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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a <tt>Pre-Depends</tt>, <tt>Depends</tt>,
480 <tt>Recommends</tt>, <tt>Build-Depends</tt>,
481 or <tt>Build-Depends-Indep</tt> relationship on a
482 non-<em>main</em> package unless a package
483 in <em>main</em> is listed as an alternative),
486 must not be so buggy that we refuse to support them,
490 must meet all policy requirements presented in this
499 <heading>The contrib archive area</heading>
502 Every package in <em>contrib</em> must comply with the DFSG.
506 In addition, the packages in <em>contrib</em>
507 <list compact="compact">
509 must not be so buggy that we refuse to support them,
513 must meet all policy requirements presented in this
521 Examples of packages which would be included in
522 <em>contrib</em> are:
523 <list compact="compact">
525 free packages which require <em>contrib</em>,
526 <em>non-free</em> packages or packages which are not
527 in our archive at all for compilation or execution,
531 wrapper packages or other sorts of free accessories for
538 <sect1 id="non-free">
539 <heading>The non-free archive area</heading>
542 Packages must be placed in <em>non-free</em> if they are
543 not compliant with the DFSG or are encumbered by patents
544 or other legal issues that make their distribution
549 In addition, the packages in <em>non-free</em>
550 <list compact="compact">
552 must not be so buggy that we refuse to support them,
556 must meet all policy requirements presented in this
557 manual that it is possible for them to meet.
559 It is possible that there are policy
560 requirements which the package is unable to
561 meet, for example, if the source is
562 unavailable. These situations will need to be
563 handled on a case-by-case basis.
572 <sect id="pkgcopyright">
573 <heading>Copyright considerations</heading>
576 Every package must be accompanied by a verbatim copy of its
577 copyright information and distribution license in the file
578 <file>/usr/share/doc/<var>package</var>/copyright</file>
579 (see <ref id="copyrightfile"> for further details).
583 We reserve the right to restrict files from being included
584 anywhere in our archives if
585 <list compact="compact">
587 their use or distribution would break a law,
590 there is an ethical conflict in their distribution or
594 we would have to sign a license for them, or
597 their distribution would conflict with other project
604 Programs whose authors encourage the user to make
605 donations are fine for the main distribution, provided
606 that the authors do not claim that not donating is
607 immoral, unethical, illegal or something similar; in such
608 a case they must go in <em>non-free</em>.
612 Packages whose copyright permission notices (or patent
613 problems) do not even allow redistribution of binaries
614 only, and where no special permission has been obtained,
615 must not be placed on the Debian FTP site and its mirrors
620 Note that under international copyright law (this applies
621 in the United States, too), <em>no</em> distribution or
622 modification of a work is allowed without an explicit
623 notice saying so. Therefore a program without a copyright
624 notice <em>is</em> copyrighted and you may not do anything
625 to it without risking being sued! Likewise if a program
626 has a copyright notice but no statement saying what is
627 permitted then nothing is permitted.
631 Many authors are unaware of the problems that restrictive
632 copyrights (or lack of copyright notices) can cause for
633 the users of their supposedly-free software. It is often
634 worthwhile contacting such authors diplomatically to ask
635 them to modify their license terms. However, this can be a
636 politically difficult thing to do and you should ask for
637 advice on the <tt>debian-legal</tt> mailing list first, as
642 When in doubt about a copyright, send mail to
643 <email>debian-legal@lists.debian.org</email>. Be prepared
644 to provide us with the copyright statement. Software
645 covered by the GPL, public domain software and BSD-like
646 copyrights are safe; be wary of the phrases "commercial
647 use prohibited" and "distribution restricted".
651 <sect id="subsections">
652 <heading>Sections</heading>
655 The packages in the archive areas <em>main</em>,
656 <em>contrib</em> and <em>non-free</em> are grouped further into
657 <em>sections</em> to simplify handling.
661 The archive area and section for each package should be
662 specified in the package's <tt>Section</tt> control record (see
663 <ref id="f-Section">). However, the maintainer of the Debian
664 archive may override this selection to ensure the consistency of
665 the Debian distribution. The <tt>Section</tt> field should be
667 <list compact="compact">
669 <em>section</em> if the package is in the
670 <em>main</em> archive area,
673 <em>area/section</em> if the package is in
674 the <em>contrib</em> or <em>non-free</em>
681 The Debian archive maintainers provide the authoritative
682 list of sections. At present, they are:
683 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
684 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
685 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
686 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
687 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
688 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
689 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
690 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
691 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
692 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
693 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
694 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
695 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
696 <em>zope</em>. The additional section <em>debian-installer</em>
697 contains special packages used by the installer and is not used
698 for normal Debian packages.
702 For more information about the sections and their definitions,
703 see the <url id="http://packages.debian.org/unstable/"
704 name="list of sections in unstable">.
708 <sect id="priorities">
709 <heading>Priorities</heading>
712 Each package should have a <em>priority</em> value, which is
713 included in the package's <em>control record</em>
714 (see <ref id="f-Priority">).
715 This information is used by the Debian package management tools to
716 separate high-priority packages from less-important packages.
720 The following <em>priority levels</em> are recognized by the
721 Debian package management tools.
723 <tag><tt>required</tt></tag>
725 Packages which are necessary for the proper
726 functioning of the system (usually, this means that
727 dpkg functionality depends on these packages).
728 Removing a <tt>required</tt> package may cause your
729 system to become totally broken and you may not even
730 be able to use <prgn>dpkg</prgn> to put things back,
731 so only do so if you know what you are doing. Systems
732 with only the <tt>required</tt> packages are probably
733 unusable, but they do have enough functionality to
734 allow the sysadmin to boot and install more software.
736 <tag><tt>important</tt></tag>
738 Important programs, including those which one would
739 expect to find on any Unix-like system. If the
740 expectation is that an experienced Unix person who
741 found it missing would say "What on earth is going on,
742 where is <prgn>foo</prgn>?", it must be an
743 <tt>important</tt> package.<footnote>
744 This is an important criterion because we are
745 trying to produce, amongst other things, a free
748 Other packages without which the system will not run
749 well or be usable must also have priority
750 <tt>important</tt>. This does
751 <em>not</em> include Emacs, the X Window System, TeX
752 or any other large applications. The
753 <tt>important</tt> packages are just a bare minimum of
754 commonly-expected and necessary tools.
756 <tag><tt>standard</tt></tag>
758 These packages provide a reasonably small but not too
759 limited character-mode system. This is what will be
760 installed by default if the user doesn't select anything
761 else. It doesn't include many large applications.
763 <tag><tt>optional</tt></tag>
765 (In a sense everything that isn't required is
766 optional, but that's not what is meant here.) This is
767 all the software that you might reasonably want to
768 install if you didn't know what it was and don't have
769 specialized requirements. This is a much larger system
770 and includes the X Window System, a full TeX
771 distribution, and many applications. Note that
772 optional packages should not conflict with each other.
774 <tag><tt>extra</tt></tag>
776 This contains all packages that conflict with others
777 with required, important, standard or optional
778 priorities, or are only likely to be useful if you
779 already know what they are or have specialized
780 requirements (such as packages containing only detached
787 Packages must not depend on packages with lower priority
788 values (excluding build-time dependencies). In order to
789 ensure this, the priorities of one or more packages may need
798 <heading>Binary packages</heading>
801 The Debian GNU/Linux distribution is based on the Debian
802 package management system, called <prgn>dpkg</prgn>. Thus,
803 all packages in the Debian distribution must be provided
804 in the <tt>.deb</tt> file format.
808 <heading>The package name</heading>
811 Every package must have a name that's unique within the Debian
816 The package name is included in the control field
817 <tt>Package</tt>, the format of which is described
818 in <ref id="f-Package">.
819 The package name is also included as a part of the file name
820 of the <tt>.deb</tt> file.
825 <heading>The version of a package</heading>
828 Every package has a version number recorded in its
829 <tt>Version</tt> control file field, described in
830 <ref id="f-Version">.
834 The package management system imposes an ordering on version
835 numbers, so that it can tell whether packages are being up- or
836 downgraded and so that package system front end applications
837 can tell whether a package it finds available is newer than
838 the one installed on the system. The version number format
839 has the most significant parts (as far as comparison is
840 concerned) at the beginning.
844 If an upstream package has problematic version numbers they
845 should be converted to a sane form for use in the
846 <tt>Version</tt> field.
850 <heading>Version numbers based on dates</heading>
853 In general, Debian packages should use the same version
854 numbers as the upstream sources.
858 However, in some cases where the upstream version number is
859 based on a date (e.g., a development "snapshot" release) the
860 package management system cannot handle these version
861 numbers without epochs. For example, dpkg will consider
862 "96May01" to be greater than "96Dec24".
866 To prevent having to use epochs for every new upstream
867 version, the date based portion of the version number
868 should be changed to the following format in such cases:
869 "19960501", "19961224". It is up to the maintainer whether
870 they want to bother the upstream maintainer to change
871 the version numbers upstream, too.
875 Note that other version formats based on dates which are
876 parsed correctly by the package management system should
877 <em>not</em> be changed.
881 Native Debian packages (i.e., packages which have been
882 written especially for Debian) whose version numbers include
883 dates should always use the "YYYYMMDD" format.
889 <sect id="maintainer">
890 <heading>The maintainer of a package</heading>
893 Every package must have a maintainer. The maintainer may be one
894 person or a group of people reachable from a common email
895 address, such as a mailing list. The maintainer is responsible
896 for maintaining the Debian packaging files, evaluating and
897 responding appropriately to reported bugs, uploading new
898 versions of the package (either directly or through a sponsor),
899 ensuring that the package is placed in the appropriate archive
900 area and included in Debian releases as appropriate for the
901 stability and utility of the package, and requesting removal of
902 the package from the Debian distribution if it is no longer
903 useful or maintainable.
907 The maintainer must be specified in the <tt>Maintainer</tt>
908 control field with their correct name and a working email
909 address. The email address given in the <tt>Maintainer</tt>
910 control field must accept mail from those role accounts in
911 Debian used to send automated mails regarding the package. This
912 includes non-spam mail from the bug-tracking system, all mail
913 from the Debian archive maintenance software, and other role
914 accounts or automated processes that are commonly agreed on by
915 the project.<footnote>
916 A sample implementation of such a whitelist written for the
917 Mailman mailing list management software is used for mailing
918 lists hosted by alioth.debian.org.
920 If one person or team maintains several packages, they should
921 use the same form of their name and email address in
922 the <tt>Maintainer</tt> fields of those packages.
926 The format of the <tt>Maintainer</tt> control field is
927 described in <ref id="f-Maintainer">.
931 If the maintainer of the package is a team of people with a
932 shared email address, the <tt>Uploaders</tt> control field must
933 be present and must contain at least one human with their
934 personal email address. See <ref id="f-Uploaders"> for the
935 syntax of that field.
939 If the maintainer of a package no longer has time or desire to
940 maintain a package, it will be orphaned according to the
941 procedure described in the Debian Developer's Reference
942 (see <ref id="related">). The maintainer then
943 becomes <tt>Debian QA Group <packages@qa.debian.org></tt>.
944 These packages are considered maintained by the Debian project
945 as a whole until someone else volunteers to take over
950 <sect id="descriptions">
951 <heading>The description of a package</heading>
954 Every Debian package must have an extended description
955 stored in the appropriate field of the control record.
956 The technical information about the format of the
957 <tt>Description</tt> field is in <ref id="f-Description">.
961 The description should describe the package (the program) to a
962 user (system administrator) who has never met it before so that
963 they have enough information to decide whether they want to
964 install it. This description should not just be copied verbatim
965 from the program's documentation.
969 Put important information first, both in the synopsis and
970 extended description. Sometimes only the first part of the
971 synopsis or of the description will be displayed. You can
972 assume that there will usually be a way to see the whole
973 extended description.
977 The description should also give information about the
978 significant dependencies and conflicts between this package
979 and others, so that the user knows why these dependencies and
980 conflicts have been declared.
984 Instructions for configuring or using the package should
985 not be included (that is what installation scripts,
986 manual pages, info files, etc., are for). Copyright
987 statements and other administrivia should not be included
988 either (that is what the copyright file is for).
991 <sect1 id="synopsis"><heading>The single line synopsis</heading>
994 The single line synopsis should be kept brief - certainly
999 Do not include the package name in the synopsis line. The
1000 display software knows how to display this already, and you
1001 do not need to state it. Remember that in many situations
1002 the user may only see the synopsis line - make it as
1003 informative as you can.
1008 <sect1 id="extendeddesc"><heading>The extended description</heading>
1011 Do not try to continue the single line synopsis into the
1012 extended description. This will not work correctly when
1013 the full description is displayed, and makes no sense
1014 where only the summary (the single line synopsis) is
1019 The extended description should describe what the package
1020 does and how it relates to the rest of the system (in terms
1021 of, for example, which subsystem it is which part of).
1025 The description field needs to make sense to anyone, even
1026 people who have no idea about any of the things the
1027 package deals with.<footnote>
1028 The blurb that comes with a program in its
1029 announcements and/or <prgn>README</prgn> files is
1030 rarely suitable for use in a description. It is
1031 usually aimed at people who are already in the
1032 community where the package is used.
1041 <heading>Dependencies</heading>
1044 Every package must specify the dependency information
1045 about other packages that are required for the first to
1050 For example, a dependency entry must be provided for any
1051 shared libraries required by a dynamically-linked executable
1052 binary in a package.
1056 Packages are not required to declare any dependencies they
1057 have on other packages which are marked <tt>Essential</tt>
1058 (see below), and should not do so unless they depend on a
1059 particular version of that package.<footnote>
1061 Essential is needed in part to avoid unresolvable dependency
1062 loops on upgrade. If packages add unnecessary dependencies
1063 on packages in this set, the chances that there
1064 <strong>will</strong> be an unresolvable dependency loop
1065 caused by forcing these Essential packages to be configured
1066 first before they need to be is greatly increased. It also
1067 increases the chances that frontends will be unable to
1068 <strong>calculate</strong> an upgrade path, even if one
1072 Also, functionality is rarely ever removed from the
1073 Essential set, but <em>packages</em> have been removed from
1074 the Essential set when the functionality moved to a
1075 different package. So depending on these packages <em>just
1076 in case</em> they stop being essential does way more harm
1083 Sometimes, a package requires another package to be installed
1084 <em>and</em> configured before it can be installed. In this
1085 case, you must specify a <tt>Pre-Depends</tt> entry for
1090 You should not specify a <tt>Pre-Depends</tt> entry for a
1091 package before this has been discussed on the
1092 <tt>debian-devel</tt> mailing list and a consensus about
1093 doing that has been reached.
1097 The format of the package interrelationship control fields is
1098 described in <ref id="relationships">.
1102 <sect id="virtual_pkg">
1103 <heading>Virtual packages</heading>
1106 Sometimes, there are several packages which offer
1107 more-or-less the same functionality. In this case, it's
1108 useful to define a <em>virtual package</em> whose name
1109 describes that common functionality. (The virtual
1110 packages only exist logically, not physically; that's why
1111 they are called <em>virtual</em>.) The packages with this
1112 particular function will then <em>provide</em> the virtual
1113 package. Thus, any other package requiring that function
1114 can simply depend on the virtual package without having to
1115 specify all possible packages individually.
1119 All packages should use virtual package names where
1120 appropriate, and arrange to create new ones if necessary.
1121 They should not use virtual package names (except privately,
1122 amongst a cooperating group of packages) unless they have
1123 been agreed upon and appear in the list of virtual package
1124 names. (See also <ref id="virtual">)
1128 The latest version of the authoritative list of virtual
1129 package names can be found in the <tt>debian-policy</tt> package.
1130 It is also available from the Debian web mirrors at
1131 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1132 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1136 The procedure for updating the list is described in the preface
1143 <heading>Base system</heading>
1146 The <tt>base system</tt> is a minimum subset of the Debian
1147 GNU/Linux system that is installed before everything else
1148 on a new system. Only very few packages are allowed to form
1149 part of the base system, in order to keep the required disk
1154 The base system consists of all those packages with priority
1155 <tt>required</tt> or <tt>important</tt>. Many of them will
1156 be tagged <tt>essential</tt> (see below).
1161 <heading>Essential packages</heading>
1164 Essential is defined as the minimal set of functionality that
1165 must be available and usable on the system at all times, even
1166 when packages are in an unconfigured (but unpacked) state.
1167 Packages are tagged <tt>essential</tt> for a system using the
1168 <tt>Essential</tt> control file field. The format of the
1169 <tt>Essential</tt> control field is described in <ref
1174 Since these packages cannot be easily removed (one has to
1175 specify an extra <em>force option</em> to
1176 <prgn>dpkg</prgn> to do so), this flag must not be used
1177 unless absolutely necessary. A shared library package
1178 must not be tagged <tt>essential</tt>; dependencies will
1179 prevent its premature removal, and we need to be able to
1180 remove it when it has been superseded.
1184 Since dpkg will not prevent upgrading of other packages
1185 while an <tt>essential</tt> package is in an unconfigured
1186 state, all <tt>essential</tt> packages must supply all of
1187 their core functionality even when unconfigured. If the
1188 package cannot satisfy this requirement it must not be
1189 tagged as essential, and any packages depending on this
1190 package must instead have explicit dependency fields as
1195 Maintainers should take great care in adding any programs,
1196 interfaces, or functionality to <tt>essential</tt> packages.
1197 Packages may assume that functionality provided by
1198 <tt>essential</tt> packages is always available without
1199 declaring explicit dependencies, which means that removing
1200 functionality from the Essential set is very difficult and is
1201 almost never done. Any capability added to an
1202 <tt>essential</tt> package therefore creates an obligation to
1203 support that capability as part of the Essential set in
1208 You must not tag any packages <tt>essential</tt> before
1209 this has been discussed on the <tt>debian-devel</tt>
1210 mailing list and a consensus about doing that has been
1215 <sect id="maintscripts">
1216 <heading>Maintainer Scripts</heading>
1219 The package installation scripts should avoid producing
1220 output which is unnecessary for the user to see and
1221 should rely on <prgn>dpkg</prgn> to stave off boredom on
1222 the part of a user installing many packages. This means,
1223 amongst other things, using the <tt>--quiet</tt> option on
1224 <prgn>install-info</prgn>.
1228 Errors which occur during the execution of an installation
1229 script must be checked and the installation must not
1230 continue after an error.
1234 Note that in general <ref id="scripts"> applies to package
1235 maintainer scripts, too.
1239 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1240 to another package without consulting the maintainer of that
1241 package first. When adding or removing diversions, package
1242 maintainer scripts must provide the <tt>--package</tt> flag
1243 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1247 All packages which supply an instance of a common command
1248 name (or, in general, filename) should generally use
1249 <prgn>update-alternatives</prgn>, so that they may be
1250 installed together. If <prgn>update-alternatives</prgn>
1251 is not used, then each package must use
1252 <tt>Conflicts</tt> to ensure that other packages are
1253 de-installed. (In this case, it may be appropriate to
1254 specify a conflict against earlier versions of something
1255 that previously did not use
1256 <prgn>update-alternatives</prgn>; this is an exception to
1257 the usual rule that versioned conflicts should be
1261 <sect1 id="maintscriptprompt">
1262 <heading>Prompting in maintainer scripts</heading>
1264 Package maintainer scripts may prompt the user if
1265 necessary. Prompting must be done by communicating
1266 through a program, such as <prgn>debconf</prgn>, which
1267 conforms to the Debian Configuration Management
1268 Specification, version 2 or higher.
1272 Packages which are essential, or which are dependencies of
1273 essential packages, may fall back on another prompting method
1274 if no such interface is available when they are executed.
1278 The Debian Configuration Management Specification is included
1279 in the <file>debconf_specification</file> files in the
1280 <package>debian-policy</package> package.
1281 It is also available from the Debian web mirrors at
1282 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1283 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1287 Packages which use the Debian Configuration Management
1288 Specification may contain an additional
1289 <prgn>config</prgn> script and a <tt>templates</tt>
1290 file in their control archive<footnote>
1291 The control.tar.gz inside the .deb.
1292 See <manref name="deb" section="5">.
1294 The <prgn>config</prgn> script might be run before the
1295 <prgn>preinst</prgn> script, and before the package is unpacked
1296 or any of its dependencies or pre-dependencies are satisfied.
1297 Therefore it must work using only the tools present in
1298 <em>essential</em> packages.<footnote>
1299 <package>Debconf</package> or another tool that
1300 implements the Debian Configuration Management
1301 Specification will also be installed, and any
1302 versioned dependencies on it will be satisfied
1303 before preconfiguration begins.
1308 Packages which use the Debian Configuration Management
1309 Specification must allow for translation of their user-visible
1310 messages by using a gettext-based system such as the one
1311 provided by the <package>po-debconf</package> package.
1315 Packages should try to minimize the amount of prompting
1316 they need to do, and they should ensure that the user
1317 will only ever be asked each question once. This means
1318 that packages should try to use appropriate shared
1319 configuration files (such as <file>/etc/papersize</file> and
1320 <file>/etc/news/server</file>), and shared
1321 <package>debconf</package> variables rather than each
1322 prompting for their own list of required pieces of
1327 It also means that an upgrade should not ask the same
1328 questions again, unless the user has used
1329 <tt>dpkg --purge</tt> to remove the package's configuration.
1330 The answers to configuration questions should be stored in an
1331 appropriate place in <file>/etc</file> so that the user can
1332 modify them, and how this has been done should be
1337 If a package has a vitally important piece of
1338 information to pass to the user (such as "don't run me
1339 as I am, you must edit the following configuration files
1340 first or you risk your system emitting badly-formatted
1341 messages"), it should display this in the
1342 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1343 prompt the user to hit return to acknowledge the
1344 message. Copyright messages do not count as vitally
1345 important (they belong in
1346 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1347 neither do instructions on how to use a program (these
1348 should be in on-line documentation, where all the users
1353 Any necessary prompting should almost always be confined
1354 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1355 script. If it is done in the <prgn>postinst</prgn>, it
1356 should be protected with a conditional so that
1357 unnecessary prompting doesn't happen if a package's
1358 installation fails and the <prgn>postinst</prgn> is
1359 called with <tt>abort-upgrade</tt>,
1360 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1370 <heading>Source packages</heading>
1372 <sect id="standardsversion">
1373 <heading>Standards conformance</heading>
1376 Source packages should specify the most recent version number
1377 of this policy document with which your package complied
1378 when it was last updated.
1382 This information may be used to file bug reports
1383 automatically if your package becomes too much out of date.
1387 The version is specified in the <tt>Standards-Version</tt>
1389 The format of the <tt>Standards-Version</tt> field is
1390 described in <ref id="f-Standards-Version">.
1394 You should regularly, and especially if your package has
1395 become out of date, check for the newest Policy Manual
1396 available and update your package, if necessary. When your
1397 package complies with the new standards you should update the
1398 <tt>Standards-Version</tt> source package field and
1399 release it.<footnote>
1400 See the file <file>upgrading-checklist</file> for
1401 information about policy which has changed between
1402 different versions of this document.
1408 <sect id="pkg-relations">
1409 <heading>Package relationships</heading>
1412 Source packages should specify which binary packages they
1413 require to be installed or not to be installed in order to
1414 build correctly. For example, if building a package
1415 requires a certain compiler, then the compiler should be
1416 specified as a build-time dependency.
1420 It is not necessary to explicitly specify build-time
1421 relationships on a minimal set of packages that are always
1422 needed to compile, link and put in a Debian package a
1423 standard "Hello World!" program written in C or C++. The
1424 required packages are called <em>build-essential</em>, and
1425 an informational list can be found in
1426 <file>/usr/share/doc/build-essential/list</file> (which is
1427 contained in the <tt>build-essential</tt>
1430 <list compact="compact">
1432 This allows maintaining the list separately
1433 from the policy documents (the list does not
1434 need the kind of control that the policy
1438 Having a separate package allows one to install
1439 the build-essential packages on a machine, as
1440 well as allowing other packages such as tasks to
1441 require installation of the build-essential
1442 packages using the depends relation.
1445 The separate package allows bug reports against
1446 the list to be categorized separately from
1447 the policy management process in the BTS.
1454 When specifying the set of build-time dependencies, one
1455 should list only those packages explicitly required by the
1456 build. It is not necessary to list packages which are
1457 required merely because some other package in the list of
1458 build-time dependencies depends on them.<footnote>
1459 The reason for this is that dependencies change, and
1460 you should list all those packages, and <em>only</em>
1461 those packages that <em>you</em> need directly. What
1462 others need is their business. For example, if you
1463 only link against <file>libimlib</file>, you will need to
1464 build-depend on <package>libimlib2-dev</package> but
1465 not against any <tt>libjpeg*</tt> packages, even
1466 though <tt>libimlib2-dev</tt> currently depends on
1467 them: installation of <package>libimlib2-dev</package>
1468 will automatically ensure that all of its run-time
1469 dependencies are satisfied.
1474 If build-time dependencies are specified, it must be
1475 possible to build the package and produce working binaries
1476 on a system with only essential and build-essential
1477 packages installed and also those required to satisfy the
1478 build-time relationships (including any implied
1479 relationships). In particular, this means that version
1480 clauses should be used rigorously in build-time
1481 relationships so that one cannot produce bad or
1482 inconsistently configured packages when the relationships
1483 are properly satisfied.
1487 <ref id="relationships"> explains the technical details.
1492 <heading>Changes to the upstream sources</heading>
1495 If changes to the source code are made that are not
1496 specific to the needs of the Debian system, they should be
1497 sent to the upstream authors in whatever form they prefer
1498 so as to be included in the upstream version of the
1503 If you need to configure the package differently for
1504 Debian or for Linux, and the upstream source doesn't
1505 provide a way to do so, you should add such configuration
1506 facilities (for example, a new <prgn>autoconf</prgn> test
1507 or <tt>#define</tt>) and send the patch to the upstream
1508 authors, with the default set to the way they originally
1509 had it. You can then easily override the default in your
1510 <file>debian/rules</file> or wherever is appropriate.
1514 You should make sure that the <prgn>configure</prgn> utility
1515 detects the correct architecture specification string
1516 (refer to <ref id="arch-spec"> for details).
1520 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1521 <prgn>configure</prgn> scripts are used, you should edit the
1522 <file>.in</file> files rather than editing the
1523 <prgn>Makefile</prgn> directly. This allows the user to
1524 reconfigure the package if necessary. You should
1525 <em>not</em> configure the package and edit the generated
1526 <prgn>Makefile</prgn>! This makes it impossible for someone
1527 else to later reconfigure the package without losing the
1533 <sect id="dpkgchangelog">
1534 <heading>Debian changelog: <file>debian/changelog</file></heading>
1537 Changes in the Debian version of the package should be
1538 briefly explained in the Debian changelog file
1539 <file>debian/changelog</file>.<footnote>
1541 Mistakes in changelogs are usually best rectified by
1542 making a new changelog entry rather than "rewriting
1543 history" by editing old changelog entries.
1546 This includes modifications
1547 made in the Debian package compared to the upstream one
1548 as well as other changes and updates to the package.
1550 Although there is nothing stopping an author who is also
1551 the Debian maintainer from using this changelog for all
1552 their changes, it will have to be renamed if the Debian
1553 and upstream maintainers become different people. In such
1554 a case, however, it might be better to maintain the package
1555 as a non-native package.
1560 The format of the <file>debian/changelog</file> allows the
1561 package building tools to discover which version of the package
1562 is being built and find out other release-specific information.
1566 That format is a series of entries like this:
1568 <example compact="compact">
1569 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1571 [optional blank line(s), stripped]
1573 * <var>change details</var>
1574 <var>more change details</var>
1576 [blank line(s), included in output of dpkg-parsechangelog]
1578 * <var>even more change details</var>
1580 [optional blank line(s), stripped]
1582 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1587 <var>package</var> and <var>version</var> are the source
1588 package name and version number.
1592 <var>distribution(s)</var> lists the distributions where
1593 this version should be installed when it is uploaded - it
1594 is copied to the <tt>Distribution</tt> field in the
1595 <file>.changes</file> file. See <ref id="f-Distribution">.
1599 <var>urgency</var> is the value for the <tt>Urgency</tt>
1600 field in the <file>.changes</file> file for the upload
1601 (see <ref id="f-Urgency">). It is not possible to specify
1602 an urgency containing commas; commas are used to separate
1603 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1604 <prgn>dpkg</prgn> changelog format (though there is
1605 currently only one useful <var>keyword</var>,
1610 The change details may in fact be any series of lines
1611 starting with at least two spaces, but conventionally each
1612 change starts with an asterisk and a separating space and
1613 continuation lines are indented so as to bring them in
1614 line with the start of the text above. Blank lines may be
1615 used here to separate groups of changes, if desired.
1619 If this upload resolves bugs recorded in the Bug Tracking
1620 System (BTS), they may be automatically closed on the
1621 inclusion of this package into the Debian archive by
1622 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1623 in the change details.<footnote>
1624 To be precise, the string should match the following
1625 Perl regular expression:
1627 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1629 Then all of the bug numbers listed will be closed by the
1630 archive maintenance script (<prgn>katie</prgn>) using the
1631 <var>version</var> of the changelog entry.
1633 This information is conveyed via the <tt>Closes</tt> field
1634 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1638 The maintainer name and email address used in the changelog
1639 should be the details of the person uploading <em>this</em>
1640 version. They are <em>not</em> necessarily those of the
1641 usual package maintainer. The information here will be
1642 copied to the <tt>Changed-By</tt> field in the
1643 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1644 and then later used to send an acknowledgement when the
1645 upload has been installed.
1649 The <var>date</var> has the following format<footnote>
1650 This is the same as the format generated by <tt>date
1652 </footnote> (compatible and with the same semantics of
1653 RFC 2822 and RFC 5322):
1654 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1656 <list compact="compact">
1658 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1661 dd is a one- or two-digit day of the month (01-31)
1664 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1667 <item>yyyy is the four-digit year (e.g. 2010)</item>
1668 <item>hh is the two-digit hour (00-23)</item>
1669 <item>mm is the two-digit minutes (00-59)</item>
1670 <item>ss is the two-digit seconds (00-60)</item>
1672 +zzzz or -zzzz is the the time zone offset from Coordinated
1673 Universal Time (UTC). "+" indicates that the time is ahead
1674 of (i.e., east of) UTC and "-" indicates that the time is
1675 behind (i.e., west of) UTC. The first two digits indicate
1676 the hour difference from UTC and the last two digits
1677 indicate the number of additional minutes difference from
1678 UTC. The last two digits must be in the range 00-59.
1684 The first "title" line with the package name must start
1685 at the left hand margin. The "trailer" line with the
1686 maintainer and date details must be preceded by exactly
1687 one space. The maintainer details and the date must be
1688 separated by exactly two spaces.
1692 The entire changelog must be encoded in UTF-8.
1696 For more information on placement of the changelog files
1697 within binary packages, please see <ref id="changelogs">.
1701 <sect id="dpkgcopyright">
1702 <heading>Copyright: <file>debian/copyright</file></heading>
1704 Every package must be accompanied by a verbatim copy of its
1705 copyright information and distribution license in the file
1706 <file>/usr/share/doc/<var>package</var>/copyright</file>
1707 (see <ref id="copyrightfile"> for further details). Also see
1708 <ref id="pkgcopyright"> for further considerations related
1709 to copyrights for packages.
1713 <heading>Error trapping in makefiles</heading>
1716 When <prgn>make</prgn> invokes a command in a makefile
1717 (including your package's upstream makefiles and
1718 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1719 means that <prgn>sh</prgn>'s usual bad error handling
1720 properties apply: if you include a miniature script as one
1721 of the commands in your makefile you'll find that if you
1722 don't do anything about it then errors are not detected
1723 and <prgn>make</prgn> will blithely continue after
1728 Every time you put more than one shell command (this
1729 includes using a loop) in a makefile command you
1730 must make sure that errors are trapped. For
1731 simple compound commands, such as changing directory and
1732 then running a program, using <tt>&&</tt> rather
1733 than semicolon as a command separator is sufficient. For
1734 more complex commands including most loops and
1735 conditionals you should include a separate <tt>set -e</tt>
1736 command at the start of every makefile command that's
1737 actually one of these miniature shell scripts.
1741 <sect id="timestamps">
1742 <heading>Time Stamps</heading>
1744 Maintainers should preserve the modification times of the
1745 upstream source files in a package, as far as is reasonably
1747 The rationale is that there is some information conveyed
1748 by knowing the age of the file, for example, you could
1749 recognize that some documentation is very old by looking
1750 at the modification time, so it would be nice if the
1751 modification time of the upstream source would be
1757 <sect id="restrictions">
1758 <heading>Restrictions on objects in source packages</heading>
1761 The source package may not contain any hard links<footnote>
1763 This is not currently detected when building source
1764 packages, but only when extracting
1768 Hard links may be permitted at some point in the
1769 future, but would require a fair amount of
1772 </footnote>, device special files, sockets or setuid or
1773 setgid files.<footnote>
1774 Setgid directories are allowed.
1779 <sect id="debianrules">
1780 <heading>Main building script: <file>debian/rules</file></heading>
1783 This file must be an executable makefile, and contains the
1784 package-specific recipes for compiling the package and
1785 building binary package(s) from the source.
1789 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1790 so that it can be invoked by saying its name rather than
1791 invoking <prgn>make</prgn> explicitly. That is, invoking
1792 either of <tt>make -f debian/rules <em>args...</em></tt>
1793 or <tt>./debian/rules <em>args...</em></tt> must result in
1798 Since an interactive <file>debian/rules</file> script makes it
1799 impossible to auto-compile that package and also makes it
1800 hard for other people to reproduce the same binary
1801 package, all <em>required targets</em> must be
1802 non-interactive. At a minimum, required targets are the
1803 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1804 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1805 <em>binary-indep</em>, and <em>build</em>. It also follows
1806 that any target that these targets depend on must also be
1811 The targets are as follows (required unless stated otherwise):
1813 <tag><tt>build</tt></tag>
1816 The <tt>build</tt> target should perform all the
1817 configuration and compilation of the package.
1818 If a package has an interactive pre-build
1819 configuration routine, the Debian source package
1820 must either be built after this has taken place (so
1821 that the binary package can be built without rerunning
1822 the configuration) or the configuration routine
1823 modified to become non-interactive. (The latter is
1824 preferable if there are architecture-specific features
1825 detected by the configuration routine.)
