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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 <tt>Pre-Depends</tt>, <tt>Depends</tt>,
480 <tt>Recommends</tt>, <tt>Build-Depends</tt>,
481 or <tt>Build-Depends-Indep</tt> relationship on a
482 non-<em>main</em> package unless a package
483 in <em>main</em> is listed as an alternative),
486 must not be so buggy that we refuse to support them,
490 must meet all policy requirements presented in this
499 <heading>The contrib archive area</heading>
502 Every package in <em>contrib</em> must comply with the DFSG.
506 In addition, the packages in <em>contrib</em>
507 <list compact="compact">
509 must not be so buggy that we refuse to support them,
513 must meet all policy requirements presented in this
521 Examples of packages which would be included in
522 <em>contrib</em> are:
523 <list compact="compact">
525 free packages which require <em>contrib</em>,
526 <em>non-free</em> packages or packages which are not
527 in our archive at all for compilation or execution,
531 wrapper packages or other sorts of free accessories for
538 <sect1 id="non-free">
539 <heading>The non-free archive area</heading>
542 Packages must be placed in <em>non-free</em> if they are
543 not compliant with the DFSG or are encumbered by patents
544 or other legal issues that make their distribution
549 In addition, the packages in <em>non-free</em>
550 <list compact="compact">
552 must not be so buggy that we refuse to support them,
556 must meet all policy requirements presented in this
557 manual that it is possible for them to meet.
559 It is possible that there are policy
560 requirements which the package is unable to
561 meet, for example, if the source is
562 unavailable. These situations will need to be
563 handled on a case-by-case basis.
572 <sect id="pkgcopyright">
573 <heading>Copyright considerations</heading>
576 Every package must be accompanied by a verbatim copy of its
577 copyright information and distribution license in the file
578 <file>/usr/share/doc/<var>package</var>/copyright</file>
579 (see <ref id="copyrightfile"> for further details).
583 We reserve the right to restrict files from being included
584 anywhere in our archives if
585 <list compact="compact">
587 their use or distribution would break a law,
590 there is an ethical conflict in their distribution or
594 we would have to sign a license for them, or
597 their distribution would conflict with other project
604 Programs whose authors encourage the user to make
605 donations are fine for the main distribution, provided
606 that the authors do not claim that not donating is
607 immoral, unethical, illegal or something similar; in such
608 a case they must go in <em>non-free</em>.
612 Packages whose copyright permission notices (or patent
613 problems) do not even allow redistribution of binaries
614 only, and where no special permission has been obtained,
615 must not be placed on the Debian FTP site and its mirrors
620 Note that under international copyright law (this applies
621 in the United States, too), <em>no</em> distribution or
622 modification of a work is allowed without an explicit
623 notice saying so. Therefore a program without a copyright
624 notice <em>is</em> copyrighted and you may not do anything
625 to it without risking being sued! Likewise if a program
626 has a copyright notice but no statement saying what is
627 permitted then nothing is permitted.
631 Many authors are unaware of the problems that restrictive
632 copyrights (or lack of copyright notices) can cause for
633 the users of their supposedly-free software. It is often
634 worthwhile contacting such authors diplomatically to ask
635 them to modify their license terms. However, this can be a
636 politically difficult thing to do and you should ask for
637 advice on the <tt>debian-legal</tt> mailing list first, as
642 When in doubt about a copyright, send mail to
643 <email>debian-legal@lists.debian.org</email>. Be prepared
644 to provide us with the copyright statement. Software
645 covered by the GPL, public domain software and BSD-like
646 copyrights are safe; be wary of the phrases "commercial
647 use prohibited" and "distribution restricted".
651 <sect id="subsections">
652 <heading>Sections</heading>
655 The packages in the archive areas <em>main</em>,
656 <em>contrib</em> and <em>non-free</em> are grouped further into
657 <em>sections</em> to simplify handling.
661 The archive area and section for each package should be
662 specified in the package's <tt>Section</tt> control record (see
663 <ref id="f-Section">). However, the maintainer of the Debian
664 archive may override this selection to ensure the consistency of
665 the Debian distribution. The <tt>Section</tt> field should be
667 <list compact="compact">
669 <em>section</em> if the package is in the
670 <em>main</em> archive area,
673 <em>area/section</em> if the package is in
674 the <em>contrib</em> or <em>non-free</em>
681 The Debian archive maintainers provide the authoritative
682 list of sections. At present, they are:
683 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
684 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
685 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
686 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
687 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
688 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
689 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
690 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
691 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
692 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
693 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
694 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
695 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
696 <em>zope</em>. The additional section <em>debian-installer</em>
697 contains special packages used by the installer and is not used
698 for normal Debian packages.
702 For more information about the sections and their definitions,
703 see the <url id="http://packages.debian.org/unstable/"
704 name="list of sections in unstable">.
708 <sect id="priorities">
709 <heading>Priorities</heading>
712 Each package should have a <em>priority</em> value, which is
713 included in the package's <em>control record</em>
714 (see <ref id="f-Priority">).
715 This information is used by the Debian package management tools to
716 separate high-priority packages from less-important packages.
720 The following <em>priority levels</em> are recognized by the
721 Debian package management tools.
723 <tag><tt>required</tt></tag>
725 Packages which are necessary for the proper
726 functioning of the system (usually, this means that
727 dpkg functionality depends on these packages).
728 Removing a <tt>required</tt> package may cause your
729 system to become totally broken and you may not even
730 be able to use <prgn>dpkg</prgn> to put things back,
731 so only do so if you know what you are doing. Systems
732 with only the <tt>required</tt> packages are probably
733 unusable, but they do have enough functionality to
734 allow the sysadmin to boot and install more software.
736 <tag><tt>important</tt></tag>
738 Important programs, including those which one would
739 expect to find on any Unix-like system. If the
740 expectation is that an experienced Unix person who
741 found it missing would say "What on earth is going on,
742 where is <prgn>foo</prgn>?", it must be an
743 <tt>important</tt> package.<footnote>
744 This is an important criterion because we are
745 trying to produce, amongst other things, a free
748 Other packages without which the system will not run
749 well or be usable must also have priority
750 <tt>important</tt>. This does
751 <em>not</em> include Emacs, the X Window System, TeX
752 or any other large applications. The
753 <tt>important</tt> packages are just a bare minimum of
754 commonly-expected and necessary tools.
756 <tag><tt>standard</tt></tag>
758 These packages provide a reasonably small but not too
759 limited character-mode system. This is what will be
760 installed by default if the user doesn't select anything
761 else. It doesn't include many large applications.
763 <tag><tt>optional</tt></tag>
765 (In a sense everything that isn't required is
766 optional, but that's not what is meant here.) This is
767 all the software that you might reasonably want to
768 install if you didn't know what it was and don't have
769 specialized requirements. This is a much larger system
770 and includes the X Window System, a full TeX
771 distribution, and many applications. Note that
772 optional packages should not conflict with each other.
774 <tag><tt>extra</tt></tag>
776 This contains all packages that conflict with others
777 with required, important, standard or optional
778 priorities, or are only likely to be useful if you
779 already know what they are or have specialized
780 requirements (such as packages containing only detached
787 Packages must not depend on packages with lower priority
788 values (excluding build-time dependencies). In order to
789 ensure this, the priorities of one or more packages may need
798 <heading>Binary packages</heading>
801 The Debian GNU/Linux distribution is based on the Debian
802 package management system, called <prgn>dpkg</prgn>. Thus,
803 all packages in the Debian distribution must be provided
804 in the <tt>.deb</tt> file format.
808 <heading>The package name</heading>
811 Every package must have a name that's unique within the Debian
816 The package name is included in the control field
817 <tt>Package</tt>, the format of which is described
818 in <ref id="f-Package">.
819 The package name is also included as a part of the file name
820 of the <tt>.deb</tt> file.
825 <heading>The version of a package</heading>
828 Every package has a version number recorded in its
829 <tt>Version</tt> control file field, described in
830 <ref id="f-Version">.
834 The package management system imposes an ordering on version
835 numbers, so that it can tell whether packages are being up- or
836 downgraded and so that package system front end applications
837 can tell whether a package it finds available is newer than
838 the one installed on the system. The version number format
839 has the most significant parts (as far as comparison is
840 concerned) at the beginning.
844 If an upstream package has problematic version numbers they
845 should be converted to a sane form for use in the
846 <tt>Version</tt> field.
850 <heading>Version numbers based on dates</heading>
853 In general, Debian packages should use the same version
854 numbers as the upstream sources.
858 However, in some cases where the upstream version number is
859 based on a date (e.g., a development "snapshot" release) the
860 package management system cannot handle these version
861 numbers without epochs. For example, dpkg will consider
862 "96May01" to be greater than "96Dec24".
866 To prevent having to use epochs for every new upstream
867 version, the date based portion of the version number
868 should be changed to the following format in such cases:
869 "19960501", "19961224". It is up to the maintainer whether
870 they want to bother the upstream maintainer to change
871 the version numbers upstream, too.
875 Note that other version formats based on dates which are
876 parsed correctly by the package management system should
877 <em>not</em> be changed.
881 Native Debian packages (i.e., packages which have been
882 written especially for Debian) whose version numbers include
883 dates should always use the "YYYYMMDD" format.
889 <sect id="maintainer">
890 <heading>The maintainer of a package</heading>
893 Every package must have a maintainer. The maintainer may be one
894 person or a group of people reachable from a common email
895 address, such as a mailing list. The maintainer is responsible
896 for maintaining the Debian packaging files, evaluating and
897 responding appropriately to reported bugs, uploading new
898 versions of the package (either directly or through a sponsor),
899 ensuring that the package is placed in the appropriate archive
900 area and included in Debian releases as appropriate for the
901 stability and utility of the package, and requesting removal of
902 the package from the Debian distribution if it is no longer
903 useful or maintainable.
907 The maintainer must be specified in the <tt>Maintainer</tt>
908 control field with their correct name and a working email
909 address. The email address given in the <tt>Maintainer</tt>
910 control field must accept mail from those role accounts in
911 Debian used to send automated mails regarding the package. This
912 includes non-spam mail from the bug-tracking system, all mail
913 from the Debian archive maintenance software, and other role
914 accounts or automated processes that are commonly agreed on by
915 the project.<footnote>
916 A sample implementation of such a whitelist written for the
917 Mailman mailing list management software is used for mailing
918 lists hosted by alioth.debian.org.
920 If one person or team maintains several packages, they should
921 use the same form of their name and email address in
922 the <tt>Maintainer</tt> fields of those packages.
926 The format of the <tt>Maintainer</tt> control field is
927 described in <ref id="f-Maintainer">.
931 If the maintainer of the package is a team of people with a
932 shared email address, the <tt>Uploaders</tt> control field must
933 be present and must contain at least one human with their
934 personal email address. See <ref id="f-Uploaders"> for the
935 syntax of that field.
939 If the maintainer of a package no longer has time or desire to
940 maintain a package, it is orphaned. The maintainer then becomes
941 <tt>Debian QA Group <packages@qa.debian.org></tt>. These
942 packages are considered maintained by the Debian project as a
943 whole until someone else volunteers to take over maintenance.
945 The detailed procedure for doing this gracefully can be found
946 in the Debian Developer's Reference, see <ref id="related">.
951 <sect id="descriptions">
952 <heading>The description of a package</heading>
955 Every Debian package must have an extended description
956 stored in the appropriate field of the control record.
957 The technical information about the format of the
958 <tt>Description</tt> field is in <ref id="f-Description">.
962 The description should describe the package (the program) to a
963 user (system administrator) who has never met it before so that
964 they have enough information to decide whether they want to
965 install it. This description should not just be copied verbatim
966 from the program's documentation.
970 Put important information first, both in the synopsis and
971 extended description. Sometimes only the first part of the
972 synopsis or of the description will be displayed. You can
973 assume that there will usually be a way to see the whole
974 extended description.
978 The description should also give information about the
979 significant dependencies and conflicts between this package
980 and others, so that the user knows why these dependencies and
981 conflicts have been declared.
985 Instructions for configuring or using the package should
986 not be included (that is what installation scripts,
987 manual pages, info files, etc., are for). Copyright
988 statements and other administrivia should not be included
989 either (that is what the copyright file is for).
992 <sect1 id="synopsis"><heading>The single line synopsis</heading>
995 The single line synopsis should be kept brief - certainly
1000 Do not include the package name in the synopsis line. The
1001 display software knows how to display this already, and you
1002 do not need to state it. Remember that in many situations
1003 the user may only see the synopsis line - make it as
1004 informative as you can.
1009 <sect1 id="extendeddesc"><heading>The extended description</heading>
1012 Do not try to continue the single line synopsis into the
1013 extended description. This will not work correctly when
1014 the full description is displayed, and makes no sense
1015 where only the summary (the single line synopsis) is
1020 The extended description should describe what the package
1021 does and how it relates to the rest of the system (in terms
1022 of, for example, which subsystem it is which part of).
1026 The description field needs to make sense to anyone, even
1027 people who have no idea about any of the things the
1028 package deals with.<footnote>
1029 The blurb that comes with a program in its
1030 announcements and/or <prgn>README</prgn> files is
1031 rarely suitable for use in a description. It is
1032 usually aimed at people who are already in the
1033 community where the package is used.
1042 <heading>Dependencies</heading>
1045 Every package must specify the dependency information
1046 about other packages that are required for the first to
1051 For example, a dependency entry must be provided for any
1052 shared libraries required by a dynamically-linked executable
1053 binary in a package.
1057 Packages are not required to declare any dependencies they
1058 have on other packages which are marked <tt>Essential</tt>
1059 (see below), and should not do so unless they depend on a
1060 particular version of that package.<footnote>
1062 Essential is needed in part to avoid unresolvable dependency
1063 loops on upgrade. If packages add unnecessary dependencies
1064 on packages in this set, the chances that there
1065 <strong>will</strong> be an unresolvable dependency loop
1066 caused by forcing these Essential packages to be configured
1067 first before they need to be is greatly increased. It also
1068 increases the chances that frontends will be unable to
1069 <strong>calculate</strong> an upgrade path, even if one
1073 Also, functionality is rarely ever removed from the
1074 Essential set, but <em>packages</em> have been removed from
1075 the Essential set when the functionality moved to a
1076 different package. So depending on these packages <em>just
1077 in case</em> they stop being essential does way more harm
1084 Sometimes, a package requires another package to be installed
1085 <em>and</em> configured before it can be installed. In this
1086 case, you must specify a <tt>Pre-Depends</tt> entry for
1091 You should not specify a <tt>Pre-Depends</tt> entry for a
1092 package before this has been discussed on the
1093 <tt>debian-devel</tt> mailing list and a consensus about
1094 doing that has been reached.
1098 The format of the package interrelationship control fields is
1099 described in <ref id="relationships">.
1103 <sect id="virtual_pkg">
1104 <heading>Virtual packages</heading>
1107 Sometimes, there are several packages which offer
1108 more-or-less the same functionality. In this case, it's
1109 useful to define a <em>virtual package</em> whose name
1110 describes that common functionality. (The virtual
1111 packages only exist logically, not physically; that's why
1112 they are called <em>virtual</em>.) The packages with this
1113 particular function will then <em>provide</em> the virtual
1114 package. Thus, any other package requiring that function
1115 can simply depend on the virtual package without having to
1116 specify all possible packages individually.
1120 All packages should use virtual package names where
1121 appropriate, and arrange to create new ones if necessary.
1122 They should not use virtual package names (except privately,
1123 amongst a cooperating group of packages) unless they have
1124 been agreed upon and appear in the list of virtual package
1125 names. (See also <ref id="virtual">)
1129 The latest version of the authoritative list of virtual
1130 package names can be found in the <tt>debian-policy</tt> package.
1131 It is also available from the Debian web mirrors at
1132 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1133 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1137 The procedure for updating the list is described in the preface
1144 <heading>Base system</heading>
1147 The <tt>base system</tt> is a minimum subset of the Debian
1148 GNU/Linux system that is installed before everything else
1149 on a new system. Only very few packages are allowed to form
1150 part of the base system, in order to keep the required disk
1155 The base system consists of all those packages with priority
1156 <tt>required</tt> or <tt>important</tt>. Many of them will
1157 be tagged <tt>essential</tt> (see below).
1162 <heading>Essential packages</heading>
1165 Essential is defined as the minimal set of functionality that
1166 must be available and usable on the system at all times, even
1167 when packages are in an unconfigured (but unpacked) state.
1168 Packages are tagged <tt>essential</tt> for a system using the
1169 <tt>Essential</tt> control file field. The format of the
1170 <tt>Essential</tt> control field is described in <ref
1175 Since these packages cannot be easily removed (one has to
1176 specify an extra <em>force option</em> to
1177 <prgn>dpkg</prgn> to do so), this flag must not be used
1178 unless absolutely necessary. A shared library package
1179 must not be tagged <tt>essential</tt>; dependencies will
1180 prevent its premature removal, and we need to be able to
1181 remove it when it has been superseded.
1185 Since dpkg will not prevent upgrading of other packages
1186 while an <tt>essential</tt> package is in an unconfigured
1187 state, all <tt>essential</tt> packages must supply all of
1188 their core functionality even when unconfigured. If the
1189 package cannot satisfy this requirement it must not be
1190 tagged as essential, and any packages depending on this
1191 package must instead have explicit dependency fields as
1196 Maintainers should take great care in adding any programs,
1197 interfaces, or functionality to <tt>essential</tt> packages.
1198 Packages may assume that functionality provided by
1199 <tt>essential</tt> packages is always available without
1200 declaring explicit dependencies, which means that removing
1201 functionality from the Essential set is very difficult and is
1202 almost never done. Any capability added to an
1203 <tt>essential</tt> package therefore creates an obligation to
1204 support that capability as part of the Essential set in
1209 You must not tag any packages <tt>essential</tt> before
1210 this has been discussed on the <tt>debian-devel</tt>
1211 mailing list and a consensus about doing that has been
1216 <sect id="maintscripts">
1217 <heading>Maintainer Scripts</heading>
1220 The package installation scripts should avoid producing
1221 output which is unnecessary for the user to see and
1222 should rely on <prgn>dpkg</prgn> to stave off boredom on
1223 the part of a user installing many packages. This means,
1224 amongst other things, using the <tt>--quiet</tt> option on
1225 <prgn>install-info</prgn>.
1229 Errors which occur during the execution of an installation
1230 script must be checked and the installation must not
1231 continue after an error.
1235 Note that in general <ref id="scripts"> applies to package
1236 maintainer scripts, too.
1240 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1241 to another package without consulting the maintainer of that
1242 package first. When adding or removing diversions, package
1243 maintainer scripts must provide the <tt>--package</tt> flag
1244 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1248 All packages which supply an instance of a common command
1249 name (or, in general, filename) should generally use
1250 <prgn>update-alternatives</prgn>, so that they may be
1251 installed together. If <prgn>update-alternatives</prgn>
1252 is not used, then each package must use
1253 <tt>Conflicts</tt> to ensure that other packages are
1254 de-installed. (In this case, it may be appropriate to
1255 specify a conflict against earlier versions of something
1256 that previously did not use
1257 <prgn>update-alternatives</prgn>; this is an exception to
1258 the usual rule that versioned conflicts should be
1262 <sect1 id="maintscriptprompt">
1263 <heading>Prompting in maintainer scripts</heading>
1265 Package maintainer scripts may prompt the user if
1266 necessary. Prompting must be done by communicating
1267 through a program, such as <prgn>debconf</prgn>, which
1268 conforms to the Debian Configuration Management
1269 Specification, version 2 or higher.
1273 Packages which are essential, or which are dependencies of
1274 essential packages, may fall back on another prompting method
1275 if no such interface is available when they are executed.
1279 The Debian Configuration Management Specification is included
1280 in the <file>debconf_specification</file> files in the
1281 <package>debian-policy</package> package.
1282 It is also available from the Debian web mirrors at
1283 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1284 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1288 Packages which use the Debian Configuration Management
1289 Specification may contain an additional
1290 <prgn>config</prgn> script and a <tt>templates</tt>
1291 file in their control archive<footnote>
1292 The control.tar.gz inside the .deb.
1293 See <manref name="deb" section="5">.
1295 The <prgn>config</prgn> script might be run before the
1296 <prgn>preinst</prgn> script, and before the package is unpacked
1297 or any of its dependencies or pre-dependencies are satisfied.
1298 Therefore it must work using only the tools present in
1299 <em>essential</em> packages.<footnote>
1300 <package>Debconf</package> or another tool that
1301 implements the Debian Configuration Management
1302 Specification will also be installed, and any
1303 versioned dependencies on it will be satisfied
1304 before preconfiguration begins.
1309 Packages which use the Debian Configuration Management
1310 Specification must allow for translation of their user-visible
1311 messages by using a gettext-based system such as the one
1312 provided by the <package>po-debconf</package> package.
1316 Packages should try to minimize the amount of prompting
1317 they need to do, and they should ensure that the user
1318 will only ever be asked each question once. This means
1319 that packages should try to use appropriate shared
1320 configuration files (such as <file>/etc/papersize</file> and
1321 <file>/etc/news/server</file>), and shared
1322 <package>debconf</package> variables rather than each
1323 prompting for their own list of required pieces of
1328 It also means that an upgrade should not ask the same
1329 questions again, unless the user has used
1330 <tt>dpkg --purge</tt> to remove the package's configuration.
1331 The answers to configuration questions should be stored in an
1332 appropriate place in <file>/etc</file> so that the user can
1333 modify them, and how this has been done should be
1338 If a package has a vitally important piece of
1339 information to pass to the user (such as "don't run me
1340 as I am, you must edit the following configuration files
1341 first or you risk your system emitting badly-formatted
1342 messages"), it should display this in the
1343 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1344 prompt the user to hit return to acknowledge the
1345 message. Copyright messages do not count as vitally
1346 important (they belong in
1347 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1348 neither do instructions on how to use a program (these
1349 should be in on-line documentation, where all the users
1354 Any necessary prompting should almost always be confined
1355 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1356 script. If it is done in the <prgn>postinst</prgn>, it
1357 should be protected with a conditional so that
1358 unnecessary prompting doesn't happen if a package's
1359 installation fails and the <prgn>postinst</prgn> is
1360 called with <tt>abort-upgrade</tt>,
1361 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1371 <heading>Source packages</heading>
1373 <sect id="standardsversion">
1374 <heading>Standards conformance</heading>
1377 Source packages should specify the most recent version number
1378 of this policy document with which your package complied
1379 when it was last updated.
1383 This information may be used to file bug reports
1384 automatically if your package becomes too much out of date.
1388 The version is specified in the <tt>Standards-Version</tt>
1390 The format of the <tt>Standards-Version</tt> field is
1391 described in <ref id="f-Standards-Version">.
1395 You should regularly, and especially if your package has
1396 become out of date, check for the newest Policy Manual
1397 available and update your package, if necessary. When your
1398 package complies with the new standards you should update the
1399 <tt>Standards-Version</tt> source package field and
1400 release it.<footnote>
1401 See the file <file>upgrading-checklist</file> for
1402 information about policy which has changed between
1403 different versions of this document.
1409 <sect id="pkg-relations">
1410 <heading>Package relationships</heading>
1413 Source packages should specify which binary packages they
1414 require to be installed or not to be installed in order to
1415 build correctly. For example, if building a package
1416 requires a certain compiler, then the compiler should be
1417 specified as a build-time dependency.
1421 It is not necessary to explicitly specify build-time
1422 relationships on a minimal set of packages that are always
1423 needed to compile, link and put in a Debian package a
1424 standard "Hello World!" program written in C or C++. The
1425 required packages are called <em>build-essential</em>, and
1426 an informational list can be found in
1427 <file>/usr/share/doc/build-essential/list</file> (which is
1428 contained in the <tt>build-essential</tt>
1431 <list compact="compact">
1433 This allows maintaining the list separately
1434 from the policy documents (the list does not
1435 need the kind of control that the policy
1439 Having a separate package allows one to install
1440 the build-essential packages on a machine, as
1441 well as allowing other packages such as tasks to
1442 require installation of the build-essential
1443 packages using the depends relation.
1446 The separate package allows bug reports against
1447 the list to be categorized separately from
1448 the policy management process in the BTS.
1455 When specifying the set of build-time dependencies, one
1456 should list only those packages explicitly required by the
1457 build. It is not necessary to list packages which are
1458 required merely because some other package in the list of
1459 build-time dependencies depends on them.<footnote>
1460 The reason for this is that dependencies change, and
1461 you should list all those packages, and <em>only</em>
1462 those packages that <em>you</em> need directly. What
1463 others need is their business. For example, if you
1464 only link against <file>libimlib</file>, you will need to
1465 build-depend on <package>libimlib2-dev</package> but
1466 not against any <tt>libjpeg*</tt> packages, even
1467 though <tt>libimlib2-dev</tt> currently depends on
1468 them: installation of <package>libimlib2-dev</package>
1469 will automatically ensure that all of its run-time
1470 dependencies are satisfied.
1475 If build-time dependencies are specified, it must be
1476 possible to build the package and produce working binaries
1477 on a system with only essential and build-essential
1478 packages installed and also those required to satisfy the
1479 build-time relationships (including any implied
1480 relationships). In particular, this means that version
1481 clauses should be used rigorously in build-time
1482 relationships so that one cannot produce bad or
1483 inconsistently configured packages when the relationships
1484 are properly satisfied.
1488 <ref id="relationships"> explains the technical details.
1493 <heading>Changes to the upstream sources</heading>
1496 If changes to the source code are made that are not
1497 specific to the needs of the Debian system, they should be
1498 sent to the upstream authors in whatever form they prefer
1499 so as to be included in the upstream version of the
1504 If you need to configure the package differently for
1505 Debian or for Linux, and the upstream source doesn't
1506 provide a way to do so, you should add such configuration
1507 facilities (for example, a new <prgn>autoconf</prgn> test
1508 or <tt>#define</tt>) and send the patch to the upstream
1509 authors, with the default set to the way they originally
1510 had it. You can then easily override the default in your
1511 <file>debian/rules</file> or wherever is appropriate.
1515 You should make sure that the <prgn>configure</prgn> utility
1516 detects the correct architecture specification string
1517 (refer to <ref id="arch-spec"> for details).
1521 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1522 <prgn>configure</prgn> scripts are used, you should edit the
1523 <file>.in</file> files rather than editing the
1524 <prgn>Makefile</prgn> directly. This allows the user to
1525 reconfigure the package if necessary. You should
1526 <em>not</em> configure the package and edit the generated
1527 <prgn>Makefile</prgn>! This makes it impossible for someone
1528 else to later reconfigure the package without losing the
1534 <sect id="dpkgchangelog">
1535 <heading>Debian changelog: <file>debian/changelog</file></heading>
1538 Changes in the Debian version of the package should be
1539 briefly explained in the Debian changelog file
1540 <file>debian/changelog</file>.<footnote>
1542 Mistakes in changelogs are usually best rectified by
1543 making a new changelog entry rather than "rewriting
1544 history" by editing old changelog entries.
1547 This includes modifications
1548 made in the Debian package compared to the upstream one
1549 as well as other changes and updates to the package.
1551 Although there is nothing stopping an author who is also
1552 the Debian maintainer from using this changelog for all
1553 their changes, it will have to be renamed if the Debian
1554 and upstream maintainers become different people. In such
1555 a case, however, it might be better to maintain the package
1556 as a non-native package.
1561 The format of the <file>debian/changelog</file> allows the
1562 package building tools to discover which version of the package
1563 is being built and find out other release-specific information.
1567 That format is a series of entries like this:
1569 <example compact="compact">
1570 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1572 [optional blank line(s), stripped]
1574 * <var>change details</var>
1575 <var>more change details</var>
1577 [blank line(s), included in output of dpkg-parsechangelog]
1579 * <var>even more change details</var>
1581 [optional blank line(s), stripped]
1583 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1588 <var>package</var> and <var>version</var> are the source
1589 package name and version number.
1593 <var>distribution(s)</var> lists the distributions where
1594 this version should be installed when it is uploaded - it
1595 is copied to the <tt>Distribution</tt> field in the
1596 <file>.changes</file> file. See <ref id="f-Distribution">.
1600 <var>urgency</var> is the value for the <tt>Urgency</tt>
1601 field in the <file>.changes</file> file for the upload
1602 (see <ref id="f-Urgency">). It is not possible to specify
1603 an urgency containing commas; commas are used to separate
1604 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1605 <prgn>dpkg</prgn> changelog format (though there is
1606 currently only one useful <var>keyword</var>,
1611 The change details may in fact be any series of lines
1612 starting with at least two spaces, but conventionally each
1613 change starts with an asterisk and a separating space and
1614 continuation lines are indented so as to bring them in
1615 line with the start of the text above. Blank lines may be
1616 used here to separate groups of changes, if desired.
1620 If this upload resolves bugs recorded in the Bug Tracking
1621 System (BTS), they may be automatically closed on the
1622 inclusion of this package into the Debian archive by
1623 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1624 in the change details.<footnote>
1625 To be precise, the string should match the following
1626 Perl regular expression:
1628 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1630 Then all of the bug numbers listed will be closed by the
1631 archive maintenance script (<prgn>katie</prgn>) using the
1632 <var>version</var> of the changelog entry.
1634 This information is conveyed via the <tt>Closes</tt> field
1635 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1639 The maintainer name and email address used in the changelog
1640 should be the details of the person uploading <em>this</em>
1641 version. They are <em>not</em> necessarily those of the
1642 usual package maintainer. The information here will be
1643 copied to the <tt>Changed-By</tt> field in the
1644 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1645 and then later used to send an acknowledgement when the
1646 upload has been installed.
1650 The <var>date</var> has the following format<footnote>
1651 This is the same as the format generated by <tt>date
1653 </footnote> (compatible and with the same semantics of
1654 RFC 2822 and RFC 5322):
1655 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1657 <list compact="compact">
1659 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1662 dd is a one- or two-digit day of the month (01-31)
1665 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1668 <item>yyyy is the four-digit year (e.g. 2010)</item>
1669 <item>hh is the two-digit hour (00-23)</item>
1670 <item>mm is the two-digit minutes (00-59)</item>
1671 <item>ss is the two-digit seconds (00-60)</item>
1673 +zzzz or -zzzz is the the time zone offset from Coordinated
1674 Universal Time (UTC). "+" indicates that the time is ahead
1675 of (i.e., east of) UTC and "-" indicates that the time is
1676 behind (i.e., west of) UTC. The first two digits indicate
1677 the hour difference from UTC and the last two digits
1678 indicate the number of additional minutes difference from
1679 UTC. The last two digits must be in the range 00-59.
1685 The first "title" line with the package name must start
1686 at the left hand margin. The "trailer" line with the
1687 maintainer and date details must be preceded by exactly
1688 one space. The maintainer details and the date must be
1689 separated by exactly two spaces.
1693 The entire changelog must be encoded in UTF-8.
1697 For more information on placement of the changelog files
1698 within binary packages, please see <ref id="changelogs">.
1702 <sect id="dpkgcopyright">
1703 <heading>Copyright: <file>debian/copyright</file></heading>
1705 Every package must be accompanied by a verbatim copy of its
1706 copyright information and distribution license in the file
1707 <file>/usr/share/doc/<var>package</var>/copyright</file>
1708 (see <ref id="copyrightfile"> for further details). Also see
1709 <ref id="pkgcopyright"> for further considerations related
1710 to copyrights for packages.
1714 <heading>Error trapping in makefiles</heading>
1717 When <prgn>make</prgn> invokes a command in a makefile
1718 (including your package's upstream makefiles and
1719 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1720 means that <prgn>sh</prgn>'s usual bad error handling
1721 properties apply: if you include a miniature script as one
1722 of the commands in your makefile you'll find that if you
1723 don't do anything about it then errors are not detected
1724 and <prgn>make</prgn> will blithely continue after
1729 Every time you put more than one shell command (this
1730 includes using a loop) in a makefile command you
1731 must make sure that errors are trapped. For
1732 simple compound commands, such as changing directory and
1733 then running a program, using <tt>&&</tt> rather
1734 than semicolon as a command separator is sufficient. For
1735 more complex commands including most loops and
1736 conditionals you should include a separate <tt>set -e</tt>
1737 command at the start of every makefile command that's
1738 actually one of these miniature shell scripts.
1742 <sect id="timestamps">
1743 <heading>Time Stamps</heading>
1745 Maintainers should preserve the modification times of the
1746 upstream source files in a package, as far as is reasonably
1748 The rationale is that there is some information conveyed
1749 by knowing the age of the file, for example, you could
1750 recognize that some documentation is very old by looking
1751 at the modification time, so it would be nice if the
1752 modification time of the upstream source would be
1758 <sect id="restrictions">
1759 <heading>Restrictions on objects in source packages</heading>
1762 The source package may not contain any hard links<footnote>
1764 This is not currently detected when building source
1765 packages, but only when extracting
1769 Hard links may be permitted at some point in the
1770 future, but would require a fair amount of
1773 </footnote>, device special files, sockets or setuid or
1774 setgid files.<footnote>
1775 Setgid directories are allowed.
1780 <sect id="debianrules">
1781 <heading>Main building script: <file>debian/rules</file></heading>
1784 This file must be an executable makefile, and contains the
1785 package-specific recipes for compiling the package and
1786 building binary package(s) from the source.
1790 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1791 so that it can be invoked by saying its name rather than
1792 invoking <prgn>make</prgn> explicitly. That is, invoking
1793 either of <tt>make -f debian/rules <em>args...</em></tt>
1794 or <tt>./debian/rules <em>args...</em></tt> must result in
1799 Since an interactive <file>debian/rules</file> script makes it
1800 impossible to auto-compile that package and also makes it
1801 hard for other people to reproduce the same binary
1802 package, all <em>required targets</em> must be
1803 non-interactive. At a minimum, required targets are the
1804 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1805 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1806 <em>binary-indep</em>, and <em>build</em>. It also follows
1807 that any target that these targets depend on must also be
1812 The targets are as follows (required unless stated otherwise):
1814 <tag><tt>build</tt></tag>
1817 The <tt>build</tt> target should perform all the
1818 configuration and compilation of the package.
1819 If a package has an interactive pre-build
1820 configuration routine, the Debian source package
1821 must either be built after this has taken place (so
1822 that the binary package can be built without rerunning
1823 the configuration) or the configuration routine
1824 modified to become non-interactive. (The latter is
1825 preferable if there are architecture-specific features
1826 detected by the configuration routine.)
