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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>
2638 The fields in the binary package paragraphs are:
2640 <list compact="compact">
2641 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2642 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2643 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2644 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2645 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2646 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2647 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2649 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2654 The syntax and semantics of the fields are described below.
2658 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2659 generate control files for binary packages (see below), by
2660 <prgn>dpkg-genchanges</prgn> to generate the
2661 <file>.changes</file> file to accompany the upload, and by
2662 <prgn>dpkg-source</prgn> when it creates the
2663 <file>.dsc</file> source control file as part of a source
2664 archive. Some fields are folded in <file>debian/control</file>,
2665 but not in any other control
2666 file. These tools are responsible for removing the line
2667 breaks from such fields when using fields from
2668 <file>debian/control</file> to generate other control files.
2672 The fields here may contain variable references - their
2673 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2674 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2675 when they generate output control files.
2676 See <ref id="substvars"> for details.
2680 <sect id="binarycontrolfiles">
2681 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2684 The <file>DEBIAN/control</file> file contains the most vital
2685 (and version-dependent) information about a binary package. It
2686 consists of a single paragraph.
2690 The fields in this file are:
2692 <list compact="compact">
2693 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2694 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2695 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2696 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2697 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2698 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2699 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2700 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2701 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2702 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2703 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2704 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2705 <item><qref id="built-using"><tt>Built-Using</tt></qref></item>
2710 <sect id="debiansourcecontrolfiles">
2711 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2714 This file consists of a single paragraph, possibly surrounded by
2715 a PGP signature. The fields of that paragraph are listed below.
2716 Their syntax is described above, in <ref id="controlsyntax">.
2718 <list compact="compact">
2719 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2720 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2721 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2722 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2723 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2724 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2725 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2726 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2727 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2728 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2729 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2730 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2731 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2732 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2737 The Debian source control file is generated by
2738 <prgn>dpkg-source</prgn> when it builds the source
2739 archive, from other files in the source package,
2740 described above. When unpacking, it is checked against
2741 the files and directories in the other parts of the
2747 <sect id="debianchangesfiles">
2748 <heading>Debian changes files -- <file>.changes</file></heading>
2751 The <file>.changes</file> files are used by the Debian archive
2752 maintenance software to process updates to packages. They
2753 consist of a single paragraph, possibly surrounded by a PGP
2754 signature. That paragraph contains information from the
2755 <file>debian/control</file> file and other data about the
2756 source package gathered via <file>debian/changelog</file>
2757 and <file>debian/rules</file>.
2761 <file>.changes</file> files have a format version that is
2762 incremented whenever the documented fields or their meaning
2763 change. This document describes format &changesversion;.
2767 The fields in this file are:
2769 <list compact="compact">
2770 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2771 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2772 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2773 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2774 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2775 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2776 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2777 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2778 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2779 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2780 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2781 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2782 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2783 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2784 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2785 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2790 <sect id="controlfieldslist">
2791 <heading>List of fields</heading>
2793 <sect1 id="f-Source">
2794 <heading><tt>Source</tt></heading>
2797 This field identifies the source package name.
2801 In <file>debian/control</file> or a <file>.dsc</file> file,
2802 this field must contain only the name of the source package.
2806 In a binary package control file or a <file>.changes</file>
2807 file, the source package name may be followed by a version
2808 number in parentheses<footnote>
2809 It is customary to leave a space after the package name
2810 if a version number is specified.
2812 This version number may be omitted (and is, by
2813 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2814 the <tt>Version</tt> field of the binary package in
2815 question. The field itself may be omitted from a binary
2816 package control file when the source package has the same
2817 name and version as the binary package.
2821 Package names (both source and binary,
2822 see <ref id="f-Package">) must consist only of lower case
2823 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2824 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2825 (<tt>.</tt>). They must be at least two characters long and
2826 must start with an alphanumeric character.
2830 <sect1 id="f-Maintainer">
2831 <heading><tt>Maintainer</tt></heading>
2834 The package maintainer's name and email address. The name
2835 must come first, then the email address inside angle
2836 brackets <tt><></tt> (in RFC822 format).
2840 If the maintainer's name contains a full stop then the
2841 whole field will not work directly as an email address due
2842 to a misfeature in the syntax specified in RFC822; a
2843 program using this field as an address must check for this
2844 and correct the problem if necessary (for example by
2845 putting the name in round brackets and moving it to the
2846 end, and bringing the email address forward).
2850 See <ref id="maintainer"> for additional requirements and
2851 information about package maintainers.
2855 <sect1 id="f-Uploaders">
2856 <heading><tt>Uploaders</tt></heading>
2859 List of the names and email addresses of co-maintainers of the
2860 package, if any. If the package has other maintainers besides
2861 the one named in the <qref id="f-Maintainer">Maintainer
2862 field</qref>, their names and email addresses should be listed
2863 here. The format of each entry is the same as that of the
2864 Maintainer field, and multiple entries must be comma
2869 This is normally an optional field, but if
2870 the <tt>Maintainer</tt> control field names a group of people
2871 and a shared email address, the <tt>Uploaders</tt> field must
2872 be present and must contain at least one human with their
2873 personal email address.
2877 The Uploaders field in <file>debian/control</file> can be folded.
2881 <sect1 id="f-Changed-By">
2882 <heading><tt>Changed-By</tt></heading>
2885 The name and email address of the person who prepared this
2886 version of the package, usually a maintainer. The syntax is
2887 the same as for the <qref id="f-Maintainer">Maintainer
2892 <sect1 id="f-Section">
2893 <heading><tt>Section</tt></heading>
2896 This field specifies an application area into which the package
2897 has been classified. See <ref id="subsections">.
2901 When it appears in the <file>debian/control</file> file,
2902 it gives the value for the subfield of the same name in
2903 the <tt>Files</tt> field of the <file>.changes</file> file.
2904 It also gives the default for the same field in the binary
2909 <sect1 id="f-Priority">
2910 <heading><tt>Priority</tt></heading>
2913 This field represents how important it is that the user
2914 have the package installed. See <ref id="priorities">.
2918 When it appears in the <file>debian/control</file> file,
2919 it gives the value for the subfield of the same name in
2920 the <tt>Files</tt> field of the <file>.changes</file> file.
2921 It also gives the default for the same field in the binary
2926 <sect1 id="f-Package">
2927 <heading><tt>Package</tt></heading>
2930 The name of the binary package.
2934 Binary package names must follow the same syntax and
2935 restrictions as source package names. See <ref id="f-Source">
2940 <sect1 id="f-Architecture">
2941 <heading><tt>Architecture</tt></heading>
2944 Depending on context and the control file used, the
2945 <tt>Architecture</tt> field can include the following sets of
2949 A unique single word identifying a Debian machine
2950 architecture as described in <ref id="arch-spec">.
2953 An architecture wildcard identifying a set of Debian
2954 machine architectures, see <ref id="arch-wildcard-spec">.
2955 <tt>any</tt> matches all Debian machine architectures
2956 and is the most frequently used.
2959 <tt>all</tt>, which indicates an
2960 architecture-independent package.
2963 <tt>source</tt>, which indicates a source package.
2969 In the main <file>debian/control</file> file in the source
2970 package, this field may contain the special
2971 value <tt>all</tt>, the special architecture
2972 wildcard <tt>any</tt>, or a list of specific and wildcard
2973 architectures separated by spaces. If <tt>all</tt>
2974 or <tt>any</tt> appears, that value must be the entire
2975 contents of the field. Most packages will use
2976 either <tt>all</tt> or <tt>any</tt>.
2980 Specifying a specific list of architectures indicates that the
2981 source will build an architecture-dependent package only on
2982 architectures included in the list. Specifying a list of
2983 architecture wildcards indicates that the source will build an
2984 architecture-dependent package on only those architectures
2985 that match any of the specified architecture wildcards.
2986 Specifying a list of architectures or architecture wildcards
2987 other than <tt>any</tt> is for the minority of cases where a
2988 program is not portable or is not useful on some
2989 architectures. Where possible, the program should be made
2994 In the Debian source control file <file>.dsc</file>, this
2995 field contains a list of architectures and architecture
2996 wildcards separated by spaces. When the list contains the
2997 architecture wildcard <tt>any</tt>, the only other value
2998 allowed in the list is <tt>all</tt>.
3002 The list may include (or consist solely of) the special
3003 value <tt>all</tt>. In other words, in <file>.dsc</file>
3004 files unlike the <file>debian/control</file>, <tt>all</tt> may
3005 occur in combination with specific architectures.
3006 The <tt>Architecture</tt> field in the Debian source control
3007 file <file>.dsc</file> is generally constructed from
3008 the <tt>Architecture</tt> fields in
3009 the <file>debian/control</file> in the source package.
3013 Specifying only <tt>any</tt> indicates that the source package
3014 isn't dependent on any particular architecture and should
3015 compile fine on any one. The produced binary package(s)
3016 will be specific to whatever the current build architecture is.
3020 Specifying only <tt>all</tt> indicates that the source package
3021 will only build architecture-independent packages.
3025 Specifying <tt>any all</tt> indicates that the source package
3026 isn't dependent on any particular architecture. The set of
3027 produced binary packages will include at least one
3028 architecture-dependant package and one architecture-independent
3033 Specifying a list of architectures or architecture wildcards
3034 indicates that the source will build an architecture-dependent
3035 package, and will only work correctly on the listed or
3036 matching architectures. If the source package also builds at
3037 least one architecture-independent package, <tt>all</tt> will
3038 also be included in the list.
3042 In a <file>.changes</file> file, the <tt>Architecture</tt>
3043 field lists the architecture(s) of the package(s) currently
3044 being uploaded. This will be a list; if the source for the
3045 package is also being uploaded, the special
3046 entry <tt>source</tt> is also present. <tt>all</tt> will be
3047 present if any architecture-independent packages are being
3048 uploaded. Architecture wildcards such as <tt>any</tt> must
3049 never occur in the <tt>Architecture</tt> field in
3050 the <file>.changes</file> file.
3054 See <ref id="debianrules"> for information on how to get
3055 the architecture for the build process.
3059 <sect1 id="f-Essential">
3060 <heading><tt>Essential</tt></heading>
3063 This is a boolean field which may occur only in the
3064 control file of a binary package or in a per-package fields
3065 paragraph of a source package control file.
3069 If set to <tt>yes</tt> then the package management system
3070 will refuse to remove the package (upgrading and replacing
3071 it is still possible). The other possible value is <tt>no</tt>,
3072 which is the same as not having the field at all.
3077 <heading>Package interrelationship fields:
3078 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3079 <tt>Recommends</tt>, <tt>Suggests</tt>,
3080 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3081 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3085 These fields describe the package's relationships with
3086 other packages. Their syntax and semantics are described
3087 in <ref id="relationships">.</p>
3090 <sect1 id="f-Standards-Version">
3091 <heading><tt>Standards-Version</tt></heading>
3094 The most recent version of the standards (the policy
3095 manual and associated texts) with which the package
3100 The version number has four components: major and minor
3101 version number and major and minor patch level. When the
3102 standards change in a way that requires every package to
3103 change the major number will be changed. Significant
3104 changes that will require work in many packages will be
3105 signaled by a change to the minor number. The major patch
3106 level will be changed for any change to the meaning of the
3107 standards, however small; the minor patch level will be
3108 changed when only cosmetic, typographical or other edits
3109 are made which neither change the meaning of the document
3110 nor affect the contents of packages.
3114 Thus only the first three components of the policy version
3115 are significant in the <em>Standards-Version</em> control
3116 field, and so either these three components or all four
3117 components may be specified.<footnote>
3118 In the past, people specified the full version number
3119 in the Standards-Version field, for example "2.3.0.0".
3120 Since minor patch-level changes don't introduce new
3121 policy, it was thought it would be better to relax
3122 policy and only require the first 3 components to be
3123 specified, in this example "2.3.0". All four
3124 components may still be used if someone wishes to do so.
3130 <sect1 id="f-Version">
3131 <heading><tt>Version</tt></heading>
3134 The version number of a package. The format is:
3135 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3139 The three components here are:
3141 <tag><var>epoch</var></tag>
3144 This is a single (generally small) unsigned integer. It
3145 may be omitted, in which case zero is assumed. If it is
3146 omitted then the <var>upstream_version</var> may not
3151 It is provided to allow mistakes in the version numbers
3152 of older versions of a package, and also a package's
3153 previous version numbering schemes, to be left behind.
3157 <tag><var>upstream_version</var></tag>
3160 This is the main part of the version number. It is
3161 usually the version number of the original ("upstream")
3162 package from which the <file>.deb</file> file has been made,
3163 if this is applicable. Usually this will be in the same
3164 format as that specified by the upstream author(s);
3165 however, it may need to be reformatted to fit into the
3166 package management system's format and comparison
3171 The comparison behavior of the package management system
3172 with respect to the <var>upstream_version</var> is
3173 described below. The <var>upstream_version</var>
3174 portion of the version number is mandatory.
3178 The <var>upstream_version</var> may contain only
3179 alphanumerics<footnote>
3180 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3182 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3183 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3184 tilde) and should start with a digit. If there is no
3185 <var>debian_revision</var> then hyphens are not allowed;
3186 if there is no <var>epoch</var> then colons are not
3191 <tag><var>debian_revision</var></tag>
3194 This part of the version number specifies the version of
3195 the Debian package based on the upstream version. It
3196 may contain only alphanumerics and the characters
3197 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3198 tilde) and is compared in the same way as the
3199 <var>upstream_version</var> is.
3203 It is optional; if it isn't present then the
3204 <var>upstream_version</var> may not contain a hyphen.
3205 This format represents the case where a piece of
3206 software was written specifically to be a Debian
3207 package, where the Debian package source must always
3208 be identical to the pristine source and therefore no
3209 revision indication is required.
3213 It is conventional to restart the
3214 <var>debian_revision</var> at <tt>1</tt> each time the
3215 <var>upstream_version</var> is increased.
3219 The package management system will break the version
3220 number apart at the last hyphen in the string (if there
3221 is one) to determine the <var>upstream_version</var> and
3222 <var>debian_revision</var>. The absence of a
3223 <var>debian_revision</var> is equivalent to a
3224 <var>debian_revision</var> of <tt>0</tt>.
3231 When comparing two version numbers, first the <var>epoch</var>
3232 of each are compared, then the <var>upstream_version</var> if
3233 <var>epoch</var> is equal, and then <var>debian_revision</var>
3234 if <var>upstream_version</var> is also equal.
3235 <var>epoch</var> is compared numerically. The
3236 <var>upstream_version</var> and <var>debian_revision</var>
3237 parts are compared by the package management system using the
3238 following algorithm:
3242 The strings are compared from left to right.
3246 First the initial part of each string consisting entirely of
3247 non-digit characters is determined. These two parts (one of
3248 which may be empty) are compared lexically. If a difference
3249 is found it is returned. The lexical comparison is a
3250 comparison of ASCII values modified so that all the letters
3251 sort earlier than all the non-letters and so that a tilde
3252 sorts before anything, even the end of a part. For example,
3253 the following parts are in sorted order from earliest to
3254 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3255 <tt>a</tt>.<footnote>
3256 One common use of <tt>~</tt> is for upstream pre-releases.
3257 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3258 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3263 Then the initial part of the remainder of each string which
3264 consists entirely of digit characters is determined. The
3265 numerical values of these two parts are compared, and any
3266 difference found is returned as the result of the comparison.
3267 For these purposes an empty string (which can only occur at
3268 the end of one or both version strings being compared) counts
3273 These two steps (comparing and removing initial non-digit
3274 strings and initial digit strings) are repeated until a
3275 difference is found or both strings are exhausted.
3279 Note that the purpose of epochs is to allow us to leave behind
3280 mistakes in version numbering, and to cope with situations
3281 where the version numbering scheme changes. It is
3282 <em>not</em> intended to cope with version numbers containing
3283 strings of letters which the package management system cannot
3284 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3285 silly orderings.<footnote>
3286 The author of this manual has heard of a package whose
3287 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3288 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3294 <sect1 id="f-Description">
3295 <heading><tt>Description</tt></heading>
3298 In a source or binary control file, the <tt>Description</tt>
3299 field contains a description of the binary package, consisting
3300 of two parts, the synopsis or the short description, and the
3301 long description. It is a multiline field with the following
3307 Description: <single line synopsis>
3308 <extended description over several lines>
3313 The lines in the extended description can have these formats:
3319 Those starting with a single space are part of a paragraph.
3320 Successive lines of this form will be word-wrapped when
3321 displayed. The leading space will usually be stripped off.
3322 The line must contain at least one non-whitespace character.
3326 Those starting with two or more spaces. These will be
3327 displayed verbatim. If the display cannot be panned
3328 horizontally, the displaying program will line wrap them "hard"
3329 (i.e., without taking account of word breaks). If it can they
3330 will be allowed to trail off to the right. None, one or two
3331 initial spaces may be deleted, but the number of spaces
3332 deleted from each line will be the same (so that you can have
3333 indenting work correctly, for example). The line must
3334 contain at least one non-whitespace character.
3338 Those containing a single space followed by a single full stop
3339 character. These are rendered as blank lines. This is the
3340 <em>only</em> way to get a blank line<footnote>
3341 Completely empty lines will not be rendered as blank lines.
3342 Instead, they will cause the parser to think you're starting
3343 a whole new record in the control file, and will therefore
3344 likely abort with an error.
3349 Those containing a space, a full stop and some more characters.
3350 These are for future expansion. Do not use them.
3356 Do not use tab characters. Their effect is not predictable.
3360 See <ref id="descriptions"> for further information on this.
3364 In a <file>.changes</file> file, the <tt>Description</tt>
3365 field contains a summary of the descriptions for the packages
3366 being uploaded. For this case, the first line of the field
3367 value (the part on the same line as <tt>Description:</tt>) is
3368 always empty. It is a multiline field, with one
3369 line per package. Each line is
3370 indented by one space and contains the name of a binary
3371 package, a space, a hyphen (<tt>-</tt>), a space, and the
3372 short description line from that package.
3376 <sect1 id="f-Distribution">
3377 <heading><tt>Distribution</tt></heading>
3380 In a <file>.changes</file> file or parsed changelog output
3381 this contains the (space-separated) name(s) of the
3382 distribution(s) where this version of the package should
3383 be installed. Valid distributions are determined by the
3384 archive maintainers.<footnote>
3385 Example distribution names in the Debian archive used in
3386 <file>.changes</file> files are:
3387 <taglist compact="compact">
3388 <tag><em>unstable</em></tag>
3390 This distribution value refers to the
3391 <em>developmental</em> part of the Debian distribution
3392 tree. Most new packages, new upstream versions of
3393 packages and bug fixes go into the <em>unstable</em>
3397 <tag><em>experimental</em></tag>
3399 The packages with this distribution value are deemed
3400 by their maintainers to be high risk. Oftentimes they
3401 represent early beta or developmental packages from
3402 various sources that the maintainers want people to
3403 try, but are not ready to be a part of the other parts
3404 of the Debian distribution tree.
3409 Others are used for updating stable releases or for
3410 security uploads. More information is available in the
3411 Debian Developer's Reference, section "The Debian
3415 The Debian archive software only supports listing a single
3416 distribution. Migration of packages to other distributions is
3417 handled outside of the upload process.
3422 <heading><tt>Date</tt></heading>
3425 This field includes the date the package was built or last
3426 edited. It must be in the same format as the <var>date</var>
3427 in a <file>debian/changelog</file> entry.
3431 The value of this field is usually extracted from the
3432 <file>debian/changelog</file> file - see
3433 <ref id="dpkgchangelog">).
3437 <sect1 id="f-Format">
3438 <heading><tt>Format</tt></heading>
3441 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3442 files, this field declares the format version of that file.
3443 The syntax of the field value is the same as that of
3444 a <qref id="f-Version">package version number</qref> except
3445 that no epoch or Debian revision is allowed. The format
3446 described in this document is <tt>&changesversion;</tt>.
3450 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3451 Debian source control</qref> files, this field declares the
3452 format of the source package. The field value is used by
3453 programs acting on a source package to interpret the list of
3454 files in the source package and determine how to unpack it.
3455 The syntax of the field value is a numeric major revision, a
3456 period, a numeric minor revision, and then an optional subtype
3457 after whitespace, which if specified is an alphanumeric word
3458 in parentheses. The subtype is optional in the syntax but may
3459 be mandatory for particular source format revisions.
3461 The source formats currently supported by the Debian archive
3462 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3463 and <tt>3.0 (quilt)</tt>.
3468 <sect1 id="f-Urgency">
3469 <heading><tt>Urgency</tt></heading>
3472 This is a description of how important it is to upgrade to
3473 this version from previous ones. It consists of a single
3474 keyword taking one of the values <tt>low</tt>,
3475 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3476 <tt>critical</tt><footnote>
3477 Other urgency values are supported with configuration
3478 changes in the archive software but are not used in Debian.
3479 The urgency affects how quickly a package will be considered
3480 for inclusion into the <tt>testing</tt> distribution and
3481 gives an indication of the importance of any fixes included
3482 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3483 treated as synonymous.
3484 </footnote> (not case-sensitive) followed by an optional
3485 commentary (separated by a space) which is usually in
3486 parentheses. For example:
3489 Urgency: low (HIGH for users of diversions)
3495 The value of this field is usually extracted from the
3496 <file>debian/changelog</file> file - see
3497 <ref id="dpkgchangelog">.
3501 <sect1 id="f-Changes">
3502 <heading><tt>Changes</tt></heading>
3505 This multiline field contains the human-readable changes data, describing
3506 the differences between the last version and the current one.
3510 The first line of the field value (the part on the same line
3511 as <tt>Changes:</tt>) is always empty. The content of the
3512 field is expressed as continuation lines, with each line
3513 indented by at least one space. Blank lines must be
3514 represented by a line consisting only of a space and a full
3519 The value of this field is usually extracted from the
3520 <file>debian/changelog</file> file - see
3521 <ref id="dpkgchangelog">).
3525 Each version's change information should be preceded by a
3526 "title" line giving at least the version, distribution(s)
3527 and urgency, in a human-readable way.
3531 If data from several versions is being returned the entry
3532 for the most recent version should be returned first, and
3533 entries should be separated by the representation of a
3534 blank line (the "title" line may also be followed by the
3535 representation of a blank line).
3539 <sect1 id="f-Binary">
3540 <heading><tt>Binary</tt></heading>
3543 This folded field is a list of binary packages. Its syntax and
3544 meaning varies depending on the control file in which it
3549 When it appears in the <file>.dsc</file> file, it lists binary
3550 packages which a source package can produce, separated by
3552 A space after each comma is conventional.
3553 </footnote>. The source package
3554 does not necessarily produce all of these binary packages for
3555 every architecture. The source control file doesn't contain
3556 details of which architectures are appropriate for which of
3557 the binary packages.
3561 When it appears in a <file>.changes</file> file, it lists the
3562 names of the binary packages being uploaded, separated by
3563 whitespace (not commas).
3567 <sect1 id="f-Installed-Size">
3568 <heading><tt>Installed-Size</tt></heading>
3571 This field appears in the control files of binary packages,
3572 and in the <file>Packages</file> files. It gives an estimate
3573 of the total amount of disk space required to install the
3574 named package. Actual installed size may vary based on block
3575 size, file system properties, or actions taken by package
3580 The disk space is given as the integer value of the estimated
3581 installed size in bytes, divided by 1024 and rounded up.
3585 <sect1 id="f-Files">
3586 <heading><tt>Files</tt></heading>
3589 This field contains a list of files with information about
3590 each one. The exact information and syntax varies with
3595 In all cases, Files is a multiline field. The first line of
3596 the field value (the part on the same line as <tt>Files:</tt>)
3597 is always empty. The content of the field is expressed as
3598 continuation lines, one line per file. Each line must be
3599 indented by one space and contain a number of sub-fields,
3600 separated by spaces, as described below.
3604 In the <file>.dsc</file> file, each line contains the MD5
3605 checksum, size and filename of the tar file and (if
3606 applicable) diff file which make up the remainder of the
3607 source package<footnote>
3608 That is, the parts which are not the <tt>.dsc</tt>.
3609 </footnote>. For example:
3612 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3613 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3615 The exact forms of the filenames are described
3616 in <ref id="pkg-sourcearchives">.
3620 In the <file>.changes</file> file this contains one line per
3621 file being uploaded. Each line contains the MD5 checksum,
3622 size, section and priority and the filename. For example:
3625 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3626 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3627 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3628 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3630 The <qref id="f-Section">section</qref>
3631 and <qref id="f-Priority">priority</qref> are the values of
3632 the corresponding fields in the main source control file. If
3633 no section or priority is specified then <tt>-</tt> should be
3634 used, though section and priority values must be specified for
3635 new packages to be installed properly.
3639 The special value <tt>byhand</tt> for the section in a
3640 <tt>.changes</tt> file indicates that the file in question
3641 is not an ordinary package file and must by installed by
3642 hand by the distribution maintainers. If the section is
3643 <tt>byhand</tt> the priority should be <tt>-</tt>.
3647 If a new Debian revision of a package is being shipped and
3648 no new original source archive is being distributed the
3649 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3650 entry for the original source archive
3651 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3652 but the <file>.changes</file> file should leave it out. In
3653 this case the original source archive on the distribution
3654 site must match exactly, byte-for-byte, the original
3655 source archive which was used to generate the
3656 <file>.dsc</file> file and diff which are being uploaded.</p>
3659 <sect1 id="f-Closes">
3660 <heading><tt>Closes</tt></heading>
3663 A space-separated list of bug report numbers that the upload
3664 governed by the .changes file closes.
3668 <sect1 id="f-Homepage">
3669 <heading><tt>Homepage</tt></heading>
3672 The URL of the web site for this package, preferably (when
3673 applicable) the site from which the original source can be
3674 obtained and any additional upstream documentation or
3675 information may be found. The content of this field is a
3676 simple URL without any surrounding characters such as
3681 <sect1 id="f-Checksums">
3682 <heading><tt>Checksums-Sha1</tt>
3683 and <tt>Checksums-Sha256</tt></heading>
3686 These multiline fields contain a list of files with a checksum and size
3687 for each one. Both <tt>Checksums-Sha1</tt>
3688 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3689 only in the checksum algorithm used: SHA-1
3690 for <tt>Checksums-Sha1</tt> and SHA-256
3691 for <tt>Checksums-Sha256</tt>.
3695 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3696 multiline fields. The first line of the field value (the part
3697 on the same line as <tt>Checksums-Sha1:</tt>
3698 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3699 of the field is expressed as continuation lines, one line per
3700 file. Each line consists of the checksum, a space, the file
3701 size, a space, and the file name. For example (from
3702 a <file>.changes</file> file):
3705 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3706 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3707 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3708 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3710 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3711 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3712 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3713 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3718 In the <file>.dsc</file> file, these fields should list all
3719 files that make up the source package. In
3720 the <file>.changes</file> file, these fields should list all
3721 files being uploaded. The list of files in these fields
3722 must match the list of files in the <tt>Files</tt> field.
3726 <sect1 id="f-DM-Upload-Allowed">
3727 <heading><tt>DM-Upload-Allowed</tt></heading>
3730 Indicates that Debian Maintainers may upload this package to
3731 the Debian archive. The only valid value is <tt>yes</tt>. If
3732 the field <tt>DM-Upload-Allowed: yes</tt> is present in the
3733 source section of the source control file of the most recent
3734 version of a package in unstable or experimental, the Debian
3735 archive will accept uploads of this package signed with a key
3736 in the Debian Maintainer keyring. See the General
3737 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3738 name="Endorse the concept of Debian Maintainers"> for more
3745 <heading>User-defined fields</heading>
3748 Additional user-defined fields may be added to the
3749 source package control file. Such fields will be
3750 ignored, and not copied to (for example) binary or
3751 Debian source control files or upload control files.
3755 If you wish to add additional unsupported fields to
3756 these output files you should use the mechanism
3761 Fields in the main source control information file with
3762 names starting <tt>X</tt>, followed by one or more of
3763 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3764 be copied to the output files. Only the part of the
3765 field name after the hyphen will be used in the output
3766 file. Where the letter <tt>B</tt> is used the field
3767 will appear in binary package control files, where the
3768 letter <tt>S</tt> is used in Debian source control
3769 files and where <tt>C</tt> is used in upload control
3770 (<tt>.changes</tt>) files.
3774 For example, if the main source information control file
3777 XBS-Comment: I stand between the candle and the star.
3779 then the binary and Debian source control files will contain the
3782 Comment: I stand between the candle and the star.
3791 <chapt id="maintainerscripts">
3792 <heading>Package maintainer scripts and installation procedure</heading>
3795 <heading>Introduction to package maintainer scripts</heading>
3798 It is possible to supply scripts as part of a package which
3799 the package management system will run for you when your
3800 package is installed, upgraded or removed.
3804 These scripts are the control information
3805 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3806 and <prgn>postrm</prgn>. They must be proper executable files;
3807 if they are scripts (which is recommended), they must start with
3808 the usual <tt>#!</tt> convention. They should be readable and
3809 executable by anyone, and must not be world-writable.
3813 The package management system looks at the exit status from
3814 these scripts. It is important that they exit with a
3815 non-zero status if there is an error, so that the package
3816 management system can stop its processing. For shell
3817 scripts this means that you <em>almost always</em> need to
3818 use <tt>set -e</tt> (this is usually true when writing shell
3819 scripts, in fact). It is also important, of course, that
3820 they exit with a zero status if everything went well.
3824 Additionally, packages interacting with users
3825 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3826 should install a <prgn>config</prgn> script as a control
3827 information file. See <ref id="maintscriptprompt"> for details.
3831 When a package is upgraded a combination of the scripts from
3832 the old and new packages is called during the upgrade
3833 procedure. If your scripts are going to be at all
3834 complicated you need to be aware of this, and may need to
3835 check the arguments to your scripts.
