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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 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>).
1967 The <tt>build</tt> target should depend on those of the
1968 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1969 are provided in the rules file.<footnote>
1970 The intent of this split is so that binary-only builds
1971 need not install the dependencies required for
1972 the <tt>build-indep</tt> target. However, this is not
1973 yet used in practice since <tt>dpkg-buildpackage
1974 -B</tt>, and therefore the autobuilders,
1975 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1976 due to the difficulties in determining whether the
1977 optional <tt>build-arch</tt> target exists.
1982 If one or both of the targets <tt>build-arch</tt> and
1983 <tt>build-indep</tt> are not provided, then invoking
1984 <file>debian/rules</file> with one of the not-provided
1985 targets as arguments should produce a exit status code
1986 of 2. Usually this is provided automatically by make
1987 if the target is missing.
1991 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1992 must not do anything that might require root privilege.
1996 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
1997 (required), <tt>binary-indep</tt> (required)
2001 The <tt>binary</tt> target must be all that is
2002 necessary for the user to build the binary package(s)
2003 produced from this source package. It is
2004 split into two parts: <prgn>binary-arch</prgn> builds
2005 the binary packages which are specific to a particular
2006 architecture, and <tt>binary-indep</tt> builds
2007 those which are not.
2010 <tt>binary</tt> may be (and commonly is) a target with
2011 no commands which simply depends on
2012 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2015 Both <tt>binary-*</tt> targets should depend on the
2016 <tt>build</tt> target, or on the appropriate
2017 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2018 provided, so that the package is built if it has not
2019 been already. It should then create the relevant
2020 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2021 make their control files and <prgn>dpkg-deb</prgn> to
2022 build them and place them in the parent of the top
2027 Both the <tt>binary-arch</tt> and
2028 <tt>binary-indep</tt> targets <em>must</em> exist.
2029 If one of them has nothing to do (which will always be
2030 the case if the source generates only a single binary
2031 package, whether architecture-dependent or not), it
2032 must still exist and must always succeed.
2036 The <tt>binary</tt> targets must be invoked as
2038 The <prgn>fakeroot</prgn> package often allows one
2039 to build a package correctly even without being
2045 <tag><tt>clean</tt> (required)</tag>
2048 This must undo any effects that the <tt>build</tt>
2049 and <tt>binary</tt> targets may have had, except
2050 that it should leave alone any output files created in
2051 the parent directory by a run of a <tt>binary</tt>
2056 If a <tt>build</tt> file is touched at the end of
2057 the <tt>build</tt> target, as suggested above, it
2058 should be removed as the first action that
2059 <tt>clean</tt> performs, so that running
2060 <tt>build</tt> again after an interrupted
2061 <tt>clean</tt> doesn't think that everything is
2066 The <tt>clean</tt> target may need to be
2067 invoked as root if <tt>binary</tt> has been
2068 invoked since the last <tt>clean</tt>, or if
2069 <tt>build</tt> has been invoked as root (since
2070 <tt>build</tt> may create directories, for
2075 <tag><tt>get-orig-source</tt> (optional)</tag>
2078 This target fetches the most recent version of the
2079 original source package from a canonical archive site
2080 (via FTP or WWW, for example), does any necessary
2081 rearrangement to turn it into the original source
2082 tar file format described below, and leaves it in the
2087 This target may be invoked in any directory, and
2088 should take care to clean up any temporary files it
2093 This target is optional, but providing it if
2094 possible is a good idea.
2098 <tag><tt>patch</tt> (optional)</tag>
2101 This target performs whatever additional actions are
2102 required to make the source ready for editing (unpacking
2103 additional upstream archives, applying patches, etc.).
2104 It is recommended to be implemented for any package where
2105 <tt>dpkg-source -x</tt> does not result in source ready
2106 for additional modification. See
2107 <ref id="readmesource">.
2113 The <tt>build</tt>, <tt>binary</tt> and
2114 <tt>clean</tt> targets must be invoked with the current
2115 directory being the package's top-level directory.
2120 Additional targets may exist in <file>debian/rules</file>,
2121 either as published or undocumented interfaces or for the
2122 package's internal use.
2126 The architectures we build on and build for are determined
2127 by <prgn>make</prgn> variables using the
2128 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2129 You can determine the Debian architecture and the GNU style
2130 architecture specification string for the build architecture as
2131 well as for the host architecture. The build architecture is
2132 the architecture on which <file>debian/rules</file> is run and
2133 the package build is performed. The host architecture is the
2134 architecture on which the resulting package will be installed
2135 and run. These are normally the same, but may be different in
2136 the case of cross-compilation (building packages for one
2137 architecture on machines of a different architecture).
2141 Here is a list of supported <prgn>make</prgn> variables:
2142 <list compact="compact">
2144 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2147 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2150 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2153 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2154 specification string)
2157 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2158 <tt>DEB_*_GNU_TYPE</tt>)
2161 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2162 <tt>DEB_*_GNU_TYPE</tt>)
2164 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2165 the build architecture or <tt>HOST</tt> for specification of the
2170 Backward compatibility can be provided in the rules file
2171 by setting the needed variables to suitable default
2172 values; please refer to the documentation of
2173 <prgn>dpkg-architecture</prgn> for details.
2177 It is important to understand that the <tt>DEB_*_ARCH</tt>
2178 string only determines which Debian architecture we are
2179 building on or for. It should not be used to get the CPU
2180 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2181 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2182 GNU style variables should generally only be used with upstream
2186 <sect1 id="debianrules-options">
2187 <heading><file>debian/rules</file> and
2188 <tt>DEB_BUILD_OPTIONS</tt></heading>
2191 Supporting the standardized environment variable
2192 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2193 contain several flags to change how a package is compiled and
2194 built. Each flag must be in the form <var>flag</var> or
2195 <var>flag</var>=<var>options</var>. If multiple flags are
2196 given, they must be separated by whitespace.<footnote>
2197 Some packages support any delimiter, but whitespace is the
2198 easiest to parse inside a makefile and avoids ambiguity with
2199 flag values that contain commas.
2201 <var>flag</var> must start with a lowercase letter
2202 (<tt>a-z</tt>) and consist only of lowercase letters,
2203 numbers (<tt>0-9</tt>), and the characters
2204 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2205 <var>options</var> must not contain whitespace. The same
2206 tag should not be given multiple times with conflicting
2207 values. Package maintainers may assume that
2208 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2212 The meaning of the following tags has been standardized:
2216 This tag says to not run any build-time test suite
2217 provided by the package.
2221 The presence of this tag means that the package should
2222 be compiled with a minimum of optimization. For C
2223 programs, it is best to add <tt>-O0</tt> to
2224 <tt>CFLAGS</tt> (although this is usually the default).
2225 Some programs might fail to build or run at this level
2226 of optimization; it may be necessary to use
2227 <tt>-O1</tt>, for example.
2231 This tag means that the debugging symbols should not be
2232 stripped from the binary during installation, so that
2233 debugging information may be included in the package.
2235 <tag>parallel=n</tag>
2237 This tag means that the package should be built using up
2238 to <tt>n</tt> parallel processes if the package build
2239 system supports this.<footnote>
2240 Packages built with <tt>make</tt> can often implement
2241 this by passing the <tt>-j</tt><var>n</var> option to
2244 If the package build system does not support parallel
2245 builds, this string must be ignored. If the package
2246 build system only supports a lower level of concurrency
2247 than <var>n</var>, the package should be built using as
2248 many parallel processes as the package build system
2249 supports. It is up to the package maintainer to decide
2250 whether the package build times are long enough and the
2251 package build system is robust enough to make supporting
2252 parallel builds worthwhile.
2258 Unknown flags must be ignored by <file>debian/rules</file>.
2262 The following makefile snippet is an example of how one may
2263 implement the build options; you will probably have to
2264 massage this example in order to make it work for your
2266 <example compact="compact">
2269 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2270 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2271 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2272 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2274 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2279 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2280 INSTALL_PROGRAM += -s
2282 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2283 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2284 MAKEFLAGS += -j$(NUMJOBS)
2289 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2290 # Code to run the package test suite.
2297 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2298 <sect id="substvars">
2299 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2302 When <prgn>dpkg-gencontrol</prgn>
2303 generates <qref id="binarycontrolfiles">binary package control
2304 files</qref> (<file>DEBIAN/control</file>), it performs variable
2305 substitutions on its output just before writing it. Variable
2306 substitutions have the form <tt>${<var>variable</var>}</tt>.
2307 The optional file <file>debian/substvars</file> contains
2308 variable substitutions to be used; variables can also be set
2309 directly from <file>debian/rules</file> using the <tt>-V</tt>
2310 option to the source packaging commands, and certain predefined
2311 variables are also available.
2315 The <file>debian/substvars</file> file is usually generated and
2316 modified dynamically by <file>debian/rules</file> targets, in
2317 which case it must be removed by the <tt>clean</tt> target.
2321 See <manref name="deb-substvars" section="5"> for full
2322 details about source variable substitutions, including the
2323 format of <file>debian/substvars</file>.</p>
2326 <sect id="debianwatch">
2327 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2330 This is an optional, recommended configuration file for the
2331 <tt>uscan</tt> utility which defines how to automatically scan
2332 ftp or http sites for newly available updates of the
2333 package. This is used
2334 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2335 tools to help with quality control and maintenance of the
2336 distribution as a whole.
2341 <sect id="debianfiles">
2342 <heading>Generated files list: <file>debian/files</file></heading>
2345 This file is not a permanent part of the source tree; it
2346 is used while building packages to record which files are
2347 being generated. <prgn>dpkg-genchanges</prgn> uses it
2348 when it generates a <file>.changes</file> file.
2352 It should not exist in a shipped source package, and so it
2353 (and any backup files or temporary files such as
2354 <file>files.new</file><footnote>
2355 <file>files.new</file> is used as a temporary file by
2356 <prgn>dpkg-gencontrol</prgn> and
2357 <prgn>dpkg-distaddfile</prgn> - they write a new
2358 version of <tt>files</tt> here before renaming it,
2359 to avoid leaving a corrupted copy if an error
2361 </footnote>) should be removed by the
2362 <tt>clean</tt> target. It may also be wise to
2363 ensure a fresh start by emptying or removing it at the
2364 start of the <tt>binary</tt> target.
2368 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2369 package, it adds an entry to <file>debian/files</file> for the
2370 <file>.deb</file> file that will be created when <tt>dpkg-deb
2371 --build</tt> is run for that binary package. So for most
2372 packages all that needs to be done with this file is to
2373 delete it in the <tt>clean</tt> target.
2377 If a package upload includes files besides the source
2378 package and any binary packages whose control files were
2379 made with <prgn>dpkg-gencontrol</prgn> then they should be
2380 placed in the parent of the package's top-level directory
2381 and <prgn>dpkg-distaddfile</prgn> should be called to add
2382 the file to the list in <file>debian/files</file>.</p>
2385 <sect id="embeddedfiles">
2386 <heading>Convenience copies of code</heading>
2389 Some software packages include in their distribution convenience
2390 copies of code from other software packages, generally so that
2391 users compiling from source don't have to download multiple
2392 packages. Debian packages should not make use of these
2393 convenience copies unless the included package is explicitly
2394 intended to be used in this way.<footnote>
2395 For example, parts of the GNU build system work like this.
2397 If the included code is already in the Debian archive in the
2398 form of a library, the Debian packaging should ensure that
2399 binary packages reference the libraries already in Debian and
2400 the convenience copy is not used. If the included code is not
2401 already in Debian, it should be packaged separately as a
2402 prerequisite if possible.
2404 Having multiple copies of the same code in Debian is
2405 inefficient, often creates either static linking or shared
2406 library conflicts, and, most importantly, increases the
2407 difficulty of handling security vulnerabilities in the
2413 <sect id="readmesource">
2414 <heading>Source package handling:
2415 <file>debian/README.source</file></heading>
2418 If running <prgn>dpkg-source -x</prgn> on a source package
2419 doesn't produce the source of the package, ready for editing,
2420 and allow one to make changes and run
2421 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2422 without taking any additional steps, creating a
2423 <file>debian/README.source</file> documentation file is
2424 recommended. This file should explain how to do all of the
2427 <item>Generate the fully patched source, in a form ready for
2428 editing, that would be built to create Debian
2429 packages. Doing this with a <tt>patch</tt> target in
2430 <file>debian/rules</file> is recommended; see
2431 <ref id="debianrules">.</item>
2432 <item>Modify the source and save those modifications so that
2433 they will be applied when building the package.</item>
2434 <item>Remove source modifications that are currently being
2435 applied when building the package.</item>
2436 <item>Optionally, document what steps are necessary to
2437 upgrade the Debian source package to a new upstream version,
2438 if applicable.</item>
2440 This explanation should include specific commands and mention
2441 any additional required Debian packages. It should not assume
2442 familiarity with any specific Debian packaging system or patch
2447 This explanation may refer to a documentation file installed by
2448 one of the package's build dependencies provided that the
2449 referenced documentation clearly explains these tasks and is not
2450 a general reference manual.
2454 <file>debian/README.source</file> may also include any other
2455 information that would be helpful to someone modifying the
2456 source package. Even if the package doesn't fit the above
2457 description, maintainers are encouraged to document in a
2458 <file>debian/README.source</file> file any source package with a
2459 particularly complex or unintuitive source layout or build
2460 system (for example, a package that builds the same source
2461 multiple times to generate different binary packages).
2467 <chapt id="controlfields">
2468 <heading>Control files and their fields</heading>
2471 The package management system manipulates data represented in
2472 a common format, known as <em>control data</em>, stored in
2473 <em>control files</em>.
2474 Control files are used for source packages, binary packages and
2475 the <file>.changes</file> files which control the installation
2476 of uploaded files<footnote>
2477 <prgn>dpkg</prgn>'s internal databases are in a similar
2482 <sect id="controlsyntax">
2483 <heading>Syntax of control files</heading>
2486 A control file consists of one or more paragraphs of
2488 The paragraphs are also sometimes referred to as stanzas.
2490 The paragraphs are separated by empty lines. Parsers may accept
2491 lines consisting solely of spaces and tabs as paragraph
2492 separators, but control files should use empty lines. Some control
2493 files allow only one paragraph; others allow several, in
2494 which case each paragraph usually refers to a different
2495 package. (For example, in source packages, the first
2496 paragraph refers to the source package, and later paragraphs
2497 refer to binary packages generated from the source.) The
2498 ordering of the paragraphs in control files is significant.
2502 Each paragraph consists of a series of data fields. Each field
2503 consists of the field name followed by a colon and then the
2504 data/value associated with that field. The field name is
2505 composed of US-ASCII characters excluding control characters,
2506 space, and colon (i.e., characters in the ranges 33-57 and
2507 59-126, inclusive). Field names must not begin with the comment
2508 character, <tt>#</tt>.
2512 The field ends at the end of the line or at the end of the last
2513 continuation line (see below). Horizontal whitespace (spaces
2514 and tabs) may occur immediately before or after the value and is
2515 ignored there; it is conventional to put a single space after
2516 the colon. For example, a field might be:
2517 <example compact="compact">
2520 the field name is <tt>Package</tt> and the field value
2525 A paragraph must not contain more than one instance of a
2526 particular field name.
2530 There are three types of fields:
2534 The field, including its value, must be a single line. Folding
2535 of the field is not permitted. This is the default field type
2536 if the definition of the field does not specify a different
2541 The value of a folded field is a logical line that may span
2542 several lines. The lines after the first are called
2543 continuation lines and must start with a space or a tab.
2544 Whitespace, including any newlines, is not significant in the
2545 field values of folded fields.<footnote>
2546 This folding method is similar to RFC 5322, allowing control
2547 files that contain only one paragraph and no multiline fields
2548 to be read by parsers written for RFC 5322.
2551 <tag>multiline</tag>
2553 The value of a multiline field may comprise multiple continuation
2554 lines. The first line of the value, the part on the same line as
2555 the field name, often has special significance or may have to be
2556 empty. Other lines are added following the same syntax as the
2557 continuation lines of the folded fields. Whitespace, including newlines,
2558 is significant in the values of multiline fields.
2564 Whitespace must not appear
2565 inside names (of packages, architectures, files or anything
2566 else) or version numbers, or between the characters of
2567 multi-character version relationships.
2571 The presence and purpose of a field, and the syntax of its
2572 value may differ between types of control files.
2576 Field names are not case-sensitive, but it is usual to
2577 capitalize the field names using mixed case as shown below.
2578 Field values are case-sensitive unless the description of the
2579 field says otherwise.
2583 Paragraph separators (empty lines) and lines consisting only of
2584 spaces and tabs are not allowed within field values or between
2585 fields. Empty lines in field values are usually escaped by
2586 representing them by a space followed by a dot.
2590 Lines starting with # without any preceding whitespace are comments
2591 lines that are only permitted in source package control files
2592 (<file>debian/control</file>). These comment lines are ignored, even
2593 between two continuation lines. They do not end logical lines.
2597 All control files must be encoded in UTF-8.
2601 <sect id="sourcecontrolfiles">
2602 <heading>Source package control files -- <file>debian/control</file></heading>
2605 The <file>debian/control</file> file contains the most vital
2606 (and version-independent) information about the source package
2607 and about the binary packages it creates.
2611 The first paragraph of the control file contains information about
2612 the source package in general. The subsequent sets each describe a
2613 binary package that the source tree builds.
2617 The fields in the general paragraph (the first one, for the source
2620 <list compact="compact">
2621 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2623 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2624 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2625 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2626 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2627 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2628 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2629 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2634 The fields in the binary package paragraphs are:
2636 <list compact="compact">
2637 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2638 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2639 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2640 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2641 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2642 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2643 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2644 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2649 The syntax and semantics of the fields are described below.
2653 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2654 generate control files for binary packages (see below), by
2655 <prgn>dpkg-genchanges</prgn> to generate the
2656 <file>.changes</file> file to accompany the upload, and by
2657 <prgn>dpkg-source</prgn> when it creates the
2658 <file>.dsc</file> source control file as part of a source
2659 archive. Some fields are folded in <file>debian/control</file>,
2660 but not in any other control
2661 file. These tools are responsible for removing the line
2662 breaks from such fields when using fields from
2663 <file>debian/control</file> to generate other control files.
2667 The fields here may contain variable references - their
2668 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2669 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2670 when they generate output control files.
2671 See <ref id="substvars"> for details.
2675 <sect id="binarycontrolfiles">
2676 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2679 The <file>DEBIAN/control</file> file contains the most vital
2680 (and version-dependent) information about a binary package. It
2681 consists of a single paragraph.
2685 The fields in this file are:
2687 <list compact="compact">
2688 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2689 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2690 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2691 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2692 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2693 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2694 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2695 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2696 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2697 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2698 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2699 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2704 <sect id="debiansourcecontrolfiles">
2705 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2708 This file consists of a single paragraph, possibly surrounded by
2709 a PGP signature. The fields of that paragraph are listed below.
2710 Their syntax is described above, in <ref id="controlsyntax">.
2712 <list compact="compact">
2713 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2714 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2715 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2716 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2717 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2718 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2719 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2720 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2721 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2722 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2723 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2724 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2725 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2726 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2731 The Debian source control file is generated by
2732 <prgn>dpkg-source</prgn> when it builds the source
2733 archive, from other files in the source package,
2734 described above. When unpacking, it is checked against
2735 the files and directories in the other parts of the
2741 <sect id="debianchangesfiles">
2742 <heading>Debian changes files -- <file>.changes</file></heading>
2745 The <file>.changes</file> files are used by the Debian archive
2746 maintenance software to process updates to packages. They
2747 consist of a single paragraph, possibly surrounded by a PGP
2748 signature. That paragraph contains information from the
2749 <file>debian/control</file> file and other data about the
2750 source package gathered via <file>debian/changelog</file>
2751 and <file>debian/rules</file>.
2755 <file>.changes</file> files have a format version that is
2756 incremented whenever the documented fields or their meaning
2757 change. This document describes format &changesversion;.
2761 The fields in this file are:
2763 <list compact="compact">
2764 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2765 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2766 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2767 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2768 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2769 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2770 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2771 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2772 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2773 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2774 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2775 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2776 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2777 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2778 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2779 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2784 <sect id="controlfieldslist">
2785 <heading>List of fields</heading>
2787 <sect1 id="f-Source">
2788 <heading><tt>Source</tt></heading>
2791 This field identifies the source package name.
2795 In <file>debian/control</file> or a <file>.dsc</file> file,
2796 this field must contain only the name of the source package.
2800 In a binary package control file or a <file>.changes</file>
2801 file, the source package name may be followed by a version
2802 number in parentheses<footnote>
2803 It is customary to leave a space after the package name
2804 if a version number is specified.
2806 This version number may be omitted (and is, by
2807 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2808 the <tt>Version</tt> field of the binary package in
2809 question. The field itself may be omitted from a binary
2810 package control file when the source package has the same
2811 name and version as the binary package.
2815 Package names (both source and binary,
2816 see <ref id="f-Package">) must consist only of lower case
2817 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2818 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2819 (<tt>.</tt>). They must be at least two characters long and
2820 must start with an alphanumeric character.
2824 <sect1 id="f-Maintainer">
2825 <heading><tt>Maintainer</tt></heading>
2828 The package maintainer's name and email address. The name
2829 must come first, then the email address inside angle
2830 brackets <tt><></tt> (in RFC822 format).
2834 If the maintainer's name contains a full stop then the
2835 whole field will not work directly as an email address due
2836 to a misfeature in the syntax specified in RFC822; a
2837 program using this field as an address must check for this
2838 and correct the problem if necessary (for example by
2839 putting the name in round brackets and moving it to the
2840 end, and bringing the email address forward).
2844 See <ref id="maintainer"> for additional requirements and
2845 information about package maintainers.
2849 <sect1 id="f-Uploaders">
2850 <heading><tt>Uploaders</tt></heading>
2853 List of the names and email addresses of co-maintainers of the
2854 package, if any. If the package has other maintainers besides
2855 the one named in the <qref id="f-Maintainer">Maintainer
2856 field</qref>, their names and email addresses should be listed
2857 here. The format of each entry is the same as that of the
2858 Maintainer field, and multiple entries must be comma
2863 This is normally an optional field, but if
2864 the <tt>Maintainer</tt> control field names a group of people
2865 and a shared email address, the <tt>Uploaders</tt> field must
2866 be present and must contain at least one human with their
2867 personal email address.
2871 The Uploaders field in <file>debian/control</file> can be folded.
2875 <sect1 id="f-Changed-By">
2876 <heading><tt>Changed-By</tt></heading>
2879 The name and email address of the person who prepared this
2880 version of the package, usually a maintainer. The syntax is
2881 the same as for the <qref id="f-Maintainer">Maintainer
2886 <sect1 id="f-Section">
2887 <heading><tt>Section</tt></heading>
2890 This field specifies an application area into which the package
2891 has been classified. See <ref id="subsections">.
2895 When it appears in the <file>debian/control</file> file,
2896 it gives the value for the subfield of the same name in
2897 the <tt>Files</tt> field of the <file>.changes</file> file.
2898 It also gives the default for the same field in the binary
2903 <sect1 id="f-Priority">
2904 <heading><tt>Priority</tt></heading>
2907 This field represents how important it is that the user
2908 have the package installed. See <ref id="priorities">.
2912 When it appears in the <file>debian/control</file> file,
2913 it gives the value for the subfield of the same name in
2914 the <tt>Files</tt> field of the <file>.changes</file> file.
2915 It also gives the default for the same field in the binary
2920 <sect1 id="f-Package">
2921 <heading><tt>Package</tt></heading>
2924 The name of the binary package.
2928 Binary package names must follow the same syntax and
2929 restrictions as source package names. See <ref id="f-Source">
2934 <sect1 id="f-Architecture">
2935 <heading><tt>Architecture</tt></heading>
2938 Depending on context and the control file used, the
2939 <tt>Architecture</tt> field can include the following sets of
2943 A unique single word identifying a Debian machine
2944 architecture as described in <ref id="arch-spec">.
2947 An architecture wildcard identifying a set of Debian
2948 machine architectures, see <ref id="arch-wildcard-spec">.
2949 <tt>any</tt> matches all Debian machine architectures
2950 and is the most frequently used.
2953 <tt>all</tt>, which indicates an
2954 architecture-independent package.
2957 <tt>source</tt>, which indicates a source package.
2963 In the main <file>debian/control</file> file in the source
2964 package, this field may contain the special
2965 value <tt>all</tt>, the special architecture
2966 wildcard <tt>any</tt>, or a list of specific and wildcard
2967 architectures separated by spaces. If <tt>all</tt>
2968 or <tt>any</tt> appears, that value must be the entire
2969 contents of the field. Most packages will use
2970 either <tt>all</tt> or <tt>any</tt>.
2974 Specifying a specific list of architectures indicates that the
2975 source will build an architecture-dependent package only on
2976 architectures included in the list. Specifying a list of
2977 architecture wildcards indicates that the source will build an
2978 architecture-dependent package on only those architectures
2979 that match any of the specified architecture wildcards.
2980 Specifying a list of architectures or architecture wildcards
2981 other than <tt>any</tt> is for the minority of cases where a
2982 program is not portable or is not useful on some
2983 architectures. Where possible, the program should be made
2988 In the Debian source control file <file>.dsc</file>, this
2989 field contains a list of architectures and architecture
2990 wildcards separated by spaces. When the list contains the
2991 architecture wildcard <tt>any</tt>, the only other value
2992 allowed in the list is <tt>all</tt>.
2996 The list may include (or consist solely of) the special
2997 value <tt>all</tt>. In other words, in <file>.dsc</file>
2998 files unlike the <file>debian/control</file>, <tt>all</tt> may
2999 occur in combination with specific architectures.
3000 The <tt>Architecture</tt> field in the Debian source control
3001 file <file>.dsc</file> is generally constructed from
3002 the <tt>Architecture</tt> fields in
3003 the <file>debian/control</file> in the source package.
3007 Specifying only <tt>any</tt> indicates that the source package
3008 isn't dependent on any particular architecture and should
3009 compile fine on any one. The produced binary package(s)
3010 will be specific to whatever the current build architecture is.
3014 Specifying only <tt>all</tt> indicates that the source package
3015 will only build architecture-independent packages.
3019 Specifying <tt>any all</tt> indicates that the source package
3020 isn't dependent on any particular architecture. The set of
3021 produced binary packages will include at least one
3022 architecture-dependant package and one architecture-independent
3027 Specifying a list of architectures or architecture wildcards
3028 indicates that the source will build an architecture-dependent
3029 package, and will only work correctly on the listed or
3030 matching architectures. If the source package also builds at
3031 least one architecture-independent package, <tt>all</tt> will
3032 also be included in the list.
3036 In a <file>.changes</file> file, the <tt>Architecture</tt>
3037 field lists the architecture(s) of the package(s) currently
3038 being uploaded. This will be a list; if the source for the
3039 package is also being uploaded, the special
3040 entry <tt>source</tt> is also present. <tt>all</tt> will be
3041 present if any architecture-independent packages are being
3042 uploaded. Architecture wildcards such as <tt>any</tt> must
3043 never occur in the <tt>Architecture</tt> field in
3044 the <file>.changes</file> file.
3048 See <ref id="debianrules"> for information on how to get
3049 the architecture for the build process.
3053 <sect1 id="f-Essential">
3054 <heading><tt>Essential</tt></heading>
3057 This is a boolean field which may occur only in the
3058 control file of a binary package or in a per-package fields
3059 paragraph of a source package control file.
3063 If set to <tt>yes</tt> then the package management system
3064 will refuse to remove the package (upgrading and replacing
3065 it is still possible). The other possible value is <tt>no</tt>,
3066 which is the same as not having the field at all.
3071 <heading>Package interrelationship fields:
3072 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3073 <tt>Recommends</tt>, <tt>Suggests</tt>,
3074 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3075 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3079 These fields describe the package's relationships with
3080 other packages. Their syntax and semantics are described
3081 in <ref id="relationships">.</p>
3084 <sect1 id="f-Standards-Version">
3085 <heading><tt>Standards-Version</tt></heading>
3088 The most recent version of the standards (the policy
3089 manual and associated texts) with which the package
3094 The version number has four components: major and minor
3095 version number and major and minor patch level. When the
3096 standards change in a way that requires every package to
3097 change the major number will be changed. Significant
3098 changes that will require work in many packages will be
3099 signaled by a change to the minor number. The major patch
3100 level will be changed for any change to the meaning of the
3101 standards, however small; the minor patch level will be
3102 changed when only cosmetic, typographical or other edits
3103 are made which neither change the meaning of the document
3104 nor affect the contents of packages.
3108 Thus only the first three components of the policy version
3109 are significant in the <em>Standards-Version</em> control
3110 field, and so either these three components or all four
3111 components may be specified.<footnote>
3112 In the past, people specified the full version number
3113 in the Standards-Version field, for example "2.3.0.0".
3114 Since minor patch-level changes don't introduce new
3115 policy, it was thought it would be better to relax
3116 policy and only require the first 3 components to be
3117 specified, in this example "2.3.0". All four
3118 components may still be used if someone wishes to do so.
3124 <sect1 id="f-Version">
3125 <heading><tt>Version</tt></heading>
3128 The version number of a package. The format is:
3129 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3133 The three components here are:
3135 <tag><var>epoch</var></tag>
3138 This is a single (generally small) unsigned integer. It
3139 may be omitted, in which case zero is assumed. If it is
3140 omitted then the <var>upstream_version</var> may not
3145 It is provided to allow mistakes in the version numbers
3146 of older versions of a package, and also a package's
3147 previous version numbering schemes, to be left behind.
3151 <tag><var>upstream_version</var></tag>
3154 This is the main part of the version number. It is
3155 usually the version number of the original ("upstream")
3156 package from which the <file>.deb</file> file has been made,
3157 if this is applicable. Usually this will be in the same
3158 format as that specified by the upstream author(s);
3159 however, it may need to be reformatted to fit into the
3160 package management system's format and comparison
3165 The comparison behavior of the package management system
3166 with respect to the <var>upstream_version</var> is
3167 described below. The <var>upstream_version</var>
3168 portion of the version number is mandatory.
3172 The <var>upstream_version</var> may contain only
3173 alphanumerics<footnote>
3174 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3176 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3177 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3178 tilde) and should start with a digit. If there is no
3179 <var>debian_revision</var> then hyphens are not allowed;
3180 if there is no <var>epoch</var> then colons are not
3185 <tag><var>debian_revision</var></tag>
3188 This part of the version number specifies the version of
3189 the Debian package based on the upstream version. It
3190 may contain only alphanumerics and the characters
3191 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3192 tilde) and is compared in the same way as the
3193 <var>upstream_version</var> is.
3197 It is optional; if it isn't present then the
3198 <var>upstream_version</var> may not contain a hyphen.
3199 This format represents the case where a piece of
3200 software was written specifically to be a Debian
3201 package, where the Debian package source must always
3202 be identical to the pristine source and therefore no
3203 revision indication is required.
3207 It is conventional to restart the
3208 <var>debian_revision</var> at <tt>1</tt> each time the
3209 <var>upstream_version</var> is increased.
3213 The package management system will break the version
3214 number apart at the last hyphen in the string (if there
3215 is one) to determine the <var>upstream_version</var> and
3216 <var>debian_revision</var>. The absence of a
3217 <var>debian_revision</var> is equivalent to a
3218 <var>debian_revision</var> of <tt>0</tt>.
3225 When comparing two version numbers, first the <var>epoch</var>
3226 of each are compared, then the <var>upstream_version</var> if
3227 <var>epoch</var> is equal, and then <var>debian_revision</var>
3228 if <var>upstream_version</var> is also equal.
