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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 <heading>The package name</heading>
809 Every package must have a name that's unique within the Debian
814 The package name is included in the control field
815 <tt>Package</tt>, the format of which is described
816 in <ref id="f-Package">.
817 The package name is also included as a part of the file name
818 of the <tt>.deb</tt> file.
823 <heading>The version of a package</heading>
826 Every package has a version number recorded in its
827 <tt>Version</tt> control file field, described in
828 <ref id="f-Version">.
832 The package management system imposes an ordering on version
833 numbers, so that it can tell whether packages are being up- or
834 downgraded and so that package system front end applications
835 can tell whether a package it finds available is newer than
836 the one installed on the system. The version number format
837 has the most significant parts (as far as comparison is
838 concerned) at the beginning.
842 If an upstream package has problematic version numbers they
843 should be converted to a sane form for use in the
844 <tt>Version</tt> field.
848 <heading>Version numbers based on dates</heading>
851 In general, Debian packages should use the same version
852 numbers as the upstream sources.
856 However, in some cases where the upstream version number is
857 based on a date (e.g., a development "snapshot" release) the
858 package management system cannot handle these version
859 numbers without epochs. For example, dpkg will consider
860 "96May01" to be greater than "96Dec24".
864 To prevent having to use epochs for every new upstream
865 version, the date based portion of the version number
866 should be changed to the following format in such cases:
867 "19960501", "19961224". It is up to the maintainer whether
868 they want to bother the upstream maintainer to change
869 the version numbers upstream, too.
873 Note that other version formats based on dates which are
874 parsed correctly by the package management system should
875 <em>not</em> be changed.
879 Native Debian packages (i.e., packages which have been
880 written especially for Debian) whose version numbers include
881 dates should always use the "YYYYMMDD" format.
887 <sect id="maintainer">
888 <heading>The maintainer of a package</heading>
891 Every package must have a maintainer. The maintainer may be one
892 person or a group of people reachable from a common email
893 address, such as a mailing list. The maintainer is responsible
894 for maintaining the Debian packaging files, evaluating and
895 responding appropriately to reported bugs, uploading new
896 versions of the package (either directly or through a sponsor),
897 ensuring that the package is placed in the appropriate archive
898 area and included in Debian releases as appropriate for the
899 stability and utility of the package, and requesting removal of
900 the package from the Debian distribution if it is no longer
901 useful or maintainable.
905 The maintainer must be specified in the <tt>Maintainer</tt>
906 control field with their correct name and a working email
907 address. The email address given in the <tt>Maintainer</tt>
908 control field must accept mail from those role accounts in
909 Debian used to send automated mails regarding the package. This
910 includes non-spam mail from the bug-tracking system, all mail
911 from the Debian archive maintenance software, and other role
912 accounts or automated processes that are commonly agreed on by
913 the project.<footnote>
914 A sample implementation of such a whitelist written for the
915 Mailman mailing list management software is used for mailing
916 lists hosted by alioth.debian.org.
918 If one person or team maintains several packages, they should
919 use the same form of their name and email address in
920 the <tt>Maintainer</tt> fields of those packages.
924 The format of the <tt>Maintainer</tt> control field is
925 described in <ref id="f-Maintainer">.
929 If the maintainer of the package is a team of people with a
930 shared email address, the <tt>Uploaders</tt> control field must
931 be present and must contain at least one human with their
932 personal email address. See <ref id="f-Uploaders"> for the
933 syntax of that field.
937 If the maintainer of a package no longer has time or desire to
938 maintain a package, it will be orphaned according to the
939 procedure described in the Debian Developer's Reference
940 (see <ref id="related">). The maintainer then
941 becomes <tt>Debian QA Group <packages@qa.debian.org></tt>.
942 These packages are considered maintained by the Debian project
943 as a whole until someone else volunteers to take over
948 <sect id="descriptions">
949 <heading>The description of a package</heading>
952 Every Debian package must have an extended description
953 stored in the appropriate field of the control record.
954 The technical information about the format of the
955 <tt>Description</tt> field is in <ref id="f-Description">.
959 The description should describe the package (the program) to a
960 user (system administrator) who has never met it before so that
961 they have enough information to decide whether they want to
962 install it. This description should not just be copied verbatim
963 from the program's documentation.
967 Put important information first, both in the synopsis and
968 extended description. Sometimes only the first part of the
969 synopsis or of the description will be displayed. You can
970 assume that there will usually be a way to see the whole
971 extended description.
975 The description should also give information about the
976 significant dependencies and conflicts between this package
977 and others, so that the user knows why these dependencies and
978 conflicts have been declared.
982 Instructions for configuring or using the package should
983 not be included (that is what installation scripts,
984 manual pages, info files, etc., are for). Copyright
985 statements and other administrivia should not be included
986 either (that is what the copyright file is for).
989 <sect1 id="synopsis"><heading>The single line synopsis</heading>
992 The single line synopsis should be kept brief - certainly
997 Do not include the package name in the synopsis line. The
998 display software knows how to display this already, and you
999 do not need to state it. Remember that in many situations
1000 the user may only see the synopsis line - make it as
1001 informative as you can.
1006 <sect1 id="extendeddesc"><heading>The extended description</heading>
1009 Do not try to continue the single line synopsis into the
1010 extended description. This will not work correctly when
1011 the full description is displayed, and makes no sense
1012 where only the summary (the single line synopsis) is
1017 The extended description should describe what the package
1018 does and how it relates to the rest of the system (in terms
1019 of, for example, which subsystem it is which part of).
1023 The description field needs to make sense to anyone, even
1024 people who have no idea about any of the things the
1025 package deals with.<footnote>
1026 The blurb that comes with a program in its
1027 announcements and/or <prgn>README</prgn> files is
1028 rarely suitable for use in a description. It is
1029 usually aimed at people who are already in the
1030 community where the package is used.
1039 <heading>Dependencies</heading>
1042 Every package must specify the dependency information
1043 about other packages that are required for the first to
1048 For example, a dependency entry must be provided for any
1049 shared libraries required by a dynamically-linked executable
1050 binary in a package.
1054 Packages are not required to declare any dependencies they
1055 have on other packages which are marked <tt>Essential</tt>
1056 (see below), and should not do so unless they depend on a
1057 particular version of that package.<footnote>
1059 Essential is needed in part to avoid unresolvable dependency
1060 loops on upgrade. If packages add unnecessary dependencies
1061 on packages in this set, the chances that there
1062 <strong>will</strong> be an unresolvable dependency loop
1063 caused by forcing these Essential packages to be configured
1064 first before they need to be is greatly increased. It also
1065 increases the chances that frontends will be unable to
1066 <strong>calculate</strong> an upgrade path, even if one
1070 Also, functionality is rarely ever removed from the
1071 Essential set, but <em>packages</em> have been removed from
1072 the Essential set when the functionality moved to a
1073 different package. So depending on these packages <em>just
1074 in case</em> they stop being essential does way more harm
1081 Sometimes, a package requires another package to be installed
1082 <em>and</em> configured before it can be installed. In this
1083 case, you must specify a <tt>Pre-Depends</tt> entry for
1088 You should not specify a <tt>Pre-Depends</tt> entry for a
1089 package before this has been discussed on the
1090 <tt>debian-devel</tt> mailing list and a consensus about
1091 doing that has been reached.
1095 The format of the package interrelationship control fields is
1096 described in <ref id="relationships">.
1100 <sect id="virtual_pkg">
1101 <heading>Virtual packages</heading>
1104 Sometimes, there are several packages which offer
1105 more-or-less the same functionality. In this case, it's
1106 useful to define a <em>virtual package</em> whose name
1107 describes that common functionality. (The virtual
1108 packages only exist logically, not physically; that's why
1109 they are called <em>virtual</em>.) The packages with this
1110 particular function will then <em>provide</em> the virtual
1111 package. Thus, any other package requiring that function
1112 can simply depend on the virtual package without having to
1113 specify all possible packages individually.
1117 All packages should use virtual package names where
1118 appropriate, and arrange to create new ones if necessary.
1119 They should not use virtual package names (except privately,
1120 amongst a cooperating group of packages) unless they have
1121 been agreed upon and appear in the list of virtual package
1122 names. (See also <ref id="virtual">)
1126 The latest version of the authoritative list of virtual
1127 package names can be found in the <tt>debian-policy</tt> package.
1128 It is also available from the Debian web mirrors at
1129 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1130 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1134 The procedure for updating the list is described in the preface
1141 <heading>Base system</heading>
1144 The <tt>base system</tt> is a minimum subset of the Debian
1145 GNU/Linux system that is installed before everything else
1146 on a new system. Only very few packages are allowed to form
1147 part of the base system, in order to keep the required disk
1152 The base system consists of all those packages with priority
1153 <tt>required</tt> or <tt>important</tt>. Many of them will
1154 be tagged <tt>essential</tt> (see below).
1159 <heading>Essential packages</heading>
1162 Essential is defined as the minimal set of functionality that
1163 must be available and usable on the system at all times, even
1164 when packages are in an unconfigured (but unpacked) state.
1165 Packages are tagged <tt>essential</tt> for a system using the
1166 <tt>Essential</tt> control file field. The format of the
1167 <tt>Essential</tt> control field is described in <ref
1172 Since these packages cannot be easily removed (one has to
1173 specify an extra <em>force option</em> to
1174 <prgn>dpkg</prgn> to do so), this flag must not be used
1175 unless absolutely necessary. A shared library package
1176 must not be tagged <tt>essential</tt>; dependencies will
1177 prevent its premature removal, and we need to be able to
1178 remove it when it has been superseded.
1182 Since dpkg will not prevent upgrading of other packages
1183 while an <tt>essential</tt> package is in an unconfigured
1184 state, all <tt>essential</tt> packages must supply all of
1185 their core functionality even when unconfigured. If the
1186 package cannot satisfy this requirement it must not be
1187 tagged as essential, and any packages depending on this
1188 package must instead have explicit dependency fields as
1193 Maintainers should take great care in adding any programs,
1194 interfaces, or functionality to <tt>essential</tt> packages.
1195 Packages may assume that functionality provided by
1196 <tt>essential</tt> packages is always available without
1197 declaring explicit dependencies, which means that removing
1198 functionality from the Essential set is very difficult and is
1199 almost never done. Any capability added to an
1200 <tt>essential</tt> package therefore creates an obligation to
1201 support that capability as part of the Essential set in
1206 You must not tag any packages <tt>essential</tt> before
1207 this has been discussed on the <tt>debian-devel</tt>
1208 mailing list and a consensus about doing that has been
1213 <sect id="maintscripts">
1214 <heading>Maintainer Scripts</heading>
1217 The package installation scripts should avoid producing
1218 output which is unnecessary for the user to see and
1219 should rely on <prgn>dpkg</prgn> to stave off boredom on
1220 the part of a user installing many packages. This means,
1221 amongst other things, using the <tt>--quiet</tt> option on
1222 <prgn>install-info</prgn>.
1226 Errors which occur during the execution of an installation
1227 script must be checked and the installation must not
1228 continue after an error.
1232 Note that in general <ref id="scripts"> applies to package
1233 maintainer scripts, too.
1237 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1238 to another package without consulting the maintainer of that
1239 package first. When adding or removing diversions, package
1240 maintainer scripts must provide the <tt>--package</tt> flag
1241 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1245 All packages which supply an instance of a common command
1246 name (or, in general, filename) should generally use
1247 <prgn>update-alternatives</prgn>, so that they may be
1248 installed together. If <prgn>update-alternatives</prgn>
1249 is not used, then each package must use
1250 <tt>Conflicts</tt> to ensure that other packages are
1251 de-installed. (In this case, it may be appropriate to
1252 specify a conflict against earlier versions of something
1253 that previously did not use
1254 <prgn>update-alternatives</prgn>; this is an exception to
1255 the usual rule that versioned conflicts should be
1259 <sect1 id="maintscriptprompt">
1260 <heading>Prompting in maintainer scripts</heading>
1262 Package maintainer scripts may prompt the user if
1263 necessary. Prompting must be done by communicating
1264 through a program, such as <prgn>debconf</prgn>, which
1265 conforms to the Debian Configuration Management
1266 Specification, version 2 or higher.
1270 Packages which are essential, or which are dependencies of
1271 essential packages, may fall back on another prompting method
1272 if no such interface is available when they are executed.
1276 The Debian Configuration Management Specification is included
1277 in the <file>debconf_specification</file> files in the
1278 <package>debian-policy</package> package.
1279 It is also available from the Debian web mirrors at
1280 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1281 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1285 Packages which use the Debian Configuration Management
1286 Specification may contain an additional
1287 <prgn>config</prgn> script and a <tt>templates</tt>
1288 file in their control archive<footnote>
1289 The control.tar.gz inside the .deb.
1290 See <manref name="deb" section="5">.
1292 The <prgn>config</prgn> script might be run before the
1293 <prgn>preinst</prgn> script, and before the package is unpacked
1294 or any of its dependencies or pre-dependencies are satisfied.
1295 Therefore it must work using only the tools present in
1296 <em>essential</em> packages.<footnote>
1297 <package>Debconf</package> or another tool that
1298 implements the Debian Configuration Management
1299 Specification will also be installed, and any
1300 versioned dependencies on it will be satisfied
1301 before preconfiguration begins.
1306 Packages which use the Debian Configuration Management
1307 Specification must allow for translation of their user-visible
1308 messages by using a gettext-based system such as the one
1309 provided by the <package>po-debconf</package> package.
1313 Packages should try to minimize the amount of prompting
1314 they need to do, and they should ensure that the user
1315 will only ever be asked each question once. This means
1316 that packages should try to use appropriate shared
1317 configuration files (such as <file>/etc/papersize</file> and
1318 <file>/etc/news/server</file>), and shared
1319 <package>debconf</package> variables rather than each
1320 prompting for their own list of required pieces of
1325 It also means that an upgrade should not ask the same
1326 questions again, unless the user has used
1327 <tt>dpkg --purge</tt> to remove the package's configuration.
1328 The answers to configuration questions should be stored in an
1329 appropriate place in <file>/etc</file> so that the user can
1330 modify them, and how this has been done should be
1335 If a package has a vitally important piece of
1336 information to pass to the user (such as "don't run me
1337 as I am, you must edit the following configuration files
1338 first or you risk your system emitting badly-formatted
1339 messages"), it should display this in the
1340 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1341 prompt the user to hit return to acknowledge the
1342 message. Copyright messages do not count as vitally
1343 important (they belong in
1344 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1345 neither do instructions on how to use a program (these
1346 should be in on-line documentation, where all the users
1351 Any necessary prompting should almost always be confined
1352 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1353 script. If it is done in the <prgn>postinst</prgn>, it
1354 should be protected with a conditional so that
1355 unnecessary prompting doesn't happen if a package's
1356 installation fails and the <prgn>postinst</prgn> is
1357 called with <tt>abort-upgrade</tt>,
1358 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1368 <heading>Source packages</heading>
1370 <sect id="standardsversion">
1371 <heading>Standards conformance</heading>
1374 Source packages should specify the most recent version number
1375 of this policy document with which your package complied
1376 when it was last updated.
1380 This information may be used to file bug reports
1381 automatically if your package becomes too much out of date.
1385 The version is specified in the <tt>Standards-Version</tt>
1387 The format of the <tt>Standards-Version</tt> field is
1388 described in <ref id="f-Standards-Version">.
1392 You should regularly, and especially if your package has
1393 become out of date, check for the newest Policy Manual
1394 available and update your package, if necessary. When your
1395 package complies with the new standards you should update the
1396 <tt>Standards-Version</tt> source package field and
1397 release it.<footnote>
1398 See the file <file>upgrading-checklist</file> for
1399 information about policy which has changed between
1400 different versions of this document.
1406 <sect id="pkg-relations">
1407 <heading>Package relationships</heading>
1410 Source packages should specify which binary packages they
1411 require to be installed or not to be installed in order to
1412 build correctly. For example, if building a package
1413 requires a certain compiler, then the compiler should be
1414 specified as a build-time dependency.
1418 It is not necessary to explicitly specify build-time
1419 relationships on a minimal set of packages that are always
1420 needed to compile, link and put in a Debian package a
1421 standard "Hello World!" program written in C or C++. The
1422 required packages are called <em>build-essential</em>, and
1423 an informational list can be found in
1424 <file>/usr/share/doc/build-essential/list</file> (which is
1425 contained in the <tt>build-essential</tt>
1428 <list compact="compact">
1430 This allows maintaining the list separately
1431 from the policy documents (the list does not
1432 need the kind of control that the policy
1436 Having a separate package allows one to install
1437 the build-essential packages on a machine, as
1438 well as allowing other packages such as tasks to
1439 require installation of the build-essential
1440 packages using the depends relation.
1443 The separate package allows bug reports against
1444 the list to be categorized separately from
1445 the policy management process in the BTS.
1452 When specifying the set of build-time dependencies, one
1453 should list only those packages explicitly required by the
1454 build. It is not necessary to list packages which are
1455 required merely because some other package in the list of
1456 build-time dependencies depends on them.<footnote>
1457 The reason for this is that dependencies change, and
1458 you should list all those packages, and <em>only</em>
1459 those packages that <em>you</em> need directly. What
1460 others need is their business. For example, if you
1461 only link against <file>libimlib</file>, you will need to
1462 build-depend on <package>libimlib2-dev</package> but
1463 not against any <tt>libjpeg*</tt> packages, even
1464 though <tt>libimlib2-dev</tt> currently depends on
1465 them: installation of <package>libimlib2-dev</package>
1466 will automatically ensure that all of its run-time
1467 dependencies are satisfied.
1472 If build-time dependencies are specified, it must be
1473 possible to build the package and produce working binaries
1474 on a system with only essential and build-essential
1475 packages installed and also those required to satisfy the
1476 build-time relationships (including any implied
1477 relationships). In particular, this means that version
1478 clauses should be used rigorously in build-time
1479 relationships so that one cannot produce bad or
1480 inconsistently configured packages when the relationships
1481 are properly satisfied.
1485 <ref id="relationships"> explains the technical details.
1490 <heading>Changes to the upstream sources</heading>
1493 If changes to the source code are made that are not
1494 specific to the needs of the Debian system, they should be
1495 sent to the upstream authors in whatever form they prefer
1496 so as to be included in the upstream version of the
1501 If you need to configure the package differently for
1502 Debian or for Linux, and the upstream source doesn't
1503 provide a way to do so, you should add such configuration
1504 facilities (for example, a new <prgn>autoconf</prgn> test
1505 or <tt>#define</tt>) and send the patch to the upstream
1506 authors, with the default set to the way they originally
1507 had it. You can then easily override the default in your
1508 <file>debian/rules</file> or wherever is appropriate.
1512 You should make sure that the <prgn>configure</prgn> utility
1513 detects the correct architecture specification string
1514 (refer to <ref id="arch-spec"> for details).
1518 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1519 <prgn>configure</prgn> scripts are used, you should edit the
1520 <file>.in</file> files rather than editing the
1521 <prgn>Makefile</prgn> directly. This allows the user to
1522 reconfigure the package if necessary. You should
1523 <em>not</em> configure the package and edit the generated
1524 <prgn>Makefile</prgn>! This makes it impossible for someone
1525 else to later reconfigure the package without losing the
1531 <sect id="dpkgchangelog">
1532 <heading>Debian changelog: <file>debian/changelog</file></heading>
1535 Changes in the Debian version of the package should be
1536 briefly explained in the Debian changelog file
1537 <file>debian/changelog</file>.<footnote>
1539 Mistakes in changelogs are usually best rectified by
1540 making a new changelog entry rather than "rewriting
1541 history" by editing old changelog entries.
1544 This includes modifications
1545 made in the Debian package compared to the upstream one
1546 as well as other changes and updates to the package.
1548 Although there is nothing stopping an author who is also
1549 the Debian maintainer from using this changelog for all
1550 their changes, it will have to be renamed if the Debian
1551 and upstream maintainers become different people. In such
1552 a case, however, it might be better to maintain the package
1553 as a non-native package.
1558 The format of the <file>debian/changelog</file> allows the
1559 package building tools to discover which version of the package
1560 is being built and find out other release-specific information.
1564 That format is a series of entries like this:
1566 <example compact="compact">
1567 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1569 [optional blank line(s), stripped]
1571 * <var>change details</var>
1572 <var>more change details</var>
1574 [blank line(s), included in output of dpkg-parsechangelog]
1576 * <var>even more change details</var>
1578 [optional blank line(s), stripped]
1580 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1585 <var>package</var> and <var>version</var> are the source
1586 package name and version number.
1590 <var>distribution(s)</var> lists the distributions where
1591 this version should be installed when it is uploaded - it
1592 is copied to the <tt>Distribution</tt> field in the
1593 <file>.changes</file> file. See <ref id="f-Distribution">.
1597 <var>urgency</var> is the value for the <tt>Urgency</tt>
1598 field in the <file>.changes</file> file for the upload
1599 (see <ref id="f-Urgency">). It is not possible to specify
1600 an urgency containing commas; commas are used to separate
1601 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1602 <prgn>dpkg</prgn> changelog format (though there is
1603 currently only one useful <var>keyword</var>,
1608 The change details may in fact be any series of lines
1609 starting with at least two spaces, but conventionally each
1610 change starts with an asterisk and a separating space and
1611 continuation lines are indented so as to bring them in
1612 line with the start of the text above. Blank lines may be
1613 used here to separate groups of changes, if desired.
1617 If this upload resolves bugs recorded in the Bug Tracking
1618 System (BTS), they may be automatically closed on the
1619 inclusion of this package into the Debian archive by
1620 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1621 in the change details.<footnote>
1622 To be precise, the string should match the following
1623 Perl regular expression:
1625 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1627 Then all of the bug numbers listed will be closed by the
1628 archive maintenance script (<prgn>katie</prgn>) using the
1629 <var>version</var> of the changelog entry.
1631 This information is conveyed via the <tt>Closes</tt> field
1632 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1636 The maintainer name and email address used in the changelog
1637 should be the details of the person uploading <em>this</em>
1638 version. They are <em>not</em> necessarily those of the
1639 usual package maintainer. The information here will be
1640 copied to the <tt>Changed-By</tt> field in the
1641 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1642 and then later used to send an acknowledgement when the
1643 upload has been installed.
1647 The <var>date</var> has the following format<footnote>
1648 This is the same as the format generated by <tt>date
1650 </footnote> (compatible and with the same semantics of
1651 RFC 2822 and RFC 5322):
1652 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1654 <list compact="compact">
1656 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1659 dd is a one- or two-digit day of the month (01-31)
1662 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1665 <item>yyyy is the four-digit year (e.g. 2010)</item>
1666 <item>hh is the two-digit hour (00-23)</item>
1667 <item>mm is the two-digit minutes (00-59)</item>
1668 <item>ss is the two-digit seconds (00-60)</item>
1670 +zzzz or -zzzz is the the time zone offset from Coordinated
1671 Universal Time (UTC). "+" indicates that the time is ahead
1672 of (i.e., east of) UTC and "-" indicates that the time is
1673 behind (i.e., west of) UTC. The first two digits indicate
1674 the hour difference from UTC and the last two digits
1675 indicate the number of additional minutes difference from
1676 UTC. The last two digits must be in the range 00-59.
1682 The first "title" line with the package name must start
1683 at the left hand margin. The "trailer" line with the
1684 maintainer and date details must be preceded by exactly
1685 one space. The maintainer details and the date must be
1686 separated by exactly two spaces.
1690 The entire changelog must be encoded in UTF-8.
1694 For more information on placement of the changelog files
1695 within binary packages, please see <ref id="changelogs">.
1699 <sect id="dpkgcopyright">
1700 <heading>Copyright: <file>debian/copyright</file></heading>
1702 Every package must be accompanied by a verbatim copy of its
1703 copyright information and distribution license in the file
1704 <file>/usr/share/doc/<var>package</var>/copyright</file>
1705 (see <ref id="copyrightfile"> for further details). Also see
1706 <ref id="pkgcopyright"> for further considerations related
1707 to copyrights for packages.
1711 <heading>Error trapping in makefiles</heading>
1714 When <prgn>make</prgn> invokes a command in a makefile
1715 (including your package's upstream makefiles and
1716 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1717 means that <prgn>sh</prgn>'s usual bad error handling
1718 properties apply: if you include a miniature script as one
1719 of the commands in your makefile you'll find that if you
1720 don't do anything about it then errors are not detected
1721 and <prgn>make</prgn> will blithely continue after
1726 Every time you put more than one shell command (this
1727 includes using a loop) in a makefile command you
1728 must make sure that errors are trapped. For
1729 simple compound commands, such as changing directory and
1730 then running a program, using <tt>&&</tt> rather
1731 than semicolon as a command separator is sufficient. For
1732 more complex commands including most loops and
1733 conditionals you should include a separate <tt>set -e</tt>
1734 command at the start of every makefile command that's
1735 actually one of these miniature shell scripts.
1739 <sect id="timestamps">
1740 <heading>Time Stamps</heading>
1742 Maintainers should preserve the modification times of the
1743 upstream source files in a package, as far as is reasonably
1745 The rationale is that there is some information conveyed
1746 by knowing the age of the file, for example, you could
1747 recognize that some documentation is very old by looking
1748 at the modification time, so it would be nice if the
1749 modification time of the upstream source would be
1755 <sect id="restrictions">
1756 <heading>Restrictions on objects in source packages</heading>
1759 The source package may not contain any hard links<footnote>
1761 This is not currently detected when building source
1762 packages, but only when extracting
1766 Hard links may be permitted at some point in the
1767 future, but would require a fair amount of
1770 </footnote>, device special files, sockets or setuid or
1771 setgid files.<footnote>
1772 Setgid directories are allowed.
1777 <sect id="debianrules">
1778 <heading>Main building script: <file>debian/rules</file></heading>
1781 This file must be an executable makefile, and contains the
1782 package-specific recipes for compiling the package and
1783 building binary package(s) from the source.
1787 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1788 so that it can be invoked by saying its name rather than
1789 invoking <prgn>make</prgn> explicitly. That is, invoking
1790 either of <tt>make -f debian/rules <em>args...</em></tt>
1791 or <tt>./debian/rules <em>args...</em></tt> must result in
1796 Since an interactive <file>debian/rules</file> script makes it
1797 impossible to auto-compile that package and also makes it
1798 hard for other people to reproduce the same binary
1799 package, all <em>required targets</em> must be
1800 non-interactive. At a minimum, required targets are the
1801 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1802 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1803 <em>binary-indep</em>, and <em>build</em>. It also follows
1804 that any target that these targets depend on must also be
1809 The targets are as follows (required unless stated otherwise):
1811 <tag><tt>build</tt></tag>
1814 The <tt>build</tt> target should perform all the
1815 configuration and compilation of the package.
1816 If a package has an interactive pre-build
1817 configuration routine, the Debian source package
1818 must either be built after this has taken place (so
1819 that the binary package can be built without rerunning
1820 the configuration) or the configuration routine
1821 modified to become non-interactive. (The latter is
1822 preferable if there are architecture-specific features
1823 detected by the configuration routine.)
1827 For some packages, notably ones where the same
1828 source tree is compiled in different ways to produce
1829 two binary packages, the <tt>build</tt> target
1830 does not make much sense. For these packages it is
1831 good enough to provide two (or more) targets
1832 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1833 for each of the ways of building the package, and a
1834 <tt>build</tt> target that does nothing. The
1835 <tt>binary</tt> target will have to build the
1836 package in each of the possible ways and make the
1837 binary package out of each.
1841 The <tt>build</tt> target must not do anything
1842 that might require root privilege.
1846 The <tt>build</tt> target may need to run the
1847 <tt>clean</tt> target first - see below.
1851 When a package has a configuration and build routine
1852 which takes a long time, or when the makefiles are
1853 poorly designed, or when <tt>build</tt> needs to
1854 run <tt>clean</tt> first, it is a good idea to
1855 <tt>touch build</tt> when the build process is
1856 complete. This will ensure that if <tt>debian/rules
1857 build</tt> is run again it will not rebuild the whole
1859 Another common way to do this is for <tt>build</tt>
1860 to depend on <prgn>build-stamp</prgn> and to do
1861 nothing else, and for the <prgn>build-stamp</prgn>
1862 target to do the building and to <tt>touch
1863 build-stamp</tt> on completion. This is
1864 especially useful if the build routine creates a
1865 file or directory called <tt>build</tt>; in such a
1866 case, <tt>build</tt> will need to be listed as
1867 a phony target (i.e., as a dependency of the
1868 <tt>.PHONY</tt> target). See the documentation of
1869 <prgn>make</prgn> for more information on phony
1875 <tag><tt>build-arch</tt> (optional),
1876 <tt>build-indep</tt> (optional)
1880 A package may also provide both of the targets
1881 <tt>build-arch</tt> and <tt>build-indep</tt>.
1882 The <tt>build-arch</tt> target, if provided, should
1883 perform all the configuration and compilation required for
1884 producing all architecture-dependant binary packages
1885 (those packages for which the body of the
1886 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1887 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1888 target, if provided, should perform all the configuration
1889 and compilation required for producing all
1890 architecture-independent binary packages (those packages
1891 for which the body of the <tt>Architecture</tt> field
1892 in <tt>debian/control</tt> is <tt>all</tt>).
1893 The <tt>build</tt> target should depend on those of the
1894 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1895 are provided in the rules file.<footnote>
1896 The intent of this split is so that binary-only builds
1897 need not install the dependencies required for
1898 the <tt>build-indep</tt> target. However, this is not
1899 yet used in practice since <tt>dpkg-buildpackage
1900 -B</tt>, and therefore the autobuilders,
1901 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1902 due to the difficulties in determining whether the
1903 optional <tt>build-arch</tt> target exists.
1908 If one or both of the targets <tt>build-arch</tt> and
1909 <tt>build-indep</tt> are not provided, then invoking
1910 <file>debian/rules</file> with one of the not-provided
1911 targets as arguments should produce a exit status code
1912 of 2. Usually this is provided automatically by make
1913 if the target is missing.
1917 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1918 must not do anything that might require root privilege.
1922 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1923 <tt>binary-indep</tt>
1927 The <tt>binary</tt> target must be all that is
1928 necessary for the user to build the binary package(s)
1929 produced from this source package. It is
1930 split into two parts: <prgn>binary-arch</prgn> builds
1931 the binary packages which are specific to a particular
1932 architecture, and <tt>binary-indep</tt> builds
1933 those which are not.
1936 <tt>binary</tt> may be (and commonly is) a target with
1937 no commands which simply depends on
1938 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1941 Both <tt>binary-*</tt> targets should depend on the
1942 <tt>build</tt> target, or on the appropriate
1943 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1944 provided, so that the package is built if it has not
1945 been already. It should then create the relevant
1946 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1947 make their control files and <prgn>dpkg-deb</prgn> to
1948 build them and place them in the parent of the top
1953 Both the <tt>binary-arch</tt> and
1954 <tt>binary-indep</tt> targets <em>must</em> exist.
1955 If one of them has nothing to do (which will always be
1956 the case if the source generates only a single binary
1957 package, whether architecture-dependent or not), it
1958 must still exist and must always succeed.
1962 The <tt>binary</tt> targets must be invoked as
1964 The <prgn>fakeroot</prgn> package often allows one
1965 to build a package correctly even without being
1971 <tag><tt>clean</tt></tag>
1974 This must undo any effects that the <tt>build</tt>
1975 and <tt>binary</tt> targets may have had, except
1976 that it should leave alone any output files created in
1977 the parent directory by a run of a <tt>binary</tt>
1982 If a <tt>build</tt> file is touched at the end of
1983 the <tt>build</tt> target, as suggested above, it
1984 should be removed as the first action that
1985 <tt>clean</tt> performs, so that running
1986 <tt>build</tt> again after an interrupted
1987 <tt>clean</tt> doesn't think that everything is
1992 The <tt>clean</tt> target may need to be
1993 invoked as root if <tt>binary</tt> has been
1994 invoked since the last <tt>clean</tt>, or if
1995 <tt>build</tt> has been invoked as root (since
1996 <tt>build</tt> may create directories, for
2001 <tag><tt>get-orig-source</tt> (optional)</tag>
2004 This target fetches the most recent version of the
2005 original source package from a canonical archive site
2006 (via FTP or WWW, for example), does any necessary
2007 rearrangement to turn it into the original source
2008 tar file format described below, and leaves it in the
2013 This target may be invoked in any directory, and
2014 should take care to clean up any temporary files it
2019 This target is optional, but providing it if
2020 possible is a good idea.
2024 <tag><tt>patch</tt> (optional)</tag>
2027 This target performs whatever additional actions are
2028 required to make the source ready for editing (unpacking
2029 additional upstream archives, applying patches, etc.).
2030 It is recommended to be implemented for any package where
2031 <tt>dpkg-source -x</tt> does not result in source ready
2032 for additional modification. See
2033 <ref id="readmesource">.
2039 The <tt>build</tt>, <tt>binary</tt> and
2040 <tt>clean</tt> targets must be invoked with the current
2041 directory being the package's top-level directory.
2046 Additional targets may exist in <file>debian/rules</file>,
2047 either as published or undocumented interfaces or for the
2048 package's internal use.
