC822; a
2694 program using this field as an address must check for this
2695 and correct the problem if necessary (for example by
2696 putting the name in round brackets and moving it to the
2697 end, and bringing the email address forward).
2701 <sect1 id="f-Uploaders">
2702 <heading><tt>Uploaders</tt></heading>
2705 List of the names and email addresses of co-maintainers of
2706 the package, if any. If the package has other maintainers
2707 beside the one named in the
2708 <qref id="f-Maintainer">Maintainer field</qref>, their names
2709 and email addresses should be listed here. The format of each
2710 entry is the same as that of the Maintainer field, and
2711 multiple entries must be comma separated. This is an optional
2716 Any parser that interprets the Uploaders field in
2717 <file>debian/control</file> must permit it to span multiple
2718 lines. Line breaks in an Uploaders field that spans multiple
2719 lines are not significant and the semantics of the field are
2720 the same as if the line breaks had not been present.
2724 <sect1 id="f-Changed-By">
2725 <heading><tt>Changed-By</tt></heading>
2728 The name and email address of the person who prepared this
2729 version of the package, usually a maintainer. The syntax is
2730 the same as for the <qref id="f-Maintainer">Maintainer
2735 <sect1 id="f-Section">
2736 <heading><tt>Section</tt></heading>
2739 This field specifies an application area into which the package
2740 has been classified. See <ref id="subsections">.
2744 When it appears in the <file>debian/control</file> file,
2745 it gives the value for the subfield of the same name in
2746 the <tt>Files</tt> field of the <file>.changes</file> file.
2747 It also gives the default for the same field in the binary
2752 <sect1 id="f-Priority">
2753 <heading><tt>Priority</tt></heading>
2756 This field represents how important it is that the user
2757 have the package installed. See <ref id="priorities">.
2761 When it appears in the <file>debian/control</file> file,
2762 it gives the value for the subfield of the same name in
2763 the <tt>Files</tt> field of the <file>.changes</file> file.
2764 It also gives the default for the same field in the binary
2769 <sect1 id="f-Package">
2770 <heading><tt>Package</tt></heading>
2773 The name of the binary package.
2777 Binary package names must follow the same syntax and
2778 restrictions as source package names. See <ref id="f-Source">
2783 <sect1 id="f-Architecture">
2784 <heading><tt>Architecture</tt></heading>
2787 Depending on context and the control file used, the
2788 <tt>Architecture</tt> field can include the following sets of
2792 A unique single word identifying a Debian machine
2793 architecture as described in <ref id="arch-spec">.
2796 An architecture wildcard identifying a set of Debian
2797 machine architectures, see <ref id="arch-wildcard-spec">.
2798 <tt>any</tt> matches all Debian machine architectures
2799 and is the most frequently used.
2802 <tt>all</tt>, which indicates an
2803 architecture-independent package.
2806 <tt>source</tt>, which indicates a source package.
2812 In the main <file>debian/control</file> file in the source
2813 package, this field may contain the special
2814 value <tt>all</tt>, the special architecture
2815 wildcard <tt>any</tt>, or a list of specific and wildcard
2816 architectures separated by spaces. If <tt>all</tt>
2817 or <tt>any</tt> appears, that value must be the entire
2818 contents of the field. Most packages will use
2819 either <tt>all</tt> or <tt>any</tt>.
2823 Specifying a specific list of architectures indicates that the
2824 source will build an architecture-dependent package only on
2825 architectures included in the list. Specifying a list of
2826 architecture wildcards indicates that the source will build an
2827 architecture-dependent package on only those architectures
2828 that match any of the specified architecture wildcards.
2829 Specifying a list of architectures or architecture wildcards
2830 other than <tt>any</tt> is for the minority of cases where a
2831 program is not portable or is not useful on some
2832 architectures. Where possible, the program should be made
2837 In the source package control file <file>.dsc</file>, this
2838 field may contain either the architecture
2839 wildcard <tt>any</tt> or a list of architectures and
2840 architecture wildcards separated by spaces. If a list is
2841 given, it may include (or consist solely of) the special
2842 value <tt>all</tt>. In other words, in <file>.dsc</file>
2843 files unlike the <file>debian/control</file>, <tt>all</tt> may
2844 occur in combination with specific architectures.
2845 The <tt>Architecture</tt> field in the source package control
2846 file <file>.dsc</file> is generally constructed from
2847 the <tt>Architecture</tt> fields in
2848 the <file>debian/control</file> in the source package.
2852 Specifying <tt>any</tt> indicates that the source package
2853 isn't dependent on any particular architecture and should
2854 compile fine on any one. The produced binary package(s)
2855 will either be specific to whatever the current build
2856 architecture is or will be architecture-independent.
2860 Specifying only <tt>all</tt> indicates that the source package
2861 will only build architecture-independent packages. If this is
2862 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2863 <tt>any</tt> implies that the source package will build at
2864 least one architecture-dependent package.
2868 Specifying a list of architectures or architecture wildcards
2869 indicates that the source will build an architecture-dependent
2870 package, and will only work correctly on the listed or
2871 matching architectures. If the source package also builds at
2872 least one architecture-independent package, <tt>all</tt> will
2873 also be included in the list.
2877 In a <file>.changes</file> file, the <tt>Architecture</tt>
2878 field lists the architecture(s) of the package(s) currently
2879 being uploaded. This will be a list; if the source for the
2880 package is also being uploaded, the special
2881 entry <tt>source</tt> is also present. <tt>all</tt> will be
2882 present if any architecture-independent packages are being
2883 uploaded. Architecture wildcards such as <tt>any</tt> must
2884 never occur in the <tt>Architecture</tt> field in
2885 the <file>.changes</file> file.
2889 See <ref id="debianrules"> for information on how to get
2890 the architecture for the build process.
2894 <sect1 id="f-Essential">
2895 <heading><tt>Essential</tt></heading>
2898 This is a boolean field which may occur only in the
2899 control file of a binary package or in a per-package fields
2900 paragraph of a main source control data file.
2904 If set to <tt>yes</tt> then the package management system
2905 will refuse to remove the package (upgrading and replacing
2906 it is still possible). The other possible value is <tt>no</tt>,
2907 which is the same as not having the field at all.
2912 <heading>Package interrelationship fields:
2913 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2914 <tt>Recommends</tt>, <tt>Suggests</tt>,
2915 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2916 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2920 These fields describe the package's relationships with
2921 other packages. Their syntax and semantics are described
2922 in <ref id="relationships">.</p>
2925 <sect1 id="f-Standards-Version">
2926 <heading><tt>Standards-Version</tt></heading>
2929 The most recent version of the standards (the policy
2930 manual and associated texts) with which the package
2935 The version number has four components: major and minor
2936 version number and major and minor patch level. When the
2937 standards change in a way that requires every package to
2938 change the major number will be changed. Significant
2939 changes that will require work in many packages will be
2940 signaled by a change to the minor number. The major patch
2941 level will be changed for any change to the meaning of the
2942 standards, however small; the minor patch level will be
2943 changed when only cosmetic, typographical or other edits
2944 are made which neither change the meaning of the document
2945 nor affect the contents of packages.
2949 Thus only the first three components of the policy version
2950 are significant in the <em>Standards-Version</em> control
2951 field, and so either these three components or all four
2952 components may be specified.<footnote>
2953 In the past, people specified the full version number
2954 in the Standards-Version field, for example "2.3.0.0".
2955 Since minor patch-level changes don't introduce new
2956 policy, it was thought it would be better to relax
2957 policy and only require the first 3 components to be
2958 specified, in this example "2.3.0". All four
2959 components may still be used if someone wishes to do so.
2965 <sect1 id="f-Version">
2966 <heading><tt>Version</tt></heading>
2969 The version number of a package. The format is:
2970 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2974 The three components here are:
2976 <tag><var>epoch</var></tag>
2979 This is a single (generally small) unsigned integer. It
2980 may be omitted, in which case zero is assumed. If it is
2981 omitted then the <var>upstream_version</var> may not
2986 It is provided to allow mistakes in the version numbers
2987 of older versions of a package, and also a package's
2988 previous version numbering schemes, to be left behind.
2992 <tag><var>upstream_version</var></tag>
2995 This is the main part of the version number. It is
2996 usually the version number of the original ("upstream")
2997 package from which the <file>.deb</file> file has been made,
2998 if this is applicable. Usually this will be in the same
2999 format as that specified by the upstream author(s);
3000 however, it may need to be reformatted to fit into the
3001 package management system's format and comparison
3006 The comparison behavior of the package management system
3007 with respect to the <var>upstream_version</var> is
3008 described below. The <var>upstream_version</var>
3009 portion of the version number is mandatory.
3013 The <var>upstream_version</var> may contain only
3014 alphanumerics<footnote>
3015 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3017 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3018 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3019 tilde) and should start with a digit. If there is no
3020 <var>debian_revision</var> then hyphens are not allowed;
3021 if there is no <var>epoch</var> then colons are not
3026 <tag><var>debian_revision</var></tag>
3029 This part of the version number specifies the version of
3030 the Debian package based on the upstream version. It
3031 may contain only alphanumerics and the characters
3032 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3033 tilde) and is compared in the same way as the
3034 <var>upstream_version</var> is.
3038 It is optional; if it isn't present then the
3039 <var>upstream_version</var> may not contain a hyphen.
3040 This format represents the case where a piece of
3041 software was written specifically to be a Debian
3042 package, where the Debian package source must always
3043 be identical to the pristine source and therefore no
3044 revision indication is required.
3048 It is conventional to restart the
3049 <var>debian_revision</var> at <tt>1</tt> each time the
3050 <var>upstream_version</var> is increased.
3054 The package management system will break the version
3055 number apart at the last hyphen in the string (if there
3056 is one) to determine the <var>upstream_version</var> and
3057 <var>debian_revision</var>. The absence of a
3058 <var>debian_revision</var> is equivalent to a
3059 <var>debian_revision</var> of <tt>0</tt>.
3066 When comparing two version numbers, first the <var>epoch</var>
3067 of each are compared, then the <var>upstream_version</var> if
3068 <var>epoch</var> is equal, and then <var>debian_revision</var>
3069 if <var>upstream_version</var> is also equal.
3070 <var>epoch</var> is compared numerically. The
3071 <var>upstream_version</var> and <var>debian_revision</var>
3072 parts are compared by the package management system using the
3073 following algorithm:
3077 The strings are compared from left to right.
3081 First the initial part of each string consisting entirely of
3082 non-digit characters is determined. These two parts (one of
3083 which may be empty) are compared lexically. If a difference
3084 is found it is returned. The lexical comparison is a
3085 comparison of ASCII values modified so that all the letters
3086 sort earlier than all the non-letters and so that a tilde
3087 sorts before anything, even the end of a part. For example,
3088 the following parts are in sorted order from earliest to
3089 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3090 <tt>a</tt>.<footnote>
3091 One common use of <tt>~</tt> is for upstream pre-releases.
3092 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3093 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3098 Then the initial part of the remainder of each string which
3099 consists entirely of digit characters is determined. The
3100 numerical values of these two parts are compared, and any
3101 difference found is returned as the result of the comparison.
3102 For these purposes an empty string (which can only occur at
3103 the end of one or both version strings being compared) counts
3108 These two steps (comparing and removing initial non-digit
3109 strings and initial digit strings) are repeated until a
3110 difference is found or both strings are exhausted.
3114 Note that the purpose of epochs is to allow us to leave behind
3115 mistakes in version numbering, and to cope with situations
3116 where the version numbering scheme changes. It is
3117 <em>not</em> intended to cope with version numbers containing
3118 strings of letters which the package management system cannot
3119 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3120 silly orderings.<footnote>
3121 The author of this manual has heard of a package whose
3122 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3123 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3129 <sect1 id="f-Description">
3130 <heading><tt>Description</tt></heading>
3133 In a source or binary control file, the <tt>Description</tt>
3134 field contains a description of the binary package, consisting
3135 of two parts, the synopsis or the short description, and the
3136 long description. The field's format is as follows:
3141 Description: <single line synopsis>
3142 <extended description over several lines>
3147 The lines in the extended description can have these formats:
3153 Those starting with a single space are part of a paragraph.
3154 Successive lines of this form will be word-wrapped when
3155 displayed. The leading space will usually be stripped off.
3159 Those starting with two or more spaces. These will be
3160 displayed verbatim. If the display cannot be panned
3161 horizontally, the displaying program will line wrap them "hard"
3162 (i.e., without taking account of word breaks). If it can they
3163 will be allowed to trail off to the right. None, one or two
3164 initial spaces may be deleted, but the number of spaces
3165 deleted from each line will be the same (so that you can have
3166 indenting work correctly, for example).
3170 Those containing a single space followed by a single full stop
3171 character. These are rendered as blank lines. This is the
3172 <em>only</em> way to get a blank line<footnote>
3173 Completely empty lines will not be rendered as blank lines.
3174 Instead, they will cause the parser to think you're starting
3175 a whole new record in the control file, and will therefore
3176 likely abort with an error.
3181 Those containing a space, a full stop and some more characters.
3182 These are for future expansion. Do not use them.
3188 Do not use tab characters. Their effect is not predictable.
3192 See <ref id="descriptions"> for further information on this.
3196 In a <file>.changes</file> file, the <tt>Description</tt>
3197 field contains a summary of the descriptions for the packages
3198 being uploaded. For this case, the first line of the field
3199 value (the part on the same line as <tt>Description:</tt>) is
3200 always empty. The content of the field is expressed as
3201 continuation lines, one line per package. Each line is
3202 indented by one space and contains the name of a binary
3203 package, a space, a hyphen (<tt>-</tt>), a space, and the
3204 short description line from that package.
3208 <sect1 id="f-Distribution">
3209 <heading><tt>Distribution</tt></heading>
3212 In a <file>.changes</file> file or parsed changelog output
3213 this contains the (space-separated) name(s) of the
3214 distribution(s) where this version of the package should
3215 be installed. Valid distributions are determined by the
3216 archive maintainers.<footnote>
3217 Example distribution names in the Debian archive used in
3218 <file>.changes</file> files are:
3219 <taglist compact="compact">
3220 <tag><em>unstable</em></tag>
3222 This distribution value refers to the
3223 <em>developmental</em> part of the Debian distribution
3224 tree. Most new packages, new upstream versions of
3225 packages and bug fixes go into the <em>unstable</em>
3229 <tag><em>experimental</em></tag>
3231 The packages with this distribution value are deemed
3232 by their maintainers to be high risk. Oftentimes they
3233 represent early beta or developmental packages from
3234 various sources that the maintainers want people to
3235 try, but are not ready to be a part of the other parts
3236 of the Debian distribution tree.
3241 Others are used for updating stable releases or for
3242 security uploads. More information is available in the
3243 Debian Developer's Reference, section "The Debian
3247 The Debian archive software only supports listing a single
3248 distribution. Migration of packages to other distributions is
3249 handled outside of the upload process.
3254 <heading><tt>Date</tt></heading>
3257 This field includes the date the package was built or last
3258 edited. It must be in the same format as the <var>date</var>
3259 in a <file>debian/changelog</file> entry.
3263 The value of this field is usually extracted from the
3264 <file>debian/changelog</file> file - see
3265 <ref id="dpkgchangelog">).
3269 <sect1 id="f-Format">
3270 <heading><tt>Format</tt></heading>
3273 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3274 files, this field declares the format version of that file.
3275 The syntax of the field value is the same as that of
3276 a <qref id="f-Version">package version number</qref> except
3277 that no epoch or Debian revision is allowed. The format
3278 described in this document is <tt>&changesversion;</tt>.
3282 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3283 Debian source control</qref> files, this field declares the
3284 format of the source package. The field value is used by
3285 programs acting on a source package to interpret the list of
3286 files in the source package and determine how to unpack it.
3287 The syntax of the field value is a numeric major revision, a
3288 period, a numeric minor revision, and then an optional subtype
3289 after whitespace, which if specified is an alphanumeric word
3290 in parentheses. The subtype is optional in the syntax but may
3291 be mandatory for particular source format revisions.
3293 The source formats currently supported by the Debian archive
3294 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3295 and <tt>3.0 (quilt)</tt>.
3300 <sect1 id="f-Urgency">
3301 <heading><tt>Urgency</tt></heading>
3304 This is a description of how important it is to upgrade to
3305 this version from previous ones. It consists of a single
3306 keyword taking one of the values <tt>low</tt>,
3307 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3308 <tt>critical</tt><footnote>
3309 Other urgency values are supported with configuration
3310 changes in the archive software but are not used in Debian.
3311 The urgency affects how quickly a package will be considered
3312 for inclusion into the <tt>testing</tt> distribution and
3313 gives an indication of the importance of any fixes included
3314 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3315 treated as synonymous.
3316 </footnote> (not case-sensitive) followed by an optional
3317 commentary (separated by a space) which is usually in
3318 parentheses. For example:
3321 Urgency: low (HIGH for users of diversions)
3327 The value of this field is usually extracted from the
3328 <file>debian/changelog</file> file - see
3329 <ref id="dpkgchangelog">.
3333 <sect1 id="f-Changes">
3334 <heading><tt>Changes</tt></heading>
3337 This field contains the human-readable changes data, describing
3338 the differences between the last version and the current one.
3342 The first line of the field value (the part on the same line
3343 as <tt>Changes:</tt>) is always empty. The content of the
3344 field is expressed as continuation lines, with each line
3345 indented by at least one space. Blank lines must be
3346 represented by a line consisting only of a space and a full
3351 The value of this field is usually extracted from the
3352 <file>debian/changelog</file> file - see
3353 <ref id="dpkgchangelog">).
3357 Each version's change information should be preceded by a
3358 "title" line giving at least the version, distribution(s)
3359 and urgency, in a human-readable way.
3363 If data from several versions is being returned the entry
3364 for the most recent version should be returned first, and
3365 entries should be separated by the representation of a
3366 blank line (the "title" line may also be followed by the
3367 representation of a blank line).
3371 <sect1 id="f-Binary">
3372 <heading><tt>Binary</tt></heading>
3375 This field is a list of binary packages. Its syntax and
3376 meaning varies depending on the control file in which it
3381 When it appears in the <file>.dsc</file> file, it lists binary
3382 packages which a source package can produce, separated by
3384 A space after each comma is conventional.
3385 </footnote>. It may span multiple lines. The source package
3386 does not necessarily produce all of these binary packages for
3387 every architecture. The source control file doesn't contain
3388 details of which architectures are appropriate for which of
3389 the binary packages.
3393 When it appears in a <file>.changes</file> file, it lists the
3394 names of the binary packages being uploaded, separated by
3395 whitespace (not commas). It may span multiple lines.
3399 <sect1 id="f-Installed-Size">
3400 <heading><tt>Installed-Size</tt></heading>
3403 This field appears in the control files of binary packages,
3404 and in the <file>Packages</file> files. It gives an estimate
3405 of the total amount of disk space required to install the
3406 named package. Actual installed size may vary based on block
3407 size, file system properties, or actions taken by package
3412 The disk space is given as the integer value of the estimated
3413 installed size in bytes, divided by 1024 and rounded up.
3417 <sect1 id="f-Files">
3418 <heading><tt>Files</tt></heading>
3421 This field contains a list of files with information about
3422 each one. The exact information and syntax varies with
3427 In all cases, Files is a multiline field. The first line of
3428 the field value (the part on the same line as <tt>Files:</tt>)
3429 is always empty. The content of the field is expressed as
3430 continuation lines, one line per file. Each line must be
3431 indented by one space and contain a number of sub-fields,
3432 separated by spaces, as described below.
3436 In the <file>.dsc</file> file, each line contains the MD5
3437 checksum, size and filename of the tar file and (if
3438 applicable) diff file which make up the remainder of the
3439 source package<footnote>
3440 That is, the parts which are not the <tt>.dsc</tt>.
3441 </footnote>. For example:
3444 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3445 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3447 The exact forms of the filenames are described
3448 in <ref id="pkg-sourcearchives">.
3452 In the <file>.changes</file> file this contains one line per
3453 file being uploaded. Each line contains the MD5 checksum,
3454 size, section and priority and the filename. For example:
3457 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3458 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3459 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3460 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3462 The <qref id="f-Section">section</qref>
3463 and <qref id="f-Priority">priority</qref> are the values of
3464 the corresponding fields in the main source control file. If
3465 no section or priority is specified then <tt>-</tt> should be
3466 used, though section and priority values must be specified for
3467 new packages to be installed properly.
3471 The special value <tt>byhand</tt> for the section in a
3472 <tt>.changes</tt> file indicates that the file in question
3473 is not an ordinary package file and must by installed by
3474 hand by the distribution maintainers. If the section is
3475 <tt>byhand</tt> the priority should be <tt>-</tt>.
3479 If a new Debian revision of a package is being shipped and
3480 no new original source archive is being distributed the
3481 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3482 entry for the original source archive
3483 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3484 but the <file>.changes</file> file should leave it out. In
3485 this case the original source archive on the distribution
3486 site must match exactly, byte-for-byte, the original
3487 source archive which was used to generate the
3488 <file>.dsc</file> file and diff which are being uploaded.</p>
3491 <sect1 id="f-Closes">
3492 <heading><tt>Closes</tt></heading>
3495 A space-separated list of bug report numbers that the upload
3496 governed by the .changes file closes.
3500 <sect1 id="f-Homepage">
3501 <heading><tt>Homepage</tt></heading>
3504 The URL of the web site for this package, preferably (when
3505 applicable) the site from which the original source can be
3506 obtained and any additional upstream documentation or
3507 information may be found. The content of this field is a
3508 simple URL without any surrounding characters such as
3513 <sect1 id="f-Checksums">
3514 <heading><tt>Checksums-Sha1</tt>
3515 and <tt>Checksums-Sha256</tt></heading>
3518 These fields contain a list of files with a checksum and size
3519 for each one. Both <tt>Checksums-Sha1</tt>
3520 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3521 only in the checksum algorithm used: SHA-1
3522 for <tt>Checksums-Sha1</tt> and SHA-256
3523 for <tt>Checksums-Sha256</tt>.
3527 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3528 multiline fields. The first line of the field value (the part
3529 on the same line as <tt>Checksums-Sha1:</tt>
3530 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3531 of the field is expressed as continuation lines, one line per
3532 file. Each line consists of the checksum, a space, the file
3533 size, a space, and the file name. For example (from
3534 a <file>.changes</file> file):
3537 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3538 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3539 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3540 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3542 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3543 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3544 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3545 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3550 In the <file>.dsc</file> file, these fields should list all
3551 files that make up the source package. In
3552 the <file>.changes</file> file, these fields should list all
3553 files being uploaded. The list of files in these fields
3554 must match the list of files in the <tt>Files</tt> field.
3560 <heading>User-defined fields</heading>
3563 Additional user-defined fields may be added to the
3564 source package control file. Such fields will be
3565 ignored, and not copied to (for example) binary or
3566 source package control files or upload control files.
3570 If you wish to add additional unsupported fields to
3571 these output files you should use the mechanism
3576 Fields in the main source control information file with
3577 names starting <tt>X</tt>, followed by one or more of
3578 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3579 be copied to the output files. Only the part of the
3580 field name after the hyphen will be used in the output
3581 file. Where the letter <tt>B</tt> is used the field
3582 will appear in binary package control files, where the
3583 letter <tt>S</tt> is used in source package control
3584 files and where <tt>C</tt> is used in upload control
3585 (<tt>.changes</tt>) files.
3589 For example, if the main source information control file
3592 XBS-Comment: I stand between the candle and the star.
3594 then the binary and source package control files will contain the
3597 Comment: I stand between the candle and the star.
3606 <chapt id="maintainerscripts">
3607 <heading>Package maintainer scripts and installation procedure</heading>
3610 <heading>Introduction to package maintainer scripts</heading>
3613 It is possible to supply scripts as part of a package which
3614 the package management system will run for you when your
3615 package is installed, upgraded or removed.
3619 These scripts are the files <prgn>preinst</prgn>,
3620 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3621 <prgn>postrm</prgn> in the control area of the package.
3622 They must be proper executable files; if they are scripts
3623 (which is recommended), they must start with the usual
3624 <tt>#!</tt> convention. They should be readable and
3625 executable by anyone, and must not be world-writable.
3629 The package management system looks at the exit status from
3630 these scripts. It is important that they exit with a
3631 non-zero status if there is an error, so that the package
3632 management system can stop its processing. For shell
3633 scripts this means that you <em>almost always</em> need to
3634 use <tt>set -e</tt> (this is usually true when writing shell
3635 scripts, in fact). It is also important, of course, that
3636 they exit with a zero status if everything went well.
3640 Additionally, packages interacting with users using
3641 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3642 install a <prgn>config</prgn> script in the control area,
3643 see <ref id="maintscriptprompt"> for details.
3647 When a package is upgraded a combination of the scripts from
3648 the old and new packages is called during the upgrade
3649 procedure. If your scripts are going to be at all
3650 complicated you need to be aware of this, and may need to
3651 check the arguments to your scripts.
3655 Broadly speaking the <prgn>preinst</prgn> is called before
3656 (a particular version of) a package is installed, and the
3657 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3658 before (a version of) a package is removed and the
3659 <prgn>postrm</prgn> afterwards.
3663 Programs called from maintainer scripts should not normally
3664 have a path prepended to them. Before installation is
3665 started, the package management system checks to see if the
3666 programs <prgn>ldconfig</prgn>,
3667 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3668 and <prgn>update-rc.d</prgn> can be found via the
3669 <tt>PATH</tt> environment variable. Those programs, and any
3670 other program that one would expect to be in the
3671 <tt>PATH</tt>, should thus be invoked without an absolute
3672 pathname. Maintainer scripts should also not reset the
3673 <tt>PATH</tt>, though they might choose to modify it by
3674 prepending or appending package-specific directories. These
3675 considerations really apply to all shell scripts.</p>
3678 <sect id="idempotency">
3679 <heading>Maintainer scripts idempotency</heading>
3682 It is necessary for the error recovery procedures that the
3683 scripts be idempotent. This means that if it is run
3684 successfully, and then it is called again, it doesn't bomb
3685 out or cause any harm, but just ensures that everything is
3686 the way it ought to be. If the first call failed, or
3687 aborted half way through for some reason, the second call
3688 should merely do the things that were left undone the first
3689 time, if any, and exit with a success status if everything
3691 This is so that if an error occurs, the user interrupts
3692 <prgn>dpkg</prgn> or some other unforeseen circumstance
3693 happens you don't leave the user with a badly-broken
3694 package when <prgn>dpkg</prgn> attempts to repeat the
3700 <sect id="controllingterminal">
3701 <heading>Controlling terminal for maintainer scripts</heading>
3704 Maintainer scripts are not guaranteed to run with a controlling
3705 terminal and may not be able to interact with the user. They
3706 must be able to fall back to noninteractive behavior if no
3707 controlling terminal is available. Maintainer scripts that
3708 prompt via a program conforming to the Debian Configuration
3709 Management Specification (see <ref id="maintscriptprompt">) may
3710 assume that program will handle falling back to noninteractive
3715 For high-priority prompts without a reasonable default answer,
3716 maintainer scripts may abort if there is no controlling
3717 terminal. However, this situation should be avoided if at all
3718 possible, since it prevents automated or unattended installs.