3229 <var>epoch</var> is compared numerically. The
3230 <var>upstream_version</var> and <var>debian_revision</var>
3231 parts are compared by the package management system using the
3232 following algorithm:
3236 The strings are compared from left to right.
3240 First the initial part of each string consisting entirely of
3241 non-digit characters is determined. These two parts (one of
3242 which may be empty) are compared lexically. If a difference
3243 is found it is returned. The lexical comparison is a
3244 comparison of ASCII values modified so that all the letters
3245 sort earlier than all the non-letters and so that a tilde
3246 sorts before anything, even the end of a part. For example,
3247 the following parts are in sorted order from earliest to
3248 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3249 <tt>a</tt>.<footnote>
3250 One common use of <tt>~</tt> is for upstream pre-releases.
3251 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3252 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3257 Then the initial part of the remainder of each string which
3258 consists entirely of digit characters is determined. The
3259 numerical values of these two parts are compared, and any
3260 difference found is returned as the result of the comparison.
3261 For these purposes an empty string (which can only occur at
3262 the end of one or both version strings being compared) counts
3267 These two steps (comparing and removing initial non-digit
3268 strings and initial digit strings) are repeated until a
3269 difference is found or both strings are exhausted.
3273 Note that the purpose of epochs is to allow us to leave behind
3274 mistakes in version numbering, and to cope with situations
3275 where the version numbering scheme changes. It is
3276 <em>not</em> intended to cope with version numbers containing
3277 strings of letters which the package management system cannot
3278 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3279 silly orderings.<footnote>
3280 The author of this manual has heard of a package whose
3281 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3282 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3288 <sect1 id="f-Description">
3289 <heading><tt>Description</tt></heading>
3292 In a source or binary control file, the <tt>Description</tt>
3293 field contains a description of the binary package, consisting
3294 of two parts, the synopsis or the short description, and the
3295 long description. It is a multiline field with the following
3301 Description: <single line synopsis>
3302 <extended description over several lines>
3307 The lines in the extended description can have these formats:
3313 Those starting with a single space are part of a paragraph.
3314 Successive lines of this form will be word-wrapped when
3315 displayed. The leading space will usually be stripped off.
3316 The line must contain at least one non-whitespace character.
3320 Those starting with two or more spaces. These will be
3321 displayed verbatim. If the display cannot be panned
3322 horizontally, the displaying program will line wrap them "hard"
3323 (i.e., without taking account of word breaks). If it can they
3324 will be allowed to trail off to the right. None, one or two
3325 initial spaces may be deleted, but the number of spaces
3326 deleted from each line will be the same (so that you can have
3327 indenting work correctly, for example). The line must
3328 contain at least one non-whitespace character.
3332 Those containing a single space followed by a single full stop
3333 character. These are rendered as blank lines. This is the
3334 <em>only</em> way to get a blank line<footnote>
3335 Completely empty lines will not be rendered as blank lines.
3336 Instead, they will cause the parser to think you're starting
3337 a whole new record in the control file, and will therefore
3338 likely abort with an error.
3343 Those containing a space, a full stop and some more characters.
3344 These are for future expansion. Do not use them.
3350 Do not use tab characters. Their effect is not predictable.
3354 See <ref id="descriptions"> for further information on this.
3358 In a <file>.changes</file> file, the <tt>Description</tt>
3359 field contains a summary of the descriptions for the packages
3360 being uploaded. For this case, the first line of the field
3361 value (the part on the same line as <tt>Description:</tt>) is
3362 always empty. It is a multiline field, with one
3363 line per package. Each line is
3364 indented by one space and contains the name of a binary
3365 package, a space, a hyphen (<tt>-</tt>), a space, and the
3366 short description line from that package.
3370 <sect1 id="f-Distribution">
3371 <heading><tt>Distribution</tt></heading>
3374 In a <file>.changes</file> file or parsed changelog output
3375 this contains the (space-separated) name(s) of the
3376 distribution(s) where this version of the package should
3377 be installed. Valid distributions are determined by the
3378 archive maintainers.<footnote>
3379 Example distribution names in the Debian archive used in
3380 <file>.changes</file> files are:
3381 <taglist compact="compact">
3382 <tag><em>unstable</em></tag>
3384 This distribution value refers to the
3385 <em>developmental</em> part of the Debian distribution
3386 tree. Most new packages, new upstream versions of
3387 packages and bug fixes go into the <em>unstable</em>
3391 <tag><em>experimental</em></tag>
3393 The packages with this distribution value are deemed
3394 by their maintainers to be high risk. Oftentimes they
3395 represent early beta or developmental packages from
3396 various sources that the maintainers want people to
3397 try, but are not ready to be a part of the other parts
3398 of the Debian distribution tree.
3403 Others are used for updating stable releases or for
3404 security uploads. More information is available in the
3405 Debian Developer's Reference, section "The Debian
3409 The Debian archive software only supports listing a single
3410 distribution. Migration of packages to other distributions is
3411 handled outside of the upload process.
3416 <heading><tt>Date</tt></heading>
3419 This field includes the date the package was built or last
3420 edited. It must be in the same format as the <var>date</var>
3421 in a <file>debian/changelog</file> entry.
3425 The value of this field is usually extracted from the
3426 <file>debian/changelog</file> file - see
3427 <ref id="dpkgchangelog">).
3431 <sect1 id="f-Format">
3432 <heading><tt>Format</tt></heading>
3435 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3436 files, this field declares the format version of that file.
3437 The syntax of the field value is the same as that of
3438 a <qref id="f-Version">package version number</qref> except
3439 that no epoch or Debian revision is allowed. The format
3440 described in this document is <tt>&changesversion;</tt>.
3444 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3445 Debian source control</qref> files, this field declares the
3446 format of the source package. The field value is used by
3447 programs acting on a source package to interpret the list of
3448 files in the source package and determine how to unpack it.
3449 The syntax of the field value is a numeric major revision, a
3450 period, a numeric minor revision, and then an optional subtype
3451 after whitespace, which if specified is an alphanumeric word
3452 in parentheses. The subtype is optional in the syntax but may
3453 be mandatory for particular source format revisions.
3455 The source formats currently supported by the Debian archive
3456 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3457 and <tt>3.0 (quilt)</tt>.
3462 <sect1 id="f-Urgency">
3463 <heading><tt>Urgency</tt></heading>
3466 This is a description of how important it is to upgrade to
3467 this version from previous ones. It consists of a single
3468 keyword taking one of the values <tt>low</tt>,
3469 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3470 <tt>critical</tt><footnote>
3471 Other urgency values are supported with configuration
3472 changes in the archive software but are not used in Debian.
3473 The urgency affects how quickly a package will be considered
3474 for inclusion into the <tt>testing</tt> distribution and
3475 gives an indication of the importance of any fixes included
3476 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3477 treated as synonymous.
3478 </footnote> (not case-sensitive) followed by an optional
3479 commentary (separated by a space) which is usually in
3480 parentheses. For example:
3483 Urgency: low (HIGH for users of diversions)
3489 The value of this field is usually extracted from the
3490 <file>debian/changelog</file> file - see
3491 <ref id="dpkgchangelog">.
3495 <sect1 id="f-Changes">
3496 <heading><tt>Changes</tt></heading>
3499 This multiline field contains the human-readable changes data, describing
3500 the differences between the last version and the current one.
3504 The first line of the field value (the part on the same line
3505 as <tt>Changes:</tt>) is always empty. The content of the
3506 field is expressed as continuation lines, with each line
3507 indented by at least one space. Blank lines must be
3508 represented by a line consisting only of a space and a full
3513 The value of this field is usually extracted from the
3514 <file>debian/changelog</file> file - see
3515 <ref id="dpkgchangelog">).
3519 Each version's change information should be preceded by a
3520 "title" line giving at least the version, distribution(s)
3521 and urgency, in a human-readable way.
3525 If data from several versions is being returned the entry
3526 for the most recent version should be returned first, and
3527 entries should be separated by the representation of a
3528 blank line (the "title" line may also be followed by the
3529 representation of a blank line).
3533 <sect1 id="f-Binary">
3534 <heading><tt>Binary</tt></heading>
3537 This folded field is a list of binary packages. Its syntax and
3538 meaning varies depending on the control file in which it
3543 When it appears in the <file>.dsc</file> file, it lists binary
3544 packages which a source package can produce, separated by
3546 A space after each comma is conventional.
3547 </footnote>. The source package
3548 does not necessarily produce all of these binary packages for
3549 every architecture. The source control file doesn't contain
3550 details of which architectures are appropriate for which of
3551 the binary packages.
3555 When it appears in a <file>.changes</file> file, it lists the
3556 names of the binary packages being uploaded, separated by
3557 whitespace (not commas).
3561 <sect1 id="f-Installed-Size">
3562 <heading><tt>Installed-Size</tt></heading>
3565 This field appears in the control files of binary packages,
3566 and in the <file>Packages</file> files. It gives an estimate
3567 of the total amount of disk space required to install the
3568 named package. Actual installed size may vary based on block
3569 size, file system properties, or actions taken by package
3574 The disk space is given as the integer value of the estimated
3575 installed size in bytes, divided by 1024 and rounded up.
3579 <sect1 id="f-Files">
3580 <heading><tt>Files</tt></heading>
3583 This field contains a list of files with information about
3584 each one. The exact information and syntax varies with
3589 In all cases, Files is a multiline field. The first line of
3590 the field value (the part on the same line as <tt>Files:</tt>)
3591 is always empty. The content of the field is expressed as
3592 continuation lines, one line per file. Each line must be
3593 indented by one space and contain a number of sub-fields,
3594 separated by spaces, as described below.
3598 In the <file>.dsc</file> file, each line contains the MD5
3599 checksum, size and filename of the tar file and (if
3600 applicable) diff file which make up the remainder of the
3601 source package<footnote>
3602 That is, the parts which are not the <tt>.dsc</tt>.
3603 </footnote>. For example:
3606 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3607 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3609 The exact forms of the filenames are described
3610 in <ref id="pkg-sourcearchives">.
3614 In the <file>.changes</file> file this contains one line per
3615 file being uploaded. Each line contains the MD5 checksum,
3616 size, section and priority and the filename. For example:
3619 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3620 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3621 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3622 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3624 The <qref id="f-Section">section</qref>
3625 and <qref id="f-Priority">priority</qref> are the values of
3626 the corresponding fields in the main source control file. If
3627 no section or priority is specified then <tt>-</tt> should be
3628 used, though section and priority values must be specified for
3629 new packages to be installed properly.
3633 The special value <tt>byhand</tt> for the section in a
3634 <tt>.changes</tt> file indicates that the file in question
3635 is not an ordinary package file and must by installed by
3636 hand by the distribution maintainers. If the section is
3637 <tt>byhand</tt> the priority should be <tt>-</tt>.
3641 If a new Debian revision of a package is being shipped and
3642 no new original source archive is being distributed the
3643 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3644 entry for the original source archive
3645 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3646 but the <file>.changes</file> file should leave it out. In
3647 this case the original source archive on the distribution
3648 site must match exactly, byte-for-byte, the original
3649 source archive which was used to generate the
3650 <file>.dsc</file> file and diff which are being uploaded.</p>
3653 <sect1 id="f-Closes">
3654 <heading><tt>Closes</tt></heading>
3657 A space-separated list of bug report numbers that the upload
3658 governed by the .changes file closes.
3662 <sect1 id="f-Homepage">
3663 <heading><tt>Homepage</tt></heading>
3666 The URL of the web site for this package, preferably (when
3667 applicable) the site from which the original source can be
3668 obtained and any additional upstream documentation or
3669 information may be found. The content of this field is a
3670 simple URL without any surrounding characters such as
3675 <sect1 id="f-Checksums">
3676 <heading><tt>Checksums-Sha1</tt>
3677 and <tt>Checksums-Sha256</tt></heading>
3680 These multiline fields contain a list of files with a checksum and size
3681 for each one. Both <tt>Checksums-Sha1</tt>
3682 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3683 only in the checksum algorithm used: SHA-1
3684 for <tt>Checksums-Sha1</tt> and SHA-256
3685 for <tt>Checksums-Sha256</tt>.
3689 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3690 multiline fields. The first line of the field value (the part
3691 on the same line as <tt>Checksums-Sha1:</tt>
3692 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3693 of the field is expressed as continuation lines, one line per
3694 file. Each line consists of the checksum, a space, the file
3695 size, a space, and the file name. For example (from
3696 a <file>.changes</file> file):
3699 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3700 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3701 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3702 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3704 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3705 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3706 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3707 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3712 In the <file>.dsc</file> file, these fields should list all
3713 files that make up the source package. In
3714 the <file>.changes</file> file, these fields should list all
3715 files being uploaded. The list of files in these fields
3716 must match the list of files in the <tt>Files</tt> field.
3720 <sect1 id="f-DM-Upload-Allowed">
3721 <heading><tt>DM-Upload-Allowed</tt></heading>
3724 The most recent version of a package uploaded to unstable or
3725 experimental must include the field <tt>DM-Upload-Allowed:
3726 yes</tt> in the source section of its source control file for
3727 the Debian archive to accept uploads signed with a key in the
3728 Debian Maintainer keyring. See the General
3729 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3730 name="Endorse the concept of Debian Maintainers"> for more
3737 <heading>User-defined fields</heading>
3740 Additional user-defined fields may be added to the
3741 source package control file. Such fields will be
3742 ignored, and not copied to (for example) binary or
3743 Debian source control files or upload control files.
3747 If you wish to add additional unsupported fields to
3748 these output files you should use the mechanism
3753 Fields in the main source control information file with
3754 names starting <tt>X</tt>, followed by one or more of
3755 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3756 be copied to the output files. Only the part of the
3757 field name after the hyphen will be used in the output
3758 file. Where the letter <tt>B</tt> is used the field
3759 will appear in binary package control files, where the
3760 letter <tt>S</tt> is used in Debian source control
3761 files and where <tt>C</tt> is used in upload control
3762 (<tt>.changes</tt>) files.
3766 For example, if the main source information control file
3769 XBS-Comment: I stand between the candle and the star.
3771 then the binary and Debian source control files will contain the
3774 Comment: I stand between the candle and the star.
3783 <chapt id="maintainerscripts">
3784 <heading>Package maintainer scripts and installation procedure</heading>
3787 <heading>Introduction to package maintainer scripts</heading>
3790 It is possible to supply scripts as part of a package which
3791 the package management system will run for you when your
3792 package is installed, upgraded or removed.
3796 These scripts are the control information
3797 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3798 and <prgn>postrm</prgn>. They must be proper executable files;
3799 if they are scripts (which is recommended), they must start with
3800 the usual <tt>#!</tt> convention. They should be readable and
3801 executable by anyone, and must not be world-writable.
3805 The package management system looks at the exit status from
3806 these scripts. It is important that they exit with a
3807 non-zero status if there is an error, so that the package
3808 management system can stop its processing. For shell
3809 scripts this means that you <em>almost always</em> need to
3810 use <tt>set -e</tt> (this is usually true when writing shell
3811 scripts, in fact). It is also important, of course, that
3812 they exit with a zero status if everything went well.
3816 Additionally, packages interacting with users
3817 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3818 should install a <prgn>config</prgn> script as a control
3819 information file. See <ref id="maintscriptprompt"> for details.
3823 When a package is upgraded a combination of the scripts from
3824 the old and new packages is called during the upgrade
3825 procedure. If your scripts are going to be at all
3826 complicated you need to be aware of this, and may need to
3827 check the arguments to your scripts.
3831 Broadly speaking the <prgn>preinst</prgn> is called before
3832 (a particular version of) a package is unpacked, and the
3833 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3834 before (a version of) a package is removed and the
3835 <prgn>postrm</prgn> afterwards.
3839 Programs called from maintainer scripts should not normally
3840 have a path prepended to them. Before installation is
3841 started, the package management system checks to see if the
3842 programs <prgn>ldconfig</prgn>,
3843 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3844 and <prgn>update-rc.d</prgn> can be found via the
3845 <tt>PATH</tt> environment variable. Those programs, and any
3846 other program that one would expect to be in the
3847 <tt>PATH</tt>, should thus be invoked without an absolute
3848 pathname. Maintainer scripts should also not reset the
3849 <tt>PATH</tt>, though they might choose to modify it by
3850 prepending or appending package-specific directories. These
3851 considerations really apply to all shell scripts.</p>
3854 <sect id="idempotency">
3855 <heading>Maintainer scripts idempotency</heading>
3858 It is necessary for the error recovery procedures that the
3859 scripts be idempotent. This means that if it is run
3860 successfully, and then it is called again, it doesn't bomb
3861 out or cause any harm, but just ensures that everything is
3862 the way it ought to be. If the first call failed, or
3863 aborted half way through for some reason, the second call
3864 should merely do the things that were left undone the first
3865 time, if any, and exit with a success status if everything
3867 This is so that if an error occurs, the user interrupts
3868 <prgn>dpkg</prgn> or some other unforeseen circumstance
3869 happens you don't leave the user with a badly-broken
3870 package when <prgn>dpkg</prgn> attempts to repeat the
3876 <sect id="controllingterminal">
3877 <heading>Controlling terminal for maintainer scripts</heading>
3880 Maintainer scripts are not guaranteed to run with a controlling
3881 terminal and may not be able to interact with the user. They
3882 must be able to fall back to noninteractive behavior if no
3883 controlling terminal is available. Maintainer scripts that
3884 prompt via a program conforming to the Debian Configuration
3885 Management Specification (see <ref id="maintscriptprompt">) may
3886 assume that program will handle falling back to noninteractive
3891 For high-priority prompts without a reasonable default answer,
3892 maintainer scripts may abort if there is no controlling
3893 terminal. However, this situation should be avoided if at all
3894 possible, since it prevents automated or unattended installs.
3895 In most cases, users will consider this to be a bug in the
3900 <sect id="exitstatus">
3901 <heading>Exit status</heading>
3904 Each script must return a zero exit status for
3905 success, or a nonzero one for failure, since the package
3906 management system looks for the exit status of these scripts
3907 and determines what action to take next based on that datum.
3911 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3916 What follows is a summary of all the ways in which maintainer
3917 scripts may be called along with what facilities those scripts
3918 may rely on being available at that time. Script names preceded
3919 by <var>new-</var> are the scripts from the new version of a
3920 package being installed, upgraded to, or downgraded to. Script
3921 names preceded by <var>old-</var> are the scripts from the old
3922 version of a package that is being upgraded from or downgraded
3927 The <prgn>preinst</prgn> script may be called in the following
3930 <tag><var>new-preinst</var> <tt>install</tt></tag>
3931 <tag><var>new-preinst</var> <tt>install</tt>
3932 <var>old-version</var></tag>
3933 <tag><var>new-preinst</var> <tt>upgrade</tt>
3934 <var>old-version</var></tag>
3936 The package will not yet be unpacked, so
3937 the <prgn>preinst</prgn> script cannot rely on any files
3938 included in its package. Only essential packages and
3939 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3940 available. Pre-dependencies will have been configured at
3941 least once, but at the time the <prgn>preinst</prgn> is
3942 called they may only be in an unpacked or "Half-Configured"
3943 state if a previous version of the pre-dependency was
3944 completely configured and has not been removed since then.
3947 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3948 <var>new-version</var></tag>
3950 Called during error handling of an upgrade that failed after
3951 unpacking the new package because the <tt>postrm
3952 upgrade</tt> action failed. The unpacked files may be
3953 partly from the new version or partly missing, so the script
3954 cannot rely on files included in the package. Package
3955 dependencies may not be available. Pre-dependencies will be
3956 at least unpacked following the same rules as above, except
3957 they may be only "Half-Installed" if an upgrade of the
3958 pre-dependency failed.<footnote>
3959 This can happen if the new version of the package no
3960 longer pre-depends on a package that had been partially
3968 The <prgn>postinst</prgn> script may be called in the following
3971 <tag><var>postinst</var> <tt>configure</tt>
3972 <var>most-recently-configured-version</var></tag>
3974 The files contained in the package will be unpacked. All
3975 package dependencies will at least be unpacked. If there
3976 are no circular dependencies involved, all package
3977 dependencies will be configured. For behavior in the case
3978 of circular dependencies, see the discussion
3979 in <ref id="binarydeps">.
3982 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3983 <var>new-version</var></tag>
3984 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3985 <tt>in-favour</tt> <var>package</var>
3986 <var>new-version</var></tag>
3987 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3988 <tag><var>deconfigured's-postinst</var>
3989 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3990 <var>failed-install-package</var> <var>version</var>
3991 [<tt>removing</tt> <var>conflicting-package</var>
3992 <var>version</var>]</tag>
3994 The files contained in the package will be unpacked. All
3995 package dependencies will at least be "Half-Installed" and
3996 will have previously been configured and not removed.
3997 However, dependencies may not be configured or even fully
3998 unpacked in some error situations.<footnote>
3999 For example, suppose packages foo and bar are installed
4000 with foo depending on bar. If an upgrade of bar were
4001 started and then aborted, and then an attempt to remove
4002 foo failed because its <prgn>prerm</prgn> script failed,
4003 foo's <tt>postinst abort-remove</tt> would be called with
4004 bar only "Half-Installed".
4006 The <prgn>postinst</prgn> should still attempt any actions
4007 for which its dependencies are required, since they will
4008 normally be available, but consider the correct error
4009 handling approach if those actions fail. Aborting
4010 the <prgn>postinst</prgn> action if commands or facilities
4011 from the package dependencies are not available is often the
4018 The <prgn>prerm</prgn> script may be called in the following
4021 <tag><var>prerm</var> <tt>remove</tt></tag>
4022 <tag><var>old-prerm</var>
4023 <tt>upgrade</tt><var>new-version</var></tag>
4024 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4025 <tt>in-favour</tt> <var>package</var>
4026 <var>new-version</var></tag>
4027 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4028 <tt>in-favour</tt> <var>package-being-installed</var>
4029 <var>version</var> [<tt>removing</tt>
4030 <var>conflicting-package</var> <var>version</var>]</tag>
4032 The package whose <prgn>prerm</prgn> is being called will be
4033 at least "Half-Installed". All package dependencies will at
4034 least be "Half-Installed" and will have previously been
4035 configured and not removed. If there was no error, all
4036 dependencies will at least be unpacked, but these actions
4037 may be called in various error states where dependencies are
4038 only "Half-Installed" due to a partial upgrade.
4041 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4042 <var>old-version</var></tag>
4044 Called during error handling when <tt>prerm upgrade</tt>
4045 fails. The new package will not yet be unpacked, and all
4046 the same constraints as for <tt>preinst upgrade</tt> apply.
4052 The <prgn>postrm</prgn> script may be called in the following
4055 <tag><var>postrm</var> <tt>remove</tt></tag>
4056 <tag><var>postrm</var> <tt>purge</tt></tag>
4057 <tag><var>old-postrm</var> <tt>upgrade</tt>
4058 <var>new-version</var></tag>
4059 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4060 <var>overwriter</var> <var>overwriter-version</var></tag>
4062 The <prgn>postrm</prgn> script is called after the package's
4063 files have been removed or replaced. The package
4064 whose <prgn>postrm</prgn> is being called may have
4065 previously been deconfigured and only be unpacked, at which
4066 point subsequent package changes do not consider its
4067 dependencies. Therefore, all <prgn>postrm</prgn> actions
4068 may only rely on essential packages and must gracefully skip
4069 any actions that require the package's dependencies if those
4070 dependencies are unavailable.<footnote>
4071 This is often done by checking whether the command or
4072 facility the <prgn>postrm</prgn> intends to call is
4073 available before calling it. For example:
4075 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4076 . /usr/share/debconf/confmodule
4080 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4081 configuration for the package
4082 if <package>debconf</package> is installed.
4086 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4087 <var>old-version</var></tag>
4089 Called when the old <tt>postrm upgrade</tt> action fails.
4090 The new package will be unpacked, but only essential
4091 packages and pre-dependencies can be relied on.
4092 Pre-dependencies will either be configured or will be
4093 "Unpacked" or "Half-Configured" but previously had been
4094 configured and was never removed.
4097 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4098 <tag><var>new-postrm</var> <tt>abort-install</tt>
4099 <var>old-version</var></tag>
4100 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4101 <var>old-version</var></tag>
4103 Called before unpacking the new package as part of the
4104 error handling of <prgn>preinst</prgn> failures. May assume
4105 the same state as <prgn>preinst</prgn> can assume.
4111 <sect id="unpackphase">
4112 <heading>Details of unpack phase of installation or upgrade</heading>
4115 The procedure on installation/upgrade/overwrite/disappear
4116 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4117 stage of <tt>dpkg --install</tt>) is as follows. In each
4118 case, if a major error occurs (unless listed below) the
4119 actions are, in general, run backwards - this means that the
4120 maintainer scripts are run with different arguments in
4121 reverse order. These are the "error unwind" calls listed
4128 If a version of the package is already installed, call
4129 <example compact="compact">
4130 <var>old-prerm</var> upgrade <var>new-version</var>
4134 If the script runs but exits with a non-zero
4135 exit status, <prgn>dpkg</prgn> will attempt:
4136 <example compact="compact">
4137 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4139 If this works, the upgrade continues. If this
4140 does not work, the error unwind:
4141 <example compact="compact">
4142 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4144 If this works, then the old-version is
4145 "Installed", if not, the old version is in a
4146 "Half-Configured" state.
4152 If a "conflicting" package is being removed at the same time,
4153 or if any package will be broken (due to <tt>Breaks</tt>):
4156 If <tt>--auto-deconfigure</tt> is
4157 specified, call, for each package to be deconfigured
4158 due to <tt>Breaks</tt>:
4159 <example compact="compact">
4160 <var>deconfigured's-prerm</var> deconfigure \
4161 in-favour <var>package-being-installed</var> <var>version</var>
4164 <example compact="compact">
4165 <var>deconfigured's-postinst</var> abort-deconfigure \
4166 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4168 The deconfigured packages are marked as
4169 requiring configuration, so that if
4170 <tt>--install</tt> is used they will be
4171 configured again if possible.
4174 If any packages depended on a conflicting
4175 package being removed and <tt>--auto-deconfigure</tt> is
4176 specified, call, for each such package:
4177 <example compact="compact">
4178 <var>deconfigured's-prerm</var> deconfigure \
4179 in-favour <var>package-being-installed</var> <var>version</var> \
4180 removing <var>conflicting-package</var> <var>version</var>
4183 <example compact="compact">
4184 <var>deconfigured's-postinst</var> abort-deconfigure \
4185 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4186 removing <var>conflicting-package</var> <var>version</var>
4188 The deconfigured packages are marked as
4189 requiring configuration, so that if
4190 <tt>--install</tt> is used they will be
4191 configured again if possible.
4194 To prepare for removal of each conflicting package, call:
4195 <example compact="compact">
4196 <var>conflictor's-prerm</var> remove \
4197 in-favour <var>package</var> <var>new-version</var>
4200 <example compact="compact">
4201 <var>conflictor's-postinst</var> abort-remove \
4202 in-favour <var>package</var> <var>new-version</var>
4211 If the package is being upgraded, call:
4212 <example compact="compact">
4213 <var>new-preinst</var> upgrade <var>old-version</var>
4215 If this fails, we call:
4217 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4224 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4226 is called. If this works, then the old version
4227 is in an "Installed" state, or else it is left
4228 in an "Unpacked" state.
4233 If it fails, then the old version is left
4234 in an "Half-Installed" state.
4241 Otherwise, if the package had some configuration
4242 files from a previous version installed (i.e., it
4243 is in the "configuration files only" state):
4244 <example compact="compact">
4245 <var>new-preinst</var> install <var>old-version</var>
4249 <var>new-postrm</var> abort-install <var>old-version</var>
4251 If this fails, the package is left in a
4252 "Half-Installed" state, which requires a
4253 reinstall. If it works, the packages is left in
4254 a "Config-Files" state.
4257 Otherwise (i.e., the package was completely purged):
4258 <example compact="compact">
4259 <var>new-preinst</var> install
4262 <example compact="compact">
4263 <var>new-postrm</var> abort-install
4265 If the error-unwind fails, the package is in a
4266 "Half-Installed" phase, and requires a
4267 reinstall. If the error unwind works, the
4268 package is in a not installed state.
4275 The new package's files are unpacked, overwriting any
4276 that may be on the system already, for example any
4277 from the old version of the same package or from
4278 another package. Backups of the old files are kept
4279 temporarily, and if anything goes wrong the package
4280 management system will attempt to put them back as
4281 part of the error unwind.
4285 It is an error for a package to contain files which
4286 are on the system in another package, unless
4287 <tt>Replaces</tt> is used (see <ref id="replaces">).
4289 The following paragraph is not currently the case:
4290 Currently the <tt>- - force-overwrite</tt> flag is
4291 enabled, downgrading it to a warning, but this may not
4297 It is a more serious error for a package to contain a
4298 plain file or other kind of non-directory where another
4299 package has a directory (again, unless
4300 <tt>Replaces</tt> is used). This error can be
4301 overridden if desired using
4302 <tt>--force-overwrite-dir</tt>, but this is not
4307 Packages which overwrite each other's files produce
4308 behavior which, though deterministic, is hard for the
4309 system administrator to understand. It can easily
4310 lead to "missing" programs if, for example, a package
4311 is unpacked which overwrites a file from another
4312 package, and is then removed again.<footnote>
4313 Part of the problem is due to what is arguably a
4314 bug in <prgn>dpkg</prgn>.
4319 A directory will never be replaced by a symbolic link
4320 to a directory or vice versa; instead, the existing
4321 state (symlink or not) will be left alone and
4322 <prgn>dpkg</prgn> will follow the symlink if there is
4331 If the package is being upgraded, call
4332 <example compact="compact">
4333 <var>old-postrm</var> upgrade <var>new-version</var>
4337 If this fails, <prgn>dpkg</prgn> will attempt:
4338 <example compact="compact">
4339 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4341 If this works, installation continues. If not,
4343 <example compact="compact">
4344 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4346 If this fails, the old version is left in a
4347 "Half-Installed" state. If it works, dpkg now
4349 <example compact="compact">
4350 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4352 If this fails, the old version is left in a
4353 "Half-Installed" state. If it works, dpkg now
4355 <example compact="compact">
4356 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4358 If this fails, the old version is in an
4365 This is the point of no return - if
4366 <prgn>dpkg</prgn> gets this far, it won't back off
4367 past this point if an error occurs. This will
4368 leave the package in a fairly bad state, which
4369 will require a successful re-installation to clear
4370 up, but it's when <prgn>dpkg</prgn> starts doing
4371 things that are irreversible.
4376 Any files which were in the old version of the package
4377 but not in the new are removed.
4381 The new file list replaces the old.
4385 The new maintainer scripts replace the old.
4389 Any packages all of whose files have been overwritten
4390 during the installation, and which aren't required for
4391 dependencies, are considered to have been removed.
4392 For each such package
4395 <prgn>dpkg</prgn> calls:
4396 <example compact="compact">
4397 <var>disappearer's-postrm</var> disappear \
4398 <var>overwriter</var> <var>overwriter-version</var>
4402 The package's maintainer scripts are removed.
4405 It is noted in the status database as being in a
4406 sane state, namely not installed (any conffiles
4407 it may have are ignored, rather than being
4408 removed by <prgn>dpkg</prgn>). Note that
4409 disappearing packages do not have their prerm
4410 called, because <prgn>dpkg</prgn> doesn't know
4411 in advance that the package is going to
4418 Any files in the package we're unpacking that are also
4419 listed in the file lists of other packages are removed
4420 from those lists. (This will lobotomize the file list
4421 of the "conflicting" package if there is one.)
4425 The backup files made during installation, above, are
4431 The new package's status is now sane, and recorded as
4436 Here is another point of no return - if the
4437 conflicting package's removal fails we do not unwind
4438 the rest of the installation; the conflicting package
4439 is left in a half-removed limbo.