3839 Broadly speaking the <prgn>preinst</prgn> is called before
3840 (a particular version of) a package is unpacked, and the
3841 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3842 before (a version of) a package is removed and the
3843 <prgn>postrm</prgn> afterwards.
3847 Programs called from maintainer scripts should not normally
3848 have a path prepended to them. Before installation is
3849 started, the package management system checks to see if the
3850 programs <prgn>ldconfig</prgn>,
3851 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3852 and <prgn>update-rc.d</prgn> can be found via the
3853 <tt>PATH</tt> environment variable. Those programs, and any
3854 other program that one would expect to be in the
3855 <tt>PATH</tt>, should thus be invoked without an absolute
3856 pathname. Maintainer scripts should also not reset the
3857 <tt>PATH</tt>, though they might choose to modify it by
3858 prepending or appending package-specific directories. These
3859 considerations really apply to all shell scripts.</p>
3862 <sect id="idempotency">
3863 <heading>Maintainer scripts idempotency</heading>
3866 It is necessary for the error recovery procedures that the
3867 scripts be idempotent. This means that if it is run
3868 successfully, and then it is called again, it doesn't bomb
3869 out or cause any harm, but just ensures that everything is
3870 the way it ought to be. If the first call failed, or
3871 aborted half way through for some reason, the second call
3872 should merely do the things that were left undone the first
3873 time, if any, and exit with a success status if everything
3875 This is so that if an error occurs, the user interrupts
3876 <prgn>dpkg</prgn> or some other unforeseen circumstance
3877 happens you don't leave the user with a badly-broken
3878 package when <prgn>dpkg</prgn> attempts to repeat the
3884 <sect id="controllingterminal">
3885 <heading>Controlling terminal for maintainer scripts</heading>
3888 Maintainer scripts are not guaranteed to run with a controlling
3889 terminal and may not be able to interact with the user. They
3890 must be able to fall back to noninteractive behavior if no
3891 controlling terminal is available. Maintainer scripts that
3892 prompt via a program conforming to the Debian Configuration
3893 Management Specification (see <ref id="maintscriptprompt">) may
3894 assume that program will handle falling back to noninteractive
3899 For high-priority prompts without a reasonable default answer,
3900 maintainer scripts may abort if there is no controlling
3901 terminal. However, this situation should be avoided if at all
3902 possible, since it prevents automated or unattended installs.
3903 In most cases, users will consider this to be a bug in the
3908 <sect id="exitstatus">
3909 <heading>Exit status</heading>
3912 Each script must return a zero exit status for
3913 success, or a nonzero one for failure, since the package
3914 management system looks for the exit status of these scripts
3915 and determines what action to take next based on that datum.
3919 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3924 What follows is a summary of all the ways in which maintainer
3925 scripts may be called along with what facilities those scripts
3926 may rely on being available at that time. Script names preceded
3927 by <var>new-</var> are the scripts from the new version of a
3928 package being installed, upgraded to, or downgraded to. Script
3929 names preceded by <var>old-</var> are the scripts from the old
3930 version of a package that is being upgraded from or downgraded
3935 The <prgn>preinst</prgn> script may be called in the following
3938 <tag><var>new-preinst</var> <tt>install</tt></tag>
3939 <tag><var>new-preinst</var> <tt>install</tt>
3940 <var>old-version</var></tag>
3941 <tag><var>new-preinst</var> <tt>upgrade</tt>
3942 <var>old-version</var></tag>
3944 The package will not yet be unpacked, so
3945 the <prgn>preinst</prgn> script cannot rely on any files
3946 included in its package. Only essential packages and
3947 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3948 available. Pre-dependencies will have been configured at
3949 least once, but at the time the <prgn>preinst</prgn> is
3950 called they may only be in an unpacked or "Half-Configured"
3951 state if a previous version of the pre-dependency was
3952 completely configured and has not been removed since then.
3955 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3956 <var>new-version</var></tag>
3958 Called during error handling of an upgrade that failed after
3959 unpacking the new package because the <tt>postrm
3960 upgrade</tt> action failed. The unpacked files may be
3961 partly from the new version or partly missing, so the script
3962 cannot rely on files included in the package. Package
3963 dependencies may not be available. Pre-dependencies will be
3964 at least unpacked following the same rules as above, except
3965 they may be only "Half-Installed" if an upgrade of the
3966 pre-dependency failed.<footnote>
3967 This can happen if the new version of the package no
3968 longer pre-depends on a package that had been partially
3976 The <prgn>postinst</prgn> script may be called in the following
3979 <tag><var>postinst</var> <tt>configure</tt>
3980 <var>most-recently-configured-version</var></tag>
3982 The files contained in the package will be unpacked. All
3983 package dependencies will at least be unpacked. If there
3984 are no circular dependencies involved, all package
3985 dependencies will be configured. For behavior in the case
3986 of circular dependencies, see the discussion
3987 in <ref id="binarydeps">.
3990 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3991 <var>new-version</var></tag>
3992 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3993 <tt>in-favour</tt> <var>package</var>
3994 <var>new-version</var></tag>
3995 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3996 <tag><var>deconfigured's-postinst</var>
3997 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3998 <var>failed-install-package</var> <var>version</var>
3999 [<tt>removing</tt> <var>conflicting-package</var>
4000 <var>version</var>]</tag>
4002 The files contained in the package will be unpacked. All
4003 package dependencies will at least be "Half-Installed" and
4004 will have previously been configured and not removed.
4005 However, dependencies may not be configured or even fully
4006 unpacked in some error situations.<footnote>
4007 For example, suppose packages foo and bar are installed
4008 with foo depending on bar. If an upgrade of bar were
4009 started and then aborted, and then an attempt to remove
4010 foo failed because its <prgn>prerm</prgn> script failed,
4011 foo's <tt>postinst abort-remove</tt> would be called with
4012 bar only "Half-Installed".
4014 The <prgn>postinst</prgn> should still attempt any actions
4015 for which its dependencies are required, since they will
4016 normally be available, but consider the correct error
4017 handling approach if those actions fail. Aborting
4018 the <prgn>postinst</prgn> action if commands or facilities
4019 from the package dependencies are not available is often the
4026 The <prgn>prerm</prgn> script may be called in the following
4029 <tag><var>prerm</var> <tt>remove</tt></tag>
4030 <tag><var>old-prerm</var>
4031 <tt>upgrade</tt><var>new-version</var></tag>
4032 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4033 <tt>in-favour</tt> <var>package</var>
4034 <var>new-version</var></tag>
4035 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4036 <tt>in-favour</tt> <var>package-being-installed</var>
4037 <var>version</var> [<tt>removing</tt>
4038 <var>conflicting-package</var> <var>version</var>]</tag>
4040 The package whose <prgn>prerm</prgn> is being called will be
4041 at least "Half-Installed". All package dependencies will at
4042 least be "Half-Installed" and will have previously been
4043 configured and not removed. If there was no error, all
4044 dependencies will at least be unpacked, but these actions
4045 may be called in various error states where dependencies are
4046 only "Half-Installed" due to a partial upgrade.
4049 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4050 <var>old-version</var></tag>
4052 Called during error handling when <tt>prerm upgrade</tt>
4053 fails. The new package will not yet be unpacked, and all
4054 the same constraints as for <tt>preinst upgrade</tt> apply.
4060 The <prgn>postrm</prgn> script may be called in the following
4063 <tag><var>postrm</var> <tt>remove</tt></tag>
4064 <tag><var>postrm</var> <tt>purge</tt></tag>
4065 <tag><var>old-postrm</var> <tt>upgrade</tt>
4066 <var>new-version</var></tag>
4067 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4068 <var>overwriter</var> <var>overwriter-version</var></tag>
4070 The <prgn>postrm</prgn> script is called after the package's
4071 files have been removed or replaced. The package
4072 whose <prgn>postrm</prgn> is being called may have
4073 previously been deconfigured and only be unpacked, at which
4074 point subsequent package changes do not consider its
4075 dependencies. Therefore, all <prgn>postrm</prgn> actions
4076 may only rely on essential packages and must gracefully skip
4077 any actions that require the package's dependencies if those
4078 dependencies are unavailable.<footnote>
4079 This is often done by checking whether the command or
4080 facility the <prgn>postrm</prgn> intends to call is
4081 available before calling it. For example:
4083 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4084 . /usr/share/debconf/confmodule
4088 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4089 configuration for the package
4090 if <package>debconf</package> is installed.
4094 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4095 <var>old-version</var></tag>
4097 Called when the old <tt>postrm upgrade</tt> action fails.
4098 The new package will be unpacked, but only essential
4099 packages and pre-dependencies can be relied on.
4100 Pre-dependencies will either be configured or will be
4101 "Unpacked" or "Half-Configured" but previously had been
4102 configured and was never removed.
4105 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4106 <tag><var>new-postrm</var> <tt>abort-install</tt>
4107 <var>old-version</var></tag>
4108 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4109 <var>old-version</var></tag>
4111 Called before unpacking the new package as part of the
4112 error handling of <prgn>preinst</prgn> failures. May assume
4113 the same state as <prgn>preinst</prgn> can assume.
4119 <sect id="unpackphase">
4120 <heading>Details of unpack phase of installation or upgrade</heading>
4123 The procedure on installation/upgrade/overwrite/disappear
4124 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4125 stage of <tt>dpkg --install</tt>) is as follows. In each
4126 case, if a major error occurs (unless listed below) the
4127 actions are, in general, run backwards - this means that the
4128 maintainer scripts are run with different arguments in
4129 reverse order. These are the "error unwind" calls listed
4136 If a version of the package is already installed, call
4137 <example compact="compact">
4138 <var>old-prerm</var> upgrade <var>new-version</var>
4142 If the script runs but exits with a non-zero
4143 exit status, <prgn>dpkg</prgn> will attempt:
4144 <example compact="compact">
4145 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4147 If this works, the upgrade continues. If this
4148 does not work, the error unwind:
4149 <example compact="compact">
4150 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4152 If this works, then the old-version is
4153 "Installed", if not, the old version is in a
4154 "Half-Configured" state.
4160 If a "conflicting" package is being removed at the same time,
4161 or if any package will be broken (due to <tt>Breaks</tt>):
4164 If <tt>--auto-deconfigure</tt> is
4165 specified, call, for each package to be deconfigured
4166 due to <tt>Breaks</tt>:
4167 <example compact="compact">
4168 <var>deconfigured's-prerm</var> deconfigure \
4169 in-favour <var>package-being-installed</var> <var>version</var>
4172 <example compact="compact">
4173 <var>deconfigured's-postinst</var> abort-deconfigure \
4174 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4176 The deconfigured packages are marked as
4177 requiring configuration, so that if
4178 <tt>--install</tt> is used they will be
4179 configured again if possible.
4182 If any packages depended on a conflicting
4183 package being removed and <tt>--auto-deconfigure</tt> is
4184 specified, call, for each such package:
4185 <example compact="compact">
4186 <var>deconfigured's-prerm</var> deconfigure \
4187 in-favour <var>package-being-installed</var> <var>version</var> \
4188 removing <var>conflicting-package</var> <var>version</var>
4191 <example compact="compact">
4192 <var>deconfigured's-postinst</var> abort-deconfigure \
4193 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4194 removing <var>conflicting-package</var> <var>version</var>
4196 The deconfigured packages are marked as
4197 requiring configuration, so that if
4198 <tt>--install</tt> is used they will be
4199 configured again if possible.
4202 To prepare for removal of each conflicting package, call:
4203 <example compact="compact">
4204 <var>conflictor's-prerm</var> remove \
4205 in-favour <var>package</var> <var>new-version</var>
4208 <example compact="compact">
4209 <var>conflictor's-postinst</var> abort-remove \
4210 in-favour <var>package</var> <var>new-version</var>
4219 If the package is being upgraded, call:
4220 <example compact="compact">
4221 <var>new-preinst</var> upgrade <var>old-version</var>
4223 If this fails, we call:
4225 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4232 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4234 is called. If this works, then the old version
4235 is in an "Installed" state, or else it is left
4236 in an "Unpacked" state.
4241 If it fails, then the old version is left
4242 in an "Half-Installed" state.
4249 Otherwise, if the package had some configuration
4250 files from a previous version installed (i.e., it
4251 is in the "configuration files only" state):
4252 <example compact="compact">
4253 <var>new-preinst</var> install <var>old-version</var>
4257 <var>new-postrm</var> abort-install <var>old-version</var>
4259 If this fails, the package is left in a
4260 "Half-Installed" state, which requires a
4261 reinstall. If it works, the packages is left in
4262 a "Config-Files" state.
4265 Otherwise (i.e., the package was completely purged):
4266 <example compact="compact">
4267 <var>new-preinst</var> install
4270 <example compact="compact">
4271 <var>new-postrm</var> abort-install
4273 If the error-unwind fails, the package is in a
4274 "Half-Installed" phase, and requires a
4275 reinstall. If the error unwind works, the
4276 package is in a not installed state.
4283 The new package's files are unpacked, overwriting any
4284 that may be on the system already, for example any
4285 from the old version of the same package or from
4286 another package. Backups of the old files are kept
4287 temporarily, and if anything goes wrong the package
4288 management system will attempt to put them back as
4289 part of the error unwind.
4293 It is an error for a package to contain files which
4294 are on the system in another package, unless
4295 <tt>Replaces</tt> is used (see <ref id="replaces">).
4297 The following paragraph is not currently the case:
4298 Currently the <tt>- - force-overwrite</tt> flag is
4299 enabled, downgrading it to a warning, but this may not
4305 It is a more serious error for a package to contain a
4306 plain file or other kind of non-directory where another
4307 package has a directory (again, unless
4308 <tt>Replaces</tt> is used). This error can be
4309 overridden if desired using
4310 <tt>--force-overwrite-dir</tt>, but this is not
4315 Packages which overwrite each other's files produce
4316 behavior which, though deterministic, is hard for the
4317 system administrator to understand. It can easily
4318 lead to "missing" programs if, for example, a package
4319 is unpacked which overwrites a file from another
4320 package, and is then removed again.<footnote>
4321 Part of the problem is due to what is arguably a
4322 bug in <prgn>dpkg</prgn>.
4327 A directory will never be replaced by a symbolic link
4328 to a directory or vice versa; instead, the existing
4329 state (symlink or not) will be left alone and
4330 <prgn>dpkg</prgn> will follow the symlink if there is
4339 If the package is being upgraded, call
4340 <example compact="compact">
4341 <var>old-postrm</var> upgrade <var>new-version</var>
4345 If this fails, <prgn>dpkg</prgn> will attempt:
4346 <example compact="compact">
4347 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4349 If this works, installation continues. If not,
4351 <example compact="compact">
4352 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4354 If this fails, the old version is left in a
4355 "Half-Installed" state. If it works, dpkg now
4357 <example compact="compact">
4358 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4360 If this fails, the old version is left in a
4361 "Half-Installed" state. If it works, dpkg now
4363 <example compact="compact">
4364 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4366 If this fails, the old version is in an
4373 This is the point of no return - if
4374 <prgn>dpkg</prgn> gets this far, it won't back off
4375 past this point if an error occurs. This will
4376 leave the package in a fairly bad state, which
4377 will require a successful re-installation to clear
4378 up, but it's when <prgn>dpkg</prgn> starts doing
4379 things that are irreversible.
4384 Any files which were in the old version of the package
4385 but not in the new are removed.
4389 The new file list replaces the old.
4393 The new maintainer scripts replace the old.
4397 Any packages all of whose files have been overwritten
4398 during the installation, and which aren't required for
4399 dependencies, are considered to have been removed.
4400 For each such package
4403 <prgn>dpkg</prgn> calls:
4404 <example compact="compact">
4405 <var>disappearer's-postrm</var> disappear \
4406 <var>overwriter</var> <var>overwriter-version</var>
4410 The package's maintainer scripts are removed.
4413 It is noted in the status database as being in a
4414 sane state, namely not installed (any conffiles
4415 it may have are ignored, rather than being
4416 removed by <prgn>dpkg</prgn>). Note that
4417 disappearing packages do not have their prerm
4418 called, because <prgn>dpkg</prgn> doesn't know
4419 in advance that the package is going to
4426 Any files in the package we're unpacking that are also
4427 listed in the file lists of other packages are removed
4428 from those lists. (This will lobotomize the file list
4429 of the "conflicting" package if there is one.)
4433 The backup files made during installation, above, are
4439 The new package's status is now sane, and recorded as
4444 Here is another point of no return - if the
4445 conflicting package's removal fails we do not unwind
4446 the rest of the installation; the conflicting package
4447 is left in a half-removed limbo.
4452 If there was a conflicting package we go and do the
4453 removal actions (described below), starting with the
4454 removal of the conflicting package's files (any that
4455 are also in the package being unpacked have already
4456 been removed from the conflicting package's file list,
4457 and so do not get removed now).
4463 <sect id="configdetails"><heading>Details of configuration</heading>
4466 When we configure a package (this happens with <tt>dpkg
4467 --install</tt> and <tt>dpkg --configure</tt>), we first
4468 update any <tt>conffile</tt>s and then call:
4469 <example compact="compact">
4470 <var>postinst</var> configure <var>most-recently-configured-version</var>
4475 No attempt is made to unwind after errors during
4476 configuration. If the configuration fails, the package is in
4477 a "Failed Config" state, and an error message is generated.
4481 If there is no most recently configured version
4482 <prgn>dpkg</prgn> will pass a null argument.
4485 Historical note: Truly ancient (pre-1997) versions of
4486 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4487 (including the angle brackets) in this case. Even older
4488 ones did not pass a second argument at all, under any
4489 circumstance. Note that upgrades using such an old dpkg
4490 version are unlikely to work for other reasons, even if
4491 this old argument behavior is handled by your postinst script.
4497 <sect id="removedetails"><heading>Details of removal and/or
4498 configuration purging</heading>
4504 <example compact="compact">
4505 <var>prerm</var> remove
4509 If prerm fails during replacement due to conflict
4511 <var>conflictor's-postinst</var> abort-remove \
4512 in-favour <var>package</var> <var>new-version</var>
4516 <var>postinst</var> abort-remove
4520 If this fails, the package is in a "Half-Configured"
4521 state, or else it remains "Installed".
4525 The package's files are removed (except <tt>conffile</tt>s).
4528 <example compact="compact">
4529 <var>postrm</var> remove
4533 If it fails, there's no error unwind, and the package is in
4534 an "Half-Installed" state.
4539 All the maintainer scripts except the <prgn>postrm</prgn>
4544 If we aren't purging the package we stop here. Note
4545 that packages which have no <prgn>postrm</prgn> and no
4546 <tt>conffile</tt>s are automatically purged when
4547 removed, as there is no difference except for the
4548 <prgn>dpkg</prgn> status.
4552 The <tt>conffile</tt>s and any backup files
4553 (<tt>~</tt>-files, <tt>#*#</tt> files,
4554 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4559 <example compact="compact">
4560 <var>postrm</var> purge
4564 If this fails, the package remains in a "Config-Files"
4569 The package's file list is removed.
4578 <chapt id="relationships">
4579 <heading>Declaring relationships between packages</heading>
4581 <sect id="depsyntax">
4582 <heading>Syntax of relationship fields</heading>
4585 These fields all have a uniform syntax. They are a list of
4586 package names separated by commas.
4590 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4591 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4592 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4593 control fields of the package, which declare
4594 dependencies on other packages, the package names listed may
4595 also include lists of alternative package names, separated
4596 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4597 if any one of the alternative packages is installed, that
4598 part of the dependency is considered to be satisfied.
4602 All of the fields except for <tt>Provides</tt> may restrict
4603 their applicability to particular versions of each named
4604 package. This is done in parentheses after each individual
4605 package name; the parentheses should contain a relation from
4606 the list below followed by a version number, in the format
4607 described in <ref id="f-Version">.
4611 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4612 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for strictly
4613 earlier, earlier or equal, exactly equal, later or equal and
4614 strictly later, respectively. The deprecated
4615 forms <tt><</tt> and <tt>></tt> were confusingly used to
4616 mean earlier/later or equal, rather than strictly earlier/later,
4617 and must not appear in new packages (though <prgn>dpkg</prgn>
4618 still supports them with a warning).
4622 Whitespace may appear at any point in the version
4623 specification subject to the rules in <ref
4624 id="controlsyntax">, and must appear where it's necessary to
4625 disambiguate; it is not otherwise significant. All of the
4626 relationship fields can only be folded in source package control files. For
4627 consistency and in case of future changes to
4628 <prgn>dpkg</prgn> it is recommended that a single space be
4629 used after a version relationship and before a version
4630 number; it is also conventional to put a single space after
4631 each comma, on either side of each vertical bar, and before
4632 each open parenthesis. When opening a continuation line in a relationship field, it
4633 is conventional to do so after a comma and before the space
4634 following that comma.
4638 For example, a list of dependencies might appear as:
4639 <example compact="compact">
4642 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4647 Relationships may be restricted to a certain set of
4648 architectures. This is indicated in brackets after each
4649 individual package name and the optional version specification.
4650 The brackets enclose a non-empty list of Debian architecture names
4651 in the format described in <ref id="arch-spec">,
4652 separated by whitespace. Exclamation marks may be prepended to
4653 each of the names. (It is not permitted for some names to be
4654 prepended with exclamation marks while others aren't.)
4658 For build relationship fields
4659 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4660 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4661 the current Debian host architecture is not in this list and
4662 there are no exclamation marks in the list, or it is in the list
4663 with a prepended exclamation mark, the package name and the
4664 associated version specification are ignored completely for the
4665 purposes of defining the relationships.
4670 <example compact="compact">
4672 Build-Depends-Indep: texinfo
4673 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4674 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4676 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4677 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4678 <tt>gnumach-dev</tt> only on hurd-i386.
4682 For binary relationship fields and the <tt>Built-Using</tt>
4683 field, the architecture restriction
4684 syntax is only supported in the source package control
4685 file <file>debian/control</file>. When the corresponding binary
4686 package control file is generated, the relationship will either
4687 be omitted or included without the architecture restriction
4688 based on the architecture of the binary package. This means
4689 that architecture restrictions must not be used in binary
4690 relationship fields for architecture-independent packages
4691 (<tt>Architecture: all</tt>).
4696 <example compact="compact">
4697 Depends: foo [i386], bar [amd64]
4699 becomes <tt>Depends: foo</tt> when the package is built on
4700 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4701 package is built on the <tt>amd64</tt> architecture, and omitted
4702 entirely in binary packages built on all other architectures.
4706 If the architecture-restricted dependency is part of a set of
4707 alternatives using <tt>|</tt>, that alternative is ignored
4708 completely on architectures that do not match the restriction.
4710 <example compact="compact">
4711 Build-Depends: foo [!i386] | bar [!amd64]
4713 is equivalent to <tt>bar</tt> on the i386 architecture, to
4714 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4715 bar</tt> on all other architectures.
4719 Relationships may also be restricted to a certain set of
4720 architectures using architecture wildcards in the format
4721 described in <ref id="arch-wildcard-spec">. The syntax for
4722 declaring such restrictions is the same as declaring
4723 restrictions using a certain set of architectures without
4724 architecture wildcards. For example:
4725 <example compact="compact">
4726 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4728 is equivalent to <tt>foo</tt> on architectures using the Linux
4729 kernel and any cpu, <tt>bar</tt> on architectures using any
4730 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4731 using a kernel other than Linux.
4735 Note that the binary package relationship fields such as
4736 <tt>Depends</tt> appear in one of the binary package
4737 sections of the control file, whereas the build-time
4738 relationships such as <tt>Build-Depends</tt> appear in the
4739 source package section of the control file (which is the
4744 <sect id="binarydeps">
4745 <heading>Binary Dependencies - <tt>Depends</tt>,
4746 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4747 <tt>Pre-Depends</tt>
4751 Packages can declare in their control file that they have
4752 certain relationships to other packages - for example, that
4753 they may not be installed at the same time as certain other
4754 packages, and/or that they depend on the presence of others.
4758 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4759 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4760 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4761 <tt>Breaks</tt> is described in <ref id="breaks">, and
4762 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4763 rest are described below.
4767 These seven fields are used to declare a dependency
4768 relationship by one package on another. Except for
4769 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4770 depending (binary) package's control file.
4771 (<tt>Enhances</tt> appears in the recommending package's
4772 control file, and <tt>Breaks</tt> appears in the version of
4773 depended-on package which causes the named package to
4778 A <tt>Depends</tt> field takes effect <em>only</em> when a
4779 package is to be configured. It does not prevent a package
4780 being on the system in an unconfigured state while its
4781 dependencies are unsatisfied, and it is possible to replace
4782 a package whose dependencies are satisfied and which is
4783 properly installed with a different version whose
4784 dependencies are not and cannot be satisfied; when this is
4785 done the depending package will be left unconfigured (since
4786 attempts to configure it will give errors) and will not
4787 function properly. If it is necessary, a
4788 <tt>Pre-Depends</tt> field can be used, which has a partial
4789 effect even when a package is being unpacked, as explained
4790 in detail below. (The other three dependency fields,
4791 <tt>Recommends</tt>, <tt>Suggests</tt> and
4792 <tt>Enhances</tt>, are only used by the various front-ends
4793 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4794 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4798 Since <tt>Depends</tt> only places requirements on the order in
4799 which packages are configured, packages in an installation run
4800 are usually all unpacked first and all configured later.
4802 This approach makes dependency resolution easier. If two
4803 packages A and B are being upgraded, the installed package A
4804 depends on exactly the installed package B, and the new
4805 package A depends on exactly the new package B (a common
4806 situation when upgrading shared libraries and their
4807 corresponding development packages), satisfying the
4808 dependencies at every stage of the upgrade would be
4809 impossible. This relaxed restriction means that both new
4810 packages can be unpacked together and then configured in their
4816 If there is a circular dependency among packages being installed
4817 or removed, installation or removal order honoring the
4818 dependency order is impossible, requiring the dependency loop be
4819 broken at some point and the dependency requirements violated
4820 for at least one package. Packages involved in circular
4821 dependencies may not be able to rely on their dependencies being
4822 configured before they themselves are configured, depending on
4823 which side of the break of the circular dependency loop they
4824 happen to be on. If one of the packages in the loop has
4825 no <prgn>postinst</prgn> script, then the cycle will be broken
4826 at that package; this ensures that all <prgn>postinst</prgn>
4827 scripts are run with their dependencies properly configured if
4828 this is possible. Otherwise the breaking point is arbitrary.
4829 Packages should therefore avoid circular dependencies where
4830 possible, particularly if they have <prgn>postinst</prgn>
4835 The meaning of the five dependency fields is as follows:
4837 <tag><tt>Depends</tt></tag>
4840 This declares an absolute dependency. A package will
4841 not be configured unless all of the packages listed in
4842 its <tt>Depends</tt> field have been correctly
4843 configured (unless there is a circular dependency as
4848 The <tt>Depends</tt> field should be used if the
4849 depended-on package is required for the depending
4850 package to provide a significant amount of
4855 The <tt>Depends</tt> field should also be used if the
4856 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4857 require the depended-on package to be unpacked or
4858 configured in order to run. In the case of <tt>postinst
4859 configure</tt>, the depended-on packages will be unpacked
4860 and configured first. (If both packages are involved in a
4861 dependency loop, this might not work as expected; see the
4862 explanation a few paragraphs back.) In the case
4863 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4864 actions, the package dependencies will normally be at
4865 least unpacked, but they may be only "Half-Installed" if a
4866 previous upgrade of the dependency failed.
4870 Finally, the <tt>Depends</tt> field should be used if the
4871 depended-on package is needed by the <prgn>postrm</prgn>
4872 script to fully clean up after the package removal. There
4873 is no guarantee that package dependencies will be
4874 available when <prgn>postrm</prgn> is run, but the
4875 depended-on package is more likely to be available if the
4876 package declares a dependency (particularly in the case
4877 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4878 script must gracefully skip actions that require a
4879 dependency if that dependency isn't available.
4883 <tag><tt>Recommends</tt></tag>
4886 This declares a strong, but not absolute, dependency.
4890 The <tt>Recommends</tt> field should list packages
4891 that would be found together with this one in all but
4892 unusual installations.
4896 <tag><tt>Suggests</tt></tag>
4898 This is used to declare that one package may be more
4899 useful with one or more others. Using this field
4900 tells the packaging system and the user that the
4901 listed packages are related to this one and can
4902 perhaps enhance its usefulness, but that installing
4903 this one without them is perfectly reasonable.
4906 <tag><tt>Enhances</tt></tag>
4908 This field is similar to Suggests but works in the
4909 opposite direction. It is used to declare that a
4910 package can enhance the functionality of another
4914 <tag><tt>Pre-Depends</tt></tag>
4917 This field is like <tt>Depends</tt>, except that it
4918 also forces <prgn>dpkg</prgn> to complete installation
4919 of the packages named before even starting the
4920 installation of the package which declares the
4921 pre-dependency, as follows:
4925 When a package declaring a pre-dependency is about to
4926 be <em>unpacked</em> the pre-dependency can be
4927 satisfied if the depended-on package is either fully
4928 configured, <em>or even if</em> the depended-on
4929 package(s) are only unpacked or in the "Half-Configured"
4930 state, provided that they have been configured
4931 correctly at some point in the past (and not removed
4932 or partially removed since). In this case, both the
4933 previously-configured and currently unpacked or
4934 "Half-Configured" versions must satisfy any version
4935 clause in the <tt>Pre-Depends</tt> field.
4939 When the package declaring a pre-dependency is about to
4940 be <em>configured</em>, the pre-dependency will be treated
4941 as a normal <tt>Depends</tt>. It will be considered
4942 satisfied only if the depended-on package has been
4943 correctly configured. However, unlike
4944 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4945 permit circular dependencies to be broken. If a circular
4946 dependency is encountered while attempting to honor
4947 <tt>Pre-Depends</tt>, the installation will be aborted.
4951 <tt>Pre-Depends</tt> are also required if the
4952 <prgn>preinst</prgn> script depends on the named package.