3719 In most cases, users will consider this to be a bug in the
3724 <sect id="exitstatus">
3725 <heading>Exit status</heading>
3728 Each script must return a zero exit status for
3729 success, or a nonzero one for failure, since the package
3730 management system looks for the exit status of these scripts
3731 and determines what action to take next based on that datum.
3735 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3740 <list compact="compact">
3742 <var>new-preinst</var> <tt>install</tt>
3745 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3748 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3751 <var>old-preinst</var> <tt>abort-upgrade</tt>
3752 <var>new-version</var>
3757 <list compact="compact">
3759 <var>postinst</var> <tt>configure</tt>
3760 <var>most-recently-configured-version</var>
3763 <var>old-postinst</var> <tt>abort-upgrade</tt>
3764 <var>new-version</var>
3767 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3768 <tt>in-favour</tt> <var>package</var>
3769 <var>new-version</var>
3772 <var>postinst</var> <tt>abort-remove</tt>
3775 <var>deconfigured's-postinst</var>
3776 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3777 <var>failed-install-package</var> <var>version</var>
3778 [<tt>removing</tt> <var>conflicting-package</var>
3784 <list compact="compact">
3786 <var>prerm</var> <tt>remove</tt>
3789 <var>old-prerm</var> <tt>upgrade</tt>
3790 <var>new-version</var>
3793 <var>new-prerm</var> <tt>failed-upgrade</tt>
3794 <var>old-version</var>
3797 <var>conflictor's-prerm</var> <tt>remove</tt>
3798 <tt>in-favour</tt> <var>package</var>
3799 <var>new-version</var>
3802 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3803 <tt>in-favour</tt> <var>package-being-installed</var>
3804 <var>version</var> [<tt>removing</tt>
3805 <var>conflicting-package</var>
3811 <list compact="compact">
3813 <var>postrm</var> <tt>remove</tt>
3816 <var>postrm</var> <tt>purge</tt>
3819 <var>old-postrm</var> <tt>upgrade</tt>
3820 <var>new-version</var>
3823 <var>new-postrm</var> <tt>failed-upgrade</tt>
3824 <var>old-version</var>
3827 <var>new-postrm</var> <tt>abort-install</tt>
3830 <var>new-postrm</var> <tt>abort-install</tt>
3831 <var>old-version</var>
3834 <var>new-postrm</var> <tt>abort-upgrade</tt>
3835 <var>old-version</var>
3838 <var>disappearer's-postrm</var> <tt>disappear</tt>
3839 <var>overwriter</var>
3840 <var>overwriter-version</var>
3846 <sect id="unpackphase">
3847 <heading>Details of unpack phase of installation or upgrade</heading>
3850 The procedure on installation/upgrade/overwrite/disappear
3851 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3852 stage of <tt>dpkg --install</tt>) is as follows. In each
3853 case, if a major error occurs (unless listed below) the
3854 actions are, in general, run backwards - this means that the
3855 maintainer scripts are run with different arguments in
3856 reverse order. These are the "error unwind" calls listed
3863 If a version of the package is already installed, call
3864 <example compact="compact">
3865 <var>old-prerm</var> upgrade <var>new-version</var>
3869 If the script runs but exits with a non-zero
3870 exit status, <prgn>dpkg</prgn> will attempt:
3871 <example compact="compact">
3872 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3874 If this works, the upgrade continues. If this
3875 does not work, the error unwind:
3876 <example compact="compact">
3877 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3879 If this works, then the old-version is
3880 "Installed", if not, the old version is in a
3881 "Half-Configured" state.
3887 If a "conflicting" package is being removed at the same time,
3888 or if any package will be broken (due to <tt>Breaks</tt>):
3891 If <tt>--auto-deconfigure</tt> is
3892 specified, call, for each package to be deconfigured
3893 due to <tt>Breaks</tt>:
3894 <example compact="compact">
3895 <var>deconfigured's-prerm</var> deconfigure \
3896 in-favour <var>package-being-installed</var> <var>version</var>
3899 <example compact="compact">
3900 <var>deconfigured's-postinst</var> abort-deconfigure \
3901 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3903 The deconfigured packages are marked as
3904 requiring configuration, so that if
3905 <tt>--install</tt> is used they will be
3906 configured again if possible.
3909 If any packages depended on a conflicting
3910 package being removed and <tt>--auto-deconfigure</tt> is
3911 specified, call, for each such package:
3912 <example compact="compact">
3913 <var>deconfigured's-prerm</var> deconfigure \
3914 in-favour <var>package-being-installed</var> <var>version</var> \
3915 removing <var>conflicting-package</var> <var>version</var>
3918 <example compact="compact">
3919 <var>deconfigured's-postinst</var> abort-deconfigure \
3920 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3921 removing <var>conflicting-package</var> <var>version</var>
3923 The deconfigured packages are marked as
3924 requiring configuration, so that if
3925 <tt>--install</tt> is used they will be
3926 configured again if possible.
3929 To prepare for removal of each conflicting package, call:
3930 <example compact="compact">
3931 <var>conflictor's-prerm</var> remove \
3932 in-favour <var>package</var> <var>new-version</var>
3935 <example compact="compact">
3936 <var>conflictor's-postinst</var> abort-remove \
3937 in-favour <var>package</var> <var>new-version</var>
3946 If the package is being upgraded, call:
3947 <example compact="compact">
3948 <var>new-preinst</var> upgrade <var>old-version</var>
3950 If this fails, we call:
3952 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3959 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3961 is called. If this works, then the old version
3962 is in an "Installed" state, or else it is left
3963 in an "Unpacked" state.
3968 If it fails, then the old version is left
3969 in an "Half-Installed" state.
3976 Otherwise, if the package had some configuration
3977 files from a previous version installed (i.e., it
3978 is in the "configuration files only" state):
3979 <example compact="compact">
3980 <var>new-preinst</var> install <var>old-version</var>
3984 <var>new-postrm</var> abort-install <var>old-version</var>
3986 If this fails, the package is left in a
3987 "Half-Installed" state, which requires a
3988 reinstall. If it works, the packages is left in
3989 a "Config-Files" state.
3992 Otherwise (i.e., the package was completely purged):
3993 <example compact="compact">
3994 <var>new-preinst</var> install
3997 <example compact="compact">
3998 <var>new-postrm</var> abort-install
4000 If the error-unwind fails, the package is in a
4001 "Half-Installed" phase, and requires a
4002 reinstall. If the error unwind works, the
4003 package is in a not installed state.
4010 The new package's files are unpacked, overwriting any
4011 that may be on the system already, for example any
4012 from the old version of the same package or from
4013 another package. Backups of the old files are kept
4014 temporarily, and if anything goes wrong the package
4015 management system will attempt to put them back as
4016 part of the error unwind.
4020 It is an error for a package to contain files which
4021 are on the system in another package, unless
4022 <tt>Replaces</tt> is used (see <ref id="replaces">).
4024 The following paragraph is not currently the case:
4025 Currently the <tt>- - force-overwrite</tt> flag is
4026 enabled, downgrading it to a warning, but this may not
4032 It is a more serious error for a package to contain a
4033 plain file or other kind of non-directory where another
4034 package has a directory (again, unless
4035 <tt>Replaces</tt> is used). This error can be
4036 overridden if desired using
4037 <tt>--force-overwrite-dir</tt>, but this is not
4042 Packages which overwrite each other's files produce
4043 behavior which, though deterministic, is hard for the
4044 system administrator to understand. It can easily
4045 lead to "missing" programs if, for example, a package
4046 is installed which overwrites a file from another
4047 package, and is then removed again.<footnote>
4048 Part of the problem is due to what is arguably a
4049 bug in <prgn>dpkg</prgn>.
4054 A directory will never be replaced by a symbolic link
4055 to a directory or vice versa; instead, the existing
4056 state (symlink or not) will be left alone and
4057 <prgn>dpkg</prgn> will follow the symlink if there is
4066 If the package is being upgraded, call
4067 <example compact="compact">
4068 <var>old-postrm</var> upgrade <var>new-version</var>
4072 If this fails, <prgn>dpkg</prgn> will attempt:
4073 <example compact="compact">
4074 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4076 If this works, installation continues. If not,
4078 <example compact="compact">
4079 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4081 If this fails, the old version is left in a
4082 "Half-Installed" state. If it works, dpkg now
4084 <example compact="compact">
4085 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4087 If this fails, the old version is left in a
4088 "Half-Installed" state. If it works, dpkg now
4090 <example compact="compact">
4091 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4093 If this fails, the old version is in an
4100 This is the point of no return - if
4101 <prgn>dpkg</prgn> gets this far, it won't back off
4102 past this point if an error occurs. This will
4103 leave the package in a fairly bad state, which
4104 will require a successful re-installation to clear
4105 up, but it's when <prgn>dpkg</prgn> starts doing
4106 things that are irreversible.
4111 Any files which were in the old version of the package
4112 but not in the new are removed.
4116 The new file list replaces the old.
4120 The new maintainer scripts replace the old.
4124 Any packages all of whose files have been overwritten
4125 during the installation, and which aren't required for
4126 dependencies, are considered to have been removed.
4127 For each such package
4130 <prgn>dpkg</prgn> calls:
4131 <example compact="compact">
4132 <var>disappearer's-postrm</var> disappear \
4133 <var>overwriter</var> <var>overwriter-version</var>
4137 The package's maintainer scripts are removed.
4140 It is noted in the status database as being in a
4141 sane state, namely not installed (any conffiles
4142 it may have are ignored, rather than being
4143 removed by <prgn>dpkg</prgn>). Note that
4144 disappearing packages do not have their prerm
4145 called, because <prgn>dpkg</prgn> doesn't know
4146 in advance that the package is going to
4153 Any files in the package we're unpacking that are also
4154 listed in the file lists of other packages are removed
4155 from those lists. (This will lobotomize the file list
4156 of the "conflicting" package if there is one.)
4160 The backup files made during installation, above, are
4166 The new package's status is now sane, and recorded as
4171 Here is another point of no return - if the
4172 conflicting package's removal fails we do not unwind
4173 the rest of the installation; the conflicting package
4174 is left in a half-removed limbo.
4179 If there was a conflicting package we go and do the
4180 removal actions (described below), starting with the
4181 removal of the conflicting package's files (any that
4182 are also in the package being installed have already
4183 been removed from the conflicting package's file list,
4184 and so do not get removed now).
4190 <sect id="configdetails"><heading>Details of configuration</heading>
4193 When we configure a package (this happens with <tt>dpkg
4194 --install</tt> and <tt>dpkg --configure</tt>), we first
4195 update any <tt>conffile</tt>s and then call:
4196 <example compact="compact">
4197 <var>postinst</var> configure <var>most-recently-configured-version</var>
4202 No attempt is made to unwind after errors during
4203 configuration. If the configuration fails, the package is in
4204 a "Failed Config" state, and an error message is generated.
4208 If there is no most recently configured version
4209 <prgn>dpkg</prgn> will pass a null argument.
4212 Historical note: Truly ancient (pre-1997) versions of
4213 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4214 (including the angle brackets) in this case. Even older
4215 ones did not pass a second argument at all, under any
4216 circumstance. Note that upgrades using such an old dpkg
4217 version are unlikely to work for other reasons, even if
4218 this old argument behavior is handled by your postinst script.
4224 <sect id="removedetails"><heading>Details of removal and/or
4225 configuration purging</heading>
4231 <example compact="compact">
4232 <var>prerm</var> remove
4236 If prerm fails during replacement due to conflict
4238 <var>conflictor's-postinst</var> abort-remove \
4239 in-favour <var>package</var> <var>new-version</var>
4243 <var>postinst</var> abort-remove
4247 If this fails, the package is in a "Half-Configured"
4248 state, or else it remains "Installed".
4252 The package's files are removed (except <tt>conffile</tt>s).
4255 <example compact="compact">
4256 <var>postrm</var> remove
4260 If it fails, there's no error unwind, and the package is in
4261 an "Half-Installed" state.
4266 All the maintainer scripts except the <prgn>postrm</prgn>
4271 If we aren't purging the package we stop here. Note
4272 that packages which have no <prgn>postrm</prgn> and no
4273 <tt>conffile</tt>s are automatically purged when
4274 removed, as there is no difference except for the
4275 <prgn>dpkg</prgn> status.
4279 The <tt>conffile</tt>s and any backup files
4280 (<tt>~</tt>-files, <tt>#*#</tt> files,
4281 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4286 <example compact="compact">
4287 <var>postrm</var> purge
4291 If this fails, the package remains in a "Config-Files"
4296 The package's file list is removed.
4305 <chapt id="relationships">
4306 <heading>Declaring relationships between packages</heading>
4308 <sect id="depsyntax">
4309 <heading>Syntax of relationship fields</heading>
4312 These fields all have a uniform syntax. They are a list of
4313 package names separated by commas.
4317 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4318 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4319 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4320 control file fields of the package, which declare
4321 dependencies on other packages, the package names listed may
4322 also include lists of alternative package names, separated
4323 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4324 if any one of the alternative packages is installed, that
4325 part of the dependency is considered to be satisfied.
4329 All of the fields except for <tt>Provides</tt> may restrict
4330 their applicability to particular versions of each named
4331 package. This is done in parentheses after each individual
4332 package name; the parentheses should contain a relation from
4333 the list below followed by a version number, in the format
4334 described in <ref id="f-Version">.
4338 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4339 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4340 strictly earlier, earlier or equal, exactly equal, later or
4341 equal and strictly later, respectively. The deprecated
4342 forms <tt><</tt> and <tt>></tt> were used to mean
4343 earlier/later or equal, rather than strictly earlier/later,
4344 so they should not appear in new packages (though
4345 <prgn>dpkg</prgn> still supports them).
4349 Whitespace may appear at any point in the version
4350 specification subject to the rules in <ref
4351 id="controlsyntax">, and must appear where it's necessary to
4352 disambiguate; it is not otherwise significant. All of the
4353 relationship fields may span multiple lines. For
4354 consistency and in case of future changes to
4355 <prgn>dpkg</prgn> it is recommended that a single space be
4356 used after a version relationship and before a version
4357 number; it is also conventional to put a single space after
4358 each comma, on either side of each vertical bar, and before
4359 each open parenthesis. When wrapping a relationship field, it
4360 is conventional to do so after a comma and before the space
4361 following that comma.
4365 For example, a list of dependencies might appear as:
4366 <example compact="compact">
4369 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4374 Relationships may be restricted to a certain set of
4375 architectures. This is indicated in brackets after each
4376 individual package name and the optional version specification.
4377 The brackets enclose a list of Debian architecture names
4378 separated by whitespace. Exclamation marks may be prepended to
4379 each of the names. (It is not permitted for some names to be
4380 prepended with exclamation marks while others aren't.)
4384 For build relationship fields
4385 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4386 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4387 the current Debian host architecture is not in this list and
4388 there are no exclamation marks in the list, or it is in the list
4389 with a prepended exclamation mark, the package name and the
4390 associated version specification are ignored completely for the
4391 purposes of defining the relationships.
4396 <example compact="compact">
4398 Build-Depends-Indep: texinfo
4399 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4400 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4402 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4403 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4404 <tt>gnumach-dev</tt> only on hurd-i386.
4408 For binary relationship fields, the architecture restriction
4409 syntax is only supported in the source package control
4410 file <file>debian/control</file>. When the corresponding binary
4411 package control file is generated, the relationship will either
4412 be omitted or included without the architecture restriction
4413 based on the architecture of the binary package. This means
4414 that architecture restrictions must not be used in binary
4415 relationship fields for architecture-independent packages
4416 (<tt>Architecture: all</tt>).
4421 <example compact="compact">
4422 Depends: foo [i386], bar [amd64]
4424 becomes <tt>Depends: foo</tt> when the package is built on
4425 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4426 package is built on the <tt>amd64</tt> architecture, and omitted
4427 entirely in binary packages built on all other architectures.
4431 If the architecture-restricted dependency is part of a set of
4432 alternatives using <tt>|</tt>, that alternative is ignored
4433 completely on architectures that do not match the restriction.
4435 <example compact="compact">
4436 Build-Depends: foo [!i386] | bar [!amd64]
4438 is equivalent to <tt>bar</tt> on the i386 architecture, to
4439 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4440 bar</tt> on all other architectures.
4444 Relationships may also be restricted to a certain set of
4445 architectures using architecture wildcards. The syntax for
4446 declaring such restrictions is the same as declaring
4447 restrictions using a certain set of architectures without
4448 architecture wildcards. For example:
4449 <example compact="compact">
4450 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4452 is equivalent to <tt>foo</tt> on architectures using the Linux
4453 kernel and any cpu, <tt>bar</tt> on architectures using any
4454 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4455 using a kernel other than Linux.
4459 Note that the binary package relationship fields such as
4460 <tt>Depends</tt> appear in one of the binary package
4461 sections of the control file, whereas the build-time
4462 relationships such as <tt>Build-Depends</tt> appear in the
4463 source package section of the control file (which is the
4468 <sect id="binarydeps">
4469 <heading>Binary Dependencies - <tt>Depends</tt>,
4470 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4471 <tt>Pre-Depends</tt>
4475 Packages can declare in their control file that they have
4476 certain relationships to other packages - for example, that
4477 they may not be installed at the same time as certain other
4478 packages, and/or that they depend on the presence of others.
4482 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4483 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4484 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4485 <tt>Breaks</tt> is described in <ref id="breaks">, and
4486 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4487 rest are described below.
4491 These seven fields are used to declare a dependency
4492 relationship by one package on another. Except for
4493 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4494 depending (binary) package's control file.
4495 (<tt>Enhances</tt> appears in the recommending package's
4496 control file, and <tt>Breaks</tt> appears in the version of
4497 depended-on package which causes the named package to
4502 A <tt>Depends</tt> field takes effect <em>only</em> when a
4503 package is to be configured. It does not prevent a package
4504 being on the system in an unconfigured state while its
4505 dependencies are unsatisfied, and it is possible to replace
4506 a package whose dependencies are satisfied and which is
4507 properly installed with a different version whose
4508 dependencies are not and cannot be satisfied; when this is
4509 done the depending package will be left unconfigured (since
4510 attempts to configure it will give errors) and will not
4511 function properly. If it is necessary, a
4512 <tt>Pre-Depends</tt> field can be used, which has a partial
4513 effect even when a package is being unpacked, as explained
4514 in detail below. (The other three dependency fields,
4515 <tt>Recommends</tt>, <tt>Suggests</tt> and
4516 <tt>Enhances</tt>, are only used by the various front-ends
4517 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4518 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4522 For this reason packages in an installation run are usually
4523 all unpacked first and all configured later; this gives
4524 later versions of packages with dependencies on later
4525 versions of other packages the opportunity to have their
4526 dependencies satisfied.
4530 In case of circular dependencies, since installation or
4531 removal order honoring the dependency order can't be
4532 established, dependency loops are broken at some point
4533 (based on rules below), and some packages may not be able to
4534 rely on their dependencies being present when being
4535 installed or removed, depending on which side of the break
4536 of the circular dependency loop they happen to be on. If one
4537 of the packages in the loop has no postinst script, then the
4538 cycle will be broken at that package, so as to ensure that
4539 all postinst scripts run with the dependencies properly
4540 configured if this is possible. Otherwise the breaking point
4545 The <tt>Depends</tt> field thus allows package maintainers
4546 to impose an order in which packages should be configured.
4550 The meaning of the five dependency fields is as follows:
4552 <tag><tt>Depends</tt></tag>
4555 This declares an absolute dependency. A package will
4556 not be configured unless all of the packages listed in
4557 its <tt>Depends</tt> field have been correctly
4562 The <tt>Depends</tt> field should be used if the
4563 depended-on package is required for the depending
4564 package to provide a significant amount of
4569 The <tt>Depends</tt> field should also be used if the
4570 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4571 <prgn>postrm</prgn> scripts require the package to be
4572 present in order to run. Note, however, that the
4573 <prgn>postrm</prgn> cannot rely on any non-essential
4574 packages to be present during the <tt>purge</tt>
4578 <tag><tt>Recommends</tt></tag>
4581 This declares a strong, but not absolute, dependency.
4585 The <tt>Recommends</tt> field should list packages
4586 that would be found together with this one in all but
4587 unusual installations.
4591 <tag><tt>Suggests</tt></tag>
4593 This is used to declare that one package may be more
4594 useful with one or more others. Using this field
4595 tells the packaging system and the user that the
4596 listed packages are related to this one and can
4597 perhaps enhance its usefulness, but that installing
4598 this one without them is perfectly reasonable.
4601 <tag><tt>Enhances</tt></tag>
4603 This field is similar to Suggests but works in the
4604 opposite direction. It is used to declare that a
4605 package can enhance the functionality of another
4609 <tag><tt>Pre-Depends</tt></tag>
4612 This field is like <tt>Depends</tt>, except that it
4613 also forces <prgn>dpkg</prgn> to complete installation
4614 of the packages named before even starting the
4615 installation of the package which declares the
4616 pre-dependency, as follows:
4620 When a package declaring a pre-dependency is about to
4621 be <em>unpacked</em> the pre-dependency can be
4622 satisfied if the depended-on package is either fully
4623 configured, <em>or even if</em> the depended-on
4624 package(s) are only unpacked or in the "Half-Configured"
4625 state, provided that they have been configured
4626 correctly at some point in the past (and not removed
4627 or partially removed since). In this case, both the
4628 previously-configured and currently unpacked or
4629 "Half-Configured" versions must satisfy any version
4630 clause in the <tt>Pre-Depends</tt> field.
4634 When the package declaring a pre-dependency is about
4635 to be <em>configured</em>, the pre-dependency will be
4636 treated as a normal <tt>Depends</tt>, that is, it will
4637 be considered satisfied only if the depended-on
4638 package has been correctly configured.
4642 <tt>Pre-Depends</tt> should be used sparingly,
4643 preferably only by packages whose premature upgrade or
4644 installation would hamper the ability of the system to
4645 continue with any upgrade that might be in progress.
4649 <tt>Pre-Depends</tt> are also required if the
4650 <prgn>preinst</prgn> script depends on the named
4651 package. It is best to avoid this situation if
4659 When selecting which level of dependency to use you should
4660 consider how important the depended-on package is to the
4661 functionality of the one declaring the dependency. Some
4662 packages are composed of components of varying degrees of
4663 importance. Such a package should list using
4664 <tt>Depends</tt> the package(s) which are required by the
4665 more important components. The other components'
4666 requirements may be mentioned as Suggestions or
4667 Recommendations, as appropriate to the components' relative
4673 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4676 When one binary package declares that it breaks another,
4677 <prgn>dpkg</prgn> will refuse to allow the package which
4678 declares <tt>Breaks</tt> be installed unless the broken
4679 package is deconfigured first, and it will refuse to
4680 allow the broken package to be reconfigured.
4684 A package will not be regarded as causing breakage merely
4685 because its configuration files are still installed; it must
4686 be at least "Half-Installed".
4690 A special exception is made for packages which declare that
4691 they break their own package name or a virtual package which
4692 they provide (see below): this does not count as a real
4697 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4698 version clause; such a <tt>Breaks</tt> is introduced in the
4699 version of an (implicit or explicit) dependency which violates
4700 an assumption or reveals a bug in earlier versions of the broken
4701 package, or which takes over a file from earlier versions of the
4702 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4703 will inform higher-level package management tools that the
4704 broken package must be upgraded before the new one.
4708 If the breaking package also overwrites some files from the
4709 older package, it should use <tt>Replaces</tt> to ensure this
4710 goes smoothly. See <ref id="replaces"> for a full discussion
4711 of taking over files from other packages, including how to
4712 use <tt>Breaks</tt> in those cases.
4716 Many of the cases where <tt>Breaks</tt> should be used were
4717 previously handled with <tt>Conflicts</tt>
4718 because <tt>Breaks</tt> did not yet exist.
4719 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4720 See <ref id="conflicts"> for more information about the
4725 <sect id="conflicts">
4726 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4729 When one binary package declares a conflict with another
4730 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4731 refuse to allow them to be installed on the system at the
4732 same time. This is a stronger restriction than <tt>Breaks</tt>,
4733 which just prevents both packages from being configured at the
4734 same time. Conflicting packages cannot be unpacked on the
4735 system at the same time.
4739 If one package is to be installed, the other must be removed
4740 first. If the package being installed is marked as replacing
4741 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4742 normally be used in this case) the one on the system, or the one
4743 on the system is marked as deselected, or both packages are
4744 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4745 automatically remove the package which is causing the conflict.
4746 Otherwise, it will halt the installation of the new package with
4747 an error. This mechanism is specifically designed to produce an
4748 error when the installed package is <tt>Essential</tt>, but the
4753 A package will not cause a conflict merely because its
4754 configuration files are still installed; it must be at least
4759 A special exception is made for packages which declare a
4760 conflict with their own package name, or with a virtual
4761 package which they provide (see below): this does not
4762 prevent their installation, and allows a package to conflict
4763 with others providing a replacement for it. You use this
4764 feature when you want the package in question to be the only
4765 package providing some feature.
4769 Normally, <tt>Breaks</tt> should be used instead
4770 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4771 stronger restriction on the ordering of package installation or
4772 upgrade and can make it more difficult for the package manager
4773 to find a correct solution to an upgrade or installation
4774 problem. <tt>Breaks</tt> should be used
4776 <item>when moving a file from one package to another (see
4777 <ref id="replaces">),</item>
4778 <item>when splitting a package (a special case of the previous
4780 <item>when the breaking package exposes a bug in or interacts
4781 badly with particular versions of the broken
4784 <tt>Conflicts</tt> should be used
4786 <item>when two packages provide the same file and will
4787 continue to do so,</item>
4788 <item>in conjunction with <tt>Provides</tt> when only one
4789 package providing a given virtual facility may be installed
4790 at a time (see <ref id="virtual">),</item>
4791 <item>in other cases where one must prevent simultaneous
4792 installation of two packages for reasons that are ongoing
4793 (not fixed in a later version of one of the packages) or
4794 that must prevent both packages from being unpacked at the
4795 same time, not just configured.</item>
4797 Be aware that adding <tt>Conflicts</tt> is normally not the best
4798 solution when two packages provide the same files. Depending on
4799 the reason for that conflict, using alternatives or renaming the
4800 files is often a better approach. See, for
4801 example, <ref id="binaries">.
4805 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4806 unless two packages cannot be installed at the same time or
4807 installing them both causes one of them to be broken or
4808 unusable. Having similar functionality or performing the same
4809 tasks as another package is not sufficient reason to
4810 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4814 A <tt>Conflicts</tt> entry may have an "earlier than" version
4815 clause if the reason for the conflict is corrected in a later
4816 version of one of the packages. However, normally the presence
4817 of an "earlier than" version clause is a sign
4818 that <tt>Breaks</tt> should have been used instead. An "earlier
4819 than" version clause in <tt>Conflicts</tt>
4820 prevents <prgn>dpkg</prgn> from upgrading or installing the
4821 package which declares such a conflict until the upgrade or
4822 removal of the conflicted-with package has been completed, which
4823 is a strong restriction.
4827 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4831 As well as the names of actual ("concrete") packages, the
4832 package relationship fields <tt>Depends</tt>,
4833 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4834 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4835 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4836 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4837 may mention "virtual packages".
4841 A <em>virtual package</em> is one which appears in the
4842 <tt>Provides</tt> control file field of another package.
