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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 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
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 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>Russ Allbery</item>
223 <item>Bill Allombert</item>
224 <item>Andrew McMillan</item>
225 <item>Manoj Srivastava</item>
226 <item>Colin Watson</item>
231 While the authors of this document have tried hard to avoid
232 typos and other errors, these do still occur. If you discover
233 an error in this manual or if you want to give any
234 comments, suggestions, or criticisms please send an email to
235 the Debian Policy List,
236 <email>debian-policy@lists.debian.org</email>, or submit a
237 bug report against the <tt>debian-policy</tt> package.
241 Please do not try to reach the individual authors or maintainers
242 of the Policy Manual regarding changes to the Policy.
247 <heading>Related documents</heading>
250 There are several other documents other than this Policy Manual
251 that are necessary to fully understand some Debian policies and
256 The external "sub-policy" documents are referred to in:
257 <list compact="compact">
258 <item><ref id="fhs"></item>
259 <item><ref id="virtual_pkg"></item>
260 <item><ref id="menus"></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 Finally, a <qref id="copyrightformat">specification for
285 machine-readable copyright files</qref> is maintained as part of
286 the <package>debian-policy</package> package using the same
287 procedure as the other policy documents. Use of this format is
292 <sect id="definitions">
293 <heading>Definitions</heading>
296 The following terms are used in this Policy Manual:
300 The character encoding specified by ANSI X3.4-1986 and its
301 predecessor standards, referred to in MIME as US-ASCII, and
302 corresponding to an encoding in eight bits per character of
303 the first 128 <url id="http://www.unicode.org/"
304 name="Unicode"> characters, with the eighth bit always zero.
308 The transformation format (sometimes called encoding) of
309 <url id="http://www.unicode.org/" name="Unicode"> defined by
310 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
311 name="RFC 3629">. UTF-8 has the useful property of having
312 ASCII as a subset, so any text encoded in ASCII is trivially
322 <heading>The Debian Archive</heading>
325 The Debian system is maintained and distributed as a
326 collection of <em>packages</em>. Since there are so many of
327 them (currently well over 15000), they are split into
328 <em>sections</em> and given <em>priorities</em> to simplify
329 the handling of them.
333 The effort of the Debian project is to build a free operating
334 system, but not every package we want to make accessible is
335 <em>free</em> in our sense (see the Debian Free Software
336 Guidelines, below), or may be imported/exported without
337 restrictions. Thus, the archive is split into areas<footnote>
338 The Debian archive software uses the term "component" internally
339 and in the Release file format to refer to the division of an
340 archive. The Debian Social Contract simply refers to "areas."
341 This document uses terminology similar to the Social Contract.
342 </footnote> based on their licenses and other restrictions.
346 The aims of this are:
348 <list compact="compact">
349 <item>to allow us to make as much software available as we can</item>
350 <item>to allow us to encourage everyone to write free software,
352 <item>to allow us to make it easy for people to produce
353 CD-ROMs of our system without violating any licenses,
354 import/export restrictions, or any other laws.</item>
359 The <em>main</em> archive area forms the <em>Debian distribution</em>.
363 Packages in the other archive areas (<tt>contrib</tt>,
364 <tt>non-free</tt>) are not considered to be part of the Debian
365 distribution, although we support their use and provide
366 infrastructure for them (such as our bug-tracking system and
367 mailing lists). This Debian Policy Manual applies to these
372 <heading>The Debian Free Software Guidelines</heading>
374 The Debian Free Software Guidelines (DFSG) form our
375 definition of "free software". These are:
377 <tag>1. Free Redistribution
380 The license of a Debian component may not restrict any
381 party from selling or giving away the software as a
382 component of an aggregate software distribution
383 containing programs from several different
384 sources. The license may not require a royalty or
385 other fee for such sale.
390 The program must include source code, and must allow
391 distribution in source code as well as compiled form.
393 <tag>3. Derived Works
396 The license must allow modifications and derived
397 works, and must allow them to be distributed under the
398 same terms as the license of the original software.
400 <tag>4. Integrity of The Author's Source Code
403 The license may restrict source-code from being
404 distributed in modified form <em>only</em> if the
405 license allows the distribution of "patch files"
406 with the source code for the purpose of modifying the
407 program at build time. The license must explicitly
408 permit distribution of software built from modified
409 source code. The license may require derived works to
410 carry a different name or version number from the
411 original software. (This is a compromise. The Debian
412 Project encourages all authors to not restrict any
413 files, source or binary, from being modified.)
415 <tag>5. No Discrimination Against Persons or Groups
418 The license must not discriminate against any person
421 <tag>6. No Discrimination Against Fields of Endeavor
424 The license must not restrict anyone from making use
425 of the program in a specific field of endeavor. For
426 example, it may not restrict the program from being
427 used in a business, or from being used for genetic
430 <tag>7. Distribution of License
433 The rights attached to the program must apply to all
434 to whom the program is redistributed without the need
435 for execution of an additional license by those
438 <tag>8. License Must Not Be Specific to Debian
441 The rights attached to the program must not depend on
442 the program's being part of a Debian system. If the
443 program is extracted from Debian and used or
444 distributed without Debian but otherwise within the
445 terms of the program's license, all parties to whom
446 the program is redistributed must have the same
447 rights as those that are granted in conjunction with
450 <tag>9. License Must Not Contaminate Other Software
453 The license must not place restrictions on other
454 software that is distributed along with the licensed
455 software. For example, the license must not insist
456 that all other programs distributed on the same medium
457 must be free software.
459 <tag>10. Example Licenses
462 The "GPL," "BSD," and "Artistic" licenses are examples of
463 licenses that we consider <em>free</em>.
470 <heading>Archive areas</heading>
473 <heading>The main archive area</heading>
476 The <em>main</em> archive area comprises the Debian
477 distribution. Only the packages in this area are considered
478 part of the distribution. None of the packages in
479 the <em>main</em> archive area require software outside of
480 that area to function. Anyone may use, share, modify and
481 redistribute the packages in this archive area
483 See <url id="http://www.debian.org/intro/free"
484 name="What Does Free Mean?"> for
485 more about what we mean by free software.
490 Every package in <em>main</em> must comply with the DFSG
491 (Debian Free Software Guidelines).
495 In addition, the packages in <em>main</em>
496 <list compact="compact">
498 must not require or recommend a package outside
499 of <em>main</em> for compilation or execution (thus, the
500 package must not declare a "Pre-Depends", "Depends",
501 "Recommends", "Build-Depends", or "Build-Depends-Indep"
502 relationship on a non-<em>main</em> package),
505 must not be so buggy that we refuse to support them,
509 must meet all policy requirements presented in this
518 <heading>The contrib archive area</heading>
521 The <em>contrib</em> archive area contains supplemental
522 packages intended to work with the Debian distribution, but
523 which require software outside of the distribution to either
528 Every package in <em>contrib</em> must comply with the DFSG.
532 In addition, the packages in <em>contrib</em>
533 <list compact="compact">
535 must not be so buggy that we refuse to support them,
539 must meet all policy requirements presented in this
546 Examples of packages which would be included in
547 <em>contrib</em> are:
548 <list compact="compact">
550 free packages which require <em>contrib</em>,
551 <em>non-free</em> packages or packages which are not
552 in our archive at all for compilation or execution,
556 wrapper packages or other sorts of free accessories for
563 <sect1 id="non-free">
564 <heading>The non-free archive area</heading>
567 The <em>non-free</em> archive area contains supplemental
568 packages intended to work with the Debian distribution that do
569 not comply with the DFSG or have other problems that make
570 their distribution problematic. They may not comply with all
571 of the policy requirements in this manual due to restrictions
572 on modifications or other limitations.
576 Packages must be placed in <em>non-free</em> if they are
577 not compliant with the DFSG or are encumbered by patents
578 or other legal issues that make their distribution
583 In addition, the packages in <em>non-free</em>
584 <list compact="compact">
586 must not be so buggy that we refuse to support them,
590 must meet all policy requirements presented in this
591 manual that it is possible for them to meet.
593 It is possible that there are policy
594 requirements which the package is unable to
595 meet, for example, if the source is
596 unavailable. These situations will need to be
597 handled on a case-by-case basis.
606 <sect id="pkgcopyright">
607 <heading>Copyright considerations</heading>
610 Every package must be accompanied by a verbatim copy of its
611 copyright information and distribution license in the file
612 <file>/usr/share/doc/<var>package</var>/copyright</file>
613 (see <ref id="copyrightfile"> for further details).
617 We reserve the right to restrict files from being included
618 anywhere in our archives if
619 <list compact="compact">
621 their use or distribution would break a law,
624 there is an ethical conflict in their distribution or
628 we would have to sign a license for them, or
631 their distribution would conflict with other project
638 Programs whose authors encourage the user to make
639 donations are fine for the main distribution, provided
640 that the authors do not claim that not donating is
641 immoral, unethical, illegal or something similar; in such
642 a case they must go in <em>non-free</em>.
646 Packages whose copyright permission notices (or patent
647 problems) do not even allow redistribution of binaries
648 only, and where no special permission has been obtained,
649 must not be placed on the Debian FTP site and its mirrors
654 Note that under international copyright law (this applies
655 in the United States, too), <em>no</em> distribution or
656 modification of a work is allowed without an explicit
657 notice saying so. Therefore a program without a copyright
658 notice <em>is</em> copyrighted and you may not do anything
659 to it without risking being sued! Likewise if a program
660 has a copyright notice but no statement saying what is
661 permitted then nothing is permitted.
665 Many authors are unaware of the problems that restrictive
666 copyrights (or lack of copyright notices) can cause for
667 the users of their supposedly-free software. It is often
668 worthwhile contacting such authors diplomatically to ask
669 them to modify their license terms. However, this can be a
670 politically difficult thing to do and you should ask for
671 advice on the <tt>debian-legal</tt> mailing list first, as
676 When in doubt about a copyright, send mail to
677 <email>debian-legal@lists.debian.org</email>. Be prepared
678 to provide us with the copyright statement. Software
679 covered by the GPL, public domain software and BSD-like
680 copyrights are safe; be wary of the phrases "commercial
681 use prohibited" and "distribution restricted".
685 <sect id="subsections">
686 <heading>Sections</heading>
689 The packages in the archive areas <em>main</em>,
690 <em>contrib</em> and <em>non-free</em> are grouped further into
691 <em>sections</em> to simplify handling.
695 The archive area and section for each package should be
696 specified in the package's <tt>Section</tt> control record (see
697 <ref id="f-Section">). However, the maintainer of the Debian
698 archive may override this selection to ensure the consistency of
699 the Debian distribution. The <tt>Section</tt> field should be
701 <list compact="compact">
703 <em>section</em> if the package is in the
704 <em>main</em> archive area,
707 <em>area/section</em> if the package is in
708 the <em>contrib</em> or <em>non-free</em>
715 The Debian archive maintainers provide the authoritative
716 list of sections. At present, they are:
717 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
718 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
719 <em>education</em>, <em>electronics</em>, <em>embedded</em>,
720 <em>fonts</em>, <em>games</em>, <em>gnome</em>, <em>graphics</em>,
721 <em>gnu-r</em>, <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
722 <em>httpd</em>, <em>interpreters</em>, <em>introspection</em>,
723 <em>java</em>, <em>kde</em>, <em>kernel</em>, <em>libs</em>,
724 <em>libdevel</em>, <em>lisp</em>, <em>localization</em>,
725 <em>mail</em>, <em>math</em>, <em>metapackages</em>, <em>misc</em>,
726 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
727 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
728 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
729 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
730 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
731 <em>zope</em>. The additional section <em>debian-installer</em>
732 contains special packages used by the installer and is not used
733 for normal Debian packages.
737 For more information about the sections and their definitions,
738 see the <url id="http://packages.debian.org/unstable/"
739 name="list of sections in unstable">.
743 <sect id="priorities">
744 <heading>Priorities</heading>
747 Each package should have a <em>priority</em> value, which is
748 included in the package's <em>control record</em>
749 (see <ref id="f-Priority">).
750 This information is used by the Debian package management tools to
751 separate high-priority packages from less-important packages.
755 The following <em>priority levels</em> are recognized by the
756 Debian package management tools.
758 <tag><tt>required</tt></tag>
760 Packages which are necessary for the proper
761 functioning of the system (usually, this means that
762 dpkg functionality depends on these packages).
763 Removing a <tt>required</tt> package may cause your
764 system to become totally broken and you may not even
765 be able to use <prgn>dpkg</prgn> to put things back,
766 so only do so if you know what you are doing. Systems
767 with only the <tt>required</tt> packages are probably
768 unusable, but they do have enough functionality to
769 allow the sysadmin to boot and install more software.
771 <tag><tt>important</tt></tag>
773 Important programs, including those which one would
774 expect to find on any Unix-like system. If the
775 expectation is that an experienced Unix person who
776 found it missing would say "What on earth is going on,
777 where is <prgn>foo</prgn>?", it must be an
778 <tt>important</tt> package.<footnote>
779 This is an important criterion because we are
780 trying to produce, amongst other things, a free
783 Other packages without which the system will not run
784 well or be usable must also have priority
785 <tt>important</tt>. This does
786 <em>not</em> include Emacs, the X Window System, TeX
787 or any other large applications. The
788 <tt>important</tt> packages are just a bare minimum of
789 commonly-expected and necessary tools.
791 <tag><tt>standard</tt></tag>
793 These packages provide a reasonably small but not too
794 limited character-mode system. This is what will be
795 installed by default if the user doesn't select anything
796 else. It doesn't include many large applications.
798 <tag><tt>optional</tt></tag>
800 (In a sense everything that isn't required is
801 optional, but that's not what is meant here.) This is
802 all the software that you might reasonably want to
803 install if you didn't know what it was and don't have
804 specialized requirements. This is a much larger system
805 and includes the X Window System, a full TeX
806 distribution, and many applications. Note that
807 optional packages should not conflict with each other.
809 <tag><tt>extra</tt></tag>
811 This contains all packages that conflict with others
812 with required, important, standard or optional
813 priorities, or are only likely to be useful if you
814 already know what they are or have specialized
815 requirements (such as packages containing only detached
822 Packages must not depend on packages with lower priority
823 values (excluding build-time dependencies). In order to
824 ensure this, the priorities of one or more packages may need
833 <heading>Binary packages</heading>
836 The Debian distribution is based on the Debian
837 package management system, called <prgn>dpkg</prgn>. Thus,
838 all packages in the Debian distribution must be provided
839 in the <tt>.deb</tt> file format.
843 A <tt>.deb</tt> package contains two sets of files: a set of files
844 to install on the system when the package is installed, and a set
845 of files that provide additional metadata about the package or
846 which are executed when the package is installed or removed. This
847 second set of files is called <em>control information files</em>.
848 Among those files are the package maintainer scripts
849 and <file>control</file>, the <qref id="binarycontrolfiles">binary
850 package control file</qref> that contains the control fields for
851 the package. Other control information files
852 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
853 file</qref> used to store shared library dependency information
854 and the <file>conffiles</file> file that lists the package's
855 configuration files (described in <ref id="config-files">).
859 There is unfortunately a collision of terminology here between
860 control information files and files in the Debian control file
861 format. Throughout this document, a <em>control file</em> refers
862 to a file in the Debian control file format. These files are
863 documented in <ref id="controlfields">. Only files referred to
864 specifically as <em>control information files</em> are the files
865 included in the control information file member of
866 the <file>.deb</file> file format used by binary packages. Most
867 control information files are not in the Debian control file
872 <heading>The package name</heading>
875 Every package must have a name that's unique within the Debian
880 The package name is included in the control field
881 <tt>Package</tt>, the format of which is described
882 in <ref id="f-Package">.
883 The package name is also included as a part of the file name
884 of the <tt>.deb</tt> file.
889 <heading>The version of a package</heading>
892 Every package has a version number recorded in its
893 <tt>Version</tt> control file field, described in
894 <ref id="f-Version">.
898 The package management system imposes an ordering on version
899 numbers, so that it can tell whether packages are being up- or
900 downgraded and so that package system front end applications
901 can tell whether a package it finds available is newer than
902 the one installed on the system. The version number format
903 has the most significant parts (as far as comparison is
904 concerned) at the beginning.
908 If an upstream package has problematic version numbers they
909 should be converted to a sane form for use in the
910 <tt>Version</tt> field.
914 <heading>Version numbers based on dates</heading>
917 In general, Debian packages should use the same version
918 numbers as the upstream sources. However, upstream version
919 numbers based on some date formats (sometimes used for
920 development or "snapshot" releases) will not be ordered
921 correctly by the package management software. For
922 example, <prgn>dpkg</prgn> will consider "96May01" to be
923 greater than "96Dec24".
927 To prevent having to use epochs for every new upstream
928 version, the date-based portion of any upstream version number
929 should be given in a way that sorts correctly: four-digit year
930 first, followed by a two-digit numeric month, followed by a
931 two-digit numeric date, possibly with punctuation between the
936 Native Debian packages (i.e., packages which have been written
937 especially for Debian) whose version numbers include dates
938 should also follow these rules. If punctuation is desired
939 between the date components, remember that hyphen (<tt>-</tt>)
940 cannot be used in native package versions. Period
941 (<tt>.</tt>) is normally a good choice.
947 <sect id="maintainer">
948 <heading>The maintainer of a package</heading>
951 Every package must have a maintainer, except for orphaned
952 packages as described below. The maintainer may be one person
953 or a group of people reachable from a common email address, such
954 as a mailing list. The maintainer is responsible for
955 maintaining the Debian packaging files, evaluating and
956 responding appropriately to reported bugs, uploading new
957 versions of the package (either directly or through a sponsor),
958 ensuring that the package is placed in the appropriate archive
959 area and included in Debian releases as appropriate for the
960 stability and utility of the package, and requesting removal of
961 the package from the Debian distribution if it is no longer
962 useful or maintainable.
966 The maintainer must be specified in the <tt>Maintainer</tt>
967 control field with their correct name and a working email
968 address. The email address given in the <tt>Maintainer</tt>
969 control field must accept mail from those role accounts in
970 Debian used to send automated mails regarding the package. This
971 includes non-spam mail from the bug-tracking system, all mail
972 from the Debian archive maintenance software, and other role
973 accounts or automated processes that are commonly agreed on by
974 the project.<footnote>
975 A sample implementation of such a whitelist written for the
976 Mailman mailing list management software is used for mailing
977 lists hosted by alioth.debian.org.
979 If one person or team maintains several packages, they should
980 use the same form of their name and email address in
981 the <tt>Maintainer</tt> fields of those packages.
985 The format of the <tt>Maintainer</tt> control field is
986 described in <ref id="f-Maintainer">.
990 If the maintainer of the package is a team of people with a
991 shared email address, the <tt>Uploaders</tt> control field must
992 be present and must contain at least one human with their
993 personal email address. See <ref id="f-Uploaders"> for the
994 syntax of that field.
998 An orphaned package is one with no current maintainer. Orphaned
999 packages should have their <tt>Maintainer</tt> control field set
1000 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1001 These packages are considered maintained by the Debian project
1002 as a whole until someone else volunteers to take over
1003 maintenance.<footnote>
1004 The detailed procedure for gracefully orphaning a package can
1005 be found in the Debian Developer's Reference
1006 (see <ref id="related">).
1011 <sect id="descriptions">
1012 <heading>The description of a package</heading>
1015 Every Debian package must have a <tt>Description</tt> control
1016 field which contains a synopsis and extended description of the
1017 package. Technical information about the format of the
1018 <tt>Description</tt> field is in <ref id="f-Description">.
1022 The description should describe the package (the program) to a
1023 user (system administrator) who has never met it before so that
1024 they have enough information to decide whether they want to
1025 install it. This description should not just be copied verbatim
1026 from the program's documentation.
1030 Put important information first, both in the synopsis and
1031 extended description. Sometimes only the first part of the
1032 synopsis or of the description will be displayed. You can
1033 assume that there will usually be a way to see the whole
1034 extended description.
1038 The description should also give information about the
1039 significant dependencies and conflicts between this package
1040 and others, so that the user knows why these dependencies and
1041 conflicts have been declared.
1045 Instructions for configuring or using the package should
1046 not be included (that is what installation scripts,
1047 manual pages, info files, etc., are for). Copyright
1048 statements and other administrivia should not be included
1049 either (that is what the copyright file is for).
1052 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1055 The single line synopsis should be kept brief - certainly
1056 under 80 characters.
1060 Do not include the package name in the synopsis line. The
1061 display software knows how to display this already, and you
1062 do not need to state it. Remember that in many situations
1063 the user may only see the synopsis line - make it as
1064 informative as you can.
1069 <sect1 id="extendeddesc"><heading>The extended description</heading>
1072 Do not try to continue the single line synopsis into the
1073 extended description. This will not work correctly when
1074 the full description is displayed, and makes no sense
1075 where only the summary (the single line synopsis) is
1080 The extended description should describe what the package
1081 does and how it relates to the rest of the system (in terms
1082 of, for example, which subsystem it is which part of).
1086 The description field needs to make sense to anyone, even
1087 people who have no idea about any of the things the
1088 package deals with.<footnote>
1089 The blurb that comes with a program in its
1090 announcements and/or <prgn>README</prgn> files is
1091 rarely suitable for use in a description. It is
1092 usually aimed at people who are already in the
1093 community where the package is used.
1101 <sect id="dependencies">
1102 <heading>Dependencies</heading>
1105 Every package must specify the dependency information
1106 about other packages that are required for the first to
1111 For example, a dependency entry must be provided for any
1112 shared libraries required by a dynamically-linked executable
1113 binary in a package.
1117 Packages are not required to declare any dependencies they
1118 have on other packages which are marked <tt>Essential</tt>
1119 (see below), and should not do so unless they depend on a
1120 particular version of that package.<footnote>
1122 Essential is needed in part to avoid unresolvable dependency
1123 loops on upgrade. If packages add unnecessary dependencies
1124 on packages in this set, the chances that there
1125 <strong>will</strong> be an unresolvable dependency loop
1126 caused by forcing these Essential packages to be configured
1127 first before they need to be is greatly increased. It also
1128 increases the chances that frontends will be unable to
1129 <strong>calculate</strong> an upgrade path, even if one
1133 Also, functionality is rarely ever removed from the
1134 Essential set, but <em>packages</em> have been removed from
1135 the Essential set when the functionality moved to a
1136 different package. So depending on these packages <em>just
1137 in case</em> they stop being essential does way more harm
1144 Sometimes, unpacking one package requires that another package
1145 be first unpacked <em>and</em> configured. In this case, the
1146 depending package must specify this dependency in
1147 the <tt>Pre-Depends</tt> control field.
1151 You should not specify a <tt>Pre-Depends</tt> entry for a
1152 package before this has been discussed on the
1153 <tt>debian-devel</tt> mailing list and a consensus about
1154 doing that has been reached.
1158 The format of the package interrelationship control fields is
1159 described in <ref id="relationships">.
1163 <sect id="virtual_pkg">
1164 <heading>Virtual packages</heading>
1167 Sometimes, there are several packages which offer
1168 more-or-less the same functionality. In this case, it's
1169 useful to define a <em>virtual package</em> whose name
1170 describes that common functionality. (The virtual
1171 packages only exist logically, not physically; that's why
1172 they are called <em>virtual</em>.) The packages with this
1173 particular function will then <em>provide</em> the virtual
1174 package. Thus, any other package requiring that function
1175 can simply depend on the virtual package without having to
1176 specify all possible packages individually.
1180 All packages should use virtual package names where
1181 appropriate, and arrange to create new ones if necessary.
1182 They should not use virtual package names (except privately,
1183 amongst a cooperating group of packages) unless they have
1184 been agreed upon and appear in the list of virtual package
1185 names. (See also <ref id="virtual">)
1189 The latest version of the authoritative list of virtual
1190 package names can be found in the <tt>debian-policy</tt> package.
1191 It is also available from the Debian web mirrors at
1192 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1193 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1197 The procedure for updating the list is described in the preface
1204 <heading>Base system</heading>
1207 The <tt>base system</tt> is a minimum subset of the Debian
1208 system that is installed before everything else
1209 on a new system. Only very few packages are allowed to form
1210 part of the base system, in order to keep the required disk
1215 The base system consists of all those packages with priority
1216 <tt>required</tt> or <tt>important</tt>. Many of them will
1217 be tagged <tt>essential</tt> (see below).
1222 <heading>Essential packages</heading>
1225 Essential is defined as the minimal set of functionality that
1226 must be available and usable on the system at all times, even
1227 when packages are in an unconfigured (but unpacked) state.
1228 Packages are tagged <tt>essential</tt> for a system using the
1229 <tt>Essential</tt> control field. The format of the
1230 <tt>Essential</tt> control field is described in <ref
1235 Since these packages cannot be easily removed (one has to
1236 specify an extra <em>force option</em> to
1237 <prgn>dpkg</prgn> to do so), this flag must not be used
1238 unless absolutely necessary. A shared library package
1239 must not be tagged <tt>essential</tt>; dependencies will
1240 prevent its premature removal, and we need to be able to
1241 remove it when it has been superseded.
1245 Since dpkg will not prevent upgrading of other packages
1246 while an <tt>essential</tt> package is in an unconfigured
1247 state, all <tt>essential</tt> packages must supply all of
1248 their core functionality even when unconfigured. If the
1249 package cannot satisfy this requirement it must not be
1250 tagged as essential, and any packages depending on this
1251 package must instead have explicit dependency fields as
1256 Maintainers should take great care in adding any programs,
1257 interfaces, or functionality to <tt>essential</tt> packages.
1258 Packages may assume that functionality provided by
1259 <tt>essential</tt> packages is always available without
1260 declaring explicit dependencies, which means that removing
1261 functionality from the Essential set is very difficult and is
1262 almost never done. Any capability added to an
1263 <tt>essential</tt> package therefore creates an obligation to
1264 support that capability as part of the Essential set in
1269 You must not tag any packages <tt>essential</tt> before
1270 this has been discussed on the <tt>debian-devel</tt>
1271 mailing list and a consensus about doing that has been
1276 <sect id="maintscripts">
1277 <heading>Maintainer Scripts</heading>
1280 The package installation scripts should avoid producing
1281 output which is unnecessary for the user to see and
1282 should rely on <prgn>dpkg</prgn> to stave off boredom on
1283 the part of a user installing many packages. This means,
1284 amongst other things, using the <tt>--quiet</tt> option on
1285 <prgn>install-info</prgn>.
1289 Errors which occur during the execution of an installation
1290 script must be checked and the installation must not
1291 continue after an error.
1295 Note that in general <ref id="scripts"> applies to package
1296 maintainer scripts, too.
1300 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1301 to another package without consulting the maintainer of that
1302 package first. When adding or removing diversions, package
1303 maintainer scripts must provide the <tt>--package</tt> flag
1304 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1308 All packages which supply an instance of a common command
1309 name (or, in general, filename) should generally use
1310 <prgn>update-alternatives</prgn>, so that they may be
1311 installed together. If <prgn>update-alternatives</prgn>
1312 is not used, then each package must use
1313 <tt>Conflicts</tt> to ensure that other packages are
1314 de-installed. (In this case, it may be appropriate to
1315 specify a conflict against earlier versions of something
1316 that previously did not use
1317 <prgn>update-alternatives</prgn>; this is an exception to
1318 the usual rule that versioned conflicts should be
1322 <sect1 id="maintscriptprompt">
1323 <heading>Prompting in maintainer scripts</heading>
1325 Package maintainer scripts may prompt the user if
1326 necessary. Prompting must be done by communicating
1327 through a program, such as <prgn>debconf</prgn>, which
1328 conforms to the Debian Configuration Management
1329 Specification, version 2 or higher.
1333 Packages which are essential, or which are dependencies of
1334 essential packages, may fall back on another prompting method
1335 if no such interface is available when they are executed.
1339 The Debian Configuration Management Specification is included
1340 in the <file>debconf_specification</file> files in the
1341 <package>debian-policy</package> package.
1342 It is also available from the Debian web mirrors at
1343 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1344 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1348 Packages which use the Debian Configuration Management
1349 Specification may contain the additional control information
1350 files <file>config</file>
1351 and <file>templates</file>. <file>config</file> is an
1352 additional maintainer script used for package configuration,
1353 and <file>templates</file> contains templates used for user
1354 prompting. The <prgn>config</prgn> script might be run before
1355 the <prgn>preinst</prgn> script and before the package is
1356 unpacked or any of its dependencies or pre-dependencies are
1357 satisfied. Therefore it must work using only the tools
1358 present in <em>essential</em> packages.<footnote>
1359 <package>Debconf</package> or another tool that
1360 implements the Debian Configuration Management
1361 Specification will also be installed, and any
1362 versioned dependencies on it will be satisfied
1363 before preconfiguration begins.
1368 Packages which use the Debian Configuration Management
1369 Specification must allow for translation of their user-visible
1370 messages by using a gettext-based system such as the one
1371 provided by the <package>po-debconf</package> package.
1375 Packages should try to minimize the amount of prompting
1376 they need to do, and they should ensure that the user
1377 will only ever be asked each question once. This means
1378 that packages should try to use appropriate shared
1379 configuration files (such as <file>/etc/papersize</file> and
1380 <file>/etc/news/server</file>), and shared
1381 <package>debconf</package> variables rather than each
1382 prompting for their own list of required pieces of
1387 It also means that an upgrade should not ask the same
1388 questions again, unless the user has used
1389 <tt>dpkg --purge</tt> to remove the package's configuration.
1390 The answers to configuration questions should be stored in an
1391 appropriate place in <file>/etc</file> so that the user can
1392 modify them, and how this has been done should be
1397 If a package has a vitally important piece of
1398 information to pass to the user (such as "don't run me
1399 as I am, you must edit the following configuration files
1400 first or you risk your system emitting badly-formatted
1401 messages"), it should display this in the
1402 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1403 prompt the user to hit return to acknowledge the
1404 message. Copyright messages do not count as vitally
1405 important (they belong in
1406 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1407 neither do instructions on how to use a program (these
1408 should be in on-line documentation, where all the users
1413 Any necessary prompting should almost always be confined
1414 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1415 script. If it is done in the <prgn>postinst</prgn>, it
1416 should be protected with a conditional so that
1417 unnecessary prompting doesn't happen if a package's
1418 installation fails and the <prgn>postinst</prgn> is
1419 called with <tt>abort-upgrade</tt>,
1420 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1430 <heading>Source packages</heading>
1432 <sect id="standardsversion">
1433 <heading>Standards conformance</heading>
1436 Source packages should specify the most recent version number
1437 of this policy document with which your package complied
1438 when it was last updated.
1442 This information may be used to file bug reports
1443 automatically if your package becomes too much out of date.
1447 The version is specified in the <tt>Standards-Version</tt>
1449 The format of the <tt>Standards-Version</tt> field is
1450 described in <ref id="f-Standards-Version">.
1454 You should regularly, and especially if your package has
1455 become out of date, check for the newest Policy Manual
1456 available and update your package, if necessary. When your
1457 package complies with the new standards you should update the
1458 <tt>Standards-Version</tt> source package field and
1459 release it.<footnote>
1460 See the file <file>upgrading-checklist</file> for
1461 information about policy which has changed between
1462 different versions of this document.
1468 <sect id="pkg-relations">
1469 <heading>Package relationships</heading>
1472 Source packages should specify which binary packages they
1473 require to be installed or not to be installed in order to
1474 build correctly. For example, if building a package
1475 requires a certain compiler, then the compiler should be
1476 specified as a build-time dependency.
1480 It is not necessary to explicitly specify build-time
1481 relationships on a minimal set of packages that are always
1482 needed to compile, link and put in a Debian package a
1483 standard "Hello World!" program written in C or C++. The
1484 required packages are called <em>build-essential</em>, and
1485 an informational list can be found in
1486 <file>/usr/share/doc/build-essential/list</file> (which is
1487 contained in the <tt>build-essential</tt>
1490 <list compact="compact">
1492 This allows maintaining the list separately
1493 from the policy documents (the list does not
1494 need the kind of control that the policy
1498 Having a separate package allows one to install
1499 the build-essential packages on a machine, as
1500 well as allowing other packages such as tasks to
1501 require installation of the build-essential
1502 packages using the depends relation.
1505 The separate package allows bug reports against
1506 the list to be categorized separately from
1507 the policy management process in the BTS.
1514 When specifying the set of build-time dependencies, one
1515 should list only those packages explicitly required by the
1516 build. It is not necessary to list packages which are
1517 required merely because some other package in the list of
1518 build-time dependencies depends on them.<footnote>
1519 The reason for this is that dependencies change, and
1520 you should list all those packages, and <em>only</em>
1521 those packages that <em>you</em> need directly. What
1522 others need is their business. For example, if you
1523 only link against <file>libimlib</file>, you will need to
1524 build-depend on <package>libimlib2-dev</package> but
1525 not against any <tt>libjpeg*</tt> packages, even
1526 though <tt>libimlib2-dev</tt> currently depends on
1527 them: installation of <package>libimlib2-dev</package>
1528 will automatically ensure that all of its run-time
1529 dependencies are satisfied.
1534 If build-time dependencies are specified, it must be
1535 possible to build the package and produce working binaries
1536 on a system with only essential and build-essential
1537 packages installed and also those required to satisfy the
1538 build-time relationships (including any implied
1539 relationships). In particular, this means that version
1540 clauses should be used rigorously in build-time
1541 relationships so that one cannot produce bad or
1542 inconsistently configured packages when the relationships
1543 are properly satisfied.
1547 <ref id="relationships"> explains the technical details.
1552 <heading>Changes to the upstream sources</heading>
1555 If changes to the source code are made that are not
1556 specific to the needs of the Debian system, they should be
1557 sent to the upstream authors in whatever form they prefer
1558 so as to be included in the upstream version of the
1563 If you need to configure the package differently for
1564 Debian or for Linux, and the upstream source doesn't
1565 provide a way to do so, you should add such configuration
1566 facilities (for example, a new <prgn>autoconf</prgn> test
1567 or <tt>#define</tt>) and send the patch to the upstream
1568 authors, with the default set to the way they originally
1569 had it. You can then easily override the default in your
1570 <file>debian/rules</file> or wherever is appropriate.
1574 You should make sure that the <prgn>configure</prgn> utility
1575 detects the correct architecture specification string
1576 (refer to <ref id="arch-spec"> for details).
1580 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1581 <prgn>configure</prgn> scripts are used, you should edit the
1582 <file>.in</file> files rather than editing the
1583 <prgn>Makefile</prgn> directly. This allows the user to
1584 reconfigure the package if necessary. You should
1585 <em>not</em> configure the package and edit the generated
1586 <prgn>Makefile</prgn>! This makes it impossible for someone
1587 else to later reconfigure the package without losing the
1593 <sect id="dpkgchangelog">
1594 <heading>Debian changelog: <file>debian/changelog</file></heading>
1597 Changes in the Debian version of the package should be
1598 briefly explained in the Debian changelog file
1599 <file>debian/changelog</file>.<footnote>
1601 Mistakes in changelogs are usually best rectified by
1602 making a new changelog entry rather than "rewriting
1603 history" by editing old changelog entries.
1606 This includes modifications
1607 made in the Debian package compared to the upstream one
1608 as well as other changes and updates to the package.
1610 Although there is nothing stopping an author who is also
1611 the Debian maintainer from using this changelog for all
1612 their changes, it will have to be renamed if the Debian
1613 and upstream maintainers become different people. In such
1614 a case, however, it might be better to maintain the package
1615 as a non-native package.
1620 The format of the <file>debian/changelog</file> allows the
1621 package building tools to discover which version of the package
1622 is being built and find out other release-specific information.
1626 That format is a series of entries like this:
1628 <example compact="compact">
1629 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1631 [optional blank line(s), stripped]
1633 * <var>change details</var>
1634 <var>more change details</var>
1636 [blank line(s), included in output of dpkg-parsechangelog]
1638 * <var>even more change details</var>
1640 [optional blank line(s), stripped]
1642 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1647 <var>package</var> and <var>version</var> are the source
1648 package name and version number.
1652 <var>distribution(s)</var> lists the distributions where
1653 this version should be installed when it is uploaded - it
1654 is copied to the <tt>Distribution</tt> field in the
1655 <file>.changes</file> file. See <ref id="f-Distribution">.
1659 <var>urgency</var> is the value for the <tt>Urgency</tt>
1660 field in the <file>.changes</file> file for the upload
1661 (see <ref id="f-Urgency">). It is not possible to specify
1662 an urgency containing commas; commas are used to separate
1663 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1664 <prgn>dpkg</prgn> changelog format (though there is
1665 currently only one useful <var>keyword</var>,
1670 The change details may in fact be any series of lines
1671 starting with at least two spaces, but conventionally each
1672 change starts with an asterisk and a separating space and
1673 continuation lines are indented so as to bring them in
1674 line with the start of the text above. Blank lines may be
1675 used here to separate groups of changes, if desired.
1679 If this upload resolves bugs recorded in the Bug Tracking
1680 System (BTS), they may be automatically closed on the
1681 inclusion of this package into the Debian archive by
1682 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1683 in the change details.<footnote>
1684 To be precise, the string should match the following
1685 Perl regular expression:
1687 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1689 Then all of the bug numbers listed will be closed by the
1690 archive maintenance script (<prgn>katie</prgn>) using the
1691 <var>version</var> of the changelog entry.
1693 This information is conveyed via the <tt>Closes</tt> field
1694 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1698 The maintainer name and email address used in the changelog
1699 should be the details of the person uploading <em>this</em>
1700 version. They are <em>not</em> necessarily those of the
1701 usual package maintainer.<footnote>
1702 If the developer uploading the package is not one of the usual
1703 maintainers of the package (as listed in
1704 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1705 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1706 fields of the package), the first line of the changelog is
1707 conventionally used to explain why a non-maintainer is
1708 uploading the package. The Debian Developer's Reference
1709 (see <ref id="related">) documents the conventions
1711 The information here will be copied to the <tt>Changed-By</tt>
1712 field in the <tt>.changes</tt> file
1713 (see <ref id="f-Changed-By">), and then later used to send an
1714 acknowledgement when the upload has been installed.