1830 For some packages, notably ones where the same
1831 source tree is compiled in different ways to produce
1832 two binary packages, the <tt>build</tt> target
1833 does not make much sense. For these packages it is
1834 good enough to provide two (or more) targets
1835 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1836 for each of the ways of building the package, and a
1837 <tt>build</tt> target that does nothing. The
1838 <tt>binary</tt> target will have to build the
1839 package in each of the possible ways and make the
1840 binary package out of each.
1844 The <tt>build</tt> target must not do anything
1845 that might require root privilege.
1849 The <tt>build</tt> target may need to run the
1850 <tt>clean</tt> target first - see below.
1854 When a package has a configuration and build routine
1855 which takes a long time, or when the makefiles are
1856 poorly designed, or when <tt>build</tt> needs to
1857 run <tt>clean</tt> first, it is a good idea to
1858 <tt>touch build</tt> when the build process is
1859 complete. This will ensure that if <tt>debian/rules
1860 build</tt> is run again it will not rebuild the whole
1862 Another common way to do this is for <tt>build</tt>
1863 to depend on <prgn>build-stamp</prgn> and to do
1864 nothing else, and for the <prgn>build-stamp</prgn>
1865 target to do the building and to <tt>touch
1866 build-stamp</tt> on completion. This is
1867 especially useful if the build routine creates a
1868 file or directory called <tt>build</tt>; in such a
1869 case, <tt>build</tt> will need to be listed as
1870 a phony target (i.e., as a dependency of the
1871 <tt>.PHONY</tt> target). See the documentation of
1872 <prgn>make</prgn> for more information on phony
1878 <tag><tt>build-arch</tt> (optional),
1879 <tt>build-indep</tt> (optional)
1883 A package may also provide both of the targets
1884 <tt>build-arch</tt> and <tt>build-indep</tt>.
1885 The <tt>build-arch</tt> target, if provided, should
1886 perform all the configuration and compilation required for
1887 producing all architecture-dependant binary packages
1888 (those packages for which the body of the
1889 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1890 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1891 target, if provided, should perform all the configuration
1892 and compilation required for producing all
1893 architecture-independent binary packages (those packages
1894 for which the body of the <tt>Architecture</tt> field
1895 in <tt>debian/control</tt> is <tt>all</tt>).
1896 The <tt>build</tt> target should depend on those of the
1897 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1898 are provided in the rules file.<footnote>
1899 The intent of this split is so that binary-only builds
1900 need not install the dependencies required for
1901 the <tt>build-indep</tt> target. However, this is not
1902 yet used in practice since <tt>dpkg-buildpackage
1903 -B</tt>, and therefore the autobuilders,
1904 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1905 due to the difficulties in determining whether the
1906 optional <tt>build-arch</tt> target exists.
1911 If one or both of the targets <tt>build-arch</tt> and
1912 <tt>build-indep</tt> are not provided, then invoking
1913 <file>debian/rules</file> with one of the not-provided
1914 targets as arguments should produce a exit status code
1915 of 2. Usually this is provided automatically by make
1916 if the target is missing.
1920 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1921 must not do anything that might require root privilege.
1925 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1926 <tt>binary-indep</tt>
1930 The <tt>binary</tt> target must be all that is
1931 necessary for the user to build the binary package(s)
1932 produced from this source package. It is
1933 split into two parts: <prgn>binary-arch</prgn> builds
1934 the binary packages which are specific to a particular
1935 architecture, and <tt>binary-indep</tt> builds
1936 those which are not.
1939 <tt>binary</tt> may be (and commonly is) a target with
1940 no commands which simply depends on
1941 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1944 Both <tt>binary-*</tt> targets should depend on the
1945 <tt>build</tt> target, or on the appropriate
1946 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1947 provided, so that the package is built if it has not
1948 been already. It should then create the relevant
1949 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1950 make their control files and <prgn>dpkg-deb</prgn> to
1951 build them and place them in the parent of the top
1956 Both the <tt>binary-arch</tt> and
1957 <tt>binary-indep</tt> targets <em>must</em> exist.
1958 If one of them has nothing to do (which will always be
1959 the case if the source generates only a single binary
1960 package, whether architecture-dependent or not), it
1961 must still exist and must always succeed.
1965 The <tt>binary</tt> targets must be invoked as
1967 The <prgn>fakeroot</prgn> package often allows one
1968 to build a package correctly even without being
1974 <tag><tt>clean</tt></tag>
1977 This must undo any effects that the <tt>build</tt>
1978 and <tt>binary</tt> targets may have had, except
1979 that it should leave alone any output files created in
1980 the parent directory by a run of a <tt>binary</tt>
1985 If a <tt>build</tt> file is touched at the end of
1986 the <tt>build</tt> target, as suggested above, it
1987 should be removed as the first action that
1988 <tt>clean</tt> performs, so that running
1989 <tt>build</tt> again after an interrupted
1990 <tt>clean</tt> doesn't think that everything is
1995 The <tt>clean</tt> target may need to be
1996 invoked as root if <tt>binary</tt> has been
1997 invoked since the last <tt>clean</tt>, or if
1998 <tt>build</tt> has been invoked as root (since
1999 <tt>build</tt> may create directories, for
2004 <tag><tt>get-orig-source</tt> (optional)</tag>
2007 This target fetches the most recent version of the
2008 original source package from a canonical archive site
2009 (via FTP or WWW, for example), does any necessary
2010 rearrangement to turn it into the original source
2011 tar file format described below, and leaves it in the
2016 This target may be invoked in any directory, and
2017 should take care to clean up any temporary files it
2022 This target is optional, but providing it if
2023 possible is a good idea.
2027 <tag><tt>patch</tt> (optional)</tag>
2030 This target performs whatever additional actions are
2031 required to make the source ready for editing (unpacking
2032 additional upstream archives, applying patches, etc.).
2033 It is recommended to be implemented for any package where
2034 <tt>dpkg-source -x</tt> does not result in source ready
2035 for additional modification. See
2036 <ref id="readmesource">.
2042 The <tt>build</tt>, <tt>binary</tt> and
2043 <tt>clean</tt> targets must be invoked with the current
2044 directory being the package's top-level directory.
2049 Additional targets may exist in <file>debian/rules</file>,
2050 either as published or undocumented interfaces or for the
2051 package's internal use.
2055 The architectures we build on and build for are determined
2056 by <prgn>make</prgn> variables using the utility
2057 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2058 You can determine the
2059 Debian architecture and the GNU style architecture
2060 specification string for the build machine (the machine type
2061 we are building on) as well as for the host machine (the
2062 machine type we are building for). Here is a list of
2063 supported <prgn>make</prgn> variables:
2064 <list compact="compact">
2066 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2069 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2072 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2075 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2076 specification string)
2079 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2080 <tt>DEB_*_GNU_TYPE</tt>)
2083 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2084 <tt>DEB_*_GNU_TYPE</tt>)
2086 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2087 the build machine or <tt>HOST</tt> for specification of the
2092 Backward compatibility can be provided in the rules file
2093 by setting the needed variables to suitable default
2094 values; please refer to the documentation of
2095 <prgn>dpkg-architecture</prgn> for details.
2099 It is important to understand that the <tt>DEB_*_ARCH</tt>
2100 string only determines which Debian architecture we are
2101 building on or for. It should not be used to get the CPU
2102 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2103 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2104 GNU style variables should generally only be used with upstream
2108 <sect1 id="debianrules-options">
2109 <heading><file>debian/rules</file> and
2110 <tt>DEB_BUILD_OPTIONS</tt></heading>
2113 Supporting the standardized environment variable
2114 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2115 contain several flags to change how a package is compiled and
2116 built. Each flag must be in the form <var>flag</var> or
2117 <var>flag</var>=<var>options</var>. If multiple flags are
2118 given, they must be separated by whitespace.<footnote>
2119 Some packages support any delimiter, but whitespace is the
2120 easiest to parse inside a makefile and avoids ambiguity with
2121 flag values that contain commas.
2123 <var>flag</var> must start with a lowercase letter
2124 (<tt>a-z</tt>) and consist only of lowercase letters,
2125 numbers (<tt>0-9</tt>), and the characters
2126 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2127 <var>options</var> must not contain whitespace. The same
2128 tag should not be given multiple times with conflicting
2129 values. Package maintainers may assume that
2130 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2134 The meaning of the following tags has been standardized:
2138 This tag says to not run any build-time test suite
2139 provided by the package.
2143 The presence of this tag means that the package should
2144 be compiled with a minimum of optimization. For C
2145 programs, it is best to add <tt>-O0</tt> to
2146 <tt>CFLAGS</tt> (although this is usually the default).
2147 Some programs might fail to build or run at this level
2148 of optimization; it may be necessary to use
2149 <tt>-O1</tt>, for example.
2153 This tag means that the debugging symbols should not be
2154 stripped from the binary during installation, so that
2155 debugging information may be included in the package.
2157 <tag>parallel=n</tag>
2159 This tag means that the package should be built using up
2160 to <tt>n</tt> parallel processes if the package build
2161 system supports this.<footnote>
2162 Packages built with <tt>make</tt> can often implement
2163 this by passing the <tt>-j</tt><var>n</var> option to
2166 If the package build system does not support parallel
2167 builds, this string must be ignored. If the package
2168 build system only supports a lower level of concurrency
2169 than <var>n</var>, the package should be built using as
2170 many parallel processes as the package build system
2171 supports. It is up to the package maintainer to decide
2172 whether the package build times are long enough and the
2173 package build system is robust enough to make supporting
2174 parallel builds worthwhile.
2180 Unknown flags must be ignored by <file>debian/rules</file>.
2184 The following makefile snippet is an example of how one may
2185 implement the build options; you will probably have to
2186 massage this example in order to make it work for your
2188 <example compact="compact">
2191 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2192 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2193 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2194 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2196 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2201 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2202 INSTALL_PROGRAM += -s
2204 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2205 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2206 MAKEFLAGS += -j$(NUMJOBS)
2211 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2212 # Code to run the package test suite.
2219 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2220 <sect id="substvars">
2221 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2224 When <prgn>dpkg-gencontrol</prgn>,
2225 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2226 generate control files they perform variable substitutions
2227 on their output just before writing it. Variable
2228 substitutions have the form <tt>${<var>variable</var>}</tt>.
2229 The optional file <file>debian/substvars</file> contains
2230 variable substitutions to be used; variables can also be set
2231 directly from <file>debian/rules</file> using the <tt>-V</tt>
2232 option to the source packaging commands, and certain
2233 predefined variables are also available.
2237 The <file>debian/substvars</file> file is usually generated and
2238 modified dynamically by <file>debian/rules</file> targets, in
2239 which case it must be removed by the <tt>clean</tt> target.
2243 See <manref name="deb-substvars" section="5"> for full
2244 details about source variable substitutions, including the
2245 format of <file>debian/substvars</file>.</p>
2248 <sect id="debianwatch">
2249 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2252 This is an optional, recommended control file for the
2253 <tt>uscan</tt> utility which defines how to automatically
2254 scan ftp or http sites for newly available updates of the
2255 package. This is used by <url id="
2256 http://dehs.alioth.debian.org/"> and other Debian QA tools
2257 to help with quality control and maintenance of the
2258 distribution as a whole.
2263 <sect id="debianfiles">
2264 <heading>Generated files list: <file>debian/files</file></heading>
2267 This file is not a permanent part of the source tree; it
2268 is used while building packages to record which files are
2269 being generated. <prgn>dpkg-genchanges</prgn> uses it
2270 when it generates a <file>.changes</file> file.
2274 It should not exist in a shipped source package, and so it
2275 (and any backup files or temporary files such as
2276 <file>files.new</file><footnote>
2277 <file>files.new</file> is used as a temporary file by
2278 <prgn>dpkg-gencontrol</prgn> and
2279 <prgn>dpkg-distaddfile</prgn> - they write a new
2280 version of <tt>files</tt> here before renaming it,
2281 to avoid leaving a corrupted copy if an error
2283 </footnote>) should be removed by the
2284 <tt>clean</tt> target. It may also be wise to
2285 ensure a fresh start by emptying or removing it at the
2286 start of the <tt>binary</tt> target.
2290 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2291 package, it adds an entry to <file>debian/files</file> for the
2292 <file>.deb</file> file that will be created when <tt>dpkg-deb
2293 --build</tt> is run for that binary package. So for most
2294 packages all that needs to be done with this file is to
2295 delete it in the <tt>clean</tt> target.
2299 If a package upload includes files besides the source
2300 package and any binary packages whose control files were
2301 made with <prgn>dpkg-gencontrol</prgn> then they should be
2302 placed in the parent of the package's top-level directory
2303 and <prgn>dpkg-distaddfile</prgn> should be called to add
2304 the file to the list in <file>debian/files</file>.</p>
2307 <sect id="embeddedfiles">
2308 <heading>Convenience copies of code</heading>
2311 Some software packages include in their distribution convenience
2312 copies of code from other software packages, generally so that
2313 users compiling from source don't have to download multiple
2314 packages. Debian packages should not make use of these
2315 convenience copies unless the included package is explicitly
2316 intended to be used in this way.<footnote>
2317 For example, parts of the GNU build system work like this.
2319 If the included code is already in the Debian archive in the
2320 form of a library, the Debian packaging should ensure that
2321 binary packages reference the libraries already in Debian and
2322 the convenience copy is not used. If the included code is not
2323 already in Debian, it should be packaged separately as a
2324 prerequisite if possible.
2326 Having multiple copies of the same code in Debian is
2327 inefficient, often creates either static linking or shared
2328 library conflicts, and, most importantly, increases the
2329 difficulty of handling security vulnerabilities in the
2335 <sect id="readmesource">
2336 <heading>Source package handling:
2337 <file>debian/README.source</file></heading>
2340 If running <prgn>dpkg-source -x</prgn> on a source package
2341 doesn't produce the source of the package, ready for editing,
2342 and allow one to make changes and run
2343 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2344 without taking any additional steps, creating a
2345 <file>debian/README.source</file> documentation file is
2346 recommended. This file should explain how to do all of the
2349 <item>Generate the fully patched source, in a form ready for
2350 editing, that would be built to create Debian
2351 packages. Doing this with a <tt>patch</tt> target in
2352 <file>debian/rules</file> is recommended; see
2353 <ref id="debianrules">.</item>
2354 <item>Modify the source and save those modifications so that
2355 they will be applied when building the package.</item>
2356 <item>Remove source modifications that are currently being
2357 applied when building the package.</item>
2358 <item>Optionally, document what steps are necessary to
2359 upgrade the Debian source package to a new upstream version,
2360 if applicable.</item>
2362 This explanation should include specific commands and mention
2363 any additional required Debian packages. It should not assume
2364 familiarity with any specific Debian packaging system or patch
2369 This explanation may refer to a documentation file installed by
2370 one of the package's build dependencies provided that the
2371 referenced documentation clearly explains these tasks and is not
2372 a general reference manual.
2376 <file>debian/README.source</file> may also include any other
2377 information that would be helpful to someone modifying the
2378 source package. Even if the package doesn't fit the above
2379 description, maintainers are encouraged to document in a
2380 <file>debian/README.source</file> file any source package with a
2381 particularly complex or unintuitive source layout or build
2382 system (for example, a package that builds the same source
2383 multiple times to generate different binary packages).
2389 <chapt id="controlfields">
2390 <heading>Control files and their fields</heading>
2393 The package management system manipulates data represented in
2394 a common format, known as <em>control data</em>, stored in
2395 <em>control files</em>.
2396 Control files are used for source packages, binary packages and
2397 the <file>.changes</file> files which control the installation
2398 of uploaded files<footnote>
2399 <prgn>dpkg</prgn>'s internal databases are in a similar
2404 <sect id="controlsyntax">
2405 <heading>Syntax of control files</heading>
2408 A control file consists of one or more paragraphs of
2410 The paragraphs are also sometimes referred to as stanzas.
2412 The paragraphs are separated by blank lines. Some control
2413 files allow only one paragraph; others allow several, in
2414 which case each paragraph usually refers to a different
2415 package. (For example, in source packages, the first
2416 paragraph refers to the source package, and later paragraphs
2417 refer to binary packages generated from the source.)
2421 Each paragraph consists of a series of data fields; each
2422 field consists of the field name, followed by a colon and
2423 then the data/value associated with that field. It ends at
2424 the end of the (logical) line. Horizontal whitespace
2425 (spaces and tabs) may occur immediately before or after the
2426 value and is ignored there; it is conventional to put a
2427 single space after the colon. For example, a field might
2429 <example compact="compact">
2432 the field name is <tt>Package</tt> and the field value
2437 A paragraph must not contain more than one instance of a
2438 particular field name.
2442 Many fields' values may span several lines; in this case
2443 each continuation line must start with a space or a tab.
2444 Any trailing spaces or tabs at the end of individual
2445 lines of a field value are ignored.
2449 In fields where it is specified that lines may not wrap,
2450 only a single line of data is allowed and whitespace is not
2451 significant in a field body. Whitespace must not appear
2452 inside names (of packages, architectures, files or anything
2453 else) or version numbers, or between the characters of
2454 multi-character version relationships.
2458 Field names are not case-sensitive, but it is usual to
2459 capitalize the field names using mixed case as shown below.
2460 Field values are case-sensitive unless the description of the
2461 field says otherwise.
2465 Blank lines, or lines consisting only of spaces and tabs,
2466 are not allowed within field values or between fields - that
2467 would mean a new paragraph.
2471 All control files must be encoded in UTF-8.
2475 <sect id="sourcecontrolfiles">
2476 <heading>Source package control files -- <file>debian/control</file></heading>
2479 The <file>debian/control</file> file contains the most vital
2480 (and version-independent) information about the source package
2481 and about the binary packages it creates.
2485 The first paragraph of the control file contains information about
2486 the source package in general. The subsequent sets each describe a
2487 binary package that the source tree builds.
2491 The fields in the general paragraph (the first one, for the source
2494 <list compact="compact">
2495 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2496 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2497 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2498 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2499 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2500 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2501 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2502 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2507 The fields in the binary package paragraphs are:
2509 <list compact="compact">
2510 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2511 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2512 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2513 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2514 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2515 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2516 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2522 The syntax and semantics of the fields are described below.
2526 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2527 generate control files for binary packages (see below), by
2528 <prgn>dpkg-genchanges</prgn> to generate the
2529 <file>.changes</file> file to accompany the upload, and by
2530 <prgn>dpkg-source</prgn> when it creates the
2531 <file>.dsc</file> source control file as part of a source
2532 archive. Many fields are permitted to span multiple lines in
2533 <file>debian/control</file> but not in any other control
2534 file. These tools are responsible for removing the line
2535 breaks from such fields when using fields from
2536 <file>debian/control</file> to generate other control files.
2540 The fields here may contain variable references - their
2541 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2542 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2543 when they generate output control files.
2544 See <ref id="substvars"> for details.
2548 In addition to the control file syntax described <qref
2549 id="controlsyntax">above</qref>, this file may also contain
2550 comment lines starting with <tt>#</tt> without any preceding
2551 whitespace. All such lines are ignored, even in the middle of
2552 continuation lines for a multiline field, and do not end a
2558 <sect id="binarycontrolfiles">
2559 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2562 The <file>DEBIAN/control</file> file contains the most vital
2563 (and version-dependent) information about a binary package. It
2564 consists of a single paragraph.
2568 The fields in this file are:
2570 <list compact="compact">
2571 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2572 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2573 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2575 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2576 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2577 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2578 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2579 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2580 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2581 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2582 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2587 <sect id="debiansourcecontrolfiles">
2588 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2591 This file consists of a single paragraph, possibly surrounded by
2592 a PGP signature. The fields of that paragraph are listed below.
2593 Their syntax is described above, in <ref id="pkg-controlfields">.
2595 <list compact="compact">
2596 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2597 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2598 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2599 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2600 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2601 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2602 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2603 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2604 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2605 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2606 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2607 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2608 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2613 The source package control file is generated by
2614 <prgn>dpkg-source</prgn> when it builds the source
2615 archive, from other files in the source package,
2616 described above. When unpacking, it is checked against
2617 the files and directories in the other parts of the
2623 <sect id="debianchangesfiles">
2624 <heading>Debian changes files -- <file>.changes</file></heading>
2627 The <file>.changes</file> files are used by the Debian archive
2628 maintenance software to process updates to packages. They
2629 consist of a single paragraph, possibly surrounded by a PGP
2630 signature. That paragraph contains information from the
2631 <file>debian/control</file> file and other data about the
2632 source package gathered via <file>debian/changelog</file>
2633 and <file>debian/rules</file>.
2637 <file>.changes</file> files have a format version that is
2638 incremented whenever the documented fields or their meaning
2639 change. This document describes format &changesversion;.
2643 The fields in this file are:
2645 <list compact="compact">
2646 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2647 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2649 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2651 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2653 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2654 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2655 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2656 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2657 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2658 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2659 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2660 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2661 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2666 <sect id="controlfieldslist">
2667 <heading>List of fields</heading>
2669 <sect1 id="f-Source">
2670 <heading><tt>Source</tt></heading>
2673 This field identifies the source package name.
2677 In <file>debian/control</file> or a <file>.dsc</file> file,
2678 this field must contain only the name of the source package.
2682 In a binary package control file or a <file>.changes</file>
2683 file, the source package name may be followed by a version
2684 number in parentheses<footnote>
2685 It is customary to leave a space after the package name
2686 if a version number is specified.
2688 This version number may be omitted (and is, by
2689 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2690 the <tt>Version</tt> field of the binary package in
2691 question. The field itself may be omitted from a binary
2692 package control file when the source package has the same
2693 name and version as the binary package.
2697 Package names (both source and binary,
2698 see <ref id="f-Package">) must consist only of lower case
2699 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2700 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2701 (<tt>.</tt>). They must be at least two characters long and
2702 must start with an alphanumeric character.
2706 <sect1 id="f-Maintainer">
2707 <heading><tt>Maintainer</tt></heading>
2710 The package maintainer's name and email address. The name
2711 must come first, then the email address inside angle
2712 brackets <tt><></tt> (in RFC822 format).
2716 If the maintainer's name contains a full stop then the
2717 whole field will not work directly as an email address due
2718 to a misfeature in the syntax specified in RFC822; a
2719 program using this field as an address must check for this
2720 and correct the problem if necessary (for example by
2721 putting the name in round brackets and moving it to the
2722 end, and bringing the email address forward).
2726 See <ref id="maintainer"> for additional requirements and
2727 information about package maintainers.
2731 <sect1 id="f-Uploaders">
2732 <heading><tt>Uploaders</tt></heading>
2735 List of the names and email addresses of co-maintainers of the
2736 package, if any. If the package has other maintainers beside
2737 the one named in the <qref id="f-Maintainer">Maintainer
2738 field</qref>, their names and email addresses should be listed
2739 here. The format of each entry is the same as that of the
2740 Maintainer field, and multiple entries must be comma
2745 This is normally an optional field, but if
2746 the <tt>Maintainer</tt> control field names a group of people
2747 and a shared email address, the <tt>Uploaders</tt> field must
2748 be present and must contain at least one human with their
2749 personal email address.
2753 Any parser that interprets the Uploaders field in
2754 <file>debian/control</file> must permit it to span multiple
2755 lines. Line breaks in an Uploaders field that spans multiple
2756 lines are not significant and the semantics of the field are
2757 the same as if the line breaks had not been present.
2761 <sect1 id="f-Changed-By">
2762 <heading><tt>Changed-By</tt></heading>
2765 The name and email address of the person who prepared this
2766 version of the package, usually a maintainer. The syntax is
2767 the same as for the <qref id="f-Maintainer">Maintainer
2772 <sect1 id="f-Section">
2773 <heading><tt>Section</tt></heading>
2776 This field specifies an application area into which the package
2777 has been classified. See <ref id="subsections">.
2781 When it appears in the <file>debian/control</file> file,
2782 it gives the value for the subfield of the same name in
2783 the <tt>Files</tt> field of the <file>.changes</file> file.
2784 It also gives the default for the same field in the binary
2789 <sect1 id="f-Priority">
2790 <heading><tt>Priority</tt></heading>
2793 This field represents how important it is that the user
2794 have the package installed. See <ref id="priorities">.
2798 When it appears in the <file>debian/control</file> file,
2799 it gives the value for the subfield of the same name in
2800 the <tt>Files</tt> field of the <file>.changes</file> file.
2801 It also gives the default for the same field in the binary
2806 <sect1 id="f-Package">
2807 <heading><tt>Package</tt></heading>
2810 The name of the binary package.
2814 Binary package names must follow the same syntax and
2815 restrictions as source package names. See <ref id="f-Source">
2820 <sect1 id="f-Architecture">
2821 <heading><tt>Architecture</tt></heading>
2824 Depending on context and the control file used, the
2825 <tt>Architecture</tt> field can include the following sets of
2829 A unique single word identifying a Debian machine
2830 architecture as described in <ref id="arch-spec">.
2833 An architecture wildcard identifying a set of Debian
2834 machine architectures, see <ref id="arch-wildcard-spec">.
2835 <tt>any</tt> matches all Debian machine architectures
2836 and is the most frequently used.
2839 <tt>all</tt>, which indicates an
2840 architecture-independent package.
2843 <tt>source</tt>, which indicates a source package.
2849 In the main <file>debian/control</file> file in the source
2850 package, this field may contain the special
2851 value <tt>all</tt>, the special architecture
2852 wildcard <tt>any</tt>, or a list of specific and wildcard
2853 architectures separated by spaces. If <tt>all</tt>
2854 or <tt>any</tt> appears, that value must be the entire
2855 contents of the field. Most packages will use
2856 either <tt>all</tt> or <tt>any</tt>.
2860 Specifying a specific list of architectures indicates that the
2861 source will build an architecture-dependent package only on
2862 architectures included in the list. Specifying a list of
2863 architecture wildcards indicates that the source will build an
2864 architecture-dependent package on only those architectures
2865 that match any of the specified architecture wildcards.
2866 Specifying a list of architectures or architecture wildcards
2867 other than <tt>any</tt> is for the minority of cases where a
2868 program is not portable or is not useful on some
2869 architectures. Where possible, the program should be made
2874 In the source package control file <file>.dsc</file>, this
2875 field may contain either the architecture
2876 wildcard <tt>any</tt> or a list of architectures and
2877 architecture wildcards separated by spaces. If a list is
2878 given, it may include (or consist solely of) the special
2879 value <tt>all</tt>. In other words, in <file>.dsc</file>
2880 files unlike the <file>debian/control</file>, <tt>all</tt> may
2881 occur in combination with specific architectures.
2882 The <tt>Architecture</tt> field in the source package control
2883 file <file>.dsc</file> is generally constructed from
2884 the <tt>Architecture</tt> fields in
2885 the <file>debian/control</file> in the source package.
2889 Specifying <tt>any</tt> indicates that the source package
2890 isn't dependent on any particular architecture and should
2891 compile fine on any one. The produced binary package(s)
2892 will either be specific to whatever the current build
2893 architecture is or will be architecture-independent.
2897 Specifying only <tt>all</tt> indicates that the source package
2898 will only build architecture-independent packages. If this is
2899 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2900 <tt>any</tt> implies that the source package will build at
2901 least one architecture-dependent package.
2905 Specifying a list of architectures or architecture wildcards
2906 indicates that the source will build an architecture-dependent
2907 package, and will only work correctly on the listed or
2908 matching architectures. If the source package also builds at
2909 least one architecture-independent package, <tt>all</tt> will
2910 also be included in the list.
2914 In a <file>.changes</file> file, the <tt>Architecture</tt>
2915 field lists the architecture(s) of the package(s) currently
2916 being uploaded. This will be a list; if the source for the
2917 package is also being uploaded, the special
2918 entry <tt>source</tt> is also present. <tt>all</tt> will be
2919 present if any architecture-independent packages are being
2920 uploaded. Architecture wildcards such as <tt>any</tt> must
2921 never occur in the <tt>Architecture</tt> field in
2922 the <file>.changes</file> file.
2926 See <ref id="debianrules"> for information on how to get
2927 the architecture for the build process.
2931 <sect1 id="f-Essential">
2932 <heading><tt>Essential</tt></heading>
2935 This is a boolean field which may occur only in the
2936 control file of a binary package or in a per-package fields
2937 paragraph of a main source control data file.
2941 If set to <tt>yes</tt> then the package management system
2942 will refuse to remove the package (upgrading and replacing
2943 it is still possible). The other possible value is <tt>no</tt>,
2944 which is the same as not having the field at all.
2949 <heading>Package interrelationship fields:
2950 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2951 <tt>Recommends</tt>, <tt>Suggests</tt>,
2952 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2953 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2957 These fields describe the package's relationships with
2958 other packages. Their syntax and semantics are described
2959 in <ref id="relationships">.</p>
2962 <sect1 id="f-Standards-Version">
2963 <heading><tt>Standards-Version</tt></heading>
2966 The most recent version of the standards (the policy
2967 manual and associated texts) with which the package
2972 The version number has four components: major and minor
2973 version number and major and minor patch level. When the
2974 standards change in a way that requires every package to
2975 change the major number will be changed. Significant
2976 changes that will require work in many packages will be
2977 signaled by a change to the minor number. The major patch
2978 level will be changed for any change to the meaning of the
2979 standards, however small; the minor patch level will be
2980 changed when only cosmetic, typographical or other edits
2981 are made which neither change the meaning of the document
2982 nor affect the contents of packages.
2986 Thus only the first three components of the policy version
2987 are significant in the <em>Standards-Version</em> control
2988 field, and so either these three components or all four
2989 components may be specified.<footnote>
2990 In the past, people specified the full version number
2991 in the Standards-Version field, for example "2.3.0.0".
2992 Since minor patch-level changes don't introduce new
2993 policy, it was thought it would be better to relax
2994 policy and only require the first 3 components to be
2995 specified, in this example "2.3.0". All four
2996 components may still be used if someone wishes to do so.
3002 <sect1 id="f-Version">
3003 <heading><tt>Version</tt></heading>
3006 The version number of a package. The format is:
3007 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3011 The three components here are:
3013 <tag><var>epoch</var></tag>
3016 This is a single (generally small) unsigned integer. It
3017 may be omitted, in which case zero is assumed. If it is
3018 omitted then the <var>upstream_version</var> may not
3023 It is provided to allow mistakes in the version numbers
3024 of older versions of a package, and also a package's
3025 previous version numbering schemes, to be left behind.
3029 <tag><var>upstream_version</var></tag>
3032 This is the main part of the version number. It is
3033 usually the version number of the original ("upstream")
3034 package from which the <file>.deb</file> file has been made,
3035 if this is applicable. Usually this will be in the same
3036 format as that specified by the upstream author(s);
3037 however, it may need to be reformatted to fit into the
3038 package management system's format and comparison
3043 The comparison behavior of the package management system
3044 with respect to the <var>upstream_version</var> is
3045 described below. The <var>upstream_version</var>
3046 portion of the version number is mandatory.
3050 The <var>upstream_version</var> may contain only
3051 alphanumerics<footnote>
3052 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3054 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3055 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3056 tilde) and should start with a digit. If there is no
3057 <var>debian_revision</var> then hyphens are not allowed;
3058 if there is no <var>epoch</var> then colons are not
3063 <tag><var>debian_revision</var></tag>
3066 This part of the version number specifies the version of
3067 the Debian package based on the upstream version. It
3068 may contain only alphanumerics and the characters
3069 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3070 tilde) and is compared in the same way as the
3071 <var>upstream_version</var> is.
3075 It is optional; if it isn't present then the
3076 <var>upstream_version</var> may not contain a hyphen.
3077 This format represents the case where a piece of
3078 software was written specifically to be a Debian
3079 package, where the Debian package source must always
3080 be identical to the pristine source and therefore no
3081 revision indication is required.
3085 It is conventional to restart the
3086 <var>debian_revision</var> at <tt>1</tt> each time the
3087 <var>upstream_version</var> is increased.
3091 The package management system will break the version
3092 number apart at the last hyphen in the string (if there
3093 is one) to determine the <var>upstream_version</var> and
3094 <var>debian_revision</var>. The absence of a
3095 <var>debian_revision</var> is equivalent to a
3096 <var>debian_revision</var> of <tt>0</tt>.
3103 When comparing two version numbers, first the <var>epoch</var>
3104 of each are compared, then the <var>upstream_version</var> if
3105 <var>epoch</var> is equal, and then <var>debian_revision</var>
3106 if <var>upstream_version</var> is also equal.
3107 <var>epoch</var> is compared numerically. The
3108 <var>upstream_version</var> and <var>debian_revision</var>
3109 parts are compared by the package management system using the
3110 following algorithm:
3114 The strings are compared from left to right.
3118 First the initial part of each string consisting entirely of
3119 non-digit characters is determined. These two parts (one of
3120 which may be empty) are compared lexically. If a difference
3121 is found it is returned. The lexical comparison is a
3122 comparison of ASCII values modified so that all the letters
3123 sort earlier than all the non-letters and so that a tilde
3124 sorts before anything, even the end of a part. For example,
3125 the following parts are in sorted order from earliest to
3126 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3127 <tt>a</tt>.<footnote>
3128 One common use of <tt>~</tt> is for upstream pre-releases.
3129 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3130 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3135 Then the initial part of the remainder of each string which
3136 consists entirely of digit characters is determined. The
3137 numerical values of these two parts are compared, and any
3138 difference found is returned as the result of the comparison.
3139 For these purposes an empty string (which can only occur at
3140 the end of one or both version strings being compared) counts
3145 These two steps (comparing and removing initial non-digit
3146 strings and initial digit strings) are repeated until a
3147 difference is found or both strings are exhausted.
3151 Note that the purpose of epochs is to allow us to leave behind
3152 mistakes in version numbering, and to cope with situations
3153 where the version numbering scheme changes. It is
3154 <em>not</em> intended to cope with version numbers containing
3155 strings of letters which the package management system cannot
3156 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3157 silly orderings.<footnote>
3158 The author of this manual has heard of a package whose
3159 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3160 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3166 <sect1 id="f-Description">
3167 <heading><tt>Description</tt></heading>
3170 In a source or binary control file, the <tt>Description</tt>
3171 field contains a description of the binary package, consisting
3172 of two parts, the synopsis or the short description, and the
3173 long description. The field's format is as follows:
3178 Description: <single line synopsis>
3179 <extended description over several lines>
3184 The lines in the extended description can have these formats:
3190 Those starting with a single space are part of a paragraph.
3191 Successive lines of this form will be word-wrapped when
3192 displayed. The leading space will usually be stripped off.