4843 The effect is as if the package(s) which provide a
4844 particular virtual package name had been listed by name
4845 everywhere the virtual package name appears. (See also <ref
4850 If there are both concrete and virtual packages of the same
4851 name, then the dependency may be satisfied (or the conflict
4852 caused) by either the concrete package with the name in
4853 question or any other concrete package which provides the
4854 virtual package with the name in question. This is so that,
4855 for example, supposing we have
4856 <example compact="compact">
4859 </example> and someone else releases an enhanced version of
4860 the <tt>bar</tt> package they can say:
4861 <example compact="compact">
4865 and the <tt>bar-plus</tt> package will now also satisfy the
4866 dependency for the <tt>foo</tt> package.
4870 If a relationship field has a version number attached, only real
4871 packages will be considered to see whether the relationship is
4872 satisfied (or the prohibition violated, for a conflict or
4873 breakage). In other words, if a version number is specified,
4874 this is a request to ignore all <tt>Provides</tt> for that
4875 package name and consider only real packages. The package
4876 manager will assume that a package providing that virtual
4877 package is not of the "right" version. A <tt>Provides</tt>
4878 field may not contain version numbers, and the version number of
4879 the concrete package which provides a particular virtual package
4880 will not be considered when considering a dependency on or
4881 conflict with the virtual package name.<footnote>
4882 It is possible that a future release of <prgn>dpkg</prgn> may
4883 add the ability to specify a version number for each virtual
4884 package it provides. This feature is not yet present,
4885 however, and is expected to be used only infrequently.
4890 To specify which of a set of real packages should be the default
4891 to satisfy a particular dependency on a virtual package, list
4892 the real package as an alternative before the virtual one.
4896 If the virtual package represents a facility that can only be
4897 provided by one real package at a time, such as
4898 the <package>mail-transport-agent</package> virtual package that
4899 requires installation of a binary that would conflict with all
4900 other providers of that virtual package (see
4901 <ref id="mail-transport-agents">), all packages providing that
4902 virtual package should also declare a conflict with it
4903 using <tt>Conflicts</tt>. This will ensure that at most one
4904 provider of that virtual package is unpacked or installed at a
4909 <sect id="replaces"><heading>Overwriting files and replacing
4910 packages - <tt>Replaces</tt></heading>
4913 Packages can declare in their control file that they should
4914 overwrite files in certain other packages, or completely
4915 replace other packages. The <tt>Replaces</tt> control file
4916 field has these two distinct purposes.
4919 <sect1><heading>Overwriting files in other packages</heading>
4922 It is usually an error for a package to contain files which
4923 are on the system in another package. However, if the
4924 overwriting package declares that it <tt>Replaces</tt> the one
4925 containing the file being overwritten, then <prgn>dpkg</prgn>
4926 will replace the file from the old package with that from the
4927 new. The file will no longer be listed as "owned" by the old
4928 package and will be taken over by the new package.
4929 Normally, <tt>Breaks</tt> should be used in conjunction
4930 with <tt>Replaces</tt>.<footnote>
4931 To see why <tt>Breaks</tt> is normally needed in addition
4932 to <tt>Replaces</tt>, consider the case of a file in the
4933 package <package>foo</package> being taken over by the
4934 package <package>foo-data</package>.
4935 <tt>Replaces</tt> will allow <package>foo-data</package> to
4936 be installed and take over that file. However,
4937 without <tt>Breaks</tt>, nothing
4938 requires <package>foo</package> to be upgraded to a newer
4939 version that knows it does not include that file and instead
4940 depends on <package>foo-data</package>. Nothing would
4941 prevent the new <package>foo-data</package> package from
4942 being installed and then removed, removing the file that it
4943 took over from <package>foo</package>. After that
4944 operation, the package manager would think the system was in
4945 a consistent state, but the <package>foo</package> package
4946 would be missing one of its files.
4951 For example, if a package <package>foo</package> is split
4952 into <package>foo</package> and <package>foo-data</package>
4953 starting at version 1.2-3, <package>foo-data</package> would
4955 <example compact="compact">
4956 Replaces: foo (<< 1.2-3)
4957 Breaks: foo (<< 1.2-3)
4959 in its control file. The new version of the
4960 package <package>foo</package> would normally have the field
4961 <example compact="compact">
4962 Depends: foo-data (>= 1.2-3)
4964 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4965 the files moved into <package>foo-data</package> are not
4966 required for normal operation).
4970 If a package is completely replaced in this way, so that
4971 <prgn>dpkg</prgn> does not know of any files it still
4972 contains, it is considered to have "disappeared". It will
4973 be marked as not wanted on the system (selected for
4974 removal) and not installed. Any <tt>conffile</tt>s
4975 details noted for the package will be ignored, as they
4976 will have been taken over by the overwriting package. The
4977 package's <prgn>postrm</prgn> script will be run with a
4978 special argument to allow the package to do any final
4979 cleanup required. See <ref id="mscriptsinstact">.
4981 Replaces is a one way relationship. You have to install
4982 the replacing package after the replaced package.
4987 For this usage of <tt>Replaces</tt>, virtual packages (see
4988 <ref id="virtual">) are not considered when looking at a
4989 <tt>Replaces</tt> field. The packages declared as being
4990 replaced must be mentioned by their real names.
4994 This usage of <tt>Replaces</tt> only takes effect when both
4995 packages are at least partially on the system at once. It is
4996 not relevant if the packages conflict unless the conflict has
5001 <sect1><heading>Replacing whole packages, forcing their
5005 Second, <tt>Replaces</tt> allows the packaging system to
5006 resolve which package should be removed when there is a
5007 conflict (see <ref id="conflicts">). This usage only takes
5008 effect when the two packages <em>do</em> conflict, so that the
5009 two usages of this field do not interfere with each other.
5013 In this situation, the package declared as being replaced
5014 can be a virtual package, so for example, all mail
5015 transport agents (MTAs) would have the following fields in
5016 their control files:
5017 <example compact="compact">
5018 Provides: mail-transport-agent
5019 Conflicts: mail-transport-agent
5020 Replaces: mail-transport-agent
5022 ensuring that only one MTA can be installed at any one
5023 time. See <ref id="virtual"> for more information about this
5028 <sect id="sourcebinarydeps">
5029 <heading>Relationships between source and binary packages -
5030 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5031 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5035 Source packages that require certain binary packages to be
5036 installed or absent at the time of building the package
5037 can declare relationships to those binary packages.
5041 This is done using the <tt>Build-Depends</tt>,
5042 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5043 <tt>Build-Conflicts-Indep</tt> control file fields.
5047 Build-dependencies on "build-essential" binary packages can be
5048 omitted. Please see <ref id="pkg-relations"> for more information.
5052 The dependencies and conflicts they define must be satisfied
5053 (as defined earlier for binary packages) in order to invoke
5054 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5056 There is no Build-Depends-Arch; this role is essentially
5057 met with Build-Depends. Anyone building the
5058 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5059 assumed to be building the whole package, and therefore
5060 installation of all build dependencies is required.
5063 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5064 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5065 not yet know how to check for its existence, and
5066 <tt>binary-arch</tt>. The purpose of the original split
5067 between <tt>Build-Depends</tt> and
5068 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5069 wouldn't need to install extra packages needed only for the
5070 binary-indep targets. But without a build-arch/build-indep
5071 split, this didn't work, since most of the work is done in
5072 the build target, not in the binary target.
5076 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5077 <tt>binary-arch</tt></tag>
5079 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5080 fields must be satisfied when these targets are invoked.
5082 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5083 and <tt>binary-indep</tt></tag>
5085 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5086 <tt>Build-Depends-Indep</tt>, and
5087 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5088 these targets are invoked.
5096 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5099 Packages containing shared libraries must be constructed with
5100 a little care to make sure that the shared library is always
5101 available. This is especially important for packages whose
5102 shared libraries are vitally important, such as the C library
5103 (currently <tt>libc6</tt>).
5107 Packages involving shared libraries should be split up into
5108 several binary packages. This section mostly deals with how
5109 this separation is to be accomplished; rules for files within
5110 the shared library packages are in <ref id="libraries"> instead.
5113 <sect id="sharedlibs-runtime">
5114 <heading>Run-time shared libraries</heading>
5117 The run-time shared library needs to be placed in a package
5118 whose name changes whenever the shared object version
5121 Since it is common place to install several versions of a
5122 package that just provides shared libraries, it is a
5123 good idea that the library package should not
5124 contain any extraneous non-versioned files, unless they
5125 happen to be in versioned directories.</p>
5127 The most common mechanism is to place it in a package
5129 <package><var>libraryname</var><var>soversion</var></package>,
5130 where <file><var>soversion</var></file> is the version number
5131 in the soname of the shared library<footnote>
5132 The soname is the shared object name: it's the thing
5133 that has to match exactly between building an executable
5134 and running it for the dynamic linker to be able run the
5135 program. For example, if the soname of the library is
5136 <file>libfoo.so.6</file>, the library package would be
5137 called <file>libfoo6</file>.
5139 Alternatively, if it would be confusing to directly append
5140 <var>soversion</var> to <var>libraryname</var> (e.g. because
5141 <var>libraryname</var> itself ends in a number), you may use
5142 <package><var>libraryname</var>-<var>soversion</var></package> and
5143 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5148 If you have several shared libraries built from the same
5149 source tree you may lump them all together into a single
5150 shared library package, provided that you change all of
5151 their sonames at once (so that you don't get filename
5152 clashes if you try to install different versions of the
5153 combined shared libraries package).
5157 The package should install the shared libraries under
5158 their normal names. For example, the <package>libgdbm3</package>
5159 package should install <file>libgdbm.so.3.0.0</file> as
5160 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5161 renamed or re-linked by any <prgn>prerm</prgn> or
5162 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5163 of renaming things safely without affecting running programs,
5164 and attempts to interfere with this are likely to lead to
5169 Shared libraries should not be installed executable, since
5170 the dynamic linker does not require this and trying to
5171 execute a shared library usually results in a core dump.
5175 The run-time library package should include the symbolic link that
5176 <prgn>ldconfig</prgn> would create for the shared libraries.
5177 For example, the <package>libgdbm3</package> package should include
5178 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5179 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5180 linker (for example <prgn>ld.so</prgn> or
5181 <prgn>ld-linux.so.*</prgn>) can find the library between the
5182 time that <prgn>dpkg</prgn> installs it and the time that
5183 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5185 The package management system requires the library to be
5186 placed before the symbolic link pointing to it in the
5187 <file>.deb</file> file. This is so that when
5188 <prgn>dpkg</prgn> comes to install the symlink
5189 (overwriting the previous symlink pointing at an older
5190 version of the library), the new shared library is already
5191 in place. In the past, this was achieved by creating the
5192 library in the temporary packaging directory before
5193 creating the symlink. Unfortunately, this was not always
5194 effective, since the building of the tar file in the
5195 <file>.deb</file> depended on the behavior of the underlying
5196 file system. Some file systems (such as reiserfs) reorder
5197 the files so that the order of creation is forgotten.
5198 Since version 1.7.0, <prgn>dpkg</prgn>
5199 reorders the files itself as necessary when building a
5200 package. Thus it is no longer important to concern
5201 oneself with the order of file creation.
5205 <sect1 id="ldconfig">
5206 <heading><tt>ldconfig</tt></heading>
5209 Any package installing shared libraries in one of the default
5210 library directories of the dynamic linker (which are currently
5211 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5212 listed in <file>/etc/ld.so.conf</file><footnote>
5214 <list compact="compact">
5215 <item>/usr/local/lib</item>
5216 <item>/usr/lib/libc5-compat</item>
5217 <item>/lib/libc5-compat</item>
5220 must use <prgn>ldconfig</prgn> to update the shared library
5225 The package maintainer scripts must only call
5226 <prgn>ldconfig</prgn> under these circumstances:
5227 <list compact="compact">
5228 <item>When the <prgn>postinst</prgn> script is run with a
5229 first argument of <tt>configure</tt>, the script must call
5230 <prgn>ldconfig</prgn>, and may optionally invoke
5231 <prgn>ldconfig</prgn> at other times.
5233 <item>When the <prgn>postrm</prgn> script is run with a
5234 first argument of <tt>remove</tt>, the script should call
5235 <prgn>ldconfig</prgn>.
5240 During install or upgrade, the preinst is called before
5241 the new files are installed, so calling "ldconfig" is
5242 pointless. The preinst of an existing package can also be
5243 called if an upgrade fails. However, this happens during
5244 the critical time when a shared libs may exist on-disk
5245 under a temporary name. Thus, it is dangerous and
5246 forbidden by current policy to call "ldconfig" at this
5251 When a package is installed or upgraded, "postinst
5252 configure" runs after the new files are safely on-disk.
5253 Since it is perfectly safe to invoke ldconfig
5254 unconditionally in a postinst, it is OK for a package to
5255 simply put ldconfig in its postinst without checking the
5256 argument. The postinst can also be called to recover from
5257 a failed upgrade. This happens before any new files are
5258 unpacked, so there is no reason to call "ldconfig" at this
5263 For a package that is being removed, prerm is
5264 called with all the files intact, so calling ldconfig is
5265 useless. The other calls to "prerm" happen in the case of
5266 upgrade at a time when all the files of the old package
5267 are on-disk, so again calling "ldconfig" is pointless.
5271 postrm, on the other hand, is called with the "remove"
5272 argument just after the files are removed, so this is
5273 the proper time to call "ldconfig" to notify the system
5274 of the fact that the shared libraries from the package
5275 are removed. The postrm can be called at several other
5276 times. At the time of "postrm purge", "postrm
5277 abort-install", or "postrm abort-upgrade", calling
5278 "ldconfig" is useless because the shared lib files are
5279 not on-disk. However, when "postrm" is invoked with
5280 arguments "upgrade", "failed-upgrade", or "disappear", a
5281 shared lib may exist on-disk under a temporary filename.
5289 <sect id="sharedlibs-support-files">
5290 <heading>Shared library support files</heading>
5293 If your package contains files whose names do not change with
5294 each change in the library shared object version, you must not
5295 put them in the shared library package. Otherwise, several
5296 versions of the shared library cannot be installed at the same
5297 time without filename clashes, making upgrades and transitions
5298 unnecessarily difficult.
5302 It is recommended that supporting files and run-time support
5303 programs that do not need to be invoked manually by users, but
5304 are nevertheless required for the package to function, be placed
5305 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5306 preferably under <file>/usr/lib/</file><var>package-name</var>.
5307 If the program or file is architecture independent, the
5308 recommendation is for it to be placed in a subdirectory of
5309 <file>/usr/share</file> instead, preferably under
5310 <file>/usr/share/</file><var>package-name</var>. Following the
5311 <var>package-name</var> naming convention ensures that the file
5312 names change when the shared object version changes.
5316 Run-time support programs that use the shared library but are
5317 not required for the library to function or files used by the
5318 shared library that can be used by any version of the shared
5319 library package should instead be put in a separate package.
5320 This package might typically be named
5321 <package><var>libraryname</var>-tools</package>; note the
5322 absence of the <var>soversion</var> in the package name.
5326 Files and support programs only useful when compiling software
5327 against the library should be included in the development
5328 package for the library.<footnote>
5329 For example, a <file><var>package-name</var>-config</file>
5330 script or <package>pkg-config</package> configuration files.
5335 <sect id="sharedlibs-static">
5336 <heading>Static libraries</heading>
5339 The static library (<file><var>libraryname.a</var></file>)
5340 is usually provided in addition to the shared version.
5341 It is placed into the development package (see below).
5345 In some cases, it is acceptable for a library to be
5346 available in static form only; these cases include:
5348 <item>libraries for languages whose shared library support
5349 is immature or unstable</item>
5350 <item>libraries whose interfaces are in flux or under
5351 development (commonly the case when the library's
5352 major version number is zero, or where the ABI breaks
5353 across patchlevels)</item>
5354 <item>libraries which are explicitly intended to be
5355 available only in static form by their upstream
5360 <sect id="sharedlibs-dev">
5361 <heading>Development files</heading>
5364 If there are development files associated with a shared library,
5365 the source package needs to generate a binary development package
5366 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5367 or if you prefer only to support one development version at a
5368 time, <package><var>libraryname</var>-dev</package>. Installing
5369 the development package must result in installation of all the
5370 development files necessary for compiling programs against that
5371 shared library.<footnote>
5372 This wording allows the development files to be split into
5373 several packages, such as a separate architecture-independent
5374 <package><var>libraryname</var>-headers</package>, provided that
5375 the development package depends on all the required additional
5381 In case several development versions of a library exist, you may
5382 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5383 <ref id="conflicts">) to ensure that the user only installs one
5384 development version at a time (as different development versions are
5385 likely to have the same header files in them, which would cause a
5386 filename clash if both were installed).
5390 The development package should contain a symlink for the associated
5391 shared library without a version number. For example, the
5392 <package>libgdbm-dev</package> package should include a symlink
5393 from <file>/usr/lib/libgdbm.so</file> to
5394 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5395 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5396 <file>libgdbm.so</file> when compiling dynamically.
5400 <sect id="sharedlibs-intradeps">
5401 <heading>Dependencies between the packages of the same library</heading>
5404 Typically the development version should have an exact
5405 version dependency on the runtime library, to make sure that
5406 compilation and linking happens correctly. The
5407 <tt>${binary:Version}</tt> substitution variable can be
5408 useful for this purpose.
5410 Previously, <tt>${Source-Version}</tt> was used, but its name
5411 was confusing and it has been deprecated since dpkg 1.13.19.
5416 <sect id="sharedlibs-shlibdeps">
5417 <heading>Dependencies between the library and other packages -
5418 the <tt>shlibs</tt> system</heading>
5421 If a package contains a binary or library which links to a
5422 shared library, we must ensure that when the package is
5423 installed on the system, all of the libraries needed are
5424 also installed. This requirement led to the creation of the
5425 <tt>shlibs</tt> system, which is very simple in its design:
5426 any package which <em>provides</em> a shared library also
5427 provides information on the package dependencies required to
5428 ensure the presence of this library, and any package which
5429 <em>uses</em> a shared library uses this information to
5430 determine the dependencies it requires. The files which
5431 contain the mapping from shared libraries to the necessary
5432 dependency information are called <file>shlibs</file> files.
5436 When a package is built which contains any shared libraries, it
5437 must provide a <file>shlibs</file> file for other packages to
5438 use. When a package is built which contains any shared
5439 libraries or compiled binaries, it must run
5440 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5441 on these to determine the libraries used and hence the
5442 dependencies needed by this package.<footnote>
5444 <prgn>dpkg-shlibdeps</prgn> will use a program
5445 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5446 the libraries directly needed by the binaries or shared
5447 libraries in the package.
5451 We say that a binary <tt>foo</tt> <em>directly</em> uses
5452 a library <tt>libbar</tt> if it is explicitly linked
5453 with that library (that is, the library is listed in the ELF
5454 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5455 to the link line when the binary is created). Other
5456 libraries that are needed by <tt>libbar</tt> are linked
5457 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5458 linker will load them automatically when it loads
5459 <tt>libbar</tt>. A package should depend on the libraries
5460 it directly uses, but not the libraries it indirectly uses.
5461 The dependencies for those libraries will automatically pull
5462 in the other libraries.
5466 A good example of where this helps is the following. We
5467 could update <tt>libimlib</tt> with a new version that
5468 supports a new graphics format called dgf (but retaining the
5469 same major version number) and depends on <tt>libdgf</tt>.
5470 If we used <prgn>ldd</prgn> to add dependencies for every
5471 library directly or indirectly linked with a binary, every
5472 package that uses <tt>libimlib</tt> would need to be
5473 recompiled so it would also depend on <tt>libdgf</tt> or it
5474 wouldn't run due to missing symbols. Since dependencies are
5475 only added based on ELF <tt>NEEDED</tt> attribute, packages
5476 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5477 having the dependency on <tt>libdgf</tt> and so they would
5478 not need rebuilding.
5484 In the following sections, we will first describe where the
5485 various <tt>shlibs</tt> files are to be found, then how to
5486 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5487 file format and how to create them if your package contains a
5492 <heading>The <tt>shlibs</tt> files present on the system</heading>
5495 There are several places where <tt>shlibs</tt> files are
5496 found. The following list gives them in the order in which
5498 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5499 (The first one which gives the required information is used.)
5505 <p><file>debian/shlibs.local</file></p>
5508 This lists overrides for this package. This file should
5509 normally not be used, but may be needed temporarily in
5510 unusual situations to work around bugs in other packages,
5511 or in unusual cases where the normally declared dependency
5512 information in the installed <file>shlibs</file> file for
5513 a library cannot be used. This file overrides information
5514 obtained from any other source.
5519 <p><file>/etc/dpkg/shlibs.override</file></p>
5522 This lists global overrides. This list is normally
5523 empty. It is maintained by the local system
5529 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5532 When packages are being built,
5533 any <file>debian/shlibs</file> files are copied into the
5534 control file area of the temporary build directory and
5535 given the name <file>shlibs</file>. These files give
5536 details of any shared libraries included in the same
5538 An example may help here. Let us say that the source
5539 package <tt>foo</tt> generates two binary
5540 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5541 When building the binary packages, the two packages are
5542 created in the directories <file>debian/libfoo2</file>
5543 and <file>debian/foo-runtime</file> respectively.
5544 (<file>debian/tmp</file> could be used instead of one of
5545 these.) Since <tt>libfoo2</tt> provides the
5546 <tt>libfoo</tt> shared library, it will require a
5547 <tt>shlibs</tt> file, which will be installed in
5548 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5549 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5550 When <prgn>dpkg-shlibdeps</prgn> is run on the
5551 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5553 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5554 determine whether <tt>foo-prog</tt>'s library
5555 dependencies are satisfied by any of the libraries
5556 provided by <tt>libfoo2</tt>. For this reason,
5557 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5558 the individual binary packages' <tt>shlibs</tt> files
5559 have been installed into the build directory.
5565 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5568 These are the <file>shlibs</file> files corresponding to
5569 all of the packages installed on the system, and are
5570 maintained by the relevant package maintainers.
5575 <p><file>/etc/dpkg/shlibs.default</file></p>
5578 This file lists any shared libraries whose packages
5579 have failed to provide correct <file>shlibs</file> files.
5580 It was used when the <file>shlibs</file> setup was first
5581 introduced, but it is now normally empty. It is
5582 maintained by the <tt>dpkg</tt> maintainer.
5590 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5591 <file>shlibs</file> files</heading>
5595 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5596 into your <file>debian/rules</file> file. If your package
5597 contains only compiled binaries and libraries (but no scripts),
5598 you can use a command such as:
5599 <example compact="compact">
5600 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5601 debian/tmp/usr/lib/*
5603 Otherwise, you will need to explicitly list the compiled
5604 binaries and libraries.<footnote>
5605 If you are using <tt>debhelper</tt>, the
5606 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5607 It will also correctly handle multi-binary packages.
5612 This command puts the dependency information into the
5613 <file>debian/substvars</file> file, which is then used by
5614 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5615 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5616 field in the control file for this to work.
5620 If you have multiple binary packages, you will need to call
5621 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5622 compiled libraries or binaries. In such a case, you will
5623 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5624 utilities to specify a different <file>substvars</file> file.
5628 If you are creating a udeb for use in the Debian Installer,
5629 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5630 should use the dependency line of type <tt>udeb</tt> by
5631 adding the <tt>-tudeb</tt> option<footnote>
5632 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5633 will automatically add this option if it knows it is
5635 </footnote>. If there is no dependency line of
5636 type <tt>udeb</tt> in the <file>shlibs</file>
5637 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5642 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5643 <ref id="pkg-dpkg-shlibdeps"> and
5644 <manref name="dpkg-shlibdeps" section="1">.
5649 <heading>The <file>shlibs</file> File Format</heading>
5652 Each <file>shlibs</file> file has the same format. Lines
5653 beginning with <tt>#</tt> are considered to be comments and
5654 are ignored. Each line is of the form:
5655 <example compact="compact">
5656 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5661 We will explain this by reference to the example of the
5662 <tt>zlib1g</tt> package, which (at the time of writing)
5663 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5667 <var>type</var> is an optional element that indicates the type
5668 of package for which the line is valid. The only type currently
5669 in use is <tt>udeb</tt>. The colon and space after the type are
5674 <var>library-name</var> is the name of the shared library,
5675 in this case <tt>libz</tt>. (This must match the name part
5676 of the soname, see below.)
5680 <var>soname-version</var> is the version part of the soname of
5681 the library. The soname is the thing that must exactly match
5682 for the library to be recognized by the dynamic linker, and is
5684 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5685 example, <tt>libz.so.1</tt>.<footnote>
5686 This can be determined using the command
5687 <example compact="compact">
5688 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5691 The version part is the part which comes after
5692 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5693 instead be of the form
5694 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5695 as <tt>libdb-4.8.so</tt>, in which case the name would
5696 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5700 <var>dependencies</var> has the same syntax as a dependency
5701 field in a binary package control file. It should give
5702 details of which packages are required to satisfy a binary
5703 built against the version of the library contained in the
5704 package. See <ref id="depsyntax"> for details.
5708 In our example, if the first version of the <tt>zlib1g</tt>
5709 package which contained a minor number of at least
5710 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5711 <tt>shlibs</tt> entry for this library could say:
5712 <example compact="compact">
5713 libz 1 zlib1g (>= 1:1.1.3)
5715 The version-specific dependency is to avoid warnings from
5716 the dynamic linker about using older shared libraries with
5721 As zlib1g also provides a udeb containing the shared library,
5722 there would also be a second line:
5723 <example compact="compact">
5724 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5730 <heading>Providing a <file>shlibs</file> file</heading>
5733 If your package provides a shared library, you need to create
5734 a <file>shlibs</file> file following the format described above.
5735 It is usual to call this file <file>debian/shlibs</file> (but if
5736 you have multiple binary packages, you might want to call it
5737 <file>debian/shlibs.<var>package</var></file> instead). Then
5738 let <file>debian/rules</file> install it in the control area:
5739 <example compact="compact">
5740 install -m644 debian/shlibs debian/tmp/DEBIAN
5742 or, in the case of a multi-binary package:
5743 <example compact="compact">
5744 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5746 An alternative way of doing this is to create the
5747 <file>shlibs</file> file in the control area directly from
5748 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5749 file at all,<footnote>
5750 This is what <prgn>dh_makeshlibs</prgn> in
5751 the <package>debhelper</package> suite does. If your package
5752 also has a udeb that provides a shared
5753 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5754 the <tt>udeb:</tt> lines if you specify the name of the udeb
5755 with the <tt>--add-udeb</tt> option.
5757 since the <file>debian/shlibs</file> file itself is ignored by
5758 <prgn>dpkg-shlibdeps</prgn>.
5762 As <prgn>dpkg-shlibdeps</prgn> reads the
5763 <file>DEBIAN/shlibs</file> files in all of the binary packages
5764 being built from this source package, all of the
5765 <file>DEBIAN/shlibs</file> files should be installed before
5766 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5774 <chapt id="opersys"><heading>The Operating System</heading>
5777 <heading>File system hierarchy</heading>
5781 <heading>File System Structure</heading>
5784 The location of all installed files and directories must
5785 comply with the Filesystem Hierarchy Standard (FHS),
5786 version 2.3, with the exceptions noted below, and except
5787 where doing so would violate other terms of Debian
5788 Policy. The following exceptions to the FHS apply:
5793 The optional rules related to user specific
5794 configuration files for applications are stored in
5795 the user's home directory are relaxed. It is
5796 recommended that such files start with the
5797 '<tt>.</tt>' character (a "dot file"), and if an
5798 application needs to create more than one dot file
5799 then the preferred placement is in a subdirectory
5800 with a name starting with a '.' character, (a "dot
5801 directory"). In this case it is recommended the
5802 configuration files not start with the '.'