4953 It is best to avoid this situation if possible.
4957 <tt>Pre-Depends</tt> should be used sparingly,
4958 preferably only by packages whose premature upgrade or
4959 installation would hamper the ability of the system to
4960 continue with any upgrade that might be in progress.
4964 You should not specify a <tt>Pre-Depends</tt> entry for a
4965 package before this has been discussed on the
4966 <tt>debian-devel</tt> mailing list and a consensus about
4967 doing that has been reached. See <ref id="dependencies">.
4974 When selecting which level of dependency to use you should
4975 consider how important the depended-on package is to the
4976 functionality of the one declaring the dependency. Some
4977 packages are composed of components of varying degrees of
4978 importance. Such a package should list using
4979 <tt>Depends</tt> the package(s) which are required by the
4980 more important components. The other components'
4981 requirements may be mentioned as Suggestions or
4982 Recommendations, as appropriate to the components' relative
4988 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4991 When one binary package declares that it breaks another,
4992 <prgn>dpkg</prgn> will refuse to allow the package which
4993 declares <tt>Breaks</tt> to be unpacked unless the broken
4994 package is deconfigured first, and it will refuse to
4995 allow the broken package to be reconfigured.
4999 A package will not be regarded as causing breakage merely
5000 because its configuration files are still installed; it must
5001 be at least "Half-Installed".
5005 A special exception is made for packages which declare that
5006 they break their own package name or a virtual package which
5007 they provide (see below): this does not count as a real
5012 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5013 version clause; such a <tt>Breaks</tt> is introduced in the
5014 version of an (implicit or explicit) dependency which violates
5015 an assumption or reveals a bug in earlier versions of the broken
5016 package, or which takes over a file from earlier versions of the
5017 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5018 will inform higher-level package management tools that the
5019 broken package must be upgraded before the new one.
5023 If the breaking package also overwrites some files from the
5024 older package, it should use <tt>Replaces</tt> to ensure this
5025 goes smoothly. See <ref id="replaces"> for a full discussion
5026 of taking over files from other packages, including how to
5027 use <tt>Breaks</tt> in those cases.
5031 Many of the cases where <tt>Breaks</tt> should be used were
5032 previously handled with <tt>Conflicts</tt>
5033 because <tt>Breaks</tt> did not yet exist.
5034 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5035 See <ref id="conflicts"> for more information about the
5040 <sect id="conflicts">
5041 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5044 When one binary package declares a conflict with another using
5045 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5046 allow them to be unpacked on the system at the same time. This
5047 is a stronger restriction than <tt>Breaks</tt>, which prevents
5048 the broken package from being configured while the breaking
5049 package is in the "Unpacked" state but allows both packages to
5050 be unpacked at the same time.
5054 If one package is to be unpacked, the other must be removed
5055 first. If the package being unpacked is marked as replacing
5056 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5057 normally be used in this case) the one on the system, or the one
5058 on the system is marked as deselected, or both packages are
5059 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5060 automatically remove the package which is causing the conflict.
5061 Otherwise, it will halt the installation of the new package with
5062 an error. This mechanism is specifically designed to produce an
5063 error when the installed package is <tt>Essential</tt>, but the
5068 A package will not cause a conflict merely because its
5069 configuration files are still installed; it must be at least
5074 A special exception is made for packages which declare a
5075 conflict with their own package name, or with a virtual
5076 package which they provide (see below): this does not
5077 prevent their installation, and allows a package to conflict
5078 with others providing a replacement for it. You use this
5079 feature when you want the package in question to be the only
5080 package providing some feature.
5084 Normally, <tt>Breaks</tt> should be used instead
5085 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5086 stronger restriction on the ordering of package installation or
5087 upgrade and can make it more difficult for the package manager
5088 to find a correct solution to an upgrade or installation
5089 problem. <tt>Breaks</tt> should be used
5091 <item>when moving a file from one package to another (see
5092 <ref id="replaces">),</item>
5093 <item>when splitting a package (a special case of the previous
5095 <item>when the breaking package exposes a bug in or interacts
5096 badly with particular versions of the broken
5099 <tt>Conflicts</tt> should be used
5101 <item>when two packages provide the same file and will
5102 continue to do so,</item>
5103 <item>in conjunction with <tt>Provides</tt> when only one
5104 package providing a given virtual facility may be unpacked
5105 at a time (see <ref id="virtual">),</item>
5106 <item>in other cases where one must prevent simultaneous
5107 installation of two packages for reasons that are ongoing
5108 (not fixed in a later version of one of the packages) or
5109 that must prevent both packages from being unpacked at the
5110 same time, not just configured.</item>
5112 Be aware that adding <tt>Conflicts</tt> is normally not the best
5113 solution when two packages provide the same files. Depending on
5114 the reason for that conflict, using alternatives or renaming the
5115 files is often a better approach. See, for
5116 example, <ref id="binaries">.
5120 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5121 unless two packages cannot be installed at the same time or
5122 installing them both causes one of them to be broken or
5123 unusable. Having similar functionality or performing the same
5124 tasks as another package is not sufficient reason to
5125 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5129 A <tt>Conflicts</tt> entry may have an "earlier than" version
5130 clause if the reason for the conflict is corrected in a later
5131 version of one of the packages. However, normally the presence
5132 of an "earlier than" version clause is a sign
5133 that <tt>Breaks</tt> should have been used instead. An "earlier
5134 than" version clause in <tt>Conflicts</tt>
5135 prevents <prgn>dpkg</prgn> from upgrading or installing the
5136 package which declares such a conflict until the upgrade or
5137 removal of the conflicted-with package has been completed, which
5138 is a strong restriction.
5142 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5146 As well as the names of actual ("concrete") packages, the
5147 package relationship fields <tt>Depends</tt>,
5148 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5149 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5150 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5151 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5152 may mention "virtual packages".
5156 A <em>virtual package</em> is one which appears in the
5157 <tt>Provides</tt> control field of another package. The effect
5158 is as if the package(s) which provide a particular virtual
5159 package name had been listed by name everywhere the virtual
5160 package name appears. (See also <ref id="virtual_pkg">)
5164 If there are both concrete and virtual packages of the same
5165 name, then the dependency may be satisfied (or the conflict
5166 caused) by either the concrete package with the name in
5167 question or any other concrete package which provides the
5168 virtual package with the name in question. This is so that,
5169 for example, supposing we have
5170 <example compact="compact">
5173 </example> and someone else releases an enhanced version of
5174 the <tt>bar</tt> package they can say:
5175 <example compact="compact">
5179 and the <tt>bar-plus</tt> package will now also satisfy the
5180 dependency for the <tt>foo</tt> package.
5184 If a relationship field has a version number attached, only real
5185 packages will be considered to see whether the relationship is
5186 satisfied (or the prohibition violated, for a conflict or
5187 breakage). In other words, if a version number is specified,
5188 this is a request to ignore all <tt>Provides</tt> for that
5189 package name and consider only real packages. The package
5190 manager will assume that a package providing that virtual
5191 package is not of the "right" version. A <tt>Provides</tt>
5192 field may not contain version numbers, and the version number of
5193 the concrete package which provides a particular virtual package
5194 will not be considered when considering a dependency on or
5195 conflict with the virtual package name.<footnote>
5196 It is possible that a future release of <prgn>dpkg</prgn> may
5197 add the ability to specify a version number for each virtual
5198 package it provides. This feature is not yet present,
5199 however, and is expected to be used only infrequently.
5204 To specify which of a set of real packages should be the default
5205 to satisfy a particular dependency on a virtual package, list
5206 the real package as an alternative before the virtual one.
5210 If the virtual package represents a facility that can only be
5211 provided by one real package at a time, such as
5212 the <package>mail-transport-agent</package> virtual package that
5213 requires installation of a binary that would conflict with all
5214 other providers of that virtual package (see
5215 <ref id="mail-transport-agents">), all packages providing that
5216 virtual package should also declare a conflict with it
5217 using <tt>Conflicts</tt>. This will ensure that at most one
5218 provider of that virtual package is unpacked or installed at a
5223 <sect id="replaces"><heading>Overwriting files and replacing
5224 packages - <tt>Replaces</tt></heading>
5227 Packages can declare in their control file that they should
5228 overwrite files in certain other packages, or completely replace
5229 other packages. The <tt>Replaces</tt> control field has these
5230 two distinct purposes.
5233 <sect1><heading>Overwriting files in other packages</heading>
5236 It is usually an error for a package to contain files which
5237 are on the system in another package. However, if the
5238 overwriting package declares that it <tt>Replaces</tt> the one
5239 containing the file being overwritten, then <prgn>dpkg</prgn>
5240 will replace the file from the old package with that from the
5241 new. The file will no longer be listed as "owned" by the old
5242 package and will be taken over by the new package.
5243 Normally, <tt>Breaks</tt> should be used in conjunction
5244 with <tt>Replaces</tt>.<footnote>
5245 To see why <tt>Breaks</tt> is normally needed in addition
5246 to <tt>Replaces</tt>, consider the case of a file in the
5247 package <package>foo</package> being taken over by the
5248 package <package>foo-data</package>.
5249 <tt>Replaces</tt> will allow <package>foo-data</package> to
5250 be installed and take over that file. However,
5251 without <tt>Breaks</tt>, nothing
5252 requires <package>foo</package> to be upgraded to a newer
5253 version that knows it does not include that file and instead
5254 depends on <package>foo-data</package>. Nothing would
5255 prevent the new <package>foo-data</package> package from
5256 being installed and then removed, removing the file that it
5257 took over from <package>foo</package>. After that
5258 operation, the package manager would think the system was in
5259 a consistent state, but the <package>foo</package> package
5260 would be missing one of its files.
5265 For example, if a package <package>foo</package> is split
5266 into <package>foo</package> and <package>foo-data</package>
5267 starting at version 1.2-3, <package>foo-data</package> would
5269 <example compact="compact">
5270 Replaces: foo (<< 1.2-3)
5271 Breaks: foo (<< 1.2-3)
5273 in its control file. The new version of the
5274 package <package>foo</package> would normally have the field
5275 <example compact="compact">
5276 Depends: foo-data (>= 1.2-3)
5278 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5279 the files moved into <package>foo-data</package> are not
5280 required for normal operation).
5284 If a package is completely replaced in this way, so that
5285 <prgn>dpkg</prgn> does not know of any files it still
5286 contains, it is considered to have "disappeared". It will
5287 be marked as not wanted on the system (selected for
5288 removal) and not installed. Any <tt>conffile</tt>s
5289 details noted for the package will be ignored, as they
5290 will have been taken over by the overwriting package. The
5291 package's <prgn>postrm</prgn> script will be run with a
5292 special argument to allow the package to do any final
5293 cleanup required. See <ref id="mscriptsinstact">.
5295 Replaces is a one way relationship. You have to install
5296 the replacing package after the replaced package.
5301 For this usage of <tt>Replaces</tt>, virtual packages (see
5302 <ref id="virtual">) are not considered when looking at a
5303 <tt>Replaces</tt> field. The packages declared as being
5304 replaced must be mentioned by their real names.
5308 This usage of <tt>Replaces</tt> only takes effect when both
5309 packages are at least partially on the system at once. It is
5310 not relevant if the packages conflict unless the conflict has
5315 <sect1><heading>Replacing whole packages, forcing their
5319 Second, <tt>Replaces</tt> allows the packaging system to
5320 resolve which package should be removed when there is a
5321 conflict (see <ref id="conflicts">). This usage only takes
5322 effect when the two packages <em>do</em> conflict, so that the
5323 two usages of this field do not interfere with each other.
5327 In this situation, the package declared as being replaced
5328 can be a virtual package, so for example, all mail
5329 transport agents (MTAs) would have the following fields in
5330 their control files:
5331 <example compact="compact">
5332 Provides: mail-transport-agent
5333 Conflicts: mail-transport-agent
5334 Replaces: mail-transport-agent
5336 ensuring that only one MTA can be unpacked at any one
5337 time. See <ref id="virtual"> for more information about this
5342 <sect id="sourcebinarydeps">
5343 <heading>Relationships between source and binary packages -
5344 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5345 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5349 Source packages that require certain binary packages to be
5350 installed or absent at the time of building the package
5351 can declare relationships to those binary packages.
5355 This is done using the <tt>Build-Depends</tt>,
5356 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5357 <tt>Build-Conflicts-Indep</tt> control fields.
5361 Build-dependencies on "build-essential" binary packages can be
5362 omitted. Please see <ref id="pkg-relations"> for more information.
5366 The dependencies and conflicts they define must be satisfied
5367 (as defined earlier for binary packages) in order to invoke
5368 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5370 There is no Build-Depends-Arch; this role is essentially
5371 met with Build-Depends. Anyone building the
5372 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5373 assumed to be building the whole package, and therefore
5374 installation of all build dependencies is required.
5377 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5378 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5379 not yet know how to check for its existence, and
5380 <tt>binary-arch</tt>. The purpose of the original split
5381 between <tt>Build-Depends</tt> and
5382 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5383 wouldn't need to install extra packages needed only for the
5384 binary-indep targets. But without a build-arch/build-indep
5385 split, this didn't work, since most of the work is done in
5386 the build target, not in the binary target.
5390 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5391 <tt>binary-arch</tt></tag>
5393 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5394 fields must be satisfied when these targets are invoked.
5396 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5397 and <tt>binary-indep</tt></tag>
5399 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5400 <tt>Build-Depends-Indep</tt>, and
5401 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5402 these targets are invoked.
5408 <sect id="built-using">
5409 <heading>Additional source packages used to build the binary
5410 - <tt>Built-Using</tt>
5414 Some binary packages incorporate parts of other packages when built
5415 but do not have to depend on those packages. Examples include
5416 linking with static libraries or incorporating source code from
5417 another package during the build. In this case, the source packages
5418 of those other packages are a required part of the complete source
5419 (the binary package is not reproducible without them).
5423 A <tt>Built-Using</tt> field must list the corresponding source
5424 package for any such binary package incorporated during the build
5426 <tt>Build-Depends</tt> in the source package is not adequate since
5427 it (rightfully) does not document the exact version used in the
5430 including an "exactly equal" ("=") version relation on the version
5431 that was used to build that binary package<footnote>
5432 The archive software might reject packages that refer to
5433 non-existent sources.
5438 A package using the source code from the gcc-4.6-source
5439 binary package built from the gcc-4.6 source package would
5440 have this field in its control file:
5441 <example compact="compact">
5442 Built-Using: gcc-4.6 (= 4.6.0-11)
5447 A package including binaries from grub2 and loadlin would
5448 have this field in its control file:
5449 <example compact="compact">
5450 Built-Using: grub2 (= 1.99-9), loadlin (= 1.6e-1)
5457 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5460 Packages containing shared libraries must be constructed with
5461 a little care to make sure that the shared library is always
5462 available. This is especially important for packages whose
5463 shared libraries are vitally important, such as the C library
5464 (currently <tt>libc6</tt>).
5468 This section deals only with public shared libraries: shared
5469 libraries that are placed in directories searched by the dynamic
5470 linker by default or which are intended to be linked against
5471 normally and possibly used by other, independent packages. Shared
5472 libraries that are internal to a particular package or that are
5473 only loaded as dynamic modules are not covered by this section and
5474 are not subject to its requirements.
5478 A shared library is identified by the <tt>SONAME</tt> attribute
5479 stored in its dynamic section. When a binary is linked against a
5480 shared library, the <tt>SONAME</tt> of the shared library is
5481 recorded in the binary's <tt>NEEDED</tt> section so that the
5482 dynamic linker knows that library must be loaded at runtime. The
5483 shared library file's full name (which usually contains additional
5484 version information not needed in the <tt>SONAME</tt>) is
5485 therefore normally not referenced directly. Instead, the shared
5486 library is loaded by its <tt>SONAME</tt>, which exists on the file
5487 system as a symlink pointing to the full name of the shared
5488 library. This symlink must be provided by the
5489 package. <ref id="sharedlibs-runtime"> describes how to do this.
5491 This is a convention of shared library versioning, but not a
5492 requirement. Some libraries use the <tt>SONAME</tt> as the full
5493 library file name instead and therefore do not need a symlink.
5494 Most, however, encode additional information about
5495 backwards-compatible revisions as a minor version number in the
5496 file name. The <tt>SONAME</tt> itself only changes when
5497 binaries linked with the earlier version of the shared library
5498 may no longer work, but the filename may change with each
5499 release of the library. See <ref id="sharedlibs-runtime"> for
5505 When linking a binary or another shared library against a shared
5506 library, the <tt>SONAME</tt> for that shared library is not yet
5507 known. Instead, the shared library is found by looking for a file
5508 matching the library name with <tt>.so</tt> appended. This file
5509 exists on the file system as a symlink pointing to the shared
5514 Shared libraries are normally split into several binary packages.
5515 The <tt>SONAME</tt> symlink is installed by the runtime shared
5516 library package, and the bare <tt>.so</tt> symlink is installed in
5517 the development package since it's only used when linking binaries
5518 or shared libraries. However, there are some exceptions for
5519 unusual shared libraries or for shared libraries that are also
5520 loaded as dynamic modules by other programs.
5524 This section is primarily concerned with how the separation of
5525 shared libraries into multiple packages should be done and how
5526 dependencies on and between shared library binary packages are
5527 managed in Debian. <ref id="libraries"> should be read in
5528 conjunction with this section and contains additional rules for
5529 the files contained in the shared library packages.
5532 <sect id="sharedlibs-runtime">
5533 <heading>Run-time shared libraries</heading>
5536 The run-time shared library must be placed in a package
5537 whose name changes whenever the <tt>SONAME</tt> of the shared
5538 library changes. This allows several versions of the shared
5539 library to be installed at the same time, allowing installation
5540 of the new version of the shared library without immediately
5541 breaking binaries that depend on the old version. Normally, the
5542 run-time shared library and its <tt>SONAME</tt> symlink should
5543 be placed in a package named
5544 <package><var>libraryname</var><var>soversion</var></package>,
5545 where <var>soversion</var> is the version number in
5546 the <tt>SONAME</tt> of the shared library.
5547 See <ref id="shlibs"> for detailed information on how to
5548 determine this version. Alternatively, if it would be confusing
5549 to directly append <var>soversion</var>
5550 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5551 itself ends in a number), you should use
5552 <package><var>libraryname</var>-<var>soversion</var></package>
5557 If you have several shared libraries built from the same source
5558 tree, you may lump them all together into a single shared
5559 library package provided that all of their <tt>SONAME</tt>s will
5560 always change together. Be aware that this is not normally the
5561 case, and if the <tt>SONAME</tt>s do not change together,
5562 upgrading such a merged shared library package will be
5563 unnecessarily difficult because of file conflicts with the old
5564 version of the package. When in doubt, always split shared
5565 library packages so that each binary package installs a single
5570 Every time the shared library ABI changes in a way that may
5571 break binaries linked against older versions of the shared
5572 library, the <tt>SONAME</tt> of the library and the
5573 corresponding name for the binary package containing the runtime
5574 shared library should change. Normally, this means
5575 the <tt>SONAME</tt> should change any time an interface is
5576 removed from the shared library or the signature of an interface
5577 (the number of parameters or the types of parameters that it
5578 takes, for example) is changed. This practice is vital to
5579 allowing clean upgrades from older versions of the package and
5580 clean transitions between the old ABI and new ABI without having
5581 to upgrade every affected package simultaneously.
5585 The <tt>SONAME</tt> and binary package name need not, and indeed
5586 normally should not, change if new interfaces are added but none
5587 are removed or changed, since this will not break binaries
5588 linked against the old shared library. Correct versioning of
5589 dependencies on the newer shared library by binaries that use
5590 the new interfaces is handled via
5591 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5592 system</qref> or via symbols files (see
5593 <manref name="deb-symbols" section="5">).
5597 The package should install the shared libraries under
5598 their normal names. For example, the <package>libgdbm3</package>
5599 package should install <file>libgdbm.so.3.0.0</file> as
5600 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5601 renamed or re-linked by any <prgn>prerm</prgn> or
5602 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5603 of renaming things safely without affecting running programs,
5604 and attempts to interfere with this are likely to lead to
5609 Shared libraries should not be installed executable, since
5610 the dynamic linker does not require this and trying to
5611 execute a shared library usually results in a core dump.
5615 The run-time library package should include the symbolic link for
5616 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5617 the shared libraries. For example,
5618 the <package>libgdbm3</package> package should include a symbolic
5619 link from <file>/usr/lib/libgdbm.so.3</file> to
5620 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5621 linker (for example <prgn>ld.so</prgn> or
5622 <prgn>ld-linux.so.*</prgn>) can find the library between the
5623 time that <prgn>dpkg</prgn> installs it and the time that
5624 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5626 The package management system requires the library to be
5627 placed before the symbolic link pointing to it in the
5628 <file>.deb</file> file. This is so that when
5629 <prgn>dpkg</prgn> comes to install the symlink
5630 (overwriting the previous symlink pointing at an older
5631 version of the library), the new shared library is already
5632 in place. In the past, this was achieved by creating the
5633 library in the temporary packaging directory before
5634 creating the symlink. Unfortunately, this was not always
5635 effective, since the building of the tar file in the
5636 <file>.deb</file> depended on the behavior of the underlying
5637 file system. Some file systems (such as reiserfs) reorder
5638 the files so that the order of creation is forgotten.
5639 Since version 1.7.0, <prgn>dpkg</prgn>
5640 reorders the files itself as necessary when building a
5641 package. Thus it is no longer important to concern
5642 oneself with the order of file creation.
5646 <sect1 id="ldconfig">
5647 <heading><tt>ldconfig</tt></heading>
5650 Any package installing shared libraries in one of the default
5651 library directories of the dynamic linker (which are currently
5652 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5653 listed in <file>/etc/ld.so.conf</file><footnote>
5654 These are currently <file>/usr/local/lib</file> plus
5655 directories under <file>/lib</file> and <file>/usr/lib</file>
5656 matching the multiarch triplet for the system architecture.
5658 must use <prgn>ldconfig</prgn> to update the shared library
5663 The package maintainer scripts must only call
5664 <prgn>ldconfig</prgn> under these circumstances:
5665 <list compact="compact">
5666 <item>When the <prgn>postinst</prgn> script is run with a
5667 first argument of <tt>configure</tt>, the script must call
5668 <prgn>ldconfig</prgn>, and may optionally invoke
5669 <prgn>ldconfig</prgn> at other times.
5671 <item>When the <prgn>postrm</prgn> script is run with a
5672 first argument of <tt>remove</tt>, the script should call
5673 <prgn>ldconfig</prgn>.
5678 During install or upgrade, the preinst is called before
5679 the new files are unpacked, so calling "ldconfig" is
5680 pointless. The preinst of an existing package can also be
5681 called if an upgrade fails. However, this happens during
5682 the critical time when a shared libs may exist on-disk
5683 under a temporary name. Thus, it is dangerous and
5684 forbidden by current policy to call "ldconfig" at this
5689 When a package is installed or upgraded, "postinst
5690 configure" runs after the new files are safely on-disk.
5691 Since it is perfectly safe to invoke ldconfig
5692 unconditionally in a postinst, it is OK for a package to
5693 simply put ldconfig in its postinst without checking the
5694 argument. The postinst can also be called to recover from
5695 a failed upgrade. This happens before any new files are
5696 unpacked, so there is no reason to call "ldconfig" at this
5701 For a package that is being removed, prerm is
5702 called with all the files intact, so calling ldconfig is
5703 useless. The other calls to "prerm" happen in the case of
5704 upgrade at a time when all the files of the old package
5705 are on-disk, so again calling "ldconfig" is pointless.
5709 postrm, on the other hand, is called with the "remove"
5710 argument just after the files are removed, so this is
5711 the proper time to call "ldconfig" to notify the system
5712 of the fact that the shared libraries from the package
5713 are removed. The postrm can be called at several other
5714 times. At the time of "postrm purge", "postrm
5715 abort-install", or "postrm abort-upgrade", calling
5716 "ldconfig" is useless because the shared lib files are
5717 not on-disk. However, when "postrm" is invoked with
5718 arguments "upgrade", "failed-upgrade", or "disappear", a
5719 shared lib may exist on-disk under a temporary filename.
5727 <sect id="sharedlibs-support-files">
5728 <heading>Shared library support files</heading>
5731 If your package contains files whose names do not change with
5732 each change in the library shared object version, you must not
5733 put them in the shared library package. Otherwise, several
5734 versions of the shared library cannot be installed at the same
5735 time without filename clashes, making upgrades and transitions
5736 unnecessarily difficult.
5740 It is recommended that supporting files and run-time support
5741 programs that do not need to be invoked manually by users, but
5742 are nevertheless required for the package to function, be placed
5743 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5744 preferably under <file>/usr/lib/</file><var>package-name</var>.
5745 If the program or file is architecture independent, the
5746 recommendation is for it to be placed in a subdirectory of
5747 <file>/usr/share</file> instead, preferably under
5748 <file>/usr/share/</file><var>package-name</var>. Following the
5749 <var>package-name</var> naming convention ensures that the file
5750 names change when the shared object version changes.
5754 Run-time support programs that use the shared library but are
5755 not required for the library to function or files used by the
5756 shared library that can be used by any version of the shared
5757 library package should instead be put in a separate package.
5758 This package might typically be named
5759 <package><var>libraryname</var>-tools</package>; note the
5760 absence of the <var>soversion</var> in the package name.
5764 Files and support programs only useful when compiling software
5765 against the library should be included in the development
5766 package for the library.<footnote>
5767 For example, a <file><var>package-name</var>-config</file>
5768 script or <package>pkg-config</package> configuration files.
5773 <sect id="sharedlibs-static">
5774 <heading>Static libraries</heading>
5777 The static library (<file><var>libraryname.a</var></file>)
5778 is usually provided in addition to the shared version.
5779 It is placed into the development package (see below).
5783 In some cases, it is acceptable for a library to be
5784 available in static form only; these cases include:
5786 <item>libraries for languages whose shared library support
5787 is immature or unstable</item>
5788 <item>libraries whose interfaces are in flux or under
5789 development (commonly the case when the library's
5790 major version number is zero, or where the ABI breaks
5791 across patchlevels)</item>
5792 <item>libraries which are explicitly intended to be
5793 available only in static form by their upstream
5798 <sect id="sharedlibs-dev">
5799 <heading>Development files</heading>
5802 If there are development files associated with a shared library,
5803 the source package needs to generate a binary development package
5804 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5805 or if you prefer only to support one development version at a
5806 time, <package><var>libraryname</var>-dev</package>. Installing
5807 the development package must result in installation of all the
5808 development files necessary for compiling programs against that
5809 shared library.<footnote>
5810 This wording allows the development files to be split into
5811 several packages, such as a separate architecture-independent
5812 <package><var>libraryname</var>-headers</package>, provided that
5813 the development package depends on all the required additional
5819 In case several development versions of a library exist, you may
5820 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5821 <ref id="conflicts">) to ensure that the user only installs one
5822 development version at a time (as different development versions are
5823 likely to have the same header files in them, which would cause a
5824 filename clash if both were unpacked).
5828 The development package should contain a symlink for the associated
5829 shared library without a version number. For example, the
5830 <package>libgdbm-dev</package> package should include a symlink
5831 from <file>/usr/lib/libgdbm.so</file> to
5832 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5833 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5834 <file>libgdbm.so</file> when compiling dynamically.
5838 If the package provides Ada Library Information
5839 (<file>*.ali</file>) files for use with GNAT, these files must be
5840 installed read-only (mode 0444) so that GNAT will not attempt to
5841 recompile them. This overrides the normal file mode requirements
5842 given in <ref id="permissions-owners">.
5846 <sect id="sharedlibs-intradeps">
5847 <heading>Dependencies between the packages of the same library</heading>
5850 Typically the development version should have an exact
5851 version dependency on the runtime library, to make sure that
5852 compilation and linking happens correctly. The
5853 <tt>${binary:Version}</tt> substitution variable can be
5854 useful for this purpose.
5856 Previously, <tt>${Source-Version}</tt> was used, but its name
5857 was confusing and it has been deprecated since dpkg 1.13.19.
5862 <sect id="sharedlibs-shlibdeps">
5863 <heading>Dependencies between the library and other packages -
5864 the <tt>shlibs</tt> system</heading>
5867 If a package contains a binary or library which links to a
5868 shared library, we must ensure that when the package is
5869 installed on the system, all of the libraries needed are
5870 also installed. This requirement led to the creation of the
5871 <tt>shlibs</tt> system, which is very simple in its design:
5872 any package which <em>provides</em> a shared library also
5873 provides information on the package dependencies required to
5874 ensure the presence of this library, and any package which
5875 <em>uses</em> a shared library uses this information to
5876 determine the dependencies it requires. The files which
5877 contain the mapping from shared libraries to the necessary
5878 dependency information are called <file>shlibs</file> files.
5882 When a package is built which contains any shared libraries, it
5883 must provide a <file>shlibs</file> file for other packages to
5884 use. When a package is built which contains any shared
5885 libraries or compiled binaries, it must run
5886 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5887 on these to determine the libraries used and hence the
5888 dependencies needed by this package.<footnote>
5890 <prgn>dpkg-shlibdeps</prgn> will use a program
5891 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5892 the libraries directly needed by the binaries or shared
5893 libraries in the package.
5897 We say that a binary <tt>foo</tt> <em>directly</em> uses
5898 a library <tt>libbar</tt> if it is explicitly linked
5899 with that library (that is, the library is listed in the ELF
5900 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5901 to the link line when the binary is created). Other
5902 libraries that are needed by <tt>libbar</tt> are linked
5903 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5904 linker will load them automatically when it loads
5905 <tt>libbar</tt>. A package should depend on the libraries
5906 it directly uses, but not the libraries it indirectly uses.
5907 The dependencies for those libraries will automatically pull
5908 in the other libraries.