3196 Those starting with two or more spaces. These will be
3197 displayed verbatim. If the display cannot be panned
3198 horizontally, the displaying program will line wrap them "hard"
3199 (i.e., without taking account of word breaks). If it can they
3200 will be allowed to trail off to the right. None, one or two
3201 initial spaces may be deleted, but the number of spaces
3202 deleted from each line will be the same (so that you can have
3203 indenting work correctly, for example).
3207 Those containing a single space followed by a single full stop
3208 character. These are rendered as blank lines. This is the
3209 <em>only</em> way to get a blank line<footnote>
3210 Completely empty lines will not be rendered as blank lines.
3211 Instead, they will cause the parser to think you're starting
3212 a whole new record in the control file, and will therefore
3213 likely abort with an error.
3218 Those containing a space, a full stop and some more characters.
3219 These are for future expansion. Do not use them.
3225 Do not use tab characters. Their effect is not predictable.
3229 See <ref id="descriptions"> for further information on this.
3233 In a <file>.changes</file> file, the <tt>Description</tt>
3234 field contains a summary of the descriptions for the packages
3235 being uploaded. For this case, the first line of the field
3236 value (the part on the same line as <tt>Description:</tt>) is
3237 always empty. The content of the field is expressed as
3238 continuation lines, one line per package. Each line is
3239 indented by one space and contains the name of a binary
3240 package, a space, a hyphen (<tt>-</tt>), a space, and the
3241 short description line from that package.
3245 <sect1 id="f-Distribution">
3246 <heading><tt>Distribution</tt></heading>
3249 In a <file>.changes</file> file or parsed changelog output
3250 this contains the (space-separated) name(s) of the
3251 distribution(s) where this version of the package should
3252 be installed. Valid distributions are determined by the
3253 archive maintainers.<footnote>
3254 Example distribution names in the Debian archive used in
3255 <file>.changes</file> files are:
3256 <taglist compact="compact">
3257 <tag><em>unstable</em></tag>
3259 This distribution value refers to the
3260 <em>developmental</em> part of the Debian distribution
3261 tree. Most new packages, new upstream versions of
3262 packages and bug fixes go into the <em>unstable</em>
3266 <tag><em>experimental</em></tag>
3268 The packages with this distribution value are deemed
3269 by their maintainers to be high risk. Oftentimes they
3270 represent early beta or developmental packages from
3271 various sources that the maintainers want people to
3272 try, but are not ready to be a part of the other parts
3273 of the Debian distribution tree.
3278 Others are used for updating stable releases or for
3279 security uploads. More information is available in the
3280 Debian Developer's Reference, section "The Debian
3284 The Debian archive software only supports listing a single
3285 distribution. Migration of packages to other distributions is
3286 handled outside of the upload process.
3291 <heading><tt>Date</tt></heading>
3294 This field includes the date the package was built or last
3295 edited. It must be in the same format as the <var>date</var>
3296 in a <file>debian/changelog</file> entry.
3300 The value of this field is usually extracted from the
3301 <file>debian/changelog</file> file - see
3302 <ref id="dpkgchangelog">).
3306 <sect1 id="f-Format">
3307 <heading><tt>Format</tt></heading>
3310 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3311 files, this field declares the format version of that file.
3312 The syntax of the field value is the same as that of
3313 a <qref id="f-Version">package version number</qref> except
3314 that no epoch or Debian revision is allowed. The format
3315 described in this document is <tt>&changesversion;</tt>.
3319 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3320 Debian source control</qref> files, this field declares the
3321 format of the source package. The field value is used by
3322 programs acting on a source package to interpret the list of
3323 files in the source package and determine how to unpack it.
3324 The syntax of the field value is a numeric major revision, a
3325 period, a numeric minor revision, and then an optional subtype
3326 after whitespace, which if specified is an alphanumeric word
3327 in parentheses. The subtype is optional in the syntax but may
3328 be mandatory for particular source format revisions.
3330 The source formats currently supported by the Debian archive
3331 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3332 and <tt>3.0 (quilt)</tt>.
3337 <sect1 id="f-Urgency">
3338 <heading><tt>Urgency</tt></heading>
3341 This is a description of how important it is to upgrade to
3342 this version from previous ones. It consists of a single
3343 keyword taking one of the values <tt>low</tt>,
3344 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3345 <tt>critical</tt><footnote>
3346 Other urgency values are supported with configuration
3347 changes in the archive software but are not used in Debian.
3348 The urgency affects how quickly a package will be considered
3349 for inclusion into the <tt>testing</tt> distribution and
3350 gives an indication of the importance of any fixes included
3351 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3352 treated as synonymous.
3353 </footnote> (not case-sensitive) followed by an optional
3354 commentary (separated by a space) which is usually in
3355 parentheses. For example:
3358 Urgency: low (HIGH for users of diversions)
3364 The value of this field is usually extracted from the
3365 <file>debian/changelog</file> file - see
3366 <ref id="dpkgchangelog">.
3370 <sect1 id="f-Changes">
3371 <heading><tt>Changes</tt></heading>
3374 This field contains the human-readable changes data, describing
3375 the differences between the last version and the current one.
3379 The first line of the field value (the part on the same line
3380 as <tt>Changes:</tt>) is always empty. The content of the
3381 field is expressed as continuation lines, with each line
3382 indented by at least one space. Blank lines must be
3383 represented by a line consisting only of a space and a full
3388 The value of this field is usually extracted from the
3389 <file>debian/changelog</file> file - see
3390 <ref id="dpkgchangelog">).
3394 Each version's change information should be preceded by a
3395 "title" line giving at least the version, distribution(s)
3396 and urgency, in a human-readable way.
3400 If data from several versions is being returned the entry
3401 for the most recent version should be returned first, and
3402 entries should be separated by the representation of a
3403 blank line (the "title" line may also be followed by the
3404 representation of a blank line).
3408 <sect1 id="f-Binary">
3409 <heading><tt>Binary</tt></heading>
3412 This field is a list of binary packages. Its syntax and
3413 meaning varies depending on the control file in which it
3418 When it appears in the <file>.dsc</file> file, it lists binary
3419 packages which a source package can produce, separated by
3421 A space after each comma is conventional.
3422 </footnote>. It may span multiple lines. The source package
3423 does not necessarily produce all of these binary packages for
3424 every architecture. The source control file doesn't contain
3425 details of which architectures are appropriate for which of
3426 the binary packages.
3430 When it appears in a <file>.changes</file> file, it lists the
3431 names of the binary packages being uploaded, separated by
3432 whitespace (not commas). It may span multiple lines.
3436 <sect1 id="f-Installed-Size">
3437 <heading><tt>Installed-Size</tt></heading>
3440 This field appears in the control files of binary packages,
3441 and in the <file>Packages</file> files. It gives an estimate
3442 of the total amount of disk space required to install the
3443 named package. Actual installed size may vary based on block
3444 size, file system properties, or actions taken by package
3449 The disk space is given as the integer value of the estimated
3450 installed size in bytes, divided by 1024 and rounded up.
3454 <sect1 id="f-Files">
3455 <heading><tt>Files</tt></heading>
3458 This field contains a list of files with information about
3459 each one. The exact information and syntax varies with
3464 In all cases, Files is a multiline field. The first line of
3465 the field value (the part on the same line as <tt>Files:</tt>)
3466 is always empty. The content of the field is expressed as
3467 continuation lines, one line per file. Each line must be
3468 indented by one space and contain a number of sub-fields,
3469 separated by spaces, as described below.
3473 In the <file>.dsc</file> file, each line contains the MD5
3474 checksum, size and filename of the tar file and (if
3475 applicable) diff file which make up the remainder of the
3476 source package<footnote>
3477 That is, the parts which are not the <tt>.dsc</tt>.
3478 </footnote>. For example:
3481 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3482 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3484 The exact forms of the filenames are described
3485 in <ref id="pkg-sourcearchives">.
3489 In the <file>.changes</file> file this contains one line per
3490 file being uploaded. Each line contains the MD5 checksum,
3491 size, section and priority and the filename. For example:
3494 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3495 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3496 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3497 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3499 The <qref id="f-Section">section</qref>
3500 and <qref id="f-Priority">priority</qref> are the values of
3501 the corresponding fields in the main source control file. If
3502 no section or priority is specified then <tt>-</tt> should be
3503 used, though section and priority values must be specified for
3504 new packages to be installed properly.
3508 The special value <tt>byhand</tt> for the section in a
3509 <tt>.changes</tt> file indicates that the file in question
3510 is not an ordinary package file and must by installed by
3511 hand by the distribution maintainers. If the section is
3512 <tt>byhand</tt> the priority should be <tt>-</tt>.
3516 If a new Debian revision of a package is being shipped and
3517 no new original source archive is being distributed the
3518 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3519 entry for the original source archive
3520 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3521 but the <file>.changes</file> file should leave it out. In
3522 this case the original source archive on the distribution
3523 site must match exactly, byte-for-byte, the original
3524 source archive which was used to generate the
3525 <file>.dsc</file> file and diff which are being uploaded.</p>
3528 <sect1 id="f-Closes">
3529 <heading><tt>Closes</tt></heading>
3532 A space-separated list of bug report numbers that the upload
3533 governed by the .changes file closes.
3537 <sect1 id="f-Homepage">
3538 <heading><tt>Homepage</tt></heading>
3541 The URL of the web site for this package, preferably (when
3542 applicable) the site from which the original source can be
3543 obtained and any additional upstream documentation or
3544 information may be found. The content of this field is a
3545 simple URL without any surrounding characters such as
3550 <sect1 id="f-Checksums">
3551 <heading><tt>Checksums-Sha1</tt>
3552 and <tt>Checksums-Sha256</tt></heading>
3555 These fields contain a list of files with a checksum and size
3556 for each one. Both <tt>Checksums-Sha1</tt>
3557 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3558 only in the checksum algorithm used: SHA-1
3559 for <tt>Checksums-Sha1</tt> and SHA-256
3560 for <tt>Checksums-Sha256</tt>.
3564 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3565 multiline fields. The first line of the field value (the part
3566 on the same line as <tt>Checksums-Sha1:</tt>
3567 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3568 of the field is expressed as continuation lines, one line per
3569 file. Each line consists of the checksum, a space, the file
3570 size, a space, and the file name. For example (from
3571 a <file>.changes</file> file):
3574 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3575 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3576 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3577 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3579 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3580 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3581 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3582 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3587 In the <file>.dsc</file> file, these fields should list all
3588 files that make up the source package. In
3589 the <file>.changes</file> file, these fields should list all
3590 files being uploaded. The list of files in these fields
3591 must match the list of files in the <tt>Files</tt> field.
3597 <heading>User-defined fields</heading>
3600 Additional user-defined fields may be added to the
3601 source package control file. Such fields will be
3602 ignored, and not copied to (for example) binary or
3603 source package control files or upload control files.
3607 If you wish to add additional unsupported fields to
3608 these output files you should use the mechanism
3613 Fields in the main source control information file with
3614 names starting <tt>X</tt>, followed by one or more of
3615 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3616 be copied to the output files. Only the part of the
3617 field name after the hyphen will be used in the output
3618 file. Where the letter <tt>B</tt> is used the field
3619 will appear in binary package control files, where the
3620 letter <tt>S</tt> is used in source package control
3621 files and where <tt>C</tt> is used in upload control
3622 (<tt>.changes</tt>) files.
3626 For example, if the main source information control file
3629 XBS-Comment: I stand between the candle and the star.
3631 then the binary and source package control files will contain the
3634 Comment: I stand between the candle and the star.
3643 <chapt id="maintainerscripts">
3644 <heading>Package maintainer scripts and installation procedure</heading>
3647 <heading>Introduction to package maintainer scripts</heading>
3650 It is possible to supply scripts as part of a package which
3651 the package management system will run for you when your
3652 package is installed, upgraded or removed.
3656 These scripts are the files <prgn>preinst</prgn>,
3657 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3658 <prgn>postrm</prgn> in the control area of the package.
3659 They must be proper executable files; if they are scripts
3660 (which is recommended), they must start with the usual
3661 <tt>#!</tt> convention. They should be readable and
3662 executable by anyone, and must not be world-writable.
3666 The package management system looks at the exit status from
3667 these scripts. It is important that they exit with a
3668 non-zero status if there is an error, so that the package
3669 management system can stop its processing. For shell
3670 scripts this means that you <em>almost always</em> need to
3671 use <tt>set -e</tt> (this is usually true when writing shell
3672 scripts, in fact). It is also important, of course, that
3673 they exit with a zero status if everything went well.
3677 Additionally, packages interacting with users using
3678 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3679 install a <prgn>config</prgn> script in the control area,
3680 see <ref id="maintscriptprompt"> for details.
3684 When a package is upgraded a combination of the scripts from
3685 the old and new packages is called during the upgrade
3686 procedure. If your scripts are going to be at all
3687 complicated you need to be aware of this, and may need to
3688 check the arguments to your scripts.
3692 Broadly speaking the <prgn>preinst</prgn> is called before
3693 (a particular version of) a package is installed, and the
3694 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3695 before (a version of) a package is removed and the
3696 <prgn>postrm</prgn> afterwards.
3700 Programs called from maintainer scripts should not normally
3701 have a path prepended to them. Before installation is
3702 started, the package management system checks to see if the
3703 programs <prgn>ldconfig</prgn>,
3704 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3705 and <prgn>update-rc.d</prgn> can be found via the
3706 <tt>PATH</tt> environment variable. Those programs, and any
3707 other program that one would expect to be in the
3708 <tt>PATH</tt>, should thus be invoked without an absolute
3709 pathname. Maintainer scripts should also not reset the
3710 <tt>PATH</tt>, though they might choose to modify it by
3711 prepending or appending package-specific directories. These
3712 considerations really apply to all shell scripts.</p>
3715 <sect id="idempotency">
3716 <heading>Maintainer scripts idempotency</heading>
3719 It is necessary for the error recovery procedures that the
3720 scripts be idempotent. This means that if it is run
3721 successfully, and then it is called again, it doesn't bomb
3722 out or cause any harm, but just ensures that everything is
3723 the way it ought to be. If the first call failed, or
3724 aborted half way through for some reason, the second call
3725 should merely do the things that were left undone the first
3726 time, if any, and exit with a success status if everything
3728 This is so that if an error occurs, the user interrupts
3729 <prgn>dpkg</prgn> or some other unforeseen circumstance
3730 happens you don't leave the user with a badly-broken
3731 package when <prgn>dpkg</prgn> attempts to repeat the
3737 <sect id="controllingterminal">
3738 <heading>Controlling terminal for maintainer scripts</heading>
3741 Maintainer scripts are not guaranteed to run with a controlling
3742 terminal and may not be able to interact with the user. They
3743 must be able to fall back to noninteractive behavior if no
3744 controlling terminal is available. Maintainer scripts that
3745 prompt via a program conforming to the Debian Configuration
3746 Management Specification (see <ref id="maintscriptprompt">) may
3747 assume that program will handle falling back to noninteractive
3752 For high-priority prompts without a reasonable default answer,
3753 maintainer scripts may abort if there is no controlling
3754 terminal. However, this situation should be avoided if at all
3755 possible, since it prevents automated or unattended installs.
3756 In most cases, users will consider this to be a bug in the
3761 <sect id="exitstatus">
3762 <heading>Exit status</heading>
3765 Each script must return a zero exit status for
3766 success, or a nonzero one for failure, since the package
3767 management system looks for the exit status of these scripts
3768 and determines what action to take next based on that datum.
3772 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3777 <list compact="compact">
3779 <var>new-preinst</var> <tt>install</tt>
3782 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3785 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3788 <var>old-preinst</var> <tt>abort-upgrade</tt>
3789 <var>new-version</var>
3794 <list compact="compact">
3796 <var>postinst</var> <tt>configure</tt>
3797 <var>most-recently-configured-version</var>
3800 <var>old-postinst</var> <tt>abort-upgrade</tt>
3801 <var>new-version</var>
3804 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3805 <tt>in-favour</tt> <var>package</var>
3806 <var>new-version</var>
3809 <var>postinst</var> <tt>abort-remove</tt>
3812 <var>deconfigured's-postinst</var>
3813 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3814 <var>failed-install-package</var> <var>version</var>
3815 [<tt>removing</tt> <var>conflicting-package</var>
3821 <list compact="compact">
3823 <var>prerm</var> <tt>remove</tt>
3826 <var>old-prerm</var> <tt>upgrade</tt>
3827 <var>new-version</var>
3830 <var>new-prerm</var> <tt>failed-upgrade</tt>
3831 <var>old-version</var>
3834 <var>conflictor's-prerm</var> <tt>remove</tt>
3835 <tt>in-favour</tt> <var>package</var>
3836 <var>new-version</var>
3839 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3840 <tt>in-favour</tt> <var>package-being-installed</var>
3841 <var>version</var> [<tt>removing</tt>
3842 <var>conflicting-package</var>
3848 <list compact="compact">
3850 <var>postrm</var> <tt>remove</tt>
3853 <var>postrm</var> <tt>purge</tt>
3856 <var>old-postrm</var> <tt>upgrade</tt>
3857 <var>new-version</var>
3860 <var>new-postrm</var> <tt>failed-upgrade</tt>
3861 <var>old-version</var>
3864 <var>new-postrm</var> <tt>abort-install</tt>
3867 <var>new-postrm</var> <tt>abort-install</tt>
3868 <var>old-version</var>
3871 <var>new-postrm</var> <tt>abort-upgrade</tt>
3872 <var>old-version</var>
3875 <var>disappearer's-postrm</var> <tt>disappear</tt>
3876 <var>overwriter</var>
3877 <var>overwriter-version</var>
3883 <sect id="unpackphase">
3884 <heading>Details of unpack phase of installation or upgrade</heading>
3887 The procedure on installation/upgrade/overwrite/disappear
3888 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3889 stage of <tt>dpkg --install</tt>) is as follows. In each
3890 case, if a major error occurs (unless listed below) the
3891 actions are, in general, run backwards - this means that the
3892 maintainer scripts are run with different arguments in
3893 reverse order. These are the "error unwind" calls listed
3900 If a version of the package is already installed, call
3901 <example compact="compact">
3902 <var>old-prerm</var> upgrade <var>new-version</var>
3906 If the script runs but exits with a non-zero
3907 exit status, <prgn>dpkg</prgn> will attempt:
3908 <example compact="compact">
3909 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3911 If this works, the upgrade continues. If this
3912 does not work, the error unwind:
3913 <example compact="compact">
3914 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3916 If this works, then the old-version is
3917 "Installed", if not, the old version is in a
3918 "Half-Configured" state.
3924 If a "conflicting" package is being removed at the same time,
3925 or if any package will be broken (due to <tt>Breaks</tt>):
3928 If <tt>--auto-deconfigure</tt> is
3929 specified, call, for each package to be deconfigured
3930 due to <tt>Breaks</tt>:
3931 <example compact="compact">
3932 <var>deconfigured's-prerm</var> deconfigure \
3933 in-favour <var>package-being-installed</var> <var>version</var>
3936 <example compact="compact">
3937 <var>deconfigured's-postinst</var> abort-deconfigure \
3938 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3940 The deconfigured packages are marked as
3941 requiring configuration, so that if
3942 <tt>--install</tt> is used they will be
3943 configured again if possible.
3946 If any packages depended on a conflicting
3947 package being removed and <tt>--auto-deconfigure</tt> is
3948 specified, call, for each such package:
3949 <example compact="compact">
3950 <var>deconfigured's-prerm</var> deconfigure \
3951 in-favour <var>package-being-installed</var> <var>version</var> \
3952 removing <var>conflicting-package</var> <var>version</var>
3955 <example compact="compact">
3956 <var>deconfigured's-postinst</var> abort-deconfigure \
3957 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3958 removing <var>conflicting-package</var> <var>version</var>
3960 The deconfigured packages are marked as
3961 requiring configuration, so that if
3962 <tt>--install</tt> is used they will be
3963 configured again if possible.
3966 To prepare for removal of each conflicting package, call:
3967 <example compact="compact">
3968 <var>conflictor's-prerm</var> remove \
3969 in-favour <var>package</var> <var>new-version</var>
3972 <example compact="compact">
3973 <var>conflictor's-postinst</var> abort-remove \
3974 in-favour <var>package</var> <var>new-version</var>
3983 If the package is being upgraded, call:
3984 <example compact="compact">
3985 <var>new-preinst</var> upgrade <var>old-version</var>
3987 If this fails, we call:
3989 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3996 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3998 is called. If this works, then the old version
3999 is in an "Installed" state, or else it is left
4000 in an "Unpacked" state.
4005 If it fails, then the old version is left
4006 in an "Half-Installed" state.
4013 Otherwise, if the package had some configuration
4014 files from a previous version installed (i.e., it
4015 is in the "configuration files only" state):
4016 <example compact="compact">
4017 <var>new-preinst</var> install <var>old-version</var>
4021 <var>new-postrm</var> abort-install <var>old-version</var>
4023 If this fails, the package is left in a
4024 "Half-Installed" state, which requires a
4025 reinstall. If it works, the packages is left in
4026 a "Config-Files" state.
4029 Otherwise (i.e., the package was completely purged):
4030 <example compact="compact">
4031 <var>new-preinst</var> install
4034 <example compact="compact">
4035 <var>new-postrm</var> abort-install
4037 If the error-unwind fails, the package is in a
4038 "Half-Installed" phase, and requires a
4039 reinstall. If the error unwind works, the
4040 package is in a not installed state.
4047 The new package's files are unpacked, overwriting any
4048 that may be on the system already, for example any
4049 from the old version of the same package or from
4050 another package. Backups of the old files are kept
4051 temporarily, and if anything goes wrong the package
4052 management system will attempt to put them back as
4053 part of the error unwind.
4057 It is an error for a package to contain files which
4058 are on the system in another package, unless
4059 <tt>Replaces</tt> is used (see <ref id="replaces">).
4061 The following paragraph is not currently the case:
4062 Currently the <tt>- - force-overwrite</tt> flag is
4063 enabled, downgrading it to a warning, but this may not
4069 It is a more serious error for a package to contain a
4070 plain file or other kind of non-directory where another
4071 package has a directory (again, unless
4072 <tt>Replaces</tt> is used). This error can be
4073 overridden if desired using
4074 <tt>--force-overwrite-dir</tt>, but this is not
4079 Packages which overwrite each other's files produce
4080 behavior which, though deterministic, is hard for the
4081 system administrator to understand. It can easily
4082 lead to "missing" programs if, for example, a package
4083 is installed which overwrites a file from another
4084 package, and is then removed again.<footnote>
4085 Part of the problem is due to what is arguably a
4086 bug in <prgn>dpkg</prgn>.
4091 A directory will never be replaced by a symbolic link
4092 to a directory or vice versa; instead, the existing
4093 state (symlink or not) will be left alone and
4094 <prgn>dpkg</prgn> will follow the symlink if there is
4103 If the package is being upgraded, call
4104 <example compact="compact">
4105 <var>old-postrm</var> upgrade <var>new-version</var>
4109 If this fails, <prgn>dpkg</prgn> will attempt:
4110 <example compact="compact">
4111 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4113 If this works, installation continues. If not,
4115 <example compact="compact">
4116 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4118 If this fails, the old version is left in a
4119 "Half-Installed" state. If it works, dpkg now
4121 <example compact="compact">
4122 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4124 If this fails, the old version is left in a
4125 "Half-Installed" state. If it works, dpkg now
4127 <example compact="compact">
4128 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4130 If this fails, the old version is in an
4137 This is the point of no return - if
4138 <prgn>dpkg</prgn> gets this far, it won't back off
4139 past this point if an error occurs. This will
4140 leave the package in a fairly bad state, which
4141 will require a successful re-installation to clear
4142 up, but it's when <prgn>dpkg</prgn> starts doing
4143 things that are irreversible.
4148 Any files which were in the old version of the package
4149 but not in the new are removed.
4153 The new file list replaces the old.
4157 The new maintainer scripts replace the old.
4161 Any packages all of whose files have been overwritten
4162 during the installation, and which aren't required for
4163 dependencies, are considered to have been removed.
4164 For each such package
4167 <prgn>dpkg</prgn> calls:
4168 <example compact="compact">
4169 <var>disappearer's-postrm</var> disappear \
4170 <var>overwriter</var> <var>overwriter-version</var>
4174 The package's maintainer scripts are removed.
4177 It is noted in the status database as being in a
4178 sane state, namely not installed (any conffiles
4179 it may have are ignored, rather than being
4180 removed by <prgn>dpkg</prgn>). Note that
4181 disappearing packages do not have their prerm
4182 called, because <prgn>dpkg</prgn> doesn't know
4183 in advance that the package is going to
4190 Any files in the package we're unpacking that are also
4191 listed in the file lists of other packages are removed
4192 from those lists. (This will lobotomize the file list
4193 of the "conflicting" package if there is one.)
4197 The backup files made during installation, above, are
4203 The new package's status is now sane, and recorded as
4208 Here is another point of no return - if the
4209 conflicting package's removal fails we do not unwind
4210 the rest of the installation; the conflicting package
4211 is left in a half-removed limbo.
4216 If there was a conflicting package we go and do the
4217 removal actions (described below), starting with the
4218 removal of the conflicting package's files (any that
4219 are also in the package being installed have already
4220 been removed from the conflicting package's file list,
4221 and so do not get removed now).
4227 <sect id="configdetails"><heading>Details of configuration</heading>
4230 When we configure a package (this happens with <tt>dpkg
4231 --install</tt> and <tt>dpkg --configure</tt>), we first
4232 update any <tt>conffile</tt>s and then call:
4233 <example compact="compact">
4234 <var>postinst</var> configure <var>most-recently-configured-version</var>
4239 No attempt is made to unwind after errors during
4240 configuration. If the configuration fails, the package is in
4241 a "Failed Config" state, and an error message is generated.
4245 If there is no most recently configured version
4246 <prgn>dpkg</prgn> will pass a null argument.
4249 Historical note: Truly ancient (pre-1997) versions of
4250 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4251 (including the angle brackets) in this case. Even older
4252 ones did not pass a second argument at all, under any
4253 circumstance. Note that upgrades using such an old dpkg
4254 version are unlikely to work for other reasons, even if
4255 this old argument behavior is handled by your postinst script.
4261 <sect id="removedetails"><heading>Details of removal and/or
4262 configuration purging</heading>
4268 <example compact="compact">
4269 <var>prerm</var> remove
4273 If prerm fails during replacement due to conflict
4275 <var>conflictor's-postinst</var> abort-remove \
4276 in-favour <var>package</var> <var>new-version</var>
4280 <var>postinst</var> abort-remove
4284 If this fails, the package is in a "Half-Configured"
4285 state, or else it remains "Installed".
4289 The package's files are removed (except <tt>conffile</tt>s).
4292 <example compact="compact">
4293 <var>postrm</var> remove
4297 If it fails, there's no error unwind, and the package is in
4298 an "Half-Installed" state.
4303 All the maintainer scripts except the <prgn>postrm</prgn>
4308 If we aren't purging the package we stop here. Note
4309 that packages which have no <prgn>postrm</prgn> and no
4310 <tt>conffile</tt>s are automatically purged when
4311 removed, as there is no difference except for the
4312 <prgn>dpkg</prgn> status.
4316 The <tt>conffile</tt>s and any backup files
4317 (<tt>~</tt>-files, <tt>#*#</tt> files,
4318 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4323 <example compact="compact">
4324 <var>postrm</var> purge
4328 If this fails, the package remains in a "Config-Files"
4333 The package's file list is removed.
4342 <chapt id="relationships">
4343 <heading>Declaring relationships between packages</heading>
4345 <sect id="depsyntax">
4346 <heading>Syntax of relationship fields</heading>
4349 These fields all have a uniform syntax. They are a list of
4350 package names separated by commas.
4354 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4355 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4356 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4357 control file fields of the package, which declare
4358 dependencies on other packages, the package names listed may
4359 also include lists of alternative package names, separated
4360 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4361 if any one of the alternative packages is installed, that
4362 part of the dependency is considered to be satisfied.
4366 All of the fields except for <tt>Provides</tt> may restrict
4367 their applicability to particular versions of each named
4368 package. This is done in parentheses after each individual
4369 package name; the parentheses should contain a relation from
4370 the list below followed by a version number, in the format
4371 described in <ref id="f-Version">.
4375 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4376 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4377 strictly earlier, earlier or equal, exactly equal, later or
4378 equal and strictly later, respectively. The deprecated
4379 forms <tt><</tt> and <tt>></tt> were used to mean
4380 earlier/later or equal, rather than strictly earlier/later,
4381 so they should not appear in new packages (though
4382 <prgn>dpkg</prgn> still supports them).
4386 Whitespace may appear at any point in the version
4387 specification subject to the rules in <ref
4388 id="controlsyntax">, and must appear where it's necessary to
4389 disambiguate; it is not otherwise significant. All of the
4390 relationship fields may span multiple lines. For
4391 consistency and in case of future changes to
4392 <prgn>dpkg</prgn> it is recommended that a single space be
4393 used after a version relationship and before a version
4394 number; it is also conventional to put a single space after
4395 each comma, on either side of each vertical bar, and before
4396 each open parenthesis. When wrapping a relationship field, it
4397 is conventional to do so after a comma and before the space
4398 following that comma.
4402 For example, a list of dependencies might appear as:
4403 <example compact="compact">
4406 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4411 Relationships may be restricted to a certain set of
4412 architectures. This is indicated in brackets after each
4413 individual package name and the optional version specification.
4414 The brackets enclose a list of Debian architecture names
4415 separated by whitespace. Exclamation marks may be prepended to
4416 each of the names. (It is not permitted for some names to be
4417 prepended with exclamation marks while others aren't.)
4421 For build relationship fields
4422 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4423 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4424 the current Debian host architecture is not in this list and
4425 there are no exclamation marks in the list, or it is in the list
4426 with a prepended exclamation mark, the package name and the
4427 associated version specification are ignored completely for the
4428 purposes of defining the relationships.
4433 <example compact="compact">
4435 Build-Depends-Indep: texinfo
4436 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4437 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4439 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4440 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4441 <tt>gnumach-dev</tt> only on hurd-i386.
4445 For binary relationship fields, the architecture restriction
4446 syntax is only supported in the source package control
4447 file <file>debian/control</file>. When the corresponding binary
4448 package control file is generated, the relationship will either
4449 be omitted or included without the architecture restriction
4450 based on the architecture of the binary package. This means
4451 that architecture restrictions must not be used in binary
4452 relationship fields for architecture-independent packages
4453 (<tt>Architecture: all</tt>).
4458 <example compact="compact">
4459 Depends: foo [i386], bar [amd64]
4461 becomes <tt>Depends: foo</tt> when the package is built on
4462 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4463 package is built on the <tt>amd64</tt> architecture, and omitted
4464 entirely in binary packages built on all other architectures.
4468 If the architecture-restricted dependency is part of a set of
4469 alternatives using <tt>|</tt>, that alternative is ignored
4470 completely on architectures that do not match the restriction.
4472 <example compact="compact">
4473 Build-Depends: foo [!i386] | bar [!amd64]
4475 is equivalent to <tt>bar</tt> on the i386 architecture, to
4476 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4477 bar</tt> on all other architectures.
4481 Relationships may also be restricted to a certain set of
4482 architectures using architecture wildcards. The syntax for
4483 declaring such restrictions is the same as declaring
4484 restrictions using a certain set of architectures without
4485 architecture wildcards. For example:
4486 <example compact="compact">
4487 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4489 is equivalent to <tt>foo</tt> on architectures using the Linux
4490 kernel and any cpu, <tt>bar</tt> on architectures using any
4491 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4492 using a kernel other than Linux.
4496 Note that the binary package relationship fields such as
4497 <tt>Depends</tt> appear in one of the binary package
4498 sections of the control file, whereas the build-time
4499 relationships such as <tt>Build-Depends</tt> appear in the
4500 source package section of the control file (which is the
4505 <sect id="binarydeps">
4506 <heading>Binary Dependencies - <tt>Depends</tt>,
4507 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4508 <tt>Pre-Depends</tt>
4512 Packages can declare in their control file that they have
4513 certain relationships to other packages - for example, that
4514 they may not be installed at the same time as certain other
4515 packages, and/or that they depend on the presence of others.
4519 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4520 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4521 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4522 <tt>Breaks</tt> is described in <ref id="breaks">, and
4523 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4524 rest are described below.
4528 These seven fields are used to declare a dependency
4529 relationship by one package on another. Except for
4530 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4531 depending (binary) package's control file.
4532 (<tt>Enhances</tt> appears in the recommending package's
4533 control file, and <tt>Breaks</tt> appears in the version of
4534 depended-on package which causes the named package to
4539 A <tt>Depends</tt> field takes effect <em>only</em> when a
4540 package is to be configured. It does not prevent a package
4541 being on the system in an unconfigured state while its
4542 dependencies are unsatisfied, and it is possible to replace
4543 a package whose dependencies are satisfied and which is
4544 properly installed with a different version whose
4545 dependencies are not and cannot be satisfied; when this is
4546 done the depending package will be left unconfigured (since
4547 attempts to configure it will give errors) and will not
4548 function properly. If it is necessary, a
4549 <tt>Pre-Depends</tt> field can be used, which has a partial
4550 effect even when a package is being unpacked, as explained
4551 in detail below. (The other three dependency fields,
4552 <tt>Recommends</tt>, <tt>Suggests</tt> and
4553 <tt>Enhances</tt>, are only used by the various front-ends
4554 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4555 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4559 For this reason packages in an installation run are usually
4560 all unpacked first and all configured later; this gives
4561 later versions of packages with dependencies on later
4562 versions of other packages the opportunity to have their
4563 dependencies satisfied.
4567 In case of circular dependencies, since installation or
4568 removal order honoring the dependency order can't be
4569 established, dependency loops are broken at some point
4570 (based on rules below), and some packages may not be able to
4571 rely on their dependencies being present when being
4572 installed or removed, depending on which side of the break
4573 of the circular dependency loop they happen to be on. If one
4574 of the packages in the loop has no postinst script, then the
4575 cycle will be broken at that package, so as to ensure that
4576 all postinst scripts run with the dependencies properly
4577 configured if this is possible. Otherwise the breaking point
4582 The <tt>Depends</tt> field thus allows package maintainers
4583 to impose an order in which packages should be configured.