1718 The <var>date</var> has the following format<footnote>
1719 This is the same as the format generated by <tt>date
1721 </footnote> (compatible and with the same semantics of
1722 RFC 2822 and RFC 5322):
1723 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1725 <list compact="compact">
1727 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1730 dd is a one- or two-digit day of the month (01-31)
1733 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1736 <item>yyyy is the four-digit year (e.g. 2010)</item>
1737 <item>hh is the two-digit hour (00-23)</item>
1738 <item>mm is the two-digit minutes (00-59)</item>
1739 <item>ss is the two-digit seconds (00-60)</item>
1741 +zzzz or -zzzz is the the time zone offset from Coordinated
1742 Universal Time (UTC). "+" indicates that the time is ahead
1743 of (i.e., east of) UTC and "-" indicates that the time is
1744 behind (i.e., west of) UTC. The first two digits indicate
1745 the hour difference from UTC and the last two digits
1746 indicate the number of additional minutes difference from
1747 UTC. The last two digits must be in the range 00-59.
1753 The first "title" line with the package name must start
1754 at the left hand margin. The "trailer" line with the
1755 maintainer and date details must be preceded by exactly
1756 one space. The maintainer details and the date must be
1757 separated by exactly two spaces.
1761 The entire changelog must be encoded in UTF-8.
1765 For more information on placement of the changelog files
1766 within binary packages, please see <ref id="changelogs">.
1770 <sect id="dpkgcopyright">
1771 <heading>Copyright: <file>debian/copyright</file></heading>
1773 Every package must be accompanied by a verbatim copy of its
1774 copyright information and distribution license in the file
1775 <file>/usr/share/doc/<var>package</var>/copyright</file>
1776 (see <ref id="copyrightfile"> for further details). Also see
1777 <ref id="pkgcopyright"> for further considerations related
1778 to copyrights for packages.
1782 <heading>Error trapping in makefiles</heading>
1785 When <prgn>make</prgn> invokes a command in a makefile
1786 (including your package's upstream makefiles and
1787 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1788 means that <prgn>sh</prgn>'s usual bad error handling
1789 properties apply: if you include a miniature script as one
1790 of the commands in your makefile you'll find that if you
1791 don't do anything about it then errors are not detected
1792 and <prgn>make</prgn> will blithely continue after
1797 Every time you put more than one shell command (this
1798 includes using a loop) in a makefile command you
1799 must make sure that errors are trapped. For
1800 simple compound commands, such as changing directory and
1801 then running a program, using <tt>&&</tt> rather
1802 than semicolon as a command separator is sufficient. For
1803 more complex commands including most loops and
1804 conditionals you should include a separate <tt>set -e</tt>
1805 command at the start of every makefile command that's
1806 actually one of these miniature shell scripts.
1810 <sect id="timestamps">
1811 <heading>Time Stamps</heading>
1813 Maintainers should preserve the modification times of the
1814 upstream source files in a package, as far as is reasonably
1816 The rationale is that there is some information conveyed
1817 by knowing the age of the file, for example, you could
1818 recognize that some documentation is very old by looking
1819 at the modification time, so it would be nice if the
1820 modification time of the upstream source would be
1826 <sect id="restrictions">
1827 <heading>Restrictions on objects in source packages</heading>
1830 The source package may not contain any hard links<footnote>
1832 This is not currently detected when building source
1833 packages, but only when extracting
1837 Hard links may be permitted at some point in the
1838 future, but would require a fair amount of
1841 </footnote>, device special files, sockets or setuid or
1842 setgid files.<footnote>
1843 Setgid directories are allowed.
1848 <sect id="debianrules">
1849 <heading>Main building script: <file>debian/rules</file></heading>
1852 This file must be an executable makefile, and contains the
1853 package-specific recipes for compiling the package and
1854 building binary package(s) from the source.
1858 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1859 so that it can be invoked by saying its name rather than
1860 invoking <prgn>make</prgn> explicitly. That is, invoking
1861 either of <tt>make -f debian/rules <em>args...</em></tt>
1862 or <tt>./debian/rules <em>args...</em></tt> must result in
1867 The following targets are required and must be implemented
1868 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1869 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1870 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1874 Since an interactive <file>debian/rules</file> script makes it
1875 impossible to auto-compile that package and also makes it hard
1876 for other people to reproduce the same binary package, all
1877 required targets must be non-interactive. It also follows that
1878 any target that these targets depend on must also be
1883 The targets are as follows:
1885 <tag><tt>build</tt> (required)</tag>
1888 The <tt>build</tt> target should perform all the
1889 configuration and compilation of the package.
1890 If a package has an interactive pre-build
1891 configuration routine, the Debian source package
1892 must either be built after this has taken place (so
1893 that the binary package can be built without rerunning
1894 the configuration) or the configuration routine
1895 modified to become non-interactive. (The latter is
1896 preferable if there are architecture-specific features
1897 detected by the configuration routine.)
1901 For some packages, notably ones where the same
1902 source tree is compiled in different ways to produce
1903 two binary packages, the <tt>build</tt> target
1904 does not make much sense. For these packages it is
1905 good enough to provide two (or more) targets
1906 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1907 for each of the ways of building the package, and a
1908 <tt>build</tt> target that does nothing. The
1909 <tt>binary</tt> target will have to build the
1910 package in each of the possible ways and make the
1911 binary package out of each.
1915 The <tt>build</tt> target must not do anything
1916 that might require root privilege.
1920 The <tt>build</tt> target may need to run the
1921 <tt>clean</tt> target first - see below.
1925 When a package has a configuration and build routine
1926 which takes a long time, or when the makefiles are
1927 poorly designed, or when <tt>build</tt> needs to
1928 run <tt>clean</tt> first, it is a good idea to
1929 <tt>touch build</tt> when the build process is
1930 complete. This will ensure that if <tt>debian/rules
1931 build</tt> is run again it will not rebuild the whole
1933 Another common way to do this is for <tt>build</tt>
1934 to depend on <prgn>build-stamp</prgn> and to do
1935 nothing else, and for the <prgn>build-stamp</prgn>
1936 target to do the building and to <tt>touch
1937 build-stamp</tt> on completion. This is
1938 especially useful if the build routine creates a
1939 file or directory called <tt>build</tt>; in such a
1940 case, <tt>build</tt> will need to be listed as
1941 a phony target (i.e., as a dependency of the
1942 <tt>.PHONY</tt> target). See the documentation of
1943 <prgn>make</prgn> for more information on phony
1949 <tag><tt>build-arch</tt> (optional),
1950 <tt>build-indep</tt> (optional)
1954 A package may also provide one or both of the targets
1955 <tt>build-arch</tt> and <tt>build-indep</tt>.
1956 The <tt>build-arch</tt> target, if provided, should
1957 perform all the configuration and compilation required for
1958 producing all architecture-dependant binary packages
1959 (those packages for which the body of the
1960 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1961 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1962 target, if provided, should perform all the configuration
1963 and compilation required for producing all
1964 architecture-independent binary packages (those packages
1965 for which the body of the <tt>Architecture</tt> field
1966 in <tt>debian/control</tt> is <tt>all</tt>).
1970 If <tt>build-arch</tt> or <tt>build-indep</tt> targets are
1971 provided in the rules file, the <tt>build</tt> target
1972 should either depend on those targets or take the same
1973 actions as invoking those targets would perform.<footnote>
1974 The intent of this split is so that binary-only builds
1975 need not install the dependencies required for
1976 the <tt>build-indep</tt> target. However, this is not
1977 yet used in practice since <tt>dpkg-buildpackage
1978 -B</tt>, and therefore the autobuilders,
1979 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1980 due to the difficulties in determining whether the
1981 optional <tt>build-arch</tt> target exists.
1986 If one or both of the targets <tt>build-arch</tt> and
1987 <tt>build-indep</tt> are not provided, then invoking
1988 <file>debian/rules</file> with one of the not-provided
1989 targets as arguments should produce a exit status code
1990 of 2. Usually this is provided automatically by make
1991 if the target is missing.
1995 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1996 must not do anything that might require root privilege.
2000 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2001 (required), <tt>binary-indep</tt> (required)
2005 The <tt>binary</tt> target must be all that is
2006 necessary for the user to build the binary package(s)
2007 produced from this source package. It is
2008 split into two parts: <prgn>binary-arch</prgn> builds
2009 the binary packages which are specific to a particular
2010 architecture, and <tt>binary-indep</tt> builds
2011 those which are not.
2014 <tt>binary</tt> may be (and commonly is) a target with
2015 no commands which simply depends on
2016 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2019 Both <tt>binary-*</tt> targets should depend on the
2020 <tt>build</tt> target, or on the appropriate
2021 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2022 provided, so that the package is built if it has not
2023 been already. It should then create the relevant
2024 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2025 make their control files and <prgn>dpkg-deb</prgn> to
2026 build them and place them in the parent of the top
2031 Both the <tt>binary-arch</tt> and
2032 <tt>binary-indep</tt> targets <em>must</em> exist.
2033 If one of them has nothing to do (which will always be
2034 the case if the source generates only a single binary
2035 package, whether architecture-dependent or not), it
2036 must still exist and must always succeed.
2040 The <tt>binary</tt> targets must be invoked as
2042 The <prgn>fakeroot</prgn> package often allows one
2043 to build a package correctly even without being
2049 <tag><tt>clean</tt> (required)</tag>
2052 This must undo any effects that the <tt>build</tt>
2053 and <tt>binary</tt> targets may have had, except
2054 that it should leave alone any output files created in
2055 the parent directory by a run of a <tt>binary</tt>
2060 If a <tt>build</tt> file is touched at the end of
2061 the <tt>build</tt> target, as suggested above, it
2062 should be removed as the first action that
2063 <tt>clean</tt> performs, so that running
2064 <tt>build</tt> again after an interrupted
2065 <tt>clean</tt> doesn't think that everything is
2070 The <tt>clean</tt> target may need to be
2071 invoked as root if <tt>binary</tt> has been
2072 invoked since the last <tt>clean</tt>, or if
2073 <tt>build</tt> has been invoked as root (since
2074 <tt>build</tt> may create directories, for
2079 <tag><tt>get-orig-source</tt> (optional)</tag>
2082 This target fetches the most recent version of the
2083 original source package from a canonical archive site
2084 (via FTP or WWW, for example), does any necessary
2085 rearrangement to turn it into the original source
2086 tar file format described below, and leaves it in the
2091 This target may be invoked in any directory, and
2092 should take care to clean up any temporary files it
2097 This target is optional, but providing it if
2098 possible is a good idea.
2102 <tag><tt>patch</tt> (optional)</tag>
2105 This target performs whatever additional actions are
2106 required to make the source ready for editing (unpacking
2107 additional upstream archives, applying patches, etc.).
2108 It is recommended to be implemented for any package where
2109 <tt>dpkg-source -x</tt> does not result in source ready
2110 for additional modification. See
2111 <ref id="readmesource">.
2117 The <tt>build</tt>, <tt>binary</tt> and
2118 <tt>clean</tt> targets must be invoked with the current
2119 directory being the package's top-level directory.
2124 Additional targets may exist in <file>debian/rules</file>,
2125 either as published or undocumented interfaces or for the
2126 package's internal use.
2130 The architectures we build on and build for are determined
2131 by <prgn>make</prgn> variables using the
2132 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2133 You can determine the Debian architecture and the GNU style
2134 architecture specification string for the build architecture as
2135 well as for the host architecture. The build architecture is
2136 the architecture on which <file>debian/rules</file> is run and
2137 the package build is performed. The host architecture is the
2138 architecture on which the resulting package will be installed
2139 and run. These are normally the same, but may be different in
2140 the case of cross-compilation (building packages for one
2141 architecture on machines of a different architecture).
2145 Here is a list of supported <prgn>make</prgn> variables:
2146 <list compact="compact">
2148 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2151 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2154 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2157 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2158 specification string)
2161 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2162 <tt>DEB_*_GNU_TYPE</tt>)
2165 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2166 <tt>DEB_*_GNU_TYPE</tt>)
2168 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2169 the build architecture or <tt>HOST</tt> for specification of the
2174 Backward compatibility can be provided in the rules file
2175 by setting the needed variables to suitable default
2176 values; please refer to the documentation of
2177 <prgn>dpkg-architecture</prgn> for details.
2181 It is important to understand that the <tt>DEB_*_ARCH</tt>
2182 string only determines which Debian architecture we are
2183 building on or for. It should not be used to get the CPU
2184 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2185 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2186 GNU style variables should generally only be used with upstream
2190 <sect1 id="debianrules-options">
2191 <heading><file>debian/rules</file> and
2192 <tt>DEB_BUILD_OPTIONS</tt></heading>
2195 Supporting the standardized environment variable
2196 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2197 contain several flags to change how a package is compiled and
2198 built. Each flag must be in the form <var>flag</var> or
2199 <var>flag</var>=<var>options</var>. If multiple flags are
2200 given, they must be separated by whitespace.<footnote>
2201 Some packages support any delimiter, but whitespace is the
2202 easiest to parse inside a makefile and avoids ambiguity with
2203 flag values that contain commas.
2205 <var>flag</var> must start with a lowercase letter
2206 (<tt>a-z</tt>) and consist only of lowercase letters,
2207 numbers (<tt>0-9</tt>), and the characters
2208 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2209 <var>options</var> must not contain whitespace. The same
2210 tag should not be given multiple times with conflicting
2211 values. Package maintainers may assume that
2212 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2216 The meaning of the following tags has been standardized:
2220 This tag says to not run any build-time test suite
2221 provided by the package.
2225 The presence of this tag means that the package should
2226 be compiled with a minimum of optimization. For C
2227 programs, it is best to add <tt>-O0</tt> to
2228 <tt>CFLAGS</tt> (although this is usually the default).
2229 Some programs might fail to build or run at this level
2230 of optimization; it may be necessary to use
2231 <tt>-O1</tt>, for example.
2235 This tag means that the debugging symbols should not be
2236 stripped from the binary during installation, so that
2237 debugging information may be included in the package.
2239 <tag>parallel=n</tag>
2241 This tag means that the package should be built using up
2242 to <tt>n</tt> parallel processes if the package build
2243 system supports this.<footnote>
2244 Packages built with <tt>make</tt> can often implement
2245 this by passing the <tt>-j</tt><var>n</var> option to
2248 If the package build system does not support parallel
2249 builds, this string must be ignored. If the package
2250 build system only supports a lower level of concurrency
2251 than <var>n</var>, the package should be built using as
2252 many parallel processes as the package build system
2253 supports. It is up to the package maintainer to decide
2254 whether the package build times are long enough and the
2255 package build system is robust enough to make supporting
2256 parallel builds worthwhile.
2262 Unknown flags must be ignored by <file>debian/rules</file>.
2266 The following makefile snippet is an example of how one may
2267 implement the build options; you will probably have to
2268 massage this example in order to make it work for your
2270 <example compact="compact">
2273 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2274 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2275 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2276 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2278 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2283 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2284 INSTALL_PROGRAM += -s
2286 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2287 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2288 MAKEFLAGS += -j$(NUMJOBS)
2293 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2294 # Code to run the package test suite.
2301 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2302 <sect id="substvars">
2303 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2306 When <prgn>dpkg-gencontrol</prgn>
2307 generates <qref id="binarycontrolfiles">binary package control
2308 files</qref> (<file>DEBIAN/control</file>), it performs variable
2309 substitutions on its output just before writing it. Variable
2310 substitutions have the form <tt>${<var>variable</var>}</tt>.
2311 The optional file <file>debian/substvars</file> contains
2312 variable substitutions to be used; variables can also be set
2313 directly from <file>debian/rules</file> using the <tt>-V</tt>
2314 option to the source packaging commands, and certain predefined
2315 variables are also available.
2319 The <file>debian/substvars</file> file is usually generated and
2320 modified dynamically by <file>debian/rules</file> targets, in
2321 which case it must be removed by the <tt>clean</tt> target.
2325 See <manref name="deb-substvars" section="5"> for full
2326 details about source variable substitutions, including the
2327 format of <file>debian/substvars</file>.</p>
2330 <sect id="debianwatch">
2331 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2334 This is an optional, recommended configuration file for the
2335 <tt>uscan</tt> utility which defines how to automatically scan
2336 ftp or http sites for newly available updates of the
2337 package. This is used
2338 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2339 tools to help with quality control and maintenance of the
2340 distribution as a whole.
2345 <sect id="debianfiles">
2346 <heading>Generated files list: <file>debian/files</file></heading>
2349 This file is not a permanent part of the source tree; it
2350 is used while building packages to record which files are
2351 being generated. <prgn>dpkg-genchanges</prgn> uses it
2352 when it generates a <file>.changes</file> file.
2356 It should not exist in a shipped source package, and so it
2357 (and any backup files or temporary files such as
2358 <file>files.new</file><footnote>
2359 <file>files.new</file> is used as a temporary file by
2360 <prgn>dpkg-gencontrol</prgn> and
2361 <prgn>dpkg-distaddfile</prgn> - they write a new
2362 version of <tt>files</tt> here before renaming it,
2363 to avoid leaving a corrupted copy if an error
2365 </footnote>) should be removed by the
2366 <tt>clean</tt> target. It may also be wise to
2367 ensure a fresh start by emptying or removing it at the
2368 start of the <tt>binary</tt> target.
2372 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2373 package, it adds an entry to <file>debian/files</file> for the
2374 <file>.deb</file> file that will be created when <tt>dpkg-deb
2375 --build</tt> is run for that binary package. So for most
2376 packages all that needs to be done with this file is to
2377 delete it in the <tt>clean</tt> target.
2381 If a package upload includes files besides the source
2382 package and any binary packages whose control files were
2383 made with <prgn>dpkg-gencontrol</prgn> then they should be
2384 placed in the parent of the package's top-level directory
2385 and <prgn>dpkg-distaddfile</prgn> should be called to add
2386 the file to the list in <file>debian/files</file>.</p>
2389 <sect id="embeddedfiles">
2390 <heading>Convenience copies of code</heading>
2393 Some software packages include in their distribution convenience
2394 copies of code from other software packages, generally so that
2395 users compiling from source don't have to download multiple
2396 packages. Debian packages should not make use of these
2397 convenience copies unless the included package is explicitly
2398 intended to be used in this way.<footnote>
2399 For example, parts of the GNU build system work like this.
2401 If the included code is already in the Debian archive in the
2402 form of a library, the Debian packaging should ensure that
2403 binary packages reference the libraries already in Debian and
2404 the convenience copy is not used. If the included code is not
2405 already in Debian, it should be packaged separately as a
2406 prerequisite if possible.
2408 Having multiple copies of the same code in Debian is
2409 inefficient, often creates either static linking or shared
2410 library conflicts, and, most importantly, increases the
2411 difficulty of handling security vulnerabilities in the
2417 <sect id="readmesource">
2418 <heading>Source package handling:
2419 <file>debian/README.source</file></heading>
2422 If running <prgn>dpkg-source -x</prgn> on a source package
2423 doesn't produce the source of the package, ready for editing,
2424 and allow one to make changes and run
2425 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2426 without taking any additional steps, creating a
2427 <file>debian/README.source</file> documentation file is
2428 recommended. This file should explain how to do all of the
2431 <item>Generate the fully patched source, in a form ready for
2432 editing, that would be built to create Debian
2433 packages. Doing this with a <tt>patch</tt> target in
2434 <file>debian/rules</file> is recommended; see
2435 <ref id="debianrules">.</item>
2436 <item>Modify the source and save those modifications so that
2437 they will be applied when building the package.</item>
2438 <item>Remove source modifications that are currently being
2439 applied when building the package.</item>
2440 <item>Optionally, document what steps are necessary to
2441 upgrade the Debian source package to a new upstream version,
2442 if applicable.</item>
2444 This explanation should include specific commands and mention
2445 any additional required Debian packages. It should not assume
2446 familiarity with any specific Debian packaging system or patch
2451 This explanation may refer to a documentation file installed by
2452 one of the package's build dependencies provided that the
2453 referenced documentation clearly explains these tasks and is not
2454 a general reference manual.
2458 <file>debian/README.source</file> may also include any other
2459 information that would be helpful to someone modifying the
2460 source package. Even if the package doesn't fit the above
2461 description, maintainers are encouraged to document in a
2462 <file>debian/README.source</file> file any source package with a
2463 particularly complex or unintuitive source layout or build
2464 system (for example, a package that builds the same source
2465 multiple times to generate different binary packages).
2471 <chapt id="controlfields">
2472 <heading>Control files and their fields</heading>
2475 The package management system manipulates data represented in
2476 a common format, known as <em>control data</em>, stored in
2477 <em>control files</em>.
2478 Control files are used for source packages, binary packages and
2479 the <file>.changes</file> files which control the installation
2480 of uploaded files<footnote>
2481 <prgn>dpkg</prgn>'s internal databases are in a similar
2486 <sect id="controlsyntax">
2487 <heading>Syntax of control files</heading>
2490 A control file consists of one or more paragraphs of
2492 The paragraphs are also sometimes referred to as stanzas.
2494 The paragraphs are separated by empty lines. Parsers may accept
2495 lines consisting solely of spaces and tabs as paragraph
2496 separators, but control files should use empty lines. Some control
2497 files allow only one paragraph; others allow several, in
2498 which case each paragraph usually refers to a different
2499 package. (For example, in source packages, the first
2500 paragraph refers to the source package, and later paragraphs
2501 refer to binary packages generated from the source.) The
2502 ordering of the paragraphs in control files is significant.
2506 Each paragraph consists of a series of data fields. Each field
2507 consists of the field name followed by a colon and then the
2508 data/value associated with that field. The field name is
2509 composed of US-ASCII characters excluding control characters,
2510 space, and colon (i.e., characters in the ranges 33-57 and
2511 59-126, inclusive). Field names must not begin with the comment
2512 character, <tt>#</tt>.
2516 The field ends at the end of the line or at the end of the last
2517 continuation line (see below). Horizontal whitespace (spaces
2518 and tabs) may occur immediately before or after the value and is
2519 ignored there; it is conventional to put a single space after
2520 the colon. For example, a field might be:
2521 <example compact="compact">
2524 the field name is <tt>Package</tt> and the field value
2529 A paragraph must not contain more than one instance of a
2530 particular field name.
2534 There are three types of fields:
2538 The field, including its value, must be a single line. Folding
2539 of the field is not permitted. This is the default field type
2540 if the definition of the field does not specify a different
2545 The value of a folded field is a logical line that may span
2546 several lines. The lines after the first are called
2547 continuation lines and must start with a space or a tab.
2548 Whitespace, including any newlines, is not significant in the
2549 field values of folded fields.<footnote>
2550 This folding method is similar to RFC 5322, allowing control
2551 files that contain only one paragraph and no multiline fields
2552 to be read by parsers written for RFC 5322.
2555 <tag>multiline</tag>
2557 The value of a multiline field may comprise multiple continuation
2558 lines. The first line of the value, the part on the same line as
2559 the field name, often has special significance or may have to be
2560 empty. Other lines are added following the same syntax as the
2561 continuation lines of the folded fields. Whitespace, including newlines,
2562 is significant in the values of multiline fields.
2568 Whitespace must not appear
2569 inside names (of packages, architectures, files or anything
2570 else) or version numbers, or between the characters of
2571 multi-character version relationships.
2575 The presence and purpose of a field, and the syntax of its
2576 value may differ between types of control files.
2580 Field names are not case-sensitive, but it is usual to
2581 capitalize the field names using mixed case as shown below.
2582 Field values are case-sensitive unless the description of the
2583 field says otherwise.
2587 Paragraph separators (empty lines) and lines consisting only of
2588 spaces and tabs are not allowed within field values or between
2589 fields. Empty lines in field values are usually escaped by
2590 representing them by a space followed by a dot.
2594 Lines starting with # without any preceding whitespace are comments
2595 lines that are only permitted in source package control files
2596 (<file>debian/control</file>). These comment lines are ignored, even
2597 between two continuation lines. They do not end logical lines.
2601 All control files must be encoded in UTF-8.
2605 <sect id="sourcecontrolfiles">
2606 <heading>Source package control files -- <file>debian/control</file></heading>
2609 The <file>debian/control</file> file contains the most vital
2610 (and version-independent) information about the source package
2611 and about the binary packages it creates.
2615 The first paragraph of the control file contains information about
2616 the source package in general. The subsequent sets each describe a
2617 binary package that the source tree builds.
2621 The fields in the general paragraph (the first one, for the source
2624 <list compact="compact">
2625 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2627 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2628 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2629 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2630 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2631 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2632 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2633 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2634 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2639 The fields in the binary package paragraphs are:
2641 <list compact="compact">
2642 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2643 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2644 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2645 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2646 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2647 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2648 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2649 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2650 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2655 The syntax and semantics of the fields are described below.
2659 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2660 generate control files for binary packages (see below), by
2661 <prgn>dpkg-genchanges</prgn> to generate the
2662 <file>.changes</file> file to accompany the upload, and by
2663 <prgn>dpkg-source</prgn> when it creates the
2664 <file>.dsc</file> source control file as part of a source
2665 archive. Some fields are folded in <file>debian/control</file>,
2666 but not in any other control
2667 file. These tools are responsible for removing the line
2668 breaks from such fields when using fields from
2669 <file>debian/control</file> to generate other control files.
2673 The fields here may contain variable references - their
2674 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2675 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2676 when they generate output control files.
2677 See <ref id="substvars"> for details.
2681 <sect id="binarycontrolfiles">
2682 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2685 The <file>DEBIAN/control</file> file contains the most vital
2686 (and version-dependent) information about a binary package. It
2687 consists of a single paragraph.
2691 The fields in this file are:
2693 <list compact="compact">
2694 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2695 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2696 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2697 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2698 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2699 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2700 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2701 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2702 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2703 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2704 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2705 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2706 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2711 <sect id="debiansourcecontrolfiles">
2712 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2715 This file consists of a single paragraph, possibly surrounded by
2716 a PGP signature. The fields of that paragraph are listed below.
2717 Their syntax is described above, in <ref id="controlsyntax">.
2719 <list compact="compact">
2720 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2721 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2722 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2723 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2724 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2725 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2726 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2727 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2728 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2729 <item><qref id="f-VCS-fields"><tt>Vcs-Browser</tt>, <tt>Vcs-Git</tt>, et al.</qref></item>
2730 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2731 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2732 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2733 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2734 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2739 The Debian source control file is generated by
2740 <prgn>dpkg-source</prgn> when it builds the source
2741 archive, from other files in the source package,
2742 described above. When unpacking, it is checked against
2743 the files and directories in the other parts of the
2749 <sect id="debianchangesfiles">
2750 <heading>Debian changes files -- <file>.changes</file></heading>
2753 The <file>.changes</file> files are used by the Debian archive
2754 maintenance software to process updates to packages. They
2755 consist of a single paragraph, possibly surrounded by a PGP
2756 signature. That paragraph contains information from the
2757 <file>debian/control</file> file and other data about the
2758 source package gathered via <file>debian/changelog</file>
2759 and <file>debian/rules</file>.
2763 <file>.changes</file> files have a format version that is
2764 incremented whenever the documented fields or their meaning
2765 change. This document describes format &changesversion;.
2769 The fields in this file are:
2771 <list compact="compact">
2772 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2773 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2774 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2775 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2776 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2777 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2778 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2779 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2780 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2781 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2782 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2783 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2784 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2785 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2786 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2787 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2792 <sect id="controlfieldslist">
2793 <heading>List of fields</heading>
2795 <sect1 id="f-Source">
2796 <heading><tt>Source</tt></heading>
2799 This field identifies the source package name.
2803 In <file>debian/control</file> or a <file>.dsc</file> file,
2804 this field must contain only the name of the source package.
2808 In a binary package control file or a <file>.changes</file>
2809 file, the source package name may be followed by a version
2810 number in parentheses<footnote>
2811 It is customary to leave a space after the package name
2812 if a version number is specified.
2814 This version number may be omitted (and is, by
2815 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2816 the <tt>Version</tt> field of the binary package in
2817 question. The field itself may be omitted from a binary
2818 package control file when the source package has the same
2819 name and version as the binary package.
2823 Package names (both source and binary,
2824 see <ref id="f-Package">) must consist only of lower case
2825 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2826 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2827 (<tt>.</tt>). They must be at least two characters long and
2828 must start with an alphanumeric character.
2832 <sect1 id="f-Maintainer">
2833 <heading><tt>Maintainer</tt></heading>
2836 The package maintainer's name and email address. The name
2837 must come first, then the email address inside angle
2838 brackets <tt><></tt> (in RFC822 format).
2842 If the maintainer's name contains a full stop then the
2843 whole field will not work directly as an email address due
2844 to a misfeature in the syntax specified in RFC822; a
2845 program using this field as an address must check for this
2846 and correct the problem if necessary (for example by
2847 putting the name in round brackets and moving it to the
2848 end, and bringing the email address forward).
2852 See <ref id="maintainer"> for additional requirements and
2853 information about package maintainers.
2857 <sect1 id="f-Uploaders">
2858 <heading><tt>Uploaders</tt></heading>
2861 List of the names and email addresses of co-maintainers of the
2862 package, if any. If the package has other maintainers besides
2863 the one named in the <qref id="f-Maintainer">Maintainer
2864 field</qref>, their names and email addresses should be listed
2865 here. The format of each entry is the same as that of the
2866 Maintainer field, and multiple entries must be comma
2871 This is normally an optional field, but if
2872 the <tt>Maintainer</tt> control field names a group of people
2873 and a shared email address, the <tt>Uploaders</tt> field must
2874 be present and must contain at least one human with their
2875 personal email address.
2879 The Uploaders field in <file>debian/control</file> can be folded.
2883 <sect1 id="f-Changed-By">
2884 <heading><tt>Changed-By</tt></heading>
2887 The name and email address of the person who prepared this
2888 version of the package, usually a maintainer. The syntax is
2889 the same as for the <qref id="f-Maintainer">Maintainer
2894 <sect1 id="f-Section">
2895 <heading><tt>Section</tt></heading>
2898 This field specifies an application area into which the package
2899 has been classified. See <ref id="subsections">.
2903 When it appears in the <file>debian/control</file> file,
2904 it gives the value for the subfield of the same name in
2905 the <tt>Files</tt> field of the <file>.changes</file> file.
2906 It also gives the default for the same field in the binary
2911 <sect1 id="f-Priority">
2912 <heading><tt>Priority</tt></heading>
2915 This field represents how important it is that the user
2916 have the package installed. See <ref id="priorities">.
2920 When it appears in the <file>debian/control</file> file,
2921 it gives the value for the subfield of the same name in
2922 the <tt>Files</tt> field of the <file>.changes</file> file.
2923 It also gives the default for the same field in the binary
2928 <sect1 id="f-Package">
2929 <heading><tt>Package</tt></heading>
2932 The name of the binary package.
2936 Binary package names must follow the same syntax and
2937 restrictions as source package names. See <ref id="f-Source">
2942 <sect1 id="f-Architecture">
2943 <heading><tt>Architecture</tt></heading>
2946 Depending on context and the control file used, the
2947 <tt>Architecture</tt> field can include the following sets of
2951 A unique single word identifying a Debian machine
2952 architecture as described in <ref id="arch-spec">.
2955 An architecture wildcard identifying a set of Debian
2956 machine architectures, see <ref id="arch-wildcard-spec">.
2957 <tt>any</tt> matches all Debian machine architectures
2958 and is the most frequently used.
2961 <tt>all</tt>, which indicates an
2962 architecture-independent package.
2965 <tt>source</tt>, which indicates a source package.
2971 In the main <file>debian/control</file> file in the source
2972 package, this field may contain the special
2973 value <tt>all</tt>, the special architecture
2974 wildcard <tt>any</tt>, or a list of specific and wildcard
2975 architectures separated by spaces. If <tt>all</tt>
2976 or <tt>any</tt> appears, that value must be the entire
2977 contents of the field. Most packages will use
2978 either <tt>all</tt> or <tt>any</tt>.
2982 Specifying a specific list of architectures indicates that the
2983 source will build an architecture-dependent package only on
2984 architectures included in the list. Specifying a list of
2985 architecture wildcards indicates that the source will build an
2986 architecture-dependent package on only those architectures
2987 that match any of the specified architecture wildcards.
2988 Specifying a list of architectures or architecture wildcards
2989 other than <tt>any</tt> is for the minority of cases where a
2990 program is not portable or is not useful on some
2991 architectures. Where possible, the program should be made
2996 In the Debian source control file <file>.dsc</file>, this
2997 field contains a list of architectures and architecture
2998 wildcards separated by spaces. When the list contains the
2999 architecture wildcard <tt>any</tt>, the only other value
3000 allowed in the list is <tt>all</tt>.
3004 The list may include (or consist solely of) the special
3005 value <tt>all</tt>. In other words, in <file>.dsc</file>
3006 files unlike the <file>debian/control</file>, <tt>all</tt> may
3007 occur in combination with specific architectures.
3008 The <tt>Architecture</tt> field in the Debian source control
3009 file <file>.dsc</file> is generally constructed from
3010 the <tt>Architecture</tt> fields in
3011 the <file>debian/control</file> in the source package.
3015 Specifying only <tt>any</tt> indicates that the source package
3016 isn't dependent on any particular architecture and should
3017 compile fine on any one. The produced binary package(s)
3018 will be specific to whatever the current build architecture is.
3022 Specifying only <tt>all</tt> indicates that the source package
3023 will only build architecture-independent packages.
3027 Specifying <tt>any all</tt> indicates that the source package
3028 isn't dependent on any particular architecture. The set of
3029 produced binary packages will include at least one
3030 architecture-dependant package and one architecture-independent
3035 Specifying a list of architectures or architecture wildcards
3036 indicates that the source will build an architecture-dependent
3037 package, and will only work correctly on the listed or
3038 matching architectures. If the source package also builds at
3039 least one architecture-independent package, <tt>all</tt> will
3040 also be included in the list.
3044 In a <file>.changes</file> file, the <tt>Architecture</tt>
3045 field lists the architecture(s) of the package(s) currently
3046 being uploaded. This will be a list; if the source for the
3047 package is also being uploaded, the special
3048 entry <tt>source</tt> is also present. <tt>all</tt> will be
3049 present if any architecture-independent packages are being
3050 uploaded. Architecture wildcards such as <tt>any</tt> must
3051 never occur in the <tt>Architecture</tt> field in
3052 the <file>.changes</file> file.
3056 See <ref id="debianrules"> for information on how to get
3057 the architecture for the build process.
3061 <sect1 id="f-Essential">
3062 <heading><tt>Essential</tt></heading>
3065 This is a boolean field which may occur only in the
3066 control file of a binary package or in a per-package fields
3067 paragraph of a source package control file.
3071 If set to <tt>yes</tt> then the package management system
3072 will refuse to remove the package (upgrading and replacing
3073 it is still possible). The other possible value is <tt>no</tt>,
3074 which is the same as not having the field at all.
3079 <heading>Package interrelationship fields:
3080 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3081 <tt>Recommends</tt>, <tt>Suggests</tt>,
3082 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3083 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3087 These fields describe the package's relationships with
3088 other packages. Their syntax and semantics are described
3089 in <ref id="relationships">.</p>
3092 <sect1 id="f-Standards-Version">
3093 <heading><tt>Standards-Version</tt></heading>
3096 The most recent version of the standards (the policy
3097 manual and associated texts) with which the package
3102 The version number has four components: major and minor
3103 version number and major and minor patch level. When the
3104 standards change in a way that requires every package to
3105 change the major number will be changed. Significant
3106 changes that will require work in many packages will be
3107 signaled by a change to the minor number. The major patch
3108 level will be changed for any change to the meaning of the
3109 standards, however small; the minor patch level will be
3110 changed when only cosmetic, typographical or other edits
3111 are made which neither change the meaning of the document
3112 nor affect the contents of packages.
3116 Thus only the first three components of the policy version
3117 are significant in the <em>Standards-Version</em> control
3118 field, and so either these three components or all four
3119 components may be specified.<footnote>
3120 In the past, people specified the full version number
3121 in the Standards-Version field, for example "2.3.0.0".
3122 Since minor patch-level changes don't introduce new
3123 policy, it was thought it would be better to relax
3124 policy and only require the first 3 components to be
3125 specified, in this example "2.3.0". All four
3126 components may still be used if someone wishes to do so.
3132 <sect1 id="f-Version">
3133 <heading><tt>Version</tt></heading>
3136 The version number of a package. The format is:
3137 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3141 The three components here are:
3143 <tag><var>epoch</var></tag>
3146 This is a single (generally small) unsigned integer. It
3147 may be omitted, in which case zero is assumed. If it is
3148 omitted then the <var>upstream_version</var> may not
3153 It is provided to allow mistakes in the version numbers
3154 of older versions of a package, and also a package's
3155 previous version numbering schemes, to be left behind.
3159 <tag><var>upstream_version</var></tag>
3162 This is the main part of the version number. It is
3163 usually the version number of the original ("upstream")
3164 package from which the <file>.deb</file> file has been made,
3165 if this is applicable. Usually this will be in the same
3166 format as that specified by the upstream author(s);
3167 however, it may need to be reformatted to fit into the
3168 package management system's format and comparison
3173 The comparison behavior of the package management system
3174 with respect to the <var>upstream_version</var> is
3175 described below. The <var>upstream_version</var>
3176 portion of the version number is mandatory.