2052 The architectures we build on and build for are determined
2053 by <prgn>make</prgn> variables using the utility
2054 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2055 You can determine the
2056 Debian architecture and the GNU style architecture
2057 specification string for the build machine (the machine type
2058 we are building on) as well as for the host machine (the
2059 machine type we are building for). Here is a list of
2060 supported <prgn>make</prgn> variables:
2061 <list compact="compact">
2063 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2066 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2069 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2072 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2073 specification string)
2076 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2077 <tt>DEB_*_GNU_TYPE</tt>)
2080 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2081 <tt>DEB_*_GNU_TYPE</tt>)
2083 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2084 the build machine or <tt>HOST</tt> for specification of the
2089 Backward compatibility can be provided in the rules file
2090 by setting the needed variables to suitable default
2091 values; please refer to the documentation of
2092 <prgn>dpkg-architecture</prgn> for details.
2096 It is important to understand that the <tt>DEB_*_ARCH</tt>
2097 string only determines which Debian architecture we are
2098 building on or for. It should not be used to get the CPU
2099 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2100 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2101 GNU style variables should generally only be used with upstream
2105 <sect1 id="debianrules-options">
2106 <heading><file>debian/rules</file> and
2107 <tt>DEB_BUILD_OPTIONS</tt></heading>
2110 Supporting the standardized environment variable
2111 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2112 contain several flags to change how a package is compiled and
2113 built. Each flag must be in the form <var>flag</var> or
2114 <var>flag</var>=<var>options</var>. If multiple flags are
2115 given, they must be separated by whitespace.<footnote>
2116 Some packages support any delimiter, but whitespace is the
2117 easiest to parse inside a makefile and avoids ambiguity with
2118 flag values that contain commas.
2120 <var>flag</var> must start with a lowercase letter
2121 (<tt>a-z</tt>) and consist only of lowercase letters,
2122 numbers (<tt>0-9</tt>), and the characters
2123 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2124 <var>options</var> must not contain whitespace. The same
2125 tag should not be given multiple times with conflicting
2126 values. Package maintainers may assume that
2127 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2131 The meaning of the following tags has been standardized:
2135 This tag says to not run any build-time test suite
2136 provided by the package.
2140 The presence of this tag means that the package should
2141 be compiled with a minimum of optimization. For C
2142 programs, it is best to add <tt>-O0</tt> to
2143 <tt>CFLAGS</tt> (although this is usually the default).
2144 Some programs might fail to build or run at this level
2145 of optimization; it may be necessary to use
2146 <tt>-O1</tt>, for example.
2150 This tag means that the debugging symbols should not be
2151 stripped from the binary during installation, so that
2152 debugging information may be included in the package.
2154 <tag>parallel=n</tag>
2156 This tag means that the package should be built using up
2157 to <tt>n</tt> parallel processes if the package build
2158 system supports this.<footnote>
2159 Packages built with <tt>make</tt> can often implement
2160 this by passing the <tt>-j</tt><var>n</var> option to
2163 If the package build system does not support parallel
2164 builds, this string must be ignored. If the package
2165 build system only supports a lower level of concurrency
2166 than <var>n</var>, the package should be built using as
2167 many parallel processes as the package build system
2168 supports. It is up to the package maintainer to decide
2169 whether the package build times are long enough and the
2170 package build system is robust enough to make supporting
2171 parallel builds worthwhile.
2177 Unknown flags must be ignored by <file>debian/rules</file>.
2181 The following makefile snippet is an example of how one may
2182 implement the build options; you will probably have to
2183 massage this example in order to make it work for your
2185 <example compact="compact">
2188 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2189 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2190 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2191 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2193 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2198 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2199 INSTALL_PROGRAM += -s
2201 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2202 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2203 MAKEFLAGS += -j$(NUMJOBS)
2208 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2209 # Code to run the package test suite.
2216 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2217 <sect id="substvars">
2218 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2221 When <prgn>dpkg-gencontrol</prgn>,
2222 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2223 generate control files they perform variable substitutions
2224 on their output just before writing it. Variable
2225 substitutions have the form <tt>${<var>variable</var>}</tt>.
2226 The optional file <file>debian/substvars</file> contains
2227 variable substitutions to be used; variables can also be set
2228 directly from <file>debian/rules</file> using the <tt>-V</tt>
2229 option to the source packaging commands, and certain
2230 predefined variables are also available.
2234 The <file>debian/substvars</file> file is usually generated and
2235 modified dynamically by <file>debian/rules</file> targets, in
2236 which case it must be removed by the <tt>clean</tt> target.
2240 See <manref name="deb-substvars" section="5"> for full
2241 details about source variable substitutions, including the
2242 format of <file>debian/substvars</file>.</p>
2245 <sect id="debianwatch">
2246 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2249 This is an optional, recommended control file for the
2250 <tt>uscan</tt> utility which defines how to automatically
2251 scan ftp or http sites for newly available updates of the
2252 package. This is used by <url id="
2253 http://dehs.alioth.debian.org/"> and other Debian QA tools
2254 to help with quality control and maintenance of the
2255 distribution as a whole.
2260 <sect id="debianfiles">
2261 <heading>Generated files list: <file>debian/files</file></heading>
2264 This file is not a permanent part of the source tree; it
2265 is used while building packages to record which files are
2266 being generated. <prgn>dpkg-genchanges</prgn> uses it
2267 when it generates a <file>.changes</file> file.
2271 It should not exist in a shipped source package, and so it
2272 (and any backup files or temporary files such as
2273 <file>files.new</file><footnote>
2274 <file>files.new</file> is used as a temporary file by
2275 <prgn>dpkg-gencontrol</prgn> and
2276 <prgn>dpkg-distaddfile</prgn> - they write a new
2277 version of <tt>files</tt> here before renaming it,
2278 to avoid leaving a corrupted copy if an error
2280 </footnote>) should be removed by the
2281 <tt>clean</tt> target. It may also be wise to
2282 ensure a fresh start by emptying or removing it at the
2283 start of the <tt>binary</tt> target.
2287 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2288 package, it adds an entry to <file>debian/files</file> for the
2289 <file>.deb</file> file that will be created when <tt>dpkg-deb
2290 --build</tt> is run for that binary package. So for most
2291 packages all that needs to be done with this file is to
2292 delete it in the <tt>clean</tt> target.
2296 If a package upload includes files besides the source
2297 package and any binary packages whose control files were
2298 made with <prgn>dpkg-gencontrol</prgn> then they should be
2299 placed in the parent of the package's top-level directory
2300 and <prgn>dpkg-distaddfile</prgn> should be called to add
2301 the file to the list in <file>debian/files</file>.</p>
2304 <sect id="embeddedfiles">
2305 <heading>Convenience copies of code</heading>
2308 Some software packages include in their distribution convenience
2309 copies of code from other software packages, generally so that
2310 users compiling from source don't have to download multiple
2311 packages. Debian packages should not make use of these
2312 convenience copies unless the included package is explicitly
2313 intended to be used in this way.<footnote>
2314 For example, parts of the GNU build system work like this.
2316 If the included code is already in the Debian archive in the
2317 form of a library, the Debian packaging should ensure that
2318 binary packages reference the libraries already in Debian and
2319 the convenience copy is not used. If the included code is not
2320 already in Debian, it should be packaged separately as a
2321 prerequisite if possible.
2323 Having multiple copies of the same code in Debian is
2324 inefficient, often creates either static linking or shared
2325 library conflicts, and, most importantly, increases the
2326 difficulty of handling security vulnerabilities in the
2332 <sect id="readmesource">
2333 <heading>Source package handling:
2334 <file>debian/README.source</file></heading>
2337 If running <prgn>dpkg-source -x</prgn> on a source package
2338 doesn't produce the source of the package, ready for editing,
2339 and allow one to make changes and run
2340 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2341 without taking any additional steps, creating a
2342 <file>debian/README.source</file> documentation file is
2343 recommended. This file should explain how to do all of the
2346 <item>Generate the fully patched source, in a form ready for
2347 editing, that would be built to create Debian
2348 packages. Doing this with a <tt>patch</tt> target in
2349 <file>debian/rules</file> is recommended; see
2350 <ref id="debianrules">.</item>
2351 <item>Modify the source and save those modifications so that
2352 they will be applied when building the package.</item>
2353 <item>Remove source modifications that are currently being
2354 applied when building the package.</item>
2355 <item>Optionally, document what steps are necessary to
2356 upgrade the Debian source package to a new upstream version,
2357 if applicable.</item>
2359 This explanation should include specific commands and mention
2360 any additional required Debian packages. It should not assume
2361 familiarity with any specific Debian packaging system or patch
2366 This explanation may refer to a documentation file installed by
2367 one of the package's build dependencies provided that the
2368 referenced documentation clearly explains these tasks and is not
2369 a general reference manual.
2373 <file>debian/README.source</file> may also include any other
2374 information that would be helpful to someone modifying the
2375 source package. Even if the package doesn't fit the above
2376 description, maintainers are encouraged to document in a
2377 <file>debian/README.source</file> file any source package with a
2378 particularly complex or unintuitive source layout or build
2379 system (for example, a package that builds the same source
2380 multiple times to generate different binary packages).
2386 <chapt id="controlfields">
2387 <heading>Control files and their fields</heading>
2390 The package management system manipulates data represented in
2391 a common format, known as <em>control data</em>, stored in
2392 <em>control files</em>.
2393 Control files are used for source packages, binary packages and
2394 the <file>.changes</file> files which control the installation
2395 of uploaded files<footnote>
2396 <prgn>dpkg</prgn>'s internal databases are in a similar
2401 <sect id="controlsyntax">
2402 <heading>Syntax of control files</heading>
2405 A control file consists of one or more paragraphs of
2407 The paragraphs are also sometimes referred to as stanzas.
2409 The paragraphs are separated by blank lines. Some control
2410 files allow only one paragraph; others allow several, in
2411 which case each paragraph usually refers to a different
2412 package. (For example, in source packages, the first
2413 paragraph refers to the source package, and later paragraphs
2414 refer to binary packages generated from the source.)
2418 Each paragraph consists of a series of data fields; each
2419 field consists of the field name, followed by a colon and
2420 then the data/value associated with that field. It ends at
2421 the end of the (logical) line. Horizontal whitespace
2422 (spaces and tabs) may occur immediately before or after the
2423 value and is ignored there; it is conventional to put a
2424 single space after the colon. For example, a field might
2426 <example compact="compact">
2429 the field name is <tt>Package</tt> and the field value
2434 A paragraph must not contain more than one instance of a
2435 particular field name.
2439 Many fields' values may span several lines; in this case
2440 each continuation line must start with a space or a tab.
2441 Any trailing spaces or tabs at the end of individual
2442 lines of a field value are ignored.
2446 In fields where it is specified that lines may not wrap,
2447 only a single line of data is allowed and whitespace is not
2448 significant in a field body. Whitespace must not appear
2449 inside names (of packages, architectures, files or anything
2450 else) or version numbers, or between the characters of
2451 multi-character version relationships.
2455 Field names are not case-sensitive, but it is usual to
2456 capitalize the field names using mixed case as shown below.
2457 Field values are case-sensitive unless the description of the
2458 field says otherwise.
2462 Blank lines, or lines consisting only of spaces and tabs,
2463 are not allowed within field values or between fields - that
2464 would mean a new paragraph.
2468 All control files must be encoded in UTF-8.
2472 <sect id="sourcecontrolfiles">
2473 <heading>Source package control files -- <file>debian/control</file></heading>
2476 The <file>debian/control</file> file contains the most vital
2477 (and version-independent) information about the source package
2478 and about the binary packages it creates.
2482 The first paragraph of the control file contains information about
2483 the source package in general. The subsequent sets each describe a
2484 binary package that the source tree builds.
2488 The fields in the general paragraph (the first one, for the source
2491 <list compact="compact">
2492 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2493 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2494 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2495 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2496 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2497 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2498 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2499 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2504 The fields in the binary package paragraphs are:
2506 <list compact="compact">
2507 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2508 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2509 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2510 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2511 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2512 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2513 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2514 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2519 The syntax and semantics of the fields are described below.
2523 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2524 generate control files for binary packages (see below), by
2525 <prgn>dpkg-genchanges</prgn> to generate the
2526 <file>.changes</file> file to accompany the upload, and by
2527 <prgn>dpkg-source</prgn> when it creates the
2528 <file>.dsc</file> source control file as part of a source
2529 archive. Many fields are permitted to span multiple lines in
2530 <file>debian/control</file> but not in any other control
2531 file. These tools are responsible for removing the line
2532 breaks from such fields when using fields from
2533 <file>debian/control</file> to generate other control files.
2537 The fields here may contain variable references - their
2538 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2539 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2540 when they generate output control files.
2541 See <ref id="substvars"> for details.
2545 In addition to the control file syntax described <qref
2546 id="controlsyntax">above</qref>, this file may also contain
2547 comment lines starting with <tt>#</tt> without any preceding
2548 whitespace. All such lines are ignored, even in the middle of
2549 continuation lines for a multiline field, and do not end a
2555 <sect id="binarycontrolfiles">
2556 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2559 The <file>DEBIAN/control</file> file contains the most vital
2560 (and version-dependent) information about a binary package. It
2561 consists of a single paragraph.
2565 The fields in this file are:
2567 <list compact="compact">
2568 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2569 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2570 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2571 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2572 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2573 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2575 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2576 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2577 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2579 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2584 <sect id="debiansourcecontrolfiles">
2585 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2588 This file consists of a single paragraph, possibly surrounded by
2589 a PGP signature. The fields of that paragraph are listed below.
2590 Their syntax is described above, in <ref id="pkg-controlfields">.
2592 <list compact="compact">
2593 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2594 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2595 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2596 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2597 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2598 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2599 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2600 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2601 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2602 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2603 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2604 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2605 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2610 The source package control file is generated by
2611 <prgn>dpkg-source</prgn> when it builds the source
2612 archive, from other files in the source package,
2613 described above. When unpacking, it is checked against
2614 the files and directories in the other parts of the
2620 <sect id="debianchangesfiles">
2621 <heading>Debian changes files -- <file>.changes</file></heading>
2624 The <file>.changes</file> files are used by the Debian archive
2625 maintenance software to process updates to packages. They
2626 consist of a single paragraph, possibly surrounded by a PGP
2627 signature. That paragraph contains information from the
2628 <file>debian/control</file> file and other data about the
2629 source package gathered via <file>debian/changelog</file>
2630 and <file>debian/rules</file>.
2634 <file>.changes</file> files have a format version that is
2635 incremented whenever the documented fields or their meaning
2636 change. This document describes format &changesversion;.
2640 The fields in this file are:
2642 <list compact="compact">
2643 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2644 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2645 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2646 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2647 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2649 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2651 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2653 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2654 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2655 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2656 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2657 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2658 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2663 <sect id="controlfieldslist">
2664 <heading>List of fields</heading>
2666 <sect1 id="f-Source">
2667 <heading><tt>Source</tt></heading>
2670 This field identifies the source package name.
2674 In <file>debian/control</file> or a <file>.dsc</file> file,
2675 this field must contain only the name of the source package.
2679 In a binary package control file or a <file>.changes</file>
2680 file, the source package name may be followed by a version
2681 number in parentheses<footnote>
2682 It is customary to leave a space after the package name
2683 if a version number is specified.
2685 This version number may be omitted (and is, by
2686 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2687 the <tt>Version</tt> field of the binary package in
2688 question. The field itself may be omitted from a binary
2689 package control file when the source package has the same
2690 name and version as the binary package.
2694 Package names (both source and binary,
2695 see <ref id="f-Package">) must consist only of lower case
2696 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2697 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2698 (<tt>.</tt>). They must be at least two characters long and
2699 must start with an alphanumeric character.
2703 <sect1 id="f-Maintainer">
2704 <heading><tt>Maintainer</tt></heading>
2707 The package maintainer's name and email address. The name
2708 must come first, then the email address inside angle
2709 brackets <tt><></tt> (in RFC822 format).
2713 If the maintainer's name contains a full stop then the
2714 whole field will not work directly as an email address due
2715 to a misfeature in the syntax specified in RFC822; a
2716 program using this field as an address must check for this
2717 and correct the problem if necessary (for example by
2718 putting the name in round brackets and moving it to the
2719 end, and bringing the email address forward).
2723 See <ref id="maintainer"> for additional requirements and
2724 information about package maintainers.
2728 <sect1 id="f-Uploaders">
2729 <heading><tt>Uploaders</tt></heading>
2732 List of the names and email addresses of co-maintainers of the
2733 package, if any. If the package has other maintainers besides
2734 the one named in the <qref id="f-Maintainer">Maintainer
2735 field</qref>, their names and email addresses should be listed
2736 here. The format of each entry is the same as that of the
2737 Maintainer field, and multiple entries must be comma
2742 This is normally an optional field, but if
2743 the <tt>Maintainer</tt> control field names a group of people
2744 and a shared email address, the <tt>Uploaders</tt> field must
2745 be present and must contain at least one human with their
2746 personal email address.
2750 Any parser that interprets the Uploaders field in
2751 <file>debian/control</file> must permit it to span multiple
2752 lines. Line breaks in an Uploaders field that spans multiple
2753 lines are not significant and the semantics of the field are
2754 the same as if the line breaks had not been present.
2758 <sect1 id="f-Changed-By">
2759 <heading><tt>Changed-By</tt></heading>
2762 The name and email address of the person who prepared this
2763 version of the package, usually a maintainer. The syntax is
2764 the same as for the <qref id="f-Maintainer">Maintainer
2769 <sect1 id="f-Section">
2770 <heading><tt>Section</tt></heading>
2773 This field specifies an application area into which the package
2774 has been classified. See <ref id="subsections">.
2778 When it appears in the <file>debian/control</file> file,
2779 it gives the value for the subfield of the same name in
2780 the <tt>Files</tt> field of the <file>.changes</file> file.
2781 It also gives the default for the same field in the binary
2786 <sect1 id="f-Priority">
2787 <heading><tt>Priority</tt></heading>
2790 This field represents how important it is that the user
2791 have the package installed. See <ref id="priorities">.
2795 When it appears in the <file>debian/control</file> file,
2796 it gives the value for the subfield of the same name in
2797 the <tt>Files</tt> field of the <file>.changes</file> file.
2798 It also gives the default for the same field in the binary
2803 <sect1 id="f-Package">
2804 <heading><tt>Package</tt></heading>
2807 The name of the binary package.
2811 Binary package names must follow the same syntax and
2812 restrictions as source package names. See <ref id="f-Source">
2817 <sect1 id="f-Architecture">
2818 <heading><tt>Architecture</tt></heading>
2821 Depending on context and the control file used, the
2822 <tt>Architecture</tt> field can include the following sets of
2826 A unique single word identifying a Debian machine
2827 architecture as described in <ref id="arch-spec">.
2830 An architecture wildcard identifying a set of Debian
2831 machine architectures, see <ref id="arch-wildcard-spec">.
2832 <tt>any</tt> matches all Debian machine architectures
2833 and is the most frequently used.
2836 <tt>all</tt>, which indicates an
2837 architecture-independent package.
2840 <tt>source</tt>, which indicates a source package.
2846 In the main <file>debian/control</file> file in the source
2847 package, this field may contain the special
2848 value <tt>all</tt>, the special architecture
2849 wildcard <tt>any</tt>, or a list of specific and wildcard
2850 architectures separated by spaces. If <tt>all</tt>
2851 or <tt>any</tt> appears, that value must be the entire
2852 contents of the field. Most packages will use
2853 either <tt>all</tt> or <tt>any</tt>.
2857 Specifying a specific list of architectures indicates that the
2858 source will build an architecture-dependent package only on
2859 architectures included in the list. Specifying a list of
2860 architecture wildcards indicates that the source will build an
2861 architecture-dependent package on only those architectures
2862 that match any of the specified architecture wildcards.
2863 Specifying a list of architectures or architecture wildcards
2864 other than <tt>any</tt> is for the minority of cases where a
2865 program is not portable or is not useful on some
2866 architectures. Where possible, the program should be made
2871 In the source package control file <file>.dsc</file>, this
2872 field may contain either the architecture
2873 wildcard <tt>any</tt> or a list of architectures and
2874 architecture wildcards separated by spaces. If a list is
2875 given, it may include (or consist solely of) the special
2876 value <tt>all</tt>. In other words, in <file>.dsc</file>
2877 files unlike the <file>debian/control</file>, <tt>all</tt> may
2878 occur in combination with specific architectures.
2879 The <tt>Architecture</tt> field in the source package control
2880 file <file>.dsc</file> is generally constructed from
2881 the <tt>Architecture</tt> fields in
2882 the <file>debian/control</file> in the source package.
2886 Specifying <tt>any</tt> indicates that the source package
2887 isn't dependent on any particular architecture and should
2888 compile fine on any one. The produced binary package(s)
2889 will either be specific to whatever the current build
2890 architecture is or will be architecture-independent.
2894 Specifying only <tt>all</tt> indicates that the source package
2895 will only build architecture-independent packages. If this is
2896 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2897 <tt>any</tt> implies that the source package will build at
2898 least one architecture-dependent package.
2902 Specifying a list of architectures or architecture wildcards
2903 indicates that the source will build an architecture-dependent
2904 package, and will only work correctly on the listed or
2905 matching architectures. If the source package also builds at
2906 least one architecture-independent package, <tt>all</tt> will
2907 also be included in the list.
2911 In a <file>.changes</file> file, the <tt>Architecture</tt>
2912 field lists the architecture(s) of the package(s) currently
2913 being uploaded. This will be a list; if the source for the
2914 package is also being uploaded, the special
2915 entry <tt>source</tt> is also present. <tt>all</tt> will be
2916 present if any architecture-independent packages are being
2917 uploaded. Architecture wildcards such as <tt>any</tt> must
2918 never occur in the <tt>Architecture</tt> field in
2919 the <file>.changes</file> file.
2923 See <ref id="debianrules"> for information on how to get
2924 the architecture for the build process.
2928 <sect1 id="f-Essential">
2929 <heading><tt>Essential</tt></heading>
2932 This is a boolean field which may occur only in the
2933 control file of a binary package or in a per-package fields
2934 paragraph of a main source control data file.
2938 If set to <tt>yes</tt> then the package management system
2939 will refuse to remove the package (upgrading and replacing
2940 it is still possible). The other possible value is <tt>no</tt>,
2941 which is the same as not having the field at all.
2946 <heading>Package interrelationship fields:
2947 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2948 <tt>Recommends</tt>, <tt>Suggests</tt>,
2949 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2950 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2954 These fields describe the package's relationships with
2955 other packages. Their syntax and semantics are described
2956 in <ref id="relationships">.</p>
2959 <sect1 id="f-Standards-Version">
2960 <heading><tt>Standards-Version</tt></heading>
2963 The most recent version of the standards (the policy
2964 manual and associated texts) with which the package
2969 The version number has four components: major and minor
2970 version number and major and minor patch level. When the
2971 standards change in a way that requires every package to
2972 change the major number will be changed. Significant
2973 changes that will require work in many packages will be
2974 signaled by a change to the minor number. The major patch
2975 level will be changed for any change to the meaning of the
2976 standards, however small; the minor patch level will be
2977 changed when only cosmetic, typographical or other edits
2978 are made which neither change the meaning of the document
2979 nor affect the contents of packages.
2983 Thus only the first three components of the policy version
2984 are significant in the <em>Standards-Version</em> control
2985 field, and so either these three components or all four
2986 components may be specified.<footnote>
2987 In the past, people specified the full version number
2988 in the Standards-Version field, for example "2.3.0.0".
2989 Since minor patch-level changes don't introduce new
2990 policy, it was thought it would be better to relax
2991 policy and only require the first 3 components to be
2992 specified, in this example "2.3.0". All four
2993 components may still be used if someone wishes to do so.
2999 <sect1 id="f-Version">
3000 <heading><tt>Version</tt></heading>
3003 The version number of a package. The format is:
3004 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3008 The three components here are:
3010 <tag><var>epoch</var></tag>
3013 This is a single (generally small) unsigned integer. It
3014 may be omitted, in which case zero is assumed. If it is
3015 omitted then the <var>upstream_version</var> may not
3020 It is provided to allow mistakes in the version numbers
3021 of older versions of a package, and also a package's
3022 previous version numbering schemes, to be left behind.
3026 <tag><var>upstream_version</var></tag>
3029 This is the main part of the version number. It is
3030 usually the version number of the original ("upstream")
3031 package from which the <file>.deb</file> file has been made,
3032 if this is applicable. Usually this will be in the same
3033 format as that specified by the upstream author(s);
3034 however, it may need to be reformatted to fit into the
3035 package management system's format and comparison
3040 The comparison behavior of the package management system
3041 with respect to the <var>upstream_version</var> is
3042 described below. The <var>upstream_version</var>
3043 portion of the version number is mandatory.
3047 The <var>upstream_version</var> may contain only
3048 alphanumerics<footnote>
3049 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3051 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3052 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3053 tilde) and should start with a digit. If there is no
3054 <var>debian_revision</var> then hyphens are not allowed;
3055 if there is no <var>epoch</var> then colons are not
3060 <tag><var>debian_revision</var></tag>
3063 This part of the version number specifies the version of
3064 the Debian package based on the upstream version. It
3065 may contain only alphanumerics and the characters
3066 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3067 tilde) and is compared in the same way as the
3068 <var>upstream_version</var> is.
3072 It is optional; if it isn't present then the
3073 <var>upstream_version</var> may not contain a hyphen.
3074 This format represents the case where a piece of
3075 software was written specifically to be a Debian
3076 package, where the Debian package source must always
3077 be identical to the pristine source and therefore no
3078 revision indication is required.
3082 It is conventional to restart the
3083 <var>debian_revision</var> at <tt>1</tt> each time the
3084 <var>upstream_version</var> is increased.
3088 The package management system will break the version
3089 number apart at the last hyphen in the string (if there
3090 is one) to determine the <var>upstream_version</var> and
3091 <var>debian_revision</var>. The absence of a
3092 <var>debian_revision</var> is equivalent to a
3093 <var>debian_revision</var> of <tt>0</tt>.
3100 When comparing two version numbers, first the <var>epoch</var>
3101 of each are compared, then the <var>upstream_version</var> if
3102 <var>epoch</var> is equal, and then <var>debian_revision</var>
3103 if <var>upstream_version</var> is also equal.
3104 <var>epoch</var> is compared numerically. The
3105 <var>upstream_version</var> and <var>debian_revision</var>
3106 parts are compared by the package management system using the
3107 following algorithm:
3111 The strings are compared from left to right.
3115 First the initial part of each string consisting entirely of
3116 non-digit characters is determined. These two parts (one of
3117 which may be empty) are compared lexically. If a difference
3118 is found it is returned. The lexical comparison is a
3119 comparison of ASCII values modified so that all the letters
3120 sort earlier than all the non-letters and so that a tilde
3121 sorts before anything, even the end of a part. For example,
3122 the following parts are in sorted order from earliest to
3123 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3124 <tt>a</tt>.<footnote>
3125 One common use of <tt>~</tt> is for upstream pre-releases.
3126 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3127 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3132 Then the initial part of the remainder of each string which
3133 consists entirely of digit characters is determined. The
3134 numerical values of these two parts are compared, and any
3135 difference found is returned as the result of the comparison.
3136 For these purposes an empty string (which can only occur at
3137 the end of one or both version strings being compared) counts
3142 These two steps (comparing and removing initial non-digit
3143 strings and initial digit strings) are repeated until a
3144 difference is found or both strings are exhausted.
3148 Note that the purpose of epochs is to allow us to leave behind
3149 mistakes in version numbering, and to cope with situations
3150 where the version numbering scheme changes. It is
3151 <em>not</em> intended to cope with version numbers containing
3152 strings of letters which the package management system cannot
3153 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3154 silly orderings.<footnote>
3155 The author of this manual has heard of a package whose
3156 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3157 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3163 <sect1 id="f-Description">
3164 <heading><tt>Description</tt></heading>
3167 In a source or binary control file, the <tt>Description</tt>
3168 field contains a description of the binary package, consisting
3169 of two parts, the synopsis or the short description, and the
3170 long description. The field's format is as follows:
3175 Description: <single line synopsis>
3176 <extended description over several lines>
3181 The lines in the extended description can have these formats:
3187 Those starting with a single space are part of a paragraph.
3188 Successive lines of this form will be word-wrapped when
3189 displayed. The leading space will usually be stripped off.
3193 Those starting with two or more spaces. These will be
3194 displayed verbatim. If the display cannot be panned
3195 horizontally, the displaying program will line wrap them "hard"
3196 (i.e., without taking account of word breaks). If it can they
3197 will be allowed to trail off to the right. None, one or two
3198 initial spaces may be deleted, but the number of spaces
3199 deleted from each line will be the same (so that you can have
3200 indenting work correctly, for example).
3204 Those containing a single space followed by a single full stop
3205 character. These are rendered as blank lines. This is the
3206 <em>only</em> way to get a blank line<footnote>
3207 Completely empty lines will not be rendered as blank lines.
3208 Instead, they will cause the parser to think you're starting
3209 a whole new record in the control file, and will therefore
3210 likely abort with an error.
3215 Those containing a space, a full stop and some more characters.
3216 These are for future expansion. Do not use them.
3222 Do not use tab characters. Their effect is not predictable.
3226 See <ref id="descriptions"> for further information on this.
3230 In a <file>.changes</file> file, the <tt>Description</tt>
3231 field contains a summary of the descriptions for the packages
3232 being uploaded. For this case, the first line of the field
3233 value (the part on the same line as <tt>Description:</tt>) is
3234 always empty. The content of the field is expressed as
3235 continuation lines, one line per package. Each line is
3236 indented by one space and contains the name of a binary
3237 package, a space, a hyphen (<tt>-</tt>), a space, and the
3238 short description line from that package.
3242 <sect1 id="f-Distribution">
3243 <heading><tt>Distribution</tt></heading>
3246 In a <file>.changes</file> file or parsed changelog output
3247 this contains the (space-separated) name(s) of the
3248 distribution(s) where this version of the package should
3249 be installed. Valid distributions are determined by the
3250 archive maintainers.<footnote>
3251 Example distribution names in the Debian archive used in
3252 <file>.changes</file> files are:
3253 <taglist compact="compact">
3254 <tag><em>unstable</em></tag>
3256 This distribution value refers to the
3257 <em>developmental</em> part of the Debian distribution
3258 tree. Most new packages, new upstream versions of
3259 packages and bug fixes go into the <em>unstable</em>
3263 <tag><em>experimental</em></tag>
3265 The packages with this distribution value are deemed
3266 by their maintainers to be high risk. Oftentimes they
3267 represent early beta or developmental packages from
3268 various sources that the maintainers want people to
3269 try, but are not ready to be a part of the other parts
3270 of the Debian distribution tree.
3275 Others are used for updating stable releases or for
3276 security uploads. More information is available in the
3277 Debian Developer's Reference, section "The Debian
3281 The Debian archive software only supports listing a single
3282 distribution. Migration of packages to other distributions is
3283 handled outside of the upload process.
3288 <heading><tt>Date</tt></heading>
3291 This field includes the date the package was built or last
3292 edited. It must be in the same format as the <var>date</var>
3293 in a <file>debian/changelog</file> entry.
3297 The value of this field is usually extracted from the
3298 <file>debian/changelog</file> file - see
3299 <ref id="dpkgchangelog">).
3303 <sect1 id="f-Format">
3304 <heading><tt>Format</tt></heading>
3307 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3308 files, this field declares the format version of that file.
3309 The syntax of the field value is the same as that of
3310 a <qref id="f-Version">package version number</qref> except
3311 that no epoch or Debian revision is allowed. The format
3312 described in this document is <tt>&changesversion;</tt>.
3316 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3317 Debian source control</qref> files, this field declares the
3318 format of the source package. The field value is used by
3319 programs acting on a source package to interpret the list of
3320 files in the source package and determine how to unpack it.
3321 The syntax of the field value is a numeric major revision, a
3322 period, a numeric minor revision, and then an optional subtype
3323 after whitespace, which if specified is an alphanumeric word
3324 in parentheses. The subtype is optional in the syntax but may
3325 be mandatory for particular source format revisions.
3327 The source formats currently supported by the Debian archive
3328 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3329 and <tt>3.0 (quilt)</tt>.
3334 <sect1 id="f-Urgency">
3335 <heading><tt>Urgency</tt></heading>
3338 This is a description of how important it is to upgrade to
3339 this version from previous ones. It consists of a single
3340 keyword taking one of the values <tt>low</tt>,
3341 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3342 <tt>critical</tt><footnote>
3343 Other urgency values are supported with configuration
3344 changes in the archive software but are not used in Debian.
3345 The urgency affects how quickly a package will be considered
3346 for inclusion into the <tt>testing</tt> distribution and
3347 gives an indication of the importance of any fixes included
3348 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3349 treated as synonymous.
3350 </footnote> (not case-sensitive) followed by an optional
3351 commentary (separated by a space) which is usually in
3352 parentheses. For example:
3355 Urgency: low (HIGH for users of diversions)
3361 The value of this field is usually extracted from the
3362 <file>debian/changelog</file> file - see
3363 <ref id="dpkgchangelog">.
3367 <sect1 id="f-Changes">
3368 <heading><tt>Changes</tt></heading>
3371 This field contains the human-readable changes data, describing
3372 the differences between the last version and the current one.
3376 The first line of the field value (the part on the same line
3377 as <tt>Changes:</tt>) is always empty. The content of the
3378 field is expressed as continuation lines, with each line
3379 indented by at least one space. Blank lines must be
3380 represented by a line consisting only of a space and a full
3385 The value of this field is usually extracted from the
3386 <file>debian/changelog</file> file - see
3387 <ref id="dpkgchangelog">).
