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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Russ Allbery</item>
223 <item>Bill Allombert</item>
224 <item>Andrew McMillan</item>
225 <item>Manoj Srivastava</item>
226 <item>Colin Watson</item>
231 While the authors of this document have tried hard to avoid
232 typos and other errors, these do still occur. If you discover
233 an error in this manual or if you want to give any
234 comments, suggestions, or criticisms please send an email to
235 the Debian Policy List,
236 <email>debian-policy@lists.debian.org</email>, or submit a
237 bug report against the <tt>debian-policy</tt> package.
241 Please do not try to reach the individual authors or maintainers
242 of the Policy Manual regarding changes to the Policy.
247 <heading>Related documents</heading>
250 There are several other documents other than this Policy Manual
251 that are necessary to fully understand some Debian policies and
256 The external "sub-policy" documents are referred to in:
257 <list compact="compact">
258 <item><ref id="fhs"></item>
259 <item><ref id="virtual_pkg"></item>
260 <item><ref id="menus"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 Finally, a <qref id="copyrightformat">specification for
285 machine-readable copyright files</qref> is maintained as part of
286 the <package>debian-policy</package> package using the same
287 procedure as the other policy documents. Use of this format is
292 <sect id="definitions">
293 <heading>Definitions</heading>
296 The following terms are used in this Policy Manual:
300 The character encoding specified by ANSI X3.4-1986 and its
301 predecessor standards, referred to in MIME as US-ASCII, and
302 corresponding to an encoding in eight bits per character of
303 the first 128 <url id="http://www.unicode.org/"
304 name="Unicode"> characters, with the eighth bit always zero.
308 The transformation format (sometimes called encoding) of
309 <url id="http://www.unicode.org/" name="Unicode"> defined by
310 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
311 name="RFC 3629">. UTF-8 has the useful property of having
312 ASCII as a subset, so any text encoded in ASCII is trivially
322 <heading>The Debian Archive</heading>
325 The Debian system is maintained and distributed as a
326 collection of <em>packages</em>. Since there are so many of
327 them (currently well over 15000), they are split into
328 <em>sections</em> and given <em>priorities</em> to simplify
329 the handling of them.
333 The effort of the Debian project is to build a free operating
334 system, but not every package we want to make accessible is
335 <em>free</em> in our sense (see the Debian Free Software
336 Guidelines, below), or may be imported/exported without
337 restrictions. Thus, the archive is split into areas<footnote>
338 The Debian archive software uses the term "component" internally
339 and in the Release file format to refer to the division of an
340 archive. The Debian Social Contract simply refers to "areas."
341 This document uses terminology similar to the Social Contract.
342 </footnote> based on their licenses and other restrictions.
346 The aims of this are:
348 <list compact="compact">
349 <item>to allow us to make as much software available as we can</item>
350 <item>to allow us to encourage everyone to write free software,
352 <item>to allow us to make it easy for people to produce
353 CD-ROMs of our system without violating any licenses,
354 import/export restrictions, or any other laws.</item>
359 The <em>main</em> archive area forms the <em>Debian distribution</em>.
363 Packages in the other archive areas (<tt>contrib</tt>,
364 <tt>non-free</tt>) are not considered to be part of the Debian
365 distribution, although we support their use and provide
366 infrastructure for them (such as our bug-tracking system and
367 mailing lists). This Debian Policy Manual applies to these
372 <heading>The Debian Free Software Guidelines</heading>
374 The Debian Free Software Guidelines (DFSG) form our
375 definition of "free software". These are:
377 <tag>1. Free Redistribution
380 The license of a Debian component may not restrict any
381 party from selling or giving away the software as a
382 component of an aggregate software distribution
383 containing programs from several different
384 sources. The license may not require a royalty or
385 other fee for such sale.
390 The program must include source code, and must allow
391 distribution in source code as well as compiled form.
393 <tag>3. Derived Works
396 The license must allow modifications and derived
397 works, and must allow them to be distributed under the
398 same terms as the license of the original software.
400 <tag>4. Integrity of The Author's Source Code
403 The license may restrict source-code from being
404 distributed in modified form <em>only</em> if the
405 license allows the distribution of "patch files"
406 with the source code for the purpose of modifying the
407 program at build time. The license must explicitly
408 permit distribution of software built from modified
409 source code. The license may require derived works to
410 carry a different name or version number from the
411 original software. (This is a compromise. The Debian
412 Project encourages all authors to not restrict any
413 files, source or binary, from being modified.)
415 <tag>5. No Discrimination Against Persons or Groups
418 The license must not discriminate against any person
421 <tag>6. No Discrimination Against Fields of Endeavor
424 The license must not restrict anyone from making use
425 of the program in a specific field of endeavor. For
426 example, it may not restrict the program from being
427 used in a business, or from being used for genetic
430 <tag>7. Distribution of License
433 The rights attached to the program must apply to all
434 to whom the program is redistributed without the need
435 for execution of an additional license by those
438 <tag>8. License Must Not Be Specific to Debian
441 The rights attached to the program must not depend on
442 the program's being part of a Debian system. If the
443 program is extracted from Debian and used or
444 distributed without Debian but otherwise within the
445 terms of the program's license, all parties to whom
446 the program is redistributed must have the same
447 rights as those that are granted in conjunction with
450 <tag>9. License Must Not Contaminate Other Software
453 The license must not place restrictions on other
454 software that is distributed along with the licensed
455 software. For example, the license must not insist
456 that all other programs distributed on the same medium
457 must be free software.
459 <tag>10. Example Licenses
462 The "GPL," "BSD," and "Artistic" licenses are examples of
463 licenses that we consider <em>free</em>.
470 <heading>Archive areas</heading>
473 <heading>The main archive area</heading>
476 The <em>main</em> archive area comprises the Debian
477 distribution. Only the packages in this area are considered
478 part of the distribution. None of the packages in
479 the <em>main</em> archive area require software outside of
480 that area to function. Anyone may use, share, modify and
481 redistribute the packages in this archive area
483 See <url id="http://www.debian.org/intro/free"
484 name="What Does Free Mean?"> for
485 more about what we mean by free software.
490 Every package in <em>main</em> must comply with the DFSG
491 (Debian Free Software Guidelines).
495 In addition, the packages in <em>main</em>
496 <list compact="compact">
498 must not require or recommend a package outside
499 of <em>main</em> for compilation or execution (thus, the
500 package must not declare a "Pre-Depends", "Depends",
501 "Recommends", "Build-Depends", or "Build-Depends-Indep"
502 relationship on a non-<em>main</em> package),
505 must not be so buggy that we refuse to support them,
509 must meet all policy requirements presented in this
518 <heading>The contrib archive area</heading>
521 The <em>contrib</em> archive area contains supplemental
522 packages intended to work with the Debian distribution, but
523 which require software outside of the distribution to either
528 Every package in <em>contrib</em> must comply with the DFSG.
532 In addition, the packages in <em>contrib</em>
533 <list compact="compact">
535 must not be so buggy that we refuse to support them,
539 must meet all policy requirements presented in this
546 Examples of packages which would be included in
547 <em>contrib</em> are:
548 <list compact="compact">
550 free packages which require <em>contrib</em>,
551 <em>non-free</em> packages or packages which are not
552 in our archive at all for compilation or execution,
556 wrapper packages or other sorts of free accessories for
563 <sect1 id="non-free">
564 <heading>The non-free archive area</heading>
567 The <em>non-free</em> archive area contains supplemental
568 packages intended to work with the Debian distribution that do
569 not comply with the DFSG or have other problems that make
570 their distribution problematic. They may not comply with all
571 of the policy requirements in this manual due to restrictions
572 on modifications or other limitations.
576 Packages must be placed in <em>non-free</em> if they are
577 not compliant with the DFSG or are encumbered by patents
578 or other legal issues that make their distribution
583 In addition, the packages in <em>non-free</em>
584 <list compact="compact">
586 must not be so buggy that we refuse to support them,
590 must meet all policy requirements presented in this
591 manual that it is possible for them to meet.
593 It is possible that there are policy
594 requirements which the package is unable to
595 meet, for example, if the source is
596 unavailable. These situations will need to be
597 handled on a case-by-case basis.
606 <sect id="pkgcopyright">
607 <heading>Copyright considerations</heading>
610 Every package must be accompanied by a verbatim copy of its
611 copyright information and distribution license in the file
612 <file>/usr/share/doc/<var>package</var>/copyright</file>
613 (see <ref id="copyrightfile"> for further details).
617 We reserve the right to restrict files from being included
618 anywhere in our archives if
619 <list compact="compact">
621 their use or distribution would break a law,
624 there is an ethical conflict in their distribution or
628 we would have to sign a license for them, or
631 their distribution would conflict with other project
638 Programs whose authors encourage the user to make
639 donations are fine for the main distribution, provided
640 that the authors do not claim that not donating is
641 immoral, unethical, illegal or something similar; in such
642 a case they must go in <em>non-free</em>.
646 Packages whose copyright permission notices (or patent
647 problems) do not even allow redistribution of binaries
648 only, and where no special permission has been obtained,
649 must not be placed on the Debian FTP site and its mirrors
654 Note that under international copyright law (this applies
655 in the United States, too), <em>no</em> distribution or
656 modification of a work is allowed without an explicit
657 notice saying so. Therefore a program without a copyright
658 notice <em>is</em> copyrighted and you may not do anything
659 to it without risking being sued! Likewise if a program
660 has a copyright notice but no statement saying what is
661 permitted then nothing is permitted.
665 Many authors are unaware of the problems that restrictive
666 copyrights (or lack of copyright notices) can cause for
667 the users of their supposedly-free software. It is often
668 worthwhile contacting such authors diplomatically to ask
669 them to modify their license terms. However, this can be a
670 politically difficult thing to do and you should ask for
671 advice on the <tt>debian-legal</tt> mailing list first, as
676 When in doubt about a copyright, send mail to
677 <email>debian-legal@lists.debian.org</email>. Be prepared
678 to provide us with the copyright statement. Software
679 covered by the GPL, public domain software and BSD-like
680 copyrights are safe; be wary of the phrases "commercial
681 use prohibited" and "distribution restricted".
685 <sect id="subsections">
686 <heading>Sections</heading>
689 The packages in the archive areas <em>main</em>,
690 <em>contrib</em> and <em>non-free</em> are grouped further into
691 <em>sections</em> to simplify handling.
695 The archive area and section for each package should be
696 specified in the package's <tt>Section</tt> control record (see
697 <ref id="f-Section">). However, the maintainer of the Debian
698 archive may override this selection to ensure the consistency of
699 the Debian distribution. The <tt>Section</tt> field should be
701 <list compact="compact">
703 <em>section</em> if the package is in the
704 <em>main</em> archive area,
707 <em>area/section</em> if the package is in
708 the <em>contrib</em> or <em>non-free</em>
715 The Debian archive maintainers provide the authoritative
716 list of sections. At present, they are:
717 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
718 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
719 <em>education</em>, <em>electronics</em>, <em>embedded</em>,
720 <em>fonts</em>, <em>games</em>, <em>gnome</em>, <em>graphics</em>,
721 <em>gnu-r</em>, <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
722 <em>httpd</em>, <em>interpreters</em>, <em>introspection</em>,
723 <em>java</em>, <em>kde</em>, <em>kernel</em>, <em>libs</em>,
724 <em>libdevel</em>, <em>lisp</em>, <em>localization</em>,
725 <em>mail</em>, <em>math</em>, <em>metapackages</em>, <em>misc</em>,
726 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
727 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
728 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
729 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
730 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
731 <em>zope</em>. The additional section <em>debian-installer</em>
732 contains special packages used by the installer and is not used
733 for normal Debian packages.
737 For more information about the sections and their definitions,
738 see the <url id="http://packages.debian.org/unstable/"
739 name="list of sections in unstable">.
743 <sect id="priorities">
744 <heading>Priorities</heading>
747 Each package should have a <em>priority</em> value, which is
748 included in the package's <em>control record</em>
749 (see <ref id="f-Priority">).
750 This information is used by the Debian package management tools to
751 separate high-priority packages from less-important packages.
755 The following <em>priority levels</em> are recognized by the
756 Debian package management tools.
758 <tag><tt>required</tt></tag>
760 Packages which are necessary for the proper
761 functioning of the system (usually, this means that
762 dpkg functionality depends on these packages).
763 Removing a <tt>required</tt> package may cause your
764 system to become totally broken and you may not even
765 be able to use <prgn>dpkg</prgn> to put things back,
766 so only do so if you know what you are doing. Systems
767 with only the <tt>required</tt> packages are probably
768 unusable, but they do have enough functionality to
769 allow the sysadmin to boot and install more software.
771 <tag><tt>important</tt></tag>
773 Important programs, including those which one would
774 expect to find on any Unix-like system. If the
775 expectation is that an experienced Unix person who
776 found it missing would say "What on earth is going on,
777 where is <prgn>foo</prgn>?", it must be an
778 <tt>important</tt> package.<footnote>
779 This is an important criterion because we are
780 trying to produce, amongst other things, a free
783 Other packages without which the system will not run
784 well or be usable must also have priority
785 <tt>important</tt>. This does
786 <em>not</em> include Emacs, the X Window System, TeX
787 or any other large applications. The
788 <tt>important</tt> packages are just a bare minimum of
789 commonly-expected and necessary tools.
791 <tag><tt>standard</tt></tag>
793 These packages provide a reasonably small but not too
794 limited character-mode system. This is what will be
795 installed by default if the user doesn't select anything
796 else. It doesn't include many large applications.
798 <tag><tt>optional</tt></tag>
800 (In a sense everything that isn't required is
801 optional, but that's not what is meant here.) This is
802 all the software that you might reasonably want to
803 install if you didn't know what it was and don't have
804 specialized requirements. This is a much larger system
805 and includes the X Window System, a full TeX
806 distribution, and many applications. Note that
807 optional packages should not conflict with each other.
809 <tag><tt>extra</tt></tag>
811 This contains all packages that conflict with others
812 with required, important, standard or optional
813 priorities, or are only likely to be useful if you
814 already know what they are or have specialized
815 requirements (such as packages containing only detached
822 Packages must not depend on packages with lower priority
823 values (excluding build-time dependencies). In order to
824 ensure this, the priorities of one or more packages may need
833 <heading>Binary packages</heading>
836 The Debian distribution is based on the Debian
837 package management system, called <prgn>dpkg</prgn>. Thus,
838 all packages in the Debian distribution must be provided
839 in the <tt>.deb</tt> file format.
843 A <tt>.deb</tt> package contains two sets of files: a set of files
844 to install on the system when the package is installed, and a set
845 of files that provide additional metadata about the package or
846 which are executed when the package is installed or removed. This
847 second set of files is called <em>control information files</em>.
848 Among those files are the package maintainer scripts
849 and <file>control</file>, the <qref id="binarycontrolfiles">binary
850 package control file</qref> that contains the control fields for
851 the package. Other control information files
852 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
853 file</qref> used to store shared library dependency information
854 and the <file>conffiles</file> file that lists the package's
855 configuration files (described in <ref id="config-files">).
859 There is unfortunately a collision of terminology here between
860 control information files and files in the Debian control file
861 format. Throughout this document, a <em>control file</em> refers
862 to a file in the Debian control file format. These files are
863 documented in <ref id="controlfields">. Only files referred to
864 specifically as <em>control information files</em> are the files
865 included in the control information file member of
866 the <file>.deb</file> file format used by binary packages. Most
867 control information files are not in the Debian control file
872 <heading>The package name</heading>
875 Every package must have a name that's unique within the Debian
880 The package name is included in the control field
881 <tt>Package</tt>, the format of which is described
882 in <ref id="f-Package">.
883 The package name is also included as a part of the file name
884 of the <tt>.deb</tt> file.
889 <heading>The version of a package</heading>
892 Every package has a version number recorded in its
893 <tt>Version</tt> control file field, described in
894 <ref id="f-Version">.
898 The package management system imposes an ordering on version
899 numbers, so that it can tell whether packages are being up- or
900 downgraded and so that package system front end applications
901 can tell whether a package it finds available is newer than
902 the one installed on the system. The version number format
903 has the most significant parts (as far as comparison is
904 concerned) at the beginning.
908 If an upstream package has problematic version numbers they
909 should be converted to a sane form for use in the
910 <tt>Version</tt> field.
914 <heading>Version numbers based on dates</heading>
917 In general, Debian packages should use the same version
918 numbers as the upstream sources. However, upstream version
919 numbers based on some date formats (sometimes used for
920 development or "snapshot" releases) will not be ordered
921 correctly by the package management software. For
922 example, <prgn>dpkg</prgn> will consider "96May01" to be
923 greater than "96Dec24".
927 To prevent having to use epochs for every new upstream
928 version, the date-based portion of any upstream version number
929 should be given in a way that sorts correctly: four-digit year
930 first, followed by a two-digit numeric month, followed by a
931 two-digit numeric date, possibly with punctuation between the
936 Native Debian packages (i.e., packages which have been written
937 especially for Debian) whose version numbers include dates
938 should also follow these rules. If punctuation is desired
939 between the date components, remember that hyphen (<tt>-</tt>)
940 cannot be used in native package versions. Period
941 (<tt>.</tt>) is normally a good choice.
947 <sect id="maintainer">
948 <heading>The maintainer of a package</heading>
951 Every package must have a maintainer, except for orphaned
952 packages as described below. The maintainer may be one person
953 or a group of people reachable from a common email address, such
954 as a mailing list. The maintainer is responsible for
955 maintaining the Debian packaging files, evaluating and
956 responding appropriately to reported bugs, uploading new
957 versions of the package (either directly or through a sponsor),
958 ensuring that the package is placed in the appropriate archive
959 area and included in Debian releases as appropriate for the
960 stability and utility of the package, and requesting removal of
961 the package from the Debian distribution if it is no longer
962 useful or maintainable.
966 The maintainer must be specified in the <tt>Maintainer</tt>
967 control field with their correct name and a working email
968 address. The email address given in the <tt>Maintainer</tt>
969 control field must accept mail from those role accounts in
970 Debian used to send automated mails regarding the package. This
971 includes non-spam mail from the bug-tracking system, all mail
972 from the Debian archive maintenance software, and other role
973 accounts or automated processes that are commonly agreed on by
974 the project.<footnote>
975 A sample implementation of such a whitelist written for the
976 Mailman mailing list management software is used for mailing
977 lists hosted by alioth.debian.org.
979 If one person or team maintains several packages, they should
980 use the same form of their name and email address in
981 the <tt>Maintainer</tt> fields of those packages.
985 The format of the <tt>Maintainer</tt> control field is
986 described in <ref id="f-Maintainer">.
990 If the maintainer of the package is a team of people with a
991 shared email address, the <tt>Uploaders</tt> control field must
992 be present and must contain at least one human with their
993 personal email address. See <ref id="f-Uploaders"> for the
994 syntax of that field.
998 An orphaned package is one with no current maintainer. Orphaned
999 packages should have their <tt>Maintainer</tt> control field set
1000 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1001 These packages are considered maintained by the Debian project
1002 as a whole until someone else volunteers to take over
1003 maintenance.<footnote>
1004 The detailed procedure for gracefully orphaning a package can
1005 be found in the Debian Developer's Reference
1006 (see <ref id="related">).
1011 <sect id="descriptions">
1012 <heading>The description of a package</heading>
1015 Every Debian package must have a <tt>Description</tt> control
1016 field which contains a synopsis and extended description of the
1017 package. Technical information about the format of the
1018 <tt>Description</tt> field is in <ref id="f-Description">.
1022 The description should describe the package (the program) to a
1023 user (system administrator) who has never met it before so that
1024 they have enough information to decide whether they want to
1025 install it. This description should not just be copied verbatim
1026 from the program's documentation.
1030 Put important information first, both in the synopsis and
1031 extended description. Sometimes only the first part of the
1032 synopsis or of the description will be displayed. You can
1033 assume that there will usually be a way to see the whole
1034 extended description.
1038 The description should also give information about the
1039 significant dependencies and conflicts between this package
1040 and others, so that the user knows why these dependencies and
1041 conflicts have been declared.
1045 Instructions for configuring or using the package should
1046 not be included (that is what installation scripts,
1047 manual pages, info files, etc., are for). Copyright
1048 statements and other administrivia should not be included
1049 either (that is what the copyright file is for).
1052 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1055 The single line synopsis should be kept brief - certainly
1056 under 80 characters.
1060 Do not include the package name in the synopsis line. The
1061 display software knows how to display this already, and you
1062 do not need to state it. Remember that in many situations
1063 the user may only see the synopsis line - make it as
1064 informative as you can.
1069 <sect1 id="extendeddesc"><heading>The extended description</heading>
1072 Do not try to continue the single line synopsis into the
1073 extended description. This will not work correctly when
1074 the full description is displayed, and makes no sense
1075 where only the summary (the single line synopsis) is
1080 The extended description should describe what the package
1081 does and how it relates to the rest of the system (in terms
1082 of, for example, which subsystem it is which part of).
1086 The description field needs to make sense to anyone, even
1087 people who have no idea about any of the things the
1088 package deals with.<footnote>
1089 The blurb that comes with a program in its
1090 announcements and/or <prgn>README</prgn> files is
1091 rarely suitable for use in a description. It is
1092 usually aimed at people who are already in the
1093 community where the package is used.
1101 <sect id="dependencies">
1102 <heading>Dependencies</heading>
1105 Every package must specify the dependency information
1106 about other packages that are required for the first to
1111 For example, a dependency entry must be provided for any
1112 shared libraries required by a dynamically-linked executable
1113 binary in a package.
1117 Packages are not required to declare any dependencies they
1118 have on other packages which are marked <tt>Essential</tt>
1119 (see below), and should not do so unless they depend on a
1120 particular version of that package.<footnote>
1122 Essential is needed in part to avoid unresolvable dependency
1123 loops on upgrade. If packages add unnecessary dependencies
1124 on packages in this set, the chances that there
1125 <strong>will</strong> be an unresolvable dependency loop
1126 caused by forcing these Essential packages to be configured
1127 first before they need to be is greatly increased. It also
1128 increases the chances that frontends will be unable to
1129 <strong>calculate</strong> an upgrade path, even if one
1133 Also, functionality is rarely ever removed from the
1134 Essential set, but <em>packages</em> have been removed from
1135 the Essential set when the functionality moved to a
1136 different package. So depending on these packages <em>just
1137 in case</em> they stop being essential does way more harm
1144 Sometimes, unpacking one package requires that another package
1145 be first unpacked <em>and</em> configured. In this case, the
1146 depending package must specify this dependency in
1147 the <tt>Pre-Depends</tt> control field.
1151 You should not specify a <tt>Pre-Depends</tt> entry for a
1152 package before this has been discussed on the
1153 <tt>debian-devel</tt> mailing list and a consensus about
1154 doing that has been reached.
1158 The format of the package interrelationship control fields is
1159 described in <ref id="relationships">.
1163 <sect id="virtual_pkg">
1164 <heading>Virtual packages</heading>
1167 Sometimes, there are several packages which offer
1168 more-or-less the same functionality. In this case, it's
1169 useful to define a <em>virtual package</em> whose name
1170 describes that common functionality. (The virtual
1171 packages only exist logically, not physically; that's why
1172 they are called <em>virtual</em>.) The packages with this
1173 particular function will then <em>provide</em> the virtual
1174 package. Thus, any other package requiring that function
1175 can simply depend on the virtual package without having to
1176 specify all possible packages individually.
1180 All packages should use virtual package names where
1181 appropriate, and arrange to create new ones if necessary.
1182 They should not use virtual package names (except privately,
1183 amongst a cooperating group of packages) unless they have
1184 been agreed upon and appear in the list of virtual package
1185 names. (See also <ref id="virtual">)
1189 The latest version of the authoritative list of virtual
1190 package names can be found in the <tt>debian-policy</tt> package.
1191 It is also available from the Debian web mirrors at
1192 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1193 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1197 The procedure for updating the list is described in the preface
1204 <heading>Base system</heading>
1207 The <tt>base system</tt> is a minimum subset of the Debian
1208 system that is installed before everything else
1209 on a new system. Only very few packages are allowed to form
1210 part of the base system, in order to keep the required disk
1215 The base system consists of all those packages with priority
1216 <tt>required</tt> or <tt>important</tt>. Many of them will
1217 be tagged <tt>essential</tt> (see below).
1222 <heading>Essential packages</heading>
1225 Essential is defined as the minimal set of functionality that
1226 must be available and usable on the system at all times, even
1227 when packages are in an unconfigured (but unpacked) state.
1228 Packages are tagged <tt>essential</tt> for a system using the
1229 <tt>Essential</tt> control field. The format of the
1230 <tt>Essential</tt> control field is described in <ref
1235 Since these packages cannot be easily removed (one has to
1236 specify an extra <em>force option</em> to
1237 <prgn>dpkg</prgn> to do so), this flag must not be used
1238 unless absolutely necessary. A shared library package
1239 must not be tagged <tt>essential</tt>; dependencies will
1240 prevent its premature removal, and we need to be able to
1241 remove it when it has been superseded.
1245 Since dpkg will not prevent upgrading of other packages
1246 while an <tt>essential</tt> package is in an unconfigured
1247 state, all <tt>essential</tt> packages must supply all of
1248 their core functionality even when unconfigured. If the
1249 package cannot satisfy this requirement it must not be
1250 tagged as essential, and any packages depending on this
1251 package must instead have explicit dependency fields as
1256 Maintainers should take great care in adding any programs,
1257 interfaces, or functionality to <tt>essential</tt> packages.
1258 Packages may assume that functionality provided by
1259 <tt>essential</tt> packages is always available without
1260 declaring explicit dependencies, which means that removing
1261 functionality from the Essential set is very difficult and is
1262 almost never done. Any capability added to an
1263 <tt>essential</tt> package therefore creates an obligation to
1264 support that capability as part of the Essential set in
1269 You must not tag any packages <tt>essential</tt> before
1270 this has been discussed on the <tt>debian-devel</tt>
1271 mailing list and a consensus about doing that has been
1276 <sect id="maintscripts">
1277 <heading>Maintainer Scripts</heading>
1280 The package installation scripts should avoid producing
1281 output which is unnecessary for the user to see and
1282 should rely on <prgn>dpkg</prgn> to stave off boredom on
1283 the part of a user installing many packages. This means,
1284 amongst other things, using the <tt>--quiet</tt> option on
1285 <prgn>install-info</prgn>.
1289 Errors which occur during the execution of an installation
1290 script must be checked and the installation must not
1291 continue after an error.
1295 Note that in general <ref id="scripts"> applies to package
1296 maintainer scripts, too.
1300 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1301 to another package without consulting the maintainer of that
1302 package first. When adding or removing diversions, package
1303 maintainer scripts must provide the <tt>--package</tt> flag
1304 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1308 All packages which supply an instance of a common command
1309 name (or, in general, filename) should generally use
1310 <prgn>update-alternatives</prgn>, so that they may be
1311 installed together. If <prgn>update-alternatives</prgn>
1312 is not used, then each package must use
1313 <tt>Conflicts</tt> to ensure that other packages are
1314 de-installed. (In this case, it may be appropriate to
1315 specify a conflict against earlier versions of something
1316 that previously did not use
1317 <prgn>update-alternatives</prgn>; this is an exception to
1318 the usual rule that versioned conflicts should be
1322 <sect1 id="maintscriptprompt">
1323 <heading>Prompting in maintainer scripts</heading>
1325 Package maintainer scripts may prompt the user if
1326 necessary. Prompting must be done by communicating
1327 through a program, such as <prgn>debconf</prgn>, which
1328 conforms to the Debian Configuration Management
1329 Specification, version 2 or higher.
1333 Packages which are essential, or which are dependencies of
1334 essential packages, may fall back on another prompting method
1335 if no such interface is available when they are executed.
1339 The Debian Configuration Management Specification is included
1340 in the <file>debconf_specification</file> files in the
1341 <package>debian-policy</package> package.
1342 It is also available from the Debian web mirrors at
1343 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1344 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1348 Packages which use the Debian Configuration Management
1349 Specification may contain the additional control information
1350 files <file>config</file>
1351 and <file>templates</file>. <file>config</file> is an
1352 additional maintainer script used for package configuration,
1353 and <file>templates</file> contains templates used for user
1354 prompting. The <prgn>config</prgn> script might be run before
1355 the <prgn>preinst</prgn> script and before the package is
1356 unpacked or any of its dependencies or pre-dependencies are
1357 satisfied. Therefore it must work using only the tools
1358 present in <em>essential</em> packages.<footnote>
1359 <package>Debconf</package> or another tool that
1360 implements the Debian Configuration Management
1361 Specification will also be installed, and any
1362 versioned dependencies on it will be satisfied
1363 before preconfiguration begins.
1368 Packages which use the Debian Configuration Management
1369 Specification must allow for translation of their user-visible
1370 messages by using a gettext-based system such as the one
1371 provided by the <package>po-debconf</package> package.
1375 Packages should try to minimize the amount of prompting
1376 they need to do, and they should ensure that the user
1377 will only ever be asked each question once. This means
1378 that packages should try to use appropriate shared
1379 configuration files (such as <file>/etc/papersize</file> and
1380 <file>/etc/news/server</file>), and shared
1381 <package>debconf</package> variables rather than each
1382 prompting for their own list of required pieces of
1387 It also means that an upgrade should not ask the same
1388 questions again, unless the user has used
1389 <tt>dpkg --purge</tt> to remove the package's configuration.
1390 The answers to configuration questions should be stored in an
1391 appropriate place in <file>/etc</file> so that the user can
1392 modify them, and how this has been done should be
1397 If a package has a vitally important piece of
1398 information to pass to the user (such as "don't run me
1399 as I am, you must edit the following configuration files
1400 first or you risk your system emitting badly-formatted
1401 messages"), it should display this in the
1402 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1403 prompt the user to hit return to acknowledge the
1404 message. Copyright messages do not count as vitally
1405 important (they belong in
1406 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1407 neither do instructions on how to use a program (these
1408 should be in on-line documentation, where all the users
1413 Any necessary prompting should almost always be confined
1414 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1415 script. If it is done in the <prgn>postinst</prgn>, it
1416 should be protected with a conditional so that
1417 unnecessary prompting doesn't happen if a package's
1418 installation fails and the <prgn>postinst</prgn> is
1419 called with <tt>abort-upgrade</tt>,
1420 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1430 <heading>Source packages</heading>
1432 <sect id="standardsversion">
1433 <heading>Standards conformance</heading>
1436 Source packages should specify the most recent version number
1437 of this policy document with which your package complied
1438 when it was last updated.
1442 This information may be used to file bug reports
1443 automatically if your package becomes too much out of date.
1447 The version is specified in the <tt>Standards-Version</tt>
1449 The format of the <tt>Standards-Version</tt> field is
1450 described in <ref id="f-Standards-Version">.
1454 You should regularly, and especially if your package has
1455 become out of date, check for the newest Policy Manual
1456 available and update your package, if necessary. When your
1457 package complies with the new standards you should update the
1458 <tt>Standards-Version</tt> source package field and
1459 release it.<footnote>
1460 See the file <file>upgrading-checklist</file> for
1461 information about policy which has changed between
1462 different versions of this document.
1468 <sect id="pkg-relations">
1469 <heading>Package relationships</heading>
1472 Source packages should specify which binary packages they
1473 require to be installed or not to be installed in order to
1474 build correctly. For example, if building a package
1475 requires a certain compiler, then the compiler should be
1476 specified as a build-time dependency.
1480 It is not necessary to explicitly specify build-time
1481 relationships on a minimal set of packages that are always
1482 needed to compile, link and put in a Debian package a
1483 standard "Hello World!" program written in C or C++. The
1484 required packages are called <em>build-essential</em>, and
1485 an informational list can be found in
1486 <file>/usr/share/doc/build-essential/list</file> (which is
1487 contained in the <tt>build-essential</tt>
1490 <list compact="compact">
1492 This allows maintaining the list separately
1493 from the policy documents (the list does not
1494 need the kind of control that the policy
1498 Having a separate package allows one to install
1499 the build-essential packages on a machine, as
1500 well as allowing other packages such as tasks to
1501 require installation of the build-essential
1502 packages using the depends relation.
1505 The separate package allows bug reports against
1506 the list to be categorized separately from
1507 the policy management process in the BTS.
1514 When specifying the set of build-time dependencies, one
1515 should list only those packages explicitly required by the
1516 build. It is not necessary to list packages which are
1517 required merely because some other package in the list of
1518 build-time dependencies depends on them.<footnote>
1519 The reason for this is that dependencies change, and
1520 you should list all those packages, and <em>only</em>
1521 those packages that <em>you</em> need directly. What
1522 others need is their business. For example, if you
1523 only link against <file>libimlib</file>, you will need to
1524 build-depend on <package>libimlib2-dev</package> but
1525 not against any <tt>libjpeg*</tt> packages, even
1526 though <tt>libimlib2-dev</tt> currently depends on
1527 them: installation of <package>libimlib2-dev</package>
1528 will automatically ensure that all of its run-time
1529 dependencies are satisfied.
1534 If build-time dependencies are specified, it must be
1535 possible to build the package and produce working binaries
1536 on a system with only essential and build-essential
1537 packages installed and also those required to satisfy the
1538 build-time relationships (including any implied
1539 relationships). In particular, this means that version
1540 clauses should be used rigorously in build-time
1541 relationships so that one cannot produce bad or
1542 inconsistently configured packages when the relationships
1543 are properly satisfied.
1547 <ref id="relationships"> explains the technical details.
1552 <heading>Changes to the upstream sources</heading>
1555 If changes to the source code are made that are not
1556 specific to the needs of the Debian system, they should be
1557 sent to the upstream authors in whatever form they prefer
1558 so as to be included in the upstream version of the
1563 If you need to configure the package differently for
1564 Debian or for Linux, and the upstream source doesn't
1565 provide a way to do so, you should add such configuration
1566 facilities (for example, a new <prgn>autoconf</prgn> test
1567 or <tt>#define</tt>) and send the patch to the upstream
1568 authors, with the default set to the way they originally
1569 had it. You can then easily override the default in your
1570 <file>debian/rules</file> or wherever is appropriate.
1574 You should make sure that the <prgn>configure</prgn> utility
1575 detects the correct architecture specification string
1576 (refer to <ref id="arch-spec"> for details).
1580 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1581 <prgn>configure</prgn> scripts are used, you should edit the
1582 <file>.in</file> files rather than editing the
1583 <prgn>Makefile</prgn> directly. This allows the user to
1584 reconfigure the package if necessary. You should
1585 <em>not</em> configure the package and edit the generated
1586 <prgn>Makefile</prgn>! This makes it impossible for someone
1587 else to later reconfigure the package without losing the
1593 <sect id="dpkgchangelog">
1594 <heading>Debian changelog: <file>debian/changelog</file></heading>
1597 Changes in the Debian version of the package should be
1598 briefly explained in the Debian changelog file
1599 <file>debian/changelog</file>.<footnote>
1601 Mistakes in changelogs are usually best rectified by
1602 making a new changelog entry rather than "rewriting
1603 history" by editing old changelog entries.
1606 This includes modifications
1607 made in the Debian package compared to the upstream one
1608 as well as other changes and updates to the package.
1610 Although there is nothing stopping an author who is also
1611 the Debian maintainer from using this changelog for all
1612 their changes, it will have to be renamed if the Debian
1613 and upstream maintainers become different people. In such
1614 a case, however, it might be better to maintain the package
1615 as a non-native package.
1620 The format of the <file>debian/changelog</file> allows the
1621 package building tools to discover which version of the package
1622 is being built and find out other release-specific information.
1626 That format is a series of entries like this:
1628 <example compact="compact">
1629 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1631 [optional blank line(s), stripped]
1633 * <var>change details</var>
1634 <var>more change details</var>
1636 [blank line(s), included in output of dpkg-parsechangelog]
1638 * <var>even more change details</var>
1640 [optional blank line(s), stripped]
1642 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1647 <var>package</var> and <var>version</var> are the source
1648 package name and version number.
1652 <var>distribution(s)</var> lists the distributions where
1653 this version should be installed when it is uploaded - it
1654 is copied to the <tt>Distribution</tt> field in the
1655 <file>.changes</file> file. See <ref id="f-Distribution">.
1659 <var>urgency</var> is the value for the <tt>Urgency</tt>
1660 field in the <file>.changes</file> file for the upload
1661 (see <ref id="f-Urgency">). It is not possible to specify
1662 an urgency containing commas; commas are used to separate
1663 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1664 <prgn>dpkg</prgn> changelog format (though there is
1665 currently only one useful <var>keyword</var>,
1670 The change details may in fact be any series of lines
1671 starting with at least two spaces, but conventionally each
1672 change starts with an asterisk and a separating space and
1673 continuation lines are indented so as to bring them in
1674 line with the start of the text above. Blank lines may be
1675 used here to separate groups of changes, if desired.
1679 If this upload resolves bugs recorded in the Bug Tracking
1680 System (BTS), they may be automatically closed on the
1681 inclusion of this package into the Debian archive by
1682 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1683 in the change details.<footnote>
1684 To be precise, the string should match the following
1685 Perl regular expression:
1687 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1689 Then all of the bug numbers listed will be closed by the
1690 archive maintenance script (<prgn>katie</prgn>) using the
1691 <var>version</var> of the changelog entry.