1829 For some packages, notably ones where the same
1830 source tree is compiled in different ways to produce
1831 two binary packages, the <tt>build</tt> target
1832 does not make much sense. For these packages it is
1833 good enough to provide two (or more) targets
1834 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1835 for each of the ways of building the package, and a
1836 <tt>build</tt> target that does nothing. The
1837 <tt>binary</tt> target will have to build the
1838 package in each of the possible ways and make the
1839 binary package out of each.
1843 The <tt>build</tt> target must not do anything
1844 that might require root privilege.
1848 The <tt>build</tt> target may need to run the
1849 <tt>clean</tt> target first - see below.
1853 When a package has a configuration and build routine
1854 which takes a long time, or when the makefiles are
1855 poorly designed, or when <tt>build</tt> needs to
1856 run <tt>clean</tt> first, it is a good idea to
1857 <tt>touch build</tt> when the build process is
1858 complete. This will ensure that if <tt>debian/rules
1859 build</tt> is run again it will not rebuild the whole
1861 Another common way to do this is for <tt>build</tt>
1862 to depend on <prgn>build-stamp</prgn> and to do
1863 nothing else, and for the <prgn>build-stamp</prgn>
1864 target to do the building and to <tt>touch
1865 build-stamp</tt> on completion. This is
1866 especially useful if the build routine creates a
1867 file or directory called <tt>build</tt>; in such a
1868 case, <tt>build</tt> will need to be listed as
1869 a phony target (i.e., as a dependency of the
1870 <tt>.PHONY</tt> target). See the documentation of
1871 <prgn>make</prgn> for more information on phony
1877 <tag><tt>build-arch</tt> (optional),
1878 <tt>build-indep</tt> (optional)
1882 A package may also provide both of the targets
1883 <tt>build-arch</tt> and <tt>build-indep</tt>.
1884 The <tt>build-arch</tt> target, if provided, should
1885 perform all the configuration and compilation required for
1886 producing all architecture-dependant binary packages
1887 (those packages for which the body of the
1888 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1889 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1890 target, if provided, should perform all the configuration
1891 and compilation required for producing all
1892 architecture-independent binary packages (those packages
1893 for which the body of the <tt>Architecture</tt> field
1894 in <tt>debian/control</tt> is <tt>all</tt>).
1895 The <tt>build</tt> target should depend on those of the
1896 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1897 are provided in the rules file.<footnote>
1898 The intent of this split is so that binary-only builds
1899 need not install the dependencies required for
1900 the <tt>build-indep</tt> target. However, this is not
1901 yet used in practice since <tt>dpkg-buildpackage
1902 -B</tt>, and therefore the autobuilders,
1903 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1904 due to the difficulties in determining whether the
1905 optional <tt>build-arch</tt> target exists.
1910 If one or both of the targets <tt>build-arch</tt> and
1911 <tt>build-indep</tt> are not provided, then invoking
1912 <file>debian/rules</file> with one of the not-provided
1913 targets as arguments should produce a exit status code
1914 of 2. Usually this is provided automatically by make
1915 if the target is missing.
1919 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1920 must not do anything that might require root privilege.
1924 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1925 <tt>binary-indep</tt>
1929 The <tt>binary</tt> target must be all that is
1930 necessary for the user to build the binary package(s)
1931 produced from this source package. It is
1932 split into two parts: <prgn>binary-arch</prgn> builds
1933 the binary packages which are specific to a particular
1934 architecture, and <tt>binary-indep</tt> builds
1935 those which are not.
1938 <tt>binary</tt> may be (and commonly is) a target with
1939 no commands which simply depends on
1940 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1943 Both <tt>binary-*</tt> targets should depend on the
1944 <tt>build</tt> target, or on the appropriate
1945 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1946 provided, so that the package is built if it has not
1947 been already. It should then create the relevant
1948 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1949 make their control files and <prgn>dpkg-deb</prgn> to
1950 build them and place them in the parent of the top
1955 Both the <tt>binary-arch</tt> and
1956 <tt>binary-indep</tt> targets <em>must</em> exist.
1957 If one of them has nothing to do (which will always be
1958 the case if the source generates only a single binary
1959 package, whether architecture-dependent or not), it
1960 must still exist and must always succeed.
1964 The <tt>binary</tt> targets must be invoked as
1966 The <prgn>fakeroot</prgn> package often allows one
1967 to build a package correctly even without being
1973 <tag><tt>clean</tt></tag>
1976 This must undo any effects that the <tt>build</tt>
1977 and <tt>binary</tt> targets may have had, except
1978 that it should leave alone any output files created in
1979 the parent directory by a run of a <tt>binary</tt>
1984 If a <tt>build</tt> file is touched at the end of
1985 the <tt>build</tt> target, as suggested above, it
1986 should be removed as the first action that
1987 <tt>clean</tt> performs, so that running
1988 <tt>build</tt> again after an interrupted
1989 <tt>clean</tt> doesn't think that everything is
1994 The <tt>clean</tt> target may need to be
1995 invoked as root if <tt>binary</tt> has been
1996 invoked since the last <tt>clean</tt>, or if
1997 <tt>build</tt> has been invoked as root (since
1998 <tt>build</tt> may create directories, for
2003 <tag><tt>get-orig-source</tt> (optional)</tag>
2006 This target fetches the most recent version of the
2007 original source package from a canonical archive site
2008 (via FTP or WWW, for example), does any necessary
2009 rearrangement to turn it into the original source
2010 tar file format described below, and leaves it in the
2015 This target may be invoked in any directory, and
2016 should take care to clean up any temporary files it
2021 This target is optional, but providing it if
2022 possible is a good idea.
2026 <tag><tt>patch</tt> (optional)</tag>
2029 This target performs whatever additional actions are
2030 required to make the source ready for editing (unpacking
2031 additional upstream archives, applying patches, etc.).
2032 It is recommended to be implemented for any package where
2033 <tt>dpkg-source -x</tt> does not result in source ready
2034 for additional modification. See
2035 <ref id="readmesource">.
2041 The <tt>build</tt>, <tt>binary</tt> and
2042 <tt>clean</tt> targets must be invoked with the current
2043 directory being the package's top-level directory.
2048 Additional targets may exist in <file>debian/rules</file>,
2049 either as published or undocumented interfaces or for the
2050 package's internal use.
2054 The architectures we build on and build for are determined
2055 by <prgn>make</prgn> variables using the utility
2056 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2057 You can determine the
2058 Debian architecture and the GNU style architecture
2059 specification string for the build machine (the machine type
2060 we are building on) as well as for the host machine (the
2061 machine type we are building for). Here is a list of
2062 supported <prgn>make</prgn> variables:
2063 <list compact="compact">
2065 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2068 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2071 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2074 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2075 specification string)
2078 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2079 <tt>DEB_*_GNU_TYPE</tt>)
2082 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2083 <tt>DEB_*_GNU_TYPE</tt>)
2085 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2086 the build machine or <tt>HOST</tt> for specification of the
2091 Backward compatibility can be provided in the rules file
2092 by setting the needed variables to suitable default
2093 values; please refer to the documentation of
2094 <prgn>dpkg-architecture</prgn> for details.
2098 It is important to understand that the <tt>DEB_*_ARCH</tt>
2099 string only determines which Debian architecture we are
2100 building on or for. It should not be used to get the CPU
2101 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2102 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2103 GNU style variables should generally only be used with upstream
2107 <sect1 id="debianrules-options">
2108 <heading><file>debian/rules</file> and
2109 <tt>DEB_BUILD_OPTIONS</tt></heading>
2112 Supporting the standardized environment variable
2113 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2114 contain several flags to change how a package is compiled and
2115 built. Each flag must be in the form <var>flag</var> or
2116 <var>flag</var>=<var>options</var>. If multiple flags are
2117 given, they must be separated by whitespace.<footnote>
2118 Some packages support any delimiter, but whitespace is the
2119 easiest to parse inside a makefile and avoids ambiguity with
2120 flag values that contain commas.
2122 <var>flag</var> must start with a lowercase letter
2123 (<tt>a-z</tt>) and consist only of lowercase letters,
2124 numbers (<tt>0-9</tt>), and the characters
2125 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2126 <var>options</var> must not contain whitespace. The same
2127 tag should not be given multiple times with conflicting
2128 values. Package maintainers may assume that
2129 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2133 The meaning of the following tags has been standardized:
2137 This tag says to not run any build-time test suite
2138 provided by the package.
2142 The presence of this tag means that the package should
2143 be compiled with a minimum of optimization. For C
2144 programs, it is best to add <tt>-O0</tt> to
2145 <tt>CFLAGS</tt> (although this is usually the default).
2146 Some programs might fail to build or run at this level
2147 of optimization; it may be necessary to use
2148 <tt>-O1</tt>, for example.
2152 This tag means that the debugging symbols should not be
2153 stripped from the binary during installation, so that
2154 debugging information may be included in the package.
2156 <tag>parallel=n</tag>
2158 This tag means that the package should be built using up
2159 to <tt>n</tt> parallel processes if the package build
2160 system supports this.<footnote>
2161 Packages built with <tt>make</tt> can often implement
2162 this by passing the <tt>-j</tt><var>n</var> option to
2165 If the package build system does not support parallel
2166 builds, this string must be ignored. If the package
2167 build system only supports a lower level of concurrency
2168 than <var>n</var>, the package should be built using as
2169 many parallel processes as the package build system
2170 supports. It is up to the package maintainer to decide
2171 whether the package build times are long enough and the
2172 package build system is robust enough to make supporting
2173 parallel builds worthwhile.
2179 Unknown flags must be ignored by <file>debian/rules</file>.
2183 The following makefile snippet is an example of how one may
2184 implement the build options; you will probably have to
2185 massage this example in order to make it work for your
2187 <example compact="compact">
2190 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2191 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2192 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2193 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2195 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2200 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2201 INSTALL_PROGRAM += -s
2203 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2204 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2205 MAKEFLAGS += -j$(NUMJOBS)
2210 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2211 # Code to run the package test suite.
2218 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2219 <sect id="substvars">
2220 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2223 When <prgn>dpkg-gencontrol</prgn>,
2224 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2225 generate control files they perform variable substitutions
2226 on their output just before writing it. Variable
2227 substitutions have the form <tt>${<var>variable</var>}</tt>.
2228 The optional file <file>debian/substvars</file> contains
2229 variable substitutions to be used; variables can also be set
2230 directly from <file>debian/rules</file> using the <tt>-V</tt>
2231 option to the source packaging commands, and certain
2232 predefined variables are also available.
2236 The <file>debian/substvars</file> file is usually generated and
2237 modified dynamically by <file>debian/rules</file> targets, in
2238 which case it must be removed by the <tt>clean</tt> target.
2242 See <manref name="deb-substvars" section="5"> for full
2243 details about source variable substitutions, including the
2244 format of <file>debian/substvars</file>.</p>
2247 <sect id="debianwatch">
2248 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2251 This is an optional, recommended control file for the
2252 <tt>uscan</tt> utility which defines how to automatically
2253 scan ftp or http sites for newly available updates of the
2254 package. This is used by <url id="
2255 http://dehs.alioth.debian.org/"> and other Debian QA tools
2256 to help with quality control and maintenance of the
2257 distribution as a whole.
2262 <sect id="debianfiles">
2263 <heading>Generated files list: <file>debian/files</file></heading>
2266 This file is not a permanent part of the source tree; it
2267 is used while building packages to record which files are
2268 being generated. <prgn>dpkg-genchanges</prgn> uses it
2269 when it generates a <file>.changes</file> file.
2273 It should not exist in a shipped source package, and so it
2274 (and any backup files or temporary files such as
2275 <file>files.new</file><footnote>
2276 <file>files.new</file> is used as a temporary file by
2277 <prgn>dpkg-gencontrol</prgn> and
2278 <prgn>dpkg-distaddfile</prgn> - they write a new
2279 version of <tt>files</tt> here before renaming it,
2280 to avoid leaving a corrupted copy if an error
2282 </footnote>) should be removed by the
2283 <tt>clean</tt> target. It may also be wise to
2284 ensure a fresh start by emptying or removing it at the
2285 start of the <tt>binary</tt> target.
2289 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2290 package, it adds an entry to <file>debian/files</file> for the
2291 <file>.deb</file> file that will be created when <tt>dpkg-deb
2292 --build</tt> is run for that binary package. So for most
2293 packages all that needs to be done with this file is to
2294 delete it in the <tt>clean</tt> target.
2298 If a package upload includes files besides the source
2299 package and any binary packages whose control files were
2300 made with <prgn>dpkg-gencontrol</prgn> then they should be
2301 placed in the parent of the package's top-level directory
2302 and <prgn>dpkg-distaddfile</prgn> should be called to add
2303 the file to the list in <file>debian/files</file>.</p>
2306 <sect id="embeddedfiles">
2307 <heading>Convenience copies of code</heading>
2310 Some software packages include in their distribution convenience
2311 copies of code from other software packages, generally so that
2312 users compiling from source don't have to download multiple
2313 packages. Debian packages should not make use of these
2314 convenience copies unless the included package is explicitly
2315 intended to be used in this way.<footnote>
2316 For example, parts of the GNU build system work like this.
2318 If the included code is already in the Debian archive in the
2319 form of a library, the Debian packaging should ensure that
2320 binary packages reference the libraries already in Debian and
2321 the convenience copy is not used. If the included code is not
2322 already in Debian, it should be packaged separately as a
2323 prerequisite if possible.
2325 Having multiple copies of the same code in Debian is
2326 inefficient, often creates either static linking or shared
2327 library conflicts, and, most importantly, increases the
2328 difficulty of handling security vulnerabilities in the
2334 <sect id="readmesource">
2335 <heading>Source package handling:
2336 <file>debian/README.source</file></heading>
2339 If running <prgn>dpkg-source -x</prgn> on a source package
2340 doesn't produce the source of the package, ready for editing,
2341 and allow one to make changes and run
2342 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2343 without taking any additional steps, creating a
2344 <file>debian/README.source</file> documentation file is
2345 recommended. This file should explain how to do all of the
2348 <item>Generate the fully patched source, in a form ready for
2349 editing, that would be built to create Debian
2350 packages. Doing this with a <tt>patch</tt> target in
2351 <file>debian/rules</file> is recommended; see
2352 <ref id="debianrules">.</item>
2353 <item>Modify the source and save those modifications so that
2354 they will be applied when building the package.</item>
2355 <item>Remove source modifications that are currently being
2356 applied when building the package.</item>
2357 <item>Optionally, document what steps are necessary to
2358 upgrade the Debian source package to a new upstream version,
2359 if applicable.</item>
2361 This explanation should include specific commands and mention
2362 any additional required Debian packages. It should not assume
2363 familiarity with any specific Debian packaging system or patch
2368 This explanation may refer to a documentation file installed by
2369 one of the package's build dependencies provided that the
2370 referenced documentation clearly explains these tasks and is not
2371 a general reference manual.
2375 <file>debian/README.source</file> may also include any other
2376 information that would be helpful to someone modifying the
2377 source package. Even if the package doesn't fit the above
2378 description, maintainers are encouraged to document in a
2379 <file>debian/README.source</file> file any source package with a
2380 particularly complex or unintuitive source layout or build
2381 system (for example, a package that builds the same source
2382 multiple times to generate different binary packages).
2388 <chapt id="controlfields">
2389 <heading>Control files and their fields</heading>
2392 The package management system manipulates data represented in
2393 a common format, known as <em>control data</em>, stored in
2394 <em>control files</em>.
2395 Control files are used for source packages, binary packages and
2396 the <file>.changes</file> files which control the installation
2397 of uploaded files<footnote>
2398 <prgn>dpkg</prgn>'s internal databases are in a similar
2403 <sect id="controlsyntax">
2404 <heading>Syntax of control files</heading>
2407 A control file consists of one or more paragraphs of
2409 The paragraphs are also sometimes referred to as stanzas.
2411 The paragraphs are separated by blank lines. Some control
2412 files allow only one paragraph; others allow several, in
2413 which case each paragraph usually refers to a different
2414 package. (For example, in source packages, the first
2415 paragraph refers to the source package, and later paragraphs
2416 refer to binary packages generated from the source.)
2420 Each paragraph consists of a series of data fields; each
2421 field consists of the field name, followed by a colon and
2422 then the data/value associated with that field. It ends at
2423 the end of the (logical) line. Horizontal whitespace
2424 (spaces and tabs) may occur immediately before or after the
2425 value and is ignored there; it is conventional to put a
2426 single space after the colon. For example, a field might
2428 <example compact="compact">
2431 the field name is <tt>Package</tt> and the field value
2436 A paragraph must not contain more than one instance of a
2437 particular field name.
2441 Many fields' values may span several lines; in this case
2442 each continuation line must start with a space or a tab.
2443 Any trailing spaces or tabs at the end of individual
2444 lines of a field value are ignored.
2448 In fields where it is specified that lines may not wrap,
2449 only a single line of data is allowed and whitespace is not
2450 significant in a field body. Whitespace must not appear
2451 inside names (of packages, architectures, files or anything
2452 else) or version numbers, or between the characters of
2453 multi-character version relationships.
2457 Field names are not case-sensitive, but it is usual to
2458 capitalize the field names using mixed case as shown below.
2459 Field values are case-sensitive unless the description of the
2460 field says otherwise.
2464 Blank lines, or lines consisting only of spaces and tabs,
2465 are not allowed within field values or between fields - that
2466 would mean a new paragraph.
2470 All control files must be encoded in UTF-8.
2474 <sect id="sourcecontrolfiles">
2475 <heading>Source package control files -- <file>debian/control</file></heading>
2478 The <file>debian/control</file> file contains the most vital
2479 (and version-independent) information about the source package
2480 and about the binary packages it creates.
2484 The first paragraph of the control file contains information about
2485 the source package in general. The subsequent sets each describe a
2486 binary package that the source tree builds.
2490 The fields in the general paragraph (the first one, for the source
2493 <list compact="compact">
2494 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2495 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2496 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2497 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2498 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2499 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2500 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2501 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2506 The fields in the binary package paragraphs are:
2508 <list compact="compact">
2509 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2510 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2511 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2512 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2513 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2514 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2515 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2516 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2521 The syntax and semantics of the fields are described below.
2525 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2526 generate control files for binary packages (see below), by
2527 <prgn>dpkg-genchanges</prgn> to generate the
2528 <file>.changes</file> file to accompany the upload, and by
2529 <prgn>dpkg-source</prgn> when it creates the
2530 <file>.dsc</file> source control file as part of a source
2531 archive. Many fields are permitted to span multiple lines in
2532 <file>debian/control</file> but not in any other control
2533 file. These tools are responsible for removing the line
2534 breaks from such fields when using fields from
2535 <file>debian/control</file> to generate other control files.
2539 The fields here may contain variable references - their
2540 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2541 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2542 when they generate output control files.
2543 See <ref id="substvars"> for details.
2547 In addition to the control file syntax described <qref
2548 id="controlsyntax">above</qref>, this file may also contain
2549 comment lines starting with <tt>#</tt> without any preceding
2550 whitespace. All such lines are ignored, even in the middle of
2551 continuation lines for a multiline field, and do not end a
2557 <sect id="binarycontrolfiles">
2558 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2561 The <file>DEBIAN/control</file> file contains the most vital
2562 (and version-dependent) information about a binary package. It
2563 consists of a single paragraph.
2567 The fields in this file are:
2569 <list compact="compact">
2570 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2571 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2572 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2573 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2574 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2575 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2576 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2577 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2578 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2579 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2580 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2581 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2586 <sect id="debiansourcecontrolfiles">
2587 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2590 This file consists of a single paragraph, possibly surrounded by
2591 a PGP signature. The fields of that paragraph are listed below.
2592 Their syntax is described above, in <ref id="pkg-controlfields">.
2594 <list compact="compact">
2595 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2596 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2597 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2598 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2599 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2600 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2601 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2602 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2603 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2604 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2605 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2606 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2607 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2612 The source package control file is generated by
2613 <prgn>dpkg-source</prgn> when it builds the source
2614 archive, from other files in the source package,
2615 described above. When unpacking, it is checked against
2616 the files and directories in the other parts of the
2622 <sect id="debianchangesfiles">
2623 <heading>Debian changes files -- <file>.changes</file></heading>
2626 The <file>.changes</file> files are used by the Debian archive
2627 maintenance software to process updates to packages. They
2628 consist of a single paragraph, possibly surrounded by a PGP
2629 signature. That paragraph contains information from the
2630 <file>debian/control</file> file and other data about the
2631 source package gathered via <file>debian/changelog</file>
2632 and <file>debian/rules</file>.
2636 <file>.changes</file> files have a format version that is
2637 incremented whenever the documented fields or their meaning
2638 change. This document describes format &changesversion;.
2642 The fields in this file are:
2644 <list compact="compact">
2645 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2646 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2647 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2649 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2651 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2653 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2654 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2655 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2656 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2657 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2658 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2659 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2660 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2665 <sect id="controlfieldslist">
2666 <heading>List of fields</heading>
2668 <sect1 id="f-Source">
2669 <heading><tt>Source</tt></heading>
2672 This field identifies the source package name.
2676 In <file>debian/control</file> or a <file>.dsc</file> file,
2677 this field must contain only the name of the source package.
2681 In a binary package control file or a <file>.changes</file>
2682 file, the source package name may be followed by a version
2683 number in parentheses<footnote>
2684 It is customary to leave a space after the package name
2685 if a version number is specified.
2687 This version number may be omitted (and is, by
2688 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2689 the <tt>Version</tt> field of the binary package in
2690 question. The field itself may be omitted from a binary
2691 package control file when the source package has the same
2692 name and version as the binary package.
2696 Package names (both source and binary,
2697 see <ref id="f-Package">) must consist only of lower case
2698 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2699 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2700 (<tt>.</tt>). They must be at least two characters long and
2701 must start with an alphanumeric character.
2705 <sect1 id="f-Maintainer">
2706 <heading><tt>Maintainer</tt></heading>
2709 The package maintainer's name and email address. The name
2710 must come first, then the email address inside angle
2711 brackets <tt><></tt> (in RFC822 format).
2715 If the maintainer's name contains a full stop then the
2716 whole field will not work directly as an email address due
2717 to a misfeature in the syntax specified in RFC822; a
2718 program using this field as an address must check for this
2719 and correct the problem if necessary (for example by
2720 putting the name in round brackets and moving it to the
2721 end, and bringing the email address forward).
2725 See <ref id="maintainer"> for additional requirements and
2726 information about package maintainers.
2730 <sect1 id="f-Uploaders">
2731 <heading><tt>Uploaders</tt></heading>
2734 List of the names and email addresses of co-maintainers of the
2735 package, if any. If the package has other maintainers besides
2736 the one named in the <qref id="f-Maintainer">Maintainer
2737 field</qref>, their names and email addresses should be listed
2738 here. The format of each entry is the same as that of the
2739 Maintainer field, and multiple entries must be comma
2744 This is normally an optional field, but if
2745 the <tt>Maintainer</tt> control field names a group of people
2746 and a shared email address, the <tt>Uploaders</tt> field must
2747 be present and must contain at least one human with their
2748 personal email address.
2752 Any parser that interprets the Uploaders field in
2753 <file>debian/control</file> must permit it to span multiple
2754 lines. Line breaks in an Uploaders field that spans multiple
2755 lines are not significant and the semantics of the field are
2756 the same as if the line breaks had not been present.
2760 <sect1 id="f-Changed-By">
2761 <heading><tt>Changed-By</tt></heading>
2764 The name and email address of the person who prepared this
2765 version of the package, usually a maintainer. The syntax is
2766 the same as for the <qref id="f-Maintainer">Maintainer
2771 <sect1 id="f-Section">
2772 <heading><tt>Section</tt></heading>
2775 This field specifies an application area into which the package
2776 has been classified. See <ref id="subsections">.
2780 When it appears in the <file>debian/control</file> file,
2781 it gives the value for the subfield of the same name in
2782 the <tt>Files</tt> field of the <file>.changes</file> file.
2783 It also gives the default for the same field in the binary
2788 <sect1 id="f-Priority">
2789 <heading><tt>Priority</tt></heading>
2792 This field represents how important it is that the user
2793 have the package installed. See <ref id="priorities">.
2797 When it appears in the <file>debian/control</file> file,
2798 it gives the value for the subfield of the same name in
2799 the <tt>Files</tt> field of the <file>.changes</file> file.
2800 It also gives the default for the same field in the binary
2805 <sect1 id="f-Package">
2806 <heading><tt>Package</tt></heading>
2809 The name of the binary package.
2813 Binary package names must follow the same syntax and
2814 restrictions as source package names. See <ref id="f-Source">
2819 <sect1 id="f-Architecture">
2820 <heading><tt>Architecture</tt></heading>
2823 Depending on context and the control file used, the
2824 <tt>Architecture</tt> field can include the following sets of
2828 A unique single word identifying a Debian machine
2829 architecture as described in <ref id="arch-spec">.
2832 An architecture wildcard identifying a set of Debian
2833 machine architectures, see <ref id="arch-wildcard-spec">.
2834 <tt>any</tt> matches all Debian machine architectures
2835 and is the most frequently used.
2838 <tt>all</tt>, which indicates an
2839 architecture-independent package.
2842 <tt>source</tt>, which indicates a source package.
2848 In the main <file>debian/control</file> file in the source
2849 package, this field may contain the special
2850 value <tt>all</tt>, the special architecture
2851 wildcard <tt>any</tt>, or a list of specific and wildcard
2852 architectures separated by spaces. If <tt>all</tt>
2853 or <tt>any</tt> appears, that value must be the entire
2854 contents of the field. Most packages will use
2855 either <tt>all</tt> or <tt>any</tt>.
2859 Specifying a specific list of architectures indicates that the
2860 source will build an architecture-dependent package only on
2861 architectures included in the list. Specifying a list of
2862 architecture wildcards indicates that the source will build an
2863 architecture-dependent package on only those architectures
2864 that match any of the specified architecture wildcards.
2865 Specifying a list of architectures or architecture wildcards
2866 other than <tt>any</tt> is for the minority of cases where a
2867 program is not portable or is not useful on some
2868 architectures. Where possible, the program should be made
2873 In the source package control file <file>.dsc</file>, this
2874 field may contain either the architecture
2875 wildcard <tt>any</tt> or a list of architectures and
2876 architecture wildcards separated by spaces. If a list is
2877 given, it may include (or consist solely of) the special
2878 value <tt>all</tt>. In other words, in <file>.dsc</file>
2879 files unlike the <file>debian/control</file>, <tt>all</tt> may
2880 occur in combination with specific architectures.
2881 The <tt>Architecture</tt> field in the source package control
2882 file <file>.dsc</file> is generally constructed from
2883 the <tt>Architecture</tt> fields in
2884 the <file>debian/control</file> in the source package.
2888 Specifying <tt>any</tt> indicates that the source package
2889 isn't dependent on any particular architecture and should
2890 compile fine on any one. The produced binary package(s)
2891 will either be specific to whatever the current build
2892 architecture is or will be architecture-independent.
2896 Specifying only <tt>all</tt> indicates that the source package
2897 will only build architecture-independent packages. If this is
2898 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2899 <tt>any</tt> implies that the source package will build at
2900 least one architecture-dependent package.
2904 Specifying a list of architectures or architecture wildcards
2905 indicates that the source will build an architecture-dependent
2906 package, and will only work correctly on the listed or
2907 matching architectures. If the source package also builds at
2908 least one architecture-independent package, <tt>all</tt> will
2909 also be included in the list.
2913 In a <file>.changes</file> file, the <tt>Architecture</tt>
2914 field lists the architecture(s) of the package(s) currently
2915 being uploaded. This will be a list; if the source for the
2916 package is also being uploaded, the special
2917 entry <tt>source</tt> is also present. <tt>all</tt> will be
2918 present if any architecture-independent packages are being
2919 uploaded. Architecture wildcards such as <tt>any</tt> must
2920 never occur in the <tt>Architecture</tt> field in
2921 the <file>.changes</file> file.
2925 See <ref id="debianrules"> for information on how to get
2926 the architecture for the build process.
2930 <sect1 id="f-Essential">
2931 <heading><tt>Essential</tt></heading>
2934 This is a boolean field which may occur only in the
2935 control file of a binary package or in a per-package fields
2936 paragraph of a main source control data file.
2940 If set to <tt>yes</tt> then the package management system
2941 will refuse to remove the package (upgrading and replacing
2942 it is still possible). The other possible value is <tt>no</tt>,
2943 which is the same as not having the field at all.
2948 <heading>Package interrelationship fields:
2949 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2950 <tt>Recommends</tt>, <tt>Suggests</tt>,
2951 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2952 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2956 These fields describe the package's relationships with
2957 other packages. Their syntax and semantics are described
2958 in <ref id="relationships">.</p>
2961 <sect1 id="f-Standards-Version">
2962 <heading><tt>Standards-Version</tt></heading>
2965 The most recent version of the standards (the policy
2966 manual and associated texts) with which the package
2971 The version number has four components: major and minor
2972 version number and major and minor patch level. When the
2973 standards change in a way that requires every package to
2974 change the major number will be changed. Significant
2975 changes that will require work in many packages will be
2976 signaled by a change to the minor number. The major patch
2977 level will be changed for any change to the meaning of the
2978 standards, however small; the minor patch level will be
2979 changed when only cosmetic, typographical or other edits
2980 are made which neither change the meaning of the document
2981 nor affect the contents of packages.
2985 Thus only the first three components of the policy version
2986 are significant in the <em>Standards-Version</em> control
2987 field, and so either these three components or all four
2988 components may be specified.<footnote>
2989 In the past, people specified the full version number
2990 in the Standards-Version field, for example "2.3.0.0".
2991 Since minor patch-level changes don't introduce new
2992 policy, it was thought it would be better to relax
2993 policy and only require the first 3 components to be
2994 specified, in this example "2.3.0". All four
2995 components may still be used if someone wishes to do so.
3001 <sect1 id="f-Version">
3002 <heading><tt>Version</tt></heading>
3005 The version number of a package. The format is:
3006 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3010 The three components here are:
3012 <tag><var>epoch</var></tag>
3015 This is a single (generally small) unsigned integer. It
3016 may be omitted, in which case zero is assumed. If it is
3017 omitted then the <var>upstream_version</var> may not
3022 It is provided to allow mistakes in the version numbers
3023 of older versions of a package, and also a package's
3024 previous version numbering schemes, to be left behind.
3028 <tag><var>upstream_version</var></tag>
3031 This is the main part of the version number. It is
3032 usually the version number of the original ("upstream")
3033 package from which the <file>.deb</file> file has been made,
3034 if this is applicable. Usually this will be in the same
3035 format as that specified by the upstream author(s);
3036 however, it may need to be reformatted to fit into the
3037 package management system's format and comparison
3042 The comparison behavior of the package management system
3043 with respect to the <var>upstream_version</var> is
3044 described below. The <var>upstream_version</var>
3045 portion of the version number is mandatory.
3049 The <var>upstream_version</var> may contain only
3050 alphanumerics<footnote>
3051 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3053 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3054 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3055 tilde) and should start with a digit. If there is no
3056 <var>debian_revision</var> then hyphens are not allowed;
3057 if there is no <var>epoch</var> then colons are not
3062 <tag><var>debian_revision</var></tag>
3065 This part of the version number specifies the version of
3066 the Debian package based on the upstream version. It
3067 may contain only alphanumerics and the characters
3068 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3069 tilde) and is compared in the same way as the
3070 <var>upstream_version</var> is.
3074 It is optional; if it isn't present then the
3075 <var>upstream_version</var> may not contain a hyphen.
3076 This format represents the case where a piece of
3077 software was written specifically to be a Debian
3078 package, where the Debian package source must always
3079 be identical to the pristine source and therefore no
3080 revision indication is required.
3084 It is conventional to restart the
3085 <var>debian_revision</var> at <tt>1</tt> each time the
3086 <var>upstream_version</var> is increased.
3090 The package management system will break the version
3091 number apart at the last hyphen in the string (if there
3092 is one) to determine the <var>upstream_version</var> and
3093 <var>debian_revision</var>. The absence of a
3094 <var>debian_revision</var> is equivalent to a
3095 <var>debian_revision</var> of <tt>0</tt>.
3102 When comparing two version numbers, first the <var>epoch</var>
3103 of each are compared, then the <var>upstream_version</var> if
3104 <var>epoch</var> is equal, and then <var>debian_revision</var>
3105 if <var>upstream_version</var> is also equal.
3106 <var>epoch</var> is compared numerically. The
3107 <var>upstream_version</var> and <var>debian_revision</var>
3108 parts are compared by the package management system using the
3109 following algorithm:
3113 The strings are compared from left to right.
3117 First the initial part of each string consisting entirely of
3118 non-digit characters is determined. These two parts (one of
3119 which may be empty) are compared lexically. If a difference
3120 is found it is returned. The lexical comparison is a
3121 comparison of ASCII values modified so that all the letters
3122 sort earlier than all the non-letters and so that a tilde
3123 sorts before anything, even the end of a part. For example,
3124 the following parts are in sorted order from earliest to
3125 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3126 <tt>a</tt>.<footnote>
3127 One common use of <tt>~</tt> is for upstream pre-releases.
3128 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3129 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3134 Then the initial part of the remainder of each string which
3135 consists entirely of digit characters is determined. The
3136 numerical values of these two parts are compared, and any
3137 difference found is returned as the result of the comparison.
3138 For these purposes an empty string (which can only occur at
3139 the end of one or both version strings being compared) counts
3144 These two steps (comparing and removing initial non-digit
3145 strings and initial digit strings) are repeated until a
3146 difference is found or both strings are exhausted.
3150 Note that the purpose of epochs is to allow us to leave behind
3151 mistakes in version numbering, and to cope with situations
3152 where the version numbering scheme changes. It is
3153 <em>not</em> intended to cope with version numbers containing
3154 strings of letters which the package management system cannot
3155 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3156 silly orderings.<footnote>
3157 The author of this manual has heard of a package whose
3158 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3159 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3165 <sect1 id="f-Description">
3166 <heading><tt>Description</tt></heading>
3169 In a source or binary control file, the <tt>Description</tt>
3170 field contains a description of the binary package, consisting
3171 of two parts, the synopsis or the short description, and the
3172 long description. The field's format is as follows:
3177 Description: <single line synopsis>
3178 <extended description over several lines>
3183 The lines in the extended description can have these formats:
3189 Those starting with a single space are part of a paragraph.
3190 Successive lines of this form will be word-wrapped when
3191 displayed. The leading space will usually be stripped off.