4444 If there was a conflicting package we go and do the
4445 removal actions (described below), starting with the
4446 removal of the conflicting package's files (any that
4447 are also in the package being unpacked have already
4448 been removed from the conflicting package's file list,
4449 and so do not get removed now).
4455 <sect id="configdetails"><heading>Details of configuration</heading>
4458 When we configure a package (this happens with <tt>dpkg
4459 --install</tt> and <tt>dpkg --configure</tt>), we first
4460 update any <tt>conffile</tt>s and then call:
4461 <example compact="compact">
4462 <var>postinst</var> configure <var>most-recently-configured-version</var>
4467 No attempt is made to unwind after errors during
4468 configuration. If the configuration fails, the package is in
4469 a "Failed Config" state, and an error message is generated.
4473 If there is no most recently configured version
4474 <prgn>dpkg</prgn> will pass a null argument.
4477 Historical note: Truly ancient (pre-1997) versions of
4478 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4479 (including the angle brackets) in this case. Even older
4480 ones did not pass a second argument at all, under any
4481 circumstance. Note that upgrades using such an old dpkg
4482 version are unlikely to work for other reasons, even if
4483 this old argument behavior is handled by your postinst script.
4489 <sect id="removedetails"><heading>Details of removal and/or
4490 configuration purging</heading>
4496 <example compact="compact">
4497 <var>prerm</var> remove
4501 If prerm fails during replacement due to conflict
4503 <var>conflictor's-postinst</var> abort-remove \
4504 in-favour <var>package</var> <var>new-version</var>
4508 <var>postinst</var> abort-remove
4512 If this fails, the package is in a "Half-Configured"
4513 state, or else it remains "Installed".
4517 The package's files are removed (except <tt>conffile</tt>s).
4520 <example compact="compact">
4521 <var>postrm</var> remove
4525 If it fails, there's no error unwind, and the package is in
4526 an "Half-Installed" state.
4531 All the maintainer scripts except the <prgn>postrm</prgn>
4536 If we aren't purging the package we stop here. Note
4537 that packages which have no <prgn>postrm</prgn> and no
4538 <tt>conffile</tt>s are automatically purged when
4539 removed, as there is no difference except for the
4540 <prgn>dpkg</prgn> status.
4544 The <tt>conffile</tt>s and any backup files
4545 (<tt>~</tt>-files, <tt>#*#</tt> files,
4546 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4551 <example compact="compact">
4552 <var>postrm</var> purge
4556 If this fails, the package remains in a "Config-Files"
4561 The package's file list is removed.
4570 <chapt id="relationships">
4571 <heading>Declaring relationships between packages</heading>
4573 <sect id="depsyntax">
4574 <heading>Syntax of relationship fields</heading>
4577 These fields all have a uniform syntax. They are a list of
4578 package names separated by commas.
4582 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4583 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4584 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4585 control fields of the package, which declare
4586 dependencies on other packages, the package names listed may
4587 also include lists of alternative package names, separated
4588 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4589 if any one of the alternative packages is installed, that
4590 part of the dependency is considered to be satisfied.
4594 All of the fields except for <tt>Provides</tt> may restrict
4595 their applicability to particular versions of each named
4596 package. This is done in parentheses after each individual
4597 package name; the parentheses should contain a relation from
4598 the list below followed by a version number, in the format
4599 described in <ref id="f-Version">.
4603 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4604 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4605 strictly earlier, earlier or equal, exactly equal, later or
4606 equal and strictly later, respectively. The deprecated
4607 forms <tt><</tt> and <tt>></tt> were used to mean
4608 earlier/later or equal, rather than strictly earlier/later,
4609 so they should not appear in new packages (though
4610 <prgn>dpkg</prgn> still supports them).
4614 Whitespace may appear at any point in the version
4615 specification subject to the rules in <ref
4616 id="controlsyntax">, and must appear where it's necessary to
4617 disambiguate; it is not otherwise significant. All of the
4618 relationship fields can only be folded in source package control files. For
4619 consistency and in case of future changes to
4620 <prgn>dpkg</prgn> it is recommended that a single space be
4621 used after a version relationship and before a version
4622 number; it is also conventional to put a single space after
4623 each comma, on either side of each vertical bar, and before
4624 each open parenthesis. When opening a continuation line in a relationship field, it
4625 is conventional to do so after a comma and before the space
4626 following that comma.
4630 For example, a list of dependencies might appear as:
4631 <example compact="compact">
4634 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4639 Relationships may be restricted to a certain set of
4640 architectures. This is indicated in brackets after each
4641 individual package name and the optional version specification.
4642 The brackets enclose a non-empty list of Debian architecture names
4643 in the format described in <ref id="arch-spec">,
4644 separated by whitespace. Exclamation marks may be prepended to
4645 each of the names. (It is not permitted for some names to be
4646 prepended with exclamation marks while others aren't.)
4650 For build relationship fields
4651 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4652 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4653 the current Debian host architecture is not in this list and
4654 there are no exclamation marks in the list, or it is in the list
4655 with a prepended exclamation mark, the package name and the
4656 associated version specification are ignored completely for the
4657 purposes of defining the relationships.
4662 <example compact="compact">
4664 Build-Depends-Indep: texinfo
4665 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4666 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4668 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4669 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4670 <tt>gnumach-dev</tt> only on hurd-i386.
4674 For binary relationship fields, the architecture restriction
4675 syntax is only supported in the source package control
4676 file <file>debian/control</file>. When the corresponding binary
4677 package control file is generated, the relationship will either
4678 be omitted or included without the architecture restriction
4679 based on the architecture of the binary package. This means
4680 that architecture restrictions must not be used in binary
4681 relationship fields for architecture-independent packages
4682 (<tt>Architecture: all</tt>).
4687 <example compact="compact">
4688 Depends: foo [i386], bar [amd64]
4690 becomes <tt>Depends: foo</tt> when the package is built on
4691 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4692 package is built on the <tt>amd64</tt> architecture, and omitted
4693 entirely in binary packages built on all other architectures.
4697 If the architecture-restricted dependency is part of a set of
4698 alternatives using <tt>|</tt>, that alternative is ignored
4699 completely on architectures that do not match the restriction.
4701 <example compact="compact">
4702 Build-Depends: foo [!i386] | bar [!amd64]
4704 is equivalent to <tt>bar</tt> on the i386 architecture, to
4705 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4706 bar</tt> on all other architectures.
4710 Relationships may also be restricted to a certain set of
4711 architectures using architecture wildcards in the format
4712 described in <ref id="arch-wildcard-spec">. The syntax for
4713 declaring such restrictions is the same as declaring
4714 restrictions using a certain set of architectures without
4715 architecture wildcards. For example:
4716 <example compact="compact">
4717 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4719 is equivalent to <tt>foo</tt> on architectures using the Linux
4720 kernel and any cpu, <tt>bar</tt> on architectures using any
4721 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4722 using a kernel other than Linux.
4726 Note that the binary package relationship fields such as
4727 <tt>Depends</tt> appear in one of the binary package
4728 sections of the control file, whereas the build-time
4729 relationships such as <tt>Build-Depends</tt> appear in the
4730 source package section of the control file (which is the
4735 <sect id="binarydeps">
4736 <heading>Binary Dependencies - <tt>Depends</tt>,
4737 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4738 <tt>Pre-Depends</tt>
4742 Packages can declare in their control file that they have
4743 certain relationships to other packages - for example, that
4744 they may not be installed at the same time as certain other
4745 packages, and/or that they depend on the presence of others.
4749 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4750 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4751 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4752 <tt>Breaks</tt> is described in <ref id="breaks">, and
4753 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4754 rest are described below.
4758 These seven fields are used to declare a dependency
4759 relationship by one package on another. Except for
4760 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4761 depending (binary) package's control file.
4762 (<tt>Enhances</tt> appears in the recommending package's
4763 control file, and <tt>Breaks</tt> appears in the version of
4764 depended-on package which causes the named package to
4769 A <tt>Depends</tt> field takes effect <em>only</em> when a
4770 package is to be configured. It does not prevent a package
4771 being on the system in an unconfigured state while its
4772 dependencies are unsatisfied, and it is possible to replace
4773 a package whose dependencies are satisfied and which is
4774 properly installed with a different version whose
4775 dependencies are not and cannot be satisfied; when this is
4776 done the depending package will be left unconfigured (since
4777 attempts to configure it will give errors) and will not
4778 function properly. If it is necessary, a
4779 <tt>Pre-Depends</tt> field can be used, which has a partial
4780 effect even when a package is being unpacked, as explained
4781 in detail below. (The other three dependency fields,
4782 <tt>Recommends</tt>, <tt>Suggests</tt> and
4783 <tt>Enhances</tt>, are only used by the various front-ends
4784 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4785 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4789 Since <tt>Depends</tt> only places requirements on the order in
4790 which packages are configured, packages in an installation run
4791 are usually all unpacked first and all configured later.
4793 This approach makes dependency resolution easier. If two
4794 packages A and B are being upgraded, the installed package A
4795 depends on exactly the installed package B, and the new
4796 package A depends on exactly the new package B (a common
4797 situation when upgrading shared libraries and their
4798 corresponding development packages), satisfying the
4799 dependencies at every stage of the upgrade would be
4800 impossible. This relaxed restriction means that both new
4801 packages can be unpacked together and then configured in their
4807 If there is a circular dependency among packages being installed
4808 or removed, installation or removal order honoring the
4809 dependency order is impossible, requiring the dependency loop be
4810 broken at some point and the dependency requirements violated
4811 for at least one package. Packages involved in circular
4812 dependencies may not be able to rely on their dependencies being
4813 configured before they themselves are configured, depending on
4814 which side of the break of the circular dependency loop they
4815 happen to be on. If one of the packages in the loop has
4816 no <prgn>postinst</prgn> script, then the cycle will be broken
4817 at that package; this ensures that all <prgn>postinst</prgn>
4818 scripts are run with their dependencies properly configured if
4819 this is possible. Otherwise the breaking point is arbitrary.
4820 Packages should therefore avoid circular dependencies where
4821 possible, particularly if they have <prgn>postinst</prgn>
4826 The meaning of the five dependency fields is as follows:
4828 <tag><tt>Depends</tt></tag>
4831 This declares an absolute dependency. A package will
4832 not be configured unless all of the packages listed in
4833 its <tt>Depends</tt> field have been correctly
4834 configured (unless there is a circular dependency as
4839 The <tt>Depends</tt> field should be used if the
4840 depended-on package is required for the depending
4841 package to provide a significant amount of
4846 The <tt>Depends</tt> field should also be used if the
4847 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4848 require the depended-on package to be unpacked or
4849 configured in order to run. In the case of <tt>postinst
4850 configure</tt>, the depended-on packages will be unpacked
4851 and configured first. (If both packages are involved in a
4852 dependency loop, this might not work as expected; see the
4853 explanation a few paragraphs back.) In the case
4854 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4855 actions, the package dependencies will normally be at
4856 least unpacked, but they may be only "Half-Installed" if a
4857 previous upgrade of the dependency failed.
4861 Finally, the <tt>Depends</tt> field should be used if the
4862 depended-on package is needed by the <prgn>postrm</prgn>
4863 script to fully clean up after the package removal. There
4864 is no guarantee that package dependencies will be
4865 available when <prgn>postrm</prgn> is run, but the
4866 depended-on package is more likely to be available if the
4867 package declares a dependency (particularly in the case
4868 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4869 script must gracefully skip actions that require a
4870 dependency if that dependency isn't available.
4874 <tag><tt>Recommends</tt></tag>
4877 This declares a strong, but not absolute, dependency.
4881 The <tt>Recommends</tt> field should list packages
4882 that would be found together with this one in all but
4883 unusual installations.
4887 <tag><tt>Suggests</tt></tag>
4889 This is used to declare that one package may be more
4890 useful with one or more others. Using this field
4891 tells the packaging system and the user that the
4892 listed packages are related to this one and can
4893 perhaps enhance its usefulness, but that installing
4894 this one without them is perfectly reasonable.
4897 <tag><tt>Enhances</tt></tag>
4899 This field is similar to Suggests but works in the
4900 opposite direction. It is used to declare that a
4901 package can enhance the functionality of another
4905 <tag><tt>Pre-Depends</tt></tag>
4908 This field is like <tt>Depends</tt>, except that it
4909 also forces <prgn>dpkg</prgn> to complete installation
4910 of the packages named before even starting the
4911 installation of the package which declares the
4912 pre-dependency, as follows:
4916 When a package declaring a pre-dependency is about to
4917 be <em>unpacked</em> the pre-dependency can be
4918 satisfied if the depended-on package is either fully
4919 configured, <em>or even if</em> the depended-on
4920 package(s) are only unpacked or in the "Half-Configured"
4921 state, provided that they have been configured
4922 correctly at some point in the past (and not removed
4923 or partially removed since). In this case, both the
4924 previously-configured and currently unpacked or
4925 "Half-Configured" versions must satisfy any version
4926 clause in the <tt>Pre-Depends</tt> field.
4930 When the package declaring a pre-dependency is about to
4931 be <em>configured</em>, the pre-dependency will be treated
4932 as a normal <tt>Depends</tt>. It will be considered
4933 satisfied only if the depended-on package has been
4934 correctly configured. However, unlike
4935 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4936 permit circular dependencies to be broken. If a circular
4937 dependency is encountered while attempting to honor
4938 <tt>Pre-Depends</tt>, the installation will be aborted.
4942 <tt>Pre-Depends</tt> are also required if the
4943 <prgn>preinst</prgn> script depends on the named package.
4944 It is best to avoid this situation if possible.
4948 <tt>Pre-Depends</tt> should be used sparingly,
4949 preferably only by packages whose premature upgrade or
4950 installation would hamper the ability of the system to
4951 continue with any upgrade that might be in progress.
4955 You should not specify a <tt>Pre-Depends</tt> entry for a
4956 package before this has been discussed on the
4957 <tt>debian-devel</tt> mailing list and a consensus about
4958 doing that has been reached. See <ref id="dependencies">.
4965 When selecting which level of dependency to use you should
4966 consider how important the depended-on package is to the
4967 functionality of the one declaring the dependency. Some
4968 packages are composed of components of varying degrees of
4969 importance. Such a package should list using
4970 <tt>Depends</tt> the package(s) which are required by the
4971 more important components. The other components'
4972 requirements may be mentioned as Suggestions or
4973 Recommendations, as appropriate to the components' relative
4979 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4982 When one binary package declares that it breaks another,
4983 <prgn>dpkg</prgn> will refuse to allow the package which
4984 declares <tt>Breaks</tt> to be unpacked unless the broken
4985 package is deconfigured first, and it will refuse to
4986 allow the broken package to be reconfigured.
4990 A package will not be regarded as causing breakage merely
4991 because its configuration files are still installed; it must
4992 be at least "Half-Installed".
4996 A special exception is made for packages which declare that
4997 they break their own package name or a virtual package which
4998 they provide (see below): this does not count as a real
5003 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5004 version clause; such a <tt>Breaks</tt> is introduced in the
5005 version of an (implicit or explicit) dependency which violates
5006 an assumption or reveals a bug in earlier versions of the broken
5007 package, or which takes over a file from earlier versions of the
5008 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5009 will inform higher-level package management tools that the
5010 broken package must be upgraded before the new one.
5014 If the breaking package also overwrites some files from the
5015 older package, it should use <tt>Replaces</tt> to ensure this
5016 goes smoothly. See <ref id="replaces"> for a full discussion
5017 of taking over files from other packages, including how to
5018 use <tt>Breaks</tt> in those cases.
5022 Many of the cases where <tt>Breaks</tt> should be used were
5023 previously handled with <tt>Conflicts</tt>
5024 because <tt>Breaks</tt> did not yet exist.
5025 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5026 See <ref id="conflicts"> for more information about the
5031 <sect id="conflicts">
5032 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5035 When one binary package declares a conflict with another using
5036 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5037 allow them to be unpacked on the system at the same time. This
5038 is a stronger restriction than <tt>Breaks</tt>, which prevents
5039 the broken package from being configured while the breaking
5040 package is in the "Unpacked" state but allows both packages to
5041 be unpacked at the same time.
5045 If one package is to be unpacked, the other must be removed
5046 first. If the package being unpacked is marked as replacing
5047 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5048 normally be used in this case) the one on the system, or the one
5049 on the system is marked as deselected, or both packages are
5050 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5051 automatically remove the package which is causing the conflict.
5052 Otherwise, it will halt the installation of the new package with
5053 an error. This mechanism is specifically designed to produce an
5054 error when the installed package is <tt>Essential</tt>, but the
5059 A package will not cause a conflict merely because its
5060 configuration files are still installed; it must be at least
5065 A special exception is made for packages which declare a
5066 conflict with their own package name, or with a virtual
5067 package which they provide (see below): this does not
5068 prevent their installation, and allows a package to conflict
5069 with others providing a replacement for it. You use this
5070 feature when you want the package in question to be the only
5071 package providing some feature.
5075 Normally, <tt>Breaks</tt> should be used instead
5076 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5077 stronger restriction on the ordering of package installation or
5078 upgrade and can make it more difficult for the package manager
5079 to find a correct solution to an upgrade or installation
5080 problem. <tt>Breaks</tt> should be used
5082 <item>when moving a file from one package to another (see
5083 <ref id="replaces">),</item>
5084 <item>when splitting a package (a special case of the previous
5086 <item>when the breaking package exposes a bug in or interacts
5087 badly with particular versions of the broken
5090 <tt>Conflicts</tt> should be used
5092 <item>when two packages provide the same file and will
5093 continue to do so,</item>
5094 <item>in conjunction with <tt>Provides</tt> when only one
5095 package providing a given virtual facility may be unpacked
5096 at a time (see <ref id="virtual">),</item>
5097 <item>in other cases where one must prevent simultaneous
5098 installation of two packages for reasons that are ongoing
5099 (not fixed in a later version of one of the packages) or
5100 that must prevent both packages from being unpacked at the
5101 same time, not just configured.</item>
5103 Be aware that adding <tt>Conflicts</tt> is normally not the best
5104 solution when two packages provide the same files. Depending on
5105 the reason for that conflict, using alternatives or renaming the
5106 files is often a better approach. See, for
5107 example, <ref id="binaries">.
5111 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5112 unless two packages cannot be installed at the same time or
5113 installing them both causes one of them to be broken or
5114 unusable. Having similar functionality or performing the same
5115 tasks as another package is not sufficient reason to
5116 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5120 A <tt>Conflicts</tt> entry may have an "earlier than" version
5121 clause if the reason for the conflict is corrected in a later
5122 version of one of the packages. However, normally the presence
5123 of an "earlier than" version clause is a sign
5124 that <tt>Breaks</tt> should have been used instead. An "earlier
5125 than" version clause in <tt>Conflicts</tt>
5126 prevents <prgn>dpkg</prgn> from upgrading or installing the
5127 package which declares such a conflict until the upgrade or
5128 removal of the conflicted-with package has been completed, which
5129 is a strong restriction.
5133 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5137 As well as the names of actual ("concrete") packages, the
5138 package relationship fields <tt>Depends</tt>,
5139 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5140 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5141 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5142 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5143 may mention "virtual packages".
5147 A <em>virtual package</em> is one which appears in the
5148 <tt>Provides</tt> control field of another package. The effect
5149 is as if the package(s) which provide a particular virtual
5150 package name had been listed by name everywhere the virtual
5151 package name appears. (See also <ref id="virtual_pkg">)
5155 If there are both concrete and virtual packages of the same
5156 name, then the dependency may be satisfied (or the conflict
5157 caused) by either the concrete package with the name in
5158 question or any other concrete package which provides the
5159 virtual package with the name in question. This is so that,
5160 for example, supposing we have
5161 <example compact="compact">
5164 </example> and someone else releases an enhanced version of
5165 the <tt>bar</tt> package they can say:
5166 <example compact="compact">
5170 and the <tt>bar-plus</tt> package will now also satisfy the
5171 dependency for the <tt>foo</tt> package.
5175 If a relationship field has a version number attached, only real
5176 packages will be considered to see whether the relationship is
5177 satisfied (or the prohibition violated, for a conflict or
5178 breakage). In other words, if a version number is specified,
5179 this is a request to ignore all <tt>Provides</tt> for that
5180 package name and consider only real packages. The package
5181 manager will assume that a package providing that virtual
5182 package is not of the "right" version. A <tt>Provides</tt>
5183 field may not contain version numbers, and the version number of
5184 the concrete package which provides a particular virtual package
5185 will not be considered when considering a dependency on or
5186 conflict with the virtual package name.<footnote>
5187 It is possible that a future release of <prgn>dpkg</prgn> may
5188 add the ability to specify a version number for each virtual
5189 package it provides. This feature is not yet present,
5190 however, and is expected to be used only infrequently.
5195 To specify which of a set of real packages should be the default
5196 to satisfy a particular dependency on a virtual package, list
5197 the real package as an alternative before the virtual one.
5201 If the virtual package represents a facility that can only be
5202 provided by one real package at a time, such as
5203 the <package>mail-transport-agent</package> virtual package that
5204 requires installation of a binary that would conflict with all
5205 other providers of that virtual package (see
5206 <ref id="mail-transport-agents">), all packages providing that
5207 virtual package should also declare a conflict with it
5208 using <tt>Conflicts</tt>. This will ensure that at most one
5209 provider of that virtual package is unpacked or installed at a
5214 <sect id="replaces"><heading>Overwriting files and replacing
5215 packages - <tt>Replaces</tt></heading>
5218 Packages can declare in their control file that they should
5219 overwrite files in certain other packages, or completely replace
5220 other packages. The <tt>Replaces</tt> control field has these
5221 two distinct purposes.
5224 <sect1><heading>Overwriting files in other packages</heading>
5227 It is usually an error for a package to contain files which
5228 are on the system in another package. However, if the
5229 overwriting package declares that it <tt>Replaces</tt> the one
5230 containing the file being overwritten, then <prgn>dpkg</prgn>
5231 will replace the file from the old package with that from the
5232 new. The file will no longer be listed as "owned" by the old
5233 package and will be taken over by the new package.
5234 Normally, <tt>Breaks</tt> should be used in conjunction
5235 with <tt>Replaces</tt>.<footnote>
5236 To see why <tt>Breaks</tt> is normally needed in addition
5237 to <tt>Replaces</tt>, consider the case of a file in the
5238 package <package>foo</package> being taken over by the
5239 package <package>foo-data</package>.
5240 <tt>Replaces</tt> will allow <package>foo-data</package> to
5241 be installed and take over that file. However,
5242 without <tt>Breaks</tt>, nothing
5243 requires <package>foo</package> to be upgraded to a newer
5244 version that knows it does not include that file and instead
5245 depends on <package>foo-data</package>. Nothing would
5246 prevent the new <package>foo-data</package> package from
5247 being installed and then removed, removing the file that it
5248 took over from <package>foo</package>. After that
5249 operation, the package manager would think the system was in
5250 a consistent state, but the <package>foo</package> package
5251 would be missing one of its files.
5256 For example, if a package <package>foo</package> is split
5257 into <package>foo</package> and <package>foo-data</package>
5258 starting at version 1.2-3, <package>foo-data</package> would
5260 <example compact="compact">
5261 Replaces: foo (<< 1.2-3)
5262 Breaks: foo (<< 1.2-3)
5264 in its control file. The new version of the
5265 package <package>foo</package> would normally have the field
5266 <example compact="compact">
5267 Depends: foo-data (>= 1.2-3)
5269 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5270 the files moved into <package>foo-data</package> are not
5271 required for normal operation).
5275 If a package is completely replaced in this way, so that
5276 <prgn>dpkg</prgn> does not know of any files it still
5277 contains, it is considered to have "disappeared". It will
5278 be marked as not wanted on the system (selected for
5279 removal) and not installed. Any <tt>conffile</tt>s
5280 details noted for the package will be ignored, as they
5281 will have been taken over by the overwriting package. The
5282 package's <prgn>postrm</prgn> script will be run with a
5283 special argument to allow the package to do any final
5284 cleanup required. See <ref id="mscriptsinstact">.
5286 Replaces is a one way relationship. You have to install
5287 the replacing package after the replaced package.
5292 For this usage of <tt>Replaces</tt>, virtual packages (see
5293 <ref id="virtual">) are not considered when looking at a
5294 <tt>Replaces</tt> field. The packages declared as being
5295 replaced must be mentioned by their real names.
5299 This usage of <tt>Replaces</tt> only takes effect when both
5300 packages are at least partially on the system at once. It is
5301 not relevant if the packages conflict unless the conflict has
5306 <sect1><heading>Replacing whole packages, forcing their
5310 Second, <tt>Replaces</tt> allows the packaging system to
5311 resolve which package should be removed when there is a
5312 conflict (see <ref id="conflicts">). This usage only takes
5313 effect when the two packages <em>do</em> conflict, so that the
5314 two usages of this field do not interfere with each other.
5318 In this situation, the package declared as being replaced
5319 can be a virtual package, so for example, all mail
5320 transport agents (MTAs) would have the following fields in
5321 their control files:
5322 <example compact="compact">
5323 Provides: mail-transport-agent
5324 Conflicts: mail-transport-agent
5325 Replaces: mail-transport-agent
5327 ensuring that only one MTA can be unpacked at any one
5328 time. See <ref id="virtual"> for more information about this
5333 <sect id="sourcebinarydeps">
5334 <heading>Relationships between source and binary packages -
5335 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5336 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5340 Source packages that require certain binary packages to be
5341 installed or absent at the time of building the package
5342 can declare relationships to those binary packages.
5346 This is done using the <tt>Build-Depends</tt>,
5347 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5348 <tt>Build-Conflicts-Indep</tt> control fields.
5352 Build-dependencies on "build-essential" binary packages can be
5353 omitted. Please see <ref id="pkg-relations"> for more information.
5357 The dependencies and conflicts they define must be satisfied
5358 (as defined earlier for binary packages) in order to invoke
5359 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5361 There is no Build-Depends-Arch; this role is essentially
5362 met with Build-Depends. Anyone building the
5363 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5364 assumed to be building the whole package, and therefore
5365 installation of all build dependencies is required.
5368 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5369 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5370 not yet know how to check for its existence, and
5371 <tt>binary-arch</tt>. The purpose of the original split
5372 between <tt>Build-Depends</tt> and
5373 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5374 wouldn't need to install extra packages needed only for the
5375 binary-indep targets. But without a build-arch/build-indep
5376 split, this didn't work, since most of the work is done in
5377 the build target, not in the binary target.
5381 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5382 <tt>binary-arch</tt></tag>
5384 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5385 fields must be satisfied when these targets are invoked.
5387 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5388 and <tt>binary-indep</tt></tag>
5390 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5391 <tt>Build-Depends-Indep</tt>, and
5392 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5393 these targets are invoked.
5401 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5404 Packages containing shared libraries must be constructed with
5405 a little care to make sure that the shared library is always
5406 available. This is especially important for packages whose
5407 shared libraries are vitally important, such as the C library
5408 (currently <tt>libc6</tt>).
5412 This section deals only with public shared libraries: shared
5413 libraries that are placed in directories searched by the dynamic
5414 linker by default or which are intended to be linked against
5415 normally and possibly used by other, independent packages. Shared
5416 libraries that are internal to a particular package or that are
5417 only loaded as dynamic modules are not covered by this section and
5418 are not subject to its requirements.
5422 A shared library is identified by the <tt>SONAME</tt> attribute
5423 stored in its dynamic section. When a binary is linked against a
5424 shared library, the <tt>SONAME</tt> of the shared library is
5425 recorded in the binary's <tt>NEEDED</tt> section so that the
5426 dynamic linker knows that library must be loaded at runtime. The
5427 shared library file's full name (which usually contains additional
5428 version information not needed in the <tt>SONAME</tt>) is
5429 therefore normally not referenced directly. Instead, the shared
5430 library is loaded by its <tt>SONAME</tt>, which exists on the file
5431 system as a symlink pointing to the full name of the shared
5432 library. This symlink must be provided by the
5433 package. <ref id="sharedlibs-runtime"> describes how to do this.
5435 This is a convention of shared library versioning, but not a
5436 requirement. Some libraries use the <tt>SONAME</tt> as the full
5437 library file name instead and therefore do not need a symlink.
5438 Most, however, encode additional information about
5439 backwards-compatible revisions as a minor version number in the
5440 file name. The <tt>SONAME</tt> itself only changes when
5441 binaries linked with the earlier version of the shared library
5442 may no longer work, but the filename may change with each
5443 release of the library. See <ref id="sharedlibs-runtime"> for
5449 When linking a binary or another shared library against a shared
5450 library, the <tt>SONAME</tt> for that shared library is not yet
5451 known. Instead, the shared library is found by looking for a file
5452 matching the library name with <tt>.so</tt> appended. This file
5453 exists on the file system as a symlink pointing to the shared
5458 Shared libraries are normally split into several binary packages.
5459 The <tt>SONAME</tt> symlink is installed by the runtime shared
5460 library package, and the bare <tt>.so</tt> symlink is installed in
5461 the development package since it's only used when linking binaries
5462 or shared libraries. However, there are some exceptions for
5463 unusual shared libraries or for shared libraries that are also
5464 loaded as dynamic modules by other programs.
5468 This section is primarily concerned with how the separation of
5469 shared libraries into multiple packages should be done and how
5470 dependencies on and between shared library binary packages are
5471 managed in Debian. <ref id="libraries"> should be read in
5472 conjunction with this section and contains additional rules for
5473 the files contained in the shared library packages.
5476 <sect id="sharedlibs-runtime">
5477 <heading>Run-time shared libraries</heading>
5480 The run-time shared library must be placed in a package
5481 whose name changes whenever the <tt>SONAME</tt> of the shared
5482 library changes. This allows several versions of the shared
5483 library to be installed at the same time, allowing installation
5484 of the new version of the shared library without immediately
5485 breaking binaries that depend on the old version. Normally, the
5486 run-time shared library and its <tt>SONAME</tt> symlink should
5487 be placed in a package named
5488 <package><var>libraryname</var><var>soversion</var></package>,
5489 where <var>soversion</var> is the version number in
5490 the <tt>SONAME</tt> of the shared library.
5491 See <ref id="shlibs"> for detailed information on how to
5492 determine this version. Alternatively, if it would be confusing
5493 to directly append <var>soversion</var>
5494 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5495 itself ends in a number), you should use
5496 <package><var>libraryname</var>-<var>soversion</var></package>
5501 If you have several shared libraries built from the same source
5502 tree, you may lump them all together into a single shared
5503 library package provided that all of their <tt>SONAME</tt>s will
5504 always change together. Be aware that this is not normally the
5505 case, and if the <tt>SONAME</tt>s do not change together,
5506 upgrading such a merged shared library package will be
5507 unnecessarily difficult because of file conflicts with the old
5508 version of the package. When in doubt, always split shared
5509 library packages so that each binary package installs a single
5514 Every time the shared library ABI changes in a way that may
5515 break binaries linked against older versions of the shared
5516 library, the <tt>SONAME</tt> of the library and the
5517 corresponding name for the binary package containing the runtime
5518 shared library should change. Normally, this means
5519 the <tt>SONAME</tt> should change any time an interface is
5520 removed from the shared library or the signature of an interface
5521 (the number of parameters or the types of parameters that it
5522 takes, for example) is changed. This practice is vital to
5523 allowing clean upgrades from older versions of the package and
5524 clean transitions between the old ABI and new ABI without having
5525 to upgrade every affected package simultaneously.
5529 The <tt>SONAME</tt> and binary package name need not, and indeed
5530 normally should not, change if new interfaces are added but none
5531 are removed or changed, since this will not break binaries
5532 linked against the old shared library. Correct versioning of
5533 dependencies on the newer shared library by binaries that use
5534 the new interfaces is handled via
5535 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5536 system</qref> or via symbols files (see
5537 <manref name="deb-symbols" section="5">).