3180 The <var>upstream_version</var> may contain only
3181 alphanumerics<footnote>
3182 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3184 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3185 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3186 tilde) and should start with a digit. If there is no
3187 <var>debian_revision</var> then hyphens are not allowed;
3188 if there is no <var>epoch</var> then colons are not
3193 <tag><var>debian_revision</var></tag>
3196 This part of the version number specifies the version of
3197 the Debian package based on the upstream version. It
3198 may contain only alphanumerics and the characters
3199 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3200 tilde) and is compared in the same way as the
3201 <var>upstream_version</var> is.
3205 It is optional; if it isn't present then the
3206 <var>upstream_version</var> may not contain a hyphen.
3207 This format represents the case where a piece of
3208 software was written specifically to be a Debian
3209 package, where the Debian package source must always
3210 be identical to the pristine source and therefore no
3211 revision indication is required.
3215 It is conventional to restart the
3216 <var>debian_revision</var> at <tt>1</tt> each time the
3217 <var>upstream_version</var> is increased.
3221 The package management system will break the version
3222 number apart at the last hyphen in the string (if there
3223 is one) to determine the <var>upstream_version</var> and
3224 <var>debian_revision</var>. The absence of a
3225 <var>debian_revision</var> is equivalent to a
3226 <var>debian_revision</var> of <tt>0</tt>.
3233 When comparing two version numbers, first the <var>epoch</var>
3234 of each are compared, then the <var>upstream_version</var> if
3235 <var>epoch</var> is equal, and then <var>debian_revision</var>
3236 if <var>upstream_version</var> is also equal.
3237 <var>epoch</var> is compared numerically. The
3238 <var>upstream_version</var> and <var>debian_revision</var>
3239 parts are compared by the package management system using the
3240 following algorithm:
3244 The strings are compared from left to right.
3248 First the initial part of each string consisting entirely of
3249 non-digit characters is determined. These two parts (one of
3250 which may be empty) are compared lexically. If a difference
3251 is found it is returned. The lexical comparison is a
3252 comparison of ASCII values modified so that all the letters
3253 sort earlier than all the non-letters and so that a tilde
3254 sorts before anything, even the end of a part. For example,
3255 the following parts are in sorted order from earliest to
3256 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3257 <tt>a</tt>.<footnote>
3258 One common use of <tt>~</tt> is for upstream pre-releases.
3259 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3260 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3265 Then the initial part of the remainder of each string which
3266 consists entirely of digit characters is determined. The
3267 numerical values of these two parts are compared, and any
3268 difference found is returned as the result of the comparison.
3269 For these purposes an empty string (which can only occur at
3270 the end of one or both version strings being compared) counts
3275 These two steps (comparing and removing initial non-digit
3276 strings and initial digit strings) are repeated until a
3277 difference is found or both strings are exhausted.
3281 Note that the purpose of epochs is to allow us to leave behind
3282 mistakes in version numbering, and to cope with situations
3283 where the version numbering scheme changes. It is
3284 <em>not</em> intended to cope with version numbers containing
3285 strings of letters which the package management system cannot
3286 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3287 silly orderings.<footnote>
3288 The author of this manual has heard of a package whose
3289 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3290 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3296 <sect1 id="f-Description">
3297 <heading><tt>Description</tt></heading>
3300 In a source or binary control file, the <tt>Description</tt>
3301 field contains a description of the binary package, consisting
3302 of two parts, the synopsis or the short description, and the
3303 long description. It is a multiline field with the following
3309 Description: <single line synopsis>
3310 <extended description over several lines>
3315 The lines in the extended description can have these formats:
3321 Those starting with a single space are part of a paragraph.
3322 Successive lines of this form will be word-wrapped when
3323 displayed. The leading space will usually be stripped off.
3324 The line must contain at least one non-whitespace character.
3328 Those starting with two or more spaces. These will be
3329 displayed verbatim. If the display cannot be panned
3330 horizontally, the displaying program will line wrap them "hard"
3331 (i.e., without taking account of word breaks). If it can they
3332 will be allowed to trail off to the right. None, one or two
3333 initial spaces may be deleted, but the number of spaces
3334 deleted from each line will be the same (so that you can have
3335 indenting work correctly, for example). The line must
3336 contain at least one non-whitespace character.
3340 Those containing a single space followed by a single full stop
3341 character. These are rendered as blank lines. This is the
3342 <em>only</em> way to get a blank line<footnote>
3343 Completely empty lines will not be rendered as blank lines.
3344 Instead, they will cause the parser to think you're starting
3345 a whole new record in the control file, and will therefore
3346 likely abort with an error.
3351 Those containing a space, a full stop and some more characters.
3352 These are for future expansion. Do not use them.
3358 Do not use tab characters. Their effect is not predictable.
3362 See <ref id="descriptions"> for further information on this.
3366 In a <file>.changes</file> file, the <tt>Description</tt>
3367 field contains a summary of the descriptions for the packages
3368 being uploaded. For this case, the first line of the field
3369 value (the part on the same line as <tt>Description:</tt>) is
3370 always empty. It is a multiline field, with one
3371 line per package. Each line is
3372 indented by one space and contains the name of a binary
3373 package, a space, a hyphen (<tt>-</tt>), a space, and the
3374 short description line from that package.
3378 <sect1 id="f-Distribution">
3379 <heading><tt>Distribution</tt></heading>
3382 In a <file>.changes</file> file or parsed changelog output
3383 this contains the (space-separated) name(s) of the
3384 distribution(s) where this version of the package should
3385 be installed. Valid distributions are determined by the
3386 archive maintainers.<footnote>
3387 Example distribution names in the Debian archive used in
3388 <file>.changes</file> files are:
3389 <taglist compact="compact">
3390 <tag><em>unstable</em></tag>
3392 This distribution value refers to the
3393 <em>developmental</em> part of the Debian distribution
3394 tree. Most new packages, new upstream versions of
3395 packages and bug fixes go into the <em>unstable</em>
3399 <tag><em>experimental</em></tag>
3401 The packages with this distribution value are deemed
3402 by their maintainers to be high risk. Oftentimes they
3403 represent early beta or developmental packages from
3404 various sources that the maintainers want people to
3405 try, but are not ready to be a part of the other parts
3406 of the Debian distribution tree.
3411 Others are used for updating stable releases or for
3412 security uploads. More information is available in the
3413 Debian Developer's Reference, section "The Debian
3417 The Debian archive software only supports listing a single
3418 distribution. Migration of packages to other distributions is
3419 handled outside of the upload process.
3424 <heading><tt>Date</tt></heading>
3427 This field includes the date the package was built or last
3428 edited. It must be in the same format as the <var>date</var>
3429 in a <file>debian/changelog</file> entry.
3433 The value of this field is usually extracted from the
3434 <file>debian/changelog</file> file - see
3435 <ref id="dpkgchangelog">).
3439 <sect1 id="f-Format">
3440 <heading><tt>Format</tt></heading>
3443 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3444 files, this field declares the format version of that file.
3445 The syntax of the field value is the same as that of
3446 a <qref id="f-Version">package version number</qref> except
3447 that no epoch or Debian revision is allowed. The format
3448 described in this document is <tt>&changesversion;</tt>.
3452 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3453 Debian source control</qref> files, this field declares the
3454 format of the source package. The field value is used by
3455 programs acting on a source package to interpret the list of
3456 files in the source package and determine how to unpack it.
3457 The syntax of the field value is a numeric major revision, a
3458 period, a numeric minor revision, and then an optional subtype
3459 after whitespace, which if specified is an alphanumeric word
3460 in parentheses. The subtype is optional in the syntax but may
3461 be mandatory for particular source format revisions.
3463 The source formats currently supported by the Debian archive
3464 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3465 and <tt>3.0 (quilt)</tt>.
3470 <sect1 id="f-Urgency">
3471 <heading><tt>Urgency</tt></heading>
3474 This is a description of how important it is to upgrade to
3475 this version from previous ones. It consists of a single
3476 keyword taking one of the values <tt>low</tt>,
3477 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3478 <tt>critical</tt><footnote>
3479 Other urgency values are supported with configuration
3480 changes in the archive software but are not used in Debian.
3481 The urgency affects how quickly a package will be considered
3482 for inclusion into the <tt>testing</tt> distribution and
3483 gives an indication of the importance of any fixes included
3484 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3485 treated as synonymous.
3486 </footnote> (not case-sensitive) followed by an optional
3487 commentary (separated by a space) which is usually in
3488 parentheses. For example:
3491 Urgency: low (HIGH for users of diversions)
3497 The value of this field is usually extracted from the
3498 <file>debian/changelog</file> file - see
3499 <ref id="dpkgchangelog">.
3503 <sect1 id="f-Changes">
3504 <heading><tt>Changes</tt></heading>
3507 This multiline field contains the human-readable changes data, describing
3508 the differences between the last version and the current one.
3512 The first line of the field value (the part on the same line
3513 as <tt>Changes:</tt>) is always empty. The content of the
3514 field is expressed as continuation lines, with each line
3515 indented by at least one space. Blank lines must be
3516 represented by a line consisting only of a space and a full
3521 The value of this field is usually extracted from the
3522 <file>debian/changelog</file> file - see
3523 <ref id="dpkgchangelog">).
3527 Each version's change information should be preceded by a
3528 "title" line giving at least the version, distribution(s)
3529 and urgency, in a human-readable way.
3533 If data from several versions is being returned the entry
3534 for the most recent version should be returned first, and
3535 entries should be separated by the representation of a
3536 blank line (the "title" line may also be followed by the
3537 representation of a blank line).
3541 <sect1 id="f-Binary">
3542 <heading><tt>Binary</tt></heading>
3545 This folded field is a list of binary packages. Its syntax and
3546 meaning varies depending on the control file in which it
3551 When it appears in the <file>.dsc</file> file, it lists binary
3552 packages which a source package can produce, separated by
3554 A space after each comma is conventional.
3555 </footnote>. The source package
3556 does not necessarily produce all of these binary packages for
3557 every architecture. The source control file doesn't contain
3558 details of which architectures are appropriate for which of
3559 the binary packages.
3563 When it appears in a <file>.changes</file> file, it lists the
3564 names of the binary packages being uploaded, separated by
3565 whitespace (not commas).
3569 <sect1 id="f-Installed-Size">
3570 <heading><tt>Installed-Size</tt></heading>
3573 This field appears in the control files of binary packages,
3574 and in the <file>Packages</file> files. It gives an estimate
3575 of the total amount of disk space required to install the
3576 named package. Actual installed size may vary based on block
3577 size, file system properties, or actions taken by package
3582 The disk space is given as the integer value of the estimated
3583 installed size in bytes, divided by 1024 and rounded up.
3587 <sect1 id="f-Files">
3588 <heading><tt>Files</tt></heading>
3591 This field contains a list of files with information about
3592 each one. The exact information and syntax varies with
3597 In all cases, Files is a multiline field. The first line of
3598 the field value (the part on the same line as <tt>Files:</tt>)
3599 is always empty. The content of the field is expressed as
3600 continuation lines, one line per file. Each line must be
3601 indented by one space and contain a number of sub-fields,
3602 separated by spaces, as described below.
3606 In the <file>.dsc</file> file, each line contains the MD5
3607 checksum, size and filename of the tar file and (if
3608 applicable) diff file which make up the remainder of the
3609 source package<footnote>
3610 That is, the parts which are not the <tt>.dsc</tt>.
3611 </footnote>. For example:
3614 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3615 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3617 The exact forms of the filenames are described
3618 in <ref id="pkg-sourcearchives">.
3622 In the <file>.changes</file> file this contains one line per
3623 file being uploaded. Each line contains the MD5 checksum,
3624 size, section and priority and the filename. For example:
3627 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3628 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3629 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3630 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3632 The <qref id="f-Section">section</qref>
3633 and <qref id="f-Priority">priority</qref> are the values of
3634 the corresponding fields in the main source control file. If
3635 no section or priority is specified then <tt>-</tt> should be
3636 used, though section and priority values must be specified for
3637 new packages to be installed properly.
3641 The special value <tt>byhand</tt> for the section in a
3642 <tt>.changes</tt> file indicates that the file in question
3643 is not an ordinary package file and must by installed by
3644 hand by the distribution maintainers. If the section is
3645 <tt>byhand</tt> the priority should be <tt>-</tt>.
3649 If a new Debian revision of a package is being shipped and
3650 no new original source archive is being distributed the
3651 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3652 entry for the original source archive
3653 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3654 but the <file>.changes</file> file should leave it out. In
3655 this case the original source archive on the distribution
3656 site must match exactly, byte-for-byte, the original
3657 source archive which was used to generate the
3658 <file>.dsc</file> file and diff which are being uploaded.</p>
3661 <sect1 id="f-Closes">
3662 <heading><tt>Closes</tt></heading>
3665 A space-separated list of bug report numbers that the upload
3666 governed by the .changes file closes.
3670 <sect1 id="f-Homepage">
3671 <heading><tt>Homepage</tt></heading>
3674 The URL of the web site for this package, preferably (when
3675 applicable) the site from which the original source can be
3676 obtained and any additional upstream documentation or
3677 information may be found. The content of this field is a
3678 simple URL without any surrounding characters such as
3683 <sect1 id="f-Checksums">
3684 <heading><tt>Checksums-Sha1</tt>
3685 and <tt>Checksums-Sha256</tt></heading>
3688 These multiline fields contain a list of files with a checksum and size
3689 for each one. Both <tt>Checksums-Sha1</tt>
3690 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3691 only in the checksum algorithm used: SHA-1
3692 for <tt>Checksums-Sha1</tt> and SHA-256
3693 for <tt>Checksums-Sha256</tt>.
3697 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3698 multiline fields. The first line of the field value (the part
3699 on the same line as <tt>Checksums-Sha1:</tt>
3700 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3701 of the field is expressed as continuation lines, one line per
3702 file. Each line consists of the checksum, a space, the file
3703 size, a space, and the file name. For example (from
3704 a <file>.changes</file> file):
3707 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3708 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3709 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3710 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3712 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3713 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3714 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3715 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3720 In the <file>.dsc</file> file, these fields should list all
3721 files that make up the source package. In
3722 the <file>.changes</file> file, these fields should list all
3723 files being uploaded. The list of files in these fields
3724 must match the list of files in the <tt>Files</tt> field.
3728 <sect1 id="f-DM-Upload-Allowed">
3729 <heading><tt>DM-Upload-Allowed</tt></heading>
3732 Indicates that Debian Maintainers may upload this package to
3733 the Debian archive. The only valid value is <tt>yes</tt>. If
3734 the field <tt>DM-Upload-Allowed: yes</tt> is present in the
3735 source section of the source control file of the most recent
3736 version of a package in unstable or experimental, the Debian
3737 archive will accept uploads of this package signed with a key
3738 in the Debian Maintainer keyring. See the General
3739 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3740 name="Endorse the concept of Debian Maintainers"> for more
3745 <sect1 id="f-VCS-fields">
3746 <heading>Version Control System (VCS) fields</heading>
3749 Debian source packages are increasingly developed using VCSs. The
3750 purpose of the following fields is to indicate a publicly accessible
3751 repository where the Debian source package is developed.
3754 <tag><tt>Vcs-Browser</tt></tag>
3757 URL of a web interface for browsing the repository.
3762 <tt>Vcs-Arch</tt>, <tt>Vcs-Bzr</tt> (Bazaar), <tt>Vcs-Cvs</tt>,
3763 <tt>Vcs-Darcs</tt>, <tt>Vcs-Git</tt>, <tt>Vcs-Hg</tt>
3764 (Mercurial), <tt>Vcs-Mtn</tt> (Monotone), <tt>Vcs-Svn</tt>
3769 The field name identifies the VCS. The field's value uses the
3770 version control system's conventional syntax for describing
3771 repository locations and should be sufficient to locate the
3772 repository used for packaging. Ideally, it also locates the
3773 branch used for development of new versions of the Debian
3777 In the case of Git, the value consists of a URL, optionally
3778 followed by the word <tt>-b</tt> and the name of a branch in
3779 the indicated repository, following the syntax of the
3780 <tt>git clone</tt> command. If no branch is specified, the
3781 packaging should be on the default branch.
3784 More than one different VCS may be specified for the same
3794 <heading>User-defined fields</heading>
3797 Additional user-defined fields may be added to the
3798 source package control file. Such fields will be
3799 ignored, and not copied to (for example) binary or
3800 Debian source control files or upload control files.
3804 If you wish to add additional unsupported fields to
3805 these output files you should use the mechanism
3810 Fields in the main source control information file with
3811 names starting <tt>X</tt>, followed by one or more of
3812 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3813 be copied to the output files. Only the part of the
3814 field name after the hyphen will be used in the output
3815 file. Where the letter <tt>B</tt> is used the field
3816 will appear in binary package control files, where the
3817 letter <tt>S</tt> is used in Debian source control
3818 files and where <tt>C</tt> is used in upload control
3819 (<tt>.changes</tt>) files.
3823 For example, if the main source information control file
3826 XBS-Comment: I stand between the candle and the star.
3828 then the binary and Debian source control files will contain the
3831 Comment: I stand between the candle and the star.
3840 <chapt id="maintainerscripts">
3841 <heading>Package maintainer scripts and installation procedure</heading>
3844 <heading>Introduction to package maintainer scripts</heading>
3847 It is possible to supply scripts as part of a package which
3848 the package management system will run for you when your
3849 package is installed, upgraded or removed.
3853 These scripts are the control information
3854 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3855 and <prgn>postrm</prgn>. They must be proper executable files;
3856 if they are scripts (which is recommended), they must start with
3857 the usual <tt>#!</tt> convention. They should be readable and
3858 executable by anyone, and must not be world-writable.
3862 The package management system looks at the exit status from
3863 these scripts. It is important that they exit with a
3864 non-zero status if there is an error, so that the package
3865 management system can stop its processing. For shell
3866 scripts this means that you <em>almost always</em> need to
3867 use <tt>set -e</tt> (this is usually true when writing shell
3868 scripts, in fact). It is also important, of course, that
3869 they exit with a zero status if everything went well.
3873 Additionally, packages interacting with users
3874 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3875 should install a <prgn>config</prgn> script as a control
3876 information file. See <ref id="maintscriptprompt"> for details.
3880 When a package is upgraded a combination of the scripts from
3881 the old and new packages is called during the upgrade
3882 procedure. If your scripts are going to be at all
3883 complicated you need to be aware of this, and may need to
3884 check the arguments to your scripts.
3888 Broadly speaking the <prgn>preinst</prgn> is called before
3889 (a particular version of) a package is unpacked, and the
3890 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3891 before (a version of) a package is removed and the
3892 <prgn>postrm</prgn> afterwards.
3896 Programs called from maintainer scripts should not normally
3897 have a path prepended to them. Before installation is
3898 started, the package management system checks to see if the
3899 programs <prgn>ldconfig</prgn>,
3900 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3901 and <prgn>update-rc.d</prgn> can be found via the
3902 <tt>PATH</tt> environment variable. Those programs, and any
3903 other program that one would expect to be in the
3904 <tt>PATH</tt>, should thus be invoked without an absolute
3905 pathname. Maintainer scripts should also not reset the
3906 <tt>PATH</tt>, though they might choose to modify it by
3907 prepending or appending package-specific directories. These
3908 considerations really apply to all shell scripts.</p>
3911 <sect id="idempotency">
3912 <heading>Maintainer scripts idempotency</heading>
3915 It is necessary for the error recovery procedures that the
3916 scripts be idempotent. This means that if it is run
3917 successfully, and then it is called again, it doesn't bomb
3918 out or cause any harm, but just ensures that everything is
3919 the way it ought to be. If the first call failed, or
3920 aborted half way through for some reason, the second call
3921 should merely do the things that were left undone the first
3922 time, if any, and exit with a success status if everything
3924 This is so that if an error occurs, the user interrupts
3925 <prgn>dpkg</prgn> or some other unforeseen circumstance
3926 happens you don't leave the user with a badly-broken
3927 package when <prgn>dpkg</prgn> attempts to repeat the
3933 <sect id="controllingterminal">
3934 <heading>Controlling terminal for maintainer scripts</heading>
3937 Maintainer scripts are not guaranteed to run with a controlling
3938 terminal and may not be able to interact with the user. They
3939 must be able to fall back to noninteractive behavior if no
3940 controlling terminal is available. Maintainer scripts that
3941 prompt via a program conforming to the Debian Configuration
3942 Management Specification (see <ref id="maintscriptprompt">) may
3943 assume that program will handle falling back to noninteractive
3948 For high-priority prompts without a reasonable default answer,
3949 maintainer scripts may abort if there is no controlling
3950 terminal. However, this situation should be avoided if at all
3951 possible, since it prevents automated or unattended installs.
3952 In most cases, users will consider this to be a bug in the
3957 <sect id="exitstatus">
3958 <heading>Exit status</heading>
3961 Each script must return a zero exit status for
3962 success, or a nonzero one for failure, since the package
3963 management system looks for the exit status of these scripts
3964 and determines what action to take next based on that datum.
3968 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3973 What follows is a summary of all the ways in which maintainer
3974 scripts may be called along with what facilities those scripts
3975 may rely on being available at that time. Script names preceded
3976 by <var>new-</var> are the scripts from the new version of a
3977 package being installed, upgraded to, or downgraded to. Script
3978 names preceded by <var>old-</var> are the scripts from the old
3979 version of a package that is being upgraded from or downgraded
3984 The <prgn>preinst</prgn> script may be called in the following
3987 <tag><var>new-preinst</var> <tt>install</tt></tag>
3988 <tag><var>new-preinst</var> <tt>install</tt>
3989 <var>old-version</var></tag>
3990 <tag><var>new-preinst</var> <tt>upgrade</tt>
3991 <var>old-version</var></tag>
3993 The package will not yet be unpacked, so
3994 the <prgn>preinst</prgn> script cannot rely on any files
3995 included in its package. Only essential packages and
3996 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3997 available. Pre-dependencies will have been configured at
3998 least once, but at the time the <prgn>preinst</prgn> is
3999 called they may only be in an unpacked or "Half-Configured"
4000 state if a previous version of the pre-dependency was
4001 completely configured and has not been removed since then.
4004 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
4005 <var>new-version</var></tag>
4007 Called during error handling of an upgrade that failed after
4008 unpacking the new package because the <tt>postrm
4009 upgrade</tt> action failed. The unpacked files may be
4010 partly from the new version or partly missing, so the script
4011 cannot rely on files included in the package. Package
4012 dependencies may not be available. Pre-dependencies will be
4013 at least unpacked following the same rules as above, except
4014 they may be only "Half-Installed" if an upgrade of the
4015 pre-dependency failed.<footnote>
4016 This can happen if the new version of the package no
4017 longer pre-depends on a package that had been partially
4025 The <prgn>postinst</prgn> script may be called in the following
4028 <tag><var>postinst</var> <tt>configure</tt>
4029 <var>most-recently-configured-version</var></tag>
4031 The files contained in the package will be unpacked. All
4032 package dependencies will at least be unpacked. If there
4033 are no circular dependencies involved, all package
4034 dependencies will be configured. For behavior in the case
4035 of circular dependencies, see the discussion
4036 in <ref id="binarydeps">.
4039 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
4040 <var>new-version</var></tag>
4041 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
4042 <tt>in-favour</tt> <var>package</var>
4043 <var>new-version</var></tag>
4044 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
4045 <tag><var>deconfigured's-postinst</var>
4046 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
4047 <var>failed-install-package</var> <var>version</var>
4048 [<tt>removing</tt> <var>conflicting-package</var>
4049 <var>version</var>]</tag>
4051 The files contained in the package will be unpacked. All
4052 package dependencies will at least be "Half-Installed" and
4053 will have previously been configured and not removed.
4054 However, dependencies may not be configured or even fully
4055 unpacked in some error situations.<footnote>
4056 For example, suppose packages foo and bar are installed
4057 with foo depending on bar. If an upgrade of bar were
4058 started and then aborted, and then an attempt to remove
4059 foo failed because its <prgn>prerm</prgn> script failed,
4060 foo's <tt>postinst abort-remove</tt> would be called with
4061 bar only "Half-Installed".
4063 The <prgn>postinst</prgn> should still attempt any actions
4064 for which its dependencies are required, since they will
4065 normally be available, but consider the correct error
4066 handling approach if those actions fail. Aborting
4067 the <prgn>postinst</prgn> action if commands or facilities
4068 from the package dependencies are not available is often the
4075 The <prgn>prerm</prgn> script may be called in the following
4078 <tag><var>prerm</var> <tt>remove</tt></tag>
4079 <tag><var>old-prerm</var>
4080 <tt>upgrade</tt><var>new-version</var></tag>
4081 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4082 <tt>in-favour</tt> <var>package</var>
4083 <var>new-version</var></tag>
4084 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4085 <tt>in-favour</tt> <var>package-being-installed</var>
4086 <var>version</var> [<tt>removing</tt>
4087 <var>conflicting-package</var> <var>version</var>]</tag>
4089 The package whose <prgn>prerm</prgn> is being called will be
4090 at least "Half-Installed". All package dependencies will at
4091 least be "Half-Installed" and will have previously been
4092 configured and not removed. If there was no error, all
4093 dependencies will at least be unpacked, but these actions
4094 may be called in various error states where dependencies are
4095 only "Half-Installed" due to a partial upgrade.
4098 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4099 <var>old-version</var></tag>
4101 Called during error handling when <tt>prerm upgrade</tt>
4102 fails. The new package will not yet be unpacked, and all
4103 the same constraints as for <tt>preinst upgrade</tt> apply.
4109 The <prgn>postrm</prgn> script may be called in the following
4112 <tag><var>postrm</var> <tt>remove</tt></tag>
4113 <tag><var>postrm</var> <tt>purge</tt></tag>
4114 <tag><var>old-postrm</var> <tt>upgrade</tt>
4115 <var>new-version</var></tag>
4116 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4117 <var>overwriter</var> <var>overwriter-version</var></tag>
4119 The <prgn>postrm</prgn> script is called after the package's
4120 files have been removed or replaced. The package
4121 whose <prgn>postrm</prgn> is being called may have
4122 previously been deconfigured and only be unpacked, at which
4123 point subsequent package changes do not consider its
4124 dependencies. Therefore, all <prgn>postrm</prgn> actions
4125 may only rely on essential packages and must gracefully skip
4126 any actions that require the package's dependencies if those
4127 dependencies are unavailable.<footnote>
4128 This is often done by checking whether the command or
4129 facility the <prgn>postrm</prgn> intends to call is
4130 available before calling it. For example:
4132 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4133 . /usr/share/debconf/confmodule
4137 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4138 configuration for the package
4139 if <package>debconf</package> is installed.
4143 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4144 <var>old-version</var></tag>
4146 Called when the old <tt>postrm upgrade</tt> action fails.
4147 The new package will be unpacked, but only essential
4148 packages and pre-dependencies can be relied on.
4149 Pre-dependencies will either be configured or will be
4150 "Unpacked" or "Half-Configured" but previously had been
4151 configured and was never removed.
4154 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4155 <tag><var>new-postrm</var> <tt>abort-install</tt>
4156 <var>old-version</var></tag>
4157 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4158 <var>old-version</var></tag>
4160 Called before unpacking the new package as part of the
4161 error handling of <prgn>preinst</prgn> failures. May assume
4162 the same state as <prgn>preinst</prgn> can assume.
4168 <sect id="unpackphase">
4169 <heading>Details of unpack phase of installation or upgrade</heading>
4172 The procedure on installation/upgrade/overwrite/disappear
4173 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4174 stage of <tt>dpkg --install</tt>) is as follows. In each
4175 case, if a major error occurs (unless listed below) the
4176 actions are, in general, run backwards - this means that the
4177 maintainer scripts are run with different arguments in
4178 reverse order. These are the "error unwind" calls listed
4185 If a version of the package is already installed, call
4186 <example compact="compact">
4187 <var>old-prerm</var> upgrade <var>new-version</var>
4191 If the script runs but exits with a non-zero
4192 exit status, <prgn>dpkg</prgn> will attempt:
4193 <example compact="compact">
4194 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4196 If this works, the upgrade continues. If this
4197 does not work, the error unwind:
4198 <example compact="compact">
4199 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4201 If this works, then the old-version is
4202 "Installed", if not, the old version is in a
4203 "Half-Configured" state.
4209 If a "conflicting" package is being removed at the same time,
4210 or if any package will be broken (due to <tt>Breaks</tt>):
4213 If <tt>--auto-deconfigure</tt> is
4214 specified, call, for each package to be deconfigured
4215 due to <tt>Breaks</tt>:
4216 <example compact="compact">
4217 <var>deconfigured's-prerm</var> deconfigure \
4218 in-favour <var>package-being-installed</var> <var>version</var>
4221 <example compact="compact">
4222 <var>deconfigured's-postinst</var> abort-deconfigure \
4223 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4225 The deconfigured packages are marked as
4226 requiring configuration, so that if
4227 <tt>--install</tt> is used they will be
4228 configured again if possible.
4231 If any packages depended on a conflicting
4232 package being removed and <tt>--auto-deconfigure</tt> is
4233 specified, call, for each such package:
4234 <example compact="compact">
4235 <var>deconfigured's-prerm</var> deconfigure \
4236 in-favour <var>package-being-installed</var> <var>version</var> \
4237 removing <var>conflicting-package</var> <var>version</var>
4240 <example compact="compact">
4241 <var>deconfigured's-postinst</var> abort-deconfigure \
4242 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4243 removing <var>conflicting-package</var> <var>version</var>
4245 The deconfigured packages are marked as
4246 requiring configuration, so that if
4247 <tt>--install</tt> is used they will be
4248 configured again if possible.
4251 To prepare for removal of each conflicting package, call:
4252 <example compact="compact">
4253 <var>conflictor's-prerm</var> remove \
4254 in-favour <var>package</var> <var>new-version</var>
4257 <example compact="compact">
4258 <var>conflictor's-postinst</var> abort-remove \
4259 in-favour <var>package</var> <var>new-version</var>
4268 If the package is being upgraded, call:
4269 <example compact="compact">
4270 <var>new-preinst</var> upgrade <var>old-version</var>
4272 If this fails, we call:
4274 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4281 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4283 is called. If this works, then the old version
4284 is in an "Installed" state, or else it is left
4285 in an "Unpacked" state.
4290 If it fails, then the old version is left
4291 in an "Half-Installed" state.
4298 Otherwise, if the package had some configuration
4299 files from a previous version installed (i.e., it
4300 is in the "configuration files only" state):
4301 <example compact="compact">
4302 <var>new-preinst</var> install <var>old-version</var>
4306 <var>new-postrm</var> abort-install <var>old-version</var>
4308 If this fails, the package is left in a
4309 "Half-Installed" state, which requires a
4310 reinstall. If it works, the packages is left in
4311 a "Config-Files" state.
4314 Otherwise (i.e., the package was completely purged):
4315 <example compact="compact">
4316 <var>new-preinst</var> install
4319 <example compact="compact">
4320 <var>new-postrm</var> abort-install
4322 If the error-unwind fails, the package is in a
4323 "Half-Installed" phase, and requires a
4324 reinstall. If the error unwind works, the
4325 package is in a not installed state.
4332 The new package's files are unpacked, overwriting any
4333 that may be on the system already, for example any
4334 from the old version of the same package or from
4335 another package. Backups of the old files are kept
4336 temporarily, and if anything goes wrong the package
4337 management system will attempt to put them back as
4338 part of the error unwind.
4342 It is an error for a package to contain files which
4343 are on the system in another package, unless
4344 <tt>Replaces</tt> is used (see <ref id="replaces">).
4346 The following paragraph is not currently the case:
4347 Currently the <tt>- - force-overwrite</tt> flag is
4348 enabled, downgrading it to a warning, but this may not
4354 It is a more serious error for a package to contain a
4355 plain file or other kind of non-directory where another
4356 package has a directory (again, unless
4357 <tt>Replaces</tt> is used). This error can be
4358 overridden if desired using
4359 <tt>--force-overwrite-dir</tt>, but this is not
4364 Packages which overwrite each other's files produce
4365 behavior which, though deterministic, is hard for the
4366 system administrator to understand. It can easily
4367 lead to "missing" programs if, for example, a package
4368 is unpacked which overwrites a file from another
4369 package, and is then removed again.<footnote>
4370 Part of the problem is due to what is arguably a
4371 bug in <prgn>dpkg</prgn>.
4376 A directory will never be replaced by a symbolic link
4377 to a directory or vice versa; instead, the existing
4378 state (symlink or not) will be left alone and
4379 <prgn>dpkg</prgn> will follow the symlink if there is
4388 If the package is being upgraded, call
4389 <example compact="compact">
4390 <var>old-postrm</var> upgrade <var>new-version</var>
4394 If this fails, <prgn>dpkg</prgn> will attempt:
4395 <example compact="compact">
4396 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4398 If this works, installation continues. If not,
4400 <example compact="compact">
4401 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4403 If this fails, the old version is left in a
4404 "Half-Installed" state. If it works, dpkg now
4406 <example compact="compact">
4407 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4409 If this fails, the old version is left in a
4410 "Half-Installed" state. If it works, dpkg now
4412 <example compact="compact">
4413 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4415 If this fails, the old version is in an
4422 This is the point of no return - if
4423 <prgn>dpkg</prgn> gets this far, it won't back off
4424 past this point if an error occurs. This will
4425 leave the package in a fairly bad state, which
4426 will require a successful re-installation to clear
4427 up, but it's when <prgn>dpkg</prgn> starts doing
4428 things that are irreversible.
4433 Any files which were in the old version of the package
4434 but not in the new are removed.
4438 The new file list replaces the old.
4442 The new maintainer scripts replace the old.
4446 Any packages all of whose files have been overwritten
4447 during the installation, and which aren't required for
4448 dependencies, are considered to have been removed.
4449 For each such package
4452 <prgn>dpkg</prgn> calls:
4453 <example compact="compact">
4454 <var>disappearer's-postrm</var> disappear \
4455 <var>overwriter</var> <var>overwriter-version</var>
4459 The package's maintainer scripts are removed.
4462 It is noted in the status database as being in a
4463 sane state, namely not installed (any conffiles
4464 it may have are ignored, rather than being
4465 removed by <prgn>dpkg</prgn>). Note that
4466 disappearing packages do not have their prerm
4467 called, because <prgn>dpkg</prgn> doesn't know
4468 in advance that the package is going to
4475 Any files in the package we're unpacking that are also
4476 listed in the file lists of other packages are removed
4477 from those lists. (This will lobotomize the file list
4478 of the "conflicting" package if there is one.)
4482 The backup files made during installation, above, are
4488 The new package's status is now sane, and recorded as
4493 Here is another point of no return - if the
4494 conflicting package's removal fails we do not unwind
4495 the rest of the installation; the conflicting package
4496 is left in a half-removed limbo.
4501 If there was a conflicting package we go and do the
4502 removal actions (described below), starting with the
4503 removal of the conflicting package's files (any that
4504 are also in the package being unpacked have already
4505 been removed from the conflicting package's file list,
4506 and so do not get removed now).
4512 <sect id="configdetails"><heading>Details of configuration</heading>
4515 When we configure a package (this happens with <tt>dpkg
4516 --install</tt> and <tt>dpkg --configure</tt>), we first
4517 update any <tt>conffile</tt>s and then call:
4518 <example compact="compact">
4519 <var>postinst</var> configure <var>most-recently-configured-version</var>
4524 No attempt is made to unwind after errors during
4525 configuration. If the configuration fails, the package is in
4526 a "Failed Config" state, and an error message is generated.
4530 If there is no most recently configured version
4531 <prgn>dpkg</prgn> will pass a null argument.
4534 Historical note: Truly ancient (pre-1997) versions of
4535 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4536 (including the angle brackets) in this case. Even older
4537 ones did not pass a second argument at all, under any
4538 circumstance. Note that upgrades using such an old dpkg
4539 version are unlikely to work for other reasons, even if
4540 this old argument behavior is handled by your postinst script.
4546 <sect id="removedetails"><heading>Details of removal and/or
4547 configuration purging</heading>
4553 <example compact="compact">
4554 <var>prerm</var> remove
4558 If prerm fails during replacement due to conflict
4560 <var>conflictor's-postinst</var> abort-remove \
4561 in-favour <var>package</var> <var>new-version</var>
4565 <var>postinst</var> abort-remove
4569 If this fails, the package is in a "Half-Configured"
4570 state, or else it remains "Installed".
4574 The package's files are removed (except <tt>conffile</tt>s).
4577 <example compact="compact">
4578 <var>postrm</var> remove
4582 If it fails, there's no error unwind, and the package is in
4583 an "Half-Installed" state.
4588 All the maintainer scripts except the <prgn>postrm</prgn>
4593 If we aren't purging the package we stop here. Note
4594 that packages which have no <prgn>postrm</prgn> and no
4595 <tt>conffile</tt>s are automatically purged when
4596 removed, as there is no difference except for the
4597 <prgn>dpkg</prgn> status.
4601 The <tt>conffile</tt>s and any backup files
4602 (<tt>~</tt>-files, <tt>#*#</tt> files,
4603 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4608 <example compact="compact">
4609 <var>postrm</var> purge
4613 If this fails, the package remains in a "Config-Files"
4618 The package's file list is removed.
4627 <chapt id="relationships">
4628 <heading>Declaring relationships between packages</heading>
4630 <sect id="depsyntax">
4631 <heading>Syntax of relationship fields</heading>
4634 These fields all have a uniform syntax. They are a list of
4635 package names separated by commas.
4639 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4640 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4641 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4642 control fields of the package, which declare
4643 dependencies on other packages, the package names listed may
4644 also include lists of alternative package names, separated
4645 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4646 if any one of the alternative packages is installed, that
4647 part of the dependency is considered to be satisfied.
4651 All of the fields except for <tt>Provides</tt> may restrict
4652 their applicability to particular versions of each named
4653 package. This is done in parentheses after each individual
4654 package name; the parentheses should contain a relation from
4655 the list below followed by a version number, in the format
4656 described in <ref id="f-Version">.