1693 This information is conveyed via the <tt>Closes</tt> field
1694 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1698 The maintainer name and email address used in the changelog
1699 should be the details of the person uploading <em>this</em>
1700 version. They are <em>not</em> necessarily those of the
1701 usual package maintainer.<footnote>
1702 If the developer uploading the package is not one of the usual
1703 maintainers of the package (as listed in
1704 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1705 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1706 fields of the package), the first line of the changelog is
1707 conventionally used to explain why a non-maintainer is
1708 uploading the package. The Debian Developer's Reference
1709 (see <ref id="related">) documents the conventions
1711 The information here will be copied to the <tt>Changed-By</tt>
1712 field in the <tt>.changes</tt> file
1713 (see <ref id="f-Changed-By">), and then later used to send an
1714 acknowledgement when the upload has been installed.
1718 The <var>date</var> has the following format<footnote>
1719 This is the same as the format generated by <tt>date
1721 </footnote> (compatible and with the same semantics of
1722 RFC 2822 and RFC 5322):
1723 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1725 <list compact="compact">
1727 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1730 dd is a one- or two-digit day of the month (01-31)
1733 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1736 <item>yyyy is the four-digit year (e.g. 2010)</item>
1737 <item>hh is the two-digit hour (00-23)</item>
1738 <item>mm is the two-digit minutes (00-59)</item>
1739 <item>ss is the two-digit seconds (00-60)</item>
1741 +zzzz or -zzzz is the the time zone offset from Coordinated
1742 Universal Time (UTC). "+" indicates that the time is ahead
1743 of (i.e., east of) UTC and "-" indicates that the time is
1744 behind (i.e., west of) UTC. The first two digits indicate
1745 the hour difference from UTC and the last two digits
1746 indicate the number of additional minutes difference from
1747 UTC. The last two digits must be in the range 00-59.
1753 The first "title" line with the package name must start
1754 at the left hand margin. The "trailer" line with the
1755 maintainer and date details must be preceded by exactly
1756 one space. The maintainer details and the date must be
1757 separated by exactly two spaces.
1761 The entire changelog must be encoded in UTF-8.
1765 For more information on placement of the changelog files
1766 within binary packages, please see <ref id="changelogs">.
1770 <sect id="dpkgcopyright">
1771 <heading>Copyright: <file>debian/copyright</file></heading>
1773 Every package must be accompanied by a verbatim copy of its
1774 copyright information and distribution license in the file
1775 <file>/usr/share/doc/<var>package</var>/copyright</file>
1776 (see <ref id="copyrightfile"> for further details). Also see
1777 <ref id="pkgcopyright"> for further considerations related
1778 to copyrights for packages.
1782 <heading>Error trapping in makefiles</heading>
1785 When <prgn>make</prgn> invokes a command in a makefile
1786 (including your package's upstream makefiles and
1787 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1788 means that <prgn>sh</prgn>'s usual bad error handling
1789 properties apply: if you include a miniature script as one
1790 of the commands in your makefile you'll find that if you
1791 don't do anything about it then errors are not detected
1792 and <prgn>make</prgn> will blithely continue after
1797 Every time you put more than one shell command (this
1798 includes using a loop) in a makefile command you
1799 must make sure that errors are trapped. For
1800 simple compound commands, such as changing directory and
1801 then running a program, using <tt>&&</tt> rather
1802 than semicolon as a command separator is sufficient. For
1803 more complex commands including most loops and
1804 conditionals you should include a separate <tt>set -e</tt>
1805 command at the start of every makefile command that's
1806 actually one of these miniature shell scripts.
1810 <sect id="timestamps">
1811 <heading>Time Stamps</heading>
1813 Maintainers should preserve the modification times of the
1814 upstream source files in a package, as far as is reasonably
1816 The rationale is that there is some information conveyed
1817 by knowing the age of the file, for example, you could
1818 recognize that some documentation is very old by looking
1819 at the modification time, so it would be nice if the
1820 modification time of the upstream source would be
1826 <sect id="restrictions">
1827 <heading>Restrictions on objects in source packages</heading>
1830 The source package may not contain any hard links<footnote>
1832 This is not currently detected when building source
1833 packages, but only when extracting
1837 Hard links may be permitted at some point in the
1838 future, but would require a fair amount of
1841 </footnote>, device special files, sockets or setuid or
1842 setgid files.<footnote>
1843 Setgid directories are allowed.
1848 <sect id="debianrules">
1849 <heading>Main building script: <file>debian/rules</file></heading>
1852 This file must be an executable makefile, and contains the
1853 package-specific recipes for compiling the package and
1854 building binary package(s) from the source.
1858 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1859 so that it can be invoked by saying its name rather than
1860 invoking <prgn>make</prgn> explicitly. That is, invoking
1861 either of <tt>make -f debian/rules <em>args...</em></tt>
1862 or <tt>./debian/rules <em>args...</em></tt> must result in
1867 The following targets are required and must be implemented
1868 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1869 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1870 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1874 Since an interactive <file>debian/rules</file> script makes it
1875 impossible to auto-compile that package and also makes it hard
1876 for other people to reproduce the same binary package, all
1877 required targets must be non-interactive. It also follows that
1878 any target that these targets depend on must also be
1883 The targets are as follows:
1885 <tag><tt>build</tt> (required)</tag>
1888 The <tt>build</tt> target should perform all the
1889 configuration and compilation of the package.
1890 If a package has an interactive pre-build
1891 configuration routine, the Debian source package
1892 must either be built after this has taken place (so
1893 that the binary package can be built without rerunning
1894 the configuration) or the configuration routine
1895 modified to become non-interactive. (The latter is
1896 preferable if there are architecture-specific features
1897 detected by the configuration routine.)
1901 For some packages, notably ones where the same
1902 source tree is compiled in different ways to produce
1903 two binary packages, the <tt>build</tt> target
1904 does not make much sense. For these packages it is
1905 good enough to provide two (or more) targets
1906 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1907 for each of the ways of building the package, and a
1908 <tt>build</tt> target that does nothing. The
1909 <tt>binary</tt> target will have to build the
1910 package in each of the possible ways and make the
1911 binary package out of each.
1915 The <tt>build</tt> target must not do anything
1916 that might require root privilege.
1920 The <tt>build</tt> target may need to run the
1921 <tt>clean</tt> target first - see below.
1925 When a package has a configuration and build routine
1926 which takes a long time, or when the makefiles are
1927 poorly designed, or when <tt>build</tt> needs to
1928 run <tt>clean</tt> first, it is a good idea to
1929 <tt>touch build</tt> when the build process is
1930 complete. This will ensure that if <tt>debian/rules
1931 build</tt> is run again it will not rebuild the whole
1933 Another common way to do this is for <tt>build</tt>
1934 to depend on <prgn>build-stamp</prgn> and to do
1935 nothing else, and for the <prgn>build-stamp</prgn>
1936 target to do the building and to <tt>touch
1937 build-stamp</tt> on completion. This is
1938 especially useful if the build routine creates a
1939 file or directory called <tt>build</tt>; in such a
1940 case, <tt>build</tt> will need to be listed as
1941 a phony target (i.e., as a dependency of the
1942 <tt>.PHONY</tt> target). See the documentation of
1943 <prgn>make</prgn> for more information on phony
1949 <tag><tt>build-arch</tt> (optional),
1950 <tt>build-indep</tt> (optional)
1954 A package may also provide one or both of the targets
1955 <tt>build-arch</tt> and <tt>build-indep</tt>.
1956 The <tt>build-arch</tt> target, if provided, should
1957 perform all the configuration and compilation required for
1958 producing all architecture-dependant binary packages
1959 (those packages for which the body of the
1960 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1961 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1962 target, if provided, should perform all the configuration
1963 and compilation required for producing all
1964 architecture-independent binary packages (those packages
1965 for which the body of the <tt>Architecture</tt> field
1966 in <tt>debian/control</tt> is <tt>all</tt>).
1970 If <tt>build-arch</tt> or <tt>build-indep</tt> targets are
1971 provided in the rules file, the <tt>build</tt> target
1972 should either depend on those targets or take the same
1973 actions as invoking those targets would perform.<footnote>
1974 The intent of this split is so that binary-only builds
1975 need not install the dependencies required for
1976 the <tt>build-indep</tt> target. However, this is not
1977 yet used in practice since <tt>dpkg-buildpackage
1978 -B</tt>, and therefore the autobuilders,
1979 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1980 due to the difficulties in determining whether the
1981 optional <tt>build-arch</tt> target exists.
1986 If one or both of the targets <tt>build-arch</tt> and
1987 <tt>build-indep</tt> are not provided, then invoking
1988 <file>debian/rules</file> with one of the not-provided
1989 targets as arguments should produce a exit status code
1990 of 2. Usually this is provided automatically by make
1991 if the target is missing.
1995 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1996 must not do anything that might require root privilege.
2000 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
2001 (required), <tt>binary-indep</tt> (required)
2005 The <tt>binary</tt> target must be all that is
2006 necessary for the user to build the binary package(s)
2007 produced from this source package. It is
2008 split into two parts: <prgn>binary-arch</prgn> builds
2009 the binary packages which are specific to a particular
2010 architecture, and <tt>binary-indep</tt> builds
2011 those which are not.
2014 <tt>binary</tt> may be (and commonly is) a target with
2015 no commands which simply depends on
2016 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2019 Both <tt>binary-*</tt> targets should depend on the
2020 <tt>build</tt> target, or on the appropriate
2021 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2022 provided, so that the package is built if it has not
2023 been already. It should then create the relevant
2024 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2025 make their control files and <prgn>dpkg-deb</prgn> to
2026 build them and place them in the parent of the top
2031 Both the <tt>binary-arch</tt> and
2032 <tt>binary-indep</tt> targets <em>must</em> exist.
2033 If one of them has nothing to do (which will always be
2034 the case if the source generates only a single binary
2035 package, whether architecture-dependent or not), it
2036 must still exist and must always succeed.
2040 The <tt>binary</tt> targets must be invoked as
2042 The <prgn>fakeroot</prgn> package often allows one
2043 to build a package correctly even without being
2049 <tag><tt>clean</tt> (required)</tag>
2052 This must undo any effects that the <tt>build</tt>
2053 and <tt>binary</tt> targets may have had, except
2054 that it should leave alone any output files created in
2055 the parent directory by a run of a <tt>binary</tt>
2060 If a <tt>build</tt> file is touched at the end of
2061 the <tt>build</tt> target, as suggested above, it
2062 should be removed as the first action that
2063 <tt>clean</tt> performs, so that running
2064 <tt>build</tt> again after an interrupted
2065 <tt>clean</tt> doesn't think that everything is
2070 The <tt>clean</tt> target may need to be
2071 invoked as root if <tt>binary</tt> has been
2072 invoked since the last <tt>clean</tt>, or if
2073 <tt>build</tt> has been invoked as root (since
2074 <tt>build</tt> may create directories, for
2079 <tag><tt>get-orig-source</tt> (optional)</tag>
2082 This target fetches the most recent version of the
2083 original source package from a canonical archive site
2084 (via FTP or WWW, for example), does any necessary
2085 rearrangement to turn it into the original source
2086 tar file format described below, and leaves it in the
2091 This target may be invoked in any directory, and
2092 should take care to clean up any temporary files it
2097 This target is optional, but providing it if
2098 possible is a good idea.
2102 <tag><tt>patch</tt> (optional)</tag>
2105 This target performs whatever additional actions are
2106 required to make the source ready for editing (unpacking
2107 additional upstream archives, applying patches, etc.).
2108 It is recommended to be implemented for any package where
2109 <tt>dpkg-source -x</tt> does not result in source ready
2110 for additional modification. See
2111 <ref id="readmesource">.
2117 The <tt>build</tt>, <tt>binary</tt> and
2118 <tt>clean</tt> targets must be invoked with the current
2119 directory being the package's top-level directory.
2124 Additional targets may exist in <file>debian/rules</file>,
2125 either as published or undocumented interfaces or for the
2126 package's internal use.
2130 The architectures we build on and build for are determined
2131 by <prgn>make</prgn> variables using the
2132 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2133 You can determine the Debian architecture and the GNU style
2134 architecture specification string for the build architecture as
2135 well as for the host architecture. The build architecture is
2136 the architecture on which <file>debian/rules</file> is run and
2137 the package build is performed. The host architecture is the
2138 architecture on which the resulting package will be installed
2139 and run. These are normally the same, but may be different in
2140 the case of cross-compilation (building packages for one
2141 architecture on machines of a different architecture).
2145 Here is a list of supported <prgn>make</prgn> variables:
2146 <list compact="compact">
2148 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2151 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2154 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2157 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2158 specification string)
2161 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2162 <tt>DEB_*_GNU_TYPE</tt>)
2165 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2166 <tt>DEB_*_GNU_TYPE</tt>)
2168 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2169 the build architecture or <tt>HOST</tt> for specification of the
2174 Backward compatibility can be provided in the rules file
2175 by setting the needed variables to suitable default
2176 values; please refer to the documentation of
2177 <prgn>dpkg-architecture</prgn> for details.
2181 It is important to understand that the <tt>DEB_*_ARCH</tt>
2182 string only determines which Debian architecture we are
2183 building on or for. It should not be used to get the CPU
2184 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2185 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2186 GNU style variables should generally only be used with upstream
2190 <sect1 id="debianrules-options">
2191 <heading><file>debian/rules</file> and
2192 <tt>DEB_BUILD_OPTIONS</tt></heading>
2195 Supporting the standardized environment variable
2196 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2197 contain several flags to change how a package is compiled and
2198 built. Each flag must be in the form <var>flag</var> or
2199 <var>flag</var>=<var>options</var>. If multiple flags are
2200 given, they must be separated by whitespace.<footnote>
2201 Some packages support any delimiter, but whitespace is the
2202 easiest to parse inside a makefile and avoids ambiguity with
2203 flag values that contain commas.
2205 <var>flag</var> must start with a lowercase letter
2206 (<tt>a-z</tt>) and consist only of lowercase letters,
2207 numbers (<tt>0-9</tt>), and the characters
2208 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2209 <var>options</var> must not contain whitespace. The same
2210 tag should not be given multiple times with conflicting
2211 values. Package maintainers may assume that
2212 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2216 The meaning of the following tags has been standardized:
2220 This tag says to not run any build-time test suite
2221 provided by the package.
2225 The presence of this tag means that the package should
2226 be compiled with a minimum of optimization. For C
2227 programs, it is best to add <tt>-O0</tt> to
2228 <tt>CFLAGS</tt> (although this is usually the default).
2229 Some programs might fail to build or run at this level
2230 of optimization; it may be necessary to use
2231 <tt>-O1</tt>, for example.
2235 This tag means that the debugging symbols should not be
2236 stripped from the binary during installation, so that
2237 debugging information may be included in the package.
2239 <tag>parallel=n</tag>
2241 This tag means that the package should be built using up
2242 to <tt>n</tt> parallel processes if the package build
2243 system supports this.<footnote>
2244 Packages built with <tt>make</tt> can often implement
2245 this by passing the <tt>-j</tt><var>n</var> option to
2248 If the package build system does not support parallel
2249 builds, this string must be ignored. If the package
2250 build system only supports a lower level of concurrency
2251 than <var>n</var>, the package should be built using as
2252 many parallel processes as the package build system
2253 supports. It is up to the package maintainer to decide
2254 whether the package build times are long enough and the
2255 package build system is robust enough to make supporting
2256 parallel builds worthwhile.
2262 Unknown flags must be ignored by <file>debian/rules</file>.
2266 The following makefile snippet is an example of how one may
2267 implement the build options; you will probably have to
2268 massage this example in order to make it work for your
2270 <example compact="compact">
2273 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2274 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2275 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2276 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2278 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2283 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2284 INSTALL_PROGRAM += -s
2286 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2287 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2288 MAKEFLAGS += -j$(NUMJOBS)
2293 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2294 # Code to run the package test suite.
2301 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2302 <sect id="substvars">
2303 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2306 When <prgn>dpkg-gencontrol</prgn>
2307 generates <qref id="binarycontrolfiles">binary package control
2308 files</qref> (<file>DEBIAN/control</file>), it performs variable
2309 substitutions on its output just before writing it. Variable
2310 substitutions have the form <tt>${<var>variable</var>}</tt>.
2311 The optional file <file>debian/substvars</file> contains
2312 variable substitutions to be used; variables can also be set
2313 directly from <file>debian/rules</file> using the <tt>-V</tt>
2314 option to the source packaging commands, and certain predefined
2315 variables are also available.
2319 The <file>debian/substvars</file> file is usually generated and
2320 modified dynamically by <file>debian/rules</file> targets, in
2321 which case it must be removed by the <tt>clean</tt> target.
2325 See <manref name="deb-substvars" section="5"> for full
2326 details about source variable substitutions, including the
2327 format of <file>debian/substvars</file>.</p>
2330 <sect id="debianwatch">
2331 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2334 This is an optional, recommended configuration file for the
2335 <tt>uscan</tt> utility which defines how to automatically scan
2336 ftp or http sites for newly available updates of the
2337 package. This is used
2338 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2339 tools to help with quality control and maintenance of the
2340 distribution as a whole.
2345 <sect id="debianfiles">
2346 <heading>Generated files list: <file>debian/files</file></heading>
2349 This file is not a permanent part of the source tree; it
2350 is used while building packages to record which files are
2351 being generated. <prgn>dpkg-genchanges</prgn> uses it
2352 when it generates a <file>.changes</file> file.
2356 It should not exist in a shipped source package, and so it
2357 (and any backup files or temporary files such as
2358 <file>files.new</file><footnote>
2359 <file>files.new</file> is used as a temporary file by
2360 <prgn>dpkg-gencontrol</prgn> and
2361 <prgn>dpkg-distaddfile</prgn> - they write a new
2362 version of <tt>files</tt> here before renaming it,
2363 to avoid leaving a corrupted copy if an error
2365 </footnote>) should be removed by the
2366 <tt>clean</tt> target. It may also be wise to
2367 ensure a fresh start by emptying or removing it at the
2368 start of the <tt>binary</tt> target.
2372 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2373 package, it adds an entry to <file>debian/files</file> for the
2374 <file>.deb</file> file that will be created when <tt>dpkg-deb
2375 --build</tt> is run for that binary package. So for most
2376 packages all that needs to be done with this file is to
2377 delete it in the <tt>clean</tt> target.
2381 If a package upload includes files besides the source
2382 package and any binary packages whose control files were
2383 made with <prgn>dpkg-gencontrol</prgn> then they should be
2384 placed in the parent of the package's top-level directory
2385 and <prgn>dpkg-distaddfile</prgn> should be called to add
2386 the file to the list in <file>debian/files</file>.</p>
2389 <sect id="embeddedfiles">
2390 <heading>Convenience copies of code</heading>
2393 Some software packages include in their distribution convenience
2394 copies of code from other software packages, generally so that
2395 users compiling from source don't have to download multiple
2396 packages. Debian packages should not make use of these
2397 convenience copies unless the included package is explicitly
2398 intended to be used in this way.<footnote>
2399 For example, parts of the GNU build system work like this.
2401 If the included code is already in the Debian archive in the
2402 form of a library, the Debian packaging should ensure that
2403 binary packages reference the libraries already in Debian and
2404 the convenience copy is not used. If the included code is not
2405 already in Debian, it should be packaged separately as a
2406 prerequisite if possible.
2408 Having multiple copies of the same code in Debian is
2409 inefficient, often creates either static linking or shared
2410 library conflicts, and, most importantly, increases the
2411 difficulty of handling security vulnerabilities in the
2417 <sect id="readmesource">
2418 <heading>Source package handling:
2419 <file>debian/README.source</file></heading>
2422 If running <prgn>dpkg-source -x</prgn> on a source package
2423 doesn't produce the source of the package, ready for editing,
2424 and allow one to make changes and run
2425 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2426 without taking any additional steps, creating a
2427 <file>debian/README.source</file> documentation file is
2428 recommended. This file should explain how to do all of the
2431 <item>Generate the fully patched source, in a form ready for
2432 editing, that would be built to create Debian
2433 packages. Doing this with a <tt>patch</tt> target in
2434 <file>debian/rules</file> is recommended; see
2435 <ref id="debianrules">.</item>
2436 <item>Modify the source and save those modifications so that
2437 they will be applied when building the package.</item>
2438 <item>Remove source modifications that are currently being
2439 applied when building the package.</item>
2440 <item>Optionally, document what steps are necessary to
2441 upgrade the Debian source package to a new upstream version,
2442 if applicable.</item>
2444 This explanation should include specific commands and mention
2445 any additional required Debian packages. It should not assume
2446 familiarity with any specific Debian packaging system or patch
2451 This explanation may refer to a documentation file installed by
2452 one of the package's build dependencies provided that the
2453 referenced documentation clearly explains these tasks and is not
2454 a general reference manual.
2458 <file>debian/README.source</file> may also include any other
2459 information that would be helpful to someone modifying the
2460 source package. Even if the package doesn't fit the above
2461 description, maintainers are encouraged to document in a
2462 <file>debian/README.source</file> file any source package with a
2463 particularly complex or unintuitive source layout or build
2464 system (for example, a package that builds the same source
2465 multiple times to generate different binary packages).
2471 <chapt id="controlfields">
2472 <heading>Control files and their fields</heading>
2475 The package management system manipulates data represented in
2476 a common format, known as <em>control data</em>, stored in
2477 <em>control files</em>.
2478 Control files are used for source packages, binary packages and
2479 the <file>.changes</file> files which control the installation
2480 of uploaded files<footnote>
2481 <prgn>dpkg</prgn>'s internal databases are in a similar
2486 <sect id="controlsyntax">
2487 <heading>Syntax of control files</heading>
2490 A control file consists of one or more paragraphs of
2492 The paragraphs are also sometimes referred to as stanzas.
2494 The paragraphs are separated by empty lines. Parsers may accept
2495 lines consisting solely of spaces and tabs as paragraph
2496 separators, but control files should use empty lines. Some control
2497 files allow only one paragraph; others allow several, in
2498 which case each paragraph usually refers to a different
2499 package. (For example, in source packages, the first
2500 paragraph refers to the source package, and later paragraphs
2501 refer to binary packages generated from the source.) The
2502 ordering of the paragraphs in control files is significant.
2506 Each paragraph consists of a series of data fields. Each field
2507 consists of the field name followed by a colon and then the
2508 data/value associated with that field. The field name is
2509 composed of US-ASCII characters excluding control characters,
2510 space, and colon (i.e., characters in the ranges 33-57 and
2511 59-126, inclusive). Field names must not begin with the comment
2512 character, <tt>#</tt>.
2516 The field ends at the end of the line or at the end of the last
2517 continuation line (see below). Horizontal whitespace (spaces
2518 and tabs) may occur immediately before or after the value and is
2519 ignored there; it is conventional to put a single space after
2520 the colon. For example, a field might be:
2521 <example compact="compact">
2524 the field name is <tt>Package</tt> and the field value
2529 A paragraph must not contain more than one instance of a
2530 particular field name.
2534 There are three types of fields:
2538 The field, including its value, must be a single line. Folding
2539 of the field is not permitted. This is the default field type
2540 if the definition of the field does not specify a different
2545 The value of a folded field is a logical line that may span
2546 several lines. The lines after the first are called
2547 continuation lines and must start with a space or a tab.
2548 Whitespace, including any newlines, is not significant in the
2549 field values of folded fields.<footnote>
2550 This folding method is similar to RFC 5322, allowing control
2551 files that contain only one paragraph and no multiline fields
2552 to be read by parsers written for RFC 5322.
2555 <tag>multiline</tag>
2557 The value of a multiline field may comprise multiple continuation
2558 lines. The first line of the value, the part on the same line as
2559 the field name, often has special significance or may have to be
2560 empty. Other lines are added following the same syntax as the
2561 continuation lines of the folded fields. Whitespace, including newlines,
2562 is significant in the values of multiline fields.
2568 Whitespace must not appear
2569 inside names (of packages, architectures, files or anything
2570 else) or version numbers, or between the characters of
2571 multi-character version relationships.
2575 The presence and purpose of a field, and the syntax of its
2576 value may differ between types of control files.
2580 Field names are not case-sensitive, but it is usual to
2581 capitalize the field names using mixed case as shown below.
2582 Field values are case-sensitive unless the description of the
2583 field says otherwise.
2587 Paragraph separators (empty lines) and lines consisting only of
2588 spaces and tabs are not allowed within field values or between
2589 fields. Empty lines in field values are usually escaped by
2590 representing them by a space followed by a dot.
2594 Lines starting with # without any preceding whitespace are comments
2595 lines that are only permitted in source package control files
2596 (<file>debian/control</file>). These comment lines are ignored, even
2597 between two continuation lines. They do not end logical lines.
2601 All control files must be encoded in UTF-8.
2605 <sect id="sourcecontrolfiles">
2606 <heading>Source package control files -- <file>debian/control</file></heading>
2609 The <file>debian/control</file> file contains the most vital
2610 (and version-independent) information about the source package
2611 and about the binary packages it creates.
2615 The first paragraph of the control file contains information about
2616 the source package in general. The subsequent sets each describe a
2617 binary package that the source tree builds.
2621 The fields in the general paragraph (the first one, for the source
2624 <list compact="compact">
2625 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2627 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2628 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2629 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2630 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2631 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2632 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2633 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2638 The fields in the binary package paragraphs are:
2640 <list compact="compact">
2641 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2642 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2643 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2644 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2645 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2646 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2647 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2653 The syntax and semantics of the fields are described below.
2657 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2658 generate control files for binary packages (see below), by
2659 <prgn>dpkg-genchanges</prgn> to generate the
2660 <file>.changes</file> file to accompany the upload, and by
2661 <prgn>dpkg-source</prgn> when it creates the
2662 <file>.dsc</file> source control file as part of a source
2663 archive. Some fields are folded in <file>debian/control</file>,
2664 but not in any other control
2665 file. These tools are responsible for removing the line
2666 breaks from such fields when using fields from
2667 <file>debian/control</file> to generate other control files.
2671 The fields here may contain variable references - their
2672 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2673 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2674 when they generate output control files.
2675 See <ref id="substvars"> for details.
2679 <sect id="binarycontrolfiles">
2680 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2683 The <file>DEBIAN/control</file> file contains the most vital
2684 (and version-dependent) information about a binary package. It
2685 consists of a single paragraph.
2689 The fields in this file are:
2691 <list compact="compact">
2692 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2693 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2694 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2695 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2696 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2697 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2698 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2699 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2700 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2701 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2702 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2703 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2708 <sect id="debiansourcecontrolfiles">
2709 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2712 This file consists of a single paragraph, possibly surrounded by
2713 a PGP signature. The fields of that paragraph are listed below.
2714 Their syntax is described above, in <ref id="controlsyntax">.
2716 <list compact="compact">
2717 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2718 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2719 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2720 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2721 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2722 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2723 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2724 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2725 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2726 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2727 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2728 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2729 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2730 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2735 The Debian source control file is generated by
2736 <prgn>dpkg-source</prgn> when it builds the source
2737 archive, from other files in the source package,
2738 described above. When unpacking, it is checked against
2739 the files and directories in the other parts of the
2745 <sect id="debianchangesfiles">
2746 <heading>Debian changes files -- <file>.changes</file></heading>
2749 The <file>.changes</file> files are used by the Debian archive
2750 maintenance software to process updates to packages. They
2751 consist of a single paragraph, possibly surrounded by a PGP
2752 signature. That paragraph contains information from the
2753 <file>debian/control</file> file and other data about the
2754 source package gathered via <file>debian/changelog</file>
2755 and <file>debian/rules</file>.
2759 <file>.changes</file> files have a format version that is
2760 incremented whenever the documented fields or their meaning
2761 change. This document describes format &changesversion;.
2765 The fields in this file are:
2767 <list compact="compact">
2768 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2769 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2770 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2771 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2772 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2773 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2774 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2775 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2776 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2777 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2778 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2779 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2780 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2781 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2782 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2783 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2788 <sect id="controlfieldslist">
2789 <heading>List of fields</heading>
2791 <sect1 id="f-Source">
2792 <heading><tt>Source</tt></heading>
2795 This field identifies the source package name.
2799 In <file>debian/control</file> or a <file>.dsc</file> file,
2800 this field must contain only the name of the source package.
2804 In a binary package control file or a <file>.changes</file>
2805 file, the source package name may be followed by a version
2806 number in parentheses<footnote>
2807 It is customary to leave a space after the package name
2808 if a version number is specified.
2810 This version number may be omitted (and is, by
2811 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2812 the <tt>Version</tt> field of the binary package in
2813 question. The field itself may be omitted from a binary
2814 package control file when the source package has the same
2815 name and version as the binary package.
2819 Package names (both source and binary,
2820 see <ref id="f-Package">) must consist only of lower case
2821 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2822 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2823 (<tt>.</tt>). They must be at least two characters long and
2824 must start with an alphanumeric character.
2828 <sect1 id="f-Maintainer">
2829 <heading><tt>Maintainer</tt></heading>
2832 The package maintainer's name and email address. The name
2833 must come first, then the email address inside angle
2834 brackets <tt><></tt> (in RFC822 format).
2838 If the maintainer's name contains a full stop then the
2839 whole field will not work directly as an email address due
2840 to a misfeature in the syntax specified in RFC822; a
2841 program using this field as an address must check for this
2842 and correct the problem if necessary (for example by
2843 putting the name in round brackets and moving it to the
2844 end, and bringing the email address forward).
2848 See <ref id="maintainer"> for additional requirements and
2849 information about package maintainers.
2853 <sect1 id="f-Uploaders">
2854 <heading><tt>Uploaders</tt></heading>
2857 List of the names and email addresses of co-maintainers of the
2858 package, if any. If the package has other maintainers besides
2859 the one named in the <qref id="f-Maintainer">Maintainer
2860 field</qref>, their names and email addresses should be listed
2861 here. The format of each entry is the same as that of the
2862 Maintainer field, and multiple entries must be comma
2867 This is normally an optional field, but if
2868 the <tt>Maintainer</tt> control field names a group of people
2869 and a shared email address, the <tt>Uploaders</tt> field must
2870 be present and must contain at least one human with their
2871 personal email address.
2875 The Uploaders field in <file>debian/control</file> can be folded.
2879 <sect1 id="f-Changed-By">
2880 <heading><tt>Changed-By</tt></heading>
2883 The name and email address of the person who prepared this
2884 version of the package, usually a maintainer. The syntax is
2885 the same as for the <qref id="f-Maintainer">Maintainer
2890 <sect1 id="f-Section">
2891 <heading><tt>Section</tt></heading>
2894 This field specifies an application area into which the package
2895 has been classified. See <ref id="subsections">.
2899 When it appears in the <file>debian/control</file> file,
2900 it gives the value for the subfield of the same name in
2901 the <tt>Files</tt> field of the <file>.changes</file> file.
2902 It also gives the default for the same field in the binary
2907 <sect1 id="f-Priority">
2908 <heading><tt>Priority</tt></heading>
2911 This field represents how important it is that the user
2912 have the package installed. See <ref id="priorities">.
2916 When it appears in the <file>debian/control</file> file,
2917 it gives the value for the subfield of the same name in
2918 the <tt>Files</tt> field of the <file>.changes</file> file.
2919 It also gives the default for the same field in the binary
2924 <sect1 id="f-Package">
2925 <heading><tt>Package</tt></heading>
2928 The name of the binary package.
2932 Binary package names must follow the same syntax and
2933 restrictions as source package names. See <ref id="f-Source">
2938 <sect1 id="f-Architecture">
2939 <heading><tt>Architecture</tt></heading>
2942 Depending on context and the control file used, the
2943 <tt>Architecture</tt> field can include the following sets of
2947 A unique single word identifying a Debian machine
2948 architecture as described in <ref id="arch-spec">.
2951 An architecture wildcard identifying a set of Debian
2952 machine architectures, see <ref id="arch-wildcard-spec">.
2953 <tt>any</tt> matches all Debian machine architectures
2954 and is the most frequently used.
2957 <tt>all</tt>, which indicates an
2958 architecture-independent package.
2961 <tt>source</tt>, which indicates a source package.
2967 In the main <file>debian/control</file> file in the source
2968 package, this field may contain the special
2969 value <tt>all</tt>, the special architecture
2970 wildcard <tt>any</tt>, or a list of specific and wildcard
2971 architectures separated by spaces. If <tt>all</tt>
2972 or <tt>any</tt> appears, that value must be the entire
2973 contents of the field. Most packages will use
2974 either <tt>all</tt> or <tt>any</tt>.
2978 Specifying a specific list of architectures indicates that the
2979 source will build an architecture-dependent package only on
2980 architectures included in the list. Specifying a list of
2981 architecture wildcards indicates that the source will build an
2982 architecture-dependent package on only those architectures
2983 that match any of the specified architecture wildcards.
2984 Specifying a list of architectures or architecture wildcards
2985 other than <tt>any</tt> is for the minority of cases where a
2986 program is not portable or is not useful on some
2987 architectures. Where possible, the program should be made
2992 In the Debian source control file <file>.dsc</file>, this
2993 field contains a list of architectures and architecture
2994 wildcards separated by spaces. When the list contains the
2995 architecture wildcard <tt>any</tt>, the only other value
2996 allowed in the list is <tt>all</tt>.
3000 The list may include (or consist solely of) the special
3001 value <tt>all</tt>. In other words, in <file>.dsc</file>
3002 files unlike the <file>debian/control</file>, <tt>all</tt> may
3003 occur in combination with specific architectures.
3004 The <tt>Architecture</tt> field in the Debian source control
3005 file <file>.dsc</file> is generally constructed from
3006 the <tt>Architecture</tt> fields in
3007 the <file>debian/control</file> in the source package.
3011 Specifying only <tt>any</tt> indicates that the source package
3012 isn't dependent on any particular architecture and should
3013 compile fine on any one. The produced binary package(s)
3014 will be specific to whatever the current build architecture is.
3018 Specifying only <tt>all</tt> indicates that the source package
3019 will only build architecture-independent packages.
3023 Specifying <tt>any all</tt> indicates that the source package
3024 isn't dependent on any particular architecture. The set of
3025 produced binary packages will include at least one
3026 architecture-dependant package and one architecture-independent
3031 Specifying a list of architectures or architecture wildcards
3032 indicates that the source will build an architecture-dependent
3033 package, and will only work correctly on the listed or
3034 matching architectures. If the source package also builds at
3035 least one architecture-independent package, <tt>all</tt> will
3036 also be included in the list.
3040 In a <file>.changes</file> file, the <tt>Architecture</tt>
3041 field lists the architecture(s) of the package(s) currently
3042 being uploaded. This will be a list; if the source for the
3043 package is also being uploaded, the special
3044 entry <tt>source</tt> is also present. <tt>all</tt> will be
3045 present if any architecture-independent packages are being
3046 uploaded. Architecture wildcards such as <tt>any</tt> must
3047 never occur in the <tt>Architecture</tt> field in
3048 the <file>.changes</file> file.
3052 See <ref id="debianrules"> for information on how to get
3053 the architecture for the build process.
3057 <sect1 id="f-Essential">
3058 <heading><tt>Essential</tt></heading>
3061 This is a boolean field which may occur only in the
3062 control file of a binary package or in a per-package fields
3063 paragraph of a source package control file.
3067 If set to <tt>yes</tt> then the package management system
3068 will refuse to remove the package (upgrading and replacing
3069 it is still possible). The other possible value is <tt>no</tt>,
3070 which is the same as not having the field at all.
3075 <heading>Package interrelationship fields:
3076 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3077 <tt>Recommends</tt>, <tt>Suggests</tt>,
3078 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3079 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3083 These fields describe the package's relationships with
3084 other packages. Their syntax and semantics are described
3085 in <ref id="relationships">.</p>
3088 <sect1 id="f-Standards-Version">
3089 <heading><tt>Standards-Version</tt></heading>
3092 The most recent version of the standards (the policy
3093 manual and associated texts) with which the package
3098 The version number has four components: major and minor
3099 version number and major and minor patch level. When the
3100 standards change in a way that requires every package to
3101 change the major number will be changed. Significant
3102 changes that will require work in many packages will be
3103 signaled by a change to the minor number. The major patch
3104 level will be changed for any change to the meaning of the
3105 standards, however small; the minor patch level will be
3106 changed when only cosmetic, typographical or other edits
3107 are made which neither change the meaning of the document
3108 nor affect the contents of packages.
3112 Thus only the first three components of the policy version
3113 are significant in the <em>Standards-Version</em> control
3114 field, and so either these three components or all four
3115 components may be specified.<footnote>
3116 In the past, people specified the full version number
3117 in the Standards-Version field, for example "2.3.0.0".
3118 Since minor patch-level changes don't introduce new
3119 policy, it was thought it would be better to relax
3120 policy and only require the first 3 components to be
3121 specified, in this example "2.3.0". All four
3122 components may still be used if someone wishes to do so.
3128 <sect1 id="f-Version">
3129 <heading><tt>Version</tt></heading>
3132 The version number of a package. The format is:
3133 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3137 The three components here are:
3139 <tag><var>epoch</var></tag>
3142 This is a single (generally small) unsigned integer. It
3143 may be omitted, in which case zero is assumed. If it is
3144 omitted then the <var>upstream_version</var> may not
3149 It is provided to allow mistakes in the version numbers
3150 of older versions of a package, and also a package's
3151 previous version numbering schemes, to be left behind.