3195 Those starting with two or more spaces. These will be
3196 displayed verbatim. If the display cannot be panned
3197 horizontally, the displaying program will line wrap them "hard"
3198 (i.e., without taking account of word breaks). If it can they
3199 will be allowed to trail off to the right. None, one or two
3200 initial spaces may be deleted, but the number of spaces
3201 deleted from each line will be the same (so that you can have
3202 indenting work correctly, for example).
3206 Those containing a single space followed by a single full stop
3207 character. These are rendered as blank lines. This is the
3208 <em>only</em> way to get a blank line<footnote>
3209 Completely empty lines will not be rendered as blank lines.
3210 Instead, they will cause the parser to think you're starting
3211 a whole new record in the control file, and will therefore
3212 likely abort with an error.
3217 Those containing a space, a full stop and some more characters.
3218 These are for future expansion. Do not use them.
3224 Do not use tab characters. Their effect is not predictable.
3228 See <ref id="descriptions"> for further information on this.
3232 In a <file>.changes</file> file, the <tt>Description</tt>
3233 field contains a summary of the descriptions for the packages
3234 being uploaded. For this case, the first line of the field
3235 value (the part on the same line as <tt>Description:</tt>) is
3236 always empty. The content of the field is expressed as
3237 continuation lines, one line per package. Each line is
3238 indented by one space and contains the name of a binary
3239 package, a space, a hyphen (<tt>-</tt>), a space, and the
3240 short description line from that package.
3244 <sect1 id="f-Distribution">
3245 <heading><tt>Distribution</tt></heading>
3248 In a <file>.changes</file> file or parsed changelog output
3249 this contains the (space-separated) name(s) of the
3250 distribution(s) where this version of the package should
3251 be installed. Valid distributions are determined by the
3252 archive maintainers.<footnote>
3253 Example distribution names in the Debian archive used in
3254 <file>.changes</file> files are:
3255 <taglist compact="compact">
3256 <tag><em>unstable</em></tag>
3258 This distribution value refers to the
3259 <em>developmental</em> part of the Debian distribution
3260 tree. Most new packages, new upstream versions of
3261 packages and bug fixes go into the <em>unstable</em>
3265 <tag><em>experimental</em></tag>
3267 The packages with this distribution value are deemed
3268 by their maintainers to be high risk. Oftentimes they
3269 represent early beta or developmental packages from
3270 various sources that the maintainers want people to
3271 try, but are not ready to be a part of the other parts
3272 of the Debian distribution tree.
3277 Others are used for updating stable releases or for
3278 security uploads. More information is available in the
3279 Debian Developer's Reference, section "The Debian
3283 The Debian archive software only supports listing a single
3284 distribution. Migration of packages to other distributions is
3285 handled outside of the upload process.
3290 <heading><tt>Date</tt></heading>
3293 This field includes the date the package was built or last
3294 edited. It must be in the same format as the <var>date</var>
3295 in a <file>debian/changelog</file> entry.
3299 The value of this field is usually extracted from the
3300 <file>debian/changelog</file> file - see
3301 <ref id="dpkgchangelog">).
3305 <sect1 id="f-Format">
3306 <heading><tt>Format</tt></heading>
3309 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3310 files, this field declares the format version of that file.
3311 The syntax of the field value is the same as that of
3312 a <qref id="f-Version">package version number</qref> except
3313 that no epoch or Debian revision is allowed. The format
3314 described in this document is <tt>&changesversion;</tt>.
3318 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3319 Debian source control</qref> files, this field declares the
3320 format of the source package. The field value is used by
3321 programs acting on a source package to interpret the list of
3322 files in the source package and determine how to unpack it.
3323 The syntax of the field value is a numeric major revision, a
3324 period, a numeric minor revision, and then an optional subtype
3325 after whitespace, which if specified is an alphanumeric word
3326 in parentheses. The subtype is optional in the syntax but may
3327 be mandatory for particular source format revisions.
3329 The source formats currently supported by the Debian archive
3330 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3331 and <tt>3.0 (quilt)</tt>.
3336 <sect1 id="f-Urgency">
3337 <heading><tt>Urgency</tt></heading>
3340 This is a description of how important it is to upgrade to
3341 this version from previous ones. It consists of a single
3342 keyword taking one of the values <tt>low</tt>,
3343 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3344 <tt>critical</tt><footnote>
3345 Other urgency values are supported with configuration
3346 changes in the archive software but are not used in Debian.
3347 The urgency affects how quickly a package will be considered
3348 for inclusion into the <tt>testing</tt> distribution and
3349 gives an indication of the importance of any fixes included
3350 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3351 treated as synonymous.
3352 </footnote> (not case-sensitive) followed by an optional
3353 commentary (separated by a space) which is usually in
3354 parentheses. For example:
3357 Urgency: low (HIGH for users of diversions)
3363 The value of this field is usually extracted from the
3364 <file>debian/changelog</file> file - see
3365 <ref id="dpkgchangelog">.
3369 <sect1 id="f-Changes">
3370 <heading><tt>Changes</tt></heading>
3373 This field contains the human-readable changes data, describing
3374 the differences between the last version and the current one.
3378 The first line of the field value (the part on the same line
3379 as <tt>Changes:</tt>) is always empty. The content of the
3380 field is expressed as continuation lines, with each line
3381 indented by at least one space. Blank lines must be
3382 represented by a line consisting only of a space and a full
3387 The value of this field is usually extracted from the
3388 <file>debian/changelog</file> file - see
3389 <ref id="dpkgchangelog">).
3393 Each version's change information should be preceded by a
3394 "title" line giving at least the version, distribution(s)
3395 and urgency, in a human-readable way.
3399 If data from several versions is being returned the entry
3400 for the most recent version should be returned first, and
3401 entries should be separated by the representation of a
3402 blank line (the "title" line may also be followed by the
3403 representation of a blank line).
3407 <sect1 id="f-Binary">
3408 <heading><tt>Binary</tt></heading>
3411 This field is a list of binary packages. Its syntax and
3412 meaning varies depending on the control file in which it
3417 When it appears in the <file>.dsc</file> file, it lists binary
3418 packages which a source package can produce, separated by
3420 A space after each comma is conventional.
3421 </footnote>. It may span multiple lines. The source package
3422 does not necessarily produce all of these binary packages for
3423 every architecture. The source control file doesn't contain
3424 details of which architectures are appropriate for which of
3425 the binary packages.
3429 When it appears in a <file>.changes</file> file, it lists the
3430 names of the binary packages being uploaded, separated by
3431 whitespace (not commas). It may span multiple lines.
3435 <sect1 id="f-Installed-Size">
3436 <heading><tt>Installed-Size</tt></heading>
3439 This field appears in the control files of binary packages,
3440 and in the <file>Packages</file> files. It gives an estimate
3441 of the total amount of disk space required to install the
3442 named package. Actual installed size may vary based on block
3443 size, file system properties, or actions taken by package
3448 The disk space is given as the integer value of the estimated
3449 installed size in bytes, divided by 1024 and rounded up.
3453 <sect1 id="f-Files">
3454 <heading><tt>Files</tt></heading>
3457 This field contains a list of files with information about
3458 each one. The exact information and syntax varies with
3463 In all cases, Files is a multiline field. The first line of
3464 the field value (the part on the same line as <tt>Files:</tt>)
3465 is always empty. The content of the field is expressed as
3466 continuation lines, one line per file. Each line must be
3467 indented by one space and contain a number of sub-fields,
3468 separated by spaces, as described below.
3472 In the <file>.dsc</file> file, each line contains the MD5
3473 checksum, size and filename of the tar file and (if
3474 applicable) diff file which make up the remainder of the
3475 source package<footnote>
3476 That is, the parts which are not the <tt>.dsc</tt>.
3477 </footnote>. For example:
3480 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3481 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3483 The exact forms of the filenames are described
3484 in <ref id="pkg-sourcearchives">.
3488 In the <file>.changes</file> file this contains one line per
3489 file being uploaded. Each line contains the MD5 checksum,
3490 size, section and priority and the filename. For example:
3493 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3494 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3495 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3496 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3498 The <qref id="f-Section">section</qref>
3499 and <qref id="f-Priority">priority</qref> are the values of
3500 the corresponding fields in the main source control file. If
3501 no section or priority is specified then <tt>-</tt> should be
3502 used, though section and priority values must be specified for
3503 new packages to be installed properly.
3507 The special value <tt>byhand</tt> for the section in a
3508 <tt>.changes</tt> file indicates that the file in question
3509 is not an ordinary package file and must by installed by
3510 hand by the distribution maintainers. If the section is
3511 <tt>byhand</tt> the priority should be <tt>-</tt>.
3515 If a new Debian revision of a package is being shipped and
3516 no new original source archive is being distributed the
3517 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3518 entry for the original source archive
3519 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3520 but the <file>.changes</file> file should leave it out. In
3521 this case the original source archive on the distribution
3522 site must match exactly, byte-for-byte, the original
3523 source archive which was used to generate the
3524 <file>.dsc</file> file and diff which are being uploaded.</p>
3527 <sect1 id="f-Closes">
3528 <heading><tt>Closes</tt></heading>
3531 A space-separated list of bug report numbers that the upload
3532 governed by the .changes file closes.
3536 <sect1 id="f-Homepage">
3537 <heading><tt>Homepage</tt></heading>
3540 The URL of the web site for this package, preferably (when
3541 applicable) the site from which the original source can be
3542 obtained and any additional upstream documentation or
3543 information may be found. The content of this field is a
3544 simple URL without any surrounding characters such as
3549 <sect1 id="f-Checksums">
3550 <heading><tt>Checksums-Sha1</tt>
3551 and <tt>Checksums-Sha256</tt></heading>
3554 These fields contain a list of files with a checksum and size
3555 for each one. Both <tt>Checksums-Sha1</tt>
3556 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3557 only in the checksum algorithm used: SHA-1
3558 for <tt>Checksums-Sha1</tt> and SHA-256
3559 for <tt>Checksums-Sha256</tt>.
3563 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3564 multiline fields. The first line of the field value (the part
3565 on the same line as <tt>Checksums-Sha1:</tt>
3566 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3567 of the field is expressed as continuation lines, one line per
3568 file. Each line consists of the checksum, a space, the file
3569 size, a space, and the file name. For example (from
3570 a <file>.changes</file> file):
3573 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3574 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3575 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3576 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3578 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3579 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3580 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3581 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3586 In the <file>.dsc</file> file, these fields should list all
3587 files that make up the source package. In
3588 the <file>.changes</file> file, these fields should list all
3589 files being uploaded. The list of files in these fields
3590 must match the list of files in the <tt>Files</tt> field.
3596 <heading>User-defined fields</heading>
3599 Additional user-defined fields may be added to the
3600 source package control file. Such fields will be
3601 ignored, and not copied to (for example) binary or
3602 source package control files or upload control files.
3606 If you wish to add additional unsupported fields to
3607 these output files you should use the mechanism
3612 Fields in the main source control information file with
3613 names starting <tt>X</tt>, followed by one or more of
3614 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3615 be copied to the output files. Only the part of the
3616 field name after the hyphen will be used in the output
3617 file. Where the letter <tt>B</tt> is used the field
3618 will appear in binary package control files, where the
3619 letter <tt>S</tt> is used in source package control
3620 files and where <tt>C</tt> is used in upload control
3621 (<tt>.changes</tt>) files.
3625 For example, if the main source information control file
3628 XBS-Comment: I stand between the candle and the star.
3630 then the binary and source package control files will contain the
3633 Comment: I stand between the candle and the star.
3642 <chapt id="maintainerscripts">
3643 <heading>Package maintainer scripts and installation procedure</heading>
3646 <heading>Introduction to package maintainer scripts</heading>
3649 It is possible to supply scripts as part of a package which
3650 the package management system will run for you when your
3651 package is installed, upgraded or removed.
3655 These scripts are the files <prgn>preinst</prgn>,
3656 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3657 <prgn>postrm</prgn> in the control area of the package.
3658 They must be proper executable files; if they are scripts
3659 (which is recommended), they must start with the usual
3660 <tt>#!</tt> convention. They should be readable and
3661 executable by anyone, and must not be world-writable.
3665 The package management system looks at the exit status from
3666 these scripts. It is important that they exit with a
3667 non-zero status if there is an error, so that the package
3668 management system can stop its processing. For shell
3669 scripts this means that you <em>almost always</em> need to
3670 use <tt>set -e</tt> (this is usually true when writing shell
3671 scripts, in fact). It is also important, of course, that
3672 they exit with a zero status if everything went well.
3676 Additionally, packages interacting with users using
3677 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3678 install a <prgn>config</prgn> script in the control area,
3679 see <ref id="maintscriptprompt"> for details.
3683 When a package is upgraded a combination of the scripts from
3684 the old and new packages is called during the upgrade
3685 procedure. If your scripts are going to be at all
3686 complicated you need to be aware of this, and may need to
3687 check the arguments to your scripts.
3691 Broadly speaking the <prgn>preinst</prgn> is called before
3692 (a particular version of) a package is installed, and the
3693 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3694 before (a version of) a package is removed and the
3695 <prgn>postrm</prgn> afterwards.
3699 Programs called from maintainer scripts should not normally
3700 have a path prepended to them. Before installation is
3701 started, the package management system checks to see if the
3702 programs <prgn>ldconfig</prgn>,
3703 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3704 and <prgn>update-rc.d</prgn> can be found via the
3705 <tt>PATH</tt> environment variable. Those programs, and any
3706 other program that one would expect to be in the
3707 <tt>PATH</tt>, should thus be invoked without an absolute
3708 pathname. Maintainer scripts should also not reset the
3709 <tt>PATH</tt>, though they might choose to modify it by
3710 prepending or appending package-specific directories. These
3711 considerations really apply to all shell scripts.</p>
3714 <sect id="idempotency">
3715 <heading>Maintainer scripts idempotency</heading>
3718 It is necessary for the error recovery procedures that the
3719 scripts be idempotent. This means that if it is run
3720 successfully, and then it is called again, it doesn't bomb
3721 out or cause any harm, but just ensures that everything is
3722 the way it ought to be. If the first call failed, or
3723 aborted half way through for some reason, the second call
3724 should merely do the things that were left undone the first
3725 time, if any, and exit with a success status if everything
3727 This is so that if an error occurs, the user interrupts
3728 <prgn>dpkg</prgn> or some other unforeseen circumstance
3729 happens you don't leave the user with a badly-broken
3730 package when <prgn>dpkg</prgn> attempts to repeat the
3736 <sect id="controllingterminal">
3737 <heading>Controlling terminal for maintainer scripts</heading>
3740 Maintainer scripts are not guaranteed to run with a controlling
3741 terminal and may not be able to interact with the user. They
3742 must be able to fall back to noninteractive behavior if no
3743 controlling terminal is available. Maintainer scripts that
3744 prompt via a program conforming to the Debian Configuration
3745 Management Specification (see <ref id="maintscriptprompt">) may
3746 assume that program will handle falling back to noninteractive
3751 For high-priority prompts without a reasonable default answer,
3752 maintainer scripts may abort if there is no controlling
3753 terminal. However, this situation should be avoided if at all
3754 possible, since it prevents automated or unattended installs.
3755 In most cases, users will consider this to be a bug in the
3760 <sect id="exitstatus">
3761 <heading>Exit status</heading>
3764 Each script must return a zero exit status for
3765 success, or a nonzero one for failure, since the package
3766 management system looks for the exit status of these scripts
3767 and determines what action to take next based on that datum.
3771 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3776 <list compact="compact">
3778 <var>new-preinst</var> <tt>install</tt>
3781 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3784 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3787 <var>old-preinst</var> <tt>abort-upgrade</tt>
3788 <var>new-version</var>
3793 <list compact="compact">
3795 <var>postinst</var> <tt>configure</tt>
3796 <var>most-recently-configured-version</var>
3799 <var>old-postinst</var> <tt>abort-upgrade</tt>
3800 <var>new-version</var>
3803 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3804 <tt>in-favour</tt> <var>package</var>
3805 <var>new-version</var>
3808 <var>postinst</var> <tt>abort-remove</tt>
3811 <var>deconfigured's-postinst</var>
3812 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3813 <var>failed-install-package</var> <var>version</var>
3814 [<tt>removing</tt> <var>conflicting-package</var>
3820 <list compact="compact">
3822 <var>prerm</var> <tt>remove</tt>
3825 <var>old-prerm</var> <tt>upgrade</tt>
3826 <var>new-version</var>
3829 <var>new-prerm</var> <tt>failed-upgrade</tt>
3830 <var>old-version</var>
3833 <var>conflictor's-prerm</var> <tt>remove</tt>
3834 <tt>in-favour</tt> <var>package</var>
3835 <var>new-version</var>
3838 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3839 <tt>in-favour</tt> <var>package-being-installed</var>
3840 <var>version</var> [<tt>removing</tt>
3841 <var>conflicting-package</var>
3847 <list compact="compact">
3849 <var>postrm</var> <tt>remove</tt>
3852 <var>postrm</var> <tt>purge</tt>
3855 <var>old-postrm</var> <tt>upgrade</tt>
3856 <var>new-version</var>
3859 <var>new-postrm</var> <tt>failed-upgrade</tt>
3860 <var>old-version</var>
3863 <var>new-postrm</var> <tt>abort-install</tt>
3866 <var>new-postrm</var> <tt>abort-install</tt>
3867 <var>old-version</var>
3870 <var>new-postrm</var> <tt>abort-upgrade</tt>
3871 <var>old-version</var>
3874 <var>disappearer's-postrm</var> <tt>disappear</tt>
3875 <var>overwriter</var>
3876 <var>overwriter-version</var>
3882 <sect id="unpackphase">
3883 <heading>Details of unpack phase of installation or upgrade</heading>
3886 The procedure on installation/upgrade/overwrite/disappear
3887 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3888 stage of <tt>dpkg --install</tt>) is as follows. In each
3889 case, if a major error occurs (unless listed below) the
3890 actions are, in general, run backwards - this means that the
3891 maintainer scripts are run with different arguments in
3892 reverse order. These are the "error unwind" calls listed
3899 If a version of the package is already installed, call
3900 <example compact="compact">
3901 <var>old-prerm</var> upgrade <var>new-version</var>
3905 If the script runs but exits with a non-zero
3906 exit status, <prgn>dpkg</prgn> will attempt:
3907 <example compact="compact">
3908 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3910 If this works, the upgrade continues. If this
3911 does not work, the error unwind:
3912 <example compact="compact">
3913 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3915 If this works, then the old-version is
3916 "Installed", if not, the old version is in a
3917 "Half-Configured" state.
3923 If a "conflicting" package is being removed at the same time,
3924 or if any package will be broken (due to <tt>Breaks</tt>):
3927 If <tt>--auto-deconfigure</tt> is
3928 specified, call, for each package to be deconfigured
3929 due to <tt>Breaks</tt>:
3930 <example compact="compact">
3931 <var>deconfigured's-prerm</var> deconfigure \
3932 in-favour <var>package-being-installed</var> <var>version</var>
3935 <example compact="compact">
3936 <var>deconfigured's-postinst</var> abort-deconfigure \
3937 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3939 The deconfigured packages are marked as
3940 requiring configuration, so that if
3941 <tt>--install</tt> is used they will be
3942 configured again if possible.
3945 If any packages depended on a conflicting
3946 package being removed and <tt>--auto-deconfigure</tt> is
3947 specified, call, for each such package:
3948 <example compact="compact">
3949 <var>deconfigured's-prerm</var> deconfigure \
3950 in-favour <var>package-being-installed</var> <var>version</var> \
3951 removing <var>conflicting-package</var> <var>version</var>
3954 <example compact="compact">
3955 <var>deconfigured's-postinst</var> abort-deconfigure \
3956 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3957 removing <var>conflicting-package</var> <var>version</var>
3959 The deconfigured packages are marked as
3960 requiring configuration, so that if
3961 <tt>--install</tt> is used they will be
3962 configured again if possible.
3965 To prepare for removal of each conflicting package, call:
3966 <example compact="compact">
3967 <var>conflictor's-prerm</var> remove \
3968 in-favour <var>package</var> <var>new-version</var>
3971 <example compact="compact">
3972 <var>conflictor's-postinst</var> abort-remove \
3973 in-favour <var>package</var> <var>new-version</var>
3982 If the package is being upgraded, call:
3983 <example compact="compact">
3984 <var>new-preinst</var> upgrade <var>old-version</var>
3986 If this fails, we call:
3988 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3995 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3997 is called. If this works, then the old version
3998 is in an "Installed" state, or else it is left
3999 in an "Unpacked" state.
4004 If it fails, then the old version is left
4005 in an "Half-Installed" state.
4012 Otherwise, if the package had some configuration
4013 files from a previous version installed (i.e., it
4014 is in the "configuration files only" state):
4015 <example compact="compact">
4016 <var>new-preinst</var> install <var>old-version</var>
4020 <var>new-postrm</var> abort-install <var>old-version</var>
4022 If this fails, the package is left in a
4023 "Half-Installed" state, which requires a
4024 reinstall. If it works, the packages is left in
4025 a "Config-Files" state.
4028 Otherwise (i.e., the package was completely purged):
4029 <example compact="compact">
4030 <var>new-preinst</var> install
4033 <example compact="compact">
4034 <var>new-postrm</var> abort-install
4036 If the error-unwind fails, the package is in a
4037 "Half-Installed" phase, and requires a
4038 reinstall. If the error unwind works, the
4039 package is in a not installed state.
4046 The new package's files are unpacked, overwriting any
4047 that may be on the system already, for example any
4048 from the old version of the same package or from
4049 another package. Backups of the old files are kept
4050 temporarily, and if anything goes wrong the package
4051 management system will attempt to put them back as
4052 part of the error unwind.
4056 It is an error for a package to contain files which
4057 are on the system in another package, unless
4058 <tt>Replaces</tt> is used (see <ref id="replaces">).
4060 The following paragraph is not currently the case:
4061 Currently the <tt>- - force-overwrite</tt> flag is
4062 enabled, downgrading it to a warning, but this may not
4068 It is a more serious error for a package to contain a
4069 plain file or other kind of non-directory where another
4070 package has a directory (again, unless
4071 <tt>Replaces</tt> is used). This error can be
4072 overridden if desired using
4073 <tt>--force-overwrite-dir</tt>, but this is not
4078 Packages which overwrite each other's files produce
4079 behavior which, though deterministic, is hard for the
4080 system administrator to understand. It can easily
4081 lead to "missing" programs if, for example, a package
4082 is installed which overwrites a file from another
4083 package, and is then removed again.<footnote>
4084 Part of the problem is due to what is arguably a
4085 bug in <prgn>dpkg</prgn>.
4090 A directory will never be replaced by a symbolic link
4091 to a directory or vice versa; instead, the existing
4092 state (symlink or not) will be left alone and
4093 <prgn>dpkg</prgn> will follow the symlink if there is
4102 If the package is being upgraded, call
4103 <example compact="compact">
4104 <var>old-postrm</var> upgrade <var>new-version</var>
4108 If this fails, <prgn>dpkg</prgn> will attempt:
4109 <example compact="compact">
4110 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4112 If this works, installation continues. If not,
4114 <example compact="compact">
4115 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4117 If this fails, the old version is left in a
4118 "Half-Installed" state. If it works, dpkg now
4120 <example compact="compact">
4121 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4123 If this fails, the old version is left in a
4124 "Half-Installed" state. If it works, dpkg now
4126 <example compact="compact">
4127 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4129 If this fails, the old version is in an
4136 This is the point of no return - if
4137 <prgn>dpkg</prgn> gets this far, it won't back off
4138 past this point if an error occurs. This will
4139 leave the package in a fairly bad state, which
4140 will require a successful re-installation to clear
4141 up, but it's when <prgn>dpkg</prgn> starts doing
4142 things that are irreversible.
4147 Any files which were in the old version of the package
4148 but not in the new are removed.
4152 The new file list replaces the old.
4156 The new maintainer scripts replace the old.
4160 Any packages all of whose files have been overwritten
4161 during the installation, and which aren't required for
4162 dependencies, are considered to have been removed.
4163 For each such package
4166 <prgn>dpkg</prgn> calls:
4167 <example compact="compact">
4168 <var>disappearer's-postrm</var> disappear \
4169 <var>overwriter</var> <var>overwriter-version</var>
4173 The package's maintainer scripts are removed.
4176 It is noted in the status database as being in a
4177 sane state, namely not installed (any conffiles
4178 it may have are ignored, rather than being
4179 removed by <prgn>dpkg</prgn>). Note that
4180 disappearing packages do not have their prerm
4181 called, because <prgn>dpkg</prgn> doesn't know
4182 in advance that the package is going to
4189 Any files in the package we're unpacking that are also
4190 listed in the file lists of other packages are removed
4191 from those lists. (This will lobotomize the file list
4192 of the "conflicting" package if there is one.)
4196 The backup files made during installation, above, are
4202 The new package's status is now sane, and recorded as
4207 Here is another point of no return - if the
4208 conflicting package's removal fails we do not unwind
4209 the rest of the installation; the conflicting package
4210 is left in a half-removed limbo.
4215 If there was a conflicting package we go and do the
4216 removal actions (described below), starting with the
4217 removal of the conflicting package's files (any that
4218 are also in the package being installed have already
4219 been removed from the conflicting package's file list,
4220 and so do not get removed now).
4226 <sect id="configdetails"><heading>Details of configuration</heading>
4229 When we configure a package (this happens with <tt>dpkg
4230 --install</tt> and <tt>dpkg --configure</tt>), we first
4231 update any <tt>conffile</tt>s and then call:
4232 <example compact="compact">
4233 <var>postinst</var> configure <var>most-recently-configured-version</var>
4238 No attempt is made to unwind after errors during
4239 configuration. If the configuration fails, the package is in
4240 a "Failed Config" state, and an error message is generated.
4244 If there is no most recently configured version
4245 <prgn>dpkg</prgn> will pass a null argument.
4248 Historical note: Truly ancient (pre-1997) versions of
4249 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4250 (including the angle brackets) in this case. Even older
4251 ones did not pass a second argument at all, under any
4252 circumstance. Note that upgrades using such an old dpkg
4253 version are unlikely to work for other reasons, even if
4254 this old argument behavior is handled by your postinst script.
4260 <sect id="removedetails"><heading>Details of removal and/or
4261 configuration purging</heading>
4267 <example compact="compact">
4268 <var>prerm</var> remove
4272 If prerm fails during replacement due to conflict
4274 <var>conflictor's-postinst</var> abort-remove \
4275 in-favour <var>package</var> <var>new-version</var>
4279 <var>postinst</var> abort-remove
4283 If this fails, the package is in a "Half-Configured"
4284 state, or else it remains "Installed".
4288 The package's files are removed (except <tt>conffile</tt>s).
4291 <example compact="compact">
4292 <var>postrm</var> remove
4296 If it fails, there's no error unwind, and the package is in
4297 an "Half-Installed" state.
4302 All the maintainer scripts except the <prgn>postrm</prgn>
4307 If we aren't purging the package we stop here. Note
4308 that packages which have no <prgn>postrm</prgn> and no
4309 <tt>conffile</tt>s are automatically purged when
4310 removed, as there is no difference except for the
4311 <prgn>dpkg</prgn> status.
4315 The <tt>conffile</tt>s and any backup files
4316 (<tt>~</tt>-files, <tt>#*#</tt> files,
4317 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4322 <example compact="compact">
4323 <var>postrm</var> purge
4327 If this fails, the package remains in a "Config-Files"
4332 The package's file list is removed.
4341 <chapt id="relationships">
4342 <heading>Declaring relationships between packages</heading>
4344 <sect id="depsyntax">
4345 <heading>Syntax of relationship fields</heading>
4348 These fields all have a uniform syntax. They are a list of
4349 package names separated by commas.
4353 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4354 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4355 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4356 control file fields of the package, which declare
4357 dependencies on other packages, the package names listed may
4358 also include lists of alternative package names, separated
4359 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4360 if any one of the alternative packages is installed, that
4361 part of the dependency is considered to be satisfied.
4365 All of the fields except for <tt>Provides</tt> may restrict
4366 their applicability to particular versions of each named
4367 package. This is done in parentheses after each individual
4368 package name; the parentheses should contain a relation from
4369 the list below followed by a version number, in the format
4370 described in <ref id="f-Version">.
4374 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4375 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4376 strictly earlier, earlier or equal, exactly equal, later or
4377 equal and strictly later, respectively. The deprecated
4378 forms <tt><</tt> and <tt>></tt> were used to mean
4379 earlier/later or equal, rather than strictly earlier/later,
4380 so they should not appear in new packages (though
4381 <prgn>dpkg</prgn> still supports them).
4385 Whitespace may appear at any point in the version
4386 specification subject to the rules in <ref
4387 id="controlsyntax">, and must appear where it's necessary to
4388 disambiguate; it is not otherwise significant. All of the
4389 relationship fields may span multiple lines. For
4390 consistency and in case of future changes to
4391 <prgn>dpkg</prgn> it is recommended that a single space be
4392 used after a version relationship and before a version
4393 number; it is also conventional to put a single space after
4394 each comma, on either side of each vertical bar, and before
4395 each open parenthesis. When wrapping a relationship field, it
4396 is conventional to do so after a comma and before the space
4397 following that comma.
4401 For example, a list of dependencies might appear as:
4402 <example compact="compact">
4405 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4410 Relationships may be restricted to a certain set of
4411 architectures. This is indicated in brackets after each
4412 individual package name and the optional version specification.
4413 The brackets enclose a list of Debian architecture names
4414 separated by whitespace. Exclamation marks may be prepended to
4415 each of the names. (It is not permitted for some names to be
4416 prepended with exclamation marks while others aren't.)
4420 For build relationship fields
4421 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4422 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4423 the current Debian host architecture is not in this list and
4424 there are no exclamation marks in the list, or it is in the list
4425 with a prepended exclamation mark, the package name and the
4426 associated version specification are ignored completely for the
4427 purposes of defining the relationships.
4432 <example compact="compact">
4434 Build-Depends-Indep: texinfo
4435 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4436 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4438 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4439 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4440 <tt>gnumach-dev</tt> only on hurd-i386.
4444 For binary relationship fields, the architecture restriction
4445 syntax is only supported in the source package control
4446 file <file>debian/control</file>. When the corresponding binary
4447 package control file is generated, the relationship will either
4448 be omitted or included without the architecture restriction
4449 based on the architecture of the binary package. This means
4450 that architecture restrictions must not be used in binary
4451 relationship fields for architecture-independent packages
4452 (<tt>Architecture: all</tt>).
4457 <example compact="compact">
4458 Depends: foo [i386], bar [amd64]
4460 becomes <tt>Depends: foo</tt> when the package is built on
4461 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4462 package is built on the <tt>amd64</tt> architecture, and omitted
4463 entirely in binary packages built on all other architectures.
4467 If the architecture-restricted dependency is part of a set of
4468 alternatives using <tt>|</tt>, that alternative is ignored
4469 completely on architectures that do not match the restriction.
4471 <example compact="compact">
4472 Build-Depends: foo [!i386] | bar [!amd64]
4474 is equivalent to <tt>bar</tt> on the i386 architecture, to
4475 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4476 bar</tt> on all other architectures.
4480 Relationships may also be restricted to a certain set of
4481 architectures using architecture wildcards. The syntax for
4482 declaring such restrictions is the same as declaring
4483 restrictions using a certain set of architectures without
4484 architecture wildcards. For example:
4485 <example compact="compact">
4486 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4488 is equivalent to <tt>foo</tt> on architectures using the Linux
4489 kernel and any cpu, <tt>bar</tt> on architectures using any
4490 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4491 using a kernel other than Linux.
4495 Note that the binary package relationship fields such as
4496 <tt>Depends</tt> appear in one of the binary package
4497 sections of the control file, whereas the build-time
4498 relationships such as <tt>Build-Depends</tt> appear in the
4499 source package section of the control file (which is the
4504 <sect id="binarydeps">
4505 <heading>Binary Dependencies - <tt>Depends</tt>,
4506 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4507 <tt>Pre-Depends</tt>
4511 Packages can declare in their control file that they have
4512 certain relationships to other packages - for example, that
4513 they may not be installed at the same time as certain other
4514 packages, and/or that they depend on the presence of others.
4518 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4519 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4520 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4521 <tt>Breaks</tt> is described in <ref id="breaks">, and
4522 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4523 rest are described below.
4527 These seven fields are used to declare a dependency
4528 relationship by one package on another. Except for
4529 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4530 depending (binary) package's control file.
4531 (<tt>Enhances</tt> appears in the recommending package's
4532 control file, and <tt>Breaks</tt> appears in the version of
4533 depended-on package which causes the named package to
4538 A <tt>Depends</tt> field takes effect <em>only</em> when a
4539 package is to be configured. It does not prevent a package
4540 being on the system in an unconfigured state while its
4541 dependencies are unsatisfied, and it is possible to replace
4542 a package whose dependencies are satisfied and which is
4543 properly installed with a different version whose
4544 dependencies are not and cannot be satisfied; when this is
4545 done the depending package will be left unconfigured (since
4546 attempts to configure it will give errors) and will not
4547 function properly. If it is necessary, a
4548 <tt>Pre-Depends</tt> field can be used, which has a partial
4549 effect even when a package is being unpacked, as explained
4550 in detail below. (The other three dependency fields,
4551 <tt>Recommends</tt>, <tt>Suggests</tt> and
4552 <tt>Enhances</tt>, are only used by the various front-ends
4553 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4554 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4558 For this reason packages in an installation run are usually
4559 all unpacked first and all configured later; this gives
4560 later versions of packages with dependencies on later
4561 versions of other packages the opportunity to have their
4562 dependencies satisfied.
4566 In case of circular dependencies, since installation or
4567 removal order honoring the dependency order can't be
4568 established, dependency loops are broken at some point
4569 (based on rules below), and some packages may not be able to
4570 rely on their dependencies being present when being
4571 installed or removed, depending on which side of the break
4572 of the circular dependency loop they happen to be on. If one
4573 of the packages in the loop has no postinst script, then the
4574 cycle will be broken at that package, so as to ensure that
4575 all postinst scripts run with the dependencies properly
4576 configured if this is possible. Otherwise the breaking point
4581 The <tt>Depends</tt> field thus allows package maintainers
4582 to impose an order in which packages should be configured.