4587 The meaning of the five dependency fields is as follows:
4589 <tag><tt>Depends</tt></tag>
4592 This declares an absolute dependency. A package will
4593 not be configured unless all of the packages listed in
4594 its <tt>Depends</tt> field have been correctly
4599 The <tt>Depends</tt> field should be used if the
4600 depended-on package is required for the depending
4601 package to provide a significant amount of
4606 The <tt>Depends</tt> field should also be used if the
4607 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4608 <prgn>postrm</prgn> scripts require the package to be
4609 present in order to run. Note, however, that the
4610 <prgn>postrm</prgn> cannot rely on any non-essential
4611 packages to be present during the <tt>purge</tt>
4615 <tag><tt>Recommends</tt></tag>
4618 This declares a strong, but not absolute, dependency.
4622 The <tt>Recommends</tt> field should list packages
4623 that would be found together with this one in all but
4624 unusual installations.
4628 <tag><tt>Suggests</tt></tag>
4630 This is used to declare that one package may be more
4631 useful with one or more others. Using this field
4632 tells the packaging system and the user that the
4633 listed packages are related to this one and can
4634 perhaps enhance its usefulness, but that installing
4635 this one without them is perfectly reasonable.
4638 <tag><tt>Enhances</tt></tag>
4640 This field is similar to Suggests but works in the
4641 opposite direction. It is used to declare that a
4642 package can enhance the functionality of another
4646 <tag><tt>Pre-Depends</tt></tag>
4649 This field is like <tt>Depends</tt>, except that it
4650 also forces <prgn>dpkg</prgn> to complete installation
4651 of the packages named before even starting the
4652 installation of the package which declares the
4653 pre-dependency, as follows:
4657 When a package declaring a pre-dependency is about to
4658 be <em>unpacked</em> the pre-dependency can be
4659 satisfied if the depended-on package is either fully
4660 configured, <em>or even if</em> the depended-on
4661 package(s) are only unpacked or in the "Half-Configured"
4662 state, provided that they have been configured
4663 correctly at some point in the past (and not removed
4664 or partially removed since). In this case, both the
4665 previously-configured and currently unpacked or
4666 "Half-Configured" versions must satisfy any version
4667 clause in the <tt>Pre-Depends</tt> field.
4671 When the package declaring a pre-dependency is about
4672 to be <em>configured</em>, the pre-dependency will be
4673 treated as a normal <tt>Depends</tt>, that is, it will
4674 be considered satisfied only if the depended-on
4675 package has been correctly configured.
4679 <tt>Pre-Depends</tt> should be used sparingly,
4680 preferably only by packages whose premature upgrade or
4681 installation would hamper the ability of the system to
4682 continue with any upgrade that might be in progress.
4686 <tt>Pre-Depends</tt> are also required if the
4687 <prgn>preinst</prgn> script depends on the named
4688 package. It is best to avoid this situation if
4696 When selecting which level of dependency to use you should
4697 consider how important the depended-on package is to the
4698 functionality of the one declaring the dependency. Some
4699 packages are composed of components of varying degrees of
4700 importance. Such a package should list using
4701 <tt>Depends</tt> the package(s) which are required by the
4702 more important components. The other components'
4703 requirements may be mentioned as Suggestions or
4704 Recommendations, as appropriate to the components' relative
4710 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4713 When one binary package declares that it breaks another,
4714 <prgn>dpkg</prgn> will refuse to allow the package which
4715 declares <tt>Breaks</tt> be installed unless the broken
4716 package is deconfigured first, and it will refuse to
4717 allow the broken package to be reconfigured.
4721 A package will not be regarded as causing breakage merely
4722 because its configuration files are still installed; it must
4723 be at least "Half-Installed".
4727 A special exception is made for packages which declare that
4728 they break their own package name or a virtual package which
4729 they provide (see below): this does not count as a real
4734 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4735 version clause; such a <tt>Breaks</tt> is introduced in the
4736 version of an (implicit or explicit) dependency which violates
4737 an assumption or reveals a bug in earlier versions of the broken
4738 package, or which takes over a file from earlier versions of the
4739 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4740 will inform higher-level package management tools that the
4741 broken package must be upgraded before the new one.
4745 If the breaking package also overwrites some files from the
4746 older package, it should use <tt>Replaces</tt> to ensure this
4747 goes smoothly. See <ref id="replaces"> for a full discussion
4748 of taking over files from other packages, including how to
4749 use <tt>Breaks</tt> in those cases.
4753 Many of the cases where <tt>Breaks</tt> should be used were
4754 previously handled with <tt>Conflicts</tt>
4755 because <tt>Breaks</tt> did not yet exist.
4756 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4757 See <ref id="conflicts"> for more information about the
4762 <sect id="conflicts">
4763 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4766 When one binary package declares a conflict with another
4767 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4768 refuse to allow them to be installed on the system at the
4769 same time. This is a stronger restriction than <tt>Breaks</tt>,
4770 which just prevents both packages from being configured at the
4771 same time. Conflicting packages cannot be unpacked on the
4772 system at the same time.
4776 If one package is to be installed, the other must be removed
4777 first. If the package being installed is marked as replacing
4778 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4779 normally be used in this case) the one on the system, or the one
4780 on the system is marked as deselected, or both packages are
4781 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4782 automatically remove the package which is causing the conflict.
4783 Otherwise, it will halt the installation of the new package with
4784 an error. This mechanism is specifically designed to produce an
4785 error when the installed package is <tt>Essential</tt>, but the
4790 A package will not cause a conflict merely because its
4791 configuration files are still installed; it must be at least
4796 A special exception is made for packages which declare a
4797 conflict with their own package name, or with a virtual
4798 package which they provide (see below): this does not
4799 prevent their installation, and allows a package to conflict
4800 with others providing a replacement for it. You use this
4801 feature when you want the package in question to be the only
4802 package providing some feature.
4806 Normally, <tt>Breaks</tt> should be used instead
4807 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4808 stronger restriction on the ordering of package installation or
4809 upgrade and can make it more difficult for the package manager
4810 to find a correct solution to an upgrade or installation
4811 problem. <tt>Breaks</tt> should be used
4813 <item>when moving a file from one package to another (see
4814 <ref id="replaces">),</item>
4815 <item>when splitting a package (a special case of the previous
4817 <item>when the breaking package exposes a bug in or interacts
4818 badly with particular versions of the broken
4821 <tt>Conflicts</tt> should be used
4823 <item>when two packages provide the same file and will
4824 continue to do so,</item>
4825 <item>in conjunction with <tt>Provides</tt> when only one
4826 package providing a given virtual facility may be installed
4827 at a time (see <ref id="virtual">),</item>
4828 <item>in other cases where one must prevent simultaneous
4829 installation of two packages for reasons that are ongoing
4830 (not fixed in a later version of one of the packages) or
4831 that must prevent both packages from being unpacked at the
4832 same time, not just configured.</item>
4834 Be aware that adding <tt>Conflicts</tt> is normally not the best
4835 solution when two packages provide the same files. Depending on
4836 the reason for that conflict, using alternatives or renaming the
4837 files is often a better approach. See, for
4838 example, <ref id="binaries">.
4842 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4843 unless two packages cannot be installed at the same time or
4844 installing them both causes one of them to be broken or
4845 unusable. Having similar functionality or performing the same
4846 tasks as another package is not sufficient reason to
4847 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4851 A <tt>Conflicts</tt> entry may have an "earlier than" version
4852 clause if the reason for the conflict is corrected in a later
4853 version of one of the packages. However, normally the presence
4854 of an "earlier than" version clause is a sign
4855 that <tt>Breaks</tt> should have been used instead. An "earlier
4856 than" version clause in <tt>Conflicts</tt>
4857 prevents <prgn>dpkg</prgn> from upgrading or installing the
4858 package which declares such a conflict until the upgrade or
4859 removal of the conflicted-with package has been completed, which
4860 is a strong restriction.
4864 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4868 As well as the names of actual ("concrete") packages, the
4869 package relationship fields <tt>Depends</tt>,
4870 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4871 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4872 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4873 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4874 may mention "virtual packages".
4878 A <em>virtual package</em> is one which appears in the
4879 <tt>Provides</tt> control file field of another package.
4880 The effect is as if the package(s) which provide a
4881 particular virtual package name had been listed by name
4882 everywhere the virtual package name appears. (See also <ref
4887 If there are both concrete and virtual packages of the same
4888 name, then the dependency may be satisfied (or the conflict
4889 caused) by either the concrete package with the name in
4890 question or any other concrete package which provides the
4891 virtual package with the name in question. This is so that,
4892 for example, supposing we have
4893 <example compact="compact">
4896 </example> and someone else releases an enhanced version of
4897 the <tt>bar</tt> package they can say:
4898 <example compact="compact">
4902 and the <tt>bar-plus</tt> package will now also satisfy the
4903 dependency for the <tt>foo</tt> package.
4907 If a relationship field has a version number attached, only real
4908 packages will be considered to see whether the relationship is
4909 satisfied (or the prohibition violated, for a conflict or
4910 breakage). In other words, if a version number is specified,
4911 this is a request to ignore all <tt>Provides</tt> for that
4912 package name and consider only real packages. The package
4913 manager will assume that a package providing that virtual
4914 package is not of the "right" version. A <tt>Provides</tt>
4915 field may not contain version numbers, and the version number of
4916 the concrete package which provides a particular virtual package
4917 will not be considered when considering a dependency on or
4918 conflict with the virtual package name.<footnote>
4919 It is possible that a future release of <prgn>dpkg</prgn> may
4920 add the ability to specify a version number for each virtual
4921 package it provides. This feature is not yet present,
4922 however, and is expected to be used only infrequently.
4927 To specify which of a set of real packages should be the default
4928 to satisfy a particular dependency on a virtual package, list
4929 the real package as an alternative before the virtual one.
4933 If the virtual package represents a facility that can only be
4934 provided by one real package at a time, such as
4935 the <package>mail-transport-agent</package> virtual package that
4936 requires installation of a binary that would conflict with all
4937 other providers of that virtual package (see
4938 <ref id="mail-transport-agents">), all packages providing that
4939 virtual package should also declare a conflict with it
4940 using <tt>Conflicts</tt>. This will ensure that at most one
4941 provider of that virtual package is unpacked or installed at a
4946 <sect id="replaces"><heading>Overwriting files and replacing
4947 packages - <tt>Replaces</tt></heading>
4950 Packages can declare in their control file that they should
4951 overwrite files in certain other packages, or completely
4952 replace other packages. The <tt>Replaces</tt> control file
4953 field has these two distinct purposes.
4956 <sect1><heading>Overwriting files in other packages</heading>
4959 It is usually an error for a package to contain files which
4960 are on the system in another package. However, if the
4961 overwriting package declares that it <tt>Replaces</tt> the one
4962 containing the file being overwritten, then <prgn>dpkg</prgn>
4963 will replace the file from the old package with that from the
4964 new. The file will no longer be listed as "owned" by the old
4965 package and will be taken over by the new package.
4966 Normally, <tt>Breaks</tt> should be used in conjunction
4967 with <tt>Replaces</tt>.<footnote>
4968 To see why <tt>Breaks</tt> is normally needed in addition
4969 to <tt>Replaces</tt>, consider the case of a file in the
4970 package <package>foo</package> being taken over by the
4971 package <package>foo-data</package>.
4972 <tt>Replaces</tt> will allow <package>foo-data</package> to
4973 be installed and take over that file. However,
4974 without <tt>Breaks</tt>, nothing
4975 requires <package>foo</package> to be upgraded to a newer
4976 version that knows it does not include that file and instead
4977 depends on <package>foo-data</package>. Nothing would
4978 prevent the new <package>foo-data</package> package from
4979 being installed and then removed, removing the file that it
4980 took over from <package>foo</package>. After that
4981 operation, the package manager would think the system was in
4982 a consistent state, but the <package>foo</package> package
4983 would be missing one of its files.
4988 For example, if a package <package>foo</package> is split
4989 into <package>foo</package> and <package>foo-data</package>
4990 starting at version 1.2-3, <package>foo-data</package> would
4992 <example compact="compact">
4993 Replaces: foo (<< 1.2-3)
4994 Breaks: foo (<< 1.2-3)
4996 in its control file. The new version of the
4997 package <package>foo</package> would normally have the field
4998 <example compact="compact">
4999 Depends: foo-data (>= 1.2-3)
5001 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5002 the files moved into <package>foo-data</package> are not
5003 required for normal operation).
5007 If a package is completely replaced in this way, so that
5008 <prgn>dpkg</prgn> does not know of any files it still
5009 contains, it is considered to have "disappeared". It will
5010 be marked as not wanted on the system (selected for
5011 removal) and not installed. Any <tt>conffile</tt>s
5012 details noted for the package will be ignored, as they
5013 will have been taken over by the overwriting package. The
5014 package's <prgn>postrm</prgn> script will be run with a
5015 special argument to allow the package to do any final
5016 cleanup required. See <ref id="mscriptsinstact">.
5018 Replaces is a one way relationship. You have to install
5019 the replacing package after the replaced package.
5024 For this usage of <tt>Replaces</tt>, virtual packages (see
5025 <ref id="virtual">) are not considered when looking at a
5026 <tt>Replaces</tt> field. The packages declared as being
5027 replaced must be mentioned by their real names.
5031 This usage of <tt>Replaces</tt> only takes effect when both
5032 packages are at least partially on the system at once. It is
5033 not relevant if the packages conflict unless the conflict has
5038 <sect1><heading>Replacing whole packages, forcing their
5042 Second, <tt>Replaces</tt> allows the packaging system to
5043 resolve which package should be removed when there is a
5044 conflict (see <ref id="conflicts">). This usage only takes
5045 effect when the two packages <em>do</em> conflict, so that the
5046 two usages of this field do not interfere with each other.
5050 In this situation, the package declared as being replaced
5051 can be a virtual package, so for example, all mail
5052 transport agents (MTAs) would have the following fields in
5053 their control files:
5054 <example compact="compact">
5055 Provides: mail-transport-agent
5056 Conflicts: mail-transport-agent
5057 Replaces: mail-transport-agent
5059 ensuring that only one MTA can be installed at any one
5060 time. See <ref id="virtual"> for more information about this
5065 <sect id="sourcebinarydeps">
5066 <heading>Relationships between source and binary packages -
5067 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5068 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5072 Source packages that require certain binary packages to be
5073 installed or absent at the time of building the package
5074 can declare relationships to those binary packages.
5078 This is done using the <tt>Build-Depends</tt>,
5079 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5080 <tt>Build-Conflicts-Indep</tt> control file fields.
5084 Build-dependencies on "build-essential" binary packages can be
5085 omitted. Please see <ref id="pkg-relations"> for more information.
5089 The dependencies and conflicts they define must be satisfied
5090 (as defined earlier for binary packages) in order to invoke
5091 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5093 There is no Build-Depends-Arch; this role is essentially
5094 met with Build-Depends. Anyone building the
5095 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5096 assumed to be building the whole package, and therefore
5097 installation of all build dependencies is required.
5100 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5101 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5102 not yet know how to check for its existence, and
5103 <tt>binary-arch</tt>. The purpose of the original split
5104 between <tt>Build-Depends</tt> and
5105 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5106 wouldn't need to install extra packages needed only for the
5107 binary-indep targets. But without a build-arch/build-indep
5108 split, this didn't work, since most of the work is done in
5109 the build target, not in the binary target.
5113 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5114 <tt>binary-arch</tt></tag>
5116 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5117 fields must be satisfied when these targets are invoked.
5119 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5120 and <tt>binary-indep</tt></tag>
5122 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5123 <tt>Build-Depends-Indep</tt>, and
5124 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5125 these targets are invoked.
5133 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5136 Packages containing shared libraries must be constructed with
5137 a little care to make sure that the shared library is always
5138 available. This is especially important for packages whose
5139 shared libraries are vitally important, such as the C library
5140 (currently <tt>libc6</tt>).
5144 Packages involving shared libraries should be split up into
5145 several binary packages. This section mostly deals with how
5146 this separation is to be accomplished; rules for files within
5147 the shared library packages are in <ref id="libraries"> instead.
5150 <sect id="sharedlibs-runtime">
5151 <heading>Run-time shared libraries</heading>
5154 The run-time shared library needs to be placed in a package
5155 whose name changes whenever the shared object version
5158 Since it is common place to install several versions of a
5159 package that just provides shared libraries, it is a
5160 good idea that the library package should not
5161 contain any extraneous non-versioned files, unless they
5162 happen to be in versioned directories.</p>
5164 The most common mechanism is to place it in a package
5166 <package><var>libraryname</var><var>soversion</var></package>,
5167 where <file><var>soversion</var></file> is the version number
5168 in the soname of the shared library<footnote>
5169 The soname is the shared object name: it's the thing
5170 that has to match exactly between building an executable
5171 and running it for the dynamic linker to be able run the
5172 program. For example, if the soname of the library is
5173 <file>libfoo.so.6</file>, the library package would be
5174 called <file>libfoo6</file>.
5176 Alternatively, if it would be confusing to directly append
5177 <var>soversion</var> to <var>libraryname</var> (e.g. because
5178 <var>libraryname</var> itself ends in a number), you may use
5179 <package><var>libraryname</var>-<var>soversion</var></package> and
5180 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5185 If you have several shared libraries built from the same
5186 source tree you may lump them all together into a single
5187 shared library package, provided that you change all of
5188 their sonames at once (so that you don't get filename
5189 clashes if you try to install different versions of the
5190 combined shared libraries package).
5194 The package should install the shared libraries under
5195 their normal names. For example, the <package>libgdbm3</package>
5196 package should install <file>libgdbm.so.3.0.0</file> as
5197 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5198 renamed or re-linked by any <prgn>prerm</prgn> or
5199 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5200 of renaming things safely without affecting running programs,
5201 and attempts to interfere with this are likely to lead to
5206 Shared libraries should not be installed executable, since
5207 the dynamic linker does not require this and trying to
5208 execute a shared library usually results in a core dump.
5212 The run-time library package should include the symbolic link that
5213 <prgn>ldconfig</prgn> would create for the shared libraries.
5214 For example, the <package>libgdbm3</package> package should include
5215 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5216 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5217 linker (for example <prgn>ld.so</prgn> or
5218 <prgn>ld-linux.so.*</prgn>) can find the library between the
5219 time that <prgn>dpkg</prgn> installs it and the time that
5220 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5222 The package management system requires the library to be
5223 placed before the symbolic link pointing to it in the
5224 <file>.deb</file> file. This is so that when
5225 <prgn>dpkg</prgn> comes to install the symlink
5226 (overwriting the previous symlink pointing at an older
5227 version of the library), the new shared library is already
5228 in place. In the past, this was achieved by creating the
5229 library in the temporary packaging directory before
5230 creating the symlink. Unfortunately, this was not always
5231 effective, since the building of the tar file in the
5232 <file>.deb</file> depended on the behavior of the underlying
5233 file system. Some file systems (such as reiserfs) reorder
5234 the files so that the order of creation is forgotten.
5235 Since version 1.7.0, <prgn>dpkg</prgn>
5236 reorders the files itself as necessary when building a
5237 package. Thus it is no longer important to concern
5238 oneself with the order of file creation.
5242 <sect1 id="ldconfig">
5243 <heading><tt>ldconfig</tt></heading>
5246 Any package installing shared libraries in one of the default
5247 library directories of the dynamic linker (which are currently
5248 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5249 listed in <file>/etc/ld.so.conf</file><footnote>
5251 <list compact="compact">
5252 <item>/usr/local/lib</item>
5253 <item>/usr/lib/libc5-compat</item>
5254 <item>/lib/libc5-compat</item>
5257 must use <prgn>ldconfig</prgn> to update the shared library
5262 The package maintainer scripts must only call
5263 <prgn>ldconfig</prgn> under these circumstances:
5264 <list compact="compact">
5265 <item>When the <prgn>postinst</prgn> script is run with a
5266 first argument of <tt>configure</tt>, the script must call
5267 <prgn>ldconfig</prgn>, and may optionally invoke
5268 <prgn>ldconfig</prgn> at other times.
5270 <item>When the <prgn>postrm</prgn> script is run with a
5271 first argument of <tt>remove</tt>, the script should call
5272 <prgn>ldconfig</prgn>.
5277 During install or upgrade, the preinst is called before
5278 the new files are installed, so calling "ldconfig" is
5279 pointless. The preinst of an existing package can also be
5280 called if an upgrade fails. However, this happens during
5281 the critical time when a shared libs may exist on-disk
5282 under a temporary name. Thus, it is dangerous and
5283 forbidden by current policy to call "ldconfig" at this
5288 When a package is installed or upgraded, "postinst
5289 configure" runs after the new files are safely on-disk.
5290 Since it is perfectly safe to invoke ldconfig
5291 unconditionally in a postinst, it is OK for a package to
5292 simply put ldconfig in its postinst without checking the
5293 argument. The postinst can also be called to recover from
5294 a failed upgrade. This happens before any new files are
5295 unpacked, so there is no reason to call "ldconfig" at this
5300 For a package that is being removed, prerm is
5301 called with all the files intact, so calling ldconfig is
5302 useless. The other calls to "prerm" happen in the case of
5303 upgrade at a time when all the files of the old package
5304 are on-disk, so again calling "ldconfig" is pointless.
5308 postrm, on the other hand, is called with the "remove"
5309 argument just after the files are removed, so this is
5310 the proper time to call "ldconfig" to notify the system
5311 of the fact that the shared libraries from the package
5312 are removed. The postrm can be called at several other
5313 times. At the time of "postrm purge", "postrm
5314 abort-install", or "postrm abort-upgrade", calling
5315 "ldconfig" is useless because the shared lib files are
5316 not on-disk. However, when "postrm" is invoked with
5317 arguments "upgrade", "failed-upgrade", or "disappear", a
5318 shared lib may exist on-disk under a temporary filename.
5326 <sect id="sharedlibs-support-files">
5327 <heading>Shared library support files</heading>
5330 If your package contains files whose names do not change with
5331 each change in the library shared object version, you must not
5332 put them in the shared library package. Otherwise, several
5333 versions of the shared library cannot be installed at the same
5334 time without filename clashes, making upgrades and transitions
5335 unnecessarily difficult.
5339 It is recommended that supporting files and run-time support
5340 programs that do not need to be invoked manually by users, but
5341 are nevertheless required for the package to function, be placed
5342 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5343 preferably under <file>/usr/lib/</file><var>package-name</var>.
5344 If the program or file is architecture independent, the
5345 recommendation is for it to be placed in a subdirectory of
5346 <file>/usr/share</file> instead, preferably under
5347 <file>/usr/share/</file><var>package-name</var>. Following the
5348 <var>package-name</var> naming convention ensures that the file
5349 names change when the shared object version changes.
5353 Run-time support programs that use the shared library but are
5354 not required for the library to function or files used by the
5355 shared library that can be used by any version of the shared
5356 library package should instead be put in a separate package.
5357 This package might typically be named
5358 <package><var>libraryname</var>-tools</package>; note the
5359 absence of the <var>soversion</var> in the package name.
5363 Files and support programs only useful when compiling software
5364 against the library should be included in the development
5365 package for the library.<footnote>
5366 For example, a <file><var>package-name</var>-config</file>
5367 script or <package>pkg-config</package> configuration files.
5372 <sect id="sharedlibs-static">
5373 <heading>Static libraries</heading>
5376 The static library (<file><var>libraryname.a</var></file>)
5377 is usually provided in addition to the shared version.
5378 It is placed into the development package (see below).
5382 In some cases, it is acceptable for a library to be
5383 available in static form only; these cases include:
5385 <item>libraries for languages whose shared library support
5386 is immature or unstable</item>
5387 <item>libraries whose interfaces are in flux or under
5388 development (commonly the case when the library's
5389 major version number is zero, or where the ABI breaks
5390 across patchlevels)</item>
5391 <item>libraries which are explicitly intended to be
5392 available only in static form by their upstream
5397 <sect id="sharedlibs-dev">
5398 <heading>Development files</heading>
5401 If there are development files associated with a shared library,
5402 the source package needs to generate a binary development package
5403 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5404 or if you prefer only to support one development version at a
5405 time, <package><var>libraryname</var>-dev</package>. Installing
5406 the development package must result in installation of all the
5407 development files necessary for compiling programs against that
5408 shared library.<footnote>
5409 This wording allows the development files to be split into
5410 several packages, such as a separate architecture-independent
5411 <package><var>libraryname</var>-headers</package>, provided that
5412 the development package depends on all the required additional
5418 In case several development versions of a library exist, you may
5419 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5420 <ref id="conflicts">) to ensure that the user only installs one
5421 development version at a time (as different development versions are
5422 likely to have the same header files in them, which would cause a
5423 filename clash if both were installed).
5427 The development package should contain a symlink for the associated
5428 shared library without a version number. For example, the
5429 <package>libgdbm-dev</package> package should include a symlink
5430 from <file>/usr/lib/libgdbm.so</file> to
5431 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5432 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5433 <file>libgdbm.so</file> when compiling dynamically.
5437 <sect id="sharedlibs-intradeps">
5438 <heading>Dependencies between the packages of the same library</heading>
5441 Typically the development version should have an exact
5442 version dependency on the runtime library, to make sure that
5443 compilation and linking happens correctly. The
5444 <tt>${binary:Version}</tt> substitution variable can be
5445 useful for this purpose.
5447 Previously, <tt>${Source-Version}</tt> was used, but its name
5448 was confusing and it has been deprecated since dpkg 1.13.19.
5453 <sect id="sharedlibs-shlibdeps">
5454 <heading>Dependencies between the library and other packages -
5455 the <tt>shlibs</tt> system</heading>
5458 If a package contains a binary or library which links to a
5459 shared library, we must ensure that when the package is
5460 installed on the system, all of the libraries needed are
5461 also installed. This requirement led to the creation of the
5462 <tt>shlibs</tt> system, which is very simple in its design:
5463 any package which <em>provides</em> a shared library also
5464 provides information on the package dependencies required to
5465 ensure the presence of this library, and any package which
5466 <em>uses</em> a shared library uses this information to
5467 determine the dependencies it requires. The files which
5468 contain the mapping from shared libraries to the necessary
5469 dependency information are called <file>shlibs</file> files.
5473 When a package is built which contains any shared libraries, it
5474 must provide a <file>shlibs</file> file for other packages to
5475 use. When a package is built which contains any shared
5476 libraries or compiled binaries, it must run
5477 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5478 on these to determine the libraries used and hence the
5479 dependencies needed by this package.<footnote>
5481 <prgn>dpkg-shlibdeps</prgn> will use a program
5482 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5483 the libraries directly needed by the binaries or shared
5484 libraries in the package.
5488 We say that a binary <tt>foo</tt> <em>directly</em> uses
5489 a library <tt>libbar</tt> if it is explicitly linked
5490 with that library (that is, the library is listed in the ELF
5491 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5492 to the link line when the binary is created). Other
5493 libraries that are needed by <tt>libbar</tt> are linked
5494 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5495 linker will load them automatically when it loads
5496 <tt>libbar</tt>. A package should depend on the libraries
5497 it directly uses, but not the libraries it indirectly uses.
5498 The dependencies for those libraries will automatically pull
5499 in the other libraries.
5503 A good example of where this helps is the following. We
5504 could update <tt>libimlib</tt> with a new version that
5505 supports a new graphics format called dgf (but retaining the
5506 same major version number) and depends on <tt>libdgf</tt>.
5507 If we used <prgn>ldd</prgn> to add dependencies for every
5508 library directly or indirectly linked with a binary, every
5509 package that uses <tt>libimlib</tt> would need to be
5510 recompiled so it would also depend on <tt>libdgf</tt> or it
5511 wouldn't run due to missing symbols. Since dependencies are
5512 only added based on ELF <tt>NEEDED</tt> attribute, packages
5513 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5514 having the dependency on <tt>libdgf</tt> and so they would
5515 not need rebuilding.
5521 In the following sections, we will first describe where the
5522 various <tt>shlibs</tt> files are to be found, then how to
5523 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5524 file format and how to create them if your package contains a
5529 <heading>The <tt>shlibs</tt> files present on the system</heading>
5532 There are several places where <tt>shlibs</tt> files are
5533 found. The following list gives them in the order in which
5535 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5536 (The first one which gives the required information is used.)
5542 <p><file>debian/shlibs.local</file></p>
5545 This lists overrides for this package. This file should
5546 normally not be used, but may be needed temporarily in
5547 unusual situations to work around bugs in other packages,
5548 or in unusual cases where the normally declared dependency
5549 information in the installed <file>shlibs</file> file for
5550 a library cannot be used. This file overrides information
5551 obtained from any other source.
5556 <p><file>/etc/dpkg/shlibs.override</file></p>
5559 This lists global overrides. This list is normally
5560 empty. It is maintained by the local system
5566 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5569 When packages are being built,
5570 any <file>debian/shlibs</file> files are copied into the
5571 control file area of the temporary build directory and
5572 given the name <file>shlibs</file>. These files give
5573 details of any shared libraries included in the same
5575 An example may help here. Let us say that the source
5576 package <tt>foo</tt> generates two binary
5577 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5578 When building the binary packages, the two packages are
5579 created in the directories <file>debian/libfoo2</file>
5580 and <file>debian/foo-runtime</file> respectively.
5581 (<file>debian/tmp</file> could be used instead of one of
5582 these.) Since <tt>libfoo2</tt> provides the
5583 <tt>libfoo</tt> shared library, it will require a
5584 <tt>shlibs</tt> file, which will be installed in
5585 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5586 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5587 When <prgn>dpkg-shlibdeps</prgn> is run on the
5588 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5590 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5591 determine whether <tt>foo-prog</tt>'s library
5592 dependencies are satisfied by any of the libraries
5593 provided by <tt>libfoo2</tt>. For this reason,
5594 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5595 the individual binary packages' <tt>shlibs</tt> files
5596 have been installed into the build directory.
5602 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5605 These are the <file>shlibs</file> files corresponding to
5606 all of the packages installed on the system, and are
5607 maintained by the relevant package maintainers.
5612 <p><file>/etc/dpkg/shlibs.default</file></p>
5615 This file lists any shared libraries whose packages
5616 have failed to provide correct <file>shlibs</file> files.
5617 It was used when the <file>shlibs</file> setup was first
5618 introduced, but it is now normally empty. It is
5619 maintained by the <tt>dpkg</tt> maintainer.
5627 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5628 <file>shlibs</file> files</heading>
5632 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5633 into your <file>debian/rules</file> file. If your package
5634 contains only compiled binaries and libraries (but no scripts),
5635 you can use a command such as:
5636 <example compact="compact">
5637 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5638 debian/tmp/usr/lib/*
5640 Otherwise, you will need to explicitly list the compiled
5641 binaries and libraries.<footnote>
5642 If you are using <tt>debhelper</tt>, the
5643 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5644 It will also correctly handle multi-binary packages.
5649 This command puts the dependency information into the
5650 <file>debian/substvars</file> file, which is then used by
5651 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5652 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5653 field in the control file for this to work.
5657 If you have multiple binary packages, you will need to call
5658 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5659 compiled libraries or binaries. In such a case, you will
5660 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5661 utilities to specify a different <file>substvars</file> file.
5665 If you are creating a udeb for use in the Debian Installer,
5666 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5667 should use the dependency line of type <tt>udeb</tt> by
5668 adding the <tt>-tudeb</tt> option<footnote>
5669 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5670 will automatically add this option if it knows it is
5672 </footnote>. If there is no dependency line of
5673 type <tt>udeb</tt> in the <file>shlibs</file>
5674 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5679 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5680 <ref id="pkg-dpkg-shlibdeps"> and
5681 <manref name="dpkg-shlibdeps" section="1">.
5686 <heading>The <file>shlibs</file> File Format</heading>
5689 Each <file>shlibs</file> file has the same format. Lines
5690 beginning with <tt>#</tt> are considered to be comments and
5691 are ignored. Each line is of the form:
5692 <example compact="compact">
5693 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5698 We will explain this by reference to the example of the
5699 <tt>zlib1g</tt> package, which (at the time of writing)
5700 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5704 <var>type</var> is an optional element that indicates the type
5705 of package for which the line is valid. The only type currently
5706 in use is <tt>udeb</tt>. The colon and space after the type are
5711 <var>library-name</var> is the name of the shared library,
5712 in this case <tt>libz</tt>. (This must match the name part
5713 of the soname, see below.)
5717 <var>soname-version</var> is the version part of the soname of
5718 the library. The soname is the thing that must exactly match
5719 for the library to be recognized by the dynamic linker, and is
5721 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5722 example, <tt>libz.so.1</tt>.<footnote>
5723 This can be determined using the command
5724 <example compact="compact">
5725 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5728 The version part is the part which comes after
5729 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5730 instead be of the form
5731 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5732 as <tt>libdb-4.8.so</tt>, in which case the name would
5733 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5737 <var>dependencies</var> has the same syntax as a dependency
5738 field in a binary package control file. It should give
5739 details of which packages are required to satisfy a binary
5740 built against the version of the library contained in the
5741 package. See <ref id="depsyntax"> for details.
5745 In our example, if the first version of the <tt>zlib1g</tt>
5746 package which contained a minor number of at least
5747 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5748 <tt>shlibs</tt> entry for this library could say:
5749 <example compact="compact">
5750 libz 1 zlib1g (>= 1:1.1.3)
5752 The version-specific dependency is to avoid warnings from
5753 the dynamic linker about using older shared libraries with
5758 As zlib1g also provides a udeb containing the shared library,
5759 there would also be a second line:
5760 <example compact="compact">
5761 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5767 <heading>Providing a <file>shlibs</file> file</heading>
5770 If your package provides a shared library, you need to create
5771 a <file>shlibs</file> file following the format described above.
5772 It is usual to call this file <file>debian/shlibs</file> (but if
5773 you have multiple binary packages, you might want to call it
5774 <file>debian/shlibs.<var>package</var></file> instead). Then
5775 let <file>debian/rules</file> install it in the control area:
5776 <example compact="compact">
5777 install -m644 debian/shlibs debian/tmp/DEBIAN
5779 or, in the case of a multi-binary package:
5780 <example compact="compact">
5781 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5783 An alternative way of doing this is to create the
5784 <file>shlibs</file> file in the control area directly from
5785 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5786 file at all,<footnote>
5787 This is what <prgn>dh_makeshlibs</prgn> in
5788 the <package>debhelper</package> suite does. If your package
5789 also has a udeb that provides a shared
5790 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5791 the <tt>udeb:</tt> lines if you specify the name of the udeb
5792 with the <tt>--add-udeb</tt> option.