4660 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4661 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4662 earlier, earlier or equal, exactly equal, later or equal and
4663 strictly later, respectively. The deprecated
4664 forms <tt><</tt> and <tt>></tt> were confusingly used to
4665 mean earlier/later or equal, rather than strictly earlier/later,
4666 and must not appear in new packages (though <prgn>dpkg</prgn>
4667 still supports them with a warning).
4671 Whitespace may appear at any point in the version
4672 specification subject to the rules in <ref
4673 id="controlsyntax">, and must appear where it's necessary to
4674 disambiguate; it is not otherwise significant. All of the
4675 relationship fields can only be folded in source package control files. For
4676 consistency and in case of future changes to
4677 <prgn>dpkg</prgn> it is recommended that a single space be
4678 used after a version relationship and before a version
4679 number; it is also conventional to put a single space after
4680 each comma, on either side of each vertical bar, and before
4681 each open parenthesis. When opening a continuation line in a relationship field, it
4682 is conventional to do so after a comma and before the space
4683 following that comma.
4687 For example, a list of dependencies might appear as:
4688 <example compact="compact">
4691 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4696 Relationships may be restricted to a certain set of
4697 architectures. This is indicated in brackets after each
4698 individual package name and the optional version specification.
4699 The brackets enclose a non-empty list of Debian architecture names
4700 in the format described in <ref id="arch-spec">,
4701 separated by whitespace. Exclamation marks may be prepended to
4702 each of the names. (It is not permitted for some names to be
4703 prepended with exclamation marks while others aren't.)
4707 For build relationship fields
4708 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4709 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4710 the current Debian host architecture is not in this list and
4711 there are no exclamation marks in the list, or it is in the list
4712 with a prepended exclamation mark, the package name and the
4713 associated version specification are ignored completely for the
4714 purposes of defining the relationships.
4719 <example compact="compact">
4721 Build-Depends-Indep: texinfo
4722 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4723 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4725 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4726 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4727 <tt>gnumach-dev</tt> only on hurd-i386.
4731 For binary relationship fields and the <tt>Built-Using</tt>
4732 field, the architecture restriction
4733 syntax is only supported in the source package control
4734 file <file>debian/control</file>. When the corresponding binary
4735 package control file is generated, the relationship will either
4736 be omitted or included without the architecture restriction
4737 based on the architecture of the binary package. This means
4738 that architecture restrictions must not be used in binary
4739 relationship fields for architecture-independent packages
4740 (<tt>Architecture: all</tt>).
4745 <example compact="compact">
4746 Depends: foo [i386], bar [amd64]
4748 becomes <tt>Depends: foo</tt> when the package is built on
4749 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4750 package is built on the <tt>amd64</tt> architecture, and omitted
4751 entirely in binary packages built on all other architectures.
4755 If the architecture-restricted dependency is part of a set of
4756 alternatives using <tt>|</tt>, that alternative is ignored
4757 completely on architectures that do not match the restriction.
4759 <example compact="compact">
4760 Build-Depends: foo [!i386] | bar [!amd64]
4762 is equivalent to <tt>bar</tt> on the i386 architecture, to
4763 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4764 bar</tt> on all other architectures.
4768 Relationships may also be restricted to a certain set of
4769 architectures using architecture wildcards in the format
4770 described in <ref id="arch-wildcard-spec">. The syntax for
4771 declaring such restrictions is the same as declaring
4772 restrictions using a certain set of architectures without
4773 architecture wildcards. For example:
4774 <example compact="compact">
4775 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4777 is equivalent to <tt>foo</tt> on architectures using the Linux
4778 kernel and any cpu, <tt>bar</tt> on architectures using any
4779 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4780 using a kernel other than Linux.
4784 Note that the binary package relationship fields such as
4785 <tt>Depends</tt> appear in one of the binary package
4786 sections of the control file, whereas the build-time
4787 relationships such as <tt>Build-Depends</tt> appear in the
4788 source package section of the control file (which is the
4793 <sect id="binarydeps">
4794 <heading>Binary Dependencies - <tt>Depends</tt>,
4795 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4796 <tt>Pre-Depends</tt>
4800 Packages can declare in their control file that they have
4801 certain relationships to other packages - for example, that
4802 they may not be installed at the same time as certain other
4803 packages, and/or that they depend on the presence of others.
4807 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4808 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4809 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4810 <tt>Breaks</tt> is described in <ref id="breaks">, and
4811 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4812 rest are described below.
4816 These seven fields are used to declare a dependency
4817 relationship by one package on another. Except for
4818 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4819 depending (binary) package's control file.
4820 (<tt>Enhances</tt> appears in the recommending package's
4821 control file, and <tt>Breaks</tt> appears in the version of
4822 depended-on package which causes the named package to
4827 A <tt>Depends</tt> field takes effect <em>only</em> when a
4828 package is to be configured. It does not prevent a package
4829 being on the system in an unconfigured state while its
4830 dependencies are unsatisfied, and it is possible to replace
4831 a package whose dependencies are satisfied and which is
4832 properly installed with a different version whose
4833 dependencies are not and cannot be satisfied; when this is
4834 done the depending package will be left unconfigured (since
4835 attempts to configure it will give errors) and will not
4836 function properly. If it is necessary, a
4837 <tt>Pre-Depends</tt> field can be used, which has a partial
4838 effect even when a package is being unpacked, as explained
4839 in detail below. (The other three dependency fields,
4840 <tt>Recommends</tt>, <tt>Suggests</tt> and
4841 <tt>Enhances</tt>, are only used by the various front-ends
4842 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4843 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4847 Since <tt>Depends</tt> only places requirements on the order in
4848 which packages are configured, packages in an installation run
4849 are usually all unpacked first and all configured later.
4851 This approach makes dependency resolution easier. If two
4852 packages A and B are being upgraded, the installed package A
4853 depends on exactly the installed package B, and the new
4854 package A depends on exactly the new package B (a common
4855 situation when upgrading shared libraries and their
4856 corresponding development packages), satisfying the
4857 dependencies at every stage of the upgrade would be
4858 impossible. This relaxed restriction means that both new
4859 packages can be unpacked together and then configured in their
4865 If there is a circular dependency among packages being installed
4866 or removed, installation or removal order honoring the
4867 dependency order is impossible, requiring the dependency loop be
4868 broken at some point and the dependency requirements violated
4869 for at least one package. Packages involved in circular
4870 dependencies may not be able to rely on their dependencies being
4871 configured before they themselves are configured, depending on
4872 which side of the break of the circular dependency loop they
4873 happen to be on. If one of the packages in the loop has
4874 no <prgn>postinst</prgn> script, then the cycle will be broken
4875 at that package; this ensures that all <prgn>postinst</prgn>
4876 scripts are run with their dependencies properly configured if
4877 this is possible. Otherwise the breaking point is arbitrary.
4878 Packages should therefore avoid circular dependencies where
4879 possible, particularly if they have <prgn>postinst</prgn>
4884 The meaning of the five dependency fields is as follows:
4886 <tag><tt>Depends</tt></tag>
4889 This declares an absolute dependency. A package will
4890 not be configured unless all of the packages listed in
4891 its <tt>Depends</tt> field have been correctly
4892 configured (unless there is a circular dependency as
4897 The <tt>Depends</tt> field should be used if the
4898 depended-on package is required for the depending
4899 package to provide a significant amount of
4904 The <tt>Depends</tt> field should also be used if the
4905 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4906 require the depended-on package to be unpacked or
4907 configured in order to run. In the case of <tt>postinst
4908 configure</tt>, the depended-on packages will be unpacked
4909 and configured first. (If both packages are involved in a
4910 dependency loop, this might not work as expected; see the
4911 explanation a few paragraphs back.) In the case
4912 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4913 actions, the package dependencies will normally be at
4914 least unpacked, but they may be only "Half-Installed" if a
4915 previous upgrade of the dependency failed.
4919 Finally, the <tt>Depends</tt> field should be used if the
4920 depended-on package is needed by the <prgn>postrm</prgn>
4921 script to fully clean up after the package removal. There
4922 is no guarantee that package dependencies will be
4923 available when <prgn>postrm</prgn> is run, but the
4924 depended-on package is more likely to be available if the
4925 package declares a dependency (particularly in the case
4926 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4927 script must gracefully skip actions that require a
4928 dependency if that dependency isn't available.
4932 <tag><tt>Recommends</tt></tag>
4935 This declares a strong, but not absolute, dependency.
4939 The <tt>Recommends</tt> field should list packages
4940 that would be found together with this one in all but
4941 unusual installations.
4945 <tag><tt>Suggests</tt></tag>
4947 This is used to declare that one package may be more
4948 useful with one or more others. Using this field
4949 tells the packaging system and the user that the
4950 listed packages are related to this one and can
4951 perhaps enhance its usefulness, but that installing
4952 this one without them is perfectly reasonable.
4955 <tag><tt>Enhances</tt></tag>
4957 This field is similar to Suggests but works in the
4958 opposite direction. It is used to declare that a
4959 package can enhance the functionality of another
4963 <tag><tt>Pre-Depends</tt></tag>
4966 This field is like <tt>Depends</tt>, except that it
4967 also forces <prgn>dpkg</prgn> to complete installation
4968 of the packages named before even starting the
4969 installation of the package which declares the
4970 pre-dependency, as follows:
4974 When a package declaring a pre-dependency is about to
4975 be <em>unpacked</em> the pre-dependency can be
4976 satisfied if the depended-on package is either fully
4977 configured, <em>or even if</em> the depended-on
4978 package(s) are only unpacked or in the "Half-Configured"
4979 state, provided that they have been configured
4980 correctly at some point in the past (and not removed
4981 or partially removed since). In this case, both the
4982 previously-configured and currently unpacked or
4983 "Half-Configured" versions must satisfy any version
4984 clause in the <tt>Pre-Depends</tt> field.
4988 When the package declaring a pre-dependency is about to
4989 be <em>configured</em>, the pre-dependency will be treated
4990 as a normal <tt>Depends</tt>. It will be considered
4991 satisfied only if the depended-on package has been
4992 correctly configured. However, unlike
4993 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4994 permit circular dependencies to be broken. If a circular
4995 dependency is encountered while attempting to honor
4996 <tt>Pre-Depends</tt>, the installation will be aborted.
5000 <tt>Pre-Depends</tt> are also required if the
5001 <prgn>preinst</prgn> script depends on the named package.
5002 It is best to avoid this situation if possible.
5006 <tt>Pre-Depends</tt> should be used sparingly,
5007 preferably only by packages whose premature upgrade or
5008 installation would hamper the ability of the system to
5009 continue with any upgrade that might be in progress.
5013 You should not specify a <tt>Pre-Depends</tt> entry for a
5014 package before this has been discussed on the
5015 <tt>debian-devel</tt> mailing list and a consensus about
5016 doing that has been reached. See <ref id="dependencies">.
5023 When selecting which level of dependency to use you should
5024 consider how important the depended-on package is to the
5025 functionality of the one declaring the dependency. Some
5026 packages are composed of components of varying degrees of
5027 importance. Such a package should list using
5028 <tt>Depends</tt> the package(s) which are required by the
5029 more important components. The other components'
5030 requirements may be mentioned as Suggestions or
5031 Recommendations, as appropriate to the components' relative
5037 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
5040 When one binary package declares that it breaks another,
5041 <prgn>dpkg</prgn> will refuse to allow the package which
5042 declares <tt>Breaks</tt> to be unpacked unless the broken
5043 package is deconfigured first, and it will refuse to
5044 allow the broken package to be reconfigured.
5048 A package will not be regarded as causing breakage merely
5049 because its configuration files are still installed; it must
5050 be at least "Half-Installed".
5054 A special exception is made for packages which declare that
5055 they break their own package name or a virtual package which
5056 they provide (see below): this does not count as a real
5061 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5062 version clause; such a <tt>Breaks</tt> is introduced in the
5063 version of an (implicit or explicit) dependency which violates
5064 an assumption or reveals a bug in earlier versions of the broken
5065 package, or which takes over a file from earlier versions of the
5066 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5067 will inform higher-level package management tools that the
5068 broken package must be upgraded before the new one.
5072 If the breaking package also overwrites some files from the
5073 older package, it should use <tt>Replaces</tt> to ensure this
5074 goes smoothly. See <ref id="replaces"> for a full discussion
5075 of taking over files from other packages, including how to
5076 use <tt>Breaks</tt> in those cases.
5080 Many of the cases where <tt>Breaks</tt> should be used were
5081 previously handled with <tt>Conflicts</tt>
5082 because <tt>Breaks</tt> did not yet exist.
5083 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5084 See <ref id="conflicts"> for more information about the
5089 <sect id="conflicts">
5090 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5093 When one binary package declares a conflict with another using
5094 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5095 allow them to be unpacked on the system at the same time. This
5096 is a stronger restriction than <tt>Breaks</tt>, which prevents
5097 the broken package from being configured while the breaking
5098 package is in the "Unpacked" state but allows both packages to
5099 be unpacked at the same time.
5103 If one package is to be unpacked, the other must be removed
5104 first. If the package being unpacked is marked as replacing
5105 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5106 normally be used in this case) the one on the system, or the one
5107 on the system is marked as deselected, or both packages are
5108 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5109 automatically remove the package which is causing the conflict.
5110 Otherwise, it will halt the installation of the new package with
5111 an error. This mechanism is specifically designed to produce an
5112 error when the installed package is <tt>Essential</tt>, but the
5117 A package will not cause a conflict merely because its
5118 configuration files are still installed; it must be at least
5123 A special exception is made for packages which declare a
5124 conflict with their own package name, or with a virtual
5125 package which they provide (see below): this does not
5126 prevent their installation, and allows a package to conflict
5127 with others providing a replacement for it. You use this
5128 feature when you want the package in question to be the only
5129 package providing some feature.
5133 Normally, <tt>Breaks</tt> should be used instead
5134 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5135 stronger restriction on the ordering of package installation or
5136 upgrade and can make it more difficult for the package manager
5137 to find a correct solution to an upgrade or installation
5138 problem. <tt>Breaks</tt> should be used
5140 <item>when moving a file from one package to another (see
5141 <ref id="replaces">),</item>
5142 <item>when splitting a package (a special case of the previous
5144 <item>when the breaking package exposes a bug in or interacts
5145 badly with particular versions of the broken
5148 <tt>Conflicts</tt> should be used
5150 <item>when two packages provide the same file and will
5151 continue to do so,</item>
5152 <item>in conjunction with <tt>Provides</tt> when only one
5153 package providing a given virtual facility may be unpacked
5154 at a time (see <ref id="virtual">),</item>
5155 <item>in other cases where one must prevent simultaneous
5156 installation of two packages for reasons that are ongoing
5157 (not fixed in a later version of one of the packages) or
5158 that must prevent both packages from being unpacked at the
5159 same time, not just configured.</item>
5161 Be aware that adding <tt>Conflicts</tt> is normally not the best
5162 solution when two packages provide the same files. Depending on
5163 the reason for that conflict, using alternatives or renaming the
5164 files is often a better approach. See, for
5165 example, <ref id="binaries">.
5169 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5170 unless two packages cannot be installed at the same time or
5171 installing them both causes one of them to be broken or
5172 unusable. Having similar functionality or performing the same
5173 tasks as another package is not sufficient reason to
5174 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5178 A <tt>Conflicts</tt> entry may have an "earlier than" version
5179 clause if the reason for the conflict is corrected in a later
5180 version of one of the packages. However, normally the presence
5181 of an "earlier than" version clause is a sign
5182 that <tt>Breaks</tt> should have been used instead. An "earlier
5183 than" version clause in <tt>Conflicts</tt>
5184 prevents <prgn>dpkg</prgn> from upgrading or installing the
5185 package which declares such a conflict until the upgrade or
5186 removal of the conflicted-with package has been completed, which
5187 is a strong restriction.
5191 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5195 As well as the names of actual ("concrete") packages, the
5196 package relationship fields <tt>Depends</tt>,
5197 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5198 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5199 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5200 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5201 may mention "virtual packages".
5205 A <em>virtual package</em> is one which appears in the
5206 <tt>Provides</tt> control field of another package. The effect
5207 is as if the package(s) which provide a particular virtual
5208 package name had been listed by name everywhere the virtual
5209 package name appears. (See also <ref id="virtual_pkg">)
5213 If there are both concrete and virtual packages of the same
5214 name, then the dependency may be satisfied (or the conflict
5215 caused) by either the concrete package with the name in
5216 question or any other concrete package which provides the
5217 virtual package with the name in question. This is so that,
5218 for example, supposing we have
5219 <example compact="compact">
5222 </example> and someone else releases an enhanced version of
5223 the <tt>bar</tt> package they can say:
5224 <example compact="compact">
5228 and the <tt>bar-plus</tt> package will now also satisfy the
5229 dependency for the <tt>foo</tt> package.
5233 If a relationship field has a version number attached, only real
5234 packages will be considered to see whether the relationship is
5235 satisfied (or the prohibition violated, for a conflict or
5236 breakage). In other words, if a version number is specified,
5237 this is a request to ignore all <tt>Provides</tt> for that
5238 package name and consider only real packages. The package
5239 manager will assume that a package providing that virtual
5240 package is not of the "right" version. A <tt>Provides</tt>
5241 field may not contain version numbers, and the version number of
5242 the concrete package which provides a particular virtual package
5243 will not be considered when considering a dependency on or
5244 conflict with the virtual package name.<footnote>
5245 It is possible that a future release of <prgn>dpkg</prgn> may
5246 add the ability to specify a version number for each virtual
5247 package it provides. This feature is not yet present,
5248 however, and is expected to be used only infrequently.
5253 To specify which of a set of real packages should be the default
5254 to satisfy a particular dependency on a virtual package, list
5255 the real package as an alternative before the virtual one.
5259 If the virtual package represents a facility that can only be
5260 provided by one real package at a time, such as
5261 the <package>mail-transport-agent</package> virtual package that
5262 requires installation of a binary that would conflict with all
5263 other providers of that virtual package (see
5264 <ref id="mail-transport-agents">), all packages providing that
5265 virtual package should also declare a conflict with it
5266 using <tt>Conflicts</tt>. This will ensure that at most one
5267 provider of that virtual package is unpacked or installed at a
5272 <sect id="replaces"><heading>Overwriting files and replacing
5273 packages - <tt>Replaces</tt></heading>
5276 Packages can declare in their control file that they should
5277 overwrite files in certain other packages, or completely replace
5278 other packages. The <tt>Replaces</tt> control field has these
5279 two distinct purposes.
5282 <sect1><heading>Overwriting files in other packages</heading>
5285 It is usually an error for a package to contain files which
5286 are on the system in another package. However, if the
5287 overwriting package declares that it <tt>Replaces</tt> the one
5288 containing the file being overwritten, then <prgn>dpkg</prgn>
5289 will replace the file from the old package with that from the
5290 new. The file will no longer be listed as "owned" by the old
5291 package and will be taken over by the new package.
5292 Normally, <tt>Breaks</tt> should be used in conjunction
5293 with <tt>Replaces</tt>.<footnote>
5294 To see why <tt>Breaks</tt> is normally needed in addition
5295 to <tt>Replaces</tt>, consider the case of a file in the
5296 package <package>foo</package> being taken over by the
5297 package <package>foo-data</package>.
5298 <tt>Replaces</tt> will allow <package>foo-data</package> to
5299 be installed and take over that file. However,
5300 without <tt>Breaks</tt>, nothing
5301 requires <package>foo</package> to be upgraded to a newer
5302 version that knows it does not include that file and instead
5303 depends on <package>foo-data</package>. Nothing would
5304 prevent the new <package>foo-data</package> package from
5305 being installed and then removed, removing the file that it
5306 took over from <package>foo</package>. After that
5307 operation, the package manager would think the system was in
5308 a consistent state, but the <package>foo</package> package
5309 would be missing one of its files.
5314 For example, if a package <package>foo</package> is split
5315 into <package>foo</package> and <package>foo-data</package>
5316 starting at version 1.2-3, <package>foo-data</package> would
5318 <example compact="compact">
5319 Replaces: foo (<< 1.2-3)
5320 Breaks: foo (<< 1.2-3)
5322 in its control file. The new version of the
5323 package <package>foo</package> would normally have the field
5324 <example compact="compact">
5325 Depends: foo-data (>= 1.2-3)
5327 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5328 the files moved into <package>foo-data</package> are not
5329 required for normal operation).
5333 If a package is completely replaced in this way, so that
5334 <prgn>dpkg</prgn> does not know of any files it still
5335 contains, it is considered to have "disappeared". It will
5336 be marked as not wanted on the system (selected for
5337 removal) and not installed. Any <tt>conffile</tt>s
5338 details noted for the package will be ignored, as they
5339 will have been taken over by the overwriting package. The
5340 package's <prgn>postrm</prgn> script will be run with a
5341 special argument to allow the package to do any final
5342 cleanup required. See <ref id="mscriptsinstact">.
5344 Replaces is a one way relationship. You have to install
5345 the replacing package after the replaced package.
5350 For this usage of <tt>Replaces</tt>, virtual packages (see
5351 <ref id="virtual">) are not considered when looking at a
5352 <tt>Replaces</tt> field. The packages declared as being
5353 replaced must be mentioned by their real names.
5357 This usage of <tt>Replaces</tt> only takes effect when both
5358 packages are at least partially on the system at once. It is
5359 not relevant if the packages conflict unless the conflict has
5364 <sect1><heading>Replacing whole packages, forcing their
5368 Second, <tt>Replaces</tt> allows the packaging system to
5369 resolve which package should be removed when there is a
5370 conflict (see <ref id="conflicts">). This usage only takes
5371 effect when the two packages <em>do</em> conflict, so that the
5372 two usages of this field do not interfere with each other.
5376 In this situation, the package declared as being replaced
5377 can be a virtual package, so for example, all mail
5378 transport agents (MTAs) would have the following fields in
5379 their control files:
5380 <example compact="compact">
5381 Provides: mail-transport-agent
5382 Conflicts: mail-transport-agent
5383 Replaces: mail-transport-agent
5385 ensuring that only one MTA can be unpacked at any one
5386 time. See <ref id="virtual"> for more information about this
5391 <sect id="sourcebinarydeps">
5392 <heading>Relationships between source and binary packages -
5393 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5394 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5398 Source packages that require certain binary packages to be
5399 installed or absent at the time of building the package
5400 can declare relationships to those binary packages.
5404 This is done using the <tt>Build-Depends</tt>,
5405 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5406 <tt>Build-Conflicts-Indep</tt> control fields.
5410 Build-dependencies on "build-essential" binary packages can be
5411 omitted. Please see <ref id="pkg-relations"> for more information.
5415 The dependencies and conflicts they define must be satisfied
5416 (as defined earlier for binary packages) in order to invoke
5417 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5419 There is no Build-Depends-Arch; this role is essentially
5420 met with Build-Depends. Anyone building the
5421 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5422 assumed to be building the whole package, and therefore
5423 installation of all build dependencies is required.
5426 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5427 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5428 not yet know how to check for its existence, and
5429 <tt>binary-arch</tt>. The purpose of the original split
5430 between <tt>Build-Depends</tt> and
5431 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5432 wouldn't need to install extra packages needed only for the
5433 binary-indep targets. But without a build-arch/build-indep
5434 split, this didn't work, since most of the work is done in
5435 the build target, not in the binary target.
5439 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5440 <tt>binary-arch</tt></tag>
5442 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5443 fields must be satisfied when these targets are invoked.
5445 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5446 and <tt>binary-indep</tt></tag>
5448 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5449 <tt>Build-Depends-Indep</tt>, and
5450 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5451 these targets are invoked.
5457 <sect id="built-using">
5458 <heading>Additional source packages used to build the binary
5459 - <tt>Built-Using</tt>
5463 Some binary packages incorporate parts of other packages when built
5464 but do not have to depend on those packages. Examples include
5465 linking with static libraries or incorporating source code from
5466 another package during the build. In this case, the source packages
5467 of those other packages are a required part of the complete source
5468 (the binary package is not reproducible without them).
5472 A <tt>Built-Using</tt> field must list the corresponding source
5473 package for any such binary package incorporated during the build
5475 <tt>Build-Depends</tt> in the source package is not adequate since
5476 it (rightfully) does not document the exact version used in the
5479 including an "exactly equal" ("=") version relation on the version
5480 that was used to build that binary package<footnote>
5481 The archive software might reject packages that refer to
5482 non-existent sources.
5487 A package using the source code from the gcc-4.6-source
5488 binary package built from the gcc-4.6 source package would
5489 have this field in its control file:
5490 <example compact="compact">
5491 Built-Using: gcc-4.6 (= 4.6.0-11)
5496 A package including binaries from grub2 and loadlin would
5497 have this field in its control file:
5498 <example compact="compact">
5499 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5506 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5509 Packages containing shared libraries must be constructed with
5510 a little care to make sure that the shared library is always
5511 available. This is especially important for packages whose
5512 shared libraries are vitally important, such as the C library
5513 (currently <tt>libc6</tt>).
5517 This section deals only with public shared libraries: shared
5518 libraries that are placed in directories searched by the dynamic
5519 linker by default or which are intended to be linked against
5520 normally and possibly used by other, independent packages. Shared
5521 libraries that are internal to a particular package or that are
5522 only loaded as dynamic modules are not covered by this section and
5523 are not subject to its requirements.
5527 A shared library is identified by the <tt>SONAME</tt> attribute
5528 stored in its dynamic section. When a binary is linked against a
5529 shared library, the <tt>SONAME</tt> of the shared library is
5530 recorded in the binary's <tt>NEEDED</tt> section so that the
5531 dynamic linker knows that library must be loaded at runtime. The
5532 shared library file's full name (which usually contains additional
5533 version information not needed in the <tt>SONAME</tt>) is
5534 therefore normally not referenced directly. Instead, the shared
5535 library is loaded by its <tt>SONAME</tt>, which exists on the file
5536 system as a symlink pointing to the full name of the shared
5537 library. This symlink must be provided by the
5538 package. <ref id="sharedlibs-runtime"> describes how to do this.
5540 This is a convention of shared library versioning, but not a
5541 requirement. Some libraries use the <tt>SONAME</tt> as the full
5542 library file name instead and therefore do not need a symlink.
5543 Most, however, encode additional information about
5544 backwards-compatible revisions as a minor version number in the
5545 file name. The <tt>SONAME</tt> itself only changes when
5546 binaries linked with the earlier version of the shared library
5547 may no longer work, but the filename may change with each
5548 release of the library. See <ref id="sharedlibs-runtime"> for
5554 When linking a binary or another shared library against a shared
5555 library, the <tt>SONAME</tt> for that shared library is not yet
5556 known. Instead, the shared library is found by looking for a file
5557 matching the library name with <tt>.so</tt> appended. This file
5558 exists on the file system as a symlink pointing to the shared
5563 Shared libraries are normally split into several binary packages.
5564 The <tt>SONAME</tt> symlink is installed by the runtime shared
5565 library package, and the bare <tt>.so</tt> symlink is installed in
5566 the development package since it's only used when linking binaries
5567 or shared libraries. However, there are some exceptions for
5568 unusual shared libraries or for shared libraries that are also
5569 loaded as dynamic modules by other programs.
5573 This section is primarily concerned with how the separation of
5574 shared libraries into multiple packages should be done and how
5575 dependencies on and between shared library binary packages are
5576 managed in Debian. <ref id="libraries"> should be read in
5577 conjunction with this section and contains additional rules for
5578 the files contained in the shared library packages.
5581 <sect id="sharedlibs-runtime">
5582 <heading>Run-time shared libraries</heading>
5585 The run-time shared library must be placed in a package
5586 whose name changes whenever the <tt>SONAME</tt> of the shared
5587 library changes. This allows several versions of the shared
5588 library to be installed at the same time, allowing installation
5589 of the new version of the shared library without immediately
5590 breaking binaries that depend on the old version. Normally, the
5591 run-time shared library and its <tt>SONAME</tt> symlink should
5592 be placed in a package named
5593 <package><var>libraryname</var><var>soversion</var></package>,
5594 where <var>soversion</var> is the version number in
5595 the <tt>SONAME</tt> of the shared library.
5596 See <ref id="shlibs"> for detailed information on how to
5597 determine this version. Alternatively, if it would be confusing
5598 to directly append <var>soversion</var>
5599 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5600 itself ends in a number), you should use
5601 <package><var>libraryname</var>-<var>soversion</var></package>
5606 If you have several shared libraries built from the same source
5607 tree, you may lump them all together into a single shared
5608 library package provided that all of their <tt>SONAME</tt>s will
5609 always change together. Be aware that this is not normally the
5610 case, and if the <tt>SONAME</tt>s do not change together,
5611 upgrading such a merged shared library package will be
5612 unnecessarily difficult because of file conflicts with the old
5613 version of the package. When in doubt, always split shared
5614 library packages so that each binary package installs a single
5619 Every time the shared library ABI changes in a way that may
5620 break binaries linked against older versions of the shared
5621 library, the <tt>SONAME</tt> of the library and the
5622 corresponding name for the binary package containing the runtime
5623 shared library should change. Normally, this means
5624 the <tt>SONAME</tt> should change any time an interface is
5625 removed from the shared library or the signature of an interface
5626 (the number of parameters or the types of parameters that it
5627 takes, for example) is changed. This practice is vital to
5628 allowing clean upgrades from older versions of the package and
5629 clean transitions between the old ABI and new ABI without having
5630 to upgrade every affected package simultaneously.
5634 The <tt>SONAME</tt> and binary package name need not, and indeed
5635 normally should not, change if new interfaces are added but none
5636 are removed or changed, since this will not break binaries
5637 linked against the old shared library. Correct versioning of
5638 dependencies on the newer shared library by binaries that use
5639 the new interfaces is handled via
5640 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5641 system</qref> or via symbols files (see
5642 <manref name="deb-symbols" section="5">).
5646 The package should install the shared libraries under
5647 their normal names. For example, the <package>libgdbm3</package>
5648 package should install <file>libgdbm.so.3.0.0</file> as
5649 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5650 renamed or re-linked by any <prgn>prerm</prgn> or
5651 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5652 of renaming things safely without affecting running programs,
5653 and attempts to interfere with this are likely to lead to
5658 Shared libraries should not be installed executable, since
5659 the dynamic linker does not require this and trying to
5660 execute a shared library usually results in a core dump.
5664 The run-time library package should include the symbolic link for
5665 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5666 the shared libraries. For example,
5667 the <package>libgdbm3</package> package should include a symbolic
5668 link from <file>/usr/lib/libgdbm.so.3</file> to
5669 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5670 linker (for example <prgn>ld.so</prgn> or
5671 <prgn>ld-linux.so.*</prgn>) can find the library between the
5672 time that <prgn>dpkg</prgn> installs it and the time that
5673 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5675 The package management system requires the library to be
5676 placed before the symbolic link pointing to it in the
5677 <file>.deb</file> file. This is so that when
5678 <prgn>dpkg</prgn> comes to install the symlink
5679 (overwriting the previous symlink pointing at an older
5680 version of the library), the new shared library is already
5681 in place. In the past, this was achieved by creating the
5682 library in the temporary packaging directory before
5683 creating the symlink. Unfortunately, this was not always
5684 effective, since the building of the tar file in the
5685 <file>.deb</file> depended on the behavior of the underlying
5686 file system. Some file systems (such as reiserfs) reorder
5687 the files so that the order of creation is forgotten.
5688 Since version 1.7.0, <prgn>dpkg</prgn>
5689 reorders the files itself as necessary when building a
5690 package. Thus it is no longer important to concern
5691 oneself with the order of file creation.
5695 <sect1 id="ldconfig">
5696 <heading><tt>ldconfig</tt></heading>
5699 Any package installing shared libraries in one of the default
5700 library directories of the dynamic linker (which are currently
5701 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5702 listed in <file>/etc/ld.so.conf</file><footnote>
5703 These are currently <file>/usr/local/lib</file> plus
5704 directories under <file>/lib</file> and <file>/usr/lib</file>
5705 matching the multiarch triplet for the system architecture.
5707 must use <prgn>ldconfig</prgn> to update the shared library
5712 The package maintainer scripts must only call
5713 <prgn>ldconfig</prgn> under these circumstances:
5714 <list compact="compact">
5715 <item>When the <prgn>postinst</prgn> script is run with a
5716 first argument of <tt>configure</tt>, the script must call
5717 <prgn>ldconfig</prgn>, and may optionally invoke
5718 <prgn>ldconfig</prgn> at other times.
5720 <item>When the <prgn>postrm</prgn> script is run with a
5721 first argument of <tt>remove</tt>, the script should call
5722 <prgn>ldconfig</prgn>.
5727 During install or upgrade, the preinst is called before
5728 the new files are unpacked, so calling "ldconfig" is
5729 pointless. The preinst of an existing package can also be
5730 called if an upgrade fails. However, this happens during
5731 the critical time when a shared libs may exist on-disk
5732 under a temporary name. Thus, it is dangerous and
5733 forbidden by current policy to call "ldconfig" at this
5738 When a package is installed or upgraded, "postinst
5739 configure" runs after the new files are safely on-disk.
5740 Since it is perfectly safe to invoke ldconfig
5741 unconditionally in a postinst, it is OK for a package to
5742 simply put ldconfig in its postinst without checking the
5743 argument. The postinst can also be called to recover from
5744 a failed upgrade. This happens before any new files are
5745 unpacked, so there is no reason to call "ldconfig" at this
5750 For a package that is being removed, prerm is
5751 called with all the files intact, so calling ldconfig is
5752 useless. The other calls to "prerm" happen in the case of
5753 upgrade at a time when all the files of the old package
5754 are on-disk, so again calling "ldconfig" is pointless.
5758 postrm, on the other hand, is called with the "remove"
5759 argument just after the files are removed, so this is
5760 the proper time to call "ldconfig" to notify the system
5761 of the fact that the shared libraries from the package
5762 are removed. The postrm can be called at several other
5763 times. At the time of "postrm purge", "postrm
5764 abort-install", or "postrm abort-upgrade", calling
5765 "ldconfig" is useless because the shared lib files are
5766 not on-disk. However, when "postrm" is invoked with
5767 arguments "upgrade", "failed-upgrade", or "disappear", a
5768 shared lib may exist on-disk under a temporary filename.
5776 <sect id="sharedlibs-support-files">
5777 <heading>Shared library support files</heading>
5780 If your package contains files whose names do not change with
5781 each change in the library shared object version, you must not
5782 put them in the shared library package. Otherwise, several
5783 versions of the shared library cannot be installed at the same
5784 time without filename clashes, making upgrades and transitions
5785 unnecessarily difficult.
5789 It is recommended that supporting files and run-time support
5790 programs that do not need to be invoked manually by users, but
5791 are nevertheless required for the package to function, be placed
5792 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5793 preferably under <file>/usr/lib/</file><var>package-name</var>.
5794 If the program or file is architecture independent, the
5795 recommendation is for it to be placed in a subdirectory of
5796 <file>/usr/share</file> instead, preferably under
5797 <file>/usr/share/</file><var>package-name</var>. Following the
5798 <var>package-name</var> naming convention ensures that the file
5799 names change when the shared object version changes.
5803 Run-time support programs that use the shared library but are
5804 not required for the library to function or files used by the
5805 shared library that can be used by any version of the shared
5806 library package should instead be put in a separate package.
5807 This package might typically be named
5808 <package><var>libraryname</var>-tools</package>; note the
5809 absence of the <var>soversion</var> in the package name.
5813 Files and support programs only useful when compiling software
5814 against the library should be included in the development
5815 package for the library.<footnote>
5816 For example, a <file><var>package-name</var>-config</file>
5817 script or <package>pkg-config</package> configuration files.
5822 <sect id="sharedlibs-static">
5823 <heading>Static libraries</heading>
5826 The static library (<file><var>libraryname.a</var></file>)
5827 is usually provided in addition to the shared version.
5828 It is placed into the development package (see below).
5832 In some cases, it is acceptable for a library to be
5833 available in static form only; these cases include:
5835 <item>libraries for languages whose shared library support
5836 is immature or unstable</item>
5837 <item>libraries whose interfaces are in flux or under
5838 development (commonly the case when the library's
5839 major version number is zero, or where the ABI breaks
5840 across patchlevels)</item>
5841 <item>libraries which are explicitly intended to be
5842 available only in static form by their upstream
5847 <sect id="sharedlibs-dev">
5848 <heading>Development files</heading>
5851 If there are development files associated with a shared library,
5852 the source package needs to generate a binary development package
5853 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5854 or if you prefer only to support one development version at a
5855 time, <package><var>libraryname</var>-dev</package>. Installing
5856 the development package must result in installation of all the
5857 development files necessary for compiling programs against that
5858 shared library.<footnote>
5859 This wording allows the development files to be split into
5860 several packages, such as a separate architecture-independent
5861 <package><var>libraryname</var>-headers</package>, provided that
5862 the development package depends on all the required additional
5868 In case several development versions of a library exist, you may
5869 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5870 <ref id="conflicts">) to ensure that the user only installs one
5871 development version at a time (as different development versions are
5872 likely to have the same header files in them, which would cause a
5873 filename clash if both were unpacked).
5877 The development package should contain a symlink for the associated
5878 shared library without a version number. For example, the
5879 <package>libgdbm-dev</package> package should include a symlink
5880 from <file>/usr/lib/libgdbm.so</file> to
5881 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5882 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5883 <file>libgdbm.so</file> when compiling dynamically.
5887 If the package provides Ada Library Information
5888 (<file>*.ali</file>) files for use with GNAT, these files must be
5889 installed read-only (mode 0444) so that GNAT will not attempt to
5890 recompile them. This overrides the normal file mode requirements
5891 given in <ref id="permissions-owners">.