5808 The requirement for amd64 to use <file>/lib64</file>
5809 for 64 bit binaries is removed.
5814 The requirement for object files, internal binaries, and
5815 libraries, including <file>libc.so.*</file>, to be located
5816 directly under <file>/lib{,32}</file> and
5817 <file>/usr/lib{,32}</file> is amended, permitting files
5818 to instead be installed to
5819 <file>/lib/<var>triplet</var></file> and
5820 <file>/usr/lib/<var>triplet</var></file>, where
5821 <tt><var>triplet</var></tt> is the value returned by
5822 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5823 architecture of the package. Packages may <em>not</em>
5824 install files to any <var>triplet</var> path other
5825 than the one matching the architecture of that package;
5826 for instance, an <tt>Architecture: amd64</tt> package
5827 containing 32-bit x86 libraries may not install these
5828 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5830 This is necessary in order to reserve the directories for
5831 use in cross-installation of library packages from other
5832 architectures, as part of the planned deployment of
5837 Applications may also use a single subdirectory under
5838 <file>/usr/lib/<var>triplet</var></file>.
5841 The execution time linker/loader, ld*, must still be made
5842 available in the existing location under /lib or /lib64
5843 since this is part of the ELF ABI for the architecture.
5848 The requirement that
5849 <file>/usr/local/share/man</file> be "synonymous"
5850 with <file>/usr/local/man</file> is relaxed to a
5855 The requirement that windowmanagers with a single
5856 configuration file call it <file>system.*wmrc</file>
5857 is removed, as is the restriction that the window
5858 manager subdirectory be named identically to the
5859 window manager name itself.
5864 The requirement that boot manager configuration
5865 files live in <file>/etc</file>, or at least are
5866 symlinked there, is relaxed to a recommendation.
5871 The following directories in the root filesystem are
5872 additionally allowed: <file>/sys</file> and
5873 <file>/selinux</file>. <footnote>These directories
5874 are used as mount points to mount virtual filesystems
5875 to get access to kernel information.</footnote>
5882 The version of this document referred here can be
5883 found in the <tt>debian-policy</tt> package or on <url
5884 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5885 name="FHS (Debian copy)"> alongside this manual (or, if
5886 you have the <package>debian-policy</package> installed,
5888 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5889 (local copy)">). The
5890 latest version, which may be a more recent version, may
5892 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5893 Specific questions about following the standard may be
5894 asked on the <tt>debian-devel</tt> mailing list, or
5895 referred to the FHS mailing list (see the
5896 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5902 <heading>Site-specific programs</heading>
5905 As mandated by the FHS, packages must not place any
5906 files in <file>/usr/local</file>, either by putting them in
5907 the file system archive to be unpacked by <prgn>dpkg</prgn>
5908 or by manipulating them in their maintainer scripts.
5912 However, the package may create empty directories below
5913 <file>/usr/local</file> so that the system administrator knows
5914 where to place site-specific files. These are not
5915 directories <em>in</em> <file>/usr/local</file>, but are
5916 children of directories in <file>/usr/local</file>. These
5917 directories (<file>/usr/local/*/dir/</file>)
5918 should be removed on package removal if they are
5923 Note that this applies only to
5924 directories <em>below</em> <file>/usr/local</file>,
5925 not <em>in</em> <file>/usr/local</file>. Packages must
5926 not create sub-directories in the
5927 directory <file>/usr/local</file> itself, except those
5928 listed in FHS, section 4.5. However, you may create
5929 directories below them as you wish. You must not remove
5930 any of the directories listed in 4.5, even if you created
5935 Since <file>/usr/local</file> can be mounted read-only from a
5936 remote server, these directories must be created and
5937 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5938 maintainer scripts and not be included in the
5939 <file>.deb</file> archive. These scripts must not fail if
5940 either of these operations fail.
5944 For example, the <tt>emacsen-common</tt> package could
5945 contain something like
5946 <example compact="compact">
5947 if [ ! -e /usr/local/share/emacs ]
5949 if mkdir /usr/local/share/emacs 2>/dev/null
5951 chown root:staff /usr/local/share/emacs
5952 chmod 2775 /usr/local/share/emacs
5956 in its <prgn>postinst</prgn> script, and
5957 <example compact="compact">
5958 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5959 rmdir /usr/local/share/emacs 2>/dev/null || true
5961 in the <prgn>prerm</prgn> script. (Note that this form is
5962 used to ensure that if the script is interrupted, the
5963 directory <file>/usr/local/share/emacs</file> will still be
5968 If you do create a directory in <file>/usr/local</file> for
5969 local additions to a package, you should ensure that
5970 settings in <file>/usr/local</file> take precedence over the
5971 equivalents in <file>/usr</file>.
5975 However, because <file>/usr/local</file> and its contents are
5976 for exclusive use of the local administrator, a package
5977 must not rely on the presence or absence of files or
5978 directories in <file>/usr/local</file> for normal operation.
5982 The <file>/usr/local</file> directory itself and all the
5983 subdirectories created by the package should (by default) have
5984 permissions 2775 (group-writable and set-group-id) and be
5985 owned by <tt>root:staff</tt>.
5990 <heading>The system-wide mail directory</heading>
5992 The system-wide mail directory
5993 is <file>/var/mail</file>. This directory is part of the
5994 base system and should not be owned by any particular mail
5995 agents. The use of the old
5996 location <file>/var/spool/mail</file> is deprecated, even
5997 though the spool may still be physically located there.
6003 <heading>Users and groups</heading>
6006 <heading>Introduction</heading>
6008 The Debian system can be configured to use either plain or
6013 Some user ids (UIDs) and group ids (GIDs) are reserved
6014 globally for use by certain packages. Because some
6015 packages need to include files which are owned by these
6016 users or groups, or need the ids compiled into binaries,
6017 these ids must be used on any Debian system only for the
6018 purpose for which they are allocated. This is a serious
6019 restriction, and we should avoid getting in the way of
6020 local administration policies. In particular, many sites
6021 allocate users and/or local system groups starting at 100.
6025 Apart from this we should have dynamically allocated ids,
6026 which should by default be arranged in some sensible
6027 order, but the behavior should be configurable.
6031 Packages other than <tt>base-passwd</tt> must not modify
6032 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6033 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6038 <heading>UID and GID classes</heading>
6040 The UID and GID numbers are divided into classes as
6046 Globally allocated by the Debian project, the same
6047 on every Debian system. These ids will appear in
6048 the <file>passwd</file> and <file>group</file> files of all
6049 Debian systems, new ids in this range being added
6050 automatically as the <tt>base-passwd</tt> package is
6055 Packages which need a single statically allocated
6056 uid or gid should use one of these; their
6057 maintainers should ask the <tt>base-passwd</tt>
6065 Dynamically allocated system users and groups.
6066 Packages which need a user or group, but can have
6067 this user or group allocated dynamically and
6068 differently on each system, should use <tt>adduser
6069 --system</tt> to create the group and/or user.
6070 <prgn>adduser</prgn> will check for the existence of
6071 the user or group, and if necessary choose an unused
6072 id based on the ranges specified in
6073 <file>adduser.conf</file>.
6077 <tag>1000-59999:</tag>
6080 Dynamically allocated user accounts. By default
6081 <prgn>adduser</prgn> will choose UIDs and GIDs for
6082 user accounts in this range, though
6083 <file>adduser.conf</file> may be used to modify this
6088 <tag>60000-64999:</tag>
6091 Globally allocated by the Debian project, but only
6092 created on demand. The ids are allocated centrally
6093 and statically, but the actual accounts are only
6094 created on users' systems on demand.
6098 These ids are for packages which are obscure or
6099 which require many statically-allocated ids. These
6100 packages should check for and create the accounts in
6101 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6102 <prgn>adduser</prgn> if it has this facility) if
6103 necessary. Packages which are likely to require
6104 further allocations should have a "hole" left after
6105 them in the allocation, to give them room to
6110 <tag>65000-65533:</tag>
6118 User <tt>nobody</tt>. The corresponding gid refers
6119 to the group <tt>nogroup</tt>.
6126 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6127 not</em> be used, because it is the error return
6136 <sect id="sysvinit">
6137 <heading>System run levels and <file>init.d</file> scripts</heading>
6139 <sect1 id="/etc/init.d">
6140 <heading>Introduction</heading>
6143 The <file>/etc/init.d</file> directory contains the scripts
6144 executed by <prgn>init</prgn> at boot time and when the
6145 init state (or "runlevel") is changed (see <manref
6146 name="init" section="8">).
6150 There are at least two different, yet functionally
6151 equivalent, ways of handling these scripts. For the sake
6152 of simplicity, this document describes only the symbolic
6153 link method. However, it must not be assumed by maintainer
6154 scripts that this method is being used, and any automated
6155 manipulation of the various runlevel behaviors by
6156 maintainer scripts must be performed using
6157 <prgn>update-rc.d</prgn> as described below and not by
6158 manually installing or removing symlinks. For information
6159 on the implementation details of the other method,
6160 implemented in the <tt>file-rc</tt> package, please refer
6161 to the documentation of that package.
6165 These scripts are referenced by symbolic links in the
6166 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6167 runlevels, <prgn>init</prgn> looks in the directory
6168 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6169 execute, where <tt><var>n</var></tt> is the runlevel that
6170 is being changed to, or <tt>S</tt> for the boot-up
6175 The names of the links all have the form
6176 <file>S<var>mm</var><var>script</var></file> or
6177 <file>K<var>mm</var><var>script</var></file> where
6178 <var>mm</var> is a two-digit number and <var>script</var>
6179 is the name of the script (this should be the same as the
6180 name of the actual script in <file>/etc/init.d</file>).
6184 When <prgn>init</prgn> changes runlevel first the targets
6185 of the links whose names start with a <tt>K</tt> are
6186 executed, each with the single argument <tt>stop</tt>,
6187 followed by the scripts prefixed with an <tt>S</tt>, each
6188 with the single argument <tt>start</tt>. (The links are
6189 those in the <file>/etc/rc<var>n</var>.d</file> directory
6190 corresponding to the new runlevel.) The <tt>K</tt> links
6191 are responsible for killing services and the <tt>S</tt>
6192 link for starting services upon entering the runlevel.
6196 For example, if we are changing from runlevel 2 to
6197 runlevel 3, init will first execute all of the <tt>K</tt>
6198 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6199 all of the <tt>S</tt> prefixed scripts in that directory.
6200 The links starting with <tt>K</tt> will cause the
6201 referred-to file to be executed with an argument of
6202 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6207 The two-digit number <var>mm</var> is used to determine
6208 the order in which to run the scripts: low-numbered links
6209 have their scripts run first. For example, the
6210 <tt>K20</tt> scripts will be executed before the
6211 <tt>K30</tt> scripts. This is used when a certain service
6212 must be started before another. For example, the name
6213 server <prgn>bind</prgn> might need to be started before
6214 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6215 can set up its access lists. In this case, the script
6216 that starts <prgn>bind</prgn> would have a lower number
6217 than the script that starts <prgn>inn</prgn> so that it
6219 <example compact="compact">
6226 The two runlevels 0 (halt) and 6 (reboot) are slightly
6227 different. In these runlevels, the links with an
6228 <tt>S</tt> prefix are still called after those with a
6229 <tt>K</tt> prefix, but they too are called with the single
6230 argument <tt>stop</tt>.
6234 <sect1 id="writing-init">
6235 <heading>Writing the scripts</heading>
6238 Packages that include daemons for system services should
6239 place scripts in <file>/etc/init.d</file> to start or stop
6240 services at boot time or during a change of runlevel.
6241 These scripts should be named
6242 <file>/etc/init.d/<var>package</var></file>, and they should
6243 accept one argument, saying what to do:
6246 <tag><tt>start</tt></tag>
6247 <item>start the service,</item>
6249 <tag><tt>stop</tt></tag>
6250 <item>stop the service,</item>
6252 <tag><tt>restart</tt></tag>
6253 <item>stop and restart the service if it's already running,
6254 otherwise start the service</item>
6256 <tag><tt>reload</tt></tag>
6257 <item><p>cause the configuration of the service to be
6258 reloaded without actually stopping and restarting
6261 <tag><tt>force-reload</tt></tag>
6262 <item>cause the configuration to be reloaded if the
6263 service supports this, otherwise restart the
6267 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6268 <tt>force-reload</tt> options should be supported by all
6269 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6274 The <file>init.d</file> scripts must ensure that they will
6275 behave sensibly (i.e., returning success and not starting
6276 multiple copies of a service) if invoked with <tt>start</tt>
6277 when the service is already running, or with <tt>stop</tt>
6278 when it isn't, and that they don't kill unfortunately-named
6279 user processes. The best way to achieve this is usually to
6280 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6285 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6286 scripts. Writing correct <file>init.d</file> scripts requires
6287 accepting various error exit statuses when daemons are already
6288 running or already stopped without aborting
6289 the <file>init.d</file> script, and common <file>init.d</file>
6290 function libraries are not safe to call with <tt>set -e</tt>
6292 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6293 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6294 in effect and echoing status messages to the console fails,
6296 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6297 to not use <tt>set -e</tt> and instead check the result of
6298 each command separately.
6302 If a service reloads its configuration automatically (as
6303 in the case of <prgn>cron</prgn>, for example), the
6304 <tt>reload</tt> option of the <file>init.d</file> script
6305 should behave as if the configuration has been reloaded
6310 The <file>/etc/init.d</file> scripts must be treated as
6311 configuration files, either (if they are present in the
6312 package, that is, in the .deb file) by marking them as
6313 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6314 by managing them correctly in the maintainer scripts (see
6315 <ref id="config-files">). This is important since we want
6316 to give the local system administrator the chance to adapt
6317 the scripts to the local system, e.g., to disable a
6318 service without de-installing the package, or to specify
6319 some special command line options when starting a service,
6320 while making sure their changes aren't lost during the next
6325 These scripts should not fail obscurely when the
6326 configuration files remain but the package has been
6327 removed, as configuration files remain on the system after
6328 the package has been removed. Only when <prgn>dpkg</prgn>
6329 is executed with the <tt>--purge</tt> option will
6330 configuration files be removed. In particular, as the
6331 <file>/etc/init.d/<var>package</var></file> script itself is
6332 usually a <tt>conffile</tt>, it will remain on the system
6333 if the package is removed but not purged. Therefore, you
6334 should include a <tt>test</tt> statement at the top of the
6336 <example compact="compact">
6337 test -f <var>program-executed-later-in-script</var> || exit 0
6342 Often there are some variables in the <file>init.d</file>
6343 scripts whose values control the behavior of the scripts,
6344 and which a system administrator is likely to want to
6345 change. As the scripts themselves are frequently
6346 <tt>conffile</tt>s, modifying them requires that the
6347 administrator merge in their changes each time the package
6348 is upgraded and the <tt>conffile</tt> changes. To ease
6349 the burden on the system administrator, such configurable
6350 values should not be placed directly in the script.
6351 Instead, they should be placed in a file in
6352 <file>/etc/default</file>, which typically will have the same
6353 base name as the <file>init.d</file> script. This extra file
6354 should be sourced by the script when the script runs. It
6355 must contain only variable settings and comments in SUSv3
6356 <prgn>sh</prgn> format. It may either be a
6357 <tt>conffile</tt> or a configuration file maintained by
6358 the package maintainer scripts. See <ref id="config-files">
6363 To ensure that vital configurable values are always
6364 available, the <file>init.d</file> script should set default
6365 values for each of the shell variables it uses, either
6366 before sourcing the <file>/etc/default/</file> file or
6367 afterwards using something like the <tt>:
6368 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6369 script must behave sensibly and not fail if the
6370 <file>/etc/default</file> file is deleted.
6374 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6375 as temporary filesystems<footnote>
6376 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6377 options in <file>/etc/default/rcS</file>.
6378 </footnote>, so the <file>init.d</file> scripts must handle this
6379 correctly. This will typically amount to creating any required
6380 subdirectories dynamically when the <file>init.d</file> script
6381 is run, rather than including them in the package and relying on
6382 <prgn>dpkg</prgn> to create them.
6387 <heading>Interfacing with the initscript system</heading>
6390 Maintainers should use the abstraction layer provided by
6391 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6392 programs to deal with initscripts in their packages'
6393 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6394 and <prgn>postrm</prgn>.
6398 Directly managing the /etc/rc?.d links and directly
6399 invoking the <file>/etc/init.d/</file> initscripts should
6400 be done only by packages providing the initscript
6401 subsystem (such as <prgn>sysv-rc</prgn> and
6402 <prgn>file-rc</prgn>).
6406 <heading>Managing the links</heading>
6409 The program <prgn>update-rc.d</prgn> is provided for
6410 package maintainers to arrange for the proper creation and
6411 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6412 or their functional equivalent if another method is being
6413 used. This may be used by maintainers in their packages'
6414 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6418 You must not include any <file>/etc/rc<var>n</var>.d</file>
6419 symbolic links in the actual archive or manually create or
6420 remove the symbolic links in maintainer scripts; you must
6421 use the <prgn>update-rc.d</prgn> program instead. (The
6422 former will fail if an alternative method of maintaining
6423 runlevel information is being used.) You must not include
6424 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6425 in the archive either. (Only the <tt>sysvinit</tt>
6430 By default <prgn>update-rc.d</prgn> will start services in
6431 each of the multi-user state runlevels (2, 3, 4, and 5)
6432 and stop them in the halt runlevel (0), the single-user
6433 runlevel (1) and the reboot runlevel (6). The system
6434 administrator will have the opportunity to customize
6435 runlevels by simply adding, moving, or removing the
6436 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6437 symbolic links are being used, or by modifying
6438 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6443 To get the default behavior for your package, put in your
6444 <prgn>postinst</prgn> script
6445 <example compact="compact">
6446 update-rc.d <var>package</var> defaults
6448 and in your <prgn>postrm</prgn>
6449 <example compact="compact">
6450 if [ "$1" = purge ]; then
6451 update-rc.d <var>package</var> remove
6453 </example>. Note that if your package changes runlevels
6454 or priority, you may have to remove and recreate the links,
6455 since otherwise the old links may persist. Refer to the
6456 documentation of <prgn>update-rc.d</prgn>.
6460 This will use a default sequence number of 20. If it does
6461 not matter when or in which order the <file>init.d</file>
6462 script is run, use this default. If it does, then you
6463 should talk to the maintainer of the <prgn>sysvinit</prgn>
6464 package or post to <tt>debian-devel</tt>, and they will
6465 help you choose a number.
6469 For more information about using <tt>update-rc.d</tt>,
6470 please consult its man page <manref name="update-rc.d"
6476 <heading>Running initscripts</heading>
6478 The program <prgn>invoke-rc.d</prgn> is provided to make
6479 it easier for package maintainers to properly invoke an
6480 initscript, obeying runlevel and other locally-defined
6481 constraints that might limit a package's right to start,
6482 stop and otherwise manage services. This program may be
6483 used by maintainers in their packages' scripts.
6487 The package maintainer scripts must use
6488 <prgn>invoke-rc.d</prgn> to invoke the
6489 <file>/etc/init.d/*</file> initscripts, instead of
6490 calling them directly.
6494 By default, <prgn>invoke-rc.d</prgn> will pass any
6495 action requests (start, stop, reload, restart...) to the
6496 <file>/etc/init.d</file> script, filtering out requests
6497 to start or restart a service out of its intended
6502 Most packages will simply need to change:
6503 <example compact="compact">/etc/init.d/<package>
6504 <action></example> in their <prgn>postinst</prgn>
6505 and <prgn>prerm</prgn> scripts to:
6506 <example compact="compact">
6507 if which invoke-rc.d >/dev/null 2>&1; then
6508 invoke-rc.d <var>package</var> <action>
6510 /etc/init.d/<var>package</var> <action>
6516 A package should register its initscript services using
6517 <prgn>update-rc.d</prgn> before it tries to invoke them
6518 using <prgn>invoke-rc.d</prgn>. Invocation of
6519 unregistered services may fail.
6523 For more information about using
6524 <prgn>invoke-rc.d</prgn>, please consult its man page
6525 <manref name="invoke-rc.d" section="8">.
6531 <heading>Boot-time initialization</heading>
6534 There used to be another directory, <file>/etc/rc.boot</file>,
6535 which contained scripts which were run once per machine
6536 boot. This has been deprecated in favour of links from
6537 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6538 described in <ref id="/etc/init.d">. Packages must not
6539 place files in <file>/etc/rc.boot</file>.
6544 <heading>Example</heading>
6547 An example on which you can base your
6548 <file>/etc/init.d</file> scripts is found in
6549 <file>/etc/init.d/skeleton</file>.
6556 <heading>Console messages from <file>init.d</file> scripts</heading>
6559 This section describes the formats to be used for messages
6560 written to standard output by the <file>/etc/init.d</file>
6561 scripts. The intent is to improve the consistency of
6562 Debian's startup and shutdown look and feel. For this
6563 reason, please look very carefully at the details. We want
6564 the messages to have the same format in terms of wording,
6565 spaces, punctuation and case of letters.
6569 Here is a list of overall rules that should be used for
6570 messages generated by <file>/etc/init.d</file> scripts.
6576 The message should fit in one line (fewer than 80
6577 characters), start with a capital letter and end with
6578 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6582 If the script is performing some time consuming task in
6583 the background (not merely starting or stopping a
6584 program, for instance), an ellipsis (three dots:
6585 <tt>...</tt>) should be output to the screen, with no
6586 leading or tailing whitespace or line feeds.
6590 The messages should appear as if the computer is telling
6591 the user what it is doing (politely :-), but should not
6592 mention "it" directly. For example, instead of:
6593 <example compact="compact">
6594 I'm starting network daemons: nfsd mountd.
6596 the message should say
6597 <example compact="compact">
6598 Starting network daemons: nfsd mountd.
6605 <tt>init.d</tt> script should use the following standard
6606 message formats for the situations enumerated below.
6612 <p>When daemons are started</p>
6615 If the script starts one or more daemons, the output
6616 should look like this (a single line, no leading
6618 <example compact="compact">
6619 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6621 The <var>description</var> should describe the
6622 subsystem the daemon or set of daemons are part of,
6623 while <var>daemon-1</var> up to <var>daemon-n</var>
6624 denote each daemon's name (typically the file name of
6629 For example, the output of <file>/etc/init.d/lpd</file>
6631 <example compact="compact">
6632 Starting printer spooler: lpd.
6637 This can be achieved by saying
6638 <example compact="compact">
6639 echo -n "Starting printer spooler: lpd"
6640 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6643 in the script. If there are more than one daemon to
6644 start, the output should look like this:
6645 <example compact="compact">
6646 echo -n "Starting remote file system services:"
6647 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6648 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6649 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6652 This makes it possible for the user to see what is
6653 happening and when the final daemon has been started.
6654 Care should be taken in the placement of white spaces:
6655 in the example above the system administrators can
6656 easily comment out a line if they don't want to start
6657 a specific daemon, while the displayed message still
6663 <p>When a system parameter is being set</p>
6666 If you have to set up different system parameters
6667 during the system boot, you should use this format:
6668 <example compact="compact">
6669 Setting <var>parameter</var> to "<var>value</var>".
6674 You can use a statement such as the following to get
6676 <example compact="compact">
6677 echo "Setting DNS domainname to \"$domainname\"."
6682 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6683 for the left and right quotation marks. A grave accent
6684 (<tt>`</tt>) is not a quote character; neither is an
6685 apostrophe (<tt>'</tt>).
6690 <p>When a daemon is stopped or restarted</p>
6693 When you stop or restart a daemon, you should issue a
6694 message identical to the startup message, except that
6695 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6696 or <tt>Restarting</tt> respectively.
6700 For example, stopping the printer daemon will look like
6702 <example compact="compact">
6703 Stopping printer spooler: lpd.
6709 <p>When something is executed</p>
6712 There are several examples where you have to run a
6713 program at system startup or shutdown to perform a
6714 specific task, for example, setting the system's clock
6715 using <prgn>netdate</prgn> or killing all processes
6716 when the system shuts down. Your message should look
6718 <example compact="compact">
6719 Doing something very useful...done.
6721 You should print the <tt>done.</tt> immediately after
6722 the job has been completed, so that the user is
6723 informed why they have to wait. You can get this
6725 <example compact="compact">
6726 echo -n "Doing something very useful..."
6735 <p>When the configuration is reloaded</p>
6738 When a daemon is forced to reload its configuration
6739 files you should use the following format:
6740 <example compact="compact">
6741 Reloading <var>description</var> configuration...done.
6743 where <var>description</var> is the same as in the
6744 daemon starting message.
6752 <heading>Cron jobs</heading>
6755 Packages must not modify the configuration file
6756 <file>/etc/crontab</file>, and they must not modify the files in
6757 <file>/var/spool/cron/crontabs</file>.</p>
6760 If a package wants to install a job that has to be executed
6761 via cron, it should place a file with the name of the
6762 package in one or more of the following directories:
6763 <example compact="compact">
6769 As these directory names imply, the files within them are
6770 executed on an hourly, daily, weekly, or monthly basis,
6771 respectively. The exact times are listed in
6772 <file>/etc/crontab</file>.</p>
6775 All files installed in any of these directories must be
6776 scripts (e.g., shell scripts or Perl scripts) so that they
6777 can easily be modified by the local system administrator.
6778 In addition, they must be treated as configuration files.
6782 If a certain job has to be executed at some other frequency or
6783 at a specific time, the package should install a file
6784 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6785 same syntax as <file>/etc/crontab</file> and is processed by
6786 <prgn>cron</prgn> automatically. The file must also be
6787 treated as a configuration file. (Note that entries in the
6788 <file>/etc/cron.d</file> directory are not handled by
6789 <prgn>anacron</prgn>. Thus, you should only use this
6790 directory for jobs which may be skipped if the system is not
6793 Unlike <file>crontab</file> files described in the IEEE Std
6794 1003.1-2008 (POSIX.1) available from
6795 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6796 name="The Open Group">, the files in
6797 <file>/etc/cron.d</file> and the file
6798 <file>/etc/crontab</file> have seven fields; namely:
6800 <item>Minute [0,59]</item>
6801 <item>Hour [0,23]</item>
6802 <item>Day of the month [1,31]</item>
6803 <item>Month of the year [1,12]</item>
6804 <item>Day of the week ([0,6] with 0=Sunday)</item>
6805 <item>Username</item>
6806 <item>Command to be run</item>
6808 Ranges of numbers are allowed. Ranges are two numbers
6809 separated with a hyphen. The specified range is inclusive.
6810 Lists are allowed. A list is a set of numbers (or ranges)
6811 separated by commas. Step values can be used in conjunction
6816 The scripts or <tt>crontab</tt> entries in these directories should
6817 check if all necessary programs are installed before they
6818 try to execute them. Otherwise, problems will arise when a
6819 package was removed but not purged since configuration files
6820 are kept on the system in this situation.