4586 The meaning of the five dependency fields is as follows:
4588 <tag><tt>Depends</tt></tag>
4591 This declares an absolute dependency. A package will
4592 not be configured unless all of the packages listed in
4593 its <tt>Depends</tt> field have been correctly
4598 The <tt>Depends</tt> field should be used if the
4599 depended-on package is required for the depending
4600 package to provide a significant amount of
4605 The <tt>Depends</tt> field should also be used if the
4606 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4607 <prgn>postrm</prgn> scripts require the package to be
4608 present in order to run. Note, however, that the
4609 <prgn>postrm</prgn> cannot rely on any non-essential
4610 packages to be present during the <tt>purge</tt>
4614 <tag><tt>Recommends</tt></tag>
4617 This declares a strong, but not absolute, dependency.
4621 The <tt>Recommends</tt> field should list packages
4622 that would be found together with this one in all but
4623 unusual installations.
4627 <tag><tt>Suggests</tt></tag>
4629 This is used to declare that one package may be more
4630 useful with one or more others. Using this field
4631 tells the packaging system and the user that the
4632 listed packages are related to this one and can
4633 perhaps enhance its usefulness, but that installing
4634 this one without them is perfectly reasonable.
4637 <tag><tt>Enhances</tt></tag>
4639 This field is similar to Suggests but works in the
4640 opposite direction. It is used to declare that a
4641 package can enhance the functionality of another
4645 <tag><tt>Pre-Depends</tt></tag>
4648 This field is like <tt>Depends</tt>, except that it
4649 also forces <prgn>dpkg</prgn> to complete installation
4650 of the packages named before even starting the
4651 installation of the package which declares the
4652 pre-dependency, as follows:
4656 When a package declaring a pre-dependency is about to
4657 be <em>unpacked</em> the pre-dependency can be
4658 satisfied if the depended-on package is either fully
4659 configured, <em>or even if</em> the depended-on
4660 package(s) are only unpacked or in the "Half-Configured"
4661 state, provided that they have been configured
4662 correctly at some point in the past (and not removed
4663 or partially removed since). In this case, both the
4664 previously-configured and currently unpacked or
4665 "Half-Configured" versions must satisfy any version
4666 clause in the <tt>Pre-Depends</tt> field.
4670 When the package declaring a pre-dependency is about
4671 to be <em>configured</em>, the pre-dependency will be
4672 treated as a normal <tt>Depends</tt>, that is, it will
4673 be considered satisfied only if the depended-on
4674 package has been correctly configured.
4678 <tt>Pre-Depends</tt> should be used sparingly,
4679 preferably only by packages whose premature upgrade or
4680 installation would hamper the ability of the system to
4681 continue with any upgrade that might be in progress.
4685 <tt>Pre-Depends</tt> are also required if the
4686 <prgn>preinst</prgn> script depends on the named
4687 package. It is best to avoid this situation if
4695 When selecting which level of dependency to use you should
4696 consider how important the depended-on package is to the
4697 functionality of the one declaring the dependency. Some
4698 packages are composed of components of varying degrees of
4699 importance. Such a package should list using
4700 <tt>Depends</tt> the package(s) which are required by the
4701 more important components. The other components'
4702 requirements may be mentioned as Suggestions or
4703 Recommendations, as appropriate to the components' relative
4709 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4712 When one binary package declares that it breaks another,
4713 <prgn>dpkg</prgn> will refuse to allow the package which
4714 declares <tt>Breaks</tt> be installed unless the broken
4715 package is deconfigured first, and it will refuse to
4716 allow the broken package to be reconfigured.
4720 A package will not be regarded as causing breakage merely
4721 because its configuration files are still installed; it must
4722 be at least "Half-Installed".
4726 A special exception is made for packages which declare that
4727 they break their own package name or a virtual package which
4728 they provide (see below): this does not count as a real
4733 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4734 version clause; such a <tt>Breaks</tt> is introduced in the
4735 version of an (implicit or explicit) dependency which violates
4736 an assumption or reveals a bug in earlier versions of the broken
4737 package, or which takes over a file from earlier versions of the
4738 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4739 will inform higher-level package management tools that the
4740 broken package must be upgraded before the new one.
4744 If the breaking package also overwrites some files from the
4745 older package, it should use <tt>Replaces</tt> to ensure this
4746 goes smoothly. See <ref id="replaces"> for a full discussion
4747 of taking over files from other packages, including how to
4748 use <tt>Breaks</tt> in those cases.
4752 Many of the cases where <tt>Breaks</tt> should be used were
4753 previously handled with <tt>Conflicts</tt>
4754 because <tt>Breaks</tt> did not yet exist.
4755 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4756 See <ref id="conflicts"> for more information about the
4761 <sect id="conflicts">
4762 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4765 When one binary package declares a conflict with another
4766 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4767 refuse to allow them to be installed on the system at the
4768 same time. This is a stronger restriction than <tt>Breaks</tt>,
4769 which just prevents both packages from being configured at the
4770 same time. Conflicting packages cannot be unpacked on the
4771 system at the same time.
4775 If one package is to be installed, the other must be removed
4776 first. If the package being installed is marked as replacing
4777 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4778 normally be used in this case) the one on the system, or the one
4779 on the system is marked as deselected, or both packages are
4780 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4781 automatically remove the package which is causing the conflict.
4782 Otherwise, it will halt the installation of the new package with
4783 an error. This mechanism is specifically designed to produce an
4784 error when the installed package is <tt>Essential</tt>, but the
4789 A package will not cause a conflict merely because its
4790 configuration files are still installed; it must be at least
4795 A special exception is made for packages which declare a
4796 conflict with their own package name, or with a virtual
4797 package which they provide (see below): this does not
4798 prevent their installation, and allows a package to conflict
4799 with others providing a replacement for it. You use this
4800 feature when you want the package in question to be the only
4801 package providing some feature.
4805 Normally, <tt>Breaks</tt> should be used instead
4806 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4807 stronger restriction on the ordering of package installation or
4808 upgrade and can make it more difficult for the package manager
4809 to find a correct solution to an upgrade or installation
4810 problem. <tt>Breaks</tt> should be used
4812 <item>when moving a file from one package to another (see
4813 <ref id="replaces">),</item>
4814 <item>when splitting a package (a special case of the previous
4816 <item>when the breaking package exposes a bug in or interacts
4817 badly with particular versions of the broken
4820 <tt>Conflicts</tt> should be used
4822 <item>when two packages provide the same file and will
4823 continue to do so,</item>
4824 <item>in conjunction with <tt>Provides</tt> when only one
4825 package providing a given virtual facility may be installed
4826 at a time (see <ref id="virtual">),</item>
4827 <item>in other cases where one must prevent simultaneous
4828 installation of two packages for reasons that are ongoing
4829 (not fixed in a later version of one of the packages) or
4830 that must prevent both packages from being unpacked at the
4831 same time, not just configured.</item>
4833 Be aware that adding <tt>Conflicts</tt> is normally not the best
4834 solution when two packages provide the same files. Depending on
4835 the reason for that conflict, using alternatives or renaming the
4836 files is often a better approach. See, for
4837 example, <ref id="binaries">.
4841 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4842 unless two packages cannot be installed at the same time or
4843 installing them both causes one of them to be broken or
4844 unusable. Having similar functionality or performing the same
4845 tasks as another package is not sufficient reason to
4846 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4850 A <tt>Conflicts</tt> entry may have an "earlier than" version
4851 clause if the reason for the conflict is corrected in a later
4852 version of one of the packages. However, normally the presence
4853 of an "earlier than" version clause is a sign
4854 that <tt>Breaks</tt> should have been used instead. An "earlier
4855 than" version clause in <tt>Conflicts</tt>
4856 prevents <prgn>dpkg</prgn> from upgrading or installing the
4857 package which declares such a conflict until the upgrade or
4858 removal of the conflicted-with package has been completed, which
4859 is a strong restriction.
4863 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4867 As well as the names of actual ("concrete") packages, the
4868 package relationship fields <tt>Depends</tt>,
4869 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4870 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4871 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4872 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4873 may mention "virtual packages".
4877 A <em>virtual package</em> is one which appears in the
4878 <tt>Provides</tt> control file field of another package.
4879 The effect is as if the package(s) which provide a
4880 particular virtual package name had been listed by name
4881 everywhere the virtual package name appears. (See also <ref
4886 If there are both concrete and virtual packages of the same
4887 name, then the dependency may be satisfied (or the conflict
4888 caused) by either the concrete package with the name in
4889 question or any other concrete package which provides the
4890 virtual package with the name in question. This is so that,
4891 for example, supposing we have
4892 <example compact="compact">
4895 </example> and someone else releases an enhanced version of
4896 the <tt>bar</tt> package they can say:
4897 <example compact="compact">
4901 and the <tt>bar-plus</tt> package will now also satisfy the
4902 dependency for the <tt>foo</tt> package.
4906 If a relationship field has a version number attached, only real
4907 packages will be considered to see whether the relationship is
4908 satisfied (or the prohibition violated, for a conflict or
4909 breakage). In other words, if a version number is specified,
4910 this is a request to ignore all <tt>Provides</tt> for that
4911 package name and consider only real packages. The package
4912 manager will assume that a package providing that virtual
4913 package is not of the "right" version. A <tt>Provides</tt>
4914 field may not contain version numbers, and the version number of
4915 the concrete package which provides a particular virtual package
4916 will not be considered when considering a dependency on or
4917 conflict with the virtual package name.<footnote>
4918 It is possible that a future release of <prgn>dpkg</prgn> may
4919 add the ability to specify a version number for each virtual
4920 package it provides. This feature is not yet present,
4921 however, and is expected to be used only infrequently.
4926 To specify which of a set of real packages should be the default
4927 to satisfy a particular dependency on a virtual package, list
4928 the real package as an alternative before the virtual one.
4932 If the virtual package represents a facility that can only be
4933 provided by one real package at a time, such as
4934 the <package>mail-transport-agent</package> virtual package that
4935 requires installation of a binary that would conflict with all
4936 other providers of that virtual package (see
4937 <ref id="mail-transport-agents">), all packages providing that
4938 virtual package should also declare a conflict with it
4939 using <tt>Conflicts</tt>. This will ensure that at most one
4940 provider of that virtual package is unpacked or installed at a
4945 <sect id="replaces"><heading>Overwriting files and replacing
4946 packages - <tt>Replaces</tt></heading>
4949 Packages can declare in their control file that they should
4950 overwrite files in certain other packages, or completely
4951 replace other packages. The <tt>Replaces</tt> control file
4952 field has these two distinct purposes.
4955 <sect1><heading>Overwriting files in other packages</heading>
4958 It is usually an error for a package to contain files which
4959 are on the system in another package. However, if the
4960 overwriting package declares that it <tt>Replaces</tt> the one
4961 containing the file being overwritten, then <prgn>dpkg</prgn>
4962 will replace the file from the old package with that from the
4963 new. The file will no longer be listed as "owned" by the old
4964 package and will be taken over by the new package.
4965 Normally, <tt>Breaks</tt> should be used in conjunction
4966 with <tt>Replaces</tt>.<footnote>
4967 To see why <tt>Breaks</tt> is normally needed in addition
4968 to <tt>Replaces</tt>, consider the case of a file in the
4969 package <package>foo</package> being taken over by the
4970 package <package>foo-data</package>.
4971 <tt>Replaces</tt> will allow <package>foo-data</package> to
4972 be installed and take over that file. However,
4973 without <tt>Breaks</tt>, nothing
4974 requires <package>foo</package> to be upgraded to a newer
4975 version that knows it does not include that file and instead
4976 depends on <package>foo-data</package>. Nothing would
4977 prevent the new <package>foo-data</package> package from
4978 being installed and then removed, removing the file that it
4979 took over from <package>foo</package>. After that
4980 operation, the package manager would think the system was in
4981 a consistent state, but the <package>foo</package> package
4982 would be missing one of its files.
4987 For example, if a package <package>foo</package> is split
4988 into <package>foo</package> and <package>foo-data</package>
4989 starting at version 1.2-3, <package>foo-data</package> would
4991 <example compact="compact">
4992 Replaces: foo (<< 1.2-3)
4993 Breaks: foo (<< 1.2-3)
4995 in its control file. The new version of the
4996 package <package>foo</package> would normally have the field
4997 <example compact="compact">
4998 Depends: foo-data (>= 1.2-3)
5000 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5001 the files moved into <package>foo-data</package> are not
5002 required for normal operation).
5006 If a package is completely replaced in this way, so that
5007 <prgn>dpkg</prgn> does not know of any files it still
5008 contains, it is considered to have "disappeared". It will
5009 be marked as not wanted on the system (selected for
5010 removal) and not installed. Any <tt>conffile</tt>s
5011 details noted for the package will be ignored, as they
5012 will have been taken over by the overwriting package. The
5013 package's <prgn>postrm</prgn> script will be run with a
5014 special argument to allow the package to do any final
5015 cleanup required. See <ref id="mscriptsinstact">.
5017 Replaces is a one way relationship. You have to install
5018 the replacing package after the replaced package.
5023 For this usage of <tt>Replaces</tt>, virtual packages (see
5024 <ref id="virtual">) are not considered when looking at a
5025 <tt>Replaces</tt> field. The packages declared as being
5026 replaced must be mentioned by their real names.
5030 This usage of <tt>Replaces</tt> only takes effect when both
5031 packages are at least partially on the system at once. It is
5032 not relevant if the packages conflict unless the conflict has
5037 <sect1><heading>Replacing whole packages, forcing their
5041 Second, <tt>Replaces</tt> allows the packaging system to
5042 resolve which package should be removed when there is a
5043 conflict (see <ref id="conflicts">). This usage only takes
5044 effect when the two packages <em>do</em> conflict, so that the
5045 two usages of this field do not interfere with each other.
5049 In this situation, the package declared as being replaced
5050 can be a virtual package, so for example, all mail
5051 transport agents (MTAs) would have the following fields in
5052 their control files:
5053 <example compact="compact">
5054 Provides: mail-transport-agent
5055 Conflicts: mail-transport-agent
5056 Replaces: mail-transport-agent
5058 ensuring that only one MTA can be installed at any one
5059 time. See <ref id="virtual"> for more information about this
5064 <sect id="sourcebinarydeps">
5065 <heading>Relationships between source and binary packages -
5066 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5067 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5071 Source packages that require certain binary packages to be
5072 installed or absent at the time of building the package
5073 can declare relationships to those binary packages.
5077 This is done using the <tt>Build-Depends</tt>,
5078 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5079 <tt>Build-Conflicts-Indep</tt> control file fields.
5083 Build-dependencies on "build-essential" binary packages can be
5084 omitted. Please see <ref id="pkg-relations"> for more information.
5088 The dependencies and conflicts they define must be satisfied
5089 (as defined earlier for binary packages) in order to invoke
5090 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5092 There is no Build-Depends-Arch; this role is essentially
5093 met with Build-Depends. Anyone building the
5094 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5095 assumed to be building the whole package, and therefore
5096 installation of all build dependencies is required.
5099 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5100 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5101 not yet know how to check for its existence, and
5102 <tt>binary-arch</tt>. The purpose of the original split
5103 between <tt>Build-Depends</tt> and
5104 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5105 wouldn't need to install extra packages needed only for the
5106 binary-indep targets. But without a build-arch/build-indep
5107 split, this didn't work, since most of the work is done in
5108 the build target, not in the binary target.
5112 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5113 <tt>binary-arch</tt></tag>
5115 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5116 fields must be satisfied when these targets are invoked.
5118 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5119 and <tt>binary-indep</tt></tag>
5121 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5122 <tt>Build-Depends-Indep</tt>, and
5123 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5124 these targets are invoked.
5132 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5135 Packages containing shared libraries must be constructed with
5136 a little care to make sure that the shared library is always
5137 available. This is especially important for packages whose
5138 shared libraries are vitally important, such as the C library
5139 (currently <tt>libc6</tt>).
5143 Packages involving shared libraries should be split up into
5144 several binary packages. This section mostly deals with how
5145 this separation is to be accomplished; rules for files within
5146 the shared library packages are in <ref id="libraries"> instead.
5149 <sect id="sharedlibs-runtime">
5150 <heading>Run-time shared libraries</heading>
5153 The run-time shared library needs to be placed in a package
5154 whose name changes whenever the shared object version
5157 Since it is common place to install several versions of a
5158 package that just provides shared libraries, it is a
5159 good idea that the library package should not
5160 contain any extraneous non-versioned files, unless they
5161 happen to be in versioned directories.</p>
5163 The most common mechanism is to place it in a package
5165 <package><var>libraryname</var><var>soversion</var></package>,
5166 where <file><var>soversion</var></file> is the version number
5167 in the soname of the shared library<footnote>
5168 The soname is the shared object name: it's the thing
5169 that has to match exactly between building an executable
5170 and running it for the dynamic linker to be able run the
5171 program. For example, if the soname of the library is
5172 <file>libfoo.so.6</file>, the library package would be
5173 called <file>libfoo6</file>.
5175 Alternatively, if it would be confusing to directly append
5176 <var>soversion</var> to <var>libraryname</var> (e.g. because
5177 <var>libraryname</var> itself ends in a number), you may use
5178 <package><var>libraryname</var>-<var>soversion</var></package> and
5179 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5184 If you have several shared libraries built from the same
5185 source tree you may lump them all together into a single
5186 shared library package, provided that you change all of
5187 their sonames at once (so that you don't get filename
5188 clashes if you try to install different versions of the
5189 combined shared libraries package).
5193 The package should install the shared libraries under
5194 their normal names. For example, the <package>libgdbm3</package>
5195 package should install <file>libgdbm.so.3.0.0</file> as
5196 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5197 renamed or re-linked by any <prgn>prerm</prgn> or
5198 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5199 of renaming things safely without affecting running programs,
5200 and attempts to interfere with this are likely to lead to
5205 Shared libraries should not be installed executable, since
5206 the dynamic linker does not require this and trying to
5207 execute a shared library usually results in a core dump.
5211 The run-time library package should include the symbolic link that
5212 <prgn>ldconfig</prgn> would create for the shared libraries.
5213 For example, the <package>libgdbm3</package> package should include
5214 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5215 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5216 linker (for example <prgn>ld.so</prgn> or
5217 <prgn>ld-linux.so.*</prgn>) can find the library between the
5218 time that <prgn>dpkg</prgn> installs it and the time that
5219 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5221 The package management system requires the library to be
5222 placed before the symbolic link pointing to it in the
5223 <file>.deb</file> file. This is so that when
5224 <prgn>dpkg</prgn> comes to install the symlink
5225 (overwriting the previous symlink pointing at an older
5226 version of the library), the new shared library is already
5227 in place. In the past, this was achieved by creating the
5228 library in the temporary packaging directory before
5229 creating the symlink. Unfortunately, this was not always
5230 effective, since the building of the tar file in the
5231 <file>.deb</file> depended on the behavior of the underlying
5232 file system. Some file systems (such as reiserfs) reorder
5233 the files so that the order of creation is forgotten.
5234 Since version 1.7.0, <prgn>dpkg</prgn>
5235 reorders the files itself as necessary when building a
5236 package. Thus it is no longer important to concern
5237 oneself with the order of file creation.
5241 <sect1 id="ldconfig">
5242 <heading><tt>ldconfig</tt></heading>
5245 Any package installing shared libraries in one of the default
5246 library directories of the dynamic linker (which are currently
5247 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5248 listed in <file>/etc/ld.so.conf</file><footnote>
5250 <list compact="compact">
5251 <item>/usr/local/lib</item>
5252 <item>/usr/lib/libc5-compat</item>
5253 <item>/lib/libc5-compat</item>
5256 must use <prgn>ldconfig</prgn> to update the shared library
5261 The package maintainer scripts must only call
5262 <prgn>ldconfig</prgn> under these circumstances:
5263 <list compact="compact">
5264 <item>When the <prgn>postinst</prgn> script is run with a
5265 first argument of <tt>configure</tt>, the script must call
5266 <prgn>ldconfig</prgn>, and may optionally invoke
5267 <prgn>ldconfig</prgn> at other times.
5269 <item>When the <prgn>postrm</prgn> script is run with a
5270 first argument of <tt>remove</tt>, the script should call
5271 <prgn>ldconfig</prgn>.
5276 During install or upgrade, the preinst is called before
5277 the new files are installed, so calling "ldconfig" is
5278 pointless. The preinst of an existing package can also be
5279 called if an upgrade fails. However, this happens during
5280 the critical time when a shared libs may exist on-disk
5281 under a temporary name. Thus, it is dangerous and
5282 forbidden by current policy to call "ldconfig" at this
5287 When a package is installed or upgraded, "postinst
5288 configure" runs after the new files are safely on-disk.
5289 Since it is perfectly safe to invoke ldconfig
5290 unconditionally in a postinst, it is OK for a package to
5291 simply put ldconfig in its postinst without checking the
5292 argument. The postinst can also be called to recover from
5293 a failed upgrade. This happens before any new files are
5294 unpacked, so there is no reason to call "ldconfig" at this
5299 For a package that is being removed, prerm is
5300 called with all the files intact, so calling ldconfig is
5301 useless. The other calls to "prerm" happen in the case of
5302 upgrade at a time when all the files of the old package
5303 are on-disk, so again calling "ldconfig" is pointless.
5307 postrm, on the other hand, is called with the "remove"
5308 argument just after the files are removed, so this is
5309 the proper time to call "ldconfig" to notify the system
5310 of the fact that the shared libraries from the package
5311 are removed. The postrm can be called at several other
5312 times. At the time of "postrm purge", "postrm
5313 abort-install", or "postrm abort-upgrade", calling
5314 "ldconfig" is useless because the shared lib files are
5315 not on-disk. However, when "postrm" is invoked with
5316 arguments "upgrade", "failed-upgrade", or "disappear", a
5317 shared lib may exist on-disk under a temporary filename.
5325 <sect id="sharedlibs-support-files">
5326 <heading>Shared library support files</heading>
5329 If your package contains files whose names do not change with
5330 each change in the library shared object version, you must not
5331 put them in the shared library package. Otherwise, several
5332 versions of the shared library cannot be installed at the same
5333 time without filename clashes, making upgrades and transitions
5334 unnecessarily difficult.
5338 It is recommended that supporting files and run-time support
5339 programs that do not need to be invoked manually by users, but
5340 are nevertheless required for the package to function, be placed
5341 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5342 preferably under <file>/usr/lib/</file><var>package-name</var>.
5343 If the program or file is architecture independent, the
5344 recommendation is for it to be placed in a subdirectory of
5345 <file>/usr/share</file> instead, preferably under
5346 <file>/usr/share/</file><var>package-name</var>. Following the
5347 <var>package-name</var> naming convention ensures that the file
5348 names change when the shared object version changes.
5352 Run-time support programs that use the shared library but are
5353 not required for the library to function or files used by the
5354 shared library that can be used by any version of the shared
5355 library package should instead be put in a separate package.
5356 This package might typically be named
5357 <package><var>libraryname</var>-tools</package>; note the
5358 absence of the <var>soversion</var> in the package name.
5362 Files and support programs only useful when compiling software
5363 against the library should be included in the development
5364 package for the library.<footnote>
5365 For example, a <file><var>package-name</var>-config</file>
5366 script or <package>pkg-config</package> configuration files.
5371 <sect id="sharedlibs-static">
5372 <heading>Static libraries</heading>
5375 The static library (<file><var>libraryname.a</var></file>)
5376 is usually provided in addition to the shared version.
5377 It is placed into the development package (see below).
5381 In some cases, it is acceptable for a library to be
5382 available in static form only; these cases include:
5384 <item>libraries for languages whose shared library support
5385 is immature or unstable</item>
5386 <item>libraries whose interfaces are in flux or under
5387 development (commonly the case when the library's
5388 major version number is zero, or where the ABI breaks
5389 across patchlevels)</item>
5390 <item>libraries which are explicitly intended to be
5391 available only in static form by their upstream
5396 <sect id="sharedlibs-dev">
5397 <heading>Development files</heading>
5400 If there are development files associated with a shared library,
5401 the source package needs to generate a binary development package
5402 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5403 or if you prefer only to support one development version at a
5404 time, <package><var>libraryname</var>-dev</package>. Installing
5405 the development package must result in installation of all the
5406 development files necessary for compiling programs against that
5407 shared library.<footnote>
5408 This wording allows the development files to be split into
5409 several packages, such as a separate architecture-independent
5410 <package><var>libraryname</var>-headers</package>, provided that
5411 the development package depends on all the required additional
5417 In case several development versions of a library exist, you may
5418 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5419 <ref id="conflicts">) to ensure that the user only installs one
5420 development version at a time (as different development versions are
5421 likely to have the same header files in them, which would cause a
5422 filename clash if both were installed).
5426 The development package should contain a symlink for the associated
5427 shared library without a version number. For example, the
5428 <package>libgdbm-dev</package> package should include a symlink
5429 from <file>/usr/lib/libgdbm.so</file> to
5430 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5431 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5432 <file>libgdbm.so</file> when compiling dynamically.
5436 <sect id="sharedlibs-intradeps">
5437 <heading>Dependencies between the packages of the same library</heading>
5440 Typically the development version should have an exact
5441 version dependency on the runtime library, to make sure that
5442 compilation and linking happens correctly. The
5443 <tt>${binary:Version}</tt> substitution variable can be
5444 useful for this purpose.
5446 Previously, <tt>${Source-Version}</tt> was used, but its name
5447 was confusing and it has been deprecated since dpkg 1.13.19.
5452 <sect id="sharedlibs-shlibdeps">
5453 <heading>Dependencies between the library and other packages -
5454 the <tt>shlibs</tt> system</heading>
5457 If a package contains a binary or library which links to a
5458 shared library, we must ensure that when the package is
5459 installed on the system, all of the libraries needed are
5460 also installed. This requirement led to the creation of the
5461 <tt>shlibs</tt> system, which is very simple in its design:
5462 any package which <em>provides</em> a shared library also
5463 provides information on the package dependencies required to
5464 ensure the presence of this library, and any package which
5465 <em>uses</em> a shared library uses this information to
5466 determine the dependencies it requires. The files which
5467 contain the mapping from shared libraries to the necessary
5468 dependency information are called <file>shlibs</file> files.
5472 When a package is built which contains any shared libraries, it
5473 must provide a <file>shlibs</file> file for other packages to
5474 use. When a package is built which contains any shared
5475 libraries or compiled binaries, it must run
5476 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5477 on these to determine the libraries used and hence the
5478 dependencies needed by this package.<footnote>
5480 <prgn>dpkg-shlibdeps</prgn> will use a program
5481 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5482 the libraries directly needed by the binaries or shared
5483 libraries in the package.
5487 We say that a binary <tt>foo</tt> <em>directly</em> uses
5488 a library <tt>libbar</tt> if it is explicitly linked
5489 with that library (that is, the library is listed in the ELF
5490 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5491 to the link line when the binary is created). Other
5492 libraries that are needed by <tt>libbar</tt> are linked
5493 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5494 linker will load them automatically when it loads
5495 <tt>libbar</tt>. A package should depend on the libraries
5496 it directly uses, but not the libraries it indirectly uses.
5497 The dependencies for those libraries will automatically pull
5498 in the other libraries.
5502 A good example of where this helps is the following. We
5503 could update <tt>libimlib</tt> with a new version that
5504 supports a new graphics format called dgf (but retaining the
5505 same major version number) and depends on <tt>libdgf</tt>.
5506 If we used <prgn>ldd</prgn> to add dependencies for every
5507 library directly or indirectly linked with a binary, every
5508 package that uses <tt>libimlib</tt> would need to be
5509 recompiled so it would also depend on <tt>libdgf</tt> or it
5510 wouldn't run due to missing symbols. Since dependencies are
5511 only added based on ELF <tt>NEEDED</tt> attribute, packages
5512 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5513 having the dependency on <tt>libdgf</tt> and so they would
5514 not need rebuilding.
5520 In the following sections, we will first describe where the
5521 various <tt>shlibs</tt> files are to be found, then how to
5522 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5523 file format and how to create them if your package contains a
5528 <heading>The <tt>shlibs</tt> files present on the system</heading>
5531 There are several places where <tt>shlibs</tt> files are
5532 found. The following list gives them in the order in which
5534 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5535 (The first one which gives the required information is used.)
5541 <p><file>debian/shlibs.local</file></p>
5544 This lists overrides for this package. This file should
5545 normally not be used, but may be needed temporarily in
5546 unusual situations to work around bugs in other packages,
5547 or in unusual cases where the normally declared dependency
5548 information in the installed <file>shlibs</file> file for
5549 a library cannot be used. This file overrides information
5550 obtained from any other source.
5555 <p><file>/etc/dpkg/shlibs.override</file></p>
5558 This lists global overrides. This list is normally
5559 empty. It is maintained by the local system
5565 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5568 When packages are being built,
5569 any <file>debian/shlibs</file> files are copied into the
5570 control file area of the temporary build directory and
5571 given the name <file>shlibs</file>. These files give
5572 details of any shared libraries included in the same
5574 An example may help here. Let us say that the source
5575 package <tt>foo</tt> generates two binary
5576 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5577 When building the binary packages, the two packages are
5578 created in the directories <file>debian/libfoo2</file>
5579 and <file>debian/foo-runtime</file> respectively.
5580 (<file>debian/tmp</file> could be used instead of one of
5581 these.) Since <tt>libfoo2</tt> provides the
5582 <tt>libfoo</tt> shared library, it will require a
5583 <tt>shlibs</tt> file, which will be installed in
5584 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5585 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5586 When <prgn>dpkg-shlibdeps</prgn> is run on the
5587 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5589 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5590 determine whether <tt>foo-prog</tt>'s library
5591 dependencies are satisfied by any of the libraries
5592 provided by <tt>libfoo2</tt>. For this reason,
5593 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5594 the individual binary packages' <tt>shlibs</tt> files
5595 have been installed into the build directory.
5601 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5604 These are the <file>shlibs</file> files corresponding to
5605 all of the packages installed on the system, and are
5606 maintained by the relevant package maintainers.
5611 <p><file>/etc/dpkg/shlibs.default</file></p>
5614 This file lists any shared libraries whose packages
5615 have failed to provide correct <file>shlibs</file> files.
5616 It was used when the <file>shlibs</file> setup was first
5617 introduced, but it is now normally empty. It is
5618 maintained by the <tt>dpkg</tt> maintainer.
5626 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5627 <file>shlibs</file> files</heading>
5631 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5632 into your <file>debian/rules</file> file. If your package
5633 contains only compiled binaries and libraries (but no scripts),
5634 you can use a command such as:
5635 <example compact="compact">
5636 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5637 debian/tmp/usr/lib/*
5639 Otherwise, you will need to explicitly list the compiled
5640 binaries and libraries.<footnote>
5641 If you are using <tt>debhelper</tt>, the
5642 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5643 It will also correctly handle multi-binary packages.
5648 This command puts the dependency information into the
5649 <file>debian/substvars</file> file, which is then used by
5650 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5651 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5652 field in the control file for this to work.
5656 If you have multiple binary packages, you will need to call
5657 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5658 compiled libraries or binaries. In such a case, you will
5659 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5660 utilities to specify a different <file>substvars</file> file.
5664 If you are creating a udeb for use in the Debian Installer,
5665 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5666 should use the dependency line of type <tt>udeb</tt> by
5667 adding the <tt>-tudeb</tt> option<footnote>
5668 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5669 will automatically add this option if it knows it is
5671 </footnote>. If there is no dependency line of
5672 type <tt>udeb</tt> in the <file>shlibs</file>
5673 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5678 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5679 <ref id="pkg-dpkg-shlibdeps"> and
5680 <manref name="dpkg-shlibdeps" section="1">.
5685 <heading>The <file>shlibs</file> File Format</heading>
5688 Each <file>shlibs</file> file has the same format. Lines
5689 beginning with <tt>#</tt> are considered to be comments and
5690 are ignored. Each line is of the form:
5691 <example compact="compact">
5692 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5697 We will explain this by reference to the example of the
5698 <tt>zlib1g</tt> package, which (at the time of writing)
5699 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5703 <var>type</var> is an optional element that indicates the type
5704 of package for which the line is valid. The only type currently
5705 in use is <tt>udeb</tt>. The colon and space after the type are
5710 <var>library-name</var> is the name of the shared library,
5711 in this case <tt>libz</tt>. (This must match the name part
5712 of the soname, see below.)
5716 <var>soname-version</var> is the version part of the soname of
5717 the library. The soname is the thing that must exactly match
5718 for the library to be recognized by the dynamic linker, and is
5720 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5721 example, <tt>libz.so.1</tt>.<footnote>
5722 This can be determined using the command
5723 <example compact="compact">
5724 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5727 The version part is the part which comes after
5728 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5729 instead be of the form
5730 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5731 as <tt>libdb-4.8.so</tt>, in which case the name would
5732 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5736 <var>dependencies</var> has the same syntax as a dependency
5737 field in a binary package control file. It should give
5738 details of which packages are required to satisfy a binary
5739 built against the version of the library contained in the
5740 package. See <ref id="depsyntax"> for details.
5744 In our example, if the first version of the <tt>zlib1g</tt>
5745 package which contained a minor number of at least
5746 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5747 <tt>shlibs</tt> entry for this library could say:
5748 <example compact="compact">
5749 libz 1 zlib1g (>= 1:1.1.3)
5751 The version-specific dependency is to avoid warnings from
5752 the dynamic linker about using older shared libraries with
5757 As zlib1g also provides a udeb containing the shared library,
5758 there would also be a second line:
5759 <example compact="compact">
5760 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5766 <heading>Providing a <file>shlibs</file> file</heading>
5769 If your package provides a shared library, you need to create
5770 a <file>shlibs</file> file following the format described above.
5771 It is usual to call this file <file>debian/shlibs</file> (but if
5772 you have multiple binary packages, you might want to call it
5773 <file>debian/shlibs.<var>package</var></file> instead). Then
5774 let <file>debian/rules</file> install it in the control area:
5775 <example compact="compact">
5776 install -m644 debian/shlibs debian/tmp/DEBIAN
5778 or, in the case of a multi-binary package:
5779 <example compact="compact">
5780 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5782 An alternative way of doing this is to create the
5783 <file>shlibs</file> file in the control area directly from
5784 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5785 file at all,<footnote>
5786 This is what <prgn>dh_makeshlibs</prgn> in
5787 the <package>debhelper</package> suite does. If your package
5788 also has a udeb that provides a shared
5789 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5790 the <tt>udeb:</tt> lines if you specify the name of the udeb
5791 with the <tt>--add-udeb</tt> option.