5912 A good example of where this helps is the following. We
5913 could update <tt>libimlib</tt> with a new version that
5914 supports a new graphics format called dgf (but retaining the
5915 same major version number) and depends on <tt>libdgf</tt>.
5916 If we used <prgn>ldd</prgn> to add dependencies for every
5917 library directly or indirectly linked with a binary, every
5918 package that uses <tt>libimlib</tt> would need to be
5919 recompiled so it would also depend on <tt>libdgf</tt> or it
5920 wouldn't run due to missing symbols. Since dependencies are
5921 only added based on ELF <tt>NEEDED</tt> attribute, packages
5922 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5923 having the dependency on <tt>libdgf</tt> and so they would
5924 not need rebuilding.
5930 In the following sections, we will first describe where the
5931 various <tt>shlibs</tt> files are to be found, then how to
5932 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5933 file format and how to create them if your package contains a
5938 <heading>The <tt>shlibs</tt> files present on the system</heading>
5941 There are several places where <tt>shlibs</tt> files are
5942 found. The following list gives them in the order in which
5944 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5945 (The first one which gives the required information is used.)
5951 <p><file>debian/shlibs.local</file></p>
5954 This lists overrides for this package. This file should
5955 normally not be used, but may be needed temporarily in
5956 unusual situations to work around bugs in other packages,
5957 or in unusual cases where the normally declared dependency
5958 information in the installed <file>shlibs</file> file for
5959 a library cannot be used. This file overrides information
5960 obtained from any other source.
5965 <p><file>/etc/dpkg/shlibs.override</file></p>
5968 This lists global overrides. This list is normally
5969 empty. It is maintained by the local system
5975 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5978 When packages are being built,
5979 any <file>debian/shlibs</file> files are copied into the
5980 control information file area of the temporary build
5981 directory and given the name <file>shlibs</file>. These
5982 files give details of any shared libraries included in the
5983 same package.<footnote>
5984 An example may help here. Let us say that the source
5985 package <tt>foo</tt> generates two binary
5986 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5987 When building the binary packages, the two packages are
5988 created in the directories <file>debian/libfoo2</file>
5989 and <file>debian/foo-runtime</file> respectively.
5990 (<file>debian/tmp</file> could be used instead of one of
5991 these.) Since <tt>libfoo2</tt> provides the
5992 <tt>libfoo</tt> shared library, it will require a
5993 <tt>shlibs</tt> file, which will be installed in
5994 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5995 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5996 When <prgn>dpkg-shlibdeps</prgn> is run on the
5997 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5999 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
6000 determine whether <tt>foo-prog</tt>'s library
6001 dependencies are satisfied by any of the libraries
6002 provided by <tt>libfoo2</tt>. For this reason,
6003 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
6004 the individual binary packages' <tt>shlibs</tt> files
6005 have been installed into the build directory.
6011 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
6014 These are the <file>shlibs</file> files corresponding to
6015 all of the packages installed on the system, and are
6016 maintained by the relevant package maintainers.
6021 <p><file>/etc/dpkg/shlibs.default</file></p>
6024 This file lists any shared libraries whose packages
6025 have failed to provide correct <file>shlibs</file> files.
6026 It was used when the <file>shlibs</file> setup was first
6027 introduced, but it is now normally empty. It is
6028 maintained by the <tt>dpkg</tt> maintainer.
6036 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
6037 <file>shlibs</file> files</heading>
6041 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
6042 into your <file>debian/rules</file> file. If your package
6043 contains only compiled binaries and libraries (but no scripts),
6044 you can use a command such as:
6045 <example compact="compact">
6046 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
6047 debian/tmp/usr/lib/*
6049 Otherwise, you will need to explicitly list the compiled
6050 binaries and libraries.<footnote>
6051 If you are using <tt>debhelper</tt>, the
6052 <prgn>dh_shlibdeps</prgn> program will do this work for you.
6053 It will also correctly handle multi-binary packages.
6058 This command puts the dependency information into the
6059 <file>debian/substvars</file> file, which is then used by
6060 <prgn>dpkg-gencontrol</prgn>. You will need to place a
6061 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
6062 field in the control file for this to work.
6066 If you have multiple binary packages, you will need to call
6067 <prgn>dpkg-shlibdeps</prgn> on each one which contains
6068 compiled libraries or binaries. In such a case, you will
6069 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
6070 utilities to specify a different <file>substvars</file> file.
6074 If you are creating a udeb for use in the Debian Installer,
6075 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6076 should use the dependency line of type <tt>udeb</tt> by
6077 adding the <tt>-tudeb</tt> option<footnote>
6078 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6079 will automatically add this option if it knows it is
6081 </footnote>. If there is no dependency line of
6082 type <tt>udeb</tt> in the <file>shlibs</file>
6083 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
6088 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
6089 <ref id="pkg-dpkg-shlibdeps"> and
6090 <manref name="dpkg-shlibdeps" section="1">.
6095 <heading>The <file>shlibs</file> File Format</heading>
6098 Each <file>shlibs</file> file has the same format. Lines
6099 beginning with <tt>#</tt> are considered to be comments and
6100 are ignored. Each line is of the form:
6101 <example compact="compact">
6102 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6107 We will explain this by reference to the example of the
6108 <tt>zlib1g</tt> package, which (at the time of writing)
6109 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
6113 <var>type</var> is an optional element that indicates the type
6114 of package for which the line is valid. The only type currently
6115 in use is <tt>udeb</tt>. The colon and space after the type are
6120 <var>library-name</var> is the name of the shared library,
6121 in this case <tt>libz</tt>. (This must match the name part
6122 of the soname, see below.)
6126 <var>soname-version</var> is the version part of the soname of
6127 the library. The soname is the thing that must exactly match
6128 for the library to be recognized by the dynamic linker, and is
6130 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
6131 example, <tt>libz.so.1</tt>.<footnote>
6132 This can be determined using the command
6133 <example compact="compact">
6134 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
6137 The version part is the part which comes after
6138 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
6139 instead be of the form
6140 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
6141 as <tt>libdb-4.8.so</tt>, in which case the name would
6142 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
6146 <var>dependencies</var> has the same syntax as a dependency
6147 field in a binary package control file. It should give
6148 details of which packages are required to satisfy a binary
6149 built against the version of the library contained in the
6150 package. See <ref id="depsyntax"> for details.
6154 In our example, if the first version of the <tt>zlib1g</tt>
6155 package which contained a minor number of at least
6156 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
6157 <tt>shlibs</tt> entry for this library could say:
6158 <example compact="compact">
6159 libz 1 zlib1g (>= 1:1.1.3)
6161 The version-specific dependency is to avoid warnings from
6162 the dynamic linker about using older shared libraries with
6167 As zlib1g also provides a udeb containing the shared library,
6168 there would also be a second line:
6169 <example compact="compact">
6170 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
6176 <heading>Providing a <file>shlibs</file> file</heading>
6179 If your package provides a shared library, you need to create
6180 a <file>shlibs</file> file following the format described above.
6181 It is usual to call this file <file>debian/shlibs</file> (but if
6182 you have multiple binary packages, you might want to call it
6183 <file>debian/shlibs.<var>package</var></file> instead). Then
6184 let <file>debian/rules</file> install it in the control
6185 information file area:
6186 <example compact="compact">
6187 install -m644 debian/shlibs debian/tmp/DEBIAN
6189 or, in the case of a multi-binary package:
6190 <example compact="compact">
6191 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
6193 An alternative way of doing this is to create the
6194 <file>shlibs</file> file in the control information file area
6195 directly from <file>debian/rules</file> without using
6196 a <file>debian/shlibs</file> file at all,<footnote>
6197 This is what <prgn>dh_makeshlibs</prgn> in
6198 the <package>debhelper</package> suite does. If your package
6199 also has a udeb that provides a shared
6200 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6201 the <tt>udeb:</tt> lines if you specify the name of the udeb
6202 with the <tt>--add-udeb</tt> option.
6204 since the <file>debian/shlibs</file> file itself is ignored by
6205 <prgn>dpkg-shlibdeps</prgn>.
6209 As <prgn>dpkg-shlibdeps</prgn> reads the
6210 <file>DEBIAN/shlibs</file> files in all of the binary packages
6211 being built from this source package, all of the
6212 <file>DEBIAN/shlibs</file> files should be installed before
6213 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6221 <chapt id="opersys"><heading>The Operating System</heading>
6224 <heading>File system hierarchy</heading>
6228 <heading>File System Structure</heading>
6231 The location of all files and directories must comply with the
6232 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6233 exceptions noted below, and except where doing so would
6234 violate other terms of Debian Policy. The following
6235 exceptions to the FHS apply:
6240 The optional rules related to user specific
6241 configuration files for applications are stored in
6242 the user's home directory are relaxed. It is
6243 recommended that such files start with the
6244 '<tt>.</tt>' character (a "dot file"), and if an
6245 application needs to create more than one dot file
6246 then the preferred placement is in a subdirectory
6247 with a name starting with a '.' character, (a "dot
6248 directory"). In this case it is recommended the
6249 configuration files not start with the '.'
6255 The requirement for amd64 to use <file>/lib64</file>
6256 for 64 bit binaries is removed.
6261 The requirement for object files, internal binaries, and
6262 libraries, including <file>libc.so.*</file>, to be located
6263 directly under <file>/lib{,32}</file> and
6264 <file>/usr/lib{,32}</file> is amended, permitting files
6265 to instead be installed to
6266 <file>/lib/<var>triplet</var></file> and
6267 <file>/usr/lib/<var>triplet</var></file>, where
6268 <tt><var>triplet</var></tt> is the value returned by
6269 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6270 architecture of the package. Packages may <em>not</em>
6271 install files to any <var>triplet</var> path other
6272 than the one matching the architecture of that package;
6273 for instance, an <tt>Architecture: amd64</tt> package
6274 containing 32-bit x86 libraries may not install these
6275 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6277 This is necessary in order to reserve the directories for
6278 use in cross-installation of library packages from other
6279 architectures, as part of the planned deployment of
6284 Applications may also use a single subdirectory under
6285 <file>/usr/lib/<var>triplet</var></file>.
6288 The execution time linker/loader, ld*, must still be made
6289 available in the existing location under /lib or /lib64
6290 since this is part of the ELF ABI for the architecture.
6295 The requirement that
6296 <file>/usr/local/share/man</file> be "synonymous"
6297 with <file>/usr/local/man</file> is relaxed to a
6302 The requirement that windowmanagers with a single
6303 configuration file call it <file>system.*wmrc</file>
6304 is removed, as is the restriction that the window
6305 manager subdirectory be named identically to the
6306 window manager name itself.
6311 The requirement that boot manager configuration
6312 files live in <file>/etc</file>, or at least are
6313 symlinked there, is relaxed to a recommendation.
6318 The additional directory <file>/run</file> in the root
6319 file system is allowed. <file>/run</file>
6320 replaces <file>/var/run</file>, and the
6321 subdirectory <file>/run/lock</file>
6322 replaces <file>/var/lock</file>, with
6323 the <file>/var</file> directories replaced by symlinks
6324 for backwards compatibility. <file>/run</file>
6325 and <file>/run/lock</file> must follow all of the
6326 requirements in the FHS for <file>/var/run</file>
6327 and <file>/var/lock</file>, respectively, such as file
6328 naming conventions, file format requirements, or the
6329 requirement that files be cleared during the boot
6330 process. Files and directories residing
6331 in <file>/run</file> should be stored on a temporary
6337 The following directories in the root filesystem are
6338 additionally allowed: <file>/sys</file> and
6339 <file>/selinux</file>. <footnote>These directories
6340 are used as mount points to mount virtual filesystems
6341 to get access to kernel information.</footnote>
6346 On GNU/Hurd systems, the following additional
6347 directories are allowed in the root
6348 filesystem: <file>/hurd</file>
6349 and <file>/servers</file>.<footnote>
6350 These directories are used to store translators and as
6351 a set of standard names for mount points,
6360 The version of this document referred here can be
6361 found in the <tt>debian-policy</tt> package or on <url
6362 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6363 name="FHS (Debian copy)"> alongside this manual (or, if
6364 you have the <package>debian-policy</package> installed,
6366 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6367 (local copy)">). The
6368 latest version, which may be a more recent version, may
6370 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6371 Specific questions about following the standard may be
6372 asked on the <tt>debian-devel</tt> mailing list, or
6373 referred to the FHS mailing list (see the
6374 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6380 <heading>Site-specific programs</heading>
6383 As mandated by the FHS, packages must not place any
6384 files in <file>/usr/local</file>, either by putting them in
6385 the file system archive to be unpacked by <prgn>dpkg</prgn>
6386 or by manipulating them in their maintainer scripts.
6390 However, the package may create empty directories below
6391 <file>/usr/local</file> so that the system administrator knows
6392 where to place site-specific files. These are not
6393 directories <em>in</em> <file>/usr/local</file>, but are
6394 children of directories in <file>/usr/local</file>. These
6395 directories (<file>/usr/local/*/dir/</file>)
6396 should be removed on package removal if they are
6401 Note that this applies only to
6402 directories <em>below</em> <file>/usr/local</file>,
6403 not <em>in</em> <file>/usr/local</file>. Packages must
6404 not create sub-directories in the
6405 directory <file>/usr/local</file> itself, except those
6406 listed in FHS, section 4.5. However, you may create
6407 directories below them as you wish. You must not remove
6408 any of the directories listed in 4.5, even if you created
6413 Since <file>/usr/local</file> can be mounted read-only from a
6414 remote server, these directories must be created and
6415 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6416 maintainer scripts and not be included in the
6417 <file>.deb</file> archive. These scripts must not fail if
6418 either of these operations fail.
6422 For example, the <tt>emacsen-common</tt> package could
6423 contain something like
6424 <example compact="compact">
6425 if [ ! -e /usr/local/share/emacs ]; then
6426 if mkdir /usr/local/share/emacs 2>/dev/null; then
6427 if chown root:staff /usr/local/share/emacs; then
6428 chmod 2775 /usr/local/share/emacs || true
6433 in its <prgn>postinst</prgn> script, and
6434 <example compact="compact">
6435 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6436 rmdir /usr/local/share/emacs 2>/dev/null || true
6438 in the <prgn>prerm</prgn> script. (Note that this form is
6439 used to ensure that if the script is interrupted, the
6440 directory <file>/usr/local/share/emacs</file> will still be
6445 If you do create a directory in <file>/usr/local</file> for
6446 local additions to a package, you should ensure that
6447 settings in <file>/usr/local</file> take precedence over the
6448 equivalents in <file>/usr</file>.
6452 However, because <file>/usr/local</file> and its contents are
6453 for exclusive use of the local administrator, a package
6454 must not rely on the presence or absence of files or
6455 directories in <file>/usr/local</file> for normal operation.
6459 The <file>/usr/local</file> directory itself and all the
6460 subdirectories created by the package should (by default) have
6461 permissions 2775 (group-writable and set-group-id) and be
6462 owned by <tt>root:staff</tt>.
6467 <heading>The system-wide mail directory</heading>
6469 The system-wide mail directory
6470 is <file>/var/mail</file>. This directory is part of the
6471 base system and should not be owned by any particular mail
6472 agents. The use of the old
6473 location <file>/var/spool/mail</file> is deprecated, even
6474 though the spool may still be physically located there.
6478 <sect1 id="fhs-run">
6479 <heading><file>/run</file> and <file>/run/lock</file></heading>
6482 The directory <file>/run</file> is cleared at boot, normally
6483 by being a mount point for a temporary file system. Packages
6484 therefore must not assume that any files or directories
6485 under <file>/run</file> other than <file>/run/lock</file>
6486 exist unless the package has arranged to create those files or
6487 directories since the last reboot. Normally, this is done by
6488 the package via an init script. See <ref id="writing-init">
6489 for more information.
6493 Packages must not include files or directories
6494 under <file>/run</file>, or under the
6495 older <file>/var/run</file> and <file>/var/lock</file> paths.
6496 The latter paths will normally be symlinks or other
6497 redirections to <file>/run</file> for backwards compatibility.
6503 <heading>Users and groups</heading>
6506 <heading>Introduction</heading>
6508 The Debian system can be configured to use either plain or
6513 Some user ids (UIDs) and group ids (GIDs) are reserved
6514 globally for use by certain packages. Because some
6515 packages need to include files which are owned by these
6516 users or groups, or need the ids compiled into binaries,
6517 these ids must be used on any Debian system only for the
6518 purpose for which they are allocated. This is a serious
6519 restriction, and we should avoid getting in the way of
6520 local administration policies. In particular, many sites
6521 allocate users and/or local system groups starting at 100.
6525 Apart from this we should have dynamically allocated ids,
6526 which should by default be arranged in some sensible
6527 order, but the behavior should be configurable.
6531 Packages other than <tt>base-passwd</tt> must not modify
6532 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6533 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6538 <heading>UID and GID classes</heading>
6540 The UID and GID numbers are divided into classes as
6546 Globally allocated by the Debian project, the same
6547 on every Debian system. These ids will appear in
6548 the <file>passwd</file> and <file>group</file> files of all
6549 Debian systems, new ids in this range being added
6550 automatically as the <tt>base-passwd</tt> package is
6555 Packages which need a single statically allocated
6556 uid or gid should use one of these; their
6557 maintainers should ask the <tt>base-passwd</tt>
6565 Dynamically allocated system users and groups.
6566 Packages which need a user or group, but can have
6567 this user or group allocated dynamically and
6568 differently on each system, should use <tt>adduser
6569 --system</tt> to create the group and/or user.
6570 <prgn>adduser</prgn> will check for the existence of
6571 the user or group, and if necessary choose an unused
6572 id based on the ranges specified in
6573 <file>adduser.conf</file>.
6577 <tag>1000-59999:</tag>
6580 Dynamically allocated user accounts. By default
6581 <prgn>adduser</prgn> will choose UIDs and GIDs for
6582 user accounts in this range, though
6583 <file>adduser.conf</file> may be used to modify this
6588 <tag>60000-64999:</tag>
6591 Globally allocated by the Debian project, but only
6592 created on demand. The ids are allocated centrally
6593 and statically, but the actual accounts are only
6594 created on users' systems on demand.
6598 These ids are for packages which are obscure or
6599 which require many statically-allocated ids. These
6600 packages should check for and create the accounts in
6601 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6602 <prgn>adduser</prgn> if it has this facility) if
6603 necessary. Packages which are likely to require
6604 further allocations should have a "hole" left after
6605 them in the allocation, to give them room to
6610 <tag>65000-65533:</tag>
6618 User <tt>nobody</tt>. The corresponding gid refers
6619 to the group <tt>nogroup</tt>.
6626 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6627 not</em> be used, because it is the error return
6636 <sect id="sysvinit">
6637 <heading>System run levels and <file>init.d</file> scripts</heading>
6639 <sect1 id="/etc/init.d">
6640 <heading>Introduction</heading>
6643 The <file>/etc/init.d</file> directory contains the scripts
6644 executed by <prgn>init</prgn> at boot time and when the
6645 init state (or "runlevel") is changed (see <manref
6646 name="init" section="8">).
6650 There are at least two different, yet functionally
6651 equivalent, ways of handling these scripts. For the sake
6652 of simplicity, this document describes only the symbolic
6653 link method. However, it must not be assumed by maintainer
6654 scripts that this method is being used, and any automated
6655 manipulation of the various runlevel behaviors by
6656 maintainer scripts must be performed using
6657 <prgn>update-rc.d</prgn> as described below and not by
6658 manually installing or removing symlinks. For information
6659 on the implementation details of the other method,
6660 implemented in the <tt>file-rc</tt> package, please refer
6661 to the documentation of that package.
6665 These scripts are referenced by symbolic links in the
6666 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6667 runlevels, <prgn>init</prgn> looks in the directory
6668 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6669 execute, where <tt><var>n</var></tt> is the runlevel that
6670 is being changed to, or <tt>S</tt> for the boot-up
6675 The names of the links all have the form
6676 <file>S<var>mm</var><var>script</var></file> or
6677 <file>K<var>mm</var><var>script</var></file> where
6678 <var>mm</var> is a two-digit number and <var>script</var>
6679 is the name of the script (this should be the same as the
6680 name of the actual script in <file>/etc/init.d</file>).
6684 When <prgn>init</prgn> changes runlevel first the targets
6685 of the links whose names start with a <tt>K</tt> are
6686 executed, each with the single argument <tt>stop</tt>,
6687 followed by the scripts prefixed with an <tt>S</tt>, each
6688 with the single argument <tt>start</tt>. (The links are
6689 those in the <file>/etc/rc<var>n</var>.d</file> directory
6690 corresponding to the new runlevel.) The <tt>K</tt> links
6691 are responsible for killing services and the <tt>S</tt>
6692 link for starting services upon entering the runlevel.
6696 For example, if we are changing from runlevel 2 to
6697 runlevel 3, init will first execute all of the <tt>K</tt>
6698 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6699 all of the <tt>S</tt> prefixed scripts in that directory.
6700 The links starting with <tt>K</tt> will cause the
6701 referred-to file to be executed with an argument of
6702 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6707 The two-digit number <var>mm</var> is used to determine
6708 the order in which to run the scripts: low-numbered links
6709 have their scripts run first. For example, the
6710 <tt>K20</tt> scripts will be executed before the
6711 <tt>K30</tt> scripts. This is used when a certain service
6712 must be started before another. For example, the name
6713 server <prgn>bind</prgn> might need to be started before
6714 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6715 can set up its access lists. In this case, the script
6716 that starts <prgn>bind</prgn> would have a lower number
6717 than the script that starts <prgn>inn</prgn> so that it
6719 <example compact="compact">
6726 The two runlevels 0 (halt) and 6 (reboot) are slightly
6727 different. In these runlevels, the links with an
6728 <tt>S</tt> prefix are still called after those with a
6729 <tt>K</tt> prefix, but they too are called with the single
6730 argument <tt>stop</tt>.
6734 <sect1 id="writing-init">
6735 <heading>Writing the scripts</heading>
6738 Packages that include daemons for system services should
6739 place scripts in <file>/etc/init.d</file> to start or stop
6740 services at boot time or during a change of runlevel.
6741 These scripts should be named
6742 <file>/etc/init.d/<var>package</var></file>, and they should
6743 accept one argument, saying what to do:
6746 <tag><tt>start</tt></tag>
6747 <item>start the service,</item>
6749 <tag><tt>stop</tt></tag>
6750 <item>stop the service,</item>
6752 <tag><tt>restart</tt></tag>
6753 <item>stop and restart the service if it's already running,
6754 otherwise start the service</item>
6756 <tag><tt>reload</tt></tag>
6757 <item><p>cause the configuration of the service to be
6758 reloaded without actually stopping and restarting
6761 <tag><tt>force-reload</tt></tag>
6762 <item>cause the configuration to be reloaded if the
6763 service supports this, otherwise restart the
6767 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6768 <tt>force-reload</tt> options should be supported by all
6769 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6774 The <file>init.d</file> scripts must ensure that they will
6775 behave sensibly (i.e., returning success and not starting
6776 multiple copies of a service) if invoked with <tt>start</tt>
6777 when the service is already running, or with <tt>stop</tt>
6778 when it isn't, and that they don't kill unfortunately-named
6779 user processes. The best way to achieve this is usually to
6780 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6785 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6786 scripts. Writing correct <file>init.d</file> scripts requires
6787 accepting various error exit statuses when daemons are already
6788 running or already stopped without aborting
6789 the <file>init.d</file> script, and common <file>init.d</file>
6790 function libraries are not safe to call with <tt>set -e</tt>
6792 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6793 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6794 in effect and echoing status messages to the console fails,
6796 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6797 to not use <tt>set -e</tt> and instead check the result of
6798 each command separately.
6802 If a service reloads its configuration automatically (as
6803 in the case of <prgn>cron</prgn>, for example), the
6804 <tt>reload</tt> option of the <file>init.d</file> script
6805 should behave as if the configuration has been reloaded
6810 The <file>/etc/init.d</file> scripts must be treated as
6811 configuration files, either (if they are present in the
6812 package, that is, in the .deb file) by marking them as
6813 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6814 by managing them correctly in the maintainer scripts (see
6815 <ref id="config-files">). This is important since we want
6816 to give the local system administrator the chance to adapt
6817 the scripts to the local system, e.g., to disable a
6818 service without de-installing the package, or to specify
6819 some special command line options when starting a service,
6820 while making sure their changes aren't lost during the next
6825 These scripts should not fail obscurely when the
6826 configuration files remain but the package has been
6827 removed, as configuration files remain on the system after
6828 the package has been removed. Only when <prgn>dpkg</prgn>
6829 is executed with the <tt>--purge</tt> option will
6830 configuration files be removed. In particular, as the
6831 <file>/etc/init.d/<var>package</var></file> script itself is
6832 usually a <tt>conffile</tt>, it will remain on the system
6833 if the package is removed but not purged. Therefore, you
6834 should include a <tt>test</tt> statement at the top of the
6836 <example compact="compact">
6837 test -f <var>program-executed-later-in-script</var> || exit 0
6842 Often there are some variables in the <file>init.d</file>
6843 scripts whose values control the behavior of the scripts,
6844 and which a system administrator is likely to want to
6845 change. As the scripts themselves are frequently
6846 <tt>conffile</tt>s, modifying them requires that the
6847 administrator merge in their changes each time the package
6848 is upgraded and the <tt>conffile</tt> changes. To ease
6849 the burden on the system administrator, such configurable
6850 values should not be placed directly in the script.
6851 Instead, they should be placed in a file in
6852 <file>/etc/default</file>, which typically will have the same
6853 base name as the <file>init.d</file> script. This extra file
6854 should be sourced by the script when the script runs. It
6855 must contain only variable settings and comments in SUSv3
6856 <prgn>sh</prgn> format. It may either be a
6857 <tt>conffile</tt> or a configuration file maintained by
6858 the package maintainer scripts. See <ref id="config-files">
6863 To ensure that vital configurable values are always
6864 available, the <file>init.d</file> script should set default
6865 values for each of the shell variables it uses, either
6866 before sourcing the <file>/etc/default/</file> file or
6867 afterwards using something like the <tt>:
6868 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6869 script must behave sensibly and not fail if the
6870 <file>/etc/default</file> file is deleted.
6874 Files and directories under <file>/run</file>, including ones
6875 referred to via the compatibility paths <file>/var/run</file>
6876 and <file>/var/lock</file>, are normally stored on a temporary
6877 filesystem and are normally not persistent across a reboot.
6878 The <file>init.d</file> scripts must handle this correctly.
6879 This will typically mean creating any required subdirectories
6880 dynamically when the <file>init.d</file> script is run.
6881 See <ref id="fhs-run"> for more information.
6886 <heading>Interfacing with the initscript system</heading>
6889 Maintainers should use the abstraction layer provided by
6890 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6891 programs to deal with initscripts in their packages'
6892 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6893 and <prgn>postrm</prgn>.
6897 Directly managing the /etc/rc?.d links and directly
6898 invoking the <file>/etc/init.d/</file> initscripts should
6899 be done only by packages providing the initscript
6900 subsystem (such as <prgn>sysv-rc</prgn> and
6901 <prgn>file-rc</prgn>).
6905 <heading>Managing the links</heading>
6908 The program <prgn>update-rc.d</prgn> is provided for
6909 package maintainers to arrange for the proper creation and
6910 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6911 or their functional equivalent if another method is being
6912 used. This may be used by maintainers in their packages'
6913 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6917 You must not include any <file>/etc/rc<var>n</var>.d</file>
6918 symbolic links in the actual archive or manually create or
6919 remove the symbolic links in maintainer scripts; you must
6920 use the <prgn>update-rc.d</prgn> program instead. (The
6921 former will fail if an alternative method of maintaining
6922 runlevel information is being used.) You must not include
6923 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6924 in the archive either. (Only the <tt>sysvinit</tt>
6929 By default <prgn>update-rc.d</prgn> will start services in
6930 each of the multi-user state runlevels (2, 3, 4, and 5)
6931 and stop them in the halt runlevel (0), the single-user
6932 runlevel (1) and the reboot runlevel (6). The system
6933 administrator will have the opportunity to customize
6934 runlevels by simply adding, moving, or removing the
6935 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6936 symbolic links are being used, or by modifying
6937 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6942 To get the default behavior for your package, put in your
6943 <prgn>postinst</prgn> script
6944 <example compact="compact">
6945 update-rc.d <var>package</var> defaults
6947 and in your <prgn>postrm</prgn>
6948 <example compact="compact">
6949 if [ "$1" = purge ]; then
6950 update-rc.d <var>package</var> remove
6952 </example>. Note that if your package changes runlevels
6953 or priority, you may have to remove and recreate the links,
6954 since otherwise the old links may persist. Refer to the
6955 documentation of <prgn>update-rc.d</prgn>.
6959 This will use a default sequence number of 20. If it does
6960 not matter when or in which order the <file>init.d</file>
6961 script is run, use this default. If it does, then you
6962 should talk to the maintainer of the <prgn>sysvinit</prgn>
6963 package or post to <tt>debian-devel</tt>, and they will
6964 help you choose a number.
6968 For more information about using <tt>update-rc.d</tt>,
6969 please consult its man page <manref name="update-rc.d"
6975 <heading>Running initscripts</heading>
6977 The program <prgn>invoke-rc.d</prgn> is provided to make
6978 it easier for package maintainers to properly invoke an
6979 initscript, obeying runlevel and other locally-defined
6980 constraints that might limit a package's right to start,
6981 stop and otherwise manage services. This program may be
6982 used by maintainers in their packages' scripts.
6986 The package maintainer scripts must use
6987 <prgn>invoke-rc.d</prgn> to invoke the
6988 <file>/etc/init.d/*</file> initscripts, instead of
6989 calling them directly.