3155 <tag><var>upstream_version</var></tag>
3158 This is the main part of the version number. It is
3159 usually the version number of the original ("upstream")
3160 package from which the <file>.deb</file> file has been made,
3161 if this is applicable. Usually this will be in the same
3162 format as that specified by the upstream author(s);
3163 however, it may need to be reformatted to fit into the
3164 package management system's format and comparison
3169 The comparison behavior of the package management system
3170 with respect to the <var>upstream_version</var> is
3171 described below. The <var>upstream_version</var>
3172 portion of the version number is mandatory.
3176 The <var>upstream_version</var> may contain only
3177 alphanumerics<footnote>
3178 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3180 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3181 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3182 tilde) and should start with a digit. If there is no
3183 <var>debian_revision</var> then hyphens are not allowed;
3184 if there is no <var>epoch</var> then colons are not
3189 <tag><var>debian_revision</var></tag>
3192 This part of the version number specifies the version of
3193 the Debian package based on the upstream version. It
3194 may contain only alphanumerics and the characters
3195 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3196 tilde) and is compared in the same way as the
3197 <var>upstream_version</var> is.
3201 It is optional; if it isn't present then the
3202 <var>upstream_version</var> may not contain a hyphen.
3203 This format represents the case where a piece of
3204 software was written specifically to be a Debian
3205 package, where the Debian package source must always
3206 be identical to the pristine source and therefore no
3207 revision indication is required.
3211 It is conventional to restart the
3212 <var>debian_revision</var> at <tt>1</tt> each time the
3213 <var>upstream_version</var> is increased.
3217 The package management system will break the version
3218 number apart at the last hyphen in the string (if there
3219 is one) to determine the <var>upstream_version</var> and
3220 <var>debian_revision</var>. The absence of a
3221 <var>debian_revision</var> is equivalent to a
3222 <var>debian_revision</var> of <tt>0</tt>.
3229 When comparing two version numbers, first the <var>epoch</var>
3230 of each are compared, then the <var>upstream_version</var> if
3231 <var>epoch</var> is equal, and then <var>debian_revision</var>
3232 if <var>upstream_version</var> is also equal.
3233 <var>epoch</var> is compared numerically. The
3234 <var>upstream_version</var> and <var>debian_revision</var>
3235 parts are compared by the package management system using the
3236 following algorithm:
3240 The strings are compared from left to right.
3244 First the initial part of each string consisting entirely of
3245 non-digit characters is determined. These two parts (one of
3246 which may be empty) are compared lexically. If a difference
3247 is found it is returned. The lexical comparison is a
3248 comparison of ASCII values modified so that all the letters
3249 sort earlier than all the non-letters and so that a tilde
3250 sorts before anything, even the end of a part. For example,
3251 the following parts are in sorted order from earliest to
3252 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3253 <tt>a</tt>.<footnote>
3254 One common use of <tt>~</tt> is for upstream pre-releases.
3255 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3256 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3261 Then the initial part of the remainder of each string which
3262 consists entirely of digit characters is determined. The
3263 numerical values of these two parts are compared, and any
3264 difference found is returned as the result of the comparison.
3265 For these purposes an empty string (which can only occur at
3266 the end of one or both version strings being compared) counts
3271 These two steps (comparing and removing initial non-digit
3272 strings and initial digit strings) are repeated until a
3273 difference is found or both strings are exhausted.
3277 Note that the purpose of epochs is to allow us to leave behind
3278 mistakes in version numbering, and to cope with situations
3279 where the version numbering scheme changes. It is
3280 <em>not</em> intended to cope with version numbers containing
3281 strings of letters which the package management system cannot
3282 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3283 silly orderings.<footnote>
3284 The author of this manual has heard of a package whose
3285 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3286 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3292 <sect1 id="f-Description">
3293 <heading><tt>Description</tt></heading>
3296 In a source or binary control file, the <tt>Description</tt>
3297 field contains a description of the binary package, consisting
3298 of two parts, the synopsis or the short description, and the
3299 long description. It is a multiline field with the following
3305 Description: <single line synopsis>
3306 <extended description over several lines>
3311 The lines in the extended description can have these formats:
3317 Those starting with a single space are part of a paragraph.
3318 Successive lines of this form will be word-wrapped when
3319 displayed. The leading space will usually be stripped off.
3320 The line must contain at least one non-whitespace character.
3324 Those starting with two or more spaces. These will be
3325 displayed verbatim. If the display cannot be panned
3326 horizontally, the displaying program will line wrap them "hard"
3327 (i.e., without taking account of word breaks). If it can they
3328 will be allowed to trail off to the right. None, one or two
3329 initial spaces may be deleted, but the number of spaces
3330 deleted from each line will be the same (so that you can have
3331 indenting work correctly, for example). The line must
3332 contain at least one non-whitespace character.
3336 Those containing a single space followed by a single full stop
3337 character. These are rendered as blank lines. This is the
3338 <em>only</em> way to get a blank line<footnote>
3339 Completely empty lines will not be rendered as blank lines.
3340 Instead, they will cause the parser to think you're starting
3341 a whole new record in the control file, and will therefore
3342 likely abort with an error.
3347 Those containing a space, a full stop and some more characters.
3348 These are for future expansion. Do not use them.
3354 Do not use tab characters. Their effect is not predictable.
3358 See <ref id="descriptions"> for further information on this.
3362 In a <file>.changes</file> file, the <tt>Description</tt>
3363 field contains a summary of the descriptions for the packages
3364 being uploaded. For this case, the first line of the field
3365 value (the part on the same line as <tt>Description:</tt>) is
3366 always empty. It is a multiline field, with one
3367 line per package. Each line is
3368 indented by one space and contains the name of a binary
3369 package, a space, a hyphen (<tt>-</tt>), a space, and the
3370 short description line from that package.
3374 <sect1 id="f-Distribution">
3375 <heading><tt>Distribution</tt></heading>
3378 In a <file>.changes</file> file or parsed changelog output
3379 this contains the (space-separated) name(s) of the
3380 distribution(s) where this version of the package should
3381 be installed. Valid distributions are determined by the
3382 archive maintainers.<footnote>
3383 Example distribution names in the Debian archive used in
3384 <file>.changes</file> files are:
3385 <taglist compact="compact">
3386 <tag><em>unstable</em></tag>
3388 This distribution value refers to the
3389 <em>developmental</em> part of the Debian distribution
3390 tree. Most new packages, new upstream versions of
3391 packages and bug fixes go into the <em>unstable</em>
3395 <tag><em>experimental</em></tag>
3397 The packages with this distribution value are deemed
3398 by their maintainers to be high risk. Oftentimes they
3399 represent early beta or developmental packages from
3400 various sources that the maintainers want people to
3401 try, but are not ready to be a part of the other parts
3402 of the Debian distribution tree.
3407 Others are used for updating stable releases or for
3408 security uploads. More information is available in the
3409 Debian Developer's Reference, section "The Debian
3413 The Debian archive software only supports listing a single
3414 distribution. Migration of packages to other distributions is
3415 handled outside of the upload process.
3420 <heading><tt>Date</tt></heading>
3423 This field includes the date the package was built or last
3424 edited. It must be in the same format as the <var>date</var>
3425 in a <file>debian/changelog</file> entry.
3429 The value of this field is usually extracted from the
3430 <file>debian/changelog</file> file - see
3431 <ref id="dpkgchangelog">).
3435 <sect1 id="f-Format">
3436 <heading><tt>Format</tt></heading>
3439 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3440 files, this field declares the format version of that file.
3441 The syntax of the field value is the same as that of
3442 a <qref id="f-Version">package version number</qref> except
3443 that no epoch or Debian revision is allowed. The format
3444 described in this document is <tt>&changesversion;</tt>.
3448 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3449 Debian source control</qref> files, this field declares the
3450 format of the source package. The field value is used by
3451 programs acting on a source package to interpret the list of
3452 files in the source package and determine how to unpack it.
3453 The syntax of the field value is a numeric major revision, a
3454 period, a numeric minor revision, and then an optional subtype
3455 after whitespace, which if specified is an alphanumeric word
3456 in parentheses. The subtype is optional in the syntax but may
3457 be mandatory for particular source format revisions.
3459 The source formats currently supported by the Debian archive
3460 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3461 and <tt>3.0 (quilt)</tt>.
3466 <sect1 id="f-Urgency">
3467 <heading><tt>Urgency</tt></heading>
3470 This is a description of how important it is to upgrade to
3471 this version from previous ones. It consists of a single
3472 keyword taking one of the values <tt>low</tt>,
3473 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3474 <tt>critical</tt><footnote>
3475 Other urgency values are supported with configuration
3476 changes in the archive software but are not used in Debian.
3477 The urgency affects how quickly a package will be considered
3478 for inclusion into the <tt>testing</tt> distribution and
3479 gives an indication of the importance of any fixes included
3480 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3481 treated as synonymous.
3482 </footnote> (not case-sensitive) followed by an optional
3483 commentary (separated by a space) which is usually in
3484 parentheses. For example:
3487 Urgency: low (HIGH for users of diversions)
3493 The value of this field is usually extracted from the
3494 <file>debian/changelog</file> file - see
3495 <ref id="dpkgchangelog">.
3499 <sect1 id="f-Changes">
3500 <heading><tt>Changes</tt></heading>
3503 This multiline field contains the human-readable changes data, describing
3504 the differences between the last version and the current one.
3508 The first line of the field value (the part on the same line
3509 as <tt>Changes:</tt>) is always empty. The content of the
3510 field is expressed as continuation lines, with each line
3511 indented by at least one space. Blank lines must be
3512 represented by a line consisting only of a space and a full
3517 The value of this field is usually extracted from the
3518 <file>debian/changelog</file> file - see
3519 <ref id="dpkgchangelog">).
3523 Each version's change information should be preceded by a
3524 "title" line giving at least the version, distribution(s)
3525 and urgency, in a human-readable way.
3529 If data from several versions is being returned the entry
3530 for the most recent version should be returned first, and
3531 entries should be separated by the representation of a
3532 blank line (the "title" line may also be followed by the
3533 representation of a blank line).
3537 <sect1 id="f-Binary">
3538 <heading><tt>Binary</tt></heading>
3541 This folded field is a list of binary packages. Its syntax and
3542 meaning varies depending on the control file in which it
3547 When it appears in the <file>.dsc</file> file, it lists binary
3548 packages which a source package can produce, separated by
3550 A space after each comma is conventional.
3551 </footnote>. The source package
3552 does not necessarily produce all of these binary packages for
3553 every architecture. The source control file doesn't contain
3554 details of which architectures are appropriate for which of
3555 the binary packages.
3559 When it appears in a <file>.changes</file> file, it lists the
3560 names of the binary packages being uploaded, separated by
3561 whitespace (not commas).
3565 <sect1 id="f-Installed-Size">
3566 <heading><tt>Installed-Size</tt></heading>
3569 This field appears in the control files of binary packages,
3570 and in the <file>Packages</file> files. It gives an estimate
3571 of the total amount of disk space required to install the
3572 named package. Actual installed size may vary based on block
3573 size, file system properties, or actions taken by package
3578 The disk space is given as the integer value of the estimated
3579 installed size in bytes, divided by 1024 and rounded up.
3583 <sect1 id="f-Files">
3584 <heading><tt>Files</tt></heading>
3587 This field contains a list of files with information about
3588 each one. The exact information and syntax varies with
3593 In all cases, Files is a multiline field. The first line of
3594 the field value (the part on the same line as <tt>Files:</tt>)
3595 is always empty. The content of the field is expressed as
3596 continuation lines, one line per file. Each line must be
3597 indented by one space and contain a number of sub-fields,
3598 separated by spaces, as described below.
3602 In the <file>.dsc</file> file, each line contains the MD5
3603 checksum, size and filename of the tar file and (if
3604 applicable) diff file which make up the remainder of the
3605 source package<footnote>
3606 That is, the parts which are not the <tt>.dsc</tt>.
3607 </footnote>. For example:
3610 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3611 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3613 The exact forms of the filenames are described
3614 in <ref id="pkg-sourcearchives">.
3618 In the <file>.changes</file> file this contains one line per
3619 file being uploaded. Each line contains the MD5 checksum,
3620 size, section and priority and the filename. For example:
3623 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3624 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3625 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3626 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3628 The <qref id="f-Section">section</qref>
3629 and <qref id="f-Priority">priority</qref> are the values of
3630 the corresponding fields in the main source control file. If
3631 no section or priority is specified then <tt>-</tt> should be
3632 used, though section and priority values must be specified for
3633 new packages to be installed properly.
3637 The special value <tt>byhand</tt> for the section in a
3638 <tt>.changes</tt> file indicates that the file in question
3639 is not an ordinary package file and must by installed by
3640 hand by the distribution maintainers. If the section is
3641 <tt>byhand</tt> the priority should be <tt>-</tt>.
3645 If a new Debian revision of a package is being shipped and
3646 no new original source archive is being distributed the
3647 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3648 entry for the original source archive
3649 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3650 but the <file>.changes</file> file should leave it out. In
3651 this case the original source archive on the distribution
3652 site must match exactly, byte-for-byte, the original
3653 source archive which was used to generate the
3654 <file>.dsc</file> file and diff which are being uploaded.</p>
3657 <sect1 id="f-Closes">
3658 <heading><tt>Closes</tt></heading>
3661 A space-separated list of bug report numbers that the upload
3662 governed by the .changes file closes.
3666 <sect1 id="f-Homepage">
3667 <heading><tt>Homepage</tt></heading>
3670 The URL of the web site for this package, preferably (when
3671 applicable) the site from which the original source can be
3672 obtained and any additional upstream documentation or
3673 information may be found. The content of this field is a
3674 simple URL without any surrounding characters such as
3679 <sect1 id="f-Checksums">
3680 <heading><tt>Checksums-Sha1</tt>
3681 and <tt>Checksums-Sha256</tt></heading>
3684 These multiline fields contain a list of files with a checksum and size
3685 for each one. Both <tt>Checksums-Sha1</tt>
3686 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3687 only in the checksum algorithm used: SHA-1
3688 for <tt>Checksums-Sha1</tt> and SHA-256
3689 for <tt>Checksums-Sha256</tt>.
3693 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3694 multiline fields. The first line of the field value (the part
3695 on the same line as <tt>Checksums-Sha1:</tt>
3696 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3697 of the field is expressed as continuation lines, one line per
3698 file. Each line consists of the checksum, a space, the file
3699 size, a space, and the file name. For example (from
3700 a <file>.changes</file> file):
3703 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3704 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3705 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3706 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3708 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3709 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3710 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3711 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3716 In the <file>.dsc</file> file, these fields should list all
3717 files that make up the source package. In
3718 the <file>.changes</file> file, these fields should list all
3719 files being uploaded. The list of files in these fields
3720 must match the list of files in the <tt>Files</tt> field.
3724 <sect1 id="f-DM-Upload-Allowed">
3725 <heading><tt>DM-Upload-Allowed</tt></heading>
3728 The most recent version of a package uploaded to unstable or
3729 experimental must include the field <tt>DM-Upload-Allowed:
3730 yes</tt> in the source section of its source control file for
3731 the Debian archive to accept uploads signed with a key in the
3732 Debian Maintainer keyring. See the General
3733 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3734 name="Endorse the concept of Debian Maintainers"> for more
3741 <heading>User-defined fields</heading>
3744 Additional user-defined fields may be added to the
3745 source package control file. Such fields will be
3746 ignored, and not copied to (for example) binary or
3747 Debian source control files or upload control files.
3751 If you wish to add additional unsupported fields to
3752 these output files you should use the mechanism
3757 Fields in the main source control information file with
3758 names starting <tt>X</tt>, followed by one or more of
3759 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3760 be copied to the output files. Only the part of the
3761 field name after the hyphen will be used in the output
3762 file. Where the letter <tt>B</tt> is used the field
3763 will appear in binary package control files, where the
3764 letter <tt>S</tt> is used in Debian source control
3765 files and where <tt>C</tt> is used in upload control
3766 (<tt>.changes</tt>) files.
3770 For example, if the main source information control file
3773 XBS-Comment: I stand between the candle and the star.
3775 then the binary and Debian source control files will contain the
3778 Comment: I stand between the candle and the star.
3787 <chapt id="maintainerscripts">
3788 <heading>Package maintainer scripts and installation procedure</heading>
3791 <heading>Introduction to package maintainer scripts</heading>
3794 It is possible to supply scripts as part of a package which
3795 the package management system will run for you when your
3796 package is installed, upgraded or removed.
3800 These scripts are the control information
3801 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3802 and <prgn>postrm</prgn>. They must be proper executable files;
3803 if they are scripts (which is recommended), they must start with
3804 the usual <tt>#!</tt> convention. They should be readable and
3805 executable by anyone, and must not be world-writable.
3809 The package management system looks at the exit status from
3810 these scripts. It is important that they exit with a
3811 non-zero status if there is an error, so that the package
3812 management system can stop its processing. For shell
3813 scripts this means that you <em>almost always</em> need to
3814 use <tt>set -e</tt> (this is usually true when writing shell
3815 scripts, in fact). It is also important, of course, that
3816 they exit with a zero status if everything went well.
3820 Additionally, packages interacting with users
3821 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3822 should install a <prgn>config</prgn> script as a control
3823 information file. See <ref id="maintscriptprompt"> for details.
3827 When a package is upgraded a combination of the scripts from
3828 the old and new packages is called during the upgrade
3829 procedure. If your scripts are going to be at all
3830 complicated you need to be aware of this, and may need to
3831 check the arguments to your scripts.
3835 Broadly speaking the <prgn>preinst</prgn> is called before
3836 (a particular version of) a package is unpacked, and the
3837 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3838 before (a version of) a package is removed and the
3839 <prgn>postrm</prgn> afterwards.
3843 Programs called from maintainer scripts should not normally
3844 have a path prepended to them. Before installation is
3845 started, the package management system checks to see if the
3846 programs <prgn>ldconfig</prgn>,
3847 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3848 and <prgn>update-rc.d</prgn> can be found via the
3849 <tt>PATH</tt> environment variable. Those programs, and any
3850 other program that one would expect to be in the
3851 <tt>PATH</tt>, should thus be invoked without an absolute
3852 pathname. Maintainer scripts should also not reset the
3853 <tt>PATH</tt>, though they might choose to modify it by
3854 prepending or appending package-specific directories. These
3855 considerations really apply to all shell scripts.</p>
3858 <sect id="idempotency">
3859 <heading>Maintainer scripts idempotency</heading>
3862 It is necessary for the error recovery procedures that the
3863 scripts be idempotent. This means that if it is run
3864 successfully, and then it is called again, it doesn't bomb
3865 out or cause any harm, but just ensures that everything is
3866 the way it ought to be. If the first call failed, or
3867 aborted half way through for some reason, the second call
3868 should merely do the things that were left undone the first
3869 time, if any, and exit with a success status if everything
3871 This is so that if an error occurs, the user interrupts
3872 <prgn>dpkg</prgn> or some other unforeseen circumstance
3873 happens you don't leave the user with a badly-broken
3874 package when <prgn>dpkg</prgn> attempts to repeat the
3880 <sect id="controllingterminal">
3881 <heading>Controlling terminal for maintainer scripts</heading>
3884 Maintainer scripts are not guaranteed to run with a controlling
3885 terminal and may not be able to interact with the user. They
3886 must be able to fall back to noninteractive behavior if no
3887 controlling terminal is available. Maintainer scripts that
3888 prompt via a program conforming to the Debian Configuration
3889 Management Specification (see <ref id="maintscriptprompt">) may
3890 assume that program will handle falling back to noninteractive
3895 For high-priority prompts without a reasonable default answer,
3896 maintainer scripts may abort if there is no controlling
3897 terminal. However, this situation should be avoided if at all
3898 possible, since it prevents automated or unattended installs.
3899 In most cases, users will consider this to be a bug in the
3904 <sect id="exitstatus">
3905 <heading>Exit status</heading>
3908 Each script must return a zero exit status for
3909 success, or a nonzero one for failure, since the package
3910 management system looks for the exit status of these scripts
3911 and determines what action to take next based on that datum.
3915 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3920 What follows is a summary of all the ways in which maintainer
3921 scripts may be called along with what facilities those scripts
3922 may rely on being available at that time. Script names preceded
3923 by <var>new-</var> are the scripts from the new version of a
3924 package being installed, upgraded to, or downgraded to. Script
3925 names preceded by <var>old-</var> are the scripts from the old
3926 version of a package that is being upgraded from or downgraded
3931 The <prgn>preinst</prgn> script may be called in the following
3934 <tag><var>new-preinst</var> <tt>install</tt></tag>
3935 <tag><var>new-preinst</var> <tt>install</tt>
3936 <var>old-version</var></tag>
3937 <tag><var>new-preinst</var> <tt>upgrade</tt>
3938 <var>old-version</var></tag>
3940 The package will not yet be unpacked, so
3941 the <prgn>preinst</prgn> script cannot rely on any files
3942 included in its package. Only essential packages and
3943 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3944 available. Pre-dependencies will have been configured at
3945 least once, but at the time the <prgn>preinst</prgn> is
3946 called they may only be in an unpacked or "Half-Configured"
3947 state if a previous version of the pre-dependency was
3948 completely configured and has not been removed since then.
3951 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3952 <var>new-version</var></tag>
3954 Called during error handling of an upgrade that failed after
3955 unpacking the new package because the <tt>postrm
3956 upgrade</tt> action failed. The unpacked files may be
3957 partly from the new version or partly missing, so the script
3958 cannot rely on files included in the package. Package
3959 dependencies may not be available. Pre-dependencies will be
3960 at least unpacked following the same rules as above, except
3961 they may be only "Half-Installed" if an upgrade of the
3962 pre-dependency failed.<footnote>
3963 This can happen if the new version of the package no
3964 longer pre-depends on a package that had been partially
3972 The <prgn>postinst</prgn> script may be called in the following
3975 <tag><var>postinst</var> <tt>configure</tt>
3976 <var>most-recently-configured-version</var></tag>
3978 The files contained in the package will be unpacked. All
3979 package dependencies will at least be unpacked. If there
3980 are no circular dependencies involved, all package
3981 dependencies will be configured. For behavior in the case
3982 of circular dependencies, see the discussion
3983 in <ref id="binarydeps">.
3986 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3987 <var>new-version</var></tag>
3988 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3989 <tt>in-favour</tt> <var>package</var>
3990 <var>new-version</var></tag>
3991 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3992 <tag><var>deconfigured's-postinst</var>
3993 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3994 <var>failed-install-package</var> <var>version</var>
3995 [<tt>removing</tt> <var>conflicting-package</var>
3996 <var>version</var>]</tag>
3998 The files contained in the package will be unpacked. All
3999 package dependencies will at least be "Half-Installed" and
4000 will have previously been configured and not removed.
4001 However, dependencies may not be configured or even fully
4002 unpacked in some error situations.<footnote>
4003 For example, suppose packages foo and bar are installed
4004 with foo depending on bar. If an upgrade of bar were
4005 started and then aborted, and then an attempt to remove
4006 foo failed because its <prgn>prerm</prgn> script failed,
4007 foo's <tt>postinst abort-remove</tt> would be called with
4008 bar only "Half-Installed".
4010 The <prgn>postinst</prgn> should still attempt any actions
4011 for which its dependencies are required, since they will
4012 normally be available, but consider the correct error
4013 handling approach if those actions fail. Aborting
4014 the <prgn>postinst</prgn> action if commands or facilities
4015 from the package dependencies are not available is often the
4022 The <prgn>prerm</prgn> script may be called in the following
4025 <tag><var>prerm</var> <tt>remove</tt></tag>
4026 <tag><var>old-prerm</var>
4027 <tt>upgrade</tt><var>new-version</var></tag>
4028 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4029 <tt>in-favour</tt> <var>package</var>
4030 <var>new-version</var></tag>
4031 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4032 <tt>in-favour</tt> <var>package-being-installed</var>
4033 <var>version</var> [<tt>removing</tt>
4034 <var>conflicting-package</var> <var>version</var>]</tag>
4036 The package whose <prgn>prerm</prgn> is being called will be
4037 at least "Half-Installed". All package dependencies will at
4038 least be "Half-Installed" and will have previously been
4039 configured and not removed. If there was no error, all
4040 dependencies will at least be unpacked, but these actions
4041 may be called in various error states where dependencies are
4042 only "Half-Installed" due to a partial upgrade.
4045 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4046 <var>old-version</var></tag>
4048 Called during error handling when <tt>prerm upgrade</tt>
4049 fails. The new package will not yet be unpacked, and all
4050 the same constraints as for <tt>preinst upgrade</tt> apply.
4056 The <prgn>postrm</prgn> script may be called in the following
4059 <tag><var>postrm</var> <tt>remove</tt></tag>
4060 <tag><var>postrm</var> <tt>purge</tt></tag>
4061 <tag><var>old-postrm</var> <tt>upgrade</tt>
4062 <var>new-version</var></tag>
4063 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4064 <var>overwriter</var> <var>overwriter-version</var></tag>
4066 The <prgn>postrm</prgn> script is called after the package's
4067 files have been removed or replaced. The package
4068 whose <prgn>postrm</prgn> is being called may have
4069 previously been deconfigured and only be unpacked, at which
4070 point subsequent package changes do not consider its
4071 dependencies. Therefore, all <prgn>postrm</prgn> actions
4072 may only rely on essential packages and must gracefully skip
4073 any actions that require the package's dependencies if those
4074 dependencies are unavailable.<footnote>
4075 This is often done by checking whether the command or
4076 facility the <prgn>postrm</prgn> intends to call is
4077 available before calling it. For example:
4079 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4080 . /usr/share/debconf/confmodule
4084 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4085 configuration for the package
4086 if <package>debconf</package> is installed.
4090 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4091 <var>old-version</var></tag>
4093 Called when the old <tt>postrm upgrade</tt> action fails.
4094 The new package will be unpacked, but only essential
4095 packages and pre-dependencies can be relied on.
4096 Pre-dependencies will either be configured or will be
4097 "Unpacked" or "Half-Configured" but previously had been
4098 configured and was never removed.
4101 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4102 <tag><var>new-postrm</var> <tt>abort-install</tt>
4103 <var>old-version</var></tag>
4104 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4105 <var>old-version</var></tag>
4107 Called before unpacking the new package as part of the
4108 error handling of <prgn>preinst</prgn> failures. May assume
4109 the same state as <prgn>preinst</prgn> can assume.
4115 <sect id="unpackphase">
4116 <heading>Details of unpack phase of installation or upgrade</heading>
4119 The procedure on installation/upgrade/overwrite/disappear
4120 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4121 stage of <tt>dpkg --install</tt>) is as follows. In each
4122 case, if a major error occurs (unless listed below) the
4123 actions are, in general, run backwards - this means that the
4124 maintainer scripts are run with different arguments in
4125 reverse order. These are the "error unwind" calls listed
4132 If a version of the package is already installed, call
4133 <example compact="compact">
4134 <var>old-prerm</var> upgrade <var>new-version</var>
4138 If the script runs but exits with a non-zero
4139 exit status, <prgn>dpkg</prgn> will attempt:
4140 <example compact="compact">
4141 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4143 If this works, the upgrade continues. If this
4144 does not work, the error unwind:
4145 <example compact="compact">
4146 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4148 If this works, then the old-version is
4149 "Installed", if not, the old version is in a
4150 "Half-Configured" state.
4156 If a "conflicting" package is being removed at the same time,
4157 or if any package will be broken (due to <tt>Breaks</tt>):
4160 If <tt>--auto-deconfigure</tt> is
4161 specified, call, for each package to be deconfigured
4162 due to <tt>Breaks</tt>:
4163 <example compact="compact">
4164 <var>deconfigured's-prerm</var> deconfigure \
4165 in-favour <var>package-being-installed</var> <var>version</var>
4168 <example compact="compact">
4169 <var>deconfigured's-postinst</var> abort-deconfigure \
4170 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4172 The deconfigured packages are marked as
4173 requiring configuration, so that if
4174 <tt>--install</tt> is used they will be
4175 configured again if possible.
4178 If any packages depended on a conflicting
4179 package being removed and <tt>--auto-deconfigure</tt> is
4180 specified, call, for each such package:
4181 <example compact="compact">
4182 <var>deconfigured's-prerm</var> deconfigure \
4183 in-favour <var>package-being-installed</var> <var>version</var> \
4184 removing <var>conflicting-package</var> <var>version</var>
4187 <example compact="compact">
4188 <var>deconfigured's-postinst</var> abort-deconfigure \
4189 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4190 removing <var>conflicting-package</var> <var>version</var>
4192 The deconfigured packages are marked as
4193 requiring configuration, so that if
4194 <tt>--install</tt> is used they will be
4195 configured again if possible.
4198 To prepare for removal of each conflicting package, call:
4199 <example compact="compact">
4200 <var>conflictor's-prerm</var> remove \
4201 in-favour <var>package</var> <var>new-version</var>
4204 <example compact="compact">
4205 <var>conflictor's-postinst</var> abort-remove \
4206 in-favour <var>package</var> <var>new-version</var>
4215 If the package is being upgraded, call:
4216 <example compact="compact">
4217 <var>new-preinst</var> upgrade <var>old-version</var>
4219 If this fails, we call:
4221 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4228 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4230 is called. If this works, then the old version
4231 is in an "Installed" state, or else it is left
4232 in an "Unpacked" state.
4237 If it fails, then the old version is left
4238 in an "Half-Installed" state.
4245 Otherwise, if the package had some configuration
4246 files from a previous version installed (i.e., it
4247 is in the "configuration files only" state):
4248 <example compact="compact">
4249 <var>new-preinst</var> install <var>old-version</var>
4253 <var>new-postrm</var> abort-install <var>old-version</var>
4255 If this fails, the package is left in a
4256 "Half-Installed" state, which requires a
4257 reinstall. If it works, the packages is left in
4258 a "Config-Files" state.
4261 Otherwise (i.e., the package was completely purged):
4262 <example compact="compact">
4263 <var>new-preinst</var> install
4266 <example compact="compact">
4267 <var>new-postrm</var> abort-install
4269 If the error-unwind fails, the package is in a
4270 "Half-Installed" phase, and requires a
4271 reinstall. If the error unwind works, the
4272 package is in a not installed state.
4279 The new package's files are unpacked, overwriting any
4280 that may be on the system already, for example any
4281 from the old version of the same package or from
4282 another package. Backups of the old files are kept
4283 temporarily, and if anything goes wrong the package
4284 management system will attempt to put them back as
4285 part of the error unwind.
4289 It is an error for a package to contain files which
4290 are on the system in another package, unless
4291 <tt>Replaces</tt> is used (see <ref id="replaces">).
4293 The following paragraph is not currently the case:
4294 Currently the <tt>- - force-overwrite</tt> flag is
4295 enabled, downgrading it to a warning, but this may not
4301 It is a more serious error for a package to contain a
4302 plain file or other kind of non-directory where another
4303 package has a directory (again, unless
4304 <tt>Replaces</tt> is used). This error can be
4305 overridden if desired using
4306 <tt>--force-overwrite-dir</tt>, but this is not
4311 Packages which overwrite each other's files produce
4312 behavior which, though deterministic, is hard for the
4313 system administrator to understand. It can easily
4314 lead to "missing" programs if, for example, a package
4315 is unpacked which overwrites a file from another
4316 package, and is then removed again.<footnote>
4317 Part of the problem is due to what is arguably a
4318 bug in <prgn>dpkg</prgn>.
4323 A directory will never be replaced by a symbolic link
4324 to a directory or vice versa; instead, the existing
4325 state (symlink or not) will be left alone and
4326 <prgn>dpkg</prgn> will follow the symlink if there is
4335 If the package is being upgraded, call
4336 <example compact="compact">
4337 <var>old-postrm</var> upgrade <var>new-version</var>
4341 If this fails, <prgn>dpkg</prgn> will attempt:
4342 <example compact="compact">
4343 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4345 If this works, installation continues. If not,
4347 <example compact="compact">
4348 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4350 If this fails, the old version is left in a
4351 "Half-Installed" state. If it works, dpkg now
4353 <example compact="compact">
4354 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4356 If this fails, the old version is left in a
4357 "Half-Installed" state. If it works, dpkg now
4359 <example compact="compact">
4360 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4362 If this fails, the old version is in an
4369 This is the point of no return - if
4370 <prgn>dpkg</prgn> gets this far, it won't back off
4371 past this point if an error occurs. This will
4372 leave the package in a fairly bad state, which
4373 will require a successful re-installation to clear
4374 up, but it's when <prgn>dpkg</prgn> starts doing
4375 things that are irreversible.
4380 Any files which were in the old version of the package
4381 but not in the new are removed.
4385 The new file list replaces the old.
4389 The new maintainer scripts replace the old.
4393 Any packages all of whose files have been overwritten
4394 during the installation, and which aren't required for
4395 dependencies, are considered to have been removed.
4396 For each such package
4399 <prgn>dpkg</prgn> calls:
4400 <example compact="compact">
4401 <var>disappearer's-postrm</var> disappear \
4402 <var>overwriter</var> <var>overwriter-version</var>
4406 The package's maintainer scripts are removed.
4409 It is noted in the status database as being in a
4410 sane state, namely not installed (any conffiles
4411 it may have are ignored, rather than being
4412 removed by <prgn>dpkg</prgn>). Note that
4413 disappearing packages do not have their prerm
4414 called, because <prgn>dpkg</prgn> doesn't know
4415 in advance that the package is going to
4422 Any files in the package we're unpacking that are also
4423 listed in the file lists of other packages are removed
4424 from those lists. (This will lobotomize the file list
4425 of the "conflicting" package if there is one.)
4429 The backup files made during installation, above, are
4435 The new package's status is now sane, and recorded as
4440 Here is another point of no return - if the
4441 conflicting package's removal fails we do not unwind
4442 the rest of the installation; the conflicting package
4443 is left in a half-removed limbo.
4448 If there was a conflicting package we go and do the
4449 removal actions (described below), starting with the
4450 removal of the conflicting package's files (any that
4451 are also in the package being unpacked have already
4452 been removed from the conflicting package's file list,
4453 and so do not get removed now).
4459 <sect id="configdetails"><heading>Details of configuration</heading>
4462 When we configure a package (this happens with <tt>dpkg
4463 --install</tt> and <tt>dpkg --configure</tt>), we first
4464 update any <tt>conffile</tt>s and then call:
4465 <example compact="compact">
4466 <var>postinst</var> configure <var>most-recently-configured-version</var>
4471 No attempt is made to unwind after errors during
4472 configuration. If the configuration fails, the package is in
4473 a "Failed Config" state, and an error message is generated.
4477 If there is no most recently configured version
4478 <prgn>dpkg</prgn> will pass a null argument.
4481 Historical note: Truly ancient (pre-1997) versions of
4482 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4483 (including the angle brackets) in this case. Even older
4484 ones did not pass a second argument at all, under any
4485 circumstance. Note that upgrades using such an old dpkg
4486 version are unlikely to work for other reasons, even if
4487 this old argument behavior is handled by your postinst script.
4493 <sect id="removedetails"><heading>Details of removal and/or
4494 configuration purging</heading>
4500 <example compact="compact">
4501 <var>prerm</var> remove
4505 If prerm fails during replacement due to conflict
4507 <var>conflictor's-postinst</var> abort-remove \
4508 in-favour <var>package</var> <var>new-version</var>
4512 <var>postinst</var> abort-remove
4516 If this fails, the package is in a "Half-Configured"
4517 state, or else it remains "Installed".
4521 The package's files are removed (except <tt>conffile</tt>s).
4524 <example compact="compact">
4525 <var>postrm</var> remove
4529 If it fails, there's no error unwind, and the package is in
4530 an "Half-Installed" state.
4535 All the maintainer scripts except the <prgn>postrm</prgn>
4540 If we aren't purging the package we stop here. Note
4541 that packages which have no <prgn>postrm</prgn> and no
4542 <tt>conffile</tt>s are automatically purged when
4543 removed, as there is no difference except for the
4544 <prgn>dpkg</prgn> status.
4548 The <tt>conffile</tt>s and any backup files
4549 (<tt>~</tt>-files, <tt>#*#</tt> files,
4550 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4555 <example compact="compact">
4556 <var>postrm</var> purge
4560 If this fails, the package remains in a "Config-Files"
4565 The package's file list is removed.
4574 <chapt id="relationships">
4575 <heading>Declaring relationships between packages</heading>
4577 <sect id="depsyntax">
4578 <heading>Syntax of relationship fields</heading>
4581 These fields all have a uniform syntax. They are a list of
4582 package names separated by commas.
4586 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4587 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4588 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4589 control fields of the package, which declare
4590 dependencies on other packages, the package names listed may
4591 also include lists of alternative package names, separated
4592 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4593 if any one of the alternative packages is installed, that
4594 part of the dependency is considered to be satisfied.
4598 All of the fields except for <tt>Provides</tt> may restrict
4599 their applicability to particular versions of each named
4600 package. This is done in parentheses after each individual
4601 package name; the parentheses should contain a relation from
4602 the list below followed by a version number, in the format
4603 described in <ref id="f-Version">.
4607 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4608 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4609 strictly earlier, earlier or equal, exactly equal, later or
4610 equal and strictly later, respectively. The deprecated
4611 forms <tt><</tt> and <tt>></tt> were used to mean
4612 earlier/later or equal, rather than strictly earlier/later,
4613 so they should not appear in new packages (though
4614 <prgn>dpkg</prgn> still supports them).