5541 The package should install the shared libraries under
5542 their normal names. For example, the <package>libgdbm3</package>
5543 package should install <file>libgdbm.so.3.0.0</file> as
5544 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5545 renamed or re-linked by any <prgn>prerm</prgn> or
5546 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5547 of renaming things safely without affecting running programs,
5548 and attempts to interfere with this are likely to lead to
5553 Shared libraries should not be installed executable, since
5554 the dynamic linker does not require this and trying to
5555 execute a shared library usually results in a core dump.
5559 The run-time library package should include the symbolic link for
5560 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5561 the shared libraries. For example,
5562 the <package>libgdbm3</package> package should include a symbolic
5563 link from <file>/usr/lib/libgdbm.so.3</file> to
5564 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5565 linker (for example <prgn>ld.so</prgn> or
5566 <prgn>ld-linux.so.*</prgn>) can find the library between the
5567 time that <prgn>dpkg</prgn> installs it and the time that
5568 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5570 The package management system requires the library to be
5571 placed before the symbolic link pointing to it in the
5572 <file>.deb</file> file. This is so that when
5573 <prgn>dpkg</prgn> comes to install the symlink
5574 (overwriting the previous symlink pointing at an older
5575 version of the library), the new shared library is already
5576 in place. In the past, this was achieved by creating the
5577 library in the temporary packaging directory before
5578 creating the symlink. Unfortunately, this was not always
5579 effective, since the building of the tar file in the
5580 <file>.deb</file> depended on the behavior of the underlying
5581 file system. Some file systems (such as reiserfs) reorder
5582 the files so that the order of creation is forgotten.
5583 Since version 1.7.0, <prgn>dpkg</prgn>
5584 reorders the files itself as necessary when building a
5585 package. Thus it is no longer important to concern
5586 oneself with the order of file creation.
5590 <sect1 id="ldconfig">
5591 <heading><tt>ldconfig</tt></heading>
5594 Any package installing shared libraries in one of the default
5595 library directories of the dynamic linker (which are currently
5596 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5597 listed in <file>/etc/ld.so.conf</file><footnote>
5598 These are currently <file>/usr/local/lib</file> plus
5599 directories under <file>/lib</file> and <file>/usr/lib</file>
5600 matching the multiarch triplet for the system architecture.
5602 must use <prgn>ldconfig</prgn> to update the shared library
5607 The package maintainer scripts must only call
5608 <prgn>ldconfig</prgn> under these circumstances:
5609 <list compact="compact">
5610 <item>When the <prgn>postinst</prgn> script is run with a
5611 first argument of <tt>configure</tt>, the script must call
5612 <prgn>ldconfig</prgn>, and may optionally invoke
5613 <prgn>ldconfig</prgn> at other times.
5615 <item>When the <prgn>postrm</prgn> script is run with a
5616 first argument of <tt>remove</tt>, the script should call
5617 <prgn>ldconfig</prgn>.
5622 During install or upgrade, the preinst is called before
5623 the new files are unpacked, so calling "ldconfig" is
5624 pointless. The preinst of an existing package can also be
5625 called if an upgrade fails. However, this happens during
5626 the critical time when a shared libs may exist on-disk
5627 under a temporary name. Thus, it is dangerous and
5628 forbidden by current policy to call "ldconfig" at this
5633 When a package is installed or upgraded, "postinst
5634 configure" runs after the new files are safely on-disk.
5635 Since it is perfectly safe to invoke ldconfig
5636 unconditionally in a postinst, it is OK for a package to
5637 simply put ldconfig in its postinst without checking the
5638 argument. The postinst can also be called to recover from
5639 a failed upgrade. This happens before any new files are
5640 unpacked, so there is no reason to call "ldconfig" at this
5645 For a package that is being removed, prerm is
5646 called with all the files intact, so calling ldconfig is
5647 useless. The other calls to "prerm" happen in the case of
5648 upgrade at a time when all the files of the old package
5649 are on-disk, so again calling "ldconfig" is pointless.
5653 postrm, on the other hand, is called with the "remove"
5654 argument just after the files are removed, so this is
5655 the proper time to call "ldconfig" to notify the system
5656 of the fact that the shared libraries from the package
5657 are removed. The postrm can be called at several other
5658 times. At the time of "postrm purge", "postrm
5659 abort-install", or "postrm abort-upgrade", calling
5660 "ldconfig" is useless because the shared lib files are
5661 not on-disk. However, when "postrm" is invoked with
5662 arguments "upgrade", "failed-upgrade", or "disappear", a
5663 shared lib may exist on-disk under a temporary filename.
5671 <sect id="sharedlibs-support-files">
5672 <heading>Shared library support files</heading>
5675 If your package contains files whose names do not change with
5676 each change in the library shared object version, you must not
5677 put them in the shared library package. Otherwise, several
5678 versions of the shared library cannot be installed at the same
5679 time without filename clashes, making upgrades and transitions
5680 unnecessarily difficult.
5684 It is recommended that supporting files and run-time support
5685 programs that do not need to be invoked manually by users, but
5686 are nevertheless required for the package to function, be placed
5687 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5688 preferably under <file>/usr/lib/</file><var>package-name</var>.
5689 If the program or file is architecture independent, the
5690 recommendation is for it to be placed in a subdirectory of
5691 <file>/usr/share</file> instead, preferably under
5692 <file>/usr/share/</file><var>package-name</var>. Following the
5693 <var>package-name</var> naming convention ensures that the file
5694 names change when the shared object version changes.
5698 Run-time support programs that use the shared library but are
5699 not required for the library to function or files used by the
5700 shared library that can be used by any version of the shared
5701 library package should instead be put in a separate package.
5702 This package might typically be named
5703 <package><var>libraryname</var>-tools</package>; note the
5704 absence of the <var>soversion</var> in the package name.
5708 Files and support programs only useful when compiling software
5709 against the library should be included in the development
5710 package for the library.<footnote>
5711 For example, a <file><var>package-name</var>-config</file>
5712 script or <package>pkg-config</package> configuration files.
5717 <sect id="sharedlibs-static">
5718 <heading>Static libraries</heading>
5721 The static library (<file><var>libraryname.a</var></file>)
5722 is usually provided in addition to the shared version.
5723 It is placed into the development package (see below).
5727 In some cases, it is acceptable for a library to be
5728 available in static form only; these cases include:
5730 <item>libraries for languages whose shared library support
5731 is immature or unstable</item>
5732 <item>libraries whose interfaces are in flux or under
5733 development (commonly the case when the library's
5734 major version number is zero, or where the ABI breaks
5735 across patchlevels)</item>
5736 <item>libraries which are explicitly intended to be
5737 available only in static form by their upstream
5742 <sect id="sharedlibs-dev">
5743 <heading>Development files</heading>
5746 If there are development files associated with a shared library,
5747 the source package needs to generate a binary development package
5748 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5749 or if you prefer only to support one development version at a
5750 time, <package><var>libraryname</var>-dev</package>. Installing
5751 the development package must result in installation of all the
5752 development files necessary for compiling programs against that
5753 shared library.<footnote>
5754 This wording allows the development files to be split into
5755 several packages, such as a separate architecture-independent
5756 <package><var>libraryname</var>-headers</package>, provided that
5757 the development package depends on all the required additional
5763 In case several development versions of a library exist, you may
5764 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5765 <ref id="conflicts">) to ensure that the user only installs one
5766 development version at a time (as different development versions are
5767 likely to have the same header files in them, which would cause a
5768 filename clash if both were unpacked).
5772 The development package should contain a symlink for the associated
5773 shared library without a version number. For example, the
5774 <package>libgdbm-dev</package> package should include a symlink
5775 from <file>/usr/lib/libgdbm.so</file> to
5776 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5777 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5778 <file>libgdbm.so</file> when compiling dynamically.
5782 If the package provides Ada Library Information
5783 (<file>*.ali</file>) files for use with GNAT, these files must be
5784 installed read-only (mode 0444) so that GNAT will not attempt to
5785 recompile them. This overrides the normal file mode requirements
5786 given in <ref id="permissions-owners">.
5790 <sect id="sharedlibs-intradeps">
5791 <heading>Dependencies between the packages of the same library</heading>
5794 Typically the development version should have an exact
5795 version dependency on the runtime library, to make sure that
5796 compilation and linking happens correctly. The
5797 <tt>${binary:Version}</tt> substitution variable can be
5798 useful for this purpose.
5800 Previously, <tt>${Source-Version}</tt> was used, but its name
5801 was confusing and it has been deprecated since dpkg 1.13.19.
5806 <sect id="sharedlibs-shlibdeps">
5807 <heading>Dependencies between the library and other packages -
5808 the <tt>shlibs</tt> system</heading>
5811 If a package contains a binary or library which links to a
5812 shared library, we must ensure that when the package is
5813 installed on the system, all of the libraries needed are
5814 also installed. This requirement led to the creation of the
5815 <tt>shlibs</tt> system, which is very simple in its design:
5816 any package which <em>provides</em> a shared library also
5817 provides information on the package dependencies required to
5818 ensure the presence of this library, and any package which
5819 <em>uses</em> a shared library uses this information to
5820 determine the dependencies it requires. The files which
5821 contain the mapping from shared libraries to the necessary
5822 dependency information are called <file>shlibs</file> files.
5826 When a package is built which contains any shared libraries, it
5827 must provide a <file>shlibs</file> file for other packages to
5828 use. When a package is built which contains any shared
5829 libraries or compiled binaries, it must run
5830 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5831 on these to determine the libraries used and hence the
5832 dependencies needed by this package.<footnote>
5834 <prgn>dpkg-shlibdeps</prgn> will use a program
5835 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5836 the libraries directly needed by the binaries or shared
5837 libraries in the package.
5841 We say that a binary <tt>foo</tt> <em>directly</em> uses
5842 a library <tt>libbar</tt> if it is explicitly linked
5843 with that library (that is, the library is listed in the ELF
5844 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5845 to the link line when the binary is created). Other
5846 libraries that are needed by <tt>libbar</tt> are linked
5847 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5848 linker will load them automatically when it loads
5849 <tt>libbar</tt>. A package should depend on the libraries
5850 it directly uses, but not the libraries it indirectly uses.
5851 The dependencies for those libraries will automatically pull
5852 in the other libraries.
5856 A good example of where this helps is the following. We
5857 could update <tt>libimlib</tt> with a new version that
5858 supports a new graphics format called dgf (but retaining the
5859 same major version number) and depends on <tt>libdgf</tt>.
5860 If we used <prgn>ldd</prgn> to add dependencies for every
5861 library directly or indirectly linked with a binary, every
5862 package that uses <tt>libimlib</tt> would need to be
5863 recompiled so it would also depend on <tt>libdgf</tt> or it
5864 wouldn't run due to missing symbols. Since dependencies are
5865 only added based on ELF <tt>NEEDED</tt> attribute, packages
5866 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5867 having the dependency on <tt>libdgf</tt> and so they would
5868 not need rebuilding.
5874 In the following sections, we will first describe where the
5875 various <tt>shlibs</tt> files are to be found, then how to
5876 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5877 file format and how to create them if your package contains a
5882 <heading>The <tt>shlibs</tt> files present on the system</heading>
5885 There are several places where <tt>shlibs</tt> files are
5886 found. The following list gives them in the order in which
5888 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5889 (The first one which gives the required information is used.)
5895 <p><file>debian/shlibs.local</file></p>
5898 This lists overrides for this package. This file should
5899 normally not be used, but may be needed temporarily in
5900 unusual situations to work around bugs in other packages,
5901 or in unusual cases where the normally declared dependency
5902 information in the installed <file>shlibs</file> file for
5903 a library cannot be used. This file overrides information
5904 obtained from any other source.
5909 <p><file>/etc/dpkg/shlibs.override</file></p>
5912 This lists global overrides. This list is normally
5913 empty. It is maintained by the local system
5919 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5922 When packages are being built,
5923 any <file>debian/shlibs</file> files are copied into the
5924 control information file area of the temporary build
5925 directory and given the name <file>shlibs</file>. These
5926 files give details of any shared libraries included in the
5927 same package.<footnote>
5928 An example may help here. Let us say that the source
5929 package <tt>foo</tt> generates two binary
5930 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5931 When building the binary packages, the two packages are
5932 created in the directories <file>debian/libfoo2</file>
5933 and <file>debian/foo-runtime</file> respectively.
5934 (<file>debian/tmp</file> could be used instead of one of
5935 these.) Since <tt>libfoo2</tt> provides the
5936 <tt>libfoo</tt> shared library, it will require a
5937 <tt>shlibs</tt> file, which will be installed in
5938 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5939 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5940 When <prgn>dpkg-shlibdeps</prgn> is run on the
5941 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5943 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5944 determine whether <tt>foo-prog</tt>'s library
5945 dependencies are satisfied by any of the libraries
5946 provided by <tt>libfoo2</tt>. For this reason,
5947 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5948 the individual binary packages' <tt>shlibs</tt> files
5949 have been installed into the build directory.
5955 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5958 These are the <file>shlibs</file> files corresponding to
5959 all of the packages installed on the system, and are
5960 maintained by the relevant package maintainers.
5965 <p><file>/etc/dpkg/shlibs.default</file></p>
5968 This file lists any shared libraries whose packages
5969 have failed to provide correct <file>shlibs</file> files.
5970 It was used when the <file>shlibs</file> setup was first
5971 introduced, but it is now normally empty. It is
5972 maintained by the <tt>dpkg</tt> maintainer.
5980 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5981 <file>shlibs</file> files</heading>
5985 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5986 into your <file>debian/rules</file> file. If your package
5987 contains only compiled binaries and libraries (but no scripts),
5988 you can use a command such as:
5989 <example compact="compact">
5990 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5991 debian/tmp/usr/lib/*
5993 Otherwise, you will need to explicitly list the compiled
5994 binaries and libraries.<footnote>
5995 If you are using <tt>debhelper</tt>, the
5996 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5997 It will also correctly handle multi-binary packages.
6002 This command puts the dependency information into the
6003 <file>debian/substvars</file> file, which is then used by
6004 <prgn>dpkg-gencontrol</prgn>. You will need to place a
6005 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
6006 field in the control file for this to work.
6010 If you have multiple binary packages, you will need to call
6011 <prgn>dpkg-shlibdeps</prgn> on each one which contains
6012 compiled libraries or binaries. In such a case, you will
6013 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
6014 utilities to specify a different <file>substvars</file> file.
6018 If you are creating a udeb for use in the Debian Installer,
6019 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6020 should use the dependency line of type <tt>udeb</tt> by
6021 adding the <tt>-tudeb</tt> option<footnote>
6022 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6023 will automatically add this option if it knows it is
6025 </footnote>. If there is no dependency line of
6026 type <tt>udeb</tt> in the <file>shlibs</file>
6027 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
6032 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
6033 <ref id="pkg-dpkg-shlibdeps"> and
6034 <manref name="dpkg-shlibdeps" section="1">.
6039 <heading>The <file>shlibs</file> File Format</heading>
6042 Each <file>shlibs</file> file has the same format. Lines
6043 beginning with <tt>#</tt> are considered to be comments and
6044 are ignored. Each line is of the form:
6045 <example compact="compact">
6046 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6051 We will explain this by reference to the example of the
6052 <tt>zlib1g</tt> package, which (at the time of writing)
6053 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
6057 <var>type</var> is an optional element that indicates the type
6058 of package for which the line is valid. The only type currently
6059 in use is <tt>udeb</tt>. The colon and space after the type are
6064 <var>library-name</var> is the name of the shared library,
6065 in this case <tt>libz</tt>. (This must match the name part
6066 of the soname, see below.)
6070 <var>soname-version</var> is the version part of the soname of
6071 the library. The soname is the thing that must exactly match
6072 for the library to be recognized by the dynamic linker, and is
6074 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
6075 example, <tt>libz.so.1</tt>.<footnote>
6076 This can be determined using the command
6077 <example compact="compact">
6078 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
6081 The version part is the part which comes after
6082 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
6083 instead be of the form
6084 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
6085 as <tt>libdb-4.8.so</tt>, in which case the name would
6086 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
6090 <var>dependencies</var> has the same syntax as a dependency
6091 field in a binary package control file. It should give
6092 details of which packages are required to satisfy a binary
6093 built against the version of the library contained in the
6094 package. See <ref id="depsyntax"> for details.
6098 In our example, if the first version of the <tt>zlib1g</tt>
6099 package which contained a minor number of at least
6100 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
6101 <tt>shlibs</tt> entry for this library could say:
6102 <example compact="compact">
6103 libz 1 zlib1g (>= 1:1.1.3)
6105 The version-specific dependency is to avoid warnings from
6106 the dynamic linker about using older shared libraries with
6111 As zlib1g also provides a udeb containing the shared library,
6112 there would also be a second line:
6113 <example compact="compact">
6114 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
6120 <heading>Providing a <file>shlibs</file> file</heading>
6123 If your package provides a shared library, you need to create
6124 a <file>shlibs</file> file following the format described above.
6125 It is usual to call this file <file>debian/shlibs</file> (but if
6126 you have multiple binary packages, you might want to call it
6127 <file>debian/shlibs.<var>package</var></file> instead). Then
6128 let <file>debian/rules</file> install it in the control
6129 information file area:
6130 <example compact="compact">
6131 install -m644 debian/shlibs debian/tmp/DEBIAN
6133 or, in the case of a multi-binary package:
6134 <example compact="compact">
6135 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
6137 An alternative way of doing this is to create the
6138 <file>shlibs</file> file in the control information file area
6139 directly from <file>debian/rules</file> without using
6140 a <file>debian/shlibs</file> file at all,<footnote>
6141 This is what <prgn>dh_makeshlibs</prgn> in
6142 the <package>debhelper</package> suite does. If your package
6143 also has a udeb that provides a shared
6144 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6145 the <tt>udeb:</tt> lines if you specify the name of the udeb
6146 with the <tt>--add-udeb</tt> option.
6148 since the <file>debian/shlibs</file> file itself is ignored by
6149 <prgn>dpkg-shlibdeps</prgn>.
6153 As <prgn>dpkg-shlibdeps</prgn> reads the
6154 <file>DEBIAN/shlibs</file> files in all of the binary packages
6155 being built from this source package, all of the
6156 <file>DEBIAN/shlibs</file> files should be installed before
6157 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6165 <chapt id="opersys"><heading>The Operating System</heading>
6168 <heading>File system hierarchy</heading>
6172 <heading>File System Structure</heading>
6175 The location of all files and directories must comply with the
6176 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6177 exceptions noted below, and except where doing so would
6178 violate other terms of Debian Policy. The following
6179 exceptions to the FHS apply:
6184 The optional rules related to user specific
6185 configuration files for applications are stored in
6186 the user's home directory are relaxed. It is
6187 recommended that such files start with the
6188 '<tt>.</tt>' character (a "dot file"), and if an
6189 application needs to create more than one dot file
6190 then the preferred placement is in a subdirectory
6191 with a name starting with a '.' character, (a "dot
6192 directory"). In this case it is recommended the
6193 configuration files not start with the '.'
6199 The requirement for amd64 to use <file>/lib64</file>
6200 for 64 bit binaries is removed.
6205 The requirement for object files, internal binaries, and
6206 libraries, including <file>libc.so.*</file>, to be located
6207 directly under <file>/lib{,32}</file> and
6208 <file>/usr/lib{,32}</file> is amended, permitting files
6209 to instead be installed to
6210 <file>/lib/<var>triplet</var></file> and
6211 <file>/usr/lib/<var>triplet</var></file>, where
6212 <tt><var>triplet</var></tt> is the value returned by
6213 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6214 architecture of the package. Packages may <em>not</em>
6215 install files to any <var>triplet</var> path other
6216 than the one matching the architecture of that package;
6217 for instance, an <tt>Architecture: amd64</tt> package
6218 containing 32-bit x86 libraries may not install these
6219 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6221 This is necessary in order to reserve the directories for
6222 use in cross-installation of library packages from other
6223 architectures, as part of the planned deployment of
6228 Applications may also use a single subdirectory under
6229 <file>/usr/lib/<var>triplet</var></file>.
6232 The execution time linker/loader, ld*, must still be made
6233 available in the existing location under /lib or /lib64
6234 since this is part of the ELF ABI for the architecture.
6239 The requirement that
6240 <file>/usr/local/share/man</file> be "synonymous"
6241 with <file>/usr/local/man</file> is relaxed to a
6246 The requirement that windowmanagers with a single
6247 configuration file call it <file>system.*wmrc</file>
6248 is removed, as is the restriction that the window
6249 manager subdirectory be named identically to the
6250 window manager name itself.
6255 The requirement that boot manager configuration
6256 files live in <file>/etc</file>, or at least are
6257 symlinked there, is relaxed to a recommendation.
6262 The additional directory <file>/run</file> in the root
6263 file system is allowed. <file>/run</file>
6264 replaces <file>/var/run</file>, and the
6265 subdirectory <file>/run/lock</file>
6266 replaces <file>/var/lock</file>, with
6267 the <file>/var</file> directories replaced by symlinks
6268 for backwards compatibility. <file>/run</file>
6269 and <file>/run/lock</file> must follow all of the
6270 requirements in the FHS for <file>/var/run</file>
6271 and <file>/var/lock</file>, respectively, such as file
6272 naming conventions, file format requirements, or the
6273 requirement that files be cleared during the boot
6274 process. Files and directories residing
6275 in <file>/run</file> should be stored on a temporary
6281 The following directories in the root filesystem are
6282 additionally allowed: <file>/sys</file> and
6283 <file>/selinux</file>. <footnote>These directories
6284 are used as mount points to mount virtual filesystems
6285 to get access to kernel information.</footnote>
6290 On GNU/Hurd systems, the following additional
6291 directories are allowed in the root
6292 filesystem: <file>/hurd</file>
6293 and <file>/servers</file>.<footnote>
6294 These directories are used to store translators and as
6295 a set of standard names for mount points,
6304 The version of this document referred here can be
6305 found in the <tt>debian-policy</tt> package or on <url
6306 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6307 name="FHS (Debian copy)"> alongside this manual (or, if
6308 you have the <package>debian-policy</package> installed,
6310 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6311 (local copy)">). The
6312 latest version, which may be a more recent version, may
6314 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6315 Specific questions about following the standard may be
6316 asked on the <tt>debian-devel</tt> mailing list, or
6317 referred to the FHS mailing list (see the
6318 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6324 <heading>Site-specific programs</heading>
6327 As mandated by the FHS, packages must not place any
6328 files in <file>/usr/local</file>, either by putting them in
6329 the file system archive to be unpacked by <prgn>dpkg</prgn>
6330 or by manipulating them in their maintainer scripts.
6334 However, the package may create empty directories below
6335 <file>/usr/local</file> so that the system administrator knows
6336 where to place site-specific files. These are not
6337 directories <em>in</em> <file>/usr/local</file>, but are
6338 children of directories in <file>/usr/local</file>. These
6339 directories (<file>/usr/local/*/dir/</file>)
6340 should be removed on package removal if they are
6345 Note that this applies only to
6346 directories <em>below</em> <file>/usr/local</file>,
6347 not <em>in</em> <file>/usr/local</file>. Packages must
6348 not create sub-directories in the
6349 directory <file>/usr/local</file> itself, except those
6350 listed in FHS, section 4.5. However, you may create
6351 directories below them as you wish. You must not remove
6352 any of the directories listed in 4.5, even if you created
6357 Since <file>/usr/local</file> can be mounted read-only from a
6358 remote server, these directories must be created and
6359 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6360 maintainer scripts and not be included in the
6361 <file>.deb</file> archive. These scripts must not fail if
6362 either of these operations fail.
6366 For example, the <tt>emacsen-common</tt> package could
6367 contain something like
6368 <example compact="compact">
6369 if [ ! -e /usr/local/share/emacs ]; then
6370 if mkdir /usr/local/share/emacs 2>/dev/null; then
6371 if chown root:staff /usr/local/share/emacs; then
6372 chmod 2775 /usr/local/share/emacs || true
6377 in its <prgn>postinst</prgn> script, and
6378 <example compact="compact">
6379 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6380 rmdir /usr/local/share/emacs 2>/dev/null || true
6382 in the <prgn>prerm</prgn> script. (Note that this form is
6383 used to ensure that if the script is interrupted, the
6384 directory <file>/usr/local/share/emacs</file> will still be
6389 If you do create a directory in <file>/usr/local</file> for
6390 local additions to a package, you should ensure that
6391 settings in <file>/usr/local</file> take precedence over the
6392 equivalents in <file>/usr</file>.
6396 However, because <file>/usr/local</file> and its contents are
6397 for exclusive use of the local administrator, a package
6398 must not rely on the presence or absence of files or
6399 directories in <file>/usr/local</file> for normal operation.
6403 The <file>/usr/local</file> directory itself and all the
6404 subdirectories created by the package should (by default) have
6405 permissions 2775 (group-writable and set-group-id) and be
6406 owned by <tt>root:staff</tt>.
6411 <heading>The system-wide mail directory</heading>
6413 The system-wide mail directory
6414 is <file>/var/mail</file>. This directory is part of the
6415 base system and should not be owned by any particular mail
6416 agents. The use of the old
6417 location <file>/var/spool/mail</file> is deprecated, even
6418 though the spool may still be physically located there.
6422 <sect1 id="fhs-run">
6423 <heading><file>/run</file> and <file>/run/lock</file></heading>
6426 The directory <file>/run</file> is cleared at boot, normally
6427 by being a mount point for a temporary file system. Packages
6428 therefore must not assume that any files or directories
6429 under <file>/run</file> other than <file>/run/lock</file>
6430 exist unless the package has arranged to create those files or
6431 directories since the last reboot. Normally, this is done by
6432 the package via an init script. See <ref id="writing-init">
6433 for more information.
6437 Packages must not include files or directories
6438 under <file>/run</file>, or under the
6439 older <file>/var/run</file> and <file>/var/lock</file> paths.
6440 The latter paths will normally be symlinks or other
6441 redirections to <file>/run</file> for backwards compatibility.
6447 <heading>Users and groups</heading>
6450 <heading>Introduction</heading>
6452 The Debian system can be configured to use either plain or
6457 Some user ids (UIDs) and group ids (GIDs) are reserved
6458 globally for use by certain packages. Because some
6459 packages need to include files which are owned by these
6460 users or groups, or need the ids compiled into binaries,
6461 these ids must be used on any Debian system only for the
6462 purpose for which they are allocated. This is a serious
6463 restriction, and we should avoid getting in the way of
6464 local administration policies. In particular, many sites
6465 allocate users and/or local system groups starting at 100.
6469 Apart from this we should have dynamically allocated ids,
6470 which should by default be arranged in some sensible
6471 order, but the behavior should be configurable.
6475 Packages other than <tt>base-passwd</tt> must not modify
6476 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6477 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6482 <heading>UID and GID classes</heading>
6484 The UID and GID numbers are divided into classes as
6490 Globally allocated by the Debian project, the same
6491 on every Debian system. These ids will appear in
6492 the <file>passwd</file> and <file>group</file> files of all
6493 Debian systems, new ids in this range being added
6494 automatically as the <tt>base-passwd</tt> package is
6499 Packages which need a single statically allocated
6500 uid or gid should use one of these; their
6501 maintainers should ask the <tt>base-passwd</tt>
6509 Dynamically allocated system users and groups.
6510 Packages which need a user or group, but can have
6511 this user or group allocated dynamically and
6512 differently on each system, should use <tt>adduser
6513 --system</tt> to create the group and/or user.
6514 <prgn>adduser</prgn> will check for the existence of
6515 the user or group, and if necessary choose an unused
6516 id based on the ranges specified in
6517 <file>adduser.conf</file>.
6521 <tag>1000-59999:</tag>
6524 Dynamically allocated user accounts. By default
6525 <prgn>adduser</prgn> will choose UIDs and GIDs for
6526 user accounts in this range, though
6527 <file>adduser.conf</file> may be used to modify this
6532 <tag>60000-64999:</tag>
6535 Globally allocated by the Debian project, but only
6536 created on demand. The ids are allocated centrally
6537 and statically, but the actual accounts are only
6538 created on users' systems on demand.
6542 These ids are for packages which are obscure or
6543 which require many statically-allocated ids. These
6544 packages should check for and create the accounts in
6545 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6546 <prgn>adduser</prgn> if it has this facility) if
6547 necessary. Packages which are likely to require
6548 further allocations should have a "hole" left after
6549 them in the allocation, to give them room to
6554 <tag>65000-65533:</tag>
6562 User <tt>nobody</tt>. The corresponding gid refers
6563 to the group <tt>nogroup</tt>.
6570 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6571 not</em> be used, because it is the error return
6580 <sect id="sysvinit">
6581 <heading>System run levels and <file>init.d</file> scripts</heading>
6583 <sect1 id="/etc/init.d">
6584 <heading>Introduction</heading>
6587 The <file>/etc/init.d</file> directory contains the scripts
6588 executed by <prgn>init</prgn> at boot time and when the
6589 init state (or "runlevel") is changed (see <manref
6590 name="init" section="8">).
6594 There are at least two different, yet functionally
6595 equivalent, ways of handling these scripts. For the sake
6596 of simplicity, this document describes only the symbolic
6597 link method. However, it must not be assumed by maintainer
6598 scripts that this method is being used, and any automated
6599 manipulation of the various runlevel behaviors by
6600 maintainer scripts must be performed using
6601 <prgn>update-rc.d</prgn> as described below and not by
6602 manually installing or removing symlinks. For information
6603 on the implementation details of the other method,
6604 implemented in the <tt>file-rc</tt> package, please refer
6605 to the documentation of that package.
6609 These scripts are referenced by symbolic links in the
6610 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6611 runlevels, <prgn>init</prgn> looks in the directory
6612 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6613 execute, where <tt><var>n</var></tt> is the runlevel that
6614 is being changed to, or <tt>S</tt> for the boot-up
6619 The names of the links all have the form
6620 <file>S<var>mm</var><var>script</var></file> or
6621 <file>K<var>mm</var><var>script</var></file> where
6622 <var>mm</var> is a two-digit number and <var>script</var>
6623 is the name of the script (this should be the same as the
6624 name of the actual script in <file>/etc/init.d</file>).
6628 When <prgn>init</prgn> changes runlevel first the targets
6629 of the links whose names start with a <tt>K</tt> are
6630 executed, each with the single argument <tt>stop</tt>,
6631 followed by the scripts prefixed with an <tt>S</tt>, each
6632 with the single argument <tt>start</tt>. (The links are
6633 those in the <file>/etc/rc<var>n</var>.d</file> directory
6634 corresponding to the new runlevel.) The <tt>K</tt> links
6635 are responsible for killing services and the <tt>S</tt>
6636 link for starting services upon entering the runlevel.
6640 For example, if we are changing from runlevel 2 to
6641 runlevel 3, init will first execute all of the <tt>K</tt>
6642 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6643 all of the <tt>S</tt> prefixed scripts in that directory.
6644 The links starting with <tt>K</tt> will cause the
6645 referred-to file to be executed with an argument of
6646 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6651 The two-digit number <var>mm</var> is used to determine
6652 the order in which to run the scripts: low-numbered links
6653 have their scripts run first. For example, the
6654 <tt>K20</tt> scripts will be executed before the
6655 <tt>K30</tt> scripts. This is used when a certain service
6656 must be started before another. For example, the name
6657 server <prgn>bind</prgn> might need to be started before
6658 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6659 can set up its access lists. In this case, the script
6660 that starts <prgn>bind</prgn> would have a lower number
6661 than the script that starts <prgn>inn</prgn> so that it
6663 <example compact="compact">
6670 The two runlevels 0 (halt) and 6 (reboot) are slightly
6671 different. In these runlevels, the links with an
6672 <tt>S</tt> prefix are still called after those with a
6673 <tt>K</tt> prefix, but they too are called with the single
6674 argument <tt>stop</tt>.