5793 since the <file>debian/shlibs</file> file itself is ignored by
5794 <prgn>dpkg-shlibdeps</prgn>.
5798 As <prgn>dpkg-shlibdeps</prgn> reads the
5799 <file>DEBIAN/shlibs</file> files in all of the binary packages
5800 being built from this source package, all of the
5801 <file>DEBIAN/shlibs</file> files should be installed before
5802 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5810 <chapt id="opersys"><heading>The Operating System</heading>
5813 <heading>File system hierarchy</heading>
5817 <heading>File System Structure</heading>
5820 The location of all installed files and directories must
5821 comply with the Filesystem Hierarchy Standard (FHS),
5822 version 2.3, with the exceptions noted below, and except
5823 where doing so would violate other terms of Debian
5824 Policy. The following exceptions to the FHS apply:
5829 The optional rules related to user specific
5830 configuration files for applications are stored in
5831 the user's home directory are relaxed. It is
5832 recommended that such files start with the
5833 '<tt>.</tt>' character (a "dot file"), and if an
5834 application needs to create more than one dot file
5835 then the preferred placement is in a subdirectory
5836 with a name starting with a '.' character, (a "dot
5837 directory"). In this case it is recommended the
5838 configuration files not start with the '.'
5844 The requirement for amd64 to use <file>/lib64</file>
5845 for 64 bit binaries is removed.
5850 The requirement for object files, internal binaries, and
5851 libraries, including <file>libc.so.*</file>, to be located
5852 directly under <file>/lib{,32}</file> and
5853 <file>/usr/lib{,32}</file> is amended, permitting files
5854 to instead be installed to
5855 <file>/lib/<var>triplet</var></file> and
5856 <file>/usr/lib/<var>triplet</var></file>, where
5857 <tt><var>triplet</var></tt> is the value returned by
5858 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5859 architecture of the package. Packages may <em>not</em>
5860 install files to any <var>triplet</var> path other
5861 than the one matching the architecture of that package;
5862 for instance, an <tt>Architecture: amd64</tt> package
5863 containing 32-bit x86 libraries may not install these
5864 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5866 This is necessary in order to reserve the directories for
5867 use in cross-installation of library packages from other
5868 architectures, as part of the planned deployment of
5873 Applications may also use a single subdirectory under
5874 <file>/usr/lib/<var>triplet</var></file>.
5877 The execution time linker/loader, ld*, must still be made
5878 available in the existing location under /lib or /lib64
5879 since this is part of the ELF ABI for the architecture.
5884 The requirement that
5885 <file>/usr/local/share/man</file> be "synonymous"
5886 with <file>/usr/local/man</file> is relaxed to a
5891 The requirement that windowmanagers with a single
5892 configuration file call it <file>system.*wmrc</file>
5893 is removed, as is the restriction that the window
5894 manager subdirectory be named identically to the
5895 window manager name itself.
5900 The requirement that boot manager configuration
5901 files live in <file>/etc</file>, or at least are
5902 symlinked there, is relaxed to a recommendation.
5907 The following directories in the root filesystem are
5908 additionally allowed: <file>/sys</file> and
5909 <file>/selinux</file>. <footnote>These directories
5910 are used as mount points to mount virtual filesystems
5911 to get access to kernel information.</footnote>
5918 The version of this document referred here can be
5919 found in the <tt>debian-policy</tt> package or on <url
5920 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5921 name="FHS (Debian copy)"> alongside this manual (or, if
5922 you have the <package>debian-policy</package> installed,
5924 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5925 (local copy)">). The
5926 latest version, which may be a more recent version, may
5928 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5929 Specific questions about following the standard may be
5930 asked on the <tt>debian-devel</tt> mailing list, or
5931 referred to the FHS mailing list (see the
5932 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5938 <heading>Site-specific programs</heading>
5941 As mandated by the FHS, packages must not place any
5942 files in <file>/usr/local</file>, either by putting them in
5943 the file system archive to be unpacked by <prgn>dpkg</prgn>
5944 or by manipulating them in their maintainer scripts.
5948 However, the package may create empty directories below
5949 <file>/usr/local</file> so that the system administrator knows
5950 where to place site-specific files. These are not
5951 directories <em>in</em> <file>/usr/local</file>, but are
5952 children of directories in <file>/usr/local</file>. These
5953 directories (<file>/usr/local/*/dir/</file>)
5954 should be removed on package removal if they are
5959 Note that this applies only to
5960 directories <em>below</em> <file>/usr/local</file>,
5961 not <em>in</em> <file>/usr/local</file>. Packages must
5962 not create sub-directories in the
5963 directory <file>/usr/local</file> itself, except those
5964 listed in FHS, section 4.5. However, you may create
5965 directories below them as you wish. You must not remove
5966 any of the directories listed in 4.5, even if you created
5971 Since <file>/usr/local</file> can be mounted read-only from a
5972 remote server, these directories must be created and
5973 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5974 maintainer scripts and not be included in the
5975 <file>.deb</file> archive. These scripts must not fail if
5976 either of these operations fail.
5980 For example, the <tt>emacsen-common</tt> package could
5981 contain something like
5982 <example compact="compact">
5983 if [ ! -e /usr/local/share/emacs ]
5985 if mkdir /usr/local/share/emacs 2>/dev/null
5987 chown root:staff /usr/local/share/emacs
5988 chmod 2775 /usr/local/share/emacs
5992 in its <prgn>postinst</prgn> script, and
5993 <example compact="compact">
5994 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5995 rmdir /usr/local/share/emacs 2>/dev/null || true
5997 in the <prgn>prerm</prgn> script. (Note that this form is
5998 used to ensure that if the script is interrupted, the
5999 directory <file>/usr/local/share/emacs</file> will still be
6004 If you do create a directory in <file>/usr/local</file> for
6005 local additions to a package, you should ensure that
6006 settings in <file>/usr/local</file> take precedence over the
6007 equivalents in <file>/usr</file>.
6011 However, because <file>/usr/local</file> and its contents are
6012 for exclusive use of the local administrator, a package
6013 must not rely on the presence or absence of files or
6014 directories in <file>/usr/local</file> for normal operation.
6018 The <file>/usr/local</file> directory itself and all the
6019 subdirectories created by the package should (by default) have
6020 permissions 2775 (group-writable and set-group-id) and be
6021 owned by <tt>root:staff</tt>.
6026 <heading>The system-wide mail directory</heading>
6028 The system-wide mail directory
6029 is <file>/var/mail</file>. This directory is part of the
6030 base system and should not be owned by any particular mail
6031 agents. The use of the old
6032 location <file>/var/spool/mail</file> is deprecated, even
6033 though the spool may still be physically located there.
6039 <heading>Users and groups</heading>
6042 <heading>Introduction</heading>
6044 The Debian system can be configured to use either plain or
6049 Some user ids (UIDs) and group ids (GIDs) are reserved
6050 globally for use by certain packages. Because some
6051 packages need to include files which are owned by these
6052 users or groups, or need the ids compiled into binaries,
6053 these ids must be used on any Debian system only for the
6054 purpose for which they are allocated. This is a serious
6055 restriction, and we should avoid getting in the way of
6056 local administration policies. In particular, many sites
6057 allocate users and/or local system groups starting at 100.
6061 Apart from this we should have dynamically allocated ids,
6062 which should by default be arranged in some sensible
6063 order, but the behavior should be configurable.
6067 Packages other than <tt>base-passwd</tt> must not modify
6068 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6069 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6074 <heading>UID and GID classes</heading>
6076 The UID and GID numbers are divided into classes as
6082 Globally allocated by the Debian project, the same
6083 on every Debian system. These ids will appear in
6084 the <file>passwd</file> and <file>group</file> files of all
6085 Debian systems, new ids in this range being added
6086 automatically as the <tt>base-passwd</tt> package is
6091 Packages which need a single statically allocated
6092 uid or gid should use one of these; their
6093 maintainers should ask the <tt>base-passwd</tt>
6101 Dynamically allocated system users and groups.
6102 Packages which need a user or group, but can have
6103 this user or group allocated dynamically and
6104 differently on each system, should use <tt>adduser
6105 --system</tt> to create the group and/or user.
6106 <prgn>adduser</prgn> will check for the existence of
6107 the user or group, and if necessary choose an unused
6108 id based on the ranges specified in
6109 <file>adduser.conf</file>.
6113 <tag>1000-59999:</tag>
6116 Dynamically allocated user accounts. By default
6117 <prgn>adduser</prgn> will choose UIDs and GIDs for
6118 user accounts in this range, though
6119 <file>adduser.conf</file> may be used to modify this
6124 <tag>60000-64999:</tag>
6127 Globally allocated by the Debian project, but only
6128 created on demand. The ids are allocated centrally
6129 and statically, but the actual accounts are only
6130 created on users' systems on demand.
6134 These ids are for packages which are obscure or
6135 which require many statically-allocated ids. These
6136 packages should check for and create the accounts in
6137 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6138 <prgn>adduser</prgn> if it has this facility) if
6139 necessary. Packages which are likely to require
6140 further allocations should have a "hole" left after
6141 them in the allocation, to give them room to
6146 <tag>65000-65533:</tag>
6154 User <tt>nobody</tt>. The corresponding gid refers
6155 to the group <tt>nogroup</tt>.
6162 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6163 not</em> be used, because it is the error return
6172 <sect id="sysvinit">
6173 <heading>System run levels and <file>init.d</file> scripts</heading>
6175 <sect1 id="/etc/init.d">
6176 <heading>Introduction</heading>
6179 The <file>/etc/init.d</file> directory contains the scripts
6180 executed by <prgn>init</prgn> at boot time and when the
6181 init state (or "runlevel") is changed (see <manref
6182 name="init" section="8">).
6186 There are at least two different, yet functionally
6187 equivalent, ways of handling these scripts. For the sake
6188 of simplicity, this document describes only the symbolic
6189 link method. However, it must not be assumed by maintainer
6190 scripts that this method is being used, and any automated
6191 manipulation of the various runlevel behaviors by
6192 maintainer scripts must be performed using
6193 <prgn>update-rc.d</prgn> as described below and not by
6194 manually installing or removing symlinks. For information
6195 on the implementation details of the other method,
6196 implemented in the <tt>file-rc</tt> package, please refer
6197 to the documentation of that package.
6201 These scripts are referenced by symbolic links in the
6202 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6203 runlevels, <prgn>init</prgn> looks in the directory
6204 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6205 execute, where <tt><var>n</var></tt> is the runlevel that
6206 is being changed to, or <tt>S</tt> for the boot-up
6211 The names of the links all have the form
6212 <file>S<var>mm</var><var>script</var></file> or
6213 <file>K<var>mm</var><var>script</var></file> where
6214 <var>mm</var> is a two-digit number and <var>script</var>
6215 is the name of the script (this should be the same as the
6216 name of the actual script in <file>/etc/init.d</file>).
6220 When <prgn>init</prgn> changes runlevel first the targets
6221 of the links whose names start with a <tt>K</tt> are
6222 executed, each with the single argument <tt>stop</tt>,
6223 followed by the scripts prefixed with an <tt>S</tt>, each
6224 with the single argument <tt>start</tt>. (The links are
6225 those in the <file>/etc/rc<var>n</var>.d</file> directory
6226 corresponding to the new runlevel.) The <tt>K</tt> links
6227 are responsible for killing services and the <tt>S</tt>
6228 link for starting services upon entering the runlevel.
6232 For example, if we are changing from runlevel 2 to
6233 runlevel 3, init will first execute all of the <tt>K</tt>
6234 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6235 all of the <tt>S</tt> prefixed scripts in that directory.
6236 The links starting with <tt>K</tt> will cause the
6237 referred-to file to be executed with an argument of
6238 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6243 The two-digit number <var>mm</var> is used to determine
6244 the order in which to run the scripts: low-numbered links
6245 have their scripts run first. For example, the
6246 <tt>K20</tt> scripts will be executed before the
6247 <tt>K30</tt> scripts. This is used when a certain service
6248 must be started before another. For example, the name
6249 server <prgn>bind</prgn> might need to be started before
6250 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6251 can set up its access lists. In this case, the script
6252 that starts <prgn>bind</prgn> would have a lower number
6253 than the script that starts <prgn>inn</prgn> so that it
6255 <example compact="compact">
6262 The two runlevels 0 (halt) and 6 (reboot) are slightly
6263 different. In these runlevels, the links with an
6264 <tt>S</tt> prefix are still called after those with a
6265 <tt>K</tt> prefix, but they too are called with the single
6266 argument <tt>stop</tt>.
6270 <sect1 id="writing-init">
6271 <heading>Writing the scripts</heading>
6274 Packages that include daemons for system services should
6275 place scripts in <file>/etc/init.d</file> to start or stop
6276 services at boot time or during a change of runlevel.
6277 These scripts should be named
6278 <file>/etc/init.d/<var>package</var></file>, and they should
6279 accept one argument, saying what to do:
6282 <tag><tt>start</tt></tag>
6283 <item>start the service,</item>
6285 <tag><tt>stop</tt></tag>
6286 <item>stop the service,</item>
6288 <tag><tt>restart</tt></tag>
6289 <item>stop and restart the service if it's already running,
6290 otherwise start the service</item>
6292 <tag><tt>reload</tt></tag>
6293 <item><p>cause the configuration of the service to be
6294 reloaded without actually stopping and restarting
6297 <tag><tt>force-reload</tt></tag>
6298 <item>cause the configuration to be reloaded if the
6299 service supports this, otherwise restart the
6303 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6304 <tt>force-reload</tt> options should be supported by all
6305 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6310 The <file>init.d</file> scripts must ensure that they will
6311 behave sensibly (i.e., returning success and not starting
6312 multiple copies of a service) if invoked with <tt>start</tt>
6313 when the service is already running, or with <tt>stop</tt>
6314 when it isn't, and that they don't kill unfortunately-named
6315 user processes. The best way to achieve this is usually to
6316 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6321 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6322 scripts. Writing correct <file>init.d</file> scripts requires
6323 accepting various error exit statuses when daemons are already
6324 running or already stopped without aborting
6325 the <file>init.d</file> script, and common <file>init.d</file>
6326 function libraries are not safe to call with <tt>set -e</tt>
6328 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6329 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6330 in effect and echoing status messages to the console fails,
6332 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6333 to not use <tt>set -e</tt> and instead check the result of
6334 each command separately.
6338 If a service reloads its configuration automatically (as
6339 in the case of <prgn>cron</prgn>, for example), the
6340 <tt>reload</tt> option of the <file>init.d</file> script
6341 should behave as if the configuration has been reloaded
6346 The <file>/etc/init.d</file> scripts must be treated as
6347 configuration files, either (if they are present in the
6348 package, that is, in the .deb file) by marking them as
6349 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6350 by managing them correctly in the maintainer scripts (see
6351 <ref id="config-files">). This is important since we want
6352 to give the local system administrator the chance to adapt
6353 the scripts to the local system, e.g., to disable a
6354 service without de-installing the package, or to specify
6355 some special command line options when starting a service,
6356 while making sure their changes aren't lost during the next
6361 These scripts should not fail obscurely when the
6362 configuration files remain but the package has been
6363 removed, as configuration files remain on the system after
6364 the package has been removed. Only when <prgn>dpkg</prgn>
6365 is executed with the <tt>--purge</tt> option will
6366 configuration files be removed. In particular, as the
6367 <file>/etc/init.d/<var>package</var></file> script itself is
6368 usually a <tt>conffile</tt>, it will remain on the system
6369 if the package is removed but not purged. Therefore, you
6370 should include a <tt>test</tt> statement at the top of the
6372 <example compact="compact">
6373 test -f <var>program-executed-later-in-script</var> || exit 0
6378 Often there are some variables in the <file>init.d</file>
6379 scripts whose values control the behavior of the scripts,
6380 and which a system administrator is likely to want to
6381 change. As the scripts themselves are frequently
6382 <tt>conffile</tt>s, modifying them requires that the
6383 administrator merge in their changes each time the package
6384 is upgraded and the <tt>conffile</tt> changes. To ease
6385 the burden on the system administrator, such configurable
6386 values should not be placed directly in the script.
6387 Instead, they should be placed in a file in
6388 <file>/etc/default</file>, which typically will have the same
6389 base name as the <file>init.d</file> script. This extra file
6390 should be sourced by the script when the script runs. It
6391 must contain only variable settings and comments in SUSv3
6392 <prgn>sh</prgn> format. It may either be a
6393 <tt>conffile</tt> or a configuration file maintained by
6394 the package maintainer scripts. See <ref id="config-files">
6399 To ensure that vital configurable values are always
6400 available, the <file>init.d</file> script should set default
6401 values for each of the shell variables it uses, either
6402 before sourcing the <file>/etc/default/</file> file or
6403 afterwards using something like the <tt>:
6404 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6405 script must behave sensibly and not fail if the
6406 <file>/etc/default</file> file is deleted.
6410 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6411 as temporary filesystems<footnote>
6412 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6413 options in <file>/etc/default/rcS</file>.
6414 </footnote>, so the <file>init.d</file> scripts must handle this
6415 correctly. This will typically amount to creating any required
6416 subdirectories dynamically when the <file>init.d</file> script
6417 is run, rather than including them in the package and relying on
6418 <prgn>dpkg</prgn> to create them.
6423 <heading>Interfacing with the initscript system</heading>
6426 Maintainers should use the abstraction layer provided by
6427 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6428 programs to deal with initscripts in their packages'
6429 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6430 and <prgn>postrm</prgn>.
6434 Directly managing the /etc/rc?.d links and directly
6435 invoking the <file>/etc/init.d/</file> initscripts should
6436 be done only by packages providing the initscript
6437 subsystem (such as <prgn>sysv-rc</prgn> and
6438 <prgn>file-rc</prgn>).
6442 <heading>Managing the links</heading>
6445 The program <prgn>update-rc.d</prgn> is provided for
6446 package maintainers to arrange for the proper creation and
6447 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6448 or their functional equivalent if another method is being
6449 used. This may be used by maintainers in their packages'
6450 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6454 You must not include any <file>/etc/rc<var>n</var>.d</file>
6455 symbolic links in the actual archive or manually create or
6456 remove the symbolic links in maintainer scripts; you must
6457 use the <prgn>update-rc.d</prgn> program instead. (The
6458 former will fail if an alternative method of maintaining
6459 runlevel information is being used.) You must not include
6460 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6461 in the archive either. (Only the <tt>sysvinit</tt>
6466 By default <prgn>update-rc.d</prgn> will start services in
6467 each of the multi-user state runlevels (2, 3, 4, and 5)
6468 and stop them in the halt runlevel (0), the single-user
6469 runlevel (1) and the reboot runlevel (6). The system
6470 administrator will have the opportunity to customize
6471 runlevels by simply adding, moving, or removing the
6472 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6473 symbolic links are being used, or by modifying
6474 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6479 To get the default behavior for your package, put in your
6480 <prgn>postinst</prgn> script
6481 <example compact="compact">
6482 update-rc.d <var>package</var> defaults
6484 and in your <prgn>postrm</prgn>
6485 <example compact="compact">
6486 if [ "$1" = purge ]; then
6487 update-rc.d <var>package</var> remove
6489 </example>. Note that if your package changes runlevels
6490 or priority, you may have to remove and recreate the links,
6491 since otherwise the old links may persist. Refer to the
6492 documentation of <prgn>update-rc.d</prgn>.
6496 This will use a default sequence number of 20. If it does
6497 not matter when or in which order the <file>init.d</file>
6498 script is run, use this default. If it does, then you
6499 should talk to the maintainer of the <prgn>sysvinit</prgn>
6500 package or post to <tt>debian-devel</tt>, and they will
6501 help you choose a number.
6505 For more information about using <tt>update-rc.d</tt>,
6506 please consult its man page <manref name="update-rc.d"
6512 <heading>Running initscripts</heading>
6514 The program <prgn>invoke-rc.d</prgn> is provided to make
6515 it easier for package maintainers to properly invoke an
6516 initscript, obeying runlevel and other locally-defined
6517 constraints that might limit a package's right to start,
6518 stop and otherwise manage services. This program may be
6519 used by maintainers in their packages' scripts.
6523 The package maintainer scripts must use
6524 <prgn>invoke-rc.d</prgn> to invoke the
6525 <file>/etc/init.d/*</file> initscripts, instead of
6526 calling them directly.
6530 By default, <prgn>invoke-rc.d</prgn> will pass any
6531 action requests (start, stop, reload, restart...) to the
6532 <file>/etc/init.d</file> script, filtering out requests
6533 to start or restart a service out of its intended
6538 Most packages will simply need to change:
6539 <example compact="compact">/etc/init.d/<package>
6540 <action></example> in their <prgn>postinst</prgn>
6541 and <prgn>prerm</prgn> scripts to:
6542 <example compact="compact">
6543 if which invoke-rc.d >/dev/null 2>&1; then
6544 invoke-rc.d <var>package</var> <action>
6546 /etc/init.d/<var>package</var> <action>
6552 A package should register its initscript services using
6553 <prgn>update-rc.d</prgn> before it tries to invoke them
6554 using <prgn>invoke-rc.d</prgn>. Invocation of
6555 unregistered services may fail.
6559 For more information about using
6560 <prgn>invoke-rc.d</prgn>, please consult its man page
6561 <manref name="invoke-rc.d" section="8">.
6567 <heading>Boot-time initialization</heading>
6570 There used to be another directory, <file>/etc/rc.boot</file>,
6571 which contained scripts which were run once per machine
6572 boot. This has been deprecated in favour of links from
6573 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6574 described in <ref id="/etc/init.d">. Packages must not
6575 place files in <file>/etc/rc.boot</file>.
6580 <heading>Example</heading>
6583 An example on which you can base your
6584 <file>/etc/init.d</file> scripts is found in
6585 <file>/etc/init.d/skeleton</file>.
6592 <heading>Console messages from <file>init.d</file> scripts</heading>
6595 This section describes the formats to be used for messages
6596 written to standard output by the <file>/etc/init.d</file>
6597 scripts. The intent is to improve the consistency of
6598 Debian's startup and shutdown look and feel. For this
6599 reason, please look very carefully at the details. We want
6600 the messages to have the same format in terms of wording,
6601 spaces, punctuation and case of letters.
6605 Here is a list of overall rules that should be used for
6606 messages generated by <file>/etc/init.d</file> scripts.
6612 The message should fit in one line (fewer than 80
6613 characters), start with a capital letter and end with
6614 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6618 If the script is performing some time consuming task in
6619 the background (not merely starting or stopping a
6620 program, for instance), an ellipsis (three dots:
6621 <tt>...</tt>) should be output to the screen, with no
6622 leading or tailing whitespace or line feeds.
6626 The messages should appear as if the computer is telling
6627 the user what it is doing (politely :-), but should not
6628 mention "it" directly. For example, instead of:
6629 <example compact="compact">
6630 I'm starting network daemons: nfsd mountd.
6632 the message should say
6633 <example compact="compact">
6634 Starting network daemons: nfsd mountd.
6641 <tt>init.d</tt> script should use the following standard
6642 message formats for the situations enumerated below.
6648 <p>When daemons are started</p>
6651 If the script starts one or more daemons, the output
6652 should look like this (a single line, no leading
6654 <example compact="compact">
6655 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6657 The <var>description</var> should describe the
6658 subsystem the daemon or set of daemons are part of,
6659 while <var>daemon-1</var> up to <var>daemon-n</var>
6660 denote each daemon's name (typically the file name of
6665 For example, the output of <file>/etc/init.d/lpd</file>
6667 <example compact="compact">
6668 Starting printer spooler: lpd.
6673 This can be achieved by saying
6674 <example compact="compact">
6675 echo -n "Starting printer spooler: lpd"
6676 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6679 in the script. If there are more than one daemon to
6680 start, the output should look like this:
6681 <example compact="compact">
6682 echo -n "Starting remote file system services:"
6683 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6684 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6685 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6688 This makes it possible for the user to see what is
6689 happening and when the final daemon has been started.
6690 Care should be taken in the placement of white spaces:
6691 in the example above the system administrators can
6692 easily comment out a line if they don't want to start
6693 a specific daemon, while the displayed message still
6699 <p>When a system parameter is being set</p>
6702 If you have to set up different system parameters
6703 during the system boot, you should use this format:
6704 <example compact="compact">
6705 Setting <var>parameter</var> to "<var>value</var>".
6710 You can use a statement such as the following to get
6712 <example compact="compact">
6713 echo "Setting DNS domainname to \"$domainname\"."
6718 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6719 for the left and right quotation marks. A grave accent
6720 (<tt>`</tt>) is not a quote character; neither is an
6721 apostrophe (<tt>'</tt>).
6726 <p>When a daemon is stopped or restarted</p>
6729 When you stop or restart a daemon, you should issue a
6730 message identical to the startup message, except that
6731 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6732 or <tt>Restarting</tt> respectively.
6736 For example, stopping the printer daemon will look like
6738 <example compact="compact">
6739 Stopping printer spooler: lpd.
6745 <p>When something is executed</p>
6748 There are several examples where you have to run a
6749 program at system startup or shutdown to perform a
6750 specific task, for example, setting the system's clock
6751 using <prgn>netdate</prgn> or killing all processes
6752 when the system shuts down. Your message should look
6754 <example compact="compact">
6755 Doing something very useful...done.
6757 You should print the <tt>done.</tt> immediately after
6758 the job has been completed, so that the user is
6759 informed why they have to wait. You can get this
6761 <example compact="compact">
6762 echo -n "Doing something very useful..."
6771 <p>When the configuration is reloaded</p>
6774 When a daemon is forced to reload its configuration
6775 files you should use the following format:
6776 <example compact="compact">
6777 Reloading <var>description</var> configuration...done.
6779 where <var>description</var> is the same as in the
6780 daemon starting message.
6788 <heading>Cron jobs</heading>
6791 Packages must not modify the configuration file
6792 <file>/etc/crontab</file>, and they must not modify the files in
6793 <file>/var/spool/cron/crontabs</file>.</p>
6796 If a package wants to install a job that has to be executed
6797 via cron, it should place a file with the name of the
6798 package in one or more of the following directories:
6799 <example compact="compact">
6805 As these directory names imply, the files within them are
6806 executed on an hourly, daily, weekly, or monthly basis,
6807 respectively. The exact times are listed in
6808 <file>/etc/crontab</file>.</p>
6811 All files installed in any of these directories must be
6812 scripts (e.g., shell scripts or Perl scripts) so that they
6813 can easily be modified by the local system administrator.
6814 In addition, they must be treated as configuration files.
6818 If a certain job has to be executed at some other frequency or
6819 at a specific time, the package should install a file
6820 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6821 same syntax as <file>/etc/crontab</file> and is processed by
6822 <prgn>cron</prgn> automatically. The file must also be
6823 treated as a configuration file. (Note that entries in the
6824 <file>/etc/cron.d</file> directory are not handled by
6825 <prgn>anacron</prgn>. Thus, you should only use this
6826 directory for jobs which may be skipped if the system is not
6829 Unlike <file>crontab</file> files described in the IEEE Std
6830 1003.1-2008 (POSIX.1) available from
6831 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6832 name="The Open Group">, the files in
6833 <file>/etc/cron.d</file> and the file
6834 <file>/etc/crontab</file> have seven fields; namely:
6836 <item>Minute [0,59]</item>
6837 <item>Hour [0,23]</item>
6838 <item>Day of the month [1,31]</item>
6839 <item>Month of the year [1,12]</item>
6840 <item>Day of the week ([0,6] with 0=Sunday)</item>
6841 <item>Username</item>
6842 <item>Command to be run</item>
6844 Ranges of numbers are allowed. Ranges are two numbers
6845 separated with a hyphen. The specified range is inclusive.
6846 Lists are allowed. A list is a set of numbers (or ranges)
6847 separated by commas. Step values can be used in conjunction
6852 The scripts or <tt>crontab</tt> entries in these directories should
6853 check if all necessary programs are installed before they
6854 try to execute them. Otherwise, problems will arise when a
6855 package was removed but not purged since configuration files
6856 are kept on the system in this situation.
6860 Any <tt>cron</tt> daemon must provide
6861 <file>/usr/bin/crontab</file> and support normal
6862 <tt>crontab</tt> entries as specified in POSIX. The daemon
6863 must also support names for days and months, ranges, and
6864 step values. It has to support <file>/etc/crontab</file>,
6865 and correctly execute the scripts in
6866 <file>/etc/cron.d</file>. The daemon must also correctly
6868 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6873 <heading>Menus</heading>
6876 The Debian <tt>menu</tt> package provides a standard
6877 interface between packages providing applications and
6878 <em>menu programs</em> (either X window managers or
6879 text-based menu programs such as <prgn>pdmenu</prgn>).
6883 All packages that provide applications that need not be
6884 passed any special command line arguments for normal
6885 operation should register a menu entry for those
6886 applications, so that users of the <tt>menu</tt> package
6887 will automatically get menu entries in their window
6888 managers, as well in shells like <tt>pdmenu</tt>.
6892 Menu entries should follow the current menu policy.
6896 The menu policy can be found in the <tt>menu-policy</tt>
6897 files in the <tt>debian-policy</tt> package.
6898 It is also available from the Debian web mirrors at
6899 <tt><url name="/doc/packaging-manuals/menu-policy/"
6900 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6904 Please also refer to the <em>Debian Menu System</em>
6905 documentation that comes with the <package>menu</package>
6906 package for information about how to register your
6912 <heading>Multimedia handlers</heading>
6915 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6916 is a mechanism for encoding files and data streams and
6917 providing meta-information about them, in particular their
6918 type (e.g. audio or video) and format (e.g. PNG, HTML,
6923 Registration of MIME type handlers allows programs like mail
6924 user agents and web browsers to invoke these handlers to
6925 view, edit or display MIME types they don't support directly.
6929 Packages which provide the ability to view/show/play,
6930 compose, edit or print MIME types should register themselves
6931 as such following the current MIME support policy.
6935 The MIME support policy can be found in the <tt>mime-policy</tt>
6936 files in the <tt>debian-policy</tt> package.
6937 It is also available from the Debian web mirrors at
6938 <tt><url name="/doc/packaging-manuals/mime-policy/"
6939 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6945 <heading>Keyboard configuration</heading>
6948 To achieve a consistent keyboard configuration so that all
6949 applications interpret a keyboard event the same way, all
6950 programs in the Debian distribution must be configured to
6951 comply with the following guidelines.
6955 The following keys must have the specified interpretations:
6958 <tag><tt><--</tt></tag>
6959 <item>delete the character to the left of the cursor</item>
6961 <tag><tt>Delete</tt></tag>
6962 <item>delete the character to the right of the cursor</item>
6964 <tag><tt>Control+H</tt></tag>
6965 <item>emacs: the help prefix</item>
6968 The interpretation of any keyboard events should be
6969 independent of the terminal that is used, be it a virtual
6970 console, an X terminal emulator, an rlogin/telnet session,
6975 The following list explains how the different programs
6976 should be set up to achieve this:
6982 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6986 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6990 X translations are set up to make
6991 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6992 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6993 is the vt220 escape code for the "delete character"
6994 key). This must be done by loading the X resources
6995 using <prgn>xrdb</prgn> on all local X displays, not
6996 using the application defaults, so that the
6997 translation resources used correspond to the
6998 <prgn>xmodmap</prgn> settings.
7002 The Linux console is configured to make
7003 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7004 generate <tt>ESC [ 3 ~</tt>.
7008 X applications are configured so that <tt><</tt>
7009 deletes left, and <tt>Delete</tt> deletes right. Motif
7010 applications already work like this.
7014 Terminals should have <tt>stty erase ^?</tt> .
7018 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7019 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7020 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7024 Emacs is programmed to map <tt>KB_Backspace</tt> or
7025 the <tt>stty erase</tt> character to
7026 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7027 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7028 <tt>^H</tt> to <tt>help</tt> as always.
7032 Other applications use the <tt>stty erase</tt>
7033 character and <tt>kdch1</tt> for the two delete keys,
7034 with ASCII DEL being "delete previous character" and
7035 <tt>kdch1</tt> being "delete character under
7043 This will solve the problem except for the following
7050 Some terminals have a <tt><--</tt> key that cannot
7051 be made to produce anything except <tt>^H</tt>. On
7052 these terminals Emacs help will be unavailable on
7053 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7054 character takes precedence in Emacs, and has been set
7055 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7056 available) can be used instead.
7060 Some operating systems use <tt>^H</tt> for <tt>stty
7061 erase</tt>. However, modern telnet versions and all
7062 rlogin versions propagate <tt>stty</tt> settings, and
7063 almost all UNIX versions honour <tt>stty erase</tt>.
7064 Where the <tt>stty</tt> settings are not propagated
7065 correctly, things can be made to work by using
7066 <tt>stty</tt> manually.
7070 Some systems (including previous Debian versions) use
7071 <prgn>xmodmap</prgn> to arrange for both
7072 <tt><--</tt> and <tt>Delete</tt> to generate
7073 <tt>KB_Delete</tt>. We can change the behavior of
7074 their X clients using the same X resources that we use
7075 to do it for our own clients, or configure our clients
7076 using their resources when things are the other way
7077 around. On displays configured like this
7078 <tt>Delete</tt> will not work, but <tt><--</tt>
7083 Some operating systems have different <tt>kdch1</tt>
7084 settings in their <tt>terminfo</tt> database for
7085 <tt>xterm</tt> and others. On these systems the
7086 <tt>Delete</tt> key will not work correctly when you
7087 log in from a system conforming to our policy, but
7088 <tt><--</tt> will.
7095 <heading>Environment variables</heading>
7098 A program must not depend on environment variables to get
7099 reasonable defaults. (That's because these environment
7100 variables would have to be set in a system-wide
7101 configuration file like <file>/etc/profile</file>, which is not
7102 supported by all shells.)
7106 If a program usually depends on environment variables for its
7107 configuration, the program should be changed to fall back to
7108 a reasonable default configuration if these environment
7109 variables are not present. If this cannot be done easily
7110 (e.g., if the source code of a non-free program is not
7111 available), the program must be replaced by a small
7112 "wrapper" shell script which sets the environment variables
7113 if they are not already defined, and calls the original program.