4618 Whitespace may appear at any point in the version
4619 specification subject to the rules in <ref
4620 id="controlsyntax">, and must appear where it's necessary to
4621 disambiguate; it is not otherwise significant. All of the
4622 relationship fields can only be folded in source package control files. For
4623 consistency and in case of future changes to
4624 <prgn>dpkg</prgn> it is recommended that a single space be
4625 used after a version relationship and before a version
4626 number; it is also conventional to put a single space after
4627 each comma, on either side of each vertical bar, and before
4628 each open parenthesis. When opening a continuation line in a relationship field, it
4629 is conventional to do so after a comma and before the space
4630 following that comma.
4634 For example, a list of dependencies might appear as:
4635 <example compact="compact">
4638 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4643 Relationships may be restricted to a certain set of
4644 architectures. This is indicated in brackets after each
4645 individual package name and the optional version specification.
4646 The brackets enclose a non-empty list of Debian architecture names
4647 in the format described in <ref id="arch-spec">,
4648 separated by whitespace. Exclamation marks may be prepended to
4649 each of the names. (It is not permitted for some names to be
4650 prepended with exclamation marks while others aren't.)
4654 For build relationship fields
4655 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4656 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4657 the current Debian host architecture is not in this list and
4658 there are no exclamation marks in the list, or it is in the list
4659 with a prepended exclamation mark, the package name and the
4660 associated version specification are ignored completely for the
4661 purposes of defining the relationships.
4666 <example compact="compact">
4668 Build-Depends-Indep: texinfo
4669 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4670 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4672 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4673 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4674 <tt>gnumach-dev</tt> only on hurd-i386.
4678 For binary relationship fields, the architecture restriction
4679 syntax is only supported in the source package control
4680 file <file>debian/control</file>. When the corresponding binary
4681 package control file is generated, the relationship will either
4682 be omitted or included without the architecture restriction
4683 based on the architecture of the binary package. This means
4684 that architecture restrictions must not be used in binary
4685 relationship fields for architecture-independent packages
4686 (<tt>Architecture: all</tt>).
4691 <example compact="compact">
4692 Depends: foo [i386], bar [amd64]
4694 becomes <tt>Depends: foo</tt> when the package is built on
4695 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4696 package is built on the <tt>amd64</tt> architecture, and omitted
4697 entirely in binary packages built on all other architectures.
4701 If the architecture-restricted dependency is part of a set of
4702 alternatives using <tt>|</tt>, that alternative is ignored
4703 completely on architectures that do not match the restriction.
4705 <example compact="compact">
4706 Build-Depends: foo [!i386] | bar [!amd64]
4708 is equivalent to <tt>bar</tt> on the i386 architecture, to
4709 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4710 bar</tt> on all other architectures.
4714 Relationships may also be restricted to a certain set of
4715 architectures using architecture wildcards in the format
4716 described in <ref id="arch-wildcard-spec">. The syntax for
4717 declaring such restrictions is the same as declaring
4718 restrictions using a certain set of architectures without
4719 architecture wildcards. For example:
4720 <example compact="compact">
4721 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4723 is equivalent to <tt>foo</tt> on architectures using the Linux
4724 kernel and any cpu, <tt>bar</tt> on architectures using any
4725 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4726 using a kernel other than Linux.
4730 Note that the binary package relationship fields such as
4731 <tt>Depends</tt> appear in one of the binary package
4732 sections of the control file, whereas the build-time
4733 relationships such as <tt>Build-Depends</tt> appear in the
4734 source package section of the control file (which is the
4739 <sect id="binarydeps">
4740 <heading>Binary Dependencies - <tt>Depends</tt>,
4741 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4742 <tt>Pre-Depends</tt>
4746 Packages can declare in their control file that they have
4747 certain relationships to other packages - for example, that
4748 they may not be installed at the same time as certain other
4749 packages, and/or that they depend on the presence of others.
4753 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4754 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4755 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4756 <tt>Breaks</tt> is described in <ref id="breaks">, and
4757 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4758 rest are described below.
4762 These seven fields are used to declare a dependency
4763 relationship by one package on another. Except for
4764 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4765 depending (binary) package's control file.
4766 (<tt>Enhances</tt> appears in the recommending package's
4767 control file, and <tt>Breaks</tt> appears in the version of
4768 depended-on package which causes the named package to
4773 A <tt>Depends</tt> field takes effect <em>only</em> when a
4774 package is to be configured. It does not prevent a package
4775 being on the system in an unconfigured state while its
4776 dependencies are unsatisfied, and it is possible to replace
4777 a package whose dependencies are satisfied and which is
4778 properly installed with a different version whose
4779 dependencies are not and cannot be satisfied; when this is
4780 done the depending package will be left unconfigured (since
4781 attempts to configure it will give errors) and will not
4782 function properly. If it is necessary, a
4783 <tt>Pre-Depends</tt> field can be used, which has a partial
4784 effect even when a package is being unpacked, as explained
4785 in detail below. (The other three dependency fields,
4786 <tt>Recommends</tt>, <tt>Suggests</tt> and
4787 <tt>Enhances</tt>, are only used by the various front-ends
4788 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4789 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4793 Since <tt>Depends</tt> only places requirements on the order in
4794 which packages are configured, packages in an installation run
4795 are usually all unpacked first and all configured later.
4797 This approach makes dependency resolution easier. If two
4798 packages A and B are being upgraded, the installed package A
4799 depends on exactly the installed package B, and the new
4800 package A depends on exactly the new package B (a common
4801 situation when upgrading shared libraries and their
4802 corresponding development packages), satisfying the
4803 dependencies at every stage of the upgrade would be
4804 impossible. This relaxed restriction means that both new
4805 packages can be unpacked together and then configured in their
4811 If there is a circular dependency among packages being installed
4812 or removed, installation or removal order honoring the
4813 dependency order is impossible, requiring the dependency loop be
4814 broken at some point and the dependency requirements violated
4815 for at least one package. Packages involved in circular
4816 dependencies may not be able to rely on their dependencies being
4817 configured before they themselves are configured, depending on
4818 which side of the break of the circular dependency loop they
4819 happen to be on. If one of the packages in the loop has
4820 no <prgn>postinst</prgn> script, then the cycle will be broken
4821 at that package; this ensures that all <prgn>postinst</prgn>
4822 scripts are run with their dependencies properly configured if
4823 this is possible. Otherwise the breaking point is arbitrary.
4824 Packages should therefore avoid circular dependencies where
4825 possible, particularly if they have <prgn>postinst</prgn>
4830 The meaning of the five dependency fields is as follows:
4832 <tag><tt>Depends</tt></tag>
4835 This declares an absolute dependency. A package will
4836 not be configured unless all of the packages listed in
4837 its <tt>Depends</tt> field have been correctly
4838 configured (unless there is a circular dependency as
4843 The <tt>Depends</tt> field should be used if the
4844 depended-on package is required for the depending
4845 package to provide a significant amount of
4850 The <tt>Depends</tt> field should also be used if the
4851 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4852 require the depended-on package to be unpacked or
4853 configured in order to run. In the case of <tt>postinst
4854 configure</tt>, the depended-on packages will be unpacked
4855 and configured first. (If both packages are involved in a
4856 dependency loop, this might not work as expected; see the
4857 explanation a few paragraphs back.) In the case
4858 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4859 actions, the package dependencies will normally be at
4860 least unpacked, but they may be only "Half-Installed" if a
4861 previous upgrade of the dependency failed.
4865 Finally, the <tt>Depends</tt> field should be used if the
4866 depended-on package is needed by the <prgn>postrm</prgn>
4867 script to fully clean up after the package removal. There
4868 is no guarantee that package dependencies will be
4869 available when <prgn>postrm</prgn> is run, but the
4870 depended-on package is more likely to be available if the
4871 package declares a dependency (particularly in the case
4872 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4873 script must gracefully skip actions that require a
4874 dependency if that dependency isn't available.
4878 <tag><tt>Recommends</tt></tag>
4881 This declares a strong, but not absolute, dependency.
4885 The <tt>Recommends</tt> field should list packages
4886 that would be found together with this one in all but
4887 unusual installations.
4891 <tag><tt>Suggests</tt></tag>
4893 This is used to declare that one package may be more
4894 useful with one or more others. Using this field
4895 tells the packaging system and the user that the
4896 listed packages are related to this one and can
4897 perhaps enhance its usefulness, but that installing
4898 this one without them is perfectly reasonable.
4901 <tag><tt>Enhances</tt></tag>
4903 This field is similar to Suggests but works in the
4904 opposite direction. It is used to declare that a
4905 package can enhance the functionality of another
4909 <tag><tt>Pre-Depends</tt></tag>
4912 This field is like <tt>Depends</tt>, except that it
4913 also forces <prgn>dpkg</prgn> to complete installation
4914 of the packages named before even starting the
4915 installation of the package which declares the
4916 pre-dependency, as follows:
4920 When a package declaring a pre-dependency is about to
4921 be <em>unpacked</em> the pre-dependency can be
4922 satisfied if the depended-on package is either fully
4923 configured, <em>or even if</em> the depended-on
4924 package(s) are only unpacked or in the "Half-Configured"
4925 state, provided that they have been configured
4926 correctly at some point in the past (and not removed
4927 or partially removed since). In this case, both the
4928 previously-configured and currently unpacked or
4929 "Half-Configured" versions must satisfy any version
4930 clause in the <tt>Pre-Depends</tt> field.
4934 When the package declaring a pre-dependency is about to
4935 be <em>configured</em>, the pre-dependency will be treated
4936 as a normal <tt>Depends</tt>. It will be considered
4937 satisfied only if the depended-on package has been
4938 correctly configured. However, unlike
4939 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4940 permit circular dependencies to be broken. If a circular
4941 dependency is encountered while attempting to honor
4942 <tt>Pre-Depends</tt>, the installation will be aborted.
4946 <tt>Pre-Depends</tt> are also required if the
4947 <prgn>preinst</prgn> script depends on the named package.
4948 It is best to avoid this situation if possible.
4952 <tt>Pre-Depends</tt> should be used sparingly,
4953 preferably only by packages whose premature upgrade or
4954 installation would hamper the ability of the system to
4955 continue with any upgrade that might be in progress.
4959 You should not specify a <tt>Pre-Depends</tt> entry for a
4960 package before this has been discussed on the
4961 <tt>debian-devel</tt> mailing list and a consensus about
4962 doing that has been reached. See <ref id="dependencies">.
4969 When selecting which level of dependency to use you should
4970 consider how important the depended-on package is to the
4971 functionality of the one declaring the dependency. Some
4972 packages are composed of components of varying degrees of
4973 importance. Such a package should list using
4974 <tt>Depends</tt> the package(s) which are required by the
4975 more important components. The other components'
4976 requirements may be mentioned as Suggestions or
4977 Recommendations, as appropriate to the components' relative
4983 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4986 When one binary package declares that it breaks another,
4987 <prgn>dpkg</prgn> will refuse to allow the package which
4988 declares <tt>Breaks</tt> to be unpacked unless the broken
4989 package is deconfigured first, and it will refuse to
4990 allow the broken package to be reconfigured.
4994 A package will not be regarded as causing breakage merely
4995 because its configuration files are still installed; it must
4996 be at least "Half-Installed".
5000 A special exception is made for packages which declare that
5001 they break their own package name or a virtual package which
5002 they provide (see below): this does not count as a real
5007 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5008 version clause; such a <tt>Breaks</tt> is introduced in the
5009 version of an (implicit or explicit) dependency which violates
5010 an assumption or reveals a bug in earlier versions of the broken
5011 package, or which takes over a file from earlier versions of the
5012 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5013 will inform higher-level package management tools that the
5014 broken package must be upgraded before the new one.
5018 If the breaking package also overwrites some files from the
5019 older package, it should use <tt>Replaces</tt> to ensure this
5020 goes smoothly. See <ref id="replaces"> for a full discussion
5021 of taking over files from other packages, including how to
5022 use <tt>Breaks</tt> in those cases.
5026 Many of the cases where <tt>Breaks</tt> should be used were
5027 previously handled with <tt>Conflicts</tt>
5028 because <tt>Breaks</tt> did not yet exist.
5029 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5030 See <ref id="conflicts"> for more information about the
5035 <sect id="conflicts">
5036 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5039 When one binary package declares a conflict with another using
5040 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5041 allow them to be unpacked on the system at the same time. This
5042 is a stronger restriction than <tt>Breaks</tt>, which prevents
5043 the broken package from being configured while the breaking
5044 package is in the "Unpacked" state but allows both packages to
5045 be unpacked at the same time.
5049 If one package is to be unpacked, the other must be removed
5050 first. If the package being unpacked is marked as replacing
5051 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5052 normally be used in this case) the one on the system, or the one
5053 on the system is marked as deselected, or both packages are
5054 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5055 automatically remove the package which is causing the conflict.
5056 Otherwise, it will halt the installation of the new package with
5057 an error. This mechanism is specifically designed to produce an
5058 error when the installed package is <tt>Essential</tt>, but the
5063 A package will not cause a conflict merely because its
5064 configuration files are still installed; it must be at least
5069 A special exception is made for packages which declare a
5070 conflict with their own package name, or with a virtual
5071 package which they provide (see below): this does not
5072 prevent their installation, and allows a package to conflict
5073 with others providing a replacement for it. You use this
5074 feature when you want the package in question to be the only
5075 package providing some feature.
5079 Normally, <tt>Breaks</tt> should be used instead
5080 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5081 stronger restriction on the ordering of package installation or
5082 upgrade and can make it more difficult for the package manager
5083 to find a correct solution to an upgrade or installation
5084 problem. <tt>Breaks</tt> should be used
5086 <item>when moving a file from one package to another (see
5087 <ref id="replaces">),</item>
5088 <item>when splitting a package (a special case of the previous
5090 <item>when the breaking package exposes a bug in or interacts
5091 badly with particular versions of the broken
5094 <tt>Conflicts</tt> should be used
5096 <item>when two packages provide the same file and will
5097 continue to do so,</item>
5098 <item>in conjunction with <tt>Provides</tt> when only one
5099 package providing a given virtual facility may be unpacked
5100 at a time (see <ref id="virtual">),</item>
5101 <item>in other cases where one must prevent simultaneous
5102 installation of two packages for reasons that are ongoing
5103 (not fixed in a later version of one of the packages) or
5104 that must prevent both packages from being unpacked at the
5105 same time, not just configured.</item>
5107 Be aware that adding <tt>Conflicts</tt> is normally not the best
5108 solution when two packages provide the same files. Depending on
5109 the reason for that conflict, using alternatives or renaming the
5110 files is often a better approach. See, for
5111 example, <ref id="binaries">.
5115 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5116 unless two packages cannot be installed at the same time or
5117 installing them both causes one of them to be broken or
5118 unusable. Having similar functionality or performing the same
5119 tasks as another package is not sufficient reason to
5120 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5124 A <tt>Conflicts</tt> entry may have an "earlier than" version
5125 clause if the reason for the conflict is corrected in a later
5126 version of one of the packages. However, normally the presence
5127 of an "earlier than" version clause is a sign
5128 that <tt>Breaks</tt> should have been used instead. An "earlier
5129 than" version clause in <tt>Conflicts</tt>
5130 prevents <prgn>dpkg</prgn> from upgrading or installing the
5131 package which declares such a conflict until the upgrade or
5132 removal of the conflicted-with package has been completed, which
5133 is a strong restriction.
5137 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5141 As well as the names of actual ("concrete") packages, the
5142 package relationship fields <tt>Depends</tt>,
5143 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5144 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5145 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5146 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5147 may mention "virtual packages".
5151 A <em>virtual package</em> is one which appears in the
5152 <tt>Provides</tt> control field of another package. The effect
5153 is as if the package(s) which provide a particular virtual
5154 package name had been listed by name everywhere the virtual
5155 package name appears. (See also <ref id="virtual_pkg">)
5159 If there are both concrete and virtual packages of the same
5160 name, then the dependency may be satisfied (or the conflict
5161 caused) by either the concrete package with the name in
5162 question or any other concrete package which provides the
5163 virtual package with the name in question. This is so that,
5164 for example, supposing we have
5165 <example compact="compact">
5168 </example> and someone else releases an enhanced version of
5169 the <tt>bar</tt> package they can say:
5170 <example compact="compact">
5174 and the <tt>bar-plus</tt> package will now also satisfy the
5175 dependency for the <tt>foo</tt> package.
5179 If a relationship field has a version number attached, only real
5180 packages will be considered to see whether the relationship is
5181 satisfied (or the prohibition violated, for a conflict or
5182 breakage). In other words, if a version number is specified,
5183 this is a request to ignore all <tt>Provides</tt> for that
5184 package name and consider only real packages. The package
5185 manager will assume that a package providing that virtual
5186 package is not of the "right" version. A <tt>Provides</tt>
5187 field may not contain version numbers, and the version number of
5188 the concrete package which provides a particular virtual package
5189 will not be considered when considering a dependency on or
5190 conflict with the virtual package name.<footnote>
5191 It is possible that a future release of <prgn>dpkg</prgn> may
5192 add the ability to specify a version number for each virtual
5193 package it provides. This feature is not yet present,
5194 however, and is expected to be used only infrequently.
5199 To specify which of a set of real packages should be the default
5200 to satisfy a particular dependency on a virtual package, list
5201 the real package as an alternative before the virtual one.
5205 If the virtual package represents a facility that can only be
5206 provided by one real package at a time, such as
5207 the <package>mail-transport-agent</package> virtual package that
5208 requires installation of a binary that would conflict with all
5209 other providers of that virtual package (see
5210 <ref id="mail-transport-agents">), all packages providing that
5211 virtual package should also declare a conflict with it
5212 using <tt>Conflicts</tt>. This will ensure that at most one
5213 provider of that virtual package is unpacked or installed at a
5218 <sect id="replaces"><heading>Overwriting files and replacing
5219 packages - <tt>Replaces</tt></heading>
5222 Packages can declare in their control file that they should
5223 overwrite files in certain other packages, or completely replace
5224 other packages. The <tt>Replaces</tt> control field has these
5225 two distinct purposes.
5228 <sect1><heading>Overwriting files in other packages</heading>
5231 It is usually an error for a package to contain files which
5232 are on the system in another package. However, if the
5233 overwriting package declares that it <tt>Replaces</tt> the one
5234 containing the file being overwritten, then <prgn>dpkg</prgn>
5235 will replace the file from the old package with that from the
5236 new. The file will no longer be listed as "owned" by the old
5237 package and will be taken over by the new package.
5238 Normally, <tt>Breaks</tt> should be used in conjunction
5239 with <tt>Replaces</tt>.<footnote>
5240 To see why <tt>Breaks</tt> is normally needed in addition
5241 to <tt>Replaces</tt>, consider the case of a file in the
5242 package <package>foo</package> being taken over by the
5243 package <package>foo-data</package>.
5244 <tt>Replaces</tt> will allow <package>foo-data</package> to
5245 be installed and take over that file. However,
5246 without <tt>Breaks</tt>, nothing
5247 requires <package>foo</package> to be upgraded to a newer
5248 version that knows it does not include that file and instead
5249 depends on <package>foo-data</package>. Nothing would
5250 prevent the new <package>foo-data</package> package from
5251 being installed and then removed, removing the file that it
5252 took over from <package>foo</package>. After that
5253 operation, the package manager would think the system was in
5254 a consistent state, but the <package>foo</package> package
5255 would be missing one of its files.
5260 For example, if a package <package>foo</package> is split
5261 into <package>foo</package> and <package>foo-data</package>
5262 starting at version 1.2-3, <package>foo-data</package> would
5264 <example compact="compact">
5265 Replaces: foo (<< 1.2-3)
5266 Breaks: foo (<< 1.2-3)
5268 in its control file. The new version of the
5269 package <package>foo</package> would normally have the field
5270 <example compact="compact">
5271 Depends: foo-data (>= 1.2-3)
5273 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5274 the files moved into <package>foo-data</package> are not
5275 required for normal operation).
5279 If a package is completely replaced in this way, so that
5280 <prgn>dpkg</prgn> does not know of any files it still
5281 contains, it is considered to have "disappeared". It will
5282 be marked as not wanted on the system (selected for
5283 removal) and not installed. Any <tt>conffile</tt>s
5284 details noted for the package will be ignored, as they
5285 will have been taken over by the overwriting package. The
5286 package's <prgn>postrm</prgn> script will be run with a
5287 special argument to allow the package to do any final
5288 cleanup required. See <ref id="mscriptsinstact">.
5290 Replaces is a one way relationship. You have to install
5291 the replacing package after the replaced package.
5296 For this usage of <tt>Replaces</tt>, virtual packages (see
5297 <ref id="virtual">) are not considered when looking at a
5298 <tt>Replaces</tt> field. The packages declared as being
5299 replaced must be mentioned by their real names.
5303 This usage of <tt>Replaces</tt> only takes effect when both
5304 packages are at least partially on the system at once. It is
5305 not relevant if the packages conflict unless the conflict has
5310 <sect1><heading>Replacing whole packages, forcing their
5314 Second, <tt>Replaces</tt> allows the packaging system to
5315 resolve which package should be removed when there is a
5316 conflict (see <ref id="conflicts">). This usage only takes
5317 effect when the two packages <em>do</em> conflict, so that the
5318 two usages of this field do not interfere with each other.
5322 In this situation, the package declared as being replaced
5323 can be a virtual package, so for example, all mail
5324 transport agents (MTAs) would have the following fields in
5325 their control files:
5326 <example compact="compact">
5327 Provides: mail-transport-agent
5328 Conflicts: mail-transport-agent
5329 Replaces: mail-transport-agent
5331 ensuring that only one MTA can be unpacked at any one
5332 time. See <ref id="virtual"> for more information about this
5337 <sect id="sourcebinarydeps">
5338 <heading>Relationships between source and binary packages -
5339 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5340 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5344 Source packages that require certain binary packages to be
5345 installed or absent at the time of building the package
5346 can declare relationships to those binary packages.
5350 This is done using the <tt>Build-Depends</tt>,
5351 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5352 <tt>Build-Conflicts-Indep</tt> control fields.
5356 Build-dependencies on "build-essential" binary packages can be
5357 omitted. Please see <ref id="pkg-relations"> for more information.
5361 The dependencies and conflicts they define must be satisfied
5362 (as defined earlier for binary packages) in order to invoke
5363 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5365 There is no Build-Depends-Arch; this role is essentially
5366 met with Build-Depends. Anyone building the
5367 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5368 assumed to be building the whole package, and therefore
5369 installation of all build dependencies is required.
5372 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5373 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5374 not yet know how to check for its existence, and
5375 <tt>binary-arch</tt>. The purpose of the original split
5376 between <tt>Build-Depends</tt> and
5377 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5378 wouldn't need to install extra packages needed only for the
5379 binary-indep targets. But without a build-arch/build-indep
5380 split, this didn't work, since most of the work is done in
5381 the build target, not in the binary target.
5385 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5386 <tt>binary-arch</tt></tag>
5388 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5389 fields must be satisfied when these targets are invoked.
5391 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5392 and <tt>binary-indep</tt></tag>
5394 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5395 <tt>Build-Depends-Indep</tt>, and
5396 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5397 these targets are invoked.
5405 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5408 Packages containing shared libraries must be constructed with
5409 a little care to make sure that the shared library is always
5410 available. This is especially important for packages whose
5411 shared libraries are vitally important, such as the C library
5412 (currently <tt>libc6</tt>).
5416 This section deals only with public shared libraries: shared
5417 libraries that are placed in directories searched by the dynamic
5418 linker by default or which are intended to be linked against
5419 normally and possibly used by other, independent packages. Shared
5420 libraries that are internal to a particular package or that are
5421 only loaded as dynamic modules are not covered by this section and
5422 are not subject to its requirements.
5426 A shared library is identified by the <tt>SONAME</tt> attribute
5427 stored in its dynamic section. When a binary is linked against a
5428 shared library, the <tt>SONAME</tt> of the shared library is
5429 recorded in the binary's <tt>NEEDED</tt> section so that the
5430 dynamic linker knows that library must be loaded at runtime. The
5431 shared library file's full name (which usually contains additional
5432 version information not needed in the <tt>SONAME</tt>) is
5433 therefore normally not referenced directly. Instead, the shared
5434 library is loaded by its <tt>SONAME</tt>, which exists on the file
5435 system as a symlink pointing to the full name of the shared
5436 library. This symlink must be provided by the
5437 package. <ref id="sharedlibs-runtime"> describes how to do this.
5439 This is a convention of shared library versioning, but not a
5440 requirement. Some libraries use the <tt>SONAME</tt> as the full
5441 library file name instead and therefore do not need a symlink.
5442 Most, however, encode additional information about
5443 backwards-compatible revisions as a minor version number in the
5444 file name. The <tt>SONAME</tt> itself only changes when
5445 binaries linked with the earlier version of the shared library
5446 may no longer work, but the filename may change with each
5447 release of the library. See <ref id="sharedlibs-runtime"> for
5453 When linking a binary or another shared library against a shared
5454 library, the <tt>SONAME</tt> for that shared library is not yet
5455 known. Instead, the shared library is found by looking for a file
5456 matching the library name with <tt>.so</tt> appended. This file
5457 exists on the file system as a symlink pointing to the shared
5462 Shared libraries are normally split into several binary packages.
5463 The <tt>SONAME</tt> symlink is installed by the runtime shared
5464 library package, and the bare <tt>.so</tt> symlink is installed in
5465 the development package since it's only used when linking binaries
5466 or shared libraries. However, there are some exceptions for
5467 unusual shared libraries or for shared libraries that are also
5468 loaded as dynamic modules by other programs.
5472 This section is primarily concerned with how the separation of
5473 shared libraries into multiple packages should be done and how
5474 dependencies on and between shared library binary packages are
5475 managed in Debian. <ref id="libraries"> should be read in
5476 conjunction with this section and contains additional rules for
5477 the files contained in the shared library packages.
5480 <sect id="sharedlibs-runtime">
5481 <heading>Run-time shared libraries</heading>
5484 The run-time shared library must be placed in a package
5485 whose name changes whenever the <tt>SONAME</tt> of the shared
5486 library changes. This allows several versions of the shared
5487 library to be installed at the same time, allowing installation
5488 of the new version of the shared library without immediately
5489 breaking binaries that depend on the old version. Normally, the
5490 run-time shared library and its <tt>SONAME</tt> symlink should
5491 be placed in a package named
5492 <package><var>libraryname</var><var>soversion</var></package>,
5493 where <var>soversion</var> is the version number in
5494 the <tt>SONAME</tt> of the shared library.
5495 See <ref id="shlibs"> for detailed information on how to
5496 determine this version. Alternatively, if it would be confusing
5497 to directly append <var>soversion</var>
5498 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5499 itself ends in a number), you should use
5500 <package><var>libraryname</var>-<var>soversion</var></package>
5505 If you have several shared libraries built from the same source
5506 tree, you may lump them all together into a single shared
5507 library package provided that all of their <tt>SONAME</tt>s will
5508 always change together. Be aware that this is not normally the
5509 case, and if the <tt>SONAME</tt>s do not change together,
5510 upgrading such a merged shared library package will be
5511 unnecessarily difficult because of file conflicts with the old
5512 version of the package. When in doubt, always split shared
5513 library packages so that each binary package installs a single
5518 Every time the shared library ABI changes in a way that may
5519 break binaries linked against older versions of the shared
5520 library, the <tt>SONAME</tt> of the library and the
5521 corresponding name for the binary package containing the runtime
5522 shared library should change. Normally, this means
5523 the <tt>SONAME</tt> should change any time an interface is
5524 removed from the shared library or the signature of an interface
5525 (the number of parameters or the types of parameters that it
5526 takes, for example) is changed. This practice is vital to
5527 allowing clean upgrades from older versions of the package and
5528 clean transitions between the old ABI and new ABI without having
5529 to upgrade every affected package simultaneously.
5533 The <tt>SONAME</tt> and binary package name need not, and indeed
5534 normally should not, change if new interfaces are added but none
5535 are removed or changed, since this will not break binaries
5536 linked against the old shared library. Correct versioning of
5537 dependencies on the newer shared library by binaries that use
5538 the new interfaces is handled via
5539 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5540 system</qref> or via symbols files (see
5541 <manref name="deb-symbols" section="5">).
5545 The package should install the shared libraries under
5546 their normal names. For example, the <package>libgdbm3</package>
5547 package should install <file>libgdbm.so.3.0.0</file> as
5548 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5549 renamed or re-linked by any <prgn>prerm</prgn> or
5550 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5551 of renaming things safely without affecting running programs,
5552 and attempts to interfere with this are likely to lead to
5557 Shared libraries should not be installed executable, since
5558 the dynamic linker does not require this and trying to
5559 execute a shared library usually results in a core dump.
5563 The run-time library package should include the symbolic link for
5564 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5565 the shared libraries. For example,
5566 the <package>libgdbm3</package> package should include a symbolic
5567 link from <file>/usr/lib/libgdbm.so.3</file> to
5568 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5569 linker (for example <prgn>ld.so</prgn> or
5570 <prgn>ld-linux.so.*</prgn>) can find the library between the
5571 time that <prgn>dpkg</prgn> installs it and the time that
5572 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5574 The package management system requires the library to be
5575 placed before the symbolic link pointing to it in the
5576 <file>.deb</file> file. This is so that when
5577 <prgn>dpkg</prgn> comes to install the symlink
5578 (overwriting the previous symlink pointing at an older
5579 version of the library), the new shared library is already
5580 in place. In the past, this was achieved by creating the
5581 library in the temporary packaging directory before
5582 creating the symlink. Unfortunately, this was not always
5583 effective, since the building of the tar file in the
5584 <file>.deb</file> depended on the behavior of the underlying
5585 file system. Some file systems (such as reiserfs) reorder
5586 the files so that the order of creation is forgotten.
5587 Since version 1.7.0, <prgn>dpkg</prgn>
5588 reorders the files itself as necessary when building a
5589 package. Thus it is no longer important to concern
5590 oneself with the order of file creation.
5594 <sect1 id="ldconfig">
5595 <heading><tt>ldconfig</tt></heading>
5598 Any package installing shared libraries in one of the default
5599 library directories of the dynamic linker (which are currently
5600 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5601 listed in <file>/etc/ld.so.conf</file><footnote>
5602 These are currently <file>/usr/local/lib</file> plus
5603 directories under <file>/lib</file> and <file>/usr/lib</file>
5604 matching the multiarch triplet for the system architecture.
5606 must use <prgn>ldconfig</prgn> to update the shared library
5611 The package maintainer scripts must only call
5612 <prgn>ldconfig</prgn> under these circumstances:
5613 <list compact="compact">
5614 <item>When the <prgn>postinst</prgn> script is run with a
5615 first argument of <tt>configure</tt>, the script must call
5616 <prgn>ldconfig</prgn>, and may optionally invoke
5617 <prgn>ldconfig</prgn> at other times.
5619 <item>When the <prgn>postrm</prgn> script is run with a
5620 first argument of <tt>remove</tt>, the script should call
5621 <prgn>ldconfig</prgn>.
5626 During install or upgrade, the preinst is called before
5627 the new files are unpacked, so calling "ldconfig" is
5628 pointless. The preinst of an existing package can also be
5629 called if an upgrade fails. However, this happens during
5630 the critical time when a shared libs may exist on-disk
5631 under a temporary name. Thus, it is dangerous and
5632 forbidden by current policy to call "ldconfig" at this
5637 When a package is installed or upgraded, "postinst
5638 configure" runs after the new files are safely on-disk.
5639 Since it is perfectly safe to invoke ldconfig
5640 unconditionally in a postinst, it is OK for a package to
5641 simply put ldconfig in its postinst without checking the
5642 argument. The postinst can also be called to recover from
5643 a failed upgrade. This happens before any new files are
5644 unpacked, so there is no reason to call "ldconfig" at this
5649 For a package that is being removed, prerm is
5650 called with all the files intact, so calling ldconfig is
5651 useless. The other calls to "prerm" happen in the case of
5652 upgrade at a time when all the files of the old package
5653 are on-disk, so again calling "ldconfig" is pointless.
5657 postrm, on the other hand, is called with the "remove"
5658 argument just after the files are removed, so this is
5659 the proper time to call "ldconfig" to notify the system
5660 of the fact that the shared libraries from the package
5661 are removed. The postrm can be called at several other
5662 times. At the time of "postrm purge", "postrm
5663 abort-install", or "postrm abort-upgrade", calling
5664 "ldconfig" is useless because the shared lib files are
5665 not on-disk. However, when "postrm" is invoked with
5666 arguments "upgrade", "failed-upgrade", or "disappear", a
5667 shared lib may exist on-disk under a temporary filename.
5675 <sect id="sharedlibs-support-files">
5676 <heading>Shared library support files</heading>
5679 If your package contains files whose names do not change with
5680 each change in the library shared object version, you must not
5681 put them in the shared library package. Otherwise, several
5682 versions of the shared library cannot be installed at the same
5683 time without filename clashes, making upgrades and transitions
5684 unnecessarily difficult.
5688 It is recommended that supporting files and run-time support
5689 programs that do not need to be invoked manually by users, but
5690 are nevertheless required for the package to function, be placed
5691 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5692 preferably under <file>/usr/lib/</file><var>package-name</var>.
5693 If the program or file is architecture independent, the
5694 recommendation is for it to be placed in a subdirectory of
5695 <file>/usr/share</file> instead, preferably under
5696 <file>/usr/share/</file><var>package-name</var>. Following the
5697 <var>package-name</var> naming convention ensures that the file
5698 names change when the shared object version changes.
5702 Run-time support programs that use the shared library but are
5703 not required for the library to function or files used by the
5704 shared library that can be used by any version of the shared
5705 library package should instead be put in a separate package.
5706 This package might typically be named
5707 <package><var>libraryname</var>-tools</package>; note the
5708 absence of the <var>soversion</var> in the package name.
5712 Files and support programs only useful when compiling software
5713 against the library should be included in the development
5714 package for the library.<footnote>
5715 For example, a <file><var>package-name</var>-config</file>
5716 script or <package>pkg-config</package> configuration files.
5721 <sect id="sharedlibs-static">
5722 <heading>Static libraries</heading>
5725 The static library (<file><var>libraryname.a</var></file>)
5726 is usually provided in addition to the shared version.
5727 It is placed into the development package (see below).
5731 In some cases, it is acceptable for a library to be
5732 available in static form only; these cases include:
5734 <item>libraries for languages whose shared library support
5735 is immature or unstable</item>
5736 <item>libraries whose interfaces are in flux or under
5737 development (commonly the case when the library's
5738 major version number is zero, or where the ABI breaks
5739 across patchlevels)</item>
5740 <item>libraries which are explicitly intended to be
5741 available only in static form by their upstream
5746 <sect id="sharedlibs-dev">
5747 <heading>Development files</heading>
5750 If there are development files associated with a shared library,
5751 the source package needs to generate a binary development package
5752 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5753 or if you prefer only to support one development version at a
5754 time, <package><var>libraryname</var>-dev</package>. Installing
5755 the development package must result in installation of all the
5756 development files necessary for compiling programs against that
5757 shared library.<footnote>
5758 This wording allows the development files to be split into
5759 several packages, such as a separate architecture-independent
5760 <package><var>libraryname</var>-headers</package>, provided that
5761 the development package depends on all the required additional
5767 In case several development versions of a library exist, you may
5768 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5769 <ref id="conflicts">) to ensure that the user only installs one
5770 development version at a time (as different development versions are
5771 likely to have the same header files in them, which would cause a
5772 filename clash if both were unpacked).
5776 The development package should contain a symlink for the associated
5777 shared library without a version number. For example, the
5778 <package>libgdbm-dev</package> package should include a symlink
5779 from <file>/usr/lib/libgdbm.so</file> to
5780 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5781 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5782 <file>libgdbm.so</file> when compiling dynamically.
5786 If the package provides Ada Library Information
5787 (<file>*.ali</file>) files for use with GNAT, these files must be
5788 installed read-only (mode 0444) so that GNAT will not attempt to
5789 recompile them. This overrides the normal file mode requirements
5790 given in <ref id="permissions-owners">.
5794 <sect id="sharedlibs-intradeps">
5795 <heading>Dependencies between the packages of the same library</heading>
5798 Typically the development version should have an exact
5799 version dependency on the runtime library, to make sure that
5800 compilation and linking happens correctly. The
5801 <tt>${binary:Version}</tt> substitution variable can be
5802 useful for this purpose.
5804 Previously, <tt>${Source-Version}</tt> was used, but its name
5805 was confusing and it has been deprecated since dpkg 1.13.19.
5810 <sect id="sharedlibs-shlibdeps">
5811 <heading>Dependencies between the library and other packages -
5812 the <tt>shlibs</tt> system</heading>
5815 If a package contains a binary or library which links to a
5816 shared library, we must ensure that when the package is
5817 installed on the system, all of the libraries needed are
5818 also installed. This requirement led to the creation of the
5819 <tt>shlibs</tt> system, which is very simple in its design:
5820 any package which <em>provides</em> a shared library also
5821 provides information on the package dependencies required to
5822 ensure the presence of this library, and any package which
5823 <em>uses</em> a shared library uses this information to
5824 determine the dependencies it requires. The files which
5825 contain the mapping from shared libraries to the necessary
5826 dependency information are called <file>shlibs</file> files.