6678 <sect1 id="writing-init">
6679 <heading>Writing the scripts</heading>
6682 Packages that include daemons for system services should
6683 place scripts in <file>/etc/init.d</file> to start or stop
6684 services at boot time or during a change of runlevel.
6685 These scripts should be named
6686 <file>/etc/init.d/<var>package</var></file>, and they should
6687 accept one argument, saying what to do:
6690 <tag><tt>start</tt></tag>
6691 <item>start the service,</item>
6693 <tag><tt>stop</tt></tag>
6694 <item>stop the service,</item>
6696 <tag><tt>restart</tt></tag>
6697 <item>stop and restart the service if it's already running,
6698 otherwise start the service</item>
6700 <tag><tt>reload</tt></tag>
6701 <item><p>cause the configuration of the service to be
6702 reloaded without actually stopping and restarting
6705 <tag><tt>force-reload</tt></tag>
6706 <item>cause the configuration to be reloaded if the
6707 service supports this, otherwise restart the
6711 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6712 <tt>force-reload</tt> options should be supported by all
6713 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6718 The <file>init.d</file> scripts must ensure that they will
6719 behave sensibly (i.e., returning success and not starting
6720 multiple copies of a service) if invoked with <tt>start</tt>
6721 when the service is already running, or with <tt>stop</tt>
6722 when it isn't, and that they don't kill unfortunately-named
6723 user processes. The best way to achieve this is usually to
6724 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6729 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6730 scripts. Writing correct <file>init.d</file> scripts requires
6731 accepting various error exit statuses when daemons are already
6732 running or already stopped without aborting
6733 the <file>init.d</file> script, and common <file>init.d</file>
6734 function libraries are not safe to call with <tt>set -e</tt>
6736 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6737 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6738 in effect and echoing status messages to the console fails,
6740 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6741 to not use <tt>set -e</tt> and instead check the result of
6742 each command separately.
6746 If a service reloads its configuration automatically (as
6747 in the case of <prgn>cron</prgn>, for example), the
6748 <tt>reload</tt> option of the <file>init.d</file> script
6749 should behave as if the configuration has been reloaded
6754 The <file>/etc/init.d</file> scripts must be treated as
6755 configuration files, either (if they are present in the
6756 package, that is, in the .deb file) by marking them as
6757 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6758 by managing them correctly in the maintainer scripts (see
6759 <ref id="config-files">). This is important since we want
6760 to give the local system administrator the chance to adapt
6761 the scripts to the local system, e.g., to disable a
6762 service without de-installing the package, or to specify
6763 some special command line options when starting a service,
6764 while making sure their changes aren't lost during the next
6769 These scripts should not fail obscurely when the
6770 configuration files remain but the package has been
6771 removed, as configuration files remain on the system after
6772 the package has been removed. Only when <prgn>dpkg</prgn>
6773 is executed with the <tt>--purge</tt> option will
6774 configuration files be removed. In particular, as the
6775 <file>/etc/init.d/<var>package</var></file> script itself is
6776 usually a <tt>conffile</tt>, it will remain on the system
6777 if the package is removed but not purged. Therefore, you
6778 should include a <tt>test</tt> statement at the top of the
6780 <example compact="compact">
6781 test -f <var>program-executed-later-in-script</var> || exit 0
6786 Often there are some variables in the <file>init.d</file>
6787 scripts whose values control the behavior of the scripts,
6788 and which a system administrator is likely to want to
6789 change. As the scripts themselves are frequently
6790 <tt>conffile</tt>s, modifying them requires that the
6791 administrator merge in their changes each time the package
6792 is upgraded and the <tt>conffile</tt> changes. To ease
6793 the burden on the system administrator, such configurable
6794 values should not be placed directly in the script.
6795 Instead, they should be placed in a file in
6796 <file>/etc/default</file>, which typically will have the same
6797 base name as the <file>init.d</file> script. This extra file
6798 should be sourced by the script when the script runs. It
6799 must contain only variable settings and comments in SUSv3
6800 <prgn>sh</prgn> format. It may either be a
6801 <tt>conffile</tt> or a configuration file maintained by
6802 the package maintainer scripts. See <ref id="config-files">
6807 To ensure that vital configurable values are always
6808 available, the <file>init.d</file> script should set default
6809 values for each of the shell variables it uses, either
6810 before sourcing the <file>/etc/default/</file> file or
6811 afterwards using something like the <tt>:
6812 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6813 script must behave sensibly and not fail if the
6814 <file>/etc/default</file> file is deleted.
6818 Files and directories under <file>/run</file>, including ones
6819 referred to via the compatibility paths <file>/var/run</file>
6820 and <file>/var/lock</file>, are normally stored on a temporary
6821 filesystem and are normally not persistent across a reboot.
6822 The <file>init.d</file> scripts must handle this correctly.
6823 This will typically mean creating any required subdirectories
6824 dynamically when the <file>init.d</file> script is run.
6825 See <ref id="fhs-run"> for more information.
6830 <heading>Interfacing with the initscript system</heading>
6833 Maintainers should use the abstraction layer provided by
6834 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6835 programs to deal with initscripts in their packages'
6836 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6837 and <prgn>postrm</prgn>.
6841 Directly managing the /etc/rc?.d links and directly
6842 invoking the <file>/etc/init.d/</file> initscripts should
6843 be done only by packages providing the initscript
6844 subsystem (such as <prgn>sysv-rc</prgn> and
6845 <prgn>file-rc</prgn>).
6849 <heading>Managing the links</heading>
6852 The program <prgn>update-rc.d</prgn> is provided for
6853 package maintainers to arrange for the proper creation and
6854 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6855 or their functional equivalent if another method is being
6856 used. This may be used by maintainers in their packages'
6857 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6861 You must not include any <file>/etc/rc<var>n</var>.d</file>
6862 symbolic links in the actual archive or manually create or
6863 remove the symbolic links in maintainer scripts; you must
6864 use the <prgn>update-rc.d</prgn> program instead. (The
6865 former will fail if an alternative method of maintaining
6866 runlevel information is being used.) You must not include
6867 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6868 in the archive either. (Only the <tt>sysvinit</tt>
6873 By default <prgn>update-rc.d</prgn> will start services in
6874 each of the multi-user state runlevels (2, 3, 4, and 5)
6875 and stop them in the halt runlevel (0), the single-user
6876 runlevel (1) and the reboot runlevel (6). The system
6877 administrator will have the opportunity to customize
6878 runlevels by simply adding, moving, or removing the
6879 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6880 symbolic links are being used, or by modifying
6881 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6886 To get the default behavior for your package, put in your
6887 <prgn>postinst</prgn> script
6888 <example compact="compact">
6889 update-rc.d <var>package</var> defaults
6891 and in your <prgn>postrm</prgn>
6892 <example compact="compact">
6893 if [ "$1" = purge ]; then
6894 update-rc.d <var>package</var> remove
6896 </example>. Note that if your package changes runlevels
6897 or priority, you may have to remove and recreate the links,
6898 since otherwise the old links may persist. Refer to the
6899 documentation of <prgn>update-rc.d</prgn>.
6903 This will use a default sequence number of 20. If it does
6904 not matter when or in which order the <file>init.d</file>
6905 script is run, use this default. If it does, then you
6906 should talk to the maintainer of the <prgn>sysvinit</prgn>
6907 package or post to <tt>debian-devel</tt>, and they will
6908 help you choose a number.
6912 For more information about using <tt>update-rc.d</tt>,
6913 please consult its man page <manref name="update-rc.d"
6919 <heading>Running initscripts</heading>
6921 The program <prgn>invoke-rc.d</prgn> is provided to make
6922 it easier for package maintainers to properly invoke an
6923 initscript, obeying runlevel and other locally-defined
6924 constraints that might limit a package's right to start,
6925 stop and otherwise manage services. This program may be
6926 used by maintainers in their packages' scripts.
6930 The package maintainer scripts must use
6931 <prgn>invoke-rc.d</prgn> to invoke the
6932 <file>/etc/init.d/*</file> initscripts, instead of
6933 calling them directly.
6937 By default, <prgn>invoke-rc.d</prgn> will pass any
6938 action requests (start, stop, reload, restart...) to the
6939 <file>/etc/init.d</file> script, filtering out requests
6940 to start or restart a service out of its intended
6945 Most packages will simply need to change:
6946 <example compact="compact">/etc/init.d/<package>
6947 <action></example> in their <prgn>postinst</prgn>
6948 and <prgn>prerm</prgn> scripts to:
6949 <example compact="compact">
6950 if which invoke-rc.d >/dev/null 2>&1; then
6951 invoke-rc.d <var>package</var> <action>
6953 /etc/init.d/<var>package</var> <action>
6959 A package should register its initscript services using
6960 <prgn>update-rc.d</prgn> before it tries to invoke them
6961 using <prgn>invoke-rc.d</prgn>. Invocation of
6962 unregistered services may fail.
6966 For more information about using
6967 <prgn>invoke-rc.d</prgn>, please consult its man page
6968 <manref name="invoke-rc.d" section="8">.
6974 <heading>Boot-time initialization</heading>
6977 There used to be another directory, <file>/etc/rc.boot</file>,
6978 which contained scripts which were run once per machine
6979 boot. This has been deprecated in favour of links from
6980 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6981 described in <ref id="/etc/init.d">. Packages must not
6982 place files in <file>/etc/rc.boot</file>.
6987 <heading>Example</heading>
6990 An example on which you can base your
6991 <file>/etc/init.d</file> scripts is found in
6992 <file>/etc/init.d/skeleton</file>.
6999 <heading>Console messages from <file>init.d</file> scripts</heading>
7002 This section describes the formats to be used for messages
7003 written to standard output by the <file>/etc/init.d</file>
7004 scripts. The intent is to improve the consistency of
7005 Debian's startup and shutdown look and feel. For this
7006 reason, please look very carefully at the details. We want
7007 the messages to have the same format in terms of wording,
7008 spaces, punctuation and case of letters.
7012 Here is a list of overall rules that should be used for
7013 messages generated by <file>/etc/init.d</file> scripts.
7019 The message should fit in one line (fewer than 80
7020 characters), start with a capital letter and end with
7021 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7025 If the script is performing some time consuming task in
7026 the background (not merely starting or stopping a
7027 program, for instance), an ellipsis (three dots:
7028 <tt>...</tt>) should be output to the screen, with no
7029 leading or tailing whitespace or line feeds.
7033 The messages should appear as if the computer is telling
7034 the user what it is doing (politely :-), but should not
7035 mention "it" directly. For example, instead of:
7036 <example compact="compact">
7037 I'm starting network daemons: nfsd mountd.
7039 the message should say
7040 <example compact="compact">
7041 Starting network daemons: nfsd mountd.
7048 <tt>init.d</tt> script should use the following standard
7049 message formats for the situations enumerated below.
7055 <p>When daemons are started</p>
7058 If the script starts one or more daemons, the output
7059 should look like this (a single line, no leading
7061 <example compact="compact">
7062 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7064 The <var>description</var> should describe the
7065 subsystem the daemon or set of daemons are part of,
7066 while <var>daemon-1</var> up to <var>daemon-n</var>
7067 denote each daemon's name (typically the file name of
7072 For example, the output of <file>/etc/init.d/lpd</file>
7074 <example compact="compact">
7075 Starting printer spooler: lpd.
7080 This can be achieved by saying
7081 <example compact="compact">
7082 echo -n "Starting printer spooler: lpd"
7083 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7086 in the script. If there are more than one daemon to
7087 start, the output should look like this:
7088 <example compact="compact">
7089 echo -n "Starting remote file system services:"
7090 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7091 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7092 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7095 This makes it possible for the user to see what is
7096 happening and when the final daemon has been started.
7097 Care should be taken in the placement of white spaces:
7098 in the example above the system administrators can
7099 easily comment out a line if they don't want to start
7100 a specific daemon, while the displayed message still
7106 <p>When a system parameter is being set</p>
7109 If you have to set up different system parameters
7110 during the system boot, you should use this format:
7111 <example compact="compact">
7112 Setting <var>parameter</var> to "<var>value</var>".
7117 You can use a statement such as the following to get
7119 <example compact="compact">
7120 echo "Setting DNS domainname to \"$domainname\"."
7125 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7126 for the left and right quotation marks. A grave accent
7127 (<tt>`</tt>) is not a quote character; neither is an
7128 apostrophe (<tt>'</tt>).
7133 <p>When a daemon is stopped or restarted</p>
7136 When you stop or restart a daemon, you should issue a
7137 message identical to the startup message, except that
7138 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7139 or <tt>Restarting</tt> respectively.
7143 For example, stopping the printer daemon will look like
7145 <example compact="compact">
7146 Stopping printer spooler: lpd.
7152 <p>When something is executed</p>
7155 There are several examples where you have to run a
7156 program at system startup or shutdown to perform a
7157 specific task, for example, setting the system's clock
7158 using <prgn>netdate</prgn> or killing all processes
7159 when the system shuts down. Your message should look
7161 <example compact="compact">
7162 Doing something very useful...done.
7164 You should print the <tt>done.</tt> immediately after
7165 the job has been completed, so that the user is
7166 informed why they have to wait. You can get this
7168 <example compact="compact">
7169 echo -n "Doing something very useful..."
7178 <p>When the configuration is reloaded</p>
7181 When a daemon is forced to reload its configuration
7182 files you should use the following format:
7183 <example compact="compact">
7184 Reloading <var>description</var> configuration...done.
7186 where <var>description</var> is the same as in the
7187 daemon starting message.
7194 <sect id="cron-jobs">
7195 <heading>Cron jobs</heading>
7198 Packages must not modify the configuration file
7199 <file>/etc/crontab</file>, and they must not modify the files in
7200 <file>/var/spool/cron/crontabs</file>.
7204 If a package wants to install a job that has to be executed via
7205 cron, it should place a file named as specified
7206 in <ref id="cron-files"> into one or more of the following
7208 <example compact="compact">
7214 As these directory names imply, the files within them are
7215 executed on an hourly, daily, weekly, or monthly basis,
7216 respectively. The exact times are listed in
7217 <file>/etc/crontab</file>.
7221 All files installed in any of these directories must be
7222 scripts (e.g., shell scripts or Perl scripts) so that they
7223 can easily be modified by the local system administrator.
7224 In addition, they must be treated as configuration files.
7228 If a certain job has to be executed at some other frequency or
7229 at a specific time, the package should install a file in
7230 <file>/etc/cron.d</file> with a name as specified
7231 in <ref id="cron-files">. This file uses the same syntax
7232 as <file>/etc/crontab</file> and is processed
7233 by <prgn>cron</prgn> automatically. The file must also be
7234 treated as a configuration file. (Note that entries in the
7235 <file>/etc/cron.d</file> directory are not handled by
7236 <prgn>anacron</prgn>. Thus, you should only use this
7237 directory for jobs which may be skipped if the system is not
7242 Unlike <file>crontab</file> files described in the IEEE Std
7243 1003.1-2008 (POSIX.1) available from
7244 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7245 name="The Open Group">, the files in
7246 <file>/etc/cron.d</file> and the file
7247 <file>/etc/crontab</file> have seven fields; namely:
7249 <item>Minute [0,59]</item>
7250 <item>Hour [0,23]</item>
7251 <item>Day of the month [1,31]</item>
7252 <item>Month of the year [1,12]</item>
7253 <item>Day of the week ([0,6] with 0=Sunday)</item>
7254 <item>Username</item>
7255 <item>Command to be run</item>
7257 Ranges of numbers are allowed. Ranges are two numbers
7258 separated with a hyphen. The specified range is inclusive.
7259 Lists are allowed. A list is a set of numbers (or ranges)
7260 separated by commas. Step values can be used in conjunction
7265 The scripts or <tt>crontab</tt> entries in these directories should
7266 check if all necessary programs are installed before they
7267 try to execute them. Otherwise, problems will arise when a
7268 package was removed but not purged since configuration files
7269 are kept on the system in this situation.
7273 Any <tt>cron</tt> daemon must provide
7274 <file>/usr/bin/crontab</file> and support normal
7275 <tt>crontab</tt> entries as specified in POSIX. The daemon
7276 must also support names for days and months, ranges, and
7277 step values. It has to support <file>/etc/crontab</file>,
7278 and correctly execute the scripts in
7279 <file>/etc/cron.d</file>. The daemon must also correctly
7281 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7284 <sect1 id="cron-files">
7285 <heading>Cron job file names</heading>
7288 The file name of a cron job file should normally match the
7289 name of the package from which it comes.
7293 If a package supplies multiple cron job files files in the
7294 same directory, the file names should all start with the name
7295 of the package (possibly modified as described below) followed
7296 by a hyphen (<tt>-</tt>) and a suitable suffix.
7300 A cron job file name must not include any period or plus
7301 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7302 cause cron to ignore the file. Underscores (<tt>_</tt>)
7303 should be used instead of <tt>.</tt> and <tt>+</tt>
7310 <heading>Menus</heading>
7313 The Debian <tt>menu</tt> package provides a standard
7314 interface between packages providing applications and
7315 <em>menu programs</em> (either X window managers or
7316 text-based menu programs such as <prgn>pdmenu</prgn>).
7320 All packages that provide applications that need not be
7321 passed any special command line arguments for normal
7322 operation should register a menu entry for those
7323 applications, so that users of the <tt>menu</tt> package
7324 will automatically get menu entries in their window
7325 managers, as well in shells like <tt>pdmenu</tt>.
7329 Menu entries should follow the current menu policy.
7333 The menu policy can be found in the <tt>menu-policy</tt>
7334 files in the <tt>debian-policy</tt> package.
7335 It is also available from the Debian web mirrors at
7336 <tt><url name="/doc/packaging-manuals/menu-policy/"
7337 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7341 Please also refer to the <em>Debian Menu System</em>
7342 documentation that comes with the <package>menu</package>
7343 package for information about how to register your
7349 <heading>Multimedia handlers</heading>
7352 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7353 is a mechanism for encoding files and data streams and
7354 providing meta-information about them, in particular their
7355 type (e.g. audio or video) and format (e.g. PNG, HTML,
7360 Registration of MIME type handlers allows programs like mail
7361 user agents and web browsers to invoke these handlers to
7362 view, edit or display MIME types they don't support directly.
7366 Packages which provide the ability to view/show/play,
7367 compose, edit or print MIME types should register themselves
7368 as such following the current MIME support policy.
7372 The <package>mime-support</package> package provides the
7373 <prgn>update-mime</prgn> program which allows packages to
7374 register programs that can show, compose, edit or print
7379 Packages containing such programs must register them
7380 with <prgn>update-mime</prgn> as documented in <manref
7381 name="update-mime" section="8">. They should <em>not</em> depend
7382 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7383 they should just put something like the following in the
7384 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7387 if [ -x /usr/sbin/update-mime ]; then
7396 <heading>Keyboard configuration</heading>
7399 To achieve a consistent keyboard configuration so that all
7400 applications interpret a keyboard event the same way, all
7401 programs in the Debian distribution must be configured to
7402 comply with the following guidelines.
7406 The following keys must have the specified interpretations:
7409 <tag><tt><--</tt></tag>
7410 <item>delete the character to the left of the cursor</item>
7412 <tag><tt>Delete</tt></tag>
7413 <item>delete the character to the right of the cursor</item>
7415 <tag><tt>Control+H</tt></tag>
7416 <item>emacs: the help prefix</item>
7419 The interpretation of any keyboard events should be
7420 independent of the terminal that is used, be it a virtual
7421 console, an X terminal emulator, an rlogin/telnet session,
7426 The following list explains how the different programs
7427 should be set up to achieve this:
7433 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7437 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7441 X translations are set up to make
7442 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7443 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7444 is the vt220 escape code for the "delete character"
7445 key). This must be done by loading the X resources
7446 using <prgn>xrdb</prgn> on all local X displays, not
7447 using the application defaults, so that the
7448 translation resources used correspond to the
7449 <prgn>xmodmap</prgn> settings.
7453 The Linux console is configured to make
7454 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7455 generate <tt>ESC [ 3 ~</tt>.
7459 X applications are configured so that <tt><</tt>
7460 deletes left, and <tt>Delete</tt> deletes right. Motif
7461 applications already work like this.
7465 Terminals should have <tt>stty erase ^?</tt> .
7469 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7470 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7471 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7475 Emacs is programmed to map <tt>KB_Backspace</tt> or
7476 the <tt>stty erase</tt> character to
7477 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7478 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7479 <tt>^H</tt> to <tt>help</tt> as always.
7483 Other applications use the <tt>stty erase</tt>
7484 character and <tt>kdch1</tt> for the two delete keys,
7485 with ASCII DEL being "delete previous character" and
7486 <tt>kdch1</tt> being "delete character under
7494 This will solve the problem except for the following
7501 Some terminals have a <tt><--</tt> key that cannot
7502 be made to produce anything except <tt>^H</tt>. On
7503 these terminals Emacs help will be unavailable on
7504 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7505 character takes precedence in Emacs, and has been set
7506 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7507 available) can be used instead.
7511 Some operating systems use <tt>^H</tt> for <tt>stty
7512 erase</tt>. However, modern telnet versions and all
7513 rlogin versions propagate <tt>stty</tt> settings, and
7514 almost all UNIX versions honour <tt>stty erase</tt>.
7515 Where the <tt>stty</tt> settings are not propagated
7516 correctly, things can be made to work by using
7517 <tt>stty</tt> manually.
7521 Some systems (including previous Debian versions) use
7522 <prgn>xmodmap</prgn> to arrange for both
7523 <tt><--</tt> and <tt>Delete</tt> to generate
7524 <tt>KB_Delete</tt>. We can change the behavior of
7525 their X clients using the same X resources that we use
7526 to do it for our own clients, or configure our clients
7527 using their resources when things are the other way
7528 around. On displays configured like this
7529 <tt>Delete</tt> will not work, but <tt><--</tt>
7534 Some operating systems have different <tt>kdch1</tt>
7535 settings in their <tt>terminfo</tt> database for
7536 <tt>xterm</tt> and others. On these systems the
7537 <tt>Delete</tt> key will not work correctly when you
7538 log in from a system conforming to our policy, but
7539 <tt><--</tt> will.
7546 <heading>Environment variables</heading>
7549 A program must not depend on environment variables to get
7550 reasonable defaults. (That's because these environment
7551 variables would have to be set in a system-wide
7552 configuration file like <file>/etc/profile</file>, which is not
7553 supported by all shells.)
7557 If a program usually depends on environment variables for its
7558 configuration, the program should be changed to fall back to
7559 a reasonable default configuration if these environment
7560 variables are not present. If this cannot be done easily
7561 (e.g., if the source code of a non-free program is not
7562 available), the program must be replaced by a small
7563 "wrapper" shell script which sets the environment variables
7564 if they are not already defined, and calls the original program.
7568 Here is an example of a wrapper script for this purpose:
7570 <example compact="compact">
7572 BAR=${BAR:-/var/lib/fubar}
7574 exec /usr/lib/foo/foo "$@"
7579 Furthermore, as <file>/etc/profile</file> is a configuration
7580 file of the <prgn>base-files</prgn> package, other packages must
7581 not put any environment variables or other commands into that
7586 <sect id="doc-base">
7587 <heading>Registering Documents using doc-base</heading>
7590 The <package>doc-base</package> package implements a
7591 flexible mechanism for handling and presenting
7592 documentation. The recommended practice is for every Debian
7593 package that provides online documentation (other than just
7594 manual pages) to register these documents with
7595 <package>doc-base</package> by installing a
7596 <package>doc-base</package> control file in
7597 <file>/usr/share/doc-base/</file>.
7600 Please refer to the documentation that comes with the
7601 <package>doc-base</package> package for information and
7610 <heading>Files</heading>
7612 <sect id="binaries">
7613 <heading>Binaries</heading>
7616 Two different packages must not install programs with
7617 different functionality but with the same filenames. (The
7618 case of two programs having the same functionality but
7619 different implementations is handled via "alternatives" or
7620 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7621 <ref id="conflicts"> respectively.) If this case happens,
7622 one of the programs must be renamed. The maintainers should
7623 report this to the <tt>debian-devel</tt> mailing list and
7624 try to find a consensus about which program will have to be
7625 renamed. If a consensus cannot be reached, <em>both</em>
7626 programs must be renamed.
7630 By default, when a package is being built, any binaries
7631 created should include debugging information, as well as
7632 being compiled with optimization. You should also turn on
7633 as many reasonable compilation warnings as possible; this
7634 makes life easier for porters, who can then look at build
7635 logs for possible problems. For the C programming language,
7636 this means the following compilation parameters should be
7638 <example compact="compact">
7640 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7642 INSTALL = install -s # (or use strip on the files in debian/tmp)
7647 Note that by default all installed binaries should be stripped,
7648 either by using the <tt>-s</tt> flag to
7649 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7650 the binaries after they have been copied into
7651 <file>debian/tmp</file> but before the tree is made into a
7656 Although binaries in the build tree should be compiled with
7657 debugging information by default, it can often be difficult to
7658 debug programs if they are also subjected to compiler
7659 optimization. For this reason, it is recommended to support the
7660 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7661 (see <ref id="debianrules-options">). This variable can contain
7662 several flags to change how a package is compiled and built.
7666 It is up to the package maintainer to decide what
7667 compilation options are best for the package. Certain
7668 binaries (such as computationally-intensive programs) will
7669 function better with certain flags (<tt>-O3</tt>, for
7670 example); feel free to use them. Please use good judgment
7671 here. Don't use flags for the sake of it; only use them
7672 if there is good reason to do so. Feel free to override
7673 the upstream author's ideas about which compilation
7674 options are best: they are often inappropriate for our
7680 <sect id="libraries">
7681 <heading>Libraries</heading>
7684 If the package is <strong>architecture: any</strong>, then
7685 the shared library compilation and linking flags must have
7686 <tt>-fPIC</tt>, or the package shall not build on some of
7687 the supported architectures<footnote>
7689 If you are using GCC, <tt>-fPIC</tt> produces code with
7690 relocatable position independent code, which is required for
7691 most architectures to create a shared library, with i386 and
7692 perhaps some others where non position independent code is
7693 permitted in a shared library.
7696 Position independent code may have a performance penalty,
7697 especially on <tt>i386</tt>. However, in most cases the
7698 speed penalty must be measured against the memory wasted on
7699 the few architectures where non position independent code is
7702 </footnote>. Any exception to this rule must be discussed on
7703 the mailing list <em>debian-devel@lists.debian.org</em>, and
7704 a rough consensus obtained. The reasons for not compiling
7705 with <tt>-fPIC</tt> flag must be recorded in the file
7706 <tt>README.Debian</tt>, and care must be taken to either
7707 restrict the architecture or arrange for <tt>-fPIC</tt> to
7708 be used on architectures where it is required.<footnote>
7710 Some of the reasons why this might be required is if the
7711 library contains hand crafted assembly code that is not
7712 relocatable, the speed penalty is excessive for compute
7713 intensive libs, and similar reasons.
7718 As to the static libraries, the common case is not to have
7719 relocatable code, since there is no benefit, unless in specific
7720 cases; therefore the static version must not be compiled
7721 with the <tt>-fPIC</tt> flag. Any exception to this rule
7722 should be discussed on the mailing list
7723 <em>debian-devel@lists.debian.org</em>, and the reasons for
7724 compiling with the <tt>-fPIC</tt> flag must be recorded in
7725 the file <tt>README.Debian</tt>. <footnote>
7727 Some of the reasons for linking static libraries with
7728 the <tt>-fPIC</tt> flag are if, for example, one needs a
7729 Perl API for a library that is under rapid development,
7730 and has an unstable API, so shared libraries are
7731 pointless at this phase of the library's development. In
7732 that case, since Perl needs a library with relocatable
7733 code, it may make sense to create a static library with
7734 relocatable code. Another reason cited is if you are
7735 distilling various libraries into a common shared
7736 library, like <tt>mklibs</tt> does in the Debian
7742 In other words, if both a shared and a static library is
7743 being built, each source unit (<tt>*.c</tt>, for example,
7744 for C files) will need to be compiled twice, for the normal
7749 Libraries should be built with threading support and to be
7750 thread-safe if the library supports this.
7754 Although not enforced by the build tools, shared libraries
7755 must be linked against all libraries that they use symbols from
7756 in the same way that binaries are. This ensures the correct
7757 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7758 system and guarantees that all libraries can be safely opened
7759 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7760 option <tt>-Wl,-z,defs</tt> when building a shared library.
7761 Since this option enforces symbol resolution at build time,
7762 a missing library reference will be caught early as a fatal
7767 All installed shared libraries should be stripped with
7768 <example compact="compact">
7769 strip --strip-unneeded <var>your-lib</var>
7771 (The option <tt>--strip-unneeded</tt> makes
7772 <prgn>strip</prgn> remove only the symbols which aren't
7773 needed for relocation processing.) Shared libraries can
7774 function perfectly well when stripped, since the symbols for
7775 dynamic linking are in a separate part of the ELF object
7777 You might also want to use the options
7778 <tt>--remove-section=.comment</tt> and
7779 <tt>--remove-section=.note</tt> on both shared libraries
7780 and executables, and <tt>--strip-debug</tt> on static
7786 Note that under some circumstances it may be useful to
7787 install a shared library unstripped, for example when
7788 building a separate package to support debugging.
7792 Shared object files (often <file>.so</file> files) that are not
7793 public libraries, that is, they are not meant to be linked
7794 to by third party executables (binaries of other packages),
7795 should be installed in subdirectories of the
7796 <file>/usr/lib</file> directory. Such files are exempt from the
7797 rules that govern ordinary shared libraries, except that
7798 they must not be installed executable and should be
7800 A common example are the so-called "plug-ins",
7801 internal shared objects that are dynamically loaded by
7802 programs using <manref name="dlopen" section="3">.
7807 Packages that use <prgn>libtool</prgn> to create and install
7808 their shared libraries install a file containing additional
7809 metadata (ending in <file>.la</file>) alongside the library.
7810 For public libraries intended for use by other packages, these
7811 files normally should not be included in the Debian package,
7812 since the information they include is not necessary to link with
7813 the shared library on Debian and can add unnecessary additional
7814 dependencies to other programs or libraries.<footnote>
7815 These files store, among other things, all libraries on which
7816 that shared library depends. Unfortunately, if
7817 the <file>.la</file> file is present and contains that
7818 dependency information, using <prgn>libtool</prgn> when
7819 linking against that library will cause the resulting program
7820 or library to be linked against those dependencies as well,
7821 even if this is unnecessary. This can create unneeded
7822 dependencies on shared library packages that would otherwise
7823 be hidden behind the library ABI, and can make library
7824 transitions to new SONAMEs unnecessarily complicated and
7825 difficult to manage.
7827 If the <file>.la</file> file is required for that library (if,
7828 for instance, it's loaded via <tt>libltdl</tt> in a way that
7829 requires that meta-information), the <tt>dependency_libs</tt>
7830 setting in the <file>.la</file> file should normally be set to
7831 the empty string. If the shared library development package has
7832 historically included the <file>.la</file>, it must be retained
7833 in the development package (with <tt>dependency_libs</tt>
7834 emptied) until all libraries that depend on it have removed or
7835 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7836 files to prevent linking with those other libraries
7837 using <prgn>libtool</prgn> from failing.
7841 If the <file>.la</file> must be included, it should be included
7842 in the development (<tt>-dev</tt>) package, unless the library
7843 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7844 library. If it is intended for use with <tt>libltdl</tt>,
7845 the <file>.la</file> files must go in the run-time library
7850 These requirements for handling of <file>.la</file> files do not
7851 apply to loadable modules or libraries not installed in
7852 directories searched by default by the dynamic linker. Packages
7853 installing loadable modules will frequently need to install
7854 the <file>.la</file> files alongside the modules so that they
7855 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7856 does not need to be modified for libraries or modules that are
7857 not installed in directories searched by the dynamic linker by
7858 default and not intended for use by other packages.