6993 By default, <prgn>invoke-rc.d</prgn> will pass any
6994 action requests (start, stop, reload, restart...) to the
6995 <file>/etc/init.d</file> script, filtering out requests
6996 to start or restart a service out of its intended
7001 Most packages will simply need to change:
7002 <example compact="compact">/etc/init.d/<package>
7003 <action></example> in their <prgn>postinst</prgn>
7004 and <prgn>prerm</prgn> scripts to:
7005 <example compact="compact">
7006 if which invoke-rc.d >/dev/null 2>&1; then
7007 invoke-rc.d <var>package</var> <action>
7009 /etc/init.d/<var>package</var> <action>
7015 A package should register its initscript services using
7016 <prgn>update-rc.d</prgn> before it tries to invoke them
7017 using <prgn>invoke-rc.d</prgn>. Invocation of
7018 unregistered services may fail.
7022 For more information about using
7023 <prgn>invoke-rc.d</prgn>, please consult its man page
7024 <manref name="invoke-rc.d" section="8">.
7030 <heading>Boot-time initialization</heading>
7033 There used to be another directory, <file>/etc/rc.boot</file>,
7034 which contained scripts which were run once per machine
7035 boot. This has been deprecated in favour of links from
7036 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
7037 described in <ref id="/etc/init.d">. Packages must not
7038 place files in <file>/etc/rc.boot</file>.
7043 <heading>Example</heading>
7046 An example on which you can base your
7047 <file>/etc/init.d</file> scripts is found in
7048 <file>/etc/init.d/skeleton</file>.
7055 <heading>Console messages from <file>init.d</file> scripts</heading>
7058 This section describes the formats to be used for messages
7059 written to standard output by the <file>/etc/init.d</file>
7060 scripts. The intent is to improve the consistency of
7061 Debian's startup and shutdown look and feel. For this
7062 reason, please look very carefully at the details. We want
7063 the messages to have the same format in terms of wording,
7064 spaces, punctuation and case of letters.
7068 Here is a list of overall rules that should be used for
7069 messages generated by <file>/etc/init.d</file> scripts.
7075 The message should fit in one line (fewer than 80
7076 characters), start with a capital letter and end with
7077 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7081 If the script is performing some time consuming task in
7082 the background (not merely starting or stopping a
7083 program, for instance), an ellipsis (three dots:
7084 <tt>...</tt>) should be output to the screen, with no
7085 leading or tailing whitespace or line feeds.
7089 The messages should appear as if the computer is telling
7090 the user what it is doing (politely :-), but should not
7091 mention "it" directly. For example, instead of:
7092 <example compact="compact">
7093 I'm starting network daemons: nfsd mountd.
7095 the message should say
7096 <example compact="compact">
7097 Starting network daemons: nfsd mountd.
7104 <tt>init.d</tt> script should use the following standard
7105 message formats for the situations enumerated below.
7111 <p>When daemons are started</p>
7114 If the script starts one or more daemons, the output
7115 should look like this (a single line, no leading
7117 <example compact="compact">
7118 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7120 The <var>description</var> should describe the
7121 subsystem the daemon or set of daemons are part of,
7122 while <var>daemon-1</var> up to <var>daemon-n</var>
7123 denote each daemon's name (typically the file name of
7128 For example, the output of <file>/etc/init.d/lpd</file>
7130 <example compact="compact">
7131 Starting printer spooler: lpd.
7136 This can be achieved by saying
7137 <example compact="compact">
7138 echo -n "Starting printer spooler: lpd"
7139 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7142 in the script. If there are more than one daemon to
7143 start, the output should look like this:
7144 <example compact="compact">
7145 echo -n "Starting remote file system services:"
7146 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7147 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7148 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7151 This makes it possible for the user to see what is
7152 happening and when the final daemon has been started.
7153 Care should be taken in the placement of white spaces:
7154 in the example above the system administrators can
7155 easily comment out a line if they don't want to start
7156 a specific daemon, while the displayed message still
7162 <p>When a system parameter is being set</p>
7165 If you have to set up different system parameters
7166 during the system boot, you should use this format:
7167 <example compact="compact">
7168 Setting <var>parameter</var> to "<var>value</var>".
7173 You can use a statement such as the following to get
7175 <example compact="compact">
7176 echo "Setting DNS domainname to \"$domainname\"."
7181 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7182 for the left and right quotation marks. A grave accent
7183 (<tt>`</tt>) is not a quote character; neither is an
7184 apostrophe (<tt>'</tt>).
7189 <p>When a daemon is stopped or restarted</p>
7192 When you stop or restart a daemon, you should issue a
7193 message identical to the startup message, except that
7194 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7195 or <tt>Restarting</tt> respectively.
7199 For example, stopping the printer daemon will look like
7201 <example compact="compact">
7202 Stopping printer spooler: lpd.
7208 <p>When something is executed</p>
7211 There are several examples where you have to run a
7212 program at system startup or shutdown to perform a
7213 specific task, for example, setting the system's clock
7214 using <prgn>netdate</prgn> or killing all processes
7215 when the system shuts down. Your message should look
7217 <example compact="compact">
7218 Doing something very useful...done.
7220 You should print the <tt>done.</tt> immediately after
7221 the job has been completed, so that the user is
7222 informed why they have to wait. You can get this
7224 <example compact="compact">
7225 echo -n "Doing something very useful..."
7234 <p>When the configuration is reloaded</p>
7237 When a daemon is forced to reload its configuration
7238 files you should use the following format:
7239 <example compact="compact">
7240 Reloading <var>description</var> configuration...done.
7242 where <var>description</var> is the same as in the
7243 daemon starting message.
7250 <sect id="cron-jobs">
7251 <heading>Cron jobs</heading>
7254 Packages must not modify the configuration file
7255 <file>/etc/crontab</file>, and they must not modify the files in
7256 <file>/var/spool/cron/crontabs</file>.
7260 If a package wants to install a job that has to be executed via
7261 cron, it should place a file named as specified
7262 in <ref id="cron-files"> into one or more of the following
7264 <example compact="compact">
7270 As these directory names imply, the files within them are
7271 executed on an hourly, daily, weekly, or monthly basis,
7272 respectively. The exact times are listed in
7273 <file>/etc/crontab</file>.
7277 All files installed in any of these directories must be
7278 scripts (e.g., shell scripts or Perl scripts) so that they
7279 can easily be modified by the local system administrator.
7280 In addition, they must be treated as configuration files.
7284 If a certain job has to be executed at some other frequency or
7285 at a specific time, the package should install a file in
7286 <file>/etc/cron.d</file> with a name as specified
7287 in <ref id="cron-files">. This file uses the same syntax
7288 as <file>/etc/crontab</file> and is processed
7289 by <prgn>cron</prgn> automatically. The file must also be
7290 treated as a configuration file. (Note that entries in the
7291 <file>/etc/cron.d</file> directory are not handled by
7292 <prgn>anacron</prgn>. Thus, you should only use this
7293 directory for jobs which may be skipped if the system is not
7298 Unlike <file>crontab</file> files described in the IEEE Std
7299 1003.1-2008 (POSIX.1) available from
7300 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7301 name="The Open Group">, the files in
7302 <file>/etc/cron.d</file> and the file
7303 <file>/etc/crontab</file> have seven fields; namely:
7305 <item>Minute [0,59]</item>
7306 <item>Hour [0,23]</item>
7307 <item>Day of the month [1,31]</item>
7308 <item>Month of the year [1,12]</item>
7309 <item>Day of the week ([0,6] with 0=Sunday)</item>
7310 <item>Username</item>
7311 <item>Command to be run</item>
7313 Ranges of numbers are allowed. Ranges are two numbers
7314 separated with a hyphen. The specified range is inclusive.
7315 Lists are allowed. A list is a set of numbers (or ranges)
7316 separated by commas. Step values can be used in conjunction
7321 The scripts or <tt>crontab</tt> entries in these directories should
7322 check if all necessary programs are installed before they
7323 try to execute them. Otherwise, problems will arise when a
7324 package was removed but not purged since configuration files
7325 are kept on the system in this situation.
7329 Any <tt>cron</tt> daemon must provide
7330 <file>/usr/bin/crontab</file> and support normal
7331 <tt>crontab</tt> entries as specified in POSIX. The daemon
7332 must also support names for days and months, ranges, and
7333 step values. It has to support <file>/etc/crontab</file>,
7334 and correctly execute the scripts in
7335 <file>/etc/cron.d</file>. The daemon must also correctly
7337 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7340 <sect1 id="cron-files">
7341 <heading>Cron job file names</heading>
7344 The file name of a cron job file should normally match the
7345 name of the package from which it comes.
7349 If a package supplies multiple cron job files files in the
7350 same directory, the file names should all start with the name
7351 of the package (possibly modified as described below) followed
7352 by a hyphen (<tt>-</tt>) and a suitable suffix.
7356 A cron job file name must not include any period or plus
7357 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7358 cause cron to ignore the file. Underscores (<tt>_</tt>)
7359 should be used instead of <tt>.</tt> and <tt>+</tt>
7366 <heading>Menus</heading>
7369 The Debian <tt>menu</tt> package provides a standard
7370 interface between packages providing applications and
7371 <em>menu programs</em> (either X window managers or
7372 text-based menu programs such as <prgn>pdmenu</prgn>).
7376 All packages that provide applications that need not be
7377 passed any special command line arguments for normal
7378 operation should register a menu entry for those
7379 applications, so that users of the <tt>menu</tt> package
7380 will automatically get menu entries in their window
7381 managers, as well in shells like <tt>pdmenu</tt>.
7385 Menu entries should follow the current menu policy.
7389 The menu policy can be found in the <tt>menu-policy</tt>
7390 files in the <tt>debian-policy</tt> package.
7391 It is also available from the Debian web mirrors at
7392 <tt><url name="/doc/packaging-manuals/menu-policy/"
7393 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7397 Please also refer to the <em>Debian Menu System</em>
7398 documentation that comes with the <package>menu</package>
7399 package for information about how to register your
7405 <heading>Multimedia handlers</heading>
7408 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7409 is a mechanism for encoding files and data streams and
7410 providing meta-information about them, in particular their
7411 type (e.g. audio or video) and format (e.g. PNG, HTML,
7416 Registration of MIME type handlers allows programs like mail
7417 user agents and web browsers to invoke these handlers to
7418 view, edit or display MIME types they don't support directly.
7422 Packages which provide the ability to view/show/play,
7423 compose, edit or print MIME types should register themselves
7424 as such following the current MIME support policy.
7428 The <package>mime-support</package> package provides the
7429 <prgn>update-mime</prgn> program which allows packages to
7430 register programs that can show, compose, edit or print
7435 Packages containing such programs must register them
7436 with <prgn>update-mime</prgn> as documented in <manref
7437 name="update-mime" section="8">. They should <em>not</em> depend
7438 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7439 they should just put something like the following in the
7440 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7443 if [ -x /usr/sbin/update-mime ]; then
7452 <heading>Keyboard configuration</heading>
7455 To achieve a consistent keyboard configuration so that all
7456 applications interpret a keyboard event the same way, all
7457 programs in the Debian distribution must be configured to
7458 comply with the following guidelines.
7462 The following keys must have the specified interpretations:
7465 <tag><tt><--</tt></tag>
7466 <item>delete the character to the left of the cursor</item>
7468 <tag><tt>Delete</tt></tag>
7469 <item>delete the character to the right of the cursor</item>
7471 <tag><tt>Control+H</tt></tag>
7472 <item>emacs: the help prefix</item>
7475 The interpretation of any keyboard events should be
7476 independent of the terminal that is used, be it a virtual
7477 console, an X terminal emulator, an rlogin/telnet session,
7482 The following list explains how the different programs
7483 should be set up to achieve this:
7489 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7493 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7497 X translations are set up to make
7498 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7499 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7500 is the vt220 escape code for the "delete character"
7501 key). This must be done by loading the X resources
7502 using <prgn>xrdb</prgn> on all local X displays, not
7503 using the application defaults, so that the
7504 translation resources used correspond to the
7505 <prgn>xmodmap</prgn> settings.
7509 The Linux console is configured to make
7510 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7511 generate <tt>ESC [ 3 ~</tt>.
7515 X applications are configured so that <tt><</tt>
7516 deletes left, and <tt>Delete</tt> deletes right. Motif
7517 applications already work like this.
7521 Terminals should have <tt>stty erase ^?</tt> .
7525 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7526 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7527 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7531 Emacs is programmed to map <tt>KB_Backspace</tt> or
7532 the <tt>stty erase</tt> character to
7533 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7534 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7535 <tt>^H</tt> to <tt>help</tt> as always.
7539 Other applications use the <tt>stty erase</tt>
7540 character and <tt>kdch1</tt> for the two delete keys,
7541 with ASCII DEL being "delete previous character" and
7542 <tt>kdch1</tt> being "delete character under
7550 This will solve the problem except for the following
7557 Some terminals have a <tt><--</tt> key that cannot
7558 be made to produce anything except <tt>^H</tt>. On
7559 these terminals Emacs help will be unavailable on
7560 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7561 character takes precedence in Emacs, and has been set
7562 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7563 available) can be used instead.
7567 Some operating systems use <tt>^H</tt> for <tt>stty
7568 erase</tt>. However, modern telnet versions and all
7569 rlogin versions propagate <tt>stty</tt> settings, and
7570 almost all UNIX versions honour <tt>stty erase</tt>.
7571 Where the <tt>stty</tt> settings are not propagated
7572 correctly, things can be made to work by using
7573 <tt>stty</tt> manually.
7577 Some systems (including previous Debian versions) use
7578 <prgn>xmodmap</prgn> to arrange for both
7579 <tt><--</tt> and <tt>Delete</tt> to generate
7580 <tt>KB_Delete</tt>. We can change the behavior of
7581 their X clients using the same X resources that we use
7582 to do it for our own clients, or configure our clients
7583 using their resources when things are the other way
7584 around. On displays configured like this
7585 <tt>Delete</tt> will not work, but <tt><--</tt>
7590 Some operating systems have different <tt>kdch1</tt>
7591 settings in their <tt>terminfo</tt> database for
7592 <tt>xterm</tt> and others. On these systems the
7593 <tt>Delete</tt> key will not work correctly when you
7594 log in from a system conforming to our policy, but
7595 <tt><--</tt> will.
7602 <heading>Environment variables</heading>
7605 A program must not depend on environment variables to get
7606 reasonable defaults. (That's because these environment
7607 variables would have to be set in a system-wide
7608 configuration file like <file>/etc/profile</file>, which is not
7609 supported by all shells.)
7613 If a program usually depends on environment variables for its
7614 configuration, the program should be changed to fall back to
7615 a reasonable default configuration if these environment
7616 variables are not present. If this cannot be done easily
7617 (e.g., if the source code of a non-free program is not
7618 available), the program must be replaced by a small
7619 "wrapper" shell script which sets the environment variables
7620 if they are not already defined, and calls the original program.
7624 Here is an example of a wrapper script for this purpose:
7626 <example compact="compact">
7628 BAR=${BAR:-/var/lib/fubar}
7630 exec /usr/lib/foo/foo "$@"
7635 Furthermore, as <file>/etc/profile</file> is a configuration
7636 file of the <prgn>base-files</prgn> package, other packages must
7637 not put any environment variables or other commands into that
7642 <sect id="doc-base">
7643 <heading>Registering Documents using doc-base</heading>
7646 The <package>doc-base</package> package implements a
7647 flexible mechanism for handling and presenting
7648 documentation. The recommended practice is for every Debian
7649 package that provides online documentation (other than just
7650 manual pages) to register these documents with
7651 <package>doc-base</package> by installing a
7652 <package>doc-base</package> control file in
7653 <file>/usr/share/doc-base/</file>.
7656 Please refer to the documentation that comes with the
7657 <package>doc-base</package> package for information and
7666 <heading>Files</heading>
7668 <sect id="binaries">
7669 <heading>Binaries</heading>
7672 Two different packages must not install programs with
7673 different functionality but with the same filenames. (The
7674 case of two programs having the same functionality but
7675 different implementations is handled via "alternatives" or
7676 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7677 <ref id="conflicts"> respectively.) If this case happens,
7678 one of the programs must be renamed. The maintainers should
7679 report this to the <tt>debian-devel</tt> mailing list and
7680 try to find a consensus about which program will have to be
7681 renamed. If a consensus cannot be reached, <em>both</em>
7682 programs must be renamed.
7686 By default, when a package is being built, any binaries
7687 created should include debugging information, as well as
7688 being compiled with optimization. You should also turn on
7689 as many reasonable compilation warnings as possible; this
7690 makes life easier for porters, who can then look at build
7691 logs for possible problems. For the C programming language,
7692 this means the following compilation parameters should be
7694 <example compact="compact">
7696 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7698 INSTALL = install -s # (or use strip on the files in debian/tmp)
7703 Note that by default all installed binaries should be stripped,
7704 either by using the <tt>-s</tt> flag to
7705 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7706 the binaries after they have been copied into
7707 <file>debian/tmp</file> but before the tree is made into a
7712 Although binaries in the build tree should be compiled with
7713 debugging information by default, it can often be difficult to
7714 debug programs if they are also subjected to compiler
7715 optimization. For this reason, it is recommended to support the
7716 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7717 (see <ref id="debianrules-options">). This variable can contain
7718 several flags to change how a package is compiled and built.
7722 It is up to the package maintainer to decide what
7723 compilation options are best for the package. Certain
7724 binaries (such as computationally-intensive programs) will
7725 function better with certain flags (<tt>-O3</tt>, for
7726 example); feel free to use them. Please use good judgment
7727 here. Don't use flags for the sake of it; only use them
7728 if there is good reason to do so. Feel free to override
7729 the upstream author's ideas about which compilation
7730 options are best: they are often inappropriate for our
7736 <sect id="libraries">
7737 <heading>Libraries</heading>
7740 If the package is <strong>architecture: any</strong>, then
7741 the shared library compilation and linking flags must have
7742 <tt>-fPIC</tt>, or the package shall not build on some of
7743 the supported architectures<footnote>
7745 If you are using GCC, <tt>-fPIC</tt> produces code with
7746 relocatable position independent code, which is required for
7747 most architectures to create a shared library, with i386 and
7748 perhaps some others where non position independent code is
7749 permitted in a shared library.
7752 Position independent code may have a performance penalty,
7753 especially on <tt>i386</tt>. However, in most cases the
7754 speed penalty must be measured against the memory wasted on
7755 the few architectures where non position independent code is
7758 </footnote>. Any exception to this rule must be discussed on
7759 the mailing list <em>debian-devel@lists.debian.org</em>, and
7760 a rough consensus obtained. The reasons for not compiling
7761 with <tt>-fPIC</tt> flag must be recorded in the file
7762 <tt>README.Debian</tt>, and care must be taken to either
7763 restrict the architecture or arrange for <tt>-fPIC</tt> to
7764 be used on architectures where it is required.<footnote>
7766 Some of the reasons why this might be required is if the
7767 library contains hand crafted assembly code that is not
7768 relocatable, the speed penalty is excessive for compute
7769 intensive libs, and similar reasons.
7774 As to the static libraries, the common case is not to have
7775 relocatable code, since there is no benefit, unless in specific
7776 cases; therefore the static version must not be compiled
7777 with the <tt>-fPIC</tt> flag. Any exception to this rule
7778 should be discussed on the mailing list
7779 <em>debian-devel@lists.debian.org</em>, and the reasons for
7780 compiling with the <tt>-fPIC</tt> flag must be recorded in
7781 the file <tt>README.Debian</tt>. <footnote>
7783 Some of the reasons for linking static libraries with
7784 the <tt>-fPIC</tt> flag are if, for example, one needs a
7785 Perl API for a library that is under rapid development,
7786 and has an unstable API, so shared libraries are
7787 pointless at this phase of the library's development. In
7788 that case, since Perl needs a library with relocatable
7789 code, it may make sense to create a static library with
7790 relocatable code. Another reason cited is if you are
7791 distilling various libraries into a common shared
7792 library, like <tt>mklibs</tt> does in the Debian
7798 In other words, if both a shared and a static library is
7799 being built, each source unit (<tt>*.c</tt>, for example,
7800 for C files) will need to be compiled twice, for the normal
7805 Libraries should be built with threading support and to be
7806 thread-safe if the library supports this.
7810 Although not enforced by the build tools, shared libraries
7811 must be linked against all libraries that they use symbols from
7812 in the same way that binaries are. This ensures the correct
7813 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7814 system and guarantees that all libraries can be safely opened
7815 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7816 option <tt>-Wl,-z,defs</tt> when building a shared library.
7817 Since this option enforces symbol resolution at build time,
7818 a missing library reference will be caught early as a fatal
7823 All installed shared libraries should be stripped with
7824 <example compact="compact">
7825 strip --strip-unneeded <var>your-lib</var>
7827 (The option <tt>--strip-unneeded</tt> makes
7828 <prgn>strip</prgn> remove only the symbols which aren't
7829 needed for relocation processing.) Shared libraries can
7830 function perfectly well when stripped, since the symbols for
7831 dynamic linking are in a separate part of the ELF object
7833 You might also want to use the options
7834 <tt>--remove-section=.comment</tt> and
7835 <tt>--remove-section=.note</tt> on both shared libraries
7836 and executables, and <tt>--strip-debug</tt> on static
7842 Note that under some circumstances it may be useful to
7843 install a shared library unstripped, for example when
7844 building a separate package to support debugging.
7848 Shared object files (often <file>.so</file> files) that are not
7849 public libraries, that is, they are not meant to be linked
7850 to by third party executables (binaries of other packages),
7851 should be installed in subdirectories of the
7852 <file>/usr/lib</file> directory. Such files are exempt from the
7853 rules that govern ordinary shared libraries, except that
7854 they must not be installed executable and should be
7856 A common example are the so-called "plug-ins",
7857 internal shared objects that are dynamically loaded by
7858 programs using <manref name="dlopen" section="3">.
7863 Packages that use <prgn>libtool</prgn> to create and install
7864 their shared libraries install a file containing additional
7865 metadata (ending in <file>.la</file>) alongside the library.
7866 For public libraries intended for use by other packages, these
7867 files normally should not be included in the Debian package,
7868 since the information they include is not necessary to link with
7869 the shared library on Debian and can add unnecessary additional
7870 dependencies to other programs or libraries.<footnote>
7871 These files store, among other things, all libraries on which
7872 that shared library depends. Unfortunately, if
7873 the <file>.la</file> file is present and contains that
7874 dependency information, using <prgn>libtool</prgn> when
7875 linking against that library will cause the resulting program
7876 or library to be linked against those dependencies as well,
7877 even if this is unnecessary. This can create unneeded
7878 dependencies on shared library packages that would otherwise
7879 be hidden behind the library ABI, and can make library
7880 transitions to new SONAMEs unnecessarily complicated and
7881 difficult to manage.
7883 If the <file>.la</file> file is required for that library (if,
7884 for instance, it's loaded via <tt>libltdl</tt> in a way that
7885 requires that meta-information), the <tt>dependency_libs</tt>
7886 setting in the <file>.la</file> file should normally be set to
7887 the empty string. If the shared library development package has
7888 historically included the <file>.la</file>, it must be retained
7889 in the development package (with <tt>dependency_libs</tt>
7890 emptied) until all libraries that depend on it have removed or
7891 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7892 files to prevent linking with those other libraries
7893 using <prgn>libtool</prgn> from failing.
7897 If the <file>.la</file> must be included, it should be included
7898 in the development (<tt>-dev</tt>) package, unless the library
7899 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7900 library. If it is intended for use with <tt>libltdl</tt>,
7901 the <file>.la</file> files must go in the run-time library
7906 These requirements for handling of <file>.la</file> files do not
7907 apply to loadable modules or libraries not installed in
7908 directories searched by default by the dynamic linker. Packages
7909 installing loadable modules will frequently need to install
7910 the <file>.la</file> files alongside the modules so that they
7911 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7912 does not need to be modified for libraries or modules that are
7913 not installed in directories searched by the dynamic linker by
7914 default and not intended for use by other packages.
7918 You must make sure that you use only released versions of
7919 shared libraries to build your packages; otherwise other
7920 users will not be able to run your binaries
7921 properly. Producing source packages that depend on
7922 unreleased compilers is also usually a bad
7929 <heading>Shared libraries</heading>
7931 This section has moved to <ref id="sharedlibs">.
7937 <heading>Scripts</heading>
7940 All command scripts, including the package maintainer
7941 scripts inside the package and used by <prgn>dpkg</prgn>,
7942 should have a <tt>#!</tt> line naming the shell to be used
7947 In the case of Perl scripts this should be
7948 <tt>#!/usr/bin/perl</tt>.
7952 When scripts are installed into a directory in the system
7953 PATH, the script name should not include an extension such
7954 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7955 language currently used to implement it.
7958 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7959 <file>init.d</file> scripts should almost certainly start
7960 with <tt>set -e</tt> so that errors are detected.
7961 <file>init.d</file> scripts are something of a special case, due
7962 to how frequently they need to call commands that are allowed to
7963 fail, and it may instead be easier to check the exit status of
7964 commands directly. See <ref id="writing-init"> for more
7965 information about writing <file>init.d</file> scripts.
7968 Every script should use <tt>set -e</tt> or check the exit status
7969 of <em>every</em> command.
7972 Scripts may assume that <file>/bin/sh</file> implements the
7973 SUSv3 Shell Command Language<footnote>
7974 Single UNIX Specification, version 3, which is also IEEE
7975 1003.1-2004 (POSIX), and is available on the World Wide Web
7976 from <url id="http://www.unix.org/version3/online.html"
7977 name="The Open Group"> after free
7978 registration.</footnote>
7979 plus the following additional features not mandated by
7981 These features are in widespread use in the Linux community
7982 and are implemented in all of bash, dash, and ksh, the most
7983 common shells users may wish to use as <file>/bin/sh</file>.
7986 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7987 must not generate a newline.</item>
7988 <item><tt>test</tt>, if implemented as a shell built-in, must
7989 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7991 <item><tt>local</tt> to create a scoped variable must be
7992 supported, including listing multiple variables in a single
7993 local command and assigning a value to a variable at the
7994 same time as localizing it. <tt>local</tt> may or
7995 may not preserve the variable value from an outer scope if
7996 no assignment is present. Uses such as:
8000 # ... use a, b, c, d ...
8003 must be supported and must set the value of <tt>c</tt> to
8006 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
8007 -<var>signal</var></tt>, where <var>signal</var> is either
8008 the name of a signal or one of the numeric signals listed in
8009 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
8010 supported if <prgn>kill</prgn> is implemented as a shell
8013 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
8014 signals must be supported. In addition to the signal
8015 numbers listed in the extension, which are the same as for
8016 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
8019 If a shell script requires non-SUSv3 features from the shell
8020 interpreter other than those listed above, the appropriate shell
8021 must be specified in the first line of the script (e.g.,
8022 <tt>#!/bin/bash</tt>) and the package must depend on the package
8023 providing the shell (unless the shell package is marked
8024 "Essential", as in the case of <prgn>bash</prgn>).
8028 You may wish to restrict your script to SUSv3 features plus the
8029 above set when possible so that it may use <file>/bin/sh</file>
8030 as its interpreter. Checking your script
8031 with <prgn>checkbashisms</prgn> from
8032 the <package>devscripts</package> package or running your script
8033 with an alternate shell such as <prgn>posh</prgn> may help
8034 uncover violations of the above requirements. If in doubt
8035 whether a script complies with these requirements,
8036 use <file>/bin/bash</file>.
8040 Perl scripts should check for errors when making any
8041 system calls, including <tt>open</tt>, <tt>print</tt>,
8042 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
8046 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
8047 scripting languages. See <em>Csh Programming Considered
8048 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
8049 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
8050 If an upstream package comes with <prgn>csh</prgn> scripts
8051 then you must make sure that they start with
8052 <tt>#!/bin/csh</tt> and make your package depend on the
8053 <prgn>c-shell</prgn> virtual package.
8057 Any scripts which create files in world-writeable
8058 directories (e.g., in <file>/tmp</file>) must use a
8059 mechanism which will fail atomically if a file with the same
8060 name already exists.
8064 The Debian base system provides the <prgn>tempfile</prgn>
8065 and <prgn>mktemp</prgn> utilities for use by scripts for
8072 <heading>Symbolic links</heading>
8075 In general, symbolic links within a top-level directory should
8076 be relative, and symbolic links pointing from one top-level
8077 directory to or into another should be absolute. (A top-level
8078 directory is a sub-directory of the root
8079 directory <file>/</file>.) For example, a symbolic link
8080 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8081 should be relative (<file>../share/bar</file>), but a symbolic
8082 link from <file>/var/run</file> to <file>/run</file> should be
8084 This is necessary to allow top-level directories to be
8085 symlinks. If linking <file>/var/run</file>
8086 to <file>/run</file> were done with the relative symbolic
8087 link <file>../run</file>, but <file>/var</file> were a
8088 symbolic link to <file>/srv/disk1</file>, the symbolic link
8089 would point to <file>/srv/run</file> rather than the intended
8095 In addition, symbolic links should be specified as short as
8096 possible, i.e., link targets like <file>foo/../bar</file> are
8101 Note that when creating a relative link using
8102 <prgn>ln</prgn> it is not necessary for the target of the
8103 link to exist relative to the working directory you're
8104 running <prgn>ln</prgn> from, nor is it necessary to change
8105 directory to the directory where the link is to be made.
8106 Simply include the string that should appear as the target
8107 of the link (this will be a pathname relative to the
8108 directory in which the link resides) as the first argument
8113 For example, in your <prgn>Makefile</prgn> or
8114 <file>debian/rules</file>, you can do things like:
8115 <example compact="compact">
8116 ln -fs gcc $(prefix)/bin/cc
8117 ln -fs gcc debian/tmp/usr/bin/cc
8118 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8119 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8124 A symbolic link pointing to a compressed file should always
8125 have the same file extension as the referenced file. (For
8126 example, if a file <file>foo.gz</file> is referenced by a
8127 symbolic link, the filename of the link has to end with
8128 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8133 <heading>Device files</heading>
8136 Packages must not include device files or named pipes in the
8141 If a package needs any special device files that are not
8142 included in the base system, it must call
8143 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8144 after notifying the user<footnote>
8145 This notification could be done via a (low-priority)
8146 debconf message, or an echo (printf) statement.