5895 <sect id="sharedlibs-intradeps">
5896 <heading>Dependencies between the packages of the same library</heading>
5899 Typically the development version should have an exact
5900 version dependency on the runtime library, to make sure that
5901 compilation and linking happens correctly. The
5902 <tt>${binary:Version}</tt> substitution variable can be
5903 useful for this purpose.
5905 Previously, <tt>${Source-Version}</tt> was used, but its name
5906 was confusing and it has been deprecated since dpkg 1.13.19.
5911 <sect id="sharedlibs-shlibdeps">
5912 <heading>Dependencies between the library and other packages -
5913 the <tt>shlibs</tt> system</heading>
5916 If a package contains a binary or library which links to a
5917 shared library, we must ensure that when the package is
5918 installed on the system, all of the libraries needed are
5919 also installed. This requirement led to the creation of the
5920 <tt>shlibs</tt> system, which is very simple in its design:
5921 any package which <em>provides</em> a shared library also
5922 provides information on the package dependencies required to
5923 ensure the presence of this library, and any package which
5924 <em>uses</em> a shared library uses this information to
5925 determine the dependencies it requires. The files which
5926 contain the mapping from shared libraries to the necessary
5927 dependency information are called <file>shlibs</file> files.
5931 When a package is built which contains any shared libraries, it
5932 must provide a <file>shlibs</file> file for other packages to
5933 use. When a package is built which contains any shared
5934 libraries or compiled binaries, it must run
5935 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5936 on these to determine the libraries used and hence the
5937 dependencies needed by this package.<footnote>
5939 <prgn>dpkg-shlibdeps</prgn> will use a program
5940 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5941 the libraries directly needed by the binaries or shared
5942 libraries in the package.
5946 We say that a binary <tt>foo</tt> <em>directly</em> uses
5947 a library <tt>libbar</tt> if it is explicitly linked
5948 with that library (that is, the library is listed in the ELF
5949 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5950 to the link line when the binary is created). Other
5951 libraries that are needed by <tt>libbar</tt> are linked
5952 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5953 linker will load them automatically when it loads
5954 <tt>libbar</tt>. A package should depend on the libraries
5955 it directly uses, but not the libraries it indirectly uses.
5956 The dependencies for those libraries will automatically pull
5957 in the other libraries.
5961 A good example of where this helps is the following. We
5962 could update <tt>libimlib</tt> with a new version that
5963 supports a new graphics format called dgf (but retaining the
5964 same major version number) and depends on <tt>libdgf</tt>.
5965 If we used <prgn>ldd</prgn> to add dependencies for every
5966 library directly or indirectly linked with a binary, every
5967 package that uses <tt>libimlib</tt> would need to be
5968 recompiled so it would also depend on <tt>libdgf</tt> or it
5969 wouldn't run due to missing symbols. Since dependencies are
5970 only added based on ELF <tt>NEEDED</tt> attribute, packages
5971 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5972 having the dependency on <tt>libdgf</tt> and so they would
5973 not need rebuilding.
5979 In the following sections, we will first describe where the
5980 various <tt>shlibs</tt> files are to be found, then how to
5981 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5982 file format and how to create them if your package contains a
5987 <heading>The <tt>shlibs</tt> files present on the system</heading>
5990 There are several places where <tt>shlibs</tt> files are
5991 found. The following list gives them in the order in which
5993 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5994 (The first one which gives the required information is used.)
6000 <p><file>debian/shlibs.local</file></p>
6003 This lists overrides for this package. This file should
6004 normally not be used, but may be needed temporarily in
6005 unusual situations to work around bugs in other packages,
6006 or in unusual cases where the normally declared dependency
6007 information in the installed <file>shlibs</file> file for
6008 a library cannot be used. This file overrides information
6009 obtained from any other source.
6014 <p><file>/etc/dpkg/shlibs.override</file></p>
6017 This lists global overrides. This list is normally
6018 empty. It is maintained by the local system
6024 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
6027 When packages are being built,
6028 any <file>debian/shlibs</file> files are copied into the
6029 control information file area of the temporary build
6030 directory and given the name <file>shlibs</file>. These
6031 files give details of any shared libraries included in the
6032 same package.<footnote>
6033 An example may help here. Let us say that the source
6034 package <tt>foo</tt> generates two binary
6035 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
6036 When building the binary packages, the two packages are
6037 created in the directories <file>debian/libfoo2</file>
6038 and <file>debian/foo-runtime</file> respectively.
6039 (<file>debian/tmp</file> could be used instead of one of
6040 these.) Since <tt>libfoo2</tt> provides the
6041 <tt>libfoo</tt> shared library, it will require a
6042 <tt>shlibs</tt> file, which will be installed in
6043 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
6044 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
6045 When <prgn>dpkg-shlibdeps</prgn> is run on the
6046 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
6048 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
6049 determine whether <tt>foo-prog</tt>'s library
6050 dependencies are satisfied by any of the libraries
6051 provided by <tt>libfoo2</tt>. For this reason,
6052 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
6053 the individual binary packages' <tt>shlibs</tt> files
6054 have been installed into the build directory.
6060 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
6063 These are the <file>shlibs</file> files corresponding to
6064 all of the packages installed on the system, and are
6065 maintained by the relevant package maintainers.
6070 <p><file>/etc/dpkg/shlibs.default</file></p>
6073 This file lists any shared libraries whose packages
6074 have failed to provide correct <file>shlibs</file> files.
6075 It was used when the <file>shlibs</file> setup was first
6076 introduced, but it is now normally empty. It is
6077 maintained by the <tt>dpkg</tt> maintainer.
6085 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
6086 <file>shlibs</file> files</heading>
6090 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
6091 into your <file>debian/rules</file> file. If your package
6092 contains only compiled binaries and libraries (but no scripts),
6093 you can use a command such as:
6094 <example compact="compact">
6095 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
6096 debian/tmp/usr/lib/*
6098 Otherwise, you will need to explicitly list the compiled
6099 binaries and libraries.<footnote>
6100 If you are using <tt>debhelper</tt>, the
6101 <prgn>dh_shlibdeps</prgn> program will do this work for you.
6102 It will also correctly handle multi-binary packages.
6107 This command puts the dependency information into the
6108 <file>debian/substvars</file> file, which is then used by
6109 <prgn>dpkg-gencontrol</prgn>. You will need to place a
6110 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
6111 field in the control file for this to work.
6115 If you have multiple binary packages, you will need to call
6116 <prgn>dpkg-shlibdeps</prgn> on each one which contains
6117 compiled libraries or binaries. In such a case, you will
6118 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
6119 utilities to specify a different <file>substvars</file> file.
6123 If you are creating a udeb for use in the Debian Installer,
6124 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6125 should use the dependency line of type <tt>udeb</tt> by
6126 adding the <tt>-tudeb</tt> option<footnote>
6127 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6128 will automatically add this option if it knows it is
6130 </footnote>. If there is no dependency line of
6131 type <tt>udeb</tt> in the <file>shlibs</file>
6132 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
6137 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
6138 <ref id="pkg-dpkg-shlibdeps"> and
6139 <manref name="dpkg-shlibdeps" section="1">.
6144 <heading>The <file>shlibs</file> File Format</heading>
6147 Each <file>shlibs</file> file has the same format. Lines
6148 beginning with <tt>#</tt> are considered to be comments and
6149 are ignored. Each line is of the form:
6150 <example compact="compact">
6151 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6156 We will explain this by reference to the example of the
6157 <tt>zlib1g</tt> package, which (at the time of writing)
6158 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
6162 <var>type</var> is an optional element that indicates the type
6163 of package for which the line is valid. The only type currently
6164 in use is <tt>udeb</tt>. The colon and space after the type are
6169 <var>library-name</var> is the name of the shared library,
6170 in this case <tt>libz</tt>. (This must match the name part
6171 of the soname, see below.)
6175 <var>soname-version</var> is the version part of the soname of
6176 the library. The soname is the thing that must exactly match
6177 for the library to be recognized by the dynamic linker, and is
6179 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
6180 example, <tt>libz.so.1</tt>.<footnote>
6181 This can be determined using the command
6182 <example compact="compact">
6183 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
6186 The version part is the part which comes after
6187 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
6188 instead be of the form
6189 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
6190 as <tt>libdb-4.8.so</tt>, in which case the name would
6191 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
6195 <var>dependencies</var> has the same syntax as a dependency
6196 field in a binary package control file. It should give
6197 details of which packages are required to satisfy a binary
6198 built against the version of the library contained in the
6199 package. See <ref id="depsyntax"> for details.
6203 In our example, if the first version of the <tt>zlib1g</tt>
6204 package which contained a minor number of at least
6205 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
6206 <tt>shlibs</tt> entry for this library could say:
6207 <example compact="compact">
6208 libz 1 zlib1g (>= 1:1.1.3)
6210 The version-specific dependency is to avoid warnings from
6211 the dynamic linker about using older shared libraries with
6216 As zlib1g also provides a udeb containing the shared library,
6217 there would also be a second line:
6218 <example compact="compact">
6219 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
6225 <heading>Providing a <file>shlibs</file> file</heading>
6228 If your package provides a shared library, you need to create
6229 a <file>shlibs</file> file following the format described above.
6230 It is usual to call this file <file>debian/shlibs</file> (but if
6231 you have multiple binary packages, you might want to call it
6232 <file>debian/shlibs.<var>package</var></file> instead). Then
6233 let <file>debian/rules</file> install it in the control
6234 information file area:
6235 <example compact="compact">
6236 install -m644 debian/shlibs debian/tmp/DEBIAN
6238 or, in the case of a multi-binary package:
6239 <example compact="compact">
6240 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
6242 An alternative way of doing this is to create the
6243 <file>shlibs</file> file in the control information file area
6244 directly from <file>debian/rules</file> without using
6245 a <file>debian/shlibs</file> file at all,<footnote>
6246 This is what <prgn>dh_makeshlibs</prgn> in
6247 the <package>debhelper</package> suite does. If your package
6248 also has a udeb that provides a shared
6249 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6250 the <tt>udeb:</tt> lines if you specify the name of the udeb
6251 with the <tt>--add-udeb</tt> option.
6253 since the <file>debian/shlibs</file> file itself is ignored by
6254 <prgn>dpkg-shlibdeps</prgn>.
6258 As <prgn>dpkg-shlibdeps</prgn> reads the
6259 <file>DEBIAN/shlibs</file> files in all of the binary packages
6260 being built from this source package, all of the
6261 <file>DEBIAN/shlibs</file> files should be installed before
6262 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6270 <chapt id="opersys"><heading>The Operating System</heading>
6273 <heading>File system hierarchy</heading>
6277 <heading>File System Structure</heading>
6280 The location of all files and directories must comply with the
6281 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6282 exceptions noted below, and except where doing so would
6283 violate other terms of Debian Policy. The following
6284 exceptions to the FHS apply:
6289 The optional rules related to user specific
6290 configuration files for applications are stored in
6291 the user's home directory are relaxed. It is
6292 recommended that such files start with the
6293 '<tt>.</tt>' character (a "dot file"), and if an
6294 application needs to create more than one dot file
6295 then the preferred placement is in a subdirectory
6296 with a name starting with a '.' character, (a "dot
6297 directory"). In this case it is recommended the
6298 configuration files not start with the '.'
6304 The requirement for amd64 to use <file>/lib64</file>
6305 for 64 bit binaries is removed.
6310 The requirement for object files, internal binaries, and
6311 libraries, including <file>libc.so.*</file>, to be located
6312 directly under <file>/lib{,32}</file> and
6313 <file>/usr/lib{,32}</file> is amended, permitting files
6314 to instead be installed to
6315 <file>/lib/<var>triplet</var></file> and
6316 <file>/usr/lib/<var>triplet</var></file>, where
6317 <tt><var>triplet</var></tt> is the value returned by
6318 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6319 architecture of the package. Packages may <em>not</em>
6320 install files to any <var>triplet</var> path other
6321 than the one matching the architecture of that package;
6322 for instance, an <tt>Architecture: amd64</tt> package
6323 containing 32-bit x86 libraries may not install these
6324 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6326 This is necessary in order to reserve the directories for
6327 use in cross-installation of library packages from other
6328 architectures, as part of the planned deployment of
6333 Applications may also use a single subdirectory under
6334 <file>/usr/lib/<var>triplet</var></file>.
6337 The execution time linker/loader, ld*, must still be made
6338 available in the existing location under /lib or /lib64
6339 since this is part of the ELF ABI for the architecture.
6344 The requirement that
6345 <file>/usr/local/share/man</file> be "synonymous"
6346 with <file>/usr/local/man</file> is relaxed to a
6351 The requirement that windowmanagers with a single
6352 configuration file call it <file>system.*wmrc</file>
6353 is removed, as is the restriction that the window
6354 manager subdirectory be named identically to the
6355 window manager name itself.
6360 The requirement that boot manager configuration
6361 files live in <file>/etc</file>, or at least are
6362 symlinked there, is relaxed to a recommendation.
6367 The additional directory <file>/run</file> in the root
6368 file system is allowed. <file>/run</file>
6369 replaces <file>/var/run</file>, and the
6370 subdirectory <file>/run/lock</file>
6371 replaces <file>/var/lock</file>, with
6372 the <file>/var</file> directories replaced by symlinks
6373 for backwards compatibility. <file>/run</file>
6374 and <file>/run/lock</file> must follow all of the
6375 requirements in the FHS for <file>/var/run</file>
6376 and <file>/var/lock</file>, respectively, such as file
6377 naming conventions, file format requirements, or the
6378 requirement that files be cleared during the boot
6379 process. Files and directories residing
6380 in <file>/run</file> should be stored on a temporary
6386 The following directories in the root filesystem are
6387 additionally allowed: <file>/sys</file> and
6388 <file>/selinux</file>. <footnote>These directories
6389 are used as mount points to mount virtual filesystems
6390 to get access to kernel information.</footnote>
6395 On GNU/Hurd systems, the following additional
6396 directories are allowed in the root
6397 filesystem: <file>/hurd</file>
6398 and <file>/servers</file>.<footnote>
6399 These directories are used to store translators and as
6400 a set of standard names for mount points,
6409 The version of this document referred here can be
6410 found in the <tt>debian-policy</tt> package or on <url
6411 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6412 name="FHS (Debian copy)"> alongside this manual (or, if
6413 you have the <package>debian-policy</package> installed,
6415 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6416 (local copy)">). The
6417 latest version, which may be a more recent version, may
6419 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6420 Specific questions about following the standard may be
6421 asked on the <tt>debian-devel</tt> mailing list, or
6422 referred to the FHS mailing list (see the
6423 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6429 <heading>Site-specific programs</heading>
6432 As mandated by the FHS, packages must not place any
6433 files in <file>/usr/local</file>, either by putting them in
6434 the file system archive to be unpacked by <prgn>dpkg</prgn>
6435 or by manipulating them in their maintainer scripts.
6439 However, the package may create empty directories below
6440 <file>/usr/local</file> so that the system administrator knows
6441 where to place site-specific files. These are not
6442 directories <em>in</em> <file>/usr/local</file>, but are
6443 children of directories in <file>/usr/local</file>. These
6444 directories (<file>/usr/local/*/dir/</file>)
6445 should be removed on package removal if they are
6450 Note that this applies only to
6451 directories <em>below</em> <file>/usr/local</file>,
6452 not <em>in</em> <file>/usr/local</file>. Packages must
6453 not create sub-directories in the
6454 directory <file>/usr/local</file> itself, except those
6455 listed in FHS, section 4.5. However, you may create
6456 directories below them as you wish. You must not remove
6457 any of the directories listed in 4.5, even if you created
6462 Since <file>/usr/local</file> can be mounted read-only from a
6463 remote server, these directories must be created and
6464 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6465 maintainer scripts and not be included in the
6466 <file>.deb</file> archive. These scripts must not fail if
6467 either of these operations fail.
6471 For example, the <tt>emacsen-common</tt> package could
6472 contain something like
6473 <example compact="compact">
6474 if [ ! -e /usr/local/share/emacs ]; then
6475 if mkdir /usr/local/share/emacs 2>/dev/null; then
6476 if chown root:staff /usr/local/share/emacs; then
6477 chmod 2775 /usr/local/share/emacs || true
6482 in its <prgn>postinst</prgn> script, and
6483 <example compact="compact">
6484 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6485 rmdir /usr/local/share/emacs 2>/dev/null || true
6487 in the <prgn>prerm</prgn> script. (Note that this form is
6488 used to ensure that if the script is interrupted, the
6489 directory <file>/usr/local/share/emacs</file> will still be
6494 If you do create a directory in <file>/usr/local</file> for
6495 local additions to a package, you should ensure that
6496 settings in <file>/usr/local</file> take precedence over the
6497 equivalents in <file>/usr</file>.
6501 However, because <file>/usr/local</file> and its contents are
6502 for exclusive use of the local administrator, a package
6503 must not rely on the presence or absence of files or
6504 directories in <file>/usr/local</file> for normal operation.
6508 The <file>/usr/local</file> directory itself and all the
6509 subdirectories created by the package should (by default) have
6510 permissions 2775 (group-writable and set-group-id) and be
6511 owned by <tt>root:staff</tt>.
6516 <heading>The system-wide mail directory</heading>
6518 The system-wide mail directory
6519 is <file>/var/mail</file>. This directory is part of the
6520 base system and should not be owned by any particular mail
6521 agents. The use of the old
6522 location <file>/var/spool/mail</file> is deprecated, even
6523 though the spool may still be physically located there.
6527 <sect1 id="fhs-run">
6528 <heading><file>/run</file> and <file>/run/lock</file></heading>
6531 The directory <file>/run</file> is cleared at boot, normally
6532 by being a mount point for a temporary file system. Packages
6533 therefore must not assume that any files or directories
6534 under <file>/run</file> other than <file>/run/lock</file>
6535 exist unless the package has arranged to create those files or
6536 directories since the last reboot. Normally, this is done by
6537 the package via an init script. See <ref id="writing-init">
6538 for more information.
6542 Packages must not include files or directories
6543 under <file>/run</file>, or under the
6544 older <file>/var/run</file> and <file>/var/lock</file> paths.
6545 The latter paths will normally be symlinks or other
6546 redirections to <file>/run</file> for backwards compatibility.
6552 <heading>Users and groups</heading>
6555 <heading>Introduction</heading>
6557 The Debian system can be configured to use either plain or
6562 Some user ids (UIDs) and group ids (GIDs) are reserved
6563 globally for use by certain packages. Because some
6564 packages need to include files which are owned by these
6565 users or groups, or need the ids compiled into binaries,
6566 these ids must be used on any Debian system only for the
6567 purpose for which they are allocated. This is a serious
6568 restriction, and we should avoid getting in the way of
6569 local administration policies. In particular, many sites
6570 allocate users and/or local system groups starting at 100.
6574 Apart from this we should have dynamically allocated ids,
6575 which should by default be arranged in some sensible
6576 order, but the behavior should be configurable.
6580 Packages other than <tt>base-passwd</tt> must not modify
6581 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6582 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6587 <heading>UID and GID classes</heading>
6589 The UID and GID numbers are divided into classes as
6595 Globally allocated by the Debian project, the same
6596 on every Debian system. These ids will appear in
6597 the <file>passwd</file> and <file>group</file> files of all
6598 Debian systems, new ids in this range being added
6599 automatically as the <tt>base-passwd</tt> package is
6604 Packages which need a single statically allocated
6605 uid or gid should use one of these; their
6606 maintainers should ask the <tt>base-passwd</tt>
6614 Dynamically allocated system users and groups.
6615 Packages which need a user or group, but can have
6616 this user or group allocated dynamically and
6617 differently on each system, should use <tt>adduser
6618 --system</tt> to create the group and/or user.
6619 <prgn>adduser</prgn> will check for the existence of
6620 the user or group, and if necessary choose an unused
6621 id based on the ranges specified in
6622 <file>adduser.conf</file>.
6626 <tag>1000-59999:</tag>
6629 Dynamically allocated user accounts. By default
6630 <prgn>adduser</prgn> will choose UIDs and GIDs for
6631 user accounts in this range, though
6632 <file>adduser.conf</file> may be used to modify this
6637 <tag>60000-64999:</tag>
6640 Globally allocated by the Debian project, but only
6641 created on demand. The ids are allocated centrally
6642 and statically, but the actual accounts are only
6643 created on users' systems on demand.
6647 These ids are for packages which are obscure or
6648 which require many statically-allocated ids. These
6649 packages should check for and create the accounts in
6650 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6651 <prgn>adduser</prgn> if it has this facility) if
6652 necessary. Packages which are likely to require
6653 further allocations should have a "hole" left after
6654 them in the allocation, to give them room to
6659 <tag>65000-65533:</tag>
6667 User <tt>nobody</tt>. The corresponding gid refers
6668 to the group <tt>nogroup</tt>.
6675 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6676 not</em> be used, because it is the error return
6685 <sect id="sysvinit">
6686 <heading>System run levels and <file>init.d</file> scripts</heading>
6688 <sect1 id="/etc/init.d">
6689 <heading>Introduction</heading>
6692 The <file>/etc/init.d</file> directory contains the scripts
6693 executed by <prgn>init</prgn> at boot time and when the
6694 init state (or "runlevel") is changed (see <manref
6695 name="init" section="8">).
6699 There are at least two different, yet functionally
6700 equivalent, ways of handling these scripts. For the sake
6701 of simplicity, this document describes only the symbolic
6702 link method. However, it must not be assumed by maintainer
6703 scripts that this method is being used, and any automated
6704 manipulation of the various runlevel behaviors by
6705 maintainer scripts must be performed using
6706 <prgn>update-rc.d</prgn> as described below and not by
6707 manually installing or removing symlinks. For information
6708 on the implementation details of the other method,
6709 implemented in the <tt>file-rc</tt> package, please refer
6710 to the documentation of that package.
6714 These scripts are referenced by symbolic links in the
6715 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6716 runlevels, <prgn>init</prgn> looks in the directory
6717 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6718 execute, where <tt><var>n</var></tt> is the runlevel that
6719 is being changed to, or <tt>S</tt> for the boot-up
6724 The names of the links all have the form
6725 <file>S<var>mm</var><var>script</var></file> or
6726 <file>K<var>mm</var><var>script</var></file> where
6727 <var>mm</var> is a two-digit number and <var>script</var>
6728 is the name of the script (this should be the same as the
6729 name of the actual script in <file>/etc/init.d</file>).
6733 When <prgn>init</prgn> changes runlevel first the targets
6734 of the links whose names start with a <tt>K</tt> are
6735 executed, each with the single argument <tt>stop</tt>,
6736 followed by the scripts prefixed with an <tt>S</tt>, each
6737 with the single argument <tt>start</tt>. (The links are
6738 those in the <file>/etc/rc<var>n</var>.d</file> directory
6739 corresponding to the new runlevel.) The <tt>K</tt> links
6740 are responsible for killing services and the <tt>S</tt>
6741 link for starting services upon entering the runlevel.
6745 For example, if we are changing from runlevel 2 to
6746 runlevel 3, init will first execute all of the <tt>K</tt>
6747 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6748 all of the <tt>S</tt> prefixed scripts in that directory.
6749 The links starting with <tt>K</tt> will cause the
6750 referred-to file to be executed with an argument of
6751 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6756 The two-digit number <var>mm</var> is used to determine
6757 the order in which to run the scripts: low-numbered links
6758 have their scripts run first. For example, the
6759 <tt>K20</tt> scripts will be executed before the
6760 <tt>K30</tt> scripts. This is used when a certain service
6761 must be started before another. For example, the name
6762 server <prgn>bind</prgn> might need to be started before
6763 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6764 can set up its access lists. In this case, the script
6765 that starts <prgn>bind</prgn> would have a lower number
6766 than the script that starts <prgn>inn</prgn> so that it
6768 <example compact="compact">
6775 The two runlevels 0 (halt) and 6 (reboot) are slightly
6776 different. In these runlevels, the links with an
6777 <tt>S</tt> prefix are still called after those with a
6778 <tt>K</tt> prefix, but they too are called with the single
6779 argument <tt>stop</tt>.
6783 <sect1 id="writing-init">
6784 <heading>Writing the scripts</heading>
6787 Packages that include daemons for system services should
6788 place scripts in <file>/etc/init.d</file> to start or stop
6789 services at boot time or during a change of runlevel.
6790 These scripts should be named
6791 <file>/etc/init.d/<var>package</var></file>, and they should
6792 accept one argument, saying what to do:
6795 <tag><tt>start</tt></tag>
6796 <item>start the service,</item>
6798 <tag><tt>stop</tt></tag>
6799 <item>stop the service,</item>
6801 <tag><tt>restart</tt></tag>
6802 <item>stop and restart the service if it's already running,
6803 otherwise start the service</item>
6805 <tag><tt>reload</tt></tag>
6806 <item><p>cause the configuration of the service to be
6807 reloaded without actually stopping and restarting
6810 <tag><tt>force-reload</tt></tag>
6811 <item>cause the configuration to be reloaded if the
6812 service supports this, otherwise restart the
6816 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6817 <tt>force-reload</tt> options should be supported by all
6818 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6823 The <file>init.d</file> scripts must ensure that they will
6824 behave sensibly (i.e., returning success and not starting
6825 multiple copies of a service) if invoked with <tt>start</tt>
6826 when the service is already running, or with <tt>stop</tt>
6827 when it isn't, and that they don't kill unfortunately-named
6828 user processes. The best way to achieve this is usually to
6829 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6834 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6835 scripts. Writing correct <file>init.d</file> scripts requires
6836 accepting various error exit statuses when daemons are already
6837 running or already stopped without aborting
6838 the <file>init.d</file> script, and common <file>init.d</file>
6839 function libraries are not safe to call with <tt>set -e</tt>
6841 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6842 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6843 in effect and echoing status messages to the console fails,
6845 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6846 to not use <tt>set -e</tt> and instead check the result of
6847 each command separately.
6851 If a service reloads its configuration automatically (as
6852 in the case of <prgn>cron</prgn>, for example), the
6853 <tt>reload</tt> option of the <file>init.d</file> script
6854 should behave as if the configuration has been reloaded
6859 The <file>/etc/init.d</file> scripts must be treated as
6860 configuration files, either (if they are present in the
6861 package, that is, in the .deb file) by marking them as
6862 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6863 by managing them correctly in the maintainer scripts (see
6864 <ref id="config-files">). This is important since we want
6865 to give the local system administrator the chance to adapt
6866 the scripts to the local system, e.g., to disable a
6867 service without de-installing the package, or to specify
6868 some special command line options when starting a service,
6869 while making sure their changes aren't lost during the next
6874 These scripts should not fail obscurely when the
6875 configuration files remain but the package has been
6876 removed, as configuration files remain on the system after
6877 the package has been removed. Only when <prgn>dpkg</prgn>
6878 is executed with the <tt>--purge</tt> option will
6879 configuration files be removed. In particular, as the
6880 <file>/etc/init.d/<var>package</var></file> script itself is
6881 usually a <tt>conffile</tt>, it will remain on the system
6882 if the package is removed but not purged. Therefore, you
6883 should include a <tt>test</tt> statement at the top of the
6885 <example compact="compact">
6886 test -f <var>program-executed-later-in-script</var> || exit 0
6891 Often there are some variables in the <file>init.d</file>
6892 scripts whose values control the behavior of the scripts,
6893 and which a system administrator is likely to want to
6894 change. As the scripts themselves are frequently
6895 <tt>conffile</tt>s, modifying them requires that the
6896 administrator merge in their changes each time the package
6897 is upgraded and the <tt>conffile</tt> changes. To ease
6898 the burden on the system administrator, such configurable
6899 values should not be placed directly in the script.
6900 Instead, they should be placed in a file in
6901 <file>/etc/default</file>, which typically will have the same
6902 base name as the <file>init.d</file> script. This extra file
6903 should be sourced by the script when the script runs. It
6904 must contain only variable settings and comments in SUSv3
6905 <prgn>sh</prgn> format. It may either be a
6906 <tt>conffile</tt> or a configuration file maintained by
6907 the package maintainer scripts. See <ref id="config-files">
6912 To ensure that vital configurable values are always
6913 available, the <file>init.d</file> script should set default
6914 values for each of the shell variables it uses, either
6915 before sourcing the <file>/etc/default/</file> file or
6916 afterwards using something like the <tt>:
6917 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6918 script must behave sensibly and not fail if the
6919 <file>/etc/default</file> file is deleted.
6923 Files and directories under <file>/run</file>, including ones
6924 referred to via the compatibility paths <file>/var/run</file>
6925 and <file>/var/lock</file>, are normally stored on a temporary
6926 filesystem and are normally not persistent across a reboot.
6927 The <file>init.d</file> scripts must handle this correctly.
6928 This will typically mean creating any required subdirectories
6929 dynamically when the <file>init.d</file> script is run.
6930 See <ref id="fhs-run"> for more information.
6935 <heading>Interfacing with the initscript system</heading>
6938 Maintainers should use the abstraction layer provided by
6939 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6940 programs to deal with initscripts in their packages'
6941 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6942 and <prgn>postrm</prgn>.
6946 Directly managing the /etc/rc?.d links and directly
6947 invoking the <file>/etc/init.d/</file> initscripts should
6948 be done only by packages providing the initscript
6949 subsystem (such as <prgn>sysv-rc</prgn> and
6950 <prgn>file-rc</prgn>).
6954 <heading>Managing the links</heading>
6957 The program <prgn>update-rc.d</prgn> is provided for
6958 package maintainers to arrange for the proper creation and
6959 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6960 or their functional equivalent if another method is being
6961 used. This may be used by maintainers in their packages'
6962 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6966 You must not include any <file>/etc/rc<var>n</var>.d</file>
6967 symbolic links in the actual archive or manually create or
6968 remove the symbolic links in maintainer scripts; you must
6969 use the <prgn>update-rc.d</prgn> program instead. (The
6970 former will fail if an alternative method of maintaining
6971 runlevel information is being used.) You must not include
6972 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6973 in the archive either. (Only the <tt>sysvinit</tt>
6978 By default <prgn>update-rc.d</prgn> will start services in
6979 each of the multi-user state runlevels (2, 3, 4, and 5)
6980 and stop them in the halt runlevel (0), the single-user
6981 runlevel (1) and the reboot runlevel (6). The system
6982 administrator will have the opportunity to customize
6983 runlevels by simply adding, moving, or removing the
6984 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6985 symbolic links are being used, or by modifying
6986 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6991 To get the default behavior for your package, put in your
6992 <prgn>postinst</prgn> script
6993 <example compact="compact">
6994 update-rc.d <var>package</var> defaults
6996 and in your <prgn>postrm</prgn>
6997 <example compact="compact">
6998 if [ "$1" = purge ]; then
6999 update-rc.d <var>package</var> remove
7001 </example>. Note that if your package changes runlevels
7002 or priority, you may have to remove and recreate the links,
7003 since otherwise the old links may persist. Refer to the
7004 documentation of <prgn>update-rc.d</prgn>.
7008 This will use a default sequence number of 20. If it does
7009 not matter when or in which order the <file>init.d</file>
7010 script is run, use this default. If it does, then you
7011 should talk to the maintainer of the <prgn>sysvinit</prgn>
7012 package or post to <tt>debian-devel</tt>, and they will
7013 help you choose a number.
7017 For more information about using <tt>update-rc.d</tt>,
7018 please consult its man page <manref name="update-rc.d"
7024 <heading>Running initscripts</heading>
7026 The program <prgn>invoke-rc.d</prgn> is provided to make
7027 it easier for package maintainers to properly invoke an
7028 initscript, obeying runlevel and other locally-defined
7029 constraints that might limit a package's right to start,
7030 stop and otherwise manage services. This program may be
7031 used by maintainers in their packages' scripts.
7035 The package maintainer scripts must use
7036 <prgn>invoke-rc.d</prgn> to invoke the
7037 <file>/etc/init.d/*</file> initscripts, instead of
7038 calling them directly.
7042 By default, <prgn>invoke-rc.d</prgn> will pass any
7043 action requests (start, stop, reload, restart...) to the
7044 <file>/etc/init.d</file> script, filtering out requests
7045 to start or restart a service out of its intended
7050 Most packages will simply need to change:
7051 <example compact="compact">/etc/init.d/<package>
7052 <action></example> in their <prgn>postinst</prgn>
7053 and <prgn>prerm</prgn> scripts to:
7054 <example compact="compact">
7055 if which invoke-rc.d >/dev/null 2>&1; then
7056 invoke-rc.d <var>package</var> <action>
7058 /etc/init.d/<var>package</var> <action>
7064 A package should register its initscript services using
7065 <prgn>update-rc.d</prgn> before it tries to invoke them
7066 using <prgn>invoke-rc.d</prgn>. Invocation of
7067 unregistered services may fail.
7071 For more information about using
7072 <prgn>invoke-rc.d</prgn>, please consult its man page
7073 <manref name="invoke-rc.d" section="8">.
7079 <heading>Boot-time initialization</heading>
7082 There used to be another directory, <file>/etc/rc.boot</file>,
7083 which contained scripts which were run once per machine
7084 boot. This has been deprecated in favour of links from
7085 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7086 described in <ref id="/etc/init.d">. Packages must not
7087 place files in <file>/etc/rc.boot</file>.
7092 <heading>Example</heading>
7095 An example on which you can base your
7096 <file>/etc/init.d</file> scripts is found in
7097 <file>/etc/init.d/skeleton</file>.
7104 <heading>Console messages from <file>init.d</file> scripts</heading>
7107 This section describes the formats to be used for messages
7108 written to standard output by the <file>/etc/init.d</file>
7109 scripts. The intent is to improve the consistency of
7110 Debian's startup and shutdown look and feel. For this
7111 reason, please look very carefully at the details. We want
7112 the messages to have the same format in terms of wording,
7113 spaces, punctuation and case of letters.
7117 Here is a list of overall rules that should be used for
7118 messages generated by <file>/etc/init.d</file> scripts.
7124 The message should fit in one line (fewer than 80
7125 characters), start with a capital letter and end with
7126 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7130 If the script is performing some time consuming task in
7131 the background (not merely starting or stopping a
7132 program, for instance), an ellipsis (three dots:
7133 <tt>...</tt>) should be output to the screen, with no
7134 leading or tailing whitespace or line feeds.
7138 The messages should appear as if the computer is telling
7139 the user what it is doing (politely :-), but should not
7140 mention "it" directly. For example, instead of:
7141 <example compact="compact">
7142 I'm starting network daemons: nfsd mountd.
7144 the message should say
7145 <example compact="compact">
7146 Starting network daemons: nfsd mountd.
7153 <tt>init.d</tt> script should use the following standard
7154 message formats for the situations enumerated below.
7160 <p>When daemons are started</p>
7163 If the script starts one or more daemons, the output
7164 should look like this (a single line, no leading
7166 <example compact="compact">
7167 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7169 The <var>description</var> should describe the
7170 subsystem the daemon or set of daemons are part of,
7171 while <var>daemon-1</var> up to <var>daemon-n</var>
7172 denote each daemon's name (typically the file name of
7177 For example, the output of <file>/etc/init.d/lpd</file>
7179 <example compact="compact">
7180 Starting printer spooler: lpd.
7185 This can be achieved by saying
7186 <example compact="compact">
7187 echo -n "Starting printer spooler: lpd"
7188 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7191 in the script. If there are more than one daemon to
7192 start, the output should look like this:
7193 <example compact="compact">
7194 echo -n "Starting remote file system services:"
7195 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7196 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7197 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7200 This makes it possible for the user to see what is
7201 happening and when the final daemon has been started.
7202 Care should be taken in the placement of white spaces:
7203 in the example above the system administrators can
7204 easily comment out a line if they don't want to start
7205 a specific daemon, while the displayed message still
7211 <p>When a system parameter is being set</p>
7214 If you have to set up different system parameters
7215 during the system boot, you should use this format:
7216 <example compact="compact">
7217 Setting <var>parameter</var> to "<var>value</var>".
7222 You can use a statement such as the following to get
7224 <example compact="compact">
7225 echo "Setting DNS domainname to \"$domainname\"."
7230 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7231 for the left and right quotation marks. A grave accent
7232 (<tt>`</tt>) is not a quote character; neither is an
7233 apostrophe (<tt>'</tt>).
7238 <p>When a daemon is stopped or restarted</p>
7241 When you stop or restart a daemon, you should issue a
7242 message identical to the startup message, except that
7243 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7244 or <tt>Restarting</tt> respectively.
7248 For example, stopping the printer daemon will look like
7250 <example compact="compact">
7251 Stopping printer spooler: lpd.
7257 <p>When something is executed</p>
7260 There are several examples where you have to run a
7261 program at system startup or shutdown to perform a
7262 specific task, for example, setting the system's clock
7263 using <prgn>netdate</prgn> or killing all processes
7264 when the system shuts down. Your message should look
7266 <example compact="compact">
7267 Doing something very useful...done.
7269 You should print the <tt>done.</tt> immediately after
7270 the job has been completed, so that the user is
7271 informed why they have to wait. You can get this
7273 <example compact="compact">
7274 echo -n "Doing something very useful..."
7283 <p>When the configuration is reloaded</p>
7286 When a daemon is forced to reload its configuration
7287 files you should use the following format:
7288 <example compact="compact">
7289 Reloading <var>description</var> configuration...done.
7291 where <var>description</var> is the same as in the
7292 daemon starting message.
7299 <sect id="cron-jobs">
7300 <heading>Cron jobs</heading>
7303 Packages must not modify the configuration file
7304 <file>/etc/crontab</file>, and they must not modify the files in
7305 <file>/var/spool/cron/crontabs</file>.
7309 If a package wants to install a job that has to be executed via
7310 cron, it should place a file named as specified
7311 in <ref id="cron-files"> into one or more of the following
7313 <example compact="compact">
7319 As these directory names imply, the files within them are
7320 executed on an hourly, daily, weekly, or monthly basis,
7321 respectively. The exact times are listed in
7322 <file>/etc/crontab</file>.