5794 since the <file>debian/shlibs</file> file itself is ignored by
5795 <prgn>dpkg-shlibdeps</prgn>.
5799 As <prgn>dpkg-shlibdeps</prgn> reads the
5800 <file>DEBIAN/shlibs</file> files in all of the binary packages
5801 being built from this source package, all of the
5802 <file>DEBIAN/shlibs</file> files should be installed before
5803 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5811 <chapt id="opersys"><heading>The Operating System</heading>
5814 <heading>File system hierarchy</heading>
5818 <heading>File System Structure</heading>
5821 The location of all installed files and directories must
5822 comply with the Filesystem Hierarchy Standard (FHS),
5823 version 2.3, with the exceptions noted below, and except
5824 where doing so would violate other terms of Debian
5825 Policy. The following exceptions to the FHS apply:
5830 The optional rules related to user specific
5831 configuration files for applications are stored in
5832 the user's home directory are relaxed. It is
5833 recommended that such files start with the
5834 '<tt>.</tt>' character (a "dot file"), and if an
5835 application needs to create more than one dot file
5836 then the preferred placement is in a subdirectory
5837 with a name starting with a '.' character, (a "dot
5838 directory"). In this case it is recommended the
5839 configuration files not start with the '.'
5845 The requirement for amd64 to use <file>/lib64</file>
5846 for 64 bit binaries is removed.
5851 The requirement for object files, internal binaries, and
5852 libraries, including <file>libc.so.*</file>, to be located
5853 directly under <file>/lib{,32}</file> and
5854 <file>/usr/lib{,32}</file> is amended, permitting files
5855 to instead be installed to
5856 <file>/lib/<var>triplet</var></file> and
5857 <file>/usr/lib/<var>triplet</var></file>, where
5858 <tt><var>triplet</var></tt> is the value returned by
5859 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5860 architecture of the package. Packages may <em>not</em>
5861 install files to any <var>triplet</var> path other
5862 than the one matching the architecture of that package;
5863 for instance, an <tt>Architecture: amd64</tt> package
5864 containing 32-bit x86 libraries may not install these
5865 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5867 This is necessary in order to reserve the directories for
5868 use in cross-installation of library packages from other
5869 architectures, as part of the planned deployment of
5874 Applications may also use a single subdirectory under
5875 <file>/usr/lib/<var>triplet</var></file>.
5878 The execution time linker/loader, ld*, must still be made
5879 available in the existing location under /lib or /lib64
5880 since this is part of the ELF ABI for the architecture.
5885 The requirement that
5886 <file>/usr/local/share/man</file> be "synonymous"
5887 with <file>/usr/local/man</file> is relaxed to a
5892 The requirement that windowmanagers with a single
5893 configuration file call it <file>system.*wmrc</file>
5894 is removed, as is the restriction that the window
5895 manager subdirectory be named identically to the
5896 window manager name itself.
5901 The requirement that boot manager configuration
5902 files live in <file>/etc</file>, or at least are
5903 symlinked there, is relaxed to a recommendation.
5908 The following directories in the root filesystem are
5909 additionally allowed: <file>/sys</file> and
5910 <file>/selinux</file>. <footnote>These directories
5911 are used as mount points to mount virtual filesystems
5912 to get access to kernel information.</footnote>
5919 The version of this document referred here can be
5920 found in the <tt>debian-policy</tt> package or on <url
5921 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5922 name="FHS (Debian copy)"> alongside this manual (or, if
5923 you have the <package>debian-policy</package> installed,
5925 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5926 (local copy)">). The
5927 latest version, which may be a more recent version, may
5929 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5930 Specific questions about following the standard may be
5931 asked on the <tt>debian-devel</tt> mailing list, or
5932 referred to the FHS mailing list (see the
5933 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5939 <heading>Site-specific programs</heading>
5942 As mandated by the FHS, packages must not place any
5943 files in <file>/usr/local</file>, either by putting them in
5944 the file system archive to be unpacked by <prgn>dpkg</prgn>
5945 or by manipulating them in their maintainer scripts.
5949 However, the package may create empty directories below
5950 <file>/usr/local</file> so that the system administrator knows
5951 where to place site-specific files. These are not
5952 directories <em>in</em> <file>/usr/local</file>, but are
5953 children of directories in <file>/usr/local</file>. These
5954 directories (<file>/usr/local/*/dir/</file>)
5955 should be removed on package removal if they are
5960 Note that this applies only to
5961 directories <em>below</em> <file>/usr/local</file>,
5962 not <em>in</em> <file>/usr/local</file>. Packages must
5963 not create sub-directories in the
5964 directory <file>/usr/local</file> itself, except those
5965 listed in FHS, section 4.5. However, you may create
5966 directories below them as you wish. You must not remove
5967 any of the directories listed in 4.5, even if you created
5972 Since <file>/usr/local</file> can be mounted read-only from a
5973 remote server, these directories must be created and
5974 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5975 maintainer scripts and not be included in the
5976 <file>.deb</file> archive. These scripts must not fail if
5977 either of these operations fail.
5981 For example, the <tt>emacsen-common</tt> package could
5982 contain something like
5983 <example compact="compact">
5984 if [ ! -e /usr/local/share/emacs ]
5986 if mkdir /usr/local/share/emacs 2>/dev/null
5988 chown root:staff /usr/local/share/emacs
5989 chmod 2775 /usr/local/share/emacs
5993 in its <prgn>postinst</prgn> script, and
5994 <example compact="compact">
5995 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5996 rmdir /usr/local/share/emacs 2>/dev/null || true
5998 in the <prgn>prerm</prgn> script. (Note that this form is
5999 used to ensure that if the script is interrupted, the
6000 directory <file>/usr/local/share/emacs</file> will still be
6005 If you do create a directory in <file>/usr/local</file> for
6006 local additions to a package, you should ensure that
6007 settings in <file>/usr/local</file> take precedence over the
6008 equivalents in <file>/usr</file>.
6012 However, because <file>/usr/local</file> and its contents are
6013 for exclusive use of the local administrator, a package
6014 must not rely on the presence or absence of files or
6015 directories in <file>/usr/local</file> for normal operation.
6019 The <file>/usr/local</file> directory itself and all the
6020 subdirectories created by the package should (by default) have
6021 permissions 2775 (group-writable and set-group-id) and be
6022 owned by <tt>root:staff</tt>.
6027 <heading>The system-wide mail directory</heading>
6029 The system-wide mail directory
6030 is <file>/var/mail</file>. This directory is part of the
6031 base system and should not be owned by any particular mail
6032 agents. The use of the old
6033 location <file>/var/spool/mail</file> is deprecated, even
6034 though the spool may still be physically located there.
6040 <heading>Users and groups</heading>
6043 <heading>Introduction</heading>
6045 The Debian system can be configured to use either plain or
6050 Some user ids (UIDs) and group ids (GIDs) are reserved
6051 globally for use by certain packages. Because some
6052 packages need to include files which are owned by these
6053 users or groups, or need the ids compiled into binaries,
6054 these ids must be used on any Debian system only for the
6055 purpose for which they are allocated. This is a serious
6056 restriction, and we should avoid getting in the way of
6057 local administration policies. In particular, many sites
6058 allocate users and/or local system groups starting at 100.
6062 Apart from this we should have dynamically allocated ids,
6063 which should by default be arranged in some sensible
6064 order, but the behavior should be configurable.
6068 Packages other than <tt>base-passwd</tt> must not modify
6069 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6070 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6075 <heading>UID and GID classes</heading>
6077 The UID and GID numbers are divided into classes as
6083 Globally allocated by the Debian project, the same
6084 on every Debian system. These ids will appear in
6085 the <file>passwd</file> and <file>group</file> files of all
6086 Debian systems, new ids in this range being added
6087 automatically as the <tt>base-passwd</tt> package is
6092 Packages which need a single statically allocated
6093 uid or gid should use one of these; their
6094 maintainers should ask the <tt>base-passwd</tt>
6102 Dynamically allocated system users and groups.
6103 Packages which need a user or group, but can have
6104 this user or group allocated dynamically and
6105 differently on each system, should use <tt>adduser
6106 --system</tt> to create the group and/or user.
6107 <prgn>adduser</prgn> will check for the existence of
6108 the user or group, and if necessary choose an unused
6109 id based on the ranges specified in
6110 <file>adduser.conf</file>.
6114 <tag>1000-59999:</tag>
6117 Dynamically allocated user accounts. By default
6118 <prgn>adduser</prgn> will choose UIDs and GIDs for
6119 user accounts in this range, though
6120 <file>adduser.conf</file> may be used to modify this
6125 <tag>60000-64999:</tag>
6128 Globally allocated by the Debian project, but only
6129 created on demand. The ids are allocated centrally
6130 and statically, but the actual accounts are only
6131 created on users' systems on demand.
6135 These ids are for packages which are obscure or
6136 which require many statically-allocated ids. These
6137 packages should check for and create the accounts in
6138 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6139 <prgn>adduser</prgn> if it has this facility) if
6140 necessary. Packages which are likely to require
6141 further allocations should have a "hole" left after
6142 them in the allocation, to give them room to
6147 <tag>65000-65533:</tag>
6155 User <tt>nobody</tt>. The corresponding gid refers
6156 to the group <tt>nogroup</tt>.
6163 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6164 not</em> be used, because it is the error return
6173 <sect id="sysvinit">
6174 <heading>System run levels and <file>init.d</file> scripts</heading>
6176 <sect1 id="/etc/init.d">
6177 <heading>Introduction</heading>
6180 The <file>/etc/init.d</file> directory contains the scripts
6181 executed by <prgn>init</prgn> at boot time and when the
6182 init state (or "runlevel") is changed (see <manref
6183 name="init" section="8">).
6187 There are at least two different, yet functionally
6188 equivalent, ways of handling these scripts. For the sake
6189 of simplicity, this document describes only the symbolic
6190 link method. However, it must not be assumed by maintainer
6191 scripts that this method is being used, and any automated
6192 manipulation of the various runlevel behaviors by
6193 maintainer scripts must be performed using
6194 <prgn>update-rc.d</prgn> as described below and not by
6195 manually installing or removing symlinks. For information
6196 on the implementation details of the other method,
6197 implemented in the <tt>file-rc</tt> package, please refer
6198 to the documentation of that package.
6202 These scripts are referenced by symbolic links in the
6203 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6204 runlevels, <prgn>init</prgn> looks in the directory
6205 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6206 execute, where <tt><var>n</var></tt> is the runlevel that
6207 is being changed to, or <tt>S</tt> for the boot-up
6212 The names of the links all have the form
6213 <file>S<var>mm</var><var>script</var></file> or
6214 <file>K<var>mm</var><var>script</var></file> where
6215 <var>mm</var> is a two-digit number and <var>script</var>
6216 is the name of the script (this should be the same as the
6217 name of the actual script in <file>/etc/init.d</file>).
6221 When <prgn>init</prgn> changes runlevel first the targets
6222 of the links whose names start with a <tt>K</tt> are
6223 executed, each with the single argument <tt>stop</tt>,
6224 followed by the scripts prefixed with an <tt>S</tt>, each
6225 with the single argument <tt>start</tt>. (The links are
6226 those in the <file>/etc/rc<var>n</var>.d</file> directory
6227 corresponding to the new runlevel.) The <tt>K</tt> links
6228 are responsible for killing services and the <tt>S</tt>
6229 link for starting services upon entering the runlevel.
6233 For example, if we are changing from runlevel 2 to
6234 runlevel 3, init will first execute all of the <tt>K</tt>
6235 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6236 all of the <tt>S</tt> prefixed scripts in that directory.
6237 The links starting with <tt>K</tt> will cause the
6238 referred-to file to be executed with an argument of
6239 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6244 The two-digit number <var>mm</var> is used to determine
6245 the order in which to run the scripts: low-numbered links
6246 have their scripts run first. For example, the
6247 <tt>K20</tt> scripts will be executed before the
6248 <tt>K30</tt> scripts. This is used when a certain service
6249 must be started before another. For example, the name
6250 server <prgn>bind</prgn> might need to be started before
6251 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6252 can set up its access lists. In this case, the script
6253 that starts <prgn>bind</prgn> would have a lower number
6254 than the script that starts <prgn>inn</prgn> so that it
6256 <example compact="compact">
6263 The two runlevels 0 (halt) and 6 (reboot) are slightly
6264 different. In these runlevels, the links with an
6265 <tt>S</tt> prefix are still called after those with a
6266 <tt>K</tt> prefix, but they too are called with the single
6267 argument <tt>stop</tt>.
6271 <sect1 id="writing-init">
6272 <heading>Writing the scripts</heading>
6275 Packages that include daemons for system services should
6276 place scripts in <file>/etc/init.d</file> to start or stop
6277 services at boot time or during a change of runlevel.
6278 These scripts should be named
6279 <file>/etc/init.d/<var>package</var></file>, and they should
6280 accept one argument, saying what to do:
6283 <tag><tt>start</tt></tag>
6284 <item>start the service,</item>
6286 <tag><tt>stop</tt></tag>
6287 <item>stop the service,</item>
6289 <tag><tt>restart</tt></tag>
6290 <item>stop and restart the service if it's already running,
6291 otherwise start the service</item>
6293 <tag><tt>reload</tt></tag>
6294 <item><p>cause the configuration of the service to be
6295 reloaded without actually stopping and restarting
6298 <tag><tt>force-reload</tt></tag>
6299 <item>cause the configuration to be reloaded if the
6300 service supports this, otherwise restart the
6304 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6305 <tt>force-reload</tt> options should be supported by all
6306 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6311 The <file>init.d</file> scripts must ensure that they will
6312 behave sensibly (i.e., returning success and not starting
6313 multiple copies of a service) if invoked with <tt>start</tt>
6314 when the service is already running, or with <tt>stop</tt>
6315 when it isn't, and that they don't kill unfortunately-named
6316 user processes. The best way to achieve this is usually to
6317 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6322 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6323 scripts. Writing correct <file>init.d</file> scripts requires
6324 accepting various error exit statuses when daemons are already
6325 running or already stopped without aborting
6326 the <file>init.d</file> script, and common <file>init.d</file>
6327 function libraries are not safe to call with <tt>set -e</tt>
6329 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6330 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6331 in effect and echoing status messages to the console fails,
6333 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6334 to not use <tt>set -e</tt> and instead check the result of
6335 each command separately.
6339 If a service reloads its configuration automatically (as
6340 in the case of <prgn>cron</prgn>, for example), the
6341 <tt>reload</tt> option of the <file>init.d</file> script
6342 should behave as if the configuration has been reloaded
6347 The <file>/etc/init.d</file> scripts must be treated as
6348 configuration files, either (if they are present in the
6349 package, that is, in the .deb file) by marking them as
6350 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6351 by managing them correctly in the maintainer scripts (see
6352 <ref id="config-files">). This is important since we want
6353 to give the local system administrator the chance to adapt
6354 the scripts to the local system, e.g., to disable a
6355 service without de-installing the package, or to specify
6356 some special command line options when starting a service,
6357 while making sure their changes aren't lost during the next
6362 These scripts should not fail obscurely when the
6363 configuration files remain but the package has been
6364 removed, as configuration files remain on the system after
6365 the package has been removed. Only when <prgn>dpkg</prgn>
6366 is executed with the <tt>--purge</tt> option will
6367 configuration files be removed. In particular, as the
6368 <file>/etc/init.d/<var>package</var></file> script itself is
6369 usually a <tt>conffile</tt>, it will remain on the system
6370 if the package is removed but not purged. Therefore, you
6371 should include a <tt>test</tt> statement at the top of the
6373 <example compact="compact">
6374 test -f <var>program-executed-later-in-script</var> || exit 0
6379 Often there are some variables in the <file>init.d</file>
6380 scripts whose values control the behavior of the scripts,
6381 and which a system administrator is likely to want to
6382 change. As the scripts themselves are frequently
6383 <tt>conffile</tt>s, modifying them requires that the
6384 administrator merge in their changes each time the package
6385 is upgraded and the <tt>conffile</tt> changes. To ease
6386 the burden on the system administrator, such configurable
6387 values should not be placed directly in the script.
6388 Instead, they should be placed in a file in
6389 <file>/etc/default</file>, which typically will have the same
6390 base name as the <file>init.d</file> script. This extra file
6391 should be sourced by the script when the script runs. It
6392 must contain only variable settings and comments in SUSv3
6393 <prgn>sh</prgn> format. It may either be a
6394 <tt>conffile</tt> or a configuration file maintained by
6395 the package maintainer scripts. See <ref id="config-files">
6400 To ensure that vital configurable values are always
6401 available, the <file>init.d</file> script should set default
6402 values for each of the shell variables it uses, either
6403 before sourcing the <file>/etc/default/</file> file or
6404 afterwards using something like the <tt>:
6405 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6406 script must behave sensibly and not fail if the
6407 <file>/etc/default</file> file is deleted.
6411 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6412 as temporary filesystems<footnote>
6413 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6414 options in <file>/etc/default/rcS</file>.
6415 </footnote>, so the <file>init.d</file> scripts must handle this
6416 correctly. This will typically amount to creating any required
6417 subdirectories dynamically when the <file>init.d</file> script
6418 is run, rather than including them in the package and relying on
6419 <prgn>dpkg</prgn> to create them.
6424 <heading>Interfacing with the initscript system</heading>
6427 Maintainers should use the abstraction layer provided by
6428 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6429 programs to deal with initscripts in their packages'
6430 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6431 and <prgn>postrm</prgn>.
6435 Directly managing the /etc/rc?.d links and directly
6436 invoking the <file>/etc/init.d/</file> initscripts should
6437 be done only by packages providing the initscript
6438 subsystem (such as <prgn>sysv-rc</prgn> and
6439 <prgn>file-rc</prgn>).
6443 <heading>Managing the links</heading>
6446 The program <prgn>update-rc.d</prgn> is provided for
6447 package maintainers to arrange for the proper creation and
6448 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6449 or their functional equivalent if another method is being
6450 used. This may be used by maintainers in their packages'
6451 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6455 You must not include any <file>/etc/rc<var>n</var>.d</file>
6456 symbolic links in the actual archive or manually create or
6457 remove the symbolic links in maintainer scripts; you must
6458 use the <prgn>update-rc.d</prgn> program instead. (The
6459 former will fail if an alternative method of maintaining
6460 runlevel information is being used.) You must not include
6461 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6462 in the archive either. (Only the <tt>sysvinit</tt>
6467 By default <prgn>update-rc.d</prgn> will start services in
6468 each of the multi-user state runlevels (2, 3, 4, and 5)
6469 and stop them in the halt runlevel (0), the single-user
6470 runlevel (1) and the reboot runlevel (6). The system
6471 administrator will have the opportunity to customize
6472 runlevels by simply adding, moving, or removing the
6473 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6474 symbolic links are being used, or by modifying
6475 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6480 To get the default behavior for your package, put in your
6481 <prgn>postinst</prgn> script
6482 <example compact="compact">
6483 update-rc.d <var>package</var> defaults
6485 and in your <prgn>postrm</prgn>
6486 <example compact="compact">
6487 if [ "$1" = purge ]; then
6488 update-rc.d <var>package</var> remove
6490 </example>. Note that if your package changes runlevels
6491 or priority, you may have to remove and recreate the links,
6492 since otherwise the old links may persist. Refer to the
6493 documentation of <prgn>update-rc.d</prgn>.
6497 This will use a default sequence number of 20. If it does
6498 not matter when or in which order the <file>init.d</file>
6499 script is run, use this default. If it does, then you
6500 should talk to the maintainer of the <prgn>sysvinit</prgn>
6501 package or post to <tt>debian-devel</tt>, and they will
6502 help you choose a number.
6506 For more information about using <tt>update-rc.d</tt>,
6507 please consult its man page <manref name="update-rc.d"
6513 <heading>Running initscripts</heading>
6515 The program <prgn>invoke-rc.d</prgn> is provided to make
6516 it easier for package maintainers to properly invoke an
6517 initscript, obeying runlevel and other locally-defined
6518 constraints that might limit a package's right to start,
6519 stop and otherwise manage services. This program may be
6520 used by maintainers in their packages' scripts.
6524 The package maintainer scripts must use
6525 <prgn>invoke-rc.d</prgn> to invoke the
6526 <file>/etc/init.d/*</file> initscripts, instead of
6527 calling them directly.
6531 By default, <prgn>invoke-rc.d</prgn> will pass any
6532 action requests (start, stop, reload, restart...) to the
6533 <file>/etc/init.d</file> script, filtering out requests
6534 to start or restart a service out of its intended
6539 Most packages will simply need to change:
6540 <example compact="compact">/etc/init.d/<package>
6541 <action></example> in their <prgn>postinst</prgn>
6542 and <prgn>prerm</prgn> scripts to:
6543 <example compact="compact">
6544 if which invoke-rc.d >/dev/null 2>&1; then
6545 invoke-rc.d <var>package</var> <action>
6547 /etc/init.d/<var>package</var> <action>
6553 A package should register its initscript services using
6554 <prgn>update-rc.d</prgn> before it tries to invoke them
6555 using <prgn>invoke-rc.d</prgn>. Invocation of
6556 unregistered services may fail.
6560 For more information about using
6561 <prgn>invoke-rc.d</prgn>, please consult its man page
6562 <manref name="invoke-rc.d" section="8">.
6568 <heading>Boot-time initialization</heading>
6571 There used to be another directory, <file>/etc/rc.boot</file>,
6572 which contained scripts which were run once per machine
6573 boot. This has been deprecated in favour of links from
6574 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6575 described in <ref id="/etc/init.d">. Packages must not
6576 place files in <file>/etc/rc.boot</file>.
6581 <heading>Example</heading>
6584 An example on which you can base your
6585 <file>/etc/init.d</file> scripts is found in
6586 <file>/etc/init.d/skeleton</file>.
6593 <heading>Console messages from <file>init.d</file> scripts</heading>
6596 This section describes the formats to be used for messages
6597 written to standard output by the <file>/etc/init.d</file>
6598 scripts. The intent is to improve the consistency of
6599 Debian's startup and shutdown look and feel. For this
6600 reason, please look very carefully at the details. We want
6601 the messages to have the same format in terms of wording,
6602 spaces, punctuation and case of letters.
6606 Here is a list of overall rules that should be used for
6607 messages generated by <file>/etc/init.d</file> scripts.
6613 The message should fit in one line (fewer than 80
6614 characters), start with a capital letter and end with
6615 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6619 If the script is performing some time consuming task in
6620 the background (not merely starting or stopping a
6621 program, for instance), an ellipsis (three dots:
6622 <tt>...</tt>) should be output to the screen, with no
6623 leading or tailing whitespace or line feeds.
6627 The messages should appear as if the computer is telling
6628 the user what it is doing (politely :-), but should not
6629 mention "it" directly. For example, instead of:
6630 <example compact="compact">
6631 I'm starting network daemons: nfsd mountd.
6633 the message should say
6634 <example compact="compact">
6635 Starting network daemons: nfsd mountd.
6642 <tt>init.d</tt> script should use the following standard
6643 message formats for the situations enumerated below.
6649 <p>When daemons are started</p>
6652 If the script starts one or more daemons, the output
6653 should look like this (a single line, no leading
6655 <example compact="compact">
6656 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6658 The <var>description</var> should describe the
6659 subsystem the daemon or set of daemons are part of,
6660 while <var>daemon-1</var> up to <var>daemon-n</var>
6661 denote each daemon's name (typically the file name of
6666 For example, the output of <file>/etc/init.d/lpd</file>
6668 <example compact="compact">
6669 Starting printer spooler: lpd.
6674 This can be achieved by saying
6675 <example compact="compact">
6676 echo -n "Starting printer spooler: lpd"
6677 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6680 in the script. If there are more than one daemon to
6681 start, the output should look like this:
6682 <example compact="compact">
6683 echo -n "Starting remote file system services:"
6684 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6685 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6686 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6689 This makes it possible for the user to see what is
6690 happening and when the final daemon has been started.
6691 Care should be taken in the placement of white spaces:
6692 in the example above the system administrators can
6693 easily comment out a line if they don't want to start
6694 a specific daemon, while the displayed message still
6700 <p>When a system parameter is being set</p>
6703 If you have to set up different system parameters
6704 during the system boot, you should use this format:
6705 <example compact="compact">
6706 Setting <var>parameter</var> to "<var>value</var>".
6711 You can use a statement such as the following to get
6713 <example compact="compact">
6714 echo "Setting DNS domainname to \"$domainname\"."
6719 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6720 for the left and right quotation marks. A grave accent
6721 (<tt>`</tt>) is not a quote character; neither is an
6722 apostrophe (<tt>'</tt>).
6727 <p>When a daemon is stopped or restarted</p>
6730 When you stop or restart a daemon, you should issue a
6731 message identical to the startup message, except that
6732 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6733 or <tt>Restarting</tt> respectively.
6737 For example, stopping the printer daemon will look like
6739 <example compact="compact">
6740 Stopping printer spooler: lpd.
6746 <p>When something is executed</p>
6749 There are several examples where you have to run a
6750 program at system startup or shutdown to perform a
6751 specific task, for example, setting the system's clock
6752 using <prgn>netdate</prgn> or killing all processes
6753 when the system shuts down. Your message should look
6755 <example compact="compact">
6756 Doing something very useful...done.
6758 You should print the <tt>done.</tt> immediately after
6759 the job has been completed, so that the user is
6760 informed why they have to wait. You can get this
6762 <example compact="compact">
6763 echo -n "Doing something very useful..."
6772 <p>When the configuration is reloaded</p>
6775 When a daemon is forced to reload its configuration
6776 files you should use the following format:
6777 <example compact="compact">
6778 Reloading <var>description</var> configuration...done.
6780 where <var>description</var> is the same as in the
6781 daemon starting message.
6789 <heading>Cron jobs</heading>
6792 Packages must not modify the configuration file
6793 <file>/etc/crontab</file>, and they must not modify the files in
6794 <file>/var/spool/cron/crontabs</file>.</p>
6797 If a package wants to install a job that has to be executed
6798 via cron, it should place a file with the name of the
6799 package in one or more of the following directories:
6800 <example compact="compact">
6806 As these directory names imply, the files within them are
6807 executed on an hourly, daily, weekly, or monthly basis,
6808 respectively. The exact times are listed in
6809 <file>/etc/crontab</file>.</p>
6812 All files installed in any of these directories must be
6813 scripts (e.g., shell scripts or Perl scripts) so that they
6814 can easily be modified by the local system administrator.
6815 In addition, they must be treated as configuration files.
6819 If a certain job has to be executed at some other frequency or
6820 at a specific time, the package should install a file
6821 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6822 same syntax as <file>/etc/crontab</file> and is processed by
6823 <prgn>cron</prgn> automatically. The file must also be
6824 treated as a configuration file. (Note that entries in the
6825 <file>/etc/cron.d</file> directory are not handled by
6826 <prgn>anacron</prgn>. Thus, you should only use this
6827 directory for jobs which may be skipped if the system is not
6830 Unlike <file>crontab</file> files described in the IEEE Std
6831 1003.1-2008 (POSIX.1) available from
6832 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6833 name="The Open Group">, the files in
6834 <file>/etc/cron.d</file> and the file
6835 <file>/etc/crontab</file> have seven fields; namely:
6837 <item>Minute [0,59]</item>
6838 <item>Hour [0,23]</item>
6839 <item>Day of the month [1,31]</item>
6840 <item>Month of the year [1,12]</item>
6841 <item>Day of the week ([0,6] with 0=Sunday)</item>
6842 <item>Username</item>
6843 <item>Command to be run</item>
6845 Ranges of numbers are allowed. Ranges are two numbers
6846 separated with a hyphen. The specified range is inclusive.
6847 Lists are allowed. A list is a set of numbers (or ranges)
6848 separated by commas. Step values can be used in conjunction
6853 The scripts or <tt>crontab</tt> entries in these directories should
6854 check if all necessary programs are installed before they
6855 try to execute them. Otherwise, problems will arise when a
6856 package was removed but not purged since configuration files
6857 are kept on the system in this situation.
6861 Any <tt>cron</tt> daemon must provide
6862 <file>/usr/bin/crontab</file> and support normal
6863 <tt>crontab</tt> entries as specified in POSIX. The daemon
6864 must also support names for days and months, ranges, and
6865 step values. It has to support <file>/etc/crontab</file>,
6866 and correctly execute the scripts in
6867 <file>/etc/cron.d</file>. The daemon must also correctly
6869 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6874 <heading>Menus</heading>
6877 The Debian <tt>menu</tt> package provides a standard
6878 interface between packages providing applications and
6879 <em>menu programs</em> (either X window managers or
6880 text-based menu programs such as <prgn>pdmenu</prgn>).
6884 All packages that provide applications that need not be
6885 passed any special command line arguments for normal
6886 operation should register a menu entry for those
6887 applications, so that users of the <tt>menu</tt> package
6888 will automatically get menu entries in their window
6889 managers, as well in shells like <tt>pdmenu</tt>.
6893 Menu entries should follow the current menu policy.
6897 The menu policy can be found in the <tt>menu-policy</tt>
6898 files in the <tt>debian-policy</tt> package.
6899 It is also available from the Debian web mirrors at
6900 <tt><url name="/doc/packaging-manuals/menu-policy/"
6901 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6905 Please also refer to the <em>Debian Menu System</em>
6906 documentation that comes with the <package>menu</package>
6907 package for information about how to register your
6913 <heading>Multimedia handlers</heading>
6916 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6917 is a mechanism for encoding files and data streams and
6918 providing meta-information about them, in particular their
6919 type (e.g. audio or video) and format (e.g. PNG, HTML,
6924 Registration of MIME type handlers allows programs like mail
6925 user agents and web browsers to invoke these handlers to
6926 view, edit or display MIME types they don't support directly.
6930 Packages which provide the ability to view/show/play,
6931 compose, edit or print MIME types should register themselves
6932 as such following the current MIME support policy.
6936 The MIME support policy can be found in the <tt>mime-policy</tt>
6937 files in the <tt>debian-policy</tt> package.
6938 It is also available from the Debian web mirrors at
6939 <tt><url name="/doc/packaging-manuals/mime-policy/"
6940 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6946 <heading>Keyboard configuration</heading>
6949 To achieve a consistent keyboard configuration so that all
6950 applications interpret a keyboard event the same way, all
6951 programs in the Debian distribution must be configured to
6952 comply with the following guidelines.
6956 The following keys must have the specified interpretations:
6959 <tag><tt><--</tt></tag>
6960 <item>delete the character to the left of the cursor</item>
6962 <tag><tt>Delete</tt></tag>
6963 <item>delete the character to the right of the cursor</item>
6965 <tag><tt>Control+H</tt></tag>
6966 <item>emacs: the help prefix</item>
6969 The interpretation of any keyboard events should be
6970 independent of the terminal that is used, be it a virtual
6971 console, an X terminal emulator, an rlogin/telnet session,
6976 The following list explains how the different programs
6977 should be set up to achieve this:
6983 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6987 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6991 X translations are set up to make
6992 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6993 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6994 is the vt220 escape code for the "delete character"
6995 key). This must be done by loading the X resources
6996 using <prgn>xrdb</prgn> on all local X displays, not
6997 using the application defaults, so that the
6998 translation resources used correspond to the
6999 <prgn>xmodmap</prgn> settings.
7003 The Linux console is configured to make
7004 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7005 generate <tt>ESC [ 3 ~</tt>.
7009 X applications are configured so that <tt><</tt>
7010 deletes left, and <tt>Delete</tt> deletes right. Motif
7011 applications already work like this.
7015 Terminals should have <tt>stty erase ^?</tt> .
7019 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7020 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7021 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7025 Emacs is programmed to map <tt>KB_Backspace</tt> or
7026 the <tt>stty erase</tt> character to
7027 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7028 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7029 <tt>^H</tt> to <tt>help</tt> as always.
7033 Other applications use the <tt>stty erase</tt>
7034 character and <tt>kdch1</tt> for the two delete keys,
7035 with ASCII DEL being "delete previous character" and
7036 <tt>kdch1</tt> being "delete character under
7044 This will solve the problem except for the following
7051 Some terminals have a <tt><--</tt> key that cannot
7052 be made to produce anything except <tt>^H</tt>. On
7053 these terminals Emacs help will be unavailable on
7054 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7055 character takes precedence in Emacs, and has been set
7056 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7057 available) can be used instead.
7061 Some operating systems use <tt>^H</tt> for <tt>stty
7062 erase</tt>. However, modern telnet versions and all
7063 rlogin versions propagate <tt>stty</tt> settings, and
7064 almost all UNIX versions honour <tt>stty erase</tt>.
7065 Where the <tt>stty</tt> settings are not propagated
7066 correctly, things can be made to work by using
7067 <tt>stty</tt> manually.
7071 Some systems (including previous Debian versions) use
7072 <prgn>xmodmap</prgn> to arrange for both
7073 <tt><--</tt> and <tt>Delete</tt> to generate
7074 <tt>KB_Delete</tt>. We can change the behavior of
7075 their X clients using the same X resources that we use
7076 to do it for our own clients, or configure our clients
7077 using their resources when things are the other way
7078 around. On displays configured like this
7079 <tt>Delete</tt> will not work, but <tt><--</tt>
7084 Some operating systems have different <tt>kdch1</tt>
7085 settings in their <tt>terminfo</tt> database for
7086 <tt>xterm</tt> and others. On these systems the
7087 <tt>Delete</tt> key will not work correctly when you
7088 log in from a system conforming to our policy, but
7089 <tt><--</tt> will.
7096 <heading>Environment variables</heading>
7099 A program must not depend on environment variables to get
7100 reasonable defaults. (That's because these environment
7101 variables would have to be set in a system-wide
7102 configuration file like <file>/etc/profile</file>, which is not
7103 supported by all shells.)
7107 If a program usually depends on environment variables for its
7108 configuration, the program should be changed to fall back to
7109 a reasonable default configuration if these environment
7110 variables are not present. If this cannot be done easily
7111 (e.g., if the source code of a non-free program is not
7112 available), the program must be replaced by a small
7113 "wrapper" shell script which sets the environment variables
7114 if they are not already defined, and calls the original program.