7117 Here is an example of a wrapper script for this purpose:
7119 <example compact="compact">
7121 BAR=${BAR:-/var/lib/fubar}
7123 exec /usr/lib/foo/foo "$@"
7128 Furthermore, as <file>/etc/profile</file> is a configuration
7129 file of the <prgn>base-files</prgn> package, other packages must
7130 not put any environment variables or other commands into that
7135 <sect id="doc-base">
7136 <heading>Registering Documents using doc-base</heading>
7139 The <package>doc-base</package> package implements a
7140 flexible mechanism for handling and presenting
7141 documentation. The recommended practice is for every Debian
7142 package that provides online documentation (other than just
7143 manual pages) to register these documents with
7144 <package>doc-base</package> by installing a
7145 <package>doc-base</package> control file via the
7146 <prgn/install-docs/ script at installation time and
7147 de-register the manuals again when the package is removed.
7150 Please refer to the documentation that comes with the
7151 <package>doc-base</package> package for information and
7160 <heading>Files</heading>
7162 <sect id="binaries">
7163 <heading>Binaries</heading>
7166 Two different packages must not install programs with
7167 different functionality but with the same filenames. (The
7168 case of two programs having the same functionality but
7169 different implementations is handled via "alternatives" or
7170 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7171 <ref id="conflicts"> respectively.) If this case happens,
7172 one of the programs must be renamed. The maintainers should
7173 report this to the <tt>debian-devel</tt> mailing list and
7174 try to find a consensus about which program will have to be
7175 renamed. If a consensus cannot be reached, <em>both</em>
7176 programs must be renamed.
7180 By default, when a package is being built, any binaries
7181 created should include debugging information, as well as
7182 being compiled with optimization. You should also turn on
7183 as many reasonable compilation warnings as possible; this
7184 makes life easier for porters, who can then look at build
7185 logs for possible problems. For the C programming language,
7186 this means the following compilation parameters should be
7188 <example compact="compact">
7190 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7192 INSTALL = install -s # (or use strip on the files in debian/tmp)
7197 Note that by default all installed binaries should be stripped,
7198 either by using the <tt>-s</tt> flag to
7199 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7200 the binaries after they have been copied into
7201 <file>debian/tmp</file> but before the tree is made into a
7206 Although binaries in the build tree should be compiled with
7207 debugging information by default, it can often be difficult to
7208 debug programs if they are also subjected to compiler
7209 optimization. For this reason, it is recommended to support the
7210 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7211 (see <ref id="debianrules-options">). This variable can contain
7212 several flags to change how a package is compiled and built.
7216 It is up to the package maintainer to decide what
7217 compilation options are best for the package. Certain
7218 binaries (such as computationally-intensive programs) will
7219 function better with certain flags (<tt>-O3</tt>, for
7220 example); feel free to use them. Please use good judgment
7221 here. Don't use flags for the sake of it; only use them
7222 if there is good reason to do so. Feel free to override
7223 the upstream author's ideas about which compilation
7224 options are best: they are often inappropriate for our
7230 <sect id="libraries">
7231 <heading>Libraries</heading>
7234 If the package is <strong>architecture: any</strong>, then
7235 the shared library compilation and linking flags must have
7236 <tt>-fPIC</tt>, or the package shall not build on some of
7237 the supported architectures<footnote>
7239 If you are using GCC, <tt>-fPIC</tt> produces code with
7240 relocatable position independent code, which is required for
7241 most architectures to create a shared library, with i386 and
7242 perhaps some others where non position independent code is
7243 permitted in a shared library.
7246 Position independent code may have a performance penalty,
7247 especially on <tt>i386</tt>. However, in most cases the
7248 speed penalty must be measured against the memory wasted on
7249 the few architectures where non position independent code is
7252 </footnote>. Any exception to this rule must be discussed on
7253 the mailing list <em>debian-devel@lists.debian.org</em>, and
7254 a rough consensus obtained. The reasons for not compiling
7255 with <tt>-fPIC</tt> flag must be recorded in the file
7256 <tt>README.Debian</tt>, and care must be taken to either
7257 restrict the architecture or arrange for <tt>-fPIC</tt> to
7258 be used on architectures where it is required.<footnote>
7260 Some of the reasons why this might be required is if the
7261 library contains hand crafted assembly code that is not
7262 relocatable, the speed penalty is excessive for compute
7263 intensive libs, and similar reasons.
7268 As to the static libraries, the common case is not to have
7269 relocatable code, since there is no benefit, unless in specific
7270 cases; therefore the static version must not be compiled
7271 with the <tt>-fPIC</tt> flag. Any exception to this rule
7272 should be discussed on the mailing list
7273 <em>debian-devel@lists.debian.org</em>, and the reasons for
7274 compiling with the <tt>-fPIC</tt> flag must be recorded in
7275 the file <tt>README.Debian</tt>. <footnote>
7277 Some of the reasons for linking static libraries with
7278 the <tt>-fPIC</tt> flag are if, for example, one needs a
7279 Perl API for a library that is under rapid development,
7280 and has an unstable API, so shared libraries are
7281 pointless at this phase of the library's development. In
7282 that case, since Perl needs a library with relocatable
7283 code, it may make sense to create a static library with
7284 relocatable code. Another reason cited is if you are
7285 distilling various libraries into a common shared
7286 library, like <tt>mklibs</tt> does in the Debian
7292 In other words, if both a shared and a static library is
7293 being built, each source unit (<tt>*.c</tt>, for example,
7294 for C files) will need to be compiled twice, for the normal
7298 You must specify the gcc option <tt>-D_REENTRANT</tt>
7299 when building a library (either static or shared) to make
7300 the library compatible with LinuxThreads.
7304 Although not enforced by the build tools, shared libraries
7305 must be linked against all libraries that they use symbols from
7306 in the same way that binaries are. This ensures the correct
7307 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7308 system and guarantees that all libraries can be safely opened
7309 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7310 option <tt>-Wl,-z,defs</tt> when building a shared library.
7311 Since this option enforces symbol resolution at build time,
7312 a missing library reference will be caught early as a fatal
7317 All installed shared libraries should be stripped with
7318 <example compact="compact">
7319 strip --strip-unneeded <var>your-lib</var>
7321 (The option <tt>--strip-unneeded</tt> makes
7322 <prgn>strip</prgn> remove only the symbols which aren't
7323 needed for relocation processing.) Shared libraries can
7324 function perfectly well when stripped, since the symbols for
7325 dynamic linking are in a separate part of the ELF object
7327 You might also want to use the options
7328 <tt>--remove-section=.comment</tt> and
7329 <tt>--remove-section=.note</tt> on both shared libraries
7330 and executables, and <tt>--strip-debug</tt> on static
7336 Note that under some circumstances it may be useful to
7337 install a shared library unstripped, for example when
7338 building a separate package to support debugging.
7342 Shared object files (often <file>.so</file> files) that are not
7343 public libraries, that is, they are not meant to be linked
7344 to by third party executables (binaries of other packages),
7345 should be installed in subdirectories of the
7346 <file>/usr/lib</file> directory. Such files are exempt from the
7347 rules that govern ordinary shared libraries, except that
7348 they must not be installed executable and should be
7350 A common example are the so-called "plug-ins",
7351 internal shared objects that are dynamically loaded by
7352 programs using <manref name="dlopen" section="3">.
7357 Packages that use <prgn>libtool</prgn> to create and install
7358 their shared libraries install a file containing additional
7359 metadata (ending in <file>.la</file>) alongside the library.
7360 For public libraries intended for use by other packages, these
7361 files normally should not be included in the Debian package,
7362 since the information they include is not necessary to link with
7363 the shared library on Debian and can add unnecessary additional
7364 dependencies to other programs or libraries.<footnote>
7365 These files store, among other things, all libraries on which
7366 that shared library depends. Unfortunately, if
7367 the <file>.la</file> file is present and contains that
7368 dependency information, using <prgn>libtool</prgn> when
7369 linking against that library will cause the resulting program
7370 or library to be linked against those dependencies as well,
7371 even if this is unnecessary. This can create unneeded
7372 dependencies on shared library packages that would otherwise
7373 be hidden behind the library ABI, and can make library
7374 transitions to new SONAMEs unnecessarily complicated and
7375 difficult to manage.
7377 If the <file>.la</file> file is required for that library (if,
7378 for instance, it's loaded via <tt>libltdl</tt> in a way that
7379 requires that meta-information), the <tt>dependency_libs</tt>
7380 setting in the <file>.la</file> file should normally be set to
7381 the empty string. If the shared library development package has
7382 historically included the <file>.la</file>, it must be retained
7383 in the development package (with <tt>dependency_libs</tt>
7384 emptied) until all libraries that depend on it have removed or
7385 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7386 files to prevent linking with those other libraries
7387 using <prgn>libtool</prgn> from failing.
7391 If the <file>.la</file> must be included, it should be included
7392 in the development (<tt>-dev</tt>) package, unless the library
7393 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7394 library. If it is intended for use with <tt>libltdl</tt>,
7395 the <file>.la</file> files must go in the run-time library
7400 These requirements for handling of <file>.la</file> files do not
7401 apply to loadable modules or libraries not installed in
7402 directories searched by default by the dynamic linker. Packages
7403 installing loadable modules will frequently need to install
7404 the <file>.la</file> files alongside the modules so that they
7405 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7406 does not need to be modified for libraries or modules that are
7407 not installed in directories searched by the dynamic linker by
7408 default and not intended for use by other packages.
7412 You must make sure that you use only released versions of
7413 shared libraries to build your packages; otherwise other
7414 users will not be able to run your binaries
7415 properly. Producing source packages that depend on
7416 unreleased compilers is also usually a bad
7423 <heading>Shared libraries</heading>
7425 This section has moved to <ref id="sharedlibs">.
7431 <heading>Scripts</heading>
7434 All command scripts, including the package maintainer
7435 scripts inside the package and used by <prgn>dpkg</prgn>,
7436 should have a <tt>#!</tt> line naming the shell to be used
7441 In the case of Perl scripts this should be
7442 <tt>#!/usr/bin/perl</tt>.
7446 When scripts are installed into a directory in the system
7447 PATH, the script name should not include an extension such
7448 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7449 language currently used to implement it.
7452 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7453 <file>init.d</file> scripts should almost certainly start
7454 with <tt>set -e</tt> so that errors are detected.
7455 <file>init.d</file> scripts are something of a special case, due
7456 to how frequently they need to call commands that are allowed to
7457 fail, and it may instead be easier to check the exit status of
7458 commands directly. See <ref id="writing-init"> for more
7459 information about writing <file>init.d</file> scripts.
7462 Every script should use <tt>set -e</tt> or check the exit status
7463 of <em>every</em> command.
7466 Scripts may assume that <file>/bin/sh</file> implements the
7467 SUSv3 Shell Command Language<footnote>
7468 Single UNIX Specification, version 3, which is also IEEE
7469 1003.1-2004 (POSIX), and is available on the World Wide Web
7470 from <url id="http://www.unix.org/version3/online.html"
7471 name="The Open Group"> after free
7472 registration.</footnote>
7473 plus the following additional features not mandated by
7475 These features are in widespread use in the Linux community
7476 and are implemented in all of bash, dash, and ksh, the most
7477 common shells users may wish to use as <file>/bin/sh</file>.
7480 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7481 must not generate a newline.</item>
7482 <item><tt>test</tt>, if implemented as a shell built-in, must
7483 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7485 <item><tt>local</tt> to create a scoped variable must be
7486 supported, including listing multiple variables in a single
7487 local command and assigning a value to a variable at the
7488 same time as localizing it. <tt>local</tt> may or
7489 may not preserve the variable value from an outer scope if
7490 no assignment is present. Uses such as:
7494 # ... use a, b, c, d ...
7497 must be supported and must set the value of <tt>c</tt> to
7501 If a shell script requires non-SUSv3 features from the shell
7502 interpreter other than those listed above, the appropriate shell
7503 must be specified in the first line of the script (e.g.,
7504 <tt>#!/bin/bash</tt>) and the package must depend on the package
7505 providing the shell (unless the shell package is marked
7506 "Essential", as in the case of <prgn>bash</prgn>).
7510 You may wish to restrict your script to SUSv3 features plus the
7511 above set when possible so that it may use <file>/bin/sh</file>
7512 as its interpreter. If your script works with <prgn>dash</prgn>
7513 (originally called <prgn>ash</prgn>), it probably complies with
7514 the above requirements, but if you are in doubt, use
7515 <file>/bin/bash</file>.
7519 Perl scripts should check for errors when making any
7520 system calls, including <tt>open</tt>, <tt>print</tt>,
7521 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7525 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7526 scripting languages. See <em>Csh Programming Considered
7527 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7528 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7529 If an upstream package comes with <prgn>csh</prgn> scripts
7530 then you must make sure that they start with
7531 <tt>#!/bin/csh</tt> and make your package depend on the
7532 <prgn>c-shell</prgn> virtual package.
7536 Any scripts which create files in world-writeable
7537 directories (e.g., in <file>/tmp</file>) must use a
7538 mechanism which will fail atomically if a file with the same
7539 name already exists.
7543 The Debian base system provides the <prgn>tempfile</prgn>
7544 and <prgn>mktemp</prgn> utilities for use by scripts for
7551 <heading>Symbolic links</heading>
7554 In general, symbolic links within a top-level directory
7555 should be relative, and symbolic links pointing from one
7556 top-level directory into another should be absolute. (A
7557 top-level directory is a sub-directory of the root
7558 directory <file>/</file>.)
7562 In addition, symbolic links should be specified as short as
7563 possible, i.e., link targets like <file>foo/../bar</file> are
7568 Note that when creating a relative link using
7569 <prgn>ln</prgn> it is not necessary for the target of the
7570 link to exist relative to the working directory you're
7571 running <prgn>ln</prgn> from, nor is it necessary to change
7572 directory to the directory where the link is to be made.
7573 Simply include the string that should appear as the target
7574 of the link (this will be a pathname relative to the
7575 directory in which the link resides) as the first argument
7580 For example, in your <prgn>Makefile</prgn> or
7581 <file>debian/rules</file>, you can do things like:
7582 <example compact="compact">
7583 ln -fs gcc $(prefix)/bin/cc
7584 ln -fs gcc debian/tmp/usr/bin/cc
7585 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7586 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7591 A symbolic link pointing to a compressed file should always
7592 have the same file extension as the referenced file. (For
7593 example, if a file <file>foo.gz</file> is referenced by a
7594 symbolic link, the filename of the link has to end with
7595 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7600 <heading>Device files</heading>
7603 Packages must not include device files or named pipes in the
7608 If a package needs any special device files that are not
7609 included in the base system, it must call
7610 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7611 after notifying the user<footnote>
7612 This notification could be done via a (low-priority)
7613 debconf message, or an echo (printf) statement.
7618 Packages must not remove any device files in the
7619 <prgn>postrm</prgn> or any other script. This is left to the
7620 system administrator.
7624 Debian uses the serial devices
7625 <file>/dev/ttyS*</file>. Programs using the old
7626 <file>/dev/cu*</file> devices should be changed to use
7627 <file>/dev/ttyS*</file>.
7631 Named pipes needed by the package must be created in
7632 the <prgn>postinst</prgn> script<footnote>
7633 It's better to use <prgn>mkfifo</prgn> rather
7634 than <prgn>mknod</prgn> to create named pipes so that
7635 automated checks for packages incorrectly creating device
7636 files with <prgn>mknod</prgn> won't have false positives.
7637 </footnote> and removed in
7638 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7643 <sect id="config-files">
7644 <heading>Configuration files</heading>
7647 <heading>Definitions</heading>
7651 <tag>configuration file</tag>
7653 A file that affects the operation of a program, or
7654 provides site- or host-specific information, or
7655 otherwise customizes the behavior of a program.
7656 Typically, configuration files are intended to be
7657 modified by the system administrator (if needed or
7658 desired) to conform to local policy or to provide
7659 more useful site-specific behavior.
7662 <tag><tt>conffile</tt></tag>
7664 A file listed in a package's <tt>conffiles</tt>
7665 file, and is treated specially by <prgn>dpkg</prgn>
7666 (see <ref id="configdetails">).
7672 The distinction between these two is important; they are
7673 not interchangeable concepts. Almost all
7674 <tt>conffile</tt>s are configuration files, but many
7675 configuration files are not <tt>conffiles</tt>.
7679 As noted elsewhere, <file>/etc/init.d</file> scripts,
7680 <file>/etc/default</file> files, scripts installed in
7681 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7682 configuration installed in <file>/etc/cron.d</file> must be
7683 treated as configuration files. In general, any script that
7684 embeds configuration information is de-facto a configuration
7685 file and should be treated as such.
7690 <heading>Location</heading>
7693 Any configuration files created or used by your package
7694 must reside in <file>/etc</file>. If there are several,
7695 consider creating a subdirectory of <file>/etc</file>
7696 named after your package.
7700 If your package creates or uses configuration files
7701 outside of <file>/etc</file>, and it is not feasible to modify
7702 the package to use <file>/etc</file> directly, put the files
7703 in <file>/etc</file> and create symbolic links to those files
7704 from the location that the package requires.
7709 <heading>Behavior</heading>
7712 Configuration file handling must conform to the following
7714 <list compact="compact">
7716 local changes must be preserved during a package
7720 configuration files must be preserved when the
7721 package is removed, and only deleted when the
7725 Obsolete configuration files without local changes may be
7726 removed by the package during upgrade.
7730 The easy way to achieve this behavior is to make the
7731 configuration file a <tt>conffile</tt>. This is
7732 appropriate only if it is possible to distribute a default
7733 version that will work for most installations, although
7734 some system administrators may choose to modify it. This
7735 implies that the default version will be part of the
7736 package distribution, and must not be modified by the
7737 maintainer scripts during installation (or at any other
7742 In order to ensure that local changes are preserved
7743 correctly, no package may contain or make hard links to
7744 conffiles.<footnote>
7745 Rationale: There are two problems with hard links.
7746 The first is that some editors break the link while
7747 editing one of the files, so that the two files may
7748 unwittingly become unlinked and different. The second
7749 is that <prgn>dpkg</prgn> might break the hard link
7750 while upgrading <tt>conffile</tt>s.
7755 The other way to do it is via the maintainer scripts. In
7756 this case, the configuration file must not be listed as a
7757 <tt>conffile</tt> and must not be part of the package
7758 distribution. If the existence of a file is required for
7759 the package to be sensibly configured it is the
7760 responsibility of the package maintainer to provide
7761 maintainer scripts which correctly create, update and
7762 maintain the file and remove it on purge. (See <ref
7763 id="maintainerscripts"> for more information.) These
7764 scripts must be idempotent (i.e., must work correctly if
7765 <prgn>dpkg</prgn> needs to re-run them due to errors
7766 during installation or removal), must cope with all the
7767 variety of ways <prgn>dpkg</prgn> can call maintainer
7768 scripts, must not overwrite or otherwise mangle the user's
7769 configuration without asking, must not ask unnecessary
7770 questions (particularly during upgrades), and must
7771 otherwise be good citizens.
7775 The scripts are not required to configure every possible
7776 option for the package, but only those necessary to get
7777 the package running on a given system. Ideally the
7778 sysadmin should not have to do any configuration other
7779 than that done (semi-)automatically by the
7780 <prgn>postinst</prgn> script.
7784 A common practice is to create a script called
7785 <file><var>package</var>-configure</file> and have the
7786 package's <prgn>postinst</prgn> call it if and only if the
7787 configuration file does not already exist. In certain
7788 cases it is useful for there to be an example or template
7789 file which the maintainer scripts use. Such files should
7790 be in <file>/usr/share/<var>package</var></file> or
7791 <file>/usr/lib/<var>package</var></file> (depending on whether
7792 they are architecture-independent or not). There should
7793 be symbolic links to them from
7794 <file>/usr/share/doc/<var>package</var>/examples</file> if
7795 they are examples, and should be perfectly ordinary
7796 <prgn>dpkg</prgn>-handled files (<em>not</em>
7797 configuration files).
7801 These two styles of configuration file handling must
7802 not be mixed, for that way lies madness:
7803 <prgn>dpkg</prgn> will ask about overwriting the file
7804 every time the package is upgraded.
7809 <heading>Sharing configuration files</heading>
7812 Packages which specify the same file as a
7813 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7814 with each other. (This is an instance of the general rule
7815 about not sharing files. Note that neither alternatives
7816 nor diversions are likely to be appropriate in this case;
7817 in particular, <prgn>dpkg</prgn> does not handle diverted
7818 <tt>conffile</tt>s well.)
7822 The maintainer scripts must not alter a <tt>conffile</tt>
7823 of <em>any</em> package, including the one the scripts
7828 If two or more packages use the same configuration file
7829 and it is reasonable for both to be installed at the same
7830 time, one of these packages must be defined as
7831 <em>owner</em> of the configuration file, i.e., it will be
7832 the package which handles that file as a configuration
7833 file. Other packages that use the configuration file must
7834 depend on the owning package if they require the
7835 configuration file to operate. If the other package will
7836 use the configuration file if present, but is capable of
7837 operating without it, no dependency need be declared.
7841 If it is desirable for two or more related packages to
7842 share a configuration file <em>and</em> for all of the
7843 related packages to be able to modify that configuration
7844 file, then the following should be done:
7845 <enumlist compact="compact">
7847 One of the related packages (the "owning" package)
7848 will manage the configuration file with maintainer
7849 scripts as described in the previous section.
7852 The owning package should also provide a program
7853 that the other packages may use to modify the
7857 The related packages must use the provided program
7858 to make any desired modifications to the
7859 configuration file. They should either depend on
7860 the core package to guarantee that the configuration
7861 modifier program is available or accept gracefully
7862 that they cannot modify the configuration file if it
7863 is not. (This is in addition to the fact that the
7864 configuration file may not even be present in the
7871 Sometimes it's appropriate to create a new package which
7872 provides the basic infrastructure for the other packages
7873 and which manages the shared configuration files. (The
7874 <tt>sgml-base</tt> package is a good example.)
7879 <heading>User configuration files ("dotfiles")</heading>
7882 The files in <file>/etc/skel</file> will automatically be
7883 copied into new user accounts by <prgn>adduser</prgn>.
7884 No other program should reference the files in
7885 <file>/etc/skel</file>.
7889 Therefore, if a program needs a dotfile to exist in
7890 advance in <file>$HOME</file> to work sensibly, that dotfile
7891 should be installed in <file>/etc/skel</file> and treated as a
7896 However, programs that require dotfiles in order to
7897 operate sensibly are a bad thing, unless they do create
7898 the dotfiles themselves automatically.
7902 Furthermore, programs should be configured by the Debian
7903 default installation to behave as closely to the upstream
7904 default behavior as possible.
7908 Therefore, if a program in a Debian package needs to be
7909 configured in some way in order to operate sensibly, that
7910 should be done using a site-wide configuration file placed
7911 in <file>/etc</file>. Only if the program doesn't support a
7912 site-wide default configuration and the package maintainer
7913 doesn't have time to add it may a default per-user file be
7914 placed in <file>/etc/skel</file>.
7918 <file>/etc/skel</file> should be as empty as we can make it.
7919 This is particularly true because there is no easy (or
7920 necessarily desirable) mechanism for ensuring that the
7921 appropriate dotfiles are copied into the accounts of
7922 existing users when a package is installed.
7928 <heading>Log files</heading>
7930 Log files should usually be named
7931 <file>/var/log/<var>package</var>.log</file>. If you have many
7932 log files, or need a separate directory for permission
7933 reasons (<file>/var/log</file> is writable only by
7934 <file>root</file>), you should usually create a directory named
7935 <file>/var/log/<var>package</var></file> and place your log
7940 Log files must be rotated occasionally so that they don't
7941 grow indefinitely; the best way to do this is to drop a log
7942 rotation configuration file into the directory
7943 <file>/etc/logrotate.d</file> and use the facilities provided by
7944 logrotate.<footnote>
7946 The traditional approach to log files has been to set up
7947 <em>ad hoc</em> log rotation schemes using simple shell
7948 scripts and cron. While this approach is highly
7949 customizable, it requires quite a lot of sysadmin work.
7950 Even though the original Debian system helped a little
7951 by automatically installing a system which can be used
7952 as a template, this was deemed not enough.
7956 The use of <prgn>logrotate</prgn>, a program developed
7957 by Red Hat, is better, as it centralizes log management.
7958 It has both a configuration file
7959 (<file>/etc/logrotate.conf</file>) and a directory where
7960 packages can drop their individual log rotation
7961 configurations (<file>/etc/logrotate.d</file>).
7964 Here is a good example for a logrotate config
7965 file (for more information see <manref name="logrotate"
7967 <example compact="compact">
7968 /var/log/foo/*.log {
7973 /etc/init.d/foo force-reload
7977 This rotates all files under <file>/var/log/foo</file>, saves 12
7978 compressed generations, and forces the daemon to reload its
7979 configuration information after the log rotation.
7983 Log files should be removed when the package is
7984 purged (but not when it is only removed). This should be
7985 done by the <prgn>postrm</prgn> script when it is called
7986 with the argument <tt>purge</tt> (see <ref
7987 id="removedetails">).
7992 <heading>Permissions and owners</heading>
7995 The rules in this section are guidelines for general use.
7996 If necessary you may deviate from the details below.
7997 However, if you do so you must make sure that what is done
7998 is secure and you should try to be as consistent as possible
7999 with the rest of the system. You should probably also
8000 discuss it on <prgn>debian-devel</prgn> first.
8004 Files should be owned by <tt>root:root</tt>, and made
8005 writable only by the owner and universally readable (and
8006 executable, if appropriate), that is mode 644 or 755.
8010 Directories should be mode 755 or (for group-writability)
8011 mode 2775. The ownership of the directory should be
8012 consistent with its mode: if a directory is mode 2775, it
8013 should be owned by the group that needs write access to
8016 When a package is upgraded, and the owner or permissions
8017 of a file included in the package has changed, dpkg
8018 arranges for the ownership and permissions to be
8019 correctly set upon installation. However, this does not
8020 extend to directories; the permissions and ownership of
8021 directories already on the system does not change on
8022 install or upgrade of packages. This makes sense, since
8023 otherwise common directories like <tt>/usr</tt> would
8024 always be in flux. To correctly change permissions of a
8025 directory the package owns, explicit action is required,
8026 usually in the <tt>postinst</tt> script. Care must be
8027 taken to handle downgrades as well, in that case.
8034 Setuid and setgid executables should be mode 4755 or 2755
8035 respectively, and owned by the appropriate user or group.
8036 They should not be made unreadable (modes like 4711 or
8037 2711 or even 4111); doing so achieves no extra security,
8038 because anyone can find the binary in the freely available
8039 Debian package; it is merely inconvenient. For the same
8040 reason you should not restrict read or execute permissions
8041 on non-set-id executables.
8045 Some setuid programs need to be restricted to particular
8046 sets of users, using file permissions. In this case they
8047 should be owned by the uid to which they are set-id, and by
8048 the group which should be allowed to execute them. They
8049 should have mode 4754; again there is no point in making
8050 them unreadable to those users who must not be allowed to
8055 It is possible to arrange that the system administrator can
8056 reconfigure the package to correspond to their local
8057 security policy by changing the permissions on a binary:
8058 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8059 described below.<footnote>
8060 Ordinary files installed by <prgn>dpkg</prgn> (as
8061 opposed to <tt>conffile</tt>s and other similar objects)
8062 normally have their permissions reset to the distributed
8063 permissions when the package is reinstalled. However,
8064 the use of <prgn>dpkg-statoverride</prgn> overrides this
8067 Another method you should consider is to create a group for
8068 people allowed to use the program(s) and make any setuid
8069 executables executable only by that group.
8073 If you need to create a new user or group for your package
8074 there are two possibilities. Firstly, you may need to
8075 make some files in the binary package be owned by this
8076 user or group, or you may need to compile the user or
8077 group id (rather than just the name) into the binary
8078 (though this latter should be avoided if possible, as in
8079 this case you need a statically allocated id).</p>
8082 If you need a statically allocated id, you must ask for a
8083 user or group id from the <tt>base-passwd</tt> maintainer,
8084 and must not release the package until you have been
8085 allocated one. Once you have been allocated one you must
8086 either make the package depend on a version of the
8087 <tt>base-passwd</tt> package with the id present in
8088 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8089 your package to create the user or group itself with the
8090 correct id (using <tt>adduser</tt>) in its
8091 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8092 the <prgn>postinst</prgn> is to be preferred if it is
8093 possible, otherwise a pre-dependency will be needed on the
8094 <tt>adduser</tt> package.)
8098 On the other hand, the program might be able to determine
8099 the uid or gid from the user or group name at runtime, so
8100 that a dynamically allocated id can be used. In this case
8101 you should choose an appropriate user or group name,
8102 discussing this on <prgn>debian-devel</prgn> and checking
8103 with the <package/base-passwd/ maintainer that it is unique and that
8104 they do not wish you to use a statically allocated id
8105 instead. When this has been checked you must arrange for
8106 your package to create the user or group if necessary using
8107 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8108 <prgn>postinst</prgn> script (again, the latter is to be
8109 preferred if it is possible).
8113 Note that changing the numeric value of an id associated
8114 with a name is very difficult, and involves searching the
8115 file system for all appropriate files. You need to think
8116 carefully whether a static or dynamic id is required, since
8117 changing your mind later will cause problems.
8120 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8122 This section is not intended as policy, but as a
8123 description of the use of <prgn>dpkg-statoverride</prgn>.
8127 If a system administrator wishes to have a file (or
8128 directory or other such thing) installed with owner and
8129 permissions different from those in the distributed Debian
8130 package, they can use the <prgn>dpkg-statoverride</prgn>
8131 program to instruct <prgn>dpkg</prgn> to use the different
8132 settings every time the file is installed. Thus the
8133 package maintainer should distribute the files with their
8134 normal permissions, and leave it for the system
8135 administrator to make any desired changes. For example, a
8136 daemon which is normally required to be setuid root, but
8137 in certain situations could be used without being setuid,
8138 should be installed setuid in the <tt>.deb</tt>. Then the
8139 local system administrator can change this if they wish.
8140 If there are two standard ways of doing it, the package
8141 maintainer can use <tt>debconf</tt> to find out the
8142 preference, and call <prgn>dpkg-statoverride</prgn> in the
8143 maintainer script if necessary to accommodate the system
8144 administrator's choice. Care must be taken during
8145 upgrades to not override an existing setting.
8149 Given the above, <prgn>dpkg-statoverride</prgn> is
8150 essentially a tool for system administrators and would not
8151 normally be needed in the maintainer scripts. There is
8152 one type of situation, though, where calls to
8153 <prgn>dpkg-statoverride</prgn> would be needed in the
8154 maintainer scripts, and that involves packages which use
8155 dynamically allocated user or group ids. In such a
8156 situation, something like the following idiom can be very
8157 helpful in the package's <prgn>postinst</prgn>, where
8158 <tt>sysuser</tt> is a dynamically allocated id:
8160 for i in /usr/bin/foo /usr/sbin/bar
8162 # only do something when no setting exists
8163 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8165 #include: debconf processing, question about foo and bar
8166 if [ "$RET" = "true" ] ; then
8167 dpkg-statoverride --update --add sysuser root 4755 $i
8172 The corresponding code to remove the override when the package
8175 for i in /usr/bin/foo /usr/sbin/bar
8177 if dpkg-statoverride --list $i >/dev/null 2>&1
8179 dpkg-statoverride --remove $i
8189 <chapt id="customized-programs">
8190 <heading>Customized programs</heading>
8192 <sect id="arch-spec">
8193 <heading>Architecture specification strings</heading>
8196 If a program needs to specify an <em>architecture specification
8197 string</em> in some place, it should select one of the strings
8198 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8199 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8200 part is sometimes elided, as when the OS is Linux.
8204 Note that we don't want to use
8205 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8206 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8207 since this would make our programs incompatible with other
8208 Linux distributions. We also don't use something like
8209 <tt><var>arch</var>-unknown-linux</tt>, since the
8210 <tt>unknown</tt> does not look very good.
8213 <sect1 id="arch-wildcard-spec">
8214 <heading>Architecture wildcards</heading>
8217 A package may specify an architecture wildcard. Architecture
8218 wildcards are in the format <tt>any</tt> (which matches every
8219 architecture), <tt><var>os</var></tt>-any, or
8220 any-<tt><var>cpu</var></tt>. <footnote>
8221 Internally, the package system normalizes the GNU triplets
8222 and the Debian arches into Debian arch triplets (which are
8223 kind of inverted GNU triplets), with the first component of
8224 the triplet representing the libc and ABI in use, and then
8225 does matching against those triplets. However, such
8226 triplets are an internal implementation detail that should
8227 not be used by packages directly. The libc and ABI portion
8228 is handled internally by the package system based on
8229 the <var>os</var> and <var>cpu</var>.
8236 <heading>Daemons</heading>
8239 The configuration files <file>/etc/services</file>,
8240 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8241 by the <prgn>netbase</prgn> package and must not be modified
8246 If a package requires a new entry in one of these files, the
8247 maintainer should get in contact with the
8248 <prgn>netbase</prgn> maintainer, who will add the entries
8249 and release a new version of the <prgn>netbase</prgn>
8254 The configuration file <file>/etc/inetd.conf</file> must not be
8255 modified by the package's scripts except via the
8256 <prgn>update-inetd</prgn> script or the
8257 <file>DebianNet.pm</file> Perl module. See their documentation
8258 for details on how to add entries.
8262 If a package wants to install an example entry into
8263 <file>/etc/inetd.conf</file>, the entry must be preceded with
8264 exactly one hash character (<tt>#</tt>). Such lines are
8265 treated as "commented out by user" by the
8266 <prgn>update-inetd</prgn> script and are not changed or
8267 activated during package updates.
8272 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8276 Some programs need to create pseudo-ttys. This should be done
8277 using Unix98 ptys if the C library supports it. The resulting
8278 program must not be installed setuid root, unless that
8279 is required for other functionality.
8283 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8284 <file>/var/log/lastlog</file> must be installed writable by
8285 group <tt>utmp</tt>. Programs which need to modify those
8286 files must be installed setgid <tt>utmp</tt>.