6824 Any <tt>cron</tt> daemon must provide
6825 <file>/usr/bin/crontab</file> and support normal
6826 <tt>crontab</tt> entries as specified in POSIX. The daemon
6827 must also support names for days and months, ranges, and
6828 step values. It has to support <file>/etc/crontab</file>,
6829 and correctly execute the scripts in
6830 <file>/etc/cron.d</file>. The daemon must also correctly
6832 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6837 <heading>Menus</heading>
6840 The Debian <tt>menu</tt> package provides a standard
6841 interface between packages providing applications and
6842 <em>menu programs</em> (either X window managers or
6843 text-based menu programs such as <prgn>pdmenu</prgn>).
6847 All packages that provide applications that need not be
6848 passed any special command line arguments for normal
6849 operation should register a menu entry for those
6850 applications, so that users of the <tt>menu</tt> package
6851 will automatically get menu entries in their window
6852 managers, as well in shells like <tt>pdmenu</tt>.
6856 Menu entries should follow the current menu policy.
6860 The menu policy can be found in the <tt>menu-policy</tt>
6861 files in the <tt>debian-policy</tt> package.
6862 It is also available from the Debian web mirrors at
6863 <tt><url name="/doc/packaging-manuals/menu-policy/"
6864 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6868 Please also refer to the <em>Debian Menu System</em>
6869 documentation that comes with the <package>menu</package>
6870 package for information about how to register your
6876 <heading>Multimedia handlers</heading>
6879 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6880 is a mechanism for encoding files and data streams and
6881 providing meta-information about them, in particular their
6882 type (e.g. audio or video) and format (e.g. PNG, HTML,
6887 Registration of MIME type handlers allows programs like mail
6888 user agents and web browsers to invoke these handlers to
6889 view, edit or display MIME types they don't support directly.
6893 Packages which provide the ability to view/show/play,
6894 compose, edit or print MIME types should register themselves
6895 as such following the current MIME support policy.
6899 The MIME support policy can be found in the <tt>mime-policy</tt>
6900 files in the <tt>debian-policy</tt> package.
6901 It is also available from the Debian web mirrors at
6902 <tt><url name="/doc/packaging-manuals/mime-policy/"
6903 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6909 <heading>Keyboard configuration</heading>
6912 To achieve a consistent keyboard configuration so that all
6913 applications interpret a keyboard event the same way, all
6914 programs in the Debian distribution must be configured to
6915 comply with the following guidelines.
6919 The following keys must have the specified interpretations:
6922 <tag><tt><--</tt></tag>
6923 <item>delete the character to the left of the cursor</item>
6925 <tag><tt>Delete</tt></tag>
6926 <item>delete the character to the right of the cursor</item>
6928 <tag><tt>Control+H</tt></tag>
6929 <item>emacs: the help prefix</item>
6932 The interpretation of any keyboard events should be
6933 independent of the terminal that is used, be it a virtual
6934 console, an X terminal emulator, an rlogin/telnet session,
6939 The following list explains how the different programs
6940 should be set up to achieve this:
6946 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6950 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6954 X translations are set up to make
6955 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6956 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6957 is the vt220 escape code for the "delete character"
6958 key). This must be done by loading the X resources
6959 using <prgn>xrdb</prgn> on all local X displays, not
6960 using the application defaults, so that the
6961 translation resources used correspond to the
6962 <prgn>xmodmap</prgn> settings.
6966 The Linux console is configured to make
6967 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6968 generate <tt>ESC [ 3 ~</tt>.
6972 X applications are configured so that <tt><</tt>
6973 deletes left, and <tt>Delete</tt> deletes right. Motif
6974 applications already work like this.
6978 Terminals should have <tt>stty erase ^?</tt> .
6982 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6983 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6984 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6988 Emacs is programmed to map <tt>KB_Backspace</tt> or
6989 the <tt>stty erase</tt> character to
6990 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6991 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6992 <tt>^H</tt> to <tt>help</tt> as always.
6996 Other applications use the <tt>stty erase</tt>
6997 character and <tt>kdch1</tt> for the two delete keys,
6998 with ASCII DEL being "delete previous character" and
6999 <tt>kdch1</tt> being "delete character under
7007 This will solve the problem except for the following
7014 Some terminals have a <tt><--</tt> key that cannot
7015 be made to produce anything except <tt>^H</tt>. On
7016 these terminals Emacs help will be unavailable on
7017 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7018 character takes precedence in Emacs, and has been set
7019 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7020 available) can be used instead.
7024 Some operating systems use <tt>^H</tt> for <tt>stty
7025 erase</tt>. However, modern telnet versions and all
7026 rlogin versions propagate <tt>stty</tt> settings, and
7027 almost all UNIX versions honour <tt>stty erase</tt>.
7028 Where the <tt>stty</tt> settings are not propagated
7029 correctly, things can be made to work by using
7030 <tt>stty</tt> manually.
7034 Some systems (including previous Debian versions) use
7035 <prgn>xmodmap</prgn> to arrange for both
7036 <tt><--</tt> and <tt>Delete</tt> to generate
7037 <tt>KB_Delete</tt>. We can change the behavior of
7038 their X clients using the same X resources that we use
7039 to do it for our own clients, or configure our clients
7040 using their resources when things are the other way
7041 around. On displays configured like this
7042 <tt>Delete</tt> will not work, but <tt><--</tt>
7047 Some operating systems have different <tt>kdch1</tt>
7048 settings in their <tt>terminfo</tt> database for
7049 <tt>xterm</tt> and others. On these systems the
7050 <tt>Delete</tt> key will not work correctly when you
7051 log in from a system conforming to our policy, but
7052 <tt><--</tt> will.
7059 <heading>Environment variables</heading>
7062 A program must not depend on environment variables to get
7063 reasonable defaults. (That's because these environment
7064 variables would have to be set in a system-wide
7065 configuration file like <file>/etc/profile</file>, which is not
7066 supported by all shells.)
7070 If a program usually depends on environment variables for its
7071 configuration, the program should be changed to fall back to
7072 a reasonable default configuration if these environment
7073 variables are not present. If this cannot be done easily
7074 (e.g., if the source code of a non-free program is not
7075 available), the program must be replaced by a small
7076 "wrapper" shell script which sets the environment variables
7077 if they are not already defined, and calls the original program.
7081 Here is an example of a wrapper script for this purpose:
7083 <example compact="compact">
7085 BAR=${BAR:-/var/lib/fubar}
7087 exec /usr/lib/foo/foo "$@"
7092 Furthermore, as <file>/etc/profile</file> is a configuration
7093 file of the <prgn>base-files</prgn> package, other packages must
7094 not put any environment variables or other commands into that
7099 <sect id="doc-base">
7100 <heading>Registering Documents using doc-base</heading>
7103 The <package>doc-base</package> package implements a
7104 flexible mechanism for handling and presenting
7105 documentation. The recommended practice is for every Debian
7106 package that provides online documentation (other than just
7107 manual pages) to register these documents with
7108 <package>doc-base</package> by installing a
7109 <package>doc-base</package> control file via the
7110 <prgn/install-docs/ script at installation time and
7111 de-register the manuals again when the package is removed.
7114 Please refer to the documentation that comes with the
7115 <package>doc-base</package> package for information and
7124 <heading>Files</heading>
7126 <sect id="binaries">
7127 <heading>Binaries</heading>
7130 Two different packages must not install programs with
7131 different functionality but with the same filenames. (The
7132 case of two programs having the same functionality but
7133 different implementations is handled via "alternatives" or
7134 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7135 <ref id="conflicts"> respectively.) If this case happens,
7136 one of the programs must be renamed. The maintainers should
7137 report this to the <tt>debian-devel</tt> mailing list and
7138 try to find a consensus about which program will have to be
7139 renamed. If a consensus cannot be reached, <em>both</em>
7140 programs must be renamed.
7144 By default, when a package is being built, any binaries
7145 created should include debugging information, as well as
7146 being compiled with optimization. You should also turn on
7147 as many reasonable compilation warnings as possible; this
7148 makes life easier for porters, who can then look at build
7149 logs for possible problems. For the C programming language,
7150 this means the following compilation parameters should be
7152 <example compact="compact">
7154 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7156 INSTALL = install -s # (or use strip on the files in debian/tmp)
7161 Note that by default all installed binaries should be stripped,
7162 either by using the <tt>-s</tt> flag to
7163 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7164 the binaries after they have been copied into
7165 <file>debian/tmp</file> but before the tree is made into a
7170 Although binaries in the build tree should be compiled with
7171 debugging information by default, it can often be difficult to
7172 debug programs if they are also subjected to compiler
7173 optimization. For this reason, it is recommended to support the
7174 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7175 (see <ref id="debianrules-options">). This variable can contain
7176 several flags to change how a package is compiled and built.
7180 It is up to the package maintainer to decide what
7181 compilation options are best for the package. Certain
7182 binaries (such as computationally-intensive programs) will
7183 function better with certain flags (<tt>-O3</tt>, for
7184 example); feel free to use them. Please use good judgment
7185 here. Don't use flags for the sake of it; only use them
7186 if there is good reason to do so. Feel free to override
7187 the upstream author's ideas about which compilation
7188 options are best: they are often inappropriate for our
7194 <sect id="libraries">
7195 <heading>Libraries</heading>
7198 If the package is <strong>architecture: any</strong>, then
7199 the shared library compilation and linking flags must have
7200 <tt>-fPIC</tt>, or the package shall not build on some of
7201 the supported architectures<footnote>
7203 If you are using GCC, <tt>-fPIC</tt> produces code with
7204 relocatable position independent code, which is required for
7205 most architectures to create a shared library, with i386 and
7206 perhaps some others where non position independent code is
7207 permitted in a shared library.
7210 Position independent code may have a performance penalty,
7211 especially on <tt>i386</tt>. However, in most cases the
7212 speed penalty must be measured against the memory wasted on
7213 the few architectures where non position independent code is
7216 </footnote>. Any exception to this rule must be discussed on
7217 the mailing list <em>debian-devel@lists.debian.org</em>, and
7218 a rough consensus obtained. The reasons for not compiling
7219 with <tt>-fPIC</tt> flag must be recorded in the file
7220 <tt>README.Debian</tt>, and care must be taken to either
7221 restrict the architecture or arrange for <tt>-fPIC</tt> to
7222 be used on architectures where it is required.<footnote>
7224 Some of the reasons why this might be required is if the
7225 library contains hand crafted assembly code that is not
7226 relocatable, the speed penalty is excessive for compute
7227 intensive libs, and similar reasons.
7232 As to the static libraries, the common case is not to have
7233 relocatable code, since there is no benefit, unless in specific
7234 cases; therefore the static version must not be compiled
7235 with the <tt>-fPIC</tt> flag. Any exception to this rule
7236 should be discussed on the mailing list
7237 <em>debian-devel@lists.debian.org</em>, and the reasons for
7238 compiling with the <tt>-fPIC</tt> flag must be recorded in
7239 the file <tt>README.Debian</tt>. <footnote>
7241 Some of the reasons for linking static libraries with
7242 the <tt>-fPIC</tt> flag are if, for example, one needs a
7243 Perl API for a library that is under rapid development,
7244 and has an unstable API, so shared libraries are
7245 pointless at this phase of the library's development. In
7246 that case, since Perl needs a library with relocatable
7247 code, it may make sense to create a static library with
7248 relocatable code. Another reason cited is if you are
7249 distilling various libraries into a common shared
7250 library, like <tt>mklibs</tt> does in the Debian
7256 In other words, if both a shared and a static library is
7257 being built, each source unit (<tt>*.c</tt>, for example,
7258 for C files) will need to be compiled twice, for the normal
7262 You must specify the gcc option <tt>-D_REENTRANT</tt>
7263 when building a library (either static or shared) to make
7264 the library compatible with LinuxThreads.
7268 Although not enforced by the build tools, shared libraries
7269 must be linked against all libraries that they use symbols from
7270 in the same way that binaries are. This ensures the correct
7271 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7272 system and guarantees that all libraries can be safely opened
7273 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7274 option <tt>-Wl,-z,defs</tt> when building a shared library.
7275 Since this option enforces symbol resolution at build time,
7276 a missing library reference will be caught early as a fatal
7281 All installed shared libraries should be stripped with
7282 <example compact="compact">
7283 strip --strip-unneeded <var>your-lib</var>
7285 (The option <tt>--strip-unneeded</tt> makes
7286 <prgn>strip</prgn> remove only the symbols which aren't
7287 needed for relocation processing.) Shared libraries can
7288 function perfectly well when stripped, since the symbols for
7289 dynamic linking are in a separate part of the ELF object
7291 You might also want to use the options
7292 <tt>--remove-section=.comment</tt> and
7293 <tt>--remove-section=.note</tt> on both shared libraries
7294 and executables, and <tt>--strip-debug</tt> on static
7300 Note that under some circumstances it may be useful to
7301 install a shared library unstripped, for example when
7302 building a separate package to support debugging.
7306 Shared object files (often <file>.so</file> files) that are not
7307 public libraries, that is, they are not meant to be linked
7308 to by third party executables (binaries of other packages),
7309 should be installed in subdirectories of the
7310 <file>/usr/lib</file> directory. Such files are exempt from the
7311 rules that govern ordinary shared libraries, except that
7312 they must not be installed executable and should be
7314 A common example are the so-called "plug-ins",
7315 internal shared objects that are dynamically loaded by
7316 programs using <manref name="dlopen" section="3">.
7321 Packages that use <prgn>libtool</prgn> to create and install
7322 their shared libraries install a file containing additional
7323 metadata (ending in <file>.la</file>) alongside the library.
7324 For public libraries intended for use by other packages, these
7325 files normally should not be included in the Debian package,
7326 since the information they include is not necessary to link with
7327 the shared library on Debian and can add unnecessary additional
7328 dependencies to other programs or libraries.<footnote>
7329 These files store, among other things, all libraries on which
7330 that shared library depends. Unfortunately, if
7331 the <file>.la</file> file is present and contains that
7332 dependency information, using <prgn>libtool</prgn> when
7333 linking against that library will cause the resulting program
7334 or library to be linked against those dependencies as well,
7335 even if this is unnecessary. This can create unneeded
7336 dependencies on shared library packages that would otherwise
7337 be hidden behind the library ABI, and can make library
7338 transitions to new SONAMEs unnecessarily complicated and
7339 difficult to manage.
7341 If the <file>.la</file> file is required for that library (if,
7342 for instance, it's loaded via <tt>libltdl</tt> in a way that
7343 requires that meta-information), the <tt>dependency_libs</tt>
7344 setting in the <file>.la</file> file should normally be set to
7345 the empty string. If the shared library development package has
7346 historically included the <file>.la</file>, it must be retained
7347 in the development package (with <tt>dependency_libs</tt>
7348 emptied) until all libraries that depend on it have removed or
7349 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7350 files to prevent linking with those other libraries
7351 using <prgn>libtool</prgn> from failing.
7355 If the <file>.la</file> must be included, it should be included
7356 in the development (<tt>-dev</tt>) package, unless the library
7357 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7358 library. If it is intended for use with <tt>libltdl</tt>,
7359 the <file>.la</file> files must go in the run-time library
7364 These requirements for handling of <file>.la</file> files do not
7365 apply to loadable modules or libraries not installed in
7366 directories searched by default by the dynamic linker. Packages
7367 installing loadable modules will frequently need to install
7368 the <file>.la</file> files alongside the modules so that they
7369 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7370 does not need to be modified for libraries or modules that are
7371 not installed in directories searched by the dynamic linker by
7372 default and not intended for use by other packages.
7376 You must make sure that you use only released versions of
7377 shared libraries to build your packages; otherwise other
7378 users will not be able to run your binaries
7379 properly. Producing source packages that depend on
7380 unreleased compilers is also usually a bad
7387 <heading>Shared libraries</heading>
7389 This section has moved to <ref id="sharedlibs">.
7395 <heading>Scripts</heading>
7398 All command scripts, including the package maintainer
7399 scripts inside the package and used by <prgn>dpkg</prgn>,
7400 should have a <tt>#!</tt> line naming the shell to be used
7405 In the case of Perl scripts this should be
7406 <tt>#!/usr/bin/perl</tt>.
7410 When scripts are installed into a directory in the system
7411 PATH, the script name should not include an extension such
7412 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7413 language currently used to implement it.
7416 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7417 <file>init.d</file> scripts should almost certainly start
7418 with <tt>set -e</tt> so that errors are detected.
7419 <file>init.d</file> scripts are something of a special case, due
7420 to how frequently they need to call commands that are allowed to
7421 fail, and it may instead be easier to check the exit status of
7422 commands directly. See <ref id="writing-init"> for more
7423 information about writing <file>init.d</file> scripts.
7426 Every script should use <tt>set -e</tt> or check the exit status
7427 of <em>every</em> command.
7430 Scripts may assume that <file>/bin/sh</file> implements the
7431 SUSv3 Shell Command Language<footnote>
7432 Single UNIX Specification, version 3, which is also IEEE
7433 1003.1-2004 (POSIX), and is available on the World Wide Web
7434 from <url id="http://www.unix.org/version3/online.html"
7435 name="The Open Group"> after free
7436 registration.</footnote>
7437 plus the following additional features not mandated by
7439 These features are in widespread use in the Linux community
7440 and are implemented in all of bash, dash, and ksh, the most
7441 common shells users may wish to use as <file>/bin/sh</file>.
7444 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7445 must not generate a newline.</item>
7446 <item><tt>test</tt>, if implemented as a shell built-in, must
7447 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7449 <item><tt>local</tt> to create a scoped variable must be
7450 supported, including listing multiple variables in a single
7451 local command and assigning a value to a variable at the
7452 same time as localizing it. <tt>local</tt> may or
7453 may not preserve the variable value from an outer scope if
7454 no assignment is present. Uses such as:
7458 # ... use a, b, c, d ...
7461 must be supported and must set the value of <tt>c</tt> to
7465 If a shell script requires non-SUSv3 features from the shell
7466 interpreter other than those listed above, the appropriate shell
7467 must be specified in the first line of the script (e.g.,
7468 <tt>#!/bin/bash</tt>) and the package must depend on the package
7469 providing the shell (unless the shell package is marked
7470 "Essential", as in the case of <prgn>bash</prgn>).
7474 You may wish to restrict your script to SUSv3 features plus the
7475 above set when possible so that it may use <file>/bin/sh</file>
7476 as its interpreter. If your script works with <prgn>dash</prgn>
7477 (originally called <prgn>ash</prgn>), it probably complies with
7478 the above requirements, but if you are in doubt, use
7479 <file>/bin/bash</file>.
7483 Perl scripts should check for errors when making any
7484 system calls, including <tt>open</tt>, <tt>print</tt>,
7485 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7489 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7490 scripting languages. See <em>Csh Programming Considered
7491 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7492 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7493 If an upstream package comes with <prgn>csh</prgn> scripts
7494 then you must make sure that they start with
7495 <tt>#!/bin/csh</tt> and make your package depend on the
7496 <prgn>c-shell</prgn> virtual package.
7500 Any scripts which create files in world-writeable
7501 directories (e.g., in <file>/tmp</file>) must use a
7502 mechanism which will fail atomically if a file with the same
7503 name already exists.
7507 The Debian base system provides the <prgn>tempfile</prgn>
7508 and <prgn>mktemp</prgn> utilities for use by scripts for
7515 <heading>Symbolic links</heading>
7518 In general, symbolic links within a top-level directory
7519 should be relative, and symbolic links pointing from one
7520 top-level directory into another should be absolute. (A
7521 top-level directory is a sub-directory of the root
7522 directory <file>/</file>.)
7526 In addition, symbolic links should be specified as short as
7527 possible, i.e., link targets like <file>foo/../bar</file> are
7532 Note that when creating a relative link using
7533 <prgn>ln</prgn> it is not necessary for the target of the
7534 link to exist relative to the working directory you're
7535 running <prgn>ln</prgn> from, nor is it necessary to change
7536 directory to the directory where the link is to be made.
7537 Simply include the string that should appear as the target
7538 of the link (this will be a pathname relative to the
7539 directory in which the link resides) as the first argument
7544 For example, in your <prgn>Makefile</prgn> or
7545 <file>debian/rules</file>, you can do things like:
7546 <example compact="compact">
7547 ln -fs gcc $(prefix)/bin/cc
7548 ln -fs gcc debian/tmp/usr/bin/cc
7549 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7550 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7555 A symbolic link pointing to a compressed file should always
7556 have the same file extension as the referenced file. (For
7557 example, if a file <file>foo.gz</file> is referenced by a
7558 symbolic link, the filename of the link has to end with
7559 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7564 <heading>Device files</heading>
7567 Packages must not include device files or named pipes in the
7572 If a package needs any special device files that are not
7573 included in the base system, it must call
7574 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7575 after notifying the user<footnote>
7576 This notification could be done via a (low-priority)
7577 debconf message, or an echo (printf) statement.
7582 Packages must not remove any device files in the
7583 <prgn>postrm</prgn> or any other script. This is left to the
7584 system administrator.
7588 Debian uses the serial devices
7589 <file>/dev/ttyS*</file>. Programs using the old
7590 <file>/dev/cu*</file> devices should be changed to use
7591 <file>/dev/ttyS*</file>.
7595 Named pipes needed by the package must be created in
7596 the <prgn>postinst</prgn> script<footnote>
7597 It's better to use <prgn>mkfifo</prgn> rather
7598 than <prgn>mknod</prgn> to create named pipes so that
7599 automated checks for packages incorrectly creating device
7600 files with <prgn>mknod</prgn> won't have false positives.
7601 </footnote> and removed in
7602 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7607 <sect id="config-files">
7608 <heading>Configuration files</heading>
7611 <heading>Definitions</heading>
7615 <tag>configuration file</tag>
7617 A file that affects the operation of a program, or
7618 provides site- or host-specific information, or
7619 otherwise customizes the behavior of a program.
7620 Typically, configuration files are intended to be
7621 modified by the system administrator (if needed or
7622 desired) to conform to local policy or to provide
7623 more useful site-specific behavior.
7626 <tag><tt>conffile</tt></tag>
7628 A file listed in a package's <tt>conffiles</tt>
7629 file, and is treated specially by <prgn>dpkg</prgn>
7630 (see <ref id="configdetails">).
7636 The distinction between these two is important; they are
7637 not interchangeable concepts. Almost all
7638 <tt>conffile</tt>s are configuration files, but many
7639 configuration files are not <tt>conffiles</tt>.
7643 As noted elsewhere, <file>/etc/init.d</file> scripts,
7644 <file>/etc/default</file> files, scripts installed in
7645 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7646 configuration installed in <file>/etc/cron.d</file> must be
7647 treated as configuration files. In general, any script that
7648 embeds configuration information is de-facto a configuration
7649 file and should be treated as such.
7654 <heading>Location</heading>
7657 Any configuration files created or used by your package
7658 must reside in <file>/etc</file>. If there are several,
7659 consider creating a subdirectory of <file>/etc</file>
7660 named after your package.
7664 If your package creates or uses configuration files
7665 outside of <file>/etc</file>, and it is not feasible to modify
7666 the package to use <file>/etc</file> directly, put the files
7667 in <file>/etc</file> and create symbolic links to those files
7668 from the location that the package requires.
7673 <heading>Behavior</heading>
7676 Configuration file handling must conform to the following
7678 <list compact="compact">
7680 local changes must be preserved during a package
7684 configuration files must be preserved when the
7685 package is removed, and only deleted when the
7689 Obsolete configuration files without local changes may be
7690 removed by the package during upgrade.
7694 The easy way to achieve this behavior is to make the
7695 configuration file a <tt>conffile</tt>. This is
7696 appropriate only if it is possible to distribute a default
7697 version that will work for most installations, although
7698 some system administrators may choose to modify it. This
7699 implies that the default version will be part of the
7700 package distribution, and must not be modified by the
7701 maintainer scripts during installation (or at any other
7706 In order to ensure that local changes are preserved
7707 correctly, no package may contain or make hard links to
7708 conffiles.<footnote>
7709 Rationale: There are two problems with hard links.
7710 The first is that some editors break the link while
7711 editing one of the files, so that the two files may
7712 unwittingly become unlinked and different. The second
7713 is that <prgn>dpkg</prgn> might break the hard link
7714 while upgrading <tt>conffile</tt>s.
7719 The other way to do it is via the maintainer scripts. In
7720 this case, the configuration file must not be listed as a
7721 <tt>conffile</tt> and must not be part of the package
7722 distribution. If the existence of a file is required for
7723 the package to be sensibly configured it is the
7724 responsibility of the package maintainer to provide
7725 maintainer scripts which correctly create, update and
7726 maintain the file and remove it on purge. (See <ref
7727 id="maintainerscripts"> for more information.) These
7728 scripts must be idempotent (i.e., must work correctly if
7729 <prgn>dpkg</prgn> needs to re-run them due to errors
7730 during installation or removal), must cope with all the
7731 variety of ways <prgn>dpkg</prgn> can call maintainer
7732 scripts, must not overwrite or otherwise mangle the user's
7733 configuration without asking, must not ask unnecessary
7734 questions (particularly during upgrades), and must
7735 otherwise be good citizens.
7739 The scripts are not required to configure every possible
7740 option for the package, but only those necessary to get
7741 the package running on a given system. Ideally the
7742 sysadmin should not have to do any configuration other
7743 than that done (semi-)automatically by the
7744 <prgn>postinst</prgn> script.
7748 A common practice is to create a script called
7749 <file><var>package</var>-configure</file> and have the
7750 package's <prgn>postinst</prgn> call it if and only if the
7751 configuration file does not already exist. In certain
7752 cases it is useful for there to be an example or template
7753 file which the maintainer scripts use. Such files should
7754 be in <file>/usr/share/<var>package</var></file> or
7755 <file>/usr/lib/<var>package</var></file> (depending on whether
7756 they are architecture-independent or not). There should
7757 be symbolic links to them from
7758 <file>/usr/share/doc/<var>package</var>/examples</file> if
7759 they are examples, and should be perfectly ordinary
7760 <prgn>dpkg</prgn>-handled files (<em>not</em>
7761 configuration files).
7765 These two styles of configuration file handling must
7766 not be mixed, for that way lies madness:
7767 <prgn>dpkg</prgn> will ask about overwriting the file
7768 every time the package is upgraded.
7773 <heading>Sharing configuration files</heading>
7776 Packages which specify the same file as a
7777 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7778 with each other. (This is an instance of the general rule
7779 about not sharing files. Note that neither alternatives
7780 nor diversions are likely to be appropriate in this case;
7781 in particular, <prgn>dpkg</prgn> does not handle diverted
7782 <tt>conffile</tt>s well.)
7786 The maintainer scripts must not alter a <tt>conffile</tt>
7787 of <em>any</em> package, including the one the scripts
7792 If two or more packages use the same configuration file
7793 and it is reasonable for both to be installed at the same
7794 time, one of these packages must be defined as
7795 <em>owner</em> of the configuration file, i.e., it will be
7796 the package which handles that file as a configuration
7797 file. Other packages that use the configuration file must
7798 depend on the owning package if they require the
7799 configuration file to operate. If the other package will
7800 use the configuration file if present, but is capable of
7801 operating without it, no dependency need be declared.
7805 If it is desirable for two or more related packages to
7806 share a configuration file <em>and</em> for all of the
7807 related packages to be able to modify that configuration
7808 file, then the following should be done:
7809 <enumlist compact="compact">
7811 One of the related packages (the "owning" package)
7812 will manage the configuration file with maintainer
7813 scripts as described in the previous section.