8151 Packages must not remove any device files in the
8152 <prgn>postrm</prgn> or any other script. This is left to the
8153 system administrator.
8157 Debian uses the serial devices
8158 <file>/dev/ttyS*</file>. Programs using the old
8159 <file>/dev/cu*</file> devices should be changed to use
8160 <file>/dev/ttyS*</file>.
8164 Named pipes needed by the package must be created in
8165 the <prgn>postinst</prgn> script<footnote>
8166 It's better to use <prgn>mkfifo</prgn> rather
8167 than <prgn>mknod</prgn> to create named pipes so that
8168 automated checks for packages incorrectly creating device
8169 files with <prgn>mknod</prgn> won't have false positives.
8170 </footnote> and removed in
8171 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8176 <sect id="config-files">
8177 <heading>Configuration files</heading>
8180 <heading>Definitions</heading>
8184 <tag>configuration file</tag>
8186 A file that affects the operation of a program, or
8187 provides site- or host-specific information, or
8188 otherwise customizes the behavior of a program.
8189 Typically, configuration files are intended to be
8190 modified by the system administrator (if needed or
8191 desired) to conform to local policy or to provide
8192 more useful site-specific behavior.
8195 <tag><tt>conffile</tt></tag>
8197 A file listed in a package's <tt>conffiles</tt>
8198 file, and is treated specially by <prgn>dpkg</prgn>
8199 (see <ref id="configdetails">).
8205 The distinction between these two is important; they are
8206 not interchangeable concepts. Almost all
8207 <tt>conffile</tt>s are configuration files, but many
8208 configuration files are not <tt>conffiles</tt>.
8212 As noted elsewhere, <file>/etc/init.d</file> scripts,
8213 <file>/etc/default</file> files, scripts installed in
8214 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8215 configuration installed in <file>/etc/cron.d</file> must be
8216 treated as configuration files. In general, any script that
8217 embeds configuration information is de-facto a configuration
8218 file and should be treated as such.
8223 <heading>Location</heading>
8226 Any configuration files created or used by your package
8227 must reside in <file>/etc</file>. If there are several,
8228 consider creating a subdirectory of <file>/etc</file>
8229 named after your package.
8233 If your package creates or uses configuration files
8234 outside of <file>/etc</file>, and it is not feasible to modify
8235 the package to use <file>/etc</file> directly, put the files
8236 in <file>/etc</file> and create symbolic links to those files
8237 from the location that the package requires.
8242 <heading>Behavior</heading>
8245 Configuration file handling must conform to the following
8247 <list compact="compact">
8249 local changes must be preserved during a package
8253 configuration files must be preserved when the
8254 package is removed, and only deleted when the
8258 Obsolete configuration files without local changes may be
8259 removed by the package during upgrade.
8263 The easy way to achieve this behavior is to make the
8264 configuration file a <tt>conffile</tt>. This is
8265 appropriate only if it is possible to distribute a default
8266 version that will work for most installations, although
8267 some system administrators may choose to modify it. This
8268 implies that the default version will be part of the
8269 package distribution, and must not be modified by the
8270 maintainer scripts during installation (or at any other
8275 In order to ensure that local changes are preserved
8276 correctly, no package may contain or make hard links to
8277 conffiles.<footnote>
8278 Rationale: There are two problems with hard links.
8279 The first is that some editors break the link while
8280 editing one of the files, so that the two files may
8281 unwittingly become unlinked and different. The second
8282 is that <prgn>dpkg</prgn> might break the hard link
8283 while upgrading <tt>conffile</tt>s.
8288 The other way to do it is via the maintainer scripts. In
8289 this case, the configuration file must not be listed as a
8290 <tt>conffile</tt> and must not be part of the package
8291 distribution. If the existence of a file is required for
8292 the package to be sensibly configured it is the
8293 responsibility of the package maintainer to provide
8294 maintainer scripts which correctly create, update and
8295 maintain the file and remove it on purge. (See <ref
8296 id="maintainerscripts"> for more information.) These
8297 scripts must be idempotent (i.e., must work correctly if
8298 <prgn>dpkg</prgn> needs to re-run them due to errors
8299 during installation or removal), must cope with all the
8300 variety of ways <prgn>dpkg</prgn> can call maintainer
8301 scripts, must not overwrite or otherwise mangle the user's
8302 configuration without asking, must not ask unnecessary
8303 questions (particularly during upgrades), and must
8304 otherwise be good citizens.
8308 The scripts are not required to configure every possible
8309 option for the package, but only those necessary to get
8310 the package running on a given system. Ideally the
8311 sysadmin should not have to do any configuration other
8312 than that done (semi-)automatically by the
8313 <prgn>postinst</prgn> script.
8317 A common practice is to create a script called
8318 <file><var>package</var>-configure</file> and have the
8319 package's <prgn>postinst</prgn> call it if and only if the
8320 configuration file does not already exist. In certain
8321 cases it is useful for there to be an example or template
8322 file which the maintainer scripts use. Such files should
8323 be in <file>/usr/share/<var>package</var></file> or
8324 <file>/usr/lib/<var>package</var></file> (depending on whether
8325 they are architecture-independent or not). There should
8326 be symbolic links to them from
8327 <file>/usr/share/doc/<var>package</var>/examples</file> if
8328 they are examples, and should be perfectly ordinary
8329 <prgn>dpkg</prgn>-handled files (<em>not</em>
8330 configuration files).
8334 These two styles of configuration file handling must
8335 not be mixed, for that way lies madness:
8336 <prgn>dpkg</prgn> will ask about overwriting the file
8337 every time the package is upgraded.
8342 <heading>Sharing configuration files</heading>
8345 If two or more packages use the same configuration file
8346 and it is reasonable for both to be installed at the same
8347 time, one of these packages must be defined as
8348 <em>owner</em> of the configuration file, i.e., it will be
8349 the package which handles that file as a configuration
8350 file. Other packages that use the configuration file must
8351 depend on the owning package if they require the
8352 configuration file to operate. If the other package will
8353 use the configuration file if present, but is capable of
8354 operating without it, no dependency need be declared.
8358 If it is desirable for two or more related packages to
8359 share a configuration file <em>and</em> for all of the
8360 related packages to be able to modify that configuration
8361 file, then the following should be done:
8362 <enumlist compact="compact">
8364 One of the related packages (the "owning" package)
8365 will manage the configuration file with maintainer
8366 scripts as described in the previous section.
8369 The owning package should also provide a program
8370 that the other packages may use to modify the
8374 The related packages must use the provided program
8375 to make any desired modifications to the
8376 configuration file. They should either depend on
8377 the core package to guarantee that the configuration
8378 modifier program is available or accept gracefully
8379 that they cannot modify the configuration file if it
8380 is not. (This is in addition to the fact that the
8381 configuration file may not even be present in the
8388 Sometimes it's appropriate to create a new package which
8389 provides the basic infrastructure for the other packages
8390 and which manages the shared configuration files. (The
8391 <tt>sgml-base</tt> package is a good example.)
8395 If the configuration file cannot be shared as described above,
8396 the packages must be marked as conflicting with each other.
8397 Two packages that specify the same file as
8398 a <tt>conffile</tt> must conflict. This is an instance of the
8399 general rule about not sharing files. Neither alternatives
8400 nor diversions are likely to be appropriate in this case; in
8401 particular, <prgn>dpkg</prgn> does not handle diverted
8402 <tt>conffile</tt>s well.
8406 When two packages both declare the same <tt>conffile</tt>, they
8407 may see left-over configuration files from each other even
8408 though they conflict with each other. If a user removes
8409 (without purging) one of the packages and installs the other,
8410 the new package will take over the <tt>conffile</tt> from the
8411 old package. If the file was modified by the user, it will be
8412 treated the same as any other locally
8413 modified <tt>conffile</tt> during an upgrade.
8417 The maintainer scripts must not alter a <tt>conffile</tt>
8418 of <em>any</em> package, including the one the scripts
8424 <heading>User configuration files ("dotfiles")</heading>
8427 The files in <file>/etc/skel</file> will automatically be
8428 copied into new user accounts by <prgn>adduser</prgn>.
8429 No other program should reference the files in
8430 <file>/etc/skel</file>.
8434 Therefore, if a program needs a dotfile to exist in
8435 advance in <file>$HOME</file> to work sensibly, that dotfile
8436 should be installed in <file>/etc/skel</file> and treated as a
8441 However, programs that require dotfiles in order to
8442 operate sensibly are a bad thing, unless they do create
8443 the dotfiles themselves automatically.
8447 Furthermore, programs should be configured by the Debian
8448 default installation to behave as closely to the upstream
8449 default behavior as possible.
8453 Therefore, if a program in a Debian package needs to be
8454 configured in some way in order to operate sensibly, that
8455 should be done using a site-wide configuration file placed
8456 in <file>/etc</file>. Only if the program doesn't support a
8457 site-wide default configuration and the package maintainer
8458 doesn't have time to add it may a default per-user file be
8459 placed in <file>/etc/skel</file>.
8463 <file>/etc/skel</file> should be as empty as we can make it.
8464 This is particularly true because there is no easy (or
8465 necessarily desirable) mechanism for ensuring that the
8466 appropriate dotfiles are copied into the accounts of
8467 existing users when a package is installed.
8473 <heading>Log files</heading>
8475 Log files should usually be named
8476 <file>/var/log/<var>package</var>.log</file>. If you have many
8477 log files, or need a separate directory for permission
8478 reasons (<file>/var/log</file> is writable only by
8479 <file>root</file>), you should usually create a directory named
8480 <file>/var/log/<var>package</var></file> and place your log
8485 Log files must be rotated occasionally so that they don't grow
8486 indefinitely. The best way to do this is to install a log
8487 rotation configuration file in the
8488 directory <file>/etc/logrotate.d</file>, normally
8489 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8490 the facilities provided by <prgn>logrotate</prgn>.
8493 The traditional approach to log files has been to set up
8494 <em>ad hoc</em> log rotation schemes using simple shell
8495 scripts and cron. While this approach is highly
8496 customizable, it requires quite a lot of sysadmin work.
8497 Even though the original Debian system helped a little
8498 by automatically installing a system which can be used
8499 as a template, this was deemed not enough.
8503 The use of <prgn>logrotate</prgn>, a program developed
8504 by Red Hat, is better, as it centralizes log management.
8505 It has both a configuration file
8506 (<file>/etc/logrotate.conf</file>) and a directory where
8507 packages can drop their individual log rotation
8508 configurations (<file>/etc/logrotate.d</file>).
8511 Here is a good example for a logrotate config
8512 file (for more information see <manref name="logrotate"
8514 <example compact="compact">
8515 /var/log/foo/*.log {
8521 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8525 This rotates all files under <file>/var/log/foo</file>, saves 12
8526 compressed generations, and tells the daemon to reopen its log
8527 files after the log rotation. It skips this log rotation
8528 (via <tt>missingok</tt>) if no such log file is present, which
8529 avoids errors if the package is removed but not purged.
8533 Log files should be removed when the package is
8534 purged (but not when it is only removed). This should be
8535 done by the <prgn>postrm</prgn> script when it is called
8536 with the argument <tt>purge</tt> (see <ref
8537 id="removedetails">).
8541 <sect id="permissions-owners">
8542 <heading>Permissions and owners</heading>
8545 The rules in this section are guidelines for general use.
8546 If necessary you may deviate from the details below.
8547 However, if you do so you must make sure that what is done
8548 is secure and you should try to be as consistent as possible
8549 with the rest of the system. You should probably also
8550 discuss it on <prgn>debian-devel</prgn> first.
8554 Files should be owned by <tt>root:root</tt>, and made
8555 writable only by the owner and universally readable (and
8556 executable, if appropriate), that is mode 644 or 755.
8560 Directories should be mode 755 or (for group-writability)
8561 mode 2775. The ownership of the directory should be
8562 consistent with its mode: if a directory is mode 2775, it
8563 should be owned by the group that needs write access to
8566 When a package is upgraded, and the owner or permissions
8567 of a file included in the package has changed, dpkg
8568 arranges for the ownership and permissions to be
8569 correctly set upon installation. However, this does not
8570 extend to directories; the permissions and ownership of
8571 directories already on the system does not change on
8572 install or upgrade of packages. This makes sense, since
8573 otherwise common directories like <tt>/usr</tt> would
8574 always be in flux. To correctly change permissions of a
8575 directory the package owns, explicit action is required,
8576 usually in the <tt>postinst</tt> script. Care must be
8577 taken to handle downgrades as well, in that case.
8583 Control information files should be owned by <tt>root:root</tt>
8584 and either mode 644 (for most files) or mode 755 (for
8585 executables such as <qref id="maintscripts">maintainer
8590 Setuid and setgid executables should be mode 4755 or 2755
8591 respectively, and owned by the appropriate user or group.
8592 They should not be made unreadable (modes like 4711 or
8593 2711 or even 4111); doing so achieves no extra security,
8594 because anyone can find the binary in the freely available
8595 Debian package; it is merely inconvenient. For the same
8596 reason you should not restrict read or execute permissions
8597 on non-set-id executables.
8601 Some setuid programs need to be restricted to particular
8602 sets of users, using file permissions. In this case they
8603 should be owned by the uid to which they are set-id, and by
8604 the group which should be allowed to execute them. They
8605 should have mode 4754; again there is no point in making
8606 them unreadable to those users who must not be allowed to
8611 It is possible to arrange that the system administrator can
8612 reconfigure the package to correspond to their local
8613 security policy by changing the permissions on a binary:
8614 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8615 described below.<footnote>
8616 Ordinary files installed by <prgn>dpkg</prgn> (as
8617 opposed to <tt>conffile</tt>s and other similar objects)
8618 normally have their permissions reset to the distributed
8619 permissions when the package is reinstalled. However,
8620 the use of <prgn>dpkg-statoverride</prgn> overrides this
8623 Another method you should consider is to create a group for
8624 people allowed to use the program(s) and make any setuid
8625 executables executable only by that group.
8629 If you need to create a new user or group for your package
8630 there are two possibilities. Firstly, you may need to
8631 make some files in the binary package be owned by this
8632 user or group, or you may need to compile the user or
8633 group id (rather than just the name) into the binary
8634 (though this latter should be avoided if possible, as in
8635 this case you need a statically allocated id).</p>
8638 If you need a statically allocated id, you must ask for a
8639 user or group id from the <tt>base-passwd</tt> maintainer,
8640 and must not release the package until you have been
8641 allocated one. Once you have been allocated one you must
8642 either make the package depend on a version of the
8643 <tt>base-passwd</tt> package with the id present in
8644 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8645 your package to create the user or group itself with the
8646 correct id (using <tt>adduser</tt>) in its
8647 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8648 the <prgn>postinst</prgn> is to be preferred if it is
8649 possible, otherwise a pre-dependency will be needed on the
8650 <tt>adduser</tt> package.)
8654 On the other hand, the program might be able to determine
8655 the uid or gid from the user or group name at runtime, so
8656 that a dynamically allocated id can be used. In this case
8657 you should choose an appropriate user or group name,
8658 discussing this on <prgn>debian-devel</prgn> and checking
8659 with the <package/base-passwd/ maintainer that it is unique and that
8660 they do not wish you to use a statically allocated id
8661 instead. When this has been checked you must arrange for
8662 your package to create the user or group if necessary using
8663 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8664 <prgn>postinst</prgn> script (again, the latter is to be
8665 preferred if it is possible).
8669 Note that changing the numeric value of an id associated
8670 with a name is very difficult, and involves searching the
8671 file system for all appropriate files. You need to think
8672 carefully whether a static or dynamic id is required, since
8673 changing your mind later will cause problems.
8676 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8678 This section is not intended as policy, but as a
8679 description of the use of <prgn>dpkg-statoverride</prgn>.
8683 If a system administrator wishes to have a file (or
8684 directory or other such thing) installed with owner and
8685 permissions different from those in the distributed Debian
8686 package, they can use the <prgn>dpkg-statoverride</prgn>
8687 program to instruct <prgn>dpkg</prgn> to use the different
8688 settings every time the file is installed. Thus the
8689 package maintainer should distribute the files with their
8690 normal permissions, and leave it for the system
8691 administrator to make any desired changes. For example, a
8692 daemon which is normally required to be setuid root, but
8693 in certain situations could be used without being setuid,
8694 should be installed setuid in the <tt>.deb</tt>. Then the
8695 local system administrator can change this if they wish.
8696 If there are two standard ways of doing it, the package
8697 maintainer can use <tt>debconf</tt> to find out the
8698 preference, and call <prgn>dpkg-statoverride</prgn> in the
8699 maintainer script if necessary to accommodate the system
8700 administrator's choice. Care must be taken during
8701 upgrades to not override an existing setting.
8705 Given the above, <prgn>dpkg-statoverride</prgn> is
8706 essentially a tool for system administrators and would not
8707 normally be needed in the maintainer scripts. There is
8708 one type of situation, though, where calls to
8709 <prgn>dpkg-statoverride</prgn> would be needed in the
8710 maintainer scripts, and that involves packages which use
8711 dynamically allocated user or group ids. In such a
8712 situation, something like the following idiom can be very
8713 helpful in the package's <prgn>postinst</prgn>, where
8714 <tt>sysuser</tt> is a dynamically allocated id:
8716 for i in /usr/bin/foo /usr/sbin/bar
8718 # only do something when no setting exists
8719 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8721 #include: debconf processing, question about foo and bar
8722 if [ "$RET" = "true" ] ; then
8723 dpkg-statoverride --update --add sysuser root 4755 $i
8728 The corresponding code to remove the override when the package
8731 for i in /usr/bin/foo /usr/sbin/bar
8733 if dpkg-statoverride --list $i >/dev/null 2>&1
8735 dpkg-statoverride --remove $i
8745 <chapt id="customized-programs">
8746 <heading>Customized programs</heading>
8748 <sect id="arch-spec">
8749 <heading>Architecture specification strings</heading>
8752 If a program needs to specify an <em>architecture specification
8753 string</em> in some place, it should select one of the strings
8754 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8755 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8756 part is sometimes elided, as when the OS is Linux.
8760 Note that we don't want to use
8761 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8762 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8763 since this would make our programs incompatible with other
8764 Linux distributions. We also don't use something like
8765 <tt><var>arch</var>-unknown-linux</tt>, since the
8766 <tt>unknown</tt> does not look very good.
8769 <sect1 id="arch-wildcard-spec">
8770 <heading>Architecture wildcards</heading>
8773 A package may specify an architecture wildcard. Architecture
8774 wildcards are in the format <tt>any</tt> (which matches every
8775 architecture), <tt><var>os</var></tt>-any, or
8776 any-<tt><var>cpu</var></tt>. <footnote>
8777 Internally, the package system normalizes the GNU triplets
8778 and the Debian arches into Debian arch triplets (which are
8779 kind of inverted GNU triplets), with the first component of
8780 the triplet representing the libc and ABI in use, and then
8781 does matching against those triplets. However, such
8782 triplets are an internal implementation detail that should
8783 not be used by packages directly. The libc and ABI portion
8784 is handled internally by the package system based on
8785 the <var>os</var> and <var>cpu</var>.
8792 <heading>Daemons</heading>
8795 The configuration files <file>/etc/services</file>,
8796 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8797 by the <prgn>netbase</prgn> package and must not be modified
8802 If a package requires a new entry in one of these files, the
8803 maintainer should get in contact with the
8804 <prgn>netbase</prgn> maintainer, who will add the entries
8805 and release a new version of the <prgn>netbase</prgn>
8810 The configuration file <file>/etc/inetd.conf</file> must not be
8811 modified by the package's scripts except via the
8812 <prgn>update-inetd</prgn> script or the
8813 <file>DebianNet.pm</file> Perl module. See their documentation
8814 for details on how to add entries.
8818 If a package wants to install an example entry into
8819 <file>/etc/inetd.conf</file>, the entry must be preceded with
8820 exactly one hash character (<tt>#</tt>). Such lines are
8821 treated as "commented out by user" by the
8822 <prgn>update-inetd</prgn> script and are not changed or
8823 activated during package updates.
8828 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8832 Some programs need to create pseudo-ttys. This should be done
8833 using Unix98 ptys if the C library supports it. The resulting
8834 program must not be installed setuid root, unless that
8835 is required for other functionality.
8839 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8840 <file>/var/log/lastlog</file> must be installed writable by
8841 group <tt>utmp</tt>. Programs which need to modify those
8842 files must be installed setgid <tt>utmp</tt>.
8847 <heading>Editors and pagers</heading>
8850 Some programs have the ability to launch an editor or pager
8851 program to edit or display a text document. Since there are
8852 lots of different editors and pagers available in the Debian
8853 distribution, the system administrator and each user should
8854 have the possibility to choose their preferred editor and
8859 In addition, every program should choose a good default
8860 editor/pager if none is selected by the user or system
8865 Thus, every program that launches an editor or pager must
8866 use the EDITOR or PAGER environment variable to determine
8867 the editor or pager the user wishes to use. If these
8868 variables are not set, the programs <file>/usr/bin/editor</file>
8869 and <file>/usr/bin/pager</file> should be used, respectively.
8873 These two files are managed through the <prgn>dpkg</prgn>
8874 "alternatives" mechanism. Every package providing an editor or
8875 pager must call the <prgn>update-alternatives</prgn> script to
8876 register as an alternative for <file>/usr/bin/editor</file>
8877 or <file>/usr/bin/pager</file> as appropriate. The alternative
8878 should have a slave alternative
8879 for <file>/usr/share/man/man1/editor.1.gz</file>
8880 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8881 corresponding manual page.
8885 If it is very hard to adapt a program to make use of the
8886 EDITOR or PAGER variables, that program may be configured to
8887 use <file>/usr/bin/sensible-editor</file> and
8888 <file>/usr/bin/sensible-pager</file> as the editor or pager
8889 program respectively. These are two scripts provided in the
8890 <package>sensible-utils</package> package that check the EDITOR
8891 and PAGER variables and launch the appropriate program, and fall
8892 back to <file>/usr/bin/editor</file>
8893 and <file>/usr/bin/pager</file> if the variable is not set.
8897 A program may also use the VISUAL environment variable to
8898 determine the user's choice of editor. If it exists, it
8899 should take precedence over EDITOR. This is in fact what
8900 <file>/usr/bin/sensible-editor</file> does.
8904 It is not required for a package to depend on
8905 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8906 package to provide such virtual packages.<footnote>
8907 The Debian base system already provides an editor and a
8913 <sect id="web-appl">
8914 <heading>Web servers and applications</heading>
8917 This section describes the locations and URLs that should
8918 be used by all web servers and web applications in the
8925 Cgi-bin executable files are installed in the
8927 <example compact="compact">
8928 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8930 or a subdirectory of that directory, and should be
8932 <example compact="compact">
8933 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8935 (possibly with a subdirectory name
8936 before <var>cgi-bin-name</var>).
8940 <p>Access to HTML documents</p>
8943 HTML documents for a package are stored in
8944 <file>/usr/share/doc/<var>package</var></file>
8945 and can be referred to as
8946 <example compact="compact">
8947 http://localhost/doc/<var>package</var>/<var>filename</var>
8952 The web server should restrict access to the document
8953 tree so that only clients on the same host can read
8954 the documents. If the web server does not support such
8955 access controls, then it should not provide access at
8956 all, or ask about providing access during installation.
8961 <p>Access to images</p>
8963 It is recommended that images for a package be stored
8964 in <tt>/usr/share/images/<var>package</var></tt> and
8965 may be referred to through an alias <tt>/images/</tt>
8968 http://localhost/images/<package>/<filename>
8975 <p>Web Document Root</p>
8978 Web Applications should try to avoid storing files in
8979 the Web Document Root. Instead they should use the
8980 /usr/share/doc/<var>package</var> directory for
8981 documents and register the Web Application via the
8982 <package>doc-base</package> package. If access to the
8983 web document root is unavoidable then use
8984 <example compact="compact">
8987 as the Document Root. This might be just a symbolic
8988 link to the location where the system administrator
8989 has put the real document root.
8992 <item><p>Providing httpd and/or httpd-cgi</p>
8994 All web servers should provide the virtual package
8995 <tt>httpd</tt>. If a web server has CGI support it should
8996 provide <tt>httpd-cgi</tt> additionally.
8999 All web applications which do not contain CGI scripts should
9000 depend on <tt>httpd</tt>, all those web applications which
9001 <tt>do</tt> contain CGI scripts, should depend on
9009 <sect id="mail-transport-agents">
9010 <heading>Mail transport, delivery and user agents</heading>
9013 Debian packages which process electronic mail, whether mail
9014 user agents (MUAs) or mail transport agents (MTAs), must
9015 ensure that they are compatible with the configuration
9016 decisions below. Failure to do this may result in lost
9017 mail, broken <tt>From:</tt> lines, and other serious brain
9022 The mail spool is <file>/var/mail</file> and the interface to
9023 send a mail message is <file>/usr/sbin/sendmail</file> (as per
9024 the FHS). On older systems, the mail spool may be
9025 physically located in <file>/var/spool/mail</file>, but all
9026 access to the mail spool should be via the
9027 <file>/var/mail</file> symlink. The mail spool is part of the
9028 base system and not part of the MTA package.
9032 All Debian MUAs, MTAs, MDAs and other mailbox accessing
9033 programs (such as IMAP daemons) must lock the mailbox in an
9034 NFS-safe way. This means that <tt>fcntl()</tt> locking must
9035 be combined with dot locking. To avoid deadlocks, a program
9036 should use <tt>fcntl()</tt> first and dot locking after
9037 this, or alternatively implement the two locking methods in
9038 a non blocking way<footnote>
9039 If it is not possible to establish both locks, the
9040 system shouldn't wait for the second lock to be
9041 established, but remove the first lock, wait a (random)
9042 time, and start over locking again.
9043 </footnote>. Using the functions <tt>maillock</tt> and
9044 <tt>mailunlock</tt> provided by the
9045 <tt>liblockfile*</tt><footnote>
9046 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
9047 to use these functions.
9048 </footnote> packages is the recommended way to realize this.
9052 Mailboxes are generally either mode 600 and owned by
9053 <var>user</var> or mode 660 and owned by
9054 <tt><var>user</var>:mail</tt><footnote>
9055 There are two traditional permission schemes for mail spools:
9056 mode 600 with all mail delivery done by processes running as
9057 the destination user, or mode 660 and owned by group mail with
9058 mail delivery done by a process running as a system user in
9059 group mail. Historically, Debian required mode 660 mail
9060 spools to enable the latter model, but that model has become
9061 increasingly uncommon and the principle of least privilege
9062 indicates that mail systems that use the first model should
9063 use permissions of 600. If delivery to programs is permitted,
9064 it's easier to keep the mail system secure if the delivery
9065 agent runs as the destination user. Debian Policy therefore
9066 permits either scheme.
9067 </footnote>. The local system administrator may choose a
9068 different permission scheme; packages should not make
9069 assumptions about the permission and ownership of mailboxes
9070 unless required (such as when creating a new mailbox). A MUA
9071 may remove a mailbox (unless it has nonstandard permissions) in
9072 which case the MTA or another MUA must recreate it if needed.
9076 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9077 be setgid mail to do the locking mentioned above (and
9078 must obviously avoid accessing other users' mailboxes
9079 using this privilege).</p>
9082 <file>/etc/aliases</file> is the source file for the system mail
9083 aliases (e.g., postmaster, usenet, etc.), it is the one
9084 which the sysadmin and <prgn>postinst</prgn> scripts may
9085 edit. After <file>/etc/aliases</file> is edited the program or
9086 human editing it must call <prgn>newaliases</prgn>. All MTA
9087 packages must come with a <prgn>newaliases</prgn> program,
9088 even if it does nothing, but older MTA packages did not do
9089 this so programs should not fail if <prgn>newaliases</prgn>
9090 cannot be found. Note that because of this, all MTA
9091 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9092 <tt>Replaces: mail-transport-agent</tt> control fields.
9096 The convention of writing <tt>forward to
9097 <var>address</var></tt> in the mailbox itself is not
9098 supported. Use a <tt>.forward</tt> file instead.</p>
9101 The <prgn>rmail</prgn> program used by UUCP
9102 for incoming mail should be <file>/usr/sbin/rmail</file>.
9103 Likewise, <prgn>rsmtp</prgn>, for receiving
9104 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9108 If your package needs to know what hostname to use on (for
9109 example) outgoing news and mail messages which are generated
9110 locally, you should use the file <file>/etc/mailname</file>. It
9111 will contain the portion after the username and <tt>@</tt>
9112 (at) sign for email addresses of users on the machine
9113 (followed by a newline).