7118 Here is an example of a wrapper script for this purpose:
7120 <example compact="compact">
7122 BAR=${BAR:-/var/lib/fubar}
7124 exec /usr/lib/foo/foo "$@"
7129 Furthermore, as <file>/etc/profile</file> is a configuration
7130 file of the <prgn>base-files</prgn> package, other packages must
7131 not put any environment variables or other commands into that
7136 <sect id="doc-base">
7137 <heading>Registering Documents using doc-base</heading>
7140 The <package>doc-base</package> package implements a
7141 flexible mechanism for handling and presenting
7142 documentation. The recommended practice is for every Debian
7143 package that provides online documentation (other than just
7144 manual pages) to register these documents with
7145 <package>doc-base</package> by installing a
7146 <package>doc-base</package> control file via the
7147 <prgn/install-docs/ script at installation time and
7148 de-register the manuals again when the package is removed.
7151 Please refer to the documentation that comes with the
7152 <package>doc-base</package> package for information and
7161 <heading>Files</heading>
7163 <sect id="binaries">
7164 <heading>Binaries</heading>
7167 Two different packages must not install programs with
7168 different functionality but with the same filenames. (The
7169 case of two programs having the same functionality but
7170 different implementations is handled via "alternatives" or
7171 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7172 <ref id="conflicts"> respectively.) If this case happens,
7173 one of the programs must be renamed. The maintainers should
7174 report this to the <tt>debian-devel</tt> mailing list and
7175 try to find a consensus about which program will have to be
7176 renamed. If a consensus cannot be reached, <em>both</em>
7177 programs must be renamed.
7181 By default, when a package is being built, any binaries
7182 created should include debugging information, as well as
7183 being compiled with optimization. You should also turn on
7184 as many reasonable compilation warnings as possible; this
7185 makes life easier for porters, who can then look at build
7186 logs for possible problems. For the C programming language,
7187 this means the following compilation parameters should be
7189 <example compact="compact">
7191 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7193 INSTALL = install -s # (or use strip on the files in debian/tmp)
7198 Note that by default all installed binaries should be stripped,
7199 either by using the <tt>-s</tt> flag to
7200 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7201 the binaries after they have been copied into
7202 <file>debian/tmp</file> but before the tree is made into a
7207 Although binaries in the build tree should be compiled with
7208 debugging information by default, it can often be difficult to
7209 debug programs if they are also subjected to compiler
7210 optimization. For this reason, it is recommended to support the
7211 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7212 (see <ref id="debianrules-options">). This variable can contain
7213 several flags to change how a package is compiled and built.
7217 It is up to the package maintainer to decide what
7218 compilation options are best for the package. Certain
7219 binaries (such as computationally-intensive programs) will
7220 function better with certain flags (<tt>-O3</tt>, for
7221 example); feel free to use them. Please use good judgment
7222 here. Don't use flags for the sake of it; only use them
7223 if there is good reason to do so. Feel free to override
7224 the upstream author's ideas about which compilation
7225 options are best: they are often inappropriate for our
7231 <sect id="libraries">
7232 <heading>Libraries</heading>
7235 If the package is <strong>architecture: any</strong>, then
7236 the shared library compilation and linking flags must have
7237 <tt>-fPIC</tt>, or the package shall not build on some of
7238 the supported architectures<footnote>
7240 If you are using GCC, <tt>-fPIC</tt> produces code with
7241 relocatable position independent code, which is required for
7242 most architectures to create a shared library, with i386 and
7243 perhaps some others where non position independent code is
7244 permitted in a shared library.
7247 Position independent code may have a performance penalty,
7248 especially on <tt>i386</tt>. However, in most cases the
7249 speed penalty must be measured against the memory wasted on
7250 the few architectures where non position independent code is
7253 </footnote>. Any exception to this rule must be discussed on
7254 the mailing list <em>debian-devel@lists.debian.org</em>, and
7255 a rough consensus obtained. The reasons for not compiling
7256 with <tt>-fPIC</tt> flag must be recorded in the file
7257 <tt>README.Debian</tt>, and care must be taken to either
7258 restrict the architecture or arrange for <tt>-fPIC</tt> to
7259 be used on architectures where it is required.<footnote>
7261 Some of the reasons why this might be required is if the
7262 library contains hand crafted assembly code that is not
7263 relocatable, the speed penalty is excessive for compute
7264 intensive libs, and similar reasons.
7269 As to the static libraries, the common case is not to have
7270 relocatable code, since there is no benefit, unless in specific
7271 cases; therefore the static version must not be compiled
7272 with the <tt>-fPIC</tt> flag. Any exception to this rule
7273 should be discussed on the mailing list
7274 <em>debian-devel@lists.debian.org</em>, and the reasons for
7275 compiling with the <tt>-fPIC</tt> flag must be recorded in
7276 the file <tt>README.Debian</tt>. <footnote>
7278 Some of the reasons for linking static libraries with
7279 the <tt>-fPIC</tt> flag are if, for example, one needs a
7280 Perl API for a library that is under rapid development,
7281 and has an unstable API, so shared libraries are
7282 pointless at this phase of the library's development. In
7283 that case, since Perl needs a library with relocatable
7284 code, it may make sense to create a static library with
7285 relocatable code. Another reason cited is if you are
7286 distilling various libraries into a common shared
7287 library, like <tt>mklibs</tt> does in the Debian
7293 In other words, if both a shared and a static library is
7294 being built, each source unit (<tt>*.c</tt>, for example,
7295 for C files) will need to be compiled twice, for the normal
7299 You must specify the gcc option <tt>-D_REENTRANT</tt>
7300 when building a library (either static or shared) to make
7301 the library compatible with LinuxThreads.
7305 Although not enforced by the build tools, shared libraries
7306 must be linked against all libraries that they use symbols from
7307 in the same way that binaries are. This ensures the correct
7308 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7309 system and guarantees that all libraries can be safely opened
7310 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7311 option <tt>-Wl,-z,defs</tt> when building a shared library.
7312 Since this option enforces symbol resolution at build time,
7313 a missing library reference will be caught early as a fatal
7318 All installed shared libraries should be stripped with
7319 <example compact="compact">
7320 strip --strip-unneeded <var>your-lib</var>
7322 (The option <tt>--strip-unneeded</tt> makes
7323 <prgn>strip</prgn> remove only the symbols which aren't
7324 needed for relocation processing.) Shared libraries can
7325 function perfectly well when stripped, since the symbols for
7326 dynamic linking are in a separate part of the ELF object
7328 You might also want to use the options
7329 <tt>--remove-section=.comment</tt> and
7330 <tt>--remove-section=.note</tt> on both shared libraries
7331 and executables, and <tt>--strip-debug</tt> on static
7337 Note that under some circumstances it may be useful to
7338 install a shared library unstripped, for example when
7339 building a separate package to support debugging.
7343 Shared object files (often <file>.so</file> files) that are not
7344 public libraries, that is, they are not meant to be linked
7345 to by third party executables (binaries of other packages),
7346 should be installed in subdirectories of the
7347 <file>/usr/lib</file> directory. Such files are exempt from the
7348 rules that govern ordinary shared libraries, except that
7349 they must not be installed executable and should be
7351 A common example are the so-called "plug-ins",
7352 internal shared objects that are dynamically loaded by
7353 programs using <manref name="dlopen" section="3">.
7358 Packages that use <prgn>libtool</prgn> to create and install
7359 their shared libraries install a file containing additional
7360 metadata (ending in <file>.la</file>) alongside the library.
7361 For public libraries intended for use by other packages, these
7362 files normally should not be included in the Debian package,
7363 since the information they include is not necessary to link with
7364 the shared library on Debian and can add unnecessary additional
7365 dependencies to other programs or libraries.<footnote>
7366 These files store, among other things, all libraries on which
7367 that shared library depends. Unfortunately, if
7368 the <file>.la</file> file is present and contains that
7369 dependency information, using <prgn>libtool</prgn> when
7370 linking against that library will cause the resulting program
7371 or library to be linked against those dependencies as well,
7372 even if this is unnecessary. This can create unneeded
7373 dependencies on shared library packages that would otherwise
7374 be hidden behind the library ABI, and can make library
7375 transitions to new SONAMEs unnecessarily complicated and
7376 difficult to manage.
7378 If the <file>.la</file> file is required for that library (if,
7379 for instance, it's loaded via <tt>libltdl</tt> in a way that
7380 requires that meta-information), the <tt>dependency_libs</tt>
7381 setting in the <file>.la</file> file should normally be set to
7382 the empty string. If the shared library development package has
7383 historically included the <file>.la</file>, it must be retained
7384 in the development package (with <tt>dependency_libs</tt>
7385 emptied) until all libraries that depend on it have removed or
7386 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7387 files to prevent linking with those other libraries
7388 using <prgn>libtool</prgn> from failing.
7392 If the <file>.la</file> must be included, it should be included
7393 in the development (<tt>-dev</tt>) package, unless the library
7394 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7395 library. If it is intended for use with <tt>libltdl</tt>,
7396 the <file>.la</file> files must go in the run-time library
7401 These requirements for handling of <file>.la</file> files do not
7402 apply to loadable modules or libraries not installed in
7403 directories searched by default by the dynamic linker. Packages
7404 installing loadable modules will frequently need to install
7405 the <file>.la</file> files alongside the modules so that they
7406 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7407 does not need to be modified for libraries or modules that are
7408 not installed in directories searched by the dynamic linker by
7409 default and not intended for use by other packages.
7413 You must make sure that you use only released versions of
7414 shared libraries to build your packages; otherwise other
7415 users will not be able to run your binaries
7416 properly. Producing source packages that depend on
7417 unreleased compilers is also usually a bad
7424 <heading>Shared libraries</heading>
7426 This section has moved to <ref id="sharedlibs">.
7432 <heading>Scripts</heading>
7435 All command scripts, including the package maintainer
7436 scripts inside the package and used by <prgn>dpkg</prgn>,
7437 should have a <tt>#!</tt> line naming the shell to be used
7442 In the case of Perl scripts this should be
7443 <tt>#!/usr/bin/perl</tt>.
7447 When scripts are installed into a directory in the system
7448 PATH, the script name should not include an extension such
7449 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7450 language currently used to implement it.
7453 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7454 <file>init.d</file> scripts should almost certainly start
7455 with <tt>set -e</tt> so that errors are detected.
7456 <file>init.d</file> scripts are something of a special case, due
7457 to how frequently they need to call commands that are allowed to
7458 fail, and it may instead be easier to check the exit status of
7459 commands directly. See <ref id="writing-init"> for more
7460 information about writing <file>init.d</file> scripts.
7463 Every script should use <tt>set -e</tt> or check the exit status
7464 of <em>every</em> command.
7467 Scripts may assume that <file>/bin/sh</file> implements the
7468 SUSv3 Shell Command Language<footnote>
7469 Single UNIX Specification, version 3, which is also IEEE
7470 1003.1-2004 (POSIX), and is available on the World Wide Web
7471 from <url id="http://www.unix.org/version3/online.html"
7472 name="The Open Group"> after free
7473 registration.</footnote>
7474 plus the following additional features not mandated by
7476 These features are in widespread use in the Linux community
7477 and are implemented in all of bash, dash, and ksh, the most
7478 common shells users may wish to use as <file>/bin/sh</file>.
7481 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7482 must not generate a newline.</item>
7483 <item><tt>test</tt>, if implemented as a shell built-in, must
7484 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7486 <item><tt>local</tt> to create a scoped variable must be
7487 supported, including listing multiple variables in a single
7488 local command and assigning a value to a variable at the
7489 same time as localizing it. <tt>local</tt> may or
7490 may not preserve the variable value from an outer scope if
7491 no assignment is present. Uses such as:
7495 # ... use a, b, c, d ...
7498 must be supported and must set the value of <tt>c</tt> to
7502 If a shell script requires non-SUSv3 features from the shell
7503 interpreter other than those listed above, the appropriate shell
7504 must be specified in the first line of the script (e.g.,
7505 <tt>#!/bin/bash</tt>) and the package must depend on the package
7506 providing the shell (unless the shell package is marked
7507 "Essential", as in the case of <prgn>bash</prgn>).
7511 You may wish to restrict your script to SUSv3 features plus the
7512 above set when possible so that it may use <file>/bin/sh</file>
7513 as its interpreter. If your script works with <prgn>dash</prgn>
7514 (originally called <prgn>ash</prgn>), it probably complies with
7515 the above requirements, but if you are in doubt, use
7516 <file>/bin/bash</file>.
7520 Perl scripts should check for errors when making any
7521 system calls, including <tt>open</tt>, <tt>print</tt>,
7522 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7526 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7527 scripting languages. See <em>Csh Programming Considered
7528 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7529 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7530 If an upstream package comes with <prgn>csh</prgn> scripts
7531 then you must make sure that they start with
7532 <tt>#!/bin/csh</tt> and make your package depend on the
7533 <prgn>c-shell</prgn> virtual package.
7537 Any scripts which create files in world-writeable
7538 directories (e.g., in <file>/tmp</file>) must use a
7539 mechanism which will fail atomically if a file with the same
7540 name already exists.
7544 The Debian base system provides the <prgn>tempfile</prgn>
7545 and <prgn>mktemp</prgn> utilities for use by scripts for
7552 <heading>Symbolic links</heading>
7555 In general, symbolic links within a top-level directory
7556 should be relative, and symbolic links pointing from one
7557 top-level directory into another should be absolute. (A
7558 top-level directory is a sub-directory of the root
7559 directory <file>/</file>.)
7563 In addition, symbolic links should be specified as short as
7564 possible, i.e., link targets like <file>foo/../bar</file> are
7569 Note that when creating a relative link using
7570 <prgn>ln</prgn> it is not necessary for the target of the
7571 link to exist relative to the working directory you're
7572 running <prgn>ln</prgn> from, nor is it necessary to change
7573 directory to the directory where the link is to be made.
7574 Simply include the string that should appear as the target
7575 of the link (this will be a pathname relative to the
7576 directory in which the link resides) as the first argument
7581 For example, in your <prgn>Makefile</prgn> or
7582 <file>debian/rules</file>, you can do things like:
7583 <example compact="compact">
7584 ln -fs gcc $(prefix)/bin/cc
7585 ln -fs gcc debian/tmp/usr/bin/cc
7586 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7587 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7592 A symbolic link pointing to a compressed file should always
7593 have the same file extension as the referenced file. (For
7594 example, if a file <file>foo.gz</file> is referenced by a
7595 symbolic link, the filename of the link has to end with
7596 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7601 <heading>Device files</heading>
7604 Packages must not include device files or named pipes in the
7609 If a package needs any special device files that are not
7610 included in the base system, it must call
7611 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7612 after notifying the user<footnote>
7613 This notification could be done via a (low-priority)
7614 debconf message, or an echo (printf) statement.
7619 Packages must not remove any device files in the
7620 <prgn>postrm</prgn> or any other script. This is left to the
7621 system administrator.
7625 Debian uses the serial devices
7626 <file>/dev/ttyS*</file>. Programs using the old
7627 <file>/dev/cu*</file> devices should be changed to use
7628 <file>/dev/ttyS*</file>.
7632 Named pipes needed by the package must be created in
7633 the <prgn>postinst</prgn> script<footnote>
7634 It's better to use <prgn>mkfifo</prgn> rather
7635 than <prgn>mknod</prgn> to create named pipes so that
7636 automated checks for packages incorrectly creating device
7637 files with <prgn>mknod</prgn> won't have false positives.
7638 </footnote> and removed in
7639 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7644 <sect id="config-files">
7645 <heading>Configuration files</heading>
7648 <heading>Definitions</heading>
7652 <tag>configuration file</tag>
7654 A file that affects the operation of a program, or
7655 provides site- or host-specific information, or
7656 otherwise customizes the behavior of a program.
7657 Typically, configuration files are intended to be
7658 modified by the system administrator (if needed or
7659 desired) to conform to local policy or to provide
7660 more useful site-specific behavior.
7663 <tag><tt>conffile</tt></tag>
7665 A file listed in a package's <tt>conffiles</tt>
7666 file, and is treated specially by <prgn>dpkg</prgn>
7667 (see <ref id="configdetails">).
7673 The distinction between these two is important; they are
7674 not interchangeable concepts. Almost all
7675 <tt>conffile</tt>s are configuration files, but many
7676 configuration files are not <tt>conffiles</tt>.
7680 As noted elsewhere, <file>/etc/init.d</file> scripts,
7681 <file>/etc/default</file> files, scripts installed in
7682 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7683 configuration installed in <file>/etc/cron.d</file> must be
7684 treated as configuration files. In general, any script that
7685 embeds configuration information is de-facto a configuration
7686 file and should be treated as such.
7691 <heading>Location</heading>
7694 Any configuration files created or used by your package
7695 must reside in <file>/etc</file>. If there are several,
7696 consider creating a subdirectory of <file>/etc</file>
7697 named after your package.
7701 If your package creates or uses configuration files
7702 outside of <file>/etc</file>, and it is not feasible to modify
7703 the package to use <file>/etc</file> directly, put the files
7704 in <file>/etc</file> and create symbolic links to those files
7705 from the location that the package requires.
7710 <heading>Behavior</heading>
7713 Configuration file handling must conform to the following
7715 <list compact="compact">
7717 local changes must be preserved during a package
7721 configuration files must be preserved when the
7722 package is removed, and only deleted when the
7726 Obsolete configuration files without local changes may be
7727 removed by the package during upgrade.
7731 The easy way to achieve this behavior is to make the
7732 configuration file a <tt>conffile</tt>. This is
7733 appropriate only if it is possible to distribute a default
7734 version that will work for most installations, although
7735 some system administrators may choose to modify it. This
7736 implies that the default version will be part of the
7737 package distribution, and must not be modified by the
7738 maintainer scripts during installation (or at any other
7743 In order to ensure that local changes are preserved
7744 correctly, no package may contain or make hard links to
7745 conffiles.<footnote>
7746 Rationale: There are two problems with hard links.
7747 The first is that some editors break the link while
7748 editing one of the files, so that the two files may
7749 unwittingly become unlinked and different. The second
7750 is that <prgn>dpkg</prgn> might break the hard link
7751 while upgrading <tt>conffile</tt>s.
7756 The other way to do it is via the maintainer scripts. In
7757 this case, the configuration file must not be listed as a
7758 <tt>conffile</tt> and must not be part of the package
7759 distribution. If the existence of a file is required for
7760 the package to be sensibly configured it is the
7761 responsibility of the package maintainer to provide
7762 maintainer scripts which correctly create, update and
7763 maintain the file and remove it on purge. (See <ref
7764 id="maintainerscripts"> for more information.) These
7765 scripts must be idempotent (i.e., must work correctly if
7766 <prgn>dpkg</prgn> needs to re-run them due to errors
7767 during installation or removal), must cope with all the
7768 variety of ways <prgn>dpkg</prgn> can call maintainer
7769 scripts, must not overwrite or otherwise mangle the user's
7770 configuration without asking, must not ask unnecessary
7771 questions (particularly during upgrades), and must
7772 otherwise be good citizens.
7776 The scripts are not required to configure every possible
7777 option for the package, but only those necessary to get
7778 the package running on a given system. Ideally the
7779 sysadmin should not have to do any configuration other
7780 than that done (semi-)automatically by the
7781 <prgn>postinst</prgn> script.
7785 A common practice is to create a script called
7786 <file><var>package</var>-configure</file> and have the
7787 package's <prgn>postinst</prgn> call it if and only if the
7788 configuration file does not already exist. In certain
7789 cases it is useful for there to be an example or template
7790 file which the maintainer scripts use. Such files should
7791 be in <file>/usr/share/<var>package</var></file> or
7792 <file>/usr/lib/<var>package</var></file> (depending on whether
7793 they are architecture-independent or not). There should
7794 be symbolic links to them from
7795 <file>/usr/share/doc/<var>package</var>/examples</file> if
7796 they are examples, and should be perfectly ordinary
7797 <prgn>dpkg</prgn>-handled files (<em>not</em>
7798 configuration files).
7802 These two styles of configuration file handling must
7803 not be mixed, for that way lies madness:
7804 <prgn>dpkg</prgn> will ask about overwriting the file
7805 every time the package is upgraded.
7810 <heading>Sharing configuration files</heading>
7813 Packages which specify the same file as a
7814 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7815 with each other. (This is an instance of the general rule
7816 about not sharing files. Note that neither alternatives
7817 nor diversions are likely to be appropriate in this case;
7818 in particular, <prgn>dpkg</prgn> does not handle diverted
7819 <tt>conffile</tt>s well.)
7823 The maintainer scripts must not alter a <tt>conffile</tt>
7824 of <em>any</em> package, including the one the scripts
7829 If two or more packages use the same configuration file
7830 and it is reasonable for both to be installed at the same
7831 time, one of these packages must be defined as
7832 <em>owner</em> of the configuration file, i.e., it will be
7833 the package which handles that file as a configuration
7834 file. Other packages that use the configuration file must
7835 depend on the owning package if they require the
7836 configuration file to operate. If the other package will
7837 use the configuration file if present, but is capable of
7838 operating without it, no dependency need be declared.
7842 If it is desirable for two or more related packages to
7843 share a configuration file <em>and</em> for all of the
7844 related packages to be able to modify that configuration
7845 file, then the following should be done:
7846 <enumlist compact="compact">
7848 One of the related packages (the "owning" package)
7849 will manage the configuration file with maintainer
7850 scripts as described in the previous section.
7853 The owning package should also provide a program
7854 that the other packages may use to modify the
7858 The related packages must use the provided program
7859 to make any desired modifications to the
7860 configuration file. They should either depend on
7861 the core package to guarantee that the configuration
7862 modifier program is available or accept gracefully
7863 that they cannot modify the configuration file if it
7864 is not. (This is in addition to the fact that the
7865 configuration file may not even be present in the
7872 Sometimes it's appropriate to create a new package which
7873 provides the basic infrastructure for the other packages
7874 and which manages the shared configuration files. (The
7875 <tt>sgml-base</tt> package is a good example.)
7880 <heading>User configuration files ("dotfiles")</heading>
7883 The files in <file>/etc/skel</file> will automatically be
7884 copied into new user accounts by <prgn>adduser</prgn>.
7885 No other program should reference the files in
7886 <file>/etc/skel</file>.
7890 Therefore, if a program needs a dotfile to exist in
7891 advance in <file>$HOME</file> to work sensibly, that dotfile
7892 should be installed in <file>/etc/skel</file> and treated as a
7897 However, programs that require dotfiles in order to
7898 operate sensibly are a bad thing, unless they do create
7899 the dotfiles themselves automatically.
7903 Furthermore, programs should be configured by the Debian
7904 default installation to behave as closely to the upstream
7905 default behavior as possible.
7909 Therefore, if a program in a Debian package needs to be
7910 configured in some way in order to operate sensibly, that
7911 should be done using a site-wide configuration file placed
7912 in <file>/etc</file>. Only if the program doesn't support a
7913 site-wide default configuration and the package maintainer
7914 doesn't have time to add it may a default per-user file be
7915 placed in <file>/etc/skel</file>.
7919 <file>/etc/skel</file> should be as empty as we can make it.
7920 This is particularly true because there is no easy (or
7921 necessarily desirable) mechanism for ensuring that the
7922 appropriate dotfiles are copied into the accounts of
7923 existing users when a package is installed.
7929 <heading>Log files</heading>
7931 Log files should usually be named
7932 <file>/var/log/<var>package</var>.log</file>. If you have many
7933 log files, or need a separate directory for permission
7934 reasons (<file>/var/log</file> is writable only by
7935 <file>root</file>), you should usually create a directory named
7936 <file>/var/log/<var>package</var></file> and place your log
7941 Log files must be rotated occasionally so that they don't
7942 grow indefinitely; the best way to do this is to drop a log
7943 rotation configuration file into the directory
7944 <file>/etc/logrotate.d</file> and use the facilities provided by
7945 logrotate.<footnote>
7947 The traditional approach to log files has been to set up
7948 <em>ad hoc</em> log rotation schemes using simple shell
7949 scripts and cron. While this approach is highly
7950 customizable, it requires quite a lot of sysadmin work.
7951 Even though the original Debian system helped a little
7952 by automatically installing a system which can be used
7953 as a template, this was deemed not enough.
7957 The use of <prgn>logrotate</prgn>, a program developed
7958 by Red Hat, is better, as it centralizes log management.
7959 It has both a configuration file
7960 (<file>/etc/logrotate.conf</file>) and a directory where
7961 packages can drop their individual log rotation
7962 configurations (<file>/etc/logrotate.d</file>).
7965 Here is a good example for a logrotate config
7966 file (for more information see <manref name="logrotate"
7968 <example compact="compact">
7969 /var/log/foo/*.log {
7974 /etc/init.d/foo force-reload
7978 This rotates all files under <file>/var/log/foo</file>, saves 12
7979 compressed generations, and forces the daemon to reload its
7980 configuration information after the log rotation.
7984 Log files should be removed when the package is
7985 purged (but not when it is only removed). This should be
7986 done by the <prgn>postrm</prgn> script when it is called
7987 with the argument <tt>purge</tt> (see <ref
7988 id="removedetails">).
7993 <heading>Permissions and owners</heading>
7996 The rules in this section are guidelines for general use.
7997 If necessary you may deviate from the details below.
7998 However, if you do so you must make sure that what is done
7999 is secure and you should try to be as consistent as possible
8000 with the rest of the system. You should probably also
8001 discuss it on <prgn>debian-devel</prgn> first.
8005 Files should be owned by <tt>root:root</tt>, and made
8006 writable only by the owner and universally readable (and
8007 executable, if appropriate), that is mode 644 or 755.
8011 Directories should be mode 755 or (for group-writability)
8012 mode 2775. The ownership of the directory should be
8013 consistent with its mode: if a directory is mode 2775, it
8014 should be owned by the group that needs write access to
8017 When a package is upgraded, and the owner or permissions
8018 of a file included in the package has changed, dpkg
8019 arranges for the ownership and permissions to be
8020 correctly set upon installation. However, this does not
8021 extend to directories; the permissions and ownership of
8022 directories already on the system does not change on
8023 install or upgrade of packages. This makes sense, since
8024 otherwise common directories like <tt>/usr</tt> would
8025 always be in flux. To correctly change permissions of a
8026 directory the package owns, explicit action is required,
8027 usually in the <tt>postinst</tt> script. Care must be
8028 taken to handle downgrades as well, in that case.
8035 Setuid and setgid executables should be mode 4755 or 2755
8036 respectively, and owned by the appropriate user or group.
8037 They should not be made unreadable (modes like 4711 or
8038 2711 or even 4111); doing so achieves no extra security,
8039 because anyone can find the binary in the freely available
8040 Debian package; it is merely inconvenient. For the same
8041 reason you should not restrict read or execute permissions
8042 on non-set-id executables.
8046 Some setuid programs need to be restricted to particular
8047 sets of users, using file permissions. In this case they
8048 should be owned by the uid to which they are set-id, and by
8049 the group which should be allowed to execute them. They
8050 should have mode 4754; again there is no point in making
8051 them unreadable to those users who must not be allowed to
8056 It is possible to arrange that the system administrator can
8057 reconfigure the package to correspond to their local
8058 security policy by changing the permissions on a binary:
8059 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8060 described below.<footnote>
8061 Ordinary files installed by <prgn>dpkg</prgn> (as
8062 opposed to <tt>conffile</tt>s and other similar objects)
8063 normally have their permissions reset to the distributed
8064 permissions when the package is reinstalled. However,
8065 the use of <prgn>dpkg-statoverride</prgn> overrides this
8068 Another method you should consider is to create a group for
8069 people allowed to use the program(s) and make any setuid
8070 executables executable only by that group.
8074 If you need to create a new user or group for your package
8075 there are two possibilities. Firstly, you may need to
8076 make some files in the binary package be owned by this
8077 user or group, or you may need to compile the user or
8078 group id (rather than just the name) into the binary
8079 (though this latter should be avoided if possible, as in
8080 this case you need a statically allocated id).</p>
8083 If you need a statically allocated id, you must ask for a
8084 user or group id from the <tt>base-passwd</tt> maintainer,
8085 and must not release the package until you have been
8086 allocated one. Once you have been allocated one you must
8087 either make the package depend on a version of the
8088 <tt>base-passwd</tt> package with the id present in
8089 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8090 your package to create the user or group itself with the
8091 correct id (using <tt>adduser</tt>) in its
8092 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8093 the <prgn>postinst</prgn> is to be preferred if it is
8094 possible, otherwise a pre-dependency will be needed on the
8095 <tt>adduser</tt> package.)
8099 On the other hand, the program might be able to determine
8100 the uid or gid from the user or group name at runtime, so
8101 that a dynamically allocated id can be used. In this case
8102 you should choose an appropriate user or group name,
8103 discussing this on <prgn>debian-devel</prgn> and checking
8104 with the <package/base-passwd/ maintainer that it is unique and that
8105 they do not wish you to use a statically allocated id
8106 instead. When this has been checked you must arrange for
8107 your package to create the user or group if necessary using
8108 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8109 <prgn>postinst</prgn> script (again, the latter is to be
8110 preferred if it is possible).
8114 Note that changing the numeric value of an id associated
8115 with a name is very difficult, and involves searching the
8116 file system for all appropriate files. You need to think
8117 carefully whether a static or dynamic id is required, since
8118 changing your mind later will cause problems.
8121 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8123 This section is not intended as policy, but as a
8124 description of the use of <prgn>dpkg-statoverride</prgn>.
8128 If a system administrator wishes to have a file (or
8129 directory or other such thing) installed with owner and
8130 permissions different from those in the distributed Debian
8131 package, they can use the <prgn>dpkg-statoverride</prgn>
8132 program to instruct <prgn>dpkg</prgn> to use the different
8133 settings every time the file is installed. Thus the
8134 package maintainer should distribute the files with their
8135 normal permissions, and leave it for the system
8136 administrator to make any desired changes. For example, a
8137 daemon which is normally required to be setuid root, but
8138 in certain situations could be used without being setuid,
8139 should be installed setuid in the <tt>.deb</tt>. Then the
8140 local system administrator can change this if they wish.
8141 If there are two standard ways of doing it, the package
8142 maintainer can use <tt>debconf</tt> to find out the
8143 preference, and call <prgn>dpkg-statoverride</prgn> in the
8144 maintainer script if necessary to accommodate the system
8145 administrator's choice. Care must be taken during
8146 upgrades to not override an existing setting.
8150 Given the above, <prgn>dpkg-statoverride</prgn> is
8151 essentially a tool for system administrators and would not
8152 normally be needed in the maintainer scripts. There is
8153 one type of situation, though, where calls to
8154 <prgn>dpkg-statoverride</prgn> would be needed in the
8155 maintainer scripts, and that involves packages which use
8156 dynamically allocated user or group ids. In such a
8157 situation, something like the following idiom can be very
8158 helpful in the package's <prgn>postinst</prgn>, where
8159 <tt>sysuser</tt> is a dynamically allocated id:
8161 for i in /usr/bin/foo /usr/sbin/bar
8163 # only do something when no setting exists
8164 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8166 #include: debconf processing, question about foo and bar
8167 if [ "$RET" = "true" ] ; then
8168 dpkg-statoverride --update --add sysuser root 4755 $i
8173 The corresponding code to remove the override when the package
8176 for i in /usr/bin/foo /usr/sbin/bar
8178 if dpkg-statoverride --list $i >/dev/null 2>&1
8180 dpkg-statoverride --remove $i
8190 <chapt id="customized-programs">
8191 <heading>Customized programs</heading>
8193 <sect id="arch-spec">
8194 <heading>Architecture specification strings</heading>
8197 If a program needs to specify an <em>architecture specification
8198 string</em> in some place, it should select one of the strings
8199 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8200 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8201 part is sometimes elided, as when the OS is Linux.
8205 Note that we don't want to use
8206 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8207 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8208 since this would make our programs incompatible with other
8209 Linux distributions. We also don't use something like
8210 <tt><var>arch</var>-unknown-linux</tt>, since the
8211 <tt>unknown</tt> does not look very good.
8214 <sect1 id="arch-wildcard-spec">
8215 <heading>Architecture wildcards</heading>
8218 A package may specify an architecture wildcard. Architecture
8219 wildcards are in the format <tt>any</tt> (which matches every
8220 architecture), <tt><var>os</var></tt>-any, or
8221 any-<tt><var>cpu</var></tt>. <footnote>
8222 Internally, the package system normalizes the GNU triplets
8223 and the Debian arches into Debian arch triplets (which are
8224 kind of inverted GNU triplets), with the first component of
8225 the triplet representing the libc and ABI in use, and then
8226 does matching against those triplets. However, such
8227 triplets are an internal implementation detail that should
8228 not be used by packages directly. The libc and ABI portion
8229 is handled internally by the package system based on
8230 the <var>os</var> and <var>cpu</var>.
8237 <heading>Daemons</heading>
8240 The configuration files <file>/etc/services</file>,
8241 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8242 by the <prgn>netbase</prgn> package and must not be modified
8247 If a package requires a new entry in one of these files, the
8248 maintainer should get in contact with the
8249 <prgn>netbase</prgn> maintainer, who will add the entries
8250 and release a new version of the <prgn>netbase</prgn>
8255 The configuration file <file>/etc/inetd.conf</file> must not be
8256 modified by the package's scripts except via the
8257 <prgn>update-inetd</prgn> script or the
8258 <file>DebianNet.pm</file> Perl module. See their documentation
8259 for details on how to add entries.
8263 If a package wants to install an example entry into
8264 <file>/etc/inetd.conf</file>, the entry must be preceded with
8265 exactly one hash character (<tt>#</tt>). Such lines are
8266 treated as "commented out by user" by the
8267 <prgn>update-inetd</prgn> script and are not changed or
8268 activated during package updates.
8273 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8277 Some programs need to create pseudo-ttys. This should be done
8278 using Unix98 ptys if the C library supports it. The resulting
8279 program must not be installed setuid root, unless that
8280 is required for other functionality.
8284 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8285 <file>/var/log/lastlog</file> must be installed writable by
8286 group <tt>utmp</tt>. Programs which need to modify those
8287 files must be installed setgid <tt>utmp</tt>.