7816 The owning package should also provide a program
7817 that the other packages may use to modify the
7821 The related packages must use the provided program
7822 to make any desired modifications to the
7823 configuration file. They should either depend on
7824 the core package to guarantee that the configuration
7825 modifier program is available or accept gracefully
7826 that they cannot modify the configuration file if it
7827 is not. (This is in addition to the fact that the
7828 configuration file may not even be present in the
7835 Sometimes it's appropriate to create a new package which
7836 provides the basic infrastructure for the other packages
7837 and which manages the shared configuration files. (The
7838 <tt>sgml-base</tt> package is a good example.)
7843 <heading>User configuration files ("dotfiles")</heading>
7846 The files in <file>/etc/skel</file> will automatically be
7847 copied into new user accounts by <prgn>adduser</prgn>.
7848 No other program should reference the files in
7849 <file>/etc/skel</file>.
7853 Therefore, if a program needs a dotfile to exist in
7854 advance in <file>$HOME</file> to work sensibly, that dotfile
7855 should be installed in <file>/etc/skel</file> and treated as a
7860 However, programs that require dotfiles in order to
7861 operate sensibly are a bad thing, unless they do create
7862 the dotfiles themselves automatically.
7866 Furthermore, programs should be configured by the Debian
7867 default installation to behave as closely to the upstream
7868 default behavior as possible.
7872 Therefore, if a program in a Debian package needs to be
7873 configured in some way in order to operate sensibly, that
7874 should be done using a site-wide configuration file placed
7875 in <file>/etc</file>. Only if the program doesn't support a
7876 site-wide default configuration and the package maintainer
7877 doesn't have time to add it may a default per-user file be
7878 placed in <file>/etc/skel</file>.
7882 <file>/etc/skel</file> should be as empty as we can make it.
7883 This is particularly true because there is no easy (or
7884 necessarily desirable) mechanism for ensuring that the
7885 appropriate dotfiles are copied into the accounts of
7886 existing users when a package is installed.
7892 <heading>Log files</heading>
7894 Log files should usually be named
7895 <file>/var/log/<var>package</var>.log</file>. If you have many
7896 log files, or need a separate directory for permission
7897 reasons (<file>/var/log</file> is writable only by
7898 <file>root</file>), you should usually create a directory named
7899 <file>/var/log/<var>package</var></file> and place your log
7904 Log files must be rotated occasionally so that they don't
7905 grow indefinitely; the best way to do this is to drop a log
7906 rotation configuration file into the directory
7907 <file>/etc/logrotate.d</file> and use the facilities provided by
7908 logrotate.<footnote>
7910 The traditional approach to log files has been to set up
7911 <em>ad hoc</em> log rotation schemes using simple shell
7912 scripts and cron. While this approach is highly
7913 customizable, it requires quite a lot of sysadmin work.
7914 Even though the original Debian system helped a little
7915 by automatically installing a system which can be used
7916 as a template, this was deemed not enough.
7920 The use of <prgn>logrotate</prgn>, a program developed
7921 by Red Hat, is better, as it centralizes log management.
7922 It has both a configuration file
7923 (<file>/etc/logrotate.conf</file>) and a directory where
7924 packages can drop their individual log rotation
7925 configurations (<file>/etc/logrotate.d</file>).
7928 Here is a good example for a logrotate config
7929 file (for more information see <manref name="logrotate"
7931 <example compact="compact">
7932 /var/log/foo/*.log {
7937 /etc/init.d/foo force-reload
7941 This rotates all files under <file>/var/log/foo</file>, saves 12
7942 compressed generations, and forces the daemon to reload its
7943 configuration information after the log rotation.
7947 Log files should be removed when the package is
7948 purged (but not when it is only removed). This should be
7949 done by the <prgn>postrm</prgn> script when it is called
7950 with the argument <tt>purge</tt> (see <ref
7951 id="removedetails">).
7956 <heading>Permissions and owners</heading>
7959 The rules in this section are guidelines for general use.
7960 If necessary you may deviate from the details below.
7961 However, if you do so you must make sure that what is done
7962 is secure and you should try to be as consistent as possible
7963 with the rest of the system. You should probably also
7964 discuss it on <prgn>debian-devel</prgn> first.
7968 Files should be owned by <tt>root:root</tt>, and made
7969 writable only by the owner and universally readable (and
7970 executable, if appropriate), that is mode 644 or 755.
7974 Directories should be mode 755 or (for group-writability)
7975 mode 2775. The ownership of the directory should be
7976 consistent with its mode: if a directory is mode 2775, it
7977 should be owned by the group that needs write access to
7980 When a package is upgraded, and the owner or permissions
7981 of a file included in the package has changed, dpkg
7982 arranges for the ownership and permissions to be
7983 correctly set upon installation. However, this does not
7984 extend to directories; the permissions and ownership of
7985 directories already on the system does not change on
7986 install or upgrade of packages. This makes sense, since
7987 otherwise common directories like <tt>/usr</tt> would
7988 always be in flux. To correctly change permissions of a
7989 directory the package owns, explicit action is required,
7990 usually in the <tt>postinst</tt> script. Care must be
7991 taken to handle downgrades as well, in that case.
7998 Setuid and setgid executables should be mode 4755 or 2755
7999 respectively, and owned by the appropriate user or group.
8000 They should not be made unreadable (modes like 4711 or
8001 2711 or even 4111); doing so achieves no extra security,
8002 because anyone can find the binary in the freely available
8003 Debian package; it is merely inconvenient. For the same
8004 reason you should not restrict read or execute permissions
8005 on non-set-id executables.
8009 Some setuid programs need to be restricted to particular
8010 sets of users, using file permissions. In this case they
8011 should be owned by the uid to which they are set-id, and by
8012 the group which should be allowed to execute them. They
8013 should have mode 4754; again there is no point in making
8014 them unreadable to those users who must not be allowed to
8019 It is possible to arrange that the system administrator can
8020 reconfigure the package to correspond to their local
8021 security policy by changing the permissions on a binary:
8022 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8023 described below.<footnote>
8024 Ordinary files installed by <prgn>dpkg</prgn> (as
8025 opposed to <tt>conffile</tt>s and other similar objects)
8026 normally have their permissions reset to the distributed
8027 permissions when the package is reinstalled. However,
8028 the use of <prgn>dpkg-statoverride</prgn> overrides this
8031 Another method you should consider is to create a group for
8032 people allowed to use the program(s) and make any setuid
8033 executables executable only by that group.
8037 If you need to create a new user or group for your package
8038 there are two possibilities. Firstly, you may need to
8039 make some files in the binary package be owned by this
8040 user or group, or you may need to compile the user or
8041 group id (rather than just the name) into the binary
8042 (though this latter should be avoided if possible, as in
8043 this case you need a statically allocated id).</p>
8046 If you need a statically allocated id, you must ask for a
8047 user or group id from the <tt>base-passwd</tt> maintainer,
8048 and must not release the package until you have been
8049 allocated one. Once you have been allocated one you must
8050 either make the package depend on a version of the
8051 <tt>base-passwd</tt> package with the id present in
8052 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8053 your package to create the user or group itself with the
8054 correct id (using <tt>adduser</tt>) in its
8055 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8056 the <prgn>postinst</prgn> is to be preferred if it is
8057 possible, otherwise a pre-dependency will be needed on the
8058 <tt>adduser</tt> package.)
8062 On the other hand, the program might be able to determine
8063 the uid or gid from the user or group name at runtime, so
8064 that a dynamically allocated id can be used. In this case
8065 you should choose an appropriate user or group name,
8066 discussing this on <prgn>debian-devel</prgn> and checking
8067 with the <package/base-passwd/ maintainer that it is unique and that
8068 they do not wish you to use a statically allocated id
8069 instead. When this has been checked you must arrange for
8070 your package to create the user or group if necessary using
8071 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8072 <prgn>postinst</prgn> script (again, the latter is to be
8073 preferred if it is possible).
8077 Note that changing the numeric value of an id associated
8078 with a name is very difficult, and involves searching the
8079 file system for all appropriate files. You need to think
8080 carefully whether a static or dynamic id is required, since
8081 changing your mind later will cause problems.
8084 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8086 This section is not intended as policy, but as a
8087 description of the use of <prgn>dpkg-statoverride</prgn>.
8091 If a system administrator wishes to have a file (or
8092 directory or other such thing) installed with owner and
8093 permissions different from those in the distributed Debian
8094 package, they can use the <prgn>dpkg-statoverride</prgn>
8095 program to instruct <prgn>dpkg</prgn> to use the different
8096 settings every time the file is installed. Thus the
8097 package maintainer should distribute the files with their
8098 normal permissions, and leave it for the system
8099 administrator to make any desired changes. For example, a
8100 daemon which is normally required to be setuid root, but
8101 in certain situations could be used without being setuid,
8102 should be installed setuid in the <tt>.deb</tt>. Then the
8103 local system administrator can change this if they wish.
8104 If there are two standard ways of doing it, the package
8105 maintainer can use <tt>debconf</tt> to find out the
8106 preference, and call <prgn>dpkg-statoverride</prgn> in the
8107 maintainer script if necessary to accommodate the system
8108 administrator's choice. Care must be taken during
8109 upgrades to not override an existing setting.
8113 Given the above, <prgn>dpkg-statoverride</prgn> is
8114 essentially a tool for system administrators and would not
8115 normally be needed in the maintainer scripts. There is
8116 one type of situation, though, where calls to
8117 <prgn>dpkg-statoverride</prgn> would be needed in the
8118 maintainer scripts, and that involves packages which use
8119 dynamically allocated user or group ids. In such a
8120 situation, something like the following idiom can be very
8121 helpful in the package's <prgn>postinst</prgn>, where
8122 <tt>sysuser</tt> is a dynamically allocated id:
8124 for i in /usr/bin/foo /usr/sbin/bar
8126 # only do something when no setting exists
8127 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8129 #include: debconf processing, question about foo and bar
8130 if [ "$RET" = "true" ] ; then
8131 dpkg-statoverride --update --add sysuser root 4755 $i
8136 The corresponding code to remove the override when the package
8139 for i in /usr/bin/foo /usr/sbin/bar
8141 if dpkg-statoverride --list $i >/dev/null 2>&1
8143 dpkg-statoverride --remove $i
8153 <chapt id="customized-programs">
8154 <heading>Customized programs</heading>
8156 <sect id="arch-spec">
8157 <heading>Architecture specification strings</heading>
8160 If a program needs to specify an <em>architecture specification
8161 string</em> in some place, it should select one of the strings
8162 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8163 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8164 part is sometimes elided, as when the OS is Linux.
8168 Note that we don't want to use
8169 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8170 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8171 since this would make our programs incompatible with other
8172 Linux distributions. We also don't use something like
8173 <tt><var>arch</var>-unknown-linux</tt>, since the
8174 <tt>unknown</tt> does not look very good.
8177 <sect1 id="arch-wildcard-spec">
8178 <heading>Architecture wildcards</heading>
8181 A package may specify an architecture wildcard. Architecture
8182 wildcards are in the format <tt>any</tt> (which matches every
8183 architecture), <tt><var>os</var></tt>-any, or
8184 any-<tt><var>cpu</var></tt>. <footnote>
8185 Internally, the package system normalizes the GNU triplets
8186 and the Debian arches into Debian arch triplets (which are
8187 kind of inverted GNU triplets), with the first component of
8188 the triplet representing the libc and ABI in use, and then
8189 does matching against those triplets. However, such
8190 triplets are an internal implementation detail that should
8191 not be used by packages directly. The libc and ABI portion
8192 is handled internally by the package system based on
8193 the <var>os</var> and <var>cpu</var>.
8200 <heading>Daemons</heading>
8203 The configuration files <file>/etc/services</file>,
8204 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8205 by the <prgn>netbase</prgn> package and must not be modified
8210 If a package requires a new entry in one of these files, the
8211 maintainer should get in contact with the
8212 <prgn>netbase</prgn> maintainer, who will add the entries
8213 and release a new version of the <prgn>netbase</prgn>
8218 The configuration file <file>/etc/inetd.conf</file> must not be
8219 modified by the package's scripts except via the
8220 <prgn>update-inetd</prgn> script or the
8221 <file>DebianNet.pm</file> Perl module. See their documentation
8222 for details on how to add entries.
8226 If a package wants to install an example entry into
8227 <file>/etc/inetd.conf</file>, the entry must be preceded with
8228 exactly one hash character (<tt>#</tt>). Such lines are
8229 treated as "commented out by user" by the
8230 <prgn>update-inetd</prgn> script and are not changed or
8231 activated during package updates.
8236 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8240 Some programs need to create pseudo-ttys. This should be done
8241 using Unix98 ptys if the C library supports it. The resulting
8242 program must not be installed setuid root, unless that
8243 is required for other functionality.
8247 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8248 <file>/var/log/lastlog</file> must be installed writable by
8249 group <tt>utmp</tt>. Programs which need to modify those
8250 files must be installed setgid <tt>utmp</tt>.
8255 <heading>Editors and pagers</heading>
8258 Some programs have the ability to launch an editor or pager
8259 program to edit or display a text document. Since there are
8260 lots of different editors and pagers available in the Debian
8261 distribution, the system administrator and each user should
8262 have the possibility to choose their preferred editor and
8267 In addition, every program should choose a good default
8268 editor/pager if none is selected by the user or system
8273 Thus, every program that launches an editor or pager must
8274 use the EDITOR or PAGER environment variable to determine
8275 the editor or pager the user wishes to use. If these
8276 variables are not set, the programs <file>/usr/bin/editor</file>
8277 and <file>/usr/bin/pager</file> should be used, respectively.
8281 These two files are managed through the <prgn>dpkg</prgn>
8282 "alternatives" mechanism. Thus every package providing an
8283 editor or pager must call the
8284 <prgn>update-alternatives</prgn> script to register these
8289 If it is very hard to adapt a program to make use of the
8290 EDITOR or PAGER variables, that program may be configured to
8291 use <file>/usr/bin/sensible-editor</file> and
8292 <file>/usr/bin/sensible-pager</file> as the editor or pager
8293 program respectively. These are two scripts provided in the
8294 <package>sensible-utils</package> package that check the EDITOR
8295 and PAGER variables and launch the appropriate program, and fall
8296 back to <file>/usr/bin/editor</file>
8297 and <file>/usr/bin/pager</file> if the variable is not set.
8301 A program may also use the VISUAL environment variable to
8302 determine the user's choice of editor. If it exists, it
8303 should take precedence over EDITOR. This is in fact what
8304 <file>/usr/bin/sensible-editor</file> does.
8308 It is not required for a package to depend on
8309 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8310 package to provide such virtual packages.<footnote>
8311 The Debian base system already provides an editor and a
8317 <sect id="web-appl">
8318 <heading>Web servers and applications</heading>
8321 This section describes the locations and URLs that should
8322 be used by all web servers and web applications in the
8329 Cgi-bin executable files are installed in the
8331 <example compact="compact">
8332 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8334 and should be referred to as
8335 <example compact="compact">
8336 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8342 <p>Access to HTML documents</p>
8345 HTML documents for a package are stored in
8346 <file>/usr/share/doc/<var>package</var></file>
8347 and can be referred to as
8348 <example compact="compact">
8349 http://localhost/doc/<var>package</var>/<var>filename</var>
8354 The web server should restrict access to the document
8355 tree so that only clients on the same host can read
8356 the documents. If the web server does not support such
8357 access controls, then it should not provide access at
8358 all, or ask about providing access during installation.
8363 <p>Access to images</p>
8365 It is recommended that images for a package be stored
8366 in <tt>/usr/share/images/<var>package</var></tt> and
8367 may be referred to through an alias <tt>/images/</tt>
8370 http://localhost/images/<package>/<filename>
8377 <p>Web Document Root</p>
8380 Web Applications should try to avoid storing files in
8381 the Web Document Root. Instead they should use the
8382 /usr/share/doc/<var>package</var> directory for
8383 documents and register the Web Application via the
8384 <package>doc-base</package> package. If access to the
8385 web document root is unavoidable then use
8386 <example compact="compact">
8389 as the Document Root. This might be just a symbolic
8390 link to the location where the system administrator
8391 has put the real document root.
8394 <item><p>Providing httpd and/or httpd-cgi</p>
8396 All web servers should provide the virtual package
8397 <tt>httpd</tt>. If a web server has CGI support it should
8398 provide <tt>httpd-cgi</tt> additionally.
8401 All web applications which do not contain CGI scripts should
8402 depend on <tt>httpd</tt>, all those web applications which
8403 <tt>do</tt> contain CGI scripts, should depend on
8411 <sect id="mail-transport-agents">
8412 <heading>Mail transport, delivery and user agents</heading>
8415 Debian packages which process electronic mail, whether mail
8416 user agents (MUAs) or mail transport agents (MTAs), must
8417 ensure that they are compatible with the configuration
8418 decisions below. Failure to do this may result in lost
8419 mail, broken <tt>From:</tt> lines, and other serious brain
8424 The mail spool is <file>/var/mail</file> and the interface to
8425 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8426 the FHS). On older systems, the mail spool may be
8427 physically located in <file>/var/spool/mail</file>, but all
8428 access to the mail spool should be via the
8429 <file>/var/mail</file> symlink. The mail spool is part of the
8430 base system and not part of the MTA package.
8434 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8435 programs (such as IMAP daemons) must lock the mailbox in an
8436 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8437 be combined with dot locking. To avoid deadlocks, a program
8438 should use <tt>fcntl()</tt> first and dot locking after
8439 this, or alternatively implement the two locking methods in
8440 a non blocking way<footnote>
8441 If it is not possible to establish both locks, the
8442 system shouldn't wait for the second lock to be
8443 established, but remove the first lock, wait a (random)
8444 time, and start over locking again.
8445 </footnote>. Using the functions <tt>maillock</tt> and
8446 <tt>mailunlock</tt> provided by the
8447 <tt>liblockfile*</tt><footnote>
8448 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8449 to use these functions.
8450 </footnote> packages is the recommended way to realize this.
8454 Mailboxes are generally either mode 600 and owned by
8455 <var>user</var> or mode 660 and owned by
8456 <tt><var>user</var>:mail</tt><footnote>
8457 There are two traditional permission schemes for mail spools:
8458 mode 600 with all mail delivery done by processes running as
8459 the destination user, or mode 660 and owned by group mail with
8460 mail delivery done by a process running as a system user in
8461 group mail. Historically, Debian required mode 660 mail
8462 spools to enable the latter model, but that model has become
8463 increasingly uncommon and the principle of least privilege
8464 indicates that mail systems that use the first model should
8465 use permissions of 600. If delivery to programs is permitted,
8466 it's easier to keep the mail system secure if the delivery
8467 agent runs as the destination user. Debian Policy therefore
8468 permits either scheme.
8469 </footnote>. The local system administrator may choose a
8470 different permission scheme; packages should not make
8471 assumptions about the permission and ownership of mailboxes
8472 unless required (such as when creating a new mailbox). A MUA
8473 may remove a mailbox (unless it has nonstandard permissions) in
8474 which case the MTA or another MUA must recreate it if needed.
8478 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8479 be setgid mail to do the locking mentioned above (and
8480 must obviously avoid accessing other users' mailboxes
8481 using this privilege).</p>
8484 <file>/etc/aliases</file> is the source file for the system mail
8485 aliases (e.g., postmaster, usenet, etc.), it is the one
8486 which the sysadmin and <prgn>postinst</prgn> scripts may
8487 edit. After <file>/etc/aliases</file> is edited the program or
8488 human editing it must call <prgn>newaliases</prgn>. All MTA
8489 packages must come with a <prgn>newaliases</prgn> program,
8490 even if it does nothing, but older MTA packages did not do
8491 this so programs should not fail if <prgn>newaliases</prgn>
8492 cannot be found. Note that because of this, all MTA
8493 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8494 <tt>Replaces: mail-transport-agent</tt> control file
8499 The convention of writing <tt>forward to
8500 <var>address</var></tt> in the mailbox itself is not
8501 supported. Use a <tt>.forward</tt> file instead.</p>
8504 The <prgn>rmail</prgn> program used by UUCP
8505 for incoming mail should be <file>/usr/sbin/rmail</file>.
8506 Likewise, <prgn>rsmtp</prgn>, for receiving
8507 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8511 If your package needs to know what hostname to use on (for
8512 example) outgoing news and mail messages which are generated
8513 locally, you should use the file <file>/etc/mailname</file>. It
8514 will contain the portion after the username and <tt>@</tt>
8515 (at) sign for email addresses of users on the machine
8516 (followed by a newline).
8520 Such a package should check for the existence of this file
8521 when it is being configured. If it exists, it should be
8522 used without comment, although an MTA's configuration script
8523 may wish to prompt the user even if it finds that this file
8524 exists. If the file does not exist, the package should
8525 prompt the user for the value (preferably using
8526 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8527 as well as using it in the package's configuration. The
8528 prompt should make it clear that the name will not just be
8529 used by that package. For example, in this situation the
8530 <tt>inn</tt> package could say something like:
8531 <example compact="compact">
8532 Please enter the "mail name" of your system. This is the
8533 hostname portion of the address to be shown on outgoing
8534 news and mail messages. The default is
8535 <var>syshostname</var>, your system's host name. Mail
8536 name ["<var>syshostname</var>"]:
8538 where <var>syshostname</var> is the output of <tt>hostname
8544 <heading>News system configuration</heading>
8547 All the configuration files related to the NNTP (news)
8548 servers and clients should be located under
8549 <file>/etc/news</file>.</p>
8552 There are some configuration issues that apply to a number
8553 of news clients and server packages on the machine. These
8557 <tag><file>/etc/news/organization</file></tag>
8559 A string which should appear as the
8560 organization header for all messages posted
8561 by NNTP clients on the machine
8564 <tag><file>/etc/news/server</file></tag>
8566 Contains the FQDN of the upstream NNTP
8567 server, or localhost if the local machine is
8572 Other global files may be added as required for cross-package news
8579 <heading>Programs for the X Window System</heading>
8582 <heading>Providing X support and package priorities</heading>
8585 Programs that can be configured with support for the X
8586 Window System must be configured to do so and must declare
8587 any package dependencies necessary to satisfy their
8588 runtime requirements when using the X Window System. If
8589 such a package is of higher priority than the X packages
8590 on which it depends, it is required that either the
8591 X-specific components be split into a separate package, or
8592 that an alternative version of the package, which includes
8593 X support, be provided, or that the package's priority be
8599 <heading>Packages providing an X server</heading>
8602 Packages that provide an X server that, directly or
8603 indirectly, communicates with real input and display
8604 hardware should declare in their control data that they
8605 provide the virtual package <tt>xserver</tt>.<footnote>
8606 This implements current practice, and provides an
8607 actual policy for usage of the <tt>xserver</tt>
8608 virtual package which appears in the virtual packages
8609 list. In a nutshell, X servers that interface
8610 directly with the display and input hardware or via
8611 another subsystem (e.g., GGI) should provide
8612 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8613 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8619 <heading>Packages providing a terminal emulator</heading>
8622 Packages that provide a terminal emulator for the X Window
8623 System which meet the criteria listed below should declare
8624 in their control data that they provide the virtual
8625 package <tt>x-terminal-emulator</tt>. They should also
8626 register themselves as an alternative for
8627 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8632 To be an <tt>x-terminal-emulator</tt>, a program must:
8633 <list compact="compact">
8635 Be able to emulate a DEC VT100 terminal, or a
8636 compatible terminal.
8640 Support the command-line option <tt>-e
8641 <var>command</var></tt>, which creates a new
8642 terminal window<footnote>
8643 "New terminal window" does not necessarily mean
8644 a new top-level X window directly parented by
8645 the window manager; it could, if the terminal
8646 emulator application were so coded, be a new
8647 "view" in a multiple-document interface (MDI).
8649 and runs the specified <var>command</var>,
8650 interpreting the entirety of the rest of the command
8651 line as a command to pass straight to exec, in the
8652 manner that <tt>xterm</tt> does.
8656 Support the command-line option <tt>-T
8657 <var>title</var></tt>, which creates a new terminal
8658 window with the window title <var>title</var>.
8665 <heading>Packages providing a window manager</heading>
8668 Packages that provide a window manager should declare in
8669 their control data that they provide the virtual package
8670 <tt>x-window-manager</tt>. They should also register
8671 themselves as an alternative for
8672 <file>/usr/bin/x-window-manager</file>, with a priority
8673 calculated as follows:
8674 <list compact="compact">
8676 Start with a priority of 20.
8680 If the window manager supports the Debian menu
8681 system, add 20 points if this support is available
8682 in the package's default configuration (i.e., no
8683 configuration files belonging to the system or user
8684 have to be edited to activate the feature); if
8685 configuration files must be modified, add only 10
8691 If the window manager complies with <url
8692 id="http://www.freedesktop.org/Standards/wm-spec"
8693 name="The Window Manager Specification Project">,
8694 written by the <url id="http://www.freedesktop.org/"
8695 name="Free Desktop Group">, add 40 points.
8699 If the window manager permits the X session to be
8700 restarted using a <em>different</em> window manager
8701 (without killing the X server) in its default
8702 configuration, add 10 points; otherwise add none.
8709 <heading>Packages providing fonts</heading>
8712 Packages that provide fonts for the X Window
8714 For the purposes of Debian Policy, a "font for the X
8715 Window System" is one which is accessed via X protocol
8716 requests. Fonts for the Linux console, for PostScript
8717 renderer, or any other purpose, do not fit this
8718 definition. Any tool which makes such fonts available
8719 to the X Window System, however, must abide by this
8722 must do a number of things to ensure that they are both
8723 available without modification of the X or font server
8724 configuration, and that they do not corrupt files used by
8725 other font packages to register information about
8729 Fonts of any type supported by the X Window System
8730 must be in a separate binary package from any
8731 executables, libraries, or documentation (except
8732 that specific to the fonts shipped, such as their
8733 license information). If one or more of the fonts
8734 so packaged are necessary for proper operation of
8735 the package with which they are associated the font
8736 package may be Recommended; if the fonts merely
8737 provide an enhancement, a Suggests relationship may
8738 be used. Packages must not Depend on font
8740 This is because the X server may retrieve fonts
8741 from the local file system or over the network
8742 from an X font server; the Debian package system
8743 is empowered to deal only with the local
8749 BDF fonts must be converted to PCF fonts with the
8750 <prgn>bdftopcf</prgn> utility (available in the
8751 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8752 placed in a directory that corresponds to their
8754 <list compact="compact">
8756 100 dpi fonts must be placed in
8757 <file>/usr/share/fonts/X11/100dpi/</file>.
8761 75 dpi fonts must be placed in
8762 <file>/usr/share/fonts/X11/75dpi/</file>.
8766 Character-cell fonts, cursor fonts, and other
8767 low-resolution fonts must be placed in
8768 <file>/usr/share/fonts/X11/misc/</file>.
8774 Type 1 fonts must be placed in
8775 <file>/usr/share/fonts/X11/Type1/</file>. If font
8776 metric files are available, they must be placed here
8781 Subdirectories of <file>/usr/share/fonts/X11/</file>
8782 other than those listed above must be neither
8783 created nor used. (The <file>PEX</file>, <file>CID</file>,
8784 <file>Speedo</file>, and <file>cyrillic</file> directories
8785 are excepted for historical reasons, but installation of
8786 files into these directories remains discouraged.)