9117 Such a package should check for the existence of this file
9118 when it is being configured. If it exists, it should be
9119 used without comment, although an MTA's configuration script
9120 may wish to prompt the user even if it finds that this file
9121 exists. If the file does not exist, the package should
9122 prompt the user for the value (preferably using
9123 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9124 as well as using it in the package's configuration. The
9125 prompt should make it clear that the name will not just be
9126 used by that package. For example, in this situation the
9127 <tt>inn</tt> package could say something like:
9128 <example compact="compact">
9129 Please enter the "mail name" of your system. This is the
9130 hostname portion of the address to be shown on outgoing
9131 news and mail messages. The default is
9132 <var>syshostname</var>, your system's host name. Mail
9133 name ["<var>syshostname</var>"]:
9135 where <var>syshostname</var> is the output of <tt>hostname
9141 <heading>News system configuration</heading>
9144 All the configuration files related to the NNTP (news)
9145 servers and clients should be located under
9146 <file>/etc/news</file>.</p>
9149 There are some configuration issues that apply to a number
9150 of news clients and server packages on the machine. These
9154 <tag><file>/etc/news/organization</file></tag>
9156 A string which should appear as the
9157 organization header for all messages posted
9158 by NNTP clients on the machine
9161 <tag><file>/etc/news/server</file></tag>
9163 Contains the FQDN of the upstream NNTP
9164 server, or localhost if the local machine is
9169 Other global files may be added as required for cross-package news
9176 <heading>Programs for the X Window System</heading>
9179 <heading>Providing X support and package priorities</heading>
9182 Programs that can be configured with support for the X
9183 Window System must be configured to do so and must declare
9184 any package dependencies necessary to satisfy their
9185 runtime requirements when using the X Window System. If
9186 such a package is of higher priority than the X packages
9187 on which it depends, it is required that either the
9188 X-specific components be split into a separate package, or
9189 that an alternative version of the package, which includes
9190 X support, be provided, or that the package's priority be
9196 <heading>Packages providing an X server</heading>
9199 Packages that provide an X server that, directly or
9200 indirectly, communicates with real input and display
9201 hardware should declare in their <tt>Provides</tt> control
9202 field that they provide the virtual
9203 package <tt>xserver</tt>.<footnote>
9204 This implements current practice, and provides an
9205 actual policy for usage of the <tt>xserver</tt>
9206 virtual package which appears in the virtual packages
9207 list. In a nutshell, X servers that interface
9208 directly with the display and input hardware or via
9209 another subsystem (e.g., GGI) should provide
9210 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9211 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9217 <heading>Packages providing a terminal emulator</heading>
9220 Packages that provide a terminal emulator for the X Window
9221 System which meet the criteria listed below should declare in
9222 their <tt>Provides</tt> control field that they provide the
9223 virtual package <tt>x-terminal-emulator</tt>. They should
9224 also register themselves as an alternative for
9225 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9226 20. That alternative should have a slave alternative
9227 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9228 pointing to the corresponding manual page.
9232 To be an <tt>x-terminal-emulator</tt>, a program must:
9233 <list compact="compact">
9235 Be able to emulate a DEC VT100 terminal, or a
9236 compatible terminal.
9240 Support the command-line option <tt>-e
9241 <var>command</var></tt>, which creates a new
9242 terminal window<footnote>
9243 "New terminal window" does not necessarily mean
9244 a new top-level X window directly parented by
9245 the window manager; it could, if the terminal
9246 emulator application were so coded, be a new
9247 "view" in a multiple-document interface (MDI).
9249 and runs the specified <var>command</var>,
9250 interpreting the entirety of the rest of the command
9251 line as a command to pass straight to exec, in the
9252 manner that <tt>xterm</tt> does.
9256 Support the command-line option <tt>-T
9257 <var>title</var></tt>, which creates a new terminal
9258 window with the window title <var>title</var>.
9265 <heading>Packages providing a window manager</heading>
9268 Packages that provide a window manager should declare in
9269 their <tt>Provides</tt> control field that they provide the
9270 virtual package <tt>x-window-manager</tt>. They should also
9271 register themselves as an alternative for
9272 <file>/usr/bin/x-window-manager</file>, with a priority
9273 calculated as follows:
9274 <list compact="compact">
9276 Start with a priority of 20.
9280 If the window manager supports the Debian menu
9281 system, add 20 points if this support is available
9282 in the package's default configuration (i.e., no
9283 configuration files belonging to the system or user
9284 have to be edited to activate the feature); if
9285 configuration files must be modified, add only 10
9291 If the window manager complies with <url
9292 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9293 name="The Window Manager Specification Project">,
9294 written by the <url id="http://www.freedesktop.org/wiki/"
9295 name="Free Desktop Group">, add 40 points.
9299 If the window manager permits the X session to be
9300 restarted using a <em>different</em> window manager
9301 (without killing the X server) in its default
9302 configuration, add 10 points; otherwise add none.
9305 That alternative should have a slave alternative
9306 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9307 pointing to the corresponding manual page.
9312 <heading>Packages providing fonts</heading>
9315 Packages that provide fonts for the X Window
9317 For the purposes of Debian Policy, a "font for the X
9318 Window System" is one which is accessed via X protocol
9319 requests. Fonts for the Linux console, for PostScript
9320 renderer, or any other purpose, do not fit this
9321 definition. Any tool which makes such fonts available
9322 to the X Window System, however, must abide by this
9325 must do a number of things to ensure that they are both
9326 available without modification of the X or font server
9327 configuration, and that they do not corrupt files used by
9328 other font packages to register information about
9332 Fonts of any type supported by the X Window System
9333 must be in a separate binary package from any
9334 executables, libraries, or documentation (except
9335 that specific to the fonts shipped, such as their
9336 license information). If one or more of the fonts
9337 so packaged are necessary for proper operation of
9338 the package with which they are associated the font
9339 package may be Recommended; if the fonts merely
9340 provide an enhancement, a Suggests relationship may
9341 be used. Packages must not Depend on font
9343 This is because the X server may retrieve fonts
9344 from the local file system or over the network
9345 from an X font server; the Debian package system
9346 is empowered to deal only with the local
9352 BDF fonts must be converted to PCF fonts with the
9353 <prgn>bdftopcf</prgn> utility (available in the
9354 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9355 placed in a directory that corresponds to their
9357 <list compact="compact">
9359 100 dpi fonts must be placed in
9360 <file>/usr/share/fonts/X11/100dpi/</file>.
9364 75 dpi fonts must be placed in
9365 <file>/usr/share/fonts/X11/75dpi/</file>.
9369 Character-cell fonts, cursor fonts, and other
9370 low-resolution fonts must be placed in
9371 <file>/usr/share/fonts/X11/misc/</file>.
9377 Type 1 fonts must be placed in
9378 <file>/usr/share/fonts/X11/Type1/</file>. If font
9379 metric files are available, they must be placed here
9384 Subdirectories of <file>/usr/share/fonts/X11/</file>
9385 other than those listed above must be neither
9386 created nor used. (The <file>PEX</file>, <file>CID</file>,
9387 <file>Speedo</file>, and <file>cyrillic</file> directories
9388 are excepted for historical reasons, but installation of
9389 files into these directories remains discouraged.)
9393 Font packages may, instead of placing files directly
9394 in the X font directories listed above, provide
9395 symbolic links in that font directory pointing to
9396 the files' actual location in the filesystem. Such
9397 a location must comply with the FHS.
9401 Font packages should not contain both 75dpi and
9402 100dpi versions of a font. If both are available,
9403 they should be provided in separate binary packages
9404 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9405 the names of the packages containing the
9406 corresponding fonts.
9410 Fonts destined for the <file>misc</file> subdirectory
9411 should not be included in the same package as 75dpi
9412 or 100dpi fonts; instead, they should be provided in
9413 a separate package with <tt>-misc</tt> appended to
9418 Font packages must not provide the files
9419 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9420 <file>fonts.scale</file> in a font directory:
9423 <file>fonts.dir</file> files must not be provided at all.
9427 <file>fonts.alias</file> and <file>fonts.scale</file>
9428 files, if needed, should be provided in the
9430 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9431 where <var>fontdir</var> is the name of the
9433 <file>/usr/share/fonts/X11/</file> where the
9434 package's corresponding fonts are stored
9435 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9436 <var>package</var> is the name of the package
9437 that provides these fonts, and
9438 <var>extension</var> is either <tt>scale</tt>
9439 or <tt>alias</tt>, whichever corresponds to
9446 Font packages must declare a dependency on
9447 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9448 or <tt>Pre-Depends</tt> control field.
9452 Font packages that provide one or more
9453 <file>fonts.scale</file> files as described above must
9454 invoke <prgn>update-fonts-scale</prgn> on each
9455 directory into which they installed fonts
9456 <em>before</em> invoking
9457 <prgn>update-fonts-dir</prgn> on that directory.
9458 This invocation must occur in both the
9459 <prgn>postinst</prgn> (for all arguments) and
9460 <prgn>postrm</prgn> (for all arguments except
9461 <tt>upgrade</tt>) scripts.
9465 Font packages that provide one or more
9466 <file>fonts.alias</file> files as described above must
9467 invoke <prgn>update-fonts-alias</prgn> on each
9468 directory into which they installed fonts. This
9469 invocation must occur in both the
9470 <prgn>postinst</prgn> (for all arguments) and
9471 <prgn>postrm</prgn> (for all arguments except
9472 <tt>upgrade</tt>) scripts.
9476 Font packages must invoke
9477 <prgn>update-fonts-dir</prgn> on each directory into
9478 which they installed fonts. This invocation must
9479 occur in both the <prgn>postinst</prgn> (for all
9480 arguments) and <prgn>postrm</prgn> (for all
9481 arguments except <tt>upgrade</tt>) scripts.
9485 Font packages must not provide alias names for the
9486 fonts they include which collide with alias names
9487 already in use by fonts already packaged.
9491 Font packages must not provide fonts with the same
9492 XLFD registry name as another font already packaged.
9498 <sect1 id="appdefaults">
9499 <heading>Application defaults files</heading>
9502 Application defaults files must be installed in the
9503 directory <file>/etc/X11/app-defaults/</file> (use of a
9504 localized subdirectory of <file>/etc/X11/</file> as described
9505 in the <em>X Toolkit Intrinsics - C Language
9506 Interface</em> manual is also permitted). They must be
9507 registered as <tt>conffile</tt>s or handled as
9508 configuration files.
9512 Customization of programs' X resources may also be
9513 supported with the provision of a file with the same name
9514 as that of the package placed in
9515 the <file>/etc/X11/Xresources/</file> directory, which
9516 must be registered as a <tt>conffile</tt> or handled as a
9517 configuration file.<footnote>
9518 Note that this mechanism is not the same as using
9519 app-defaults; app-defaults are tied to the client
9520 binary on the local file system, whereas X resources
9521 are stored in the X server and affect all connecting
9528 <heading>Installation directory issues</heading>
9531 Historically, packages using the X Window System used a
9532 separate set of installation directories from other packages.
9533 This practice has been discontinued and packages using the X
9534 Window System should now generally be installed in the same
9535 directories as any other package. Specifically, packages must
9536 not install files under the <file>/usr/X11R6/</file> directory
9537 and the <file>/usr/X11R6/</file> directory hierarchy should be
9538 regarded as obsolete.
9542 Include files previously installed under
9543 <file>/usr/X11R6/include/X11/</file> should be installed into
9544 <file>/usr/include/X11/</file>. For files previously
9545 installed into subdirectories of
9546 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9547 determine if subdirectories of <file>/usr/lib/</file> and
9548 <file>/usr/share/</file> can be used. If not, a subdirectory
9549 of <file>/usr/lib/X11/</file> should be used.
9553 Configuration files for window, display, or session managers
9554 or other applications that are tightly integrated with the X
9555 Window System may be placed in a subdirectory
9556 of <file>/etc/X11/</file> corresponding to the package name.
9557 Other X Window System applications should use
9558 the <file>/etc/</file> directory unless otherwise mandated by
9559 policy (such as for <ref id="appdefaults">).
9565 <heading>Perl programs and modules</heading>
9568 Perl programs and modules should follow the current Perl policy.
9572 The Perl policy can be found in the <tt>perl-policy</tt>
9573 files in the <tt>debian-policy</tt> package.
9574 It is also available from the Debian web mirrors at
9575 <tt><url name="/doc/packaging-manuals/perl-policy/"
9576 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9581 <heading>Emacs lisp programs</heading>
9584 Please refer to the "Debian Emacs Policy" for details of how to
9585 package emacs lisp programs.
9589 The Emacs policy is available in
9590 <file>debian-emacs-policy.gz</file> of the
9591 <package>emacsen-common</package> package.
9592 It is also available from the Debian web mirrors at
9593 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9594 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9599 <heading>Games</heading>
9602 The permissions on <file>/var/games</file> are mode 755, owner
9603 <tt>root</tt> and group <tt>root</tt>.
9607 Each game decides on its own security policy.</p>
9610 Games which require protected, privileged access to
9611 high-score files, saved games, etc., may be made
9612 set-<em>group</em>-id (mode 2755) and owned by
9613 <tt>root:games</tt>, and use files and directories with
9614 appropriate permissions (770 <tt>root:games</tt>, for
9615 example). They must not be made
9616 set-<em>user</em>-id, as this causes security problems. (If
9617 an attacker can subvert any set-user-id game they can
9618 overwrite the executable of any other, causing other players
9619 of these games to run a Trojan horse program. With a
9620 set-group-id game the attacker only gets access to less
9621 important game data, and if they can get at the other
9622 players' accounts at all it will take considerably more
9626 Some packages, for example some fortune cookie programs, are
9627 configured by the upstream authors to install with their
9628 data files or other static information made unreadable so
9629 that they can only be accessed through set-id programs
9630 provided. You should not do this in a Debian package: anyone can
9631 download the <file>.deb</file> file and read the data from it,
9632 so there is no point making the files unreadable. Not
9633 making the files unreadable also means that you don't have
9634 to make so many programs set-id, which reduces the risk of a
9638 As described in the FHS, binaries of games should be
9639 installed in the directory <file>/usr/games</file>. This also
9640 applies to games that use the X Window System. Manual pages
9641 for games (X and non-X games) should be installed in
9642 <file>/usr/share/man/man6</file>.</p>
9648 <heading>Documentation</heading>
9651 <heading>Manual pages</heading>
9654 You should install manual pages in <prgn>nroff</prgn> source
9655 form, in appropriate places under <file>/usr/share/man</file>.
9656 You should only use sections 1 to 9 (see the FHS for more
9657 details). You must not install a pre-formatted "cat page".
9661 Each program, utility, and function should have an
9662 associated manual page included in the same package. It is
9663 suggested that all configuration files also have a manual
9664 page included as well. Manual pages for protocols and other
9665 auxiliary things are optional.
9669 If no manual page is available, this is considered as a bug
9670 and should be reported to the Debian Bug Tracking System (the
9671 maintainer of the package is allowed to write this bug report
9672 themselves, if they so desire). Do not close the bug report
9673 until a proper man page is available.<footnote>
9674 It is not very hard to write a man page. See the
9675 <url id="http://www.schweikhardt.net/man_page_howto.html"
9676 name="Man-Page-HOWTO">,
9677 <manref name="man" section="7">, the examples created
9678 by <prgn>dh_make</prgn>, the helper
9679 program <prgn>help2man</prgn>, or the
9680 directory <file>/usr/share/doc/man-db/examples</file>.
9685 You may forward a complaint about a missing man page to the
9686 upstream authors, and mark the bug as forwarded in the
9687 Debian bug tracking system. Even though the GNU Project do
9688 not in general consider the lack of a man page to be a bug,
9689 we do; if they tell you that they don't consider it a bug
9690 you should leave the bug in our bug tracking system open
9695 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9699 If one man page needs to be accessible via several names it
9700 is better to use a symbolic link than the <file>.so</file>
9701 feature, but there is no need to fiddle with the relevant
9702 parts of the upstream source to change from <file>.so</file> to
9703 symlinks: don't do it unless it's easy. You should not
9704 create hard links in the manual page directories, nor put
9705 absolute filenames in <file>.so</file> directives. The filename
9706 in a <file>.so</file> in a man page should be relative to the
9707 base of the man page tree (usually
9708 <file>/usr/share/man</file>). If you do not create any links
9709 (whether symlinks, hard links, or <tt>.so</tt> directives)
9710 in the file system to the alternate names of the man page,
9711 then you should not rely on <prgn>man</prgn> finding your
9712 man page under those names based solely on the information in
9713 the man page's header.<footnote>
9714 Supporting this in <prgn>man</prgn> often requires
9715 unreasonable processing time to find a manual page or to
9716 report that none exists, and moves knowledge into man's
9717 database that would be better left in the file system.
9718 This support is therefore deprecated and will cease to
9719 be present in the future.
9724 Manual pages in locale-specific subdirectories of
9725 <file>/usr/share/man</file> should use either UTF-8 or the usual
9726 legacy encoding for that language (normally the one corresponding
9727 to the shortest relevant locale name in
9728 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9729 <file>/usr/share/man/fr</file> should use either UTF-8 or
9730 ISO-8859-1.<footnote>
9731 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9732 use. In future, all manual pages will be required to use
9738 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9739 included in the subdirectory name unless it indicates a
9740 significant difference in the language, as this excludes
9741 speakers of the language in other countries.<footnote>
9742 At the time of writing, Chinese and Portuguese are the main
9743 languages with such differences, so <file>pt_BR</file>,
9744 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9749 If a localized version of a manual page is provided, it should
9750 either be up-to-date or it should be obvious to the reader that
9751 it is outdated and the original manual page should be used
9752 instead. This can be done either by a note at the beginning of
9753 the manual page or by showing the missing or changed portions in
9754 the original language instead of the target language.
9759 <heading>Info documents</heading>
9762 Info documents should be installed in <file>/usr/share/info</file>.
9763 They should be compressed with <tt>gzip -9</tt>.
9767 The <prgn>install-info</prgn> program maintains a directory of
9768 installed info documents in <file>/usr/share/info/dir</file> for
9769 the use of info readers.<footnote>
9770 It was previously necessary for packages installing info
9771 documents to run <prgn>install-info</prgn> from maintainer
9772 scripts. This is no longer necessary. The installation
9773 system now uses dpkg triggers.
9775 This file must not be included in packages. Packages containing
9776 info documents should depend on <tt>dpkg (>= 1.15.4) |
9777 install-info</tt> to ensure that the directory file is properly
9778 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9783 Info documents should contain section and directory entry
9784 information in the document for the use
9785 of <prgn>install-info</prgn>. The section should be specified
9786 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9787 space and the section of this info page. The directory entry or
9788 entries should be included between
9789 a <tt>START-INFO-DIR-ENTRY</tt> line and
9790 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9792 INFO-DIR-SECTION Individual utilities
9793 START-INFO-DIR-ENTRY
9794 * example: (example). An example info directory entry.
9797 To determine which section to use, you should look
9798 at <file>/usr/share/info/dir</file> on your system and choose
9799 the most relevant (or create a new section if none of the
9800 current sections are relevant).<footnote>
9801 Normally, info documents are generated from Texinfo source.
9802 To include this information in the generated info document, if
9803 it is absent, add commands like:
9805 @dircategory Individual utilities
9807 * example: (example). An example info directory entry.
9810 to the Texinfo source of the document and ensure that the info
9811 documents are rebuilt from source during the package build.
9817 <heading>Additional documentation</heading>
9820 Any additional documentation that comes with the package may
9821 be installed at the discretion of the package maintainer.
9822 Plain text documentation should be installed in the directory
9823 <file>/usr/share/doc/<var>package</var></file>, where
9824 <var>package</var> is the name of the package, and
9825 compressed with <tt>gzip -9</tt> unless it is small.
9829 If a package comes with large amounts of documentation which
9830 many users of the package will not require you should create
9831 a separate binary package to contain it, so that it does not
9832 take up disk space on the machines of users who do not need
9833 or want it installed.</p>
9836 It is often a good idea to put text information files
9837 (<file>README</file>s, changelogs, and so forth) that come with
9838 the source package in <file>/usr/share/doc/<var>package</var></file>
9839 in the binary package. However, you don't need to install
9840 the instructions for building and installing the package, of
9844 Packages must not require the existence of any files in
9845 <file>/usr/share/doc/</file> in order to function
9847 The system administrator should be able to
9848 delete files in <file>/usr/share/doc/</file> without causing
9849 any programs to break.
9851 Any files that are referenced by programs but are also
9852 useful as stand alone documentation should be installed under
9853 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9854 <file>/usr/share/doc/<var>package</var></file>.
9858 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9859 link to another directory in <file>/usr/share/doc</file> only if
9860 the two packages both come from the same source and the
9861 first package Depends on the second.<footnote>
9863 Please note that this does not override the section on
9864 changelog files below, so the file
9865 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9866 must refer to the changelog for the current version of
9867 <var>package</var> in question. In practice, this means
9868 that the sources of the target and the destination of the
9869 symlink must be the same (same source package and
9876 Former Debian releases placed all additional documentation
9877 in <file>/usr/doc/<var>package</var></file>. This has been
9878 changed to <file>/usr/share/doc/<var>package</var></file>,
9879 and packages must not put documentation in the directory
9880 <file>/usr/doc/<var>package</var></file>. <footnote>
9881 At this phase of the transition, we no longer require a
9882 symbolic link in <file>/usr/doc/</file>. At a later point,
9883 policy shall change to make the symbolic links a bug.
9889 <heading>Preferred documentation formats</heading>
9892 The unification of Debian documentation is being carried out
9896 If your package comes with extensive documentation in a
9897 markup format that can be converted to various other formats
9898 you should if possible ship HTML versions in a binary
9899 package, in the directory
9900 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9901 its subdirectories.<footnote>
9902 The rationale: The important thing here is that HTML
9903 docs should be available in <em>some</em> package, not
9904 necessarily in the main binary package.
9909 Other formats such as PostScript may be provided at the
9910 package maintainer's discretion.
9914 <sect id="copyrightfile">
9915 <heading>Copyright information</heading>
9918 Every package must be accompanied by a verbatim copy of its
9919 copyright information and distribution license in the file
9920 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9921 file must neither be compressed nor be a symbolic link.
9925 In addition, the copyright file must say where the upstream
9926 sources (if any) were obtained, and should name the original
9931 Packages in the <em>contrib</em> or <em>non-free</em> archive
9932 areas should state in the copyright file that the package is not
9933 part of the Debian distribution and briefly explain why.
9937 A copy of the file which will be installed in
9938 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9939 be in <file>debian/copyright</file> in the source package.
9943 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9944 link to another directory in <file>/usr/share/doc</file> only if
9945 the two packages both come from the same source and the
9946 first package Depends on the second. These rules are important
9947 because <file>copyright</file> files must be extractable by
9952 Packages distributed under the Apache license (version 2.0), the
9953 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9954 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9955 1.3) should refer to the corresponding files
9956 under <file>/usr/share/common-licenses</file>,<footnote>
9959 <file>/usr/share/common-licenses/Apache-2.0</file>,
9960 <file>/usr/share/common-licenses/Artistic</file>,
9961 <file>/usr/share/common-licenses/GPL-1</file>,
9962 <file>/usr/share/common-licenses/GPL-2</file>,
9963 <file>/usr/share/common-licenses/GPL-3</file>,
9964 <file>/usr/share/common-licenses/LGPL-2</file>,
9965 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9966 <file>/usr/share/common-licenses/LGPL-3</file>,
9967 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9968 <file>/usr/share/common-licenses/GFDL-1.3</file>
9969 respectively. The University of California BSD license is
9970 also included in <package>base-files</package> as
9971 <file>/usr/share/common-licenses/BSD</file>, but given the
9972 brevity of this license, its specificity to code whose
9973 copyright is held by the Regents of the University of
9974 California, and the frequency of minor wording changes, its
9975 text should be included in the copyright file rather than
9976 referencing this file.
9978 </footnote> rather than quoting them in the copyright
9983 You should not use the copyright file as a general <file>README</file>
9984 file. If your package has such a file it should be
9985 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9986 <file>README.Debian</file> or some other appropriate place.
9990 All copyright files must be encoded in UTF-8.
9993 <sect1 id="copyrightformat">
9994 <heading>Machine-readable copyright information</heading>
9997 A specification for a standard, machine-readable format
9998 for <file>debian/copyright</file> files is maintained as part
9999 of the <package>debian-policy</package> package. This
10000 document may be found in the <file>copyright-format</file>
10001 files in the <package>debian-policy</package> package. It is
10002 also available from the Debian web mirrors at
10003 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
10004 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
10008 Use of this format is optional.
10014 <heading>Examples</heading>
10017 Any examples (configurations, source files, whatever),
10018 should be installed in a directory
10019 <file>/usr/share/doc/<var>package</var>/examples</file>. These
10020 files should not be referenced by any program: they're there
10021 for the benefit of the system administrator and users as
10022 documentation only. Architecture-specific example files
10023 should be installed in a directory
10024 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
10026 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
10027 latter directory itself may be a symbolic link to the
10032 If the purpose of a package is to provide examples, then the
10033 example files may be installed into
10034 <file>/usr/share/doc/<var>package</var></file>.
10038 <sect id="changelogs">
10039 <heading>Changelog files</heading>
10042 Packages that are not Debian-native must contain a
10043 compressed copy of the <file>debian/changelog</file> file from
10044 the Debian source tree in
10045 <file>/usr/share/doc/<var>package</var></file> with the name
10046 <file>changelog.Debian.gz</file>.
10050 If an upstream changelog is available, it should be accessible as
10051 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
10052 plain text. If the upstream changelog is distributed in
10053 HTML, it should be made available in that form as
10054 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
10055 and a plain text <file>changelog.gz</file> should be generated
10056 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10057 the upstream changelog files do not already conform to this
10058 naming convention, then this may be achieved either by
10059 renaming the files, or by adding a symbolic link, at the
10060 maintainer's discretion.<footnote>
10061 Rationale: People should not have to look in places for
10062 upstream changelogs merely because they are given
10063 different names or are distributed in HTML format.
10068 All of these files should be installed compressed using
10069 <tt>gzip -9</tt>, as they will become large with time even
10070 if they start out small.
10074 If the package has only one changelog which is used both as
10075 the Debian changelog and the upstream one because there is
10076 no separate upstream maintainer then that changelog should
10077 usually be installed as
10078 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10079 there is a separate upstream maintainer, but no upstream
10080 changelog, then the Debian changelog should still be called
10081 <file>changelog.Debian.gz</file>.
10085 For details about the format and contents of the Debian
10086 changelog file, please see <ref id="dpkgchangelog">.
10091 <appendix id="pkg-scope">
10092 <heading>Introduction and scope of these appendices</heading>
10095 These appendices are taken essentially verbatim from the
10096 now-deprecated Packaging Manual, version 3.2.1.0. They are
10097 the chapters which are likely to be of use to package
10098 maintainers and which have not already been included in the
10099 policy document itself. Most of these sections are very likely
10100 not relevant to policy; they should be treated as
10101 documentation for the packaging system. Please note that these
10102 appendices are included for convenience, and for historical
10103 reasons: they used to be part of policy package, and they have
10104 not yet been incorporated into dpkg documentation. However,
10105 they still have value, and hence they are presented here.
10109 They have not yet been checked to ensure that they are
10110 compatible with the contents of policy, and if there are any
10111 contradictions, the version in the main policy document takes
10112 precedence. The remaining chapters of the old Packaging
10113 Manual have also not been read in detail to ensure that there
10114 are not parts which have been left out. Both of these will be
10115 done in due course.
10119 Certain parts of the Packaging manual were integrated into the
10120 Policy Manual proper, and removed from the appendices. Links
10121 have been placed from the old locations to the new ones.
10125 <prgn>dpkg</prgn> is a suite of programs for creating binary
10126 package files and installing and removing them on Unix
10128 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10129 work on or be ported to other systems.
10134 The binary packages are designed for the management of
10135 installed executable programs (usually compiled binaries) and
10136 their associated data, though source code examples and
10137 documentation are provided as part of some packages.</p>
10140 This manual describes the technical aspects of creating Debian
10141 binary packages (<file>.deb</file> files). It documents the
10142 behavior of the package management programs
10143 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10144 they interact with packages.</p>
10147 It also documents the interaction between
10148 <prgn>dselect</prgn>'s core and the access method scripts it
10149 uses to actually install the selected packages, and describes
10150 how to create a new access method.</p>
10153 This manual does not go into detail about the options and
10154 usage of the package building and installation tools. It
10155 should therefore be read in conjunction with those programs'
10160 The utility programs which are provided with <prgn>dpkg</prgn>
10161 for managing various system configuration and similar issues,
10162 such as <prgn>update-rc.d</prgn> and
10163 <prgn>install-info</prgn>, are not described in detail here -
10164 please see their man pages.
10168 It is assumed that the reader is reasonably familiar with the
10169 <prgn>dpkg</prgn> System Administrators' manual.
10170 Unfortunately this manual does not yet exist.
10174 The Debian version of the FSF's GNU hello program is provided as
10175 an example for people wishing to create Debian packages. However,
10176 while the examples are helpful, they do not replace the need to
10177 read and follow the Policy and Programmer's Manual.</p>
10180 <appendix id="pkg-binarypkg">
10181 <heading>Binary packages (from old Packaging Manual)</heading>
10184 The binary package has two main sections. The first part
10185 consists of various control information files and scripts used
10186 by <prgn>dpkg</prgn> when installing and removing. See <ref
10187 id="pkg-controlarea">.
10191 The second part is an archive containing the files and
10192 directories to be installed.
10196 In the future binary packages may also contain other
10197 components, such as checksums and digital signatures. The
10198 format for the archive is described in full in the
10199 <file>deb(5)</file> man page.
10203 <sect id="pkg-bincreating"><heading>Creating package files -
10204 <prgn>dpkg-deb</prgn>
10208 All manipulation of binary package files is done by
10209 <prgn>dpkg-deb</prgn>; it's the only program that has
10210 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10211 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10212 will spot that the options requested are appropriate to
10213 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10218 In order to create a binary package you must make a
10219 directory tree which contains all the files and directories
10220 you want to have in the file system data part of the package.
10221 In Debian-format source packages this directory is usually
10222 <file>debian/tmp</file>, relative to the top of the package's
10227 They should have the locations (relative to the root of the
10228 directory tree you're constructing) ownerships and
10229 permissions which you want them to have on the system when
10230 they are installed.
10234 With current versions of <prgn>dpkg</prgn> the uid/username
10235 and gid/groupname mappings for the users and groups being
10236 used should be the same on the system where the package is
10237 built and the one where it is installed.
10241 You need to add one special directory to the root of the
10242 miniature file system tree you're creating:
10243 <prgn>DEBIAN</prgn>. It should contain the control
10244 information files, notably the binary package control file
10245 (see <ref id="pkg-controlfile">).