7862 You must make sure that you use only released versions of
7863 shared libraries to build your packages; otherwise other
7864 users will not be able to run your binaries
7865 properly. Producing source packages that depend on
7866 unreleased compilers is also usually a bad
7873 <heading>Shared libraries</heading>
7875 This section has moved to <ref id="sharedlibs">.
7881 <heading>Scripts</heading>
7884 All command scripts, including the package maintainer
7885 scripts inside the package and used by <prgn>dpkg</prgn>,
7886 should have a <tt>#!</tt> line naming the shell to be used
7891 In the case of Perl scripts this should be
7892 <tt>#!/usr/bin/perl</tt>.
7896 When scripts are installed into a directory in the system
7897 PATH, the script name should not include an extension such
7898 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7899 language currently used to implement it.
7902 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7903 <file>init.d</file> scripts should almost certainly start
7904 with <tt>set -e</tt> so that errors are detected.
7905 <file>init.d</file> scripts are something of a special case, due
7906 to how frequently they need to call commands that are allowed to
7907 fail, and it may instead be easier to check the exit status of
7908 commands directly. See <ref id="writing-init"> for more
7909 information about writing <file>init.d</file> scripts.
7912 Every script should use <tt>set -e</tt> or check the exit status
7913 of <em>every</em> command.
7916 Scripts may assume that <file>/bin/sh</file> implements the
7917 SUSv3 Shell Command Language<footnote>
7918 Single UNIX Specification, version 3, which is also IEEE
7919 1003.1-2004 (POSIX), and is available on the World Wide Web
7920 from <url id="http://www.unix.org/version3/online.html"
7921 name="The Open Group"> after free
7922 registration.</footnote>
7923 plus the following additional features not mandated by
7925 These features are in widespread use in the Linux community
7926 and are implemented in all of bash, dash, and ksh, the most
7927 common shells users may wish to use as <file>/bin/sh</file>.
7930 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7931 must not generate a newline.</item>
7932 <item><tt>test</tt>, if implemented as a shell built-in, must
7933 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7935 <item><tt>local</tt> to create a scoped variable must be
7936 supported, including listing multiple variables in a single
7937 local command and assigning a value to a variable at the
7938 same time as localizing it. <tt>local</tt> may or
7939 may not preserve the variable value from an outer scope if
7940 no assignment is present. Uses such as:
7944 # ... use a, b, c, d ...
7947 must be supported and must set the value of <tt>c</tt> to
7950 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7951 -<var>signal</var></tt>, where <var>signal</var> is either
7952 the name of a signal or one of the numeric signals listed in
7953 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7954 supported if <prgn>kill</prgn> is implemented as a shell
7957 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7958 signals must be supported. In addition to the signal
7959 numbers listed in the extension, which are the same as for
7960 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7963 If a shell script requires non-SUSv3 features from the shell
7964 interpreter other than those listed above, the appropriate shell
7965 must be specified in the first line of the script (e.g.,
7966 <tt>#!/bin/bash</tt>) and the package must depend on the package
7967 providing the shell (unless the shell package is marked
7968 "Essential", as in the case of <prgn>bash</prgn>).
7972 You may wish to restrict your script to SUSv3 features plus the
7973 above set when possible so that it may use <file>/bin/sh</file>
7974 as its interpreter. Checking your script
7975 with <prgn>checkbashisms</prgn> from
7976 the <package>devscripts</package> package or running your script
7977 with <prgn>posh</prgn> may help uncover violations of the above
7978 requirements. If in doubt whether a script complies with these
7979 requirements, use <file>/bin/bash</file>.
7983 Perl scripts should check for errors when making any
7984 system calls, including <tt>open</tt>, <tt>print</tt>,
7985 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7989 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7990 scripting languages. See <em>Csh Programming Considered
7991 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7992 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7993 If an upstream package comes with <prgn>csh</prgn> scripts
7994 then you must make sure that they start with
7995 <tt>#!/bin/csh</tt> and make your package depend on the
7996 <prgn>c-shell</prgn> virtual package.
8000 Any scripts which create files in world-writeable
8001 directories (e.g., in <file>/tmp</file>) must use a
8002 mechanism which will fail atomically if a file with the same
8003 name already exists.
8007 The Debian base system provides the <prgn>tempfile</prgn>
8008 and <prgn>mktemp</prgn> utilities for use by scripts for
8015 <heading>Symbolic links</heading>
8018 In general, symbolic links within a top-level directory should
8019 be relative, and symbolic links pointing from one top-level
8020 directory to or into another should be absolute. (A top-level
8021 directory is a sub-directory of the root
8022 directory <file>/</file>.) For example, a symbolic link
8023 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8024 should be relative (<file>../share/bar</file>), but a symbolic
8025 link from <file>/var/run</file> to <file>/run</file> should be
8027 This is necessary to allow top-level directories to be
8028 symlinks. If linking <file>/var/run</file>
8029 to <file>/run</file> were done with the relative symbolic
8030 link <file>../run</file>, but <file>/var</file> were a
8031 symbolic link to <file>/srv/disk1</file>, the symbolic link
8032 would point to <file>/srv/run</file> rather than the intended
8038 In addition, symbolic links should be specified as short as
8039 possible, i.e., link targets like <file>foo/../bar</file> are
8044 Note that when creating a relative link using
8045 <prgn>ln</prgn> it is not necessary for the target of the
8046 link to exist relative to the working directory you're
8047 running <prgn>ln</prgn> from, nor is it necessary to change
8048 directory to the directory where the link is to be made.
8049 Simply include the string that should appear as the target
8050 of the link (this will be a pathname relative to the
8051 directory in which the link resides) as the first argument
8056 For example, in your <prgn>Makefile</prgn> or
8057 <file>debian/rules</file>, you can do things like:
8058 <example compact="compact">
8059 ln -fs gcc $(prefix)/bin/cc
8060 ln -fs gcc debian/tmp/usr/bin/cc
8061 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8062 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8067 A symbolic link pointing to a compressed file should always
8068 have the same file extension as the referenced file. (For
8069 example, if a file <file>foo.gz</file> is referenced by a
8070 symbolic link, the filename of the link has to end with
8071 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8076 <heading>Device files</heading>
8079 Packages must not include device files or named pipes in the
8084 If a package needs any special device files that are not
8085 included in the base system, it must call
8086 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8087 after notifying the user<footnote>
8088 This notification could be done via a (low-priority)
8089 debconf message, or an echo (printf) statement.
8094 Packages must not remove any device files in the
8095 <prgn>postrm</prgn> or any other script. This is left to the
8096 system administrator.
8100 Debian uses the serial devices
8101 <file>/dev/ttyS*</file>. Programs using the old
8102 <file>/dev/cu*</file> devices should be changed to use
8103 <file>/dev/ttyS*</file>.
8107 Named pipes needed by the package must be created in
8108 the <prgn>postinst</prgn> script<footnote>
8109 It's better to use <prgn>mkfifo</prgn> rather
8110 than <prgn>mknod</prgn> to create named pipes so that
8111 automated checks for packages incorrectly creating device
8112 files with <prgn>mknod</prgn> won't have false positives.
8113 </footnote> and removed in
8114 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8119 <sect id="config-files">
8120 <heading>Configuration files</heading>
8123 <heading>Definitions</heading>
8127 <tag>configuration file</tag>
8129 A file that affects the operation of a program, or
8130 provides site- or host-specific information, or
8131 otherwise customizes the behavior of a program.
8132 Typically, configuration files are intended to be
8133 modified by the system administrator (if needed or
8134 desired) to conform to local policy or to provide
8135 more useful site-specific behavior.
8138 <tag><tt>conffile</tt></tag>
8140 A file listed in a package's <tt>conffiles</tt>
8141 file, and is treated specially by <prgn>dpkg</prgn>
8142 (see <ref id="configdetails">).
8148 The distinction between these two is important; they are
8149 not interchangeable concepts. Almost all
8150 <tt>conffile</tt>s are configuration files, but many
8151 configuration files are not <tt>conffiles</tt>.
8155 As noted elsewhere, <file>/etc/init.d</file> scripts,
8156 <file>/etc/default</file> files, scripts installed in
8157 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8158 configuration installed in <file>/etc/cron.d</file> must be
8159 treated as configuration files. In general, any script that
8160 embeds configuration information is de-facto a configuration
8161 file and should be treated as such.
8166 <heading>Location</heading>
8169 Any configuration files created or used by your package
8170 must reside in <file>/etc</file>. If there are several,
8171 consider creating a subdirectory of <file>/etc</file>
8172 named after your package.
8176 If your package creates or uses configuration files
8177 outside of <file>/etc</file>, and it is not feasible to modify
8178 the package to use <file>/etc</file> directly, put the files
8179 in <file>/etc</file> and create symbolic links to those files
8180 from the location that the package requires.
8185 <heading>Behavior</heading>
8188 Configuration file handling must conform to the following
8190 <list compact="compact">
8192 local changes must be preserved during a package
8196 configuration files must be preserved when the
8197 package is removed, and only deleted when the
8201 Obsolete configuration files without local changes may be
8202 removed by the package during upgrade.
8206 The easy way to achieve this behavior is to make the
8207 configuration file a <tt>conffile</tt>. This is
8208 appropriate only if it is possible to distribute a default
8209 version that will work for most installations, although
8210 some system administrators may choose to modify it. This
8211 implies that the default version will be part of the
8212 package distribution, and must not be modified by the
8213 maintainer scripts during installation (or at any other
8218 In order to ensure that local changes are preserved
8219 correctly, no package may contain or make hard links to
8220 conffiles.<footnote>
8221 Rationale: There are two problems with hard links.
8222 The first is that some editors break the link while
8223 editing one of the files, so that the two files may
8224 unwittingly become unlinked and different. The second
8225 is that <prgn>dpkg</prgn> might break the hard link
8226 while upgrading <tt>conffile</tt>s.
8231 The other way to do it is via the maintainer scripts. In
8232 this case, the configuration file must not be listed as a
8233 <tt>conffile</tt> and must not be part of the package
8234 distribution. If the existence of a file is required for
8235 the package to be sensibly configured it is the
8236 responsibility of the package maintainer to provide
8237 maintainer scripts which correctly create, update and
8238 maintain the file and remove it on purge. (See <ref
8239 id="maintainerscripts"> for more information.) These
8240 scripts must be idempotent (i.e., must work correctly if
8241 <prgn>dpkg</prgn> needs to re-run them due to errors
8242 during installation or removal), must cope with all the
8243 variety of ways <prgn>dpkg</prgn> can call maintainer
8244 scripts, must not overwrite or otherwise mangle the user's
8245 configuration without asking, must not ask unnecessary
8246 questions (particularly during upgrades), and must
8247 otherwise be good citizens.
8251 The scripts are not required to configure every possible
8252 option for the package, but only those necessary to get
8253 the package running on a given system. Ideally the
8254 sysadmin should not have to do any configuration other
8255 than that done (semi-)automatically by the
8256 <prgn>postinst</prgn> script.
8260 A common practice is to create a script called
8261 <file><var>package</var>-configure</file> and have the
8262 package's <prgn>postinst</prgn> call it if and only if the
8263 configuration file does not already exist. In certain
8264 cases it is useful for there to be an example or template
8265 file which the maintainer scripts use. Such files should
8266 be in <file>/usr/share/<var>package</var></file> or
8267 <file>/usr/lib/<var>package</var></file> (depending on whether
8268 they are architecture-independent or not). There should
8269 be symbolic links to them from
8270 <file>/usr/share/doc/<var>package</var>/examples</file> if
8271 they are examples, and should be perfectly ordinary
8272 <prgn>dpkg</prgn>-handled files (<em>not</em>
8273 configuration files).
8277 These two styles of configuration file handling must
8278 not be mixed, for that way lies madness:
8279 <prgn>dpkg</prgn> will ask about overwriting the file
8280 every time the package is upgraded.
8285 <heading>Sharing configuration files</heading>
8288 If two or more packages use the same configuration file
8289 and it is reasonable for both to be installed at the same
8290 time, one of these packages must be defined as
8291 <em>owner</em> of the configuration file, i.e., it will be
8292 the package which handles that file as a configuration
8293 file. Other packages that use the configuration file must
8294 depend on the owning package if they require the
8295 configuration file to operate. If the other package will
8296 use the configuration file if present, but is capable of
8297 operating without it, no dependency need be declared.
8301 If it is desirable for two or more related packages to
8302 share a configuration file <em>and</em> for all of the
8303 related packages to be able to modify that configuration
8304 file, then the following should be done:
8305 <enumlist compact="compact">
8307 One of the related packages (the "owning" package)
8308 will manage the configuration file with maintainer
8309 scripts as described in the previous section.
8312 The owning package should also provide a program
8313 that the other packages may use to modify the
8317 The related packages must use the provided program
8318 to make any desired modifications to the
8319 configuration file. They should either depend on
8320 the core package to guarantee that the configuration
8321 modifier program is available or accept gracefully
8322 that they cannot modify the configuration file if it
8323 is not. (This is in addition to the fact that the
8324 configuration file may not even be present in the
8331 Sometimes it's appropriate to create a new package which
8332 provides the basic infrastructure for the other packages
8333 and which manages the shared configuration files. (The
8334 <tt>sgml-base</tt> package is a good example.)
8338 If the configuration file cannot be shared as described above,
8339 the packages must be marked as conflicting with each other.
8340 Two packages that specify the same file as
8341 a <tt>conffile</tt> must conflict. This is an instance of the
8342 general rule about not sharing files. Neither alternatives
8343 nor diversions are likely to be appropriate in this case; in
8344 particular, <prgn>dpkg</prgn> does not handle diverted
8345 <tt>conffile</tt>s well.
8349 When two packages both declare the same <tt>conffile</tt>, they
8350 may see left-over configuration files from each other even
8351 though they conflict with each other. If a user removes
8352 (without purging) one of the packages and installs the other,
8353 the new package will take over the <tt>conffile</tt> from the
8354 old package. If the file was modified by the user, it will be
8355 treated the same as any other locally
8356 modified <tt>conffile</tt> during an upgrade.
8360 The maintainer scripts must not alter a <tt>conffile</tt>
8361 of <em>any</em> package, including the one the scripts
8367 <heading>User configuration files ("dotfiles")</heading>
8370 The files in <file>/etc/skel</file> will automatically be
8371 copied into new user accounts by <prgn>adduser</prgn>.
8372 No other program should reference the files in
8373 <file>/etc/skel</file>.
8377 Therefore, if a program needs a dotfile to exist in
8378 advance in <file>$HOME</file> to work sensibly, that dotfile
8379 should be installed in <file>/etc/skel</file> and treated as a
8384 However, programs that require dotfiles in order to
8385 operate sensibly are a bad thing, unless they do create
8386 the dotfiles themselves automatically.
8390 Furthermore, programs should be configured by the Debian
8391 default installation to behave as closely to the upstream
8392 default behavior as possible.
8396 Therefore, if a program in a Debian package needs to be
8397 configured in some way in order to operate sensibly, that
8398 should be done using a site-wide configuration file placed
8399 in <file>/etc</file>. Only if the program doesn't support a
8400 site-wide default configuration and the package maintainer
8401 doesn't have time to add it may a default per-user file be
8402 placed in <file>/etc/skel</file>.
8406 <file>/etc/skel</file> should be as empty as we can make it.
8407 This is particularly true because there is no easy (or
8408 necessarily desirable) mechanism for ensuring that the
8409 appropriate dotfiles are copied into the accounts of
8410 existing users when a package is installed.
8416 <heading>Log files</heading>
8418 Log files should usually be named
8419 <file>/var/log/<var>package</var>.log</file>. If you have many
8420 log files, or need a separate directory for permission
8421 reasons (<file>/var/log</file> is writable only by
8422 <file>root</file>), you should usually create a directory named
8423 <file>/var/log/<var>package</var></file> and place your log
8428 Log files must be rotated occasionally so that they don't grow
8429 indefinitely. The best way to do this is to install a log
8430 rotation configuration file in the
8431 directory <file>/etc/logrotate.d</file>, normally
8432 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8433 the facilities provided by <prgn>logrotate</prgn>.
8436 The traditional approach to log files has been to set up
8437 <em>ad hoc</em> log rotation schemes using simple shell
8438 scripts and cron. While this approach is highly
8439 customizable, it requires quite a lot of sysadmin work.
8440 Even though the original Debian system helped a little
8441 by automatically installing a system which can be used
8442 as a template, this was deemed not enough.
8446 The use of <prgn>logrotate</prgn>, a program developed
8447 by Red Hat, is better, as it centralizes log management.
8448 It has both a configuration file
8449 (<file>/etc/logrotate.conf</file>) and a directory where
8450 packages can drop their individual log rotation
8451 configurations (<file>/etc/logrotate.d</file>).
8454 Here is a good example for a logrotate config
8455 file (for more information see <manref name="logrotate"
8457 <example compact="compact">
8458 /var/log/foo/*.log {
8464 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8468 This rotates all files under <file>/var/log/foo</file>, saves 12
8469 compressed generations, and tells the daemon to reopen its log
8470 files after the log rotation. It skips this log rotation
8471 (via <tt>missingok</tt>) if no such log file is present, which
8472 avoids errors if the package is removed but not purged.
8476 Log files should be removed when the package is
8477 purged (but not when it is only removed). This should be
8478 done by the <prgn>postrm</prgn> script when it is called
8479 with the argument <tt>purge</tt> (see <ref
8480 id="removedetails">).
8484 <sect id="permissions-owners">
8485 <heading>Permissions and owners</heading>
8488 The rules in this section are guidelines for general use.
8489 If necessary you may deviate from the details below.
8490 However, if you do so you must make sure that what is done
8491 is secure and you should try to be as consistent as possible
8492 with the rest of the system. You should probably also
8493 discuss it on <prgn>debian-devel</prgn> first.
8497 Files should be owned by <tt>root:root</tt>, and made
8498 writable only by the owner and universally readable (and
8499 executable, if appropriate), that is mode 644 or 755.
8503 Directories should be mode 755 or (for group-writability)
8504 mode 2775. The ownership of the directory should be
8505 consistent with its mode: if a directory is mode 2775, it
8506 should be owned by the group that needs write access to
8509 When a package is upgraded, and the owner or permissions
8510 of a file included in the package has changed, dpkg
8511 arranges for the ownership and permissions to be
8512 correctly set upon installation. However, this does not
8513 extend to directories; the permissions and ownership of
8514 directories already on the system does not change on
8515 install or upgrade of packages. This makes sense, since
8516 otherwise common directories like <tt>/usr</tt> would
8517 always be in flux. To correctly change permissions of a
8518 directory the package owns, explicit action is required,
8519 usually in the <tt>postinst</tt> script. Care must be
8520 taken to handle downgrades as well, in that case.
8526 Control information files should be owned by <tt>root:root</tt>
8527 and either mode 644 (for most files) or mode 755 (for
8528 executables such as <qref id="maintscripts">maintainer
8533 Setuid and setgid executables should be mode 4755 or 2755
8534 respectively, and owned by the appropriate user or group.
8535 They should not be made unreadable (modes like 4711 or
8536 2711 or even 4111); doing so achieves no extra security,
8537 because anyone can find the binary in the freely available
8538 Debian package; it is merely inconvenient. For the same
8539 reason you should not restrict read or execute permissions
8540 on non-set-id executables.
8544 Some setuid programs need to be restricted to particular
8545 sets of users, using file permissions. In this case they
8546 should be owned by the uid to which they are set-id, and by
8547 the group which should be allowed to execute them. They
8548 should have mode 4754; again there is no point in making
8549 them unreadable to those users who must not be allowed to
8554 It is possible to arrange that the system administrator can
8555 reconfigure the package to correspond to their local
8556 security policy by changing the permissions on a binary:
8557 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8558 described below.<footnote>
8559 Ordinary files installed by <prgn>dpkg</prgn> (as
8560 opposed to <tt>conffile</tt>s and other similar objects)
8561 normally have their permissions reset to the distributed
8562 permissions when the package is reinstalled. However,
8563 the use of <prgn>dpkg-statoverride</prgn> overrides this
8566 Another method you should consider is to create a group for
8567 people allowed to use the program(s) and make any setuid
8568 executables executable only by that group.
8572 If you need to create a new user or group for your package
8573 there are two possibilities. Firstly, you may need to
8574 make some files in the binary package be owned by this
8575 user or group, or you may need to compile the user or
8576 group id (rather than just the name) into the binary
8577 (though this latter should be avoided if possible, as in
8578 this case you need a statically allocated id).</p>
8581 If you need a statically allocated id, you must ask for a
8582 user or group id from the <tt>base-passwd</tt> maintainer,
8583 and must not release the package until you have been
8584 allocated one. Once you have been allocated one you must
8585 either make the package depend on a version of the
8586 <tt>base-passwd</tt> package with the id present in
8587 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8588 your package to create the user or group itself with the
8589 correct id (using <tt>adduser</tt>) in its
8590 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8591 the <prgn>postinst</prgn> is to be preferred if it is
8592 possible, otherwise a pre-dependency will be needed on the
8593 <tt>adduser</tt> package.)
8597 On the other hand, the program might be able to determine
8598 the uid or gid from the user or group name at runtime, so
8599 that a dynamically allocated id can be used. In this case
8600 you should choose an appropriate user or group name,
8601 discussing this on <prgn>debian-devel</prgn> and checking
8602 with the <package/base-passwd/ maintainer that it is unique and that
8603 they do not wish you to use a statically allocated id
8604 instead. When this has been checked you must arrange for
8605 your package to create the user or group if necessary using
8606 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8607 <prgn>postinst</prgn> script (again, the latter is to be
8608 preferred if it is possible).
8612 Note that changing the numeric value of an id associated
8613 with a name is very difficult, and involves searching the
8614 file system for all appropriate files. You need to think
8615 carefully whether a static or dynamic id is required, since
8616 changing your mind later will cause problems.
8619 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8621 This section is not intended as policy, but as a
8622 description of the use of <prgn>dpkg-statoverride</prgn>.
8626 If a system administrator wishes to have a file (or
8627 directory or other such thing) installed with owner and
8628 permissions different from those in the distributed Debian
8629 package, they can use the <prgn>dpkg-statoverride</prgn>
8630 program to instruct <prgn>dpkg</prgn> to use the different
8631 settings every time the file is installed. Thus the
8632 package maintainer should distribute the files with their
8633 normal permissions, and leave it for the system
8634 administrator to make any desired changes. For example, a
8635 daemon which is normally required to be setuid root, but
8636 in certain situations could be used without being setuid,
8637 should be installed setuid in the <tt>.deb</tt>. Then the
8638 local system administrator can change this if they wish.
8639 If there are two standard ways of doing it, the package
8640 maintainer can use <tt>debconf</tt> to find out the
8641 preference, and call <prgn>dpkg-statoverride</prgn> in the
8642 maintainer script if necessary to accommodate the system
8643 administrator's choice. Care must be taken during
8644 upgrades to not override an existing setting.
8648 Given the above, <prgn>dpkg-statoverride</prgn> is
8649 essentially a tool for system administrators and would not
8650 normally be needed in the maintainer scripts. There is
8651 one type of situation, though, where calls to
8652 <prgn>dpkg-statoverride</prgn> would be needed in the
8653 maintainer scripts, and that involves packages which use
8654 dynamically allocated user or group ids. In such a
8655 situation, something like the following idiom can be very
8656 helpful in the package's <prgn>postinst</prgn>, where
8657 <tt>sysuser</tt> is a dynamically allocated id:
8659 for i in /usr/bin/foo /usr/sbin/bar
8661 # only do something when no setting exists
8662 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8664 #include: debconf processing, question about foo and bar
8665 if [ "$RET" = "true" ] ; then
8666 dpkg-statoverride --update --add sysuser root 4755 $i
8671 The corresponding code to remove the override when the package
8674 for i in /usr/bin/foo /usr/sbin/bar
8676 if dpkg-statoverride --list $i >/dev/null 2>&1
8678 dpkg-statoverride --remove $i
8688 <chapt id="customized-programs">
8689 <heading>Customized programs</heading>
8691 <sect id="arch-spec">
8692 <heading>Architecture specification strings</heading>
8695 If a program needs to specify an <em>architecture specification
8696 string</em> in some place, it should select one of the strings
8697 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8698 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8699 part is sometimes elided, as when the OS is Linux.
8703 Note that we don't want to use
8704 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8705 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8706 since this would make our programs incompatible with other
8707 Linux distributions. We also don't use something like
8708 <tt><var>arch</var>-unknown-linux</tt>, since the
8709 <tt>unknown</tt> does not look very good.
8712 <sect1 id="arch-wildcard-spec">
8713 <heading>Architecture wildcards</heading>
8716 A package may specify an architecture wildcard. Architecture
8717 wildcards are in the format <tt>any</tt> (which matches every
8718 architecture), <tt><var>os</var></tt>-any, or
8719 any-<tt><var>cpu</var></tt>. <footnote>
8720 Internally, the package system normalizes the GNU triplets
8721 and the Debian arches into Debian arch triplets (which are
8722 kind of inverted GNU triplets), with the first component of
8723 the triplet representing the libc and ABI in use, and then
8724 does matching against those triplets. However, such
8725 triplets are an internal implementation detail that should
8726 not be used by packages directly. The libc and ABI portion
8727 is handled internally by the package system based on
8728 the <var>os</var> and <var>cpu</var>.
8735 <heading>Daemons</heading>
8738 The configuration files <file>/etc/services</file>,
8739 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8740 by the <prgn>netbase</prgn> package and must not be modified
8745 If a package requires a new entry in one of these files, the
8746 maintainer should get in contact with the
8747 <prgn>netbase</prgn> maintainer, who will add the entries
8748 and release a new version of the <prgn>netbase</prgn>
8753 The configuration file <file>/etc/inetd.conf</file> must not be
8754 modified by the package's scripts except via the
8755 <prgn>update-inetd</prgn> script or the
8756 <file>DebianNet.pm</file> Perl module. See their documentation
8757 for details on how to add entries.
8761 If a package wants to install an example entry into
8762 <file>/etc/inetd.conf</file>, the entry must be preceded with
8763 exactly one hash character (<tt>#</tt>). Such lines are
8764 treated as "commented out by user" by the
8765 <prgn>update-inetd</prgn> script and are not changed or
8766 activated during package updates.
8771 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8775 Some programs need to create pseudo-ttys. This should be done
8776 using Unix98 ptys if the C library supports it. The resulting
8777 program must not be installed setuid root, unless that
8778 is required for other functionality.
8782 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8783 <file>/var/log/lastlog</file> must be installed writable by
8784 group <tt>utmp</tt>. Programs which need to modify those
8785 files must be installed setgid <tt>utmp</tt>.
8790 <heading>Editors and pagers</heading>
8793 Some programs have the ability to launch an editor or pager
8794 program to edit or display a text document. Since there are
8795 lots of different editors and pagers available in the Debian
8796 distribution, the system administrator and each user should
8797 have the possibility to choose their preferred editor and
8802 In addition, every program should choose a good default
8803 editor/pager if none is selected by the user or system
8808 Thus, every program that launches an editor or pager must
8809 use the EDITOR or PAGER environment variable to determine
8810 the editor or pager the user wishes to use. If these
8811 variables are not set, the programs <file>/usr/bin/editor</file>
8812 and <file>/usr/bin/pager</file> should be used, respectively.
8816 These two files are managed through the <prgn>dpkg</prgn>
8817 "alternatives" mechanism. Every package providing an editor or
8818 pager must call the <prgn>update-alternatives</prgn> script to
8819 register as an alternative for <file>/usr/bin/editor</file>
8820 or <file>/usr/bin/pager</file> as appropriate. The alternative
8821 should have a slave alternative
8822 for <file>/usr/share/man/man1/editor.1.gz</file>
8823 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8824 corresponding manual page.
8828 If it is very hard to adapt a program to make use of the
8829 EDITOR or PAGER variables, that program may be configured to
8830 use <file>/usr/bin/sensible-editor</file> and
8831 <file>/usr/bin/sensible-pager</file> as the editor or pager
8832 program respectively. These are two scripts provided in the
8833 <package>sensible-utils</package> package that check the EDITOR
8834 and PAGER variables and launch the appropriate program, and fall
8835 back to <file>/usr/bin/editor</file>
8836 and <file>/usr/bin/pager</file> if the variable is not set.
8840 A program may also use the VISUAL environment variable to
8841 determine the user's choice of editor. If it exists, it
8842 should take precedence over EDITOR. This is in fact what
8843 <file>/usr/bin/sensible-editor</file> does.
8847 It is not required for a package to depend on
8848 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8849 package to provide such virtual packages.<footnote>
8850 The Debian base system already provides an editor and a
8856 <sect id="web-appl">
8857 <heading>Web servers and applications</heading>
8860 This section describes the locations and URLs that should
8861 be used by all web servers and web applications in the
8868 Cgi-bin executable files are installed in the
8870 <example compact="compact">
8871 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8873 or a subdirectory of that directory, and should be
8875 <example compact="compact">
8876 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8878 (possibly with a subdirectory name
8879 before <var>cgi-bin-name</var>).
8883 <p>Access to HTML documents</p>
8886 HTML documents for a package are stored in
8887 <file>/usr/share/doc/<var>package</var></file>
8888 and can be referred to as
8889 <example compact="compact">
8890 http://localhost/doc/<var>package</var>/<var>filename</var>
8895 The web server should restrict access to the document
8896 tree so that only clients on the same host can read
8897 the documents. If the web server does not support such
8898 access controls, then it should not provide access at
8899 all, or ask about providing access during installation.
8904 <p>Access to images</p>
8906 It is recommended that images for a package be stored
8907 in <tt>/usr/share/images/<var>package</var></tt> and
8908 may be referred to through an alias <tt>/images/</tt>
8911 http://localhost/images/<package>/<filename>
8918 <p>Web Document Root</p>
8921 Web Applications should try to avoid storing files in
8922 the Web Document Root. Instead they should use the
8923 /usr/share/doc/<var>package</var> directory for
8924 documents and register the Web Application via the
8925 <package>doc-base</package> package. If access to the
8926 web document root is unavoidable then use
8927 <example compact="compact">
8930 as the Document Root. This might be just a symbolic
8931 link to the location where the system administrator
8932 has put the real document root.
8935 <item><p>Providing httpd and/or httpd-cgi</p>
8937 All web servers should provide the virtual package
8938 <tt>httpd</tt>. If a web server has CGI support it should
8939 provide <tt>httpd-cgi</tt> additionally.
8942 All web applications which do not contain CGI scripts should
8943 depend on <tt>httpd</tt>, all those web applications which
8944 <tt>do</tt> contain CGI scripts, should depend on
8952 <sect id="mail-transport-agents">
8953 <heading>Mail transport, delivery and user agents</heading>
8956 Debian packages which process electronic mail, whether mail
8957 user agents (MUAs) or mail transport agents (MTAs), must
8958 ensure that they are compatible with the configuration
8959 decisions below. Failure to do this may result in lost
8960 mail, broken <tt>From:</tt> lines, and other serious brain
8965 The mail spool is <file>/var/mail</file> and the interface to
8966 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8967 the FHS). On older systems, the mail spool may be
8968 physically located in <file>/var/spool/mail</file>, but all
8969 access to the mail spool should be via the
8970 <file>/var/mail</file> symlink. The mail spool is part of the
8971 base system and not part of the MTA package.