8292 <heading>Editors and pagers</heading>
8295 Some programs have the ability to launch an editor or pager
8296 program to edit or display a text document. Since there are
8297 lots of different editors and pagers available in the Debian
8298 distribution, the system administrator and each user should
8299 have the possibility to choose their preferred editor and
8304 In addition, every program should choose a good default
8305 editor/pager if none is selected by the user or system
8310 Thus, every program that launches an editor or pager must
8311 use the EDITOR or PAGER environment variable to determine
8312 the editor or pager the user wishes to use. If these
8313 variables are not set, the programs <file>/usr/bin/editor</file>
8314 and <file>/usr/bin/pager</file> should be used, respectively.
8318 These two files are managed through the <prgn>dpkg</prgn>
8319 "alternatives" mechanism. Thus every package providing an
8320 editor or pager must call the
8321 <prgn>update-alternatives</prgn> script to register these
8326 If it is very hard to adapt a program to make use of the
8327 EDITOR or PAGER variables, that program may be configured to
8328 use <file>/usr/bin/sensible-editor</file> and
8329 <file>/usr/bin/sensible-pager</file> as the editor or pager
8330 program respectively. These are two scripts provided in the
8331 <package>sensible-utils</package> package that check the EDITOR
8332 and PAGER variables and launch the appropriate program, and fall
8333 back to <file>/usr/bin/editor</file>
8334 and <file>/usr/bin/pager</file> if the variable is not set.
8338 A program may also use the VISUAL environment variable to
8339 determine the user's choice of editor. If it exists, it
8340 should take precedence over EDITOR. This is in fact what
8341 <file>/usr/bin/sensible-editor</file> does.
8345 It is not required for a package to depend on
8346 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8347 package to provide such virtual packages.<footnote>
8348 The Debian base system already provides an editor and a
8354 <sect id="web-appl">
8355 <heading>Web servers and applications</heading>
8358 This section describes the locations and URLs that should
8359 be used by all web servers and web applications in the
8366 Cgi-bin executable files are installed in the
8368 <example compact="compact">
8369 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8371 and should be referred to as
8372 <example compact="compact">
8373 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8379 <p>Access to HTML documents</p>
8382 HTML documents for a package are stored in
8383 <file>/usr/share/doc/<var>package</var></file>
8384 and can be referred to as
8385 <example compact="compact">
8386 http://localhost/doc/<var>package</var>/<var>filename</var>
8391 The web server should restrict access to the document
8392 tree so that only clients on the same host can read
8393 the documents. If the web server does not support such
8394 access controls, then it should not provide access at
8395 all, or ask about providing access during installation.
8400 <p>Access to images</p>
8402 It is recommended that images for a package be stored
8403 in <tt>/usr/share/images/<var>package</var></tt> and
8404 may be referred to through an alias <tt>/images/</tt>
8407 http://localhost/images/<package>/<filename>
8414 <p>Web Document Root</p>
8417 Web Applications should try to avoid storing files in
8418 the Web Document Root. Instead they should use the
8419 /usr/share/doc/<var>package</var> directory for
8420 documents and register the Web Application via the
8421 <package>doc-base</package> package. If access to the
8422 web document root is unavoidable then use
8423 <example compact="compact">
8426 as the Document Root. This might be just a symbolic
8427 link to the location where the system administrator
8428 has put the real document root.
8431 <item><p>Providing httpd and/or httpd-cgi</p>
8433 All web servers should provide the virtual package
8434 <tt>httpd</tt>. If a web server has CGI support it should
8435 provide <tt>httpd-cgi</tt> additionally.
8438 All web applications which do not contain CGI scripts should
8439 depend on <tt>httpd</tt>, all those web applications which
8440 <tt>do</tt> contain CGI scripts, should depend on
8448 <sect id="mail-transport-agents">
8449 <heading>Mail transport, delivery and user agents</heading>
8452 Debian packages which process electronic mail, whether mail
8453 user agents (MUAs) or mail transport agents (MTAs), must
8454 ensure that they are compatible with the configuration
8455 decisions below. Failure to do this may result in lost
8456 mail, broken <tt>From:</tt> lines, and other serious brain
8461 The mail spool is <file>/var/mail</file> and the interface to
8462 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8463 the FHS). On older systems, the mail spool may be
8464 physically located in <file>/var/spool/mail</file>, but all
8465 access to the mail spool should be via the
8466 <file>/var/mail</file> symlink. The mail spool is part of the
8467 base system and not part of the MTA package.
8471 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8472 programs (such as IMAP daemons) must lock the mailbox in an
8473 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8474 be combined with dot locking. To avoid deadlocks, a program
8475 should use <tt>fcntl()</tt> first and dot locking after
8476 this, or alternatively implement the two locking methods in
8477 a non blocking way<footnote>
8478 If it is not possible to establish both locks, the
8479 system shouldn't wait for the second lock to be
8480 established, but remove the first lock, wait a (random)
8481 time, and start over locking again.
8482 </footnote>. Using the functions <tt>maillock</tt> and
8483 <tt>mailunlock</tt> provided by the
8484 <tt>liblockfile*</tt><footnote>
8485 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8486 to use these functions.
8487 </footnote> packages is the recommended way to realize this.
8491 Mailboxes are generally either mode 600 and owned by
8492 <var>user</var> or mode 660 and owned by
8493 <tt><var>user</var>:mail</tt><footnote>
8494 There are two traditional permission schemes for mail spools:
8495 mode 600 with all mail delivery done by processes running as
8496 the destination user, or mode 660 and owned by group mail with
8497 mail delivery done by a process running as a system user in
8498 group mail. Historically, Debian required mode 660 mail
8499 spools to enable the latter model, but that model has become
8500 increasingly uncommon and the principle of least privilege
8501 indicates that mail systems that use the first model should
8502 use permissions of 600. If delivery to programs is permitted,
8503 it's easier to keep the mail system secure if the delivery
8504 agent runs as the destination user. Debian Policy therefore
8505 permits either scheme.
8506 </footnote>. The local system administrator may choose a
8507 different permission scheme; packages should not make
8508 assumptions about the permission and ownership of mailboxes
8509 unless required (such as when creating a new mailbox). A MUA
8510 may remove a mailbox (unless it has nonstandard permissions) in
8511 which case the MTA or another MUA must recreate it if needed.
8515 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8516 be setgid mail to do the locking mentioned above (and
8517 must obviously avoid accessing other users' mailboxes
8518 using this privilege).</p>
8521 <file>/etc/aliases</file> is the source file for the system mail
8522 aliases (e.g., postmaster, usenet, etc.), it is the one
8523 which the sysadmin and <prgn>postinst</prgn> scripts may
8524 edit. After <file>/etc/aliases</file> is edited the program or
8525 human editing it must call <prgn>newaliases</prgn>. All MTA
8526 packages must come with a <prgn>newaliases</prgn> program,
8527 even if it does nothing, but older MTA packages did not do
8528 this so programs should not fail if <prgn>newaliases</prgn>
8529 cannot be found. Note that because of this, all MTA
8530 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8531 <tt>Replaces: mail-transport-agent</tt> control file
8536 The convention of writing <tt>forward to
8537 <var>address</var></tt> in the mailbox itself is not
8538 supported. Use a <tt>.forward</tt> file instead.</p>
8541 The <prgn>rmail</prgn> program used by UUCP
8542 for incoming mail should be <file>/usr/sbin/rmail</file>.
8543 Likewise, <prgn>rsmtp</prgn>, for receiving
8544 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8548 If your package needs to know what hostname to use on (for
8549 example) outgoing news and mail messages which are generated
8550 locally, you should use the file <file>/etc/mailname</file>. It
8551 will contain the portion after the username and <tt>@</tt>
8552 (at) sign for email addresses of users on the machine
8553 (followed by a newline).
8557 Such a package should check for the existence of this file
8558 when it is being configured. If it exists, it should be
8559 used without comment, although an MTA's configuration script
8560 may wish to prompt the user even if it finds that this file
8561 exists. If the file does not exist, the package should
8562 prompt the user for the value (preferably using
8563 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8564 as well as using it in the package's configuration. The
8565 prompt should make it clear that the name will not just be
8566 used by that package. For example, in this situation the
8567 <tt>inn</tt> package could say something like:
8568 <example compact="compact">
8569 Please enter the "mail name" of your system. This is the
8570 hostname portion of the address to be shown on outgoing
8571 news and mail messages. The default is
8572 <var>syshostname</var>, your system's host name. Mail
8573 name ["<var>syshostname</var>"]:
8575 where <var>syshostname</var> is the output of <tt>hostname
8581 <heading>News system configuration</heading>
8584 All the configuration files related to the NNTP (news)
8585 servers and clients should be located under
8586 <file>/etc/news</file>.</p>
8589 There are some configuration issues that apply to a number
8590 of news clients and server packages on the machine. These
8594 <tag><file>/etc/news/organization</file></tag>
8596 A string which should appear as the
8597 organization header for all messages posted
8598 by NNTP clients on the machine
8601 <tag><file>/etc/news/server</file></tag>
8603 Contains the FQDN of the upstream NNTP
8604 server, or localhost if the local machine is
8609 Other global files may be added as required for cross-package news
8616 <heading>Programs for the X Window System</heading>
8619 <heading>Providing X support and package priorities</heading>
8622 Programs that can be configured with support for the X
8623 Window System must be configured to do so and must declare
8624 any package dependencies necessary to satisfy their
8625 runtime requirements when using the X Window System. If
8626 such a package is of higher priority than the X packages
8627 on which it depends, it is required that either the
8628 X-specific components be split into a separate package, or
8629 that an alternative version of the package, which includes
8630 X support, be provided, or that the package's priority be
8636 <heading>Packages providing an X server</heading>
8639 Packages that provide an X server that, directly or
8640 indirectly, communicates with real input and display
8641 hardware should declare in their control data that they
8642 provide the virtual package <tt>xserver</tt>.<footnote>
8643 This implements current practice, and provides an
8644 actual policy for usage of the <tt>xserver</tt>
8645 virtual package which appears in the virtual packages
8646 list. In a nutshell, X servers that interface
8647 directly with the display and input hardware or via
8648 another subsystem (e.g., GGI) should provide
8649 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8650 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8656 <heading>Packages providing a terminal emulator</heading>
8659 Packages that provide a terminal emulator for the X Window
8660 System which meet the criteria listed below should declare
8661 in their control data that they provide the virtual
8662 package <tt>x-terminal-emulator</tt>. They should also
8663 register themselves as an alternative for
8664 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8669 To be an <tt>x-terminal-emulator</tt>, a program must:
8670 <list compact="compact">
8672 Be able to emulate a DEC VT100 terminal, or a
8673 compatible terminal.
8677 Support the command-line option <tt>-e
8678 <var>command</var></tt>, which creates a new
8679 terminal window<footnote>
8680 "New terminal window" does not necessarily mean
8681 a new top-level X window directly parented by
8682 the window manager; it could, if the terminal
8683 emulator application were so coded, be a new
8684 "view" in a multiple-document interface (MDI).
8686 and runs the specified <var>command</var>,
8687 interpreting the entirety of the rest of the command
8688 line as a command to pass straight to exec, in the
8689 manner that <tt>xterm</tt> does.
8693 Support the command-line option <tt>-T
8694 <var>title</var></tt>, which creates a new terminal
8695 window with the window title <var>title</var>.
8702 <heading>Packages providing a window manager</heading>
8705 Packages that provide a window manager should declare in
8706 their control data that they provide the virtual package
8707 <tt>x-window-manager</tt>. They should also register
8708 themselves as an alternative for
8709 <file>/usr/bin/x-window-manager</file>, with a priority
8710 calculated as follows:
8711 <list compact="compact">
8713 Start with a priority of 20.
8717 If the window manager supports the Debian menu
8718 system, add 20 points if this support is available
8719 in the package's default configuration (i.e., no
8720 configuration files belonging to the system or user
8721 have to be edited to activate the feature); if
8722 configuration files must be modified, add only 10
8728 If the window manager complies with <url
8729 id="http://www.freedesktop.org/Standards/wm-spec"
8730 name="The Window Manager Specification Project">,
8731 written by the <url id="http://www.freedesktop.org/"
8732 name="Free Desktop Group">, add 40 points.
8736 If the window manager permits the X session to be
8737 restarted using a <em>different</em> window manager
8738 (without killing the X server) in its default
8739 configuration, add 10 points; otherwise add none.
8746 <heading>Packages providing fonts</heading>
8749 Packages that provide fonts for the X Window
8751 For the purposes of Debian Policy, a "font for the X
8752 Window System" is one which is accessed via X protocol
8753 requests. Fonts for the Linux console, for PostScript
8754 renderer, or any other purpose, do not fit this
8755 definition. Any tool which makes such fonts available
8756 to the X Window System, however, must abide by this
8759 must do a number of things to ensure that they are both
8760 available without modification of the X or font server
8761 configuration, and that they do not corrupt files used by
8762 other font packages to register information about
8766 Fonts of any type supported by the X Window System
8767 must be in a separate binary package from any
8768 executables, libraries, or documentation (except
8769 that specific to the fonts shipped, such as their
8770 license information). If one or more of the fonts
8771 so packaged are necessary for proper operation of
8772 the package with which they are associated the font
8773 package may be Recommended; if the fonts merely
8774 provide an enhancement, a Suggests relationship may
8775 be used. Packages must not Depend on font
8777 This is because the X server may retrieve fonts
8778 from the local file system or over the network
8779 from an X font server; the Debian package system
8780 is empowered to deal only with the local
8786 BDF fonts must be converted to PCF fonts with the
8787 <prgn>bdftopcf</prgn> utility (available in the
8788 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8789 placed in a directory that corresponds to their
8791 <list compact="compact">
8793 100 dpi fonts must be placed in
8794 <file>/usr/share/fonts/X11/100dpi/</file>.
8798 75 dpi fonts must be placed in
8799 <file>/usr/share/fonts/X11/75dpi/</file>.
8803 Character-cell fonts, cursor fonts, and other
8804 low-resolution fonts must be placed in
8805 <file>/usr/share/fonts/X11/misc/</file>.
8811 Type 1 fonts must be placed in
8812 <file>/usr/share/fonts/X11/Type1/</file>. If font
8813 metric files are available, they must be placed here
8818 Subdirectories of <file>/usr/share/fonts/X11/</file>
8819 other than those listed above must be neither
8820 created nor used. (The <file>PEX</file>, <file>CID</file>,
8821 <file>Speedo</file>, and <file>cyrillic</file> directories
8822 are excepted for historical reasons, but installation of
8823 files into these directories remains discouraged.)
8827 Font packages may, instead of placing files directly
8828 in the X font directories listed above, provide
8829 symbolic links in that font directory pointing to
8830 the files' actual location in the filesystem. Such
8831 a location must comply with the FHS.
8835 Font packages should not contain both 75dpi and
8836 100dpi versions of a font. If both are available,
8837 they should be provided in separate binary packages
8838 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8839 the names of the packages containing the
8840 corresponding fonts.
8844 Fonts destined for the <file>misc</file> subdirectory
8845 should not be included in the same package as 75dpi
8846 or 100dpi fonts; instead, they should be provided in
8847 a separate package with <tt>-misc</tt> appended to
8852 Font packages must not provide the files
8853 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8854 <file>fonts.scale</file> in a font directory:
8857 <file>fonts.dir</file> files must not be provided at all.
8861 <file>fonts.alias</file> and <file>fonts.scale</file>
8862 files, if needed, should be provided in the
8864 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8865 where <var>fontdir</var> is the name of the
8867 <file>/usr/share/fonts/X11/</file> where the
8868 package's corresponding fonts are stored
8869 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8870 <var>package</var> is the name of the package
8871 that provides these fonts, and
8872 <var>extension</var> is either <tt>scale</tt>
8873 or <tt>alias</tt>, whichever corresponds to
8880 Font packages must declare a dependency on
8881 <tt>xfonts-utils</tt> in their control
8886 Font packages that provide one or more
8887 <file>fonts.scale</file> files as described above must
8888 invoke <prgn>update-fonts-scale</prgn> on each
8889 directory into which they installed fonts
8890 <em>before</em> invoking
8891 <prgn>update-fonts-dir</prgn> on that directory.
8892 This invocation must occur in both the
8893 <prgn>postinst</prgn> (for all arguments) and
8894 <prgn>postrm</prgn> (for all arguments except
8895 <tt>upgrade</tt>) scripts.
8899 Font packages that provide one or more
8900 <file>fonts.alias</file> files as described above must
8901 invoke <prgn>update-fonts-alias</prgn> on each
8902 directory into which they installed fonts. This
8903 invocation must occur in both the
8904 <prgn>postinst</prgn> (for all arguments) and
8905 <prgn>postrm</prgn> (for all arguments except
8906 <tt>upgrade</tt>) scripts.
8910 Font packages must invoke
8911 <prgn>update-fonts-dir</prgn> on each directory into
8912 which they installed fonts. This invocation must
8913 occur in both the <prgn>postinst</prgn> (for all
8914 arguments) and <prgn>postrm</prgn> (for all
8915 arguments except <tt>upgrade</tt>) scripts.
8919 Font packages must not provide alias names for the
8920 fonts they include which collide with alias names
8921 already in use by fonts already packaged.
8925 Font packages must not provide fonts with the same
8926 XLFD registry name as another font already packaged.
8932 <sect1 id="appdefaults">
8933 <heading>Application defaults files</heading>
8936 Application defaults files must be installed in the
8937 directory <file>/etc/X11/app-defaults/</file> (use of a
8938 localized subdirectory of <file>/etc/X11/</file> as described
8939 in the <em>X Toolkit Intrinsics - C Language
8940 Interface</em> manual is also permitted). They must be
8941 registered as <tt>conffile</tt>s or handled as
8942 configuration files.
8946 Customization of programs' X resources may also be
8947 supported with the provision of a file with the same name
8948 as that of the package placed in
8949 the <file>/etc/X11/Xresources/</file> directory, which
8950 must be registered as a <tt>conffile</tt> or handled as a
8951 configuration file.<footnote>
8952 Note that this mechanism is not the same as using
8953 app-defaults; app-defaults are tied to the client
8954 binary on the local file system, whereas X resources
8955 are stored in the X server and affect all connecting
8962 <heading>Installation directory issues</heading>
8965 Historically, packages using the X Window System used a
8966 separate set of installation directories from other packages.
8967 This practice has been discontinued and packages using the X
8968 Window System should now generally be installed in the same
8969 directories as any other package. Specifically, packages must
8970 not install files under the <file>/usr/X11R6/</file> directory
8971 and the <file>/usr/X11R6/</file> directory hierarchy should be
8972 regarded as obsolete.
8976 Include files previously installed under
8977 <file>/usr/X11R6/include/X11/</file> should be installed into
8978 <file>/usr/include/X11/</file>. For files previously
8979 installed into subdirectories of
8980 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8981 determine if subdirectories of <file>/usr/lib/</file> and
8982 <file>/usr/share/</file> can be used. If not, a subdirectory
8983 of <file>/usr/lib/X11/</file> should be used.
8987 Configuration files for window, display, or session managers
8988 or other applications that are tightly integrated with the X
8989 Window System may be placed in a subdirectory
8990 of <file>/etc/X11/</file> corresponding to the package name.
8991 Other X Window System applications should use
8992 the <file>/etc/</file> directory unless otherwise mandated by
8993 policy (such as for <ref id="appdefaults">).
8998 <heading>The OSF/Motif and OpenMotif libraries</heading>
9001 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9002 OpenMotif libraries</em><footnote>
9003 OSF/Motif and OpenMotif are collectively referred to as
9004 "Motif" in this policy document.
9006 should be compiled against and tested with LessTif (a free
9007 re-implementation of Motif) instead. If the maintainer
9008 judges that the program or programs do not work
9009 sufficiently well with LessTif to be distributed and
9010 supported, but do so when compiled against Motif, then two
9011 versions of the package should be created; one linked
9012 statically against Motif and with <tt>-smotif</tt>
9013 appended to the package name, and one linked dynamically
9014 against Motif and with <tt>-dmotif</tt> appended to the
9019 Both Motif-linked versions are dependent
9020 upon non-DFSG-compliant software and thus cannot be
9021 uploaded to the <em>main</em> distribution; if the
9022 software is itself DFSG-compliant it may be uploaded to
9023 the <em>contrib</em> distribution. While known existing
9024 versions of Motif permit unlimited redistribution of
9025 binaries linked against the library (whether statically or
9026 dynamically), it is the package maintainer's
9027 responsibility to determine whether this is permitted by
9028 the license of the copy of Motif in their possession.
9034 <heading>Perl programs and modules</heading>
9037 Perl programs and modules should follow the current Perl policy.
9041 The Perl policy can be found in the <tt>perl-policy</tt>
9042 files in the <tt>debian-policy</tt> package.
9043 It is also available from the Debian web mirrors at
9044 <tt><url name="/doc/packaging-manuals/perl-policy/"
9045 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9050 <heading>Emacs lisp programs</heading>
9053 Please refer to the "Debian Emacs Policy" for details of how to
9054 package emacs lisp programs.
9058 The Emacs policy is available in
9059 <file>debian-emacs-policy.gz</file> of the
9060 <package>emacsen-common</package> package.
9061 It is also available from the Debian web mirrors at
9062 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9063 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9068 <heading>Games</heading>
9071 The permissions on <file>/var/games</file> are mode 755, owner
9072 <tt>root</tt> and group <tt>root</tt>.
9076 Each game decides on its own security policy.</p>
9079 Games which require protected, privileged access to
9080 high-score files, saved games, etc., may be made
9081 set-<em>group</em>-id (mode 2755) and owned by
9082 <tt>root:games</tt>, and use files and directories with
9083 appropriate permissions (770 <tt>root:games</tt>, for
9084 example). They must not be made
9085 set-<em>user</em>-id, as this causes security problems. (If
9086 an attacker can subvert any set-user-id game they can
9087 overwrite the executable of any other, causing other players
9088 of these games to run a Trojan horse program. With a
9089 set-group-id game the attacker only gets access to less
9090 important game data, and if they can get at the other
9091 players' accounts at all it will take considerably more
9095 Some packages, for example some fortune cookie programs, are
9096 configured by the upstream authors to install with their
9097 data files or other static information made unreadable so
9098 that they can only be accessed through set-id programs
9099 provided. You should not do this in a Debian package: anyone can
9100 download the <file>.deb</file> file and read the data from it,
9101 so there is no point making the files unreadable. Not
9102 making the files unreadable also means that you don't have
9103 to make so many programs set-id, which reduces the risk of a
9107 As described in the FHS, binaries of games should be
9108 installed in the directory <file>/usr/games</file>. This also
9109 applies to games that use the X Window System. Manual pages
9110 for games (X and non-X games) should be installed in
9111 <file>/usr/share/man/man6</file>.</p>
9117 <heading>Documentation</heading>
9120 <heading>Manual pages</heading>
9123 You should install manual pages in <prgn>nroff</prgn> source
9124 form, in appropriate places under <file>/usr/share/man</file>.
9125 You should only use sections 1 to 9 (see the FHS for more
9126 details). You must not install a pre-formatted "cat page".
9130 Each program, utility, and function should have an
9131 associated manual page included in the same package. It is
9132 suggested that all configuration files also have a manual
9133 page included as well. Manual pages for protocols and other
9134 auxiliary things are optional.
9138 If no manual page is available, this is considered as a bug
9139 and should be reported to the Debian Bug Tracking System (the
9140 maintainer of the package is allowed to write this bug report
9141 themselves, if they so desire). Do not close the bug report
9142 until a proper man page is available.<footnote>
9143 It is not very hard to write a man page. See the
9144 <url id="http://www.schweikhardt.net/man_page_howto.html"
9145 name="Man-Page-HOWTO">,
9146 <manref name="man" section="7">, the examples
9147 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9148 the helper program <prgn>help2man</prgn>, or the
9149 directory <file>/usr/share/doc/man-db/examples</file>.
9154 You may forward a complaint about a missing man page to the
9155 upstream authors, and mark the bug as forwarded in the
9156 Debian bug tracking system. Even though the GNU Project do
9157 not in general consider the lack of a man page to be a bug,
9158 we do; if they tell you that they don't consider it a bug
9159 you should leave the bug in our bug tracking system open
9164 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9168 If one man page needs to be accessible via several names it
9169 is better to use a symbolic link than the <file>.so</file>
9170 feature, but there is no need to fiddle with the relevant
9171 parts of the upstream source to change from <file>.so</file> to
9172 symlinks: don't do it unless it's easy. You should not
9173 create hard links in the manual page directories, nor put
9174 absolute filenames in <file>.so</file> directives. The filename
9175 in a <file>.so</file> in a man page should be relative to the
9176 base of the man page tree (usually
9177 <file>/usr/share/man</file>). If you do not create any links
9178 (whether symlinks, hard links, or <tt>.so</tt> directives)
9179 in the file system to the alternate names of the man page,
9180 then you should not rely on <prgn>man</prgn> finding your
9181 man page under those names based solely on the information in
9182 the man page's header.<footnote>
9183 Supporting this in <prgn>man</prgn> often requires
9184 unreasonable processing time to find a manual page or to
9185 report that none exists, and moves knowledge into man's
9186 database that would be better left in the file system.
9187 This support is therefore deprecated and will cease to
9188 be present in the future.
9193 Manual pages in locale-specific subdirectories of
9194 <file>/usr/share/man</file> should use either UTF-8 or the usual
9195 legacy encoding for that language (normally the one corresponding
9196 to the shortest relevant locale name in
9197 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9198 <file>/usr/share/man/fr</file> should use either UTF-8 or
9199 ISO-8859-1.<footnote>
9200 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9201 use. In future, all manual pages will be required to use
9207 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9208 included in the subdirectory name unless it indicates a
9209 significant difference in the language, as this excludes
9210 speakers of the language in other countries.<footnote>
9211 At the time of writing, Chinese and Portuguese are the main
9212 languages with such differences, so <file>pt_BR</file>,
9213 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9218 If a localized version of a manual page is provided, it should
9219 either be up-to-date or it should be obvious to the reader that
9220 it is outdated and the original manual page should be used
9221 instead. This can be done either by a note at the beginning of
9222 the manual page or by showing the missing or changed portions in
9223 the original language instead of the target language.
9228 <heading>Info documents</heading>
9231 Info documents should be installed in <file>/usr/share/info</file>.
9232 They should be compressed with <tt>gzip -9</tt>.
9236 The <prgn>install-info</prgn> program maintains a directory of
9237 installed info documents in <file>/usr/share/info/dir</file> for
9238 the use of info readers.<footnote>
9239 It was previously necessary for packages installing info
9240 documents to run <prgn>install-info</prgn> from maintainer
9241 scripts. This is no longer necessary. The installation
9242 system now uses dpkg triggers.
9244 This file must not be included in packages. Packages containing
9245 info documents should depend on <tt>dpkg (>= 1.15.4) |
9246 install-info</tt> to ensure that the directory file is properly
9247 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9252 Info documents should contain section and directory entry
9253 information in the document for the use
9254 of <prgn>install-info</prgn>. The section should be specified
9255 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9256 space and the section of this info page. The directory entry or
9257 entries should be included between
9258 a <tt>START-INFO-DIR-ENTRY</tt> line and
9259 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9261 INFO-DIR-SECTION Individual utilities
9262 START-INFO-DIR-ENTRY
9263 * example: (example). An example info directory entry.
9266 To determine which section to use, you should look
9267 at <file>/usr/share/info/dir</file> on your system and choose
9268 the most relevant (or create a new section if none of the
9269 current sections are relevant).<footnote>
9270 Normally, info documents are generated from Texinfo source.
9271 To include this information in the generated info document, if
9272 it is absent, add commands like:
9274 @dircategory Individual utilities
9276 * example: (example). An example info directory entry.
9279 to the Texinfo source of the document and ensure that the info
9280 documents are rebuilt from source during the package build.
9286 <heading>Additional documentation</heading>
9289 Any additional documentation that comes with the package may
9290 be installed at the discretion of the package maintainer.
9291 Plain text documentation should be installed in the directory
9292 <file>/usr/share/doc/<var>package</var></file>, where
9293 <var>package</var> is the name of the package, and
9294 compressed with <tt>gzip -9</tt> unless it is small.
9298 If a package comes with large amounts of documentation which
9299 many users of the package will not require you should create
9300 a separate binary package to contain it, so that it does not
9301 take up disk space on the machines of users who do not need
9302 or want it installed.</p>
9305 It is often a good idea to put text information files
9306 (<file>README</file>s, changelogs, and so forth) that come with
9307 the source package in <file>/usr/share/doc/<var>package</var></file>
9308 in the binary package. However, you don't need to install
9309 the instructions for building and installing the package, of
9313 Packages must not require the existence of any files in
9314 <file>/usr/share/doc/</file> in order to function
9316 The system administrator should be able to
9317 delete files in <file>/usr/share/doc/</file> without causing
9318 any programs to break.
9320 Any files that are referenced by programs but are also
9321 useful as stand alone documentation should be installed under
9322 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9323 <file>/usr/share/doc/<var>package</var></file>.
9327 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9328 link to another directory in <file>/usr/share/doc</file> only if
9329 the two packages both come from the same source and the
9330 first package Depends on the second.<footnote>
9332 Please note that this does not override the section on
9333 changelog files below, so the file
9334 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9335 must refer to the changelog for the current version of
9336 <var>package</var> in question. In practice, this means
9337 that the sources of the target and the destination of the
9338 symlink must be the same (same source package and
9345 Former Debian releases placed all additional documentation
9346 in <file>/usr/doc/<var>package</var></file>. This has been
9347 changed to <file>/usr/share/doc/<var>package</var></file>,
9348 and packages must not put documentation in the directory
9349 <file>/usr/doc/<var>package</var></file>. <footnote>
9350 At this phase of the transition, we no longer require a
9351 symbolic link in <file>/usr/doc/</file>. At a later point,
9352 policy shall change to make the symbolic links a bug.
9358 <heading>Preferred documentation formats</heading>
9361 The unification of Debian documentation is being carried out
9365 If your package comes with extensive documentation in a
9366 markup format that can be converted to various other formats
9367 you should if possible ship HTML versions in a binary
9368 package, in the directory
9369 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9370 its subdirectories.<footnote>
9371 The rationale: The important thing here is that HTML
9372 docs should be available in <em>some</em> package, not
9373 necessarily in the main binary package.
9378 Other formats such as PostScript may be provided at the
9379 package maintainer's discretion.
9383 <sect id="copyrightfile">
9384 <heading>Copyright information</heading>
9387 Every package must be accompanied by a verbatim copy of its
9388 copyright information and distribution license in the file
9389 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9390 file must neither be compressed nor be a symbolic link.
9394 In addition, the copyright file must say where the upstream
9395 sources (if any) were obtained. It should name the original
9396 authors of the package and the Debian maintainer(s) who were
9397 involved with its creation.
9401 Packages in the <em>contrib</em> or <em>non-free</em> archive
9402 areas should state in the copyright file that the package is not
9403 part of the Debian GNU/Linux distribution and briefly explain
9408 A copy of the file which will be installed in
9409 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9410 be in <file>debian/copyright</file> in the source package.
9414 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9415 link to another directory in <file>/usr/share/doc</file> only if
9416 the two packages both come from the same source and the
9417 first package Depends on the second. These rules are
9418 important because copyrights must be extractable by
9423 Packages distributed under the Apache license (version 2.0), the
9424 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9425 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9426 1.3) should refer to the corresponding files
9427 under <file>/usr/share/common-licenses</file>,<footnote>
9430 <file>/usr/share/common-licenses/Apache-2.0</file>,
9431 <file>/usr/share/common-licenses/Artistic</file>,
9432 <file>/usr/share/common-licenses/GPL-1</file>,
9433 <file>/usr/share/common-licenses/GPL-2</file>,
9434 <file>/usr/share/common-licenses/GPL-3</file>,
9435 <file>/usr/share/common-licenses/LGPL-2</file>,
9436 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9437 <file>/usr/share/common-licenses/LGPL-3</file>,
9438 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9439 <file>/usr/share/common-licenses/GFDL-1.3</file>
9440 respectively. The University of California BSD license is
9441 also included in <package>base-files</package> as
9442 <file>/usr/share/common-licenses/BSD</file>, but given the
9443 brevity of this license, its specificity to code whose
9444 copyright is held by the Regents of the University of
9445 California, and the frequency of minor wording changes, its
9446 text should be included in the copyright file rather than
9447 referencing this file.
9449 </footnote> rather than quoting them in the copyright
9454 You should not use the copyright file as a general <file>README</file>
9455 file. If your package has such a file it should be
9456 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9457 <file>README.Debian</file> or some other appropriate place.</p>
9461 <heading>Examples</heading>
9464 Any examples (configurations, source files, whatever),
9465 should be installed in a directory
9466 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9467 files should not be referenced by any program: they're there
9468 for the benefit of the system administrator and users as
9469 documentation only. Architecture-specific example files
9470 should be installed in a directory
9471 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9473 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9474 latter directory itself may be a symbolic link to the
9479 If the purpose of a package is to provide examples, then the
9480 example files may be installed into
9481 <file>/usr/share/doc/<var>package</var></file>.
9485 <sect id="changelogs">
9486 <heading>Changelog files</heading>
9489 Packages that are not Debian-native must contain a
9490 compressed copy of the <file>debian/changelog</file> file from
9491 the Debian source tree in
9492 <file>/usr/share/doc/<var>package</var></file> with the name
9493 <file>changelog.Debian.gz</file>.
9497 If an upstream changelog is available, it should be accessible as
9498 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9499 plain text. If the upstream changelog is distributed in
9500 HTML, it should be made available in that form as
9501 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9502 and a plain text <file>changelog.gz</file> should be generated
9503 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9504 the upstream changelog files do not already conform to this
9505 naming convention, then this may be achieved either by
9506 renaming the files, or by adding a symbolic link, at the
9507 maintainer's discretion.<footnote>
9508 Rationale: People should not have to look in places for
9509 upstream changelogs merely because they are given
9510 different names or are distributed in HTML format.
9515 All of these files should be installed compressed using
9516 <tt>gzip -9</tt>, as they will become large with time even
9517 if they start out small.
9521 If the package has only one changelog which is used both as
9522 the Debian changelog and the upstream one because there is
9523 no separate upstream maintainer then that changelog should
9524 usually be installed as
9525 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9526 there is a separate upstream maintainer, but no upstream
9527 changelog, then the Debian changelog should still be called
9528 <file>changelog.Debian.gz</file>.