10249 The <prgn>DEBIAN</prgn> directory will not appear in the
10250 file system archive of the package, and so won't be installed
10251 by <prgn>dpkg</prgn> when the package is unpacked.
10255 When you've prepared the package, you should invoke:
10257 dpkg --build <var>directory</var>
10262 This will build the package in
10263 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10264 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10265 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10266 build the package.)
10270 See the man page <manref name="dpkg-deb" section="8"> for details of how
10271 to examine the contents of this newly-created file. You may find the
10272 output of following commands enlightening:
10274 dpkg-deb --info <var>filename</var>.deb
10275 dpkg-deb --contents <var>filename</var>.deb
10276 dpkg --contents <var>filename</var>.deb
10278 To view the copyright file for a package you could use this command:
10280 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10285 <sect id="pkg-controlarea">
10286 <heading>Package control information files</heading>
10289 The control information portion of a binary package is a
10290 collection of files with names known to <prgn>dpkg</prgn>.
10291 It will treat the contents of these files specially - some
10292 of them contain information used by <prgn>dpkg</prgn> when
10293 installing or removing the package; others are scripts which
10294 the package maintainer wants <prgn>dpkg</prgn> to run.
10298 It is possible to put other files in the package control
10299 information file area, but this is not generally a good idea
10300 (though they will largely be ignored).
10304 Here is a brief list of the control information files supported
10305 by <prgn>dpkg</prgn> and a summary of what they're used for.
10310 <tag><tt>control</tt>
10313 This is the key description file used by
10314 <prgn>dpkg</prgn>. It specifies the package's name
10315 and version, gives its description for the user,
10316 states its relationships with other packages, and so
10317 forth. See <ref id="sourcecontrolfiles"> and
10318 <ref id="binarycontrolfiles">.
10322 It is usually generated automatically from information
10323 in the source package by the
10324 <prgn>dpkg-gencontrol</prgn> program, and with
10325 assistance from <prgn>dpkg-shlibdeps</prgn>.
10326 See <ref id="pkg-sourcetools">.
10330 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10335 These are executable files (usually scripts) which
10336 <prgn>dpkg</prgn> runs during installation, upgrade
10337 and removal of packages. They allow the package to
10338 deal with matters which are particular to that package
10339 or require more complicated processing than that
10340 provided by <prgn>dpkg</prgn>. Details of when and
10341 how they are called are in <ref id="maintainerscripts">.
10345 It is very important to make these scripts idempotent.
10346 See <ref id="idempotency">.
10350 The maintainer scripts are not guaranteed to run with a
10351 controlling terminal and may not be able to interact with
10352 the user. See <ref id="controllingterminal">.
10356 <tag><tt>conffiles</tt>
10359 This file contains a list of configuration files which
10360 are to be handled automatically by <prgn>dpkg</prgn>
10361 (see <ref id="pkg-conffiles">). Note that not necessarily
10362 every configuration file should be listed here.
10365 <tag><tt>shlibs</tt>
10368 This file contains a list of the shared libraries
10369 supplied by the package, with dependency details for
10370 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10371 when it determines what dependencies are required in a
10372 package control file. The <tt>shlibs</tt> file format
10373 is described on <ref id="shlibs">.
10378 <sect id="pkg-controlfile">
10379 <heading>The main control information file: <tt>control</tt></heading>
10382 The most important control information file used by
10383 <prgn>dpkg</prgn> when it installs a package is
10384 <tt>control</tt>. It contains all the package's "vital
10389 The binary package control files of packages built from
10390 Debian sources are made by a special tool,
10391 <prgn>dpkg-gencontrol</prgn>, which reads
10392 <file>debian/control</file> and <file>debian/changelog</file> to
10393 find the information it needs. See <ref id="pkg-sourcepkg"> for
10398 The fields in binary package control files are listed in
10399 <ref id="binarycontrolfiles">.
10403 A description of the syntax of control files and the purpose
10404 of the fields is available in <ref id="controlfields">.
10409 <heading>Time Stamps</heading>
10412 See <ref id="timestamps">.
10417 <appendix id="pkg-sourcepkg">
10418 <heading>Source packages (from old Packaging Manual) </heading>
10421 The Debian binary packages in the distribution are generated
10422 from Debian sources, which are in a special format to assist
10423 the easy and automatic building of binaries.
10426 <sect id="pkg-sourcetools">
10427 <heading>Tools for processing source packages</heading>
10430 Various tools are provided for manipulating source packages;
10431 they pack and unpack sources and help build of binary
10432 packages and help manage the distribution of new versions.
10436 They are introduced and typical uses described here; see
10437 <manref name="dpkg-source" section="1"> for full
10438 documentation about their arguments and operation.
10442 For examples of how to construct a Debian source package,
10443 and how to use those utilities that are used by Debian
10444 source packages, please see the <prgn>hello</prgn> example
10448 <sect1 id="pkg-dpkg-source">
10450 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10455 This program is frequently used by hand, and is also
10456 called from package-independent automated building scripts
10457 such as <prgn>dpkg-buildpackage</prgn>.
10461 To unpack a package it is typically invoked with
10463 dpkg-source -x <var>.../path/to/filename</var>.dsc
10468 with the <file><var>filename</var>.tar.gz</file> and
10469 <file><var>filename</var>.diff.gz</file> (if applicable) in
10470 the same directory. It unpacks into
10471 <file><var>package</var>-<var>version</var></file>, and if
10473 <file><var>package</var>-<var>version</var>.orig</file>, in
10474 the current directory.
10478 To create a packed source archive it is typically invoked:
10480 dpkg-source -b <var>package</var>-<var>version</var>
10485 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10486 <file>.diff.gz</file> (if appropriate) in the current
10487 directory. <prgn>dpkg-source</prgn> does not clean the
10488 source tree first - this must be done separately if it is
10493 See also <ref id="pkg-sourcearchives">.</p>
10497 <sect1 id="pkg-dpkg-buildpackage">
10499 <prgn>dpkg-buildpackage</prgn> - overall package-building
10504 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10505 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10506 targets <tt>clean</tt>, <tt>build</tt> and
10507 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10508 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10509 source and binary package upload.
10513 It is usually invoked by hand from the top level of the
10514 built or unbuilt source directory. It may be invoked with
10515 no arguments; useful arguments include:
10516 <taglist compact="compact">
10517 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10520 Do not sign the <tt>.changes</tt> file or the
10521 source package <tt>.dsc</tt> file, respectively.</p>
10523 <tag><tt>-p<var>sign-command</var></tt></tag>
10526 Invoke <var>sign-command</var> instead of finding
10527 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10528 <var>sign-command</var> must behave just like
10529 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10531 <tag><tt>-r<var>root-command</var></tt></tag>
10534 When root privilege is required, invoke the command
10535 <var>root-command</var>. <var>root-command</var>
10536 should invoke its first argument as a command, from
10537 the <prgn>PATH</prgn> if necessary, and pass its
10538 second and subsequent arguments to the command it
10539 calls. If no <var>root-command</var> is supplied
10540 then <var>dpkg-buildpackage</var> will use
10541 the <prgn>fakeroot</prgn> command, which is sufficient
10542 to build most packages without actually requiring root
10545 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10548 Two types of binary-only build and upload - see
10549 <manref name="dpkg-source" section="1">.
10556 <sect1 id="pkg-dpkg-gencontrol">
10558 <prgn>dpkg-gencontrol</prgn> - generates binary package
10563 This program is usually called from <file>debian/rules</file>
10564 (see <ref id="pkg-sourcetree">) in the top level of the source
10569 This is usually done just before the files and directories in the
10570 temporary directory tree where the package is being built have their
10571 permissions and ownerships set and the package is constructed using
10572 <prgn>dpkg-deb/</prgn>
10574 This is so that the control file which is produced has
10575 the right permissions
10580 <prgn>dpkg-gencontrol</prgn> must be called after all the
10581 files which are to go into the package have been placed in
10582 the temporary build directory, so that its calculation of
10583 the installed size of a package is correct.
10587 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10588 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10589 variable substitutions created by
10590 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10595 For a package which generates only one binary package, and
10596 which builds it in <file>debian/tmp</file> relative to the top
10597 of the source package, it is usually sufficient to call
10598 <prgn>dpkg-gencontrol</prgn>.
10602 Sources which build several binaries will typically need
10605 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10606 </example> The <tt>-P</tt> tells
10607 <prgn>dpkg-gencontrol</prgn> that the package is being
10608 built in a non-default directory, and the <tt>-p</tt>
10609 tells it which package's control file should be generated.
10613 <prgn>dpkg-gencontrol</prgn> also adds information to the
10614 list of files in <file>debian/files</file>, for the benefit of
10615 (for example) a future invocation of
10616 <prgn>dpkg-genchanges</prgn>.</p>
10619 <sect1 id="pkg-dpkg-shlibdeps">
10621 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10626 This program is usually called from <file>debian/rules</file>
10627 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10628 id="pkg-sourcetree">), in the top level of the source tree.
10632 Its arguments are executables and shared libraries
10635 They may be specified either in the locations in the
10636 source tree where they are created or in the locations
10637 in the temporary build tree where they are installed
10638 prior to binary package creation.
10640 </footnote> for which shared library dependencies should
10641 be included in the binary package's control file.
10645 If some of the found shared libraries should only
10646 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10647 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10648 by using the <tt>-d<var>dependency-field</var></tt> option
10649 before those executable(s). (Each <tt>-d</tt> option
10650 takes effect until the next <tt>-d</tt>.)
10654 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10655 output control file to be modified. Instead by default it
10656 adds to the <file>debian/substvars</file> file variable
10657 settings like <tt>shlibs:Depends</tt>. These variable
10658 settings must be referenced in dependency fields in the
10659 appropriate per-binary-package sections of the source
10664 For example, a package that generates an essential part
10665 which requires dependencies, and optional parts that
10666 which only require a recommendation, would separate those
10667 two sets of dependencies into two different fields.<footnote>
10668 At the time of writing, an example for this was the
10669 <package/xmms/ package, with Depends used for the xmms
10670 executable, Recommends for the plug-ins and Suggests for
10671 even more optional features provided by unzip.
10673 It can say in its <file>debian/rules</file>:
10675 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10676 -dRecommends <var>optionalpart anotheroptionalpart</var>
10678 and then in its main control file <file>debian/control</file>:
10681 Depends: ${shlibs:Depends}
10682 Recommends: ${shlibs:Recommends}
10688 Sources which produce several binary packages with
10689 different shared library dependency requirements can use
10690 the <tt>-p<var>varnameprefix</var></tt> option to override
10691 the default <tt>shlibs:</tt> prefix (one invocation of
10692 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10693 They can thus produce several sets of dependency
10694 variables, each of the form
10695 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10696 which can be referred to in the appropriate parts of the
10697 binary package control files.
10702 <sect1 id="pkg-dpkg-distaddfile">
10704 <prgn>dpkg-distaddfile</prgn> - adds a file to
10705 <file>debian/files</file>
10709 Some packages' uploads need to include files other than
10710 the source and binary package files.
10714 <prgn>dpkg-distaddfile</prgn> adds a file to the
10715 <file>debian/files</file> file so that it will be included in
10716 the <file>.changes</file> file when
10717 <prgn>dpkg-genchanges</prgn> is run.
10721 It is usually invoked from the <tt>binary</tt> target of
10722 <file>debian/rules</file>:
10724 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10726 The <var>filename</var> is relative to the directory where
10727 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10728 is usually the directory above the top level of the source
10729 tree. The <file>debian/rules</file> target should put the
10730 file there just before or just after calling
10731 <prgn>dpkg-distaddfile</prgn>.
10735 The <var>section</var> and <var>priority</var> are passed
10736 unchanged into the resulting <file>.changes</file> file.
10741 <sect1 id="pkg-dpkg-genchanges">
10743 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10744 upload control file
10748 This program is usually called by package-independent
10749 automatic building scripts such as
10750 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10755 It is usually called in the top level of a built source
10756 tree, and when invoked with no arguments will print out a
10757 straightforward <file>.changes</file> file based on the
10758 information in the source package's changelog and control
10759 file and the binary and source packages which should have
10765 <sect1 id="pkg-dpkg-parsechangelog">
10767 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10768 representation of a changelog
10772 This program is used internally by
10773 <prgn>dpkg-source</prgn> et al. It may also occasionally
10774 be useful in <file>debian/rules</file> and elsewhere. It
10775 parses a changelog, <file>debian/changelog</file> by default,
10776 and prints a control-file format representation of the
10777 information in it to standard output.
10781 <sect1 id="pkg-dpkg-architecture">
10783 <prgn>dpkg-architecture</prgn> - information about the build and
10788 This program can be used manually, but is also invoked by
10789 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10790 environment or make variables which specify the build and host
10791 architecture for the package building process.
10796 <sect id="pkg-sourcetree">
10797 <heading>The Debian package source tree</heading>
10800 The source archive scheme described later is intended to
10801 allow a Debian package source tree with some associated
10802 control information to be reproduced and transported easily.
10803 The Debian package source tree is a version of the original
10804 program with certain files added for the benefit of the
10805 packaging process, and with any other changes required
10806 made to the rest of the source code and installation
10811 The extra files created for Debian are in the subdirectory
10812 <file>debian</file> of the top level of the Debian package
10813 source tree. They are described below.
10816 <sect1 id="pkg-debianrules">
10817 <heading><file>debian/rules</file> - the main building script</heading>
10820 See <ref id="debianrules">.
10824 <sect1 id="pkg-srcsubstvars">
10825 <heading><file>debian/substvars</file> and variable substitutions</heading>
10828 See <ref id="substvars">.
10834 <heading><file>debian/files</file></heading>
10837 See <ref id="debianfiles">.
10841 <sect1><heading><file>debian/tmp</file>
10845 This is the canonical temporary location for the
10846 construction of binary packages by the <tt>binary</tt>
10847 target. The directory <file>tmp</file> serves as the root of
10848 the file system tree as it is being constructed (for
10849 example, by using the package's upstream makefiles install
10850 targets and redirecting the output there), and it also
10851 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10852 id="pkg-bincreating">.
10856 If several binary packages are generated from the same
10857 source tree it is usual to use several
10858 <file>debian/tmp<var>something</var></file> directories, for
10859 example <file>tmp-a</file> or <file>tmp-doc</file>.
10863 Whatever <file>tmp</file> directories are created and used by
10864 <tt>binary</tt> must of course be removed by the
10865 <tt>clean</tt> target.</p></sect1>
10869 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10873 As it exists on the FTP site, a Debian source package
10874 consists of three related files. You must have the right
10875 versions of all three to be able to use them.
10880 <tag>Debian source control file - <tt>.dsc</tt></tag>
10882 This file is a control file used by <prgn>dpkg-source</prgn>
10883 to extract a source package.
10884 See <ref id="debiansourcecontrolfiles">.
10888 Original source archive -
10890 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10896 This is a compressed (with <tt>gzip -9</tt>)
10897 <prgn>tar</prgn> file containing the source code from
10898 the upstream authors of the program.
10903 Debian package diff -
10905 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10911 This is a unified context diff (<tt>diff -u</tt>)
10912 giving the changes which are required to turn the
10913 original source into the Debian source. These changes
10914 may only include editing and creating plain files.
10915 The permissions of files, the targets of symbolic
10916 links and the characteristics of special files or
10917 pipes may not be changed and no files may be removed
10922 All the directories in the diff must exist, except the
10923 <file>debian</file> subdirectory of the top of the source
10924 tree, which will be created by
10925 <prgn>dpkg-source</prgn> if necessary when unpacking.
10929 The <prgn>dpkg-source</prgn> program will
10930 automatically make the <file>debian/rules</file> file
10931 executable (see below).</p></item>
10936 If there is no original source code - for example, if the
10937 package is specially prepared for Debian or the Debian
10938 maintainer is the same as the upstream maintainer - the
10939 format is slightly different: then there is no diff, and the
10941 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10942 and preferably contains a directory named
10943 <file><var>package</var>-<var>version</var></file>.
10948 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10951 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10952 Debian source package. However, if it is not available it
10953 is possible to unpack a Debian source archive as follows:
10954 <enumlist compact="compact">
10957 Untar the tarfile, which will create a <file>.orig</file>
10961 <p>Rename the <file>.orig</file> directory to
10962 <file><var>package</var>-<var>version</var></file>.</p>
10966 Create the subdirectory <file>debian</file> at the top of
10967 the source tree.</p>
10969 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10971 <item><p>Untar the tarfile again if you want a copy of the original
10972 source code alongside the Debian version.</p>
10977 It is not possible to generate a valid Debian source archive
10978 without using <prgn>dpkg-source</prgn>. In particular,
10979 attempting to use <prgn>diff</prgn> directly to generate the
10980 <file>.diff.gz</file> file will not work.
10984 <heading>Restrictions on objects in source packages</heading>
10987 The source package may not contain any hard links
10989 This is not currently detected when building source
10990 packages, but only when extracting
10994 Hard links may be permitted at some point in the
10995 future, but would require a fair amount of
10997 </footnote>, device special files, sockets or setuid or
11000 Setgid directories are allowed.
11005 The source packaging tools manage the changes between the
11006 original and Debian source using <prgn>diff</prgn> and
11007 <prgn>patch</prgn>. Turning the original source tree as
11008 included in the <file>.orig.tar.gz</file> into the Debian
11009 package source must not involve any changes which cannot be
11010 handled by these tools. Problematic changes which cause
11011 <prgn>dpkg-source</prgn> to halt with an error when
11012 building the source package are:
11013 <list compact="compact">
11014 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
11016 <item><p>Changing the targets of symbolic links.</p>
11018 <item><p>Creating directories, other than <file>debian</file>.</p>
11020 <item><p>Changes to the contents of binary files.</p></item>
11021 </list> Changes which cause <prgn>dpkg-source</prgn> to
11022 print a warning but continue anyway are:
11023 <list compact="compact">
11026 Removing files, directories or symlinks.
11028 Renaming a file is not treated specially - it is
11029 seen as the removal of the old file (which
11030 generates a warning, but is otherwise ignored),
11031 and the creation of the new one.
11037 Changed text files which are missing the usual final
11038 newline (either in the original or the modified
11043 Changes which are not represented, but which are not detected by
11044 <prgn>dpkg-source</prgn>, are:
11045 <list compact="compact">
11046 <item><p>Changing the permissions of files (other than
11047 <file>debian/rules</file>) and directories.</p></item>
11052 The <file>debian</file> directory and <file>debian/rules</file>
11053 are handled specially by <prgn>dpkg-source</prgn> - before
11054 applying the changes it will create the <file>debian</file>
11055 directory, and afterwards it will make
11056 <file>debian/rules</file> world-executable.
11062 <appendix id="pkg-controlfields">
11063 <heading>Control files and their fields (from old Packaging Manual)</heading>
11066 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11067 data in a common format, known as control files. Binary and
11068 source packages have control data as do the <file>.changes</file>
11069 files which control the installation of uploaded files, and
11070 <prgn>dpkg</prgn>'s internal databases are in a similar
11075 <heading>Syntax of control files</heading>
11078 See <ref id="controlsyntax">.
11082 It is important to note that there are several fields which
11083 are optional as far as <prgn>dpkg</prgn> and the related
11084 tools are concerned, but which must appear in every Debian
11085 package, or whose omission may cause problems.
11090 <heading>List of fields</heading>
11093 See <ref id="controlfieldslist">.
11097 This section now contains only the fields that didn't belong
11098 to the Policy manual.
11101 <sect1 id="pkg-f-Filename">
11102 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11105 These fields in <tt>Packages</tt> files give the
11106 filename(s) of (the parts of) a package in the
11107 distribution directories, relative to the root of the
11108 Debian hierarchy. If the package has been split into
11109 several parts the parts are all listed in order, separated
11114 <sect1 id="pkg-f-Size">
11115 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11118 These fields in <file>Packages</file> files give the size (in
11119 bytes, expressed in decimal) and MD5 checksum of the
11120 file(s) which make(s) up a binary package in the
11121 distribution. If the package is split into several parts
11122 the values for the parts are listed in order, separated by
11127 <sect1 id="pkg-f-Status">
11128 <heading><tt>Status</tt></heading>
11131 This field in <prgn>dpkg</prgn>'s status file records
11132 whether the user wants a package installed, removed or
11133 left alone, whether it is broken (requiring
11134 re-installation) or not and what its current state on the
11135 system is. Each of these pieces of information is a
11140 <sect1 id="pkg-f-Config-Version">
11141 <heading><tt>Config-Version</tt></heading>
11144 If a package is not installed or not configured, this
11145 field in <prgn>dpkg</prgn>'s status file records the last
11146 version of the package which was successfully
11151 <sect1 id="pkg-f-Conffiles">
11152 <heading><tt>Conffiles</tt></heading>
11155 This field in <prgn>dpkg</prgn>'s status file contains
11156 information about the automatically-managed configuration
11157 files held by a package. This field should <em>not</em>
11158 appear anywhere in a package!
11163 <heading>Obsolete fields</heading>
11166 These are still recognized by <prgn>dpkg</prgn> but should
11167 not appear anywhere any more.
11169 <taglist compact="compact">
11171 <tag><tt>Revision</tt></tag>
11172 <tag><tt>Package-Revision</tt></tag>
11173 <tag><tt>Package_Revision</tt></tag>
11175 The Debian revision part of the package version was
11176 at one point in a separate control field. This
11177 field went through several names.
11180 <tag><tt>Recommended</tt></tag>
11181 <item>Old name for <tt>Recommends</tt>.</item>
11183 <tag><tt>Optional</tt></tag>
11184 <item>Old name for <tt>Suggests</tt>.</item>
11186 <tag><tt>Class</tt></tag>
11187 <item>Old name for <tt>Priority</tt>.</item>
11196 <appendix id="pkg-conffiles">
11197 <heading>Configuration file handling (from old Packaging Manual)</heading>
11200 <prgn>dpkg</prgn> can do a certain amount of automatic
11201 handling of package configuration files.
11205 Whether this mechanism is appropriate depends on a number of
11206 factors, but basically there are two approaches to any
11207 particular configuration file.
11211 The easy method is to ship a best-effort configuration in the
11212 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11213 handle updates. If the user is unlikely to want to edit the
11214 file, but you need them to be able to without losing their
11215 changes, and a new package with a changed version of the file
11216 is only released infrequently, this is a good approach.
11220 The hard method is to build the configuration file from
11221 scratch in the <prgn>postinst</prgn> script, and to take the
11222 responsibility for fixing any mistakes made in earlier
11223 versions of the package automatically. This will be
11224 appropriate if the file is likely to need to be different on
11228 <sect><heading>Automatic handling of configuration files by
11233 A package may contain a control information file called
11234 <tt>conffiles</tt>. This file should be a list of filenames
11235 of configuration files needing automatic handling, separated
11236 by newlines. The filenames should be absolute pathnames,
11237 and the files referred to should actually exist in the
11242 When a package is upgraded <prgn>dpkg</prgn> will process
11243 the configuration files during the configuration stage,
11244 shortly before it runs the package's <prgn>postinst</prgn>
11249 For each file it checks to see whether the version of the
11250 file included in the package is the same as the one that was
11251 included in the last version of the package (the one that is
11252 being upgraded from); it also compares the version currently
11253 installed on the system with the one shipped with the last
11258 If neither the user nor the package maintainer has changed
11259 the file, it is left alone. If one or the other has changed
11260 their version, then the changed version is preferred - i.e.,
11261 if the user edits their file, but the package maintainer
11262 doesn't ship a different version, the user's changes will
11263 stay, silently, but if the maintainer ships a new version
11264 and the user hasn't edited it the new version will be
11265 installed (with an informative message). If both have
11266 changed their version the user is prompted about the problem
11267 and must resolve the differences themselves.
11271 The comparisons are done by calculating the MD5 message
11272 digests of the files, and storing the MD5 of the file as it
11273 was included in the most recent version of the package.
11277 When a package is installed for the first time
11278 <prgn>dpkg</prgn> will install the file that comes with it,
11279 unless that would mean overwriting a file already on the
11284 However, note that <prgn>dpkg</prgn> will <em>not</em>
11285 replace a conffile that was removed by the user (or by a
11286 script). This is necessary because with some programs a
11287 missing file produces an effect hard or impossible to
11288 achieve in another way, so that a missing file needs to be
11289 kept that way if the user did it.
11293 Note that a package should <em>not</em> modify a
11294 <prgn>dpkg</prgn>-handled conffile in its maintainer
11295 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11296 the user confusing and possibly dangerous options for
11297 conffile update when the package is upgraded.</p>
11300 <sect><heading>Fully-featured maintainer script configuration
11305 For files which contain site-specific information such as
11306 the hostname and networking details and so forth, it is
11307 better to create the file in the package's
11308 <prgn>postinst</prgn> script.
11312 This will typically involve examining the state of the rest
11313 of the system to determine values and other information, and
11314 may involve prompting the user for some information which
11315 can't be obtained some other way.
11319 When using this method there are a couple of important
11320 issues which should be considered:
11324 If you discover a bug in the program which generates the
11325 configuration file, or if the format of the file changes
11326 from one version to the next, you will have to arrange for
11327 the postinst script to do something sensible - usually this
11328 will mean editing the installed configuration file to remove
11329 the problem or change the syntax. You will have to do this
11330 very carefully, since the user may have changed the file,
11331 perhaps to fix the very problem that your script is trying
11332 to deal with - you will have to detect these situations and
11333 deal with them correctly.
11337 If you do go down this route it's probably a good idea to
11338 make the program that generates the configuration file(s) a
11339 separate program in <file>/usr/sbin</file>, by convention called
11340 <file><var>package</var>config</file> and then run that if
11341 appropriate from the post-installation script. The
11342 <tt><var>package</var>config</tt> program should not
11343 unquestioningly overwrite an existing configuration - if its
11344 mode of operation is geared towards setting up a package for
11345 the first time (rather than any arbitrary reconfiguration
11346 later) you should have it check whether the configuration
11347 already exists, and require a <tt>--force</tt> flag to
11348 overwrite it.</p></sect>
11351 <appendix id="pkg-alternatives"><heading>Alternative versions of
11352 an interface - <prgn>update-alternatives</prgn> (from old
11357 When several packages all provide different versions of the
11358 same program or file it is useful to have the system select a
11359 default, but to allow the system administrator to change it
11360 and have their decisions respected.
11364 For example, there are several versions of the <prgn>vi</prgn>
11365 editor, and there is no reason to prevent all of them from
11366 being installed at once, each under their own name
11367 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11368 Nevertheless it is desirable to have the name <tt>vi</tt>
11369 refer to something, at least by default.
11373 If all the packages involved cooperate, this can be done with
11374 <prgn>update-alternatives</prgn>.
11378 Each package provides its own version under its own name, and
11379 calls <prgn>update-alternatives</prgn> in its postinst to
11380 register its version (and again in its prerm to deregister
11385 See the man page <manref name="update-alternatives"
11386 section="8"> for details.
11390 If <prgn>update-alternatives</prgn> does not seem appropriate
11391 you may wish to consider using diversions instead.</p>
11394 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11395 package's version of a file (from old Packaging Manual)
11399 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11400 when it reinstalls the package it belongs to, and to have it
11401 put the file from the package somewhere else instead.
11405 This can be used locally to override a package's version of a
11406 file, or by one package to override another's version (or
11407 provide a wrapper for it).
11411 Before deciding to use a diversion, read <ref
11412 id="pkg-alternatives"> to see if you really want a diversion
11413 rather than several alternative versions of a program.
11417 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11418 and updated by a special program <prgn>dpkg-divert</prgn>.
11419 Please see <manref name="dpkg-divert" section="8"> for full
11420 details of its operation.
11424 When a package wishes to divert a file from another, it should
11425 call <prgn>dpkg-divert</prgn> in its preinst to add the
11426 diversion and rename the existing file. For example,
11427 supposing that a <prgn>smailwrapper</prgn> package wishes to
11428 install a wrapper around <file>/usr/sbin/smail</file>:
11430 dpkg-divert --package smailwrapper --add --rename \
11431 --divert /usr/sbin/smail.real /usr/sbin/smail
11432 </example> The <tt>--package smailwrapper</tt> ensures that
11433 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11434 can bypass the diversion and get installed as the true version.
11435 It's safe to add the diversion unconditionally on upgrades since
11436 it will be left unchanged if it already exists, but
11437 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11438 message, make the command conditional on the version from which
11439 the package is being upgraded:
11441 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11442 dpkg-divert --package smailwrapper --add --rename \
11443 --divert /usr/sbin/smail.real /usr/sbin/smail
11445 </example> where <tt>1.0-2</tt> is the version at which the
11446 diversion was first added to the package. Running the command
11447 during abort-upgrade is pointless but harmless.
11451 The postrm has to do the reverse:
11453 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11454 dpkg-divert --package smailwrapper --remove --rename \
11455 --divert /usr/sbin/smail.real /usr/sbin/smail
11457 </example> If the diversion was added at a particular version, the
11458 postrm should also handle the failure case of upgrading from an
11459 older version (unless the older version is so old that direct
11460 upgrades are no longer supported):
11462 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11463 dpkg-divert --package smailwrapper --remove --rename \
11464 --divert /usr/sbin/smail.real /usr/sbin/smail
11466 </example> where <tt>1.0-2</tt> is the version at which the
11467 diversion was first added to the package. The postrm should not
11468 remove the diversion on upgrades both because there's no reason to
11469 remove the diversion only to immediately re-add it and since the
11470 postrm of the old package is run after unpacking so the removal of
11471 the diversion will fail.
11475 Do not attempt to divert a file which is vitally important for
11476 the system's operation - when using <prgn>dpkg-divert</prgn>
11477 there is a time, after it has been diverted but before
11478 <prgn>dpkg</prgn> has installed the new version, when the file
11479 does not exist.</p>
11484 <!-- Local variables: -->
11485 <!-- indent-tabs-mode: t -->
11487 <!-- vim:set ai sts=2 sw=2 tw=76: -->