3391 Each version's change information should be preceded by a
3392 "title" line giving at least the version, distribution(s)
3393 and urgency, in a human-readable way.
3397 If data from several versions is being returned the entry
3398 for the most recent version should be returned first, and
3399 entries should be separated by the representation of a
3400 blank line (the "title" line may also be followed by the
3401 representation of a blank line).
3405 <sect1 id="f-Binary">
3406 <heading><tt>Binary</tt></heading>
3409 This field is a list of binary packages. Its syntax and
3410 meaning varies depending on the control file in which it
3415 When it appears in the <file>.dsc</file> file, it lists binary
3416 packages which a source package can produce, separated by
3418 A space after each comma is conventional.
3419 </footnote>. It may span multiple lines. The source package
3420 does not necessarily produce all of these binary packages for
3421 every architecture. The source control file doesn't contain
3422 details of which architectures are appropriate for which of
3423 the binary packages.
3427 When it appears in a <file>.changes</file> file, it lists the
3428 names of the binary packages being uploaded, separated by
3429 whitespace (not commas). It may span multiple lines.
3433 <sect1 id="f-Installed-Size">
3434 <heading><tt>Installed-Size</tt></heading>
3437 This field appears in the control files of binary packages,
3438 and in the <file>Packages</file> files. It gives an estimate
3439 of the total amount of disk space required to install the
3440 named package. Actual installed size may vary based on block
3441 size, file system properties, or actions taken by package
3446 The disk space is given as the integer value of the estimated
3447 installed size in bytes, divided by 1024 and rounded up.
3451 <sect1 id="f-Files">
3452 <heading><tt>Files</tt></heading>
3455 This field contains a list of files with information about
3456 each one. The exact information and syntax varies with
3461 In all cases, Files is a multiline field. The first line of
3462 the field value (the part on the same line as <tt>Files:</tt>)
3463 is always empty. The content of the field is expressed as
3464 continuation lines, one line per file. Each line must be
3465 indented by one space and contain a number of sub-fields,
3466 separated by spaces, as described below.
3470 In the <file>.dsc</file> file, each line contains the MD5
3471 checksum, size and filename of the tar file and (if
3472 applicable) diff file which make up the remainder of the
3473 source package<footnote>
3474 That is, the parts which are not the <tt>.dsc</tt>.
3475 </footnote>. For example:
3478 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3479 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3481 The exact forms of the filenames are described
3482 in <ref id="pkg-sourcearchives">.
3486 In the <file>.changes</file> file this contains one line per
3487 file being uploaded. Each line contains the MD5 checksum,
3488 size, section and priority and the filename. For example:
3491 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3492 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3493 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3494 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3496 The <qref id="f-Section">section</qref>
3497 and <qref id="f-Priority">priority</qref> are the values of
3498 the corresponding fields in the main source control file. If
3499 no section or priority is specified then <tt>-</tt> should be
3500 used, though section and priority values must be specified for
3501 new packages to be installed properly.
3505 The special value <tt>byhand</tt> for the section in a
3506 <tt>.changes</tt> file indicates that the file in question
3507 is not an ordinary package file and must by installed by
3508 hand by the distribution maintainers. If the section is
3509 <tt>byhand</tt> the priority should be <tt>-</tt>.
3513 If a new Debian revision of a package is being shipped and
3514 no new original source archive is being distributed the
3515 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3516 entry for the original source archive
3517 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3518 but the <file>.changes</file> file should leave it out. In
3519 this case the original source archive on the distribution
3520 site must match exactly, byte-for-byte, the original
3521 source archive which was used to generate the
3522 <file>.dsc</file> file and diff which are being uploaded.</p>
3525 <sect1 id="f-Closes">
3526 <heading><tt>Closes</tt></heading>
3529 A space-separated list of bug report numbers that the upload
3530 governed by the .changes file closes.
3534 <sect1 id="f-Homepage">
3535 <heading><tt>Homepage</tt></heading>
3538 The URL of the web site for this package, preferably (when
3539 applicable) the site from which the original source can be
3540 obtained and any additional upstream documentation or
3541 information may be found. The content of this field is a
3542 simple URL without any surrounding characters such as
3547 <sect1 id="f-Checksums">
3548 <heading><tt>Checksums-Sha1</tt>
3549 and <tt>Checksums-Sha256</tt></heading>
3552 These fields contain a list of files with a checksum and size
3553 for each one. Both <tt>Checksums-Sha1</tt>
3554 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3555 only in the checksum algorithm used: SHA-1
3556 for <tt>Checksums-Sha1</tt> and SHA-256
3557 for <tt>Checksums-Sha256</tt>.
3561 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3562 multiline fields. The first line of the field value (the part
3563 on the same line as <tt>Checksums-Sha1:</tt>
3564 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3565 of the field is expressed as continuation lines, one line per
3566 file. Each line consists of the checksum, a space, the file
3567 size, a space, and the file name. For example (from
3568 a <file>.changes</file> file):
3571 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3572 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3573 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3574 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3576 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3577 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3578 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3579 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3584 In the <file>.dsc</file> file, these fields should list all
3585 files that make up the source package. In
3586 the <file>.changes</file> file, these fields should list all
3587 files being uploaded. The list of files in these fields
3588 must match the list of files in the <tt>Files</tt> field.
3594 <heading>User-defined fields</heading>
3597 Additional user-defined fields may be added to the
3598 source package control file. Such fields will be
3599 ignored, and not copied to (for example) binary or
3600 source package control files or upload control files.
3604 If you wish to add additional unsupported fields to
3605 these output files you should use the mechanism
3610 Fields in the main source control information file with
3611 names starting <tt>X</tt>, followed by one or more of
3612 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3613 be copied to the output files. Only the part of the
3614 field name after the hyphen will be used in the output
3615 file. Where the letter <tt>B</tt> is used the field
3616 will appear in binary package control files, where the
3617 letter <tt>S</tt> is used in source package control
3618 files and where <tt>C</tt> is used in upload control
3619 (<tt>.changes</tt>) files.
3623 For example, if the main source information control file
3626 XBS-Comment: I stand between the candle and the star.
3628 then the binary and source package control files will contain the
3631 Comment: I stand between the candle and the star.
3640 <chapt id="maintainerscripts">
3641 <heading>Package maintainer scripts and installation procedure</heading>
3644 <heading>Introduction to package maintainer scripts</heading>
3647 It is possible to supply scripts as part of a package which
3648 the package management system will run for you when your
3649 package is installed, upgraded or removed.
3653 These scripts are the files <prgn>preinst</prgn>,
3654 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3655 <prgn>postrm</prgn> in the control area of the package.
3656 They must be proper executable files; if they are scripts
3657 (which is recommended), they must start with the usual
3658 <tt>#!</tt> convention. They should be readable and
3659 executable by anyone, and must not be world-writable.
3663 The package management system looks at the exit status from
3664 these scripts. It is important that they exit with a
3665 non-zero status if there is an error, so that the package
3666 management system can stop its processing. For shell
3667 scripts this means that you <em>almost always</em> need to
3668 use <tt>set -e</tt> (this is usually true when writing shell
3669 scripts, in fact). It is also important, of course, that
3670 they exit with a zero status if everything went well.
3674 Additionally, packages interacting with users using
3675 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3676 install a <prgn>config</prgn> script in the control area,
3677 see <ref id="maintscriptprompt"> for details.
3681 When a package is upgraded a combination of the scripts from
3682 the old and new packages is called during the upgrade
3683 procedure. If your scripts are going to be at all
3684 complicated you need to be aware of this, and may need to
3685 check the arguments to your scripts.
3689 Broadly speaking the <prgn>preinst</prgn> is called before
3690 (a particular version of) a package is installed, and the
3691 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3692 before (a version of) a package is removed and the
3693 <prgn>postrm</prgn> afterwards.
3697 Programs called from maintainer scripts should not normally
3698 have a path prepended to them. Before installation is
3699 started, the package management system checks to see if the
3700 programs <prgn>ldconfig</prgn>,
3701 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3702 and <prgn>update-rc.d</prgn> can be found via the
3703 <tt>PATH</tt> environment variable. Those programs, and any
3704 other program that one would expect to be in the
3705 <tt>PATH</tt>, should thus be invoked without an absolute
3706 pathname. Maintainer scripts should also not reset the
3707 <tt>PATH</tt>, though they might choose to modify it by
3708 prepending or appending package-specific directories. These
3709 considerations really apply to all shell scripts.</p>
3712 <sect id="idempotency">
3713 <heading>Maintainer scripts idempotency</heading>
3716 It is necessary for the error recovery procedures that the
3717 scripts be idempotent. This means that if it is run
3718 successfully, and then it is called again, it doesn't bomb
3719 out or cause any harm, but just ensures that everything is
3720 the way it ought to be. If the first call failed, or
3721 aborted half way through for some reason, the second call
3722 should merely do the things that were left undone the first
3723 time, if any, and exit with a success status if everything
3725 This is so that if an error occurs, the user interrupts
3726 <prgn>dpkg</prgn> or some other unforeseen circumstance
3727 happens you don't leave the user with a badly-broken
3728 package when <prgn>dpkg</prgn> attempts to repeat the
3734 <sect id="controllingterminal">
3735 <heading>Controlling terminal for maintainer scripts</heading>
3738 Maintainer scripts are not guaranteed to run with a controlling
3739 terminal and may not be able to interact with the user. They
3740 must be able to fall back to noninteractive behavior if no
3741 controlling terminal is available. Maintainer scripts that
3742 prompt via a program conforming to the Debian Configuration
3743 Management Specification (see <ref id="maintscriptprompt">) may
3744 assume that program will handle falling back to noninteractive
3749 For high-priority prompts without a reasonable default answer,
3750 maintainer scripts may abort if there is no controlling
3751 terminal. However, this situation should be avoided if at all
3752 possible, since it prevents automated or unattended installs.
3753 In most cases, users will consider this to be a bug in the
3758 <sect id="exitstatus">
3759 <heading>Exit status</heading>
3762 Each script must return a zero exit status for
3763 success, or a nonzero one for failure, since the package
3764 management system looks for the exit status of these scripts
3765 and determines what action to take next based on that datum.
3769 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3774 <list compact="compact">
3776 <var>new-preinst</var> <tt>install</tt>
3779 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3782 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3785 <var>old-preinst</var> <tt>abort-upgrade</tt>
3786 <var>new-version</var>
3791 <list compact="compact">
3793 <var>postinst</var> <tt>configure</tt>
3794 <var>most-recently-configured-version</var>
3797 <var>old-postinst</var> <tt>abort-upgrade</tt>
3798 <var>new-version</var>
3801 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3802 <tt>in-favour</tt> <var>package</var>
3803 <var>new-version</var>
3806 <var>postinst</var> <tt>abort-remove</tt>
3809 <var>deconfigured's-postinst</var>
3810 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3811 <var>failed-install-package</var> <var>version</var>
3812 [<tt>removing</tt> <var>conflicting-package</var>
3818 <list compact="compact">
3820 <var>prerm</var> <tt>remove</tt>
3823 <var>old-prerm</var> <tt>upgrade</tt>
3824 <var>new-version</var>
3827 <var>new-prerm</var> <tt>failed-upgrade</tt>
3828 <var>old-version</var>
3831 <var>conflictor's-prerm</var> <tt>remove</tt>
3832 <tt>in-favour</tt> <var>package</var>
3833 <var>new-version</var>
3836 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3837 <tt>in-favour</tt> <var>package-being-installed</var>
3838 <var>version</var> [<tt>removing</tt>
3839 <var>conflicting-package</var>
3845 <list compact="compact">
3847 <var>postrm</var> <tt>remove</tt>
3850 <var>postrm</var> <tt>purge</tt>
3853 <var>old-postrm</var> <tt>upgrade</tt>
3854 <var>new-version</var>
3857 <var>new-postrm</var> <tt>failed-upgrade</tt>
3858 <var>old-version</var>
3861 <var>new-postrm</var> <tt>abort-install</tt>
3864 <var>new-postrm</var> <tt>abort-install</tt>
3865 <var>old-version</var>
3868 <var>new-postrm</var> <tt>abort-upgrade</tt>
3869 <var>old-version</var>
3872 <var>disappearer's-postrm</var> <tt>disappear</tt>
3873 <var>overwriter</var>
3874 <var>overwriter-version</var>
3880 <sect id="unpackphase">
3881 <heading>Details of unpack phase of installation or upgrade</heading>
3884 The procedure on installation/upgrade/overwrite/disappear
3885 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3886 stage of <tt>dpkg --install</tt>) is as follows. In each
3887 case, if a major error occurs (unless listed below) the
3888 actions are, in general, run backwards - this means that the
3889 maintainer scripts are run with different arguments in
3890 reverse order. These are the "error unwind" calls listed
3897 If a version of the package is already installed, call
3898 <example compact="compact">
3899 <var>old-prerm</var> upgrade <var>new-version</var>
3903 If the script runs but exits with a non-zero
3904 exit status, <prgn>dpkg</prgn> will attempt:
3905 <example compact="compact">
3906 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3908 If this works, the upgrade continues. If this
3909 does not work, the error unwind:
3910 <example compact="compact">
3911 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3913 If this works, then the old-version is
3914 "Installed", if not, the old version is in a
3915 "Half-Configured" state.
3921 If a "conflicting" package is being removed at the same time,
3922 or if any package will be broken (due to <tt>Breaks</tt>):
3925 If <tt>--auto-deconfigure</tt> is
3926 specified, call, for each package to be deconfigured
3927 due to <tt>Breaks</tt>:
3928 <example compact="compact">
3929 <var>deconfigured's-prerm</var> deconfigure \
3930 in-favour <var>package-being-installed</var> <var>version</var>
3933 <example compact="compact">
3934 <var>deconfigured's-postinst</var> abort-deconfigure \
3935 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3937 The deconfigured packages are marked as
3938 requiring configuration, so that if
3939 <tt>--install</tt> is used they will be
3940 configured again if possible.
3943 If any packages depended on a conflicting
3944 package being removed and <tt>--auto-deconfigure</tt> is
3945 specified, call, for each such package:
3946 <example compact="compact">
3947 <var>deconfigured's-prerm</var> deconfigure \
3948 in-favour <var>package-being-installed</var> <var>version</var> \
3949 removing <var>conflicting-package</var> <var>version</var>
3952 <example compact="compact">
3953 <var>deconfigured's-postinst</var> abort-deconfigure \
3954 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3955 removing <var>conflicting-package</var> <var>version</var>
3957 The deconfigured packages are marked as
3958 requiring configuration, so that if
3959 <tt>--install</tt> is used they will be
3960 configured again if possible.
3963 To prepare for removal of each conflicting package, call:
3964 <example compact="compact">
3965 <var>conflictor's-prerm</var> remove \
3966 in-favour <var>package</var> <var>new-version</var>
3969 <example compact="compact">
3970 <var>conflictor's-postinst</var> abort-remove \
3971 in-favour <var>package</var> <var>new-version</var>
3980 If the package is being upgraded, call:
3981 <example compact="compact">
3982 <var>new-preinst</var> upgrade <var>old-version</var>
3984 If this fails, we call:
3986 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3993 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3995 is called. If this works, then the old version
3996 is in an "Installed" state, or else it is left
3997 in an "Unpacked" state.
4002 If it fails, then the old version is left
4003 in an "Half-Installed" state.
4010 Otherwise, if the package had some configuration
4011 files from a previous version installed (i.e., it
4012 is in the "configuration files only" state):
4013 <example compact="compact">
4014 <var>new-preinst</var> install <var>old-version</var>
4018 <var>new-postrm</var> abort-install <var>old-version</var>
4020 If this fails, the package is left in a
4021 "Half-Installed" state, which requires a
4022 reinstall. If it works, the packages is left in
4023 a "Config-Files" state.
4026 Otherwise (i.e., the package was completely purged):
4027 <example compact="compact">
4028 <var>new-preinst</var> install
4031 <example compact="compact">
4032 <var>new-postrm</var> abort-install
4034 If the error-unwind fails, the package is in a
4035 "Half-Installed" phase, and requires a
4036 reinstall. If the error unwind works, the
4037 package is in a not installed state.
4044 The new package's files are unpacked, overwriting any
4045 that may be on the system already, for example any
4046 from the old version of the same package or from
4047 another package. Backups of the old files are kept
4048 temporarily, and if anything goes wrong the package
4049 management system will attempt to put them back as
4050 part of the error unwind.
4054 It is an error for a package to contain files which
4055 are on the system in another package, unless
4056 <tt>Replaces</tt> is used (see <ref id="replaces">).
4058 The following paragraph is not currently the case:
4059 Currently the <tt>- - force-overwrite</tt> flag is
4060 enabled, downgrading it to a warning, but this may not
4066 It is a more serious error for a package to contain a
4067 plain file or other kind of non-directory where another
4068 package has a directory (again, unless
4069 <tt>Replaces</tt> is used). This error can be
4070 overridden if desired using
4071 <tt>--force-overwrite-dir</tt>, but this is not
4076 Packages which overwrite each other's files produce
4077 behavior which, though deterministic, is hard for the
4078 system administrator to understand. It can easily
4079 lead to "missing" programs if, for example, a package
4080 is installed which overwrites a file from another
4081 package, and is then removed again.<footnote>
4082 Part of the problem is due to what is arguably a
4083 bug in <prgn>dpkg</prgn>.
4088 A directory will never be replaced by a symbolic link
4089 to a directory or vice versa; instead, the existing
4090 state (symlink or not) will be left alone and
4091 <prgn>dpkg</prgn> will follow the symlink if there is
4100 If the package is being upgraded, call
4101 <example compact="compact">
4102 <var>old-postrm</var> upgrade <var>new-version</var>
4106 If this fails, <prgn>dpkg</prgn> will attempt:
4107 <example compact="compact">
4108 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4110 If this works, installation continues. If not,
4112 <example compact="compact">
4113 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4115 If this fails, the old version is left in a
4116 "Half-Installed" state. If it works, dpkg now
4118 <example compact="compact">
4119 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4121 If this fails, the old version is left in a
4122 "Half-Installed" state. If it works, dpkg now
4124 <example compact="compact">
4125 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4127 If this fails, the old version is in an
4134 This is the point of no return - if
4135 <prgn>dpkg</prgn> gets this far, it won't back off
4136 past this point if an error occurs. This will
4137 leave the package in a fairly bad state, which
4138 will require a successful re-installation to clear
4139 up, but it's when <prgn>dpkg</prgn> starts doing
4140 things that are irreversible.
4145 Any files which were in the old version of the package
4146 but not in the new are removed.
4150 The new file list replaces the old.
4154 The new maintainer scripts replace the old.
4158 Any packages all of whose files have been overwritten
4159 during the installation, and which aren't required for
4160 dependencies, are considered to have been removed.
4161 For each such package
4164 <prgn>dpkg</prgn> calls:
4165 <example compact="compact">
4166 <var>disappearer's-postrm</var> disappear \
4167 <var>overwriter</var> <var>overwriter-version</var>
4171 The package's maintainer scripts are removed.
4174 It is noted in the status database as being in a
4175 sane state, namely not installed (any conffiles
4176 it may have are ignored, rather than being
4177 removed by <prgn>dpkg</prgn>). Note that
4178 disappearing packages do not have their prerm
4179 called, because <prgn>dpkg</prgn> doesn't know
4180 in advance that the package is going to
4187 Any files in the package we're unpacking that are also
4188 listed in the file lists of other packages are removed
4189 from those lists. (This will lobotomize the file list
4190 of the "conflicting" package if there is one.)
4194 The backup files made during installation, above, are
4200 The new package's status is now sane, and recorded as
4205 Here is another point of no return - if the
4206 conflicting package's removal fails we do not unwind
4207 the rest of the installation; the conflicting package
4208 is left in a half-removed limbo.
4213 If there was a conflicting package we go and do the
4214 removal actions (described below), starting with the
4215 removal of the conflicting package's files (any that
4216 are also in the package being installed have already
4217 been removed from the conflicting package's file list,
4218 and so do not get removed now).
4224 <sect id="configdetails"><heading>Details of configuration</heading>
4227 When we configure a package (this happens with <tt>dpkg
4228 --install</tt> and <tt>dpkg --configure</tt>), we first
4229 update any <tt>conffile</tt>s and then call:
4230 <example compact="compact">
4231 <var>postinst</var> configure <var>most-recently-configured-version</var>
4236 No attempt is made to unwind after errors during
4237 configuration. If the configuration fails, the package is in
4238 a "Failed Config" state, and an error message is generated.
4242 If there is no most recently configured version
4243 <prgn>dpkg</prgn> will pass a null argument.
4246 Historical note: Truly ancient (pre-1997) versions of
4247 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4248 (including the angle brackets) in this case. Even older
4249 ones did not pass a second argument at all, under any
4250 circumstance. Note that upgrades using such an old dpkg
4251 version are unlikely to work for other reasons, even if
4252 this old argument behavior is handled by your postinst script.
4258 <sect id="removedetails"><heading>Details of removal and/or
4259 configuration purging</heading>
4265 <example compact="compact">
4266 <var>prerm</var> remove
4270 If prerm fails during replacement due to conflict
4272 <var>conflictor's-postinst</var> abort-remove \
4273 in-favour <var>package</var> <var>new-version</var>
4277 <var>postinst</var> abort-remove
4281 If this fails, the package is in a "Half-Configured"
4282 state, or else it remains "Installed".
4286 The package's files are removed (except <tt>conffile</tt>s).
4289 <example compact="compact">
4290 <var>postrm</var> remove
4294 If it fails, there's no error unwind, and the package is in
4295 an "Half-Installed" state.
4300 All the maintainer scripts except the <prgn>postrm</prgn>
4305 If we aren't purging the package we stop here. Note
4306 that packages which have no <prgn>postrm</prgn> and no
4307 <tt>conffile</tt>s are automatically purged when
4308 removed, as there is no difference except for the
4309 <prgn>dpkg</prgn> status.
4313 The <tt>conffile</tt>s and any backup files
4314 (<tt>~</tt>-files, <tt>#*#</tt> files,
4315 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4320 <example compact="compact">
4321 <var>postrm</var> purge
4325 If this fails, the package remains in a "Config-Files"
4330 The package's file list is removed.
4339 <chapt id="relationships">
4340 <heading>Declaring relationships between packages</heading>
4342 <sect id="depsyntax">
4343 <heading>Syntax of relationship fields</heading>
4346 These fields all have a uniform syntax. They are a list of
4347 package names separated by commas.
4351 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4352 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4353 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4354 control file fields of the package, which declare
4355 dependencies on other packages, the package names listed may
4356 also include lists of alternative package names, separated
4357 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4358 if any one of the alternative packages is installed, that
4359 part of the dependency is considered to be satisfied.
4363 All of the fields except for <tt>Provides</tt> may restrict
4364 their applicability to particular versions of each named
4365 package. This is done in parentheses after each individual
4366 package name; the parentheses should contain a relation from
4367 the list below followed by a version number, in the format
4368 described in <ref id="f-Version">.
4372 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4373 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4374 strictly earlier, earlier or equal, exactly equal, later or
4375 equal and strictly later, respectively. The deprecated
4376 forms <tt><</tt> and <tt>></tt> were used to mean
4377 earlier/later or equal, rather than strictly earlier/later,
4378 so they should not appear in new packages (though
4379 <prgn>dpkg</prgn> still supports them).
4383 Whitespace may appear at any point in the version
4384 specification subject to the rules in <ref
4385 id="controlsyntax">, and must appear where it's necessary to
4386 disambiguate; it is not otherwise significant. All of the
4387 relationship fields may span multiple lines. For
4388 consistency and in case of future changes to
4389 <prgn>dpkg</prgn> it is recommended that a single space be
4390 used after a version relationship and before a version
4391 number; it is also conventional to put a single space after
4392 each comma, on either side of each vertical bar, and before
4393 each open parenthesis. When wrapping a relationship field, it
4394 is conventional to do so after a comma and before the space
4395 following that comma.
4399 For example, a list of dependencies might appear as:
4400 <example compact="compact">
4403 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4408 Relationships may be restricted to a certain set of
4409 architectures. This is indicated in brackets after each
4410 individual package name and the optional version specification.
4411 The brackets enclose a list of Debian architecture names
4412 separated by whitespace. Exclamation marks may be prepended to
4413 each of the names. (It is not permitted for some names to be
4414 prepended with exclamation marks while others aren't.)
4418 For build relationship fields
4419 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4420 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4421 the current Debian host architecture is not in this list and
4422 there are no exclamation marks in the list, or it is in the list
4423 with a prepended exclamation mark, the package name and the
4424 associated version specification are ignored completely for the
4425 purposes of defining the relationships.
4430 <example compact="compact">
4432 Build-Depends-Indep: texinfo
4433 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4434 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4436 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4437 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4438 <tt>gnumach-dev</tt> only on hurd-i386.
4442 For binary relationship fields, the architecture restriction
4443 syntax is only supported in the source package control
4444 file <file>debian/control</file>. When the corresponding binary
4445 package control file is generated, the relationship will either
4446 be omitted or included without the architecture restriction
4447 based on the architecture of the binary package. This means
4448 that architecture restrictions must not be used in binary
4449 relationship fields for architecture-independent packages
4450 (<tt>Architecture: all</tt>).
4455 <example compact="compact">
4456 Depends: foo [i386], bar [amd64]
4458 becomes <tt>Depends: foo</tt> when the package is built on
4459 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4460 package is built on the <tt>amd64</tt> architecture, and omitted
4461 entirely in binary packages built on all other architectures.
4465 If the architecture-restricted dependency is part of a set of
4466 alternatives using <tt>|</tt>, that alternative is ignored
4467 completely on architectures that do not match the restriction.
4469 <example compact="compact">
4470 Build-Depends: foo [!i386] | bar [!amd64]
4472 is equivalent to <tt>bar</tt> on the i386 architecture, to
4473 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4474 bar</tt> on all other architectures.
4478 Relationships may also be restricted to a certain set of
4479 architectures using architecture wildcards. The syntax for
4480 declaring such restrictions is the same as declaring
4481 restrictions using a certain set of architectures without
4482 architecture wildcards. For example:
4483 <example compact="compact">
4484 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4486 is equivalent to <tt>foo</tt> on architectures using the Linux
4487 kernel and any cpu, <tt>bar</tt> on architectures using any
4488 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4489 using a kernel other than Linux.
4493 Note that the binary package relationship fields such as
4494 <tt>Depends</tt> appear in one of the binary package
4495 sections of the control file, whereas the build-time
4496 relationships such as <tt>Build-Depends</tt> appear in the
4497 source package section of the control file (which is the
4502 <sect id="binarydeps">
4503 <heading>Binary Dependencies - <tt>Depends</tt>,
4504 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4505 <tt>Pre-Depends</tt>
4509 Packages can declare in their control file that they have
4510 certain relationships to other packages - for example, that
4511 they may not be installed at the same time as certain other
4512 packages, and/or that they depend on the presence of others.
4516 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4517 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4518 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4519 <tt>Breaks</tt> is described in <ref id="breaks">, and
4520 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4521 rest are described below.
4525 These seven fields are used to declare a dependency
4526 relationship by one package on another. Except for
4527 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4528 depending (binary) package's control file.
4529 (<tt>Enhances</tt> appears in the recommending package's
4530 control file, and <tt>Breaks</tt> appears in the version of
4531 depended-on package which causes the named package to
4536 A <tt>Depends</tt> field takes effect <em>only</em> when a
4537 package is to be configured. It does not prevent a package
4538 being on the system in an unconfigured state while its
4539 dependencies are unsatisfied, and it is possible to replace
4540 a package whose dependencies are satisfied and which is
4541 properly installed with a different version whose
4542 dependencies are not and cannot be satisfied; when this is
4543 done the depending package will be left unconfigured (since
4544 attempts to configure it will give errors) and will not
4545 function properly. If it is necessary, a
4546 <tt>Pre-Depends</tt> field can be used, which has a partial
4547 effect even when a package is being unpacked, as explained
4548 in detail below. (The other three dependency fields,
4549 <tt>Recommends</tt>, <tt>Suggests</tt> and
4550 <tt>Enhances</tt>, are only used by the various front-ends
4551 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4552 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4556 For this reason packages in an installation run are usually
4557 all unpacked first and all configured later; this gives
4558 later versions of packages with dependencies on later
4559 versions of other packages the opportunity to have their
4560 dependencies satisfied.
4564 In case of circular dependencies, since installation or
4565 removal order honoring the dependency order can't be
4566 established, dependency loops are broken at some point
4567 (based on rules below), and some packages may not be able to
4568 rely on their dependencies being present when being
4569 installed or removed, depending on which side of the break
4570 of the circular dependency loop they happen to be on. If one
4571 of the packages in the loop has no postinst script, then the
4572 cycle will be broken at that package, so as to ensure that
4573 all postinst scripts run with the dependencies properly
4574 configured if this is possible. Otherwise the breaking point
4579 The <tt>Depends</tt> field thus allows package maintainers
4580 to impose an order in which packages should be configured.
4584 The meaning of the five dependency fields is as follows:
4586 <tag><tt>Depends</tt></tag>
4589 This declares an absolute dependency. A package will
4590 not be configured unless all of the packages listed in
4591 its <tt>Depends</tt> field have been correctly
4596 The <tt>Depends</tt> field should be used if the
4597 depended-on package is required for the depending
4598 package to provide a significant amount of
4603 The <tt>Depends</tt> field should also be used if the
4604 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4605 <prgn>postrm</prgn> scripts require the package to be
4606 present in order to run. Note, however, that the
4607 <prgn>postrm</prgn> cannot rely on any non-essential
4608 packages to be present during the <tt>purge</tt>
4612 <tag><tt>Recommends</tt></tag>
4615 This declares a strong, but not absolute, dependency.
4619 The <tt>Recommends</tt> field should list packages
4620 that would be found together with this one in all but
4621 unusual installations.
4625 <tag><tt>Suggests</tt></tag>
4627 This is used to declare that one package may be more
4628 useful with one or more others. Using this field
4629 tells the packaging system and the user that the
4630 listed packages are related to this one and can
4631 perhaps enhance its usefulness, but that installing
4632 this one without them is perfectly reasonable.
4635 <tag><tt>Enhances</tt></tag>
4637 This field is similar to Suggests but works in the
4638 opposite direction. It is used to declare that a
4639 package can enhance the functionality of another
4643 <tag><tt>Pre-Depends</tt></tag>
4646 This field is like <tt>Depends</tt>, except that it
4647 also forces <prgn>dpkg</prgn> to complete installation
4648 of the packages named before even starting the
4649 installation of the package which declares the
4650 pre-dependency, as follows:
4654 When a package declaring a pre-dependency is about to
4655 be <em>unpacked</em> the pre-dependency can be
4656 satisfied if the depended-on package is either fully
4657 configured, <em>or even if</em> the depended-on
4658 package(s) are only unpacked or in the "Half-Configured"
4659 state, provided that they have been configured
4660 correctly at some point in the past (and not removed
4661 or partially removed since). In this case, both the
4662 previously-configured and currently unpacked or
4663 "Half-Configured" versions must satisfy any version
4664 clause in the <tt>Pre-Depends</tt> field.
4668 When the package declaring a pre-dependency is about
4669 to be <em>configured</em>, the pre-dependency will be
4670 treated as a normal <tt>Depends</tt>, that is, it will
4671 be considered satisfied only if the depended-on
4672 package has been correctly configured.
4676 <tt>Pre-Depends</tt> should be used sparingly,
4677 preferably only by packages whose premature upgrade or
4678 installation would hamper the ability of the system to
4679 continue with any upgrade that might be in progress.
4683 <tt>Pre-Depends</tt> are also required if the
4684 <prgn>preinst</prgn> script depends on the named
4685 package. It is best to avoid this situation if
4693 When selecting which level of dependency to use you should
4694 consider how important the depended-on package is to the
4695 functionality of the one declaring the dependency. Some
4696 packages are composed of components of varying degrees of
4697 importance. Such a package should list using
4698 <tt>Depends</tt> the package(s) which are required by the
4699 more important components. The other components'
4700 requirements may be mentioned as Suggestions or
4701 Recommendations, as appropriate to the components' relative
4707 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4710 When one binary package declares that it breaks another,
4711 <prgn>dpkg</prgn> will refuse to allow the package which
4712 declares <tt>Breaks</tt> be installed unless the broken
4713 package is deconfigured first, and it will refuse to
4714 allow the broken package to be reconfigured.
4718 A package will not be regarded as causing breakage merely
4719 because its configuration files are still installed; it must
4720 be at least "Half-Installed".
4724 A special exception is made for packages which declare that
4725 they break their own package name or a virtual package which
4726 they provide (see below): this does not count as a real
4731 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4732 version clause; such a <tt>Breaks</tt> is introduced in the
4733 version of an (implicit or explicit) dependency which violates
4734 an assumption or reveals a bug in earlier versions of the broken
4735 package, or which takes over a file from earlier versions of the
4736 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4737 will inform higher-level package management tools that the
4738 broken package must be upgraded before the new one.
4742 If the breaking package also overwrites some files from the
4743 older package, it should use <tt>Replaces</tt> to ensure this
4744 goes smoothly. See <ref id="replaces"> for a full discussion
4745 of taking over files from other packages, including how to
4746 use <tt>Breaks</tt> in those cases.
4750 Many of the cases where <tt>Breaks</tt> should be used were
4751 previously handled with <tt>Conflicts</tt>
4752 because <tt>Breaks</tt> did not yet exist.