5830 When a package is built which contains any shared libraries, it
5831 must provide a <file>shlibs</file> file for other packages to
5832 use. When a package is built which contains any shared
5833 libraries or compiled binaries, it must run
5834 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5835 on these to determine the libraries used and hence the
5836 dependencies needed by this package.<footnote>
5838 <prgn>dpkg-shlibdeps</prgn> will use a program
5839 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5840 the libraries directly needed by the binaries or shared
5841 libraries in the package.
5845 We say that a binary <tt>foo</tt> <em>directly</em> uses
5846 a library <tt>libbar</tt> if it is explicitly linked
5847 with that library (that is, the library is listed in the ELF
5848 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5849 to the link line when the binary is created). Other
5850 libraries that are needed by <tt>libbar</tt> are linked
5851 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5852 linker will load them automatically when it loads
5853 <tt>libbar</tt>. A package should depend on the libraries
5854 it directly uses, but not the libraries it indirectly uses.
5855 The dependencies for those libraries will automatically pull
5856 in the other libraries.
5860 A good example of where this helps is the following. We
5861 could update <tt>libimlib</tt> with a new version that
5862 supports a new graphics format called dgf (but retaining the
5863 same major version number) and depends on <tt>libdgf</tt>.
5864 If we used <prgn>ldd</prgn> to add dependencies for every
5865 library directly or indirectly linked with a binary, every
5866 package that uses <tt>libimlib</tt> would need to be
5867 recompiled so it would also depend on <tt>libdgf</tt> or it
5868 wouldn't run due to missing symbols. Since dependencies are
5869 only added based on ELF <tt>NEEDED</tt> attribute, packages
5870 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5871 having the dependency on <tt>libdgf</tt> and so they would
5872 not need rebuilding.
5878 In the following sections, we will first describe where the
5879 various <tt>shlibs</tt> files are to be found, then how to
5880 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5881 file format and how to create them if your package contains a
5886 <heading>The <tt>shlibs</tt> files present on the system</heading>
5889 There are several places where <tt>shlibs</tt> files are
5890 found. The following list gives them in the order in which
5892 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5893 (The first one which gives the required information is used.)
5899 <p><file>debian/shlibs.local</file></p>
5902 This lists overrides for this package. This file should
5903 normally not be used, but may be needed temporarily in
5904 unusual situations to work around bugs in other packages,
5905 or in unusual cases where the normally declared dependency
5906 information in the installed <file>shlibs</file> file for
5907 a library cannot be used. This file overrides information
5908 obtained from any other source.
5913 <p><file>/etc/dpkg/shlibs.override</file></p>
5916 This lists global overrides. This list is normally
5917 empty. It is maintained by the local system
5923 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5926 When packages are being built,
5927 any <file>debian/shlibs</file> files are copied into the
5928 control information file area of the temporary build
5929 directory and given the name <file>shlibs</file>. These
5930 files give details of any shared libraries included in the
5931 same package.<footnote>
5932 An example may help here. Let us say that the source
5933 package <tt>foo</tt> generates two binary
5934 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5935 When building the binary packages, the two packages are
5936 created in the directories <file>debian/libfoo2</file>
5937 and <file>debian/foo-runtime</file> respectively.
5938 (<file>debian/tmp</file> could be used instead of one of
5939 these.) Since <tt>libfoo2</tt> provides the
5940 <tt>libfoo</tt> shared library, it will require a
5941 <tt>shlibs</tt> file, which will be installed in
5942 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5943 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5944 When <prgn>dpkg-shlibdeps</prgn> is run on the
5945 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5947 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5948 determine whether <tt>foo-prog</tt>'s library
5949 dependencies are satisfied by any of the libraries
5950 provided by <tt>libfoo2</tt>. For this reason,
5951 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5952 the individual binary packages' <tt>shlibs</tt> files
5953 have been installed into the build directory.
5959 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5962 These are the <file>shlibs</file> files corresponding to
5963 all of the packages installed on the system, and are
5964 maintained by the relevant package maintainers.
5969 <p><file>/etc/dpkg/shlibs.default</file></p>
5972 This file lists any shared libraries whose packages
5973 have failed to provide correct <file>shlibs</file> files.
5974 It was used when the <file>shlibs</file> setup was first
5975 introduced, but it is now normally empty. It is
5976 maintained by the <tt>dpkg</tt> maintainer.
5984 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5985 <file>shlibs</file> files</heading>
5989 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5990 into your <file>debian/rules</file> file. If your package
5991 contains only compiled binaries and libraries (but no scripts),
5992 you can use a command such as:
5993 <example compact="compact">
5994 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5995 debian/tmp/usr/lib/*
5997 Otherwise, you will need to explicitly list the compiled
5998 binaries and libraries.<footnote>
5999 If you are using <tt>debhelper</tt>, the
6000 <prgn>dh_shlibdeps</prgn> program will do this work for you.
6001 It will also correctly handle multi-binary packages.
6006 This command puts the dependency information into the
6007 <file>debian/substvars</file> file, which is then used by
6008 <prgn>dpkg-gencontrol</prgn>. You will need to place a
6009 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
6010 field in the control file for this to work.
6014 If you have multiple binary packages, you will need to call
6015 <prgn>dpkg-shlibdeps</prgn> on each one which contains
6016 compiled libraries or binaries. In such a case, you will
6017 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
6018 utilities to specify a different <file>substvars</file> file.
6022 If you are creating a udeb for use in the Debian Installer,
6023 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6024 should use the dependency line of type <tt>udeb</tt> by
6025 adding the <tt>-tudeb</tt> option<footnote>
6026 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6027 will automatically add this option if it knows it is
6029 </footnote>. If there is no dependency line of
6030 type <tt>udeb</tt> in the <file>shlibs</file>
6031 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
6036 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
6037 <ref id="pkg-dpkg-shlibdeps"> and
6038 <manref name="dpkg-shlibdeps" section="1">.
6043 <heading>The <file>shlibs</file> File Format</heading>
6046 Each <file>shlibs</file> file has the same format. Lines
6047 beginning with <tt>#</tt> are considered to be comments and
6048 are ignored. Each line is of the form:
6049 <example compact="compact">
6050 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6055 We will explain this by reference to the example of the
6056 <tt>zlib1g</tt> package, which (at the time of writing)
6057 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
6061 <var>type</var> is an optional element that indicates the type
6062 of package for which the line is valid. The only type currently
6063 in use is <tt>udeb</tt>. The colon and space after the type are
6068 <var>library-name</var> is the name of the shared library,
6069 in this case <tt>libz</tt>. (This must match the name part
6070 of the soname, see below.)
6074 <var>soname-version</var> is the version part of the soname of
6075 the library. The soname is the thing that must exactly match
6076 for the library to be recognized by the dynamic linker, and is
6078 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
6079 example, <tt>libz.so.1</tt>.<footnote>
6080 This can be determined using the command
6081 <example compact="compact">
6082 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
6085 The version part is the part which comes after
6086 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
6087 instead be of the form
6088 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
6089 as <tt>libdb-4.8.so</tt>, in which case the name would
6090 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
6094 <var>dependencies</var> has the same syntax as a dependency
6095 field in a binary package control file. It should give
6096 details of which packages are required to satisfy a binary
6097 built against the version of the library contained in the
6098 package. See <ref id="depsyntax"> for details.
6102 In our example, if the first version of the <tt>zlib1g</tt>
6103 package which contained a minor number of at least
6104 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
6105 <tt>shlibs</tt> entry for this library could say:
6106 <example compact="compact">
6107 libz 1 zlib1g (>= 1:1.1.3)
6109 The version-specific dependency is to avoid warnings from
6110 the dynamic linker about using older shared libraries with
6115 As zlib1g also provides a udeb containing the shared library,
6116 there would also be a second line:
6117 <example compact="compact">
6118 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
6124 <heading>Providing a <file>shlibs</file> file</heading>
6127 If your package provides a shared library, you need to create
6128 a <file>shlibs</file> file following the format described above.
6129 It is usual to call this file <file>debian/shlibs</file> (but if
6130 you have multiple binary packages, you might want to call it
6131 <file>debian/shlibs.<var>package</var></file> instead). Then
6132 let <file>debian/rules</file> install it in the control
6133 information file area:
6134 <example compact="compact">
6135 install -m644 debian/shlibs debian/tmp/DEBIAN
6137 or, in the case of a multi-binary package:
6138 <example compact="compact">
6139 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
6141 An alternative way of doing this is to create the
6142 <file>shlibs</file> file in the control information file area
6143 directly from <file>debian/rules</file> without using
6144 a <file>debian/shlibs</file> file at all,<footnote>
6145 This is what <prgn>dh_makeshlibs</prgn> in
6146 the <package>debhelper</package> suite does. If your package
6147 also has a udeb that provides a shared
6148 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6149 the <tt>udeb:</tt> lines if you specify the name of the udeb
6150 with the <tt>--add-udeb</tt> option.
6152 since the <file>debian/shlibs</file> file itself is ignored by
6153 <prgn>dpkg-shlibdeps</prgn>.
6157 As <prgn>dpkg-shlibdeps</prgn> reads the
6158 <file>DEBIAN/shlibs</file> files in all of the binary packages
6159 being built from this source package, all of the
6160 <file>DEBIAN/shlibs</file> files should be installed before
6161 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6169 <chapt id="opersys"><heading>The Operating System</heading>
6172 <heading>File system hierarchy</heading>
6176 <heading>File System Structure</heading>
6179 The location of all files and directories must comply with the
6180 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6181 exceptions noted below, and except where doing so would
6182 violate other terms of Debian Policy. The following
6183 exceptions to the FHS apply:
6188 The optional rules related to user specific
6189 configuration files for applications are stored in
6190 the user's home directory are relaxed. It is
6191 recommended that such files start with the
6192 '<tt>.</tt>' character (a "dot file"), and if an
6193 application needs to create more than one dot file
6194 then the preferred placement is in a subdirectory
6195 with a name starting with a '.' character, (a "dot
6196 directory"). In this case it is recommended the
6197 configuration files not start with the '.'
6203 The requirement for amd64 to use <file>/lib64</file>
6204 for 64 bit binaries is removed.
6209 The requirement for object files, internal binaries, and
6210 libraries, including <file>libc.so.*</file>, to be located
6211 directly under <file>/lib{,32}</file> and
6212 <file>/usr/lib{,32}</file> is amended, permitting files
6213 to instead be installed to
6214 <file>/lib/<var>triplet</var></file> and
6215 <file>/usr/lib/<var>triplet</var></file>, where
6216 <tt><var>triplet</var></tt> is the value returned by
6217 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6218 architecture of the package. Packages may <em>not</em>
6219 install files to any <var>triplet</var> path other
6220 than the one matching the architecture of that package;
6221 for instance, an <tt>Architecture: amd64</tt> package
6222 containing 32-bit x86 libraries may not install these
6223 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6225 This is necessary in order to reserve the directories for
6226 use in cross-installation of library packages from other
6227 architectures, as part of the planned deployment of
6232 Applications may also use a single subdirectory under
6233 <file>/usr/lib/<var>triplet</var></file>.
6236 The execution time linker/loader, ld*, must still be made
6237 available in the existing location under /lib or /lib64
6238 since this is part of the ELF ABI for the architecture.
6243 The requirement that
6244 <file>/usr/local/share/man</file> be "synonymous"
6245 with <file>/usr/local/man</file> is relaxed to a
6250 The requirement that windowmanagers with a single
6251 configuration file call it <file>system.*wmrc</file>
6252 is removed, as is the restriction that the window
6253 manager subdirectory be named identically to the
6254 window manager name itself.
6259 The requirement that boot manager configuration
6260 files live in <file>/etc</file>, or at least are
6261 symlinked there, is relaxed to a recommendation.
6266 The additional directory <file>/run</file> in the root
6267 file system is allowed. <file>/run</file>
6268 replaces <file>/var/run</file>, and the
6269 subdirectory <file>/run/lock</file>
6270 replaces <file>/var/lock</file>, with
6271 the <file>/var</file> directories replaced by symlinks
6272 for backwards compatibility. <file>/run</file>
6273 and <file>/run/lock</file> must follow all of the
6274 requirements in the FHS for <file>/var/run</file>
6275 and <file>/var/lock</file>, respectively, such as file
6276 naming conventions, file format requirements, or the
6277 requirement that files be cleared during the boot
6278 process. Files and directories residing
6279 in <file>/run</file> should be stored on a temporary
6285 The following directories in the root filesystem are
6286 additionally allowed: <file>/sys</file> and
6287 <file>/selinux</file>. <footnote>These directories
6288 are used as mount points to mount virtual filesystems
6289 to get access to kernel information.</footnote>
6294 On GNU/Hurd systems, the following additional
6295 directories are allowed in the root
6296 filesystem: <file>/hurd</file>
6297 and <file>/servers</file>.<footnote>
6298 These directories are used to store translators and as
6299 a set of standard names for mount points,
6308 The version of this document referred here can be
6309 found in the <tt>debian-policy</tt> package or on <url
6310 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6311 name="FHS (Debian copy)"> alongside this manual (or, if
6312 you have the <package>debian-policy</package> installed,
6314 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6315 (local copy)">). The
6316 latest version, which may be a more recent version, may
6318 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6319 Specific questions about following the standard may be
6320 asked on the <tt>debian-devel</tt> mailing list, or
6321 referred to the FHS mailing list (see the
6322 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6328 <heading>Site-specific programs</heading>
6331 As mandated by the FHS, packages must not place any
6332 files in <file>/usr/local</file>, either by putting them in
6333 the file system archive to be unpacked by <prgn>dpkg</prgn>
6334 or by manipulating them in their maintainer scripts.
6338 However, the package may create empty directories below
6339 <file>/usr/local</file> so that the system administrator knows
6340 where to place site-specific files. These are not
6341 directories <em>in</em> <file>/usr/local</file>, but are
6342 children of directories in <file>/usr/local</file>. These
6343 directories (<file>/usr/local/*/dir/</file>)
6344 should be removed on package removal if they are
6349 Note that this applies only to
6350 directories <em>below</em> <file>/usr/local</file>,
6351 not <em>in</em> <file>/usr/local</file>. Packages must
6352 not create sub-directories in the
6353 directory <file>/usr/local</file> itself, except those
6354 listed in FHS, section 4.5. However, you may create
6355 directories below them as you wish. You must not remove
6356 any of the directories listed in 4.5, even if you created
6361 Since <file>/usr/local</file> can be mounted read-only from a
6362 remote server, these directories must be created and
6363 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6364 maintainer scripts and not be included in the
6365 <file>.deb</file> archive. These scripts must not fail if
6366 either of these operations fail.
6370 For example, the <tt>emacsen-common</tt> package could
6371 contain something like
6372 <example compact="compact">
6373 if [ ! -e /usr/local/share/emacs ]; then
6374 if mkdir /usr/local/share/emacs 2>/dev/null; then
6375 if chown root:staff /usr/local/share/emacs; then
6376 chmod 2775 /usr/local/share/emacs || true
6381 in its <prgn>postinst</prgn> script, and
6382 <example compact="compact">
6383 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6384 rmdir /usr/local/share/emacs 2>/dev/null || true
6386 in the <prgn>prerm</prgn> script. (Note that this form is
6387 used to ensure that if the script is interrupted, the
6388 directory <file>/usr/local/share/emacs</file> will still be
6393 If you do create a directory in <file>/usr/local</file> for
6394 local additions to a package, you should ensure that
6395 settings in <file>/usr/local</file> take precedence over the
6396 equivalents in <file>/usr</file>.
6400 However, because <file>/usr/local</file> and its contents are
6401 for exclusive use of the local administrator, a package
6402 must not rely on the presence or absence of files or
6403 directories in <file>/usr/local</file> for normal operation.
6407 The <file>/usr/local</file> directory itself and all the
6408 subdirectories created by the package should (by default) have
6409 permissions 2775 (group-writable and set-group-id) and be
6410 owned by <tt>root:staff</tt>.
6415 <heading>The system-wide mail directory</heading>
6417 The system-wide mail directory
6418 is <file>/var/mail</file>. This directory is part of the
6419 base system and should not be owned by any particular mail
6420 agents. The use of the old
6421 location <file>/var/spool/mail</file> is deprecated, even
6422 though the spool may still be physically located there.
6426 <sect1 id="fhs-run">
6427 <heading><file>/run</file> and <file>/run/lock</file></heading>
6430 The directory <file>/run</file> is cleared at boot, normally
6431 by being a mount point for a temporary file system. Packages
6432 therefore must not assume that any files or directories
6433 under <file>/run</file> other than <file>/run/lock</file>
6434 exist unless the package has arranged to create those files or
6435 directories since the last reboot. Normally, this is done by
6436 the package via an init script. See <ref id="writing-init">
6437 for more information.
6441 Packages must not include files or directories
6442 under <file>/run</file>, or under the
6443 older <file>/var/run</file> and <file>/var/lock</file> paths.
6444 The latter paths will normally be symlinks or other
6445 redirections to <file>/run</file> for backwards compatibility.
6451 <heading>Users and groups</heading>
6454 <heading>Introduction</heading>
6456 The Debian system can be configured to use either plain or
6461 Some user ids (UIDs) and group ids (GIDs) are reserved
6462 globally for use by certain packages. Because some
6463 packages need to include files which are owned by these
6464 users or groups, or need the ids compiled into binaries,
6465 these ids must be used on any Debian system only for the
6466 purpose for which they are allocated. This is a serious
6467 restriction, and we should avoid getting in the way of
6468 local administration policies. In particular, many sites
6469 allocate users and/or local system groups starting at 100.
6473 Apart from this we should have dynamically allocated ids,
6474 which should by default be arranged in some sensible
6475 order, but the behavior should be configurable.
6479 Packages other than <tt>base-passwd</tt> must not modify
6480 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6481 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6486 <heading>UID and GID classes</heading>
6488 The UID and GID numbers are divided into classes as
6494 Globally allocated by the Debian project, the same
6495 on every Debian system. These ids will appear in
6496 the <file>passwd</file> and <file>group</file> files of all
6497 Debian systems, new ids in this range being added
6498 automatically as the <tt>base-passwd</tt> package is
6503 Packages which need a single statically allocated
6504 uid or gid should use one of these; their
6505 maintainers should ask the <tt>base-passwd</tt>
6513 Dynamically allocated system users and groups.
6514 Packages which need a user or group, but can have
6515 this user or group allocated dynamically and
6516 differently on each system, should use <tt>adduser
6517 --system</tt> to create the group and/or user.
6518 <prgn>adduser</prgn> will check for the existence of
6519 the user or group, and if necessary choose an unused
6520 id based on the ranges specified in
6521 <file>adduser.conf</file>.
6525 <tag>1000-59999:</tag>
6528 Dynamically allocated user accounts. By default
6529 <prgn>adduser</prgn> will choose UIDs and GIDs for
6530 user accounts in this range, though
6531 <file>adduser.conf</file> may be used to modify this
6536 <tag>60000-64999:</tag>
6539 Globally allocated by the Debian project, but only
6540 created on demand. The ids are allocated centrally
6541 and statically, but the actual accounts are only
6542 created on users' systems on demand.
6546 These ids are for packages which are obscure or
6547 which require many statically-allocated ids. These
6548 packages should check for and create the accounts in
6549 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6550 <prgn>adduser</prgn> if it has this facility) if
6551 necessary. Packages which are likely to require
6552 further allocations should have a "hole" left after
6553 them in the allocation, to give them room to
6558 <tag>65000-65533:</tag>
6566 User <tt>nobody</tt>. The corresponding gid refers
6567 to the group <tt>nogroup</tt>.
6574 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6575 not</em> be used, because it is the error return
6584 <sect id="sysvinit">
6585 <heading>System run levels and <file>init.d</file> scripts</heading>
6587 <sect1 id="/etc/init.d">
6588 <heading>Introduction</heading>
6591 The <file>/etc/init.d</file> directory contains the scripts
6592 executed by <prgn>init</prgn> at boot time and when the
6593 init state (or "runlevel") is changed (see <manref
6594 name="init" section="8">).
6598 There are at least two different, yet functionally
6599 equivalent, ways of handling these scripts. For the sake
6600 of simplicity, this document describes only the symbolic
6601 link method. However, it must not be assumed by maintainer
6602 scripts that this method is being used, and any automated
6603 manipulation of the various runlevel behaviors by
6604 maintainer scripts must be performed using
6605 <prgn>update-rc.d</prgn> as described below and not by
6606 manually installing or removing symlinks. For information
6607 on the implementation details of the other method,
6608 implemented in the <tt>file-rc</tt> package, please refer
6609 to the documentation of that package.
6613 These scripts are referenced by symbolic links in the
6614 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6615 runlevels, <prgn>init</prgn> looks in the directory
6616 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6617 execute, where <tt><var>n</var></tt> is the runlevel that
6618 is being changed to, or <tt>S</tt> for the boot-up
6623 The names of the links all have the form
6624 <file>S<var>mm</var><var>script</var></file> or
6625 <file>K<var>mm</var><var>script</var></file> where
6626 <var>mm</var> is a two-digit number and <var>script</var>
6627 is the name of the script (this should be the same as the
6628 name of the actual script in <file>/etc/init.d</file>).
6632 When <prgn>init</prgn> changes runlevel first the targets
6633 of the links whose names start with a <tt>K</tt> are
6634 executed, each with the single argument <tt>stop</tt>,
6635 followed by the scripts prefixed with an <tt>S</tt>, each
6636 with the single argument <tt>start</tt>. (The links are
6637 those in the <file>/etc/rc<var>n</var>.d</file> directory
6638 corresponding to the new runlevel.) The <tt>K</tt> links
6639 are responsible for killing services and the <tt>S</tt>
6640 link for starting services upon entering the runlevel.
6644 For example, if we are changing from runlevel 2 to
6645 runlevel 3, init will first execute all of the <tt>K</tt>
6646 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6647 all of the <tt>S</tt> prefixed scripts in that directory.
6648 The links starting with <tt>K</tt> will cause the
6649 referred-to file to be executed with an argument of
6650 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6655 The two-digit number <var>mm</var> is used to determine
6656 the order in which to run the scripts: low-numbered links
6657 have their scripts run first. For example, the
6658 <tt>K20</tt> scripts will be executed before the
6659 <tt>K30</tt> scripts. This is used when a certain service
6660 must be started before another. For example, the name
6661 server <prgn>bind</prgn> might need to be started before
6662 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6663 can set up its access lists. In this case, the script
6664 that starts <prgn>bind</prgn> would have a lower number
6665 than the script that starts <prgn>inn</prgn> so that it
6667 <example compact="compact">
6674 The two runlevels 0 (halt) and 6 (reboot) are slightly
6675 different. In these runlevels, the links with an
6676 <tt>S</tt> prefix are still called after those with a
6677 <tt>K</tt> prefix, but they too are called with the single
6678 argument <tt>stop</tt>.
6682 <sect1 id="writing-init">
6683 <heading>Writing the scripts</heading>
6686 Packages that include daemons for system services should
6687 place scripts in <file>/etc/init.d</file> to start or stop
6688 services at boot time or during a change of runlevel.
6689 These scripts should be named
6690 <file>/etc/init.d/<var>package</var></file>, and they should
6691 accept one argument, saying what to do:
6694 <tag><tt>start</tt></tag>
6695 <item>start the service,</item>
6697 <tag><tt>stop</tt></tag>
6698 <item>stop the service,</item>
6700 <tag><tt>restart</tt></tag>
6701 <item>stop and restart the service if it's already running,
6702 otherwise start the service</item>
6704 <tag><tt>reload</tt></tag>
6705 <item><p>cause the configuration of the service to be
6706 reloaded without actually stopping and restarting
6709 <tag><tt>force-reload</tt></tag>
6710 <item>cause the configuration to be reloaded if the
6711 service supports this, otherwise restart the
6715 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6716 <tt>force-reload</tt> options should be supported by all
6717 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6722 The <file>init.d</file> scripts must ensure that they will
6723 behave sensibly (i.e., returning success and not starting
6724 multiple copies of a service) if invoked with <tt>start</tt>
6725 when the service is already running, or with <tt>stop</tt>
6726 when it isn't, and that they don't kill unfortunately-named
6727 user processes. The best way to achieve this is usually to
6728 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6733 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6734 scripts. Writing correct <file>init.d</file> scripts requires
6735 accepting various error exit statuses when daemons are already
6736 running or already stopped without aborting
6737 the <file>init.d</file> script, and common <file>init.d</file>
6738 function libraries are not safe to call with <tt>set -e</tt>
6740 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6741 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6742 in effect and echoing status messages to the console fails,
6744 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6745 to not use <tt>set -e</tt> and instead check the result of
6746 each command separately.
6750 If a service reloads its configuration automatically (as
6751 in the case of <prgn>cron</prgn>, for example), the
6752 <tt>reload</tt> option of the <file>init.d</file> script
6753 should behave as if the configuration has been reloaded
6758 The <file>/etc/init.d</file> scripts must be treated as
6759 configuration files, either (if they are present in the
6760 package, that is, in the .deb file) by marking them as
6761 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6762 by managing them correctly in the maintainer scripts (see
6763 <ref id="config-files">). This is important since we want
6764 to give the local system administrator the chance to adapt
6765 the scripts to the local system, e.g., to disable a
6766 service without de-installing the package, or to specify
6767 some special command line options when starting a service,
6768 while making sure their changes aren't lost during the next
6773 These scripts should not fail obscurely when the
6774 configuration files remain but the package has been
6775 removed, as configuration files remain on the system after
6776 the package has been removed. Only when <prgn>dpkg</prgn>
6777 is executed with the <tt>--purge</tt> option will
6778 configuration files be removed. In particular, as the
6779 <file>/etc/init.d/<var>package</var></file> script itself is
6780 usually a <tt>conffile</tt>, it will remain on the system
6781 if the package is removed but not purged. Therefore, you
6782 should include a <tt>test</tt> statement at the top of the
6784 <example compact="compact">
6785 test -f <var>program-executed-later-in-script</var> || exit 0
6790 Often there are some variables in the <file>init.d</file>
6791 scripts whose values control the behavior of the scripts,
6792 and which a system administrator is likely to want to
6793 change. As the scripts themselves are frequently
6794 <tt>conffile</tt>s, modifying them requires that the
6795 administrator merge in their changes each time the package
6796 is upgraded and the <tt>conffile</tt> changes. To ease
6797 the burden on the system administrator, such configurable
6798 values should not be placed directly in the script.
6799 Instead, they should be placed in a file in
6800 <file>/etc/default</file>, which typically will have the same
6801 base name as the <file>init.d</file> script. This extra file
6802 should be sourced by the script when the script runs. It
6803 must contain only variable settings and comments in SUSv3
6804 <prgn>sh</prgn> format. It may either be a
6805 <tt>conffile</tt> or a configuration file maintained by
6806 the package maintainer scripts. See <ref id="config-files">
6811 To ensure that vital configurable values are always
6812 available, the <file>init.d</file> script should set default
6813 values for each of the shell variables it uses, either
6814 before sourcing the <file>/etc/default/</file> file or
6815 afterwards using something like the <tt>:
6816 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6817 script must behave sensibly and not fail if the
6818 <file>/etc/default</file> file is deleted.
6822 Files and directories under <file>/run</file>, including ones
6823 referred to via the compatibility paths <file>/var/run</file>
6824 and <file>/var/lock</file>, are normally stored on a temporary
6825 filesystem and are normally not persistent across a reboot.
6826 The <file>init.d</file> scripts must handle this correctly.
6827 This will typically mean creating any required subdirectories
6828 dynamically when the <file>init.d</file> script is run.
6829 See <ref id="fhs-run"> for more information.
6834 <heading>Interfacing with the initscript system</heading>
6837 Maintainers should use the abstraction layer provided by
6838 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6839 programs to deal with initscripts in their packages'
6840 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6841 and <prgn>postrm</prgn>.
6845 Directly managing the /etc/rc?.d links and directly
6846 invoking the <file>/etc/init.d/</file> initscripts should
6847 be done only by packages providing the initscript
6848 subsystem (such as <prgn>sysv-rc</prgn> and
6849 <prgn>file-rc</prgn>).
6853 <heading>Managing the links</heading>
6856 The program <prgn>update-rc.d</prgn> is provided for
6857 package maintainers to arrange for the proper creation and
6858 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6859 or their functional equivalent if another method is being
6860 used. This may be used by maintainers in their packages'
6861 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6865 You must not include any <file>/etc/rc<var>n</var>.d</file>
6866 symbolic links in the actual archive or manually create or
6867 remove the symbolic links in maintainer scripts; you must
6868 use the <prgn>update-rc.d</prgn> program instead. (The
6869 former will fail if an alternative method of maintaining
6870 runlevel information is being used.) You must not include
6871 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6872 in the archive either. (Only the <tt>sysvinit</tt>
6877 By default <prgn>update-rc.d</prgn> will start services in
6878 each of the multi-user state runlevels (2, 3, 4, and 5)
6879 and stop them in the halt runlevel (0), the single-user
6880 runlevel (1) and the reboot runlevel (6). The system
6881 administrator will have the opportunity to customize
6882 runlevels by simply adding, moving, or removing the
6883 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6884 symbolic links are being used, or by modifying
6885 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6890 To get the default behavior for your package, put in your
6891 <prgn>postinst</prgn> script
6892 <example compact="compact">
6893 update-rc.d <var>package</var> defaults
6895 and in your <prgn>postrm</prgn>
6896 <example compact="compact">
6897 if [ "$1" = purge ]; then
6898 update-rc.d <var>package</var> remove
6900 </example>. Note that if your package changes runlevels
6901 or priority, you may have to remove and recreate the links,
6902 since otherwise the old links may persist. Refer to the
6903 documentation of <prgn>update-rc.d</prgn>.
6907 This will use a default sequence number of 20. If it does
6908 not matter when or in which order the <file>init.d</file>
6909 script is run, use this default. If it does, then you
6910 should talk to the maintainer of the <prgn>sysvinit</prgn>
6911 package or post to <tt>debian-devel</tt>, and they will
6912 help you choose a number.
6916 For more information about using <tt>update-rc.d</tt>,
6917 please consult its man page <manref name="update-rc.d"
6923 <heading>Running initscripts</heading>
6925 The program <prgn>invoke-rc.d</prgn> is provided to make
6926 it easier for package maintainers to properly invoke an
6927 initscript, obeying runlevel and other locally-defined
6928 constraints that might limit a package's right to start,
6929 stop and otherwise manage services. This program may be
6930 used by maintainers in their packages' scripts.
6934 The package maintainer scripts must use
6935 <prgn>invoke-rc.d</prgn> to invoke the
6936 <file>/etc/init.d/*</file> initscripts, instead of
6937 calling them directly.
6941 By default, <prgn>invoke-rc.d</prgn> will pass any
6942 action requests (start, stop, reload, restart...) to the
6943 <file>/etc/init.d</file> script, filtering out requests
6944 to start or restart a service out of its intended
6949 Most packages will simply need to change:
6950 <example compact="compact">/etc/init.d/<package>
6951 <action></example> in their <prgn>postinst</prgn>
6952 and <prgn>prerm</prgn> scripts to:
6953 <example compact="compact">
6954 if which invoke-rc.d >/dev/null 2>&1; then
6955 invoke-rc.d <var>package</var> <action>
6957 /etc/init.d/<var>package</var> <action>
6963 A package should register its initscript services using
6964 <prgn>update-rc.d</prgn> before it tries to invoke them
6965 using <prgn>invoke-rc.d</prgn>. Invocation of
6966 unregistered services may fail.
6970 For more information about using
6971 <prgn>invoke-rc.d</prgn>, please consult its man page
6972 <manref name="invoke-rc.d" section="8">.
6978 <heading>Boot-time initialization</heading>
6981 There used to be another directory, <file>/etc/rc.boot</file>,
6982 which contained scripts which were run once per machine
6983 boot. This has been deprecated in favour of links from
6984 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6985 described in <ref id="/etc/init.d">. Packages must not
6986 place files in <file>/etc/rc.boot</file>.
6991 <heading>Example</heading>
6994 An example on which you can base your
6995 <file>/etc/init.d</file> scripts is found in
6996 <file>/etc/init.d/skeleton</file>.
7003 <heading>Console messages from <file>init.d</file> scripts</heading>
7006 This section describes the formats to be used for messages
7007 written to standard output by the <file>/etc/init.d</file>
7008 scripts. The intent is to improve the consistency of
7009 Debian's startup and shutdown look and feel. For this
7010 reason, please look very carefully at the details. We want
7011 the messages to have the same format in terms of wording,
7012 spaces, punctuation and case of letters.
7016 Here is a list of overall rules that should be used for
7017 messages generated by <file>/etc/init.d</file> scripts.
7023 The message should fit in one line (fewer than 80
7024 characters), start with a capital letter and end with
7025 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7029 If the script is performing some time consuming task in
7030 the background (not merely starting or stopping a
7031 program, for instance), an ellipsis (three dots:
7032 <tt>...</tt>) should be output to the screen, with no
7033 leading or tailing whitespace or line feeds.
7037 The messages should appear as if the computer is telling
7038 the user what it is doing (politely :-), but should not
7039 mention "it" directly. For example, instead of:
7040 <example compact="compact">
7041 I'm starting network daemons: nfsd mountd.
7043 the message should say
7044 <example compact="compact">
7045 Starting network daemons: nfsd mountd.
7052 <tt>init.d</tt> script should use the following standard
7053 message formats for the situations enumerated below.
7059 <p>When daemons are started</p>
7062 If the script starts one or more daemons, the output
7063 should look like this (a single line, no leading
7065 <example compact="compact">
7066 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7068 The <var>description</var> should describe the
7069 subsystem the daemon or set of daemons are part of,
7070 while <var>daemon-1</var> up to <var>daemon-n</var>
7071 denote each daemon's name (typically the file name of
7076 For example, the output of <file>/etc/init.d/lpd</file>
7078 <example compact="compact">
7079 Starting printer spooler: lpd.
7084 This can be achieved by saying
7085 <example compact="compact">
7086 echo -n "Starting printer spooler: lpd"
7087 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7090 in the script. If there are more than one daemon to
7091 start, the output should look like this:
7092 <example compact="compact">
7093 echo -n "Starting remote file system services:"
7094 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7095 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7096 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7099 This makes it possible for the user to see what is
7100 happening and when the final daemon has been started.
7101 Care should be taken in the placement of white spaces:
7102 in the example above the system administrators can
7103 easily comment out a line if they don't want to start
7104 a specific daemon, while the displayed message still
7110 <p>When a system parameter is being set</p>
7113 If you have to set up different system parameters
7114 during the system boot, you should use this format:
7115 <example compact="compact">
7116 Setting <var>parameter</var> to "<var>value</var>".
7121 You can use a statement such as the following to get
7123 <example compact="compact">
7124 echo "Setting DNS domainname to \"$domainname\"."
7129 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7130 for the left and right quotation marks. A grave accent
7131 (<tt>`</tt>) is not a quote character; neither is an
7132 apostrophe (<tt>'</tt>).
7137 <p>When a daemon is stopped or restarted</p>
7140 When you stop or restart a daemon, you should issue a
7141 message identical to the startup message, except that
7142 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7143 or <tt>Restarting</tt> respectively.
7147 For example, stopping the printer daemon will look like
7149 <example compact="compact">
7150 Stopping printer spooler: lpd.
7156 <p>When something is executed</p>
7159 There are several examples where you have to run a
7160 program at system startup or shutdown to perform a
7161 specific task, for example, setting the system's clock
7162 using <prgn>netdate</prgn> or killing all processes
7163 when the system shuts down. Your message should look
7165 <example compact="compact">
7166 Doing something very useful...done.
7168 You should print the <tt>done.</tt> immediately after
7169 the job has been completed, so that the user is
7170 informed why they have to wait. You can get this
7172 <example compact="compact">
7173 echo -n "Doing something very useful..."
7182 <p>When the configuration is reloaded</p>
7185 When a daemon is forced to reload its configuration
7186 files you should use the following format:
7187 <example compact="compact">
7188 Reloading <var>description</var> configuration...done.
7190 where <var>description</var> is the same as in the
7191 daemon starting message.
7198 <sect id="cron-jobs">
7199 <heading>Cron jobs</heading>
7202 Packages must not modify the configuration file
7203 <file>/etc/crontab</file>, and they must not modify the files in
7204 <file>/var/spool/cron/crontabs</file>.
7208 If a package wants to install a job that has to be executed via
7209 cron, it should place a file named as specified
7210 in <ref id="cron-files"> into one or more of the following
7212 <example compact="compact">
7218 As these directory names imply, the files within them are
7219 executed on an hourly, daily, weekly, or monthly basis,
7220 respectively. The exact times are listed in
7221 <file>/etc/crontab</file>.
7225 All files installed in any of these directories must be
7226 scripts (e.g., shell scripts or Perl scripts) so that they
7227 can easily be modified by the local system administrator.