7326 All files installed in any of these directories must be
7327 scripts (e.g., shell scripts or Perl scripts) so that they
7328 can easily be modified by the local system administrator.
7329 In addition, they must be treated as configuration files.
7333 If a certain job has to be executed at some other frequency or
7334 at a specific time, the package should install a file in
7335 <file>/etc/cron.d</file> with a name as specified
7336 in <ref id="cron-files">. This file uses the same syntax
7337 as <file>/etc/crontab</file> and is processed
7338 by <prgn>cron</prgn> automatically. The file must also be
7339 treated as a configuration file. (Note that entries in the
7340 <file>/etc/cron.d</file> directory are not handled by
7341 <prgn>anacron</prgn>. Thus, you should only use this
7342 directory for jobs which may be skipped if the system is not
7347 Unlike <file>crontab</file> files described in the IEEE Std
7348 1003.1-2008 (POSIX.1) available from
7349 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7350 name="The Open Group">, the files in
7351 <file>/etc/cron.d</file> and the file
7352 <file>/etc/crontab</file> have seven fields; namely:
7354 <item>Minute [0,59]</item>
7355 <item>Hour [0,23]</item>
7356 <item>Day of the month [1,31]</item>
7357 <item>Month of the year [1,12]</item>
7358 <item>Day of the week ([0,6] with 0=Sunday)</item>
7359 <item>Username</item>
7360 <item>Command to be run</item>
7362 Ranges of numbers are allowed. Ranges are two numbers
7363 separated with a hyphen. The specified range is inclusive.
7364 Lists are allowed. A list is a set of numbers (or ranges)
7365 separated by commas. Step values can be used in conjunction
7370 The scripts or <tt>crontab</tt> entries in these directories should
7371 check if all necessary programs are installed before they
7372 try to execute them. Otherwise, problems will arise when a
7373 package was removed but not purged since configuration files
7374 are kept on the system in this situation.
7378 Any <tt>cron</tt> daemon must provide
7379 <file>/usr/bin/crontab</file> and support normal
7380 <tt>crontab</tt> entries as specified in POSIX. The daemon
7381 must also support names for days and months, ranges, and
7382 step values. It has to support <file>/etc/crontab</file>,
7383 and correctly execute the scripts in
7384 <file>/etc/cron.d</file>. The daemon must also correctly
7386 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7389 <sect1 id="cron-files">
7390 <heading>Cron job file names</heading>
7393 The file name of a cron job file should normally match the
7394 name of the package from which it comes.
7398 If a package supplies multiple cron job files files in the
7399 same directory, the file names should all start with the name
7400 of the package (possibly modified as described below) followed
7401 by a hyphen (<tt>-</tt>) and a suitable suffix.
7405 A cron job file name must not include any period or plus
7406 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7407 cause cron to ignore the file. Underscores (<tt>_</tt>)
7408 should be used instead of <tt>.</tt> and <tt>+</tt>
7415 <heading>Menus</heading>
7418 The Debian <tt>menu</tt> package provides a standard
7419 interface between packages providing applications and
7420 <em>menu programs</em> (either X window managers or
7421 text-based menu programs such as <prgn>pdmenu</prgn>).
7425 All packages that provide applications that need not be
7426 passed any special command line arguments for normal
7427 operation should register a menu entry for those
7428 applications, so that users of the <tt>menu</tt> package
7429 will automatically get menu entries in their window
7430 managers, as well in shells like <tt>pdmenu</tt>.
7434 Menu entries should follow the current menu policy.
7438 The menu policy can be found in the <tt>menu-policy</tt>
7439 files in the <tt>debian-policy</tt> package.
7440 It is also available from the Debian web mirrors at
7441 <tt><url name="/doc/packaging-manuals/menu-policy/"
7442 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7446 Please also refer to the <em>Debian Menu System</em>
7447 documentation that comes with the <package>menu</package>
7448 package for information about how to register your
7454 <heading>Multimedia handlers</heading>
7457 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7458 is a mechanism for encoding files and data streams and
7459 providing meta-information about them, in particular their
7460 type (e.g. audio or video) and format (e.g. PNG, HTML,
7465 Registration of MIME type handlers allows programs like mail
7466 user agents and web browsers to invoke these handlers to
7467 view, edit or display MIME types they don't support directly.
7471 Packages which provide the ability to view/show/play,
7472 compose, edit or print MIME types should register themselves
7473 as such following the current MIME support policy.
7477 The <package>mime-support</package> package provides the
7478 <prgn>update-mime</prgn> program which allows packages to
7479 register programs that can show, compose, edit or print
7484 Packages containing such programs must register them
7485 with <prgn>update-mime</prgn> as documented in <manref
7486 name="update-mime" section="8">. They should <em>not</em> depend
7487 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7488 they should just put something like the following in the
7489 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7492 if [ -x /usr/sbin/update-mime ]; then
7501 <heading>Keyboard configuration</heading>
7504 To achieve a consistent keyboard configuration so that all
7505 applications interpret a keyboard event the same way, all
7506 programs in the Debian distribution must be configured to
7507 comply with the following guidelines.
7511 The following keys must have the specified interpretations:
7514 <tag><tt><--</tt></tag>
7515 <item>delete the character to the left of the cursor</item>
7517 <tag><tt>Delete</tt></tag>
7518 <item>delete the character to the right of the cursor</item>
7520 <tag><tt>Control+H</tt></tag>
7521 <item>emacs: the help prefix</item>
7524 The interpretation of any keyboard events should be
7525 independent of the terminal that is used, be it a virtual
7526 console, an X terminal emulator, an rlogin/telnet session,
7531 The following list explains how the different programs
7532 should be set up to achieve this:
7538 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7542 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7546 X translations are set up to make
7547 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7548 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7549 is the vt220 escape code for the "delete character"
7550 key). This must be done by loading the X resources
7551 using <prgn>xrdb</prgn> on all local X displays, not
7552 using the application defaults, so that the
7553 translation resources used correspond to the
7554 <prgn>xmodmap</prgn> settings.
7558 The Linux console is configured to make
7559 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7560 generate <tt>ESC [ 3 ~</tt>.
7564 X applications are configured so that <tt><</tt>
7565 deletes left, and <tt>Delete</tt> deletes right. Motif
7566 applications already work like this.
7570 Terminals should have <tt>stty erase ^?</tt> .
7574 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7575 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7576 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7580 Emacs is programmed to map <tt>KB_Backspace</tt> or
7581 the <tt>stty erase</tt> character to
7582 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7583 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7584 <tt>^H</tt> to <tt>help</tt> as always.
7588 Other applications use the <tt>stty erase</tt>
7589 character and <tt>kdch1</tt> for the two delete keys,
7590 with ASCII DEL being "delete previous character" and
7591 <tt>kdch1</tt> being "delete character under
7599 This will solve the problem except for the following
7606 Some terminals have a <tt><--</tt> key that cannot
7607 be made to produce anything except <tt>^H</tt>. On
7608 these terminals Emacs help will be unavailable on
7609 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7610 character takes precedence in Emacs, and has been set
7611 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7612 available) can be used instead.
7616 Some operating systems use <tt>^H</tt> for <tt>stty
7617 erase</tt>. However, modern telnet versions and all
7618 rlogin versions propagate <tt>stty</tt> settings, and
7619 almost all UNIX versions honour <tt>stty erase</tt>.
7620 Where the <tt>stty</tt> settings are not propagated
7621 correctly, things can be made to work by using
7622 <tt>stty</tt> manually.
7626 Some systems (including previous Debian versions) use
7627 <prgn>xmodmap</prgn> to arrange for both
7628 <tt><--</tt> and <tt>Delete</tt> to generate
7629 <tt>KB_Delete</tt>. We can change the behavior of
7630 their X clients using the same X resources that we use
7631 to do it for our own clients, or configure our clients
7632 using their resources when things are the other way
7633 around. On displays configured like this
7634 <tt>Delete</tt> will not work, but <tt><--</tt>
7639 Some operating systems have different <tt>kdch1</tt>
7640 settings in their <tt>terminfo</tt> database for
7641 <tt>xterm</tt> and others. On these systems the
7642 <tt>Delete</tt> key will not work correctly when you
7643 log in from a system conforming to our policy, but
7644 <tt><--</tt> will.
7651 <heading>Environment variables</heading>
7654 A program must not depend on environment variables to get
7655 reasonable defaults. (That's because these environment
7656 variables would have to be set in a system-wide
7657 configuration file like <file>/etc/profile</file>, which is not
7658 supported by all shells.)
7662 If a program usually depends on environment variables for its
7663 configuration, the program should be changed to fall back to
7664 a reasonable default configuration if these environment
7665 variables are not present. If this cannot be done easily
7666 (e.g., if the source code of a non-free program is not
7667 available), the program must be replaced by a small
7668 "wrapper" shell script which sets the environment variables
7669 if they are not already defined, and calls the original program.
7673 Here is an example of a wrapper script for this purpose:
7675 <example compact="compact">
7677 BAR=${BAR:-/var/lib/fubar}
7679 exec /usr/lib/foo/foo "$@"
7684 Furthermore, as <file>/etc/profile</file> is a configuration
7685 file of the <prgn>base-files</prgn> package, other packages must
7686 not put any environment variables or other commands into that
7691 <sect id="doc-base">
7692 <heading>Registering Documents using doc-base</heading>
7695 The <package>doc-base</package> package implements a
7696 flexible mechanism for handling and presenting
7697 documentation. The recommended practice is for every Debian
7698 package that provides online documentation (other than just
7699 manual pages) to register these documents with
7700 <package>doc-base</package> by installing a
7701 <package>doc-base</package> control file in
7702 <file>/usr/share/doc-base/</file>.
7705 Please refer to the documentation that comes with the
7706 <package>doc-base</package> package for information and
7715 <heading>Files</heading>
7717 <sect id="binaries">
7718 <heading>Binaries</heading>
7721 Two different packages must not install programs with
7722 different functionality but with the same filenames. (The
7723 case of two programs having the same functionality but
7724 different implementations is handled via "alternatives" or
7725 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7726 <ref id="conflicts"> respectively.) If this case happens,
7727 one of the programs must be renamed. The maintainers should
7728 report this to the <tt>debian-devel</tt> mailing list and
7729 try to find a consensus about which program will have to be
7730 renamed. If a consensus cannot be reached, <em>both</em>
7731 programs must be renamed.
7735 By default, when a package is being built, any binaries
7736 created should include debugging information, as well as
7737 being compiled with optimization. You should also turn on
7738 as many reasonable compilation warnings as possible; this
7739 makes life easier for porters, who can then look at build
7740 logs for possible problems. For the C programming language,
7741 this means the following compilation parameters should be
7743 <example compact="compact">
7745 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7747 INSTALL = install -s # (or use strip on the files in debian/tmp)
7752 Note that by default all installed binaries should be stripped,
7753 either by using the <tt>-s</tt> flag to
7754 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7755 the binaries after they have been copied into
7756 <file>debian/tmp</file> but before the tree is made into a
7761 Although binaries in the build tree should be compiled with
7762 debugging information by default, it can often be difficult to
7763 debug programs if they are also subjected to compiler
7764 optimization. For this reason, it is recommended to support the
7765 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7766 (see <ref id="debianrules-options">). This variable can contain
7767 several flags to change how a package is compiled and built.
7771 It is up to the package maintainer to decide what
7772 compilation options are best for the package. Certain
7773 binaries (such as computationally-intensive programs) will
7774 function better with certain flags (<tt>-O3</tt>, for
7775 example); feel free to use them. Please use good judgment
7776 here. Don't use flags for the sake of it; only use them
7777 if there is good reason to do so. Feel free to override
7778 the upstream author's ideas about which compilation
7779 options are best: they are often inappropriate for our
7785 <sect id="libraries">
7786 <heading>Libraries</heading>
7789 If the package is <strong>architecture: any</strong>, then
7790 the shared library compilation and linking flags must have
7791 <tt>-fPIC</tt>, or the package shall not build on some of
7792 the supported architectures<footnote>
7794 If you are using GCC, <tt>-fPIC</tt> produces code with
7795 relocatable position independent code, which is required for
7796 most architectures to create a shared library, with i386 and
7797 perhaps some others where non position independent code is
7798 permitted in a shared library.
7801 Position independent code may have a performance penalty,
7802 especially on <tt>i386</tt>. However, in most cases the
7803 speed penalty must be measured against the memory wasted on
7804 the few architectures where non position independent code is
7807 </footnote>. Any exception to this rule must be discussed on
7808 the mailing list <em>debian-devel@lists.debian.org</em>, and
7809 a rough consensus obtained. The reasons for not compiling
7810 with <tt>-fPIC</tt> flag must be recorded in the file
7811 <tt>README.Debian</tt>, and care must be taken to either
7812 restrict the architecture or arrange for <tt>-fPIC</tt> to
7813 be used on architectures where it is required.<footnote>
7815 Some of the reasons why this might be required is if the
7816 library contains hand crafted assembly code that is not
7817 relocatable, the speed penalty is excessive for compute
7818 intensive libs, and similar reasons.
7823 As to the static libraries, the common case is not to have
7824 relocatable code, since there is no benefit, unless in specific
7825 cases; therefore the static version must not be compiled
7826 with the <tt>-fPIC</tt> flag. Any exception to this rule
7827 should be discussed on the mailing list
7828 <em>debian-devel@lists.debian.org</em>, and the reasons for
7829 compiling with the <tt>-fPIC</tt> flag must be recorded in
7830 the file <tt>README.Debian</tt>. <footnote>
7832 Some of the reasons for linking static libraries with
7833 the <tt>-fPIC</tt> flag are if, for example, one needs a
7834 Perl API for a library that is under rapid development,
7835 and has an unstable API, so shared libraries are
7836 pointless at this phase of the library's development. In
7837 that case, since Perl needs a library with relocatable
7838 code, it may make sense to create a static library with
7839 relocatable code. Another reason cited is if you are
7840 distilling various libraries into a common shared
7841 library, like <tt>mklibs</tt> does in the Debian
7847 In other words, if both a shared and a static library is
7848 being built, each source unit (<tt>*.c</tt>, for example,
7849 for C files) will need to be compiled twice, for the normal
7854 Libraries should be built with threading support and to be
7855 thread-safe if the library supports this.
7859 Although not enforced by the build tools, shared libraries
7860 must be linked against all libraries that they use symbols from
7861 in the same way that binaries are. This ensures the correct
7862 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7863 system and guarantees that all libraries can be safely opened
7864 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7865 option <tt>-Wl,-z,defs</tt> when building a shared library.
7866 Since this option enforces symbol resolution at build time,
7867 a missing library reference will be caught early as a fatal
7872 All installed shared libraries should be stripped with
7873 <example compact="compact">
7874 strip --strip-unneeded <var>your-lib</var>
7876 (The option <tt>--strip-unneeded</tt> makes
7877 <prgn>strip</prgn> remove only the symbols which aren't
7878 needed for relocation processing.) Shared libraries can
7879 function perfectly well when stripped, since the symbols for
7880 dynamic linking are in a separate part of the ELF object
7882 You might also want to use the options
7883 <tt>--remove-section=.comment</tt> and
7884 <tt>--remove-section=.note</tt> on both shared libraries
7885 and executables, and <tt>--strip-debug</tt> on static
7891 Note that under some circumstances it may be useful to
7892 install a shared library unstripped, for example when
7893 building a separate package to support debugging.
7897 Shared object files (often <file>.so</file> files) that are not
7898 public libraries, that is, they are not meant to be linked
7899 to by third party executables (binaries of other packages),
7900 should be installed in subdirectories of the
7901 <file>/usr/lib</file> directory. Such files are exempt from the
7902 rules that govern ordinary shared libraries, except that
7903 they must not be installed executable and should be
7905 A common example are the so-called "plug-ins",
7906 internal shared objects that are dynamically loaded by
7907 programs using <manref name="dlopen" section="3">.
7912 Packages that use <prgn>libtool</prgn> to create and install
7913 their shared libraries install a file containing additional
7914 metadata (ending in <file>.la</file>) alongside the library.
7915 For public libraries intended for use by other packages, these
7916 files normally should not be included in the Debian package,
7917 since the information they include is not necessary to link with
7918 the shared library on Debian and can add unnecessary additional
7919 dependencies to other programs or libraries.<footnote>
7920 These files store, among other things, all libraries on which
7921 that shared library depends. Unfortunately, if
7922 the <file>.la</file> file is present and contains that
7923 dependency information, using <prgn>libtool</prgn> when
7924 linking against that library will cause the resulting program
7925 or library to be linked against those dependencies as well,
7926 even if this is unnecessary. This can create unneeded
7927 dependencies on shared library packages that would otherwise
7928 be hidden behind the library ABI, and can make library
7929 transitions to new SONAMEs unnecessarily complicated and
7930 difficult to manage.
7932 If the <file>.la</file> file is required for that library (if,
7933 for instance, it's loaded via <tt>libltdl</tt> in a way that
7934 requires that meta-information), the <tt>dependency_libs</tt>
7935 setting in the <file>.la</file> file should normally be set to
7936 the empty string. If the shared library development package has
7937 historically included the <file>.la</file>, it must be retained
7938 in the development package (with <tt>dependency_libs</tt>
7939 emptied) until all libraries that depend on it have removed or
7940 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7941 files to prevent linking with those other libraries
7942 using <prgn>libtool</prgn> from failing.
7946 If the <file>.la</file> must be included, it should be included
7947 in the development (<tt>-dev</tt>) package, unless the library
7948 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7949 library. If it is intended for use with <tt>libltdl</tt>,
7950 the <file>.la</file> files must go in the run-time library
7955 These requirements for handling of <file>.la</file> files do not
7956 apply to loadable modules or libraries not installed in
7957 directories searched by default by the dynamic linker. Packages
7958 installing loadable modules will frequently need to install
7959 the <file>.la</file> files alongside the modules so that they
7960 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7961 does not need to be modified for libraries or modules that are
7962 not installed in directories searched by the dynamic linker by
7963 default and not intended for use by other packages.
7967 You must make sure that you use only released versions of
7968 shared libraries to build your packages; otherwise other
7969 users will not be able to run your binaries
7970 properly. Producing source packages that depend on
7971 unreleased compilers is also usually a bad
7978 <heading>Shared libraries</heading>
7980 This section has moved to <ref id="sharedlibs">.
7986 <heading>Scripts</heading>
7989 All command scripts, including the package maintainer
7990 scripts inside the package and used by <prgn>dpkg</prgn>,
7991 should have a <tt>#!</tt> line naming the shell to be used
7996 In the case of Perl scripts this should be
7997 <tt>#!/usr/bin/perl</tt>.
8001 When scripts are installed into a directory in the system
8002 PATH, the script name should not include an extension such
8003 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
8004 language currently used to implement it.
8007 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
8008 <file>init.d</file> scripts should almost certainly start
8009 with <tt>set -e</tt> so that errors are detected.
8010 <file>init.d</file> scripts are something of a special case, due
8011 to how frequently they need to call commands that are allowed to
8012 fail, and it may instead be easier to check the exit status of
8013 commands directly. See <ref id="writing-init"> for more
8014 information about writing <file>init.d</file> scripts.
8017 Every script should use <tt>set -e</tt> or check the exit status
8018 of <em>every</em> command.
8021 Scripts may assume that <file>/bin/sh</file> implements the
8022 SUSv3 Shell Command Language<footnote>
8023 Single UNIX Specification, version 3, which is also IEEE
8024 1003.1-2004 (POSIX), and is available on the World Wide Web
8025 from <url id="http://www.unix.org/version3/online.html"
8026 name="The Open Group"> after free
8027 registration.</footnote>
8028 plus the following additional features not mandated by
8030 These features are in widespread use in the Linux community
8031 and are implemented in all of bash, dash, and ksh, the most
8032 common shells users may wish to use as <file>/bin/sh</file>.
8035 <item><tt>echo -n</tt>, if implemented as a shell built-in,
8036 must not generate a newline.</item>
8037 <item><tt>test</tt>, if implemented as a shell built-in, must
8038 support <tt>-a</tt> and <tt>-o</tt> as binary logical
8040 <item><tt>local</tt> to create a scoped variable must be
8041 supported, including listing multiple variables in a single
8042 local command and assigning a value to a variable at the
8043 same time as localizing it. <tt>local</tt> may or
8044 may not preserve the variable value from an outer scope if
8045 no assignment is present. Uses such as:
8049 # ... use a, b, c, d ...
8052 must be supported and must set the value of <tt>c</tt> to
8055 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8056 -<var>signal</var></tt>, where <var>signal</var> is either
8057 the name of a signal or one of the numeric signals listed in
8058 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8059 supported if <prgn>kill</prgn> is implemented as a shell
8062 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8063 signals must be supported. In addition to the signal
8064 numbers listed in the extension, which are the same as for
8065 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8068 If a shell script requires non-SUSv3 features from the shell
8069 interpreter other than those listed above, the appropriate shell
8070 must be specified in the first line of the script (e.g.,
8071 <tt>#!/bin/bash</tt>) and the package must depend on the package
8072 providing the shell (unless the shell package is marked
8073 "Essential", as in the case of <prgn>bash</prgn>).
8077 You may wish to restrict your script to SUSv3 features plus the
8078 above set when possible so that it may use <file>/bin/sh</file>
8079 as its interpreter. Checking your script
8080 with <prgn>checkbashisms</prgn> from
8081 the <package>devscripts</package> package or running your script
8082 with an alternate shell such as <prgn>posh</prgn> may help
8083 uncover violations of the above requirements. If in doubt
8084 whether a script complies with these requirements,
8085 use <file>/bin/bash</file>.
8089 Perl scripts should check for errors when making any
8090 system calls, including <tt>open</tt>, <tt>print</tt>,
8091 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8095 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8096 scripting languages. See <em>Csh Programming Considered
8097 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8098 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8099 If an upstream package comes with <prgn>csh</prgn> scripts
8100 then you must make sure that they start with
8101 <tt>#!/bin/csh</tt> and make your package depend on the
8102 <prgn>c-shell</prgn> virtual package.
8106 Any scripts which create files in world-writeable
8107 directories (e.g., in <file>/tmp</file>) must use a
8108 mechanism which will fail atomically if a file with the same
8109 name already exists.
8113 The Debian base system provides the <prgn>tempfile</prgn>
8114 and <prgn>mktemp</prgn> utilities for use by scripts for
8121 <heading>Symbolic links</heading>
8124 In general, symbolic links within a top-level directory should
8125 be relative, and symbolic links pointing from one top-level
8126 directory to or into another should be absolute. (A top-level
8127 directory is a sub-directory of the root
8128 directory <file>/</file>.) For example, a symbolic link
8129 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8130 should be relative (<file>../share/bar</file>), but a symbolic
8131 link from <file>/var/run</file> to <file>/run</file> should be
8133 This is necessary to allow top-level directories to be
8134 symlinks. If linking <file>/var/run</file>
8135 to <file>/run</file> were done with the relative symbolic
8136 link <file>../run</file>, but <file>/var</file> were a
8137 symbolic link to <file>/srv/disk1</file>, the symbolic link
8138 would point to <file>/srv/run</file> rather than the intended
8144 In addition, symbolic links should be specified as short as
8145 possible, i.e., link targets like <file>foo/../bar</file> are
8150 Note that when creating a relative link using
8151 <prgn>ln</prgn> it is not necessary for the target of the
8152 link to exist relative to the working directory you're
8153 running <prgn>ln</prgn> from, nor is it necessary to change
8154 directory to the directory where the link is to be made.
8155 Simply include the string that should appear as the target
8156 of the link (this will be a pathname relative to the
8157 directory in which the link resides) as the first argument
8162 For example, in your <prgn>Makefile</prgn> or
8163 <file>debian/rules</file>, you can do things like:
8164 <example compact="compact">
8165 ln -fs gcc $(prefix)/bin/cc
8166 ln -fs gcc debian/tmp/usr/bin/cc
8167 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8168 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8173 A symbolic link pointing to a compressed file should always
8174 have the same file extension as the referenced file. (For
8175 example, if a file <file>foo.gz</file> is referenced by a
8176 symbolic link, the filename of the link has to end with
8177 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8182 <heading>Device files</heading>
8185 Packages must not include device files or named pipes in the
8190 If a package needs any special device files that are not
8191 included in the base system, it must call
8192 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8193 after notifying the user<footnote>
8194 This notification could be done via a (low-priority)
8195 debconf message, or an echo (printf) statement.
8200 Packages must not remove any device files in the
8201 <prgn>postrm</prgn> or any other script. This is left to the
8202 system administrator.
8206 Debian uses the serial devices
8207 <file>/dev/ttyS*</file>. Programs using the old
8208 <file>/dev/cu*</file> devices should be changed to use
8209 <file>/dev/ttyS*</file>.
8213 Named pipes needed by the package must be created in
8214 the <prgn>postinst</prgn> script<footnote>
8215 It's better to use <prgn>mkfifo</prgn> rather
8216 than <prgn>mknod</prgn> to create named pipes so that
8217 automated checks for packages incorrectly creating device
8218 files with <prgn>mknod</prgn> won't have false positives.
8219 </footnote> and removed in
8220 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8225 <sect id="config-files">
8226 <heading>Configuration files</heading>
8229 <heading>Definitions</heading>
8233 <tag>configuration file</tag>
8235 A file that affects the operation of a program, or
8236 provides site- or host-specific information, or
8237 otherwise customizes the behavior of a program.
8238 Typically, configuration files are intended to be
8239 modified by the system administrator (if needed or
8240 desired) to conform to local policy or to provide
8241 more useful site-specific behavior.
8244 <tag><tt>conffile</tt></tag>
8246 A file listed in a package's <tt>conffiles</tt>
8247 file, and is treated specially by <prgn>dpkg</prgn>
8248 (see <ref id="configdetails">).
8254 The distinction between these two is important; they are
8255 not interchangeable concepts. Almost all
8256 <tt>conffile</tt>s are configuration files, but many
8257 configuration files are not <tt>conffiles</tt>.
8261 As noted elsewhere, <file>/etc/init.d</file> scripts,
8262 <file>/etc/default</file> files, scripts installed in
8263 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8264 configuration installed in <file>/etc/cron.d</file> must be
8265 treated as configuration files. In general, any script that
8266 embeds configuration information is de-facto a configuration
8267 file and should be treated as such.
8272 <heading>Location</heading>
8275 Any configuration files created or used by your package
8276 must reside in <file>/etc</file>. If there are several,
8277 consider creating a subdirectory of <file>/etc</file>
8278 named after your package.
8282 If your package creates or uses configuration files
8283 outside of <file>/etc</file>, and it is not feasible to modify
8284 the package to use <file>/etc</file> directly, put the files
8285 in <file>/etc</file> and create symbolic links to those files
8286 from the location that the package requires.
8291 <heading>Behavior</heading>
8294 Configuration file handling must conform to the following
8296 <list compact="compact">
8298 local changes must be preserved during a package
8302 configuration files must be preserved when the
8303 package is removed, and only deleted when the
8307 Obsolete configuration files without local changes may be
8308 removed by the package during upgrade.
8312 The easy way to achieve this behavior is to make the
8313 configuration file a <tt>conffile</tt>. This is
8314 appropriate only if it is possible to distribute a default
8315 version that will work for most installations, although
8316 some system administrators may choose to modify it. This
8317 implies that the default version will be part of the
8318 package distribution, and must not be modified by the
8319 maintainer scripts during installation (or at any other
8324 In order to ensure that local changes are preserved
8325 correctly, no package may contain or make hard links to
8326 conffiles.<footnote>
8327 Rationale: There are two problems with hard links.
8328 The first is that some editors break the link while
8329 editing one of the files, so that the two files may
8330 unwittingly become unlinked and different. The second
8331 is that <prgn>dpkg</prgn> might break the hard link
8332 while upgrading <tt>conffile</tt>s.
8337 The other way to do it is via the maintainer scripts. In
8338 this case, the configuration file must not be listed as a
8339 <tt>conffile</tt> and must not be part of the package
8340 distribution. If the existence of a file is required for
8341 the package to be sensibly configured it is the
8342 responsibility of the package maintainer to provide
8343 maintainer scripts which correctly create, update and
8344 maintain the file and remove it on purge. (See <ref
8345 id="maintainerscripts"> for more information.) These
8346 scripts must be idempotent (i.e., must work correctly if
8347 <prgn>dpkg</prgn> needs to re-run them due to errors
8348 during installation or removal), must cope with all the
8349 variety of ways <prgn>dpkg</prgn> can call maintainer
8350 scripts, must not overwrite or otherwise mangle the user's
8351 configuration without asking, must not ask unnecessary
8352 questions (particularly during upgrades), and must
8353 otherwise be good citizens.
8357 The scripts are not required to configure every possible
8358 option for the package, but only those necessary to get
8359 the package running on a given system. Ideally the
8360 sysadmin should not have to do any configuration other
8361 than that done (semi-)automatically by the
8362 <prgn>postinst</prgn> script.
8366 A common practice is to create a script called
8367 <file><var>package</var>-configure</file> and have the
8368 package's <prgn>postinst</prgn> call it if and only if the
8369 configuration file does not already exist. In certain
8370 cases it is useful for there to be an example or template
8371 file which the maintainer scripts use. Such files should
8372 be in <file>/usr/share/<var>package</var></file> or
8373 <file>/usr/lib/<var>package</var></file> (depending on whether
8374 they are architecture-independent or not). There should
8375 be symbolic links to them from
8376 <file>/usr/share/doc/<var>package</var>/examples</file> if
8377 they are examples, and should be perfectly ordinary
8378 <prgn>dpkg</prgn>-handled files (<em>not</em>
8379 configuration files).
8383 These two styles of configuration file handling must
8384 not be mixed, for that way lies madness:
8385 <prgn>dpkg</prgn> will ask about overwriting the file
8386 every time the package is upgraded.
8391 <heading>Sharing configuration files</heading>
8394 If two or more packages use the same configuration file
8395 and it is reasonable for both to be installed at the same
8396 time, one of these packages must be defined as
8397 <em>owner</em> of the configuration file, i.e., it will be
8398 the package which handles that file as a configuration
8399 file. Other packages that use the configuration file must
8400 depend on the owning package if they require the
8401 configuration file to operate. If the other package will
8402 use the configuration file if present, but is capable of
8403 operating without it, no dependency need be declared.
8407 If it is desirable for two or more related packages to
8408 share a configuration file <em>and</em> for all of the
8409 related packages to be able to modify that configuration
8410 file, then the following should be done:
8411 <enumlist compact="compact">
8413 One of the related packages (the "owning" package)
8414 will manage the configuration file with maintainer
8415 scripts as described in the previous section.
8418 The owning package should also provide a program
8419 that the other packages may use to modify the
8423 The related packages must use the provided program
8424 to make any desired modifications to the
8425 configuration file. They should either depend on
8426 the core package to guarantee that the configuration
8427 modifier program is available or accept gracefully
8428 that they cannot modify the configuration file if it
8429 is not. (This is in addition to the fact that the
8430 configuration file may not even be present in the
8437 Sometimes it's appropriate to create a new package which
8438 provides the basic infrastructure for the other packages
8439 and which manages the shared configuration files. (The
8440 <tt>sgml-base</tt> package is a good example.)
8444 If the configuration file cannot be shared as described above,
8445 the packages must be marked as conflicting with each other.
8446 Two packages that specify the same file as
8447 a <tt>conffile</tt> must conflict. This is an instance of the
8448 general rule about not sharing files. Neither alternatives
8449 nor diversions are likely to be appropriate in this case; in
8450 particular, <prgn>dpkg</prgn> does not handle diverted
8451 <tt>conffile</tt>s well.
8455 When two packages both declare the same <tt>conffile</tt>, they
8456 may see left-over configuration files from each other even
8457 though they conflict with each other. If a user removes
8458 (without purging) one of the packages and installs the other,
8459 the new package will take over the <tt>conffile</tt> from the
8460 old package. If the file was modified by the user, it will be
8461 treated the same as any other locally
8462 modified <tt>conffile</tt> during an upgrade.
8466 The maintainer scripts must not alter a <tt>conffile</tt>
8467 of <em>any</em> package, including the one the scripts
8473 <heading>User configuration files ("dotfiles")</heading>
8476 The files in <file>/etc/skel</file> will automatically be
8477 copied into new user accounts by <prgn>adduser</prgn>.
8478 No other program should reference the files in
8479 <file>/etc/skel</file>.
8483 Therefore, if a program needs a dotfile to exist in
8484 advance in <file>$HOME</file> to work sensibly, that dotfile
8485 should be installed in <file>/etc/skel</file> and treated as a
8490 However, programs that require dotfiles in order to
8491 operate sensibly are a bad thing, unless they do create
8492 the dotfiles themselves automatically.
8496 Furthermore, programs should be configured by the Debian
8497 default installation to behave as closely to the upstream
8498 default behavior as possible.
8502 Therefore, if a program in a Debian package needs to be
8503 configured in some way in order to operate sensibly, that
8504 should be done using a site-wide configuration file placed
8505 in <file>/etc</file>. Only if the program doesn't support a
8506 site-wide default configuration and the package maintainer
8507 doesn't have time to add it may a default per-user file be
8508 placed in <file>/etc/skel</file>.
8512 <file>/etc/skel</file> should be as empty as we can make it.
8513 This is particularly true because there is no easy (or
8514 necessarily desirable) mechanism for ensuring that the
8515 appropriate dotfiles are copied into the accounts of
8516 existing users when a package is installed.
8522 <heading>Log files</heading>
8524 Log files should usually be named
8525 <file>/var/log/<var>package</var>.log</file>. If you have many
8526 log files, or need a separate directory for permission
8527 reasons (<file>/var/log</file> is writable only by
8528 <file>root</file>), you should usually create a directory named
8529 <file>/var/log/<var>package</var></file> and place your log
8534 Log files must be rotated occasionally so that they don't grow
8535 indefinitely. The best way to do this is to install a log
8536 rotation configuration file in the
8537 directory <file>/etc/logrotate.d</file>, normally
8538 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8539 the facilities provided by <prgn>logrotate</prgn>.
8542 The traditional approach to log files has been to set up
8543 <em>ad hoc</em> log rotation schemes using simple shell
8544 scripts and cron. While this approach is highly
8545 customizable, it requires quite a lot of sysadmin work.
8546 Even though the original Debian system helped a little
8547 by automatically installing a system which can be used
8548 as a template, this was deemed not enough.
8552 The use of <prgn>logrotate</prgn>, a program developed
8553 by Red Hat, is better, as it centralizes log management.
8554 It has both a configuration file
8555 (<file>/etc/logrotate.conf</file>) and a directory where
8556 packages can drop their individual log rotation
8557 configurations (<file>/etc/logrotate.d</file>).
8560 Here is a good example for a logrotate config
8561 file (for more information see <manref name="logrotate"
8563 <example compact="compact">
8564 /var/log/foo/*.log {
8570 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8574 This rotates all files under <file>/var/log/foo</file>, saves 12
8575 compressed generations, and tells the daemon to reopen its log
8576 files after the log rotation. It skips this log rotation
8577 (via <tt>missingok</tt>) if no such log file is present, which
8578 avoids errors if the package is removed but not purged.
8582 Log files should be removed when the package is
8583 purged (but not when it is only removed). This should be
8584 done by the <prgn>postrm</prgn> script when it is called
8585 with the argument <tt>purge</tt> (see <ref
8586 id="removedetails">).
8590 <sect id="permissions-owners">
8591 <heading>Permissions and owners</heading>
8594 The rules in this section are guidelines for general use.
8595 If necessary you may deviate from the details below.
8596 However, if you do so you must make sure that what is done
8597 is secure and you should try to be as consistent as possible
8598 with the rest of the system. You should probably also
8599 discuss it on <prgn>debian-devel</prgn> first.
8603 Files should be owned by <tt>root:root</tt>, and made
8604 writable only by the owner and universally readable (and
8605 executable, if appropriate), that is mode 644 or 755.
8609 Directories should be mode 755 or (for group-writability)
8610 mode 2775. The ownership of the directory should be
8611 consistent with its mode: if a directory is mode 2775, it
8612 should be owned by the group that needs write access to
8615 When a package is upgraded, and the owner or permissions
8616 of a file included in the package has changed, dpkg
8617 arranges for the ownership and permissions to be
8618 correctly set upon installation. However, this does not
8619 extend to directories; the permissions and ownership of
8620 directories already on the system does not change on
8621 install or upgrade of packages. This makes sense, since
8622 otherwise common directories like <tt>/usr</tt> would
8623 always be in flux. To correctly change permissions of a
8624 directory the package owns, explicit action is required,
8625 usually in the <tt>postinst</tt> script. Care must be
8626 taken to handle downgrades as well, in that case.
8632 Control information files should be owned by <tt>root:root</tt>
8633 and either mode 644 (for most files) or mode 755 (for
8634 executables such as <qref id="maintscripts">maintainer
8639 Setuid and setgid executables should be mode 4755 or 2755
8640 respectively, and owned by the appropriate user or group.
8641 They should not be made unreadable (modes like 4711 or
8642 2711 or even 4111); doing so achieves no extra security,
8643 because anyone can find the binary in the freely available
8644 Debian package; it is merely inconvenient. For the same
8645 reason you should not restrict read or execute permissions
8646 on non-set-id executables.