4753 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4754 See <ref id="conflicts"> for more information about the
4759 <sect id="conflicts">
4760 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4763 When one binary package declares a conflict with another
4764 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4765 refuse to allow them to be installed on the system at the
4766 same time. This is a stronger restriction than <tt>Breaks</tt>,
4767 which just prevents both packages from being configured at the
4768 same time. Conflicting packages cannot be unpacked on the
4769 system at the same time.
4773 If one package is to be installed, the other must be removed
4774 first. If the package being installed is marked as replacing
4775 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4776 normally be used in this case) the one on the system, or the one
4777 on the system is marked as deselected, or both packages are
4778 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4779 automatically remove the package which is causing the conflict.
4780 Otherwise, it will halt the installation of the new package with
4781 an error. This mechanism is specifically designed to produce an
4782 error when the installed package is <tt>Essential</tt>, but the
4787 A package will not cause a conflict merely because its
4788 configuration files are still installed; it must be at least
4793 A special exception is made for packages which declare a
4794 conflict with their own package name, or with a virtual
4795 package which they provide (see below): this does not
4796 prevent their installation, and allows a package to conflict
4797 with others providing a replacement for it. You use this
4798 feature when you want the package in question to be the only
4799 package providing some feature.
4803 Normally, <tt>Breaks</tt> should be used instead
4804 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4805 stronger restriction on the ordering of package installation or
4806 upgrade and can make it more difficult for the package manager
4807 to find a correct solution to an upgrade or installation
4808 problem. <tt>Breaks</tt> should be used
4810 <item>when moving a file from one package to another (see
4811 <ref id="replaces">),</item>
4812 <item>when splitting a package (a special case of the previous
4814 <item>when the breaking package exposes a bug in or interacts
4815 badly with particular versions of the broken
4818 <tt>Conflicts</tt> should be used
4820 <item>when two packages provide the same file and will
4821 continue to do so,</item>
4822 <item>in conjunction with <tt>Provides</tt> when only one
4823 package providing a given virtual facility may be installed
4824 at a time (see <ref id="virtual">),</item>
4825 <item>in other cases where one must prevent simultaneous
4826 installation of two packages for reasons that are ongoing
4827 (not fixed in a later version of one of the packages) or
4828 that must prevent both packages from being unpacked at the
4829 same time, not just configured.</item>
4831 Be aware that adding <tt>Conflicts</tt> is normally not the best
4832 solution when two packages provide the same files. Depending on
4833 the reason for that conflict, using alternatives or renaming the
4834 files is often a better approach. See, for
4835 example, <ref id="binaries">.
4839 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4840 unless two packages cannot be installed at the same time or
4841 installing them both causes one of them to be broken or
4842 unusable. Having similar functionality or performing the same
4843 tasks as another package is not sufficient reason to
4844 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4848 A <tt>Conflicts</tt> entry may have an "earlier than" version
4849 clause if the reason for the conflict is corrected in a later
4850 version of one of the packages. However, normally the presence
4851 of an "earlier than" version clause is a sign
4852 that <tt>Breaks</tt> should have been used instead. An "earlier
4853 than" version clause in <tt>Conflicts</tt>
4854 prevents <prgn>dpkg</prgn> from upgrading or installing the
4855 package which declares such a conflict until the upgrade or
4856 removal of the conflicted-with package has been completed, which
4857 is a strong restriction.
4861 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4865 As well as the names of actual ("concrete") packages, the
4866 package relationship fields <tt>Depends</tt>,
4867 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4868 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4869 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4870 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4871 may mention "virtual packages".
4875 A <em>virtual package</em> is one which appears in the
4876 <tt>Provides</tt> control file field of another package.
4877 The effect is as if the package(s) which provide a
4878 particular virtual package name had been listed by name
4879 everywhere the virtual package name appears. (See also <ref
4884 If there are both concrete and virtual packages of the same
4885 name, then the dependency may be satisfied (or the conflict
4886 caused) by either the concrete package with the name in
4887 question or any other concrete package which provides the
4888 virtual package with the name in question. This is so that,
4889 for example, supposing we have
4890 <example compact="compact">
4893 </example> and someone else releases an enhanced version of
4894 the <tt>bar</tt> package they can say:
4895 <example compact="compact">
4899 and the <tt>bar-plus</tt> package will now also satisfy the
4900 dependency for the <tt>foo</tt> package.
4904 If a relationship field has a version number attached, only real
4905 packages will be considered to see whether the relationship is
4906 satisfied (or the prohibition violated, for a conflict or
4907 breakage). In other words, if a version number is specified,
4908 this is a request to ignore all <tt>Provides</tt> for that
4909 package name and consider only real packages. The package
4910 manager will assume that a package providing that virtual
4911 package is not of the "right" version. A <tt>Provides</tt>
4912 field may not contain version numbers, and the version number of
4913 the concrete package which provides a particular virtual package
4914 will not be considered when considering a dependency on or
4915 conflict with the virtual package name.<footnote>
4916 It is possible that a future release of <prgn>dpkg</prgn> may
4917 add the ability to specify a version number for each virtual
4918 package it provides. This feature is not yet present,
4919 however, and is expected to be used only infrequently.
4924 To specify which of a set of real packages should be the default
4925 to satisfy a particular dependency on a virtual package, list
4926 the real package as an alternative before the virtual one.
4930 If the virtual package represents a facility that can only be
4931 provided by one real package at a time, such as
4932 the <package>mail-transport-agent</package> virtual package that
4933 requires installation of a binary that would conflict with all
4934 other providers of that virtual package (see
4935 <ref id="mail-transport-agents">), all packages providing that
4936 virtual package should also declare a conflict with it
4937 using <tt>Conflicts</tt>. This will ensure that at most one
4938 provider of that virtual package is unpacked or installed at a
4943 <sect id="replaces"><heading>Overwriting files and replacing
4944 packages - <tt>Replaces</tt></heading>
4947 Packages can declare in their control file that they should
4948 overwrite files in certain other packages, or completely
4949 replace other packages. The <tt>Replaces</tt> control file
4950 field has these two distinct purposes.
4953 <sect1><heading>Overwriting files in other packages</heading>
4956 It is usually an error for a package to contain files which
4957 are on the system in another package. However, if the
4958 overwriting package declares that it <tt>Replaces</tt> the one
4959 containing the file being overwritten, then <prgn>dpkg</prgn>
4960 will replace the file from the old package with that from the
4961 new. The file will no longer be listed as "owned" by the old
4962 package and will be taken over by the new package.
4963 Normally, <tt>Breaks</tt> should be used in conjunction
4964 with <tt>Replaces</tt>.<footnote>
4965 To see why <tt>Breaks</tt> is normally needed in addition
4966 to <tt>Replaces</tt>, consider the case of a file in the
4967 package <package>foo</package> being taken over by the
4968 package <package>foo-data</package>.
4969 <tt>Replaces</tt> will allow <package>foo-data</package> to
4970 be installed and take over that file. However,
4971 without <tt>Breaks</tt>, nothing
4972 requires <package>foo</package> to be upgraded to a newer
4973 version that knows it does not include that file and instead
4974 depends on <package>foo-data</package>. Nothing would
4975 prevent the new <package>foo-data</package> package from
4976 being installed and then removed, removing the file that it
4977 took over from <package>foo</package>. After that
4978 operation, the package manager would think the system was in
4979 a consistent state, but the <package>foo</package> package
4980 would be missing one of its files.
4985 For example, if a package <package>foo</package> is split
4986 into <package>foo</package> and <package>foo-data</package>
4987 starting at version 1.2-3, <package>foo-data</package> would
4989 <example compact="compact">
4990 Replaces: foo (<< 1.2-3)
4991 Breaks: foo (<< 1.2-3)
4993 in its control file. The new version of the
4994 package <package>foo</package> would normally have the field
4995 <example compact="compact">
4996 Depends: foo-data (>= 1.2-3)
4998 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4999 the files moved into <package>foo-data</package> are not
5000 required for normal operation).
5004 If a package is completely replaced in this way, so that
5005 <prgn>dpkg</prgn> does not know of any files it still
5006 contains, it is considered to have "disappeared". It will
5007 be marked as not wanted on the system (selected for
5008 removal) and not installed. Any <tt>conffile</tt>s
5009 details noted for the package will be ignored, as they
5010 will have been taken over by the overwriting package. The
5011 package's <prgn>postrm</prgn> script will be run with a
5012 special argument to allow the package to do any final
5013 cleanup required. See <ref id="mscriptsinstact">.
5015 Replaces is a one way relationship. You have to install
5016 the replacing package after the replaced package.
5021 For this usage of <tt>Replaces</tt>, virtual packages (see
5022 <ref id="virtual">) are not considered when looking at a
5023 <tt>Replaces</tt> field. The packages declared as being
5024 replaced must be mentioned by their real names.
5028 This usage of <tt>Replaces</tt> only takes effect when both
5029 packages are at least partially on the system at once. It is
5030 not relevant if the packages conflict unless the conflict has
5035 <sect1><heading>Replacing whole packages, forcing their
5039 Second, <tt>Replaces</tt> allows the packaging system to
5040 resolve which package should be removed when there is a
5041 conflict (see <ref id="conflicts">). This usage only takes
5042 effect when the two packages <em>do</em> conflict, so that the
5043 two usages of this field do not interfere with each other.
5047 In this situation, the package declared as being replaced
5048 can be a virtual package, so for example, all mail
5049 transport agents (MTAs) would have the following fields in
5050 their control files:
5051 <example compact="compact">
5052 Provides: mail-transport-agent
5053 Conflicts: mail-transport-agent
5054 Replaces: mail-transport-agent
5056 ensuring that only one MTA can be installed at any one
5057 time. See <ref id="virtual"> for more information about this
5062 <sect id="sourcebinarydeps">
5063 <heading>Relationships between source and binary packages -
5064 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5065 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5069 Source packages that require certain binary packages to be
5070 installed or absent at the time of building the package
5071 can declare relationships to those binary packages.
5075 This is done using the <tt>Build-Depends</tt>,
5076 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5077 <tt>Build-Conflicts-Indep</tt> control file fields.
5081 Build-dependencies on "build-essential" binary packages can be
5082 omitted. Please see <ref id="pkg-relations"> for more information.
5086 The dependencies and conflicts they define must be satisfied
5087 (as defined earlier for binary packages) in order to invoke
5088 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5090 There is no Build-Depends-Arch; this role is essentially
5091 met with Build-Depends. Anyone building the
5092 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5093 assumed to be building the whole package, and therefore
5094 installation of all build dependencies is required.
5097 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5098 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5099 not yet know how to check for its existence, and
5100 <tt>binary-arch</tt>. The purpose of the original split
5101 between <tt>Build-Depends</tt> and
5102 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5103 wouldn't need to install extra packages needed only for the
5104 binary-indep targets. But without a build-arch/build-indep
5105 split, this didn't work, since most of the work is done in
5106 the build target, not in the binary target.
5110 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5111 <tt>binary-arch</tt></tag>
5113 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5114 fields must be satisfied when these targets are invoked.
5116 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5117 and <tt>binary-indep</tt></tag>
5119 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5120 <tt>Build-Depends-Indep</tt>, and
5121 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5122 these targets are invoked.
5130 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5133 Packages containing shared libraries must be constructed with
5134 a little care to make sure that the shared library is always
5135 available. This is especially important for packages whose
5136 shared libraries are vitally important, such as the C library
5137 (currently <tt>libc6</tt>).
5141 Packages involving shared libraries should be split up into
5142 several binary packages. This section mostly deals with how
5143 this separation is to be accomplished; rules for files within
5144 the shared library packages are in <ref id="libraries"> instead.
5147 <sect id="sharedlibs-runtime">
5148 <heading>Run-time shared libraries</heading>
5151 The run-time shared library needs to be placed in a package
5152 whose name changes whenever the shared object version
5155 Since it is common place to install several versions of a
5156 package that just provides shared libraries, it is a
5157 good idea that the library package should not
5158 contain any extraneous non-versioned files, unless they
5159 happen to be in versioned directories.</p>
5161 The most common mechanism is to place it in a package
5163 <package><var>libraryname</var><var>soversion</var></package>,
5164 where <file><var>soversion</var></file> is the version number
5165 in the soname of the shared library<footnote>
5166 The soname is the shared object name: it's the thing
5167 that has to match exactly between building an executable
5168 and running it for the dynamic linker to be able run the
5169 program. For example, if the soname of the library is
5170 <file>libfoo.so.6</file>, the library package would be
5171 called <file>libfoo6</file>.
5173 Alternatively, if it would be confusing to directly append
5174 <var>soversion</var> to <var>libraryname</var> (e.g. because
5175 <var>libraryname</var> itself ends in a number), you may use
5176 <package><var>libraryname</var>-<var>soversion</var></package> and
5177 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5182 If you have several shared libraries built from the same
5183 source tree you may lump them all together into a single
5184 shared library package, provided that you change all of
5185 their sonames at once (so that you don't get filename
5186 clashes if you try to install different versions of the
5187 combined shared libraries package).
5191 The package should install the shared libraries under
5192 their normal names. For example, the <package>libgdbm3</package>
5193 package should install <file>libgdbm.so.3.0.0</file> as
5194 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5195 renamed or re-linked by any <prgn>prerm</prgn> or
5196 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5197 of renaming things safely without affecting running programs,
5198 and attempts to interfere with this are likely to lead to
5203 Shared libraries should not be installed executable, since
5204 the dynamic linker does not require this and trying to
5205 execute a shared library usually results in a core dump.
5209 The run-time library package should include the symbolic link that
5210 <prgn>ldconfig</prgn> would create for the shared libraries.
5211 For example, the <package>libgdbm3</package> package should include
5212 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5213 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5214 linker (for example <prgn>ld.so</prgn> or
5215 <prgn>ld-linux.so.*</prgn>) can find the library between the
5216 time that <prgn>dpkg</prgn> installs it and the time that
5217 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5219 The package management system requires the library to be
5220 placed before the symbolic link pointing to it in the
5221 <file>.deb</file> file. This is so that when
5222 <prgn>dpkg</prgn> comes to install the symlink
5223 (overwriting the previous symlink pointing at an older
5224 version of the library), the new shared library is already
5225 in place. In the past, this was achieved by creating the
5226 library in the temporary packaging directory before
5227 creating the symlink. Unfortunately, this was not always
5228 effective, since the building of the tar file in the
5229 <file>.deb</file> depended on the behavior of the underlying
5230 file system. Some file systems (such as reiserfs) reorder
5231 the files so that the order of creation is forgotten.
5232 Since version 1.7.0, <prgn>dpkg</prgn>
5233 reorders the files itself as necessary when building a
5234 package. Thus it is no longer important to concern
5235 oneself with the order of file creation.
5239 <sect1 id="ldconfig">
5240 <heading><tt>ldconfig</tt></heading>
5243 Any package installing shared libraries in one of the default
5244 library directories of the dynamic linker (which are currently
5245 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5246 listed in <file>/etc/ld.so.conf</file><footnote>
5248 <list compact="compact">
5249 <item>/usr/local/lib</item>
5250 <item>/usr/lib/libc5-compat</item>
5251 <item>/lib/libc5-compat</item>
5254 must use <prgn>ldconfig</prgn> to update the shared library
5259 The package maintainer scripts must only call
5260 <prgn>ldconfig</prgn> under these circumstances:
5261 <list compact="compact">
5262 <item>When the <prgn>postinst</prgn> script is run with a
5263 first argument of <tt>configure</tt>, the script must call
5264 <prgn>ldconfig</prgn>, and may optionally invoke
5265 <prgn>ldconfig</prgn> at other times.
5267 <item>When the <prgn>postrm</prgn> script is run with a
5268 first argument of <tt>remove</tt>, the script should call
5269 <prgn>ldconfig</prgn>.
5274 During install or upgrade, the preinst is called before
5275 the new files are installed, so calling "ldconfig" is
5276 pointless. The preinst of an existing package can also be
5277 called if an upgrade fails. However, this happens during
5278 the critical time when a shared libs may exist on-disk
5279 under a temporary name. Thus, it is dangerous and
5280 forbidden by current policy to call "ldconfig" at this
5285 When a package is installed or upgraded, "postinst
5286 configure" runs after the new files are safely on-disk.
5287 Since it is perfectly safe to invoke ldconfig
5288 unconditionally in a postinst, it is OK for a package to
5289 simply put ldconfig in its postinst without checking the
5290 argument. The postinst can also be called to recover from
5291 a failed upgrade. This happens before any new files are
5292 unpacked, so there is no reason to call "ldconfig" at this
5297 For a package that is being removed, prerm is
5298 called with all the files intact, so calling ldconfig is
5299 useless. The other calls to "prerm" happen in the case of
5300 upgrade at a time when all the files of the old package
5301 are on-disk, so again calling "ldconfig" is pointless.
5305 postrm, on the other hand, is called with the "remove"
5306 argument just after the files are removed, so this is
5307 the proper time to call "ldconfig" to notify the system
5308 of the fact that the shared libraries from the package
5309 are removed. The postrm can be called at several other
5310 times. At the time of "postrm purge", "postrm
5311 abort-install", or "postrm abort-upgrade", calling
5312 "ldconfig" is useless because the shared lib files are
5313 not on-disk. However, when "postrm" is invoked with
5314 arguments "upgrade", "failed-upgrade", or "disappear", a
5315 shared lib may exist on-disk under a temporary filename.
5323 <sect id="sharedlibs-support-files">
5324 <heading>Shared library support files</heading>
5327 If your package contains files whose names do not change with
5328 each change in the library shared object version, you must not
5329 put them in the shared library package. Otherwise, several
5330 versions of the shared library cannot be installed at the same
5331 time without filename clashes, making upgrades and transitions
5332 unnecessarily difficult.
5336 It is recommended that supporting files and run-time support
5337 programs that do not need to be invoked manually by users, but
5338 are nevertheless required for the package to function, be placed
5339 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5340 preferably under <file>/usr/lib/</file><var>package-name</var>.
5341 If the program or file is architecture independent, the
5342 recommendation is for it to be placed in a subdirectory of
5343 <file>/usr/share</file> instead, preferably under
5344 <file>/usr/share/</file><var>package-name</var>. Following the
5345 <var>package-name</var> naming convention ensures that the file
5346 names change when the shared object version changes.
5350 Run-time support programs that use the shared library but are
5351 not required for the library to function or files used by the
5352 shared library that can be used by any version of the shared
5353 library package should instead be put in a separate package.
5354 This package might typically be named
5355 <package><var>libraryname</var>-tools</package>; note the
5356 absence of the <var>soversion</var> in the package name.
5360 Files and support programs only useful when compiling software
5361 against the library should be included in the development
5362 package for the library.<footnote>
5363 For example, a <file><var>package-name</var>-config</file>
5364 script or <package>pkg-config</package> configuration files.
5369 <sect id="sharedlibs-static">
5370 <heading>Static libraries</heading>
5373 The static library (<file><var>libraryname.a</var></file>)
5374 is usually provided in addition to the shared version.
5375 It is placed into the development package (see below).
5379 In some cases, it is acceptable for a library to be
5380 available in static form only; these cases include:
5382 <item>libraries for languages whose shared library support
5383 is immature or unstable</item>
5384 <item>libraries whose interfaces are in flux or under
5385 development (commonly the case when the library's
5386 major version number is zero, or where the ABI breaks
5387 across patchlevels)</item>
5388 <item>libraries which are explicitly intended to be
5389 available only in static form by their upstream
5394 <sect id="sharedlibs-dev">
5395 <heading>Development files</heading>
5398 If there are development files associated with a shared library,
5399 the source package needs to generate a binary development package
5400 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5401 or if you prefer only to support one development version at a
5402 time, <package><var>libraryname</var>-dev</package>. Installing
5403 the development package must result in installation of all the
5404 development files necessary for compiling programs against that
5405 shared library.<footnote>
5406 This wording allows the development files to be split into
5407 several packages, such as a separate architecture-independent
5408 <package><var>libraryname</var>-headers</package>, provided that
5409 the development package depends on all the required additional
5415 In case several development versions of a library exist, you may
5416 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5417 <ref id="conflicts">) to ensure that the user only installs one
5418 development version at a time (as different development versions are
5419 likely to have the same header files in them, which would cause a
5420 filename clash if both were installed).
5424 The development package should contain a symlink for the associated
5425 shared library without a version number. For example, the
5426 <package>libgdbm-dev</package> package should include a symlink
5427 from <file>/usr/lib/libgdbm.so</file> to
5428 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5429 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5430 <file>libgdbm.so</file> when compiling dynamically.
5434 <sect id="sharedlibs-intradeps">
5435 <heading>Dependencies between the packages of the same library</heading>
5438 Typically the development version should have an exact
5439 version dependency on the runtime library, to make sure that
5440 compilation and linking happens correctly. The
5441 <tt>${binary:Version}</tt> substitution variable can be
5442 useful for this purpose.
5444 Previously, <tt>${Source-Version}</tt> was used, but its name
5445 was confusing and it has been deprecated since dpkg 1.13.19.
5450 <sect id="sharedlibs-shlibdeps">
5451 <heading>Dependencies between the library and other packages -
5452 the <tt>shlibs</tt> system</heading>
5455 If a package contains a binary or library which links to a
5456 shared library, we must ensure that when the package is
5457 installed on the system, all of the libraries needed are
5458 also installed. This requirement led to the creation of the
5459 <tt>shlibs</tt> system, which is very simple in its design:
5460 any package which <em>provides</em> a shared library also
5461 provides information on the package dependencies required to
5462 ensure the presence of this library, and any package which
5463 <em>uses</em> a shared library uses this information to
5464 determine the dependencies it requires. The files which
5465 contain the mapping from shared libraries to the necessary
5466 dependency information are called <file>shlibs</file> files.
5470 When a package is built which contains any shared libraries, it
5471 must provide a <file>shlibs</file> file for other packages to
5472 use. When a package is built which contains any shared
5473 libraries or compiled binaries, it must run
5474 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5475 on these to determine the libraries used and hence the
5476 dependencies needed by this package.<footnote>
5478 <prgn>dpkg-shlibdeps</prgn> will use a program
5479 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5480 the libraries directly needed by the binaries or shared
5481 libraries in the package.
5485 We say that a binary <tt>foo</tt> <em>directly</em> uses
5486 a library <tt>libbar</tt> if it is explicitly linked
5487 with that library (that is, the library is listed in the ELF
5488 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5489 to the link line when the binary is created). Other
5490 libraries that are needed by <tt>libbar</tt> are linked
5491 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5492 linker will load them automatically when it loads
5493 <tt>libbar</tt>. A package should depend on the libraries
5494 it directly uses, but not the libraries it indirectly uses.
5495 The dependencies for those libraries will automatically pull
5496 in the other libraries.
5500 A good example of where this helps is the following. We
5501 could update <tt>libimlib</tt> with a new version that
5502 supports a new graphics format called dgf (but retaining the
5503 same major version number) and depends on <tt>libdgf</tt>.
5504 If we used <prgn>ldd</prgn> to add dependencies for every
5505 library directly or indirectly linked with a binary, every
5506 package that uses <tt>libimlib</tt> would need to be
5507 recompiled so it would also depend on <tt>libdgf</tt> or it
5508 wouldn't run due to missing symbols. Since dependencies are
5509 only added based on ELF <tt>NEEDED</tt> attribute, packages
5510 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5511 having the dependency on <tt>libdgf</tt> and so they would
5512 not need rebuilding.
5518 In the following sections, we will first describe where the
5519 various <tt>shlibs</tt> files are to be found, then how to
5520 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5521 file format and how to create them if your package contains a
5526 <heading>The <tt>shlibs</tt> files present on the system</heading>
5529 There are several places where <tt>shlibs</tt> files are
5530 found. The following list gives them in the order in which
5532 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5533 (The first one which gives the required information is used.)
5539 <p><file>debian/shlibs.local</file></p>
5542 This lists overrides for this package. This file should
5543 normally not be used, but may be needed temporarily in
5544 unusual situations to work around bugs in other packages,
5545 or in unusual cases where the normally declared dependency
5546 information in the installed <file>shlibs</file> file for
5547 a library cannot be used. This file overrides information
5548 obtained from any other source.
5553 <p><file>/etc/dpkg/shlibs.override</file></p>
5556 This lists global overrides. This list is normally
5557 empty. It is maintained by the local system
5563 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5566 When packages are being built,
5567 any <file>debian/shlibs</file> files are copied into the
5568 control file area of the temporary build directory and
5569 given the name <file>shlibs</file>. These files give
5570 details of any shared libraries included in the same
5572 An example may help here. Let us say that the source
5573 package <tt>foo</tt> generates two binary
5574 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5575 When building the binary packages, the two packages are
5576 created in the directories <file>debian/libfoo2</file>
5577 and <file>debian/foo-runtime</file> respectively.
5578 (<file>debian/tmp</file> could be used instead of one of
5579 these.) Since <tt>libfoo2</tt> provides the
5580 <tt>libfoo</tt> shared library, it will require a
5581 <tt>shlibs</tt> file, which will be installed in
5582 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5583 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5584 When <prgn>dpkg-shlibdeps</prgn> is run on the
5585 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5587 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5588 determine whether <tt>foo-prog</tt>'s library
5589 dependencies are satisfied by any of the libraries
5590 provided by <tt>libfoo2</tt>. For this reason,
5591 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5592 the individual binary packages' <tt>shlibs</tt> files
5593 have been installed into the build directory.
5599 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5602 These are the <file>shlibs</file> files corresponding to
5603 all of the packages installed on the system, and are
5604 maintained by the relevant package maintainers.
5609 <p><file>/etc/dpkg/shlibs.default</file></p>
5612 This file lists any shared libraries whose packages
5613 have failed to provide correct <file>shlibs</file> files.
5614 It was used when the <file>shlibs</file> setup was first
5615 introduced, but it is now normally empty. It is
5616 maintained by the <tt>dpkg</tt> maintainer.
5624 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5625 <file>shlibs</file> files</heading>
5629 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5630 into your <file>debian/rules</file> file. If your package
5631 contains only compiled binaries and libraries (but no scripts),
5632 you can use a command such as:
5633 <example compact="compact">
5634 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5635 debian/tmp/usr/lib/*
5637 Otherwise, you will need to explicitly list the compiled
5638 binaries and libraries.<footnote>
5639 If you are using <tt>debhelper</tt>, the
5640 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5641 It will also correctly handle multi-binary packages.
5646 This command puts the dependency information into the
5647 <file>debian/substvars</file> file, which is then used by
5648 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5649 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5650 field in the control file for this to work.
5654 If you have multiple binary packages, you will need to call
5655 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5656 compiled libraries or binaries. In such a case, you will
5657 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5658 utilities to specify a different <file>substvars</file> file.
5662 If you are creating a udeb for use in the Debian Installer,
5663 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5664 should use the dependency line of type <tt>udeb</tt> by
5665 adding the <tt>-tudeb</tt> option<footnote>
5666 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5667 will automatically add this option if it knows it is
5669 </footnote>. If there is no dependency line of
5670 type <tt>udeb</tt> in the <file>shlibs</file>
5671 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5676 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5677 <ref id="pkg-dpkg-shlibdeps"> and
5678 <manref name="dpkg-shlibdeps" section="1">.
5683 <heading>The <file>shlibs</file> File Format</heading>
5686 Each <file>shlibs</file> file has the same format. Lines
5687 beginning with <tt>#</tt> are considered to be comments and
5688 are ignored. Each line is of the form:
5689 <example compact="compact">
5690 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5695 We will explain this by reference to the example of the
5696 <tt>zlib1g</tt> package, which (at the time of writing)
5697 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5701 <var>type</var> is an optional element that indicates the type
5702 of package for which the line is valid. The only type currently
5703 in use is <tt>udeb</tt>. The colon and space after the type are
5708 <var>library-name</var> is the name of the shared library,
5709 in this case <tt>libz</tt>. (This must match the name part
5710 of the soname, see below.)
5714 <var>soname-version</var> is the version part of the soname of
5715 the library. The soname is the thing that must exactly match
5716 for the library to be recognized by the dynamic linker, and is
5718 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5719 example, <tt>libz.so.1</tt>.<footnote>
5720 This can be determined using the command
5721 <example compact="compact">
5722 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5725 The version part is the part which comes after
5726 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5727 instead be of the form
5728 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5729 as <tt>libdb-4.8.so</tt>, in which case the name would
5730 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5734 <var>dependencies</var> has the same syntax as a dependency
5735 field in a binary package control file. It should give
5736 details of which packages are required to satisfy a binary
5737 built against the version of the library contained in the
5738 package. See <ref id="depsyntax"> for details.
5742 In our example, if the first version of the <tt>zlib1g</tt>
5743 package which contained a minor number of at least
5744 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5745 <tt>shlibs</tt> entry for this library could say:
5746 <example compact="compact">
5747 libz 1 zlib1g (>= 1:1.1.3)
5749 The version-specific dependency is to avoid warnings from
5750 the dynamic linker about using older shared libraries with
5755 As zlib1g also provides a udeb containing the shared library,
5756 there would also be a second line:
5757 <example compact="compact">
5758 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5764 <heading>Providing a <file>shlibs</file> file</heading>
5767 If your package provides a shared library, you need to create
5768 a <file>shlibs</file> file following the format described above.
5769 It is usual to call this file <file>debian/shlibs</file> (but if
5770 you have multiple binary packages, you might want to call it
5771 <file>debian/shlibs.<var>package</var></file> instead). Then
5772 let <file>debian/rules</file> install it in the control area:
5773 <example compact="compact">
5774 install -m644 debian/shlibs debian/tmp/DEBIAN
5776 or, in the case of a multi-binary package:
5777 <example compact="compact">
5778 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5780 An alternative way of doing this is to create the
5781 <file>shlibs</file> file in the control area directly from
5782 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5783 file at all,<footnote>
5784 This is what <prgn>dh_makeshlibs</prgn> in
5785 the <package>debhelper</package> suite does. If your package
5786 also has a udeb that provides a shared
5787 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5788 the <tt>udeb:</tt> lines if you specify the name of the udeb
5789 with the <tt>--add-udeb</tt> option.
5791 since the <file>debian/shlibs</file> file itself is ignored by
5792 <prgn>dpkg-shlibdeps</prgn>.
5796 As <prgn>dpkg-shlibdeps</prgn> reads the
5797 <file>DEBIAN/shlibs</file> files in all of the binary packages
5798 being built from this source package, all of the
5799 <file>DEBIAN/shlibs</file> files should be installed before
5800 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5808 <chapt id="opersys"><heading>The Operating System</heading>
5811 <heading>File system hierarchy</heading>
5815 <heading>File System Structure</heading>
5818 The location of all installed files and directories must
5819 comply with the Filesystem Hierarchy Standard (FHS),
5820 version 2.3, with the exceptions noted below, and except
5821 where doing so would violate other terms of Debian
5822 Policy. The following exceptions to the FHS apply:
5827 The optional rules related to user specific
5828 configuration files for applications are stored in
5829 the user's home directory are relaxed. It is
5830 recommended that such files start with the
5831 '<tt>.</tt>' character (a "dot file"), and if an
5832 application needs to create more than one dot file
5833 then the preferred placement is in a subdirectory
5834 with a name starting with a '.' character, (a "dot
5835 directory"). In this case it is recommended the
5836 configuration files not start with the '.'
5842 The requirement for amd64 to use <file>/lib64</file>
5843 for 64 bit binaries is removed.
5848 The requirement for object files, internal binaries, and
5849 libraries, including <file>libc.so.*</file>, to be located
5850 directly under <file>/lib{,32}</file> and
5851 <file>/usr/lib{,32}</file> is amended, permitting files
5852 to instead be installed to
5853 <file>/lib/<var>triplet</var></file> and
5854 <file>/usr/lib/<var>triplet</var></file>, where
5855 <tt><var>triplet</var></tt> is the value returned by
5856 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5857 architecture of the package. Packages may <em>not</em>
5858 install files to any <var>triplet</var> path other
5859 than the one matching the architecture of that package;
5860 for instance, an <tt>Architecture: amd64</tt> package
5861 containing 32-bit x86 libraries may not install these
5862 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5864 This is necessary in order to reserve the directories for
5865 use in cross-installation of library packages from other
5866 architectures, as part of the planned deployment of
5871 Applications may also use a single subdirectory under
5872 <file>/usr/lib/<var>triplet</var></file>.
5875 The execution time linker/loader, ld*, must still be made
5876 available in the existing location under /lib or /lib64
5877 since this is part of the ELF ABI for the architecture.
5882 The requirement that
5883 <file>/usr/local/share/man</file> be "synonymous"
5884 with <file>/usr/local/man</file> is relaxed to a
5889 The requirement that windowmanagers with a single
5890 configuration file call it <file>system.*wmrc</file>
5891 is removed, as is the restriction that the window
5892 manager subdirectory be named identically to the
5893 window manager name itself.
5898 The requirement that boot manager configuration
5899 files live in <file>/etc</file>, or at least are
5900 symlinked there, is relaxed to a recommendation.