8975 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8976 programs (such as IMAP daemons) must lock the mailbox in an
8977 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8978 be combined with dot locking. To avoid deadlocks, a program
8979 should use <tt>fcntl()</tt> first and dot locking after
8980 this, or alternatively implement the two locking methods in
8981 a non blocking way<footnote>
8982 If it is not possible to establish both locks, the
8983 system shouldn't wait for the second lock to be
8984 established, but remove the first lock, wait a (random)
8985 time, and start over locking again.
8986 </footnote>. Using the functions <tt>maillock</tt> and
8987 <tt>mailunlock</tt> provided by the
8988 <tt>liblockfile*</tt><footnote>
8989 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8990 to use these functions.
8991 </footnote> packages is the recommended way to realize this.
8995 Mailboxes are generally either mode 600 and owned by
8996 <var>user</var> or mode 660 and owned by
8997 <tt><var>user</var>:mail</tt><footnote>
8998 There are two traditional permission schemes for mail spools:
8999 mode 600 with all mail delivery done by processes running as
9000 the destination user, or mode 660 and owned by group mail with
9001 mail delivery done by a process running as a system user in
9002 group mail. Historically, Debian required mode 660 mail
9003 spools to enable the latter model, but that model has become
9004 increasingly uncommon and the principle of least privilege
9005 indicates that mail systems that use the first model should
9006 use permissions of 600. If delivery to programs is permitted,
9007 it's easier to keep the mail system secure if the delivery
9008 agent runs as the destination user. Debian Policy therefore
9009 permits either scheme.
9010 </footnote>. The local system administrator may choose a
9011 different permission scheme; packages should not make
9012 assumptions about the permission and ownership of mailboxes
9013 unless required (such as when creating a new mailbox). A MUA
9014 may remove a mailbox (unless it has nonstandard permissions) in
9015 which case the MTA or another MUA must recreate it if needed.
9019 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9020 be setgid mail to do the locking mentioned above (and
9021 must obviously avoid accessing other users' mailboxes
9022 using this privilege).</p>
9025 <file>/etc/aliases</file> is the source file for the system mail
9026 aliases (e.g., postmaster, usenet, etc.), it is the one
9027 which the sysadmin and <prgn>postinst</prgn> scripts may
9028 edit. After <file>/etc/aliases</file> is edited the program or
9029 human editing it must call <prgn>newaliases</prgn>. All MTA
9030 packages must come with a <prgn>newaliases</prgn> program,
9031 even if it does nothing, but older MTA packages did not do
9032 this so programs should not fail if <prgn>newaliases</prgn>
9033 cannot be found. Note that because of this, all MTA
9034 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9035 <tt>Replaces: mail-transport-agent</tt> control fields.
9039 The convention of writing <tt>forward to
9040 <var>address</var></tt> in the mailbox itself is not
9041 supported. Use a <tt>.forward</tt> file instead.</p>
9044 The <prgn>rmail</prgn> program used by UUCP
9045 for incoming mail should be <file>/usr/sbin/rmail</file>.
9046 Likewise, <prgn>rsmtp</prgn>, for receiving
9047 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9051 If your package needs to know what hostname to use on (for
9052 example) outgoing news and mail messages which are generated
9053 locally, you should use the file <file>/etc/mailname</file>. It
9054 will contain the portion after the username and <tt>@</tt>
9055 (at) sign for email addresses of users on the machine
9056 (followed by a newline).
9060 Such a package should check for the existence of this file
9061 when it is being configured. If it exists, it should be
9062 used without comment, although an MTA's configuration script
9063 may wish to prompt the user even if it finds that this file
9064 exists. If the file does not exist, the package should
9065 prompt the user for the value (preferably using
9066 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9067 as well as using it in the package's configuration. The
9068 prompt should make it clear that the name will not just be
9069 used by that package. For example, in this situation the
9070 <tt>inn</tt> package could say something like:
9071 <example compact="compact">
9072 Please enter the "mail name" of your system. This is the
9073 hostname portion of the address to be shown on outgoing
9074 news and mail messages. The default is
9075 <var>syshostname</var>, your system's host name. Mail
9076 name ["<var>syshostname</var>"]:
9078 where <var>syshostname</var> is the output of <tt>hostname
9084 <heading>News system configuration</heading>
9087 All the configuration files related to the NNTP (news)
9088 servers and clients should be located under
9089 <file>/etc/news</file>.</p>
9092 There are some configuration issues that apply to a number
9093 of news clients and server packages on the machine. These
9097 <tag><file>/etc/news/organization</file></tag>
9099 A string which should appear as the
9100 organization header for all messages posted
9101 by NNTP clients on the machine
9104 <tag><file>/etc/news/server</file></tag>
9106 Contains the FQDN of the upstream NNTP
9107 server, or localhost if the local machine is
9112 Other global files may be added as required for cross-package news
9119 <heading>Programs for the X Window System</heading>
9122 <heading>Providing X support and package priorities</heading>
9125 Programs that can be configured with support for the X
9126 Window System must be configured to do so and must declare
9127 any package dependencies necessary to satisfy their
9128 runtime requirements when using the X Window System. If
9129 such a package is of higher priority than the X packages
9130 on which it depends, it is required that either the
9131 X-specific components be split into a separate package, or
9132 that an alternative version of the package, which includes
9133 X support, be provided, or that the package's priority be
9139 <heading>Packages providing an X server</heading>
9142 Packages that provide an X server that, directly or
9143 indirectly, communicates with real input and display
9144 hardware should declare in their <tt>Provides</tt> control
9145 field that they provide the virtual
9146 package <tt>xserver</tt>.<footnote>
9147 This implements current practice, and provides an
9148 actual policy for usage of the <tt>xserver</tt>
9149 virtual package which appears in the virtual packages
9150 list. In a nutshell, X servers that interface
9151 directly with the display and input hardware or via
9152 another subsystem (e.g., GGI) should provide
9153 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9154 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9160 <heading>Packages providing a terminal emulator</heading>
9163 Packages that provide a terminal emulator for the X Window
9164 System which meet the criteria listed below should declare in
9165 their <tt>Provides</tt> control field that they provide the
9166 virtual package <tt>x-terminal-emulator</tt>. They should
9167 also register themselves as an alternative for
9168 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9169 20. That alternative should have a slave alternative
9170 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9171 pointing to the corresponding manual page.
9175 To be an <tt>x-terminal-emulator</tt>, a program must:
9176 <list compact="compact">
9178 Be able to emulate a DEC VT100 terminal, or a
9179 compatible terminal.
9183 Support the command-line option <tt>-e
9184 <var>command</var></tt>, which creates a new
9185 terminal window<footnote>
9186 "New terminal window" does not necessarily mean
9187 a new top-level X window directly parented by
9188 the window manager; it could, if the terminal
9189 emulator application were so coded, be a new
9190 "view" in a multiple-document interface (MDI).
9192 and runs the specified <var>command</var>,
9193 interpreting the entirety of the rest of the command
9194 line as a command to pass straight to exec, in the
9195 manner that <tt>xterm</tt> does.
9199 Support the command-line option <tt>-T
9200 <var>title</var></tt>, which creates a new terminal
9201 window with the window title <var>title</var>.
9208 <heading>Packages providing a window manager</heading>
9211 Packages that provide a window manager should declare in
9212 their <tt>Provides</tt> control field that they provide the
9213 virtual package <tt>x-window-manager</tt>. They should also
9214 register themselves as an alternative for
9215 <file>/usr/bin/x-window-manager</file>, with a priority
9216 calculated as follows:
9217 <list compact="compact">
9219 Start with a priority of 20.
9223 If the window manager supports the Debian menu
9224 system, add 20 points if this support is available
9225 in the package's default configuration (i.e., no
9226 configuration files belonging to the system or user
9227 have to be edited to activate the feature); if
9228 configuration files must be modified, add only 10
9234 If the window manager complies with <url
9235 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9236 name="The Window Manager Specification Project">,
9237 written by the <url id="http://www.freedesktop.org/wiki/"
9238 name="Free Desktop Group">, add 40 points.
9242 If the window manager permits the X session to be
9243 restarted using a <em>different</em> window manager
9244 (without killing the X server) in its default
9245 configuration, add 10 points; otherwise add none.
9248 That alternative should have a slave alternative
9249 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9250 pointing to the corresponding manual page.
9255 <heading>Packages providing fonts</heading>
9258 Packages that provide fonts for the X Window
9260 For the purposes of Debian Policy, a "font for the X
9261 Window System" is one which is accessed via X protocol
9262 requests. Fonts for the Linux console, for PostScript
9263 renderer, or any other purpose, do not fit this
9264 definition. Any tool which makes such fonts available
9265 to the X Window System, however, must abide by this
9268 must do a number of things to ensure that they are both
9269 available without modification of the X or font server
9270 configuration, and that they do not corrupt files used by
9271 other font packages to register information about
9275 Fonts of any type supported by the X Window System
9276 must be in a separate binary package from any
9277 executables, libraries, or documentation (except
9278 that specific to the fonts shipped, such as their
9279 license information). If one or more of the fonts
9280 so packaged are necessary for proper operation of
9281 the package with which they are associated the font
9282 package may be Recommended; if the fonts merely
9283 provide an enhancement, a Suggests relationship may
9284 be used. Packages must not Depend on font
9286 This is because the X server may retrieve fonts
9287 from the local file system or over the network
9288 from an X font server; the Debian package system
9289 is empowered to deal only with the local
9295 BDF fonts must be converted to PCF fonts with the
9296 <prgn>bdftopcf</prgn> utility (available in the
9297 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9298 placed in a directory that corresponds to their
9300 <list compact="compact">
9302 100 dpi fonts must be placed in
9303 <file>/usr/share/fonts/X11/100dpi/</file>.
9307 75 dpi fonts must be placed in
9308 <file>/usr/share/fonts/X11/75dpi/</file>.
9312 Character-cell fonts, cursor fonts, and other
9313 low-resolution fonts must be placed in
9314 <file>/usr/share/fonts/X11/misc/</file>.
9320 Type 1 fonts must be placed in
9321 <file>/usr/share/fonts/X11/Type1/</file>. If font
9322 metric files are available, they must be placed here
9327 Subdirectories of <file>/usr/share/fonts/X11/</file>
9328 other than those listed above must be neither
9329 created nor used. (The <file>PEX</file>, <file>CID</file>,
9330 <file>Speedo</file>, and <file>cyrillic</file> directories
9331 are excepted for historical reasons, but installation of
9332 files into these directories remains discouraged.)
9336 Font packages may, instead of placing files directly
9337 in the X font directories listed above, provide
9338 symbolic links in that font directory pointing to
9339 the files' actual location in the filesystem. Such
9340 a location must comply with the FHS.
9344 Font packages should not contain both 75dpi and
9345 100dpi versions of a font. If both are available,
9346 they should be provided in separate binary packages
9347 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9348 the names of the packages containing the
9349 corresponding fonts.
9353 Fonts destined for the <file>misc</file> subdirectory
9354 should not be included in the same package as 75dpi
9355 or 100dpi fonts; instead, they should be provided in
9356 a separate package with <tt>-misc</tt> appended to
9361 Font packages must not provide the files
9362 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9363 <file>fonts.scale</file> in a font directory:
9366 <file>fonts.dir</file> files must not be provided at all.
9370 <file>fonts.alias</file> and <file>fonts.scale</file>
9371 files, if needed, should be provided in the
9373 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9374 where <var>fontdir</var> is the name of the
9376 <file>/usr/share/fonts/X11/</file> where the
9377 package's corresponding fonts are stored
9378 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9379 <var>package</var> is the name of the package
9380 that provides these fonts, and
9381 <var>extension</var> is either <tt>scale</tt>
9382 or <tt>alias</tt>, whichever corresponds to
9389 Font packages must declare a dependency on
9390 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9391 or <tt>Pre-Depends</tt> control field.
9395 Font packages that provide one or more
9396 <file>fonts.scale</file> files as described above must
9397 invoke <prgn>update-fonts-scale</prgn> on each
9398 directory into which they installed fonts
9399 <em>before</em> invoking
9400 <prgn>update-fonts-dir</prgn> on that directory.
9401 This invocation must occur in both the
9402 <prgn>postinst</prgn> (for all arguments) and
9403 <prgn>postrm</prgn> (for all arguments except
9404 <tt>upgrade</tt>) scripts.
9408 Font packages that provide one or more
9409 <file>fonts.alias</file> files as described above must
9410 invoke <prgn>update-fonts-alias</prgn> on each
9411 directory into which they installed fonts. This
9412 invocation must occur in both the
9413 <prgn>postinst</prgn> (for all arguments) and
9414 <prgn>postrm</prgn> (for all arguments except
9415 <tt>upgrade</tt>) scripts.
9419 Font packages must invoke
9420 <prgn>update-fonts-dir</prgn> on each directory into
9421 which they installed fonts. This invocation must
9422 occur in both the <prgn>postinst</prgn> (for all
9423 arguments) and <prgn>postrm</prgn> (for all
9424 arguments except <tt>upgrade</tt>) scripts.
9428 Font packages must not provide alias names for the
9429 fonts they include which collide with alias names
9430 already in use by fonts already packaged.
9434 Font packages must not provide fonts with the same
9435 XLFD registry name as another font already packaged.
9441 <sect1 id="appdefaults">
9442 <heading>Application defaults files</heading>
9445 Application defaults files must be installed in the
9446 directory <file>/etc/X11/app-defaults/</file> (use of a
9447 localized subdirectory of <file>/etc/X11/</file> as described
9448 in the <em>X Toolkit Intrinsics - C Language
9449 Interface</em> manual is also permitted). They must be
9450 registered as <tt>conffile</tt>s or handled as
9451 configuration files.
9455 Customization of programs' X resources may also be
9456 supported with the provision of a file with the same name
9457 as that of the package placed in
9458 the <file>/etc/X11/Xresources/</file> directory, which
9459 must be registered as a <tt>conffile</tt> or handled as a
9460 configuration file.<footnote>
9461 Note that this mechanism is not the same as using
9462 app-defaults; app-defaults are tied to the client
9463 binary on the local file system, whereas X resources
9464 are stored in the X server and affect all connecting
9471 <heading>Installation directory issues</heading>
9474 Historically, packages using the X Window System used a
9475 separate set of installation directories from other packages.
9476 This practice has been discontinued and packages using the X
9477 Window System should now generally be installed in the same
9478 directories as any other package. Specifically, packages must
9479 not install files under the <file>/usr/X11R6/</file> directory
9480 and the <file>/usr/X11R6/</file> directory hierarchy should be
9481 regarded as obsolete.
9485 Include files previously installed under
9486 <file>/usr/X11R6/include/X11/</file> should be installed into
9487 <file>/usr/include/X11/</file>. For files previously
9488 installed into subdirectories of
9489 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9490 determine if subdirectories of <file>/usr/lib/</file> and
9491 <file>/usr/share/</file> can be used. If not, a subdirectory
9492 of <file>/usr/lib/X11/</file> should be used.
9496 Configuration files for window, display, or session managers
9497 or other applications that are tightly integrated with the X
9498 Window System may be placed in a subdirectory
9499 of <file>/etc/X11/</file> corresponding to the package name.
9500 Other X Window System applications should use
9501 the <file>/etc/</file> directory unless otherwise mandated by
9502 policy (such as for <ref id="appdefaults">).
9508 <heading>Perl programs and modules</heading>
9511 Perl programs and modules should follow the current Perl policy.
9515 The Perl policy can be found in the <tt>perl-policy</tt>
9516 files in the <tt>debian-policy</tt> package.
9517 It is also available from the Debian web mirrors at
9518 <tt><url name="/doc/packaging-manuals/perl-policy/"
9519 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9524 <heading>Emacs lisp programs</heading>
9527 Please refer to the "Debian Emacs Policy" for details of how to
9528 package emacs lisp programs.
9532 The Emacs policy is available in
9533 <file>debian-emacs-policy.gz</file> of the
9534 <package>emacsen-common</package> package.
9535 It is also available from the Debian web mirrors at
9536 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9537 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9542 <heading>Games</heading>
9545 The permissions on <file>/var/games</file> are mode 755, owner
9546 <tt>root</tt> and group <tt>root</tt>.
9550 Each game decides on its own security policy.</p>
9553 Games which require protected, privileged access to
9554 high-score files, saved games, etc., may be made
9555 set-<em>group</em>-id (mode 2755) and owned by
9556 <tt>root:games</tt>, and use files and directories with
9557 appropriate permissions (770 <tt>root:games</tt>, for
9558 example). They must not be made
9559 set-<em>user</em>-id, as this causes security problems. (If
9560 an attacker can subvert any set-user-id game they can
9561 overwrite the executable of any other, causing other players
9562 of these games to run a Trojan horse program. With a
9563 set-group-id game the attacker only gets access to less
9564 important game data, and if they can get at the other
9565 players' accounts at all it will take considerably more
9569 Some packages, for example some fortune cookie programs, are
9570 configured by the upstream authors to install with their
9571 data files or other static information made unreadable so
9572 that they can only be accessed through set-id programs
9573 provided. You should not do this in a Debian package: anyone can
9574 download the <file>.deb</file> file and read the data from it,
9575 so there is no point making the files unreadable. Not
9576 making the files unreadable also means that you don't have
9577 to make so many programs set-id, which reduces the risk of a
9581 As described in the FHS, binaries of games should be
9582 installed in the directory <file>/usr/games</file>. This also
9583 applies to games that use the X Window System. Manual pages
9584 for games (X and non-X games) should be installed in
9585 <file>/usr/share/man/man6</file>.</p>
9591 <heading>Documentation</heading>
9594 <heading>Manual pages</heading>
9597 You should install manual pages in <prgn>nroff</prgn> source
9598 form, in appropriate places under <file>/usr/share/man</file>.
9599 You should only use sections 1 to 9 (see the FHS for more
9600 details). You must not install a pre-formatted "cat page".
9604 Each program, utility, and function should have an
9605 associated manual page included in the same package. It is
9606 suggested that all configuration files also have a manual
9607 page included as well. Manual pages for protocols and other
9608 auxiliary things are optional.
9612 If no manual page is available, this is considered as a bug
9613 and should be reported to the Debian Bug Tracking System (the
9614 maintainer of the package is allowed to write this bug report
9615 themselves, if they so desire). Do not close the bug report
9616 until a proper man page is available.<footnote>
9617 It is not very hard to write a man page. See the
9618 <url id="http://www.schweikhardt.net/man_page_howto.html"
9619 name="Man-Page-HOWTO">,
9620 <manref name="man" section="7">, the examples created
9621 by <prgn>dh_make</prgn>, the helper
9622 program <prgn>help2man</prgn>, or the
9623 directory <file>/usr/share/doc/man-db/examples</file>.
9628 You may forward a complaint about a missing man page to the
9629 upstream authors, and mark the bug as forwarded in the
9630 Debian bug tracking system. Even though the GNU Project do
9631 not in general consider the lack of a man page to be a bug,
9632 we do; if they tell you that they don't consider it a bug
9633 you should leave the bug in our bug tracking system open
9638 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9642 If one man page needs to be accessible via several names it
9643 is better to use a symbolic link than the <file>.so</file>
9644 feature, but there is no need to fiddle with the relevant
9645 parts of the upstream source to change from <file>.so</file> to
9646 symlinks: don't do it unless it's easy. You should not
9647 create hard links in the manual page directories, nor put
9648 absolute filenames in <file>.so</file> directives. The filename
9649 in a <file>.so</file> in a man page should be relative to the
9650 base of the man page tree (usually
9651 <file>/usr/share/man</file>). If you do not create any links
9652 (whether symlinks, hard links, or <tt>.so</tt> directives)
9653 in the file system to the alternate names of the man page,
9654 then you should not rely on <prgn>man</prgn> finding your
9655 man page under those names based solely on the information in
9656 the man page's header.<footnote>
9657 Supporting this in <prgn>man</prgn> often requires
9658 unreasonable processing time to find a manual page or to
9659 report that none exists, and moves knowledge into man's
9660 database that would be better left in the file system.
9661 This support is therefore deprecated and will cease to
9662 be present in the future.
9667 Manual pages in locale-specific subdirectories of
9668 <file>/usr/share/man</file> should use either UTF-8 or the usual
9669 legacy encoding for that language (normally the one corresponding
9670 to the shortest relevant locale name in
9671 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9672 <file>/usr/share/man/fr</file> should use either UTF-8 or
9673 ISO-8859-1.<footnote>
9674 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9675 use. In future, all manual pages will be required to use
9681 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9682 included in the subdirectory name unless it indicates a
9683 significant difference in the language, as this excludes
9684 speakers of the language in other countries.<footnote>
9685 At the time of writing, Chinese and Portuguese are the main
9686 languages with such differences, so <file>pt_BR</file>,
9687 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9692 If a localized version of a manual page is provided, it should
9693 either be up-to-date or it should be obvious to the reader that
9694 it is outdated and the original manual page should be used
9695 instead. This can be done either by a note at the beginning of
9696 the manual page or by showing the missing or changed portions in
9697 the original language instead of the target language.
9702 <heading>Info documents</heading>
9705 Info documents should be installed in <file>/usr/share/info</file>.
9706 They should be compressed with <tt>gzip -9</tt>.
9710 The <prgn>install-info</prgn> program maintains a directory of
9711 installed info documents in <file>/usr/share/info/dir</file> for
9712 the use of info readers.<footnote>
9713 It was previously necessary for packages installing info
9714 documents to run <prgn>install-info</prgn> from maintainer
9715 scripts. This is no longer necessary. The installation
9716 system now uses dpkg triggers.
9718 This file must not be included in packages. Packages containing
9719 info documents should depend on <tt>dpkg (>= 1.15.4) |
9720 install-info</tt> to ensure that the directory file is properly
9721 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9726 Info documents should contain section and directory entry
9727 information in the document for the use
9728 of <prgn>install-info</prgn>. The section should be specified
9729 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9730 space and the section of this info page. The directory entry or
9731 entries should be included between
9732 a <tt>START-INFO-DIR-ENTRY</tt> line and
9733 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9735 INFO-DIR-SECTION Individual utilities
9736 START-INFO-DIR-ENTRY
9737 * example: (example). An example info directory entry.
9740 To determine which section to use, you should look
9741 at <file>/usr/share/info/dir</file> on your system and choose
9742 the most relevant (or create a new section if none of the
9743 current sections are relevant).<footnote>
9744 Normally, info documents are generated from Texinfo source.
9745 To include this information in the generated info document, if
9746 it is absent, add commands like:
9748 @dircategory Individual utilities
9750 * example: (example). An example info directory entry.
9753 to the Texinfo source of the document and ensure that the info
9754 documents are rebuilt from source during the package build.
9760 <heading>Additional documentation</heading>
9763 Any additional documentation that comes with the package may
9764 be installed at the discretion of the package maintainer.
9765 Plain text documentation should be installed in the directory
9766 <file>/usr/share/doc/<var>package</var></file>, where
9767 <var>package</var> is the name of the package, and
9768 compressed with <tt>gzip -9</tt> unless it is small.
9772 If a package comes with large amounts of documentation which
9773 many users of the package will not require you should create
9774 a separate binary package to contain it, so that it does not
9775 take up disk space on the machines of users who do not need
9776 or want it installed.</p>
9779 It is often a good idea to put text information files
9780 (<file>README</file>s, changelogs, and so forth) that come with
9781 the source package in <file>/usr/share/doc/<var>package</var></file>
9782 in the binary package. However, you don't need to install
9783 the instructions for building and installing the package, of
9787 Packages must not require the existence of any files in
9788 <file>/usr/share/doc/</file> in order to function
9790 The system administrator should be able to
9791 delete files in <file>/usr/share/doc/</file> without causing
9792 any programs to break.
9794 Any files that are referenced by programs but are also
9795 useful as stand alone documentation should be installed under
9796 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9797 <file>/usr/share/doc/<var>package</var></file>.
9801 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9802 link to another directory in <file>/usr/share/doc</file> only if
9803 the two packages both come from the same source and the
9804 first package Depends on the second.<footnote>
9806 Please note that this does not override the section on
9807 changelog files below, so the file
9808 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9809 must refer to the changelog for the current version of
9810 <var>package</var> in question. In practice, this means
9811 that the sources of the target and the destination of the
9812 symlink must be the same (same source package and
9819 Former Debian releases placed all additional documentation
9820 in <file>/usr/doc/<var>package</var></file>. This has been
9821 changed to <file>/usr/share/doc/<var>package</var></file>,
9822 and packages must not put documentation in the directory
9823 <file>/usr/doc/<var>package</var></file>. <footnote>
9824 At this phase of the transition, we no longer require a
9825 symbolic link in <file>/usr/doc/</file>. At a later point,
9826 policy shall change to make the symbolic links a bug.
9832 <heading>Preferred documentation formats</heading>
9835 The unification of Debian documentation is being carried out
9839 If your package comes with extensive documentation in a
9840 markup format that can be converted to various other formats
9841 you should if possible ship HTML versions in a binary
9842 package, in the directory
9843 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9844 its subdirectories.<footnote>
9845 The rationale: The important thing here is that HTML
9846 docs should be available in <em>some</em> package, not
9847 necessarily in the main binary package.
9852 Other formats such as PostScript may be provided at the
9853 package maintainer's discretion.
9857 <sect id="copyrightfile">
9858 <heading>Copyright information</heading>
9861 Every package must be accompanied by a verbatim copy of its
9862 copyright information and distribution license in the file
9863 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9864 file must neither be compressed nor be a symbolic link.
9868 In addition, the copyright file must say where the upstream
9869 sources (if any) were obtained, and should name the original
9874 Packages in the <em>contrib</em> or <em>non-free</em> archive
9875 areas should state in the copyright file that the package is not
9876 part of the Debian distribution and briefly explain why.
9880 A copy of the file which will be installed in
9881 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9882 be in <file>debian/copyright</file> in the source package.
9886 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9887 link to another directory in <file>/usr/share/doc</file> only if
9888 the two packages both come from the same source and the
9889 first package Depends on the second. These rules are important
9890 because <file>copyright</file> files must be extractable by
9895 Packages distributed under the Apache license (version 2.0), the
9896 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9897 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9898 1.3) should refer to the corresponding files
9899 under <file>/usr/share/common-licenses</file>,<footnote>
9902 <file>/usr/share/common-licenses/Apache-2.0</file>,
9903 <file>/usr/share/common-licenses/Artistic</file>,
9904 <file>/usr/share/common-licenses/GPL-1</file>,
9905 <file>/usr/share/common-licenses/GPL-2</file>,
9906 <file>/usr/share/common-licenses/GPL-3</file>,
9907 <file>/usr/share/common-licenses/LGPL-2</file>,
9908 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9909 <file>/usr/share/common-licenses/LGPL-3</file>,
9910 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9911 <file>/usr/share/common-licenses/GFDL-1.3</file>
9912 respectively. The University of California BSD license is
9913 also included in <package>base-files</package> as
9914 <file>/usr/share/common-licenses/BSD</file>, but given the
9915 brevity of this license, its specificity to code whose
9916 copyright is held by the Regents of the University of
9917 California, and the frequency of minor wording changes, its
9918 text should be included in the copyright file rather than
9919 referencing this file.
9921 </footnote> rather than quoting them in the copyright
9926 You should not use the copyright file as a general <file>README</file>
9927 file. If your package has such a file it should be
9928 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9929 <file>README.Debian</file> or some other appropriate place.
9932 <sect1 id="copyrightformat">
9933 <heading>Machine-readable copyright information</heading>
9936 A specification for a standard, machine-readable format
9937 for <file>debian/copyright</file> files is maintained as part
9938 of the <package>debian-policy</package> package. This
9939 document may be found in the <file>copyright-format</file>
9940 files in the <package>debian-policy</package> package. It is
9941 also available from the Debian web mirrors at
9942 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
9943 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
9947 Use of this format is optional.
9953 <heading>Examples</heading>
9956 Any examples (configurations, source files, whatever),
9957 should be installed in a directory
9958 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9959 files should not be referenced by any program: they're there
9960 for the benefit of the system administrator and users as
9961 documentation only. Architecture-specific example files
9962 should be installed in a directory
9963 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9965 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9966 latter directory itself may be a symbolic link to the
9971 If the purpose of a package is to provide examples, then the
9972 example files may be installed into
9973 <file>/usr/share/doc/<var>package</var></file>.
9977 <sect id="changelogs">
9978 <heading>Changelog files</heading>
9981 Packages that are not Debian-native must contain a
9982 compressed copy of the <file>debian/changelog</file> file from
9983 the Debian source tree in
9984 <file>/usr/share/doc/<var>package</var></file> with the name
9985 <file>changelog.Debian.gz</file>.
9989 If an upstream changelog is available, it should be accessible as
9990 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9991 plain text. If the upstream changelog is distributed in
9992 HTML, it should be made available in that form as
9993 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9994 and a plain text <file>changelog.gz</file> should be generated
9995 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9996 the upstream changelog files do not already conform to this
9997 naming convention, then this may be achieved either by
9998 renaming the files, or by adding a symbolic link, at the
9999 maintainer's discretion.<footnote>
10000 Rationale: People should not have to look in places for
10001 upstream changelogs merely because they are given
10002 different names or are distributed in HTML format.
10007 All of these files should be installed compressed using
10008 <tt>gzip -9</tt>, as they will become large with time even
10009 if they start out small.
10013 If the package has only one changelog which is used both as
10014 the Debian changelog and the upstream one because there is
10015 no separate upstream maintainer then that changelog should
10016 usually be installed as
10017 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10018 there is a separate upstream maintainer, but no upstream
10019 changelog, then the Debian changelog should still be called
10020 <file>changelog.Debian.gz</file>.
10024 For details about the format and contents of the Debian
10025 changelog file, please see <ref id="dpkgchangelog">.
10030 <appendix id="pkg-scope">
10031 <heading>Introduction and scope of these appendices</heading>
10034 These appendices are taken essentially verbatim from the
10035 now-deprecated Packaging Manual, version 3.2.1.0. They are
10036 the chapters which are likely to be of use to package
10037 maintainers and which have not already been included in the
10038 policy document itself. Most of these sections are very likely
10039 not relevant to policy; they should be treated as
10040 documentation for the packaging system. Please note that these
10041 appendices are included for convenience, and for historical
10042 reasons: they used to be part of policy package, and they have
10043 not yet been incorporated into dpkg documentation. However,
10044 they still have value, and hence they are presented here.
10048 They have not yet been checked to ensure that they are
10049 compatible with the contents of policy, and if there are any
10050 contradictions, the version in the main policy document takes
10051 precedence. The remaining chapters of the old Packaging
10052 Manual have also not been read in detail to ensure that there
10053 are not parts which have been left out. Both of these will be
10054 done in due course.
10058 Certain parts of the Packaging manual were integrated into the
10059 Policy Manual proper, and removed from the appendices. Links
10060 have been placed from the old locations to the new ones.
10064 <prgn>dpkg</prgn> is a suite of programs for creating binary
10065 package files and installing and removing them on Unix
10067 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10068 work on or be ported to other systems.
10073 The binary packages are designed for the management of
10074 installed executable programs (usually compiled binaries) and
10075 their associated data, though source code examples and
10076 documentation are provided as part of some packages.</p>
10079 This manual describes the technical aspects of creating Debian
10080 binary packages (<file>.deb</file> files). It documents the
10081 behavior of the package management programs
10082 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10083 they interact with packages.</p>
10086 It also documents the interaction between
10087 <prgn>dselect</prgn>'s core and the access method scripts it
10088 uses to actually install the selected packages, and describes
10089 how to create a new access method.</p>
10092 This manual does not go into detail about the options and
10093 usage of the package building and installation tools. It
10094 should therefore be read in conjunction with those programs'
10099 The utility programs which are provided with <prgn>dpkg</prgn>
10100 for managing various system configuration and similar issues,
10101 such as <prgn>update-rc.d</prgn> and
10102 <prgn>install-info</prgn>, are not described in detail here -
10103 please see their man pages.