8650 Some setuid programs need to be restricted to particular
8651 sets of users, using file permissions. In this case they
8652 should be owned by the uid to which they are set-id, and by
8653 the group which should be allowed to execute them. They
8654 should have mode 4754; again there is no point in making
8655 them unreadable to those users who must not be allowed to
8660 It is possible to arrange that the system administrator can
8661 reconfigure the package to correspond to their local
8662 security policy by changing the permissions on a binary:
8663 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8664 described below.<footnote>
8665 Ordinary files installed by <prgn>dpkg</prgn> (as
8666 opposed to <tt>conffile</tt>s and other similar objects)
8667 normally have their permissions reset to the distributed
8668 permissions when the package is reinstalled. However,
8669 the use of <prgn>dpkg-statoverride</prgn> overrides this
8672 Another method you should consider is to create a group for
8673 people allowed to use the program(s) and make any setuid
8674 executables executable only by that group.
8678 If you need to create a new user or group for your package
8679 there are two possibilities. Firstly, you may need to
8680 make some files in the binary package be owned by this
8681 user or group, or you may need to compile the user or
8682 group id (rather than just the name) into the binary
8683 (though this latter should be avoided if possible, as in
8684 this case you need a statically allocated id).</p>
8687 If you need a statically allocated id, you must ask for a
8688 user or group id from the <tt>base-passwd</tt> maintainer,
8689 and must not release the package until you have been
8690 allocated one. Once you have been allocated one you must
8691 either make the package depend on a version of the
8692 <tt>base-passwd</tt> package with the id present in
8693 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8694 your package to create the user or group itself with the
8695 correct id (using <tt>adduser</tt>) in its
8696 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8697 the <prgn>postinst</prgn> is to be preferred if it is
8698 possible, otherwise a pre-dependency will be needed on the
8699 <tt>adduser</tt> package.)
8703 On the other hand, the program might be able to determine
8704 the uid or gid from the user or group name at runtime, so
8705 that a dynamically allocated id can be used. In this case
8706 you should choose an appropriate user or group name,
8707 discussing this on <prgn>debian-devel</prgn> and checking
8708 with the <package/base-passwd/ maintainer that it is unique and that
8709 they do not wish you to use a statically allocated id
8710 instead. When this has been checked you must arrange for
8711 your package to create the user or group if necessary using
8712 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8713 <prgn>postinst</prgn> script (again, the latter is to be
8714 preferred if it is possible).
8718 Note that changing the numeric value of an id associated
8719 with a name is very difficult, and involves searching the
8720 file system for all appropriate files. You need to think
8721 carefully whether a static or dynamic id is required, since
8722 changing your mind later will cause problems.
8725 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8727 This section is not intended as policy, but as a
8728 description of the use of <prgn>dpkg-statoverride</prgn>.
8732 If a system administrator wishes to have a file (or
8733 directory or other such thing) installed with owner and
8734 permissions different from those in the distributed Debian
8735 package, they can use the <prgn>dpkg-statoverride</prgn>
8736 program to instruct <prgn>dpkg</prgn> to use the different
8737 settings every time the file is installed. Thus the
8738 package maintainer should distribute the files with their
8739 normal permissions, and leave it for the system
8740 administrator to make any desired changes. For example, a
8741 daemon which is normally required to be setuid root, but
8742 in certain situations could be used without being setuid,
8743 should be installed setuid in the <tt>.deb</tt>. Then the
8744 local system administrator can change this if they wish.
8745 If there are two standard ways of doing it, the package
8746 maintainer can use <tt>debconf</tt> to find out the
8747 preference, and call <prgn>dpkg-statoverride</prgn> in the
8748 maintainer script if necessary to accommodate the system
8749 administrator's choice. Care must be taken during
8750 upgrades to not override an existing setting.
8754 Given the above, <prgn>dpkg-statoverride</prgn> is
8755 essentially a tool for system administrators and would not
8756 normally be needed in the maintainer scripts. There is
8757 one type of situation, though, where calls to
8758 <prgn>dpkg-statoverride</prgn> would be needed in the
8759 maintainer scripts, and that involves packages which use
8760 dynamically allocated user or group ids. In such a
8761 situation, something like the following idiom can be very
8762 helpful in the package's <prgn>postinst</prgn>, where
8763 <tt>sysuser</tt> is a dynamically allocated id:
8765 for i in /usr/bin/foo /usr/sbin/bar
8767 # only do something when no setting exists
8768 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8770 #include: debconf processing, question about foo and bar
8771 if [ "$RET" = "true" ] ; then
8772 dpkg-statoverride --update --add sysuser root 4755 $i
8777 The corresponding code to remove the override when the package
8780 for i in /usr/bin/foo /usr/sbin/bar
8782 if dpkg-statoverride --list $i >/dev/null 2>&1
8784 dpkg-statoverride --remove $i
8794 <chapt id="customized-programs">
8795 <heading>Customized programs</heading>
8797 <sect id="arch-spec">
8798 <heading>Architecture specification strings</heading>
8801 If a program needs to specify an <em>architecture specification
8802 string</em> in some place, it should select one of the strings
8803 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8804 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8805 part is sometimes elided, as when the OS is Linux.
8809 Note that we don't want to use
8810 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8811 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8812 since this would make our programs incompatible with other
8813 Linux distributions. We also don't use something like
8814 <tt><var>arch</var>-unknown-linux</tt>, since the
8815 <tt>unknown</tt> does not look very good.
8818 <sect1 id="arch-wildcard-spec">
8819 <heading>Architecture wildcards</heading>
8822 A package may specify an architecture wildcard. Architecture
8823 wildcards are in the format <tt>any</tt> (which matches every
8824 architecture), <tt><var>os</var></tt>-any, or
8825 any-<tt><var>cpu</var></tt>. <footnote>
8826 Internally, the package system normalizes the GNU triplets
8827 and the Debian arches into Debian arch triplets (which are
8828 kind of inverted GNU triplets), with the first component of
8829 the triplet representing the libc and ABI in use, and then
8830 does matching against those triplets. However, such
8831 triplets are an internal implementation detail that should
8832 not be used by packages directly. The libc and ABI portion
8833 is handled internally by the package system based on
8834 the <var>os</var> and <var>cpu</var>.
8841 <heading>Daemons</heading>
8844 The configuration files <file>/etc/services</file>,
8845 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8846 by the <prgn>netbase</prgn> package and must not be modified
8851 If a package requires a new entry in one of these files, the
8852 maintainer should get in contact with the
8853 <prgn>netbase</prgn> maintainer, who will add the entries
8854 and release a new version of the <prgn>netbase</prgn>
8859 The configuration file <file>/etc/inetd.conf</file> must not be
8860 modified by the package's scripts except via the
8861 <prgn>update-inetd</prgn> script or the
8862 <file>DebianNet.pm</file> Perl module. See their documentation
8863 for details on how to add entries.
8867 If a package wants to install an example entry into
8868 <file>/etc/inetd.conf</file>, the entry must be preceded with
8869 exactly one hash character (<tt>#</tt>). Such lines are
8870 treated as "commented out by user" by the
8871 <prgn>update-inetd</prgn> script and are not changed or
8872 activated during package updates.
8877 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8881 Some programs need to create pseudo-ttys. This should be done
8882 using Unix98 ptys if the C library supports it. The resulting
8883 program must not be installed setuid root, unless that
8884 is required for other functionality.
8888 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8889 <file>/var/log/lastlog</file> must be installed writable by
8890 group <tt>utmp</tt>. Programs which need to modify those
8891 files must be installed setgid <tt>utmp</tt>.
8896 <heading>Editors and pagers</heading>
8899 Some programs have the ability to launch an editor or pager
8900 program to edit or display a text document. Since there are
8901 lots of different editors and pagers available in the Debian
8902 distribution, the system administrator and each user should
8903 have the possibility to choose their preferred editor and
8908 In addition, every program should choose a good default
8909 editor/pager if none is selected by the user or system
8914 Thus, every program that launches an editor or pager must
8915 use the EDITOR or PAGER environment variable to determine
8916 the editor or pager the user wishes to use. If these
8917 variables are not set, the programs <file>/usr/bin/editor</file>
8918 and <file>/usr/bin/pager</file> should be used, respectively.
8922 These two files are managed through the <prgn>dpkg</prgn>
8923 "alternatives" mechanism. Every package providing an editor or
8924 pager must call the <prgn>update-alternatives</prgn> script to
8925 register as an alternative for <file>/usr/bin/editor</file>
8926 or <file>/usr/bin/pager</file> as appropriate. The alternative
8927 should have a slave alternative
8928 for <file>/usr/share/man/man1/editor.1.gz</file>
8929 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8930 corresponding manual page.
8934 If it is very hard to adapt a program to make use of the
8935 EDITOR or PAGER variables, that program may be configured to
8936 use <file>/usr/bin/sensible-editor</file> and
8937 <file>/usr/bin/sensible-pager</file> as the editor or pager
8938 program respectively. These are two scripts provided in the
8939 <package>sensible-utils</package> package that check the EDITOR
8940 and PAGER variables and launch the appropriate program, and fall
8941 back to <file>/usr/bin/editor</file>
8942 and <file>/usr/bin/pager</file> if the variable is not set.
8946 A program may also use the VISUAL environment variable to
8947 determine the user's choice of editor. If it exists, it
8948 should take precedence over EDITOR. This is in fact what
8949 <file>/usr/bin/sensible-editor</file> does.
8953 It is not required for a package to depend on
8954 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8955 package to provide such virtual packages.<footnote>
8956 The Debian base system already provides an editor and a
8962 <sect id="web-appl">
8963 <heading>Web servers and applications</heading>
8966 This section describes the locations and URLs that should
8967 be used by all web servers and web applications in the
8974 Cgi-bin executable files are installed in the
8976 <example compact="compact">
8977 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8979 or a subdirectory of that directory, and should be
8981 <example compact="compact">
8982 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8984 (possibly with a subdirectory name
8985 before <var>cgi-bin-name</var>).
8989 <p>Access to HTML documents</p>
8992 HTML documents for a package are stored in
8993 <file>/usr/share/doc/<var>package</var></file>
8994 and can be referred to as
8995 <example compact="compact">
8996 http://localhost/doc/<var>package</var>/<var>filename</var>
9001 The web server should restrict access to the document
9002 tree so that only clients on the same host can read
9003 the documents. If the web server does not support such
9004 access controls, then it should not provide access at
9005 all, or ask about providing access during installation.
9010 <p>Access to images</p>
9012 It is recommended that images for a package be stored
9013 in <tt>/usr/share/images/<var>package</var></tt> and
9014 may be referred to through an alias <tt>/images/</tt>
9017 http://localhost/images/<package>/<filename>
9024 <p>Web Document Root</p>
9027 Web Applications should try to avoid storing files in
9028 the Web Document Root. Instead they should use the
9029 /usr/share/doc/<var>package</var> directory for
9030 documents and register the Web Application via the
9031 <package>doc-base</package> package. If access to the
9032 web document root is unavoidable then use
9033 <example compact="compact">
9036 as the Document Root. This might be just a symbolic
9037 link to the location where the system administrator
9038 has put the real document root.
9041 <item><p>Providing httpd and/or httpd-cgi</p>
9043 All web servers should provide the virtual package
9044 <tt>httpd</tt>. If a web server has CGI support it should
9045 provide <tt>httpd-cgi</tt> additionally.
9048 All web applications which do not contain CGI scripts should
9049 depend on <tt>httpd</tt>, all those web applications which
9050 <tt>do</tt> contain CGI scripts, should depend on
9058 <sect id="mail-transport-agents">
9059 <heading>Mail transport, delivery and user agents</heading>
9062 Debian packages which process electronic mail, whether mail
9063 user agents (MUAs) or mail transport agents (MTAs), must
9064 ensure that they are compatible with the configuration
9065 decisions below. Failure to do this may result in lost
9066 mail, broken <tt>From:</tt> lines, and other serious brain
9071 The mail spool is <file>/var/mail</file> and the interface to
9072 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9073 the FHS). On older systems, the mail spool may be
9074 physically located in <file>/var/spool/mail</file>, but all
9075 access to the mail spool should be via the
9076 <file>/var/mail</file> symlink. The mail spool is part of the
9077 base system and not part of the MTA package.
9081 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9082 programs (such as IMAP daemons) must lock the mailbox in an
9083 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9084 be combined with dot locking. To avoid deadlocks, a program
9085 should use <tt>fcntl()</tt> first and dot locking after
9086 this, or alternatively implement the two locking methods in
9087 a non blocking way<footnote>
9088 If it is not possible to establish both locks, the
9089 system shouldn't wait for the second lock to be
9090 established, but remove the first lock, wait a (random)
9091 time, and start over locking again.
9092 </footnote>. Using the functions <tt>maillock</tt> and
9093 <tt>mailunlock</tt> provided by the
9094 <tt>liblockfile*</tt><footnote>
9095 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9096 to use these functions.
9097 </footnote> packages is the recommended way to realize this.
9101 Mailboxes are generally either mode 600 and owned by
9102 <var>user</var> or mode 660 and owned by
9103 <tt><var>user</var>:mail</tt><footnote>
9104 There are two traditional permission schemes for mail spools:
9105 mode 600 with all mail delivery done by processes running as
9106 the destination user, or mode 660 and owned by group mail with
9107 mail delivery done by a process running as a system user in
9108 group mail. Historically, Debian required mode 660 mail
9109 spools to enable the latter model, but that model has become
9110 increasingly uncommon and the principle of least privilege
9111 indicates that mail systems that use the first model should
9112 use permissions of 600. If delivery to programs is permitted,
9113 it's easier to keep the mail system secure if the delivery
9114 agent runs as the destination user. Debian Policy therefore
9115 permits either scheme.
9116 </footnote>. The local system administrator may choose a
9117 different permission scheme; packages should not make
9118 assumptions about the permission and ownership of mailboxes
9119 unless required (such as when creating a new mailbox). A MUA
9120 may remove a mailbox (unless it has nonstandard permissions) in
9121 which case the MTA or another MUA must recreate it if needed.
9125 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9126 be setgid mail to do the locking mentioned above (and
9127 must obviously avoid accessing other users' mailboxes
9128 using this privilege).</p>
9131 <file>/etc/aliases</file> is the source file for the system mail
9132 aliases (e.g., postmaster, usenet, etc.), it is the one
9133 which the sysadmin and <prgn>postinst</prgn> scripts may
9134 edit. After <file>/etc/aliases</file> is edited the program or
9135 human editing it must call <prgn>newaliases</prgn>. All MTA
9136 packages must come with a <prgn>newaliases</prgn> program,
9137 even if it does nothing, but older MTA packages did not do
9138 this so programs should not fail if <prgn>newaliases</prgn>
9139 cannot be found. Note that because of this, all MTA
9140 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9141 <tt>Replaces: mail-transport-agent</tt> control fields.
9145 The convention of writing <tt>forward to
9146 <var>address</var></tt> in the mailbox itself is not
9147 supported. Use a <tt>.forward</tt> file instead.</p>
9150 The <prgn>rmail</prgn> program used by UUCP
9151 for incoming mail should be <file>/usr/sbin/rmail</file>.
9152 Likewise, <prgn>rsmtp</prgn>, for receiving
9153 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9157 If your package needs to know what hostname to use on (for
9158 example) outgoing news and mail messages which are generated
9159 locally, you should use the file <file>/etc/mailname</file>. It
9160 will contain the portion after the username and <tt>@</tt>
9161 (at) sign for email addresses of users on the machine
9162 (followed by a newline).
9166 Such a package should check for the existence of this file
9167 when it is being configured. If it exists, it should be
9168 used without comment, although an MTA's configuration script
9169 may wish to prompt the user even if it finds that this file
9170 exists. If the file does not exist, the package should
9171 prompt the user for the value (preferably using
9172 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9173 as well as using it in the package's configuration. The
9174 prompt should make it clear that the name will not just be
9175 used by that package. For example, in this situation the
9176 <tt>inn</tt> package could say something like:
9177 <example compact="compact">
9178 Please enter the "mail name" of your system. This is the
9179 hostname portion of the address to be shown on outgoing
9180 news and mail messages. The default is
9181 <var>syshostname</var>, your system's host name. Mail
9182 name ["<var>syshostname</var>"]:
9184 where <var>syshostname</var> is the output of <tt>hostname
9190 <heading>News system configuration</heading>
9193 All the configuration files related to the NNTP (news)
9194 servers and clients should be located under
9195 <file>/etc/news</file>.</p>
9198 There are some configuration issues that apply to a number
9199 of news clients and server packages on the machine. These
9203 <tag><file>/etc/news/organization</file></tag>
9205 A string which should appear as the
9206 organization header for all messages posted
9207 by NNTP clients on the machine
9210 <tag><file>/etc/news/server</file></tag>
9212 Contains the FQDN of the upstream NNTP
9213 server, or localhost if the local machine is
9218 Other global files may be added as required for cross-package news
9225 <heading>Programs for the X Window System</heading>
9228 <heading>Providing X support and package priorities</heading>
9231 Programs that can be configured with support for the X
9232 Window System must be configured to do so and must declare
9233 any package dependencies necessary to satisfy their
9234 runtime requirements when using the X Window System. If
9235 such a package is of higher priority than the X packages
9236 on which it depends, it is required that either the
9237 X-specific components be split into a separate package, or
9238 that an alternative version of the package, which includes
9239 X support, be provided, or that the package's priority be
9245 <heading>Packages providing an X server</heading>
9248 Packages that provide an X server that, directly or
9249 indirectly, communicates with real input and display
9250 hardware should declare in their <tt>Provides</tt> control
9251 field that they provide the virtual
9252 package <tt>xserver</tt>.<footnote>
9253 This implements current practice, and provides an
9254 actual policy for usage of the <tt>xserver</tt>
9255 virtual package which appears in the virtual packages
9256 list. In a nutshell, X servers that interface
9257 directly with the display and input hardware or via
9258 another subsystem (e.g., GGI) should provide
9259 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9260 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9266 <heading>Packages providing a terminal emulator</heading>
9269 Packages that provide a terminal emulator for the X Window
9270 System which meet the criteria listed below should declare in
9271 their <tt>Provides</tt> control field that they provide the
9272 virtual package <tt>x-terminal-emulator</tt>. They should
9273 also register themselves as an alternative for
9274 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9275 20. That alternative should have a slave alternative
9276 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9277 pointing to the corresponding manual page.
9281 To be an <tt>x-terminal-emulator</tt>, a program must:
9282 <list compact="compact">
9284 Be able to emulate a DEC VT100 terminal, or a
9285 compatible terminal.
9289 Support the command-line option <tt>-e
9290 <var>command</var></tt>, which creates a new
9291 terminal window<footnote>
9292 "New terminal window" does not necessarily mean
9293 a new top-level X window directly parented by
9294 the window manager; it could, if the terminal
9295 emulator application were so coded, be a new
9296 "view" in a multiple-document interface (MDI).
9298 and runs the specified <var>command</var>,
9299 interpreting the entirety of the rest of the command
9300 line as a command to pass straight to exec, in the
9301 manner that <tt>xterm</tt> does.
9305 Support the command-line option <tt>-T
9306 <var>title</var></tt>, which creates a new terminal
9307 window with the window title <var>title</var>.
9314 <heading>Packages providing a window manager</heading>
9317 Packages that provide a window manager should declare in
9318 their <tt>Provides</tt> control field that they provide the
9319 virtual package <tt>x-window-manager</tt>. They should also
9320 register themselves as an alternative for
9321 <file>/usr/bin/x-window-manager</file>, with a priority
9322 calculated as follows:
9323 <list compact="compact">
9325 Start with a priority of 20.
9329 If the window manager supports the Debian menu
9330 system, add 20 points if this support is available
9331 in the package's default configuration (i.e., no
9332 configuration files belonging to the system or user
9333 have to be edited to activate the feature); if
9334 configuration files must be modified, add only 10
9340 If the window manager complies with <url
9341 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9342 name="The Window Manager Specification Project">,
9343 written by the <url id="http://www.freedesktop.org/wiki/"
9344 name="Free Desktop Group">, add 40 points.
9348 If the window manager permits the X session to be
9349 restarted using a <em>different</em> window manager
9350 (without killing the X server) in its default
9351 configuration, add 10 points; otherwise add none.
9354 That alternative should have a slave alternative
9355 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9356 pointing to the corresponding manual page.
9361 <heading>Packages providing fonts</heading>
9364 Packages that provide fonts for the X Window
9366 For the purposes of Debian Policy, a "font for the X
9367 Window System" is one which is accessed via X protocol
9368 requests. Fonts for the Linux console, for PostScript
9369 renderer, or any other purpose, do not fit this
9370 definition. Any tool which makes such fonts available
9371 to the X Window System, however, must abide by this
9374 must do a number of things to ensure that they are both
9375 available without modification of the X or font server
9376 configuration, and that they do not corrupt files used by
9377 other font packages to register information about
9381 Fonts of any type supported by the X Window System
9382 must be in a separate binary package from any
9383 executables, libraries, or documentation (except
9384 that specific to the fonts shipped, such as their
9385 license information). If one or more of the fonts
9386 so packaged are necessary for proper operation of
9387 the package with which they are associated the font
9388 package may be Recommended; if the fonts merely
9389 provide an enhancement, a Suggests relationship may
9390 be used. Packages must not Depend on font
9392 This is because the X server may retrieve fonts
9393 from the local file system or over the network
9394 from an X font server; the Debian package system
9395 is empowered to deal only with the local
9401 BDF fonts must be converted to PCF fonts with the
9402 <prgn>bdftopcf</prgn> utility (available in the
9403 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9404 placed in a directory that corresponds to their
9406 <list compact="compact">
9408 100 dpi fonts must be placed in
9409 <file>/usr/share/fonts/X11/100dpi/</file>.
9413 75 dpi fonts must be placed in
9414 <file>/usr/share/fonts/X11/75dpi/</file>.
9418 Character-cell fonts, cursor fonts, and other
9419 low-resolution fonts must be placed in
9420 <file>/usr/share/fonts/X11/misc/</file>.
9426 Type 1 fonts must be placed in
9427 <file>/usr/share/fonts/X11/Type1/</file>. If font
9428 metric files are available, they must be placed here
9433 Subdirectories of <file>/usr/share/fonts/X11/</file>
9434 other than those listed above must be neither
9435 created nor used. (The <file>PEX</file>, <file>CID</file>,
9436 <file>Speedo</file>, and <file>cyrillic</file> directories
9437 are excepted for historical reasons, but installation of
9438 files into these directories remains discouraged.)
9442 Font packages may, instead of placing files directly
9443 in the X font directories listed above, provide
9444 symbolic links in that font directory pointing to
9445 the files' actual location in the filesystem. Such
9446 a location must comply with the FHS.
9450 Font packages should not contain both 75dpi and
9451 100dpi versions of a font. If both are available,
9452 they should be provided in separate binary packages
9453 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9454 the names of the packages containing the
9455 corresponding fonts.
9459 Fonts destined for the <file>misc</file> subdirectory
9460 should not be included in the same package as 75dpi
9461 or 100dpi fonts; instead, they should be provided in
9462 a separate package with <tt>-misc</tt> appended to
9467 Font packages must not provide the files
9468 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9469 <file>fonts.scale</file> in a font directory:
9472 <file>fonts.dir</file> files must not be provided at all.
9476 <file>fonts.alias</file> and <file>fonts.scale</file>
9477 files, if needed, should be provided in the
9479 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9480 where <var>fontdir</var> is the name of the
9482 <file>/usr/share/fonts/X11/</file> where the
9483 package's corresponding fonts are stored
9484 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9485 <var>package</var> is the name of the package
9486 that provides these fonts, and
9487 <var>extension</var> is either <tt>scale</tt>
9488 or <tt>alias</tt>, whichever corresponds to
9495 Font packages must declare a dependency on
9496 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9497 or <tt>Pre-Depends</tt> control field.
9501 Font packages that provide one or more
9502 <file>fonts.scale</file> files as described above must
9503 invoke <prgn>update-fonts-scale</prgn> on each
9504 directory into which they installed fonts
9505 <em>before</em> invoking
9506 <prgn>update-fonts-dir</prgn> on that directory.
9507 This invocation must occur in both the
9508 <prgn>postinst</prgn> (for all arguments) and
9509 <prgn>postrm</prgn> (for all arguments except
9510 <tt>upgrade</tt>) scripts.
9514 Font packages that provide one or more
9515 <file>fonts.alias</file> files as described above must
9516 invoke <prgn>update-fonts-alias</prgn> on each
9517 directory into which they installed fonts. This
9518 invocation must occur in both the
9519 <prgn>postinst</prgn> (for all arguments) and
9520 <prgn>postrm</prgn> (for all arguments except
9521 <tt>upgrade</tt>) scripts.
9525 Font packages must invoke
9526 <prgn>update-fonts-dir</prgn> on each directory into
9527 which they installed fonts. This invocation must
9528 occur in both the <prgn>postinst</prgn> (for all
9529 arguments) and <prgn>postrm</prgn> (for all
9530 arguments except <tt>upgrade</tt>) scripts.
9534 Font packages must not provide alias names for the
9535 fonts they include which collide with alias names
9536 already in use by fonts already packaged.
9540 Font packages must not provide fonts with the same
9541 XLFD registry name as another font already packaged.
9547 <sect1 id="appdefaults">
9548 <heading>Application defaults files</heading>
9551 Application defaults files must be installed in the
9552 directory <file>/etc/X11/app-defaults/</file> (use of a
9553 localized subdirectory of <file>/etc/X11/</file> as described
9554 in the <em>X Toolkit Intrinsics - C Language
9555 Interface</em> manual is also permitted). They must be
9556 registered as <tt>conffile</tt>s or handled as
9557 configuration files.
9561 Customization of programs' X resources may also be
9562 supported with the provision of a file with the same name
9563 as that of the package placed in
9564 the <file>/etc/X11/Xresources/</file> directory, which
9565 must be registered as a <tt>conffile</tt> or handled as a
9566 configuration file.<footnote>
9567 Note that this mechanism is not the same as using
9568 app-defaults; app-defaults are tied to the client
9569 binary on the local file system, whereas X resources
9570 are stored in the X server and affect all connecting
9577 <heading>Installation directory issues</heading>
9580 Historically, packages using the X Window System used a
9581 separate set of installation directories from other packages.
9582 This practice has been discontinued and packages using the X
9583 Window System should now generally be installed in the same
9584 directories as any other package. Specifically, packages must
9585 not install files under the <file>/usr/X11R6/</file> directory
9586 and the <file>/usr/X11R6/</file> directory hierarchy should be
9587 regarded as obsolete.
9591 Include files previously installed under
9592 <file>/usr/X11R6/include/X11/</file> should be installed into
9593 <file>/usr/include/X11/</file>. For files previously
9594 installed into subdirectories of
9595 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9596 determine if subdirectories of <file>/usr/lib/</file> and
9597 <file>/usr/share/</file> can be used. If not, a subdirectory
9598 of <file>/usr/lib/X11/</file> should be used.
9602 Configuration files for window, display, or session managers
9603 or other applications that are tightly integrated with the X
9604 Window System may be placed in a subdirectory
9605 of <file>/etc/X11/</file> corresponding to the package name.
9606 Other X Window System applications should use
9607 the <file>/etc/</file> directory unless otherwise mandated by
9608 policy (such as for <ref id="appdefaults">).
9614 <heading>Perl programs and modules</heading>
9617 Perl programs and modules should follow the current Perl policy.
9621 The Perl policy can be found in the <tt>perl-policy</tt>
9622 files in the <tt>debian-policy</tt> package.
9623 It is also available from the Debian web mirrors at
9624 <tt><url name="/doc/packaging-manuals/perl-policy/"
9625 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9630 <heading>Emacs lisp programs</heading>
9633 Please refer to the "Debian Emacs Policy" for details of how to
9634 package emacs lisp programs.
9638 The Emacs policy is available in
9639 <file>debian-emacs-policy.gz</file> of the
9640 <package>emacsen-common</package> package.
9641 It is also available from the Debian web mirrors at
9642 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9643 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9648 <heading>Games</heading>
9651 The permissions on <file>/var/games</file> are mode 755, owner
9652 <tt>root</tt> and group <tt>root</tt>.
9656 Each game decides on its own security policy.</p>
9659 Games which require protected, privileged access to
9660 high-score files, saved games, etc., may be made
9661 set-<em>group</em>-id (mode 2755) and owned by
9662 <tt>root:games</tt>, and use files and directories with
9663 appropriate permissions (770 <tt>root:games</tt>, for
9664 example). They must not be made
9665 set-<em>user</em>-id, as this causes security problems. (If
9666 an attacker can subvert any set-user-id game they can
9667 overwrite the executable of any other, causing other players
9668 of these games to run a Trojan horse program. With a
9669 set-group-id game the attacker only gets access to less
9670 important game data, and if they can get at the other
9671 players' accounts at all it will take considerably more
9675 Some packages, for example some fortune cookie programs, are
9676 configured by the upstream authors to install with their
9677 data files or other static information made unreadable so
9678 that they can only be accessed through set-id programs
9679 provided. You should not do this in a Debian package: anyone can
9680 download the <file>.deb</file> file and read the data from it,
9681 so there is no point making the files unreadable. Not
9682 making the files unreadable also means that you don't have
9683 to make so many programs set-id, which reduces the risk of a
9687 As described in the FHS, binaries of games should be
9688 installed in the directory <file>/usr/games</file>. This also
9689 applies to games that use the X Window System. Manual pages
9690 for games (X and non-X games) should be installed in
9691 <file>/usr/share/man/man6</file>.</p>
9697 <heading>Documentation</heading>
9700 <heading>Manual pages</heading>
9703 You should install manual pages in <prgn>nroff</prgn> source
9704 form, in appropriate places under <file>/usr/share/man</file>.
9705 You should only use sections 1 to 9 (see the FHS for more
9706 details). You must not install a pre-formatted "cat page".
9710 Each program, utility, and function should have an
9711 associated manual page included in the same package. It is
9712 suggested that all configuration files also have a manual
9713 page included as well. Manual pages for protocols and other
9714 auxiliary things are optional.
9718 If no manual page is available, this is considered as a bug
9719 and should be reported to the Debian Bug Tracking System (the
9720 maintainer of the package is allowed to write this bug report
9721 themselves, if they so desire). Do not close the bug report
9722 until a proper man page is available.<footnote>
9723 It is not very hard to write a man page. See the
9724 <url id="http://www.schweikhardt.net/man_page_howto.html"
9725 name="Man-Page-HOWTO">,
9726 <manref name="man" section="7">, the examples created
9727 by <prgn>dh_make</prgn>, the helper
9728 program <prgn>help2man</prgn>, or the
9729 directory <file>/usr/share/doc/man-db/examples</file>.
9734 You may forward a complaint about a missing man page to the
9735 upstream authors, and mark the bug as forwarded in the
9736 Debian bug tracking system. Even though the GNU Project do
9737 not in general consider the lack of a man page to be a bug,
9738 we do; if they tell you that they don't consider it a bug
9739 you should leave the bug in our bug tracking system open
9744 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9748 If one man page needs to be accessible via several names it
9749 is better to use a symbolic link than the <file>.so</file>
9750 feature, but there is no need to fiddle with the relevant
9751 parts of the upstream source to change from <file>.so</file> to
9752 symlinks: don't do it unless it's easy. You should not
9753 create hard links in the manual page directories, nor put
9754 absolute filenames in <file>.so</file> directives. The filename
9755 in a <file>.so</file> in a man page should be relative to the
9756 base of the man page tree (usually
9757 <file>/usr/share/man</file>). If you do not create any links
9758 (whether symlinks, hard links, or <tt>.so</tt> directives)
9759 in the file system to the alternate names of the man page,
9760 then you should not rely on <prgn>man</prgn> finding your
9761 man page under those names based solely on the information in
9762 the man page's header.<footnote>
9763 Supporting this in <prgn>man</prgn> often requires
9764 unreasonable processing time to find a manual page or to
9765 report that none exists, and moves knowledge into man's
9766 database that would be better left in the file system.
9767 This support is therefore deprecated and will cease to
9768 be present in the future.
9773 Manual pages in locale-specific subdirectories of
9774 <file>/usr/share/man</file> should use either UTF-8 or the usual
9775 legacy encoding for that language (normally the one corresponding
9776 to the shortest relevant locale name in
9777 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9778 <file>/usr/share/man/fr</file> should use either UTF-8 or
9779 ISO-8859-1.<footnote>
9780 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9781 use. In future, all manual pages will be required to use
9787 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9788 included in the subdirectory name unless it indicates a
9789 significant difference in the language, as this excludes
9790 speakers of the language in other countries.<footnote>
9791 At the time of writing, Chinese and Portuguese are the main
9792 languages with such differences, so <file>pt_BR</file>,
9793 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9798 If a localized version of a manual page is provided, it should
9799 either be up-to-date or it should be obvious to the reader that
9800 it is outdated and the original manual page should be used
9801 instead. This can be done either by a note at the beginning of
9802 the manual page or by showing the missing or changed portions in
9803 the original language instead of the target language.
9808 <heading>Info documents</heading>
9811 Info documents should be installed in <file>/usr/share/info</file>.
9812 They should be compressed with <tt>gzip -9</tt>.
9816 The <prgn>install-info</prgn> program maintains a directory of
9817 installed info documents in <file>/usr/share/info/dir</file> for
9818 the use of info readers.<footnote>
9819 It was previously necessary for packages installing info
9820 documents to run <prgn>install-info</prgn> from maintainer
9821 scripts. This is no longer necessary. The installation
9822 system now uses dpkg triggers.
9824 This file must not be included in packages. Packages containing
9825 info documents should depend on <tt>dpkg (>= 1.15.4) |
9826 install-info</tt> to ensure that the directory file is properly
9827 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9832 Info documents should contain section and directory entry
9833 information in the document for the use
9834 of <prgn>install-info</prgn>. The section should be specified
9835 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9836 space and the section of this info page. The directory entry or
9837 entries should be included between
9838 a <tt>START-INFO-DIR-ENTRY</tt> line and
9839 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9841 INFO-DIR-SECTION Individual utilities
9842 START-INFO-DIR-ENTRY
9843 * example: (example). An example info directory entry.
9846 To determine which section to use, you should look
9847 at <file>/usr/share/info/dir</file> on your system and choose
9848 the most relevant (or create a new section if none of the
9849 current sections are relevant).<footnote>
9850 Normally, info documents are generated from Texinfo source.
9851 To include this information in the generated info document, if
9852 it is absent, add commands like:
9854 @dircategory Individual utilities
9856 * example: (example). An example info directory entry.
9859 to the Texinfo source of the document and ensure that the info
9860 documents are rebuilt from source during the package build.
9866 <heading>Additional documentation</heading>
9869 Any additional documentation that comes with the package may
9870 be installed at the discretion of the package maintainer.
9871 Plain text documentation should be installed in the directory
9872 <file>/usr/share/doc/<var>package</var></file>, where
9873 <var>package</var> is the name of the package, and
9874 compressed with <tt>gzip -9</tt> unless it is small.
9878 If a package comes with large amounts of documentation which
9879 many users of the package will not require you should create
9880 a separate binary package to contain it, so that it does not
9881 take up disk space on the machines of users who do not need
9882 or want it installed.</p>
9885 It is often a good idea to put text information files
9886 (<file>README</file>s, changelogs, and so forth) that come with
9887 the source package in <file>/usr/share/doc/<var>package</var></file>
9888 in the binary package. However, you don't need to install
9889 the instructions for building and installing the package, of
9893 Packages must not require the existence of any files in
9894 <file>/usr/share/doc/</file> in order to function
9896 The system administrator should be able to
9897 delete files in <file>/usr/share/doc/</file> without causing
9898 any programs to break.
9900 Any files that are referenced by programs but are also
9901 useful as stand alone documentation should be installed under
9902 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9903 <file>/usr/share/doc/<var>package</var></file>.
9907 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9908 link to another directory in <file>/usr/share/doc</file> only if
9909 the two packages both come from the same source and the
9910 first package Depends on the second.<footnote>
9912 Please note that this does not override the section on
9913 changelog files below, so the file
9914 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9915 must refer to the changelog for the current version of
9916 <var>package</var> in question. In practice, this means
9917 that the sources of the target and the destination of the
9918 symlink must be the same (same source package and
9925 Former Debian releases placed all additional documentation
9926 in <file>/usr/doc/<var>package</var></file>. This has been
9927 changed to <file>/usr/share/doc/<var>package</var></file>,
9928 and packages must not put documentation in the directory
9929 <file>/usr/doc/<var>package</var></file>. <footnote>
9930 At this phase of the transition, we no longer require a
9931 symbolic link in <file>/usr/doc/</file>. At a later point,
9932 policy shall change to make the symbolic links a bug.
9938 <heading>Preferred documentation formats</heading>
9941 The unification of Debian documentation is being carried out
9945 If your package comes with extensive documentation in a
9946 markup format that can be converted to various other formats
9947 you should if possible ship HTML versions in a binary
9948 package, in the directory
9949 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9950 its subdirectories.<footnote>
9951 The rationale: The important thing here is that HTML
9952 docs should be available in <em>some</em> package, not
9953 necessarily in the main binary package.
9958 Other formats such as PostScript may be provided at the
9959 package maintainer's discretion.
9963 <sect id="copyrightfile">
9964 <heading>Copyright information</heading>
9967 Every package must be accompanied by a verbatim copy of its
9968 copyright information and distribution license in the file
9969 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9970 file must neither be compressed nor be a symbolic link.
9974 In addition, the copyright file must say where the upstream
9975 sources (if any) were obtained, and should name the original
9980 Packages in the <em>contrib</em> or <em>non-free</em> archive
9981 areas should state in the copyright file that the package is not
9982 part of the Debian distribution and briefly explain why.
9986 A copy of the file which will be installed in
9987 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9988 be in <file>debian/copyright</file> in the source package.