5905 The following directories in the root filesystem are
5906 additionally allowed: <file>/sys</file> and
5907 <file>/selinux</file>. <footnote>These directories
5908 are used as mount points to mount virtual filesystems
5909 to get access to kernel information.</footnote>
5916 The version of this document referred here can be
5917 found in the <tt>debian-policy</tt> package or on <url
5918 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5919 name="FHS (Debian copy)"> alongside this manual (or, if
5920 you have the <package>debian-policy</package> installed,
5922 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5923 (local copy)">). The
5924 latest version, which may be a more recent version, may
5926 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5927 Specific questions about following the standard may be
5928 asked on the <tt>debian-devel</tt> mailing list, or
5929 referred to the FHS mailing list (see the
5930 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5936 <heading>Site-specific programs</heading>
5939 As mandated by the FHS, packages must not place any
5940 files in <file>/usr/local</file>, either by putting them in
5941 the file system archive to be unpacked by <prgn>dpkg</prgn>
5942 or by manipulating them in their maintainer scripts.
5946 However, the package may create empty directories below
5947 <file>/usr/local</file> so that the system administrator knows
5948 where to place site-specific files. These are not
5949 directories <em>in</em> <file>/usr/local</file>, but are
5950 children of directories in <file>/usr/local</file>. These
5951 directories (<file>/usr/local/*/dir/</file>)
5952 should be removed on package removal if they are
5957 Note that this applies only to
5958 directories <em>below</em> <file>/usr/local</file>,
5959 not <em>in</em> <file>/usr/local</file>. Packages must
5960 not create sub-directories in the
5961 directory <file>/usr/local</file> itself, except those
5962 listed in FHS, section 4.5. However, you may create
5963 directories below them as you wish. You must not remove
5964 any of the directories listed in 4.5, even if you created
5969 Since <file>/usr/local</file> can be mounted read-only from a
5970 remote server, these directories must be created and
5971 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5972 maintainer scripts and not be included in the
5973 <file>.deb</file> archive. These scripts must not fail if
5974 either of these operations fail.
5978 For example, the <tt>emacsen-common</tt> package could
5979 contain something like
5980 <example compact="compact">
5981 if [ ! -e /usr/local/share/emacs ]
5983 if mkdir /usr/local/share/emacs 2>/dev/null
5985 chown root:staff /usr/local/share/emacs
5986 chmod 2775 /usr/local/share/emacs
5990 in its <prgn>postinst</prgn> script, and
5991 <example compact="compact">
5992 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5993 rmdir /usr/local/share/emacs 2>/dev/null || true
5995 in the <prgn>prerm</prgn> script. (Note that this form is
5996 used to ensure that if the script is interrupted, the
5997 directory <file>/usr/local/share/emacs</file> will still be
6002 If you do create a directory in <file>/usr/local</file> for
6003 local additions to a package, you should ensure that
6004 settings in <file>/usr/local</file> take precedence over the
6005 equivalents in <file>/usr</file>.
6009 However, because <file>/usr/local</file> and its contents are
6010 for exclusive use of the local administrator, a package
6011 must not rely on the presence or absence of files or
6012 directories in <file>/usr/local</file> for normal operation.
6016 The <file>/usr/local</file> directory itself and all the
6017 subdirectories created by the package should (by default) have
6018 permissions 2775 (group-writable and set-group-id) and be
6019 owned by <tt>root:staff</tt>.
6024 <heading>The system-wide mail directory</heading>
6026 The system-wide mail directory
6027 is <file>/var/mail</file>. This directory is part of the
6028 base system and should not be owned by any particular mail
6029 agents. The use of the old
6030 location <file>/var/spool/mail</file> is deprecated, even
6031 though the spool may still be physically located there.
6037 <heading>Users and groups</heading>
6040 <heading>Introduction</heading>
6042 The Debian system can be configured to use either plain or
6047 Some user ids (UIDs) and group ids (GIDs) are reserved
6048 globally for use by certain packages. Because some
6049 packages need to include files which are owned by these
6050 users or groups, or need the ids compiled into binaries,
6051 these ids must be used on any Debian system only for the
6052 purpose for which they are allocated. This is a serious
6053 restriction, and we should avoid getting in the way of
6054 local administration policies. In particular, many sites
6055 allocate users and/or local system groups starting at 100.
6059 Apart from this we should have dynamically allocated ids,
6060 which should by default be arranged in some sensible
6061 order, but the behavior should be configurable.
6065 Packages other than <tt>base-passwd</tt> must not modify
6066 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6067 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6072 <heading>UID and GID classes</heading>
6074 The UID and GID numbers are divided into classes as
6080 Globally allocated by the Debian project, the same
6081 on every Debian system. These ids will appear in
6082 the <file>passwd</file> and <file>group</file> files of all
6083 Debian systems, new ids in this range being added
6084 automatically as the <tt>base-passwd</tt> package is
6089 Packages which need a single statically allocated
6090 uid or gid should use one of these; their
6091 maintainers should ask the <tt>base-passwd</tt>
6099 Dynamically allocated system users and groups.
6100 Packages which need a user or group, but can have
6101 this user or group allocated dynamically and
6102 differently on each system, should use <tt>adduser
6103 --system</tt> to create the group and/or user.
6104 <prgn>adduser</prgn> will check for the existence of
6105 the user or group, and if necessary choose an unused
6106 id based on the ranges specified in
6107 <file>adduser.conf</file>.
6111 <tag>1000-59999:</tag>
6114 Dynamically allocated user accounts. By default
6115 <prgn>adduser</prgn> will choose UIDs and GIDs for
6116 user accounts in this range, though
6117 <file>adduser.conf</file> may be used to modify this
6122 <tag>60000-64999:</tag>
6125 Globally allocated by the Debian project, but only
6126 created on demand. The ids are allocated centrally
6127 and statically, but the actual accounts are only
6128 created on users' systems on demand.
6132 These ids are for packages which are obscure or
6133 which require many statically-allocated ids. These
6134 packages should check for and create the accounts in
6135 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6136 <prgn>adduser</prgn> if it has this facility) if
6137 necessary. Packages which are likely to require
6138 further allocations should have a "hole" left after
6139 them in the allocation, to give them room to
6144 <tag>65000-65533:</tag>
6152 User <tt>nobody</tt>. The corresponding gid refers
6153 to the group <tt>nogroup</tt>.
6160 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6161 not</em> be used, because it is the error return
6170 <sect id="sysvinit">
6171 <heading>System run levels and <file>init.d</file> scripts</heading>
6173 <sect1 id="/etc/init.d">
6174 <heading>Introduction</heading>
6177 The <file>/etc/init.d</file> directory contains the scripts
6178 executed by <prgn>init</prgn> at boot time and when the
6179 init state (or "runlevel") is changed (see <manref
6180 name="init" section="8">).
6184 There are at least two different, yet functionally
6185 equivalent, ways of handling these scripts. For the sake
6186 of simplicity, this document describes only the symbolic
6187 link method. However, it must not be assumed by maintainer
6188 scripts that this method is being used, and any automated
6189 manipulation of the various runlevel behaviors by
6190 maintainer scripts must be performed using
6191 <prgn>update-rc.d</prgn> as described below and not by
6192 manually installing or removing symlinks. For information
6193 on the implementation details of the other method,
6194 implemented in the <tt>file-rc</tt> package, please refer
6195 to the documentation of that package.
6199 These scripts are referenced by symbolic links in the
6200 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6201 runlevels, <prgn>init</prgn> looks in the directory
6202 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6203 execute, where <tt><var>n</var></tt> is the runlevel that
6204 is being changed to, or <tt>S</tt> for the boot-up
6209 The names of the links all have the form
6210 <file>S<var>mm</var><var>script</var></file> or
6211 <file>K<var>mm</var><var>script</var></file> where
6212 <var>mm</var> is a two-digit number and <var>script</var>
6213 is the name of the script (this should be the same as the
6214 name of the actual script in <file>/etc/init.d</file>).
6218 When <prgn>init</prgn> changes runlevel first the targets
6219 of the links whose names start with a <tt>K</tt> are
6220 executed, each with the single argument <tt>stop</tt>,
6221 followed by the scripts prefixed with an <tt>S</tt>, each
6222 with the single argument <tt>start</tt>. (The links are
6223 those in the <file>/etc/rc<var>n</var>.d</file> directory
6224 corresponding to the new runlevel.) The <tt>K</tt> links
6225 are responsible for killing services and the <tt>S</tt>
6226 link for starting services upon entering the runlevel.
6230 For example, if we are changing from runlevel 2 to
6231 runlevel 3, init will first execute all of the <tt>K</tt>
6232 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6233 all of the <tt>S</tt> prefixed scripts in that directory.
6234 The links starting with <tt>K</tt> will cause the
6235 referred-to file to be executed with an argument of
6236 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6241 The two-digit number <var>mm</var> is used to determine
6242 the order in which to run the scripts: low-numbered links
6243 have their scripts run first. For example, the
6244 <tt>K20</tt> scripts will be executed before the
6245 <tt>K30</tt> scripts. This is used when a certain service
6246 must be started before another. For example, the name
6247 server <prgn>bind</prgn> might need to be started before
6248 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6249 can set up its access lists. In this case, the script
6250 that starts <prgn>bind</prgn> would have a lower number
6251 than the script that starts <prgn>inn</prgn> so that it
6253 <example compact="compact">
6260 The two runlevels 0 (halt) and 6 (reboot) are slightly
6261 different. In these runlevels, the links with an
6262 <tt>S</tt> prefix are still called after those with a
6263 <tt>K</tt> prefix, but they too are called with the single
6264 argument <tt>stop</tt>.
6268 <sect1 id="writing-init">
6269 <heading>Writing the scripts</heading>
6272 Packages that include daemons for system services should
6273 place scripts in <file>/etc/init.d</file> to start or stop
6274 services at boot time or during a change of runlevel.
6275 These scripts should be named
6276 <file>/etc/init.d/<var>package</var></file>, and they should
6277 accept one argument, saying what to do:
6280 <tag><tt>start</tt></tag>
6281 <item>start the service,</item>
6283 <tag><tt>stop</tt></tag>
6284 <item>stop the service,</item>
6286 <tag><tt>restart</tt></tag>
6287 <item>stop and restart the service if it's already running,
6288 otherwise start the service</item>
6290 <tag><tt>reload</tt></tag>
6291 <item><p>cause the configuration of the service to be
6292 reloaded without actually stopping and restarting
6295 <tag><tt>force-reload</tt></tag>
6296 <item>cause the configuration to be reloaded if the
6297 service supports this, otherwise restart the
6301 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6302 <tt>force-reload</tt> options should be supported by all
6303 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6308 The <file>init.d</file> scripts must ensure that they will
6309 behave sensibly (i.e., returning success and not starting
6310 multiple copies of a service) if invoked with <tt>start</tt>
6311 when the service is already running, or with <tt>stop</tt>
6312 when it isn't, and that they don't kill unfortunately-named
6313 user processes. The best way to achieve this is usually to
6314 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6319 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6320 scripts. Writing correct <file>init.d</file> scripts requires
6321 accepting various error exit statuses when daemons are already
6322 running or already stopped without aborting
6323 the <file>init.d</file> script, and common <file>init.d</file>
6324 function libraries are not safe to call with <tt>set -e</tt>
6326 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6327 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6328 in effect and echoing status messages to the console fails,
6330 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6331 to not use <tt>set -e</tt> and instead check the result of
6332 each command separately.
6336 If a service reloads its configuration automatically (as
6337 in the case of <prgn>cron</prgn>, for example), the
6338 <tt>reload</tt> option of the <file>init.d</file> script
6339 should behave as if the configuration has been reloaded
6344 The <file>/etc/init.d</file> scripts must be treated as
6345 configuration files, either (if they are present in the
6346 package, that is, in the .deb file) by marking them as
6347 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6348 by managing them correctly in the maintainer scripts (see
6349 <ref id="config-files">). This is important since we want
6350 to give the local system administrator the chance to adapt
6351 the scripts to the local system, e.g., to disable a
6352 service without de-installing the package, or to specify
6353 some special command line options when starting a service,
6354 while making sure their changes aren't lost during the next
6359 These scripts should not fail obscurely when the
6360 configuration files remain but the package has been
6361 removed, as configuration files remain on the system after
6362 the package has been removed. Only when <prgn>dpkg</prgn>
6363 is executed with the <tt>--purge</tt> option will
6364 configuration files be removed. In particular, as the
6365 <file>/etc/init.d/<var>package</var></file> script itself is
6366 usually a <tt>conffile</tt>, it will remain on the system
6367 if the package is removed but not purged. Therefore, you
6368 should include a <tt>test</tt> statement at the top of the
6370 <example compact="compact">
6371 test -f <var>program-executed-later-in-script</var> || exit 0
6376 Often there are some variables in the <file>init.d</file>
6377 scripts whose values control the behavior of the scripts,
6378 and which a system administrator is likely to want to
6379 change. As the scripts themselves are frequently
6380 <tt>conffile</tt>s, modifying them requires that the
6381 administrator merge in their changes each time the package
6382 is upgraded and the <tt>conffile</tt> changes. To ease
6383 the burden on the system administrator, such configurable
6384 values should not be placed directly in the script.
6385 Instead, they should be placed in a file in
6386 <file>/etc/default</file>, which typically will have the same
6387 base name as the <file>init.d</file> script. This extra file
6388 should be sourced by the script when the script runs. It
6389 must contain only variable settings and comments in SUSv3
6390 <prgn>sh</prgn> format. It may either be a
6391 <tt>conffile</tt> or a configuration file maintained by
6392 the package maintainer scripts. See <ref id="config-files">
6397 To ensure that vital configurable values are always
6398 available, the <file>init.d</file> script should set default
6399 values for each of the shell variables it uses, either
6400 before sourcing the <file>/etc/default/</file> file or
6401 afterwards using something like the <tt>:
6402 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6403 script must behave sensibly and not fail if the
6404 <file>/etc/default</file> file is deleted.
6408 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6409 as temporary filesystems<footnote>
6410 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6411 options in <file>/etc/default/rcS</file>.
6412 </footnote>, so the <file>init.d</file> scripts must handle this
6413 correctly. This will typically amount to creating any required
6414 subdirectories dynamically when the <file>init.d</file> script
6415 is run, rather than including them in the package and relying on
6416 <prgn>dpkg</prgn> to create them.
6421 <heading>Interfacing with the initscript system</heading>
6424 Maintainers should use the abstraction layer provided by
6425 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6426 programs to deal with initscripts in their packages'
6427 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6428 and <prgn>postrm</prgn>.
6432 Directly managing the /etc/rc?.d links and directly
6433 invoking the <file>/etc/init.d/</file> initscripts should
6434 be done only by packages providing the initscript
6435 subsystem (such as <prgn>sysv-rc</prgn> and
6436 <prgn>file-rc</prgn>).
6440 <heading>Managing the links</heading>
6443 The program <prgn>update-rc.d</prgn> is provided for
6444 package maintainers to arrange for the proper creation and
6445 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6446 or their functional equivalent if another method is being
6447 used. This may be used by maintainers in their packages'
6448 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6452 You must not include any <file>/etc/rc<var>n</var>.d</file>
6453 symbolic links in the actual archive or manually create or
6454 remove the symbolic links in maintainer scripts; you must
6455 use the <prgn>update-rc.d</prgn> program instead. (The
6456 former will fail if an alternative method of maintaining
6457 runlevel information is being used.) You must not include
6458 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6459 in the archive either. (Only the <tt>sysvinit</tt>
6464 By default <prgn>update-rc.d</prgn> will start services in
6465 each of the multi-user state runlevels (2, 3, 4, and 5)
6466 and stop them in the halt runlevel (0), the single-user
6467 runlevel (1) and the reboot runlevel (6). The system
6468 administrator will have the opportunity to customize
6469 runlevels by simply adding, moving, or removing the
6470 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6471 symbolic links are being used, or by modifying
6472 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6477 To get the default behavior for your package, put in your
6478 <prgn>postinst</prgn> script
6479 <example compact="compact">
6480 update-rc.d <var>package</var> defaults
6482 and in your <prgn>postrm</prgn>
6483 <example compact="compact">
6484 if [ "$1" = purge ]; then
6485 update-rc.d <var>package</var> remove
6487 </example>. Note that if your package changes runlevels
6488 or priority, you may have to remove and recreate the links,
6489 since otherwise the old links may persist. Refer to the
6490 documentation of <prgn>update-rc.d</prgn>.
6494 This will use a default sequence number of 20. If it does
6495 not matter when or in which order the <file>init.d</file>
6496 script is run, use this default. If it does, then you
6497 should talk to the maintainer of the <prgn>sysvinit</prgn>
6498 package or post to <tt>debian-devel</tt>, and they will
6499 help you choose a number.
6503 For more information about using <tt>update-rc.d</tt>,
6504 please consult its man page <manref name="update-rc.d"
6510 <heading>Running initscripts</heading>
6512 The program <prgn>invoke-rc.d</prgn> is provided to make
6513 it easier for package maintainers to properly invoke an
6514 initscript, obeying runlevel and other locally-defined
6515 constraints that might limit a package's right to start,
6516 stop and otherwise manage services. This program may be
6517 used by maintainers in their packages' scripts.
6521 The package maintainer scripts must use
6522 <prgn>invoke-rc.d</prgn> to invoke the
6523 <file>/etc/init.d/*</file> initscripts, instead of
6524 calling them directly.
6528 By default, <prgn>invoke-rc.d</prgn> will pass any
6529 action requests (start, stop, reload, restart...) to the
6530 <file>/etc/init.d</file> script, filtering out requests
6531 to start or restart a service out of its intended
6536 Most packages will simply need to change:
6537 <example compact="compact">/etc/init.d/<package>
6538 <action></example> in their <prgn>postinst</prgn>
6539 and <prgn>prerm</prgn> scripts to:
6540 <example compact="compact">
6541 if which invoke-rc.d >/dev/null 2>&1; then
6542 invoke-rc.d <var>package</var> <action>
6544 /etc/init.d/<var>package</var> <action>
6550 A package should register its initscript services using
6551 <prgn>update-rc.d</prgn> before it tries to invoke them
6552 using <prgn>invoke-rc.d</prgn>. Invocation of
6553 unregistered services may fail.
6557 For more information about using
6558 <prgn>invoke-rc.d</prgn>, please consult its man page
6559 <manref name="invoke-rc.d" section="8">.
6565 <heading>Boot-time initialization</heading>
6568 There used to be another directory, <file>/etc/rc.boot</file>,
6569 which contained scripts which were run once per machine
6570 boot. This has been deprecated in favour of links from
6571 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6572 described in <ref id="/etc/init.d">. Packages must not
6573 place files in <file>/etc/rc.boot</file>.
6578 <heading>Example</heading>
6581 An example on which you can base your
6582 <file>/etc/init.d</file> scripts is found in
6583 <file>/etc/init.d/skeleton</file>.
6590 <heading>Console messages from <file>init.d</file> scripts</heading>
6593 This section describes the formats to be used for messages
6594 written to standard output by the <file>/etc/init.d</file>
6595 scripts. The intent is to improve the consistency of
6596 Debian's startup and shutdown look and feel. For this
6597 reason, please look very carefully at the details. We want
6598 the messages to have the same format in terms of wording,
6599 spaces, punctuation and case of letters.
6603 Here is a list of overall rules that should be used for
6604 messages generated by <file>/etc/init.d</file> scripts.
6610 The message should fit in one line (fewer than 80
6611 characters), start with a capital letter and end with
6612 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6616 If the script is performing some time consuming task in
6617 the background (not merely starting or stopping a
6618 program, for instance), an ellipsis (three dots:
6619 <tt>...</tt>) should be output to the screen, with no
6620 leading or tailing whitespace or line feeds.
6624 The messages should appear as if the computer is telling
6625 the user what it is doing (politely :-), but should not
6626 mention "it" directly. For example, instead of:
6627 <example compact="compact">
6628 I'm starting network daemons: nfsd mountd.
6630 the message should say
6631 <example compact="compact">
6632 Starting network daemons: nfsd mountd.
6639 <tt>init.d</tt> script should use the following standard
6640 message formats for the situations enumerated below.
6646 <p>When daemons are started</p>
6649 If the script starts one or more daemons, the output
6650 should look like this (a single line, no leading
6652 <example compact="compact">
6653 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6655 The <var>description</var> should describe the
6656 subsystem the daemon or set of daemons are part of,
6657 while <var>daemon-1</var> up to <var>daemon-n</var>
6658 denote each daemon's name (typically the file name of
6663 For example, the output of <file>/etc/init.d/lpd</file>
6665 <example compact="compact">
6666 Starting printer spooler: lpd.
6671 This can be achieved by saying
6672 <example compact="compact">
6673 echo -n "Starting printer spooler: lpd"
6674 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6677 in the script. If there are more than one daemon to
6678 start, the output should look like this:
6679 <example compact="compact">
6680 echo -n "Starting remote file system services:"
6681 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6682 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6683 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6686 This makes it possible for the user to see what is
6687 happening and when the final daemon has been started.
6688 Care should be taken in the placement of white spaces:
6689 in the example above the system administrators can
6690 easily comment out a line if they don't want to start
6691 a specific daemon, while the displayed message still
6697 <p>When a system parameter is being set</p>
6700 If you have to set up different system parameters
6701 during the system boot, you should use this format:
6702 <example compact="compact">
6703 Setting <var>parameter</var> to "<var>value</var>".
6708 You can use a statement such as the following to get
6710 <example compact="compact">
6711 echo "Setting DNS domainname to \"$domainname\"."
6716 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6717 for the left and right quotation marks. A grave accent
6718 (<tt>`</tt>) is not a quote character; neither is an
6719 apostrophe (<tt>'</tt>).
6724 <p>When a daemon is stopped or restarted</p>
6727 When you stop or restart a daemon, you should issue a
6728 message identical to the startup message, except that
6729 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6730 or <tt>Restarting</tt> respectively.
6734 For example, stopping the printer daemon will look like
6736 <example compact="compact">
6737 Stopping printer spooler: lpd.
6743 <p>When something is executed</p>
6746 There are several examples where you have to run a
6747 program at system startup or shutdown to perform a
6748 specific task, for example, setting the system's clock
6749 using <prgn>netdate</prgn> or killing all processes
6750 when the system shuts down. Your message should look
6752 <example compact="compact">
6753 Doing something very useful...done.
6755 You should print the <tt>done.</tt> immediately after
6756 the job has been completed, so that the user is
6757 informed why they have to wait. You can get this
6759 <example compact="compact">
6760 echo -n "Doing something very useful..."
6769 <p>When the configuration is reloaded</p>
6772 When a daemon is forced to reload its configuration
6773 files you should use the following format:
6774 <example compact="compact">
6775 Reloading <var>description</var> configuration...done.
6777 where <var>description</var> is the same as in the
6778 daemon starting message.
6786 <heading>Cron jobs</heading>
6789 Packages must not modify the configuration file
6790 <file>/etc/crontab</file>, and they must not modify the files in
6791 <file>/var/spool/cron/crontabs</file>.</p>
6794 If a package wants to install a job that has to be executed
6795 via cron, it should place a file with the name of the
6796 package in one or more of the following directories:
6797 <example compact="compact">
6803 As these directory names imply, the files within them are
6804 executed on an hourly, daily, weekly, or monthly basis,
6805 respectively. The exact times are listed in
6806 <file>/etc/crontab</file>.</p>
6809 All files installed in any of these directories must be
6810 scripts (e.g., shell scripts or Perl scripts) so that they
6811 can easily be modified by the local system administrator.
6812 In addition, they must be treated as configuration files.
6816 If a certain job has to be executed at some other frequency or
6817 at a specific time, the package should install a file
6818 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6819 same syntax as <file>/etc/crontab</file> and is processed by
6820 <prgn>cron</prgn> automatically. The file must also be
6821 treated as a configuration file. (Note that entries in the
6822 <file>/etc/cron.d</file> directory are not handled by
6823 <prgn>anacron</prgn>. Thus, you should only use this
6824 directory for jobs which may be skipped if the system is not
6827 Unlike <file>crontab</file> files described in the IEEE Std
6828 1003.1-2008 (POSIX.1) available from
6829 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6830 name="The Open Group">, the files in
6831 <file>/etc/cron.d</file> and the file
6832 <file>/etc/crontab</file> have seven fields; namely:
6834 <item>Minute [0,59]</item>
6835 <item>Hour [0,23]</item>
6836 <item>Day of the month [1,31]</item>
6837 <item>Month of the year [1,12]</item>
6838 <item>Day of the week ([0,6] with 0=Sunday)</item>
6839 <item>Username</item>
6840 <item>Command to be run</item>
6842 Ranges of numbers are allowed. Ranges are two numbers
6843 separated with a hyphen. The specified range is inclusive.
6844 Lists are allowed. A list is a set of numbers (or ranges)
6845 separated by commas. Step values can be used in conjunction
6850 The scripts or <tt>crontab</tt> entries in these directories should
6851 check if all necessary programs are installed before they
6852 try to execute them. Otherwise, problems will arise when a
6853 package was removed but not purged since configuration files
6854 are kept on the system in this situation.
6858 Any <tt>cron</tt> daemon must provide
6859 <file>/usr/bin/crontab</file> and support normal
6860 <tt>crontab</tt> entries as specified in POSIX. The daemon
6861 must also support names for days and months, ranges, and
6862 step values. It has to support <file>/etc/crontab</file>,
6863 and correctly execute the scripts in
6864 <file>/etc/cron.d</file>. The daemon must also correctly
6866 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6871 <heading>Menus</heading>
6874 The Debian <tt>menu</tt> package provides a standard
6875 interface between packages providing applications and
6876 <em>menu programs</em> (either X window managers or
6877 text-based menu programs such as <prgn>pdmenu</prgn>).
6881 All packages that provide applications that need not be
6882 passed any special command line arguments for normal
6883 operation should register a menu entry for those
6884 applications, so that users of the <tt>menu</tt> package
6885 will automatically get menu entries in their window
6886 managers, as well in shells like <tt>pdmenu</tt>.
6890 Menu entries should follow the current menu policy.
6894 The menu policy can be found in the <tt>menu-policy</tt>
6895 files in the <tt>debian-policy</tt> package.
6896 It is also available from the Debian web mirrors at
6897 <tt><url name="/doc/packaging-manuals/menu-policy/"
6898 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6902 Please also refer to the <em>Debian Menu System</em>
6903 documentation that comes with the <package>menu</package>
6904 package for information about how to register your
6910 <heading>Multimedia handlers</heading>
6913 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6914 is a mechanism for encoding files and data streams and
6915 providing meta-information about them, in particular their
6916 type (e.g. audio or video) and format (e.g. PNG, HTML,
6921 Registration of MIME type handlers allows programs like mail
6922 user agents and web browsers to invoke these handlers to
6923 view, edit or display MIME types they don't support directly.
6927 Packages which provide the ability to view/show/play,
6928 compose, edit or print MIME types should register themselves
6929 as such following the current MIME support policy.
6933 The MIME support policy can be found in the <tt>mime-policy</tt>
6934 files in the <tt>debian-policy</tt> package.
6935 It is also available from the Debian web mirrors at
6936 <tt><url name="/doc/packaging-manuals/mime-policy/"
6937 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6943 <heading>Keyboard configuration</heading>
6946 To achieve a consistent keyboard configuration so that all
6947 applications interpret a keyboard event the same way, all
6948 programs in the Debian distribution must be configured to
6949 comply with the following guidelines.
6953 The following keys must have the specified interpretations:
6956 <tag><tt><--</tt></tag>
6957 <item>delete the character to the left of the cursor</item>
6959 <tag><tt>Delete</tt></tag>
6960 <item>delete the character to the right of the cursor</item>
6962 <tag><tt>Control+H</tt></tag>
6963 <item>emacs: the help prefix</item>
6966 The interpretation of any keyboard events should be
6967 independent of the terminal that is used, be it a virtual
6968 console, an X terminal emulator, an rlogin/telnet session,
6973 The following list explains how the different programs
6974 should be set up to achieve this:
6980 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6984 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6988 X translations are set up to make
6989 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6990 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6991 is the vt220 escape code for the "delete character"
6992 key). This must be done by loading the X resources
6993 using <prgn>xrdb</prgn> on all local X displays, not
6994 using the application defaults, so that the
6995 translation resources used correspond to the
6996 <prgn>xmodmap</prgn> settings.
7000 The Linux console is configured to make
7001 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7002 generate <tt>ESC [ 3 ~</tt>.
7006 X applications are configured so that <tt><</tt>
7007 deletes left, and <tt>Delete</tt> deletes right. Motif
7008 applications already work like this.
7012 Terminals should have <tt>stty erase ^?</tt> .
7016 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7017 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7018 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7022 Emacs is programmed to map <tt>KB_Backspace</tt> or
7023 the <tt>stty erase</tt> character to
7024 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7025 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7026 <tt>^H</tt> to <tt>help</tt> as always.
7030 Other applications use the <tt>stty erase</tt>
7031 character and <tt>kdch1</tt> for the two delete keys,
7032 with ASCII DEL being "delete previous character" and
7033 <tt>kdch1</tt> being "delete character under
7041 This will solve the problem except for the following
7048 Some terminals have a <tt><--</tt> key that cannot
7049 be made to produce anything except <tt>^H</tt>. On
7050 these terminals Emacs help will be unavailable on
7051 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7052 character takes precedence in Emacs, and has been set
7053 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7054 available) can be used instead.
7058 Some operating systems use <tt>^H</tt> for <tt>stty
7059 erase</tt>. However, modern telnet versions and all
7060 rlogin versions propagate <tt>stty</tt> settings, and
7061 almost all UNIX versions honour <tt>stty erase</tt>.
7062 Where the <tt>stty</tt> settings are not propagated
7063 correctly, things can be made to work by using
7064 <tt>stty</tt> manually.
7068 Some systems (including previous Debian versions) use
7069 <prgn>xmodmap</prgn> to arrange for both
7070 <tt><--</tt> and <tt>Delete</tt> to generate
7071 <tt>KB_Delete</tt>. We can change the behavior of
7072 their X clients using the same X resources that we use
7073 to do it for our own clients, or configure our clients
7074 using their resources when things are the other way
7075 around. On displays configured like this
7076 <tt>Delete</tt> will not work, but <tt><--</tt>
7081 Some operating systems have different <tt>kdch1</tt>
7082 settings in their <tt>terminfo</tt> database for
7083 <tt>xterm</tt> and others. On these systems the
7084 <tt>Delete</tt> key will not work correctly when you
7085 log in from a system conforming to our policy, but
7086 <tt><--</tt> will.
7093 <heading>Environment variables</heading>
7096 A program must not depend on environment variables to get
7097 reasonable defaults. (That's because these environment
7098 variables would have to be set in a system-wide
7099 configuration file like <file>/etc/profile</file>, which is not
7100 supported by all shells.)
7104 If a program usually depends on environment variables for its
7105 configuration, the program should be changed to fall back to
7106 a reasonable default configuration if these environment
7107 variables are not present. If this cannot be done easily
7108 (e.g., if the source code of a non-free program is not
7109 available), the program must be replaced by a small
7110 "wrapper" shell script which sets the environment variables
7111 if they are not already defined, and calls the original program.
7115 Here is an example of a wrapper script for this purpose:
7117 <example compact="compact">
7119 BAR=${BAR:-/var/lib/fubar}
7121 exec /usr/lib/foo/foo "$@"
7126 Furthermore, as <file>/etc/profile</file> is a configuration
7127 file of the <prgn>base-files</prgn> package, other packages must
7128 not put any environment variables or other commands into that
7133 <sect id="doc-base">
7134 <heading>Registering Documents using doc-base</heading>
7137 The <package>doc-base</package> package implements a
7138 flexible mechanism for handling and presenting
7139 documentation. The recommended practice is for every Debian
7140 package that provides online documentation (other than just
7141 manual pages) to register these documents with
7142 <package>doc-base</package> by installing a
7143 <package>doc-base</package> control file via the
7144 <prgn/install-docs/ script at installation time and
7145 de-register the manuals again when the package is removed.
7148 Please refer to the documentation that comes with the
7149 <package>doc-base</package> package for information and
7158 <heading>Files</heading>
7160 <sect id="binaries">
7161 <heading>Binaries</heading>
7164 Two different packages must not install programs with
7165 different functionality but with the same filenames. (The
7166 case of two programs having the same functionality but
7167 different implementations is handled via "alternatives" or
7168 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7169 <ref id="conflicts"> respectively.) If this case happens,
7170 one of the programs must be renamed. The maintainers should
7171 report this to the <tt>debian-devel</tt> mailing list and
7172 try to find a consensus about which program will have to be
7173 renamed. If a consensus cannot be reached, <em>both</em>
7174 programs must be renamed.
7178 By default, when a package is being built, any binaries
7179 created should include debugging information, as well as
7180 being compiled with optimization. You should also turn on
7181 as many reasonable compilation warnings as possible; this
7182 makes life easier for porters, who can then look at build
7183 logs for possible problems. For the C programming language,
7184 this means the following compilation parameters should be
7186 <example compact="compact">
7188 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7190 INSTALL = install -s # (or use strip on the files in debian/tmp)
7195 Note that by default all installed binaries should be stripped,
7196 either by using the <tt>-s</tt> flag to
7197 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7198 the binaries after they have been copied into
7199 <file>debian/tmp</file> but before the tree is made into a
7204 Although binaries in the build tree should be compiled with
7205 debugging information by default, it can often be difficult to
7206 debug programs if they are also subjected to compiler
7207 optimization. For this reason, it is recommended to support the
7208 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7209 (see <ref id="debianrules-options">). This variable can contain
7210 several flags to change how a package is compiled and built.