8291 <heading>Editors and pagers</heading>
8294 Some programs have the ability to launch an editor or pager
8295 program to edit or display a text document. Since there are
8296 lots of different editors and pagers available in the Debian
8297 distribution, the system administrator and each user should
8298 have the possibility to choose their preferred editor and
8303 In addition, every program should choose a good default
8304 editor/pager if none is selected by the user or system
8309 Thus, every program that launches an editor or pager must
8310 use the EDITOR or PAGER environment variable to determine
8311 the editor or pager the user wishes to use. If these
8312 variables are not set, the programs <file>/usr/bin/editor</file>
8313 and <file>/usr/bin/pager</file> should be used, respectively.
8317 These two files are managed through the <prgn>dpkg</prgn>
8318 "alternatives" mechanism. Thus every package providing an
8319 editor or pager must call the
8320 <prgn>update-alternatives</prgn> script to register these
8325 If it is very hard to adapt a program to make use of the
8326 EDITOR or PAGER variables, that program may be configured to
8327 use <file>/usr/bin/sensible-editor</file> and
8328 <file>/usr/bin/sensible-pager</file> as the editor or pager
8329 program respectively. These are two scripts provided in the
8330 <package>sensible-utils</package> package that check the EDITOR
8331 and PAGER variables and launch the appropriate program, and fall
8332 back to <file>/usr/bin/editor</file>
8333 and <file>/usr/bin/pager</file> if the variable is not set.
8337 A program may also use the VISUAL environment variable to
8338 determine the user's choice of editor. If it exists, it
8339 should take precedence over EDITOR. This is in fact what
8340 <file>/usr/bin/sensible-editor</file> does.
8344 It is not required for a package to depend on
8345 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8346 package to provide such virtual packages.<footnote>
8347 The Debian base system already provides an editor and a
8353 <sect id="web-appl">
8354 <heading>Web servers and applications</heading>
8357 This section describes the locations and URLs that should
8358 be used by all web servers and web applications in the
8365 Cgi-bin executable files are installed in the
8367 <example compact="compact">
8368 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8370 and should be referred to as
8371 <example compact="compact">
8372 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8378 <p>Access to HTML documents</p>
8381 HTML documents for a package are stored in
8382 <file>/usr/share/doc/<var>package</var></file>
8383 and can be referred to as
8384 <example compact="compact">
8385 http://localhost/doc/<var>package</var>/<var>filename</var>
8390 The web server should restrict access to the document
8391 tree so that only clients on the same host can read
8392 the documents. If the web server does not support such
8393 access controls, then it should not provide access at
8394 all, or ask about providing access during installation.
8399 <p>Access to images</p>
8401 It is recommended that images for a package be stored
8402 in <tt>/usr/share/images/<var>package</var></tt> and
8403 may be referred to through an alias <tt>/images/</tt>
8406 http://localhost/images/<package>/<filename>
8413 <p>Web Document Root</p>
8416 Web Applications should try to avoid storing files in
8417 the Web Document Root. Instead they should use the
8418 /usr/share/doc/<var>package</var> directory for
8419 documents and register the Web Application via the
8420 <package>doc-base</package> package. If access to the
8421 web document root is unavoidable then use
8422 <example compact="compact">
8425 as the Document Root. This might be just a symbolic
8426 link to the location where the system administrator
8427 has put the real document root.
8430 <item><p>Providing httpd and/or httpd-cgi</p>
8432 All web servers should provide the virtual package
8433 <tt>httpd</tt>. If a web server has CGI support it should
8434 provide <tt>httpd-cgi</tt> additionally.
8437 All web applications which do not contain CGI scripts should
8438 depend on <tt>httpd</tt>, all those web applications which
8439 <tt>do</tt> contain CGI scripts, should depend on
8447 <sect id="mail-transport-agents">
8448 <heading>Mail transport, delivery and user agents</heading>
8451 Debian packages which process electronic mail, whether mail
8452 user agents (MUAs) or mail transport agents (MTAs), must
8453 ensure that they are compatible with the configuration
8454 decisions below. Failure to do this may result in lost
8455 mail, broken <tt>From:</tt> lines, and other serious brain
8460 The mail spool is <file>/var/mail</file> and the interface to
8461 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8462 the FHS). On older systems, the mail spool may be
8463 physically located in <file>/var/spool/mail</file>, but all
8464 access to the mail spool should be via the
8465 <file>/var/mail</file> symlink. The mail spool is part of the
8466 base system and not part of the MTA package.
8470 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8471 programs (such as IMAP daemons) must lock the mailbox in an
8472 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8473 be combined with dot locking. To avoid deadlocks, a program
8474 should use <tt>fcntl()</tt> first and dot locking after
8475 this, or alternatively implement the two locking methods in
8476 a non blocking way<footnote>
8477 If it is not possible to establish both locks, the
8478 system shouldn't wait for the second lock to be
8479 established, but remove the first lock, wait a (random)
8480 time, and start over locking again.
8481 </footnote>. Using the functions <tt>maillock</tt> and
8482 <tt>mailunlock</tt> provided by the
8483 <tt>liblockfile*</tt><footnote>
8484 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8485 to use these functions.
8486 </footnote> packages is the recommended way to realize this.
8490 Mailboxes are generally either mode 600 and owned by
8491 <var>user</var> or mode 660 and owned by
8492 <tt><var>user</var>:mail</tt><footnote>
8493 There are two traditional permission schemes for mail spools:
8494 mode 600 with all mail delivery done by processes running as
8495 the destination user, or mode 660 and owned by group mail with
8496 mail delivery done by a process running as a system user in
8497 group mail. Historically, Debian required mode 660 mail
8498 spools to enable the latter model, but that model has become
8499 increasingly uncommon and the principle of least privilege
8500 indicates that mail systems that use the first model should
8501 use permissions of 600. If delivery to programs is permitted,
8502 it's easier to keep the mail system secure if the delivery
8503 agent runs as the destination user. Debian Policy therefore
8504 permits either scheme.
8505 </footnote>. The local system administrator may choose a
8506 different permission scheme; packages should not make
8507 assumptions about the permission and ownership of mailboxes
8508 unless required (such as when creating a new mailbox). A MUA
8509 may remove a mailbox (unless it has nonstandard permissions) in
8510 which case the MTA or another MUA must recreate it if needed.
8514 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8515 be setgid mail to do the locking mentioned above (and
8516 must obviously avoid accessing other users' mailboxes
8517 using this privilege).</p>
8520 <file>/etc/aliases</file> is the source file for the system mail
8521 aliases (e.g., postmaster, usenet, etc.), it is the one
8522 which the sysadmin and <prgn>postinst</prgn> scripts may
8523 edit. After <file>/etc/aliases</file> is edited the program or
8524 human editing it must call <prgn>newaliases</prgn>. All MTA
8525 packages must come with a <prgn>newaliases</prgn> program,
8526 even if it does nothing, but older MTA packages did not do
8527 this so programs should not fail if <prgn>newaliases</prgn>
8528 cannot be found. Note that because of this, all MTA
8529 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8530 <tt>Replaces: mail-transport-agent</tt> control file
8535 The convention of writing <tt>forward to
8536 <var>address</var></tt> in the mailbox itself is not
8537 supported. Use a <tt>.forward</tt> file instead.</p>
8540 The <prgn>rmail</prgn> program used by UUCP
8541 for incoming mail should be <file>/usr/sbin/rmail</file>.
8542 Likewise, <prgn>rsmtp</prgn>, for receiving
8543 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8547 If your package needs to know what hostname to use on (for
8548 example) outgoing news and mail messages which are generated
8549 locally, you should use the file <file>/etc/mailname</file>. It
8550 will contain the portion after the username and <tt>@</tt>
8551 (at) sign for email addresses of users on the machine
8552 (followed by a newline).
8556 Such a package should check for the existence of this file
8557 when it is being configured. If it exists, it should be
8558 used without comment, although an MTA's configuration script
8559 may wish to prompt the user even if it finds that this file
8560 exists. If the file does not exist, the package should
8561 prompt the user for the value (preferably using
8562 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8563 as well as using it in the package's configuration. The
8564 prompt should make it clear that the name will not just be
8565 used by that package. For example, in this situation the
8566 <tt>inn</tt> package could say something like:
8567 <example compact="compact">
8568 Please enter the "mail name" of your system. This is the
8569 hostname portion of the address to be shown on outgoing
8570 news and mail messages. The default is
8571 <var>syshostname</var>, your system's host name. Mail
8572 name ["<var>syshostname</var>"]:
8574 where <var>syshostname</var> is the output of <tt>hostname
8580 <heading>News system configuration</heading>
8583 All the configuration files related to the NNTP (news)
8584 servers and clients should be located under
8585 <file>/etc/news</file>.</p>
8588 There are some configuration issues that apply to a number
8589 of news clients and server packages on the machine. These
8593 <tag><file>/etc/news/organization</file></tag>
8595 A string which should appear as the
8596 organization header for all messages posted
8597 by NNTP clients on the machine
8600 <tag><file>/etc/news/server</file></tag>
8602 Contains the FQDN of the upstream NNTP
8603 server, or localhost if the local machine is
8608 Other global files may be added as required for cross-package news
8615 <heading>Programs for the X Window System</heading>
8618 <heading>Providing X support and package priorities</heading>
8621 Programs that can be configured with support for the X
8622 Window System must be configured to do so and must declare
8623 any package dependencies necessary to satisfy their
8624 runtime requirements when using the X Window System. If
8625 such a package is of higher priority than the X packages
8626 on which it depends, it is required that either the
8627 X-specific components be split into a separate package, or
8628 that an alternative version of the package, which includes
8629 X support, be provided, or that the package's priority be
8635 <heading>Packages providing an X server</heading>
8638 Packages that provide an X server that, directly or
8639 indirectly, communicates with real input and display
8640 hardware should declare in their control data that they
8641 provide the virtual package <tt>xserver</tt>.<footnote>
8642 This implements current practice, and provides an
8643 actual policy for usage of the <tt>xserver</tt>
8644 virtual package which appears in the virtual packages
8645 list. In a nutshell, X servers that interface
8646 directly with the display and input hardware or via
8647 another subsystem (e.g., GGI) should provide
8648 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8649 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8655 <heading>Packages providing a terminal emulator</heading>
8658 Packages that provide a terminal emulator for the X Window
8659 System which meet the criteria listed below should declare
8660 in their control data that they provide the virtual
8661 package <tt>x-terminal-emulator</tt>. They should also
8662 register themselves as an alternative for
8663 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8668 To be an <tt>x-terminal-emulator</tt>, a program must:
8669 <list compact="compact">
8671 Be able to emulate a DEC VT100 terminal, or a
8672 compatible terminal.
8676 Support the command-line option <tt>-e
8677 <var>command</var></tt>, which creates a new
8678 terminal window<footnote>
8679 "New terminal window" does not necessarily mean
8680 a new top-level X window directly parented by
8681 the window manager; it could, if the terminal
8682 emulator application were so coded, be a new
8683 "view" in a multiple-document interface (MDI).
8685 and runs the specified <var>command</var>,
8686 interpreting the entirety of the rest of the command
8687 line as a command to pass straight to exec, in the
8688 manner that <tt>xterm</tt> does.
8692 Support the command-line option <tt>-T
8693 <var>title</var></tt>, which creates a new terminal
8694 window with the window title <var>title</var>.
8701 <heading>Packages providing a window manager</heading>
8704 Packages that provide a window manager should declare in
8705 their control data that they provide the virtual package
8706 <tt>x-window-manager</tt>. They should also register
8707 themselves as an alternative for
8708 <file>/usr/bin/x-window-manager</file>, with a priority
8709 calculated as follows:
8710 <list compact="compact">
8712 Start with a priority of 20.
8716 If the window manager supports the Debian menu
8717 system, add 20 points if this support is available
8718 in the package's default configuration (i.e., no
8719 configuration files belonging to the system or user
8720 have to be edited to activate the feature); if
8721 configuration files must be modified, add only 10
8727 If the window manager complies with <url
8728 id="http://www.freedesktop.org/Standards/wm-spec"
8729 name="The Window Manager Specification Project">,
8730 written by the <url id="http://www.freedesktop.org/"
8731 name="Free Desktop Group">, add 40 points.
8735 If the window manager permits the X session to be
8736 restarted using a <em>different</em> window manager
8737 (without killing the X server) in its default
8738 configuration, add 10 points; otherwise add none.
8745 <heading>Packages providing fonts</heading>
8748 Packages that provide fonts for the X Window
8750 For the purposes of Debian Policy, a "font for the X
8751 Window System" is one which is accessed via X protocol
8752 requests. Fonts for the Linux console, for PostScript
8753 renderer, or any other purpose, do not fit this
8754 definition. Any tool which makes such fonts available
8755 to the X Window System, however, must abide by this
8758 must do a number of things to ensure that they are both
8759 available without modification of the X or font server
8760 configuration, and that they do not corrupt files used by
8761 other font packages to register information about
8765 Fonts of any type supported by the X Window System
8766 must be in a separate binary package from any
8767 executables, libraries, or documentation (except
8768 that specific to the fonts shipped, such as their
8769 license information). If one or more of the fonts
8770 so packaged are necessary for proper operation of
8771 the package with which they are associated the font
8772 package may be Recommended; if the fonts merely
8773 provide an enhancement, a Suggests relationship may
8774 be used. Packages must not Depend on font
8776 This is because the X server may retrieve fonts
8777 from the local file system or over the network
8778 from an X font server; the Debian package system
8779 is empowered to deal only with the local
8785 BDF fonts must be converted to PCF fonts with the
8786 <prgn>bdftopcf</prgn> utility (available in the
8787 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8788 placed in a directory that corresponds to their
8790 <list compact="compact">
8792 100 dpi fonts must be placed in
8793 <file>/usr/share/fonts/X11/100dpi/</file>.
8797 75 dpi fonts must be placed in
8798 <file>/usr/share/fonts/X11/75dpi/</file>.
8802 Character-cell fonts, cursor fonts, and other
8803 low-resolution fonts must be placed in
8804 <file>/usr/share/fonts/X11/misc/</file>.
8810 Type 1 fonts must be placed in
8811 <file>/usr/share/fonts/X11/Type1/</file>. If font
8812 metric files are available, they must be placed here
8817 Subdirectories of <file>/usr/share/fonts/X11/</file>
8818 other than those listed above must be neither
8819 created nor used. (The <file>PEX</file>, <file>CID</file>,
8820 <file>Speedo</file>, and <file>cyrillic</file> directories
8821 are excepted for historical reasons, but installation of
8822 files into these directories remains discouraged.)
8826 Font packages may, instead of placing files directly
8827 in the X font directories listed above, provide
8828 symbolic links in that font directory pointing to
8829 the files' actual location in the filesystem. Such
8830 a location must comply with the FHS.
8834 Font packages should not contain both 75dpi and
8835 100dpi versions of a font. If both are available,
8836 they should be provided in separate binary packages
8837 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8838 the names of the packages containing the
8839 corresponding fonts.
8843 Fonts destined for the <file>misc</file> subdirectory
8844 should not be included in the same package as 75dpi
8845 or 100dpi fonts; instead, they should be provided in
8846 a separate package with <tt>-misc</tt> appended to
8851 Font packages must not provide the files
8852 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8853 <file>fonts.scale</file> in a font directory:
8856 <file>fonts.dir</file> files must not be provided at all.
8860 <file>fonts.alias</file> and <file>fonts.scale</file>
8861 files, if needed, should be provided in the
8863 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8864 where <var>fontdir</var> is the name of the
8866 <file>/usr/share/fonts/X11/</file> where the
8867 package's corresponding fonts are stored
8868 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8869 <var>package</var> is the name of the package
8870 that provides these fonts, and
8871 <var>extension</var> is either <tt>scale</tt>
8872 or <tt>alias</tt>, whichever corresponds to
8879 Font packages must declare a dependency on
8880 <tt>xfonts-utils</tt> in their control
8885 Font packages that provide one or more
8886 <file>fonts.scale</file> files as described above must
8887 invoke <prgn>update-fonts-scale</prgn> on each
8888 directory into which they installed fonts
8889 <em>before</em> invoking
8890 <prgn>update-fonts-dir</prgn> on that directory.
8891 This invocation must occur in both the
8892 <prgn>postinst</prgn> (for all arguments) and
8893 <prgn>postrm</prgn> (for all arguments except
8894 <tt>upgrade</tt>) scripts.
8898 Font packages that provide one or more
8899 <file>fonts.alias</file> files as described above must
8900 invoke <prgn>update-fonts-alias</prgn> on each
8901 directory into which they installed fonts. This
8902 invocation must occur in both the
8903 <prgn>postinst</prgn> (for all arguments) and
8904 <prgn>postrm</prgn> (for all arguments except
8905 <tt>upgrade</tt>) scripts.
8909 Font packages must invoke
8910 <prgn>update-fonts-dir</prgn> on each directory into
8911 which they installed fonts. This invocation must
8912 occur in both the <prgn>postinst</prgn> (for all
8913 arguments) and <prgn>postrm</prgn> (for all
8914 arguments except <tt>upgrade</tt>) scripts.
8918 Font packages must not provide alias names for the
8919 fonts they include which collide with alias names
8920 already in use by fonts already packaged.
8924 Font packages must not provide fonts with the same
8925 XLFD registry name as another font already packaged.
8931 <sect1 id="appdefaults">
8932 <heading>Application defaults files</heading>
8935 Application defaults files must be installed in the
8936 directory <file>/etc/X11/app-defaults/</file> (use of a
8937 localized subdirectory of <file>/etc/X11/</file> as described
8938 in the <em>X Toolkit Intrinsics - C Language
8939 Interface</em> manual is also permitted). They must be
8940 registered as <tt>conffile</tt>s or handled as
8941 configuration files.
8945 Customization of programs' X resources may also be
8946 supported with the provision of a file with the same name
8947 as that of the package placed in
8948 the <file>/etc/X11/Xresources/</file> directory, which
8949 must be registered as a <tt>conffile</tt> or handled as a
8950 configuration file.<footnote>
8951 Note that this mechanism is not the same as using
8952 app-defaults; app-defaults are tied to the client
8953 binary on the local file system, whereas X resources
8954 are stored in the X server and affect all connecting
8961 <heading>Installation directory issues</heading>
8964 Historically, packages using the X Window System used a
8965 separate set of installation directories from other packages.
8966 This practice has been discontinued and packages using the X
8967 Window System should now generally be installed in the same
8968 directories as any other package. Specifically, packages must
8969 not install files under the <file>/usr/X11R6/</file> directory
8970 and the <file>/usr/X11R6/</file> directory hierarchy should be
8971 regarded as obsolete.
8975 Include files previously installed under
8976 <file>/usr/X11R6/include/X11/</file> should be installed into
8977 <file>/usr/include/X11/</file>. For files previously
8978 installed into subdirectories of
8979 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8980 determine if subdirectories of <file>/usr/lib/</file> and
8981 <file>/usr/share/</file> can be used. If not, a subdirectory
8982 of <file>/usr/lib/X11/</file> should be used.
8986 Configuration files for window, display, or session managers
8987 or other applications that are tightly integrated with the X
8988 Window System may be placed in a subdirectory
8989 of <file>/etc/X11/</file> corresponding to the package name.
8990 Other X Window System applications should use
8991 the <file>/etc/</file> directory unless otherwise mandated by
8992 policy (such as for <ref id="appdefaults">).
8997 <heading>The OSF/Motif and OpenMotif libraries</heading>
9000 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9001 OpenMotif libraries</em><footnote>
9002 OSF/Motif and OpenMotif are collectively referred to as
9003 "Motif" in this policy document.
9005 should be compiled against and tested with LessTif (a free
9006 re-implementation of Motif) instead. If the maintainer
9007 judges that the program or programs do not work
9008 sufficiently well with LessTif to be distributed and
9009 supported, but do so when compiled against Motif, then two
9010 versions of the package should be created; one linked
9011 statically against Motif and with <tt>-smotif</tt>
9012 appended to the package name, and one linked dynamically
9013 against Motif and with <tt>-dmotif</tt> appended to the
9018 Both Motif-linked versions are dependent
9019 upon non-DFSG-compliant software and thus cannot be
9020 uploaded to the <em>main</em> distribution; if the
9021 software is itself DFSG-compliant it may be uploaded to
9022 the <em>contrib</em> distribution. While known existing
9023 versions of Motif permit unlimited redistribution of
9024 binaries linked against the library (whether statically or
9025 dynamically), it is the package maintainer's
9026 responsibility to determine whether this is permitted by
9027 the license of the copy of Motif in their possession.
9033 <heading>Perl programs and modules</heading>
9036 Perl programs and modules should follow the current Perl policy.
9040 The Perl policy can be found in the <tt>perl-policy</tt>
9041 files in the <tt>debian-policy</tt> package.
9042 It is also available from the Debian web mirrors at
9043 <tt><url name="/doc/packaging-manuals/perl-policy/"
9044 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9049 <heading>Emacs lisp programs</heading>
9052 Please refer to the "Debian Emacs Policy" for details of how to
9053 package emacs lisp programs.
9057 The Emacs policy is available in
9058 <file>debian-emacs-policy.gz</file> of the
9059 <package>emacsen-common</package> package.
9060 It is also available from the Debian web mirrors at
9061 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9062 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9067 <heading>Games</heading>
9070 The permissions on <file>/var/games</file> are mode 755, owner
9071 <tt>root</tt> and group <tt>root</tt>.
9075 Each game decides on its own security policy.</p>
9078 Games which require protected, privileged access to
9079 high-score files, saved games, etc., may be made
9080 set-<em>group</em>-id (mode 2755) and owned by
9081 <tt>root:games</tt>, and use files and directories with
9082 appropriate permissions (770 <tt>root:games</tt>, for
9083 example). They must not be made
9084 set-<em>user</em>-id, as this causes security problems. (If
9085 an attacker can subvert any set-user-id game they can
9086 overwrite the executable of any other, causing other players
9087 of these games to run a Trojan horse program. With a
9088 set-group-id game the attacker only gets access to less
9089 important game data, and if they can get at the other
9090 players' accounts at all it will take considerably more
9094 Some packages, for example some fortune cookie programs, are
9095 configured by the upstream authors to install with their
9096 data files or other static information made unreadable so
9097 that they can only be accessed through set-id programs
9098 provided. You should not do this in a Debian package: anyone can
9099 download the <file>.deb</file> file and read the data from it,
9100 so there is no point making the files unreadable. Not
9101 making the files unreadable also means that you don't have
9102 to make so many programs set-id, which reduces the risk of a
9106 As described in the FHS, binaries of games should be
9107 installed in the directory <file>/usr/games</file>. This also
9108 applies to games that use the X Window System. Manual pages
9109 for games (X and non-X games) should be installed in
9110 <file>/usr/share/man/man6</file>.</p>
9116 <heading>Documentation</heading>
9119 <heading>Manual pages</heading>
9122 You should install manual pages in <prgn>nroff</prgn> source
9123 form, in appropriate places under <file>/usr/share/man</file>.
9124 You should only use sections 1 to 9 (see the FHS for more
9125 details). You must not install a pre-formatted "cat page".
9129 Each program, utility, and function should have an
9130 associated manual page included in the same package. It is
9131 suggested that all configuration files also have a manual
9132 page included as well. Manual pages for protocols and other
9133 auxiliary things are optional.
9137 If no manual page is available, this is considered as a bug
9138 and should be reported to the Debian Bug Tracking System (the
9139 maintainer of the package is allowed to write this bug report
9140 themselves, if they so desire). Do not close the bug report
9141 until a proper man page is available.<footnote>
9142 It is not very hard to write a man page. See the
9143 <url id="http://www.schweikhardt.net/man_page_howto.html"
9144 name="Man-Page-HOWTO">,
9145 <manref name="man" section="7">, the examples
9146 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9147 the helper program <prgn>help2man</prgn>, or the
9148 directory <file>/usr/share/doc/man-db/examples</file>.
9153 You may forward a complaint about a missing man page to the
9154 upstream authors, and mark the bug as forwarded in the
9155 Debian bug tracking system. Even though the GNU Project do
9156 not in general consider the lack of a man page to be a bug,
9157 we do; if they tell you that they don't consider it a bug
9158 you should leave the bug in our bug tracking system open
9163 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9167 If one man page needs to be accessible via several names it
9168 is better to use a symbolic link than the <file>.so</file>
9169 feature, but there is no need to fiddle with the relevant
9170 parts of the upstream source to change from <file>.so</file> to
9171 symlinks: don't do it unless it's easy. You should not
9172 create hard links in the manual page directories, nor put
9173 absolute filenames in <file>.so</file> directives. The filename
9174 in a <file>.so</file> in a man page should be relative to the
9175 base of the man page tree (usually
9176 <file>/usr/share/man</file>). If you do not create any links
9177 (whether symlinks, hard links, or <tt>.so</tt> directives)
9178 in the file system to the alternate names of the man page,
9179 then you should not rely on <prgn>man</prgn> finding your
9180 man page under those names based solely on the information in
9181 the man page's header.<footnote>
9182 Supporting this in <prgn>man</prgn> often requires
9183 unreasonable processing time to find a manual page or to
9184 report that none exists, and moves knowledge into man's
9185 database that would be better left in the file system.
9186 This support is therefore deprecated and will cease to
9187 be present in the future.
9192 Manual pages in locale-specific subdirectories of
9193 <file>/usr/share/man</file> should use either UTF-8 or the usual
9194 legacy encoding for that language (normally the one corresponding
9195 to the shortest relevant locale name in
9196 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9197 <file>/usr/share/man/fr</file> should use either UTF-8 or
9198 ISO-8859-1.<footnote>
9199 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9200 use. In future, all manual pages will be required to use
9206 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9207 included in the subdirectory name unless it indicates a
9208 significant difference in the language, as this excludes
9209 speakers of the language in other countries.<footnote>
9210 At the time of writing, Chinese and Portuguese are the main
9211 languages with such differences, so <file>pt_BR</file>,
9212 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9217 If a localized version of a manual page is provided, it should
9218 either be up-to-date or it should be obvious to the reader that
9219 it is outdated and the original manual page should be used
9220 instead. This can be done either by a note at the beginning of
9221 the manual page or by showing the missing or changed portions in
9222 the original language instead of the target language.
9227 <heading>Info documents</heading>
9230 Info documents should be installed in <file>/usr/share/info</file>.
9231 They should be compressed with <tt>gzip -9</tt>.
9235 The <prgn>install-info</prgn> program maintains a directory of
9236 installed info documents in <file>/usr/share/info/dir</file> for
9237 the use of info readers.<footnote>
9238 It was previously necessary for packages installing info
9239 documents to run <prgn>install-info</prgn> from maintainer
9240 scripts. This is no longer necessary. The installation
9241 system now uses dpkg triggers.
9243 This file must not be included in packages. Packages containing
9244 info documents should depend on <tt>dpkg (>= 1.15.4) |
9245 install-info</tt> to ensure that the directory file is properly
9246 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9251 Info documents should contain section and directory entry
9252 information in the document for the use
9253 of <prgn>install-info</prgn>. The section should be specified
9254 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9255 space and the section of this info page. The directory entry or
9256 entries should be included between
9257 a <tt>START-INFO-DIR-ENTRY</tt> line and
9258 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9260 INFO-DIR-SECTION Individual utilities
9261 START-INFO-DIR-ENTRY
9262 * example: (example). An example info directory entry.
9265 To determine which section to use, you should look
9266 at <file>/usr/share/info/dir</file> on your system and choose
9267 the most relevant (or create a new section if none of the
9268 current sections are relevant).<footnote>
9269 Normally, info documents are generated from Texinfo source.
9270 To include this information in the generated info document, if
9271 it is absent, add commands like:
9273 @dircategory Individual utilities
9275 * example: (example). An example info directory entry.
9278 to the Texinfo source of the document and ensure that the info
9279 documents are rebuilt from source during the package build.
9285 <heading>Additional documentation</heading>
9288 Any additional documentation that comes with the package may
9289 be installed at the discretion of the package maintainer.
9290 Plain text documentation should be installed in the directory
9291 <file>/usr/share/doc/<var>package</var></file>, where
9292 <var>package</var> is the name of the package, and
9293 compressed with <tt>gzip -9</tt> unless it is small.
9297 If a package comes with large amounts of documentation which
9298 many users of the package will not require you should create
9299 a separate binary package to contain it, so that it does not
9300 take up disk space on the machines of users who do not need
9301 or want it installed.</p>
9304 It is often a good idea to put text information files
9305 (<file>README</file>s, changelogs, and so forth) that come with
9306 the source package in <file>/usr/share/doc/<var>package</var></file>
9307 in the binary package. However, you don't need to install
9308 the instructions for building and installing the package, of
9312 Packages must not require the existence of any files in
9313 <file>/usr/share/doc/</file> in order to function
9315 The system administrator should be able to
9316 delete files in <file>/usr/share/doc/</file> without causing
9317 any programs to break.
9319 Any files that are referenced by programs but are also
9320 useful as stand alone documentation should be installed under
9321 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9322 <file>/usr/share/doc/<var>package</var></file>.
9326 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9327 link to another directory in <file>/usr/share/doc</file> only if
9328 the two packages both come from the same source and the
9329 first package Depends on the second.<footnote>
9331 Please note that this does not override the section on
9332 changelog files below, so the file
9333 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9334 must refer to the changelog for the current version of
9335 <var>package</var> in question. In practice, this means
9336 that the sources of the target and the destination of the
9337 symlink must be the same (same source package and
9344 Former Debian releases placed all additional documentation
9345 in <file>/usr/doc/<var>package</var></file>. This has been
9346 changed to <file>/usr/share/doc/<var>package</var></file>,
9347 and packages must not put documentation in the directory
9348 <file>/usr/doc/<var>package</var></file>. <footnote>
9349 At this phase of the transition, we no longer require a
9350 symbolic link in <file>/usr/doc/</file>. At a later point,
9351 policy shall change to make the symbolic links a bug.
9357 <heading>Preferred documentation formats</heading>
9360 The unification of Debian documentation is being carried out
9364 If your package comes with extensive documentation in a
9365 markup format that can be converted to various other formats
9366 you should if possible ship HTML versions in a binary
9367 package, in the directory
9368 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9369 its subdirectories.<footnote>
9370 The rationale: The important thing here is that HTML
9371 docs should be available in <em>some</em> package, not
9372 necessarily in the main binary package.
9377 Other formats such as PostScript may be provided at the
9378 package maintainer's discretion.
9382 <sect id="copyrightfile">
9383 <heading>Copyright information</heading>
9386 Every package must be accompanied by a verbatim copy of its
9387 copyright information and distribution license in the file
9388 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9389 file must neither be compressed nor be a symbolic link.
9393 In addition, the copyright file must say where the upstream
9394 sources (if any) were obtained. It should name the original
9395 authors of the package and the Debian maintainer(s) who were
9396 involved with its creation.
9400 Packages in the <em>contrib</em> or <em>non-free</em> archive
9401 areas should state in the copyright file that the package is not
9402 part of the Debian GNU/Linux distribution and briefly explain
9407 A copy of the file which will be installed in
9408 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9409 be in <file>debian/copyright</file> in the source package.
9413 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9414 link to another directory in <file>/usr/share/doc</file> only if
9415 the two packages both come from the same source and the
9416 first package Depends on the second. These rules are
9417 important because copyrights must be extractable by
9422 Packages distributed under the Apache license (version 2.0), the
9423 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9424 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9425 1.3) should refer to the corresponding files
9426 under <file>/usr/share/common-licenses</file>,<footnote>
9429 <file>/usr/share/common-licenses/Apache-2.0</file>,
9430 <file>/usr/share/common-licenses/Artistic</file>,
9431 <file>/usr/share/common-licenses/GPL-1</file>,
9432 <file>/usr/share/common-licenses/GPL-2</file>,
9433 <file>/usr/share/common-licenses/GPL-3</file>,
9434 <file>/usr/share/common-licenses/LGPL-2</file>,
9435 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9436 <file>/usr/share/common-licenses/LGPL-3</file>,
9437 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9438 <file>/usr/share/common-licenses/GFDL-1.3</file>
9439 respectively. The University of California BSD license is
9440 also included in <package>base-files</package> as
9441 <file>/usr/share/common-licenses/BSD</file>, but given the
9442 brevity of this license, its specificity to code whose
9443 copyright is held by the Regents of the University of
9444 California, and the frequency of minor wording changes, its
9445 text should be included in the copyright file rather than
9446 referencing this file.
9448 </footnote> rather than quoting them in the copyright
9453 You should not use the copyright file as a general <file>README</file>
9454 file. If your package has such a file it should be
9455 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9456 <file>README.Debian</file> or some other appropriate place.</p>
9460 <heading>Examples</heading>
9463 Any examples (configurations, source files, whatever),
9464 should be installed in a directory
9465 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9466 files should not be referenced by any program: they're there
9467 for the benefit of the system administrator and users as
9468 documentation only. Architecture-specific example files
9469 should be installed in a directory
9470 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9472 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9473 latter directory itself may be a symbolic link to the
9478 If the purpose of a package is to provide examples, then the
9479 example files may be installed into
9480 <file>/usr/share/doc/<var>package</var></file>.
9484 <sect id="changelogs">
9485 <heading>Changelog files</heading>
9488 Packages that are not Debian-native must contain a
9489 compressed copy of the <file>debian/changelog</file> file from
9490 the Debian source tree in
9491 <file>/usr/share/doc/<var>package</var></file> with the name
9492 <file>changelog.Debian.gz</file>.
9496 If an upstream changelog is available, it should be accessible as
9497 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9498 plain text. If the upstream changelog is distributed in
9499 HTML, it should be made available in that form as
9500 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9501 and a plain text <file>changelog.gz</file> should be generated
9502 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9503 the upstream changelog files do not already conform to this
9504 naming convention, then this may be achieved either by
9505 renaming the files, or by adding a symbolic link, at the
9506 maintainer's discretion.<footnote>
9507 Rationale: People should not have to look in places for
9508 upstream changelogs merely because they are given
9509 different names or are distributed in HTML format.
9514 All of these files should be installed compressed using
9515 <tt>gzip -9</tt>, as they will become large with time even
9516 if they start out small.
9520 If the package has only one changelog which is used both as
9521 the Debian changelog and the upstream one because there is
9522 no separate upstream maintainer then that changelog should
9523 usually be installed as
9524 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9525 there is a separate upstream maintainer, but no upstream
9526 changelog, then the Debian changelog should still be called
9527 <file>changelog.Debian.gz</file>.