8790 Font packages may, instead of placing files directly
8791 in the X font directories listed above, provide
8792 symbolic links in that font directory pointing to
8793 the files' actual location in the filesystem. Such
8794 a location must comply with the FHS.
8798 Font packages should not contain both 75dpi and
8799 100dpi versions of a font. If both are available,
8800 they should be provided in separate binary packages
8801 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8802 the names of the packages containing the
8803 corresponding fonts.
8807 Fonts destined for the <file>misc</file> subdirectory
8808 should not be included in the same package as 75dpi
8809 or 100dpi fonts; instead, they should be provided in
8810 a separate package with <tt>-misc</tt> appended to
8815 Font packages must not provide the files
8816 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8817 <file>fonts.scale</file> in a font directory:
8820 <file>fonts.dir</file> files must not be provided at all.
8824 <file>fonts.alias</file> and <file>fonts.scale</file>
8825 files, if needed, should be provided in the
8827 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8828 where <var>fontdir</var> is the name of the
8830 <file>/usr/share/fonts/X11/</file> where the
8831 package's corresponding fonts are stored
8832 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8833 <var>package</var> is the name of the package
8834 that provides these fonts, and
8835 <var>extension</var> is either <tt>scale</tt>
8836 or <tt>alias</tt>, whichever corresponds to
8843 Font packages must declare a dependency on
8844 <tt>xfonts-utils</tt> in their control
8849 Font packages that provide one or more
8850 <file>fonts.scale</file> files as described above must
8851 invoke <prgn>update-fonts-scale</prgn> on each
8852 directory into which they installed fonts
8853 <em>before</em> invoking
8854 <prgn>update-fonts-dir</prgn> on that directory.
8855 This invocation must occur in both the
8856 <prgn>postinst</prgn> (for all arguments) and
8857 <prgn>postrm</prgn> (for all arguments except
8858 <tt>upgrade</tt>) scripts.
8862 Font packages that provide one or more
8863 <file>fonts.alias</file> files as described above must
8864 invoke <prgn>update-fonts-alias</prgn> on each
8865 directory into which they installed fonts. This
8866 invocation must occur in both the
8867 <prgn>postinst</prgn> (for all arguments) and
8868 <prgn>postrm</prgn> (for all arguments except
8869 <tt>upgrade</tt>) scripts.
8873 Font packages must invoke
8874 <prgn>update-fonts-dir</prgn> on each directory into
8875 which they installed fonts. This invocation must
8876 occur in both the <prgn>postinst</prgn> (for all
8877 arguments) and <prgn>postrm</prgn> (for all
8878 arguments except <tt>upgrade</tt>) scripts.
8882 Font packages must not provide alias names for the
8883 fonts they include which collide with alias names
8884 already in use by fonts already packaged.
8888 Font packages must not provide fonts with the same
8889 XLFD registry name as another font already packaged.
8895 <sect1 id="appdefaults">
8896 <heading>Application defaults files</heading>
8899 Application defaults files must be installed in the
8900 directory <file>/etc/X11/app-defaults/</file> (use of a
8901 localized subdirectory of <file>/etc/X11/</file> as described
8902 in the <em>X Toolkit Intrinsics - C Language
8903 Interface</em> manual is also permitted). They must be
8904 registered as <tt>conffile</tt>s or handled as
8905 configuration files.
8909 Customization of programs' X resources may also be
8910 supported with the provision of a file with the same name
8911 as that of the package placed in
8912 the <file>/etc/X11/Xresources/</file> directory, which
8913 must be registered as a <tt>conffile</tt> or handled as a
8914 configuration file.<footnote>
8915 Note that this mechanism is not the same as using
8916 app-defaults; app-defaults are tied to the client
8917 binary on the local file system, whereas X resources
8918 are stored in the X server and affect all connecting
8925 <heading>Installation directory issues</heading>
8928 Historically, packages using the X Window System used a
8929 separate set of installation directories from other packages.
8930 This practice has been discontinued and packages using the X
8931 Window System should now generally be installed in the same
8932 directories as any other package. Specifically, packages must
8933 not install files under the <file>/usr/X11R6/</file> directory
8934 and the <file>/usr/X11R6/</file> directory hierarchy should be
8935 regarded as obsolete.
8939 Include files previously installed under
8940 <file>/usr/X11R6/include/X11/</file> should be installed into
8941 <file>/usr/include/X11/</file>. For files previously
8942 installed into subdirectories of
8943 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8944 determine if subdirectories of <file>/usr/lib/</file> and
8945 <file>/usr/share/</file> can be used. If not, a subdirectory
8946 of <file>/usr/lib/X11/</file> should be used.
8950 Configuration files for window, display, or session managers
8951 or other applications that are tightly integrated with the X
8952 Window System may be placed in a subdirectory
8953 of <file>/etc/X11/</file> corresponding to the package name.
8954 Other X Window System applications should use
8955 the <file>/etc/</file> directory unless otherwise mandated by
8956 policy (such as for <ref id="appdefaults">).
8961 <heading>The OSF/Motif and OpenMotif libraries</heading>
8964 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8965 OpenMotif libraries</em><footnote>
8966 OSF/Motif and OpenMotif are collectively referred to as
8967 "Motif" in this policy document.
8969 should be compiled against and tested with LessTif (a free
8970 re-implementation of Motif) instead. If the maintainer
8971 judges that the program or programs do not work
8972 sufficiently well with LessTif to be distributed and
8973 supported, but do so when compiled against Motif, then two
8974 versions of the package should be created; one linked
8975 statically against Motif and with <tt>-smotif</tt>
8976 appended to the package name, and one linked dynamically
8977 against Motif and with <tt>-dmotif</tt> appended to the
8982 Both Motif-linked versions are dependent
8983 upon non-DFSG-compliant software and thus cannot be
8984 uploaded to the <em>main</em> distribution; if the
8985 software is itself DFSG-compliant it may be uploaded to
8986 the <em>contrib</em> distribution. While known existing
8987 versions of Motif permit unlimited redistribution of
8988 binaries linked against the library (whether statically or
8989 dynamically), it is the package maintainer's
8990 responsibility to determine whether this is permitted by
8991 the license of the copy of Motif in their possession.
8997 <heading>Perl programs and modules</heading>
9000 Perl programs and modules should follow the current Perl policy.
9004 The Perl policy can be found in the <tt>perl-policy</tt>
9005 files in the <tt>debian-policy</tt> package.
9006 It is also available from the Debian web mirrors at
9007 <tt><url name="/doc/packaging-manuals/perl-policy/"
9008 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9013 <heading>Emacs lisp programs</heading>
9016 Please refer to the "Debian Emacs Policy" for details of how to
9017 package emacs lisp programs.
9021 The Emacs policy is available in
9022 <file>debian-emacs-policy.gz</file> of the
9023 <package>emacsen-common</package> package.
9024 It is also available from the Debian web mirrors at
9025 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9026 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9031 <heading>Games</heading>
9034 The permissions on <file>/var/games</file> are mode 755, owner
9035 <tt>root</tt> and group <tt>root</tt>.
9039 Each game decides on its own security policy.</p>
9042 Games which require protected, privileged access to
9043 high-score files, saved games, etc., may be made
9044 set-<em>group</em>-id (mode 2755) and owned by
9045 <tt>root:games</tt>, and use files and directories with
9046 appropriate permissions (770 <tt>root:games</tt>, for
9047 example). They must not be made
9048 set-<em>user</em>-id, as this causes security problems. (If
9049 an attacker can subvert any set-user-id game they can
9050 overwrite the executable of any other, causing other players
9051 of these games to run a Trojan horse program. With a
9052 set-group-id game the attacker only gets access to less
9053 important game data, and if they can get at the other
9054 players' accounts at all it will take considerably more
9058 Some packages, for example some fortune cookie programs, are
9059 configured by the upstream authors to install with their
9060 data files or other static information made unreadable so
9061 that they can only be accessed through set-id programs
9062 provided. You should not do this in a Debian package: anyone can
9063 download the <file>.deb</file> file and read the data from it,
9064 so there is no point making the files unreadable. Not
9065 making the files unreadable also means that you don't have
9066 to make so many programs set-id, which reduces the risk of a
9070 As described in the FHS, binaries of games should be
9071 installed in the directory <file>/usr/games</file>. This also
9072 applies to games that use the X Window System. Manual pages
9073 for games (X and non-X games) should be installed in
9074 <file>/usr/share/man/man6</file>.</p>
9080 <heading>Documentation</heading>
9083 <heading>Manual pages</heading>
9086 You should install manual pages in <prgn>nroff</prgn> source
9087 form, in appropriate places under <file>/usr/share/man</file>.
9088 You should only use sections 1 to 9 (see the FHS for more
9089 details). You must not install a pre-formatted "cat page".
9093 Each program, utility, and function should have an
9094 associated manual page included in the same package. It is
9095 suggested that all configuration files also have a manual
9096 page included as well. Manual pages for protocols and other
9097 auxiliary things are optional.
9101 If no manual page is available, this is considered as a bug
9102 and should be reported to the Debian Bug Tracking System (the
9103 maintainer of the package is allowed to write this bug report
9104 themselves, if they so desire). Do not close the bug report
9105 until a proper man page is available.<footnote>
9106 It is not very hard to write a man page. See the
9107 <url id="http://www.schweikhardt.net/man_page_howto.html"
9108 name="Man-Page-HOWTO">,
9109 <manref name="man" section="7">, the examples
9110 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9111 the helper program <prgn>help2man</prgn>, or the
9112 directory <file>/usr/share/doc/man-db/examples</file>.
9117 You may forward a complaint about a missing man page to the
9118 upstream authors, and mark the bug as forwarded in the
9119 Debian bug tracking system. Even though the GNU Project do
9120 not in general consider the lack of a man page to be a bug,
9121 we do; if they tell you that they don't consider it a bug
9122 you should leave the bug in our bug tracking system open
9127 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9131 If one man page needs to be accessible via several names it
9132 is better to use a symbolic link than the <file>.so</file>
9133 feature, but there is no need to fiddle with the relevant
9134 parts of the upstream source to change from <file>.so</file> to
9135 symlinks: don't do it unless it's easy. You should not
9136 create hard links in the manual page directories, nor put
9137 absolute filenames in <file>.so</file> directives. The filename
9138 in a <file>.so</file> in a man page should be relative to the
9139 base of the man page tree (usually
9140 <file>/usr/share/man</file>). If you do not create any links
9141 (whether symlinks, hard links, or <tt>.so</tt> directives)
9142 in the file system to the alternate names of the man page,
9143 then you should not rely on <prgn>man</prgn> finding your
9144 man page under those names based solely on the information in
9145 the man page's header.<footnote>
9146 Supporting this in <prgn>man</prgn> often requires
9147 unreasonable processing time to find a manual page or to
9148 report that none exists, and moves knowledge into man's
9149 database that would be better left in the file system.
9150 This support is therefore deprecated and will cease to
9151 be present in the future.
9156 Manual pages in locale-specific subdirectories of
9157 <file>/usr/share/man</file> should use either UTF-8 or the usual
9158 legacy encoding for that language (normally the one corresponding
9159 to the shortest relevant locale name in
9160 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9161 <file>/usr/share/man/fr</file> should use either UTF-8 or
9162 ISO-8859-1.<footnote>
9163 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9164 use. In future, all manual pages will be required to use
9170 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9171 included in the subdirectory name unless it indicates a
9172 significant difference in the language, as this excludes
9173 speakers of the language in other countries.<footnote>
9174 At the time of writing, Chinese and Portuguese are the main
9175 languages with such differences, so <file>pt_BR</file>,
9176 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9181 If a localized version of a manual page is provided, it should
9182 either be up-to-date or it should be obvious to the reader that
9183 it is outdated and the original manual page should be used
9184 instead. This can be done either by a note at the beginning of
9185 the manual page or by showing the missing or changed portions in
9186 the original language instead of the target language.
9191 <heading>Info documents</heading>
9194 Info documents should be installed in <file>/usr/share/info</file>.
9195 They should be compressed with <tt>gzip -9</tt>.
9199 The <prgn>install-info</prgn> program maintains a directory of
9200 installed info documents in <file>/usr/share/info/dir</file> for
9201 the use of info readers.<footnote>
9202 It was previously necessary for packages installing info
9203 documents to run <prgn>install-info</prgn> from maintainer
9204 scripts. This is no longer necessary. The installation
9205 system now uses dpkg triggers.
9207 This file must not be included in packages. Packages containing
9208 info documents should depend on <tt>dpkg (>= 1.15.4) |
9209 install-info</tt> to ensure that the directory file is properly
9210 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9215 Info documents should contain section and directory entry
9216 information in the document for the use
9217 of <prgn>install-info</prgn>. The section should be specified
9218 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9219 space and the section of this info page. The directory entry or
9220 entries should be included between
9221 a <tt>START-INFO-DIR-ENTRY</tt> line and
9222 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9224 INFO-DIR-SECTION Individual utilities
9225 START-INFO-DIR-ENTRY
9226 * example: (example). An example info directory entry.
9229 To determine which section to use, you should look
9230 at <file>/usr/share/info/dir</file> on your system and choose
9231 the most relevant (or create a new section if none of the
9232 current sections are relevant).<footnote>
9233 Normally, info documents are generated from Texinfo source.
9234 To include this information in the generated info document, if
9235 it is absent, add commands like:
9237 @dircategory Individual utilities
9239 * example: (example). An example info directory entry.
9242 to the Texinfo source of the document and ensure that the info
9243 documents are rebuilt from source during the package build.
9249 <heading>Additional documentation</heading>
9252 Any additional documentation that comes with the package may
9253 be installed at the discretion of the package maintainer.
9254 Plain text documentation should be installed in the directory
9255 <file>/usr/share/doc/<var>package</var></file>, where
9256 <var>package</var> is the name of the package, and
9257 compressed with <tt>gzip -9</tt> unless it is small.
9261 If a package comes with large amounts of documentation which
9262 many users of the package will not require you should create
9263 a separate binary package to contain it, so that it does not
9264 take up disk space on the machines of users who do not need
9265 or want it installed.</p>
9268 It is often a good idea to put text information files
9269 (<file>README</file>s, changelogs, and so forth) that come with
9270 the source package in <file>/usr/share/doc/<var>package</var></file>
9271 in the binary package. However, you don't need to install
9272 the instructions for building and installing the package, of
9276 Packages must not require the existence of any files in
9277 <file>/usr/share/doc/</file> in order to function
9279 The system administrator should be able to
9280 delete files in <file>/usr/share/doc/</file> without causing
9281 any programs to break.
9283 Any files that are referenced by programs but are also
9284 useful as stand alone documentation should be installed under
9285 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9286 <file>/usr/share/doc/<var>package</var></file>.
9290 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9291 link to another directory in <file>/usr/share/doc</file> only if
9292 the two packages both come from the same source and the
9293 first package Depends on the second.<footnote>
9295 Please note that this does not override the section on
9296 changelog files below, so the file
9297 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9298 must refer to the changelog for the current version of
9299 <var>package</var> in question. In practice, this means
9300 that the sources of the target and the destination of the
9301 symlink must be the same (same source package and
9308 Former Debian releases placed all additional documentation
9309 in <file>/usr/doc/<var>package</var></file>. This has been
9310 changed to <file>/usr/share/doc/<var>package</var></file>,
9311 and packages must not put documentation in the directory
9312 <file>/usr/doc/<var>package</var></file>. <footnote>
9313 At this phase of the transition, we no longer require a
9314 symbolic link in <file>/usr/doc/</file>. At a later point,
9315 policy shall change to make the symbolic links a bug.
9321 <heading>Preferred documentation formats</heading>
9324 The unification of Debian documentation is being carried out
9328 If your package comes with extensive documentation in a
9329 markup format that can be converted to various other formats
9330 you should if possible ship HTML versions in a binary
9331 package, in the directory
9332 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9333 its subdirectories.<footnote>
9334 The rationale: The important thing here is that HTML
9335 docs should be available in <em>some</em> package, not
9336 necessarily in the main binary package.
9341 Other formats such as PostScript may be provided at the
9342 package maintainer's discretion.
9346 <sect id="copyrightfile">
9347 <heading>Copyright information</heading>
9350 Every package must be accompanied by a verbatim copy of its
9351 copyright information and distribution license in the file
9352 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9353 file must neither be compressed nor be a symbolic link.
9357 In addition, the copyright file must say where the upstream
9358 sources (if any) were obtained. It should name the original
9359 authors of the package and the Debian maintainer(s) who were
9360 involved with its creation.
9364 Packages in the <em>contrib</em> or <em>non-free</em> archive
9365 areas should state in the copyright file that the package is not
9366 part of the Debian GNU/Linux distribution and briefly explain
9371 A copy of the file which will be installed in
9372 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9373 be in <file>debian/copyright</file> in the source package.
9377 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9378 link to another directory in <file>/usr/share/doc</file> only if
9379 the two packages both come from the same source and the
9380 first package Depends on the second. These rules are
9381 important because copyrights must be extractable by
9386 Packages distributed under the Apache license (version 2.0), the
9387 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9388 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9389 1.3) should refer to the corresponding files
9390 under <file>/usr/share/common-licenses</file>,<footnote>
9393 <file>/usr/share/common-licenses/Apache-2.0</file>,
9394 <file>/usr/share/common-licenses/Artistic</file>,
9395 <file>/usr/share/common-licenses/GPL-1</file>,
9396 <file>/usr/share/common-licenses/GPL-2</file>,
9397 <file>/usr/share/common-licenses/GPL-3</file>,
9398 <file>/usr/share/common-licenses/LGPL-2</file>,
9399 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9400 <file>/usr/share/common-licenses/LGPL-3</file>,
9401 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9402 <file>/usr/share/common-licenses/GFDL-1.3</file>
9403 respectively. The University of California BSD license is
9404 also included in <package>base-files</package> as
9405 <file>/usr/share/common-licenses/BSD</file>, but given the
9406 brevity of this license, its specificity to code whose
9407 copyright is held by the Regents of the University of
9408 California, and the frequency of minor wording changes, its
9409 text should be included in the copyright file rather than
9410 referencing this file.
9412 </footnote> rather than quoting them in the copyright
9417 You should not use the copyright file as a general <file>README</file>
9418 file. If your package has such a file it should be
9419 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9420 <file>README.Debian</file> or some other appropriate place.</p>
9424 <heading>Examples</heading>
9427 Any examples (configurations, source files, whatever),
9428 should be installed in a directory
9429 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9430 files should not be referenced by any program: they're there
9431 for the benefit of the system administrator and users as
9432 documentation only. Architecture-specific example files
9433 should be installed in a directory
9434 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9436 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9437 latter directory itself may be a symbolic link to the
9442 If the purpose of a package is to provide examples, then the
9443 example files may be installed into
9444 <file>/usr/share/doc/<var>package</var></file>.
9448 <sect id="changelogs">
9449 <heading>Changelog files</heading>
9452 Packages that are not Debian-native must contain a
9453 compressed copy of the <file>debian/changelog</file> file from
9454 the Debian source tree in
9455 <file>/usr/share/doc/<var>package</var></file> with the name
9456 <file>changelog.Debian.gz</file>.
9460 If an upstream changelog is available, it should be accessible as
9461 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9462 plain text. If the upstream changelog is distributed in
9463 HTML, it should be made available in that form as
9464 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9465 and a plain text <file>changelog.gz</file> should be generated
9466 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9467 the upstream changelog files do not already conform to this
9468 naming convention, then this may be achieved either by
9469 renaming the files, or by adding a symbolic link, at the
9470 maintainer's discretion.<footnote>
9471 Rationale: People should not have to look in places for
9472 upstream changelogs merely because they are given
9473 different names or are distributed in HTML format.
9478 All of these files should be installed compressed using
9479 <tt>gzip -9</tt>, as they will become large with time even
9480 if they start out small.
9484 If the package has only one changelog which is used both as
9485 the Debian changelog and the upstream one because there is
9486 no separate upstream maintainer then that changelog should
9487 usually be installed as
9488 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9489 there is a separate upstream maintainer, but no upstream
9490 changelog, then the Debian changelog should still be called
9491 <file>changelog.Debian.gz</file>.
9495 For details about the format and contents of the Debian
9496 changelog file, please see <ref id="dpkgchangelog">.
9501 <appendix id="pkg-scope">
9502 <heading>Introduction and scope of these appendices</heading>
9505 These appendices are taken essentially verbatim from the
9506 now-deprecated Packaging Manual, version 3.2.1.0. They are
9507 the chapters which are likely to be of use to package
9508 maintainers and which have not already been included in the
9509 policy document itself. Most of these sections are very likely
9510 not relevant to policy; they should be treated as
9511 documentation for the packaging system. Please note that these
9512 appendices are included for convenience, and for historical
9513 reasons: they used to be part of policy package, and they have
9514 not yet been incorporated into dpkg documentation. However,
9515 they still have value, and hence they are presented here.
9519 They have not yet been checked to ensure that they are
9520 compatible with the contents of policy, and if there are any
9521 contradictions, the version in the main policy document takes
9522 precedence. The remaining chapters of the old Packaging
9523 Manual have also not been read in detail to ensure that there
9524 are not parts which have been left out. Both of these will be
9529 Certain parts of the Packaging manual were integrated into the
9530 Policy Manual proper, and removed from the appendices. Links
9531 have been placed from the old locations to the new ones.
9535 <prgn>dpkg</prgn> is a suite of programs for creating binary
9536 package files and installing and removing them on Unix
9538 <prgn>dpkg</prgn> is targeted primarily at Debian
9539 GNU/Linux, but may work on or be ported to other
9545 The binary packages are designed for the management of
9546 installed executable programs (usually compiled binaries) and
9547 their associated data, though source code examples and
9548 documentation are provided as part of some packages.</p>
9551 This manual describes the technical aspects of creating Debian
9552 binary packages (<file>.deb</file> files). It documents the
9553 behavior of the package management programs
9554 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9555 they interact with packages.</p>
9558 It also documents the interaction between
9559 <prgn>dselect</prgn>'s core and the access method scripts it
9560 uses to actually install the selected packages, and describes
9561 how to create a new access method.</p>
9564 This manual does not go into detail about the options and
9565 usage of the package building and installation tools. It
9566 should therefore be read in conjunction with those programs'
9571 The utility programs which are provided with <prgn>dpkg</prgn>
9572 for managing various system configuration and similar issues,
9573 such as <prgn>update-rc.d</prgn> and
9574 <prgn>install-info</prgn>, are not described in detail here -
9575 please see their man pages.
9579 It is assumed that the reader is reasonably familiar with the
9580 <prgn>dpkg</prgn> System Administrators' manual.
9581 Unfortunately this manual does not yet exist.
9585 The Debian version of the FSF's GNU hello program is provided
9586 as an example for people wishing to create Debian
9587 packages. The Debian <prgn>debmake</prgn> package is
9588 recommended as a very helpful tool in creating and maintaining
9589 Debian packages. However, while the tools and examples are
9590 helpful, they do not replace the need to read and follow the
9591 Policy and Programmer's Manual.</p>
9594 <appendix id="pkg-binarypkg">
9595 <heading>Binary packages (from old Packaging Manual)</heading>
9598 The binary package has two main sections. The first part
9599 consists of various control information files and scripts used
9600 by <prgn>dpkg</prgn> when installing and removing. See <ref
9601 id="pkg-controlarea">.
9605 The second part is an archive containing the files and
9606 directories to be installed.
9610 In the future binary packages may also contain other
9611 components, such as checksums and digital signatures. The
9612 format for the archive is described in full in the
9613 <file>deb(5)</file> man page.
9617 <sect id="pkg-bincreating"><heading>Creating package files -
9618 <prgn>dpkg-deb</prgn>
9622 All manipulation of binary package files is done by
9623 <prgn>dpkg-deb</prgn>; it's the only program that has
9624 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9625 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9626 will spot that the options requested are appropriate to
9627 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9632 In order to create a binary package you must make a
9633 directory tree which contains all the files and directories
9634 you want to have in the file system data part of the package.
9635 In Debian-format source packages this directory is usually
9636 <file>debian/tmp</file>, relative to the top of the package's
9641 They should have the locations (relative to the root of the
9642 directory tree you're constructing) ownerships and
9643 permissions which you want them to have on the system when
9648 With current versions of <prgn>dpkg</prgn> the uid/username
9649 and gid/groupname mappings for the users and groups being
9650 used should be the same on the system where the package is
9651 built and the one where it is installed.
9655 You need to add one special directory to the root of the
9656 miniature file system tree you're creating:
9657 <prgn>DEBIAN</prgn>. It should contain the control
9658 information files, notably the binary package control file
9659 (see <ref id="pkg-controlfile">).
9663 The <prgn>DEBIAN</prgn> directory will not appear in the
9664 file system archive of the package, and so won't be installed
9665 by <prgn>dpkg</prgn> when the package is installed.
9669 When you've prepared the package, you should invoke:
9671 dpkg --build <var>directory</var>
9676 This will build the package in
9677 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9678 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9679 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9684 See the man page <manref name="dpkg-deb" section="8"> for details of how
9685 to examine the contents of this newly-created file. You may find the
9686 output of following commands enlightening:
9688 dpkg-deb --info <var>filename</var>.deb
9689 dpkg-deb --contents <var>filename</var>.deb
9690 dpkg --contents <var>filename</var>.deb
9692 To view the copyright file for a package you could use this command:
9694 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9699 <sect id="pkg-controlarea">
9700 <heading>Package control information files</heading>
9703 The control information portion of a binary package is a
9704 collection of files with names known to <prgn>dpkg</prgn>.
9705 It will treat the contents of these files specially - some
9706 of them contain information used by <prgn>dpkg</prgn> when
9707 installing or removing the package; others are scripts which
9708 the package maintainer wants <prgn>dpkg</prgn> to run.
9712 It is possible to put other files in the package control
9713 area, but this is not generally a good idea (though they
9714 will largely be ignored).
9718 Here is a brief list of the control info files supported by
9719 <prgn>dpkg</prgn> and a summary of what they're used for.
9724 <tag><tt>control</tt>
9727 This is the key description file used by
9728 <prgn>dpkg</prgn>. It specifies the package's name
9729 and version, gives its description for the user,
9730 states its relationships with other packages, and so
9731 forth. See <ref id="sourcecontrolfiles"> and
9732 <ref id="binarycontrolfiles">.
9736 It is usually generated automatically from information
9737 in the source package by the
9738 <prgn>dpkg-gencontrol</prgn> program, and with
9739 assistance from <prgn>dpkg-shlibdeps</prgn>.
9740 See <ref id="pkg-sourcetools">.
9744 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9749 These are executable files (usually scripts) which
9750 <prgn>dpkg</prgn> runs during installation, upgrade
9751 and removal of packages. They allow the package to
9752 deal with matters which are particular to that package
9753 or require more complicated processing than that
9754 provided by <prgn>dpkg</prgn>. Details of when and
9755 how they are called are in <ref id="maintainerscripts">.
9759 It is very important to make these scripts idempotent.
9760 See <ref id="idempotency">.
9764 The maintainer scripts are not guaranteed to run with a
9765 controlling terminal and may not be able to interact with
9766 the user. See <ref id="controllingterminal">.