7214 It is up to the package maintainer to decide what
7215 compilation options are best for the package. Certain
7216 binaries (such as computationally-intensive programs) will
7217 function better with certain flags (<tt>-O3</tt>, for
7218 example); feel free to use them. Please use good judgment
7219 here. Don't use flags for the sake of it; only use them
7220 if there is good reason to do so. Feel free to override
7221 the upstream author's ideas about which compilation
7222 options are best: they are often inappropriate for our
7228 <sect id="libraries">
7229 <heading>Libraries</heading>
7232 If the package is <strong>architecture: any</strong>, then
7233 the shared library compilation and linking flags must have
7234 <tt>-fPIC</tt>, or the package shall not build on some of
7235 the supported architectures<footnote>
7237 If you are using GCC, <tt>-fPIC</tt> produces code with
7238 relocatable position independent code, which is required for
7239 most architectures to create a shared library, with i386 and
7240 perhaps some others where non position independent code is
7241 permitted in a shared library.
7244 Position independent code may have a performance penalty,
7245 especially on <tt>i386</tt>. However, in most cases the
7246 speed penalty must be measured against the memory wasted on
7247 the few architectures where non position independent code is
7250 </footnote>. Any exception to this rule must be discussed on
7251 the mailing list <em>debian-devel@lists.debian.org</em>, and
7252 a rough consensus obtained. The reasons for not compiling
7253 with <tt>-fPIC</tt> flag must be recorded in the file
7254 <tt>README.Debian</tt>, and care must be taken to either
7255 restrict the architecture or arrange for <tt>-fPIC</tt> to
7256 be used on architectures where it is required.<footnote>
7258 Some of the reasons why this might be required is if the
7259 library contains hand crafted assembly code that is not
7260 relocatable, the speed penalty is excessive for compute
7261 intensive libs, and similar reasons.
7266 As to the static libraries, the common case is not to have
7267 relocatable code, since there is no benefit, unless in specific
7268 cases; therefore the static version must not be compiled
7269 with the <tt>-fPIC</tt> flag. Any exception to this rule
7270 should be discussed on the mailing list
7271 <em>debian-devel@lists.debian.org</em>, and the reasons for
7272 compiling with the <tt>-fPIC</tt> flag must be recorded in
7273 the file <tt>README.Debian</tt>. <footnote>
7275 Some of the reasons for linking static libraries with
7276 the <tt>-fPIC</tt> flag are if, for example, one needs a
7277 Perl API for a library that is under rapid development,
7278 and has an unstable API, so shared libraries are
7279 pointless at this phase of the library's development. In
7280 that case, since Perl needs a library with relocatable
7281 code, it may make sense to create a static library with
7282 relocatable code. Another reason cited is if you are
7283 distilling various libraries into a common shared
7284 library, like <tt>mklibs</tt> does in the Debian
7290 In other words, if both a shared and a static library is
7291 being built, each source unit (<tt>*.c</tt>, for example,
7292 for C files) will need to be compiled twice, for the normal
7296 You must specify the gcc option <tt>-D_REENTRANT</tt>
7297 when building a library (either static or shared) to make
7298 the library compatible with LinuxThreads.
7302 Although not enforced by the build tools, shared libraries
7303 must be linked against all libraries that they use symbols from
7304 in the same way that binaries are. This ensures the correct
7305 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7306 system and guarantees that all libraries can be safely opened
7307 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7308 option <tt>-Wl,-z,defs</tt> when building a shared library.
7309 Since this option enforces symbol resolution at build time,
7310 a missing library reference will be caught early as a fatal
7315 All installed shared libraries should be stripped with
7316 <example compact="compact">
7317 strip --strip-unneeded <var>your-lib</var>
7319 (The option <tt>--strip-unneeded</tt> makes
7320 <prgn>strip</prgn> remove only the symbols which aren't
7321 needed for relocation processing.) Shared libraries can
7322 function perfectly well when stripped, since the symbols for
7323 dynamic linking are in a separate part of the ELF object
7325 You might also want to use the options
7326 <tt>--remove-section=.comment</tt> and
7327 <tt>--remove-section=.note</tt> on both shared libraries
7328 and executables, and <tt>--strip-debug</tt> on static
7334 Note that under some circumstances it may be useful to
7335 install a shared library unstripped, for example when
7336 building a separate package to support debugging.
7340 Shared object files (often <file>.so</file> files) that are not
7341 public libraries, that is, they are not meant to be linked
7342 to by third party executables (binaries of other packages),
7343 should be installed in subdirectories of the
7344 <file>/usr/lib</file> directory. Such files are exempt from the
7345 rules that govern ordinary shared libraries, except that
7346 they must not be installed executable and should be
7348 A common example are the so-called "plug-ins",
7349 internal shared objects that are dynamically loaded by
7350 programs using <manref name="dlopen" section="3">.
7355 Packages that use <prgn>libtool</prgn> to create and install
7356 their shared libraries install a file containing additional
7357 metadata (ending in <file>.la</file>) alongside the library.
7358 For public libraries intended for use by other packages, these
7359 files normally should not be included in the Debian package,
7360 since the information they include is not necessary to link with
7361 the shared library on Debian and can add unnecessary additional
7362 dependencies to other programs or libraries.<footnote>
7363 These files store, among other things, all libraries on which
7364 that shared library depends. Unfortunately, if
7365 the <file>.la</file> file is present and contains that
7366 dependency information, using <prgn>libtool</prgn> when
7367 linking against that library will cause the resulting program
7368 or library to be linked against those dependencies as well,
7369 even if this is unnecessary. This can create unneeded
7370 dependencies on shared library packages that would otherwise
7371 be hidden behind the library ABI, and can make library
7372 transitions to new SONAMEs unnecessarily complicated and
7373 difficult to manage.
7375 If the <file>.la</file> file is required for that library (if,
7376 for instance, it's loaded via <tt>libltdl</tt> in a way that
7377 requires that meta-information), the <tt>dependency_libs</tt>
7378 setting in the <file>.la</file> file should normally be set to
7379 the empty string. If the shared library development package has
7380 historically included the <file>.la</file>, it must be retained
7381 in the development package (with <tt>dependency_libs</tt>
7382 emptied) until all libraries that depend on it have removed or
7383 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7384 files to prevent linking with those other libraries
7385 using <prgn>libtool</prgn> from failing.
7389 If the <file>.la</file> must be included, it should be included
7390 in the development (<tt>-dev</tt>) package, unless the library
7391 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7392 library. If it is intended for use with <tt>libltdl</tt>,
7393 the <file>.la</file> files must go in the run-time library
7398 These requirements for handling of <file>.la</file> files do not
7399 apply to loadable modules or libraries not installed in
7400 directories searched by default by the dynamic linker. Packages
7401 installing loadable modules will frequently need to install
7402 the <file>.la</file> files alongside the modules so that they
7403 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7404 does not need to be modified for libraries or modules that are
7405 not installed in directories searched by the dynamic linker by
7406 default and not intended for use by other packages.
7410 You must make sure that you use only released versions of
7411 shared libraries to build your packages; otherwise other
7412 users will not be able to run your binaries
7413 properly. Producing source packages that depend on
7414 unreleased compilers is also usually a bad
7421 <heading>Shared libraries</heading>
7423 This section has moved to <ref id="sharedlibs">.
7429 <heading>Scripts</heading>
7432 All command scripts, including the package maintainer
7433 scripts inside the package and used by <prgn>dpkg</prgn>,
7434 should have a <tt>#!</tt> line naming the shell to be used
7439 In the case of Perl scripts this should be
7440 <tt>#!/usr/bin/perl</tt>.
7444 When scripts are installed into a directory in the system
7445 PATH, the script name should not include an extension such
7446 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7447 language currently used to implement it.
7450 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7451 <file>init.d</file> scripts should almost certainly start
7452 with <tt>set -e</tt> so that errors are detected.
7453 <file>init.d</file> scripts are something of a special case, due
7454 to how frequently they need to call commands that are allowed to
7455 fail, and it may instead be easier to check the exit status of
7456 commands directly. See <ref id="writing-init"> for more
7457 information about writing <file>init.d</file> scripts.
7460 Every script should use <tt>set -e</tt> or check the exit status
7461 of <em>every</em> command.
7464 Scripts may assume that <file>/bin/sh</file> implements the
7465 SUSv3 Shell Command Language<footnote>
7466 Single UNIX Specification, version 3, which is also IEEE
7467 1003.1-2004 (POSIX), and is available on the World Wide Web
7468 from <url id="http://www.unix.org/version3/online.html"
7469 name="The Open Group"> after free
7470 registration.</footnote>
7471 plus the following additional features not mandated by
7473 These features are in widespread use in the Linux community
7474 and are implemented in all of bash, dash, and ksh, the most
7475 common shells users may wish to use as <file>/bin/sh</file>.
7478 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7479 must not generate a newline.</item>
7480 <item><tt>test</tt>, if implemented as a shell built-in, must
7481 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7483 <item><tt>local</tt> to create a scoped variable must be
7484 supported, including listing multiple variables in a single
7485 local command and assigning a value to a variable at the
7486 same time as localizing it. <tt>local</tt> may or
7487 may not preserve the variable value from an outer scope if
7488 no assignment is present. Uses such as:
7492 # ... use a, b, c, d ...
7495 must be supported and must set the value of <tt>c</tt> to
7499 If a shell script requires non-SUSv3 features from the shell
7500 interpreter other than those listed above, the appropriate shell
7501 must be specified in the first line of the script (e.g.,
7502 <tt>#!/bin/bash</tt>) and the package must depend on the package
7503 providing the shell (unless the shell package is marked
7504 "Essential", as in the case of <prgn>bash</prgn>).
7508 You may wish to restrict your script to SUSv3 features plus the
7509 above set when possible so that it may use <file>/bin/sh</file>
7510 as its interpreter. If your script works with <prgn>dash</prgn>
7511 (originally called <prgn>ash</prgn>), it probably complies with
7512 the above requirements, but if you are in doubt, use
7513 <file>/bin/bash</file>.
7517 Perl scripts should check for errors when making any
7518 system calls, including <tt>open</tt>, <tt>print</tt>,
7519 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7523 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7524 scripting languages. See <em>Csh Programming Considered
7525 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7526 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7527 If an upstream package comes with <prgn>csh</prgn> scripts
7528 then you must make sure that they start with
7529 <tt>#!/bin/csh</tt> and make your package depend on the
7530 <prgn>c-shell</prgn> virtual package.
7534 Any scripts which create files in world-writeable
7535 directories (e.g., in <file>/tmp</file>) must use a
7536 mechanism which will fail atomically if a file with the same
7537 name already exists.
7541 The Debian base system provides the <prgn>tempfile</prgn>
7542 and <prgn>mktemp</prgn> utilities for use by scripts for
7549 <heading>Symbolic links</heading>
7552 In general, symbolic links within a top-level directory
7553 should be relative, and symbolic links pointing from one
7554 top-level directory into another should be absolute. (A
7555 top-level directory is a sub-directory of the root
7556 directory <file>/</file>.)
7560 In addition, symbolic links should be specified as short as
7561 possible, i.e., link targets like <file>foo/../bar</file> are
7566 Note that when creating a relative link using
7567 <prgn>ln</prgn> it is not necessary for the target of the
7568 link to exist relative to the working directory you're
7569 running <prgn>ln</prgn> from, nor is it necessary to change
7570 directory to the directory where the link is to be made.
7571 Simply include the string that should appear as the target
7572 of the link (this will be a pathname relative to the
7573 directory in which the link resides) as the first argument
7578 For example, in your <prgn>Makefile</prgn> or
7579 <file>debian/rules</file>, you can do things like:
7580 <example compact="compact">
7581 ln -fs gcc $(prefix)/bin/cc
7582 ln -fs gcc debian/tmp/usr/bin/cc
7583 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7584 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7589 A symbolic link pointing to a compressed file should always
7590 have the same file extension as the referenced file. (For
7591 example, if a file <file>foo.gz</file> is referenced by a
7592 symbolic link, the filename of the link has to end with
7593 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7598 <heading>Device files</heading>
7601 Packages must not include device files or named pipes in the
7606 If a package needs any special device files that are not
7607 included in the base system, it must call
7608 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7609 after notifying the user<footnote>
7610 This notification could be done via a (low-priority)
7611 debconf message, or an echo (printf) statement.
7616 Packages must not remove any device files in the
7617 <prgn>postrm</prgn> or any other script. This is left to the
7618 system administrator.
7622 Debian uses the serial devices
7623 <file>/dev/ttyS*</file>. Programs using the old
7624 <file>/dev/cu*</file> devices should be changed to use
7625 <file>/dev/ttyS*</file>.
7629 Named pipes needed by the package must be created in
7630 the <prgn>postinst</prgn> script<footnote>
7631 It's better to use <prgn>mkfifo</prgn> rather
7632 than <prgn>mknod</prgn> to create named pipes so that
7633 automated checks for packages incorrectly creating device
7634 files with <prgn>mknod</prgn> won't have false positives.
7635 </footnote> and removed in
7636 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7641 <sect id="config-files">
7642 <heading>Configuration files</heading>
7645 <heading>Definitions</heading>
7649 <tag>configuration file</tag>
7651 A file that affects the operation of a program, or
7652 provides site- or host-specific information, or
7653 otherwise customizes the behavior of a program.
7654 Typically, configuration files are intended to be
7655 modified by the system administrator (if needed or
7656 desired) to conform to local policy or to provide
7657 more useful site-specific behavior.
7660 <tag><tt>conffile</tt></tag>
7662 A file listed in a package's <tt>conffiles</tt>
7663 file, and is treated specially by <prgn>dpkg</prgn>
7664 (see <ref id="configdetails">).
7670 The distinction between these two is important; they are
7671 not interchangeable concepts. Almost all
7672 <tt>conffile</tt>s are configuration files, but many
7673 configuration files are not <tt>conffiles</tt>.
7677 As noted elsewhere, <file>/etc/init.d</file> scripts,
7678 <file>/etc/default</file> files, scripts installed in
7679 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7680 configuration installed in <file>/etc/cron.d</file> must be
7681 treated as configuration files. In general, any script that
7682 embeds configuration information is de-facto a configuration
7683 file and should be treated as such.
7688 <heading>Location</heading>
7691 Any configuration files created or used by your package
7692 must reside in <file>/etc</file>. If there are several,
7693 consider creating a subdirectory of <file>/etc</file>
7694 named after your package.
7698 If your package creates or uses configuration files
7699 outside of <file>/etc</file>, and it is not feasible to modify
7700 the package to use <file>/etc</file> directly, put the files
7701 in <file>/etc</file> and create symbolic links to those files
7702 from the location that the package requires.
7707 <heading>Behavior</heading>
7710 Configuration file handling must conform to the following
7712 <list compact="compact">
7714 local changes must be preserved during a package
7718 configuration files must be preserved when the
7719 package is removed, and only deleted when the
7723 Obsolete configuration files without local changes may be
7724 removed by the package during upgrade.
7728 The easy way to achieve this behavior is to make the
7729 configuration file a <tt>conffile</tt>. This is
7730 appropriate only if it is possible to distribute a default
7731 version that will work for most installations, although
7732 some system administrators may choose to modify it. This
7733 implies that the default version will be part of the
7734 package distribution, and must not be modified by the
7735 maintainer scripts during installation (or at any other
7740 In order to ensure that local changes are preserved
7741 correctly, no package may contain or make hard links to
7742 conffiles.<footnote>
7743 Rationale: There are two problems with hard links.
7744 The first is that some editors break the link while
7745 editing one of the files, so that the two files may
7746 unwittingly become unlinked and different. The second
7747 is that <prgn>dpkg</prgn> might break the hard link
7748 while upgrading <tt>conffile</tt>s.
7753 The other way to do it is via the maintainer scripts. In
7754 this case, the configuration file must not be listed as a
7755 <tt>conffile</tt> and must not be part of the package
7756 distribution. If the existence of a file is required for
7757 the package to be sensibly configured it is the
7758 responsibility of the package maintainer to provide
7759 maintainer scripts which correctly create, update and
7760 maintain the file and remove it on purge. (See <ref
7761 id="maintainerscripts"> for more information.) These
7762 scripts must be idempotent (i.e., must work correctly if
7763 <prgn>dpkg</prgn> needs to re-run them due to errors
7764 during installation or removal), must cope with all the
7765 variety of ways <prgn>dpkg</prgn> can call maintainer
7766 scripts, must not overwrite or otherwise mangle the user's
7767 configuration without asking, must not ask unnecessary
7768 questions (particularly during upgrades), and must
7769 otherwise be good citizens.
7773 The scripts are not required to configure every possible
7774 option for the package, but only those necessary to get
7775 the package running on a given system. Ideally the
7776 sysadmin should not have to do any configuration other
7777 than that done (semi-)automatically by the
7778 <prgn>postinst</prgn> script.
7782 A common practice is to create a script called
7783 <file><var>package</var>-configure</file> and have the
7784 package's <prgn>postinst</prgn> call it if and only if the
7785 configuration file does not already exist. In certain
7786 cases it is useful for there to be an example or template
7787 file which the maintainer scripts use. Such files should
7788 be in <file>/usr/share/<var>package</var></file> or
7789 <file>/usr/lib/<var>package</var></file> (depending on whether
7790 they are architecture-independent or not). There should
7791 be symbolic links to them from
7792 <file>/usr/share/doc/<var>package</var>/examples</file> if
7793 they are examples, and should be perfectly ordinary
7794 <prgn>dpkg</prgn>-handled files (<em>not</em>
7795 configuration files).
7799 These two styles of configuration file handling must
7800 not be mixed, for that way lies madness:
7801 <prgn>dpkg</prgn> will ask about overwriting the file
7802 every time the package is upgraded.
7807 <heading>Sharing configuration files</heading>
7810 Packages which specify the same file as a
7811 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7812 with each other. (This is an instance of the general rule
7813 about not sharing files. Note that neither alternatives
7814 nor diversions are likely to be appropriate in this case;
7815 in particular, <prgn>dpkg</prgn> does not handle diverted
7816 <tt>conffile</tt>s well.)
7820 The maintainer scripts must not alter a <tt>conffile</tt>
7821 of <em>any</em> package, including the one the scripts
7826 If two or more packages use the same configuration file
7827 and it is reasonable for both to be installed at the same
7828 time, one of these packages must be defined as
7829 <em>owner</em> of the configuration file, i.e., it will be
7830 the package which handles that file as a configuration
7831 file. Other packages that use the configuration file must
7832 depend on the owning package if they require the
7833 configuration file to operate. If the other package will
7834 use the configuration file if present, but is capable of
7835 operating without it, no dependency need be declared.
7839 If it is desirable for two or more related packages to
7840 share a configuration file <em>and</em> for all of the
7841 related packages to be able to modify that configuration
7842 file, then the following should be done:
7843 <enumlist compact="compact">
7845 One of the related packages (the "owning" package)
7846 will manage the configuration file with maintainer
7847 scripts as described in the previous section.
7850 The owning package should also provide a program
7851 that the other packages may use to modify the
7855 The related packages must use the provided program
7856 to make any desired modifications to the
7857 configuration file. They should either depend on
7858 the core package to guarantee that the configuration
7859 modifier program is available or accept gracefully
7860 that they cannot modify the configuration file if it
7861 is not. (This is in addition to the fact that the
7862 configuration file may not even be present in the
7869 Sometimes it's appropriate to create a new package which
7870 provides the basic infrastructure for the other packages
7871 and which manages the shared configuration files. (The
7872 <tt>sgml-base</tt> package is a good example.)
7877 <heading>User configuration files ("dotfiles")</heading>
7880 The files in <file>/etc/skel</file> will automatically be
7881 copied into new user accounts by <prgn>adduser</prgn>.
7882 No other program should reference the files in
7883 <file>/etc/skel</file>.
7887 Therefore, if a program needs a dotfile to exist in
7888 advance in <file>$HOME</file> to work sensibly, that dotfile
7889 should be installed in <file>/etc/skel</file> and treated as a
7894 However, programs that require dotfiles in order to
7895 operate sensibly are a bad thing, unless they do create
7896 the dotfiles themselves automatically.
7900 Furthermore, programs should be configured by the Debian
7901 default installation to behave as closely to the upstream
7902 default behavior as possible.
7906 Therefore, if a program in a Debian package needs to be
7907 configured in some way in order to operate sensibly, that
7908 should be done using a site-wide configuration file placed
7909 in <file>/etc</file>. Only if the program doesn't support a
7910 site-wide default configuration and the package maintainer
7911 doesn't have time to add it may a default per-user file be
7912 placed in <file>/etc/skel</file>.
7916 <file>/etc/skel</file> should be as empty as we can make it.
7917 This is particularly true because there is no easy (or
7918 necessarily desirable) mechanism for ensuring that the
7919 appropriate dotfiles are copied into the accounts of
7920 existing users when a package is installed.
7926 <heading>Log files</heading>
7928 Log files should usually be named
7929 <file>/var/log/<var>package</var>.log</file>. If you have many
7930 log files, or need a separate directory for permission
7931 reasons (<file>/var/log</file> is writable only by
7932 <file>root</file>), you should usually create a directory named
7933 <file>/var/log/<var>package</var></file> and place your log
7938 Log files must be rotated occasionally so that they don't
7939 grow indefinitely; the best way to do this is to drop a log
7940 rotation configuration file into the directory
7941 <file>/etc/logrotate.d</file> and use the facilities provided by
7942 logrotate.<footnote>
7944 The traditional approach to log files has been to set up
7945 <em>ad hoc</em> log rotation schemes using simple shell
7946 scripts and cron. While this approach is highly
7947 customizable, it requires quite a lot of sysadmin work.
7948 Even though the original Debian system helped a little
7949 by automatically installing a system which can be used
7950 as a template, this was deemed not enough.
7954 The use of <prgn>logrotate</prgn>, a program developed
7955 by Red Hat, is better, as it centralizes log management.
7956 It has both a configuration file
7957 (<file>/etc/logrotate.conf</file>) and a directory where
7958 packages can drop their individual log rotation
7959 configurations (<file>/etc/logrotate.d</file>).
7962 Here is a good example for a logrotate config
7963 file (for more information see <manref name="logrotate"
7965 <example compact="compact">
7966 /var/log/foo/*.log {
7971 /etc/init.d/foo force-reload
7975 This rotates all files under <file>/var/log/foo</file>, saves 12
7976 compressed generations, and forces the daemon to reload its
7977 configuration information after the log rotation.
7981 Log files should be removed when the package is
7982 purged (but not when it is only removed). This should be
7983 done by the <prgn>postrm</prgn> script when it is called
7984 with the argument <tt>purge</tt> (see <ref
7985 id="removedetails">).
7990 <heading>Permissions and owners</heading>
7993 The rules in this section are guidelines for general use.
7994 If necessary you may deviate from the details below.
7995 However, if you do so you must make sure that what is done
7996 is secure and you should try to be as consistent as possible
7997 with the rest of the system. You should probably also
7998 discuss it on <prgn>debian-devel</prgn> first.
8002 Files should be owned by <tt>root:root</tt>, and made
8003 writable only by the owner and universally readable (and
8004 executable, if appropriate), that is mode 644 or 755.
8008 Directories should be mode 755 or (for group-writability)
8009 mode 2775. The ownership of the directory should be
8010 consistent with its mode: if a directory is mode 2775, it
8011 should be owned by the group that needs write access to
8014 When a package is upgraded, and the owner or permissions
8015 of a file included in the package has changed, dpkg
8016 arranges for the ownership and permissions to be
8017 correctly set upon installation. However, this does not
8018 extend to directories; the permissions and ownership of
8019 directories already on the system does not change on
8020 install or upgrade of packages. This makes sense, since
8021 otherwise common directories like <tt>/usr</tt> would
8022 always be in flux. To correctly change permissions of a
8023 directory the package owns, explicit action is required,
8024 usually in the <tt>postinst</tt> script. Care must be
8025 taken to handle downgrades as well, in that case.
8032 Setuid and setgid executables should be mode 4755 or 2755
8033 respectively, and owned by the appropriate user or group.
8034 They should not be made unreadable (modes like 4711 or
8035 2711 or even 4111); doing so achieves no extra security,
8036 because anyone can find the binary in the freely available
8037 Debian package; it is merely inconvenient. For the same
8038 reason you should not restrict read or execute permissions
8039 on non-set-id executables.
8043 Some setuid programs need to be restricted to particular
8044 sets of users, using file permissions. In this case they
8045 should be owned by the uid to which they are set-id, and by
8046 the group which should be allowed to execute them. They
8047 should have mode 4754; again there is no point in making
8048 them unreadable to those users who must not be allowed to
8053 It is possible to arrange that the system administrator can
8054 reconfigure the package to correspond to their local
8055 security policy by changing the permissions on a binary:
8056 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8057 described below.<footnote>
8058 Ordinary files installed by <prgn>dpkg</prgn> (as
8059 opposed to <tt>conffile</tt>s and other similar objects)
8060 normally have their permissions reset to the distributed
8061 permissions when the package is reinstalled. However,
8062 the use of <prgn>dpkg-statoverride</prgn> overrides this
8065 Another method you should consider is to create a group for
8066 people allowed to use the program(s) and make any setuid
8067 executables executable only by that group.
8071 If you need to create a new user or group for your package
8072 there are two possibilities. Firstly, you may need to
8073 make some files in the binary package be owned by this
8074 user or group, or you may need to compile the user or
8075 group id (rather than just the name) into the binary
8076 (though this latter should be avoided if possible, as in
8077 this case you need a statically allocated id).</p>
8080 If you need a statically allocated id, you must ask for a
8081 user or group id from the <tt>base-passwd</tt> maintainer,
8082 and must not release the package until you have been
8083 allocated one. Once you have been allocated one you must
8084 either make the package depend on a version of the
8085 <tt>base-passwd</tt> package with the id present in
8086 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8087 your package to create the user or group itself with the
8088 correct id (using <tt>adduser</tt>) in its
8089 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8090 the <prgn>postinst</prgn> is to be preferred if it is
8091 possible, otherwise a pre-dependency will be needed on the
8092 <tt>adduser</tt> package.)
8096 On the other hand, the program might be able to determine
8097 the uid or gid from the user or group name at runtime, so
8098 that a dynamically allocated id can be used. In this case
8099 you should choose an appropriate user or group name,
8100 discussing this on <prgn>debian-devel</prgn> and checking
8101 with the <package/base-passwd/ maintainer that it is unique and that
8102 they do not wish you to use a statically allocated id
8103 instead. When this has been checked you must arrange for
8104 your package to create the user or group if necessary using
8105 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8106 <prgn>postinst</prgn> script (again, the latter is to be
8107 preferred if it is possible).
8111 Note that changing the numeric value of an id associated
8112 with a name is very difficult, and involves searching the
8113 file system for all appropriate files. You need to think
8114 carefully whether a static or dynamic id is required, since
8115 changing your mind later will cause problems.
8118 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8120 This section is not intended as policy, but as a
8121 description of the use of <prgn>dpkg-statoverride</prgn>.
8125 If a system administrator wishes to have a file (or
8126 directory or other such thing) installed with owner and
8127 permissions different from those in the distributed Debian
8128 package, they can use the <prgn>dpkg-statoverride</prgn>
8129 program to instruct <prgn>dpkg</prgn> to use the different
8130 settings every time the file is installed. Thus the
8131 package maintainer should distribute the files with their
8132 normal permissions, and leave it for the system
8133 administrator to make any desired changes. For example, a
8134 daemon which is normally required to be setuid root, but
8135 in certain situations could be used without being setuid,
8136 should be installed setuid in the <tt>.deb</tt>. Then the
8137 local system administrator can change this if they wish.
8138 If there are two standard ways of doing it, the package
8139 maintainer can use <tt>debconf</tt> to find out the
8140 preference, and call <prgn>dpkg-statoverride</prgn> in the
8141 maintainer script if necessary to accommodate the system
8142 administrator's choice. Care must be taken during
8143 upgrades to not override an existing setting.
8147 Given the above, <prgn>dpkg-statoverride</prgn> is
8148 essentially a tool for system administrators and would not
8149 normally be needed in the maintainer scripts. There is
8150 one type of situation, though, where calls to
8151 <prgn>dpkg-statoverride</prgn> would be needed in the
8152 maintainer scripts, and that involves packages which use
8153 dynamically allocated user or group ids. In such a
8154 situation, something like the following idiom can be very
8155 helpful in the package's <prgn>postinst</prgn>, where
8156 <tt>sysuser</tt> is a dynamically allocated id:
8158 for i in /usr/bin/foo /usr/sbin/bar
8160 # only do something when no setting exists
8161 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8163 #include: debconf processing, question about foo and bar
8164 if [ "$RET" = "true" ] ; then
8165 dpkg-statoverride --update --add sysuser root 4755 $i
8170 The corresponding code to remove the override when the package
8173 for i in /usr/bin/foo /usr/sbin/bar
8175 if dpkg-statoverride --list $i >/dev/null 2>&1
8177 dpkg-statoverride --remove $i
8187 <chapt id="customized-programs">
8188 <heading>Customized programs</heading>
8190 <sect id="arch-spec">
8191 <heading>Architecture specification strings</heading>
8194 If a program needs to specify an <em>architecture specification
8195 string</em> in some place, it should select one of the strings
8196 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8197 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8198 part is sometimes elided, as when the OS is Linux.
8202 Note that we don't want to use
8203 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8204 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8205 since this would make our programs incompatible with other
8206 Linux distributions. We also don't use something like
8207 <tt><var>arch</var>-unknown-linux</tt>, since the
8208 <tt>unknown</tt> does not look very good.
8211 <sect1 id="arch-wildcard-spec">
8212 <heading>Architecture wildcards</heading>
8215 A package may specify an architecture wildcard. Architecture
8216 wildcards are in the format <tt>any</tt> (which matches every
8217 architecture), <tt><var>os</var></tt>-any, or
8218 any-<tt><var>cpu</var></tt>. <footnote>
8219 Internally, the package system normalizes the GNU triplets
8220 and the Debian arches into Debian arch triplets (which are
8221 kind of inverted GNU triplets), with the first component of
8222 the triplet representing the libc and ABI in use, and then
8223 does matching against those triplets. However, such
8224 triplets are an internal implementation detail that should
8225 not be used by packages directly. The libc and ABI portion
8226 is handled internally by the package system based on
8227 the <var>os</var> and <var>cpu</var>.
8234 <heading>Daemons</heading>
8237 The configuration files <file>/etc/services</file>,
8238 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8239 by the <prgn>netbase</prgn> package and must not be modified
8244 If a package requires a new entry in one of these files, the
8245 maintainer should get in contact with the
8246 <prgn>netbase</prgn> maintainer, who will add the entries
8247 and release a new version of the <prgn>netbase</prgn>
8252 The configuration file <file>/etc/inetd.conf</file> must not be
8253 modified by the package's scripts except via the
8254 <prgn>update-inetd</prgn> script or the
8255 <file>DebianNet.pm</file> Perl module. See their documentation
8256 for details on how to add entries.
8260 If a package wants to install an example entry into
8261 <file>/etc/inetd.conf</file>, the entry must be preceded with
8262 exactly one hash character (<tt>#</tt>). Such lines are
8263 treated as "commented out by user" by the
8264 <prgn>update-inetd</prgn> script and are not changed or
8265 activated during package updates.
8270 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8274 Some programs need to create pseudo-ttys. This should be done
8275 using Unix98 ptys if the C library supports it. The resulting
8276 program must not be installed setuid root, unless that
8277 is required for other functionality.
8281 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8282 <file>/var/log/lastlog</file> must be installed writable by
8283 group <tt>utmp</tt>. Programs which need to modify those
8284 files must be installed setgid <tt>utmp</tt>.
8289 <heading>Editors and pagers</heading>
8292 Some programs have the ability to launch an editor or pager
8293 program to edit or display a text document. Since there are
8294 lots of different editors and pagers available in the Debian
8295 distribution, the system administrator and each user should
8296 have the possibility to choose their preferred editor and
8301 In addition, every program should choose a good default
8302 editor/pager if none is selected by the user or system
8307 Thus, every program that launches an editor or pager must
8308 use the EDITOR or PAGER environment variable to determine
8309 the editor or pager the user wishes to use. If these
8310 variables are not set, the programs <file>/usr/bin/editor</file>
8311 and <file>/usr/bin/pager</file> should be used, respectively.
8315 These two files are managed through the <prgn>dpkg</prgn>
8316 "alternatives" mechanism. Thus every package providing an
8317 editor or pager must call the
8318 <prgn>update-alternatives</prgn> script to register these
8323 If it is very hard to adapt a program to make use of the
8324 EDITOR or PAGER variables, that program may be configured to
8325 use <file>/usr/bin/sensible-editor</file> and
8326 <file>/usr/bin/sensible-pager</file> as the editor or pager
8327 program respectively. These are two scripts provided in the
8328 <package>sensible-utils</package> package that check the EDITOR
8329 and PAGER variables and launch the appropriate program, and fall
8330 back to <file>/usr/bin/editor</file>
8331 and <file>/usr/bin/pager</file> if the variable is not set.
8335 A program may also use the VISUAL environment variable to
8336 determine the user's choice of editor. If it exists, it
8337 should take precedence over EDITOR. This is in fact what
8338 <file>/usr/bin/sensible-editor</file> does.