9532 For details about the format and contents of the Debian
9533 changelog file, please see <ref id="dpkgchangelog">.
9538 <appendix id="pkg-scope">
9539 <heading>Introduction and scope of these appendices</heading>
9542 These appendices are taken essentially verbatim from the
9543 now-deprecated Packaging Manual, version 3.2.1.0. They are
9544 the chapters which are likely to be of use to package
9545 maintainers and which have not already been included in the
9546 policy document itself. Most of these sections are very likely
9547 not relevant to policy; they should be treated as
9548 documentation for the packaging system. Please note that these
9549 appendices are included for convenience, and for historical
9550 reasons: they used to be part of policy package, and they have
9551 not yet been incorporated into dpkg documentation. However,
9552 they still have value, and hence they are presented here.
9556 They have not yet been checked to ensure that they are
9557 compatible with the contents of policy, and if there are any
9558 contradictions, the version in the main policy document takes
9559 precedence. The remaining chapters of the old Packaging
9560 Manual have also not been read in detail to ensure that there
9561 are not parts which have been left out. Both of these will be
9566 Certain parts of the Packaging manual were integrated into the
9567 Policy Manual proper, and removed from the appendices. Links
9568 have been placed from the old locations to the new ones.
9572 <prgn>dpkg</prgn> is a suite of programs for creating binary
9573 package files and installing and removing them on Unix
9575 <prgn>dpkg</prgn> is targeted primarily at Debian
9576 GNU/Linux, but may work on or be ported to other
9582 The binary packages are designed for the management of
9583 installed executable programs (usually compiled binaries) and
9584 their associated data, though source code examples and
9585 documentation are provided as part of some packages.</p>
9588 This manual describes the technical aspects of creating Debian
9589 binary packages (<file>.deb</file> files). It documents the
9590 behavior of the package management programs
9591 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9592 they interact with packages.</p>
9595 It also documents the interaction between
9596 <prgn>dselect</prgn>'s core and the access method scripts it
9597 uses to actually install the selected packages, and describes
9598 how to create a new access method.</p>
9601 This manual does not go into detail about the options and
9602 usage of the package building and installation tools. It
9603 should therefore be read in conjunction with those programs'
9608 The utility programs which are provided with <prgn>dpkg</prgn>
9609 for managing various system configuration and similar issues,
9610 such as <prgn>update-rc.d</prgn> and
9611 <prgn>install-info</prgn>, are not described in detail here -
9612 please see their man pages.
9616 It is assumed that the reader is reasonably familiar with the
9617 <prgn>dpkg</prgn> System Administrators' manual.
9618 Unfortunately this manual does not yet exist.
9622 The Debian version of the FSF's GNU hello program is provided
9623 as an example for people wishing to create Debian
9624 packages. The Debian <prgn>debmake</prgn> package is
9625 recommended as a very helpful tool in creating and maintaining
9626 Debian packages. However, while the tools and examples are
9627 helpful, they do not replace the need to read and follow the
9628 Policy and Programmer's Manual.</p>
9631 <appendix id="pkg-binarypkg">
9632 <heading>Binary packages (from old Packaging Manual)</heading>
9635 The binary package has two main sections. The first part
9636 consists of various control information files and scripts used
9637 by <prgn>dpkg</prgn> when installing and removing. See <ref
9638 id="pkg-controlarea">.
9642 The second part is an archive containing the files and
9643 directories to be installed.
9647 In the future binary packages may also contain other
9648 components, such as checksums and digital signatures. The
9649 format for the archive is described in full in the
9650 <file>deb(5)</file> man page.
9654 <sect id="pkg-bincreating"><heading>Creating package files -
9655 <prgn>dpkg-deb</prgn>
9659 All manipulation of binary package files is done by
9660 <prgn>dpkg-deb</prgn>; it's the only program that has
9661 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9662 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9663 will spot that the options requested are appropriate to
9664 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9669 In order to create a binary package you must make a
9670 directory tree which contains all the files and directories
9671 you want to have in the file system data part of the package.
9672 In Debian-format source packages this directory is usually
9673 <file>debian/tmp</file>, relative to the top of the package's
9678 They should have the locations (relative to the root of the
9679 directory tree you're constructing) ownerships and
9680 permissions which you want them to have on the system when
9685 With current versions of <prgn>dpkg</prgn> the uid/username
9686 and gid/groupname mappings for the users and groups being
9687 used should be the same on the system where the package is
9688 built and the one where it is installed.
9692 You need to add one special directory to the root of the
9693 miniature file system tree you're creating:
9694 <prgn>DEBIAN</prgn>. It should contain the control
9695 information files, notably the binary package control file
9696 (see <ref id="pkg-controlfile">).
9700 The <prgn>DEBIAN</prgn> directory will not appear in the
9701 file system archive of the package, and so won't be installed
9702 by <prgn>dpkg</prgn> when the package is installed.
9706 When you've prepared the package, you should invoke:
9708 dpkg --build <var>directory</var>
9713 This will build the package in
9714 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9715 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9716 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9721 See the man page <manref name="dpkg-deb" section="8"> for details of how
9722 to examine the contents of this newly-created file. You may find the
9723 output of following commands enlightening:
9725 dpkg-deb --info <var>filename</var>.deb
9726 dpkg-deb --contents <var>filename</var>.deb
9727 dpkg --contents <var>filename</var>.deb
9729 To view the copyright file for a package you could use this command:
9731 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9736 <sect id="pkg-controlarea">
9737 <heading>Package control information files</heading>
9740 The control information portion of a binary package is a
9741 collection of files with names known to <prgn>dpkg</prgn>.
9742 It will treat the contents of these files specially - some
9743 of them contain information used by <prgn>dpkg</prgn> when
9744 installing or removing the package; others are scripts which
9745 the package maintainer wants <prgn>dpkg</prgn> to run.
9749 It is possible to put other files in the package control
9750 area, but this is not generally a good idea (though they
9751 will largely be ignored).
9755 Here is a brief list of the control info files supported by
9756 <prgn>dpkg</prgn> and a summary of what they're used for.
9761 <tag><tt>control</tt>
9764 This is the key description file used by
9765 <prgn>dpkg</prgn>. It specifies the package's name
9766 and version, gives its description for the user,
9767 states its relationships with other packages, and so
9768 forth. See <ref id="sourcecontrolfiles"> and
9769 <ref id="binarycontrolfiles">.
9773 It is usually generated automatically from information
9774 in the source package by the
9775 <prgn>dpkg-gencontrol</prgn> program, and with
9776 assistance from <prgn>dpkg-shlibdeps</prgn>.
9777 See <ref id="pkg-sourcetools">.
9781 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9786 These are executable files (usually scripts) which
9787 <prgn>dpkg</prgn> runs during installation, upgrade
9788 and removal of packages. They allow the package to
9789 deal with matters which are particular to that package
9790 or require more complicated processing than that
9791 provided by <prgn>dpkg</prgn>. Details of when and
9792 how they are called are in <ref id="maintainerscripts">.
9796 It is very important to make these scripts idempotent.
9797 See <ref id="idempotency">.
9801 The maintainer scripts are not guaranteed to run with a
9802 controlling terminal and may not be able to interact with
9803 the user. See <ref id="controllingterminal">.
9807 <tag><tt>conffiles</tt>
9810 This file contains a list of configuration files which
9811 are to be handled automatically by <prgn>dpkg</prgn>
9812 (see <ref id="pkg-conffiles">). Note that not necessarily
9813 every configuration file should be listed here.
9816 <tag><tt>shlibs</tt>
9819 This file contains a list of the shared libraries
9820 supplied by the package, with dependency details for
9821 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9822 when it determines what dependencies are required in a
9823 package control file. The <tt>shlibs</tt> file format
9824 is described on <ref id="shlibs">.
9829 <sect id="pkg-controlfile">
9830 <heading>The main control information file: <tt>control</tt></heading>
9833 The most important control information file used by
9834 <prgn>dpkg</prgn> when it installs a package is
9835 <tt>control</tt>. It contains all the package's "vital
9840 The binary package control files of packages built from
9841 Debian sources are made by a special tool,
9842 <prgn>dpkg-gencontrol</prgn>, which reads
9843 <file>debian/control</file> and <file>debian/changelog</file> to
9844 find the information it needs. See <ref id="pkg-sourcepkg"> for
9849 The fields in binary package control files are listed in
9850 <ref id="binarycontrolfiles">.
9854 A description of the syntax of control files and the purpose
9855 of the fields is available in <ref id="controlfields">.
9860 <heading>Time Stamps</heading>
9863 See <ref id="timestamps">.
9868 <appendix id="pkg-sourcepkg">
9869 <heading>Source packages (from old Packaging Manual) </heading>
9872 The Debian binary packages in the distribution are generated
9873 from Debian sources, which are in a special format to assist
9874 the easy and automatic building of binaries.
9877 <sect id="pkg-sourcetools">
9878 <heading>Tools for processing source packages</heading>
9881 Various tools are provided for manipulating source packages;
9882 they pack and unpack sources and help build of binary
9883 packages and help manage the distribution of new versions.
9887 They are introduced and typical uses described here; see
9888 <manref name="dpkg-source" section="1"> for full
9889 documentation about their arguments and operation.
9893 For examples of how to construct a Debian source package,
9894 and how to use those utilities that are used by Debian
9895 source packages, please see the <prgn>hello</prgn> example
9899 <sect1 id="pkg-dpkg-source">
9901 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9906 This program is frequently used by hand, and is also
9907 called from package-independent automated building scripts
9908 such as <prgn>dpkg-buildpackage</prgn>.
9912 To unpack a package it is typically invoked with
9914 dpkg-source -x <var>.../path/to/filename</var>.dsc
9919 with the <file><var>filename</var>.tar.gz</file> and
9920 <file><var>filename</var>.diff.gz</file> (if applicable) in
9921 the same directory. It unpacks into
9922 <file><var>package</var>-<var>version</var></file>, and if
9924 <file><var>package</var>-<var>version</var>.orig</file>, in
9925 the current directory.
9929 To create a packed source archive it is typically invoked:
9931 dpkg-source -b <var>package</var>-<var>version</var>
9936 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9937 <file>.diff.gz</file> (if appropriate) in the current
9938 directory. <prgn>dpkg-source</prgn> does not clean the
9939 source tree first - this must be done separately if it is
9944 See also <ref id="pkg-sourcearchives">.</p>
9948 <sect1 id="pkg-dpkg-buildpackage">
9950 <prgn>dpkg-buildpackage</prgn> - overall package-building
9955 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9956 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9957 targets <tt>clean</tt>, <tt>build</tt> and
9958 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9959 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9960 source and binary package upload.
9964 It is usually invoked by hand from the top level of the
9965 built or unbuilt source directory. It may be invoked with
9966 no arguments; useful arguments include:
9967 <taglist compact="compact">
9968 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9971 Do not sign the <tt>.changes</tt> file or the
9972 source package <tt>.dsc</tt> file, respectively.</p>
9974 <tag><tt>-p<var>sign-command</var></tt></tag>
9977 Invoke <var>sign-command</var> instead of finding
9978 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9979 <var>sign-command</var> must behave just like
9980 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9982 <tag><tt>-r<var>root-command</var></tt></tag>
9985 When root privilege is required, invoke the command
9986 <var>root-command</var>. <var>root-command</var>
9987 should invoke its first argument as a command, from
9988 the <prgn>PATH</prgn> if necessary, and pass its
9989 second and subsequent arguments to the command it
9990 calls. If no <var>root-command</var> is supplied
9991 then <var>dpkg-buildpackage</var> will take no
9992 special action to gain root privilege, so that for
9993 most packages it will have to be invoked as root to
9996 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9999 Two types of binary-only build and upload - see
10000 <manref name="dpkg-source" section="1">.
10007 <sect1 id="pkg-dpkg-gencontrol">
10009 <prgn>dpkg-gencontrol</prgn> - generates binary package
10014 This program is usually called from <file>debian/rules</file>
10015 (see <ref id="pkg-sourcetree">) in the top level of the source
10020 This is usually done just before the files and directories in the
10021 temporary directory tree where the package is being built have their
10022 permissions and ownerships set and the package is constructed using
10023 <prgn>dpkg-deb/</prgn>
10025 This is so that the control file which is produced has
10026 the right permissions
10031 <prgn>dpkg-gencontrol</prgn> must be called after all the
10032 files which are to go into the package have been placed in
10033 the temporary build directory, so that its calculation of
10034 the installed size of a package is correct.
10038 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10039 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10040 variable substitutions created by
10041 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10046 For a package which generates only one binary package, and
10047 which builds it in <file>debian/tmp</file> relative to the top
10048 of the source package, it is usually sufficient to call
10049 <prgn>dpkg-gencontrol</prgn>.
10053 Sources which build several binaries will typically need
10056 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10057 </example> The <tt>-P</tt> tells
10058 <prgn>dpkg-gencontrol</prgn> that the package is being
10059 built in a non-default directory, and the <tt>-p</tt>
10060 tells it which package's control file should be generated.
10064 <prgn>dpkg-gencontrol</prgn> also adds information to the
10065 list of files in <file>debian/files</file>, for the benefit of
10066 (for example) a future invocation of
10067 <prgn>dpkg-genchanges</prgn>.</p>
10070 <sect1 id="pkg-dpkg-shlibdeps">
10072 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10077 This program is usually called from <file>debian/rules</file>
10078 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10079 id="pkg-sourcetree">), in the top level of the source tree.
10083 Its arguments are executables and shared libraries
10086 They may be specified either in the locations in the
10087 source tree where they are created or in the locations
10088 in the temporary build tree where they are installed
10089 prior to binary package creation.
10091 </footnote> for which shared library dependencies should
10092 be included in the binary package's control file.
10096 If some of the found shared libraries should only
10097 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10098 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10099 by using the <tt>-d<var>dependency-field</var></tt> option
10100 before those executable(s). (Each <tt>-d</tt> option
10101 takes effect until the next <tt>-d</tt>.)
10105 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10106 output control file to be modified. Instead by default it
10107 adds to the <file>debian/substvars</file> file variable
10108 settings like <tt>shlibs:Depends</tt>. These variable
10109 settings must be referenced in dependency fields in the
10110 appropriate per-binary-package sections of the source
10115 For example, a package that generates an essential part
10116 which requires dependencies, and optional parts that
10117 which only require a recommendation, would separate those
10118 two sets of dependencies into two different fields.<footnote>
10119 At the time of writing, an example for this was the
10120 <package/xmms/ package, with Depends used for the xmms
10121 executable, Recommends for the plug-ins and Suggests for
10122 even more optional features provided by unzip.
10124 It can say in its <file>debian/rules</file>:
10126 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10127 -dRecommends <var>optionalpart anotheroptionalpart</var>
10129 and then in its main control file <file>debian/control</file>:
10132 Depends: ${shlibs:Depends}
10133 Recommends: ${shlibs:Recommends}
10139 Sources which produce several binary packages with
10140 different shared library dependency requirements can use
10141 the <tt>-p<var>varnameprefix</var></tt> option to override
10142 the default <tt>shlibs:</tt> prefix (one invocation of
10143 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10144 They can thus produce several sets of dependency
10145 variables, each of the form
10146 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10147 which can be referred to in the appropriate parts of the
10148 binary package control files.
10153 <sect1 id="pkg-dpkg-distaddfile">
10155 <prgn>dpkg-distaddfile</prgn> - adds a file to
10156 <file>debian/files</file>
10160 Some packages' uploads need to include files other than
10161 the source and binary package files.
10165 <prgn>dpkg-distaddfile</prgn> adds a file to the
10166 <file>debian/files</file> file so that it will be included in
10167 the <file>.changes</file> file when
10168 <prgn>dpkg-genchanges</prgn> is run.
10172 It is usually invoked from the <tt>binary</tt> target of
10173 <file>debian/rules</file>:
10175 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10177 The <var>filename</var> is relative to the directory where
10178 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10179 is usually the directory above the top level of the source
10180 tree. The <file>debian/rules</file> target should put the
10181 file there just before or just after calling
10182 <prgn>dpkg-distaddfile</prgn>.
10186 The <var>section</var> and <var>priority</var> are passed
10187 unchanged into the resulting <file>.changes</file> file.
10192 <sect1 id="pkg-dpkg-genchanges">
10194 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10195 upload control file
10199 This program is usually called by package-independent
10200 automatic building scripts such as
10201 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10206 It is usually called in the top level of a built source
10207 tree, and when invoked with no arguments will print out a
10208 straightforward <file>.changes</file> file based on the
10209 information in the source package's changelog and control
10210 file and the binary and source packages which should have
10216 <sect1 id="pkg-dpkg-parsechangelog">
10218 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10219 representation of a changelog
10223 This program is used internally by
10224 <prgn>dpkg-source</prgn> et al. It may also occasionally
10225 be useful in <file>debian/rules</file> and elsewhere. It
10226 parses a changelog, <file>debian/changelog</file> by default,
10227 and prints a control-file format representation of the
10228 information in it to standard output.
10232 <sect1 id="pkg-dpkg-architecture">
10234 <prgn>dpkg-architecture</prgn> - information about the build and
10239 This program can be used manually, but is also invoked by
10240 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10241 environment or make variables which specify the build and host
10242 architecture for the package building process.
10247 <sect id="pkg-sourcetree">
10248 <heading>The Debian package source tree</heading>
10251 The source archive scheme described later is intended to
10252 allow a Debian package source tree with some associated
10253 control information to be reproduced and transported easily.
10254 The Debian package source tree is a version of the original
10255 program with certain files added for the benefit of the
10256 packaging process, and with any other changes required
10257 made to the rest of the source code and installation
10262 The extra files created for Debian are in the subdirectory
10263 <file>debian</file> of the top level of the Debian package
10264 source tree. They are described below.
10267 <sect1 id="pkg-debianrules">
10268 <heading><file>debian/rules</file> - the main building script</heading>
10271 See <ref id="debianrules">.
10275 <sect1 id="pkg-srcsubstvars">
10276 <heading><file>debian/substvars</file> and variable substitutions</heading>
10279 See <ref id="substvars">.
10285 <heading><file>debian/files</file></heading>
10288 See <ref id="debianfiles">.
10292 <sect1><heading><file>debian/tmp</file>
10296 This is the canonical temporary location for the
10297 construction of binary packages by the <tt>binary</tt>
10298 target. The directory <file>tmp</file> serves as the root of
10299 the file system tree as it is being constructed (for
10300 example, by using the package's upstream makefiles install
10301 targets and redirecting the output there), and it also
10302 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10303 id="pkg-bincreating">.
10307 If several binary packages are generated from the same
10308 source tree it is usual to use several
10309 <file>debian/tmp<var>something</var></file> directories, for
10310 example <file>tmp-a</file> or <file>tmp-doc</file>.
10314 Whatever <file>tmp</file> directories are created and used by
10315 <tt>binary</tt> must of course be removed by the
10316 <tt>clean</tt> target.</p></sect1>
10320 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10324 As it exists on the FTP site, a Debian source package
10325 consists of three related files. You must have the right
10326 versions of all three to be able to use them.
10331 <tag>Debian source control file - <tt>.dsc</tt></tag>
10333 This file is a control file used by <prgn>dpkg-source</prgn>
10334 to extract a source package.
10335 See <ref id="debiansourcecontrolfiles">.
10339 Original source archive -
10341 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10347 This is a compressed (with <tt>gzip -9</tt>)
10348 <prgn>tar</prgn> file containing the source code from
10349 the upstream authors of the program.
10354 Debian package diff -
10356 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10362 This is a unified context diff (<tt>diff -u</tt>)
10363 giving the changes which are required to turn the
10364 original source into the Debian source. These changes
10365 may only include editing and creating plain files.
10366 The permissions of files, the targets of symbolic
10367 links and the characteristics of special files or
10368 pipes may not be changed and no files may be removed
10373 All the directories in the diff must exist, except the
10374 <file>debian</file> subdirectory of the top of the source
10375 tree, which will be created by
10376 <prgn>dpkg-source</prgn> if necessary when unpacking.
10380 The <prgn>dpkg-source</prgn> program will
10381 automatically make the <file>debian/rules</file> file
10382 executable (see below).</p></item>
10387 If there is no original source code - for example, if the
10388 package is specially prepared for Debian or the Debian
10389 maintainer is the same as the upstream maintainer - the
10390 format is slightly different: then there is no diff, and the
10392 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10393 and preferably contains a directory named
10394 <file><var>package</var>-<var>version</var></file>.
10399 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10402 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10403 Debian source package. However, if it is not available it
10404 is possible to unpack a Debian source archive as follows:
10405 <enumlist compact="compact">
10408 Untar the tarfile, which will create a <file>.orig</file>
10412 <p>Rename the <file>.orig</file> directory to
10413 <file><var>package</var>-<var>version</var></file>.</p>
10417 Create the subdirectory <file>debian</file> at the top of
10418 the source tree.</p>
10420 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10422 <item><p>Untar the tarfile again if you want a copy of the original
10423 source code alongside the Debian version.</p>
10428 It is not possible to generate a valid Debian source archive
10429 without using <prgn>dpkg-source</prgn>. In particular,
10430 attempting to use <prgn>diff</prgn> directly to generate the
10431 <file>.diff.gz</file> file will not work.
10435 <heading>Restrictions on objects in source packages</heading>
10438 The source package may not contain any hard links
10440 This is not currently detected when building source
10441 packages, but only when extracting
10445 Hard links may be permitted at some point in the
10446 future, but would require a fair amount of
10448 </footnote>, device special files, sockets or setuid or
10451 Setgid directories are allowed.
10456 The source packaging tools manage the changes between the
10457 original and Debian source using <prgn>diff</prgn> and
10458 <prgn>patch</prgn>. Turning the original source tree as
10459 included in the <file>.orig.tar.gz</file> into the Debian
10460 package source must not involve any changes which cannot be
10461 handled by these tools. Problematic changes which cause
10462 <prgn>dpkg-source</prgn> to halt with an error when
10463 building the source package are:
10464 <list compact="compact">
10465 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10467 <item><p>Changing the targets of symbolic links.</p>
10469 <item><p>Creating directories, other than <file>debian</file>.</p>
10471 <item><p>Changes to the contents of binary files.</p></item>
10472 </list> Changes which cause <prgn>dpkg-source</prgn> to
10473 print a warning but continue anyway are:
10474 <list compact="compact">
10477 Removing files, directories or symlinks.
10479 Renaming a file is not treated specially - it is
10480 seen as the removal of the old file (which
10481 generates a warning, but is otherwise ignored),
10482 and the creation of the new one.
10488 Changed text files which are missing the usual final
10489 newline (either in the original or the modified
10494 Changes which are not represented, but which are not detected by
10495 <prgn>dpkg-source</prgn>, are:
10496 <list compact="compact">
10497 <item><p>Changing the permissions of files (other than
10498 <file>debian/rules</file>) and directories.</p></item>
10503 The <file>debian</file> directory and <file>debian/rules</file>
10504 are handled specially by <prgn>dpkg-source</prgn> - before
10505 applying the changes it will create the <file>debian</file>
10506 directory, and afterwards it will make
10507 <file>debian/rules</file> world-executable.
10513 <appendix id="pkg-controlfields">
10514 <heading>Control files and their fields (from old Packaging Manual)</heading>
10517 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10518 data in a common format, known as control files. Binary and
10519 source packages have control data as do the <file>.changes</file>
10520 files which control the installation of uploaded files, and
10521 <prgn>dpkg</prgn>'s internal databases are in a similar
10526 <heading>Syntax of control files</heading>
10529 See <ref id="controlsyntax">.
10533 It is important to note that there are several fields which
10534 are optional as far as <prgn>dpkg</prgn> and the related
10535 tools are concerned, but which must appear in every Debian
10536 package, or whose omission may cause problems.
10541 <heading>List of fields</heading>
10544 See <ref id="controlfieldslist">.
10548 This section now contains only the fields that didn't belong
10549 to the Policy manual.
10552 <sect1 id="pkg-f-Filename">
10553 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10556 These fields in <tt>Packages</tt> files give the
10557 filename(s) of (the parts of) a package in the
10558 distribution directories, relative to the root of the
10559 Debian hierarchy. If the package has been split into
10560 several parts the parts are all listed in order, separated
10565 <sect1 id="pkg-f-Size">
10566 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10569 These fields in <file>Packages</file> files give the size (in
10570 bytes, expressed in decimal) and MD5 checksum of the
10571 file(s) which make(s) up a binary package in the
10572 distribution. If the package is split into several parts
10573 the values for the parts are listed in order, separated by
10578 <sect1 id="pkg-f-Status">
10579 <heading><tt>Status</tt></heading>
10582 This field in <prgn>dpkg</prgn>'s status file records
10583 whether the user wants a package installed, removed or
10584 left alone, whether it is broken (requiring
10585 re-installation) or not and what its current state on the
10586 system is. Each of these pieces of information is a
10591 <sect1 id="pkg-f-Config-Version">
10592 <heading><tt>Config-Version</tt></heading>
10595 If a package is not installed or not configured, this
10596 field in <prgn>dpkg</prgn>'s status file records the last
10597 version of the package which was successfully
10602 <sect1 id="pkg-f-Conffiles">
10603 <heading><tt>Conffiles</tt></heading>
10606 This field in <prgn>dpkg</prgn>'s status file contains
10607 information about the automatically-managed configuration
10608 files held by a package. This field should <em>not</em>
10609 appear anywhere in a package!
10614 <heading>Obsolete fields</heading>
10617 These are still recognized by <prgn>dpkg</prgn> but should
10618 not appear anywhere any more.
10620 <taglist compact="compact">
10622 <tag><tt>Revision</tt></tag>
10623 <tag><tt>Package-Revision</tt></tag>
10624 <tag><tt>Package_Revision</tt></tag>
10626 The Debian revision part of the package version was
10627 at one point in a separate control file field. This
10628 field went through several names.
10631 <tag><tt>Recommended</tt></tag>
10632 <item>Old name for <tt>Recommends</tt>.</item>
10634 <tag><tt>Optional</tt></tag>
10635 <item>Old name for <tt>Suggests</tt>.</item>
10637 <tag><tt>Class</tt></tag>
10638 <item>Old name for <tt>Priority</tt>.</item>
10647 <appendix id="pkg-conffiles">
10648 <heading>Configuration file handling (from old Packaging Manual)</heading>
10651 <prgn>dpkg</prgn> can do a certain amount of automatic
10652 handling of package configuration files.
10656 Whether this mechanism is appropriate depends on a number of
10657 factors, but basically there are two approaches to any
10658 particular configuration file.
10662 The easy method is to ship a best-effort configuration in the
10663 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10664 handle updates. If the user is unlikely to want to edit the
10665 file, but you need them to be able to without losing their
10666 changes, and a new package with a changed version of the file
10667 is only released infrequently, this is a good approach.
10671 The hard method is to build the configuration file from
10672 scratch in the <prgn>postinst</prgn> script, and to take the
10673 responsibility for fixing any mistakes made in earlier
10674 versions of the package automatically. This will be
10675 appropriate if the file is likely to need to be different on
10679 <sect><heading>Automatic handling of configuration files by
10684 A package may contain a control area file called
10685 <tt>conffiles</tt>. This file should be a list of filenames
10686 of configuration files needing automatic handling, separated
10687 by newlines. The filenames should be absolute pathnames,
10688 and the files referred to should actually exist in the
10693 When a package is upgraded <prgn>dpkg</prgn> will process
10694 the configuration files during the configuration stage,
10695 shortly before it runs the package's <prgn>postinst</prgn>
10700 For each file it checks to see whether the version of the
10701 file included in the package is the same as the one that was
10702 included in the last version of the package (the one that is
10703 being upgraded from); it also compares the version currently
10704 installed on the system with the one shipped with the last
10709 If neither the user nor the package maintainer has changed
10710 the file, it is left alone. If one or the other has changed
10711 their version, then the changed version is preferred - i.e.,
10712 if the user edits their file, but the package maintainer
10713 doesn't ship a different version, the user's changes will
10714 stay, silently, but if the maintainer ships a new version
10715 and the user hasn't edited it the new version will be
10716 installed (with an informative message). If both have
10717 changed their version the user is prompted about the problem
10718 and must resolve the differences themselves.
10722 The comparisons are done by calculating the MD5 message
10723 digests of the files, and storing the MD5 of the file as it
10724 was included in the most recent version of the package.
10728 When a package is installed for the first time
10729 <prgn>dpkg</prgn> will install the file that comes with it,
10730 unless that would mean overwriting a file already on the
10735 However, note that <prgn>dpkg</prgn> will <em>not</em>
10736 replace a conffile that was removed by the user (or by a
10737 script). This is necessary because with some programs a
10738 missing file produces an effect hard or impossible to
10739 achieve in another way, so that a missing file needs to be
10740 kept that way if the user did it.
10744 Note that a package should <em>not</em> modify a
10745 <prgn>dpkg</prgn>-handled conffile in its maintainer
10746 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10747 the user confusing and possibly dangerous options for
10748 conffile update when the package is upgraded.</p>
10751 <sect><heading>Fully-featured maintainer script configuration
10756 For files which contain site-specific information such as
10757 the hostname and networking details and so forth, it is
10758 better to create the file in the package's
10759 <prgn>postinst</prgn> script.
10763 This will typically involve examining the state of the rest
10764 of the system to determine values and other information, and
10765 may involve prompting the user for some information which
10766 can't be obtained some other way.
10770 When using this method there are a couple of important
10771 issues which should be considered:
10775 If you discover a bug in the program which generates the
10776 configuration file, or if the format of the file changes
10777 from one version to the next, you will have to arrange for
10778 the postinst script to do something sensible - usually this
10779 will mean editing the installed configuration file to remove
10780 the problem or change the syntax. You will have to do this
10781 very carefully, since the user may have changed the file,
10782 perhaps to fix the very problem that your script is trying
10783 to deal with - you will have to detect these situations and
10784 deal with them correctly.
10788 If you do go down this route it's probably a good idea to
10789 make the program that generates the configuration file(s) a
10790 separate program in <file>/usr/sbin</file>, by convention called
10791 <file><var>package</var>config</file> and then run that if
10792 appropriate from the post-installation script. The
10793 <tt><var>package</var>config</tt> program should not
10794 unquestioningly overwrite an existing configuration - if its
10795 mode of operation is geared towards setting up a package for
10796 the first time (rather than any arbitrary reconfiguration
10797 later) you should have it check whether the configuration
10798 already exists, and require a <tt>--force</tt> flag to
10799 overwrite it.</p></sect>
10802 <appendix id="pkg-alternatives"><heading>Alternative versions of
10803 an interface - <prgn>update-alternatives</prgn> (from old
10808 When several packages all provide different versions of the
10809 same program or file it is useful to have the system select a
10810 default, but to allow the system administrator to change it
10811 and have their decisions respected.
10815 For example, there are several versions of the <prgn>vi</prgn>
10816 editor, and there is no reason to prevent all of them from
10817 being installed at once, each under their own name
10818 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10819 Nevertheless it is desirable to have the name <tt>vi</tt>
10820 refer to something, at least by default.
10824 If all the packages involved cooperate, this can be done with
10825 <prgn>update-alternatives</prgn>.
10829 Each package provides its own version under its own name, and
10830 calls <prgn>update-alternatives</prgn> in its postinst to
10831 register its version (and again in its prerm to deregister
10836 See the man page <manref name="update-alternatives"
10837 section="8"> for details.
10841 If <prgn>update-alternatives</prgn> does not seem appropriate
10842 you may wish to consider using diversions instead.</p>
10845 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10846 package's version of a file (from old Packaging Manual)
10850 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10851 when it reinstalls the package it belongs to, and to have it
10852 put the file from the package somewhere else instead.
10856 This can be used locally to override a package's version of a
10857 file, or by one package to override another's version (or
10858 provide a wrapper for it).
10862 Before deciding to use a diversion, read <ref
10863 id="pkg-alternatives"> to see if you really want a diversion
10864 rather than several alternative versions of a program.
10868 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10869 and updated by a special program <prgn>dpkg-divert</prgn>.
10870 Please see <manref name="dpkg-divert" section="8"> for full
10871 details of its operation.
10875 When a package wishes to divert a file from another, it should
10876 call <prgn>dpkg-divert</prgn> in its preinst to add the
10877 diversion and rename the existing file. For example,
10878 supposing that a <prgn>smailwrapper</prgn> package wishes to
10879 install a wrapper around <file>/usr/sbin/smail</file>:
10881 dpkg-divert --package smailwrapper --add --rename \
10882 --divert /usr/sbin/smail.real /usr/sbin/smail
10883 </example> The <tt>--package smailwrapper</tt> ensures that
10884 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10885 can bypass the diversion and get installed as the true version.
10886 It's safe to add the diversion unconditionally on upgrades since
10887 it will be left unchanged if it already exists, but
10888 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10889 message, make the command conditional on the version from which
10890 the package is being upgraded:
10892 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10893 dpkg-divert --package smailwrapper --add --rename \
10894 --divert /usr/sbin/smail.real /usr/sbin/smail
10896 </example> where <tt>1.0-2</tt> is the version at which the
10897 diversion was first added to the package. Running the command
10898 during abort-upgrade is pointless but harmless.
10902 The postrm has to do the reverse:
10904 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10905 dpkg-divert --package smailwrapper --remove --rename \
10906 --divert /usr/sbin/smail.real /usr/sbin/smail
10908 </example> If the diversion was added at a particular version, the
10909 postrm should also handle the failure case of upgrading from an
10910 older version (unless the older version is so old that direct
10911 upgrades are no longer supported):
10913 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10914 dpkg-divert --package smailwrapper --remove --rename \
10915 --divert /usr/sbin/smail.real /usr/sbin/smail
10917 </example> where <tt>1.02-2</tt> is the version at which the
10918 diversion was first added to the package. The postrm should not
10919 remove the diversion on upgrades both because there's no reason to
10920 remove the diversion only to immediately re-add it and since the
10921 postrm of the old package is run after unpacking so the removal of
10922 the diversion will fail.
10926 Do not attempt to divert a file which is vitally important for
10927 the system's operation - when using <prgn>dpkg-divert</prgn>
10928 there is a time, after it has been diverted but before
10929 <prgn>dpkg</prgn> has installed the new version, when the file
10930 does not exist.</p>
10935 <!-- Local variables: -->
10936 <!-- indent-tabs-mode: t -->
10938 <!-- vim:set ai et sts=2 sw=2 tw=76: -->