10107 It is assumed that the reader is reasonably familiar with the
10108 <prgn>dpkg</prgn> System Administrators' manual.
10109 Unfortunately this manual does not yet exist.
10113 The Debian version of the FSF's GNU hello program is provided as
10114 an example for people wishing to create Debian packages. However,
10115 while the examples are helpful, they do not replace the need to
10116 read and follow the Policy and Programmer's Manual.</p>
10119 <appendix id="pkg-binarypkg">
10120 <heading>Binary packages (from old Packaging Manual)</heading>
10123 The binary package has two main sections. The first part
10124 consists of various control information files and scripts used
10125 by <prgn>dpkg</prgn> when installing and removing. See <ref
10126 id="pkg-controlarea">.
10130 The second part is an archive containing the files and
10131 directories to be installed.
10135 In the future binary packages may also contain other
10136 components, such as checksums and digital signatures. The
10137 format for the archive is described in full in the
10138 <file>deb(5)</file> man page.
10142 <sect id="pkg-bincreating"><heading>Creating package files -
10143 <prgn>dpkg-deb</prgn>
10147 All manipulation of binary package files is done by
10148 <prgn>dpkg-deb</prgn>; it's the only program that has
10149 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10150 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10151 will spot that the options requested are appropriate to
10152 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10157 In order to create a binary package you must make a
10158 directory tree which contains all the files and directories
10159 you want to have in the file system data part of the package.
10160 In Debian-format source packages this directory is usually
10161 <file>debian/tmp</file>, relative to the top of the package's
10166 They should have the locations (relative to the root of the
10167 directory tree you're constructing) ownerships and
10168 permissions which you want them to have on the system when
10169 they are installed.
10173 With current versions of <prgn>dpkg</prgn> the uid/username
10174 and gid/groupname mappings for the users and groups being
10175 used should be the same on the system where the package is
10176 built and the one where it is installed.
10180 You need to add one special directory to the root of the
10181 miniature file system tree you're creating:
10182 <prgn>DEBIAN</prgn>. It should contain the control
10183 information files, notably the binary package control file
10184 (see <ref id="pkg-controlfile">).
10188 The <prgn>DEBIAN</prgn> directory will not appear in the
10189 file system archive of the package, and so won't be installed
10190 by <prgn>dpkg</prgn> when the package is unpacked.
10194 When you've prepared the package, you should invoke:
10196 dpkg --build <var>directory</var>
10201 This will build the package in
10202 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10203 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10204 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10205 build the package.)
10209 See the man page <manref name="dpkg-deb" section="8"> for details of how
10210 to examine the contents of this newly-created file. You may find the
10211 output of following commands enlightening:
10213 dpkg-deb --info <var>filename</var>.deb
10214 dpkg-deb --contents <var>filename</var>.deb
10215 dpkg --contents <var>filename</var>.deb
10217 To view the copyright file for a package you could use this command:
10219 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10224 <sect id="pkg-controlarea">
10225 <heading>Package control information files</heading>
10228 The control information portion of a binary package is a
10229 collection of files with names known to <prgn>dpkg</prgn>.
10230 It will treat the contents of these files specially - some
10231 of them contain information used by <prgn>dpkg</prgn> when
10232 installing or removing the package; others are scripts which
10233 the package maintainer wants <prgn>dpkg</prgn> to run.
10237 It is possible to put other files in the package control
10238 information file area, but this is not generally a good idea
10239 (though they will largely be ignored).
10243 Here is a brief list of the control information files supported
10244 by <prgn>dpkg</prgn> and a summary of what they're used for.
10249 <tag><tt>control</tt>
10252 This is the key description file used by
10253 <prgn>dpkg</prgn>. It specifies the package's name
10254 and version, gives its description for the user,
10255 states its relationships with other packages, and so
10256 forth. See <ref id="sourcecontrolfiles"> and
10257 <ref id="binarycontrolfiles">.
10261 It is usually generated automatically from information
10262 in the source package by the
10263 <prgn>dpkg-gencontrol</prgn> program, and with
10264 assistance from <prgn>dpkg-shlibdeps</prgn>.
10265 See <ref id="pkg-sourcetools">.
10269 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10274 These are executable files (usually scripts) which
10275 <prgn>dpkg</prgn> runs during installation, upgrade
10276 and removal of packages. They allow the package to
10277 deal with matters which are particular to that package
10278 or require more complicated processing than that
10279 provided by <prgn>dpkg</prgn>. Details of when and
10280 how they are called are in <ref id="maintainerscripts">.
10284 It is very important to make these scripts idempotent.
10285 See <ref id="idempotency">.
10289 The maintainer scripts are not guaranteed to run with a
10290 controlling terminal and may not be able to interact with
10291 the user. See <ref id="controllingterminal">.
10295 <tag><tt>conffiles</tt>
10298 This file contains a list of configuration files which
10299 are to be handled automatically by <prgn>dpkg</prgn>
10300 (see <ref id="pkg-conffiles">). Note that not necessarily
10301 every configuration file should be listed here.
10304 <tag><tt>shlibs</tt>
10307 This file contains a list of the shared libraries
10308 supplied by the package, with dependency details for
10309 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10310 when it determines what dependencies are required in a
10311 package control file. The <tt>shlibs</tt> file format
10312 is described on <ref id="shlibs">.
10317 <sect id="pkg-controlfile">
10318 <heading>The main control information file: <tt>control</tt></heading>
10321 The most important control information file used by
10322 <prgn>dpkg</prgn> when it installs a package is
10323 <tt>control</tt>. It contains all the package's "vital
10328 The binary package control files of packages built from
10329 Debian sources are made by a special tool,
10330 <prgn>dpkg-gencontrol</prgn>, which reads
10331 <file>debian/control</file> and <file>debian/changelog</file> to
10332 find the information it needs. See <ref id="pkg-sourcepkg"> for
10337 The fields in binary package control files are listed in
10338 <ref id="binarycontrolfiles">.
10342 A description of the syntax of control files and the purpose
10343 of the fields is available in <ref id="controlfields">.
10348 <heading>Time Stamps</heading>
10351 See <ref id="timestamps">.
10356 <appendix id="pkg-sourcepkg">
10357 <heading>Source packages (from old Packaging Manual) </heading>
10360 The Debian binary packages in the distribution are generated
10361 from Debian sources, which are in a special format to assist
10362 the easy and automatic building of binaries.
10365 <sect id="pkg-sourcetools">
10366 <heading>Tools for processing source packages</heading>
10369 Various tools are provided for manipulating source packages;
10370 they pack and unpack sources and help build of binary
10371 packages and help manage the distribution of new versions.
10375 They are introduced and typical uses described here; see
10376 <manref name="dpkg-source" section="1"> for full
10377 documentation about their arguments and operation.
10381 For examples of how to construct a Debian source package,
10382 and how to use those utilities that are used by Debian
10383 source packages, please see the <prgn>hello</prgn> example
10387 <sect1 id="pkg-dpkg-source">
10389 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10394 This program is frequently used by hand, and is also
10395 called from package-independent automated building scripts
10396 such as <prgn>dpkg-buildpackage</prgn>.
10400 To unpack a package it is typically invoked with
10402 dpkg-source -x <var>.../path/to/filename</var>.dsc
10407 with the <file><var>filename</var>.tar.gz</file> and
10408 <file><var>filename</var>.diff.gz</file> (if applicable) in
10409 the same directory. It unpacks into
10410 <file><var>package</var>-<var>version</var></file>, and if
10412 <file><var>package</var>-<var>version</var>.orig</file>, in
10413 the current directory.
10417 To create a packed source archive it is typically invoked:
10419 dpkg-source -b <var>package</var>-<var>version</var>
10424 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10425 <file>.diff.gz</file> (if appropriate) in the current
10426 directory. <prgn>dpkg-source</prgn> does not clean the
10427 source tree first - this must be done separately if it is
10432 See also <ref id="pkg-sourcearchives">.</p>
10436 <sect1 id="pkg-dpkg-buildpackage">
10438 <prgn>dpkg-buildpackage</prgn> - overall package-building
10443 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10444 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10445 targets <tt>clean</tt>, <tt>build</tt> and
10446 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10447 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10448 source and binary package upload.
10452 It is usually invoked by hand from the top level of the
10453 built or unbuilt source directory. It may be invoked with
10454 no arguments; useful arguments include:
10455 <taglist compact="compact">
10456 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10459 Do not sign the <tt>.changes</tt> file or the
10460 source package <tt>.dsc</tt> file, respectively.</p>
10462 <tag><tt>-p<var>sign-command</var></tt></tag>
10465 Invoke <var>sign-command</var> instead of finding
10466 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10467 <var>sign-command</var> must behave just like
10468 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10470 <tag><tt>-r<var>root-command</var></tt></tag>
10473 When root privilege is required, invoke the command
10474 <var>root-command</var>. <var>root-command</var>
10475 should invoke its first argument as a command, from
10476 the <prgn>PATH</prgn> if necessary, and pass its
10477 second and subsequent arguments to the command it
10478 calls. If no <var>root-command</var> is supplied
10479 then <var>dpkg-buildpackage</var> will take no
10480 special action to gain root privilege, so that for
10481 most packages it will have to be invoked as root to
10484 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10487 Two types of binary-only build and upload - see
10488 <manref name="dpkg-source" section="1">.
10495 <sect1 id="pkg-dpkg-gencontrol">
10497 <prgn>dpkg-gencontrol</prgn> - generates binary package
10502 This program is usually called from <file>debian/rules</file>
10503 (see <ref id="pkg-sourcetree">) in the top level of the source
10508 This is usually done just before the files and directories in the
10509 temporary directory tree where the package is being built have their
10510 permissions and ownerships set and the package is constructed using
10511 <prgn>dpkg-deb/</prgn>
10513 This is so that the control file which is produced has
10514 the right permissions
10519 <prgn>dpkg-gencontrol</prgn> must be called after all the
10520 files which are to go into the package have been placed in
10521 the temporary build directory, so that its calculation of
10522 the installed size of a package is correct.
10526 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10527 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10528 variable substitutions created by
10529 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10534 For a package which generates only one binary package, and
10535 which builds it in <file>debian/tmp</file> relative to the top
10536 of the source package, it is usually sufficient to call
10537 <prgn>dpkg-gencontrol</prgn>.
10541 Sources which build several binaries will typically need
10544 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10545 </example> The <tt>-P</tt> tells
10546 <prgn>dpkg-gencontrol</prgn> that the package is being
10547 built in a non-default directory, and the <tt>-p</tt>
10548 tells it which package's control file should be generated.
10552 <prgn>dpkg-gencontrol</prgn> also adds information to the
10553 list of files in <file>debian/files</file>, for the benefit of
10554 (for example) a future invocation of
10555 <prgn>dpkg-genchanges</prgn>.</p>
10558 <sect1 id="pkg-dpkg-shlibdeps">
10560 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10565 This program is usually called from <file>debian/rules</file>
10566 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10567 id="pkg-sourcetree">), in the top level of the source tree.
10571 Its arguments are executables and shared libraries
10574 They may be specified either in the locations in the
10575 source tree where they are created or in the locations
10576 in the temporary build tree where they are installed
10577 prior to binary package creation.
10579 </footnote> for which shared library dependencies should
10580 be included in the binary package's control file.
10584 If some of the found shared libraries should only
10585 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10586 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10587 by using the <tt>-d<var>dependency-field</var></tt> option
10588 before those executable(s). (Each <tt>-d</tt> option
10589 takes effect until the next <tt>-d</tt>.)
10593 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10594 output control file to be modified. Instead by default it
10595 adds to the <file>debian/substvars</file> file variable
10596 settings like <tt>shlibs:Depends</tt>. These variable
10597 settings must be referenced in dependency fields in the
10598 appropriate per-binary-package sections of the source
10603 For example, a package that generates an essential part
10604 which requires dependencies, and optional parts that
10605 which only require a recommendation, would separate those
10606 two sets of dependencies into two different fields.<footnote>
10607 At the time of writing, an example for this was the
10608 <package/xmms/ package, with Depends used for the xmms
10609 executable, Recommends for the plug-ins and Suggests for
10610 even more optional features provided by unzip.
10612 It can say in its <file>debian/rules</file>:
10614 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10615 -dRecommends <var>optionalpart anotheroptionalpart</var>
10617 and then in its main control file <file>debian/control</file>:
10620 Depends: ${shlibs:Depends}
10621 Recommends: ${shlibs:Recommends}
10627 Sources which produce several binary packages with
10628 different shared library dependency requirements can use
10629 the <tt>-p<var>varnameprefix</var></tt> option to override
10630 the default <tt>shlibs:</tt> prefix (one invocation of
10631 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10632 They can thus produce several sets of dependency
10633 variables, each of the form
10634 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10635 which can be referred to in the appropriate parts of the
10636 binary package control files.
10641 <sect1 id="pkg-dpkg-distaddfile">
10643 <prgn>dpkg-distaddfile</prgn> - adds a file to
10644 <file>debian/files</file>
10648 Some packages' uploads need to include files other than
10649 the source and binary package files.
10653 <prgn>dpkg-distaddfile</prgn> adds a file to the
10654 <file>debian/files</file> file so that it will be included in
10655 the <file>.changes</file> file when
10656 <prgn>dpkg-genchanges</prgn> is run.
10660 It is usually invoked from the <tt>binary</tt> target of
10661 <file>debian/rules</file>:
10663 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10665 The <var>filename</var> is relative to the directory where
10666 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10667 is usually the directory above the top level of the source
10668 tree. The <file>debian/rules</file> target should put the
10669 file there just before or just after calling
10670 <prgn>dpkg-distaddfile</prgn>.
10674 The <var>section</var> and <var>priority</var> are passed
10675 unchanged into the resulting <file>.changes</file> file.
10680 <sect1 id="pkg-dpkg-genchanges">
10682 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10683 upload control file
10687 This program is usually called by package-independent
10688 automatic building scripts such as
10689 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10694 It is usually called in the top level of a built source
10695 tree, and when invoked with no arguments will print out a
10696 straightforward <file>.changes</file> file based on the
10697 information in the source package's changelog and control
10698 file and the binary and source packages which should have
10704 <sect1 id="pkg-dpkg-parsechangelog">
10706 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10707 representation of a changelog
10711 This program is used internally by
10712 <prgn>dpkg-source</prgn> et al. It may also occasionally
10713 be useful in <file>debian/rules</file> and elsewhere. It
10714 parses a changelog, <file>debian/changelog</file> by default,
10715 and prints a control-file format representation of the
10716 information in it to standard output.
10720 <sect1 id="pkg-dpkg-architecture">
10722 <prgn>dpkg-architecture</prgn> - information about the build and
10727 This program can be used manually, but is also invoked by
10728 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10729 environment or make variables which specify the build and host
10730 architecture for the package building process.
10735 <sect id="pkg-sourcetree">
10736 <heading>The Debian package source tree</heading>
10739 The source archive scheme described later is intended to
10740 allow a Debian package source tree with some associated
10741 control information to be reproduced and transported easily.
10742 The Debian package source tree is a version of the original
10743 program with certain files added for the benefit of the
10744 packaging process, and with any other changes required
10745 made to the rest of the source code and installation
10750 The extra files created for Debian are in the subdirectory
10751 <file>debian</file> of the top level of the Debian package
10752 source tree. They are described below.
10755 <sect1 id="pkg-debianrules">
10756 <heading><file>debian/rules</file> - the main building script</heading>
10759 See <ref id="debianrules">.
10763 <sect1 id="pkg-srcsubstvars">
10764 <heading><file>debian/substvars</file> and variable substitutions</heading>
10767 See <ref id="substvars">.
10773 <heading><file>debian/files</file></heading>
10776 See <ref id="debianfiles">.
10780 <sect1><heading><file>debian/tmp</file>
10784 This is the canonical temporary location for the
10785 construction of binary packages by the <tt>binary</tt>
10786 target. The directory <file>tmp</file> serves as the root of
10787 the file system tree as it is being constructed (for
10788 example, by using the package's upstream makefiles install
10789 targets and redirecting the output there), and it also
10790 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10791 id="pkg-bincreating">.
10795 If several binary packages are generated from the same
10796 source tree it is usual to use several
10797 <file>debian/tmp<var>something</var></file> directories, for
10798 example <file>tmp-a</file> or <file>tmp-doc</file>.
10802 Whatever <file>tmp</file> directories are created and used by
10803 <tt>binary</tt> must of course be removed by the
10804 <tt>clean</tt> target.</p></sect1>
10808 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10812 As it exists on the FTP site, a Debian source package
10813 consists of three related files. You must have the right
10814 versions of all three to be able to use them.
10819 <tag>Debian source control file - <tt>.dsc</tt></tag>
10821 This file is a control file used by <prgn>dpkg-source</prgn>
10822 to extract a source package.
10823 See <ref id="debiansourcecontrolfiles">.
10827 Original source archive -
10829 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10835 This is a compressed (with <tt>gzip -9</tt>)
10836 <prgn>tar</prgn> file containing the source code from
10837 the upstream authors of the program.
10842 Debian package diff -
10844 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10850 This is a unified context diff (<tt>diff -u</tt>)
10851 giving the changes which are required to turn the
10852 original source into the Debian source. These changes
10853 may only include editing and creating plain files.
10854 The permissions of files, the targets of symbolic
10855 links and the characteristics of special files or
10856 pipes may not be changed and no files may be removed
10861 All the directories in the diff must exist, except the
10862 <file>debian</file> subdirectory of the top of the source
10863 tree, which will be created by
10864 <prgn>dpkg-source</prgn> if necessary when unpacking.
10868 The <prgn>dpkg-source</prgn> program will
10869 automatically make the <file>debian/rules</file> file
10870 executable (see below).</p></item>
10875 If there is no original source code - for example, if the
10876 package is specially prepared for Debian or the Debian
10877 maintainer is the same as the upstream maintainer - the
10878 format is slightly different: then there is no diff, and the
10880 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10881 and preferably contains a directory named
10882 <file><var>package</var>-<var>version</var></file>.
10887 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10890 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10891 Debian source package. However, if it is not available it
10892 is possible to unpack a Debian source archive as follows:
10893 <enumlist compact="compact">
10896 Untar the tarfile, which will create a <file>.orig</file>
10900 <p>Rename the <file>.orig</file> directory to
10901 <file><var>package</var>-<var>version</var></file>.</p>
10905 Create the subdirectory <file>debian</file> at the top of
10906 the source tree.</p>
10908 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10910 <item><p>Untar the tarfile again if you want a copy of the original
10911 source code alongside the Debian version.</p>
10916 It is not possible to generate a valid Debian source archive
10917 without using <prgn>dpkg-source</prgn>. In particular,
10918 attempting to use <prgn>diff</prgn> directly to generate the
10919 <file>.diff.gz</file> file will not work.
10923 <heading>Restrictions on objects in source packages</heading>
10926 The source package may not contain any hard links
10928 This is not currently detected when building source
10929 packages, but only when extracting
10933 Hard links may be permitted at some point in the
10934 future, but would require a fair amount of
10936 </footnote>, device special files, sockets or setuid or
10939 Setgid directories are allowed.
10944 The source packaging tools manage the changes between the
10945 original and Debian source using <prgn>diff</prgn> and
10946 <prgn>patch</prgn>. Turning the original source tree as
10947 included in the <file>.orig.tar.gz</file> into the Debian
10948 package source must not involve any changes which cannot be
10949 handled by these tools. Problematic changes which cause
10950 <prgn>dpkg-source</prgn> to halt with an error when
10951 building the source package are:
10952 <list compact="compact">
10953 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10955 <item><p>Changing the targets of symbolic links.</p>
10957 <item><p>Creating directories, other than <file>debian</file>.</p>
10959 <item><p>Changes to the contents of binary files.</p></item>
10960 </list> Changes which cause <prgn>dpkg-source</prgn> to
10961 print a warning but continue anyway are:
10962 <list compact="compact">
10965 Removing files, directories or symlinks.
10967 Renaming a file is not treated specially - it is
10968 seen as the removal of the old file (which
10969 generates a warning, but is otherwise ignored),
10970 and the creation of the new one.
10976 Changed text files which are missing the usual final
10977 newline (either in the original or the modified
10982 Changes which are not represented, but which are not detected by
10983 <prgn>dpkg-source</prgn>, are:
10984 <list compact="compact">
10985 <item><p>Changing the permissions of files (other than
10986 <file>debian/rules</file>) and directories.</p></item>
10991 The <file>debian</file> directory and <file>debian/rules</file>
10992 are handled specially by <prgn>dpkg-source</prgn> - before
10993 applying the changes it will create the <file>debian</file>
10994 directory, and afterwards it will make
10995 <file>debian/rules</file> world-executable.
11001 <appendix id="pkg-controlfields">
11002 <heading>Control files and their fields (from old Packaging Manual)</heading>
11005 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11006 data in a common format, known as control files. Binary and
11007 source packages have control data as do the <file>.changes</file>
11008 files which control the installation of uploaded files, and
11009 <prgn>dpkg</prgn>'s internal databases are in a similar
11014 <heading>Syntax of control files</heading>
11017 See <ref id="controlsyntax">.
11021 It is important to note that there are several fields which
11022 are optional as far as <prgn>dpkg</prgn> and the related
11023 tools are concerned, but which must appear in every Debian
11024 package, or whose omission may cause problems.
11029 <heading>List of fields</heading>
11032 See <ref id="controlfieldslist">.
11036 This section now contains only the fields that didn't belong
11037 to the Policy manual.
11040 <sect1 id="pkg-f-Filename">
11041 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11044 These fields in <tt>Packages</tt> files give the
11045 filename(s) of (the parts of) a package in the
11046 distribution directories, relative to the root of the
11047 Debian hierarchy. If the package has been split into
11048 several parts the parts are all listed in order, separated
11053 <sect1 id="pkg-f-Size">
11054 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11057 These fields in <file>Packages</file> files give the size (in
11058 bytes, expressed in decimal) and MD5 checksum of the
11059 file(s) which make(s) up a binary package in the
11060 distribution. If the package is split into several parts
11061 the values for the parts are listed in order, separated by
11066 <sect1 id="pkg-f-Status">
11067 <heading><tt>Status</tt></heading>
11070 This field in <prgn>dpkg</prgn>'s status file records
11071 whether the user wants a package installed, removed or
11072 left alone, whether it is broken (requiring
11073 re-installation) or not and what its current state on the
11074 system is. Each of these pieces of information is a
11079 <sect1 id="pkg-f-Config-Version">
11080 <heading><tt>Config-Version</tt></heading>
11083 If a package is not installed or not configured, this
11084 field in <prgn>dpkg</prgn>'s status file records the last
11085 version of the package which was successfully
11090 <sect1 id="pkg-f-Conffiles">
11091 <heading><tt>Conffiles</tt></heading>
11094 This field in <prgn>dpkg</prgn>'s status file contains
11095 information about the automatically-managed configuration
11096 files held by a package. This field should <em>not</em>
11097 appear anywhere in a package!
11102 <heading>Obsolete fields</heading>
11105 These are still recognized by <prgn>dpkg</prgn> but should
11106 not appear anywhere any more.
11108 <taglist compact="compact">
11110 <tag><tt>Revision</tt></tag>
11111 <tag><tt>Package-Revision</tt></tag>
11112 <tag><tt>Package_Revision</tt></tag>
11114 The Debian revision part of the package version was
11115 at one point in a separate control field. This
11116 field went through several names.
11119 <tag><tt>Recommended</tt></tag>
11120 <item>Old name for <tt>Recommends</tt>.</item>
11122 <tag><tt>Optional</tt></tag>
11123 <item>Old name for <tt>Suggests</tt>.</item>
11125 <tag><tt>Class</tt></tag>
11126 <item>Old name for <tt>Priority</tt>.</item>
11135 <appendix id="pkg-conffiles">
11136 <heading>Configuration file handling (from old Packaging Manual)</heading>
11139 <prgn>dpkg</prgn> can do a certain amount of automatic
11140 handling of package configuration files.
11144 Whether this mechanism is appropriate depends on a number of
11145 factors, but basically there are two approaches to any
11146 particular configuration file.
11150 The easy method is to ship a best-effort configuration in the
11151 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11152 handle updates. If the user is unlikely to want to edit the
11153 file, but you need them to be able to without losing their
11154 changes, and a new package with a changed version of the file
11155 is only released infrequently, this is a good approach.
11159 The hard method is to build the configuration file from
11160 scratch in the <prgn>postinst</prgn> script, and to take the
11161 responsibility for fixing any mistakes made in earlier
11162 versions of the package automatically. This will be
11163 appropriate if the file is likely to need to be different on
11167 <sect><heading>Automatic handling of configuration files by
11172 A package may contain a control information file called
11173 <tt>conffiles</tt>. This file should be a list of filenames
11174 of configuration files needing automatic handling, separated
11175 by newlines. The filenames should be absolute pathnames,
11176 and the files referred to should actually exist in the
11181 When a package is upgraded <prgn>dpkg</prgn> will process
11182 the configuration files during the configuration stage,
11183 shortly before it runs the package's <prgn>postinst</prgn>
11188 For each file it checks to see whether the version of the
11189 file included in the package is the same as the one that was
11190 included in the last version of the package (the one that is
11191 being upgraded from); it also compares the version currently
11192 installed on the system with the one shipped with the last
11197 If neither the user nor the package maintainer has changed
11198 the file, it is left alone. If one or the other has changed
11199 their version, then the changed version is preferred - i.e.,
11200 if the user edits their file, but the package maintainer
11201 doesn't ship a different version, the user's changes will
11202 stay, silently, but if the maintainer ships a new version
11203 and the user hasn't edited it the new version will be
11204 installed (with an informative message). If both have
11205 changed their version the user is prompted about the problem
11206 and must resolve the differences themselves.
11210 The comparisons are done by calculating the MD5 message
11211 digests of the files, and storing the MD5 of the file as it
11212 was included in the most recent version of the package.
11216 When a package is installed for the first time
11217 <prgn>dpkg</prgn> will install the file that comes with it,
11218 unless that would mean overwriting a file already on the
11223 However, note that <prgn>dpkg</prgn> will <em>not</em>
11224 replace a conffile that was removed by the user (or by a
11225 script). This is necessary because with some programs a
11226 missing file produces an effect hard or impossible to
11227 achieve in another way, so that a missing file needs to be
11228 kept that way if the user did it.
11232 Note that a package should <em>not</em> modify a
11233 <prgn>dpkg</prgn>-handled conffile in its maintainer
11234 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11235 the user confusing and possibly dangerous options for
11236 conffile update when the package is upgraded.</p>
11239 <sect><heading>Fully-featured maintainer script configuration
11244 For files which contain site-specific information such as
11245 the hostname and networking details and so forth, it is
11246 better to create the file in the package's
11247 <prgn>postinst</prgn> script.
11251 This will typically involve examining the state of the rest
11252 of the system to determine values and other information, and
11253 may involve prompting the user for some information which
11254 can't be obtained some other way.
11258 When using this method there are a couple of important
11259 issues which should be considered:
11263 If you discover a bug in the program which generates the
11264 configuration file, or if the format of the file changes
11265 from one version to the next, you will have to arrange for
11266 the postinst script to do something sensible - usually this
11267 will mean editing the installed configuration file to remove
11268 the problem or change the syntax. You will have to do this
11269 very carefully, since the user may have changed the file,
11270 perhaps to fix the very problem that your script is trying
11271 to deal with - you will have to detect these situations and
11272 deal with them correctly.
11276 If you do go down this route it's probably a good idea to
11277 make the program that generates the configuration file(s) a
11278 separate program in <file>/usr/sbin</file>, by convention called
11279 <file><var>package</var>config</file> and then run that if
11280 appropriate from the post-installation script. The
11281 <tt><var>package</var>config</tt> program should not
11282 unquestioningly overwrite an existing configuration - if its
11283 mode of operation is geared towards setting up a package for
11284 the first time (rather than any arbitrary reconfiguration
11285 later) you should have it check whether the configuration
11286 already exists, and require a <tt>--force</tt> flag to
11287 overwrite it.</p></sect>
11290 <appendix id="pkg-alternatives"><heading>Alternative versions of
11291 an interface - <prgn>update-alternatives</prgn> (from old
11296 When several packages all provide different versions of the
11297 same program or file it is useful to have the system select a
11298 default, but to allow the system administrator to change it
11299 and have their decisions respected.
11303 For example, there are several versions of the <prgn>vi</prgn>
11304 editor, and there is no reason to prevent all of them from
11305 being installed at once, each under their own name
11306 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11307 Nevertheless it is desirable to have the name <tt>vi</tt>
11308 refer to something, at least by default.
11312 If all the packages involved cooperate, this can be done with
11313 <prgn>update-alternatives</prgn>.
11317 Each package provides its own version under its own name, and
11318 calls <prgn>update-alternatives</prgn> in its postinst to
11319 register its version (and again in its prerm to deregister
11324 See the man page <manref name="update-alternatives"
11325 section="8"> for details.
11329 If <prgn>update-alternatives</prgn> does not seem appropriate
11330 you may wish to consider using diversions instead.</p>
11333 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11334 package's version of a file (from old Packaging Manual)
11338 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11339 when it reinstalls the package it belongs to, and to have it
11340 put the file from the package somewhere else instead.
11344 This can be used locally to override a package's version of a
11345 file, or by one package to override another's version (or
11346 provide a wrapper for it).
11350 Before deciding to use a diversion, read <ref
11351 id="pkg-alternatives"> to see if you really want a diversion
11352 rather than several alternative versions of a program.
11356 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11357 and updated by a special program <prgn>dpkg-divert</prgn>.
11358 Please see <manref name="dpkg-divert" section="8"> for full
11359 details of its operation.
11363 When a package wishes to divert a file from another, it should
11364 call <prgn>dpkg-divert</prgn> in its preinst to add the
11365 diversion and rename the existing file. For example,
11366 supposing that a <prgn>smailwrapper</prgn> package wishes to
11367 install a wrapper around <file>/usr/sbin/smail</file>:
11369 dpkg-divert --package smailwrapper --add --rename \
11370 --divert /usr/sbin/smail.real /usr/sbin/smail
11371 </example> The <tt>--package smailwrapper</tt> ensures that
11372 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11373 can bypass the diversion and get installed as the true version.
11374 It's safe to add the diversion unconditionally on upgrades since
11375 it will be left unchanged if it already exists, but
11376 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11377 message, make the command conditional on the version from which
11378 the package is being upgraded:
11380 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11381 dpkg-divert --package smailwrapper --add --rename \
11382 --divert /usr/sbin/smail.real /usr/sbin/smail
11384 </example> where <tt>1.0-2</tt> is the version at which the
11385 diversion was first added to the package. Running the command
11386 during abort-upgrade is pointless but harmless.
11390 The postrm has to do the reverse:
11392 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11393 dpkg-divert --package smailwrapper --remove --rename \
11394 --divert /usr/sbin/smail.real /usr/sbin/smail
11396 </example> If the diversion was added at a particular version, the
11397 postrm should also handle the failure case of upgrading from an
11398 older version (unless the older version is so old that direct
11399 upgrades are no longer supported):
11401 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11402 dpkg-divert --package smailwrapper --remove --rename \
11403 --divert /usr/sbin/smail.real /usr/sbin/smail
11405 </example> where <tt>1.0-2</tt> is the version at which the
11406 diversion was first added to the package. The postrm should not
11407 remove the diversion on upgrades both because there's no reason to
11408 remove the diversion only to immediately re-add it and since the
11409 postrm of the old package is run after unpacking so the removal of
11410 the diversion will fail.
11414 Do not attempt to divert a file which is vitally important for
11415 the system's operation - when using <prgn>dpkg-divert</prgn>
11416 there is a time, after it has been diverted but before
11417 <prgn>dpkg</prgn> has installed the new version, when the file
11418 does not exist.</p>
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