8342 It is not required for a package to depend on
8343 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8344 package to provide such virtual packages.<footnote>
8345 The Debian base system already provides an editor and a
8351 <sect id="web-appl">
8352 <heading>Web servers and applications</heading>
8355 This section describes the locations and URLs that should
8356 be used by all web servers and web applications in the
8363 Cgi-bin executable files are installed in the
8365 <example compact="compact">
8366 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8368 and should be referred to as
8369 <example compact="compact">
8370 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8376 <p>Access to HTML documents</p>
8379 HTML documents for a package are stored in
8380 <file>/usr/share/doc/<var>package</var></file>
8381 and can be referred to as
8382 <example compact="compact">
8383 http://localhost/doc/<var>package</var>/<var>filename</var>
8388 The web server should restrict access to the document
8389 tree so that only clients on the same host can read
8390 the documents. If the web server does not support such
8391 access controls, then it should not provide access at
8392 all, or ask about providing access during installation.
8397 <p>Access to images</p>
8399 It is recommended that images for a package be stored
8400 in <tt>/usr/share/images/<var>package</var></tt> and
8401 may be referred to through an alias <tt>/images/</tt>
8404 http://localhost/images/<package>/<filename>
8411 <p>Web Document Root</p>
8414 Web Applications should try to avoid storing files in
8415 the Web Document Root. Instead they should use the
8416 /usr/share/doc/<var>package</var> directory for
8417 documents and register the Web Application via the
8418 <package>doc-base</package> package. If access to the
8419 web document root is unavoidable then use
8420 <example compact="compact">
8423 as the Document Root. This might be just a symbolic
8424 link to the location where the system administrator
8425 has put the real document root.
8428 <item><p>Providing httpd and/or httpd-cgi</p>
8430 All web servers should provide the virtual package
8431 <tt>httpd</tt>. If a web server has CGI support it should
8432 provide <tt>httpd-cgi</tt> additionally.
8435 All web applications which do not contain CGI scripts should
8436 depend on <tt>httpd</tt>, all those web applications which
8437 <tt>do</tt> contain CGI scripts, should depend on
8445 <sect id="mail-transport-agents">
8446 <heading>Mail transport, delivery and user agents</heading>
8449 Debian packages which process electronic mail, whether mail
8450 user agents (MUAs) or mail transport agents (MTAs), must
8451 ensure that they are compatible with the configuration
8452 decisions below. Failure to do this may result in lost
8453 mail, broken <tt>From:</tt> lines, and other serious brain
8458 The mail spool is <file>/var/mail</file> and the interface to
8459 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8460 the FHS). On older systems, the mail spool may be
8461 physically located in <file>/var/spool/mail</file>, but all
8462 access to the mail spool should be via the
8463 <file>/var/mail</file> symlink. The mail spool is part of the
8464 base system and not part of the MTA package.
8468 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8469 programs (such as IMAP daemons) must lock the mailbox in an
8470 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8471 be combined with dot locking. To avoid deadlocks, a program
8472 should use <tt>fcntl()</tt> first and dot locking after
8473 this, or alternatively implement the two locking methods in
8474 a non blocking way<footnote>
8475 If it is not possible to establish both locks, the
8476 system shouldn't wait for the second lock to be
8477 established, but remove the first lock, wait a (random)
8478 time, and start over locking again.
8479 </footnote>. Using the functions <tt>maillock</tt> and
8480 <tt>mailunlock</tt> provided by the
8481 <tt>liblockfile*</tt><footnote>
8482 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8483 to use these functions.
8484 </footnote> packages is the recommended way to realize this.
8488 Mailboxes are generally either mode 600 and owned by
8489 <var>user</var> or mode 660 and owned by
8490 <tt><var>user</var>:mail</tt><footnote>
8491 There are two traditional permission schemes for mail spools:
8492 mode 600 with all mail delivery done by processes running as
8493 the destination user, or mode 660 and owned by group mail with
8494 mail delivery done by a process running as a system user in
8495 group mail. Historically, Debian required mode 660 mail
8496 spools to enable the latter model, but that model has become
8497 increasingly uncommon and the principle of least privilege
8498 indicates that mail systems that use the first model should
8499 use permissions of 600. If delivery to programs is permitted,
8500 it's easier to keep the mail system secure if the delivery
8501 agent runs as the destination user. Debian Policy therefore
8502 permits either scheme.
8503 </footnote>. The local system administrator may choose a
8504 different permission scheme; packages should not make
8505 assumptions about the permission and ownership of mailboxes
8506 unless required (such as when creating a new mailbox). A MUA
8507 may remove a mailbox (unless it has nonstandard permissions) in
8508 which case the MTA or another MUA must recreate it if needed.
8512 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8513 be setgid mail to do the locking mentioned above (and
8514 must obviously avoid accessing other users' mailboxes
8515 using this privilege).</p>
8518 <file>/etc/aliases</file> is the source file for the system mail
8519 aliases (e.g., postmaster, usenet, etc.), it is the one
8520 which the sysadmin and <prgn>postinst</prgn> scripts may
8521 edit. After <file>/etc/aliases</file> is edited the program or
8522 human editing it must call <prgn>newaliases</prgn>. All MTA
8523 packages must come with a <prgn>newaliases</prgn> program,
8524 even if it does nothing, but older MTA packages did not do
8525 this so programs should not fail if <prgn>newaliases</prgn>
8526 cannot be found. Note that because of this, all MTA
8527 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8528 <tt>Replaces: mail-transport-agent</tt> control file
8533 The convention of writing <tt>forward to
8534 <var>address</var></tt> in the mailbox itself is not
8535 supported. Use a <tt>.forward</tt> file instead.</p>
8538 The <prgn>rmail</prgn> program used by UUCP
8539 for incoming mail should be <file>/usr/sbin/rmail</file>.
8540 Likewise, <prgn>rsmtp</prgn>, for receiving
8541 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8545 If your package needs to know what hostname to use on (for
8546 example) outgoing news and mail messages which are generated
8547 locally, you should use the file <file>/etc/mailname</file>. It
8548 will contain the portion after the username and <tt>@</tt>
8549 (at) sign for email addresses of users on the machine
8550 (followed by a newline).
8554 Such a package should check for the existence of this file
8555 when it is being configured. If it exists, it should be
8556 used without comment, although an MTA's configuration script
8557 may wish to prompt the user even if it finds that this file
8558 exists. If the file does not exist, the package should
8559 prompt the user for the value (preferably using
8560 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8561 as well as using it in the package's configuration. The
8562 prompt should make it clear that the name will not just be
8563 used by that package. For example, in this situation the
8564 <tt>inn</tt> package could say something like:
8565 <example compact="compact">
8566 Please enter the "mail name" of your system. This is the
8567 hostname portion of the address to be shown on outgoing
8568 news and mail messages. The default is
8569 <var>syshostname</var>, your system's host name. Mail
8570 name ["<var>syshostname</var>"]:
8572 where <var>syshostname</var> is the output of <tt>hostname
8578 <heading>News system configuration</heading>
8581 All the configuration files related to the NNTP (news)
8582 servers and clients should be located under
8583 <file>/etc/news</file>.</p>
8586 There are some configuration issues that apply to a number
8587 of news clients and server packages on the machine. These
8591 <tag><file>/etc/news/organization</file></tag>
8593 A string which should appear as the
8594 organization header for all messages posted
8595 by NNTP clients on the machine
8598 <tag><file>/etc/news/server</file></tag>
8600 Contains the FQDN of the upstream NNTP
8601 server, or localhost if the local machine is
8606 Other global files may be added as required for cross-package news
8613 <heading>Programs for the X Window System</heading>
8616 <heading>Providing X support and package priorities</heading>
8619 Programs that can be configured with support for the X
8620 Window System must be configured to do so and must declare
8621 any package dependencies necessary to satisfy their
8622 runtime requirements when using the X Window System. If
8623 such a package is of higher priority than the X packages
8624 on which it depends, it is required that either the
8625 X-specific components be split into a separate package, or
8626 that an alternative version of the package, which includes
8627 X support, be provided, or that the package's priority be
8633 <heading>Packages providing an X server</heading>
8636 Packages that provide an X server that, directly or
8637 indirectly, communicates with real input and display
8638 hardware should declare in their control data that they
8639 provide the virtual package <tt>xserver</tt>.<footnote>
8640 This implements current practice, and provides an
8641 actual policy for usage of the <tt>xserver</tt>
8642 virtual package which appears in the virtual packages
8643 list. In a nutshell, X servers that interface
8644 directly with the display and input hardware or via
8645 another subsystem (e.g., GGI) should provide
8646 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8647 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8653 <heading>Packages providing a terminal emulator</heading>
8656 Packages that provide a terminal emulator for the X Window
8657 System which meet the criteria listed below should declare
8658 in their control data that they provide the virtual
8659 package <tt>x-terminal-emulator</tt>. They should also
8660 register themselves as an alternative for
8661 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8666 To be an <tt>x-terminal-emulator</tt>, a program must:
8667 <list compact="compact">
8669 Be able to emulate a DEC VT100 terminal, or a
8670 compatible terminal.
8674 Support the command-line option <tt>-e
8675 <var>command</var></tt>, which creates a new
8676 terminal window<footnote>
8677 "New terminal window" does not necessarily mean
8678 a new top-level X window directly parented by
8679 the window manager; it could, if the terminal
8680 emulator application were so coded, be a new
8681 "view" in a multiple-document interface (MDI).
8683 and runs the specified <var>command</var>,
8684 interpreting the entirety of the rest of the command
8685 line as a command to pass straight to exec, in the
8686 manner that <tt>xterm</tt> does.
8690 Support the command-line option <tt>-T
8691 <var>title</var></tt>, which creates a new terminal
8692 window with the window title <var>title</var>.
8699 <heading>Packages providing a window manager</heading>
8702 Packages that provide a window manager should declare in
8703 their control data that they provide the virtual package
8704 <tt>x-window-manager</tt>. They should also register
8705 themselves as an alternative for
8706 <file>/usr/bin/x-window-manager</file>, with a priority
8707 calculated as follows:
8708 <list compact="compact">
8710 Start with a priority of 20.
8714 If the window manager supports the Debian menu
8715 system, add 20 points if this support is available
8716 in the package's default configuration (i.e., no
8717 configuration files belonging to the system or user
8718 have to be edited to activate the feature); if
8719 configuration files must be modified, add only 10
8725 If the window manager complies with <url
8726 id="http://www.freedesktop.org/Standards/wm-spec"
8727 name="The Window Manager Specification Project">,
8728 written by the <url id="http://www.freedesktop.org/"
8729 name="Free Desktop Group">, add 40 points.
8733 If the window manager permits the X session to be
8734 restarted using a <em>different</em> window manager
8735 (without killing the X server) in its default
8736 configuration, add 10 points; otherwise add none.
8743 <heading>Packages providing fonts</heading>
8746 Packages that provide fonts for the X Window
8748 For the purposes of Debian Policy, a "font for the X
8749 Window System" is one which is accessed via X protocol
8750 requests. Fonts for the Linux console, for PostScript
8751 renderer, or any other purpose, do not fit this
8752 definition. Any tool which makes such fonts available
8753 to the X Window System, however, must abide by this
8756 must do a number of things to ensure that they are both
8757 available without modification of the X or font server
8758 configuration, and that they do not corrupt files used by
8759 other font packages to register information about
8763 Fonts of any type supported by the X Window System
8764 must be in a separate binary package from any
8765 executables, libraries, or documentation (except
8766 that specific to the fonts shipped, such as their
8767 license information). If one or more of the fonts
8768 so packaged are necessary for proper operation of
8769 the package with which they are associated the font
8770 package may be Recommended; if the fonts merely
8771 provide an enhancement, a Suggests relationship may
8772 be used. Packages must not Depend on font
8774 This is because the X server may retrieve fonts
8775 from the local file system or over the network
8776 from an X font server; the Debian package system
8777 is empowered to deal only with the local
8783 BDF fonts must be converted to PCF fonts with the
8784 <prgn>bdftopcf</prgn> utility (available in the
8785 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8786 placed in a directory that corresponds to their
8788 <list compact="compact">
8790 100 dpi fonts must be placed in
8791 <file>/usr/share/fonts/X11/100dpi/</file>.
8795 75 dpi fonts must be placed in
8796 <file>/usr/share/fonts/X11/75dpi/</file>.
8800 Character-cell fonts, cursor fonts, and other
8801 low-resolution fonts must be placed in
8802 <file>/usr/share/fonts/X11/misc/</file>.
8808 Type 1 fonts must be placed in
8809 <file>/usr/share/fonts/X11/Type1/</file>. If font
8810 metric files are available, they must be placed here
8815 Subdirectories of <file>/usr/share/fonts/X11/</file>
8816 other than those listed above must be neither
8817 created nor used. (The <file>PEX</file>, <file>CID</file>,
8818 <file>Speedo</file>, and <file>cyrillic</file> directories
8819 are excepted for historical reasons, but installation of
8820 files into these directories remains discouraged.)
8824 Font packages may, instead of placing files directly
8825 in the X font directories listed above, provide
8826 symbolic links in that font directory pointing to
8827 the files' actual location in the filesystem. Such
8828 a location must comply with the FHS.
8832 Font packages should not contain both 75dpi and
8833 100dpi versions of a font. If both are available,
8834 they should be provided in separate binary packages
8835 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8836 the names of the packages containing the
8837 corresponding fonts.
8841 Fonts destined for the <file>misc</file> subdirectory
8842 should not be included in the same package as 75dpi
8843 or 100dpi fonts; instead, they should be provided in
8844 a separate package with <tt>-misc</tt> appended to
8849 Font packages must not provide the files
8850 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8851 <file>fonts.scale</file> in a font directory:
8854 <file>fonts.dir</file> files must not be provided at all.
8858 <file>fonts.alias</file> and <file>fonts.scale</file>
8859 files, if needed, should be provided in the
8861 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8862 where <var>fontdir</var> is the name of the
8864 <file>/usr/share/fonts/X11/</file> where the
8865 package's corresponding fonts are stored
8866 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8867 <var>package</var> is the name of the package
8868 that provides these fonts, and
8869 <var>extension</var> is either <tt>scale</tt>
8870 or <tt>alias</tt>, whichever corresponds to
8877 Font packages must declare a dependency on
8878 <tt>xfonts-utils</tt> in their control
8883 Font packages that provide one or more
8884 <file>fonts.scale</file> files as described above must
8885 invoke <prgn>update-fonts-scale</prgn> on each
8886 directory into which they installed fonts
8887 <em>before</em> invoking
8888 <prgn>update-fonts-dir</prgn> on that directory.
8889 This invocation must occur in both the
8890 <prgn>postinst</prgn> (for all arguments) and
8891 <prgn>postrm</prgn> (for all arguments except
8892 <tt>upgrade</tt>) scripts.
8896 Font packages that provide one or more
8897 <file>fonts.alias</file> files as described above must
8898 invoke <prgn>update-fonts-alias</prgn> on each
8899 directory into which they installed fonts. This
8900 invocation must occur in both the
8901 <prgn>postinst</prgn> (for all arguments) and
8902 <prgn>postrm</prgn> (for all arguments except
8903 <tt>upgrade</tt>) scripts.
8907 Font packages must invoke
8908 <prgn>update-fonts-dir</prgn> on each directory into
8909 which they installed fonts. This invocation must
8910 occur in both the <prgn>postinst</prgn> (for all
8911 arguments) and <prgn>postrm</prgn> (for all
8912 arguments except <tt>upgrade</tt>) scripts.
8916 Font packages must not provide alias names for the
8917 fonts they include which collide with alias names
8918 already in use by fonts already packaged.
8922 Font packages must not provide fonts with the same
8923 XLFD registry name as another font already packaged.
8929 <sect1 id="appdefaults">
8930 <heading>Application defaults files</heading>
8933 Application defaults files must be installed in the
8934 directory <file>/etc/X11/app-defaults/</file> (use of a
8935 localized subdirectory of <file>/etc/X11/</file> as described
8936 in the <em>X Toolkit Intrinsics - C Language
8937 Interface</em> manual is also permitted). They must be
8938 registered as <tt>conffile</tt>s or handled as
8939 configuration files.
8943 Customization of programs' X resources may also be
8944 supported with the provision of a file with the same name
8945 as that of the package placed in
8946 the <file>/etc/X11/Xresources/</file> directory, which
8947 must be registered as a <tt>conffile</tt> or handled as a
8948 configuration file.<footnote>
8949 Note that this mechanism is not the same as using
8950 app-defaults; app-defaults are tied to the client
8951 binary on the local file system, whereas X resources
8952 are stored in the X server and affect all connecting
8959 <heading>Installation directory issues</heading>
8962 Historically, packages using the X Window System used a
8963 separate set of installation directories from other packages.
8964 This practice has been discontinued and packages using the X
8965 Window System should now generally be installed in the same
8966 directories as any other package. Specifically, packages must
8967 not install files under the <file>/usr/X11R6/</file> directory
8968 and the <file>/usr/X11R6/</file> directory hierarchy should be
8969 regarded as obsolete.
8973 Include files previously installed under
8974 <file>/usr/X11R6/include/X11/</file> should be installed into
8975 <file>/usr/include/X11/</file>. For files previously
8976 installed into subdirectories of
8977 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8978 determine if subdirectories of <file>/usr/lib/</file> and
8979 <file>/usr/share/</file> can be used. If not, a subdirectory
8980 of <file>/usr/lib/X11/</file> should be used.
8984 Configuration files for window, display, or session managers
8985 or other applications that are tightly integrated with the X
8986 Window System may be placed in a subdirectory
8987 of <file>/etc/X11/</file> corresponding to the package name.
8988 Other X Window System applications should use
8989 the <file>/etc/</file> directory unless otherwise mandated by
8990 policy (such as for <ref id="appdefaults">).
8995 <heading>The OSF/Motif and OpenMotif libraries</heading>
8998 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8999 OpenMotif libraries</em><footnote>
9000 OSF/Motif and OpenMotif are collectively referred to as
9001 "Motif" in this policy document.
9003 should be compiled against and tested with LessTif (a free
9004 re-implementation of Motif) instead. If the maintainer
9005 judges that the program or programs do not work
9006 sufficiently well with LessTif to be distributed and
9007 supported, but do so when compiled against Motif, then two
9008 versions of the package should be created; one linked
9009 statically against Motif and with <tt>-smotif</tt>
9010 appended to the package name, and one linked dynamically
9011 against Motif and with <tt>-dmotif</tt> appended to the
9016 Both Motif-linked versions are dependent
9017 upon non-DFSG-compliant software and thus cannot be
9018 uploaded to the <em>main</em> distribution; if the
9019 software is itself DFSG-compliant it may be uploaded to
9020 the <em>contrib</em> distribution. While known existing
9021 versions of Motif permit unlimited redistribution of
9022 binaries linked against the library (whether statically or
9023 dynamically), it is the package maintainer's
9024 responsibility to determine whether this is permitted by
9025 the license of the copy of Motif in their possession.
9031 <heading>Perl programs and modules</heading>
9034 Perl programs and modules should follow the current Perl policy.
9038 The Perl policy can be found in the <tt>perl-policy</tt>
9039 files in the <tt>debian-policy</tt> package.
9040 It is also available from the Debian web mirrors at
9041 <tt><url name="/doc/packaging-manuals/perl-policy/"
9042 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9047 <heading>Emacs lisp programs</heading>
9050 Please refer to the "Debian Emacs Policy" for details of how to
9051 package emacs lisp programs.
9055 The Emacs policy is available in
9056 <file>debian-emacs-policy.gz</file> of the
9057 <package>emacsen-common</package> package.
9058 It is also available from the Debian web mirrors at
9059 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9060 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9065 <heading>Games</heading>
9068 The permissions on <file>/var/games</file> are mode 755, owner
9069 <tt>root</tt> and group <tt>root</tt>.
9073 Each game decides on its own security policy.</p>
9076 Games which require protected, privileged access to
9077 high-score files, saved games, etc., may be made
9078 set-<em>group</em>-id (mode 2755) and owned by
9079 <tt>root:games</tt>, and use files and directories with
9080 appropriate permissions (770 <tt>root:games</tt>, for
9081 example). They must not be made
9082 set-<em>user</em>-id, as this causes security problems. (If
9083 an attacker can subvert any set-user-id game they can
9084 overwrite the executable of any other, causing other players
9085 of these games to run a Trojan horse program. With a
9086 set-group-id game the attacker only gets access to less
9087 important game data, and if they can get at the other
9088 players' accounts at all it will take considerably more
9092 Some packages, for example some fortune cookie programs, are
9093 configured by the upstream authors to install with their
9094 data files or other static information made unreadable so
9095 that they can only be accessed through set-id programs
9096 provided. You should not do this in a Debian package: anyone can
9097 download the <file>.deb</file> file and read the data from it,
9098 so there is no point making the files unreadable. Not
9099 making the files unreadable also means that you don't have
9100 to make so many programs set-id, which reduces the risk of a
9104 As described in the FHS, binaries of games should be
9105 installed in the directory <file>/usr/games</file>. This also
9106 applies to games that use the X Window System. Manual pages
9107 for games (X and non-X games) should be installed in
9108 <file>/usr/share/man/man6</file>.</p>
9114 <heading>Documentation</heading>
9117 <heading>Manual pages</heading>
9120 You should install manual pages in <prgn>nroff</prgn> source
9121 form, in appropriate places under <file>/usr/share/man</file>.
9122 You should only use sections 1 to 9 (see the FHS for more
9123 details). You must not install a pre-formatted "cat page".
9127 Each program, utility, and function should have an
9128 associated manual page included in the same package. It is
9129 suggested that all configuration files also have a manual
9130 page included as well. Manual pages for protocols and other
9131 auxiliary things are optional.
9135 If no manual page is available, this is considered as a bug
9136 and should be reported to the Debian Bug Tracking System (the
9137 maintainer of the package is allowed to write this bug report
9138 themselves, if they so desire). Do not close the bug report
9139 until a proper man page is available.<footnote>
9140 It is not very hard to write a man page. See the
9141 <url id="http://www.schweikhardt.net/man_page_howto.html"
9142 name="Man-Page-HOWTO">,
9143 <manref name="man" section="7">, the examples
9144 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9145 the helper program <prgn>help2man</prgn>, or the
9146 directory <file>/usr/share/doc/man-db/examples</file>.
9151 You may forward a complaint about a missing man page to the
9152 upstream authors, and mark the bug as forwarded in the
9153 Debian bug tracking system. Even though the GNU Project do
9154 not in general consider the lack of a man page to be a bug,
9155 we do; if they tell you that they don't consider it a bug
9156 you should leave the bug in our bug tracking system open
9161 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9165 If one man page needs to be accessible via several names it
9166 is better to use a symbolic link than the <file>.so</file>
9167 feature, but there is no need to fiddle with the relevant
9168 parts of the upstream source to change from <file>.so</file> to
9169 symlinks: don't do it unless it's easy. You should not
9170 create hard links in the manual page directories, nor put
9171 absolute filenames in <file>.so</file> directives. The filename
9172 in a <file>.so</file> in a man page should be relative to the
9173 base of the man page tree (usually
9174 <file>/usr/share/man</file>). If you do not create any links
9175 (whether symlinks, hard links, or <tt>.so</tt> directives)
9176 in the file system to the alternate names of the man page,
9177 then you should not rely on <prgn>man</prgn> finding your
9178 man page under those names based solely on the information in
9179 the man page's header.<footnote>
9180 Supporting this in <prgn>man</prgn> often requires
9181 unreasonable processing time to find a manual page or to
9182 report that none exists, and moves knowledge into man's
9183 database that would be better left in the file system.
9184 This support is therefore deprecated and will cease to
9185 be present in the future.
9190 Manual pages in locale-specific subdirectories of
9191 <file>/usr/share/man</file> should use either UTF-8 or the usual
9192 legacy encoding for that language (normally the one corresponding
9193 to the shortest relevant locale name in
9194 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9195 <file>/usr/share/man/fr</file> should use either UTF-8 or
9196 ISO-8859-1.<footnote>
9197 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9198 use. In future, all manual pages will be required to use
9204 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9205 included in the subdirectory name unless it indicates a
9206 significant difference in the language, as this excludes
9207 speakers of the language in other countries.<footnote>
9208 At the time of writing, Chinese and Portuguese are the main
9209 languages with such differences, so <file>pt_BR</file>,
9210 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9215 If a localized version of a manual page is provided, it should
9216 either be up-to-date or it should be obvious to the reader that
9217 it is outdated and the original manual page should be used
9218 instead. This can be done either by a note at the beginning of
9219 the manual page or by showing the missing or changed portions in
9220 the original language instead of the target language.
9225 <heading>Info documents</heading>
9228 Info documents should be installed in <file>/usr/share/info</file>.
9229 They should be compressed with <tt>gzip -9</tt>.
9233 The <prgn>install-info</prgn> program maintains a directory of
9234 installed info documents in <file>/usr/share/info/dir</file> for
9235 the use of info readers.<footnote>
9236 It was previously necessary for packages installing info
9237 documents to run <prgn>install-info</prgn> from maintainer
9238 scripts. This is no longer necessary. The installation
9239 system now uses dpkg triggers.
9241 This file must not be included in packages. Packages containing
9242 info documents should depend on <tt>dpkg (>= 1.15.4) |
9243 install-info</tt> to ensure that the directory file is properly
9244 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9249 Info documents should contain section and directory entry
9250 information in the document for the use
9251 of <prgn>install-info</prgn>. The section should be specified
9252 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9253 space and the section of this info page. The directory entry or
9254 entries should be included between
9255 a <tt>START-INFO-DIR-ENTRY</tt> line and
9256 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9258 INFO-DIR-SECTION Individual utilities
9259 START-INFO-DIR-ENTRY
9260 * example: (example). An example info directory entry.
9263 To determine which section to use, you should look
9264 at <file>/usr/share/info/dir</file> on your system and choose
9265 the most relevant (or create a new section if none of the
9266 current sections are relevant).<footnote>
9267 Normally, info documents are generated from Texinfo source.
9268 To include this information in the generated info document, if
9269 it is absent, add commands like:
9271 @dircategory Individual utilities
9273 * example: (example). An example info directory entry.
9276 to the Texinfo source of the document and ensure that the info
9277 documents are rebuilt from source during the package build.
9283 <heading>Additional documentation</heading>
9286 Any additional documentation that comes with the package may
9287 be installed at the discretion of the package maintainer.
9288 Plain text documentation should be installed in the directory
9289 <file>/usr/share/doc/<var>package</var></file>, where
9290 <var>package</var> is the name of the package, and
9291 compressed with <tt>gzip -9</tt> unless it is small.
9295 If a package comes with large amounts of documentation which
9296 many users of the package will not require you should create
9297 a separate binary package to contain it, so that it does not
9298 take up disk space on the machines of users who do not need
9299 or want it installed.</p>
9302 It is often a good idea to put text information files
9303 (<file>README</file>s, changelogs, and so forth) that come with
9304 the source package in <file>/usr/share/doc/<var>package</var></file>
9305 in the binary package. However, you don't need to install
9306 the instructions for building and installing the package, of
9310 Packages must not require the existence of any files in
9311 <file>/usr/share/doc/</file> in order to function
9313 The system administrator should be able to
9314 delete files in <file>/usr/share/doc/</file> without causing
9315 any programs to break.
9317 Any files that are referenced by programs but are also
9318 useful as stand alone documentation should be installed under
9319 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9320 <file>/usr/share/doc/<var>package</var></file>.
9324 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9325 link to another directory in <file>/usr/share/doc</file> only if
9326 the two packages both come from the same source and the
9327 first package Depends on the second.<footnote>
9329 Please note that this does not override the section on
9330 changelog files below, so the file
9331 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9332 must refer to the changelog for the current version of
9333 <var>package</var> in question. In practice, this means
9334 that the sources of the target and the destination of the
9335 symlink must be the same (same source package and
9342 Former Debian releases placed all additional documentation
9343 in <file>/usr/doc/<var>package</var></file>. This has been
9344 changed to <file>/usr/share/doc/<var>package</var></file>,
9345 and packages must not put documentation in the directory
9346 <file>/usr/doc/<var>package</var></file>. <footnote>
9347 At this phase of the transition, we no longer require a
9348 symbolic link in <file>/usr/doc/</file>. At a later point,
9349 policy shall change to make the symbolic links a bug.
9355 <heading>Preferred documentation formats</heading>
9358 The unification of Debian documentation is being carried out
9362 If your package comes with extensive documentation in a
9363 markup format that can be converted to various other formats
9364 you should if possible ship HTML versions in a binary
9365 package, in the directory
9366 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9367 its subdirectories.<footnote>
9368 The rationale: The important thing here is that HTML
9369 docs should be available in <em>some</em> package, not
9370 necessarily in the main binary package.
9375 Other formats such as PostScript may be provided at the
9376 package maintainer's discretion.
9380 <sect id="copyrightfile">
9381 <heading>Copyright information</heading>
9384 Every package must be accompanied by a verbatim copy of its
9385 copyright information and distribution license in the file
9386 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9387 file must neither be compressed nor be a symbolic link.
9391 In addition, the copyright file must say where the upstream
9392 sources (if any) were obtained. It should name the original
9393 authors of the package and the Debian maintainer(s) who were
9394 involved with its creation.
9398 Packages in the <em>contrib</em> or <em>non-free</em> archive
9399 areas should state in the copyright file that the package is not
9400 part of the Debian GNU/Linux distribution and briefly explain
9405 A copy of the file which will be installed in
9406 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9407 be in <file>debian/copyright</file> in the source package.
9411 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9412 link to another directory in <file>/usr/share/doc</file> only if
9413 the two packages both come from the same source and the
9414 first package Depends on the second. These rules are
9415 important because copyrights must be extractable by
9420 Packages distributed under the Apache license (version 2.0), the
9421 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9422 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9423 1.3) should refer to the corresponding files
9424 under <file>/usr/share/common-licenses</file>,<footnote>
9427 <file>/usr/share/common-licenses/Apache-2.0</file>,
9428 <file>/usr/share/common-licenses/Artistic</file>,
9429 <file>/usr/share/common-licenses/GPL-1</file>,
9430 <file>/usr/share/common-licenses/GPL-2</file>,
9431 <file>/usr/share/common-licenses/GPL-3</file>,
9432 <file>/usr/share/common-licenses/LGPL-2</file>,
9433 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9434 <file>/usr/share/common-licenses/LGPL-3</file>,
9435 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9436 <file>/usr/share/common-licenses/GFDL-1.3</file>
9437 respectively. The University of California BSD license is
9438 also included in <package>base-files</package> as
9439 <file>/usr/share/common-licenses/BSD</file>, but given the
9440 brevity of this license, its specificity to code whose
9441 copyright is held by the Regents of the University of
9442 California, and the frequency of minor wording changes, its
9443 text should be included in the copyright file rather than
9444 referencing this file.
9446 </footnote> rather than quoting them in the copyright
9451 You should not use the copyright file as a general <file>README</file>
9452 file. If your package has such a file it should be
9453 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9454 <file>README.Debian</file> or some other appropriate place.</p>
9458 <heading>Examples</heading>
9461 Any examples (configurations, source files, whatever),
9462 should be installed in a directory
9463 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9464 files should not be referenced by any program: they're there
9465 for the benefit of the system administrator and users as
9466 documentation only. Architecture-specific example files
9467 should be installed in a directory
9468 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9470 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9471 latter directory itself may be a symbolic link to the
9476 If the purpose of a package is to provide examples, then the
9477 example files may be installed into
9478 <file>/usr/share/doc/<var>package</var></file>.
9482 <sect id="changelogs">
9483 <heading>Changelog files</heading>
9486 Packages that are not Debian-native must contain a
9487 compressed copy of the <file>debian/changelog</file> file from
9488 the Debian source tree in
9489 <file>/usr/share/doc/<var>package</var></file> with the name
9490 <file>changelog.Debian.gz</file>.
9494 If an upstream changelog is available, it should be accessible as
9495 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9496 plain text. If the upstream changelog is distributed in
9497 HTML, it should be made available in that form as
9498 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9499 and a plain text <file>changelog.gz</file> should be generated
9500 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9501 the upstream changelog files do not already conform to this
9502 naming convention, then this may be achieved either by
9503 renaming the files, or by adding a symbolic link, at the
9504 maintainer's discretion.<footnote>
9505 Rationale: People should not have to look in places for
9506 upstream changelogs merely because they are given
9507 different names or are distributed in HTML format.
9512 All of these files should be installed compressed using
9513 <tt>gzip -9</tt>, as they will become large with time even
9514 if they start out small.
9518 If the package has only one changelog which is used both as
9519 the Debian changelog and the upstream one because there is
9520 no separate upstream maintainer then that changelog should
9521 usually be installed as
9522 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9523 there is a separate upstream maintainer, but no upstream
9524 changelog, then the Debian changelog should still be called
9525 <file>changelog.Debian.gz</file>.
9529 For details about the format and contents of the Debian
9530 changelog file, please see <ref id="dpkgchangelog">.
9535 <appendix id="pkg-scope">
9536 <heading>Introduction and scope of these appendices</heading>
9539 These appendices are taken essentially verbatim from the
9540 now-deprecated Packaging Manual, version 3.2.1.0. They are
9541 the chapters which are likely to be of use to package
9542 maintainers and which have not already been included in the
9543 policy document itself. Most of these sections are very likely
9544 not relevant to policy; they should be treated as
9545 documentation for the packaging system. Please note that these
9546 appendices are included for convenience, and for historical
9547 reasons: they used to be part of policy package, and they have
9548 not yet been incorporated into dpkg documentation. However,
9549 they still have value, and hence they are presented here.