7228 In addition, they must be treated as configuration files.
7232 If a certain job has to be executed at some other frequency or
7233 at a specific time, the package should install a file in
7234 <file>/etc/cron.d</file> with a name as specified
7235 in <ref id="cron-files">. This file uses the same syntax
7236 as <file>/etc/crontab</file> and is processed
7237 by <prgn>cron</prgn> automatically. The file must also be
7238 treated as a configuration file. (Note that entries in the
7239 <file>/etc/cron.d</file> directory are not handled by
7240 <prgn>anacron</prgn>. Thus, you should only use this
7241 directory for jobs which may be skipped if the system is not
7246 Unlike <file>crontab</file> files described in the IEEE Std
7247 1003.1-2008 (POSIX.1) available from
7248 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7249 name="The Open Group">, the files in
7250 <file>/etc/cron.d</file> and the file
7251 <file>/etc/crontab</file> have seven fields; namely:
7253 <item>Minute [0,59]</item>
7254 <item>Hour [0,23]</item>
7255 <item>Day of the month [1,31]</item>
7256 <item>Month of the year [1,12]</item>
7257 <item>Day of the week ([0,6] with 0=Sunday)</item>
7258 <item>Username</item>
7259 <item>Command to be run</item>
7261 Ranges of numbers are allowed. Ranges are two numbers
7262 separated with a hyphen. The specified range is inclusive.
7263 Lists are allowed. A list is a set of numbers (or ranges)
7264 separated by commas. Step values can be used in conjunction
7269 The scripts or <tt>crontab</tt> entries in these directories should
7270 check if all necessary programs are installed before they
7271 try to execute them. Otherwise, problems will arise when a
7272 package was removed but not purged since configuration files
7273 are kept on the system in this situation.
7277 Any <tt>cron</tt> daemon must provide
7278 <file>/usr/bin/crontab</file> and support normal
7279 <tt>crontab</tt> entries as specified in POSIX. The daemon
7280 must also support names for days and months, ranges, and
7281 step values. It has to support <file>/etc/crontab</file>,
7282 and correctly execute the scripts in
7283 <file>/etc/cron.d</file>. The daemon must also correctly
7285 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7288 <sect1 id="cron-files">
7289 <heading>Cron job file names</heading>
7292 The file name of a cron job file should normally match the
7293 name of the package from which it comes.
7297 If a package supplies multiple cron job files files in the
7298 same directory, the file names should all start with the name
7299 of the package (possibly modified as described below) followed
7300 by a hyphen (<tt>-</tt>) and a suitable suffix.
7304 A cron job file name must not include any period or plus
7305 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7306 cause cron to ignore the file. Underscores (<tt>_</tt>)
7307 should be used instead of <tt>.</tt> and <tt>+</tt>
7314 <heading>Menus</heading>
7317 The Debian <tt>menu</tt> package provides a standard
7318 interface between packages providing applications and
7319 <em>menu programs</em> (either X window managers or
7320 text-based menu programs such as <prgn>pdmenu</prgn>).
7324 All packages that provide applications that need not be
7325 passed any special command line arguments for normal
7326 operation should register a menu entry for those
7327 applications, so that users of the <tt>menu</tt> package
7328 will automatically get menu entries in their window
7329 managers, as well in shells like <tt>pdmenu</tt>.
7333 Menu entries should follow the current menu policy.
7337 The menu policy can be found in the <tt>menu-policy</tt>
7338 files in the <tt>debian-policy</tt> package.
7339 It is also available from the Debian web mirrors at
7340 <tt><url name="/doc/packaging-manuals/menu-policy/"
7341 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7345 Please also refer to the <em>Debian Menu System</em>
7346 documentation that comes with the <package>menu</package>
7347 package for information about how to register your
7353 <heading>Multimedia handlers</heading>
7356 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7357 is a mechanism for encoding files and data streams and
7358 providing meta-information about them, in particular their
7359 type (e.g. audio or video) and format (e.g. PNG, HTML,
7364 Registration of MIME type handlers allows programs like mail
7365 user agents and web browsers to invoke these handlers to
7366 view, edit or display MIME types they don't support directly.
7370 Packages which provide the ability to view/show/play,
7371 compose, edit or print MIME types should register themselves
7372 as such following the current MIME support policy.
7376 The <package>mime-support</package> package provides the
7377 <prgn>update-mime</prgn> program which allows packages to
7378 register programs that can show, compose, edit or print
7383 Packages containing such programs must register them
7384 with <prgn>update-mime</prgn> as documented in <manref
7385 name="update-mime" section="8">. They should <em>not</em> depend
7386 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7387 they should just put something like the following in the
7388 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7391 if [ -x /usr/sbin/update-mime ]; then
7400 <heading>Keyboard configuration</heading>
7403 To achieve a consistent keyboard configuration so that all
7404 applications interpret a keyboard event the same way, all
7405 programs in the Debian distribution must be configured to
7406 comply with the following guidelines.
7410 The following keys must have the specified interpretations:
7413 <tag><tt><--</tt></tag>
7414 <item>delete the character to the left of the cursor</item>
7416 <tag><tt>Delete</tt></tag>
7417 <item>delete the character to the right of the cursor</item>
7419 <tag><tt>Control+H</tt></tag>
7420 <item>emacs: the help prefix</item>
7423 The interpretation of any keyboard events should be
7424 independent of the terminal that is used, be it a virtual
7425 console, an X terminal emulator, an rlogin/telnet session,
7430 The following list explains how the different programs
7431 should be set up to achieve this:
7437 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7441 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7445 X translations are set up to make
7446 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7447 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7448 is the vt220 escape code for the "delete character"
7449 key). This must be done by loading the X resources
7450 using <prgn>xrdb</prgn> on all local X displays, not
7451 using the application defaults, so that the
7452 translation resources used correspond to the
7453 <prgn>xmodmap</prgn> settings.
7457 The Linux console is configured to make
7458 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7459 generate <tt>ESC [ 3 ~</tt>.
7463 X applications are configured so that <tt><</tt>
7464 deletes left, and <tt>Delete</tt> deletes right. Motif
7465 applications already work like this.
7469 Terminals should have <tt>stty erase ^?</tt> .
7473 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7474 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7475 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7479 Emacs is programmed to map <tt>KB_Backspace</tt> or
7480 the <tt>stty erase</tt> character to
7481 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7482 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7483 <tt>^H</tt> to <tt>help</tt> as always.
7487 Other applications use the <tt>stty erase</tt>
7488 character and <tt>kdch1</tt> for the two delete keys,
7489 with ASCII DEL being "delete previous character" and
7490 <tt>kdch1</tt> being "delete character under
7498 This will solve the problem except for the following
7505 Some terminals have a <tt><--</tt> key that cannot
7506 be made to produce anything except <tt>^H</tt>. On
7507 these terminals Emacs help will be unavailable on
7508 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7509 character takes precedence in Emacs, and has been set
7510 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7511 available) can be used instead.
7515 Some operating systems use <tt>^H</tt> for <tt>stty
7516 erase</tt>. However, modern telnet versions and all
7517 rlogin versions propagate <tt>stty</tt> settings, and
7518 almost all UNIX versions honour <tt>stty erase</tt>.
7519 Where the <tt>stty</tt> settings are not propagated
7520 correctly, things can be made to work by using
7521 <tt>stty</tt> manually.
7525 Some systems (including previous Debian versions) use
7526 <prgn>xmodmap</prgn> to arrange for both
7527 <tt><--</tt> and <tt>Delete</tt> to generate
7528 <tt>KB_Delete</tt>. We can change the behavior of
7529 their X clients using the same X resources that we use
7530 to do it for our own clients, or configure our clients
7531 using their resources when things are the other way
7532 around. On displays configured like this
7533 <tt>Delete</tt> will not work, but <tt><--</tt>
7538 Some operating systems have different <tt>kdch1</tt>
7539 settings in their <tt>terminfo</tt> database for
7540 <tt>xterm</tt> and others. On these systems the
7541 <tt>Delete</tt> key will not work correctly when you
7542 log in from a system conforming to our policy, but
7543 <tt><--</tt> will.
7550 <heading>Environment variables</heading>
7553 A program must not depend on environment variables to get
7554 reasonable defaults. (That's because these environment
7555 variables would have to be set in a system-wide
7556 configuration file like <file>/etc/profile</file>, which is not
7557 supported by all shells.)
7561 If a program usually depends on environment variables for its
7562 configuration, the program should be changed to fall back to
7563 a reasonable default configuration if these environment
7564 variables are not present. If this cannot be done easily
7565 (e.g., if the source code of a non-free program is not
7566 available), the program must be replaced by a small
7567 "wrapper" shell script which sets the environment variables
7568 if they are not already defined, and calls the original program.
7572 Here is an example of a wrapper script for this purpose:
7574 <example compact="compact">
7576 BAR=${BAR:-/var/lib/fubar}
7578 exec /usr/lib/foo/foo "$@"
7583 Furthermore, as <file>/etc/profile</file> is a configuration
7584 file of the <prgn>base-files</prgn> package, other packages must
7585 not put any environment variables or other commands into that
7590 <sect id="doc-base">
7591 <heading>Registering Documents using doc-base</heading>
7594 The <package>doc-base</package> package implements a
7595 flexible mechanism for handling and presenting
7596 documentation. The recommended practice is for every Debian
7597 package that provides online documentation (other than just
7598 manual pages) to register these documents with
7599 <package>doc-base</package> by installing a
7600 <package>doc-base</package> control file in
7601 <file>/usr/share/doc-base/</file>.
7604 Please refer to the documentation that comes with the
7605 <package>doc-base</package> package for information and
7614 <heading>Files</heading>
7616 <sect id="binaries">
7617 <heading>Binaries</heading>
7620 Two different packages must not install programs with
7621 different functionality but with the same filenames. (The
7622 case of two programs having the same functionality but
7623 different implementations is handled via "alternatives" or
7624 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7625 <ref id="conflicts"> respectively.) If this case happens,
7626 one of the programs must be renamed. The maintainers should
7627 report this to the <tt>debian-devel</tt> mailing list and
7628 try to find a consensus about which program will have to be
7629 renamed. If a consensus cannot be reached, <em>both</em>
7630 programs must be renamed.
7634 By default, when a package is being built, any binaries
7635 created should include debugging information, as well as
7636 being compiled with optimization. You should also turn on
7637 as many reasonable compilation warnings as possible; this
7638 makes life easier for porters, who can then look at build
7639 logs for possible problems. For the C programming language,
7640 this means the following compilation parameters should be
7642 <example compact="compact">
7644 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7646 INSTALL = install -s # (or use strip on the files in debian/tmp)
7651 Note that by default all installed binaries should be stripped,
7652 either by using the <tt>-s</tt> flag to
7653 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7654 the binaries after they have been copied into
7655 <file>debian/tmp</file> but before the tree is made into a
7660 Although binaries in the build tree should be compiled with
7661 debugging information by default, it can often be difficult to
7662 debug programs if they are also subjected to compiler
7663 optimization. For this reason, it is recommended to support the
7664 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7665 (see <ref id="debianrules-options">). This variable can contain
7666 several flags to change how a package is compiled and built.
7670 It is up to the package maintainer to decide what
7671 compilation options are best for the package. Certain
7672 binaries (such as computationally-intensive programs) will
7673 function better with certain flags (<tt>-O3</tt>, for
7674 example); feel free to use them. Please use good judgment
7675 here. Don't use flags for the sake of it; only use them
7676 if there is good reason to do so. Feel free to override
7677 the upstream author's ideas about which compilation
7678 options are best: they are often inappropriate for our
7684 <sect id="libraries">
7685 <heading>Libraries</heading>
7688 If the package is <strong>architecture: any</strong>, then
7689 the shared library compilation and linking flags must have
7690 <tt>-fPIC</tt>, or the package shall not build on some of
7691 the supported architectures<footnote>
7693 If you are using GCC, <tt>-fPIC</tt> produces code with
7694 relocatable position independent code, which is required for
7695 most architectures to create a shared library, with i386 and
7696 perhaps some others where non position independent code is
7697 permitted in a shared library.
7700 Position independent code may have a performance penalty,
7701 especially on <tt>i386</tt>. However, in most cases the
7702 speed penalty must be measured against the memory wasted on
7703 the few architectures where non position independent code is
7706 </footnote>. Any exception to this rule must be discussed on
7707 the mailing list <em>debian-devel@lists.debian.org</em>, and
7708 a rough consensus obtained. The reasons for not compiling
7709 with <tt>-fPIC</tt> flag must be recorded in the file
7710 <tt>README.Debian</tt>, and care must be taken to either
7711 restrict the architecture or arrange for <tt>-fPIC</tt> to
7712 be used on architectures where it is required.<footnote>
7714 Some of the reasons why this might be required is if the
7715 library contains hand crafted assembly code that is not
7716 relocatable, the speed penalty is excessive for compute
7717 intensive libs, and similar reasons.
7722 As to the static libraries, the common case is not to have
7723 relocatable code, since there is no benefit, unless in specific
7724 cases; therefore the static version must not be compiled
7725 with the <tt>-fPIC</tt> flag. Any exception to this rule
7726 should be discussed on the mailing list
7727 <em>debian-devel@lists.debian.org</em>, and the reasons for
7728 compiling with the <tt>-fPIC</tt> flag must be recorded in
7729 the file <tt>README.Debian</tt>. <footnote>
7731 Some of the reasons for linking static libraries with
7732 the <tt>-fPIC</tt> flag are if, for example, one needs a
7733 Perl API for a library that is under rapid development,
7734 and has an unstable API, so shared libraries are
7735 pointless at this phase of the library's development. In
7736 that case, since Perl needs a library with relocatable
7737 code, it may make sense to create a static library with
7738 relocatable code. Another reason cited is if you are
7739 distilling various libraries into a common shared
7740 library, like <tt>mklibs</tt> does in the Debian
7746 In other words, if both a shared and a static library is
7747 being built, each source unit (<tt>*.c</tt>, for example,
7748 for C files) will need to be compiled twice, for the normal
7753 Libraries should be built with threading support and to be
7754 thread-safe if the library supports this.
7758 Although not enforced by the build tools, shared libraries
7759 must be linked against all libraries that they use symbols from
7760 in the same way that binaries are. This ensures the correct
7761 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7762 system and guarantees that all libraries can be safely opened
7763 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7764 option <tt>-Wl,-z,defs</tt> when building a shared library.
7765 Since this option enforces symbol resolution at build time,
7766 a missing library reference will be caught early as a fatal
7771 All installed shared libraries should be stripped with
7772 <example compact="compact">
7773 strip --strip-unneeded <var>your-lib</var>
7775 (The option <tt>--strip-unneeded</tt> makes
7776 <prgn>strip</prgn> remove only the symbols which aren't
7777 needed for relocation processing.) Shared libraries can
7778 function perfectly well when stripped, since the symbols for
7779 dynamic linking are in a separate part of the ELF object
7781 You might also want to use the options
7782 <tt>--remove-section=.comment</tt> and
7783 <tt>--remove-section=.note</tt> on both shared libraries
7784 and executables, and <tt>--strip-debug</tt> on static
7790 Note that under some circumstances it may be useful to
7791 install a shared library unstripped, for example when
7792 building a separate package to support debugging.
7796 Shared object files (often <file>.so</file> files) that are not
7797 public libraries, that is, they are not meant to be linked
7798 to by third party executables (binaries of other packages),
7799 should be installed in subdirectories of the
7800 <file>/usr/lib</file> directory. Such files are exempt from the
7801 rules that govern ordinary shared libraries, except that
7802 they must not be installed executable and should be
7804 A common example are the so-called "plug-ins",
7805 internal shared objects that are dynamically loaded by
7806 programs using <manref name="dlopen" section="3">.
7811 Packages that use <prgn>libtool</prgn> to create and install
7812 their shared libraries install a file containing additional
7813 metadata (ending in <file>.la</file>) alongside the library.
7814 For public libraries intended for use by other packages, these
7815 files normally should not be included in the Debian package,
7816 since the information they include is not necessary to link with
7817 the shared library on Debian and can add unnecessary additional
7818 dependencies to other programs or libraries.<footnote>
7819 These files store, among other things, all libraries on which
7820 that shared library depends. Unfortunately, if
7821 the <file>.la</file> file is present and contains that
7822 dependency information, using <prgn>libtool</prgn> when
7823 linking against that library will cause the resulting program
7824 or library to be linked against those dependencies as well,
7825 even if this is unnecessary. This can create unneeded
7826 dependencies on shared library packages that would otherwise
7827 be hidden behind the library ABI, and can make library
7828 transitions to new SONAMEs unnecessarily complicated and
7829 difficult to manage.
7831 If the <file>.la</file> file is required for that library (if,
7832 for instance, it's loaded via <tt>libltdl</tt> in a way that
7833 requires that meta-information), the <tt>dependency_libs</tt>
7834 setting in the <file>.la</file> file should normally be set to
7835 the empty string. If the shared library development package has
7836 historically included the <file>.la</file>, it must be retained
7837 in the development package (with <tt>dependency_libs</tt>
7838 emptied) until all libraries that depend on it have removed or
7839 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7840 files to prevent linking with those other libraries
7841 using <prgn>libtool</prgn> from failing.
7845 If the <file>.la</file> must be included, it should be included
7846 in the development (<tt>-dev</tt>) package, unless the library
7847 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7848 library. If it is intended for use with <tt>libltdl</tt>,
7849 the <file>.la</file> files must go in the run-time library
7854 These requirements for handling of <file>.la</file> files do not
7855 apply to loadable modules or libraries not installed in
7856 directories searched by default by the dynamic linker. Packages
7857 installing loadable modules will frequently need to install
7858 the <file>.la</file> files alongside the modules so that they
7859 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7860 does not need to be modified for libraries or modules that are
7861 not installed in directories searched by the dynamic linker by
7862 default and not intended for use by other packages.
7866 You must make sure that you use only released versions of
7867 shared libraries to build your packages; otherwise other
7868 users will not be able to run your binaries
7869 properly. Producing source packages that depend on
7870 unreleased compilers is also usually a bad
7877 <heading>Shared libraries</heading>
7879 This section has moved to <ref id="sharedlibs">.
7885 <heading>Scripts</heading>
7888 All command scripts, including the package maintainer
7889 scripts inside the package and used by <prgn>dpkg</prgn>,
7890 should have a <tt>#!</tt> line naming the shell to be used
7895 In the case of Perl scripts this should be
7896 <tt>#!/usr/bin/perl</tt>.
7900 When scripts are installed into a directory in the system
7901 PATH, the script name should not include an extension such
7902 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7903 language currently used to implement it.
7906 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7907 <file>init.d</file> scripts should almost certainly start
7908 with <tt>set -e</tt> so that errors are detected.
7909 <file>init.d</file> scripts are something of a special case, due
7910 to how frequently they need to call commands that are allowed to
7911 fail, and it may instead be easier to check the exit status of
7912 commands directly. See <ref id="writing-init"> for more
7913 information about writing <file>init.d</file> scripts.
7916 Every script should use <tt>set -e</tt> or check the exit status
7917 of <em>every</em> command.
7920 Scripts may assume that <file>/bin/sh</file> implements the
7921 SUSv3 Shell Command Language<footnote>
7922 Single UNIX Specification, version 3, which is also IEEE
7923 1003.1-2004 (POSIX), and is available on the World Wide Web
7924 from <url id="http://www.unix.org/version3/online.html"
7925 name="The Open Group"> after free
7926 registration.</footnote>
7927 plus the following additional features not mandated by
7929 These features are in widespread use in the Linux community
7930 and are implemented in all of bash, dash, and ksh, the most
7931 common shells users may wish to use as <file>/bin/sh</file>.
7934 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7935 must not generate a newline.</item>
7936 <item><tt>test</tt>, if implemented as a shell built-in, must
7937 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7939 <item><tt>local</tt> to create a scoped variable must be
7940 supported, including listing multiple variables in a single
7941 local command and assigning a value to a variable at the
7942 same time as localizing it. <tt>local</tt> may or
7943 may not preserve the variable value from an outer scope if
7944 no assignment is present. Uses such as:
7948 # ... use a, b, c, d ...
7951 must be supported and must set the value of <tt>c</tt> to
7954 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7955 -<var>signal</var></tt>, where <var>signal</var> is either
7956 the name of a signal or one of the numeric signals listed in
7957 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7958 supported if <prgn>kill</prgn> is implemented as a shell
7961 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7962 signals must be supported. In addition to the signal
7963 numbers listed in the extension, which are the same as for
7964 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7967 If a shell script requires non-SUSv3 features from the shell
7968 interpreter other than those listed above, the appropriate shell
7969 must be specified in the first line of the script (e.g.,
7970 <tt>#!/bin/bash</tt>) and the package must depend on the package
7971 providing the shell (unless the shell package is marked
7972 "Essential", as in the case of <prgn>bash</prgn>).
7976 You may wish to restrict your script to SUSv3 features plus the
7977 above set when possible so that it may use <file>/bin/sh</file>
7978 as its interpreter. Checking your script
7979 with <prgn>checkbashisms</prgn> from
7980 the <package>devscripts</package> package or running your script
7981 with <prgn>posh</prgn> may help uncover violations of the above
7982 requirements. If in doubt whether a script complies with these
7983 requirements, use <file>/bin/bash</file>.
7987 Perl scripts should check for errors when making any
7988 system calls, including <tt>open</tt>, <tt>print</tt>,
7989 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7993 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7994 scripting languages. See <em>Csh Programming Considered
7995 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7996 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7997 If an upstream package comes with <prgn>csh</prgn> scripts
7998 then you must make sure that they start with
7999 <tt>#!/bin/csh</tt> and make your package depend on the
8000 <prgn>c-shell</prgn> virtual package.
8004 Any scripts which create files in world-writeable
8005 directories (e.g., in <file>/tmp</file>) must use a
8006 mechanism which will fail atomically if a file with the same
8007 name already exists.
8011 The Debian base system provides the <prgn>tempfile</prgn>
8012 and <prgn>mktemp</prgn> utilities for use by scripts for
8019 <heading>Symbolic links</heading>
8022 In general, symbolic links within a top-level directory should
8023 be relative, and symbolic links pointing from one top-level
8024 directory to or into another should be absolute. (A top-level
8025 directory is a sub-directory of the root
8026 directory <file>/</file>.) For example, a symbolic link
8027 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8028 should be relative (<file>../share/bar</file>), but a symbolic
8029 link from <file>/var/run</file> to <file>/run</file> should be
8031 This is necessary to allow top-level directories to be
8032 symlinks. If linking <file>/var/run</file>
8033 to <file>/run</file> were done with the relative symbolic
8034 link <file>../run</file>, but <file>/var</file> were a
8035 symbolic link to <file>/srv/disk1</file>, the symbolic link
8036 would point to <file>/srv/run</file> rather than the intended
8042 In addition, symbolic links should be specified as short as
8043 possible, i.e., link targets like <file>foo/../bar</file> are
8048 Note that when creating a relative link using
8049 <prgn>ln</prgn> it is not necessary for the target of the
8050 link to exist relative to the working directory you're
8051 running <prgn>ln</prgn> from, nor is it necessary to change
8052 directory to the directory where the link is to be made.
8053 Simply include the string that should appear as the target
8054 of the link (this will be a pathname relative to the
8055 directory in which the link resides) as the first argument
8060 For example, in your <prgn>Makefile</prgn> or
8061 <file>debian/rules</file>, you can do things like:
8062 <example compact="compact">
8063 ln -fs gcc $(prefix)/bin/cc
8064 ln -fs gcc debian/tmp/usr/bin/cc
8065 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8066 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8071 A symbolic link pointing to a compressed file should always
8072 have the same file extension as the referenced file. (For
8073 example, if a file <file>foo.gz</file> is referenced by a
8074 symbolic link, the filename of the link has to end with
8075 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8080 <heading>Device files</heading>
8083 Packages must not include device files or named pipes in the
8088 If a package needs any special device files that are not
8089 included in the base system, it must call
8090 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8091 after notifying the user<footnote>
8092 This notification could be done via a (low-priority)
8093 debconf message, or an echo (printf) statement.
8098 Packages must not remove any device files in the
8099 <prgn>postrm</prgn> or any other script. This is left to the
8100 system administrator.
8104 Debian uses the serial devices
8105 <file>/dev/ttyS*</file>. Programs using the old
8106 <file>/dev/cu*</file> devices should be changed to use
8107 <file>/dev/ttyS*</file>.
8111 Named pipes needed by the package must be created in
8112 the <prgn>postinst</prgn> script<footnote>
8113 It's better to use <prgn>mkfifo</prgn> rather
8114 than <prgn>mknod</prgn> to create named pipes so that
8115 automated checks for packages incorrectly creating device
8116 files with <prgn>mknod</prgn> won't have false positives.
8117 </footnote> and removed in
8118 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8123 <sect id="config-files">
8124 <heading>Configuration files</heading>
8127 <heading>Definitions</heading>
8131 <tag>configuration file</tag>
8133 A file that affects the operation of a program, or
8134 provides site- or host-specific information, or
8135 otherwise customizes the behavior of a program.
8136 Typically, configuration files are intended to be
8137 modified by the system administrator (if needed or
8138 desired) to conform to local policy or to provide
8139 more useful site-specific behavior.
8142 <tag><tt>conffile</tt></tag>
8144 A file listed in a package's <tt>conffiles</tt>
8145 file, and is treated specially by <prgn>dpkg</prgn>
8146 (see <ref id="configdetails">).
8152 The distinction between these two is important; they are
8153 not interchangeable concepts. Almost all
8154 <tt>conffile</tt>s are configuration files, but many
8155 configuration files are not <tt>conffiles</tt>.
8159 As noted elsewhere, <file>/etc/init.d</file> scripts,
8160 <file>/etc/default</file> files, scripts installed in
8161 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8162 configuration installed in <file>/etc/cron.d</file> must be
8163 treated as configuration files. In general, any script that
8164 embeds configuration information is de-facto a configuration
8165 file and should be treated as such.
8170 <heading>Location</heading>
8173 Any configuration files created or used by your package
8174 must reside in <file>/etc</file>. If there are several,
8175 consider creating a subdirectory of <file>/etc</file>
8176 named after your package.
8180 If your package creates or uses configuration files
8181 outside of <file>/etc</file>, and it is not feasible to modify
8182 the package to use <file>/etc</file> directly, put the files
8183 in <file>/etc</file> and create symbolic links to those files
8184 from the location that the package requires.
8189 <heading>Behavior</heading>
8192 Configuration file handling must conform to the following
8194 <list compact="compact">
8196 local changes must be preserved during a package
8200 configuration files must be preserved when the
8201 package is removed, and only deleted when the
8205 Obsolete configuration files without local changes may be
8206 removed by the package during upgrade.
8210 The easy way to achieve this behavior is to make the
8211 configuration file a <tt>conffile</tt>. This is
8212 appropriate only if it is possible to distribute a default
8213 version that will work for most installations, although
8214 some system administrators may choose to modify it. This
8215 implies that the default version will be part of the
8216 package distribution, and must not be modified by the
8217 maintainer scripts during installation (or at any other
8222 In order to ensure that local changes are preserved
8223 correctly, no package may contain or make hard links to
8224 conffiles.<footnote>
8225 Rationale: There are two problems with hard links.
8226 The first is that some editors break the link while
8227 editing one of the files, so that the two files may
8228 unwittingly become unlinked and different. The second
8229 is that <prgn>dpkg</prgn> might break the hard link
8230 while upgrading <tt>conffile</tt>s.
8235 The other way to do it is via the maintainer scripts. In
8236 this case, the configuration file must not be listed as a
8237 <tt>conffile</tt> and must not be part of the package
8238 distribution. If the existence of a file is required for
8239 the package to be sensibly configured it is the
8240 responsibility of the package maintainer to provide
8241 maintainer scripts which correctly create, update and
8242 maintain the file and remove it on purge. (See <ref
8243 id="maintainerscripts"> for more information.) These
8244 scripts must be idempotent (i.e., must work correctly if
8245 <prgn>dpkg</prgn> needs to re-run them due to errors
8246 during installation or removal), must cope with all the
8247 variety of ways <prgn>dpkg</prgn> can call maintainer
8248 scripts, must not overwrite or otherwise mangle the user's
8249 configuration without asking, must not ask unnecessary
8250 questions (particularly during upgrades), and must
8251 otherwise be good citizens.
8255 The scripts are not required to configure every possible
8256 option for the package, but only those necessary to get
8257 the package running on a given system. Ideally the
8258 sysadmin should not have to do any configuration other
8259 than that done (semi-)automatically by the
8260 <prgn>postinst</prgn> script.
8264 A common practice is to create a script called
8265 <file><var>package</var>-configure</file> and have the
8266 package's <prgn>postinst</prgn> call it if and only if the
8267 configuration file does not already exist. In certain
8268 cases it is useful for there to be an example or template
8269 file which the maintainer scripts use. Such files should
8270 be in <file>/usr/share/<var>package</var></file> or
8271 <file>/usr/lib/<var>package</var></file> (depending on whether
8272 they are architecture-independent or not). There should
8273 be symbolic links to them from
8274 <file>/usr/share/doc/<var>package</var>/examples</file> if
8275 they are examples, and should be perfectly ordinary
8276 <prgn>dpkg</prgn>-handled files (<em>not</em>
8277 configuration files).
8281 These two styles of configuration file handling must
8282 not be mixed, for that way lies madness:
8283 <prgn>dpkg</prgn> will ask about overwriting the file
8284 every time the package is upgraded.
8289 <heading>Sharing configuration files</heading>
8292 If two or more packages use the same configuration file
8293 and it is reasonable for both to be installed at the same
8294 time, one of these packages must be defined as
8295 <em>owner</em> of the configuration file, i.e., it will be
8296 the package which handles that file as a configuration
8297 file. Other packages that use the configuration file must
8298 depend on the owning package if they require the
8299 configuration file to operate. If the other package will
8300 use the configuration file if present, but is capable of
8301 operating without it, no dependency need be declared.
8305 If it is desirable for two or more related packages to
8306 share a configuration file <em>and</em> for all of the
8307 related packages to be able to modify that configuration
8308 file, then the following should be done:
8309 <enumlist compact="compact">
8311 One of the related packages (the "owning" package)
8312 will manage the configuration file with maintainer
8313 scripts as described in the previous section.
8316 The owning package should also provide a program
8317 that the other packages may use to modify the
8321 The related packages must use the provided program
8322 to make any desired modifications to the
8323 configuration file. They should either depend on
8324 the core package to guarantee that the configuration
8325 modifier program is available or accept gracefully
8326 that they cannot modify the configuration file if it
8327 is not. (This is in addition to the fact that the
8328 configuration file may not even be present in the
8335 Sometimes it's appropriate to create a new package which
8336 provides the basic infrastructure for the other packages
8337 and which manages the shared configuration files. (The
8338 <tt>sgml-base</tt> package is a good example.)
8342 If the configuration file cannot be shared as described above,
8343 the packages must be marked as conflicting with each other.
8344 Two packages that specify the same file as
8345 a <tt>conffile</tt> must conflict. This is an instance of the
8346 general rule about not sharing files. Neither alternatives
8347 nor diversions are likely to be appropriate in this case; in
8348 particular, <prgn>dpkg</prgn> does not handle diverted
8349 <tt>conffile</tt>s well.
8353 When two packages both declare the same <tt>conffile</tt>, they
8354 may see left-over configuration files from each other even
8355 though they conflict with each other. If a user removes
8356 (without purging) one of the packages and installs the other,
8357 the new package will take over the <tt>conffile</tt> from the
8358 old package. If the file was modified by the user, it will be
8359 treated the same as any other locally
8360 modified <tt>conffile</tt> during an upgrade.
8364 The maintainer scripts must not alter a <tt>conffile</tt>
8365 of <em>any</em> package, including the one the scripts
8371 <heading>User configuration files ("dotfiles")</heading>
8374 The files in <file>/etc/skel</file> will automatically be
8375 copied into new user accounts by <prgn>adduser</prgn>.
8376 No other program should reference the files in
8377 <file>/etc/skel</file>.
8381 Therefore, if a program needs a dotfile to exist in
8382 advance in <file>$HOME</file> to work sensibly, that dotfile
8383 should be installed in <file>/etc/skel</file> and treated as a
8388 However, programs that require dotfiles in order to
8389 operate sensibly are a bad thing, unless they do create
8390 the dotfiles themselves automatically.
8394 Furthermore, programs should be configured by the Debian
8395 default installation to behave as closely to the upstream
8396 default behavior as possible.
8400 Therefore, if a program in a Debian package needs to be
8401 configured in some way in order to operate sensibly, that
8402 should be done using a site-wide configuration file placed
8403 in <file>/etc</file>. Only if the program doesn't support a
8404 site-wide default configuration and the package maintainer
8405 doesn't have time to add it may a default per-user file be
8406 placed in <file>/etc/skel</file>.
8410 <file>/etc/skel</file> should be as empty as we can make it.
8411 This is particularly true because there is no easy (or
8412 necessarily desirable) mechanism for ensuring that the
8413 appropriate dotfiles are copied into the accounts of
8414 existing users when a package is installed.
8420 <heading>Log files</heading>
8422 Log files should usually be named
8423 <file>/var/log/<var>package</var>.log</file>. If you have many
8424 log files, or need a separate directory for permission
8425 reasons (<file>/var/log</file> is writable only by
8426 <file>root</file>), you should usually create a directory named
8427 <file>/var/log/<var>package</var></file> and place your log
8432 Log files must be rotated occasionally so that they don't grow
8433 indefinitely. The best way to do this is to install a log
8434 rotation configuration file in the
8435 directory <file>/etc/logrotate.d</file>, normally
8436 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8437 the facilities provided by <prgn>logrotate</prgn>.
8440 The traditional approach to log files has been to set up
8441 <em>ad hoc</em> log rotation schemes using simple shell
8442 scripts and cron. While this approach is highly
8443 customizable, it requires quite a lot of sysadmin work.
8444 Even though the original Debian system helped a little
8445 by automatically installing a system which can be used
8446 as a template, this was deemed not enough.
8450 The use of <prgn>logrotate</prgn>, a program developed
8451 by Red Hat, is better, as it centralizes log management.
8452 It has both a configuration file
8453 (<file>/etc/logrotate.conf</file>) and a directory where
8454 packages can drop their individual log rotation
8455 configurations (<file>/etc/logrotate.d</file>).
8458 Here is a good example for a logrotate config
8459 file (for more information see <manref name="logrotate"
8461 <example compact="compact">
8462 /var/log/foo/*.log {
8468 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8472 This rotates all files under <file>/var/log/foo</file>, saves 12
8473 compressed generations, and tells the daemon to reopen its log
8474 files after the log rotation. It skips this log rotation
8475 (via <tt>missingok</tt>) if no such log file is present, which
8476 avoids errors if the package is removed but not purged.
8480 Log files should be removed when the package is
8481 purged (but not when it is only removed). This should be
8482 done by the <prgn>postrm</prgn> script when it is called
8483 with the argument <tt>purge</tt> (see <ref
8484 id="removedetails">).
8488 <sect id="permissions-owners">
8489 <heading>Permissions and owners</heading>
8492 The rules in this section are guidelines for general use.
8493 If necessary you may deviate from the details below.
8494 However, if you do so you must make sure that what is done
8495 is secure and you should try to be as consistent as possible
8496 with the rest of the system. You should probably also
8497 discuss it on <prgn>debian-devel</prgn> first.
8501 Files should be owned by <tt>root:root</tt>, and made
8502 writable only by the owner and universally readable (and
8503 executable, if appropriate), that is mode 644 or 755.
8507 Directories should be mode 755 or (for group-writability)
8508 mode 2775. The ownership of the directory should be
8509 consistent with its mode: if a directory is mode 2775, it
8510 should be owned by the group that needs write access to
8513 When a package is upgraded, and the owner or permissions
8514 of a file included in the package has changed, dpkg
8515 arranges for the ownership and permissions to be
8516 correctly set upon installation. However, this does not
8517 extend to directories; the permissions and ownership of
8518 directories already on the system does not change on
8519 install or upgrade of packages. This makes sense, since
8520 otherwise common directories like <tt>/usr</tt> would
8521 always be in flux. To correctly change permissions of a
8522 directory the package owns, explicit action is required,
8523 usually in the <tt>postinst</tt> script. Care must be
8524 taken to handle downgrades as well, in that case.
8530 Control information files should be owned by <tt>root:root</tt>
8531 and either mode 644 (for most files) or mode 755 (for
8532 executables such as <qref id="maintscripts">maintainer
8537 Setuid and setgid executables should be mode 4755 or 2755
8538 respectively, and owned by the appropriate user or group.
8539 They should not be made unreadable (modes like 4711 or
8540 2711 or even 4111); doing so achieves no extra security,
8541 because anyone can find the binary in the freely available
8542 Debian package; it is merely inconvenient. For the same
8543 reason you should not restrict read or execute permissions
8544 on non-set-id executables.
8548 Some setuid programs need to be restricted to particular
8549 sets of users, using file permissions. In this case they
8550 should be owned by the uid to which they are set-id, and by
8551 the group which should be allowed to execute them. They
8552 should have mode 4754; again there is no point in making
8553 them unreadable to those users who must not be allowed to
8558 It is possible to arrange that the system administrator can
8559 reconfigure the package to correspond to their local
8560 security policy by changing the permissions on a binary:
8561 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8562 described below.<footnote>
8563 Ordinary files installed by <prgn>dpkg</prgn> (as
8564 opposed to <tt>conffile</tt>s and other similar objects)
8565 normally have their permissions reset to the distributed
8566 permissions when the package is reinstalled. However,
8567 the use of <prgn>dpkg-statoverride</prgn> overrides this
8570 Another method you should consider is to create a group for
8571 people allowed to use the program(s) and make any setuid
8572 executables executable only by that group.