9770 <tag><tt>conffiles</tt>
9773 This file contains a list of configuration files which
9774 are to be handled automatically by <prgn>dpkg</prgn>
9775 (see <ref id="pkg-conffiles">). Note that not necessarily
9776 every configuration file should be listed here.
9779 <tag><tt>shlibs</tt>
9782 This file contains a list of the shared libraries
9783 supplied by the package, with dependency details for
9784 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9785 when it determines what dependencies are required in a
9786 package control file. The <tt>shlibs</tt> file format
9787 is described on <ref id="shlibs">.
9792 <sect id="pkg-controlfile">
9793 <heading>The main control information file: <tt>control</tt></heading>
9796 The most important control information file used by
9797 <prgn>dpkg</prgn> when it installs a package is
9798 <tt>control</tt>. It contains all the package's "vital
9803 The binary package control files of packages built from
9804 Debian sources are made by a special tool,
9805 <prgn>dpkg-gencontrol</prgn>, which reads
9806 <file>debian/control</file> and <file>debian/changelog</file> to
9807 find the information it needs. See <ref id="pkg-sourcepkg"> for
9812 The fields in binary package control files are listed in
9813 <ref id="binarycontrolfiles">.
9817 A description of the syntax of control files and the purpose
9818 of the fields is available in <ref id="controlfields">.
9823 <heading>Time Stamps</heading>
9826 See <ref id="timestamps">.
9831 <appendix id="pkg-sourcepkg">
9832 <heading>Source packages (from old Packaging Manual) </heading>
9835 The Debian binary packages in the distribution are generated
9836 from Debian sources, which are in a special format to assist
9837 the easy and automatic building of binaries.
9840 <sect id="pkg-sourcetools">
9841 <heading>Tools for processing source packages</heading>
9844 Various tools are provided for manipulating source packages;
9845 they pack and unpack sources and help build of binary
9846 packages and help manage the distribution of new versions.
9850 They are introduced and typical uses described here; see
9851 <manref name="dpkg-source" section="1"> for full
9852 documentation about their arguments and operation.
9856 For examples of how to construct a Debian source package,
9857 and how to use those utilities that are used by Debian
9858 source packages, please see the <prgn>hello</prgn> example
9862 <sect1 id="pkg-dpkg-source">
9864 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9869 This program is frequently used by hand, and is also
9870 called from package-independent automated building scripts
9871 such as <prgn>dpkg-buildpackage</prgn>.
9875 To unpack a package it is typically invoked with
9877 dpkg-source -x <var>.../path/to/filename</var>.dsc
9882 with the <file><var>filename</var>.tar.gz</file> and
9883 <file><var>filename</var>.diff.gz</file> (if applicable) in
9884 the same directory. It unpacks into
9885 <file><var>package</var>-<var>version</var></file>, and if
9887 <file><var>package</var>-<var>version</var>.orig</file>, in
9888 the current directory.
9892 To create a packed source archive it is typically invoked:
9894 dpkg-source -b <var>package</var>-<var>version</var>
9899 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9900 <file>.diff.gz</file> (if appropriate) in the current
9901 directory. <prgn>dpkg-source</prgn> does not clean the
9902 source tree first - this must be done separately if it is
9907 See also <ref id="pkg-sourcearchives">.</p>
9911 <sect1 id="pkg-dpkg-buildpackage">
9913 <prgn>dpkg-buildpackage</prgn> - overall package-building
9918 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9919 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9920 targets <tt>clean</tt>, <tt>build</tt> and
9921 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9922 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9923 source and binary package upload.
9927 It is usually invoked by hand from the top level of the
9928 built or unbuilt source directory. It may be invoked with
9929 no arguments; useful arguments include:
9930 <taglist compact="compact">
9931 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9934 Do not sign the <tt>.changes</tt> file or the
9935 source package <tt>.dsc</tt> file, respectively.</p>
9937 <tag><tt>-p<var>sign-command</var></tt></tag>
9940 Invoke <var>sign-command</var> instead of finding
9941 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9942 <var>sign-command</var> must behave just like
9943 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9945 <tag><tt>-r<var>root-command</var></tt></tag>
9948 When root privilege is required, invoke the command
9949 <var>root-command</var>. <var>root-command</var>
9950 should invoke its first argument as a command, from
9951 the <prgn>PATH</prgn> if necessary, and pass its
9952 second and subsequent arguments to the command it
9953 calls. If no <var>root-command</var> is supplied
9954 then <var>dpkg-buildpackage</var> will take no
9955 special action to gain root privilege, so that for
9956 most packages it will have to be invoked as root to
9959 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9962 Two types of binary-only build and upload - see
9963 <manref name="dpkg-source" section="1">.
9970 <sect1 id="pkg-dpkg-gencontrol">
9972 <prgn>dpkg-gencontrol</prgn> - generates binary package
9977 This program is usually called from <file>debian/rules</file>
9978 (see <ref id="pkg-sourcetree">) in the top level of the source
9983 This is usually done just before the files and directories in the
9984 temporary directory tree where the package is being built have their
9985 permissions and ownerships set and the package is constructed using
9986 <prgn>dpkg-deb/</prgn>
9988 This is so that the control file which is produced has
9989 the right permissions
9994 <prgn>dpkg-gencontrol</prgn> must be called after all the
9995 files which are to go into the package have been placed in
9996 the temporary build directory, so that its calculation of
9997 the installed size of a package is correct.
10001 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10002 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10003 variable substitutions created by
10004 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10009 For a package which generates only one binary package, and
10010 which builds it in <file>debian/tmp</file> relative to the top
10011 of the source package, it is usually sufficient to call
10012 <prgn>dpkg-gencontrol</prgn>.
10016 Sources which build several binaries will typically need
10019 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10020 </example> The <tt>-P</tt> tells
10021 <prgn>dpkg-gencontrol</prgn> that the package is being
10022 built in a non-default directory, and the <tt>-p</tt>
10023 tells it which package's control file should be generated.
10027 <prgn>dpkg-gencontrol</prgn> also adds information to the
10028 list of files in <file>debian/files</file>, for the benefit of
10029 (for example) a future invocation of
10030 <prgn>dpkg-genchanges</prgn>.</p>
10033 <sect1 id="pkg-dpkg-shlibdeps">
10035 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10040 This program is usually called from <file>debian/rules</file>
10041 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10042 id="pkg-sourcetree">), in the top level of the source tree.
10046 Its arguments are executables and shared libraries
10049 They may be specified either in the locations in the
10050 source tree where they are created or in the locations
10051 in the temporary build tree where they are installed
10052 prior to binary package creation.
10054 </footnote> for which shared library dependencies should
10055 be included in the binary package's control file.
10059 If some of the found shared libraries should only
10060 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10061 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10062 by using the <tt>-d<var>dependency-field</var></tt> option
10063 before those executable(s). (Each <tt>-d</tt> option
10064 takes effect until the next <tt>-d</tt>.)
10068 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10069 output control file to be modified. Instead by default it
10070 adds to the <file>debian/substvars</file> file variable
10071 settings like <tt>shlibs:Depends</tt>. These variable
10072 settings must be referenced in dependency fields in the
10073 appropriate per-binary-package sections of the source
10078 For example, a package that generates an essential part
10079 which requires dependencies, and optional parts that
10080 which only require a recommendation, would separate those
10081 two sets of dependencies into two different fields.<footnote>
10082 At the time of writing, an example for this was the
10083 <package/xmms/ package, with Depends used for the xmms
10084 executable, Recommends for the plug-ins and Suggests for
10085 even more optional features provided by unzip.
10087 It can say in its <file>debian/rules</file>:
10089 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10090 -dRecommends <var>optionalpart anotheroptionalpart</var>
10092 and then in its main control file <file>debian/control</file>:
10095 Depends: ${shlibs:Depends}
10096 Recommends: ${shlibs:Recommends}
10102 Sources which produce several binary packages with
10103 different shared library dependency requirements can use
10104 the <tt>-p<var>varnameprefix</var></tt> option to override
10105 the default <tt>shlibs:</tt> prefix (one invocation of
10106 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10107 They can thus produce several sets of dependency
10108 variables, each of the form
10109 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10110 which can be referred to in the appropriate parts of the
10111 binary package control files.
10116 <sect1 id="pkg-dpkg-distaddfile">
10118 <prgn>dpkg-distaddfile</prgn> - adds a file to
10119 <file>debian/files</file>
10123 Some packages' uploads need to include files other than
10124 the source and binary package files.
10128 <prgn>dpkg-distaddfile</prgn> adds a file to the
10129 <file>debian/files</file> file so that it will be included in
10130 the <file>.changes</file> file when
10131 <prgn>dpkg-genchanges</prgn> is run.
10135 It is usually invoked from the <tt>binary</tt> target of
10136 <file>debian/rules</file>:
10138 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10140 The <var>filename</var> is relative to the directory where
10141 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10142 is usually the directory above the top level of the source
10143 tree. The <file>debian/rules</file> target should put the
10144 file there just before or just after calling
10145 <prgn>dpkg-distaddfile</prgn>.
10149 The <var>section</var> and <var>priority</var> are passed
10150 unchanged into the resulting <file>.changes</file> file.
10155 <sect1 id="pkg-dpkg-genchanges">
10157 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10158 upload control file
10162 This program is usually called by package-independent
10163 automatic building scripts such as
10164 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10169 It is usually called in the top level of a built source
10170 tree, and when invoked with no arguments will print out a
10171 straightforward <file>.changes</file> file based on the
10172 information in the source package's changelog and control
10173 file and the binary and source packages which should have
10179 <sect1 id="pkg-dpkg-parsechangelog">
10181 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10182 representation of a changelog
10186 This program is used internally by
10187 <prgn>dpkg-source</prgn> et al. It may also occasionally
10188 be useful in <file>debian/rules</file> and elsewhere. It
10189 parses a changelog, <file>debian/changelog</file> by default,
10190 and prints a control-file format representation of the
10191 information in it to standard output.
10195 <sect1 id="pkg-dpkg-architecture">
10197 <prgn>dpkg-architecture</prgn> - information about the build and
10202 This program can be used manually, but is also invoked by
10203 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10204 environment or make variables which specify the build and host
10205 architecture for the package building process.
10210 <sect id="pkg-sourcetree">
10211 <heading>The Debian package source tree</heading>
10214 The source archive scheme described later is intended to
10215 allow a Debian package source tree with some associated
10216 control information to be reproduced and transported easily.
10217 The Debian package source tree is a version of the original
10218 program with certain files added for the benefit of the
10219 packaging process, and with any other changes required
10220 made to the rest of the source code and installation
10225 The extra files created for Debian are in the subdirectory
10226 <file>debian</file> of the top level of the Debian package
10227 source tree. They are described below.
10230 <sect1 id="pkg-debianrules">
10231 <heading><file>debian/rules</file> - the main building script</heading>
10234 See <ref id="debianrules">.
10238 <sect1 id="pkg-srcsubstvars">
10239 <heading><file>debian/substvars</file> and variable substitutions</heading>
10242 See <ref id="substvars">.
10248 <heading><file>debian/files</file></heading>
10251 See <ref id="debianfiles">.
10255 <sect1><heading><file>debian/tmp</file>
10259 This is the canonical temporary location for the
10260 construction of binary packages by the <tt>binary</tt>
10261 target. The directory <file>tmp</file> serves as the root of
10262 the file system tree as it is being constructed (for
10263 example, by using the package's upstream makefiles install
10264 targets and redirecting the output there), and it also
10265 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10266 id="pkg-bincreating">.
10270 If several binary packages are generated from the same
10271 source tree it is usual to use several
10272 <file>debian/tmp<var>something</var></file> directories, for
10273 example <file>tmp-a</file> or <file>tmp-doc</file>.
10277 Whatever <file>tmp</file> directories are created and used by
10278 <tt>binary</tt> must of course be removed by the
10279 <tt>clean</tt> target.</p></sect1>
10283 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10287 As it exists on the FTP site, a Debian source package
10288 consists of three related files. You must have the right
10289 versions of all three to be able to use them.
10294 <tag>Debian source control file - <tt>.dsc</tt></tag>
10296 This file is a control file used by <prgn>dpkg-source</prgn>
10297 to extract a source package.
10298 See <ref id="debiansourcecontrolfiles">.
10302 Original source archive -
10304 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10310 This is a compressed (with <tt>gzip -9</tt>)
10311 <prgn>tar</prgn> file containing the source code from
10312 the upstream authors of the program.
10317 Debian package diff -
10319 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10325 This is a unified context diff (<tt>diff -u</tt>)
10326 giving the changes which are required to turn the
10327 original source into the Debian source. These changes
10328 may only include editing and creating plain files.
10329 The permissions of files, the targets of symbolic
10330 links and the characteristics of special files or
10331 pipes may not be changed and no files may be removed
10336 All the directories in the diff must exist, except the
10337 <file>debian</file> subdirectory of the top of the source
10338 tree, which will be created by
10339 <prgn>dpkg-source</prgn> if necessary when unpacking.
10343 The <prgn>dpkg-source</prgn> program will
10344 automatically make the <file>debian/rules</file> file
10345 executable (see below).</p></item>
10350 If there is no original source code - for example, if the
10351 package is specially prepared for Debian or the Debian
10352 maintainer is the same as the upstream maintainer - the
10353 format is slightly different: then there is no diff, and the
10355 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10356 and preferably contains a directory named
10357 <file><var>package</var>-<var>version</var></file>.
10362 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10365 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10366 Debian source package. However, if it is not available it
10367 is possible to unpack a Debian source archive as follows:
10368 <enumlist compact="compact">
10371 Untar the tarfile, which will create a <file>.orig</file>
10375 <p>Rename the <file>.orig</file> directory to
10376 <file><var>package</var>-<var>version</var></file>.</p>
10380 Create the subdirectory <file>debian</file> at the top of
10381 the source tree.</p>
10383 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10385 <item><p>Untar the tarfile again if you want a copy of the original
10386 source code alongside the Debian version.</p>
10391 It is not possible to generate a valid Debian source archive
10392 without using <prgn>dpkg-source</prgn>. In particular,
10393 attempting to use <prgn>diff</prgn> directly to generate the
10394 <file>.diff.gz</file> file will not work.
10398 <heading>Restrictions on objects in source packages</heading>
10401 The source package may not contain any hard links
10403 This is not currently detected when building source
10404 packages, but only when extracting
10408 Hard links may be permitted at some point in the
10409 future, but would require a fair amount of
10411 </footnote>, device special files, sockets or setuid or
10414 Setgid directories are allowed.
10419 The source packaging tools manage the changes between the
10420 original and Debian source using <prgn>diff</prgn> and
10421 <prgn>patch</prgn>. Turning the original source tree as
10422 included in the <file>.orig.tar.gz</file> into the Debian
10423 package source must not involve any changes which cannot be
10424 handled by these tools. Problematic changes which cause
10425 <prgn>dpkg-source</prgn> to halt with an error when
10426 building the source package are:
10427 <list compact="compact">
10428 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10430 <item><p>Changing the targets of symbolic links.</p>
10432 <item><p>Creating directories, other than <file>debian</file>.</p>
10434 <item><p>Changes to the contents of binary files.</p></item>
10435 </list> Changes which cause <prgn>dpkg-source</prgn> to
10436 print a warning but continue anyway are:
10437 <list compact="compact">
10440 Removing files, directories or symlinks.
10442 Renaming a file is not treated specially - it is
10443 seen as the removal of the old file (which
10444 generates a warning, but is otherwise ignored),
10445 and the creation of the new one.
10451 Changed text files which are missing the usual final
10452 newline (either in the original or the modified
10457 Changes which are not represented, but which are not detected by
10458 <prgn>dpkg-source</prgn>, are:
10459 <list compact="compact">
10460 <item><p>Changing the permissions of files (other than
10461 <file>debian/rules</file>) and directories.</p></item>
10466 The <file>debian</file> directory and <file>debian/rules</file>
10467 are handled specially by <prgn>dpkg-source</prgn> - before
10468 applying the changes it will create the <file>debian</file>
10469 directory, and afterwards it will make
10470 <file>debian/rules</file> world-executable.
10476 <appendix id="pkg-controlfields">
10477 <heading>Control files and their fields (from old Packaging Manual)</heading>
10480 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10481 data in a common format, known as control files. Binary and
10482 source packages have control data as do the <file>.changes</file>
10483 files which control the installation of uploaded files, and
10484 <prgn>dpkg</prgn>'s internal databases are in a similar
10489 <heading>Syntax of control files</heading>
10492 See <ref id="controlsyntax">.
10496 It is important to note that there are several fields which
10497 are optional as far as <prgn>dpkg</prgn> and the related
10498 tools are concerned, but which must appear in every Debian
10499 package, or whose omission may cause problems.
10504 <heading>List of fields</heading>
10507 See <ref id="controlfieldslist">.
10511 This section now contains only the fields that didn't belong
10512 to the Policy manual.
10515 <sect1 id="pkg-f-Filename">
10516 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10519 These fields in <tt>Packages</tt> files give the
10520 filename(s) of (the parts of) a package in the
10521 distribution directories, relative to the root of the
10522 Debian hierarchy. If the package has been split into
10523 several parts the parts are all listed in order, separated
10528 <sect1 id="pkg-f-Size">
10529 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10532 These fields in <file>Packages</file> files give the size (in
10533 bytes, expressed in decimal) and MD5 checksum of the
10534 file(s) which make(s) up a binary package in the
10535 distribution. If the package is split into several parts
10536 the values for the parts are listed in order, separated by
10541 <sect1 id="pkg-f-Status">
10542 <heading><tt>Status</tt></heading>
10545 This field in <prgn>dpkg</prgn>'s status file records
10546 whether the user wants a package installed, removed or
10547 left alone, whether it is broken (requiring
10548 re-installation) or not and what its current state on the
10549 system is. Each of these pieces of information is a
10554 <sect1 id="pkg-f-Config-Version">
10555 <heading><tt>Config-Version</tt></heading>
10558 If a package is not installed or not configured, this
10559 field in <prgn>dpkg</prgn>'s status file records the last
10560 version of the package which was successfully
10565 <sect1 id="pkg-f-Conffiles">
10566 <heading><tt>Conffiles</tt></heading>
10569 This field in <prgn>dpkg</prgn>'s status file contains
10570 information about the automatically-managed configuration
10571 files held by a package. This field should <em>not</em>
10572 appear anywhere in a package!
10577 <heading>Obsolete fields</heading>
10580 These are still recognized by <prgn>dpkg</prgn> but should
10581 not appear anywhere any more.
10583 <taglist compact="compact">
10585 <tag><tt>Revision</tt></tag>
10586 <tag><tt>Package-Revision</tt></tag>
10587 <tag><tt>Package_Revision</tt></tag>
10589 The Debian revision part of the package version was
10590 at one point in a separate control file field. This
10591 field went through several names.
10594 <tag><tt>Recommended</tt></tag>
10595 <item>Old name for <tt>Recommends</tt>.</item>
10597 <tag><tt>Optional</tt></tag>
10598 <item>Old name for <tt>Suggests</tt>.</item>
10600 <tag><tt>Class</tt></tag>
10601 <item>Old name for <tt>Priority</tt>.</item>
10610 <appendix id="pkg-conffiles">
10611 <heading>Configuration file handling (from old Packaging Manual)</heading>
10614 <prgn>dpkg</prgn> can do a certain amount of automatic
10615 handling of package configuration files.
10619 Whether this mechanism is appropriate depends on a number of
10620 factors, but basically there are two approaches to any
10621 particular configuration file.
10625 The easy method is to ship a best-effort configuration in the
10626 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10627 handle updates. If the user is unlikely to want to edit the
10628 file, but you need them to be able to without losing their
10629 changes, and a new package with a changed version of the file
10630 is only released infrequently, this is a good approach.
10634 The hard method is to build the configuration file from
10635 scratch in the <prgn>postinst</prgn> script, and to take the
10636 responsibility for fixing any mistakes made in earlier
10637 versions of the package automatically. This will be
10638 appropriate if the file is likely to need to be different on
10642 <sect><heading>Automatic handling of configuration files by
10647 A package may contain a control area file called
10648 <tt>conffiles</tt>. This file should be a list of filenames
10649 of configuration files needing automatic handling, separated
10650 by newlines. The filenames should be absolute pathnames,
10651 and the files referred to should actually exist in the
10656 When a package is upgraded <prgn>dpkg</prgn> will process
10657 the configuration files during the configuration stage,
10658 shortly before it runs the package's <prgn>postinst</prgn>
10663 For each file it checks to see whether the version of the
10664 file included in the package is the same as the one that was
10665 included in the last version of the package (the one that is
10666 being upgraded from); it also compares the version currently
10667 installed on the system with the one shipped with the last
10672 If neither the user nor the package maintainer has changed
10673 the file, it is left alone. If one or the other has changed
10674 their version, then the changed version is preferred - i.e.,
10675 if the user edits their file, but the package maintainer
10676 doesn't ship a different version, the user's changes will
10677 stay, silently, but if the maintainer ships a new version
10678 and the user hasn't edited it the new version will be
10679 installed (with an informative message). If both have
10680 changed their version the user is prompted about the problem
10681 and must resolve the differences themselves.
10685 The comparisons are done by calculating the MD5 message
10686 digests of the files, and storing the MD5 of the file as it
10687 was included in the most recent version of the package.
10691 When a package is installed for the first time
10692 <prgn>dpkg</prgn> will install the file that comes with it,
10693 unless that would mean overwriting a file already on the
10698 However, note that <prgn>dpkg</prgn> will <em>not</em>
10699 replace a conffile that was removed by the user (or by a
10700 script). This is necessary because with some programs a
10701 missing file produces an effect hard or impossible to
10702 achieve in another way, so that a missing file needs to be
10703 kept that way if the user did it.
10707 Note that a package should <em>not</em> modify a
10708 <prgn>dpkg</prgn>-handled conffile in its maintainer
10709 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10710 the user confusing and possibly dangerous options for
10711 conffile update when the package is upgraded.</p>
10714 <sect><heading>Fully-featured maintainer script configuration
10719 For files which contain site-specific information such as
10720 the hostname and networking details and so forth, it is
10721 better to create the file in the package's
10722 <prgn>postinst</prgn> script.
10726 This will typically involve examining the state of the rest
10727 of the system to determine values and other information, and
10728 may involve prompting the user for some information which
10729 can't be obtained some other way.
10733 When using this method there are a couple of important
10734 issues which should be considered:
10738 If you discover a bug in the program which generates the
10739 configuration file, or if the format of the file changes
10740 from one version to the next, you will have to arrange for
10741 the postinst script to do something sensible - usually this
10742 will mean editing the installed configuration file to remove
10743 the problem or change the syntax. You will have to do this
10744 very carefully, since the user may have changed the file,
10745 perhaps to fix the very problem that your script is trying
10746 to deal with - you will have to detect these situations and
10747 deal with them correctly.
10751 If you do go down this route it's probably a good idea to
10752 make the program that generates the configuration file(s) a
10753 separate program in <file>/usr/sbin</file>, by convention called
10754 <file><var>package</var>config</file> and then run that if
10755 appropriate from the post-installation script. The
10756 <tt><var>package</var>config</tt> program should not
10757 unquestioningly overwrite an existing configuration - if its
10758 mode of operation is geared towards setting up a package for
10759 the first time (rather than any arbitrary reconfiguration
10760 later) you should have it check whether the configuration
10761 already exists, and require a <tt>--force</tt> flag to
10762 overwrite it.</p></sect>
10765 <appendix id="pkg-alternatives"><heading>Alternative versions of
10766 an interface - <prgn>update-alternatives</prgn> (from old
10771 When several packages all provide different versions of the
10772 same program or file it is useful to have the system select a
10773 default, but to allow the system administrator to change it
10774 and have their decisions respected.
10778 For example, there are several versions of the <prgn>vi</prgn>
10779 editor, and there is no reason to prevent all of them from
10780 being installed at once, each under their own name
10781 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10782 Nevertheless it is desirable to have the name <tt>vi</tt>
10783 refer to something, at least by default.
10787 If all the packages involved cooperate, this can be done with
10788 <prgn>update-alternatives</prgn>.
10792 Each package provides its own version under its own name, and
10793 calls <prgn>update-alternatives</prgn> in its postinst to
10794 register its version (and again in its prerm to deregister
10799 See the man page <manref name="update-alternatives"
10800 section="8"> for details.
10804 If <prgn>update-alternatives</prgn> does not seem appropriate
10805 you may wish to consider using diversions instead.</p>
10808 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10809 package's version of a file (from old Packaging Manual)
10813 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10814 when it reinstalls the package it belongs to, and to have it
10815 put the file from the package somewhere else instead.
10819 This can be used locally to override a package's version of a
10820 file, or by one package to override another's version (or
10821 provide a wrapper for it).
10825 Before deciding to use a diversion, read <ref
10826 id="pkg-alternatives"> to see if you really want a diversion
10827 rather than several alternative versions of a program.
10831 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10832 and updated by a special program <prgn>dpkg-divert</prgn>.
10833 Please see <manref name="dpkg-divert" section="8"> for full
10834 details of its operation.
10838 When a package wishes to divert a file from another, it should
10839 call <prgn>dpkg-divert</prgn> in its preinst to add the
10840 diversion and rename the existing file. For example,
10841 supposing that a <prgn>smailwrapper</prgn> package wishes to
10842 install a wrapper around <file>/usr/sbin/smail</file>:
10844 dpkg-divert --package smailwrapper --add --rename \
10845 --divert /usr/sbin/smail.real /usr/sbin/smail
10846 </example> The <tt>--package smailwrapper</tt> ensures that
10847 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10848 can bypass the diversion and get installed as the true version.
10849 It's safe to add the diversion unconditionally on upgrades since
10850 it will be left unchanged if it already exists, but
10851 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10852 message, make the command conditional on the version from which
10853 the package is being upgraded:
10855 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10856 dpkg-divert --package smailwrapper --add --rename \
10857 --divert /usr/sbin/smail.real /usr/sbin/smail
10859 </example> where <tt>1.0-2</tt> is the version at which the
10860 diversion was first added to the package. Running the command
10861 during abort-upgrade is pointless but harmless.
10865 The postrm has to do the reverse:
10867 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10868 dpkg-divert --package smailwrapper --remove --rename \
10869 --divert /usr/sbin/smail.real /usr/sbin/smail
10871 </example> If the diversion was added at a particular version, the
10872 postrm should also handle the failure case of upgrading from an
10873 older version (unless the older version is so old that direct
10874 upgrades are no longer supported):
10876 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10877 dpkg-divert --package smailwrapper --remove --rename \
10878 --divert /usr/sbin/smail.real /usr/sbin/smail
10880 </example> where <tt>1.02-2</tt> is the version at which the
10881 diversion was first added to the package. The postrm should not
10882 remove the diversion on upgrades both because there's no reason to
10883 remove the diversion only to immediately re-add it and since the
10884 postrm of the old package is run after unpacking so the removal of
10885 the diversion will fail.
10889 Do not attempt to divert a file which is vitally important for
10890 the system's operation - when using <prgn>dpkg-divert</prgn>
10891 there is a time, after it has been diverted but before
10892 <prgn>dpkg</prgn> has installed the new version, when the file
10893 does not exist.</p>
10898 <!-- Local variables: -->
10899 <!-- indent-tabs-mode: t -->
10901 <!-- vim:set ai et sts=2 sw=2 tw=76: -->