9553 They have not yet been checked to ensure that they are
9554 compatible with the contents of policy, and if there are any
9555 contradictions, the version in the main policy document takes
9556 precedence. The remaining chapters of the old Packaging
9557 Manual have also not been read in detail to ensure that there
9558 are not parts which have been left out. Both of these will be
9563 Certain parts of the Packaging manual were integrated into the
9564 Policy Manual proper, and removed from the appendices. Links
9565 have been placed from the old locations to the new ones.
9569 <prgn>dpkg</prgn> is a suite of programs for creating binary
9570 package files and installing and removing them on Unix
9572 <prgn>dpkg</prgn> is targeted primarily at Debian
9573 GNU/Linux, but may work on or be ported to other
9579 The binary packages are designed for the management of
9580 installed executable programs (usually compiled binaries) and
9581 their associated data, though source code examples and
9582 documentation are provided as part of some packages.</p>
9585 This manual describes the technical aspects of creating Debian
9586 binary packages (<file>.deb</file> files). It documents the
9587 behavior of the package management programs
9588 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9589 they interact with packages.</p>
9592 It also documents the interaction between
9593 <prgn>dselect</prgn>'s core and the access method scripts it
9594 uses to actually install the selected packages, and describes
9595 how to create a new access method.</p>
9598 This manual does not go into detail about the options and
9599 usage of the package building and installation tools. It
9600 should therefore be read in conjunction with those programs'
9605 The utility programs which are provided with <prgn>dpkg</prgn>
9606 for managing various system configuration and similar issues,
9607 such as <prgn>update-rc.d</prgn> and
9608 <prgn>install-info</prgn>, are not described in detail here -
9609 please see their man pages.
9613 It is assumed that the reader is reasonably familiar with the
9614 <prgn>dpkg</prgn> System Administrators' manual.
9615 Unfortunately this manual does not yet exist.
9619 The Debian version of the FSF's GNU hello program is provided
9620 as an example for people wishing to create Debian
9621 packages. The Debian <prgn>debmake</prgn> package is
9622 recommended as a very helpful tool in creating and maintaining
9623 Debian packages. However, while the tools and examples are
9624 helpful, they do not replace the need to read and follow the
9625 Policy and Programmer's Manual.</p>
9628 <appendix id="pkg-binarypkg">
9629 <heading>Binary packages (from old Packaging Manual)</heading>
9632 The binary package has two main sections. The first part
9633 consists of various control information files and scripts used
9634 by <prgn>dpkg</prgn> when installing and removing. See <ref
9635 id="pkg-controlarea">.
9639 The second part is an archive containing the files and
9640 directories to be installed.
9644 In the future binary packages may also contain other
9645 components, such as checksums and digital signatures. The
9646 format for the archive is described in full in the
9647 <file>deb(5)</file> man page.
9651 <sect id="pkg-bincreating"><heading>Creating package files -
9652 <prgn>dpkg-deb</prgn>
9656 All manipulation of binary package files is done by
9657 <prgn>dpkg-deb</prgn>; it's the only program that has
9658 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9659 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9660 will spot that the options requested are appropriate to
9661 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9666 In order to create a binary package you must make a
9667 directory tree which contains all the files and directories
9668 you want to have in the file system data part of the package.
9669 In Debian-format source packages this directory is usually
9670 <file>debian/tmp</file>, relative to the top of the package's
9675 They should have the locations (relative to the root of the
9676 directory tree you're constructing) ownerships and
9677 permissions which you want them to have on the system when
9682 With current versions of <prgn>dpkg</prgn> the uid/username
9683 and gid/groupname mappings for the users and groups being
9684 used should be the same on the system where the package is
9685 built and the one where it is installed.
9689 You need to add one special directory to the root of the
9690 miniature file system tree you're creating:
9691 <prgn>DEBIAN</prgn>. It should contain the control
9692 information files, notably the binary package control file
9693 (see <ref id="pkg-controlfile">).
9697 The <prgn>DEBIAN</prgn> directory will not appear in the
9698 file system archive of the package, and so won't be installed
9699 by <prgn>dpkg</prgn> when the package is installed.
9703 When you've prepared the package, you should invoke:
9705 dpkg --build <var>directory</var>
9710 This will build the package in
9711 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9712 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9713 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9718 See the man page <manref name="dpkg-deb" section="8"> for details of how
9719 to examine the contents of this newly-created file. You may find the
9720 output of following commands enlightening:
9722 dpkg-deb --info <var>filename</var>.deb
9723 dpkg-deb --contents <var>filename</var>.deb
9724 dpkg --contents <var>filename</var>.deb
9726 To view the copyright file for a package you could use this command:
9728 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9733 <sect id="pkg-controlarea">
9734 <heading>Package control information files</heading>
9737 The control information portion of a binary package is a
9738 collection of files with names known to <prgn>dpkg</prgn>.
9739 It will treat the contents of these files specially - some
9740 of them contain information used by <prgn>dpkg</prgn> when
9741 installing or removing the package; others are scripts which
9742 the package maintainer wants <prgn>dpkg</prgn> to run.
9746 It is possible to put other files in the package control
9747 area, but this is not generally a good idea (though they
9748 will largely be ignored).
9752 Here is a brief list of the control info files supported by
9753 <prgn>dpkg</prgn> and a summary of what they're used for.
9758 <tag><tt>control</tt>
9761 This is the key description file used by
9762 <prgn>dpkg</prgn>. It specifies the package's name
9763 and version, gives its description for the user,
9764 states its relationships with other packages, and so
9765 forth. See <ref id="sourcecontrolfiles"> and
9766 <ref id="binarycontrolfiles">.
9770 It is usually generated automatically from information
9771 in the source package by the
9772 <prgn>dpkg-gencontrol</prgn> program, and with
9773 assistance from <prgn>dpkg-shlibdeps</prgn>.
9774 See <ref id="pkg-sourcetools">.
9778 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9783 These are executable files (usually scripts) which
9784 <prgn>dpkg</prgn> runs during installation, upgrade
9785 and removal of packages. They allow the package to
9786 deal with matters which are particular to that package
9787 or require more complicated processing than that
9788 provided by <prgn>dpkg</prgn>. Details of when and
9789 how they are called are in <ref id="maintainerscripts">.
9793 It is very important to make these scripts idempotent.
9794 See <ref id="idempotency">.
9798 The maintainer scripts are not guaranteed to run with a
9799 controlling terminal and may not be able to interact with
9800 the user. See <ref id="controllingterminal">.
9804 <tag><tt>conffiles</tt>
9807 This file contains a list of configuration files which
9808 are to be handled automatically by <prgn>dpkg</prgn>
9809 (see <ref id="pkg-conffiles">). Note that not necessarily
9810 every configuration file should be listed here.
9813 <tag><tt>shlibs</tt>
9816 This file contains a list of the shared libraries
9817 supplied by the package, with dependency details for
9818 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9819 when it determines what dependencies are required in a
9820 package control file. The <tt>shlibs</tt> file format
9821 is described on <ref id="shlibs">.
9826 <sect id="pkg-controlfile">
9827 <heading>The main control information file: <tt>control</tt></heading>
9830 The most important control information file used by
9831 <prgn>dpkg</prgn> when it installs a package is
9832 <tt>control</tt>. It contains all the package's "vital
9837 The binary package control files of packages built from
9838 Debian sources are made by a special tool,
9839 <prgn>dpkg-gencontrol</prgn>, which reads
9840 <file>debian/control</file> and <file>debian/changelog</file> to
9841 find the information it needs. See <ref id="pkg-sourcepkg"> for
9846 The fields in binary package control files are listed in
9847 <ref id="binarycontrolfiles">.
9851 A description of the syntax of control files and the purpose
9852 of the fields is available in <ref id="controlfields">.
9857 <heading>Time Stamps</heading>
9860 See <ref id="timestamps">.
9865 <appendix id="pkg-sourcepkg">
9866 <heading>Source packages (from old Packaging Manual) </heading>
9869 The Debian binary packages in the distribution are generated
9870 from Debian sources, which are in a special format to assist
9871 the easy and automatic building of binaries.
9874 <sect id="pkg-sourcetools">
9875 <heading>Tools for processing source packages</heading>
9878 Various tools are provided for manipulating source packages;
9879 they pack and unpack sources and help build of binary
9880 packages and help manage the distribution of new versions.
9884 They are introduced and typical uses described here; see
9885 <manref name="dpkg-source" section="1"> for full
9886 documentation about their arguments and operation.
9890 For examples of how to construct a Debian source package,
9891 and how to use those utilities that are used by Debian
9892 source packages, please see the <prgn>hello</prgn> example
9896 <sect1 id="pkg-dpkg-source">
9898 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9903 This program is frequently used by hand, and is also
9904 called from package-independent automated building scripts
9905 such as <prgn>dpkg-buildpackage</prgn>.
9909 To unpack a package it is typically invoked with
9911 dpkg-source -x <var>.../path/to/filename</var>.dsc
9916 with the <file><var>filename</var>.tar.gz</file> and
9917 <file><var>filename</var>.diff.gz</file> (if applicable) in
9918 the same directory. It unpacks into
9919 <file><var>package</var>-<var>version</var></file>, and if
9921 <file><var>package</var>-<var>version</var>.orig</file>, in
9922 the current directory.
9926 To create a packed source archive it is typically invoked:
9928 dpkg-source -b <var>package</var>-<var>version</var>
9933 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9934 <file>.diff.gz</file> (if appropriate) in the current
9935 directory. <prgn>dpkg-source</prgn> does not clean the
9936 source tree first - this must be done separately if it is
9941 See also <ref id="pkg-sourcearchives">.</p>
9945 <sect1 id="pkg-dpkg-buildpackage">
9947 <prgn>dpkg-buildpackage</prgn> - overall package-building
9952 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9953 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9954 targets <tt>clean</tt>, <tt>build</tt> and
9955 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9956 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9957 source and binary package upload.
9961 It is usually invoked by hand from the top level of the
9962 built or unbuilt source directory. It may be invoked with
9963 no arguments; useful arguments include:
9964 <taglist compact="compact">
9965 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9968 Do not sign the <tt>.changes</tt> file or the
9969 source package <tt>.dsc</tt> file, respectively.</p>
9971 <tag><tt>-p<var>sign-command</var></tt></tag>
9974 Invoke <var>sign-command</var> instead of finding
9975 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9976 <var>sign-command</var> must behave just like
9977 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9979 <tag><tt>-r<var>root-command</var></tt></tag>
9982 When root privilege is required, invoke the command
9983 <var>root-command</var>. <var>root-command</var>
9984 should invoke its first argument as a command, from
9985 the <prgn>PATH</prgn> if necessary, and pass its
9986 second and subsequent arguments to the command it
9987 calls. If no <var>root-command</var> is supplied
9988 then <var>dpkg-buildpackage</var> will take no
9989 special action to gain root privilege, so that for
9990 most packages it will have to be invoked as root to
9993 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9996 Two types of binary-only build and upload - see
9997 <manref name="dpkg-source" section="1">.
10004 <sect1 id="pkg-dpkg-gencontrol">
10006 <prgn>dpkg-gencontrol</prgn> - generates binary package
10011 This program is usually called from <file>debian/rules</file>
10012 (see <ref id="pkg-sourcetree">) in the top level of the source
10017 This is usually done just before the files and directories in the
10018 temporary directory tree where the package is being built have their
10019 permissions and ownerships set and the package is constructed using
10020 <prgn>dpkg-deb/</prgn>
10022 This is so that the control file which is produced has
10023 the right permissions
10028 <prgn>dpkg-gencontrol</prgn> must be called after all the
10029 files which are to go into the package have been placed in
10030 the temporary build directory, so that its calculation of
10031 the installed size of a package is correct.
10035 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10036 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10037 variable substitutions created by
10038 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10043 For a package which generates only one binary package, and
10044 which builds it in <file>debian/tmp</file> relative to the top
10045 of the source package, it is usually sufficient to call
10046 <prgn>dpkg-gencontrol</prgn>.
10050 Sources which build several binaries will typically need
10053 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10054 </example> The <tt>-P</tt> tells
10055 <prgn>dpkg-gencontrol</prgn> that the package is being
10056 built in a non-default directory, and the <tt>-p</tt>
10057 tells it which package's control file should be generated.
10061 <prgn>dpkg-gencontrol</prgn> also adds information to the
10062 list of files in <file>debian/files</file>, for the benefit of
10063 (for example) a future invocation of
10064 <prgn>dpkg-genchanges</prgn>.</p>
10067 <sect1 id="pkg-dpkg-shlibdeps">
10069 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10074 This program is usually called from <file>debian/rules</file>
10075 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10076 id="pkg-sourcetree">), in the top level of the source tree.
10080 Its arguments are executables and shared libraries
10083 They may be specified either in the locations in the
10084 source tree where they are created or in the locations
10085 in the temporary build tree where they are installed
10086 prior to binary package creation.
10088 </footnote> for which shared library dependencies should
10089 be included in the binary package's control file.
10093 If some of the found shared libraries should only
10094 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10095 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10096 by using the <tt>-d<var>dependency-field</var></tt> option
10097 before those executable(s). (Each <tt>-d</tt> option
10098 takes effect until the next <tt>-d</tt>.)
10102 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10103 output control file to be modified. Instead by default it
10104 adds to the <file>debian/substvars</file> file variable
10105 settings like <tt>shlibs:Depends</tt>. These variable
10106 settings must be referenced in dependency fields in the
10107 appropriate per-binary-package sections of the source
10112 For example, a package that generates an essential part
10113 which requires dependencies, and optional parts that
10114 which only require a recommendation, would separate those
10115 two sets of dependencies into two different fields.<footnote>
10116 At the time of writing, an example for this was the
10117 <package/xmms/ package, with Depends used for the xmms
10118 executable, Recommends for the plug-ins and Suggests for
10119 even more optional features provided by unzip.
10121 It can say in its <file>debian/rules</file>:
10123 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10124 -dRecommends <var>optionalpart anotheroptionalpart</var>
10126 and then in its main control file <file>debian/control</file>:
10129 Depends: ${shlibs:Depends}
10130 Recommends: ${shlibs:Recommends}
10136 Sources which produce several binary packages with
10137 different shared library dependency requirements can use
10138 the <tt>-p<var>varnameprefix</var></tt> option to override
10139 the default <tt>shlibs:</tt> prefix (one invocation of
10140 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10141 They can thus produce several sets of dependency
10142 variables, each of the form
10143 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10144 which can be referred to in the appropriate parts of the
10145 binary package control files.
10150 <sect1 id="pkg-dpkg-distaddfile">
10152 <prgn>dpkg-distaddfile</prgn> - adds a file to
10153 <file>debian/files</file>
10157 Some packages' uploads need to include files other than
10158 the source and binary package files.
10162 <prgn>dpkg-distaddfile</prgn> adds a file to the
10163 <file>debian/files</file> file so that it will be included in
10164 the <file>.changes</file> file when
10165 <prgn>dpkg-genchanges</prgn> is run.
10169 It is usually invoked from the <tt>binary</tt> target of
10170 <file>debian/rules</file>:
10172 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10174 The <var>filename</var> is relative to the directory where
10175 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10176 is usually the directory above the top level of the source
10177 tree. The <file>debian/rules</file> target should put the
10178 file there just before or just after calling
10179 <prgn>dpkg-distaddfile</prgn>.
10183 The <var>section</var> and <var>priority</var> are passed
10184 unchanged into the resulting <file>.changes</file> file.
10189 <sect1 id="pkg-dpkg-genchanges">
10191 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10192 upload control file
10196 This program is usually called by package-independent
10197 automatic building scripts such as
10198 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10203 It is usually called in the top level of a built source
10204 tree, and when invoked with no arguments will print out a
10205 straightforward <file>.changes</file> file based on the
10206 information in the source package's changelog and control
10207 file and the binary and source packages which should have
10213 <sect1 id="pkg-dpkg-parsechangelog">
10215 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10216 representation of a changelog
10220 This program is used internally by
10221 <prgn>dpkg-source</prgn> et al. It may also occasionally
10222 be useful in <file>debian/rules</file> and elsewhere. It
10223 parses a changelog, <file>debian/changelog</file> by default,
10224 and prints a control-file format representation of the
10225 information in it to standard output.
10229 <sect1 id="pkg-dpkg-architecture">
10231 <prgn>dpkg-architecture</prgn> - information about the build and
10236 This program can be used manually, but is also invoked by
10237 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10238 environment or make variables which specify the build and host
10239 architecture for the package building process.
10244 <sect id="pkg-sourcetree">
10245 <heading>The Debian package source tree</heading>
10248 The source archive scheme described later is intended to
10249 allow a Debian package source tree with some associated
10250 control information to be reproduced and transported easily.
10251 The Debian package source tree is a version of the original
10252 program with certain files added for the benefit of the
10253 packaging process, and with any other changes required
10254 made to the rest of the source code and installation
10259 The extra files created for Debian are in the subdirectory
10260 <file>debian</file> of the top level of the Debian package
10261 source tree. They are described below.
10264 <sect1 id="pkg-debianrules">
10265 <heading><file>debian/rules</file> - the main building script</heading>
10268 See <ref id="debianrules">.
10272 <sect1 id="pkg-srcsubstvars">
10273 <heading><file>debian/substvars</file> and variable substitutions</heading>
10276 See <ref id="substvars">.
10282 <heading><file>debian/files</file></heading>
10285 See <ref id="debianfiles">.
10289 <sect1><heading><file>debian/tmp</file>
10293 This is the canonical temporary location for the
10294 construction of binary packages by the <tt>binary</tt>
10295 target. The directory <file>tmp</file> serves as the root of
10296 the file system tree as it is being constructed (for
10297 example, by using the package's upstream makefiles install
10298 targets and redirecting the output there), and it also
10299 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10300 id="pkg-bincreating">.
10304 If several binary packages are generated from the same
10305 source tree it is usual to use several
10306 <file>debian/tmp<var>something</var></file> directories, for
10307 example <file>tmp-a</file> or <file>tmp-doc</file>.
10311 Whatever <file>tmp</file> directories are created and used by
10312 <tt>binary</tt> must of course be removed by the
10313 <tt>clean</tt> target.</p></sect1>
10317 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10321 As it exists on the FTP site, a Debian source package
10322 consists of three related files. You must have the right
10323 versions of all three to be able to use them.
10328 <tag>Debian source control file - <tt>.dsc</tt></tag>
10330 This file is a control file used by <prgn>dpkg-source</prgn>
10331 to extract a source package.
10332 See <ref id="debiansourcecontrolfiles">.
10336 Original source archive -
10338 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10344 This is a compressed (with <tt>gzip -9</tt>)
10345 <prgn>tar</prgn> file containing the source code from
10346 the upstream authors of the program.
10351 Debian package diff -
10353 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10359 This is a unified context diff (<tt>diff -u</tt>)
10360 giving the changes which are required to turn the
10361 original source into the Debian source. These changes
10362 may only include editing and creating plain files.
10363 The permissions of files, the targets of symbolic
10364 links and the characteristics of special files or
10365 pipes may not be changed and no files may be removed
10370 All the directories in the diff must exist, except the
10371 <file>debian</file> subdirectory of the top of the source
10372 tree, which will be created by
10373 <prgn>dpkg-source</prgn> if necessary when unpacking.
10377 The <prgn>dpkg-source</prgn> program will
10378 automatically make the <file>debian/rules</file> file
10379 executable (see below).</p></item>
10384 If there is no original source code - for example, if the
10385 package is specially prepared for Debian or the Debian
10386 maintainer is the same as the upstream maintainer - the
10387 format is slightly different: then there is no diff, and the
10389 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10390 and preferably contains a directory named
10391 <file><var>package</var>-<var>version</var></file>.
10396 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10399 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10400 Debian source package. However, if it is not available it
10401 is possible to unpack a Debian source archive as follows:
10402 <enumlist compact="compact">
10405 Untar the tarfile, which will create a <file>.orig</file>
10409 <p>Rename the <file>.orig</file> directory to
10410 <file><var>package</var>-<var>version</var></file>.</p>
10414 Create the subdirectory <file>debian</file> at the top of
10415 the source tree.</p>
10417 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10419 <item><p>Untar the tarfile again if you want a copy of the original
10420 source code alongside the Debian version.</p>
10425 It is not possible to generate a valid Debian source archive
10426 without using <prgn>dpkg-source</prgn>. In particular,
10427 attempting to use <prgn>diff</prgn> directly to generate the
10428 <file>.diff.gz</file> file will not work.
10432 <heading>Restrictions on objects in source packages</heading>
10435 The source package may not contain any hard links
10437 This is not currently detected when building source
10438 packages, but only when extracting
10442 Hard links may be permitted at some point in the
10443 future, but would require a fair amount of
10445 </footnote>, device special files, sockets or setuid or
10448 Setgid directories are allowed.
10453 The source packaging tools manage the changes between the
10454 original and Debian source using <prgn>diff</prgn> and
10455 <prgn>patch</prgn>. Turning the original source tree as
10456 included in the <file>.orig.tar.gz</file> into the Debian
10457 package source must not involve any changes which cannot be
10458 handled by these tools. Problematic changes which cause
10459 <prgn>dpkg-source</prgn> to halt with an error when
10460 building the source package are:
10461 <list compact="compact">
10462 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10464 <item><p>Changing the targets of symbolic links.</p>
10466 <item><p>Creating directories, other than <file>debian</file>.</p>
10468 <item><p>Changes to the contents of binary files.</p></item>
10469 </list> Changes which cause <prgn>dpkg-source</prgn> to
10470 print a warning but continue anyway are:
10471 <list compact="compact">
10474 Removing files, directories or symlinks.
10476 Renaming a file is not treated specially - it is
10477 seen as the removal of the old file (which
10478 generates a warning, but is otherwise ignored),
10479 and the creation of the new one.
10485 Changed text files which are missing the usual final
10486 newline (either in the original or the modified
10491 Changes which are not represented, but which are not detected by
10492 <prgn>dpkg-source</prgn>, are:
10493 <list compact="compact">
10494 <item><p>Changing the permissions of files (other than
10495 <file>debian/rules</file>) and directories.</p></item>
10500 The <file>debian</file> directory and <file>debian/rules</file>
10501 are handled specially by <prgn>dpkg-source</prgn> - before
10502 applying the changes it will create the <file>debian</file>
10503 directory, and afterwards it will make
10504 <file>debian/rules</file> world-executable.
10510 <appendix id="pkg-controlfields">
10511 <heading>Control files and their fields (from old Packaging Manual)</heading>
10514 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10515 data in a common format, known as control files. Binary and
10516 source packages have control data as do the <file>.changes</file>
10517 files which control the installation of uploaded files, and
10518 <prgn>dpkg</prgn>'s internal databases are in a similar
10523 <heading>Syntax of control files</heading>
10526 See <ref id="controlsyntax">.
10530 It is important to note that there are several fields which
10531 are optional as far as <prgn>dpkg</prgn> and the related
10532 tools are concerned, but which must appear in every Debian
10533 package, or whose omission may cause problems.
10538 <heading>List of fields</heading>
10541 See <ref id="controlfieldslist">.
10545 This section now contains only the fields that didn't belong
10546 to the Policy manual.
10549 <sect1 id="pkg-f-Filename">
10550 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10553 These fields in <tt>Packages</tt> files give the
10554 filename(s) of (the parts of) a package in the
10555 distribution directories, relative to the root of the
10556 Debian hierarchy. If the package has been split into
10557 several parts the parts are all listed in order, separated
10562 <sect1 id="pkg-f-Size">
10563 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10566 These fields in <file>Packages</file> files give the size (in
10567 bytes, expressed in decimal) and MD5 checksum of the
10568 file(s) which make(s) up a binary package in the
10569 distribution. If the package is split into several parts
10570 the values for the parts are listed in order, separated by
10575 <sect1 id="pkg-f-Status">
10576 <heading><tt>Status</tt></heading>
10579 This field in <prgn>dpkg</prgn>'s status file records
10580 whether the user wants a package installed, removed or
10581 left alone, whether it is broken (requiring
10582 re-installation) or not and what its current state on the
10583 system is. Each of these pieces of information is a
10588 <sect1 id="pkg-f-Config-Version">
10589 <heading><tt>Config-Version</tt></heading>
10592 If a package is not installed or not configured, this
10593 field in <prgn>dpkg</prgn>'s status file records the last
10594 version of the package which was successfully
10599 <sect1 id="pkg-f-Conffiles">
10600 <heading><tt>Conffiles</tt></heading>
10603 This field in <prgn>dpkg</prgn>'s status file contains
10604 information about the automatically-managed configuration
10605 files held by a package. This field should <em>not</em>
10606 appear anywhere in a package!
10611 <heading>Obsolete fields</heading>
10614 These are still recognized by <prgn>dpkg</prgn> but should
10615 not appear anywhere any more.
10617 <taglist compact="compact">
10619 <tag><tt>Revision</tt></tag>
10620 <tag><tt>Package-Revision</tt></tag>
10621 <tag><tt>Package_Revision</tt></tag>
10623 The Debian revision part of the package version was
10624 at one point in a separate control file field. This
10625 field went through several names.
10628 <tag><tt>Recommended</tt></tag>
10629 <item>Old name for <tt>Recommends</tt>.</item>
10631 <tag><tt>Optional</tt></tag>
10632 <item>Old name for <tt>Suggests</tt>.</item>
10634 <tag><tt>Class</tt></tag>
10635 <item>Old name for <tt>Priority</tt>.</item>
10644 <appendix id="pkg-conffiles">
10645 <heading>Configuration file handling (from old Packaging Manual)</heading>
10648 <prgn>dpkg</prgn> can do a certain amount of automatic
10649 handling of package configuration files.
10653 Whether this mechanism is appropriate depends on a number of
10654 factors, but basically there are two approaches to any
10655 particular configuration file.
10659 The easy method is to ship a best-effort configuration in the
10660 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10661 handle updates. If the user is unlikely to want to edit the
10662 file, but you need them to be able to without losing their
10663 changes, and a new package with a changed version of the file
10664 is only released infrequently, this is a good approach.
10668 The hard method is to build the configuration file from
10669 scratch in the <prgn>postinst</prgn> script, and to take the
10670 responsibility for fixing any mistakes made in earlier
10671 versions of the package automatically. This will be
10672 appropriate if the file is likely to need to be different on
10676 <sect><heading>Automatic handling of configuration files by
10681 A package may contain a control area file called
10682 <tt>conffiles</tt>. This file should be a list of filenames
10683 of configuration files needing automatic handling, separated
10684 by newlines. The filenames should be absolute pathnames,
10685 and the files referred to should actually exist in the
10690 When a package is upgraded <prgn>dpkg</prgn> will process
10691 the configuration files during the configuration stage,
10692 shortly before it runs the package's <prgn>postinst</prgn>
10697 For each file it checks to see whether the version of the
10698 file included in the package is the same as the one that was
10699 included in the last version of the package (the one that is
10700 being upgraded from); it also compares the version currently
10701 installed on the system with the one shipped with the last
10706 If neither the user nor the package maintainer has changed
10707 the file, it is left alone. If one or the other has changed
10708 their version, then the changed version is preferred - i.e.,
10709 if the user edits their file, but the package maintainer
10710 doesn't ship a different version, the user's changes will
10711 stay, silently, but if the maintainer ships a new version
10712 and the user hasn't edited it the new version will be
10713 installed (with an informative message). If both have
10714 changed their version the user is prompted about the problem
10715 and must resolve the differences themselves.
10719 The comparisons are done by calculating the MD5 message
10720 digests of the files, and storing the MD5 of the file as it
10721 was included in the most recent version of the package.
10725 When a package is installed for the first time
10726 <prgn>dpkg</prgn> will install the file that comes with it,
10727 unless that would mean overwriting a file already on the
10732 However, note that <prgn>dpkg</prgn> will <em>not</em>
10733 replace a conffile that was removed by the user (or by a
10734 script). This is necessary because with some programs a
10735 missing file produces an effect hard or impossible to
10736 achieve in another way, so that a missing file needs to be
10737 kept that way if the user did it.
10741 Note that a package should <em>not</em> modify a
10742 <prgn>dpkg</prgn>-handled conffile in its maintainer
10743 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10744 the user confusing and possibly dangerous options for
10745 conffile update when the package is upgraded.</p>
10748 <sect><heading>Fully-featured maintainer script configuration
10753 For files which contain site-specific information such as
10754 the hostname and networking details and so forth, it is
10755 better to create the file in the package's
10756 <prgn>postinst</prgn> script.
10760 This will typically involve examining the state of the rest
10761 of the system to determine values and other information, and
10762 may involve prompting the user for some information which
10763 can't be obtained some other way.
10767 When using this method there are a couple of important
10768 issues which should be considered:
10772 If you discover a bug in the program which generates the
10773 configuration file, or if the format of the file changes
10774 from one version to the next, you will have to arrange for
10775 the postinst script to do something sensible - usually this
10776 will mean editing the installed configuration file to remove
10777 the problem or change the syntax. You will have to do this
10778 very carefully, since the user may have changed the file,
10779 perhaps to fix the very problem that your script is trying
10780 to deal with - you will have to detect these situations and
10781 deal with them correctly.
10785 If you do go down this route it's probably a good idea to
10786 make the program that generates the configuration file(s) a
10787 separate program in <file>/usr/sbin</file>, by convention called
10788 <file><var>package</var>config</file> and then run that if
10789 appropriate from the post-installation script. The
10790 <tt><var>package</var>config</tt> program should not
10791 unquestioningly overwrite an existing configuration - if its
10792 mode of operation is geared towards setting up a package for
10793 the first time (rather than any arbitrary reconfiguration
10794 later) you should have it check whether the configuration
10795 already exists, and require a <tt>--force</tt> flag to
10796 overwrite it.</p></sect>
10799 <appendix id="pkg-alternatives"><heading>Alternative versions of
10800 an interface - <prgn>update-alternatives</prgn> (from old
10805 When several packages all provide different versions of the
10806 same program or file it is useful to have the system select a
10807 default, but to allow the system administrator to change it
10808 and have their decisions respected.
10812 For example, there are several versions of the <prgn>vi</prgn>
10813 editor, and there is no reason to prevent all of them from
10814 being installed at once, each under their own name
10815 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10816 Nevertheless it is desirable to have the name <tt>vi</tt>
10817 refer to something, at least by default.
10821 If all the packages involved cooperate, this can be done with
10822 <prgn>update-alternatives</prgn>.
10826 Each package provides its own version under its own name, and
10827 calls <prgn>update-alternatives</prgn> in its postinst to
10828 register its version (and again in its prerm to deregister
10833 See the man page <manref name="update-alternatives"
10834 section="8"> for details.
10838 If <prgn>update-alternatives</prgn> does not seem appropriate
10839 you may wish to consider using diversions instead.</p>
10842 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10843 package's version of a file (from old Packaging Manual)
10847 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10848 when it reinstalls the package it belongs to, and to have it
10849 put the file from the package somewhere else instead.
10853 This can be used locally to override a package's version of a
10854 file, or by one package to override another's version (or
10855 provide a wrapper for it).
10859 Before deciding to use a diversion, read <ref
10860 id="pkg-alternatives"> to see if you really want a diversion
10861 rather than several alternative versions of a program.
10865 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10866 and updated by a special program <prgn>dpkg-divert</prgn>.
10867 Please see <manref name="dpkg-divert" section="8"> for full
10868 details of its operation.
10872 When a package wishes to divert a file from another, it should
10873 call <prgn>dpkg-divert</prgn> in its preinst to add the
10874 diversion and rename the existing file. For example,
10875 supposing that a <prgn>smailwrapper</prgn> package wishes to
10876 install a wrapper around <file>/usr/sbin/smail</file>:
10878 dpkg-divert --package smailwrapper --add --rename \
10879 --divert /usr/sbin/smail.real /usr/sbin/smail
10880 </example> The <tt>--package smailwrapper</tt> ensures that
10881 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10882 can bypass the diversion and get installed as the true version.
10883 It's safe to add the diversion unconditionally on upgrades since
10884 it will be left unchanged if it already exists, but
10885 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10886 message, make the command conditional on the version from which
10887 the package is being upgraded:
10889 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10890 dpkg-divert --package smailwrapper --add --rename \
10891 --divert /usr/sbin/smail.real /usr/sbin/smail
10893 </example> where <tt>1.0-2</tt> is the version at which the
10894 diversion was first added to the package. Running the command
10895 during abort-upgrade is pointless but harmless.
10899 The postrm has to do the reverse:
10901 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10902 dpkg-divert --package smailwrapper --remove --rename \
10903 --divert /usr/sbin/smail.real /usr/sbin/smail
10905 </example> If the diversion was added at a particular version, the
10906 postrm should also handle the failure case of upgrading from an
10907 older version (unless the older version is so old that direct
10908 upgrades are no longer supported):
10910 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10911 dpkg-divert --package smailwrapper --remove --rename \
10912 --divert /usr/sbin/smail.real /usr/sbin/smail
10914 </example> where <tt>1.02-2</tt> is the version at which the
10915 diversion was first added to the package. The postrm should not
10916 remove the diversion on upgrades both because there's no reason to
10917 remove the diversion only to immediately re-add it and since the
10918 postrm of the old package is run after unpacking so the removal of
10919 the diversion will fail.
10923 Do not attempt to divert a file which is vitally important for
10924 the system's operation - when using <prgn>dpkg-divert</prgn>
10925 there is a time, after it has been diverted but before
10926 <prgn>dpkg</prgn> has installed the new version, when the file
10927 does not exist.</p>
10932 <!-- Local variables: -->
10933 <!-- indent-tabs-mode: t -->
10935 <!-- vim:set ai et sts=2 sw=2 tw=76: -->