8576 If you need to create a new user or group for your package
8577 there are two possibilities. Firstly, you may need to
8578 make some files in the binary package be owned by this
8579 user or group, or you may need to compile the user or
8580 group id (rather than just the name) into the binary
8581 (though this latter should be avoided if possible, as in
8582 this case you need a statically allocated id).</p>
8585 If you need a statically allocated id, you must ask for a
8586 user or group id from the <tt>base-passwd</tt> maintainer,
8587 and must not release the package until you have been
8588 allocated one. Once you have been allocated one you must
8589 either make the package depend on a version of the
8590 <tt>base-passwd</tt> package with the id present in
8591 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8592 your package to create the user or group itself with the
8593 correct id (using <tt>adduser</tt>) in its
8594 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8595 the <prgn>postinst</prgn> is to be preferred if it is
8596 possible, otherwise a pre-dependency will be needed on the
8597 <tt>adduser</tt> package.)
8601 On the other hand, the program might be able to determine
8602 the uid or gid from the user or group name at runtime, so
8603 that a dynamically allocated id can be used. In this case
8604 you should choose an appropriate user or group name,
8605 discussing this on <prgn>debian-devel</prgn> and checking
8606 with the <package/base-passwd/ maintainer that it is unique and that
8607 they do not wish you to use a statically allocated id
8608 instead. When this has been checked you must arrange for
8609 your package to create the user or group if necessary using
8610 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8611 <prgn>postinst</prgn> script (again, the latter is to be
8612 preferred if it is possible).
8616 Note that changing the numeric value of an id associated
8617 with a name is very difficult, and involves searching the
8618 file system for all appropriate files. You need to think
8619 carefully whether a static or dynamic id is required, since
8620 changing your mind later will cause problems.
8623 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8625 This section is not intended as policy, but as a
8626 description of the use of <prgn>dpkg-statoverride</prgn>.
8630 If a system administrator wishes to have a file (or
8631 directory or other such thing) installed with owner and
8632 permissions different from those in the distributed Debian
8633 package, they can use the <prgn>dpkg-statoverride</prgn>
8634 program to instruct <prgn>dpkg</prgn> to use the different
8635 settings every time the file is installed. Thus the
8636 package maintainer should distribute the files with their
8637 normal permissions, and leave it for the system
8638 administrator to make any desired changes. For example, a
8639 daemon which is normally required to be setuid root, but
8640 in certain situations could be used without being setuid,
8641 should be installed setuid in the <tt>.deb</tt>. Then the
8642 local system administrator can change this if they wish.
8643 If there are two standard ways of doing it, the package
8644 maintainer can use <tt>debconf</tt> to find out the
8645 preference, and call <prgn>dpkg-statoverride</prgn> in the
8646 maintainer script if necessary to accommodate the system
8647 administrator's choice. Care must be taken during
8648 upgrades to not override an existing setting.
8652 Given the above, <prgn>dpkg-statoverride</prgn> is
8653 essentially a tool for system administrators and would not
8654 normally be needed in the maintainer scripts. There is
8655 one type of situation, though, where calls to
8656 <prgn>dpkg-statoverride</prgn> would be needed in the
8657 maintainer scripts, and that involves packages which use
8658 dynamically allocated user or group ids. In such a
8659 situation, something like the following idiom can be very
8660 helpful in the package's <prgn>postinst</prgn>, where
8661 <tt>sysuser</tt> is a dynamically allocated id:
8663 for i in /usr/bin/foo /usr/sbin/bar
8665 # only do something when no setting exists
8666 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8668 #include: debconf processing, question about foo and bar
8669 if [ "$RET" = "true" ] ; then
8670 dpkg-statoverride --update --add sysuser root 4755 $i
8675 The corresponding code to remove the override when the package
8678 for i in /usr/bin/foo /usr/sbin/bar
8680 if dpkg-statoverride --list $i >/dev/null 2>&1
8682 dpkg-statoverride --remove $i
8692 <chapt id="customized-programs">
8693 <heading>Customized programs</heading>
8695 <sect id="arch-spec">
8696 <heading>Architecture specification strings</heading>
8699 If a program needs to specify an <em>architecture specification
8700 string</em> in some place, it should select one of the strings
8701 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8702 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8703 part is sometimes elided, as when the OS is Linux.
8707 Note that we don't want to use
8708 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8709 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8710 since this would make our programs incompatible with other
8711 Linux distributions. We also don't use something like
8712 <tt><var>arch</var>-unknown-linux</tt>, since the
8713 <tt>unknown</tt> does not look very good.
8716 <sect1 id="arch-wildcard-spec">
8717 <heading>Architecture wildcards</heading>
8720 A package may specify an architecture wildcard. Architecture
8721 wildcards are in the format <tt>any</tt> (which matches every
8722 architecture), <tt><var>os</var></tt>-any, or
8723 any-<tt><var>cpu</var></tt>. <footnote>
8724 Internally, the package system normalizes the GNU triplets
8725 and the Debian arches into Debian arch triplets (which are
8726 kind of inverted GNU triplets), with the first component of
8727 the triplet representing the libc and ABI in use, and then
8728 does matching against those triplets. However, such
8729 triplets are an internal implementation detail that should
8730 not be used by packages directly. The libc and ABI portion
8731 is handled internally by the package system based on
8732 the <var>os</var> and <var>cpu</var>.
8739 <heading>Daemons</heading>
8742 The configuration files <file>/etc/services</file>,
8743 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8744 by the <prgn>netbase</prgn> package and must not be modified
8749 If a package requires a new entry in one of these files, the
8750 maintainer should get in contact with the
8751 <prgn>netbase</prgn> maintainer, who will add the entries
8752 and release a new version of the <prgn>netbase</prgn>
8757 The configuration file <file>/etc/inetd.conf</file> must not be
8758 modified by the package's scripts except via the
8759 <prgn>update-inetd</prgn> script or the
8760 <file>DebianNet.pm</file> Perl module. See their documentation
8761 for details on how to add entries.
8765 If a package wants to install an example entry into
8766 <file>/etc/inetd.conf</file>, the entry must be preceded with
8767 exactly one hash character (<tt>#</tt>). Such lines are
8768 treated as "commented out by user" by the
8769 <prgn>update-inetd</prgn> script and are not changed or
8770 activated during package updates.
8775 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8779 Some programs need to create pseudo-ttys. This should be done
8780 using Unix98 ptys if the C library supports it. The resulting
8781 program must not be installed setuid root, unless that
8782 is required for other functionality.
8786 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8787 <file>/var/log/lastlog</file> must be installed writable by
8788 group <tt>utmp</tt>. Programs which need to modify those
8789 files must be installed setgid <tt>utmp</tt>.
8794 <heading>Editors and pagers</heading>
8797 Some programs have the ability to launch an editor or pager
8798 program to edit or display a text document. Since there are
8799 lots of different editors and pagers available in the Debian
8800 distribution, the system administrator and each user should
8801 have the possibility to choose their preferred editor and
8806 In addition, every program should choose a good default
8807 editor/pager if none is selected by the user or system
8812 Thus, every program that launches an editor or pager must
8813 use the EDITOR or PAGER environment variable to determine
8814 the editor or pager the user wishes to use. If these
8815 variables are not set, the programs <file>/usr/bin/editor</file>
8816 and <file>/usr/bin/pager</file> should be used, respectively.
8820 These two files are managed through the <prgn>dpkg</prgn>
8821 "alternatives" mechanism. Every package providing an editor or
8822 pager must call the <prgn>update-alternatives</prgn> script to
8823 register as an alternative for <file>/usr/bin/editor</file>
8824 or <file>/usr/bin/pager</file> as appropriate. The alternative
8825 should have a slave alternative
8826 for <file>/usr/share/man/man1/editor.1.gz</file>
8827 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8828 corresponding manual page.
8832 If it is very hard to adapt a program to make use of the
8833 EDITOR or PAGER variables, that program may be configured to
8834 use <file>/usr/bin/sensible-editor</file> and
8835 <file>/usr/bin/sensible-pager</file> as the editor or pager
8836 program respectively. These are two scripts provided in the
8837 <package>sensible-utils</package> package that check the EDITOR
8838 and PAGER variables and launch the appropriate program, and fall
8839 back to <file>/usr/bin/editor</file>
8840 and <file>/usr/bin/pager</file> if the variable is not set.
8844 A program may also use the VISUAL environment variable to
8845 determine the user's choice of editor. If it exists, it
8846 should take precedence over EDITOR. This is in fact what
8847 <file>/usr/bin/sensible-editor</file> does.
8851 It is not required for a package to depend on
8852 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8853 package to provide such virtual packages.<footnote>
8854 The Debian base system already provides an editor and a
8860 <sect id="web-appl">
8861 <heading>Web servers and applications</heading>
8864 This section describes the locations and URLs that should
8865 be used by all web servers and web applications in the
8872 Cgi-bin executable files are installed in the
8874 <example compact="compact">
8875 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8877 or a subdirectory of that directory, and should be
8879 <example compact="compact">
8880 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8882 (possibly with a subdirectory name
8883 before <var>cgi-bin-name</var>).
8887 <p>Access to HTML documents</p>
8890 HTML documents for a package are stored in
8891 <file>/usr/share/doc/<var>package</var></file>
8892 and can be referred to as
8893 <example compact="compact">
8894 http://localhost/doc/<var>package</var>/<var>filename</var>
8899 The web server should restrict access to the document
8900 tree so that only clients on the same host can read
8901 the documents. If the web server does not support such
8902 access controls, then it should not provide access at
8903 all, or ask about providing access during installation.
8908 <p>Access to images</p>
8910 It is recommended that images for a package be stored
8911 in <tt>/usr/share/images/<var>package</var></tt> and
8912 may be referred to through an alias <tt>/images/</tt>
8915 http://localhost/images/<package>/<filename>
8922 <p>Web Document Root</p>
8925 Web Applications should try to avoid storing files in
8926 the Web Document Root. Instead they should use the
8927 /usr/share/doc/<var>package</var> directory for
8928 documents and register the Web Application via the
8929 <package>doc-base</package> package. If access to the
8930 web document root is unavoidable then use
8931 <example compact="compact">
8934 as the Document Root. This might be just a symbolic
8935 link to the location where the system administrator
8936 has put the real document root.
8939 <item><p>Providing httpd and/or httpd-cgi</p>
8941 All web servers should provide the virtual package
8942 <tt>httpd</tt>. If a web server has CGI support it should
8943 provide <tt>httpd-cgi</tt> additionally.
8946 All web applications which do not contain CGI scripts should
8947 depend on <tt>httpd</tt>, all those web applications which
8948 <tt>do</tt> contain CGI scripts, should depend on
8956 <sect id="mail-transport-agents">
8957 <heading>Mail transport, delivery and user agents</heading>
8960 Debian packages which process electronic mail, whether mail
8961 user agents (MUAs) or mail transport agents (MTAs), must
8962 ensure that they are compatible with the configuration
8963 decisions below. Failure to do this may result in lost
8964 mail, broken <tt>From:</tt> lines, and other serious brain
8969 The mail spool is <file>/var/mail</file> and the interface to
8970 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8971 the FHS). On older systems, the mail spool may be
8972 physically located in <file>/var/spool/mail</file>, but all
8973 access to the mail spool should be via the
8974 <file>/var/mail</file> symlink. The mail spool is part of the
8975 base system and not part of the MTA package.
8979 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8980 programs (such as IMAP daemons) must lock the mailbox in an
8981 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8982 be combined with dot locking. To avoid deadlocks, a program
8983 should use <tt>fcntl()</tt> first and dot locking after
8984 this, or alternatively implement the two locking methods in
8985 a non blocking way<footnote>
8986 If it is not possible to establish both locks, the
8987 system shouldn't wait for the second lock to be
8988 established, but remove the first lock, wait a (random)
8989 time, and start over locking again.
8990 </footnote>. Using the functions <tt>maillock</tt> and
8991 <tt>mailunlock</tt> provided by the
8992 <tt>liblockfile*</tt><footnote>
8993 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8994 to use these functions.
8995 </footnote> packages is the recommended way to realize this.
8999 Mailboxes are generally either mode 600 and owned by
9000 <var>user</var> or mode 660 and owned by
9001 <tt><var>user</var>:mail</tt><footnote>
9002 There are two traditional permission schemes for mail spools:
9003 mode 600 with all mail delivery done by processes running as
9004 the destination user, or mode 660 and owned by group mail with
9005 mail delivery done by a process running as a system user in
9006 group mail. Historically, Debian required mode 660 mail
9007 spools to enable the latter model, but that model has become
9008 increasingly uncommon and the principle of least privilege
9009 indicates that mail systems that use the first model should
9010 use permissions of 600. If delivery to programs is permitted,
9011 it's easier to keep the mail system secure if the delivery
9012 agent runs as the destination user. Debian Policy therefore
9013 permits either scheme.
9014 </footnote>. The local system administrator may choose a
9015 different permission scheme; packages should not make
9016 assumptions about the permission and ownership of mailboxes
9017 unless required (such as when creating a new mailbox). A MUA
9018 may remove a mailbox (unless it has nonstandard permissions) in
9019 which case the MTA or another MUA must recreate it if needed.
9023 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9024 be setgid mail to do the locking mentioned above (and
9025 must obviously avoid accessing other users' mailboxes
9026 using this privilege).</p>
9029 <file>/etc/aliases</file> is the source file for the system mail
9030 aliases (e.g., postmaster, usenet, etc.), it is the one
9031 which the sysadmin and <prgn>postinst</prgn> scripts may
9032 edit. After <file>/etc/aliases</file> is edited the program or
9033 human editing it must call <prgn>newaliases</prgn>. All MTA
9034 packages must come with a <prgn>newaliases</prgn> program,
9035 even if it does nothing, but older MTA packages did not do
9036 this so programs should not fail if <prgn>newaliases</prgn>
9037 cannot be found. Note that because of this, all MTA
9038 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9039 <tt>Replaces: mail-transport-agent</tt> control fields.
9043 The convention of writing <tt>forward to
9044 <var>address</var></tt> in the mailbox itself is not
9045 supported. Use a <tt>.forward</tt> file instead.</p>
9048 The <prgn>rmail</prgn> program used by UUCP
9049 for incoming mail should be <file>/usr/sbin/rmail</file>.
9050 Likewise, <prgn>rsmtp</prgn>, for receiving
9051 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9055 If your package needs to know what hostname to use on (for
9056 example) outgoing news and mail messages which are generated
9057 locally, you should use the file <file>/etc/mailname</file>. It
9058 will contain the portion after the username and <tt>@</tt>
9059 (at) sign for email addresses of users on the machine
9060 (followed by a newline).
9064 Such a package should check for the existence of this file
9065 when it is being configured. If it exists, it should be
9066 used without comment, although an MTA's configuration script
9067 may wish to prompt the user even if it finds that this file
9068 exists. If the file does not exist, the package should
9069 prompt the user for the value (preferably using
9070 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9071 as well as using it in the package's configuration. The
9072 prompt should make it clear that the name will not just be
9073 used by that package. For example, in this situation the
9074 <tt>inn</tt> package could say something like:
9075 <example compact="compact">
9076 Please enter the "mail name" of your system. This is the
9077 hostname portion of the address to be shown on outgoing
9078 news and mail messages. The default is
9079 <var>syshostname</var>, your system's host name. Mail
9080 name ["<var>syshostname</var>"]:
9082 where <var>syshostname</var> is the output of <tt>hostname
9088 <heading>News system configuration</heading>
9091 All the configuration files related to the NNTP (news)
9092 servers and clients should be located under
9093 <file>/etc/news</file>.</p>
9096 There are some configuration issues that apply to a number
9097 of news clients and server packages on the machine. These
9101 <tag><file>/etc/news/organization</file></tag>
9103 A string which should appear as the
9104 organization header for all messages posted
9105 by NNTP clients on the machine
9108 <tag><file>/etc/news/server</file></tag>
9110 Contains the FQDN of the upstream NNTP
9111 server, or localhost if the local machine is
9116 Other global files may be added as required for cross-package news
9123 <heading>Programs for the X Window System</heading>
9126 <heading>Providing X support and package priorities</heading>
9129 Programs that can be configured with support for the X
9130 Window System must be configured to do so and must declare
9131 any package dependencies necessary to satisfy their
9132 runtime requirements when using the X Window System. If
9133 such a package is of higher priority than the X packages
9134 on which it depends, it is required that either the
9135 X-specific components be split into a separate package, or
9136 that an alternative version of the package, which includes
9137 X support, be provided, or that the package's priority be
9143 <heading>Packages providing an X server</heading>
9146 Packages that provide an X server that, directly or
9147 indirectly, communicates with real input and display
9148 hardware should declare in their <tt>Provides</tt> control
9149 field that they provide the virtual
9150 package <tt>xserver</tt>.<footnote>
9151 This implements current practice, and provides an
9152 actual policy for usage of the <tt>xserver</tt>
9153 virtual package which appears in the virtual packages
9154 list. In a nutshell, X servers that interface
9155 directly with the display and input hardware or via
9156 another subsystem (e.g., GGI) should provide
9157 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9158 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9164 <heading>Packages providing a terminal emulator</heading>
9167 Packages that provide a terminal emulator for the X Window
9168 System which meet the criteria listed below should declare in
9169 their <tt>Provides</tt> control field that they provide the
9170 virtual package <tt>x-terminal-emulator</tt>. They should
9171 also register themselves as an alternative for
9172 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9173 20. That alternative should have a slave alternative
9174 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9175 pointing to the corresponding manual page.
9179 To be an <tt>x-terminal-emulator</tt>, a program must:
9180 <list compact="compact">
9182 Be able to emulate a DEC VT100 terminal, or a
9183 compatible terminal.
9187 Support the command-line option <tt>-e
9188 <var>command</var></tt>, which creates a new
9189 terminal window<footnote>
9190 "New terminal window" does not necessarily mean
9191 a new top-level X window directly parented by
9192 the window manager; it could, if the terminal
9193 emulator application were so coded, be a new
9194 "view" in a multiple-document interface (MDI).
9196 and runs the specified <var>command</var>,
9197 interpreting the entirety of the rest of the command
9198 line as a command to pass straight to exec, in the
9199 manner that <tt>xterm</tt> does.
9203 Support the command-line option <tt>-T
9204 <var>title</var></tt>, which creates a new terminal
9205 window with the window title <var>title</var>.
9212 <heading>Packages providing a window manager</heading>
9215 Packages that provide a window manager should declare in
9216 their <tt>Provides</tt> control field that they provide the
9217 virtual package <tt>x-window-manager</tt>. They should also
9218 register themselves as an alternative for
9219 <file>/usr/bin/x-window-manager</file>, with a priority
9220 calculated as follows:
9221 <list compact="compact">
9223 Start with a priority of 20.
9227 If the window manager supports the Debian menu
9228 system, add 20 points if this support is available
9229 in the package's default configuration (i.e., no
9230 configuration files belonging to the system or user
9231 have to be edited to activate the feature); if
9232 configuration files must be modified, add only 10
9238 If the window manager complies with <url
9239 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9240 name="The Window Manager Specification Project">,
9241 written by the <url id="http://www.freedesktop.org/wiki/"
9242 name="Free Desktop Group">, add 40 points.
9246 If the window manager permits the X session to be
9247 restarted using a <em>different</em> window manager
9248 (without killing the X server) in its default
9249 configuration, add 10 points; otherwise add none.
9252 That alternative should have a slave alternative
9253 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9254 pointing to the corresponding manual page.
9259 <heading>Packages providing fonts</heading>
9262 Packages that provide fonts for the X Window
9264 For the purposes of Debian Policy, a "font for the X
9265 Window System" is one which is accessed via X protocol
9266 requests. Fonts for the Linux console, for PostScript
9267 renderer, or any other purpose, do not fit this
9268 definition. Any tool which makes such fonts available
9269 to the X Window System, however, must abide by this
9272 must do a number of things to ensure that they are both
9273 available without modification of the X or font server
9274 configuration, and that they do not corrupt files used by
9275 other font packages to register information about
9279 Fonts of any type supported by the X Window System
9280 must be in a separate binary package from any
9281 executables, libraries, or documentation (except
9282 that specific to the fonts shipped, such as their
9283 license information). If one or more of the fonts
9284 so packaged are necessary for proper operation of
9285 the package with which they are associated the font
9286 package may be Recommended; if the fonts merely
9287 provide an enhancement, a Suggests relationship may
9288 be used. Packages must not Depend on font
9290 This is because the X server may retrieve fonts
9291 from the local file system or over the network
9292 from an X font server; the Debian package system
9293 is empowered to deal only with the local
9299 BDF fonts must be converted to PCF fonts with the
9300 <prgn>bdftopcf</prgn> utility (available in the
9301 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9302 placed in a directory that corresponds to their
9304 <list compact="compact">
9306 100 dpi fonts must be placed in
9307 <file>/usr/share/fonts/X11/100dpi/</file>.
9311 75 dpi fonts must be placed in
9312 <file>/usr/share/fonts/X11/75dpi/</file>.
9316 Character-cell fonts, cursor fonts, and other
9317 low-resolution fonts must be placed in
9318 <file>/usr/share/fonts/X11/misc/</file>.
9324 Type 1 fonts must be placed in
9325 <file>/usr/share/fonts/X11/Type1/</file>. If font
9326 metric files are available, they must be placed here
9331 Subdirectories of <file>/usr/share/fonts/X11/</file>
9332 other than those listed above must be neither
9333 created nor used. (The <file>PEX</file>, <file>CID</file>,
9334 <file>Speedo</file>, and <file>cyrillic</file> directories
9335 are excepted for historical reasons, but installation of
9336 files into these directories remains discouraged.)
9340 Font packages may, instead of placing files directly
9341 in the X font directories listed above, provide
9342 symbolic links in that font directory pointing to
9343 the files' actual location in the filesystem. Such
9344 a location must comply with the FHS.
9348 Font packages should not contain both 75dpi and
9349 100dpi versions of a font. If both are available,
9350 they should be provided in separate binary packages
9351 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9352 the names of the packages containing the
9353 corresponding fonts.
9357 Fonts destined for the <file>misc</file> subdirectory
9358 should not be included in the same package as 75dpi
9359 or 100dpi fonts; instead, they should be provided in
9360 a separate package with <tt>-misc</tt> appended to
9365 Font packages must not provide the files
9366 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9367 <file>fonts.scale</file> in a font directory:
9370 <file>fonts.dir</file> files must not be provided at all.
9374 <file>fonts.alias</file> and <file>fonts.scale</file>
9375 files, if needed, should be provided in the
9377 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9378 where <var>fontdir</var> is the name of the
9380 <file>/usr/share/fonts/X11/</file> where the
9381 package's corresponding fonts are stored
9382 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9383 <var>package</var> is the name of the package
9384 that provides these fonts, and
9385 <var>extension</var> is either <tt>scale</tt>
9386 or <tt>alias</tt>, whichever corresponds to
9393 Font packages must declare a dependency on
9394 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9395 or <tt>Pre-Depends</tt> control field.
9399 Font packages that provide one or more
9400 <file>fonts.scale</file> files as described above must
9401 invoke <prgn>update-fonts-scale</prgn> on each
9402 directory into which they installed fonts
9403 <em>before</em> invoking
9404 <prgn>update-fonts-dir</prgn> on that directory.
9405 This invocation must occur in both the
9406 <prgn>postinst</prgn> (for all arguments) and
9407 <prgn>postrm</prgn> (for all arguments except
9408 <tt>upgrade</tt>) scripts.
9412 Font packages that provide one or more
9413 <file>fonts.alias</file> files as described above must
9414 invoke <prgn>update-fonts-alias</prgn> on each
9415 directory into which they installed fonts. This
9416 invocation must occur in both the
9417 <prgn>postinst</prgn> (for all arguments) and
9418 <prgn>postrm</prgn> (for all arguments except
9419 <tt>upgrade</tt>) scripts.
9423 Font packages must invoke
9424 <prgn>update-fonts-dir</prgn> on each directory into
9425 which they installed fonts. This invocation must
9426 occur in both the <prgn>postinst</prgn> (for all
9427 arguments) and <prgn>postrm</prgn> (for all
9428 arguments except <tt>upgrade</tt>) scripts.
9432 Font packages must not provide alias names for the
9433 fonts they include which collide with alias names
9434 already in use by fonts already packaged.
9438 Font packages must not provide fonts with the same
9439 XLFD registry name as another font already packaged.
9445 <sect1 id="appdefaults">
9446 <heading>Application defaults files</heading>
9449 Application defaults files must be installed in the
9450 directory <file>/etc/X11/app-defaults/</file> (use of a
9451 localized subdirectory of <file>/etc/X11/</file> as described
9452 in the <em>X Toolkit Intrinsics - C Language
9453 Interface</em> manual is also permitted). They must be
9454 registered as <tt>conffile</tt>s or handled as
9455 configuration files.
9459 Customization of programs' X resources may also be
9460 supported with the provision of a file with the same name
9461 as that of the package placed in
9462 the <file>/etc/X11/Xresources/</file> directory, which
9463 must be registered as a <tt>conffile</tt> or handled as a
9464 configuration file.<footnote>
9465 Note that this mechanism is not the same as using
9466 app-defaults; app-defaults are tied to the client
9467 binary on the local file system, whereas X resources
9468 are stored in the X server and affect all connecting
9475 <heading>Installation directory issues</heading>
9478 Historically, packages using the X Window System used a
9479 separate set of installation directories from other packages.
9480 This practice has been discontinued and packages using the X
9481 Window System should now generally be installed in the same
9482 directories as any other package. Specifically, packages must
9483 not install files under the <file>/usr/X11R6/</file> directory
9484 and the <file>/usr/X11R6/</file> directory hierarchy should be
9485 regarded as obsolete.
9489 Include files previously installed under
9490 <file>/usr/X11R6/include/X11/</file> should be installed into
9491 <file>/usr/include/X11/</file>. For files previously
9492 installed into subdirectories of
9493 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9494 determine if subdirectories of <file>/usr/lib/</file> and
9495 <file>/usr/share/</file> can be used. If not, a subdirectory
9496 of <file>/usr/lib/X11/</file> should be used.
9500 Configuration files for window, display, or session managers
9501 or other applications that are tightly integrated with the X
9502 Window System may be placed in a subdirectory
9503 of <file>/etc/X11/</file> corresponding to the package name.
9504 Other X Window System applications should use
9505 the <file>/etc/</file> directory unless otherwise mandated by
9506 policy (such as for <ref id="appdefaults">).
9512 <heading>Perl programs and modules</heading>
9515 Perl programs and modules should follow the current Perl policy.
9519 The Perl policy can be found in the <tt>perl-policy</tt>
9520 files in the <tt>debian-policy</tt> package.
9521 It is also available from the Debian web mirrors at
9522 <tt><url name="/doc/packaging-manuals/perl-policy/"
9523 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9528 <heading>Emacs lisp programs</heading>
9531 Please refer to the "Debian Emacs Policy" for details of how to
9532 package emacs lisp programs.
9536 The Emacs policy is available in
9537 <file>debian-emacs-policy.gz</file> of the
9538 <package>emacsen-common</package> package.
9539 It is also available from the Debian web mirrors at
9540 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9541 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9546 <heading>Games</heading>
9549 The permissions on <file>/var/games</file> are mode 755, owner
9550 <tt>root</tt> and group <tt>root</tt>.
9554 Each game decides on its own security policy.</p>
9557 Games which require protected, privileged access to
9558 high-score files, saved games, etc., may be made
9559 set-<em>group</em>-id (mode 2755) and owned by
9560 <tt>root:games</tt>, and use files and directories with
9561 appropriate permissions (770 <tt>root:games</tt>, for
9562 example). They must not be made
9563 set-<em>user</em>-id, as this causes security problems. (If
9564 an attacker can subvert any set-user-id game they can
9565 overwrite the executable of any other, causing other players
9566 of these games to run a Trojan horse program. With a
9567 set-group-id game the attacker only gets access to less
9568 important game data, and if they can get at the other
9569 players' accounts at all it will take considerably more
9573 Some packages, for example some fortune cookie programs, are
9574 configured by the upstream authors to install with their
9575 data files or other static information made unreadable so
9576 that they can only be accessed through set-id programs
9577 provided. You should not do this in a Debian package: anyone can
9578 download the <file>.deb</file> file and read the data from it,
9579 so there is no point making the files unreadable. Not
9580 making the files unreadable also means that you don't have
9581 to make so many programs set-id, which reduces the risk of a
9585 As described in the FHS, binaries of games should be
9586 installed in the directory <file>/usr/games</file>. This also
9587 applies to games that use the X Window System. Manual pages
9588 for games (X and non-X games) should be installed in
9589 <file>/usr/share/man/man6</file>.</p>
9595 <heading>Documentation</heading>
9598 <heading>Manual pages</heading>
9601 You should install manual pages in <prgn>nroff</prgn> source
9602 form, in appropriate places under <file>/usr/share/man</file>.
9603 You should only use sections 1 to 9 (see the FHS for more
9604 details). You must not install a pre-formatted "cat page".
9608 Each program, utility, and function should have an
9609 associated manual page included in the same package. It is
9610 suggested that all configuration files also have a manual
9611 page included as well. Manual pages for protocols and other
9612 auxiliary things are optional.
9616 If no manual page is available, this is considered as a bug
9617 and should be reported to the Debian Bug Tracking System (the
9618 maintainer of the package is allowed to write this bug report
9619 themselves, if they so desire). Do not close the bug report
9620 until a proper man page is available.<footnote>
9621 It is not very hard to write a man page. See the
9622 <url id="http://www.schweikhardt.net/man_page_howto.html"
9623 name="Man-Page-HOWTO">,
9624 <manref name="man" section="7">, the examples created
9625 by <prgn>dh_make</prgn>, the helper
9626 program <prgn>help2man</prgn>, or the
9627 directory <file>/usr/share/doc/man-db/examples</file>.
9632 You may forward a complaint about a missing man page to the
9633 upstream authors, and mark the bug as forwarded in the
9634 Debian bug tracking system. Even though the GNU Project do
9635 not in general consider the lack of a man page to be a bug,
9636 we do; if they tell you that they don't consider it a bug
9637 you should leave the bug in our bug tracking system open
9642 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9646 If one man page needs to be accessible via several names it
9647 is better to use a symbolic link than the <file>.so</file>
9648 feature, but there is no need to fiddle with the relevant
9649 parts of the upstream source to change from <file>.so</file> to
9650 symlinks: don't do it unless it's easy. You should not
9651 create hard links in the manual page directories, nor put
9652 absolute filenames in <file>.so</file> directives. The filename
9653 in a <file>.so</file> in a man page should be relative to the
9654 base of the man page tree (usually
9655 <file>/usr/share/man</file>). If you do not create any links
9656 (whether symlinks, hard links, or <tt>.so</tt> directives)
9657 in the file system to the alternate names of the man page,
9658 then you should not rely on <prgn>man</prgn> finding your
9659 man page under those names based solely on the information in
9660 the man page's header.<footnote>
9661 Supporting this in <prgn>man</prgn> often requires
9662 unreasonable processing time to find a manual page or to
9663 report that none exists, and moves knowledge into man's
9664 database that would be better left in the file system.
9665 This support is therefore deprecated and will cease to
9666 be present in the future.
9671 Manual pages in locale-specific subdirectories of
9672 <file>/usr/share/man</file> should use either UTF-8 or the usual
9673 legacy encoding for that language (normally the one corresponding
9674 to the shortest relevant locale name in
9675 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9676 <file>/usr/share/man/fr</file> should use either UTF-8 or
9677 ISO-8859-1.<footnote>
9678 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9679 use. In future, all manual pages will be required to use
9685 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9686 included in the subdirectory name unless it indicates a
9687 significant difference in the language, as this excludes
9688 speakers of the language in other countries.<footnote>
9689 At the time of writing, Chinese and Portuguese are the main
9690 languages with such differences, so <file>pt_BR</file>,
9691 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9696 If a localized version of a manual page is provided, it should
9697 either be up-to-date or it should be obvious to the reader that
9698 it is outdated and the original manual page should be used
9699 instead. This can be done either by a note at the beginning of
9700 the manual page or by showing the missing or changed portions in
9701 the original language instead of the target language.
9706 <heading>Info documents</heading>
9709 Info documents should be installed in <file>/usr/share/info</file>.
9710 They should be compressed with <tt>gzip -9</tt>.
9714 The <prgn>install-info</prgn> program maintains a directory of
9715 installed info documents in <file>/usr/share/info/dir</file> for
9716 the use of info readers.<footnote>
9717 It was previously necessary for packages installing info
9718 documents to run <prgn>install-info</prgn> from maintainer
9719 scripts. This is no longer necessary. The installation
9720 system now uses dpkg triggers.
9722 This file must not be included in packages. Packages containing
9723 info documents should depend on <tt>dpkg (>= 1.15.4) |
9724 install-info</tt> to ensure that the directory file is properly
9725 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9730 Info documents should contain section and directory entry
9731 information in the document for the use
9732 of <prgn>install-info</prgn>. The section should be specified
9733 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9734 space and the section of this info page. The directory entry or
9735 entries should be included between
9736 a <tt>START-INFO-DIR-ENTRY</tt> line and
9737 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9739 INFO-DIR-SECTION Individual utilities
9740 START-INFO-DIR-ENTRY
9741 * example: (example). An example info directory entry.
9744 To determine which section to use, you should look
9745 at <file>/usr/share/info/dir</file> on your system and choose
9746 the most relevant (or create a new section if none of the
9747 current sections are relevant).<footnote>
9748 Normally, info documents are generated from Texinfo source.
9749 To include this information in the generated info document, if
9750 it is absent, add commands like:
9752 @dircategory Individual utilities
9754 * example: (example). An example info directory entry.
9757 to the Texinfo source of the document and ensure that the info
9758 documents are rebuilt from source during the package build.
9764 <heading>Additional documentation</heading>
9767 Any additional documentation that comes with the package may
9768 be installed at the discretion of the package maintainer.
9769 Plain text documentation should be installed in the directory
9770 <file>/usr/share/doc/<var>package</var></file>, where
9771 <var>package</var> is the name of the package, and
9772 compressed with <tt>gzip -9</tt> unless it is small.
9776 If a package comes with large amounts of documentation which
9777 many users of the package will not require you should create
9778 a separate binary package to contain it, so that it does not
9779 take up disk space on the machines of users who do not need
9780 or want it installed.</p>
9783 It is often a good idea to put text information files
9784 (<file>README</file>s, changelogs, and so forth) that come with
9785 the source package in <file>/usr/share/doc/<var>package</var></file>
9786 in the binary package. However, you don't need to install
9787 the instructions for building and installing the package, of
9791 Packages must not require the existence of any files in
9792 <file>/usr/share/doc/</file> in order to function
9794 The system administrator should be able to
9795 delete files in <file>/usr/share/doc/</file> without causing
9796 any programs to break.
9798 Any files that are referenced by programs but are also
9799 useful as stand alone documentation should be installed under
9800 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9801 <file>/usr/share/doc/<var>package</var></file>.
9805 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9806 link to another directory in <file>/usr/share/doc</file> only if
9807 the two packages both come from the same source and the
9808 first package Depends on the second.<footnote>
9810 Please note that this does not override the section on
9811 changelog files below, so the file
9812 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9813 must refer to the changelog for the current version of
9814 <var>package</var> in question. In practice, this means
9815 that the sources of the target and the destination of the
9816 symlink must be the same (same source package and
9823 Former Debian releases placed all additional documentation
9824 in <file>/usr/doc/<var>package</var></file>. This has been
9825 changed to <file>/usr/share/doc/<var>package</var></file>,
9826 and packages must not put documentation in the directory
9827 <file>/usr/doc/<var>package</var></file>. <footnote>
9828 At this phase of the transition, we no longer require a
9829 symbolic link in <file>/usr/doc/</file>. At a later point,
9830 policy shall change to make the symbolic links a bug.
9836 <heading>Preferred documentation formats</heading>
9839 The unification of Debian documentation is being carried out
9843 If your package comes with extensive documentation in a
9844 markup format that can be converted to various other formats
9845 you should if possible ship HTML versions in a binary
9846 package, in the directory
9847 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9848 its subdirectories.<footnote>
9849 The rationale: The important thing here is that HTML
9850 docs should be available in <em>some</em> package, not
9851 necessarily in the main binary package.
9856 Other formats such as PostScript may be provided at the
9857 package maintainer's discretion.
9861 <sect id="copyrightfile">
9862 <heading>Copyright information</heading>
9865 Every package must be accompanied by a verbatim copy of its
9866 copyright information and distribution license in the file
9867 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9868 file must neither be compressed nor be a symbolic link.
9872 In addition, the copyright file must say where the upstream
9873 sources (if any) were obtained, and should name the original
9878 Packages in the <em>contrib</em> or <em>non-free</em> archive
9879 areas should state in the copyright file that the package is not
9880 part of the Debian distribution and briefly explain why.
9884 A copy of the file which will be installed in
9885 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9886 be in <file>debian/copyright</file> in the source package.