9531 For details about the format and contents of the Debian
9532 changelog file, please see <ref id="dpkgchangelog">.
9537 <appendix id="pkg-scope">
9538 <heading>Introduction and scope of these appendices</heading>
9541 These appendices are taken essentially verbatim from the
9542 now-deprecated Packaging Manual, version 3.2.1.0. They are
9543 the chapters which are likely to be of use to package
9544 maintainers and which have not already been included in the
9545 policy document itself. Most of these sections are very likely
9546 not relevant to policy; they should be treated as
9547 documentation for the packaging system. Please note that these
9548 appendices are included for convenience, and for historical
9549 reasons: they used to be part of policy package, and they have
9550 not yet been incorporated into dpkg documentation. However,
9551 they still have value, and hence they are presented here.
9555 They have not yet been checked to ensure that they are
9556 compatible with the contents of policy, and if there are any
9557 contradictions, the version in the main policy document takes
9558 precedence. The remaining chapters of the old Packaging
9559 Manual have also not been read in detail to ensure that there
9560 are not parts which have been left out. Both of these will be
9565 Certain parts of the Packaging manual were integrated into the
9566 Policy Manual proper, and removed from the appendices. Links
9567 have been placed from the old locations to the new ones.
9571 <prgn>dpkg</prgn> is a suite of programs for creating binary
9572 package files and installing and removing them on Unix
9574 <prgn>dpkg</prgn> is targeted primarily at Debian
9575 GNU/Linux, but may work on or be ported to other
9581 The binary packages are designed for the management of
9582 installed executable programs (usually compiled binaries) and
9583 their associated data, though source code examples and
9584 documentation are provided as part of some packages.</p>
9587 This manual describes the technical aspects of creating Debian
9588 binary packages (<file>.deb</file> files). It documents the
9589 behavior of the package management programs
9590 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9591 they interact with packages.</p>
9594 It also documents the interaction between
9595 <prgn>dselect</prgn>'s core and the access method scripts it
9596 uses to actually install the selected packages, and describes
9597 how to create a new access method.</p>
9600 This manual does not go into detail about the options and
9601 usage of the package building and installation tools. It
9602 should therefore be read in conjunction with those programs'
9607 The utility programs which are provided with <prgn>dpkg</prgn>
9608 for managing various system configuration and similar issues,
9609 such as <prgn>update-rc.d</prgn> and
9610 <prgn>install-info</prgn>, are not described in detail here -
9611 please see their man pages.
9615 It is assumed that the reader is reasonably familiar with the
9616 <prgn>dpkg</prgn> System Administrators' manual.
9617 Unfortunately this manual does not yet exist.
9621 The Debian version of the FSF's GNU hello program is provided
9622 as an example for people wishing to create Debian
9623 packages. The Debian <prgn>debmake</prgn> package is
9624 recommended as a very helpful tool in creating and maintaining
9625 Debian packages. However, while the tools and examples are
9626 helpful, they do not replace the need to read and follow the
9627 Policy and Programmer's Manual.</p>
9630 <appendix id="pkg-binarypkg">
9631 <heading>Binary packages (from old Packaging Manual)</heading>
9634 The binary package has two main sections. The first part
9635 consists of various control information files and scripts used
9636 by <prgn>dpkg</prgn> when installing and removing. See <ref
9637 id="pkg-controlarea">.
9641 The second part is an archive containing the files and
9642 directories to be installed.
9646 In the future binary packages may also contain other
9647 components, such as checksums and digital signatures. The
9648 format for the archive is described in full in the
9649 <file>deb(5)</file> man page.
9653 <sect id="pkg-bincreating"><heading>Creating package files -
9654 <prgn>dpkg-deb</prgn>
9658 All manipulation of binary package files is done by
9659 <prgn>dpkg-deb</prgn>; it's the only program that has
9660 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9661 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9662 will spot that the options requested are appropriate to
9663 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9668 In order to create a binary package you must make a
9669 directory tree which contains all the files and directories
9670 you want to have in the file system data part of the package.
9671 In Debian-format source packages this directory is usually
9672 <file>debian/tmp</file>, relative to the top of the package's
9677 They should have the locations (relative to the root of the
9678 directory tree you're constructing) ownerships and
9679 permissions which you want them to have on the system when
9684 With current versions of <prgn>dpkg</prgn> the uid/username
9685 and gid/groupname mappings for the users and groups being
9686 used should be the same on the system where the package is
9687 built and the one where it is installed.
9691 You need to add one special directory to the root of the
9692 miniature file system tree you're creating:
9693 <prgn>DEBIAN</prgn>. It should contain the control
9694 information files, notably the binary package control file
9695 (see <ref id="pkg-controlfile">).
9699 The <prgn>DEBIAN</prgn> directory will not appear in the
9700 file system archive of the package, and so won't be installed
9701 by <prgn>dpkg</prgn> when the package is installed.
9705 When you've prepared the package, you should invoke:
9707 dpkg --build <var>directory</var>
9712 This will build the package in
9713 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9714 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9715 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9720 See the man page <manref name="dpkg-deb" section="8"> for details of how
9721 to examine the contents of this newly-created file. You may find the
9722 output of following commands enlightening:
9724 dpkg-deb --info <var>filename</var>.deb
9725 dpkg-deb --contents <var>filename</var>.deb
9726 dpkg --contents <var>filename</var>.deb
9728 To view the copyright file for a package you could use this command:
9730 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9735 <sect id="pkg-controlarea">
9736 <heading>Package control information files</heading>
9739 The control information portion of a binary package is a
9740 collection of files with names known to <prgn>dpkg</prgn>.
9741 It will treat the contents of these files specially - some
9742 of them contain information used by <prgn>dpkg</prgn> when
9743 installing or removing the package; others are scripts which
9744 the package maintainer wants <prgn>dpkg</prgn> to run.
9748 It is possible to put other files in the package control
9749 area, but this is not generally a good idea (though they
9750 will largely be ignored).
9754 Here is a brief list of the control info files supported by
9755 <prgn>dpkg</prgn> and a summary of what they're used for.
9760 <tag><tt>control</tt>
9763 This is the key description file used by
9764 <prgn>dpkg</prgn>. It specifies the package's name
9765 and version, gives its description for the user,
9766 states its relationships with other packages, and so
9767 forth. See <ref id="sourcecontrolfiles"> and
9768 <ref id="binarycontrolfiles">.
9772 It is usually generated automatically from information
9773 in the source package by the
9774 <prgn>dpkg-gencontrol</prgn> program, and with
9775 assistance from <prgn>dpkg-shlibdeps</prgn>.
9776 See <ref id="pkg-sourcetools">.
9780 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9785 These are executable files (usually scripts) which
9786 <prgn>dpkg</prgn> runs during installation, upgrade
9787 and removal of packages. They allow the package to
9788 deal with matters which are particular to that package
9789 or require more complicated processing than that
9790 provided by <prgn>dpkg</prgn>. Details of when and
9791 how they are called are in <ref id="maintainerscripts">.
9795 It is very important to make these scripts idempotent.
9796 See <ref id="idempotency">.
9800 The maintainer scripts are not guaranteed to run with a
9801 controlling terminal and may not be able to interact with
9802 the user. See <ref id="controllingterminal">.
9806 <tag><tt>conffiles</tt>
9809 This file contains a list of configuration files which
9810 are to be handled automatically by <prgn>dpkg</prgn>
9811 (see <ref id="pkg-conffiles">). Note that not necessarily
9812 every configuration file should be listed here.
9815 <tag><tt>shlibs</tt>
9818 This file contains a list of the shared libraries
9819 supplied by the package, with dependency details for
9820 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9821 when it determines what dependencies are required in a
9822 package control file. The <tt>shlibs</tt> file format
9823 is described on <ref id="shlibs">.
9828 <sect id="pkg-controlfile">
9829 <heading>The main control information file: <tt>control</tt></heading>
9832 The most important control information file used by
9833 <prgn>dpkg</prgn> when it installs a package is
9834 <tt>control</tt>. It contains all the package's "vital
9839 The binary package control files of packages built from
9840 Debian sources are made by a special tool,
9841 <prgn>dpkg-gencontrol</prgn>, which reads
9842 <file>debian/control</file> and <file>debian/changelog</file> to
9843 find the information it needs. See <ref id="pkg-sourcepkg"> for
9848 The fields in binary package control files are listed in
9849 <ref id="binarycontrolfiles">.
9853 A description of the syntax of control files and the purpose
9854 of the fields is available in <ref id="controlfields">.
9859 <heading>Time Stamps</heading>
9862 See <ref id="timestamps">.
9867 <appendix id="pkg-sourcepkg">
9868 <heading>Source packages (from old Packaging Manual) </heading>
9871 The Debian binary packages in the distribution are generated
9872 from Debian sources, which are in a special format to assist
9873 the easy and automatic building of binaries.
9876 <sect id="pkg-sourcetools">
9877 <heading>Tools for processing source packages</heading>
9880 Various tools are provided for manipulating source packages;
9881 they pack and unpack sources and help build of binary
9882 packages and help manage the distribution of new versions.
9886 They are introduced and typical uses described here; see
9887 <manref name="dpkg-source" section="1"> for full
9888 documentation about their arguments and operation.
9892 For examples of how to construct a Debian source package,
9893 and how to use those utilities that are used by Debian
9894 source packages, please see the <prgn>hello</prgn> example
9898 <sect1 id="pkg-dpkg-source">
9900 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9905 This program is frequently used by hand, and is also
9906 called from package-independent automated building scripts
9907 such as <prgn>dpkg-buildpackage</prgn>.
9911 To unpack a package it is typically invoked with
9913 dpkg-source -x <var>.../path/to/filename</var>.dsc
9918 with the <file><var>filename</var>.tar.gz</file> and
9919 <file><var>filename</var>.diff.gz</file> (if applicable) in
9920 the same directory. It unpacks into
9921 <file><var>package</var>-<var>version</var></file>, and if
9923 <file><var>package</var>-<var>version</var>.orig</file>, in
9924 the current directory.
9928 To create a packed source archive it is typically invoked:
9930 dpkg-source -b <var>package</var>-<var>version</var>
9935 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9936 <file>.diff.gz</file> (if appropriate) in the current
9937 directory. <prgn>dpkg-source</prgn> does not clean the
9938 source tree first - this must be done separately if it is
9943 See also <ref id="pkg-sourcearchives">.</p>
9947 <sect1 id="pkg-dpkg-buildpackage">
9949 <prgn>dpkg-buildpackage</prgn> - overall package-building
9954 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9955 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9956 targets <tt>clean</tt>, <tt>build</tt> and
9957 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9958 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9959 source and binary package upload.
9963 It is usually invoked by hand from the top level of the
9964 built or unbuilt source directory. It may be invoked with
9965 no arguments; useful arguments include:
9966 <taglist compact="compact">
9967 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9970 Do not sign the <tt>.changes</tt> file or the
9971 source package <tt>.dsc</tt> file, respectively.</p>
9973 <tag><tt>-p<var>sign-command</var></tt></tag>
9976 Invoke <var>sign-command</var> instead of finding
9977 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9978 <var>sign-command</var> must behave just like
9979 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9981 <tag><tt>-r<var>root-command</var></tt></tag>
9984 When root privilege is required, invoke the command
9985 <var>root-command</var>. <var>root-command</var>
9986 should invoke its first argument as a command, from
9987 the <prgn>PATH</prgn> if necessary, and pass its
9988 second and subsequent arguments to the command it
9989 calls. If no <var>root-command</var> is supplied
9990 then <var>dpkg-buildpackage</var> will take no
9991 special action to gain root privilege, so that for
9992 most packages it will have to be invoked as root to
9995 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9998 Two types of binary-only build and upload - see
9999 <manref name="dpkg-source" section="1">.
10006 <sect1 id="pkg-dpkg-gencontrol">
10008 <prgn>dpkg-gencontrol</prgn> - generates binary package
10013 This program is usually called from <file>debian/rules</file>
10014 (see <ref id="pkg-sourcetree">) in the top level of the source
10019 This is usually done just before the files and directories in the
10020 temporary directory tree where the package is being built have their
10021 permissions and ownerships set and the package is constructed using
10022 <prgn>dpkg-deb/</prgn>
10024 This is so that the control file which is produced has
10025 the right permissions
10030 <prgn>dpkg-gencontrol</prgn> must be called after all the
10031 files which are to go into the package have been placed in
10032 the temporary build directory, so that its calculation of
10033 the installed size of a package is correct.
10037 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10038 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10039 variable substitutions created by
10040 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10045 For a package which generates only one binary package, and
10046 which builds it in <file>debian/tmp</file> relative to the top
10047 of the source package, it is usually sufficient to call
10048 <prgn>dpkg-gencontrol</prgn>.
10052 Sources which build several binaries will typically need
10055 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10056 </example> The <tt>-P</tt> tells
10057 <prgn>dpkg-gencontrol</prgn> that the package is being
10058 built in a non-default directory, and the <tt>-p</tt>
10059 tells it which package's control file should be generated.
10063 <prgn>dpkg-gencontrol</prgn> also adds information to the
10064 list of files in <file>debian/files</file>, for the benefit of
10065 (for example) a future invocation of
10066 <prgn>dpkg-genchanges</prgn>.</p>
10069 <sect1 id="pkg-dpkg-shlibdeps">
10071 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10076 This program is usually called from <file>debian/rules</file>
10077 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10078 id="pkg-sourcetree">), in the top level of the source tree.
10082 Its arguments are executables and shared libraries
10085 They may be specified either in the locations in the
10086 source tree where they are created or in the locations
10087 in the temporary build tree where they are installed
10088 prior to binary package creation.
10090 </footnote> for which shared library dependencies should
10091 be included in the binary package's control file.
10095 If some of the found shared libraries should only
10096 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10097 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10098 by using the <tt>-d<var>dependency-field</var></tt> option
10099 before those executable(s). (Each <tt>-d</tt> option
10100 takes effect until the next <tt>-d</tt>.)
10104 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10105 output control file to be modified. Instead by default it
10106 adds to the <file>debian/substvars</file> file variable
10107 settings like <tt>shlibs:Depends</tt>. These variable
10108 settings must be referenced in dependency fields in the
10109 appropriate per-binary-package sections of the source
10114 For example, a package that generates an essential part
10115 which requires dependencies, and optional parts that
10116 which only require a recommendation, would separate those
10117 two sets of dependencies into two different fields.<footnote>
10118 At the time of writing, an example for this was the
10119 <package/xmms/ package, with Depends used for the xmms
10120 executable, Recommends for the plug-ins and Suggests for
10121 even more optional features provided by unzip.
10123 It can say in its <file>debian/rules</file>:
10125 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10126 -dRecommends <var>optionalpart anotheroptionalpart</var>
10128 and then in its main control file <file>debian/control</file>:
10131 Depends: ${shlibs:Depends}
10132 Recommends: ${shlibs:Recommends}
10138 Sources which produce several binary packages with
10139 different shared library dependency requirements can use
10140 the <tt>-p<var>varnameprefix</var></tt> option to override
10141 the default <tt>shlibs:</tt> prefix (one invocation of
10142 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10143 They can thus produce several sets of dependency
10144 variables, each of the form
10145 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10146 which can be referred to in the appropriate parts of the
10147 binary package control files.
10152 <sect1 id="pkg-dpkg-distaddfile">
10154 <prgn>dpkg-distaddfile</prgn> - adds a file to
10155 <file>debian/files</file>
10159 Some packages' uploads need to include files other than
10160 the source and binary package files.
10164 <prgn>dpkg-distaddfile</prgn> adds a file to the
10165 <file>debian/files</file> file so that it will be included in
10166 the <file>.changes</file> file when
10167 <prgn>dpkg-genchanges</prgn> is run.
10171 It is usually invoked from the <tt>binary</tt> target of
10172 <file>debian/rules</file>:
10174 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10176 The <var>filename</var> is relative to the directory where
10177 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10178 is usually the directory above the top level of the source
10179 tree. The <file>debian/rules</file> target should put the
10180 file there just before or just after calling
10181 <prgn>dpkg-distaddfile</prgn>.
10185 The <var>section</var> and <var>priority</var> are passed
10186 unchanged into the resulting <file>.changes</file> file.
10191 <sect1 id="pkg-dpkg-genchanges">
10193 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10194 upload control file
10198 This program is usually called by package-independent
10199 automatic building scripts such as
10200 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10205 It is usually called in the top level of a built source
10206 tree, and when invoked with no arguments will print out a
10207 straightforward <file>.changes</file> file based on the
10208 information in the source package's changelog and control
10209 file and the binary and source packages which should have
10215 <sect1 id="pkg-dpkg-parsechangelog">
10217 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10218 representation of a changelog
10222 This program is used internally by
10223 <prgn>dpkg-source</prgn> et al. It may also occasionally
10224 be useful in <file>debian/rules</file> and elsewhere. It
10225 parses a changelog, <file>debian/changelog</file> by default,
10226 and prints a control-file format representation of the
10227 information in it to standard output.
10231 <sect1 id="pkg-dpkg-architecture">
10233 <prgn>dpkg-architecture</prgn> - information about the build and
10238 This program can be used manually, but is also invoked by
10239 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10240 environment or make variables which specify the build and host
10241 architecture for the package building process.
10246 <sect id="pkg-sourcetree">
10247 <heading>The Debian package source tree</heading>
10250 The source archive scheme described later is intended to
10251 allow a Debian package source tree with some associated
10252 control information to be reproduced and transported easily.
10253 The Debian package source tree is a version of the original
10254 program with certain files added for the benefit of the
10255 packaging process, and with any other changes required
10256 made to the rest of the source code and installation
10261 The extra files created for Debian are in the subdirectory
10262 <file>debian</file> of the top level of the Debian package
10263 source tree. They are described below.
10266 <sect1 id="pkg-debianrules">
10267 <heading><file>debian/rules</file> - the main building script</heading>
10270 See <ref id="debianrules">.
10274 <sect1 id="pkg-srcsubstvars">
10275 <heading><file>debian/substvars</file> and variable substitutions</heading>
10278 See <ref id="substvars">.
10284 <heading><file>debian/files</file></heading>
10287 See <ref id="debianfiles">.
10291 <sect1><heading><file>debian/tmp</file>
10295 This is the canonical temporary location for the
10296 construction of binary packages by the <tt>binary</tt>
10297 target. The directory <file>tmp</file> serves as the root of
10298 the file system tree as it is being constructed (for
10299 example, by using the package's upstream makefiles install
10300 targets and redirecting the output there), and it also
10301 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10302 id="pkg-bincreating">.
10306 If several binary packages are generated from the same
10307 source tree it is usual to use several
10308 <file>debian/tmp<var>something</var></file> directories, for
10309 example <file>tmp-a</file> or <file>tmp-doc</file>.
10313 Whatever <file>tmp</file> directories are created and used by
10314 <tt>binary</tt> must of course be removed by the
10315 <tt>clean</tt> target.</p></sect1>
10319 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10323 As it exists on the FTP site, a Debian source package
10324 consists of three related files. You must have the right
10325 versions of all three to be able to use them.
10330 <tag>Debian source control file - <tt>.dsc</tt></tag>
10332 This file is a control file used by <prgn>dpkg-source</prgn>
10333 to extract a source package.
10334 See <ref id="debiansourcecontrolfiles">.
10338 Original source archive -
10340 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10346 This is a compressed (with <tt>gzip -9</tt>)
10347 <prgn>tar</prgn> file containing the source code from
10348 the upstream authors of the program.
10353 Debian package diff -
10355 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10361 This is a unified context diff (<tt>diff -u</tt>)
10362 giving the changes which are required to turn the
10363 original source into the Debian source. These changes
10364 may only include editing and creating plain files.
10365 The permissions of files, the targets of symbolic
10366 links and the characteristics of special files or
10367 pipes may not be changed and no files may be removed
10372 All the directories in the diff must exist, except the
10373 <file>debian</file> subdirectory of the top of the source
10374 tree, which will be created by
10375 <prgn>dpkg-source</prgn> if necessary when unpacking.
10379 The <prgn>dpkg-source</prgn> program will
10380 automatically make the <file>debian/rules</file> file
10381 executable (see below).</p></item>
10386 If there is no original source code - for example, if the
10387 package is specially prepared for Debian or the Debian
10388 maintainer is the same as the upstream maintainer - the
10389 format is slightly different: then there is no diff, and the
10391 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10392 and preferably contains a directory named
10393 <file><var>package</var>-<var>version</var></file>.
10398 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10401 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10402 Debian source package. However, if it is not available it
10403 is possible to unpack a Debian source archive as follows:
10404 <enumlist compact="compact">
10407 Untar the tarfile, which will create a <file>.orig</file>
10411 <p>Rename the <file>.orig</file> directory to
10412 <file><var>package</var>-<var>version</var></file>.</p>
10416 Create the subdirectory <file>debian</file> at the top of
10417 the source tree.</p>
10419 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10421 <item><p>Untar the tarfile again if you want a copy of the original
10422 source code alongside the Debian version.</p>
10427 It is not possible to generate a valid Debian source archive
10428 without using <prgn>dpkg-source</prgn>. In particular,
10429 attempting to use <prgn>diff</prgn> directly to generate the
10430 <file>.diff.gz</file> file will not work.
10434 <heading>Restrictions on objects in source packages</heading>
10437 The source package may not contain any hard links
10439 This is not currently detected when building source
10440 packages, but only when extracting
10444 Hard links may be permitted at some point in the
10445 future, but would require a fair amount of
10447 </footnote>, device special files, sockets or setuid or
10450 Setgid directories are allowed.
10455 The source packaging tools manage the changes between the
10456 original and Debian source using <prgn>diff</prgn> and
10457 <prgn>patch</prgn>. Turning the original source tree as
10458 included in the <file>.orig.tar.gz</file> into the Debian
10459 package source must not involve any changes which cannot be
10460 handled by these tools. Problematic changes which cause
10461 <prgn>dpkg-source</prgn> to halt with an error when
10462 building the source package are:
10463 <list compact="compact">
10464 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10466 <item><p>Changing the targets of symbolic links.</p>
10468 <item><p>Creating directories, other than <file>debian</file>.</p>
10470 <item><p>Changes to the contents of binary files.</p></item>
10471 </list> Changes which cause <prgn>dpkg-source</prgn> to
10472 print a warning but continue anyway are:
10473 <list compact="compact">
10476 Removing files, directories or symlinks.
10478 Renaming a file is not treated specially - it is
10479 seen as the removal of the old file (which
10480 generates a warning, but is otherwise ignored),
10481 and the creation of the new one.
10487 Changed text files which are missing the usual final
10488 newline (either in the original or the modified
10493 Changes which are not represented, but which are not detected by
10494 <prgn>dpkg-source</prgn>, are:
10495 <list compact="compact">
10496 <item><p>Changing the permissions of files (other than
10497 <file>debian/rules</file>) and directories.</p></item>
10502 The <file>debian</file> directory and <file>debian/rules</file>
10503 are handled specially by <prgn>dpkg-source</prgn> - before
10504 applying the changes it will create the <file>debian</file>
10505 directory, and afterwards it will make
10506 <file>debian/rules</file> world-executable.
10512 <appendix id="pkg-controlfields">
10513 <heading>Control files and their fields (from old Packaging Manual)</heading>
10516 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10517 data in a common format, known as control files. Binary and
10518 source packages have control data as do the <file>.changes</file>
10519 files which control the installation of uploaded files, and
10520 <prgn>dpkg</prgn>'s internal databases are in a similar
10525 <heading>Syntax of control files</heading>
10528 See <ref id="controlsyntax">.
10532 It is important to note that there are several fields which
10533 are optional as far as <prgn>dpkg</prgn> and the related
10534 tools are concerned, but which must appear in every Debian
10535 package, or whose omission may cause problems.
10540 <heading>List of fields</heading>
10543 See <ref id="controlfieldslist">.
10547 This section now contains only the fields that didn't belong
10548 to the Policy manual.
10551 <sect1 id="pkg-f-Filename">
10552 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10555 These fields in <tt>Packages</tt> files give the
10556 filename(s) of (the parts of) a package in the
10557 distribution directories, relative to the root of the
10558 Debian hierarchy. If the package has been split into
10559 several parts the parts are all listed in order, separated
10564 <sect1 id="pkg-f-Size">
10565 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10568 These fields in <file>Packages</file> files give the size (in
10569 bytes, expressed in decimal) and MD5 checksum of the
10570 file(s) which make(s) up a binary package in the
10571 distribution. If the package is split into several parts
10572 the values for the parts are listed in order, separated by
10577 <sect1 id="pkg-f-Status">
10578 <heading><tt>Status</tt></heading>
10581 This field in <prgn>dpkg</prgn>'s status file records
10582 whether the user wants a package installed, removed or
10583 left alone, whether it is broken (requiring
10584 re-installation) or not and what its current state on the
10585 system is. Each of these pieces of information is a
10590 <sect1 id="pkg-f-Config-Version">
10591 <heading><tt>Config-Version</tt></heading>
10594 If a package is not installed or not configured, this
10595 field in <prgn>dpkg</prgn>'s status file records the last
10596 version of the package which was successfully
10601 <sect1 id="pkg-f-Conffiles">
10602 <heading><tt>Conffiles</tt></heading>
10605 This field in <prgn>dpkg</prgn>'s status file contains
10606 information about the automatically-managed configuration
10607 files held by a package. This field should <em>not</em>
10608 appear anywhere in a package!
10613 <heading>Obsolete fields</heading>
10616 These are still recognized by <prgn>dpkg</prgn> but should
10617 not appear anywhere any more.
10619 <taglist compact="compact">
10621 <tag><tt>Revision</tt></tag>
10622 <tag><tt>Package-Revision</tt></tag>
10623 <tag><tt>Package_Revision</tt></tag>
10625 The Debian revision part of the package version was
10626 at one point in a separate control file field. This
10627 field went through several names.
10630 <tag><tt>Recommended</tt></tag>
10631 <item>Old name for <tt>Recommends</tt>.</item>
10633 <tag><tt>Optional</tt></tag>
10634 <item>Old name for <tt>Suggests</tt>.</item>
10636 <tag><tt>Class</tt></tag>
10637 <item>Old name for <tt>Priority</tt>.</item>
10646 <appendix id="pkg-conffiles">
10647 <heading>Configuration file handling (from old Packaging Manual)</heading>
10650 <prgn>dpkg</prgn> can do a certain amount of automatic
10651 handling of package configuration files.
10655 Whether this mechanism is appropriate depends on a number of
10656 factors, but basically there are two approaches to any
10657 particular configuration file.
10661 The easy method is to ship a best-effort configuration in the
10662 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10663 handle updates. If the user is unlikely to want to edit the
10664 file, but you need them to be able to without losing their
10665 changes, and a new package with a changed version of the file
10666 is only released infrequently, this is a good approach.
10670 The hard method is to build the configuration file from
10671 scratch in the <prgn>postinst</prgn> script, and to take the
10672 responsibility for fixing any mistakes made in earlier
10673 versions of the package automatically. This will be
10674 appropriate if the file is likely to need to be different on
10678 <sect><heading>Automatic handling of configuration files by
10683 A package may contain a control area file called
10684 <tt>conffiles</tt>. This file should be a list of filenames
10685 of configuration files needing automatic handling, separated
10686 by newlines. The filenames should be absolute pathnames,
10687 and the files referred to should actually exist in the
10692 When a package is upgraded <prgn>dpkg</prgn> will process
10693 the configuration files during the configuration stage,
10694 shortly before it runs the package's <prgn>postinst</prgn>
10699 For each file it checks to see whether the version of the
10700 file included in the package is the same as the one that was
10701 included in the last version of the package (the one that is
10702 being upgraded from); it also compares the version currently
10703 installed on the system with the one shipped with the last
10708 If neither the user nor the package maintainer has changed
10709 the file, it is left alone. If one or the other has changed
10710 their version, then the changed version is preferred - i.e.,
10711 if the user edits their file, but the package maintainer
10712 doesn't ship a different version, the user's changes will
10713 stay, silently, but if the maintainer ships a new version
10714 and the user hasn't edited it the new version will be
10715 installed (with an informative message). If both have
10716 changed their version the user is prompted about the problem
10717 and must resolve the differences themselves.
10721 The comparisons are done by calculating the MD5 message
10722 digests of the files, and storing the MD5 of the file as it
10723 was included in the most recent version of the package.
10727 When a package is installed for the first time
10728 <prgn>dpkg</prgn> will install the file that comes with it,
10729 unless that would mean overwriting a file already on the
10734 However, note that <prgn>dpkg</prgn> will <em>not</em>
10735 replace a conffile that was removed by the user (or by a
10736 script). This is necessary because with some programs a
10737 missing file produces an effect hard or impossible to
10738 achieve in another way, so that a missing file needs to be
10739 kept that way if the user did it.
10743 Note that a package should <em>not</em> modify a
10744 <prgn>dpkg</prgn>-handled conffile in its maintainer
10745 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10746 the user confusing and possibly dangerous options for
10747 conffile update when the package is upgraded.</p>
10750 <sect><heading>Fully-featured maintainer script configuration
10755 For files which contain site-specific information such as
10756 the hostname and networking details and so forth, it is
10757 better to create the file in the package's
10758 <prgn>postinst</prgn> script.
10762 This will typically involve examining the state of the rest
10763 of the system to determine values and other information, and
10764 may involve prompting the user for some information which
10765 can't be obtained some other way.
10769 When using this method there are a couple of important
10770 issues which should be considered:
10774 If you discover a bug in the program which generates the
10775 configuration file, or if the format of the file changes
10776 from one version to the next, you will have to arrange for
10777 the postinst script to do something sensible - usually this
10778 will mean editing the installed configuration file to remove
10779 the problem or change the syntax. You will have to do this
10780 very carefully, since the user may have changed the file,
10781 perhaps to fix the very problem that your script is trying
10782 to deal with - you will have to detect these situations and
10783 deal with them correctly.
10787 If you do go down this route it's probably a good idea to
10788 make the program that generates the configuration file(s) a
10789 separate program in <file>/usr/sbin</file>, by convention called
10790 <file><var>package</var>config</file> and then run that if
10791 appropriate from the post-installation script. The
10792 <tt><var>package</var>config</tt> program should not
10793 unquestioningly overwrite an existing configuration - if its
10794 mode of operation is geared towards setting up a package for
10795 the first time (rather than any arbitrary reconfiguration
10796 later) you should have it check whether the configuration
10797 already exists, and require a <tt>--force</tt> flag to
10798 overwrite it.</p></sect>
10801 <appendix id="pkg-alternatives"><heading>Alternative versions of
10802 an interface - <prgn>update-alternatives</prgn> (from old
10807 When several packages all provide different versions of the
10808 same program or file it is useful to have the system select a
10809 default, but to allow the system administrator to change it
10810 and have their decisions respected.
10814 For example, there are several versions of the <prgn>vi</prgn>
10815 editor, and there is no reason to prevent all of them from
10816 being installed at once, each under their own name
10817 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10818 Nevertheless it is desirable to have the name <tt>vi</tt>
10819 refer to something, at least by default.
10823 If all the packages involved cooperate, this can be done with
10824 <prgn>update-alternatives</prgn>.
10828 Each package provides its own version under its own name, and
10829 calls <prgn>update-alternatives</prgn> in its postinst to
10830 register its version (and again in its prerm to deregister
10835 See the man page <manref name="update-alternatives"
10836 section="8"> for details.
10840 If <prgn>update-alternatives</prgn> does not seem appropriate
10841 you may wish to consider using diversions instead.</p>
10844 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10845 package's version of a file (from old Packaging Manual)
10849 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10850 when it reinstalls the package it belongs to, and to have it
10851 put the file from the package somewhere else instead.
10855 This can be used locally to override a package's version of a
10856 file, or by one package to override another's version (or
10857 provide a wrapper for it).
10861 Before deciding to use a diversion, read <ref
10862 id="pkg-alternatives"> to see if you really want a diversion
10863 rather than several alternative versions of a program.
10867 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10868 and updated by a special program <prgn>dpkg-divert</prgn>.
10869 Please see <manref name="dpkg-divert" section="8"> for full
10870 details of its operation.
10874 When a package wishes to divert a file from another, it should
10875 call <prgn>dpkg-divert</prgn> in its preinst to add the
10876 diversion and rename the existing file. For example,
10877 supposing that a <prgn>smailwrapper</prgn> package wishes to
10878 install a wrapper around <file>/usr/sbin/smail</file>:
10880 dpkg-divert --package smailwrapper --add --rename \
10881 --divert /usr/sbin/smail.real /usr/sbin/smail
10882 </example> The <tt>--package smailwrapper</tt> ensures that
10883 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10884 can bypass the diversion and get installed as the true version.
10885 It's safe to add the diversion unconditionally on upgrades since
10886 it will be left unchanged if it already exists, but
10887 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10888 message, make the command conditional on the version from which
10889 the package is being upgraded:
10891 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10892 dpkg-divert --package smailwrapper --add --rename \
10893 --divert /usr/sbin/smail.real /usr/sbin/smail
10895 </example> where <tt>1.0-2</tt> is the version at which the
10896 diversion was first added to the package. Running the command
10897 during abort-upgrade is pointless but harmless.
10901 The postrm has to do the reverse:
10903 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10904 dpkg-divert --package smailwrapper --remove --rename \
10905 --divert /usr/sbin/smail.real /usr/sbin/smail
10907 </example> If the diversion was added at a particular version, the
10908 postrm should also handle the failure case of upgrading from an
10909 older version (unless the older version is so old that direct
10910 upgrades are no longer supported):
10912 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10913 dpkg-divert --package smailwrapper --remove --rename \
10914 --divert /usr/sbin/smail.real /usr/sbin/smail
10916 </example> where <tt>1.02-2</tt> is the version at which the
10917 diversion was first added to the package. The postrm should not
10918 remove the diversion on upgrades both because there's no reason to
10919 remove the diversion only to immediately re-add it and since the
10920 postrm of the old package is run after unpacking so the removal of
10921 the diversion will fail.
10925 Do not attempt to divert a file which is vitally important for
10926 the system's operation - when using <prgn>dpkg-divert</prgn>
10927 there is a time, after it has been diverted but before
10928 <prgn>dpkg</prgn> has installed the new version, when the file
10929 does not exist.</p>
10934 <!-- Local variables: -->
10935 <!-- indent-tabs-mode: t -->
10937 <!-- vim:set ai et sts=2 sw=2 tw=76: -->