9992 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9993 link to another directory in <file>/usr/share/doc</file> only if
9994 the two packages both come from the same source and the
9995 first package Depends on the second. These rules are important
9996 because <file>copyright</file> files must be extractable by
10001 Packages distributed under the Apache license (version 2.0), the
10002 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
10003 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
10004 1.3) should refer to the corresponding files
10005 under <file>/usr/share/common-licenses</file>,<footnote>
10008 <file>/usr/share/common-licenses/Apache-2.0</file>,
10009 <file>/usr/share/common-licenses/Artistic</file>,
10010 <file>/usr/share/common-licenses/GPL-1</file>,
10011 <file>/usr/share/common-licenses/GPL-2</file>,
10012 <file>/usr/share/common-licenses/GPL-3</file>,
10013 <file>/usr/share/common-licenses/LGPL-2</file>,
10014 <file>/usr/share/common-licenses/LGPL-2.1</file>,
10015 <file>/usr/share/common-licenses/LGPL-3</file>,
10016 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
10017 <file>/usr/share/common-licenses/GFDL-1.3</file>
10018 respectively. The University of California BSD license is
10019 also included in <package>base-files</package> as
10020 <file>/usr/share/common-licenses/BSD</file>, but given the
10021 brevity of this license, its specificity to code whose
10022 copyright is held by the Regents of the University of
10023 California, and the frequency of minor wording changes, its
10024 text should be included in the copyright file rather than
10025 referencing this file.
10027 </footnote> rather than quoting them in the copyright
10032 You should not use the copyright file as a general <file>README</file>
10033 file. If your package has such a file it should be
10034 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
10035 <file>README.Debian</file> or some other appropriate place.
10039 All copyright files must be encoded in UTF-8.
10042 <sect1 id="copyrightformat">
10043 <heading>Machine-readable copyright information</heading>
10046 A specification for a standard, machine-readable format
10047 for <file>debian/copyright</file> files is maintained as part
10048 of the <package>debian-policy</package> package. This
10049 document may be found in the <file>copyright-format</file>
10050 files in the <package>debian-policy</package> package. It is
10051 also available from the Debian web mirrors at
10052 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10053 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10057 Use of this format is optional.
10063 <heading>Examples</heading>
10066 Any examples (configurations, source files, whatever),
10067 should be installed in a directory
10068 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10069 files should not be referenced by any program: they're there
10070 for the benefit of the system administrator and users as
10071 documentation only. Architecture-specific example files
10072 should be installed in a directory
10073 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10075 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10076 latter directory itself may be a symbolic link to the
10081 If the purpose of a package is to provide examples, then the
10082 example files may be installed into
10083 <file>/usr/share/doc/<var>package</var></file>.
10087 <sect id="changelogs">
10088 <heading>Changelog files</heading>
10091 Packages that are not Debian-native must contain a
10092 compressed copy of the <file>debian/changelog</file> file from
10093 the Debian source tree in
10094 <file>/usr/share/doc/<var>package</var></file> with the name
10095 <file>changelog.Debian.gz</file>.
10099 If an upstream changelog is available, it should be accessible as
10100 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10101 plain text. If the upstream changelog is distributed in
10102 HTML, it should be made available in that form as
10103 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10104 and a plain text <file>changelog.gz</file> should be generated
10105 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10106 the upstream changelog files do not already conform to this
10107 naming convention, then this may be achieved either by
10108 renaming the files, or by adding a symbolic link, at the
10109 maintainer's discretion.<footnote>
10110 Rationale: People should not have to look in places for
10111 upstream changelogs merely because they are given
10112 different names or are distributed in HTML format.
10117 All of these files should be installed compressed using
10118 <tt>gzip -9</tt>, as they will become large with time even
10119 if they start out small.
10123 If the package has only one changelog which is used both as
10124 the Debian changelog and the upstream one because there is
10125 no separate upstream maintainer then that changelog should
10126 usually be installed as
10127 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10128 there is a separate upstream maintainer, but no upstream
10129 changelog, then the Debian changelog should still be called
10130 <file>changelog.Debian.gz</file>.
10134 For details about the format and contents of the Debian
10135 changelog file, please see <ref id="dpkgchangelog">.
10140 <appendix id="pkg-scope">
10141 <heading>Introduction and scope of these appendices</heading>
10144 These appendices are taken essentially verbatim from the
10145 now-deprecated Packaging Manual, version 3.2.1.0. They are
10146 the chapters which are likely to be of use to package
10147 maintainers and which have not already been included in the
10148 policy document itself. Most of these sections are very likely
10149 not relevant to policy; they should be treated as
10150 documentation for the packaging system. Please note that these
10151 appendices are included for convenience, and for historical
10152 reasons: they used to be part of policy package, and they have
10153 not yet been incorporated into dpkg documentation. However,
10154 they still have value, and hence they are presented here.
10158 They have not yet been checked to ensure that they are
10159 compatible with the contents of policy, and if there are any
10160 contradictions, the version in the main policy document takes
10161 precedence. The remaining chapters of the old Packaging
10162 Manual have also not been read in detail to ensure that there
10163 are not parts which have been left out. Both of these will be
10164 done in due course.
10168 Certain parts of the Packaging manual were integrated into the
10169 Policy Manual proper, and removed from the appendices. Links
10170 have been placed from the old locations to the new ones.
10174 <prgn>dpkg</prgn> is a suite of programs for creating binary
10175 package files and installing and removing them on Unix
10177 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10178 work on or be ported to other systems.
10183 The binary packages are designed for the management of
10184 installed executable programs (usually compiled binaries) and
10185 their associated data, though source code examples and
10186 documentation are provided as part of some packages.</p>
10189 This manual describes the technical aspects of creating Debian
10190 binary packages (<file>.deb</file> files). It documents the
10191 behavior of the package management programs
10192 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10193 they interact with packages.</p>
10196 It also documents the interaction between
10197 <prgn>dselect</prgn>'s core and the access method scripts it
10198 uses to actually install the selected packages, and describes
10199 how to create a new access method.</p>
10202 This manual does not go into detail about the options and
10203 usage of the package building and installation tools. It
10204 should therefore be read in conjunction with those programs'
10209 The utility programs which are provided with <prgn>dpkg</prgn>
10210 for managing various system configuration and similar issues,
10211 such as <prgn>update-rc.d</prgn> and
10212 <prgn>install-info</prgn>, are not described in detail here -
10213 please see their man pages.
10217 It is assumed that the reader is reasonably familiar with the
10218 <prgn>dpkg</prgn> System Administrators' manual.
10219 Unfortunately this manual does not yet exist.
10223 The Debian version of the FSF's GNU hello program is provided as
10224 an example for people wishing to create Debian packages. However,
10225 while the examples are helpful, they do not replace the need to
10226 read and follow the Policy and Programmer's Manual.</p>
10229 <appendix id="pkg-binarypkg">
10230 <heading>Binary packages (from old Packaging Manual)</heading>
10233 The binary package has two main sections. The first part
10234 consists of various control information files and scripts used
10235 by <prgn>dpkg</prgn> when installing and removing. See <ref
10236 id="pkg-controlarea">.
10240 The second part is an archive containing the files and
10241 directories to be installed.
10245 In the future binary packages may also contain other
10246 components, such as checksums and digital signatures. The
10247 format for the archive is described in full in the
10248 <file>deb(5)</file> man page.
10252 <sect id="pkg-bincreating"><heading>Creating package files -
10253 <prgn>dpkg-deb</prgn>
10257 All manipulation of binary package files is done by
10258 <prgn>dpkg-deb</prgn>; it's the only program that has
10259 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10260 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10261 will spot that the options requested are appropriate to
10262 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10267 In order to create a binary package you must make a
10268 directory tree which contains all the files and directories
10269 you want to have in the file system data part of the package.
10270 In Debian-format source packages this directory is usually
10271 <file>debian/tmp</file>, relative to the top of the package's
10276 They should have the locations (relative to the root of the
10277 directory tree you're constructing) ownerships and
10278 permissions which you want them to have on the system when
10279 they are installed.
10283 With current versions of <prgn>dpkg</prgn> the uid/username
10284 and gid/groupname mappings for the users and groups being
10285 used should be the same on the system where the package is
10286 built and the one where it is installed.
10290 You need to add one special directory to the root of the
10291 miniature file system tree you're creating:
10292 <prgn>DEBIAN</prgn>. It should contain the control
10293 information files, notably the binary package control file
10294 (see <ref id="pkg-controlfile">).
10298 The <prgn>DEBIAN</prgn> directory will not appear in the
10299 file system archive of the package, and so won't be installed
10300 by <prgn>dpkg</prgn> when the package is unpacked.
10304 When you've prepared the package, you should invoke:
10306 dpkg --build <var>directory</var>
10311 This will build the package in
10312 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10313 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10314 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10315 build the package.)
10319 See the man page <manref name="dpkg-deb" section="8"> for details of how
10320 to examine the contents of this newly-created file. You may find the
10321 output of following commands enlightening:
10323 dpkg-deb --info <var>filename</var>.deb
10324 dpkg-deb --contents <var>filename</var>.deb
10325 dpkg --contents <var>filename</var>.deb
10327 To view the copyright file for a package you could use this command:
10329 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10334 <sect id="pkg-controlarea">
10335 <heading>Package control information files</heading>
10338 The control information portion of a binary package is a
10339 collection of files with names known to <prgn>dpkg</prgn>.
10340 It will treat the contents of these files specially - some
10341 of them contain information used by <prgn>dpkg</prgn> when
10342 installing or removing the package; others are scripts which
10343 the package maintainer wants <prgn>dpkg</prgn> to run.
10347 It is possible to put other files in the package control
10348 information file area, but this is not generally a good idea
10349 (though they will largely be ignored).
10353 Here is a brief list of the control information files supported
10354 by <prgn>dpkg</prgn> and a summary of what they're used for.
10359 <tag><tt>control</tt>
10362 This is the key description file used by
10363 <prgn>dpkg</prgn>. It specifies the package's name
10364 and version, gives its description for the user,
10365 states its relationships with other packages, and so
10366 forth. See <ref id="sourcecontrolfiles"> and
10367 <ref id="binarycontrolfiles">.
10371 It is usually generated automatically from information
10372 in the source package by the
10373 <prgn>dpkg-gencontrol</prgn> program, and with
10374 assistance from <prgn>dpkg-shlibdeps</prgn>.
10375 See <ref id="pkg-sourcetools">.
10379 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10384 These are executable files (usually scripts) which
10385 <prgn>dpkg</prgn> runs during installation, upgrade
10386 and removal of packages. They allow the package to
10387 deal with matters which are particular to that package
10388 or require more complicated processing than that
10389 provided by <prgn>dpkg</prgn>. Details of when and
10390 how they are called are in <ref id="maintainerscripts">.
10394 It is very important to make these scripts idempotent.
10395 See <ref id="idempotency">.
10399 The maintainer scripts are not guaranteed to run with a
10400 controlling terminal and may not be able to interact with
10401 the user. See <ref id="controllingterminal">.
10405 <tag><tt>conffiles</tt>
10408 This file contains a list of configuration files which
10409 are to be handled automatically by <prgn>dpkg</prgn>
10410 (see <ref id="pkg-conffiles">). Note that not necessarily
10411 every configuration file should be listed here.
10414 <tag><tt>shlibs</tt>
10417 This file contains a list of the shared libraries
10418 supplied by the package, with dependency details for
10419 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10420 when it determines what dependencies are required in a
10421 package control file. The <tt>shlibs</tt> file format
10422 is described on <ref id="shlibs">.
10427 <sect id="pkg-controlfile">
10428 <heading>The main control information file: <tt>control</tt></heading>
10431 The most important control information file used by
10432 <prgn>dpkg</prgn> when it installs a package is
10433 <tt>control</tt>. It contains all the package's "vital
10438 The binary package control files of packages built from
10439 Debian sources are made by a special tool,
10440 <prgn>dpkg-gencontrol</prgn>, which reads
10441 <file>debian/control</file> and <file>debian/changelog</file> to
10442 find the information it needs. See <ref id="pkg-sourcepkg"> for
10447 The fields in binary package control files are listed in
10448 <ref id="binarycontrolfiles">.
10452 A description of the syntax of control files and the purpose
10453 of the fields is available in <ref id="controlfields">.
10458 <heading>Time Stamps</heading>
10461 See <ref id="timestamps">.
10466 <appendix id="pkg-sourcepkg">
10467 <heading>Source packages (from old Packaging Manual) </heading>
10470 The Debian binary packages in the distribution are generated
10471 from Debian sources, which are in a special format to assist
10472 the easy and automatic building of binaries.
10475 <sect id="pkg-sourcetools">
10476 <heading>Tools for processing source packages</heading>
10479 Various tools are provided for manipulating source packages;
10480 they pack and unpack sources and help build of binary
10481 packages and help manage the distribution of new versions.
10485 They are introduced and typical uses described here; see
10486 <manref name="dpkg-source" section="1"> for full
10487 documentation about their arguments and operation.
10491 For examples of how to construct a Debian source package,
10492 and how to use those utilities that are used by Debian
10493 source packages, please see the <prgn>hello</prgn> example
10497 <sect1 id="pkg-dpkg-source">
10499 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10504 This program is frequently used by hand, and is also
10505 called from package-independent automated building scripts
10506 such as <prgn>dpkg-buildpackage</prgn>.
10510 To unpack a package it is typically invoked with
10512 dpkg-source -x <var>.../path/to/filename</var>.dsc
10517 with the <file><var>filename</var>.tar.gz</file> and
10518 <file><var>filename</var>.diff.gz</file> (if applicable) in
10519 the same directory. It unpacks into
10520 <file><var>package</var>-<var>version</var></file>, and if
10522 <file><var>package</var>-<var>version</var>.orig</file>, in
10523 the current directory.
10527 To create a packed source archive it is typically invoked:
10529 dpkg-source -b <var>package</var>-<var>version</var>
10534 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10535 <file>.diff.gz</file> (if appropriate) in the current
10536 directory. <prgn>dpkg-source</prgn> does not clean the
10537 source tree first - this must be done separately if it is
10542 See also <ref id="pkg-sourcearchives">.</p>
10546 <sect1 id="pkg-dpkg-buildpackage">
10548 <prgn>dpkg-buildpackage</prgn> - overall package-building
10553 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10554 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10555 targets <tt>clean</tt>, <tt>build</tt> and
10556 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10557 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10558 source and binary package upload.
10562 It is usually invoked by hand from the top level of the
10563 built or unbuilt source directory. It may be invoked with
10564 no arguments; useful arguments include:
10565 <taglist compact="compact">
10566 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10569 Do not sign the <tt>.changes</tt> file or the
10570 source package <tt>.dsc</tt> file, respectively.</p>
10572 <tag><tt>-p<var>sign-command</var></tt></tag>
10575 Invoke <var>sign-command</var> instead of finding
10576 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10577 <var>sign-command</var> must behave just like
10578 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10580 <tag><tt>-r<var>root-command</var></tt></tag>
10583 When root privilege is required, invoke the command
10584 <var>root-command</var>. <var>root-command</var>
10585 should invoke its first argument as a command, from
10586 the <prgn>PATH</prgn> if necessary, and pass its
10587 second and subsequent arguments to the command it
10588 calls. If no <var>root-command</var> is supplied
10589 then <var>dpkg-buildpackage</var> will use
10590 the <prgn>fakeroot</prgn> command, which is sufficient
10591 to build most packages without actually requiring root
10594 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10597 Two types of binary-only build and upload - see
10598 <manref name="dpkg-source" section="1">.
10605 <sect1 id="pkg-dpkg-gencontrol">
10607 <prgn>dpkg-gencontrol</prgn> - generates binary package
10612 This program is usually called from <file>debian/rules</file>
10613 (see <ref id="pkg-sourcetree">) in the top level of the source
10618 This is usually done just before the files and directories in the
10619 temporary directory tree where the package is being built have their
10620 permissions and ownerships set and the package is constructed using
10621 <prgn>dpkg-deb/</prgn>
10623 This is so that the control file which is produced has
10624 the right permissions
10629 <prgn>dpkg-gencontrol</prgn> must be called after all the
10630 files which are to go into the package have been placed in
10631 the temporary build directory, so that its calculation of
10632 the installed size of a package is correct.
10636 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10637 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10638 variable substitutions created by
10639 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10644 For a package which generates only one binary package, and
10645 which builds it in <file>debian/tmp</file> relative to the top
10646 of the source package, it is usually sufficient to call
10647 <prgn>dpkg-gencontrol</prgn>.
10651 Sources which build several binaries will typically need
10654 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10655 </example> The <tt>-P</tt> tells
10656 <prgn>dpkg-gencontrol</prgn> that the package is being
10657 built in a non-default directory, and the <tt>-p</tt>
10658 tells it which package's control file should be generated.
10662 <prgn>dpkg-gencontrol</prgn> also adds information to the
10663 list of files in <file>debian/files</file>, for the benefit of
10664 (for example) a future invocation of
10665 <prgn>dpkg-genchanges</prgn>.</p>
10668 <sect1 id="pkg-dpkg-shlibdeps">
10670 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10675 This program is usually called from <file>debian/rules</file>
10676 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10677 id="pkg-sourcetree">), in the top level of the source tree.
10681 Its arguments are executables and shared libraries
10684 They may be specified either in the locations in the
10685 source tree where they are created or in the locations
10686 in the temporary build tree where they are installed
10687 prior to binary package creation.
10689 </footnote> for which shared library dependencies should
10690 be included in the binary package's control file.
10694 If some of the found shared libraries should only
10695 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10696 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10697 by using the <tt>-d<var>dependency-field</var></tt> option
10698 before those executable(s). (Each <tt>-d</tt> option
10699 takes effect until the next <tt>-d</tt>.)
10703 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10704 output control file to be modified. Instead by default it
10705 adds to the <file>debian/substvars</file> file variable
10706 settings like <tt>shlibs:Depends</tt>. These variable
10707 settings must be referenced in dependency fields in the
10708 appropriate per-binary-package sections of the source
10713 For example, a package that generates an essential part
10714 which requires dependencies, and optional parts that
10715 which only require a recommendation, would separate those
10716 two sets of dependencies into two different fields.<footnote>
10717 At the time of writing, an example for this was the
10718 <package/xmms/ package, with Depends used for the xmms
10719 executable, Recommends for the plug-ins and Suggests for
10720 even more optional features provided by unzip.
10722 It can say in its <file>debian/rules</file>:
10724 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10725 -dRecommends <var>optionalpart anotheroptionalpart</var>
10727 and then in its main control file <file>debian/control</file>:
10730 Depends: ${shlibs:Depends}
10731 Recommends: ${shlibs:Recommends}
10737 Sources which produce several binary packages with
10738 different shared library dependency requirements can use
10739 the <tt>-p<var>varnameprefix</var></tt> option to override
10740 the default <tt>shlibs:</tt> prefix (one invocation of
10741 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10742 They can thus produce several sets of dependency
10743 variables, each of the form
10744 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10745 which can be referred to in the appropriate parts of the
10746 binary package control files.
10751 <sect1 id="pkg-dpkg-distaddfile">
10753 <prgn>dpkg-distaddfile</prgn> - adds a file to
10754 <file>debian/files</file>
10758 Some packages' uploads need to include files other than
10759 the source and binary package files.
10763 <prgn>dpkg-distaddfile</prgn> adds a file to the
10764 <file>debian/files</file> file so that it will be included in
10765 the <file>.changes</file> file when
10766 <prgn>dpkg-genchanges</prgn> is run.
10770 It is usually invoked from the <tt>binary</tt> target of
10771 <file>debian/rules</file>:
10773 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10775 The <var>filename</var> is relative to the directory where
10776 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10777 is usually the directory above the top level of the source
10778 tree. The <file>debian/rules</file> target should put the
10779 file there just before or just after calling
10780 <prgn>dpkg-distaddfile</prgn>.
10784 The <var>section</var> and <var>priority</var> are passed
10785 unchanged into the resulting <file>.changes</file> file.
10790 <sect1 id="pkg-dpkg-genchanges">
10792 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10793 upload control file
10797 This program is usually called by package-independent
10798 automatic building scripts such as
10799 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10804 It is usually called in the top level of a built source
10805 tree, and when invoked with no arguments will print out a
10806 straightforward <file>.changes</file> file based on the
10807 information in the source package's changelog and control
10808 file and the binary and source packages which should have
10814 <sect1 id="pkg-dpkg-parsechangelog">
10816 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10817 representation of a changelog
10821 This program is used internally by
10822 <prgn>dpkg-source</prgn> et al. It may also occasionally
10823 be useful in <file>debian/rules</file> and elsewhere. It
10824 parses a changelog, <file>debian/changelog</file> by default,
10825 and prints a control-file format representation of the
10826 information in it to standard output.
10830 <sect1 id="pkg-dpkg-architecture">
10832 <prgn>dpkg-architecture</prgn> - information about the build and
10837 This program can be used manually, but is also invoked by
10838 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10839 environment or make variables which specify the build and host
10840 architecture for the package building process.
10845 <sect id="pkg-sourcetree">
10846 <heading>The Debian package source tree</heading>
10849 The source archive scheme described later is intended to
10850 allow a Debian package source tree with some associated
10851 control information to be reproduced and transported easily.
10852 The Debian package source tree is a version of the original
10853 program with certain files added for the benefit of the
10854 packaging process, and with any other changes required
10855 made to the rest of the source code and installation
10860 The extra files created for Debian are in the subdirectory
10861 <file>debian</file> of the top level of the Debian package
10862 source tree. They are described below.
10865 <sect1 id="pkg-debianrules">
10866 <heading><file>debian/rules</file> - the main building script</heading>
10869 See <ref id="debianrules">.
10873 <sect1 id="pkg-srcsubstvars">
10874 <heading><file>debian/substvars</file> and variable substitutions</heading>
10877 See <ref id="substvars">.
10883 <heading><file>debian/files</file></heading>
10886 See <ref id="debianfiles">.
10890 <sect1><heading><file>debian/tmp</file>
10894 This is the canonical temporary location for the
10895 construction of binary packages by the <tt>binary</tt>
10896 target. The directory <file>tmp</file> serves as the root of
10897 the file system tree as it is being constructed (for
10898 example, by using the package's upstream makefiles install
10899 targets and redirecting the output there), and it also
10900 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10901 id="pkg-bincreating">.
10905 If several binary packages are generated from the same
10906 source tree it is usual to use several
10907 <file>debian/tmp<var>something</var></file> directories, for
10908 example <file>tmp-a</file> or <file>tmp-doc</file>.
10912 Whatever <file>tmp</file> directories are created and used by
10913 <tt>binary</tt> must of course be removed by the
10914 <tt>clean</tt> target.</p></sect1>
10918 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10922 As it exists on the FTP site, a Debian source package
10923 consists of three related files. You must have the right
10924 versions of all three to be able to use them.
10929 <tag>Debian source control file - <tt>.dsc</tt></tag>
10931 This file is a control file used by <prgn>dpkg-source</prgn>
10932 to extract a source package.
10933 See <ref id="debiansourcecontrolfiles">.
10937 Original source archive -
10939 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10945 This is a compressed (with <tt>gzip -9</tt>)
10946 <prgn>tar</prgn> file containing the source code from
10947 the upstream authors of the program.
10952 Debian package diff -
10954 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10960 This is a unified context diff (<tt>diff -u</tt>)
10961 giving the changes which are required to turn the
10962 original source into the Debian source. These changes
10963 may only include editing and creating plain files.
10964 The permissions of files, the targets of symbolic
10965 links and the characteristics of special files or
10966 pipes may not be changed and no files may be removed
10971 All the directories in the diff must exist, except the
10972 <file>debian</file> subdirectory of the top of the source
10973 tree, which will be created by
10974 <prgn>dpkg-source</prgn> if necessary when unpacking.
10978 The <prgn>dpkg-source</prgn> program will
10979 automatically make the <file>debian/rules</file> file
10980 executable (see below).</p></item>
10985 If there is no original source code - for example, if the
10986 package is specially prepared for Debian or the Debian
10987 maintainer is the same as the upstream maintainer - the
10988 format is slightly different: then there is no diff, and the
10990 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10991 and preferably contains a directory named
10992 <file><var>package</var>-<var>version</var></file>.
10997 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
11000 <tt>dpkg-source -x</tt> is the recommended way to unpack a
11001 Debian source package. However, if it is not available it
11002 is possible to unpack a Debian source archive as follows:
11003 <enumlist compact="compact">
11006 Untar the tarfile, which will create a <file>.orig</file>
11010 <p>Rename the <file>.orig</file> directory to
11011 <file><var>package</var>-<var>version</var></file>.</p>
11015 Create the subdirectory <file>debian</file> at the top of
11016 the source tree.</p>
11018 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
11020 <item><p>Untar the tarfile again if you want a copy of the original
11021 source code alongside the Debian version.</p>
11026 It is not possible to generate a valid Debian source archive
11027 without using <prgn>dpkg-source</prgn>. In particular,
11028 attempting to use <prgn>diff</prgn> directly to generate the
11029 <file>.diff.gz</file> file will not work.
11033 <heading>Restrictions on objects in source packages</heading>
11036 The source package may not contain any hard links
11038 This is not currently detected when building source
11039 packages, but only when extracting
11043 Hard links may be permitted at some point in the
11044 future, but would require a fair amount of
11046 </footnote>, device special files, sockets or setuid or
11049 Setgid directories are allowed.
11054 The source packaging tools manage the changes between the
11055 original and Debian source using <prgn>diff</prgn> and
11056 <prgn>patch</prgn>. Turning the original source tree as
11057 included in the <file>.orig.tar.gz</file> into the Debian
11058 package source must not involve any changes which cannot be
11059 handled by these tools. Problematic changes which cause
11060 <prgn>dpkg-source</prgn> to halt with an error when
11061 building the source package are:
11062 <list compact="compact">
11063 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11065 <item><p>Changing the targets of symbolic links.</p>
11067 <item><p>Creating directories, other than <file>debian</file>.</p>
11069 <item><p>Changes to the contents of binary files.</p></item>
11070 </list> Changes which cause <prgn>dpkg-source</prgn> to
11071 print a warning but continue anyway are:
11072 <list compact="compact">
11075 Removing files, directories or symlinks.
11077 Renaming a file is not treated specially - it is
11078 seen as the removal of the old file (which
11079 generates a warning, but is otherwise ignored),
11080 and the creation of the new one.
11086 Changed text files which are missing the usual final
11087 newline (either in the original or the modified
11092 Changes which are not represented, but which are not detected by
11093 <prgn>dpkg-source</prgn>, are:
11094 <list compact="compact">
11095 <item><p>Changing the permissions of files (other than
11096 <file>debian/rules</file>) and directories.</p></item>
11101 The <file>debian</file> directory and <file>debian/rules</file>
11102 are handled specially by <prgn>dpkg-source</prgn> - before
11103 applying the changes it will create the <file>debian</file>
11104 directory, and afterwards it will make
11105 <file>debian/rules</file> world-executable.
11111 <appendix id="pkg-controlfields">
11112 <heading>Control files and their fields (from old Packaging Manual)</heading>
11115 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11116 data in a common format, known as control files. Binary and
11117 source packages have control data as do the <file>.changes</file>
11118 files which control the installation of uploaded files, and
11119 <prgn>dpkg</prgn>'s internal databases are in a similar
11124 <heading>Syntax of control files</heading>
11127 See <ref id="controlsyntax">.
11131 It is important to note that there are several fields which
11132 are optional as far as <prgn>dpkg</prgn> and the related
11133 tools are concerned, but which must appear in every Debian
11134 package, or whose omission may cause problems.
11139 <heading>List of fields</heading>
11142 See <ref id="controlfieldslist">.
11146 This section now contains only the fields that didn't belong
11147 to the Policy manual.
11150 <sect1 id="pkg-f-Filename">
11151 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11154 These fields in <tt>Packages</tt> files give the
11155 filename(s) of (the parts of) a package in the
11156 distribution directories, relative to the root of the
11157 Debian hierarchy. If the package has been split into
11158 several parts the parts are all listed in order, separated
11163 <sect1 id="pkg-f-Size">
11164 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11167 These fields in <file>Packages</file> files give the size (in
11168 bytes, expressed in decimal) and MD5 checksum of the
11169 file(s) which make(s) up a binary package in the
11170 distribution. If the package is split into several parts
11171 the values for the parts are listed in order, separated by
11176 <sect1 id="pkg-f-Status">
11177 <heading><tt>Status</tt></heading>
11180 This field in <prgn>dpkg</prgn>'s status file records
11181 whether the user wants a package installed, removed or
11182 left alone, whether it is broken (requiring
11183 re-installation) or not and what its current state on the
11184 system is. Each of these pieces of information is a
11189 <sect1 id="pkg-f-Config-Version">
11190 <heading><tt>Config-Version</tt></heading>
11193 If a package is not installed or not configured, this
11194 field in <prgn>dpkg</prgn>'s status file records the last
11195 version of the package which was successfully
11200 <sect1 id="pkg-f-Conffiles">
11201 <heading><tt>Conffiles</tt></heading>
11204 This field in <prgn>dpkg</prgn>'s status file contains
11205 information about the automatically-managed configuration
11206 files held by a package. This field should <em>not</em>
11207 appear anywhere in a package!
11212 <heading>Obsolete fields</heading>
11215 These are still recognized by <prgn>dpkg</prgn> but should
11216 not appear anywhere any more.
11218 <taglist compact="compact">
11220 <tag><tt>Revision</tt></tag>
11221 <tag><tt>Package-Revision</tt></tag>
11222 <tag><tt>Package_Revision</tt></tag>
11224 The Debian revision part of the package version was
11225 at one point in a separate control field. This
11226 field went through several names.
11229 <tag><tt>Recommended</tt></tag>
11230 <item>Old name for <tt>Recommends</tt>.</item>
11232 <tag><tt>Optional</tt></tag>
11233 <item>Old name for <tt>Suggests</tt>.</item>
11235 <tag><tt>Class</tt></tag>
11236 <item>Old name for <tt>Priority</tt>.</item>
11245 <appendix id="pkg-conffiles">
11246 <heading>Configuration file handling (from old Packaging Manual)</heading>
11249 <prgn>dpkg</prgn> can do a certain amount of automatic
11250 handling of package configuration files.
11254 Whether this mechanism is appropriate depends on a number of
11255 factors, but basically there are two approaches to any
11256 particular configuration file.
11260 The easy method is to ship a best-effort configuration in the
11261 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11262 handle updates. If the user is unlikely to want to edit the
11263 file, but you need them to be able to without losing their
11264 changes, and a new package with a changed version of the file
11265 is only released infrequently, this is a good approach.
11269 The hard method is to build the configuration file from
11270 scratch in the <prgn>postinst</prgn> script, and to take the
11271 responsibility for fixing any mistakes made in earlier
11272 versions of the package automatically. This will be
11273 appropriate if the file is likely to need to be different on
11277 <sect><heading>Automatic handling of configuration files by
11282 A package may contain a control information file called
11283 <tt>conffiles</tt>. This file should be a list of filenames
11284 of configuration files needing automatic handling, separated
11285 by newlines. The filenames should be absolute pathnames,
11286 and the files referred to should actually exist in the
11291 When a package is upgraded <prgn>dpkg</prgn> will process
11292 the configuration files during the configuration stage,
11293 shortly before it runs the package's <prgn>postinst</prgn>
11298 For each file it checks to see whether the version of the
11299 file included in the package is the same as the one that was
11300 included in the last version of the package (the one that is
11301 being upgraded from); it also compares the version currently
11302 installed on the system with the one shipped with the last
11307 If neither the user nor the package maintainer has changed
11308 the file, it is left alone. If one or the other has changed
11309 their version, then the changed version is preferred - i.e.,
11310 if the user edits their file, but the package maintainer
11311 doesn't ship a different version, the user's changes will
11312 stay, silently, but if the maintainer ships a new version
11313 and the user hasn't edited it the new version will be
11314 installed (with an informative message). If both have
11315 changed their version the user is prompted about the problem
11316 and must resolve the differences themselves.
11320 The comparisons are done by calculating the MD5 message
11321 digests of the files, and storing the MD5 of the file as it
11322 was included in the most recent version of the package.
11326 When a package is installed for the first time
11327 <prgn>dpkg</prgn> will install the file that comes with it,
11328 unless that would mean overwriting a file already on the
11333 However, note that <prgn>dpkg</prgn> will <em>not</em>
11334 replace a conffile that was removed by the user (or by a
11335 script). This is necessary because with some programs a
11336 missing file produces an effect hard or impossible to
11337 achieve in another way, so that a missing file needs to be
11338 kept that way if the user did it.
11342 Note that a package should <em>not</em> modify a
11343 <prgn>dpkg</prgn>-handled conffile in its maintainer
11344 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11345 the user confusing and possibly dangerous options for
11346 conffile update when the package is upgraded.</p>
11349 <sect><heading>Fully-featured maintainer script configuration
11354 For files which contain site-specific information such as
11355 the hostname and networking details and so forth, it is
11356 better to create the file in the package's
11357 <prgn>postinst</prgn> script.
11361 This will typically involve examining the state of the rest
11362 of the system to determine values and other information, and
11363 may involve prompting the user for some information which
11364 can't be obtained some other way.
11368 When using this method there are a couple of important
11369 issues which should be considered:
11373 If you discover a bug in the program which generates the
11374 configuration file, or if the format of the file changes
11375 from one version to the next, you will have to arrange for
11376 the postinst script to do something sensible - usually this
11377 will mean editing the installed configuration file to remove
11378 the problem or change the syntax. You will have to do this
11379 very carefully, since the user may have changed the file,
11380 perhaps to fix the very problem that your script is trying
11381 to deal with - you will have to detect these situations and
11382 deal with them correctly.
11386 If you do go down this route it's probably a good idea to
11387 make the program that generates the configuration file(s) a
11388 separate program in <file>/usr/sbin</file>, by convention called
11389 <file><var>package</var>config</file> and then run that if
11390 appropriate from the post-installation script. The
11391 <tt><var>package</var>config</tt> program should not
11392 unquestioningly overwrite an existing configuration - if its
11393 mode of operation is geared towards setting up a package for
11394 the first time (rather than any arbitrary reconfiguration
11395 later) you should have it check whether the configuration
11396 already exists, and require a <tt>--force</tt> flag to
11397 overwrite it.</p></sect>
11400 <appendix id="pkg-alternatives"><heading>Alternative versions of
11401 an interface - <prgn>update-alternatives</prgn> (from old
11406 When several packages all provide different versions of the
11407 same program or file it is useful to have the system select a
11408 default, but to allow the system administrator to change it
11409 and have their decisions respected.
11413 For example, there are several versions of the <prgn>vi</prgn>
11414 editor, and there is no reason to prevent all of them from
11415 being installed at once, each under their own name
11416 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11417 Nevertheless it is desirable to have the name <tt>vi</tt>
11418 refer to something, at least by default.
11422 If all the packages involved cooperate, this can be done with
11423 <prgn>update-alternatives</prgn>.
11427 Each package provides its own version under its own name, and
11428 calls <prgn>update-alternatives</prgn> in its postinst to
11429 register its version (and again in its prerm to deregister
11434 See the man page <manref name="update-alternatives"
11435 section="8"> for details.
11439 If <prgn>update-alternatives</prgn> does not seem appropriate
11440 you may wish to consider using diversions instead.</p>
11443 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11444 package's version of a file (from old Packaging Manual)
11448 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11449 when it reinstalls the package it belongs to, and to have it
11450 put the file from the package somewhere else instead.
11454 This can be used locally to override a package's version of a
11455 file, or by one package to override another's version (or
11456 provide a wrapper for it).
11460 Before deciding to use a diversion, read <ref
11461 id="pkg-alternatives"> to see if you really want a diversion
11462 rather than several alternative versions of a program.
11466 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11467 and updated by a special program <prgn>dpkg-divert</prgn>.
11468 Please see <manref name="dpkg-divert" section="8"> for full
11469 details of its operation.
11473 When a package wishes to divert a file from another, it should
11474 call <prgn>dpkg-divert</prgn> in its preinst to add the
11475 diversion and rename the existing file. For example,
11476 supposing that a <prgn>smailwrapper</prgn> package wishes to
11477 install a wrapper around <file>/usr/sbin/smail</file>:
11479 dpkg-divert --package smailwrapper --add --rename \
11480 --divert /usr/sbin/smail.real /usr/sbin/smail
11481 </example> The <tt>--package smailwrapper</tt> ensures that
11482 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11483 can bypass the diversion and get installed as the true version.
11484 It's safe to add the diversion unconditionally on upgrades since
11485 it will be left unchanged if it already exists, but
11486 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11487 message, make the command conditional on the version from which
11488 the package is being upgraded:
11490 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11491 dpkg-divert --package smailwrapper --add --rename \
11492 --divert /usr/sbin/smail.real /usr/sbin/smail
11494 </example> where <tt>1.0-2</tt> is the version at which the
11495 diversion was first added to the package. Running the command
11496 during abort-upgrade is pointless but harmless.
11500 The postrm has to do the reverse:
11502 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11503 dpkg-divert --package smailwrapper --remove --rename \
11504 --divert /usr/sbin/smail.real /usr/sbin/smail
11506 </example> If the diversion was added at a particular version, the
11507 postrm should also handle the failure case of upgrading from an
11508 older version (unless the older version is so old that direct
11509 upgrades are no longer supported):
11511 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11512 dpkg-divert --package smailwrapper --remove --rename \
11513 --divert /usr/sbin/smail.real /usr/sbin/smail
11515 </example> where <tt>1.0-2</tt> is the version at which the
11516 diversion was first added to the package. The postrm should not
11517 remove the diversion on upgrades both because there's no reason to
11518 remove the diversion only to immediately re-add it and since the
11519 postrm of the old package is run after unpacking so the removal of
11520 the diversion will fail.
11524 Do not attempt to divert a file which is vitally important for
11525 the system's operation - when using <prgn>dpkg-divert</prgn>
11526 there is a time, after it has been diverted but before
11527 <prgn>dpkg</prgn> has installed the new version, when the file
11528 does not exist.</p>
11533 <!-- Local variables: -->
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