9890 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9891 link to another directory in <file>/usr/share/doc</file> only if
9892 the two packages both come from the same source and the
9893 first package Depends on the second. These rules are important
9894 because <file>copyright</file> files must be extractable by
9899 Packages distributed under the Apache license (version 2.0), the
9900 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9901 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9902 1.3) should refer to the corresponding files
9903 under <file>/usr/share/common-licenses</file>,<footnote>
9906 <file>/usr/share/common-licenses/Apache-2.0</file>,
9907 <file>/usr/share/common-licenses/Artistic</file>,
9908 <file>/usr/share/common-licenses/GPL-1</file>,
9909 <file>/usr/share/common-licenses/GPL-2</file>,
9910 <file>/usr/share/common-licenses/GPL-3</file>,
9911 <file>/usr/share/common-licenses/LGPL-2</file>,
9912 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9913 <file>/usr/share/common-licenses/LGPL-3</file>,
9914 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9915 <file>/usr/share/common-licenses/GFDL-1.3</file>
9916 respectively. The University of California BSD license is
9917 also included in <package>base-files</package> as
9918 <file>/usr/share/common-licenses/BSD</file>, but given the
9919 brevity of this license, its specificity to code whose
9920 copyright is held by the Regents of the University of
9921 California, and the frequency of minor wording changes, its
9922 text should be included in the copyright file rather than
9923 referencing this file.
9925 </footnote> rather than quoting them in the copyright
9930 You should not use the copyright file as a general <file>README</file>
9931 file. If your package has such a file it should be
9932 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9933 <file>README.Debian</file> or some other appropriate place.
9936 <sect1 id="copyrightformat">
9937 <heading>Machine-readable copyright information</heading>
9940 A specification for a standard, machine-readable format
9941 for <file>debian/copyright</file> files is maintained as part
9942 of the <package>debian-policy</package> package. This
9943 document may be found in the <file>copyright-format</file>
9944 files in the <package>debian-policy</package> package. It is
9945 also available from the Debian web mirrors at
9946 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
9947 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
9951 Use of this format is optional.
9957 <heading>Examples</heading>
9960 Any examples (configurations, source files, whatever),
9961 should be installed in a directory
9962 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9963 files should not be referenced by any program: they're there
9964 for the benefit of the system administrator and users as
9965 documentation only. Architecture-specific example files
9966 should be installed in a directory
9967 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9969 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9970 latter directory itself may be a symbolic link to the
9975 If the purpose of a package is to provide examples, then the
9976 example files may be installed into
9977 <file>/usr/share/doc/<var>package</var></file>.
9981 <sect id="changelogs">
9982 <heading>Changelog files</heading>
9985 Packages that are not Debian-native must contain a
9986 compressed copy of the <file>debian/changelog</file> file from
9987 the Debian source tree in
9988 <file>/usr/share/doc/<var>package</var></file> with the name
9989 <file>changelog.Debian.gz</file>.
9993 If an upstream changelog is available, it should be accessible as
9994 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9995 plain text. If the upstream changelog is distributed in
9996 HTML, it should be made available in that form as
9997 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9998 and a plain text <file>changelog.gz</file> should be generated
9999 from it using, for example, <tt>lynx -dump -nolist</tt>. If
10000 the upstream changelog files do not already conform to this
10001 naming convention, then this may be achieved either by
10002 renaming the files, or by adding a symbolic link, at the
10003 maintainer's discretion.<footnote>
10004 Rationale: People should not have to look in places for
10005 upstream changelogs merely because they are given
10006 different names or are distributed in HTML format.
10011 All of these files should be installed compressed using
10012 <tt>gzip -9</tt>, as they will become large with time even
10013 if they start out small.
10017 If the package has only one changelog which is used both as
10018 the Debian changelog and the upstream one because there is
10019 no separate upstream maintainer then that changelog should
10020 usually be installed as
10021 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10022 there is a separate upstream maintainer, but no upstream
10023 changelog, then the Debian changelog should still be called
10024 <file>changelog.Debian.gz</file>.
10028 For details about the format and contents of the Debian
10029 changelog file, please see <ref id="dpkgchangelog">.
10034 <appendix id="pkg-scope">
10035 <heading>Introduction and scope of these appendices</heading>
10038 These appendices are taken essentially verbatim from the
10039 now-deprecated Packaging Manual, version 3.2.1.0. They are
10040 the chapters which are likely to be of use to package
10041 maintainers and which have not already been included in the
10042 policy document itself. Most of these sections are very likely
10043 not relevant to policy; they should be treated as
10044 documentation for the packaging system. Please note that these
10045 appendices are included for convenience, and for historical
10046 reasons: they used to be part of policy package, and they have
10047 not yet been incorporated into dpkg documentation. However,
10048 they still have value, and hence they are presented here.
10052 They have not yet been checked to ensure that they are
10053 compatible with the contents of policy, and if there are any
10054 contradictions, the version in the main policy document takes
10055 precedence. The remaining chapters of the old Packaging
10056 Manual have also not been read in detail to ensure that there
10057 are not parts which have been left out. Both of these will be
10058 done in due course.
10062 Certain parts of the Packaging manual were integrated into the
10063 Policy Manual proper, and removed from the appendices. Links
10064 have been placed from the old locations to the new ones.
10068 <prgn>dpkg</prgn> is a suite of programs for creating binary
10069 package files and installing and removing them on Unix
10071 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10072 work on or be ported to other systems.
10077 The binary packages are designed for the management of
10078 installed executable programs (usually compiled binaries) and
10079 their associated data, though source code examples and
10080 documentation are provided as part of some packages.</p>
10083 This manual describes the technical aspects of creating Debian
10084 binary packages (<file>.deb</file> files). It documents the
10085 behavior of the package management programs
10086 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10087 they interact with packages.</p>
10090 It also documents the interaction between
10091 <prgn>dselect</prgn>'s core and the access method scripts it
10092 uses to actually install the selected packages, and describes
10093 how to create a new access method.</p>
10096 This manual does not go into detail about the options and
10097 usage of the package building and installation tools. It
10098 should therefore be read in conjunction with those programs'
10103 The utility programs which are provided with <prgn>dpkg</prgn>
10104 for managing various system configuration and similar issues,
10105 such as <prgn>update-rc.d</prgn> and
10106 <prgn>install-info</prgn>, are not described in detail here -
10107 please see their man pages.
10111 It is assumed that the reader is reasonably familiar with the
10112 <prgn>dpkg</prgn> System Administrators' manual.
10113 Unfortunately this manual does not yet exist.
10117 The Debian version of the FSF's GNU hello program is provided as
10118 an example for people wishing to create Debian packages. However,
10119 while the examples are helpful, they do not replace the need to
10120 read and follow the Policy and Programmer's Manual.</p>
10123 <appendix id="pkg-binarypkg">
10124 <heading>Binary packages (from old Packaging Manual)</heading>
10127 The binary package has two main sections. The first part
10128 consists of various control information files and scripts used
10129 by <prgn>dpkg</prgn> when installing and removing. See <ref
10130 id="pkg-controlarea">.
10134 The second part is an archive containing the files and
10135 directories to be installed.
10139 In the future binary packages may also contain other
10140 components, such as checksums and digital signatures. The
10141 format for the archive is described in full in the
10142 <file>deb(5)</file> man page.
10146 <sect id="pkg-bincreating"><heading>Creating package files -
10147 <prgn>dpkg-deb</prgn>
10151 All manipulation of binary package files is done by
10152 <prgn>dpkg-deb</prgn>; it's the only program that has
10153 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10154 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10155 will spot that the options requested are appropriate to
10156 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10161 In order to create a binary package you must make a
10162 directory tree which contains all the files and directories
10163 you want to have in the file system data part of the package.
10164 In Debian-format source packages this directory is usually
10165 <file>debian/tmp</file>, relative to the top of the package's
10170 They should have the locations (relative to the root of the
10171 directory tree you're constructing) ownerships and
10172 permissions which you want them to have on the system when
10173 they are installed.
10177 With current versions of <prgn>dpkg</prgn> the uid/username
10178 and gid/groupname mappings for the users and groups being
10179 used should be the same on the system where the package is
10180 built and the one where it is installed.
10184 You need to add one special directory to the root of the
10185 miniature file system tree you're creating:
10186 <prgn>DEBIAN</prgn>. It should contain the control
10187 information files, notably the binary package control file
10188 (see <ref id="pkg-controlfile">).
10192 The <prgn>DEBIAN</prgn> directory will not appear in the
10193 file system archive of the package, and so won't be installed
10194 by <prgn>dpkg</prgn> when the package is unpacked.
10198 When you've prepared the package, you should invoke:
10200 dpkg --build <var>directory</var>
10205 This will build the package in
10206 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10207 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10208 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10209 build the package.)
10213 See the man page <manref name="dpkg-deb" section="8"> for details of how
10214 to examine the contents of this newly-created file. You may find the
10215 output of following commands enlightening:
10217 dpkg-deb --info <var>filename</var>.deb
10218 dpkg-deb --contents <var>filename</var>.deb
10219 dpkg --contents <var>filename</var>.deb
10221 To view the copyright file for a package you could use this command:
10223 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10228 <sect id="pkg-controlarea">
10229 <heading>Package control information files</heading>
10232 The control information portion of a binary package is a
10233 collection of files with names known to <prgn>dpkg</prgn>.
10234 It will treat the contents of these files specially - some
10235 of them contain information used by <prgn>dpkg</prgn> when
10236 installing or removing the package; others are scripts which
10237 the package maintainer wants <prgn>dpkg</prgn> to run.
10241 It is possible to put other files in the package control
10242 information file area, but this is not generally a good idea
10243 (though they will largely be ignored).
10247 Here is a brief list of the control information files supported
10248 by <prgn>dpkg</prgn> and a summary of what they're used for.
10253 <tag><tt>control</tt>
10256 This is the key description file used by
10257 <prgn>dpkg</prgn>. It specifies the package's name
10258 and version, gives its description for the user,
10259 states its relationships with other packages, and so
10260 forth. See <ref id="sourcecontrolfiles"> and
10261 <ref id="binarycontrolfiles">.
10265 It is usually generated automatically from information
10266 in the source package by the
10267 <prgn>dpkg-gencontrol</prgn> program, and with
10268 assistance from <prgn>dpkg-shlibdeps</prgn>.
10269 See <ref id="pkg-sourcetools">.
10273 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10278 These are executable files (usually scripts) which
10279 <prgn>dpkg</prgn> runs during installation, upgrade
10280 and removal of packages. They allow the package to
10281 deal with matters which are particular to that package
10282 or require more complicated processing than that
10283 provided by <prgn>dpkg</prgn>. Details of when and
10284 how they are called are in <ref id="maintainerscripts">.
10288 It is very important to make these scripts idempotent.
10289 See <ref id="idempotency">.
10293 The maintainer scripts are not guaranteed to run with a
10294 controlling terminal and may not be able to interact with
10295 the user. See <ref id="controllingterminal">.
10299 <tag><tt>conffiles</tt>
10302 This file contains a list of configuration files which
10303 are to be handled automatically by <prgn>dpkg</prgn>
10304 (see <ref id="pkg-conffiles">). Note that not necessarily
10305 every configuration file should be listed here.
10308 <tag><tt>shlibs</tt>
10311 This file contains a list of the shared libraries
10312 supplied by the package, with dependency details for
10313 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10314 when it determines what dependencies are required in a
10315 package control file. The <tt>shlibs</tt> file format
10316 is described on <ref id="shlibs">.
10321 <sect id="pkg-controlfile">
10322 <heading>The main control information file: <tt>control</tt></heading>
10325 The most important control information file used by
10326 <prgn>dpkg</prgn> when it installs a package is
10327 <tt>control</tt>. It contains all the package's "vital
10332 The binary package control files of packages built from
10333 Debian sources are made by a special tool,
10334 <prgn>dpkg-gencontrol</prgn>, which reads
10335 <file>debian/control</file> and <file>debian/changelog</file> to
10336 find the information it needs. See <ref id="pkg-sourcepkg"> for
10341 The fields in binary package control files are listed in
10342 <ref id="binarycontrolfiles">.
10346 A description of the syntax of control files and the purpose
10347 of the fields is available in <ref id="controlfields">.
10352 <heading>Time Stamps</heading>
10355 See <ref id="timestamps">.
10360 <appendix id="pkg-sourcepkg">
10361 <heading>Source packages (from old Packaging Manual) </heading>
10364 The Debian binary packages in the distribution are generated
10365 from Debian sources, which are in a special format to assist
10366 the easy and automatic building of binaries.
10369 <sect id="pkg-sourcetools">
10370 <heading>Tools for processing source packages</heading>
10373 Various tools are provided for manipulating source packages;
10374 they pack and unpack sources and help build of binary
10375 packages and help manage the distribution of new versions.
10379 They are introduced and typical uses described here; see
10380 <manref name="dpkg-source" section="1"> for full
10381 documentation about their arguments and operation.
10385 For examples of how to construct a Debian source package,
10386 and how to use those utilities that are used by Debian
10387 source packages, please see the <prgn>hello</prgn> example
10391 <sect1 id="pkg-dpkg-source">
10393 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10398 This program is frequently used by hand, and is also
10399 called from package-independent automated building scripts
10400 such as <prgn>dpkg-buildpackage</prgn>.
10404 To unpack a package it is typically invoked with
10406 dpkg-source -x <var>.../path/to/filename</var>.dsc
10411 with the <file><var>filename</var>.tar.gz</file> and
10412 <file><var>filename</var>.diff.gz</file> (if applicable) in
10413 the same directory. It unpacks into
10414 <file><var>package</var>-<var>version</var></file>, and if
10416 <file><var>package</var>-<var>version</var>.orig</file>, in
10417 the current directory.
10421 To create a packed source archive it is typically invoked:
10423 dpkg-source -b <var>package</var>-<var>version</var>
10428 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10429 <file>.diff.gz</file> (if appropriate) in the current
10430 directory. <prgn>dpkg-source</prgn> does not clean the
10431 source tree first - this must be done separately if it is
10436 See also <ref id="pkg-sourcearchives">.</p>
10440 <sect1 id="pkg-dpkg-buildpackage">
10442 <prgn>dpkg-buildpackage</prgn> - overall package-building
10447 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10448 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10449 targets <tt>clean</tt>, <tt>build</tt> and
10450 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10451 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10452 source and binary package upload.
10456 It is usually invoked by hand from the top level of the
10457 built or unbuilt source directory. It may be invoked with
10458 no arguments; useful arguments include:
10459 <taglist compact="compact">
10460 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10463 Do not sign the <tt>.changes</tt> file or the
10464 source package <tt>.dsc</tt> file, respectively.</p>
10466 <tag><tt>-p<var>sign-command</var></tt></tag>
10469 Invoke <var>sign-command</var> instead of finding
10470 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10471 <var>sign-command</var> must behave just like
10472 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10474 <tag><tt>-r<var>root-command</var></tt></tag>
10477 When root privilege is required, invoke the command
10478 <var>root-command</var>. <var>root-command</var>
10479 should invoke its first argument as a command, from
10480 the <prgn>PATH</prgn> if necessary, and pass its
10481 second and subsequent arguments to the command it
10482 calls. If no <var>root-command</var> is supplied
10483 then <var>dpkg-buildpackage</var> will take no
10484 special action to gain root privilege, so that for
10485 most packages it will have to be invoked as root to
10488 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10491 Two types of binary-only build and upload - see
10492 <manref name="dpkg-source" section="1">.
10499 <sect1 id="pkg-dpkg-gencontrol">
10501 <prgn>dpkg-gencontrol</prgn> - generates binary package
10506 This program is usually called from <file>debian/rules</file>
10507 (see <ref id="pkg-sourcetree">) in the top level of the source
10512 This is usually done just before the files and directories in the
10513 temporary directory tree where the package is being built have their
10514 permissions and ownerships set and the package is constructed using
10515 <prgn>dpkg-deb/</prgn>
10517 This is so that the control file which is produced has
10518 the right permissions
10523 <prgn>dpkg-gencontrol</prgn> must be called after all the
10524 files which are to go into the package have been placed in
10525 the temporary build directory, so that its calculation of
10526 the installed size of a package is correct.
10530 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10531 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10532 variable substitutions created by
10533 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10538 For a package which generates only one binary package, and
10539 which builds it in <file>debian/tmp</file> relative to the top
10540 of the source package, it is usually sufficient to call
10541 <prgn>dpkg-gencontrol</prgn>.
10545 Sources which build several binaries will typically need
10548 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10549 </example> The <tt>-P</tt> tells
10550 <prgn>dpkg-gencontrol</prgn> that the package is being
10551 built in a non-default directory, and the <tt>-p</tt>
10552 tells it which package's control file should be generated.
10556 <prgn>dpkg-gencontrol</prgn> also adds information to the
10557 list of files in <file>debian/files</file>, for the benefit of
10558 (for example) a future invocation of
10559 <prgn>dpkg-genchanges</prgn>.</p>
10562 <sect1 id="pkg-dpkg-shlibdeps">
10564 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10569 This program is usually called from <file>debian/rules</file>
10570 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10571 id="pkg-sourcetree">), in the top level of the source tree.
10575 Its arguments are executables and shared libraries
10578 They may be specified either in the locations in the
10579 source tree where they are created or in the locations
10580 in the temporary build tree where they are installed
10581 prior to binary package creation.
10583 </footnote> for which shared library dependencies should
10584 be included in the binary package's control file.
10588 If some of the found shared libraries should only
10589 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10590 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10591 by using the <tt>-d<var>dependency-field</var></tt> option
10592 before those executable(s). (Each <tt>-d</tt> option
10593 takes effect until the next <tt>-d</tt>.)
10597 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10598 output control file to be modified. Instead by default it
10599 adds to the <file>debian/substvars</file> file variable
10600 settings like <tt>shlibs:Depends</tt>. These variable
10601 settings must be referenced in dependency fields in the
10602 appropriate per-binary-package sections of the source
10607 For example, a package that generates an essential part
10608 which requires dependencies, and optional parts that
10609 which only require a recommendation, would separate those
10610 two sets of dependencies into two different fields.<footnote>
10611 At the time of writing, an example for this was the
10612 <package/xmms/ package, with Depends used for the xmms
10613 executable, Recommends for the plug-ins and Suggests for
10614 even more optional features provided by unzip.
10616 It can say in its <file>debian/rules</file>:
10618 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10619 -dRecommends <var>optionalpart anotheroptionalpart</var>
10621 and then in its main control file <file>debian/control</file>:
10624 Depends: ${shlibs:Depends}
10625 Recommends: ${shlibs:Recommends}
10631 Sources which produce several binary packages with
10632 different shared library dependency requirements can use
10633 the <tt>-p<var>varnameprefix</var></tt> option to override
10634 the default <tt>shlibs:</tt> prefix (one invocation of
10635 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10636 They can thus produce several sets of dependency
10637 variables, each of the form
10638 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10639 which can be referred to in the appropriate parts of the
10640 binary package control files.
10645 <sect1 id="pkg-dpkg-distaddfile">
10647 <prgn>dpkg-distaddfile</prgn> - adds a file to
10648 <file>debian/files</file>
10652 Some packages' uploads need to include files other than
10653 the source and binary package files.
10657 <prgn>dpkg-distaddfile</prgn> adds a file to the
10658 <file>debian/files</file> file so that it will be included in
10659 the <file>.changes</file> file when
10660 <prgn>dpkg-genchanges</prgn> is run.
10664 It is usually invoked from the <tt>binary</tt> target of
10665 <file>debian/rules</file>:
10667 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10669 The <var>filename</var> is relative to the directory where
10670 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10671 is usually the directory above the top level of the source
10672 tree. The <file>debian/rules</file> target should put the
10673 file there just before or just after calling
10674 <prgn>dpkg-distaddfile</prgn>.
10678 The <var>section</var> and <var>priority</var> are passed
10679 unchanged into the resulting <file>.changes</file> file.
10684 <sect1 id="pkg-dpkg-genchanges">
10686 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10687 upload control file
10691 This program is usually called by package-independent
10692 automatic building scripts such as
10693 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10698 It is usually called in the top level of a built source
10699 tree, and when invoked with no arguments will print out a
10700 straightforward <file>.changes</file> file based on the
10701 information in the source package's changelog and control
10702 file and the binary and source packages which should have
10708 <sect1 id="pkg-dpkg-parsechangelog">
10710 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10711 representation of a changelog
10715 This program is used internally by
10716 <prgn>dpkg-source</prgn> et al. It may also occasionally
10717 be useful in <file>debian/rules</file> and elsewhere. It
10718 parses a changelog, <file>debian/changelog</file> by default,
10719 and prints a control-file format representation of the
10720 information in it to standard output.
10724 <sect1 id="pkg-dpkg-architecture">
10726 <prgn>dpkg-architecture</prgn> - information about the build and
10731 This program can be used manually, but is also invoked by
10732 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10733 environment or make variables which specify the build and host
10734 architecture for the package building process.
10739 <sect id="pkg-sourcetree">
10740 <heading>The Debian package source tree</heading>
10743 The source archive scheme described later is intended to
10744 allow a Debian package source tree with some associated
10745 control information to be reproduced and transported easily.
10746 The Debian package source tree is a version of the original
10747 program with certain files added for the benefit of the
10748 packaging process, and with any other changes required
10749 made to the rest of the source code and installation
10754 The extra files created for Debian are in the subdirectory
10755 <file>debian</file> of the top level of the Debian package
10756 source tree. They are described below.
10759 <sect1 id="pkg-debianrules">
10760 <heading><file>debian/rules</file> - the main building script</heading>
10763 See <ref id="debianrules">.
10767 <sect1 id="pkg-srcsubstvars">
10768 <heading><file>debian/substvars</file> and variable substitutions</heading>
10771 See <ref id="substvars">.
10777 <heading><file>debian/files</file></heading>
10780 See <ref id="debianfiles">.
10784 <sect1><heading><file>debian/tmp</file>
10788 This is the canonical temporary location for the
10789 construction of binary packages by the <tt>binary</tt>
10790 target. The directory <file>tmp</file> serves as the root of
10791 the file system tree as it is being constructed (for
10792 example, by using the package's upstream makefiles install
10793 targets and redirecting the output there), and it also
10794 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10795 id="pkg-bincreating">.
10799 If several binary packages are generated from the same
10800 source tree it is usual to use several
10801 <file>debian/tmp<var>something</var></file> directories, for
10802 example <file>tmp-a</file> or <file>tmp-doc</file>.
10806 Whatever <file>tmp</file> directories are created and used by
10807 <tt>binary</tt> must of course be removed by the
10808 <tt>clean</tt> target.</p></sect1>
10812 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10816 As it exists on the FTP site, a Debian source package
10817 consists of three related files. You must have the right
10818 versions of all three to be able to use them.
10823 <tag>Debian source control file - <tt>.dsc</tt></tag>
10825 This file is a control file used by <prgn>dpkg-source</prgn>
10826 to extract a source package.
10827 See <ref id="debiansourcecontrolfiles">.
10831 Original source archive -
10833 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10839 This is a compressed (with <tt>gzip -9</tt>)
10840 <prgn>tar</prgn> file containing the source code from
10841 the upstream authors of the program.
10846 Debian package diff -
10848 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10854 This is a unified context diff (<tt>diff -u</tt>)
10855 giving the changes which are required to turn the
10856 original source into the Debian source. These changes
10857 may only include editing and creating plain files.
10858 The permissions of files, the targets of symbolic
10859 links and the characteristics of special files or
10860 pipes may not be changed and no files may be removed
10865 All the directories in the diff must exist, except the
10866 <file>debian</file> subdirectory of the top of the source
10867 tree, which will be created by
10868 <prgn>dpkg-source</prgn> if necessary when unpacking.
10872 The <prgn>dpkg-source</prgn> program will
10873 automatically make the <file>debian/rules</file> file
10874 executable (see below).</p></item>
10879 If there is no original source code - for example, if the
10880 package is specially prepared for Debian or the Debian
10881 maintainer is the same as the upstream maintainer - the
10882 format is slightly different: then there is no diff, and the
10884 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10885 and preferably contains a directory named
10886 <file><var>package</var>-<var>version</var></file>.
10891 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10894 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10895 Debian source package. However, if it is not available it
10896 is possible to unpack a Debian source archive as follows:
10897 <enumlist compact="compact">
10900 Untar the tarfile, which will create a <file>.orig</file>
10904 <p>Rename the <file>.orig</file> directory to
10905 <file><var>package</var>-<var>version</var></file>.</p>
10909 Create the subdirectory <file>debian</file> at the top of
10910 the source tree.</p>
10912 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10914 <item><p>Untar the tarfile again if you want a copy of the original
10915 source code alongside the Debian version.</p>
10920 It is not possible to generate a valid Debian source archive
10921 without using <prgn>dpkg-source</prgn>. In particular,
10922 attempting to use <prgn>diff</prgn> directly to generate the
10923 <file>.diff.gz</file> file will not work.
10927 <heading>Restrictions on objects in source packages</heading>
10930 The source package may not contain any hard links
10932 This is not currently detected when building source
10933 packages, but only when extracting
10937 Hard links may be permitted at some point in the
10938 future, but would require a fair amount of
10940 </footnote>, device special files, sockets or setuid or
10943 Setgid directories are allowed.
10948 The source packaging tools manage the changes between the
10949 original and Debian source using <prgn>diff</prgn> and
10950 <prgn>patch</prgn>. Turning the original source tree as
10951 included in the <file>.orig.tar.gz</file> into the Debian
10952 package source must not involve any changes which cannot be
10953 handled by these tools. Problematic changes which cause
10954 <prgn>dpkg-source</prgn> to halt with an error when
10955 building the source package are:
10956 <list compact="compact">
10957 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10959 <item><p>Changing the targets of symbolic links.</p>
10961 <item><p>Creating directories, other than <file>debian</file>.</p>
10963 <item><p>Changes to the contents of binary files.</p></item>
10964 </list> Changes which cause <prgn>dpkg-source</prgn> to
10965 print a warning but continue anyway are:
10966 <list compact="compact">
10969 Removing files, directories or symlinks.
10971 Renaming a file is not treated specially - it is
10972 seen as the removal of the old file (which
10973 generates a warning, but is otherwise ignored),
10974 and the creation of the new one.
10980 Changed text files which are missing the usual final
10981 newline (either in the original or the modified
10986 Changes which are not represented, but which are not detected by
10987 <prgn>dpkg-source</prgn>, are:
10988 <list compact="compact">
10989 <item><p>Changing the permissions of files (other than
10990 <file>debian/rules</file>) and directories.</p></item>
10995 The <file>debian</file> directory and <file>debian/rules</file>
10996 are handled specially by <prgn>dpkg-source</prgn> - before
10997 applying the changes it will create the <file>debian</file>
10998 directory, and afterwards it will make
10999 <file>debian/rules</file> world-executable.
11005 <appendix id="pkg-controlfields">
11006 <heading>Control files and their fields (from old Packaging Manual)</heading>
11009 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11010 data in a common format, known as control files. Binary and
11011 source packages have control data as do the <file>.changes</file>
11012 files which control the installation of uploaded files, and
11013 <prgn>dpkg</prgn>'s internal databases are in a similar
11018 <heading>Syntax of control files</heading>
11021 See <ref id="controlsyntax">.
11025 It is important to note that there are several fields which
11026 are optional as far as <prgn>dpkg</prgn> and the related
11027 tools are concerned, but which must appear in every Debian
11028 package, or whose omission may cause problems.
11033 <heading>List of fields</heading>
11036 See <ref id="controlfieldslist">.
11040 This section now contains only the fields that didn't belong
11041 to the Policy manual.
11044 <sect1 id="pkg-f-Filename">
11045 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11048 These fields in <tt>Packages</tt> files give the
11049 filename(s) of (the parts of) a package in the
11050 distribution directories, relative to the root of the
11051 Debian hierarchy. If the package has been split into
11052 several parts the parts are all listed in order, separated
11057 <sect1 id="pkg-f-Size">
11058 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11061 These fields in <file>Packages</file> files give the size (in
11062 bytes, expressed in decimal) and MD5 checksum of the
11063 file(s) which make(s) up a binary package in the
11064 distribution. If the package is split into several parts
11065 the values for the parts are listed in order, separated by
11070 <sect1 id="pkg-f-Status">
11071 <heading><tt>Status</tt></heading>
11074 This field in <prgn>dpkg</prgn>'s status file records
11075 whether the user wants a package installed, removed or
11076 left alone, whether it is broken (requiring
11077 re-installation) or not and what its current state on the
11078 system is. Each of these pieces of information is a
11083 <sect1 id="pkg-f-Config-Version">
11084 <heading><tt>Config-Version</tt></heading>
11087 If a package is not installed or not configured, this
11088 field in <prgn>dpkg</prgn>'s status file records the last
11089 version of the package which was successfully
11094 <sect1 id="pkg-f-Conffiles">
11095 <heading><tt>Conffiles</tt></heading>
11098 This field in <prgn>dpkg</prgn>'s status file contains
11099 information about the automatically-managed configuration
11100 files held by a package. This field should <em>not</em>
11101 appear anywhere in a package!
11106 <heading>Obsolete fields</heading>
11109 These are still recognized by <prgn>dpkg</prgn> but should
11110 not appear anywhere any more.
11112 <taglist compact="compact">
11114 <tag><tt>Revision</tt></tag>
11115 <tag><tt>Package-Revision</tt></tag>
11116 <tag><tt>Package_Revision</tt></tag>
11118 The Debian revision part of the package version was
11119 at one point in a separate control field. This
11120 field went through several names.
11123 <tag><tt>Recommended</tt></tag>
11124 <item>Old name for <tt>Recommends</tt>.</item>
11126 <tag><tt>Optional</tt></tag>
11127 <item>Old name for <tt>Suggests</tt>.</item>
11129 <tag><tt>Class</tt></tag>
11130 <item>Old name for <tt>Priority</tt>.</item>
11139 <appendix id="pkg-conffiles">
11140 <heading>Configuration file handling (from old Packaging Manual)</heading>
11143 <prgn>dpkg</prgn> can do a certain amount of automatic
11144 handling of package configuration files.
11148 Whether this mechanism is appropriate depends on a number of
11149 factors, but basically there are two approaches to any
11150 particular configuration file.
11154 The easy method is to ship a best-effort configuration in the
11155 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11156 handle updates. If the user is unlikely to want to edit the
11157 file, but you need them to be able to without losing their
11158 changes, and a new package with a changed version of the file
11159 is only released infrequently, this is a good approach.
11163 The hard method is to build the configuration file from
11164 scratch in the <prgn>postinst</prgn> script, and to take the
11165 responsibility for fixing any mistakes made in earlier
11166 versions of the package automatically. This will be
11167 appropriate if the file is likely to need to be different on
11171 <sect><heading>Automatic handling of configuration files by
11176 A package may contain a control information file called
11177 <tt>conffiles</tt>. This file should be a list of filenames
11178 of configuration files needing automatic handling, separated
11179 by newlines. The filenames should be absolute pathnames,
11180 and the files referred to should actually exist in the
11185 When a package is upgraded <prgn>dpkg</prgn> will process
11186 the configuration files during the configuration stage,
11187 shortly before it runs the package's <prgn>postinst</prgn>
11192 For each file it checks to see whether the version of the
11193 file included in the package is the same as the one that was
11194 included in the last version of the package (the one that is
11195 being upgraded from); it also compares the version currently
11196 installed on the system with the one shipped with the last
11201 If neither the user nor the package maintainer has changed
11202 the file, it is left alone. If one or the other has changed
11203 their version, then the changed version is preferred - i.e.,
11204 if the user edits their file, but the package maintainer
11205 doesn't ship a different version, the user's changes will
11206 stay, silently, but if the maintainer ships a new version
11207 and the user hasn't edited it the new version will be
11208 installed (with an informative message). If both have
11209 changed their version the user is prompted about the problem
11210 and must resolve the differences themselves.
11214 The comparisons are done by calculating the MD5 message
11215 digests of the files, and storing the MD5 of the file as it
11216 was included in the most recent version of the package.
11220 When a package is installed for the first time
11221 <prgn>dpkg</prgn> will install the file that comes with it,
11222 unless that would mean overwriting a file already on the
11227 However, note that <prgn>dpkg</prgn> will <em>not</em>
11228 replace a conffile that was removed by the user (or by a
11229 script). This is necessary because with some programs a
11230 missing file produces an effect hard or impossible to
11231 achieve in another way, so that a missing file needs to be
11232 kept that way if the user did it.
11236 Note that a package should <em>not</em> modify a
11237 <prgn>dpkg</prgn>-handled conffile in its maintainer
11238 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11239 the user confusing and possibly dangerous options for
11240 conffile update when the package is upgraded.</p>
11243 <sect><heading>Fully-featured maintainer script configuration
11248 For files which contain site-specific information such as
11249 the hostname and networking details and so forth, it is
11250 better to create the file in the package's
11251 <prgn>postinst</prgn> script.
11255 This will typically involve examining the state of the rest
11256 of the system to determine values and other information, and
11257 may involve prompting the user for some information which
11258 can't be obtained some other way.
11262 When using this method there are a couple of important
11263 issues which should be considered:
11267 If you discover a bug in the program which generates the
11268 configuration file, or if the format of the file changes
11269 from one version to the next, you will have to arrange for
11270 the postinst script to do something sensible - usually this
11271 will mean editing the installed configuration file to remove
11272 the problem or change the syntax. You will have to do this
11273 very carefully, since the user may have changed the file,
11274 perhaps to fix the very problem that your script is trying
11275 to deal with - you will have to detect these situations and
11276 deal with them correctly.
11280 If you do go down this route it's probably a good idea to
11281 make the program that generates the configuration file(s) a
11282 separate program in <file>/usr/sbin</file>, by convention called
11283 <file><var>package</var>config</file> and then run that if
11284 appropriate from the post-installation script. The
11285 <tt><var>package</var>config</tt> program should not
11286 unquestioningly overwrite an existing configuration - if its
11287 mode of operation is geared towards setting up a package for
11288 the first time (rather than any arbitrary reconfiguration
11289 later) you should have it check whether the configuration
11290 already exists, and require a <tt>--force</tt> flag to
11291 overwrite it.</p></sect>
11294 <appendix id="pkg-alternatives"><heading>Alternative versions of
11295 an interface - <prgn>update-alternatives</prgn> (from old
11300 When several packages all provide different versions of the
11301 same program or file it is useful to have the system select a
11302 default, but to allow the system administrator to change it
11303 and have their decisions respected.
11307 For example, there are several versions of the <prgn>vi</prgn>
11308 editor, and there is no reason to prevent all of them from
11309 being installed at once, each under their own name
11310 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11311 Nevertheless it is desirable to have the name <tt>vi</tt>
11312 refer to something, at least by default.
11316 If all the packages involved cooperate, this can be done with
11317 <prgn>update-alternatives</prgn>.
11321 Each package provides its own version under its own name, and
11322 calls <prgn>update-alternatives</prgn> in its postinst to
11323 register its version (and again in its prerm to deregister
11328 See the man page <manref name="update-alternatives"
11329 section="8"> for details.
11333 If <prgn>update-alternatives</prgn> does not seem appropriate
11334 you may wish to consider using diversions instead.</p>
11337 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11338 package's version of a file (from old Packaging Manual)
11342 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11343 when it reinstalls the package it belongs to, and to have it
11344 put the file from the package somewhere else instead.
11348 This can be used locally to override a package's version of a
11349 file, or by one package to override another's version (or
11350 provide a wrapper for it).
11354 Before deciding to use a diversion, read <ref
11355 id="pkg-alternatives"> to see if you really want a diversion
11356 rather than several alternative versions of a program.
11360 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11361 and updated by a special program <prgn>dpkg-divert</prgn>.
11362 Please see <manref name="dpkg-divert" section="8"> for full
11363 details of its operation.
11367 When a package wishes to divert a file from another, it should
11368 call <prgn>dpkg-divert</prgn> in its preinst to add the
11369 diversion and rename the existing file. For example,
11370 supposing that a <prgn>smailwrapper</prgn> package wishes to
11371 install a wrapper around <file>/usr/sbin/smail</file>:
11373 dpkg-divert --package smailwrapper --add --rename \
11374 --divert /usr/sbin/smail.real /usr/sbin/smail
11375 </example> The <tt>--package smailwrapper</tt> ensures that
11376 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11377 can bypass the diversion and get installed as the true version.
11378 It's safe to add the diversion unconditionally on upgrades since
11379 it will be left unchanged if it already exists, but
11380 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11381 message, make the command conditional on the version from which
11382 the package is being upgraded:
11384 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11385 dpkg-divert --package smailwrapper --add --rename \
11386 --divert /usr/sbin/smail.real /usr/sbin/smail
11388 </example> where <tt>1.0-2</tt> is the version at which the
11389 diversion was first added to the package. Running the command
11390 during abort-upgrade is pointless but harmless.
11394 The postrm has to do the reverse:
11396 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11397 dpkg-divert --package smailwrapper --remove --rename \
11398 --divert /usr/sbin/smail.real /usr/sbin/smail
11400 </example> If the diversion was added at a particular version, the
11401 postrm should also handle the failure case of upgrading from an
11402 older version (unless the older version is so old that direct
11403 upgrades are no longer supported):
11405 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11406 dpkg-divert --package smailwrapper --remove --rename \
11407 --divert /usr/sbin/smail.real /usr/sbin/smail
11409 </example> where <tt>1.0-2</tt> is the version at which the
11410 diversion was first added to the package. The postrm should not
11411 remove the diversion on upgrades both because there's no reason to
11412 remove the diversion only to immediately re-add it and since the
11413 postrm of the old package is run after unpacking so the removal of
11414 the diversion will fail.
11418 Do not attempt to divert a file which is vitally important for
11419 the system's operation - when using <prgn>dpkg-divert</prgn>
11420 there is a time, after it has been diverted but before
11421 <prgn>dpkg</prgn> has installed the new version, when the file
11422 does not exist.</p>
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